JPH01275271A - Running control device for vehicle - Google Patents

Abstract

PURPOSE:To raise the stability in car running and secure the safety by putting one of the two control mechanism, a four-wheel steering control mechanism and a front-and-rear-wheel driving force distribution control mechanism, which remains to operate normally into the failsafe side, when the other is in failure. CONSTITUTION:When a car is running normally, detection signals from a steering angle sensor 20, a car speed sensor 23, etc., are fed into a controller 19 to decide the optimum front-and-rear-wheel driving force distributing proportion, which suits best the running conditions and road surface condition, and a front wheel driving clutch 8 is controlled to perform 4WD drive. If judgement at this time is that 4WD is in failure, the driving force distributing proportion shall be corrected so as to raise the front wheel driving force. It it then judged whether sensors and solenoids necessary for 4WD control are in failure, and if yes, the 4WD control shall be interrupted. If no, a solenoid proportional pressure regulator valve 18 is controlled in accordance with the driving force distributing proportion corrected as mentioned above, and the clutch pressure of a clutch 8 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a vehicle travel control device that includes a four-wheel steering control mechanism and a four-wheel drive front and rear wheel drive force distribution control mechanism.

(Prior Art) For vehicles using this type of conventional vehicle travel control device, for example, Japanese Patent Application No.
There is one described in Publication No. 22686, and there is a 4-wheel drive (
Regarding driving force distribution control of 4WD), for example, see the Society of Automotive Engineers of Japan Symposium ``Applications of Control Theory and Automobile Control JP41.
．． (published in 1985) and was installed in the Nissan Cue-X, and there is also one described in Japanese Patent Application No. 1983-33892. The former is a torque sprint 4WD vehicle that employs an electronic control system, and employs full-time 4WD with a hydraulic multi-plate clutch in the middle of the front wheel drive shaft. Since the torque capacity of a hydraulic multi-disc clutch is approximately proportional to the applied oil pressure, the hydraulic multi-disc clutch is used as a torque limiting device by varying the applied oil pressure. In other words, the torque capacity of the hydraulic multi-disc clutch is T
c and the transmission output torque is T,
The distribution of torque between the front wheels and the rear wheels is Tc: (T-Tc
), by detecting torque T (or something similar) and adjusting the applied oil pressure, Tc can be adjusted appropriately.
That is, by identifying and selecting the driving state of the vehicle based on the information from the wheel rotation speed sensor and the accelerator opening sensor, the desired front-rear torque distribution can be obtained. However, the rear wheel drive system does not have a hydraulic clutch and is directly connected, so it cannot be converted to a front-wheel drive vehicle.

Also, as a vehicle equipped with 4WS and 4WD at the same time,
For example, there is the Mitsubishi Gear Run, but this vehicle's front and rear wheel drive force distribution control does not use an electronic control method.

(Problems to be Solved by the Invention) In the case of a system failure, does the driving control device of a vehicle that employs the above-mentioned 4WS system or 4WD system take into consideration the driving stability of the system and control the driving side electronically or mechanically? It has a fail-safe function that performs fl. However, in a vehicle configured to be equipped with 4WS and 4WD at the same time, 4WS, 4W
D The characteristics assume that both systems are operating normally, and the effect on the other system when one system fails has not been taken into consideration. There is a problem in that, together with the operation of the other normal system, the running stability of the vehicle as a whole is impaired.

(Means for Solving the Problems) The present invention attempts to solve the above-mentioned problems by incorporating system J and fail information in a vehicle travel control device that controls an iS and 4WD system. In a vehicle travel control device for a vehicle comprising a control mechanism and a four-wheel drive front and rear wheel drive force distribution control mechanism, the above-mentioned 4
When one of the wheel steering control mechanism and the front and rear wheel drive distribution control mechanism fails, the other normally operating control mechanism is activated to a fail-safe side based on the failure information so as to improve the stability of vehicle running. It is characterized by being configured to allow

(Operation) When a vehicle equipped with a 4-wheel steering control mechanism and a 4-wheel drive front/rear wheel drive force distribution control mechanism is running with both control mechanisms operating normally, one of the control mechanisms fails. teeth,
Fail information is input to the vehicle travel control device. Based on this, the vehicle running control device operates the other normally operating control JBJa mechanism to the fail-safe side so that the stability of re-running the vehicle is improved, thereby improving the running stability as a function of the entire vehicle. Therefore, it is possible to realize an extremely safe vehicle travel control device that has a fail-safe function that ensures safety.

