JP4166499B2 - Actuator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an actuator, and more particularly, to an electric feed screw actuator, and more particularly to an actuator that is effective for raising and lying a bed of a medical bed.
[0002]
[Prior art]
In the medical bed, in order to reduce the burden of sleeping and eating on the patient, the bed of the bed is raised or laid down by an electric feed screw actuator.
[0003]
As a conventional actuator used for a medical bed, a motor connected to a housing, a feed screw shaft rotatably supported by the housing, and a motor interposed between an output shaft and a feed screw shaft of the motor A speed reducer that decelerates the rotation of the output shaft and transmits it to the feed screw shaft, a nut screwed to the feed screw shaft so as to be able to advance and retreat, a moving cylinder connected to move integrally with the nut, and this movement And a support cylinder that is slidably fitted to the outside of the end portion on the housing side of the cylinder and the end on the housing side is supported by the housing, and the front end of the movable cylinder is connected to a bed serving as a load. Some are configured to do so.
[0004]
In an actuator used for such a medical bed, it is necessary to detect the current position of the moving cylinder in order to reliably stop the moving cylinder at the forward limit position or the backward limit position. As an actuator configured to detect the current position of the moving cylinder, for example, as shown in Japanese Patent Laid-Open No. 9-190225, the rotation of the lead screw shaft is decelerated and transmitted via a reduction gear group. A rotating shaft, a moving body that is screwed to a screw portion screwed to the rotating shaft and moves along the axial direction of the rotating shaft by decelerating rotation, and a slide that varies the resistance value following the movement of the moving body. Some have a drive position detecting means (potentiometer) composed of a dynamic resistor (potentiometer).
[0005]
[Problems to be solved by the invention]
However, the actuator equipped with the drive position detecting means described above is configured such that the rotation of the feed screw shaft is transmitted to the rotating shaft at a reduced speed via the reduction gear group. There is a problem that the dimension in the axial direction becomes large.
[0006]
An object of the present invention is to provide an actuator that can detect the current position of a movable cylinder while preventing the housing from becoming large.
[0007]
[Means for Solving the Problems]
An actuator according to the present invention includes a motor coupled to a housing,
A feed screw shaft rotatably supported by the housing;
A speed reduction 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 it to the feed screw shaft;
A nut threadably engaged with the feed screw shaft;
A moving cylinder coupled to the nut so as to move integrally;
In an actuator comprising a potentiometer that detects the position of the movable cylinder based on the rotational speed of the feed screw shaft ,
The potentiometer sensor includes a carrier that rotates the feed screw shaft and synchronization,
A sensor gear that intermittently rotates by engaging with a protrusion protruding from the outer periphery of the carrier;
A rotating shaft to which the sensor gear is fixed;
A potentiometer that varies the resistance value following the rotation of the rotating shaft ,
The potentiometer is installed on a motor cord cover placed on a side surface of the housing so that the rotation axis is parallel to the center axis of the carrier.
It is characterized by that.
[0008]
In the above-described means, the rotation of the feed screw shaft is intermittently transmitted to the rotation shaft of the potentiometer via the carrier protrusion and the sensor gear, so that the reduction rotation gear group can be omitted, and the radial direction of the housing and An increase in the dimension in the axial direction can be prevented.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0010]
As shown in FIG. 1, the actuator according to the present embodiment is configured to raise and lower the bed of a medical bed (hereinafter referred to as a bed). That is, the housing 11 which is the fixed end side of the actuator 10 is rotatably supported by the frame 2 of the bed 1 by the pivot 3, and the distal end of the moving cylinder 62 which will be described later which becomes the free end side of the actuator 10 is the bed 4. The link 5 for raising and lowering is rotatably connected by a connecting pin 72 described later. With the actuator 10 shortened, the bed 4 of the bed 1 is lying down horizontally as shown in FIG. 1 (a), and when the actuator 10 is extended, the bed 4 is shown in FIG. 1 (b). It is supposed to stand up like you are.
