JP2008095790A - Linear actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent ON-timing of a switch from being advanced or delayed. <P>SOLUTION: The linear actuator 10 comprises a shaft 16 rotated by driving force of a motor 30; a nut 19 linearly moved by rotation of the shaft 16; a movable cylinder 12 connected with the nut 19; and a pair of limit switches 65 and 65 for detecting a stroke end of the movable cylinder 12. A striker 72 is slidably laid over a guide 70 laid in parallel to the moving direction of the nut 19, a protruding portion 75 of a projection part 74 of the nut 19 is linked with a recessed part 73 of the striker 72, and the striker 72 is linked with detecting elements 66 and 66 of the limit switches 65 and 65. Since the striker is moved in parallel to the limit switches, the striker can turn ON the switches at a fixed time even if the movable cylinder precesses. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a linear actuator, and more particularly to an electric feed screw type linear actuator, and is effective for use in, for example, raising or lowering a bed of a medical / care bed or tilting a bed of a back or knee. About things.

  In medical / nursing care beds, the bed of the bed is moved up and down and the bed of the back and knees is tilted with an electric feed screw linear actuator to reduce the burden of sleeping on the patient. ing.

  As a linear actuator used in a medical / nursing care bed, a shaft having a male screw part, a worm gear reduction device that transmits the rotation of the motor to the shaft at a reduced speed, and a shaft rotating by screwing into the male screw part of the shaft It is equipped with a female screw member (feed nut) that moves forward and backward by the movement and a moving cylinder that is connected to the female screw member and moves forward and backward with respect to the housing, and is a link that moves the bed bed up and down and tilts the bed bed and knee bed Some of the movable cylinders are configured to be coupled by a coupling tool.

This type of conventional linear actuator is equipped with a limit switch that detects the stroke end of the moving cylinder, and the motor operation is automatically stopped by detecting the stroke end of the moving cylinder with the limit switch. (For example, refer to Patent Document 1).
JP 2004-218720 A

  However, in the above-described linear actuator, when the shaft rotates, a sawtooth motion occurs, and this scratch motion causes a phenomenon that the female screw member moves while swinging up and down and left and right together with the shaft. In this case, when the female screw member pushes the limit switch, the position of the female screw member approaches or is far from the limit switch, and the timing at which the limit switch is turned on becomes earlier or later. there were.

  An object of the present invention is to provide a linear actuator that can prevent the timing at which a limit switch is turned on from being advanced or delayed.

Representative inventions disclosed in the present application are as follows.
(1) In a linear actuator including a shaft that is rotated by a driving force of a motor, a moving body that linearly moves in response to the rotation of the shaft, and a switch that detects a stroke end of the moving body,
A linear actuator characterized in that a striker provided so as to be movable in parallel with a moving direction of the moving body is linked to the moving body and linked to the switch.
(2) The linear actuator according to (1), wherein the striker is slidably supported by a guide laid parallel to the moving direction of the moving body.
(3) The striker and the movable body are linked by a concave portion and a convex portion arranged in a direction orthogonal to the moving direction of the movable body. Linear actuator.

  According to the present invention, since the striker moves in parallel with respect to the switch, the striker can turn on the switch at a constant timing even if the moving body performs a sliding motion.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the linear actuator according to the present embodiment is configured to raise and lower the bed on the back of a medical / care bed (hereinafter referred to as a bed).
That is, as shown in FIG. 2, the linear actuator 10 includes a housing 11 and a moving cylinder 12 as a moving body that moves forward and backward with respect to the housing 11, and the housing 11 that is a fixed end side of the linear actuator 10. Is pivotally supported on the frame 2 of the bed 1 by a pivot 3 so that the tip of the movable cylinder 12 which is the free end of the linear actuator 10 is a link 5 for raising and lowering a sleeping bed 4 (hereinafter referred to as a sleeping bed). Are pivotally connected to each other by a pivot 6.
As shown in FIG. 1A, the bed 4 is lying down horizontally with the moving cylinder 12 of the linear actuator 10 shortened, and when the moving cylinder 12 of the linear actuator 10 is extended, the bed 4 is As shown in FIG. 1B, the robot stands up.

