JP2017020600A - Actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator capable of sufficiently securing strength of a nut, by improving a structure capable of circulating air on both sides of the nut in movement of the nut.SOLUTION: An actuator includes a housing, a screw arranged in the housing, a nut screwed into the screw, and a movable part fastened to the nut. The actuator is characterized in that provided is an air flow passage in which air on both sides of the nut mutually circulates when the nut is moved to the housing side, and the strength of the nut is secured.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an actuator that moves a movable part fixed to the nut back and forth by a screw-nut mechanism including a screw and a nut installed in a housing, in particular, the air flow on both sides of the nut during nut movement. It is related with what was devised so that the intensity | strength of a nut could fully be ensured by improving the structure to enable.

For example, Patent Literature 1 and Patent Literature 2 disclose conventional actuators.
The electric cylinder described in Patent Document 1 includes a cylinder case, and a ball screw is disposed in the cylinder case, and a ball nut is screwed into the ball screw. An output rod that can be projected and retracted is fixed to the ball nut at the front end of the cylinder case. A rotating shaft of a motor is connected to the rear end of the ball screw via a coupling. When the ball screw is rotated and driven by the motor, the ball nut and thus the rod are moved back and forth.

  The ball nut is formed with a through hole extending in the moving direction of the ball nut. When the ball nut is moved in the cylinder case through the through-hole, air on both sides of the ball nut is circulated to make the movement of the ball nut smooth.

  Further, the linear actuator described in Patent Document 2 has the same configuration as that of the electric cylinder described in Patent Document 1, and a groove for air circulation is formed on the outer peripheral side of the nut.

Japanese Utility Model Publication No. 2-150451 Japanese Utility Model Publication No. 2-41386

The conventional configuration has the following problems.
That is, since the ball nut and the nut are formed with through holes and grooves for air circulation, there is a concern that the strength of the ball nut and the nut cannot be sufficiently secured. Such a problem is particularly noticeable when the diameter of the ball nut or nut is reduced.

  The present invention has been made on the basis of such points, and the object of the present invention is to sufficiently secure the strength of the nut by improving the configuration that allows air to flow on both sides of the nut when the nut is moved. It is to provide an actuator.

In order to achieve the above object, an actuator according to claim 1 of the present invention includes a housing, a screw disposed in the housing, a nut screwed to the screw, and a movable part fixed to the nut. And an air flow passage through which air on both sides of the nut flows when the nut is moved to the housing side is provided.
According to a second aspect of the present invention, in the actuator according to the first aspect, the air flow passage is an air circulation groove provided on the inner peripheral surface of the housing.
According to a third aspect of the present invention, in the actuator according to the second aspect, the nut is provided with a rotation restricting convex portion directly or indirectly, and the rotation restricting convex portion is provided on the inner peripheral surface of the housing. A rotation restricting recess for restricting the rotation of the nut accompanying the rotation of the screw by engaging the portion, and the air flow groove is an inner peripheral surface of the housing, and the rotation restricting recess It is provided in parts other than.
According to a fourth aspect of the present invention, in the actuator according to the second aspect, the nut is provided with a rotation restricting convex portion directly or indirectly, and the rotation restricting convex portion is provided on the inner peripheral surface of the housing. A rotation restricting recess for restricting the rotation of the nut associated with the rotation of the screw by engaging the portion, and the air flow groove is provided between the rotation restricting protrusion and the rotation restricting recess. It is characterized by being formed.
The actuator according to claim 5 is the actuator according to claim 4, wherein the air circulation groove is formed between the rotation restricting convex portion and the rotation restricting concave portion and radially outward. It is characterized by.
The actuator according to claim 6 is the actuator according to any one of claims 2 to 5, wherein the air circulation groove is extended and formed along a moving direction of the nut. Is.

