JP2009216144A - Variable damping force damper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable damping force damper 10 capable of reducing the wear of a sliding surface 2 of a cylinder tube 12 and a piston 16 even when filled with fluid 6 in which a magnetic particle is dispersed. <P>SOLUTION: A plurality of grooves 5 are provided in at least one sliding surface 2 of the cylinder tube 12 and the piston 16. Each direction along the plurality of grooves 5 is at least one of a parallel direction, a perpendicular direction and a slanting direction with respect to the direction parallel to the axial direction of the cylinder tube 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a variable damping force damper filled with a fluid in which magnetic particles are dispersed.

The variable damping force damper is used, for example, to attenuate the vibration of the vehicle body in a road vehicle or the like. As a variable damping force damper, one filled with a fluid in which magnetic particles are dispersed has been proposed (for example, see Patent Document 1).
US Pat. No. 6,464,051

  In a conventional variable damping force damper, a cylinder tube is filled with a fluid in which magnetic particles are dispersed, and a piston is disposed so that the inside of the cylinder tube is divided into a first oil chamber and a second oil chamber. . When the vibration of the vehicle body is transmitted to the piston, the piston attenuates the vibration while sliding with respect to the cylinder tube.

  Assuming use in an environment in which lateral force is applied to the variable damping force damper, a vibration test was performed by applying lateral force to the piston, and the sliding surfaces of the cylinder tube and the piston were worn. If rattling occurs between the cylinder tube and the piston due to this wear, the damping force may be reduced, noise may be generated, or the sealing performance between the rod supporting the piston and the rod guide may be reduced. It was done. Naturally, some wear occurs on the sliding surface, but the inventor has considered that the wear is increased by the fluid in which the magnetic particles are dispersed, leading to the present invention.

  The present invention solves this problem of wear, and provides a variable damping force damper capable of reducing wear of sliding surfaces of a cylinder tube and a piston even when a fluid in which magnetic particles are dispersed is filled. The purpose is to do.

  The present invention is characterized in that, in a variable damping force damper filled with a fluid in which magnetic particles are dispersed, a plurality of grooves are provided on at least one sliding surface of the cylinder tube and the piston. Since there is a clearance between the sliding surface of the cylinder tube and the sliding surface of the piston, magnetic particles have entered the cylinder tube and the piston while the magnetic particles are pressed against the sliding surfaces of the cylinder tube and the piston. By sliding, it is considered that the magnetic particles function as an abrasive and wear increases. Here, if a groove is provided on the sliding surface, the magnetic particles in the groove do not press against the sliding surface and thus do not contribute to wear. Further, magnetic particles outside the groove can move on the sliding surface and enter the groove by sliding between the cylinder tube and the piston. Further, since the groove serves as a flow path for the fluid and the magnetic particles also flow through the groove, it is difficult for the magnetic particles to flow into a position where they are pressed against the sliding surfaces of the cylinder tube and the piston. From these facts, by providing the grooves, it is possible to reduce wear due to the magnetic particles.

  Each direction along the plurality of grooves is preferably at least one of a parallel direction, a vertical direction, and an oblique direction with respect to a direction parallel to the axial direction of the cylinder tube. If the direction is parallel, the fluid can easily flow into the groove and the flow path of the fluid can be easily formed. Therefore, it is difficult for the magnetic particles to flow into a position where the magnetic particles are sandwiched between the sliding surfaces of the cylinder tube and the piston. Thus, wear due to magnetic particles can be reduced. In the vertical direction, the magnetic particles outside the groove move on the sliding surface by sliding between the cylinder tube and the piston, but move in the parallel direction, which is the sliding direction. In the direction, the vertical grooves are always arranged across the grooves, so that the magnetic particles can be easily put in the grooves. And if it is a diagonal direction, the effect of both a parallel direction and a perpendicular | vertical direction can be exhibited.

  Each direction along the plurality of grooves is preferably parallel or oblique with respect to a direction parallel to the axial direction of the cylinder tube. The effect in the parallel direction described above can be exhibited.

  ADVANTAGE OF THE INVENTION According to this invention, even if it fills with the fluid which the magnetic particle has disperse | distributed, the variable damping force damper which can reduce wear of the sliding surface of a cylinder tube and a piston can be provided.

  FIG. 1 shows a longitudinal sectional view of a variable damping force damper 10 according to an embodiment of the present invention. The variable damping force damper 10 has a so-called monotube type structure, and a cylindrical cylinder tube 12 filled with MRF (Magneto-Rheological Fluid) 6, On the other hand, a piston rod 13 that slides in the axial direction, a piston 16 that is attached to the tip of the piston rod 13 and divides the inside of the cylinder tube 12 into a first oil chamber 14 and a second oil chamber 15, and a second oil chamber 15 and a free piston 18 that defines a high-pressure gas chamber 17.

