JPH06317116A - Self-diagnostic device for variable valve timing control device - Google Patents

Abstract

PURPOSE:To diagnose troubles, including mechanical, troubles in addition to electric troubles in a variable valve timing control device. CONSTITUTION:An average effective pressure Pi is calculated based on a detected signal of a cylinder-internal pressure sensor 10. In this case, when the average effective pressure falls within a specified diagnosis range containing ON-range and OFF-range of variable valve timing control, an average effective pressure PiON in ON-controlled state and an average effective pressure PiOFF in OFF-controlled state are respectively determined. Further the deviation DELTAPi ( PiON-PiOFF) of the average effective pressure PiON from the average effective pressure PiOFF is calculated, and when DELTAPi is below a specified judging value, the variable valve timing control device is judged to be in trouble.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-diagnosis device for a variable valve timing control device, and more particularly to a technique for diagnosing a failure of a variable valve timing control device which variably controls valve timing of an internal combustion engine according to a control signal. .

[0002]

2. Description of the Related Art Conventionally, a variable valve timing control device has been provided for operating a variable valve timing mechanism for switching the opening / closing timing of an intake valve of an engine in accordance with engine operating conditions. Increasing the amount of overlap in the open state of the valve to increase the filling efficiency by using the intake inertial force (edited by "New model car manual (FGY32-1)" published by Nissan Motor Co., Ltd. Date: August 1991 etc.).

In the variable valve timing control device as described above, the variable valve timing control solenoid is turned on / off by a control signal output from a control unit for inputting, for example, a rotation signal and an intake air amount signal.
By doing so, the hydraulic pressure for operating the variable valve timing mechanism is controlled to switch the opening / closing timing of the intake valve.

[0004]

By the way, as a method of diagnosing a failure of the variable valve timing control device as described above, it is determined whether or not a desired control signal is transmitted to the variable valve timing control solenoid. There was a method of confirming by taking a control signal into the control unit from a signal line near the variable valve timing control solenoid.

However, according to such a method, the variable valve timing control solenoid is actually turned on even though the ON control signal is output.
If the solenoid is operating normally without switching to the operating state suitable for N control, or the hydraulic circuit or valve timing variable mechanism is abnormal, the desired switching control is performed. It was not possible to diagnose a mechanical failure that does not exist, and in some cases, the valve timing was not switched to the desired state, but the valve timing was erroneously diagnosed as normal.

The present invention has been made in view of the above problems, and in a variable valve timing control device for an engine,
It is an object of the present invention to provide a self-diagnosis device capable of performing a diagnosis including mechanical failure and to improve the diagnosis performance.

[0007]

The present invention is a self-diagnosis device for a variable valve timing control device which variably controls the valve timing of an internal combustion engine based on a control signal output from a control unit, which is shown in FIG. Is configured as follows. In FIG. 1, the combustion pressure measuring means is a means for measuring the combustion pressure of the engine, and the self-diagnosing means is the variable based on the value of the combustion pressure measured by the combustion pressure measuring means according to the control signal. Performs a failure diagnosis of the valve timing control device.

[0008]

According to this structure, the variable control of the valve timing causes a change in the charging efficiency, which causes a change in the combustion pressure. Therefore, if the valve timing is actually switched according to the control signal. , Should indicate the combustion pressure corresponding to the desired valve timing, and conversely, when the desired valve timing is not controlled, the combustion pressure does not change according to the control signal. Therefore, it is possible to diagnose whether or not the valve timing is actually switched according to the control signal by providing a means for measuring the combustion pressure and monitoring the combustion pressure measured by the means according to the control signal. I chose

[0009]

EXAMPLES Examples of the present invention will be described below. FIG. 2 is a diagram showing a configuration example of a variable valve timing control device according to the present invention. An internal combustion engine to which the variable valve timing control device is applied includes an intake side camshaft and an exhaust side camshaft independently of each other. It is a thing.

The variable valve timing control device shown in FIG. 2 is attached to the intake cam sprocket 1 and has a variable valve timing mechanism 3 for variably controlling the phases of a crankshaft (not shown) and the intake camshaft 2. A variable valve timing control solenoid 4 that controls the supply of hydraulic pressure for operating the variable valve timing mechanism 3, and a control that outputs an on / off control signal to the variable valve timing control solenoid 4 according to the operating conditions of the engine. And the unit 5.

