JPH08346B2 - Method of controlling temperature of heat generating part of machine tool - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention cools a heat generating portion such as a spindle head of a machine tool or a nut portion of a feed screw with a circulating cooling liquid, and a cooling device so that the temperature of the heat generating portion matches a target value. The present invention relates to a method for controlling the temperature of a heat generating part of a machine tool by feedback control.

[0002]

2. Description of the Related Art Generally, a machine tool generates heat in accordance with machining conditions such as a rotation speed of a spindle and a cutting resistance of a work, and causes a temperature difference between a spindle head and a machine base supporting the spindle head. As a result, heat distortion occurs in each part of the machine tool, leading to a decrease in machining accuracy.To prevent this, a cooling liquid is circulated in the spindle head to absorb the heat generation, and the spindle temperature and the machine base temperature A cooling system is provided to perform feedback control so as to always maintain a constant difference.

An example of a cooling system for this machine tool is shown in FIG.
Shown in A circulation path 3 is provided through the area of the bearing 2 of the spindle head 1 of the machine tool, and a tank 5 is provided therein by a pump 5.
The cooling fluid inside is circulating. A cooling device 6 is arranged in the middle of the circulation path 3, supplies the refrigerant gas cooled by the refrigeration compressor 9 to the heat exchanger 8 through the refrigerant gas circulation path, and is supplied to the cooling liquid in the circulation path 3 passing therethrough. It is configured to perform heat exchange between them to cool them. The temperature of the cooling liquid which has cooled the bearing region of the spindle head and has been raised in temperature is detected by the temperature detection means 7 provided in the return circulation path 3 and continuously input to the control unit 11. Then, the difference between the detected coolant temperature and the temperature of the machine base or the room temperature which is the reference temperature is calculated, and the control unit 11 turns on the cooling device 6 so that the difference matches the target value.・ The OFF command is issued and feedback control is being performed.

[0004]

Even if the refrigerating compressor 9 is immediately stopped when the temperature of the cooling liquid detected in the return circulation passage falls below the reference temperature, the circulation passage 3 in the outward passage from the cooling device to the spindle head is stopped. Since the cooling liquid already cooled to a low temperature is filled in and the refrigerant gas in the heat exchanger 8 is also in a low temperature state, the low temperature cooling liquid continues to be supplied to the spindle head for several tens of seconds. There is a tendency for the head to become supercooled. Such supercooling of the spindle head naturally increases the dimensional change of the spindle and reduces the machining accuracy, which is not preferable.

The present invention prevents the supercooling of the heat-generating part such as the spindle head due to the time delay during the off operation of the refrigerating compressor provided in the cooling liquid circulation path in the prior art,
The purpose is to improve the machining accuracy of machine tools.

[0006]

In a first aspect of the present invention, a cooling liquid is supplied to the heat generating portion through an outward path of a circulation path provided between a heat generating portion of a machine tool and a cooling device, and the circulation is performed. In a temperature control method for a heat generating portion of a machine tool configured to return the cooling liquid whose temperature has been raised through a return path of a passage to a cooling device again, a bypass circuit bypassing the heat generating portion between an outward path and a return path of the circulation path. Is provided, a part of the cooling liquid flowing through the circulation path is always branched to the bypass circuit, and in the return path of the circulation path, on the downstream side of the confluence point between the regular circulation path passing through the heat generating part and the bypass circuit. A temperature control method for a heat generating part of a machine tool is proposed, which is characterized by detecting the temperature of a cooling liquid and performing feedback control for adjusting the cooling capacity of a cooling device by using this as a control variable.

In the second aspect of the present invention, the cooling liquid is supplied to the heat generating part through the outward path of the circulation path provided between the heat generating part of the machine tool and the cooling device, and the temperature is raised through the return path of the circulation path. In the temperature control method for a heat generating portion of a machine tool configured to return the cooling liquid to the cooling device again, a bypass circuit that bypasses the heat generating portion is provided between the outward path and the return path of the circulation path, and the circulation path is provided. A part of the cooling liquid flowing through the bypass circuit is always branched to the bypass circuit, and in the return path of the circulation path, there are two of the regular circulation path passing through the heat generating part and the upstream side and the downstream side of the confluence point of the bypass circuit. The temperature of the cooling liquid is detected at each place to obtain the first temperature and the second temperature, respectively, and the cooling capacity of the cooling device is increased with the first temperature as a control variable and the cooling capacity of the cooling device with the second temperature as a control variable. Reduce the feedback Temperature control method of the heat generating portion of a machine tool and performing control is proposed.

