Direct acting device

Abstract

The direct drive device (10) has a bearing (14) fitted to the outer periphery of a ball screw (12), a nut holder (30) through which the ball screw (12) is inserted, and a bearing pressing member (22) fixed to a motor housing (16) in a state where the ball screw (12) is inserted into a through hole (36), which restricts the axial movement of the bearing (14) in the motor housing (16), the bearing pressing member (22) having a cutout portion (40) extending radially from the inner peripheral surface of the through hole (36) to the outer peripheral surface of the bearing pressing member (22).

Description

TECHNICAL FIELD

[0001] The present application relates to a linear motion device having a nut that moves in an axial direction with respect to a ball screw as the ball screw rotates. BACKGROUND

[0002] Conventionally, there is a linear motion device having a nut that moves in an axial direction with respect to a ball screw as the ball screw rotates (for example, Japanese Patent Application Publication No. 2017-67197). SUMMARY

[0003] A bearing for supporting the ball screw and a restriction member for restricting movement of the bearing are attached to the ball screw. In order to perform maintenance of the linear motion device, the worker sometimes detaches the restriction member from the ball screw. The worker needs to detach the bearing from the ball screw in order to detach the restriction member from the ball screw. Therefore, the maintenance of the linear motion device requires man-hours. Therefore, it is required to improve the work efficiency of the maintenance of the linear motion device.

[0004] The present application was made in order to solve the above-described problems, and has an object to provide a linear motion device capable of improving the work efficiency of maintenance.

[0005] A linear motion device according to an embodiment of the present application includes a ball screw, a nut that moves in an axial direction with respect to the ball screw as the ball screw rotates, a bearing that is attached to an outer periphery of the ball screw, a housing that supports the ball screw via the bearing, a nut holder that internally holds the nut and through which the ball screw is inserted, and a restriction member that has a through-hole in a center portion, is disposed between the bearing and the nut holder, is fixed to the housing in a state in which the ball screw is inserted into the through-hole, restricts movement of the bearing in the axial direction within the housing, and has a cutout portion that extends in a radial direction from an inner peripheral surface of the through-hole to an outer peripheral surface of the restriction member.

[0006] According to the present application, it is possible to improve the work efficiency of maintenance of the linear motion device. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 is an exploded view of a linear motion device.

[0008] Figure 2 is a view of a state in which a bearing pressing member is detached from a ball screw.

[0009] Figure 3 is an exploded view of a linear motion device of a comparative example.

[0010] Figure 4 is a view of a state in which a bearing pressing member is detached from a ball screw. DETAILED DESCRIPTION

[0011] [First Embodiment]

[0012] [Structure of Linear Motion Device]

[0013] Figure 1 is an exploded view of a linear motion device 10 of the present embodiment. The linear motion device 10 is, for example, a device for linearly moving a table of a machine tool. The linear motion device 10 has a ball screw 12, a bearing 14, a motor housing 16, a bearing pressing member 22, a motor 24, a nut 26, and a nut holder 30. Hereinafter, the respective components constituting the linear motion device 10 will be described using the X axis shown in Figure 1 The X axis direction is parallel to the axial direction of the ball screw 12. The end portion of the ball screw 12 on which the bearing 14 is mounted is set as the positive side, and the end portion on the opposite side is set as the negative side.

[0014] The motor housing 16 has a support portion (support hole) 18 that is perforated in a manner that the side surface 16-1 on the negative side in the X axis direction is open. The bearing 14 is fitted to the end portion of the ball screw 12 on the positive side in the X axis direction. The lock nut 20 is mounted to the end portion of the ball screw 12 on the positive side in the X axis direction. The lock nut 20 is disposed at a position closer to the end surface of the ball screw 12 on the positive side in the X axis direction than the bearing 14. The bearing 14 is prevented from falling off from the ball screw 12 by the lock nut 20. The end portion of the ball screw 12 on the positive side in the X axis direction is inserted into the support portion 18 together with the bearing 14. The ball screw 12 is supported to the motor housing 16 via the bearing 14. The bearing pressing member 22 is fitted to the ball screw 12. The bearing pressing member 22 is disposed at a position farther from the end surface of the ball screw 12 on the positive side in the X axis direction than the bearing 14. The opening of the support portion 18 is closed by the bearing pressing member 22 in a state where the ball screw 12 is inserted into the support portion 18 together with the bearing 14. The bearing pressing member 22 is fixed to the side surface 16-1 of the motor housing 16 by a bolt 38. The bearing pressing member 22 restricts movement in a direction in which the bearing 14 and the ball screw 12 are separated from the support portion 18. The motor housing 16 is fixed to, for example, a bed of a machine tool. The motor housing 16 corresponds to the housing of the present application.

