JPH1127899A - Linear actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a linear actuator capable of preventing the overload of a motor with a low-cost structure. SOLUTION: A pin 102, provided on a screw shaft 86, is inserted into a engaging groove 76 of a gear 56. As the gear 56 rotates, the groove 76 presses the pin 102 to cause it to rotate. This motion rotates the screw shaft 86 to cause a piston 112 to slide via a nut 104. Also, when the rotation of the screw shaft 86 slides the piston 112 in a contracting direction, a force in a reverse direction acts on the nut 104 so as to stop its slide. As the screw shaft 86 slides while rotating, the pin 102 is disengaged from the groove 76. This disengagement inhibits the turning effect of the gear 56 from being transmitted to the screw shaft 86, which then stops the rotation of the screwshaft 86 and the movement of the piston 112.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to furniture for carrying people,
For example, the present invention relates to a linear actuator used for turning a backrest, a leg rest, and the like in a chair, a nursing bed, and the like.

[0002]

2. Description of the Related Art Chairs used in barber shops, beauty salons, etc.
Normally, a backrest that supports the back of a seated person and a legrest that supports the lower leg pivot vertically and can change between a normal sitting posture and a supine posture.

[0003] In addition, a hydraulic cylinder has been used for turning such a backrest or a legrest. However, the hydraulic cylinder cannot adjust the vertical rotation speed, and requires periodic maintenance. In addition, there are drawbacks such as oil leakage during maintenance. Therefore, in recent years, it has been considered to apply a linear actuator in which a piston rod reciprocates by the rotational force of a motor instead of the hydraulic cylinder.

[0004]

By the way, in such a chair, for example, when the leg rest is turned downward in a state where an obstacle is placed below the leg rest which has been turned upward, the leg rest may be obstructed. There is a possibility that the motor may be overloaded by contact with an object and a reaction force from the obstacle.

[0005] Such a problem is caused, for example, by providing an obstacle detection sensor such as a pressure sensor on a leg rest, and stopping the motor when the sensor detects that the leg rest has come into contact with an obstacle. However, such sensors are expensive and costly.

The present invention has been made in view of the above circumstances, and has as its object to obtain a linear actuator that can prevent overload of a motor with an inexpensive configuration.

[0007]

According to a first aspect of the present invention, there is provided a linear actuator used for turning a backrest of a retractable chair, a leg rest, or a bed of a nursing care bed. A rotating shaft that is rotated by a force, a moving body that receives the rotational force of the rotating shaft and moves substantially linearly to displace the load supporting portion;
And a clutch means for connecting the rotating shaft and the moving body and releasing the connection when a load is applied to the moving moving body in a direction substantially opposite to the moving direction.

According to the linear actuator having the above structure, when a load substantially in the direction opposite to the moving direction is applied to the moving body that is moved by the rotational force of the rotating shaft, for example, the moving body is moved in the moving direction or the moving body is moved. There is an obstacle on the moving direction side of a movable part such as a backrest of a retractable chair, a leg rest or a bed of a nursing care bed directly or indirectly connected to the moving object or the movable part. When the pressing force is applied by the driving force of the motor and the pressing reaction force acts on the moving body, the connection between the rotating shaft and the moving body by the clutch means is released. As a result, the rotational force of the rotating shaft is not transmitted to the moving body, and the moving body stops. In this state, although the motor is driven, the driving force is not transmitted to the moving body, so that the moving body does not press the obstacle by the driving force of the motor, and accordingly, the motor of the previous motor is driven. The reaction force from the obstacle according to the driving force is also eliminated. For this reason, overload of the motor can be prevented.

The clutch means in the present invention may have any structure as long as it connects the rotating shaft and the moving body by mechanical contact, and may be a meshing clutch or a friction clutch.

Further, in the present invention, it is only necessary that the torque can be transmitted from the rotating shaft to the moving body or the torque can be cut off by the clutch means. Therefore, the clutch means may be directly connected to at least one of the rotating shaft and the moving body, and the driving force transmission of a gear or the like may be performed between at least one of the rotating shaft and the moving body and the clutch means. The connection may be made indirectly through means.