As shown in FIGS. 3 and 4, the variable valve timing control solenoid 4 includes the rod when the solenoid provided on the base end side (upper side in FIGS. 3 and 4) is in an off (non-energized) state. 11 is retracted to the solenoid side, and when the solenoid is on (energized), the rod 11
Extends away from the solenoid. On the other hand, at the tip of the housing 12 supported so as to surround the rod 11, there is internally provided a cylindrical valve body 13 which is guided by the inner peripheral surface of the housing 12 and moves in the axial direction. The valve body 13 is biased toward the rod 11 side by a coil spring 14 which is interposed between the valve body 13 and the tip end portion of the housing 12, and the biasing force causes the valve body 13 to contact the tip end surface of the rod 11. As a result, the valve body 13 moves in the axial direction in conjunction with the forward / backward movement of the rod 11.

An inlet hole 15 is provided in the peripheral wall of the front end of the housing 12 for introducing hydraulic oil pressure-fed from a hydraulic source (not shown) into the space surrounded by the inner periphery of the housing 12 and the inside of the valve body 13. It is open. Further, the valve body 13 is provided with a communication hole 16 for discharging the hydraulic oil introduced through the introduction hole 15 into a space surrounded by the inner circumference of the housing 12 and the outer circumference of the rod 11 outside the valve body 13. . Further, a drain hole 17 facing a space surrounded by the inner circumference of the housing 12 and the outer circumference of the rod 11 is opened in the peripheral wall of the housing 12.

Here, when the variable valve timing control solenoid 4 is in the off (non-energized) state, the rod 11 retreats to the solenoid side so that the valve body 13 is housed.
12 away from the tip, in this state the peripheral wall of the valve body 13 and the introduction hole 15 do not interfere, the hydraulic oil is introduced into the housing 12 against the introduction hole 15, through the communication hole 16 in the housing 12. And is discharged from the drain hole 17.

On the other hand, when the variable valve timing control solenoid 4 is in the ON (energized) state, the rod 11 moves to the valve body.
By extending to the 13 side, the valve body 13 descends toward the tip of the housing 12, and the peripheral wall of the valve body 13 closes the introduction hole 15 from the inside, so the hydraulic oil is discharged through the drain hole 17. It will not be done. The hydraulic oil passage 18 communicating with the introduction hole 15 communicates with the hydraulic oil passage of the variable valve timing mechanism 3 on the upstream side thereof, and when the solenoid 4 is off, the hydraulic oil is discharged through the drain hole 17. As a result, the hydraulic pressure does not act on the variable valve timing mechanism 3, and when the solenoid 4 is turned on and the drain hole 17 is closed, the hydraulic pressure acts on the variable valve timing mechanism 3.

The working oil passage 18 communicates with a working oil passage 19 provided in the camshaft 2 before reaching the solenoid 4, and the working oil is not discharged from the solenoid 4 side when the solenoid 4 is on. Then, the hydraulic oil passage 19
The hydraulic oil supplied to the cam sprocket 1 reaches the front surface of the plunger 21 built in the cam sprocket 1 via the hydraulic oil passage 20 provided in the cam sprocket 1. And plunger 21
The hydraulic oil that has reached the front surface of the cylinder acts to press the plunger 21 against the camshaft 2 side due to the hydraulic pressure.

Since the plunger 21 meshes with the cam sprocket 1 and the cam shaft 2 by the helical gear 22, when it is pressed by the hydraulic pressure, it moves axially to the stopper position while rotating, and at this time, the cam sprocket 1 Since it is fixed by a timing chain (not shown), the camshaft 2 side is the plunger.
It rotates with 21 and cam sprocket 1 and cam shaft 2
The relative position in the circumferential direction with changes.

On the other hand, when the control solenoid 4 is turned off, the hydraulic oil is discharged through the drain hole 17 of the solenoid 4, so that the force for pressing the plunger 21 against the camshaft 2 is lost, and the plunger 21 is removed. 21 is returned to the original position separated from the side of the camshaft 2 by the urging force of the return spring 23. In this way, in the variable valve timing control device of the present embodiment, the phase of the intake side camshaft 2 is changed with respect to the crankshaft to change the phase of the intake side cam with the operating angle kept constant. In the embodiment, FIG.
As shown in (a) and (b), the opening timing of the intake valve is delayed when the solenoid 4 is off, and conversely, the opening timing of the intake valve is early when the solenoid 4 is on and the amount of overlap with the exhaust valve is large. Is increasing.

