JP2006292096A - Shock absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shock absorber adjusting its damping force without using MR fluid. <P>SOLUTION: This shock absorber comprises: a cylinder 20 in which working fluid is sealed and a piston rod 31 are inserted and retracted from its one end face; and a piston 30 displaceable integrally with the piston rod longitudinally on an inner peripheral face of the cylinder. The shock absorber has a working fluid reservoir 32 communicated with the cylinder 20, and an exciter 33 mounted on the reservoir 32 and generating magnetic field, and the working fluid is partially separated and reserved in the reservoir 32 when the exciter 33 generates magnetic field. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a shock absorber for a vehicle, and more particularly to a shock absorber capable of adjusting a damping force of a shock absorber.

  The shock absorber provided in the vehicle suspension system quickly attenuates the vibration of a spring provided in parallel with the shock absorber and stabilizes the vehicle body. The shock absorber reduces the vibration of the spring by the viscous resistance when a working fluid such as oil having a predetermined viscosity passes through the orifice.

  Since the vibration generated in the vehicle greatly changes depending on the road surface condition, speed, and the like, a shock absorber that can adjust the damping force has been proposed (for example, see Patent Document 1). The shock absorber described in Patent Document 1 uses a magnetic fluid whose viscosity is reversibly changed with respect to a magnetic field (hereinafter referred to as MR fluid) as a working fluid, and the damping force acting on the spring can be adjusted by controlling the application of the magnetic field. It is said.

However, since the MR fluid has a high viscosity even when no magnetic field is applied, the damping with respect to vibration becomes rough. For this reason, a double-tube shock absorber that can simultaneously use MR fluid and a predetermined working fluid has been proposed (see, for example, Patent Document 2). In the shock absorber described in Patent Document 2, a predetermined working fluid is filled in an outer cylinder of a coaxial double pipe, and the inner cylinder is movably inserted into the working chamber of the outer cylinder. The internal cylinder is filled with MR fluid, and a piston having a coil is movably inserted. In such a shock absorber, it is possible to react sensitively to the impact by the working fluid having a relatively low viscosity, and it is possible to adjust the damping force acting on the spring by passing an electric current through the coil and adjusting the viscosity of the MR fluid.
US Pat. No. 5,284,330 JP 2002-195340 A

  However, since the MR fluid of the shock absorber described in Patent Document 1 or 2 is obtained by dispersing minute magnets in oil, the density of the magnets causes precipitation of the magnets. The MR fluid in which precipitation occurs and becomes non-uniform does not change to a desired viscosity even when a magnetic field is applied, and it is difficult to appropriately adjust the damping force.

  In addition, when the viscosity is adjusted so that the change in the viscosity of the MR fluid has a desired width, there is a problem that a large magnetic circuit and a magnetic shielding circuit are required.

  In view of the above problems, an object of the present invention is to provide a shock absorber capable of adjusting a damping force without using an MR fluid.

  In order to solve the above-described problem, a cylinder that is filled with a working fluid and that allows the piston rod to enter and exit from one end surface thereof, a piston that can be displaced integrally with the piston rod in the major axis direction on the inner peripheral surface of the cylinder, A shock absorber having a working fluid reservoir communicated with a cylinder, and an exciter (eg, magnetic field generator 33) provided in the reservoir (eg, sub-cylinder 32, reservoir chamber R4). When the magnetic field is generated, a part of the working fluid is separated from the working fluid and stored in the reservoir.

  According to the present invention, it is possible to provide a shock absorber capable of adjusting a damping force without using an MR fluid by separating a part of the working fluid.

  In one form of the shock absorber of the present invention, the magnetic ionic liquid is mixed with the working fluid, and when the exciter generates a magnetic field, the magnetic ionic liquid is accommodated in the reservoir.

  According to the present invention, since the magnetic ionic liquid is stored in the reservoir and the viscosity of the working fluid is lowered, the damping force can be adjusted.

  Further, in one embodiment of the shock absorber of the present invention, two or more kinds of magnetic ionic liquids having different ionization levels are mixed in the working fluid, and the magnetic material stored in the reservoir according to the strength of the magnetic field of the exciter. The amount of the ionic liquid varies. According to the present invention, the damping force can be adjusted according to the strength of the magnetic field.

