JP2009041698A - Linear actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear actuator with an accurate parallel movement and a long stroke while restraining cost increase. <P>SOLUTION: In the linear actuator, a lower mounting frame 11 and an upper mounting frame 21 are horizontally arranged facing each other, a lower screw shaft 30 and an upper screw shaft 40 are vertically supported on the lower mounting frame 11 and the upper mounting frame 21, a lower rotary shaft 51 and an upper rotary shaft 61 are rotatably supported on the lower mounting frame 11 and the upper mounting frame 21, a lower nut 55 screwed into the lower screw shaft 30 and an upper nut 65 screwed into the upper screw shaft 40 are respectively fixed on the lower rotary shaft 51 and the upper rotary shaft 61, and the lower rotary shaft 51 and the upper rotary shaft 61 are driven by a worm-wheel reduction gear at a forward and reverse rotation state. The lower mounting frame 11 and the upper mounting frame 21 are connected by a parallel ruler mechanism 12. Cost increase for the linear actuator can be restrained since a guide mechanism having sliding resistance can be saved. <P>COPYRIGHT: (C)2009,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 a knee. About things.

In the medical / nursing care bed, in order to reduce the burden of sleeping on the patient, the bed of the bed is moved up and down and the bed of the back and knees is inclined by an electric feed screw type linear actuator. .
In medical / nursing care beds, the lower the height, the easier it is to descend from the bed, and there is no risk of injury when falling from the bed. On the other side, the higher the height, the easier it is to give medical examinations and care.
Therefore, it is advantageous that the linear actuator used for the medical / care bed has a long stroke.

As a conventional linear actuator with a long stroke, a pair of movable bodies supported by a sliding guide mechanism and movable in opposite directions, and a pair of rotatably supported on the pair of movable bodies, respectively. There is provided a rotary shaft, one drive device that rotates both rotary shafts, and a pair of feed screw shaft devices that move the moving bodies in opposite directions by rotation of the rotary shafts. . (For example, refer to Patent Document 1).
JP 2007-92879 A

In the above-described linear actuator, in order to ensure the parallel movement of the moving body that receives an uneven load of the bed, it is necessary to minimize the clearance of the guide mechanism that guides the movement of the moving body by sliding.
If the processing accuracy and assembly accuracy of the guide mechanism parts are strictly set to meet the requirement, the initial cost will increase.
On the other hand, if the driving force of the driving device of the guide mechanism is set to be high in order to overcome the sliding resistance, the power consumption increases and the initial cost and running cost increase.

  An object of the present invention is to provide a linear actuator having a highly accurate parallel movement and a long stroke while suppressing an increase in cost.

Typical means for solving the above-described problems are as follows.
(1) A pair of movable bodies movable in opposite directions, a pair of rotary shafts rotatably supported by the pair of movable bodies, a drive device that rotates the rotary shafts, and the rotary shafts A linear actuator comprising: a pair of feed screw shaft devices that move the moving bodies in opposite directions by rotation of the moving body; and a parallel ruler mechanism that relatively translates the pair of moving bodies. .
(2) The linear actuator according to (1), wherein the parallel links of the parallel ruler mechanism are interlocked by a transmission mechanism so as to synchronize with each other.

According to the linear actuator described above, since the pair of moving bodies are configured to be moved in directions opposite to each other by the feed screw shaft device, a long stroke can be created.
Since the pair of moving bodies are coupled so as to move in parallel by a parallel ruler mechanism, it is possible to avoid the adverse effects caused by sliding friction.

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

As shown in FIG. 1, a linear actuator 10 according to the present embodiment is configured to move a bed of a medical / care bed (hereinafter referred to as a bed) 1 horizontally.
That is, as shown in FIG. 1, the linear actuator 10 includes a lower mounting frame 11 and an upper mounting frame 21 as a pair of movable bodies that are movable in opposite directions, and is shown in FIG. As shown, the lower mounting frame 11 that is the fixed end side of the linear actuator 10 is fixed to the frame 2 of the bed 1, and the upper mounting frame 21 that is the free end side of the linear actuator 10 is a bed (hereinafter referred to as a bed). ) 3.
As shown in FIG. 1 (a), with the linear actuator 10 shortened, the bed 3 is lowered horizontally to the lower limit position, and as shown in FIG. 1 (b), the linear actuator When 10 is extended, the bed 3 is raised horizontally.
Moreover, the bed 3 can be inclined by moving the pair of linear actuators 10 and 10 individually.

