JP2014109294A - Linear actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linear actuator having a ball screw structure which can obtain stable positioning accuracy at which wobbling in the axial direction is not caused, and a hysteresis difference at the reciprocating movement of an output shaft is not generated, and furthermore, can reduce noise at the movement of the output shaft.SOLUTION: A linear actuator comprises: stators 103, 104; a rotor which is rotatably arranged; a retainer 114 for accommodating an output shaft 150 inside, and having a plurality of recesses which are formed in a dot manner in positions along a spiral groove; a pair of bearings 110, 111 for rotatably supporting the rotor 130; a front housing 101; and an end housing 102. The end housing 102 energizes the bearing 111 in the axial direction, and the rotor 130 receives pressure in the axial direction.

Description

  The present invention relates to a linear actuator that converts rotational motion into linear motion, and more particularly to a linear actuator having a ball screw structure.

  A linear actuator that converts the rotational movement of a rotor into a linear movement of an output shaft and outputs the linear movement is known (for example, see Patent Document 1). In the linear actuator as described in Patent Document 1, a male screw is provided on the output shaft, a female screw is provided on the receiving side, and the rotational motion is converted into a linear motion in the axial direction by meshing them. In this structure, since the frictional resistance of the screw portion is large, the efficiency is poor and the torque of the motor is not effectively transmitted to the output shaft.

  As a structure to cope with this problem, a ball screw type linear actuator that generates a large thrust even with a small torque by cutting a ball screw on the shaft and forming a ball groove on the receiving side and holding the ball in the ball groove Has been proposed (see, for example, Patent Document 2).

JP 2002-122203 A JP 2012-175829 A

  However, in the linear actuator described in Patent Document 2, if the variation in component accuracy or the assembly accuracy is poor, shakiness in the axial direction occurs, and a hysteresis difference occurs in the reciprocating movement of the output shaft, resulting in stable positioning accuracy. May not be obtained. Further, this rattling may cause noise.

  In such a background, the present invention can obtain stable positioning accuracy with no backlash in the axial direction, no hysteresis difference in the reciprocating movement of the output shaft, and noise during movement of the output shaft. An object of the present invention is to provide a linear actuator having a ball screw structure with a simple structure that can be reduced.

  The invention according to claim 1 is an output shaft, a stator, a rotor rotatably arranged inside the stator, a part of the rotor, and a cylindrical shape in which the output shaft is accommodated inside the rotor. A retainer having a plurality of recesses arranged in a dotted manner at a position along the spiral groove of the output shaft on the inner peripheral surface thereof, and rotatably supporting the rotor and pivoting the rotor A pair of bearings sandwiched in a direction, a front housing disposed on one side of the stator, an end housing disposed on the other side of the stator, and one end of the pair of bearings in the axial direction by the end housing. Urging means for urging, and a ball is held in each of the plurality of recesses of the retainer, and when the rotor rotates, the screw of the output shaft is held in the state where the ball is held in the recess. Moves along the groove, the output shaft is a linear actuator, characterized in that movement in the axial direction with respect to the stator.

  According to the first aspect of the present invention, since the rotor composed of a plurality of parts is urged and sandwiched from both sides in the axial direction, the structure of the rotor is strong while having a simple structure. For this reason, there is no shakiness in the axial direction, stable positioning accuracy with no hysteresis difference in the reciprocating movement of the output shaft can be obtained, and noise during movement of the output shaft can be reduced. it can.

  According to a second aspect of the present invention, in the first aspect of the invention, the end housing includes a base portion joined to the stator and a boss portion including the urging means, and the base portion and the boss portion. Are screwed together by a screw structure, and the boss portion is in contact with one side of the pair of bearings from the axial direction and biased. According to the second aspect of the present invention, the state in which the rotor is urged in the axial direction is generated by tightening the screw structure.

