JP2000054869A - Diagnostic device for variable valve timing mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform failure diagnosis based on the abnormal of a rotational phase with high accuracy even though detected signals from a cam sensor are dispersed in a variable valve timing mechanism varying the rotational phase of a camshaft. SOLUTION: When a diagnostic condition is set up (S1), the rotational phase of a camshaft is detected (S2) as a generation interval from the detected signal of a crank angle sensor to the detected signal of a cam sensor. This detected rotational phase of the camshaft and a target value are compared with each other and existence of failure is judged (S3), and when judging failure, a diagnostic counter is counted up (S4), and when judging as normal (judgment having no failure), the diagnostic counter is cleared (S7). When the diagnostic counter shows a predetermined value N or more and failures are judged successively N times or more, the final failure diagnostic signal is outputted (S5→S6).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diagnostic apparatus for a variable valve timing mechanism, and more particularly, to a failure diagnosis technique for a variable valve timing mechanism that continuously changes a valve timing by changing a rotation phase of a camshaft of an engine. .

[0002]

2. Description of the Related Art Conventionally, in a vehicle engine, an intake valve and / or
Alternatively, a variable valve timing mechanism that advances or delays the opening / closing timing of an exhaust valve has been known (see Japanese Patent Application Laid-Open Nos. Hei 7-233713 and Hei 8-246820).

[0003]

If the variable valve timing mechanism cannot control the target valve timing (rotational phase), the operability of the engine is greatly impaired. It is desired to diagnose whether they match.

Here, when the actual valve timing is detected as the rotational phase of the camshaft with respect to the crankshaft,
Although it is necessary to take out a rotation signal from the camshaft, for example, when a plurality of detected portions formed on a plate supported by the camshaft are detected by a detecting device such as an electromagnetic pickup or a Hall element, the plurality of detected portions are detected. Although the valve timing (rotational phase) is actually constant due to the variation in the formation position of the detected portion, the detection result of the rotational phase varies for each of the detected portions, and as a result, There is a possibility that the detection result of the rotation phase exceeds the failure determination level and the occurrence of the failure is erroneously diagnosed (see FIG. 6).

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a diagnostic apparatus which does not erroneously diagnose the occurrence of a failure even if the detection result of the rotational phase varies among the detected parts. Aim.

[0006]

Therefore, the invention according to claim 1 is configured as shown in FIG. In FIG. 1, a variable valve timing mechanism is a mechanism that changes the rotation phase of a camshaft of an engine to continuously change valve timing. The rotation phase detection means detects the rotation phase of the camshaft, and the failure determination means compares a target rotation phase with an actual rotation phase detected by the rotation phase detection means to determine the variable valve timing mechanism. Is determined.

The failure diagnosis signal output means finally diagnoses the occurrence of a failure in the variable valve timing mechanism when the failure determination by the failure determination means continues for a predetermined number of times, and outputs a failure diagnosis signal. Output. According to such a configuration, even if the actual rotation phase of the camshaft is compared with the target, and an abnormality in the rotation phase is determined, it is not immediately determined as a failure of the variable valve timing mechanism,
The failure is finally diagnosed only when the failure determination based on the detection result of the rotational phase is continued for a predetermined number of times or more.

According to the present invention, the rotation phase detecting means includes a cam sensor for extracting a plurality of rotation signals per cycle from a camshaft, a crank angle sensor for extracting a rotation signal from a crankshaft, and a rotation from the cam sensor. And a phase difference detecting means for detecting a phase difference between the signal and the rotation signal from the crank angle sensor.

According to this configuration, the cam sensor is a sensor that extracts a plurality of rotation signals per cycle from the camshaft, and includes a plurality of detected parts. If there are variations in the formation positions of the detected parts. Although the detection result of the rotation phase varies, the final failure determination is not performed unless the detection result of the rotation phase continuously exceeds the failure determination level.

According to the third aspect of the present invention, the failure diagnosis signal output means counts up a counter every time a failure is determined by the failure determination means, and clears the counter when the failure determination means determines normality. Clearing means for outputting a failure diagnosis signal when the value of the counter is equal to or greater than a predetermined value.

According to this configuration, the value of the counter is counted up each time a failure is determined based on the detection result of the rotational phase. However, when the counter is cleared at the normal determination, the value of the counter decreases the number of continuous failure determinations. That is, when the value of the counter is equal to or more than the predetermined value, it means that the number of consecutive failure determinations is equal to or more than the predetermined value.

[0012]

According to the first aspect of the present invention, even if a failure is determined temporarily due to a variation in the detection result of the rotation phase, the final failure is not determined for the variable valve timing mechanism. This has the effect of preventing erroneous diagnosis due to the variation.

