JP2003301912A - Actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an actuator for preventing reverse rotation due to loading, while reducing its size and weight. <P>SOLUTION: The actuator 10 to be used for a medical bed comprises a motor 20 connected to the rear end of a housing 11, a feed screw shaft 50 pivotally supported on an extension from an output shaft 25 of the motor 20 at the front end of the housing 11, a planetary gear 31 provided between the motor output shaft 25 and the feed screw shaft 50 for reducing the rotating speed of the output shaft 25 and transmitting it to the feed screw shaft 50, a nut 64 threaded to the feed screw shaft 50 movably forward and backward, a moving cylinder 62 fixed to the nut 64, and a supporting cylinder 60 threaded into the housing 11 for slidably and rotatably supporting the moving cylinder 62. As the motor output shaft and the feed screw shaft are arranged in line, the size and weight of the actuator is reduced. As the planetary gear has an extremely large reduction ratio, reverse rotation working force at a loading side is effectively braked. <P>COPYRIGHT: (C)2004,JPO

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an actuator, and more particularly to an electric feed screw actuator, for example, for raising or lowering a bed of a medical bed. About what is effective to use. 2. Description of the Related Art In a medical bed, in order to reduce the burden of sleeping and eating on a patient, the bed of the bed is raised and lowered by an electric feed screw type actuator. As a conventional actuator of this kind, a feed screw shaft rotatably supported by a housing is configured to be driven forward and reverse by a motor with a worm gear reduction device via a bevel gear device. A nut connected to a moving cylinder that moves in the axial direction is screwed into the male screw part for feeding formed on the outer periphery of the feed screw shaft so as to be able to advance and retreat, and the front end of the moving cylinder is connected to a load. Some are configured as follows. Japanese Patent Application Laid-Open No. 2000-291768 discloses an example of a conventional actuator of this type. [0005] However, in the above-described actuator, the feed screw shaft, the output shaft of the motor with the worm gear reduction device, and the bevel gear device have a three-axis structure. However, there is a problem that the shape is reduced and the degree of freedom in layout is reduced. Further, in an actuator provided with a brake device and a one-way clutch for preventing reverse rotation of the feed screw shaft, not only the size and weight of the actuator are further increased by the amount of the brake device and the one-way clutch, but also High accuracy is required for parts. An object of the present invention is to provide an actuator capable of preventing reverse rotation due to a load while reducing the size and weight. [0007] An actuator according to the present invention is provided with a motor connected to one end of a housing, and is rotatably arranged at the other end of the housing on an extension of an output shaft of the motor. A feed screw shaft supported by a planetary gear device interposed between the output shaft of the motor and the feed screw shaft to reduce the rotation of the output shaft of the motor and transmit the rotation to the feed screw shaft; It is characterized by comprising a nut screwed to the feed screw shaft so as to be able to advance and retreat, and a moving cylinder connected to the nut so as to move integrally therewith. According to the above-mentioned means, the output shaft of the motor and the feed screw shaft are arranged in a straight line, and the rotation of the output shaft of the motor is reduced by the planetary gear device and transmitted to the feed screw shaft. With such a configuration, the size and weight of the actuator can be reduced. An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the actuator according to the present embodiment is configured to raise and lower a bed of a medical bed (hereinafter, referred to as a bed). That is, the housing 11 on the fixed end side of the actuator 10 is rotatably supported by the frame 2 of the bed 1 by the pivot 3, and
A free end side of a moving cylinder 62 described later is rotatably connected to a link 5 for raising and lowering the bed 4 by a connecting pin 72 described later. When the actuator 10 is shortened, the bed 4 of the bed 1 is horizontally laid down as shown in FIG. 1A, and when the actuator 10 is extended, the bed 4 is shown in FIG. 1B. It is supposed to stand up. As shown in FIG. 2, the actuator 10 has a housing 11 formed in a substantially cylindrical shape. A pair of support holes 12 are provided at positions on the outer peripheral surface of the housing 11 perpendicular to the cylinder core. 12 (see FIG. 1). A motor 20 is concentrically arranged and connected to one end (hereinafter, referred to as a rear end) of the housing 11. As shown in FIG.
1 has an outer diameter equal to (not necessarily equal to) the outer diameter of the housing 11 and is formed in a cylindrical shape with one end closed, and is joined to the rear end of the housing 11 by an intaglio. A plurality of magnets 22 are annularly arranged and fixed on the inner peripheral surface of the yoke 21.
A brush holder stay 24 on which a pair of brush holders 23, 23 is installed is put on the opening of the housing 11 side. An output shaft 25 is provided on the center line between the closing wall of the yoke 21 and the brush holder stay 24, and the armature 26 and the commutator 2 are mounted on the output shaft 25.
7 are fixed. The output shaft 25 includes a bearing metal 28 fitted into a closing wall of the yoke 21 and an internal gear 33 described later.
