JP2008273280A - Acceleration slip detector for four-wheel drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acceleration slip detector for a four-wheel drive capable of reliably detecting a slip state even in the case that an adequate vehicle body speed cannot be obtained by the integration of an imaginary sensor value such as on an uphill road surface. <P>SOLUTION: The acceleration slip detector for the four-wheel drive comprises a wheel acceleration calculation means for calculating wheel acceleration based on the wheel speed, an acceleration slip determination means for determining the acceleration slip state of the vehicle when the wheel acceleration exceeds an acceleration slip determination threshold, and an acceleration slip determination release means for releasing the determination of the acceleration slip state when the wheel acceleration is below the slip determination threshold when the acceleration slip state is determined, and when it is determined that an accelerator is turned off. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an acceleration slip detection device for a four-wheel drive vehicle.

Conventionally, in the acceleration slip detection device for a four-wheel drive vehicle described in Patent Document 1, the vehicle speed is calculated by integrating the acceleration detected by the longitudinal acceleration sensor, and the difference between the vehicle speed and the wheel speed is calculated. If it is equal to or greater than the slip determination threshold, it is determined as a slip state, and if it is equal to or less than the grip determination threshold, it is determined as a grip state.
JP-A-1-113669

  However, in the above prior art, the vehicle body speed is calculated based on the detection value of the longitudinal acceleration sensor. For this reason, an acceleration greater than the actual longitudinal acceleration is detected on the uphill road surface, and the calculated value of the vehicle speed exceeds the actual value, and an appropriate vehicle speed cannot be obtained.

  Therefore, the difference between the vehicle speed and the wheel speed increases during a normal slip, but in the conventional technology, the difference between the vehicle speed and the wheel speed decreases when the uphill road surface slips. Regardless, there was a problem that the grip state was determined.

  The present invention has been made paying attention to the above problems, and the object of the present invention is to ensure a slip state even when an appropriate vehicle speed cannot be obtained by integration of acceleration sensor values such as an uphill road surface. It is another object of the present invention to provide an acceleration slip detection device for a four-wheel drive vehicle that can be detected.

  In order to achieve the above object, according to the present invention, in an acceleration slip detection device for a four-wheel drive vehicle, wheel acceleration calculation means for calculating wheel acceleration based on wheel speed, and when the wheel acceleration exceeds an acceleration slip determination threshold value Acceleration slip determination means for determining an acceleration slip state of the vehicle, and determination of the acceleration slip state when the wheel acceleration is less than the slip determination threshold and the accelerator is off when the acceleration slip state is determined. And an acceleration slip determination canceling means for canceling.

  Therefore, it is possible to determine acceleration slip regardless of the detection value of the longitudinal acceleration sensor, and even if the vehicle body speed cannot be obtained by integration of acceleration sensor values, such as uphill road surfaces, the slip state can be ensured. It is possible to provide an acceleration slip detection device for a four-wheel drive vehicle that can be detected easily.

  Hereinafter, the best mode for realizing an acceleration slip detection device for a four-wheel drive vehicle according to the present invention will be described based on an embodiment shown in the drawings.

[System configuration]
FIG. 1 is a system configuration diagram of a vehicle equipped with an acceleration slip detection device for a four-wheel drive vehicle according to a first embodiment. The vehicle is a four-wheel drive vehicle, and shows a front-wheel drive-based four-wheel drive vehicle that distributes the driving force of the front wheels to the rear wheels.

  The system generally includes a control unit ECU, a hydraulic unit HU, a yaw rate sensor 3, a lateral acceleration sensor 4, and a longitudinal acceleration sensor 5. The acceleration slip is detected by the control unit ECU.

  Each wheel FL to RR is provided with a wheel cylinder W / C (FL to RR), respectively, and supplied with hydraulic oil from the hydraulic unit HU via a pipe A (FL to RR) to generate a braking force. . Each wheel FL to RR is provided with a wheel speed sensor 7 and outputs each wheel speed VWS (FL to RR) to the control unit ECU.

  The steering mechanism 2 is provided with a steering angle sensor 6 and outputs the steering angle θ to the control unit ECU. The accelerator pedal 10 is provided with an accelerator opening sensor 11, which outputs the accelerator opening APO to the control unit ECU via the engine controller ECM. The control unit ECU drives the hydraulic unit HU based on each input information to generate a braking force.

  The torque of the engine ENG is transmitted to the front wheels FL and FR via the transmission T / M and is also transmitted to the rear wheels RL and RR via the transfer T / F.