As described above, according to the actuator according to claim 1 of the present invention, the housing, the screw disposed in the housing, the nut screwed to the screw, the movable part fixed to the nut, And an air flow passage through which air on both sides of the nut circulates when the nut is moved to the housing side is provided. Can provide sufficient strength of the nut by not providing an air circulation groove.
Further, according to the actuator according to claim 2, in the actuator according to claim 1, since the air flow passage is an air circulation groove provided in the inner peripheral surface of the housing, it can be easily formed.
According to the actuator according to claim 3, in the actuator according to claim 2, the nut is provided with a rotation restricting convex portion directly or indirectly, and the rotation restricting convex portion is provided on the inner peripheral surface of the housing. A rotation restricting recess for restricting the rotation of the nut associated with the rotation of the screw by engagement of the protrusion is provided, and the air circulation groove is an inner peripheral surface of the housing and is used for the rotation restricting. Since it is provided in parts other than a recessed part, the said groove | channel for air distribution can be ensured large, and the movement of the said nut can be made smoother.
According to an actuator according to claim 4, in the actuator according to claim 2, the nut is provided with a rotation restricting convex portion directly or indirectly, and the rotation restricting convex portion is provided on the inner peripheral surface of the housing. A rotation restricting recess for restricting the rotation of the nut accompanying the rotation of the screw by engagement of the protrusion is provided, and the air flow groove is formed between the rotation restricting protrusion and the rotation restricting recess. Since it is formed in between, the air flow groove can also be used to hold the lubricant in the rotation restricting recess on the housing side.
According to an actuator according to claim 5, in the actuator according to claim 4, the groove for air flow is formed between the rotation restricting projection and the rotation restricting recess and radially outward. Therefore, a large air circulation groove can be secured.
According to an actuator according to claim 6, in the actuator according to any one of claims 2 to 5, the air circulation groove extends and is formed along the moving direction of the nut, so that the housing Can be obtained, for example, by extrusion, facilitating production and reducing costs.

It is a figure which shows the 1st Embodiment of this invention and is a perspective view of an actuator. It is a figure which shows the 1st Embodiment of this invention, and is II-II sectional drawing of FIG. It is a figure which shows the 1st Embodiment of this invention and is an enlarged view of the III section of FIG. It is a figure which shows the 1st Embodiment of this invention, and is IV-IV sectional drawing of FIG. FIG. 5A is a perspective view of a nut housing member, and FIG. 5B is a Vb-Vb arrow view of FIG. 6A and 6B are views showing a first embodiment of the present invention, in which FIG. 6A is a perspective view of a rotation restricting member, and FIG. 6B is a view taken in the direction of arrows VIb-VIb in FIG. It is a figure which shows the 2nd Embodiment of this invention, and is a cross-sectional view of an actuator. It is a figure which shows the 3rd Embodiment of this invention, and is a cross-sectional view of an actuator.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
The actuator 1 according to the first embodiment has a hollow housing 3 as shown in FIG. In this housing 3, for example, as shown in FIG. 2, a rod 5 as a movable portion is installed so as to be movable in the front-rear direction (left-right direction in FIG. 2). The tip of the rod 5 (left side in FIG. 2) is disposed so as to be able to protrude and retract outside the housing 3, and a tip fitting 6 is screwed and fixed to the tip 5 via the tip fitting 6. An attachment object (not shown) is installed.

As shown in FIGS. 2 to 4, the rod 5 is a hollow member, and a ball screw shaft 11 is installed therein. A spiral groove 12 is formed on the outer peripheral surface of the ball screw shaft 11. The ball screw shaft 11 is rotatably supported by bearings 15, 15 housed in a bearing case 13 installed on the rear end side (right end side in FIG. 2) of the housing 3. The ball screw shaft 11 is rotated and driven by a motor 19 built in a motor case 17 installed on the rear end side (right end side in FIG. 2) of the bearing case 13. The rear end side (right end side in FIG. 2) of the ball screw shaft 11 and the output shaft 21 of the motor 19 are connected by an Oldham coupling mechanism 23.
The Oldham coupling mechanism 23 is engaged with the hub 23a fixed to the ball screw shaft 11, the hub 23b fixed to the output shaft 21 of the motor 19, and the hub 23a and the hub 23b. It is configured by a slider 23c.

  An encoder 25 is installed on the rear end side of the motor 19 so that the rotation direction and rotation angle of the output shaft 21 of the motor 19 can be detected.

