JPS5981273A - 4-wheel steering device of vehicle - Google Patents

Abstract

PURPOSE:To prevent the occurrence of an accidental contact of car body with the side wall of a garage during starting and to enable rear wheels to be steered as required, by installing a controller which brings a rear steering angle in iso- phased state from opposite-phased state according to an increase in the car speed and sets the rear wheel steering angle to zero, a certain set time after starting. CONSTITUTION:A rear wheel steering device 7 is controlled by a controller 19 comprising a steering sensor 20, a car speed sensor 21, and a rear wheel steering angle sensor 22. The controller 19 brings a front and a rear wheel steering angle from opposite-phased relation therebetween to iso-phased relation therebetween, and this improves a turning radius and maneuverability. Further, a rear wheel angle is set to zero, a certain set time after starting, and this permits prevention of the occurrence of any accidental contact of car body with the side wall of a garage during starting therefrom.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a four-wheel steering system for a vehicle that controls the steering of the rear wheels as well as the @wheels through steering operation, and in particular, the rear wheel steering angle characteristic relative to the front wheel steering angle varies depending on the vehicle speed. Concerning improvements to things that change depending on the situation.

In general, in this type of 4im # steering device, in order to reduce the minimum turning radius of the vehicle so that the vehicle can easily turn around or park in the garage, the steering direction of the front wheels is set in the low vehicle speed range below the set speed. The rear wheels are controlled to be steered in the opposite direction (opposite phase). However, when a vehicle is stored in a garage close to a side wall, etc., when the vehicle is taken out of the garage, the rear part of the vehicle juts out laterally due to the anti-phase steering of the rear wheels, and comes into contact with the garage side wall, etc.7. ! i (will occur.

Therefore, conventionally, as disclosed in Japanese Patent Application Laid-Open No. 56-167562, etc., a set speed (for example, 40 KI
At low vehicle speeds below 20 mm/h or below, the rear wheel steering angle is controlled to zero regardless of front wheel steering, and the rear wheels are positioned in the longitudinal direction of the vehicle to prevent lateral movement of the rear of the vehicle. A device has been proposed that prevents contact accidents from occurring.

However, the distance to enter and exit the garage is usually 10km/
This is done at an extremely low speed of less than h, and the range of change in vehicle speed at that time is small. For this reason, in the above-mentioned proposal that controls the rear wheel steering angle to zero based on the vehicle speed, there is a strong tendency that the rear wheel steering angle is not controlled in a timely manner, and as a result, it is difficult to reduce the minimum turning radius. There is a drawback that the rear wheel steering angle may remain controlled to zero even when the four-wheel steering system is required, and the four-wheel steering system cannot be used effectively.

The present invention has been made in view of this point, and by controlling the rear wheel steering angle to always be zero during a set time when starting, the rear wheels can be surely controlled to be steered to the opposite phase when necessary. The purpose of this is to prevent accidents involving contact with the side walls of the garage, etc., when the vehicle starts moving.

In order to achieve this object, the configuration of the present invention includes a steering device that steers the front wheels, and a configuration that controls the rear wheel steering angle to zero during a set time for steering the rear wheels. When the vehicle starts, the controller forcibly controls the rear wheel steering angle to zero for a set time period, regardless of the front wheel steering angle.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the overall configuration of a four-wheel steering device according to an embodiment of the present invention. Reference numeral 1 denotes a steering device for steering left and right front wheels 2a and 2b, and the steering device 1 includes a steering wheel 3, It consists of a rack and pinion mechanism 4, left and right tie rods 5.5, and left and right knuckle arms 6.6.

