JP2682620B2 - Hydraulic shock absorber - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement of a hydraulic shock absorber used for a front fork or the like of a motorcycle. (Prior Art) As a front fork of a two-wheeled vehicle, for example, a hydraulic shock absorber as shown in FIG. 3 is known (Kaikai Sho 53-88692).
issue). A seat pipe 3 is vertically installed at the center of the outer tube 1, and a piston rod 4 is vertically installed at the center of an inner tube 2 slidably inserted inside the outer tube 1.
Is a shock absorber configured so that the piston 5 formed at the tip of the piston rod 4 slides inside the seat pipe 3 by inserting the sheet pipe 3 into the seat pipe 3. Oil chambers A and B are formed above and below the piston 5 inside the seat pipe 3, and an oil chamber C is formed between the outer tube 1 and the seat pipe 3, and the inside thereof is filled with hydraulic oil. An oil reservoir chamber D communicating with the oil chamber C is provided inside the inner tube 2, and air is enclosed above the oil surface. The oil chambers A and B communicate with each other through an oil hole (not shown) that extends vertically through the piston 5, and the oil chambers B and C communicate with each other through an orifice 20 formed in the seat pipe 3. Further, the outer tube 1 and the inner tube 2 are urged in the separating direction by a suspension spring 8 which passes through the inside of the oil reservoir D and abuts both ends of the upper end of the inner tube 2 and the upper end of the seat pipe 3. It During operation of the pressure side of the shock absorber, as the inner tube 2 and the piston 5 enter the outer tube 1 and the seat pipe 3, respectively, the working oil in the oil chamber B that shrinks expands through the oil hole of the piston 5. While flowing into the chamber A, the working oil corresponding to the intrusion volume of the piston rod 4 flows out from the orifice 20 into the oil chamber C. Then, the outflowing hydraulic oil and the hydraulic oil equivalent to the volume of the inner tube 2 entering the outer tube 1 flow into the oil reservoir chamber D from the oil chamber C, and the enclosed air is compressed by the rising oil surface. At this time, the orifice 20 generates a damping force according to the flow rate of the hydraulic oil flowing out, and the compressed air in the oil reservoir chamber D repels the pressure side operation of the shock absorber together with the suspension spring 8. On the other hand, when the shock absorber shifts to the expansion side operation, the hydraulic oil in the oil chamber A flows into the oil chamber B, and
The hydraulic oil that has flowed into the oil reservoir chamber D flows back to the oil chambers C and B,
The oil level in the oil sump D falls. (Problems to be Solved by the Invention) By the way, when the shock absorber expands or contracts greatly or operates at high speed, the amount of oil in the oil reservoir chamber D fluctuates drastically, and the rapidly increased hydraulic oil blows up into the enclosed air, Air may be entrained in the hydraulic oil that sharply decreases, and the expansion and contraction of the suspension pulling 8 may disturb the oil surface, so that the oil reservoir chamber D causes so-called aeration in which air is mixed with the hydraulic oil. It was a condition that was easy to cause. When the bubbles mixed in the hydraulic oil reach the oil chambers A and B in this manner, when the oil chambers A and B are contracted, the bubbles are compressed to slow down the pressure rise and the flow rate of the orifice 20 is reduced. Therefore, the generated damping force also becomes small. Therefore, this shock absorber may not be able to sufficiently cope with violent operation. SUMMARY OF THE INVENTION The present invention provides a hydraulic shock absorber having a structure in which the sealed air is not mixed with the hydraulic oil in order to solve the above problems in the hydraulic shock absorber in which air that absorbs oil amount fluctuations is enclosed in an inner tube. To aim. (Means for Achieving the Object) According to the present invention, an inner tube is slidably inserted inside an outer tube, and a seat pipe vertically installed at one central portion of these tubes is installed vertically on the other tube. The piston rod is inserted slidably, and the piston rod side oil chamber A on the piston rod side and the seat pipe side oil on the seat pipe side are vertically arranged in the seat pipe defined by the piston formed at the tip of the piston rod. A chamber B is formed, a seat pipe outer oil chamber C is formed outside the seat pipe, and a tube oil reservoir chamber D communicating with the seat pipe outer oil chamber C is provided inside the tube connecting the piston rod. In a hydraulic shock absorber in which a suspension spring for urging the tube and the inner tube in the separating direction is arranged in the oil reservoir chamber D in the tube, The ton rod is formed in a hollow shape, and a portion projecting to the outside of the seat pipe at the time of maximum compression is formed to have a larger diameter than a portion located in the seat pipe, and an oil reservoir chamber E in a piston rod in which air is sealed is provided therein. The piston rod side oil chamber A, the seat pipe side oil chamber B, and the piston rod inside oil reservoir chamber E constitute a working oil distribution system defined by the seat pipe outside oil chamber C and the tube inside oil reservoir chamber D. In addition, a damping force generating means is provided in the middle of this distribution system. (Operation) The hydraulic oil equivalent to the volume of the piston rod penetrating into the seat pipe during pressure side operation is contained in the oil reservoir chamber E, and the hydraulic oil equivalent to the volume of the inner tube penetrating into the outer tube is contained in the oil reservoir chamber D. It Further, at this time, since the lower portion of the piston rod entering the seat pipe is formed to have a smaller diameter than the upper portion, the oil amount in the oil reservoir chamber E can be changed little, while the upper portion of the piston rod in which the oil reservoir chamber E is installed is Since it has a large diameter, the fluctuation of the oil level in the oil reservoir E is small, and the suspension spring that disturbs the oil level due to the expansion and contraction operation also has the oil reservoir E.
