Floating joints and linear actuators

Abstract

To provide a floating joint and a linear actuator facilitating axial alignment or parallelism confirming while maintaining a rotation-preventive function of an output screw shaft by a direct-acting driven device, by interposing an elastic body regulated in rotation between joint components A / B.SOLUTION: On the inner side in a diametrical direction of a case 30 fastened to a driven device, a cylinder body 300 fastened to an output screw shaft 2 is internally installed. Between an inner periphery of the case 30 and an outer periphery of the cylinder body 300, a cylindrical elastic body 33 is interposed, and an engaging portion is interposed, which engages with an outer peripheral surface of the cylindrical elastic body 33 and an inner peripheral surface of the case 30.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a floating joint and a linear actuator. In detail, the present invention relates to a floating joint as a connecting member used when connecting an output screw shaft of a linear actuator having a screw nut that screws into an output screw shaft and has the function of converting the rotation of a motor into linear motion of the output screw shaft by the screw nut to a driven device, and to a guided linear actuator that uses the floating joint. [Background technology]

[0002] Conventionally, examples of connection structures between an output screw shaft of this type of linear actuator and a driven device include those shown in Patent Documents 1 and 2. As an example, a problem that occurs when a linear actuator 51 is assembled to a general linear motion device 50 using a connection structure as shown in FIGS. 8(a) and 8(b) will be described. The linear motion device 50 has a guide rail 54 on a base plate 53, and is composed of a guide block 55 guided by the guide rail 54, and an L-shaped table 56 fixed to the guide block 55. The tip of the ball screw shaft 43, which is the output screw shaft of the linear actuator 51, is connected to one end face of the table 56 of the linear motion device 50, and when the ball screw shaft 43 of the linear actuator 51 moves, the table 56 moves linearly together with the guide block 55 along the guide rail 54.

[0003] When assembling the linear actuator 51 to the linear motion device 50, it is necessary to assemble with high precision the coaxiality of the ball screw shaft 43, which is the output screw shaft, with respect to datum A, which is the center of rotation, and the perpendicularity of the ball screw shaft 43, which is the output screw shaft, with respect to datum B, which is the assembly part of the linear actuator 51 and the actuator mounting plate 52. The coaxiality of the ball screw shaft 43, which is the output screw shaft, with respect to datum A and the perpendicularity of the ball screw shaft 43, which is the output screw shaft, with respect to datum B, each need to be precisely regulated to about φ0.02 to 0.05. To achieve this, it is necessary to ensure the accuracy of the parts and adjust the assembly, and there is also the problem that measurements to confirm the accuracy are very time-consuming. Patent Document 1 discloses a linear actuator with an output screw shaft guide mechanism that can solve the above problems by guiding the outer periphery of a ball screw shaft 43 or a sliding screw shaft, which is an output screw shaft.

[0004] Patent Document 2 discloses a cylinder joint which is a connecting member between a cylinder rod of a fluid pressure cylinder and a driven device, and which has a misalignment adjustment mechanism that makes it easy to align the axes and adjust the parallelism. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-78464 A [Patent Document 2] Japanese Patent Application Publication No. 9-42305 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in Patent Document 1, it was difficult to realize a highly accurate attachment at low cost due to the influence of the runout accuracy and outer diameter accuracy of the output screw shaft itself. Patent Document 2 is a joint that connects between the cylinder rod of a fluid pressure cylinder and a driven device, and its center misalignment adjustment mechanism rotates freely. A linear actuator that is screwed onto an output screw shaft and has the function of converting the rotational motion of the screw nut into the linear motion of the output screw shaft can perform linear motion by restricting the rotation of the output screw shaft by connecting it to a driven device that moves linearly with the output screw shaft, so a joint like that in Patent Document 2 could not be used.

