JP2011120331A - Linear actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear actuator that can flexibly cope with different specifications and also is superior in assembability, reliability, and layout properties while suppressing an increase of cost. <P>SOLUTION: The linear actuator performs ON and OFF of micro switches 11 and 12, which detect the position of a piston 9 by the sliding action of a slider 15. When a screw nut 8 shifts in the directions of each stop position L and U, accompanying the rotation of a motor 2, a striker 25 abuts on respective abutments 23 and 24 of the slider 15, and the slider 15 shifts in the directions of respective stop positions L and U together with the striker 25. The micro switches 11 and 12 are fixed to the slider 15, and when the screw nut 8 comes into each stop position L and U, switch buttons 11a and 12a abut on the slants 14a and 14b of a switch projection 14, and each micro switch 11 and 12 works and the motor 2 stops. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electric linear actuator that is used, for example, in an operation part of a medical / nursing care bed, and more particularly to an operation structure of a microswitch that regulates an operation range of the actuator.

  2. Description of the Related Art Conventionally, in the medical / nursing care field, an electric bed that moves the bed up and down, reclines, and the like with an electric actuator has been widely used in order to reduce the burden on the patient and caregiver. As such an electric bed actuator, a feed screw type linear actuator is often used in which a shaft provided with a male screw portion is driven to rotate by an electric motor and a female screw member screwed to the shaft is driven along the shaft. ing.

  The feed screw type linear actuator includes a shaft having a male screw portion and a worm gear reduction device that transmits the rotation of the motor at a reduced speed to the shaft. A female screw member (feeding nut) that is screwed into the male screw portion and moves by the rotation of the shaft is attached to the shaft. A moving cylinder is connected to the female screw member, and the moving cylinder moves together with the female screw member. A link for moving the bed up and down and tilting the back and knees of the bed is connected to the moving cylinder via a coupling tool. When the motor rotates, the shaft is decelerated and rotates, and the moving cylinder moves as the shaft rotates. When the moving cylinder moves forward and backward with respect to the actuator case, the bed is moved up and down, reclining, and the like by a link mechanism connected to the moving cylinder.

  On the other hand, in this type of linear actuator, a limit switch (microswitch) is used to detect the stroke end of the moving cylinder. For example, Patent Document 1 describes a configuration in which the operation of a motor is automatically stopped by detecting a stroke end of a moving cylinder with a limit switch.

  Also, a linear actuator provided with a striker for operating a limit switch has been proposed in order to ensure the stop position accuracy of the actuator (for example, Patent Document 2). FIG. 5 is an explanatory diagram showing a configuration of a linear actuator provided with a striker. The linear actuator 50 shown in FIG. 5 includes a motor 51 that is a driving source and a motor unit 53 in which a speed reduction mechanism 52 is accommodated, and a limit switch unit 55 in which a limit switch 54 is disposed. The limit switches 54 a and 54 b are installed at the upper and lower limit positions of the actuator stroke in the limit switch unit 55.

  In the limit switch unit 55, an elongated board 56 corresponding to the stroke is provided, and lower limit and upper limit limit switches 54a and 54b are arranged on the elongated board. The limit switches 54 a and 54 b on the substrate are configured as a unit together with other circuit elements, and are arranged around the piston (movable cylinder) 58 in the case 57. The piston 58 is fixed to a screw nut 60 that is screwed onto the shaft 59. The shaft 59 is rotationally driven by the motor 51, and the piston 58 moves in the axial direction together with the screw nut 60 as the shaft 59 rotates. A striker 62 is also attached to the screw nut 60 via a spring 61. The striker 62 contacts the limit switches 54 a and 54 b at the movement limit position of the linear actuator 50. Then, when the striker 62 pushes the buttons of the limit switches 54a and 54b, the actuator stops at a predetermined movement limit.

JP 2004-218720 A JP 2008-95790 A JP 2008-95791 A

  However, in such a linear actuator, a variety of limit switch units are required due to differences in actuator specifications (stroke length). Therefore, it is necessary to use new boards and other parts for each specification, increasing the number of parts. However, there has been a problem of increasing the product cost. In addition, since the substrate attached to the limit switch unit is narrow and narrow, the substrate is likely to be deformed, which causes a problem of reducing the reliability of the actuator. In this case, the elongated board has poor solder workability and is difficult to manufacture with a mold, which causes a cost increase and requires a holder for holding the long board in the case, so the number of parts increases. There was also a problem of doing. Furthermore, it is necessary to arrange a board, a limit switch, a striker, and the like in the case, and there is a problem that a part for accommodating these components protrudes from the apparatus, the apparatus becomes large, and the layout is not good.

