A joint structure, a linear motion conversion mechanism equipped with the joint structure, and an electric actuator equipped with the joint structure.

Abstract

To provide a joining structure capable of absorbing misalignment between two members joined to each other and reducing wear compared with conventional techniques, a linear motion conversion mechanism equipped with the joining structure, and an electric actuator equipped with the joining structure.SOLUTION: A joining structure 8 includes: a pair of arm portions 10 provided on a first joining object 4; a pin 12 provided between the arm portions 10; a spherical bearing 14 which is externally inserted to the pin 12 and moves along an axial direction of the pin 12; and an insertion part 16 that is provided on a second joining target 6 and is connected to the spherical bearing 14 so as to be rotatable relative to the center point of the spherical bearing 14, the pair of arm portion 10 having a long hole 50 into which the pin 12 is inserted, and which extends in a direction intersecting an axial direction of the pin 12.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a joint structure, a linear motion conversion mechanism including the joint structure, and an electric actuator including the joint structure.

Background Art

[0002] Conventionally, a configuration of a spool valve that moves a spool shaft such as a hydraulic control valve by an electric actuator is known. In a spool valve, various techniques for absorbing misalignment between the electric actuator and the spool shaft have been proposed in order to prevent occurrence of malfunction due to misalignment (eccentricity, angular deviation, etc.) between the electric actuator and the spool shaft.

[0003] For example, Patent Document 1 discloses a joint structure provided between an electric actuator and a spool shaft for absorbing misalignment. The joint structure includes a motor-side connecting portion connected to the electric actuator, a spool-side connecting portion connected to the spool shaft, and a ball interposed between the motor-side connecting portion and the spool-side connecting portion for connecting the motor-side connecting portion and the spool-side connecting portion. The joint structure is configured as a ball joint in which the motor-side connecting portion and the spool-side connecting portion rotate relative to each other around the center point of the ball. According to the technique described in Patent Document 1, it is said that by relative rotation of each member around the center point of the ball, angular deviation between the axis of the spool shaft and the axis of the electric actuator can be absorbed (allowed). Further, by fitting the ball to the motor-side connecting portion or the spool-side connecting portion so as to be relatively movable, the motor-side connecting portion and the spool-side connecting portion can be moved relative to each other in two directions orthogonal to the axial direction of the electric actuator. Thereby, it is said that eccentricity between the axis of the spool shaft and the axis of the electric actuator can be absorbed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] However, in the technology described in Patent Document 1, the contact between the motor-side coupling and the ball is a line contact. Therefore, in the technology described in Patent Document 1, the contact pressure between the ball and the coupling becomes high, which may cause wear on each component. Furthermore, wear on the components may cause looseness and motion errors.

[0006] Therefore, the present invention aims to provide a joining structure that can absorb misalignment between two members joined to each other and reduce wear compared to the prior art, a linear motion conversion mechanism equipped with this joining structure, and an electric actuator equipped with this joining structure. [Means for solving the problem]

[0007] To solve the above problems, this invention proposes the following means. A joining structure according to a first aspect of the present invention is a joining structure for joining a first joining object and a second joining object to each other, comprising: a pair of arms provided on the first joining object; a pin provided between the arms; a spherical bearing fitted onto the pin and moving along the axial direction of the pin; and an insertion portion provided on the second joining object and connected to the spherical bearing so as to be rotatable relative to the spherical bearing around the center point of the spherical bearing, wherein the pair of arms have an elongated hole extending in a direction intersecting the axial direction of the pin into which the pin is inserted. Furthermore, the elongated hole extends in directions perpendicular to the direction connecting the first jointed object and the spherical bearing, and in the axial direction of the pin. .

[0008] A linear motion conversion mechanism comprising a joint structure according to a first aspect of the present invention comprises a joint structure for joining a first object to be joined and a linear motion conversion mechanism to each other, the joint structure comprising a pair of arms provided on the first object to be joined, a pin provided between the arms, a spherical bearing fitted onto the pin and moving along the axial direction of the pin, and an insertion portion provided on the linear motion conversion mechanism comprising the joint structure and connected to the spherical bearing so as to be rotatable relative to the spherical bearing about the center point of the spherical bearing, the pair of arms having an elongated hole extending in a direction intersecting the axial direction of the pin into which the pin is inserted Furthermore, the elongated hole extends in directions perpendicular to the direction connecting the first jointed object and the spherical bearing, and in the axial direction of the pin. . Furthermore, an electric actuator having a joint structure according to the first aspect of the present invention comprises a motor that rotates a rotating shaft and a linear motion conversion mechanism having the above-described joint structure, wherein the linear motion conversion mechanism having the joint structure has a linear motion member that is connected to the joint structure and capable of linear motion, and converts the rotational motion of the motor into linear motion of the linear motion member. [Effects of the Invention]

