FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
CONTROL APPARATUS AND METHOD FOR INTERNAL COMBUSTION ENGINE;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3, MARUNOUCHI
2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION
AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
2
Description
Title of Invention: CONTROL APPARATUS AND METHOD FOR INTERNAL
COMBUSTION ENGINE
5 Technical Field
[0001] The present invention relates to a control unit for an
internal combustion engine and a control method for an internal
combustion engine, and more particularly, to a control unit for
an internal combustion engine and a control method for an internal
10 combustion engine which involve a function of estimating a flow
rate of a combustion-supporting gas supplied into a combustion
chamber.
Background Art
15 [0002] In a case of controlling output of an internal
combustion engine, an engine intake gas flow rate being a flow rate
of a combustion-supporting gas, typically outside air, supplied
into a combustion chamber is an important parameter. When this
engine intake gas flow rate can be grasped with accuracy, it is
20 possible to achieve satisfactory output and combustibility of the
internal combustion engine by controlling a fuel injection amount
and an ignition timing which correspond to the engine intake gas
flow rate.
[0003] In Patent Literature 1, there is described a technology
25 for estimating an engine intake gas flow rate by providing a pressure
3
sensor in an intake pipe of an internal combustion engine and
sequentially integrating measured values of the pressure sensor
in an intake stroke.
5 Citation List
Patent Literature
[0004] [PTL 1] JP 2009-127618 A
Summary of Invention
10 Technical Problem
[0005] However, with the technology of Patent Literature 1,
it takes much time to perform calculation for sequentially
integrating the measured values of the pressure sensor in an intake
stroke, and hence it is difficult to determine the fuel injection
15 amount before a start of a compression stroke following the intake
stroke.
[0006] The present invention has been made in order to solve
the above-mentioned problem, and has an object to provide a control
unit for an internal combustion engine and a control method for
20 an internal combustion engine which are capable of estimating an
engine intake gas flow rate at high speed.
Solution to Problem
[0007] In order to solve the above-mentioned problem,
25 according to one embodiment of the present invention, there is
4
provided a control unit for an internal combustion engine including:
an intake pressure detection unit configured to detect each of an
intake pressure at a start time of an intake stroke of the internal
combustion engine and an intake pressure at a completion time of
5 the intake stroke; a rotation speed detection unit configured to
detect a rotation speed of the internal combustion engine; an
outside air temperature detection unit configured to detect an
outside air temperature of the internal combustion engine; an engine
temperature detection unit configured to detect an engine
10 temperature of the internal combustion engine; a throttle opening
degree detection unit configured to detect a throttle opening degree
of the internal combustion engine; and an estimation unit configured
to estimate an engine intake gas flow rate being a flow rate of
a combustion-supporting gas supplied into a combustion chamber of
15 the internal combustion engine, based on the intake pressure at
the start time of the intake stroke, the intake pressure at the
completion time of the intake stroke, the rotation speed, the
outside air temperature, the engine temperature, and the throttle
opening degree.
20 [0008] Further, according to one embodiment of the present
invention, there is provided a control method for an internal
combustion engine, including the steps of: detecting each of an
intake pressure at a start time of an intake stroke of the internal
combustion engine and an intake pressure at a completion time of
25 the intake stroke; detecting a rotation speed of the internal
5
combustion engine; detecting an outside air temperature of the
internal combustion engine; detecting an engine temperature of the
internal combustion engine; detecting a throttle opening degree
of the internal combustion engine; and estimating an engine intake
5 gas flow rate being a flow rate of a combustion-supporting gas
supplied into a combustion chamber of the internal combustion engine,
based on the intake pressure at the start time of the intake stroke,
the intake pressure at the completion time of the intake stroke,
the rotation speed, the outside air temperature, the engine
10 temperature, and the throttle opening degree.
Advantageous Effects of Invention
[0009] According to the control unit for an internal
combustion engine and the control method for an internal combustion
15 engine of the present invention, it is possible to estimate the
engine intake gas flow rate at high speed.
Brief Description of Drawings
[0010] FIG. 1 is a diagram for illustrating a configuration
20 of an internal combustion engine and a control unit according to
a first embodiment of the present invention.
FIG. 2 is a diagram for schematically illustrating an internal
configuration of the control unit of FIG. 1.
FIG. 3 is a diagram for illustrating an internal circuit
25 configuration of the control unit of FIG. 1.
6
FIG. 4 is a graph for showing a change in intake pressure
immediately after a start of cranking of the internal combustion
engine of FIG. 1.
FIG. 5 is a graph for showing a change in intake pressure after
5 a lapse of a certain time period from the start of the cranking
of the internal combustion engine of FIG. 1.
FIG. 6 is a graph for showing a correlation between an engine
intake gas flow rate estimated by the control unit of FIG. 1 and
an engine intake gas flow rate separately calculated based on a
10 measured value of an A/F sensor and a fuel injection amount.
FIG. 7 is a flow chart for illustrating details of estimation
processing for an engine intake gas flow rate and control processing
for an internal combustion engine which are performed by the control
unit of FIG. 1.
15 FIG. 8 is a graph for showing behaviors of intake pressures
of an internal combustion engine A and an internal combustion engine
B having the same specifications in a third embodiment of the present
invention.
FIG. 9 is a diagram for illustrating an internal circuit
20 configuration of a control unit according to a fourth embodiment
of the present invention.
FIG. 10 is a diagram for illustrating an internal circuit
configuration of a control unit according to a fifth embodiment
of the present invention.
25 FIG. 11 is a graph for showing a change in intake pressure
7
immediately after a start of cranking of an internal combustion
engine in the fifth embodiment.
FIG. 12 is a flow chart for illustrating details of estimation
processing for an engine temperature, estimation processing for
5 an engine intake gas flow rate, and control processing for the
internal combustion engine which are performed by the control unit
according to the fifth embodiment.
Description of Embodiments
10 [0011] Now, details of embodiments of the invention disclosed
in the present application are described with reference to the
accompanying drawings. It should be noted, however, that each of
the embodiments described below is merely an example, and the
present invention is not limited to the embodiments.
15 [0012] First Embodiment
FIG. 1 is a diagram for illustrating a configuration of an
internal combustion engine 100 and a control unit 150 according
to a first embodiment of the present invention. The internal
combustion engine 100 and the control unit 150 according to the
20 first embodiment are mounted on a vehicle.
[0013] (1-1. Configuration of Internal Combustion Engine)
The internal combustion engine 100 is a four-cycle gasoline
engine, and performs an intake stroke, a compression stroke, an
expansion stroke, and an exhaust stroke in one combustion cycle.
25 [0014] The internal combustion engine 100 includes a
8
combustion chamber 101 for combusting an air-fuel mixture of a
combustion-supporting gas, typically outside air, and a fuel. The
combustion chamber 101 is formed of a cylinder head 102, a cylinder
block 103, and a piston 104.
