JP2007174877A - Precision linear actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized and inexpensive precision linear actuator, in which the constituent members are arranged linearly along the output axis and original position can be mechanically detected. <P>SOLUTION: In a precision linear actuator, comprising a housing, a motor, a decelerating mechanism section, a driving section and a linear operation section, the driving section has a screwing section with the linear operation section formed into a small diameter, relative to the connecting section with the decelerating mechanism section, and has a stepped portion at a boundary between the screwing section and the connecting section, the stepped portion is provided with a driving section protrusion protruding toward the linear operating section side, and the base end section of the linear operating section is provided with an operation protrusion, protruding toward the drive section side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a precision linear actuator using a small motor.

  Linear actuators that convert motor rotational motion into linear motion are used in a wide variety of mechanical devices, including lifting devices such as lifters, welfare equipment such as nursing beds, and medical equipment such as CT scanners. Various types have been proposed.

  In Patent Document 1 (Japanese Patent Laid-Open No. 2000-152557), the torque of the housing, the rotating shaft supported inside the housing, the electric motor fixed to the housing, and the motor driving shaft is increased to increase the torque. A speed reducer that transmits to the rotating shaft, a multi-threaded male threaded portion provided on a part of the rotating shaft, a synthetic resin nut member having a female threaded portion that is directly screwed with the male threaded portion, and a base end portion An output shaft member coupled and fixed to the nut member, a spacer for receiving a thrust load applied to the rotating shaft, an intermediate tube disposed around the rotating shaft, an outer peripheral surface of the intermediate tube, and an inner periphery of the housing An electric linear actuator including a one-way clutch, a thrust plate, and a bearing provided between surfaces is disclosed.

  In Patent Document 2 (Japanese Patent Laid-Open No. 2001-54255), a very small diameter small motor with a speed reducer, an outer housing fitted and fixed at the outer periphery of the speed reducer of the small motor, and the same direction as the motor output shaft are disclosed. A linear drive microactuator having a drive mechanism including a rail member arranged, a slider member having a female screw portion on the inner diameter side, and a screw member having a male screw portion on the outer periphery is disclosed.

  Patent Document 3 (Japanese Patent Laid-Open No. 2003-184988) discloses a motor unit, an expansion / contraction mechanism unit that expands and contracts an actuator rod, and a driving force that is transmitted to the expansion / contraction mechanism unit after the rotational speed of the motor unit is reduced. A linear actuator provided with a transmission mechanism, a clutch mechanism, and a manual operation mechanism has been proposed, and the use of a sun gear and a planetary gear is disclosed for the driving force transmission mechanism.

JP 2000-152557 A JP 2001-54255 A JP 2003-184988 A

  In the prior art as described above, for example, in Patent Document 1, since it is intended to be used for an electric bed for nursing care, miniaturization and simplification of the mechanism are not so required. Multiple limit switches are used to detect the position of the output shaft, and a one-way clutch is used to prevent the output shaft from being inadvertently displaced, making the mechanism complicated and difficult to downsize. Not only that, but also the manufacturing cost is expensive. Also, the worm mechanism employed as the speed reduction mechanism has a drawback that the shape becomes large, and is not suitable for a small precision actuator.

  Further, the linear drive microactuator of Patent Document 2 is small because it is assumed to be incorporated in a medical instrument such as an endoscope. However, in this actuator, one or more rail members are arranged to support the slider member that is an actual operating portion, and the rail member and the screw member for driving the slider member are supported at the end of the actuator. is doing. Therefore, the object to be operated linearly must be arranged on the side surface of the slider member. Further, since the position detection mechanism is not provided, the origin position cannot be detected unless position detection is performed separately by a sensor or the like.

  Furthermore, since the linear actuator of Patent Document 3 is intended to be used for an electric nursing bed, a manual operation mechanism is provided in the direction of the output shaft, so that the motor unit cannot be disposed on the output shaft. It has a structure. In addition, since the clutch mechanism for switching between motor driving and manual operation is provided, the structure is complicated and the manufacturing cost is expensive. As described above, the linear actuator of this document is also difficult to use as a small and inexpensive precision actuator.

  As a linear actuator for electrical control of an automobile or the like, which is an intended purpose of the present invention, not only a small size and high reliability but also a precision actuator for controlling a very small displacement is required.

  The present invention has been made in view of the above problems, and provides a small and inexpensive precision actuator in which constituent members are linearly arranged along an output shaft and the origin position can be mechanically detected. For the purpose.

