JP2000002309A - Actuator - Google Patents

Abstract

(57) [Problem] To provide an electric actuator which can reduce bearing loss at the time of rotation transmission and which can employ a small-torque high-speed motor as a drive source. An electric motor is rotated by a thrust shaft.
And the rotational motion of the thrust shaft 11 is converted into a linear motion of the thrust rod 34. When the electric motor 11 is further rotated in a state where the advance of the thrust rod 34 is stopped, the thrust shaft 15 is moved in a direction opposite to the traveling direction of the thrust rod 34 so far. At this time, the thrust rod 34 after stopping the electric motor 11 is compressed by the elastic member 55 being compressed.
Is held. Here, the electric motor 11
Since only one ball bearing 72, which has conventionally been used for two, is used for the large pulley 24 that transmits the rotation of the thrust shaft, the number of bearings can be reduced and bearing loss of the thrust shaft 15 can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator for converting a rotary motion of a rotary drive source such as an electric motor into a linear motion to linearly move a linear member in an axial direction thereof.

[0002]

2. Description of the Related Art Various types of actuators having a mechanism for converting a rotary motion into a linear motion are known. The operations required for this type of actuator include a feed operation between predetermined positions, a clamp operation of a target work, and a pressing or pulling operation after the feed operation of the target work.

An example of an electric actuator capable of performing a pressing operation and a pulling operation after a feeding operation of a target work will be described with reference to FIG. In this electric actuator, the rotation of the electric motor 101 is controlled by the small pulley 10.
2, transmitted to the thrust shaft 105 via a power transmission mechanism consisting of a synchro belt 103 and a large pulley 104. The thrust shaft 105 has a threaded portion 106 on its outer peripheral surface.
The female thread portion 108 of the feed nut 107 is screwed into the external thread portion 106. A thrust rod 109 is attached to the feed nut 107. The feed nut 107 or the thrust rod 109 is prevented from rotating around the axial direction by some rotation preventing mechanism, and the rotation of the thrust shaft 105 is converted into a linear motion of the feed nut 107 and the thrust rod 109.

On the outer peripheral side of the thrust shaft 105, there is provided an elastic member 110 formed by superposing a plurality of disc springs for storing rotational energy in series. When the electric motor 101 is further rotated while the thrust rod 109 has sent a work (not shown) to the front end (or the rear end) of the stroke end, the thrust rod 109 is prevented from further moving forward (or backward). Therefore, the thrust shaft 105 is displaced in the opposite direction, and the displacement compresses the elastic member 110 in the axial direction. In order to allow the thrust shaft 105 to move in the axial direction with respect to the large pulley 104, the thrust shaft 105 and the large pulley 10
4 is a slide key 11 that engages with the other.
1 is provided.

When the amount of displacement of the thrust shaft 105 in the reverse direction, that is, the amount of compression of the elastic member 110 reaches a predetermined amount, the magnet 112 attached to the thrust shaft 105
Is detected by the thrust sensor 113, and a thrust detection signal is output to a control device (not shown). The non-excited operation type electromagnetic brake 114 is operated based on the thrust detection signal, and the electric motor 101 is braked. When the power supply to the electric motor 101 is stopped in this state, the elastic member 110
The thrust rod 109 is pushed (or pulled) by the repulsion force, and the pressing operation (or the pulling operation) of the work is held in a non-energized state.

In order to release the pressing operation (or the pulling operation) of the work, the lock of the electromagnetic brake 114 is released and the electric motor 101 is rotated in the reverse direction. Then, the compression of the elastic member 110 due to the reverse movement of the thrust shaft 5 is eliminated, so that the thrust sensor 113 outputs a no-thrust detection signal to the control device. Then, the operation shifts to the next operation based on the no thrust detection signal.

Here, in the transmission mechanism for converting the rotational movement of the electric motor 101 into a linear movement of the thrust rod 109, a pair of ball bearings 115, 116 and an elastic member 110 provided at both axial ends of the large pulley 104. A pair of ball bearings 117 and 118 provided at both ends in the axial direction and a needle bearing 119 provided between the outer peripheral surface of the tip of the thrust shaft 105 and the inner peripheral surface of the thrust rod 109 are provided.

The above-described electric actuator is excellent in that it has a simple structure, is small, lightweight, and can be manufactured at low cost. Further, it is excellent in that a thrust force such as a pressing operation can be held by the elastic member 110 that stores energy when the electric motor 101 is not energized.

[0009]

By the way, in the field of the above-mentioned electric actuator, it is required to manufacture the actuator smaller, lighter and cheaper. In order to obtain a predetermined output while satisfying this demand, the electric motor 101
The most effective measure is to use a small-torque high-speed motor. That is, even with a small torque type motor,
By rotating at a high speed, a predetermined output can be obtained.