The linear actuator according to claim 2 is
2. The linear actuator according to claim 1, wherein the clutch unit includes an engaged body provided on one of the rotating shaft and the moving body, and an engaged body provided on one of the rotating shaft and the moving body. 3. Is provided, and engages with the engaged body by a load in a substantially same direction as a specific moving direction of the moving body acting on the moving body, and a working direction is substantially opposite to the load in the substantially same direction and And an engaging body that is separated from the engaging body when a load exceeding the load in the substantially same direction acts on the moving body.

In the linear actuator having the above structure, a load in a direction substantially the same as the specific moving direction of the moving body acts on the moving body, so that the engaging body engages with the engaged body and the rotating shaft and the moving body are separated from each other. Be linked. Thereby, the rotating force of the rotating shaft (that is, the driving force of the motor) is transmitted to the moving body, and the moving body moves.

Here, when a load in a direction substantially opposite to the load acting on the moving body exceeds the load in the substantially same direction acting on the moving body, the engaging body is disengaged from the engaged body and the engagement is released. Is done. As a result, the connection between the rotating shaft and the moving body is released, the rotational force of the rotating shaft is not transmitted to the moving body, and the moving body stops. In this state, although the motor is driven, its driving force is not transmitted to the moving body, and the reaction force from an obstacle or the like corresponding to this driving force is also eliminated. Can be prevented.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIGS.

FIG. 5 is a side view of a chair 20 to which the linear actuator 10 is applied. As shown in this figure, the chair 20 includes a base plate 22 fixed to a house floor 21 or the like by bolts or the like (not shown). The base plate 22 is disposed with the vertical direction as the longitudinal direction. A column 24 is provided. A seat 26 in which a cushioning material such as a spring or a cushion material is accommodated inside a flat bag-like bag formed of a sheet material such as leather, synthetic leather, or cloth is fixed to an upper end portion of the support column 24. It is used for sitting.

A part of the peripheral end of the seat 26 is inverted.
A backrest portion 30 is connected via a rod-like, pipe-like, or plate-like connecting member 28 that is curved in a U-shape.
The weight of the upper body of the person seated on the seat 26 can be supported from behind (in the direction of arrow A in FIG. 5). Like the seat 26, the backrest portion 30 also has a flat bag-shaped bag made of leather, synthetic leather, cloth, or the like, and a cushioning material such as a spring or a cushion material is accommodated inside the bag. Have been.

On the other hand, a leg rest 32 is provided on the side opposite to the backrest 30 via the support post 24. The leg rest 32 is connected to the column 24 so as to be able to pivot around the hinge 34 via the hinge 34 so that the leg of the person seated on the seat 26 can be supported from behind (in the direction of arrow A in FIG. 5). It has become.

A linear actuator 10 is provided on the upper end side of the column 24. Here, FIG. 1 shows an enlarged side view of the linear actuator 10. As shown in this figure, the linear actuator 1
0 has a gear housing 42. A fixed portion 44 having a through hole (not shown) is formed in the outer peripheral portion of the gear housing 42, and a joint 46 that penetrates the through hole of the fixed portion 44 is fixed to the support column 24 so that the gear housing 42 is fixed. 42 is rotatably supported around a joint 46 (in the direction of arrow B in FIG. 1).

A motor mounting portion 48 is formed in the gear housing 42, and a rotating shaft 52 of the motor 50 is provided.
The side is inserted into the inside of the gear housing 42 and fixed by fixing means (not shown) such as a screw. The motor 50 is connected to the motor 5 through connection means such as a cable.
It is electrically connected to a control device for controlling the normal rotation drive, reverse rotation drive, stop, drive speed, and the like of 0, and further electrically connected to a power supply (all not shown).

A plurality of gears 54 and 56 are arranged inside the gear housing 42. The gear 54 includes a rotating shaft 52
A large-diameter gear portion 60 formed with a greater number of teeth than the gear 58 fixed to the distal end of the gear portion and meshing with the gear 58; a large-diameter gear portion having a smaller diameter than the large-diameter gear portion 60 and a smaller number of teeth; Small-diameter gear portion 62 formed coaxially and integrally with
And a shaft 6 penetrating through the centers of the large-diameter gear portion 60 and the small-diameter gear portion 62 and having both ends supported by bearing portions 64 formed on the inner wall of the gear housing 42.
6 rotatably supported.

