JPH0463660A - Main spindle temperature control method for machine tool and device - Google Patents

Abstract

PURPOSE:To perform the delicate control of the main spindle temperature by changing the reference opening of a proportional control valve based on memory to change the basic cooling capacity of a liquid temperature regulator so that the cooling capacity compensating the estimated heat generation quantity by the new rotating speed is obtained when the rotating speed of a main spindle is changed. CONSTITUTION:The relation between the rotating speed of a main spindle and the cooling capacity required to compensate the heat corresponding to it and the relation between the opening of a proportional control valve 11 and a liquid temperature regulator A are stored in a memory 26 in advance. The reference opening of the proportional control valve 11 is changed by the first control means 27 based on memory to change the basic cooling capacity of the liquid temperature regulator A so that the cooling capacity compensating the estimated heat generation quantity by the new rotating speed is obtained when the rotating speed of the main spindle is changed.

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 match a target value. and a device for realizing this.

[Conventional technology]

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 head and the machine base that supports it.

This causes thermal distortion in various parts of the machine tool, leading to a decrease in machining accuracy (therefore, to prevent this, a coolant is circulated around the spindle head to absorb the heat generation, and the temperature of the spindle and the machine base are adjusted. A cooling system is provided that performs feedback control to maintain the difference between the two at a constant value.

The conventional spindle temperature control method is, for example, Japanese Patent Publication No. 48379.
As disclosed in Publication No. 7, 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 stopped. 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, it is necessary to quickly cool/heat a large amount of cooling liquid, so the heater and cooling machine must have extremely large capacities.

Therefore, when these heaters and coolers turn on and off, a considerable heat shock is applied to the machine tool.
On the contrary, it has a negative 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. 7, the amount of heat generated by a bearing that supports the main shaft increases approximately in proportion to the square of the main shaft rotational speed. For this reason, in the case of machine tools where work is performed according to a machine program in which the spindle rotational speed varies over a wide range from high to low speeds, in the system described above, the cooler and heater are designed to reduce the amount of heat generated at the maximum rotation of the spindle. This has resulted in a very large scale, and the heat shock during on/off times tends to increase more and more.

The present invention solves the problems of the conventional technology, and provides a spindle temperature control method that can handle a wide range of spindle rotational speeds from low to high speeds, and that causes less heat shock to the machine, and also realizes the same. The purpose is to provide a device for

[Means to solve the problem]

The purpose of this is to install a liquid temperature regulator that can adjust the temperature of the coolant by adjusting the flow rate of the coolant gas through a proportional control valve in the middle of the circulation circuit that circulates the coolant to the spindle device of the machine tool. , Feedback control 1 for adjusting the opening degree of the proportional control valve based on the detected spindle temperature of the spindle; Ah, the relationship between the spindle rotational speed and the cooling capacity required to compensate for the corresponding heat generation, as well as the relationship between the opening degree of the proportional control valve and the cooling capacity of the liquid temperature controller, are stored in advance. Then, when the rotational speed of the main shaft changes, the reference opening degree of the proportional control valve is changed based on the memory so that the cooling capacity compensates for the expected amount of heat generated due to the new rotational speed. This is achieved by a method for controlling the main shaft temperature of a machine tool, which is characterized by changing the basic cooling capacity of a liquid temperature controller.

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 fluid through a spindle device of a machine tool to maintain the spindle temperature of the spindle device at a target value. A liquid temperature regulator equipped with a proportional control valve that can control the flow rate of refrigerant gas by adjusting the opening degree provided in the middle of the liquid circulation path, and a liquid temperature controller that compensates for the rotational speed of the main shaft and the corresponding heat generation. storage means for storing in advance the relationship between the required cooling capacity and the relationship between the opening degree of the proportional control valve and the cooling capacity of the liquid temperature controller; a first control means for adjusting a reference opening degree of a proportional control valve of the liquid temperature regulator so as to obtain a cooling capacity corresponding to a new spindle rotational speed based on the relationship between the first and second spindles; Spindle temperature of a machine tool, characterized in that it comprises a temperature detection means, and a second control means for operating the liquid temperature regulator so that the spindle temperature detected by the temperature detection means coincides with the target value. A control device is also provided.

[Function] While the machine tool is operated at a constant spindle speed,
Based on the main shaft temperature detected by the detection means, feedback control is performed in which the opening degree of the proportional control valve of the liquid temperature regulator is adjusted by a command from the second control means so that the main shaft temperature matches the target value. When the rotational speed of the main shaft is changed by the rotation program, the relationship between the rotational speed of the main shaft and the corresponding required cooling capacity and the opening degree of the proportional control valve stored in the storage means are changed regardless of this feedback control. Based on the relationship between and the cooling capacity, the first control means immediately issues a command to the proportional control valve to change its standard opening, and adjusts the basic cooling capacity of the liquid temperature controller to the expected heat generation due to the new spindle rotation speed. Correct the value to accommodate the amount. Then, feedback control is performed by adjusting the opening degree of the proportional control valve around this reference opening degree until the main shaft rotational speed is changed again.

