JPH02293268A - Rear-wheel steering gear for four-wheel steering vehicle - Google Patents

Abstract

PURPOSE:To simplify a steering gear in structure as well as to ensure its displacement transfer by installing a piston, a spring mechanism, a rotary rear-wheel steering control valve and a magnetic clutch, constituting a rear-wheel steering displacement control mechanism, on the same shaft with a feedback shaft. CONSTITUTION:A piston 13 constituting a rear-wheel steering displacement transfer mechanism 14 is moved in a cylinder 12 by a hydraulic signal conformed to a car speed, thereby setting a turning range up to a groove side edge of an engaging means 23 at the side of an output shaft 21 adjoining a notch groove 22 in the piston 13 down to a variable play, and front-wheel steering information is inputted out of an input shaft 20, then a rotary rear-wheel steering control valve 15 in a gap with a feedback shaft 32 connected to the output shaft 21 displaceably in rotation is selected, steering rear wheels. In this case, a magnetic clutch 38 or the like, selectively clamping those of piston 13, centering spring mechanism 36, control valve 15 and feedback signal system constituting the rear-wheel steering control mechanism 14, is set up on the same shaft with the feedback shaft 32. Thus, a structure is simplified and simultaneously displacement transfer can be done accurately.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is suitable for use in obtaining tight turning ability at low speeds by steering the rear wheels in the opposite direction in conjunction with the front wheels by steering operation. This paper relates to improvements to rear wheel steering devices for four-wheel steering vehicles. [Conventional technology] In recent years, turning the rear wheels in the opposite direction or the same direction according to the amount of steering (steering amount) of the front wheels has been developed to improve the ability to turn around at low speeds, and to improve turning ability during medium and high speed driving. Four-wheel steering vehicles that can improve driving stability are attracting attention. For example, when driving at low speeds, the front wheels are steered with a large steering angle. At this time, by setting the steering directions of the front and rear wheels in opposite phases (reverse direction steering), the vehicle's turning radius is minimized and the turning (small turning) performance is improved. It is particularly suitable for use in long vehicles such as trucks. As a rear wheel steering device for this type of four-wheel steering vehicle, for example,
Publication No. 9-12111054, JP-A-59-1437
Publication No. 89, Japanese Utility Model Publication No. 81-53271, Japanese Patent Application Publication No. 1989
Including the hydraulic device shown in Publication No. 1-87685 etc.
Various proposals have been made to date. Especially in hydraulic equipment,
By selectively supplying hydraulic pressure controlled to a predetermined pressure using a servo valve, etc. to the left and right chambers of the hydraulic cylinders used to steer the rear wheels, the rear wheels can be steered in the desired direction. Compared to a mechanical device in which the front and rear wheels are mechanically connected by a connecting shaft, it had the advantage of a greater degree of freedom in terms of movement and structure. [Problems to be Solved by the Invention] However, the above-mentioned conventional device still has advantages and disadvantages in terms of both structure and operational performance, and there is still room for improvement in putting it into practical use. For example, this type of rear wheel steering device requires the minimum number of component parts, unitizes each part to improve workability and assembly, and reduces manufacturing costs, as well as hydraulic piping, electrical wiring, etc. It is desired that the motors be efficient, that they can be arranged in line, that various drive controls can be performed easily and appropriately, and that there are sufficient measures against failures. What is needed in response to these demands is a control system structure that can appropriately steer the rear wheels in conjunction with the steering operation of the front wheels that accompanies steering operations. In particular, when the rear wheels are steered in conjunction with the steering operation of the front wheels, the start point of the rear wheel steering operation and its maximum steering angle are adjusted and controlled depending on the vehicle speed, and the turning from the front wheels to the rear wheels is controlled. It is desirable to have a configuration that allows for some play in the transmission of steering pressure and to efficiently transmit steering information to the rear wheel steering control valve, and in consideration of these points, the above-mentioned requirements have been satisfied. Some measures are needed to obtain this. [Means for Solving the Problems] In order to meet such demands, a rear wheel steering device for a four-wheel steering vehicle according to the present invention includes a piston that moves within a cylinder according to the vehicle speed, and a rear wheel steering device for a four-wheel steering vehicle according to the present invention. a displacement transmission control mechanism for rear wheel steering that transmits the amount of steering displacement on