  In addition, in the apparatus as shown in FIG. 5, the work of attaching the striker 62 to the screw nut 60 is a work of interposing the spring 61 between the two, so that the workability is poor and the structure of the apparatus is complicated. It was.

  An object of the present invention is to provide a linear actuator that can flexibly cope with actuators having different specifications and is excellent in assembling property, reliability, and layout property while suppressing an increase in cost.

  The linear actuator of the present invention detects a shaft that is rotated by the driving force of a motor, a moving body that moves linearly in response to the rotation of the shaft, and a state in which the moving body is positioned at a moving end on one side. A striker that moves together with the movable body, and a striker that moves with the movable body, and a striker that moves with the movable body. And a slider for operating the first or second switch by moving the movable body to a predetermined position.

  In the present invention, a slider that moves in conjunction with a striker that moves with the moving body is provided, and a switch that detects the position of the moving body is turned ON / OFF by the movement of the slider. When the moving body moves in the vicinity of each moving end with the rotation of the shaft, the striker and the slider cooperate, and when the moving body comes to each moving end, the first or second switch is moved by the operation of the slider. Operates selectively. Thereby, the stop position of the actuator can be controlled with high accuracy while having a simple structure, and the assembling work is also simplified.

  In the linear actuator, the first and second switches are attached to the slider and moved together with the slider, and the striker and the slider are brought into contact with each other in the vicinity of each moving end as the movable body moves. After the striker comes into contact, the slider and the striker are moved together so that only the first switch is operated when the moving body reaches the moving end on one side, and the moving body moves on the other side. Only the second switch may be operated when it reaches the end.

  The Lini actuator is further provided with a switch pressing means that abuts on a switch button provided on each of the first and second switches and selectively turns on or off the first or second switch, and the switch pressing means However, when the moving body comes to the moving end on one side, it contacts the switch button of the first switch, and when the moving body comes to the moving end on the other side, the switch button of the second switch You may make it contact | abut.

  The linear actuator includes a case in which the shaft is accommodated and a frame connected to the case and in which the first and second switches are accommodated, and the slider is disposed in the case and the movable body. The switch pressing means may be installed in the frame so as to face each of the switch buttons.

  Further, the switch pressing means has a first contact slope that contacts the switch button of the first switch when the moving body reaches the moving end on one side, and the moving body on the moving end on the other side. You may provide the 2nd contact slope which contact | abuts to the said switch button of a said 2nd switch when it comes.

  In addition, the slider is provided with a striker moving groove in which the striker is accommodated and the striker can move along the moving direction of the moving body, and the moving body is provided on one side of the striker moving groove. A first contact portion that contacts the striker when positioned near the moving end, and a second contact portion that contacts the striker when the moving body is positioned near the moving end on the other side; The striker moving toward each moving end may move in the direction of each moving end together with the slider after contacting the first or second contact portion.

  According to the Lini actuator of the present invention, the Lini actuator includes a shaft that is rotated by the driving force of the motor, a moving body that linearly moves in response to the rotation of the shaft, and a switch that detects the position of the moving body. In addition to providing a striker that moves with the moving body, and a slider that moves in conjunction with the striker, the slider is turned on and off by the operation of this slider. The position can be controlled with high accuracy. In addition, the simple device structure simplifies the assembly work, reduces the cause of failure, and improves the reliability of the device. Furthermore, if a striker is set according to the stroke of the actuator, the specification can be easily changed, and it is not necessary to design and manufacture a new part for each specification, thereby reducing the product cost.

It is explanatory drawing which shows the structure of the linear actuator which is one Example of this invention. It is sectional drawing along the AA line of the linear actuator of FIG. 5 is an explanatory diagram showing a state of the linear actuator at a lower limit stop position L. FIG. 5 is an explanatory diagram showing a state of the linear actuator at an upper limit stop position U. FIG. It is explanatory drawing which shows the structure of the conventional linear actuator provided with the striker.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing a configuration of a linear actuator 1 according to an embodiment of the present invention. The linear actuator 1 of the present embodiment is used as a drive source for raising and lowering a back mat of a medical / nursing bed, for example. The linear actuator 1 includes a motor unit 4 in which a motor 2 as a driving source and a speed reduction mechanism unit 3 are accommodated. A body frame 5 is attached to the motor unit 4. A case 6 is attached to the main body frame 5. In the case 6, a screw shaft 7 connected to the speed reduction mechanism unit 3 and a screw nut 8 screwed onto the screw shaft 7 are accommodated.