Further, reference numeral 7 denotes a rear wheel steering device for steering left and right rear wheels 8a, 8b, and the rear wheel steering device 7 is configured to steer left and right rear wheels 8a, 8b at both ends.
knuckle arms 9, 9 and tie rod 10 to a, 8b
．． A rod 1 extending in the transverse direction of the vehicle body is connected via a rod 10.
The hydraulic actuator 11 has a hydraulic actuator 1a. The hydraulic actuator 11 is equipped with return springs 112 and 11f fixed to the rod 11, respectively. The rear wheel steering device 7 also includes a hydraulic pump 13 that sucks oil in an oil reservoir 12 and supplies it to the hydraulic γ actuator 11, an electric motor 14 that drives the hydraulic pump 13, and a hydraulic actuator from the hydraulic pump 13. 1
1 is provided with a switching valve 15 for switching the direction of pressure oil supply to 1. The switching valve has a spool 15a and a spool 15.
Pilot chambers 15b and 15C formed at both left and right ends of a
Return springs 15d and 15e are respectively installed in the pilot chambers 15b and 15C to position the spoo/L' 15a at the neutral position shown in the figure.

Further, the rear wheel steering device 7 includes a pilot hydraulic pump 17 which sucks oil in the oil reservoir 16 and supplies pressure oil to each pilot chamber 15b, 15C of the switching valve 15. A pilot switching valve 18 for switching the direction of pressure oil supply to each of the pilot chambers 15b and 15C is provided.

The pilot switching valve 18 has a forward position 18a that allows pressurized oil to be supplied to the pilot chamber 15C on the right side, and a reverse position 18b that allows pressurized oil to be supplied to the left pilot chamber 15b.
When it is in the forward direction position 18m, by supplying pressure oil to the right pilot chamber 15C, the sprue/l/15a of the switching valve 15 is moved to the left by an amount corresponding to the oil pressure. By generating a differential pressure between the oil pressures acting on both pressure chambers 11C and 11d of the hydraulic actuator 11 in accordance with the amount of spool movement and increasing the hydraulic pressure to the right wheel hydraulic chamber 11d, the hydraulic pressure is increased. The rod 11a of the actuator 11 is moved to the right by an amount corresponding to the differential pressure, and the rear wheels 8a and 8b are steered to the right (clockwise), and the pilot switching valve 18 is in the reverse direction position 18b. Sometimes, the rod j1a of the hydraulic actuator 11 is
The steering wheel is configured to steer to the left (counterclockwise).

Further, reference numeral 19 denotes a controller for controlling the operation of the rear wheel steering device 7, and the controller 19 includes a steering angle sensor 20 that outputs the steering angle of the steering wheel 3 by 411, and a vehicle speed a vehicle speed sensor 21 that detects the
Each detection signal is inputted to a rear wheel steering sensor 22 that detects the amount of left and right movement of a. The controller 19 also includes a pilot electric motor 23 that drives the pilot hydraulic pump 17 and a spool 18 of the pilot switching valve 18.
An excitation coil 18d that attracts and moves C is connected. Further, inside the controller 19, the characteristics of the rod movement amount SA of the hydraulic actuator 11 with respect to the steering angle θS as shown in FIG. A characteristic storage unit 24 in which input is stored is provided. As can be seen from the figure, the characteristics of the above rear wheel turning angle θR are as follows:
In the following speed ranges, the phases are opposite, and in the speed range where the vehicle speed is higher than the speed VO, the phases are the same, so that the characteristics change depending on the vehicle speed. Further, inside the controller 19, the characteristic storage unit stores the target rod movement amount (“target rear wheel turning angle”) of the hydraulic actuator 11 in response to rain detection signals from the steering angle sensor 20 and vehicle speed sensor 21. A target steering angle calculation unit 25 calculates based on the characteristics of 24, and a target rod movement amount signal from the calculation unit 25 is compared with an actual rod movement amount signal from the rear wheel steering sensor 22, and a calculation is made according to the difference. A first comparator 26 that generates a difference signal, a triangular wave generator 27 that generates a triangular wave as shown in FIG. A second comparator 28 that discriminates the size based on the second comparator 28 and a first transistor 29 that is turned on in response to an output signal from the second comparator 28.
The pilot motor 23 is configured to be driven and controlled by the ON operation of the pilot motor 23. Therefore, when the difference between the target rod movement amount and the actual movement amount is large, the difference signal value of the first comparator 26 also increases accordingly, as shown by the broken line in FIG. As the output signal becomes a signal with a high conduction rate as shown in FIG. While increasing the discharge pressure of the switching valve 15 to increase the spool movement amount of the switching valve 15, when the difference between the target rod movement amount and the actual rod movement amount is small,
The difference signal value of the first comparator 26 also becomes smaller (shown by the dashed line in C) of the same figure), and the output signal of the second comparator on the second day becomes a signal with a low conduction rate as shown in C of the same figure. As a result, the rotational speed of the pilot motor 23 is lowered, the discharge pressure of the pilot hydraulic pump 17 is lowered, and the amount of spool movement of the switching valve 15 is reduced.

