JP6805961B2 - Ball screw device and actuator - Google Patents

Description

The present invention relates to a ball screw device and an actuator.

Actuators equipped with a ball screw device that converts rotational motion into linear motion are known. The ball screw device includes a screw shaft, a nut, and a plurality of balls arranged between the screw shaft and the nut. One of the screw shaft and the nut rotates and the other rotates in a linear motion. The ball screw device is provided with a stopper to prevent the nut from deviating from the screw shaft. For example, Patent Document 1 describes an example of a stopper.

Japanese Unexamined Patent Publication No. 2012-159191

According to the technique of Patent Document 1, it is possible to reduce the material cost as compared with the case where the stopper is formed by cutting. However, a step for forming the stopper is necessary.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a ball screw device capable of preventing a screw shaft from falling off from a nut and simplifying a manufacturing process.

In order to achieve the above object, the ball screw device according to one aspect of the present invention includes a screw shaft having a stopper, a nut having a first keyway along the axial direction of the screw shaft, and the screw shaft and the nut. A plurality of rolling elements provided between them, a power transmission member provided on the outer periphery of the nut and having a second key groove along the axial direction, and a key fitted in the first key groove and the second key groove. The stopper overlaps the end face of the nut when viewed from the axial direction, and the tip of the key projects toward the stopper side from the end face.

As a result, the key transmits the torque applied to the power transmission member to the nut. Further, the key hits the stopper when the screw shaft moves by a predetermined amount. As a result, the rotation of the nut is restricted and the movement of the screw shaft is stopped. Further, the first key groove and the second key groove are originally required for the member that transmits the torque to the nut. Therefore, the processing does not increase in the nut manufacturing process. Therefore, the ball screw device can prevent the screw shaft from falling off from the nut and can simplify the manufacturing process.

As described above of the ball screw device, the nut includes a holding member attached to the nut, the nut has a first holding groove along the circumferential direction, and the key is opposite to the end face of the first holding groove. A base portion located on the side, a protruding portion located on the end face side of the first holding groove, and a second holding groove located between the base portion and the protruding portion and connected to the first holding groove are provided. It is desirable that the holding member fits into the first holding groove and the second holding groove and is in contact with the base portion.

As a result, the holding member fitted in the first holding groove does not move in the axial direction with respect to the nut. Since the holding member contacts the base, the key cannot move to the end face side of the nut. Therefore, the key is prevented from falling off from the nut.

In the above aspect of the ball screw device, the power transmission member includes a convex portion that protrudes from the surface of the second key groove in a direction orthogonal to the axial direction, and the key is more like an end surface than the convex portion. It is desirable that the base portion located on the opposite side and the projecting portion located on the end face side of the convex portion are provided, and the convex portion is in contact with the base portion.

As a result, the key does not move to the end face side of the nut. The protrusion prevents the key from falling out of the nut.

In the above aspect of the ball screw device, it is desirable that the nut includes a cross groove that intersects the first key groove, and the key has a protrusion that fits into the cross groove.

As a result, the key does not move relative to the nut. The cross grooves and protrusions prevent the key from moving from the nut in the axial direction of the screw shaft and falling off.

The actuator of one aspect of the present invention includes the ball screw device, a housing that supports the nut via a bearing, and a motor that generates power transmitted to the power transmission member.

As a result, the actuator includes a ball screw device that can simplify the manufacturing process, so that the actuator can be easily manufactured.

According to the present invention, it is possible to provide a ball screw device that can prevent the screw shaft from falling off from the nut and can simplify the manufacturing process.

FIG. 1 is a cross-sectional view of the actuator according to the present embodiment. FIG. 2 is a cross-sectional view of the ball screw device according to the present embodiment. FIG. 3 is a perspective view of the ball screw device according to the present embodiment. FIG. 4 is a perspective view of the power transmission member according to the present embodiment. FIG. 5 is a perspective view of the nut according to the present embodiment. FIG. 6 is a perspective view of the key according to the present embodiment. FIG. 7 is a cross-sectional view of the ball screw device according to the first modification. FIG. 8 is a perspective view of the key according to the first modification. FIG. 9 is a cross-sectional view of the ball screw device according to the second modification. FIG. 10 is a perspective view of the ball screw device according to the third modification. FIG. 11 is a plan view of the ball screw device according to the third modification. FIG. 12 is a perspective view of the key according to the third modification.

Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiments for carrying out the following inventions (hereinafter referred to as embodiments). In addition, the components in the following embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, that is, those in a so-called equal range. Further, the components disclosed in the following embodiments can be appropriately combined.

