Description Title of Invention: TEMPERATURE PREDICTION DEVICE AND TEMPERATURE PREDICTION METHOD FOR INTERNAL COMBUSTION ENGINE
Technical Field
[0001] The present invention relates to a temperature prediction device and a temperature prediction method, in which a temperature of an internal combustion engine is predicted with the use of an intake pressure inside an intake pipe.
Background Art
[0002] Hitherto, an electronic control unit called "ECU" has been installed in a vehicle. The ECU is mainly formed of a microcomputer, and is configured to control operation of an internal combustion engine for a vehicle involving driving, for example. Various parameters are involved in such control of the operation of the internal combustion engine. As one of the parameters involved in the control, temperature information of the internal combustion engine is known.
[0003] When there is adopted feedback control in which a dedicated temperature sensor is arranged in an internal combustion engine main body, and in which the ECU controls the internal combustion engine with the use of a measurement result obtained by the temperature sensor, a delay is caused from a response time of the ECU to a measurement time of the temperature sensor, and

hence it is difficult to control the internal combustion engine appropriately.
[0004] To address the above-mentioned problem, there has been proposed a method in which a temperature of an internal combustion engine main body at startup of the internal combustion engine, a temperature of an intake pipe at a given time, and a model for simulation are used to predict a temperature of the internal combustion engine main body at the given time (see Patent Literature 1, for example). In the related-art technology described in Patent Literature 1, as configurations used to know the temperature of the internal combustion engine main body at startup of the internal combustion engine, there are proposed a direct detection configuration and an indirect detection configuration. In the direct detection configuration, a dedicated temperature sensor is arranged on a housing of the internal combustion engine main body, and the temperature of the internal combustion engine main body is directly detected by the temperature sensor. In the indirect detection configuration, a temperature of engine oil or a temperature of cooling water of the internal combustion engine is directly detected, and the temperature of the internal combustion engine main body is indirectly detected by temperature prediction based on a result of the detection.
[0005] There is also proposed a method of predicting, assuming that a temperature inside an intake pipe at startup of the internal combustion engine and an atmospheric temperature match, the

temperature of the intake pipe based on a pressure inside a cylinder of the internal combustion engine and the atmospheric temperature around the internal combustion engine (see Patent Literature 2, for example).
Citation List Patent Literature
[0006] [PTL 1] JP 2005-83240 A [PTL 2] JP 2006-132526 A
Summary of Invention Technical Problem
[0007] However, when the above-mentioned direct detection configuration is applied in order to know the temperature of the internal combustion engine main body, it is required to prepare a heat-resistant temperature sensor capable of enduring an increase in temperature of the internal combustion engine main body. It is also required to perform operations, such as an operation of applying processing, for example, opening a hole for attaching the temperature sensor, on a surface of the internal combustion engine main body, and an operation of attaching the temperature sensor. Alternatively, when the above-mentioned indirect detection configuration is applied in order to know the temperature of the internal combustion engine main body, it is required to prepare a heat-resistant temperature sensor capable of enduring an increase

in temperature of the engine oil or the cooling water, and it is further required to perform the above-mentioned operations as described above.
[0008] In other words, with the related-art technology described in Patent Literature 1, even when any one of the direct detection configuration and the indirect detection configuration is applied in order to know the temperature of the internal combustion engine main body, there is a fear that increases in wiring and parts cause increases in manufacturing cost and working load. As a result, the costs of parts and manufacturing may remain high.
[0009] With the related-art technology described in Patent Literature 2, it is assumed that the temperature inside the intake pipe at startup of the internal combustion engine and the atmospheric temperature match as described above. Accordingly, an assumed range is varied depending on a time interval between the startup of the internal combustion engine and the stop of the internal combustion engine, and accuracy of predicting the temperature may be reduced. Therefore, for example, when the temperature of the internal combustion engine main body is predicted in the related-art technology described in Patent Literature 1 with the use of the temperature of the intake pipe predicted by applying the related-art technology described in Patent Literature 2, there is a fear that the accuracy of predicting the temperature of the internal combustion engine main body may be further reduced.
[0010] The present invention has been made in view of the

above-mentioned circumstances, and therefore has an object to provide a temperature prediction device and a temperature prediction method for an internal combustion engine, with which a temperature of the internal combustion engine can be predicted at a relatively low cost without using a dedicated temperature sensor that is compatible with high temperature.
Solution to Problem
[0011] According to one embodiment of the present invention, there is provided a temperature prediction device for an internal combustion engine, which is configured to predict a temperature of the internal combustion engine, the internal combustion engine being configured to perform an intake stroke, in which outside air is taken in from an intake pipe into a combustion chamber, and to ignite fuel injected into the outside air taken in in the intake stroke to cause combustion in the combustion chamber, the temperature prediction device including: an outside air pressure acquisition unit configured to acquire an intake pressure in the intake pipe as an outside air pressure at a timing within a period from when the internal combustion engine is started from a stopped state to when the internal combustion engine starts rotating; an intake representative pressure acquisition unit configured to acquire the intake pressure as an intake representative pressure at a timing within a period from when the internal combustion engine starts the rotation to when the combustion is started; a parameter

information acquisition unit configured to acquire a number of revolutions per unit time of the internal combustion engine; an initial temperature prediction unit configured to predict, based on the outside air pressure acquired by the outside air pressure acquisition unit, the intake representative pressure acquired by the intake representative pressure acquisition unit, and the number of revolutions acquired by the parameter information acquisition unit, an initial temperature of the internal combustion engine in a period from the start of the internal combustion engine to when the combustion is started; and a temperature prediction unit configured to predict, with use of the initial temperature predicted by the initial temperature prediction unit, a temperature of the internal combustion engine after the combustion is started. [0012] According to one embodiment of the present invention, there is provided a temperature prediction method for an internal combustion engine, for predicting a temperature of the internal combustion engine, the internal combustion engine being configured to perform an intake stroke, in which outside air is taken in from an intake pipe into a combustion chamber, and to ignite fuel injected into the outside air taken in in the intake stroke to cause combustion in the combustion chamber, the temperature prediction method including the steps of: acquiring an intake pressure in the intake pipe as an outside air pressure at a timing within a period from when the internal combustion engine is started from a stopped state to when the internal combustion engine starts rotating;

acquiring the intake pressure as an intake representative pressure and acquiring a number of revolutions per unit time of the internal combustion engine at a timing within a period from when the internal combustion engine starts the rotation to when the combustion is started; predicting, based on the acquired outside air pressure, the acquired intake representative pressure, and the acquired number of revolutions, an initial temperature of the internal combustion engine in a period from the start of the internal combustion engine to when the combustion is started; and predicting, with use of the predicted initial temperature, a temperature of the internal combustion engine after the combustion is started.
Advantageous Effects of Invention
[0013] According to the present invention, there can be provided the temperature prediction device and the temperature prediction method for an internal combustion engine, with which the temperature of the internal combustion engine can be predicted at a relatively low cost without using a dedicated temperature sensor that is compatible with high temperature.
Brief Description of Drawings
[0014] FIG. 1 is a diagram of a configuration of an internal combustion engine including a temperature prediction device for the internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is a schematic graph for showing a change in pressure of an intake pipe of the internal combustion engine in the first embodiment of the present invention.
FIG. 3 is a schematic graph for showing correlation between an intake pressure and a main body temperature in the first embodiment of the present invention.
FIG. 4 is a flow chart for illustrating a series of operations of the temperature prediction device for the internal combustion engine according to the first embodiment of the present invention.
FIG. 5 is a schematic graph for showing a change in pressure of an intake pipe of an internal combustion engine in a second embodiment of the present invention.
FIG. 6 is a schematic graph for showing a change in pressure of an intake pipe of an internal combustion engine in a third embodiment of the present invention.
FIG. 7 is a schematic graph for showing a change in pressure of an intake pipe of an internal combustion engine in a fourth embodiment of the present invention.
FIG. 8 is a flow chart for illustrating a series of operations of predicting an initial temperature by a temperature prediction device for the internal combustion engine in the fourth embodiment of the present invention.
Description of Embodiments [0015] Now, a temperature prediction device and a temperature

