JP3402817B2 - Hydraulic shock absorber - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a front fork which is interposed between a vehicle body and an axle to attenuate vibration from a road surface in a motorcycle or the like. The present invention relates to a hydraulic shock absorber used as a hydraulic shock absorber. 2. Description of the Related Art A conventional hydraulic shock absorber has been proposed, for example, as described in Japanese Utility Model Laid-Open No. 3-139931. [0003] In this method, a piston at the end of a piston rod attached to an inner tube is slidably provided in a damper cylinder filled with hydraulic oil, and during a compression stroke, hydraulic oil according to the volume of penetration of the piston rod is supplied. From the damper cylinder, the oil is introduced into an elastic partition member of a bellows provided on the outer periphery of the damper cylinder through an oil hole formed in a head cap or the like, thereby compensating the volume. [0004] However, in such a conventional hydraulic shock absorber, in order to control the hydraulic operation with high precision, the hydraulic oil inside the damper cylinder uses an oil seal, packing, and O. While it is configured to be completely sealed by a ring, etc., during hydraulic shock absorbing operation,
Oil adhering to the piston rod, for example, oil other than hydraulic oil in the damper cylinder, more specifically, lubrication injected into the fitting inside the outer tube on the vehicle body side and the inner tube on the axle side However, there is a problem that the oil for forming the gas spring chamber becomes an oil film and enters the damper cylinder. [0005] For this reason, a situation in which a predetermined amount of oil is accumulated inside the damper cylinder due to the intrusion of the oil, and the oil pressure inside the damper cylinder rises,
There has been a problem that the elastic partition member is excessively expanded, and the durability thereof is significantly deteriorated. [0006] In addition, when the tight sealing of the piston rod sliding or the like is increased due to the necessity of ensuring the complete sealing as described above, the sliding resistance of the piston rod against the seal or the like increases, and the operation of the piston rod increases. There are problems such as worsening the performance. The present invention has been made in view of the above-mentioned conventional problems. Even if the pressure of the hydraulic oil in the damper cylinder rises due to the intrusion of oil from the outside, the present invention is applied to this damper cylinder. The oil amount and the oil pressure of the hydraulic shock absorber can be maintained at the set values, whereby the interference of the seal with the piston rod and the like can be reduced, and the contact pressure can be reduced, thereby improving the operability of the hydraulic shock absorber. It is an object to provide a hydraulic shock absorber. A hydraulic shock absorber according to the present invention has an outer tube having a damper cylinder inside and outside of which separates an oil chamber and a gas chamber outside a damper, and slides inside the outer tube. An inner tube that is freely provided and holds a piston rod end having a piston that slides in the damper cylinder, and an oil reservoir that can expand and contract on the outer periphery of the upper portion of the damper cylinder are separated by an elastic partition member. The oil reservoir communicates with an oil chamber in the damper cylinder through an oil hole provided in the damper cylinder, and closes an upper end of the damper cylinder and the outer tube, and has an oil passage communicating with the oil chamber. A top cap having a continuous valve chamber in the cap, and a relief valve in the valve chamber in the cap. Are slidably supported by a relief spring, and when the oil in the oil chamber exceeds a set pressure, the valve chamber in the cap and the gas chamber outside the damper are communicated with each other. In the hydraulic shock absorber according to the present invention, when the piston rod enters the damper cylinder during the compression stroke, the hydraulic oil in the damper cylinder compressed by the piston rod flows out into the elastic partition member. , Inflating it. During the compression stroke, the pressure in the damper cylinder rises. However, when oil in the oil chamber outside the damper cylinder other than the above-mentioned hydraulic oil enters the damper cylinder, the internal pressure oil amount further increases. To rise. When the pressure exceeds a set value, the relief valve is opened to allow a part of the hydraulic oil in the damper cylinder to pass through the oil passage provided in the top cap to the outside gas of the damper in the outer tube. Drain into the room,
Controls the amount of hydraulic oil in the damper cylinder at a constant level. An embodiment of the present invention will be described below with reference to the drawings. In FIGS. 1 and 2, reference numeral 1 denotes an outer tube constituting a hydraulic shock absorber, and 2 denotes an inner tube of the outer tube 1. Is a top cap that closes one end of the outer tube 1, and 4 is a damper cylinder whose one end is closed and held by the top cap 3. Reference numeral 5 denotes a hollow rod whose upper end is fixed to the lower surface of the top cap 3. An oil passage 5b is formed in the center of the hollow rod 5, and a valve at the upper end of the hollow rod 5 which is continuous with the oil passage 5b. The tip of the needle valve 6 screwed into and out of the center of the top cap 3 faces the hole 5a. Reference numeral 7 denotes a hollow portion formed between the top cap 3 and the hollow rod 5, and reference numeral 8 denotes an upper end portion of the hollow rod 5, and one end communicates with the hollow portion 7 and the valve hole 5a. The other end communicates with the oil chamber 9 in the damper cylinder 4. The upper part of the damper cylinder 4 is provided with a plurality of oil holes 10 communicating with the inside and the outside of the damper cylinder 4. A partition member 11 is attached. The elastic partitioning member 11 has a tubular shape, upper and lower ends thereof are sandwiched between holding members 12 and 13, and is mounted on the outer periphery of the damper cylinder 4 via an O-ring 14 in an oil-tight manner. ing. Reference numeral 15 denotes a ring-shaped valve chamber in the cap formed on the lower surface of the top cap 3 so as to surround the outer periphery of the upper end of the damper cylinder 4. The relief valve 17 is provided on the outer periphery of the damper cylinder 4 in the cap valve chamber 15 so as to be slidable in the axial direction. Further, the relief valves 18 and 19 are