As shown in FIG. 2, the housing 11 of the linear actuator 10 is formed in a substantially cylindrical shape using resin, and a round pipe is provided at one end portion (hereinafter referred to as a tip portion) of the housing 11. One end of the support cylinder 13 formed in a shape is integrally formed.
A pair of anti-rotation portions 14 for preventing the female screw member from rotating are laid on the inner peripheral surface of the support cylinder 13 over substantially the entire length. Both anti-rotation parts 14 and 14 are formed in a key groove shape extending in the axial direction to a constant width and constant height (see FIG. 5).
A plug 15 is fitted into the front end opening of the support cylinder 13.

A shaft 16 is mounted on the cylindrical center of the support cylinder 13. A male screw portion 17 for feeding is formed on the outer periphery of the region corresponding to the support tube 13 of the shaft 16, and a nut 19 as a female screw member into which the female screw portion 18 is screwed is attached to the male screw portion 17 so as to be able to advance and retract. Has been.
A pair of anti-rotation portions 20 formed in a key shape are formed on the outer peripheral portion of the base end portion of the nut 19, and the anti-rotation portions 20, 20 are pivoted on the anti-rotation portions 14, 14 of the support cylinder 13. It is slidably fitted in the direction (see FIG. 5).
Accordingly, the nut 19 is configured to slide in the axial direction in a state in which the nut 19 is prevented from being rotated around the support cylinder 13 by the rotation preventing portions 14 and 20.

A slider 21 is slidably fitted to one side of the outer periphery of the shaft 16 on the front end side of the nut 19, and the base end surface of the slider 21 is able to abut on the front end surface of the nut 19. That is, the slider 21 follows in principle in accordance with the advancement and retraction of the nut 19.
An annular groove 22 is formed in the outer peripheral portion of the base end portion of the slider 21, and a pin 23 fixed to the movable cylinder 12 is inserted into the annular groove 22.
A base end portion of the movable cylinder 12 formed in a round pipe shape longer than the support cylinder 13 is fitted into the outer periphery of the distal end portion of the nut 19 so as to be freely inserted and removed, and the movable cylinder 12 is inserted into the annular groove 22. The pin 23 is connected to the slider 21.
The distal end portion of the moving cylinder 12 protrudes forward from a plug 15 fitted to the support cylinder 13, and the intermediate portion of the moving cylinder 12 is slidably supported by the plug 15.
A guide ring 24 is fitted to the tip of the shaft 16, and the outer periphery of the guide ring 24 slides on the inner peripheral surface of the movable cylinder 12 in the axial direction.

As shown in FIG. 1, a pair of mounting holes 25 are opened at the tip of the movable cylinder 12 so as to face each other. A connecting tool 26 for connecting the moving cylinder 12 to the link 5 of the bed 1 is fitted in the opening of the moving cylinder 12. A through hole 27 is formed at the distal end of the connector 26 so as to be aligned with both the mounting holes 25 and 25.
The movable cylinder 12 is connected to the link 5 by inserting the pivot 6 into both the mounting holes 25, 25 and the through hole 27.

As shown in FIG. 2, a motor 30 is attached to the base end portion of the housing 11 at a right angle. A rotation shaft 31 of the motor 30 is inserted into the housing 11 so as to be orthogonal to the shaft 16, and a worm 32 is formed at the tip of the rotation shaft 31.
A worm wheel 33 is fitted to a portion of the shaft 16 intersecting with the worm 32 so as to rotate integrally, and the worm wheel 33 is engaged with the worm wheel 33.
A rolling bearing 34 is installed in a portion of the housing 11 adjacent to the worm wheel 33 of the shaft 16, and the rolling bearing 34 supports the shaft 16 rotatably.
A one-way clutch 35 is installed in a portion of the housing 11 adjacent to the rolling bearing 34. The one-way clutch 35 is configured to function as a one-way clutch.

As shown in FIG. 1 and FIGS. 3 to 5, a switch assembly installation tube 40 having a rectangular tube shape with a rectangular cross section is integrally formed on a part of the outer periphery of the support tube 13 over the entire length. The switch assembly installation chamber 41 is formed by the hollow portion of the switch assembly installation cylinder 40.
As shown in FIG. 4, a cap 42 covers the switch assembly installation cylinder 40 so as to close the switch assembly installation chamber 41. The cap 42 has a through hole 44 into which the attachment length adjusting bolt 43 is inserted and a through hole 46 into which the stroke adjusting bolt 45 is inserted.
A cap 47 that covers the attachment length adjusting bolt 43 and the stroke adjusting bolt 45 is detachably attached to the cap 42.

