Gear transmission mechanism and linear actuator

Abstract

To improve the life of a gear.SOLUTION: Provided is a gear transmission mechanism that includes: a plurality of gears each of which is supported by its corresponding shaft and rotates to mesh with each other; a support structure that supports the plurality of gears; a spline that rotates a target shaft to which a target gear, which is one of the gears, is fixed, and allows the target shaft to move together with the target gear in an axial direction of the target shaft; and a positioning member which determines a position of the target shaft in the axial direction. The positioning member is attachable to and detachable from the support structure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gear transmission mechanism and a linear actuator. [Background technology]

[0002] Patent Document 1 discloses a linear motion actuator that includes a feed screw that is rotated by a gear transmission mechanism and a linear motion portion that is moved linearly in accordance with the rotation of the feed screw. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-127567 Summary of the Invention [Problem to be solved by the invention]

[0004] The gears in a gear transmission mechanism are subjected to loads, so the longer the gear life, the better.

[0005] Therefore, the present invention provides a technique that can improve the life of gears. [Means for solving the problem]

[0006] One aspect of the present invention provides a gear transmission mechanism. The gear transmission mechanism includes a plurality of gears supported by shafts and rotating in mesh with each other, a support structure supporting the plurality of gears, a target shaft to which a target gear, one of the gears, is fixed, a spline that rotates the target shaft and allows the target shaft to move together with the target gear in the axial direction of the target shaft, and a positioning member that is detachable from the support structure.

[0007] By attaching or detaching the positioning member to or from the support structure, the target gear can be moved together with the target shaft. This allows the area of the target gear that meshes with other gears to be changed. In this way, the area on which the load is applied to the target gear can be changed. By using the target gear after changing the area on which the load is applied, the life of the target gear can be improved.

[0008] The gear transmission mechanism may further include a motor supported by the support structure and configured to rotate one of the gears. The support structure may have a gear space in which the gears are arranged. The positioning member may be disposed on the opposite side of the gear space from the motor. A spline sleeve of the spline may be disposed closer to the motor than the gear space. In this case, the positioning member is disposed on the opposite side of the gear space from the motor, and the spline sleeve of the spline is disposed closer to the motor than the gear space, so that the positioning member can be easily attached to and detached from the support structure, for example, when attaching or detaching the positioning member to or from the support structure, there is no need to remove the motor and gear from the support structure.

[0009] The gear transmission mechanism may further include a bearing that rotatably supports the target shaft, and a bearing support that supports the bearing and is attached to the support structure. The positioning member may be sandwiched between the bearing support and the support structure. The positioning member may be detachable from the support structure while the target shaft remains inserted in the bearing. In this case, although the positioning member is sandwiched between the bearing support and the support structure, the positioning member can be attached to and detached from the support structure without removing the bearing from the bearing support or the target shaft from the bearing.

[0010] The positioning member may cover the entire circumference of the target shaft and may be divisible into a plurality of pieces that are rotationally symmetric about the axis of the target shaft. Since the positioning member can be divided into multiple pieces that are rotationally symmetrical about the axis of the target shaft, the positioning member can be easily attached to and detached from the support structure. In addition, since the positioning member covers the entire circumference of the target shaft, the target shaft can be protected from foreign matter such as dust and water.

[0011] The gear transmission mechanism may include a plurality of positioning members that are detachable from the support structure. In this case, the area of the target gear that meshes with other gears can be changed multiple times, thereby improving the life of the target gear.

[0012] The target gear may be a drive gear driven by a motor. In this case, it is possible to change the area in which the drive gear, which receives the most load among the multiple gears, meshes with the other gears, thereby improving the life of the drive gear which receives the most load.

