JPH0579458B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention absorbs heat generated from the spindle of a machine tool during operation by a circulating coolant, and controls the temperature of the spindle to a target value. This invention relates to a method and an apparatus for realizing the same.

[Conventional technology]

In general, 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 generation, and the temperature of the spindle and the machine base are adjusted. A cooling system is provided which controls the difference to always maintain a constant value.

The conventional spindle temperature control method is, for example,
- As disclosed in Publication No. 3797, it is equipped with a cooler that has the ability to sufficiently cool the expected maximum heat generation amount of the spindle, and the difference between the spindle temperature and the reference temperature (atmospheric temperature or machine base temperature) is maintained at a predetermined level. If the temperature rises above the specified value, the cooler is activated 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. is configured to stop. This system also includes a heater in case it is necessary to raise the temperature of the coolant.

[Problem to be solved by the invention]

However, in this method, since it is necessary to rapidly cool/heat a large amount of cooling liquid, both the heater and the cooler must have large capacities. Therefore, if these heaters or coolers are turned on or
When turned off, a considerable amount of heat shock is applied to the machine tool, adversely affecting 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. For this reason,
When the spindle rotational 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 a very high level that corresponds to the amount of heat generated at the maximum rotation of the spindle. As the scale becomes larger, the heat shock during on/off times tends to increase more and more.

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. The purpose is to provide a device for

[Means to solve the problem]

This purpose is to provide a method for controlling a spindle temperature of a machine tool in which a coolant is circulated through a spindle device of a machine tool through a liquid temperature controller to maintain the spindle temperature of the spindle device at a target value. A first liquid temperature regulator and a second liquid temperature regulator are provided in series or in parallel in the path, and a relationship between a spindle rotational speed of the spindle device and a cooling capacity that compensates for heat generation corresponding to the spindle rotational speed is stored in advance. , operating the first liquid temperature regulator so as to generate the pre-stored cooling capacity corresponding to the rotational speed of the spindle device, and detecting the spindle temperature of the spindle device; This is achieved by a method for controlling the main shaft temperature of a machine tool, which is characterized in that the cooling capacity of the second liquid temperature regulator is adjusted so that the temperature reaches 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 relationships 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 spindle device;
a spindle temperature detection means for detecting the spindle temperature of the spindle device; and a second control means for operating the second liquid temperature regulator so that the temperature detected by the spindle temperature detection means becomes the target value. There is also provided a spindle temperature control device for a machine tool, characterized by comprising:.

[Effect]

While the machine tool is in operation, the first liquid temperature regulator is subjected to feedforward control 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. be done. 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 controller performs feedback so that the main shaft temperature matches the target value based on a command from the second control means based on the main shaft temperature measured in real time by the main shaft temperature detection means. controlled.

Thus, according to the present invention, the storage means, the first
By combining feed forward control corresponding to the spindle rotation speed by the control means and the first liquid temperature regulator, and feedback control by the spindle temperature detection means, the second control means and the second liquid temperature regulator, fine control can be achieved. This allows fine control of the spindle temperature with a small heat shock.

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.

A spindle device 1 of a machine tool is supplied with a cooling liquid in a tank 4 by a pump 5 through a circulation path 3 to an area of a bearing 2 in order to cool down heat generated during rotation.

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 coolant passes through the circulation path via the heat exchangers 8 and 8'. is configured to cool the

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 a refrigerant gas circulation path 10 extending from the refrigeration compressor 9 to the heat exchanger 8, and each bypass is provided with a switching valve 11, 12. 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 for open
%, the cooling capacity can be switched in four stages, such as 35% cooling capacity when both are open, and 0% cooling capacity when the refrigeration compressor 9 is stopped. .

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

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 spindle is largely dependent on its rotational speed as mentioned above, the cooling capacity of the first liquid temperature controller A is first changed in conjunction with the change in the rotational speed of the spindle, and the feed is adjusted accordingly. Forward control is performed to cancel most of the heat generation, and if the main shaft temperature is insufficient or excessive, a second control is performed.
Feedback control is performed by changing the cooling capacity of liquid temperature regulator B.

The switching command for the switching valve of the first liquid temperature controller A is as follows:
This is performed by a first control means built into 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.
Depending on the spindle rotational speed data input from the NC device, switching commands are issued to the valves to achieve the optimal 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 spindle temperature, a detected value of the temperature of the coolant immediately before returning to the tank 4 is input in real time by the thermometer 14 to the temperature controller 15 constituting the second control means. In this second control means 15, a predetermined target value of the spindle temperature is compared with this detected value, and a switching command is generated to the switching valves 11' and 12' according to the difference. , the second liquid temperature regulator B is operated with an appropriate cooling capacity.

To explain the actual operation based on Fig. 2, when the main shaft rotational speed is low (lower than L), the main shaft heat generation is small, so the refrigeration compressor of the first liquid temperature controller A is in a stopped state (that is, the cooling capacity is low). 0%), and only feedback control by the second liquid temperature regulator B is performed. When the spindle rotational speed increases and exceeds L, the first liquid temperature controller A is switched and operated to provide a cooling capacity corresponding to the changed spindle rotational speed, thereby performing feed forward control. That is, when the spindle rotation speed is between L and M, the cooling capacity is 35%, and when the spindle rotation speed is between L and M,
65% cooling capacity during H, if H is exceeded
Operates at 100% cooling capacity. During this time, the second liquid temperature regulator B continues the feedback control.

An example of the result of controlling the temperature of the spindle using the control system of the present invention is shown in Figure 3a.
An example using only conventional feedback control is shown in FIG. 3b. 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 example described above, the cooling capacity of the liquid temperature regulator is switched to four stages, but the number of switching stages is not limited to this and can be set appropriately as necessary. Further, each of the first liquid temperature regulator and the second liquid temperature regulator may 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.

〔Effect of the invention〕

As described in detail above, according to the present invention, two liquid temperature controllers are used to feed-forward control the spindle temperature by changing the cooling capacity according to the spindle rotation speed on one side, and Since feedback control is performed according to the detected actual spindle temperature, heat shock caused by turning the liquid temperature regulator on and off 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. , Figure 3 a, b
is a chart showing the results of controlling the spindle temperature according to the present invention and the results obtained using the conventional method, FIG. 4 is a diagram showing the relationship between the rotational speed of the spindle and the resulting heat generation amount of the spindle bearing, and FIG. 5 is a diagram showing the result of controlling the spindle temperature according to the present invention. FIG. 2 is a schematic diagram of a coolant circulation path showing the configuration of a second embodiment of the main shaft temperature control system of FIG. 1... Main shaft device, 2... Bearing, 3... Coolant circulation path, 4... Tank, 5... Pump, 8, 8'...
...Heat exchanger, 9,9'...Refrigerating compressor, 10,1
0'... Refrigerant gas circulation path, 11, 12, 11', 1
2'...Switching valve, 13...Computer, 14
...Thermometer, 15...Temperature controller, A...
First liquid temperature regulator, B...second liquid temperature regulator.

Claims (1)

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