JP4976862B2 - Magnetorheological fluid shock absorber manufacturing method - Google Patents

Description

  The present invention relates to a magnetorheological fluid shock absorber using a magnetorheological fluid whose apparent viscosity is changed by the action of a magnetic field and a method for manufacturing the same.

  Some shock absorbers mounted on vehicles such as automobiles generate a damping force by applying a magnetic field to a flow path through which the magnetorheological fluid passes to change the apparent viscosity of the magnetorheological fluid.

  As this type of shock absorber, there is a structure in which a piston assembly is fixed to a rod and the piston assembly is slidably disposed in a cylinder.

  Patent Literature 1 discloses a shock absorber including a piston core, a magnetic flux ring, and an end plate disposed at an end of the piston core.

In assembling the shock absorber described in Patent Document 1, a compression load is applied by a crimp die in a state where each member is arranged in an assembly die, and the magnetic flux ring and the pair of end plates are coupled via the crimp member. Is done by.
US Pat. No. 6,260,675

  However, since the shock absorber in Patent Document 1 requires a dedicated mold for assembly, the shock absorber cannot be easily assembled.

  Thus, the shock absorber using the magnetorheological fluid is composed of a plurality of members such as a member for forming a channel through which the magnetorheological fluid passes and a coil for applying a magnetic field to the channel. Assembling takes a lot of effort.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a magnetorheological fluid shock absorber having a simple structure that can be easily assembled.

The present invention includes a cylinder in which a magnetorheological fluid whose viscosity is changed by the action of a magnetic field is sealed, a piston assembly that is slidably disposed in the cylinder and defines the inside of the cylinder in two fluid chambers, A passage formed in the piston assembly through which the magnetorheological fluid passes between the two fluid chambers by sliding of the piston assembly, and a coil accommodated in the piston assembly for applying a magnetic field to the passage; In the manufacturing method of the magnetorheological fluid shock absorber including the rod to which the piston assembly is coupled, the piston assembly includes a large-diameter portion around which the coil is wound around a part of an outer peripheral surface, and the large-diameter portion. A cylindrical piston core composed of a small-diameter portion having a small diameter, and the piston core arranged at a predetermined interval on the outer periphery of the piston core The piston core includes a cylindrical piston ring that forms the flow path between the piston ring, an annular plate that is provided integrally with the piston ring, and a nut that fixes the plate to the piston core. The inner peripheral surface of the plate integrated with the piston ring is inserted into the outer peripheral surface of the small diameter portion of the piston core while being in sliding contact with the central axis direction of the piston core, and the plate is inserted into the large diameter portion and the small diameter of the piston core. It is a method for manufacturing a magnetorheological fluid shock absorber, wherein the nut is screwed into the piston core so as to be pressed against a step portion with respect to the portion .

  According to the present invention, the piston assembly that forms the flow path through which the magnetorheological fluid passes is constituted by a piston core, a piston ring, and a plate that fixes the piston ring to the piston core, and the piston assembly is fastened to the rod. . As described above, the magnetorheological fluid shock absorber according to the present invention has a simple structure, and can be easily assembled without requiring a special jig such as a mold at the time of assembly. Further, only one plate is required, which has the effect of reducing the number of parts, reducing pressure loss, and centering.

  A magnetorheological fluid shock absorber 100 according to a first embodiment of the present invention will be described with reference to FIG.

  FIG. 1 is a partial cross-sectional view including a piston assembly 2 of a magnetorheological fluid shock absorber 100.

  The magnetorheological fluid shock absorber 100 is interposed between a vehicle body and an axle of a vehicle such as an automobile, and functions as a shock absorber that suppresses changes in the vehicle body posture.

  The magnetorheological fluid shock absorber 100 includes a bottomed thin cylindrical cylinder 1 and a piston assembly that is slidably disposed in the cylinder 1 and that defines two fluid chambers 30 and 31 in the sliding direction in the cylinder 1. 2 and a rod 40 having one end connected to the piston assembly 2 and the other end protruding from the cylinder 1 and fixed to an external body member or the like (not shown).

