JP6375175B2 - Oil cooler and control method of motor operated valve in oil cooler - Google Patents

Description

  The present invention relates to an oil cooler that controls the temperature of cooling oil circulated in a machine tool and suppresses thermal deformation that affects machining accuracy, and a method for controlling an electric valve in the oil cooler.

  The machine tool body deforms due to environmental temperature, heat from the heat generating part, and the like. Since the deformation of the airframe affects the processing accuracy, conventionally, the temperature of each part of the airframe has been controlled to a constant temperature. Various methods of temperature control have been proposed, but a constant flow-controlled cooling oil that is normally temperature-controlled is always supplied to the heat generating part of the machine tool to cool the heat generating part.

JP 2007-38329 A

  However, since the temperature control device of Patent Document 12 described above drives a refrigerator (compressor) by inverter control to change and control the rotation speed, an inverter control drive device is necessary, and the cost of the temperature control device is reduced. However, there is a problem that the temperature control device increases in size.

  SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to reduce the cost and improve the temperature control accuracy without the need for inverter control of the compressor.

For this reason, the first invention radiates and liquefies the heat of the circulation circuit for circulating the cooling oil to the machine tool, the refrigerator for compressing the refrigerant, and the gaseous refrigerant compressed by the refrigerator. A condenser, an expansion valve for constricting and expanding the liquefied refrigerant, and for exchanging heat with the cooling oil returned from the machine tool by the refrigerant in a gas-liquid mixed state of low-pressure and low-temperature constricted and expanded A heat exchanger, a bypass path for bypassing the condenser and introducing the refrigerant immediately after leaving the refrigerator into the heat exchanger, and an electric valve provided in the middle of the bypass path In oil cooler,
A cooling oil temperature sensor for detecting a return oil temperature that is the temperature of the cooling oil after cooling the spindle head rotatably supporting the spindle of the machine tool;
Correction means for correcting the return oil temperature detected by the cooling oil temperature sensor in accordance with the number of rotations of a motor that rotates the spindle of the machine tool;
Calculation means for subtracting a reference temperature set for the machine tool from the temperature corrected by the correction means;
Determining means for determining whether the calculated temperature obtained by subtraction by the calculating means is 0 or more;
A calculating means for calculating a pulse output value by performing PID control based on the calculated temperature when the determining means determines that the value is 0 or more;
Control means for controlling the motor-operated valve to have a predetermined opening based on the pulse output value calculated by the calculating means is provided.

The second invention is a circuit for circulating a cooling oil to a machine tool, a refrigerator for compressing a refrigerant, and heat for radiating and liquefying heat of a gaseous refrigerant compressed by the refrigerator. A condenser, an expansion valve for constricting and expanding the liquefied refrigerant, and heat for exchanging heat with the cooling oil returned from the machine tool by the condensated low-pressure low-temperature gas-liquid mixed state refrigerant An exchanger, a bypass passage for introducing the refrigerant immediately after leaving the refrigerator into the heat exchanger by bypassing the condenser, and an electric valve provided in the middle of the bypass passage, A method for controlling an electric valve in an oil cooler that controls the opening degree of the electric valve,
A cooling oil temperature sensor detects a return oil temperature that is a temperature of the cooling oil after cooling a spindle head that rotatably supports the spindle of the machine tool;
The return oil temperature detected by the cooling oil temperature sensor is corrected according to the number of rotations of a motor that rotates the spindle,
Subtract the reference temperature set for the machine tool from the corrected temperature,
Judge whether the calculated temperature obtained by subtraction is 0 or more,
If it is determined that it is 0 or more, based on the calculated temperature, PID control is performed to calculate a pulse output value,
Control is performed so that the motor-operated valve has a predetermined opening based on the calculated pulse output value.

  According to the present invention, it is not necessary to perform inverter control of the compressor, cost can be reduced, and temperature control accuracy can be improved.