However, when a small-torque high-speed motor is used as the electric motor 101, the bearing loss increases due to the high-speed rotation, and the bearing torque is easily affected by the small torque.

Therefore, in the conventional structure shown in FIG. 5, there are a total of five bearings in relation to the thrust shaft 105, and the bearing loss increases, resulting in poor efficiency as a whole. Therefore, there is a problem that it is difficult to use a small-torque high-speed motor as the electric motor 101.

In the conventional structure shown in FIG.
Is supported on both sides by two ball bearings 115, 116,
The positions in the radial direction and the axial direction are fixed, respectively. Therefore, concentricity between the large pulley 104 and the thrust shaft 105 is required. This is because when the concentricity of the large pulley 104 and the thrust shaft 105 is not sufficiently obtained, the thrust shaft 105 is displaced when the thrust shaft 105 is displaced in the opposite direction.
This is because a friction loss between the motor and the large pulley 104 occurs. Therefore, the large pulley 104 and the thrust shaft 10
In order to increase the accuracy of the concentricity of No. 5, the cost was high.

Of course, the above problem does not occur if the rotation transmitting mechanism from the electric motor 101 to the thrust shaft 105 is realized by a gear mechanism composed of a combination of a plurality of gears. However, since the noise level of the gear mechanism is incomparably higher than that of the belt-type transmission mechanism, and there are cases where it is difficult to adopt it depending on the application or model, the belt-type transmission mechanism is often advantageous. If the above problem can be solved while using a belt-type transmission mechanism, an electric actuator that has a very wide range of applications and meets needs can be obtained.

The present invention has been made in view of the above circumstances, and has as its object to reduce bearing loss during rotation transmission and to employ a small-torque high-speed rotary drive source. An object of the present invention is to provide an actuator.

Another object of the present invention is to provide an actuator capable of suppressing an increase in cost due to centering between a rotating member and a rotating wheel such as a pulley.

[0016]

According to the first aspect of the present invention, there is provided a rotary member rotatably supported in an actuator body by driving a rotary drive source. When the linear member is linearly moved in the axial direction by converting the rotational movement of the rotary member into a linear movement of the linear member, and when the linear movement of the linear member is restricted, the rotary member is moved to the linear member. And the repulsive force obtained by compressing the elastic member when the rotating member moves in the reverse direction is used as the thrust of the linear member, and the thrust is used when the rotation drive source stops. Is held by the elastic member, a rotating wheel is supported on the rotating member so as to be integrally rotatable and relatively movable in the axial direction. To Ri rotation of the rotary drive source so as to transmit the rotary member, between the rotating wheel and the actuator body and only one intermediate bearing for holding in position relative to the actuator body to the rotating wheel.

When the rotary drive source is driven to rotate by the above means, the rotating wheel is rotated via the cord, whereby the rotating member is rotated. Then, the rotational motion is converted into a linear motion of the linear member, and the linear member moves linearly.
Thereafter, when the movement of the rectilinear member is restricted, for example, when a pressing mechanism provided on the rectilinear member presses the work at a predetermined position, the rotating member moves in a direction opposite to the moving direction of the rectilinear member so far. Moving. At this time, the rotating member can move in the reverse direction by a displacement amount corresponding to the amount of compression of the elastic member, and the repulsive force stored in the elastic member at that time becomes the thrust of the rectilinear member when the rotation drive source stops.

Here, in the present invention, the rotating wheel is supported so as to be able to rotate integrally and relatively move in the axial direction, and the rotating wheel is positioned between the rotating wheel and the actuator body at a predetermined position with respect to the actuator body. , Only one bearing is interposed. Thus, the holding of the rotating wheel in position is ensured by a single bearing.

Therefore, according to the first aspect of the present invention,
By reducing the number of bearings for supporting the rotating wheel from two to one, bearing loss can be reduced. or,
It becomes possible to employ a small torque high-speed rotary drive source. Further, cost reduction and downsizing can be achieved by reducing the number of bearings.

According to a second aspect of the present invention, in the actuator according to the first aspect, at least one of between the bearing and the actuator main body or between the bearing and the rotating wheel extends in the axial direction. A gap was formed, and a gap was formed in a direction orthogonal to the axial direction between at least one of the bearing and the actuator body or between the bearing and the rotating wheel.

By the above means, a gap is formed between at least one of the actuator body or the rotating wheel and the bearing in the axial direction and in the direction perpendicular thereto. As a result, free rotation of the bearing with respect to the actuator body and the rotating wheel is guaranteed, so that bearing loss can be further reduced. Moreover, since the center of rotation of the rotating wheel does not depend on the bearing but only on the rotating member, the rotating wheel and the rotating member are always concentric. As a result, a high degree of concentricity between the rotating wheel and the rotating member is not required at the time of manufacture or assembly, and cost reduction can be promoted.