[0011]
As shown in FIG. 2, the actuator 10 includes a housing 11 formed in a substantially cylindrical shape, and a pair of support holes 12 and 12 (see FIG. 1) has been established. A motor 20 is concentrically disposed and connected to one end (hereinafter referred to as a rear end) of the housing 11. As shown in FIG. 3, the yoke 21 of the motor 20 is formed in a cylindrical shape whose outer diameter is equal to (but not necessarily equal to) the outer diameter of the housing 11 and whose one end is closed, An indicia is coupled to the rear end of the housing 11. A plurality of magnets 22 are annularly arranged and fixed on the inner peripheral surface of the yoke 21, and a brush holder stay 24 in which a pair of brush holders 23, 23 are installed in the opening of the yoke 21 on the housing 11 side. Is covered. An output shaft 25 is installed on the center line between the closed wall of the yoke 21 and the brush holder stay 24, and an armature 26 and a commutator 27 are fixed to the output shaft 25. The output shaft 25 is rotatably supported by a bearing metal 28 fitted in the closing wall of the yoke 21, and a rolling bearing 29 and an oil seal 30 fitted in a holder portion 35 of an internal gear 33 described later. The brush holders 23 and 23 held by the brush holder stay 24 are in sliding contact with the brush.
[0012]
A housing chamber 13 for housing the planetary gear device 31 is formed concentrically in a cylindrical hole shape at the rear end portion of the housing 11, and the planetary gear device 31 is inserted into the housing chamber 13 from an opening at the rear end. Inserted and stored. As shown in FIG. 4, the planetary gear device 31 includes a sun gear 32, an internal gear 33, and three planetary gears 34, and the sun gear 32 is integrally formed at the tip of the output shaft 25. Has been. 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 portion 35 protruding from the rear end portion of the internal gear 33. The three planetary gears 34 are arranged at equal intervals in the circumferential direction between the sun gear 32 and the internal gear 33, and the sun gear 32, the internal gear 33 and each planetary gear 34 have an axial force. Each spur gear is formed so as not to act.
[0013]
A rolling bearing 36 is fitted in the interior of the internal gear 33 of the storage chamber 13, and the rolling bearing 36 rotatably supports a carrier 37 formed in a two-stage cylindrical shape. Three support holes 38 are concentrically arranged at equal intervals in the circumferential direction on the end face of the carrier 37 on the planetary gear unit 31 side, and are recessed in parallel in the axial direction. One end of 39 is press-fitted. Each planetary gear 34 is rotatably supported on each support shaft 39, and the carrier 37 rotates together with the revolution of the planetary gear 34 with respect to the sun gear 32. A rear end portion of the feed screw shaft 50 is inserted on the center line of the carrier 37, and the insertion end portion of the feed screw shaft 50 allows slight movement in the axial direction by the serration coupling portion 40, while They are connected so as to rotate together. A protrusion 41 is provided on the outer periphery of the carrier 37.
[0014]
As shown in FIG. 3, a potentiometer 42 that detects the current position of the moving cylinder 62, which will be described later, is installed on a part (hereinafter referred to as a lower part) of the planetary gear device 31 in the housing 11. Has been. As shown in FIG. 5, the potentiometer 42 includes a potentiometer (sliding resistor) 43 that changes the resistance value following the rotation of the rotating shaft 44 and converts the resistance value into an electrical signal. A rotating shaft 44 is installed on a motor cord cover 47 placed on the lower portion of the housing 11 so as to be parallel to the center line of the carrier 37. A sensor gear 45 is fixed orthogonally to the tip of the rotary shaft 44 of the potentiometer 43. As shown in FIG. 4, the sensor gear 45 has a protrusion 41 protruding from the outer periphery of the carrier 37. The carrier 37 is engaged every rotation. Further, the sensor gear 45 is engaged with the tip of an anti-rotation claw 46 protruding from the motor cord cover 47, and the sensor gear 45 is prevented from rotating by the anti-rotation claw 46. Incidentally, a motor cord 48 for supplying electric power to the motor 20 is inserted into the motor cord cover 47.
