Electric Cylinder Device

Abstract

To suppress uneven wear of components due to shift of center positions of a piston and of a cylinder.SOLUTION: An electric cylinder device 10 comprises a third gear 20 that rotates by receiving rotation of an electric motor 14, and a direct-acting conversion mechanism 16 that converts rotation of the third gear 20 into linear motion of the piston 13 inside the cylinder 11, where a nut 23 which is a direct-acting part of the direct-acting conversion mechanism 16 is connected to the piston 13 so that the nut and the piston are permitted to be relatively displaced in a radial direction R.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electric cylinder device. [Background technology]

[0002] There is known an electric cylinder device that converts the rotation of an electric motor into linear motion and outputs the motion, as seen in Patent Document 1. One electric cylinder device is a device that includes a cylinder and a piston disposed therein, and converts the rotation of the electric motor into linear motion to linearly move the piston within the cylinder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-266149 Summary of the Invention [Problem to be solved by the invention]

[0004] When assembling an electric cylinder device, if the cylinder and piston are assembled with the center position misaligned, the piston will come into contact with the cylinder on one side, generating a radial load. If the electric cylinder device is operated with such a radial load generated, the load may cause uneven wear on the components of the electric cylinder device. For this reason, high precision is required for the assembly of the components of the electric cylinder device, which is a factor that reduces the productivity of the electric cylinder device. [Means for solving the problem]

[0005] An electric cylinder device that solves the above problems includes a piston disposed inside the cylinder, a rotary input part that rotates in response to rotation of an electric motor, a linear motion conversion mechanism including a rotating part that rotates when the rotation of the rotary input part is transmitted and a linear motion part that moves linearly in response to the rotation of the rotating part, thereby acting on the linear motion of the piston, and a housing that has a cylinder disposed inside and accommodates the piston, the rotary input part, and the linear motion conversion mechanism. Two of the components of the electric cylinder device, a first component and a second component, are allowed to move relative to the piston in a radial direction, which is a direction perpendicular to the axial direction of the piston. The first component displaces the piston relative to the cylinder in the radial direction in response to its relative radial displacement with respect to the second component.

[0006] The piston of the electric cylinder device configured as described above is allowed to move radially relative to the cylinder. Meanwhile, the radial load acting between the piston and the cylinder is alleviated by their relative radial movement. Therefore, in the electric cylinder device, uneven wear of the components of the electric cylinder device due to misalignment of the piston and cylinder is unlikely to occur. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view of an electric cylinder device according to a first embodiment. [Figure 2] 2 is a cross-sectional view of the piston and its surroundings of the electric cylinder device of FIG. 1. [Figure 3] 1. FIG. 4 is a cross-sectional view of a connecting portion of a piston and a nut in a modified example of the electric cylinder device of FIG. [Figure 4] 1. FIG. 4 is a cross-sectional view of a piston and its periphery in a modified example of the electric cylinder device of FIG. [Figure 5] 1. FIG. 4 is a cross-sectional view of a piston and its periphery in a modified example of the electric cylinder device of FIG. [Figure 6] 1. FIG. 4 is a cross-sectional view of a piston and its periphery in a modified example of the electric cylinder device of FIG. [Figure 7]1. FIG. 4 is a cross-sectional view of a piston and its periphery in a modified example of the electric cylinder device of FIG. [Figure 8] 1. FIG. 4 is a cross-sectional view of a piston and its periphery in a modified example of the electric cylinder device of FIG. [Figure 9] FIG. 6 is a cross-sectional view of an electric cylinder device according to a second embodiment. [Figure 10] 10 is a cross-sectional view of a connecting portion between a screw shaft and an input gear in the electric cylinder device of FIG. 9. [Figure 11] FIG. 11 is a cross-sectional view taken along line 11-11 in FIG. [Figure 12] 10 is a cross-sectional view of a connection portion between a screw shaft and an input gear in a modified example of the electric cylinder device of FIG. 9. [Figure 13] FIG. 13 is a cross-sectional view taken along line 13-13 in FIG. [Figure 14] FIG. 10 is a cross-sectional view of an electric cylinder device according to a third embodiment. [Figure 15] FIG. 10 is a cross-sectional view of an electric cylinder device according to a fourth embodiment. [Figure 16] FIG. 16 is a cross-sectional view of a bearing and its surroundings in a modified example of the electric cylinder device of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] (First embodiment) A first embodiment of an electric cylinder device will be described below with reference to Figures 1 and 2. An electric cylinder device 10 of this embodiment is configured as a device that generates hydraulic pressure for generating a braking force for a vehicle.

[0009] <Configuration of electric cylinder device 10> As shown in FIG. 1 , an electric cylinder device 10 of this embodiment includes a housing 12 in which a cylinder 11 is provided, and a piston 13 arranged inside the cylinder 11 so as to be capable of linear motion in the axial direction. The electric cylinder device 10 also includes an electric motor 14, a rotation transmission mechanism 15, and a linear motion conversion mechanism 16. The piston 13, the rotation transmission mechanism 15, and the linear motion conversion mechanism 16 are installed inside the housing 12. In the electric cylinder device 10 of this embodiment, the electric motor 14 is attached to the outer periphery of the housing 12. The rotation transmission mechanism 15 and the linear motion conversion mechanism 16 are housed in the internal space of the housing 12 which is connected to the cylinder 11.

