JP2010014196A - Single cylinder-type hydraulic shock absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single cylinder-type hydraulic shock absorber which is capable of preventing hydraulic fluid from leaking to the outside of a cylinder. <P>SOLUTION: The single cylinder-type hydraulic shock absorber comprises: a cylinder; a free piston 2 which is slidably inserted into the cylinder 1 to divide the interior of the cylinder 1 into an oil room L and a gas room G; a piston 3 which is slidably inserted into the cylinder 1 to divide the oil chamber L into two operation rooms R1, R2; and a rod 4 which is movably inserted into the cylinder 1 to be coupled to the piston 3. A communication means which makes communication between the oil room L and the gas room G when the free piston 2 strokes with a number of strokes outside of the upper, lower or both limits of a normal stroke number range S. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an improvement of a single cylinder type hydraulic shock absorber.

  A conventional single cylinder type hydraulic shock absorber includes a cylinder, a free piston that is slidably inserted into the cylinder, and divides the cylinder into an oil chamber filled with hydraulic oil and a gas chamber filled with gas, and a cylinder A piston that is slidably inserted into the oil chamber to divide the oil chamber into two working chambers, and a rod that is slidably inserted into the cylinder and connected to the piston. The vibration is attenuated by being interposed between the two.

In this way, in the single cylinder type hydraulic shock absorber, a free piston is provided and a gas chamber is provided in the cylinder. This is because the rod moves into and out of the cylinder during expansion and contraction. This is because the hydraulic oil generally has poor compressibility, so that the volume change is compensated by the volume change of the gas chamber (see, for example, Patent Document 1).
JP-A-2005-321020

  The single cylinder type hydraulic shock absorber described above attenuates vibration by absorbing vibration energy and converting it into thermal energy, so that the temperature of the hydraulic oil sealed in the cylinder rises by repeatedly expanding and contracting. Become. Since the volume of hydraulic oil expands when the temperature rises, the pressure in the cylinder increases because the free piston is pushed down in proportion to the volume expansion to compress the gas chamber, but if the oil temperature becomes abnormally high, If the pressure inside the cylinder becomes too large and the pressure resistance of the seal member that seals the periphery of the rod is exceeded, hydraulic oil may leak out of the shock absorber.

  Further, when the hydraulic oil leaks out of the cylinder due to deterioration of the seal member over time, the conventional single cylinder type hydraulic shock absorber has no way to suppress the hydraulic oil leakage. .

  In addition, if the leakage of hydraulic oil to the outside of the cylinder is left unattended, there is a concern that it may affect the natural environment. Therefore, it is desired to suppress the hydraulic oil leakage.

  Therefore, the present invention was devised to improve the above-described points, and an object of the present invention is to provide a single cylinder type hydraulic shock absorber capable of suppressing leakage of hydraulic oil to the outside of the cylinder. It is to be.

  The problem-solving means of the present invention includes a cylinder, a free piston that is slidably inserted into the cylinder and that divides the cylinder into an oil chamber and a gas chamber, and a slidably inserted into the cylinder. In a single cylinder type hydraulic shock absorber having a piston partitioned into two working chambers and a rod that is movably inserted into the cylinder and connected to the piston, the free piston has an upper limit, a lower limit, or both of the normal stroke range. A communication means is provided for communicating the oil chamber and the gas chamber when the stroke is exceeded.

  According to the single cylinder type hydraulic shock absorber of the present invention, when the free piston strokes exceeding the upper limit or the lower limit of the normal stroke range or both of them, the gas chamber and the oil chamber are communicated. Leakage can be suppressed.

  Hereinafter, the present invention will be described based on an embodiment shown in the drawings. FIG. 1 is a longitudinal sectional view of a single cylinder type hydraulic shock absorber according to an embodiment of the present invention.

