JP2014178023A - Ball screw mechanism and actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an influence on component elements of a bearing and a ball screw even when a locking portion and a stopper portion collide with each other under a comparatively large load.SOLUTION: Two locking portions 61, 62 are separately disposed on positions different in phases by 180 degrees in the circumferential direction, of a nut 30 to which rotary motion is transmitted from a torque transmitting member 71 and which is rotatably supported by a bearing 40. Two stopper portions 51, 52 kept into contact with two locking portions, are separately disposed on positions different in phases by 180 degrees in the circumferential direction, of a screw shaft 20 where the motion is converted into the linear motion.

Description

  The present invention relates to a ball screw mechanism and an actuator suitable for a linear actuator.

  2. Description of the Related Art Conventionally, a ball screw type direct acting actuator has been widely used as a power conversion device that obtains a large axial output from a relatively small input torque by using a ball screw that converts rotational motion into linear motion. When a relatively small input torque from a drive source such as an electric motor is input to a screw shaft (or nut) constituting a ball screw via a speed reduction mechanism, the screw shaft (or nut) is rotated in a desired direction. The rotational motion of the screw shaft (or nut) is converted into linear motion of the nut (or screw shaft) screwed with the screw shaft (or nut) via a plurality of balls. Then, the linear motion of the nut (or screw shaft) is taken out from the output shaft connected to the nut (or directly from the screw shaft).

This ball screw type linear motion actuator is a means for forcibly limiting the process in order to prevent damage to the device driven by the actuator as well as damage to the actuator when the predetermined linear motion process is exceeded. Wearing is required.
Therefore, for example, as disclosed in Patent Document 1, a structure including a stopper is employed. However, in the technique described in Patent Document 1, the stopper contact surface provided on the nut and the stopper provided on the screw shaft are in contact at one place.

For this reason, when the stopper contact surface and the stopper collide or contact with a relatively large load, the bearing and ball screw elements that support the rotational movement of the screw shaft (or nut) are unstable. The impact load was likely to be applied, and the ball screw could be damaged.
Further, for example, as disclosed in Patent Document 2, a nut as a rotational motion element, a screw shaft as a linear motion element that converts the rotational motion of the nut into a linear motion, and a radial direction at an end of the screw shaft A ball screw type linear motion actuator including a pair of guide protrusions protruding outward and a guide member disposed in a fixed portion that supports the screw shaft to guide the pair of guide protrusions in the axial direction Are known.

Japanese Patent Laid-Open No. 10-078100 JP 2012-229800 A

Here, when the structure provided with the stopper of Patent Document 1 is adopted in the apparatus of Patent Document 2, a large collision load is input to the guide member, and the function of guiding the screw shaft may be lost.
Therefore, the present invention has been made paying attention to the unsolved problems of the above conventional example, and even if the locking portion and the stopper portion collide with a relatively large load, the ball screw bearing and the ball screw are configured. It is an object of the present invention to provide a ball screw mechanism and an actuator that can be used stably over a long period of time by suppressing the influence on each element that further performs, further, each element that constitutes the actuator, or each element that is driven by the actuator.

  In order to achieve the above object, a ball screw mechanism according to an aspect of the present invention corresponds to a screw shaft having a spiral screw shaft rolling path on an outer peripheral surface, and the screw shaft rolling path on an inner peripheral surface. A nut provided with a spiral nut rolling path, a plurality of rolling elements interposed between the screw shaft rolling path and the nut rolling path so as to be freely rollable, and the nut and the screw shaft. A torque transmission member that transmits rotational motion to one side, and a bearing that supports one of the nut and screw shaft that performs rotational motion, and the rotational motion transmitted from the torque transmission member is transmitted to the nut and screw shaft In the ball screw mechanism for converting to the other of the two as a linear motion, one of the nut and the screw shaft to which the rotational motion is transmitted from the torque transmitting member is spaced apart at a position 180 degrees out of phase in the circumferential direction. The locking part is formed and straight Two stopper portions with which the two locking portions abut on the other of the nut and the screw shaft converted as motion are formed at positions 180 degrees apart from each other in the circumferential direction. Is preferred.