According to the third aspect of the present invention, the rotating member supports the rotating wheel so as to be integrally rotatable and relatively movable in the axial direction. The rotation of the rotation drive source is transmitted to the rotating member, and a bearing for holding the rotating wheel at a predetermined position with respect to the actuator body is interposed between the rotating wheel and the actuator body, and between the bearing and the actuator body. Or, a gap is formed in the axial direction between at least one of the bearing and the rotating wheel, and at least one of between the bearing and the actuator body or between the bearing and the rotating wheel. Formed a gap in a direction perpendicular to the axial direction.

According to the above-mentioned means, the third aspect of the present invention does not necessarily achieve the effect and effect of reducing the number of bearings in the first aspect of the present invention, but the other aspects of the first and second aspects of the present invention. Performs all functions and effects.

According to a fourth aspect of the present invention, in the actuator according to any one of the first to third aspects,
The bearing is a ball bearing, the inner ring of which is disposed on the outer peripheral side of one of the rotating wheel or the actuator body, and the outer ring is disposed on the other inner peripheral side of the rotating wheel or the actuator body. Configuration.

According to the above-mentioned means, in the invention according to claim 4, as a bearing, the characteristics of the ball bearing in which the rolling friction value is small are utilized, and the inner ring and the outer ring make good use of the characteristic that can tolerate a slight inclination. Can be reduced. In addition, the requirement for geometric rotation accuracy of the rotating wheel such as the rotating member and the pulley can be further reduced.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment will be described below with reference to FIGS. As shown in FIG. 1, an actuator main body 2 forming a large frame of an electric actuator 1 as an actuator includes a first frame 3, a long and cylindrical second frame 4 disposed in front of the first frame 3. A tubular intermediate bracket 5 connecting the two frames 3 and 4; a rear bracket 6 connected to the rear end of the first frame 3; a front bracket 7 connected to the front end of the second frame 4; And a rear cover 9 connected to the rear end of the bearing guide boss 8.

The upper portion of the first frame 3 protrudes above the second frame 4, and an electric motor 11 as a rotary drive source is fixed to the front end face of the protruding portion of the first frame 3. . In the present embodiment, a small-torque high-speed induction motor is used as the electric motor 11. The output shaft 12 of the electric motor 11 is
It protrudes toward the internal space of the frame 3.

A non-excitation operation type electromagnetic brake 13 is fixed to the electric motor 11. Therefore, the electric motor 11
When the electromagnetic brake 13 is in a non-excited state while the power supply to the power supply is stopped, the output shaft 12 is locked by the action of the electromagnetic brake 13. On the other hand, when the electric motor 11 is energized and the electromagnetic brake 13 is in the excited state, the braking action of the electric brake 13 is released and the output shaft 12 is rotated.

The thrust shaft 15 as a rotating member is formed in a long and rod shape, and is accommodated so as to extend over substantially the entire length of the actuator body 2. Thrust shaft 1
5 is rotatably supported by ball bearings 16 and 17 as a pair of bearings spaced apart in the longitudinal direction of the thrust shaft 15.

In the first frame 3 and the rear bracket 6, a power transmission mechanism 21 for transmitting the rotational force of the output shaft 12 to the thrust shaft 15 is accommodated. Power transmission mechanism 21
Is constituted by a belt-type transmission mechanism.

The power transmission mechanism 21 will be described. A small pulley 22 is fixed to the output shaft 12 and the output shaft 1
2, the small pulley 22 is rotated. A slide key 23 is fixed to the outer periphery on the rear end side of the thrust shaft 15. Thrust shaft 15 corresponding to slide key 23
Large pulley 2 forming a pulley as a rotating wheel on the outer peripheral surface of
4 are provided. Large pulley 24 is slide key 23
Is supported so as to be able to rotate integrally with the thrust shaft 15 and to be relatively movable in the axial direction with respect to the thrust shaft 15. A synchro belt 25 composed of an endless timing belt as a cord is mounted on the small pulley 22 and the large pulley 24.

Accordingly, the rotational force of the output shaft 12 is transmitted to the thrust shaft 15 via the small pulley 22, the synchro belt 25 and the large pulley 24. That is, as the output shaft 12 rotates, the thrust shaft 15 rotates while the torque is amplified while being reduced based on the diameter ratio (for example, 1: 2) of the small pulley 22 and the large pulley 24.

An external thread portion 31 is formed on the outer peripheral surface of the thrust shaft 15 in the axial direction over the entire region on the distal end side. An external thread 3 is provided on the inner periphery of the feed nut 32 as a linear feed portion.
An internal thread portion 33 having the same pitch as 1 is formed and screwed to the external thread portion 31 of the thrust shaft 15. The thrust shaft 15 and the feed nut 32 constitute a converting means for converting a rotary motion into a linear motion.

