JPH0740184A - Lubricating oil temperature control method and device for machine tool - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a lubricating oil temperature control method and device for a machine tool that controls the temperature of lubricating oil circulated in a spindle device and maintains the spindle temperature at a predetermined value without delay. In the lubricating oil circulation circuit for supplying and recovering the lubricating oil discharged from the cooling means 11 and the lubricating oil of the bypass circuit 17 to the main shaft portion 5 through the variable mixing valve 3,
The C program is pre-read, the next spindle speed is detected, and the discharge capacity of the cooling means 11 is changed to the cooling heat amount corresponding to the next spindle speed, if necessary, before shifting the spindle speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling a lubricating oil temperature of a machine tool, and in particular, circulates and absorbs heat generated in a spindle portion of a machine tool to cool the spindle oil to a predetermined value. The present invention relates to a method and an apparatus for controlling a lubricating oil temperature of a machine tool to be maintained.

[0002]

2. Description of the Related Art Generally, a machine tool generates heat in accordance with machining conditions such as the number of revolutions of the spindle and machining resistance, and there is a difference between the temperature of the spindle and the temperature of the machine body of the machine tool away from the spindle. Occurs. For this reason, thermal strain is generated in each part of the machine tool according to the machining conditions, which is an obstacle to highly accurate machining. A countermeasure against this problem is disclosed in Japanese Patent Publication No. 48-3797. The disclosed oil temperature control device controls the oil temperature of the lubricating oil so that the oil temperature of the lubricating oil follows the fluctuation of the atmospheric temperature so as to always maintain a constant temperature difference with respect to the atmospheric temperature.

However, in the above oil temperature control device, the circulation time of the lubricating oil, the time delay until the heat from the main shaft, which is a heating element, is transmitted to the lubricating oil, and is further detected as the output of the temperature detector, etc. Therefore, it is difficult to control the oil temperature with good responsiveness. In particular, when the machining conditions are drastically changed, such as when the rotational speed of the spindle changes, the amount of heat generated changes, and immediately after the change, it is difficult to control the oil temperature with good response. To address this problem, the present applicant has disclosed an invention entitled "Method and apparatus for controlling spindle temperature of machine tool" in Japanese Patent Laid-Open No. 64-51253 as a countermeasure. The disclosed control method and device, so that the temperature difference between the main shaft portion and the machine body portion apart from the main shaft portion becomes constant even immediately after the machining conditions that cause the change in the heat generation amount of the main spindle change. To control the temperature of the lubricating oil supplied to the spindle, and to eliminate the machining error due to the thermal expansion change of the spindle, stop the normal feedback control for a predetermined time from the time when the machining conditions suddenly change, When the feedback control is stopped, the temperature of the lubricating oil is immediately cooled or heated by the oil temperature controller so as to reach the set temperature set in advance according to the processing conditions, and the lubricating oil is supplied to the main spindle part. A machine tool spindle temperature control method and apparatus are provided.

However, since the spindle temperature control method and apparatus for a machine tool described above starts the temperature control of the lubricating oil immediately after the machining conditions that cause the heat generation amount of the spindle to change, the spindle is rotated at high speed. When switching to a number,
The main shaft switches to a predetermined high speed in a short time of a few seconds and raises the oil temperature of the main shaft, while the oil temperature controller takes several minutes to cool the lubricating oil to the set temperature according to the processing conditions. There is a problem that it takes time, cooling cannot be done in time, and the responsiveness of oil temperature control is insufficient. Therefore, it is conceivable to prepare a cooling lubricating oil in advance and immediately supply the prepared cooling lubricating oil to the main spindle immediately after the processing conditions change, but in this case, the maximum load of the main spindle is required. On the other hand, it is necessary to always prepare a predetermined amount of cooling lubricating oil with a cooling capacity that can cope with the change from the minimum rotation speed used to the maximum rotation speed used, which leads to large-scale equipment and wasteful energy consumption. There's a problem.

[0005]

SUMMARY OF THE INVENTION Therefore, the object of the present invention is to eliminate the above-mentioned problems, that is, even if the spindle speed is increased from a low speed to a high speed, a lubricating oil of an appropriate temperature is immediately supplied to the main shaft portion, Work that eliminates sudden changes in spindle temperature, eliminates machining errors due to changes in spindle thermal expansion, improves machining accuracy, does not require an oil temperature controller with unnecessarily large cooling capacity, and does not consume energy. To provide a method and an apparatus for controlling a lubricating oil temperature of a machine.