  In order to solve the above problems, a precision linear actuator according to the present invention comprises a housing having at least an inner surface formed in a cylindrical shape, a motor fixed in the housing, a speed reduction mechanism connected to a drive shaft of the motor, A cylindrical shape in which a base end portion is fitted to the output shaft so as to follow the rotation of the output shaft of the speed reduction mechanism portion and locked in the rotation direction, and a male screw is formed on the outer peripheral portion on the distal end side. The drive part and a bottomed cylindrical shape having an inner surface cavity on the base end side, an internal thread is formed on the inner surface of the cavity, an operating projection is provided on the surface of the terminal bottom part, and the female part of the cavity part is further provided. A linear actuator comprising a screw that is screwed with a male screw of the drive unit by a screw and an outer surface that is in slidable contact with the inner surface of the housing, the drive unit being connected to the speed reduction mechanism unit Against the department The screwed portion with the linear operating portion is formed in a small diameter, and has a step portion at the boundary between the two, and the stepped portion is provided with a drive projection that protrudes toward the linear operating portion side, and the linear operation The base end portion of the portion is provided with an operating portion protrusion protruding toward the driving portion side.

  The housing has a stepped portion therein, and a portion for accommodating the driving portion and the linear operating portion is formed with a small diameter, and a supporting flange portion is provided at a base end portion on the speed reduction mechanism portion side of the driving portion. It is desirable to be formed and locked by the stepped portion.

  In addition, it is possible to adopt a configuration in which at least one guide pin protrudes from the outer periphery of the linear operating portion and is fitted in a guide groove provided on the inner surface of the housing.

  It is preferable that a tip of the speed reduction mechanism unit output shaft has a cruciform protrusion and is fitted in a cruciform recess provided inside the support flange of the drive unit.

  It is desirable that the motor, the speed reduction mechanism unit, the drive unit, and the linear operation unit are linearly arranged along the central axis of the actuator.

  The outer shape of the housing is preferably cylindrical.

  As the speed reduction mechanism, a planetary gear mechanism including a sun gear and a plurality of planetary gears can be employed.

  As the motor, a stepping motor or a DC motor is desirable.

  By adopting the configuration described in claim 1, the drive unit does not move in the output shaft direction, only the linear operation unit is guided to the inner surface of the housing and can move reliably in the output shaft direction. When retreating toward the motor or the speed reduction mechanism, the operating part projection provided at the base end of the linear operating part enters the rotation path of the driving part projection provided at the stepped part of the driving part and becomes the driving part projection. Since the rotation of the drive unit can be stopped by the contact, the origin position of the linear operation unit can be mechanically detected. Since the origin can be detected by a simple mechanism, it is not necessary to use a sensor or the like, the manufacturing cost can be kept low, and the manufacturing is facilitated.

  By adopting the configuration described in claim 2, since the inner step portion of the housing supports the support flange portion of the drive portion as a bearing, movement of the drive portion in the output shaft direction can be suppressed.

  By providing the guide pin described in claim 3 on the outer periphery of the linear operating portion and storing it in the guide groove provided on the inner surface of the housing, the linear operating portion is restricted in rotation and stably guided in the output shaft direction.

  A connecting member is used for connecting the speed reduction mechanism portion and the drive portion by fitting the cross-like projection at the tip of the output shaft of the speed reduction mechanism portion according to claim 4 and a cross-shaped recess provided inside the support flange of the drive portion. And the rotational output of the output shaft can be reliably transmitted to the drive unit.

  According to the fifth aspect of the present invention, a compact actuator can be achieved by linearly arranging the motor, the speed reduction mechanism, the drive unit, and the linear operation unit along the central axis of the actuator.

  As described in claim 6, by making the outer shape of the housing cylindrical, the space efficiency at the place where the actuator is attached can be improved.

  Various types known in the art can be used as the speed reduction mechanism, but space efficiency can be improved by employing a planetary gear mechanism composed of a sun gear and a plurality of planetary gears.

  Various types of commercially available motors can be used as the actuator drive source, but by using a stepping motor or a DC motor, precise control suitable for the actuator of the present invention is possible.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of an embodiment of a precision actuator according to the present invention. A motor 1 is fixed in a housing 3 having at least an inner surface formed in a cylindrical shape, and an output shaft 11 of the motor is connected to the speed reduction mechanism unit 2. A cross-shaped protrusion 27 is formed on the output shaft 25 of the speed reduction mechanism unit 2 in a direction perpendicular to the shaft, and is fitted and connected to the cross-shaped recess 43 of the drive unit 4.

