JP2017145872A - Relative motion member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a relative motion member which has a plurality of members relatively moving, and which can control frictional resistance when the members move.SOLUTION: A relative motion member includes a first member made of an insulator, a second member relatively rotatable to the first member and made of an insulator, and a lubricant filled in a space between the first member and the second member. The lubricant includes an ER fluid, and in the space, one or a plurality of electrodes for forming an electric field including a vertical direction component with respect to a relative motion direction of the first member and the second member are respectively provided in the first member and the second member.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a relative motion member, and more particularly to a relative motion member applicable to a thrust slide bearing that can be used for a suspension in an automobile.

  A strut suspension used for a front wheel of a four-wheeled vehicle generally has a structure in which a coil spring is combined with a strut assembly in which a hydraulic shock absorber is built in an outer cylinder integrated with a main shaft. In such suspension, there are a type in which the piston rod of the strut assembly rotates and a type in which the piston rod does not rotate when the strut assembly rotates together with the coil spring in the steering operation. In order to allow smooth rotation of the strut assembly, a synthetic resin thrust sliding bearing is used between the mounting mechanism of the strut assembly to the vehicle body and the upper spring seat member made of sheet metal that receives one end of the coil spring. (For example, refer to Patent Documents 1 and 2).

  In such a thrust sliding bearing, in order to improve the steering feeling when steering the steering wheel, it is desired to operate with the lowest possible frictional resistance against the input from the steering wheel. On the other hand, with respect to input from the road surface (disturbance caused by overcoming obstacles, etc.), a certain level of frictional resistance is required in order to improve the straight running stability.

Japanese Patent No. 5157210 Japanese Patent No. 5673110

  However, conventional thrust plain bearings have a friction specification that gives priority to either the steering feeling or the straight running stability in response to the above conflicting requirements. It was difficult to achieve both. Therefore, if the frictional resistance can be controlled as necessary, the frictional resistance can be reduced during steering, and the frictional resistance can be increased during straight traveling, which is useful because the above problems can be solved. It is.

  On the other hand, such control of frictional resistance may be desired not only in thrust sliding bearings for automobile suspensions but also in those in which a plurality of members move relative to each other. It would be useful if resistance control could be realized.

  The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is a relative motion member in which a plurality of members relatively move, and a relative motion capable of controlling a frictional resistance during the motion of the plurality of members. It is to provide a member.

  The relative motion member of the present invention includes a first member made of an insulator, a second member made of an insulator that can move relative to the first member, and sliding between the first member and the second member. A relative motion member having a lubricant interposed between the surfaces, wherein the lubricant contains an ER fluid, and the relative motion direction of the first member and the second member is between the sliding surfaces. One or a plurality of electrodes for forming an electric field including a vertical direction component is provided on each of the first member and the second member.

  When an electric field is applied, the ER fluid forms a chain aggregate parallel to the electric field. In addition, the ability of the ER fluid to form chain aggregates parallel to the electric field varies depending on the magnitude of the applied electric field strength. Specifically, when the electric field strength is large, the aggregate forming ability is large, and conversely, when the electric field strength is small, the aggregate forming ability is small. Therefore, in the relative motion member of the present invention, the ER fluid is included in the lubricant that is interposed between the sliding surfaces of the first member and the second member, so that the electrodes provided on the first member and the second member can be connected to each other. Further, when an electric field including a direction component perpendicular to the relative motion direction of the first member and the second member is formed, the ER fluid forms a chain aggregate parallel to the electric field, and the viscosity of the lubricant increases. To do. As a result, viscous resistance is generated in the lubricant, and braking is applied to the relative movement of the first member and the second member. Further, the viscous resistance of the lubricant changes according to the magnitude of the electric field strength. Therefore, by adjusting the electric field strength between the electrodes, it is possible to control the frictional resistance with respect to the relative movement of the first member and the second member.