5 [0015] The internal combustion engine 100 includes: an intake
passage 105 for supplying a combustion-supporting gas into the
combustion chamber 101; and an exhaust passage 120 for discharging
an exhaust gas generated in the combustion chamber 101.
[0016] The intake passage 105 is provided with an air filter
10 106, a throttle valve 107, and an intake pressure sensor 108 in
the stated order from an upstream side.
[0017] The throttle valve 107 is a valve for adjusting an
opening degree of the intake passage 105. An opening degree of the
throttle valve 107 is changed depending on an operation amount of
15 an accelerator by a driver. Through changing of the opening degree
of the throttle valve 107, a flow rate of the combustion-supporting
gas supplied into the combustion chamber 101 through the intake
passage 105 is adjusted.
[0018] The intake pressure sensor 108 outputs a signal
20 corresponding to a pressure of the combustion-supporting gas in
an intake pipe 105a which is located on a downstream side of the
intake passage 105 than the throttle valve 107, that is, a signal
corresponding to an intake pressure. The output signal of the
intake pressure sensor 108 is input to the control unit 150.
25 [0019] In addition, the intake passage 105 is provided with:
9
a bypass passage 109 for bypassing the throttle valve 107 to connect
the upstream side and downstream side of the throttle valve 107;
and an idle speed control valve 110 for adjusting an opening degree
of the bypass passage 109.
5 [0020] The idle speed control valve 110 controls a rotation
speed of the internal combustion engine 100 by adjusting the flow
rate of the combustion-supporting gas flowing through the bypass
passage 109 during an idling operation of the internal combustion
engine 100.
10 [0021] An injector 111 for injecting a fuel into a vicinity
of an intake port is provided on a downstream side of the intake
pressure sensor 108 in the intake pipe 105a. A fuel pumped from
a fuel tank 112 by a fuel pump 113 is supplied to the injector 111.
The injector 111 operates based on a control signal output from
15 the control unit 150.
[0022] The cylinder head 102 forming a top part of the
combustion chamber 101 is provided with an ignition plug 114 for
igniting an air-fuel mixture of a combustion-supporting gas and
a fuel. An electrode at a tip of the ignition plug 114 is exposed
20 to the inside of the combustion chamber 101. The ignition plug 114
is supplied with ignition energy from the control unit 150.
[0023] The cylinder head 102 is also provided with an intake
valve 115 for opening and closing a flow passage from the intake
passage 105 to the combustion chamber 101, and an exhaust valve
25 116 for opening and closing a flow passage from the combustion
10
chamber 101 to the exhaust passage 120.
[0024] The piston 104 forming a bottom part of the combustion
chamber 101 is coupled to a crankshaft 118 through intermediation
of a connecting rod 117. The piston 104 vertically reciprocates
5 in the cylinder block 103 in accordance with rotation of the
crankshaft 118.
[0025] In a vicinity of the crankshaft 118, a crank angle
sensor 119 for outputting a signal corresponding to a rotation angle
of the crankshaft 118 is provided. The output signal of the crank
10 angle sensor 119 is input to the control unit 150.
[0026] A plurality of protrusions are provided at set
intervals in a circumferential direction on an outer peripheral
portion of a rotor (not shown) that rotates integrally with the
crankshaft 118. The crank angle sensor 119 outputs a rectangular
15 crank signal when those protrusions cross the crank angle sensor
119.
[0027] In the first embodiment, the plurality of protrusions
are provided at every rotation angle of 30 degrees of the crankshaft
118. However, no protrusion is provided at a specific spot within
20 a rotation angle of 360 degrees of the crankshaft 118. Thus, the
control unit 150 can recognize that the crankshaft 118 has been
rotated by 360 degrees.
[0028] The control unit 150 can discriminate a position of the
piston 104 based on the rotation angle of the crankshaft 118.
25 Specifically, the control unit 150 can discriminate that the piston
11
104 is located at a position of each of a top dead center and a
bottom dead center.
[0029] As described above, the internal combustion engine 100
in the first embodiment is a four-cycle engine, and performs the
5 intake stroke, the compression stroke, the expansion stroke, and
the exhaust stroke in one combustion cycle. The control unit 150
can discriminate the current stroke of the internal combustion
engine 100 and the current position of the piston 104 based on the
pressure in the intake pipe 105a acquired from the intake pressure
10 sensor 108 and the rotation angle of the crankshaft 118 acquired
from the crank angle sensor 119.
[0030] The control unit 150 controls, for example, a fuel
injection amount and an ignition timing by outputting a fuel
injection control signal to the injector 111 based on the current
15 stroke of the internal combustion engine 100 and the current
position of the piston 104.
[0031] A three-way catalyst 121 is provided on a downstream
side of the exhaust passage 120.
[0032] (1-2. Operation of Internal Combustion Engine)
20 At a time of an operation of the internal combustion engine
100, the injector 111 injects a fuel into the combustion-supporting
gas flowing in the intake pipe 105a in front of the intake valve
115. Thus, the air-fuel mixture of the combustion-supporting gas
and the fuel is formed. The intake valve 115 supplies the formed
25 air-fuel mixture into the combustion chamber 101 by an opening
12
operation. The ignition plug 114 ignites the air-fuel mixture in
the combustion chamber 101 by a discharge spark. Thus, the air-fuel
mixture is combusted in the combustion chamber 101.
[0033] Work is performed on the outside of the internal
5 combustion engine 100 through the combustion of the air-fuel mixture
in the combustion chamber 101. Specifically, the crankshaft 118
is rotated through intermediation of the piston 104 and the
connecting rod 117, and combustion energy of the air-fuel mixture
is converted into rotational energy. The exhaust valve 116
10 discharges the exhaust gas generated by the combustion of the
air-fuel mixture into the exhaust passage 120 by the opening
operation.
[0034] (1-3. Configuration of Control Apparatus)
FIG. 2 is a diagram for schematically illustrating an internal
15 configuration of the control unit 150 for controlling the operation
of the internal combustion engine 100. The control unit 150
includes an intake pressure detection unit 151, a rotation speed
detection unit 152, an outside air temperature detection unit 153,
an engine temperature detection unit 154, a throttle opening degree
20 detection unit 155, an estimation unit 156, and a control unit 157.
[0035] The intake pressure detection unit 151 detects each of
an intake pressure at a start time of an intake stroke of the internal
combustion engine 100 and an intake pressure at a completion time
of the intake stroke of the internal combustion engine 100.
25 Specifically, the intake pressure detection unit 151 detects each
13
of the intake pressure at the start time of the intake stroke and
the intake pressure at the completion time of the intake stroke
based on the intake pressure acquired from the intake pressure
sensor 108 and the crank angle acquired from the crank angle sensor
5 119.
