JP4729434B2 - Magnetorheological fluid shock absorber - Google Patents

Description

  The present invention relates to a magnetorheological fluid shock absorber using a magnetorheological fluid whose apparent viscosity changes due to the action of a magnetic field.

  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.

The assembly of the shock absorber described in Patent Document 1 is performed by applying a compressive load with a crimp die and connecting the magnetic flux ring and the end plate via the crimp member in a state where each member is disposed in the assembly die. Is called.
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 that is slidably disposed in the cylinder and defines the inside of the cylinder in two fluid chambers, and the piston A magnetic passage that is formed in the piston and through which the magnetorheological fluid passes by sliding, a coil that is housed inside the piston and that acts on a magnetic field in the passage, and a rod that is connected to the piston. A viscous fluid damper, wherein the piston is inserted into the rod and the coil is wound around the outer periphery of the piston core, and the outer periphery of the piston core is disposed at a predetermined interval on the outer periphery of the piston core. by and a piston ring forming part of the flow path, the outer periphery of the rod, the two annular stepped portion is formed between the, In order from the end side, a first fastening portion in which a male screw is formed, a positioning portion having a smooth outer periphery, and a second fastening portion in which a male screw is formed are formed, and the piston ring has an inner periphery that is the first portion of the rod. A plate portion fastened to the two fastening portions, and a ring portion surrounding the outer periphery of the piston core with a predetermined interval, and the piston core is fitted into the positioning portion of the rod and the first fastening portion And one end is fitted into a groove formed in the plate portion of the piston ring .

  According to the present invention, the piston forming the flow path through which the magnetorheological fluid passes is constituted by the piston core and the piston ring, both of which are directly 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.

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

(Embodiment 1)
A magnetorheological fluid shock absorber 100 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1A is a cross-sectional view of the magnetorheological fluid shock absorber 100, FIG. 1B is a view taken in the direction of arrow B in FIG. 1A, and FIG. 1C is a view taken in the direction of arrow C in FIG. It is. Note that the cross-sectional view shown in FIG. 1A is an A-O-A cross section in FIG.

  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 cylindrical cylinder 1 and a piston 2 that is slidably disposed in the cylinder 1 and defines the inside of the cylinder 1 into two fluid chambers 3 and 4.

  The piston 2 is connected to one end of the rod 5. The other end of the rod 5 extends to the outside of the cylinder 1.

  A magnetorheological fluid is sealed in the cylinder 1. 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. 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.

  A gas chamber (not shown) is provided in the cylinder 1 to compensate for volume changes in the cylinder 1 due to the entry and withdrawal of the rod 5.

  The piston 2 includes a piston core 6 fastened to the distal end side of the rod 5 and a piston ring 7 fastened to the proximal end side of the rod 5. The piston core 6 and the piston ring 7 are made of a magnetic material.

  By forming two annular stepped portions 5a and 5b on the outer periphery of one end of the rod 5, a first fastening portion 5c, a positioning portion 5d, and a second fastening portion 5e having a small diameter are formed from the tip side. Male screws are formed on the first fastening portion 5c and the second fastening portion 5e, and the outer periphery of the positioning portion 5d is formed in a smooth shape.

  As shown in FIG. 2, the piston core 6 is a substantially cylindrical member having a through hole 6f penetrating in the axial direction. By forming an annular step portion 6g on the inner periphery of the through hole 6f, a smooth positioning hole 6a and a fastening portion 6b having a smaller diameter than the positioning hole 6a and a female screw are formed. .

  The rod 5 and the piston core 6 are positioned coaxially when the positioning portion 5d and the positioning hole 6a are closely fitted, and are fastened when the first fastening portion 5c and the fastening portion 6b are engaged with each other. Is done.

  The piston ring 7 is disposed on the outer periphery of the piston core 6 with a predetermined interval, and is fastened to the second fastening portion 5 e of the rod 5. Thereby, between the outer periphery of the piston core 6 and the inner periphery of the piston ring 7, the annular flow path 8a which comprises a part of flow path through which a magnetorheological fluid passes is formed.

