JPH05180299A - Actuator - Google Patents

Abstract

PURPOSE:To improve an easily replaceable property and an impact resistant load property in a driving motor by shortening the length of a two-freedom- degree actuator having a driving shaft on which a ball screw nut and a ball spline nut are fitted. CONSTITUTION:A driving motor 35 is arranged in parallel with a driving shaft 2, and a ball screw nut 5 is connected to an output shaft 35a of the driving motor through a belt 36, and a ball spline nut 6 is connected through a belt 26 to a rotation transmitting shaft 18 connected to the output shaft 35a of the driving motor through a clutch 22 and a brake 21. The driving motor is mountable/demountable without disassembling an actuator. A rotational phase shift to a command value of the ball spline nut 6 caused by an impact load is detected/corrected by means of a rotational position detector 40, so that accuracy of the actuator can be guaranteed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator suitable for use in machine tools, scalar type robots, and other industrial machine devices, and more particularly to an actuator having two degrees of freedom, one axis being slide and one rotation.

[0002]

2. Description of the Related Art As a conventional actuator of this type, there is, for example, one disclosed in Japanese Patent Laid-Open No. 61-38892. In this structure, a motor having a hollow motor shaft is fixed to the inner surface of the housing, and one drive shaft is loosely inserted into the hollow motor shaft. On the outer peripheral surface of the drive shaft, a ball screw groove is formed in the rear part and a ball spline groove is formed in the front part.A ball screw nut is formed in the ball screw groove part in the rear part, and a ball spline groove part is formed in the front part. With each ball spline nut fitted,
Each nut is rotatably supported in the same housing via a support bearing. The ball screw nut is connected to the rear end of the hollow motor shaft so as to rotate integrally therewith. On the other hand, the ball spline nut is arranged on the opposite side of the ball screw nut across the motor, but a drive conversion device including an electromagnetic clutch and a brake is interposed between the ball spline nut and the motor. The clutch rotor is fixed to the front end of the hollow motor shaft, and the brake is fixed to the ball spline nut.
The electromagnetic coils of the clutch and the brake are controlled so that when one is on, the other is off. When the motor is rotated with the clutch on and the brake off, the hollow motor shaft rotates to rotate the clutch rotor. Is transmitted to the ball spline nut through the rotation of. At this time, the ball spline nut rotates due to brake off, which causes the drive shaft to rotate.

On the other hand, when the motor is rotated with the clutch off and the brake on, the rotation of the hollow motor shaft is not transmitted to the clutch rotor, and the ball spline nut is blocked by the brake. Therefore, the rotation of the hollow shaft is transmitted only to the ball screw nut, which causes the drive shaft to move linearly in the axial direction. in this way,
By controlling the rotation of the ball screw nut and the ball spline nut, the drive shaft can be operated with two degrees of freedom, that is, slide and rotation.

[0004]

However, the above-mentioned conventional actuator has a structure in which the ball screw nut, the motor, the clutch, the brake, and the ball spline nut are arranged in a row along one drive shaft in the housing. Therefore, there is a problem that the total length of the actuator becomes too long and it is difficult to handle. In addition, it is necessary to remove the motor when the motor breaks down or when the specifications are changed. In that case, all the parts arranged in series are taken out from the housing, and each of them is fitted to the drive shaft through many balls. The nut has to be removed from the drive shaft, and it is not easy to replace or change the motor.

Further, the drive conversion device equipped with an electromagnetic clutch and a brake is liable to cause a slip due to an impact load from the outside, etc., and when it is repeatedly turned on and off, a slight deviation is accumulated, and a ball screw nut and a ball There is a high possibility that a rotation phase difference will occur between the spline nut and the spline nut, and if left unattended, the drive shaft position accuracy will deteriorate.

Therefore, the present invention has been made by paying attention to the above-mentioned conventional problems, and the actuator main body is provided by arranging the drive shaft, in which the ball screw nut and the ball spline nut are fitted, and the motor in parallel. It is an object of the present invention to provide an actuator that does not become too long, allows motors to be replaced without removing each nut from the drive shaft, makes it easy to handle, and guarantees high positional accuracy against impact loads and accumulated errors. Has a purpose.

[0007]

According to the present invention for achieving the above object, a ball screw nut and a ball spline nut are screwed through a ball to a drive shaft having a ball screw groove and a ball spline groove. The both nuts are related to an actuator having two degrees of freedom of slide and rotation, which is rotatably supported by a housing through a rolling motion of a rolling element of a bearing portion and connected to a drive motor. The ball screw nut is arranged in parallel with the drive shaft and is connected to a pulley directly connected to the output shaft of the drive motor via a belt, and the ball spline nut is connected to the output shaft of the drive motor via a clutch and a brake. Connected via a belt to the pulley of the rotation transmission shaft that has been connected, the reduction ratio on the ball screw nut side and the ball spline nut And it sets the reduction ratio in the same, characterized in that attached to the ball screw nut and the rotational position detector either nut or the rotation transmission shaft for detecting the rotation of the ball spline nut.