According to the second aspect of the present invention, even if the detection result of the rotation phase varies for each of the detected parts due to the variation in the formation positions of the plurality of detected parts provided in the cam sensor, an erroneous diagnosis due to the variation occurs. There is an effect that can be prevented. According to the third aspect of the present invention, it is possible to easily obtain the number of times of continuous failure determination based on the detection result of the rotation phase, thereby easily causing an erroneous diagnosis due to a variation in the detection result of the rotation phase. The effect is that it can be prevented.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram illustrating a system configuration of an engine including a variable valve timing mechanism. In FIG. 2, air measured by a throttle valve 2 is supplied to a cylinder via an intake valve 3, and combustion exhaust is discharged via an exhaust valve 4 to the engine 1. The intake valve 3 and the exhaust valve 4 are opened and closed by cams provided on the intake camshaft and the exhaust camshaft, respectively.

The intake-side camshaft 5 is provided with a variable valve timing mechanism 6 for changing the rotational phase of the camshaft to continuously advance or delay the opening / closing timing of the intake valve 3. The variable valve timing mechanism 6 is a hydraulic mechanism that continuously changes the rotation phase by hydraulic pressure supplied by a positive displacement hydraulic pump driven by an engine. For example, a hydraulic pressure mechanism that acts in the advance direction of the rotation phase And a hydraulic pressure acting in the retard direction to control the rotational phase of the camshaft to a target rotational phase. The hydraulic pressure is adjusted by a hydraulic control signal from the control unit 7. Has become.

Further, the variable valve timing mechanism 6 is provided with a mechanical stopper for restricting the change of the rotation phase in both the retard direction and the advance direction of the rotation phase. The most advanced position and the most retarded position are defined. Further, a return spring that biases toward the most retarded position is provided. The direction in which the rotational phase of the camshaft 5 is retarded is a direction in which the amount of overlap between the exhaust valve and the intake valve decreases.

In the present embodiment, the variable valve timing mechanism 6 is configured to change the opening / closing timing of the intake valve 3.
May be configured to change the opening / closing timing of
The opening and closing timing of both the intake valve 3 and the exhaust valve 4 may be changed. A control unit 7 containing a microcomputer includes a crank angle sensor 8 for outputting a crankshaft rotation signal, a cam sensor 9 for outputting a rotation signal of the intake camshaft 5, and an air flow meter 10 for detecting an intake air amount of the engine 1. , Engine 1
A detection signal from the water temperature sensor 11 or the like for detecting the cooling water temperature Tw is input.

As shown in FIG. 3, the cam sensor 9 has a concave portion 9a as a portion to be detected formed at every 90 °, a plate 9b supported by the cam shaft 5, and a hole for detecting the concave portion 9a. And a detection device 9c composed of elements. The engine 1 of the present embodiment is an in-line four-cylinder engine,
90 °, which is the interval at which the concave portions 9a are formed, is 18 ° in crank angle.
The crank angle of 180 ° corresponds to the stroke phase difference of each cylinder. On the other hand, the crank angle sensor 8 outputs a detection signal every 180 degrees of the crank angle (see FIG. 4).

The control unit 7 sets a target rotation phase (target valve timing) in the variable valve timing mechanism 6 according to, for example, an engine load, an engine rotation speed Ne, and a coolant temperature Tw, and corresponds to the target value. Outputs hydraulic control signal. Further, as shown in the flowchart of FIG. 5, the control unit 7 has a function of performing a failure diagnosis of the variable valve timing mechanism 6 by software. The function of the failure diagnosis will be described in detail below.

The flowchart of FIG. 5 is executed every time a detection signal is output from the crank angle sensor 8 at every crank angle of 180 °.
It is determined whether the diagnosis condition is satisfied. For example, it is preferable that the diagnosis condition be that a predetermined time or more has elapsed since the step change of the target rotational phase.

If the diagnostic conditions are not satisfied, the program proceeds to S7
Then, as will be described later, the diagnostic counter for counting the number of failure determinations is cleared, and this routine ends. On the other hand, when it is determined that the diagnosis condition is satisfied, the process proceeds to S2 (rotational phase detecting means), and the rotational phase of the cam shaft 5 is detected. As shown in FIG. 4, the rotation phase of the camshaft is detected by measuring the time from when the detection signal from the crank angle sensor 8 is generated to when the detection signal is generated from the cam sensor 9, and the time is used as the engine time at that time. This is performed by converting the angle into an angle based on the rotation speed (phase difference detecting means). In the present embodiment, four detection signals are output from the cam sensor 9 per cycle (per rotation of the camshaft 5), so that the rotation phases detected four times during one cycle are the four detection signals of the cam sensor 9, respectively. The detection is performed based on the concave portion 9a.