The bearings 35 are rotatably supported by rolling bearings 29 and oil seals 30 fitted in the holder portions 35, and the brushes of the brush holders 23, 23 held by the brush holder stays 24 are in sliding contact with the commutator 27. . At the rear end of the housing 11, a storage chamber 13 for storing the planetary gear set 31 is formed concentrically in a cylindrical hole shape.
1 is inserted and stored from the opening at the rear end. FIG.
As shown in FIG.
2 and an internal gear 33 and three planetary gears 34,
The sun gear 32 is formed integrally with the tip of the output shaft 25. The internal gear 33 is fitted into the storage chamber 13 and is prevented from rotating, and a rolling bearing 29 and an oil seal 30 are fitted and held in a holder 35 projecting from the rear end of the internal gear 33. The three planetary gears 34 are arranged at regular intervals in the circumferential direction and mesh with each other between the sun gear 32 and the internal gear 33. The sun gear 32, the internal gear 33, and each of the planetary gears 34 have an axial force. Each is formed on a spur gear so as not to act. A rolling bearing 36 is fitted in the inner gear 33 of the storage chamber 13 and rotatably supports a carrier 37 formed in a two-stage cylindrical shape. On the end face of the carrier 37 on the planetary gear unit 31 side, three support holes 38 are arranged concentrically at equal intervals in the circumferential direction and are sunk parallel to the axial direction. One end of each of 39 is press-fitted. Each support shaft 3
Each of the planet gears 9 is rotatably supported on the carrier 9, and the carrier 37 rotates together with the revolution of the planet gear 34 with respect to the sun gear 32. The rear end of the feed screw shaft 50 is inserted on the center line of the carrier 37, and the insertion end of the feed screw shaft 50 is allowed to move slightly in the axial direction by the serration connecting portion 40, and is connected to the carrier 37. They are connected so as to rotate together. A protrusion 41 is provided on the outer periphery of the carrier 37. As shown in FIG.
A potentiometer 42 for detecting a current position of a moving cylinder 62 described later is provided on a part (hereinafter referred to as a lower part) outside the planetary gear device 31 in FIG. As shown in FIG. 5, the potentiometer 42
4 is provided with a potentiometer (sliding resistor) 43 that changes the resistance value and converts the resistance value into an electric signal following the rotation of the motor 4. The potentiometer 43 is attached to a motor code cover 47 attached to the lower part of the housing 11 by a rotating shaft. 44 is installed so as to be parallel to the center line of the carrier 37. A sensor gear 45 is orthogonally fixed to the tip of the rotary shaft 44 of the potentiometer 43. As shown in FIG. 4, the sensor gear 45 has a projection 41 protruding from the outer periphery of the carrier 37. The carrier 37 is engaged every one rotation. The sensor gear 45 is meshed with the tip of an anti-spin claw 46 projecting from the motor cord cover 47, and the sensor gear 45 is prevented from rotating by the anti-spin 46. A motor cord 48 for supplying electric power to the motor 20 is inserted through the motor cord cover 47. As shown in FIGS. 2 and 3, the feed screw shaft 50 having the male feed screw portion 51 is inserted into the carrier 37 through the opening of the support hole 14 formed at the front end of the housing 11. And are connected by a serration connecting unit 40. A flanged cylindrical holder 52 is fitted around the outer periphery of the rear end of the feed screw shaft 50 behind the feed male screw portion 51, and a stopper 5 is provided.
3, the rolling bearing 1 is fitted on the outer periphery of the holder 52 in the support hole 14 of the housing 11.
5 are fitted. On the other hand, a slider 54 is fitted around the outer periphery of the front end of the feed screw shaft 50,
Is in sliding contact with an inner peripheral surface of a moving cylinder 62 described later. The front end of the housing 11 has a female screw 17
A male screw portion 61 formed on the outer periphery of the rear end of the elongated cylindrical support cylinder 60 is screwed into the female screw portion 17. Rear end face of support cylinder 60 and rolling bearing 1
The seal member 16 is sandwiched between the first and fifth members. A rear end of a movable cylinder 62 formed in a cylindrical shape that is thinner than the support cylinder 60 is slidably fitted into the support cylinder 60, and a female screw carved at the rear end of a hollow portion of the movable cylinder 62. A male screw portion 65 engraved on the outer periphery of the nut 64 is screwed into the portion 63 and is fixed by a pin 66. The feed male screw part 51 of the feed screw shaft 50 is screwed into the nut 64 so as to be relatively movable forward and backward. Is set smaller than a normal lead angle.