  As shown in FIG. 1, a single cylinder type hydraulic shock absorber D according to an embodiment is slidably inserted into a cylinder 1 and divided into an oil chamber L and a gas chamber G. A free piston 2 that is slidably inserted into the cylinder 1 to divide the oil chamber L into two working chambers R1 and R2, and a slidably inserted into the cylinder 1 that is coupled to the piston 3. Rod 4 and communication means for communicating the oil chamber L and the gas chamber G when the free piston 2 strokes beyond the upper and lower limits of the normal stroke range.

  The working chambers R1 and R2 are filled with working oil, and the gas chamber G is filled with an inert gas such as nitrogen at a predetermined pressure.

  The cylinder 1 is closed at the lower end in FIG. 1 by a cap 7 and at the upper end in FIG. 1 by an annular rod guide 5. A free piston 2 is slidably inserted into the cylinder 1, and the inside of the cylinder 1 is divided into a gas chamber G and an oil chamber L. The free piston 2 is in sliding contact with the inner periphery of the cylinder 1 on the outer periphery. A seal ring 2a is provided to tightly seal the gas chamber G and the oil chamber L, thereby disconnecting them.

  The rod 4 is pivotally supported by an annular rod guide 5 that is provided at the upper end of the cylinder 1 and seals the inside of the cylinder 1, and protrudes out of the cylinder 1. The single cylinder type hydraulic shock absorber D can be interposed, for example, between a vehicle body and an axle in a vehicle via a mounting portion (not shown) provided. A seal member 8 for sealing the outer periphery of the rod 4 is provided above the rod guide 5, and the space between the cylinder 1 and the rod 4 is sealed by the seal member 8, and the cylinder 1 is sealed. Maintained.

  The piston 3 is provided with a passage communicating the pressure chamber R1 and the pressure chamber R2, and a damping force generating element 6b is provided in the middle of the passage 6a. The damping force generation element 6b may be any element that gives resistance to the flow of liquid when the liquid passes through the passage 6a and causes a predetermined pressure loss. Specifically, for example, an attenuation such as an orifice or a leaf valve is used. A valve can be employed. In the illustrated embodiment, only one passage 6a is provided. However, a plurality of passages 6a may be provided, and only the liquid flow from the working chamber R1 toward the working chamber R2 is allowed. A passage for passage and a one-way passage for allowing only the flow of liquid from the working chamber R2 to the working chamber R1 may be provided in parallel.

  In the single cylinder type hydraulic shock absorber D, when the piston 3 moves in the vertical direction in FIG. 1 with respect to the cylinder 1, the working chamber R 1 (R 2) whose volume decreases as the piston 3 moves. A resistance is given to the flow of the liquid that moves through the passage 6a to the working chamber R2 (R1) whose volume increases, causing pressure loss, and holding the differential pressure between the working chamber R1 and the working chamber R2 to exert a damping force. Thus, the volume change in the cylinder 1 due to the rod 4 entering and exiting the cylinder 1 is compensated for by the change in the volume of the gas chamber G as the free piston 2 moves in the cylinder 1. ing.

  In this way, the free piston 2 strokes in the cylinder 1 so that the pressure in the gas chamber G and the pressure in the oil chamber L are balanced when the piston 3 strokes in the vertical direction in FIG. However, when the pressure in the cylinder 1 is used within the pressure range that should be allowed by design, the free piston 2 is in a range where the stroke is made in the cylinder 1, that is, in a state where the single cylinder type hydraulic shock absorber is normal. In the normal stroke range S that strokes in the cylinder 1, the free piston 2 is in sliding contact with the inner periphery of the cylinder 1 to prevent communication between the gas chamber G and the oil chamber L.

  On the other hand, when the free piston 2 moves up and down beyond the upper limit and lower limit of the normal stroke range S described above, the cylinder 1 has an inner diameter so that the gas chamber G and the oil chamber L can communicate with each other. Expanded diameter portions 1a and 1b formed by expanding the diameter in the axial width longer than the axial length of the free piston 2 are provided. That is, in this embodiment, the communication means is configured to include the enlarged diameter portions 1 a and 1 b formed in the cylinder 1.

