JPS6340367Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a power steering device.

As a conventional power steering device, there is one shown in FIGS. 1 and 2, for example. In the figure, 10 is a power cylinder, a valve housing 11 is fixed to one end of the power cylinder, and a servo device 1 that controls the supply and discharge of pressure oil to and from the power cylinder is attached to the valve housing 11.
2 is stored. A piston 13 is slidably attached to the power cylinder 10, and the piston 13 moves the inside of the power cylinder 10 into the left chamber 10a.
and the right ventricle 10b. A rack 14 is provided on the outer periphery of the piston 13, and a sector gear 1 provided on a cross shaft 15 is connected to this rack 14.
6 is engaged. The crossshaft 15 is connected to the steering wheels via the required steering linkage.

The servo device 12 includes a main valve member 17 fitted into the valve housing 11, and an A spool valve 18 and a B spool valve 19 rotatably housed in valve chambers formed on both sides of the main valve member 17. A steering shaft 20 is integrally connected to these spool valves 18 and 19, and this steering shaft 20 is connected to a steering wheel (not shown). Main valve member 1
A threaded shaft 21 is integrally provided at one end of the piston 7, and this threaded shaft 21 is inserted into the power cylinder 10 and is screwed into the piston 13 via a ball screw 22. Further, the screw shaft 21 is connected to the steering shaft 20 via a torsion bar 23 having flexibility. In addition, 2
5 and 26 are pressure oil supply ports and discharge ports provided in the valve housing 11. 27 and 28 are pressure oil passages formed in the power cylinder 10 and the valve housing 11, with the passage 27 opening into the left chamber 10a of the power cylinder 10, and the passage 28 opening into the right chamber 10b of the power cylinder 10. ,
By operating the servo valve device 12 by operating the steering wheel, the pressure oil from the supply port 25 is routed to the passage 27,
28 , and the other side communicates with the outlet 26 .

On the other hand, in FIG. 2, the cross shaft 15 is connected to the lower casing 10c of the power cylinder 10,
A cover 29 sealing the pressure chamber 10b inside the casing 10c is provided with bearings 30 and 3, respectively.
1, and adjacent thereto a high pressure seal 3 rotatably sealing the cross shaft 15.
2,33 are interposed. Also, high pressure seal 3
A dust seal 34 is further interposed on the outside of 2. Here, the high pressure seals 32 and 33 are for sealing the pressure oil in the pressure chamber 10b, and the dust seal 34 is for preventing dust etc. from entering the pressure chamber 10b from the outside.
2, 33 from aging and damage.
The cover 29 side end of the cross shaft 15 is
It is rotatably supported by a head 36a of a position regulating member 36 screwed through the cover 29.

In such a power steering system, when a steering wheel (not shown) is rotated clockwise, the A spool valve 18
By the operation of , pressure oil from the supply port 25 is supplied to the left chamber 10a of the power cylinder via the passage 27,
As a result, the piston 13 is urged to the right and moves. At this time, the right ventricle 10b is discharged through the outlet 26 through the passage 28 by the operation of the B spool valve 19.
is connected to. The piston 13 is provided with a rack 14 which meshes with the sector gear 16 of the cross shaft 15.
5 is assisted in clockwise rotational movement. A Pitman arm (not shown) is connected to the cross shaft 15, and the rotation of the cross shaft 15 is transmitted to the Pitman arm, and a steering link device connected thereto changes the direction of the wheels. Then, by rotating the steering wheel counterclockwise,
The supply port 2 is opened by the operation of the spool valves 18 and 19.
Pressure oil from the piston 1 enters the right chamber 10b of the power cylinder 10 through the passage 28, while the left chamber 10a is communicated with the discharge port 26 through the passage 27.
3 moves to the left. As a result, the wheels are turned left and right via the cross shaft 15 and the pitman arm. In this way, the steering operation of the wheels can be easily performed by rotating the steering wheels.

In addition, the high pressure seal 32 and the dust seal 34
The structure near the section is shown in FIG. 3 when it is enlarged. That is, the lower casing 10c
A high pressure seal 32 and a dust seal 34 are attached to both sides of the support portion of the ring-shaped protrusion 37, and grease is interposed in the rotation gap G between the protrusion 37 and the cross shaft 15 between these seals 32 and 34. The cross shaft 15 is rotated smoothly and the dust seal 34 is lubricated.

However, in such a seal structure, the lip 32a of the high-pressure seal 32 is repeatedly pressed and released against the circumferential surface of the cross shaft 15 due to pressure fluctuations in the pressure chamber 10b, resulting in a volume increase in the gap G. High pressure seal 32 and dust seal 3
4 has a so-called breathing effect, and the grease leaks out of the dust seal 34. Taking advantage of the change in the volume of the gap G, the dust attached to this grease enters the gap G again, gradually staining the high-pressure seal 32 and causing the grease to leak out. It will deteriorate.

