JPH0741662Y2 - Power steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial field of application >> The present invention relates to a power steering device, and more particularly to a power steering device that can use hydraulic pressure to apply force for switching the steering angles of the left and right steered wheels when the vehicle turns. Regarding the device.

<< Prior Art >> When changing the steering direction of a vehicle, the steering angle of the left and right steered wheels is increased or decreased. In this case, a power steering device is often used in which a steering force applied to a steering wheel is urged by using a power cylinder that is hydraulically operated to turn a vehicle with good operability.

Among the power steering devices of this type, those of the integral power steering type, in which the steering gear, the link and the hydraulic control unit are integrated, are excellent in wearability and widely used, and an example thereof is JP-A-59-59. -45267 publication.

An example of this type of power steering apparatus is shown in FIG. Here, the rack 1 and the pinion 2 that form the steering gear are housed in the housing 3 and the outer cylinder 4. A piston 5 is integrally attached to an intermediate position of the rack 1, and its left and right ends are connected to a steering angle operation link of a left and right steering shaft (not shown). The left and right hydraulic chambers 6 are located at the left and right sides of the piston 5,
7 are provided. A rotary valve type well-known hydraulic control unit 8, a pump 9 and a low pressure side tank are provided in both hydraulic chambers 6 and 7.
A hydraulic circuit 11 with 10 is connected.

In this device, the hydraulic control section 8 performs an oil passage switching operation according to the direction of the torque generated by the steering force applied to the steering handle 12 to control the supply and discharge of the high-pressure oil supplied to the left and right hydraulic chambers 6, 7. . That is, when the steering handle 12 is turned to the right, high pressure oil is supplied to the right hydraulic chamber 7 on the side for urging the steering wheel to steer the steering wheel to the right, and the left hydraulic chamber 6
Is switched to communicate with the tank 10. Similarly, when the handle 12 is turned to the left, high pressure oil is supplied to the left hydraulic chamber 6 and the right hydraulic chamber 7 is connected to the tank 10.

By adopting such a configuration, the steering force applied from the steering handle 12 is transmitted to the left and right steered wheels via the rack 1, and at the same time, the pressing force by the hydraulic pressure from the left and right hydraulic chambers 6, 7 is simultaneously applied to the rack 1 side. Added as a force,
This makes it easy to change the steering angle of the steered wheels.

<Problems to be solved by the invention> As described above, the conventional integral power steering type power steering device is provided with the two hydraulic chambers 6 and 7 on the left and right sides of the piston integrated with the rack. Requires oil pipes 13 and 14 for connecting the hydraulic control unit 8 and the hydraulic control unit 8, respectively, and the hydraulic control unit 8 itself has a complicated structure, which causes a problem of difficulty in reducing the cost of the apparatus.

Then, the objective of this invention is providing the power steering device which can take a simplified structure.

<< Means for Solving the Problems >> A power steering device according to the present invention is a rack that is slidably supported in an outer cylinder and that increases and decreases the steering angle of the left and right steered wheels. A pinion including an output shaft that meshes for transmission and an input shaft that is connected to the output shaft via a torsion bar, and a hydraulic chamber disposed on one side of a piston integrally attached to the rack. When,
The hydraulic circuit has a hydraulic circuit that connects the hydraulic chamber and the pump, and a return spring that abuts on the other side of the piston to apply a pressing force toward the hydraulic chamber. The hydraulic circuit includes the hydraulic chamber and the pump. A branch passage extending from the space to the low pressure side tank is provided, and the flow rate of the oil discharged to the tank is increased along with the increase in the relative rotation in one direction between the input and output shafts of the pinion on the branch passage, Squeezing means for reducing the amount of discharged oil according to an increase in relative rotation is attached, and the squeezing means is arranged to balance the pressing force based on the hydraulic pressure of the hydraulic chamber with the pressing force of the return spring when the piston is in the neutral position. It is characterized by having a set configuration.

