JP3752387B2 - Diagnosis device for hydraulic variable valve timing mechanism - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a diagnostic device for a hydraulic variable valve timing mechanism, and more particularly to a failure diagnostic technique for a hydraulic variable valve timing mechanism that continuously changes valve timing by changing the rotational phase of an engine camshaft by hydraulic pressure.
[0002]
[Prior art]
Conventionally, in a vehicle engine, a variable valve timing mechanism is known in which the opening / closing timing of an intake valve and / or an exhaust valve is advanced or delayed by changing the rotational phase of a camshaft by hydraulic pressure (Japanese Patent Application Laid-Open No. 7-101). No. 233713, JP-A-8-246820, etc.).
[0003]
[Problems to be solved by the invention]
By the way, in the variable valve timing mechanism, if the target valve timing (rotation phase) cannot be controlled, the operability of the engine is greatly impaired. Therefore, it is diagnosed whether the actual valve timing matches the target. It is desirable.
[0004]
However, in the hydraulic variable valve timing mechanism, the actual valve timing gradually approaches the target after the change due to the response delay of the hydraulic pressure with respect to the step change of the target valve timing (rotation phase). Become. For this reason, if the actual valve timing is compared with the target immediately after the step change of the target, a failure is erroneously diagnosed based on the fact that there is a relatively large deviation between the two.
[0005]
Therefore, it is preferable to prohibit the diagnosis within a predetermined time immediately after the change of the target, but since there is a variation in the hydraulic pressure response, it is necessary to extend the time for which the diagnosis is prohibited in order to avoid erroneous diagnosis, On the other hand, there is a problem that the opportunity for diagnosis is lost. On the other hand, if the time for which the diagnosis is prohibited is relatively short in order to secure the diagnosis opportunity, the diagnosis is performed during the delay in the response of the hydraulic pressure, resulting in a misdiagnosis. There was a problem that there was a possibility.
[0006]
The present invention has been made in view of the above problems, and an object thereof is to provide a diagnostic device for a hydraulic variable valve timing mechanism capable of ensuring a diagnosis opportunity while avoiding a misdiagnosis due to a delay in response of hydraulic pressure. And
[0007]
[Means for Solving the Problems]
Therefore, the invention according to claim 1 is a hydraulic variable valve timing mechanism that continuously changes the valve timing by changing the rotational phase of the camshaft of the engine by the hydraulic pressure supplied by the hydraulic pump driven by the engine. Rotation phase detection means for detecting the rotation phase of the camshaft, and a target rotation phase and an actual rotation phase detected by the rotation phase detection means are compared to diagnose a failure of the hydraulic variable valve timing mechanism. A diagnostic means for performing, a diagnostic prohibiting means for prohibiting diagnosis by the diagnostic means until a delay time elapses from a change in the target rotational phase, and a delay time change for changing the delay time according to the engine speed And means.
[0008]
According to such a configuration, within the delay time immediately after the target rotational phase changes, a diagnosis is made to avoid erroneously diagnosing the occurrence of a failure based on the difference between the target and the actual rotational phase due to a delay in hydraulic response. Is prohibited . Here, the pump supplies hydraulic fluid to the hydraulic type variable valve timing mechanism is a pump of the type driven by the engine, the delay time is changed in accordance with the engine rotational speed correlating to discharging of the pump.
[0009]
According to a second aspect of the present invention , in the hydraulic variable valve timing mechanism that continuously changes the valve timing by changing the rotation phase of the camshaft of the engine by oil pressure, the rotation phase detection means detects the rotation phase of the camshaft. And a diagnostic means for diagnosing a failure of the hydraulic variable valve timing mechanism by comparing a target rotational phase and an actual rotational phase detected by the rotational phase detecting means, and a change in the target rotational phase. A diagnosis prohibiting unit that prohibits a diagnosis by the diagnostic unit and a delay time changing unit that changes the delay time according to an oil temperature until a delay time elapses. . According to such a configuration, by changing the delay time according to the oil temperature that correlates with the viscosity of the hydraulic oil, the delay time is changed in response to variations in the hydraulic response delay due to the viscosity.