the front wheels to the rear wheels with variable play; A rotary type that operates a power cylinder for steering the rear wheels by switching and controlling the hydraulic passage from the rear wheel hydraulic source according to the amount of rotational displacement of the output shaft obtained by the control mechanism. a control valve for rear wheel steering; a signal system that feeds back the movement of the rear wheel steering link mechanism to this control valve; an electromagnetic clutch that selectively connects this signal system to the control valve; A centering spring mechanism for returning to the position and rotating it is arranged on the input and output shafts coaxially located together with the feedback shaft of the signal system as a displacement take-out shaft. [Operation] According to the present invention, by moving the piston within the cylinder using a hydraulic signal controlled according to the vehicle speed, the piston is moved up to the groove side edge of the engagement means on the output shaft side facing the notch groove in the piston. The rotational range of the output shaft can be obtained as variable play, and a rear wheel steering control valve, which is a rotary valve, is provided between the output shaft and a feedback shaft coaxially connected to the feedback shaft for rotational displacement. In addition to controlling the steering of the rear wheels according to the steering displacement information of the front wheels, the system also uses a centering spring mechanism for restoring the control valve to its neutral position and an electromagnetic clutch that transmits the movement of the rear wheels using a feedback signal system. It has an integrated 2-2-1-2 structure including the [Embodiment] Figures 1 to 10 show an embodiment of the rear wheel steering device for a four-wheel steering vehicle according to the present invention. The steering link mechanism (only the rear wheel side is designated by reference numeral 1, and the front wheel side is not shown) is independently driven by hydraulic power cylinders 2 and 3, and only the steering displacement information on the front wheel side is used as a hydraulic signal. A signal system 5 that transmits the rear wheel steering drive system and also feeds back the rear wheel side steering displacement (rod displacement amount of the power cylinder 3) to the control system (rear wheel steering control valve 15 described later) via the tension cable 4. A rear wheel steering device 1O having a configuration equipped with the following will be explained. Here, 6 and 7 are oil pumps for supplying pressure oil to the front and rear wheel side power cylinders 2.3, 8 is an oil tank, and the pressure oil from the front wheel side pump 6 is supplied to the front wheel side power cylinder 2.3 through the hydraulic piping 6a. A well-known front wheel side power steering device is constructed in which the oil is guided to the cylinder 2 and returned to the oil tank 8 through the return pipe 6b. Further, 9 is an on-board battery, and in Fig. 9, hydraulic piping is shown as a double line, and electrical wiring is shown as a single solid line. In addition, oil bomb 6
, 7 is a dual pump driven simultaneously by an automobile engine (not shown), but is not limited to this.
The front and rear wheels may be configured with independent hydraulic systems. In addition, as shown in FIGS. 8(a) and 9, the NIO of this embodiment also proportionally controls the pressure oil supply flow rate using a pump mechanism in the oil reservoir llb using a motor lla that is driven according to the vehicle speed. A motor pump l1 which is a possible hydraulic source,
One chamber 12a is located on the discharge side (MP) of this motor pump 11.
The other chamber 12b (the right chamber in the figure) is connected to the pressure oil return side (MT) of the motor pump 11 in the cylinder 12, and the two chambers 12a and 12b are fixed to communicate with each other. A rear wheel steering displacement device that movably supports a piston l3 having a throttle 13a and selectively transmits steering displacement information on the front wheel side to the rear wheel side with a required variable play according to the movement position of the piston l3. A transmission control mechanism 14, and a rear wheel rotor that controls switching of the hydraulic passage from the oil pump 7, which is a rear wheel side hydraulic pressure source, in accordance with the displacement amount obtained by the control mechanism 14, and operates the power steering 3 for steering the rear wheels. It is equipped with a control valve 15 for the rudder. Here, the motor pump 11 uses the current from the battery 9 obtained by calculating and amplifying the signal from the vehicle speed sensor 16 by the signal controller 17a and the power controller 17b to increase the vehicle speed to 20K.
■The drive is selectively controlled only when the pressure is less than /h, and it is configured to supply the required pressure oil supply flow rate. In addition,
As shown in FIG. 8(b), the proportional flow rate supply means using the motor pump ti, etc. described above includes a vehicle speed sensor 16.
Variable diaphragm 1 that is opened and closed by the controller based on signals from
An electromagnetic proportional flow control valve 18 having a valve 8a may be used, in which case the front wheel pump 6 (the rear wheel pump 7 may also be used).
