JPH04101752A - Control method for main spindle of machine tool - Google Patents

Abstract

PURPOSE:To automatically set a gear ratio or pulley ratio, by inputting to a counter the output signal of a motor encoder fitted to a motor and that of the main spindle position detector fitted to the main spindle, at the low speed running time of the motor and operating the gear ratio of a speed change gear based on the counter number of this counter. CONSTITUTION:The main spindle 6 of a machine tool is controlled by a motor 3 via a speed change gear 5. In this case, the output signal of the motor encoder 4 fitted to the motor 3 and that of the main spindle position detector 7 fitted to the main spindle 6 are input to a counter 11. The gear change ratio of the speed change gear 5 is operated based on the count number of this counter 11, and the operated gear change ratio is stored in a memory 14.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is directed to a main spindle drive system of a machine tool that is driven via a speed change gear or a belt pulley. Regarding how to set up automatically.

[Conventional technology]

The main spindle of an NC lathe or machining center is often driven via a variable speed gear in order to expand the speed range of constant output characteristics and accommodate various cutting conditions.

Others use a combination of belts and pulleys to achieve the required speed.

This gear ratio or pulley ratio must be set as a parameter in the main shaft control device for the following purposes.

(1) To use as a conversion factor to display the rotational speed of the main shaft by counting the number of pulses of a pulse encoder mounted on the motor shaft for motor control.

(2) As a fixed-position stop for automatic tool exchange, a single-point stop is usually sufficient, so a single-point position detector is used as the position detector on the spindle. This is used as a conversion coefficient when converting the encoder signal of the motor to the equivalent pulse signal on the main shaft, as a means of complementing the interval between position signals and improving control performance.

(3) To obtain a converted motor rotation angle signal on the main shaft in order to make the main shaft rotation angle and feed amount of the feed shaft proportional during tapping.

Conventionally, this parameter was set in the drive inverter based on the machine specifications (for example, Japanese Patent Application Laid-Open No. 64-59
(See Publication No. 409).

[Problem to be solved by the invention]

In the above method, if the setting is incorrect, it is difficult to detect the error, and not only is sufficient performance not obtained, but there is a possibility that danger such as overspeeding may occur.

Therefore, an object of the present invention is to provide a method for controlling a spindle of a machine tool that solves such problems.

[Means to solve the problem]

In order to achieve this object, the present invention provides a main shaft control method for a machine tool in which the main shaft of a machine tool is controlled by an electric motor via a transmission, in which an output of a motor encoder attached to the motor is provided when the motor is operated at a low speed. Inputting the signal and the output signal of the main shaft position detector attached to the main shaft into a counter, calculating the gear ratio of the transmission based on the count number of the 20 counter, and storing the calculated gear ratio, Further, an alarm is issued when the calculated gear ratio differs from the set gear ratio.

[Effect]

The invention allows gear ratios or pulley ratios to be automatically set or verified.

〔Example〕

Embodiments of the present invention will be described using the drawings.

FIG. 2 is a block diagram of the spindle drive system of the machine tool. 1 is a power supply, 2 is an inverter, and 3 is an AC motor.The inverter 2 drives the AC motor 3 at variable speed, but because dynamic characteristics are required, vector control is often adopted for AC motors. The signal MP from the electric motor encoder 4 attached to the shaft of 3
Vector control and speed control are performed using G. Also,
A main shaft position detector 7 is attached to the main body of the main shaft 6 which is driven via a speed change gear or belt pulley 5 . In the case of machining centers, a - point position detector is often used because the machine mainly stops at a fixed position for automatic tool change, but in lathes, a multi-pulse encoder is used for processing such as thread cutting. Often used as a detector.

FIG. 3 is a block diagram illustrating a method for automatically setting or verifying gear ratios or pulley ratios.

A counter 11 provided in the inverter 2 compares the number of pulses of the motor encoder 4 and the number of pulses of the spindle position detector 7. For example, when a one-point position detector is used, this can be achieved by setting and resetting the counter 11 with the main shaft pulse SPG and counting the pulse MPG of the motor encoder 4 that arrives during one rotation of the main shaft. This calculation is performed by CPU10. Furthermore, when a multi-pulse encoder is used, MPG and SPG are counted for a certain period of time using separate counters, and the speed ratio is calculated from the counted values. The obtained gear ratio or pulley ratio is stored in non-volatile memory (NVRAM) 14. In addition, if the gear ratio or pulley ratio parameters have already been set in the nonvolatile memory (NVRAM) 14 by the gear ratio/pulley ratio setting device 13, they will be compared and verified, and if there is an error, an alarm will be set.
2 generates an alarm signal.

FIG. 1 is a flowchart for implementing the invention. First, the AC electric motor 113 is operated at low speed (step 1). If a multi-pulse encoder is used, the main shaft pulse SPG and the pulse M of the motor encoder 4
Start counting PG (step 2'), after a certain period of time has elapsed (step 39), stop counting (step 4'), and calculate the gear ratio or boolean ratio using the following formula (1) (step 5) .

However, N5PG: Number of counts of spindle pulses N□,: Number of counts of motor encoder pulses n8,: Number of pulses per one rotation of the spindle nnrG: @Number of pulses per one rotation of the motor Also, when a one-point position detector is used , that one point position body symbol SP
Wait for the rising edge of G (step 2). When a rising edge is detected, start counting MPG (
Step 3). Next, wait again for the rising edge of the SPG (step 4). Once a rising edge is detected,
The MPG counter is stopped (step 5), and the gear ratio or pulley ratio is determined using the following equation (2) using the count value (step 6).

The gear ratio or pulley ratio determined by the above formula is compared with a value preset in the NVRAM 14, and if they are not equal, an alarm signal is output (step 8).

(Effects of the Invention) As described above, according to the present invention, the gear ratio or boolean ratio can be automatically set or verified in the spindle drive system of a machine tool, thereby preventing performance degradation due to parameter input errors. becomes possible.

[Brief explanation of the drawing]

Fig. 1 is a flowchart for realizing the present invention, Fig. 2 is a block diagram of the spindle drive system, and Fig. 3 is a block diagram illustrating a method for automatically setting or verifying a gear ratio or boolean ratio. . 1... Source, 2... Inverter, 3... AC motor, 4... Motor encoder, 5... Speed change gear or belt pulley, 6... Main shaft, 7... Main shaft position Detector, 10... CPtJ, 11... Counter, 12
...Alarm device, 13...Gear ratio/pulley ratio setting device, 14...Non-volatile memory (NVRAM) Patent applicant Yasuyo Electric Manufacturing Co., Ltd. King 1 side Figure 2 PG

Claims (1)

[Scope of Claims] 1. In a machine tool spindle control method in which the spindle of a machine tool is controlled by an electric motor via a transmission device, when the electric motor is operating at a low speed, an output signal of a motor encoder attached to the electric motor and an output signal of a motor encoder attached to the electric motor are connected to the spindle of the machine tool. A machine tool characterized by inputting an output signal of an attached spindle position detector to a counter, calculating a gear ratio of the transmission device based on the count number of the counter, and storing the calculated gear ratio. spindle control method. 2. In a spindle control method for a machine tool in which the spindle of a machine tool is controlled by an electric motor via a transmission, when the electric motor is operating at low speed, an output signal of a motor encoder attached to the electric motor and a spindle position detector attached to the spindle are detected. inputting the output signal of the output signal into a counter, calculating the gear ratio of the transmission device based on the count number of the counter, and outputting an alarm signal if the calculated gear ratio is different from the set gear ratio. Features of machine tool spindle control method.