Turning on / off of the solenoid 4 is controlled by a control signal from the control unit 5, and the solenoid 4 is turned on / off according to engine operating conditions.
In order to turn it off and change the opening / closing timing of the intake valve in accordance with the operating conditions, the control unit 5 includes a crank angle sensor 8, an engine rotation signal Ne from the air flow meter 9,
The engine intake air amount signal Q is input.

Then, the control unit 5 incorporating the microcomputer has the intake air amount signal Q and the rotation signal N.
The engine load equivalent value (for example, the basic injection amount Tp) is calculated from e and the valve timing control map (see FIG. 6) set in advance with the engine load and the rotation as parameters is referred to so that the solenoid 4 is turned on. It is determined to be off, and the on / off control signal corresponding to the determination is output to the solenoid 4.

Further, in the present embodiment, the control unit 5 is provided with the function of performing self-diagnosis of the variable valve timing control device having the above-mentioned configuration. A detection signal from an in-cylinder pressure sensor 10 (combustion pressure measuring means) for detecting pressure is input. The in-cylinder pressure sensor 10 may be of a type that is provided as a washer of an ignition plug, or may be of a type that directly detects the pressure in the combustion chamber to detect the pressure.

The state of self-diagnosis in the control unit 5 will be described below with reference to the flowchart of FIG.
In this embodiment, the function as self-diagnosis means is as follows.
As shown in the flow chart of FIG. 7, the control unit 5
Is equipped with software. In the flowchart of FIG. 7, first, in step 1 (denoted as S1 in the figure; the same applies hereinafter), the detection signal from the in-cylinder pressure sensor 10 is integrated within a predetermined crank angle range to obtain an average effective pressure equivalent value P.
Find i.

In the next step 2, it is determined whether or not the operating conditions are within the diagnostic region surrounded by double lines on the operating region map having the engine load and the engine rotation of FIG. 6 as parameters. In the diagnosis area, the engine load range is set to be narrow so that a substantially constant average effective pressure can be obtained unless the valve timing is variable, and the control signal is turned on by normal variable valve timing control. The range of engine rotation and engine load is set so as to straddle the region and the OFF region.

Here, when the operating condition is within the diagnostic range, the routine proceeds to step 3, where it is judged which of the ON signal and the OFF signal is being outputted as the control signal. Then, when the control signal is ON, the process proceeds to step 4, and when the control signal is ON in the diagnostic region and the average effective pressure Pi calculated in step 1 is calculated, the average value is calculated. Is set to Pi _ON as data corresponding to the ON state of the control signal.

On the other hand, when the control signal is OFF,
Proceed to step 5, and the control signal is OFF in the diagnostic area
When the average effective pressure P calculated in step 1 is
The average value of i is calculated, and the average value is set to Pi _OFF as data corresponding to the OFF state of the control signal. In step 6, a deviation between the average effective pressure Pi _OFF the mean effective pressure Pi _ON and OFF states of the ON state in the diagnostic area determined as described above, to set the deviation in .DELTA.Pi.

In the next step 7, the deviation ΔPi is compared with a predetermined judgment value, and the control signal is turned on in the diagnostic area.
It is determined whether or not the change in the average effective pressure Pi due to OFF is equal to or larger than a predetermined value. That is, in the diagnostic region as shown in FIG. 6, when the control signal is ON, the opening timing of the intake valve is advanced, the overlap amount with the opening timing of the exhaust valve is increased, and the charging efficiency is increased, so that The average effective pressure Pi becomes larger than when the control signal is OFF (see FIG. 8).

Therefore, if the desired valve timing is switched according to ON / OFF of the control signal, the deviation ΔPi (← Pi _ON- Pi _OFF ) becomes a predetermined value or more, and the control signal is _{turned on} due to some failure. -In an abnormal state where the actual valve timing does not change and is constant even when switched OFF, the average effective pressure Pi is substantially constant regardless of ON / OFF of the control signal, and the deviation Δ
Pi becomes smaller than that in the normal state.