[0013] Another aspect of the present invention provides a linear motion actuator, the linear motion actuator including the gear transmission mechanism, a feed screw rotated by the gear transmission mechanism, and a linear motion part moved linearly in accordance with the rotation of the feed screw. [Effects of the Invention]

[0014] In accordance with an embodiment of the present invention, the life of the gear can be improved. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view showing a linear actuator having a gear transmission mechanism according to an embodiment of the present invention in a retracted state. [Figure 2] FIG. 2 is a cross-sectional view showing the linear actuator of FIG. 1 in an extended state. [Figure 3] 3 is a cross-sectional view of the gear transmission mechanism of FIG. 1 before the positioning member (spacer) is removed to obtain the state of FIG. [Figure 4] FIG. 4 is a left side view of the linear motion actuator of FIG. [Figure 5] FIG. 5 is a left side view of a linear motion actuator according to a modified example of the embodiment of the present invention. [Figure 6] FIG. 6 is a cross-sectional view showing the linear actuator in a retracted state at the stage of use with the positioning member (spacer) removed. [Figure 7] FIG. 7 is a cross-sectional view showing the linear actuator of FIG. 6 in an extended state. [Figure 8] FIG. 8 is a cross-sectional view showing a linear actuator having a gear transmission mechanism according to another embodiment of the present invention in a retracted state. DETAILED DESCRIPTION OF THE INVENTION

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The drawings are not necessarily drawn to scale, and some features may be exaggerated or omitted.

[0017] As shown in FIGS. 1 and 2, a gear transmission mechanism 1 according to an embodiment of the present invention is used in a linear actuator 30.

[0018] The gear transmission mechanism 1 is driven by a motor 2. The motor 2 is, for example, a servo motor or a stepping motor. The motor 2 has a rotating shaft 2a. The motor 2 is fixed to a bracket 3, and the rotating shaft 2a passes through a hole formed in an end wall 3a of the bracket 3. The bracket 3 is made of a rigid material such as metal or resin. The end wall 3a of the bracket 3 is fixed to a housing 31 of a linear actuator 30 with screws.

[0019] The gear transmission mechanism 1 is driven by a rotating shaft 2a of a motor 2. The gear transmission mechanism 1 has a first gear 7, a second gear 8, and a third gear 9. The first gear (target gear) 7 is a drive gear that is directly driven by the rotating shaft 2a of the motor 2 and rotates together with the rotating shaft 2a. As will be described later, the shaft 2e to which the first gear 7 is fixed is a spline shaft with a spline 2b.

[0020] The second gear 8 meshes with the first gear 7 and is driven to rotate by the first gear 7. The second gear 8 is fixed to a rotating shaft 8a and rotates together with the rotating shaft 8a. For example, the second gear 8 is fixed to the rotating shaft 8a by a key 8b. The rotating shaft 8a is rotatably supported by rolling bearings 17 and 18.

[0021] The third gear 9 meshes with the second gear 8 and is driven to rotate by the second gear 8. The third gear 9 is fixed to a rotating shaft 9a and rotates together with the rotating shaft 9a. For example, the third gear 9 is fixed to the rotating shaft 9a with a key 9b. The rotating shaft 9a is rotatably supported by rolling bearings 11 and 12. In this embodiment, the rotating shaft 9a is the output shaft of the gear transmission mechanism 1, and a feed screw 34 of the linear motion actuator 30 is formed on an extension of the rotating shaft 9a.

[0022] In this way, the gears 7, 8, and 9 are supported by the shafts 2e, 8a, and 9a, respectively, and rotate while meshing with each other.

[0023] The linear actuator 30 has the above-mentioned gear transmission mechanism 1, a housing (support structure) 31, a cover (support structure) 32, an end mounting portion 33, a feed screw 34, a nut (straight portion) 35, a linear rod (straight portion) 36, and an end mounting portion 37. The housing 31 and the cover 32 are made of a rigid material such as metal or resin, and form a support structure that supports the gear transmission mechanism 1, the motor 2, the feed screw 34, the nut 35, and the linear motion rod (linear motion portion).

[0024] The housing 31 has a gear space 20 in which gears 7, 8, and 9 are arranged. A cover 32 covers the gear space 20 and is fixed to the housing 31 with screws. The housing 31 has a lower portion 31a, a central portion 31b, an upper portion 31c, and a guide sleeve 31d. Here, "upper" and "lower" refer to the top and bottom in the drawing, and are not intended to limit the position in which the linear motion actuator 30 is used.

