1. A method of diagnosing responsiveness of a pressure sensor (10) provided in an intake manifold (4) of a spark-ignition engine (1), the method comprising: measuring, by the pressure sensor (10), a pressure pulsation amplitude generated by intake pulsation when the engine (1) is idle; extracting a measurement maximum value (MAP_H) and a measurement minimum value (MAP_L) from measured pressure sensor signal information; performing a calculation with reference to a normal maximum value and a normal minimum value stored in advance in a control device of the engine (1) when the pressure sensor (10) is normal, the measurement maximum value (MAP_H) and the measurement minimum value (MAP_L); and judging that the responsiveness of the pressure sensor (10) deteriorates when a result of the calculation satisfies a predetermined responsiveness deterioration condition.

2. The method of claim 1, further comprising: a crank angle sensor that detects a crank angle of the engine; wherein the pressure sensor signal information is subjected to analog to digital conversion while being sampled and held for each predetermined crank angle, and the measurement maximum value (MAP_H) and the measurement minimum value (MAP_L) are extracted from the pressure sensor signal information measured during one cycle of the engine (1).

3. The method of claim 1, wherein the measurement minimum value (MAP_L) is referred to based on load information of the engine (1), the load information being obtained through the control device of the engine (1).

4. The method of claim 1, wherein obtaining a pre-correction reference value (MAP_H0) by using the engine (1) revolutions per minute and the measurement minimum value (MAP_L) as input values and performing interpolation from map data indicating a correspondence between the engine (1) revolutions per minute and the measurement minimum value (MAP_L) stored in advance in the control device of the engine (1), obtaining a corrected reference value (MAP_Hs) by using the pre-correction reference value (MAP_H0) as an input value and performing interpolation from table data indicating a correspondence between an atmospheric pressure and the pre-correction reference value (MAP_H0) stored in advance in the control device of the engine (1) , obtaining a difference value (H_diff) by subtracting the measurement maximum value (MAP_H) from the corrected reference value (MAP_Hs), determining, when a predetermined determination start condition is satisfied, whether the difference value (H_diff) is within a range from a predetermined allowable upper limit value (MAP_H_high) to a predetermined allowable lower limit value (MAP_H_low), and if a result of the determination is negative, it is judged that the predetermined responsiveness deterioration condition is satisfied and the responsiveness of the pressure sensor (10) deteriorates.

5. The method of claim 4, wherein in the determination, when the result of the determination is continuously established to be negative for more than a predetermined time or a predetermined number of times, it is judged that the responsiveness deterioration condition is satisfied and the responsiveness of the pressure sensor (10) deteriorates.

6. The method of claim 4, wherein the determination start condition is that the revolutions per minute of the engine (1) is equal to or lower than a predetermined revolutions per minute threshold value, and a temperature of the engine (1) is equal to or lower than a predetermined temperature threshold value.

7. The method according to any one of claims 1 to 6, wherein temporary failure determination is made at a point of time when the responsiveness deterioration condition is satisfied, and after the temporary failure determination is made, when normality of each sensor that measures the crank angle of the engine (1), the revolutions per minute of the engine (1), or the temperature of the engine (1) is confirmed, failure confirmation determination is made, and it is judged that the responsiveness of the pressure sensor (10) deteriorates.

Description:TECHNICAL FIELD
[0001]
The present invention relates to a method of diagnosing responsiveness of a pressure sensor provided in an intake manifold of a spark-ignition engine.