[0015]
As shown in FIGS. 2 and 3, the feed screw shaft 50 in which the feed male screw portion 51 is formed is inserted into the carrier 37 from the opening of the support hole 14 formed in the front end portion of the housing 11, and serrated. They are coupled by the coupling unit 40. A holder 52 formed in a cylindrical shape with a hook is fitted on the outer periphery of the rear end portion on the rear side of the feed male screw portion 51 in the feed screw shaft 50, and the position of the holder 52 is restricted by a stopper 53. A rolling bearing 15 fitted in the support hole 14 of the housing 11 is fitted on the outer periphery of the housing 11. On the other hand, a slider 54 is fitted to the outer periphery of the front end portion of the feed screw shaft 50, and the outer peripheral surface of the slider 54 is in sliding contact with the inner peripheral surface of the movable cylinder 62 described later.
[0016]
A female screw portion 17 is formed at the front end portion of the housing 11, and a male screw portion 61 formed on the outer periphery of the rear end portion of the elongated cylindrical support tube 60 is screwed into the female screw portion 17. A seal member 16 is sandwiched between the rear end surface of the support tube 60 and the rolling bearing 15. A rear end portion of a movable cylinder 62 formed in a cylindrical shape that is longer than the support cylinder 60 is slidably fitted into the support cylinder 60, and a female screw engraved at the rear end portion of the hollow portion of the movable cylinder 62. A male thread 65 engraved on the outer periphery of the nut 64 is screwed into the part 63 and is fixed by a pin 66. The feed screw shaft 50 of the feed screw shaft 50 is screwed into the nut 64 so as to be relatively movable back and forth. The feed screw thread portion 51 of the feed screw shaft 50 is controlled to reduce the load-side reverse rotation force. The lead angle is set smaller than the normal lead angle. When the slider 54 fitted to the outer periphery of the feed screw shaft 50 is slidably contacted with the inner peripheral surface of the moving cylinder 62, the front end portion of the feed screw shaft 50 is slidably and rotatably supported by the moving cylinder 62. ing.
[0017]
As shown in FIG. 2, a position adjusting female threaded portion 67 is engraved at the front end of the hollow portion of the moving cylinder 62, and a cylinder is positioned at the center of the position adjusting female threaded portion 67 of the moving cylinder 62. A pair of long holes 68 that are long in the center direction are opened so as to face each other and extend in the tube center direction. A coupling tool 69 is screwed into the position adjusting female thread portion 67 so as to be able to advance and retreat in the cylinder center direction. A coupling hole 70 through which the coupling pin 72 is inserted is perpendicular to the center of the coupling tool 69. Opened in the direction. A tool engaging portion 71 for engaging a tool such as a spanner is formed at the front end of the connector 69. The connecting tool 69 is screwed into the position adjusting female thread portion 67 of the movable cylinder 62 with the tool engaging portion 71 directed in the opposite direction. In this state, the connecting tool 69 is attached to the front end portion of the movable cylinder 62 so that the position in the axial direction can be adjusted, and the connecting hole 70 is formed into both elongated holes by adjusting the rotational position. 68 and 68 are aligned. The outer diameter of the connecting hole 70 and the width in the short direction of both the long holes 68 and 68 are set to be equal, and are set to be approximately equal to the outer diameter of the connecting pin 72. The connecting pin 72 is set so as to be able to be inserted into the long hole 68 and the connecting hole 70, and is also set so as to be able to be inserted into a connecting hole (not shown) provided in the bracket on the bed bed side. In this state, it is configured to be prevented from coming off outside the bracket.