[0010] The rotation transmission mechanism 15 is a mechanism that transmits the rotation of the electric motor 14 to the linear motion conversion mechanism 16. The electric cylinder device 10 of this embodiment is equipped with a gear mechanism consisting of three gears as the rotation transmission mechanism 15. Specifically, there are three gears: a first gear 18 connected to a motor shaft 17, which is the output shaft of the electric motor 14; a third gear 20 connected to the linear motion conversion mechanism 16; and a second gear 19 interposed between the first gear 18 and the third gear 20. The third gear 20 has a greater number of teeth than the first gear 18. Therefore, the rotation of the electric motor 14 is reduced in speed and transmitted to the linear motion conversion mechanism 16. The third gear 20 is rotatably supported by a bearing component 21 and is installed inside the housing 12. In this embodiment, the third gear 20 corresponds to a rotation input component that rotates in response to the rotation of the electric motor 14.

[0011] The linear motion conversion mechanism 16 is a mechanism that converts the rotation of the electric motor 14, transmitted via the rotation transmission mechanism 15, into linear motion of the piston 13 inside the cylinder 11. The electric cylinder device 10 of this embodiment is equipped with a feed screw mechanism having a screw shaft 22 and a nut 23 as the linear motion conversion mechanism 16. The screw shaft 22 is connected to the third gear 20 so as to rotate integrally therewith. The nut 23 is connected to the piston 13. Details of the connection structure between the piston 13 and the nut 23 will be described later. The nut 23 moves linearly in the extension direction of the rotation axis O of the screw shaft 22, i.e., in the axial direction of the piston 13, in response to the rotation of the screw shaft 22. The linear motion of the nut 23 affects the linear motion of the piston 13. In the electric cylinder device 10 of this embodiment, the screw shaft 22 corresponds to the rotating part of the linear motion conversion mechanism 16, and the nut 23 corresponds to the linear motion part of the linear motion conversion mechanism 16.

[0012] A fluid chamber 24 into which brake fluid is introduced is defined by the piston 13 inside the cylinder 11. The volume of the fluid chamber 24 changes depending on the movement position of the piston 13 inside the cylinder 11. In the following description, the direction of linear movement of the piston 13 inside the cylinder 11, i.e., the direction of linear movement S of the piston 13, in which the volume of the fluid chamber 24 decreases, is referred to as the front of the electric cylinder device 10. Furthermore, the direction of linear movement S in which the volume of the fluid chamber 24 increases is referred to as the rear of the electric cylinder device 10. Furthermore, the linear movement of the piston 13 toward the front inside the cylinder 11 is referred to as the advancement of the piston 13, and the linear movement of the piston 13 toward the rear inside the cylinder 11 is referred to as the retreat of the piston 13. The movement position of the piston 13 when it is moved farthest within its linear movement range inside the cylinder 11 is referred to as the most retreated position of the piston 13.

[0013] The housing 12 has two ports communicating with the cylinder 11: an input port 25 for introducing brake fluid into the fluid chamber 24, and an output port 26 for discharging brake fluid from the fluid chamber 24. Seal components 27 and 28 are installed on the inner wall of the cylinder 11, respectively, behind and in front of the opening of the input port 25. The seal components 27 and 28 are components for preventing leakage of brake fluid from the fluid chamber 24 through the clearance between the cylinder 11 and the piston 13. The input port 25 is in communication with the fluid chamber 24 when the piston 13 is located in the most retracted position. When the piston 13 advances a certain distance from the most retracted position, the opening of the input port 25 to the cylinder 11 is blocked by the piston 13, thereby blocking communication between the input port 25 and the fluid chamber 24. The output port 26 remains in communication with the fluid chamber 24 regardless of the position of the piston 13.

[0014] In such an electric cylinder device 10, the linear motion conversion mechanism 16 converts the rotation of the electric motor 14, which is transmitted via the rotation transmission mechanism 15, into linear motion and transmits it to the piston 13, thereby moving the piston 13 within the cylinder 11. When the piston 13 blocks the opening of the input port 25 to the cylinder 11, only the output port 26 is in communication with the fluid chamber 24. When the piston 13 moves forward in this state, the brake fluid within the fluid chamber 24 is pressed by the piston 13 and discharged from the output port 26. A braking device provided with such an electric cylinder device 10 generates a braking force for the vehicle by transmitting the pressing force of the piston 13 to a friction member via the brake fluid discharged from the output port 26.

[0015] <Connection structure of piston 13 and nut 23> Next, the connection structure between the piston 13 and the nut 23 will be described in detail with reference to Figure 2. In the following description, the direction perpendicular to the linear motion direction S of the piston 13 in the cylinder 11 will be referred to as the radial direction R.

[0016] 2, a recess 29 into which the front end of the nut 23 is inserted is provided at the rear end of the piston 13. The recess 29 has an inner diameter larger than the outer diameter of the nut 23. That is, the rear end of the piston 13 and the front end of the nut 23 overlap in the linear motion direction S. A seal ring 30 serving as an elastic component is sandwiched in the gap between the recess 29 and the nut 23 in the radial direction R.

[0017] The recess 29 has a tapered surface 31 that slopes inward in the radial direction R as it extends forward. Meanwhile, the front end of the nut 23 is formed into a convex spherical surface 32. The piston 13 and the nut 23 are assembled together with the convex spherical surface 32 of the nut 23 in line contact with the tapered surface 31 of the recess 29. In this embodiment, the tapered surface 31 corresponds to the contact surface that contacts the end face of the linear motion part in the linear motion direction S. Furthermore, the convex spherical surface 32 of the nut 23 corresponds to the end face of the linear motion part. Furthermore, in this embodiment, the piston 13 corresponds to the first component, and the nut 23, which is the linear motion part of the linear motion conversion mechanism 16, corresponds to the second component.