As shown in FIGS. 2 to 7, the lower mounting frame 11 and the upper mounting frame 21 of the linear actuator 10 are both formed into a frame shape having a substantially rectangular shape in plan view and an opening on one main surface. The opening surfaces are arranged horizontally so as to face each other.
The lower mounting frame 11 and the upper mounting frame 21 are connected by a parallel rule mechanism 12 so as to move while maintaining horizontal.
That is, the base end portion of the pair of lower links 13 and 13 is rotatably supported by the pins 14 and 14 on the lower mounting frame 11 which is one of the pieces having parallel edges, and in parallel. On the upper mounting frame 21, which is the other of the pieces having edges, the base end portions of the pair of upper links 23, 23 are rotatably supported by the pins 24, 24, respectively, and the pair of lower links 13, The free ends of 13 and the free ends of the pair of upper links 23 and 23 are rotatably connected by pins 15 and 15, respectively.
One lower link 13 and the opposite upper link 23 form parallel links, and the pair of lower links 13 and 13 and the pair of upper links 23 and 23 are set to the same length. ing.
The pair of lower links 13 and 13 are formed in a channel steel shape, and are arranged symmetrically so that the opening sides face each other. The pair of upper links 23, 23 are formed in a channel-type steel shape smaller than the lower link 13, and are arranged symmetrically so that the closed sides face each other.

A pair of fan gears 16, 16 are fixed to the base end portions of the pair of lower links 13, 13 so as to rotate around the pins 14, 14, respectively. Are meshed so as to be synchronized with each other.
A pair of fan gears 26, 26 are fixed to the base ends of the pair of upper links 23, 23 so as to rotate around the pins 24, 24, respectively. They are meshed so as to be synchronized with each other.

On the upper surface of the bottom wall of the lower mounting frame 11, a lower screw shaft 30 having a male screw portion 31 on the outer periphery is vertically erected and fixed by a support tool 32.
On the lower surface of the ceiling wall of the upper mounting frame 21, an upper screw shaft 40 having an external thread portion 41 on the outer periphery is suspended vertically and fixed by a support tool 42.

A housing 50 is disposed between the lower mounting frame 11 and the upper mounting frame 21.
As shown in FIG. 5, a lower rotary shaft 51 formed in a cylindrical shape is disposed on an extension line of the lower screw shaft 30 in the housing 50, and the lower rotary shaft 51 is disposed in the middle portion. It is rotatably supported by the arranged rolling bearing 52 and the sliding bearings 53 and 54 arranged at the upper end portion and the lower end portion, respectively.
A lower nut 55 is fitted on the inner periphery of the lower end of the lower rotary shaft 51 so as to rotate integrally. The lower nut 55 is screwed to the male screw portion 31 of the lower screw shaft 30 so as to be able to advance and retract. ing.
A lower worm wheel 56 is fitted at an upper adjacent position of the rolling bearing 52 on the outer periphery of the lower rotating shaft 51 and is fixed so as to rotate integrally.
On the extension line of the upper screw shaft 40 in the housing 50, an upper rotating shaft 61 formed in a cylindrical shape is disposed. The upper rotating shaft 61 includes a rolling bearing 62 disposed in an intermediate portion, an upper end portion, and a lower end portion. Are rotatably supported by sliding bearings 63 and 64, respectively.
An upper nut 65 is fitted on the inner periphery of the upper end of the upper rotating shaft 61 and is fixed so as to rotate integrally. The upper nut 65 is threadably engaged with the male screw portion 41 of the upper screw shaft 40 so as to advance and retract.
An upper worm wheel 66 is fitted at a position adjacent to the lower side of the rolling bearing 62 on the outer periphery of the upper rotating shaft 61 and is fixed so as to rotate integrally.