[0009] According to the joining structure, linear motion conversion mechanism equipped with the joining structure, and electric actuator equipped with the joining structure of the present invention, misalignment between two members that are joined to each other can be absorbed, and wear can be reduced compared to the conventional technology. [Brief explanation of the drawing]

[0010] [Figure 1] A plan view of a spool valve using a linear motion conversion mechanism and an electric actuator equipped with a joint structure according to the first embodiment. [Figure 2] This is an enlarged cross-sectional view of part II in Figure 1, showing a cross-sectional view of a linear motion conversion mechanism with a joint structure and an electric actuator with a joint structure. [Figure 3] This is an enlarged view of part III in Figure 2, showing the state after rotation around the Y-axis. [Figure 4] This is an enlarged view of section IV in Figure 2, showing the state after translation in the Z-axis direction. [Figure 5] This is a bottom view of the joint structure, showing it rotated around the Z-axis. [Figure 6] This is a bottom view of the joint structure, showing its state after being translated in the Y-axis direction. [Figure 7] A cross-sectional view of a linear motion conversion mechanism and an electric actuator equipped with a joint structure according to the second embodiment. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to the drawings. In the following description, the axis coaxial with the spool shaft 4 will be referred to as the X-axis, the direction along the X-axis will be referred to as the X-axis direction, and the directions perpendicular to the X-axis will be referred to as the Y-axis direction and the Z-axis direction, respectively. In addition, the axis coaxial with the pin 12 of the joint structure 8 will be described as the Z-axis, and the axes perpendicular to the X-axis and Z-axis will be referred to as the Y-axis, respectively.

[0012] (First Embodiment) (Spool valve) Figure 1 is a plan view of a spool valve 1 using a linear motion conversion mechanism 35 equipped with a joint structure 8 and an electric actuator 6 equipped with the joint structure 8 according to the first embodiment. As shown in Figure 1, the spool valve 1 of this embodiment is a spool valve provided in a hydraulic supply device for supplying hydraulic fluid to an actuator such as an industrial machine. The actuator of the industrial machine is driven at a speed corresponding to the supplied flow rate, and the hydraulic supply device has a spool valve 1 as shown in Figure 1 to control the flow rate of hydraulic fluid supplied to the actuator of the industrial machine. The spool valve 1 is a linearly driven electric spool valve 1. The spool valve 1 comprises a housing 2, a spool shaft 4, and an electric actuator 6 having a connecting structure 8.

[0013] (housing) The housing 2 is, for example, a valve block. At least a part of the hydraulic supply device is accommodated in the housing 2. A spool hole 21 and a plurality of oil passages 22 are formed in the housing 2. The spool hole 21 extends along the X-axis direction so as to penetrate the housing 2. In the present embodiment, the housing 2 has, as the plurality of oil passages 22, a first oil passage 22a, a second oil passage 22b, a third oil passage 22c, and a fourth oil passage 22d. The first to fourth oil passages 22a, 22b, 22c, 22d are respectively connected to the spool hole 21 at different positions.

[0014] Specifically, the first to third oil passages 22a, 22b, 22c are arranged side by side in the X-axis direction and extend along a direction orthogonal to the X-axis (the -Z-axis direction in FIG. 1). The inner ends of the first to third oil passages 22a, 22b, 22c communicate with the spool hole 21. The outer ends of the first to third oil passages 22a, 22b, 22c communicate with the outside of the housing 2. The fourth oil passage 22d extends on the opposite side (+Z-axis direction) of the first to third oil passages 22a, 22b, 22c with respect to the spool hole 21,迂回したのち、再び反対側(-Z軸方向)に延びることによりスプール孔21とハウジング2の外部とを連通している。第一から第四の油通路22a,22b,22c,22dは、図示しない油圧ポンプやアクチュエータ等に繋がっており、4つの油通路22a,22b,22c,22dにそれぞれ作動油が流れるようになっている。

[0015] (Spool shaft) The spool shaft 4 is inserted into the spool hole 21 of the housing 2. The spool shaft 4 is provided on one side (+X-axis direction) in the X-axis direction with respect to the plurality of oil passages 22. The spool shaft 4 extends along the X-axis direction and is movable along the X-axis direction within the spool hole 21 of the housing 2. The spool shaft 4 is formed in a cylindrical shape with its axial direction as the central axis. The outer diameter of the spool shaft 4 substantially coincides with the inner diameter of the spool hole 21. In addition, a plurality of grooves, slits, etc. (not shown) may be formed on the outer peripheral surface of the spool shaft 4.