  In addition, a ball screw mechanism according to an aspect of the present invention includes a screw shaft having a spiral screw shaft rolling path on an outer peripheral surface, and a spiral nut rolling corresponding to the screw shaft rolling path on an inner peripheral surface. Rotating motion is transmitted to one of the nut and the screw shaft, a nut provided with a moving path, a plurality of rolling elements interposed between the screw shaft rolling path and the nut rolling path, and the nut and the screw shaft. And a bearing that supports one of the nut and the screw shaft that performs a rotational motion, and the rotational motion transmitted from the torque transmission member is linearly moved to the other of the nut and the screw shaft. In the ball screw mechanism to be converted, the torque transmission member is formed with two locking portions spaced apart from each other by 180 degrees in the circumferential direction, and the nut and screw shaft are converted as a linear motion. On the other hand, the two locking portions It is preferable that the stopper portion of the abutment for two positions are spaced apart at different positions of 180 degree phase in the circumferential direction.

In the ball screw mechanism according to one aspect of the present invention, it is preferable that the torque transmission member is a pulley member to which a rotational force is transmitted via a belt.
In the ball screw mechanism according to an aspect of the present invention, it is preferable that the torque transmission member is a driven gear that meshes with a drive gear and transmits a rotational force.
In the ball screw mechanism according to one aspect of the present invention, it is preferable that at least one of the locking portion and the stopper portion be adjustable in a circumferential phase.

Furthermore, in the ball screw mechanism according to one aspect of the present invention, the phase when the locking portion and the stopper portion abut is approximately 90 degrees with respect to the direction in which the tangential force of the torque transmitting member acts. It is preferable to arrange in.
The actuator according to one embodiment of the present invention preferably includes the above-described ball screw mechanism.

  According to the ball screw mechanism and the actuator according to the present invention, the member that is rotated is separated from the position where the phase is different by 180 degrees in the circumferential direction, and the two locking portions are formed to be converted into linear motion. In addition, since the two stopper portions with which the two locking portions abut are formed at positions 180 degrees apart from each other in the circumferential direction, the locking portion and the stopper portion collide with each other. Even when the stopper and stopper come into contact with a relatively large load, the influence on the ball screw bearing, each element constituting the ball screw, each element constituting the actuator, or each element driven by the actuator Can be used stably over a long period of time.

It is a front view which shows the ball screw mechanism of 1st Embodiment which concerns on this invention. It is a side view which shows the ball screw mechanism of 1st Embodiment. It is a figure which shows the stopper member which comprises the ball screw mechanism of 1st Embodiment. It is a front view which shows the ball screw mechanism of 2nd Embodiment which concerns on this invention. It is a side view which shows the ball screw mechanism of 3rd and 4th embodiment which concerns on this invention. It is a figure which shows the effect | action of the ball screw mechanism of 3rd and 4th embodiment which concerns on this invention. It is a figure explaining the ball screw mechanism of the structure different from 3rd and 4th embodiment which concerns on this invention. It is a front view which shows the ball screw mechanism of 5th Embodiment which concerns on this invention. It is a front view which shows the ball screw mechanism of 6th Embodiment which concerns on this invention.

DESCRIPTION OF EMBODIMENTS Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings.
[First Embodiment]
1 to 3 show a ball screw mechanism 10 used as an actuator according to a first embodiment of the present invention.

As shown in FIG. 1, the ball screw mechanism 10 of the present embodiment includes a screw shaft 20, a nut 30, a screw groove 21 provided on the outer periphery of the screw shaft 20, and a screw groove provided on the inner periphery of the nut 30. A ball (not shown), which is a plurality of rolling elements, is provided so as to be freely rollable between the two.
A flange portion 33 is provided at the axially central portion of the nut 30. A torque transmission member 71 is attached to the outer periphery of the flange portion 33 by spline coupling (see FIG. 2).

