JP3300941B2 - Linear actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric linear actuator.

[0002]

2. Description of the Related Art Electric linear actuators have recently been used, for example, to raise a bed.

[0003] As a structure for stopping the mounting portion at the stroke end of the linear actuator, a limit switch is provided inside the linear actuator.

FIG. 8 shows a conventional linear actuator 10.
0 is a simple longitudinal sectional view of FIG.
The fixed mechanism 106 is provided on the gear mechanism 104. Inside the fixed cylinder 106, a driving cylinder 108 as a driving part is housed, and inside the driving cylinder 108, a screw shaft 110 is housed. The screw shaft 110 is connected to the gear mechanism 104, and rotates at a predetermined rotation speed when the motor 102 rotates. When the screw shaft 110 rotates, the nut 112 screwed with the screw shaft 110 moves in the axial direction, and the drive cylinder 108 attached to the nut 112 moves.

In this case, a pair of limit switches 114 and 116 are provided to stop the driving cylinder 108 at the stroke end. The nut 112 is provided with a projection 118 for operating the limit switches 114 and 116, and the nut 112 moves to operate the limit switches 114 and 116 and stop the motor 102.

[0006]

The conventional linear actuator 100 described above has a structure in which limit switches 114 and 116 are disposed at both ends of a stroke end, so that the structure becomes complicated and a screw shaft is formed. 1
10, a limit switch 11 on the outer peripheral side of the drive cylinder 108
There is a problem in that the arrangement around 4,116 becomes large due to the arrangement of 4,116.

Further, the conventional linear actuator 100
In this case, the limit switches are arranged at both ends of the stroke end.For linear actuators with different strokes, it is necessary to move and install the limit switch for each type of linear actuator. However, there is a problem that the manufacturing process becomes complicated.

Accordingly, the present invention has been made in view of the above problems, and provides a linear actuator in which a structure for stopping a driving cylinder at a stroke end is simplified.

[0009]

Linear actuator according to claim 1 of the present invention According to an aspect of the drive cylinder is disposed within the fixed cylinder, before
The screw shaft is rotatable inside the fixed cylinder and
The screw shaft is arranged so as not to move, and the screw shaft is rotated by a motor so that the nut screwed with the screw shaft is engaged.
And the drive cylinder held by this nut
A linear actuator to move the protruding portion is provided on the outer periphery of the nut, and a first limit switch and a second limit switch for the motor to ON state or OFF state provided axially inside the fixed barrel movably arranged switch rod along a first stop disposed at one end of the switch rod, the other end of the switch rod
A second stop arranged in part, the operating piece is provided between the ends of said switch rod, the projecting portion of the nut is possible to press the first stop of the switch rod, actuating piece of the switch rod move and by operating the first limit switch is stopped in a state in which the drive cylinder is most protruding from the fixed cylinder, the protruding portion of the nut said switch
When moving between the first stop and the second stop of the rod
The operating piece of the switch rod is moved and the second limit switch is operated by moving the operating piece of the switch rod when the protruding portion of the nut pushes the second stop portion of the switch rod without the operating piece of the switch rod moving. The driving cylinder is stopped in a state where the driving cylinder is most housed inside the fixed cylinder.

A linear actuator according to a second aspect of the present invention is the linear actuator according to the first aspect, wherein a slide groove is provided along the axial direction inside the fixed cylinder, and the switch rod is movable only in the axial direction along the slide groove. It was done.

According to a third aspect of the present invention, there is provided the linear actuator according to the first aspect, wherein a ring-shaped slide plate is rotatably fitted to an outer peripheral portion of the nut, and the projecting portion projects from the outer peripheral portion of the slide plate. It was made.

According to the linear actuator of the present invention,
The limit switch does not need to be rearranged according to the difference in the stroke of the linear actuator, and the used part is unified, so that it is possible to easily cope with the use of various strokes. Further, since there is no need to arrange limit switches at both stroke ends, the circumference of the shaft is compact.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A linear actuator 10 according to one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 and FIG. 2 are longitudinal sectional views schematically illustrating the structure of a linear actuator 10 according to this embodiment. First, the structure of the linear actuator 10 will be described with reference to FIGS.

On the base side of the linear actuator 10,
A motor 12 is mounted, and a gear mechanism 14 is connected to a shaft of the motor 12. A fixed cylinder 16 is attached from the gear mechanism 14 toward the distal end. The gear mechanism 14, the fixed cylinder 16, and the motor 12 are housed in a casing 56. In the description of the present embodiment, the side to which the motor 12 is attached is referred to as a rear portion, and the distal end side is referred to as a front portion.

