JPS61211171A - Power steering device - Google Patents

Abstract

PURPOSE:To steer the rear wheel optimally by absorbing the forward/rearward vibration of tire through resilient member of suspension member of rear wheel while enabling determination of steering amount of rear wheel with correspondence to the car speed thereby making the steering characteristic of the rear wheel against the front wheel adjustable. CONSTITUTION:A rear wheel suspension member 11 for supporting the rear wheel 2 through semi-trailing arm 12 is supported through rubber bushes 10 to the chassis at the opposite ends. Then the rubber bushes 10 are deformed resiliently through function of rear wheel power cylinders 4 (4A, 4B) arranged at the opposite ends of the member 11 to steer the rear wheel 2. Supply/ discharge of pressure oil against the cylinder 4 is controlled through a control valve 6 arranged on a pinion shaft 14. A washer 42 is controlled properly to adjust the fulcrum of roll lever 26A in the control valve 6 through an adjust pin 40. Consequently, the power cylinder characteristic of rear wheel can be adjusted easily.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a rack-and-pinion type power steering device mainly used in automobiles, and particularly relates to a power cylinder for front wheel steering and a power steering device for rear wheel steering. The present invention relates to a rack-and-pinion power steering device in which control valves for operating cylinders are arranged in parallel on a single pinion shaft.

(Prior Art and Problems to be Solved by the Invention) A power steering device uses hydraulic power to assist the rotation of a steering wheel and transmits the rotation to the wheel steering arm via a mechanism consisting of a pinion and a rack. , various proposals have been made in the past, but in all cases, it is used only for front wheel steering. The power steering system was not used effectively due to the limited space available.

By the way, the rear wheels generally go straight regardless of the steering of the front wheels, so when making a curve while driving, the main forces are cornering force in the lateral direction, rolling resistance in the rear direction, and straight movement in the direction of the tire rotation surface. A moment called self-lining torque that tries to return the vehicle to its original direction acts on the contact surface with the road surface, causing sideslip, which impairs steering stability and wears out the tires, reducing durability. This phenomenon becomes more pronounced as the vehicle speed increases, even for the same steering angle. Therefore,
In order to eliminate these drawbacks, four-wheel drive systems have been proposed that reduce sideslip, but these have the problems of being extremely complex and expensive.

The purpose of the present invention is to effectively cut off the front and rear images of the tires, synchronize the operation of the front wheel steering system, and determine rear wheel steering according to the vehicle speed, thereby improving the tracking delay of the rear wheels and stabilizing driving. It is an object of the present invention to provide a power steering device that can improve performance and maneuverability, and in this case, to easily adjust the characteristics of the device, thereby improving processability and assemblability of the device.

(Means for Solving the Problem) As a means for solving the problem, the power steering device according to the present invention includes a front wheel steering power cylinder that outputs an output to steer the front wheels, and a suspension made of rubber bushes or the like. A power cylinder for rear wheel steering that forcibly displaces this elastic body of a rear wheel suspension attached to the vehicle body via an elastic body and outputs an output to steer the rear wheels in a direction opposite to the steering direction of the front wheels. , comprising a control valve that operates each of the power cylinders, and a flow control valve that is provided in the middle of the fluid supply road of the control valve that operates the power cylinder for rear wheel steering and that controls the fluid flow rate in accordance with the traveling speed of the vehicle. In the power steering device, both control valves are connected to a pinion shaft integrally formed with a pinion shaft that engages with a rack connected to a steering arm of the vehicle via a tie rod and rotates together with the steering handle. They are arranged in parallel and are configured to be controlled by the rocking displacement of each rocking lever fitted to this pinion shaft, and the rocking lever of the control valve for operating the power cylinder for rear wheel steering is The swing fulcrum is characterized by being provided with a lever length adjustment mechanism.

(Function) According to the above configuration, the longitudinal vibration of the tire which is received from the unevenness of the road surface while driving is absorbed by the elastic body of the suspension member of the rear wheel. On the other hand, when changing lanes or slaloming while driving at high speed, the output from the rear wheel power cylinder is applied to the elastic body of the rear wheel suspension member to forcibly deform it, and the Steering the rear wheels.