  According to a third aspect of the present invention, in the first aspect of the present invention, the urging means is a spring member disposed between the end housing and one of the pair of bearings. To do. According to the third aspect of the present invention, a state occurs in which the rotor is urged in the axial direction by the spring member.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the retainer has a structure that can be divided into a plurality of parts in the circumferential direction. According to invention of Claim 4, a retainer can be shape | molded from resin as a raw material, and cost reduction can be aimed at.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, further comprising a pair of sleeves having a cylindrical shape mounted on the outer periphery of the retainer from the front and rear in the axial direction. The sleeve is provided with a concavo-convex structure at the edge portions of the sleeves facing each other, and a protrusion that fits into the concavo-convex structure is provided on the outer periphery of the retainer. According to the fifth aspect of the present invention, a rotor having a simple and strong structure can be obtained.

  The invention according to claim 6 is the invention according to claim 5, wherein one of the pair of sleeves is in axial contact with one of the pair of bearings, and the other of the pair of sleeves is the pair of sleeves. By contacting the other of the bearings in the axial direction, a member constituted by the retainer and the pair of sleeves mounted on the outer periphery of the retainer is sandwiched in a state of being biased in the axial direction by the pair of bearings. It is characterized by. According to the sixth aspect of the present invention, although the structure is simple, the structure in which the pair of sleeves and the retainer are coupled to each other can be made strong with less play.

  The invention according to claim 7 is the invention according to claim 5 or 6, wherein the concavo-convex structure provided at the edge portion of each of the pair of sleeves includes a concave portion and a concave portion, and a convex portion and a convex portion. Is fixed to the retainer with an adhesive in a state where the concave portions face each other, and the gap between the concave portion and the concave portion functions as an adhesive reservoir for the adhesive. According to the seventh aspect of the present invention, a strong structure can be obtained with a simple structure.

  According to an eighth aspect of the present invention, in the invention according to any one of the fifth to seventh aspects, the retainer includes a first retainer piece, a second retainer piece, and a third retainer that are divided in the circumferential direction. The first retainer piece and the second retainer piece are the same member, and the third retainer piece is in contact with the opposing concavo-convex structure in each of the pair of sleeves, The protrusions functioning as positioning of the opposing concavo-convex structures and rotation stopping of the pair of sleeves are provided. According to the eighth aspect of the invention, a structure for retaining the retainer with respect to the pair of sleeves is obtained.

  The invention according to claim 9 is the invention according to any one of claims 1 to 8, wherein a pin projecting radially from the output shaft and an inner periphery of the front housing are provided to receive the pin. A pin accommodating portion extending in the axial direction and a stopper that can contact the pin, and the pin reciprocates in the axial direction inside the pin accommodating portion and comes into contact with the stopper so that the output The movement of the shaft in the axial direction is restricted. According to the ninth aspect of the present invention, the presence of the stopper prevents the bearing from being troubled due to the sudden reverse movement of the output shaft.

  According to the present invention, it is possible to obtain a stable positioning accuracy that is free from backlash in the axial direction, has no hysteresis difference in the reciprocating movement of the output shaft, and further reduces noise during the movement of the output shaft. A linear actuator having a simple ball screw structure can be obtained.

It is a disassembled perspective view of the linear actuator of embodiment. It is sectional drawing of the linear actuator of embodiment. It is a perspective view which shows the state which isolate | separated the sleeve and the retainer. It is a perspective view which shows the state which decomposed | disassembled the retainer. It is sectional drawing of the linear actuator of other embodiment.

1. First embodiment (structure)
The linear actuator 100 of embodiment is shown by FIG. 1 and FIG. The linear actuator 100 includes a front housing 101, an end housing 102, a stator 103, a stator 104, and an output shaft 150. The output shaft 150 is formed with a spiral groove 150a constituting a ball screw. The output shaft 150 is driven by a mechanism described later, and moves in the axial direction with respect to the front housing 101. As the output shaft 150 moves in the axial direction, a function as a linear actuator can be obtained. FIG. 1 shows drive coil (stator coils) 105 and 106 and four terminal pins 107 to which ends of windings constituting the drive coils 105 and 106 are connected. A wiring for supplying a driving current from the outside is connected to the terminal pin 107.