  Hereinafter, the piston ring 7 will be described.

  As shown in FIG. 3, the piston ring 7 includes a plate portion 7 a that is fastened to the rod 5 and slides with the inner periphery of the cylinder 1, and a ring portion 7 b that surrounds the outer periphery of the piston core 6 with a predetermined interval.

  The plate portion 7a has a through hole 7h penetrating in the axial direction, and a fastening portion 7i having a female screw is formed on the inner periphery of the through hole 7h. When the fastening portion 7i and the second fastening portion 5e of the rod 5 are screwed and meshed, the rod 5 and the piston ring 7 are fastened.

  The outer periphery 7c of the plate portion 7a slides with the inner periphery of the cylinder 1, and a sealing material (not shown) for preventing the passage of the magnetorheological fluid between the outer periphery 7c and the inner periphery of the cylinder 1 is provided on the outer periphery 7c. Provided.

  An annular groove 7d is formed on the surface of the plate portion 7a facing the piston core 6, and one end of the piston core 6 is fitted into the groove 7d.

  The ring portion 7b is formed integrally with the outer edge portion of the plate portion 7a and extending in parallel with the inner periphery of the cylinder 1. Between the inner periphery of the ring portion 7b and the outer periphery of the piston core 6 is an annular flow path 8a.

  Annular grooves 7f and 7g are respectively formed on both surfaces of the plate part 7a, and a part of the annular grooves 7f and 7g communicate with each other, whereby a plurality of arc-shaped through-holes 7e (this embodiment) are formed in the plate part 7a. In the form of 4).

  Thereby, the fluid chamber 3 and the fluid chamber 4 communicate with each other by the annular flow path 8a and the arc-shaped through path 7e. The annular flow path 8a and the through path 7e constitute a flow path 8 through which the magnetorheological fluid passes.

  As described above, the flow path 8 communicates with the fluid chamber 3 through the through hole 7e on the base end side of the rod 5, but opens in an annular shape with respect to the fluid chamber 4 on the tip end side of the rod 5. This is because the piston core 6 and the piston ring 7 are both directly fastened to the rod 5, so that no member for fixing the piston 2 is required on the rod 5 tip side, and the tip of the piston ring 7, that is, the ring This is because the tip of the portion 7b becomes a free end. When the flow path 8 opens in an annular shape with respect to the fluid chamber 4, the magnetorheological fluid in the fluid chamber 4 easily flows into the flow path 8.

  As described above, the piston core 6 and the piston ring 7 are fastened to the tip of the rod 5, whereby the flow path 8 that connects the fluid chamber 3 and the fluid chamber 4 is formed in the piston 2. The magnetorheological fluid passes through the flow path 8 by sliding inside.

  The annular groove 7f formed in the plate portion 7a is preferably opened in a tapered shape with respect to the fluid chamber 3, as shown in FIG. With this configuration, the plurality of through holes 7 e formed in the plate portion 7 a are opened in a tapered shape with respect to the fluid chamber 3. This makes it easier for the magnetorheological fluid in the fluid chamber 3 to flow into the flow path 8, and prevents foreign matter such as iron from accumulating on the surface of the plate portion 7a facing the fluid chamber 3.

  A coil 9 is wound around the outer periphery of the piston core 6. Specifically, an annular step portion 6c is formed on the outer periphery of the piston core 6, and the coil 9 is disposed in a small diameter portion on the outer periphery of the piston core 6 and is formed of an annular shape made of the step portion 6c and a magnetic material. It is clamped by the yoke 10.

  Alternatively, the yoke 10 and the piston core 6 may be integrally formed so that an annular recess is formed on the outer periphery of the piston core 6 and the coil 9 may be accommodated in the recess.

  Thus, the coil 9 is housed inside the piston 2 and is formed facing the flow path 8. Accordingly, when a current is passed through the coil 9, the coil 9 generates a magnetic force, and the magnetic force flows through the flow path 8 through the magnetic path formed by the piston core 6, the yoke 10, and the ring portion 7b. Will act.