It is preferable to connect the piping 19a separated from the flow divider l9 in the middle of the hydraulic piping from the control valve l8 to the control valve l8. According to such a configuration, pressure oil whose supply amount is controlled according to the vehicle speed is supplied to one of the cylinder side chambers 12a and 12b constituting the displacement transmission control mechanism 14, and the piston l3
By circulating the pressure oil to the return side via the other chamber side using the fixed throttle 13a provided in the piston 13 at a large or small flow rate.
The amount of movement of the piston l3 is selected, and steering information can be transmitted from the front wheel side to the rear wheel side according to the movement position of the piston l3 with the required idle stroke. That is, the above-mentioned control mechanism 14 is shown in FIGS. 1 and 2(a). To explain in detail using (b) etc., 20 indicates that the steering displacement information on the front wheel side is connected to the output shaft of the front wheel side power cylinder 2 (which may be part of the steering system by the steering handle 2a), etc. The input shaft 2l is an output shaft disposed coaxially with the input shaft 20, which constitutes a displacement extraction shaft. A piston 13 is connected to the input shaft 20 by a spline connection in the rotational direction and supported so as to be movable only in the axial direction, and a part of the piston 13 is connected to the piston 13 as shown in FIG. 2(a). (
As shown in b), a notched groove 22 is formed whose groove width gradually widens and opens toward one end in the axial direction, allowing the transmission play stroke to be varied. In order to form the notched groove 22, the piston 13 is divided into two parts as shown at 13A and 13B in the figure, and then integrated with screws.
23 is provided on the output shaft 21 so as to be inserted into the above-mentioned notched groove 22, and is fitted into the spherical bearing 23a so that the portion in contact with the side edge of the groove 22 contacts and engages with precision. The engagement means constituted by the sleeve 23b, as shown in Fig. 2(b).
As is clear from the figure, the idle stroke until the engagement means 23 comes into contact with the side edge of the groove 22 changes depending on the position of the piston l3. Therefore, within the cylinder 12, the bomb side chamber 12a
The piston 13 is constantly urged by a spring 24 toward
However, when the motor pump 11 (MP) moves in the axial direction due to the pressure difference generated before and after the fixed throttle 13a due to an increase or decrease in the flow of pressure oil supplied from the motor pump 11 (MP), the input shaft 20 on the front wheel side uses the stroke specified at the movement position as play. The rotation of is shown in Figure 3 (a
). As is clear from (b), the power is transmitted to the output shaft 21 side, and the steering angle of the rear wheels with respect to the front wheels changes as shown in the characteristic curve shown in FIG. 4 depending on the vehicle speed. According to this configuration. The fFN has a simple structure that allows the rear wheel steering angle to be controlled to the required state according to the vehicle speed, allowing it to function as a four-wheel steered vehicle. In addition, a piston 13 that responds to the vehicle speed is provided on the displacement extraction shaft by the input and output shafts 20 and 21, and a mechanism is provided between these pistons 13 and the output shaft 2l to connect them with variable play. Not only can this be easily performed, but since the two functions can be easily achieved by a piston placed on the shaft, the structure is simple and it has the advantage of being easy to integrate into a vehicle. In addition, in this example,
The piston 13 that changes the play stroke described above,
Although the movement of the piston l3 is determined by the magnitude of the flow rate of the pressure oil, the movement of the piston l3 is obtained by the differential pressure passing through the fixed throttle 13a, and the fluctuation in the flow rate may be small, making it possible to improve the accuracy of the mechanism. be. Now, according to the present invention, the rear wheel steering control valve l5 is provided as a rotary valve coaxially with the piston 13 constituting the rear wheel steering displacement transmission control mechanism 14 described above, and the centering spring mechanism 36 and the feedback The electromagnetic clutch 38, which selectively connects the signal system 5, etc., are also placed on the same axis to form a unit, thereby simplifying the configuration of each part and ensuring reliable displacement transmission. Here, the schematic configuration of the rear wheel steering device 10 exemplified in this embodiment will be briefly explained using FIG. 1, FIG. 9, etc.
In the case of 0, a rear wheel steering control valve 15 for switching the hydraulic circuit to the rear wheel side power cylinder 3 is arranged in parallel on the displacement take-off shaft (20, 2i) to the rear wheel steering displacement transmission mechanism 14 mentioned above. In the rear wheel steering control mechanism unit, the control valve l
5 is connected to the output shaft 21 through a torsion bar 31 so as to be relatively rotatable.