[0016] The spool shaft 4 is connected to a linear motion conversion mechanism 35 provided with a joining structure 8 and an electric actuator 6 provided with a joining structure 8 via the joining structure 8, which will be described in detail later. As the linear motion conversion mechanism 35 provided with the joining structure 8 and the electric actuator 6 provided with the joining structure 8 are driven, it moves along the axial direction within the spool hole 21. By the movement of the spool shaft 4 along the axial direction of the spool hole 21, it becomes possible to flow hydraulic oil at a desired flow rate through each of the four oil passages 22.

[0017] (Electric actuator provided with a joining structure) FIG. 2 is an enlarged cross-sectional view of part II of FIG. 1. As shown in FIGS. 1 and 2, the electric actuator 6 provided with the joining structure 8 is a so-called linear motion type electric actuator 6 provided with the joining structure 8. The electric actuator 6 provided with the joining structure 8 is provided on the side opposite to the oil passage 22 with respect to the spool shaft 4 and is connected to the spool shaft 4 via the joining structure 8. The electric actuator 6 provided with the joining structure 8 is adapted to reciprocate the spool shaft 4 in the axial direction by supplying electric power. As shown in FIG. 2, the electric actuator 6 provided with the joining structure 8 has a housing 30, a motor 31, and a linear motion conversion mechanism 35 provided with the joining structure 8.

[0018] The housing 30 is formed in a cylindrical shape with the X axis coaxial with the spool shaft as the central axis. The end portion of the housing 30 located on the spool shaft 4 side is fitted and connected to the spool hole 21 of the housing 2. The housing 30 is integrated with the housing 2 by being connected to the housing 2. A motor 31 is attached to the end portion of the housing 30 on the side opposite to the spool shaft 4.

[0019] Motor 31 is a so-called servo motor. Motor 31 has a stator and a rotor (not shown), and a rotating shaft 32 is connected to the rotor. A control device (not shown) is connected to the stator, and the rotor (i.e., the rotating shaft 32) is rotated at a predetermined rotational speed according to the voltage applied from the control device. The rotating shaft 32 has its rotation center in the X-axis direction and extends toward the spool shaft 4 side (-X direction).

[0020] The linear motion conversion mechanism 35, which includes the joint structure 8, is connected to the rotating shaft 32 of the motor 31 and is housed in the housing 30. The linear motion conversion mechanism 35, which includes the joint structure 8, has a linear motion member (in this embodiment, a ball screw shaft 38) that can move linearly along the X-axis, and is a mechanism for converting rotational motion around the X-axis output from the rotating shaft 32 of the motor 31 into linear motion along the X-axis direction. In this embodiment, a ball screw mechanism is used as the linear motion conversion mechanism 35, which includes the joint structure 8. In the following description, the linear motion conversion mechanism 35, which includes the joint structure 8, may sometimes be simply referred to as the ball screw mechanism 35, which includes the joint structure 8.

[0021] The ball screw mechanism 35, which includes a joint structure 8, comprises a ball screw nut 37, a ball screw shaft 38, and the joint structure 8. The ball screw nut 37 is formed in a cylindrical shape that is slightly smaller than the housing 30. Multiple bearings 45 are provided on the outer circumferential surface of the ball screw nut 37. The ball screw nut 37 is mounted to the housing 30 so as to be rotatable relative to it by these bearings 45. The ball screw nut 37 is connected to the rotating shaft 32 of the motor 31. Therefore, when the motor 31 is driven and the rotating shaft 32 rotates, the ball screw nut 37 rotates integrally with the rotating shaft 32 around the X axis. Multiple grooves for holding spheres 39 are formed on the inner circumferential surface of the ball screw nut 37. When the ball screw nut 37 rotates, the spheres 39 circulate circumferentially along the grooves on the inner circumferential surface of the ball screw nut 37.

