JPH02293221A - Drive force distribution controlling device for four-wheel drive car - Google Patents

Abstract

PURPOSE:To secure running safety at the time of an abnormality by holding a tightening force just before detection of the abnormality when the abnormality by an input senser signal is detected, returning to a normal control when the abnormality is a temporary one, and decreasing the tightening force gradually to zero when the abnormality is continued for a predetermined time. CONSTITUTION:A drive force distribution control means (d) controls the distribution of drive force of a torque distribution clutch (a) based on vehicle information outputted by an input senser (b). In the meanwhile, an input senser abnormality detecting means (c) monitors the input senser (b), and if an abnormality is detected, the drive force distribution control means (d) immediately holds the tightening force just before detection of the abnormality. If a senser signal returns to normal within a predetermined time, operation is returned to normal control. If the abnormality continues for more than a predetermined time after detection of the abnormality, the tightening force is controlled to get gradually to zero after the time. In this constitution, running safety can be secured at the time of an input senser abnormality.

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 in which front and rear wheel drive force distribution can be changed, and in particular, to a measure against input sensor failure.

(Prior Art) Conventionally, as a driving force distribution control device for a four-wheel drive vehicle, sensor signals from a front wheel rotation sensor and a rear wheel rotation sensor are used, for example, as described in Japanese Patent Application Laid-Open No. 62-253527. There is a known device that calculates the difference in rotational speed between the front and rear wheels based on the difference in rotational speed between the front and rear wheels, increases or decreases the clutch engagement force according to the difference in the rotational speed between the front and rear wheels, and varies the distribution of engine driving force between the front and rear wheels.

This conventional source states that when the input sensor is abnormal and the vehicle speed is high, the clutch engagement force immediately before the abnormality is maintained to prevent sudden changes in vehicle behavior, and when the input sensor is abnormal and the vehicle speed is low, , a fail-safe technology has been demonstrated that reduces tight corner flaking and drive system load by gradually reducing clutch engagement force.

(Problem to be solved by the invention) However, in such a conventional driving force distribution control device, at low vehicle speeds, sensor abnormalities from the input sensor may occur due to temporary open (disconnection) or short circuit. Even in such cases, control is performed to reduce the clutch engagement force from the moment an abnormality is detected, so the clutch engagement force may change suddenly when the sensor signal becomes normal and normal control is restored, which may affect vehicle behavior. This will allow sudden changes in the situation.

In addition, when the wheel rotation sensor, etc. is abnormal and the vehicle speed is low, control is performed to reduce the clutch engagement force from the moment the abnormality is detected, so a slight change in the drive force distribution will affect the turning limit performance. If a sensor abnormality occurs during low-speed cornering on a road with a low friction coefficient, such as a rainy road or a wet/snowy road, the above-mentioned reduction in the fastening force may cause a sudden change in vehicle behavior.

Furthermore, since the sensor malfunction countermeasure includes the vehicle speed condition, it is a prerequisite that the sensor providing the vehicle speed information is normal, and if it is abnormal, the expected fail-safe operation cannot be expected.

For example, if a wheel rotation sensor becomes abnormal during high-speed turning, and the sensor that provides vehicle speed information outputs an abnormal signal indicating a low speed, the clutch engagement force may decrease from the time the sensor abnormality is detected. This allows sudden changes in vehicle behavior.

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.
In rural areas, torque split type four-wheel drive vehicles that transmit torque through a clutch for torque distribution do not receive FW due to temporary or continuous sensor abnormality and driving conditions such as vehicle speed and road surface friction coefficient. The objective is to ensure vehicle running safety when an input sensor is abnormal.

(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, when a sensor is detected, the fastening force is first held; If the abnormality is temporary, the system returns to normal control, and if the abnormality persists, the system gradually returns to two-wheel drive.

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, an input sensor b that detects vehicle information necessary for driving force distribution control, and an input sensor abnormality detection means C that detects an abnormality in the sensor signal from the input sensor b. When an abnormality is detected by the input sensor abnormality detection means C, the fastening force immediately before the abnormality detection is maintained, and if the abnormality detection is temporary, the normal control (Torx blit control based on the sensor signal) is restored. , when the abnormality detection state continues for a predetermined period of time, the driving force distribution control means d performs control to gradually reduce the fastening force held from the point in time after the elapse of that period to zero. .