A driving cylinder 18 is arranged inside the fixed cylinder 16, and a screw shaft 20 is arranged inside the driving cylinder 18. The screw shaft 20 is connected to the gear mechanism 14 and is rotatably supported by a pair of bearings 22 and 24. A head 54 is attached to the front end of the driving cylinder 18.

A nut 26 having a female screw portion is screwed into the screw shaft 20, and this nut 26 moves,
The drive cylinder 18 attached to the front end is moved in the axial direction.

An O-ring 2 is provided at the tip of the fixed cylinder 16.
8 is provided and is in contact with the drive cylinder 18. This has a waterproof effect.

Further, an O-ring 3 is also provided at the tip of the screw shaft 20.
0 is provided and is in contact with the inner peripheral surface of the drive cylinder 18. This has a waterproof effect.

A ring-shaped slide plate 32 is sandwiched and formed around the outer periphery of the nut 26. The slide plate 32 can freely rotate in the circumferential direction with respect to the nut 26, and one protrusion 34 protrudes from the outer peripheral portion.

A slide groove 36 is provided in the inner peripheral side of the fixed cylinder 16 in the axial direction, and a switch rod 38 is provided in the slide groove 36 so as to be movable in the axial direction. A front stop 40 is provided at the front end side of the switch rod 38.
Is provided, and a rear end portion is provided at a rear end portion. The protrusion 34 of the nut 26 is arranged to press the front stop 40 and the rear stop 42. Further, an operation piece 44 protrudes from the rear side of the switch rod 38. The structure of the slide groove 36 will be described with reference to a detailed drawing of the linear actuator 10 described later.

In the vicinity of the gear mechanism 104 of the fixed cylinder 16, a first limit switch 46 and a second limit switch 48 are arranged so as to face each other. The switch 46a of the first limit switch 46 and the switch 48b of the second limit switch 48 are pressed by the operating piece 44.

The operation state of the linear actuator 10 will be described with reference to FIGS.

FIG. 1 is a longitudinal sectional view showing a state in which the driving cylinder 18 is most housed inside the fixed cylinder 16, and FIG. In position.

When the motor 12 is operated and the driving cylinder 18 is in the most retracted state, the nut 26 is
Move to the rearmost position of 0. In this case, the projection 34 of the slide plate 32 moves the rear stop 42 of the switch rod 38 rearward, and at the same time, the operating piece 44
Moves backward, presses the switch portion 48a of the second limit switch 48, and the second limit switch 48 is turned off.
State. As a result, the operation of the motor 12 is stopped, and the driving cylinder 18 stops in the state where it is most housed in the fixed cylinder 16.

On the other hand, the motor 12 is rotated by a command signal or the like,
When the drive cylinder 18 protrudes from the fixed cylinder 16, the nut 26 moves near the front end of the screw shaft 20. The protrusion 34 of the slide plate 32 presses the front stop 40 forward, and the switch rod 38 moves forward. The operating piece 44 presses the switch portion 46a of the first limit switch 46, and the first
The limit switch 46 is turned off. As a result, the motor 12 stops, and the protrusion of the driving cylinder 18 also stops.

With the above structure, even if the first limit switch 46 and the second limit switch 48 are arranged in a pair in the vicinity, even if the switch rod 38 is used, the switch rod 38 can be used.
N / OFF is possible, and the position of the most complicated limit switch can be fixed regardless of the length of the stroke. Therefore, even if the stroke of the linear actuator 10 is different, it can be dealt with by changing the positions of the front stop portion 40 and the rear stop portion 42 of the switch rod 38, so that the used part can be unified and various stroke specifications can be achieved. Can be easily handled. Also,
First limit switch 46 and second limit switch 48
It is not necessary to dispose at both stroke ends, so that the circumference around the axis becomes compact.

Further, the drive cylinder 18 and the nut 26 are prevented from rotating by being fixed by passing a fixing pin through a mounting hole of the mounting rod. The ring may rotate due to friction. In this case, even if the nut 26 rotates,
Since the slide plate 32 only moves in the axial direction along the slide groove 36 of the fixed cylinder 16, the switch rod 3
8, the first limit switch 46 and the second limit switch 48 can be reliably switched.