BACKGROUND ART
[0002]
Conventionally, as a means for improving fuel consumption and traveling performance in a spark-ignition engine mounted in a vehicle or the like, for example, an electronically controlled throttle control device that electronically opens and closes a throttle by using an electronic control system instead of mechanically opening and closing the throttle by an accelerator operation by a driver is widely used. The electronically controlled throttle control device is described in, for example, JP H05-240073 A (Patent Literature 1) and JP 2008-038872 A (Patent Literature 2).
[0003]
In the electronically controlled throttle control device, for the purpose of controlling an air-fuel ratio of an engine by an electronically controlled unit device (hereinafter referred to as “ECU”) in order to perform engine control with high accuracy, a pressure sensor is used in an intake system and an exhaust system in order to measure a pressure of a mixed gas containing fuel and air taken into the engine and a pressure of an exhaust gas.
[0004]
Usually, an intake system of a spark-ignition engine has an intake filter, a throttle, and an intake manifold continuously provided therein, and an air-fuel ratio of an engine is controlled by using a pressure sensor provided in the intake manifold and configured to output an intake pressure as pressure sensor signal information depending on the magnitude of a voltage.
[0005]
In this pressure sensor, a functional deterioration failure such as a change in characteristics or a decrease in responsiveness may occur depending on a use period. Since a normal pressure value cannot be detected due to a functional deterioration failure, accuracy of engine control decreases such that exhaust gas deteriorates, which may cause an engine stall in the worst case.
[0006]
On the other hand, for example, as illustrated in FIG. 8, there is known a method of performing failure diagnosis from a rise time (Δtr) or a fall time (Δtd) of a pressure sensor signal output from a pressure sensor that performs sampling for each signal of a crank position sensor (CPS) under an acceleration condition when a driver steps on an accelerator pedal.
[0007]
However, such a conventional failure diagnosis method requires a driver's operation of stepping on an accelerator pedal. Therefore, there is no guarantee that a diagnosis condition is satisfied during a driving period (driving cycle), and there are two problems in that a diagnosis execution rate is unstable, and it is difficult for a human operation to reproduce a fixed acceleration, acceleration from a fixed vehicle speed, and the like every time, causing deterioration in diagnostic accuracy.

CITATION LIST
Patent Literature
[0008]
Patent Literature 1: JP H05-240073 A
Patent Literature 2: JP 2008-038872 A

SUMMARY OF INVENTION
Technical Problem
[0009]
An object of the present invention is to provide a method of diagnosing responsiveness of a pressure sensor provided in an intake manifold, which is capable of achieving both of not depending on driver's operation and improving diagnostic accuracy.

Solution to Problem
[0010]
The present invention made to solve the above-described problems is a method of diagnosing responsiveness of a pressure sensor provided in an intake manifold of a spark-ignition engine, the method characterized by including:
measuring, by the pressure sensor, a pressure pulsation amplitude generated by intake pulsation when an engine is idle; extracting a measurement maximum value and a measurement minimum value from measured pressure sensor signal information; performing a calculation with reference to a normal maximum value and a normal minimum value stored in advance in a control device of the engine when the pressure sensor is normal, the measurement maximum value and the measurement minimum value; and judging that the responsiveness of the pressure sensor deteriorates when a result of the calculation satisfies a predetermined responsiveness deterioration condition.
[0011]
According to the above invention, the pressure pulsation amplitude is measured at the time of idling of the engine, and a calculation is performed with reference to the measurement maximum value of the pressure pulsation amplitude and the measurement minimum value thereof, and the normal maximum value and the normal minimum value stored in advance when the pressure sensor is normal, thereby making it possible not only to reliably perform diagnosis without depending on the operation of a driver, but also to diagnose, with high accuracy, the responsiveness of the pressure sensor provided in the intake manifold by performing the diagnosis at the time of idling instead of the transient state.
[0012]
In the present invention, a crank angle sensor is detecting the crank angle of the engine is provided, and the pressure sensor signal information is subjected to analog-digital conversion while being sampled and held at predetermined angles. When the measurement maximum value and the measurement minimum value are extracted from the pressure sensor signal information measured during in one cycle of the engine, information on the measurement maximum value and the measurement minimum value can be easily obtained with high accuracy.
[0013]
In the present invention, it is also possible to refer to the measurement minimum value based on load information of the engine obtained through the control device of the engine.
[0014]
In the present invention, obtaining a pre-correction reference value by using the engine revolutions per minute (RPM) and the measurement minimum value as input values and performing interpolation from map data indicating a correspondence between the engine revolutions per minute and the measurement minimum value stored in advance in the control device of the engine, obtaining a corrected reference value by using the pre-correction reference value as an input value and performing interpolation from table data indicating a correspondence between an atmospheric pressure and the pre-correction reference value stored in advance in the control device of the engine, obtaining a difference value by subtracting the measurement maximum value from the corrected reference value, and determining, when a predetermined determination start condition is satisfied, whether the difference value is within a range from a predetermined allowable upper limit value to a predetermined allowable lower limit value, and if a result of the determination is negative, it is judged that the predetermined responsiveness deterioration condition is satisfied and the responsiveness of the pressure sensor deteriorates. In the above-described manner, since the corrected reference value can be derived in consideration of the influence of atmospheric pressure, it is possible to achieve, for example, improvement in determination accuracy.
[0015]
In the present invention, in the determination, when the negative determination result is continuously established for more than a predetermined time or a predetermined number of times, it is judged that the responsiveness deterioration condition is satisfied and the responsiveness of the pressure sensor deteriorates. In the above-described manner, it is possible to achieve, for example, improvement in determination accuracy.
[0016]
In the present invention, the determination start condition is that the revolutions per minute of the engine is equal to or lower than a predetermined RPM threshold value, and a temperature of the engine is equal to or lower than a predetermined temperature threshold value. In the above-described manner, it is possible to achieve, for example, improvement in determination accuracy.
[0017]
In the present invention, temporary failure determination is made at a point of time when the responsiveness deterioration condition is satisfied, and after the temporary failure determination is made, when normality of each sensor that measures the crank angle of the engine, the revolutions per minute of the engine, or the temperature of the engine is confirmed, failure confirmation determination is made, and it is judged that the responsiveness of the pressure sensor deteriorates. In the above-described manner, it is possible to avoid, for example, erroneous detection.