  A shock absorber capable of adjusting a damping force without using an MR fluid can be provided.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view of a shock absorber according to the present embodiment. The shock absorber 1 is a so-called mono-cylinder type shock absorber composed of constituent members of a cylinder 20 and a piston 30.

  The cylinder 20 is filled with a working fluid 25, and an annular rod guide 26 is assembled on the inner peripheral surface of the upper end portion. A cylindrical piston rod 31 is inserted into the cylinder 20 from its upper end surface through a sealing material 27 and a rod guide 13 so as to be able to enter and exit liquid-tightly. The upper end portion of the piston rod 31 is fixed to a vehicle body (not shown).

  An annular piston 30 is assembled to the lower end portion of the piston rod 31 so as to be displaced integrally with the piston rod 31 in the long axis direction. The piston 30 is incorporated in the cylinder 20 so as to be liquid-tight and slidable on the inner peripheral surface thereof, and the cylinder 20 is partitioned into upper and lower chambers R1 and R2.

  At least two communication passages 30a are formed in the piston 30 as orifices that allow the upper and lower chambers R1 and R2 to communicate with each other and provide oil path resistance to the flow of hydraulic oil. A one-way valve is fixed to the communication passage 30a. One communication passage 30a permits only the flow of working fluid from the upper chamber R1 to the lower chamber R2, and the other communication passage 30a extends from the lower chamber R2 to the upper chamber. Only allow the working fluid to flow into R1.

  The cylinder 20 has a gas chamber 23 partitioned by a floating piston 21 on the end portion 22 side. The gas chamber 23 is filled with, for example, nitrogen gas, and absorbs fluctuations in the internal volume of the cylinder 20 caused by the piston rod 31 when the piston 30 moves up and down. The floating piston 21 is a piston that can move up and down in accordance with the volume fluctuation of the gas chamber 23.

  The cylinder 20 has a sub-cylinder 32 connected in communication, and the working fluid 25 can flow between the cylinder 20 and the sub-cylinder 32 through the communication path 32a. The sub cylinder 32 includes a magnetic field generator 33. The magnetic field generator 33 is a device that generates a magnetic field with a current coil or the like. The magnetic field generator 33 is connected to the damping force control device, and the generation of the magnetic field is controlled by the damping force control device, and thereby the damping force of the shock absorber 1 is controlled.

  The working fluid 25 will be described. The working fluid 25 is a fluid composed of at least one magnetic ionic liquid and oil generally used for a shock absorber (hereinafter referred to as normal oil). A magnetic ionic liquid is an ionic liquid consisting of only positive ions having positive charges and negative ions having negative charges, and since it has magnetism, it is strongly attracted to the magnets when the magnets are brought closer.

The magnetic ionic liquid is liquid at room temperature, has excellent high temperature stability, and is non-volatile. In addition, magnetic ionic liquids are scientifically stable and are unlikely to become separate liquids when mixed with other oils, and the viscosity and permeability of each oil are present independently on a macro scale. Therefore, the magnetic ionic liquid and the normal oil can be separated from the mixed state into the magnetic ionic liquid and the normal oil by using, for example, a magnet, and can be mixed again. As the magnetic ionic liquid, for example, 1-butyl-3-methyl-imidazolium iron chloride (III), bmim [FeCl ₄ ] is used.

  FIG. 2 is a view for explaining the physical properties of the working fluid 25. In FIG. 2, viscosity is shown as a physical property, but the same applies to other physical properties such as magnetic permeability. 2A shows a state where no magnetic field is applied to the working fluid 25, and FIG. 2B shows a state where a magnetic field is applied to the working fluid 25.

  In a state where no magnetic field is applied, the working fluid 25 is in a state where the magnetic ionic liquid 25a and the normal oil 25b are mixed, and exhibits a viscosity η2. When a magnetic field is applied to the working fluid 25 by the magnet 39, the magnetic ionic liquid 25a is attracted to the magnet 39, and the magnetic ionic liquid 25a and the normal oil 25b are separated.