[0025] The gear space 20 is formed across the lower portion 31a, the central portion 31b and the upper portion 31c.

[0026] The lower portion 31a and the central portion 31b support the motor 2. That is, the end wall 3a of the bracket 3 to which the motor 2 is fixed is fixed to the lower portion 31a and the central portion 31b of the housing 31. The lower portion 31a and the central portion 31b are formed with a cavity 31e in which the spline 2b is disposed.

[0027] The rolling bearing 17 that supports the rotating shaft 8a and therefore the second gear 8 is fixed to the central portion 31b of the housing 31. The rolling bearing 18 that supports the rotating shaft 8a is fixed to the cover 32.

[0028] The rolling bearings 11 and 12 that support the rotating shaft 9a and therefore the third gear 9 are supported by a bearing housing 13, and the bearing housing 13 is fixed with screws to a central portion 31b and an upper portion 31c of a housing 31 of the linear motion actuator 30. The rolling bearings 11 and 12 are enclosed by the bearing housing 13 and a bearing cover 14. The bearing cover 14 is fixed with screws to the bearing housing 13. The bearing cover 14, together with the housing 31 and the cover 32, defines the gear space 20.

[0029] The guide sleeve 31d is cylindrical and is integrally connected to the central portion 31b and the upper portion 31c. The guide sleeve 31d guides the linear motion of the linear motion rod .

[0030] The end attachment portion 33 is integrally connected to the cover 32. The end attachment portion 33 has a circular through-hole formed therein.

[0031] The feed screw 34 is a part of the rotating shaft 9a of the third gear 9. The feed screw 34 is arranged coaxially with the guide sleeve 31d. The feed screw 34 may be a trapezoidal screw, a ball screw (e.g., a circulating ball screw), or various types of roller screws. The roller screw may be, for example, a planetary roller screw, a circulating roller screw, or other roller screws.

[0032] The nut 35 engages with the feed screw 34 and is fixed to the linear motion rod 36 with a screw. The linear motion rod 36 is a cylindrical pipe made of a rigid material such as metal or resin. The linear motion rod 36 is arranged coaxially with the feed screw 34 and the guide sleeve 31d. The linear motion rod 36 is arranged in the internal space of the guide sleeve 31d so as to be able to reciprocate along the axial direction. The feed screw 34 is arranged in the internal space of the linear motion rod 36.

[0033] The linear motion rod 36 is prevented from rotating relative to the guide sleeve 31d by a rotation prevention mechanism (for example, a key or spline) not shown. Therefore, when the feed screw 34 rotates, the nut 35 engaged with the feed screw 34 and the linear motion rod 36 fixed to the nut 35 are moved linearly along the axial direction of the feed screw 34.

[0034] 1 shows the retracted state of the linear actuator 30 (more precisely, the retracted state of the linear rod 36). In this way, the feed screw 34, which is an extension of the rotary shaft 9a, is rotated by the gear transmission mechanism 1, and the nut (linear portion) 35 and the linear rod (linear portion) 36 are moved linearly in accordance with the rotation of the feed screw 34.

[0035] When the gear transmission mechanism 1 is rotated in the reverse direction, the linear motion rod 36 is extended, as opposed to the state shown in Figure 1. Figure 2 shows the linear motion actuator 30 in an extended state (more precisely, the linear motion rod 36 in an extended state). In this way, the linear motion rod 36 is reciprocated.

[0036] The range (stroke) over which the linear motion rod 36 can move linearly is finite. Therefore, the motor 2 is controlled by a motor driver (not shown) so as to rotate within a finite angular range. In this way, when the gear transmission mechanism 1 is provided in the linear motion actuator 30, the motor 2 is rotated within a finite angular range, and the gears 7, 8, and 9 of the gear transmission mechanism 1 also rotate within a limited angular range.