A ball screw nut 31 is screwed onto the ball screw shaft 11. The ball screw nut 31 includes a substantially cylindrical ball screw nut main body 33 and end caps 35a and 35b installed on both ends of the ball screw nut main body 33 in the front-rear direction. A spiral groove (not shown) is formed on the inner peripheral surface of the ball screw nut body 33, and a no-load circulation path (not shown) is formed inside the ball screw nut body 33. In addition, return paths (not shown) are formed in the end caps 35a and 35b, respectively. The space between the spiral groove 12 of the ball screw shaft 11 and the spiral groove (not shown) of the ball screw nut body 33, the return path (not shown) of the end cap 35a, and the unloaded circulation path (not shown) of the ball screw nut body 33 A plurality of steel balls (not shown) roll and circulate in a return path (not shown) of the end cap 35b.
A flange portion 37 projects from the rear end of the ball screw nut body 33.
An annular lubricating member 8 is installed between the end cap 35 a and the inner peripheral stepped portion of the rod 5.

  As shown in FIG. 2, the rod 5 is fixed to the ball screw nut 31 via a nut housing member 41. As shown in FIG. 5, the nut housing member 41 has a substantially cylindrical shape, and the ball screw nut 31 is housed therein. As shown in FIG. 2, a female screw portion 43 is formed in the vicinity of the approximate center of the inner peripheral surface of the nut housing member 41 in the front-rear direction (left-right direction in FIG. 2). A male screw portion 45 formed on the rear end side (right side in FIG. 2) of the rod 5 is screwed into the female screw portion 43.

  Further, the inner peripheral surface of the nut housing member 41 has a reduced diameter on the rear side (right side in FIG. 2) of the female screw portion 43, and the front side surface (the left side surface in FIG. 2) of the reduced diameter portion. ) Is the nut contact portion 47. The flange portion 37 is sandwiched between the rear end surface of the rod 5 (the right side surface in FIG. 2) and the nut contact portion 47. That is, by screwing and fixing the rod 5 to the nut housing member 41, the flange portion 37 is sandwiched between the rear end surface (the right side surface in FIG. 2) of the rod 5 and the nut contact portion 47. As a result, the rod 5, the nut housing member 41, and the ball screw nut 31 are integrated.

Further, in the vicinity of the center of the nut housing member 41 in the front-rear direction (the direction from the lower left to the upper right in FIG. 5A), there are three anti-rotation engagement protrusions 48a at equal intervals in the circumferential direction. 48b and 48c protrude and are formed.
Further, on the outer peripheral surface of the nut housing member 41, between the rotation-preventing engagement convex portions 48a, 48b, 48c, front-rear movement-preventing engagement concave portions 49, 49, 49 are formed.

  Further, on the rear end side (upper right side in FIG. 5A) of the outer periphery side of the nut housing member 41, jig convex portions 50, 50, 50 (in FIG. Are projected and formed. These jig projections 50, 50, 50 are used when the nut housing member 41 is gripped by a jig (not shown) when the rod 5 is screwed into the nut housing member 41.

Further, as shown in FIGS. 2 and 3, a resin rotation restricting member 51 is crowned on the outer peripheral side of the nut housing member 41.
The material of the rotation restricting member 51 is not limited to resin, and may be made of metal, for example.

  As shown in FIG. 6, the rotation restricting member 51 includes a rotation restricting member main body 53. The rotation restricting member main body 53 is formed in a substantially cylindrical shape by forming a slit 52 in a substantially cylindrical member. It has a cross-sectional shape. Fixing engagement convex portions 55a, 55b, and 55c are projected and formed at three locations on the outer peripheral side of the rotation restricting member main body 53 at regular intervals in the circumferential direction. Anti-rotation engagement recesses 56a, 56b, and 56c are formed on the inner peripheral sides of the fixing engagement protrusions 55a, 55b, and 55c, respectively.

Further, the fixing engagement projection 55c is provided across the slit 52 is divided into right fixing engagement projection 55c ₁ and the left fixing engagement projection 55c _2. Further, rotation preventing engagement recesses 56c are also provided across the slit 52 is divided into right rotation preventing engagement recess 56c ₁ and engaging a left anti-rotation engagement recess 56c _2.