[0008]

Since the drive motor is arranged in parallel with the drive shaft and the output of the drive motor is transmitted to each nut by the belt,
The length is shortened, and the motor can be attached and detached without removing any nuts from the drive shaft. When the motor is driven with the clutch off and the brake on, the rotation transmission shaft does not rotate, so only the ball screw nut is rotationally driven with the ball spline nut in the non-rotation state, and the drive shaft slides in the axial direction. Further, when the motor is driven with the clutch on and the brake off, the rotation transmission shaft is also driven, so that both nuts rotate together and the drive shaft rotates. Since the reduction ratio on the ball screw nut side and the reduction ratio on the ball spline nut side are set to be the same, both nuts rotate synchronously. However, when an impact load or the like from the outside is received, slippage may occur due to the torque transmission mechanism including the clutch and the brake, and the phase shift of each nut may occur. Further, there is a possibility that a slight positional deviation may be accumulated by repeatedly turning on and off.

Therefore, the rotational phase detector detects the phase difference between the rotation of the ball screw nut and the ball spline nut and corrects the phase shift of each nut, thereby ensuring high positional accuracy even against impact loads. To do.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 3 show an embodiment of the present invention. In the figure, 2 is a ball screw shaft as a drive shaft. The ball screw shaft 2 is provided with a spiral ball screw groove 3 made of a Gothic arch groove and a ball spline groove 4 linear in the axial direction over the entire length of the shaft. Formed, and a ball screw nut 5 and a ball spline nut 6 are mounted respectively. The ball screw nut 5 has a Gothic arch-shaped ball screw groove (not shown) corresponding to the ball screw groove 3 formed of a Gothic arch groove on the inner peripheral surface,
A large number of balls (not shown) are rotatably interposed between the ball screw groove of the nut and the ball screw groove 3 of the ball screw shaft 2. Although not shown, the ball screw nut 5 has a circulation path for these balls.
The ball moves spirally while rolling in the screw groove as the ball screw shaft 2 and the ball screw nut 5 rotate relative to each other, and goes through the screw groove once and a half to three and a half times and then through the return passage in the nut. It has a known structure that returns to the original position and repeats circulation. The ball screw nut 5 is rotatably supported by a housing 5A of the ball screw nut via a support bearing 7.

On the other hand, the ball spline nut 6 has a ball spline groove (not shown) corresponding to the ball spline groove 4 linearly extending along the ball screw shaft 2 on its inner peripheral surface, and the ball spline groove of the nut is formed. A large number of balls (not shown) are rotatably interposed between and the ball spline groove 4 of the ball screw shaft 2. Although not shown, the ball spline nut 6 is formed with a circulation path for these balls, and the balls roll in the screw groove together with the relative linear movement between the ball screw shaft 2 and the ball spline nut 6. While moving in a linear direction, it reaches the end of the nut, enters the return passage in the nut, makes a U-turn, returns to the original position, and repeats circulation. The ball spline nut 6 is also rotatably supported by the housing 6A of the ball spline nut via the support bearing 8.

A pulley 11 is attached to the front end portion (left end portion in FIG. 1) of the ball screw nut 5 so as to project from the housing 5A. Similarly, at the front end portion of the ball spline nut 6 as well, the pulley 12 is extended from the housing 6A.
Is installed. Ball screw nut housing 5
A, the pulley 11, the housing 6A for the ball spline nut, and the pulley 12 are housed in a lower portion of a common casing 13, and a drive switching mechanism 15 is arranged in a space above the casing 13. ..

The drive switching mechanism 15 includes a casing 13
Has a rotation transmission shaft 18 which is rotatably supported via bearings 16 and 17 and which is arranged parallel to the ball screw shaft 2, and one pulley 20 mounted on the rotation transmission shaft 18 and an electromagnetic brake. (Hereinafter referred to as brake) 21, electromagnetic clutch (hereinafter referred to as clutch) 22
And the other pulley 24 that is integrally rotatably connected to the rotor 23 of the clutch 22. The one pulley 20 is fixed to the rotation transmission shaft 18 via a key 25, and is connected to the pulley 12 attached to the ball spline nut 6 by a timing belt 26.
A brake wheel 27 of the brake 21 is fitted and fixed to the rotation transmission shaft 18, and a brake piece 28 that is separated from and in contact with the brake wheel 27 and a brake coil 29 for driving the brake piece 28 are attached to the casing 13. A clutch drive plate 31 driven by the clutch coil 30 is attached to the rotation transmission shaft 18 via a key 32 so as to be integrally rotatable. on the other hand,
The rotor 23 of the clutch 22 is integrally connected to the other pulley 24 as described above, and the pulley 24 is a key 33 which is used to output the output shaft 35 of the motor 35 as a drive motor.
The timing belt 36 is connected to the pulley 11 fixed to the ball screw nut 5 and attached to the ball screw nut 5.