[0037] The linear motion rod 36, which is a cylindrical pipe, has an end wall 36a. The end attachment portion 37 is integrally connected to the end wall 36a of the linear motion rod 36. The end attachment portion 37 has a circular through-hole formed therein.

[0038] The end mounting portions 33 and 37 are attached to equipment or a structure in which the linear motion actuator 30 is used. The through holes formed in the end mounting portions 33 and 37 are used for attachment to the equipment or a structure.

[0039] For example, the linear actuator 30 may be used for lateral vibration damping of rail cars or other transportation equipment, or for lateral vibration damping of buildings, with one of the end mounts 33, 37 attached to one side of the equipment or structure and the other attached to the other side of the equipment or structure. Alternatively, the linear actuator 30 may be used as an electromagnetic suspension for transportation equipment or buildings, with one of the end mounts 33, 37 attached to the top of the equipment or structure and the other attached to the bottom of the equipment or structure.

[0040] Although not absolutely necessary, plain bearings 38, 39 are interposed between the outer circumferential surface of the linear motion rod 36 and the inner circumferential surface of the guide sleeve 31d to facilitate the linear motion of the linear motion rod 36. The plain bearings 38, 39 are, for example, cylindrical bushings. However, each of the plain bearings 38, 39 may also be a split plain bearing having multiple arc-shaped pieces. In this embodiment, the plain bearing 38 is disposed in a circumferential groove formed on the outer circumferential surface of the linear motion rod 36. The outer circumferential surface of the plain bearing 38 is in slidable contact with the inner circumferential surface of the guide sleeve 31d. On the other hand, the plain bearing 39 is disposed in a circumferential groove formed on the inner circumferential surface of the guide sleeve 31d. The inner circumferential surface of the plain bearing 39 is in slidable contact with the outer circumferential surface of the linear motion rod 36.

[0041] Although not absolutely necessary, a stopper 34a is fixed with a screw to the end of the lead screw 34. The stopper 34a limits the range of linear movement of the linear acting rod 36. When the linear acting rod 36 is further extended from the state shown in FIG. 2 to its maximum extension, the stopper 34a comes into contact with the nut 35, preventing the nut 35 from moving and thus preventing further extension of the linear acting rod 36. When the linear acting rod 36 is in its maximum retracted state as shown in FIG. 1, the stopper 34a comes into contact with the end wall 36a of the linear acting rod 36, preventing further retraction of the linear acting rod 36.

[0042] In order to improve the life of any of the gears 7, 8, and 9 of the gear transmission mechanism 1, in this embodiment, a mechanism is provided for changing the area where a load is applied to any of the gears (target gears) of the gear transmission mechanism 1. Hereinafter, it is assumed that the first gear 7 driven by the motor 2 is the target gear whose load region is changed. As shown in Figure 1, the thickness of the first gear 7 is greater than the thicknesses of the other gears 8 and 9.

[0043] A spline 2b is attached to a rotating shaft 2a of the motor 2. The spline 2b has a shaft coupling 2c, a spline sleeve 2d, and a spline shaft 2e. The shaft coupling 2c is a cylindrical socket having an end wall that closes an internal cylindrical cavity, and the end wall of the shaft coupling 2c is fixed to the rotating shaft 2a by a key 2f.

[0044] The spline sleeve 2d is fixed to the shaft coupling 2c. A portion of the spline sleeve 2d is inserted into a cavity inside the shaft coupling 2c. The spline sleeve 2d is disposed closer to the motor 2 than the gear space 20.

[0045] The spline sleeve 2d is engaged with the spline shaft 2e. The spline sleeve 2d may be a ball spline sleeve, and the spline shaft 2e may be a ball spline shaft. However, the spline sleeve 2d may be another type of spline sleeve, and the spline shaft 2e may be another type of spline shaft. When the rotating shaft 2a of the motor 2 rotates about its axis, the shaft coupling 2c, the spline sleeve 2d, and the spline shaft 2e also rotate about the axis of the rotating shaft 2a.