In the third aspect of the present invention, the cooling liquid is supplied to the heat generating portion through the outward path of the circulation path provided between the heat generating portion of the machine tool and the cooling device, and the temperature is raised through the return path of the circulation path. In the method of controlling the temperature of a heat generating portion of a machine tool configured to return the cooling liquid to the cooling device again, a bypass circuit that bypasses the heat generating portion is provided between the outward path and the return path of the circulation path, and the cooling device Only when the cooling capacity is increased, a part of the cooling liquid flowing in the circulation path is branched to the bypass circuit, and in the return path of the circulation path, a confluence point between the regular circulation path passing through the heat generating part and the bypass circuit. A temperature control method for a heat generating part of a machine tool is proposed, which is characterized in that the temperature of the cooling liquid is constantly detected on the downstream side of the above, and feedback control is performed by using this as a control variable to adjust the cooling capacity of the cooling device.

[0009]

In the first aspect of the present invention, the temperature of the cooling liquid, which has been raised by cooling the heat generating part, is detected after the cooling liquid is constantly flowing in the bypass circuit. Appear in. Therefore, the cooling capacity control of the cooling device, for example, the on / off operation is performed in a shorter cycle with an earlier phase than in the conventional case, and the temperature fluctuation of the heat generating part due to the supercooling of the cooling liquid is reduced.

In the second aspect, the temperatures of the cooling liquids are detected at two points upstream and downstream of the confluence point with the bypass circuit in the return path of the circulation path, and the first temperature on the upstream side, that is, the heat generating portion is cooled. The cooling capacity increasing control of the cooling device is performed based on the temperature of the raised cooling liquid, for example, the ON operation is performed, and the cooling device of the cooling device is cooled based on the downstream second temperature that is cooled by merging with the cold cooling liquid flowing through the bypass circuit. Cooling capacity reduction control, for example, off operation is performed. Therefore, the first
Compared with the mode, the cooling device can be turned on earlier in phase, and the temperature variation of the heat generating portion is further reduced.

In the third aspect, during the cooling capacity reduction control of the cooling device, for example, the bypass circuit is closed when the cooling device is stopped, and only when the cooling capacity of the cooling device is increased, for example, when the cooling device is operating. Since the cooling liquid is branched to the bypass circuit, it is possible to obtain the same effect as that of the second mode even though there is only one temperature detection point.

Based on the preferred embodiment shown in the drawings,
The present invention will be described in more detail.

[0013]

1 shows a first embodiment in which the present invention is applied to a cooling system for a spindle head of a machine tool. A coolant is supplied by a pump 5 to a bearing portion 2 of a spindle head 1 of a machine tool through a circulation path 3.

A cooling device consisting of a heat exchanger 8 in which the refrigerant gas cooled by the refrigeration compressor 9 circulates is provided in the middle of the circulation path 3, and the cooling liquid in the circulation path which has heated the spindle head to raise its temperature. Is configured to cool. A bypass circuit 7 that bypasses the spindle head 1 is provided between the forward path 3a and the return path 3b of the circulation path 3 in addition to the regular circulation path that passes through the spindle head 1. A throttle valve 13 is provided in the bypass circuit 12, and while the pump 5 is operating, a predetermined amount of cooling liquid is always branched from the regular circulation path before being supplied to the spindle head 1 and is again returned to the cooling device side. To return to.

Therefore, on the downstream side of the confluence point P between the bypass circuit 12 provided on the return path 3b side of the circulation path 3 and the regular circulation path, the spindle head 1 is cooled to the same temperature as this. The heated cooling liquid and the cold cooling liquid supplied through the bypass circuit 12 join together. In the present invention, the temperature detecting means 7 is installed at a point immediately downstream of the meeting point P, the liquid temperature of the combined cooling liquid is detected, and this is used as a control variable to turn on the refrigerating compressor 9 of the cooling device. It is characterized by performing the OFF operation and performing feedback control so that the temperature of the spindle head becomes a constant value.

That is, the detected temperature T is controlled by the control unit 1
1, which is compared with a separately detected reference temperature (temperature of the machine base of the machine tool or room temperature) R. T>
In the case of R, the refrigerating compressor 9 is operated to further lower the temperature of the circulating cooling liquid, and conversely, in the case of T <R, the refrigerating compressor 9 is stopped to further lower the temperature of the cooling liquid. prevent. A flow chart of this control is shown in FIG.