ADVANTAGEOUS EFFECTS OF INVENTION
[0018]
According to the present invention, it is possible to reliably and highly-accurately diagnose responsiveness of a pressure sensor provided in an intake manifold without depending on the operation of a driver.

BRIEF DESCRIPTION OF DRAWINGS
[0019]
FIG. 1 is a schematic view illustrating a peripheral configuration of a spark-ignition single cylinder engine for carrying out the present invention;
FIG. 2 is a graph illustrating a pressure waveform inside an intake manifold having different revolutions per minute of an engine;
FIG. 3 is a graph illustrating a pressure waveform inside an intake manifold having a different engine load;
FIG. 4 is a graph illustrating a correlation between a pressure and an engine load in a case where a load is applied to an engine when the engine has constant revolutions per minute;
FIG. 5 is a block diagram illustrating a method of diagnosing responsiveness of a MAP sensor according to the present invention;
FIG. 6 is a graph of a pressure measurement value of a normal MAP sensor;
FIG. 7 is a graph of a pressure measurement value of a degraded MAP sensor; and
FIG. 8 is a timing chart illustrating a conventional method of detecting a failure in responsiveness change of the MAP sensor.

DESCRIPTION OF EMBODIMENTS
[0020]
Hereinafter, embodiments of the present invention are described with reference to the drawings.
[0021]
FIG. 1 is a diagram illustrating a peripheral configuration of a spark-ignition single cylinder engine when a method of diagnosing responsiveness of a pressure sensor provided in an intake manifold of the present invention is performed.
[0022]
First, a principle of appearance of pressure pulsation in a pressure sensor 10 (MAP sensor) provided in an intake manifold will be described with reference to FIG. 1. In an intake passage of a single cylinder engine 1, a throttle valve 3 that controls a supply amount of intake air supplied via an air cleaner 2 installed upstream and an intake manifold 4 are provided, and the pressure sensor 10 (MAP sensor) is attached to the intake manifold 4. Intake air is supplied to the engine 1 downstream of the intake manifold 4 via an intake valve 5, and a piston 6 performs reciprocating motion in a cylinder of the engine 1.
[0023]
When the intake valve 5 is opened, the intake air in the intake manifold 4 is suctioned by a positive displacement pump formed by the piston 6, and when the throttle valve 3 on the upstream side is closed, the pressure in the intake manifold 4 drops sharply.
[0024]
On the other hand, when the intake valve 5 is closed, there is no air flow (Qac) suctioned into the cylinder of the engine 1, so that the pressure in the intake manifold 4 is slowly recovered to the atmospheric pressure by the air (Qath) flowing in from the throttle valve 3.
[0025]
The responsiveness diagnosis of the present invention focuses on the above-described phenomenon. Pressure pulsation varies depending on engine revolutions per minute and an engine load. As the engine speed is higher, movement of the piston 6 becomes faster, so that the pressure pulsation becomes small, as illustrated in FIG. 2. Furthermore, when the engine load is high, the throttle valve 3 remains open. Accordingly, in this case as well, the pressure pulsation also becomes small, as illustrated in FIG. 3.
[0026]
It is noted that, when a load is applied to an engine while the engine has constant revolutions per minute, the correlation between the pressure and the engine load at that time is as illustrated in a graph in FIG. 4. That is, since a measurement minimum value (MAP_L) and the engine load are in a proportional relationship, it can be said that the measurement minimum value (MAP_L) can be referred to based on the engine load information.
[0027]
As described above, when the pressure pulsation is small, failure diagnosis is not accurate, so in the present invention, deterioration in responsiveness of the MAP sensor is detected near idle conditions with low rotation and low load.
[0028]