[0046] A cylindrical portion 2g is provided at the end of the spline shaft 2e. For example, a first gear 7 is fixed to the cylindrical portion 2g with a key 2h. Therefore, the spline 2b transmits the rotation of the rotating shaft 2a of the motor 2 to the first gear 7. In other words, the spline 2b rotates the spline shaft (target shaft) 2e to which the first gear 7 is fixed.

[0047] A small-diameter cylindrical portion 2i having a smaller diameter than the cylindrical portion 2g is provided at the tip of the spline shaft 2e. The small-diameter cylindrical portion 2i is rotatably supported by rolling bearings 21 and 22. The rolling bearings 21 and 22 are supported by a bearing housing (bearing support) 23. The bearing housing 23 is fixed to the cover 32 by screws 24. A bearing cover 25 is fixed to the bearing housing 23 by screws 26. The rolling bearings 21 and 22 are enclosed by the bearing housing 23 and the bearing cover 25. In the embodiment, two rolling bearings 21 and 22 are provided, but the number of bearings supporting the spline shaft 2e is not limited to two, and may be one, or three or more.

[0048] In the spline 2b, the spline shaft 2e is movable relative to the spline sleeve 2d in the axial direction of the spline shaft 2e together with the first gear 7. In this embodiment, the gear transmission mechanism 1 has a spacer (positioning member) 27 that determines the position of the spline shaft 2e in the axial direction.

[0049] The spacer 27 is detachable from the cover 32. When the spacer 27 is attached to the cover 32, the spacer 27 is disposed on the opposite side of the motor 2 across the gear space 20, and is interposed between the bearing housing 23 and the cover 32.

[0050] The spacer 27 is formed with through holes 27a into which the screws 24 for attaching the bearing housing 23 to the cover 32 are inserted. The bearing housing 23 is formed with through holes 23a into which the screws 24 are inserted. The through holes 23a and 27a are not internally threaded. On the other hand, the cover 32 is formed with threaded holes 32a into which the screws 24 are screwed.

[0051] In this embodiment, when the spacer 27 is attached to the cover 32, the spacer 27 covers the entire circumference of the small-diameter cylindrical portion 2i of the spline shaft 2e. Therefore, the spacer 27 can protect the spline shaft 2e from foreign matter such as dust and water.

[0052] 1 and 2, an operator can remove the screw 24 from the gear transmission mechanism 1 and then remove the spacer 27 from the cover 32. As shown in FIG. 3, the spacer 27 can be attached to and detached from the cover 32 while the small-diameter cylindrical portion 2i of the spline shaft 2e remains inserted in the bearings 21 and 22.

[0053] Specifically, the spacer 27 can be divided into two pieces 27b and 27c that are rotationally symmetrical about the axis of the spline shaft 2e, as shown in Fig. 4. Fig. 4 is a left side view of the linear motion actuator 30. However, the screws 24 are not shown. When the pieces 27b and 27c shown in Fig. 4 are combined, they form the spacer 27 having a regular octagonal outline, which is placed on the bearing housing 23 also having a regular octagonal outline, and the through hole 27a of the spacer 27 is aligned with the through hole 23a of the bearing housing 23 and the screw hole 32a of the cover 32 (see Figs. 1 and 2).

[0054] Although not shown, the spacer 27 may be separable into three or more pieces that are rotationally symmetric about the axis of the spline shaft 2e. The spacer 27 covers the entire circumference of the small-diameter cylindrical portion 2i of the spline shaft 2e and is sandwiched between the bearing housing 23 and the cover 32. However, because the spacer 27 can be separable into multiple pieces 27b, 27c that are rotationally symmetric about the axis of the spline shaft 2e, the spacer 27 can be easily removed from the cover 32, as shown by arrow A in Figure 4. Furthermore, as shown in Figure 3, when removing the spacer 27 from the cover 32, there is no need to remove the bearings 21, 22 from the bearing housing 23 or remove the spline shaft 2e from the bearings 21, 22.

