JPH0453749B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a device for steering both the front wheels and the rear wheels of a four-wheeled vehicle such as an automobile. It relates to a four-wheel steering device that also steers the rear wheels, and in particular, it is a four-wheel steering device for a vehicle that has an improved control mechanism that sets the rear wheel steering angle in accordance with the driving condition such as the front wheel steering angle. It is related to.

(Prior art) Conventionally, the steering system for four-wheeled vehicles steers only the front wheels, and the rear wheels do not actively steer the rear wheels, although they do some toe-in or toe-out depending on the driving situation, regardless of the steering of the front wheels. It is not designed to turn the ship. However, recently, a four-wheel steering device has been proposed that steers both the front wheels and the rear wheels, and research on this type of device is being conducted.

According to the four-wheel steering system, convenient maneuvering that was previously impossible and driving with improved steering performance are possible depending on various driving conditions of the vehicle. for example,
When maneuvering a vehicle at extremely low speeds, such as parallel parking or parking in a garage, by steering the rear wheels in the opposite direction to the front wheels (this is called anti-phase), it is possible to significantly change the direction of the vehicle. This makes it possible or easy to park in narrow spaces, which was previously impossible or extremely difficult. Furthermore, when steering a vehicle at extremely low speeds, if the rear wheels are steered in the same direction as the front wheels (this is called in-phase), the entire vehicle can be moved in parallel, making it easier to park or park the vehicle. It's often convenient.

On the other hand, when changing lanes while driving at medium to high speeds, if four-wheel steering is performed in the same phase, lateral force is applied to the front and rear wheels at the same time, making it possible to change lanes smoothly without phase lag, thereby suppressing yawing. This allows you to change lanes at high speed without fear. Furthermore, when cornering, the direction of the vehicle can be effectively changed by steering the rear wheels in opposite phases.

The four-wheel steering system for a vehicle as described above generally includes a steering system that steers the front wheels, and an actuator that drives a rear wheel steering member to drive the rear wheels, as disclosed in, for example, Japanese Patent Laid-Open No. 11173/1983. It has a rear wheel steering device that steers the wheels, and a controller that controls the rear wheel steering device. A control signal corresponding to the steering angle is output, and the actuator is actuated by the control signal. The wheel steering angle is set in accordance with the vehicle speed as well as the front wheel steering angle.)

In order to accurately steer the rear wheels according to the target rear wheel steering angle set as described above, as shown in the above-mentioned Japanese Patent Laid-Open No. 57-11173,
A rear wheel turning angle sensor may be provided, and the measured rear wheel turning angle signal detected by the rear wheel turning angle sensor may be fed back to the rear wheel turning angle control system to perform so-called feedback control.

However, when such feedback control is performed, the responsiveness of the rear wheel turning angle control becomes poor, and problems occur such as the rear wheel turning not being able to follow the front wheel turning especially when a quick steering operation is performed.

(Object of the Invention) The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a four-wheel steering device for a vehicle in which the responsiveness of rear wheel steering control is sufficiently improved. It is.

(Structure of the Invention) A four-wheel steering device for a vehicle according to the present invention is provided with the above-described steering device, a rear wheel steering device, and a controller, and basically uses a measured rear wheel steering angle signal to steer the rear wheels. Adopting so-called open control that does not return feedback to the angle control system, the target rear wheel turning angle and the rear wheel turning angle sensor are determined by the controller only for a predetermined period after receiving the output of the start detection means that detects the start state of the vehicle. The present invention is characterized in that a starting correction means is provided which outputs a correction signal to the actuator to perform feedback control by comparing the measured rear wheel turning angle detected with the measured rear wheel turning angle and reducing the deviation.

(Effects of the Invention) If the rear wheel turning angle is controlled by open control, control responsiveness is improved compared to the case where feedback control is performed, and the above-mentioned problems are solved. In addition, since the above-mentioned start-up correction means is provided, even if the front or rear wheels go into a recess or run over a protruding object when parking, for example, and the basic correspondence between the two steering angles becomes incorrect, Immediately after the vehicle starts, the rear wheels are set to a steering angle that optimally corresponds to the front wheel steering angle, thereby preventing the vehicle from running abnormally when the vehicle starts.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 schematically shows a four-wheel steering system for a vehicle according to a first embodiment of the present invention. A steering device 2 that steers left and right front wheels 1, 1 includes a steering wheel 3 and a rack and pinion mechanism 4 that converts rotational motion of the wheel 3 into linear reciprocating motion.
, right and left tie rods 5, 5 and knuckle arms 6, 6, which transmit the operation of the mechanism 4 to the front wheels 1, 1 and steer them.