[0015] The end portion of the ball screw 12 on the positive side in the X axis direction is connected to a drive shaft of the motor 24 inside the motor housing 16. Thereby, the ball screw 12 is rotated around the shaft by the motor 24. The nut 26 is screwed to the ball screw 12 via balls that are not shown. The nut 26 moves relative to the ball screw 12 in the X axis direction along with rotation of the ball screw 12.

[0016] Nut 26 is held in nut retainer 30. Nut retainer 30 has a through hole 32 extending along the X-axis, and nut 26 is housed within the through hole 32. The diameter of the through hole 32 is larger than the outer diameter of bearing 14. Nut 26 has a flange 28. Flange 28 is formed at the negative end of nut 26 in the X-axis direction. With nut 26 housed in the through hole 32 of nut retainer 30, flange 28 is fixed to the negative side of nut retainer 30 in the X-axis direction by bolts 34. Thus, nut retainer 30 and nut 26 move together relative to ball screw 12 in the X-axis direction. For example, a machine tool table is fixed in nut retainer 30. Thus, the table and nut retainer 30 perform linear motion together.

[0017] The bearing pressing member 22 is formed as a circular plate with a through hole 36 in its center. The diameter of the through hole 36 of the bearing pressing member 22 is smaller than the outer diameter of the outer ring of the bearing 14 and larger than the outer diameter of the inner ring. The outer diameter of the bearing pressing member 22 is larger than the diameter of the through hole 32 of the nut retainer 30. The bearing pressing member 22 has a cutout 40 that extends radially from the inner circumferential surface of the through hole 36 to the outer circumferential surface of the bearing pressing member 22. The width of the cutout 40 is smaller than the outer diameter of the ball screw 12. The bearing pressing member 22 corresponds to the limiting member of the present invention.

[0018] Figure 2 This diagram shows the bearing pressing component 22 removed from the ball screw 12. Figure 2 As shown, the ball screw 12 has two parallel planar portions 42-1 and 42-2 formed by cutting off the outer peripheral surface of a portion of its outer peripheral surface. The thickness of the portion of the ball screw 12 sandwiched between the two planar portions 42-1 and 42-2 is formed to be thinner than the width of the cut portion 40 of the bearing pressing member 22.

[0019] The operator pulls the bearing pressing member 22 out of the ball screw 12 along the cut portion 40 at the locations where the flat portions 42-1 and 42-2 are formed on the ball screw 12. This allows the bearing pressing member 22 to be removed from the ball screw 12. Alternatively, the operator presses the bearing pressing member 22 into the ball screw 12 along the cut portion 40 at the locations where the flat portions 42-1 and 42-2 are formed on the ball screw 12. This allows the bearing pressing member 22 to be installed on the ball screw 12.

[0020] [Effects]

[0021] Figure 3This is an exploded view of the comparative example direct-acting device 44. The shape of the bearing pressing member 22 of the comparative example direct-acting device 44 differs partially from the shape of the bearing pressing member 22 of the direct-acting device 10 of this embodiment. The bearing pressing member 22 of the comparative example direct-acting device 44 does not have a structure equivalent to the cutout portion 40 of the direct-acting device 10 of this embodiment. The other components of the comparative example direct-acting device 44 are the same as those of the direct-acting device 10 of this embodiment.

