JPH09138182A - Pressure sensor diagnostic unit for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diagnose the abnormality of pressure sensor for detecting the intake pressure of internal combustion engine. SOLUTION: On condition that the idle rotation control system is normal during steady state running and the external load is constant, the opening of an auxiliary air control valve is varied forcibly (S1-S3, S5) and constant torque control is performed at the ignition timing (S6). A decision is made that a pressure sensor is normal (S9) when the pressure difference ΔP between an intake pressure PA measure immediately before variation (S4) and an intake pressure PB detected after variation (S7) comes within a reference range ΔP0 . A decision is made that the pressure sensor is abnormal (S10) when the pressure difference ΔP devirates from the reference range ΔP0 and an alarm lamp is lighted (S11).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for diagnosing whether a pressure sensor for detecting intake pressure downstream of a throttle valve of an internal combustion engine has an abnormality.

[0002]

2. Description of the Related Art As an electronically controlled fuel injection device for an internal combustion engine, there is a device in which a fuel injection amount is set on the basis of intake pressure on the downstream side of a throttle valve (referred to as a D-Jetro system). That is, based on the intake pressure, correction is made by the engine speed and intake temperature to set the fuel injection amount corresponding to the intake charging efficiency, and the injection pulse signal having the pulse width corresponding to the fuel injection amount is set to the electromagnetic fuel. It outputs to the injection valve to control the fuel injection amount.

[0003]

In the D-JETRO system, since the intake pressure on the downstream side of the throttle valve is detected by the pressure sensor, if there is an abnormality in the pressure sensor, the driving performance and the exhaust purification performance are impaired. . The present invention has been made in view of such conventional problems, and an object of the present invention is to enable an abnormality in a pressure sensor to be accurately diagnosed.

[0004]

Therefore, as shown in FIG. 1, the invention according to claim 1 includes gas flow rate control means for controlling the gas flow rate into the intake passage downstream of the throttle valve, while the throttle valve is provided. In an internal combustion engine equipped with a pressure sensor for detecting the pressure in the intake passage downstream of the valve, a gas flow rate forced change means for forcibly changing the gas flow rate by a predetermined amount by the gas flow rate control means, and a forced change in the gas flow rate. A constant torque control means for controlling the internal engine torque to be kept constant, and a diagnostic means for diagnosing whether or not there is an abnormality in the pressure sensor based on a change in the output value of the pressure sensor due to the forced change in the gas flow rate. It is characterized by including and.

With this configuration, the gas flow rate forced change means forcibly changes the gas flow rate to the downstream side of the throttle valve through the gas flow rate control means while the engine torque is kept constant by the torque constant control means. Since the flow rate of the intake air to the engine is maintained constant, the amount of gas on the downstream side of the throttle valve increases by a predetermined amount. If the pressure sensor is normal, a change in intake pressure commensurate with the amount of change in the gas amount is detected. However, if an abnormality occurs in the pressure sensor, the change in intake pressure cannot be detected. It is possible to diagnose whether or not there is an abnormality in the pressure sensor based on the change in the output value of.

Further, in the invention according to claim 2, the gas flow rate control means controls the auxiliary air flow rate by controlling the opening degree of the auxiliary air control valve interposed in the auxiliary air passage bypassing the throttle valve. It was decided to be an idle speed control device that controls and controls the engine speed during idling.

With this configuration, the gas flow rate forced change means changes the opening control amount of the auxiliary air control valve by a predetermined amount to accurately change the gas flow amount to the downstream side of the throttle valve by a predetermined amount. Therefore, high diagnostic accuracy of the pressure sensor is secured. In the invention according to claim 3, the gas flow rate control means controls the opening degree of an EGR valve interposed in an EGR passage connecting an exhaust passage of an engine and an intake passage on the downstream side of the throttle valve. Therefore, the EGR device recirculates a part of the exhaust gas to the intake system.

With this configuration, the gas flow rate forced change means can accurately change the gas flow rate to the downstream side of the throttle valve by a predetermined amount by changing the opening control amount of the EGR valve by a predetermined amount. As a result, high diagnostic accuracy of the pressure sensor is secured. Further, in the invention according to claim 4, the gas flow rate forced change means forces the gas flow rate by the gas flow rate control means when the gear position of the transmission connected to the output shaft of the engine is neutral. It was decided to change by a predetermined amount.

With this configuration, the diagnosis can be executed in a stable idle state when the vehicle is not traveling. In the invention according to claim 5, the torque constant control means controls the ignition timing of the engine to control the torque constant.

With this configuration, the constant torque control can be easily and responsively performed by controlling the ignition timing of the engine. Further, in the invention according to claim 6, the torque constant control means controls the amount of fuel supplied to the engine to control the torque constant.

With this configuration, the torque constant control can be performed easily and highly accurately by controlling the fuel supply amount to the engine.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2 showing an embodiment, a throttle valve 3 is provided in an intake passage 2 of an internal combustion engine 1, and a pressure sensor for detecting intake pressure is provided in a collector portion 2A of the intake passage 2 downstream of the throttle valve 3. 21 is interposed, and the fuel injection amount from the fuel injection valve 4 described later is controlled based on the intake pressure detected by the pressure sensor 21.