  The details are shown in FIG. FIG. 2 is a cross-sectional view taken along the line A-A ′ of FIG. 1. A cruciform protrusion 27 provided at the distal end of the output shaft of the speed reduction mechanism portion is fitted into a cruciform recess at the base end portion of the drive portion, and transmits the rotation from the motor to the drive portion.

  The drive unit 4 has a cylindrical shape, and is provided with a support flange 41 at the outer peripheral portion at the base end portion. The drive unit 4 is supported by the inner step portion 33 of the housing 3 to suppress stress in the output shaft direction. Further, the drive unit 4 is formed with a small diameter on the end side with respect to the connecting part with the speed reduction mechanism unit 2, and a male screw 45 is formed on the surface of the small diameter part. Further, a stepped portion 42 is provided at the boundary between the connecting portion and the small diameter portion, and a drive portion projection 44 is formed in a part of the boundary along the small diameter portion in the output shaft direction.

  The linear actuating portion 5 has a bottomed cylindrical shape having an inner surface cavity 51 on the base end side, and a female screw 53 is formed on the inner surface of the cavity, and the male screw 45 of the drive unit 4 is formed in the female screw portion 53. Are screwed together. Further, the outer peripheral surface of the linear operating portion 5 is in contact with the inner surface of the housing 3 and is slidable in the output shaft direction. Further, at least one guide pin 54 is provided on the outer peripheral surface of the linear operation portion, and is fitted into a guide groove 32 formed on the inner surface of the housing 3. Thereby, it is suppressed that the linear action | operation part 5 rotates with rotation of the drive part 4. FIG. A cross-sectional view of the guide pin 54 is shown in FIG. An actuating rod 55 is provided on the surface of the bottom end of the linear actuating unit, and this actuating rod 55 acts on the object to be actuated.

  In addition, an operating portion protrusion 52 is formed on the peripheral edge of the inner surface cavity, which is the base end portion of the linear operating portion 5, and comes into contact with the driving portion protrusion 44 of the driving portion 4 in the rotation direction. Since it functions as a stopper that limits rotation, the origin position can be mechanically detected.

  An example of the speed reduction mechanism used in the above embodiment is shown in FIGS. FIG. 4 is a cross-sectional view of the speed reduction mechanism, in which the output shaft 11 of the motor is coupled to the shaft of the sun gear 21. Fixed internal teeth 22 are formed at a certain distance on the peripheral edge of the sun gear 21, and engagement with the three planetary gears 23 is restricted by the sun gear 21 and the fixed internal teeth 22. Further, the planetary gear 23 is also meshed with the output shaft gear 24 on the one hand, whereby the rotation from the motor is reduced and the torque is increased and then transmitted to the output shaft 25.

  The outer shape of the actuator according to the present invention is preferably a round shape because all the internal components are round, and the round shape makes it easy to mount and inexpensive to manufacture.

  Next, the operation of the above embodiment will be described. As the stepping motor or the DC motor 1 rotates, the rotation is transmitted to the speed reduction mechanism unit 2 coupled through the motor output shaft. In the reduction mechanism unit 2, as described above, the planetary gear 23 decelerates the motor rotation, increases the torque, and outputs the rotation to the output shaft 25. This rotation is transmitted to the drive unit 4 through the coupling of the cruciform protrusion 27 and the cruciform recess 43. The drive unit 4 is restricted from moving in the output shaft direction of the drive unit 4 on the one hand by the cross-shaped projection 27 of the speed reduction mechanism unit 2 and on the other hand by the support of the drive unit support flange 41 by the step 33 of the housing 3. Therefore, it receives the air sub-point of the output shaft of the speed reduction mechanism and rotates on the spot. Further, the drive unit 4 is meshed with a female screw 53 of an inner surface cavity 51 of the linear operation unit 5 at a small-diameter male screw 45. The linear operating portion is also slidably supported on the outer periphery of the housing by the inner surface of the housing, and the guide pin 54 provided on the outer periphery is guided by being fitted into the guide groove 32 on the inner surface of the housing. The rotation is restricted, and the movement in the output shaft direction is performed without rotating with the rotation of the drive unit.