The slider 54 fitted on the outer periphery of the feed screw shaft 50 is slid on the inner peripheral surface of the moving cylinder 62, so that the feed screw shaft 5
The front end of the cylinder 0 is slidably and rotatably supported by the movable cylinder 62. As shown in FIG. 2, a female screw 67 for position adjustment is formed at the front end of the hollow portion of the moving cylinder 62, and the center position of the female screw 67 for position adjustment of the moving cylinder 62 is adjusted. A pair of long holes 68 long in the direction of the cylinder center are formed so as to face each other and extend in the direction of the cylinder center.
A connecting member 69 is screwed into the position adjusting female screw portion 67 so as to be able to advance and retreat in the cylinder center direction. A connecting hole 70 for inserting a connecting pin 72 is inserted in the center of the connecting member 69 at right angles to the axis. It is opened through the direction. A tool engaging portion 71 for engaging a tool such as a spanner is formed at the front end of the connecting tool 69. The connecting tool 69 has the female screw 67 for adjusting the position of the movable cylinder 62 with the tool engaging portion 71 turned in the opposite direction.
Is screwed into. In this state, the connecting tool 69 is mounted on the front end of the movable barrel 62 so that the position in the axial direction can be adjusted. 68, 68. The outer diameter of the connection hole 70 and the width in the short direction of both the long holes 68 are set to be substantially equal to the outer diameter of the connection pin 72. The connecting pin 72 is set so as to be able to be inserted through the long hole 68 and the connecting hole 70, and is also set so as to be able to be inserted through a connecting hole (not shown) formed in a bracket on the bed side of the bed. It is configured to be prevented from falling outside of the bracket in the folded state. When the connecting member 69 is connected to the bed of the bed, the nut 64 and the moving cylinder 62 are prevented from rotating with respect to the supporting cylinder 60. The rotation of the nut 64 is stopped by the movement of the nut 64.
To move linearly. The operation will be described below. The actuator 10 is mounted on the bed 1 as shown in FIG. Actuator 10
When the motor 20 is rotated in the forward direction from the state shown in FIG.
The rotation of No. 5 is reduced and transmitted to the feed screw shaft 50 via the planetary gear device 31 and the carrier 37. When the feed screw shaft 50 is rotated in the forward direction, the nut 64
The moving cylinder 62 connected to the nut 64 is pushed out of the supporting cylinder 60.
The bed 4 of the bed 1 connected to the connector 69 of the moving cylinder 62 is raised by the advance of the moving cylinder 62. The number of rotations of the carrier 37 for transmitting the rotation of the output shaft 25 at a reduced speed is counted by the potentiometer 42 and transmitted to a controller for controlling the operation of the bed 1. That is, when the carrier 37 rotates, the projection 41 protruding from the carrier 37 feeds and rotates the sensor gear 45 of the potentiometer 42 one tooth at a time for each rotation of the carrier 37, so that the rotation shaft 44 of the potentiometer 42 is rotated. Is rotated intermittently, the potentiometer 42 measures the number of rotations of the carrier 37 in a state of being thinned out in proportion. Thus, the potentiometer 4
Since the number of teeth of the sensor gear 45 can be set small by measuring the number of rotations of the carrier 37 in proportion to the number of rotations of the carrier 37, the outer diameter of the actuator 10 Can be suppressed small. In addition, the effective stroke of the movable cylinder 62 can be set long. When the potentiometer voltage corresponding to the predetermined position is detected, the controller stops the motor 20. When the operation of the motor 20 is stopped, the load on the bed 4 of the bed 1 (eg, the weight of the patient) acts on the nut 64 via the movable cylinder 62 as a force in the direction of retracting the nut 64. For this reason, the feed screw shaft 50 is brought into a state in which a load-side reverse rotation acting force for reversely rotating the moving cylinder 62, that is, the load side, is applied by the action of the feed male screw portion 51 of the feed screw shaft 50. The load-side reverse rotation acting force applied to the feed screw shaft 50 tends to be transmitted to the output shaft 25 of the motor 20 via the planetary gear device 31. In the present embodiment, the feed male screw of the feed screw shaft 50 is used. Since the lead angle of the portion 51 is set to be small, the load-side reverse rotation acting force itself is suppressed to be small, so that the output shaft 25 of the motor 20 cannot be reliably rotated by the load-side reverse rotation force. . Therefore, the actuator 10 can always reliably support the load on the bed 4 of the bed 1. Next, when the motor 20 is rotated in the reverse direction, the reverse rotation driving force of the output shaft 25 is transmitted to the feed screw shaft 50 via the planetary gear unit 31. When the feed screw shaft 50 is driven to rotate in the reverse direction, the nut 64, which is screwed to the feed male screw portion 51 of the feed screw shaft 50 so as to be able to advance and retreat and is prevented from rotating with respect to the support cylinder 60, retreats along the support cylinder 60. Therefore, the moving cylinder 62 connected to the nut 64 is drawn into the supporting cylinder 60. By retreating the moving cylinder 62, the bed 1 connected to the coupling 69 of the moving cylinder 62 is moved.
