JP2004308780A - Damping force adjustment type damper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the power consumption in coils in a damping force adjustment type damper using the magnetic fluid. <P>SOLUTION: A piston 6 connected with a piston rod 7 is fitted in a cylinder 2 in which the magnetic fluid is sealed. Extension-side and contraction-side disc valves 21, 22 are mounted on extension-side and contraction-side passages 19 of the piston 6, and extension-side and contraction-side back-pressure chambers 25, 26 are mounted at back sides of the disc valves. The coils 12 are mounted in adjacent to the expansion-side and contraction-side auxiliary passages 29, 34 for circulating the magnetic fluid to the extension-side and contraction-side back-pressure chambers 25, 26. The magnetic field is made to act on the magnetic fluid of the extension-side and contraction-side auxiliary passages 29, 34 by energizing the coils 12, whereby the viscosity is changed and the damping force is adjusted, Here, as the valve opening pressures of the extension-side and contraction-side disc valves 21, 22 are adjusted by internal pressures of the extension-side and contraction-side back-pressure chambers 25, 26, a flow rate of the magnetic fluid to which the magnetic field is acted, can be reduced and the power consumption can be reduced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
[Industrial applications]
The present invention relates to a damping force-adjustable shock absorber using a magnetic fluid whose viscosity changes by the action of a magnetic field.
[0002]
[Prior art]
Generally, a damping force-adjustable shock absorber mounted on a suspension device of a vehicle such as an automobile is configured such that a piston having a piston rod connected thereto is slidably fitted in a cylinder filled with an oil liquid, The damping force adjustment valve is provided in the passage through which the oil flows through the sliding of the oil, and the damping force adjustment valve is operated by an actuator such as a proportional solenoid or a stepping motor to change the flow area of the oil liquid. The damping force is adjusted by causing the damping force.
[0003]
By the way, the conventional damping force adjusting type shock absorber has problems such as a delay in response of the actuator to a control current, a decrease in performance due to wear of the damping force adjusting valve, and a variation in performance due to a complicated structure.
[0004]
Therefore, as described in Patent Document 1, for example, a magnetic fluid whose viscosity changes by the action of a magnetic field is used instead of the oil liquid, and a coil is inserted in a passage through which the magnetic fluid flows instead of the damping force adjusting valve. Various damping force-adjusting shock absorbers have been proposed in which a damping force is adjusted by disposing the magnetic fluid on a magnetic fluid to change its viscosity.
[0005]
[Patent Document 1]
US Patent No. 6,095,486 [0006]
As a result, when the control current to the coil is reduced, the magnetic field acting on the passage is weakened, the viscosity of the magnetic fluid is reduced and the damping force is reduced, and when the control current is increased, the magnetic field acting on the passage is increased, The viscosity of the magnetic fluid increases, and the damping force increases.
[0007]
The damping force-adjusting shock absorber using such a magnetic fluid has a simple structure, and since the damping force is adjusted by changing the viscosity itself of the magnetic fluid, the response to the control current is fast, and the wear is reduced. It is possible to expect an operation and an effect that the mechanical performance hardly decreases due to the above.
[0008]
[Problems to be solved by the invention]
However, the conventional damping force-adjusting shock absorber using a magnetic fluid has the following problems. To sufficiently reduce the damping force on the soft side, it is necessary to increase the flow rate of the magnetic fluid. However, in order to generate a sufficiently large damping force for a large flow rate of the magnetic fluid, the control current to the coil must be controlled. And the capacity of the coil needs to be increased, which causes problems such as an increase in power consumption and an increase in the size of the coil.
[0009]
In this case, it is conceivable to increase the diameter or the content of the magnetic particles in the magnetic fluid, but the dispersion state of the magnetic fluid becomes unstable or the sealing material of the shock absorber is easily deteriorated. This can cause problems.
