JPH0457651A - Method and apparatus for controlling spindle temperature of machine tool - Google Patents

Abstract

PURPOSE:To provide a spindle cooling method adaptable to the rotational speed of the spindle over a wide range without few heat shocks by combining feed- forward control corresponding to the roational speed of the spindle with feed- back control corresponding to the spindle temperature. CONSTITUTION:Liquid temperature regulators A, B are disposed in series on the way of a cooling liquid circulating path 3 leading to a spindle device 1 to cool the cooling liquid through heat exchangers 8, 8. A chage-over valve of a first liquid temperature regulator A is changed over according to a command from a first control means built in a computer 13 so that an optimum cooling capacity is provided according to the rotational speed data of a spindle inputted from a NC device. Referring to a second liquid temperature regulator B, a detected temperature value of the cooling liquid right before returning to a tank 4 is inputted in real time from a thermometer 14 to a controller 15 and a change-over command is given to change-over valves 11', 12' according to a difference between a desired value and the detected value of spindle temperature to operate the second liquid temperature regulator B with a proper cooling capacity.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for absorbing heat generated in the spindle of a machine tool during operation by a circulating coolant and controlling the temperature of the spindle to a target value. The present invention relates to a device for realizing this.

[Prior art] Generally, machine tools generate heat depending on machining conditions such as the rotational speed of the spindle and the cutting resistance of the workpiece, resulting in a temperature difference between the spindle and the machine base that supports it. .

This causes thermal distortion in various parts of the machine tool and reduces machining accuracy. To prevent this, coolant is circulated around the spindle head to absorb heat and reduce the difference between the spindle temperature and the temperature of the machine base. A cooling system is provided which is controlled to maintain a constant value at all times.

The conventional spindle temperature control method is, for example,
As disclosed in Publication No. 97, it is equipped with a cooler capable of sufficiently cooling the expected maximum heat generation amount of the spindle, and the difference between the spindle temperature and the reference temperature (atmospheric temperature or machine stand temperature) is a predetermined value. If the temperature rises above the specified value, the cooler is operated to cool the coolant, the cooled coolant is circulated to lower the main shaft temperature, and when this drops to a predetermined value, the cooler is activated. Configured to stop. This system also includes a heater in case it is necessary to raise the temperature of the coolant.

[Problems to be Solved by the Invention] However, in this system, it is necessary to quickly cool/heat a large amount of cooling liquid, so the heater and cooler must have extremely large capacities.

Therefore, when these heaters and coolers are turned on and off, a considerable amount of heat shock is applied to the machine tool, which has an adverse effect on machining accuracy.

It is well known that the amount of heat generated by the spindle has a positive correlation with its rotation speed. For example, as shown in FIG. 4, the amount of heat generated by the bearing that supports the main shaft is approximately proportional to the square of the main shaft rotation speed. Therefore, when the spindle rotation speed changes over a wide range from low speed to high speed depending on the machining conditions, in the system described above, the cooler and heater must be adjusted to the maximum amount of heat generated when the spindle rotates at maximum speed. heat shock during on/off times tends to increase.

The present invention solves the problems of the prior art, and provides a method for cooling a spindle that can handle a wide range of spindle rotational speeds from low to high speeds, and that causes less heat shock to the machine, as well as a method for implementing the method. The purpose is to provide a device for

(Means for Solving the Problem) This purpose is to maintain the spindle temperature of the machine tool at a target value by circulating a coolant through a liquid temperature controller in the spindle device of the machine tool. In the control method, a first liquid temperature regulator and a second liquid temperature regulator are provided in series or in parallel in the cooling liquid circulation path, and the spindle rotation speed of the spindle device and the heat generation corresponding to the spindle rotation speed are compensated for. The relationship between the cooling capacity and the cooling capacity is stored in advance, and the first liquid temperature controller is operated so as to generate the pre-stored cooling capacity that corresponds to the rotational speed of the main spindle device, and This is achieved by a method for controlling the spindle temperature of a machine tool, which comprises detecting the spindle temperature and adjusting the cooling capacity of the second liquid temperature regulator so that the detected temperature becomes the target value.

Further, as a device for carrying out this method, there is provided a spindle temperature control device for a machine tool which circulates a cooling liquid through a spindle device of a machine tool to maintain the spindle temperature of the spindle device at a target value. A first liquid temperature regulator and a second liquid temperature regulator arranged in series or in parallel in a liquid circulation path, a main spindle rotation speed of the main spindle device, and a cooling capacity that compensates for heat generation corresponding to the main spindle rotation speed. a storage means for storing the relationship in advance;
a first control means for operating the first liquid temperature controller so as to obtain a cooling capacity stored in the storage means that corresponds to the rotational speed of the main spindle device; and detecting a main shaft temperature of the main spindle device. A machine tool comprising: a spindle temperature detecting means; and a second control means for operating the second liquid temperature regulator so that the temperature detected by the spindle temperature detecting means reaches the target value. A spindle temperature control device is also provided.