A motor 70 is horizontally installed in the housing 50, and the motor 70 is configured to drive a worm shaft 71 on which a worm 72 is formed to rotate forward and backward. The worm shaft 71 is inserted between the lower worm wheel 56 and the upper worm wheel 66, and the lower worm wheel 56 and the upper worm wheel 66 are engaged with the worm 72 from both sides, respectively.
That is, the motor 70, the worm shaft 71, the lower worm wheel 56, and the upper worm wheel 66 constitute one drive device that rotates the lower rotation shaft 51 and the upper rotation shaft 61 simultaneously in the forward and reverse directions.
The lower nut 55 that rotates integrally with the lower rotation shaft 51, the upper nut 65 that rotates integrally with the upper rotation shaft 61, the lower screw shaft 30, and the upper screw shaft 40 are lowered by the rotation of both the rotation shafts 51, 61. A pair of feed screw shaft devices are configured at the top and bottom to move the side mounting frame 11 and the upper mounting frame 21 in opposite directions.

A potentiometer 80 is installed upward in the housing 50, and a driven gear 82 is fixed to the sensor shaft 81 of the potentiometer 80. The driven gear 82 is meshed with a driving gear 83 fixed to the upper rotating shaft 61.
The potentiometer 80 is configured to measure the position of the upper mounting frame 21, that is, the height of the bed 3, by measuring the rotational speed of the upper rotating shaft 61 via the driven gear 82 and the driving gear 83.

  For convenience, although not shown, the linear actuator 10 is covered with a telescope structure.

  Next, functions and effects will be described.

  As shown in FIG. 1, two linear actuators 10 and 10 are horizontally disposed on the head side and the foot side of the bed 1, respectively, and the lower mounting frame 11 of both linear actuators 10 and 10 is a bed. The upper mounting frame 21 is connected to the bed 3 side.

  After the linear actuator 10 is assembled to the bed 1, the operator presses the operation button on the positive rotation side to raise the bed 3, so that the motor 70 is rotated in the forward direction from the state of FIG. Then, the driving force of the motor 70 is simultaneously transmitted to the lower worm wheel 56 and the upper worm wheel 66 by the worm 72 of the same worm shaft 71, and the lower rotating shaft 51 fixed to the lower worm wheel 56; Since the upper rotating shaft 61 fixed to the upper worm wheel 66 is simultaneously rotated in the forward direction, a lower nut 55 fixed to the lower rotating shaft 51 and an upper nut fixed to the upper rotating shaft 61 are provided. 65 are simultaneously rotated in the positive direction.

When the lower nut 55 and the upper nut 65 are simultaneously rotated in the forward direction, the lower nut 55 and the upper nut 65 are respectively screwed to the lower screw shaft 30 and the upper screw shaft 40 so as to advance and retract in the vertical direction. Therefore, the lower nut 55 is raised by the male screw portion 31 of the lower screw shaft 30, and the upper nut 65 is raised by the male screw portion 41 of the upper screw shaft 40.
When the lower nut 55 rises with respect to the lower screw shaft 30 and the upper nut 65 rises with respect to the upper screw shaft 40, the housing 50 in which the lower nut 55 and the upper nut 65 are installed becomes the lower nut. 55 and the upper nut 65 follow the rise. That is, the space between the lower mounting frame 11 and the upper mounting frame 21 increases.
At this time, since the lower mounting frame 11 and the upper mounting frame 21 are guided by the parallel ruler mechanism 12, they move in parallel. Moreover, since the parallel links 13 and 23, 13 and 23 of the parallel ruler mechanism 12 are synchronized by the fan gears 16 and 26, they move vertically without shifting in the lateral (horizontal) direction.
Since the lower mounting frame 11 is fixed to the frame 2 of the bed 1 and the upper mounting frame 21 is connected to the bed 3 of the bed 1, as shown in FIG. Goes up.

