JP2001117641A - Electric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dispense with providing sensors for detecting the stroke end of an object to be operated in an electric actuator for driving the object by a motor. SOLUTION: This device is provided with a direction of rotation detecting means for detecting the direction of rotation of a motor for driving an object to be operated, a current value detecting means for detecting a current value running through the motor, and a motor-inverting means for inverting the direction of rotation of the motor when the current value exceeds a current value decided beforehand for inversion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric actuator for driving an operating body by a motor.

[0002]

2. Description of the Related Art Conventionally, actuators such as air cylinders and hydraulic cylinders are known as fluid actuators using a fluid. On the other hand, recently, from the viewpoints of energy saving, environmental protection, and the like, electric actuators that reciprocate by driving an operating body with a motor have been developed.

[0003] In such an electric actuator, the stroke of the operating body is detected by a sensor such as a limit switch, and the operating body is reciprocated by changing the rotation direction of the motor.

[0004]

However, in the conventional electric actuator, since the stroke end of the operating body is detected by the sensor, a space for mounting the sensor is required, which hinders miniaturization of the electric actuator. There was a problem. Further, since the sensor is relatively expensive, there is a problem that the manufacturing cost of the electric actuator increases.

Further, since the sensor and the drive circuit of the motor are separated from each other, there is a problem that factors of failure increase and reliability is reduced. The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide an electric actuator which can eliminate the need for a sensor for detecting a stroke end or the like of an operating body.

[0006]

According to a first aspect of the present invention, there is provided an electric actuator, comprising: a rotation direction detecting means for detecting a rotation direction of a motor driving an operating body; a current value detecting means for detecting a current value flowing through the motor; Motor reversing means for reversing the rotation direction of the motor when the current value exceeds a predetermined reversing current value.

According to a second aspect of the present invention, there is provided the electric actuator according to the first aspect, wherein the current value detecting means is connected to the motor reversing means within a predetermined start-up current generation estimated time from the reversal of the rotation direction of the motor. The present invention is characterized by having a starting current elimination timer means for eliminating the output of the current value. According to a third aspect of the present invention, in the electric actuator according to the first or second aspect, the motor reversing means is configured to rotate the motor in a rotational direction of the motor after a lapse of a predetermined time after the current value exceeds the predetermined value. Characterized by having intermittent drive timer means for inverting

(Operation) In the electric actuator according to the first aspect, when the operating body is located at the stroke end or the like, the operation of the operating body is blocked, and the current value flowing to the motor detected by the current value detecting means increases. When the current value exceeds a predetermined reversing current value, the motor reversing means reverses the rotation direction of the motor.

In the electric actuator according to the present invention, the starting current elimination timer means sets a predetermined starting current generation time from a reversal of the rotation direction of the motor within a predetermined estimated starting current generation time.
The output of the current value from the current value detecting means to the motor reversing means is excluded. That is, when the rotation direction of the motor is reversed,
The current value may increase due to the generation of the starting current. Since the output of the current value from the current value detecting means to the motor reversing means is excluded during the estimated starting current generation time, the motor is prevented from re-inverting due to the starting current.

According to the third aspect of the present invention, the rotation direction of the motor is reversed by the intermittent drive timer means after a lapse of a predetermined time after the current value exceeds a predetermined value, and the operating body is intermittently driven.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a control block of the control device of FIG.
FIG. 2 shows a first embodiment of the electric actuator of the present invention. In the electric actuator shown in FIG. 2, the motor 11, the speed reducer 13, the power transmission unit 15, and the operating unit 17
Are arranged in series.

That is, for example, the rotation of the motor 11 composed of a small DC motor is transmitted to the screw shaft 19 disposed in the power transmission unit 15 via the speed reducer 13. The screw shaft 19 is connected to a rotation shaft 21 arranged in the power transmission unit 15. The rotating shaft 21 is supported by a cylinder 23 of the power transmission unit 15 via a bearing 25.

A screw 27 is formed at the tip of the rotating shaft 21. The screw portion 27 is screwed to a slide member 31 arranged in the cylinder 29 of the operating portion 17. The slide member 31 is formed to have a rectangular cross section, and is movable along a rectangular guide surface 29 a formed on the cylinder 29 by rotation of the screw portion 27.

An operating body 33 is connected to the slide member 31, and a blind hole 33a in which the screw portion 27 can be accommodated is formed at the rear of the operating body 33. Moving body 3
3 is supported on the inner surface of the cylinder 29 via a guide member 35. In the electric actuator described above, when the control device 37 rotates the motor 11, the screw shaft 19 is rotated.
Is rotated, and the screw portion 27 of the rotating shaft 21 is rotated by the rotation of the screw shaft 19.