The "start time of the intake stroke" refers to a timing near
before and after a timing of the top dead center at which the exhaust
stroke is switched to the intake stroke. Meanwhile, the
"completion time of the intake stroke" refers to a timing near before
10 and after a timing of the bottom dead center at which the intake
stroke is switched to the compression stroke.
[0036] The rotation speed detection unit 152 detects a
rotation speed of the crankshaft 118, that is, a rotation speed
of the internal combustion engine 100, based on the output signal
15 of the crank angle sensor 119.
[0037] The outside air temperature detection unit 153 detects
a temperature of an external environment of the internal combustion
engine 100, that is, an outside air temperature, based on an output
signal of an outside air temperature sensor 131 provided near an
20 inlet of the intake passage 105.
[0038] The engine temperature detection unit 154 detects an
engine temperature being a temperature of a main body of the internal
combustion engine 100 based on an output signal of an engine
temperature sensor 132 provided in a vicinity of the combustion
25 chamber 101.
14
[0039] The throttle opening degree detection unit 155 detects
a throttle opening degree based on an output signal of a throttle
opening degree sensor 133 for outputting a signal corresponding
to the opening degree of the throttle valve 107.
5 [0040] The estimation unit 156 estimates an engine intake gas
flow rate being the flow rate of the combustion-supporting gas
supplied from the intake pipe 105a into the combustion chamber 101,
based on the intake pressure at the start time of the intake stroke,
the intake pressure at the completion time of the intake stroke,
10 the rotation speed, the outside air temperature, the engine
temperature, and the throttle opening degree which are described
above.
[0041] The control unit 157 controls the fuel injection amount
and the ignition timing of the internal combustion engine 100 by
15 driving the injector 111 and the ignition plug 114 based on the
engine intake gas flow rate estimated by the estimation unit 156.
[0042] The functions of the components 151 to 157 of the
control unit 150 are implemented by an internal processing circuit
of the control unit 150. Specifically, as illustrated in FIG. 3,
20 on a circuit board 140 of the control unit 150, an arithmetic
processing circuit 90, memory circuits 91a and 91b for exchanging
data with the arithmetic processing circuit 90, an input circuit
92 for inputting a signal input from the outside to the arithmetic
processing circuit 90, an output circuit 93 for outputting a signal
25 output from the arithmetic processing circuit 90 to the outside,
15
and a power supply circuit 94 are arranged.
[0043] The arithmetic processing circuit 90 is formed of, for
example, a central processing unit (CPU).
[0044] The memory circuit 91a is a nonvolatile memory circuit
5 formed of, for example, an electrically erasable programmable read
only memory (EEPROM).
[0045] The memory circuit 91b is a volatile memory circuit
formed of, for example, a random access memory (RAM).
[0046] Each of output signal lines from the intake pressure
10 sensor 108, the crank angle sensor 119, the outside air temperature
sensor 131, the engine temperature sensor 132, and the throttle
opening degree sensor 133 is connected to the input circuit 92.
The input circuit 92 includes an analog/digital (A/D) converter
(not shown) for converting an analog output signal output by those
15 sensors into a digital signal being capable of input to the
arithmetic processing circuit 90.
[0047] The injector 111 and the ignition plug 114 are connected
to the output circuit 93. The output circuit 93 includes a drive
circuit (not shown) for outputting the control signal from the
20 arithmetic processing circuit 90 to those electric loads.
[0048] The functions of the components 151 to 157 of the
control unit 150 are implemented when a software program stored
in advance in the memory circuit 91a is executed by the arithmetic
processing circuit 90 and the circuits 90 to 93 cooperate with one
25 another. Constants, determination pressure values, and other
16
setting data to be used by the components 151 to 157 are stored
in advance in the memory circuit 91a as part of the software program.
[0049]
5 FIG. 4 is a graph for showing a change in intake pressure
immediately after a start of cranking of the internal combustion
engine 100. The horizontal axis of FIG. 4 represents a piston crank
number indicating the position of the piston 104. The vertical axis
of FIG. 4 represents an intake pressure.
10 [0050] The piston crank number refers to a number
corresponding to the rotation angle of the crankshaft 118, and is
taken a value of from 0 to 23. The piston crank number of "0"
corresponds to a rotation angle of 0 degrees of the crankshaft 118.
The piston crank number of "1" corresponds to a rotation angle of
15 30 degrees of the crankshaft 118. In the same manner, the piston
crank number "12" corresponds to a rotation angle of 360 degrees
of the crankshaft 118, and the piston crank number "23" corresponds
to a rotation angle of 690 degrees of the crankshaft 118.
[0051] In FIG. 4, in the intake stroke, the piston 104 is
20 lowered from the top dead center toward the bottom dead center.
At this time, the intake valve 115 is in an open state, and the
exhaust valve 116 is in a closed state.
[0052] In the compression stroke, the piston 104 is raised from
the bottom dead center toward the top dead center. At this time,
25 the intake valve 115 and the exhaust valve 116 remain in a closed
17
state.
[0053] In the expansion stroke, the piston 104 is lowered from
the top dead center toward the bottom dead center. At this time,
the intake valve 115 and the exhaust valve 116 remain in a closed
5 state.
[0054] In the exhaust stroke, the piston 104 is raised from
the bottom dead center toward the top dead center. At this time,
the intake valve 115 remains in a closed state, and the exhaust
valve 116 is in an open state.
10 [0055] In the compression stroke, the expansion stroke, and
the exhaust stroke which are described above, the intake valve 115
is in a closed state. The throttle valve 107 is also in a closed
state. However, when the outside air flows into the intake pipe
105a through gaps of the throttle valve 107 and the idle speed
15 control valve 110, the pressure in the intake pipe 105a, that is,
the intake pressure, is to rise toward an atmospheric pressure.
[0056] In addition, until the fuel injection by the injector
111 is started, the intake pressure is changed due to, for example,
the vertical movement of the piston 104, the opening/closing
20 operation of each valve, and the gap of the throttle valve 107 as
well.
[0057]
FIG. 5 is a graph for showing a change in intake pressure after
25 a lapse of a certain time period from the start of the cranking
18
of the internal combustion engine 100. The horizontal axis of FIG.
5 represents a piston crank number indicating the position of the
piston 104. The vertical axis of FIG. 5 represents an intake
pressure.
5 [0058] In FIG. 5, in the intake stroke, the piston 104 is
lowered toward the bottom dead center. At this time, the intake
valve 115 is in an open state, and the exhaust valve 116 is in a
closed state. In addition, the fuel injection is performed by the
injector 111. Thus, the air-fuel mixture in the intake pipe 105a
10 is supplied into the combustion chamber 101, and the intake pressure
becomes a negative pressure lower than the atmospheric pressure.
When the piston 104 reaches the bottom dead center, the intake valve
115 is a closed state, and the stroke shifts from the intake stroke
to the compression stroke.