  The MRF 6 is a fluid in which magnetic particles having ferromagnetism having a spherical shape and an average particle diameter of about several μm as a dispersoid are dispersed in oil such as uniform mineral oil as a dispersion medium. The MRF 6 is liquid like a general hydraulic fluid when not receiving a magnetic field, and exhibits a behavior as a Newtonian fluid. However, when an external magnetic field is applied, the MRF 6 is uniformly dispersed in the MRF 6. The ferromagnetic magnetic particles that have been connected are linked along the direction of the magnetic field to form chain clusters. Since this cluster resists deformation (flow), the apparent viscosity increases rapidly, and shows the behavior of a plastic fluid having a yield stress during flow. Such a viscosity change due to the magnetic field of the MRF 6 is reversible, and the state of the original Newtonian fluid is quickly returned by removing the magnetic field. Further, the degree of change in viscosity can be adjusted by adjusting the strength of the magnetic field. Further, the state change between the Newtonian fluid and the plastic fluid of MRF6 occurs at a very high speed and is on the order of several milliseconds.

  In the cylinder tube 12, an eyepiece 12 a is provided at the end where the hole for inserting the piston rod 13 is not formed. For example, when the variable damping force damper 10 is used for an automobile suspension, a bolt (not shown) is fitted into the eyepiece 12a, and this bolt is connected to a trailing arm that is a wheel side member. Further, an end portion (not shown) of the piston rod 13 is connected to a damper base (an upper portion of the wheel house) which is a vehicle body side member.

  The piston 16 includes side covers 32a and 32b provided at ends in the axial direction, and a cylindrical piston ring 1 surrounding the side covers 32a and 32b. The piston ring 1 has a sliding surface 2 that slides with an inner peripheral surface that is a sliding surface of the cylinder tube 12 at the center. And the taper surfaces 3 and 4 are provided in the both ends of both sides on both sides of the center part. The tapered surfaces 3 and 4 do not slide with respect to the inner peripheral surface of the cylinder tube 12, and prevent the piston ring 1 from being caught in the cylinder tube 12 during sliding to prevent slipping.

  The MRF 6 is filled in the first oil chamber 14 and the second oil chamber 15 inside the cylinder tube 12, but the MRF 6 can flow between the first oil chamber 14 and the second oil chamber 15 in the piston 16. A communication hole is provided. When the piston 16 slides with respect to the cylinder tube 12, the volume of the first oil chamber 14 and the second oil chamber 15 changes, and the MRF 6 flows through the communication hole. The piston 16 has a built-in electromagnetic coil. By applying a magnetic field to the MRF 6 flowing in the communication hole by the electromagnetic coil, the viscosity of the MRF 6 is changed, and the damping force of the variable damping force damper 10 is variably controlled. ing. When vibration is generated on the wheel side while the vehicle is running, the vibration is transmitted to the cylinder tube 12, and the piston 16 and the cylinder tube 12 slide on each other, so that a damping force is generated and transmitted from the wheel side to the vehicle body side. Vibration is attenuated.

  Specifically, the sliding of the piston 16 and the cylinder tube 12 occurs on the sliding surface 2 of the piston ring 1 and the sliding surface of the inner peripheral surface of the cylinder tube 12. A plurality of grooves 5 are provided on at least one sliding surface 2 of the piston 16 and the cylinder tube 12. FIG. 1 shows a case where a plurality of grooves 5 are provided in the piston 16 as an example.

  Each direction along the plurality of grooves 5 is at least one of a parallel direction, a vertical direction, and an oblique direction with respect to a direction parallel to the axial direction of the cylinder tube 12. In FIG. 1, the case of the diagonal direction is shown as an example.

  In the free piston 18, the high pressure gas chamber 17 is kept airtight by the O-ring 18a. When the pressure difference between the second oil chamber 15 and the high pressure gas chamber 17 occurs, the free piston 18 slides in the cylinder tube 12 so as to eliminate the pressure difference.

  In FIG. 2, the longitudinal cross-sectional view of the part of piston 16 is shown. The piston 16 includes a main body member 31 that is fitted to the piston rod 13, side covers 32 a and 32 b that are respectively provided at axial ends of the main body member 31, and a magnetic member that is embedded in the main body member 31 in the vicinity of the outer periphery of the main body member 31. A cylindrical piston ring 1 that surrounds the body member 31 so that a constant gap 35c is formed between a fluid valve (MLV) 33 (corresponding to the electromagnetic coil) and the outer periphery of the body member 31. And.