The thrust rod 34 as a rectilinear member is formed in a long and cylindrical shape, and is housed in the second frame 4 with the distal end of the thrust shaft 15 inserted therein. The base end of the thrust rod 34 is fixed to the feed nut 32, and the thrust rod 34 and the feed nut 32 are integrally formed. The tip of the thrust rod 34 penetrates through the front bracket 7 and protrudes to the outside.

The feed nut 32 or the thrust rod 34 is prevented from rotating around the axial direction by an appropriate rotation preventing mechanism (not shown). Therefore, the thrust shaft 15
Is rotated, the feed nut 32 and the thrust rod 34 are integrally advanced and retracted in the axial direction based on the screwing relationship between the thrust shaft 15 and the feed nut 32 and the rotation preventing structure on the thrust rod 34 side.

A connecting fitting 35 is fixed to the tip of the thrust rod 34, and a mating machine (not shown) is connected to the connecting fitting 35. Here, the partner machine refers to, for example, a pressing mechanism or a pulling mechanism, and conveys a work to a predetermined position by the partner machine with the advance and retreat of the thrust rod 34.
At that predetermined position, a pressing force or a pulling force is applied to the work.

A needle bearing 41 which is in contact with the inner peripheral surface of the thrust rod 34 is mounted on the outer peripheral surface of the distal end of the thrust shaft 15. The needle bearing 41 has a support function of supporting the thrust rod 34 together with the feed nut 32 at a position separated from the feed nut 32, and a guide function of guiding the advance / retreat operation of the thrust rod 34 and smoothing the advance / retreat operation. It has.

A metal bearing 42 is mounted on the inner peripheral surface of the front bracket 7 to be in contact with the outer peripheral surface of the thrust rod 34. The metal bearing 42 prevents the thrust rod 34 from directly contacting the front bracket 7 with the thrust rod 34.
A guiding function is provided for guiding the forward / backward movement of the vehicle and smoothing the forward / backward movement. Metal bearing 42 is thrust rod 3
The support function and the guide function of the thrust rod 34 are firmly secured by cooperation with the needle bearing 41.

In the actuator body 2, the front end of the intermediate bracket 5 and the rear end of the front bracket 7
Cushion rubbers 43 and 44 each having elasticity as a buffer member are mounted. Back cushion rubber 4
3 abuts against the rear surface of the feed nut 32 at the stroke end on the rear end side of the thrust rod 34, thereby alleviating the impact together with the role of a stopper for stopping the stroke output when an abnormal operation state occurs. is there. The front cushion rubber 44 is in contact with the front surface of the feed nut 32 at the stroke end on the front end side of the thrust rod 34, thereby functioning as a stopper for stopping the stroke output when an abnormal operation state is caused, and reducing the impact. Is what you do.

A magnet 45 is mounted on the outer peripheral surface of the feed nut 32 as a portion to be detected. Actuator body 2
, That is, on the outer surface of the second frame 4, a pair of position detection sensors 46 and 47 as position detection means are mounted. The rear position detection sensor 46 is the feed nut 32
When the thrust rod 34 is located at the rear end position, the magnetism of the magnet 45 is detected and a rear end position detection signal is output to an external control device (not shown). Also, the front position detection sensor 4
When the feed nut 32 and the thrust rod 34 are arranged at the front end position, 7 detects the magnetism of the magnet 45 and outputs a front end position detection signal to the control device.

Next, the configuration of the ball bearings 16 and 17 and the surrounding structure will be described. In the actuator body 2, a first locking wall 51 is formed on the first frame 3 so as to protrude inward, and the intermediate bracket 5 is also provided with a first locking wall 51 at a position away from the first locking wall 51 in a forward direction. A second locking wall 52 protruding toward is formed. The pair of ball bearings 16 and 17 are disposed between the locking walls 51 and 52.

The outer rings of the ball bearings 16 and 17 are accommodated in the inner peripheral surface of the actuator main body 2, that is, the inner peripheral surface of the first frame 3 or the intermediate bracket 5 so as to be slidable in the axial direction. The thrust shaft 15 is loosely inserted into the inner rings of the ball bearings 16 and 17, and the inner rings of the ball bearings 16 and 17 are slidable in the axial direction with respect to the outer peripheral surface of the thrust shaft 15.

A first locking piece 53 protruding outward is formed on the outer peripheral surface of the thrust shaft 15, and a second locking piece protruding outward is also provided at a position further away from the first locking piece 53. A piece 54 is formed. The distance between the first locking piece 53 and the second locking piece 54 in the axial direction is determined by the locking walls 51 and 5.
The distance between the two is substantially the same. Initial state, that is, FIG.
In the state of the above, both locking walls 51, 52 and both locking pieces 53, 54
And the same positional relationship is maintained in the axial direction.