[0010]
According to a third aspect of the present invention, there is provided a hydraulic variable valve timing mechanism for continuously changing a valve timing by changing a rotation phase of a cam shaft of an engine by oil pressure, and a rotation phase detecting means for detecting the rotation phase of the cam shaft. And a diagnostic means for diagnosing a failure of the hydraulic variable valve timing mechanism by comparing a target rotational phase and an actual rotational phase detected by the rotational phase detecting means, and a change in the target rotational phase. A diagnosis prohibiting means for prohibiting diagnosis by the diagnostic means until a delay time elapses, and a delay time changing means for changing the delay time in accordance with a change width of a target rotational phase. It is characterized by that. According to such a configuration, when the change width of the target rotational phase is large and the time required for the actual rotational phase to catch up with the target is long, the delay time can be changed longer.
[0011]
According to a fourth aspect of the present invention, in the hydraulic variable valve timing mechanism for continuously changing the valve timing by changing the rotation phase of the cam shaft of the engine by the hydraulic pressure, the rotation phase detecting means for detecting the rotation phase of the cam shaft. And a diagnostic means for diagnosing a failure of the hydraulic variable valve timing mechanism by comparing a target rotational phase and an actual rotational phase detected by the rotational phase detecting means, and a change in the target rotational phase. Until the delay time elapses, first diagnosis prohibiting means for prohibiting diagnosis by the diagnostic means, delay time changing means for changing the delay time according to operating conditions, and after completion of the diagnostic processing by the diagnostic means And second diagnosis prohibiting means for prohibiting diagnosis by the diagnostic means until the target rotational phase changes again. . According to this configuration, when the diagnosis is performed after the delay time has elapsed from the change in the target rotational phase, the diagnosis is prohibited until the step change in the target rotational phase occurs again.
[0012]
According to a fifth aspect of the present invention, the second diagnosis prohibiting means determines, based on a binary signal, whether or not the target rotational phase has changed again after the completion of the diagnostic processing by the diagnostic means. .
[0013]
【The invention's effect】
According to the first aspect of the present invention, there is an effect that the delay time can be appropriately set corresponding to the difference in the hydraulic response depending on the discharge amount of the pump supplying hydraulic oil . According to the second aspect of the present invention, there is an effect that the delay time can be appropriately set corresponding to the difference in the hydraulic response due to the viscosity of the hydraulic oil according to the oil temperature.
[0014]
According to the third aspect of the present invention, the delay time can be set appropriately in response to the change in the time required for the actual rotation phase to approach the target rotation phase due to the difference in the change width of the target rotation phase. effective. According to the fourth and fifth aspects of the present invention, diagnosis can be avoided while the actual rotational phase catches up with the target, and diagnosis is prohibited until the target rotational phase changes again after completion of the diagnostic process. There is an effect that can be done.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a system configuration of an engine provided with a hydraulic variable valve timing mechanism. In FIG. 1 , the air measured by the throttle valve 2 is supplied to the engine 1 through the intake valve 3 into the cylinder, and the combustion exhaust is discharged through the exhaust valve 4. The intake valve 3 and the exhaust valve 4 are opened and closed by cams provided on the intake side cam shaft and the exhaust side cam shaft, respectively.
[0016]
The intake side camshaft 5 is provided with a variable valve timing mechanism 6 that continuously advances or slows the opening / closing timing of the intake valve 3 by changing the rotational phase of the camshaft. The variable valve timing mechanism 6 is a hydraulic mechanism that continuously changes the rotational phase by the hydraulic pressure supplied by a positive displacement hydraulic pump driven by an engine. For example, the variable valve timing mechanism 6 is a hydraulic pressure that acts in the advance direction of the rotational phase. And the hydraulic pressure acting in the retarding direction are respectively controlled to control the rotational phase of the camshaft to a target rotational phase, and the hydraulic pressure is adjusted by a hydraulic pressure control signal from the control unit 7. It has become.
[0017]
Further, the variable valve timing mechanism 6 is provided with mechanical stoppers for restricting the change of the rotational phase in both the retarded direction and the advanced direction of the rotational phase. The position and the most retarded angle position are defined. Furthermore, a return spring that biases toward the most retarded position is provided. The retarding direction of the rotational phase of the camshaft 5 is a direction in which the overlap amount between the exhaust valve and the intake valve decreases.