Then, by the rotation of the screw portion 27, the slide member 31 moves in the axial direction of the cylinder 29, and the operating body 33 connected to the slide member 31 is moved. In this embodiment, the slide member 31 is reciprocated between a front end position A and a rear end position B shown in FIG. That is, the slide member 31 moves forward from the state shown in FIG.
When it collides with the rear end of the guide member 35 fixed to the front end of the motor, the motor 11 is reversed, and the slide member 31 is moved rearward.

When the rear end of the slide member 31 collides with the positioning member 39 fixed to the power transmission unit 15, the motor 11 is reversed, and the slide member 31 is moved forward. FIG. 1 shows a control block of the above-described control device 37. In the control device 37, an origin return switch 41, a reciprocating switch 43, a constant load switch 45, and an operation stop switch 47 are arranged in parallel.

The home position return switch 41 is connected to the home position return unit 4.
9 is connected to the motor 11. That is, the origin return means 49 is a means for positioning the slide member 31 at the rear end position (origin) B as shown in FIG. 2, and when the origin return switch 41 is turned on, the slide member 31 is turned on. The motor 1 is moved to the positioning member 39 side.
1 is driven.

Then, when the slide member 31 collides with the positioning member 39 and the current value of the motor 11 exceeds a predetermined current value (reversing current value described later), the driving of the motor 11 is stopped. The reciprocating switch 43 is a switch for reciprocating the slide member 31, that is, the operating body 33.
1 connected.

The reciprocation control means 51 includes a rotation direction detecting means 53, a current value detecting means 55, a starting current eliminating timer means 57, a motor reversing means 59, and an intermittent driving timer means 61. External signals from the speed setting means 63 and the timer setting means 65 are input to the reciprocation control means 51.

The rotation direction detecting means 53 detects the rotation direction of the motor 11 for driving the operating body 33. That is, the rotation direction detecting means 53 detects the rotation direction of the motor 11 by detecting the positive / negative relationship of the voltage currently applied to the DC motor 11.

In this embodiment, for example, FIG.
When viewed from the arrow C direction, when the motor 11 is rotating clockwise, the slide member 31 is moved forward, and when it is rotating left, the slide member 31 is moved rearward. The current value detecting means 55 detects a current value flowing through the motor 11. That is, the current value of the motor 11 is
As shown in FIG. 3, when the motor 11 is started, the starting current I
It increases with the occurrence of 1.

When the slide member 31 moves,
Although substantially constant at a predetermined current value I2, the sliding member 3
When 1 collides with the guide member 35 at the front end position A,
When the slide member 31 collides with the positioning member 39 at the rear end position B, the current value increases and becomes the current value I3. The starting current elimination timer means 57 eliminates the output of the current value from the current value detecting means 55 to the motor reversing means 59 within a predetermined estimated starting current generation time T1 from the reversal of the rotation direction of the motor 11.

That is, when the rotation direction of the motor 11 is reversed, the current value increases due to the generation of the starting current I1, as shown in FIG.
7, a time T1 from the reversal of the motor 11 to the end of the generation of the starting current I1 is set in advance as an estimated starting current generation time. 55 to motor reversing means 5
The output of the current value to 9 is eliminated.

Accordingly, the motor 11 is prevented from re-inverting due to the starting current I1. The motor reversing means 59
The current value of the motor 11 is a predetermined reversal current value I4
Is exceeded, the rotation direction of the motor 11 is reversed. That is, in the motor reversing means 59, a current value slightly lower than the maximum current value generated when the motor 11 is reversed is set as the reversing current value I4, and the current value of the motor 11 exceeds the reversing current value I4. Then, when the current value I3 actually becomes maximum, the rotation direction of the motor 11 is reversed.

The reversal of the rotation direction of the motor 11 is performed by rotating the motor 11 so that the rotation of the motor 11 detected by the rotation direction detecting means 53 is reversed.
That is, as shown in FIG. 3, the current flow is switched between forward and backward. The intermittent drive timer means 61 outputs the current value after the current value exceeds a predetermined reversal current value I4.
Actually, a predetermined time T2 has elapsed since the current value I3 became maximum.
After the elapse, the rotation direction of the motor 11 is reversed.

In this embodiment, the intermittent drive timer means 6 is controlled by an external input from the timer setting means 65.
The predetermined time T2 set to 1 can be changed arbitrarily, whereby the operating body 33 is intermittently driven after a desired time. In this embodiment, the voltage applied to the motor 11 is changed by an external input from the speed setting unit 63, and the speed of the slide member 31 is set to a desired value.