On the other hand, the gear 56 has a larger diameter and a larger number of teeth than the small diameter gear portion 62 of the gear 54, and
A large-diameter gear portion 68 meshed with the gear is provided. Also,
As shown in FIGS. 1 to 4, the gear 56 is formed with a circular concave portion 72 that is open at one axial end thereof and that is circular in a plan view (as shown in FIG. 4). The bottom of the concave portion 72 is a smooth plane, and a through hole 74 having a smaller diameter than the concave portion 72 is formed at the center. A pair of engaging grooves 76 are formed radially around the through hole 74 at the bottom of the concave portion 72.

A circular hole 78 is formed coaxially with the gear 56 on the outer wall of the gear housing 42 at one axial end of the gear 56.
Is formed around the circular hole 78, and a cylindrical cylinder 82 is disposed coaxially with the circular hole 78.
It is fixed to the gear housing 42 by a fixing means such as a screw via a metal fitting 84 bent in a letter shape. A screw shaft 86 is arranged inside the cylinder 82.

The screw shaft 86 is connected to the main body 8.
An external thread is formed on the outer peripheral portion of the main body 8, and a shaft portion 94 having a smaller diameter than the main body portion 88 extends coaxially from an end of the main body portion 88 on the gear housing 42 side.
The shaft portion 94 is connected to the gear housing 4 of the cylinder 82.
A ball bearing 96 provided inside the two side ends,
A ball bearing 98 provided inside the gear housing 42 and on the side opposite to the ball bearing 96 via the gear 56 is rotatably supported so as to be able to rotate smoothly.

The shaft portion 94 passes through the through hole 74 of the gear 56 between the ball bearing 96 and the ball bearing 98, and is rotatable relative to the gear 56. Further, a pair of cylindrical pins 102 as engaging bodies (in a broad sense, as clutch means) are opposed to each other via the shaft portion 94 on the outer peripheral portion of the portion of the shaft portion 94 that has entered the gear housing 42. Has been extended. These pins 102 can enter (engage) into the above-described engagement groove 76. When the gear 56 rotates in a state where each pin 102 enters the engagement groove 76 (the state shown in FIG. 2), the engagement The inner peripheral portion of the mating groove 76 presses the outer peripheral portion of the pin 102 in the rotation direction to rotate the shaft portion 94 (that is, the screw shaft 86). That is, in the present embodiment, the gear 56 is the engaged body described in claim 2, and the clutch means described in claim 1 is configured together with the pin 102.

On the other hand, as shown in FIGS. 1 to 3, a nut 104 is screwed into the main body 88 of the screw shaft 86. The nut 104 has a portion on the gear housing 42 side that is slightly smaller than the inner peripheral portion of the cylinder 82 than the axially intermediate portion. It is in contact with the inner circumference. On the other hand, the portion of the nut 104 opposite to the gear housing 42 from the axially intermediate portion is a small-diameter portion 106 whose diameter is sufficiently smaller than the inner diameter of the inner peripheral portion of the gear housing 42. Bottomed cylindrical piston 112 housed inside gear housing 42
Of the gear housing 42 is press-fitted and integrated. In the present embodiment, the piston 112 is press-fitted into the nut 104 so as to be integrated. However, a female screw is formed on the inner peripheral portion of the end of the piston 112 on the gear housing 42 side, and the screw shaft 86 is formed. May be screwed to the main body portion 88 of the main body.

A gap is formed between the bottom of the piston 112 and the end of the screw shaft 86, and the size of this gap (ie, the gap between the bottom of the piston 112 and the end of the screw shaft 86). At least, the screw shaft 86 can be displaced toward the bottom of the piston 112 until the pin 102 is disengaged from the engagement groove 78.