FIGS. 3 and 4 show the linear actuator 1.
0 is a detailed drawing, the structure of which is similar to the simple longitudinal sectional view described above. However, the details will be described in order. 5 is a cross-sectional view taken along the line CC in FIG. 4, and FIG. 6 is a cross-sectional view taken along the line DD in FIG.

First, a spring 50 is attached to the switch 46a so that the switch 46a of the first limit switch 46 is always turned off. Similarly, a spring 52 is provided for the switch portion 48a of the second limit switch 48. When the limit switch itself has a built-in spring, the springs 50 and 52 are unnecessary.

As is apparent from FIG.
Has a shape in which the lower portion is widened, and the switch rod 38 can be stored in the widened portion. With such a shape, the switch rod 38 does not come off the slide groove 36.

The switch rod 38 can move freely in the slide groove 36 in the axial direction, but its movement is restricted in the circumferential direction. Further, since the fixed cylinder 16 has a closed outer shape and a simple circular shape, if the groove diameter for mounting the O-ring 28 is selected so as to match the slide groove 36 as a means for securing waterproofness, FIG. If r1 is the dimension of the slide groove 36 and r2 is the radius of the groove for mounting the O-ring 28, r1 = r2, and the O-ring 28 can be used.

[0033]

As described above, according to the linear actuator of the present invention, it is not necessary to arrange two limit switches according to the difference in the stroke of the linear actuator, so that the used part can be unified, and various stroke specifications can be easily achieved. Can respond. Further, since there is no need to dispose limit switches at both stroke ends, the circumference of the shaft becomes compact.

[Brief description of the drawings]

FIG. 1 is a simple vertical sectional view of a linear actuator showing an embodiment of the present invention, in which a driving cylinder is most housed.

FIG. 2 is also a state in which a driving cylinder is most protruded.

FIG. 3 is a detailed drawing of the linear actuator according to the present embodiment, showing a state in which a driving cylinder is most housed.

FIG. 4 shows a state in which the driving cylinder is most protruded.

FIG. 5 is a sectional view taken along the line CC in FIG.

FIG. 6 is a sectional view taken along line DD in FIG. 4;

FIG. 7 is a diagram showing a relationship between a dimension of a slide groove and a diameter of a groove for mounting an O-ring.

FIG. 8 is a longitudinal sectional view of a conventional linear actuator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Linear actuator 12 Motor 14 Gear mechanism 16 Fixed cylinder 18 Drive cylinder 20 Screw shaft 26 Nut 32 Slide plate 34 Projection part 36 Slide groove 38 Switch rod 40 Front stop part 42 Rear stop part 44 Working piece 46 First limit switch 48 Second Limit switch

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-9-250509 (JP, A) JP-A 51-45595 (JP, U) JP-A 47-20636 (JP, Y1) JP-A 47- 14028 (JP, Y1) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16H 25/00-25/24 B25J 19/00 G05D 3/12 H02K 7/06

Claims (3)

(57) [Claims] A driving cylinder disposed inside the fixed cylinder;
The screw shaft is rotatable inside and does not move in the axial direction.
Disposed so odd, by rotating the screw shaft by the motor, the nut which is screwed with the screw shaft
The drive cylinder held by the nut moves in the axial direction.
A linear actuator that, the projecting portion is provided on the outer periphery of the nut, and a first limit switch and a second limit switch for the motor to ON state or OFF state provided along the axial direction inside the fixed barrel movably arranged switch rod Te, a first stop disposed at one end of the switch rod, the second stop disposed on the other end of said switch rod, actuation between the ends of said switch rod When the protrusion of the nut presses the first stop of the switch rod, the operation piece of the switch rod moves to operate the first limit switch, and the drive cylinder is fixed. The switch rod is stopped in a state of being most protruded from the cylinder, and the protrusion of the nut is a first stop of the switch rod.
When moving between the switch and the second stop,
The operating piece of the switch rod does not move, and the protrusion of the nut presses the second stop of the switch rod, so that the operating piece of the switch rod moves to operate the second limit switch, A linear actuator, wherein the driving cylinder is stopped in a state where the driving cylinder is most housed inside the fixed cylinder. 2. A linear actuator according to claim 1, wherein a slide groove is provided in the fixed cylinder along the axial direction, and the switch rod is movable only in the axial direction along the slide groove. . 3. The linear device according to claim 1, wherein a ring-shaped slide plate is rotatably fitted to an outer peripheral portion of said nut, and said projecting portion projects from an outer peripheral portion of said slide plate. Actuator.