The motor 35 is detachably attached to the outside of the casing 13 by attaching means such as bolts (not shown). The brake 21 and the clutch 22 of the drive switching mechanism 15 are controlled so that when one is on, the other is off. That is, when the rotor 23 of the clutch 22 and the clutch drive plate 31 are connected, the brake 2
When the brake wheel 27 and the brake piece 28 of No. 1 are disconnected, and conversely, the rotor 23 of the clutch 22 and the clutch drive plate 31 are disconnected, the brake wheel 27 of the brake 21 and the brake piece 28 are connected. As described above, the energization of the brake coil 29 and the clutch coil 30 is controlled.

The motor 35 is, for example, a servo motor, and the detector 38 detects the position and speed of the motor shaft, and is feedback-controlled in a semi-closed loop. In addition, one of the end faces of the ball screw nut 5 and the ball spline nut 6 (which may be the end face of the pulley fixed to each nut) detects the rotational position in order to detect the rotational phase difference between the nuts 5 and 6. The container 40 is provided. This is the motor 35
The torque of the clutch / brake drive switching mechanism 15
Since it is transmitted to the ball screw nut 5 and the ball spline nut 6 via the, when an impact load from the outside is applied, a slip occurs on the coupling surface of the brake 21 and the clutch 22, and each nut 5, 6 There is a possibility that a phase shift occurs, and in that case, the rotational position detector 40 causes the clutch 2
This is to detect the phase shift with respect to the command value of the ball spline nut 6 that is rotationally transmitted via 2, and use the detection information to control the energization of the brake coil 29 and the clutch coil 30 to perform the correction operation. As the rotary position detector 40 used for this, there is, for example, an optical rotary encoder, and in that case, either an incremental type or an absolute type can be used. If it is cut off, the absolute position will not be known, and it will be necessary to search for a mechanical absolute position detection mark with another sensor after turning on the power. Therefore, an absolute type optical rotary encoder capable of detecting the absolute position is preferable.

In the illustrated ball screw shaft 2, the robot hand 42 is attached to the front end and the rotary joint 43 is attached to the rear end. A lower limiter 44 for detecting the robot hand 42 and restricting the backward movement limit of the ball screw shaft 2 is provided on the lower front surface of the casing 13, and a rotary joint 43 is provided on the rear surface of the casing 13 for detecting the ball screw shaft 2. The limiter 45 that regulates the forward limit of 2
Each is installed. 46 is a mechanical stopper.

Next, the operation will be described. The above-mentioned actuator is mounted, for example, by fixing the casing 13 to a mounting portion such as a machine tool or a robot (not shown). When the motor 35 is driven in a state where the rotor 23 of the clutch 22 is disengaged from the clutch drive plate 31 and the brake wheel 27 of the brake 21 is in pressure contact with the brake piece 28, the motor 35 is directly connected to the motor output shaft 35a. The driven pulley 24 rotates, and the ball screw nut 5 is rotationally driven by transmission of the pulley 11 via the timing belt 36. On the other hand, the rotation transmitting shaft 18 is separated from the motor output shaft 35a by the disengagement of the clutch 22 and is in the free rotation mode, but it is restricted by the brake 21 and cannot rotate. This braking force is applied to the pulley 20 fixed to the rotation transmission shaft 18,
It is transmitted to the ball spline nut 6 connected through the timing belt 26 and the pulley 12 to prevent its rotation. Thus, when only the ball screw nut 5 is rotationally driven with the ball spline nut 6 in the non-rotating state, the ball screw shaft 2 is guided by the balls of the ball spline nut 6 fitted in the ball spline groove 4. It slid in the axial direction and moves forward and backward according to the rotation direction of the motor 35.