  If the viscosity of the magnetic ionic liquid 25a is η1 and the viscosity of the normal oil 25b is η0, the magnetic ionic liquid 25a usually has a higher viscosity than the normal oil 25b, and therefore η1> η0. Further, the working fluid 25 in which the magnetic ionic liquid 25a and the normal normal oil 25b are mixed has a viscosity lower than η1 and higher than η0, so that η1> η2> η0.

  In the case of the shock absorber 1 of FIG. 1, when the magnetic field generator 33 generates a magnetic field, the magnetic ionic liquid 25a is accommodated in the sub-cylinder 32, and when the magnetic field generator 33 stops generating the magnetic field, The liquid will be released. Therefore, the viscosity of the working fluid can be adjusted by turning on and off the magnetic field of the magnetic field generator 33.

  That is, in the shock absorber 1, the piston 30 moves in the viscous resistance of the viscosity η2 when no magnetic field is generated. Further, when the magnetic field is generated, the magnetic ionic liquid 25a is accommodated in the sub-cylinder 32. Therefore, the piston 30 moves in the viscous resistance of the viscosity η0. That is, the damping force of the shock absorber 1 can be adjusted in two stages. The attracted magnetic ionic liquid 25a is redispersed by the operation of the shock absorber when the magnetic field disappears.

  As will be described later, it is preferable that the magnetic field generator 33 is provided with a magnetization shielding means, and the magnetic field generator 33 generates a magnetic field to prevent the shock absorber 1 or the surrounding metal from being magnetized.

  The damping force control device will be described. FIG. 3 shows a functional block diagram of the damping force control device. Information sent from the vehicle information input means 41 or the attenuation level setting means 42 is input to the damping force control device 43.

  An acceleration sensor (hereinafter referred to as G sensor 44) and a temperature sensor 45 are connected to the vehicle information input means 41. The G sensor 44 detects acceleration in the vertical direction and the front-rear direction of the vehicle. The damping force control device 43 generates a magnetic field in the magnetic field generation device 33 and attenuates the shock absorber 1 when traveling on a road with large irregularities based on the vertical acceleration sent from the vehicle information input means 41. Reduce power. In addition, when braking is applied to the vehicle and acceleration exceeding a predetermined threshold is detected in the front-rear direction, the magnetic field generator 33 does not generate a magnetic field, thereby increasing the damping force and decreasing the pitching amount. Can do.

  The temperature sensor 45 preferably detects the temperature of the working fluid, and detects, for example, the temperature near the shock absorber 1. When the temperature is high, the damping force control device 43 increases the damping force of the shock absorber 1 by making the magnetic field generation device 33 not generate a magnetic field (makes the working fluid highly viscous). Further, when the temperature is low, the damping force control device 43 generates a magnetic field in the magnetic field generation device 33 to reduce the damping force of the shock absorber 1 (makes the working fluid have a low viscosity). Therefore, in the shock absorber 1 using the working fluid mixed with the magnetic ionic liquid, the damping force can be automatically adjusted according to the running state and temperature of the vehicle.

  Further, the damping level setting means 42 enables the user (for example, a driver) to set the damping force of the shock absorber 1. For example, when the user prefers a low damping force (when he prefers a soft riding comfort), the magnetic field generator 33 generates a magnetic field to reduce the damping force of the shock absorber 1 (the working fluid has a low viscosity). Further, when the user prefers a high damping force (when he prefers a hard riding feeling), the damping force of the shock absorber 1 is increased by making the magnetic field generator 33 not generate a magnetic field (the working fluid is made highly viscous).

  As described above, the shock absorber according to the present embodiment can adjust the damping force by changing the viscosity of the working fluid by mixing the magnetic ionic liquid with the working fluid. The damping force can be set by the user according to his / her preference, and is automatically controlled in accordance with the traveling state and environment of the vehicle, so that a vehicle with excellent riding comfort can be provided.

[Modification of working fluid]
A modification of the working fluid will be described. In FIG. 2, the working fluid in which normal oil and one magnetic ionic liquid are mixed has been described. In this modification, a working fluid in which three kinds of magnetic ionic liquids are mixed will be described. As described above, the magnetic ionic liquid is unlikely to become another liquid even when mixed with other oils, and the viscosity and permeability of each oil are present independently on a macro basis. For this reason, the viscosity of the working fluid tends to be determined according to the viscosity of each magnetic ionic liquid constituting the working fluid.

