JP2002005303A - Sealing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that backup effect was insufficient because a conventional backup ring was positioned apart from a lip along an axial direction on an inner peripheral part of a seal member and the lip conventionally fastens a rod too strong when a high pressure was applied to a back surface of the lip to impart exceeded wear resistance and to deteriorate durability. SOLUTION: In a seal member 22, a fastening force regulating member 28 is attached on a back surface 27 of a lip 24. The fastening force regulating member 28 is made to be zigzag by forming a metal thin plate or the like. The fastening force regulating member 28 receives a high pressure at an outside of the lip 24 along a radial direction to securely regulate the increase of fastening force of the lip 24. The fastening force regulating 28 is springy and also works as a fastening ring giving the lip 24 fastening force under an ordinary pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sealing device for sealing between a housing and a rod.

[0002]

2. Description of the Related Art Conventionally, there is a rack and pinion type steering device which obtains a steering assist force by hydraulic pressure. In this type of power steering device, a rack shaft is disposed in a gear housing and a cylinder tube connected to each other so as to be able to reciprocate in the axial direction. The rack shaft meshes with a pinion in the gear housing, and both ends of the rack shaft protrude outside the gear housing and the cylinder tube, respectively, and are connected to steering wheels via tie rods.

[0003] The sealing device for sealing between the rack shaft and the cylinder tube includes a sealing member having a lip that contacts the rod. Further, a tightening force of the lip to the rod is provided by a tightening ring composed of a tension coil spring arranged so as to surround the rear surface of the lip.

[0004]

When the operating oil pressure rises to a level exceeding, for example, 100 kg / cm ² , an excessive pressure is applied to the back surface of the lip.
The frictional resistance of the lip to the rod increases. As a result, there is a problem that the wear of the lip is promoted and the life of the sealing device is shortened. Therefore, conventionally, a backup ring made of a synthetic resin that is in contact with the shaft at a predetermined distance in the axial direction from the lip is provided on the inner peripheral portion of the seal member.
However, since the lip is backed up at a position away from the lip in the axial direction, the backup effect is not sufficient, and it does not contribute much to the improvement of the lip durability. Also, there is a concern about the durability of the backup ring itself that is in sliding contact with the shaft.

[0005] On the other hand, there is a similar problem in a rod seal for a water pump of an automobile. The present invention has been made in view of the above problems, and an object of the present invention is to provide a sealing device having excellent durability.

[0006]

In order to achieve the above object, the present invention relates to a sealing device for sealing between a housing and a rod, wherein an annular seal having an inner peripheral portion having a lip contacting an outer peripheral surface of the rod. And a clamping force regulating means disposed radially outward of the lip and regulating the clamping force of the lip to the rod when the internal pressure applied to the back surface of the lip increases. is there.

With this configuration, even if an excessive internal pressure acts on the back surface of the lip, the tightening force of the lip on the rod does not increase excessively. Therefore, the lip does not have excessive frictional resistance, and the durability can be improved. In addition, since the tightening force regulating member is disposed radially outward of the lip, it is possible to reliably prevent the lip from contracting when the pressure is increased. Furthermore, a backup ring made of a synthetic resin, which was conventionally provided on the inner peripheral portion of the sealing member at a distance from the lip in the axial direction and had a problem in durability, can be eliminated. Can contribute.

[0008] The tightening force regulating means may include an annular member attached to the back surface of the lip. If it is an annular member, it can receive high pressure even if it is thin, and can suppress the tightening force of the lip on the rod. As the annular member, for example, a thin plate made of steel, aluminum, or resin can be used. The same effect can be obtained when the tightening force regulating means includes an annular member buried between the lip and the back surface of the lip. In addition, since the annular member is embedded, the adhesion between the annular member and the seal member is high, which is more preferable in terms of durability.

In some cases, the annular member includes a slit for reducing the interval in accordance with the contraction of the back surface of the lip. In this case, even if a rigid material is used, the slit can provide elasticity that can withstand the expansion and contraction of the back surface of the lip. Then, at the time of contraction in which the slit interval is narrowed, it is possible to withstand a sufficiently large circumferential stress. In some cases, the tightening force restricting means also serves as a spring that applies a tightening force to the rod to the lip. In this case, the manufacturing cost can be reduced by simplifying the structure.

In some cases, the tightening force regulating means includes a plurality of hardened portions formed by surface-treating the rear surface of the lip and arranged at intervals in the circumferential direction. In this case, since a part of the seal member also functions as the tightening force regulating means, the manufacturing cost can be reduced by simplifying the structure. Further, since the tightening force regulating means is formed integrally with the seal member, the adhesion between the two is high, which is preferable in terms of durability.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a partially cutaway side view of a main part of a power steering device including a sealing device according to an embodiment of the present invention. With reference to FIG. 1, a power steering device 1 includes a rack and pinion mechanism with hydraulic power assist including a rack shaft 2 having rack teeth 2a and a pinion (not shown).