  Holes 35a and 35b are formed in the side covers 32a and 32b, respectively. In the piston 16, the holes 35a and 35b and the gap 35c communicate with each other to form the communication hole. The first oil chamber 14 and the second oil chamber 15 communicate with each other through the communication hole, and the MRF 6 can be circulated through the communication hole. When a current is supplied from the control device (not shown) to the MLV 33 through the wiring 36 disposed inside the piston rod 13 and the piston 16, a magnetic field is applied to the MRF 6 that flows through the gap 35c, and the magnetism contained in the MRF 6 The particles form chain clusters, increasing the apparent viscosity of MRF6 passing through gap 35c. The damping force can be variably controlled by controlling the magnitude of the magnetic field applied to the MRF 6.

  The piston ring 1 has a cylindrical shape, and both ends thereof are closely fitted to the side covers 32a and 32b by caulking or the like. As shown in FIG. 2, the outer diameter of the piston ring 1 is not constant in the axial direction, and the outer diameter is constant in the constant length range of the central portion, but the outer diameter is increased toward both ends of the piston ring 1. Is getting shorter. A portion having a constant outer diameter is a sliding surface 2 that slides with respect to the inner peripheral surface of the cylinder tube 12 substantially. Further, both end portions are tapered surfaces 3 and 4.

  As shown in FIG. 2, the cylinder tube 12 has a structure in which a nickel (Ni) plating film 22 is formed on the inner peripheral surface of a cylinder base material 21 made of metal such as iron (Fe) or stainless steel. . The piston 16 and the free piston 18 (see FIG. 1) slide against the Ni plating film 22. The Ni plating film 22 is crystalline, and its Vickers hardness is 800 VHN (Vickers Hardness Number) or more. Thus, since the high hardness Ni plating film 22 has excellent wear resistance, the aged wear of the inner peripheral surface (sliding surface) of the cylinder tube 12 is suppressed, and the damping force of the variable damping force damper 10 is reduced. Can be kept constant over a long period of time.

The Ni plating film 22 is formed by performing electroless Ni plating on the inner peripheral surface of the cylinder tube 12 and heat-treating the Ni plating film thus formed at 200 ° C. to 600 ° C. for 0.5 to 5 hours. be able to. The Ni plating film (before heat treatment) formed by electroless Ni plating is amorphous, but this Ni plating film (before heat treatment) is crystallized by the heat treatment. This is because, in the chemical reaction process of electroless Ni plating, the Ni plating film (before heat treatment) formed by electroless Ni plating generally contains phosphorus (P), and Ni and P are separated by heat treatment. This is because a chemical reaction occurs and a crystal phase of Ni ₃ P is formed.

  The Ni plating film 22 may further contain one or more selected from boron (B), tungsten (W), boron nitride (BN), and silicon carbide (SiC) (hereinafter referred to as “additional component”). preferable. B and W are present in the Ni plating film 22 in a form chemically bonded to Ni, while BN and SiC are dispersed in the Ni plating film 22 to constitute a metal-ceramic composite material. B, W, BN and SiC can each be contained in the Ni plating film 22 by eutectoid from the plating solution.

Further, the additive component to the Ni plating film 22 is not limited to the various elements (metals) and compounds described above. For example, boron carbide (B ₄ C), silicon nitride (Si ₃ N ₄ ), alumina ( Al ₂ O ₃ ), zirconia (ZrO ₂ ), aluminum nitride (AlN), diamond (C), or the like can also be used.

  FIG. 3 schematically shows an endurance test execution method. In the durability test, a sliding range of a certain length in the axial direction of the cylinder tube 12 in a state where a side force F (lateral force) of a certain magnitude is applied in the radial direction (here, vertically downward) of the piston 16. The piston 16 was reciprocated inside. Then, by measuring the inner diameter change of the cylinder tube 12 in the sliding range, the tube wear amount Δtt, which is the wear amount of the Ni plating film 22, was obtained. Furthermore, the piston wear amount Δtp, which is the wear amount of the sliding surface 2, was determined by measuring the change in the outer diameter of the piston ring 1.

In the variable damping force damper 10, since it is necessary to make metal contact (sliding) between the cylinder tube 12 and the piston 16, the difference between the inner diameter of the cylinder tube 12 and the outer diameter of the sliding surface 2 of the piston 16, that is, the cylinder tube. A clearance (gap) 7 between 12 and the piston 16 is provided with high accuracy. Specifically, it is set to a value of about 50 μm.