  The nut 30 is rotatably supported by a rolling bearing 40 including an outer ring 41, an inner ring 42, and a rolling element 43. The rolling bearing 40 may be a rolling bearing with a seal that seals an opening formed by the outer ring 41 and the inner ring 42 of the rolling bearing 40 in which grease or the like is selectively enclosed. Alternatively, a cage for holding the rolling elements 43 at equal intervals in the circumferential direction may be provided. Furthermore, although the rolling element 43 is illustrated as a ball (ball), it may have a roller or the like selectively. Also, multi-point contact bearings such as so-called three-point contact ball bearings and four-point contact ball bearings can be used.

The inner ring 42 of the rolling bearing 40 and the outer periphery of the nut 30 are press-fitted with a tightening margin. Therefore, the torque transmission member 71 is attached so as not to be displaced relative to the nut 30 in the circumferential direction by spline coupling and in the axial direction by the inner ring 42 of the rolling bearing 40.
The torque transmission member 71 rotates around the screw shaft 20 by a rotation input (not shown) from the outside. The rolling bearing 40 has an outer ring 41 fixed to a housing (not shown) or the like. Therefore, in this embodiment, the screw shaft 20 is driven in the axial direction when the nut 30 fixed in the axial direction is rotated by a rotation input from the outside.

Moreover, the 1st latching | locking part 61 and the 2nd latching | locking part 62 are provided in the phase (refer FIG. 2) of the circumferential direction at the one end surface part of the nut 30. FIG.
A stopper member 50 is attached to an end surface portion corresponding to one end surface of the nut 30 of the screw shaft 20 via an attachment member 23.
The stopper member 50 is provided with a first stopper portion 51 and a second stopper portion 52 at a phase of 180 degrees in the circumferential direction (see FIG. 2).

  In the state shown in FIG. 1, when the nut 30 further rotates, the first locking portion 61 contacts the first stopper portion 51 and the second locking portion 62 contacts the second stopper portion 52 at the same time. The state, that is, the state where the first locking portion 61 and the first stopper portion 51, the second locking portion 62 and the second stopper portion 52 are simultaneously brought into contact with each other and the rotation of the nut 30 is stopped when one more rotation is made. Is.

FIG. 2 shows a state where the first locking portion 61 is in contact with the first stopper portion 51 and the second locking portion 62 is in contact with the second stopper portion 52.
The stopper member 50 is attached to an engagement portion 24 formed on the screw shaft 20 so as not to rotate relative to the screw shaft 20.
FIG. 3A is a perspective view for explaining details of the stopper member 50. A spline 55 is formed on the inner periphery of the stopper member 50. By engaging and attaching the spline 55 and a spline (not shown) formed on the screw shaft 20, the stopper member 50 is firmly attached to the screw shaft 20 without relative rotation.

Further, as shown in FIG. 3B, the stopper member 50 is provided with keys 56 and 57 protruding on the inner periphery, and a key groove (not shown) into which the keys 56 and 57 are fitted on the screw shaft 20. By being engaged and attached, the stopper member 50 is firmly attached to the screw shaft 20 without being relatively rotated.
Here, referring to FIG. 1, a preferable state of the relative positions of the stopper member 50 and the nut 30 in the axial direction, and the first stopper portion 51, the second stopper portion, the first locking portion 61, and the second locking portion 62. The preferable form of will be described.

In the state shown in FIG. 1, that is, in a state where the first locking portion 61 and the first stopper portion 51, the second locking portion 62 and the second stopper portion 52 come into contact with each other after one rotation, the second indicated by the symbol a. The distance between the end portion of the stopper portion 52 and the end portion of the second locking portion 62 is set shorter than the lead of the screw groove 21 (screw groove 31).
Further, the distance between the end portion of the second stopper portion 52 and the end portion of the first locking portion 61 indicated by the symbol b is set to be longer than half of the lead of the screw groove 21 (screw groove 31). Yes.

Further, the distance between the end portion of the first stopper portion 51 and the end portion of the first locking portion 61 indicated by reference symbol c is set to be shorter than the lead of the screw groove 21 (screw groove 31).
Further, the distance between the end portion of the first stopper portion 51 and the end portion of the second locking portion 62 indicated by the symbol d is set to be longer than half of the lead of the screw groove 21 (screw groove 31). Yes.