  A piston (moving body) 9 is attached to the screw nut 8. The piston 9 is movable in the axial direction (left-right direction in FIG. 1) with respect to the case 6. When the screw shaft 7 is rotationally driven by the motor 2, the piston 9 moves in the axial direction together with the screw nut 8 and advances and retreats on the right end side of the case 6. In the linear actuator 1, the case 6 and the main body frame 5 on the fixed end side are swingably attached to a bed frame (not shown). On the other hand, the tip of the piston 9 which is the free end side is connected to a link mechanism (not shown) for raising and lowering the mat on the back of the bed. When the piston 9 of the linear actuator 1 is in a shortened state, the mat is lying down horizontally, and when the piston 9 extends, the mat gradually rises.

  The linear actuator 1 is provided with microswitches 11 and 12 for detecting and regulating the forward / backward position of the piston 9 in order to limit the lying / standing position of the mat. The micro switch 11 is a switch for stopping the piston 9 at the left movement limit position (position where the mat is in a horizontal state: hereinafter referred to as a lower limit stop position L). Is a switch for stopping at a movement limit position on the right side of the drawing (a position where the mat is in an upright state: hereinafter referred to as an upper limit stop position U). The microswitches 11 and 12 are mounted on a printed circuit board 13 disposed in the main body frame 5.

  In the micro switches 11 and 12, switches having the same specifications are arranged in parallel in opposite directions, and the switch buttons 11a and 12a of the micro switches 11 and 12 sandwich the central axis Os of the screw shaft 7 as shown in FIG. Are arranged symmetrically. The switch buttons 11a and 12a are also arranged symmetrically with respect to the center M of the microswitches 11 and 12 (see FIG. 3). That is, the switch button 11a is arranged at a position shifted by a distance S toward the lower limit stop position L with respect to the center M, while the switch button 12a is also moved by a distance S toward the upper limit stop position U with respect to the center M. Arranged at the shifted position.

  A switch protrusion (switch pressing means) 14 is provided above the switch buttons 11 a and 12 a in the main body frame 5. The microswitches 11 and 12 are turned on / off when the switch protrusion 14 contacts and separates from the switch buttons 11a and 12a. As shown in FIG. 1, the switch protrusion 14 is formed in a mountain shape having slopes on both sides. The slope 14a (first contact slope) on the lower limit stop position L side (left side in FIG. 1) of the switch protrusion 14 is in contact with the switch button 11a to turn on / off the lower limit stop microswitch 11. Similarly, the slope 14b (second contact slope) on the upper limit stop position U side (right side in FIG. 1) contacts the switch button 12a to turn the upper limit stop microswitch 12 ON / OFF.

  Thus, in the linear actuator 1, the micro switches 11 and 12 are centrally mounted on the printed circuit board 13, and the printed circuit board 13 can be installed in the main body frame 5. For this reason, the overhang of the case 6 can be minimized, the apparatus can be miniaturized, and the layout of the linear actuator can be improved. In addition, since the microswitches 11 and 12 are centrally arranged, the printed circuit boards 13 can be integrated into one type regardless of stroke variations, and the types of components can be reduced and the cost can be reduced. Further, since it is not necessary to use an elongated printed board as in the case of a conventional linear actuator, bending of the board is less likely to occur, solder workability is improved, and manufacturing with a mold is also possible. In addition, since a holder member for holding the printed circuit board in the case is not necessary, the assembling work is simplified and the production cost is reduced.

  In the linear actuator 1, these microswitches 11 and 12 are turned ON / OFF by a slider 15 that interlocks with the screw nut 8. As shown in FIG. 2, the slider 15 includes a switch base 16 and a slide plate 17 and is attached to a slider accommodating portion 18 provided in the case 6. On the switch base 16, a printed circuit board 13 on which the micro switches 11 and 12 are mounted is fixed. The slide plate 17 is integrated with the switch base 16 and has a flange portion 19 extending along the axial direction. On the other hand, a slider holding groove 21 is formed in the slider accommodating portion 18 along the axial direction. The flange portion 19 is slidably attached in the slider holding groove 21 along the axial direction.