[0018]
Since the connecting tool 69 is connected to the bed side of the bed, the nut 64 and the moving cylinder 62 are prevented from rotating with respect to the support cylinder 60, so that the moving cylinder 62 is protected from the rotational movement of the nut 64. Thus, the rotation is prevented, and the nut 64 moves linearly with respect to the support cylinder 60 as the nut 64 advances and retreats.
[0019]
The operation will be described below.
[0020]
The actuator 10 is assembled to the bed 1 as shown in FIG. After the actuator 10 is assembled to the bed 1, when the motor 20 is rotated in the forward direction from the state of FIG. 1A, the rotation of the output shaft 25 is caused to feed through the planetary gear device 31 and the carrier 37. The shaft 50 is decelerated and transmitted. When the feed screw shaft 50 is rotated in the forward direction, the nut 64 is advanced along the support cylinder 60, so that the movable cylinder 62 connected to the nut 64 is pushed out of the support cylinder 60. As the moving cylinder 62 advances, the bed 4 of the bed 1 connected to the connecting tool 69 of the moving cylinder 62 rises.
[0021]
The rotational speed of the carrier 37 that transmits the rotational force of the output shaft 25 at a reduced speed is counted by the potentiometer 42 and transmitted to a controller that controls the operation of the bed 1. In other words, when the carrier 37 rotates, the protrusion 41 protruding from the carrier 37 feeds and rotates the sensor gear 45 of the potentiometer 42 for each rotation of the carrier 37, thereby rotating the rotating shaft 44 of the potentiometer 42. Therefore, the potentiometer 42 measures the rotational speed of the carrier 37 in a decelerated state. In this way, the potentiometer 42 can set the number of teeth of the sensor gear 45 to be small by measuring the rotational speed of the carrier 37 proportionally, so that the reduction gear group is abolished, The outer diameter of the actuator 10 can be suppressed small. In addition, the effective stroke of the movable cylinder 62 can be set longer.
[0022]
For example, as shown in FIG. 6A, when the effective stroke L of the potentiometer 43 is 15 mm and the effective stroke of the moving cylinder 62 is 150 mm, the effective stroke of the moving cylinder 62 is 150 mm. In order to measure within the 15 mm range of the 43 effective strokes, it is necessary to reduce the moving amount of the moving cylinder 62 to “1/10”. When the “rotation number per 1 mm” determined by the lead angle of the feed male screw portion 51 of the feed screw shaft 50 is set to 10 rotations, it is 10 to reduce “1 mm” to “1/10”. Since the rotation must be decelerated to one revolution, the reduction gear group that decelerates ten revolutions of the feed screw shaft 50 to one revolution of the rotary shaft 44 of the potentiometer 43 becomes “1/10”. Now, in order to simplify the explanation, the reduction ratio of the one-stage reduction gear group will be examined. Since the number of gear teeth substantially depends on the diameter, assuming that the diameter of the driving gear on the feed screw shaft side is 20 mm, the diameter of the driven gear on the potentiometer side is as large as 200 mm. That is, the dimension in the radial direction of the housing for installing the potentiometer is extremely large. If the number of stages of the reduction gear group is increased in order to suppress the radial dimension, the axial dimension becomes large.
[0023]
In the present embodiment, when the feed screw shaft 50 rotates once, only one tooth of the sensor gear 45 is fed by the projection 41 projecting from the carrier 37. That is, when the number of teeth of the sensor gear 45 is set to 10, the sensor gear 45 rotates once when the feed screw shaft 50 rotates ten times. Then, by setting the potentiometer 43 to move by 0.1 mm when the sensor gear 45, that is, the rotation shaft 44 makes one rotation, the effective stroke of 150 mm of the movable cylinder 62 is reduced to 15 mm of the effective stroke of the potentiometer 43. That's right.