  A recess 6 d that opens toward the fluid chamber 4 is formed at the tip of the piston 2, that is, the tip of the piston core 6. A hollow portion 5f that penetrates the rod 5 in the axial direction and a communication hole 6e that is formed in the piston core 6 and opens to the step portion 6c communicate with the recess 6d. The lead wire 9a of the coil 9 is guided to the recess 6d through the communication hole 6e, and is guided to the outside of the rod 5 through the annular washer 12 disposed on the bottom surface of the recess 6d and the hollow portion 5f of the rod 5. And connected to a controller (not shown) mounted on the vehicle. In this way, the drive current from the controller is input to the coil 9.

  The concave portion 6d is filled with a sealing material 13 such as an adhesive or a resin so that the magnetorheological fluid does not flow outside through the concave portion 6d of the piston core 6 and the hollow portion 5f of the rod 5. Since the fluid chamber 4 and the rod 5 can be isolated by filling the concave portion 6d that opens toward the fluid chamber 4 with the seal material 13, it is necessary to fill the hollow portion 5f of the rod 5 with the seal material 13 There is also no need to consider the seal between the piston core 6 and the rod 5. Thus, high airtightness can be obtained only by filling the recess 6d with the sealing material 13.

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

  When the piston 2 slides in the cylinder 1, the magnetorheological fluid in the fluid chambers 3 and 4 on both sides of the piston 2 moves through the flow path 8. 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 8.

  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 8.

  In addition, when the axis | shaft of the flow path 8 and the rod 5 has shifted | deviated, disorder will arise in the flow of the magnetorheological fluid which passes the flow path 8. FIG. In that case, the damping force of the magnetorheological fluid shock absorber 100 varies and adversely affects the controllability of the damping force.

  Therefore, high accuracy is required for the coaxiality between the flow path 8 and the rod 5. The coaxiality of the flow path 8 with respect to the rod 5 is determined by the relative positions of the piston core 6 and the piston ring 7. The piston core 6 is positioned coaxially with respect to the rod 5 by fitting the positioning hole 6 a to the positioning portion 5 d of the rod 5. Therefore, the coaxiality of the flow path 8 with respect to the rod 5 depends on the dimensional accuracy of the fastening portion between the piston ring 7 and the rod 5. For this reason, by controlling the size of the fastening portion between the piston ring 7 and the rod 5, the coaxiality of the flow path 8 with respect to the rod 5 can be maintained with high accuracy, and variation in the damping force of the magnetorheological fluid shock absorber 100 can be maintained. Can be prevented.

  Next, a method for assembling the magnetorheological fluid shock absorber 100 will be described.

  First, before assembling the piston 2 to the rod 5, as shown in FIG. 4, the coil 9 wound annularly around the outer periphery of the piston core 6 is inserted and brought into contact with the step portion 6c. Next, the annular yoke 10 is inserted into the outer periphery of the piston core 6, and the coil 9 is sandwiched between the step portion 6 c and the yoke 10.

  Next, the annular washer 12 is disposed on the bottom surface of the recess 6d. Then, the lead wire 9a of the coil 9 is inserted into the communication hole 6e, led to the recess 6d, and passed through the hole 12a of the washer 12. In this state, the sealing material 13 is injected into the recess 6d, and the sealing material 13 is filled into the recess 6d and the communication hole 6e.

  The sealing material 13 is filled by sealing the gap from the back of the washer 12 so that the sealing material 13 does not leak from the gap between the hole 12a of the washer 12 and the lead wire 9a.

  As described above, the piston core assembly 15 shown in FIG. 4 can be obtained.

  In order to assemble the piston 2 to the rod 5, first, the piston ring 7 is inserted into the rod 5 from the tip side, and the fastening portion 7 i of the plate portion 7 a is screwed to the second fastening portion 5 e of the rod 5. Thereby, the piston ring 7 is fastened to the rod 5.

