JPH0538256Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an oil leak control mechanism for a hydraulic shock absorber used in motorcycles and the like.

(Prior Art) As a hydraulic shock absorber used in motorcycles, etc., for example, a cylinder is disposed inside an outer tube, a piston rod is exposed from above in the cylinder, and the tip of the piston rod is connected to the inside of the cylinder. A piston that slides on the circumferential surface is installed, and a rod guide that supports the upper end of the cylinder and guides the piston rod is fitted to the upper end of the outer tube.Above the rod guide is an oil seal that slides on the outer circumferential surface of the piston rod. The rod guide is fitted with a return oil passage that communicates with the reservoir chamber formed between the outer circumferential surface of the cylinder and the inner circumferential surface of the outer tube.

In this hydraulic shock absorber, when the piston rod moves upward during the extension stroke, the hydraulic oil in the upper oil chamber flows upward through the gap between the piston rod and the rod guide (hereinafter also referred to as "guide clearance"), and The oil is returned to the reservoir chamber through the return oil path.

(Problem to be solved by the invention) However, in the above-mentioned hydraulic shock absorber,
The guide clearance, which is the gap between the rod guide and the piston rod, has variations in opening amount due to manufacturing variations in the piston rod and rod guide and displacement during movement of the piston rod. The damping force changes and a stable damping force cannot be obtained. Further, changes in damping force due to variations in guide clearance tend to occur in the low speed range, which is important in terms of characteristics.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides an oil chamber between the rod guide and the oil seal by interposing a seal that makes sliding contact with the outer peripheral surface of the piston rod. This oil chamber was communicated with a reservoir chamber formed between the inner circumferential surface of the outer tube and the outer circumferential surface of the cylinder through a return oil passage, and an orifice was formed in the return oil passage.

(Function) The hydraulic oil in the upper oil chamber returns from the gap (guide clearance) between the piston rod and rod guide and returns to the reservoir chamber through the oil passage and orifice.
At this time, due to the presence of the orifice, the leakage amount of the hydraulic oil returning to the reservoir chamber becomes approximately constant, and even if the guide clearance changes, changes in the damping force are suppressed.

(Example) An example of the present invention will be described below based on the accompanying drawings.

FIG. 1 is a cross-sectional view showing a hydraulic shock absorber according to the present invention, FIG. 2 is an enlarged cross-sectional view of a main part of the shock absorber, and FIG. 3 is an exploded perspective view of a main part of the shock absorber.

This hydraulic shock absorber has a cylinder 2 installed in an outer tube 1, a piston rod 3 inserted into the cylinder 2 from above, and a piston 5 that slides on the inner peripheral surface of the cylinder 2 at the tip of the piston rod 3. An oil passage 6 for generating a damping force is formed in the piston 5, and a valve 7 for opening and closing the oil passage 6 is attached.

A rod guide 8 for guiding the piston rod 3 is fitted in the upper end of the outer tube 1, and a bush 9 that slides on the outer circumferential surface of the piston rod 3 is fitted on the inner circumferential surface of the rod guide 8.
The upper end of the cylinder 2 is fitted onto the outer peripheral surface of the lower end of the rod guide 8, and a protrusion 10 is formed on the upper surface of the rod guide 8. Further, an oil seal 11 is held within the upper end of the outer tube 2 and is in sliding contact with the outer peripheral surface of the piston rod 3.

A seal 14 is fitted between the rod guide 8 and the oil seal 11, and the seal 14 is formed by embedding a reinforcing member 13 in an elastic body that slides on the outer circumferential surface of the piston rod 3 within the upper inner peripheral surface of the rod guide 8. An oil chamber 15 is formed between the upper surface of the rod guide 8 and the outer circumferential surface of the rod guide 8, and this oil chamber 15 is communicated with a reservoir chamber SR formed between the outer circumferential surface of the cylinder 2 and the inner circumferential surface of the outer tube 1. Return oil passages 16a, 16b, and 16c are formed.

Further, a ring plate 18 and a ring plate 19 are laminated and sandwiched between the outer peripheral lower end surface of the seal 14 and the protrusion 10 of the rod guide 8, and the ring plate 18 has a clearance (guide) between the piston rod 3 and the bush 9 of the rod guide 8. The orifice 20 is formed with an opening area smaller than the clearance (clearance), and is interposed in the return oil passage 16a that communicates the oil chamber 15 and the reservoir chamber SR. Further, a ring plate 21 is interposed between the seal 14 and the oil seal 11, and an oil passage 22 consisting of a notch is formed in the ring plate 21.