[0006]

To achieve the above object, a lubricating oil temperature control method for a machine tool, in which the lubricating oil cooled by a cooling means is circulated to a spindle portion of the machine tool to maintain the spindle temperature at a predetermined value. In advance, the required cooling heat quantity corresponding to the spindle rotation speed is stored in advance, the machining program of the machine tool is pre-read, and it is detected that the spindle rotation speed is changed from low speed to high speed. A portion of the return lubricating oil from the main spindle portion is kept as it is until the cooling oil amount of the required cooling heat amount corresponding to the next high-speed main spindle speed is discharged from the cooling means and a shift of the main spindle speed is executed. It is mixed with the lubricating oil discharged from the cooling means, and its mixing ratio is adjusted so that the required amount of cooling heat of the lubricating oil corresponding to the current main spindle speed is supplied to the main spindle portion. Stop the cooling Lubricating oil temperature control method for a machine tool so as to supply only the lubricating oil discharged from the stage to immediately the main shaft portion is provided.

Further, in the lubricating oil temperature control device for a machine tool, which circulates the lubricating oil cooled by the cooling means to the spindle portion of the machine tool to maintain the spindle temperature at a predetermined value, the lubricating oil is returned from the spindle portion. The bypass is divided into two pipes, the bypass circuit for lubricating oil is provided in parallel with the cooling means, and the lubricating oil discharged from the cooling means and the lubricating oil from the bypass circuit are mixed and supplied to the main shaft portion. Variable mixing valve, a storage means for storing in advance the required cooling heat quantity corresponding to the spindle speed, and a cooling heat quantity change required time for increasing the cooling heat quantity of the lubricating oil by the cooling means; When it is detected that the spindle speed is changed from low speed to high speed by pre-reading the machining program, the required cooling heat quantity corresponding to the next high speed spindle speed and the time required for changing the cooling heat quantity are stored from the storage means. Therefore, the required cooling heat quantity of the cooling means is changed to the obtained value before the main spindle speed is changed, and the required cooling heat amount of lubricating oil corresponding to the current main spindle speed is changed until the main spindle speed is changed. The mixing ratio of the variable mixing valve is adjusted so as to be supplied to the main shaft portion, and after the main shaft speed is changed, the mixing by the variable mixing valve is stopped,
There is provided a lubricating oil temperature control device for a machine tool, comprising: a control unit configured to immediately supply only the lubricating oil discharged from the cooling unit to the spindle unit.

[0008]

The method and apparatus for controlling the lubricating oil temperature of the machine tool of the present invention pre-reads the machining program of the machine tool, detects in advance that the rotational speed of the spindle is changed from low speed to high speed, and detects the lubricating oil in time for the speed change. The cooling means is operated so that the required amount of cooling heat of lubricating oil corresponding to the next high speed spindle speed is discharged. Until the main spindle speed is changed, the mixing ratio of the variable mixing valve is adjusted so that the required amount of cooling heat of the lubricating oil corresponding to the current main spindle speed is supplied to the main shaft portion. After the main shaft rotation speed is changed, the mixing ratio of the variable mixing valve is immediately changed so that only the lubricating oil having the required cooling heat amount corresponding to the high speed main shaft rotation discharged from the cooling means is supplied to the main shaft portion. Therefore, the lubricating oil temperature can be controlled with good response.

[0009]

EXAMPLES Referring to FIG. 1 below, a spindle 5 of a machine tool
A method of controlling the temperature of the lubricating oil circulating between the oil temperature adjusting means and the oil temperature adjusting means will be described. 2 and 3 are flowcharts showing the processing of the oil temperature control when switching the spindle speed. For the sake of convenience, it will be described from the point where a predetermined work is machined by the spindle 5 of the machine tool based on a predetermined machining program loaded in the NC device 10 shown in FIG. In FIG. 1, the lubricating oil recovered from the main shaft portion 5 by the circulation pump 30 is branched into two branches, one of which is passed through a cooling circuit 15 in which the temperature of the lubricating oil can be adjusted by the cooling means 11, and the other of which is temperature adjusted. Lubricating oil is circulated and supplied to the main shaft portion 5 through the bypass circuit 17 which is not performed and merged by the variable mixing valve 3 to lubricate and cool the main shaft portion 5. In the steady state except before and after the spindle speed change, the control means 9 performs feedback control of the cooling capacity of the cooling means 11 so that the difference between the temperature of the spindle part 5 and the room temperature maintains a predetermined value. Reference numerals 21 to 25 are temperature sensors such as thermistors, whose detected temperatures are T _A , T _B , T _C and T _{D in order.}
And T _E. Reference numeral 25 denotes a temperature sensor for detecting room temperature, which is attached to a bed (not shown) of the machine tool in this embodiment, and 24 denotes a temperature sensor for detecting the temperature of the spindle 5 of the machine tool. In this embodiment, it is attached so that the temperature of the lubricating oil returning from the main shaft portion 5 can be measured. Further, reference numerals 27 and 28 are flow meters,
These are for measuring the circulating oil amounts Q _A and Q _B , respectively. The outputs T _A , T _B , T _C , T _D and T _E of the temperature sensor are connected to the control means 9 for processing, and the flow rates Q _A , Q
_{B is} also connected to the control means 9 and processed.