Here, since the rising stroke of the bed 3 at this time is the sum of the rising stroke of the lower nut 55 and the rising stroke of the upper nut 65, the linear actuator 10 according to the present embodiment can raise the bed 3 to the maximum. The stroke is the sum of the effective length of the lower screw shaft 30 and the effective length of the upper screw shaft 40.
That is, the maximum stroke of the linear actuator 10 according to the present embodiment is twice the maximum stroke of a normal linear actuator having one screw shaft.
In addition, because the drive unit is placed at the approximate center of each screw shaft, and the drive unit is not included in the total length of the linear actuator like a normal linear actuator, when setting the same maximum stroke, The total height when the linear actuator 10 according to the present embodiment is shortened is less than half of the total height of a normal linear actuator having one screw shaft.
For example, compared with a normal linear actuator, it becomes 1/2 and 1/4.

When the operation of the motor 70 is stopped, the load of the bed 3 of the bed 1 (the patient's weight, etc.) forces the lower screw shaft 30 and the upper screw shaft 40 to rotate the lower nut 55 and the upper nut 65 in the reverse direction. Therefore, a so-called load-side reverse rotation force is applied to the lower rotary shaft 51 to which the lower nut 55 is fixed and the upper rotary shaft 61 to which the upper nut 65 is fixed. .
In the present embodiment, since the lower rotary shaft 51 and the upper rotary shaft 61 are respectively fixed to the lower worm wheel 56 and the upper worm wheel 66 that mesh with the worm 72 of the worm shaft 71, the lower rotary shaft 51 and the upper rotary shaft 61 are not reversely rotated by the load-side reverse rotational force. This is because the lead of the rotating shaft and the friction coefficient are selected with a good balance.
Therefore, the linear actuator 10 can be supported with the load of the bed 3 being lifted.

Thereafter, when the operator presses the operation button on the reverse rotation side to lie down on the bed 3 and the motor 70 is rotated in the reverse direction, the driving force of the motor 70 is lowered by the worm 72 of the same worm shaft 71. The lower rotating shaft 51 fixed to the lower worm wheel 56 and the upper rotating shaft 61 fixed to the upper worm wheel 66 are simultaneously transmitted to the side worm wheel 56 and the upper worm wheel 66 simultaneously in the opposite directions. In order to rotate, the lower nut 55 fixed to the lower rotating shaft 51 and the upper nut 65 fixed to the upper rotating shaft 61 are simultaneously rotated in opposite directions.
This does not generate an axial force on the armature shaft of the motor, eliminates the need for a thrust bearing in the motor, and improves efficiency.

When the lower nut 55 and the upper nut 65 are simultaneously rotated in the opposite directions, the lower nut 55 and the upper nut 65 are respectively screwed to the lower screw shaft 30 and the upper screw shaft 40 so as to be able to advance and retract in the vertical direction. Therefore, the lower nut 55 is lowered by the male screw portion 31 of the lower screw shaft 30, and the upper nut 65 is lowered by the male screw portion 41 of the upper screw shaft 40.
When the lower nut 55 is lowered with respect to the lower screw shaft 30 and the upper nut 65 is lowered with respect to the upper screw shaft 40, the housing 50 in which the lower nut 55 and the upper nut 65 are installed becomes the lower nut. It follows that 55 and the upper nut 65 descend, and descends. That is, the interval between the lower mounting frame 11 and the upper mounting frame 21 is closed.
Since the lower mounting frame 11 is fixed to the frame 2 of the bed 1 and the upper mounting frame 21 is connected to the bed 3 of the bed 1, as shown in FIG. Goes down.

When the operation of the motor 70 is stopped, the load (the patient's weight and the like) of the bed 3 is mechanically supported by the frame 2 of the bed 1.
Even if the load-side reverse rotational force described above is applied to the lower rotary shaft 51 and the upper rotary shaft 61 while the bed 3 is lowered, the reverse rotation of the lower rotary shaft 51 and the upper rotary shaft 61 has been described above. It will be prevented by the action.

  According to the present embodiment, the following effects can be obtained.