  FIG. 4A is a diagram showing the viscosity and the degree of ionization of three types of magnetic ionic liquids mixed in the working fluid. The viscosity of the magnetic ionic liquid A was ηA, the viscosity of the magnetic ionic liquid B was ηB, and the viscosity of the magnetic ionic liquid C was ηC. Further, ηA> ηB> ηC> η0 (normal oil).

  The degree of ionization is magnetic ionic liquid A> magnetic ionic liquid B> magnetic ionic liquid C. Accordingly, the magnetic ionic liquid A having a high degree of ionization is affected by a magnetic force by a weak magnetic field, and the magnetic ionic liquid C having a low degree of ionization is not affected by a magnetic force unless it is a stronger magnetic field.

  FIG. 4B is a diagram showing the relationship between the configuration of the working fluid, which changes depending on the strength of the magnetic field of the magnetic field generator 33, and the viscosity and damping force. When no magnetic field is generated, the working fluid is composed of normal oil + magnetic ionic liquids A, B, and C. The viscosity of the working fluid when the strength of the magnetic field is zero is the largest because it contains the magnetic ionic liquid A having the highest viscosity.

  When a weak magnetic field is generated, the magnetic ionic liquid A is attracted to the magnetic field generator 33, so that the configuration of the working fluid is normal oil + magnetic ionic liquids B and C. Further, the viscosity of the working fluid in this case is the second largest because it does not include only the magnetic ionic liquid A having the highest viscosity.

  When a medium magnetic field is generated, the magnetic ionic liquids A and B are attracted to the magnetic field generator 33, so that the configuration of the working fluid is normal oil + magnetic ionic liquid C. Further, the viscosity of the working fluid in this case is small because it does not include the magnetic ionic liquid A having the highest viscosity and the magnetic ionic liquid B having the next highest viscosity.

  When a strong magnetic field is generated, the magnetic ionic liquids A to C are attracted to the magnetic field generator 33, so that the configuration of the working fluid is only normal oil. In this case, the viscosity of the working fluid is further reduced.

  Since the damping force of the shock absorber 1 is large when the viscosity of the working fluid is large and small when the viscosity is small, the damping force of the shock absorber can be adjusted by controlling the strength of the magnetic field.

  Therefore, when three types of magnetic ionic liquids are mixed as shown in FIG. 4A, the damping force control device can adjust the damping force of the shock absorber 1 in four stages.

  Next, a case where the damping force of the shock absorber 1 is maintained at the same level even when there is a temperature change using a working fluid whose viscosity can be adjusted in four stages will be described. FIG. 5A is a diagram illustrating an example of the relationship between the temperature detected by the temperature sensor 45 and the damping force of the shock absorber 1. If the detected temperature is high, the damping force control ECU 43 sets the magnetic field strength to zero. If the detected temperature is room temperature, the damping force control ECU 43 sets the strength of the magnetic field to be small. Similarly, if the detected temperature is a low temperature 1, the damping force control ECU 43 sets the strength of the magnetic field as medium, and if the detected temperature is a low temperature 2 (<low temperature 1), the damping force control ECU 43 generates a magnetic field. The intensity of the magnetic field of the device 33 is increased.

  That is, the strength of the magnetic field is controlled so that the higher the temperature, the higher the viscosity. If the temperature of the working fluid fluctuates, the viscosity of the working fluid will also change and the damping force of the shock absorber will also fluctuate. Therefore, the damping force of the shock absorber 1 can be kept stable.

  A case where the damping force of the shock absorber 1 is adjusted in four stages according to the user's preference will be described. FIG. 5B is a diagram showing an example of the relationship between the setting of the working fluid viscosity switch and the damping force of the shock absorber 1. When the user sets the changeover switch to high viscosity, the damping force control ECU 43 sets the magnetic field strength to zero. According to FIG.4 (b), when the intensity | strength of a magnetic field is 0, a damping force becomes large. When the user sets the changeover switch to the normal viscosity, the damping force control ECU 43 sets the strength of the magnetic field to be small. According to FIG. 4B, when the strength of the magnetic field is small, the damping force is medium. When the user sets the change-over switch to low viscosity 1, the damping force control ECU 43 sets the strength of the magnetic field to medium. According to FIG. 4B, the damping force is small when the strength of the magnetic field is medium. When the user sets the changeover switch to low viscosity 2 (<low viscosity 1), the damping force control ECU 43 increases the strength of the magnetic field. According to FIG. 4B, when the strength of the magnetic field is large, the damping force is further reduced.