[Function] During operation of the machine tool, the first liquid temperature regulator is feedforward controlled in response to a command from the first control means so as to output a cooling capacity that compensates for the amount of heat generated corresponding to the current spindle rotation speed. Ru. As a result, most of the heat generated by the spindle is cooled down, and only a small amount of cooling capacity remains necessary to bring the spindle temperature into agreement with the target value. When the rotation speed of the main shaft is changed, the cooling capacity of the first liquid temperature regulator is also changed, and the temperature of the cooling liquid is adjusted so that most of the heat generated by the main shaft is compensated for.

On the other hand, the second liquid temperature regulator is feedback-controlled by a command from the second control means based on the main shaft temperature measured in real time by the main shaft temperature detection means so that the main shaft temperature matches the target value.

As described above, according to the present invention, the storage means, the first control means, and the feedforward control corresponding to the spindle rotation speed by the first liquid temperature regulator, the spindle temperature detection means, the second control means, and the second liquid temperature control device are performed. By combining feedback control with a temperature controller, fine-grained spindle temperature control with minimal heat shock is possible.

Hereinafter, the present invention will be explained in more detail based on preferred embodiments shown in the drawings.

〔Example〕

FIG. 1 is a schematic diagram showing the principle of spindle temperature control of a machine tool according to the present invention.

In order to cool down the heat generated during rotation of the spindle device l of the machine tool, cooling fluid in a tank 4 is supplied by a pump 5 to the area of the bearing 2 through a circulation path 3.

In the middle of this circulation path 3, a first liquid temperature regulator A and a second liquid temperature regulator B are arranged in series with each other, and the heat exchanger 8.
8. The cooling liquid passing through the circulation path is cooled.

The first liquid temperature controller A is selected to have a cooling capacity that cancels out the amount of heat generated by the main shaft at the expected maximum rotational speed of the main shaft. This first liquid temperature regulator 6 has two bypasses in the middle of the refrigerant gas circulation path 10 from the refrigeration compressor 9 to the heat exchanger 8, and each bypass has a switching valve 11.1.
It has 2.

When these switching valves 11 and 12 are both in the closed position, all the refrigerant gas flows to the heat exchanger 8 and the cooling capacity becomes the largest (this is defined as 100% cooling capacity), and one is closed and the other is in the closed position. 65% if open, 3 if both are open
The cooling capacity can be switched in four stages, such that the cooling capacity is 5%, and when the refrigeration compressor 9 is stopped, the cooling capacity is 0%.

Similarly, the second liquid temperature controller B also has two bypasses in the refrigerant gas circulation path 10, and each has a switching valve 11", a 12°
It is equipped with When both valves are closed, the cooling capacity is 100%, and when one is closed and the other is open, the cooling capacity is 50%.
%1 When both are opened, the value becomes 10%, and when the refrigeration compressor 9'' is stopped, the value becomes 0%.

The present invention is characterized in that the cooling of the spindle device is finely controlled by combining the two liquid temperature cooling devices A and B. That is, in view of the fact that the amount of heat generated by the main shaft is largely dependent on its rotational speed as mentioned above, the cooling capacity of the first liquid temperature controller A is first changed in accordance with the change in the rotational speed of the main shaft, and feedforward is performed. Control is performed to cancel out most of the heat generation, and if there is a deficiency or excess in the main shaft temperature as a result of detection, feedback control is performed by changing the cooling capacity of the second liquid temperature controller B. It is.

A switching command for the switching valve of the first liquid temperature regulator A is issued by a first control means built in the computer 13.

The memory of this computer 13 stores a relational expression (see Fig. 2) between the expected spindle rotation speed of the machine tool and the cooling capacity required to cancel the heat generated at that time, and the NC device According to the rotational speed data of the main shaft input from the controller, a switching command is issued to the valve to achieve the optimum cooling capacity.

On the other hand, switching of the switching valve of the second liquid temperature regulator B is performed as follows. First, as a representative value of the main shaft temperature, the detected value of the temperature of the coolant immediately before returning to the tank 4 is measured by the thermometer 14.
The temperature controller 1 constituting the second control means
5. It is human-powered in real time. This second control means 15
, the detected value is compared with a predetermined target value of the main shaft temperature, and the changeover valve 1 is adjusted according to the difference.
A switching command is issued at 1° to 12°, and the second liquid temperature regulator B is operated at an appropriate cooling capacity.

