JP2682618B2 - 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. 2 is known (actual exploitation 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 biased in the separating direction by a suspension spring 13 which passes through the inside of the oil reservoir D and abuts both ends 2 of the upper end of the inner tube 2 and the upper end of the seat pipe 3. To be done. 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 corresponding to the flow rate of the operating oil flowing out, and the compressed air in the oil reservoir chamber D repels the suspension spring 13 against the pressure side operation of the shock absorber. 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, The air may be entrapped in the hydraulic oil that sharply decreases, and the expansion and contraction of the suspension pulling 13 may disturb the oil surface. Therefore, 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. The present invention provides a hydraulic shock absorber having a structure in which the sealed air is unlikely to be mixed into the hydraulic oil in order to solve the above problems in the hydraulic shock absorber in which air that absorbs oil amount fluctuations is sealed in the inner tube. With the goal. (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 slidably inserted, and the piston formed at the tip of the piston rod defines the interior of the seat pipe into a piston rod side oil chamber A on the piston rod side and a seat pipe side oil chamber B on the seat pipe side. Then, the piston rod side oil chamber A, the seat pipe side oil chamber B, and the seat pipe outer side oil chamber C outside the seat pipe are filled with the working oil, and the working oil is circulated between these oil chambers. An oil reservoir chamber D inside a tube, in which air for allowing excess hydraulic oil to flow in due to a change in the capacity of the oil chamber, is provided inside the tube that connects the piston rod, In a hydraulic shock absorber in which a suspension spring for urging a tube and an inner tube in a separating direction is arranged in the oil reservoir chamber D in the tube, a piston rod is formed in a hollow shape and protrudes to the outside of the seat pipe at the time of maximum compression. A portion having a larger diameter than a portion located in the seat pipe and having an air filled piston rod oil reservoir chamber E therein is provided, and the piston rod side oil chamber A, the seat pipe side oil chamber B and this piston are provided. The oil storage chamber in the rod E constitutes a hydraulic fluid distribution system defined by the oil chamber C in the outside of the seat pipe and the oil storage chamber D in the tube, and a damping force adjusting means is provided in the middle of the distribution system. A partition wall member is provided between the air in the internal oil reservoir chamber E and the working oil, the partition wall member moving in accordance with the increasing / decreasing amount of oil, and a tube end portion for connecting the piston rod to the inside of the piston rod. Was suspended from the guide, comprising a damping force generating means in this guide, the damping force generating means is adjustable in the tube ends. (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 surface of the oil reservoir E changes stably, and aeration is unlikely to occur. Further, the damping force generating means interposed in the hydraulic oil flow system connected to the oil reservoir chamber E inside the piston rod is adjusted to an appropriate value from outside the hydraulic shock absorber. Therefore, an appropriate damping force can be stably obtained by this damping force generating means. (Example) FIG. 1 shows an example 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 on the extension side for allowing hydraulic oil to flow from the oil chambers A to B under a predetermined resistance and allowing oil passage in the opposite direction without resistance. An oil passage 6 that penetrates the piston 5 and opens into the oil chamber B is formed inside the piston rod 4. Further, inside the base end portion 4A where the diameter of the piston rod 4 is enlarged, an oil reservoir chamber E is provided which communicates with a lower oil passage 6 via valve devices 7 and 8 which are compression side damping force generating means. The valve device 7 allows the hydraulic oil in the oil chamber B to flow into the oil reservoir chamber E through the oil passage 6 under a certain pressure or more, and opens in the opposite direction without resistance to operate the hydraulic oil in the oil reservoir chamber E. It is configured to return to the chamber B.
Further, the valve device 8 includes a needle valve 8A that is axially displaced by an external operation and a valve seat 8B that is provided opposite to the needle valve 8A.
The needle valve 8A is housed inside a guide 10 that extends vertically through the oil reservoir E, and is operated by a dial 11 attached to the upper end of the inner tube 2. The valve device 8 is provided in parallel with the valve device 7, and generates resistance to the oil passage between the oil reservoir chamber E and the oil passage 6 according to the displacement position of the needle valve 8A. Air is enclosed above the oil surface of the oil reservoir E, and a float 12 is provided between the oil surface and the air. 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 13 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 5A without any resistance, while the working oil corresponding to the intrusion volume of the piston rod 4 passes through the valve device 8 from the oil passage 6. Flow into the oil sump chamber E and float 12
The enclosed air inside is compressed via. Then, the pressure side damping force is generated by the resistance when the inflowing hydraulic oil passes through the valve device 8. When the pressure difference between the oil passage 6 and the oil reservoir E becomes larger than a certain value, the valve device 7 is opened to prevent the excessive damping force by assisting the inflow of hydraulic oil. On the other hand, outside the piston rod 4, the suspension spring 13 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 13 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 E 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 reservoir E flows into the oil reservoir 6 through the valve device 7 without resistance, and the oil level in the oil reservoir E lowers. At the same time, the hydraulic oil in the oil chamber A that contracts passes through the valve device 5A. And flows into the oil chamber B while generating the extension side damping force. 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 oil amount fluctuation in the oil reservoir E is equivalent to only the volume of the piston rod 4 entering the seat pipe 3, and the oil amount fluctuation corresponding to the volume of the inner tube 2 entering the outer tube 1 is the oil amount. It is absorbed in the storage chamber D.