Next, each step of the flowcharts of FIGS. 2 and 3 will be described. (Step S1): The spindle rotational speed N1 is read from the NC device 10 and stored in the storage unit N of the storage means 7, and i = 0. (Step S2): One block ahead of the currently executed block of the machining program is read and i = i + 1 is calculated. (Step S3): It is determined whether or not the block read in step S2 is a spindle rotation speed change command. If YES, the process proceeds to step S5, i = n, and if NO, the process proceeds to step S4. (Step S4): The time required to execute the command of the block read in step S2 is calculated and ti (i =
, 1, 2, ..., N) are stored. (Step S5): The execution time ti of each block calculated until the block of the spindle rotation speed change command is read is added to obtain the total sum ts = t1 + t2 + ... + tn, and the current time to is added to the spindle rotation from tc = t0 + ts. The time tc at which the shift starts is calculated and stored. (Step S6): The current rotation speed N1 is compared with the rotation speed N2 of the spindle rotation speed change command in step S3, and N1 = N2
When N1 <N2, that is, when shifting from low speed to high speed, the procedure proceeds to step S11. When N1> N2, that is, when shifting from high speed to low speed, the procedure proceeds to step S31. (Step S7): The normal feedback control of the lubricating oil temperature is continued.

Next, the case of shifting from low speed to high speed will be described. (Step S11): A cooling heat amount W required for the spindle rotational speed N1 and a cooling heat amount W2 required for the spindle rotational speed N2 are obtained from a comparison table shown in FIG. 4A described later, and the cooling heat amount W is determined as the spindle rotational speed N2. The required time tr required to increase the cooling heat amount W2 required for the above is obtained from the comparison table shown in FIG. (Step S12): The required time tr is subtracted from the gear shift start time tc to obtain and store the cooling start time ts. (Step S13): Current time to and cooling start time ts
And when to <ts, that is, when the cooling start time ts has not yet come, the process proceeds to step S14 to provide a waiting time, and when to = ts, step S1.
5 and proceed to S17. (Step S14): Return to step S13 after a predetermined time. (Step S15): The normal feedback control of the lubricating oil temperature is temporarily stopped, and the required cooling heat amount W of the cooling means 11 is increased to the cooling heat amount W2 corresponding to the rotation speed N2. (Step S16): The mixing ratio of the variable mixing valve is changed, that is, the cooling valve 13 is throttled and the heating valve is heated so that the oil temperature T _C supplied to the main shaft portion becomes an appropriate temperature corresponding to the current rotational speed N1. Open 14 The opening of each valve is shown in Fig. 4.
It is obtained from the control table of (C). (Step S17): The current cooling heat amount W and the required cooling heat amount W2 corresponding to the rotation speed N2 are compared. When W> W2, that is, when the required cooling heat amount has not yet been reached, the process proceeds to step S18. When W = W2, step S
Proceed to 19. (Step S18): Return to step S15 after a predetermined time. (Step S19): The gear shift command is read, and a command for changing the spindle rotational speed N from N1 to N2 is output to the NC device,
The cooling valve 13 is fully opened and the heating valve 14 is fully closed. Then resume normal feedback control.

Next, the case of shifting from high speed to low speed will be described. (Step S31): It is read that the spindle speed changes from N1 to N2. (Step S32): The normal feedback control is temporarily stopped, and the mixing ratio of the variable mixing valve is changed, that is, cooling is performed so that the oil temperature T _C supplied to the main shaft portion becomes an appropriate temperature corresponding to the rotation speed N2. The valve 13 is squeezed and the heating valve 14 is opened. The opening degree of each valve is obtained from the comparison table of FIG. (Step S33): The current cooling heat amount W is set to the spindle rotation speed N.
The required cooling heat amount W2 corresponding to 2 is reduced. (Step S34): The current cooling heat amount W and the required cooling heat amount W2 corresponding to the rotation speed N2 are compared, and when W = W2, the process proceeds to step S35, and when W> W2, the step S35.
Proceed to 36. (Step S35): The cooling valve 13 is fully opened and the heating valve 14 is fully closed. Then resume normal feedback control. (Step S36): Return to step S32 after a predetermined time.