An application case of the present invention is illustrated in FIG. 5. First, as illustrated in FIG. 5(1), when the engine is at idle under low speed and low load conditions, a measurement maximum value (MAP_H) and a measurement minimum value (MAP_L) are measured from signals output from a crank angle sensor (CPS) and values output from a MAP sensor (pressure sensor). At this time, pressure sensor signal information is sampled and held for each predetermined crank angle and converted from analog to digital. From the pressure sensor signal information (MAP sensor values) measured during one cycle of the engine, the measurement maximum value (MAP_H) and the measurement minimum value (MAP_L) can be extracted.
[0029]
As illustrated in FIG. 6 and FIG. 7, when a normal MAP sensor is compared with a degraded MAP sensor, a deviation between the maximum measurement value (MAP_H) and the minimum measurement value (MAP_L) of the degraded MAP sensor is smaller.
[0030]
Using the above-described result, as illustrated in FIG. 5(2), when a difference value (H_diff) between a corrected reference value (MAP_Hs) based on a normal MAP sensor value and the measurement maximum value (MAP_H) falls within a range from a predetermined allowable upper limit value (MAP_H_high) to a predetermined allowable lower limit value (MAP_H_low), it can be said to be normal.
[0031]
The corrected reference value (MAP_Hs) [kPa] is derived by table interpolation from the atmospheric pressure [kPa] and the pre-correction reference value (MAP_H0), taking into account the effect of the atmospheric pressure. The pre-correction reference value (MAP_H0) is calculated by map interpolation from the engine revolutions per minute and the measurement minimum value (MAP_L).
[0032]
The map interpolation refers to calculating, by any interpolation method such as linear interpolation, the pre-correction reference value (MAP_H0) from map data in which correspondence between the engine revolutions per minute [rpm] and the measurement minimum value (MAP_L) [kPa] is indicated by two axes (two dimensions) prepared in advance using the engine revolutions per minute [rpm] and the measurement minimum value (MAP_L) [kPa] as respective input values.
[0033]
The table interpolation refers to calculation by any interpolation method such as linear interpolation from table data in which correspondence between the atmospheric pressure [kPa] and the pre-correction reference value (MAP_H0) [kPa] prepared in advance is indicated on one axis (one dimension) using the pre-correction reference value (MAP_H0) as an input value. The map data and table data can be stored in advance, for example, in the control unit of the engine 1.
[0034]
In addition, since it is desirable to perform this normality determination under stable conditions, as illustrated in FIG. 5(3), the determination is performed under determination conditions other than high rotation and high load, and when the engine temperature is equal to or higher than a certain level. It is determined whether the difference value (H_diff) is within a range from the predetermined allowable upper limit value (MAP_H_high) to the predetermined allowable lower limit value (MAP_H_low). If the determination result is positive, temporary normality determination is made, and if the determination result is negative, temporary failure determination is made.
[0035]
In FIG. 5(4), normality of other sensors (a crank angle sensor, an engine revolutions per minute sensor, an engine temperature sensor, and the like) used in the determination conditions of FIG. 5(3) is confirmed, and when each sensor is normal, normality/failure determination of the MAP sensor is finally confirmed in FIG. 5(5).
[0036]
As described above, according to the present invention, by using the maximum measurement value (MAP_H) and the minimum measurement value (MAP_L) in a cycle without using an acceleration condition, a stable responsiveness diagnosis execution rate can be obtained regardless of the operation of a driver. Furthermore, responsiveness can be diagnosed not in the transient state but in the steady state, thereby contributing to improvement in accuracy of the responsiveness diagnosis.