[0007] Furthermore, as shown in FIGS. 9 to 11, a connection member adopted for an output screw shaft 62 of a linear actuator 61 and a linearly moving table 65 arranged on a guide 66 is conceivable. As this connecting member, a rotation-restricted joint part 64 may be considered, which is composed of a joint part 63A having a non-circular part, for example having two flat surfaces, on the output screw shaft 62 and a joint part 63B which fits into the non-circular part 63a of the joint part 63A on the table 65 side with a small gap g, however, there are problems as described below. (a) Stopping accuracy deteriorates. (b) There is a delay in table movement relative to the linear actuator movement. (c) Wear particles generated from the contact area of ​​the joint parts 63A / B are scattered around. (d) If installed horizontally, the mass of the joint part 63A applies a radial load to the ball screw, which reduces its lifespan.

[0008] The present invention has been made in response to these conventional problems (disadvantages), and has an object to provide a floating joint and linear actuator that can solve the above-mentioned problems by interposing an elastic body that restricts rotation between joint parts A and B. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the present invention provides a floating joint that connects between an output screw shaft of a linear actuator, which includes a screw nut that screws into an output screw shaft and converts the rotation of a motor into linear motion of the output screw shaft by the screw nut, and a driven device driven by the linear actuator, the floating joint comprising: a cylindrical body fastened to the output screw shaft disposed inside the radial direction of a case fastened to the driven device; a cylindrical elastic body interposed between the inner periphery of the case and the outer periphery of the cylindrical body; and an engaging portion that engages with the outer periphery of the cylindrical elastic body and the inner periphery of the case. A pulley is used as the cylindrical body, and a tooth groove portion that meshes with the outer teeth of the pulley is provided on the inner peripheral surface of the cylindrical elastic body, and the position in the rotational direction is regulated by the engagement of the inner peripheral tooth groove portion of the cylindrical elastic body that meshes with the outer peripheral teeth of the pulley. The point is... The present invention also provides a linear actuator comprising an output screw shaft and a screw nut that screws into the output screw shaft, the rotation of a motor being converted into linear motion of the output screw shaft by the screw nut, a guide section provided on the outer surface of a linear actuator case along the direction of linear motion of the output screw shaft, a moving element that slides along the guide section, and the moving element connected to the output screw shaft, the linear actuator further comprising a cylinder fastened to the output screw shaft that is fitted inside the case in the radial direction and fastened to a driven device, a cylindrical elastic body interposed between the inner periphery of the case and the outer periphery of the cylinder, and an engaging section that engages with the outer periphery of the cylindrical elastic body and the inner periphery of the case. A pulley is used as the cylindrical body, and a tooth groove portion that meshes with the outer teeth of the pulley is provided on the inner peripheral surface of the cylindrical elastic body, and the position in the rotation direction is regulated by the engagement of the inner peripheral tooth groove portion of the cylindrical elastic body that meshes with the outer peripheral teeth of the pulley. The feature is that the movable element is fastened via a floating joint. Effect of the Invention

[0010] According to the present invention, when connecting the output screw shaft of a linear actuator having a screw nut that screws into an output screw shaft and has the function of converting the rotation of a motor into linear motion of the output screw shaft to a linear driving device, the floating joint of the present application can be used to easily align the axis and adjust the parallelism while maintaining the anti-rotation function of the output screw shaft by the linear driving device. Furthermore, by using the floating joint of the present invention, there is no limit to the load that can be placed on the linear actuator with respect to its thrust. [Brief description of the drawings]

