JPH0516978B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spindle cooling control device for a machine tool. More specifically, the present invention relates to a spindle rotation speed synchronized spindle cooling control device that controls a spindle cooling device in synchronization with the rotation speed of a machine tool.

[Prior Art] In the spindle head of a machine tool, a rotating spindle that holds a tool or workpiece is supported by a bearing.
Therefore, the entire spindle head generates heat due to rolling friction or sliding friction of the bearing portion. The generated heat is the main cause of thermal deformation of the spindle head.
The spindle head is cooled by passing cooling oil cooled by a cooling device through the spindle head. The cooling device is
The cooling oil is always controlled to a set temperature.

This set temperature is often set to be the same as room temperature. This means that when the set temperature is lowered below room temperature,
Condensation forms on the spindle head. Therefore, cooling oil is not normally set at a temperature lower than room temperature.

[Problems to be Solved by the Invention] It has been experimentally known that the amount of heat generated from the spindle head is related to the rotational speed of the spindle. The conventional cooling device described above only indirectly controls the temperature of the spindle head by controlling the heat generated energy of the spindle head by simply keeping the cooling oil constant. Temperature changes within the spindle head are not directly fed back to the cooling system. If the cooling device has a sufficient capacity for the amount of heat generated by the spindle, even if the amount of heat generated by the spindle head changes, the steady-state deviation at the set temperature will be small and there will be no problem. However, the cooling device
inevitably become larger.

Particularly in the case of a machine tool in which the spindle rotational speed fluctuates rapidly, the temperature of the spindle head will rise unless these thermal fluctuations are quickly dealt with. Therefore, the temperature of the spindle head increases the displacement of the spindle head, resulting in a reduction in machining accuracy. Further, in the conventional cooling system described above, there was a large time delay in temperature correction operation, and the amount of steady-state deviation in which the temperature fluctuated up and down was large. The present invention solves the above-mentioned problems and achieves the following objects.

SUMMARY OF THE INVENTION An object of the present invention is to provide a spindle rotation speed synchronized type spindle cooling device that controls the cooling device according to the rotation speed of the spindle per unit time.

Another object of the present invention is to provide a spindle rotation synchronized type spindle cooling device in which the response speed of the cooling device is increased and the steady-state deviation of the temperature of the spindle head is small.

[Means for solving the above problems] The present invention takes the following means to solve the above problems.

In a rotating shaft cooling device having a cooling means for cooling cooling oil for cooling sliding friction heat of a rotating shaft of a machine tool or the like, and a cooling control means for controlling the cooling means, the rotational speed of the rotating shaft and a calorific value calculation means for calculating the calorific value by integrating the time and time, and inputting the output of the calorific value calculating means to the cooling control means, and controlling the cooling means before the temperature of the cooling oil changes to control the rotation. This is a main shaft cooling control device that synchronizes the number of revolutions of the main shaft and includes automatic temperature adjustment conversion means for keeping the temperature of the shaft constant.

[Operation] The number of rotations of the spindle per unit time is integrated, and the cooling device is controlled based on this integrated value to maintain the spindle head at a constant temperature.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. The machine tool 1 includes a spindle head 3 that rotatably supports the spindle with a bearing. The spindle cooling device 2 is a cooling device for cooling the spindle head 3. This cooling device itself is a known technology. The frictional work E generated per unit time due to the rotation of the main shaft varies depending on the type and structure of the bearing. For example, in the case of a journal bearing, it is known that E=2πnμWΥ. However, μ: coefficient of friction, W: vertical load on the main shaft, r: radius of the main shaft,
n: Rotation speed per unit time of the main shaft.

It can be seen that the amount of heat generated is proportional to the number of rotations per unit time. The rotation speed n per unit time is detected from a shaft encoder provided on a servo motor for driving the main shaft. The total amount of heat generation is the value obtained by integrating the amount of frictional work E per unit time over time. The calorific value calculation unit 4 is a calculation means that calculates the calorific value for each unit time. The calorific value calculation section 4 is a known calculation means composed of a microcomputer.

The output signal from the calorific value calculation section 4 is input to the automatic temperature adjustment conversion control section 5. The automatic temperature adjustment conversion control section 5 receives an output signal from the calorific value calculation section 4 and outputs a control signal to the main shaft cooling device 2. This output signal is an analog signal such as a voltage. In the oil tank 10 of the main shaft cooling device 2,
Cooling oil is stored. A pump 1 is installed in the oil tank 10.
1 suction pipe 12 is inserted. The suction pipe 12 is
This is for pumping cooling oil from an oil tank 10 with a pump 11. The cooling oil is sent to the spindle head 3 through the pipe 13 to cool the spindle head 3.

The pump 11 is rotationally driven by a motor 15.
The motor 15 is controlled by a control section 26. The cooler 16 compresses refrigerant gas (fluorocarbon) for cooling the cooling oil in the oil tank 10 . The refrigerant gas cooled by the cooler 16 passes through the cooling pipe 17 and enters the oil tank 10 to cool the cooling oil in the oil tank 10 . The propeller 18 stirs the cooling oil in the oil tank 10 to keep it at a uniform temperature. The propeller 18 is rotationally driven by a motor (not shown) that drives the cooler 16.

The hot water temperature detection sensor 20 detects the temperature of cooling oil in the oil tank 10. Oil temperature detection sensor 20
is a thermistor resistance thermometer that uses a semiconductor as an element. The output of the oil temperature detection sensor 20 is input to the oil temperature detection section 21. The oil temperature detection section 21 amplifies the output signal, which is an analog quantity, from the oil temperature detection sensor 20 and sends it to the temperature difference calculation section 24 . Room temperature detection sensor 2
Similarly, 3 is a thermistor resistance thermometer. The output of the room temperature detection sensor 23 is input to the room temperature detection section 22.