Reference Signs List
[0037]
1 ENGINE
2 AIR CLEANER
3 THROTTLE VALVE
4 INTAKE MANIFOLD
5 INTAKE VALVE
6 PISTON
10 PRESSURE SENSOR
, C , Claims:1. A method of diagnosing responsiveness of a pressure sensor (10) provided in an intake manifold (4) of a spark-ignition engine (1), the method comprising:
measuring, by the pressure sensor (10), a pressure pulsation amplitude generated by intake pulsation when the engine (1) is idle;
extracting a measurement maximum value (MAP_H) and a measurement minimum value (MAP_L) from measured pressure sensor signal information;
performing a calculation with reference to a normal maximum value and a normal minimum value stored in advance in a control device of the engine (1) when the pressure sensor (10) is normal, the measurement maximum value (MAP_H) and the measurement minimum value (MAP_L); and
judging that the responsiveness of the pressure sensor (10) deteriorates when a result of the calculation satisfies a predetermined responsiveness deterioration condition.

2. The method of claim 1, further comprising:
a crank angle sensor that detects a crank angle of the engine; wherein
the pressure sensor signal information is subjected to analog to digital conversion while being sampled and held for each predetermined crank angle, and the measurement maximum value (MAP_H) and the measurement minimum value (MAP_L) are extracted from the pressure sensor signal information measured during one cycle of the engine (1).

3. The method of claim 1, wherein
the measurement minimum value (MAP_L) is referred to based on load information of the engine (1), the load information being obtained through the control device of the engine (1).

4. The method of claim 1, wherein
obtaining a pre-correction reference value (MAP_H0) by using the engine (1) revolutions per minute and the measurement minimum value (MAP_L) as input values and performing interpolation from map data indicating a correspondence between the engine (1) revolutions per minute and the measurement minimum value (MAP_L) stored in advance in the control device of the engine (1),
obtaining a corrected reference value (MAP_Hs) by using the pre-correction reference value (MAP_H0) as an input value and performing interpolation from table data indicating a correspondence between an atmospheric pressure and the pre-correction reference value (MAP_H0) stored in advance in the control device of the engine (1) ,
obtaining a difference value (H_diff) by subtracting the measurement maximum value (MAP_H) from the corrected reference value (MAP_Hs),
determining, when a predetermined determination start condition is satisfied, whether the difference value (H_diff) is within a range from a predetermined allowable upper limit value (MAP_H_high) to a predetermined allowable lower limit value (MAP_H_low), and
if a result of the determination is negative, it is judged that the predetermined responsiveness deterioration condition is satisfied and the responsiveness of the pressure sensor (10) deteriorates.

5. The method of claim 4, wherein
in the determination, when the result of the determination is continuously established to be negative for more than a predetermined time or a predetermined number of times, it is judged that the responsiveness deterioration condition is satisfied and the responsiveness of the pressure sensor (10) deteriorates.

6. The method of claim 4, wherein
the determination start condition is that the revolutions per minute of the engine (1) is equal to or lower than a predetermined revolutions per minute threshold value, and a temperature of the engine (1) is equal to or lower than a predetermined temperature threshold value.

7. The method according to any one of claims 1 to 6, wherein
temporary failure determination is made at a point of time when the responsiveness deterioration condition is satisfied, and
after the temporary failure determination is made, when normality of each sensor that measures the crank angle of the engine (1), the revolutions per minute of the engine (1), or the temperature of the engine (1) is confirmed, failure confirmation determination is made, and it is judged that the responsiveness of the pressure sensor (10) deteriorates.