According to this method, as shown in FIG. 3, the transition curve of the temperature of the combined cooling liquid (shown by a chain line) is the transition curve of the temperature of the return cooling liquid (dotted line) in which the spindle head 1 is cooled and raised in temperature. Is always lower than the value shown in (). Therefore, when the operation of the refrigerating compressor 9 is started based on this, the temperature of the spindle head 1 reaches a maximum temperature which is slightly higher than in the case of the conventional control system shown in FIG. However, this refrigeration compressor 9
By this operation, the temperature of the combined cooling liquid is lowered to the reference temperature R earlier than in the conventional method, so the refrigeration compressor 9 is stopped again in a cycle shorter than in the conventional method. As a result, the minimum temperature in the transition curve (shown by the solid line) of the temperature of the cooling liquid at the cooling device outlet is maintained higher than that in the conventional system. That is, since the supercooling of the cooling liquid is prevented, the fluctuation range δ of the temperature of the spindle head 1 (the temperature of the cooling liquid returned from the spindle head) becomes small, and the deterioration of the machining accuracy due to the thermal expansion / contraction of the spindle is prevented. Get off.

FIG. 5 shows a second embodiment of the present invention which is a further improvement of the first embodiment described above. In this example, a bypass circuit 12 having a throttle valve 13 is provided as in the first embodiment. The first temperature detecting means 7a and the second temperature detecting means 7b are provided immediately upstream and downstream of the confluence point P between the bypass circuit 12 and the return path 3b of the regular circulation path 3. That is, the first temperature detecting means 7a detects the temperature T ₁ (first temperature) of the returned cooling liquid which has cooled the spindle head 1 and increased in temperature, and the second temperature detecting means 7b connects this returning cooling liquid and the bypass circuit 12 to each other. The temperature T ₂ (second temperature) of the merged liquid with the cooling liquid that has passed through is detected.

The detected first and second temperatures T ₁ and T ₂ are input to the control unit 11 where they are compared with a separately detected reference temperature R. Then, when T ₁ > R, the refrigeration compressor 9 is operated, and when T ₂ <R, the refrigeration compressor 9 is stopped to perform an on / off operation to keep the spindle head temperature constant. Perform feedback control. A flow chart of this control is shown in FIG.

According to the second embodiment, when the refrigeration compressor 9 is turned on and off, the operation is started earlier based on the first temperature at the high temperature level, and the operation is stopped based on the second temperature at the low temperature level. Since it is performed earlier, it is possible to prevent the cooling liquid from being overcooled, and also to suppress the maximum temperature of the spindle head to the same level as the conventional method. FIG. 7 shows a third embodiment of the present invention. In this example, the configuration in which the bypass circuit 12 having the throttle valve 13 is provided and the temperature detecting means 7 is provided on the downstream side of the confluence point P is the same as that of the first embodiment shown in FIG. The difference is that the bypass circuit 12
An on / off valve 14 is provided in series with the throttle valve 13, and by opening / closing the on / off valve 14, it is possible to allow or prevent the flow of the cooling liquid to the bypass circuit 12. .

The on / off operation of the refrigerating compressor 9 is based on the comparison between the coolant temperature T detected by the temperature detecting means 7 and the reference temperature R, as in the case of the first embodiment. It is performed by the command from 11. The feature of the third embodiment is that the control unit 11 issues a shutoff command to the on / off valve 14 in synchronism with the operation command for the refrigeration compressor 5 to stop the shunting of the coolant to the bypass circuit 12. On the other hand, on the other hand, an opening command is issued to the on / off valve 14 in synchronization with the stop command to the refrigeration compressor 9, and the bypass circuit 12 is caused to start shunting.

With this configuration, when the refrigeration compressor 9 is operating, the cooling liquid is diverted to the bypass circuit 12,
The temperature detecting means 7 detects the liquid temperature which has become low due to the return cooling liquid from the spindle head and the cooling liquid passing through the bypass circuit joining, and based on this, the refrigeration compressor is stopped early. Further, when the refrigeration compressor 9 is stopped, there is no shunt to the bypass circuit, so the temperature of the return cooling liquid from the spindle head is detected as it is, and the operation of the refrigeration compressor is restarted based on this. It This results in the same effect as the second embodiment.