Next, the effect of the ball screw mechanism 10 of this embodiment is demonstrated.
In the ball mechanism 10 of this embodiment, when the nut 30 is rotated once from the state of FIG. 1 together with the torque transmission member 71 by external rotation input, the first locking portion 61 of the nut 30 is the first stopper portion of the screw shaft 20. At the same time, the second locking portion 62 of the nut 30 contacts the second stopper portion 52 of the screw shaft 20 and the two locking portions and the stopper portion come into contact with each other. Even when the parts collide or when the locking part and the stopper part come into contact with each other with a relatively large load, the influence on each element constituting the rolling bearing 40 and the ball screw mechanism 10 can be suppressed. An actuator that can be used stably can be provided.

  Moreover, the axial length of the 1st stopper part 51, the 2nd stopper part 52, the 1st latching | locking part 61, and the 2nd latching | locking part 62 by having set to the distance of the code | symbol ad of FIG. The axis of the contact surface between the first stopper portion 51 and the first locking portion 61 and the contact surface between the second stopper portion 52 and the second locking portion 62 in a state in which the length is not longer than necessary. It is possible to ensure the length of the contact portion in the direction (ie, the allowance). That is, by ensuring the length of the abutting portion (capping allowance), it is possible to reduce the generation of a scooping force that occurs at the time of abutment.

In addition, when this embodiment is adopted in Patent Document 2 (Japanese Patent Laid-Open No. 2012-229800) described above, the collision load input to the guide member of Patent Document 2 due to contact between the two locking portions and the stopper portion. And the function of guiding the screw shaft can be maintained.
Further, a spline 55 is formed on the inner periphery of the stopper member 50, and the stopper member 50 is attached to the screw shaft 20 by engaging the spline 55 with the spline formed on the screw shaft 20. If the splines 55 are formed at a relatively fine pitch, the first stopper portion 51 and the second stopper portion 52 provided on the stopper member 50, the first locking portion 61 provided on the nut 30 and the first stopper portion The phase in the rotational direction (circumferential direction) with the two locking portions 62 can be adjusted easily and accurately.

[Second Embodiment]
FIG. 4 shows a ball screw mechanism 11 according to a second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the same component as the structure shown in FIGS. 1-3, and the description is abbreviate | omitted.
In the ball screw mechanism 11 according to the present embodiment, a first locking portion 61 and a second locking portion 62 are provided on the end surface of the torque transmission member 71 facing the stopper member with a phase of 180 degrees in the circumferential direction. Yes.
When the torque rotating member 71 rotates, the first locking portion 61 contacts the first stopper portion 51, and at the same time, the second locking portion 62 contacts the second stopper portion 52, and the rotation of the nut 30 stops. The state to be performed is shown.

  According to the ball mechanism 11 of the present embodiment, when the torque transmission member 71 rotates once by external rotation input, the first locking portion 61 of the torque transmission member 71 contacts the first stopper portion 51 of the screw shaft 20. At the same time, the second locking portion 62 of the torque transmission member 71 abuts on the second stopper portion 52 of the screw shaft 20 and the two locking portions and the stopper portion come into contact with each other, so that the locking portion and the stopper portion collide with each other. Even when the locking portion and the stopper portion are contacted with a relatively large load, the influence on the elements constituting the rolling bearing 40 and the ball screw mechanism 11 can be suppressed, and stable over a long period of time. A usable actuator can be provided.

[Third and fourth embodiments]
Next, FIG. 5 to FIG. 7 show the ball screw mechanisms of the third and fourth embodiments according to the present invention. In the present embodiment, similarly to the first embodiment shown in FIGS. 1 to 3, the first locking portion 61 and the second locking portion 62 are arranged in the circumferential direction on one end surface portion of the nut 30. The phase is 180 degrees.

  A torque transmission member 72 of the ball screw mechanism 13 of the third embodiment shown in FIG. 5A is a pulley member to which a rotational force is transmitted via a belt 73 (hereinafter referred to as a pulley member 72). In this figure, an arrow indicated by a broken line indicates a reaction force against a tangential force of the pulley member 72, and an arrow indicated by a solid line indicates a torque and a moment generated by the first locking portion 61 and the second locking portion 62. ing.