In the relative motion member of the present invention, when the first member and the second member are relatively moved under a condition in which a voltage applied to the one or more electrodes is constant, the sliding is performed by the one or more electrodes. It is preferable that the electric field strength formed between the moving surfaces changes. In such a configuration, even if the voltage applied to the electrode is constant, the first member and the second member move relative to each other, so that the viscosity of the lubricant is changed by the change in electric field strength formed between the sliding surfaces. The resistance changes, and it becomes possible to change the frictional resistance against the relative movement of the first member and the second member. Examples of the configuration in which the electric field strength formed between the sliding surfaces is changed by the one or more electrodes include the following configurations.
(1) In the direction perpendicular to the relative movement direction of the first member and the second member, a plurality of at least one electrode of the first member and the second member are provided in a discrete state, and The overlapping area of the electrodes is provided to change in accordance with the relative movement of the first member and the second member. Since the electric field strength between the pair of electrodes increases in proportion to the area of the opposing electrodes, in this configuration, the electric field strength is changed by changing the overlapping area of the electrodes according to the relative movement of the first member and the second member. Changes.
(2) The electrodes of the first member and the second member are arranged such that when the first member and the second member move relative to each other in a certain direction, the first member and the electrode between the one electrode and the other electrode The integral value along the relative movement stroke of the second member is provided to change. Since the electric field strength between the pair of electrodes decreases in inverse proportion to the distance between the electrodes facing each other, in this configuration, along the relative movement process of the first member and the second member at the distance between one electrode and the other electrode. The electric field strength changes as the integrated value changes.

  In the relative motion member of the present invention, when the first member and the second member are relatively moved in the first direction with respect to a certain position, the first member and the second member are relatively moved in a second direction different from the first direction. Sometimes, it is preferable that the electric field intensity change mode has symmetry or asymmetry in at least a part of the movable range of the first member and the second member in the first direction and the second direction. The electric field strength is asymmetric when the first member and the second member are relatively moved in a first direction from a certain reference position and when the first member and the second member are relatively moved in a second direction different from the first direction. In this case, the change mode of the viscous resistance of the lubricant is different in at least a part of the movable range of the first member and the second member. Conversely, when the electric field strength has symmetry, the change mode of the viscous resistance of the lubricant is the same. That is, the integral value has symmetry or asymmetry, so that the first member and the second member at a certain reference position relatively move in either the first direction or the second direction, thereby causing the viscosity of the lubricant. The change mode of the resistance can be the same or different. As a result, it can be set as the structure that the change aspect of the frictional resistance according to the relative movement direction of the 1st member and the 2nd member is the same or changes in a certain reference position. For example, the first member and the second member at a certain reference position can be configured such that the frictional resistance increases in the first direction and the frictional resistance decreases in the second direction. Therefore, in a device having a plurality of members that move relative to each other, it is possible to meet various demands regarding the control of the frictional resistance of the plurality of members.

  The relative motion member of the present invention is preferably used as a thrust slide bearing for a suspension of an automobile because it enables control of frictional resistance with respect to steering of a steering wheel as required. For example, it is possible to control such that the frictional resistance is reduced during steering of the steering wheel and the frictional resistance is increased during straight traveling.

The perspective view which shows one Embodiment of the thrust slide bearing to which the relative motion member of this invention is applied. FIG. 2 is a top view of the thrust slide bearing shown in FIG. Sectional drawing along the AB line | wire of FIG. Sectional drawing which shows the aspect which made the position of the electrode of a lower case differ from the position shown in FIG. The schematic diagram which shows the state which looked at the electrode provided in upper case (5A) and lower case (5B) from upper direction. The thrust slide bearing which has an electrode shown in FIG. 5, and the graph which shows resistance with respect to the rotation angle of an upper case. The schematic diagram which shows the state which looked at the electrode provided in the upper case (7A) and the lower case (7B) from upper direction. FIG. 8 is a cross-sectional view (8A) along the line PQ of the electrode of FIG. 7, and a cross-sectional view (8B) along the line RS. The thrust slide bearing which has an electrode shown in FIGS. 7 and 8 is a graph which shows the frictional resistance with respect to the rotation angle of an upper case. Sectional drawing (10A) along the PQ line of the electrode of the aspect different from FIG. 7, and sectional drawing (10B) along RS. The thrust slide bearing which has an electrode shown in FIG. 10, and shows the frictional resistance with respect to the rotation angle of an upper case.