[0022] The outer diameter of the bearing pressing member 22 is larger than the diameter of the through hole 32 of the nut retainer 30, so the bearing pressing member 22 cannot pass through the inner circumference of the nut retainer 30. On the other hand, the outer diameter of the bearing 14 is smaller than the diameter of the through hole 32 of the nut retainer 30, so the bearing 14 can pass through the inner circumference of the nut retainer 30.

[0023] Therefore, when disassembling the direct-acting device 44, if the bearing pressing component 22 is removed from the ball screw 12, the operator can pull the ball screw 12 out of the nut retainer 30 even with the bearing 14 installed on the ball screw 12. Similarly, when assembling the direct-acting device 44, if the bearing pressing component 22 is removed from the ball screw 12, the operator can insert the ball screw 12 into the nut retainer 30 even with the bearing 14 installed on the ball screw 12.

[0024] However, in the construction of the comparative example direct-acting device 44, when the operator removes the bearing pressing component 22 from the ball screw 12, the bearing 14 also needs to be removed from the ball screw 12. Similarly, when the operator installs the bearing pressing component 22 onto the ball screw 12, the bearing 14 needs to be removed from the ball screw 12. In the comparative example direct-acting device 44, maintenance requires time; therefore, a direct-acting device that can improve maintenance efficiency is required.

[0025] In the direct-acting device 10 of this embodiment, the bearing pressing member 22 has a cutout 40. Therefore, with the bearing 14 installed on the ball screw 12, the operator can remove the bearing pressing member 22 from the ball screw 12. This allows the operator to pull the ball screw 12 out of the nut retainer 30 without removing the bearing 14. Alternatively, with the bearing 14 installed on the ball screw 12, the operator can install the bearing pressing member 22 onto the ball screw 12. This allows the operator to insert the ball screw 12 into the nut retainer 30. Then, without removing the bearing 14 from the ball screw 12, the operator can install the bearing pressing member 22 onto the ball screw 12. Therefore, the maintenance efficiency of the direct-acting device 10 can be improved.

[0026] In the direct-acting device 10 of this embodiment, the ball screw 12 has two parallel planar portions 42-1 and 42-2 formed by cutting off its outer peripheral surface. The width of the cut portion 40 of the bearing pressing member 22 is formed to be smaller than the outer diameter of the ball screw 12. As a result, the strength of the bearing pressing member 22 can be ensured.

[0027] [Second Implementation]

[0028] Figure 4 This diagram shows the bearing pressing component 22 removed from the ball screw 12. Figure 4 As shown, the ball screw 12 has a flat portion 46 formed by cutting off a portion of its outer peripheral surface. The thickness of the flat portion 46 and the outer peripheral surface of the ball screw 12 is formed to be thinner than the width of the cut portion 40 of the bearing pressing member 22. Figure 4 The cutout 40 shown is formed offset from the center of the through hole 36. Therefore, the extension of the centerline in the width direction of the cutout 40 does not pass through the center of the through hole 36. On the other hand, Figure 2 The cutout 40 shown extends toward the center of the through hole 36. Therefore, the extension of the centerline of the cutout 40 in the width direction passes through the center of the through hole 36. The entire cutout 40 is connected to the through hole 36 in the width direction. The cutout 40 can be formed offset from the center of the through hole 36, or it can extend toward the center of the through hole 36. Other structural features are the same as those of the direct-acting device 10 in the first embodiment.

[0029] [Effects]

[0030] In the direct-acting device 10 of this embodiment, the ball screw 12 has a flat portion 46 formed by cutting off a portion of the outer peripheral surface of the ball screw 12. The width of the cut portion 40 of the bearing pressing member 22 is formed to be smaller than the outer diameter of the ball screw 12. In this embodiment, one flat portion 46 is formed in the ball screw 12, therefore, compared with the case where two flat portions 42-1 and 42-2 are formed in the ball screw 12 as in the first embodiment, the strength of the bearing pressing member 22 can be ensured.