To explain the actual operation based on Fig. 2, while the spindle rotation speed is low (less than L), the spindle heat generation is small, so the first
The refrigeration compressor of the liquid temperature regulator A is maintained in a stopped state (that is, the cooling capacity is 0%), and only feedback control by the second liquid temperature regulator ffi machine B is performed. When the spindle rotational speed increases and exceeds L, the first liquid temperature regulator A is switched and operated to provide a cooling capacity corresponding to the changed spindle rotational speed, thereby performing feedforward control. That is, when the spindle rotational speed is between LM, the cooling capacity is 35%, between M and H, the cooling capacity is 65%, and when it exceeds H, the cooling capacity is 100%. During this time, the second liquid temperature control @B continues feedback control.

FIG. 3(a) shows an example of the result of controlling the temperature of the spindle using the control system of the present invention, and FIG. 3(b) shows an example using only conventional feedback control. According to this, it is clear that in the case of the present invention, the return oil temperature, which is a representative value of the spindle temperature, has little variation and is excellently controlled.

In the above example, the cooling capacity of the liquid temperature regulator is switched to four stages, but the number of switching stages is not limited to this (it can be set appropriately as necessary). , the first liquid temperature regulator and the second liquid temperature regulator may each be composed of a plurality of liquid temperature regulators.

Note that in the embodiment shown in FIG. 1, the first liquid temperature regulator A and the second liquid temperature regulator B are arranged in series, but even if two liquid temperature regulators are arranged in parallel. The same effect can be obtained.

[Effects of the Invention] As described above in detail, according to the present invention, two liquid temperature controllers are used to feedforward control the spindle temperature by changing the cooling capacity according to the spindle rotation speed. On the other hand, since feedback control is performed according to the detected actual spindle temperature, heat shock caused by turning on and off the liquid temperature regulator when cooling the spindle is extremely reduced.

Furthermore, even when the rotational speed of the spindle is changed stepwise, cooling overshoot and undershoot are reduced, cooling efficiency is improved, and machining accuracy is improved.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a coolant circulation path showing the configuration of a spindle temperature control system for a machine tool according to the present invention, and Fig. 2 is a diagram of the relationship between the rotational speed of the spindle and the cooling capacity required to compensate for the heat generated by this. , FIGS. 3(a) and 3(b) are charts showing the results of controlling the spindle temperature according to the present invention and those using the conventional method. FIG. 4 shows the relationship between the rotational speed of the spindle and the resulting heat generation amount of the spindle bearing. FIG. 5 is a schematic diagram of a coolant circulation path showing the configuration of a second embodiment of the spindle temperature control system for a machine tool according to the present invention. 1 - Main shaft device 2 - Bearing 3 - Coolant circulation path 4 - Tank 5 - Pump 8.8'' - Heat exchanger 9.9' - Refrigeration compressor 10.10° - Refrigerant gas circulation path 11.12.11 ', 12=-Switching valve 13--Computer 14-Thermometer 15=-Temperature controller A...-First liquid temperature regulator B--Second liquid temperature regulator Main shaft rotation speed diagram (G) (b) Diagram

Claims (1)

[Scope of Claims] 1. A method for controlling the spindle temperature of a machine tool, in which a cooling liquid is circulated through a spindle device of the machine tool through a liquid temperature controller, and the spindle temperature of the spindle device is maintained at a target value. A first liquid temperature regulator and a second liquid temperature regulator are provided in series or in parallel in a cooling liquid circulation path, and there is a relationship between a spindle rotation speed of the spindle device and a cooling capacity that compensates for heat generation corresponding to the spindle rotation speed. is stored in advance and corresponds to the rotational speed of the spindle device,
The first liquid temperature regulator is operated so that the pre-stored cooling capacity is generated, the main shaft temperature of the main shaft device is detected, and the second liquid temperature controller is operated so that the detected temperature becomes the target value. A method for controlling the spindle temperature of a machine tool, the method comprising adjusting the cooling capacity of a liquid temperature controller. 2. In a spindle temperature control device for a machine tool, which circulates a coolant through a spindle device of a machine tool and maintains the spindle temperature of the spindle device at a target value, the device is arranged in series or parallel to the coolant circulation path. storage means for storing in advance the relationship between the first liquid temperature regulator and the second liquid temperature regulator, the spindle rotational speed of the spindle device and the cooling capacity that compensates for the heat generation corresponding to the spindle rotational speed; a first control means for operating the first liquid temperature controller so as to obtain a cooling capacity stored in the storage means corresponding to the rotational speed of the spindle device; and a spindle for detecting the spindle temperature of the spindle device. A main shaft of a machine tool, comprising: a temperature detecting means; and a second controlling means for operating the second liquid temperature regulator so that the temperature detected by the main shaft temperature detecting means reaches the target value. Temperature control device.