The constant load switch 45 is provided with a constant load control means 6.
7 is connected to the motor 11. That is, the constant load control means 67 is a means for pressing the object 69 to another member 71 with a predetermined force F by the operating body 33 as shown in FIG. Then, the operating body 33 moves to the object 69 side, and the object 69
Then, the motor 11 is driven so as to press the object 69 with a predetermined force F.

In this embodiment, the voltage applied to the motor 11 can be changed by an external input from the load setting means 73, whereby the pressing force F against the object 69 is set to a desired value. It is possible.

The operation stop switch 47 is connected to the operation stop means 7.
When the operation stop switch 75 is turned on, the drive of the motor 11 is stopped instantaneously. In this embodiment, when the control of the origin return, the reciprocating movement, and the constant load is being performed, the interlock control is performed, and the control is continued until the operation stop switch 47 is turned on.

Further, at the moment when the power of the control device 37 is turned on, all the signals are automatically reset, and occurrence of a malfunction is reliably prevented. In the electric actuator described above, when the operating body 33 is located at the stroke end, the operation of the operating body 33 is blocked, and the rotation direction of the motor 11 is reversed by utilizing the fact that the value of the current flowing through the motor 11 increases. In addition, a sensor for detecting the stroke end of the operating body 33 can be eliminated.

Although the guide member 35 is fixed to the tip of the cylinder 29 in FIG. 2, the guide member 35 may be fixed to the cylinder 29 so that it can be moved in and out. Thereby, the stroke can be made variable. Further, in the apparatus shown in FIG. 2, by providing a stopper (not shown) at an arbitrary position during the stroke of the operating body 33, the reciprocating movement can be performed by changing the forward end position.

In the above-described electric actuator,
The output of the current value from the current value detecting means 55 to the motor reversing means 59 is excluded by the starting current eliminating timer means 57 within a predetermined estimated starting current generation time T1 from the reversal of the rotation direction of the motor 11. Therefore, the occurrence of the start-up current I1 immediately after the inversion of the motor 11 prevents the motor 11 from being inverted again, thereby preventing the motor 11 from malfunctioning.

Further, in the above-described electric actuator, the intermittent drive timer means 61 causes the motor 1 to move after a predetermined time T2 has elapsed since the current value exceeded a predetermined value.
Since the rotation direction is reversed, the operating body 33 can be easily and reliably driven intermittently. FIGS. 5 and 6 show a second embodiment of the electric actuator of the present invention. In this embodiment, the present invention is applied to a swing actuator.

That is, in this embodiment, the motor 11
Is transmitted to the worm 81 arranged on the apparatus main body 79 via the coupling 77. Then, the rotation of the worm 81 is transmitted to the worm wheel 83 arranged on the apparatus main body 79. A semicircular cam groove 85 is formed on one surface of the worm wheel 83, and the tip of the pin member 87 is inserted into the cam groove 85.

A swing rotation shaft 89 is connected to the center of the other surface of the worm wheel 83. In this electric actuator, when the control device 37 drives the motor 11 to rotate, the worm 81 rotates and the worm wheel 83 rotates. In this embodiment, the worm wheel 83 swings by a predetermined angle between one end A and the other end B of the cam groove 85 shown in FIG. It is rocked.

That is, when the worm wheel 83 rotates leftward from the state shown in FIG. 5, one end A of the cam groove 85 collides with the pin member 87, and the motor 11 is reversed by the motor reversing means 59. When the worm wheel 83 rotates rightward due to the reversal of the motor 11, the other end B of the cam groove 85 collides with the pin member 87, and the motor 11 is reversed by the motor reversing means 59, whereby the oscillating rotation is performed. The shaft 89 is swung at a predetermined angle.

In the electric actuator of this embodiment,
When the one end A and the other end B of the cam groove 85 formed in the worm wheel 83 collide with the pin member 87, the operation of the worm wheel 83 is blocked and the current value flowing to the motor 11 is increased. Since the rotation direction of the motor 11 is reversed, a sensor for detecting the rotation angle of the worm wheel 83 or the swing rotation shaft 89 can be eliminated.

It should be noted that the control device 37 of this embodiment sets the front end position A and the rear end position B of the slide member 31 in the first embodiment to the cam groove 85 of the worm wheel 83.
By replacing the one end A and the other end B, the configuration can be substantially the same as that of the first embodiment. Therefore, the same reference numerals are given to the same components as those of the first embodiment. The detailed description is omitted.

FIGS. 7 and 8 show a third embodiment of the electric actuator according to the present invention. In this embodiment, the present invention is applied to an actuator for a gripper. That is, in this embodiment, the rotation of the motor 11 is transmitted to the gears 95 and 97 arranged on the apparatus main body 93 via the screw shaft 91. And the rotation of the gear 97
It is transmitted to a pair of grips 99 arranged on the device main body 93.