Inside the controller 19, there is a start operation detection section 30 that detects a start operation by detecting the depression of the accelerator or the shift of a gear to a low position, and a timer that operates in response to an output signal from the detection section 30. 31, and a second timer 31 that is turned on in response to an output signal from the timer 31 (a signal that is at the rHJ level for one second as shown in FIG. 5).
The relay 33 includes a transistor 32 and a relay 33 that is turned on when the second transistor 32 is turned on.
The normally closed contact 33a of No. 3 is interposed in the power supply circuit 34 of the pilot motor 23. Therefore, when starting the vehicle, the pilot motor 23 is activated during the time T set by the timer 31.
By deactivating the pilot hydraulic pump 17, the switching valve 15 and the hydraulic actuator 11 are placed in a neutral state, and the rear wheel steering angle is controlled to zero.

Although not shown, the controller 19 controls the pilot switching valve 18 when the steering wheel 3 is steered clockwise.
is positioned in the forward direction position 18a, and is configured to be positioned in the reverse direction position 18b when steered counterclockwise. Note that 35 is an in-vehicle battery.

Next, to explain the operation of the above embodiment, when the vehicle starts, the start operation detection section 30 of the controller 19 generates an output signal, and the timer 31 activates "HJ" for a set time T.
Generates an output signal that is a level. For this reason, the second transistor 32 is activated, and then the relay 33 is activated and its normally open contact 33m is opened, and the pilot motor 2
No. 3 feed circuit 34 is opened. As a result, the pilot electric motor 23 is deactivated, and the pilot hydraulic pump 17
The discharge pressure becomes zero, and the switching valve 15 is positioned at a neutral position by the urging force of the return springs 15a and 15e. In addition, along with this, the hydraulic pressures to the respective hydraulic chambers 11C and 11d of the hydraulic actuator 11 become equal, and the hydraulic actuator 11 is positioned at the neutral position by the biasing force of the return springs 11e and 11f. As a result, the steering angles of the rear wheels 8a and 8b are controlled to zero and become parallel to the longitudinal direction of the vehicle body. Therefore, even if the vehicle is stored in the garage close to the side wall, etc., the rear part of the vehicle will not protrude laterally when the vehicle is taken out of the garage, thereby preventing accidents in which the vehicle comes into contact with the garage side wall, etc. can.

Then, when the set time T of the timer 31 has elapsed, the vehicle has almost left the garage, and it is desired that the minimum turning radius becomes small in order to enter the predetermined road.

At this time, the relay 33 of the controller 19 is turned off by the rLJ level output of the timer 31, and the power supply circuit 34 of the ilot electric head 23 is closed due to the closing of its normally closed contact 33a. The rotational speed of the pilot electric motor 23 increases or decreases depending on the flow rate of one output word from the second comparator 28, and the discharge pressure of the pilot hydraulic pump 17 also changes in height accordingly. The spool movement amount also changes accordingly, and eventually the rod 11a of the hydraulic actuator 11 converges to the target rod movement amount in the characteristic storage section 24.

As a result, the rear wheels sa and sb are steered to the target steering angle of the opposite phase based on the characteristics of the characteristic storage section 24 (see FIG. 3), and the vehicle is steered to the target steering angle of the rear wheels 8a and 8b in the opposite phase. This reduces the minimum turning radius.

Therefore, by controlling the rear turning angle to zero after the initial jt at the time of starting, it is possible to prevent collision accidents with the garage side wall, etc. at the rear of the vehicle body. If required, 1 rear wheel 8a, 8b
Since the wheels are steered in opposite phases, this requirement can be reliably satisfied, and the four-wheel steering system can be used effectively.