[0011] [Figure 1] 1A and 1B show an embodiment in which a linear motion device and a linear actuator according to the present invention are connected by a floating joint of the present application, where (a) is a front view and (b) is a plan view of (a). [Diagram 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Diagram 3] FIG. 2 is an enlarged cross-sectional view showing a floating joint portion of part B in FIG. [Figure 4A]FIG. 2 is an exploded perspective view showing the floating joint portion of FIG. [Figure 4B] FIG. 4B is an enlarged view showing a floating joint portion of FIG. 4A. [Figure 5A] FIG. 4 is an exploded perspective view showing another embodiment of the floating joint of the present invention. [Figure 5B] FIG. 5B is an enlarged view showing a floating joint portion of FIG. 5A. [Figure 6] 1 is a vertical cross-sectional view showing a linear actuator to which the floating joint of the present invention is applied. [Figure 7] 1 is a cross-sectional view showing an embodiment of a guided linear actuator of the present invention. [Figure 8] 1A and 1B show a conventional linear motion device, in which (a) is a plan view and (b) is a front view of (a). [Figure 9] 1A and 1B show a linear motion device using a conventional joint part, where (a) is a plan view and (b) is a front view of (a). [Figure 10] 9(b) is a cross-sectional view taken along line CC in FIG. [Figure 11] FIG. 11 is a partially enlarged view of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention shown in FIG. 1 to FIG. 4A and FIG. 4B will be described with reference to the drawings. 1(a) and (b) are diagrams showing an embodiment in which a linear motion device and a linear actuator according to an embodiment of the present invention are connected by a floating joint of the present application. 1 to 4, 1 denotes a linear actuator constituting a linear motion device 10, 2 denotes an output screw shaft of the linear actuator 1, and 3 denotes a floating joint to which the linear motion of the linear actuator 1 is transmitted via the output screw shaft 2. This floating joint 3 includes a case 30 consisting of a case A31 and a case B32 which are fastened to each other. The case A31 includes a cylindrical elastic body 33 disposed on an inner peripheral surface 31b of a hollow portion 31a of the case A31, a pulley 34 disposed as a cylindrical body 300 on the inner peripheral side of the elastic body 33, i.e., on the radially inner side, and a pulley fixing bolt 35 disposed on the axis of the pulley 34, i.e., on the inner peripheral side, for fixing the pulley 34. An insertion hole 31d through which the output screw shaft 2 is inserted is formed on the side wall surface 31c on the linear actuator 1 side of the case A31, through which the output screw shaft 2 is inserted, and the output screw shaft 2 is inserted into the hollow portion 31a of the case A31 through this insertion hole 31d.

[0013] The output screw shaft 2 is disposed in contact with an end face 34a of a pulley 34 disposed inside the hollow portion 31a on the linear actuator 1 side. A plurality of groove-shaped engagement recesses 31e (four in the illustrated example) are formed in the axial direction at regular intervals along the circumferential direction on the inner peripheral surface 31b of the hollow portion 31a of the case A31. A plurality of screw holes 31f (four in the illustrated example) are formed in the axial direction at regular intervals along the circumferential direction on the wall surface portion surrounding the engagement recesses 31e. A protrusion 33a serving as an engagement portion that engages with the engagement recess 31e is formed along the axial direction on the outer peripheral surface of the cylindrical elastic body 33. A tooth groove portion 33b that engages with teeth 34b formed on the outer peripheral surface of the pulley 34 is formed along the inner peripheral surface in the axial direction on the inner peripheral surface of the cylindrical elastic body 33.

[0014] A pulley fixing bolt 35 is fitted in an insertion hole 34c formed on the inside of the pulley 34, and this pulley fixing bolt 35 passes through an insertion hole 34c formed on the axis of the end face 34a of the pulley 34, and is screwed from the tip of the output screw shaft 2 to a threaded portion (not shown) on the axis of the output screw shaft 2 and fastened, with the head of the pulley fixing bolt 35 engaging with the inner wall surface of the end face 34a of the pulley 34 to fix the pulley 34.

[0015] Case B32 is fastened to case A31 via case A fixing bolts 36 which are inserted and screwed along the axial direction into screw holes 31f provided at regular intervals in the circumferential direction on the end face of the peripheral edge of case A31 through insertion holes 32a provided on the peripheral edge. A gap δ is formed between case B32 and the opposing surface of pulley 34, and a slope 34T which is wider on the outer circumferential side toward the inner circumferential side is formed on the outer circumferential end face of pulley 34. This slope 34T is spaced apart from the gap δ between case B32 and case B32. 1 The inner clearance δ 2 The gap width is made larger than that of 1 +δ>δ 2 +δ. Gap δ 2 At the lower end, +δ coincides with the gap δ and becomes a vertical plane. On the other hand, the pulley 34 is also spaced from the case A31 by a gap δ 1 However, there is a gap δ on the inner circumference. 2 is formed on the end surface.