[0018] <Effects of the First Embodiment> The operation and effects of this embodiment will be described. In such an electric cylinder device 10, there is a possibility that the third gear 20 and the linear motion conversion mechanism 16 may be assembled to the housing 12 in a state where they are misaligned with respect to the center position of the cylinder 11 during assembly. Misalignment here refers to the rotation axis O of the third gear 20 and the linear motion conversion mechanism 16 being misaligned parallel to the central axis of the cylinder 11. At this time, if no relative displacement in the radial direction R of the piston 13 with respect to the cylinder 11 is allowed, a load in the radial direction R acts between the cylinder 11 and the piston 13. This load may cause uneven wear in the components of the electric cylinder device 10, such as the cylinder 11, piston 13, screw shaft 22, and nut 23.

[0019] In contrast, the piston 13 of the electric cylinder device 10 of this embodiment is connected to the nut 23 in a state where relative displacement in the radial direction R is permitted through elastic deformation of the seal ring 30. Meanwhile, the nut 23 is assembled to the housing 12 in which the cylinder 11 is provided via the screw shaft 22, the third gear 20, and the bearing component 21. In this electric cylinder device 10, the piston 13 is assembled to the electric cylinder device 10 in a state where relative displacement in the radial direction R with respect to the cylinder 11 is permitted. Therefore, even if the above-mentioned center position deviation occurs, the piston 13 is displaced relative to the cylinder 11 in the radial direction R, thereby mitigating the load in the radial direction R acting between the cylinder 11 and the piston 13. Therefore, the electric cylinder device 10 of this embodiment has the effect of suppressing uneven wear of the components due to deviation in the center positions of the piston 13 and the cylinder 11.

[0020] Furthermore, when assembling the electric cylinder device 10, the third gear 20 and the linear motion conversion mechanism 16 may be assembled to the housing 12 with the rotation axis O tilted relative to the central axis of the cylinder 11. Such tilt of the rotation axis O relative to the central axis of the cylinder 11 may also cause a load in the radial direction R to be generated between the cylinder 11 and the piston 13, which may result in uneven wear of the components of the electric cylinder device 10. In this regard, in this embodiment, the contact between the nut 23 and the piston 13 in the linear motion direction S is line contact between the tapered surface 31 and the convex spherical surface 32. This allows tilting of the piston 13 relative to the nut 23. Therefore, the electric cylinder device 10 of this embodiment also has the effect of suppressing uneven wear of the components due to tilt of the rotation axis O relative to the central axis of the cylinder 11.

[0021] In the electric cylinder device 10, when the piston 13 moves forward in the cylinder 11, a compressive reaction force of the brake fluid in the fluid chamber 24 is applied to the piston 13. Therefore, a greater thrust is required when the piston 13 moves forward than when it moves backward. In this embodiment, the piston 13 has a tapered surface 31 that contacts a convex spherical surface 32, which is the end face of the nut 23 in the linear motion direction S. Furthermore, a seal ring 30, which is an elastic part, is interposed in the gap between the piston 13 and the nut 23 in the radial direction R. In this embodiment, when the piston 13 moves forward, the convex spherical surface 32 of the nut 23 directly presses against the tapered surface 31 of the piston 13, thereby transmitting thrust from the nut 23 to the piston 13. In contrast, when the piston 13 moves linearly backward, thrust is transmitted from the nut 23 to the piston 13 through friction between the nut 23 and the seal ring 30. With this transmission through friction of the seal ring 30, the thrust that can be transmitted from the nut 23 to the piston 13 is smaller than when the piston 13 moves forward. However, as described above, when retracting, a larger thrust is not required than when advancing, and therefore the thrust required for retracting the piston 13 can be sufficiently transmitted even through the friction of the seal ring 30. In such a case, the piston 13 can be connected to the nut 23 simply by inserting the front end of the nut 23, which has the seal ring 30 attached to its outer periphery, into the recess 29 of the piston 13. This makes it easier to connect the piston 13 and the nut 23 when assembling the electric cylinder device 10.

[0022] <Modification of the first embodiment> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0023] In the above embodiment, the contact surface of the piston 13 with the convex spherical surface 32 of the nut 23 is the tapered surface 31. The shape of the contact surface of the piston 13 with the convex spherical surface 32 may be changed. For example, the contact surface of the piston 13 with the convex spherical surface 32 may be a concave spherical surface with a smaller curvature than the convex spherical surface 32, or a flat surface perpendicular to the linear motion direction S. In these cases, the contact between the nut 23 and the piston 13 in the linear motion direction S is line contact. Therefore, even in such a case, uneven wear of the components caused by both a misalignment of the center positions of the piston 13 and the cylinder 11 and an inclination of the rotation axis O with respect to the central axis of the cylinder 11 can be suppressed.

[0024] The contact surface of the piston 13 with the convex spherical surface 32 of the nut 23 may be a concave spherical surface with the same curvature as the convex spherical surface 32. Furthermore, the contact surfaces of both the nut 23 and the piston 13 may be flat surfaces perpendicular to the linear motion direction S. In these cases, the contact between the nut 23 and the piston 13 in the linear motion direction S is surface contact. Therefore, even in such cases, uneven wear of the components due to misalignment of the center positions of the piston 13 and the cylinder 11 can be suppressed.