On the other hand, a rear wheel steering device 8 for steering the left and right rear wheels 7, 7 includes a rear wheel operating rod 9 held slidably in the left and right directions on the vehicle body, and tie rods 10 at both left and right ends of the rod 9, respectively. The rear wheels 7 have left and right knuckle arms 11, 11 connected to each other through a shaft 10, and the rear wheels 7, 7 are steered by the axial movement of the operating rod 9. And the operating rod 9 has a rack 12.
A pinion 1 is formed and meshes with the rack 12.
3 is a pair of bevel gears 15,
16 and pinion shaft 17, the rear wheels 7, 7 are steered in accordance with the direction and amount of rotation of the pulse motor 14.

Further, the rear wheel operating rod 9 passes through the power cylinder 18, and a piston 19 that partitions the inside of the cylinder 18 into left and right hydraulic chambers 18a, 18b is fixed to the operating rod 9.
Hydraulic passages 21a and 21b led from a control valve 20 provided around the pinion shaft 17 are connected to the a and 18b, respectively, and a pump 23 driven by the control valve 20 and a motor 22 is connected to the a and 18b, respectively. A hydraulic pressure supply passage 24 and a return passage 25 are provided between them. here,
The control valve 20 is connected to the pulse motor 1
4, the hydraulic pressure supplied from the pump 23 via the hydraulic pressure supply passage 24 is applied to one of the hydraulic chambers 18 of the power cylinder 18 according to the direction of the rotational force.
a or 18b, and acts to return the hydraulic oil in the other hydraulic chamber 18b or 18a to the pump 23 via the return passage 25. Therefore, when the operating rod 9 is moved in the axial direction by the pulse motor 14 via the bevel gears 15, 16, pinion shaft 17, pinion 13 and rack 12, the hydraulic pressure introduced into the power cylinder 18 is applied to the piston. 19 to assist the movement of the operating rod 9.

The pulse motor 14 and the pump drive motor 22 are operated by the signals A and B output from the controller 26, respectively, but the controller 26 also receives a vehicle speed signal C output from the vehicle speed sensor 27. A front wheel steering angle sensor 28 detects the position of the front wheel steering member in the steering device 2, for example, the steering angle of the steering wheel 3.
The front wheel steering angle signal D from
Rear wheel steering angle sensor 29 detects the stroke amount of
A rear wheel steering angle signal E from the ignition switch 31 and a pulse signal F from the ignition switch 31 are input.

Next, the configuration of the controller 26 will be explained with reference to FIG. The vehicle speed signal C from the vehicle speed sensor 27 and the front wheel turning angle signal D from the front wheel turning angle sensor 28 are input to the rear wheel turning angle calculating section 30.
This calculation unit 30 has an optimum rear wheel steering angle θr for the front wheel steering angle θf and the vehicle speed V as shown in FIG. 3, for example.
According to this characteristic, a target rear wheel turning angle θro corresponding to the vehicle speed V and the front wheel turning angle θf indicated by the signals C and D is calculated. here,
The rear wheel steering characteristics shown in Figure 3 are such that at low speeds, as the front wheel steering angle θf increases, the rear wheel steering angle θr becomes smaller at the steering ratio θr/θf and in phase (the front and rear wheels are steered in the same direction). At the same time, when the front wheel steering angle exceeds a certain value, the phase reverses (the front and rear wheels are steered in opposite directions), and at high speeds, as the front wheel steering angle θf increases, the rear Steering ratio θr/θf with large wheel steering angle θr
The steering ratio θr/θf increases with the same phase and gradually decreases when the front wheel steering angle exceeds a certain value. This is to make the minimum turning radius as small as possible when the vehicle turns at low speeds, and to realize a quick course change when changing lanes at high speeds.