It consists of a sleeve part 21a provided at the end of the shaft 2 and a rotor 33. The configuration and operation of this valve 15 are well known, and it switches the pressure oil passage between the pump 7 (P) and tank 8 (T) and the rear wheel cylinder chambers CI and C2. If such a configuration is adopted, the members constituting the rear wheel steering control system can be made into a unit as described above, and reliability in operation can also be improved. moreover,
Reference numeral 34 designates an engagement pin 34 that protrudes from the output shaft 21 and the valve body 35 by utilizing the space inside the cylinder left chamber 12a.
A coil spring (see Fig. 5), which is an anti-cushion ring wound around the shaft with a and 34b sandwiched between them, biases the control valve 15 so that it always returns to its absolute position (neutral position). Centering spring mechanism 3
6 has been constructed, and its advantages are obvious. Also, 37
is a cable connecting lever, one end of which is connected to an arm 5a provided on a part of the rear wheel side link mechanism l, and the other end of the tension cable 4 of the feedback signal system 5 is connected to feed back the actual position of the rear wheel side; Displacement take-out shaft (20
．． The sleeve 37a is rotatably mounted on a feedback shaft 32 disposed coaxially with the sleeve 37a as shown in FIGS. 1 and 7.
A well-known electromagnetic clutch 38 is provided between the feedback shaft 7a and the feedback shaft 32, and is configured to selectively connect these two members. By normally separating the rear wheel steering control system from the feedback system and connecting it when necessary, a feedback signal transmission system 5 is obtained that can constantly adjust the misalignment between the rear wheels and the control valve l5 and absorb suspension motion. It's for this reason. Note that 37b is a spring for absorbing backlash that urges the lever 37 to a certain position. Here, in this example, contrary to a general rotary valve,
The sleeve 21a is connected to the input shaft side, and the rotor 33 is connected to the output side (feedback side).
This is to connect the connection lever 37 side to the rotor 33, which has small inertia. In particular, in the present invention, the mechanism unit 30 includes a piston l3 that constitutes the rear wheel steering displacement transmission control mechanism 14;
The centering spring mechanism 36, the rotary rear wheel steering control valve l5, and the electromagnetic clutch 38 are arranged on the input and output shafts 20 and 21, which are coaxially disposed together with the feedback shaft 32 of the feedback signal system 5 as a displacement take-out shaft. By having such a unit configuration, the overall configuration of the device is simplified, and the mechanism unit 30 is also superior in terms of ease of assembly and installation into a vehicle. , the practical advantages are great. here,
The output shaft 21, rotor 33, and sleeve 2 connected via the feedback shaft 32 and torsion bar 31 mentioned above.
As 1a, it is advantageous from a practical point of view to repurpose and use parts used in rotary flow path switching valves for front wheel side power steering devices that have been commonly used in the past. Reference numeral 40 denotes a flange member which is provided on the input shaft 20 in the cylinder 12 and also serves as a spring holder for the coil spring 24 that biases the piston 13. As shown in FIG. First and second rear wheel turning start point detection switches 4 which mechanically detect the state by being selectively engaged and disengaged by front wheel turning input to the shaft 20;
3. 44, and these detection switches 43 and 44 control the rear wheel steering control system to a state where the rear wheels can be steered. That is, this type of rear wheel steering device 10 has a vehicle speed of 20
It is preferable to activate it only when driving at a low speed of Km/h or less and when the steering wheel 2a is operated, and desirably keep it inactive at other times. However, in order to perform rear wheel steering using hydraulic control, it is desirable to place the hydraulic system and the electrical system that controls it in advance in a standby state in which rear wheel steering is possible, and for this reason, in this embodiment, the timing is shifted. Two actuated mechanical switches are placed in positions that allow the front wheels to be turned before the rear wheels are turned. To explain this simply, as is clear from FIGS. 9 and 10, the hydraulic circuit system of the device 10 has a mechanism that allows the rear wheels to be steered or steered when the hydraulic system or electrical system fails. In order to prevent problems caused by the condition being maintained, a bypass pipe 50a is provided between the supply side hydraulic pipe of the rear wheel side pump 6 and the return side pipe, and these two pipes are normally in a communicating state, and the rear wheel steering system side An electromagnetic emergency valve 50 is interposed to maintain a state in which hydraulic pressure cannot be supplied to the rear wheel steering system, and when the rear wheel steering system is energized, this communication is cut off and hydraulic pressure is supplied. Furthermore, a manual switch 5l is also provided on this energizing circuit to deactivate the rear wheel steering system in response to a driver's request to actively maintain two-wheel steering depending on driving conditions. Note that 52 in FIG. A separate circuit configuration with IOA fuses 53 and 54 interposed,