A switch assembly 50 shown in FIG. 6 is accommodated in the switch assembly installation chamber 41 so as to be slidable in the longitudinal direction.
The switch assembly 50 includes a holder 51 made of a steel plate or the like and formed in an elongated cylindrical shape having a substantially square cross section. The holder 51 is formed in substantially the same shape as the switch assembly installation chamber 41, and can slide in the longitudinal direction while being accommodated in the switch assembly installation chamber 41.
In the holder 51, one side wall and one end face wall are opened.
The closed wall 52 of the holder 51 has a female screw hole 53 into which the attachment length adjusting bolt 43 is screwed and a through hole 54 into which the stroke adjusting bolt 45 is inserted (see FIG. 4).
A pair of guide rails 56, 56 are laid on the pair of side walls 55, 55 facing each other.

In the holder 51, a pair of switch units 60 shown in FIG. 7 are disposed on the proximal end side and the distal end side, respectively. The pair of switch units 60, 60 are slid in the longitudinal direction by both guide rails 56, 56. It is supported freely.
The proximal-side switch unit (hereinafter referred to as the proximal-side switch unit 60A when necessary to be distinguished) and the distal-side switch unit (also referred to as the distal-side switch unit 60B) are symmetrical. Arranged in shape.

Here, the configuration of the switch unit will be described with reference to FIG.
As shown in FIG. 7, the switch unit 60 includes a switch stay 61, and the switch stay 61 is formed in a generally rectangular boat shape that is narrower than the width of the holder 51. A pair of terminals 62 and 62 and a diode 63 are mounted on one main surface (hereinafter referred to as an upper surface) of the switch stay 61, and a plurality of lead wires 64 are laid.
A limit switch 65 is disposed and fixed on the lower surface of the switch stay 61 so that the detector 66 faces downward. A lead wire 64 is electrically connected to the limit switch 65.

As shown in FIG. 3, the proximal end side switch unit 60 </ b> A disposed at the proximal end portion of the holder 51 is electrically connected to the coupler 68 by the lead wire 67 and is positioned in the holder 51. It has become.
As shown in FIG. 4, a female screw hole 69 into which a stroke adjusting bolt 45 is screwed into a side wall facing the closing wall 52 of the holder 51 of the distal end side switch unit 60 </ b> B disposed at the distal end portion of the holder 51. Has been established.

As shown in FIGS. 3 to 5, a guide 70 is laid under the switch assembly 50 in parallel with the switch assembly 50. The guide 70 is formed in an elongated frame shape having a length substantially equal to that of the holder 51, and a pair of guide rails 71 and 71 are formed on the inner side surfaces of the long sides facing each other.
As shown in FIG. 3 and FIG. 4, a striker 72 is slidably extended in the longitudinal direction between the guide rails 71, 71, and the striker 72 is a pair installed on the switch assembly 50. Both limit switches 65 and 65 are turned on by contacting the detectors 66 and 66 of the limit switches 65 and 65, respectively.
The striker 72 has a recess 73.
On the other hand, a protruding portion 74 protrudes radially outward from a part of the outer periphery of the nut 19, and a protruding portion 75 protrudes on the surface of the protruding portion 74 facing the striker 72 side. The convex portion 75 of the nut 19 is inserted into the concave portion 73 of the striker 72 so as to be displaceable in a direction approaching and separating from the limit switch 65.

  Next, functions and effects will be described.

As shown in FIGS. 3 to 5 in advance, the switch assembly 50 is installed in the switch assembly installation chamber 41, and the proximal switch unit 60A and the distal switch unit for defining the stroke of the movable cylinder 12 are provided. The distance from 60B is adjusted by the stroke adjusting bolt 45.
That is, by rotating the stroke adjusting bolt 45 screwed into the female screw hole 69 of the distal end side switch unit 60B and moving the distal end side switch unit 60B along the guide rail 56 of the switch assembly 50, the proximal end side switch The distance between the unit 60A and the front end side switch unit 60B is adjusted to a preset dimension.