(Example) Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is described in the above-mentioned Japanese Patent Application No. 63-33892, and shows a wheel drive system and a rear wheel auxiliary steering system of a vehicle used to implement the device of the present invention. II in the figure.

IR is the front wheel, 2L and 2R are the rear wheels, and 3 is the steering wheel.

First, to explain the wheel drive system, 4 is the engine, 5 is the transmission, and the transmission power from the engine 4 through the transmission 5 is constantly transferred to the propeller shaft 6.
It reaches the rear wheel differential gear 7 via , and drives the rear wheels 2L and 2R.

On the other hand, the shifting power from the transmission 5 is transmitted to the front wheel differential gear 10 via the propeller shaft 9 by the front wheel drive clutch 8 as appropriate, and then to the front wheels IL and IR.
It is used for driving.

Next, to explain the steering system of the vehicle, the front wheels IL and IR can be steered by the steering wheel 3 via the steering gear 11 as usual, and the rear wheels 2L.

2R enables steering by the rear wheel steering actuator 12.

The actuator 12 is a spring center type hydraulic actuator, and when hydraulic pressure is supplied to the chamber 12R, the rear wheels 2L and 2R are auxiliarily steered to the right by a steering angle proportional to the pressure, and the rear wheels 2L and 2R are auxiliarily steered to the right. When hydraulic pressure is supplied to the rear wheels 2L and 2R, the rear wheels 2L and 2R are assisted to the left by a steering angle proportional to the pressure.

An electromagnetic proportional rear wheel steering control valve 13 is provided to control the hydraulic pressure to the actuator chambers 12L and 1211, and this valve 13 is provided with variable throttles 13a, 13b, 13c, and 13d connected in a bridge manner, and a pump 14 is connected to this bridge circuit. Oil passages 16 and 17 from the reservoir 15 and the actuator chambers 12L and 12R are connected, respectively. The valve 13 is further a solenoid 13L.

13R, these solenoids fully open variable throttles 13a, 13b, 13c, and 13d, respectively, to bring both actuator chambers 1217 and 12R into a no-pressure state (equilibrium state), and the current of solenoid 13L or 13R is adjusted to , or variable apertures 13c and 13d when turned on by IR.
Also 13a.

13b to the opening degree according to the current value, and the actuator chamber 121. Alternatively, it is assumed that hydraulic pressure corresponding to the current value IL or IR is supplied to 121'l. As described above, the hydraulic pressure assists in steering the rear wheels in the corresponding direction by an angle corresponding to the hydraulic pressure.

The front wheel drive clutch 8 directs torque according to the clutch pressure PC to the front wheels, and the clutch pressure PC is controlled by the electromagnetic proportional pressure regulating valve 18.
Controlled by The valve 18 normally maintains the clutch pressure PC at zero, and the driving current for the solenoid 1.8a is ■. As the pressure increases, the pressure of the pump 14 is directed toward the clutch 8, thereby increasing the clutch pressure PC.

Drive current of solenoids 13L, 13R, 18a ■1.
.

IR and I are controlled by a controller 19, which includes a steering angle sensor 20 that detects the steering angle θ.
and the rotational speed ω of wheels IL, IR, 2L, 2R, 1. ω, 2. ω1. ．． Wheel rotation sensor 211.21L that detects ωr2 In addition to the signals from 22L and 22R, the signal from the vehicle speed sensor 23 that detects the vehicle speed ■ and the signal from the throttle opening sensor 24 that detects the throttle opening Tl+ are input, respectively. . Controller 19
Based on this input information, functions as shown in FIGS. 3-4 at regular intervals Δ to control the solenoid drive current IC (front wheel drive force control, that is, front and rear wheel drive force distribution control) and control the solenoid drive current 1. ,．． 1. control (rear wheel auxiliary steering).

As shown in detail in FIG. 2, the controller 19 here includes a 4WS controller 1 to a roller 19a and a 4WD controller 1.9b. (signals) shall be sent and received. Although the controllers 9a and 19b are of separate type here, they may be of an integrated type.

First, to explain the flowchart of the front and rear wheel drive force distribution control for four-wheel drive shown in FIG.
4WD control is performed to determine the optimal front and rear wheel drive force distribution ratio according to driving conditions and road surface conditions, for example, by the method described in the above-mentioned Japanese Patent Application No. 63-33892.

