JPH0775814B2 - Method and device for controlling spindle temperature of machine tool - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention absorbs the heat generation of a spindle by changing the supply temperature of circulating fluid, and the temperature difference between the temperature of the spindle and the temperature of the machine body is the amount of heat generated by the spindle. The present invention relates to a spindle temperature control method for a machine tool and a device for controlling the temperature so that the machining temperature is kept constant regardless of changes in machining conditions that cause changes in temperature.

[Prior 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 separated from the spindle. Cause 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 Examined Patent Publication No. 48-3797. This discloses a liquid temperature control device that controls so that the liquid temperature of the circulating liquid always follows the fluctuation of the atmospheric temperature so as to keep a constant temperature difference with respect to the atmospheric temperature.

[Problems to be solved by the invention]

However, in the above-mentioned liquid temperature control device, the circulation time of the circulating liquid, the time from the heat from the main shaft, which is the heating element, to the circulating liquid, and the time delay until it is sensed as the output of the temperature detector have good responsiveness. It is difficult to control the oil temperature. 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 liquid temperature with good responsiveness.

Therefore, according to the present invention, in order to solve such a problem, the temperature difference between the main shaft portion and the machine body portion separated from the main shaft portion is constant even immediately after the machining conditions causing the change in the heat generation amount of the main spindle are changed. Therefore, it is intended to eliminate a processing error due to a change in thermal expansion of the main shaft with respect to the machine body.

[Means for solving problems]

In view of the above object, the present invention immediately heats or cools the circulating fluid supplied to the spindle head so as to reach a preset temperature when there is a change in the processing condition that causes the amount of heat generated by the spindle to change. . More specifically, first of all, a liquid having a cooling action in the spindle head is circulated between the liquid temperature control supply device and
Feedback control for detecting the temperature of the main spindle and the temperature of the machine body of the machine tool separated from the main spindle, and adjusting the circulating fluid temperature so that the temperature difference between the main spindle temperature and the machine body temperature becomes constant. In the method for controlling the spindle temperature of a machine tool, the fluid temperature of the fluid temperature adjusting and supplying device is preset and stored in correspondence with the machining conditions that cause the heat generation amount of the spindle to change, and the machining conditions are changed. At that point, the feedback control is stopped for a predetermined time, and when the feedback control is stopped, the supply temperature of the liquid temperature adjusting and supplying device is circulated to the set temperature corresponding to the changed machining condition, and the predetermined time elapses. A spindle temperature control method for a machine tool, characterized in that the circulating fluid temperature is adjusted after returning to the above-mentioned feel back control.

Secondly, a liquid temperature adjusting and supplying device that circulates a liquid having a cooling action in the spindle head and cools or heats the circulating liquid to adjust the supply liquid temperature, and a spindle part in the spindle head. A first temperature detector for detecting the temperature, and a second temperature detector for detecting the temperature of the machine body part of the machine tool separated from the main shaft part,
Control temperature command means for issuing a temperature control command to the liquid temperature control supply device so that the temperature difference between the spindle temperature and the machine body temperature detected by the first and second temperature detectors becomes constant, and Storage means for presetting and storing the supply liquid temperature of the liquid temperature adjusting and supplying device in correspondence with the processing condition causing the change in the amount of heat generation of the spindle, and the liquid temperature adjusting and supplying device when the processing condition is changed. Set liquid temperature command means for issuing a command to the liquid temperature adjusting and supplying device so that the supply liquid temperature of the storage device becomes the set temperature stored in the storage means, and from the adjusting temperature command means at the time when the processing conditions are changed. The command is stopped for a predetermined time so that the command from the set liquid temperature command means is issued to the liquid temperature adjusting and supplying device, and after the predetermined time has elapsed, the command from the set liquid temperature command means is stopped and the adjusted temperature command is issued. Command from the means to adjust the liquid temperature Providing spindle temperature control device for a machine tool, characterized by comprising a switching means adapted to emit to the sheet unit.

[Work]

With such a configuration, the feedback control is temporarily stopped immediately after the machining condition is changed, the supply liquid temperature is actively adjusted to a preset temperature suitable for the machining condition stored in advance, and the predetermined time elapses. When the supply liquid temperature reaches the set temperature, the feedback control is restored again, so that it is possible to quickly respond to changes in the amount of heat generated from the spindle due to changes in the machining conditions such as spindle speed and machining load.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the accompanying drawings. FIG. 1 is a system diagram of a spindle temperature control device according to the present invention, FIG. 2 is a flow chart for explaining its operation, FIG. 3 is an explanatory view of the principle of the oil temperature adjusting feeder shown in FIG. 1, and FIG.
FIG. 5 is a temperature detection circuit diagram used in the figure, and FIG. 5 is a differential temperature detection circuit diagram used in the adjustment temperature command means of FIG.
FIG. 6 is a measurement data diagram showing the effect obtained by using the spindle temperature control device of FIG.