That is, on the bottom surface of the grip 99, a rack 101 meshing with the gear 97 is formed.
The pair of grips 99 are movably guided by a guide member 103 arranged on the apparatus main body 93. Positioning members 105 are arranged at positions on both sides of the pair of grips 99 of the apparatus main body 93.

In this electric actuator, the control device 3
7, when the motor 11 is rotationally driven, the screw shaft 91 and the gears 95 and 97 are rotated, and the pair of grips 99 are moved in the closing direction or the opening direction. In this embodiment, the pair of grips 99 is moved from the state shown in FIG.
Is moved in the closing direction, and when an object is gripped between the pair of grips 99 or the pair of grips 99 is directly in contact, the current value generated in the motor 11 increases.

Then, after a predetermined time T
After a lapse of two hours, the motor 11 is reversed and the pair of grips 9
9 is moved in the opening direction. And a pair of grips 9
When 9 collides with positioning member 105, the current value generated in motor 11 increases, and after a lapse of a predetermined time T2 from the increase in the current value, motor 11 is reversed.

In the electric actuator of this embodiment,
When the pair of grips 99 grips or directly contacts an object or collides with the positioning member 105, the operation of the pair of grips 99 is blocked, and the rotation of the motor 11 Since the directions are reversed, a sensor for detecting the operation state of the pair of grips 99 can be eliminated.

It should be noted that the control device 37 of this embodiment changes the front end position A and the rear end position B of the slide member 31 in the first embodiment to, for example, the position where a pair of grips 99 directly contact, and the positioning member. By substituting a position that collides with 105, it is possible to configure substantially the same as in the first embodiment. Therefore, the same reference numerals are given to the same components as those in the first embodiment, and detailed description is omitted. I do.

In this embodiment, by selecting the constant load control means 67 of the first embodiment, an object can be easily and reliably gripped between the pair of grips 99 with a predetermined force. Become. In the electric actuator according to the above-described embodiment, the current value of the motor 11 increases when the operating body 33 collides with an obstacle during the movement. Therefore, the presence of the obstacle is detected based on the increase in the current value. Can be.

Further, if a force is applied during the movement of the operating body 33, the current value of the motor 11 increases.
The magnitude of the force can be determined from the current value of.

[0048]

As described above, in the electric actuator according to the first aspect, when the operating body is located at the stroke end or the like, the operation of the operating body is blocked, and the electric current flowing through the motor is increased. Since the rotation direction is reversed, a sensor for detecting the stroke end of the moving body or the like can be eliminated.

In the electric actuator according to the second aspect, the starting current elimination timer means sets a predetermined starting current generation time from a reversal of the rotation direction of the motor within a predetermined estimated starting current generation time.
Since the output of the current value from the current value detection means to the motor reversing means is eliminated, the occurrence of a start-up current immediately after the motor reversal prevents the motor from re-reversing, thereby preventing the motor from malfunctioning. Can be prevented.
In the electric actuator according to the third aspect, the intermittent drive timer means reverses the rotation direction of the motor after a lapse of a predetermined time after the current value exceeds a predetermined value. It can be driven intermittently.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a control device of FIG. 2;

FIG. 2 is an explanatory diagram showing a first embodiment of the electric actuator of the present invention.

FIG. 3 is an explanatory diagram showing a current value generated in a motor of the electric actuator of FIG. 2;

FIG. 4 is an explanatory diagram showing constant load control of the electric actuator of FIG. 2;

FIG. 5 is a front view showing a second embodiment of the electric actuator of the present invention.

FIG. 6 is a side view of FIG. 5;

FIG. 7 is a front view showing a third embodiment of the electric actuator of the present invention.

FIG. 8 is a side view of FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Motor 33 Operating body 53 Rotation direction detecting means 55 Current value detecting means 57 Starting current eliminating timer means 59 Motor reversing means 61 Intermittent driving timer means

Claims (3)

[Claims] 1. A rotating direction detecting means for detecting a rotating direction of a motor for driving an operating body, a current value detecting means for detecting a current value flowing through the motor, and a reversing current value having a predetermined current value. And a motor reversing means for reversing the rotation direction of the motor when the rotation of the motor is exceeded. 2. The electric actuator according to claim 1, wherein the output of the current value from the current value detection means to the motor inversion means is performed within a predetermined start-up current generation expected time from the reversal of the rotation direction of the motor. An electric actuator comprising a start-up current elimination timer means for elimination. 3. The electric actuator according to claim 1, wherein the motor reversing means reverses the rotation direction of the motor after a lapse of a predetermined time after the current value exceeds the predetermined value. An electric actuator comprising intermittent drive timer means.