JPH02267028A - Driving power distribution controller of four-wheel drive vehicle - Google Patents

Abstract

PURPOSE:To avoid generation of objectionable conditions such as decreased durability of a driving system by detecting the improper output value of the difference between rotational speeds of front wheels and rear wheels based on the possible continuous accelerating and decelerating times of a vehicle, and carrying out prescribed fail-safe operation immediately if any abnormal condition is found. CONSTITUTION:A torque distribution switch (a) is provided on the way to one engine driving system of front and rear wheels for the other engine driving system of the front and rear wheels, and the tightening command value suited to the output from the detecting means (b) of the difference between rotational speeds of front and rear wheels is outputted from a driving power distribution control means (c) to change the distribution of transmitted engine driving force. A detecting means (d) for abnormal output value of the difference in rotational speed, if the duration of the condition where the detected value of the detecting means (b) is above a prescribed point goes beyond the setting time based on the possible continuous accelerating and decelerating time of a vehicle, detects it as an abnormal output, so that a fail-safe operating means (e) carries out a prescribed fail-safe operation. It is thus possible to prevent objectionable conditions such as decreased durability of the driving system, increased traveling resistance and generated tight corner braking.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a drive force distribution control device for a four-wheel drive vehicle that is capable of changing drive force distribution between front and rear wheels, and particularly to fail-safe technology thereof.

(Prior Art) Conventionally, as a driving force distribution control device for a four-wheel drive vehicle, for example, as described in Japanese Patent Laid-Open No. 13331/1980, a rotational speed difference detected by front and rear wheel rotational speed difference detection means is used. A device is known that increases or decreases the clutch engagement force based on the output value and varies the distribution of engine drive power between the front and rear wheels.This device suppresses drive wheel slip while taking advantage of the maneuverability that is the advantage of rear-wheel drive vehicles. In order to improve performance, the relationship between the front and rear wheel rotational speed difference (rear wheel - front wheel) and the clutch engagement force (front wheel drive torque) is determined.When the front and rear wheel rotational speed difference is small, the front wheel drive torque is reduced, The setting is such that the front wheel drive torque increases as the torque increases, and the control is such that the difference in rotational speed between the front and rear wheels always converges to zero.

(Problem to be Solved by the Invention) However, in such a conventional driving force distribution control device, the clutch of the torque distribution clutch is Since this is a device that controls the fastening force, if the output value of the front and rear wheel rotational speed difference, which is control input information, is abnormal for some reason, the predetermined If the output value is the difference in rotational speed between the front and rear wheels, the clutch engagement force will always be applied, and when the difference in rotational speed between the front and rear wheels actually occurs, the latch will be latched if the difference in rotational speed between the front and rear wheels is greater than the required value. A fastening force is applied, resulting in problems such as a decrease in the durability of the drive system, an increase in running resistance, and occurrence of tight corner flex.

In addition, causes for abnormal front and rear wheel rotational speed difference output values include, for example, an abnormality in the wheel speed sensor (different number of teeth on the sensor rotor, temporary disconnection of the sensor and harness, etc.) and tires of the front and rear wheels with different diameters ( Temper tire installation, tire wear, air pressure, etc.)
etc.

The present invention was made with attention to the above-mentioned problems, and the present invention directly transmits engine driving force to one of the front and rear wheels.
On the other hand, it is an object of the present invention to promptly solve the problem that occurs when an abnormality in the output value of the difference in rotational speed between front and rear wheels is left unaddressed in a four-wheel drive vehicle of a torque split type in which torque is transmitted via a torque distribution clutch.

(Means for Solving the Problems) In order to solve the above problems, in the driving force distribution control device for a four-wheel drive vehicle of the present invention, an abnormality in the output value of the front and rear wheel rotational speed difference is detected during a continuous acceleration/deceleration period of the vehicle. Detection is based on the system, and when an abnormality is detected, a predetermined fail-safe operation is immediately performed.

In other words, as shown in the complaint response diagram in Figure 1, a drive system that connects the engine directly to one of the front and rear wheels is installed midway through the drive system to the other of the front and rear wheels, and the engine driving force to be transmitted is transferred from the outside. A torque distribution clutch a that can be changed by engagement force control, and a driving force distribution control means C that outputs an engagement force command value to the torque distribution clutch according to the output value from the front and rear wheel rotational speed difference detection means. and rotational speed difference output value abnormality detection, which detects that the output value is abnormal when the output value of the front and rear wheel rotational speed difference exceeds a set time based on the duration of the state exceeding a predetermined value or the continuous acceleration/deceleration time of the vehicle. means d;
The present invention is characterized by comprising fail-safe operation means e that performs a predetermined fail-safe operation when an abnormality signal is output from the rotational speed difference output value abnormality detection means d.