[0055] 5 is a left side view of a linear motion actuator 30 according to a modified embodiment of the present invention, with the screw 24 not shown. 5, a spacer 27d is used instead of the spacer 27. The spacer 27d has a substantially U-shape. The spacer 27d is superimposed on the bearing housing 23 having a regular octagonal outline, and the through hole 27a of the spacer 27 is aligned with the through hole 23a of the bearing housing 23 and the screw hole 32a of the cover 32 (see FIGS. 1 and 2).

[0056] In this modified example, even when the spacer 27d is sandwiched between the bearing housing 23 and the cover 32, it is not possible to cover the entire circumference of the small diameter cylindrical portion 2i of the spline shaft 2e. However, because the spacer 27d is open on one side, it is easy to remove the spacer 27d from the cover 32 as shown by arrow B in Fig. 5. Furthermore, as shown in Fig. 3, when removing the spacer 27d from the cover 32, there is no need to remove the bearings 21 and 22 from the bearing housing 23 or remove the spline shaft 2e from the bearings 21 and 22.

[0057] As shown in Figure 3, after removing the spacer 27 or 27d from the cover 32, the worker moves the bearing housing 23, the spline shaft 2e, and the first gear 7 along the axial direction of the spline shaft 2e toward the motor 2, as shown in Figures 6 and 7. As a result, the first gear 7 moves closer to the spline sleeve 2d. Thereafter, a screw 24A, which is shorter than the screw 24, is inserted into the through hole 23a of the bearing housing 23 and screwed into the screw hole 32a of the cover 32.

[0058] In this way, the gear transmission mechanism 1 can be transitioned from the first use stage shown in Figures 1 and 2 to the second use stage shown in Figures 6 and 7 by removing the spacer 27 from the cover 32. As is clear from a comparison of the use stages shown in FIGS. 1 and 2 with the use stages shown in FIGS. 6 and 7, the area of the first gear 7 that meshes with the second gear 8 is changed. In this way, the area on which the load is applied can be changed in the first gear 7. By using the first gear 7 after changing the area on which the load is applied, the life of the first gear 7 can be improved.

[0059] The spacer 27 is disposed on the opposite side of the motor 2 across the gear space 20, and the spline sleeve 2d of the spline 2b is disposed closer to the motor 2 than the gear space 20. Therefore, the spacer 27 can be easily removed from the cover 32. For example, when removing the spacer 27 from the cover 32, it is not necessary to remove the motor 2 and the gears 7, 8, 9 from the support structure (the housing 31 and the cover 32).

[0060] Figure 6 shows the linear actuator 30 in a retracted state (more precisely, the linear rod 36 in a retracted state). Figure 7 shows the linear actuator 30 in an extended state (more precisely, the linear rod 36 in an extended state). The feed screw 34, which is an extension of the rotary shaft 9a, is rotated by the gear transmission mechanism 1, and the nut 35 and linear rod 36 are moved linearly in accordance with the rotation of the feed screw 34. By reversing the gear transmission mechanism 1, the nut 35 and linear rod 36 are reciprocated.

[0061] In the above description, the gear transmission mechanism 1 is transitioned from the first use stage shown in Figures 1 and 2 to the second use stage shown in Figures 6 and 7 by removing the spacer 27 from the cover 32. Conversely, the gear transmission mechanism 1 may be transitioned from the use stage shown in Figures 6 and 7 to the use stage shown in Figures 1 and 2 by attaching the spacer 27 to the cover 32. In other words, the use stage shown in Figures 1 and 2 may occur before or after the use stage shown in Figures 6 and 7. 1 and 2, the worker removes the screw 24A from the gear transmission mechanism 1 in the state shown in FIGS. 6 and 7. Then, as shown in FIG. 3, the worker moves the bearing housing 23, the spline shaft 2e, and the first gear 7 along the axial direction of the spline shaft 2e so as to move away from the motor 2. As a result, the first gear 7 moves away from the spline sleeve 2d.