An elastic member 55 is provided between the ball bearings 16 and 17 in which a plurality of (here, six) disc springs are stacked in series in the axial direction. In this embodiment, each disc spring has an inner diameter supporting structure.

At the rear end of the thrust shaft 15, a magnet 61 as a detected part is mounted. Actuator body 2
A thrust sensor 62 is mounted on the outer surface of the rear cover 9 at a position corresponding to the magnet 61.

As shown in FIG. 1, the thrust sensor 62 detects the magnetism of the magnet 61 when no thrust is generated, and outputs a non-thrust detection signal to the outside. On the other hand, when the thrust is generated, the magnet 6
A thrust detection signal is output in view of the fact that the magnetism No. 1 is not detected.

Next, the structure around the large pulley 24 will be described specifically with reference to FIG. An annular projection 71 projecting rearward and surrounding the thrust shaft 15 is formed integrally with the large pulley 24. An inner ring 73 of a ball bearing 72 is fixed to an outer peripheral surface of the protrusion 71. The fixing is performed by a step 74 formed on the outer peripheral surface of the protruding portion 71 and a C-ring 75 mounted on the outer peripheral surface of the protruding portion 71.

On the other hand, the outer ring 76 of the ball bearing 72 has a gap α in the radial direction with the actuator body 2 and a gap β in the axial direction. FIGS. 1 and 2 show the gaps α and β larger than the actual gaps in order to clearly show the existence of the gaps α.
mm and the gap β are set to about 0.1 to 0.2 mm. Therefore, the outer ring 76 of the ball bearing 72 normally has the gaps α and β with respect to the inside of the actuator body 2.
Is in a non-fixed state due to the presence of the inner ring 73, and is rotated following the rotation of the inner ring 73. Of course, the movement of the ball bearing 72 beyond the gaps α and β is restricted by the engagement of the outer ring 76 with the actuator body 2, that is, a part of the bearing guide boss 8 and the rear cover 9. A part of the bearing guide boss 8 and the rear cover 9 constitutes a regulating portion.

Next, the operation of the electric actuator 1 configured as described above will be described. First, a description will be given of a case where the connection fitting 35 is provided with a pressing mechanism, and the pressing operation is performed after the work is fed to the side away from the electric actuator 1.

When the electric motor 11 is driven from the state of FIG. 1 based on a command from a control device (not shown), the output shaft 1
2 rotates, and the rotation is transmitted to the thrust shaft 15 via the small pulley 22, the synchro belt 25, and the large pulley 24. That is, as the output shaft 12 rotates, the thrust shaft 15 rotates.

Along with this rotation, a force pulling upward in FIGS. 1 and 2 is generated on the large pulley 24 by the synchro belt 25. Accordingly, the thrust shaft 15 has its base end pointed by an arrow γ in FIG. It flexes slightly in the direction shown, ie upwards. The size of the gap α is set so that the gap α in the radial direction of the ball bearing 72 is larger than the amount of deflection. Therefore, regardless of the upward deflection of the thrust shaft 15 due to the driving of the drive motor 11, the outer ring 76 of the ball bearing 72 is not pressed against the inner peripheral surface of the actuator body 2, and the free rotation of the outer ring 76 is guaranteed. Is done.

With the rotation of the thrust shaft 15, the feed nut 32 or the thrust rod 34, which has been prevented from rotating, advances integrally in the axial direction due to the screwing relationship between the external thread 31 and the internal thread 33. Connection fitting 35 at the tip of thrust rod 34
Moves the work to a predetermined target position as the thrust rod 34 advances.

At the same time, since the feed nut 32 has also reached the predetermined target position, the position detection sensor 47 detects the magnetism of the magnet 45 and outputs a front end position detection signal to the control device.
The control device determines from the front end position detection signal that the work has reached the predetermined target position, and switches from the feeding operation to the pressing operation. As this switching, there are a method of switching the feeding operation to a low speed and a method of maintaining the same speed, but in any case, the feeding operation is continued.

At this point, the amount of compression of the elastic member 55 remains in the initial state. Further, since the outer ring 76 of the ball bearing 72 is freely rotated with respect to the actuator body 2, the inner ring 7 is rotated with the rotation of the large pulley 24 and the thrust shaft 15.
It goes around with 3. Therefore, during the previous feeding operation,
No bearing loss occurs due to the ball bearing 72.