(Function) When the rotational speed difference output value is normal, the driving force distribution control means d outputs a fastening force command value according to the output value from the front and rear wheel rotational speed difference detection means C to the torque distribution clutch a. Ru.

Therefore, the distribution of driving force to the front and rear wheels is optimally controlled to suppress drive wheel slip.

When the rotational speed difference output value is abnormal, the rotational speed difference output value abnormality detection means e determines the duration of the state in which the front and rear wheel rotational speed difference output value exceeds a predetermined value for a set time based on the continuous acceleration/deceleration time of the vehicle. When it exceeds the rotational speed difference output value, it is detected that the rotation speed difference output value is abnormal, and the fail-safe operation means f performs a predetermined fail-safe operation such as weakening the clutch engagement force or issuing an alarm.

Therefore, an abnormality in the front and rear wheel rotational speed difference output value is accurately detected, and problems that may occur if this output value abnormality is left untreated, such as decreased durability of the drive system, increased running resistance, and occurrence of tight corner flex, etc. can be quickly resolved.

(Example) Embodiments of the present invention will be described below based on the drawings.

Figure 2 shows the torque split control system of a four-wheel drive vehicle (
1 is an overall system diagram including a drive system to which a driving force distribution control device (driving force distribution control device) is applied and a braking system to which a four-wheel anti-lock brake control system is applied. First, the configuration of the torque split control system will be described.

The vehicle to which the torque split control system of the embodiment is applied is a rear wheel-based four-wheel drive vehicle, and its drive system includes an engine 1. Transmission 2゜Transfer input shaft 3
．． Rear propeller shaft 4. rear differential 5
．． Rear wheel 6. Transfer output shaft Y, front propeller shaft 8°, front differential 9. The engine driving force passing through the transmission 2 is directly transmitted to the rear wheels 6, and the front wheels 10 are provided with a transfer clutch provided between the transfer input and output shafts 3 and 7 of the front wheel drive system. transmitted via device 11.

The torque split control system that optimally controls the distribution of driving force between the front and rear wheels while achieving both driving performance and steering performance is based on the transfer clutch device 11 that incorporates a wet type multi-friction clutch (for example, 6:
3-325379), a control oil pressure generator 20 that generates the control oil pressure Pc that becomes the clutch engagement force, and a solenoid valve 28 provided in the control oil pressure generator 20 from various human power sensors 30. The torque split control section 4 of the control unit C/U outputs a predetermined solenoid drive current control based on the information of
0 and an alarm lamp 50 that lights up in the event of various abnormalities.

The hydraulic control device 20 includes a motor 22 that is driven or stopped by a relief switch 21, and a hydraulic pump 2 that is operated by the motor 22 to draw water from a reservoir tank 23.
4, and pump discharge pressure (-sinking pressure) from the hydraulic pump 24
Accumulator 2 that stores via check valve 25
6 and the line pressure (secondary pressure) from the accumulator 26
and a solenoid valve 28 that adjusts the hydraulic pressure Pc to a predetermined control hydraulic pressure Pc using a solenoid drive current IETS from the torque split control section 40, and the hydraulic oil of the control hydraulic pressure Pc is supplied to the clutch port via a control hydraulic vibrator 29.

The various human power sensors 30 include a left front wheel rotation sensor 30a, a right front wheel rotation sensor 30b, and a left rear wheel rotation sensor 3, as shown in the block diagram of the system electronic control system in FIG.
0C1 Right rear wheel rotation sensor 30d, accelerator opening sensor 3
0e, lateral acceleration sensor 30f, drive current sensor 309.
It has a control oil pressure sensor 30h and a front wheel axle torque sensor 301.

As shown in the block diagram of the system electronic control system in FIG. 3, the torque split control section 40 includes a left front wheel speed calculation circuit 40a, a right front wheel speed calculation circuit 40b, a left rear wheel speed calculation circuit 40c7, and a right rear wheel speed calculation circuit. Circuit 40d, front wheel speed calculation circuit 40
e, Rear wheel speed calculation circuit 40f1 Rotational speed difference calculation circuit 409
．． Lateral acceleration output value correction circuit 40h, gain calculation circuit 40
1 fastening force calculation circuit 40j, dither signal generation circuit 40,
Solenoid drive circuit 40!1 Rotational speed difference output value abnormality detection circuit 40m, lateral acceleration sensor abnormality detection circuit 40n, clutch abnormality detection circuit 40o, abnormality judgment threshold circuit 40p
, has a fail-safe circuit 40q.