prediction method for an internal combustion engine according to embodiments of the present invention disclosed in this application are described in detail with reference to the accompanying drawings. In the illustration of the drawings, the same components or corresponding components are denoted by the same reference symbols, and the overlapping description thereof is herein omitted.
[0016] Further, the following embodiments are merely an example, and the present invention is not limited in any way by these embodiments. Further, the internal combustion engine to which the present invention is applied is an internal combustion engine for a vehicle, for example, and in the following embodiments, a case in which the present invention is applied to an internal combustion engine for a vehicle is exemplified.
[0017] First Embodiment
A temperature prediction device 121 for an internal combustion engine according to a first embodiment of the present invention is described with reference to FIG. 1. FIG. 1 is a diagram of a configuration of an internal combustion engine 100 including the temperature prediction device 121 for an internal combustion engine according to the first embodiment of the present invention.
[0018] The internal combustion engine 100 is a motor configured to perform an intake stroke, in which outside air is taken in from an intake pipe 101a into a combustion chamber 105, and to ignite fuel injected into the outside air taken in in the intake stroke to cause combustion in the combustion chamber 105.

More specifically, the internal combustion engine 100 is a four-cycle gasoline internal combustion engine operated with four strokes of the intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke being one combustion cycle.
[0019] The internal combustion engine 100 includes an intake passage 101, an air filter 102, a throttle valve 103, an intake pressure sensor 104, the combustion chamber 105, a bypass passage 106, an idle speed control valve 107, a fuel pump 108, a fuel tank 109, an injector 110, an intake valve 111, an ignition plug 112, a piston 113, a connecting rod 114, a crankshaft 115, an exhaust valve 116, an exhaust passage 117, a crank angle sensor 118, a three-way catalyst 119, an oxygen sensor 120, and the temperature prediction device 121.
[0020] An internal combustion engine main body 100a includes the piston 113, the connecting rod 114, and the crankshaft 115, which are covered by a cylinder, the intake valve 111, the exhaust valve 116, and the ignition plug 112, which are installed in a cylinder head, and the combustion chamber 105, which is located above the piston 113 and is sandwiched between the piston 113 and the cylinder head.
[0021] In the intake passage 101 of the internal combustion engine 100, the air filter 102, the throttle valve 103, and the intake pressure sensor 104 are provided in the stated order from an upstream side.
[0022] The intake pressure sensor 104 is configured to detect

an intake pressure of gas inside the intake pipe 101a corresponding to the intake passage 101 on a downstream side of the throttle valve
103. The intake pressure sensor 104 is communicably connected to
the temperature prediction device 121, which is to be described
later, to provide a result of the detection as intake pressure
information to the temperature prediction device 121.
[0023] The bypass passage 106 and the idle speed control valve 107 are provided to the intake passage 101 so that the upstream side and the downstream side of the throttle valve 103 communicate to each other.
[0024] In the intake pipe 101a, the injector 110 configured to inject and supply the fuel, which has been pumped from the fuel tank 109 by the fuel pump 108, into the vicinity of an intake port is provided on the downstream side of the intake pressure sensor
104. The injector 110 is communicably connected to the temperature
prediction device 121, which is to be described later.
[0025] The intake valve 111, through which air is taken in, is provided in the combustion chamber 105 of the internal combustion engine main body 100a, and the intake passage 101 is connected to the combustion chamber 105 via the intake valve 111. The exhaust valve 116, through which air is exhausted, is further provided in the combustion chamber 105, and the combustion chamber 105 is connected to the exhaust passage 117 via the exhaust valve 116.
[0026] The ignition plug 112, from which an electrode is projected, is provided above the combustion chamber 105. The

ignition plug 112 is communicably connected to the temperature prediction device 121, which is to be described later. The piston 113 configured to reciprocate vertically is provided below the combustion chamber 105. The piston 113 is coupled to the crankshaft 115 through the connecting rod 114.
[0027] Near the crankshaft 115, there is provided the crank angle sensor 118 configured to detect a rotation angle of the crankshaft 115. The crank angle sensor 118 is communicably connected to the temperature prediction device 121, which is to be described later, to provide a result of the detection as crank angle information to the temperature prediction device 121.
[0028] On the downstream side of the exhaust passage 117, there is provided the three-way catalyst 119 configured to clean NOx, HC, and CO of combustion exhaust gas from the combustion chamber 105. On the upstream side of the three-way catalyst 119 in the exhaust passage 117, there is provided the oxygen sensor 120 configured to detect an oxygen concentration in the exhaust gas. The oxygen sensor 120 is communicably connected to the temperature prediction device 121, which is to be described later, to provide a result of the detection as oxygen information to the temperature prediction device 121.
[0029] The throttle valve 103 is configured to adjust an opening degree of a throttle. Air from which dust is removed by the air filter 102 is supplied to the combustion chamber 105 through the intake passage 101. The throttle valve 103 is configured to

control a flow rate of the air to be supplied to the combustion chamber 105 by adjusting the opening degree of the throttle. When viewed from a viewpoint of a driving side, the throttle valve 103 is configured to control the opening degree adjustment of the throttle depending on an operation amount of an accelerator (not shown) operated by a driver. The idle speed control valve 107 provided in the bypass passage 106 is configured to adjust a flow rate of air flowing through the bypass passage 106 in order to control the number of revolutions of the internal combustion engine 100 during idling operation of the internal combustion engine 100. [0030] The injector 110 is configured to inject the fuel into the air that has passed through the intake pipe 101a to form air-fuel mixture before the intake valve 111. The intake valve 111 is configured to supply the formed air-fuel mixture to the combustion chamber 105. The ignition plug 112 provided in the combustion chamber 105 ignites the air-fuel mixture supplied to the combustion chamber 105 with discharge spark to burn the air-fuel mixture. [0031] Work is provided to the outside by the combustion of the air-fuel mixture. Specifically, the crankshaft 115 is rotated via the piston 113 and the connecting rod 114, and rotational energy is extracted from the combustion of the air-fuel mixture. The exhaust valve 116 discharges the exhaust gas generated by the combustion of the air-fuel mixture to the exhaust passage 117 through an opening operation. [0032] In an outer peripheral portion of a rotor configured

to be rotated integrally with the crankshaft 115, a plurality of protrusions are provided at equal intervals in a circumferential direction of the outer peripheral portion. When the protrusions cross the crank angle sensor 118, the crank angle sensor 118 outputs rectangular crank signals as the crank angle information. In the first embodiment, as a specific example, it is assumed that the plurality of protrusions are provided every 30° with respect to a center of the crankshaft 115.
[0033] The outer peripheral portion of the rotor includes a toothless portion in which some of the plurality of protrusions provided at equal intervals are missing. With this configuration, when the crankshaft 115 is rotated by 360° at the most, the temperature prediction device 121 can determine a position of the piston 113 based on a detection value of the crank angle sensor 118. Therefore, the temperature prediction device 121 can recognize that the piston 113 has reached a top dead center and a bottom dead center. Further, when the internal combustion engine 100 is a four-cycle internal combustion engine, the temperature prediction device 121 can determine four strokes (that is, the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke) of the internal combustion engine main body 100a and recognize a detailed position of the piston 113 based on the detection value of the crank angle sensor 118 and a detection value of the intake pressure sensor 104.
[0034] The temperature prediction device 121 is configured to

