JPS6042161A - Four-wheel steering gear for vehicle - Google Patents

Abstract

PURPOSE:To seize anything trouble in a sensor system in an accurate manner and thereby keep off any abnormal steering as well as to improve the safety of car driving, by discriminating the trouble in the sensor system in a way of comparison between a front wheel roll-steering angle and a critical front wheel roll-steering angle, while making a rear wheel roll-steering angle turn to zero. CONSTITUTION:Signals out of a speed sensor 5 and a front wheel roll-steering angle sensor 6 are inputted into an automatic control device 8. On the basis of these signals, a rear wheel roll-steering angle is calculated, while a pulse signal is outputted to a pulse motor 20, and an output shaft of the pulse motor 20 rotates. And, a rod 16 shifts in an axial direction whereby rear wheels 3 are roll-steered, and a power cylinder 21 operates, assiting the roll-steering of these rear wheels 3. When trouble in a sensor system is discriminated at a discrimination device 9, a safety control device 10 operates, causing a roll-steering angle of these rear wheels 3 to come to zero. When an absolute value of the front wheel roll-steering angle exceeds a critical front wheel roll-steering angle, it is discriminated that there is anything unusual in the sensor system so that these rear wheels 3 are prevented from being abnormally steered.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a wheel steering system for a vehicle.

(Prior art) An example of a vehicle steering system is disclosed in Japanese Patent Application Publication No. 2003-011002.
It is disclosed in the publication No. This wheel steering system connects the front wheels and rear wheels with a link member, etc., and increases the steering angle ratio of the rear wheels to the front wheels as the vehicle speed increases or decreases based on signals from the vehicle speed sensor. However, if the vehicle speed sensor malfunctions and a signal indicating a vehicle speed higher than the actual vehicle speed is output, the rear wheels will be steered abnormally.

Further, in the above-mentioned conventional technology, the steering operation of the front wheels is mechanically transmitted to the rear wheels by a link member or the like.
It is also conceivable that the steering angle of the front wheels is detected by a sensor, and the steering angle of the rear wheels is electrically controlled based on the detection signal and the detection signal from the vehicle speed sensor. When performing such control,
In addition to the vehicle speed sensor, an abnormality in the front wheel steering angle sensor is also a problem. That is, if a signal indicating a larger steering angle than the actual front wheel steering angle is output, the rear wheels will be abnormally steered.

Therefore, in response to abnormalities in the sensor system, the maximum vehicle speed and maximum front wheel steering angle determined from the vehicle's driving behavior are determined, and whether or not the signal from each sensor exceeds these maximum values is determined. It is also possible to judge. However, for example, it is impossible for a vehicle driver to know that the steering angle of the front wheels is maximum when the vehicle speed is maximum, and it is clear that such a state is causing an abnormality in the sensor system. There is a problem in that an abnormality in the sensor system cannot be detected as long as the signal and front wheel steering angle signal are within the permissible range of the output of each sensor.

(Object of the Invention) In view of the fact that countermeasures against sensor system abnormalities are an extremely important issue for safe vehicle operation in a vehicle steering system, the present invention aims to solve the problem by grasping the relationship between vehicle speed and front wheel steering angle. Then, by checking whether the driving condition specified by both the signal from the vehicle speed sensor and the signal from the IF1 wheel steering angle sensor is a possible condition based on the driving characteristics of the vehicle, an abnormality in the sensor system is determined. This system aims to improve vehicle driving safety by preventing abnormal steering.

(Configuration of the Invention) The configuration of the present invention is clearly shown in FIG. That is, the wheel steering device for a vehicle according to the present invention includes a steering device 2 that steers the front wheels 1 of the vehicle, a rear wheel steering device 4 that steers the rear wheels 6, and a vehicle speed sensor 5 that detects the vehicle speed. It includes a front wheel steering angle sensor 6 that detects the steering angle of the front wheels 1, and a controller 7 that controls the operation of the rear wheel steering device 4.