  Therefore, as shown in FIG. 5B, if the user can select the viscosity of the working fluid, the damping force of the shock absorber 1 can be adjusted according to the user's preference.

[Modification of shock absorber]
So far, the embodiment has been described in which the damping force of the mono-cylinder type shock absorber is adjusted by the working fluid including the magnetic ionic liquid. However, the shock absorber type can accommodate the magnetic ionic liquid in a predetermined portion by a magnetic field. Any type may be used.

  FIG. 6A shows a schematic cross-sectional view of the twin tube type shock absorber 2. The shock absorber 2 has a double structure including a cylindrical inner cylinder 50 and a cylindrical outer cylinder 51. In FIG. 6 (a), the same components as those in FIG.

  The inner cylinder 50 is filled with the working fluid 25, and an annular rod guide 13 is assembled on the inner peripheral surface of the upper end portion. A cylindrical piston rod 31 is inserted into the inner cylinder 50 from its upper end surface through a sealing material 27 and a rod guide 26 so as to be able to enter and exit liquid-tightly. The upper end portion of the piston rod 31 is fixed to a vehicle body (not shown).

  An annular piston 30 is assembled to the lower end portion of the piston rod 31 so as to be displaced integrally with the piston rod 31 in the long axis direction. The piston 30 is incorporated in the inner cylinder 50 so as to be liquid-tight and slidable on the inner peripheral surface thereof, and the inner cylinder 50 is partitioned into upper and lower chambers R1, R2.

  At least two communication passages 30a are formed in the piston 30 as orifices that allow the upper and lower chambers R1 and R2 to communicate with each other and provide oil path resistance to the flow of hydraulic oil. A one-way valve is fixed to the communication passage 30a. One communication passage 30a permits only the flow of working fluid from the upper chamber R1 to the lower chamber R2, and the other communication passage 30a extends from the lower chamber R2 to the upper chamber. Only allow the working fluid to flow into R1.

  The outer cylinder 51 forms a reservoir chamber R3 between the outer cylinder 51 and the outer peripheral surface of the inner cylinder 50. Further, a disk-like base valve 54 is assembled so as to partition the lower lid 57 integral with the outer cylinder 51 and the lower end surface of the inner cylinder 50, thereby forming a reservoir chamber R4.

  The base valve 54 is formed with a communication passage 59 that allows the reservoir chamber R4 and the lower chamber R2 to communicate with each other, and the working fluid is filled through the communication passage 59. The base valve 54 is formed with a communication passage 55 that allows the reservoir chamber R3 and the reservoir chamber R4 to communicate with each other. Gases such as nitrogen and air are sealed in the reservoir chamber R3, and working fluid flows in through the communication passage 55.

  The inner volume of the inner cylinder 50 occupied by the working fluid changes due to the piston rod 31 entering and leaving the inner cylinder 50. This change in volume is caused by the inflow and outflow of the working fluid into the reservoir chamber R3 via the communication passages 59 and 55. Absorbed. The communication path 59 functions as an orifice that provides oil path resistance to the flow of hydraulic oil, and together with the communication path 30a, an appropriate damping force acts on the intrusion and withdrawal of the piston rod 31.

  The reservoir chamber R4 is provided with a magnetic field generator 33. In addition, the magnetic field generator 33 is provided with a magnetization shielding means 61, which prevents the shock absorber 2 or the surrounding metal from being magnetized by the magnetic field generator 33 generating a magnetic field. From the viewpoint of strength and cost, the shock absorber 2 is preferably formed of metal, but the reservoir chamber R4 may be formed of a material that is not magnetized, such as fiber reinforced resin.