The O-ring 20 inserted into the inner and outer circumferences of the valve 7 is interposed between the relief valve 17 and the sandwiching member 12 at the upper part of the outer periphery of the damper cylinder 4 facing the O-ring. This is a relief spring that urges upward at a constant pressure. Reference numeral 21 denotes an adjusting screw which is screwed in from the upper end of the top cap 3 to adjust the volume of the valve chamber 15 in the cap. Reference numeral 22 denotes a seal ring inserted between the top cap 3 and the outer tube 1. is there. On the other hand, a damping force generating valve 23 is provided at the lower end of the hollow rod 5 so as to divide the upper oil chamber 9 in the damper cylinder 4 into two chambers. In the lower damper cylinder 4, a piston 25 attached to the upper end of a piston rod 24 is slidably disposed. The lower end of the piston rod 24 is
The inner tube 2 is fixed to the bottom of the inner tube 2 that slides reciprocally (up and down) in the outer tube 1. Reference numeral 27 denotes a spring interposed between a spring receiver 28 fixed to the outer periphery of the damper cylinder 4 and a part of the inner tube 2. Next, the operation will be described. First, when the hydraulic shock absorber receives a shock and enters a compression stroke, the inner tube 2 enters the outer tube 1, whereby the piston rod 24 and the piston 25 are connected to the damper cylinder 4. Move up inside. For this reason, a part of the hydraulic oil in the damper cylinder 4 above the piston 25 flows out to the oil chamber 9 while generating a predetermined damping force through the valve 23, and the other part of the hydraulic oil. Flows into the oil chamber 30 between the elastic partition member 11 and the damper cylinder 4 through the oil hole 10 together with the hydraulic oil flowing into the oil chamber 9 through the oil passage 5 b and the valve hole 5 a in the hollow rod 5. . For this reason, as the compression process proceeds,
As the oil amount and oil pressure in the oil reservoir 30 increase, the elastic partition member 11 gradually expands. With the increase in the oil pressure, the oil pressure in the oil chamber 9 is transmitted through the oil hole 8, the hollow portion 7, and the oil passage hole 31 into the cap valve chamber 15 serving as the cap oil chamber. The relief valve 17 in the valve chamber 15 in the cap is slightly pushed down against the spring 20. On the other hand, during the above-described compression stroke, lubricating oil other than hydraulic oil attached to the piston rod 24 may enter the oil chamber 9 in the damper cylinder 4 for some reason. In such a case, the amount of the working oil in the oil chamber 9 is increased by the lubricating oil, and the pressure in the oil chamber 9 further increases. However, since the pressure increase is transmitted to the cap valve chamber 15 through the hollow portion 7 and the oil passage hole 31, the relief valve 17 is lowered when the pressure exceeds a set level. . For this reason, a gap having a size calculated in advance is formed between the relief valve 17 and the stepped portion 16, and the oil pressure in the valve chamber 15 in the cap is passed through this gap, and the lower portion becomes an oil sump. Of the outer tube 1 in the upper part of the outer tube 1. Therefore, it is possible to prevent the elastic partition member 11 from being expanded more than necessary due to the increase in pressure, to avoid deterioration in quality and durability due to fatigue of the elastic partition member 11, and to prevent sealing of a sliding portion of the piston rod. Therefore, it is not necessary to unnecessarily increase the interference, and the operation performance can be improved by reducing the sliding resistance. As described above, according to the present invention, an outer tube having an oil chamber and a damper cylinder for separating an oil chamber and a gas chamber outside a damper, and a slidable interior of the outer tube. An inner tube that holds a piston rod end having a piston that slides in the damper cylinder; and an oil reservoir that is provided on the outer periphery of the upper part of the damper cylinder and that can expand and contract. An elastic partition member in which the reservoir communicates with the oil chamber through an oil hole provided in the damper cylinder, an upper end of the damper cylinder and the outer tube, and an oil passage that communicates with the oil chamber. And a top cap having a valve chamber in the cap,
A relief valve is slidably supported in the valve chamber in the cap by a relief spring, and when the oil in the oil chamber exceeds a set pressure, the valve chamber in the cap communicates with the gas chamber outside the damper. Because we configured
Even if the pressure of the hydraulic oil in the damper cylinder rises due to the intrusion of oil from the outside, the oil amount and oil pressure in the damper cylinder can be maintained at the set values, and as a result, the sealing margin for the piston rod etc. can be reduced. In addition, there is an effect that a contact pressure can be reduced, and the operability of the hydraulic shock absorber can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged front sectional view showing a main part of a hydraulic shock absorber according to one preferred embodiment of the present invention. FIG. 2 is a front cross-sectional view showing the entire hydraulic shock absorber according to one embodiment of the present invention, partially cut away; [Description of Signs] 1 outer tube 2 inner tube 3 top cap 4 damper cylinder 9 oil reservoir 10 oil hole 11 elastic partition member 15 cap chamber 17 relief valve 20 relief spring 24 piston rod 25 piston 30 oil reservoir 31 through Oil hole 32 Gas chamber outside damper

Claims (1)

(1) An outer tube having a damper cylinder inside and outside of which separates an oil chamber and a gas chamber outside a damper; and the damper is slidably provided in the outer tube. An inner tube that holds a piston rod end having a piston that slides in the cylinder, and an oil reservoir that can expand and contract around the upper periphery of the damper cylinder are separated by an elastic partition member. An oil hole communicating with the oil chamber in the damper cylinder through an oil hole provided in the damper cylinder, closes an upper end of the damper cylinder and the outer tube, and communicates with the oil chamber and a valve in the cap connected to the oil hole. A top cap having a chamber, and a slidably supported by a relief spring in the valve chamber in the cap; When oil exceeds the set pressure, the hydraulic shock absorber and a relief valve for communicating the inside the cap valve chamber and the damper outer gas chamber.