control the internal combustion engine 100 in terms of a fuel injection amount, an air-fuel ratio, or the like by outputting a fuel injection command to the injector 110 depending on the position of the piston 113.
[0035] As described above, the temperature prediction device 121 is communicably connected to the intake pressure sensor 104, the injector 110, the ignition plug 112, the crank angle sensor 118, the oxygen sensor 120, and the like.
[0036] The temperature prediction device 121 is implemented by a microcomputer configured to execute arithmetic processing, a read only memory (ROM) configured to store program data, fixed value data, and other such data, a random access memory (RAM) in which stored data is updated and sequentially rewritten, a power supply, an output processing circuit, an input processing circuit, an A/D conversion circuit, a power device, and a communication IC, for example.
[0037] The temperature prediction device 121 is configured to predict a temperature (hereinafter referred to as "main body temperature") of the internal combustion engine main body 100a based on the detection value of the intake pressure sensor 104. The temperature prediction device 121 is also configured to control the fuel injection amount from the injector 110 based on the predicted main body temperature.
[0038] Next, starting of the internal combustion engine 100 is described with reference to FIG. 2. FIG. 2 is a schematic graph

for showing a change in pressure of the intake pipe 101a of the internal combustion engine 100 in the first embodiment of the present invention. In FIG. 2, the horizontal axis indicates a crank number indicating the position of the piston, and the vertical axis indicates an intake pressure Pm, which is an internal pressure of the intake pipe 101a.
[0039] In FIG. 2, a case in which the crankshaft 115 is rotated twice in one combustion cycle is assumed, and hence crank numbers for two revolutions are assigned to the plurality of protrusions provided every 30° in the outer peripheral portion of the rotor configured to rotate integrally with the crankshaft 115, respectively. As shown in FIG. 2, in one combustion cycle, numbers 0 to 11 are sequentially assigned to the protrusions in the first revolution (that is, the compression stroke and the expansion stroke) of the crankshaft 115, and numbers 12 to 23 are sequentially assigned to the protrusions in the second revolution (that is, the exhaust stroke and the intake stroke) of the crankshaft 115.
[0040] When the internal combustion engine 100 is stopped to power off the internal combustion engine 100, the temperature prediction device 121 is also powered off, and power supply to the temperature prediction device 121 is stopped. In this case, each information items that have been acquired from the intake pressure sensor 104, the crank angle sensor 118, and the oxygen sensor 120 by the temperature prediction device 121 are lost unless otherwise stored in a memory.

[0041] Next, when the internal combustion engine 100 is powered on, and the temperature prediction device 121 is powered on along therewith, the power is supplied to the temperature prediction device 121. In this case, the temperature prediction device 121 starts acquiring information items from the intake pressure sensor 104, the crank angle sensor 118, and the oxygen sensor 120. Intake pressure information acquired from the intake pressure sensor 104 immediately after the internal combustion engine 100 is powered on can be treated as information on atmospheric pressure around a vehicle in which the internal combustion engine 100 is installed.
[0042] Next, at startup of the internal combustion engine main body 100a, a starter motor or the like rotates the crankshaft 115 to move the piston 113. In the process of starting the internal combustion engine main body 100a, the temperature prediction device 121 detects that the internal combustion engine main body 100a is in the intake stroke based on the information items acquired from the crank angle sensor 118 and the intake pressure sensor 104.
[0043] In the intake stroke, the piston 113 descends toward the bottom dead center, the intake valve 111 is opened, and the exhaust valve 116 is closed, with the result that the gas in the intake pipe 101a is introduced into the combustion chamber 105, and that a gas pressure inside the intake pipe 101a becomes a negative pressure. When the piston 113 passes through the bottom dead center, the intake valve 111 is closed, and then a transition

is made from the intake stroke to the compression stroke.
[0044] The compression stroke is a step in which the gas in the combustion chamber 105 is compressed by the piston 113 configured to move in a vertical direction in the cylinder along with the rotation of the crankshaft 115. The expansion stroke, to which a transition is made from the compression stroke, is a step in which the gas in the combustion chamber 105 is expanded by the piston 113.
[0045] More specifically, in the compression stroke, the gas containing the air that has been introduced into the combustion chamber 105 as a main component is compressed with ascending of the piston 113 in the combustion chamber 105. Further, when the piston 113 reaches near the top dead center, the intake valve 111 is opened while the fuel is injected by the injector 110, with the result that the fuel is introduced into the combustion chamber 105. Then, when the intake valve 111 is closed, and the fuel is ignited inside the combustion chamber 105 by the ignition plug 112, the combustion occurs. During the combustion, the transition is made to the expansion stroke with both of the intake valve 111 and the exhaust valve 116 being closed, and the piston 113 descends toward the bottom dead center. Thereafter, when the piston 113 reaches near the bottom dead center, the exhaust valve 116 is opened, and the combustion gas in the combustion chamber 105 is discharged through the exhaust passage 117.
[0046] Meanwhile, inside the intake pipe 101a in the

compression stroke, the expansion stroke, and the exhaust stroke, to which the transition is made from the intake stroke before the ignition by the ignition plug 112, the intake valve 111 is closed, and the throttle valve 103 is further closed. During this period, outside air flows in from a gap of the throttle valve 103, for example, and the inside of the intake pipe 101a is substantially changed to the atmospheric pressure. Before the transition from the compression stroke to the expansion stroke, and before the fuel injection is started, gas is moved inside the intake pipe 101a by a pressure difference due to the vertical movement of the piston 113 and opening and closing of the valves accompanying therewith.
[0047] In this example, the main body temperature predicted by the temperature prediction device 121 is a parameter that is very important in controlling the internal combustion engine 100. Further, an initial temperature is different depending on operating conditions during the stop of the internal combustion engine 100 before the internal combustion engine 100 is started, and on an elapsed time period from the stop.
[0048] The "initial temperature" as used herein means a main body temperature of the internal combustion engine 100 in a period from when the power of the internal combustion engine 100 is switched from OFF to ON such that the internal combustion engine 100 is started from a stopped state to when the combustion starts in the combustion chamber 105.
[0049] Therefore, focusing attention on the gas pressure

inside the intake pipe 101a before the fuel is injected in the internal combustion engine 100, a test assuming different elapsed time periods was conducted after the internal combustion engine 100 is completely stopped. Specifically, behavior of the intake pressure after the internal combustion engine 100 had been started and before the combustion was started was studied by using a single-cylinder gasoline internal combustion engine as the internal combustion engine 100 and setting five initial temperatures (specifically, 25°C, 60°C, 80°C, 100°C, and 115°C). [0050] When the power of the internal combustion engine 100 is switched from OFF to ON, detection signals from the intake pressure sensor 104, the crank angle sensor 118, and the oxygen sensor 120, which are provided to the internal combustion engine 100, are input to the temperature prediction device 121. At this time, the pressure of the intake pipe 101a indicates the atmospheric pressure, and hence an outside air pressure (ambient environmental pressure) outside the internal combustion engine 100 is known by the detection result obtained by the intake pressure sensor 104. [0051] When the power of the internal combustion engine 100 is switched from OFF to ON, the internal combustion engine 100 is started from the stopped state. When the internal combustion engine main body 100a is started, the starter motor or the like rotates the crankshaft 115 such that the piston 113 starts moving. During a period from when the internal combustion engine 100 is started to when the crankshaft 115 starts rotating, the pressure

of the intake pipe 101a assumes substantially the atmospheric pressure.
[0052] Then, when the intake stroke is started with the rotation of the crankshaft 115, the gas in the intake pipe 101a is taken into the combustion chamber 105, and hence the gas pressure of the intake pipe 101a is reduced from the atmospheric pressure to about 40 kPa. The change in pressure in the intake stroke is fast, and a difference in change in pressure was not found for the five initial temperatures.
[0053] As can be seen from the above description, the intake pressure detected by the intake pressure sensor 104 in the period from when the internal combustion engine 100 is started from the stopped state to when the crankshaft 115 starts rotating can be defined as the outside air pressure.
[0054] Meanwhile, at the bottom dead center, at which the internal combustion engine 100 shifts from the intake stroke to the compression stroke, correlation between the initial temperature and the intake pressure was found, and indicated a tendency that as the initial temperature became high, the intake pressure at the bottom dead center became high. Therefore, the intake pressure detected by the intake pressure sensor 104 when the piston 113 is positioned at the bottom dead center, at which the transition is made from the intake stroke to the compression stroke, is defined as an intake representative pressure. [0055] The above-mentioned temperature test was conducted