When the rotation restricting member 51 is covered with the nut housing member 41, the rotation preventing engagement convex portions 48 a, 48 b, 48 b, 48 b of the nut housing member 41 are provided in the rotation preventing engagement recesses 56 a, 56 b, 56 c. 48c is engaged.
Further, both outer circumferential surfaces of the rotation preventing engagement convex portions 48a, 48b, and 48c are brought into contact with inner circumferential surfaces of the rotation preventing engagement concave portions 56a, 56b, and 56c of the rotation restricting member main body 53. As a result, the relative rotation of the rotation restricting member 51 and the nut accommodating member 41 and thus the ball screw nut 31 is restricted.

  In addition, engagement protrusions 57, 57, 57 for preventing back-and-forth movement are formed inside the rotation restricting member 51 and between the engagement recesses 56a, 56b, 56c for preventing rotation. These forward / backward movement preventing engagement protrusions 57, 57, 57 are engaged with forward / backward movement prevention engagement recesses 49, 49, 49 of the nut housing member 41. The front-rear direction outer end surface of the front-rear movement preventing engagement protrusion 57 is in contact with the inner end surface of the front-rear movement-preventing engagement concave portion 49 in the front-rear direction (left-right direction in FIG. 2). The relative movement of the member 51 and the nut housing member 41 and thus the ball screw nut 31 in the front-rear direction (left-right direction in FIG. 2) is restricted.

On the outer peripheral side of the rotation restricting member main body 53, rotation restricting convex portions 61, 61, 61 are projected and formed between the fixing engaging convex portions 55a, 55b, 55c. These rotation restricting convex portions 61, 61, 61 are arranged at equal intervals in the circumferential direction. On the other hand, as shown in FIG. 4, three grooves 63, 63, 63 serving as rotation restricting recesses are extended and formed in the front-rear direction (perpendicular to the plane of FIG. 4A) inside the housing 3. Has been. The rotation restricting convex portions 61, 61, 61 are engaged with the grooves 63, 63, 63, thereby restricting the rotation of the ball screw nut 31 when the ball screw shaft 11 is rotated. The ball screw nut 31 and thus the rod 5 are guided in the front-rear direction (left-right direction in FIG. 2).
On the inner peripheral side of the housing 3, grooves 64, 64, 64 corresponding to the fixing engaging convex portions 55a, 55b, 55c are formed. The fixing engaging convex portions 55a, 55b, and 55c are configured to restrict rotation by engaging with the grooves 64, 64, and 64 through a slight gap.

  Further, as shown in FIG. 6A, the rotation restricting convex portions 61, 61, 61 each have a notch 65 formed on the rear end side (upper right end side in FIG. 6A). The both sides of the notch 65 are elastic holding portions 67 and 67. The outer side portions of these elastic holding portions 67 and 67 have a shape protruding outward. When the rotation restricting convex portions 61, 61, 61 are press-fitted into the grooves 63, 63, 63, the elastic holding portions 67, 67 are elastically deformed in a direction approaching each other, and thereby an elastic holding force Will be demonstrated. The elastic holding portions 67 and 67 are configured to absorb an impact caused by vibration during operation by appropriately elastically deforming in the groove 63. In addition, a through hole 68 having a substantially circular shape is formed in the back of the notch portion 65 to reduce the thickness of the base portions of the elastic holding portions 67 and 67. Thereby, the elastic holding portions 67 and 67 are configured to be easily elastically deformed.

  Further, a stopper contact portion 73 is integrally provided on the front end side (the left side in FIG. 6A) of the rotation restricting member main body 53 via three support portions 71, 71, 71. As shown in FIGS. 2 and 3, the stopper abutting portion 73 is formed on the front end side of the nut housing member 41 (the left end side in FIG. 3) when the rotation regulating member 51 is crowned by the nut housing member 41. ) Protruding and arranged. As shown in FIG. 2, a stopper 75 is installed on the front end side (left end side in FIG. 2) inside the housing 3, and when the ball screw nut 31 and the nut accommodating member 41 are moved to the front end ( The stopper abutting portion 73 is abutted against the stopper 75. Thereby, the nut housing member 41 is prevented from coming into direct contact with the stopper 75.