  The slide plate 17 is also formed with a striker moving groove 22 extending along the axial direction. Both end portions of the striker moving groove 22 are closed by contact walls, the lower limit stop position L side end is the lower limit side contact portion 23, and the upper limit stop position U side end is the upper limit side. A contact portion 24 is provided. The striker moving groove 22 is open on the lower surface side in FIG. 1, and a striker 25 provided on the screw nut 8 is accommodated in the groove. When the screw shaft 7 is rotationally driven, the striker 25 moves in the striker moving groove 22 in the axial direction together with the screw nut 8.

  In the linear actuator 1 having such a slider 15, lower limit and upper limit stop position control is performed as follows. First, in the state of FIG. 1, the striker 25 is not in contact with any of the contact portions 23, 24, and the slider 15 is in a neutral state. At this time, the switch protrusion 14 is not in a state of pressing any of the switch buttons 11a and 12a, and the micro switches 11 and 12 are in the OFF state. In the linear actuator 1, when the screw nut 8 is at the intermediate position between the lower limit and the upper limit, the slider 15 surely returns to the neutral state. For this reason, there is no need to provide a return mechanism using a spring or the like to prevent the striker from holding the switch button at an intermediate position, the device structure is simplified, cost reduction and reliability Improvement is achieved. In this way, when the screw nut 8 is in the intermediate position, the power supply to the motor 2 is not cut off, and if the bed reclining switch is operated, the mat operates in both the lying down and standing directions.

  In the state of FIG. 1, for example, when the reclining switch is operated in the direction of lying down the mat, the screw nut 8 moves in the lower limit stop position L direction (left direction in FIG. 1; one side) as the motor 2 rotates. To do. When the screw nut 8 moves in the direction of the lower limit stop position L, the striker 25 also moves in the striker movement groove 22 in the same direction and contacts the lower limit side contact portion 23. In this state, when the screw nut 8 further moves in the direction of the lower limit stop position L, the striker 25 pushes the lower limit side contact portion 23 leftward, and the slider 15 moves leftward. As the slider 15 moves, the microswitches 11 and 12 on the slider 15 also move to the left, and the switch button 11a eventually contacts the slope 14a of the switch protrusion 14.

  Then, along with the movement of the screw nut 8, the switch button 11a is pushed in by the inclined surface 14a, and the micro switch 11 is turned on. As a result, the power supply to the motor 2 is interrupted, the rotation of the screw shaft 7 is stopped, the piston 9 is shortened, and the mat is in a horizontally lying state. In this state, the slope 14b of the switch protrusion 14 is away from the switch button 12a, and the microswitch 12 does not operate.

  On the other hand, in the state of FIG. 1, for example, when the reclining switch is operated in the direction of raising the mat, the screw nut 8 is moved in the upper limit stop position U direction (right direction in FIG. 1; the other side) as the motor 2 rotates. Move to. When the screw nut 8 moves in the upper limit stop position U direction, the striker 25 moves in the striker movement groove 22 in the upper limit stop position U direction and abuts on the upper limit side contact portion 24, contrary to the previous case. In this state, when the screw nut 8 further moves in the direction of the upper limit stop position U, the striker 25 pushes the upper limit side contact portion 24 to the right, and the slider 15 moves to the right. When the slider 15 is moved, the microswitches 11 and 12 on the slider 15 are also moved to the right, and the switch button 12a comes into contact with the inclined surface 14b of the switch protrusion 14 before long.

  Then, along with the movement of the screw nut 8, the switch button 12a is pushed in by the inclined surface 14b, and the micro switch 12 is turned on. As a result, the power supply to the motor 2 is interrupted, the rotation of the screw shaft 7 is stopped, the piston 9 is extended, and the mat is in an upright state. In this case as well, the switch button 11a is in a released state, and the micro switch 11 does not operate.