  The sliding surface 2 of the piston ring 1 is provided with a groove 5, but in the durability test, the direction along the groove 5 is the axis (core) direction of the cylinder tube 12, that is, the direction parallel to the sliding direction. Thus, the piston ring 1 having the groove 5 with an angle of 45 ° was used. The number of grooves 5 was 40, the maximum groove width was 0.5 mm, and the maximum groove depth was 1.3 mm.

  The inner diameter of the cylinder tube 12 was about φ46 mm (tolerance: 5 μm or less), the outer diameter of the sliding surface 2 of the piston ring 1 was about φ45.9 mm, and the clearance 7 was about 50 μm. The length of the sliding surface 2 in the sliding direction was 13 mm, and the sliding range was 70 mm. The material of the piston ring 1 was S25C (carbon steel for machine structure).

  FIG. 4 is a graph showing the relationship of the tube wear amount Δtt to the piston wear amount Δtp, which is the result of the durability test. As a result, in the case of the piston ring 1 whose angle along the groove 5 is at an angle of 45 ° with respect to the direction parallel to the axial direction of the cylinder tube 12, the tube wear amount Δtt is 24 [μm]. The amount Δtp was 40 [μm]. The sum of the tube wear amount Δtt and the piston wear amount Δtp was 64 [μm].

As shown in FIG. 4, the piston ring 1 and the cylinder tube 12 are produced under other conditions, and an endurance test is performed to measure the tube wear amount Δtt and the piston wear amount Δtp. In other words, as a first modification of the present embodiment, the piston ring 1 whose direction along the groove 5 is perpendicular to the direction parallel to the axial direction of the cylinder tube 12 (so-called lateral groove) is manufactured, and an endurance test is performed. Yes. As a result of the durability test, the tube wear amount Δtt was 37 [μm], and the piston wear amount Δtp was 67 [μm]. The sum of the tube wear amount Δtt and the piston wear amount Δtp was 104 [μm].

  In addition, as a comparative example of the present embodiment, three piston rings 1 not provided with the grooves 5 are produced and subjected to a durability test three times. As a result of the first durability test, the tube wear amount Δtt was 51 [μm], and the piston wear amount Δtp was 81 [μm]. As a result of the second durability test, the tube wear amount Δtt was 42 [μm], and the piston wear amount Δtp was 62 [μm]. As a result of the third durability test, the tube wear amount Δtt was 33 [μm], and the piston wear amount Δtp was 54 [μm]. The sum of the tube wear amount Δtt and the piston wear amount Δtp was 132 [μm], 104 [μm], and 87 [μm], respectively, and the average value was 108 [μm].

  The fact that the sum of the tube wear amount Δtt and the piston wear amount Δtp is small indicates that the change in the clearance 7 (see FIG. 3) is small. Therefore, the smaller this sum is, the more the first through the clearance 7 becomes. The movement of the MRF 6 between the oil chamber 14 and the second oil chamber 15 can be suppressed over a long period, and the damping performance can be maintained high over a long period. Then, it was found that the sum can be reduced by providing the grooves 5 such as the oblique grooves and the lateral grooves as compared with the case without the grooves. Further, it has been found that the sum of the oblique grooves can be made smaller than that of the lateral grooves.

  Next, a mechanism that can reduce the sum of the tube wear amount Δtt and the piston wear amount Δtp by the groove 5 was considered.

  FIG. 5A shows a schematic side view around the sliding surface 2 in which the oblique groove 5 of the piston 16 is formed during the durability test. When the piston 16 moves in the sliding direction, the MRF 6 flows in the clearance 7 in the direction opposite to the sliding direction.

FIG. 5B is a cross-sectional view taken along arrow AA in FIG. By the side force F, the piston 16 is in pressure contact with the cylinder tube 12, and in particular, a pressure contact surface 8 in which a part of the sliding surface 2 is in pressure contact with the cylinder tube 12 is formed. There is no clearance 7 on the pressure contact surface 8, and there is a clearance 7 on the sliding surface 2 that is not the pressure contact surface 8. Then, wear occurs on the pressure contact surface 8. In addition to the flow of the MRF 6 in the direction opposite to the sliding direction shown in FIG. 5A, the clearance 7 includes a flow of MRF 6 that flows in the direction of the pressure contact surface 8 and a direction of the pressure contact surface 8. It is considered that a flow of MRF 6 that flows out occurs. The reason will be described with reference to FIG.

FIG. 5C shows the flow of the MRF 6 around the pressure contact surface 8 where wear occurs. Since the cylinder tube 12 is in pressure contact with the pressure contact surface 8, the MRF 6 does not flow in. On the other hand, the groove 5 is covered with the cylinder tube 12 and has a pipe shape, so that the MRF 6 flows into the groove 5. The MRF 6 flows in the groove 5 and flows out of the groove 5.