It is configured so that it can be driven by signals from controllers 17a and 17b. Furthermore, 55 is a vehicle speed control bypass valve arranged in parallel with the emergency valve 50 to selectively open and close the supply side and the return side in the hydraulic circuit system from the rear wheel side bomb 7, and is 20K8 or more. Sometimes it is operated so that no pressure oil is supplied to the rear wheel steering system. Reference numeral 56 is a vehicle speed switch attached to a speedometer, etc., which is turned off when the vehicle speed is 20 km/h or more, and turned on when the vehicle speed is 20 km/h or less. Further, a cable breakage switch for disabling the rear wheel steering system when a breakage or the like occurs in the cable 4 that is connected in series to the vehicle speed switch 56 and constitutes the feedback signal system 5 at 57, Furthermore, an electromagnetic clutch 38 is connected in series with these and in parallel with the vehicle speed control bypass valve 55. Reference numeral 60 denotes a rear wheel neutral position locking mechanism designed to restrict movement on the power cylinder 3 side in the rear wheel side steering link mechanism l. A position lock operation detection switch 6l is attached, and the hydraulic pressure for operating this locking mechanism 60 is led from the middle of the hydraulic piping from the rear wheel pump 7 via a flow divider 58, and this hydraulic piping An electromagnetic rear wheel neutral position lock control valve 62 is installed in the middle to open and close the pressure oil residue using an electric signal. Here, 63 is an unloading valve provided upstream of the control valve 62 to maintain a constant oil pressure to the lock mechanism 60, and 64 is an accumulator downstream thereof for accumulating pressure oil. Although not shown in the drawings, the rear wheel neutral position locking mechanism 60 normally restrains movement by engaging a lock pin with a tie rod or the like that constitutes the rear wheel side steering link mechanism 1 using the biasing force of a spring. At the same time, the lock is released by pulling out the loft pin using pressure oil supply. Further, 65 is a check valve for preventing oil pressure failure, which is provided in the middle of the oil pressure supply path to the rear wheel side power cylinder 3, and is used to restore the rotation to the neutral position when the rear wheels are operated in the event of a failure of the hydraulic system.

In order to operate the rear wheel steering system using such various electromagnetic valves and electrical switches, the rear wheel turning start point detection switches 43 and 44 and the rear wheel neutral position lock operation detection switch 6l are activated. It is configured by combining these two systems, and this allows rear wheel steering control to be performed in the required state.
That is, the engine is started with the ignition switch 52, and the bombs 6 and 7 send pressurized oil to the steering systems on the front and rear wheels. At this time, the pressure oil divided by the flow divider 58 passes through the unloading valve 63 and is sequentially accumulated in the accumulator 64 between the neutral position lock control valves that are in the OFF state, increasing the oil pressure in this part.
Further, since the vehicle speed control bypass valve 55 is in an OFF state, the remaining pressure oil is returned to the tank 8 side through this. On the other hand, the pressure sleeve from the motor pump l1 flows into the valve section of the transmission control mechanism 14. In this state, when a steering operation is performed using the steering wheel 2a, the front wheels are steered and the input shaft 20
rotates, and at a predetermined rotation angle (QA in Figure 6), switch 4 is turned.
3 (SW-A) is turned on, thereby operating the vehicle speed control bypass valve 55, cutting off the short circuit to the tank, guiding the discharged oil to the control valve l5, and turning on the electromagnetic clutch 38. The amount of handle rotation increases, Q
At B, the switch 4 (SW-8) is turned on, the neutral position port 7 control valve 62 is opened, and high pressure is guided to the neutral position locking mechanism 60, the port 7 pin is pulled out, and the rear wheel side is It is kept in a state where it can be steered. Further, when the handle is steered beyond the stroke QC defined by the notch groove 22 in the control mechanism 14, the output shaft 2l, which is the input side of the control valve l5, is rotated, thereby operating the valve l5. Pressure oil is guided to one of the left and right chambers of the rear wheel power cylinder 3 to steer the rear wheels, and a feedback signal system 5 using the tension cable 4 changes the steering amount to the feedback shaft 32 in the control valve l5. Feedback is provided to control the desired operating state. Here, the above-mentioned steering wheel steering angle QC can be determined by changing the discharge flow rate from the motor bomb 1l depending on the vehicle speed.