[0024]
FIG. 6B is a graph showing the relationship between the potentiometer's potentiometer voltage and the moving cylinder stroke, where the vertical axis represents the potentio voltage and the horizontal axis represents the moving cylinder stroke. Since the potentiometer voltage is proportional to the sliding amount of the potentiometer 43, the current position of the movable cylinder 62 is displayed by the potentiometer voltage value by corresponding the effective stroke of the potentiometer between the maximum value and the minimum value of the potentiometer voltage. Can do.
[0025]
When the potentiometer voltage corresponding to the predetermined position of the moving cylinder 62 is detected, the controller stops the motor 20. When the operation of the motor 20 is stopped, the load of the bed 4 of the bed 1 (such as the patient's weight) acts as a force in a direction to retract the nut 64 via the movable cylinder 62. For this reason, the feed screw shaft 50 is subjected to the action of the feed male screw portion 51 of the feed screw shaft 50 so that the load side reverse rotation force to be rotated in the reverse direction from the movable cylinder 62, that is, the load side. The load-side reverse rotational force applied to the feed screw shaft 50 is transmitted to the output shaft 25 of the motor 20 via the planetary gear unit 31. In the present embodiment, the feed male screw of the feed screw shaft 50 is used. By setting the lead angle of the portion 51 to be small, the load-side reverse rotation force itself is suppressed to be small, and therefore 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 of the bed 4 of the bed 1.
[0026]
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 device 31. When the feed screw shaft 50 is driven in reverse rotation, the nut 64 that is screwed to the feed male screw portion 51 of the feed screw shaft 50 so as to advance and retreat and is prevented from rotating with respect to the support tube 60 moves backward along the support tube 60. Therefore, the movable cylinder 62 connected to the nut 64 is drawn into the support cylinder 60. As the moving cylinder 62 moves backward, the bed 4 of the bed 1 connected to the connecting tool 69 of the moving cylinder 62 is laid down. Also at this time, the current position of the movable cylinder 62 is detected by the potentiometer 42.
[0027]
When the bed 4 is lowered to the original position as shown in FIG. 1B, the motor 20 is automatically stopped based on the detection of the potentiometer 42. Since the bed 4 is normally mechanically supported by the frame 2 of the bed 1 in a state where the nut 64 is returned to the original retracted position, the reverse rotational force from the bed 4 of the bed 1, that is, the load side, causes feed screw. There is no addition to the shaft 50. However, even if the load side reverse rotation force is always applied to the feed screw shaft 50 in the 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.
[0028]
According to the present embodiment, the following effects can be obtained.
[0029]
1) The sensor gear that rotates intermittently by engaging with the protrusion that protrudes on the outer periphery of the carrier that rotates synchronously with the feed screw shaft is fixed to the rotation shaft of the potentiometer, so that it projects against the carrier when the feed screw shaft rotates. Since only one tooth of the sensor gear can be advanced by the provided projection, the effective stroke length of the movable cylinder can be reduced to the effective stroke length of the potentiometer.
[0030]
2) Since the rotation of the lead screw shaft is intermittently transmitted to the rotary shaft of the potentiometer via the carrier protrusion and the sensor gear, the reduction gear group can be omitted. Compared with the case where a reduction gear group is interposed between the rotary shaft of the potentiometer, the radial and axial dimensions of the housing can be greatly reduced.
[0031]
3) By engaging the idling prevention claw with the sensor gear, it is possible to prevent idling of the sensor gear when the carrier protrusion is separated from the teeth of the sensor gear, so the current position of the moving cylinder due to the potentiometer's potentiometer voltage. Decrease in display accuracy can be prevented.
[0032]
4) The feed screw shaft for moving the moving cylinder back and forth and the output shaft of the motor that drives the feed screw shaft for rotation are arranged on a straight line, and the rotation of the motor output shaft is decelerated between the feed screw shaft and the output shaft. By interposing the planetary gear device that transmits to the feed screw shaft, the actuator can be configured in a straight line as a whole, so that the size and weight of the actuator can be reduced.
