JPH0433109A - Main shaft driving device for machine tool - Google Patents

Abstract

PURPOSE:To highly precisely drive a main shaft by providing a signal conversion means converting the output of a high resolution position detector into rotational speed and setting a speed loop gain larger than that at the time of a speed control mode. CONSTITUTION:In the case of a machining operation, a speed detection signal omegar is outputted from a switch 22 and a speed deviation signal DELTAomegar from a switch 24. In the case of a C-shaft operation, a switch 13 is switched to a con tact point(b) and the switches 22 and 24 are interlocked and switched to the contact point (b). Thus, a position detection signal thetar from the high resolution position detector 6 is converted into the speed detection signal omegar by a position- speed conversion circuit 21. A speed command DELTAomegar and the speed deviation signal DELTAomegar are compared in a comparator 14, the speed deviation signal DELTAomegar is outputted and it is inputted to a speed loop gain circuit 23 through a speed loop gain circuit change-over switch 24. Here, the loop gain is improved and is inputted to a power conversion circuit 16 and the main shaft is highly precise ly operated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for driving a built-in spindle motor of a machine tool.

[Prior art 1] Figures 3 and 4 are diagrams showing the main spindle drive device of a conventional machine tool, where Fig. 3 is a configuration diagram of main parts, and Fig. 4 is a block circuit diagram of the main spindle drive control device. .

In Figure 3, (11 is the speed command ω, position command θ, etc.)
(2) Numerical control device (hereinafter referred to as NC) that outputs
is the main shaft drive control device (hereinafter referred to as the control device) connected to the NC[1], (3) is the built-in main shaft electric motor (hereinafter referred to as the electric motor) connected to the control device (2), (4
) is the main shaft of the machine tool driven by the electric motor (3),
(5) is coupled to the main shaft (4), and has a low resolution capable of detecting the rotational speed of the main shaft (4) up to high speed rotation and generating the speed detection signal ω1 by outputting, for example, 4,096 pulses/rotation. The speed detector (6) is a high-resolution position detector that is coupled to the main shaft (4) and is capable of detecting l/1000° and generating a position detection signal θ1 by outputting, for example, 360,000 pulses/rotation. It is a vessel. Note that the control device (2), the electric motor (3), the low-resolution speed pressure detector (5), and the high-resolution position detector (6) constitute a main shaft drive device of the machine tool.

In Fig. 4, (11) is the position command θI and the position detection signal θ1.
A comparator that compares and outputs a position error signal Δθ1,
121 is connected to the comparator (11) and receives the position error signal Δθ1
The position loop gain circuit (13) has a contact (a) to which the speed command ωI is input, and a contact (bl) to which the output of the position loop gain circuit (12) is input.
In the speed control mode that controls the rotational speed of 4), that is, the turning operation mode that turns a rotating workpiece (not shown), the contact fa) is set to the position control mode that controls the rotational position of the spindle (4), that is, C In axis operation mode, the contact (b
), and (14) is the output ωI of the mode selection switch (13) and the speed detection signal ω.
A comparator that compares , and outputs a speed deviation signal Δω, (
15) is a speed loop gain circuit that amplifies the speed deviation signal Δω by a gain A, and (16) is a power conversion circuit that converts the output of the speed loop gain circuit (15) into electric power to be supplied to the electric motor (3).

A conventional main shaft drive device for a machine tool is constructed as described above and operates as follows.

First, when operating in the turning operation mode, the mode changeover switch (13) is turned on to the contact (al).

A speed command ωI corresponding to the target rotation speed of the main shaft (4) is output from the NC (1), and a control device (2) performs control to cause the speed ω of the electric motor (3) to follow the speed command ωI. That is, the speed command ω,° and the speed detection signal ω are compared by a comparator (14), and a speed deviation signal Δω is output from the comparator (14), which is amplified by a speed loop gain circuit (15). The power conversion circuit (16) converts it into electric power that drives the electric motor (3). The electric motor (3) is then controlled to follow the speed command ωI.