Further, since the clearance 7 is adjacent to the pressure contact surface 8 and the groove 5 is an oblique groove, the opening of the oblique groove 5 is in contact with the clearance 7. Therefore, it is considered that a flow of MRF 6 that flows from the clearance 7 toward the pressure contact surface 8 and a flow of MRF 6 that flows from the direction of the pressure contact surface 8 to the clearance 7 occur.

  FIG. 5 (d) shows an enlarged view of the window 37 of FIG. 5 (c). The magnetic particles 9 are dispersed in the MRF 6. The cylinder particles and the piston slide while the magnetic particles 9 are in pressure contact with the sliding surfaces of the cylinder tube 12 and the piston 16 on the pressure contact surface 8. The magnetic particles 9 function as an abrasive and wear occurs. However, since the magnetic particles 9 in the groove 5 are not pressed against the sliding surface 2, they do not contribute to wear. Further, the magnetic particles 9 outside the groove 5 on the pressure contact surface 8 can move on the pressure contact surface 8 and enter the groove by sliding between the cylinder tube 12 and the piston 16. Further, the groove 5 serves as a flow path for the magnetic particles 9, and the magnetic particles 9 flow through the grooves 5, so that the magnetic particles 9 do not easily flow onto the pressure contact surface 8. For these reasons, by providing the oblique grooves 5, it is possible to reduce the wear caused by the magnetic particles 9.

(Modification 1)
In the above description, the oblique groove has been described as an example. Next, a lateral groove will be described as a first modification of the embodiment.

  FIG. 6A shows a schematic side view around the sliding surface 2 in which the lateral groove 5 of the piston 16 is formed during the durability test. When the piston 16 moves in the sliding direction, the MRF 6 flows in the clearance 7 in the direction opposite to the sliding direction.

FIG. 6B is a cross-sectional view taken along arrow AA in FIG. By the side force F, the piston 16 is in pressure contact with the cylinder tube 12, and in particular, a pressure contact surface 8 in which a part of the sliding surface 2 is in pressure contact with the cylinder tube 12 is formed. There is no clearance 7 on the pressure contact surface 8, and there is a clearance 7 on the sliding surface 2 that is not the pressure contact surface 8. Then, wear occurs on the pressure contact surface 8. In addition, it is considered that the MRF 6 flows out from the direction of the pressure contact surface 8 in the clearance 7 in addition to the flow of the MRF 6 in the direction opposite to the sliding direction shown in FIG. The reason will be described with reference to FIG.

FIG. 6C shows the flow of the MRF 6 around the pressure contact surface 8 where wear occurs. Since the cylinder tube 12 is in pressure contact with the pressure contact surface 8, the MRF 6 does not flow, but even if it flows, the MRF 6 flows into the groove 5 immediately after. The MRF 6 once flowing into the groove 5 flows in the groove 5 and flows out from the opening of the groove 5. Since the opening of the lateral groove 5 is in contact with the clearance 7, it is considered that the MRF 6 flows out from the direction of the pressure contact surface 8 to the clearance 7.

FIG. 6 (d) shows an enlarged view of the window 37 of FIG. 6 (c). The magnetic particles 9 outside the groove 5 on the pressure contact surface 8 move on the pressure contact surface 8 by sliding between the cylinder tube 12 and the piston 16 and can surely enter the groove 5. Further, the groove 5 serves as a flow path for the magnetic particles 9, and the magnetic particles flow through the groove 5, so that the magnetic particles 9 in the groove 5 do not easily flow onto the pressure contact surface 8. For these reasons, by providing the lateral grooves 5, it is possible to reduce the wear caused by the magnetic particles 9. Incidentally, in the horizontal groove, there is no opening through which the magnetic particles 9 directly flow without exceeding the pressure contact surface 8 as compared with the vertical groove, so that it is difficult to form the flow path of the magnetic particles 9, and the effect of reducing wear is correspondingly reduced. Seems to have declined.

(Modification 2)
Next, a vertical groove will be described as a second modification of the embodiment.

  FIG. 7A shows a schematic side view around the sliding surface 2 in which the longitudinal groove 5 of the piston 16 is formed during the durability test. The direction along the longitudinal groove 5 is parallel to the sliding direction. When the piston 16 moves in the sliding direction, the MRF 6 flows in the clearance 7 in the direction opposite to the sliding direction.