(1) A lower mounting frame and an upper mounting frame that are relatively movable up and down, a pair of rotating shafts rotatably supported on the lower mounting frame and the upper mounting frame, and for rotating both the rotating shafts By providing a motor and a pair of feed screw shaft devices that move the lower mounting frame and the upper mounting frame relatively up and down by rotation of both rotating shafts, the maximum stroke of the linear actuator can be reduced to the effective length of the pair of rotating shafts. Therefore, it can be extended to twice the maximum stroke of a normal linear actuator. On the other hand, when the same maximum stroke is set, the total height when the linear actuator is shortened can be reduced to half or less of the total height of the normal linear actuator.

(2) According to the above (1), when the medical / nursing care bed is used for the linear actuator according to the present embodiment, the initial height of the medical / nursing care bed can be set low. It is easy to get down from the bed, and both heels get to the floor, so even a short person can get up easily.

(3) On the other hand, according to the maximum stroke of the linear actuator according to the present embodiment, it is possible to sufficiently secure the height of the bed for medical / nursing care at the time of medical care or nursing care. It becomes easy to give and care.

(4) By connecting the upper mounting frame and the lower mounting frame with a parallel ruler mechanism, the upper mounting frame, that is, the bed, can be moved up and down vertically while maintaining the level, so that the upper mounting frame can be moved vertically. The guide mechanism for guiding can be omitted.

(5) By omitting the guide mechanism, it is possible to avoid the adverse effects caused by the sliding resistance of the guide mechanism, so that the initial cost and the running cost of the linear actuator and thus the medical / care bed can be reduced.

  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 nut of the feed screw shaft device is not limited to the rotation shaft side, and the screw shaft of the feed screw shaft device may be disposed on the rotation shaft side.

  The driving force transmission device that transmits the rotation of the motor to the pair of rotating shafts is not limited to the worm gear reduction device, and a planetary gear reduction device or the like may be used.

  In the above-described embodiment, the case where the linear actuator is used for a medical / care bed has been described. However, the actuator according to the present invention is not limited to this and can be applied to applications such as automobile electrical components.

It is a side 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 falling state, (b) has shown the raising state Yes. It is a front view of the descent state which shows the linear actuator which is one embodiment of this invention. It is the side view. (A) is a top view, (b) is a fragmentary sectional view which passes along a worm axis. It is sectional drawing which follows the VV line of FIG. It is a front view which shows a raise state. It is the side view.

Explanation of symbols

1 ... Bed (medical / care bed), 2 ... Frame, 3 ... Sleeping bed,
DESCRIPTION OF SYMBOLS 10 ... Linear actuator, 11 ... Lower side attachment frame (moving body), 12 ... Parallel ruler mechanism,
13 ... Lower link, 14 ... Pin, 15 ... Pin, 16 ... Fan gear,
21 ... Upper mounting frame (moving body), 23 ... Upper link, 24 ... Pin, 26 ... Fan gear,
30 ... Lower screw shaft, 31 ... Male screw part, 32 ... Supporting tool,
40 ... Upper screw shaft, 41 ... Male screw part, 42 ... Supporting tool,
DESCRIPTION OF SYMBOLS 50 ... Housing, 51 ... Lower rotating shaft, 52 ... Rolling bearing, 53, 54 ... Sliding bearing, 55 ... Lower nut, 56 ... Lower worm wheel,
61 ... Upper rotating shaft, 62 ... Rolling bearing, 63, 64 ... Sliding bearing, 65 ... Upper nut, 66 ... Upper worm wheel,
70 ... motor, 71 ... worm shaft, 72 ... worm,
80 ... Potentiometer, 81 ... Sensor shaft, 82 ... Driven gear, 83 ... Drive gear.

Claims (2)

  A pair of moving bodies that are movable in opposite directions, a pair of rotating shafts rotatably supported by the pair of moving bodies, a drive device that rotates the rotating shafts, and rotation of the rotating shafts. A linear actuator comprising: a pair of feed screw shaft devices that move the two moving bodies in opposite directions; and a parallel ruler mechanism that relatively translates the pair of moving bodies.   The linear actuator according to claim 1, wherein the parallel links of the parallel ruler mechanism are interlocked by a transmission mechanism so as to synchronize with each other.

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