  The engine controller ECM controls the engine ENG based on the accelerator opening APO. The transmission control unit ATCM performs bidirectional communication with the engine controller ECM and outputs a shift command to the transmission T / M.

(Normal braking)
When the brake pedal 9 is depressed by the driver, the pedaling force is assisted by the booster 12 to generate a master cylinder pressure, and each wheel cylinder W / C (FL to RR) is increased.

(During vehicle behavior control)
At the time of vehicle behavior control, the braking force is calculated in the control unit ECU based on each input information, and the hydraulic pressure unit HU is driven to generate the wheel cylinder pressure.

[Acceleration slip judgment control processing]
FIG. 2 is a flowchart illustrating a flow of acceleration slip determination control processing according to the first embodiment. Even when the appropriate vehicle speed VI cannot be obtained by integrating the acceleration sensor values, it is determined that the vehicle is in a non-slip state if the accelerator is off in order to reliably detect the slip state. Hereinafter, each step will be described.

  In step S1, the wheel acceleration ΔVWS (FL to RR) of each wheel FL to RR is calculated based on each wheel speed VWS (FL to RR), and the process proceeds to step S2.

In step S2, the result of the acceleration slip determination in the previous control is confirmed. If the acceleration slip determination flag is set, the process proceeds to step S3 as a slip state, and if not, the process proceeds to step S7 as a non-slip state.
The vehicle of the present application is a front wheel drive base and it is unlikely that the vehicle will slip from the rear wheels RL and RR first, and if at least the front wheels FL and FR are in an acceleration slip state, the rudder will not work, and a sensor system failure is detected. For this reason, the correlation between the plurality of pieces of sensor information being compared is lost, and there is a risk of erroneous diagnosis as a sensor failure.
Therefore, when both the wheel accelerations of the FL and FR wheels exceed the slip determination threshold (steps S2 → S7 → S8), it is determined that the vehicle is in an acceleration slip state.

  In step S3, it is determined whether or not the wheel acceleration of the FR wheel is less than the acceleration slip determination threshold. If YES, the process proceeds to step S4, and if NO, the control is terminated.

  In step S4, it is determined whether or not the wheel acceleration of the FL wheel is less than the acceleration slip determination threshold. If YES, the process proceeds to step S5, and if NO, the control is terminated.

In step S5, it is determined whether or not the accelerator opening APO is equal to or less than the accelerator-off determination threshold. If YES, the process proceeds to step S6, and if NO, the control is terminated.
Even if the wheel acceleration falls below the slip determination threshold, the risk of slipping has not been resolved if the accelerator opening is large. For this reason, if the acceleration slip cancellation determination is immediately performed when the slip determination threshold is not reached, the slip is erroneously detected even though the slip continues.
Therefore, after determining the slip of the front wheels FL and FR (steps S3 and S4), it is determined whether or not the accelerator is off by comparing the accelerator opening APO and the accelerator off determination threshold value. Therefore, the control is terminated while the slip determination flag is set (step S5).

In step S6, the acceleration slip determination flag is cleared and the control is terminated.
Even in the acceleration slip state (step S2) in the previous control, the wheel accelerations of the FL and FR wheels are both less than the slip determination threshold value and the accelerator opening APO is off (steps S3 → S4 → S5). The acceleration slip determination flag is cleared immediately, and the acceleration slip determination flag is cleared.

  In step S7, it is determined whether or not the wheel acceleration of the FR wheel is greater than or equal to the acceleration slip determination threshold. If YES, the process proceeds to step S8, and if NO, the control is terminated.

  In step S8, it is determined whether or not the wheel acceleration of the FL wheel is greater than or equal to the acceleration slip determination threshold. If YES, the process proceeds to step S9, and if NO, the control is terminated.

  In step S9, an acceleration slip determination flag is set, and the control is terminated.

[Change over time during acceleration slip judgment control]
FIG. 3 is a time chart during acceleration slip determination control in the first embodiment. The wheel speed and the wheel acceleration indicate a wheel speed VWS (FL, FR) and a wheel acceleration ΔVWS (FL, FR) of the front wheels FL, FR.

(Time t1)
At time t1, the wheel acceleration ΔVWS (FL, FR) increases as the wheel speed VWS (FL, FR) increases, and the acceleration slip determination flag is set above the slip determination threshold.

(Time t2)
At time t2, the accelerator opening APO falls below the OFF determination threshold, and the acceleration slip determination flag is cleared.