The controller 7 includes a vehicle speed sensor 5 and a front wheel steering angle sensor 6.
an automatic control means 8 which outputs a control signal to the rear wheel steering device 4 so that the steering angle characteristic of the rear wheels 6 relative to the front wheels 1 changes depending on the vehicle speed in response to the output from the vehicle; and a determination device which determines a failure of the sensor system. and a safety/safety control means 10 that receives the output of the determination means 9 and sets the steering angle of the rear wheels 6 to zero. The determining means 9 then compares the front wheel steering angle obtained from the output from the front wheel steering angle sensor 6 with the allowable critical front wheel steering angle determined from the output from the vehicle speed sensor 5, and determines the magnitude thereof. However, when the front wheel turning angle measured by the front wheel turning angle sensor 6 exceeds the critical front wheel turning angle, an activation signal is output to the safety control means 10.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 2 to 5.

As shown in FIG. 2, the steering device 2 that steers the left and right front wheels 1, 1 of the vehicle includes a steering wheel 11, a steering pinion mechanism 12 that converts the rotational motion of the steering wheel 11 into linear reciprocating motion, A tie opening that transmits the operation of this rack and pinion mechanism 12 to the front wheels 1, 1.
Throat 13a + 13a and knuckle arm 13
and a transmission means 16 consisting of 13b and 13b.

On the other hand, the rear wheel steering device 4 that steers the left and right rear wheels 6, 6,
A rod 16 is connected to the rear wheel 6.6 via knuckle arms 14, 14 and tie rods 15.15.

This rod 16 moves in the left-right direction by the rotation of a pinion 18 that meshes with its rank portion 17 to steer the rear wheels 6 and 3. The pinion 18 is connected to a pulse motor 20 via a transmission mechanism 19 consisting of a pair of bevel gears.
There is.

In addition, the rod 16 passes through the power cylinder 21,
A piston 24 that partitions the inside of the power cylinder 21 into left and right hydraulic chambers 22, 23 is fixed to the rod 16. Each hydraulic chamber 22 , 23 is connected to an oil pump 60 via a hydraulic passage 25 , 26 , a control valve 27 , an oil supply passage 28 , and an oil return passage 29 , and an electric motor 61 is connected to the oil pump 30 .

The control valve 27 detects the rotational direction of the pinion 18 and communicates the oil supply passage 28 with one hydraulic chamber 22 or 26 and the oil return passage F829 with the other hydraulic chamber 26 or 22, and also communicates the oil supply passage 28 with one hydraulic chamber 22 or 26 and the oil return passage F829 with the other hydraulic chamber 26 or 22. The hydraulic pressure is controlled to a pressure corresponding to the rotational force of the pinion 18, and the hydraulic pressure introduced into the power cylinder 21 moves the rod 16,
In other words, the steering force of the rear wheels 6, 6 is assisted.

The operation of the pulse motor 20 and the electric motor 1 is controlled by control signals output from the controller 7. This controller 7 includes a vehicle speed sensor 5, t;tllII+i1, which detects the vehicle speed.
A front wheel steering angle sensor 6 detects the steering angle of the steering wheel 1 from the steering angle of the steering wheel 11, a rear wheel steering angle sensor 62 detects the steering angle of the rear wheel 1, and a rear wheel steering angle sensor 62 detects the steering angle of the front wheel 1 and the rear wheel 6. A display means 66 for displaying graphics, a mode switch 64 for setting the steering mode of the rear wheels, and a battery 65 are connected. In FIG. 1, 36 is a steering angle (front wheel turning angle) detection section, 67 is a pulse motor rotation angle detection section, and the rear wheel turning angle sensor 62 is connected to the pulse motor 20.
The steering angle 1!16 behind is detected from the rotation angle of .

Next, the specific configuration of the controller 7 will be explained.