[0022] The ball screw shaft 38 is a rod-shaped member extending in the X-axis direction. The ball screw shaft 38 is located inside the ball screw nut 37. The ball screw shaft 38 is configured to move along the X-axis direction as the ball screw nut 37 rotates. A male thread is formed on the outer circumferential surface of the ball screw shaft 38. The ball screw shaft 38 is screwed into the inner circumferential surface of the ball screw nut 37 via a ball 39. In this embodiment, the ball screw shaft 38 functions as a linear motion member. That is, the ball screw shaft 38 moves along the screw axis (X-axis) in one axial direction and the other axial direction by rotating the ball screw nut 37. The other end of the ball screw shaft 38, located on the opposite side of the motor 31 in the X-axis direction, extends to the vicinity of the opening of the housing 30 and is connected to the insertion portion 16 (see Figure 3) of the joint structure 8, which will be described later. A groove 38a is formed on the outer circumferential surface of the other end of the ball screw shaft 38 along the X-axis direction. The tip of the pin 46, which is attached near the opening of the housing 30, engages with the groove 38a, preventing the ball screw shaft 38 from rotating together with the rotation of the ball screw nut 37.

[0023] (joint structure) The joining structure 8 is located on the X-axis and is provided between the spool shaft 4 and the ball screw shaft 38 of the electric actuator 6 equipped with the joining structure 8. The joining structure 8 joins the spool shaft 4 (the first joining target in the claim) to the linear motion conversion mechanism 35 equipped with the joining structure 8 and the electric actuator 6 equipped with the joining structure 8 (the second joining target in the claim). In other words, the joining structure 8 is a structure for joining two linearly moving joining targets to each other. The joining structure 8 of this embodiment is capable of absorbing (allowing) angular misalignment and eccentricity between the axes of the output-side member (for example, the axis of the spool shaft 4) with respect to the axis of the input-side member (for example, the axis of the linear motion conversion mechanism 35 equipped with the joining structure 8 and the axis of the electric actuator 6 equipped with the joining structure 8) among the two joining targets.

[0024] Figure 3 is an enlarged view of part III of Figure 2, showing the state when rotated around the Y-axis. In other words, Figure 3 shows the state when an angular misalignment around the Y-axis occurs between the spool shaft 4 and the linear motion conversion mechanism 35 equipped with the connecting structure 8 and the electric actuator 6 equipped with the connecting structure 8. Figure 4 is an enlarged view of part IV of Figure 2, showing the state when translated in the Z-axis direction. In other words, Figure 4 shows the state when eccentricity in the Z-axis direction occurs between the spool shaft 4 and the linear motion conversion mechanism 35 equipped with the connecting structure 8 and the electric actuator 6 equipped with the connecting structure 8. Figure 5 is a bottom view of the connecting structure 8 (i.e., a view of Figure 3 from below), showing the state when rotated around the Z-axis. In other words, Figure 5 shows the state when an angular misalignment around the Z-axis occurs between the spool shaft 4 and the linear motion conversion mechanism 35 equipped with the connecting structure 8 and the electric actuator 6 equipped with the connecting structure 8. Figure 6 is a bottom view of the connecting structure 8, showing the state when translated in the Y-axis direction. In other words, Figure 6 shows the state when eccentricity in the Y-axis direction occurs between the spool shaft 4 and the linear motion conversion mechanism 35, which has a connecting structure 8, and the electric actuator 6, which also has a connecting structure 8. As shown in Figures 3 to 6, the joint structure 8 is a so-called clevis joint having a pair of arm portions 10, a pin 12, a spherical bearing 14, and an insertion portion 16.

[0025] As shown in Figures 3 and 4, the pair of arms 10 are components that constitute the female part of the clevis joint. The pair of arms 10 are attached to one end of the spool shaft 4, which is the first object to be joined, on one axial side (+X axis). The pair of arms 10 are spaced apart from each other in the Z axis direction. More specifically, the pair of arms 10 has a first arm 41 located relatively on the +Z direction side and a second arm 42 located on the -Z direction side of the first arm 41. The first arm 41 and the second arm 42 are formed to be of the same shape. Each of the pair of arms 10 protrudes from the spool shaft 4 in the direction of the +X axis. The pair of arms 10 are formed in a plate shape with the Z direction as the thickness direction.

[0026] As shown in Figures 5 and 6, each of the pair of arms 10 has an elongated hole 50 formed therein. The elongated hole 50 formed in the first arm 41 and the elongated hole 50 formed in the second arm 42 have the same shape and are located in positions that overlap when viewed from the Z-axis direction. The elongated holes 50 penetrate each arm 10 in the Z-axis direction. When viewed from the Z-axis direction, the elongated holes 50 are formed in an oval shape that extends in the Y-axis direction (with the Y-axis as the major axis). In other words, the elongated holes 50 extend in directions perpendicular to the direction connecting the spool shaft 4 and the spherical bearing 14 (X-axis direction) and the axial direction of the pin 12 (Z-axis direction).