under an environment in which the internal combustion engine 100 is arranged, that is, under an environment in which an outside air temperature and the outside air pressure were 25°C and 1 atm, respectively. Meanwhile, the intake pressure is affected by the outside air pressure and the outside air temperature. Further, a traveling speed of the gas flowing into the intake pipe 101a and a traveling speed of the gas discharged from the intake pipe 101a and traveling to the combustion chamber 105 depend on the number of revolutions per unit time (hereinafter referred to as "internal combustion engine speed") of the internal combustion engine main body 100a.
[0056] In view of the above, a verification test was conducted at different outside air temperatures and different outside air pressures to obtain an empirical formula taking the above-mentioned parameters into consideration. A result thereof is expressed in Equation (1). FIG. 3 is a schematic graph for showing correlation between the intake pressure and the main body temperature in the first embodiment of the present invention. [0057] TENG0=a(P/P0-b)c • T0d-Nee (1) [0058] In Equation (1),
TENG0 represents an initial temperature of the internal combustion engine main body,
P0 represents an outside air pressure,
P represents an intake representative pressure,
T0 represents an outside air temperature,

Ne represents an internal combustion engine speed, and "a", "b", "c", "d", and "e" represent constants.
[0059] As can be seen from Equation (1) above and FIG. 3, it was found that the initial temperature can be predicted uniquely with the use of the intake pressure detected by the intake pressure sensor 104.
[0060] Further, as can be seen from the above, even when dedicated sensor, wiring, thermoelectric transducer, and other devices configured to obtain the initial temperature are not provided to the internal combustion engine main body 100a, as long as the outside air pressure, the intake representative pressure, the outside air temperature, and the internal combustion engine speed are known, the initial temperature adapted also to an operating environment of the internal combustion engine 100 can be predicted in accordance with Equation (1).
[0061] In this example, the outside air pressure is an intake pressure (hereinafter referred to as "first pressure") detected by the intake pressure sensor 104 during the period from when the internal combustion engine 100 is started from the stopped state to when the crankshaft 115 starts rotating. The temperature prediction device 121 is configured to acquire the intake pressure as the outside air pressure at a timing within a period from when the internal combustion engine 100 is started from the stopped state to when the internal combustion engine main body 100a starts rotating. The function of acquiring the outside air pressure is

assumed by an outside air pressure acquisition unit included in the temperature prediction device 121.
[0062] The intake representative pressure is an intake pressure (hereinafter referred to as "second pressure") detected by the intake pressure sensor 104 when the piston 113 is positioned at the bottom dead center, at which the transition is made from the intake stroke to the compression stroke. The temperature prediction device 121 is configured to acquire the intake pressure as the intake representative pressure at a timing within a period from when the internal combustion engine main body 100a starts rotating to when combustion is started in the combustion chamber 105. In the first embodiment, as a specific example of the timing, a timing at which the piston 113 reaches the bottom dead center, at which the transition is made from the intake stroke to the compression stroke, is exemplified. The function of acquiring the intake representative pressure is assumed by an intake representative pressure acquisition unit included in the temperature prediction device 121.
[0063] The outside air temperature is a value obtained by a method of direct detection with the use of an outside air temperature sensor, or a method of indirect prediction with the use of a detection value of another sensor, for example. The temperature prediction device 121 is configured to acquire the outside air temperature by the above-mentioned method. The function of acquiring the outside air temperature is assumed by an outside air

temperature acquisition unit included in the temperature prediction device 121.
[0064] The internal combustion engine speed is calculated based on the crank angle information detected by the crank angle sensor 118. In order to calculate the internal combustion engine speed, a timer configured to measure the time it takes to detect a certain crank angle is specifically required in addition to the crank angle sensor 118. The temperature prediction device 121 is configured to acquire the internal combustion engine speed by the above-mentioned method at a timing within the period from when the internal combustion engine main body 100a starts rotating to when the combustion is started in the combustion chamber 105. The function of acquiring the internal combustion engine speed is assumed by a parameter information acquisition unit included in the temperature prediction device 121.
[0065] The temperature prediction device 121 stores the above-mentioned Equation (1) and the constants "a" to "e" relating to Equation (1) in a non-volatile memory, or stores a mapping table defined based on Equation (1) and the constants in the non-volatile memory. The temperature prediction device 121 acquires the outside air pressure, the intake representative pressure, the outside air temperature, and the internal combustion engine speed as described above. The temperature prediction device 121 predicts the initial temperature by calculation with the use of those acquired parameters and the stored constants "a" to "e" in accordance with Equation

(1). The function of predicting the initial temperature is assumed by an initial temperature prediction unit included in the temperature prediction device 121.
[0066] Next, description is given of a method of sequentially predicting the main body temperature after the combustion is started with the predicted initial temperature being an initial value. The main body temperature in the period from when the internal combustion engine 100 is started to when the combustion is started is equivalent to the initial temperature predicted by the above-mentioned method.
[0067] In contrast, after the combustion in the combustion chamber 105 is started, the main body temperature is predicted by the following method. Specifically, a main body temperature after time At is predicted by calculation based on energy balance of the internal combustion engine main body 100a.
[0068] Here, when a main body temperature at a time t is
presented by TENG(t), a main body temperature at a time t+At after
the time At has elapsed from the time t is represented by TENG(t+At),
and TENG(t+At)-TENG(t)=ATENG, ATENG/At can be expressed as Equation
(2). Further, total energy QOUT output from the internal combustion
engine main body 100a can be expressed as Equation (3). In Equation
(3), the second term on the right side indicates heat discharge,
and the first term on the right side indicates other output energy.
[0069] M-CP-ATENG/At=QIN-QOUT (2)
QOUT=E (Qj)+(3 (TENG (t)-T0) (3)

[0070] In Equation (2) and Equation (3),
M represents a weight (kg) of the internal combustion engine main body 100a,
CP represents specific heat (J/(kg-K)) of the internal combustion engine main body 100a,
QIN represents total energy (J/s) input to the internal combustion engine main body 100a,
QOUT represents total energy (J/s) output from the internal combustion engine main body 100a,
Qj represents output energy of an individual element j from the internal combustion engine main body 100a,
T0 represents an outside air temperature (K),
t represents time (s), and
(3 represents a constant (W/K).
For QIN, a part or all of the total energy becomes energy of a flow rate of the fuel supplied to the internal combustion engine 100.
[0071] The temperature prediction device 121 stores the above-mentioned Equation (2) and Equation (3), the constants M and CP relating to Equation (2), and the constant (3 relating to Equation (3) in the non-volatile memory. The temperature prediction device 121 calculates the above-mentioned QIN, QOUT, and Qj, and further acquires the outside air temperature. The temperature prediction device 121 calculates ATENG by solving Equation (2) and Equation (3) with the use of the calculated QIN, QOUT, and Qj, the acquired

outside air temperature, and the stored M, CP, and (3, and predicts the main body temperature TENG(t+At) with the use of ATENG. [0072] The above-mentioned time At indicates a time interval of timings of fuel injection of the internal combustion engine 100, for example. Further, in the above-mentioned calculation, the temperature in the initial state, that is, the outside air temperature is used. The temperature prediction device 121 acquires the outside air temperature by applying the method of direct detection with the use of the outside air temperature sensor, or the method of indirect prediction with the use of the detection value of another sensor, for example.
[0073] The temperature prediction device 121 thus predicts the main body temperature after the combustion is started in the combustion chamber 105 based on the energy balance of the internal combustion engine main body 100a with the use of the predicted initial temperature. The function of predicting the main body temperature after the combustion is started is assumed by a temperature prediction unit included in the temperature prediction device 121.
[0074] Next, a series of operations of the temperature prediction device 121 according to the first embodiment is described with reference to FIG. 4. FIG. 4 is a flow chart for illustrating the series of operations of the temperature prediction device 121 for the internal combustion engine according to the first embodiment of the present invention.