Subsequently, the operation of pressing the work at the predetermined target position starts. At the time of the pressing operation, the work cannot advance further, so that the thrust rod 34 and the feed nut 32 provided integrally with the mating machine and the connection fitting 35 cannot further advance and remain stopped. . Nevertheless, since the electric motor 11 continues to rotate,
The thrust shaft 15 starts to move backward in the axial direction due to the screwing relationship between the external thread portion 31 and the internal thread portion 33. The backward movement of the thrust shaft 15 is realized by the thrust shaft 15 sliding in the axial direction with respect to the large pulley 24.

The reverse movement of the thrust shaft 15 causes the second
The locking piece 54 is moved backward while being engaged with the ball bearing 17 on the front side, and the ball bearing 17 is retracted integrally with the thrust shaft 15. At this time, slippage occurs between the outer ring of the ball bearing 17 and the inner peripheral surface of the actuator body 2. on the other hand,
Since the rear ball bearing 16 is engaged with the first locking wall 51, the position does not change even if the thrust shaft 15 moves backward.

When the thrust shaft 15 moves backward, the elastic member 55 is compressed, and the elastic member 55 stores the driving energy from the power source of the electric motor 11 and the rotational energy from the rotating body. That is, the pressing force is stored by the repulsive force based on the elastic force of the elastic member 55.

At this time, since the magnet 61 mounted on the thrust shaft 15 moves backward by the same displacement as the displacement of the thrust shaft 15, the magnet 61 is disposed at a position shifted rearward from a position facing the thrust sensor 62. ing. Therefore, a thrust generation signal is output from the thrust sensor 62 to the control device.

Here, when the thrust shaft 15 is retracted,
Due to the sliding friction between the thrust shaft 15 and the large pulley 72, a force is generated on the large pulley 72 to move backward. However, since the ball bearing 72 is fixed to the large pulley 72, the movement to the retreating side is almost restricted.
However, in this case, since the outer ring 76 of the ball bearing 72 is pressed against the inner surface of the actuator body 2, bearing loss due to the ball bearing 72 occurs.

The control device stops the excitation of the electric motor 11 on the basis of an AND condition between the previously input front end position detection signal from the position detection sensor 47 and the thrust generation signal from the thrust sensor 62 as a necessary condition. Electromagnetic brake 13 at the same time
And stop the excitation to activate the brake. Then, the thrust shaft 15 is stopped at a position where the thrust shaft 15 is further retracted by a small amount due to an inertia moment in a rotating portion of the electric motor 11 or the like. The repulsive force stored in the elastic member 55 is held as a pressing force for pressing the work even when the electric motor 11 is stopped.

Next, when the pressing operation is released, the electromagnetic brake 13 is first excited to release the brake, and the electric motor 11 is driven to rotate in a direction opposite to the conventional direction. Thereby, the repulsive force stored in the elastic member 55 is released, and the elastic member 55 returns to its original state. Then, the thrust shaft 15 is advanced, and the magnet 61 is displaced together with the thrust shaft 15, and the thrust sensor 62 outputs a non-thrust detection signal to the control device.

Thereafter, the thrust rod 34 is retracted due to the threaded relationship between the external thread 31 and the internal thread 33. As a result, the front end position detection signal output from the position detection sensor 47 to the control device is also stopped and returns to the initial position shown in FIG.

When the connecting bracket 35 is provided with a pulling mechanism, and when the pulling operation is performed after the work is fed to the side approaching the electric actuator 1, the electric actuator 1 operates in a manner opposite to the above description of the operation. I do.

Therefore, according to this embodiment, the following effects can be obtained. (1) The number of bearings that lead to loss of rotational force transmission is reduced by one from the number of bearings of the conventional structure. That is, the bearing on the left side of the large pulley 24 is eliminated, and the bearing that leads to bearing loss is replaced with the ball bearing 1.
6, 17, and four needle bearings 41 and ball bearings 72. Therefore, even if it is assumed that all of these bearings generate the same bearing loss as the conventional structure shown in FIG. 5, the bearing loss can be reduced by about 20%.

(2) As the number of bearings decreases, the cost can be reduced in addition to the bearing loss, and the length of the electric actuator 1 in the axial direction can be reduced, which contributes to downsizing. I do.

(3) The outer race 76 of the ball bearing 72 has gaps α and β between itself and the actuator body 2 in the radial direction and the axial direction. Therefore, the thrust shaft 1
During a normal feeding operation in which the 5 does not move backward, the outer ring 76 of the ball bearing 72 rotates together with the inner ring 73, so that no bearing loss occurs here. As a result, during normal feed operation, the number of bearings that generate bearing loss is three except for the ball bearing 72, so that the bearing loss is reduced by about 40% compared to the conventional structure.
It can be reduced near.