FIG. 4 is a view showing a comparison table. (A) is a required cooling heat quantity corresponding to the spindle rotation speed, (B) is a cooling heat quantity change required time corresponding to the spindle rotation speed difference before and after gear shifting, and ( C) is a diagram showing the opening of the variable mixing valve corresponding to the absolute value of the difference between the oil temperature T _C supplied to the main shaft and the discharge oil temperature T _A of the cooling means 11. In the comparison table shown in FIG. 4A, the left column shows the spindle rotation speed, and the right column requests the cooling means 11 to make the oil temperature a proper temperature when the spindle has the rotation speed shown in the left column. An example of the required cooling heat amount is shown. According to this comparison table, for example, when the rotational speed of the spindle changes from 5000 RPM to 10000 RPM, the required cooling heat amount at 5000 RPM is 1 KW and the required cooling heat amount at 10000 RPM is 3 KW, so 3-1 = 2 (KW) It can be seen that more cooling heat is required. When the spindle speed is in the left column, the data of the required cooling heat amount W corresponding to the spindle speed is directly obtained from this comparison table, but it corresponds to the spindle speed when the spindle speed is not in the left column. The data of the required cooling heat amount W to be obtained is obtained by proportional distribution from the data before and after the main spindle speed.

In the comparison table shown in FIG. 4B, the left column shows the spindle speed difference before and after shifting, and the right column shows when the spindle is shifted to the speed difference shown in the left column. The time required to supply the required additional cooling heat quantity to the cooling means 11 and to supply the required cooling heat quantity required to the cooling means 11 at the spindle speed after the gear shift, that is, the cooling heat quantity change required time An example is shown. When the spindle rotational speed difference is in the left column, the cooling heat quantity change required time tr data corresponding to the spindle rotational speed is directly obtained from this comparison table. The data of the cooling heat quantity change required time tr corresponding to the rotation speed is obtained by proportional distribution from the data before and after the main shaft rotation speed difference.

In the comparison table shown in FIG. 4C, the left column shows the absolute value of the temperature difference between the discharge oil temperature T _A of the cooling means 11 and the oil temperature T _C supplied to the main shaft portion 5, The right column shows an example of the ratio (%) of the opening degrees of the cooling valve 13 and the heating valve 14 which constitute the variable mixing valve corresponding to each temperature difference shown in the left column. The opening ratio determines the mixing ratio of the variable mixing valve 3. Incidentally, when the temperature difference between the oil temperature T _A and T _C is in the left column determine the data of the mixing ratio of the variable mixing valve 3 corresponding to the temperature difference directly from the control table, but the oil temperature T _A and T _When the temperature difference between _C is not in the left column, the mixing ratio of the variable mixing valve corresponding to that temperature difference is proportionally distributed from the data before and after the temperature difference. (A) to (C) of FIG. 4 above
It is needless to say that each data may be stored in advance in the form of a function instead of the comparison table.

FIG. 5A is a diagram showing a spindle speed, FIG. 5B is a lubricating oil temperature, and FIG. 5C is a time chart of flow rate. In this figure, the horizontal axis represents time (min),
The vertical axis represents the rotational speed (RPM) in FIG. 5- (A), the temperature (° C.) in FIG. 5- (B), and the flow rate (1 / s) in FIG. 5- (C). By the speed change command of the spindle rotation of the machining program, the rotational speed N of the spindle is increased from the rotational speed N1 at the current time t0 to the rotational speed N2 at the time t3, and decelerated from the rotational speed N2 at the time t3 to the rotational speed N3 at the time t4. The changes in the oil temperature and the flow rate of the lubricating oil in each part when the above is performed will be described below.

