JP4815482B2 - Hydraulic shock absorber - Google Patents

Description

The present invention relates to a hydraulic shock absorber that damps vibrations.

The hydraulic shock absorber is used, for example, to attenuate vibrations of a vehicle body in a road vehicle or the like. In the hydraulic shock absorber, a cylinder is partitioned by pistons into first and second fluid chambers. When vibration occurs in the vehicle body, fluid flows between the first and second fluid chambers in synchronization with the vibration. The vibration is attenuated by the resistance generated during the flow. In order to cause the fluid to flow between the first and second fluid chambers, it has been proposed to provide a through hole in the piston or to hollow out the piston rod in the axial direction (see, for example, Patent Document 1).
JP 2000-110881 A

  As in Patent Document 1, the fluid passages in which the fluid flows between the first and second fluid chambers are provided in the piston and the piston rod, respectively, because the damping force for damping the vibration is This is because a variable damping force hydraulic shock absorber that changes depending on the generation state is configured. Since the fluid passage provided in the piston can be formed by providing a through hole in the piston, it can be formed relatively easily. On the other hand, the fluid passage provided in the piston rod needs to be provided with a radial flow path extending from the outer peripheral surface toward the axial flow path while making the piston rod hollow to make an axial flow path. It becomes complicated and the manufacturing cost increases. Thus, as the fluid passage, two or more passages are required, and in addition to the fluid passage by the through hole provided in the piston, at least one more fluid passage is desired. In the fluid passage provided in the conventional piston rod, Since the production is complicated, an alternative fluid passage has been desired.

  Then, an object of this invention is to provide the hydraulic buffer which can manufacture a fluid channel | path easily to a piston rod.

In the present invention , a piston that is slidably fitted into a cylinder and divides the inside of the cylinder into first and second fluid chambers, and a piston that is joined to the piston and slidably penetrates the end wall of the cylinder. In the hydraulic shock absorber provided with a rod, the piston rod has a groove on the outer peripheral surface that penetrates the piston and extends from the first fluid chamber to the second fluid chamber. wherein the second fluid chamber that passes with each other through the groove. According to this, since the first fluid chamber and the second fluid chamber communicate with each other by the groove provided on the outer peripheral surface of the piston rod, the fluid flows between the first and second fluid chambers in the groove. It can function as a fluid passage. In principle, it is easy to manufacture a hydraulic shock absorber because a fluid passage can be constructed simply by adding a manufacturing process for forming a groove on the outer peripheral surface of the piston rod and without greatly changing other manufacturing processes. The manufacturing cost can be reduced.

In the present invention, the opening state adjusting means adjusts the area of the opening of the groove facing the first fluid chamber or the second fluid chamber according to the sliding state of the piston rod with respect to the cylinder. Ru equipped with. The opening of the groove facing the first fluid chamber or the second fluid chamber is considered to correspond to an opening of a fluid passage through which fluid flows between the first and second fluid chambers. Therefore, by adjusting (increasing or decreasing) the area of the opening, the flow rate of the fluid flowing through the fluid passage can be adjusted, and further, the damping force of the hydraulic shock absorber can be adjusted. Since the damping force of the hydraulic shock absorber can be adjusted by the sliding state of the piston rod with respect to the cylinder according to the vehicle behavior when the hydraulic shock absorber is mounted on the vehicle, the operability and ride comfort Can contribute to the improvement.

In the present invention, the opening state adjusting means is supported by the piston or the piston rod, and moving means that is arranged away from the cylinder and moves in the axial direction of the piston rod to adjust the area of the opening. Biasing means for biasing the moving means in the axial direction, and the moving means moves against the biasing force of the biasing means in accordance with the acceleration of the piston to adjust the area of the opening When the piston rod moves with acceleration, and the acceleration of the piston rod is less than or equal to a predetermined value, the moving means is urged by the urging means to cover the opening, and the acceleration of the piston rod is increased. When the predetermined value is exceeded, the moving means moves relative to the urging force of the urging means to open the opening . When the moving means functions as a mass and the piston rod moves with acceleration due to vibration, the moving means tries to stay at the previous position, and the biasing means expands and contracts according to the acceleration. As a result, the positional relationship between the moving means and the piston rod as well as the positional relationship with the opening is determined according to the amount of expansion and contraction, and the area of the opening can be adjusted.