First, referring to FIG. 1, in the structure of a machine tool, a spindle head 16 is attached to a column 12 erected on a bed 10 which is a base so as to be vertically movable. A head shaft 18, which is rotatably supported by a horizontal bearing, is housed and held in a head 16. On the other hand, a work table 14 for mounting and fixing the work W is provided on the bed 10 in front of the column 12 and is movable in the left-right direction or the front-back direction. In the present embodiment, the machine tool having the above configuration is an NC machine tool whose drive is controlled by the NC device 20.

Since the main shaft 18 rotates and receives machining resistance generated between the work and the tool, the main shaft 18 generates heat due to frictional resistance with the support portion and the like. A pump 92 (see FIG. 3) in the oil temperature adjusting feeder 22 absorbs the generated heat to prevent the temperature of the main shaft 18 and its surroundings from increasing and lubricates the bearing portion.
Circulate using. That is, it is supplied to the spindle head 16 via the outward path 42, and after performing the cooling and lubrication effect, the return path
It is configured to return via 44.

Oil temperature adjustment feeder to adjust the temperature of this circulating oil to an appropriate temperature
22 includes an oil temperature controller 24 having a cooler and a heater. On the other hand, in order to maintain the temperature difference between the temperature of the main shaft portion and the temperature of the machine body part separated from the main shaft portion at a predetermined value, the oil temperature in the return path 44 is a first temperature detector as a substitute for the main shaft portion temperature. Measured with the first thermistor resistance thermometer 40, the bed 10 is used as a representative of the fuselage part, and the temperature is measured with the second thermistor resistance thermometer 38 which is the second temperature detector. It is installed in 10 suitable places. These measured values are transmitted to the adjustment temperature command means 28, and the adjustment temperature command means 28
Inside, a temperature command is transmitted to the oil temperature controller 24 based on the measured temperatures of both by a method described later, and the oil temperature controller 24 heats or cools the circulating oil based on the command. In this way, feedback control for maintaining the differential temperature at a predetermined value is performed.

However, if only the above feedback control is performed, it is difficult to perform quick temperature control according to the change in heat generation immediately after a change in the machining conditions such as a change in the rotation speed of the spindle 18, a change in machining resistance, or a change in machining resistance. The machining conditions that cause the amount of heat generated by the spindle to change include spindle speed, machining resistance, tool feed rate, tool depth, tool type, workpiece type, and the presence or absence of cutting oil. We paid attention to the fact that there is a nearly constant relationship between these processing conditions and the amount of heat generated by the spindle. Therefore, a set oil temperature command means 32 is provided, and for example, the NC device 20 described above
Receives the spindle speed command 46, which is one of the machining conditions, from
A temperature command is issued to the oil temperature controller 24 in order to adjust the supply oil temperature of the circulating oil to a set temperature corresponding to the commanded rotation speed for a predetermined time after the change of the rotation speed. At this time, the switching means 34, which has received the signal from the set temperature command means 32, stops the temperature command from the adjusted temperature command means 28 to the oil temperature controller 24 for a predetermined time, and then transmits again. Furthermore, in order to determine the command temperature transmitted by the set temperature command means 32, it is necessary to conduct an experiment in advance to know the appropriate supply oil temperature for various spindle rotation speeds.
The set temperature thus determined is stored in the storage means 36 as a correspondence table with the spindle rotational speed. Table 1 shows an example of this correspondence table. The set temperature of the circulating oil in Table 1 is shown as a set adjustment temperature that should be minus the main shaft target temperature obtained by adding the temperature difference to the bed temperature. The correspondence table can be input to the set temperature command means 32 via an operation panel (not shown) electrically connected to the storage means 36.

When a spindle rotation speed that is not in the above table is commanded, the set adjustment temperature is determined by proportionally distributing the rotation speed in the table above and below the rotation speed. Furthermore, the data in Table 1 above is an example, and since it changes depending on the type of machine tool, the type of circulating oil, and other conditions, the set temperature of the circulating oil is stored parametrically.
It has an operation panel that can be stored in the 36.

When a stop signal for the spindle 18 is sent from the NC device 20, the circulation valve 26 is closed to stop the supply of the circulating oil to the spindle head 16, and the circulation valve 26 operates so as to run idle.