[0025] As shown in Figure 3, the nut 23 and the piston 13 are arranged so that a gap is provided between them in the linear direction S. An elastic component 33, separate from the seal ring 30, may be sandwiched in the gap, i.e., the gap between the nut 23 and the piston 13 in the radial direction R. In this case, the elastic component 33 allows tilting of the piston 13 relative to the nut 23 by elastic deformation. This reduces uneven wear of the components due to both misalignment of the center positions of the piston 13 and the cylinder 11 and tilting of the rotation axis O relative to the central axis of the cylinder 11.

[0026] As shown in FIG. 4, an elastic element 34 may be installed between the nut 23 and the piston 13, sandwiched in both the translatory direction S and the radial direction R. In this case, the elastic element 34 allows tilting of the piston 13 relative to the nut 23 through elastic deformation. This reduces uneven wear of the components due to both misalignment of the center positions of the piston 13 and the cylinder 11 and tilting of the rotation axis O relative to the central axis of the cylinder 11. The elastic element 34 also functions as the seal ring 30 in the above embodiment. That is, the elastic element 34 transmits thrust from the nut 23 to the piston 13 through friction when the piston 13 moves translatory backward. Therefore, a single elastic element 34 alone can achieve the same effect as in the case of FIG. 3.

[0027] As shown in FIG. 5, a cap part 35 with a hemispherical front end may be fixed to the nut 23 so that the cap part 35 comes into contact with the piston 13. In this case, the cap part 35 makes point contact with the piston 13. Even in this case, tilting of the piston 13 relative to the nut 23 is permitted. This reduces uneven wear of the components due to both misalignment of the center positions of the piston 13 and the cylinder 11 and tilting of the rotation axis O relative to the central axis of the cylinder 11. As shown by the solid line in FIG. 5, the contact surface of the piston 13 with the cap part 35 may be a flat surface perpendicular to the linear motion direction S. Alternatively, as shown by the dashed line in FIG. 5, the contact surface of the piston 13 with the cap part 35 may be a concave spherical surface with a smaller curvature than the front end of the cap part 35. The concave spherical surface increases the strength of the piston 13 compared to a flat surface.

[0028] As shown in Figure 6, a cap part 37 having a spherical protrusion 36 at its front end may be fixed to the nut 23. In this case, the spherical protrusion 36 of the cap part 37 also makes point contact with the piston 13, allowing the piston 13 to tilt relative to the nut 23. Therefore, even in this case, uneven wear of the components due to both misalignment of the center positions of the piston 13 and cylinder 11 and tilt of the rotation axis O relative to the central axis of the cylinder 11 can be suppressed. Note that, in the case of Figure 6, the contact surface of the piston 13 with the spherical protrusion 36 is a spherical surface with a smaller curvature than the spherical protrusion 36, but it may also be a flat surface perpendicular to the linear motion direction S.

[0029] As shown in FIG. 7 , the elastic element 38 is installed sandwiched between the nut 23 and the piston 13 in the linear motion direction S. The elastic element 38 may be fixed to both the nut 23 and the piston 13 by adhesive or the like. In this case, the elastic element 38 allows for relative displacement in the radial direction R and inclination of the piston 13 relative to the nut 23 through elastic deformation. Therefore, even in this case, uneven wear of the components due to both misalignment of the center positions of the piston 13 and the cylinder 11 and inclination of the rotation axis O relative to the central axis of the cylinder 11 can be suppressed. Furthermore, because the elastic element 38 is fixed to both the nut 23 and the piston 13, thrust can be transmitted from the nut 23 to the piston 13 during both forward and backward linear motion.

[0030] A connecting part 39 as shown in FIG. 8 may be provided instead of the seal ring 30. The connecting part 39 is installed in a mounting groove 40 provided on the outer periphery of the nut 23. The connecting part 39 has a protrusion 41 that can protrude outward in the radial direction R from the mounting groove 40. When pressure is applied inward in the radial direction R to the protrusion 41, the connecting part 39 elastically deforms so that the amount of protrusion 41 protruding from the mounting groove 40 decreases. Meanwhile, an engagement groove 42 with which the protrusion 41 can engage is formed on the inner periphery of the piston 13. The nut 23 and the piston 13 are connected with each other while the protrusion 41 of the connecting part 39 is engaged with the engagement groove 42. In this case, when the piston 13 retracts, thrust is transmitted from the nut 23 to the piston 13 via the connecting part 39. When the electric cylinder device 10 is assembled, the tip of the nut 23 to which the connecting part 39 is attached is inserted into the recess 29 of the piston 13, thereby connecting the piston 13 and the nut 23 with a snap-fit ​​engagement. Therefore, the operation of connecting the nut 23 and the piston 13 when assembling the electric cylinder device 10 becomes easy.

[0031] (Second embodiment) Next, a second embodiment of the electric cylinder device will be described in detail with reference to Figures 9 to 11. In this embodiment, the same components as those in the above embodiment will be denoted by the same reference numerals, and detailed description thereof will be omitted.