The rack shaft 2 is slidably supported in the axial direction inside a cylinder tube 3 extending in the left-right direction of the vehicle body and a gear housing 4 connected to one end of the cylinder tube 3. Both ends of the rack shaft 2 are connected via ball joints 6 to tie rods 5 respectively connected to front wheels (not shown). A rod 7 is formed on a part of the rack shaft 2, and the space between the rod 7 and the cylinder tube 3 surrounding the rod 7 is sealed by rod seals 8, 8 as a pair of left and right sealing devices. Thus, a power cylinder 9 for generating a steering assist force is configured. A cylinder 9a of the power cylinder 9 is constituted by a part of the cylinder tube 3.

The gear housing 4 includes the cylinder tube 3
And a main housing 11 extending upwardly obliquely with respect to the support cylindrical portion 10. 12 is a steering wheel 13
The input shaft of the power steering device 1 connected to the
The upper end of 2 protrudes from main housing 11. Although not shown, an output shaft forming a pinion and a torsion bar for connecting the input shaft 12 and the output shaft to each other so as to be capable of relative angular displacement are accommodated in the main housing 11.

In the main housing 11, pressure oil from the hydraulic pump P is supplied to the left and right oil chambers 15 and 16 of the power cylinder 9 separated from each other by a piston 14 based on the relative angular displacement between the input and output shafts. And a control valve C for returning the oil from the other oil chamber to the oil tank T. In FIG.
17 is a port 18 connecting the control valve C and the oil chamber 15
Reference numeral 19 denotes an oil passage which communicates the control valve C and the oil chamber 16 via a port 20.

The rod seal 8 on the gear housing 4 side is
It is press-fitted into the cylinder 9a at a position where it comes into contact with the end of the support cylinder portion 10. The other rod seal 8 is positioned in contact with a rack bush 21 fixed to an end of the cylinder 9a. Referring to FIG. 2, which is an enlarged cross-sectional view of a main part of power cylinder 9, rod seal 8 includes an annular rubber seal member 22 and an annular core metal 23 having a substantially L-shaped cross section. ing. The metal core 23 is vulcanized and bonded to the seal member 22 so that the seal member 22 is
To reinforce.

The seal member 22 has an inner peripheral portion 25 that forms a lip 24 that contacts the rod 7, and an outer peripheral portion 26 that is pressed into the inner peripheral surface 9b of the cylinder 9a. Conventionally, the core metal 23 is formed on the inner peripheral portion 25 of the seal member 22.
A backup ring made of a synthetic resin is disposed at a position closer to the rod 7 so as to be in sliding contact with the rod 7. In the present embodiment, such a conventional backup ring that is in sliding contact with the rod 7 is omitted.

In place of the conventional backup ring, a tightening force regulating member 28 for preventing the tightening force from excessively increasing when the internal pressure rises is attached to the back surface 27 of the lip 24 of the seal member 22. Have been. The tightening force regulating member 28 normally functions as a tightening ring that increases the tightening force (tightening force) of the lip 24 on the rod 7. That is, the tightening force regulating member 28 also serves as a tightening ring. The tightening force regulating member 28 surrounds the periphery of the back surface while alternately folding back in a zigzag shape (meandering shape), and is formed by, for example, sheet metal forming a thin plate made of steel, aluminum, or resin. The tightening force regulating member 28 may be vulcanized and bonded to the back surface 27 of the lip 24, or may be bonded using an adhesive.

More specifically, the tightening force regulating member 28
A number of parallel first portions 29 extending in a meandering direction
And one end of the first portion 29 adjacent to the first side.
And a second portion 30 connecting the other end of the first portion 29 to the end of the first portion 29 adjacent to the other side. Adjacent first part 2
A slit 31 is formed between 9 and 29, and the slit width s decreases as the internal pressure increases. When the internal pressure reaches a set value, the slit width s becomes substantially zero. As a result, the tightening force regulating member 28 has a substantially cylindrical shape, and can exhibit rigidity that can withstand circumferential stress due to internal pressure. The reason why the slit width s does not have to be 0 is that a circumferential stress against internal pressure may be generated in a state where the rubber of the seal member 22 is sandwiched between the slits 31.

According to this embodiment, when a high internal pressure is applied to the back surface 27 of the lip 24, the tightening force regulating member 2
7, the amount of contraction of the back surface 27 of the lip 24 in the circumferential direction can be regulated. Therefore, the tightening force of the lip 24 on the rod 7 does not increase excessively. As a result, the lip 24 does not have excessive frictional resistance, and the durability can be improved. In particular, since the tightening force regulating member 28 is formed of an annular member, it can receive a high pressure even when it is thin, and is easy to manufacture because the annular member is attached to the back surface of the lip.