  Further, in the present invention, a cover provided on the outer peripheral surface of the piston rod adjacent to the piston is provided, a through hole is provided in a part of the cover directly above the groove, and the moving means includes the It is preferable to move on the through hole. According to this, substantially the groove opening can be provided away from the piston. In accordance with this, the moving means can also be provided away from the piston. The moving means can move in the direction from the moving means in the axial direction of the piston rod to the piston, or in the direction in which the moving means moves away from the piston, without being obstructed by the piston. The damping force of the hydraulic shock absorber can be adjusted regardless of the direction of movement.

  Further, in the present invention, on the outer peripheral surface of the piston rod, there is a step portion separated axially inward from both ends of the groove, and the piston is disposed away from the end portion of the groove by the step portion. Preferably it is. The piston is positioned by the stepped portion, and the positioned piston does not cover both ends of the groove. Therefore, the groove can be exposed to the first fluid chamber and the second fluid chamber, and the first and second fluids can be exposed. A fluid passage communicating between the chambers can be reliably formed.

Moreover, in this invention, it is preferable to have a through-hole which penetrates the said piston and connects the said 1st fluid chamber and the said 2nd fluid chamber. Since the first fluid chamber and the second fluid chamber communicate with each other through the through hole, the through hole can function as a fluid passage through which the fluid flows between the first and second fluid chambers. The through-hole penetrating the piston can be easily produced at low cost. Thus, the hydraulic shock absorber can be provided with two fluid passages, a first fluid passage formed by a through-hole penetrating the piston and a second fluid passage formed by a groove provided on the outer peripheral surface of the piston rod. The damping force hydraulic shock absorber can be configured easily and at low cost.

  ADVANTAGE OF THE INVENTION According to this invention, the hydraulic shock absorber which can manufacture a fluid channel | path easily to a piston rod can be provided.

  FIG. 1 is a longitudinal sectional view of a hydraulic shock absorber 1 according to an embodiment of the present invention. The hydraulic shock absorber 1 has a so-called monotube type (de-carvone type) structure, but it goes without saying that the present invention can also be applied to a twin tube type structure. The hydraulic shock absorber 1 includes a cylindrical cylinder 2 filled with fluid such as oil or MRF (Magneto-Rheological Fluid), and a slidably fitted inside the cylinder 2 so that the cylinder 2 has a first fluid chamber. 4 and the piston 3 partitioned into the second fluid chamber 5, the piston rod 6 joined to the piston 3 and slidably penetrating the end wall of the cylinder 2, and the second fluid chamber 5 and the high-pressure gas chamber 10 are defined. And a free piston 11.

  In the cylinder 2, an eyepiece 2 a is provided at the end where the hole for inserting the piston rod 6 is not formed. For example, when the hydraulic shock absorber 1 is used for an automobile suspension, a bolt (not shown) is fitted into the eyepiece 2a, and the bolt is connected to a trailing arm that is a wheel side member. Further, an end (not shown) of the piston rod 6 is connected to a damper base (an upper part of the wheel house) which is a vehicle body side member.

  The piston rod 6 penetrates the piston 3. A groove 7 extending from the first fluid chamber 4 to the second fluid chamber 5 is provided on the outer peripheral surface of the piston rod 6. The first fluid chamber 4 and the second fluid chamber 5 communicate with each other through the groove 7, and details will be described later.

  The piston rod 6 is provided with opening state adjusting means 9. Although details will be described later, the opening state adjusting means 9 adjusts the area of the opening of the groove 7 facing the second fluid chamber 5 according to the sliding state of the piston rod 6 with respect to the cylinder 2. Further, the piston 3 is provided with a through hole 8 that allows the first fluid chamber 4 and the second fluid chamber 5 to communicate with each other.

  In the free piston 11, the high pressure gas chamber 10 is kept airtight by an O-ring. When the pressure difference between the second fluid chamber 5 and the high-pressure gas chamber 10 occurs, the free piston 11 slides in the cylinder 2 so as to eliminate the pressure difference.

