JPH03167074A - Four-wheel steering device - Google Patents

Abstract

PURPOSE:To make rear-wheel steering control performable with a simple mechanism by linking up a hydraulic pump for supplying pressure oil to a rear-wheel steering device, to a differential, and also linking up the valve rod of a spool valve in this rear wheel steering device to the gearbox of a front-wheel steering mechanism. CONSTITUTION:In a rear-wheel steering device, which receives hydraulic pressure from a hydraulic pump 7 via a spool valve 11 and provides a hydraulic cylinder 10 for steering rear wheels 9 by means of motion in the lateral direction of a piston rod 13, the hydraulic pump 7 is linked to a differential 8 on the front side, and made drivable by means of rotation of a ring gear of this differential 8 at time of traveling. In addition, the spool valve 11 is composed of a nearly cylindrical valve housing 17 being set up in front of the hydraulic cylinder 10 in a fixed form and a valve rod 8 being fitted in this housing free of axial slide motion and rotatably, with its part engaged with the housing 17 through a screw, while this valve rod 18 is linked up with the gearbox of a front-wheel steering mechanism 1 via a shaft 30.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a four-wheel steering device configured to steer rear wheels in addition to front wheels under predetermined conditions.

[Conventional technology]

There are various types of four-wheel steering systems, but one typical one is one that changes the steering ratio (the ratio of the steering angle of the rear wheels to the steering angle of the front wheels) depending on the vehicle speed. There is a so-called vehicle speed sensitive type. For example, Japanese Patent Application Laid-open No. 6]-85274 discloses a power cylinder that receives the hydraulic pressure necessary for steering the rear wheels, moves a piston rod, transmits the movement to the rear wheels, and steers them, and a hydraulic pump. A vehicle speed-sensitive four-wheel steering system equipped with a control valve to control the hydraulic pressure of the engine and transmit it to the power cylinder, as well as a phase control mechanism to control the steering ratio according to vehicle speed, etc. A device has been proposed. The phase control mechanism includes a control yoke that is rotated by a stepping motor, and a bevel gear that is connected to a front steering gear via a shaft and rotated by a direction and an angle corresponding to the steering operation. Rotation of the bevel gear is converted into left-right movement of the valve rod of the control valve. Also, the stepping motor is controlled by a controller that determines the steering ratio according to the vehicle speed. The controller receives signals from the vehicle speed sensor and controls the rotation of the stepping motor and control yoke. The phase control system has a complex structure consisting of a large number of parts such as the rotation of the control yoke and the Heherg motor.
Since the 4B mechanism must also be provided, there is a problem that the mechanism as a whole becomes complicated and that a large amount of space must be secured for the apparatus. The present invention was devised under the above circumstances, and is a vehicle speed-sensitive type that can control the steering ratio according to vehicle speed etc. without providing an electronic control device and can be configured with a simple mechanism. The object of the present invention is to solve the above-mentioned conventional problems by providing a four-wheel steering system.

[Means to solve the problem]

In order to solve the above problems, the present invention takes the following technical measures. That is, the four-wheel steering device of the present invention includes a hydraulic pump, a hydraulic cylinder that steers the rear wheels by the left-right movement of a piston rod, and a hydraulic cylinder that is interposed between the hydraulic pump and the hydraulic cylinder, The rotations of the cylinder right chamber of the cylinder and the cylinder gear are synthesized within the phase control mechanism to determine the stroke direction and amount of the valve rod of the control valve. The oil path between the left ventricle and the left ventricle is switched and the hydraulic pressure is adjusted. Therefore, when the power cylinder is activated, the steering direction and steering ratio of the rear wheels steered by the power cylinder can be controlled in accordance with the vehicle speed and the steering angle.