In the present embodiment, the on / off control of the cooling device has been described as an example, but the cooling capacity can be adjusted by controlling the flow rate of the circulating cooling liquid and the refrigerant gas circulating in the refrigeration compressor. There are methods of controlling the flow rate, controlling the number of stages by providing a plurality of stages of refrigeration compressors, and either of them may be used.
Further, the temperature control of the heat generating portion of the machine tool of the present invention can be applied to the cooling of the nut portion of the feed screw, the temperature control of the coolant supplied to the processing portion, and the like by the same method.

[0024]

As described above in detail, in the present invention, a bypass circuit that does not pass through the heat generating portion is provided in the circulation path of the cooling liquid for the heat generating portion of the machine tool, and the temperature of the returned cooling from the heat generating portion is increased. The temperature of the mixed liquid of the liquid and the cold cooling liquid flowing in the bypass circuit is detected, and this is used as a control variable when adjusting the cooling capacity of the cooling device for the cooling liquid. As a result, the phase of the refrigeration compressor can be stopped earlier than in the conventional control system of the same type, and the increase in the temperature fluctuation of the heat generating part due to the supercooling of the cooling liquid can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a system of a first embodiment of the present invention.

FIG. 2 is a flowchart of control according to the first embodiment.

FIG. 3 is a time-dependent change curve of the temperature of the cooling liquid of each part showing the control result of the first embodiment.

FIG. 4 is a time-dependent change curve of the temperature of the cooling liquid of each part in the conventional control method.

FIG. 5 is a schematic diagram showing a system of a second embodiment of the present invention.

FIG. 6 is a flow chart of control of the second embodiment.

FIG. 7 is a schematic diagram showing a system of a third embodiment of the present invention.

FIG. 8 is a schematic diagram of a conventional control method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Spindle head 2 ... Bearing 3 ... Circulation path 4 ... Tank 5 ... Pump 6 ... Cooling device 7 ... Temperature detection means 8 ... Heat exchanger 9 ... Refrigeration compressor 11 ... Control unit 12 ... Bypass circuit 13 ... Throttle valve 14 ... ON・ Off valve

Claims (3)

[Claims] 1. A coolant is supplied to the heat-generating portion through an outward path of a circulation path provided between a heat-generating part of a machine tool and a cooling device, and the coolant which is heated through a return path of the circulation path is cooled again. In a method for controlling a temperature of a heat generating portion of a machine tool configured to return to a return path, a bypass circuit that bypasses the heat generating portion is provided between an outward path and a return path of the circulation path, and a part of the coolant flowing through the circulation path. Is always branched to the bypass circuit, and in the return path of the circulation path, the temperature of the cooling liquid is detected at the downstream side of the confluence point between the regular circulation path passing through the heat generating part and the bypass circuit, and this is used as a control variable. A method for controlling the temperature of a heat generating part of a machine tool, which is characterized by performing feedback control for adjusting a cooling capacity of a cooling device. 2. The cooling liquid is supplied to the heat generating portion through the outward path of the circulation path provided between the heat generating part of the machine tool and the cooling device, and the cooling liquid heated up through the return path of the circulation path is cooled again. In a method for controlling a temperature of a heat generating portion of a machine tool configured to return to a return path, a bypass circuit that bypasses the heat generating portion is provided between an outward path and a return path of the circulation path, and a part of the coolant flowing through the circulation path. Is always branched to the bypass circuit, and in the return path of the circulation path, the temperature of the cooling liquid is controlled at two points, that is, the upstream side and the downstream side of the confluence point of the regular circulation path passing through the heat generating part and the bypass circuit. The first temperature and the second temperature are detected and feedback control is performed to increase the cooling capacity of the cooling device by using the first temperature as a control variable and reduce the cooling capacity of the cooling device by using the second temperature as a control variable. Characterized by Method of controlling temperature of heat generating part of machine tool. 3. The cooling liquid is supplied to the heat generating part through an outward path of a circulation path provided between a heat generating part of a machine tool and a cooling device, and the cooling liquid whose temperature has been raised through a return path of the circulation path is cooled again. In a temperature control method for a heat generating portion of a machine tool configured to return to the above, a bypass circuit that bypasses the heat generating portion is provided between the outward path and the return path of the circulation path, and when the cooling device increases the cooling capacity. A part of the cooling liquid flowing only in the circulation path is branched to the bypass circuit, and in the return path of the circulation path, the cooling liquid is always provided on the downstream side of the confluence point between the regular circulation path passing through the heat generating part and the bypass circuit. The temperature control method for the heat generating part of the machine tool is characterized in that the temperature of the machine tool is detected and feedback control is performed to adjust the cooling capacity of the cooling device using this as a control variable.