JPS63214548A - Failure diagnosing device for vehicle speed sensor - Google Patents

Abstract

PURPOSE:To prevent erroneous judgment during slip by providing vehicle speed sensors on both front and rear sides so that when the difference between signals the sensors is large, a failure is determined in consideration with a time factor. CONSTITUTION:Discriminating sections 33, 32 receive pulse signals from front and rear wheel side vehicle speed sensors 26, 25 and determine vehicle speeds VF, VR, and a comparing part 50 in a fail-safe control section 39 compares the difference in vehicle speed ¦VR-VF¦ with a set value S. If ¦VR-VF¦>S, a counting section sets a predetermined time T0. After the time T0 elapses, a failure judging section 52 judges whether or not either the front wheel side speed VF or the rear wheel side vehicle VR is substantially zero, and a vehicle speed determining section 53 delivers a normal vehicle speed VR or VR to a control system. Thus, it is possible to surely prevent erroneous judgment during instant slip.

Description

[Detailed description of the invention] [Industrial use distribution]

The present invention relates to a failure diagnosis device for a vehicle in which vehicle speed sensors are provided on the front and rear wheels, and more particularly, to a device that prevents erroneous determination of temporary slippage.

[Conventional technology]

In the electronic control of automatic transmissions such as automatic transmission (AT) vehicles, the vehicle speed parameter plays an important role, so in consideration of the failure of this vehicle speed sensor, two vehicle speed sensors are generally installed to prevent failure. I am doing safe. Here, in a four-wheel drive vehicle, two vehicle speed sensors are provided on the front and rear wheels, and are also used for control when a slip occurs. Therefore, conventionally, regarding the above-mentioned four-wheel drive vehicle in which vehicle speed sensors are provided on the front and rear wheels, for example, Japanese Patent Application Laid-Open No. 56-138020
There is a prior art in the publication No. Here, it is shown that the vehicle speed difference between the front and rear wheels is detected and controlled, and this vehicle speed difference may also be used to determine the failure of the vehicle speed sensor. However, the front and rear wheel rotational speeds do not always match due to differences in tire effective diameter, etc., so it is not possible to determine a failure simply based on the difference.Furthermore, a failure in the vehicle speed sensor may be caused by a disconnection or short circuit in the circuit, causing no pulse signal to be output. Therefore, when the vehicle speed difference is greater than or equal to a set value, it is detected whether one of the vehicle speeds is zero or close to zero, and the output of the non-faulty vehicle speed sensor is used. If both vehicle speed sensors are normal,
The output of the vehicle speed sensor determined at the beginning is used.

[Problems to be solved by the invention]

By the way, in the prior art described above, even when a temporary slip occurs in one of the front and rear wheels, failure determination is immediately started when the vehicle speed difference increases. Then, there is a risk that the vehicle speed sensor on the side where the slip is not occurring may be mistakenly determined to be malfunctioning. The present invention has been made in view of the above points, and provides a fault diagnosis device for a vehicle speed sensor that correctly determines a fault in the vehicle speed sensor under normal driving conditions excluding the occurrence of a temporary slip. is intended to provide.

[Means to solve the problem]

In order to achieve the above object, the present invention provides vehicle speed sensors on each of the front and rear wheels, and in a control system that uses the vehicle speed sensor output determined first from one of them, when the difference between the two vehicle speed sensors is large, the time The system is configured such that failure determination groups are provided in consideration of various factors, and when one vehicle speed sensor is determined to be malfunctioning after the predetermined period of time has elapsed, the output of the other vehicle speed sensor is used.

[For production]

Based on the above configuration, even if the vehicle speed difference between the front and rear wheels is large, a failure is determined after a predetermined period of time has elapsed. This excludes cases where the vehicle slips temporarily and immediately recovers, and is only determined to be in a true failure state. I come to do it. In this manner, the present invention makes it possible to prevent erroneous determinations and improve failure determination accuracy.