[Problem to be solved by the invention]

However, the four-wheel steering system disclosed in the above publication has the following problems. In other words, in order to change the steering ratio according to the vehicle speed,
An electronic control device (controller) is required to control the stepping motor, but since the electronic control device itself is relatively expensive, the cost of constructing a four-wheel steering system is high. Moreover, in addition to the above-mentioned electronic control device, the above-mentioned control yoke, bevel gear, and a spool valve for switching the delivery of oil to the left chamber of the stenobin are provided, and the above-mentioned hydraulic pump is connected to a differential device, The spool valve is configured to be driven by the rotation of a final gear or a differential case in the differential device during driving, and the spool valve has a valve rod inserted into the valve housing so as to be axially slidable and rotatable. In addition, a part of the valve rod is screwed into an appropriate part of the valve housing, and rotation of the valve rod causes the valve rod to move in the axial direction within the valve housing to switch the oil passage. The valve rod is mechanically connected to a gear box of the front wheel steering mechanism so as to be rotated in a predetermined direction in response to rotation of the steering wheel.

[Operation and effects of the invention]

When the hydraulic cylinder receives hydraulic pressure from the hydraulic pump and its piston rod is moved in a predetermined direction left and right, the rear wheels are steered in a predetermined direction.There is a hydraulic cylinder between the hydraulic cylinder and the hydraulic pump. A spool valve is installed to switch the delivery of oil to the right cylinder chamber and left cylinder chamber, and by switching the oil passage described above, the direction of movement of the piston loft, that is, the rotation of the rear wheel, is changed. The rudder direction can be controlled. Further, by adjusting the magnitude of the hydraulic pressure supplied to the hydraulic cylinder, the stroke amount of the piston rod, that is, the amount of steering of the rear wheels can be controlled. In the case of the present invention, the hydraulic pump is connected to the differential device, and is configured to transmit and drive the rotational power of the final gear or differential case in the differential device. The rotation speed of the final gear and the like of the differential device is proportional to the vehicle speed, and as the vehicle speed increases, the rotation speed increases accordingly. Therefore, the discharge pressure of the hydraulic pump is changed according to the vehicle speed, and the higher the speed, the more the oil passage to the upper right chamber is opened, and when the steering wheel is turned to the left, the oil passage to the left chamber of the cylinder is opened. This means that the oil passage is opened. Therefore, the moving direction of the piston rod of the hydraulic cylinder and the steering direction of the rear wheels change depending on the steering direction of the steering wheel, and the rear wheels can be steered in a predetermined direction according to the steering direction of the steering wheel. In addition, the amount of movement of the valve rod in the oil passage opening/closing direction within the valve housing changes depending on the amount of steering, so the amount of discharge pressure from the spool valve to the hydraulic cylinder is changed depending on the amount of steering. , the amount of steering of the rear wheels can also be controlled. By the way, as described above, in the present invention, the steering ratio can be changed according to the vehicle speed, and the amount of steering of the rear wheels can be increased or decreased according to the steering angle. However, in order to realize such a four-wheel steering system, the steering ratio and steering amount corresponding to the vehicle speed and steering angle are determined, and based on these, the hydraulic cylinders, etc. Since the discharge pressure for controlling the hydraulic pressure increases, the magnitude of the hydraulic pressure supplied to the hydraulic cylinder also changes depending on the vehicle speed, and the higher the vehicle speed, the greater the magnitude of the supplied hydraulic pressure increases. This means that the amount of movement of the piston rod of the hydraulic cylinder, or in other words, the amount of steering of the rear wheels, is changed in accordance with the vehicle speed. That is, the steering ratio changes depending on the vehicle speed. On the other hand, a spool valve that switches an oil path to a hydraulic cylinder has a valve rod connected to a front wheel steering mechanism, and the valve rod is rotated in a predetermined direction in response to rotation of the steering wheel. In addition, the valve rod is
Due to the threaded fit with the pulp housing, when it rotates,
Since the oil passage is configured to be moved in the axial direction within the pulp housing to switch the oil passage, the oil passage between the hydraulic pump and the hydraulic cylinder can be opened by turning the steering wheel. In this case, the oil delivery route to the hydraulic cylinder also changes depending on the steering direction. For example, when the steering wheel is turned to the right, there is no need to provide a cylinder electronic control device, and there is no need to provide a complicated mechanical device such as a phase control mechanism as seen in the conventional example. Therefore, when configuring the device, this can be done at low cost, and the mechanism of the entire device can be simplified. Additionally, less space must be secured in the vehicle for mounting the device.