  In the case of such a linear actuator, it is necessary to fix the operation origin position in order to ensure the operation accuracy, but in the case of this embodiment, the positioning can be performed by a very simple mechanical mechanism. That is, the drive part protrusion which has a level | step-difference part in the boundary of the screwing part of the connection part with the deceleration mechanism part 2 of the drive part 4, and the linear action | operation part 5, and protrudes toward this linear action | operation part 5 side in this step part. 44 is provided, and the base end portion of the linear operating portion 5 is provided with an operating portion protrusion 52 that protrudes toward the driving portion 4 side. The drive unit protrusion 44 rotates as the drive unit 4 rotates, but the operation unit protrusion 52 simply moves linearly along the output shaft because the operation unit itself does not rotate. Therefore, when the linear operating unit 5 moves in a direction approaching the driving unit 4 due to the rotation of the driving unit 4, the operating unit projection 52 enters the rotating track of the driving unit projection 44 at a certain time and rotates. The contact of the protrusion 44 stops the rotation of the drive unit 4. That is, this time can be the origin position of the actuator.

  In the case of automobile control, precision equipment assembly, IC and display manufacturing equipment, etc., a small actuator is required and a very precise operation is required. The accuracy may be on the order of 0.2 microns. As such a small precision actuator, an actuator according to the present invention using a stepping motor or a DC motor is optimal.

It is sectional drawing of one Example of the precision actuator by this invention. It is sectional drawing in the A-A 'line of the Example shown in FIG. It is sectional drawing of the linear action | operation part guide pin part of the Example shown in FIG. It is a cross-sectional view of the speed reduction mechanism used in the embodiment shown in FIG. It is sectional drawing which shows the planetary gear arrangement | positioning of the deceleration mechanism part shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor 2 Deceleration mechanism part 3 Housing 4 Drive part 5 Linear action part 6 Lead wire 11 Motor output shaft 21 Sun gear 22 Fixed internal gear 23 Planetary gear 24 Output shaft gear 25 Output shaft 26 Casing 27 Cross-shaped protrusion 31 Outer step part 32 Guide groove 33 Inner step portion 41 Support flange 42 Step portion 43 Cross-shaped recess 44 Drive portion protrusion 45 Male thread portion 51 Internal cavity portion 52 Actuation portion protrusion 53 Female thread portion 54 Guide pin 55 Actuation rod

Claims (8)

A housing having at least an inner surface formed in a cylindrical shape, a motor fixed in the housing, a speed reduction mechanism connected to a drive shaft of the motor, and a base end portion for rotation of the output shaft of the speed reduction mechanism A cylindrical drive unit that is fitted to the output shaft so as to follow and is locked in the rotational direction and has a male screw formed on the outer peripheral portion on the distal end side, and a bottomed base portion having an inner cavity on the base end side It is cylindrical and has a female screw formed on the inner surface of the cavity, and an operating projection is provided on the surface of the bottom of the terminal. Further, the female screw of the hollow part is screwed with the male screw of the driving part, and the outer surface. Is a linear actuator comprising a linear operating part slidably in contact with the inner surface of the housing, wherein the drive part has a threaded part with the linear operating part with respect to the connecting part with the speed reduction mechanism part. It is formed in a small diameter and has a step on the boundary between the two. The step portion is provided with a drive projection that protrudes toward the linear actuation portion, and the base end portion of the linear actuation portion is provided with an actuation portion projection that projects toward the drive portion. A precision linear actuator characterized by The housing has a stepped portion therein, and a portion for accommodating the driving portion and the linear operating portion is formed with a small diameter, and a supporting flange portion is provided at a base end portion on the speed reduction mechanism portion side of the driving portion. The precision linear actuator according to claim 1, wherein the precision linear actuator is formed and locked by the stepped portion. 3. The precision linear actuator according to claim 1, wherein at least one guide pin protrudes from an outer periphery of the linear operation portion and is fitted in a guide groove provided on the inner surface of the housing. The tip of the speed-reduction mechanism part output shaft has a cross-shaped projection formed thereon, and is fitted into a cross-shaped recess provided inside the support flange of the drive part. The precision linear actuator described. 5. The precision linear actuator according to claim 1, wherein the motor, the speed reduction mechanism section, the drive section, and the linear operation section are linearly arranged along a central axis of the actuator. . The precision linear actuator according to claim 1, wherein an outer shape of the housing is cylindrical. The precision linear actuator according to any one of claims 1 to 6, wherein the speed reduction mechanism is a planetary gear mechanism including a sun gear and a plurality of planetary gears. The precision linear actuator according to any one of claims 1 to 7, wherein the motor is a stepping motor or a DC motor.

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