  That is, when the free piston 2 is displaced upward in FIG. 1 and the lower end of the seal ring 2a exceeds the lower end of the enlarged diameter portion 1a, a gap formed between the outer periphery of the free piston 2 and the enlarged diameter portion 1a. The gas chamber G and the oil chamber L pass through, and the gas in the gas chamber G flows into the oil chamber L. On the contrary, hydraulic oil heavier than the gas moves from the oil chamber L into the gas chamber G. Yes. When the free piston 2 is displaced downward in FIG. 1 and the upper end of the seal ring 2a exceeds the upper end of the enlarged diameter portion 1a downward, a gap formed between the outer periphery of the free piston 2 and the enlarged diameter portion 1a. The gas chamber G and the oil chamber L pass through, and the gas in the gas chamber G flows into the oil chamber L. On the contrary, hydraulic oil heavier than the gas moves from the oil chamber L into the gas chamber G. Yes.

  In this embodiment, since the communication between the gas chamber G and the oil chamber L is cut off by the seal ring 2a provided on the outer periphery of the free piston 2, the normal stroke range S described above is based on the seal ring 2a. When the seal ring 2a is determined and faces the enlarged diameter portions 1a and 1b, the gas chamber G and the oil chamber L are communicated with each other.

  Accordingly, in this single cylinder type hydraulic shock absorber D, when the expansion and contraction is repeated and the temperature of the hydraulic oil becomes abnormally high, the volume of the gas chamber G decreases due to the pressure increase in the cylinder 1. The free piston 2 strokes beyond the lower limit of the normal stroke range S, and the gas chamber G and the oil chamber L communicate with each other, so that a gas that is lighter than the hydraulic oil accumulates upward in FIG. Even if there is a gap between the rod 4 and the seal member 8, only the gas leaks, and leakage of hydraulic oil to the outside of the cylinder 1 can be prevented.

  Further, when hydraulic oil leaks due to aging deterioration of the seal member 8 or the like, the hydraulic oil amount decreases in the cylinder 1, so that the free piston 2 strokes beyond the upper limit of the normal stroke range S. Since the gas chamber G and the oil chamber L communicate with each other, it is assumed that a gas lighter than the hydraulic oil is accumulated upward in FIG. 1 of the cylinder 1 so that a gap is formed between the rod 4 and the seal member 8. Also, only the gas leaks, and the continuation of leakage of hydraulic oil to the outside of the cylinder 1 can be stopped. Therefore, according to the single cylinder type hydraulic shock absorber D, the leakage of the hydraulic oil to the outside of the cylinder 1 can be suppressed, so that the influence on the natural environment can be reduced.

  As described above, since the communication between the gas chamber G and the oil chamber L is cut off by the seal ring 2a, the axial lengths of the enlarged diameter portions 1a and 1b are longer than the axial length of the seal ring 2a. However, as described above, by setting the axial length of the enlarged diameter portions 1a and 1b to be longer than the axial length of the free piston 2, the communication between the gas chamber G and the oil chamber L can be improved. At this time, the gas can be quickly moved to the oil chamber L, and the leakage of the hydraulic oil to the outside of the cylinder 1 can be quickly suppressed.

  Further, in this way, the communication means is to provide the enlarged diameter portions 1 a and 1 b in the cylinder 1, and the inner diameters of the enlarged diameter portions 1 a and 1 b are set larger than the outer diameter of the free piston 2. Even if welding distortion occurs by welding the bracket B that supports the sensor, the brake hose and the like to the enlarged diameter portions 1a and 1b, the normal stroke of the free piston 2 is not hindered. In other words, since the bracket B can be directly welded to the side of the cylinder 1 of the single cylinder type hydraulic shock absorber D, it is necessary to set the bracket B to be long and weld it to the end of the cylinder 1. Thus, the bracket B can be reduced in size and the bending strength of the bracket B can be easily secured, and since the outer periphery of the cylinder 1 is not covered with the bracket B over a wide area, the heat dissipation can be improved.