(Embodiment 1)
FIG. 1 is a cross-sectional view of the actuator according to the present embodiment. FIG. 2 is a cross-sectional view of the ball screw device according to the present embodiment. FIG. 3 is a perspective view of the ball screw device according to the present embodiment. FIG. 4 is a perspective view of the power transmission member according to the present embodiment. FIG. 5 is a perspective view of the nut according to the present embodiment. FIG. 6 is a perspective view of the key according to the present embodiment.

As shown in FIG. 1, the actuator 1 includes a housing 10, a motor 11, a first power transmission member 13, a second power transmission member 17, a bearing 5, and a ball screw device 2.

As shown in FIG. 1, the housing 10 is a hollow member. A motor 11, a first power transmission member 13, a second power transmission member 17, a bearing 5, and a ball screw device 2 are arranged inside the housing 10.

The motor 11 is supported by the housing 10. The motor 11 includes a shaft 110 that rotates about a rotation shaft Z2. As shown in FIG. 1, the first power transmission member 13 is fixed to the shaft 110. The first power transmission member 13 is, for example, a pulley. When the motor 11 is driven, the first power transmission member 13 rotates together with the shaft 110. The second power transmission member 17 is, for example, a belt. The second power transmission member 17 is in contact with the outer peripheral surface of the first power transmission member 13.

The bearing 5 is supported by the housing 10. The bearing 5 is arranged between the housing 10 and the ball screw device 2. The bearing 5 includes an outer ring 51, an inner ring 53, and a plurality of rolling elements 52. The outer ring 51 is fixed to the housing 10. The inner ring 53 is fixed to the nut 4 of the ball screw device 2. The rolling element 52 is arranged between the outer ring 51 and the inner ring 53.

As shown in FIG. 1, the ball screw device 2 includes a screw shaft 3, a nut 4, a plurality of rolling elements 6, a third power transmission member 15, a key 7, and a holding member 8.

The screw shaft 3 is a rod-shaped member and has a screw groove on the outer peripheral surface. The screw shaft 3 is provided with a stopper 35 at an end portion in the axial direction. In the following description, the axial direction of the screw shaft 3 is simply described as the axial direction. The stopper 35 projects in the radial direction. The radial direction is orthogonal to the axial direction. As shown in FIGS. 1 and 3, the stopper 35 overlaps the end face 40 of the nut 4 when viewed from the axial direction. The screw shaft 3 penetrates the nut 4. When the nut 4 rotates, the screw shaft 3 moves linearly along the axial direction.

The nut 4 is provided with a thread groove on the inner peripheral surface. The nut 4 rotates about the rotation shaft Z1. The plurality of rolling elements 6 are arranged in a spiral space formed by the thread groove of the screw shaft 3 and the thread groove of the nut 4. The rolling element 6 circulates in the spiral space. As shown in FIG. 3, the nut 4 includes a top hole 41, a top 42, a flange 49, a first key groove 45, and a first holding groove 48.

The top hole 41 is a hole that penetrates the nut 4 in the radial direction. The frame 42 is fitted into the frame hole 41. The frame 42 is a member for circulating the rolling element 6. The frame 42 is also called a deflector. The rolling element 6 that has reached the position of the piece 42 is returned by the piece 42 to the spiral space between the screw shaft 3 and the nut 4. The frame 42 is omitted in the drawings except for one shown in FIG.

As shown in FIG. 5, the flange 49 is arranged at the axial end of the nut 4. The flange 49 projects in the radial direction from the outer peripheral surface of the nut 4 and is annular. As shown in FIG. 1, the inner ring 53 of the bearing 5 is in contact with the flange 49. The nut 4 is positioned by the flange 49.

As shown in FIG. 5, the first key groove 45 is a groove along the axial direction. The first keyway 45 extends axially from the end surface 40 of the nut 4 on the side opposite to the flange 49. That is, the first keyway 45 is opened at the end surface 40 of the nut 4. For example, the first keyway 45 is substantially rectangular when viewed from the axial direction. As shown in FIG. 5, the first keyway 45 includes a bottom surface 451, a side surface 452, a side surface 453, and a side surface 454. For example, the bottom surface 451 is a plane orthogonal to the radial direction. The side surface 452 and the side surface 453 are planes orthogonal to the bottom surface 451. The side surface 452 faces the side surface 453. The side surface 454 is a curved surface connecting the side surface 452 and the side surface 453.