First, the oil temperature of each part will be described. At times t0 to t1, the spindle rotation speed N is N1, and T _A
And T _C are constant at T1, and at times t1 to t3,
Here, the time t1 is a time tr minutes before the time t3 at which the acceleration starts from the spindle speed N1 to N2, and the current cooling heat amount W described in the above-mentioned flowchart is required for the spindle speed N1 to the spindle speed N2. This is the time required to increase the cooling heat amount W2. T _C is constant as it is from time t1 to time t3, but T _A supplies the necessary cooling heat amount of the spindle speed N2 to the spindle portion at time t1 so that the cooling capacity of the cooling means 11 is adjusted to a stable oil temperature T2. Because it changes, time t1
At t2 to t2, the mixing ratio of the variable mixing valve is changed, and when the main spindle speed becomes N2, the cooling means 11 supplies the required cooling heat amount to the main spindle portion 5 and decreases until it reaches a stable oil temperature T2. From T3 to T3, T2 is constant. From time t3 to t4, T _A and T _C are constant at T2,
At time t3, it is already T2, and the problem of insufficient cooling in the conventional technique is solved. After time t4, the spindle rotation speed is immediately changed to N3 at time t4, and the cooling means 11 is switched to the cooling capacity corresponding to the spindle rotation speed N3. Therefore, the cooling valve 13 is immediately throttled and the valve 14 is opened, and at the same time, the temperature T _C becomes T3.
Then, after time t4, it becomes constant at T3. Since the cooling capacity of the cooling means 11 is changed so that the temperature T _A becomes the temperature T3 after the time t4, the temperature T _A gradually increases until it becomes T3 at the time t5 and becomes constant at the time T3 after the time t5.

Next, the flow rate of each part will be described. Time t
At 0 to t1, the spindle rotational speed N is N1, and as shown in the comparison table of FIG. 4A, the cooling means 11 supplies the required amount of cooling oil corresponding to the spindle rotational speed N to the spindle portion 5. However, this is performed by adjusting the cooling capacity of the cooling means 11 by adjusting the inverter of the cooling means 11, and the mixing ratio of the variable mixing valve 3 during normal machining at the spindle speed N, that is, the cooling valve 13 and the heating valve 14. As for the opening degree, 13 is fully opened and 14 is fully closed. Since Q _A and Q _B from time t0 to t1 are the cooling capacity of the cooling means 11 corresponding to the spindle speed N1 and the valve 13 is fully open and the valve 14 is fully closed, Q _A is Q.
It becomes a value obtained from the formula of × (T _A −T _D ) = W. Here, W is the current amount of cooling heat obtained by the cooling means 11. Q _B is 0 because the valve 14 is fully closed.
At time t1, the cooling capacity of the cooling means 11 is changed, but T _C
The mixing ratio of the variable mixing valve 3 is changed in order to keep the temperature constant. That is, the cooling valve 13 is narrowed and the heating valve 14 is opened. At time t2, the cooling means 11 has the rotation speed N2.
Since the cooling capacity corresponding to is reached, the flow rate Q _A gradually decreases from the time t1 to t2, the flow rate Q _B gradually increases, and becomes constant at the value of the time t2 from the time t2 to t3. Q _A and Q _B between time t3~t4, the rotational speed of the spindle changes the mixing ratio of the variable mixing valve 3 becomes N2 at time t3,
That is, regarding the opening degrees of the cooling valve 13 and the heating valve 14, 13 is fully opened and 14 is fully closed. Thus Q _A is based on the amount of heat to oil temperature T2 to stably by supplying necessary cooling heat of the spindle rotation speed N2 to the main shaft _{5, Q × (T A -T} D) = W
The value obtained from the equation is, and Q _B is 0 because the valve 14 is fully closed. At time t4, the spindle speed N is changed to N3, the cooling capacity of the cooling means 11 is changed, and the mixing ratio of the variable mixing valve 3 is changed so as to keep T _C constant and prevent overcooling as in the prior art. That is, the cooling valve 13 is narrowed and the heating valve 14 is opened. Therefore, from time t4 to t5, the flow rate Q _A gradually increases, Q _B gradually decreases to 0, and after time t5 it becomes constant at the value at time t5. The value of Q _A at this time is the spindle speed N after time t4.
Oil temperature T that supplies the required amount of cooling heat of 3 to the spindle 5 and stabilizes
Based on 3 to heat, the value obtained from the equation _{Q × (T A -T D)} = W.