The target signal G carrying the target rear wheel turning angle θro calculated by the rear wheel turning angle calculation unit 30 as described above is as follows:
It is input to the driver 32 of the pulse motor 14.
The driver 32 receives this signal G and turns the rear wheels 7, 7.
A pulse signal A is output to rotate the pulse motor 14 so that the target rear wheel turning angle θro is set to the target rear wheel turning angle θro. When the pulse signal A is output, a drive signal B is output to the pump drive motor 22 shown in FIG.

On the other hand, the measured signal E indicating the measured rear wheel turning angle θr outputted from the rear wheel turning angle sensor 29 and the target signal G indicating the target rear wheel turning angle θro calculated by the calculation section 30 are sent to the comparator 33. is input. The comparator 33 also receives a regular correction operation signal H output from a steering angle sensor 34 that detects the regular correction timing.
An operation signal J, which is the gate output of an OR gate 36, is inputted with a starting correction operation signal I outputted from a T flip-flop 35 to which the pulse signal F is inputted.

Here, the steering angle sensor 34 receives the front wheel turning angle signal D and adjusts the steering angle of the steering wheel 3 corresponding to the front wheel turning angle θf indicated by the signal D to a predetermined angle such as ±0°. When the normal correction operation signal H is reached, the normal correction operation signal H is output. On the other hand, the T flip-flop 35 has the ignition switch 31 turned on.
Due to the upedge of the pulse signal F that is generated when the engine is set to the START state from
The pulse signal F that is generated when the switch is turned back on from
The output state is returned to the L (Low) level signal output state by the application of . The comparator 33 operates temporarily only when the operation signal J is input, and compares the target rear wheel turning angle θro indicated by the signals G and E with the measured rear wheel turning angle θr, and calculates the difference according to the deviation amount. A correction signal (pulse signal) K for reducing the deviation is sent to the pulse motor 14.
output to the driver 32 of.

In this embodiment, the pump 23 may be driven by an engine.

Next, the operation of the above embodiment will be explained.
When the steering wheel 3 is steered while the vehicle is running, the left and right front wheels 1, 1 are steered according to the steering direction and steering angle, and the steering angle θf and the vehicle speed V at that time are detected by the sensor 28, 27, and input as signals D and C to the rear wheel turning angle calculating section 30 of the controller 26. Based on the front wheel turning angle θf and the vehicle speed V indicated by the signals D and C, the calculation unit 30 calculates a target rear wheel turning angle θro according to preset characteristics as shown in FIG. , outputs the corresponding target signal G to the driver 32. The driver 32 generates a pulse signal A corresponding to this target signal G and inputs it to the pulse motor 14. Therefore, the pulse motor 14 in the rear wheel steering device 8 rotates by the number of times corresponding to the pulse signal A, that is, the number of times corresponding to the target rear wheel turning angle θro, and the bevel gears 15,1
6, pinion shaft 17, pinion 13 and rack 1
2 to move the rear wheel operating rod 9 in the axial direction. As a result, the rear wheels 7, 7 are steered so as to match or substantially match the target rear wheel turning angle θro. At this time, the power cylinder 18 is activated to assist the movement of the operating rod 9.

When the rear wheels 7, 7 are steered as described above, the steered angle θr is detected by the rear wheel steered angle sensor 29 and inputted to the comparator 33 of the controller 26 as an actual measurement signal E. The comparator 33 does not operate unless the operation signal J is input. Therefore, normally, unilateral control, that is, open control, is performed from the controller 26 to the rear wheel steering device 8, and when the actual measurement signal E of the rear wheel steering angle θr is fed back to perform feedback control. The steering delay and hunting of the rear wheels 7, 7 that occur do not occur.