(Function) When the input sensor is abnormal due to a temporary short circuit or an oven, etc., the driving force distribution control means d immediately changes the fastening force immediately before the abnormality is detected when the input sensor abnormality detection stage C detects the abnormality. The control is held, and then, when the sensor signal becomes normal, control is performed to return to normal control.

Therefore, in the case of a temporary abnormality among input sensor abnormalities, the change in clutch engagement force in the time period before and after the abnormality is minimized, so almost no change in vehicle behavior occurs, and the vehicle is safe to drive. gender is ensured.

When the input sensor is abnormal due to continuous short-circuit or open circuit, etc., the driving force distribution control means d operates continuously until a predetermined time elapses from the time of abnormality detection when the input sensor abnormality detection step C is detected. The fastening force immediately before detection is held, and thereafter, control is performed to gradually reduce the fastening force to zero.

Therefore, when the input sensor is abnormal, when the blades are constant, the drive force distribution is fixed for a predetermined period of time, regardless of the vehicle speed or the road surface friction coefficient, and then the drive force distribution is gradually changed to the two-wheel drive direction. Therefore, even when the vehicle is turning at high speed on the most unstable road with a low coefficient of friction, sudden changes in vehicle behavior are prevented and the running safety of the vehicle is ensured.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. Second
The figure is an overall system diagram including a drive system to which a torque split control system (driving force distribution control device) for a four-wheel drive vehicle is applied. First, the configuration will be explained.

The vehicle to which the Torx Brit control system of the embodiment is applied is a double-wheel-based four-wheel drive vehicle, and its drive system includes an engine 1. Transmission 2, transfer input shaft 3
．． Rear brake roller shaft 4, rear differential 5
, a rear wheel 6, a transfer output shaft 7, a front propeller shaft 8, a front differential 9, and a front wheel 10. Engine driving force that has passed through the transmission 2 is directly transmitted to the rear wheel 6, and the front wheel 10 The power is transmitted to the front wheel drive system via a transfer clutch device 11 provided between the transfer input and output shafts 3 and 7.

The torque blit 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 multi-disc friction clutch (for example, Showa 63
-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 2o from various human force sensors 30. The torque split controller 40 outputs a predetermined dither current l* based on the information.

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 (primary pressure) from the hydraulic pump 24
Accumulator 2 stores the amount of water via check valve 25.
6 and the line pressure (secondary pressure) from the accumulator 26
and a solenoid valve 28 that adjusts the control pressure Pc to a predetermined control pressure Pc by a solenoid-driven dither current i* from the Torx blit control unit 40, and the hydraulic fluid of the control pressure Pc passes through the control hydraulic vibrator 29 and enters the clutch port. Supplied.

As shown in the block diagram of the system electronic control system in FIG. 3, the various input 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.
0C, right rear wheel rotation sensor 30d, first lateral acceleration sensor 3
0e, and a second lateral acceleration sensor 30f.

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 transport speed calculation circuit 40b, a left rear wheel speed calculation circuit 40c, and a right rear wheel speed calculation circuit. Arithmetic circuit 40d. Front wheel speed calculation circuit 40
e, rear transport speed calculation circuit 40f, rotational speed difference calculation circuit 409
, fastening force calculation circuit 40h, TIJ-1 conversion circuit 401, dither current output circuit 40j, front and rear wheel rotational speed difference dead zone setting circuit 40k, lateral acceleration calculation circuit 40I2,
Gain calculation circuit 40m, rotation sensor oven detection circuit 4
0n, rotation sensor short detection circuit 40o, lateral acceleration sensor abnormality detection circuit 40p, fail safe cycle? It has 40q.

In addition, in the figure, A/D is an A/D converter, and D/A is a D/A converter.

In addition, the fail safe circuit 40q includes each sensor 30a to
An alarm lamp 50 is connected that lights up when the sensor signal from 30f is abnormal.

Next, the effect will be explained.

FIG. 4 is a flowchart showing the flow of the front and rear wheel drive force distribution control operation performed by the Torx Brit controller 40 (control cycle: 10 msec). Each step will be explained in order below.