<Operation> When the piston goes straight, the piston receives the pressing force of the hydraulic pressure in the hydraulic chamber and the pressing force of the return spring equally, and is held at the neutral position. When the steering wheel is steered in one direction, one-way relative rotation occurs between the input and output shafts according to the ground resistance of the tire, and the hydraulic fluid in the hydraulic circuit is discharged from the branch passage to the tank through the enlarged squeezing means. As a result, the pressure in the hydraulic chamber drops. Therefore, the pressing force of the return spring increases the force for urging the piston, and the pressing force of the return spring assists the steering in one direction. Next, when steered in the other direction, relative rotation in the other direction occurs between the input and output shafts, and the squeezing means operates in the direction to close the branch passage, increasing the pressure in the hydraulic circuit and hydraulic chamber, and attaching the piston. The urging force is such that the hydraulic pressure in the hydraulic chamber becomes larger than the pressing force of the return spring, and the hydraulic pressure in the hydraulic chamber assists the steering. Here, the steering assisting direction is switched by supplying / discharging hydraulic fluid to / from one hydraulic chamber via only one hydraulic circuit.

<< Embodiment >> An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a power steering apparatus according to the present invention, and FIG. 2 shows a hydraulic circuit of the apparatus.

This power steering apparatus adopts an integral power steering type including a rack and pinion type steering gear and a rotary valve type hydraulic control unit. Rack 20 and pinion 21 that form the steering gear are housing
It is housed in an outer cylinder 23 integrally connected to the housing 22 and the housing 22.

A rack gear 201 is formed on the rack 20 and meshes with a gear (not shown) on the pinion 21 side. This rack
A piston 24, which is slidably contacted with the outer cylinder 23, is integrally mounted at an intermediate position of the 20. A hydraulic chamber 26 is provided between the piston 24 and the seal 25 on the housing 22 side. Cylinder
A return spring 28 is disposed between the other end 23 and the end cover 27 which also serves as a bearing. The rack 20 has a straight shape, and its left and right ends are respectively connected to the steering angle operation links for the left and right steered wheels (not shown) via ball joints 29, 29. Reference numerals 30 and 30 indicate dust boots.

The pinion 21 is the lower end pinion gear 211 (see FIG. 3).
And a hydraulic pressure control unit 31 located above it, and a coupling unit 32 for connecting the steering shaft (not shown) at the upper end thereof.

As shown in FIG. 2 and FIG. 3, the hydraulic control unit 31 here is a rotary valve 23 that rotates integrally with the pinion gear 211, which is an output shaft, and a rotary valve 23 that is relatively rotatably fitted inside the rotary valve 23. Input shaft 50 which is the input shaft to
And a torsion bar 49 which is fitted inside the input shaft 50 through the central oil passage 25. Of this,
The upper end of the torsion bar 49 and the input shaft 50 are integrally connected to the connecting portion 32, and the lower end of the torsion bar 49 is integrally connected to the pinion gear 211 side. Therefore, the torsion bar 26 is twisted under the steering force applied from the steering handle (not shown), and the rotary valve 23 and the input shaft are rotated according to the rotation difference between the upper and lower ends thereof.
A rotation difference occurs between 50. Here, the housing 22 has a tank port 33 and a pump port 34 on the upper and lower sides thereof, and the rotary valve 23 has a lower annular passage 35 and an inlet port 36 on the lower stage thereof.
However, the upper annular passage 37 and the outlet 38 are formed in the upper stage thereof, and the input shaft 50 is formed with the lower stopper 39 in the lower stage and the upper stopper 40 in the upper stage as the squeezing means.

Further, the hydraulic chamber 26 is connected to the pump 41 via a hydraulic circuit 47, and a branch portion 45 is provided between the hydraulic chamber 47 and the pump 41 in the hydraulic circuit 47. This branch
45 is connected to the pump port 34, and the pump port 34
Is communicated with the inflow port 36 through the lower annular path 35 at all times, and the tank port 33 is communicated with the low pressure side tank 42, thereby forming a branch path extending from the hydraulic chamber 26 to the pump to the low pressure side tank. is doing.

The hydraulic pump 41 used here is configured to be driven by receiving the rotational force of the engine, and to generate a uniform discharge pressure in almost all the commonly used rotation regions.

In such a power steering system, the hydraulic pump 41 is driven as the engine is driven, and the hydraulic pressure is transmitted to the hydraulic circuit 47. As long as no steering force is applied to the steering wheel, the piston 24 and the rack 20 slide to a position where the hydraulic pressure and the spring 28 balance each other, that is, the neutral position, and the vehicle is kept straight.
At this time, the vertical squeezers 40, 39 face the upper and lower outflow and inflow ports 38, 36 at 1/2 opening, respectively, and as shown in FIG. Is being supplied.