[0010]
The present invention has been made in view of the above points, and has a wide damping force adjustment range, low power consumption, and a damping force adjustment type using a magnetic fluid capable of achieving a small coil size. It is an object to provide a shock absorber.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a damping force-adjustable shock absorber according to the first aspect of the present invention includes a cylinder in which a magnetic fluid is sealed, a piston slidably fitted in the cylinder, and a piston. A piston rod connected to the valve body, a passage through which the magnetic fluid flows by sliding the piston, a valve body that controls the flow of the magnetic fluid in the passage to generate a damping force, and is provided on the back side of the valve body. A back pressure chamber that controls the opening of the valve body by applying an internal pressure in the valve closing direction of the valve body, and a sub-passage that allows a magnetic fluid to flow through the back pressure chamber by sliding of the piston. And a coil for applying a magnetic field to the sub-passage.
With this configuration, when a magnetic field is generated by energizing the coil, the viscosity of the magnetic fluid flowing through the sub passage changes due to the action of the magnetic field, and the flow resistance changes, so that the damping force can be adjusted. At this time, the internal pressure of the back pressure chamber changes and the valve opening pressure of the valve body can be adjusted.
According to a second aspect of the present invention, in the damping force adjusting type shock absorber according to the first aspect, the coil is provided on the piston rod.
With this configuration, it is possible to wire the coil conductor to the piston rod.
Also, in the damping force adjusting type shock absorber according to the third aspect of the present invention, in the configuration of the first or second aspect, the passage, the valve body, the back pressure chamber, the auxiliary passage, and the coil may each include the piston It is characterized in that two systems are provided which operate during the extension stroke and the contraction stroke of the rod.
With this configuration, it is possible to independently control the damping force during the extension stroke and the contraction stroke in accordance with the control current to the two coils.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
A first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, a damping force-adjustable shock absorber 1 according to the first embodiment is a single-cylinder shock absorber in which a free piston 3 is slidably fitted on the bottom side of a cylinder 2. , A cylinder 2 is defined by a free piston 3 into a gas chamber 4 on the bottom side and a fluid chamber 5 on the opposite side.
[0013]
A piston 6 is slidably fitted in the fluid chamber 5, and the piston 6 defines the inside of the fluid chamber 5 into two chambers, an upper cylinder chamber 5A and a lower cylinder chamber 5B. One end of a hollow piston rod 7 is connected to the piston 6, and the other end of the piston rod 7 is inserted into a guide seal 8 attached to the upper end of the cylinder 2 and extended to the outside. I have.
[0014]
A magnetic fluid is sealed in the fluid chamber 5, and a high-pressure gas is sealed in the gas chamber 4. A magnetic fluid is a fluid whose viscosity changes by the action of a magnetic field.For example, a magnetic fluid is known as a composite material in which ferromagnetic ultrafine particles are stably and uniformly dispersed in a liquid serving as a medium. The viscosity increases in accordance with.
[0015]
Next, details of the piston 6 and the piston rod 7 will be described with reference to FIG.
As shown in FIG. 2, an annular or cylindrical fixing member 9, a retainer 10, a bush 11, a coil 12, and a piston are formed on the outer periphery of a stepped small diameter portion 8 formed at one end of a piston rod 7. The main body 13, the bush 14, and the retainer 15 are fitted, and these are fixed by a cap 16 screwed to a screw portion at the tip of the small diameter portion 8. Further, a fixing member 17 is fitted around the outer periphery of the retainer 15 and the cap 16, and is fixed by a nut 18 screwed to a screw portion at the tip of the cap 16.
[0016]
The piston body 13 is provided with an extension-side passage 19 (passage) and a contraction-side passage 20 (passage) for communicating between the cylinder upper and lower chambers 5A and 5B. The expansion-side passage 19 is provided with an expansion-side disk valve 21 (valve element) that controls the flow from the cylinder upper chamber 5A to the cylinder lower chamber 5B to generate a damping force. A compression-side disk valve 22 (valve element) for controlling the flow from the chamber 5B to the cylinder upper chamber 5A to generate a damping force is provided.