  FIG. 2 shows a perspective cross-sectional view of the piston 3 and its surroundings. A plurality of grooves 7 are formed on the outer peripheral surface of the piston rod 6. Each of the plurality of grooves 7 is formed in parallel with the axial direction of the piston rod 6. Each of the plurality of grooves 7 is provided from the first fluid chamber 4 to the second fluid chamber 5. The length of the groove 7 is longer than the length of the piston 3, and an intermediate portion of the groove 7 is covered by the piston 3, but both ends of the groove 7 protrude from the piston 3, and one end thereof is disposed on the first fluid chamber 4 side. The other end is disposed in the second fluid chamber 5.

  Further, on the outer peripheral surface of the piston rod 6, a step portion 6 a is formed at a position away from both ends of the groove 7 inward in the axial direction. The diameter of the piston rod 6 is narrower on the piston 3 side than the opposite side, with the stepped portion 6a as a boundary. Since the height of the stepped portion 6a is shallower than the depth of the groove 7, the groove 7 is also formed in the narrowed piston rod 6.

  First, a washer 15, a disk valve (compression) 16, a piston 3, a disk valve (tension) 17, a cover 14, an urging means 13, a moving means 12, and an urging means 13 are attached to the thinned piston rod 6. They are fitted in this order, and finally, they are fixed by nuts 18 so as not to fall off the piston rod 6. The cover 14, the urging unit 13, the moving unit 12, and the urging unit 13 constitute the opening state adjusting unit 9. The urging means 13, the moving means 12, and the urging means 13 are fitted into the cylindrical portion of the cover 14 in this order.

  Since the step portion 6 a is separated from both ends of the groove 7, the piston 3 can be disposed away from both ends of the groove 7 by the step portion 6 a, and the opening of the groove 7 can be exposed to the first fluid chamber 4. it can. Further, since the length of the groove 7 is longer than that of the piston 3, the other end of the groove 7 can be exposed to the second fluid chamber 5 as an opening of the groove 7. The piston rod 6 penetrates the piston 3. A groove 7 formed on the outer peripheral surface of the piston rod 6 extends from the first fluid chamber 4 to the second fluid chamber 5 across the piston 3. The first fluid chamber 4 and the second fluid chamber 5 can be communicated with each other via a groove 7, and the groove 7 allows the fluid to flow between the first fluid chamber 4 and the second fluid chamber 5. It functions as two fluid passages. In general, it is easy to form a groove such as the groove 7 on the surface like the outer peripheral surface of the piston rod 6.

  The cover 14 constituting the opening state adjusting means 9 is provided adjacent to the piston 3 on the outer peripheral surface of the piston rod 6 and has a cylindrical portion and a flange portion. The cylindrical portion is fitted into the piston rod 6, the flange portion is joined to the cylindrical portion, and the disk valve (tension) 17 is pressed against the piston 3. A through-hole 14 a is provided in the cylindrical portion of the cover 14 at a position immediately above the groove 7 and away from the piston 3. The moving means 12 is supported by being urged by the urging means 13 so as to be movable on the through hole 14a. The moving means 12 moves in the axial direction of the piston rod 6 to adjust the area of the opening. The biasing means 13 is supported by the piston 3 or the piston rod 6 and biases the moving means 12 in the axial direction. As the biasing means 13, a coil spring can be used as shown in FIG. 2. However, the biasing means 13 is not limited to this, and may be another spring or an elastic body such as rubber.

  When the moving means 12 moves and the through hole 14a is exposed to the second fluid chamber 5, the groove 7 communicates with the second fluid chamber 5 through the through hole 14a. That is, the opening of the groove 7 with respect to the second fluid chamber 5 can be considered as the through hole 14a.

  And since the moving means 12 is supported by the biasing means 13, when the piston rod 6 vibrates (moves) in accordance with the sliding state of the piston rod 6 with respect to the cylinder 2 (the expansion / contraction acceleration of the hydraulic shock absorber 1), A so-called inertia force acts on the moving means 12 to stay there, and the positional relationship between the moving means 12 and the piston rod 6 as well as the through hole 14a varies. The reaction of the inertia force is the urging force by the urging means 13, but the moving means 12 is moved by this urging force, and the area of the opening is adjusted.