Further, FIG. 6 shows a @2 embodiment of the present invention, in which, instead of the rear wheel steering device 7 configured with a hydraulically controlled type in the first embodiment, a link mechanism interlocked with the steering device 1 is provided. (In addition, the same reference numerals will be given to the parts of the first embodiment shown in Section 1, and the explanation thereof will be omitted.)
. ,.

7. A first I-shaped sink 37 arranged in the longitudinal direction of the vehicle body is connected to the rank 4a of the rack and pinion mechanism 4 via an L-shaped sink 36. shape sunk 3
By rotating 6 and 9 about the fulcrum 36a, the ■-shaped socket 37 is moved in the longitudinal direction of the vehicle body. At the line end of the I-type sunk 37, there is one end 3 of a lever ratio variable sink 38 arranged in the lateral direction of the vehicle body.
8. a are connected. On the 3rd day of the variable lever ratio link, the lever is attached to a movable support that can freely slide along the variable link 3 day.
9 is provided, and one end of the variable lever ratio link $8 is moved in the longitudinal direction of the vehicle body in response to the movement of the first L-shaped sink 37, using the position of the movable fulcrum 39 as the fulcrum. . Further, a second 1-type link 40 arranged in the longitudinal direction of the vehicle body is connected to the center portion 38b of the variable lever ratio link 38, and an L-shaped link 40 is connected to the rear end of the I-type link 40.
A rod 42 in the transverse direction of the vehicle body is connected to the tie rods 10° 10 of the left and right rear wheels aa and sb via a sunk 41. By moving the second I-shape sunk 40 in the longitudinal direction of the vehicle body, the L By rotating the shaft 41 about its fulcrum 41a, the rod 42 is moved in the lateral direction of the vehicle body to steer the left and right rear wheels 8as and 8b. The above constitutes the rear wheel steering device 7'.

, and a movable fulcrum 39 of the variable lever ratio link 38.
is connected to a threaded member 45 that threads onto the insert pin 44 on the side of the car body which is rotationally driven by the 'R motor 43.Electric 1 m! By moving the threaded member 45 in the lateral direction of the vehicle body by the rotation of the insert pin 44 accompanying the rotational drive of the lever 43, the movable fulcrum 39 is moved northward on the lever and slid in the lateral direction of the vehicle body along the variable link 38. The movable fulcrum 39 is connected to the central portion 38 as shown in the figure.
When positioned to the right of the variable link 38, the center portion 38b of the variable link 38 moves in the same direction as the one end 38a interlocking with the first L-shaped link 37, thereby moving the second ■-shaped link 40. is moved in the same direction as the first I-shaped link 37 to steer the rear wheels sa and sb in the same phase as the front wheels 2a and 2b, while the movable fulcrum 39 is moved between one end 38a of the variable link 38 and the center portion 38b. When positioned between the central part 38
By interlocking one end 38a in the opposite direction, the second ■
The rear wheels sa and sb are steered in the opposite phase to the front wheels 2a and 2b by moving the sunk 40 in the opposite direction to the first I-shape sunk 37, and the movable fulcrum 39 is moved to the center portion 38b. When the second I-shaped sunk 40 stops moving regardless of the movement of the one end 38a in the longitudinal direction of the vehicle body, the rear wheels sa,
The steering angle of ab is set to zero, that is, the rear wheels sa and sb are steered in a direction parallel to the longitudinal direction of the vehicle body.
゛Furthermore, the controller 19 has input and stored in advance the rear wheel steering angle characteristics with respect to the front wheel steering angle, that is, the fulcrum position characteristics of the movable fulcrum 39 with respect to the front wheel steering angle, and the controller 19 has a variable lever ratio. Rear wheel steering sensor 22' detects the position of the movable fulcrum 39 on the link 38
detection signal is input. As shown in FIG. 7, the controller 19' is equipped with a zero command signal generator 46 that commands the target rear wheel turning angle to be zero, and the contact 33b of the relay 33 is The zero command signal generation section 46 and the target turning angle calculation section 25 are selectively connected to the first comparator 26, and when the relay 33 is turned off, the target turning angle calculation section 25 is selected, and the relay 33 is turned ON, the zero command signal generating section 46 is selected. Other configurations are listed in 1 above.
This is similar to the example.