In S3, a failure determination of the variable valve timing mechanism is performed based on whether the absolute value of the deviation between the rotation phase detected in S2 and the target rotation phase is equal to or greater than a predetermined value (failure determination). means). Here, if the absolute value of the deviation is equal to or more than a predetermined value and a failure determination of the variable valve timing mechanism is made, the process proceeds to S4, where the diagnostic counter is incremented by 1 (count-up means). Is smaller than the predetermined value and the actual rotational phase substantially matches the target value, the routine proceeds to S7, where the diagnostic counter is cleared (reset to 0) (clear means). Therefore, the diagnostic counter counts the number of times that a failure is determined continuously.

When the diagnostic counter is incremented by one in S4, the process proceeds to S5, and it is determined whether or not the count number of the diagnostic counter is equal to or more than a predetermined value N. If the count value of the diagnostic counter is equal to or greater than the predetermined value N, the process proceeds to S6, where a final failure determination of the variable valve timing mechanism 6 is performed, and a failure diagnostic signal is output (failure diagnostic signal). Output means).

Incidentally, based on the output of the failure diagnosis signal,
It is preferable that a warning is issued on the driver's seat of the vehicle on which the engine 1 is mounted to alert the user of the occurrence of a failure in the variable valve timing mechanism 6 or that the history of the failure determination is stored in the control unit 7. As described above, if the failure diagnosis signal is output for the first time when the failure determination is continuously performed at the predetermined value N or more, as shown in FIG. Even if the rotational phase detected for each concave portion 9a varies, and even if a rotational phase abnormality is temporarily detected due to the variation, the final failure diagnosis is not performed based on the abnormality detection, and the variation is detected. This can prevent erroneous diagnosis from occurring.

It is apparent that the configuration of the cam sensor 9 is not limited to the configuration shown in FIG.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a diagnostic apparatus according to the first embodiment.

FIG. 2 is a system configuration diagram of an engine according to the embodiment.

FIG. 3 is a diagram showing a configuration of a cam sensor according to the embodiment.

FIG. 4 is a time chart showing characteristics of detection signals of a cam sensor and a crank angle sensor in the embodiment.

FIG. 5 is a flowchart illustrating diagnostic control according to the embodiment;

FIG. 6 is a time chart showing characteristics of a rotation phase due to variations in cam sensors.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Throttle valve 3 Intake valve 4 Exhaust valve 5 Intake side camshaft 6 Variable valve timing mechanism 7 Control unit 8 Crank angle sensor 9 Cam angle sensor 10 Air flow meter 11 Water temperature sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 45/00 362 F02D 45/00 362K G01M 15/00 G01M 15/00 Z F-term (Reference) 2G087 AA01 AA15 BB17 CC02 CC03 EE21 FF21 3G016 AA08 AA19 BA02 BA05 BA38 BB04 CA13 CA27 DA01 DA22 DA23 GA00 3G084 BA23 DA21 EA04 EA07 EA11 EB02 EB22 EB24 EC02 EC03 FA00 FA38 3G092 AA11 DA10 DA12 EA08 EB08 EB17 EB08 EB08 HE04Z

Claims (3)

[Claims] 1. A variable valve timing mechanism for continuously changing a valve timing by changing a rotation phase of a camshaft of an engine, wherein: a rotation phase detection means for detecting a rotation phase of the camshaft; Comparing the actual rotation phase detected by the rotation phase detection means with a failure determination means for performing a failure determination of the variable valve timing mechanism; and the failure determination by the failure determination means is continuously performed a predetermined number of times or more. And a failure diagnosis signal output means for finally diagnosing the occurrence of a failure in the variable valve timing mechanism and outputting a failure diagnosis signal. . 2. A cam sensor for extracting a plurality of rotation signals per cycle from a camshaft, a crank angle sensor for extracting rotation signals from a crankshaft, a rotation signal from the cam sensor, and the crank angle sensor. The diagnostic device for a variable valve timing mechanism according to claim 1, further comprising: a phase difference detecting unit configured to detect a phase difference between the rotation signal and the rotation signal. 3. The failure diagnosis signal output means includes: a count-up means for counting up a counter for each failure determination by the failure determination means; and a clear means for clearing the counter when the failure determination means determines normality. The diagnostic device for a variable valve timing mechanism according to claim 1, wherein the diagnostic device is configured to output a failure diagnostic signal when a value of the counter is equal to or greater than a predetermined value.