A fuel injection valve 4 for injecting fuel for each cylinder is provided in each branch portion 2B of the downstream side manifold portion of the intake passage 2, and an air cleaner 5 is provided at the upstream end portion of the intake passage 2. There is. Further, an auxiliary air passage 6 bypassing the throttle valve 3 and an electromagnetic auxiliary air control valve 7 interposed in the auxiliary air passage 6 are provided, and the auxiliary air control valve 7 is provided from the control unit 8. The control signal opening degree is controlled, and the auxiliary air flow rate is controlled so that the engine rotation speed is feedback-controlled to the target rotation speed during idling.

Further, an EGR passage 10 connecting the exhaust passage 9 of the engine 1 and the intake passage 2 downstream of the throttle valve 3
And an EGR valve 11 interposed in the EGR passage 10, and NOx reduction is achieved by controlling the opening degree of the EGR valve 11 and controlling the EGR amount in a predetermined operating region. For each control described above, signals from various sensors are input to the control unit 8.

A crank angle sensor 12 is provided as each of the various sensors, and the engine speed Ne can be calculated from the cycle T _REF of the reference signal REF output at each predetermined crank angle. A water temperature sensor 13 is provided to detect the engine cooling water temperature Tw. In addition, a throttle sensor 14 that detects the opening of the throttle valve 3, a neutral switch 1 that is turned on at the transmission neutral position.
5. A vehicle speed sensor 16 for detecting the vehicle speed VSP is provided.

Further, each cylinder of the engine 1 is provided with an ignition plug 18, and an ignition timing (ignition advance value) A by the ignition plug 17 is provided.
The control of the DVT is performed by the ignition timing signal from the control unit 8. In the internal combustion engine having such a configuration, the presence or absence of abnormality of the pressure sensor 21 is diagnosed.

The pressure sensor diagnosis routine according to the first embodiment will be described with reference to the flowchart of FIG. In step (denoted as S in the drawing; the same applies hereinafter) 1, it is determined by diagnosis whether the idle rotation control system by the auxiliary air control 7 is normal. When it is determined that the idle rotation control system is normal, the process proceeds to step 2 and it is determined whether the vehicle is traveling normally. Specifically, the throttle valve opening, the engine rotation speed N, and the vehicle speed VSP are substantially constant, so that it is determined that the vehicle is traveling normally.

When it is determined in step 2 that the vehicle is running normally, the routine proceeds to step 3 where it is determined whether the external load such as a lamp is kept constant. If it is determined in step 3 that the external load is maintained constant, the process proceeds to step 4, and the intake pressure P _A detected by the pressure sensor 21 is read. In step 5, the opening degree of the auxiliary air control valve 7 is forcibly increased by a fixed amount (or decreased by a fixed amount).

In step 6, the spark plug 18 is provided so as to eliminate the torque change due to the change in the opening degree of the auxiliary air control valve 7.
Control the ignition timing or the fuel injection amount of the fuel injection valve 4. In step 7, the intake pressure P _B detected by the pressure sensor 21 is read. In step 8, the differential pressure between the intake pressure P _A read in step 3 before the opening change of the auxiliary air control valve 7 and the intake pressure P _B read in step 7 after the opening change of the auxiliary air control valve 7. It is determined whether or not ΔP is within a reference range ΔP ₀ set in advance corresponding to the opening change amount of the auxiliary air control valve 7.

If it is determined in step 8 that the differential pressure of the intake pressure is within the reference range ΔP ₀ , the process proceeds to step 9, where it is determined that the pressure sensor 21 is normal,
If it is determined that it is outside the reference range ΔP ₀ , the step
Proceed to step 10 and determine that the pressure sensor 21 is abnormal, and
Turn on (MIL). In step 11, the pressure sensor 21
The control is switched to fail-safe control corresponding to the above abnormality, for example, control such as setting the fuel injection amount according to the throttle valve opening and the engine rotation speed N.

With this configuration, the auxiliary air control valve 7 is forcibly changed to a predetermined opening degree to change the auxiliary air flow rate to the throttle valve downstream side by a predetermined amount, while the ignition timing control or the fuel injection is performed during that time. By keeping the engine torque constant in response to the change of the auxiliary air flow rate by the amount control, the intake air flow rate to the engine is kept constant, so that the intake air amount on the downstream side of the throttle valve increases by a predetermined amount.

If the pressure sensor 21 is normal, the change in intake pressure falls within the reference range in accordance with the change in the gas amount, but if an abnormality occurs in the pressure sensor 21, the change in intake pressure is changed to the reference value. Since it does not fall within the range, it is possible to accurately diagnose whether or not there is an abnormality in the pressure sensor 21. The pressure sensor diagnosis routine according to the second embodiment is shown in the flowchart of FIG.

