JPH02114879A - Controller for spindle motor - Google Patents

Abstract

PURPOSE:To improve the capacity of speed detection by installing two kinds of speed detectors having different resolution, a changeover switch selecting either one of these speed detectors and a speed detector computing motor speed corresponding to the resolution of the speed detector selected by the changeover switch. CONSTITUTION:Two kinds of speed detectors 5a, 5b of a speed detector 5a being used at the time of intermediate and low speed revolution and having normal resolution and a speed detector 5b being employed at the time of high speed revolution and having low resolution, changeover switches 9a, 9b selecting either one of these speed detectors 5a, 5b and a speed detector 7a computing motor speed corresponding to the resolution of the speed detector selected by the changeover switches 9a, 9b are mounted. Consequently, when a spindle motor 4 is operated, motor speed is controlled by using the speed detector having normal resolution when the motor is worked in intermediate and low speed revolution regions, and the speed detector is changed over to the speed detector having low resolution and motor speed is controlled when the motor is operated in a high speed revolution region. Accordingly, a controller controlling speed within a wide range with high accuracy and having excellent noise resistance can be acquired.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to speed control of a spindle motor of a machine tool or the like.

[Prior Art] FIG. 4 is a block diagram showing a schematic configuration of a conventional main shaft motor control device. In the figure, 1 is a speed control circuit, 2
is a PWH circuit and a converter circuit.

A power conversion circuit composed of an inverter circuit, etc., 3 is a commercial power supply, 4 is a main shaft motor, 5 is a speed detector with sine wave output or square wave output, 6 is a speed detector receiver circuit, and 7 is a speed detection circuit. .

Next, the operation of the conventional spindle motor control device described above will be explained. The difference between the command speed given from the outside and the motor speed calculated by the speed detection circuit 7 is input to the speed control circuit 1, and the current required to maintain the command speed is determined according to the difference between the command speed and the motor speed. Calculate the command. The power conversion circuit 2 converts a current corresponding to the current command obtained from the speed control circuit 1 using a commercial power source 3 and supplies the converted current to the main shaft motor 4 . The speed of the main shaft motor 4 is detected by a speed detector 5, such as an encoder, directly connected to the motor shaft, and outputs pulses with a frequency proportional to the motor rotation speed. A speed detector receiver circuit 6 receives an encoder signal from an encoder (speed detector 5), and a speed detection circuit 7 calculates the motor speed from the output frequency of the encoder. In this way, speed control circuit 1, power conversion circuit 2. Main shaft motor 4. Speed detector 5° Speed detector receiver circuit 6. Speed control by a closed loop consisting of the speed detection circuit 7 allows the main shaft motor 4 to maintain a motor speed corresponding to the commanded speed.

Here, a speed calculation method when an encoder is used as the speed detector 5 will be explained. In the case of an encoder that outputs A pulses per rotation of the spindle motor 4, the spindle motor 4 has a motor speed N[r, p.

Since the output frequency f of the encoder is expressed as during the rotation at m], the number p of pulses input to the speed detection circuit 7 during unit time (sampling time) T [seconds] is as follows. Therefore, motor speed N [r, p, m
] is determined. Here, A and T are known and 6
0/A-T indicates the speed per pulse of the encoder, that is, the speed resolution, and the longer the sampling time T is, the higher the number of output pulses from the encoder is, the better the resolution will be. Furthermore, as shown in equation (3) above, the motor speed N [r, p, m] depends on the sampling time T
It can be seen that the speed resolution is proportional to the number of pulses input within the range, and is constant over the entire speed range.

In addition, as is well known, the speed ripple, torque ripple magnitude, and responsiveness to load fluctuations of the spindle motor 4 are greatly influenced by speed detection accuracy and resolution, and in order to ensure high responsiveness and smooth speed control performance, It is essential to further improve speed detection accuracy and resolution.