  Hereinafter, an embodiment of a relative motion member of the present invention will be described with reference to the drawings. In the following embodiments, the relative motion member of the present invention is applied to a thrust slide bearing for a suspension of an automobile. FIG. 1 is a perspective view of a thrust slide bearing 10 to which the present invention is applied. The thrust slide bearing 10 shown in FIG. 1 includes an upper case 12 as an annular first member made of an insulator, and a lower case 14 as an annular second member made of an insulator, which is superimposed on the upper case 12; An annular bearing piece 16 is provided between the upper case 12 and the lower case 14. The upper case 12 and the lower case 14 are overlapped with each other with an appropriate clearance so as to relatively smoothly rotate via the bearing piece 16. Further, the thrust portion 16A of the bearing piece 16 is provided with a plurality of grooves 16B extending radially in the radial direction and capable of holding a lubricant at equal intervals in the circumferential direction.

  A lubricant containing ER fluid is interposed between the sliding surfaces located between the upper case 12 and the lower case 14 and the bearing piece 16. As the lubricant, a known lubricant such as grease can be used. Further, ER (electrorheological) fluids are those whose rheological properties are reversibly changed by application and removal of an electric field, and various types are known. For example, polyethylene glycol, phenol resin, ion exchange resin, cellulose and the like can be mentioned, and among these, it is preferable to use polyethylene glycol. A general ER fluid uses solid fine particles as dispersed particles. However, if the solid fine particles are dispersed in grease, the fine particles are buried in the sliding surface and promote wear of the sliding portion. On the other hand, since polyethylene glycol is liquid and does not promote wear on the sliding surface, it can be suitably used.

  Each of the upper case 12 and the lower case 14 has an electrode 18 that forms an electric field including a direction component perpendicular to the relative rotation direction of the upper case 12 and the lower case 14 with the bearing piece 16 interposed therebetween. , 20 are buried. As shown in FIG. 2, the upper case 12 is provided with electrodes 18 over the entire circumferential direction. Although not shown, the lower case 14 is also provided with electrodes 20 over the entire circumferential direction in the same manner as the upper case 12. Yes. And the electrodes 18 and 20 are connected to the power supply 21 via wiring, as shown in FIG. Although FIG. 3 shows a state in which the electrode 18 is connected to the positive electrode and the electrode 20 is connected to the negative electrode, the reverse is also possible. The electrodes 18 and 20 are embedded in the upper case 12 and the lower case 14, respectively, but may be provided in contact with the upper case 12 and the lower case 14.

  In the above configuration, when the power supply 21 connected to the electrodes 18 and 20 is turned off, the ER fluid in the lubricant flows in a disorderly manner. When the power source 21 is turned on and an electric field is formed between the electrodes 18 and 20, the ER fluid in the lubricant forms a chain aggregate parallel to the electric field, and the lubricant is more than in the state where the power source 21 is off. The viscosity resistance increases because the viscosity of the resin increases. Therefore, when the upper case 12 rotates relative to the lower case 14 via the bearing piece 16, a frictional resistance is generated by the lubricant containing the ER fluid, and the upper case 12 and the lower case 14 rotate relative to each other. Braking is applied. That is, the viscosity of the lubricant containing the ER fluid can be controlled by adjusting the power source 21 connected to the electrodes 18 and 20, in other words, by adjusting the magnitude of the electric field strength between the two electrodes. It is possible to control the frictional resistance with respect to the relative rotation of the lower case 14.

  In FIG. 3, the electrode 20 embedded in the lower case 14 is provided in the vicinity of the bearing piece 16, but may be provided in the lower portion of the lower case 14 as shown in FIG. 4. However, since the ER fluid in the lubricant containing the ER fluid has a constant applied voltage, the closer to the electrode, the easier it is to form a chain-like aggregate parallel to the electric field as described above. The form shown in FIG. 3 is preferred.

  In the above embodiment, the electrode is provided in the entire circumferential direction of the upper case 12 and the lower case 14. However, the present invention is not limited to this, and the circumferential direction of at least one of the upper case 12 and the lower case 14 is not limited thereto. An electrode may be provided in part. In this case, the positions and areas where the electrodes are provided may be different between the upper case 12 and the lower case 14.

  Moreover, although the form which provides an electrode in the upper case 12 and the lower case 14 was shown in the above embodiment, you may provide the electrode 20 provided in the lower case 14 in the bearing piece 16. FIG. Even in this case, since the lubricant containing the ER fluid is interposed on the sliding surface between the upper case 12 and the bearing piece 16, the same effect as that of the above embodiment is exhibited. Further, in addition to a mode in which electrodes are provided on the upper case 12 and the bearing piece 16, a mode in which electrodes are provided on the bearing piece 16 and the lower case 14 may be used, or the upper case 12, the lower case 14, and the bearing piece 16 may be provided. Any of the three may be provided with electrodes.