FIG. 7B is a cross-sectional view taken along the line AA in FIG. Although the pressure contact surface 8 is formed by the side force F, only the flow of the MRF 6 in the direction opposite to the sliding direction shown in FIG. 7A is generated in the clearance 7 and flows out from the direction of the pressure contact surface 8. It is considered that the flow of MRF6 that flows in does not occur. The reason will be described with reference to FIG.

  FIG. 7C shows the flow of the MRF 6 around the pressure contact surface 8 where wear occurs. Since the cylinder tube 12 is in pressure contact with the pressure contact surface 8, the MRF 6 does not flow, and the longitudinal groove 5 is covered with the cylinder tube 12 and is formed in a pipe shape, and is open toward the flow of the MRF 6. It flows into the longitudinal groove 5. The MRF 6 flows through the vertical groove 5 and flows out of the vertical groove 5.

Further, although the clearance 7 is adjacent to the pressure contact surface 8, the groove 5 is a vertical groove, so that the opening of the vertical groove 5 does not occur in the clearance 7. For this reason, the flow of MRF 6 that flows from the clearance 7 toward the pressure contact surface 8 and the flow of MRF 6 that flows from the direction of the pressure contact surface 8 to the clearance 7 do not occur.

FIG. 7 (d) shows an enlarged view of the window 37 of FIG. 7 (c). Since the magnetic particles 9 in the longitudinal groove 5 are not pressed against the sliding surface 2, they do not contribute to wear. Further, the vertical groove 5 becomes a flow path for the magnetic particles 9, and the magnetic particles flow through the grooves 5, so that the magnetic particles 9 are less likely to flow onto the pressure contact surface 8. From these facts, by providing the longitudinal grooves 5, it is possible to reduce wear due to the magnetic particles 9.

(Modification 3)
Next, as a third modification of the embodiment, a crossed groove 5 of an oblique groove in the screw winding direction and an oblique groove in the reverse screw winding direction will be described.

  FIG. 8A shows a schematic side view around the sliding surface 2 in which the oblique grooves 5 are formed in the screwing direction and the reverse screwing direction of the piston 16 during the durability test. When the piston 16 moves in the sliding direction, the MRF 6 flows in the clearance 7 in the direction opposite to the sliding direction.

FIG. 8B is a cross-sectional view taken along the line AA in FIG. The pressure surface 8 is formed by the side force F, and the clearance 7 has a pressure contact surface 8 on both sides of the pressure contact surface 8 in addition to the flow of the MRF 6 in the direction opposite to the sliding direction shown in FIG. It is considered that the flow of MRF 6 flowing in the direction of and the flow of MRF 6 flowing out of the direction of the pressure contact surface 8 occur, so that the flow reciprocates so as to reciprocate. The reason will be described with reference to FIG.

  FIG. 8C shows the flow of the MRF 6 around the pressure contact surface 8 where wear occurs. Since the cylinder tube 12 is in pressure contact with the pressure contact surface 8, the MRF 6 does not flow, and the groove 5 is covered with the cylinder tube 12 and is in a pipe shape, so that the MRF 6 flows into the groove 5. The MRF 6 flows through the groove 5 and flows out of the groove 5.

Further, since the clearance 7 is adjacent to the pressure contact surface 8 and the groove 5 is an oblique groove, the opening of the oblique groove 5 is in contact with the clearance 7. For this reason, it is considered that a flow of MRF 6 that flows from the clearance 7 toward the pressure contact surface 8 and a flow of MRF 6 that flows from the direction of the pressure contact surface 8 to the clearance 7 occur on each side.

FIG. 8D shows an enlarged view of the window 37 in FIG. Since the magnetic particles 9 in the groove 5 are not pressed against the sliding surface 2, they do not contribute to wear. Also, the magnetic particles 9 outside the groove 5 on the pressure contact surface 8 can move on the pressure contact surface 8 and enter the groove 5 by sliding between the cylinder tube 12 and the piston 16. Further, the groove 5 serves as a flow path for the magnetic particles 9, and the magnetic particles 9 flow through the grooves 5, so that the magnetic particles 9 do not easily flow onto the pressure contact surface 8. For these reasons, it is possible to reduce the wear caused by the magnetic particles 9 by providing the diagonal grooves 5 that cross each other.

(Modification 4)
Next, as a modified example 4 of the embodiment, a crossed groove 5 of a lateral groove and an oblique groove will be described.

  FIG. 9A shows a schematic side view of the periphery of the sliding surface 2 in which the cross groove 5 of the transverse groove and the oblique groove of the piston 16 is formed in the durability test. When the piston 16 moves in the sliding direction, the MRF 6 flows in the clearance 7 in the direction opposite to the sliding direction.