  The stators 103 (cup type stator yoke) and 104 (cup type stator yoke) constitute a stator yoke of a claw pole type stepping motor, which is made of a magnetic material (such as electromagnetic soft iron or rolled steel plate) and is axially arranged. It has a cylindrical shape provided with extending pole teeth 103a and 104a. The stator 103 is combined with an inner stator yoke 122 having pole teeth 122a that mesh with the pole teeth 103a with a gap. A resin bobbin 108 around which the drive coil 105 is wound is housed in a space between the stator 103 and the inner stator yoke 122. The stator 104 is combined with an inner stator yoke 123 having pole teeth 123a that mesh with the pole teeth 104a with a gap. A resin bobbin 109 around which the drive coil 106 is wound is housed in a space between the stator 104 and the inner stator yoke 123. The bobbins 108 and 109 are provided with terminal base portions 108a and 109a for erecting the terminal pins 107, respectively. The stators 103 and 104 are coupled in the axial direction with the inner stator yokes 122 and 123 inside.

  The stator 103 is coupled to the front housing 101, and the stator 104 is coupled to the end housing 102. The end housing 102 is composed of two members, a substantially cylindrical boss part 102a whose one end is closed and a substantially disk-shaped base part 102b. A male screw portion 102c is formed at a portion of the outer periphery of the boss portion 102a that contacts the base portion 102b. Further, a female screw portion 102d is formed at a portion of the inner periphery of the boss portion 102b that contacts the base portion 102a. The male screw portion 102c and the female screw portion 102d have a structure in which they are engaged with each other. When both are engaged and screwed together, the boss portion 102a and the base portion 102b are coupled by a screw structure, and the end housing 102 is configured.

  A bearing 110 is attached by being fitted inside the stator 103 (axial center side), and a bearing 111 is fitted by being fitted inside the stator 104. As described above, the end housing 102 is configured by connecting the boss portion 102a and the base portion 102b with a screw structure. However, the end surface of the boss portion 102a is formed by screwing the boss portion 102a into the base portion 102b. The left end surface in FIG. 2 is in contact with the outer ring 111a of the bearing 111, and the bearing 111 is biased in the axial direction (left direction in the figure) with a predetermined pressure.

  The bearing 110 holds the cylindrical sleeve 112 in a freely rotatable state, and the outer ring 110a is in axial contact with a disk-like stopper 160 described later, and the inner ring 110b is in axial contact with the stepped portion 112d of the sleeve 112. In contact. The bearing 111 holds the cylindrical sleeve 113 in a rotatable state, its outer ring 111a is in contact with the boss portion 102a in the axial direction, and its inner ring 111b is in contact with the step portion 113d of the sleeve 113 in the axial direction. .

  A substantially cylindrical retainer 114 is held inside the sleeves 112 and 113. The substantially cylindrical rotor magnets 115 and 116 made of permanent magnets are fixed to the outside of the sleeves 112 and 113. The rotor magnets 115 and 116 have a magnetic pole structure magnetized with NSNS ··· along the circumferential direction. The sleeves 112 and 113 are made of a magnetic material and also function as back yokes for the rotor magnets 115 and 116. Further, the outer side of the rotor magnet 115 faces the pole teeth 103a and 122a with a gap, and the outer side of the rotor magnet 116 faces the pole teeth 104a and 123a with a gap.

  A rotor 130 is constituted by the sleeves 112 and 113, the retainer 114, and the rotor magnets 115 and 116. The rotor 130 is rotatably held inside the stators 103 and 104 by bearings 110 and 111.

  As shown in FIGS. 3 and 4, the hollow cylindrical retainer 114 includes a first retainer piece 114a, a second retainer piece 114, and a third retainer piece 114c that are divided into three in the circumferential direction. . The first retainer piece 114a and the second retainer piece 114b are members having the same shape, and are provided with meshing shapes indicated by reference numerals 118 and 119. The outer periphery of the third retainer piece 114c has an axial center. A positioning member 117 that is a protrusion protruding in a direction away from the positioning member 117 is provided. The sleeves 112 and 113 and the retainer 114 are integrated by covering a pair of hollow cylindrical sleeves 112 and 113 from both ends of the retainer 114 in the axial direction.

