JPS636201A - Servo actuator - Google Patents

Abstract

PURPOSE:To make it possible to control accurately a positioning servo actuator applied to machine tools or the like by changing over a valve device by the rotation of a control motor through a differential gear mechanism and controlling the drive of a fluid pressure motor. CONSTITUTION:When a stepping motor 14 is rotated up to the specified objective speed of revolution by a controller 20, a large gear 16 is rotated through a control input shaft 7 and a small gear 15 for making planet gears 17 rotate an output gear 19. The rotation of the output gear 19 shifts a working rod 10 to the right, for example, through an output shaft 6, pinion 8, and rack 9. This leads to the change over of a directional control valve 12 for rotating a pneumatic motor 1 to which a load is connected at the output shaft 12. At this time, a feed back shaft 3 and main input shaft 5 are rotated, and the working rod 10 is shifted to the left through a train or gears 18, 17, and 19, the pinion 8, and the rack 9. This motion continues until the directional control valve 12 is changed over.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a servo actuator for positioning, and is used in machine tools and various other automated machines.

(Prior Art and its Problems) Conventionally, stepping motors have been widely used to determine the stop position, control the rotation angle, and the rotation speed. Stepping motors have the advantage of being able to stop at regular step angles, allowing for highly accurate positioning, high responsiveness, and open-loop control.
On the other hand, they have the disadvantage that they generally have low output, and those with high output are expensive. In order to compensate for this drawback, a device was developed in which the output of the stepping motor was increased.
-26581 is publicly known. In this system, an outer retainer is placed around a screw rotated by a pulse motor, and an inner retainer is torque-connected to a feed pack shaft rotated by a hydraulic motor, and the inner retainer follows the rotation of the screw via a NAND. The outer cage is used to rotate the
The nozzle flamber system is operated by converting the rotational displacement of the screw into the axial displacement of the outer cage. However, according to this, since a screw is used to compare the rotation of the hydraulic motor, which is a control amount, and the rotation of the pulse motor, which is an input amount, the structure of this part is complicated, and accuracy may be affected due to backlash etc. Problems include problems such as the need for torque coupling between the hydraulic motor and the feedback shaft due to the small amount of overtravel allowed for the screw when the system does not operate properly.

In addition, since a spool valve operated by a nozzle flamper is used as a servo valve, it has a complex structure, is difficult to adjust, and is vulnerable to foreign substances such as dust, so there are problems in that it requires time and effort to manage the hydraulic fluid. be.

(Means for Solving the Problems) In view of the above-mentioned circumstances, the present invention provides a servo actuator that is relatively simple in structure and easy to adjust, without using a conventional screw. The technical means for this purpose is a fluid pressure motor 1 having 2111 ports for supplying and discharging fluid that are operated in opposite directions, and a main input shaft 5 that is rotated by the fluid pressure motor 1. A driven differential gear W4 and a valve device 11° which is switched by the rotation of the output shaft 6 of the differential gear W4 and selectively supplies fluid to each of the ports 1a and lb according to the direction of rotation thereof. 12, and a control input shaft 7 of the differential gear device 4.
and a control motor 14 that rotationally drives the.

(Example) Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, a pneumatic motor 1 has an output shaft 2 that drives a load and a feedback shaft 3 that rotates integrally with the output shaft 2. This feedback shaft 3 is the main input shaft of a differential gear device 4. 5 is connected to drive rotation. A pinion 8 is attached to the output shaft 6 of the differential gear device 4, and an operating loft 10 having a rack 9 that meshes with the pinion 8 is operated in the left-right direction to switch the switching valves 11, 12. It has become. Each of the switching valves 11, 12 is a poppet valve, and when activated, the pneumatic source 13 is connected to the ports Ha, lb of the pneumatic motor 1.

The control input shaft 7 of the differential gear device 4 is a steering wheel and a ping motor 1.
4, and the small gear 15
This causes the large gear 16 to rotate, and as a result, the planetary gear 17, in which two gears 17a and 17b having different diameters are coaxially connected, revolves around the input gear 18 and the output gear 19. Therefore, the rotation ratio (reduction ratio) between the main input shaft 5 and the output shaft 6 of the differential gear device 4 is 1/a, and the control input shaft 7 is
Assuming that the rotation ratio (reduction ratio) with the output shaft 6 is 1/b, the main input shaft 5 rotates n1 times, and the control input shaft 7 rotates n2 times.
The rotational speed n3 of the output shaft 6 is a b , and the stepping motor 14 is controlled by the control device 20
The rotational speed, number of rotations, or angle of rotation is controlled by the following. The throttle valves 21 and 22 are for adjusting the rotational speed of the pneumatic motor 1, and are adjusted in accordance with the load connected to the output shaft 2 and the like. Throttle valve 21
．． 22 may also be used with a check valve.