Therefore, the oil amount in the oil reservoir E does not fluctuate much, and the oil reservoir E
Since the oil surface inside is separated from the air by the float 12, the oil surface inside the oil reservoir E is vertically displaced while maintaining stability regardless of the sliding speed of the shock absorber and the stroke size. Further, since the suspension spring 13 that expands and contracts with the operation of the shock absorber is disposed in the oil sump chamber D, the oil surface of the oil sump chamber E is not disturbed by this expansion and contraction operation. Therefore, there is no possibility that the air filled in the oil reservoir E will be mixed with the hydraulic oil,
Since the working oil flowing between the loose oil chambers A and B and the oil reservoir chamber E does not contain bubbles, stable damping force can be obtained on both the compression side and the expansion side. Even if the enclosed air is mixed with the working oil in the oil reservoir D as the suspension spring 13 expands and contracts, this working oil does not flow into the seat pipe 3 and the piston rod 4, so that the generated damping force Has no effect on (Effects of the Invention) As described above, according to the present invention, the piston rod is formed to be hollow, the upper portion thereof is formed to have a large diameter, and another oil reservoir chamber E in which air is enclosed is provided in the piston rod. And B and the oil reservoir chamber E constitute a hydraulic oil distribution system defined by the oil chamber C and the oil reservoir chamber D, and a damping force adjusting means is provided in the middle of the distribution system so that the oil reservoir chamber E Is provided with a partition wall member that moves according to the amount of oil that increases or decreases between the air and the hydraulic oil, and a guide is vertically provided inside the piston rod from the end of the tube that connects the piston rod, and a damping force is applied to this guide. Since the damping force generating means can be adjusted at the tube end portion, a change in the amount of oil in the oil reservoir chamber E in the piston rod when the shock absorber is activated changes the amount of oil in the piston pipe. In addition to the volume of The oil reservoir chamber E provided at the upper part of the piston has a large diameter and can keep the fluctuation of the oil surface small, and since the suspension spring is arranged outside the piston rod, the oil reservoir inside the piston rod is The oil level in the chamber is not disturbed by the expansion and contraction of the suspension spring, and the damping force generating means of the hydraulic oil flow system in the piston rod can be adjusted from the outside, so an appropriate damping force can be selected. it can. Therefore, in the oil reservoir E in the piston rod, air is unlikely to be mixed into the working oil, and the damping force generating means interposed in the distribution system of the working oil always stabilizes an appropriate damping force against impact. Occur. 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, and FIG. 2 is a sectional view of a hydraulic shock absorber showing a conventional example. 1 ... Outer tube, 2 ... Inner tube, 3 ... Sheet pipe, 4 ... Piston rod, 5 ... Piston, 5A, 7, 8 ...
Valve device, A, B, C ... Oil chamber, D, E ... Oil reservoir chamber.

Claims (1)

(57) [Claims] The inner tube is slidably inserted inside the outer tube, and the piston rod vertically installed on the other tube is slidably inserted inside the seat pipe vertically installed at the center of one of these tubes. A piston formed at the tip of the rod defines the inside of the seat pipe into a piston rod side oil chamber A on the piston rod side and a seat pipe side oil chamber B on the seat pipe side. The piston rod side oil chamber A and the seat pipe side The oil chamber B and the seat pipe outer oil chamber C on the outer side of the seat pipe are filled with hydraulic oil, the hydraulic oil is circulated between these oil chambers, and the surplus hydraulic oil accompanying the capacity change of these oil chambers is caused to flow in. An oil reservoir chamber D containing air is provided inside the tube that connects the piston rod, and the outer tube and inner tube are attached in the separating direction. In the hydraulic shock absorber in which the suspension spring is disposed in the oil reservoir chamber D in the tube, the piston rod is formed to be hollow, and the portion projecting to the outside of the seat pipe at the time of the maximum compression is located more than the portion located in the seat pipe. Is also formed with a large diameter, and an oil reservoir chamber E in the piston rod in which air is enclosed is provided in the piston rod side oil chamber A.
The seat pipe side oil chamber B and the piston rod inner oil reservoir chamber E constitute a working oil distribution system defined by the seat pipe outer oil chamber C and the tube inner oil reservoir chamber D, and in the middle of this distribution system. Is provided with a damping force adjusting means, and is provided with a partition member that moves between the air in the piston rod oil reservoir chamber E and the working oil in accordance with the amount of increasing / decreasing oil, and the piston rod is connected to the inside of the piston rod. A hydraulic shock absorber characterized in that a guide is hung from the end of the tube, and the guide is provided with a damping force generating means, and the damping force generating means is adjustable at the tube end.