On the other hand, speed detector receiver circuit 6. The speed detection circuit 7 stores the allowable frequency generated due to the circuit configuration and the encoder output frequency f=A-NI1. It is made to have the minimum necessary filter characteristics to be able to receive AX/60 [H2], and also has rough noise resistance, which means that there is a limit to the permissible human frequency. Become.

[Problems to be Solved by the Invention] Since the conventional spindle motor control device described above is configured as described above, the number of pulses per rotation of the encoder as the speed detector 5 and the speed detector receiver circuit 6 are The maximum rotational speed and speed resolution of the spindle motor 4 are determined by the allowable frequency, so speed resolution must be sacrificed for high-speed rotation, and the allowable rotational speed must be lowered to obtain high-speed resolution. There was a problem.

This invention was made to solve the above-mentioned problems, and it uses high-resolution operation and high-speed operation depending on the driving situation, and performs high-precision and wide-range speed control.
Moreover, it is an object of the present invention to obtain a control device for a spindle motor that has excellent noise resistance.

[Means to solve the problem] A main shaft motor control device according to the present invention is a medium-sized main shaft motor control device.

Two types of speed detectors, a normal resolution speed detector used during low speed rotation and a low resolution speed detector used during high speed rotation, a changeover switch for selecting one of these speed detectors, and a changeover switch for selecting one of these speed detectors; The speed detection circuit calculates the motor speed according to the resolution of the speed detector selected by the changeover switch.

[Operation] When operating the spindle motor in the present invention, the spindle motor control device uses a speed detector with normal resolution to control the motor speed when operating the spindle motor in the medium and low speed rotation range, and When operating in the speed rotation range, the motor speed is controlled by switching to a speed detector with lower resolution.

[Embodiment] Fig. 1 is a block diagram showing a schematic configuration of a control device for a spindle motor which is an embodiment of the present invention. Explanation will be omitted. In the figure, 5a is a speed detector with normal resolution attached to the motor shaft opposite to the load side of the main shaft motor 4, and 5b is a speed detector with low resolution also attached to the motor shaft opposite to the load side. 9a and 9b are the above 2
The speed detection signal of the speed detector 5a, 5b selected by the changeover switch 9a, 9b has a characteristic of allowable frequency fin-max. do. Speed detectors 5a, 5b selected by changeover switches 9a, 9b
The speed detection signal is manually inputted to the speed detection circuit 7a via the speed detector receiver circuit 6, and the motor speed is calculated according to the resolution of the speed detector being selected. In addition, the changeover switch 9
a.

The switching of 9b is performed by the switching circuit 8 of the speed detection circuit.

Fig. 2 is a characteristic diagram showing the relationship between the motor speed of the spindle motor and the output frequency of the speed detector in the spindle motor control device shown in Fig. 1, and Fig. 3 is a speed detection diagram in the spindle motor control device shown in Fig. 1. It is a figure showing an example of a container. In Figure 3,
Non-contact type speed detectors 5a, 5b are shown as speed detectors, each consisting of a detection section composed of a gear and a magnetic resistance element, etc. Two types of gears 1 with different numbers of teeth that determine resolution are shown.
0a.

10b is attached to the motor shaft opposite to the load side of the main shaft motor 4.

Next, the operation of the spindle motor control device according to the embodiment of the present invention will be described. Normally, the spindle motor 4 in a machine tool is used for heavy cutting such as rough cutting or tapping in a medium or low speed range, and for finishing work with a light cutting load in a high speed range. For this reason, high responsiveness to load fluctuations and smooth operating characteristics through advanced speed control are required, especially in the medium and low speed ranges. On the other hand, in the high-speed range, load fluctuations are small, so high-speed operation performance is required.

Therefore, in the case of medium or low speed operation, the selector switch 9a
is turned on, the selector switch 9a is turned off, and a high-resolution speed detector 5a, for example a high-resolution encoder, is used. The resolution of the encoder (speed detector 5a) is A
+ [pulses/rotation] is the motor speed N + [r-1
]-m], the output frequency f of the above encoder is
1 is f + = A + · H + / 60 from the above formula (1)
[H2, and the allowable frequency f of the speed detector receiver circuit 6 is within the range of 1n-0° (middle and low speed range), that is, the motor speed N + < 6 Of; n-may/
Use with A+.

