JPS59214582A - Rectilinear motion actuator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] An object of the present invention is to provide a linear motion actuator that incorporates a device for accurately determining the thrust force f received by a linear motion actuator, and that has a drive mechanism incorporating a ball screw that is comprehensively miniaturized. That's true.

A linear motion actuator is used, for example, to feed an XY table. In this case, a precise feed amount is required. To meet this requirement, a method has been adopted in which the absolute position is detected and corrected using an mIJ near sensor mounted on an XY table.

Furthermore, actuators used in NC, CNC, etc. tend to be required to be able to accurately control even the locus determined by the total feed rate of two or three axes.

In contrast, conventional linear actuators have a structure in which a ball screw is externally attached to a DC motor, and accuracy is achieved by increasing the rigidity of the mechanical system that supports the ball screw. However, when performing transient motion, has the drawback of not being able to provide era-specific accuracy. To correct this, it is necessary to determine the thrust of the actuator and measure the relationship between the thrust and the amount of deformation in advance, but there was no suitable means for measuring the thrust.

In this invention, a nut part that is threaded with a ball screw bolt is connected to the yoke and arranged in a center hole provided in the axial direction in the yoke of the motor rotor, and the rotor connects the nut part to the yoke through a thrust bearing. It is characterized in that a strain gauge is added to a part of the end cover that is supported by the end cover and receives the thrust when the bolt moves linearly due to the rotation of the rotor.

FIG. 1 shows one embodiment of the present invention, which uses a so-called brushless servo motor that rotates a magnet.

A fixed iron core 2 made of laminated iron plates is arranged inside a housing 1, and an armature winding 3 is wound around this. A rotor is provided with a gap maintained between the iron core 2 and the rotor. The rotor is composed of a yoke 5 and a magnet 4 made of, for example, fluorontium ferrite or a rare earth cobalt magnet. Rotational force is obtained by passing current through the armature winding 3. A nut 6 that is threadedly engaged with a port 9 of a pole screw is connected to the inside of the yoke 5, and the yoke 5 rotates together with the shafts 7 and 8. The bolt 9 is externally fixed to, for example, an XY table, and moves in the axial direction when the rotor rotates. Therefore, the thrust when sending the table is 6 nuts.
is transmitted to the rotor, producing a reaction force on the rotor. Angular bearings 10°11 supporting the rotor are supported by end covers 12 and 13. Therefore, the reaction force of the linear motion will be applied to the end cap. Sensors 16 and 17, such as strain gauges, are attached to the inside of the end cap to detect the stress generated in the end cap by the reaction force. The output of the sensor can be converted into a thrust signal by suitable electrical circuitry.

FIG. 2 shows an example of a detection circuit using a strain gauge. When the actuator applies thrust to the right side, the sensor 16 captures the reaction force. When applying thrust to the left side,
A sensor 17 captures the reaction force.

When incorporating the actuator into the device, the side of the end cap is typically used. To prevent detection sensitivity from changing on the mounting surface, attach the mounting plate 14.1 to the mating machine.
5 is provided.

FIG. 3 shows an example in which a suitable number of windows 22 are opened in the end cover 12 and the sensor 16 is placed on the lip 23 near the outer circumference. By concentrating stress on the ribs, the detection sensitivity of the sensor can be increased.

According to the present invention, since the linearly moving mechanical elements are incorporated into the rotor of the motor, there is an overall advantage that the actuator can be made smaller. Additionally, by attaching a thrust detection sensor to the actuator itself, it was possible to improve the accuracy of thrust detection. The conventional method of predicting thrust from motor torque introduces errors such as bearing friction, but the present invention detects the thrust of the linear motion part itself, making it easy to correct for mechanical system deflection. This has the effect of allowing precise positioning.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of the linear motion actuator of the present invention;
FIG. 2 is a thrust detection circuit diagram, and FIG. 3 is a back view of the end cover. DESCRIPTION OF SYMBOLS 1... Housing, 2... Stator core, 3... Armature winding, 4... Magnet, 5... Yoke, 6... Nut, 7.8... Rotating shaft, 9...pol), 10.1
1...Bearing, 12゜13...End cover, 14.15...
・Number board, 16.17°18.19...Sensor, 2
0...' Ichihara, 21... Output Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A nut portion that is screwed onto the bolt of the ball screw is integrally connected to the yoke in the center hole of the yoke of the rotor of the motor, and the rotor is supported by the end cover of the motor via a thrust bearing. The bolt that is screwed into the nut is configured to move linearly as the rotor rotates, and a sensor is added to the ring difference to detect the strain stress generated by the thrust of the bolt. motion actuator.