[Effect of Example 1]
(1) In the acceleration slip detection device for a four-wheel drive vehicle, wheel acceleration calculation means (step S1) for calculating the wheel acceleration ΔVWS based on the wheel speed VWS, and when the wheel acceleration ΔVWS exceeds the acceleration slip determination threshold, Acceleration slip determination means (steps S7 and S8) for determining the acceleration slip state, and when the wheel acceleration ΔVWS falls below the slip determination threshold when the acceleration slip state is determined and the accelerator is determined to be off (steps S3 → S4) → S5), it has acceleration slip determination cancellation means (step S6) for canceling the determination of the acceleration slip state.

Even if the wheel acceleration falls below the slip determination threshold, the risk of slipping has not been resolved if the accelerator opening is large. For this reason, if the acceleration slip cancellation determination is immediately performed when the slip determination threshold is not reached, the slip is erroneously detected even though the slip continues.
Therefore, after determining the slip of the front wheels FL and FR (steps S3 and S4), it is determined whether or not the accelerator is off by comparing the accelerator opening APO and the accelerator off determination threshold value. Therefore, the control is terminated while the slip determination flag is set (step S5).

  As a result, acceleration slip determination can be performed regardless of the detection value of the longitudinal acceleration sensor, and even if the vehicle body speed VI cannot be obtained by integration of acceleration sensor values such as an uphill road surface, the slip state Can be reliably detected. The idea of the present application can also be applied to a vehicle not equipped with a longitudinal acceleration sensor.

  Example 2 will be described. Since the basic configuration is the same as that of the first embodiment, only different points will be described. In the first embodiment, the acceleration slip is determined based on the wheel acceleration ΔVWS that is a differential value of the wheel speed VWS. In the second embodiment, the vehicle speed VI is calculated, and the acceleration is performed based on the difference ΔV between the vehicle speed VI and the wheel speed VWS. It differs in that it makes a slip judgment.

  In the second embodiment, the lowest value of the wheel speeds VWS (FL to RR) is set as the vehicle body speed VI. In this case, when all the four wheels slip, the vehicle body speed VI becomes a value higher than the actual value. Therefore, an upper limit value is set for the vehicle body speed VI.

[Acceleration Slip Judgment Control Processing in Embodiment 2]
FIG. 4 is a flowchart showing a flow of acceleration slip determination control processing in the second embodiment.

  In step S10, the vehicle body speed VI is calculated, and the process proceeds to step S11.

  In step S11, it is determined whether or not the acceleration slip determination flag is set in the previous control. If YES, the process proceeds to step S12, and if NO, the process proceeds to step S16.

  In step S12, it is determined whether or not the difference ΔV between the wheel speed VWS (FR) of the FR wheel and the vehicle body speed VI is less than the acceleration slip determination threshold. If YES, the process proceeds to step S13, and if NO, the control is terminated.

  In step S13, it is determined whether or not the difference ΔV between the wheel speed VWS (FL) of the FL wheel and the vehicle body speed VI is less than the acceleration slip determination threshold. If YES, the process proceeds to step S14, and if NO, the control is terminated.

  In step S14, it is determined whether or not the accelerator opening APO is equal to or less than the accelerator-off determination threshold. If YES, the process proceeds to step S15, and if NO, the control is terminated.

  In step S15, the acceleration slip determination flag is cleared and the control is terminated.

  In step S16, it is determined whether or not the difference ΔV (FR) between the wheel speed VWS (FR) of the FR wheels and the vehicle body speed VI is equal to or greater than the acceleration slip determination threshold value. If YES, the process proceeds to step S17. finish.

  In step S17, it is determined whether or not the difference ΔV (FL) between the wheel speed VWS (FL) of the FL wheel and the vehicle body speed VI is equal to or greater than the acceleration slip determination threshold value. If YES, the process proceeds to step S18. finish.

  In step S18, an acceleration slip determination flag is set, and the control is terminated.

[Change in Acceleration Slip Judgment with Time in Example 2]
FIG. 5 is a time chart of the acceleration slip determination control in the second embodiment.

(Time t3)
At time t3, the difference ΔV between the wheel speed VWS (FL, FR) and the vehicle body speed VI becomes equal to or greater than the slip determination threshold, and the acceleration slip determination flag is set.

(Time t4)
Although the difference ΔV falls below the acceleration slip determination threshold at time t4, the acceleration slip determination flag is not cleared because the accelerator opening APO is greater than or equal to the accelerator off determination threshold.

(Time t5)
At time t5, the difference falls below the acceleration slip determination threshold, the accelerator opening APO falls below the off determination threshold, and the acceleration slip determination flag is cleared.