[0027] As shown in Figures 3 and 4, the pin 12 is inserted into the elongated holes 50 of the pair of arms 10. The pin 12 is provided to extend in the Z-axis direction across the pair of arms 10. The pin 12 has a body 51 and a head 52. The body 51 is formed in a cylindrical shape extending in the Z-axis direction. The outer diameter of the body 51 is equal to or slightly smaller than the width dimension of the elongated holes 50 of the pair of arms 10. Both axial ends of the body 51 are inserted into the elongated holes 50 of the pair of arms 10. The head 52 is integrally provided on one end of the body 51 in the axial direction (the end on the +Z axis side). The head 52 is formed in a cylindrical shape with a larger outer diameter than the body 51. The outer diameter of the head 52 is greater than the width dimension of the elongated hole 50 along the X-axis direction. The head 52 abuts against the surface of the first arm 41 that faces away from the second arm 42. The axial position (Z-direction) of the pin 12 is determined by the contact of the head 52 with the first arm 41. When the head 52 is in contact with the first arm 41, the other end of the main body 51 of the pin 12 (the end on the -Z axis side) protrudes further toward the negative side in the Z-axis direction than the second arm 42. The other end of the main body 51 of the pin 12 may be provided with, for example, a projection or crimp (not shown) to prevent the pin 12 from coming loose. The method of fixing the pin 12 to the arm 10 is not limited to this.

[0028] The spherical bearing 14 is located midway along the pin 12, between a pair of arms 10. A pin insertion hole 55 is formed in the center of the spherical bearing 14, oriented along the Z-axis direction. The spherical bearing 14 is externally fitted onto the pin 12 by inserting the pin 12 into the pin insertion hole 55. The outer shape of the spherical bearing 14 is that of a sphere with its upper and lower ends cut off. The height dimension of the spherical bearing 14 along the Z-axis direction is smaller than the distance dimension between the first arm 41 and the second arm 42. The spherical bearing 14 is mounted so as to be movable along the axial direction of the pin 12 (see also Figure 4).

[0029] The insertion portion 16 is a component that constitutes the female part of the clevis joint. The insertion portion 16 is attached to the other axial (-X axis) end of the ball screw shaft 38 of the linear motion conversion mechanism 35 and the electric actuator 6, which are the second objects to be joined, and which are the joint structure 8. The insertion portion 16 protrudes toward the spool shaft 4 side from the ball screw shaft 38 of the linear motion conversion mechanism 35 and the electric actuator 6, which are the joint structure 8. The insertion portion 16 is inserted between the pair of arm portions 10. The insertion portion 16 is provided with a bearing retaining hole 58. The inner circumferential surface of the bearing retaining hole 58 is a spherical sliding surface. The spherical sliding surface has an inner surface shape that corresponds to the outer surface shape of the spherical bearing 14 and rotatably engages with the spherical bearing 14. As a result, the insertion portion 16 is connected to the spherical bearing 14 so as to be rotatable relative to the spherical bearing 14 around the center point O of the spherical bearing 14 (see also Figure 3).

[0030] With the configuration described above, the joint structure 8 transmits linear motion from the linear motion conversion mechanism 35 equipped with the joint structure 8 and the electric actuator 6 equipped with the joint structure 8 to the spool shaft 4, causing the spool shaft 4 to move linearly along the X-axis direction. Here, as described above, the insertion portion 16 attached to the linear motion conversion mechanism 35 equipped with the joint structure 8 and the electric actuator 6 equipped with the joint structure 8 is connected to the pair of arm portions 10 attached to the spool shaft 4 so as to be movable and rotatable in multiple directions. Firstly, as shown in Figure 4, the spherical bearing 14 moves between the pair of arm portions 10, so that the insertion portion 16 can move in parallel with respect to the pair of arm portions 10 in the axial direction of the pin 12, i.e., in the Z-axis direction (see arrow A in Figure 4). Secondly, as shown in Figure 6, the pin 12 moves along the longitudinal direction of the elongated hole 50, so that the insertion portion 16 can move in parallel with respect to the pair of arm portions 10 in the longitudinal direction of the elongated hole 50, i.e., in the Y-axis direction (see arrow B in Figure 6). Thirdly, as shown in Figure 3, the insertion portion 16 rotates around the spherical bearing 14, allowing the insertion portion 16 to rotate in the pitch direction, i.e., around the Y-axis, with respect to the center point O of the spherical bearing 14 relative to the pair of arm portions 10 (see arrow C in Figure 3). Fourthly, as shown in Figure 5, the insertion portion 16 rotates around the spherical bearing 14, allowing the insertion portion 16 to rotate in the yaw direction, i.e., around the Z-axis, with respect to the center point O of the spherical bearing 14 relative to the pair of arm portions 10 (see arrow D in Figure 5). Fifthly, for example, as shown in Figure 4, the insertion portion 16 rotates around the spherical bearing 14 around the X-axis, allowing the insertion portion 16 to rotate in the roll direction, i.e., around a central axis parallel to the X-axis, with respect to the pair of arm portions 10 (see arrow E in Figure 4). Furthermore, by combining these translations and rotations, it is possible to move to desired relative angles and relative positions.

