JP2009228861A - Shock absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shock absorber providing a stable damping characteristic even when the temperature of a working fluid changes. <P>SOLUTION: This shock absorber 1 for generating damping force by expansion operation, has a cylinder 10 sealed with the working fluid, a piston 2 slidingly arranged in this cylinder 10, a rod 5 for fixing the piston 2 to one end, a piston penetrating flow passage 6 communicating two fluid chambers 3 and 4 defined by the piston 2, passing the working fluid by sliding of the piston 2 and applying resistance to the working fluid, a bypass flow passage 65 arranged in parallel to this piston penetrating flow passage 6 and shunting the two fluid chambers 3 and 4, and a temperature compensating valve 60 interposed in this bypass flow passage 65. This temperature compensating valve 60 changes the opening area of the bypass flow passage 65 by deformation by a temperature change in a shape memory alloy, and compensates for a change in the damping force caused by a viscosity change by a temperature change in the working fluid. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a shock absorber, particularly a shock absorber mounted on a vehicle.

As a shock absorber mounted on a vehicle such as an automobile, there is a shock absorber that uses a magnetic viscous fluid whose apparent viscosity changes due to the action of a magnetic field as a working fluid, and is provided with a fixed throttle through which the working fluid passes during expansion and contraction operation ( For example, see Patent Document 1.)
US Pat. No. 6,260,675

  In the case of a shock absorber that uses a magnetorheological fluid as the working fluid and is provided with a fixed throttle, it does not have a damping valve that changes the resistance applied to the working fluid.For example, even if the viscosity of the working fluid increases at low temperatures, the damping force There was a problem that the increase could not be suppressed.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a shock absorber capable of obtaining a stable damping force characteristic even when the temperature of the working fluid changes.

  The present invention is a shock absorber that generates a damping force by an expansion and contraction operation, a cylinder in which a working fluid is enclosed, a piston that is slidably disposed in the cylinder, and a rod that has a piston fixed to one end thereof. A piston penetrating passage that communicates two fluid chambers defined by the piston, allows the working fluid to pass by sliding of the piston and provides resistance to the working fluid, and is provided in parallel with the piston penetrating passage. A bypass passage for short-circuiting the two fluid chambers, and a temperature compensation valve interposed in the bypass passage. The temperature compensation valve reduces the opening area of the bypass passage by deformation due to temperature change of the shape memory alloy. It is characterized in that a change in damping force due to a change in viscosity due to a change in temperature of the working fluid is compensated.

  According to the present invention, the temperature compensation valve can change the opening area of the bypass flow path according to the temperature change of the working fluid, and can make the damping force characteristic of the shock absorber constant regardless of the temperature of the working fluid.

  Embodiments of the present invention will be described below with reference to the drawings.

  A shock absorber 1 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view of the shock absorber 1, and FIG. 2 is a view taken in the direction of arrow A in FIG.

  The shock absorber 1 is interposed between a vehicle body of a vehicle such as an automobile and an axle, and generates a damping force that suppresses vibration of the axle by an expansion / contraction operation.

  The shock absorber 1 includes a cylindrical cylinder 10 in which a working fluid is sealed, and a piston 2 that is slidably disposed in the cylinder 10 and that defines the inside of the cylinder 10 in two fluid chambers 3 and 4. .

  The piston 2 is connected to one end of a rod 5. The other end of the rod 5 extends to the outside of the cylinder 10.

  A gas chamber (not shown) is provided in the cylinder 10 to compensate for volume changes in the cylinder 10 due to the entry and exit of the rod 5.

  The piston 2 includes a cylindrical piston core 20 through which the rod 5 is inserted, and an annular ring body 50 disposed on the outer periphery of the piston core 20 with a predetermined interval. One end of the rod 5 is fitted in the hole of the piston core 20.

  Between the outer periphery of the piston core 20 and the inner periphery of the ring body 50, an annular piston passage 6 through which the working fluid passes is formed. In this manner, the piston through flow path 6 communicates the two fluid chambers 3 and 4 defined by the piston 2.