[0016] Case B 32 is fastened to an L-shaped table 7 serving as a linearly driven device via a case B fixing bolt 37 in a screw hole 32b provided in the central axis. The table 7 is fixed to a guide block 6 attached to a guide rail 5 arranged on a base plate 4 via a table fixing bolt 8, and the floating joint 3 reliably transmits the linear motion of the linear motion device 10 to the table 7.

[0017] Next, the operation of the above embodiment will be described. First, the configuration of the linear motion device 10 will be described. The linear actuator 1 is mounted on a base plate 4 and fixed by a fixing means (not shown). A guide rail 5 is provided on the base plate 4, and a guide block 6 that slides on the guide rail 5 is mounted on the guide rail 5. The guide block 6 moves linearly while being guided along the guide rail 5. An L-shaped table 7 is fixed to the guide block 6 via a table fixing bolt 8, and the surface of the table 7 that is not fixed to the guide block 6 and the tip of the output screw shaft 2 of the linear actuator 1 are connected and joined by a floating joint 3. When the output screw shaft 2 of the linear actuator 1 moves, the table 7 moves linearly together with the guide block 6 along the guide rail 5.

[0018] The floating joint 3 has a misalignment adjustment mechanism using a cylindrical elastic body 33 and pulley 34 housed in the case 30, which makes it easy to align the axes and adjust the parallelism, and also has a function of restricting the rotation of the shaft. As shown in Figures 4A and 4B, the floating joint 3 is composed of case A 31 and case B 32, which constitute the case 30, a cylindrical elastic body 33, and a pulley 34. The output screw shaft 2 and pulley 34 are connected with a pulley fixing bolt 35, case A 31 and case B 32 are connected with a case A fixing bolt 36, and case B 32 and table 7 are connected with a case B fixing bolt 37.

[0019] When the case A31 and the case B32 are joined by the bolt 36 for fixing the case A, a gap of about 70 μm is provided between the case B32 and the pulley 34. A number of teeth 34b are formed in the circumferential direction along the axial direction on the outer periphery of the pulley 34. The cylindrical elastic body 33 has several protrusions 33a formed in the circumferential direction on the outer periphery along the axial direction, and a tooth groove portion 33b that meshes with the teeth 34b on the outer periphery of the pulley 34 is formed on the inner periphery. The protrusions 33a on the outer periphery of the cylindrical elastic body 33 are fitted and fixed in the groove-shaped engagement recess 31e of the case A31, and the teeth 34b on the outer periphery of the pulley 34 mesh with the tooth groove portion 33b on the inner periphery of the cylindrical elastic body 33, thereby restricting the position in the rotational direction. Furthermore, the cylindrical elastic body 33 also has a center misalignment adjustment mechanism by its elastic force. The pulley 34 is made of a metal such as aluminum, and the cylindrical elastic body 33 is preferably made of polyurethane.

[0020] Therefore, when assembling the linear actuator 1 to the linear motion device 10, the coaxiality of the output screw shaft 2, which is the center of rotation, and the perpendicularity of the output screw shaft 2 with respect to the assembly portion of the linear actuator 1 and base plate 4 must be precisely controlled to approximately φ0.02 to 0.05, but by using the floating joint 3, this precision can be absorbed, making assembly easy.

[0021] 5A and 5B show another embodiment of the present invention in which the same parts as those in FIGS. 4A and 4B are given the same reference numerals and the description of the same parts is omitted. In this case, instead of pulley 34 arranged as cylindrical body 300 in FIGS. 4A and 4B, cylindrical part 302 with a knurled outer periphery is used, and cylindrical part 302 is inserted into the inner surface of cylindrical elastic body 301 to be molded as a single unit. A similar structure can be achieved at low cost by integrally molding the cylindrical elastic body 301 with the cylindrical part 302.