In step 80, a rotation sensor signal SW F based on a sine waveform voltage signal is generated from each wheel rotation sensor 30a to 30d.
L * S W F R + S W R L + S
W R R and both lateral acceleration sensors 30e. Lateral acceleration sensor signal SYOl+ by analog voltage signal from 30f
SVG2 is input.

In step 81, the left front wheel speed VWF and the right front wheel speed VWFR+ are determined depending on the cycle of the converter output of the rotation sensor signal.
The left rear wheel speed V■ and the right rear wheel speed VWRR are calculated.

In step 82, as an input calculation process, the front wheel speed V
WF is calculated, and the above left rear wheel speed VWRL and right rear wheel speed VW are calculated.
The rear wheel speed VWR is calculated from the average value with RR, and both lateral acceleration sensor signals Svc++ sya. Which average value is used to calculate the lateral acceleration Y6.

Steps 83 to 88 include each rotation sensor 30a,
30b, 30c. This is an oven detection processing step for detecting whether or not the signal line 30d is interrupted.

In step 83, if normal, the rotation sensor signal Sw, (i=FL, FR, R
L, RR) is the constant voltage value V. Oven abnormality is determined based on whether or not it is C.

If SWH = Vcc, proceed to step 84 and indicate ozone abnormality detection.
If TWo,=VCC is rewritten to 1, the process proceeds to step 85, indicating that the oven is normally detected.
Set to 0.

Then, the process proceeds from step 84 or step 85 to step 86, and ①. It is determined whether 1 is greater than or equal to the set timer value T, (for example, 0.5 sec).

TWOi≧T. In this case, the process advances to step 87, where Fwo+=1 is set indicating that oven abnormality is confirmed, and TWO
If i<T, the process advances to step 88 and FWo. = set to O.

Steps 89 to 94 are performed for each rotation sensor 30a.
30b, 30c. This is a short-circuit detection processing step for detecting whether or not the signal line 30d is short-circuited.

In step 89, if normal, the rotation sensor signal SWi based on the sine waveform voltage signal is OV (volt), and the wheel speed VW other than the rotation sensor (however, wheels other than J:1) is equal to or higher than the set voltage value VWlh. A short-circuit abnormality is determined based on whether or not.

If YES, the process advances to step 90 to indicate short abnormality detection.<Tws+=Tws. + 1, and in the case of NO, the process advances to step 91, where the flag is set to Tws+=O, indicating normal detection of short circuit.

Then, the process proceeds from step 90 or step 91 to step 92, where it is determined whether ■ws i is greater than or equal to the set timer value T2 (for example, 2 seconds).

In the case of TWSi≧D, the process advances to step 93, where Fws+=1 is set indicating that the short abnormality is confirmed, and TWSi
<T2, the process advances to step 94, and the FW. ．． = set to O.

Steps 95 to 100 include both lateral acceleration sensors 3
This is a sensor abnormality detection processing step for detecting whether or not the sensors 0e and 30f are abnormal.

In step 95, the lateral acceleration sensor signal Sya+. which should be approximately zero if the sensor is normal. The difference in the absolute voltage values of Svaz is the set voltage value V. A sensor abnormality is determined based on whether or not the above conditions are met.

If YES in step 95, proceed to step 96 and indicate sensor abnormality detection (TyoNa" Tva
It is rewritten to Na+1, and in the case of No, step 9
Proceed to step 7 and indicate normal sensor detection. < T-aNa =
Set to 0.

The process then proceeds from step 96 or step 97 to step 98, where it is determined whether TYQNG is greater than the set timer value T3 (for example, 0.5 sec) l;J.

If TvaNa≧T3, the process advances to step 99, where Fy (HNa=' is set, indicating that the open abnormality is confirmed,
If TVGNG<T3, the process advances to step 100 and is set to FYGNG-0 indicating that the sensor abnormality is undetermined.

Steps 101 to 103 are clutch engagement force calculation processing steps.

In step 101, the front and rear wheel rotational speed difference △Vw (=Vwq VwF:
However, △VW≧O) is calculated.

In step 102, the clutch engagement force control gain κ,
is the lateral acceleration Y. It is calculated using the following formula based on the reciprocal of .