[0062] Thereafter, the spacer 27 or 27d is attached to the cover 32. At this time, the screw 24, which is longer than the screw 24A, is inserted into the through-hole 23a of the bearing housing 23 and the through-hole 27a of the spacer 27 or spacer 27d, and is then screwed into the threaded hole 32a of the cover 32. The spacer 27 can be attached to and detached from the cover 32 while the small-diameter cylindrical portion 2i of the spline shaft 2e remains inserted in the bearings 21 and 22. The spacer 27 covers the entire circumference of the small-diameter cylindrical portion 2i of the spline shaft 2e and is sandwiched between the bearing housing 23 and the cover 32. However, as shown in Figure 4, the spacer 27 is made up of multiple pieces 27b, 27c that are rotationally symmetrical about the axis of the spline shaft 2e, so it is easy to attach the spacer 27 to the cover 32. Furthermore, when attaching the spacer 27 to the cover 32, there is no need to remove the bearings 21, 22 from the bearing housing 23 or remove the spline shaft 2e from the bearings 21, 22.

[0063] 5, the spacer 27d is open on one side, making it easy to attach the spacer 27d to the cover 32. Furthermore, as shown in FIG. 3, when attaching the spacer 27d to the cover 32, there is no need to remove the bearings 21 and 22 from the bearing housing 23 or remove the spline shaft 2e from the bearings 21 and 22.

[0064] In this way, the gear transmission mechanism 1 can be transitioned from the first use stage shown in Figures 6 and 7 to the second use stage shown in Figures 1 and 2 by attaching the spacer 27 to the cover 32. This makes it possible to change the load-bearing region of the first gear 7. By using the first gear 7 after changing the load-bearing region, the life of the first gear 7 can be improved.

[0065] The spacer 27 is disposed on the opposite side of the motor 2 across the gear space 20, and the spline sleeve 2d of the spline 2b is disposed closer to the motor 2 than the gear space 20. Therefore, the spacer 27 can be easily attached to the cover 32. For example, when attaching the spacer 27 to the cover 32, there is no need to remove the motor 2 and the gears 7, 8, 9 from the support structure (the housing 31 and the cover 32).

[0066] FIG. 8 shows a linear actuator 30 in a retracted state having a gear transmission mechanism 1A according to another embodiment of the present invention. The gear transmission mechanism 1A includes two spacers 27 that are detachable from the cover 32. When these spacers 27 are attached to the cover 32, the spacers 27 are positioned on opposite sides of the motor 2 across the gear space 20, overlap each other, and are interposed between the bearing housing 23 and the cover 32.

[0067] Each spacer 27 is formed with a through hole 27a into which a screw 24B is inserted to attach the bearing housing 23 to the cover 32. The screw 24B is longer than the screw 24 shown in Figures 1 and 2. The bearing housing 23 is formed with a through hole 23a into which the screw 24B is inserted. The through holes 23a and 27a are not internally threaded. On the other hand, the cover 32 is formed with a screw hole 32a into which the screw 24B is screwed. The axial length of the first gear 7 used in the gear transmission mechanism 1A is greater than the axial length of the first gear 7 shown in FIGS.

[0068] In the gear transmission mechanism 1A, the region of the first gear 7 that meshes with the second gear 8 can be changed multiple times. That is, when two spacers 27 are used as shown in FIG. 8, the region of the first gear 7 on the right in FIG. 8 meshes with the second gear 8. Although not shown, when one spacer 27 is used, the region of the first gear 7 in the center in FIG. 8 meshes with the second gear 8. When there is no spacer 27, the region of the first gear 7 on the left in FIG. 8 meshes with the second gear 8. This increases the lifespan of the first gear 7.

[0069] Three or more spacers 27 may be provided. Each spacer 27 may be separable into a plurality of pieces 27b and 27c as shown in Figure 4. Alternatively, instead of each spacer 27, a plurality of spacers 27d (see Figure 5) may be used.