[0022] An example of the linear actuator 1 used in the above embodiment is shown in FIG. A rotor 202B of a motor unit 201 is fastened to a small diameter portion 203A of a hollow shaft 203, and an inner ring of a thrust and radial bearing 204 is fixed to a large diameter portion 203B of the hollow shaft 203 with a lock nut 206. A ball screw nut 211 is disposed in the large diameter portion 203B of the hollow shaft 203, and a flange portion 211A of the ball screw nut 211 is fastened to the lock nut 206 with a ball screw nut fastening screw 214. Therefore, by switching the excitation of a winding (not shown) of the stator 202A, the rotor 202B rotates, and the ball screw nut 211 also rotates in synchronization with the rotor 202B. A ball screw shaft 212 is screwed into the ball screw nut 211, and the tip of the ball screw shaft 212 is fixed to a load (not shown) to be moved linearly so as to prevent rotation, so that the ball screw shaft 212 moves linearly when the ball screw nut 211 rotates.

[0023] When the linear actuator 1 shown in Fig. 6 is applied to the linear motion device 10 shown in Fig. 1, the guide block 6 and table 7 become a mechanism that moves linearly while being guided by the guide rail 5. The surface of the table 7 and the tip of a ball screw shaft 212 serving as the output screw shaft 2 of the linear actuator 1 are connected through a rotation-restricted floating joint 3. Since the ball screw shaft 212 is fixed to the table 7 serving as the load to be moved linearly so as to prevent rotation, the ball screw shaft 212 moves linearly as the ball screw nut 211 rotates.

[0024] In this case, the ball screw shaft 212 is used as the output screw shaft 2 of the linear actuator 1, but a configuration of a sliding screw shaft and a sliding screw nut may also be used. Furthermore, as the linear actuator 1, the ball screw nut 211 is rotated by the motor unit 201, and the ball screw shaft 212 is fixed to prevent rotation and moves linearly. However, a linear actuator in which the ball screw shaft 212 is rotated by a motor, a rod or the like fixed to the ball screw nut 211 is fixed to prevent rotation, and the ball screw nut 211 and the rod move linearly may also be used.

[0025] Other embodiments will now be described. Fig. 7 shows a structure in which the floating joint 3 of the present invention is applied to a linear actuator provided with a linear guide mechanism of a single guide block (as shown in Fig. 6(b) of JP 2018-48693 A). In this embodiment, a guide mechanism is attached to the outside of the linear actuator 1.

[0026] Here, the structure of the guide mechanism of the linear actuator 400 will be described. Case 407 is provided with guide rail attachment portion 407A, and guide rail 408 is attached with screws 420. Guide block 409 moves along guide rail 408. Table 410 serving as a slider is connected to guide block 409, and a joint portion 410a bent downward is provided at the tip of table 410. In the structure of JP 2018-48693 A, the tip of the ball screw / output shaft 412 is directly fastened to this joint portion 410a with a screw. When the ball screw / output shaft 412 moves, the table 410 and the guide block 409 move in synchronization with each other via the joint portion 410a.

[0027] In this case, as shown in Fig. 1, instead of assembling the linear actuator 1 to the guide, guide rail, and table of the linear motion mechanism 10, a linear motion guide mechanism of a single guide block is provided in the linear actuator 400, so that the coaxiality of the ball screw / output shaft and the perpendicularity with the joint can be produced with high precision by increasing the precision of each part such as the case, guide rail, guide block, and table, and the assembly precision at the manufacturing stage. However, when a load is applied on the table 410 and linearly driven, the table 410, guide block 409, guide rail 408, and guide rail mounting part 407A bend, and a radial load is applied to the ball screw / output shaft 412, which causes a problem that the load that can be placed on the table 410 is limited relative to the thrust of the linear actuator.