[0017]
Cylindrical movable members 23 and 24 are slidably fitted to the outer circumferences of the fixed members 9 and 17, respectively, and one ends of the movable members 23 and 24 are respectively connected to the compression-side disk valve 22 and the extension-side disk valve. 21 in a liquid-tight manner, and on the back side of the expansion-side disk valve 21 and the compression-side disk valve 22, respectively, an expansion-side back pressure chamber 25 (back pressure chamber) and a compression-side back pressure chamber 26 (back pressure chamber). Is formed. The movable members 23 and 24 are pressed against the extension-side disc valve 21 and the contraction-side disc valve 22 by leaf springs 27 and 28, respectively.
[0018]
The extension-side back pressure chamber 25 communicates with the extension-side passage 19 via an extension-side sub-passage 29 (sub-passage) formed by a groove provided in the retainer 15 and a passage 30 formed in the fixing member 17. . Further, the extension side back pressure chamber 25 is communicated with the cylinder lower chamber 5B via a passage 31 formed in the fixing member 17. The passage 31 is provided with an orifice 32 and a disk valve 33 for controlling the flow from the extension side back pressure chamber 25 to the cylinder lower chamber 5B.
[0019]
Similarly, the contraction side back pressure chamber 26 communicates with the contraction side passage 20 via a contraction side auxiliary passage 34 (sub passage) formed by a groove provided in the retainer 10 and a passage 35 formed in the fixing member 9. Have been. Further, the compression-side back pressure chamber 26 is communicated with the cylinder upper chamber 5A via a passage 36 formed in the fixing member 9. The passage 36 is provided with an orifice 37 and a disc valve 38 for controlling the flow from the compression-side back pressure chamber 26 to the cylinder upper chamber 5A.
[0020]
The coil 12 is arranged adjacent to an extension side sub-passage 29 communicating with the extension side back pressure chamber 25 and a contraction side sub-passage 34 communicating with the contraction side back pressure chamber 26. The passages 29 and 34 and the periphery of the coil 12 are made of a magnetic material, and the magnetic field generated by the coil 12 acts on the magnetic fluid flowing through the extension-side and contraction-side sub-passages 29 and 34. The conducting wire 39 of the coil 12 is inserted into a bore 39 in the hollow piston rod 7, extends outside from the tip of the piston rod 7, and is connected to a controller (not shown).
[0021]
Next, the operation of the present embodiment configured as described above will be described.
During the extension stroke of the piston rod 7, the magnetic fluid in the cylinder upper chamber 5 </ b> A passes through the extension-side passage 19 and slides before the extension-side disc valve 21 is opened due to the sliding of the piston 6 in the cylinder 2. After flowing through the side auxiliary passage 29, the extension side back pressure chamber 25 and the passage 31 to the cylinder lower chamber 5B, a damping force is generated by the orifice 32 and the disk valve 33, and the extension side disk valve 21 is opened, the cylinder lower chamber is opened. 5B, and a damping force is generated by the extension-side disk valve 21. At this time, the volume change of the fluid chamber 5 due to the retreat of the piston rod 7 from the cylinder 2 is compensated for by the movement of the free piston 3 and the expansion of the high-pressure gas in the gas chamber 4.
[0022]
Then, the damping force can be adjusted by the control current from the controller to the coil 12. At the time of non-energization, the pressure of the magnetic fluid flowing into the extension side back pressure chamber 25 via the extension side sub-passage 29 acts in the valve closing direction of the extension side disk valve 21, and the valve opening pressure of the extension side disk bubble 21 is reduced. Since it rises, the damping force increases, and it becomes hard characteristics. When the coil 12 is excited by energization, the magnetic field acts on the magnetic fluid flowing through the extension side sub-passage 29 and its viscosity increases, so that the flow resistance of the extension side sub-passage 29 increases and the extension side back pressure increases. The pressure in the chamber 25 decreases. As a result, the valve opening pressure of the extension-side disk valve 21 decreases, and the damping force decreases, resulting in a soft characteristic.