  Furthermore, since heat dissipation can be improved, the fall of the damping force exerted by the single cylinder type hydraulic shock absorber due to the temperature rise can be suppressed, and the riding comfort in the vehicle can be improved.

  In addition, the single cylinder type hydraulic shock absorber D according to the present invention is lighter than the conventional single cylinder type hydraulic shock absorber, which can use only a long bracket because of its structure. Since it can be reduced in size and can be firmly welded to the outer periphery of the cylinder 1, there is an advantage that fatigue of the bracket B to which vibration is constantly input during traveling of the vehicle can be suppressed. In addition, by reducing the size of the bracket B, the moment load acting on the bracket B can be reduced when the sensor or the brake hose is assembled into the hole of the bracket B by screwing or the like.

  Furthermore, since the light and small bracket B can be used, it is possible to prevent the bracket B from exhibiting chatter vibration when vibration is input while the vehicle is running. Deterioration due to vibration of a certain sensor or brake hose is suppressed, and the chance of interference with other members of the brake hose can be reduced.

  In the above description, the enlarged diameter portions 1a and 1b are provided above and below the normal stroke range S of the free piston 2. However, in order to prevent only hydraulic oil leakage due to abnormally high temperature of the hydraulic oil, the lower expansion portion is prevented. Only the diameter portion 1b may be provided, and only the upper diameter-enlarged portion 1a may be provided in order to suppress only hydraulic fluid leakage when the seal member 8 is deteriorated.

  Further, since the communicating means are the enlarged diameter portions 1a and 1b provided by enlarging a part of the cylinder 1, the processing is easy. However, when the free piston 2 deviates from the normal stroke range, the free piston 2 is bypassed. For example, a groove longer than the axial length of the seal ring 2a is formed along the axial direction on the inner circumference of the cylinder 1 so long as the gas chamber G and the oil chamber L communicate with each other. The chamber L may be communicated, or a passage that opens into the cylinder 1 may be provided outside the cylinder 1 so that the gas chamber G and the oil chamber L communicate with each other.

  This is the end of the description of the embodiment of the present invention, but the scope of the present invention is of course not limited to the details shown or described.

It is a longitudinal cross-sectional view of the single cylinder type hydraulic shock absorber in one embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder 1a, 1b Expanding part 2 Free piston 2a Seal ring 3 Piston 4 Rod 5 Rod guide 6a Passage 6b Damping force generating element 7 Cap 8 Seal member B Bracket D Single cylinder type hydraulic shock absorber G Gas chamber L Oil chamber R1 , R2 Working chamber S Normal stroke range of free piston

Claims (3)

A cylinder, a free piston that is slidably inserted into the cylinder and partitions the cylinder into an oil chamber and a gas chamber, and a piston that is slidably inserted into the cylinder and partitions the oil chamber into two working chambers In a single cylinder type hydraulic shock absorber having a rod that is movably inserted into the cylinder and connected to the piston, the oil chamber and the gas when the free piston strokes beyond the upper limit or lower limit of the normal stroke range or both A single-cylinder hydraulic shock absorber provided with communication means for communicating with a chamber. The communication means includes an enlarged diameter portion formed by enlarging the inner diameter of the cylinder above and / or below the normal stroke range of the free piston, and a gap is provided between the outer circumference of the free piston and the inner circumference of the enlarged diameter portion. The single cylinder type hydraulic shock absorber according to claim 1, wherein the oil chamber and the gas chamber are made to communicate with each other. The single cylinder type hydraulic shock absorber according to claim 2, wherein a bracket for supporting a sensor and a brake hose is welded to an enlarged diameter portion formed in the cylinder.

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