JPH06317117A - Self-diagnostic device for variable valve timing control device - Google Patents

Abstract

PURPOSE:To diagnose troubles of the device, including mechanical troubles in a variable valve timing control device for changing the amount of overlap of intake and exhaust valves. CONSTITUTION:Whether a variable valve timing control solenoid 4 is turned ON or OFF is judged, and based on the judged results and the engine-operating conditions, judging levels QRON, QROFF for intake air pulsations are set. Then, the judging levels QRON and QROFF are compared with the pulsating width QP-P actually determined from output of an air flow-meter 9. Trouble with variable valve timing control device is diagnosed depending on whether pulsations conforming to a pulsating level predicted from ON-OFF states of the solenoid 4 and the engine-operating conditions are generated or not.

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 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 is provided, and the intake valve and the exhaust gas are operated at high engine speed and high load. Increasing the amount of overlap in the open state of the valve to increase the charging 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]

SUMMARY OF THE INVENTION 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 from a control unit. Configured as shown. In FIG. 1, the pulsation detection means detects the pulsation level of engine intake air, and the pulsation level diagnosis means is set for each engine operating condition according to the pulsation level detected by the pulsation detection means and the control signal. According to the comparison result, the variable valve timing control device is diagnosed for a failure.

Further, in FIG. 2, when the valve timing is switched based on the control signal, the pulsation level change diagnosing means changes the pulsation level detected by the pulsation detecting means according to the valve timing switching. And a failure of the variable valve timing control device is diagnosed based on the change amount.

[0009]

With this configuration, the intake pulsation level predicted according to the desired valve timing control state and the operating condition by the control signal is compared with the actually detected pulsation level, and the pulsation level is adjusted according to the operating condition. The failure of the variable valve timing control device is diagnosed based on the difference with respect to the predicted value.

That is, based on the difference between the pulsation level when the variable valve timing control device is operating normally and the pulsation level when the original control operation is not performed,
The failure of the variable valve timing control device is diagnosed. For example, under operating conditions where the amount of overlap between the intake valve and the exhaust valve should be reduced, even though a control signal is output to reduce the amount of overlap, the amount of overlap is actually controlled to be large. If so, the intake inertial force increases due to the increase in the overlap amount, and the pulsation becomes larger than in the normal state. Therefore, failure diagnosis can be performed by capturing the difference in the pulsation level.

Further, since the intake inertia force changes and the pulsation level changes due to the variable valve timing as described above, when the valve timing is switched according to the control signal, the pulsation level changes according to the switching. If the valve timing has been switched, but the absolute value of the change in the pulsation level is small, it can be estimated that the desired switching control has not been performed, and the variable valve timing control device has failed. Can diagnose.

[0012]

EXAMPLES Examples of the present invention will be described below. FIG. 3 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. It is a thing.

The variable valve timing control device shown in FIG. 3 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. 4 and 5, the variable valve timing control solenoid 4 has the rod provided when the solenoid provided on the base end side (upper side in FIGS. 4 and 5) is in the 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 an unillustrated hydraulic source 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 retracts to the solenoid side, so that the valve body 13 is moved to the housing.
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 hydraulic oil passage 18 communicates with a hydraulic oil passage 19 provided in the camshaft 2 before reaching the solenoid 4, and the hydraulic 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 side is lost, and the plunger 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 in the off state, and conversely, the opening timing of the intake valve is early when the solenoid 4 is in the on state, and the overlap amount with the exhaust valve is increased. 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 an air flow meter 9 such as a hot wire type, and an 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 is calculated from e and the on / off state of the solenoid 4 is determined by referring to the valve timing control map (see FIG. 7) that is preset with the engine load and rotation as parameters, and the determination is performed. An on / off control signal corresponding to the above 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. The state of self-diagnosis in the control unit 5 will be described below with reference to the flowcharts of FIGS. 8 and 9. In the present embodiment, the control unit 5 has a software function as a pulsation level diagnosis means as shown in the flow chart of FIG. 9, and the pulsation detection means has a function as shown in FIG. This is realized by the software function of the control unit 5 and the air flow meter 9 shown in the flowchart of FIG.

The flowchart of FIG. 8 shows a program for obtaining the pulsation width (value corresponding to the pulsation level of the intake air) Q _PP of the intake air amount Q detected by the air flow meter 9. In the flowchart of FIG. 8, first,
In step 1 (denoted as S1 in the figure; the same applies hereinafter), the voltage signal Us output from the air flow meter 9 according to the intake air amount Q is A / D converted and read.

Then, in the next step 2, the maximum value Q
_MAX is compared with the output signal Us read this time, and when the output signal Us exceeds the maximum value Q _MAX , the routine proceeds to step 3, where the output signal Us read this time is set to the maximum value Q _MAX . Further, in step 4, the minimum value Q _MIN is compared with the output signal Us read this time, and when the output signal Us falls below the minimum value Q _MIN , the process proceeds to step 5 and the output signal Us read this time is changed to the minimum value Q _MIN. Set to.