[0023]
Also, during the compression stroke of the piston rod 7, the magnetic fluid on the cylinder lower chamber 5B side passes through the compression-side passage 20, and before the compression-side disk valve 22 is opened, the compression-side auxiliary passage 34, the compression-side back pressure chamber. After passing through the passage 26 and the passage 35 to the upper cylinder chamber 5A, a damping force is generated by the orifice 37 and the disk valve 38, and when the compression-side disk valve 22 is opened, it flows directly to the cylinder upper chamber 5A, and the compression-side disk valve 22 generates a damping force. At this time, a change in the volume of the fluid chamber 5 due to the penetration of the piston rod 7 into the cylinder 2 is compensated by the movement of the free piston 3 to compress the high-pressure gas in the gas chamber 4.
[0024]
Then, similarly to the extension stroke, the damping force can be adjusted by the control current from the controller to the coil 12. At the time of non-energization, the pressure of the magnetic fluid flowing into the compression side back pressure chamber 26 via the compression side auxiliary passage 34 acts in the valve closing direction of the compression side disk valve 22, and the valve opening pressure of the compression side disk bubble 22 is reduced. Since it rises, the damping force increases and it becomes hard. When the coil 12 is energized by energization, the magnetic field acts on the magnetic fluid flowing through the contraction side sub-passage 34 and its viscosity increases, so that the flow resistance of the contraction side sub-passage 34 increases and the compression side back pressure increases. The pressure in the chamber 26 decreases. As a result, the valve opening pressure of the contraction-side disk valve 22 decreases, and the damping force decreases, resulting in a soft characteristic.
[0025]
Thus, the damping force on the extension side and the contraction side can be adjusted by the control current to the coil 12. At this time, since the internal pressure of the extension side and compression side back pressure chambers 25 and 26 is changed by the flow resistance of the magnetic fluid flowing through the extension side and compression side sub-passages 29 and 34 to adjust the damping force, a magnetic field is applied. Since the flow rate of the fluid is reduced, the power consumption can be reduced while ensuring a sufficient adjustment range of the damping force. Since the capacity of the coil 12 is small, the coil 12 can be reduced in size and can be arranged in the piston rod portion, and the conducting wire 39 of the coil 12 is inserted into the bore 40 of the hollow piston rod 7. This makes it possible to easily connect to an external controller. Further, since it is not necessary to excessively increase the viscosity of the magnetic fluid, there is no problem of instability of the dispersion state of the magnetic fluid and deterioration of the sealing material of the shock absorber.
[0026]
Next, a second embodiment of the present invention will be described with reference to FIG. Note that the second embodiment has a structure generally similar to that of the first embodiment except that the configuration of a passage communicating with the extension-side back pressure chamber 25 is different. And only the different parts will be described in detail.
As shown in FIG. 3, the extension-side disc valve 21 is provided with a fixed orifice 52, and the upstream side of the extension-side back pressure chamber 25 is connected to the extension-side passage 19 via the fixed orifice 52. On the back side of the extension-side disc valve 21, there is provided a check valve 53 that allows only the flow from the extension-side passage 19 side of the fixed orifice 52 to the extension-side back pressure chamber 25 side.
[0027]
On the downstream side of the extension side back pressure chamber 25, an orifice 32 is formed by a passage 55 provided in the retainer 54, an extension side sub-passage 56 formed by a groove provided in the retainer 15, and a passage 50 provided in the fixing member 17. And a disc valve 33 communicating with the lower cylinder chamber 5B. The extension side sub-passage 56 is disposed adjacent to the coil 12, and the magnetic field generated by the coil 12 acts on the magnetic fluid flowing through the extension side sub-passage 56.
[0028]
Next, the operation of the present embodiment configured as described above will be described.