As shown in FIG. 5A, in the ball screw mechanism 13 of the present embodiment, the first locking portion 61 of the nut 30 abuts on the first stopper portion 51 of the screw shaft 20, and the second locking of the nut 30 is performed. It arrange | positions so that the phase when the part 62 contact | abuts to the 2nd stopper part 52 of the screw shaft 20 may be about 90 degree | times with respect to the direction where the tangential force of the pulley member 72 acts.
As shown in FIG. 6, the ball screw mechanism 13 of the present embodiment can receive the tangential force of the pulley member 72 at the first locking portion 61 and the second locking portion 62, and a moment acts on the rolling bearing 40. Without this, the input radial load can be reduced.

  Here, FIG. 7 shows that the phase when the first locking part 61 abuts on the first stopper part 51 and the second locking part 62 abuts on the second stopper part 52 is tangent to the pulley member 72. In this case, the tangential force of the pulley member 72 cannot be received by the first locking portion 61 and the second locking portion 62. The tangential force of the pulley member 72 is supported by the rolling bearing 40, and a moment generated by the tangential force acts on the rolling bearing 40.

  Therefore, in the ball screw mechanism 13 of the present embodiment, the phase when the first locking portion 61 is in contact with the first stopper portion 51 and the second locking portion 62 is in contact with the second stopper portion 52 is Since the tangential force of the pulley member 72 is arranged to be approximately 90 degrees with respect to the acting direction, the tangential force of the pulley member 72 is received by the first locking portion 61 and the second locking portion 62. Thus, the moment does not act on the rolling bearing 40, the input radial load can be reduced, and the rotational motion can be converted stably into a linear motion over a long period of time.

Further, the torque transmission member 74 of the ball screw mechanism 14 shown in FIG. 5B according to the fourth embodiment is a driven gear that meshes with the drive gear 75 and transmits the rotational force (hereinafter referred to as the driven gear 74 and the like). Called). In this figure, an arrow indicated by a broken line indicates a reaction force against a tangential force of the driven gear 74, and an arrow indicated by a solid line indicates a torque and a moment generated by the first locking portion 61 and the second locking portion 62. ing.
In the ball screw mechanism 14 of the present embodiment, the first locking portion 61 of the nut 30 abuts on the first stopper portion 51 of the screw shaft 20, and the second locking portion 62 of the nut 30 is the second stopper of the screw shaft 20. It arrange | positions so that the phase when contacting the part 52 may be about 90 degree | times with respect to the direction where the tangential force of the driven gear 74 acts.

According to the ball screw mechanism 14 of the present embodiment, the tangential force of the driven gear 74 can be received by the first locking portion 61 and the second locking portion 62 as in the pulley member 72 shown in FIG. Since no moment acts on the bearing 40 and the input radial load can be reduced, the rotational motion can be stably converted into a linear motion over a long period of time.
The torque transmission member used as the pulley member 72 or the driven gear 74 is a molded part that is easy to manufacture, such as a casting, and is compared with the case where the outer periphery of the nut 30 is ground to produce the pulley part and the gear part. Thus, the manufacturing cost can be greatly reduced.

[Fifth and sixth embodiments]
Next, FIG.8 and FIG.9 shows the ball screw mechanism of 5th and 6th embodiment which concerns on this invention.
In the ball screw mechanism 15 shown in the fifth embodiment shown in FIG. 8, the inner ring 42 constituting the rolling bearing 40 is attached to the outer periphery of the nut 30 by interference fit, and the outer ring 41 is attached to the housing 80 by clearance fit. In addition, the outer ring 41 is fixed to the housing 80 with a screw member 81.

Thus, by fixing the outer ring 41 attached to the housing 80 with a clearance fit with the screw member 81, the rolling bearing 40 can be easily attached between the housing 80 and the nut 30 of the ball screw mechanism 15. it can.
Further, in the ball screw mechanism 16 shown in the sixth embodiment shown in FIG. 9, the inner ring 42 constituting the rolling bearing 40 is attached to the outer periphery of the nut 30 by clearance fitting, and the outer ring 41 is attached to the housing 80 by a clamping spring. In addition, the inner ring 42 is fixed to the outer periphery of the nut 30 with a screw member 82.