  Next, the piston core assembly 15 is inserted into the rod 5 from the tip side, the positioning hole 6a of the piston core 6 is fitted into the positioning portion 5d of the rod 5, and the fastening portion 6b is connected to the first fastening portion 5c of the rod 5. Screwed on. Thereby, the piston core 6 is fastened coaxially with the rod 5. An O-ring 16 is provided on the outer periphery of the positioning portion 5d of the rod 5 to prevent leakage of the magnetorheological fluid between the rod 5 and the piston core 6.

  Thus, by fastening the piston ring 7 and the piston core 6 to the rod 5, the piston 2 is fixed to the rod 5, and a flow path 8 is formed in the piston 2.

  Finally, the magnetic viscous fluid shock absorber 100 can be obtained by inserting the rod 5 to which the piston 2 is fixed into the cylinder 1.

  As described above, according to the first embodiment, the piston 2 which divides the inside of the cylinder 1 into the fluid chambers 3 and 4 and forms the flow path 8 is composed of the piston core 6 on the tip side of the rod 5 and the five rods. The piston core 6 and the piston ring 7 are both directly fastened to the rod 5. That is, the piston core 6 and the piston ring 7 in the first embodiment are members constituting the piston 2 and also have a function of a fastening member for fastening the piston 2 to the rod 5.

  Thus, the magnetorheological fluid shock absorber 100 according to the first embodiment has a simple structure with a small number of parts. Therefore, the assembly of the magnetorheological fluid shock absorber 100 does not require a special jig such as a mold at the time of assembly, and can be performed only by assembling the piston ring 7 and the piston core 6 in order from the distal end side of the rod 5. Therefore, it can be performed easily.

  Other aspects of the first embodiment will be described below.

  As shown in FIG. 5, an annular dust wiper 18 that slides with the inner periphery of the cylinder 1 may be provided on the outer periphery of the ring portion 7 b. Foreign matter such as iron powder easily adheres to the inner periphery of the cylinder 1, and in this case, the slidability of the piston 2 with respect to the inner periphery of the cylinder 1 is deteriorated. However, by providing the dust wiper 18, foreign matter adhering to the inner periphery of the cylinder 1 can be removed, so that the slidability of the piston 2 can be kept good.

  In the first embodiment, the piston core 6 is fastened to the front end side of the rod 5 and the piston ring 7 is fastened to the base end side of the rod 5. However, the piston core 6 is connected to the base end side of the rod 5 and the piston ring 7 is connected to the rod. Of course, it is also possible to be constructed so as to be fastened to the tip side. In this case, the flow path 8 opens in an annular shape with respect to the fluid chamber 3 on the rod base end side, and the recess filled with the sealing material 13 is formed at the tip of the piston ring 7. Will be.

(Embodiment 2)
Next, the magnetorheological fluid shock absorber 200 according to the second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a cross-sectional view of the magnetorheological fluid damper 200.

  Since the configuration of the magnetorheological fluid shock absorber 200 according to the second embodiment is substantially the same as that of the magnetorheological fluid shock absorber 100 according to the first embodiment described above, differences will be mainly described. The same components as those of the magnetorheological fluid shock absorber 100 are denoted by the same reference numerals and description thereof is omitted.

  A difference between the magnetorheological fluid shock absorber 100 of the second embodiment and the magnetorheological fluid shock absorber 100 is that the piston ring 7 is made of a non-magnetic material and is annular on the inner periphery of the ring portion 7b of the piston ring 7. The magnetic ring 20 is provided.

  As described above, the piston ring 7 in the magnetorheological fluid shock absorber 200 is composed of the magnetic material only in the inner periphery of the ring part 7b facing the flow path 8 through which the magnetorheological fluid passes, and the other part is a nonmagnetic material. Consists of.

  The piston ring 7 is mainly composed of aluminum which is a nonmagnetic material. The magnetic ring 20 is press-fitted into the inner periphery of the ring portion 7 b and is assembled integrally with the piston ring 7.

  The assembly of the magnetorheological fluid damper 200 is performed by sequentially fastening the assembled piston ring 7 and piston core 6 to the rod 5.