Next, in step 52, it is determined whether or not the 4WS system has failed based on the presence or absence of the 4WS failure signal.
If it is determined that the WS has failed, the driving force distribution ratio is corrected in step 53 so that the driving force for the front wheels is increased, and then the control proceeds to step 55. If it is determined in step 52 that the 4WS is in normal operation, the correction value is set to zero in step 54 to determine the driving force distribution ratio, and then the control proceeds to step 55.

In step 55, 4WD is activated depending on whether the sensor or solenoid required to control the 4WD system has failed or not.
It is determined whether there is a system failure or not, and if it is determined that there is a 4WD failure, it is determined in step 56 to cancel the 4WD control, and in step 57 a 4WD failure signal is output to the 4WS controller 19a.

On the other hand, if it is determined in step 55 that the iD is operating normally, in step 58 the electromagnetic force that activates the clutch 8 is used to perform duty control on the front and rear wheel drive forces so that the drive force distribution ratio determined in step 53 or 54 is achieved. Proportional pressure regulating valve 1
A drive current IC is output to the solenoid 18a.

Note that after steps 57 and 58, control returns to step 51 and is executed repeatedly.

Due to the 4WD control described above, if the 4WD system fails and the 4WD system is operating normally, 4WD control is performed that concentrates the driving force of the front wheels.
By controlling the clutch pressure PC to a corresponding value, the appropriate torque can be transmitted to the front wheels, the front and rear wheel drive force distribution can be made appropriate, and the running stability of the vehicle can be improved against the tendency for understeer. .

Next, to explain the flowchart of the four-wheel steering control shown in FIG. 4, in step 71, the steering wheel steering angle θ and the vehicle speed ■ are read, and in the next step 72, the steering wheel steering angle θ and the vehicle speed The deviation is such that the yaw rate gain characteristics are flat with respect to the steering frequency.
That is, a proportional constant for the rear wheels and a differential constant τ for the rear wheels are calculated from the vehicle speed (2) so that the yaw rate is generated without phase delay in proportion to the front wheel steering regardless of the steering speed, and then calculated using the rear wheels.

Next, in step 73, it is determined whether or not the 4WD system has failed based on the presence or absence of the 4WD failure signal, and the 4WD system
If it is determined that the D-fail has occurred, in step 74, correction is made to increase the in-phase control by setting the proportional constant K to +Δ, or to decrease the differential constant τ to τ−τ−Δτ, or to decrease the differential constant τ to τ−τ−Δτ, or τ−
After performing any of the corrections to set the value to 0, the control returns to step 7.
Proceed to 6. If it is determined in step 73 that the 4WD is operating normally, the correction value is set to zero and set as a constant in step 75.
After determining τ and Tr, control shall proceed to step 76.

In step 76, the rear wheel auxiliary steering angle δ is calculated based on the constants obtained in steps 71, 74, and 75, τ, and Tr using the following equation. It should be noted that equation (2) is an example of the rear wheel auxiliary steering angle calculation equation, but instead, δ, ·re control)
, δ1-(K-τ・S) θ (-next advance control), longitudinal actual steering ratio primary/primary control described in the publication, however, B, ,B,
, τ7. τ1 is a function of vehicle speed, δ.

is the front wheel steering angle).

In the next step 77, the sensor and solenoid necessary for controlling the 4WS system are determined to have failed.
It is determined whether there is a failure in the WS system, and if it is determined that it is a 4WS fail, it is decided to cancel the iS control in step 78, and the 411IS fail signal is set to 4W in step 79.
Output to D controller 9b.

On the other hand, if it is determined in step 77 that the 4WS is operating normally, then in step 80 the rear wheels are controlled by the rear wheel auxiliary steering angle δr obtained in step 76 based on the correction value in step 74 or 75. Solenoid 1 of electromagnetic proportional rear wheel steering control valve 13 that operates actuator 12
Drive current 1.3L and 13R respectively. , T□ are output. Note that after steps 79 and 80, control returns to step 71 and is executed repeatedly.

With the 4WS control described above, when the 4WD system fails and the 4WS system operates normally, the rear wheel auxiliary steering angle δr increases and the in-phase control amount increases.
Since the control is performed, the running stability of the vehicle can be improved to reduce the tendency for understeer.