  The open / closed state of the opening (through hole 14a), more specifically, the area of the opening differs depending on the positional relationship of the moving means 12 with respect to the opening (through hole 14a), thereby changing the resistance of the fluid flow. Therefore, the damping force of the hydraulic shock absorber 1 can be adjusted.

  Since the through hole 14a is provided away from the piston 3, the moving means 12 arranged in accordance with this can also be provided away from the piston 3. The moving means 12 can move in the direction from the moving means 12 in the axial direction of the piston rod 6 toward the piston 3 and in the direction in which the moving means 12 moves away from the piston 3 without being prevented from moving by the piston 3. Therefore, the damping force of the hydraulic shock absorber 1 can be adjusted regardless of which direction the piston rod 6 moves due to vibration.

  The piston 3 is provided with a through hole 8 that allows the first fluid chamber 4 and the second fluid chamber 5 to communicate with each other. Since the first fluid chamber 4 and the second fluid chamber 5 communicate with each other through the through hole 8, the through hole 8 serves as a first fluid passage through which the fluid flows between the first fluid chamber 4 and the second fluid chamber 5. Can function. Since the through-hole 8 simply passes through the piston 3, it can be manufactured easily and at low cost. Thus, the hydraulic shock absorber 1 is provided with two fluid passages, a first fluid passage by the through hole 8 penetrating the piston 3 and a second fluid passage by the groove 7 provided on the outer peripheral surface of the piston rod 6. Therefore, the variable damping force hydraulic shock absorber can be configured easily and at low cost.

  The through hole 8 has a through hole 8 whose opening on the first fluid chamber 4 side is blocked by a disk valve (compression) 16 and a disk valve (tension) 17 on the second fluid chamber 5 side. There is a through-hole 8 whose opening is closed.

  3 (a) and 3 (b) show the flow of fluid when the piston rod 6 moves with low acceleration and a high damping force is generated in the hydraulic shock absorber 1 by arrows. When the acceleration of the piston rod 6 (the expansion / contraction acceleration of the hydraulic shock absorber 1) is equal to or less than a predetermined value (low acceleration), the moving means 12 is urged by the urging means 13 to completely open the through hole 14a (opening of the groove 7). The covered state is reached, and no fluid flows through the groove 7 (second fluid passage). The fluid passes from the second fluid chamber 5 through the through hole 8 (first fluid passage) not blocked by the disc valve (tension) 17 and pushes and bends the disc valve (compression) 16 while the first fluid chamber 4 Move to. Since the fluid passage through which the fluid can pass is only the first fluid passage, a high damping force is generated in the hydraulic shock absorber 1.

  4 (a) and 4 (b) show the flow of fluid when the piston rod 6 moves with high acceleration and a low damping force is generated in the hydraulic shock absorber 1 by arrows. When the acceleration of the piston rod 6 (the expansion and contraction acceleration of the hydraulic shock absorber 1) is a high acceleration exceeding a predetermined value, the moving means 12 moves relative to the urging force of the urging means 13 and the through hole 14a (groove 7). Open). Thereby, the fluid also flows in the groove 7 (second fluid passage). Since the fluid passage through which the fluid can pass is the first fluid passage and the second fluid passage, the damping force generated in the hydraulic shock absorber 1 is reduced. According to the above, the damping force can be adjusted according to the acceleration of the piston rod 6 (the expansion / contraction acceleration of the hydraulic shock absorber 1).

  FIG. 5A and FIG. 5B are cross-sectional views of the piston 3 and its surroundings of a hydraulic shock absorber 1 according to a modification of the embodiment of the present invention. FIG. 5A shows the flow of fluid when the piston rod 6 moves with low acceleration and a low damping force opposite to that of the embodiment is generated in the hydraulic shock absorber 1 with arrows. b) shows the flow of fluid when the piston rod 6 moves with high acceleration and a high damping force opposite to that of the embodiment is generated in the hydraulic shock absorber 1 by arrows. In the modified example, when the acceleration of the piston rod 6 (the expansion / contraction acceleration of the hydraulic shock absorber 1) is equal to or less than a predetermined value (low acceleration), the moving means 12 urges the urging means 13 as shown in FIG. As a result, the through hole 14a (opening of the groove 7) is opened, and the fluid also flows through the groove 7 (second fluid passage). Since the fluid passage through which the fluid can pass becomes the first fluid passage and the second fluid passage, the damping force generated in the hydraulic shock absorber 1 can be reduced. On the other hand, when the acceleration of the piston rod 6 (the expansion / contraction acceleration of the hydraulic shock absorber 1) is a high acceleration exceeding a predetermined value, the moving means 12 moves relative to the urging force of the urging means 13 and the through hole 14a ( Close the opening of the groove 7. This prevents fluid from flowing into the groove 7 (second fluid passage). Since the fluid passage through which the fluid can pass is only the first fluid passage, the damping force generated in the hydraulic shock absorber 1 increases. Also according to the modification, the damping force can be adjusted according to the acceleration of the piston rod 6 (the expansion / contraction acceleration of the hydraulic shock absorber 1).