The linear actuator 10 is assembled to the bed 1 as shown in FIG.
That is, when the pivot 3 is inserted into the frame 2 of the bed 1 and is inserted into the housing 11 of the linear actuator 10, the linear actuator 10 is pivotally supported by the pivot 3 on the frame 2 of the bed 1. By inserting the pivot 6 of the link 5 on the side into the mounting hole 25 on the movable cylinder 12 side of the linear actuator 10 and the through hole 27 of the connector 26, the linear actuator 10 is rotatably connected to the bed 4 by the pivot 6. The

At this time, when the mounting position of the movable cylinder 12 with respect to the link 5 varies, the mounting length of the switch assembly 50 that defines the zero point of the movable cylinder 12 is adjusted by the mounting length adjusting bolt 43.
That is, by rotating the mounting length adjusting bolt 43 screwed into the female screw hole 53 of the switch assembly 50 and moving the switch assembly 50 forward and backward along the inner peripheral surface of the switch assembly installation chamber 41, The position with respect to the switch assembly installation chamber 41 is adjusted.
Note that, after the adjustment, the attachment length adjusting bolt 43 and the stroke adjusting bolt 45 are covered with the cap 47, whereby an erroneous operation can be prevented.

After the linear actuator 10 is assembled to the bed 1, the operator presses the operation button on the forward rotation side to stand the bed 4 and the motor 30 is rotated in the forward direction from the state of FIG. Then, the driving force of the rotating shaft 31 is transmitted to the shaft 16 via the worm 32 and the worm wheel 33.
When the shaft 16 is rotated forward by the motor 30, the nut 19 is advanced along the support cylinder 13, so that the movable cylinder 12 connected to the nut 19 is pushed out of the support cylinder 13.
As the moving cylinder 12 moves forward, the bed 4 of the bed 1 connected to the connecting tool 26 of the moving cylinder 12 is raised.

As shown in FIGS. 3 and 5A, the striker 72 that has pushed the detector 66 of the limit switch 65 of the base end side switch unit 60 </ b> A when the bed 1 is lying down is recessed in the protruding portion 74 of the nut 19. 73 and the projection 75 are linked to each other, so that the detector 66 of the limit switch 65 is separated from the detector 66 by the spring of the limit switch 65 (not shown). The return operation is performed (see the imaginary line in FIG. 4).
By the return operation of the detector 66, the limit switch 65 is turned off, so that the motor 30 continues to rotate.

The nut 19 moves along the shaft 16, and the striker 72 linked to the protruding portion 74 of the nut 19 comes into contact with the detector 66 of the limit switch 65 of the distal end side switch unit 60B protruding when the bed 1 is lying down. When pushed in, the limit switch 65 of the front end side switch unit 60B is turned ON, so that the motor 30 automatically stops.
At this time, even if the sawtooth motion is applied to the shaft 16 and the protrusion 74 of the nut 19 moves up and down, left and right, the striker 72 is guided by the guide rails 71 and 71 to move in parallel, Since the striker 72 is not affected by the movement, the striker 72 can always contact the detector 66 of the limit switch 65 of the distal end side switch unit 60B in a constant state. Therefore, the limit switch 65 of the distal end side switch unit 60B is always turned on under certain conditions.

Thereafter, when the operator presses the operation button on the reverse rotation side to lie down on the bed 4 and the motor 30 is rotated in the reverse direction, the reverse rotation driving force of the rotary shaft 31 causes the worm 32 and the worm wheel 33 to move. Via the shaft 16.
When the shaft 16 is reversely rotated by the motor 30, the nut 19 is retracted along the support cylinder 13, so that the movable cylinder 12 connected to the nut 19 is drawn into the support cylinder 13.
As the moving cylinder 12 moves backward, the bed 4 of the bed 1 connected to the connecting tool 26 of the moving cylinder 12 is brought down.

As described above, the striker 72 that has pushed the detector 66 of the limit switch 65 of the distal end side switch unit 60B when the bed 1 stands up is linked to the protrusion 74 of the nut 19 by the recess 73 and the protrusion 75. Thus, the nut 66 moves away from the detector 66 of the limit switch 65 with the start of the retraction of the nut 19, so that the detector 66 is restored by a spring (not shown) of the limit switch 65 (see the imaginary line in FIG. 4).
By the return operation of the detector 66, the limit switch 65 is turned off, so that the motor 30 continues to rotate.