Next, the operation of this system will be described with reference to FIG.
When the NC device 20 issues a command for the spindle speed in step 52, the circulation valve 26 opens in step 54, and oil is supplied to the spindle head 16. In this case, if the circulation valve 26 is originally in the open state, the open state is maintained, and if the closed state is the open state. Then, in step 56, using the current bed temperature measurement data, the command temperature obtained by subtracting the set adjustment temperature as shown in Table 1 from the target temperature of the main spindle (that is, the current bed temperature + differential temperature) is used. Command the oil temperature controller 24. At the same time, as described above, the command signal from the regulated temperature command means 28 to the oil temperature controller 24 is interrupted by the switching means 34, and in step 60, this state is continued for a predetermined time, for example, 3 minutes by the action of the timer. After that, the command from the set oil temperature command means 32 to the oil temperature controller 24 is cut off again, and the oil temperature controller 24 is operated by the adjusted temperature command means 28 (step 62). The predetermined time set in the timer in step 60 can be parametrically changed.

In step 62, the temperature obtained by subtracting the target temperature of the main spindle (ie, the current bed measured temperature + differential temperature) from the current measured temperature of the main spindle (oil temperature of the return path 44), that is, the error temperature, is commanded one time before. The temperature subtracted from the specified temperature is set as the current command temperature. While the main shaft 18 is rotating at the same rotation speed, only the feedback control of step 62 is continued without passing through steps 56 and 60 by step 68. The above steps are repeated until there is a stop command for the spindle 18 (step 64), and when the circulation valve 26 receives the spindle stop command from the NC device 20, step 66
Thus, the circulation valve 26 is closed and the oil supply to the spindle head 16 is stopped. If there is no spindle stop command and there is a rotation speed change command, the circulation valve remains open.
I do. Even when the machine tool shifts from the stopped state for a long time to the operating state such as the first thing in the morning, the steps 54, 56 and 60 are sequentially processed.

Here, it was explained that the temperature difference between the spindle temperature and the bed temperature is controlled to be always constant, but the temperature difference is zero, that is, the spindle temperature is controlled to be always equal to the bed temperature. Then, the thermal balance of the machine tool becomes the best. In this case, the formula in step 56 is the command temperature = current bed temperature-set adjustment temperature, and the formula in step 62 is
Command temperature = previous command temperature− (current spindle temperature−current bed temperature).

FIG. 3 shows a principle diagram of the oil temperature adjusting and supplying device 22 (FIG. 1), and since it is a known technical content, it will be briefly described. As the cooler, the refrigerant gas 70 that has cooled the circulating oil 75 by passing through the evaporator 73 is made high in temperature and pressure by the compressor 76,
The heat is liquefied through a condenser 80 having a fan 78, is atomized through an expansion valve 72, and enters the evaporator 73 in a cooling tank 74 that cools the circulating oil 75. Then, heat is absorbed from the circulating oil 75 and vaporized. Further, a heater 82 is provided in the middle of the flow path of the circulating oil 75, and the cooler and the heater 82 are connected to each other according to the command temperature from the adjusting temperature command means 28 or the set oil temperature command means 32 shown in FIG. Switch operation. This switching means is omitted.

On the other hand, the circulating oil 75 is circulated by a pump 92, and two valves 88 and 90 are provided in the middle thereof. The above-mentioned circulation valve open state means that the valve 88 is open and the valve 90 is closed, while the closed state means that the valve 88 is closed.
Means that the valve is closed and the valve 90 is opened.

FIG. 4 shows an example of a circuit for extracting the temperature as a voltage by using the thermistor resistance thermometer 38 or 40. This is a well-known circuit using the operational amplifier 106 and the like, and the terminal 104 is an output terminal.

Further, FIG. 5 shows an example of a circuit for extracting the temperature difference between the temperature of the bed 38 and the oil temperature of the return path 44 measured by using the thermistor resistance thermometers 38 and 40 as a voltage. Operational amplifier
This is a well-known circuit using 108 and the like, and the terminal 110 is an output terminal.