In the second embodiment, instead of changing the opening of the auxiliary air control valve 7 by a predetermined amount in the first embodiment, the opening of the EGR valve 12 is changed by a predetermined amount. The other points are the same as those of the first embodiment, and the same functions and effects are obtained. The third embodiment is shown in the flowchart shown in FIG.

In the third embodiment, instead of the determination of steady running in step 2 of the first embodiment, step
In 32, based on the signal from the neutral switch 15, it is determined whether or not the gear position of the transmission is the neutral position, and when it is determined to be the neutral position, the process proceeds to step 33 and thereafter. The other configurations are exactly the same as those of the first embodiment, and have the same functions and effects. Also, instead of controlling the auxiliary air control valve, the second
The same applies to the case where the EGR control valve may be controlled as in the above embodiment.

[0025]

As described above, according to the invention of claim 1, the gas flow rate to the downstream side of the throttle valve is forcibly changed by a predetermined amount, while maintaining the engine torque constant during that period to the engine. By maintaining a constant intake air flow rate and increasing the gas amount on the downstream side of the throttle valve by a predetermined amount,
Whether or not there is an abnormality in the pressure sensor can be easily diagnosed based on the change in the output value of the intake pressure during that time.

Further, according to the second aspect of the present invention, by changing the opening control amount of the auxiliary air control valve by a predetermined amount, the gas flow rate to the downstream side of the throttle valve can be accurately changed by the predetermined amount. As a result, high diagnostic accuracy of the pressure sensor is secured. According to the invention of claim 3,
By changing the opening control amount of the EGR valve by a predetermined amount,
The gas flow rate to the downstream side of the throttle valve can be accurately changed by a predetermined amount, so that high diagnostic accuracy of the pressure sensor is secured.

According to the invention of claim 4, the pressure sensor is diagnosed in the neutral state, so that the diagnosis can be executed in the stable idle state when the vehicle is not running. According to the fifth aspect of the present invention, the torque constant control can be performed easily and with good responsiveness by controlling the ignition timing of the engine and controlling the torque constant during the pressure sensor diagnosis.

According to the sixth aspect of the invention, the torque constant control is performed easily and highly accurately by controlling the fuel supply amount to the engine and controlling the torque constant during the pressure sensor diagnosis. You can

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration and functions of the present invention.

FIG. 2 is a system schematic diagram showing an embodiment of the present invention.

FIG. 3 is a flowchart showing a pressure sensor diagnosis routine according to the first embodiment.

FIG. 4 is a flowchart showing a pressure sensor diagnosis routine according to a second embodiment.

FIG. 5 is a flowchart showing a pressure sensor diagnosis routine according to a third embodiment.

[Explanation of symbols]

 1 Internal Combustion Engine 2 Intake Passage 3 Throttle Valve 4 Fuel Injection Valve 6 Auxiliary Air Passage 7 Auxiliary Air Control Valve 9 Exhaust Passage 10 EGR Passage 11 EGR Valve 12 Crank Angle Sensor 14 Throttle Sensor 15 Neutral Switch 16 Vehicle Speed Sensor 17 Spark Plug 21 Pressure Sensor

Claims (6)

[Claims] 1. An internal combustion engine comprising: a gas flow rate control means for controlling a gas flow rate into an intake passage downstream of a throttle valve; and a pressure sensor for detecting a pressure in an intake passage downstream of the throttle valve. A gas flow rate forced change means for forcibly changing the gas flow rate by a predetermined amount by the gas flow rate control means; a torque constant control means for controlling the engine torque during the forced change of the gas flow rate to be constant; A pressure sensor diagnostic device for an internal combustion engine, comprising: a diagnostic means for diagnosing whether or not there is an abnormality in the pressure sensor based on a change in the output value of the pressure sensor due to a forced change in the flow rate. 2. The gas flow rate control means controls the auxiliary air flow rate by controlling the opening degree of an auxiliary air control valve interposed in an auxiliary air passage that bypasses the throttle valve to rotate the engine at idle. The pressure sensor diagnostic device for an internal combustion engine according to claim 1, which is an idle speed control device for controlling a speed. 3. The gas flow rate control means connects an exhaust passage of an engine and an intake passage downstream of the throttle valve with an EG.
The pressure sensor diagnostic device for an internal combustion engine according to claim 1, wherein the EGR device is an EGR device that recirculates a part of exhaust gas to an intake system by controlling an opening of an EGR valve interposed in the R passage. 4. The gas flow rate forced change means forcibly changes the gas flow rate by a predetermined amount by the gas flow rate control means when the gear position of the transmission connected to the output shaft of the engine is neutral. The pressure sensor diagnostic device for an internal combustion engine according to any one of claims 1 to 3. 5. The pressure sensor diagnostic device for an internal combustion engine according to claim 1, wherein the constant torque control means controls the ignition timing of the engine to keep the torque constant. 6. The pressure sensor diagnostic device for an internal combustion engine according to claim 1, wherein the constant torque control means controls the fuel supply amount to the engine to control the torque constant. .