[Explanation of Examples]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows the overall configuration of the four-wheel steering system of this example. The front wheel steering mechanism 1 uses a rank and pinion type steering gear similar to that used in boats. steering wheel 2
When the rack lever 3 is turned, the rack lever 3 is moved in the vehicle width direction, and the movement of the rack lever 3 is transmitted to the front wheel 6 via the tie rod 4 and the knuckle arm 5.
The front wheels 6 are steered in a predetermined direction. On the other hand, the device for steering the rear wheels is basically operated by the hydraulic pump 7 and the hydraulic pressure from the hydraulic pump 7, and the rear wheel is steered by the left and right movement of the piston rod 13 during the operation. a hydraulic cylinder IO for steering the wheels 9;
It consists of a spool valve 11 interposed between a hydraulic pump 7 and a hydraulic cylinder 0. The hydraulic pump 7 is connected to a differential device 8 on the front side, and in this example, a gear (as shown) attached to the pump shaft is engaged with a link gear (as shown) in the differential device 8. , so that the rotational power can be extracted. Therefore, the hydraulic pump 7 is driven by the rotation of the ring gear during traveling. Note that, for example, a Hoehn pump or the like can be used as the hydraulic pump 6. The hydraulic cylinder 10 is disposed laterally at the rear of the vehicle, and the pistons 0- and 13.13 protruding from both ends of the cylinder 12 are connected to link arms 14b and 14b of the rear wheel steering mechanism, respectively, by ball joints. Into 2
8 and Roso [member 29, the rear link arm 1 while elastically deforming the rubber bush 16 with the movement of the ring 9.
4b is moved in the opposite direction. In addition, piston rod 1
The left and right rubber bushes 16.16 disposed between the link arms 14b and 14b function as centering springs that return the piston and piston rod of the hydraulic cylinder 10 to the neutral position. In addition, the spool valve 11 is located at the rear of the vehicle.
1. A substantially cylindrical valve housing 17 that is disposed in front of the hydraulic cylinder 10 and is provided in a fixed manner, and a valve rod 18 that is fitted into the valve housing 17 so as to be slidable in the axial direction and rotatable. Equipped with. As can be clearly seen from Figure 2, the valve housing I7
is provided with inboats 19a and 19b for introducing oil sent from the hydraulic pump 7, and a return boat 20 for sending the oil back to the reservoir pump 27 or the pump 7 side. In addition, each of the above boats 19.
20 in the circumferential direction via a rubber bush 16 which will be described later. The above rear wheel steering mechanism is shown in Figures 1 and 3.
As shown in the figure, a pair of front and rear parallel link arms 14a and 14b whose outer ends are connected to the wheel support of the rear wheel 9 (when shown) are provided on both sides of the hydraulic cylinder 10, and each link The inner end of the arm is supported by a rubber bush 16 on a vehicle body side support shaft 5 extending in the longitudinal direction. As described above, the rond members 29 are connected to the left and right piston rods 13.13 of the hydraulic cylinder 10.
．． 29 to the left and right rear link arms 14b, 14.
It is connected to the inner end of b via the rubber bush 16 (see FIG. 3). Therefore, when the piston rod 13.13 is moved in a predetermined left or right direction during operation of the hydraulic cylinder 10, the rear link arms 14b, 14b are moved in the same direction as the piston rod 13, and the movement of the link arms 14b, 14b is acts on the rear wheels 9.9 as a force to steer them in a predetermined direction. At this time, the front link arms 14a, 14a are connected to the cylinder left chamber boat 22 for sending oil to the cylinder left chamber 21 of the hydraulic cylinder 10, and the cylinder right chamber 23 at a position separated from the rear. A cylinder right chamber boat 24 is provided for delivering oil. On the other hand, the valve rod 18 has a threaded shaft portion 25 formed at its rear end portion screwed into the valve housing 18 . Thus, the valve rod 18 is fed and slides axially within the valve housing 17 during its rotation. Further, the valve rod 18 is provided with oil passage opening grooves 26a and 26b formed over the entire circumference in the circumferential direction at two positions spaced apart in the axial direction in the intermediate portion thereof. In the neutral state as shown in FIG. 2, the inboard 19a and
The cylinder left chamber boat 22 and the return boat 20 are communicated with each other via the oil passage opening groove 2.6a on the front side, and the inboard boat 19b is connected to the cylinder right chamber boat 24 and the return boat 20. are communicated via an oil passage opening a26b on the rear side. In this state, each inboard 19a, 19b and outboard 22, 24 are communicated with the return boat 20, and hydraulic pressure can act on both the cylinder left chamber 21 and the cylinder right chamber 23. Since the condition is