Next, when operating in C-axis operation mode, select NC (1).
The output of is switched to the position command θI.

The control device (2) detects this and switches the mode changeover switch (13) to contact (b). Position command θI
and the position detection signal θ1 are compared by the comparator (111), and the position deviation signal Δθ1 is outputted from the comparator (11) and inputted to the comparator (14).The subsequent operation is the same as in the above turning operation mode. The main shaft (4) is controlled to follow the position command θr' via the electric motor (3).

[Problems to be Solved by the Invention] In the conventional spindle drive device of a machine tool as described above, the speed of the spindle (4) is controlled in the turning operation mode, and the C
Since the position of the spindle (4) is controlled by the axis operation mode, when controlling the C-axis position, the position loop gain and speed loop gain are adjusted to obtain responsiveness that can withstand C-axis cutting. It is necessary to sufficiently increase each of them, but since the resolution of the speed detector (5) is low and the speed detection signal is low, there is a problem that the speed loop gain cannot be increased sufficiently.

This invention was made to solve the above problems, and even in the C-axis operation mode, the speed loop gain can be sufficiently increased, the C-wheel cutting performance will not be impaired, and high performance and high precision can be achieved. It is an object of the present invention to provide a main shaft drive device for a machine tool that can be expected to operate.

[Means for Solving the Problems] The spindle drive device for a machine tool according to the present invention has a signal conversion function that converts the output of a high-resolution position detector that detects the rotational position of the spindle into a rotational speed in the spindle position control mode. In addition to providing means, the speed loop gain is set larger than in the speed control mode.

[Function] In the present invention, in the position control mode, the rotational speed is obtained from the output of the high-resolution position detector and the speed loop gain is increased, so the speed can be detected with high precision and the gain can be increased. becomes possible.

[Embodiment] Fig. 1 and Fig. 2 are diagrams showing an embodiment of the present invention, in which Fig. 1 is a block circuit diagram of a control device, and Fig. 2 is an explanatory diagram of mode switching operation, which is similar to the conventional device. The parts shown are indicated by the same reference numerals. Note that FIG. 3 is also used in this embodiment.

In FIG. 1, (21) is a position-speed conversion circuit that differentiates the position detection signal θ and converts it into a speed detection signal ω; (22)
is a speed detector changeover switch that is switched in conjunction with the mode changeover switch (13), the contact (a) is connected to the low resolution speed detector (5), and the contact (b) is connected to the position-speed conversion circuit (21). It is connected to the. (23) is the gain A
(24) is a speed loop gain circuit changeover switch that is switched in conjunction with the mode changeover switch (13);
The contact (al) is connected to the speed loop gain circuit (15), and the contact fb is connected to the speed loop gain circuit (23).

Next, the operation of this embodiment will be explained.

First, in the case of turning operation mode, the speed detection signal ω1 is output from the speed detector changeover switch (22), and the speed deviation signal Δω is output from the speed loop gain circuit changeover switch (24).
The output is substantially the same as that shown in FIG.

In the case of the C-axis operation mode, the mode selector switch (13) is switched to contact (b) as described above, and in conjunction with this, the speed detector selector switch (22) and the speed loop gain circuit selector switch (24) is also switched to contact (b). Now, the position detection signal θ from the high-resolution position detector (6) is converted to the position-velocity conversion circuit (21).
is converted into a speed detection signal ω. Speed command ΔωI
and the speed detection signal ω, are compared by the comparator (14), and a speed deviation signal Δω is output, which is then sent to the speed loop gain circuit (2) via the speed loop gain circuit changeover switch (24).
3) is input. Here, the loop gain is increased and
It is input to the power conversion circuit (16). The following operations are as described above.

Next, the operation when switching from the turning operation mode to the C-axis operation mode will be explained with reference to FIG.

In the figure, (31) is the speed of the main shaft (4), (31a) is the speed during the rapid traverse period, (32) is the C-axis operation mode period, (3
3) indicates the return-to-origin completion period, and (34) indicates the changeover switch contact setting period.