On the other hand, in the case of high-speed operation, the encoder (speed detector 5
Since the output frequency f1 of a) exceeds the permissible frequency f in -□8 of the speed detector receiver circuit 6, the changeover switch 9a is turned OFF and the changeover switch 9b is turned ON. 5b) is used. If the resolution of this encoder is A2 [pulses/rotation] (A I> A 2 ), the output frequency f2 of the encoder is f 2 = A 2...N2/
60 [H2co], and in the same speed detector receiver circuit 6, motor speed N2 = 60 f 2 / A2 < 6 Of in-m
Up to ax/A2 is acceptable. If the resolution of the encoder (speed detector 5b) is 1/2, the speed resolution is also 1/2.
/2, but it means that it can run at twice the speed.

In addition, when calculating the motor speed, the speed detection circuit 7a
When the encoder (speed detector 5a) is selected, the resolution is 60 / A + T, and when the encoder (speed detector 5b) is selected, the resolution is 6° / A 2 · T, respectively, counted within the sampling time T. The motor speed is calculated by multiplying the input cabling number. The speed detection circuit switching circuit 8 determines which encoder to select among the encoders (speed detectors 5a and 5b) based on the command speed given from the outside, and turns ON and OFF the changeover switches 9a and 9b. Instruct. In this way, the motor speed can always be accurately detected with appropriate speed resolution depending on the operating state of the spindle motor 4.

In addition, in the above embodiment, a speed detector using an encoder using gears and a magnetic resistance element was used as an example, but a type that converts the rotation speed into voltage and outputs it, such as a tacho generator, may be used as the speed detector. , and in the case of a spindle motor control device that detects the motor speed using an A/D converter,
The present invention can be used.

In addition, in the embodiment described above, a control device for a high-speed spindle motor was shown as an example, but in the case of spindle C-axis control (contour control),
Since it is necessary to detect precise speeds of several tens of rotations [1.-13-m] or less, we installed a high-resolution speed detector and used the high-resolution speed detector only for the C-axis. The present invention can be utilized in such a way that accurate speed detection in a speed range becomes possible.

[Effects of the Invention] As described above, the spindle motor control device of the present invention can be used for speed detectors with normal resolution used during medium and low speed rotation, and speed detectors with low resolution used during high speed rotation. It consists of two types of speed detectors, a changeover switch for selecting one of these speeddetectors, and a speed detection circuit that calculates the motor speed according to the resolution of the speed detector selected by the changeover switch. Therefore, not only can highly accurate speed detection capability and a wide speed control range be ensured, but also the calculation of the motor speed can be processed by software, which simplifies the configuration and provides excellent effects such as making the device inexpensive.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a schematic configuration of a spindle motor control device according to an embodiment of the present invention, and Fig. 2 shows the motor speed of the spindle motor and the output frequency of the speed detector in the spindle motor control device of Fig. 1. 3 is a diagram showing an example of the speed detector in the control device for the spindle motor shown in FIG. 1, and FIG. 4 is a block diagram showing the schematic configuration of the conventional control device for the spindle motor. be. In the figure, 1...speed control circuit, 2...-power conversion circuit, 3...commercial power supply, 4...main shaft motor, 5.5
a. 5b... Speed detector, 6... Speed detector receiver circuit, 7.7a... Speed detection circuit, 8... Speed detection circuit switching circuit, 9a, 9b-... Changeover switch, 10a,
10b...gear. In addition, the same symbols in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] A spindle motor control device that controls motor speed using a motor speed detection signal from a speed detector includes two types of speed detectors with different resolutions, a changeover switch that selects one of these speed detectors, and a switch that selects one of these speed detectors. A control device for a spindle motor, comprising: a speed detection circuit that calculates a motor speed according to the resolution of a speed detector selected by a switch.