15 [0059] In the compression stroke, the piston 104 is raised from
the bottom dead center toward the top dead center. At this time,
the air-fuel mixture in the combustion chamber 101 is compressed
as the piston 104 is raised. After that, the discharge is performed
by the ignition plug 114. Thus, the air-fuel mixture is combusted
20 in the combustion chamber 101, and the stroke shifts from the
compression stroke to the expansion stroke while the intake valve
115 and the exhaust valve 116 remain in a closed state.
[0060] In the expansion stroke, the piston 104 is lowered from
the top dead center toward the bottom dead center. When the piston
25 104 reaches the bottom dead center, the stroke shifts from the
19
expansion stroke to the exhaust stroke.
[0061] In the exhaust stroke, the piston 104 is raised from
the bottom dead center toward the top dead center. At this time,
the exhaust valve 116 is in an open state, and the exhaust gas
5 generated by the combustion in the combustion chamber 101 is
discharged into the exhaust passage 120.
[0062]
As described above, in a case of controlling output of the
10 internal combustion engine 100, the flow rate of the
combustion-supporting gas supplied into the combustion chamber 101
and the fuel injection amount are important parameters. The
control unit 150 according to the first embodiment estimates the
engine intake gas flow rate being the flow rate of the
15 combustion-supporting gas supplied into the combustion chamber 101
mainly based on the pressure in the intake pipe 105a, that is, the
intake pressure. Hereinafter, details of a method of estimating
the engine intake gas flow rate in the control unit 150 according
to the first embodiment are described.
20 [0063]
First, the inventors of the present application used the
actual internal combustion engine 100 to acquire test data under
conditions that the outside air temperature was 25°C, 35°C, and
45°C, and that the rotation speed of the internal combustion engine
25 100 was 2,800 rpm, 5,000 rpm, and 7,000 rpm.
20
[0064] In addition, in order to set the above-mentioned
conditions, the throttle opening degree was adjusted to be constant
at, for example, 20 degrees, 35 degrees, and 45 degrees to create
states in which the throttle opening degree was stable, to thereby
5 carry out tests.
[0065] In addition, the temperature of the main body of the
internal combustion engine 100, that is, the engine temperature,
was changed as a parameter within a range of from 40°C to 145°C.
[0066] In addition, in order to obtain a reference value of
10 the engine intake gas flow rate, an air-fuel ratio (A/F) sensor
(not shown) was provided in the exhaust passage 120, and the engine
intake gas flow rate was separately calculated based on a measured
value of the A/F sensor and the fuel injection amount of the injector
111. The A/F sensor refers to a sensor for measuring a ratio of
15 an air flow rate to an air-fuel mixture flow rate based on an oxygen
concentration in the exhaust gas.
[0067]
Next, the inventors of the present application derived the
following empirical formula for estimating the engine intake gas
20 flow rate from the intake pressure based on the above-mentioned
test data. At this time, consideration was given to the facts that:
the intake pressure is affected by the outside air temperature;
a moving speed of the combustion-supporting gas flowing into the
combustion chamber 101 from the intake pipe 105a depends on the
25 rotation speed of the internal combustion engine 100; and the
21
combustion-supporting gas supplied into the combustion chamber 101
is expanded in volume by being heated by the engine temperature
being the temperature of the main body of the internal combustion
engine 100.
[0068] Q=a·Aθ·g(P1,P2)·P1b·Tac·Ted·Nee 5 -f (1)
[0069] In the above-mentioned formula: P1 represents the
intake pressure at the start time of the intake stroke; P2 represents
the intake pressure at the completion time of the intake stroke;
Ne represents the rotation speed; Ta represents the outside air
10 temperature; Te represents the engine temperature; Aθ represents
the throttle opening degree; "a", "b", "c", "d", "e", and "f" each
represent a constant; g(P1,P2) represents a variable determined
from P1 and P2; and Q represents the engine intake gas flow rate.
[0070] The intake pressure P1 at the start time of the intake
15 stroke is obtained by selecting the maximum value from among values
of intake pressures at four points within a range of from a 60-degree
advance crank angle to a 30-degree lag crank angle as the basis
for the top dead center at which the stroke shifts from the exhaust
stroke to the intake stroke, more specifically, within a range of
20 from the crank number of "16" to the crank number of "19" of FIG.
5.
[0071] The intake pressure P2 at the completion time of the
intake stroke is set to an intake pressure at a 30-degree advance
crank angle as the basis for the bottom dead center at which the
25 stroke shifts from the intake stroke to the compression stroke,
22
more specifically, at the crank number of "23" of FIG. 5.
[0072] A timing to measure the intake pressure P2 at the
completion time of the intake stroke is advanced from the bottom
dead center because a timing to start to close the intake valve
5 115 may be advanced from the bottom dead center due to the fact
that the intake valve 115 is not closed instantaneously at the bottom
dead center.
[0073] Another purpose therefore is to eliminate a possibility
that the combustion-supporting gas once supplied into the
10 combustion chamber 101 may flow back to the intake pipe 105a due
to an influence of the piston 104 that has passed the bottom dead
center before the intake valve 115 is completely closed.
[0074] It is conceivable that an opening/closing timing of the
intake valve 115 is changed depending on design of the internal
15 combustion engine 100. Therefore, the timing to measure the intake
pressure P2 is not limited to the timing of the 30-degree advance
angle of the bottom dead center. The timing to measure the intake
pressure P2 may be set to a timing of an appropriate crank angle
at which disturbance is reduced in the first half of the compression
20 stroke.
[0075] In addition, the minimum unit for detecting the crank
angle is not limited to the 30 degrees. The crank angle may be
detected in units of, for example, 15 degrees or 10 degrees.
[0076] FIG. 6 is a graph for showing a correlation between an
25 engine intake gas flow rate Q estimated in accordance with Formula
23
(1) and an engine intake gas flow rate separately calculated based
on the measured value of the A/F sensor and the fuel injection
amount.
[0077] It was confirmed that the engine intake gas flow rate
5 Q estimated in accordance with Formula (1) and the engine intake
gas flow rate separately calculated based on the measured value
of the A/F sensor and the fuel injection amount were expressed by
a linear relationship that passes through the origin with a slope≈1.
An error exhibited at this time was about ±3%.
10 [0078] FIG. 7 is a flow chart for illustrating details of
estimation processing for the engine intake gas flow rate Q and
control processing for the internal combustion engine 100 which
are performed by the control unit 150 according to the first
embodiment.
15 [0079] In Step S701, the control unit 150 is powered on, and
the operations of various sensors are started. At this stage, the
cranking of the internal combustion engine 100 is not started yet.
[0080] In Step S702, the cranking of the internal combustion
engine 100 is started.
20 [0081] In Step S703, the intake pressure detection unit 151
of the control unit 150 detects the intake pressure P1 at the start
time of the intake stroke based on the output signal of the intake
pressure sensor 108 and the output signal of the crank angle sensor
119.