κ, = αh /YO (However, κ.≦βh) For example, α
,=1 and β,=10.

At step +03, the clutch engagement force Tav is calculated from the control gain Kh and the front and rear wheel rotational speed difference ΔvW (this is expressed as a control characteristic map as shown in FIG. 5).

Steps 104 to 111 are output processing steps for obtaining predetermined clutch engagement force air corresponding to normality and abnormality.

In step 104, each flag indicating whether an abnormality has been confirmed is checked.
It is determined whether the sum of NG is O.

In step 105, each flag indicating whether an abnormality has been detected is checked. It is determined whether the sum of H, Tws+, and TVGNG is 0.

If both of step 104 and step 105 are O, and it is determined that all input sensors 30a to 30f are normal with no abnormality detected or confirmed, the process proceeds to step 106, and the clutch obtained in step 103 is Processing is performed to set the engagement force TAv to a clutch engagement force command value T.

Also, although the answer is YES in step 104, step 1
05 is NO, and ``An abnormality has been detected in one of the input sensors 30a to 30f, but if the abnormality has not yet been determined, the process proceeds to step 107, and the control is determined one control period before (IOmsec before). The clutch engagement force command value Tu-+ is the clutch engagement force command value ■. Processing is performed to make it.

Also, if the answer is No in step 104, the input sensor 30a
~ If any of 3Of is determined to be abnormal,
Proceeding to step 108, the clutch engagement force command value TIJ-1 obtained one control cycle ago is changed to the engagement force reduction value △.
A process is performed in which the value obtained by subtracting T (for example, 0.OOIkgm) is set as a clutch engagement force command value, and at the same time, in step 109, a lighting command for the alarm lamp 50 is output.

In step 110, the clutch engagement force command value air obtained in step 106, step 107, or step 108 is given in advance. −1 is converted into solenoid drive current i using the characteristic table.

In step 111, a dither current l* (for example, i±0.1A I001-12) is applied to the solenoid valve 28.
is output.

Next, the driving force distribution control operation will be explained separately for when the sensor is normal, when the sensor is temporarily abnormal, and when the sensor is continuously abnormal.

(b) When the sensors are normal When each sensor 30a to 30f is normal, the fourth
In the flowchart shown in the figure, Step 101 → Step 102 → Step 103 → Step 104 → Step 105 → Step 106 → Step 110 - Step 1
11, and as shown in Fig. 5, as the front and rear wheel rotational speed difference △vw increases, the clutch engagement force command value T1 increases, and the drive force distribution to the front wheels increases. This suppresses drive wheel slip caused by excessive distribution of drive force to the rear wheels.

Furthermore, by determining the control gain κ according to the reciprocal of the lateral acceleration Y0, tight corner braking is effective when cornering on a high friction coefficient road where the lateral acceleration Y6 is large and the control gain κ is small. In addition, the generation of lateral acceleration Y6 is small and the control gain κ is prevented. When turning on a road with a low friction coefficient where the friction coefficient is large, the occurrence of drive wheel slip can be minimized by distributing the drive force in the four-wheel drive direction.

(Example) When a sensor temporal abnormality occurs When the sensors 30a to 30f are abnormal due to a temporary short circuit or an oven, etc., each flag TWOi+T indicating whether an abnormality has been detected is set in the flowchart of FIG.
Since the sum of WSi + TYGNG is no longer O, the flow proceeds from step 103 to step 104 - step 105 → step 107 → step 110 → step 111, and in step 107, one control period before ( +
The clutch engagement force command value TLI-1 obtained at the time (before Omsec) is set as the clutch engagement force command value ■. By doing so, as soon as any input sensor abnormality is detected, the fastening force immediately before the abnormality detection is maintained.

After that, when the sensor signal from the sensor that outputs the abnormal signal becomes normal, each flag TWO indicating whether an abnormality has been detected
i+ rws+. The sum of TYGNG' becomes 0,
Step 103 to Step 104 → Step 105-
The process proceeds to step 106 - step 110 - step 111, and control is performed to return to normal control.

Therefore, in the case of a temporary abnormality among input sensor abnormalities, the change in clutch engagement force in the time period before and after the abnormality is minimized, so almost no change in vehicle behavior occurs, and the vehicle is safe to drive. gender is ensured.