[0033]
5) By setting the lead angle of the lead screw shaft to be small, it is possible to prevent the lead screw shaft from being rotated by the load side reverse rotation force without using a brake device or a one-way clutch. .
[0034]
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.
[0035]
For example, the number of protrusions projecting on the outer periphery of the carrier is not limited to one, and may be two or more, which corresponds to the reduction ratio between the carrier and the sensor gear by adjusting the number of protrusions. The thinning rate can be set appropriately.
[0036]
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 can be applied to uses such as automobile electrical components.
[0037]
【The invention's effect】
As described above, according to the present invention, the current position of the movable cylinder can be detected while preventing the housing from becoming large.
[Brief description of the drawings]
FIGS. 1A and 1B are front views showing a main part of a medical bed in which an actuator according to an embodiment of the present invention is used, wherein FIG. 1A shows a lying state and FIG. 1B shows a standing state.
FIG. 2 is a partially cut side view showing an actuator according to an embodiment of the present invention.
FIG. 3 is a partially cut 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 taken along line bb in FIG. 4A, and FIG. 4C is taken along line cc in FIG. It is sectional drawing which follows.
FIG. 5 is a perspective view showing a potentiometer.
6A is an electric circuit diagram showing a potentiometer, and FIG. 6B is a graph showing a relationship between a potentiometer potentiometer voltage and a moving cylinder stroke.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Bed (medical bed), 2 ... Frame, 3 ... Axis, 4 ... Bed, 5 ... Link, 10 ... Actuator, 11 ... Housing, 12 ... Support hole, 13 ... Storage room, 14 ... Support hole, 15 ... Rolling bearing, 16 ... sealing member, 17 ... female thread, 20 ... motor, 21 ... yoke, 22 ... magnet, 23 ... brush holder, 24 ... brush holder stay, 25 ... output shaft, 26 ... armature, 27 ... commutator, 28 Metal bearings 29 Rolling bearings 30 Oil seals 31 Planetary gear devices 32 Sun gears 33 Internal gears 34 Planetary gears 35 Holder units 36 Rolling bearings 37 Carriers 38 DESCRIPTION OF SYMBOLS ... Support hole, 39 ... Support shaft, 40 ... Serration coupling part, 41 ... Protrusion, 42 ... Potentiometer, 43 ... Potentiometer, 44 ... Rotating shaft, 45 ... Sensor tooth 46 ... idling prevention claw, 47 ... motor cord cover, 48 ... motor cord, 50 ... feed screw shaft, 51 ... male screw portion for feeding, 52 ... holder, 53 ... stopper, 54 ... slider, 60 ... support cylinder, 61 ... Male thread part 62 ... Moving cylinder 63 ... Female thread part 64 ... Nuts 65 ... Male thread part 66 ... Pins 67 ... Female thread part for position adjustment 68 ... Long hole 69 ... Connecting tool 70 ... Connecting hole 71 ... Tool engaging part, 72 ... Connecting pin.

Claims (2)

A motor coupled to the housing;
A feed screw shaft rotatably supported by the housing;
A speed reduction 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 it to the feed screw shaft;
A nut threadably engaged with the feed screw shaft;
A moving cylinder coupled to the nut so as to move integrally;
In an actuator comprising a potentiometer that detects the position of the movable cylinder based on the rotational speed of the feed screw shaft ,
The potentiometer sensor includes a carrier that rotates the feed screw shaft and synchronization,
A sensor gear that intermittently rotates by engaging with a protrusion protruding from the outer periphery of the carrier;
A rotating shaft to which the sensor gear is fixed;
A potentiometer that varies the resistance value following the rotation of the rotating shaft ,
The potentiometer is installed on a motor cord cover placed on a side surface of the housing so that the rotation axis is parallel to the center axis of the carrier.
An actuator characterized by that. The actuator according to claim 1, wherein an idling prevention pawl is engaged with the sensor gear.

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