Bed 4 is lying down. When the bed 4 is lowered to its original position as shown in FIG. 1B, the motor 20 is automatically stopped based on the measurement of the potentiometer 42. And
In a state where the nut 64 has returned to the original retracted position, the bed 4 is usually mechanically supported by the frame 2 of the bed 1, and thus the reverse rotation force from the bed 4 of the bed 1, that is, the load side, causes the feed screw shaft 50. Never join. However,
Even if the load-side reverse rotation acting force is always applied to the feed screw shaft 50 in a state where the bed 4 of the bed 1 is lying down, the reverse rotation of the feed screw shaft 50 is reliably prevented by the above-described action. According to the present embodiment, the following effects can be obtained. 1) A feed screw shaft for moving the moving cylinder forward and backward and an output shaft of a motor for rotating and driving the feed screw shaft are arranged in a straight line, and the output shaft of the motor is provided between the feed screw shaft and the output shaft. By interposing the planetary gear device that reduces the rotation and transmits the rotation to the feed screw shaft, the actuator can be configured as a whole in a straight line, so that the size and weight of the actuator can be reduced. 2) By setting the lead angle of the feed screw shaft to be small, it is possible to prevent the feed screw shaft from being rotated by the load-side reverse rotation acting force without interposing a brake device, a one-way clutch or the like. be able to. The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the scope of the invention. For example, in the above-described embodiment, the case where the actuator is used for a medical bed has been described. However, the actuator according to the present invention is not limited to this, and may be applied to applications such as automobile electrical components. it can. As described above, according to the present invention,
By arranging the feed screw shaft for moving the moving cylinder forward and backward and the output shaft of the motor for rotating and driving the feed screw shaft on a straight line, the size and weight of the actuator can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view showing a main part of a medical bed using an actuator according to an embodiment of the present invention;
(A) shows a lying state and (b) shows a standing state. FIG. 2 is a partially cut-away side view showing an actuator according to an embodiment of the present invention. FIG. 3 is a partially cutaway side view showing a main part. 4A and 4B show a planetary gear device, in which FIG. 4A is a side sectional view, FIG. 4B is a sectional view along line bb of FIG. 4A, and FIG. 4C is line cc of FIG. It is sectional drawing which follows. FIG. 5 is a perspective view showing a potentiometer. [Description of Signs] 1 ... bed (medical bed), 2 ... frame, 3 ... axis, 4 ... bed, 5 ... link, 10 ... actuator, 1
DESCRIPTION OF SYMBOLS 1 ... Housing, 12 ... Support hole, 13 ... Storage room, 14 ...
Support hole, 15: rolling bearing, 16: sealing member, 17:
Female thread portion, 20: motor, 21: yoke, 22: magnet, 23: brush holder, 24: brush holder stay, 25: output shaft, 26: armature, 27: commutator, 28: bearing metal, 29: rolling bearing, 30 ... Oil seal, 31 ... Planetary gear, 32 ... Sun gear, 3
3 ... internal gear, 34 ... planetary gear, 35 ... holder part, 36 ...
Rolling bearing, 37 carrier, 38 support hole, 39 support shaft, 40 serration coupling part, 41 projection, 42
Potentiometer, 43: Potentiometer, 44: Rotating shaft, 45: Sensor gear, 46: Anti-rotation claw, 47:
Motor code cover, 48 ... Motor code, 50 ... Feed screw shaft, 51 ... Male screw part for feed, 52 ... Holder, 53 ...
Stopper, 54 ... Slider, 60 ... Support cylinder, 61 ... Male thread, 62 ... Movable cylinder, 63 ... Female thread, 64 ... Nut,
65 ... male screw part, 66 ... pin, 67 ... female screw part for position adjustment, 68 ... long hole, 69 ... connecting tool, 70 ... connecting hole, 71 ...
Tool engaging portion, 72 ... connecting pin.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // A61G 7/00 A61G 7/00 F term (reference) 3J062 AA27 AA38 AB21 AC07 BA12 BA19 CD02 CD22 CD57 4C040 AA05 BB06 DD03 EE05 5H605 AA07 BB05 BB09 CC08 DD09 EB06 EB10 5H607 AA12 BB01 BB04 BB14 BB26 CC03 DD08 DD19 EE33 EE52 GG01 GG08 GG09 HH01

Claims (1)

Claims: 1. A motor connected to one end of a housing, and a feed screw shaft rotatably supported at the other end of the housing on an extension of an output shaft of the motor. A planetary gear device interposed between the output shaft of the motor and the feed screw shaft for reducing the rotation of the output shaft of the motor and transmitting the reduced rotation to the feed screw shaft; An actuator comprising: a threaded nut; and a movable cylinder connected to the nut so as to move integrally therewith.