Since it does not exist inside, the oil level in the oil reservoir E changes stably. Therefore, even if the amount of oil in the oil reservoir chamber E changes drastically as the shock absorber expands and contracts, air does not mix with the hydraulic fluid, and the hydraulic fluid that does not contain air bubbles allows the damping force generating means to generate a stable damping force. Generate. (Embodiment) FIGS. 1 and 2 show an embodiment of the present invention. Reference numeral 1 is an outer tube, 2 is an inner tube which is slidably inserted into the inner tube from above, and a hollow piston rod 4 vertically installed in the inner tube 2 is attached to a seat pipe 3 standing from the bottom of the outer tube 1. A piston 5 which is slidably inserted and formed around the tip of the piston 5 is slidably contacted with the inside of the seat pipe 3. The interior of the seat pipe 3 is defined by a piston 5 into an upper oil chamber A and a lower oil chamber B,
The piston 5 is provided with a valve device 5A as a damping force generating means for giving a predetermined resistance to the oil passage from the oil chambers A to B, and a valve device 5B giving a predetermined resistance to the oil passage from the oil chambers B to A. To be dressed.
An oil passage 6 that penetrates the piston 5 and opens into the oil chamber B is formed inside the piston rod 4. Further, an oil passage 6 is provided inside the base end 4A in which the diameter of the piston rod 4 is enlarged.
An oil reservoir chamber E is provided which communicates with the oil chamber B via. A bag-shaped bellows 7 having air sealed inside is provided as a partition member on the upper part of the oil reservoir E. The bellows 7 is made of an elastic material that can freely expand and contract, and expands and contracts according to increase and decrease in the amount of oil stored outside to change the internal air volume. An oil chamber C is provided between the outer tube 1 and the seat pipe 3.
Is formed. The oil chamber C communicates with an oil reservoir chamber D formed between the inner tube 2 and the piston rod 4 through an opening at the lower end of the inner tube 2. Air is filled above the oil surface of the oil reservoir D, and the inner tube 2 is provided inside.
A suspension spring 8 is provided which abuts both ends of the base end portion and the upper end portion of the seat pipe 3 and biases the outer tube 1 and the inner tube 2 in the extending direction. The oil chamber C and the oil reservoir chamber D are isolated from the oil chambers A and B and the oil reservoir chamber E by the seat pipe 3 and the piston rod 4, and the flow of the working oil is cut off. Next, the operation will be described. In the pressure side operation of the shock absorber, the inner tube 2 enters the outer tube 1 and the piston rod 4 enters the seat pipe 3, and the piston 5 slides downward inside the seat pipe 3. As a result, the working oil in the contracting oil chamber B flows into the expanding oil chamber A through the valve device 5B while generating a compression-side damping force, while the working oil corresponding to the intrusion volume of the piston rod 4 is discharged from the oil passage 6. It flows into the oil reservoir chamber E and compresses the enclosed air inside through the bellows 7. On the other hand, outside the piston rod 4, the suspension spring 8 bends, and the working oil in the oil chamber C flows into the oil reservoir chamber D from the opening at the lower end of the inner tube 2 to raise the oil level and remove the enclosed air inside. Compress. In this way, the suspension spring 8 and the repulsive force of the compressed air in the oil reservoirs D and E repel the pressure side operation of the shock absorber, and the oil flow resistance from the oil chamber B to the oil reservoir chamber A damps the pressure side operation. To do. Also, when the shock absorber turns to the extension side operation, the oil chamber B expands.