The nut 19 moves backward along the shaft 16, and the striker 72 linked to the protruding portion 74 of the nut 19 contacts the detector 66 of the limit switch 65 of the proximal-side switch unit 60 </ b> A protruding when the bed 1 stands. Then, since the limit switch 65 of the base end side switch unit 60A is turned on, the motor 30 is automatically stopped.
At this time, even if the sawtooth motion is applied to the shaft 16 and the protrusion 74 of the nut 19 moves up and down, left and right, the striker 72 is guided by the guide rails 71 and 71 to move in parallel, Since the striker 72 is not affected by the movement, the striker 72 can always contact the detector 66 of the limit switch 65 of the proximal end side switch unit 60A in a fixed state. Accordingly, the limit switch 65 of the base end side switch unit 60A is always turned on under a certain condition.

  When the operation of the motor 30 is stopped, the load (the patient's weight and the like) of the bed 4 of the bed 1 is mechanically supported by the frame 2 of the bed 1.

  Needless to say, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

  For example, the switch is not limited to a limit switch, and a proximity switch or the like may be used.

It is a front view which shows the principal part of the bed for medical care which used the linear actuator which is one embodiment of this invention, (a) has shown the lying state, (b) has shown the standing state. It is a plane sectional view showing a linear actuator which is one embodiment of the present invention. It is front sectional drawing which shows the base end part of a switch assembly installation cylinder. It is front sectional drawing which similarly shows a front-end | tip part. (A) is sectional drawing which follows the aa line of FIG. 3, (b) is sectional drawing which follows the bb line of FIG. The switch assembly is shown, (a) is sectional drawing which follows the aa line of (b), (b) is front sectional drawing. The switch unit is shown, (a) is a top view, (b) is a front view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Bed (medical / care bed), 2 ... Frame, 3 ... Pivot, 4 ... Bed, 5 ... Link, 6 ... Pivot, 10 ... Linear actuator, 11 ... Housing, 12 ... Moving cylinder, 13 ... Supporting cylinder, DESCRIPTION OF SYMBOLS 14 ... Anti-rotation part, 15 ... Plug, 16 ... Shaft, 17 ... Male screw part, 18 ... Female screw part, 19 ... Nut (female screw member), 20 ... Non-rotation part, 21 ... Slider, 22 ... Annular groove, 23 ... Pin 24 ... Guide ring, 25 ... Mounting hole, 26 ... Connector, 27 ... Through hole.
DESCRIPTION OF SYMBOLS 30 ... Motor, 31 ... Rotary shaft, 32 ... Worm, 33 ... Worm wheel, 34 ... Rolling bearing, 35 ... One-way clutch.
DESCRIPTION OF SYMBOLS 40 ... Switch assembly installation cylinder, 41 ... Switch assembly installation chamber, 42 ... Cap, 43 ... Installation length adjustment bolt, 44 ... Through-hole, 45 ... Stroke adjustment bolt, 46 ... Through-hole, 47 ... Cap
DESCRIPTION OF SYMBOLS 50 ... Switch assembly, 51 ... Holder, 52 ... Closure wall, 53 ... Female screw hole, 54 ... Through-hole, 55 ... Side wall, 56 ... Guide rail.
60 ... Switch unit, 60A ... Base end side switch unit, 60B ... Front end side switch unit, 61 ... Switch stay, 62 ... Terminal, 63 ... Diode, 64 ... Lead wire, 65 ... Limit switch (switch), 66 ... Detector , 67 ... lead wire, 68 ... coupler, 69 ... female screw hole.
70 ... guide, 71 ... guide rail, 72 ... striker, 73 ... concave, 74 ... projection, 75 ... convex.

Claims (3)

In a linear actuator comprising a shaft that is rotated by a driving force of a motor, a moving body that linearly moves in response to the rotation of the shaft, and a switch that detects a stroke end of the moving body,
A linear actuator characterized in that a striker provided so as to be movable in parallel with a moving direction of the moving body is linked to the moving body and linked to the switch.   2. The linear actuator according to claim 1, wherein the striker is slidably supported by a guide laid parallel to a moving direction of the moving body.   The linear actuator according to claim 1, wherein the striker and the moving body are linked by a concave portion and a convex portion that are arranged in a direction orthogonal to a moving direction of the moving body.

Images