  A magnetorheological fluid is sealed in the cylinder 1, and this 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. It is. 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.

  Note that a gas chamber (not shown) is provided in the cylinder 1 to compensate for volume changes in the cylinder 1 as the rod 40 enters and exits the cylinder 1.

  The piston assembly 2 that slides in the cylinder 1 includes a cylindrical piston core 3 in which an end of a rod 40 is screwed, and a pipe-shaped ring body that is coaxially disposed on the outer periphery of the piston core 3 with a predetermined interval. 4. The piston core 3 and the ring body 4 are made of a magnetic material.

  Hereinafter, the detailed shape of the piston core 3 will be described with reference to FIG.

The piston core 3 has a cylindrical shape and forms a small diameter portion 17 and a large diameter portion 18 having different outer diameters. And the annular recessed part 8 is formed in a part of outer peripheral surface of this large diameter part 18. As shown in FIG. A male screw 20 is formed on the outer peripheral surface of the small diameter portion 17 from the end portion.

  Two types of through holes 14 and 15 having different diameters are formed stepwise in the central axis direction on the inner peripheral surface of the piston core 3, and the large diameter side through hole 14 is formed inside the outer diameter side small diameter portion 17. The internal thread 16 is cut from the end of a part of the through hole 14 and is engaged with the external thread 40a formed on the outer peripheral surface of the end of the rod 40 as shown in FIG. The piston assembly 2 is fixed to the base. Further, in order to prevent the flow of the magnetorheological fluid at the threaded portion between the male screw 40a of the rod 40 and the female screw 16 of the piston core 3, a first O-ring 32 is installed at this interface.

  On the other hand, a groove portion 7 is formed in the radial direction so as to communicate with the concave portion 8 of the piston core 3 in the through hole 15 on the small diameter side formed inside the large diameter 18 on the outer diameter side. A character-shaped pin 10 is arranged in the axial direction. The pin 10 is made of a conductive material, and one end of the pin 10 extends into the recess 8 and the other end extends into the through hole 14.

  A coil 9 that generates a magnetic field when energized is wound around the recess 8 formed in the large-diameter portion 18, and an end thereof is connected to one end of the pin 10. The other end of the pin 10 is disposed in the through hole 14 through the through hole 15 and is connected to an electric wire 41 that passes through the hollow rod 40 and is connected to a controller (not shown). The controller controls the amount of current supplied to the coil 9 and controls the magnetic field generated by the coil 9.

  And the resin is filled in the state which installed the pin 10 in the groove part 7 and the small diameter through-hole 15 in which the pin 10 is installed, and the position of the pin 10 is fixed. Here, as shown in FIG. 1, the second O-ring 33 is installed at this interface so that the magnetorheological fluid does not flow between the filled resin and the piston core 3.

  Returning to FIG. 1, an annular flow path 6 through which the magnetorheological fluid passes is formed according to the difference between the outer diameter of the large-diameter portion 18 of the piston core 3 and the inner diameter of the ring body 4 installed on the outer peripheral side thereof. Is done. As described above, the annular flow path 6 is formed in the piston assembly 2, and the magnetic fluid passes through the flow path 6 by the piston assembly 2 sliding in the cylinder 1 as the rod 40 slides.

  A coil 9 is wound around an annular recess 8 formed on the outer peripheral surface of the large diameter portion 18 of the piston core 3, and the coil 9 is formed facing the flow path 6. Therefore, as described above, when a current is passed through the coil 9 under the control of a controller (not shown), the coil 9 generates a magnetic force, and the magnetic force flows through the flow path 6 formed by the piston core 3 and the ring body 4. It will act on the magnetorheological fluid.

  An annular plate 11 is inserted into the small diameter portion 17 of the piston core 3. Here, the inner peripheral surface 24 of the plate 11 is in sliding contact with the small diameter portion 17 of the piston core 3 and abuts against the step portion 2 m between the small diameter portion 17 and the large diameter portion 18.