  At the end of the sleeve 112 facing the sleeve 113, a concavo-convex structure 112c composed of a concave portion 112a and a convex portion 112b is provided. In addition, a concave-convex structure 113c including a concave portion 113a and a convex portion 113b is provided at an end portion of the sleeve 113 facing the sleeve 112. In a state where the end portion of the sleeve 112 and the end portion of the sleeve 113 are opposed to each other, the concave portion 112a and the concave portion 113a face each other in the axial direction, and the convex portion 112b and the convex portion 113b face each other.

  The sleeve 112 is provided with an annular stepped portion 112d extending in the circumferential direction, and the stepped portion 112d contacts the inner ring 110b of the bearing 110 as shown in FIG. The sleeve 113 is provided with an annular step 113d extending in the circumferential direction, and the step 113d contacts the inner ring 111b of the bearing 111 as shown in FIG.

  A positioning member 117, which is a protrusion, is provided on the outer periphery of the retainer 114c. In the assembled state, the positioning member 117 is fitted into a gap formed in a portion where the concave portion 112a and the concave portion 113a face each other, and the positioning member 117 is fitted into the concave and convex structures 112c and 113c. The positioning member 117 determines the positional relationship between the sleeve 112 and the sleeve 113 in the direction around the axis, and determines the positional relationship between the sleeves 112 and 113 and the retainer 114. Further, the positioning member 117 provides a structure for preventing the sleeves 112 and 113 from rotating with respect to the retainer 114. A plurality of gaps are formed in the portion where the concave portion 112a and the concave portion 113a face each other, but the positioning member 117 is fitted in one place, and the other gap portions are formed in the sleeves 112 and 113 and the retainer. 114 functions as an adhesive reservoir for adhesive.

  On the inner peripheral surface of the retainer 114, a plurality of substantially hemispherical concave portions 120 arranged along the spiral direction are provided. A plurality of recesses 120 are arranged in a dotted manner at intervals along the spiral direction in which the spiral groove 150a formed in the output shaft 150 extends. A ball 121 is held in contact with each of the recesses 120. Here, the ball 121 is not fixed to the inside of the recess 120 but is held in a state of being simply in contact with the grease. The ball 121 is held in a state of being constrained inside the recess 120 while being in contact with the concave surface of the recess 120. In this example, the plurality of recesses 120 are arranged side by side along the circumference on which the spiral makes one rotation. The spiral shape in which the plurality of recesses 120 are arranged has a state matched to the pitch of the spiral groove 150a provided in the output shaft 150 (see FIGS. 1 and 2). Here, the ball 121 held in each of the plurality of recesses 120 contacts the spiral groove 150a of the output shaft 150 in a state where it can roll.

  In this example, the inner surface of the recess 120 has a hemispherical concave surface in which the ball 121 can be accommodated, but the inner surface shape of the concave portion 120 may be a hemispherical shape as long as it is a concave curved surface that can receive the ball 121. It is not limited.

  As shown in FIG. 2, in the state where the output shaft 150 is assembled to the inside of the retainer 114 via the ball 121, the inside of the retainer 114 and the outside of the output shaft 150 are indirect with the ball 121 interposed therebetween. Are biting. That is, a plurality of recesses 120 are provided inside the retainer 114 (see FIG. 4), and the balls 121 are held in contact with each of the plurality of recesses 120, and the balls 121 are further connected to the output shaft 150. The spiral groove 150a (see FIG. 2) is in contact in a state where it can roll.

  When the output shaft 150 is fixed and the retainer 114 is rotated around the axis, the ball 121 is rolled inside the spiral groove 150a along the spiral direction with the ball 121 held inside the recess 120, and the retainer 114 outputs. It moves in the axial direction while rotating with respect to the shaft 150. On the other hand, when the retainer 114 does not move in the axial direction and can rotate, and the output shaft 150 cannot rotate further, when the retainer 114 is rotated around the axis, the ball 121 becomes a spiral groove 150a. The output shaft 150 moves in the axial direction with respect to the retainer 114 while rolling inside. That is, the rotational motion of the retainer 114 is converted into the straight motion of the output shaft 150.