Furthermore, there is another structure near the high pressure seal 32 and dust seal 34 shown in FIG.
In this case, the dust seal 38 has a low pressure seal lip 38a provided toward the gap G side to enhance the sealing function of the gap G, and a dust lip 38b to prevent dust from entering. In this case, it is not possible to achieve a sufficient seal.

On the other hand, in order to improve the drawbacks caused by the breathing action of the high-pressure seal 32, there is a system that connects the gap G with a hydraulic oil reservoir (not shown) to prevent the effects caused by the breathing action of the high-pressure seal 32. Proposed. However, since the gap G is filled with hydraulic oil, the above-mentioned cross shaft 15
Although it is no longer necessary to apply grease to smooth the rotation of the dust seal 38, it is essential that the dust seal 38 is provided with a low pressure seal lip 38a to seal the hydraulic oil in the gap G. Not only is the shape complicated and expensive, but the passage connecting the gap G and the reservoir (not shown) is long and difficult to process.

The present invention improves these conventional drawbacks by providing a hole that communicates with the atmosphere between the high-pressure seal and the dust seal that rotatably seal the cross shaft, thereby allowing outside air to flow freely into the above-mentioned gap. By communicating with each other, the pore pressure is always maintained at approximately constant atmospheric pressure, and the breathing action of the high-pressure seal and dust seal prevents dust from entering the gap, thereby sealing each seal. Provided is a power steering device that maintains performance, extends the life of a high-pressure seal, and thereby stabilizes power steering.

FIG. 5 is a sectional view of a main part of a power steering system showing an embodiment of the present invention, and the same components as those shown in FIG. 4 are given the same reference numerals. High pressure seal 32
A through hole 39 extending through the thickness of the lower casing 10c is communicated with the gap G sandwiched and sealed between the dust seal 38 and the through hole 39.
The other end communicates with the outside of the lower casing 10c, that is, with the outside air. That is, the gap G is always maintained at atmospheric pressure. By doing this,
A pressure change from high pressure to low pressure occurs in the pressure chamber 10b, and the lip 32a of the high pressure seal 32 is pressed against and released from the circumferential surface of the cross shaft 15, causing a volume change in the gap G. However, the change does not result in a pressure fluctuation in the gap G, and the air can be released to the outside air. This prevents dust from entering the gap G from the low pressure seal lip 38a and dust lip 38b of the dust seal 38 due to the above-mentioned breathing action of the high pressure seal 32. Further, the atmosphere opening end of the passage 39 is located below the axis of the cross shaft 15 in the lower casing 10.
By providing the seal at the lower part of the seal c, dust and the like will not enter there and reach the high pressure seal 32 during vehicle assembly. In this way, dust and the like do not enter into the gap G, thereby preventing deterioration and damage of the high-pressure seal 32 due to adhesion of dust and the like, thereby increasing durability. Generally, in order to improve the sealing performance of the dust seal, a garter spring is provided or the lip is thickened to increase the tension.
In this case, other problems such as increased friction occur. However, in the present invention, since the gap G is at atmospheric pressure and communicates with the outside air, the lip of the dust seal 38 can be made thinner, and the friction can also be kept small, so that the operation of the cross shaft 15 can be made smoother. . Although the dust seal 38 has been described as having two lips 38a and 38b, since the pressure in the gap G is atmospheric pressure, the low pressure seal lip 38a is not necessarily necessary, and an inexpensive dust seal 38 can be used. can. Further, since the through hole 39 only passes through the thickness of the lower casing 10c, processing is easy.

As explained above, according to the present invention, a cross shaft that penetrates inside and outside of the lower casing forming a part of the pressure chamber of the power cylinder, which meshes with the piston that slides inside the power cylinder by hydraulic pressure, In a power steering device that is rotatably sealed by a high pressure seal and a dust seal, a through hole communicating with the atmosphere is opened between the high pressure seal and the dust seal, so that the power steering device can be rotated freely due to pressure fluctuations in the pressure chamber. Therefore, even if the high-pressure seal fluctuates, the pressure in the gap between the high-pressure seal and the dust seal will not fluctuate. Therefore, dust, etc. will not enter the gap from the dust seal side and adhere to the high-pressure seal and the dust seal. As a result, it is possible to suppress deterioration of these components, to continuously seal the cross shaft with a high sealing function, and to obtain a power steering device having excellent durability.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional power steering device, Fig. 2 is a schematic sectional view near line A-A in Fig. 1, and Figs. 3 and 4 are main parts of a conventional seal mounting structure. FIG. 5 is an enlarged sectional view showing the seal structure of the present invention in detail. 10...Power cylinder, 10a, 10b...
Pressure chamber, 10c... lower casing, 13... piston, 15... cross shaft, 32... high pressure seal, 38... dust seal, 39... through hole,
G... Gap.

Claims (1)

[Claims for Utility Model Registration] (1) High pressure A power steering device rotatably sealed by a seal and a dust seal, the power steering device comprising a through hole communicating with the atmosphere between the high pressure seal and the dust seal. (2) The power steering device according to claim 1, wherein the through hole passes through the lower casing and opens to the atmosphere below the axis of the cross shaft.