25 [0082] In Step S704, the intake pressure detection unit 151
24
of the control unit 150 detects the intake pressure P2 at the
completion time of the intake stroke based on the output signal
of the intake pressure sensor 108 and the output signal of the crank
angle sensor 119.
5 [0083] In Step S705, the rotation speed detection unit 152 of
the control unit 150 detects the rotation speed Ne of the internal
combustion engine 100 based on the output signal of the crank angle
sensor 119.
[0084] In Step S706, the outside air temperature detection
10 unit 153 of the control unit 150 detects the outside air temperature
Ta based on the output signal of the outside air temperature sensor
131.
[0085] In Step S707, the engine temperature detection unit 154
of the control unit 150 detects the engine temperature Te being
15 the temperature of the main body of the internal combustion engine
100 based on the output signal of the engine temperature sensor
132.
[0086] In Step S708, the throttle opening degree detection
unit 155 of the control unit 150 detects the throttle opening degree
20 Aθ based on the output signal of the throttle opening degree sensor
133.
[0087] In Step S709, the estimation unit 156 of the control
unit 150 estimates the engine intake gas flow rate Q being the flow
rate of the combustion-supporting gas supplied from the intake pipe
25 105a into the combustion chamber 101 in accordance with Formula
25
(1) including the intake pressure P1 at the start time of the intake
stroke, the intake pressure P2 at the completion time of the intake
stroke, the rotation speed Ne, the outside air temperature Ta, the
engine temperature Te, and the throttle opening degree Aθ.
5 [0088] In Step S710, the control unit 157 of the control unit
150 controls the fuel injection amount and the ignition timing of
the internal combustion engine 100 by driving the injector 111 and
the ignition plug 114 based on the engine intake gas flow rate Q
estimated by the estimation unit 156.
10 [0089] After that, the control unit 150 repeats the processing
steps from Step S703 to Step S710. Thus, while the control unit
150 sequentially estimates the engine intake gas flow rate Q, the
control unit 150 can control the fuel injection amount and the
ignition timing based on the estimated value.
15 [0090] As described above, the control unit 150 according to
the first embodiment estimates the engine intake gas flow rate Q
being the flow rate of the combustion-supporting gas supplied into
the combustion chamber 101 in accordance with Formula (1) including
the intake pressure P1 at the start time of the intake stroke, the
20 intake pressure P2 at the completion time of the intake stroke,
the rotation speed Ne, the outside air temperature Ta, the engine
temperature Te, and the throttle opening degree Aθ.
[0091] At this time, the calculation of the equation (1) is
much faster than the calculation of sequentially integrating the
25 measured values of the pressure sensor in the intake stroke
26
described in Patent Literature 1. In addition, as confirmed with
reference to FIG. 6, the estimated value calculated in accordance
with Formula (1) is extremely high in accuracy.
[0092] The order and timings of the processing steps from Step
5 S705 to Step S708 illustrated in FIG. 7 are not limited thereto.
The processing steps may be performed between Step S703 and Step
S704, and may be performed in a different order.
[0093] Second Embodiment
Next, the control unit 150 for an internal combustion engine
10 according to a second embodiment of the present invention is
described. A method of estimating the engine intake gas flow rate
Q is different between the second embodiment and the first
embodiment described above. In the following description,
detailed descriptions of the same or similar configurations as those
15 of the first embodiment are omitted.
[0094] The estimation unit 156 of the control unit 150
according to the second embodiment changes the value of each
constant in Formula (1) depending on the throttle opening degree
Aθ detected by the throttle opening degree sensor 133.
20 [0095] Specifically, when the throttle opening degree Aθ is
smaller than 50%, Formula (1) is calculated with the constants being
set to a=a1, b=b1, c=c1, d=d1, e=e1, and f=f1. Meanwhile, when the
throttle opening degree Aθ is equal to or larger than 50%, Formula
(1) is calculated with the constants being set to a=a2, b=b2, c=c2,
25 d=d2, e=e2, and f=f2.
27
[0096] In the same manner as in the first embodiment, the
engine intake gas flow rate Q estimated in accordance with the
above-mentioned method and the engine intake gas flow rate
separately calculated based on the measured value of the A/F sensor
5 and the fuel injection amount were compared with each other. As
a result, in the same manner as in the first embodiment shown in
FIG. 6, it was confirmed that both were expressed by the linear
relationship that passes through the origin with the slope≈1. In
addition, the error exhibited at this time was about ±1.5%.
10 [0097] As described above, the control unit 150 according to
the second embodiment changes the value of each constant in Formula
(1) depending on the throttle opening degree Aθ. Thus, the engine
intake gas flow rate Q can be estimated with higher accuracy.
[0098] In the second embodiment described above, the value of
15 each constant is changed by taking two cases divided by setting
the throttle opening degree of 50% as a boundary value. However,
the boundary value is not limited to 50%, and may be another value.
In addition, a plurality of boundary values may be set for division
into three or more cases.
20 [0099] Third Embodiment
Next, the control unit 150 for an internal combustion engine
according to a third embodiment of the present invention is
described. A method of estimating the engine intake gas flow rate
Q is different between the third embodiment and the first embodiment
25 described above.
28
[0100] In general, even in internal combustion engines having
the same specifications, individual differences in behavior of the
intake pressure are observed. Therefore, the inventors of the
present application carried out comparative tests on two internal
5 combustion engines having the same specifications under the same
conditions in order to investigate individual differences in
behavior of the intake pressure between the internal combustion
engines.
[0101] FIG. 8 is a graph for showing behaviors of intake
10 pressures of two internal combustion engines having the same
specifications, namely, an internal combustion engine A and an
internal combustion engine B. When the control unit 150 is powered
on, an intake pressure Po is input from the intake pressure sensor
108 to the control unit 150 before the cranking is started.
15 [0102] As can be understood from this graph, in the internal
combustion engine A and the internal combustion engine B,
differences in behavior of the intake pressure are observed before
and after the bottom dead center between the intake stroke and the
compression stroke and in the compression stroke, the expansion
20 stroke, and the exhaust stroke even under the same conditions.
[0103] Specifically, as the intake pressure at the bottom dead
center between the intake stroke and the compression stroke becomes
lower, the pressure recovers more slowly in the compression stroke,
the expansion stroke, and the exhaust stroke, and the intake
25 pressure at the same piston crank number becomes lower.
29
[0104] The reason why the behavior of the intake pressure
differs even between the internal combustion engines having the
same specifications is considered to be that each individual
internal combustion engine differs in resistance of the intake gas
5 due to, for example, a closing degree of the throttle valve and
an opening degree of the idle speed control valve. Therefore, even
the internal combustion engines having the same specifications are
considered to cause differences in behavior of the intake pressure
depending on, for example, accuracy of parts and assembly accuracy.