[0032] <Configuration of electric cylinder device 110 according to second embodiment> FIG. 9 shows a cross-sectional view of an electric cylinder device 110 of a second embodiment. Although not shown in the cross section of FIG. 9, the electric cylinder device 110 of this embodiment includes an electric motor 14, a first gear 18, a second gear 19, an input port 25, and an output port 26, similar to the electric cylinder device 10 of FIG. 1. The electric cylinder device 110 also includes a piston 113 that is integrally connected to a nut 123. That is, the piston 113 of the electric cylinder device 110 is connected to the nut 123 in a state that does not allow relative displacement in the radial direction R with respect to the nut 123. On the other hand, in the electric cylinder device 110 of this embodiment, the third gear 120 and the screw shaft 122 are connected in a state that allows relative displacement in the radial direction R and tilting of the rotation axis O.

[0033] FIG. 10 shows a cross-sectional view of the connection portion between the third gear 120 and the screw shaft 122. FIG. 11 shows a cross-sectional view of the same connection portion taken along line 11-11 in FIG. 10. As shown in FIG. 10, an insertion shaft 140 having a smaller diameter than the other portions is provided at the rear end of the screw shaft 122. A step portion 141 between the insertion shaft 140 and the other portions of the screw shaft 122 has a convex spherical surface. The screw shaft 122 is also provided with protrusions 142 that protrude outward in the radial direction R from the insertion shaft 140. Although four protrusions 142 are shown in FIG. 11, the number of protrusions 142 may be one or more.

[0034] On the other hand, the third gear 120 is provided with a tapered surface 143 that slopes inward in the radial direction R as it extends rearward. The third gear 120 is also provided with an insertion hole 144 that extends from its rear end face to the tapered surface 143. The insertion hole 144 has an inner diameter larger than the outer diameter of the insertion shaft 140. Around the insertion hole 144, engagement grooves 145, the number of which is the same as the number of protrusions 142 of the screw shaft 122, are provided so as to extend radially outward in the radial direction R.

[0035] When connecting the third gear 120 and the screw shaft 122, the insertion shaft 140 is inserted into the insertion hole 144 until the stepped portion 141 contacts the tapered surface 143. Since the stepped portion 141 is a convex spherical surface, the contact between the stepped portion 141 and the tapered surface 143 is line contact. At this time, the tip of the insertion shaft 140 protrudes rearward from the third gear 120. A snap ring 146 is attached to the portion of the insertion shaft 140 protruding rearward from the third gear 120 to prevent the screw shaft 122 from coming off the third gear 120, thereby connecting the third gear 120 and the screw shaft 122. As shown in FIG. 11 , the third gear 120 and the screw shaft 122 are loosely fitted with a gap in the radial direction R between the insertion shaft 140 and the protrusion 142 and the insertion hole 144 and the engagement groove 145.

[0036] <Effects of the Second Embodiment> In the electric cylinder device 110 of this embodiment, the third gear 120 and the screw shaft 122 are connected with a gap in the radial direction R. That is, the screw shaft 122 is connected to the third gear 120 with relative displacement in the radial direction R permitted. The third gear 120 is attached to a housing 12 in which the cylinder 11 is provided via a bearing component 21. The screw shaft 122 is connected to the piston 113 via a nut 123. Therefore, in the electric cylinder device 110, relative displacement of the piston 113 in the radial direction R with respect to the cylinder 11 is permitted through relative displacement of the screw shaft 122 with respect to the third gear 120. Furthermore, the projection 142 meshes with the engagement groove 145, so that the rotation of the third gear 120 is transmitted to the screw shaft 122. Therefore, the electric cylinder device 110 of this embodiment has the effect of suppressing uneven wear of components due to misalignment of the center positions of the piston 113 and the cylinder 11. Additionally, the electric cylinder device 110 has the advantage of being able to simultaneously perform the function of transmitting rotation from the third gear 120, which is a rotation input component, to the screw shaft 122, which is a rotating part. In the electric cylinder device 110 of this embodiment, the screw shaft 122, which is a rotating part of the linear motion conversion mechanism 16, corresponds to the first component, and the third gear 20, which is a rotation input component, corresponds to the second component. Furthermore, the engagement groove 145 provided in the third gear 120, which is a rotation input part, corresponds to the first recess, and the protrusion 142 provided on the screw shaft 122, which is a rotating part of the linear motion conversion mechanism 16, corresponds to the second protrusion.

[0037] Additionally, the third gear 120 and the screw shaft 122 are connected with a line contact between the stepped portion 141, which is a convex spherical surface, and the tapered surface 143. This allows the rotation axis of the screw shaft 122 to tilt relative to the rotation axis of the third gear 120. The tilting of both rotation axes also allows the rotation axis O to tilt relative to the central axis of the cylinder 11. Therefore, the electric cylinder device 110 of this embodiment has the effect of suppressing uneven wear of the components due to the tilt of the rotation axis O relative to the central axis of the cylinder 11.