At this time, in addition to synchronizing the movement of the front wheel steering system, the amount of pressure oil supplied to the rear wheel power cylinders is controlled by a control signal based on a detection signal corresponding to the vehicle speed, so the rear wheels are steered optimally. Ru. In addition, after the power steering device has been assembled, the lever length of the swinging lever of the control valve for operating the power cylinder for rear wheel steering can be adjusted to adjust the steering characteristics of the rear wheels relative to the front wheels, ensuring reliable rear wheel steering characteristics. It is possible to set it correctly.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 to 3. The power steering device includes a front wheel power cylinder 3 and a rear wheel power cylinder 4 (4A, 4B) that generate steering assist force for the front wheels 1 and rear wheels 2, and pressure oil supply to each of the power cylinders 3 and 4. A control valve for operating a power cylinder for front wheel steering (hereinafter simply referred to as a front wheel control valve) 5 for controlling the direction, and a control valve for operating a power cylinder for rear wheel steering (hereinafter simply referred to as a rear wheel control valve) 6; an oil pump 7.8 supplying pressure oil to both power cylinders 3.4 via a control valve 5.6;
and a flow rate control valve 9 provided in a pressure oil supply path to the rear wheel control valve 6.

The front wheel power cylinder 3 has its cylinder rod connected to a tie rod, so that the output of the power cylinder 3 is directly transmitted to the front wheels. On the other hand, the cylinder rods of the power cylinders 4 (4A, 4B) for the rear wheels are pivotally mounted near both ends of a suspension member 11 connected to the vehicle body 60 via rubber bushes 10. The output is such that the suspension member 11 can be rotated around the swing axis 11A without resisting the elastic force of the rubber bush 10.

Further, since the rear wheel 2 is connected to the suspension member 11 by the suspension arm 12, it is rotated together with the suspension arm 12, and is steered in the same direction as the steering direction of the front wheel 1, which will be described later. .

FIG. 2 shows the structure around the pinion shaft 14 connected to the steering handle 62, showing a pinion 14A integrally formed on the pinion shaft 14 and a rack 14B connected to the piston of the power cylinder 3 for the front wheels. are in mesh with each other, and the pinion shaft 14 rotates by operating the handle.
A rack 14B is slid by a pinion 14A of the pinion shaft, and the front wheels 1 are steered via a tie rod and a steering arm.

A control valve 5.6 is arranged in parallel to this pinion shaft 14, and the front wheel control valve 5 has the following structure.

The front wheel valve 5 is provided with a valve spool 15 that moves in a direction perpendicular to the pinion shaft 14 and supplies pressurized oil from the pump 7 to the power cylinder 3 in a selected direction. The spool 15 is slidably inserted into a sleeve portion 17 formed in the valve block body 16A.

The pinion shaft 14 is rotatably supported by bearings 18A118B disposed in the gear box 16B before and after the pinion 14A.

As shown in FIG. 3, the valve spool 15 has annular grooves 20 and 21 that form a pressure oil passage with the sleeve portion 17.
is provided in the sleeve portion 1, and the annular groove 20 is provided in the sleeve portion 1.
．． A pump boat 19, a cylinder boat 22, 23, and a tank boat 2 that cooperate with the pump boat 21 to selectively communicate the hydraulic chamber of the front wheel power cylinder 3 with the pump side or the tank side.
4 is formed, and when the valve spool 15 moves to the right or left from the neutral position shown in FIG. The direction in which pressure oil is supplied to the power cylinder 3 is switched. Note that 58 is a neutral holding spring for the spool 15.

Further, a pin hole 25 is formed in the valve spool 15 and is perpendicular to the pinion shaft 14. A swing lever 26 connecting the spool 15 and the pinion shaft 14 is formed in the pin hole 25.
One end is disposed through an opening 28 formed in a partition wall 16G of the valve block body 16A that separates the valve spool 15 and pinion shaft 14.