  Next, when the upper case 12 and the lower case 14 are relatively rotated under a condition where the voltage applied to the one or more electrodes is constant, the upper case 12 and the lower case 14 are A mode in which the electric field strength formed during the period changes will be described.

  FIG. 5 is a top view showing a form in which a plurality (four) of electrodes 18 and 20 of the upper case 12 (FIG. 5A) and the lower case 14 (FIG. 5B) are provided in the circumferential direction, and the electrodes are only seen through. ) And substantially the same components as in FIGS. As shown in FIG. 5, both the upper case 12 and the lower case 14 are provided with electrodes having the same radial direction area at the same interval (interval corresponding to 45 °). In FIG. 5, the electrodes of the upper case 12 and the lower case 14 in a state in which the point A and the point B coincide with each other in the direction perpendicular to the relative rotation direction of the upper case 12 and the lower case 14 (θ = 0 °). The area where 18 and 20 overlap is maximized. Accordingly, when the power source connected to the electrodes 18 and 20 is turned on in this state, the viscous resistance of the lubricant becomes maximum. When the upper case 12 rotates with the power turned on, the overlapping area of the electrodes 18 and 20 decreases, and the ER fluid to which the electric field is applied decreases, so the viscosity resistance of the lubricant decreases. FIG. 6 is a graph showing the rotation angle of the upper case 12 and the magnitude of the viscous resistance force of the lubricant with respect to the rotation angle. As shown in FIG. 6, for example, when the upper case 12 rotates clockwise from 0 °, the viscous resistance decreases, and when the upper case 12 rotates 45 ° (θ = 45 °), the overlapping area of the electrodes 18 and 20 is as follows. 0, and the viscous resistance of the lubricant in the power-on state is minimized. When the upper case 12 is further rotated clockwise, the viscous resistance is increased. When the upper case 12 is rotated 90 ° (θ = 90 °), the overlapping area of the electrodes 18 and 20 is maximized again. That is, even when the power is on, the viscous resistance of the lubricant can be changed by rotating the upper case 12. Therefore, for example, when the power source is turned from the on state to the off state in the state where the overlapping area of the electrodes 18 and 20 is maximum, the viscous resistance is rapidly reduced. However, in the form shown in FIG. When the power is turned off after the shaft is rotated by a predetermined angle, the viscous resistance of the lubricant can be smoothly reduced without rapidly decreasing. Therefore, for example, when the thrust slide bearing 10 of this embodiment is applied to a strut type suspension used for a front wheel of a four-wheel vehicle, the handling is operated and the power is turned off immediately after the upper case 12 rotates. Then, a smooth operation feeling can be obtained without suddenly lightening the handle.

  In FIG. 5, the electrodes 18 and 20 are provided with an area corresponding to an angle of 45 °, but the present invention is not limited to this angle and may have an area corresponding to an arbitrary angle. Similarly, in FIG. 5, the electrodes 18 and 20 are provided at regular intervals, but the intervals may be random. Further, the upper case 12 and the lower case 14 may not be provided with the same area / interval, or may be different from each other.

  Further, in the graph shown in FIG. 6, the graph is symmetric with respect to an angle of 45 °. In the upper case 12 and the lower case 14, at least one of the number, area, and interval of the electrodes is set. By changing the angle, it is possible to change the angle that is the symmetry reference of the graph or to make the graph asymmetric. That is, it is possible to adjust the change in the viscosity resistance of the lubricant that changes due to the relative rotation of the upper case 12.

  Next, when the upper case 12 and the lower case 14 are relatively rotated in a certain direction, the electrodes of the upper case 12 and the lower case 14 are relative to each other between the upper case 12 and the lower case 14. The form provided so that the integral value along a rotation stroke may be changed will be described with reference to FIGS.