[0038] <Modification of the second embodiment> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0039] As shown in FIGS. 12 and 13, an insertion shaft 221 may be provided in the third gear 220, and an insertion hole 223 may be provided in the threaded shaft 222. The insertion shaft 221, which protrudes forward along the rotation axis O, is connected to the third gear 220 in FIG. 12 so as to rotate integrally therewith. The insertion shaft 221 is fixed to the third gear 220 with its rear end protruding rearward from the third gear 220. A snap ring 224 is attached to the portion of the insertion shaft 140 protruding rearward from the third gear 220 to prevent the insertion shaft 221 from slipping out of the third gear 220. A convex spherical surface 225 is provided at the front end of the insertion shaft 221. A plurality of protrusions 226 are provided on the side surface of the insertion shaft 221 so as to protrude radially outward in the radial direction R. Although four protrusions 226 are shown in FIG. 13, the number of protrusions 226 may be one or more. On the other hand, the screw shaft 222 is provided with an insertion hole 223 extending forward from its rear end. The insertion hole 223 has an inner diameter larger than the outer diameter of the insertion shaft 221. Furthermore, around the insertion hole 223 in the screw shaft 222, engagement grooves 227 are provided, the same number as the number of protrusions 226 provided on the insertion shaft 221, so as to extend radially outward in the radial direction R. The protrusions 226 mesh with the engagement grooves 227, thereby transmitting the rotation of the third gear 220 to the screw shaft 222. There is a loose fit between the protrusions 226 and the engagement grooves 227. Furthermore, a tapered surface 228 is provided at the front end of the insertion hole 223, which is inclined inward in the radial direction R as it extends forward. The third gear 220 and the screw shaft 222 are coupled together with the convex spherical surface 225 of the insertion shaft 221 in contact with the tapered surface 228 of the insertion hole 223. The contact between the convex spherical surface 225 and the tapered surface 228 is line contact. The third gear 220 and the threaded shaft 222 connected in this manner allow relative displacement of the threaded shaft 222 in the radial direction R with respect to the third gear 220. Therefore, even in such a case, there is an effect of suppressing uneven wear of the components due to deviation of the center positions of the piston 113 and the cylinder 11. Furthermore, the third gear 220 and the threaded shaft 222 are connected in a line contact state, allowing tilting of the rotation axis of the threaded shaft 222 with respect to the rotation axis of the third gear 220.Therefore, even in such a case, it is possible to suppress uneven wear of the components due to the inclination of the rotation axis O with respect to the central axis of the cylinder 11. In this modified example, the protrusion 226 provided on the third gear 220 corresponds to the first convex portion, and the engagement groove 227 provided on the screw shaft 222 corresponds to the second concave portion.

[0040] The screw shafts 122, 222 may be prevented from coming off the third gears 120, 220 by a method other than the snap ring 224. The third gears 120, 220 and the screw shafts 122, 222 may be connected in a surface contact state. Even in this case, if the screw shafts 122, 222 are allowed to be displaced relative to the third gears 120, 220 in the radial direction R, uneven wear of the components due to misalignment of the piston 113 and the cylinder 11 can be suppressed.

[0041] (Third embodiment) Next, a third embodiment of the electric cylinder device will be described in detail with reference to Fig. 14. In this embodiment, the same components as those in the above embodiment will be denoted by the same reference numerals, and detailed description thereof will be omitted.

[0042] <Configuration of electric cylinder device 310 according to the third embodiment> Fig. 14 shows a cross-sectional view of an electric cylinder device 310 of the third embodiment. Although not shown in the cross section of Fig. 14, the electric cylinder device 310 of this embodiment includes an electric motor 14, a first gear 18, a second gear 19, an input port 25, and an output port 26, similar to the electric cylinder device 10 of Fig. 1. The electric cylinder device 310 also includes a piston 113 connected integrally with a nut 123, similar to the electric cylinder device 110 of Fig. 9. The electric cylinder device 310 also includes a third gear 20 connected integrally with a screw shaft 22, similar to the electric cylinder device 10 of Fig. 1.

[0043] 14 has a first housing part 311 in which the cylinder 11 is provided, and a second housing part 312 in which the third gear 20 is installed. The first housing part 311 and the second housing part 312 are connected so as to be able to move relatively in the radial direction R, with their surfaces perpendicular to the linear motion direction S abutting against each other.

[0044] In the example shown in FIG. 14 , a first housing component 311 and a second housing component 312 are connected using a plurality of bolts 313. The first housing component 311 and the second housing component 312 are provided on their outer peripheries with flanges 314, 315 that protrude outward in the radial direction R. The flange 314 of the first housing component 311 is provided with a through hole 316 that penetrates the flange 314 in the linear motion direction S. The through hole 316 has an inner diameter that is larger than the axial diameter of the bolt 313. Meanwhile, the flange 315 of the second housing component 312 is provided with a threaded hole 317 that extends in the linear motion direction S. An internal thread is formed on the inner periphery of the threaded hole 317 for threading the bolt 313. The bolt 313 is threaded into the threaded hole 317 through the through hole 316, with a spring washer 318 sandwiched between the head of the bolt 313 and the flange 314.

[0045] Furthermore, a ring-shaped seal ring 319 made of an elastic material is interposed between the butted surfaces of the first housing part 311 and the second housing part 312. The seal ring 319 is disposed so as to surround the outside of the cylinder 11 in the radial direction R.

[0046] <Effects of the Third Embodiment> In the electric cylinder device 310 of this embodiment, the first housing component 311 and the second housing component 312 are connected together in a state that allows relative displacement in the radial direction R. A cylinder 11 is provided inside the first housing component 311. Furthermore, a third gear 20, to which a piston 113 is connected via a linear motion conversion mechanism 16, is attached inside the second housing component 312. Therefore, in the electric cylinder device 310, relative displacement of the piston 113 in the radial direction R with respect to the cylinder 11 is allowed through relative displacement of the first housing component 311 and the second housing component 312 in the radial direction R. Therefore, the electric cylinder device 310 of this embodiment has the effect of suppressing uneven wear of the components due to misalignment of the center positions of the piston 113 and the cylinder 11. In addition, this embodiment has the advantage of only dividing the housing, and the internal structure of the housing can be maintained as in the conventional embodiment, thereby minimizing the scale of modification. In the electric cylinder device 310 of this embodiment, the second housing part 312 corresponds to the first component part, and the first housing part 311 corresponds to the second component part.