It is a figure for showing circulation of a refrigerant and circulation of cooling oil in a machine tool and an oil cooler. It is a control block diagram. It is a figure which shows a flowchart.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a view for showing circulation of a refrigerant in a machine tool 1 and an oil cooler 5 and circulation of a cooling oil (cooling oil) as a cooling medium, and a tool or a workpiece in the machine tool 1 is attached thereto. Then, the spindle head, which is rotatably supported by the spindle, is cooled to control the temperature.

  The oil cooler 5 includes a refrigerant circulation circuit 3 in the right part of FIG. 1 and an oil circulation circuit 4 in the left part. The oil cooler 5 is provided so as to cool the spindle head of the machine tool 1 and the spindle. The refrigerant circulation circuit 3 is a circuit through which the refrigerant circulates, and the oil circulation circuit 4 is a circuit through which the cooling oil circulates with the machine tool 1.

  First, the refrigerant circulation circuit 3 will be described. A refrigerant in a gas state is compressed by the compressor 7 and sent to a condenser 8 as a heat exchanger. The motor 7A of the compressor 7 is driven at a constant rotational speed without using an inverter control drive device. In the condenser 8, the heat of the gaseous refrigerant which has been compressed by the compressor 7 and whose temperature has risen is dissipated and liquefied. The condenser 8 is cooled by air cooling by a condenser blower 9 provided with a fan motor 9A.

  Then, the refrigerant liquefied by the condenser 8 is removed of foreign matters by the strainer 10, and then is squeezed and expanded when passing through the capillary tube 11 as an expansion valve to be in a low-temperature and low-pressure gas-liquid mixed state. This low-temperature and low-pressure gas-liquid mixed refrigerant flows into the heat exchanger (cooler) 12 and cools the cooling oil (cooling oil that is a cooling medium) stored in the heat exchanger 12. is there. The refrigerant in a gas-liquid mixed state takes the heat of the cooling oil in the heat exchanger 12 and vaporizes, and the cooling oil in the heat exchanger 12 can be efficiently cooled by the heat of vaporization. Then, the refrigerant flowing out of the heat exchanger 12 returns to the compressor 5 via the accumulator 14 which is a gas-liquid separator, and thus the refrigerant described above circulates in the refrigerant circulation circuit 3. Become.

  The refrigerant circulation circuit 3 is adjusted to reduce the cooling capacity for cooling the cooling oil by flowing into the heat exchanger without cooling a part of the gaseous refrigerant compressed by the compressor 7 and having risen in temperature. A bypass path 15 is added, and an electric valve 16 that is opened and closed by a motor 16A that is a bypass valve that is a flow rate adjusting valve is provided in the bypass path 15. That is, when the motor-operated valve 16 is in an open state, a gaseous high-temperature refrigerant is mixed with a low-temperature refrigerant and flows into the heat exchanger according to the degree of opening, so that the cooling capacity is gradually reduced. When the motor-operated valve 16 is in a fully closed state, the high-temperature refrigerant is not mixed and the cooling capacity is maximized. By controlling the opening of the motor-operated valve 16, the cooling capacity can be changed and controlled.

  As shown by a dotted line in FIG. 1, a bypass passage 15A is formed so that a part of the gaseous refrigerant compressed by the compressor 7 and having a temperature rise is returned between the heat exchanger and the accumulator 14. The electric valve 16 that is opened and closed by the motor 16A may be provided in the bypass passage 15A.

  Reference numeral 18 denotes a high-pressure switch, which is a compressor protection switch that operates when the pressure of the refrigerant on the discharge side of the condenser 8 reaches a high pressure exceeding a predetermined pressure. When operated, the operation of the compressor 7 is stopped. It is.

  Next, the oil circulation circuit 4 will be described. An oil feed pump 20 provided in the oil circulation circuit 4 is driven by a drive motor 20A, and cooling oil (cooling that is a cooling medium) in the oil circulation circuit 4 is described. Circulating oil) at a constant flow rate.

  Then, after the cooling oil flowing through the oil circulation pipe 23 is cooled by the heat exchanger, it is sent to the machine tool 1 by the oil feed pump 20 to cool the spindle head of the machine tool 1. To cool the main shaft.