To this end, the rotor 2 of the clutch 22
3 and the clutch drive plate 31 are connected to the clutch on,
When the motor 35 is driven in a brake-off state in which the brake wheel 27 and the brake piece 28 of the brake 21 are separated, the pulley 24 directly connected to the motor output shaft 35 a rotates, and the pulley 11 of the pulley 11 passes through the timing belt 36. This is transmitted and the ball screw nut 5 is rotationally driven. Also,
The rotation transmission shaft 18 is connected to the motor output shaft 35a when the clutch 22 is turned on to enter the integrated rotation mode, and is not restrained by the brake 21.
Is transmitted to the ball transmission spline nut 6, which is connected via the rotation transmission shaft 18, the pulley 20 fixed to the rotation transmission shaft 18, the timing belt 26, and the pulley 12. Reduction ratio of a set of pulleys 24, 11 on the ball screw nut 5 side and pulleys 20, 12 on the ball spline nut 6 side
Since the reduction ratio of the pair is set to be the same, both nuts 5 and 6 rotate accurately in synchronization. In this way both nuts 5,
When 6 rotates together, the ball screw shaft 2 is rotationally driven in the forward and reverse directions according to the rotating direction of the ball spline nut 6.

If an impact load from the outside is applied,
If slippage occurs on the coupling surface of the brake 21 and the clutch 22, there is a possibility that a rotational phase shift will occur between the ball screw nut 5 and the ball spline nut 6. In that case, the rotational position detector 40 detects the phase shift with respect to the command value of the ball spline nut 6, and controls the operation of the brake 21 and the clutch 22 based on the detection signal to control the position of the ball spline nut 6 with respect to the command value. Correct the phase difference. As a result, the positional accuracy error of the ball screw shaft 2 due to the accumulation of the phase difference is prevented, and the accuracy of the actuator is ensured.

According to the above-described embodiment, the motor 35 can be easily removed by removing the mounting bolt to the casing 13, and the ball screw nut 5 and the ball spline nut 6 need to be removed from the ball screw shaft 2. Since there is no such problem, the motor can be easily and quickly changed even if the specifications are changed or there is a failure. Further, the actuator main body can be much shorter in length than the conventional ones in which each component is attached to the ball screw shaft 2 in series, which is compact and lightweight and easy to handle.

Further, it is possible to guarantee the high accuracy by correcting the influence of the impact load and the like. FIG. 4 shows another embodiment.
In this embodiment, a rotary encoder 4 which is a rotation detector is used.
0 is attached to the tip of the rotation transmission shaft 18. In this case, the rotation detector 40 detects the rotation of the rotation transmission shaft 18 to indirectly detect the rotation speed of the ball spline nut 6. The detected value is sent to the controller 51 via the pulse counter 50, compared with a preset command value, and a signal corresponding to the result is sent to the driver 52 to send the command value of the ball spline nut 6 in the same manner as above. The phase difference with respect to is corrected.

Other configurations, operations and effects are essentially the same.

[0023]

As described above, according to the actuator of the present invention, a driving power source such as a driving motor, a clutch and a brake is arranged in parallel with the driving shaft, and a ball screw nut and a ball spline nut fitted to the driving shaft. In addition, since the motor output is transmitted through the belt, the drive motor can be easily attached and detached without removing the nuts from the drive shaft, and maintenance is facilitated.

Further, the length of the actuator main body is shortened and the weight is reduced, so that it is easy to handle. Further, there is an effect that a highly accurate actuator having high impact load resistance can be obtained while having two degrees of freedom of slide and rotation.

[Brief description of drawings]

FIG. 1 is a front view showing a notched essential part of an embodiment of the present invention.

FIG. 2 is a bottom view of FIG.

FIG. 3 is a left side view of FIG. 1 (however, a robot hand is not attached).

FIG. 4 is a front view showing a notched main part of another embodiment of the present invention.

[Explanation of symbols]

 2 Drive shaft (ball screw shaft) 3 Ball screw groove 4 Ball spline groove 5 Ball screw nut 6 Ball spline nut 7 Bearing 8 Bearing 11 Pulley 12 Pulley 18 Rotation transmission shaft 20 Pulley 21 Brake 22 Clutch 24 Pulley 26 Belt 35 Drive motor ( Motor) 35a (motor) output shaft 36 belt 40 rotational position detector

Claims (1)

[Claims] 1. A ball screw nut and a ball spline nut are screwed via balls to a drive shaft having a ball screw groove and a ball spline groove, and both nuts are rotatably supported by a housing via bearings. An actuator having two degrees of freedom of slide and rotation connected to the drive motor, the drive motor is disposed in parallel with the drive shaft, and the ball screw nut is directly connected to the output shaft of the drive motor. Connected to the pulley via a belt, and the ball spline nut is connected via a belt to the pulley of the rotation transmission shaft connected to the output shaft of the drive motor via a clutch and a brake. And the reduction ratio on the side of the ball spline nut are set to the same, and the ball screw nut and Actuator, characterized in that attached to either the nut or the rotation transmitting shaft rotational position detector for detecting the rotation of Le spline nut.