[0047] <Modification of the third embodiment> If the first housing part 311 and the second housing part 312 are allowed to be displaced relative to each other in the radial direction R, they may be connected as follows.

[0048] The first housing part 311 and the second housing part 312 are connected together by a method other than bolt fastening. The seal ring 319 may be omitted.

[0049] The first housing part 311 and the second housing part 312 are connected with a sheet made of an elastic material such as rubber sandwiched between their mating surfaces. (Fourth embodiment) Next, a fourth embodiment of the electric cylinder device will be described in detail with reference to Fig. 15. In this embodiment, the same components as those in the above-described embodiment will be denoted by the same reference numerals, and detailed description thereof will be omitted.

[0050] <Configuration of electric cylinder device 410 according to the fourth embodiment> Fig. 15 shows a cross-sectional view of an electric cylinder device 410 of a fourth embodiment. Although not shown in the cross section of Fig. 15, the electric cylinder device 410 of this embodiment includes an electric motor 14, a first gear 18, a second gear 19, an input port 25, and an output port 26, similar to the electric cylinder device 10 of Fig. 1. The electric cylinder device 410 also includes a piston 113 integrally connected with a nut 123, similar to the electric cylinder device 110 of Fig. 9. The electric cylinder device 410 also includes a third gear 20 integrally connected with a screw shaft 22, similar to the electric cylinder device 10 of Fig. 1.

[0051] As shown in FIG. 15 , the electric cylinder device 410 includes a rolling bearing 414, which rotatably supports the third gear 20, and which has a rolling element 413 interposed between an inner ring 411 and an outer ring 412. The inner ring 411 of the rolling bearing 414 is fixed to the third gear 20, and the outer ring 412 is fixed to the inner wall of the housing 12. The inner ring 411 is attached to the third gear 20 with its inner circumferential surface and front side surface in contact with the third gear 20. The outer ring 412 is attached to the housing 12 with its rear side surface in contact with the inner wall of the housing 12. Furthermore, a seal ring 415, which is an elastic component, is interposed between the outer circumferential surface of the outer ring 412 and the inner wall of the housing 12. That is, the rolling bearing 414 is attached to the housing 12 with relative displacement in the radial direction R being permitted by elastic deformation of the seal ring 415. The third gear 20, to which the piston 113 is connected via the linear motion conversion mechanism 16, is connected to the inner wall of the housing 12 via the rolling bearing 414. Therefore, in such an electric cylinder device 410, the piston 113 is installed in a state in which relative displacement in the radial direction R with respect to the housing 12 in which the cylinder 11 is provided is permitted.

[0052] <Effects of the Fourth Embodiment> In the electric cylinder device 410 of this embodiment, relative displacement of the piston 113 in the radial direction R with respect to the cylinder 11 is permitted through relative displacement of the rolling bearing 414 in the radial direction R with respect to the housing 12. Therefore, the electric cylinder device 410 of this embodiment has the effect of suppressing uneven wear of components due to misalignment of the center positions of the piston 113 and the cylinder 11. In addition, this embodiment allows relative displacement at a location far from the tip of the piston 113, so uneven wear can be effectively suppressed. Note that if the rolling bearing 414 moves too freely, the shaft will become more wobbly. Therefore, it is preferable to provide an elastic component between the rolling bearing 414 and the housing 12 to provide an aligning function. In the electric cylinder device 410 of this embodiment, the rolling bearing 414 corresponds to the first component, and the housing 12 corresponds to the second component.

[0053] <Modification of the Fourth Embodiment> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0054] 16, an elastic part 416 may be interposed between the rear side surface of the outer ring 412 of the rolling bearing 414 and the inner wall of the housing 12. In this case, the elastic deformation of the elastic part 416 allows the rotation axis of the third gear 20 to tilt relative to the housing 12. This prevents uneven wear of the components due to the tilt of the rotation axis O relative to the central axis of the cylinder 11.

[0055] A seal ring 415 may be interposed between the inner peripheral surface of the inner ring 411 of the rolling bearing 414 and the third gear 20. In this case, the elastic deformation of the seal ring 415 allows the piston 113 to be displaced relative to the cylinder 11 in the radial direction R. Therefore, in this case, uneven wear of the components due to misalignment of the piston 113 and the cylinder 11 can be suppressed.

[0056] (Modifications of each embodiment) The above-described embodiments can be further modified and implemented as follows: The above-described embodiments and the following modifications can be implemented in combination with each other within the scope of technical compatibility.

[0057] The number of gears constituting the rotation transmission mechanism 15 may be changed. A mechanism other than the gear mechanism shown in Fig. 1 may be used as the rotation transmission mechanism 15. For example, a wrapping transmission mechanism or a planetary gear mechanism can be used as the rotation transmission mechanism 15. In this case, the rotating part connected to the rotating part of the linear motion conversion mechanism 16 in the rotation transmission mechanism 15 corresponds to the rotation input part.

[0058] The electric motor 14 may be directly connected to the linear motion conversion mechanism 16 without providing the rotation transmission mechanism 15. In this case, the motor shaft 17 becomes the part corresponding to the rotation input part. A mechanism in which the screw shaft moves linearly in response to the rotation of the nut, i.e., a mechanism in which the nut is the rotating part and the screw shaft is the linear part, may be employed for the linear motion conversion mechanism 16. In this case, the nut is connected to the rotation input part, and the screw shaft is connected to the pistons 13, 113. The connection structure of the nut 23 and piston 13 in the first embodiment and its modified examples can be employed as the connection structure of the screw shaft and piston 13 in this case.