As described above, the inner ring 42 attached to the outer periphery of the nut 30 with a clearance fit is fixed by the screw member 82, so that the rolling bearing 40 can be easily attached between the housing 80 and the nut 30 of the ball screw mechanism 16. be able to.
As described above, the scope of the present invention is not limited to the above embodiment. For example, the screw shaft can be a member that rotates by rotational input, and the nut can be a drive member that moves in the axial direction. Furthermore, the circumferential dimension of each stopper part and the locking part, the shape of the contact surface formed by the stopper part and the locking part, etc. can be arbitrarily set within the scope of the present invention. Is possible.

  DESCRIPTION OF SYMBOLS 10, 11, 13, 14, 15, 16 ... Ball screw mechanism, 20, 21 ... Screw shaft, 23 ... Mounting member, 24 ... Engagement part, 30 ... Nut, 31 ... Screw groove, 33 ... Flange part, 40 ... Rolling bearing, 41 ... outer ring, 42 ... inner ring, 43 ... rolling element, 50 ... stopper member, 51 ... first stopper part, 52 ... second stopper part, 55 ... spline, 56, 57 ... key, 61 ... first engagement Stop part, 62 ... second locking part, 71 ... gear member, 72 ... pulley member (torque transmission member), 73 ... belt, 74 ... driven gear (torque transmission member), 75 ... drive gear, 80 ... housing, 81 , 82 ... Screw member

Claims (7)

A screw shaft provided with a spiral screw shaft rolling path on the outer peripheral surface; a nut provided with a spiral nut rolling path corresponding to the screw shaft rolling path on the inner peripheral surface; and the screw shaft rolling path And a plurality of rolling elements interposed between the nut rolling paths so as to be freely rollable, a torque transmission member transmitting rotational motion to one of the nut and the screw shaft, the nut performing rotational motion, and the nut A ball screw mechanism that includes a bearing that supports one of the screw shafts, and that converts the rotational motion transmitted from the torque transmitting member to the other of the nut and the screw shaft as a linear motion;
One of the nut and the screw shaft to which rotational motion is transmitted from the torque transmitting member is formed with two locking portions spaced apart from each other by 180 degrees in the circumferential direction,
On the other side of the nut and the screw shaft that are converted as a linear motion, two stopper portions with which the two locking portions abut are formed spaced apart at positions that are 180 degrees out of phase in the circumferential direction. A ball screw mechanism. A screw shaft provided with a spiral screw shaft rolling path on the outer peripheral surface; a nut provided with a spiral nut rolling path corresponding to the screw shaft rolling path on the inner peripheral surface; and the screw shaft rolling path And a plurality of rolling elements interposed between the nut rolling paths so as to be freely rollable, a torque transmission member transmitting rotational motion to one of the nut and the screw shaft, the nut performing rotational motion, and the nut A ball screw mechanism that includes a bearing that supports one of the screw shafts, and that converts the rotational motion transmitted from the torque transmitting member to the other of the nut and the screw shaft as a linear motion;
The torque transmission member is formed with two locking portions spaced apart at different positions by 180 degrees in the circumferential direction,
On the other side of the nut and the screw shaft that are converted as a linear motion, two stopper portions with which the two locking portions abut are formed spaced apart at positions that are 180 degrees out of phase in the circumferential direction. A ball screw mechanism.   The ball screw mechanism according to claim 1, wherein the torque transmission member is a pulley member to which a rotational force is transmitted via a belt.   3. The ball screw mechanism according to claim 1, wherein the torque transmission member is a driven gear that meshes with a drive gear and transmits a rotational force.   5. The ball screw mechanism according to claim 1, wherein at least one of the locking portion and the stopper portion is adjustable in a circumferential phase.   6. The arrangement according to claim 1, wherein a phase when the locking portion and the stopper portion abut each other is approximately 90 degrees with respect to a direction in which a tangential force of the torque transmitting member acts. The ball screw mechanism according to any one of claims.   An actuator comprising the ball screw mechanism according to any one of claims 1 to 6.

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