  Further, as shown in FIG. 3, the plate 11 is formed with through holes 21 penetrating in the sliding direction at predetermined intervals in the circumferential direction. The through holes 21 are formed between the piston core 3 and the ring body 4. Open to face the flow path 6. Therefore, the flow of the magnetorheological fluid flowing through the flow path 6 is not hindered.

Further, a flange portion 22 is formed at the outer peripheral side end portion of the plate 11 so as to extend in the central axis direction. The collar portion 22 and the small diameter portion 19 of the ring body 4 are caulked to fix the ring body 4 to the plate 11. Then, the plate 11 and the ring body 4 are integrated.

A nut 12 that is screwed into a male screw 20 formed on the outer peripheral surface of the small diameter portion 17 of the piston core 3 is provided. It is pressed against the stepped portion 2m formed by the diameter difference with the diameter portion 18 and fixed. As shown in FIG. 4, the nut 12 has two surfaces obtained by processing a part of a circular outer peripheral shape in parallel to ensure the workability at the time of tightening the nut.

  As shown in FIG. 1, in a state where the piston assembly 2 is disposed in the cylinder 1, the piston assembly 2 is slidable in the cylinder 1, and therefore, between the inner peripheral surface of the cylinder 1 and the outer peripheral surface of the ring body 4. There is a slight gap. Therefore, when the piston assembly 2 slides, a magnetic viscous fluid flows in the gap. This flow may be disturbed by the eccentricity of the ring body 4 or the rod 40. In this case, the damping force of the magnetorheological fluid shock absorber 100 varies, which adversely affects the controllability of the damping force. Become.

  In order to prevent such an adverse effect on the controllability of the damping force, an annular seal member 34 that slides on the inner peripheral surface of the cylinder 1 may be provided on the outer peripheral surface of the ring body 4 as shown in FIG. .

  The seal member 34 prevents passage of the magnetorheological fluid between the outer periphery of the ring body 4 and the inner periphery of the cylinder 1 when the piston assembly 2 slides. Therefore, the occurrence of variation in the damping force of the magnetorheological fluid shock absorber 100 can be prevented, and adverse effects on the controllability of the damping force can be prevented.

  By providing the seal member 34, the flow path through which the magnetorheological fluid passes is only the flow path 6. The coaxiality of the flow path 6 with respect to the rod 40 is determined by the relative position of the piston core 3 and the ring body 4. The relative position between the piston core 3 and the ring body 4 depends on the dimensional accuracy with the plate 11. Therefore, by controlling the dimensions of the piston core 3, the ring body 4, and the plate 11, the disturbance of the flow of the magnetorheological fluid passing through the flow path 6 can be prevented, and the damping force of the magnetorheological fluid buffer 100 can be prevented. Variations can be prevented.

  The operation of the magnetorheological fluid shock absorber 100 including the piston assembly 2 configured as described above will be described.

  When the piston assembly 2 slides in the cylinder 1, the magnetorheological fluid in the fluid chambers 30 and 31 on both sides of the piston assembly 2 moves through the flow path 6. At this time, when a current is passed through the coil 9, a magnetic force acts on the magnetorheological fluid, and the viscosity of the magnetorheological fluid changes. Thereby, the magnetorheological fluid shock absorber 100 generates a damping force corresponding to the magnitude of the viscosity resistance of the magnetorheological fluid flowing through the flow path 6.

  As the current of the coil 9 increases, the viscosity of the magnetorheological fluid increases and the damping force generated by the magnetorheological fluid shock absorber 100 also increases. As described above, the damping force generated by the magnetorheological fluid shock absorber 100 is adjusted by changing the current flowing through the coil 9 and changing the strength of the magnetic field acting on the flow path 6.

  Next, a method for assembling the magnetorheological fluid shock absorber 100 will be described in detail with reference to FIG.