When the coil 12 is not energized, the internal pressure of the compression side back pressure chamber 26 increases on the compression side, as in the first embodiment, and the damping force has a hard characteristic. On the other hand, on the extension side, the magnetic fluid flowing through the extension-side passage 19 is subjected to the fixed orifice 52, the extension-side back pressure chamber 25, the passage 55, the extension-side sub-passage 56, and the passage before the extension-side disc valve 21 is opened. 50, but flows into the lower cylinder chamber 5B. However, since the flow resistance of the extension side sub-passage 56 downstream of the extension side back pressure chamber 25 is reduced by the non-energization of the coil 12, the extension side back pressure chamber 25, the opening pressure of the extension-side disc valve 21 decreases, and the damping force has a soft characteristic. Therefore, the damping force characteristics are compression-side hard and extension-side soft.
[0029]
When the coil 12 is excited by energization, the internal pressure of the compression-side back pressure chamber 26 decreases on the compression side, as in the first embodiment, and the damping force has a soft characteristic. On the other hand, on the extension side, the flow resistance on the downstream side of the extension side back pressure chamber 25 increases due to the magnetic field of the coil 12, so that the internal pressure of the extension side back pressure chamber 25 increases, and the valve opening pressure of the extension disc valve 21 increases. Increases, and the damping force has a hard characteristic. Therefore, the damping force is soft on the contraction side and hard on the extension side.
[0030]
In this way, in addition to the operation and effect of the first embodiment, when performing the damping force control based on the Skyhook theory, in order to enhance the response of the damping force control, the damping force characteristics on the extension side and the contraction side are changed. It is possible to execute so-called reversal control for reversing (adjusting the contraction side to the soft side when the extension side is the hard side, and adjusting the contraction side to the hard side when the extension side is the soft side).
[0031]
Next, a third embodiment of the present invention will be described with reference to FIG. The third embodiment has the same structure as the first embodiment except that the piston rod portion is different. Therefore, the same reference numerals are given to the same parts, and only different parts are described. This will be described in detail.
[0032]
As shown in FIG. 4, the damping force-adjustable shock absorber 41 according to the third embodiment includes two coils, an extension coil 44 and a compression coil 45, which are respectively housed in substantially cylindrical cases 42 and 43. ing. A case 43, a cylindrical retainer 46, and a case 42 are fitted around the outer periphery of the small diameter portion 8 of the piston rod 7, and are fixed by the cap 16. The fixing member 9, the piston body 13, The fixing member 17 is fitted and fixed by the nut 18.
[0033]
The extension side sub-passage 29 for communicating the extension side passage 19 with the extension side back pressure chamber 25 is formed between the extension side coil 44, the retainer 46 and the cap 16, and is connected to the passage 30 of the fixing member 17. ing. The periphery of the extension side sub-passage 29 and the extension side coil 44 is made of a magnetic material, and the magnetic field generated by the extension side coil 44 acts on the magnetic fluid flowing through the extension side sub passage 29.
[0034]
A contraction side auxiliary passage 34 for communicating the contraction side passage 20 with the contraction side back pressure chamber 26 is formed between the contraction side coil 45, the piston rod 7 and the retainer 46, and is connected to the passage 35 of the fixing member 9. Have been. A region around the contraction side sub-passage 34 and the contraction side coil 45 is made of a magnetic material, and the magnetic field generated by the contraction side coil 45 acts on the magnetic fluid flowing through the contraction side sub passage 34.
[0035]
The conductors 47 and 48 of the extension side coil 44 and the contraction side coil 45 are inserted into the bore 39 in the hollow piston rod 7, extended from the tip of the piston rod 7 to the outside, and sent to a controller (not shown). Connected.
[0036]
With this configuration, at the time of the extension stroke of the piston rod 7, the damping force is adjusted by changing the magnetic field acting on the magnetic fluid flowing through the extension side sub-passage 29 by the control current to the extension side coil 44. During the contraction stroke, the damping force can be adjusted by changing the magnetic field acting on the magnetic fluid flowing through the contraction side sub-passage 34 by the control current to the contraction side coil 45.