  A pair of annular plates 11 and 12 are disposed at both ends of the piston 2. Of the pair of plates 11, 12, the first plate 11 on the rod 5 side abuts on the annular corner 25 formed on the piston core 20 and abuts on the annular step 55 formed on the ring body 50, It is pressed by a nut 21 screwed with a male screw formed on the piston core 20. The second plate 12 on the opposite side of the rod 5 is in contact with the annular corner portion 26 formed in the piston core 20, and is in contact with the annular step portion 56 formed in the ring body 50, and is formed in the piston core 20. It is pressed by a nut 22 that is screwed with a male screw. In this way, the piston core 20 and the ring body 50 are sandwiched between the pair of plates 11 and 12, and the annular piston through-flow channel 6 is interposed between the inner peripheral surface of the ring body 50 and the outer peripheral surface of the piston core 20. Are formed with a uniform channel width.

  A plurality of arc-shaped through-holes 11a and 12a communicating with the piston through-flow passage 6 in a state of being engaged with the piston 2 are formed in the plates 11 and 12 (four in this embodiment).

  Thereby, when the piston 2 slides in the cylinder 10, the working fluid moves back and forth between the fluid chamber 3 and the fluid chamber 4 through the through holes 11 a and 12 a and the piston through passage 6. When the working fluid passes through the piston passage 6, resistance is applied to the working fluid, and the shock absorber 1 generates a damping force.

  Here, as in the present embodiment, when the piston through flow path 6 through which the working fluid passes is an annular gap, the flow rate of the working fluid flowing through the piston through flow path 6 is expressed by the following equation (1). The

Q = (πdh ³ ΔP) / (12 μl) (1)
Q: Working fluid flow rate, d: Channel diameter, h: Channel gap amount, l: Channel length, ΔP: Differential pressure, μ: Working fluid viscosity As can be seen from the above equation (1), the shock absorber 1 The basic characteristics of this change depending on the viscosity μ of the working fluid.

  The shock absorber 1 encloses a magnetorheological fluid as a working fluid. The magnetorheological fluid changes its apparent viscosity by the action of a magnetic field, and is a liquid in which fine particles having ferromagnetism are dispersed in a liquid such as oil. The viscosity of the magnetorheological fluid can be adjusted by changing the strength of the applied magnetic field and is restored to its original state by removing the magnetic field.

  The piston core 20 and the ring body 50 are made of a magnetic material. An annular recess 8 is formed on the outer periphery of the piston core 20, and the coil 40 is accommodated in the recess 8. The coil 40 is wound around the outer periphery of the piston core 20 and is provided facing the piston through flow path 6.

  By passing an electric current through the coil 40, the coil 40 generates a magnetic field. The magnetic field forms a magnetic circuit via the piston core 20 and the ring body 50, and gives a magnetic force to the magnetorheological fluid flowing through the piston through-flow path 6. .

  A drive current from a controller (not shown) mounted on the vehicle is input to the coil 40 via a lead wire 49. A lead wire 49 extending from the coil 40 is inserted through the recess 24 formed in the piston core 20 and through the hollow portion 51 of the rod 5 and is connected to the controller. Mold resin is formed between the lead wire 49 and the hollow portion 51 and the recess 24.

  When the piston 2 slides in the cylinder 10, the magnetorheological fluid in the fluid chambers 3, 4 on both sides of the piston 2 moves through the piston through passage 6. At this time, when an electric current is passed through the coil 40, a magnetic field acts on the magnetorheological fluid flowing through the piston through passage 6 and the viscosity of the magnetorheological fluid changes. Thereby, the shock absorber 1 generates a damping force corresponding to the magnitude of the viscous resistance of the magnetorheological fluid flowing through the piston through flow path 6.

  As the current of the coil 40 increases, the viscosity of the magnetorheological fluid increases and the damping force generated by the shock absorber 1 also increases. As described above, the damping force generated by the shock absorber 1 is adjusted by changing the amount of current applied to the coil 40 and changing the strength of the magnetic field acting on the magnetorheological fluid flowing through the piston through-flow channel 6.

  The shock absorber 1 that uses a magnetorheological fluid as the working fluid is provided with the piston penetrating channel 6 as a fixed throttle, and thus is generated in the piston penetrating channel 6 by increasing the viscosity of the magnetorheological fluid at a low temperature, for example. Damping force increases.

  Accordingly, the shock absorber 1 includes a temperature compensation valve 60 that compensates for a change in damping force of the shock absorber caused by a viscosity change due to a temperature change of the magnetorheological fluid due to a deformation due to a temperature change of the shape memory alloy.

  In the piston 2, a bypass channel 65 that short-circuits the two fluid chambers 3 and 4 is provided in parallel with the piston penetration channel 6. This bypass flow path 65 short-circuits the fluid chamber 3 and the fluid chamber 4 and provides resistance to the magnetorheological fluid.

