A method for simulating a fault of a response delay of a VVT system

Abstract

The application discloses a fault simulation method for VVT system response delay monitoring, comprising the following steps: S1, enabling the fault simulation function; S2, waiting for appropriate conditions and entering response diagnosis sampling; S3, taking the current VVT actual position as the required position of control and maintaining unchanged; S4, waiting for the completion of response diagnosis sampling; S5, calculating the VVT actual position change rate in the sampling process; S6, comparing the VVT actual position change rate with the diagnosis threshold of response delay; and S6, determining the fault result, and whether the fault simulation function is enabled can be determined according to the use requirement through the selection of the function switch. The fault simulation method for VVT system response delay monitoring has the effect that the VVT control under normal scenes is not affected, the function is only turned on when the fault needs to be simulated, and the flexibility is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicle diagnostic technology, and particularly relates to a fault simulation method for VVT system response delay monitoring. BACKGROUND

[0002] As an important component for improving the performance of gasoline engines, the continuously variable valve timing system / VVT (Variable Valve Timing) can adjust the opening and closing time of the intake valve according to the engine operating condition, and is widely used in the field of gasoline engines. The OBD system needs to monitor the working state of the VVT system to ensure that the system is working normally. The fault modes monitored by the OBD system include target error and response delay.

[0003] Since the VVT system is mainly composed of a phaser, a camshaft position sensor, a VVT control solenoid and VVT control software, the components in the system are fixedly installed inside the engine body. The opening of the solenoid is controlled by the control software to change the direction of the internal oil circuit, and the relative movement in the phaser is driven by the oil to change the valve timing relationship. Therefore, it is difficult to simulate the VVT response delay fault by processing the hardware.

[0004] The existing VVT response delay simulation scheme generally has the following three means, 1, by adjusting the PID parameters of VVT control, the actual position change of VVT is slowed down; 2, a resistor is connected in series on the control solenoid line; 3, an additional VVT control valve is connected on the control wire harness, and the actual position is always 0. The above-mentioned three fault simulation methods cannot reliably and stably demonstrate the fault, and the specific problems are as follows: scheme 1: it will affect the response rate in all operating conditions, and when the diagnosis is not sampled, it will also make the VVT response slow, and it is difficult for the diagnosis to enter (it is necessary to ensure that the actual VVT position and the expected VVT position are small in deviation to enter the response delay fault). In addition, if the control parameter adjustment is not appropriate, the target error fault will be reported in advance in the long-term steady state operating condition, and the demonstration fails; scheme 2: similar to scheme 1, by connecting a resistor, the control voltage of the VVT is divided, the actual control voltage is small, the speed in all operating conditions is slow, and the entering of the diagnosis is affected. In addition, the long-term position control deviation will cause the target error fault to be reported in advance, and the demonstration fails; scheme 3: the actual VVT position is always unchanged, and the target error fault is easily reported, and the demonstration fails. SUMMARY

[0005] In view of the above problems, the present application provides a fault simulation method for VVT system response delay monitoring, which aims to solve the problems in the prior art.

[0006] The specific technical solutions are as follows:

[0007] A fault simulation method for VVT system response delay monitoring, comprising the following steps:

[0008] S1, enabling the fault simulation function;

[0009] S2, waiting for appropriate conditions and entering response diagnosis sampling;

[0010] S3, taking the current VVT actual position as the control demand position and maintaining it unchanged;

[0011] S4, waiting for the completion of response diagnosis sampling;

[0012] S5, calculating the VVT actual position change rate during sampling;

[0013] S6, comparing the VVT actual position change rate with the diagnosis threshold of response delay;

[0014] S7, determining the fault result.

[0015] The fault simulation method for VVT system response delay monitoring has the following characteristics: the fault simulation function enabling in step S1 comprises:

[0016] When it is necessary to simulate the VVT system response delay fault, the function switch is turned on to ensure that the fault simulation function is enabled, and after the current driving cycle and the diagnosis conditions are met, the fault simulation mode is entered, that is, the actual position of the VVT at the current time is taken as the control target.

[0017] The fault simulation method for VVT system response delay monitoring has the following characteristics: the appropriate conditions in step S2 include the following three:

[0018] a, the deviation between the actual VVT position and the expected VVT position is small and lasts for a certain time;

[0019] b, the expected position change amount is counted, and when the change amount is greater than the limit value, the expected position change rate in this period of time is calculated;

[0020] c, when the expected position change rate is greater than the limit value, the response delay diagnosis sampling is entered.

[0021] The VVT system response lag monitoring fault simulation method has the characteristics that, in the step S3, the current VVT actual position is taken as the required position for controlling the VVT action and remains unchanged due to the fault simulation function, and the position deviation of the VVT, that is, the difference between the actual position and the expected position, is 0, and the VVT actual position remains basically unchanged after the PID control.