  The rotation restricting member 51 is connected to the front end side (FIG. 5 (FIG. 5 (a)) because the stopper contact portion 73 is integrally provided on the front end side (left side in FIG. 6A) of the rotation restricting member main body 53. a) Crowned by the nut housing member 41 from the lower left side in the middle).

  Further, as shown in FIG. 4, air flow grooves 77 are formed as air flow passages between the adjacent grooves 63 and 64 on the inner peripheral surface of the housing 3. These air circulation grooves 77 are extended and formed along the moving direction of the ball screw nut 31 (the direction perpendicular to the paper surface in FIG. 4). Since the front and rear ends of the housing 3 are closed by the stopper 75 and the bearing case 13, the air urged by the movement of the ball screw nut 31 through the air circulation groove 77 is By allowing the ball screw nut 31 to flow between both sides, the ball screw nut 31 can be moved smoothly.

Next, the operation of the first embodiment will be described.
First, when the ball screw shaft 11 is rotated by the motor 19, the ball screw nut 31, the nut housing member 41, and the rod 5 are moved in the front-rear direction (left-right direction in FIG. 2).
At this time, the engagement structure between the rotation restricting convex portions 61, 61, 61 of the rotation restricting member 51 and the grooves 63, 63, 63 inside the housing 3, and the fixing engaging convex portions 55a, 55b, 55c, The engagement structure with the grooves 64, 64, 64 restricts the rotation of the ball screw nut 31 and guides it in the front-rear direction (left-right direction in FIG. 2).
The elastic holding portions 67 and 67 of the individual rotation restricting convex portions 61 are housed in the groove 63 so as to be elastically deformable, and are elastically deformed to cause vibration during movement of the ball screw nut 31. The absorbed impact is absorbed, and noise generated when the actuator 1 is driven is reduced.

  When the ball screw nut 31 and the nut housing member 41 are moved to the front end (moved to the left in FIG. 2), the stopper contact portion 73 is brought into contact with the stopper 75, and the nut housing member Since 41 does not directly contact the stopper 75, the nut housing portion 41 can be prevented from being damaged and protected.

  Further, when the ball screw nut 31 is moved, air on both sides of the ball screw nut 31 flows between each other through the air circulation groove 77, thereby The movement is smooth.

Next, effects of the first embodiment will be described.
First, when the ball screw nut 31 is moved, air on both sides of the ball screw nut 31 flows between each other through the air circulation groove 77, thereby The movement can be made smooth.
Further, since the air circulation groove 77 is formed in the housing 3 and is not formed in the ball screw nut 31, the strength of the ball screw nut 31 can be sufficiently ensured.
Further, since the air circulation groove 77 is formed in a portion other than the groove 63 and the groove 64 of the housing 3, that is, a thick portion of the housing 3, the air circulation groove 77 can be secured large. The ball screw nut 31 can be moved more smoothly.
Further, since the air circulation groove 77 is extended and formed along the moving direction of the ball screw nut 31 (perpendicular to the paper surface in FIG. 4), the housing 3 can be obtained by, for example, extrusion molding. The manufacturing can be facilitated and the cost can be reduced.

Next, a second embodiment of the present invention will be described with reference to FIG.
The actuator 81 according to the second embodiment is provided with an air circulation groove at a location different from that of the actuator 1 of the first embodiment. That is, as shown in FIG. 7, in the first embodiment, the air circulation groove 77 is formed between the adjacent grooves 63 and 64, but in the case of this second embodiment, An air circulation groove 83 as an air flow passage is formed at the bottom of the groove 63 and the groove 64.
Other configurations are the same as those in the first embodiment, and the same parts are denoted by the same reference numerals in the drawings, and the description thereof is omitted.

In the case of the second embodiment, in addition to the operations and effects in the first embodiment, the following operations and effects are achieved.
First, since the air circulation groove 83 is provided at the bottom of the groove 63 and the groove 64, the lubricant for making the operation of the rotation restricting member 51 smooth can be held there.
Even if the lubricant is held in the air circulation groove 83, the air circulation is not hindered.
In addition, since the air circulation groove 83 is formed at the bottom of the grooves 63 and 64, for example, there is less space restriction compared to the case where it is provided at the side of the grooves 63 and 64, and a larger air circulation. The working groove 83 can be secured, whereby the ball screw nut 31 can be moved more smoothly.