The signal input to the room temperature detection section 22 is amplified and sent to the temperature difference calculation section 24. Temperature difference calculation unit 24
compares the output values from the oil temperature detection section 21 and the room temperature detection section 22, calculates the difference in temperature between the two, and then outputs the result to the comparison section 2.
Send to 5. The output signal from the temperature difference calculation section 24 and the output signal from the automatic temperature adjustment conversion control section 5 are input to the comparison section 25 . The automatic temperature adjustment conversion control section 5 converts the digital signal from the calorific value calculation section 4 into an analog quantity such as voltage. For example, a plurality of relays R ₁ to Rn are selected to convert a digital signal into an analog quantity (not shown).

The comparison section 25 adds both input signals from the temperature difference calculation section 24 and the automatic temperature adjustment conversion control section 5 and sends the result to the control section 26 . The control unit 26 operates the cooler 16 by controlling it on and off according to the magnitude of the output signal of the comparison unit 25. A target value for keeping the temperature of the spindle head 3 constant (often room temperature) is controlled by the output of the automatic temperature adjustment conversion control section 5.

As understood from the above description, this embodiment can be said to be a cascade control system because the target value is controlled by the output of another control device. The cooling oil temperature is quickly corrected by the operations of the calorific value calculation section 4 and the automatic temperature adjustment conversion control section 5. Spindle head 3
Since the time constant of temperature rise is long, controllability is significantly improved.

Operation The flowchart shown in FIG. 2 shows the operation of the calorific value calculation section 5. As for the spindle rotation speed, the rotation speed of the spindle drive servo motor is sampled at every time interval T using a sample value signal (pulse signal). The sampled data is held in a hold circuit. In this example, sampling is performed every few seconds. In step _P1 , the timer TM1 determines the timing for converting the sampled data into temperature setting data, that is, data for controlling the main shaft cooling device 2.

In step _P2 , the sampling data is converted into temperature setting data. This converted data is output as a digital value to the automatic temperature adjustment conversion control section 5. The automatic temperature adjustment conversion control unit 5 selects a plurality of relays and converts a digital quantity into an analog voltage. In step _P4 , timer TM1 is initialized.

Initialize the sampled data in step _P5 . If NO at step P ₁ , step
Count TM1 at _P3 and go to step _P6 . In step _P6 , it is determined whether or not timer TM1 has timed up, and if YES, the process returns to step _P1 . If NO, proceed to step _P7 . In step _P7 , it is determined whether or not the main shaft is rotating, and if it is, the process proceeds to step _P8 . In step _P8 , Sc=Sn is determined.

However, S: Spindle rotational speed when the spindle rotation command is issued from the CNC device 6 Sn: Old rotational speed of the spindle when the spindle is rotating Tn: Time during which the spindle was rotating at the rotational speed of Sn In step _P9 , Save Sc rotation speed in Sn memory. At step _P11 , timer Tn is set and starts counting time. In step _P11 , it is determined whether the spindle has stopped. If YES, the calculation time of timer Tn is added at step _P12 . If step _P11 is NO, return to step _P1 . In step _P13 , timer Tn is reset.

At the same time, in steps P ₁₄ to P ₁₈ , the spindle rotation speed
Count the rotation time for Sn+ ₁ . In this way, the rotation time can be accumulated for each spindle rotation speed. The thus integrated data is processed using a predetermined coefficient, and is then processed by the comparison unit 25 of the main shaft cooling device 2.
is sent as an analog signal such as voltage.

[Other Embodiments] What is shown in FIG. 3 shows other embodiments. 1st
Components that are the same as those in the illustrated embodiment are designated by the same reference numerals. The calorific value calculated by the calorific value calculation unit 4 is transmitted to the calorific value communication unit 19. Calorific value communication section 19
sends the calculated calorific value digital signal to the calorific value receiver 27. The calorific value receiving unit 27 receives this signal, converts it into an analog value, and sends it to the control unit 26. The temperature regulator 28 is a set temperature for freely adjusting the temperature of the spindle head 3 to a desired temperature. Temporary cooling is performed based on the received calorific value data. However, this data will be discarded if supercooling occurs.

Although the above-mentioned embodiments are all main shaft cooling devices for machine tools, there is no need to be limited to this, and other devices may be used as long as the shaft rotates. Also,
In the embodiment described above, the rotation speed of the main shaft is detected from the shaft encoder, but it is also possible to read the S function (rotation speed command according to the ISO standard) command value of the NC program. In the embodiment described above, the vertical load W to the main shaft was not considered as constant, but the vertical load may be detected with a strain gauge or the like, and this detected value may also be included in the calculation of the amount of heat generated.

[Effects of the Invention] As described in detail above, since the temperature setting for cooling the spindle is changed in response to changes in the spindle rotation speed, fluctuations in the temperature of the spindle head are small. Therefore, the main shaft displacement can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a first embodiment of the present invention, and FIG.
The figure is a flowchart showing the operation of the calorific value calculation section.
FIG. 3 is a diagram showing another embodiment. 1... Machine tool, 2... Spindle cooling device, 3...
Spindle head, 4... calorific value calculation section, 5... automatic temperature adjustment conversion control section.

Claims (1)

[Claims] 1. A cooling means for cooling cooling oil for cooling the sliding friction heat of a rotating shaft of a machine tool, etc.;
A rotating shaft cooling device having a cooling control means for controlling the cooling means, a heating value calculating means for calculating a calorific value by integrating the rotational speed and time of the rotating shaft, and an output of the calorific value calculating means A spindle rotation speed synchronized spindle cooling control device comprising automatic temperature adjustment converting means inputted to a cooling control means and controlling the cooling means to keep the temperature of the rotating shaft constant before the temperature of the cooling oil changes. .