The hydraulic oil in the oil chamber E flows into the oil passage 6 without resistance from the oil passage 6, and the bellows 7 in the oil chamber E swells. It flows into the oil chamber B while being generated. Further, the hydraulic oil in the oil storage chamber D flows into the expanding oil chamber C, and the oil level in the oil storage chamber D also drops. In the above-described expansion and contraction operation, the hydraulic oil in the oil reservoir chamber E is always separated from the air by the bellows 7 which expands and contracts according to the amount of oil, so that the oil reservoir chamber is irrespective of the sliding speed and stroke size of the shock absorber. There is no risk of air entering the hydraulic oil inside E. Therefore, the working oil flowing between the loose oil chambers A and B and the oil reservoir chamber E does not contain bubbles, and both valve devices 5A and 5B generate a stable damping force. In addition, even if enclosed air is mixed with the working oil in the oil reservoir D as the suspension spring 8 expands and contracts,
Since this hydraulic oil does not flow into the seat pipe 3 and the piston rod 4, it does not affect the generated damping force. FIG. 2 shows a free piston 9 provided in the oil reservoir E as a partition member for separating hydraulic oil and air. In this case, the free piston moves up and down as the amount of oil in the oil reservoir E increases and decreases. Sliding causes the same effect as above. In addition,
Here, a valve device 10 is interposed between the oil passage 6 and the oil reservoir E as a compression side damping force generating means. (Effects of the Invention) As described above, according to the present invention, the piston rod is formed hollow and the upper portion thereof is formed to have a large diameter. And B and the oil sump chamber E constitute a hydraulic oil distribution system defined by the oil chamber C and the oil sump chamber D, and a damping force generating means is provided in the middle of the distribution system. The change in the amount of oil in the oil reservoir E inside the piston rod at this time is only the volume of the lower part of the small-diameter piston rod that enters the seat pipe, and the oil amount in the oil reservoir E provided above the large-diameter piston rod is small. Since the fluctuation of the surface can be suppressed to a small level and the suspension spring is arranged outside the piston rod, the oil surface of the oil reservoir chamber E inside the piston rod is not disturbed by the expansion and contraction of the suspension spring. So the oil reservoir inside this piston rod In E, even if the shock absorber expands and contracts violently, air is unlikely to be mixed into the hydraulic fluid, and the damping force generating means interposed in the hydraulic fluid distribution system always provides stable damping due to the circulation of the hydraulic fluid containing no bubbles. Power is generated. Therefore, the shock absorbing function is not impaired even in a heavy operation, and the reliability of the shock absorber is improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a hydraulic shock absorber showing an embodiment of the present invention, FIG. 2 is a sectional view of a hydraulic shock absorber showing another embodiment, and FIG. 3 is a conventional example. It is sectional drawing of a hydraulic shock absorber. 1 ... Outer tube, 2 ... Inner tube, 3 ... Seat pipe, 4 ... Piston rod, 5 ... Piston, 5A, 5B ...
Valve device, 7 ... Bellows, A, B, C ... Oil chamber, D, E ... Oil reservoir chamber.

Claims (1)

(57) [Claims] The inner tube is slidably inserted into the inner side of the outer tube, and the piston rod vertically inserted into the other tube is slidably inserted into the inner side of the seat pipe vertically installed at the center of one of these tubes. The piston rod side oil chamber A on the piston rod side is vertically arranged in the seat pipe defined by the piston formed at the tip of the rod.
And a seat pipe side oil chamber B on the seat pipe side, a seat pipe outer side oil chamber C is formed outside the seat pipe, and a tube communicating with the seat pipe outer side oil chamber C inside the tube connecting the piston rod. Inner oil reservoir D
In the hydraulic shock absorber in which a suspension spring that urges the outer tube and the inner tube in the separating direction is provided in the oil reservoir chamber D in the tube, the piston rod is formed hollow, and the seat pipe outside The piston rod-side oil chamber A and the seat pipe-side oil chamber B are provided with a piston rod-side oil reservoir chamber E in which a portion protruding inward is formed to have a larger diameter than a portion located in the seat pipe and air is enclosed therein. And the piston rod oil reservoir chamber E constitute a working oil distribution system defined by the seat pipe outer oil chamber C and the tube oil reservoir chamber D, and a damping force generating means is provided in the middle of the distribution system. A hydraulic shock absorber characterized by being provided.