[0022] The VVT system response lag monitoring fault simulation method has the characteristics that, in the step S4, the conditions for waiting for the completion of the response diagnosis sampling are:

[0023] a. The sampling time meets the minimum time requirement;

[0024] b. The expected VVT change rate is less than a certain limit value or the expected VVT position deviation from the actual VVT position is small;

[0025] c. The VVT change direction needs to be kept in one direction during the sampling process.

[0026] The VVT system response lag monitoring fault simulation method has the characteristics that, in the step S5, the calculation method is that the VVT actual position change rate = position change amount / sampling time, when the fault simulation function is enabled, the actual VVT position remains unchanged after the sampling starts, and the calculated rate is 0; and when the fault simulation function is not enabled, the actual position changes according to the expected VVT change, and the calculated rate is large.

[0027] The VVT system response lag monitoring fault simulation method has the characteristics that, in the step S6, the comparison method is that, when the VVT actual position change rate is less than the response lag diagnosis threshold value, it is judged that the VVT response lag fault occurs; and when the VVT actual position change rate is greater than the response lag diagnosis threshold value, it is considered that the VVT response is normal and is not in a fault state.

[0028] In summary, the beneficial effects of the scheme are:

[0029] In the VVT system response lag monitoring fault simulation method, whether the fault simulation function is enabled can be determined by selecting the function switch according to the use requirements. The VVT system response lag monitoring fault simulation method has the effect of not affecting the VVT control in the normal scenario, and only opens the function when the fault needs to be simulated, and has the effect of high flexibility.

[0030] The VVT system response lag monitoring fault simulation method provided by the application has the effect of simulating faults and having less influence on engine performance.

[0031] The VVT system response lag monitoring fault simulation method provided by the application has the effect of simulating faults and having less influence on engine performance. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The VVT system response lag monitoring fault simulation method provided by the application has the effect of simulating faults and having less influence on engine performance. DETAILED DESCRIPTION

[0033] The technical solutions of the application will be clearly and completely described below with reference to the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, but not all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0034] It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other without conflict.

[0035] The application will be further described below with reference to specific embodiments, but the application is not limited by the embodiments.

[0036] Figure 1 The VVT system response lag monitoring fault simulation method provided by the application has the effect of simulating faults and having less influence on engine performance. Figure 1 The VVT system response lag monitoring fault simulation method provided by the application has the effect of simulating faults and having less influence on engine performance.

[0037] S1, enabling a fault simulation function;

[0038] S2, waiting for appropriate conditions and entering in response to diagnostic sampling;

[0039] S3, taking the current VVT actual position as a control demand position and maintaining unchanged;

[0040] S4, waiting for completion of response to diagnostic sampling;

[0041] S5, calculating a VVT actual position change rate in a sampling process;

[0042] S6, compare the VVT actual position change rate with the diagnostic threshold of response delay;

[0043] S7, determine the fault result.

[0044] It should be noted that, since in the daily use of the vehicle, the VVT system is normal, the control and response of the VVT can meet the normal use needs of the vehicle. When the fault simulation is needed, the fault simulation function is turned on, and in this mode, the simulation fault function can be enabled.

[0045] In the above embodiment, the fault simulation function enabling in step S1 includes:

[0046] When the response delay fault of the VVT system needs to be simulated, the function switch is turned on to ensure that the fault simulation function is enabled, and after the diagnostic conditions are met, the fault simulation mode is entered in the current driving cycle, that is, the actual position of the VVT at the current time is taken as the control target.

[0047] It should be noted that a function switch is set in the software, and the function is only turned on when the response delay fault needs to be demonstrated. For normal use scenarios, the function is not turned on, and it will not affect the normal work of the VVT system.

[0048] In the above embodiment, the appropriate conditions in step S2 include the following three:

[0049] a. The deviation between the actual VVT position and the expected VVT position is small and lasts for a certain time;

[0050] b. The change amount of the expected position is counted, and when the change amount is greater than the limit value, the change rate of the expected position in this period of time is calculated;

[0051] c. When the change rate of the expected position is greater than the limit value, the response delay diagnostic sampling is entered.

[0052] In the above embodiment, step S3 further includes: after entering the response delay diagnostic sampling, since the fault simulation function is enabled, the current VVT actual position is taken as the demand position for controlling the VVT actuation and remains unchanged, and lasts until the sampling is completed, in this process, the position deviation of the VVT, that is, the difference between the actual position and the expected position, is 0, and after PID control, the VVT actual position is basically unchanged.

[0053] In the above embodiment, the condition for waiting for the response diagnostic sampling to be completed in step S4 is:

[0054] a. The sampling time meets the minimum time requirement;

[0055] b. The rate of change of the desired VVT is less than a certain limit value or the deviation between the desired VVT position and the actual VVT position is small;

[0056] c. During the sampling process, the change direction of the VVT needs to be kept in one direction.

[0057] It should be noted that after entering the diagnosis, the demand VVT position will further change according to the operating conditions of the engine, the expected position rate after a certain position change is calculated, and when the change rate of the demand position is large enough, the response delay diagnosis can be further performed in this case. When the demand rate decreases or the deviation between the actual position and the demand position is small, and the minimum sampling time condition of the diagnosis is met, the sampling is ended. At this time, the expected position will be switched to the position according to the working condition table, and the actual VVT position will be released and no longer locked.