As shown in the block diagram of the system electronic control system in FIG. 3, the warning lamps 50 include a rotational speed difference abnormality warning lamp 50a, a lateral acceleration sensor abnormality warning lamp 50b, and a clutch abnormality warning lamp 50C.

Here, the configuration of the rotational speed difference output value abnormality detection device, which is a characteristic configuration of the present invention, will be explained with reference to the functional block diagram shown in FIG.

The front wheel rotational speed difference detection means includes a calculation circuit 40 for each wheel speed.
a to 40f, and the front wheel speed VWF and rear wheel speed VW based on the average value.
Arithmetic circuits 40e and 40f for calculating 11 and rear wheel speed VW
It is constituted by a rotational speed difference calculation circuit 409 that calculates a rotational speed difference ΔvW between the front and rear wheels based on a subtracted value obtained by subtracting the front wheel speed VWF from R.

The rotational speed difference output value abnormality detection means and the fail-safe operation means detect the absolute value 1Δvwl of the front and rear wheel rotational speed difference ΔvW from the rotational speed difference calculation circuit 409 and the acceleration/deceleration threshold value α.

(for example, 2 km/h) and a timer for detecting the time T (timer value) during which Pa1'' is continuously output from the comparator. , a fail-safe circuit 40q that outputs a command to turn on the warning lamp 50a and a command to reduce the clutch engagement force when the timer value T exceeds the set timer value T (for example, 5m1n).

Also, input sensors, electronic control systems, and hydraulic control systems.

The configuration of a clutch abnormality detection device that detects a clutch abnormality in which excessive latch engagement force remains due to a failure of the transfer clutch device 11 or the condition of tires with different diameters will be explained with reference to the functional block diagram in FIG. do.

This clutch abnormality detection device includes a drive current sensor 309,
A control oil pressure sensor 30h, a front wheel shaft torque sensor 30i,
It is composed of an abnormality judgment threshold circuit 40p, a clutch abnormality detection circuit 40o, and a fail-safe circuit 40q, and monitors three types of data: solenoid drive current, □8, control oil pressure Pc, and front wheel axle torque ■. However, if even one of these data exceeds each abnormality determination threshold value for a set period of time, a clutch abnormality is detected and a predetermined fail-safe operation is performed.

Therefore, by applying this clutch abnormality detection device,
It is possible to prevent deterioration of the durability of the drive system, increase in running resistance, occurrence of tight corner braking, etc. due to the continuation of excessive latch fastening force.

Next, the configuration of the four-wheel anti-lock brake control system will be explained with reference to FIGS. 2 and 3.

The braking system to which the four-wheel anti-lock brake control system of the embodiment is applied is, as shown in FIG. 2, a brake pedal 60. Booster 61. Mask cylinder 62. Actuator 63. Wheel cylinders 64a, 64b, 64c,
64d, brake piping 65, 66a, 66b, 66c,
It is equipped with 66d.

By controlling the braking force so that the slip ratio of each wheel, which is calculated from the vehicle speed and each wheel speed, converges to around 0.15 to 0.3, the wheels are locked during sudden braking or braking on low μ roads. The four-wheel anti-lock brake control system that prevents this includes the actuator 63 having a three-position switching solenoid valve and a hydraulic pump motor, and increases brake fluid pressure based on information from various human power sensors 30 for the actuator 63. It is composed of an anti-lock brake control section 70 of a control unit C/υ that outputs drive commands for pressure reduction and holding, and a warning lamp 50 that lights up in the event of various abnormalities.

As shown in the block diagram of the system electronic control system in FIG. 3, the various human power sensors 30 include a front left wheel rotation sensor 3 that has a longitudinal acceleration sensor 30j and provides necessary information.
0a, right front wheel rotation sensor 30b, left rear wheel rotation sensor 30
The C1 right rear wheel rotation sensor 30d and the like are shared with the torque split control system.

As shown in the block diagram of the system electronic control system in FIG. 3, the anti-lock brake control section 70 includes a vehicle speed calculation circuit 708. Anti-lock control circuit 70b, actuator drive circuit 70C1 longitudinal acceleration sensor abnormality detection circuit 7
0C, and has a fail-safe circuit 70d.

The warning lamp 50 includes a longitudinal acceleration sensor abnormality warning lamp 50d.

Next, the effect will be explained.

(B) When the rotational speed difference output value is normal When the rotational speed difference △vw of the front and rear wheels output from the rotational speed difference calculation circuit 409 is normal, the torque split control unit 40 of the embodiment uses the normal front and rear wheel driving force. Distribution control is performed.