  The piston core 20 has a hole 41 extending in the axial direction of the piston 2, a pair of holes 42, 43 extending from the hole 41 in the radial direction of the piston 2, and a hole 44 extending from the holes 42, 43 in the axial direction of the piston 2, 45 are formed, and the bypass channel 65 is defined by these.

  The temperature compensation valve 60 includes a spool 61 interposed in the bypass passage 65, and the bypass passage 65 is opened and closed by the spool 61.

  The cylindrical spool 61 is slidably inserted into the hole 41 extending in the axial direction. In the middle of the spool 61, a groove 61a having a small outer diameter is formed, and the pair of holes 42 and 43 extending in the radial direction are closed at the closed position shown in FIG. A pair of holes 42 and 43 extending in the radial direction at the closed position shown in FIG.

  A shape memory spring 62 is provided at one end of the spool 61, and a bias spring 63 is provided at the other end, and the spool 61 is sandwiched between the shape memory spring 62 and the bias spring 63.

  The coil-shaped shape memory spring 62 expands when its temperature rises above a predetermined value, and contracts when its temperature falls below a predetermined value.

  The coiled bias spring 63 is compressed and interposed between one end of the spool 61 and the spring receiver 45 screwed into the piston core 20. By changing the screwing position of the spring receiver 45, the spring load applied to the spool 61 by the bias spring 63 is adjusted.

  The spool 61 moves due to the difference in restoring force between the shape memory spring 62 and the bias spring 63, and is referred to as an opening area (hereinafter referred to as “short-circuit area”) of the bypass channel 65 that short-circuits the fluid chamber 3 and the fluid chamber 4. ) To give resistance to the magnetorheological fluid passing through the bypass passage 65.

  Next, when the piston 2 slides in the cylinder 10, the spool in the bypass flow path 65 when the magnetorheological fluid in the fluid chambers 3 and 4 on both sides of the piston 2 moves through the piston through flow path 6 is used. The operation of 61 will be described.

  When the temperature of the magnetorheological fluid rises from the reference temperature, the viscosity of the magnetorheological fluid becomes smaller than the viscosity at the reference temperature. In this case, since the magnetorheological fluid is likely to pass through the piston through-channel 6, the damping force generated in the piston through-channel 6 is reduced. However, the restoring force of the shape memory spring 62 increases, and the spool 61 is pushed to decrease the opening area of the bypass channel 65 and move in a direction to increase the damping force.

  On the other hand, when the temperature of the magnetorheological fluid decreases from the reference temperature, the viscosity of the magnetorheological fluid increases compared to the viscosity at the reference temperature. In this case, since the magnetorheological fluid becomes difficult to pass through the piston through-flow channel 6, the damping force generated in the piston through-flow channel 6 increases. However, the restoring force of the shape memory spring 62 is reduced, and the spool 61 is pushed by the opposing bias spring 63 and slides as shown in FIG. 3B to increase the opening area of the bypass passage 65.

  Thus, the bypass flow path 65 provided in parallel with the piston through flow path 6 operates so as to compensate for the change in the damping force of the shock absorber 1 due to the viscosity change of the magnetorheological fluid due to the temperature change.

  Therefore, even when the temperature of the magnetorheological fluid changes from the reference temperature, the deformation characteristic of the shape memory spring 62 is set so that the damping force characteristic of the shock absorber 1 is equivalent to that at the reference temperature. For example, the damping flow characteristic of the shock absorber 1 can be made constant regardless of the temperature of the magnetorheological fluid by opening and closing the bypass passage 65 via the spool 61. Thereby, even when the shock absorber 1 is used in an environment where the environmental temperature changes drastically, the change in damping force due to the viscosity change of the magnetorheological fluid due to the temperature change is compensated, and the current flowing through the coil 40 is adjusted. Thus, a desired damping force can be obtained.

  In the present embodiment, the shock absorber 1 generates a damping force by an expansion / contraction operation, and includes a cylinder 10 in which a working fluid is sealed, a piston 2 that is slidably disposed in the cylinder 10, and a piston at one end. 2 is connected to the rod 5 to which the piston 2 is fixed, and the two fluid chambers 3 and 4 defined by the piston 2. A passage 6, a bypass passage 65 provided in parallel with the piston through-passage 6 and short-circuiting the two fluid chambers 3 and 4, and a temperature compensation valve 60 interposed in the bypass passage 65, This temperature compensation valve 60 changes the opening area of the bypass passage 65 by deformation due to temperature change of the shape memory alloy, and compensates for change in damping force due to viscosity change due to temperature change of the working fluid. And wherein the door.