[0018]
In the present embodiment, the variable valve timing mechanism 6 is configured to change the opening / closing timing of the intake valve 3, but may be configured to change the opening / closing timing of the exhaust valve 4 instead of the intake valve 3. However, a configuration in which the opening / closing timing of both the intake valve 3 and the exhaust valve 4 is changed may be employed. The control unit 7 incorporating the microcomputer includes a crank angle sensor 8 that outputs a rotation signal of the crankshaft, a cam angle sensor 9 that outputs a rotation signal of the intake camshaft 5, and an air flow that detects the intake air amount of the engine 1. The detection signal from the water temperature sensor 11 etc. which detects the cooling water temperature Tw of the meter 10 and the engine 1 is input.
[0019]
Then, for example, a target rotational phase (target valve timing) in the variable valve timing mechanism 6 is set according to the engine load, the engine rotational speed Ne, and the coolant temperature Tw, and a hydraulic pressure control signal corresponding to the target value is output. . Further, as shown in the flowchart of FIG. 2 , the control unit 7 has a function of performing a fault diagnosis of the variable valve timing mechanism 6 in software, and the function of the fault diagnosis will be described in detail below.
[0020]
In the flowchart of FIG. 2 , in S1, the engine speed Ne and the coolant temperature Tw are read. In S1, the coolant temperature Tw is used as a temperature correlated with the temperature of the hydraulic oil of the variable valve timing mechanism 6. Therefore, an oil temperature sensor for directly detecting the temperature of the hydraulic oil is provided, The detection result of the oil temperature sensor may be used instead of the cooling water temperature Tw.
[0021]
In S2, a map in which the basic delay time is stored in advance according to the engine speed Ne and the cooling water temperature Tw is referred to, and the basic delay time corresponding to the engine speed Ne and the cooling water temperature Tw read in S1 is searched ( Delay time changing means). The basic delay time is a basic value of a delay time from when a target rotational phase step change is made until diagnosis is performed (see FIG. 3 ), and the engine rotational speed Ne is high and constitutes the variable valve timing mechanism 6. When the discharge amount of the hydraulic pump is large, the response of the hydraulic pressure change becomes faster. Therefore, the basic delay time is set shorter as the engine speed Ne is higher. Further, when the coolant temperature Tw is low and the hydraulic oil temperature is estimated to be low, the hydraulic oil viscosity is low and leakage in the hydraulic path is reduced, so that the response to the hydraulic pressure change is faster than when the oil temperature is high. Therefore, the basic delay time is set shorter as the cooling water temperature Tw (oil temperature) is lower.
[0022]
In S3, it is determined whether or not there has been a step change in the target rotational phase (valve timing). When there is a step change in the target rotational phase, the process proceeds to S4, and a correction coefficient k for correcting the basic delay time is set according to the target rotational phase change width ΔT. Here, since the delay time until reaching the target becomes longer as the change width ΔT is larger, the correction coefficient k is set to correct the basic delay time more as the change width ΔT is larger. It has become.
[0023]
In S5, the basic delay time is multiplied by the correction coefficient k, and the result is set to the final delay time (delay time changing means). In S6, 1 is set in the flag F to indicate that the target rotational phase is in a state immediately after the step change. After S6, the process proceeds to S8, where it is determined whether or not the delay time has elapsed. If the delay time has not elapsed, the routine is terminated without performing diagnosis, and within the delay time. Diagnosis is prohibited (diagnosis prohibition means , first diagnosis prohibition means ).
[0024]
From the next time, if it is determined that there is no step change in the target rotational phase in S3, the process proceeds to S7 for determining the flag F. However, since 1 is set in the flag F, the process proceeds from S7 to S8. It is determined whether or not the delay time has passed again. When it is determined in S8 that the delay time has elapsed, the process proceeds to S9 (diagnostic means) to execute diagnostic processing.
[0025]
Specifically, an actual rotational phase difference between the crankshaft and the camshaft is detected based on detection signals from the crank angle sensor 8 and the cam angle sensor 9 (rotation phase detecting means), and the detected actual rotational position is detected. When the deviation between the phase difference and the target rotational phase at that time is greater than or equal to a predetermined value, the occurrence of a failure is determined, and if the deviation is less than the predetermined value, normality determination is performed. When the diagnosis process in S9 is completed, the process proceeds to S10 and the flag F is reset to zero. Therefore, until the step change of the target rotational phase occurs again, it is determined in S7 that the flag F is 0, so that this routine is terminated without making a diagnosis (second diagnosis prohibiting means) .