  After cooling the spindle head, the cooling oil returning to the oil circulation circuit 4 is detected by a cooling oil temperature detection sensor 22 and sent again to the machine tool 1 and then returned to the heat exchanger and cooled. The

  Next, in FIG. 2 which is a control block diagram, a microcomputer (hereinafter referred to as “microcomputer”) 25 which is a temperature control means controls the opening degree of the motor-operated valve 16 and the spindle of the machine tool 1. The temperature of the spindle head that supports the head is controlled.

  The microcomputer 25 is connected to the CPU 26 via a bus line as a control means for controlling the oil cooler 5 in an integrated manner, and stores a program related to the control. A ROM (Read Only Memory) 27 and a RAM (Random Access Memory) 28 for storing various data are provided.

  A display device 30, an input device 31, and the like are connected to the CPU 26 of the microcomputer 25, which is a temperature control means, via an interface 29. The ROM 27 stores a program related to PID control for controlling the opening degree of the motor-operated valve 16.

  The CPU 26 serves as calculation (calculation) means, correction means, determination means, comparison means, command means, control means, and the like.

  Here, the above-described PID control will be briefly described. This PID control outputs a proportional operation (P operation) for outputting an output proportional to the deviation between the current value and the set value, and an output proportional to the integral of the deviation. The sum of (I operation) and differential operation (D operation) that outputs an output proportional to the differential of the deviation is output and controlled toward the target value. The proportional action (P action) is an action that operates an operation amount proportional to the deviation between the current value and the set value within the proportional band, and the integral action (I action) is when an offset appears. It is an operation that works to eliminate the offset in the same way as manual reset by changing the operation amount, and the differential operation (D operation) depends on the degree of change when the detected temperature starts to change due to disturbance or the like. This is an operation for preventing a control result from fluctuating greatly by adding a large correction operation while the deviation is small. By this PID control, highly accurate, high-speed response and highly stable control can be performed.

  The CPU 26 is connected to the cooling oil temperature detection sensor 22 for detecting the temperature (return oil temperature) of the cooling oil that has returned after cooling the spindle head of the machine tool 1 and the oil. The motor 16A of the motor-operated valve 16, which is each drive source of the cooler 5, the motor 7A of the compressor 16, the fan motor 9A of the blower 9, the drive motor 20A of the oil feed pump 20, etc. are connected. Yes.

  On the other hand, the machine tool 1 is also provided with a microcomputer (hereinafter referred to as “microcomputer”) 35 having a CPU, a RAM, a ROM, and the like. A reference temperature detection sensor 37 is connected to the microcomputer 35, and a motor 36 for rotating the spindle and an encoder 38 for grasping the rotation angle of the motor 36 are connected.

  The reference temperature is generally set to room temperature or the temperature of a member having a large heat capacity in the components of the machine tool 1, and the temperature measured by the reference temperature sensor 37 is set as the reference temperature. In the present embodiment, the reference temperature detection sensor 37 is provided in a member (part) having a large heat capacity among the components of the machine tool 1 serving as a reference part, and the temperature detected by the reference temperature detection sensor 37 is a reference temperature. Set as That is, in the machine tool 1, the reference temperature detected by the reference temperature detection sensor 37 is sent to the oil cooler 5 by the microcomputer 35, and is set and stored as a reference temperature in the RAM 28 by the CPU 26. Note that the temperature detected by the reference temperature detection sensor 37 is not limited to the method of setting and storing the temperature in the RAM 28 as the reference temperature, and for example, using the display device 30 and the input device 31, an administrator ( A user may set the reference temperature and store it in the RAM 28 according to a command from the CPU 26.

  The following description is based on the flowchart of FIG. 3 in which the opening degree of the motor-operated valve 16 is controlled and adjusted with the above configuration. First, the reference temperature detection sensor 37 detects the reference temperature at a predetermined part of the machine tool 1 and the cooling oil temperature detection sensor 22 cools the spindle head of the machine tool 1 before the oil circulation circuit. The temperature of the cooling oil returned to 4 is detected (step S01).