In the above-mentioned servo actuator, a load is connected to the output shaft 2, and the control device 20 controls the rotation of the stepping motor 14 to a predetermined target value or according to a predetermined sequence. When the step-2 pin motor 14 rotates, it is connected to the large gear 16 via the control input shaft 7 and the small gear 15.
The output gear 19 is rotated by the planetary gear 17 which revolves around the non-rotating input gear 1, and the operating rod 10 is rotated through the output shaft 6, pinion 8 and rack 9.
moves in the direction of its axis. Now, if the actuating iron lO moves to the right in the figure, the switching valve 12 switches, compressed air is supplied to the port 1b, and the pneumatic motor 1 rotates.

This rotates the input gear 18 via the feedback shaft 3 and the main input shaft 5, which moves the actuating rod 10 to the left via the planetary gear 17, output gear 19, pinion 8 and rack 9. The switching valve 12 returns to its original switching position (
This operation continues until the supply of compressed air to 1b is stopped. Therefore, the stepping motor 14 is n2
When rotated, the pneumatic motor 1 will rotate by n2Xa/b.

According to the embodiment described above, the rotation of the pneumatic motor 1 is controlled by the rotation of the stepping motor 14, and it is possible to perform highly accurate control and obtain a large output. Since the differential gear device 4 is used, it is possible to select one having various rotation ratios, and it is possible to select one that improves controllability depending on the purpose of use. Compared to the conventional structure using screws,
It is a combination of spur gears and has a simple structure as there are no sliding parts. In order to protect against excessive rotation input from the main input shaft 5 and control input shaft 7, for example, a torque limiter or the like is provided between the output shaft 6 and the pinion 8, so that the pinion 8 will not rotate in response to excessive torque. Therefore, by providing such a protection device at only one location, protection is provided from excessive input due to poor adjustment or overload. Since poppet valves are used as the switching valves 11 and 12, they are resistant to foreign matter such as dust, and the compressed air can be easily managed and adjusted.

In the above-described embodiment, a reduction gear may be further provided on the main input shaft 5, control input shaft 7, and output shaft 6, and the speed reduction device is not limited to the above-mentioned differential gear device 4. It may also be a gear device.

Instead of the pneumatic motor 1, a cylinder that operates linearly may be used, and this motion may be converted into rotational motion using a rack and pinion, etc., and connected to the main input shaft 5. Hydraulic pressure may be used instead of pneumatic pressure. , the switching valves 11 and 12 may be configured integrally.
A lever or the like may be used in place of the pinion 8. Note that the position or rotation angle control can also be performed using a single-acting actuator balanced with the spring pressure and a poppet valve on one side.

(Effects of the Invention) According to the present invention, a large output can be extracted from the fluid pressure motor by controlling the rotation of the control motor whose rotation is easy to control. Since it does not use a screw like the conventional structure, the structure is simple and adjustment is easy. By using a poppet valve as the valve device, compressed air and hydraulic oil can be easily managed and adjusted.

[Brief explanation of the drawing]

The drawing is a circuit diagram including a cross section of a differential gear device showing an embodiment of the present invention. l...Pneumatic motor (fluid pressure motor), la, l
b...Port, 4...Differential gear device, 5...Main input shaft, 6...Output shaft, 7...Control input shaft, Il, 1
2...Switching valve (valve device), 14...Stepping motor (control motor).

Claims (4)

[Claims] 1. A fluid pressure motor having two ports for supplying and discharging fluid that operate in opposite directions, a differential gear device whose main input shaft is rotationally driven by the fluid pressure motor, and an output shaft of the differential gear device. A servo actuator comprising: a valve device that is switched by the rotation of the valve device and selectively supplies fluid to each port according to the rotation direction of the valve device; and a control motor that rotationally drives a control input shaft of the differential gear device. 2. 2. The servo actuator according to claim 1, wherein the differential gear device is formed by combining a large number of spur gears. 3. The servo actuator according to claim 1 or 2, wherein the valve device is a poppet valve. 4. The servo actuator according to any one of claims 1 to 3, wherein the control motor is a stepping motor.