[0031] (Effect, Action) According to the joint structure 8, the linear motion conversion mechanism 35 equipped with the joint structure 8, and the electric actuator 6 equipped with the joint structure 8 of this embodiment, the joint structure 8 comprises a pair of arms 10, a pin 12, a spherical bearing 14, and an insertion part 16, the pair of arms 10 having elongated holes 50. Since the insertion part 16 is mounted so as to be rotatable relative to the spherical bearing 14, the rotation of the insertion part 16 relative to the spherical bearing 14 can absorb (allow) the inclination (angular deviation) of the axis of the spool shaft 4 with respect to the axis of the linear motion conversion mechanism 35 equipped with the joint structure 8 and the electric actuator 6 equipped with the joint structure 8. Specifically, the pitch direction deviation, yaw direction deviation, and roll direction deviation between the axis of the linear motion conversion mechanism 35 equipped with the joint structure 8 and the electric actuator 6 equipped with the joint structure 8 and the axis of the spool shaft 4 can be absorbed. Furthermore, the spherical bearing 14 moves along the axial direction of the pin 12, which allows for the absorption (tolerance) of the Z-axis misalignment (eccentricity) between the axis of the electric actuator 6 equipped with the joint structure 8 and the axis of the spool shaft 4. In addition, the elongated hole 50 extends in a direction intersecting the axial direction of the pin 12, and the pin 12 is inserted into the elongated hole 50. As a result, the pin 12 can move along the long axis direction of the elongated hole 50. This allows for the absorption of eccentricity in the direction along the axial direction of the elongated hole 50 (Y-axis direction) between the axis of the linear motion conversion mechanism 35 equipped with the joint structure 8 and the axis of the electric actuator 6 equipped with the joint structure 8 and the axis of the spool shaft 4. In the joint structure 8, the spherical bearing 14 is provided with a pin insertion hole 55, and the pair of arm portions 10 and the insertion portion 16 (spherical bearing 14) are connected by a pin 12 with a circular cross-section inserted into the pin insertion hole 55. This allows the inner circumferential surface of the spherical bearing 14 (i.e., the inner circumferential surface of the pin insertion hole 55) and the pin 12 to be in surface contact. Surface contact can also be made between the spherical bearing 14 and the insertion portion 16. As a result, the contact pressure can be kept lower compared to conventional technology in which the motor-side connecting portion and the spool-side connecting portion are connected via a ball, and the contact pressure between the ball and one of the connecting portions is line contact. Specifically, by making the contact between the pin 12 and the spherical bearing 14, and between the spherical bearing 14 and the insertion portion 16, the contact pressure between the parts can be kept low. In addition, since the contact pressure can be reduced by making the contact between the pin 12 and the spherical bearing 14, the joint structure 8 can be made smaller. As a result, even if the area of ​​line contact (contact length) between the pin 12 and the elongated hole 50 is enlarged to reduce contact pressure, for example, the overall size of the joint structure 8 can be kept to a minimum. Similarly, the size of the spool valve 1 equipped with this joint structure 8 can be kept to a minimum. Therefore, compared to the conventional technology, wear due to line contact can be reduced while the overall size of the device can be reduced. Therefore, it is possible to provide a joining structure 8 that can absorb misalignment between two members that are joined together, and that can reduce wear compared to conventional technology.