[0031] [Variation Example]

[0032] The outer diameter of the bearing 14 can also be made smaller than the inner diameter of the nut 26. Therefore, if the bearing pressing member 22 is removed from the ball screw 12, the operator can pull the ball screw 12 out of the nut 26 with the bearing 14 installed. Alternatively, with the bearing 14 installed, the operator can insert the ball screw 12 into the nut 26. Then, without removing the bearing 14 from the ball screw 12, the operator can install the bearing pressing member 22 onto the ball screw 12.

[0033] [Technical Ideas Derived from Implementation Methods]

[0034] The following describes the technical concepts that can be grasped from the above-described embodiments.

[0035] A direct-acting device 10 includes: a ball screw 12; a nut 26 that moves axially relative to the ball screw as the ball screw rotates; a bearing 14 mounted on the outer periphery of the ball screw; a housing 16 that supports the ball screw via the bearing; a nut retainer 30 that internally holds the nut and through which the ball screw passes; and a limiting member 22 having a through hole 36 at its center, disposed between the bearing and the nut retainer, fixed to the housing when the ball screw is inserted into the through hole, limiting the axial movement of the bearing within the housing, the limiting member having: a cutout 40 extending radially from the inner peripheral surface of the through hole to the outer peripheral surface of the limiting member.

[0036] In the aforementioned direct-acting device, the ball screw may also have a planar portion 42-1, 42-2, 46 formed by cutting off at least a portion of the outer peripheral surface of the ball screw.

[0037] In the aforementioned direct-acting device, the ball screw may also have two planar portions 42-1 and 42-2, which are formed parallel to each other.

[0038] In the aforementioned direct-acting device, the outer diameter of the limiting member may be larger than the inner diameter of the nut retainer.

[0039] In the aforementioned direct-acting device, the outer diameter of the bearing may also be smaller than the inner diameter of the nut retainer.

[0040] In the aforementioned direct-acting device, the inner diameter of the through hole may also be smaller than the outer diameter of the bearing.

[0041] In the aforementioned direct-acting device, the housing may also have a support portion 18, which has an opening on the side 16-1 for the ball screw and the bearing to be inserted together, and the limiting member is fixed to the side of the housing at the opening of the support portion.

Claims

1. A direct-acting device (10), comprising: Ball screw (12); Nut (26), which moves axially relative to the ball screw as the ball screw rotates; Bearing (14), which is assembled on the outer periphery of the ball screw; Housing (16) which supports the ball screw via the bearing; A nut retainer (30) internally holds the nut and through which the ball screw passes; and A limiting component (22), having a through hole (36) at its center, is disposed between the bearing and the nut retainer and is fixed to the housing when the ball screw is inserted into the through hole, thereby limiting the axial movement of the bearing within the housing. The direct-acting device is characterized in that... The limiting member has a cutout (40) that extends radially from the inner peripheral surface of the through hole to the outer peripheral surface of the limiting member. The ball screw has a planar portion (42-1, 42-2, 46) formed by cutting off at least a portion of the outer peripheral surface of the ball screw. When the limiting member is removed from the ball screw, the limiting member is pulled out of the ball screw along the cut portion at the location where the flat portion is formed on the ball screw. When the limiting member is installed on the ball screw, the limiting member is pressed into the ball screw along the cut at the location where the flat portion is formed on the ball screw.

2. The direct-acting device according to claim 1, characterized in that, The ball screw has two planar portions (42-1, 42-2). The two planar portions are formed parallel to each other.

3. The direct-acting device according to claim 1 or 2, characterized in that, The outer diameter of the limiting component is formed to be larger than the inner diameter of the nut retainer.

4. The direct-acting device according to claim 1 or 2, characterized in that, The outer diameter of the bearing is formed to be smaller than the inner diameter of the nut retainer.

5. The direct-acting device according to claim 1 or 2, characterized in that, The inner diameter of the through hole is smaller than the outer diameter of the bearing.

6. The direct-acting device according to claim 1 or 2, characterized in that, The housing has a support portion (18) that is open on the side (16-1) for inserting the ball screw and the bearing together. The limiting component is fixed to the side of the housing at the opening of the support portion.

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