The controller 7 includes a vehicle speed sensor 5 and a front wheel steering angle sensor 6.
and determining means 9 for determining whether or not there is a failure in the sensor system based on the output from the vehicle speed sensor 5 and the front wheel steering angle sensor 6 in response to the determination by the determination means 9 that there is a failure in the sensor system. The vehicle is equipped with an automatic control means 8 which controls the operation of the rear wheel steering device 4 according to the operation of the vehicle, and a safety control means 10 which sets the rear wheel steering angle to zero upon receiving a determination by the determining means 9 that there is a failure.

The determination means 9 determines the vehicle speed @ area based on the vehicle speed signal inputted from the vehicle speed sensor (pulse generator) 5 through the input protection section 68 and the counting section 39 that counts the number of pulses, as shown in FIG. From the vehicle speed region determination section 40 and the front wheel steering angle sensor 6 to the A/D conversion section 41 and the encoding section 4
The front wheel steering angle determination section 46 determines whether or not the front wheel steering angle signal inputted through the vehicle speed signal 2 is possible in terms of the driving characteristics of the vehicle in relation to the vehicle speed signal.

Specifically, in the second input protection unit 68, 44 is an integrating circuit for stabilizing the pulse signal from the vehicle speed sensor 5;
Reference numeral 45 denotes a hysteresis-controlled inverter exhibiting a buffer effect, and noise is removed by this input protection section 68. Further, in the counting section 39, the vehicle speed is determined by the number of pulses r.

On the other hand, the front wheel steering angle sensor 6 uses a potentiometer.
The tonta signal from this front wheel steering angle sensor 6 is A.
/D converter 41 converts it into a digital quantity (pulse), and encoder 42! It is encoded with a decimal code.
It can be seen as an IJ wheel steering wheel.

Therefore, as shown in FIG. 7, the vehicle speed region determining section 40
Preset boundary vehicle speed V lim and maximum vehicle speed VmaX
Low speed @ range below Vzim and Vlim~■max
The system is divided into a medium-high vehicle speed region and an abnormal vehicle speed region exceeding VmaX, and it is determined to which vehicle speed region the vehicle speed signal from the counting section 69 belongs. "2. Vlim is the state when the steering wheel 11 is steered to the lock position, that is, the maximum front wheel turning angle θFmax (when turning to the right)
, -θFmax (when steering to the left) is the upper limit value of the vehicle speed at which the vehicle can travel, and vmax is the maximum value of the vehicle speed that is allowable for the vehicle's functionality.

Then, when the vehicle speed signal from the counting section 69 belongs to the abnormal vehicle speed region, the vehicle speed region determination section 40 determines that the automatic control means 8
It outputs an operation command signal to the front wheel steering angle determination section 46 when the vehicle speed belongs to another vehicle speed range.

On the other hand, the front wheel steering angle determining section 46 determines the maximum allowable front wheel steering angle at the vehicle speed corresponding to the output signal of the counting section 39;
In other words, the critical front wheel turning angle f(v) is determined and the encoder 4
Absolute value of the front wheel steering angle corresponding to the output signal of 2 1θF1
Determine whether or not exceeds the critical front wheel steering angle [(V),
If it exceeds 0, an operation command signal @ is output to the safety control means 10, and when it exceeds 0, an operation command signal is output to the automatic control means 8.

9. The pre-critical steering angle f(y) is the maximum +j in the low vehicle speed region.
fj transverse steering angle f(V) - θFmax,
In the medium and high vehicle speed region, the above θFmax, critical vehicle speed V lim
, the maximum vehicle speed VmaX, and the maximum front wheel turning angle θFlim allowable based on this vmax.

f(V)=K(IIV+Kβ) The characteristic of this critical front wheel turning angle with respect to vehicle speed is shown in FIG.

The automatic control means 8 receives the operation command signal from the front wheel turning angle determination section 46 and determines the vehicle speed detected by the vehicle speed sensor 5 and the one-wheel one-wheel turning angle detected by the front wheel turning angle sensor 6. It includes a calculation unit that calculates the optimum turning angle of the rear wheels 6 relative to the turning angle of the front wheels 1. An example of the characteristics of the steering angle ratio θR/θF between the rear wheel steering angle θ and the front wheel steering angle θF stored in this calculating section with respect to the vehicle speed is shown in FIG. The steering angle θk is calculated, and the pulse motor 2
A control signal is output to 0.