1 is a longitudinal sectional view of a hydraulic shock absorber according to an embodiment of the present invention. It is a perspective sectional view of the piston which comprises the hydraulic shock absorber concerning the embodiment of the present invention, and its circumference. The flow of the fluid when the piston rod moves with low acceleration and a high damping force is generated in the hydraulic shock absorber is shown, (a) is a sectional view of the piston and its periphery, and (b) is a perspective sectional view. . The flow of the fluid when the piston rod moves with high acceleration and a low damping force is generated in the hydraulic shock absorber is shown, (a) is a sectional view of the piston and its periphery, and (b) is a perspective sectional view. . (A) is a piston showing the flow of fluid when a piston rod constituting a hydraulic shock absorber according to a modification of the embodiment of the present invention moves with low acceleration and a low damping force is generated in the hydraulic shock absorber, and FIG. 5B is a cross-sectional view of the periphery, and FIG. 5B is a cross-sectional view of the piston and its periphery showing the flow of fluid when the piston rod moves with high acceleration and a high damping force is generated in the hydraulic shock absorber.

Explanation of symbols

1 Hydraulic Shock Absorber 2 Cylinder 2a Eyepiece 3 Piston 4 First Fluid Chamber 5 Second Fluid Chamber 6 Piston Rod 7 Groove (Second Fluid Passage)
8 Through hole (first fluid passage)
9 Opening state adjusting means 10 High-pressure gas chamber 11 Free piston 12 Moving means (mass)
13 Biasing means 14 Cover 14a Through hole 15 Washer 16 Disc valve (compression)
17 Disc valve (tension)

Claims (4)

A piston that slidably fits in the cylinder and divides the cylinder into first and second fluid chambers; and a piston rod that is joined to the piston and slidably penetrates the end wall of the cylinder. In the hydraulic shock absorber
The piston rod has a groove passing through the piston and extending from the first fluid chamber to the second fluid chamber on an outer peripheral surface, and the first fluid chamber and the second fluid chamber have the groove. Communicate through
An opening state adjusting means for adjusting an area of an opening of the groove facing the first fluid chamber or the second fluid chamber according to a sliding state of the piston rod with respect to the cylinder;
The opening state adjusting means includes
A moving means arranged away from the cylinder and moving in the axial direction of the piston rod to adjust the area of the opening;
A biasing means supported by the piston or the piston rod and biasing the moving means in the axial direction;
In accordance with the acceleration of the piston, the moving means moves against the urging force of the urging means, and adjusts the area of the opening ,
When the piston rod moves with acceleration and the acceleration of the piston rod is not more than a predetermined value, the moving means is biased by the biasing means and covers the opening, and the acceleration of the piston rod is When the value is exceeded, the moving means moves relative to the urging force of the urging means to open the opening . A cover provided on the outer peripheral surface of the piston rod adjacent to the piston;
The hydraulic shock absorber according to claim 1 , wherein a through hole is provided in a part of the cover directly above the groove, and the moving means moves on the through hole. On the outer peripheral surface of the piston rod, there is a step portion that is axially separated from both ends of the groove,
The hydraulic shock absorber according to claim 1 or 2 , wherein the piston is disposed away from an end of the groove by the stepped portion. The hydraulic shock absorber according to any one of claims 1 to 3 , further comprising a through hole that penetrates the piston and communicates the first fluid chamber and the second fluid chamber.

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