JPH032468Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in rack-and-pinion power steering devices used primarily in automobiles.

Steering devices that transmit the rotation of the steering wheel to the wheel steering arms via a mechanism consisting of a pinion and a rack are characterized by a simple structure and excellent operational response. A power steering device has been proposed in which a pinion type steering device is hydraulically power assisted.

This device will be explained with reference to FIGS. 1 and 2. The main body of the device is generally composed of a rack-and-pinion gear device 1, a control valve 2, and an output drive section (power cylinder) 3. 4A is a rack formed at one end of a rack shaft 4 connected to a steering link (tie rod etc. not shown), and 5 is a pinion, which is housed in a gear box 6 together with the control valve 2.

A pinion 5 that meshes with the rack 4A is formed integrally with a pinion shaft 7 and is supported by a gear box 6 via bearings 8 and 9 provided before and after the pinion 5.

The bearings 8 and 9 are mounted on the rack 4 as shown in FIG.
Oval long hole 10 whose long axis is parallel to A
The outer race 11 of the bearings 8 and 9 is inserted into the pinion shaft 7, and the pinion shaft 7 is formed so that it can be displaced by a predetermined distance left and right.

On the other hand, the control valve 2 is disposed obliquely to the pinion shaft 7, and
A pressure passage (not shown) is formed that selectively communicates A and 3B with the pump side or the tank side.

This control valve 2 is fitted onto the pinion shaft 7,
One end engages with the other end of a drive lever 12 supported by a part of the gearbox 6, and switching is performed by the arcuate swinging motion of the drive lever 12.

With this configuration, when the pinion shaft 7 is rotated in any direction by operating a handle (not shown), the resistance of the rack 4A connected to the steering link is large, so the rack 4A is rotated in this rotation direction. The pinion 5 is displaced by the amount allowed by the elongated hole 10 along. At this time, the drive lever 12
uses a part of the gearbox 6 as a fulcrum and swings in the direction of displacement of the pinion 5. This causes the control valve 2 engaged with the drive lever 12 to be switched and displaced. With this switching of the control valve 2, pressure oil is supplied to the power cylinder 3, and the rack shaft 4 is driven in the direction of rotation of the pinion 5.

On the other hand, in the power cylinder 3, a cylinder 13 is fitted and fixed to a part of the gear box 6, and a rack shaft 4 is supported by an outer box 14 fixed to the end of the cylinder 13 via a bush 15, and is fixed to the rack shaft 4. Hydraulic chamber 3 due to piston 16 provided
A and 3B are defined.

Of these hydraulic chambers 3A and 3B, the seal of the hydraulic chamber 3A is based on the oil seal 17 provided in the outer box 14, but since the rack shaft 4 is guided by the bush 15, the oil seal 17 and the rack shaft 4 There is less eccentricity. As a result, the sealing is complete and there is no reduction in output due to oil leakage.

On the other hand, the seal of the hydraulic chamber 3B is similarly
An inner box 19 housing the oil seal 18 is fixed to the cylinder 13 with screws 20 so as to be in contact with the end of the gear box 6, and is sealed from the outside with an O-ring 24.

However, the rack 4A forming the end of the rack shaft 4
The pinion 5 is meshed with the pinion 5, and the pinion 5 is
is crimped to. Therefore, the tooth surfaces of the pinion 5 and rack 4A, or the pressure pad 23
When the pinion 5 rotates, the contact surface of the pinion 5 may be worn, or the rack shaft 4 may be bent by 0.1 mm to 0.2 mm due to heat treatment.
The point of contact with the piston 16 and the bush 15 becomes eccentric, making it impossible to support the rack shaft 4 at three points in cooperation with the piston 16 and the bush 15. As a result, the pinion 5 side of the rack shaft 4 bends eccentrically with the piston 16 as a fulcrum, and as a result, there are places where the lip of the oil seal 18 cannot follow the surface of the rack shaft 4, causing pressure in the hydraulic chamber 3B. Oil may leak to the gearbox 6 side, resulting in insufficient output.

In order to prevent this oil leakage, various measures have been proposed in the past.

In FIG. 4, a garter spring 25 in the oil seal 24 causes the lip 25A to follow the surface of the rack shaft 4 which is eccentric. However, if the eccentricity of the rack shaft 4 is large, the sealing effect may be insufficient. Become complete.

FIG. 5 shows how the oil seal 26 is connected to the gear box 6.
The floating inner tube 27 is provided at the free end of the floating inner tube 27, which can swing relative to the rack shaft 4, and a perfect sealing effect can be obtained regardless of the degree of eccentricity of the rack shaft 4. However, it has the disadvantage of a complicated structure and high cost.