[0075] In Step S101, when the power of the internal combustion engine main body 100a is switched from OFF to ON, the processing proceeds to Step S102.
[0076] In Step S102, the temperature prediction device 121 acquires various parameters required to predict the initial temperature TENG0, and the processing proceeds to Step S103. Specifically, the temperature prediction device 121 acquires the first pressure and the second pressure as the outside air pressure and the intake representative pressure from the intake pressure sensor 104, respectively, and acquires the outside air temperature and the internal combustion engine speed by the above-mentioned method. The temperature prediction device 121 also acquires Equation (1) and the constants "a" to "e" relating to Equation (1) from the non-volatile memory.
[0077] In Step S103, the temperature prediction device 121 predicts the initial temperature TENG0 in accordance with Equation
(1) with the use of the various parameters acquired in Step S102 and the constants "a" to "e", and the processing proceeds to Step S104.
[0078] In Step S104, the temperature prediction device 121 sets, as the main body temperature TENG(t), the initial temperature TENG0 predicted in Step S103, and the processing proceeds to Step S105.
[0079] In Step S105, the temperature prediction device 121 acquires various parameters required to calculate QIN, QOUT, and Qj,

and the processing proceeds to Step S106.
[0080] In Step S106, the temperature prediction device 121 calculates QIN, QOUT, and Qj with the use of the various parameters acquired in Step S105, and the processing proceeds to Step S107.
[0081] In Step S107, the temperature prediction device 121 predicts a main body temperature TENG(t+At) in accordance with Equation (2) and Equation (3) with the use of QIN, QOUT, and Qj calculated in Step S106 and the constants M, CP, and (3. Then, the processing proceeds to Step S108, and returns to Step S104 in order to predict a main body temperature after time has further elapsed.
[0082] In Step S108, the temperature prediction device 121 controls the fuel injection amount from the injector 110 based on the main body temperature TENG(t+At) predicted in Step S107.
[0083] When the processing returns from Step S107 to Step S104, the temperature prediction device 121 sets, as the main body temperature TENG(t), the main body temperature TENG(t+At) predicted in Step S107, and performs the processing of Step S104 and the subsequent steps again. In this manner, the temperature prediction device 121 controls the fuel injection amount while sequentially predicting the main body temperature over time by repeatedly performing the processing of Step S104 and the subsequent steps with the use of the initial temperature TENG0 predicted in Step S103.
[0084] In this manner, the temperature prediction device 121 controls the fuel injection in injecting the fuel based on the predicted main body temperature. The function of controlling the

fuel injection is assumed by a fuel injection control unit included in the temperature prediction device 121.
[0085] As described above, according to the first embodiment, there is adopted the configuration in which the initial temperature of the internal combustion engine main body is predicted based on the intake pressure acquired as the outside air pressure at the timing within the period from when the internal combustion engine is started from the stopped state to when the internal combustion engine starts rotating, the intake pressure acquired as the intake representative pressure at the timing within the period from when the internal combustion engine starts rotating to when the combustion is started in the combustion chamber, and the internal combustion engine speed acquired at the timing, and in which the main body temperature of the internal combustion engine main body after the combustion is started is predicted with the use of the predicted initial temperature.
[0086] In the related art, there is adopted a configuration in which a temperature sensor is installed in the internal combustion engine main body, and in which combustion conditions
(for example, adjustment of the throttle opening degree for setting the air flow rate) are controlled depending on a temperature state of the internal combustion engine main body. In contrast, in the first embodiment, the above-mentioned configuration is adopted, with the result that the temperature of the internal combustion engine main body after the combustion is started can be predicted

without installing the temperature sensor in the internal combustion engine main body.
[0087] With the above-mentioned configuration, a dedicated temperature sensor that is compatible with high temperature of the internal combustion engine main body can be eliminated, and as a result, processing on the internal combustion engine main body accompanying the installation of the temperature sensor can be eliminated, and the wirings can be eliminated. Therefore, the temperature of the internal combustion engine main body can be predicted with relatively low cost.
[0088] Though not mentioned in the first embodiment, a detection value of the oxygen sensor 120 provided in the exhaust passage 117 may be used for controlling the air-fuel ratio of the internal combustion engine 100, for example, and may further be used as a limiting value for the air-fuel ratio.
[0089] In the first embodiment, an example of the operation of the internal combustion engine main body 100a has been described. However, the present invention is not limited thereto, and the timing and order of opening or closing the exhaust valve 116 or the intake valve 111 may be changed in accordance with characteristics of the internal combustion engine main body 100a.
[0090] For example, the intake valve 111 and the exhaust valve 116 may be operated to be opened at the same time at the time point of transition from the exhaust stroke to the intake stroke. Alternatively, the intake valve 111 or the exhaust valve 116 may

be operated to be opened or closed before the piston 113 reaches the top dead center or the bottom dead center. Further, the timing to open or close the valves is often determined depending on a cam shaft adapted for the rotation of the crankshaft 115. However, regarding control of a so-called "variable valve mechanism", in which the timing to open or close the valves is changed, the temperature prediction device 121 may control the timing to open or close the valves in a period until the internal combustion engine 100 reaches a preset temperature depending on the predicted initial temperature, for example.
[0091] The internal combustion engine speed mentioned in the first embodiment may be the number of revolutions that is local in time, which is calculated from between adjacent protrusions provided to the crankshaft 115.
[0092] In the first embodiment, there has been described the configuration in which the prediction of the temperature of the internal combustion engine 100 and the operation control based on the temperature prediction are executed by the temperature prediction device 121, but the present invention is not limited to the configuration. Specifically, there may be adopted a configuration in which an ECU is provided separately from the temperature prediction device 121, and in which the ECU executes the operation control based on the temperature prediction, for example. [0093] Second Embodiment

In a second embodiment of the present invention, description is given of a temperature prediction device 121 in which the processing of acquiring the intake representative pressure is different from that in the first embodiment described above. In the second embodiment, description on points similar to the first embodiment described above is omitted, and points different from the first embodiment described above are mainly described.
[0094] In the second embodiment, a basic configuration of an internal combustion engine 100 is similar to that in the first embodiment described above, while a control program installed in the temperature prediction device 121, specifically, processing of acquiring the intake representative pressure, which is executed by the temperature prediction device 121, is different from that in the first embodiment described above.
[0095] FIG. 5 is a schematic graph for showing a change in pressure of the intake pipe 101a of the internal combustion engine 100 in the second embodiment of the present invention.
[0096] As in the first embodiment described above, with the start of the internal combustion engine main body 100a, the starter motor or the like rotates the crankshaft 115. At this time, the temperature prediction device 121 detects, based on information items from the intake pressure sensor 104 and the crank angle sensor 118, the bottom dead center at which the internal combustion engine main body 100a transitions from the intake stroke to the compression stroke. The temperature prediction device 121 acquires, after

detecting the bottom dead center, the intake pressure from the intake pressure sensor 104 at a timing at which the crank angle sensor 118 detects the protrusion having a crank number of 2, for example, and defines the intake pressure as the intake representative pressure.
[0097] Here, in the first embodiment described above, the temperature prediction device 121 is configured to acquire the intake pressure from the intake pressure sensor 104 at the timing when the position of the piston 113 reaches the bottom dead center, and to set the intake pressure as the intake representative pressure. It should be noted, however, that in an actual internal combustion engine main body 100a, the timing at which the position of the piston 113 reaches the bottom dead center is a timing at which the transition is made from the intake stroke to the compression stroke, and hence it is considered that the intake valve 111 is often in an opening or closing operation. In this case, an amount of travel of the gas between the intake pipe 101a and the combustion chamber 105 is determined based on the gap between the combustion chamber 105 and the intake valve 111, and hence the intake pressure tends to vary.
[0098] To address the above-mentioned problem, in the second embodiment, the intake pressure detected by the intake pressure sensor 104 during the compression stroke and the expansion stroke from when the position of the piston 113 passes through the bottom dead center and the intake valve 111 is closed to when the exhaust