As shown in FIG. 5, the first holding groove 48 is a groove along the circumferential direction of the nut 4. The circumferential direction is a tangential direction centered on the rotation axis Z1. The depth (length in the radial direction) of the first holding groove 48 is smaller than the depth of the first key groove 45. Both ends of the first holding groove 48 are connected to the first key groove 45. One end of the first holding groove 48 is open on the side surface 452. The other end of the first holding groove 48 is open on the side surface 453.

The third power transmission member 15 is provided outside the nut 4 in the radial direction. The third power transmission member 15 is a pulley as shown in FIG. As shown in FIG. 1, the third power transmission member 15 is in contact with the bearing 5. The second power transmission member 17 shown in FIG. 1 is in contact with the outer peripheral surface of the third power transmission member 15. The second power transmission member 17 is bridged over the first power transmission member 13 and the third power transmission member 15. The torque generated by the motor 11 is transmitted to the third power transmission member 15 via the first power transmission member 13 and the second power transmission member 17.

The third power transmission member 15 is provided with a second key groove 151 as shown in FIG. The second keyway 151 is provided on the inner peripheral surface of the tubular third power transmission member 15. The second key groove 151 is a groove along the axial direction. That is, the second keyway 151 is parallel to the first keyway 45. The second keyway 151 extends from one end to the other end of the third power transmission member 15 in the axial direction.

The key 7 is a member that connects the third power transmission member 15 and the nut 4. The key 7 fits into the first key groove 45 and the second key groove 151 as shown in FIG. The key 7 transmits the torque applied to the third power transmission member 15 to the nut 4. As shown in FIG. 3, the key 7 protrudes from the end surface 40 of the nut 4 toward the stopper 35 of the screw shaft 3. As shown in FIG. 6, the key 7 includes a base portion 71, a protruding portion 73, a connecting portion 72, a hook portion 75, and a second holding groove 78.

The base 71 has, for example, a rectangular parallelepiped shape. As shown in FIG. 3, the base portion 71 is arranged on the side surface 454 side of the first key groove 45 with respect to the first holding groove 48. The protrusion 73 has, for example, a rectangular parallelepiped shape. The protruding portion 73 is connected to the base portion 71 by a connecting portion 72. The thickness of the protruding portion 73 in the radial direction is larger than the thickness of the connecting portion 72 in the radial direction. As a result, a second holding groove 78 is formed between the base portion 71 and the protruding portion 73. Further, the strength of the protruding portion 73 is likely to be improved. The protrusion 73 is arranged on the stopper 35 side of the first key groove 45 with respect to the first holding groove 48. The protruding portion 73 projects toward the stopper 35 from the end surface 40 of the nut 4. The hook portion 75 extends inward in the radial direction from the protruding portion 73. The hook portion 75 is in contact with the end surface 40 of the nut 4. The second holding groove 78 is a groove formed in the base portion 71 and the protruding portion 73. The second holding groove 78 is connected to the first holding groove 48 of the nut 4. An annular groove is formed by the second holding groove 78 and the first holding groove 48.

The holding member 8 is a member that regulates the axial movement of the key 7. The holding member 8 is a substantially C-shaped member, which is also called a retaining ring, for example. The holding member 8 is fitted into the first holding groove 48 and the second holding groove 78. That is, the holding member 8 straddles the nut 4 and the key 7. The holding member 8 fitted in the first holding groove 48 does not move in the axial direction with respect to the nut 4. Since the holding member 8 is fitted in the second holding groove 78, the key 7 does not move axially with respect to the nut 4. Therefore, the movement of the key 7 in the axial direction is restricted.

The holding member 8 is also a member that regulates the axial movement of the third power transmission member 15. The holding member 8 is in contact with the third power transmission member 15 as shown in FIG. Since one end of the third power transmission member 15 in the axial direction is in contact with the bearing 5 shown in FIG. 1 and the other end is in contact with the holding member 8, the movement of the third power transmission member 15 in the axial direction is restricted.

When the motor 11 is driven, the nut 4 rotates about the rotation shaft Z1. When the nut 4 rotates, the screw shaft 3 moves straight. Therefore, the stopper 35 approaches the nut 4. When the amount of movement of the screw shaft 3 reaches a predetermined amount, the protruding portion 73 and the hook portion 75 of the key 7 come into contact with the stopper 35. As a result, the rotation of the nut 4 is stopped. The key 7 and the stopper 35 prevent the screw shaft 3 from falling off from the nut 4.