[0058] In the above embodiment, the calculation method in step S5 is: VVT actual position change rate = position change amount / sampling time. When the fault simulation function is enabled, the actual VVT position does not change after the sampling starts, and the calculated rate is 0. When the fault simulation function is not enabled, the actual position changes according to the expected VVT change, and the calculated rate is larger.

[0059] In the above embodiment, the comparison method of step S6 is: when the VVT actual position change rate is less than the response delay diagnosis threshold, it is judged that the VVT response delay fault occurs; when the VVT actual position change rate is greater than the response delay diagnosis threshold, it is considered that the VVT response is normal and is not in a fault state.

[0060] It should be noted that the diagnosis threshold is the response delay fault judgment standard, which is set according to the actual response rate of the normal state VVT system and the VVT actual response rate in the fault state. The diagnosis limit value is generally about 2° / s, and the response rate of the normal VVT system is generally above 10° / s.

[0061] The working principle is that a function switch is set, which is only started when the response delay fault needs to be demonstrated, and for normal use scene, the function is not opened, which does not affect the normal work of the VVT system. After the function is started, the response delay monitoring condition needs to be met, and when the monitoring condition is not met, the normal control of the VVT is not disturbed, so as to more easily enter the diagnosis state. When the response delay monitoring condition is met, the actual position of the VVT at this time is assigned to the target position of the VVT control, and is maintained unchanged in the diagnosis sampling window. After entering the diagnosis sampling window, the actual position of the VVT no longer changes, and after other diagnosis sampling completion conditions are met (minimum sampling time, expected position change rate, deviation of the actual position from the expected position, etc.), the change rate of the actual position can be calculated, the change rate of the actual position is compared with the preset diagnosis threshold of the response delay, and the fault can be judged, that is, the delay fault simulation is completed.

[0062] The above is only the preferred embodiment of the present application, and does not limit the implementation and protection scope of the present application. For those skilled in the art, it should be realized that any equivalent replacement and obvious change made by applying the content of the present application should be included in the protection scope of the present application.

Claims

1. A method of fault simulation for monitoring response sluggishness of a VVT system, characterized by, The method comprises the following steps: S1, enabling the fault simulation function, turning on the function switch, and ensuring that the fault simulation function is enabled; S2, waiting for suitable conditions and entering the diagnostic sampling in response, the suitable conditions including the following three: a. The deviation between the actual VVT position and the expected VVT position is small, and the deviation is maintained for a certain period of time; b. The variation amount of the expected position is counted, and when the variation amount is greater than the limit value, the variation rate of the expected position in the time period from the start of the expected position to the expected position variation amount greater than the limit value is calculated; c. When the variation rate of the expected position is greater than the limit value, the sampling in response to the slow diagnosis is entered; S3, taking the current continuous variable valve timing system VVT actual position as the required position of control, and maintaining the position unchanged, and continuing until the sampling is completed; S4, waiting for the completion of the sampling in response to the diagnosis, and the conditions for waiting for the completion of the sampling in response to the diagnosis include: a. The sampling time meets the minimum time requirement; b. The variation rate of the expected VVT is less than a certain limit value or the deviation between the expected VVT position and the actual VVT position is small; c. During the sampling process, the variation direction of the VVT needs to be maintained in one direction; S5, calculating the VVT actual position variation rate during the sampling process; S6, comparing the VVT actual position variation rate with the diagnosis threshold of the slow response; S7, determining the fault result.

2. The method of claim 1, wherein: The enabling of the fault simulation function in the step S1 includes: When the VVT system response slow fault needs to be simulated, the VVT actual position at the current time is taken as the control target in the current driving cycle and after the diagnosis conditions are met.

3. The method of claim 2, wherein: The step S3 further includes: after entering the sampling in response to the slow diagnosis, due to the enabling of the fault simulation function, the current VVT actual position is taken as the required position of the VVT actuation control and maintained unchanged, and the process continues until the sampling is completed, and during the process, the position deviation of the VVT, i.e. the difference between the actual position and the expected position, is 0, and after the PID control, it is ensured that the VVT actual position is basically unchanged.

4. The method of claim 3, wherein: The calculation method in the step S5 is VVT actual position variation rate = position variation amount / sampling time, when the fault simulation function is enabled, the actual VVT position is unchanged after the sampling starts, and the calculated rate is 0; and when the fault simulation function is not enabled, the actual position changes according to the expected VVT, and the calculated rate is larger.

5. The method of claim 4, wherein: The comparison method of the step S6 is that when the VVT actual position variation rate is less than the slow response diagnosis threshold, it is determined that the VVT response slow fault occurs; and when the VVT actual position variation rate is greater than the slow response diagnosis threshold, it is considered that the VVT response is normal and is not in a fault state.

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