valve 116 is opened near the top dead center is set as the intake representative pressure.
[0099] In other words, the temperature prediction device 121 acquires the intake pressure as the intake representative pressure not at the time point at which the position of the piston 113 reaches the bottom dead center as in the first embodiment described above, but at a timing within a period after a time point at which the piston 113 reaches the bottom dead center, at which the transition is made from the intake stroke to the compression stroke, to when the piston 113 passes through the top dead center, at which the transition is made from the compression stroke to the expansion stroke, and reaches the next bottom dead center. With this configuration, the intake pressure having a value that is relatively stable without being affected by opening or closing of the valves can be set as the intake representative pressure. [0100] During the expansion stroke, the intake pressure gradually approaches the outside air pressure, and hence the difference in intake pressure due to a difference in main body temperature or outside air temperature is small. Therefore, taking accuracy into consideration, it is desired that the intake pressure detected by the intake pressure sensor 104 at a timing in the compression stroke after the intake valve 111 is closed be set as the intake representative pressure.
[0101] As described above, according to the second embodiment, in contrast to the configuration in the first embodiment described

above, there is adopted the configuration in which the intake pressure is acquired as the intake representative pressure at the timing within the period from when the piston reaches the bottom dead center, at which the transition is made from the intake stroke to the compression stroke, to when the piston passes through the top dead center, at which the transition is made from the compression stroke to the expansion stroke, and reaches the next bottom dead center. Also with this configuration, effects similar to those of the first embodiment described above can be obtained.
[0102] In the second embodiment, there has been described the case in which one intake pressure detected by the intake pressure sensor 104 at a particular timing is set as the intake representative pressure, but the present invention is not limited thereto.
[0103] Specifically, an average value of a plurality of intake pressures detected by the intake pressure sensor 104 at a plurality of successive timings may be set as the intake representative pressure. In this case, there is an effect that, even when noise is contained in the detection value of the intake pressure sensor 104, the noise can be reduced.
[0104] Third Embodiment
In a third embodiment of the present invention, description is given of a temperature prediction device 121 in which the processing of acquiring the intake representative pressure is different from that in the first and second embodiments described above. In the third embodiment, description on points similar to

the first and second embodiments described above is omitted, and points different from the first and second embodiments described above are mainly described.
[0105] In the third embodiment, a basic configuration of an internal combustion engine 100 is similar to that in the first and second embodiments described above, while a control program installed in the temperature prediction device 121, specifically, processing of acquiring the intake representative pressure, which is executed by the temperature prediction device 121, is different from that in the first and second embodiments described above. [0106] FIG. 6 is a schematic graph for showing a change in pressure of the intake pipe 101a of the internal combustion engine 100 in the third embodiment of the present invention. [0107] As in the first embodiment described above, with the start of the internal combustion engine main body 100a, the starter motor or the like rotates the crankshaft 115. At this time, the temperature prediction device 121 detects, based on information items from the intake pressure sensor 104 and the crank angle sensor 118, the bottom dead center at which the internal combustion engine main body 100a transitions from the intake stroke to the compression stroke. The temperature prediction device 121 acquires, after detecting the bottom dead center, a first intake pressure and a second intake pressure, from the intake pressure sensor 104 at timings at which the crank angle sensor 118 detects the protrusions having crank numbers of 2 and 5, respectively, for example, and

defines a differential pressure of the two intake pressures as the intake representative pressure.
[0108] Specifically, the temperature prediction device 121 acquires the first intake pressure and the second intake pressure at two timings that are different in time within a period from when the piston 113 reaches the bottom dead center, at which the transition is made from the intake stroke to the compression stroke, to when the piston 113 passes through the top dead center, at which the transition is made from the compression stroke to the expansion stroke, and reaches the next bottom dead center, respectively. The temperature prediction device 121 acquires a differential pressure of the thus-acquired first intake pressure and second intake pressure as the intake representative pressure. [0109] The differential pressure can be replaced by the flow rate of the outside air flowing into the intake pipe 101a, and involves a time term. In this example, when a time difference between the two timings is short time, the outside air flowing into the intake pipe 101a is hardly affected by the main body temperature, and when the time difference is long time, on the contrary, the outside air tends to be affected by the main body temperature. Therefore, it is required to consider thermohydrodynamically the effect of heating from the internal combustion engine to the inflow outside air, which depends on the time difference between the timings, but there is an advantage of being organizable in a dimension involving the time term with respect to the inflow outside

air, with the result that the main body temperature can be predicted with higher accuracy.
[0110] As described above, according to the third embodiment, in contrast to the configuration in the first embodiment described above, there is adopted the configuration in which the first intake pressure and the second intake pressure are acquired at different timings within the period from when the piston reaches the bottom dead center, at which the transition is made from the intake stroke to the compression stroke, to when the piston passes through the top dead center, at which the transition is made from the compression stroke to the expansion stroke, and reaches the next bottom dead center, and the differential pressure between the acquired first intake pressure and the acquired second intake pressure is acquired as the intake representative pressure. Also with this configuration, effects similar to those of the first embodiment described above can be obtained.
[0111] In the third embodiment, the timings at which the first intake pressure and the second intake pressure are acquired from the intake pressure sensor 104 are set to the timings at which the crank angle sensor 118 detects the protrusions having the crank numbers of 2 and 5 after the bottom dead center, respectively, but the present invention is not limited thereto.
[0112] Specifically, the timings at which the two intake pressures are acquired may be any timings after the bottom dead center, at which the transition is made from the intake stroke to

the compression stroke, and within a period from the compression stroke to when the expansion stroke and the exhaust stroke are complete. It should be noted, however, that it is desired that the timing to acquire the intake pressure for the first time (that is, first intake pressure) be a timing at which the effect of the internal combustion engine main body 100a is noticeable, that is, a timing after, and as close as possible to, the bottom dead center, at which the transition is made from the intake stroke to the compression stroke.
[0113] Fourth Embodiment
In a fourth embodiment of the present invention, description is given of a temperature prediction device 121 configured to predict the initial temperature by a method that is different from the first to third embodiments described above. In the fourth embodiment, description on points similar to the first to third embodiments described above is omitted, and points different from the first to third embodiments described above are mainly described.
[0114] In the fourth embodiment, a basic configuration of an internal combustion engine 100 is similar to the first to third embodiments described above, while a control program installed in the temperature prediction device 121, specifically, operation of predicting the initial temperature, which is executed by the temperature prediction device 121, is different from the first to third embodiments described above.
[0115] FIG. 7 is a schematic graph for showing a change in

pressure of the intake pipe 101a of the internal combustion engine 100 in the fourth embodiment of the present invention.
[0116] In FIG. 7, there is assumed a case in which, when the internal combustion engine 100 is in the stopped state, the piston 113 is stopped in the middle of the intake stroke. As in the first embodiment described above, with the start of the internal combustion engine main body 100a, the starter motor or the like rotates the crankshaft 115. At this time, the temperature prediction device 121 detects, based on information items from the intake pressure sensor 104 and the crank angle sensor 118, a first bottom dead center that comes the first time, at which the internal combustion engine main body 100a transitions from the intake stroke to the compression stroke, after the internal combustion engine main body 100a is started. After the temperature prediction device 121 detects the first bottom dead center, the internal combustion engine main body 100a transitions from the compression stroke to the expansion stroke through a first top dead center, transitions from the expansion stroke to the exhaust stroke through a second bottom dead center, and transitions from the exhaust stroke to the intake stroke through a second top dead center.
[0117] After the internal combustion engine main body 100a transitions from the above-mentioned intake stroke to the compression stroke through a third bottom dead center, the temperature prediction device 121 acquires the intake pressure from the intake pressure sensor 104 at a timing when the crank angle