[0028] Therefore, as shown in Fig. 7, the above problem can be solved by inserting and connecting a floating joint 3 having the structure described in Figs. 3 to 5A and 5B to the fastening portion between the joint portion 410a bent downward at the tip of the table 410 and the tip of the ball screw / output shaft 412. In the floating joint 3 in Fig. 7, the same parts as those in Fig. 3 are given the same reference numerals, and the description of the same parts is omitted. The ball screw / output shaft 412 corresponds to the output screw shaft 2 of the linear actuator 1 shown in Figs. 1(a) and (b), and is connected to the joint portion 410a via the floating joint 3. It is fixed to the joint portion 410a via the bolt 37 for fixing the case B. When a load is applied to table 410 and it is driven linearly, the deflection of table 410 is absorbed by floating joint 3, and therefore radial load is not directly applied to ball screw / output shaft 412. Therefore, the load that can be placed on table 410 is not limited by the thrust of linear actuator 400.

[0029] According to the above embodiment, by providing the following configuration as a floating joint, the following effects can be achieved. (i) A floating joint 3 that connects between the output screw shaft 2 of a linear actuator 1, which is provided with a screw nut 211 that screws onto the output screw shaft 2 and converts the rotation of a motor 201 into linear motion of the output screw shaft 2 by the screw nut 211, and a driven device driven by the linear actuator 1, in which a cylindrical body 300 fastened to the output screw shaft 2 is installed inside the radial direction of a case 30 fastened to the driven device, a cylindrical elastic body 33 is interposed between the inner circumference of the case 30 and the outer circumference of the cylindrical body 300, and an engagement portion is provided between the outer circumference surface of the cylindrical elastic body 33 and the inner circumference surface of the case 30, thereby making it easy to align the axis and adjust the parallelism while maintaining the anti-rotation function of the output screw shaft 2 by the linear driving device. (ii) The cylindrical elastic body 33 has a plurality of axial protrusions 33a at regular intervals along the circumferential direction as the engaging portion, while the inner peripheral surface of the case 30 has an engaging recess 31e along the circumferential direction that engages with the protrusions 33a. Therefore, the axis alignment and parallelism adjustment can be easily performed while the anti-rotation function of the output screw shaft 2 by the linear driving device is sufficiently maintained. (iii) A pulley 34 is used as the cylindrical body 300, and a tooth groove portion 33b that meshes with the outer teeth 34b of the pulley 34 is provided on the inner surface of the cylindrical elastic body 33, and the position in the rotational direction can be regulated by the engagement of the inner tooth groove portion 33b of the cylindrical elastic body 33 that meshes with the outer teeth 34b of the pulley 34. (iv) As the cylinder 300, a cylindrical part 302 having a knurled outer periphery is used, and the cylindrical part 302 is inserted into the inner surface of the cylindrical elastic body 301 to be molded as a single unit. Therefore, by molding the cylindrical elastic body 301 and the cylindrical part 302 as a single unit, a similar structure can be obtained at low cost.