[0037]
Accordingly, in addition to the operation and effect of the first embodiment, the damping force on the extension side and the damping force on the contraction side are independently controlled by the control currents to the extension side coil 44 and the contraction side coil 45 in two systems. Therefore, the degree of freedom in adjusting the damping force can be increased. When performing damping force control based on the Skyhook theory, in order to enhance the response of the damping force control, a so-called reversal control that reverses the damping force characteristics on the extension side and the contraction side (when the extension side is the hard side, the contraction side is softened). Side, and when the extension side is the soft side, the contraction side is adjusted to the hard side).
[0038]
At this time, the extension side sub-passage 29 and the extension side coil 44 and the contraction side sub-passage 34 and the contraction side coil 45 are separated by the retainer 46 and are magnetically cut off. The magnetic fluid in the sub passage 34 is less likely to be affected, and the magnetic field of the contraction side coil 45 is less likely to affect the magnetic fluid in the extension side passage 29. Thereby, it is possible to prevent the extension-side and contraction-side damping forces from affecting each other, and it is possible to enhance the accuracy of the damping force control.
[0039]
Next, a fourth embodiment of the present invention will be described with reference to FIG. Note that the fourth embodiment has generally the same structure as the third embodiment except that the configuration of the passage communicating with the extension-side and compression-side back pressure chambers is different. The same reference numerals are given and only different portions will be described in detail.
[0040]
In the damping force adjusting type shock absorber 48 according to the fourth embodiment, the extension side back pressure chamber 25 is connected to the extension side passage 19 by a fixed orifice 49 provided in the extension side disc valve 21. The extension side sub-passage 29 is formed between the case 42 and the extension side coil 44, one end of which is connected to the extension back pressure chamber 25, and the other end of which is a passage 50 provided in the fixed member 17. And is connected to the cylinder lower chamber 5B via the orifice 32 and the disc valve 33.
[0041]
The compression side back pressure chamber 26 is connected to the compression side passage 20 by a fixed orifice 51 provided in the compression side disc valve 22. The contraction side sub-passage 34 is formed between the case 43 and the contraction side coil 45, one end of which is connected to the contraction side back pressure chamber 26, and the other end of which is a passage 52 provided in the fixing member 9. And is connected to the upper cylinder chamber 5A via an orifice 37 and a disc valve 38.
[0042]
With this configuration, during the extension stroke of the piston rod 7, the magnetic fluid flowing through the extension-side passage 19, before the extension-side disk valve 21 is opened, the fixed orifice 49, the extension-side back pressure chamber 25, and the extension fluid. The air flows into the cylinder lower chamber 5 </ b> B through the side auxiliary passage 29 and the passage 50, and a damping force is generated by the orifice 32 and the disc valve 33. Then, the magnetic field of the extension side coil 44 acts on the magnetic fluid flowing through the extension side sub-passage 29 to change the flow resistance, whereby the damping force can be adjusted.
[0043]
At this time, when the extension side coil 44 is de-energized, the flow resistance of the extension side sub-passage 29 downstream of the extension side back pressure chamber 25 decreases, and the damping force before the extension side disk valve 21 opens is reduced. The internal pressure of the extension side back pressure chamber 25 decreases, the valve opening pressure of the extension side disc valve 21 decreases, and the damping force has a soft characteristic. When the control current to the extension side coil 44 is increased, the flow resistance of the extension side sub-passage 29 downstream of the extension side back pressure chamber 25 increases due to the action of the magnetic field, and the extension side disk valve 21 is opened before opening. , The internal pressure of the extension-side back pressure chamber 25 increases, the valve opening pressure of the extension-side disc valve 21 increases, and the damping force has a hard characteristic.
[0044]
During the compression stroke of the piston rod 7, the magnetic fluid flowing through the compression-side passage 20 passes through the fixed orifice 51, the compression-side back pressure chamber 26, the compression-side auxiliary passage 34, and the passage 52 before the compression-side disc valve 22 is opened. The orifice 37 and the disc valve 38 generate a damping force. The damping force can be adjusted by applying the magnetic field of the contraction side coil 45 to the magnetic fluid flowing through the contraction side sub-passage 34 and changing the flow resistance.