[0032] The elongated hole 50 extends along directions perpendicular to the direction connecting the spool shaft 4, which is the first object to be joined, and the linear motion conversion mechanism 35, which has the joining structure 8, and the electric actuator 6, which has the joining structure 8 (or the direction connecting the spool shaft 4 and the spherical bearing 14) (X-axis direction), and the axial direction of the pin 12 (Z-axis direction). This allows for the absorption of eccentricity in the Y-axis direction, which is perpendicular to the axis of the pin 12. Therefore, eccentricity and angular displacement in various directions can be absorbed more effectively.

[0033] The linear motion conversion mechanism 35, which includes the joint structure 8, comprises a ball screw nut 37 connected to the rotating shaft 32 of the motor 31, a ball screw shaft 38 that is screwed into the ball screw nut 37 and moves in a linear motion, and the joint structure 8. By using a ball screw mechanism as the linear motion conversion mechanism 35 with the joint structure 8, it is possible to provide a spool valve 1 that simplifies the configuration while absorbing misalignment and reducing wear as described above. Furthermore, the versatility of the spool valve 1 can be increased.

[0034] (Second Embodiment) Next, a second embodiment of the present invention will be described. In the following description, components similar to those in the first embodiment described above will be denoted by the same reference numerals and their descriptions will be omitted as appropriate. Note that the specific configurations are not limited to these embodiments and can be modified as appropriate without departing from the spirit of the present invention. Figure 7 is a cross-sectional view of a linear motion conversion mechanism 235 equipped with a joint structure 8 and an electric actuator 6 equipped with a joint structure 8 according to the second embodiment. Figure 7 corresponds to Figure 2 in the first embodiment. In this embodiment, the configuration of the linear motion conversion mechanism 235 equipped with a joint structure 8 in the electric actuator 6 equipped with a joint structure 8 differs from that of the first embodiment described above.

[0035] In the second embodiment, the linear motion conversion mechanism 235 of the electric actuator 6, which is equipped with the connecting structure 8, has a linear motion member (in this embodiment, a ball screw nut 237) that can move linearly along the X axis, and is a ball screw mechanism 235 equipped with the connecting structure 8 that converts rotational motion about the X axis output from the rotation shaft 32 of the motor 31 into linear motion along the X axis direction.

[0036] The ball screw mechanism 235, which includes the joint structure 8, comprises a ball screw shaft 238, a ball screw nut 237, and the joint structure 8. The ball screw shaft 238 is a rod-shaped member extending in the X-axis direction. The ball screw shaft 238 is mounted to the housing 30 by a bearing 245 so as to be rotatable relative to it. The ball screw shaft 238 is connected to the rotating shaft 32 of the motor 31. Therefore, when the motor 31 is driven and the rotating shaft 32 rotates, the ball screw shaft 238 rotates integrally with the rotating shaft 32 around the X-axis. A male thread is formed on the outer circumferential surface of the ball screw shaft 238.

[0037] The ball screw nut 237 is provided on the outer circumference of the ball screw shaft 238. The ball screw nut 237 is formed in a cylindrical shape that is slightly smaller than the housing 30. The ball screw nut 237 is configured to move along the X-axis direction as the ball screw shaft 238 rotates. Multiple grooves for holding the ball spheres 39 are formed on the inner circumferential surface of the ball screw nut 237. The ball screw nut 237 is screwed to the outer circumferential surface of the ball screw shaft 238 via the ball spheres 39. When the ball screw shaft 238 rotates, the ball spheres 39 circulate circumferentially along the grooves on the inner circumferential surface of the ball screw nut 237. In this embodiment, the ball screw nut 237 functions as a linear motion member. That is, the ball screw nut 237 moves along the screw axis (X-axis) in one axial direction and the other axial direction as the ball screw shaft 238 rotates. The other end of the ball screw nut 237, located on the opposite side of the motor 31 in the X-axis direction, extends to the vicinity of the opening of the housing 30 and is connected to the insertion portion 16 of the joint structure 8. A groove 238a is formed on the outer circumferential surface of the other end of the ball screw nut 237 along the X-axis direction. The tip of the pin 46, which is attached near the opening of the housing 30, engages with the groove 238a, preventing the ball screw nut 237 from rotating with the rotation of the ball screw shaft 238. A separate component (not shown), such as a slider, may be provided between the ball screw nut 237 and the housing 30 to allow linear motion of the ball screw nut 237 relative to the housing 30.