According to the present invention, the standard opening degree of the proportional control valve is changed in immediate response to a change in the spindle rotation speed, and the basic cooling capacity of the liquid temperature controller is adjusted to correspond to the amount of heat generated by the new spindle rotation speed. Therefore, compared to the conventional method using only feedback control, it is possible to perform highly accurate control with less overshoot and undershoot of the spindle temperature, which is the controlled object.

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 the spindle device 1 of the machine tool, a pump 5 supplies cooling fluid in a tank 4 to the region of the bearing 2 through a circulation path 3 in order to cool down heat generated during rotation.

A liquid temperature regulator A is disposed in the middle of this circulation path 3. This liquid temperature regulator A has a function of supplying the refrigerant gas cooled by the refrigeration compressor 9 to the heat exchanger 8 through the refrigerant gas circulation path IO, and cooling the coolant in the circulation path 3 passing therethrough. . The cooling capacity of this liquid temperature moderator A is determined by the proportional control valve 11 provided in the middle of the refrigerant gas circulation path 10.
It can be changed by adjusting the opening degree.

To explain this in more detail with reference to FIG. 2, the proportional control valve 11 has a valve body 14 having an inlet 12 and an outlet 13, each connected to a refrigerant gas circulation path 10. A housing 15 enters into the valve body 14 from the inlet 12 side, and a flow control opening 16 is provided vertically penetrating the side wall of the housing 15. With this configuration, the refrigerant gas flowing through the circulation path 10 is
is introduced into the valve body 14 through the flow control opening 16 and discharged from the outlet 13.

A control rod 17 movably passes through the flow rate control opening 16 in the vertical direction, and the flow rate control opening 1 is controlled depending on the vertical position of the control rod 17.
6 is configured to control the flow rate of refrigerant gas passing through the refrigerant gas.

An electromagnet 18 having a vertical through hole 20 at its center is installed in the valve casing above the control rod 17, and a piston rod 19 is installed in the through hole 20 so as to be movable up and down. The lower end of the piston rod 19 is fixed to the upper end of the control roller 17. The control rod 17 is urged upward by a spring 21, and when the repulsion force by the electromagnet 18 is not acting, it occupies the highest position, and its valve body 22 is far away from the flow control opening 16, so that it is in the highest position. The control opening 16 is at its maximum opening.

When power is supplied to the coil of the TFA stone 18 from the cable 35, a repulsive force is generated, and the piston rod 19 overcomes the upward biasing force of the spring 21 and descends. Along with this, the control rod 17 also descends, and its valve body 22 is control opening 1
6 and reduce its opening. Since the repulsive force of the electromagnet 18 changes depending on the value of the voltage applied to the coil, the opening degree of the flow rate control valve 160 can be controlled proportionally by controlling the applied voltage.

It is obvious that if the flow rate of the refrigerant gas flowing through the circulation path 10 decreases, the cooling capacity of the liquid temperature controller A decreases, and conversely, if the flow rate of the refrigerant gas increases, the cooling capacity increases. Therefore, the cooling capacity of the liquid temperature regulator can be controlled proportionally by controlling the applied voltage.

According to the spindle temperature control method of the present invention, during steady operation, that is, when the machine tool is operated at a constant spindle rotation speed, the temperature of the coolant immediately before returning to the tank 4 is detected as the representative value of the spindle temperature. detected by the computer 23,
4 is manually controlled in real time by the second control means 25 built into the second control means 25. A target value for the spindle temperature is stored in advance in the second control means 25, and the detected spindle temperature is compared with this target value, and if there is a difference, the voltage applied to the electromagnet 18 is adjusted. . As a result, the opening degree of the proportional control valve 11 is corrected, and the cooling capacity of the liquid temperature regulator A is finely adjusted.
The spindle temperature approaches the target value.

In this feedback control during steady operation, the opening degree of the proportional control valve 11 is proportionally adjusted around the reference opening degree according to the difference between the target temperature and the detected temperature. In normal feedback control in a steady state, this standard opening degree is determined by the cooling capacity required to cancel out the spindle rotational speed and the resulting heat generation amount of the spindle as shown in Figure 3 after a certain amount of time has passed. will inevitably converge to a constant value depending on the relationship between It takes a considerable amount of time for the standard opening to settle naturally, and during that time there is a tendency for significant overshoot or undershoot to occur in the control results.

In the present invention, when there is such a sudden change in the spindle rotation speed, - this feedback control is immediately discontinued, and the cooling capacity of the liquid temperature controller A is immediately adjusted to the amount of heat expected to be generated due to the new spindle rotation speed. The reference opening degree of the proportional control valve 11 is changed so that it becomes a value necessary to compensate for. This reference opening degree adjustment command is based on the rotational speed of the main shaft as shown in FIG. The first control means built in the computer 24 is determined by the relationship between the voltage applied to the electromagnet of the proportional control valve and the cooling capacity of the liquid temperature controller A as shown in FIG. 27 to the operating circuit 28 of the proportional control valve 11.