As shown in Figure 2 (bl), during operation in the turning operation mode, the signal to select the C-axis operation mode at time t1 is
[l) to the control device (2), the control device (
2) is from turning operation mode, that is, speed control mode to C
In order to switch to the axis operation mode, that is, the position control mode, first a return-to-origin operation shown in FIG. 2(c) is performed. This return-to-origin operation is completed (before time ti,
As shown in FIG. 2(d), each selector switch fl] (
221 (24) is set to contact fa).

When the home return operation is completed at time t2, each changeover switch (131 (22) +241) is switched to contact (b), and the same state is maintained until the C-axis operation mode is canceled at time t3.C-axis In operation mode, the main shaft (
For 5), it is desirable that the velocity loop gain be high in order to withstand steep responses. The rotational speed of the main shaft (5) in the C-axis operation mode is extremely low (approximately 200 rpm).
(below), one of the important factors to increase the gain is to increase the detection resolution and accuracy of the speed detector.

To this end, using the low-resolution speed detector (5) configured for high-speed rotation (approximately 6.OQOrpm) also for low-speed rotation such as in the C-axis operation mode will impede gain improvement. In this example, if limited to the low speed rotation range,
Since the high-resolution position detector (6), which has no problem in terms of the response frequency capability of the side ratio circuit, is also used as a speed detector, it is possible to increase the gain.

In the above embodiment, the control device (2) is the comparator (]1) (1
4), each changeover switch [131 (221, 241, etc.) is shown configured using hardware, but the power element (not shown) constituting the power conversion circuit (16) and its control circuit (not shown) It is also possible to construct means equivalent to the comparators (11) (14), each changeover switch f13) f22) (241, etc.) on the program by using software, that is, using a computer system, with the exception of some parts. .

[Effects of the Invention] As explained above, in this invention, in the spindle position control mode, a signal conversion means is provided for converting the output of a high-resolution position detector that detects the rotational position of the spindle into a rotational speed, and a speed loop gain is also provided. Since the speed is set to a higher value than in the speed control mode, the speed can be detected with high accuracy and the gain can be increased, which has the effect of enabling high-performance and high-precision spindle operation.

[Brief explanation of drawings]

Figure IJ1 and Figure 2 are diagrams showing an embodiment of the spindle drive device for a machine tool according to the present invention, Figure 1 is a block circuit diagram of the control device, Figure 2 is an explanatory diagram of mode switching operation, Figure 3, Figure 4 is a diagram showing the main shaft drive device of a conventional machine tool.
FIG. 3 is a configuration diagram of main parts, and FIG. 4 is a block circuit diagram of the main shaft drive control device of FIG. 3. In the figure, (1) is a numerical controller, (2) is a spindle drive control device, (3) is a built-in spindle motor, (4) is a spindle, (5) is a low resolution speed detector, (6) is a high resolution The position detector, (12) is the position loop gain circuit, (
13) is a mode selection switch, (15) is a speed loop gain circuit, (21) is a signal conversion means (position-speed conversion circuit), +23) is a gain setting means (speed loop gain circuit), and ω is a speed detection signal , θ1 is a position detection signal. Note that the same reference numerals in the figures indicate the same parts. Shoki 1990 10

Claims (1)

[Claims] a speed loop that negatively feeds back the rotational speed of the spindle through a low-resolution speed detector coupled to a built-in spindle motor that drives the spindle of the machine tool; The motor has a position loop that provides negative feedback on the rotational position of the main shaft, and by selecting either a speed control mode that controls the rotational speed of the main shaft or a position control mode that controls the rotational position of the main shaft, A device for controlling rotational speed and rotational position, comprising a signal converting means for inputting a negative feedback signal of the rotational position when the position control mode is selected and converting it into a rotation speed, and the speed loop when the position control mode is selected. A spindle drive device for a machine tool, comprising gain setting means for setting the gain of the speed control mode to be larger than that when the speed control mode is selected.