[0030] According to the above embodiment, the linear actuator has the following configuration, and thus can provide the following effects. (v) A linear actuator 1 is provided with a screw nut 211 that screws onto an output screw shaft 2, and the rotation of a motor is converted into linear motion of the output screw shaft 2 by the screw nut 211. A guide portion is provided on the outer surface of a linear actuator case along the direction of linear motion of the output screw shaft 2 of the linear actuator 1, a moving element 410 that slides along the guide portion is provided, and the moving element 410 is connected to the output screw shaft 2. A cylinder 300 fastened to the output screw shaft 2 is fitted inside the radial direction of a case 30 fastened to a driven device, a cylindrical elastic body 33 is interposed between the inner circumference of the case 30 and the outer circumference of the cylinder 300, and the cylindrical elastic body 33 is fastened to the moving element via a floating joint 3 having an engaging portion that engages with the outer circumference of the cylindrical elastic body 33 and the inner circumference of the case 30. Therefore, there is no limit to the load that can be placed on the thrust of the linear actuator 1 equipped with a floating joint 3. (vi) As for the floating joint 3, a pulley 34 fastened to the output screw shaft 2 is mounted as a cylindrical body 300 on the radially inside of a case 30 fastened to the moving element, a cylindrical elastic body 33 is interposed between the inner periphery of the case 30 and the outer periphery of the pulley 34, and an engagement portion is provided between the outer periphery of the cylindrical elastic body 33 and the inner periphery of the case 30, which engage with each other. A tooth groove portion 33b that engages with the teeth 34b on the outer periphery of the pulley 34 is provided on the inner periphery of the cylindrical elastic body 33, so that the position in the rotational direction can be regulated by the engagement of the tooth groove portion 33b on the inner periphery of the cylindrical elastic body 33 that engages with the teeth 34b on the outer periphery of the pulley 34. (vii) The cylindrical elastic body 33 has a plurality of axial protrusions 33a at regular intervals along the circumferential direction as the engaging portion, while the inner peripheral surface of the case 30 has engaging recesses 31e along the circumferential direction which engage with the protrusions 33a. Therefore, the axis alignment and parallelism adjustment can be easily performed while the anti-rotation function of the output screw shaft 2 by the linear driving device is sufficiently maintained. (viii) The position in the rotational direction can be regulated by the engagement of the tooth groove portion 33b on the inner circumference of the cylindrical elastic body 33 which meshes with the teeth 34b on the outer circumference of the pulley 34. (ix) The cylindrical body 300 uses a cylindrical part 302 having a knurled outer periphery, and is molded integrally by inserting the cylindrical part 302 into the inner surface of the cylindrical elastic body 301. Therefore, a similar structure can be obtained at low cost by molding the cylindrical elastic body 301 and the cylindrical part 302 integrally.

[0031] As described above, the floating joint and linear actuator according to the present invention provide the following advantages. (A) When the floating joint according to the present invention is used, the following effects can be achieved compared to when it is not used. The linear actuator 1 has a screw nut that screws into the output screw shaft and has the function of converting the rotation of a motor into linear motion of the output screw shaft. When connecting the output screw shaft 2 to a linear driving device, the floating joint 3 of the present application can be used to easily align the axis and adjust the parallelism while maintaining the anti-rotation function of the output screw shaft 2 by the linear driving device. Furthermore, in the linear actuator 1 equipped with the floating joint 3, there is no limit to the load that can be placed on the linear actuator 1 with respect to its thrust. (B) When the floating joint 3 according to the present invention is used, the following effects can be achieved compared to when the joint part shown in FIG. 9 is used. The stopping accuracy when using the floating joint 3 can be improved. The delay in the operation of the table 7 relative to the operation of the linear actuator 1 can be reduced. This can prevent wear particles generated from the floating joint 3 from scattering. When installed horizontally, the radial load on the output screw shaft 2 of a ball screw or the like caused by the mass of the floating joint 3 can be reduced, preventing a reduction in the life span. [Industrial Applicability]

[0032] It goes without saying that the present invention is not limited to the above-described embodiment in terms of the structures of the floating joint 3 and the linear actuator 1, and that they can be modified as appropriate within the scope of the technical scope of the present invention. [Explanation of symbols]

[0033] 1,400 Linear Actuators 2 Output screw shaft 3 Floating joint 4 Base plate 5 Guide rail 6 Guide Block 7 Tables 8 Table fixing bolts 10. Linear motion devices 30 cases 31 Case A 31a Hollow part 31b Inner surface 31c Side wall 31d Through hole 31e Engagement recess (engagement portion) 32 Case B 32a Insertion hole 32b screw hole 33 Cylindrical elastic body 33a Projection (engaging part) 33b Tooth space 34 Pulley (cylinder 300) 34a End face 34b Teeth 34T slope 35 Pulley fixing bolt 36 Case A fixing bolt 37 Case B fixing bolt 300 Cylinder 302 Cylindrical part (cylinder body 300) 412 Ball screw and output shaft