However, when the steering wheel 3 is steered and the steering angle reaches the predetermined angle (for example, ±0°), the regular correction operation signal H is input from the steering angle sensor 34 to the OR gate 36, and the OR When the operation signal J is input from the gate 36 to the comparator 33, the comparator 33 operates and the actual measurement signal E from the rear wheel steering angle sensor 29 is output.
and the target signal G from the calculation section 30 are compared.
Then, the target rear wheel turning angle θro indicated by both signals G and E
If there is a difference between the measured rear wheel turning angle θr,
A correction signal K that reduces the deviation according to the amount of deviation.
is output to the driver 32. Therefore, the pulse motor 14 performs a correction operation so that the actual rear wheel turning angle θr matches the target rear wheel turning angle θro. As a result, the accumulation of control errors due to the open control described above is reduced or eliminated, and optimal rear wheel steering characteristics can be obtained again. Here, since the above correction operation is temporarily performed only when the steering angle of the steering wheel 3 reaches a predetermined angle, the advantages of the open control described above are essentially maintained.

Further, when the ignition switch 31 is set to START and the engine starter motor (not shown) is driven, the T flip-flop 35 outputs the starting correction operation signal I.
is output. Therefore, the operation signal J is input from the OR gate 36 to the comparator 33, and the pulse motor 14 is operated to correct as described above, so that the actual rear wheel turning angle θr matches or almost matches the target rear wheel turning angle θro. be done. In this way, when starting, the rear wheel steering angle θr
Of course, by making this correction, if open control errors have accumulated during driving before the engine stops, the errors will be reduced or eliminated.
When the vehicle is parked, the front wheels 1, 1 or the rear wheels 7, 7 may, for example, fall into a recess, ride on a protruding object, or even be parked on a slope.
Even if the basic correspondence between the rear wheels 7 and 7 is incorrect, the rear wheels 7 and 7 are immediately set to the steering angle θr that optimally corresponds to the front wheel steering angle θf when the engine is started, and the vehicle is Abnormal driving is prevented. As explained above, in this embodiment, the ignition switch 31 constitutes the start detection means, the T flip-flop 35, the OR gate 36, and the comparator 3.
3 constitutes a start correction means.

In the first embodiment described above, the front wheel turning angle sensor 28 and the steering angle sensor 34 set the timing for regular correction, while the ignition switch 31 and the T flip-flop 35 set the timing for starting correction. At each correction time, the comparator 33
Although the rear wheel turning angle θr is corrected by the following, other known means may be used as means for setting the correction timing. Especially in the case of starting correction, even if the correction is applied at the same time as the engine starts, it is difficult to steer the rear wheels 7 while the vehicle is stopped unless the capacity of the pulse motor 14 and power cylinder 18 is particularly large. The start correction may be performed after the vehicle actually starts. To this end, the starting correction timing setting means shown by the symbol S in FIG. Just replace it.

In the second embodiment shown in FIG. 4, the pulse signal F from the ignition switch 31,
A start signal M from a start sensor 40 that detects the start of the vehicle is input to an AND gate 41, and a gate output I' of the AND gate 41 is passed through a timer 42 to form a start correction operation signal I. That is, when the ignition switch 31 is in the ON state and the vehicle starts, the AND gate 41 outputs a gate output I'. The signal is input to the OR gate 36 in FIG. 1 for a period of time and is then cut. By doing so, the rear wheel turning angle θr can be corrected when the vehicle actually starts moving. Additionally, a start sensor 4 detects the start of the vehicle.
0, a rotation speed sensor that detects that the engine rotation speed has exceeded a predetermined rotation speed, a front wheel 1,
1 or a sensor that detects the rotation of the rear wheels 7, 7;
Furthermore, a sensor or the like that detects release of the parking brake may be used. and the start sensor 40
By inputting the pulse signal F of the ignition switch 31 to the AND gate 41 along with the start signal M of This will prevent things like this from happening. In this embodiment, an ignition switch 31, a starting sensor 40 and
The AND gate 41 constitutes a start detection means,
Timer 42 connects OR gate 36 and comparator 33
(See FIG. 2) together constitute a start correction means.

As shown in FIG. 5, the start correction timing setting means S'' in which a timer 50 similar to the above-mentioned timer 42 is directly connected to the ignition switch 31 is replaced with the means S of FIG. Therefore, it is also possible to set the timing at which the correction ends. In this embodiment, the ignition switch 31 constitutes a start detection means, and the timer 50
OR gate 36 and comparator 33 (see Figure 2)
Together with this, it constitutes a start correction means.