Even when the hydraulic pump 7 is driven, the hydraulic cylinder 10 does not operate. That is, the piston rod 13.13 is not moved and therefore the rear wheel 9 is also not steered. For example, the valve loft 18 is slid rearward from the neutral state, opening the rear oil passage! 26b takes a position where only the cylinder right chamber boat 24 and the inboard boat 19b communicate with each other, and the oil passage opening groove 26a on the front side takes a position where only the cylinder left chamber boat 22 and the return boat 20 communicate with each other. In this state (hereinafter, the position of the valve rod at this time will be referred to as the cylinder right chamber oil delivery position), oil is sent into the cylinder right chamber 23. At this time, due to the pressure increase in the cylinder right chamber 23, the piston port 13 is moved leftward in FIG. 1, and the rear wheel 9 is accordingly steered rightward. 5] and the valve rod 18, and by connecting the above-mentioned binion to the front end of the torque shaft 30 and the front end of the valve rod 18 to the rear end, the rotation of the steering wheel 2 is controlled. The structure is such that the valve rod 18 can be rotated in accordance with the above. It should be noted that since the valve rod 18 moves in the front-rear direction when it rotates, it is connected to the torque shaft 30 by spline fitting so as to be non-rotatable and relatively displaceable in the axial direction. Furthermore, in this example, the rear wheels 9 are configured to be steered only in the same phase (in the same direction as the front wheels 6) with respect to the front wheels 6 during medium and high speed turns. Therefore, when the steering wheel is turned to the right, the valve rod 18 assumes the cylinder right chamber oil delivery position, and when the steering wheel is turned to the left, the valve rod 18 takes the cylinder left chamber oil delivery position. Take the valve rod 18
The direction of rotation is set. Furthermore, the ring gear of the differential device 8 that drives the hydraulic pump 7 is
0 to the reservoir tank 27 side. On the other hand, the valve rod 18 is slid forward from the neutral state,
Open the oil passage on the front side? $ 26 a is in a position where only the port 22 for the cylinder left chamber and the import port 19b are in communication, and the oil passage opening groove 26b on the rear side is in a position where only the boat 24 for the cylinder right chamber and the return port 20 are in communication (hereinafter , the position of the valve rod at this time is referred to as the cylinder left chamber oil delivery position), contrary to the above case, the piston rod 13 is moved to the right in FIG.
Accordingly, the rear wheels 9 are steered to the left. Further, the valve rod 18 is mechanically linked to the front wheel steering mechanism 1, so that it is rotated in a predetermined direction according to the rotation of the steering wheel 2 during steering operation. In the case of this example, a pinion (shown in the figure) is provided in the gearbox to mesh with the rack rod 3 and take out the movement of the rack rod 3 in the vehicle width direction as a rotational motion, while the front wheel steering mechanism 6 has a pinion whose rotational speed is Although it is proportional to the vehicle speed, the hydraulic pump 7 generates enough hydraulic pressure to operate the hydraulic cylinder 10 only when the rotation speed of the ring gear reaches a predetermined value or higher, in other words, when the vehicle speed reaches a predetermined speed or higher. It is composed of water. The setting speed is 35 to 45 (
It is preferable to set the speed at a range of approximately 1 km/h. In the four-wheel steering system of this example having the above configuration, when the steering wheel is turned during medium/high speed driving, the valve rod 18 of the spool valve 11 is rotated in a predetermined direction, thereby causing the pressure to be applied to the hydraulic cylinder 10. The oil delivery is controlled and the rear wheels 9 are steered in a predetermined direction. In this case, when the steering wheel is turned to the right, the valve rod 18
takes the above-mentioned cylinder right chamber oil delivery position, and due to the pressure increase in the cylinder right chambers 2 and 3 of the hydraulic cylinder 10, the piston rod 13 is moved to the left in FIG.
The rear wheels 9 are steered in the same direction as the front wheels 6, that is, to the right. On the other hand, when the steering wheel is turned to the left, the valve rod 18 assumes the cylinder left chamber oil delivery position,
Due to the increase in pressure within the cylinder left chamber 21 of the hydraulic cylinder 10, the piston rod 13 is moved to the right in FIG. 1, and the rear wheel 9, like the front wheel 6, is steered to the left. By the way, when turning at medium to high speeds, the higher the speed and the larger the steering angle, the more the vehicle will skid. It is desirable to change the amount of steering of the rear wheels in the same phase direction according to the vehicle speed and the steering angle, but in the case of this four-wheel steering system, the steering ratio is changed according to the vehicle speed, and the steering angle is changed according to the vehicle speed. Since the amount of steering of the rear wheels 9 can be increased or decreased depending on the steering angle, the above requirements can be fully met. That is, since the rotation speed of the ring gear of the differential device 8 that drives the hydraulic pump 7 is proportional to the vehicle speed, the discharge pressure of the hydraulic pump 7 increases as the speed increases. Therefore, as the speed increases, the oil pressure supplied to the hydraulic cylinder 7 also increases, and the stroke amount of the piston rod 13 increases, so the amount of steering of the rear wheels 9 may increase. Furthermore, it goes without saying that the specific structure of the spool valve and the connection structure between the spool valve and the front wheel steering mechanism are not limited to those of the above embodiments. Furthermore, in the above embodiment, a tapped hole was provided on the valve bousing side and a screw shaft portion was provided on the halogen prod side to screw fit the valve housing and the valve rod of the spool valve. Is the threaded fit between the LJ valve bousing and the valve rod a spiral on the one hand? The concept also includes a case in which a spiral groove is provided on the other hand and a spiral groove is fitted into the spiral groove described in 1.