  As described above, in the linear actuator 1 according to the present invention, the microswitches 11 and 12 are turned on / off by the movement of the slider 15, so that the stop position of the actuator can be controlled with high accuracy while having a simple structure. . In particular, since the microswitches 11 and 12 and the switch protrusion 14 are installed on the main body frame 5 side, stable stop position accuracy can be ensured even if each dimensional tolerance is accumulated, and the stop position accuracy is improved. In addition, the simple device structure simplifies the assembly work, reduces the cause of failure, and improves the reliability of the device. Furthermore, if a striker is set according to the stroke of the actuator, the specification can be easily changed, and it is not necessary to design and manufacture a new part for each specification, thereby reducing the product cost.

  Since the switch buttons 11a and 12a of the microswitches 11 and 12 are pushed down from above by the inclined surfaces 14a and 14b of the switch projection 14, they are close to the operation method recommended by the switch manufacturer (ON / OFF from the vertical direction). A switch can be used, improving the reliability and durability of the device. Further, since it is not necessary to assemble a spring or the like to the striker, the assembling work is simplified, the cause of failure is reduced, and the reliability of the apparatus is improved.

It goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.
For example, in the above-described embodiment, the example in which the linear actuator of the present invention is used for the operating part of the medical / nursing bed has been shown. It can be widely applied to various machines and devices having

DESCRIPTION OF SYMBOLS 1 Linear actuator 2 Motor 3 Deceleration mechanism part 4 Motor unit 5 Main body frame 6 Case 7 Screw shaft 8 Screw nut 9 Piston 11 Micro switch (1st switch)
11a switch button 12 micro switch (second switch)
12a Switch button 13 Printed circuit board 14 Switch protrusion (switch pressing means)
14a Slope (first contact slope)
14b Slope (second contact slope)
15 Slider 16 Switch base 17 Slide plate 18 Slider receiving portion 19 Flange portion 21 Slider holding groove 22 Strike moving groove 23 Lower limit side contact portion 24 Upper limit side contact portion 25 Strike 50 Linear actuator 51 Motor 52 Deceleration mechanism portion 53 Motor unit 54 Limit switch 54a, 54b Limit switch 55 Limit switch unit 56 Substrate 57 Case 58 Piston 59 Shaft 60 Screw nut 61 Spring 62 Striker L Lower limit stop position U Upper limit stop position Os Center axis M Micro switch center S Micro switch center and switch button Distance between

Claims (6)

A shaft that is rotated by the driving force of the motor; a moving body that moves linearly in response to the rotation of the shaft; a first switch that detects a state in which the moving body is positioned at a moving end on one side; A second switch for detecting a state in which the moving body is located at the moving end on the other side,
A striker that moves with the moving body;
And a slider that moves in conjunction with the striker and activates the first or second switch by moving the movable body to a predetermined position. The Lini actuator according to claim 1, wherein
The first and second switches are attached to the slider and move with the slider;
The striker comes into contact with the slider in the vicinity of each moving end as the moving body moves,
The slider moves with the striker after the striker abuts, and when the moving body comes to the moving end on one side, only the first switch is operated, and the moving body moves to the moving end on the other side. Only the second switch is actuated when coming. The linear actuator according to claim 2, wherein
The Lini actuator further has a switch pressing means that abuts on a switch button provided in each of the first and second switches, and selectively turns on or off the first or second switch,
The switch pressing means abuts against the switch button of the first switch when the moving body comes to the one side moving end, and when the moving body comes to the other side moving end, the second switch A linear actuator that contacts the switch button. The linear actuator according to claim 3,
The linear actuator has a case in which the shaft is accommodated, and a frame that is connected to the case and accommodates the first and second switches,
The slider is slidably held in the case along the moving direction of the moving body,
The linear actuator according to claim 1, wherein the switch pressing means is installed in the frame so as to face the switch buttons. The linear actuator according to claim 3 or 4,
The switch pressing means includes a first contact slope that contacts the switch button of the first switch when the moving body comes to the moving end on one side, and the moving body comes to the moving end on the other side. And a second contact slope that contacts the switch button of the second switch. In the linear actuator according to any one of claims 1 to 4,
The slider has a striker moving groove in which the striker is accommodated and the striker is movable along a moving direction of the moving body,
The striker moving groove includes a first contact portion that contacts the striker when the moving body is positioned near one moving end, and the striker moving groove when the moving body is positioned near the moving end on the other side. A second abutting portion that abuts with
The linear actuator according to claim 1, wherein the striker moving toward each moving end moves in the direction of each moving end along with the slider after contacting the first or second contact portion.

Images