【Example】

Embodiments of the present invention will be described below based on the drawings. Referring to FIG. 1, an outline of a four-wheel drive vehicle with an automatic transmission will be described. First, the crankshaft 1 of the engine E is connected to a torque converter 3. which has a lock-up clutch 2. It is connected to an automatic transmission 5 via an input shaft 4, and an output shaft 6 of the automatic transmission 5 is connected to a reduction gear 7, a front drive shaft 8. Front differential equipped! Transmission is configured directly to the front wheels via t9. Further, the output shaft 6 is connected to a transfer clutch 10. Rear drive shaft 1
1. Transmission is also configured to the rear wheels via the propeller shaft 12, rear differential device 13, etc. On the other hand, the automatic transmission l15 is provided with an electronic hydraulic control device 14, and the line pressure is controlled by a line pressure signal from a control unit 15 provided here. In addition, the lock-up clutch 2 is engaged when the two shift signals are turned on and off, and the 4W
The clutch torque of the transfer clutch 10 is variably controlled by the D signal. The control unit 15 includes a range switch 20. Idle switch 21. Cruise control signal 222 forced FF switch 23. Anti-skid braking switch 24. Rear wheel speed sensor 25. Front wheel speed sensor 26. The ignition pulse 27 signal is input. Also, the throttle sensor 28. An output signal from a torque converter oil (ATF) oil temperature sensor 29 is input via an A/D converter 31 . Rear wheel speed sensor 25. The signal of the front wheel speed sensor 26 is transmitted to each discrimination section 32.
．． 33, the vehicle speed is determined, and the ignition pulse 27 is used in a determination section 34 to determine the engine rotation speed. The control unit 15 is roughly divided into a gear shift control section 35, a line pressure control section 36. Lockup control section 37.4WD control section 38. Fail safe control unit 39. Abnormal part storage unit 4
0. It has a self-diagnosis control section 41. The speed change control section 35 is
The line pressure control unit 36 performs normal shift control, normal pattern and power pattern switching control, etc. The line pressure control unit 36 controls normal line pressure, gear shifting, and starting. The lock-up control unit 37 controls conditions within a predetermined range. At times, Rockara 1 is controlled. The 4WD control unit 38 performs clutch torque control under various driving conditions, occurrence of slip, and when the vehicle is stopped. The failsafe control section 39 includes a rear wheel speed sensor 25. Front wheel speed sensor 26. Throttle sensor 28. Range switch 2
0° Determine whether or not there is a failure in a solenoid (not shown), and perform control in the event of failure and forced FF control during vehicle inspection, etc.
The self-diagnosis control section 41 investigates the location where the failure has occurred and displays it on each monitor 43 via the monitor output control section 42. Shift control section 35. Line pressure control section 36. Lockup control section 3
7 and the output signals of the 4WD control section 38 are input to a solenoid output control section 44, which outputs on/off or duty ratio line pressure, speed change, lockup, and 4WD signals. Referring to FIG. 2, failure diagnosis of the vehicle speed sensor will be described.Front wheel vehicle speed sensor 26. The pulse signal of the rear wheel speed sensor 25 is subjected to vehicle speed determination by each determining section 32, 33, and the front and rear wheel speeds VF and VFL are input to the comparison section 50 of the fail-safe control section 39, and the vehicle speed difference IVIIL-VFI is determined from the set value S.
(for example, 10kIl/h). Then, when l Vl'L - VF l > SIJM, a certain time To is set in the count M51, and after this time To has elapsed, the failure determination unit 52 determines which of the front and rear wheel vehicle speeds VF and VR is approximately zero. , the vehicle speed determination unit 53 determines the normal vehicle speed ■
It is designed to output λ or VF. Next, the operation of the vehicle speed sensor failure diagnosis apparatus configured as described above will be described with reference to the flowchart of FIG. First, detect the car Mfl l VFL -VF I, and
In the case of VR-VF l≦S, the counter value of time To is always kept constant, and the rear wheel vehicle speed VR with less slip is output from the vehicle speed determination unit 53 and used for various controls. On the other hand, when a vehicle speed difference of 1.lambda.-VFI>S occurs, time To begins to be subtracted in the timer interrupt routine, and during this time the vehicle speed is maintained at the rear wheel speed VR described above. And time To
When 'ro=o' has elapsed, a failure is determined, and if the temporary slip returns to the original state and vH≠0,
Then, the rear wheel speed ■ is output. On the other hand, if the rear wheel speed sensor 25 is out of order and v4=o, the front wheel speed VF is determined by the vehicle speed determination section 53, and this front wheel speed VF is output instead to perform various controls. Note that the present invention can be applied not only to the FF base of the embodiment but also to a front engine/rear drive or a rear engine/rear drive base.

【Effect of the invention】

As described above, according to the present invention, in the failure determination based on the difference between the front and rear wheels and the sensor, by excluding the time of slip, it is possible to prevent erroneous determination in the time of slip. . Since the slip is temporary, the slip state can be easily and reliably removed with time.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an embodiment of the failure diagnosis device of the present invention, FIG. 2 is a block diagram of the main parts, and FIG. 3 is a flowchart of the operation. 25... Rear wheel speed sensor, 26... Front wheel speed sensor, 50... Comparison section, 51... Counting section, 52... Failure determining section, 53... Vehicle speed determining section Patent applicant Fuji Heavy Industries Co., Ltd. Agent Patent Attorney: Nobu Kobashi Jundo Patent Attorney: Susumu Murai

Claims (1)

[Claims] In a control system in which vehicle speed sensors are provided on each of the front and rear wheels and the output of the vehicle speed sensor determined first from one of the two is used, when the difference between the two vehicle speed sensors is large, the time factor is taken into account. A failure diagnosis device for a vehicle speed sensor, characterized in that a failure determination section is provided, and when one vehicle speed sensor is determined to be failure after the predetermined time elapses, the output of the other vehicle speed sensor is used.