  The output shaft 150 is provided with a pin 151 extending in a direction orthogonal to the axial direction (up and down direction in the figure). The pin 151 functions as an anti-rotation member that prevents the output shaft 150 from rotating about the axis relative to the front housing 101 (stator 103, 104). 151 is accommodated in a pin accommodating chamber 152 provided on the inner peripheral surface of the front housing 101 in a state in which movement in the axial direction is possible. The pin accommodating chamber 152 is a groove-like space extending in the axial direction. When the output shaft 150 tries to rotate, the pin 151 comes into contact with the side wall of the pin accommodating chamber 152, and the rotation of the output shaft 150 is restricted. On the other hand, the pin 151 can be moved in the axial direction while being accommodated in the pin accommodating chamber 152, thereby allowing the output shaft 150 to move in the axial direction relative to the front housing 101. As shown in FIG. 2, the output shaft 150 is held inside the front housing 101 by a bearing 153 so as to be movable in the axial direction.

  A stopper 160 is disposed inside the front housing 101. The stopper 160 has a substantially ring shape with a hole through which the output shaft 150 is inserted at the center. When the pin 151 contacts the stopper 160, the further movement of the output shaft 150 in the right direction in FIG. 2 is restricted. One side of the stopper 160 (the right side in FIG. 2) is in contact with the outer ring 110 a of the bearing 110, and the other side (the left side in FIG. 2) is in contact with the stepped portion 101 a inside the housing 101. Further, the stopper 160 has a concave surface that is opposed to the inner ring 110b so as not to contact the inner ring 110b.

(Example of operation)
A drive current whose polarity alternately changes is supplied to the drive coils 105 and 106 via the terminal pin 107. Then, according to the principle of the claw pole type stepping motor, the repulsive force and the attractive force in the circumferential direction act between the drive coils 105, 106 and the rotor magnets 115, 116, and the sleeves 112, 113, the retainer 114, and the rotor 130 constituted by the rotor magnets 115 and 116 rotate.

  At this time, the ball 121 is constrained by the recess 120 and constrained by the spiral groove 150a of the output shaft 150. Further, the output shaft 150 cannot be rotated by the function of the pin 151. Move in the axial direction. The direction of movement of the output shaft 150 is reversed when the direction of rotation of the retainer 114 is reversed. Thus, the output shaft 150 is linearly moved by rotating the retainer 114.

(Advantage 1)
As described above, the linear actuator 100 includes the stators 103 and 104, the rotor 130 that is rotatably arranged, the output shaft 150 in which the spiral groove is formed, and the output shaft 150 inside, and the position along the spiral groove. And a pair of bearings 110 and 111 for rotatably supporting the rotor 130, a front housing 101, and an end housing 102. The end housing 102 supports the bearing 111 in the axial direction. The rotor 130 has a structure in which the pressure is received in the axial direction while being sandwiched between the bearings 110 and 111.

  In this structure, the boss portion 102a pushes and urges the outer ring 111a of one bearing 111 in the axial direction based on the principle of tightening the screw. This urging force is applied to the 113 sleeve from the inner ring 111b through the step 113d. The sleeve 113 is applied to the sleeve 112 via the retainer 114. Since the step 112d of the sleeve 112 is in contact with the inner ring 110b of the bearing 110, a biasing force is applied to the bearing 110.

  Therefore, the member shown in FIG. 3 constituted by the retainer 114 and the pair of sleeves 112 and 113 attached to the outer periphery thereof is sandwiched between the pair of bearings 111 and 110 while being urged in the axial direction. That is, a state in which the sleeves 112 and 113 sandwich the retainer 114 with pressure in the axial direction is obtained by the axial biasing force acting on the outer ring 111a from the boss portion 102a. According to this structure, the joining structure of the parts shown in FIG. 3 is more robust and free of rattling, and shakiness in the axial direction due to parts accuracy and assembly precision in the structure shown in FIG. 3 is suppressed. Further, by suppressing the shakiness in the axial direction, it is possible to suppress the occurrence of a problem that causes a hysteresis difference in the reciprocating movement of the output shaft 150 and the problem that a stable positioning accuracy cannot be obtained. Moreover, the generation of noise due to rattling can be suppressed.

  In particular, when the retainer 114 is divided in the circumferential direction, as will be described later (Advantage 2), there is an advantage that the retainer 114 can be easily molded from a resin as a raw material. Since the divided structures are combined, there is a tendency that it is disadvantageous in terms of play caused by component accuracy and assembly accuracy. However, since the sleeves 113 and 114 are pushed by the bearings 111 and 110 from both sides in the axial direction and the integrity of the structure shown in FIG. 3 is strengthened, the occurrence of the above-described play is suppressed.

(Advantage 2)
A gap is formed between the concave portion 112a of the sleeve 112 and the concave portion 113a of the sleeve 113. By fitting the positioning member 117 of the retainer piece 114c into this gap, the positional relationship between the sleeves 112 and 113 and the retainer 114 is determined. The positioning member 117 functions as a rotation stopper for the retainer 114. Further, the gap formed between the other recess 112a and the recess 113a is filled with an adhesive for bonding the sleeves 112, 113 and the retainer 114 to each other, and functions as an adhesive reservoir.

  By dividing the retainer 114 holding the ball 121 in this way into a plurality of retainer pieces 114a to 114c, resin molding can be facilitated and the cost can be reduced. In addition, the retainer piece 114c is provided with a positioning member 117 which is a projection, and is fitted into a gap formed between the pair of sleeves 112 and 113, whereby the retainer 114 and the sleeves 112 and 113 can be aligned. In addition, the structure of the rotation stopper of the retainer 114 can be easily obtained.

(Advantage 3)
Further, by disposing the stopper 160, the possibility that a problem occurs in the bearing 110 is suppressed. That is, if the stopper 160 is not provided and the shaft 150 moves backward vigorously for some reason, the pin 151 directly contacts the bearing 110 with an impact. As a result, there is a possibility that problems such as misalignment and distortion of the outer ring 110a and the inner ring 110b, and misalignment of the bearing ball may occur. On the other hand, by disposing the stopper 160, the pin 151 does not directly collide with the bearing 110, and even if the pin 151 moves backward vigorously and collides with the stopper 160, the impact is caused by the stopper 160. Since it is alleviated, the occurrence of the above-described problems can be suppressed.

2. Second Embodiment FIG. 5 shows an example of a structure in which a part of the linear actuator 100 shown in FIG. 1 is modified. The structure of FIG. 5 is different from the structure of FIG. 1 in that the structure of the end housing 102 and the spring member 161 are provided, and the other structure is the same as that of FIG.

  In the structure of FIG. 5, the end housing 102 is not divided unlike the case of FIG. A spring member 161 is disposed on the surface of the end housing 102 that faces the bearing 111. The spring member 161 is a disc spring and is in contact with the end housing 102 and the outer ring 111a of the bearing 111 in the axial direction. The spring member 161 is compressed in the axial direction, and urges the outer ring 111a of the bearing 111 in the axial direction (left direction in FIG. 5) with a predetermined pressure.

  In this case as well, as in the case of the first embodiment of FIG. 1, the sleeves 112 and 113 receive a pressure to pinch the retainer 114 in the axial direction, and the structure of FIG. 3 becomes stronger and less rattling. The spring member 161 can use a wave washer in addition to the disc spring.

3. Other Embodiments of the present invention include various modifications that can be conceived by those skilled in the art, and the effects of the present invention are not limited to the above-described contents. That is, various additions, modifications, and partial deletions can be made without departing from the concept and spirit of the present invention derived from the contents defined in the claims and equivalents thereof.

  The present invention can be used for a linear actuator.

DESCRIPTION OF SYMBOLS 100 ... Linear actuator, 101 ... Front housing, 101a ... Step part, 102 ... End housing, 102a ... Boss part, 102b ... Base part 1, 102c ... Male screw part, 102d ... Female screw part, 103 ... Stator (cup type stator yoke) , 103a ... pole teeth, 104 ... stator (cup type stator yoke), 104a ... pole teeth, 105 ... drive coil, 106 ... drive coil, 107 ... terminal pin, 108 ... bobbin, 109 ... bobbin, 109a ... terminal base , 110 ... bearing, 110 a ... outer ring, 110 b ... inner ring, 111 ... bearing, 111 a ... outer ring, 111 b ... inner ring, 112 ... sleeve, 112 a ... concave part, 112 b ... convex part, 112 c ... uneven structure, 112 d ... step part, 113 ... Sleeve, 113a ... concave, 113b ... convex, 113c ... concave structure, 1 3d: Stepped portion, 114: Retainer, 114a: Retainer divided piece, 114b ... Retainer divided piece, 114c ... Retainer divided piece, 115 ... Rotor magnet, 116 ... Rotor magnet, 117 ... Positioning member, 118 ... Engagement shape, 119 ... Engagement Shape, 120 ... recess, 121 ... ball, 122 ... inner stator yoke, 122a ... pole tooth, 123 ... inner stator yoke, 123a ... pole tooth, 130 ... rotor, 150 ... output shaft, 150a ... spiral groove, 151 ... pin, 152 ... Pin accommodating part, 153 ... Bearing, 160 ... Stopper, 161 ... Spring member.

Claims (9)

An output shaft;
A stator,
A rotor rotatably disposed inside the stator;
A part of the rotor, having a cylindrical structure in which the output shaft is housed inside, and a plurality of dots arranged at positions along the spiral groove of the output shaft on the inner peripheral surface thereof A retainer with a recess,
A pair of bearings that rotatably support the rotor and sandwich the rotor in the axial direction;
A front housing disposed on one side of the stator;
An end housing disposed on the other side of the stator;
Biasing means for biasing one of the pair of bearings in the axial direction by the end housing;
When the ball is held in each of the plurality of recesses of the retainer and the rotor rotates, the ball is moved along the spiral groove of the output shaft while being held in the recess, and the output shaft is A linear actuator that moves in an axial direction with respect to a stator.   The end housing includes a base portion joined to the stator and a boss portion including the urging means. The base portion and the boss portion are screwed together by a screw structure, and the boss portion is formed by the pair of bearings. 2. The linear actuator according to claim 1, wherein the linear actuator is urged by contacting with one side in an axial direction.   The linear actuator according to claim 1, wherein the biasing means is a spring member disposed between the end housing and one of the pair of bearings.   The linear actuator according to any one of claims 1 to 3, wherein the retainer has a structure that can be divided into a plurality of parts in a circumferential direction. A pair of sleeves having a cylindrical shape mounted on the outer periphery of the retainer from the front and rear in the axial direction,
A concavo-convex structure is provided on the edge portion of the pair of sleeves facing each other,
5. The linear actuator according to claim 1, wherein a protrusion that fits into the concavo-convex structure is provided on an outer periphery of the retainer.   One of the pair of sleeves contacts one of the pair of bearings in the axial direction, and the other of the pair of sleeves contacts the other of the pair of bearings in the axial direction, so that the retainer and the retainer 6. The linear actuator according to claim 5, wherein a member constituted by the pair of sleeves mounted on the outer periphery is sandwiched in a state of being biased in the axial direction by the pair of bearings. The concavo-convex structures provided at the edge portions of each of the pair of sleeves are fixed to the retainer using an adhesive in a state where the concave portion and the concave portion, and the convex portion and the convex portion face each other,
The linear actuator according to claim 5, wherein a gap between the concave portion and the portion where the concave portion is opposed functions as an adhesive reservoir for the adhesive. The retainer includes a first retainer piece, a second retainer piece, and a third retainer piece that are divided in the circumferential direction.
The first retainer piece and the second retainer piece are the same member,
The third retainer piece is provided with the protrusions that contact the opposing concavo-convex structures of the pair of sleeves, function as alignment of the opposing concavo-convex structures, and function as a rotation stopper for the pair of sleeves. The linear actuator according to claim 5, wherein the linear actuator is provided. A pin protruding radially from the output shaft;
A pin housing portion provided in an inner periphery of the front housing and extending in an axial direction for housing the pin;
A stopper with which the pin can contact,
9. The axial movement of the output shaft is restricted by the pin reciprocating in the axial direction inside the pin housing portion and coming into contact with the stopper. A linear actuator according to claim 1.

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