Next, a third embodiment of the present invention will be described with reference to FIG.
The actuator 91 according to the third embodiment has a combination of the actuator 1 of the first embodiment and the actuator 81 of the second embodiment. That is, both the air circulation groove 77 and the air circulation groove 83 are formed as air flow passages on the inner peripheral surface of the housing 3.
Other configurations are the same as those of the first and second embodiments, and the same portions are denoted by the same reference numerals in the drawings, and the description thereof is omitted.

  In the case of the third embodiment, both the functions and effects of the first embodiment and the functions and effects of the second embodiment are achieved. In addition, since more air circulation grooves 77 and 83 are secured, the ball screw nut 31 can be moved more smoothly.

The present invention is not limited to the first to third embodiments.
First, in the case of the first to third embodiments, the air flow channel has been described as an example of the air flow passage. However, a hole, a combination of the groove and the hole, or the like may be used.
In addition, the number of air circulation grooves, the cross-sectional shape, and the like are not particularly limited.
Moreover, when providing the groove | channel for air circulation in the recessed part for rotation control, it is not limited to a bottom part, For example, the structure provided in a side part is also considered.
In the case of the first to third embodiments, the rotation restricting convex portion engaged with the rotation restricting concave portion is formed on the rotation restricting member covered with the ball screw nut. The rotation restricting convex portion may be provided directly on the ball screw nut.
In addition to the rod, various things such as a slider can be considered as the movable part.
Moreover, in the case of the said 1st-3rd embodiment, although the case where the inside of a housing was hold | maintained airtightly was mentioned as an example, it demonstrated similarly, and it can apply similarly to the structure which is connected with external air. is there.
In addition, the illustrated configuration is an example, and various cases can be considered.

  The present invention relates to an actuator that moves a movable part fixed to the nut back and forth by a screw-nut mechanism including a screw and a nut installed in a housing, for example, and enables air flow on both sides of the nut when the nut is moved. The present invention relates to a device devised so that the strength of the nut can be sufficiently secured by improving the configuration to be applied, and is particularly suitable for an actuator used in an industrial robot.

1 Actuator 3 Housing 5 Rod (Moving part)
11 Ball screw shaft (screw)
31 Ball screw nut (nut)
61 Convex part for rotation regulation 63 Groove (concave part for rotation regulation)
77 Air flow groove 81 Actuator 83 Air flow groove 91 Actuator

Claims (6)

A housing;
A screw disposed in the housing;
A nut screwed onto the screw;
A movable part fixed to the nut;
Comprising
An actuator provided with an air flow passage through which air on both sides of the nut circulates when the nut is moved to the housing side. The actuator according to claim 1, wherein
The actuator according to claim 1, wherein the air flow passage is an air circulation groove provided on an inner peripheral surface of the housing. The actuator according to claim 2, wherein
The nut is provided with a rotation restricting projection directly or indirectly,
The inner circumferential surface of the housing is provided with a rotation restricting recess for restricting the rotation of the nut associated with the rotation of the screw by the engagement of the rotation restricting convex portion.
The actuator according to claim 1, wherein the air flow groove is provided in an inner peripheral surface of the housing other than the rotation restricting recess. The actuator according to claim 2, wherein
The nut is provided with a rotation restricting projection directly or indirectly,
The inner circumferential surface of the housing is provided with a rotation restricting recess for restricting the rotation of the nut associated with the rotation of the screw by the engagement of the rotation restricting convex portion.
The actuator according to claim 1, wherein the air flow groove is formed between the rotation restricting convex portion and the rotation restricting concave portion. The actuator according to claim 4, wherein
The actuator according to claim 1, wherein the air flow groove is formed radially outward between the rotation restricting convex portion and the rotation restricting concave portion. The actuator according to any one of claims 2 to 5,
The actuator according to claim 1, wherein the air circulation groove is extended and formed along a moving direction of the nut.

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