When the maximum value Q _MAX and the minimum value Q _MIN are obtained, the maximum value Q _MAX and the minimum value Q are calculated in step 6.
The deviation from _MIN , that is, the pulsation width Q _PP of the intake air amount Q is calculated (see FIG. 10). Although the flow chart of FIG. 8 is simplified, in actuality, the point immediately before the intake air amount Q changes from an increasing change to a decreasing change is determined as a maximum value Q _MAX , and similarly, the intake air amount decreases. From the point immediately before the change to the increase change is obtained as the minimum value Q _MIN , and the maximum value Q _MAX ,
Each time the minimum value Q _MIN is determined, the maximum value Q _MAX - is intended for obtaining the minimum value Q _MIN = Q _PP as pulsation width Q _PP, further averaging pulsation width Q _PP obtained as above It may be configured to.

On the other hand, in the flowchart of FIG. 9, the self-diagnosis of the variable valve timing control device is performed based on the pulsation width Q _PP obtained as described above. In the flowchart of FIG. 9, in step 11, ON / OFF of the control signal sent to the variable valve timing control solenoid 4 is judged, and when the ON control signal is output, the process proceeds to step 12.

In step 12, the lower limit value Q _RON of the pulsation width Q _PP generated when the valve timing is controlled in advance corresponding to the ON of the control signal is _divided by the engine load Tp and the engine rotation speed Ne. Refer to the map stored for each operating region, and control signal O with the current engine load and rotation.
Lower limit value Q _RON that does not fall when the valve timing is controlled to have a large overlap corresponding to N
(See Figure 11).

Then, in the next step 13, the lower limit value Q _RON is compared with the pulsation width Q _PP actually obtained by the flowchart of FIG. Here, when the actual pulsation width Q _PP is below the lower limit value Q _RON , the control signal is output to increase the overlap amount, but in reality, the overlap amount is not large. In other words, it is determined that the desired valve timing has not been switched to, and the process proceeds to step 14 to determine the system failure.

That is, at a valve timing with a large overlap amount, a relatively large intake pulsation occurs due to an increase in intake inertia force, and the lower limit value Q _RON becomes an intake pulsation that occurs when the overlap amount is large. Therefore, the pulsation width Q _PP is set to the lower limit value Q.
_When it falls below _RON , even if it is ON as a control signal, the overlap amount is not actually large, and it can be determined that a mechanical failure has occurred.

On the other hand, in step 11, the solenoid 4 is turned off.
If it is determined that the control signal of is output,
Advances to 15, the upper limit value Q _ROFF pulsation width Q _PP that occurs when it is controlled to the valve timing commensurate to OFF in advance in the control signal, the engine load Tp and the engine rotational speed Ne and the segmented be operated in each area by Set the upper limit value _QROFF that does not exceed when the valve timing is controlled with a small overlap corresponding to the control signal OFF under the current engine load and rotation by referring to the map stored in (see FIG. 11). .

[0032] Then, in the next step 16, compares the pulsation width Q _PP which is being sought by the flowchart of fact the said upper limit Q _ROFF Figure 8. Here, when the actual pulsation width Q _PP exceeds the upper limit value _QROFF , the control signal is output to reduce the overlap amount, but the overlap amount is not actually reduced. In other words, it is determined that the desired valve timing has not been switched to, and the process proceeds to step 17 to determine the system failure.

That is, the pulsation width Q _PP is the upper limit value Q
If it exceeds _ROFF , it is predicted that a large intake pulsation is occurring because the overlap amount is actually large even if it is OFF as the control signal.
It can be judged that a mechanical failure has occurred. In the above embodiment, the self-diagnosis is performed based on whether or not the detected pulsation width Q _PP is at the level predicted from the valve timing control signal at that time and the operating condition. as long switching timing is large lap amount, since the pulsation width Q _PP should increase changes, based on a deviation between the pulsation width Q _PP in the pulsation width Q _PP and oN state in the OFF state of the control signal, the normal It is also possible to self-diagnose whether the valve timing is switched.

Such an embodiment will be described with reference to the flowchart of FIG. In this embodiment, the control unit 5 has a software function as a diagnosing means based on the pulsation level change, as shown in the flowchart of FIG. In the flowchart of FIG. 12, first, in step 21, the control signal O sent to the solenoid 4 is turned off.
Determine N / OFF.

Here, for example, when it is determined that the ON control signal is output, the routine proceeds to step 22, and the pulsation width Q _PP obtained in the flowchart of FIG. 8 is set to the data corresponding to the ON state of the control signal. As Q _P-PON . In the next step 23, it is determined whether or not the elapsed time after the control signal is switched from OFF to ON matches the predetermined time (see FIG. 13). When it is determined that the time does not match the predetermined time, that is, the control signal is OF
A transitional state of switching the valve timing before a predetermined time has passed after switching from F to ON, or
When the control signal is in a stable ON state, this routine is directly terminated without performing diagnosis.