This invention is intended to solve the above-mentioned problems. By floatingly supporting the inner box containing the oil seal inside the cylinder via an elastic seal ring, the output drive unit (power cylinder) can be easily constructed. It is an object of the present invention to provide a rack-and-pinion type power steering device that can reliably prevent oil leakage from the gear to the gear device side.

The present invention will be explained below based on the embodiments shown in the drawings.

As shown in FIG. 6, the inner box 28 is in contact with the end of the gear box 6 and is housed between the cylinder 13 and the rack shaft 4 with a clearance formed therebetween.

Two annular grooves 29 and 30 are formed on the outer peripheral surface of this inner box 28, and the annular groove 29 on the gear box 6 side and the cylinder 13 opposite thereto are formed.
A wiring ring 32 is housed between the inner box 28 and an annular groove 31 formed on the inner peripheral surface of the inner box 28.
is locked. An O-ring 33 is housed in the other annular groove 30, and the O-ring 33 allows displacement in a direction orthogonal to the axis of the inner box 28, and seals the hydraulic chamber 3B from the outside.

On the other hand, an oil seal 34 that makes sliding contact with the rack shaft 4 is housed in the inner circumferential end of the inner box 33 to seal the hydraulic chamber 3B to the gear box 6 side.

In this way, the inner box 28 is supported between the rack shaft 4 and the cylinder 13 in a floating state.

The other parts have the same structure as the conventional device shown in FIGS. 1 and 2, so their explanation will be omitted here.

Next, the effect will be explained.

If the rack shaft 4 is bent, for example, upward to the left (as shown), the upper lip of the oil seal 34 is pressed, while the lower lip tends to separate from the lower surface of the rack shaft 4. However, at this time, due to the pressing force exerted by the rack shaft 4 on the upper lip of the oil seal 33, the upper side of the O-ring 33 is compressed, and the inner box 28 moves upward by that amount.
By moving the inner box 28 upward,
The lower lip of the oil seal 34, which attempts to separate from the rack shaft 4, follows the surface of the rack shaft 4 without separating. As a result, the oil seal 34 of the hydraulic chamber 3B is reliably sealed to the gearbox 6 side.

On the other hand, even if the inner box 28 moves upward, the upper side of the O-ring 33 is compressed, while the lower side swells, and the entire circumference remains in contact with the inner circumference of the cylinder 13. The seal is securely maintained.

In this case, since the inner box 28 is stationary without moving together with the rack shaft 4, the contact between the O-ring 33 and the inner periphery of the cylinder 13 is not a sliding contact, and reliable sealing performance is maintained. be.

Furthermore, when the hydraulic chamber 3B is on the low pressure side, the inner box 28 is locked by the wiring 32 and is prevented from moving toward the piston 16.

This device is assembled by fitting the wire ring 32 and O-ring 33 into the annular grooves 29 and 30 of the inner box 28, respectively, and pushing the wire ring 32 and O-ring 33 into the cylinder 13. 32 expands into the annular groove 31 of the cylinder 13 and is locked therein, while the O-ring 33 positions the cylinder 13 and the rack shaft 4 in a floating position, making this operation extremely easy.

As explained above, according to the present invention, the inner box has a floating support structure, so oil leakage from the output drive section (power cylinder) of the rack-and-pinion power steering device to the gear device side can be prevented with a simple structure. There is a definite preventive effect.

[Brief explanation of the drawing]

Fig. 1 is an external view including a partial sectional view showing a conventional device, Fig. 2 is a vertical sectional view, and Fig. 3 is a -
4 and 5 are cross-sectional views showing the main parts of other conventional devices, and FIG. 6 is a cross-sectional view showing the main parts of an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Gear device, 2...Control valve, 3...Output drive unit, 4...Rack shaft, 4A...Rack, 5
... Pinion, 6 ... Gear box, 13 ... Cylinder, 14 ... Outer box, 15 ... Bush, 16 ... Piston, 23 ... Pressure pad, 28 ... Inner box, 29 to 31 ...
Annular groove, 32...Wiring, 33...O ring, 34...Oil seal.

Claims (1)

[Scope of utility model registration request] A rack-and-pinion gear device, a control valve that switches based on input rotation from a handle, and a piston provided on a rack shaft that is formed integrally with the rack and is connected to the wheels are housed in a cylinder attached to the gear device. In the power steering device, the power steering device is equipped with an output drive unit and selectively supplies pressure oil to the output drive unit via the control valve, and an oil seal that slides into contact with the easy shaft is housed in an end of the cylinder. An inner box is arranged, a gap is formed between the inner periphery of the inner box and the rack shaft, and an elastic sealing member is similarly interposed in the gap formed between the outer periphery of the inner box and the inner periphery of the cylinder. , the inner box is supported eccentrically in the radial direction with respect to the rack shaft and the cylinder based on the elasticity of the oil seal and the elastic seal member, and means is provided for locking the inner box with respect to the cylinder in the axial direction. A power steering device characterized by: