JP2013148108A - Electric linear actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric linear actuator which is achieved in compactness by reducing the number of part items, blocks and reduces the propagation of vibration caused by rattling between a gear and a gear shaft, and achieved in low noise caused by the rattling of the gear shaft itself.SOLUTION: Bag holes 11, 12 for accommodating a screw shaft 10 are formed at an abutting part between a first housing 2a and a second housing 2b, a reduction mechanism 6 comprises an input gear 3 fixed to a motor shaft 3a, an intermediate gear 4 engaged with the input gear 3, and an output gear 5 engaged with the intermediate gear 4 and integrally fixed to a nut 18. A gear shaft 22 is fit-inserted into the first housing 2a and the second housing 2b via a synthetic-resin made bush 23, a synthetic-resin made bush 24 is interposed between the gear shaft 22 and the intermediate gear 4, and synthetic-resin made ring washers 25 are attached to both sides of the intermediate gear 4.

Description

  The present invention relates to an electric linear actuator provided with a ball screw mechanism used in a drive unit of a general industrial electric motor or automobile, and more specifically, a rotational input from an electric motor is applied to the ball screw in an automobile transmission or a parking brake. The present invention relates to an electric linear actuator that converts a linear motion of a drive shaft through a mechanism.

  In electric actuators used in various drive units, a gear mechanism such as a trapezoidal screw or a rack and pinion is generally used as a mechanism for converting the rotational motion of the electric motor into a linear motion in the axial direction. Since these conversion mechanisms involve a sliding contact portion, the power loss is large, and it is necessary to increase the size of the electric motor and increase the power consumption. Therefore, a ball screw mechanism has been adopted as a more efficient actuator.

  For example, in a relatively small ship that drives a screw with an internal combustion engine, the wire connected to a lever operated by an operator can be switched between the rotation of the screw in the forward direction and the rotation of the screw in the reverse direction. And the dog clutch is switched via this wire and engaged with the forward gear or the reverse gear. However, in recent years, electric actuators that switch dog clutches electrically have been developed to save labor.

  Here, it is necessary to consider that the electric actuator for ships is used on the open sea, and it is desired to develop it with a concept different from that of a general actuator. For example, since a general linear actuator is often controlled by detecting displacement in the axial direction, a limit switch is provided at a portion that is displaced in the axial direction. In many cases, the electric motor serving as the drive source of the actuator is assembled in a state of being exposed on the outer wall of the housing.

  However, if the stroke position of the linear actuator is detected with the limit switch, the forward position and the reverse position of the dog clutch are detected at two positions. In this case, since the position in the middle cannot be detected, there is a problem that when the dog clutch stops between two positions for some reason, the drive circuit cannot determine in which direction the dog clutch should be moved.

  As an electric actuator that solves such a problem, one shown in FIG. 8 is known. The electric actuator 100 includes a cylindrical housing 101, an electric motor 102 attached to the housing 101, a first power transmission mechanism including a plurality of gears for transmitting the rotational force of the electric motor 102, and a measurement shaft 113a. And a second power transmission mechanism that includes a plurality of gears and that transmits the rotational force of the electric motor 102 to the measurement shaft 113a of the potentiometer 113.

  The housing 101 includes a housing main body 101A, a cover member 101B assembled to an end surface thereof, and a motor bracket 101C. The housing body 101A has a motor chamber 101a and a screw shaft chamber 101b, and a motor 102 is disposed in the motor chamber 101a. The electric motor 102 is fixed to a plate-like motor bracket 101C. The motor bracket 101C is attached so that the outer ring of the ball bearing 114 is sandwiched between the housing main body 101A and the motor chamber 101a and the screw shaft chamber 101b of the housing main body 101A are closed.

  A rotating shaft 102a of the electric motor 102 protrudes from the motor bracket 101C, and a first gear 103 is attached to the end of the rotating shaft 102a so as not to be relatively rotatable by press-fitting. A second gear 105 is rotatably disposed around the long shaft 104 whose one end is press-fitted into the bag hole of the motor bracket 101C, and meshes with the large gear portion 106a of the first gear 103 and the third gear 106. Yes.

  The third gear 106 has a large gear portion 106a and a small gear portion 106b formed coaxially, and is attached to the end portion of the screw shaft 107 so as not to be relatively rotatable by serration coupling. A support member 108 is attached to the motor bracket 101C so as to cover a part of the third gear 106. Here, the first gear 103, the second gear 105, and the third gear 106 constitute a first power transmission mechanism.

  A fourth gear 109 disposed adjacent to the second gear 105 is rotatably supported around the long shaft 104. In the fourth gear 109, a large gear portion 109a and a small gear portion 109b that are meshed with the small gear portion 106b of the third gear 106 are formed coaxially.

  The small gear portion 109 b of the fourth gear 109 meshes with the large gear portion 111 a of the fifth gear 111 that is rotatably supported with respect to the short shaft 110 implanted in the support member 108 in parallel with the long shaft 104. ing. The fifth gear 111 has a large gear portion 111a and a small gear portion 111b formed coaxially. The small gear portion 111 b meshes with a sixth gear 112 that is disposed adjacent to the fifth gear 111 and rotatably supported around the long shaft 104.

  The potentiometer 113 as a sensor is fitted and disposed in the hole of the cover member 101B. The measurement shaft 113a of the potentiometer 113 is connected to the sixth gear 112 and rotates integrally. The tip of the long shaft 104 extending in a cantilever manner is supported by the potentiometer 113 via the sixth gear 112 and the measurement shaft 113a. Here, the first gear 103, the second gear 105, the third gear 106, the fourth gear 109, the fifth gear 111, and the sixth gear 112 constitute a second power transmission mechanism.

  The right end side of the screw shaft 107 is rotatably supported by a ball bearing 114 with respect to the housing main body 101A. The screw shaft 107 penetrates the cylindrical nut 115 and forms a male screw groove 107a on the left end side. A female screw groove 115a is formed on the inner peripheral surface of the nut 115 so as to face the male screw groove 107a, and a large number of balls 116 are arranged to roll in a spiral space formed by both the screw grooves 107a and 115a. Has been. The nut 115 is provided with a detent with respect to the housing main body 101A, and is relatively movable in the axial direction within the screw shaft chamber 101b, and is not relatively rotatable. A nut 115 as an axial movement element, a screw shaft 107 as a rotation element, and a ball 116 as a rolling element constitute a ball screw mechanism, and the ball screw mechanism and the drive shaft 117 constitute a drive mechanism. To do.

  The left end of the screw shaft 107 penetrates into a bag hole 117a formed in the round shaft-shaped drive shaft 117. The right end of the drive shaft 117 is coaxially fitted to the nut 115 and is connected by a pin so as to move integrally. The drive shaft 117 is supported by the bush 118 so as to be movable in the axial direction with respect to the housing main body 101A. A hole 117b for connecting to a link member (not shown) is formed at the end of the drive shaft 117 protruding from the housing main body 101A.

  The rotational force of the rotating shaft 102a is transmitted to the measuring shaft 113a of the potentiometer 113 via the first gear 103, the second gear 105, the third gear 106, the fourth gear 109, the fifth gear 111, and the sixth gear 112. The A signal corresponding to the rotation of the measuring shaft 113a is input from the potentiometer 113 to a drive circuit (not shown). If it is determined that the screw shaft 107 has rotated by a predetermined rotation amount based on this signal, the drive circuit stops the power supply to the electric motor 102. On the other hand, when the operator operates a lever (not shown) in the reverse direction, electric power having a reverse polarity is supplied to the electric motor 102 and the rotating shaft 102a rotates in the reverse direction. Then, the drive shaft 117 of the electric actuator 100 moves in the retracting direction.

  As described above, the centers of the second gear 105, the fourth gear 109, and the sixth gear 112 coincide with each other and are rotatably disposed around the same long shaft 104, so that a reduction ratio with a high gear ratio can be obtained. A compact configuration can be achieved while using a five-stage gear train. In this way, in the electric actuator 100 in which a plurality of gears are built in, the three gears have the same rotation center axis. This means that the number of center axes is reduced, and the support holes for housings that support the center axes. There are many advantages such as being reduced.

  Moreover, since the rotational displacement of the screw shaft 107 is detected by the potentiometer 113 instead of detecting the displacement position by a limit switch or the like, arbitrary position control is possible. When the rotation of the screw shaft 107 is directly detected, the screw shaft 107 is multi-rotation, and thus the rotational displacement decelerated through the gear train of the second power transmission mechanism is detected by the potentiometer 113. On the other hand, the rotational motion output from the electric motor 102 is decelerated through the gear train and transmitted to the screw shaft 107. By providing a common rotation center shaft in a part of the two gear trains, a compact layout is possible, and there is a great contribution in terms of cost (for example, see Patent Document 1).

JP 2008-228557 A

  In such a conventional electric actuator 100, the number of parts is large and noise is caused by backlash of all parts. However, low noise is strongly demanded due to demands for vehicle comfort. In particular, since this type of electric actuator 100 has a plurality of gears rotatably arranged on the same axis, such as the measurement shaft 113a, backlash and shaft runout of these gears occur. These backlashes and vibrations become a source of vibration and cause noise.

  Further, in order for the electric actuator 100 having a multi-stage gear (spur gear) between the screw shaft 107 and the potentiometer 113 to obtain a large reduction, it is necessary to increase the difference in the number of teeth between the small gear and the large gear. This not only increases the number of parts and the number of parts, but also increases the size of the electric actuator 100 that accommodates each gear.

  The present invention has been made in view of the above-described problems of the prior art, and while reducing the number of parts and reducing the size, vibration propagation due to play between the gear and the gear shaft is cut off and reduced. An electric linear actuator that realizes low noise due to backlash of the shaft itself can be provided.

  In order to achieve such an object, the invention according to claim 1 of the present invention includes a housing, an electric motor attached to the housing, and a speed reduction mechanism that transmits the rotational force of the electric motor via a motor shaft. And a ball screw mechanism that converts the rotational motion of the electric motor into a linear motion in the axial direction of the drive shaft via the speed reduction mechanism, and the ball screw mechanism is supported via a support bearing mounted on the housing. A nut that is rotatably and non-movable in the axial direction and has a spiral thread groove formed on the inner periphery, and is inserted into the nut via a large number of balls and is coaxially integrated with the drive shaft. An electric linear actuator comprising a screw shaft that is formed on the outer periphery and has a helical screw groove corresponding to the screw groove of the nut, and is supported so as to be non-rotatable and axially movable with respect to the housing. The housing comprises a first housing and a second housing abutted on an end surface thereof, and the screw shaft is accommodated in the abutting portion of the first housing and the second housing. A gear hole is formed in the first housing and the second housing, and a gear and a gear shaft constituting the speed reduction mechanism, or between the housing and the gear shaft One or both are provided with a synthetic resin bush, and the gear is rotatably supported with respect to the housing.

  As described above, a reduction mechanism that transmits the rotational force of the electric motor and a ball screw mechanism that converts the rotational movement of the electric motor into the linear movement in the axial direction of the drive shaft via the reduction mechanism are provided. , A nut that is rotatably supported through a support bearing mounted on the housing and is not movable in the axial direction, and has a helical thread groove formed on the inner periphery, and the nut is inserted through a number of balls. A screw shaft that is coaxially integrated with the drive shaft, has a helical screw groove corresponding to the screw groove of the nut on the outer periphery, and is supported so as to be non-rotatable and axially movable with respect to the housing. In the electric linear actuator configured as described above, the housing is composed of a first housing and a second housing abutted on the end face, and the screw shaft is accommodated in the abutting portion of the first housing and the second housing. A gear hole is formed in the first housing and the second housing, and the gear and the gear shaft constituting the speed reduction mechanism, or between the housing and the gear shaft are formed. In addition, since a bush made of synthetic resin is interposed in both, and the gear is rotatably supported with respect to the housing, vibration transmission due to play between the intermediate gear and the gear shaft is cut off and reduced, An electric linear actuator that realizes low noise due to looseness of the gear shaft itself can be provided.

  According to a second aspect of the present invention, the speed reduction mechanism includes an input gear fixed to the motor shaft, an intermediate gear meshed with the input gear, meshed with the intermediate gear, and integrated with the nut. An output gear fixed to the first housing and the second housing, and a gear shaft is fitted between the gear shaft and the intermediate gear and between the housing and the gear shaft. One or both may be provided with a synthetic resin bush.

  According to a third aspect of the present invention, the bush may be press-fitted into the inner diameter of the intermediate gear with a predetermined bearing clearance between the bush and the gear shaft.

  Further, as in the invention described in claim 4, if the bush is integrally joined to the inner diameter of the intermediate gear by insert molding with a predetermined bearing clearance between the gear shaft, the number of parts is reduced. In addition, the number of assembly steps can be reduced and the cost can be reduced.

  Further, as in the invention described in claim 5, if the width of the bush is set smaller than the tooth width of the intermediate gear, wear and deformation of the bush side surface due to friction can be prevented, and smooth Rotational performance can be obtained and the axial position of the intermediate gear can be stabilized.

  According to a sixth aspect of the present invention, the intermediate gear is press-fitted and fixed to the gear shaft, and the gear shaft is fitted and inserted into the first housing and the second housing via a bush. May be.

  Further, as in the invention described in claim 7, if the bush is formed in a U-shaped cup shape and is press-fitted and fixed so as to cover the end of the gear shaft, the gear shaft collides with the housing. Even so, the impact can be suppressed and wear of the housing can be suppressed.

  Further, as in the invention according to claim 8, the gear shaft is fitted and inserted into the first housing and the second housing via a bush, and the bush, the first housing, and the second housing If a predetermined axial clearance is provided between them, misalignment is allowed and smooth rotation performance can be ensured.

  Further, as in the ninth aspect of the invention, one of the end portions of the gear shaft is press-fitted into one of the first housing and the second housing, and the other end portion is If a clearance fit is set on the other of the first housing and the second housing, misalignment is allowed and smooth rotation performance can be ensured.

  Further, as in the invention described in claim 10, if ring-shaped synthetic resin washers are attached to both sides of the intermediate gear, the intermediate gear is in direct contact with the first and second housings. It is possible to prevent the first and second housings from being worn.

  If the width of the tooth portion of the intermediate gear is smaller than the tooth width as in the invention described in claim 11, the contact area with the washer can be reduced, and the frictional resistance during rotation is reduced. And smooth rotation performance can be obtained.

  An electric linear actuator according to the present invention includes a housing, an electric motor attached to the housing, a reduction mechanism that transmits the rotational force of the electric motor via a motor shaft, and the electric motor via the reduction mechanism. And a ball screw mechanism that converts the rotational motion of the drive shaft into a linear motion in the axial direction of the drive shaft, and this ball screw mechanism is supported by a support bearing mounted on the housing so as to be rotatable and non-movable in the axial direction. And a nut having a spiral thread groove formed on the inner periphery, and inserted into the nut via a number of balls, integrated coaxially with the drive shaft, and corresponding to the thread groove of the nut on the outer periphery. An electric linear actuator comprising a screw shaft that is formed so as to be non-rotatable and axially movable with respect to the housing. The housing is composed of a first housing and a second housing abutted on the end face, and a bag hole for accommodating the screw shaft is formed in the abutting portion of the first housing and the second housing. In addition, a gear shaft is fitted and inserted into the first housing and the second housing, and the gear and the gear shaft constituting the speed reduction mechanism, and one or both of the housing and the gear shaft are included. Since a synthetic resin bush is interposed and the gear is rotatably supported with respect to the housing, vibration propagation due to play between the intermediate gear and the gear shaft is cut off and reduced, and the gear shaft itself An electric linear actuator that realizes low noise due to backlash can be provided.

1 is a longitudinal sectional view showing an embodiment of an electric linear actuator according to the present invention. It is a longitudinal cross-sectional view which shows the actuator main body of FIG. It is a principal part enlarged view which shows the intermediate | middle gear part of FIG. It is explanatory drawing which shows the dimensional relationship of each part of FIG. It is a principal part enlarged view which shows the modification of the intermediate gear part of FIG. It is a principal part enlarged view which shows the other modification of the intermediate gear part of FIG. It is a principal part enlarged view which shows the other modification of the intermediate gear part of FIG. It is a longitudinal cross-sectional view which shows the conventional electric linear actuator.

  An aluminum alloy housing, an electric motor attached to the housing, a reduction mechanism that transmits the rotational force of the electric motor via a motor shaft, and the rotational movement of the electric motor is driven via the reduction mechanism A ball screw mechanism for converting the shaft into a linear motion in the axial direction, and this ball screw mechanism is supported by a support bearing mounted on the housing so as to be rotatable and non-movable in the axial direction. A nut formed with a helical thread groove, and a helical screw that is inserted into the nut through a large number of balls, is coaxially integrated with the drive shaft, and corresponds to the thread groove of the nut on the outer periphery An electric linear actuator comprising a screw shaft formed with a groove and supported so as to be non-rotatable and axially movable with respect to the housing, wherein the housing has a first housing. And a second housing abutted on the end face, the electric motor is attached to the first housing, and the screw shaft is fitted to the abutting portion of the first housing and the second housing. A bag hole for receiving is formed, and the speed reduction mechanism is engaged with an input gear fixed to the motor shaft, an intermediate gear meshed with the input gear, meshed with the intermediate gear, and fixed integrally with the nut. A gear shaft is inserted into the first housing and the second housing via a synthetic resin bush, and a synthetic resin bush is interposed between the gear shaft and the intermediate gear. In addition, ring-shaped synthetic resin washers are mounted on both sides of the intermediate gear.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 is a longitudinal sectional view showing an embodiment of an electric linear actuator according to the present invention, FIG. 2 is a longitudinal sectional view showing an actuator body of FIG. 1, and FIG. 3 is a main portion showing an intermediate gear portion of FIG. 4 is an explanatory view showing the dimensional relationship of each part of FIG. 3, FIG. 5 is an enlarged view of a main part showing a modification of the intermediate gear part of FIG. 3, and FIG. 6 is an illustration of the intermediate gear part of FIG. The principal part enlarged view which shows another modification, FIG. 7 is the principal part enlarged view which shows the other modification of the intermediate | middle gear part of FIG.

  As shown in FIG. 1, the electric linear actuator 1 includes a cylindrical housing 2, an electric motor (not shown) attached to the housing 2, and an input gear attached to a motor shaft 3a of the electric motor. 3 and an output gear 5 meshed with the intermediate gear 4, and the rotational motion of the electric motor is converted into a linear motion in the axial direction of the drive shaft 7 via the speed reduction mechanism 6. A ball screw mechanism 8 and an actuator body 9 including the ball screw mechanism 8.

  The housing 2 is formed of an aluminum alloy such as A6063TE or ADC12 by aluminum die casting, and includes a first housing 2a and a second housing 2b abutted on the end face, and is integrally formed by a fixing bolt (not shown). It is fixed. An electric motor is attached to the first housing 2a, and bag holes 11 and 12 for accommodating the screw shaft 10 are formed at the abutting portions of the first housing 2a and the second housing 2b. Yes.

  The motor shaft 3a of the electric motor is rotatably supported by a rolling bearing 13 comprising a deep groove ball bearing mounted on the second housing 2b. . The output gear 5 that meshes with the intermediate gear 4 that is a spur gear is integrally fixed to a nut 18 that constitutes a ball screw mechanism 8 described later via a key 14.

  The drive shaft 7 is configured integrally with a screw shaft 10 constituting the ball screw mechanism 8, and locking pins 15, 15 are implanted at one end portion (right end portion in the figure) of the drive shaft 7. A sleeve 17 is fitted into the bag hole 12 of the second housing 2b, and concave grooves 17a and 17a extending in the axial direction are formed on the inner periphery of the sleeve 17 by grinding. The concave grooves 17a and 17a are arranged opposite to each other in the circumferential direction, and the locking pins 15 and 15 of the screw shaft 10 are engaged with the concave grooves 17a and 17a, respectively, so that the screw shaft 10 cannot rotate. And is supported so as to be movable in the axial direction. The sleeve 17 is prevented from coming off in the axial direction by a retaining ring 28 for a hole attached to the opening of the bag hole 12 of the second housing 2b.

  Here, the sleeve 17 is made of a sintered alloy prepared by adjusting a metal powder into a plastic shape and molding it with an injection molding machine. In this injection molding, first, metal powder and a binder made of plastic and wax are kneaded by a kneader, and the kneaded product is granulated into pellets. The granulated pellets are molded by so-called MIM (Metal Injection Molding), which is supplied to a hopper of an injection molding machine and pushed into a mold in a heated and melted state. A sintered alloy formed by such an MIM can be easily and accurately formed into a desired shape / dimension even if it has a high workability and a complicated shape.

  As the metal powder, a material that can be subsequently carburized and hardened, for example, C (carbon) is 0.13 wt%, Ni (nickel) is 0.21 wt%, Cr (chromium) is 1.1 wt%, Cu (copper) Exemplifies SCM415 which is 0.04 wt%, Mn (manganese) is 0.76 wt%, Mo (molybdenum) is 0.19 wt%, Si (silicon) is 0.20 wt%, and the rest is Fe (iron). Can do. The sleeve 17 is performed by adjusting the carburizing quenching and tempering temperatures. In addition to this, as the material of the sleeve 17, Ni is contained in an amount of 3.0 to 10.0 wt% and has excellent workability and corrosion resistance (FEN8 of Japanese Powder Metallurgy Industry Standard), or C is 0.07 wt%. %, Cr is 17 wt%, Ni is 4 wt%, Cu is 4 wt%, and the remainder is precipitation hardened stainless steel SUS630 made of Fe or the like. This SUS630 can appropriately increase the surface hardness in the range of 20 to 33 HRC by solution heat treatment, and can ensure toughness and high hardness.

  On the other hand, the locking pin 15 that engages with the concave groove 17a is formed of high carbon chromium bearing steel such as SUJ2 or carburized bearing steel such as SCr435, and the surface thereof has a carbon content of 0.80 wt% or more and 58 HRC or more. The carbonitriding layer is formed. In addition, by applying the needle roller used for the needle roller bearing to the locking pin 15, a surface hardness of 58HRC or more can be obtained, the wear resistance is excellent, the availability is good, and the cost is low. Can be achieved.

  As shown in an enlarged view in FIG. 2, the ball screw mechanism 8 includes a screw shaft 10 and a nut 18 that is externally inserted to the screw shaft 10 via a ball 19. The screw shaft 10 has a spiral thread groove 10a formed on the outer periphery. On the other hand, the nut 18 is formed with a helical thread groove 18a corresponding to the thread groove 10a of the screw shaft 10 on the inner periphery, and a large number of balls 19 are accommodated between these thread grooves 10a and 18a so as to be able to roll. ing. The nut 18 is supported to the housings 2a and 2b via the two support bearings 20 and 20 so as to be rotatable and not movable in the axial direction. Reference numeral 21 denotes a piece member that constitutes a circulation member by connecting the thread grooves 18a of the nut 18, and the piece member 21 allows an infinite circulation of a large number of balls 19.

  The cross-sectional shape of each of the thread grooves 10a and 18a may be a circular arc shape or a gothic arc shape, but here, a gothic arc shape that allows a large contact angle with the ball 19 and a small axial clearance can be set. Is formed. Thereby, the rigidity with respect to an axial load becomes high and generation | occurrence | production of a vibration can be suppressed.

  The nut 18 is made of case-hardened steel such as SCM415 or SCM420, and its surface is subjected to hardening treatment in a range of 55 to 62 HRC by vacuum carburizing and quenching. Thereby, the buffing etc. for the scale removal after the heat treatment can be omitted, and the cost can be reduced. On the other hand, the screw shaft 10 is made of medium carbon steel such as S55C or case-hardened steel such as SCM415 or SCM420, and its surface is hardened in the range of 55 to 62 HRC by induction hardening or carburizing hardening.

  An output gear 5 constituting the speed reduction mechanism 6 is fixed to the outer peripheral surface 18b of the nut 18 via a key 14, and two support bearings 20 and 20 are press-fitted on both sides of the output gear 5 via a predetermined squeeze. Has been. Thereby, even if a thrust load is applied from the drive shaft 7, it is possible to prevent the axial displacement between the support bearings 20 and 20 and the output gear 5. Further, the two support bearings 20 and 20 are constituted by sealed deep groove ball bearings having shield plates 20a and 20a attached to both ends, and leakage of the lubricating grease enclosed in the bearings to the outside and from the outside This prevents wear powder from entering the bearing.

  Further, in the present embodiment, the support bearing 20 that rotatably supports the nut 18 is composed of deep groove ball bearings having the same specifications, and thus is loaded from the drive shaft 7 through the thrust load and the output gear 5 described above. Both radial loads can be applied, and confirmation work for preventing misassembly during assembly can be simplified, and assembling workability can be improved. Here, the deep groove ball bearings having the same specifications refer to bearings having the same inner diameter, outer diameter, width dimension, rolling element size, number, bearing internal clearance, and the like.

  In addition, one of the pair of support bearings 20 and 20 is attached to the first housing 2a via a washer 29 made of a ring-shaped elastic member. The washer 29 is formed by press working from an austenitic stainless steel plate (JIS standard SUS304 type or the like) having high strength and wear resistance or a rust-proof cold rolled steel plate (JIS standard SPCC type or the like). It consists of a wave washer. The inner diameter D is formed larger than the inner ring outer diameter d of the support bearing 20. As a result, the axial backlash of the pair of support bearings 20 and 20 can be eliminated, smooth rotation performance can be obtained, and the washer 29 can be in contact with only the outer ring of the support bearing 20 to form a rotating ring. Therefore, even if a reverse thrust load is generated and the nut 18 is pressed against the first housing 2a, the inner ring of the support bearing 20 is prevented from coming into contact with the housing 2a and the frictional force is prevented from increasing, and the locked state Can be surely prevented.

  Here, the intermediate gear 4 constituting the speed reduction mechanism 6 will be described. As shown in FIG. 3, the gear shaft 22 is fitted into the first and second housings 2 a and 2 b via bushes 23. Specifically, the bush 23 is press-fitted into the housings 2a and 2b, and is inserted between the gear shaft 22 via a predetermined radial clearance. A predetermined axial clearance δ is provided between the bush 23 and the first and second housings 2a and 2b. Thereby, misalignment (assembly error) is allowed and smooth rotation performance can be ensured. Here, the bush 23 may be press-fitted into the gear shaft 22 and may be inserted between the first and second housings 2a and 2b via a predetermined radial clearance.

  The intermediate gear 4 is rotatably supported on the gear shaft 22 via a bush (sliding bearing) 24. The bush 24 is press-fitted into the inner diameter 4 a of the intermediate gear 4 with a predetermined bearing clearance (radial clearance) between the bush 24 and the gear shaft 22. The bushes 23 and 24 are formed of a thermoplastic synthetic resin such as PA (polyamide) 66 filled with a predetermined amount of a fibrous reinforcing material such as GF (glass fiber). As a result, the number of parts is reduced to achieve compactness, and the vibration propagation due to the backlash between the intermediate gear 4 and the gear shaft 22 is cut off and reduced, and the low noise due to the backlash of the gear shaft 22 itself is realized. An actuator can be provided. If the bush 24 is integrally joined to the inner diameter 4a of the intermediate gear 4 by insert molding, the number of parts can be reduced, the number of assembling steps can be reduced, and the cost can be reduced.

  In addition, as a fibrous reinforcement, not only GF but CF (carbon fiber), an aramid fiber, a boron fiber, etc. can be illustrated other than this. Other materials for the bushing 23 include thermoplastic synthetic resins called so-called engineering plastics such as PPA (polyphthalamide) and PBT (polybutylene terephthalate), polyphenylene sulfide (PPS), and polyether ether ketone (PEEK). ), Thermoplastic synthetic resins called super engineering plastics such as polyamideimide (PAI), or thermosetting synthetic resins such as phenolic resin (PF), epoxy resin (EP), polyimide resin (PI), etc. It may be.

  Moreover, ring-shaped washers 25 and 25 are mounted on both sides of the intermediate gear 4 to prevent the intermediate gear 4 from coming into direct contact with the first and second housings 2a and 2b. Here, as shown in FIG. 4, the width Wh of the tooth portion 4b of the intermediate gear 4 is formed smaller than the tooth width Wg (Wh <Wg). Thereby, a contact area with the washer 25 can be made small, and friction performance at the time of rotation can be suppressed and smooth rotation performance can be obtained. Here, the washer 25 is formed of a thermoplastic synthetic resin such as PA66 filled with a predetermined amount of a fibrous reinforcing material such as GF.

  Further, the width Wb of the bush 24 is set smaller than the tooth width Wg of the intermediate gear 4. Thereby, abrasion and deformation of the side surface of the bush 24 due to friction can be prevented, smooth rotation performance can be obtained, and the axial position of the intermediate gear 4 can be stabilized.

  FIG. 5 shows a modification of FIG. The gear shaft 22 is implanted in the first and second housings 2 a and 2 b, and the intermediate gear 4 is rotatably supported on the gear shaft 22 via a bush 24. In the present embodiment, one end portion of the end portion of the gear shaft 22, for example, the end portion on the first housing 2a side is press-fitted, and the other end portion on the second housing 2b side is set to a clearance fit. ing. Thereby, misalignment (assembly error) is allowed and smooth rotation performance can be ensured.

  FIG. 6 shows another modification of FIG. The gear shaft 22 is fitted and inserted into the first and second housings 2a and 2b via bushes 23. The intermediate gear 26 is press-fitted and fixed to the gear shaft 22 and is rotatably supported via the bush 23 with respect to the first and second housings 2a and 2b. As a result, the play between the intermediate gear 26 and the gear shaft 22 can be prevented, and the vibration propagation due to the play between the gear shaft 22 and the housings 2a and 2b can be cut off and reduced to reduce noise.

  FIG. 7 shows another modification of FIG. The gear shaft 22 is fitted into the first and second housings 2a and 2b via bushes 27. The intermediate gear 4 is rotatably supported on the gear shaft 22 via a bush 24. The bush 24 is press-fitted into the inner diameter 4 a of the intermediate gear 4 with a predetermined bearing clearance (radial clearance) between the bush 24 and the gear shaft 22. In this embodiment, the bush 27 is made of a thermoplastic synthetic resin such as PA66 filled with a predetermined amount of a fibrous reinforcing material such as GF, and is formed in a cup shape having a U-shaped cross section. It is press-fitted and fixed so as to cover it. Thereby, vibration propagation due to play between the intermediate gear 4 and the gear shaft 22 can be cut off and reduced, and noise due to play of the gear shaft 22 itself can be reduced, and the gear shaft 22 collides with the housings 2a and 2b. However, the impact can be suppressed and the wear of the housings 2a and 2b can be suppressed.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and is merely an example, and various modifications can be made without departing from the scope of the present invention. Of course, the scope of the present invention is indicated by the description of the scope of claims, and further, the equivalent meanings described in the scope of claims and all modifications within the scope of the scope of the present invention are included. Including.

  An electric linear actuator according to the present invention is used in a drive unit of a general industrial electric motor, automobile, etc., and has a ball screw mechanism that converts rotational input from an electric motor into linear motion of a drive shaft via the ball screw mechanism. It can be applied to the provided electric linear actuator.

DESCRIPTION OF SYMBOLS 1 Electric linear actuator 2 Housing 2a 1st housing 2b 2nd housing 3 Input gear 3a Motor shaft 4, 26 Intermediate gear 4a Inner gear inner diameter 4b Tooth part 5 Output gear 6 Reduction gear mechanism 7 Drive shaft 8 Ball screw mechanism 9 Actuator Main body 10 Screw shaft 10a, 18a Screw groove 11, 12 Cap hole 13 Rolling bearing 14 Key 15 Locking pin 17 Sleeve 17a Recessed groove 18 Nut 18b Nut outer peripheral surface 19 Ball 20 Support bearing 20a Shield plate 21 Frame member 22 Gear shaft 23 , 24, 27 Bush 25, 29 Washer 28 Retaining ring 100 Electric actuator 101 Housing 101A Housing main body 101B Cover member 101C Electric motor bracket 101a Motor chamber 101b Screw shaft chamber 102 Electric motor 102a Rotating shaft 103 First gear 104 Long Shaft 105 Second gear 106 Third gear 106a Large gear portion 106b Small gear portion 107 Screw shaft 107a Male screw groove 108 Support member 109 Fourth gear 109a Large gear portion 109b Small gear portion 110 Short shaft 111 Fifth gear 111a Large gear portion 111b Small gear portion 112 Sixth gear 113 Potentiometer 113a Measuring shaft 114 Ball bearing 115 Nut 115a Female thread groove 116 Ball 117 Drive shaft 117a Bag hole 117b Hole 118 Bush D Washer inner diameter d Support bearing inner ring outer diameter Wh Intermediate gear tooth Width Wb Bearing bush width Wg Intermediate gear tooth width δ Axial clearance between bush and housing

Claims (11)

A housing;
An electric motor attached to the housing;
A speed reduction mechanism for transmitting the rotational force of the electric motor via the motor shaft;
A ball screw mechanism that converts the rotational motion of the electric motor to linear motion in the axial direction of the drive shaft via the speed reduction mechanism;
The ball screw mechanism is rotatably supported via a support bearing mounted on the housing and is not axially movable, and a nut having a helical thread groove formed on the inner periphery,
The nut is inserted through a large number of balls and is integrated coaxially with the drive shaft. A spiral screw groove corresponding to the screw groove of the nut is formed on the outer periphery, and the nut cannot rotate with respect to the housing. And an electric linear actuator composed of a screw shaft supported so as to be axially movable,
The housing comprises a first housing and a second housing abutted on the end face, and a bag hole for accommodating the screw shaft in the abutting portion of the first housing and the second housing. A gear shaft is formed and inserted into the first housing and the second housing, and the gear and the gear shaft constituting the speed reduction mechanism, and either or both of the housing and the gear shaft are formed. An electric linear actuator characterized in that a synthetic resin bush is interposed between the gears and the gear is rotatably supported with respect to the housing.   The speed reduction mechanism includes an input gear fixed to the motor shaft, an intermediate gear meshing with the input gear, an output gear meshing with the intermediate gear and integrally fixed to the nut, A gear shaft is fitted and inserted into the housing and the second housing, and a synthetic resin bush is interposed between the gear shaft and the intermediate gear, between the housing and the gear shaft, or both. The electric linear actuator according to claim 1.   The electric linear actuator according to claim 1 or 2, wherein the bush is press-fitted into an inner diameter of the intermediate gear with a predetermined bearing clearance between the bush and the gear shaft.   The electric linear actuator according to claim 1 or 2, wherein the bush is integrally joined to the inner diameter of the intermediate gear by insert molding with a predetermined bearing clearance between the bush and the gear shaft.   The electric linear actuator according to any one of claims 2 to 4, wherein a width of the bush is set smaller than a tooth width of the intermediate gear.   3. The electric linear actuator according to claim 1, wherein the intermediate gear is press-fitted and fixed to the gear shaft, and the gear shaft is fitted and inserted into the first housing and the second housing via a bush.   The electric linear actuator according to claim 1 or 6, wherein the bush is formed in a cup shape having a U-shaped cross section and is press-fitted and fixed so as to cover an end portion of the gear shaft.   The gear shaft is fitted and inserted into the first housing and the second housing via a bush, and a predetermined axial clearance is provided between the bush, the first housing, and the second housing. The electric linear actuator according to claim 1, 6 or 7.   One of the ends of the gear shaft is press-fitted into one of the first housing and the second housing, and the other end is a gap between the other of the first housing and the second housing. The electric linear actuator according to claim 1 or 2, wherein the electric linear actuator is set to be fitted.   The electric linear actuator according to claim 1, wherein ring-shaped synthetic resin washers are mounted on both sides of the intermediate gear.   The electric linear actuator according to claim 10, wherein a width of a tooth portion of the intermediate gear is smaller than a tooth width.

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