JPH0531641A - Rotary table - Google Patents

Abstract

PURPOSE:To provide a rotation speed ranging from a low speed to a high speed and to rotate a work at a given turning speed. CONSTITUTION:An AC electric motor and a DC electric motor are provided. An AC rotor 3 and a DC rotor 5 of the respective electric motors are engaged with a rotary shaft 1. Switchies to either one of the electric motors is carried out according to the turning speed of a work and the rotary shaft 1 is driven throughout a range from low speed rotation to high speed rotation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary table for a machine tool, and more particularly to a rotary table suitable for selecting a turning speed in a range from low speed rotation to high speed rotation.

[0002]

2. Description of the Related Art In a conventional rotary table, a DC motor is generally suitable when high torque is required at low speed rotation, and an AC motor is generally suitable when high torque is required at high speed rotation. However, it is intended for low-speed rotation, the rotation speed control is in the range of several hundreds of rotations or less, and it is intended for high-speed rotation, and the rotation speed control is in the range of hundreds to thousands of rotations. Therefore, it is not configured such that one turning table can select a turning speed in a range from low speed rotation to high speed rotation and drive with high torque.

[0003]

Since the conventional rotary table cannot be driven in the rotational speed range from low speed rotation to high speed rotation, for example, the workpiece fixed to the rotary table is rotated at low speed to perform rough cutting. After that, when performing a turning process by rotating at a high speed as it is, there is a problem that a predetermined high speed rotation cannot be obtained and the process is difficult.

An object of the present invention is to provide a rotary table which can be driven in a range from low speed rotation to high speed rotation to rotate a work material at a predetermined turning speed.

[0005]

In order to achieve the above-mentioned object, a rotary table according to the present invention comprises a rotary shaft rotatably supported by a bearing and a drive means for driving the rotary shaft. In a rotary table which is held at one end of a rotary shaft and rotated at a predetermined turning speed, drive means are formed by an AC electric motor and a DC electric motor, and rotors of the AC electric motor and the DC electric motor are fitted to the rotary shaft and turned. According to the speed, one of the electric motors is switched to drive the rotary shaft from low speed rotation to high speed rotation. The DC electric motor may have a configuration including a brush moving mechanism.

[0006]

According to the present invention, since the rotors of the high-speed rotating AC electric motor and the low-speed rotating DC electric motor are fitted to the rotating shafts, either one of the electric motors is selected according to the turning speed of the material to be cut. Is switched to. The rotary shaft is driven in a range from low speed rotation to high speed rotation, and the work material is rotated at a predetermined turning speed.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 1, a static pressure air bearing portion (bearing) 2 having an air supply hole for preventing heat generation at high speed rotation,
The rotary shaft 1 rotatably supported by the hydrostatic air bearing unit 2, the AC rotor 3 and the DC rotor 5 fitted to one end of the rotary shaft 1, and the outer periphery of the AC rotor 3 are provided so as to face each other. AC stator 4, DC stator 6 provided to face the outer periphery of DC rotor 5, brush 7 and commutator 8 in contact with DC stator 6, and non-contact high resolution used at low speed rotation. This is a configuration including a functional rotary encoder 9. The AC rotor 3 and the AC stator 6 form a high-speed rotating AC motor, and the DC rotor 5, the DC stator 6, the brush 7 and the commutator 8 form a low-speed rotating DC motor.

The operation of this embodiment will be described. During high speed rotation, the AC rotor is energized to drive the rotating shaft, and during low speed rotation, the DC rotor is energized via the brush and commutator to drive the rotating shaft. Switching to either the AC electric motor or the DC electric motor is executed by the drive control unit by selecting the electric motor according to the turning speed of the material to be cut.

Another embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 2, the rotary shaft 1 rotatably supported by two bearing portions 22 provided with a predetermined distance,
The AC rotor 3 fitted between the two bearing portions 22 and the AC stator 4 provided so as to face the outer circumference of the AC rotor 3.
A direct current rotor 5 fitted to the other end of the rotary shaft 1; a direct current stator 6 provided to face the outer periphery of the direct current rotor 5;
The brush 7 and the commutator 8 are in contact with the DC stator 6 and have a configuration. As shown in FIG. 3, the brush moving mechanism is rotatably connected to the magnet 16 that drives the shaft 16 in the arrow direction by energization and the shaft 16, and the brush 7 is connected to the commutator 8 via the brush holder 13. The lever 12 for pressing or separating, the holder 11 in which the brush holder 13 is slidably accommodated and fixed, and the lever 12 built in the holder 11 and the brush holder 13 via a flange.
A spring 14 that biases the brush 7 toward the side and a spring 15 that adjusts the biasing force of the brush 7 toward the commutator 8.

The operation of the other embodiment will be described. Switching of the rotation speed of the rotary shaft is the same as that of the embodiment shown in FIG. During high-speed rotation, when the magnet 10 is energized, the shaft 16 moves leftward in the drawing, the lever 12 rotates through a fulcrum, and one end of the lever 12 is pressed against the brush holder 13. The brush 7 contacts the commutator 8 by moving to the right in the drawing by overcoming the urging force of the brush 7. However, the DC motor not only functions as a generator at high speed rotation and generates back electromotive force,
Since there is a possibility that the brush may be worn and generate heat or vibration during high-speed rotation, the energization of the magnet 10 is stopped to restore the lever 12, and the urging force of the spring 14 restores the brush holder 13 to restore the brush. 7 is separated from the commutator 8. A gap is formed between the brush 7 and the commutator 8, the function of the DC motor is stopped, and the brush 7 is prevented from being worn. Therefore, during low-speed rotation, the magnet 10 is energized before the DC generator is driven, the brush 7 and the commutator 8 are brought into contact with each other, and then the DC generator is driven. At the time of high speed rotation, after turning off the energization of the magnet 10, the high speed stator 4 of the AC generator is energized to rotate the rotating shaft 1 at high speed.

According to the present invention, from the turning process requiring high speed rotation to the roughing process requiring low speed rotation, the same rotary table can be used for processing, so that the setup time of the material to be cut can be shortened, and Since the material to be cut is fixed once, the processing accuracy is improved. In addition, since the brush and commutator can be brought out of contact with each other during high-speed rotation, it is not necessary to take countermeasures against the back electromotive force of the DC motor in the control system, but the life of the brush is improved and heat generation and vibration are prevented. You can

[0013]

According to the present invention, the material to be cut can be processed at a predetermined turning speed in the range from low speed rotation to high speed rotation by switching either the AC motor or the DC motor. The setup time is shortened and the processing accuracy is improved.

Further, since the brush can be separated from the commutator during high-speed rotation, the life of the brush can be improved and heat generation and vibration can be prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the present invention.

FIG. 3 is a cross-sectional view taken along the line AA of FIG.

[Explanation of symbols]

1 rotation axis 2 Hydrostatic air bearing (bearing) 3 AC rotor 4 AC stator 5 DC rotor 6 DC stator 7 brushes 8 commutator

Claims (2)

[Claims] 1. A rotary table comprising: a rotary shaft supported by bearings; and a drive means for driving the rotary shaft, wherein a workpiece is held at one end of the rotary shaft and rotated at a predetermined turning speed. The drive means is formed by an AC motor and a DC motor, the rotors of the AC motor and the DC motor are fitted to the rotary shaft, and the motor is switched to one of the motors according to the turning speed. A rotary table that drives a rotary shaft from low-speed rotation to high-speed rotation. 2. The rotary table according to claim 1, wherein the DC motor includes a brush moving mechanism.