After the setting of this new reference opening degree is completed, the above-described feedback control by measuring the main shaft temperature and adjusting the opening degree of the proportional control valve 11 based on the measurement is resumed.

The control according to the present invention described above will be explained with reference to the flowchart shown in FIG. 5. As shown in the flowchart shown in FIG. The newly set spindle rotation speed is input to the first control means 27. Based on the relationship between the spindle rotation speed and the required cooling capacity stored in the memory 26, and the relationship between the voltage applied to the electromagnet 18 of the proportional control valve 11 and the cooling capacity of the liquid temperature regulator, the first control means 27 calculates the following: In order to obtain a cooling capacity corresponding to the new spindle rotation speed, a reference voltage to be applied to the electromagnet of the proportional control valve is selected, and as shown by reference numeral 32, this is sent as a command signal to the operation circuit 28 of the proportional control valve 11. . As a result, the standard opening degree of the proportional control valve 11 is newly set, and the cooling capacity of the liquid temperature regulator A is adjusted in immediate response to the change in the spindle rotation speed.

After a short period of time, indicated by reference numeral 33, elapses until the entire system stabilizes, the feedback control indicated by reference numeral 34 is restored, and the reference voltage is adjusted proportionally based on the difference between the detected spindle temperature and the target temperature. Proportional control to adjust the opening degree of control valve 11 continues.

FIG. 6(a) shows the control result of the spindle temperature when changing the spindle rotational speed by the control system of the present invention. If this is compared with the control result using only feedback shown in FIG. 6(b), the effects of the present invention will become even clearer.

[Effects of the Invention] As detailed above, according to the present invention, when the spindle rotation speed is changed during feedback control of the spindle temperature by adjusting the opening degree of the proportional control valve of the liquid temperature controller, Once the feedback control is interrupted, the standard opening of the proportional control valve is immediately changed in accordance with the new spindle rotation speed, so that the cooling capacity necessary to compensate for the predicted spindle heat generation can be output. The setting of the liquid temperature controller was changed in 2015, and the feedback control was continued again based on the new standard opening, so the spindle rotation speed, which was likely to occur with conventional on-off feedback control, was reduced. Control overshoot and undershoot during changes are reduced, allowing fine-grained spindle temperature control.

[Brief explanation of drawings]

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, FIG. 2 is a side sectional view showing the configuration of a proportional control valve used in the present invention, and FIG. Figure 4 shows the relationship between the rotational speed of the main shaft and the cooling capacity required to compensate for the heat generated by it, and Figure 4 shows the relationship between the voltage applied to the electromagnet of the proportional control valve and the resulting cooling capacity of liquid temperature controller A. 5 is a flowchart showing the control procedure of the present invention, and FIGS. 6(a) and 6(b) are graphs of experimental data showing the control results of the spindle temperature according to the present invention and the control results according to the conventional method. FIG. 7 is a diagram showing the relationship between the rotational speed of the main shaft and the amount of heat generated by the main shaft bearing. A...-Liquid temperature controller l...-Main shaft device 3-Cooling liquid circulation path 10-Refrigerant gas circulation path Proportional control valve Flow rate control opening Electromagnet-Temperature detector Computer Second control means Memory--First control means

Claims (1)

[Scope of Claims] 1. A liquid temperature control valve in which the temperature of the coolant can be adjusted by adjusting the flow rate of the coolant gas through a proportional control valve in the middle of a circulation circuit that circulates the coolant to the spindle device of the machine tool. A spindle temperature control method for a machine tool, wherein a regulator is provided and the spindle temperature is maintained at a target value by feedback control that adjusts the opening degree of the proportional control valve based on the detected spindle temperature of the spindle. The relationship between the spindle rotational speed and the cooling capacity required to compensate for the corresponding heat generation, and the relationship between the opening degree of the proportional control valve and the cooling capacity of the liquid temperature regulator are stored in advance. Then, when the rotational speed of the main shaft changes, the reference opening degree of the proportional control valve is changed based on the memory so that the cooling capacity compensates for the expected amount of heat generated due to the new rotational speed, and the liquid temperature is changed. A method for controlling the spindle temperature of a machine tool, characterized by changing the basic cooling capacity of a 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 provided in the middle of the circulation path for the coolant. A liquid temperature controller equipped with a proportional control valve that can control the flow rate of refrigerant gas by adjusting the opening, and the relationship between the rotational speed of the main shaft and the cooling capacity necessary to compensate for the corresponding heat generation, and the proportional control valve. A storage means stores in advance the relationship between the opening degree of the control valve and the cooling capacity of the liquid temperature regulator, and when the spindle rotation speed changes, a new spindle is set based on the relationship stored in the storage means. a first control means for adjusting the reference opening degree of the proportional control valve of the liquid temperature regulator so as to obtain a cooling capacity corresponding to the rotational speed; a temperature detection means for detecting the temperature of the main shaft; A spindle temperature control device for a machine tool, comprising: second control means for operating the liquid temperature regulator so that the detected spindle temperature matches the target value.