[0059] The electric cylinder devices of the above embodiments and their modifications may be modified so that the piston applies a direct pressure to the outside, and may be used as an electric cylinder device for a dry-type braking device in which the piston pressure is directly transmitted to a friction member to generate a braking force. Also, the electric cylinder devices of the above embodiments and modifications may be used for purposes other than braking devices. [Explanation of symbols]

[0060] 10, 110, 310, 410... Electric cylinder device 11...Cylinder 12. Housing 13,113...Piston 14...Electric motor 15...Rotation transmission mechanism 16...Linear motion conversion mechanism 17...Motor shaft 18...1st gear 19…2nd gear 20, 120, 220...3rd gear 21...Bearing parts 22, 122, 222...Screw shaft 23,123...Nut 24…liquid chamber 25...Input port 26...Output port 27, 28...Sealing parts 29...recess 30,319,415...Seal ring 31,143,228...Tapered surface 32,225…Convex spherical surface 33, 34, 38, 416...Elastic parts 35, 37...Cap parts 36…Spheroidal process 39...Connecting parts 40...Mounting groove 41,142,226…protrusion 42, 145, 227...Engagement groove 140,221...insertion shaft 144,223...Insertion hole 146,224...Snap ring 311...First housing part 312...Second housing part 313...Bolt 314, 315...Flanges 316...Through hole 317...Screw hole 318...Spring washer 411...Inner circle 412...Outer ring 413...Rolling element 414...Rolling bearings

Claims

1. an electric cylinder device comprising: a piston arranged inside a cylinder; a rotation input part that rotates in response to rotation of an electric motor; a linear motion conversion mechanism including a rotating part that rotates when the rotation of the rotation input part is transmitted; and a linear motion part that acts on the linear motion of the piston by moving linearly in response to the rotation of the rotating part; and a housing in which the cylinder is provided and which accommodates the piston, the rotation input part, and the linear motion conversion mechanism, The piston and the linear motion portion, which are two of the components of the electric cylinder device, are allowed to undergo relative displacement in a radial direction, which is a direction perpendicular to the axial direction of the piston, The piston is a component that is displaced relative to the cylinder in the radial direction in response to the relative displacement in the radial direction with respect to the linear motion portion, the piston and the linear motion portion include an overlapping portion in the axial direction, and an elastic component is provided in a gap in the radial direction of the overlapping portion. Electric cylinder device.

2. an electric cylinder device comprising: a piston arranged inside a cylinder; a rotation input part that rotates in response to rotation of an electric motor; a linear motion conversion mechanism including a rotating part that rotates when the rotation of the rotation input part is transmitted; and a linear motion part that acts on the linear motion of the piston by moving linearly in response to the rotation of the rotating part; and a housing in which the cylinder is provided and which accommodates the piston, the rotation input part, and the linear motion conversion mechanism, a first component and a second component, which are two of the components of the electric cylinder device, are allowed to move relative to each other in a radial direction, which is a direction perpendicular to the axial direction of the piston; and the first component is a component that displaces the piston relative to the cylinder in the radial direction in response to the relative displacement of the first component with respect to the second component in the radial direction, The first component is the rotating part, and the second component is the rotation input part, and a first convex part or a first concave part provided on the rotation input part engages with a second concave part or a second convex part provided on the rotating part, thereby transmitting the rotation of the rotation input part to the rotating part, and there is a loose fit between the first convex part and the second concave part, or between the first concave part and the second convex part. Electric cylinder device.

3. an electric cylinder device comprising: a piston arranged inside a cylinder; a rotation input part that rotates in response to rotation of an electric motor; a linear motion conversion mechanism including a rotating part that rotates when the rotation of the rotation input part is transmitted; and a linear motion part that acts on the linear motion of the piston by moving linearly in response to the rotation of the rotating part; and a housing in which the cylinder is provided and which accommodates the piston, the rotation input part, and the linear motion conversion mechanism, a first component and a second component, which are two of the components of the electric cylinder device, are allowed to move relative to each other in a radial direction, which is a direction perpendicular to the axial direction of the piston; and the first component is a component that displaces the piston relative to the cylinder in the radial direction in response to the relative displacement of the first component with respect to the second component in the radial direction, The first component is a bearing component that rotatably supports the rotation input component, the second component is the housing, and an elastic component is provided in a gap between the bearing component and the housing. Electric cylinder device.

4. an electric cylinder device comprising: a piston arranged inside a cylinder; a rotation input part that rotates in response to rotation of an electric motor; a linear motion conversion mechanism including a rotating part that rotates when the rotation of the rotation input part is transmitted; and a linear motion part that acts on the linear motion of the piston by moving linearly in response to the rotation of the rotating part; and a housing in which the cylinder is provided and which accommodates the piston, the rotation input part, and the linear motion conversion mechanism, a first component and a second component, which are two of the components of the electric cylinder device, are allowed to move relative to each other in a radial direction, which is a direction perpendicular to the axial direction of the piston; and the first component is a component that displaces the piston relative to the cylinder in the radial direction in response to the relative displacement of the first component with respect to the second component in the radial direction, The housing has a first housing part in which the cylinder is provided and a second housing part in which the rotation input part is installed, and the first component part is the second housing part, and the second component part is the first housing part. Electric cylinder device.

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