The bottom of the piston 112 is directed toward a bracket 116 provided on the opposite side of the leg rest 32 from the abutment portion of the leg rest 32 by a joint 118 toward the joint 118 (in the direction of arrow C in FIG. 1). It is pivotably connected. The piston 112 is connected to the joint 1
By being connected to the bracket 116 via 18, it is impossible to rotate around its own axis. Therefore, the nut 104 integrated with the piston 112 cannot rotate inside the cylinder 82.

Further, limiters 120 are provided on the outer peripheral portions near both ends in the axial direction of the cylinder 82, respectively. These limiters 120 are electrically connected to the control device of the motor 50 via a cable or the like,
Upon detecting that the nut 104 has moved along the screw shaft 86 to the vicinity of both ends in the axial direction of the cylinder 82, the above-described control device stops the motor 50.

Next, the operation and effect of this embodiment will be described. In the chair 20 to which the present linear actuator 10 is applied, the weight of the leg rest 32 is determined when the person is not seated on the chair 20, and the weight of the leg rest 32 when the person is seated on the chair 20. If a load from the lower leg of the person acts on the leg rest 32, the sum of the load and the load acts on the screw shaft 86 via the piston 112 and the nut 104. Thereby, the shaft portion 9
4 is pressed against the bottom of the engagement groove 76 formed in the gear 56. Therefore, in this state, when the control device is operated to drive the motor 50 to rotate forward, the rotating shaft 52 rotates forward, and this rotational force is transmitted to the gear 56 via the gear 54, and the gear 56 rotates forward. When the gear 56 rotates in the forward direction, the inner peripheral portion of the engagement groove 76 presses the pin 102 in the forward rotation direction, and the shaft portion 94 (the screw shaft 86).
To rotate forward. When the screw shaft 86 rotates, the nut 104 reversely rotates around the main body 88, and slides toward the leg rest 32 by one pitch of the male screw of the main body 88 for every rotation to push out the piston 112. As a result, the piston 112 presses the leg rest 32 in a direction away from the cylinder 82 and the distance between the joint 46 and the joint 118 becomes longer than before the forward rotation, so that the leg rest 32 is raised around the hinge 34 (see FIG. 1). It turns in the direction of the arrow D) and becomes the two-dot chain line state in FIG. 1, and the lower leg of the person sitting on the chair 20 is lifted.

If the motor 50 is driven in the reverse direction in this state, the rotation shaft 52, the gear 54, the gear 56, and the screw shaft 86 rotate in the direction opposite to the direction of the normal rotation of the motor. It rotates relatively around the portion 88 and slides toward the gear housing 42 by one pitch of the external thread of the main body 88 for each rotation. When the nut 104 slides toward the gear housing 42, the piston 112 moves toward the gear housing 42 due to the weight of the leg rest 32 and the load from the lower leg of the person, whereby the joint 46 and the joint 118 are reversed. Because the leg rest 32 is shorter than the front,
It turns around downward (in the direction of the arrow E in FIG. 3) and becomes a solid line state in FIG. 1, and the chair 20 is in a normal seated state.

Here, for example, when the motor 50 is driven to rotate in the reverse direction in a state where the obstacle 132 is placed below the leg rest 32 that has been swung upward and lifted, the leg rest 32 comes into contact with the obstacle 132. If the nut 104 attempts to move toward the gear housing 42 in this contact state,
The leg rest 32 is moved downward around the hinge 34 so that the obstacle 13
2 and the leg rest 32 is moved by the reaction
2 presses the leg rest 32 upward around the hinge 34. Since this pressing reaction force acts on the nut 104 via the leg rest 32 and the piston 112, the nut 104 cannot slide toward the gear housing 42 (the direction of arrow F in FIG. 2) even if the screw shaft 86 rotates in the reverse direction. Therefore, when the screw shaft 86 reverses, as shown in FIG. 3, the nut 104 does not slide toward the gear housing 42, but the screw shaft 86 itself moves toward the leg rest 32 (in the direction of arrow G in FIG. 3).
The shaft portion 94 moves toward the legrest 32 with respect to the gear 56. As a result, the pin 102 is separated from the engagement groove 76. In this disengaged state, the inner peripheral portion of the engagement groove 76 cannot press the pin 102, so that even if the gear 56 rotates (reversely rotates), the rotational force is not transmitted to the screw shaft 86. That is, in this state, although the leg rest 32 does not pivot downward, a force that prevents reverse driving does not act on the motor 50, and the motor 5
Since 0 is reversely driven very smoothly, no overload occurs.