On the other hand, when it is determined in step 23 that the elapsed time after the control signal is switched from OFF to ON matches the predetermined time, the routine proceeds to step 24, where the pulsation width obtained most recently in the flowchart of FIG. Q _PP and pulsation width Q _P-POFF required in the OFF state before switching
A deviation from (pulsation width Q _PP just before switching from OFF to ON) is obtained, and it is determined whether or not the deviation (Q _{PP -QP-POFF} ) is a predetermined value or more.

As described above, by comparing the pulsation width immediately before switching from the control signal with the pulsation width at the time when it is estimated that the valve timing has actually been switched after switching the control signal, The two pulsation widths are sampled in a short time, and the change of the pulsation width due to ON / OFF of the control signal can be determined under substantially the same operating conditions.

Thus, in step 24, the pulsation width Q _PP in the OFF state before switching and the pulsation width Q _PP in the ON state after switching are set under substantially the same operating conditions.
Therefore, when the control signal is switched to ON and the valve timing is actually switched to a direction in which the overlap amount increases, the pulsation width increases due to an increase in intake inertia force. Q _PP should show an increasing change above a certain level.

In other words, when the control signal is switched from OFF to ON, if the pulsation width Q _{P- P} does not show an increase change commensurate with the switching of the valve timing, control is performed by a mechanical failure. It can be determined that the valve timing has not been switched according to the switching of the signal, and in this case, the process proceeds to step 25 to determine the system failure.

Similarly, even when the control signal is switched from ON to OFF, the pulsation width Q _{PP ON} in the ON state immediately before switching is obtained, and the valve timing is actually switched after being switched OFF. Pulsation width Q _PP and the pulsation width Q when the time to be considered has elapsed
_{When PP ON} is compared with Q _{PP ON-} Q _PP is not equal to or more than a predetermined value, it is determined that the valve timing switching according to the control signal is not actually performed, and the system failure is determined (step 26-Step 28).

Note that the control signal switching determined in step 23 or step 27 in the flowchart of FIG. 12 may be performed based on a preset desired switching condition. Forced ON
-It may be configured to switch off. Further, in each of the above embodiments, the pulsation level of the engine intake air is regarded as a change in the intake air amount, but the pulsation may be detected by another parameter such as pressure fluctuation.

Further, in the above-described 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.

[0043]

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 from the control unit, the intake pulsation is changed according to the switching of the valve timing. The fact that the valve timing is actually switched is diagnosed by utilizing the change in the level, so there is a mechanical failure of the valve timing control mechanism in addition to an electrical failure of the control signal output system. Can be diagnosed, and it is possible to provide highly reliable diagnostic results.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing the basic configuration of the present invention.

FIG. 3 is a system schematic diagram showing an embodiment of the present invention.

FIG. 4 is a diagram showing a state of hydraulic control when a control signal is on.

FIG. 5 is a diagram showing a state of hydraulic control in the off state of a control signal.

FIG. 6 is a diagram showing a change in opening / closing timing of an intake valve due to ON / OFF of a control signal.

FIG. 7 is a diagram showing an on / off operation region of a control signal.

FIG. 8 is a flowchart showing detection of an intake pulsation level according to the embodiment.

FIG. 9 is a flowchart showing diagnostic control based on pulsation level determination.

FIG. 10 is a diagram showing detection characteristics of pulsation width.

FIG. 11 is a diagram for explaining characteristics of a predetermined value used for pulsation level determination.

FIG. 12 is a flowchart showing diagnostic control based on a pulsation width change associated with valve timing switching control.

FIG. 13 is a diagram showing a pulsation width determination characteristic when switching valve timing.

[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 18-20 hydraulic fluid passage 21 plunger 22 helical gear 23 return spring

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

Claims (2)

[Claims] 1. A self-diagnosis device of a variable valve timing control device for variably controlling valve timing of an internal combustion engine based on a control signal from a control unit, comprising pulsation detecting means for detecting a pulsation level of engine intake air, The pulsation level detected by the pulsation detecting means is compared with a predetermined level set for each engine operating condition according to the control signal, and a failure of the variable valve timing control device is diagnosed based on the comparison result. A self-diagnosis device for a variable valve timing control device, comprising: pulsation level diagnosis means. 2. A self-diagnosis device of a variable valve timing control device for variably controlling valve timing of an internal combustion engine based on a control signal from a control unit, comprising pulsation detecting means for detecting a pulsation level of engine intake air, When the valve timing is switched based on the control signal, a change amount of the pulsation level detected by the pulsation detection means is obtained according to the valve timing switching, and the variable valve timing control device of the variable valve timing control device is based on the change amount. A self-diagnosis device for a variable valve timing control device, comprising: a pulsation level change diagnosing means for diagnosing a failure;