This swing lever 26 has a ring portion 30 fitted to the pinion shaft 14, and a support pin 31 and a drive pin 32 are protruded at symmetrical positions passing through the center of the ring portion 30, and the tip thereof has a spherical surface. A fulcrum portion 33 and a drive portion 35 each having a shape are provided. The fulcrum portion 33 is located in the hole 3 of the collar 36 press-fitted into the valve block body 16A.
6a, and the drive portion 35 is fitted into the bottle hole 25 of the valve spool 15.

The control valve 6 is the front wheel control valve 5 shown in FIG.
Since the structure is almost the same as that of the control valve 5, the same structural parts will be given the same reference numerals as the respective constituent parts of the control valve 5, and the explanation thereof will be omitted, and only the different parts will be explained. A support pin 31A protruding from the ring portion 30 of the swing lever 26A fitted to the pinion shaft 14 is supported by an adjustment pin 40 screwed into the valve block main body 16a. The adjustment pin 40 is provided with a protrusion 41 that comes into contact with the inner peripheral surface of the hole 31B formed in the support bin 31A. Adjust the adjustment pin 4 by rotating the hexagonal head 40B.
0 can be tightened and fixed to the valve spring body 16a.

As a result, the tip position of the protrusion 41 of the adjustment pin 40 is determined, and the swing fulcrum position of the swing lever 26A is determined. The washer 42 is formed in a U-shape and can be replaced with a number of other washers of different thicknesses.By replacing this washer 42 with a washer of a different thickness, the swing lever can be adjusted. 26
The swing fulcrum position of A can be adjusted as desired.

In the above configuration, when the steering handle 62 is operated to rotate the pinion shaft 14 in either direction, the resistance of the rack 14B connected to the tie rod etc. is large.
The pinion shaft 14 tends to be displaced along the rack 14B in this rotational direction.

As a result, since the respective ring portions 30 of the swing levers 26 and 26A are fitted to the pinion shaft 14, the swing levers 26 and 26A move as the pinion shaft 14 swings in the displacement direction as shown by arrow A in FIG. , the drive section 3 is centered around the fulcrum section 33.41.
5 simultaneously swing in the same direction as shown by arrow B.

As a result, both valve spools 15 are switched and displaced, pressure oil is supplied to the front and rear power cylinders 3.4, the front power cylinder 3 outputs output to steer the front wheels 1, and at the same time the rear power cylinder 4 (4Δ, 4B) are output, and the rear wheels 2 are steered in the same direction as the front wheels 1 are steered.

The flow rate control valve 9 (see Fig. 1) provided in the middle of the pressure oil supply path to the control valve 6 is composed of an electromagnetic valve with a variable throttle passage, and operates a solenoid by a signal from the controller 50. The aperture m is adjusted, and the rear wheel power cylinder 4 (
4A14B), the direction of the flow m supplied is adjusted. The controller 50 predicts the lateral acceleration that will act on the vehicle body due to steering at the vehicle speed based on a control signal corresponding to a vehicle speed signal from a vehicle speed sensor 52 installed on the axle or drive shaft, etc., and calculates the desired acceleration. Wheel steering! The flow rate control valve 9 is controlled by outputting a valve opening signal that satisfies (desirable supply flow rate to the rear wheel power cylinder 4).

In this way, in this embodiment, the rear wheels 2 can be steered by the flow control valve 9 according to the driver's intention and to a desired amount of rear wheel turning relative to the amount of front wheel steering. Therefore, the followability of rear wheel steering can be optimally maintained and stable steering can be performed without slipping of the rear wheels 2. Furthermore, in this embodiment, by selecting the washer 42 as appropriate and adjusting the swinging fulcrum position of the swinging lever 26A of the rear wheel control valve 6 using the adjustment bin 40, the assembly of the power steering device to the vehicle is completed. After that, the power cylinder characteristics of the rear wheels can be easily adjusted to the desired characteristic values.

For example, in FIG. 4, desirable front wheel power cylinder characteristic curves and rear wheel power steering characteristic curves in the power steering device of the present invention are Ll and t, respectively.
5 and L2, the target steering characteristic of the entire system is indicated by A.