[Effect of Example 2]
(2) Vehicle speed calculation means (step S10) for calculating the vehicle speed VI based on the vehicle information (wheel speed VWS), and when the difference ΔV between the wheel speed VWS and the vehicle speed VI exceeds the acceleration slip determination threshold, Acceleration slip determination means (steps S16 and S17) for determining the acceleration slip state, and when it is determined that the acceleration slip state is detected, the difference ΔV is below the acceleration slip determination threshold value and the accelerator is determined to be off (step S12 → S13 → S14), and an acceleration slip determination canceling means (step S15) for canceling the determination of the acceleration slip state.

  Thereby, the same effect as Example 1 can be acquired.

  Example 3 will be described. In the third embodiment, a sensor failure diagnosis process based on the acceleration slip determination of the first and second embodiments will be described.

  In order to detect a failure in the sensor system, there is a method that uses a correlation between a plurality of pieces of sensor information. Specifically, there is a method of converting the outputs of the yaw rate sensor 3, the lateral acceleration sensor 4 and the steering angle sensor 6 into a common unit and comparing these outputs.

  However, if slip occurs, the rudder becomes ineffective, and the correlation between the sensor information is lost. If sensor failure diagnosis is performed at this time, there is a risk of erroneous diagnosis as abnormal even if the sensor is normal. Therefore, sensor failure diagnosis is not performed while the acceleration slip determination flag is set.

[Sensor fault diagnosis permission flow]
FIG. 6 is a sensor failure diagnosis permission flow.

  In step S20, the output unit of the output signal of each wheel speed sensor 7 is converted, and the process proceeds to step S21.

  In step S21, it is determined whether or not the acceleration slip determination flag is set. If YES, the control ends. If NO, the process proceeds to step S22.

  In step S22, a sensor failure diagnosis process is executed and the control is terminated.

[Effect of Example 3]
The reliability of sensor failure diagnosis can be improved by not performing sensor failure diagnosis during acceleration slip determination in which an accurate correlation between sensor values cannot be obtained.

[Other embodiments]
The best mode for carrying out the present invention has been described based on the embodiments. However, the specific configuration of the present invention is not limited to each embodiment, and the scope of the invention is not deviated. Design changes and the like are included in the present invention.

1 is a system configuration diagram of a vehicle equipped with an acceleration slip detection device for a four-wheel drive vehicle in Embodiment 1. FIG. 3 is a flowchart illustrating a flow of acceleration slip determination control processing in the first embodiment. 3 is a time chart at the time of acceleration slip determination control in the first embodiment. 6 is a flowchart illustrating a flow of acceleration slip determination control processing in the second embodiment. 6 is a time chart of acceleration slip determination control in Embodiment 2. It is a sensor failure diagnosis permission flow in Example 3.

Explanation of symbols

2 Steering mechanism 3 Yaw rate sensor 4 Lateral acceleration sensor 5 Longitudinal acceleration sensor 6 Steering angle sensor 7 Wheel speed sensor 9 Brake pedal 10 Accelerator pedal 11 Accelerator opening sensor 12 Booster A Piping ATCM Transmission control unit ECM Engine controller ECU Control unit ENG Engine FL ~ RR Wheel HU Hydraulic unit T / F Transfer T / M Transmission W / C Wheel cylinder

Claims (2)

In an acceleration slip detection device for a four-wheel drive vehicle,
Wheel acceleration calculating means for calculating wheel acceleration based on the wheel speed;
Acceleration slip determination means for determining an acceleration slip state of the vehicle when the wheel acceleration exceeds an acceleration slip determination threshold;
Acceleration slip determination canceling means for canceling the determination of the acceleration slip state when the wheel acceleration falls below the slip determination threshold when it is determined that the acceleration slip state is determined and the accelerator is determined to be off. An acceleration slip detection device for a four-wheel drive vehicle. In an acceleration slip detection device for a four-wheel drive vehicle,
Vehicle body speed calculating means for calculating the vehicle body speed based on the vehicle information;
An acceleration slip determination means for determining an acceleration slip state of the vehicle when a difference between the wheel speed and the vehicle body speed exceeds an acceleration slip determination threshold;
Acceleration slip determination that cancels the determination of the acceleration slip state when it is determined that the difference between the wheel speed and the vehicle body speed is less than the acceleration slip determination threshold value and the accelerator is off when the acceleration slip state is determined. An acceleration slip detection device for a four-wheel drive vehicle, comprising: a release means.

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