  Further, as shown in FIG. 6B, the magnetic field generator 33 may be configured to be in direct contact with the working fluid. In FIG. 6B, the magnetic field generator 33 is inserted directly into the reservoir chamber R4. Since the working fluid can be directly magnetized, the magnetic field generator 33 can be downsized.

  In the shock absorber as shown in FIG. 6 (a) or (b), since the magnetic ionic liquid is accommodated in the reservoir chamber R4 when the magnetic field generator 33 generates a magnetic field, the viscosity of the working fluid, that is, attenuation of the shock absorber. You can adjust the power. The adjustment step of the damping force may be two steps, or may be four steps or more.

  Further, even a twin-tube shock absorber can accommodate a magnetic ionic liquid by providing a sub-cylinder as shown in FIG. FIG. 7A shows a schematic sectional view of a twin tube type shock absorber 3 having a sub cylinder. In FIG. 7A, the same components as those in FIG. 6 are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 7A, the reservoir chamber R4 and the sub-cylinder 32 are connected, and the working fluid is circulated through the communication path 32a. A magnetic field generator 33 is provided on the upper portion of the sub cylinder 32. When the shock absorber 3, particularly the sub cylinder 32, is made of metal, a magnetization shielding means is provided to prevent the shock absorber 2 or surrounding metal from being magnetized. Further, the sub cylinder 32 may be formed of a material that is not magnetized, such as resin.

  Further, as shown in FIG. 7B, the magnetic field generator 33 may be configured to be in direct contact with the working fluid. In FIG. 7B, the magnetic field generator 33 is inserted directly into the sub cylinder 32. Since the working fluid can be directly magnetized, the magnetic field generator 33 can be downsized.

  In the shock absorber as shown in FIG. 7A or 7B, the magnetic ionic liquid is accommodated in the sub-cylinder 32 when the magnetic field generator 33 generates a magnetic field, so that the viscosity of the working fluid, that is, the shock absorber is attenuated. You can adjust the power. The adjustment step of the damping force may be two steps, or may be four steps or more.

  As described above, the shock absorber according to the present embodiment can adjust the damping force by mixing the magnetic ionic liquid with the working fluid. The magnetic ionic liquid is unlikely to cause precipitation or the like unlike the MR fluid, so that the viscosity can be adjusted appropriately. In the case of a magnetic ionic liquid, the magnetic field generator 33 and the magnetic shielding circuit 61 can be reduced in size, so that the arrangement is easy and the increase in cost and vehicle weight can be suppressed.

It is a schematic sectional drawing of a shock absorber. It is a figure for demonstrating the physical property of a working fluid. It is a functional block diagram of a damping force control device. It is an example of the physical property of the magnetic ionic liquid mixed with the working fluid. It is a figure which shows the relationship between the strength of a magnetic field, and the damping force of a shock absorber. It is a schematic sectional drawing of a twin tube type shock absorber. It is a schematic sectional drawing of the twin tube type shock absorber which has a subcylinder.

Explanation of symbols

1, 2, 3 Shock absorber 20 Cylinder 21 Floating piston 23 Gas chamber 25 Working fluid 26 Rod guide 27 Sealing material 30 Piston 31 Piston rod 33 Magnetic field generator
50 Inner cylinder 51 Outer cylinder 54 Base valve 61 Magnetic shielding circuit

Claims (3)

A cylinder filled with a working fluid and allowing the piston rod to enter and exit from one end surface;
In a shock absorber having an inner peripheral surface in the cylinder in a major axis direction and a piston that can be displaced integrally with the piston rod,
A reservoir of the working fluid in communication with the cylinder;
An exciter provided in the reservoir,
When the exciter generates a magnetic field, a part of the working fluid is separated from the working fluid and stored in the reservoir.
Shock absorber characterized by that. A magnetic ionic liquid is mixed with the working fluid;
When the exciter generates a magnetic field, the magnetic ionic liquid is stored in the reservoir.
The shock absorber according to claim 1. Two or more kinds of magnetic ionic liquids having different degrees of ionization are mixed in the working fluid,
Depending on the strength of the magnetic field of the exciter, the amount of the magnetic ionic liquid stored in the reservoir varies.
The shock absorber according to claim 1 or 2.

Images