sensor 118 detects the protrusion having the crank number of 2, for example, and sets the intake pressure as the intake representative pressure.
[0118] Here, in a case where the internal combustion engine 100 is started from the state in which the piston 113 is stopped in the middle of the intake stroke, even when the piston 113 is moved to the bottom dead center after the start, a capacity is reduced and the intake pressure is increased as compared to the case in which the air is fully taken in in the intake stroke.
[0119] To address the above-mentioned problems, in the fourth embodiment, the temperature prediction device 121 acquires the intake pressure from the intake pressure sensor 104 after detecting the bottom dead center, at which the transition is made from the intake stroke to the compression stroke, based on the information items from the intake pressure sensor 104 and the crank angle sensor 118, and at a timing when the crank angle sensor 118 detects the protrusion having the crank number of 2, for example. When the acquired intake pressure is higher than a set pressure value, which has been set in advance, the temperature prediction device 121 controls so that the crankshaft 115 continues to rotate.
[0120] Then, the temperature prediction device 121 acquires the intake pressure detected by the intake pressure sensor 104 in the compression stroke that comes the second time after the third bottom dead center without operating the injector 110 and the ignition plug 112, and sets the intake pressure as the intake

representative pressure.
[0121] That is, the temperature prediction device 121 is configured to acquire the intake pressure as the intake representative pressure at a timing within a period from when the piston 113 reaches the bottom dead center, at which the transition is made from the intake stroke to the compression stroke, to when the piston 113 passes through the top dead center, at which the transition is made from the compression stroke to the expansion stroke, and reaches the next bottom dead center, and to reacquire, when the acquired intake representative pressure is higher than the set pressure value, the intake pressure as the intake representative pressure at a timing within the period that comes next.
[0122] The above-mentioned configuration is effective in a case where the piston 113 is stopped in the middle of the intake stroke as described above, in a case where an accurate detection value cannot be acquired, for example, when an error in reading the detection value of the intake pressure sensor 104 occurs, or in other cases, for example. As a result, reliability of the intake representative pressure can be increased.
[0123] Next, a series of operations of predicting the initial temperature by the temperature prediction device 121 in the fourth embodiment of the present invention is described with reference to FIG. 8. FIG. 8 is a flow chart for illustrating the series of operations of predicting the initial temperature by the temperature

prediction device 121 for an internal combustion engine in the fourth embodiment of the present invention.
[0124] In Step S201, when the power of the internal combustion engine 100 is switched from OFF to ON, the processing proceeds to Step S202.
[0125] In Step S202, with the internal combustion engine 100 being powered on in Step S201, the intake pressure sensor 104, the crank angle sensor 118, and other sensors are operated, and the processing proceeds to Step S203.
[0126] In Step S203, the temperature prediction device 121 acquires, as the outside air pressure, the first pressure detected by the intake pressure sensor 104, and the processing proceeds to Step S204.
[0127] In Step S204, the temperature prediction device 121 acquires the outside air temperature by the method described above in the first embodiment, and the processing proceeds to Step S205.
[0128] In Step S205, the temperature prediction device 121 controls the starter motor or the like to rotate the crankshaft 115, and the processing proceeds to Step S206.
[0129] In Step S206, the temperature prediction device 121 acquires Equation (1) required to predict the initial temperature, and the constants "a" to "e" relating to Equation (1) from the non-volatile memory, and the processing proceeds to Step S207.
[0130] In Step S207, the temperature prediction device 121 detects the bottom dead center (first bottom dead center), at which

the transition is made from the intake stroke to the compression stroke, and then acquires an intake pressure from the intake pressure sensor 104 in the compression stroke, and the processing proceeds to Step S208.
[0131] In Step S208, the temperature prediction device 121 determines whether the intake pressure acquired in Step S207 is higher than the set pressure value. When the intake pressure acquired in Step S207 is higher than the set pressure value, the processing returns to Step S207.
[0132] When the processing returns to Step S207, the temperature prediction device 121 detects the next bottom dead center (third bottom dead center), at which the transition is made from the intake stroke to the compression stroke, and then reacquires an intake pressure from the intake pressure sensor 104 in the compression stroke, and the processing proceeds to Step S208.
[0133] In contrast, when the intake pressure acquired in Step S207 is the set pressure value or less, the processing proceeds to Step S209.
[0134] In Step S209, the temperature prediction device 121 acquires the internal combustion engine speed by the method described above in the first embodiment, and the processing proceeds to Step S210.
[0135] In Step S210, the temperature prediction device 121 sets the intake pressure that is acquired in Step S207 and is the set pressure value or less as the intake representative pressure.

Subsequently, the temperature prediction device 121 predicts the initial temperature in accordance with Equation (1) with the use of the intake representative pressure, the outside air pressure and the outside air temperature acquired in Step S203 and Step S204, the constants "a" to "e" acquired in Step S206, and the internal combustion engine speed acquired in Step S209. Then, the processing proceeds to Step S211.
[0136] In Step S211, the temperature prediction device 121 has successfully predicted the initial temperature in Step S210, and hence the temperature prediction device 121 controls the injector 110 and the ignition plug 112 to be operated at particular timings.
[0137] In this manner, the temperature prediction device 121 is configured to control fuel injection in injecting the fuel for the first time based on the predicted initial temperature. The function of controlling the first fuel injection after the initial temperature is predicted is assumed by a first fuel injection control unit included in the temperature prediction device 121.
[0138] As described above, according to the fourth embodiment, there is adopted the configuration in which the intake pressure is acquired as the intake representative pressure at the timing within the period from when the piston reaches the bottom dead center, at which the transition is made from the intake stroke to the compression stroke, to when the piston passes through the top dead center, at which the transition is made from the compression stroke to the expansion stroke, and reaches the next bottom dead center,

and, when the acquired intake representative pressure is higher than the set pressure value, the intake pressure is reacquired as the intake representative pressure at the timing within the period that comes next. Also with this configuration, effects similar to those of the first embodiment described above can be obtained.
[0139] Fifth Embodiment
In a fifth embodiment of the present invention, description is given of a temperature prediction device 121 that is different from the first embodiment described above in the method of predicting the main body temperature after the combustion is started in the combustion chamber 105. In the fifth embodiment, description on points similar to the first to fourth embodiments described above is omitted, and points different from the first to fourth embodiments described above are mainly described.
[0140] In the fifth embodiment, a basic configuration of an internal combustion engine 100 is similar to that in the first to fourth embodiments described above, while a control program installed in the temperature prediction device 121, specifically, operation of predicting the main body temperature after the combustion is started, which is executed by the temperature prediction device 121, is different from that in the first to fourth embodiments described above. Further, it is assumed that the temperature prediction device 121 in the fifth embodiment predicts the initial temperature by any one of the methods in the first to fourth embodiments described above.

[0141] The operation of predicting the main body temperature after the combustion is started, which is executed by the temperature prediction device 121, is as follows. Specifically, in a process in which the intake air passes through the throttle valve 103, the intake pipe 101a, the intake valve 111, and the combustion chamber 105, an intake temperature per unit time is determined through thermohydrodynamic modeling through use of the law of conservation of mass, an equation of state, an orifice equation, or the like. Further, the intake temperature and the main body temperature are correlated, and when the correlation is replaced by an empirical formula, the main body temperature can be predicted with the use of the intake temperature.
[0142] Therefore, the temperature prediction device 121 acquires the intake temperature by the above-mentioned method, and predicts the main body temperature with the use of the predicted initial temperature and the acquired intake temperature by using the above-mentioned correlation.
[0143] As described above, according to the fifth embodiment, there is adopted the configuration in which the main body temperature of the internal combustion engine is predicted with the use of the predicted initial temperature and the acquired intake temperature based on the correlation between the main body temperature of the internal combustion engine and the intake temperature. Also with this configuration, effects similar to those of the first to fourth embodiments described above can be

obtained.
[0144] In the embodiments described above, there has been described the case in which the present invention is applied to predict the temperature of the internal combustion engine main body. However, the present invention is not limited thereto, and the present invention can be applied to predict a temperature of a substance that exhibits substantially the same temperature behavior as the internal combustion engine main body. For example, in addition to the temperature of the internal combustion engine main body, the present invention can be applied to predict a temperature of engine oil of the internal combustion engine, or a temperature of cooling water of the internal combustion engine, for example. [0145] The outside air pressure acquisition unit, the intake representative pressure acquisition unit, the parameter information acquisition unit, the initial temperature prediction unit, and the temperature prediction unit described above may be implemented as software by one control unit, for example, an ECU, or may be prepared as separate pieces of hardware. [0146] Further, the present invention is not limited to the specific details as mentioned and described above and the representative embodiments. Modification examples and effects easily derived by a person skilled in the art are also included in the present invention. Thus, various changes may be made without departing from the general scope of the present invention defined by the claims and equivalents thereof.