The ring plate 19 is provided to prevent the seal 14 from blocking the orifice 20 of the ring plate 18, and by forming an orifice directly on the upper surface of the rod guide 8 with a groove or the like, the ring plate 18 can be closed. It can also be omitted.

Furthermore, a cap 24 is fitted onto the upper end of the outer tube 1, and a cap 25 is screwed onto the lower end.

With the above structure, when the piston rod 3 moves upward during the extension stroke of the hydraulic shock absorber, the hydraulic oil in the upper oil chamber S1 flows into the lower oil chamber S2 through the oil path (not shown) of the piston 5. damping force is generated.

At this time, part of the hydraulic oil in the upper oil chamber S1 passes through the gap (guide clearance) between the piston rod 3 and the bush 9 of the rod guide 8 to the oil chamber 1 formed by the upper surface of the rod guide 8 and the seal 14.
5. The flow rate of the hydraulic oil flowing into the oil chamber 15 is controlled by an orifice 20 formed in the ring plate 10, and the hydraulic oil flows into the reservoir chamber SR through return oil passages 16a, 16b, and 16c of the rod guide 8.

In this case, the smaller the guide clearance, the smaller the amount of hydraulic oil leaking through the guide clearance and the larger the damping force generated by the piston 5, and the larger the guide clearance, the larger the amount of hydraulic oil leaking through the guide clearance. Although the damping force generated by the piston 5 becomes smaller, since the orifice 20 is interposed in the return oil passage 16a in this hydraulic shock absorber, the amount of hydraulic oil flowing into the oil chamber 15 through the guide clearance increases. Reservoir chamber through orifice 20
Since the return amount (leakage amount) of the hydraulic oil returning to the SR is kept substantially constant, the damping force derived from the piston 5 is kept substantially constant.

In addition, some of the hydraulic oil that has passed through the seal 14 is scraped off by the oil seal 11 and is removed from the oil passage 22 formed in the ring plate 21 and the rod guide 8.
through the return oil passages 16b and 16c to the reservoir chamber.
Returned to SR. Furthermore, if the orifice 20 were to become clogged, leak control would no longer be possible;
The hydraulic oil that has passed through the seal 14 is transferred to the oil seal 11
The oil passage 22 formed in the ring plate 21 and the return oil passage 16 of the rod guide 8 are scraped off by the
Since the oil is returned to the reservoir chamber SR through b and 16c, oil leakage can be prevented.

(Effects of the invention) As explained above, according to the invention, an oil chamber is formed by the seal provided above the rod guide, and an orifice is inserted into the return oil passage that communicates this oil chamber with the reservoir chamber. As a result, the amount of hydraulic oil leaking from the guide clearance to the reservoir chamber through the return oil path becomes approximately constant, and even if there are variations in the guide clearance, the generated damping force remains approximately constant, resulting in a stable damping force. It will be done.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a hydraulic shock absorber according to the present invention, FIG. 2 is an enlarged cross-sectional view of a main part of the shock absorber, and FIG. 3 is an exploded perspective view of a main part of the shock absorber. In the drawings, 1 is an outer tube, 2 is a cylinder, 3 is a piston rod, 5 is a piston, 8 is a rod guide, 9 is a bush, 10 is an oil seal, 14 is a seal, 16a, 16b, 16c are return oil passages, 18 is the ring plate, 20 is the orifice, S1 is the upper oil chamber, and SR is the reservoir chamber.

Claims (1)

[Scope of utility model registration request] A cylinder is disposed inside the outer tube, and a piston rod is placed inside the cylinder from above. A piston that slides on the inner peripheral surface of the cylinder is installed at the tip of the piston rod, and a piston rod is installed at the upper end of the outer tube. In a hydraulic shock absorber, a rod guide is fitted to guide the piston rod, and an oil seal that slides on the outer circumferential surface of the piston rod is fitted above the rod guide.A seal that slides on the outer circumferential surface of the piston rod is interposed between the rod guide and the oil seal. An oil chamber is formed between the rod guide and the upper surface of the rod guide, and this oil chamber and a reservoir chamber formed between the inner peripheral surface of the outer tube and the outer peripheral surface of the cylinder are communicated via a return oil passage. An oil leak control mechanism for a hydraulic shock absorber characterized by an orifice formed in the road.