Therefore, the flow of the basic front and rear wheel drive force distribution control operation will be explained with reference to the flowchart shown in FIG.

In step 80, each wheel rotation sensor 30a.

Sensor signals of left front wheel rotation speed NFL+right front wheel rotation speed NFR+left rear wheel rotation speed NRL+right rear wheel rotation speed NRR+lateral acceleration Y9 are read from 30b, 30c, 30d and the lateral acceleration sensor 30f.

In step 81, the left front wheel rotation speed NFL read in the step 80 + the right front wheel rotation speed NFR + the left rear wheel rotation speed N
Left front wheel speed VW from each of RL + right rear wheel rotation speed NRR
Front right wheel speed VWFR+rear left wheel speed VWRL+rear right wheel speed VWRR is calculated.

In step 82, the left front wheel speed VWFL and the right front wheel speed V
Front wheel speed νWF is calculated from WFR.

In step 83, the left rear wheel speed VWRL and the right rear wheel speed V
Rear wheel speed VWR is calculated from WRR.

In step 84, a front and rear wheel rotational speed difference ΔVW (-VwRVwF) is calculated from the front wheel speed VWF and the rear wheel speed VWR.

In step 85, the gain K is determined by the reciprocal of the lateral acceleration Y9.
is calculated.

At step 86, the clutch engagement force TM is calculated from the front and rear wheel rotational speed difference ΔVw, the gain, and the engagement force calculation formula (which has the relationship shown in FIG. 7 if shown on the map).

In step 87, the solenoid drive current ■, □6 that provides the clutch engagement force ■2 determined in step 86 is determined.
or is output to the solenoid valve 28.

Therefore, the larger the front and rear wheel rotational speed difference Δvw, the greater the clutch engagement force T1. Since I increases and the distribution of driving force to the front wheels increases, driving wheel slip caused by excessive driving force to the rear wheels, which are driving wheels, is suppressed.

Furthermore, by determining the gain K according to the lateral acceleration Yg, when driving on a road with a high road surface friction coefficient where the lateral acceleration Y9 is large, the gain is made small to effectively prevent tight Kona braking, etc. When driving on a low friction coefficient road where Y9 is small and tight co-def 1 noki is hardly a problem, increase the gain and distribute the driving force equally to the four wheels to minimize the occurrence of drive wheel slip. It can be suppressed.

(b) When the rotational speed difference output value is abnormal When the front and rear wheel rotational speed difference △vW output from the rotational speed difference calculation circuit 409 is abnormal, the rotational speed difference output value abnormality detection device shown in FIG. 4 is activated. do.

Therefore, the flow of the rotational speed difference output value abnormality detection operation by interrupt processing will be explained with reference to the flowchart of FIG.

In step 90, the absolute value of the front and rear wheel rotational speed difference △VW is 1.
Δvwl is read.

In step 91, the acceleration/deceleration flag α・FLG determines whether it is acceleration/deceleration, α・FLG=1, or not α・FLG=
0 is determined.

Then, when α·FLG=1, the process proceeds to step 94, and when α·FLG=O, the process proceeds to step 92.

In step 92, the absolute value of the front and rear wheel rotational speed difference ΔVW is 1.
△Vw] is the acceleration/deceleration threshold α. It is determined whether the

And 1Δvw1>α. When 1ΔV=l≦α0, the process proceeds to step 93, and when 1ΔV=l≦α0, the process returns to step 90.

In step 93, the acceleration/deceleration flag is rewritten from α·FLG”0 to α·FLG=4.

In step 94, when α・FLG=1 in step 91 and the vehicle is in a predetermined acceleration/deceleration state, similarly to step 92, the absolute value ΔV9,1 of the front and rear wheel rotational speed difference ΔVw or the acceleration/deceleration threshold is determined. α. It will be judged whether it exceeds the

If IΔvwl≦α0, the process proceeds to step 97, where the timer value is cleared, and the process proceeds to step 9B, where α・'1-G is rewritten from 1 to 0.

In step 95, the timer value, which is the duration of α·FLG=1, is added by the control activation time t every time one step passes.

In step 96, the lower continuation timer value of α·FLG=1 is lower than the set timer value set based on the possible continuous acceleration/deceleration time of the vehicle. (for example, 5m1n).

Then, when T<T o, the process returns to step 90, and T≧
When the result is To, the process advances to step 99.

In step 99, a lighting command is given to the alarm lamp 50s and the clutch engagement forces T and J are set to 1, for example, 0.001 kgm/
It is reduced at a rate of tonsec, and a command to gradually shift to the two-wheel drive direction is output.