[0045]
At this time, when the compression side coil 45 is not energized, the flow resistance of the compression side auxiliary passage 34 downstream of the compression side back pressure chamber 26 decreases, and the damping force before the compression side disk valve 22 is opened decreases. The internal pressure of the compression side back pressure chamber 26 decreases, the valve opening pressure of the compression side disc valve 22 decreases, and the damping force has a soft characteristic. When the control current to the contraction side coil 45 is increased, the flow resistance of the contraction side sub-passage 34 downstream of the contraction side back pressure chamber 26 increases due to the action of the magnetic field. , The internal pressure of the compression-side back pressure chamber 26 increases, and the opening pressure of the compression-side disc valve 22 increases, so that the damping force has a hard characteristic.
[0046]
In this manner, the damping force on the extension side and the damping force on the compression side can be independently controlled by the control currents to the two systems of the extension side coil 44 and the contraction side coil 45, and the same operation as in the third embodiment described above. , The effect can be achieved.
[0047]
【The invention's effect】
As described above in detail, according to the damping force adjusting type shock absorber according to the first aspect of the present invention, when a magnetic field is generated by energizing the coil, the viscosity of the magnetic fluid flowing through the sub passage changes due to the action of the magnetic field. Since the flow resistance changes, the damping force can be adjusted. At this time, the internal pressure of the back pressure chamber changes and the valve opening pressure of the valve body can be adjusted. As a result, the flow rate of the magnetic fluid for applying the magnetic field is reduced, so that the power consumption can be reduced while ensuring a sufficient adjustment range of the damping force, and the coil can be reduced in size.
According to the damping force-adjustable shock absorber according to the second aspect of the present invention, the conductor of the coil can be wired to the piston rod, and can be easily connected to an external controller.
Further, according to the damping force adjusting type shock absorber according to the third aspect of the invention, it is possible to independently control the damping force during the extension stroke and the contraction stroke according to the control current to the two coils. Become.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a damping force adjustable shock absorber according to a first embodiment of the present invention.
FIG. 2 is an enlarged view showing a main part of the apparatus shown in FIG. 1;
FIG. 3 is an enlarged longitudinal sectional view showing a main part of a damping force adjustable shock absorber according to a second embodiment of the present invention.
FIG. 4 is an enlarged longitudinal sectional view showing a main part of a damping force adjustable shock absorber according to a third embodiment of the present invention.
FIG. 5 is an enlarged longitudinal sectional view showing a main part of a damping force adjustable shock absorber according to a fourth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Damping force adjustable shock absorber 2 Cylinder 6 Piston 7 Piston rod 12 Coil 19 Extension side passage (passage)
20 Shrinkage side passage (passage)
21 Expansion side disc valve (valve element)
22 Retraction side disc valve (valve element)
25 Back pressure chamber on extension side (back pressure chamber)
26 Compression side back pressure chamber (back pressure chamber)
29 Extension side sub-passage (sub-passage)
34 Contraction side sub-passage (sub-passage)

Claims (3)

A cylinder in which the magnetic fluid is sealed, a piston slidably fitted in the cylinder, a piston rod connected to the piston, a passage through which the magnetic fluid flows by sliding the piston, A valve body that controls the flow of the magnetic fluid to generate a damping force, and is provided on the back side of the valve body, and controls the opening of the valve body by applying an internal pressure in the valve closing direction of the valve body. A damping force adjusting type comprising: a back pressure chamber, a sub-passage through which a magnetic fluid flows through the back pressure chamber by sliding the piston, and a coil that applies a magnetic field to the sub-passage. Shock absorber. The damping force adjustable shock absorber according to claim 1, wherein the coil is provided on the piston rod. The said passage, the said valve body, the said back pressure chamber, the said sub-passage, and the said coil are each provided with 2 systems | systems which operate at the time of the expansion stroke and the contraction stroke of the said piston rod, respectively. 3. The damping force adjustable shock absorber according to 2.

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