  7 to 9 are forms in which the distance between the electrodes 18 and 20 of the upper case 12 and the lower case 14 continuously changes when the upper case 12 and the lower case 14 are relatively rotated in a certain direction. The thickness of the electrode 18 of the upper case 12 is formed so as to continuously change in the rotation direction as shown in FIG. 8A, and the thickness of the electrode 20 of the lower case 14 is constant as shown in FIG. 8B. All four electrodes 18 of the upper case 12 have the same shape, and the direction in which the thickness changes is the same. In such a configuration, when the upper case 12 is rotated clockwise with respect to the lower case 14 in FIG. 7, for example, the distance between the electrodes 18 and 20 is increased. That is, due to the relative rotation of the upper case 12 and the lower case 14, the electrodes 18 and 20 are provided such that the integral value along the relative rotation process of the upper case 12 and the lower case 14 with the distance therebetween changes. Yes.

  Here, the integral value along the relative rotation stroke of the upper case 12 and the lower case 14 in the interval between the electrodes 18 and 20 is a line integral along the entire circumferential direction of the interval between the electrodes 18 and 20. It is the integral value of the interval that changes with relative rotation of the upper case 12 and the lower case 14, and shows the same tendency as the change shown in FIG.

  As described above, the ER fluid hardly forms a chain-like aggregate parallel to the electric field in inverse proportion to the distance between the electrodes, and the viscosity of the lubricant decreases as the distance between the electrodes increases. Accordingly, the viscosity resistance of the lubricant can be changed by changing the distance between the electrodes in accordance with the rotation of the upper case 12. 7 and 8, the upper case 12 is watched from the state where the point A and the point B coincide with each other in the direction perpendicular to the relative rotation direction of the upper case 12 and the lower case 14 (θ = 0 °). When rotated in the direction, the overlapping area of the electrodes 18 and 20 decreases, so that the ER fluid to which the electric field is applied decreases. At the same time, since the distance between the electrodes 18 and 20 is increased according to the rotation of the upper case 12, the electric field applied to the ER fluid is weakened. Therefore, in comparison with the embodiment shown in FIG. 5, the graph showing the change in the viscous resistance force of the lubricant with respect to the rotation angle of the upper case 12 has a steep slope as shown in FIG.

  In the present embodiment, the viscosity resistance of the lubricant that changes due to the relative rotation of the upper case 12 and the lower case 14 can be adjusted by changing the inclination angle of the electrode 18 in the circumferential direction. In FIG. 8, only the electrode 18 has a shape whose thickness changes, but the electrode 20 may have a similar shape. Also in this case, the viscous resistance of the lubricant that changes due to the relative rotation of the upper case 12 and the lower case 14 can be adjusted by changing the inclination angle of the electrode 20 in the circumferential direction.

  7-9, the space | interval of the electrodes 18 and 20 of the upper case 12 and the lower case changed continuously was shown, but the space | interval changes the form which changes in steps as shown in FIG. It is good. In the present embodiment, similarly to the embodiments shown in FIGS. 7 to 9, the upper case 12 is in a state where the point A and the point B coincide with each other (θ = 0 °) when viewed from the rotation axis direction of the upper case 12 and the lower case 14. Is rotated, the overlapping area of the electrodes 18 and 20 is reduced, so that the ER fluid to which an electric field is applied is reduced. At the same time, since the interval between the electrodes 18 and 20 decreases stepwise in accordance with the rotation of the upper case 12, the interval increases rapidly at the stepped portion, and the electric field applied to the ER fluid decreases rapidly. Therefore, in comparison with the embodiment shown in FIG. 5, the graph showing the change in the frictional resistance of the lubricant with respect to the rotation angle of the upper case 12 has a steep slope as shown in FIG. Have.

  In this embodiment, by changing at least one of the position of the stepped portion of the stepped upper case 12, the number of stepped portions, and the difference in thickness at the stepped portion, the relative rotation of the upper case 12 The viscosity resistance of the changing lubricant can be adjusted.

  As described above, in the rotation direction of the upper case 12, the lower case 14, and the bearing piece 16, the distance between the electrodes of the upper case 12 and the lower case 14 is integrated along the relative rotation process of the upper case 12 and the lower case 14. By setting the values to change, the viscous resistance of the lubricant can be changed in various manners by the relative rotation of the upper case 12, the lower case 14, and the bearing piece 16.

  Further, when the upper case 12 and the lower case 14 are relatively rotated in the first direction with respect to a certain position, and when the upper case 12 and the lower case 14 are relatively rotated in a second direction different from the first direction, In at least a part of the movable range of the first member and the second member in the direction and the second direction, the change mode of the electric field strength can be set to have symmetry or asymmetry.