Therefore, during the set time T when starting, the relay 33
The zero signal generator 46 is selected by the ON operation, and the controller 19' positions the movable fulcrum 39 at the center portion 38b of the variable lever ratio link 38 by controlling the operation of the electric motor 43, so that the rear wheel turning angle is forced to zero. controlled by. Furthermore, after the set time T has elapsed, the target steering angle calculation unit 25 is selected by turning off the relay 33, and the position of the movable fulcrum 39 is controlled based on the rear wheel steering angle characteristics of the characteristic storage unit 24. The wheels sa and ab are the front wheels 2a and 2b based on the above characteristics.
It is steered in the opposite phase.

Therefore, as in the above embodiment, it is possible to prevent a collision accident at the time of starting, and when necessary, the rear wheels sa and sb are reliably steered to opposite phases, making effective use of the four-wheel steering system. can do.

In the above description, the timer 31 measures the set time T at the time of starting the vehicle, but it goes without saying that the set time T may be measured by other means. For example, as shown in FIG. 8, a mileage accumulating section 47 for accumulating the mileage after starting is provided, and the actual mileage signal from this accumulation section 47 is compared with a reference value corresponding to the set mileage using a comparator 48. By doing so, it is possible to measure the set time T.

As explained above, according to the present invention, when the vehicle starts,
During the set time, the rear wheel steering angle is forcibly controlled to zero by the operation control of the rear wheel steering device by the controller, so that when necessary, the rear wheel steering angle is By controlling the wheels to an appropriate steering angle, it is possible to prevent collisions with garage side walls, etc. when starting, thereby improving vehicle safety while effectively utilizing the vehicle's four-wheel steering system. This is something that can be improved.

[Brief explanation of the drawing]

The front side shows an embodiment of the present invention, FIG. 1 is an overall schematic configuration diagram showing the first embodiment, FIG. 2 is a diagram showing the internal configuration of the controller in FIG. 1, and FIG. FIG. 4 is a diagram showing the characteristics of the rear wheel steering angle with respect to the stored front wheel steering angle.
A) to (C) are diagrams showing the output waveform of the triangular wave generator and the output waveform of the second comparator, FIG. 5 is a diagram showing the output waveform of the timer, and FIG. 6 is an overall schematic configuration diagram showing the second embodiment. , FIG. 7 is a diagram showing the internal configuration of the controller in FIG. 6,
FIG. 8 is a diagram showing a modification of the timer. 1... Steering device, 2a, 2b... Front wheel, 7
7/... Rear wheel steering device, sa, sb... Rear wheel, 11
...Hydraulic actuator, 13...Hydraulic pump, 15
...Switching valve, 17...Pilot hydraulic pump, 18
...Pilot switching valve, 19.19'...Controller 20...Steering angle sensor, 21...
・Vehicle speed sensor, 22.22'...d Rear wheel steering sensor, 2
3...Pilot motor, 24...Characteristics storage unit, 2
5... Target steering angle calculation unit, 26... First comparator % 27... Triangular wave generation unit, 28... Second comparator, 29... First transistor, 30... Start operation detection Part, 31... Timer 32... Second transistor, 33... Relay+, 3B... Lever ratio variable link, aSa... One end, 38b... Center part, 39...
・Movable fulcrum, 46... Zero command signal generator, 47...
Mileage accumulating section, 48... Comparator patent applicant Toyo Kogyo Co., Ltd.

Claims (1)

[Claims] (1) A steering device that steers the front wheels; a rear wheel steering device that steers the rear wheels; and a controller that controls the rear wheel steering device according to a front wheel steering angle; The rear wheel steering angle characteristic with respect to the steering angle changes from opposite phase to the same phase as the vehicle speed increases, and the rear wheel steering angle is controlled to be zero for a set time after the vehicle starts. A 4'@steering device for a vehicle characterized by the following.