Next, a fourth embodiment of the present invention will be described with reference to FIG. 6, in which a controller 126 having a different start correction timing setting means is used. In this Fig. 6, as in Figs. 4 and 5, elements and signals equivalent to those in Fig. 2 are given the same symbols as in Fig. 2, and duplicate explanations thereof are omitted. do. In this embodiment, the regular correction timing is set by the front wheel turning angle sensor 28 and the first steering angle sensor 100, which is similar to the steering angle sensor 34 in the first embodiment, and the start correction timing is set by: The first steering angle sensor 10
0, a second steering angle sensor 101 to which the front wheel steering angle signal D is input, and an R-S flip-flop 1.
02, 103, 104, and the ignition switch 31.

The second steering angle sensor 101 is similar to the steering angle sensor 34, but when it detects the steering wheel steering angle (for example, about ±60°) that is often set at the time of starting, it outputs an H level signal.
Also outputs R-S flip-flop 10
2, 103, and 104 are R if the above H level signal I'' is output when the ignition switch 31 is turned on and the pulse signal F rises.
-S flip-flop 104 to OR gate 36
If the starting correction operation signal I is input to the starting point and the output of this H level signal I'' is maintained, the next time the ignition switch 31 is set to START, the pulse signal F will be applied. Conditions are set to cut off the operation signal I. Therefore, correction of the rear wheel turning angle θr at the time of starting is performed only when the steering wheel 3 is set to a predetermined steering angle, and the starter motor The correction operation is completed when the ignition switch 31 is driven.In this way, it is also possible to set the timing of the correction end using the ignition switch 31.As explained above, in this embodiment, the ignition switch 31 The start detection means is composed of a second steering angle sensor 101, an R-S flip-flop 102,
103, 104, OR gate 36 and comparator 3
3 constitutes a start correction means.

In all of the four embodiments described above, the start correction timing (start or end, or both) is set by the ignition switch 31. The start correction timing may be set using a combination of the sensor 40 and a timer, etc., without using the ignition switch 31.

Furthermore, in the above embodiment, the timing of regular correction is set by the steering angle of the steering wheel 3 corresponding to the steering angle of the front wheels 1, 1.
The regular correction may be performed by directly detecting the front wheel turning angle and when the front wheel turning angle reaches a predetermined angle, or when the rear wheel turning angle reaches a predetermined angle.

[Brief explanation of the drawing]

FIG. 1 is an overall control system diagram of a four-wheel steering system for a vehicle according to a first embodiment of the present invention, FIG. 2 is a block diagram of a controller in the first embodiment, and FIG. A characteristic diagram showing an example of wheel steering characteristics, FIG. 4 is a block diagram showing a part of the controller in the second embodiment of the invention, and FIG. 5 is a block diagram showing part of the controller in the third embodiment of the invention. 6 are block diagrams of a controller in a fourth embodiment of the present invention. 1...Front wheel, 2...Steering device, 7...
Rear wheel, 8... Rear wheel steering device, 9... Rear wheel steering member (rear wheel operating rod), 14... Pulse motor, 2
6,126... Controller, 28... Front wheel steering angle sensor, 29... Rear wheel steering angle sensor, 31...
Ignition switch, 33... Comparator, 3
4,100,101...Steering angle sensor, 35...
T flip-flop, 36...OR gate, 40
...Start sensor, 41...AND gate, 42,
50...Timer, 102, 103, 104...R
-S flipflop.

Claims (1)

[Claims] 1. A four-wheel steering device for a vehicle, comprising a steering device for steering front wheels, a rear wheel steering device for steering rear wheels, and a controller for controlling the rear wheel steering device according to a predetermined driving condition. , the controller outputs a control signal corresponding to a preset target rear wheel steering angle according to a predetermined driving condition, and the rear wheel steering device has an actuator that operates in response to this control signal, and It is configured to drive the rear wheel steering member, and while the rear wheel is controlled by open control under the rear wheel steering control state, after receiving the output of the start detection means that detects the start state of the vehicle. only for a specified period,
Comparing the target rear wheel steering angle determined by the controller with the measured rear wheel steering angle detected by the rear wheel steering angle sensor, and outputting a correction signal for reducing the deviation to the actuator to perform feedback control, a start correction means is provided. 4 of the vehicle characterized by comprising:
Wheel steering device.