On the other hand, the safety control means 10 receives an operation command signal from the vehicle speed region determining section 40 or the front wheel steering angle determining section 46, and
It outputs a signal to the relay 46 to cut the control signal transmission from the automatic control means 8 to the rear wheel steering device 4, and the rear wheel 6 is set to a return spring attached to the knuckle arm 14 so that the steering angle is zero. becomes.

A program for operating the controller 7 with respect to the determining means 9 is shown in the form of a flowchart in FIG. That is, in step (2), it is determined whether the vehicle speed (2) is smaller than the maximum vehicle speed VmaX, that is, whether or not the abnormal vehicle speed region does not belong. (with an abnormality), the process proceeds to step (3), where safety control is performed by the safety control means 10. In the above step ■, the vehicle speed ■ is the critical vehicle speed Vli
It is determined whether the vehicle speed is greater than m, that is, whether it belongs to the middle/high vehicle speed @ range (belongs to the low vehicle speed range). If YES, the process proceeds to step (2), and if NO, the process proceeds to step (2).

In step ■, the absolute value of the front wheel steering angle 1θF1 is the critical front wheel steering angle 'f (v) = KQI v in the medium and high vehicle speed @ range.
It is determined whether or not the value is smaller than β. If YES, the process proceeds to step 3, where automatic control is performed by the automatic control means 8; if NO (at least one of the vehicle speed sensor 5 and the front wheel steering angle sensor 6 There is an abnormality on one side) is a step■
Safety control is then carried out. On the other hand, in step ■, the above 10F1 is the critical front wheel steering angle f(V) in the low vehicle speed region.
It is determined whether or not it is smaller than -θFmax. If YES, proceed to step ■ to perform automatic control; if NO (there is an abnormality in the front wheel steering angle sensor 6), proceed to step ■ to perform safety control. Each will be done.

In addition, in FIG. 2, the display means 33 is a transmission type liquid crystal display means provided on the driver's seat side.
It includes a steering direction display segment 47 that graphically displays the steering direction of the steering wheel 1 and the rear wheels 6, and a vehicle behavior display segment 48 that graphically displays the behavior of the vehicle.

The operation of the display means 36 is controlled by the controller 7 based on signals from the ifJ wheel turning angle sensor 6 and the rear wheel turning angle sensor 62.

The 5-mode switch 64 is used for low vehicle speeds (for example, JQ
km/b or less), auto mode that steers the rear @j6 in the opposite phase to the front wheel 1, club mode that steers the rear 1'& 3 in the same phase as the front wheel 1, and steering of the rear wheel O. This is a switch that allows the driver to select from three modes, including two-wheel mode in which the angle is always zero, and manually set it. The signal from this mode switch 64 is transmitted to the controller 7.
The controller 7 operates according to the mode selected by the mode switch 64. In this case, the controller 7 operates the automatic control means 8 by selecting the automatic mode.

Next, to explain the operation of the embodiment, when the steering wheel 11 is steered while the vehicle is running, iQ M 1 +1 is steered according to the steering direction and steering angle, and the determination means 9 detects an abnormality on the sensor basis. If it is determined that there is no steering wheel, the automatic control means 8 is activated and the rear wheel steering device 4 is controlled. In other words, signals from the vehicle speed sensor 5 and the front wheel steering angle sensor 6 are input to the automatic control means 8, and based on these signals, the rear wheel steering angle θk is calculated according to the characteristics shown in FIG. A pulse signal corresponding to f6 is output to the pulse motor 20. As a result, the output shaft of the pulse motor 20 rotates at an angle corresponding to the pulse signal, and the transmission mechanism 19
．． Rod 16 via pinion 18 and rack part 17
moves in the axial direction, and the rear wheels 6°6 are steered. At this time, the power cylinder 21 is activated to assist in steering the rear wheels 6, 6.