  FIG. 9B is a cross-sectional view taken along arrow AA in FIG. The pressure force contact surface 8 is formed by the side force F, and the MRF 6 flows out from the direction of the pressure contact surface 8 in the clearance 7 in addition to the flow of the MRF 6 in the direction opposite to the sliding direction shown in FIG. The flow of is occurring. The magnitude of the flow flowing out from the MRF 6 is different on the left and right sides of the pressure contact surface 8.

  FIG. 9C shows the flow of the MRF 6 around the pressure contact surface 8 where wear occurs. Since the cylinder tube 12 is in pressure contact with the pressure contact surface 8, the MRF 6 does not flow, and the groove 5 is covered with the cylinder tube 12 and is in a pipe shape, so that the MRF 6 flows into the groove 5. The MRF 6 flows through the groove 5 and flows out of the groove 5.

  Further, since the clearance 7 is adjacent to the pressure contact surface 8 and the groove 5 is a lateral groove and an oblique groove, the opening of the lateral groove and the opening of the oblique groove are in contact with the clearance 7. For this reason, in the clearance 7 on one side, the flow of the MRF 6 that flows out from the horizontal groove and the oblique groove occurs, and on the other side, the flow of MRF 6 that flows out of the horizontal groove and flows in from the oblique groove is considered to occur. . This creates a difference in flow magnitude on both sides.

  FIG. 9 (d) shows an enlarged view of the window 37 of FIG. 9 (c). Since the magnetic particles 9 in the groove 5 are not pressed against the sliding surface 2, they do not contribute to wear. Further, the magnetic particles 9 outside the groove 5 on the pressure contact surface 8 can move on the pressure contact surface 8 by sliding between the cylinder tube 12 and the piston 16, and can enter the groove 5, particularly, the lateral groove. Further, the grooves 5, particularly the oblique grooves, serve as flow paths for the magnetic particles 9, and the magnetic particles 9 flow through the grooves 5, so that the magnetic particles 9 are less likely to flow onto the pressure contact surface 8. From these facts, it is possible to reduce wear due to the magnetic particles 9 by providing the grooves 5 with lateral grooves and oblique grooves.

(Modification 5)
Next, as a modified example 5 of the embodiment, a crossed groove 5 of a horizontal groove and a vertical groove will be described.

  FIG. 10A is a schematic side view of the periphery of the sliding surface 2 in which the crossed groove 5 of the vertical groove and the horizontal groove of the piston 16 is formed in the durability test. When the piston 16 moves in the sliding direction, the MRF 6 flows in the clearance 7 in the direction opposite to the sliding direction.

  FIG. 10B is a cross-sectional view taken along the line AA in FIG. The pressure surface 8 is formed by the side force F, and the MRF 6 flows out from the direction of the pressure contact surface 8 in the clearance 7 in addition to the flow of the MRF 6 in the direction opposite to the sliding direction shown in FIG. The flow of is occurring.

  FIG. 10C shows the flow of the MRF 6 around the pressure contact surface 8 where wear occurs. Since the cylinder tube 12 is in pressure contact with the pressure contact surface 8, the MRF 6 does not flow, and the groove 5 is covered with the cylinder tube 12 and has a pipe shape, so that the MRF 6 flows into the groove 5, particularly the vertical groove. The MRF 6 flows in the groove 5 in particular in the vertical groove, and flows out of the groove 5 in particular in the vertical groove.

  Further, since the clearance 7 is adjacent to the pressure contact surface 8 and the groove 5 is a horizontal groove and a vertical groove, the opening of the horizontal groove is in contact with the clearance 7. For this reason, a part of the MRF 6 flows from the vertical groove into the horizontal groove and flows out from the horizontal groove to the clearance 7.

  FIG. 10 (d) shows an enlarged view of the window 37 of FIG. 10 (c). Since the magnetic particles 9 in the groove 5 are not pressed against the sliding surface 2, they do not contribute to wear. Further, the magnetic particles 9 outside the groove 5 on the pressure contact surface 8 can move on the pressure contact surface 8 by sliding between the cylinder tube 12 and the piston 16 and can enter the groove 5, particularly the lateral groove. Further, the grooves 5, particularly the longitudinal grooves, serve as flow paths for the magnetic particles 9, and the magnetic particles 9 flow through the grooves 5, particularly the longitudinal grooves, so that the magnetic particles 9 do not easily flow onto the pressure contact surface 8. For these reasons, by providing vertical grooves and horizontal grooves in the grooves 5, it is possible to reduce wear due to the magnetic particles 9.