(4) The outer ring 76 of the ball bearing 72 has a gap α in the radial direction between the outer ring 76 and the actuator main body 2. It is set to be sufficiently large even when various factors such as the amount of deflection of the thrust rod 15 generated by being pulled by the pulley 25, dimensional change due to temperature, variation in processing accuracy, and assembly error are considered. The center of rotation of the large pulley 24 is the ball bearing 72.
, The large pulley 24 and the thrust shaft 15 are always concentric. As a result, a high degree of concentricity between the large pulley 24 and the thrust shaft 15 is not required at the time of manufacture or assembly, and the cost reduction can be promoted together with the reduction in the number of bearings.

(5) By reducing the bearing loss as described above, a small-torque high-speed motor can be used as the electric motor 11. Along with this, it is possible to obtain a predetermined output while satisfying the requirements for making the electric actuator 1 smaller, lighter and cheaper.
Further, the use range of the belt type transmission mechanism having an extremely low noise level as compared with the gear mechanism is widened.

(6) The thrust rod 34 is formed in a cylindrical shape, so that most of the thrust shaft 15 is accommodated therein. Thereby, the total length of the electric actuator 1 can be shortened.

In addition to the embodiments described above, there are other embodiments as follows. As shown in FIG. 3, the disc spring constituting the elastic member 55 may be of an outer diameter guide type in which the outer diameter side is guided by the inner surface of the actuator body 2 (the intermediate bracket 5).

The clearances α and β are provided between the outer ring 76 of the ball bearing 72 and the actuator body 2. On the contrary, the outer ring 76 is mounted on the actuator body 2, and the clearances α and β are formed by the inner ring 73 and the large pulley. The same effect can be expected even if provided between them. A similar effect can be expected even when the gap α is provided both between the outer ring 76 and the actuator body 2 and between the inner ring 73 and the large pulley 24 and the gap β is provided on at least one of them.

The inner and outer relationship between the actuator main body 2 and the large pulley 24 is reversed, and the inner ring 73 of the ball bearing 72 is disposed on the outer peripheral side of the actuator main body 2 and the outer ring 76 is disposed on the inner peripheral side of the large pulley 24. It is also possible to change the design of the arrangement.

The electric actuator 1 shown in FIGS.
In the above, the clearances α and β between the ball bearing 72 and the actuator main body 2 are provided in the radial direction and the axial direction, respectively. However, as shown in FIG. The actuator body 2 may be fixed to the inner surface. Also in this case, only one bearing is required to support the large pulley 24, and the cost can be reduced while reducing bearing loss as compared with the conventional structure.

Although the ball bearing 72 is provided only on the rear end side of the large pulley 24, a ball bearing may be provided only on the front end side of the large pulley 24. The ball bearings 72 having the gaps α and β may be provided on both sides of the large pulley 24. In this case, the number of bearings is the same as the conventional structure, but bearing loss can be reduced.

In addition to providing the slide key 23 for transmitting the rotation between the thrust shaft 15 and the large pulley 24, the fitting portion between the thrust shaft 15 and the large pulley 24 may be formed by a spline, a hexagon bar, or the like. Can be realized by making it non-circular.

As the bearings 16, 17, 41, 42, 72, any other bearings such as needle bearings, metal bearings, ball bearings and the like can be used. It is preferable to use as small a ball bearing as possible.

As the elastic member 55, other elastic means, such as a coil spring, a leaf spring, and urethane rubber, having elasticity and capable of storing energy of the spring may be used other than the disc spring. Further, the overlapping arrangement of the disc springs may be arranged in parallel.

Although the electric motor 11 is used as the rotary drive source, particularly an induction motor, other electric motors such as a servo motor may be used, and a rotary machine such as a non-electric air motor may be used. The type of the rotary drive source is not limited.

Here, when a servomotor is used, the position can be detected by the pulse signal of the encoder, so that the feed operation can be electronically arbitrarily performed with high accuracy, and the position detection sensors 46 and 47 become unnecessary. There are advantages. Also,
By using the torque control function of the servomotor, the thrust can be controlled more precisely in smaller units. The thrust sensor 62 can confirm that the thrust value satisfies the level,
Can be applied to improve reliability.

As the synchro belt 25, a rope other than the timing belt, such as a belt or a chain, may be used. The screwing relationship between the thrust shaft 15 and the feed nut 32 is
In addition to the mechanical screwing relationship between the external thread 31 and the internal thread 33,
It is also possible to have a magnetic screwing relationship with a magnetic screw.

The relationship between the external thread portion 31 and the internal thread portion 33 may be reversed so that an internal thread portion is provided on the thrust shaft 15 side and a thread portion is provided on the feed nut 32 side. The thrust sensor 62, which is a magnetic sensor, detects the magnet 61 to determine whether or not the thrust is held. However, other than the combination of the magnet and the magnetic sensor, optical detection such as a photo sensor or the like is used. Mechanical detection of a limit switch or the like is also possible, and the type of the thrust sensor 62 is not particularly limited. Further, the thrust sensor 62 may be configured to continuously detect a change in the position of the magnet 61 serving as the detected portion. The same applies to the position detection sensors 46 and 47.