  Thereby, the temperature compensation valve 60 can change the opening area of the bypass flow path 65 according to the temperature change of the working fluid, and can make the damping force characteristic of the shock absorber 1 constant regardless of the temperature of the working fluid.

In the present embodiment, the temperature compensation valve 60 includes a hole 41 formed in the piston 2,
A cylindrical spool 61 slidably inserted into the hole 41, a shape memory spring 62 made of a shape memory alloy provided alongside one end of the spool 61 and having a restoring force that changes due to a temperature change, and the spool 61 And a bias spring 63 that clamps the spool 61 between the shape memory spring 62 and the spool 61 by adjusting the balance between the restoring force of the shape memory spring 62 and the restoring force of the bias spring 63. This is characterized in that the opening area of the bypass channel 65 is changed.

  Thereby, the temperature compensation valve 60 can accurately adjust the sliding position of the spool 61 according to the temperature change of the working fluid, and can make the damping force characteristic of the shock absorber 1 constant regardless of the temperature of the working fluid.

  In the present embodiment, the working fluid is a magnetorheological fluid, and the piston 2 includes a piston core 20 around which a rod 40 is inserted and a coil 40 that applies a magnetic field to the piston through-flow path 6 is wound. And a ring body 50 that forms a piston through passage 6 between the piston core 20 and the outer periphery of the piston core 20.

  As a result, the temperature compensation valve 60 compensates for a change in damping force due to a change in the viscosity of the magnetorheological fluid due to a change in temperature. The viscous resistance can be adjusted to obtain a desired damping force.

  In the present embodiment, the bypass flow path 65 is formed in the piston core 20, and the bypass flow path 65 is disposed inside the coil 40.

  As a result, the magnetoviscous fluid flowing through the bypass passage 65 is suppressed from being affected by the magnetic field generated by the coil 40, and the temperature compensation valve 60 reduces the change in damping force caused by the viscosity change of the magnetorheological fluid due to the temperature change. Compensation and adjusting the current flowing through the coil 40 to adjust the viscous resistance of the magnetorheological fluid flowing through the piston through flow path 6 to obtain a desired damping force.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

The present invention can be applied to a shock absorber mounted on a vehicle.

Sectional drawing of the shock absorber which shows embodiment of this invention. Similarly, A arrow view of FIG. Similarly (a), (b) is sectional drawing which shows operation | movement of a spool.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Buffer 2 Piston 3, 4 Fluid 5 Rod 6 Piston penetration flow path 10 Cylinder 20 Piston core 40 Coil 60 Temperature compensation valve 61 Spool 62 Shape memory spring 63 Bias spring 65 Bypass passage

Claims (4)

A shock absorber that generates a damping force by expansion and contraction operation,
A cylinder filled with a working fluid;
A piston slidably disposed within the cylinder;
A rod to which the piston is fixed at one end;
A piston through-flow path that communicates two fluid chambers defined by the piston, passes the working fluid by sliding of the piston, and imparts resistance to the working fluid;
A bypass flow path provided in parallel with the piston through flow path and short-circuiting the two fluid chambers;
A temperature compensation valve interposed in the bypass flow path,
The temperature compensation valve changes the opening area of the bypass flow path by deformation due to temperature change of the shape memory alloy, and compensates for a change in damping force due to a viscosity change due to a temperature change of the working fluid. . The temperature compensation valve is
A hole formed in the piston;
A cylindrical spool slidably inserted into the hole;
A shape memory spring made of the shape memory alloy provided alongside one end of the spool and having a restoring force that changes due to a temperature change;
A bias spring provided side by side with the other end of the spool, and holding the spool between the shape memory spring;
The shock absorber according to claim 1, wherein the spool is moved by changing a restoring force of the shape memory spring and a restoring force of the bias spring to change an opening area of the bypass channel. The working fluid is a magnetorheological fluid
The piston has a piston core around which a coil is inserted to apply a magnetic field to the piston through-flow path while the rod is inserted;
The shock absorber according to claim 1, further comprising: a ring body that is disposed on an outer periphery of the piston core at a predetermined interval and that forms the piston through-flow passage between the piston core and the outer periphery of the piston core. . Forming the bypass channel in the piston core;
The shock absorber according to any one of claims 1 to 3, wherein the bypass channel is arranged inside the coil.

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