The second key groove 151 does not necessarily have to extend from one end to the other end in the axial direction of the third power transmission member 15. The axial length of the second keyway 151 may be at least the length of the base 71 in the axial direction.

As described above, the ball screw device 2 is located between the screw shaft 3 having the stopper 35, the nut 4 having the first keyway 45 along the axial direction of the screw shaft 3, and the screw shaft 3 and the nut 4. A plurality of rolling elements 6 provided, a power transmission member (third power transmission member 15) provided on the outer periphery of the nut 4 and having a second key groove 151 along the axial direction, a first key groove 45, and a second key. A key 7 that fits into the groove 151 is provided. The stopper 35 overlaps with the end face 40 of the nut 4 when viewed from the axial direction. The tip of the key 7 protrudes toward the stopper 35 from the end face 40.

As a result, the key 7 transmits the torque applied to the power transmission member (third power transmission member 15) to the nut 4. Further, the key 7 hits the stopper 35 when the screw shaft 3 moves by a predetermined amount. As a result, the rotation of the nut 4 is restricted, and the movement of the screw shaft 3 is stopped. Further, the first key groove 45 and the second key groove 151 are originally required for the member that transmits the torque to the nut 4. Therefore, the processing does not increase in the manufacturing process of the nut 4. Therefore, the ball screw device 2 can prevent the screw shaft 3 from falling off from the nut 4 and can simplify the manufacturing process.

Further, the ball screw device 2 includes a holding member 8 attached to the nut 4. The nut 4 includes a first holding groove 48 along the circumferential direction. The key 7 has a base portion 71 located on the side opposite to the end surface 40 of the first holding groove 48, a protruding portion 73 located on the end surface 40 side of the first holding groove 48, and a base portion 71 and a protruding portion 73. A second holding groove 78 is provided which is located between them and is connected to the first holding groove 48. The holding member 8 fits into the first holding groove 48 and the second holding groove 78, and is in contact with the base portion 71.

As a result, the holding member 8 fitted in the first holding groove 48 does not move in the axial direction with respect to the nut 4. Since the holding member 8 is in contact with the base 71, the key 7 cannot move to the end face 40 side of the nut 4. Therefore, the key 7 is prevented from falling off from the nut 4.

Further, the actuator 1 includes a ball screw device 2, a housing 10 that supports the nut 4 via a bearing 5, and a motor 11 that generates power transmitted to a power transmission member (third power transmission member 15).

As a result, the actuator 1 includes the ball screw device 2 that can simplify the manufacturing process, so that the actuator 1 can be easily manufactured.

(First modification)
FIG. 7 is a cross-sectional view of the ball screw device according to the first modification. FIG. 8 is a perspective view of the key according to the first modification. The same components as those described in the above-described embodiment are designated by the same reference numerals, and duplicate description will be omitted.

The ball screw device 2A of the first modification includes a key 7A different from the key 7 described above. The key 7A includes a protrusion 73A as shown in FIG. As shown in FIG. 8, the thickness of the protruding portion 73A in the radial direction is equal to the thickness of the connecting portion 72 in the radial direction. As a result, the shape of the key 7A is simplified, so that the key 7A can be easily manufactured.

(Second modification)
FIG. 9 is a cross-sectional view of the ball screw device according to the second modification. The same components as those described in the above-described embodiment are designated by the same reference numerals, and duplicate description will be omitted.

The ball screw device 2B according to the second modification includes a third power transmission member 15B different from the above-mentioned third power transmission member 15. The third power transmission member 15B includes a convex portion 155 as shown in FIG. The convex portion 155 is a protrusion protruding inward in the radial direction from the surface of the second key groove 151. For example, the convex portion 155 is provided at the end portion of the second keyway 151 on the end face 40 side of the nut 4. The convex portion 155 is located on the end face 40 side of the base portion 71 of the key 7. The convex portion 155 is in contact with the base portion 71.

In the ball screw device 2B of the second modification, the key 7A of the first modification may be applied. That is, the ball screw device 2B may include the key 7A instead of the key 7.

As described above, the power transmission member (third power transmission member 15B) includes a convex portion 155 projecting from the surface of the second key groove 151 in a direction orthogonal to the axial direction. The key 7 includes a base portion 71 located on the opposite side of the convex portion 155 from the end surface 40, and a protruding portion 73 located on the end surface 40 side of the convex portion 155. The convex portion 155 is in contact with the base portion 71.

As a result, the key 7 does not move to the end face 40 side of the nut 4. The protrusion 155 prevents the key 7 from falling off the nut 4.