  As described above, in the second embodiment, only the portion facing the flow path 8 in the piston ring 7 is made of a magnetic material, and the other portions are made of a light non-magnetic material. Therefore, according to the second embodiment, the weight of the piston 2 can be reduced while forming a magnetic passage around the flow path 8, so that the damping force generated by the magnetorheological fluid shock absorber 200 is not impaired. The operation of the piston 2 can be improved.

  Further, since the outer periphery of the piston 2 is made of a nonmagnetic material, the magnetic force flowing through the magnetic passage around the flow path 8 does not leak to the outside of the cylinder 1 and is disposed around the magnetorheological fluid buffer 200. It is possible to prevent adverse effects due to magnetic force on other devices.

  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.

(A) It is sectional drawing which shows the magnetorheological fluid shock absorber 100 in Embodiment 1 of this invention. (B) It is a B arrow line view in Fig.1 (a). (C) It is a C arrow line view in Fig.1 (a). 2 is a cross-sectional view showing a piston core 6. FIG. It is sectional drawing which shows the piston ring. 2 is a cross-sectional view showing a piston core assembly 15. FIG. It is a figure which shows the other aspect of the magnetorheological fluid shock absorber 100 in Embodiment 1 of this invention. It is sectional drawing which shows the magnetorheological fluid shock absorber 200 in Embodiment 2 of this invention.

Explanation of symbols

100, 200 Magnetorheological fluid shock absorber 1 Cylinder 2 Pistons 3, 4 Fluid chamber 5 Rod 6 Piston core 7 Piston ring 7a Plate portion 7b Ring portion 8 Flow path 9 Coil 10 Yoke 13 Sealing material 15 Piston core assembly 20 Magnetic ring

Claims (7)

A cylinder filled with a magnetorheological fluid whose viscosity is changed by the action of a magnetic field;
A piston slidably disposed within the cylinder and defining two fluid chambers within the cylinder;
A flow path formed in the piston and through which the magnetorheological fluid passes by sliding of the piston;
A coil that is housed in the piston and causes a magnetic field to act on the flow path;
A rod to which the piston is coupled;
A magnetorheological fluid damper comprising:
The piston is
A piston core inserted into the rod and wound with the coil on the outer periphery;
And a piston ring forming part of the flow path between the outer periphery of the piston core by being arranged at a predetermined interval on an outer periphery of the piston core,
By forming two annular step portions on the outer periphery of the rod, a first fastening portion in which a male screw is formed, a positioning portion having a smooth outer periphery, and a second in which a male screw is formed in order from the tip side. A fastening part is formed,
The piston ring is
A plate portion whose inner periphery is fastened to the second fastening portion of the rod;
A ring part surrounding the outer periphery of the piston core with a predetermined interval,
The piston core is fitted to the positioning portion of the rod and fastened to the first fastening portion, and one end is fitted to a groove portion formed in the plate portion of the piston ring. Magnetorheological fluid shock absorber. The tip of the piston ring is a free end,
2. The magnetorheological fluid shock absorber according to claim 1, wherein the flow path is annularly opened with respect to the fluid chamber on a free end side of the piston ring. 3. The magnetorheological fluid buffer according to claim 1, wherein the two fluid chambers communicate with each other by forming a through-hole communicating with a part of the flow path in the plate portion. vessel. The piston ring is made of a nonmagnetic material,
The magnetorheological fluid shock absorber according to any one of claims 1 to 3, wherein an annular magnetic ring is press-fitted into an inner periphery of the ring portion. The magnetorheological fluid shock absorber according to claim 3 , wherein the through hole of the plate portion opens in a tapered shape with respect to the fluid chamber. The magnetorheological fluid shock absorber according to any one of claims 1 to 5 , wherein a dust wiper that slides on an inner periphery of the cylinder is provided on an outer periphery of the piston ring. A recess that opens toward the fluid chamber is formed at the tip of the piston,
The rod is formed with a hollow portion that penetrates in the axial direction and communicates with the concave portion,
The lead wire of the coil is guided to the outside of the rod by passing through the concave portion and the hollow portion of the rod,
The magnetorheological fluid shock absorber according to any one of claims 1 to 6 , wherein the recess is filled with a sealing material.