When the determination means 9 determines that there is an abnormality in the sensor system, the safety control means 10 is activated and the steering angle of the rear 1I1813 becomes zero. In this case, in the medium to high vehicle speed region, it is determined whether the vehicle driving state specified by both the vehicle speed ■ and the front wheel steering angle θF is a possible state in terms of vehicle functionality. Even if the output signals of the front wheel steering angle sensor 6 do not exceed VmaX and θFmax, if the detected absolute value IθF1 of the front wheel steering angle exceeds the critical front wheel steering angle f (v), it is determined that there is an abnormality in the sensor system. Therefore, even if there is a slight abnormality in the sensor system, the rear wheels 6 will not be abnormally steered.

In the above embodiment, the critical front wheel steering angle is determined by the vehicle speed V.
However, through vehicle running tests, we determined the critical front wheel steering angle characteristics with respect to vehicle speed ■, and created a map for sensor system failure determination regarding vehicle speed ■ and front wheel steering angle θF from those characteristics. , the presence or absence of a failure may be determined based on signals from the vehicle speed sensor 5 and the front wheel steering angle sensor 6.

Also, based on the above characteristics, the critical 10-wheel steering angle is determined by the vehicle speed
Alternatively, the critical front wheel turning angle may be calculated by approximating it to a multidimensional function and inputting a signal of the vehicle speed.

Further, in the above embodiment, the safety control means 10 cuts the signal from the automatic control means 8 to the rear wheel steering device 4 (turns off the power), but the safety control means 10 cuts the signal from the automatic control means 8 to the rear wheel steering device 4. A signal may be sent to forcibly drive the rear N13 so that the steering angle becomes zero.

Furthermore, the oil pump 60 in FIG. 2 may be driven by an engine.

(Effects of the Invention) According to the present invention, the critical front wheel turning angle that is functionally allowable for the vehicle with respect to the vehicle speed is determined by the output from the vehicle speed sensor, and the front wheel turning angle is obtained by the output from the front wheel turning angle sensor. Since a failure in the sensor system is determined by comparing the angle with the above-mentioned critical nfJ steering angle and the rear wheel steering angle is set to zero, it is possible to accurately detect a failure in the sensor system and prevent abnormal steering of the rear wheels. I can do it,
Increases safety when driving a vehicle.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the present invention, Fig. 2 is a block diagram of an embodiment, Fig. 3 is a block diagram of the portion related to the determination means of the controller, and Fig. 7 shows the relationship between vehicle speed and critical front wheel turning angle. FIG. 5 is a characteristic diagram showing the relationship between vehicle speed and steering angle ratio, and FIG. 6 is a flowchart showing the mode of control related to the determination means. 1...Front wheel, 2...Steering device,
3... Rear wheel, 4... Rear wheel steering device, 5...
...Vehicle speed sensor, 6...Front wheel steering angle sensor, 7
... Controller, 8 ... Automatic control means, 9 ... Judgment means, 10 ... Safety control means Figure 3 Figure 4

Claims (1)

[Claims] (1) A steering device that steers the front wheels, a rear wheel steering device that steers the rear wheels, and a vehicle speed sensor that detects vehicle speed;
The controller includes a front wheel steering angle sensor that detects the front wheel steering angle, and a controller that controls the rear wheel steering device in response to output signals from the vehicle speed sensor and the front wheel steering angle sensor. It is determined by the front wheel steering angle obtained from the output from the front wheel steering angle sensor and the front wheel steering angle obtained from the output from the front wheel steering angle sensor and the output from the vehicle speed sensor. a determination means for comparing and determining an allowable critical 1f+wheel steering angle; and a determination means for determining the rear wheel steering angle to zero in response to an output of the determination means when the front wheel steering angle detected by the front wheel steering angle sensor exceeds the maximum front wheel steering angle. A wheel steering device for a vehicle, characterized in that it is equipped with a safety control means.