This changes depending on the movement position of the piston 13 of the control mechanism 14 described above, and the control valve 15 is rotationally displaced with the required play, allowing the rear wheels to be steered. In addition, when the vehicle speed becomes 20K layer/h or more, the vehicle speed switch 5
6 is turned off, the vehicle speed control bypass valve 55 is turned off, a recirculation path to the tank is formed, and the electromagnetic clutch 38 and the like are also turned off. In this case, it is preferable to configure the structure so that the energization to the motor bomb l1 is also turned off. Furthermore, if any abnormal condition occurs while the vehicle is running, or if the electrical system or hydraulic system fails, it is preferable to use the emergency valve 50, manual switch 51, or the like to put the rear wheels in a non-steerable state. By connecting switches SW-A and 91-C in parallel, even if SW-A is turned off, the rear wheel steering system remains active as long as the rear wheels are not locked in the neutral position, and the four-wheel steering system is maintained. It is now possible to maintain the running speed. Here, L
What is desirable in configuring the rear wheel steering device described above,
The purpose of this system is to ensure straight-line performance when driving at high speeds and driving stability on low-friction roads such as snowy roads.The rear wheel steering system is placed in standby and active states only when necessary, and placed in a low two-wheel drive state when not needed. The aim is to create a configuration that ensures two-wheel steering. Furthermore, one of the problems with installing the above-mentioned rear wheel steering device is the loss of driving force due to a failure in the rear wheel steering drive system and the failure in the command transmission system of the rear wheel steering control system. When this happens, it is necessary to keep the rear wheels locked in a neutral state and use two-wheel steering, so it is better to adopt the configuration described above. In addition, a problem in configuring the rear wheel steering device 1O described above is that it is required to position and incorporate the neutral position on the side of this device 1O and the vehicle side, and in particular, the rear wheel steering start point detection switch 43 is required to be installed. It is desirable that the positioning portion between the .44 and the input shaft 20 side be correctly connected to the vehicle side. In this embodiment, in order to solve such a problem, as shown in FIG. A neutral positioning mechanism 48 is provided in which the input shaft 20 is pressed against the input shaft 20 with a spring 47, and the input shaft 20 is positioned with respect to the unit body, so that the input shaft 20 can be easily positioned with respect to the vehicle side. ing. Of course, this pole 46 is always movable by steering the steering wheel, but it does not hinder the movement of the input shaft 20. In addition,
The present invention is not limited to the structure of the embodiment described above, and the shape, structure, etc. of each part of the rear wheel steering device 1tlO may be modified or changed as appropriate, and various modifications may be considered. For example, in the embodiment described above, in order to move the piston 13 constituting the displacement transmission control mechanism 14 for rear wheel steering, the piston 13 is
Although a flow control method has been described in which a fixed throttle 13a is provided inside the vehicle, and a pressure difference is generated by flowing pressure oil through the fixed throttle 13a, the flow rate of which is proportionally controlled according to the vehicle speed. However, the present invention is not limited to this. First, an electromagnetic proportional pressure control valve with a variable throttle is provided in the middle of the hydraulic passage, and the pressure on the lower waterfall side is introduced to both sides of the piston 13, and the differential pressure is used to control the piston l3.