  In this case, the reference temperature detected by the reference temperature detection sensor 37 is sent from the microcomputer 35 of the machine tool 1 to the CPU 26 of the oil cooler 5, set in the RAM 28, stored and stored, and the cooling oil. The temperature of the cooling oil detected by the temperature detection sensor 22 is also stored and stored in the RAM 28 according to a command from the CPU 26.

  Next, the CPU 26 controls to correct the detected temperature of the cooling oil that has returned to the oil circulation circuit 4 based on the number of revolutions of the motor 36 that rotates the spindle of the machine tool 1 (step S02). . That is, when the rotation speed changes in a predetermined time, for example, 1 minute, it is conceivable to correct the detected temperature of the cooling oil according to the change. Specifically, when the change in the rotation speed when increasing is large, when the change is middle, when the change is small, for example, a multiplier (in order of a small number, for example, “1.09”, respectively) at the detected temperature of the cooling oil. ”,“ 1.06 ”,“ 1.03 ”), and when the change in the rotation speed is small, medium, or large, for example, the detection of the cooling oil, respectively. The CPU 26 calculates the product by multiplying the temperature by a multiplier (in order, smaller numbers, for example, “0.97”, “0.94”, “0.91”).

  Note that the correction method is not limited to the above-described method, and correction may be made in accordance with the number of rotations of the motor 36 that rotates the spindle of the machine tool 1. As another method, for example, the motor 36 It is possible to divide the number of rotations by a certain range and multiply the respective multipliers determined according to these divisions, and various methods are conceivable.

  Thus, the CPU 25 obtains information on the rotational speed of the motor 36 that rotates the spindle from the machine tool 1, that is, the CPU 25 receives the rotational angle information from the encoder 38 and the motor from the microcomputer 35 receives the rotational angle information. It is possible to obtain the rotation speed information of 36 and quickly control the motor 16 to control and adjust the opening degree of the motor-operated valve 16 according to the change in the rotation speed of the motor 36. That is, even if the rotational speed of the motor 36 for rotating the spindle of the machine tool 1 is increased, a time (time lag) is reflected until the temperature of the cooling oil returning from the machine tool 1 is reflected, and the load fluctuation Although the hunting width of the temperature of the return cooling oil at the time increases, according to the present invention as described above, the hunting width can be reduced as much as possible by obtaining the rotational speed information of the motor 36 in advance.

  Next, the CPU 26 calculates by subtracting the reference temperature detected in step S01 from the corrected temperature obtained by multiplying the detected temperature of the cooling oil by the multiplier described above (step S03).

  Then, the CPU 26 determines whether or not the calculated temperature obtained by the calculation in step 03 is 0 (zero) or more (step S04). In this case, if it is not 0 or more, that is, if it is a negative value, the CPU 26 controls to stop the operation of the motor 16A of the compressor 16 (step S06) and returns to step S01. .

  If it is determined in step S04 that the CPU 26 is greater than or equal to 0, the CPU 26 next determines whether or not the compressor 7 is in operation (step S06) and is calculated in step S03. Based on the calculated temperature, the CPU 26 performs PID control to calculate a pulse output value (step S07).

  Then, in step S06, if it is determined that the compressor 7 is not in operation, control is performed to start the operation (step S08), and if it is determined that operation is in progress, control is performed to continue operation (step S08). Step S09).

  Then, after step S07, the CPU 26 controls the motor 16A based on the calculated pulse output value so that the motor-operated valve 16 has a predetermined opening (step S10), and then returns to step S01.

  In this case, the opening degree of the motor-operated valve 16 is in a fully open state, and the gap between the valve body and the valve seat is 0.7 mm, and this is controlled in accordance with, for example, 1440 division according to the pulse output value. It can be controlled with extremely high accuracy. When the calculated temperature calculated by subtracting the reference temperature from the corrected temperature obtained in step S03 is equal to or higher than a predetermined temperature, a gap between the valve seat and the valve body of the motor-operated valve 16 is closed. When the calculated temperature decreases, the operation of gradually opening the gap is quickly performed by the above-described PID control. Therefore, when the calculated temperature decreases, the gap is gradually opened, and a part of the warm refrigerant passing through the compressor 16 flows to the heat exchanger 12 via the bypass 15, and the correction is performed. The difference between the later temperature and the calculated temperature is controlled to be a target numerical value, and as a result, the temperature of the spindle head always maintains a constant temperature difference with respect to the reference temperature. .