10 [0105] The inventors of the present application attempted to
use an individual value α previously fitted to each individual
internal combustion engine without setting the constant "a" in
Formula (1) for estimating the engine intake gas flow rate Q to
a constant value. As a result, the inventors of the present
15 application found that it is possible to estimate the engine intake
gas flow rate Q of each individual internal combustion engine with
high accuracy by setting the individual value α as the constant
"a" even when the constants "b", "c", "d", "e", and "f" still have
the constant values.
20 [0106] The inventors of the present application also found
that there is a correlation between the individual value α and a
pressure difference |P3-Po| between the intake pressure Po
immediately before the start of the cranking and the intake pressure
P3 at the completion time of the first intake stroke after the start
25 of cranking.
30
[0107] In consideration of the above-mentioned findings, the
nonvolatile memory circuit 91a of the control unit 150 for an
internal combustion engine according to the third embodiment stores
a map indicating a relationship between the individual value α and
5 the pressure difference |P3-Po| between the intake pressure Po
immediately before the start of the cranking and the intake pressure
P3 at the completion time of the first intake stroke.
[0108] The intake pressure detection unit 151 of the control
unit 150 detects each of the intake pressure Po immediately before
10 the start of the cranking and the intake pressure P3 at the
completion time of the first intake stroke.
[0109] The estimation unit 156 of the control unit 150
estimates the individual value α based on the map indicating the
relationship between the pressure difference |P3-Po| and the
15 individual value α. After that, the estimation unit 156 estimates
the engine intake gas flow rate Q with the constant being set as
a=α in accordance with Formula (1).
[0110] As described above, the control unit 150 according to
the third embodiment changes the value of the constant "a" in Formula
20 (1) based on the pressure difference |P3-Po| between the intake
pressure Po immediately before the start of the cranking and the
intake pressure P3 at the completion time of the first intake stroke.
Thus, the engine intake gas flow rate Q can be estimated with higher
accuracy in consideration of the individual differences between
25 the internal combustion engines.
31
[0111] Fourth Embodiment
Next, the control unit 150 for an internal combustion engine
according to a fourth embodiment of the present invention is
described. A method of detecting the outside air temperature Ta
5 is different between the fourth embodiment and the first embodiment
described above.
[0112] FIG. 9 is a diagram for illustrating an internal circuit
configuration of the control unit 150 according to the fourth
embodiment. A first temperature sensor 495 and a second
10 temperature sensor 496 are arranged on a circuit board 440 of the
control unit 150. The control unit 150 is not provided with the
outside air temperature sensor present in the first embodiment.
[0113] The first temperature sensor 495 is arranged closer to
a power supply circuit 494 than the second temperature sensor 496.
15 The power supply circuit 494 is located on one end of a straight
line connecting the first temperature sensor 495 and the second
temperature sensor 496. In addition, a heat generating element and
a local heat sink are not present on the straight line connecting
the first temperature sensor 495 and the second temperature sensor
20 496.
[0114] The outside air temperature detection unit 153 in the
fourth embodiment estimates a temperature Tr of a region R present
outside the circuit board 440 and located on the other end of the
straight line in accordance with the following formula, and sets
25 the estimated temperature Tr as the outside air temperature Ta.
32
[0115] Tr=T2-U/h(T1-T2) (2)
[0116] In the above-mentioned formula: Tr represents the
temperature of the region R; T1 represents the detected value of
the first temperature sensor 495; T2 represents the detected value
5 of the second temperature sensor 496; U represents a constant (W/K)
obtained by multiplying and dividing a plurality of constants
obtained from a heat balance; and "h" represents a coefficient
(W/K).
[0117] In the control unit 150 according to the fourth
10 embodiment, the first temperature sensor 495 and the second
temperature sensor 496 can be arranged directly on the circuit board
440 of the control unit 150. Therefore, each sensor itself has a
simple structure, and it is not required to provide, for example,
a cable for connecting the first temperature sensor 495 and the
15 second temperature sensor 496 to the control unit 150. In addition,
it is not required to provide, for example, a thermoelectric
converter.
[0118] As described above, the control unit 150 according to
the fourth embodiment estimates the temperature Tr of the region
20 R present outside the circuit board 440 and located on the straight
line connecting the first temperature sensor 495 and the second
temperature sensor 496, and sets the estimated temperature Tr as
the outside air temperature Ta. Thus, cost reduction by an order
of magnitude or more is expected as compared with a case in which
25 the outside air temperature sensor is used as in the first embodiment.
33
In addition, improvement in work efficiency of an assembly process
is expected.
[0119] Fifth Embodiment
Next, the control unit 150 for an internal combustion engine
5 according to a fifth embodiment of the present invention is
described. A method of detecting the engine temperature Te is
different between the fifth embodiment and the first embodiment
described above.
[0120] FIG. 10 is a diagram for illustrating an internal
10 circuit configuration of the control unit 150 according to the fifth
embodiment. A circuit board 540 of the control unit 150 is not
provided with the engine temperature sensor present in the first
embodiment.
[0121] In general, the engine temperature immediately before
15 the start of the cranking of the internal combustion engine 100,
that is, an initial engine temperature Teo, differs depending on,
for example, an operating state before a stop of the internal
combustion engine 100 and an elapsed time since the stop. However,
the intake pressure immediately before the start of the cranking
20 of the internal combustion engine 100 is substantially equal to
an outside air pressure. In addition, the intake pressure during
a period from the start of the cranking of the internal combustion
engine 100 until the first intake stroke is entered is substantially
equal to the outside air pressure. After that, when the internal
25 combustion engine 100 enters the first intake stroke, the intake
34
pressure is lowered from the outside air pressure to about 40 kPa.
[0122] The inventors of the present application found that:
there is a correlation between the initial engine temperature Teo
and the intake pressure at the bottom dead center at which the stroke
5 shifted from the first intake stroke to the compression stroke;
and in particular, as the initial engine temperature Teo becomes
higher, the intake pressure at the bottom dead center also becomes
higher.
[0123] The inventors of the present application attempted to
10 estimate the initial engine temperature Teo with an intake pressure
P4 immediately after a start of the first compression stroke being
set as a representative pressure based on the above-mentioned
findings. The intake pressure P4 is specifically an intake
pressure at a 60-degree lag crank angle as the basis for the bottom
15 dead center at which the stroke shifts from the first intake stroke
to the compression stroke, more specifically, at the crank number
of "2" of FIG. 11.
[0124] The intake pressure is affected by the outside air
pressure and the outside air temperature. In addition, the moving
20 speed of the combustion-supporting gas moving from the intake pipe
105a into the combustion chamber 101 depends on the rotation speed
Ne of the internal combustion engine 100. Therefore, the inventors
of the present application acquired test data under conditions of
different outside air pressures and different outside air
25 temperatures, and derived the following empirical formula based
35
on the test data.