The above-mentioned 4WD II control and 4WS control will be qualitatively explained.

First, let's talk about 4WD control.
As stated in JP 29-39 (written by Masaichi Kondo, published in June 1976), the directional stability of the vehicle is expressed as the constant between 8 and 0, and if and > 0, it is stable (and dβ M corresponds to a tendency to oversteer), and if - is 0, it becomes unstable dβ (corresponds to a tendency to oversteer). Therefore, when the driving force T is positive, the larger the front wheel drive force distribution α is, the greater the static stability is, and the static stability is correspondingly improved (understeer (backwards)). Become).

Next, talking about 4WS control, for example, the daily amount Cue
- In the case of the
00%), and the stability of the vehicle decreases.

In such a case, if the proportionality constant K is increased using the iS control described above, the steady-state gain of the yaw rate and the yaw rate phase delay will decrease from the solid line shown in the diagram to the dotted line, as shown in the steering response characteristic diagram of four-wheel steering in Figure 5. Since the damping of the yaw boat is improved, vehicle characteristics with improved stability can be obtained, which compensates for the effects of 4WD system failure.

Vehicle characteristics with improved stability can also be obtained by decreasing the differential constant τ to τ-τ-Δτ or τ-0 using 4WS control to lower the gain (however, the steering response gain is slightly reduced). do).

Note that if the 4WS system fails and the system becomes 2WS control, the understeer tendency will weaken and the steering response gain will increase, as shown by the dashed line in Figure 5, which may cause the driver to feel strange. 4WI3%1ltt
The effect of increasing the front wheel drive distribution of ll can solve that problem.

(Effects of the Invention) Thus, as described above, the vehicle travel control device of the present invention has four
The failure information of one control mechanism of the wheel rudder control mechanism and the front and rear wheel drive distribution control mechanism of four-wheel drive is taken in, and the other normally operating control mechanism is set to the fail-safe side so that the stability of vehicle running is improved. Therefore, it is possible to realize an extremely safe vehicle running control device that has a fail-safe function that ensures running stability as a function of the entire vehicle.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a vehicle used in an embodiment of the device of the present invention, FIG. 2 is a diagram showing details of the travel control device of this embodiment, and FIGS. 3 and 4 are four-wheel steering, respectively. FIG. 5 is a flowchart showing control and front and rear wheel drive force distribution control of four-wheel drive. FIG. 5 is a characteristic diagram showing steering response characteristics of four-wheel steering. LL, IR...Front wheel 2L, 2R...
Rear wheel 3... Steering wheel 4... Engine 5... Transmission 6... Propeller shirt I- 7... Rear wheel differential gear 8... Front wheel drive clutch 9... Propeller shaft 10... - Front wheel differential gear 11... Steering gear 12... Rear wheel steering actuator 13... Electromagnetic proportional rear wheel steering control valve 14... Pump 18... Electromagnetic proportional pressure regulating valve 19... Controller 20...Steering angle sensor 21L, 21R, 22L, 22R...Wheel rotation sensor 23...Vehicle speed sensor 24...Throttle opening sensor Patent applicant Hidetoshi Sugimura, Patent attorney representing Nissan Motor Co., Ltd. Written by patent attorney Oki Sugimura No. 3
Figure 5 TART I General command Ω horse section ψ Kaka song division control from Hayabusa, front and rear car trays, horse heavy j7J West Koko ratio 5Thi4WS7x
Haiku signal has 99 ks 54 NO Iri R' Sei I 14, Naiku, Mokinkudo 9
and #ν and〉Dopa h゛4WD Shizute Art
Yes Fu・Iru→＼?
56N. 5B4WD% Axis - Positive rear horse sector 1st position west side 4th ratio and 4wS control 4WD solenoid F' horse sector movement shift fC variable output Failed word output cuff ■force■

Claims (1)

[Scope of Claims] 1. A vehicle travel control device for a vehicle comprising a four-wheel steering control mechanism and a four-wheel drive front and rear wheel drive force distribution control mechanism, comprising: the four-wheel steering control mechanism and the front and rear wheel drive force distribution control mechanism; A vehicle running system characterized in that, when one of the mechanisms fails, the other normally operating control mechanism is operated in a fail-safe manner based on the failure information so as to improve the stability of vehicle running. Control device.