[0026]
According to the above configuration, when the delay time elapses after the target rotational phase has changed in steps, it is estimated that the actual rotational phase has reached the target rotational phase, and a failure occurs if the target rotational phase does not substantially match the target. The delay time is set in response to the fact that the hydraulic response until reaching the target differs depending on the engine speed Ne, the coolant temperature Tw (oil temperature), and the step change amount ΔT of the target rotation phase. Since the change is made, if it is normal, the diagnosis can be surely performed in a time close to the shortest time to reach the target, and the diagnosis opportunity can be ensured while ensuring the diagnosis accuracy.
[0027]
In the above embodiment, three parameters of the engine speed Ne, the cooling water temperature Tw (oil temperature), and the step change amount ΔT of the target rotation phase are used as parameters for changing the delay time. Only one or a combination of the two may be used.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of an engine in an embodiment.
FIG. 2 is a flowchart showing diagnosis control in the embodiment.
FIG. 3 is a time chart showing diagnosis timing in the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Throttle valve 3 ... Intake valve 4 ... Exhaust valve 5 ... Intake side cam shaft 6 ... Variable valve timing mechanism 7 ... Control unit 8 ... Crank angle sensor 9 ... Cam angle sensor
10 ... Air flow meter
11 ... Water temperature sensor

Claims (5)

In the hydraulic variable valve timing mechanism that continuously changes the valve timing by changing the rotation phase of the cam shaft of the engine by the hydraulic pressure supplied by the hydraulic pump driven by the engine ,
Rotational phase detection means for detecting the rotational phase of the camshaft;
A diagnostic means for performing a fault diagnosis of the hydraulic variable valve timing mechanism by comparing a target rotational phase and an actual rotational phase detected by the rotational phase detecting means;
Diagnosis prohibiting means for prohibiting diagnosis by the diagnostic means until a delay time elapses from a change in the target rotational phase;
A delay time changing means for changing the delay time according to the engine speed ;
An apparatus for diagnosing a hydraulic variable valve timing mechanism, comprising: In the hydraulic variable valve timing mechanism that continuously changes the valve timing by changing the rotational phase of the camshaft of the engine by hydraulic pressure,
Rotational phase detection means for detecting the rotational phase of the camshaft;
A diagnostic means for performing a fault diagnosis of the hydraulic variable valve timing mechanism by comparing a target rotational phase and an actual rotational phase detected by the rotational phase detecting means;
Diagnosis prohibiting means for prohibiting diagnosis by the diagnostic means until a delay time elapses from a change in the target rotational phase;
Delay time changing means for changing the delay time according to the oil temperature;
An apparatus for diagnosing a hydraulic variable valve timing mechanism, comprising: In the hydraulic variable valve timing mechanism that continuously changes the valve timing by changing the rotational phase of the camshaft of the engine by hydraulic pressure,
Rotational phase detection means for detecting the rotational phase of the camshaft;
A diagnostic means for performing a fault diagnosis of the hydraulic variable valve timing mechanism by comparing a target rotational phase and an actual rotational phase detected by the rotational phase detecting means;
Diagnosis prohibiting means for prohibiting diagnosis by the diagnostic means until a delay time elapses from a change in the target rotational phase;
A delay time changing means for changing the delay time according to a change width of a target rotational phase;
An apparatus for diagnosing a hydraulic variable valve timing mechanism, comprising: In the hydraulic variable valve timing mechanism that continuously changes the valve timing by changing the rotational phase of the cam shaft of the engine by hydraulic pressure,
Rotational phase detection means for detecting the rotational phase of the camshaft;
A diagnostic means for performing a fault diagnosis of the hydraulic variable valve timing mechanism by comparing a target rotational phase and an actual rotational phase detected by the rotational phase detection means;
First diagnosis prohibiting means for prohibiting diagnosis by the diagnostic means until a delay time elapses from a change in the target rotational phase;
Delay time changing means for changing the delay time according to operating conditions;
Second diagnostic prohibiting means for prohibiting diagnosis by the diagnostic means until the target rotational phase changes again after completion of the diagnostic processing by the diagnostic means;
An apparatus for diagnosing a hydraulic variable valve timing mechanism, comprising: 5. The hydraulic pressure according to claim 4, wherein the second diagnosis prohibiting unit determines based on a binary signal whether or not the target rotational phase has changed again after completion of the diagnostic process by the diagnostic unit. Type variable valve timing mechanism diagnostic device.

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