It is also possible to interpose a heating means such as a heater in the middle of the bypass circuit 17 to further speed up the response when shifting from high speed to low speed. Further, in the present embodiment, the mixing ratio of the variable mixing valve is adjusted and controlled by the data stored in advance in the storage means as shown in FIG. 4C, but the control means 9 controls the difference between the temperature T _D and the temperature T _E. May be adjusted and controlled by feedback control such that

[0020]

As described above, according to the method and apparatus for controlling the lubricating oil temperature of the machine tool of the present invention, there is no insufficient cooling or supercooling due to delay, and the lubricating oil having an appropriate temperature is constantly supplied to the main shaft portion. It is possible to eliminate the thermal displacement of the spindle, that is, without heating or subcooling the spindle,
As a result, processing accuracy is improved. Further, according to the lubricating oil temperature control method and apparatus for a machine tool of the present invention, it is only necessary to prepare a cooling device having the same capacity as the maximum heat generation amount, and it is not necessary to perform supercooling due to insufficient cooling due to cooling delay. Therefore, it is not necessary to provide a cooling device having a capacity larger than the maximum calorific value, which is economical and wastes cooling energy.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a lubricating oil temperature control device for a machine tool according to an embodiment of the present invention.

FIG. 2 is a flowchart (1) showing a process of oil temperature control when switching the main shaft rotation speed.

FIG. 3 is a flowchart (2) showing a process of oil temperature control when switching the spindle speed.

FIG. 4 is a view showing a comparison table, in which (A) is a required cooling heat quantity corresponding to the spindle rotation speed, (B) is a cooling heat quantity change required time corresponding to the spindle rotation speed difference before and after gear shifting, and (C). FIG. 6 is a diagram showing an opening degree of a variable mixing valve corresponding to an absolute value of a difference between an oil temperature T _C supplied to a main shaft portion and a discharge oil temperature T _A of a cooling means.

5A is a diagram showing a main shaft rotation speed, FIG. 5B is a lubricating oil temperature of each portion, and FIG. 5C is a time chart showing a temporal change of a flow rate.

[Explanation of symbols]

 3 ... Variable mixing valve 5 ... Main shaft part 7 ... Storage means 9 ... Control means 10 ... NC device 11 ... Cooling means 13 ... Cooling valve 14 ... Heating valve 15 ... Cooling circuit 17 ... Bypass circuit 21, 22, 23, 24 , 25 ... Temperature sensor 27, 28 ... Flowmeter 30 ... Pump

Claims (2)

[Claims] 1. A method for controlling a lubricating oil temperature of a machine tool, wherein a lubricating oil cooled by a cooling means is circulated to a spindle part of a machine tool to maintain a spindle temperature at a predetermined value, and a required cooling heat amount corresponding to a spindle speed. It is necessary to correspond to the next high-speed spindle rotation speed before changing the spindle rotation speed by detecting in advance the machining program of the machine tool and detecting that the spindle rotation speed changes from low speed to high speed. The lubricating oil of the cooling heat amount is discharged from the cooling means, and a part of the returning lubricating oil from the main shaft portion is mixed with the lubricating oil discharged from the cooling means as it is until the shift of the spindle speed is executed. , The mixing ratio is adjusted so that the necessary amount of cooling heat of the lubricating oil corresponding to the current main spindle speed is supplied to the main spindle part, and after the main spindle speed is changed, the mixing is stopped and the lubrication is discharged from the cooling means. Oil only instantly Lubricating oil temperature control method of a machine tool, characterized in that it has to be supplied to the serial spindle unit. 2. A lubricating oil temperature control device for a machine tool, wherein lubricating oil cooled by cooling means is circulated to a spindle portion of a machine tool to maintain a spindle temperature at a predetermined value, wherein the lubricating oil is returned from the spindle portion. A bypass circuit for lubricating oil provided in parallel with the cooling means and a lubricating oil discharged from the cooling means and lubricating oil from the bypass circuit are mixed and supplied to the main shaft portion. A variable mixing valve, a storage unit that stores in advance a required cooling heat amount corresponding to the spindle speed, and a cooling heat amount change time required to increase the cooling heat amount of the lubricating oil by the cooling unit; When it is detected that the spindle speed is changed from low speed to high speed by pre-reading the machining program, the required cooling heat quantity corresponding to the next high speed spindle speed and the time required to change the cooling heat quantity are obtained from the storage means. , The required cooling heat amount of the cooling means is changed to the obtained value prior to the shift of the main spindle speed, and the required cooling heat amount of lubricating oil corresponding to the current main spindle speed is changed until the main spindle speed is changed. The mixing ratio of the variable mixing valve is adjusted so as to be supplied to the main shaft portion, the mixing by the variable mixing valve is stopped after the main shaft rotation speed is changed, and only the lubricating oil discharged from the cooling means is immediately added to the main shaft portion. And a control means for supplying the lubricating oil temperature to the machine tool.