The rear surface 27 of the lip 24 may have a substantially V-shaped cross section as shown in FIG. 2 similar to the case where a conventional tightening ring is arranged, or FIG. As shown in FIG. Next, FIG. 5 shows another embodiment of the present invention. Referring to FIG. 5, in the present embodiment, a fastening ring 33 made of a tension coil spring similar to the conventional one is wound around back surface 27 of lip 24, and lip 24 and back surface 27 of lip 24 are used as fastening force regulating members. An annular member 34 buried therebetween is provided. As shown in FIG. 6A, slits 35 formed by slits may be formed in the annular member 34, or slits formed by notches on the inner circumference and the outer circumference as shown in FIG. 36 may be formed. When the internal pressure is applied, as shown in FIGS. 6B and 7B, the width of these slits 35 and 36 is reduced,
The point that a circumferential stress against the internal pressure is generated by the annular member 34 is the same as in the above embodiment.

According to this embodiment, the durability can be improved as in the above-described embodiment. In addition, since the annular member 34 as the tightening force regulating member is embedded in the seal member 22, the adhesion between the annular member 34 and the seal member 22 is extremely high, which is more preferable in terms of durability. Next, FIG. 8 shows still another embodiment of the present invention. Referring to FIG. 8, the present embodiment is different from the embodiment of FIG. 2 in the following. That is, 1) In the embodiment of FIG. 2, a member separate from the seal member 22 is attached to the back surface 27 of the lip 24 as the tightening force regulating member 28, but in the present embodiment, the back surface 27 of the lip 24 is Is partly surface-treated to form a tightening force regulating portion 37. As shown in FIG. 9, the tightening force regulating portion 37 is constituted by a plurality of hardening portions 38 arranged at intervals d in the circumferential direction,
For example, it is formed by curing a part of the back surface 27 of the lip 24 by irradiating a laser beam. 2) In the embodiment of FIG. 2, the tightening force regulating member 28 also serves as a conventional tightening ring, but in the present embodiment, the same tightening ring 33 as in the related art is arranged so as to surround the back surface 27 of the lip 24. are doing.

In this embodiment, a predetermined tightening force is applied to the rod 7 by the tightening ring 33 under normal internal pressure. When the internal pressure increases, the distance d between the adjacent hardened portions 38, 38 is reduced to substantially zero, and the large number of hardened portions 38 function as a ring-shaped structure that receives circumferential stress due to the internal pressure as a whole. As a result, it is possible to prevent the lip 24 from exerting an excessive tightening force on the rod 7, and it is possible to improve the durability.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention, for example, the present invention is applied to a rod seal for a rotating shaft of a water pump. .

[Brief description of the drawings]

FIG. 1 is a partially broken side view of a power steering device in which a sealing device according to an embodiment of the present invention is applied to a power cylinder.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a schematic plan view of a tightening force regulating member.

FIG. 4 is a sectional view of a main part of a sealing device according to another embodiment of the present invention.

FIG. 5 is a sectional view of a main part of a sealing device according to still another embodiment of the present invention.

FIGS. 6A and 6B are front views of an annular member serving as a tightening force regulating member applied to the embodiment of FIG. 5, wherein FIG. 6A shows a normal internal pressure state and FIG. 6B shows a high internal pressure state.

FIGS. 7A and 7B are front views of another embodiment of an annular member serving as a tightening force regulating member applied to the embodiment of FIG. 5, wherein FIG. 7A shows a normal internal pressure state and FIG. I have.

FIG. 8 is a sectional view of a main part of a sealing device according to still another embodiment of the present invention.

FIG. 9 is a schematic plan view of a tightening force regulating unit.

[Explanation of symbols]

 Reference Signs List 7 rod 8 rod seal (sealing device) 9a cylinder 22 sealing member 23 core metal 24 lip 25 inner peripheral portion 27 back surface 28 clamping force regulating member 29 first portion 30 second portion 31 slit s slit width 32 back surface 33 fastening Ring 34 Annular member (tightening force regulating member) 35, 36 Slit 37 Tightening force regulating section 38 Hardened section

Claims (6)

[Claims] 1. A sealing device for sealing between a housing and a rod, comprising: an annular sealing member having an inner peripheral portion having a lip in contact with an outer peripheral surface of the rod; and a lip disposed radially outward of the lip. And a tightening force restricting means for restricting a tightening force of the lip to the rod when an internal pressure applied to the back surface of the lip increases. 2. A sealing device according to claim 1, wherein said tightening force regulating means includes an annular member attached to a back surface of said lip. 3. The sealing device according to claim 1, wherein said tightening force restricting means includes an annular member embedded between the lip and a back surface of the lip. 4. An annular member according to claim 2, wherein said annular member includes a slit for reducing the interval according to shrinkage of the back surface of the lip.
Or the sealing device according to 3. 5. The sealing device according to claim 1, wherein said tightening force restricting means also serves as a spring for applying a tightening force to the lip to the lip. 6. The sealing device according to claim 1, wherein said tightening force regulating means includes a plurality of hardened portions formed by surface-treating the rear surface of the lip and arranged at intervals in the circumferential direction.