[0038] According to the linear motion conversion mechanism 235 and electric actuator 6 equipped with the joint structure 8 of the second embodiment, by connecting the ball screw shaft 238 to the rotation shaft 32 of the motor 31 and using the ball screw nut 237 as a linear motion member, the same effects as those of the first embodiment described above can be achieved. Therefore, the versatility of the linear motion conversion mechanism 235 and electric actuator 6 equipped with the joint structure 8 can be increased.

[0039] It should be noted that the technical scope of the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. For example, in the first and second embodiments described above, an example was given in which a ball screw mechanism was used as the linear motion conversion mechanism 35,235 equipped with the joint structure 8, but the invention is not limited to this. The linear motion conversion mechanism 35 equipped with the joint structure 8 can be any mechanism capable of converting rotational motion into linear motion, and a mechanism other than a ball screw mechanism equipped with the joint structure 8 may be used.

[0040] In the first embodiment described above, a configuration was described in which a pair of arms 10 are directly attached to the spool shaft 4. However, a fixing part or the like may be separately provided between the pair of arms 10 and the spool shaft 4 to connect the spool shaft 4 and the arms 10. In this case, the fixing part and the arms 10 may be integrally formed, or they may be formed from separate components. The elongated hole 50 may be a through-hole penetrating the arm portion 10, or it may be a recess provided in the arm portion 10. [Explanation of Symbols]

[0041] 1,201 Spool valve 4. Spool shaft (first joint target) 6. Electric actuator with a joint structure (second joint target) 8 Joint structure 10 pairs of arms 12 pins 14 Spherical bearings 16 Insertion part 31 Motor 32 Rotation axis 35,235 Linear motion conversion mechanism with joint structure 37 Ball screw nut 38. Ball screw shaft (linear motion component) 41 First arm (arm) 42 Second arm (arm) 50 long hole 237 Ball screw nut (linear motion component) 238 Ball screw shaft O (center point of a spherical bearing)

Claims

1. A joining structure that joins a first joining target and a second joining target to each other, A pair of arms provided on the first object to be joined, A pin provided between the aforementioned arms, A spherical bearing is fitted onto the pin and moves along the axial direction of the pin, An insertion portion is provided on the second object to be joined, and is connected to the spherical bearing so as to be rotatable relative to the spherical bearing around the center point of the spherical bearing, Equipped with, The pair of arms have elongated holes into which the pin is inserted, extending in a direction intersecting the axial direction of the pin. The elongated hole extends in directions perpendicular to the direction connecting the first object to be joined and the spherical bearing, and in the axial direction of the pin. Joint structure.

2. In a linear motion converter mechanism having a joining structure that joins a first object to be joined and a linear motion converter mechanism to each other, The aforementioned joint structure is A pair of arms provided on the first object to be joined, A pin provided between the aforementioned arms, A spherical bearing is fitted onto the pin and moves along the axial direction of the pin, A linear motion conversion mechanism having the aforementioned joint structure is provided with an insertion portion that is connected to the spherical bearing so as to be rotatable relative to the spherical bearing around the center point of the spherical bearing, Equipped with, The pair of arms have elongated holes into which the pin is inserted, extending in a direction intersecting the axial direction of the pin. The elongated hole extends in directions perpendicular to the direction connecting the first object to be joined and the spherical bearing, and in the axial direction of the pin. A linear motion conversion mechanism equipped with a joint structure.

3. An electric actuator having a joint structure, A motor that rotates the rotating shaft, A linear motion conversion mechanism comprising the joint structure described in claim 2, It has, The linear motion conversion mechanism having the aforementioned joint structure has a linear motion member that is connected to the joint structure and capable of linear motion, and converts the rotational motion of the motor into linear motion of the linear motion member. An electric actuator equipped with a joint structure.

4. The elongated hole extends in a direction perpendicular to the direction connecting the first object to be joined and the electric actuator having the joining structure, and in the axial direction of the pin. An electric actuator comprising the joining structure described in claim 3.

5. The linear motion conversion mechanism having the aforementioned joint structure is A ball screw nut connected to the rotating shaft of the motor, A ball screw shaft that is screwed into the inner circumference of the aforementioned ball screw nut and moves in a linear motion, Having, An electric actuator comprising the joining structure described in claim 3 or claim 4.

6. The linear motion conversion mechanism having the aforementioned joint structure is A ball screw shaft connected to the aforementioned rotating shaft, A ball screw nut is screwed onto the outer circumference of the ball screw and moves in a linear motion, A connecting member that connects the ball screw nut and the joint structure, Having, An electric actuator comprising the joining structure described in claim 3 or claim 4.

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