Characteristic means other than the claims and their effects, which are grasped by the embodiments described above, are listed below. (1) The conversion from the rotational motion to the linear motion is performed by rotating the rotary member in a screwing relationship with the operating member side in accordance with the driving of the rotary drive source in a state where the rotation is stopped around the axial direction of the rectilinear member. The actuator according to any one of claims 1 to 4, wherein the actuator is formed by: According to this means,
Conversion from rotary motion to linear motion can be easily performed.

(2) The rotating member and the straight-moving member are formed in a cylindrical shape to form a housing therein, and at least a part of the other is housed in the housing. Actuator. According to this means, the overall length of the actuator can be reduced, and the screw surface can be protected from dust.

(3) The actuator according to any one of claims 1 to 4, wherein the elastic member is formed by stacking a plurality of disc springs coaxially. According to this means, the amount of displacement of the rotating member in the reverse direction and the thrust applied to the linear member can be adjusted and set by the number of superposed disc springs,
In addition, the length of the elastic member, and thus the length of the actuator, can be shortened by using a disc spring.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view showing an embodiment of an electric actuator.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is an essential part cross-sectional view showing another embodiment of the electric actuator.

FIG. 4 is a partially cutaway front view showing another embodiment of the electric actuator.

FIG. 5 is a partially cutaway front view showing a conventional example of an electric actuator.

[Explanation of symbols]

1 ... electric actuator as actuator, 2 ...
Actuator body, 11: electric motor as rotary drive source, 15: thrust shaft as rotary member, 24 ... large pulley as rotary wheel, 25 ... synchro belt as rope, 34 ... thrust rod as linear member, 55 ... Elastic member, 72 ... Ball bearing as bearing, 73 ... Inner ring, 7
6: outer ring, α, β: gap.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shin Ito Komaki-shi, Aichi 3005 Kita-gaiyama character Hayasaki 300F F-term (reference) 5H607 AA00 BB01 BB06 CC01 CC03 CC05 CC07 CC09 DD03 DD17 EE08 EE19 EE52 FF11 GG08 GG09 HH01 HH09 JJ05

Claims (4)

[Claims] A rotary member rotatably supported in an actuator body is rotated by driving a rotary drive source, and the rotary member is converted to a linear member by converting the rotary member into a linear member. When the linear movement of the rectilinear member is restricted, the rotating member can be moved in the opposite direction to the rectilinear member, and the elastic member is moved when the rotating member moves in the reverse direction. The repulsive force obtained by compression is used as the thrust of the rectilinear member, and the thrust is held by the elastic member when the rotary drive source is stopped. It is supported so as to be relatively movable in the axial direction, a rope is mounted on the rotating wheel, and the rotation of the rotary drive source is transmitted to the rotating member by the rope, and the rotation between the rotating wheel and the actuator body is performed. Actuators only one interposed a bearing for holding in position relative to the actuator body by the same rotation car. 2. A gap is formed in the axial direction between at least one of the bearing and the actuator main body or between the bearing and the rotating wheel, and the gap is formed between the bearing and the actuator main body or the bearing. 2. The actuator according to claim 1, wherein a gap is formed between at least one of the wheel and the rotating wheel in a direction orthogonal to the axial direction. 3. A rotary member rotatably supported in the actuator body is rotated by driving a rotary drive source, and the rotary member is converted into a linear motion of the linear member by converting the rotary motion of the rotary member into a linear motion of the linear member. When the linear movement of the rectilinear member is restricted, the rotating member can be moved in the opposite direction to the rectilinear member, and the elastic member is moved when the rotating member moves in the reverse direction. The repulsive force obtained by compression is used as the thrust of the rectilinear member, and the thrust is held by the elastic member when the rotary drive source is stopped. It is supported so as to be relatively movable in the axial direction, a rope is mounted on the rotating wheel, and the rotation of the rotary drive source is transmitted to the rotating member by the rope, and the rotation between the rotating wheel and the actuator body is performed. Interposes a bearing for holding the rotating wheel at a predetermined position with respect to the actuator body, and has a gap in the axial direction between at least one of the bearing and the actuator body or between the bearing and the rotating wheel. An actuator, wherein a gap is formed between at least one of the bearing and the actuator body or between the bearing and the rotating wheel in a direction orthogonal to the axial direction. 4. The bearing is a ball bearing, an inner ring of which is disposed on an outer peripheral side of one of the rotating wheel and the actuator main body, and an outer ring is the other inner peripheral side of the rotating wheel or the actuator main body. The actuator according to any one of claims 1 to 3, wherein