Here, acceleration/deceleration threshold α. How to determine the set timer value T and the set timer value T will be explained.

For example, the acceleration is 3.5km/h/sea (0,I
9) Okm/h → Approximately 70 km/h to reach 250 km/h
It takes sec.

In other words, if the acceleration is 3.5 km/h/sec, it is about 7
It can be said that 0 sec is the time during which the vehicle can continuously accelerate. Therefore, the acceleration/deceleration threshold α. The timer value is set in consideration of the continuous acceleration time of the vehicle and the time that would cause actual damage to the system. As a result, as shown in FIG. 9, the acceleration/deceleration threshold α. and set the timer value below. An appropriate value can be set by setting the relationship to be inversely proportional to Y.

As explained above, abnormalities in the wheel speed sensor (wrong number of teeth on the sensor rotor, temporary disconnection of the sensor and harness, etc.), tires of the front and rear wheels of different diameters (wear of one tempered tire, air pressure, etc.), etc. The cause is the difference in rotational speed between the front and rear wheels ΔVW
The absolute value 1Δvwl is the acceleration/deceleration threshold α. If the condition exceeds the set timer value To for a period of time exceeding the set timer value To,
As soon as it is detected that the front and rear wheel rotational speed difference ΔVw is abnormal, a fail-safe operation is performed in which the clutch engagement force T is weakened or the warning lamp 50a is turned on.

Therefore, problems that occur when abnormalities in the front and rear wheel rotational speed difference output values are left unaddressed, such as decreased durability of the drive system, increased running resistance, and occurrence of tight corner braking, can be quickly resolved.

Although the embodiment has been described above based on the drawings, the specific configuration and control contents are not limited to this embodiment.

For example, in the embodiment, an example of application to a drive force distribution control device for a rear wheel-based four-wheel drive vehicle in which the rear wheels are directly connected to the engine drive was shown. It can also be applied to the drive force distribution control system of four-wheel drive vehicles.

(Effects of the Invention) As explained above, in the driving force distribution control device for a four-wheel drive vehicle of the present invention, an abnormality in the front and rear wheel rotational speed difference output value is detected based on the continuous acceleration/deceleration time of the vehicle. The system uses a torque split type system that directly transmits engine driving force to one of the front and rear wheels and transmits it to the other through a torque distribution clutch. In a four-wheel drive vehicle, an effect can be obtained in that a problem that occurs when an abnormality in the front and rear wheel rotational speed difference output value is left unaddressed can be quickly resolved.

[Brief explanation of drawings]

Fig. 1 is a claim correspondence diagram showing a driving force distribution control device for a four-wheel drive vehicle according to the present invention, and Fig. 2 is a diagram showing a complaint response diagram showing a driving force distribution control device for a four-wheel drive vehicle according to the present invention. Overall schematic diagram showing the drive system, braking system, and control system, Part 3
The figure is a block diagram showing the electronic control system used in the embodiment device, Figure 4 is a functional block diagram showing the front and rear wheel rotational speed difference output value abnormality detection device, and Figure 5 is a functional block diagram showing the clutch abnormality detection device. , Figure 6 is a flowchart of the main routine showing front and rear wheel drive force distribution control operation, Figure 7 is a basic front and rear wheel drive force distribution control characteristic diagram, and Figure 8 is a flowchart of front and rear wheel rotational speed difference output value abnormality detection operation. FIG. 9 is a flowchart of the subroutine showing the flow of the acceleration/deceleration threshold α. and the set timer value T. What is the relationship characteristic diagram? a... Torque distribution clutch b... Front and rear wheel rotation speed difference detection means C... Driving force distribution control means d... Rotation speed difference output value abnormality detection means e... Fail-safe operation means

Claims (1)

[Scope of Claims] 1) A drive system that is directly connected to the engine to one of the front and rear wheels is provided in the middle of the drive system to the other of the front and rear wheels, and the transmitted engine drive force can be changed by external fastening force control. a torque distribution clutch, which outputs a fastening force command value to the torque distribution clutch according to an output value from the front and rear wheel rotational speed difference detection means; A rotational speed difference output value abnormality detecting means for detecting that the output value is abnormal when the duration of the state exceeding a predetermined value exceeds a set time based on the continuous acceleration/deceleration possible time of the vehicle; and the rotational speed difference output value abnormality. A drive force distribution control device for a four-wheel drive vehicle, comprising: fail-safe activation means for performing a predetermined fail-safe operation when an abnormal signal is output from the detection means.