[0070] Although the present invention has been shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that changes may be made in form and detail without departing from the scope of the invention as set forth in the appended claims. Such changes, modifications and alterations are intended to be included within the scope of the invention.

[0071] For example, the application of the gear transmission mechanism 1 according to the present invention is not limited to linear actuators, and the gear transmission mechanism 1 may be used in various other devices in which gears rotate within a limited angular range, such as robot arms.

[0072] In this embodiment, the gear whose load area is changed is the first gear 7, which is the drive gear. This improves the life of the drive gear that receives the most load among the gears 7, 8, and 9. However, the load area of the gear 8 or 9 may be changed by making the rotating shaft 8a or 9a movable in the axial direction using a spline and moving the gear 8 or 9 in the axial direction.

[0073] Furthermore, the positions of the bearings that support the rotating shafts to which the gears are attached may be changed, or bearings may be added.

[0074] In the embodiment, the gear transmission mechanism 1 has three gears 7, 8, and 9, but the number of gears provided in the gear transmission mechanism may be two, or may be four or more. [Explanation of symbols]

[0075] DESCRIPTION OF SYMBOLS 1,1A...gear transmission mechanism, 2...motor, 2a...rotating shaft, 2b...spline, 2c...shaft coupling, 2d...spline sleeve, 2e...spline shaft (target shaft), 2f...key, 2g...cylindrical portion, 2h...key, 2i...small diameter cylindrical portion, 3...bracket, 3a...end wall, 7...first gear (target gear), 8...second gear, 8a...rotating shaft, 8b...key, 9...third gear, 9a...rotating shaft, 9b...key, 11,12...rolling bearing, 13...bearing housing, 14...bearing cover, 17,18...rolling bearing, 20...gear space, 21,22...rolling bearing, 23...bearing housing (bearing support) support), 23a...through hole, 24, 24A, 24B...screw, 25...bearing cover, 26...screw, 27...spacer (positioning member), 27a...through hole, 27b, 27c...piece, 27d...spacer, 30...linear actuator, 31...housing (support structure), 31a...lower part, 31b...central part, 31c...upper part, 31d...guide sleeve, 31e...cavity, 32...cover (support structure), 32a...threaded hole, 33...end mounting part, 34...feed screw, 34a...stopper, 35...nut (straight movement part), 36...linear movement rod (straight movement part), 36a...end wall, 37...end mounting part, 38, 39...slide bearing

Claims

1. A plurality of gears that are supported by shafts and rotate while meshing with each other; a support structure supporting the plurality of gears; a spline that rotates a target shaft to which a target gear, which is one of the gears, is fixed and allows the target shaft to move together with the target gear in the axial direction of the target shaft; a positioning member for determining a position of the target shaft in the axial direction, The positioning member is detachable from the support structure. A gear transmission mechanism characterized by:

2. a motor supported by the support structure for rotating one of the plurality of gears; the support structure has a gear space in which the plurality of gears are arranged, the positioning member is disposed on the opposite side of the motor across the gear space, The spline sleeve of the spline is located closer to the motor than the gear space.

2. The gear transmission mechanism according to claim 1.

3. a bearing that rotatably supports the target shaft; a bearing support attached to the support structure and supporting the bearing; the positioning member is adapted to be sandwiched between the bearing support and the support structure; The positioning member is detachable from the support structure while the target shaft remains inserted in the bearing.

2. The gear transmission mechanism according to claim 1.

4. The positioning member covers the entire circumference of the target shaft and can be divided into a plurality of pieces that are rotationally symmetric about the axis of the target shaft.

4. The gear transmission mechanism according to claim 3.

5. a plurality of positioning members that are detachable from the support structure; 2. The gear transmission mechanism according to claim 1.

6. The target gear is a drive gear driven by a motor.

2. The gear transmission mechanism according to claim 1.

7. A gear transmission mechanism according to any one of claims 1 to 6; a feed screw rotated by the gear transmission mechanism; a linear movement portion that moves linearly in accordance with the rotation of the feed screw; A linear actuator characterized by:

Images