In this state, the load on the obstacle 132 is only the sum of the weight of the leg rest 32 and the load on the lower leg of the seated person, and the reverse driving force of the motor 50 does not act on the leg rest 32. For this reason, the leg rest 32 due to the breakage of the obstacle 132 or the reaction force from the obstacle 132
Can be prevented from being damaged.

Next, when the obstacle 132 is removed from this state so that no pressing reaction force acts on the leg rest 32 from the obstacle 132, the weight of the leg rest 32 and the load on the lower leg of the seated person are reduced. Piston 112, nut 10
4 acts on the screw shaft 86. As a result, the screw shaft 86 moves to the gear housing 42 side together with the piston 112 and the nut 104, and the pin 1
02 contacts the bottom of the recess 72. Further, when the gear 56 reversely or forwardly rotates by a predetermined angle in this contact state, the pin 10
The pin 102 enters the engaging groove 76 with the engaging groove 2 facing the engaging groove 76. As a result, the screw shaft 86 and the gear 56 are again connected to each other, and the rotational driving force of the motor 50 is transmitted to the screw shaft 86 so that the screw shaft 86 rotates. Therefore, even if the connection state between the screw shaft 86 and the gear 56 is released by the pressing reaction force from the obstacle 132, the connection is basically made again by removing the obstacle 132, so that the screw shaft 86 and the gear 56 are connected. No special operation is required to restore the connection with the gear 56.

The various effects described above are achieved by providing an obstacle detection sensor such as a pressure sensor on the leg rest 32 and automatically stopping the motor 50 when the leg rest 32 and the obstacle 132 come into contact with each other. With this configuration, the same effect can be obtained. However, in the present embodiment, the gear 56 and the screw shaft 86 can be rotated relative to each other, and when the pin 102 enters the engagement groove 76, the gear 5
6 and the screw shaft 86 are connected, and when the pin 102 is detached from the engagement groove 76, the connection state is released. Therefore, expensive parts such as an obstacle detection sensor such as a pressure sensor are separately provided. The cost is lower than in the configuration.

In this embodiment, the linear actuator 10 is applied for turning the legrest 32. For example, the backrest 30 of the chair 20 can be pivotally moved up and down by a hinge or the like. When the backrest 30 is connected, the linear actuator 10 may be used for turning the backrest 30.

Further, as shown in FIG. 6, the linear actuator 10 may be applied to a nursing bed 150.

That is, this nursing bed 150 is arranged in the longitudinal direction of the bed 156 on which the futon 154 and the like are laid.
4 156A from the middle part of the person lying on the body in the height direction)
(The leg side of the person sleeping on the futon 154) and the other end side 156B
(The side of the head of the person who sleeps on the futon 154) is divided into two parts, which are relatively rotatably connected by a hinge 158.
A bracket 116 is formed on the other end 156B of the bed 156 on the side opposite to the futon 154, and the piston 1
The bottom of 12 is pivotally connected around a joint 118.

On the other hand, the fixed portion 44 of the gear housing 42 is pivotally connected to the beam 162 connecting the legs 160 of the base 159 of the nursing bed 150 by a joint 46. Therefore, the linear actuator 10
When the motor 50 is rotated in the forward direction, the other end 156B of the bed 156 turns upward from a horizontal state with the one end 156A (solid line state in FIG. 6) to a desired inclination angle (a two-dot chain line in FIG. 6). State), and when the motor 50 is driven to rotate in the reverse direction from the state of turning upward, the other end 156 of the bed 156
B pivots downward relative to one end 156A.