  For example, in FIG. 9, when the case of θ = 20 ° is used as a reference, the electrode is used when the upper case 12 rotates clockwise as the first direction and when counterclockwise as the second direction. 18 and 20 have different electric field strength changes. Specifically, the electric field strength is low when the upper case 12 is rotated clockwise, and is high when the upper case 12 is rotated counterclockwise. That is, in this case, the electric field intensity change mode is asymmetric. In this case, the viscous resistance of the lubricant decreases when the upper case 12 rotates clockwise, and increases when the upper case 12 rotates counterclockwise. By configuring as described above, for example, the upper case 12 and the lower case 14 have a large frictional resistance in the first direction and a small frictional resistance in the second direction that is different from the first direction at a certain reference position. It can be set as the structure which becomes.

  On the other hand, in FIG. 9, when the case of θ = 45 ° is used as a reference, the upper case 12 is electroded when it rotates clockwise in the first direction and when it rotates counterclockwise in the second direction. The change mode of the electric field strength between 18 and 20 is the same. Specifically, the electric field strength is high both when the upper case 12 rotates clockwise and when it rotates counterclockwise. That is, in this case, the electric field intensity changing mode has symmetry. In this case, the viscous resistance of the lubricant increases both when the upper case 12 rotates clockwise and when it rotates counterclockwise.

  As described above, the first member and the first member are determined by determining the reference position in consideration of the symmetry of the change mode of the electric field strength formed between the sliding surfaces located between the first member and the second member. Variations in the change in the viscous resistance according to the relative rotation of the second member are increased, and various controls are possible.

  In the above embodiment, the mode in which the relative motion member of the present invention is applied to the thrust slide bearing has been shown. However, the present invention is not limited thereto, and may be applied as long as the two members move relatively. can do. For example, the shape of the two members does not have to be annular, and can be filled with a lubricant between the two members, such as a disk shape or a plate shape, and can be provided with electrodes on the two members. The present invention can be applied if it exists. Further, the relative movement of the two members is not limited to rotation, and may be linear movement, swinging, or the like. Further, it may be a translational movement in which the two members move in the same direction or in opposite directions.

10 Thrust sliding bearing (relative motion member)
12 Upper case (first member)
14 Lower case (second member)
16 Bearing piece 18 20 Electrode

Claims (7)

A first member made of an insulator;
A second member made of an insulator capable of moving relative to the first member;
A relative motion member having a lubricant interposed between sliding surfaces of the first member and the second member,
The lubricant comprises an ER fluid;
One or a plurality of electrodes for forming an electric field including a direction component perpendicular to the relative motion direction of the first member and the second member between the sliding surfaces are the first member and the second member. A relative motion member provided on each of the members.   2. The relative motion member according to claim 1, wherein the one or more electrodes when the first member and the second member are relatively moved under a condition that a voltage applied to the one or the plurality of electrodes is constant. The relative motion member is characterized in that the electric field strength formed between the sliding surfaces changes.   The relative motion member according to claim 2, wherein at least one electrode of the first member and the second member is provided in a discrete state, and the relative motion direction of the first member and the second member. The relative motion member is provided so that an overlapping area of the electrodes changes in accordance with a relative motion of the first member and the second member in a direction perpendicular to the first member.   4. The relative motion member according to claim 2, wherein the electrodes of the first member and the second member are configured such that when the first member and the second member move relative to each other in a certain direction, A relative motion member provided so that an integral value along a relative motion stroke of the first member and the second member at a distance from an electrode changes.   5. The relative motion member according to claim 2, wherein when the first member and the second member are relatively moved in a first direction with a certain position as a reference, the first direction and Is different when the relative movement is performed in different second directions, and at least part of the movable range of the first member and the second member in the first direction and the second direction, the change mode of the electric field strength is symmetric. A relative motion member characterized by having properties.   5. The relative motion member according to claim 2, wherein when the first member and the second member are relatively moved in a first direction with a certain position as a reference, the first direction and And when the relative movement is performed in different second directions, the variation of the electric field strength is asymmetric in at least part of the movable range of the first member and the second member in the first direction and the second direction. And a relative motion member.   The relative motion member according to claim 1, wherein the relative motion member is used as a thrust slide bearing for an automobile suspension.