Of course, it is also possible to adopt a pressure control method that moves the . [Effects of the Invention] As explained above, according to the rear wheel steering device for a four-wheel steering vehicle according to the present invention, the amount of steering displacement on the front wheel side is determined by the movement position of the piston that is moved within the cylinder according to the vehicle speed. a displacement transmission control mechanism for rear wheel steering that transmits the displacement to the rear wheels with variable play; a displacement take-out shaft consisting of an output shaft disposed coaxially with an input shaft rotated by the steering operation of the front wheels; A rotary rear wheel steering control valve that switches and controls the hydraulic passage from the rear wheel hydraulic power source depending on the amount of rotational displacement at the output shaft to operate the rear wheel steering power cylinder, and a rear wheel steering link attached to this control valve. A feedback shaft of the feedback signal system includes a signal system that feeds back the movement of the mechanism, an electromagnetic clutch that selectively connects the feedback signal system to the control valve, and a centering spring mechanism that rotates the control valve to return to the neutral position. In addition, the displacement take-out shaft is arranged on the input and output shafts that are coaxially arranged, so despite the simple configuration, it is possible to adjust the steering angle of the rear wheels relative to the steering angle of the front wheels according to the vehicle speed. It has various excellent effects such as variable control, appropriately transmitting steering displacement information from the front wheel side to the rear wheel side, and improving maneuverability such as tight turning ability when the vehicle is running at low speed. Further, according to the present invention,
A rear wheel steering displacement transmission control mechanism that controls the transmission of steering displacement information from the front wheels to the rear wheels according to the vehicle speed, a rotary rear wheel steering control valve, a centering spring mechanism, an electromagnetic clutch, etc. coaxially installed. This not only simplifies the configuration and makes it easier to integrate into vehicles, but also
It has the advantage of being able to properly and reliably transmit displacement from the front wheels to the rear wheels. Furthermore, in the present invention, the front and rear wheel side steering link mechanisms are independently driven, and the rear wheel steering device can be configured by simply adding a steering signal output section on the front wheel side, which simplifies the configuration of each part. It has the advantage of being easy to assemble and has a large degree of freedom in terms of installation space, as well as being able to achieve appropriate rear wheel steering conditions.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a rear wheel steering control mechanism unit showing an embodiment of a rear wheel steering device for a four-wheel steering vehicle according to the present invention;
FIGS. 2(a) and 2(b) are a schematic perspective view and an enlarged view of the main parts for explaining the configuration for varying the displacement transmission play stroke, and FIG. 3(a). (b) is a cross-sectional view taken along the line ■--■ of Fig. 1 and an explanatory diagram showing its movement. Fig. 4 is a characteristic diagram showing the relationship between the front and rear wheel steering angles. Figs. 5 and 6 are the same as Fig. 1. The v-v line of
71-TI line sectional view, FIG. 7 is a side view of a portion of the feedback cable connection lever, and FIG. 8(a). (b) is a hydraulic circuit diagram showing the relationship between the proportional flow supply means and the displacement transmission control mechanism for rear wheel steering, and its modification diagram; Figure 9 is a schematic configuration diagram of the entire device; Figure 10 is its electrical circuit. This is a diagram. 1...Rear wheel side steering link mechanism, 2.3...Front,
Power cylinder for rear wheel steering, 5... Feedback signal system, 6.7... Front and rear wheel side oil pumps, 8...
... Oil tank, 10 ... Rear wheel steering device, l1
...Motor bomb, l2...Cylinder, l3.
... Piston, l4... Displacement transmission control mechanism for rear wheel steering, l5... Control valve for rear wheel steering, l6...
・Vehicle speed sensor, l8...electromagnetic proportional flow control valve,
20. 21... Input, output shaft, 22... Notch groove, z3... Engagement means, 30... Rear wheel steering control mechanism unit}. 31●・War・Torsion bar, 32・
... Feedback shaft, 36... Centering spring mechanism, 38... Electromagnetic clutch. Patent Applicant: Automobile Equipment Co., Ltd. Isukiichi Automobile Co., Ltd. Representative: Masagi Yamakawa 21 (Cl) 4th Ward r-81) No. 5X:- r11111

Claims (1)

[Claims] It has a piston that is moved within a cylinder by a hydraulic signal supplied under proportional control according to the vehicle speed, and the amount of steering displacement on the front wheels is transmitted to the rear wheels with variable play depending on the position of the piston. A displacement transmission control mechanism for wheel steering, a displacement output shaft consisting of an input shaft rotated by the steering operation of the front wheels and an output shaft disposed coaxially with the input shaft, and a displacement transmission control mechanism obtained by the displacement transmission control mechanism. A rotary rear wheel steering system that operates a rear wheel steering power cylinder that switches and controls the hydraulic passage from the rear wheel hydraulic source according to the amount of rotational displacement at the output shaft, and controls the rear wheel steering link mechanism to steer the rear wheel steering link mechanism. a feedback system that feeds back movement of the rear wheel steering link mechanism to the rear wheel steering control valve, and an electromagnetic clutch that selectively connects the feedback system to the rear wheel steering control valve; A piston, a centering spring mechanism, and a rotary rear wheel steering control valve, comprising a centering spring mechanism for returning and rotating the rear wheel steering control valve to a neutral position, and constituting the rear wheel steering displacement transmission control mechanism; A rear wheel steering device for a four-wheel steering vehicle, characterized in that an electromagnetic clutch is disposed on input and output shafts coaxially disposed together with a feedback shaft of the feedback system as a displacement take-out shaft.