[0125] Teo=A(P4/Po-B)C·TaD·NeE (3)
[0126] In the above-mentioned formula: Teo represents the
initial engine temperature; Po represents the intake pressure
5 immediately before the start of the cranking; P4 represents the
intake pressure immediately after the start of the first compression
stroke; Ta represents the outside air temperature; Ne represents
the rotation speed; and A, B, C, D, and E each represent a constant.
[0127] In addition, when the initial engine temperature Teo
10 is estimated, the engine temperature Te after a time Δt can be
estimated based on an energy balance of the internal combustion
engine 100. Specifically, an increase amount ΔTe of the engine
temperature Te during the period of time Δt satisfies a relationship
of Formula (4). Meanwhile, a total sum of energy output from the
15 internal combustion engine 100 is expressed by Formula (5). In
Formula (5), the second term on the right-hand side indicates an
amount of heat dissipation, and the first term on the right-hand
side indicates other output energy.
[0128] M·CP·ΔTe/Δt=Qin-Qout (4)
20 Qout=Σ(Qj)+β(Te-Ta) (5)
[0129] In the above-mentioned formulae: M represents a weight
(kg) of the main body of the internal combustion engine 100; CP
represents a specific heat (J/(kg·K)) of the main body of the
internal combustion engine 100; Qin represents a total sum of energy
25 (J/s) input to the main body of the internal combustion engine 100;
36
Qout represents the total sum of energy (J/s) output from the main
body of the internal combustion engine 100; Qj represents output
energy (J/s) of an individual element "j" of the main body of the
internal combustion engine 100; Ta represents the outside air
5 temperature (K); "t" represents the time (s); and β represents a
constant (W/K).
[0130] FIG. 12 is a flow chart for illustrating details of
estimation processing for the engine temperature Te, estimation
processing for the engine intake gas flow rate Q, and control
10 processing for the internal combustion engine 100 which are
performed by the control unit 150 according to the fifth embodiment.
[0131] In Step S1201, the control unit 150 is powered on, and
the operations of various sensors are started. At this stage, the
cranking of the internal combustion engine 100 is not started yet.
15 [0132] In Step S1202, the intake pressure detection unit 151
of the control unit 150 detects the intake pressure Po immediately
before the start of the cranking based on the output signal of the
intake pressure sensor 108.
[0133] In Step S1203, the outside air temperature detection
20 unit 153 of the control unit 150 detects the outside air temperature
Ta based on the output signal of the outside air temperature sensor
131.
[0134] In Step S1204, the cranking of the internal combustion
engine 100 is started.
25 [0135] In Step S1205, the intake pressure detection unit 151
37
of the control unit 150 detects the intake pressure P4 immediately
after the start of the first compression stroke based on the output
signal of the intake pressure sensor 108 and the output signal of
the crank angle sensor 119.
5 [0136] In Step S1206, the rotation speed detection unit 152
of the control unit 150 detects the rotation speed Ne of the internal
combustion engine 100 based on the output signal of the crank angle
sensor 119.
[0137] In Step S1207, the engine temperature detection unit
10 154 of the control unit 150 estimates the initial engine temperature
Teo from the intake pressure Po immediately before the start of
the cranking, the outside air temperature Ta, the intake pressure
P4 immediately after the start of the first compression stroke,
and the rotation speed Ne in accordance with Formula (3).
15 [0138] In Step S1208, the intake pressure detection unit 151
of the control unit 150 detects the intake pressure P1 at the start
time of the intake stroke as shown in FIG. 5 based on the output
signal of the intake pressure sensor 108 and the output signal of
the crank angle sensor 119.
20 [0139] In Step S1209, the intake pressure detection unit 151
of the control unit 150 detects the intake pressure P2 at the
completion time of the intake stroke as shown in FIG. 5 based on
the output signal of the intake pressure sensor 108 and the output
signal of the crank angle sensor 119.
25 [0140] In Step S1210, the rotation speed detection unit 152
38
of the control unit 150 detects the rotation speed Ne of the internal
combustion engine 100 based on the output signal of the crank angle
sensor 119.
[0141] In Step S1211, the outside air temperature detection
5 unit 153 of the control unit 150 detects the outside air temperature
Ta based on the output signal of the outside air temperature sensor
131.
[0142] In Step S1212, the throttle opening degree detection
unit 155 of the control unit 150 detects the throttle opening degree
10 Aθ based on the output signal of the throttle opening degree sensor
133.
[0143] In Step S1213, the estimation unit 156 of the control
unit 150 estimates the engine intake gas flow rate Q being the flow
rate of the combustion-supporting gas supplied from the intake pipe
15 105a into the combustion chamber 101 in accordance with Formula
(1).
[0144] In Step S1214, the control unit 157 of the control unit
150 controls the fuel injection amount and the ignition timing of
the internal combustion engine 100 by driving the injector 111 and
20 the ignition plug 114 based on the engine intake gas flow rate Q
estimated by the estimation unit 156.
[0145] In Step S1215, the engine temperature detection unit
154 of the control unit 150 estimates the input energy Qin, the
output energy Qout, and the output energy Qj.
25 [0146] In Step S1216, the engine temperature detection unit
39
154 of the control unit 150 estimates the increase amount ΔTe of
the engine temperature Te in accordance with Formula (4) and Formula
(5), and estimates the engine temperature Te after the time Δt based
on the estimated value.
5 [0147] After that, the control unit 150 repeats the processing
steps from Step S1208 to Step S1216. Thus, while the control unit
150 sequentially estimates the engine temperature Te and the engine
intake gas flow rate Q, the control unit 150 can control the fuel
injection amount and the ignition timing based on the estimated
10 values.
[0148] As described above, the control unit 150 according to
the fifth embodiment estimates the initial engine temperature Teo
being the engine temperature immediately before the start of the
cranking of the internal combustion engine 100 based on the intake
15 pressure Po immediately before the start of the cranking, the intake
pressure P4 immediately after the start of the first compression
stroke, the outside air temperature Ta, and the rotation speed Ne.
The control unit 150 sequentially estimates the engine temperature
Te based on the estimated initial engine temperature Teo and the
20 energy balance of the internal combustion engine 100.
[0149] Examples of an operation mode of the internal
combustion engine 100 have been described above in the first to
fifth embodiments, but the operation mode of the internal combustion
engine 100 is not limited thereto. For example, the
25 opening/closing timings of the intake valve 115 and the exhaust
40
valve 116 may be changed depending on characteristics of the
internal combustion engine 100. Specifically, the intake valve 115
and the exhaust valve 116 may be configured to be opened
simultaneously at the top dead center between the exhaust stroke
5 and the intake stroke. In addition, the intake valve 115 and the
exhaust valve 116 may be opened and closed before the piston 104
reaches the top dead center or the bottom dead center.