  As described above, feedback control is performed by changing and controlling the opening degree of the motor-operated valve 16 by PID control, and the rotational speed of the spindle by the motor 36 is from a stopped state to several thousand revolutions per minute or more. Since the temperature fluctuates, the temperature of the spindle head supporting the spindle is cooled and temperature control is performed so that the temperature of the spindle head always maintains a constant temperature difference with respect to the reference temperature.

  Although the embodiments of the present invention have been described above, various alternatives, modifications, and variations can be made by those skilled in the art based on the above description, and the present invention is not limited to the various embodiments described above without departing from the spirit of the present invention. It encompasses alternatives, modifications or variations.

DESCRIPTION OF SYMBOLS 1 Machine tool 4 Oil circulation circuit 7 Compressor 16 Electric valve 16A Motor 22 Cooling oil temperature detection sensor 26 CPU
36 Motor 37 Reference temperature detection sensor

Claims (2)

A circulation circuit for circulating cooling oil to the machine tool, a refrigerator for compressing the refrigerant, a condenser for dissipating the heat of the gaseous refrigerant compressed by the refrigerator and liquefying, and the liquefied An expansion valve for constricting and expanding the refrigerant, a heat exchanger for exchanging heat with the cooling oil returned from the machine tool by the condensated low-pressure low-temperature gas-liquid mixed state, and the refrigerator In an oil cooler comprising a bypass path for introducing the refrigerant immediately after leaving the condenser into the heat exchanger by bypassing the condenser, and an electric valve provided in the middle of the bypass path,
A cooling oil temperature sensor for detecting a return oil temperature that is the temperature of the cooling oil after cooling the spindle head rotatably supporting the spindle of the machine tool;
Correction means for correcting the return oil temperature detected by the cooling oil temperature sensor in accordance with the number of rotations of a motor that rotates the spindle of the machine tool;
Calculation means for subtracting a reference temperature set for the machine tool from the temperature corrected by the correction means;
Determining means for determining whether the calculated temperature obtained by subtraction by the calculating means is 0 or more;
A calculating means for calculating a pulse output value by performing PID control based on the calculated temperature when the determining means determines that the value is 0 or more;
An oil cooler comprising: control means for controlling the motor-operated valve to have a predetermined opening based on the pulse output value calculated by the calculating means. A circulation circuit for circulating cooling oil to the machine tool, a refrigerator for compressing the refrigerant, a condenser for dissipating the heat of the gaseous refrigerant compressed by the refrigerator and liquefying, and the liquefied An expansion valve for constricting and expanding the refrigerant, a heat exchanger for exchanging heat with the cooling oil returned from the machine tool by the condensated low-pressure low-temperature gas-liquid mixed state, and the refrigerator A bypass passage for introducing the refrigerant immediately after leaving the condenser into the heat exchanger by bypassing the condenser, and an electric valve provided in the middle of the bypass passage, and controlling the opening degree of the electric valve A method for controlling an electric valve in an oil cooler,
A cooling oil temperature sensor detects a return oil temperature that is a temperature of the cooling oil after cooling a spindle head that rotatably supports the spindle of the machine tool;
The return oil temperature detected by the cooling oil temperature sensor is corrected according to the number of rotations of a motor that rotates the spindle,
Subtract the reference temperature set for the machine tool from the corrected temperature,
Judge whether the calculated temperature obtained by subtraction is 0 or more,
If it is determined that it is 0 or more, based on the calculated temperature, PID control is performed to calculate a pulse output value,
A method for controlling a motor-operated valve in an oil cooler, wherein the motor-operated valve is controlled to have a predetermined opening based on the calculated pulse output value.

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