Therefore, in the step 7, the deviation Δ
If the deviation ΔPi is greater than or equal to the determination value and it is determined that the change in the average effective pressure Pi due to ON / OFF of the control signal is normal, Pi proceeds to step 8. , Determine the normality of the variable valve timing system. On the other hand, when the deviation ΔPi is less than the determination value, the valve timing is not properly switched even if the control signal is turned on / off, and thus the control signal is turned on.
It is estimated that the change in the average effective pressure Pi between the OFF states is small, and the process proceeds to step 9 to judge the failure of the variable valve timing system.

As described above, in this embodiment, the failure of the variable valve timing control device is diagnosed by whether or not the change of the average effective pressure Pi (combustion pressure) corresponding to the switching of the valve timing is obtained. Therefore, not only the electrical failure of the control signal transmission system but also the mechanical failure of the variable mechanism can be diagnosed, and a highly reliable diagnostic result can be provided.

In the above embodiment, the diagnostic area including the ON area and the OFF area in the normal ON / OFF control is set, but as shown in FIG. 9, the diagnostic area is set in the ON area or the OFF area in the normal control. When the control signal is set and falls within such a range, the control signal is forcibly switched ON / OFF to set the combustion pressure (average effective pressure) in the ON control state and the combustion pressure (average effective pressure) in the OFF control state. It may be configured to sample each.

Further, in the above embodiment, the average effective pressure equivalent value is calculated by integrating the combustion pressure, and the diagnosis is made based on the average effective pressure. However, the combustion pressure at a predetermined crank angle position or the predetermined crank angle position is determined. The configuration may be such that the maximum combustion pressure within the angular range is obtained and the diagnosis is performed. Furthermore, the combustion pressure and OFF in the ON state of the control signal
The combustion pressure (or average effective pressure) predicted from the ON / OFF of the control signal and the operating conditions and the actually measured combustion pressure (average effective pressure) are not compared with the combustion pressure in the state. It may be configured such that self-diagnosis is performed by comparison.

Further, in the above embodiment, the opening / closing timing of the intake valve is variable while the operating angle is constant, but a variable valve timing control device having a configuration in which the operating angle (lift amount) is changed with the opening / closing timing may be used. Also, even when the valve timing is changed while the operating angle is constant, it is obvious that the variable mechanism is not limited to the above-mentioned variable mechanism.

[0032]

As described above, according to the present invention, in the variable valve timing control device for variably controlling the valve timing of the internal combustion engine based on the control signal output from the control unit, the combustion pressure is changed by switching the valve timing. By utilizing the changing characteristics, the self-diagnosis is performed based on the measured value of the combustion pressure according to the control signal. There is an effect that a failure can be diagnosed and a highly reliable diagnosis result can be provided.

[Brief description of drawings]

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

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

FIG. 3 is a diagram showing a state of hydraulic control when a control signal is on.

FIG. 4 is a diagram showing a state of hydraulic control in the off state of a control signal.

FIG. 5 is a diagram showing a change in opening / closing timing of an intake valve according to a control signal.

FIG. 6 is a diagram showing an on / off control region of a control signal and a diagnostic region.

FIG. 7 is a flowchart showing self-diagnosis control of the embodiment.

FIG. 8 is a combustion pressure diagram for explaining the diagnostic characteristics of the embodiment.

FIG. 9 is a diagram showing an on / off control region of a control signal and a diagnostic region.

[Explanation of symbols]

 1 cam sprocket 2 cam shaft 3 variable valve timing mechanism 4 variable valve timing control solenoid 5 control unit 8 crank angle sensor 9 air flow meter 10 in-cylinder pressure sensor 18 to 20 hydraulic fluid passage 21 plunger 22 helical gear 23 return spring

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G01M 15/00 Z 7324-2G

Claims (1)

[Claims] 1. A self-diagnosis device for a variable valve timing control device for variably controlling valve timing of an internal combustion engine based on a control signal output from a control unit, comprising combustion pressure measuring means for measuring combustion pressure of the engine. A self-diagnosis means for diagnosing a failure of the variable valve timing control device based on a value of the combustion pressure measured by the combustion pressure measurement means according to the control signal. Self-diagnosis device for variable valve timing controller.