(Modification 6)
Next, as a sixth modification of the embodiment, a groove 5 in which a longitudinal groove and an oblique groove cross each other will be described. FIG. 11 shows a schematic side view of the periphery of the sliding surface 2 in which the crossed groove 5 of the longitudinal groove and the oblique groove of the piston 16 is formed in the durability test. By providing the longitudinal grooves and the oblique grooves in the groove 5, the above-described effects of the longitudinal grooves and the oblique grooves can be obtained, so that wear due to the magnetic particles 9 can be reduced.

    In addition, in embodiment and its modifications 1-6, although the linear groove | channel was illustrated as the groove | channel 5, not only this but the curved groove | channel and the meandering groove | channel may be sufficient.

It is a longitudinal cross-sectional view of the variable damping force damper (oblique groove) which concerns on embodiment of this invention. It is a longitudinal cross-sectional view of the part of the piston which comprises the variable damping force damper which concerns on embodiment of this invention. It is the figure which showed typically the implementation method of an endurance test. It is a graph which shows the relationship of tube wear amount (DELTA) tt with respect to piston wear amount (DELTA) tp which is a result of an endurance test. (A) is a typical side view around the sliding surface of the piston (oblique groove) during the durability test, (b) is a cross-sectional view taken along the line AA in (a), and (c). (A) is a figure which shows the flow of MRF around the press-contact surface in which abrasion arises, (d) is an enlarged view of the window of (c), and has shown the flow of the magnetic particle. (A) is a schematic side view around the sliding surface of the piston (Modification 1, lateral groove) during the durability test, (b) is a cross-sectional view taken along the line AA in (a), (C) is a figure which shows the flow of MRF around the pressure-contact surface in which wear occurs, and (d) is an enlarged view of the window of (c) and shows the flow of magnetic particles. (A) is a typical side view around the sliding surface of the piston (Modification 2, vertical groove) during the durability test, and (b) is a cross-sectional view taken along the line AA in (a). (C) is a figure which shows the flow of MRF around the press-contact surface in which abrasion occurs, (d) is an enlarged view of the window of (c) and shows the flow of magnetic particles. (A) is a schematic side view around the sliding surface of the piston (Modification 3, cross of diagonal grooves in the screwing direction and the reverse screwing direction) during the durability test, and (b) is a diagram of (a). It is arrow sectional drawing of an AA direction, (c) is a figure which shows the flow of MRF around the pressure-contact surface in which wear arises, (d) is an enlarged view of the window of (c), and the flow of a magnetic particle Is shown. (A) is a typical side view around a sliding surface of a piston (Modification 4, cross of a transverse groove and an oblique groove) at the time of an endurance test, and (b) is an arrow view in the AA direction of (a). It is sectional drawing, (c) is a figure which shows the flow of MRF around the press-contact surface in which abrasion arises, (d) is an enlarged view of the window of (c), and has shown the flow of the magnetic particle. (A) is a typical side view around a sliding surface of a piston (Modification 5, cross of a longitudinal groove and a transverse groove) during an endurance test, and (b) is an arrow view in the AA direction of (a). It is sectional drawing, (c) is a figure which shows the flow of MRF around the press-contact surface in which abrasion arises, (d) is an enlarged view of the window of (c), and has shown the flow of the magnetic particle. It is a typical side view around the sliding surface of the piston (Modification 6, cross of a longitudinal groove and a slanting groove) at the time of an endurance test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piston ring 2 Sliding surface 3, 4 Tapered surface 5 Groove 6 MRF (magnetic fluid or magnetorheological fluid)
7 Clearance 8 Pressure contact surface 9 Magnetic particle 10 Variable damping force damper 12 Cylinder tube 12a Eyepiece 13 Piston rod 14 First oil chamber 15 Second oil chamber 16 Piston 17 High-pressure gas chamber 18 Free piston 18a O-ring 21 Cylinder base material 22 Ni plating Membrane 31 Body member 32a, 32b Side cover 33 MLV (magnetic fluid valve, electromagnetic coil)
35a, 35b hole 35c gap 36 wiring 37 window F side force

Claims (3)

In a variable damping force damper filled with a fluid in which magnetic particles are dispersed,
A variable damping force damper, wherein a plurality of grooves are provided on at least one sliding surface of a cylinder tube and a piston.   The direction along each of the plurality of grooves is at least one of a parallel direction, a vertical direction, and an oblique direction with respect to a direction parallel to the axial direction of the cylinder tube. The variable damping force damper described.   2. The variable damping force damper according to claim 1, wherein each direction along the plurality of grooves is parallel or oblique to a direction parallel to an axial direction of the cylinder tube.

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