(Third modification example)
FIG. 10 is a perspective view of the ball screw device according to the third modification. FIG. 11 is a plan view of the ball screw device according to the third modification. FIG. 12 is a perspective view of the key according to the third modification. The same components as those described in the above-described embodiment are designated by the same reference numerals, and duplicate description will be omitted.

The ball screw device 2C according to the third modification includes a nut 4C different from the nut 4 described above, and a key 7C different from the key 7 described above.

As shown in FIG. 10, the nut 4C includes a cross groove 456 and a cross groove 457. The crossing groove 456 and the crossing groove 457 intersect the first key groove 45. The cross groove 456 extends in the circumferential direction from the first key groove 45. The cross groove 457 extends in the circumferential direction from the first key groove 45 and extends in the direction opposite to the cross groove 456. For example, the axial position of the cross groove 456 is equal to the axial position of the cross groove 457. The cross groove 456 and the cross groove 457 are located on the side opposite to the end face 40 from the first holding groove 48.

As shown in FIG. 12, the key 7C includes a protrusion 76 and a protrusion 77. For example, the protrusions 76 and 77 project from the base 71 in the circumferential direction. As shown in FIG. 10, the protrusion 76 fits into the cross groove 456, and the protrusion 77 fits into the cross groove 457.

In addition, in the key 7C of the third modification, the protruding portion 73A of the key 7A of the first modification may be applied. That is, the key 7C may include the protrusion 73A instead of the protrusion 73.

The positions of the cross groove 456 and the cross groove 457 do not necessarily have to be the positions described above. For example, the cross groove 456 and the cross groove 457 may be located closer to the end face 40 than the first holding groove 48. The axial position of the cross groove 456 may be different from the axial position of the cross groove 457. Further, the key 7C does not necessarily have to include both the cross groove 456 and the cross groove 457, and may include at least one of the cross groove 456 and the cross groove 457.

As described above, the nut 4C includes a cross groove 456 and a cross groove 457 that intersect the first key groove 45. The key 7C includes a protrusion 76 that fits into the cross groove 456. The key 7C includes a protrusion 77 that fits into the cross groove 457.

As a result, the key 7C does not move relative to the nut 4C. The cross groove 456, cross groove 457, protrusion 76 and protrusion 77 prevent the key 7C from moving axially from the nut 4C and falling off.

1 Actuator 10 Housing 110 Shaft 11 Motor 13 1st power transmission member 15, 15B 3rd power transmission member 151 2nd key groove 155 Convex 17 2nd power transmission member 2, 2A, 2B, 2C Ball screw device 3 Screw shaft 35 Stopper 4, 4C Nut 40 End face 41 Top hole 42 Top 45 First key groove 451 Bottom surface 452, 453, 454 Side surface 456, 457 Cross groove 48 First holding groove 49 Flange 5 Bearing 6 Rolling element 7, 7A, 7C Key 71 Base 72 Connecting part 73, 73A Protruding part 75 Hook part 76, 77 Protruding 78 Second holding groove 8 Holding member

Claims (5)

A screw shaft with a stopper and
A nut having a first keyway along the axial direction of the screw shaft,
A plurality of rolling elements provided between the screw shaft and the nut,
A power transmission member provided on the outer circumference of the nut and having a second keyway along the axial direction.
A key that fits into the first keyway and the second keyway,
With
The stopper overlaps with the end face of the nut when viewed from the axial direction.
A ball screw device in which the tip of the key projects toward the stopper side from the end face. It has a holding member that can be attached to the nut.
The nut has a first holding groove along the circumferential direction.
The key is located between a base portion located on the side opposite to the end face of the first holding groove, a protruding portion located on the end face side of the first holding groove, and the base portion and the protruding portion. A second holding groove located and connected to the first holding groove is provided.
The ball screw device according to claim 1, wherein the holding member fits into the first holding groove and the second holding groove and is in contact with the base portion. The power transmission member includes a convex portion that projects in a direction orthogonal to the axial direction from the surface of the second key groove.
The key includes a base portion located on the side opposite to the end face of the convex portion, and a protruding portion located on the end face side of the convex portion.
The ball screw device according to claim 1, wherein the convex portion is in contact with the base portion. The nut comprises a cross groove that intersects the first key groove.
The ball screw device according to any one of claims 1 to 3, wherein the key includes a protrusion that fits into the cross groove. The ball screw device according to any one of claims 1 to 4.
A housing that supports the nut via bearings,
A motor that generates power transmitted to the power transmission member,
Actuator with.

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