When the characteristics of both power cylinders 3.4 were investigated after the power steering device according to this embodiment was assembled to the vehicle body, it was found that:
Suppose that the characteristics of the front wheel power cylinder 4 are L2 in Fig. 4.
When the characteristic shown by A or 12B is reached, the swing lever 26 of the control valve 6 is adjusted by the adjustment bin 40.
By changing the swing fulcrum position of A, L2A or 1
It is possible to modify the characteristic indicated by 2B to the desired characteristic indicated by L2. In other words, if the steering characteristics of the entire system indicated by symbol B or C shown in FIG. It also means that it can be easily adjusted to the indicated characteristics.

FIG. 5 shows the main parts of a second embodiment of the present invention, in which the adjustment pin 44 can be tightened and fixed to the valve block main body 16a by a lock nut 45 and a set pin 46 screwed onto the adjustment pin 44. It has become.

FIG. 6 shows the main part of a third embodiment of the present invention, in which a spherical bearing 48 is provided at the tip of the adjustment bin 47, and this bearing 48 supports the protrusion 41 of the swing lever 26A. The means for fixing the adjustment bin 47 is the same as in the second embodiment.

(Effects of the Invention) As described above, according to the present invention, it is possible to block the longitudinal vibrations that the tires receive due to unevenness of the road surface while driving, prevent them from being transmitted to the vehicle body, and also prevent vibrations when changing lanes while driving at high speed or slalom. Since the tracking delay of the rear wheels is improved, sideslip is eliminated, driving stability and handling are improved. Since the wheel-side steering characteristics can be adjusted, the optimum target steering characteristics can be easily obtained, and the processability and assemblability of the device can be improved, making it practical and ensuring optimal performance of the front and rear wheel steering system. It has the effect that it can.

[Brief explanation of drawings]

Fig. 1 is the overall R factor of the first embodiment of the present invention, Fig. 2 is a cross-sectional view of the control valve arrangement position used in this embodiment, and Fig. 3 is a cross-section along the If-If line in Fig. 2. 4 is a characteristic curve diagram showing the input/output characteristics of the power cylinder of the power steering II according to the present invention, FIG. 5 is a sectional view of the main part of the second embodiment of the present invention, and FIG. 6 is a characteristic curve diagram showing the input/output characteristics of the power cylinder of the power steering II according to the present invention. FIG. 3 is a cross-sectional view of main parts of a third embodiment of the present invention. 1... Front wheel, 2... Rear wheel, 3... Power cylinder for front wheels, 4 (4A, 4B>... Power cylinder for rear wheels, 5... Control valve that controls the power cylinder for front wheels , 6... Control valve for controlling the rear wheel power cylinder, 9... Flow rate control valve, 14... Pinion shaft,
14A...Pinion, 14B...Rack, 15...
・Valve spool, 26.26A... Vibration lever, 4
0.44.47...Adjust bin, 50...Controller. Patent applicant Nissan Motor Co., Ltd. Kayaba Kogyo Co., Ltd. Figure 1 Figure 3

Claims (1)

[Claims] The power cylinder for front wheel steering outputs power to steer the front wheels, and the suspension member is attached to the vehicle body via an elastic body such as a rubber bush.The elastic body of the rear wheel suspension member is forcibly displaced to steer the front wheel. A power cylinder for rear wheel steering that outputs an output to steer the rear wheels in the same direction as the steering direction, a control valve that operates with each of the power cylinders, and a fluid for the control valve that operates the power cylinder for rear wheel steering. A power steering device including a flow control valve provided in the middle of a supply path and controlling a fluid flow rate according to the speed of the vehicle, wherein both control valves are connected to a front wheel steering arm via a tie rod. They are arranged in parallel to a pinion shaft formed integrally with the pinion that meshes with the rack and rotates together with the steering handle, and are controlled by the rocking displacement of each rocking lever fitted to this pinion shaft. 1. A power steering device characterized in that a lever length adjustment mechanism is provided at a swinging fulcrum of a swinging lever of a control valve for operating a power cylinder for steering rear wheels.