[Brief Description of the Drawings] The first figure is a diagram schematically showing the overall configuration of a four-wheel steering device according to an embodiment of the present invention, the second figure is an enlarged sectional view of a spool valve according to an embodiment, and the third figure is a diagram schematically showing the overall configuration of a four-wheel steering device according to an embodiment of the present invention. The figure is a sectional view showing a connection structure between a piston rod of a hydraulic cylinder and a rear wheel steering member according to an embodiment. The larger it gets. Further, as the amount of steering increases, the amount of movement of the valve rod 18 increases, and accordingly, the opening degree of the oil passage between the oil in boat and the oil out boat increases, and the spool valve 1
Since the discharge pressure from the rear wheel 9 increases, the amount of turning of the rear wheels 9 increases or decreases depending on the steering angle of the steering wheel. In order to achieve such a four-wheel steering system that is sensitive to vehicle speed and steering angle, the present invention utilizes an electronic system for controlling the steering ratio according to vehicle speed, etc., as seen in conventional examples. Since there is no need to provide a control device or phase control mechanism,
The device can be constructed at low cost, and the mechanism of the device can also be made very simple. Note that the scope of the present invention is not limited to the embodiments described above. For example, in constructing a structure in which the rear wheels can be steered by the movement of the piston rod of a hydraulic cylinder, the rear wheels are connected to the piston rod via a tie rod and a knuckle arm. , 7... Hydraulic pump, 8...
Differential device, 9... Rear wheel, 10... Hydraulic cylinder, 11... Spool valve, 13... Piston rod, 17... Valve bousing, 18...
・Knoll blonde・

Claims (1)

[Claims] (1) A hydraulic pump, a hydraulic cylinder that steers the rear wheels by the left-right movement of a piston rod, and a hydraulic cylinder that is interposed between the hydraulic pump and the hydraulic cylinder and flows into the cylinder right chamber and cylinder left chamber of the hydraulic cylinder. a spool valve that switches the delivery of oil, and the hydraulic pump is connected to a differential device and is driven by the rotation of a final gear or a differential case in the differential device when the vehicle is running. The above-mentioned spool valve is configured such that the valve rod is slidably and rotatably inserted into the valve housing in the axial direction, and a part of the valve rod is screwed into an appropriate part of the valve housing. The valve rod is configured to move in the axial direction within the valve housing to switch the oil passage when the steering wheel rotates, while the valve rod is connected to a front wheel steering mechanism so that it can be rotated in a predetermined direction according to the rotation of the steering wheel. A four-wheel steering device characterized by being mechanically connected to a gearbox.