Further, in the nursing bed 150 to which the present linear actuator 10 is applied, similarly to the chair 20 described above, when the other end 156B of the bed 156 turns downward, the other end of the bed 156 turned upward. Even if the other end 156B of the bed 156 is turned downward with an obstacle (not shown) placed between the side 156B and the base 159, the other end 156B of the bed 156 contacts the obstacle. And the other end 1
When a reaction force from an obstacle acts on 56B, the pin 102 of the linear actuator 10 is detached from the engagement groove 76 (see FIGS. 1 to 4), so that a force that hinders the reverse rotation act on the motor 50. In addition, the motor 50 is driven to rotate in the reverse direction very smoothly, so that no overload occurs.

Further, in the present embodiment, a pair of engagement grooves 76 are formed in the concave portion 72 of the gear 56, and these engagement grooves 7
6 corresponding to the shaft portion 94 (the screw shaft 8
6), a pair of pins 102 as an engaging body is provided, but the screw shaft 86 is
Any structure may be used as long as the engagement body can be disengaged from the engagement groove when the engagement body moves in the direction away from 2 (that is, when a pressing reaction force from the obstacle 132 acts). So, for example,
The number of the engagement grooves 76 and the pins 102 may be plural or three or more. Further, an external gear as an engagement body may be formed on a part of the outer periphery of the shaft portion 94, and an internal gear as an engagement groove that can be fitted into the external gear may be formed in the concave portion 72.

In this embodiment, when the screw shaft 86 rotates by receiving the rotational force of the gear 56, the nut 1
Although the nut 104 is configured to slide, the nut 104 is provided with an engaging body such as a pin 102 so that the nut 104 rotates by receiving the rotational force of the gear 56.
The screw shaft 86 itself screwed into the screw shaft 86 cannot be rotated and the piston 112 is provided on the nut 104 or the screw shaft 86 itself is configured as a piston so that the screw shaft 86 slides when the nut 104 rotates. Is also good.

Further, in the present embodiment, the gear 56 is used as an engaged body, and the pin 102 as the engaging body is provided on the screw shaft 86. For example, the engagement groove is formed at the end of the screw shaft 86. It is also possible to adopt a configuration in which the screw shaft 86 is used as an engaged body by providing the same, and an engaging body is provided in the gear 56 to be engaged with the screw shaft 86.

Further, the present invention is not limited to the linear actuator 10 having the cylinder 82 and the piston 112 as in the present embodiment. For example, even if a linear actuator is configured so that the pinion rotates due to the rotational force of the output shaft of the motor and the rotational force of the pinion is transmitted to the rack and the rack moves linearly, a clutch is provided between the pinion and the output shaft. The same effect can be obtained by providing the means.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a configuration of a linear actuator according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of FIG. 1 and is a side view showing a state in which a pin (engagement body) has entered an engagement groove of a gear (engaged body).

FIG. 3 is a side view corresponding to FIG. 2, showing a state in which a pin (engagement body) is disengaged from an engagement groove of a gear (engaged body).

FIG. 4 is a plan view of the gear (engaged body) in a state where a pin (engaged body) has entered an engagement groove of the gear (engaged body).

FIG. 5 is a side view showing an overall configuration of a chair to which the linear actuator is applied.

FIG. 6 is a side view of a nursing bed to which a linear actuator is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Linear actuator 20 Chair 32 Leg rest 50 Motor 52 Rotating shaft 56 Gear (engaged body, clutch means) 102 Pin (engaged body, clutch means) 112 Piston (moving body) 150 Nursing bed 156 Bed

Claims (2)

[Claims] 1. A linear actuator used for turning a backrest or a leg rest of a retractable chair or a bed of a nursing bed, etc., comprising: a rotating shaft rotated by a driving force of a motor; and a rotation of the rotating shaft. A moving body that moves substantially linearly under the force to displace the load supporting portion, and connects the rotating shaft and the moving body, and applies a load on the moving moving body in a direction substantially opposite to the moving direction. And a clutch means for releasing the connection when is actuated. 2. The clutch means, wherein: an engaged body provided on one of the rotating shaft and the moving body; and an clutched body provided on the other of the rotating shaft and the moving body. The load is applied to the moving body in a direction substantially the same as a specific moving direction of the moving body, and the movable body is engaged with the engaged body. 2. The linear actuator according to claim 1, further comprising: an engaging body that separates from the engaging body when a load exceeding the load on the moving body acts on the moving body. 3.