  First, in the step (a), the coil 9 is wound around the recess 8 of the piston core 3 and the pin 10 connected to the coil 9 is installed in the groove 7. An electric wire 41 connected to a controller (not shown) is connected to the pin 10.

  In the next step (b), the groove portion 7 is filled with resin, and the pin 10 is fixed at a predetermined position. Here, a second O-ring 33 that prohibits the flow of the magnetorheological fluid between the filled resin and the piston core 3 is installed.

In the step (c), the inner peripheral surface 24 of the plate 11 on which the ring body 4 is crimped in advance is inserted in sliding contact with the small diameter portion 17 of the piston core 3, and then the nut 12 is screwed onto the male screw 20 of the piston core 3. The plate 11 is pressed against the stepped portion 2m and fixed. By fixing the plate 11 on which the ring body 4 is crimped to the piston core 3, the flow path 6 is reliably formed between the ring body 4 and the piston core 3.

  By such a process, the piston assembly 2 as shown in step (d) is formed, and the male screw 40 a of the rod 40 is screwed to the female thread 16 of the piston assembly 2, and the piston assembly 2 is fixed to the rod 40. The rod 40 is formed with a through hole penetrating the axis of the rod 40, and an electric wire 41 is disposed in the through hole and connected to a controller (not shown).

  As described above, according to the present invention, the flow path 6 through which the magnetorheological fluid passes is integrated by caulking the ring body 4 to the plate 11 and slidingly contacting the plate 11 with the piston core 3. The piston assembly 2 is formed by fixing with the above, and the flow path 6 is formed between the piston core 3 and the ring body 4. Further, the piston assembly 2 is fixed to the rod 40 by screwing the male screw 40 a of the rod 40 to the female screw 16 of the piston core 3.

  Therefore, since the magnetorheological fluid shock absorber 100 of the present invention has a simple structure, the assembly can be performed simply by assembling each member to the piston core 3 in order. And no special jigs such as molds are required for assembly.

  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 magnetorheological fluid shock absorber mounted on a vehicle.

It is sectional drawing which shows the magnetorheological fluid shock absorber 100 to which this invention is applied. 2 is a cross-sectional view showing a piston core 3. FIG. FIG. 6 is a cross-sectional view showing a plate 11. FIG. 4 is a cross-sectional view showing a nut 12. It is sectional drawing which shows the ring body. It is a figure explaining the assembly process of the piston assembly.

Explanation of symbols

1: cylinder 2: piston assembly 3: piston core 4: ring body 6: flow path 8: recess 9: coil 10: pin 11: plate 12: nut 30, 31: fluid chamber 40: rod 100: magnetorheological fluid buffer

Claims (1)

A cylinder filled with a magnetorheological fluid whose viscosity is changed by the action of a magnetic field;
A piston assembly that is slidably disposed in the cylinder, and that defines two fluid chambers in the cylinder;
A flow path formed in the piston assembly through which the magnetorheological fluid passes between the two fluid chambers by sliding of the piston assembly;
A coil housed in the piston assembly and causing a magnetic field to act on the flow path;
A rod to which the piston assembly is coupled;
In a method of manufacturing a magnetorheological fluid shock absorber comprising:
The piston assembly is
A cylindrical piston core comprising a large-diameter portion around which the coil is wound around a part of the outer peripheral surface, and a small-diameter portion having a smaller diameter than the large-diameter portion;
A cylindrical piston ring that forms the flow path between the piston core and the outer peripheral surface of the piston core by being arranged at a predetermined interval on the outer periphery of the piston core;
An annular plate provided integrally with the piston ring;
A nut for fixing the plate to the piston core;
The inner peripheral surface of the plate integrated with the piston ring is inserted into the outer peripheral surface of the small-diameter portion of the piston core while being in sliding contact with the central axis direction of the piston core,
A method of manufacturing a magnetorheological fluid shock absorber, wherein the nut is screwed into the piston core so as to press the plate against a step portion between the large diameter portion and the small diameter portion of the piston core. .