Reference Signs List
[0147] 100 internal combustion engine, 100a internal combustion engine main body, 101 intake passage, 101a intake pipe, 102 air filter, 103 throttle valve, 104 intake pressure sensor, 105 combustion chamber, 106 bypass passage, 107 idle speed control valve, 108 fuel pump, 109 fuel tank, 110 injector, 111 intake valve, 112 ignition plug, 113 piston, 114 connecting rod, 115 crankshaft, 116 exhaust valve, 117 exhaust passage, 118 crank angle sensor, 119 three-way catalyst, 120 oxygen sensor, 121 temperature prediction device

WE CLAIM:
[Claim 1] A temperature prediction device for an internal combustion engine, which is configured to predict a temperature of the internal combustion engine, the internal combustion engine being configured to perform an intake stroke, in which outside air is taken in from an intake pipe into a combustion chamber, and to ignite fuel injected into the outside air taken in in the intake stroke to cause combustion in the combustion chamber, the temperature prediction device comprising:
an outside air pressure acquisition unit configured to acquire an intake pressure in the intake pipe as an outside air pressure at a timing within a period from when the internal combustion engine is started from a stopped state to when the internal combustion engine starts rotating;
an intake representative pressure acquisition unit configured to acquire the intake pressure as an intake representative pressure at a timing within a period from when the internal combustion engine starts the rotation to when the combustion is started;
a parameter information acquisition unit configured to acquire a number of revolutions per unit time of the internal combustion engine;
an initial temperature prediction unit configured to predict, based on the outside air pressure acquired by the outside air pressure acquisition unit, the intake representative pressure

acquired by the intake representative pressure acquisition unit, and the number of revolutions acquired by the parameter information acquisition unit, an initial temperature of the internal combustion engine in a period from the start of the internal combustion engine to when the combustion is started; and
a temperature prediction unit configured to predict, with use of the initial temperature predicted by the initial temperature prediction unit, a temperature of the internal combustion engine after the combustion is started.
[Claim 2] The temperature prediction device for an internal combustion engine according to claim 1, further comprising an outside air temperature acquisition unit configured to acquire an outside air temperature,
wherein the initial temperature prediction unit is configured to predict the initial temperature based on the outside air pressure acquired by the outside air pressure acquisition unit, the intake representative pressure acquired by the intake representative pressure acquisition unit, the number of revolutions acquired by the parameter information acquisition unit, and the outside air temperature acquired by the outside air temperature acquisition unit.
[Claim 3] The temperature prediction device for an internal combustion engine according to claim 2, wherein the initial

temperature prediction unit is configured to predict the initial temperature in accordance with the following expression:
TENG0=a(P/P0-b) c • T0d-Nee, where P0 represents the outside air pressure, P represents the intake representative pressure, Ne represents the number of revolutions, T0 represents the outside air temperature, "a", "b", "c", "d", and "e" represent constants, and TENG0 represents the initial temperature.
[Claim 4] The temperature prediction device for an internal combustion engine according to any one of claims 1 to 3,
wherein the internal combustion engine is further configured to perform a compression stroke, in which gas in the combustion chamber is compressed by a piston configured to move along with the rotation, and an expansion stroke, in which the gas in the combustion chamber is expanded by the piston, and
wherein the intake representative pressure acquisition unit is configured to acquire the intake pressure as the intake representative pressure at a timing within a period from when the piston reaches a bottom dead center, at which transition is made from the intake stroke to the compression stroke, to when the piston passes through a top dead center, at which transition is made from the compression stroke to the expansion stroke, and reaches a next bottom dead center.

[Claim 5] The temperature prediction device for an internal combustion engine according to claim 4, wherein the intake representative pressure acquisition unit is configured to acquire the intake pressure as the intake representative pressure at a timing when the piston reaches the bottom dead center, at which the transition is made from the intake stroke to the compression stroke.
[Claim 6] The temperature prediction device for an internal combustion engine according to any one of claims 1 to 3,
wherein the internal combustion engine is further configured to perform a compression stroke, in which gas in the combustion chamber is compressed by a piston configured to move along with the rotation, and an expansion stroke, in which the gas in the combustion chamber is expanded by the piston, and
wherein the intake representative pressure acquisition unit is configured to acquire a first intake pressure and a second intake pressure at different timings within a period from when the piston reaches a bottom dead center, at which transition is made from the intake stroke to the compression stroke, to when the piston passes through a top dead center, at which transition is made from the compression stroke to the expansion stroke, and reaches a next bottom dead center, and to acquire a differential pressure between the acquired first intake pressure and the acquired second intake pressure as the intake representative pressure.

[Claim 7] The temperature prediction device for an internal combustion engine according to any one of claims 1 to 3,
wherein the internal combustion engine is further configured to perform a compression stroke, in which gas in the combustion chamber is compressed by a piston configured to move along with the rotation, and an expansion stroke, in which the gas in the combustion chamber is expanded by the piston, and
wherein the intake representative pressure acquisition unit is configured to acquire the intake pressure as the intake representative pressure at a timing within a period from when the piston reaches a bottom dead center, at which transition is made from the intake stroke to the compression stroke, to when the piston passes through a top dead center, at which transition is made from the compression stroke to the expansion stroke, and reaches a next bottom dead center, and to reacquire, when the acquired intake representative pressure is higher than a set pressure value, the intake pressure as the intake representative pressure at a timing within the period that comes next.
[Claim 8] The temperature prediction device for an internal combustion engine according to any one of claims 1 to 7, further comprising a fuel injection control unit configured to control fuel injection when the fuel is to be injected, based on the temperature of the internal combustion engine after the combustion is started,

which is predicted by the temperature prediction unit.
[Claim 9] The temperature prediction device for an internal combustion engine according to any one of claims 1 to 8, further comprising a first fuel injection control unit configured to control, based on the initial temperature predicted by the initial temperature prediction unit, fuel injection when the fuel is to be injected for a first time after the initial temperature is predicted.
[Claim 10] A temperature prediction method for an internal combustion engine, for predicting a temperature of the internal combustion engine, the internal combustion engine being configured to perform an intake stroke, in which outside air is taken in from an intake pipe into a combustion chamber, and to ignite fuel injected into the outside air taken in in the intake stroke to cause combustion in the combustion chamber, the temperature prediction method comprising the steps of:
acquiring an intake pressure in the intake pipe as an outside air pressure at a timing within a period from when the internal combustion engine is started from a stopped state to when the internal combustion engine starts rotating;
acquiring the intake pressure as an intake representative pressure and acquiring a number of revolutions per unit time of the internal combustion engine at a timing within a period from

when the internal combustion engine starts the rotation to when the combustion is started;
predicting, based on the acquired outside air pressure, the acquired intake representative pressure, and the acquired number of revolutions, an initial temperature of the internal combustion engine in a period from the start of the internal combustion engine to when the combustion is started; and
predicting, with use of the predicted initial temperature, a temperature of the internal combustion engine after the combustion is started.