Next, assume that the steering wheel is turned to the right. In this case, the upper and lower squeezers 40, 39 are further outflowed vertically, and the area facing the outlets 38, 36 is further narrowed. As a result, the relief pressure on the hydraulic chamber 26 side increases, and the pressure based on this relief pressure returns to P The difference from the pressing force S (P <S) generated by the spring 28 is added to the steering force as an urging force F by hydraulic pressure to easily turn the steered wheels to the right.

Next, assume that the steering wheel is turned to the left. In this case, the vertical squeezing 40, 39 expands the upper and lower outflow, the area facing the inflow ports 38, 36, as a result, the relief pressure on the hydraulic chamber 26 side is reduced, and the pressing force P1 and the return pressure based on this relief pressure Spring
The difference between the pressing force S1 of 28 (P1 <S1) is added to the steering force as the biasing force F1 by the return spring, and the steering wheel is easily turned to the left.

In the power steering system shown in FIG. 1, when the engine is stopped and the hydraulic pressure drops, only the pressing force of the return spring 28 works and the steered wheels are cut to the left. The fifth measure against this is
A directional control valve 44 as shown can be utilized. Directional control valve
Reference numeral 44 is a solenoid valve that simultaneously opens and closes a flow path 46 between the hydraulic pump 41 and the branch portion 45 and a branch path 47 between the branch portion 45 and the hydraulic chamber 26. A valve drive circuit 48 is connected to the directional control valve 44,
While receiving the rotation information of an engine rotation sensor (not shown), the circuit outputs an ON output to open the directional control valve 44. Therefore, when the engine is stopped, the control valve 44 is closed to prevent the oil in the hydraulic chamber 26 from flowing out to the tank 42 or the hydraulic pump 41, and the left and right steered wheels can be held in a neutral state.

<Effect of the Invention> The present invention is designed to switch the steering assisting direction by supplying and discharging hydraulic oil to and from one hydraulic chamber only through one hydraulic circuit. With only one hydraulic circuit corresponding to this, switching to a desired steering angle can be facilitated, the structure can be simplified, and the cost of the entire apparatus can be reduced.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a power steering device as an embodiment of the present invention, FIG. 2 is a hydraulic circuit diagram of the same steering device, and FIG. 3 is a sectional view of a hydraulic control unit in the same steering device. FIG. 4 is a steering force (handle torque) -relief pressure characteristic diagram of the steering apparatus, FIG. 5 is a hydraulic circuit diagram in a power steering apparatus as another embodiment of the present invention, and FIG. It is a schematic general view of the conventional power steering apparatus. 20: rack, 21: pinion, 211: pinion gear (output shaft), 22 ... housing, 23 ... outer cylinder, 24 ... piston, 26 ... hydraulic chamber, 28 ... return spring, 31 ... … Hydraulic control, 36 …… Inlet, 38 …… Outlet, 39 …… Downward squeeze,
40 …… Top squeeze, 41 …… Hydraulic pump, 42 …… Tank, 43
...... Branch path, 47 …… hydraulic circuit, 49 …… torsion bar,
50 …… Input shaft (input shaft).

Claims (1)

[Scope of utility model registration request] 1. A rack that is slidably supported in an outer cylinder and that increases and decreases the steering angle of the left and right steered wheels, an output shaft that meshes to transmit a steering force to the rack, and an output shaft with respect to the output shaft. Pinion consisting of an input shaft connected through a torsion bar, a hydraulic chamber provided only on one side of the piston integrally attached to the rack, and a hydraulic pressure connecting the hydraulic chamber and the pump. A circuit and a return spring that abuts against the other side of the piston to apply a pressing force toward the hydraulic chamber, and the hydraulic circuit includes a branch extending from between the hydraulic chamber and the pump to the low pressure side tank. A passage is provided, and on the branch passage, the flow rate of oil discharged to the tank is increased in accordance with an increase in relative rotation between the input and output shafts of the pinion in one direction, and the amount of oil discharged is increased in accordance with an increase in relative rotation in the other direction. Squeezing means to reduce Serial piston power steering apparatus characterized by having a structure in which the throttle means is set so that the pressing force of the return spring and the pressing force based on the hydraulic pressure of the hydraulic chamber and is balanced when in the neutral position.