[0150] Further, a variable valve timing mechanism for changing
the opening/closing timing of one or both of the intake valve 115
10 and the exhaust valve 116 may be provided. In this case, the control
unit 157 of the control unit 150 may change the opening/closing
timing of one or both of the intake valve 115 and the exhaust valve
116 by controlling the variable valve timing mechanism based on
the engine temperature immediately before the start of the cranking
15 and the engine temperature after the start of the cranking.
[0151] Further, the first to fifth embodiments have been
described above on the assumption that the estimation processing
for the engine intake gas flow rate Q and the control processing
for the internal combustion engine 100 based on the estimation
20 processing are all performed by a single control unit 150. However,
the estimation processing for the engine intake gas flow rate Q
and the control processing for the internal combustion engine 100
based on the estimation processing may be performed by separate
apparatus. Further, the control unit 150 may be formed of a
25 plurality of apparatus in place of a single apparatus.
41
[0152] Further, in the first to fifth embodiments described
above, the temperature of a target exhibiting the same temperature
behavior as that of the main body of the internal combustion engine
100, for example, engine oil or cooling water may be estimated in
5 place of the engine temperature Te being the temperature of the
main body of the internal combustion engine 100.
[0153] Further, in the first to fifth embodiments described
above, the intake pressure detection unit 151 detects the intake
pressure by acquiring the output signal of the intake pressure
10 sensor 108 at a specific timing. In place thereof, the intake
pressure detection unit 151 may continuously acquire the output
signal of the intake pressure sensor 108, perform a moving average
or other noise removal processing, and then detect the intake
pressure at a specific timing.
15 [0154] Further, the order and timings of the processing steps
from Step S1210 to Step S1212 are not limited thereto. The
processing steps may be performed between Step S1208 and Step S1209,
and may be performed in a different order.
[0155] Further, in the first to fifth embodiments described
20 above, physical quantities may be measured in other units. Further,
the units of physical quantities may be standardized or may be made
dimensionless.
Reference Signs List
25 [0156] 100 internal combustion engine, 150 control unit, 151
42
intake pressure detection unit, 152 rotation speed detection unit,
153 outside air temperature detection unit, 154 engine temperature
detection unit, 155 throttle opening degree detection unit, 156
estimation unit, 157 control unit, 440 circuit board, 494 power
5 supply circuit, 495 first temperature sensor, 496 second
temperature sensor
43
We Claim :
[Claim 1] A control unit for an internal combustion engine,
comprising:
an intake pressure detection unit configured to detect each
5 of an intake pressure at a start time of an intake stroke of the
internal combustion engine and an intake pressure at a completion
time of the intake stroke;
a rotation speed detection unit configured to detect a
rotation speed of the internal combustion engine;
10 an outside air temperature detection unit configured to
detect an outside air temperature of the internal combustion engine;
an engine temperature detection unit configured to detect an
engine temperature of the internal combustion engine;
a throttle opening degree detection unit configured to detect
15 a throttle opening degree of the internal combustion engine; and
an estimation unit configured to estimate an engine intake
gas flow rate being a flow rate of a combustion-supporting gas
supplied into a combustion chamber of the internal combustion engine,
based on the intake pressure at the start time of the intake stroke,
20 the intake pressure at the completion time of the intake stroke,
the rotation speed, the outside air temperature, the engine
temperature, and the throttle opening degree.
[Claim 2] The control unit for an internal combustion engine
25 according to claim 1, wherein the estimation unit is configured
44
to estimate the engine intake gas flow rate in accordance with the
following formula:
Q=a·Aθ·g(P1,P2)·P1b·Tac·Ted·Nee-f (1)
where: P1 represents the intake pressure at the start time
5 of the intake stroke; P2 represents the intake pressure at the
completion time of the intake stroke; Ta represents the outside
air temperature; Te represents the engine temperature; Aθ
represents the throttle opening degree; "a", "b", "c", "d", "e",
and "f" each represent a constant; "g" represents a variable
10 determined based on the intake pressure at the start time of the
intake stroke and the intake pressure at the completion time of
the intake stroke; and Q represents the engine intake gas flow rate.
[Claim 3] The control unit for an internal combustion engine
15 according to claim 2, wherein the estimation unit is configured
to change a value of each of the constants "a", "b", "c", "d", "e",
and "f" depending on the throttle opening degree Aθ.
[Claim 4] The control unit for an internal combustion engine
20 according to claim 2,
wherein the intake pressure detection unit is configured to
detect each of an intake pressure immediately before a start of
cranking of the internal combustion engine and an intake pressure
at a completion time of a first intake stroke, and
25 wherein the estimation unit is configured to change a value
45
of the constant "a" based on the intake pressure immediately before
the start of the cranking and the intake pressure at the completion
time of the first intake stroke.
5 [Claim 5] The control unit for an internal combustion engine
according to any one of claims 1 to 4, further comprising:
a circuit board;
a power supply circuit arranged on the circuit board;
a first temperature sensor arranged on the circuit board; and
10 a second temperature sensor arranged on the circuit board,
wherein the power supply circuit is located on one end of a
straight line connecting the first temperature sensor and the second
temperature sensor, and
wherein the outside air temperature detection unit is
15 configured to estimate a temperature of a region present outside
the circuit board and located on the other end of the straight line,
and set the estimated temperature as the outside air temperature.
[Claim 6] The control unit for an internal combustion engine
20 according to any one of claims 1 to 5,
wherein the intake pressure detection unit is configured to
detect each of an intake pressure immediately before a start of
cranking of the internal combustion engine and an intake pressure
immediately after a start of a first compression stroke, and
25 wherein the engine temperature detection unit is configured
46
to estimate an initial engine temperature being an engine
temperature immediately before the start of the cranking of the
internal combustion engine, based on the intake pressure
immediately before the start of the cranking and the intake pressure
5 immediately after the start of the first compression stroke, the
outside air temperature, and the rotation speed.
[Claim 7] The control unit for an internal combustion engine
according to claim 6, wherein the engine temperature detection unit
10 is configured to sequentially estimate the engine temperature based
on the initial engine temperature and an energy balance of the
internal combustion engine.
[Claim 8] A control method for an internal combustion engine,
15 comprising the steps of:
detecting each of an intake pressure at a start time of an
intake stroke of the internal combustion engine and an intake
pressure at a completion time of the intake stroke;
detecting a rotation speed of the internal combustion engine;
20 detecting an outside air temperature of the internal
combustion engine;
detecting an engine temperature of the internal combustion
engine;
detecting a throttle opening degree of the internal
25 combustion engine; and
47
estimating an engine intake gas flow rate being a flow rate
of a combustion-supporting gas supplied into a combustion chamber
of the internal combustion engine, based on the intake pressure
at the start time of the intake stroke, the intake pressure at the
5 completion time of the intake stroke, the rotation speed, the
outside air temperature, the engine temperature, and the throttle
opening degree.