Claims

1. A floating joint for connecting between an output screw shaft of a linear actuator, the output screw shaft of which is provided with a screw nut screwed into the output screw shaft, and a driven device driven by the linear actuator, the output screw shaft being converted by the screw nut into linear motion of the output screw shaft, A floating joint characterized in that a cylindrical body fastened to the output screw shaft is mounted radially inside a case fastened to the driven device, a cylindrical elastic body is interposed between the inner periphery of the case and the outer periphery of the cylindrical body, and an engagement portion is provided between the outer periphery of the cylindrical elastic body and the inner periphery of the case, a pulley is used as the cylindrical body, and a tooth groove portion is provided on the inner periphery of the cylindrical elastic body that engages with the teeth on the outer periphery of the pulley, and the rotational position is regulated by the engagement of the tooth groove portion on the inner periphery of the cylindrical elastic body that engages with the teeth on the outer periphery of the pulley.

2. A floating joint for connecting between an output screw shaft of a linear actuator, the output screw shaft of which is provided with a screw nut screwed into the output screw shaft, and a driven device driven by the linear actuator, the output screw shaft being converted by the screw nut into linear motion of the output screw shaft, A floating joint characterized in that a cylindrical body fastened to the output screw shaft is mounted radially inside a case fastened to the driven device, a cylindrical elastic body is interposed between the inner periphery of the case and the outer periphery of the cylindrical body, and an engaging portion is provided between the outer periphery of the cylindrical elastic body and the inner periphery of the case, and a cylindrical part with a knurled outer periphery is used as the cylindrical body, and the cylindrical part is inserted into the inner side of the cylindrical elastic body to be integrally molded.

3. 3. A floating joint as described in claim 1 or 2, wherein the cylindrical elastic body has a plurality of axial protrusions at regular intervals along the circumferential direction as the engagement portion, while the inner surface of the case has engagement recesses along the circumferential direction that engage with the protrusions.

4. A linear actuator is provided with a screw nut that screws into an output screw shaft, and the rotation of a motor is converted into linear motion of the output screw shaft by the screw nut. The linear actuator is provided with a guide section on an outer surface of a linear actuator case along the direction of linear motion of the output screw shaft, a slider that slides along the guide section, and the slider is connected to the output screw shaft, A linear actuator characterized in that a cylindrical body fastened to the output screw shaft is mounted inside a case fastened to a driven device in the radial direction, a cylindrical elastic body is interposed between the inner periphery of the case and the outer periphery of the cylindrical body, and an engagement portion is provided between the outer periphery of the cylindrical elastic body and the inner periphery of the case, the cylindrical body being used as a pulley, and a tooth groove portion is provided on the inner periphery of the cylindrical elastic body that engages with the teeth on the outer periphery of the pulley, and the linear actuator is fastened to the slider via a floating joint whose rotational position is regulated by the engagement of the tooth groove portion on the inner periphery of the cylindrical elastic body that engages with the teeth on the outer periphery of the pulley.

5. A linear actuator is provided with a screw nut that screws into an output screw shaft, and the rotation of a motor is converted into linear motion of the output screw shaft by the screw nut. The linear actuator is provided with a guide section on an outer surface of a linear actuator case along the direction of linear motion of the output screw shaft, a slider that slides along the guide section, and the slider is connected to the output screw shaft, A linear actuator characterized in that a cylindrical body fastened to the output screw shaft is fitted inside the radial direction of a case fastened to a driven device, a cylindrical elastic body is interposed between the inner periphery of the case and the outer periphery of the cylindrical body, and an engaging portion is provided between the outer periphery of the cylindrical elastic body and the inner periphery of the case, and the cylindrical body is a cylindrical part with a knurled outer periphery, and is fastened to the slider via a floating joint that is integrally molded by inserting the cylindrical part into the inner side of the cylindrical elastic body.

6. A linear actuator as described in claim 4 or 5, wherein the cylindrical elastic body has a plurality of axial protrusions at regular intervals along the circumferential direction as the engagement portion, while the inner surface of the case has engagement recesses along the circumferential direction that engage with the protrusions.

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