(c) When the sensor continues to be abnormal When the sensors 30a to 30f are abnormal due to a continuous short circuit or an oven, etc., when an abnormality is detected, first, one control cycle is determined in step 107, as in the case of a temporary sensor abnormality. The clutch engagement force command value TIJ-1 obtained before (+Omsec ago) is set as the clutch engagement force command value Te, and the engagement force immediately before the abnormality detection is maintained.

If this abnormality detection state continues for a predetermined period of time for determining whether or not the abnormality has been determined, each flag FW indicating whether or not the abnormality has been determined is determined in step 104. ．． ,FWSi+FY
Since the sum of GNG is no longer 0, the flow proceeds from step 103 to step 104 - step 108 → step 109 → step 110 → step 111. At step 108, control is performed to gradually reduce the fastening force to zero, and at step 109, a command to turn on the alarm lamp 50 is output.

Therefore, in the event of a continuous abnormality among input sensor abnormalities, the driving force distribution is fixed for a predetermined period of time and then gradually changed to the two-wheel drive direction, regardless of the vehicle speed or the road surface friction coefficient. Therefore, even when the vehicle is turning at high speed on the most unstable road with a low friction coefficient, sudden changes in vehicle behavior are prevented and the running safety of the vehicle is ensured.

By the way, Figure 6 shows the rotation sensor signal SWF L of the left front wheel.
In the time chart for the case where the opening becomes a temporary oven and then becomes continuously open, if the abnormality of the rotation sensor signal SWFL of the left front wheel is left unchecked, the dotted line characteristic of the front wheel drive force distribution ratio will change. However, in the case of the example, the driving force distribution ratio hardly changes as shown by the solid line characteristic of the front wheel side driving force distribution ratio, and moreover, when the sensor is abnormal, the driving force distribution ratio changes suddenly. If this happens, it is understood that the vehicle will gradually shift to the safer rear wheel drive direction.

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

Further, in the embodiment, a rotation sensor and a lateral acceleration sensor for each wheel are shown as input sensors, but the input sensor is not limited to the embodiment as long as the sensor is used as a sensor that provides necessary information for driving force distribution control.

Further, the specific sensor abnormality detection method is not limited to the embodiment.

(Effects of the Invention) As explained above, in the driving force distribution control device for a four-wheel drive vehicle of the present invention, when a sensor abnormality is detected, the fastening force is first maintained so that the abnormality is temporary. In some cases, the device returns to normal control, and in other cases, it gradually returns to two-wheel drive.This system directly transmits engine driving force to one of the front and rear wheels, while distributing torque to the other. In a four-wheel drive vehicle with a split-type torque transmission, which transmits torque through a clutch, the vehicle is not affected by temporary or continuous sensor abnormality and driving conditions such as vehicle speed and road friction coefficient. This has the effect of ensuring running safety.

[Brief explanation of the drawing]

FIG. 1 is a complaint 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 drive force distribution control device for a four-wheel drive vehicle according to an embodiment of the present invention. Fig. 3 is a block diagram showing the electronic control system used in the embodiment device, Fig. 4 is a flowchart showing the front and rear wheel drive force distribution control operation, and Fig. 5 is an overall schematic diagram showing the system and control system. FIG. 6, which is a clutch engagement force characteristic diagram with respect to the wheel rotational speed difference, is a time chart when the rotation sensor becomes temporarily open abnormality and continues oven abnormality. a... Torque distribution clutch b... Input sensor C... Input sensor abnormality detection means d... One driving force distribution control 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. an input sensor that detects vehicle information necessary for driving force distribution control, an input sensor abnormality detection means that detects an abnormality in a sensor signal from the input sensor, and an abnormality detected by the input sensor abnormality detection means. When detected, the tightening force immediately before the abnormality is detected is maintained, and when the abnormality detection is temporary, normal control is restored, and when the abnormality detection state continues for a predetermined period of time, the tightening force is maintained from the point at which the abnormality is detected. 1. A driving force distribution control device for a four-wheel drive vehicle, comprising: a driving force distribution control means for gradually reducing a fastening force to zero.