FIG. 6 (a) is a measurement result when the spindle temperature control is performed only by the conventional feedback control, and FIG. 6 (b) is shown.
Is a measurement result in the case of using the spindle temperature control device of the present invention, in both measurement results the vertical axis is the temperature, the horizontal axis is the time, the alternate long and short dash line 114,114 'indicates the temperature fluctuation of the bed 10,
Dashed lines 116 and 116 'indicate fluctuations in the oil temperature supplied from the oil temperature adjusting feeder 22 to the spindle head 16, and solid lines 112 and 112' indicate the oil temperature in the return path 44,
That is, it shows the temperature fluctuation of the main shaft portion. (A) shows the result when the spindle speed is changed from 0 to 4000 rpm, that is, the feedback control, that is, the step 62 in FIG. 2 is not performed and only 62 is performed. Does not approach the target bed temperature 114 '. The temperature fluctuation 112 'of the main shaft during this time is about 3 ° C. On the other hand, in (b), the spindle is first rotated at 4000 rpm for 7 minutes and then 2
The spindle was rotated at 400 rpm for 6 minutes. At this time, the time during which the command from the adjusting temperature command means 28 is stopped in step 60 of FIG. 2 is 3 minutes. As can be seen from this figure, since the supply oil temperature 116 does not have an overshoot like 116 'in (a), the spindle temperature 112 approaches the bed temperature 114 in about 3 minutes. During this time, the temperature fluctuation 112 of the main shaft portion is as good as 1 ° C. or less. In this measurement experiment, the temperature of the main shaft and the temperature of the bed were controlled to match. The bed temperatures 114 and 114 'are almost constant at 22 ° C. Further, in (b), when the spindle speed is reduced from 4000 rpm to 2400 rpm, the supply oil temperature 116 rises because the amount of heat generated from the spindle decreases, so that the heating oil temperature 116 for heating is increased by the heater. 82 is activated.

In the embodiment described above, the spindle rotation speed is taken as the machining condition that causes the heat generation amount of the spindle to change, but the same idea can be applied to other machining conditions such as machining resistance and tool feed speed.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, it becomes possible to control the oil temperature with good responsiveness even immediately after the machining conditions that cause the heat generation amount of the main spindle to change. There is no change in the relative thermal expansion displacement of the work piece, so that there is no error in the relative position between the tool attached to the spindle and the work on the work table, and the machining accuracy is improved.

[Brief description of drawings]

FIG. 1 is a system diagram of a spindle temperature control device according to the present invention,
FIG. 2 is a flow chart for explaining the operation thereof, FIG. 3 is an explanatory view of the principle of the oil temperature adjusting feeder shown in FIG. 1, FIG. 4 is a temperature detection circuit diagram used in FIG. 1, and FIG. FIG. 6 is a diagram showing a differential temperature detecting circuit used in the adjusting temperature command means shown in FIG.
The measurement data figure which shows the effect acquired using the spindle temperature control apparatus of the figure. 10 …… Bed, 16 …… Spindle head, 18 …… Spindle, 22 …… Oil temperature adjustment feeder, 24 …… Oil temperature controller, 26 …… Circulation valve, 28 …… Adjusted temperature command means, 32 …… Setting oil temperature command means, 34 ... switching means, 36 ... storage means, 38 ... second thermistor resistance thermometer, 40 ... first thermistor resistance thermometer.

Claims (11)

[Claims] 1. A liquid having a cooling action in a spindle head is circulated between a liquid temperature adjusting feeder and a temperature of a spindle portion and a temperature of a machine body portion of a machine tool separated from the spindle portion are detected, In a spindle temperature control method for a machine tool, which performs feedback control to adjust the circulating fluid temperature so that the temperature difference between the spindle temperature and the machine body temperature becomes constant, the spindle temperature of the liquid temperature adjusting feeder is adjusted to the spindle temperature. Is set and stored in advance corresponding to the processing conditions that cause the change in the heat generation amount of, and the feedback control is stopped for a predetermined time when the processing conditions are changed,
When the feedback control is stopped, the supply temperature of the liquid temperature adjusting and supplying device is circulated at the set temperature corresponding to the changed processing condition, and is circulated, and after the lapse of the predetermined time, is returned to the feedback control to adjust the circulating liquid temperature. A method for controlling a spindle temperature of a machine tool, characterized in that 2. The spindle temperature control method for a machine tool according to claim 1, wherein the temperature difference between the spindle temperature and the machine body temperature is constant at zero. 3. The supply liquid temperature of the liquid temperature adjusting and supplying device corresponding to the preset and stored processing conditions is set as an adjustment temperature to be adjusted with respect to the temperature difference between the spindle temperature and the machine body temperature. The method for controlling the spindle temperature of a machine tool according to claim 1 or 2, wherein the method is stored. 4. A spindle temperature control method for a machine tool according to any one of claims 1 to 3, wherein the machining condition is a rotational speed of the spindle. 5. A liquid temperature adjusting feeder for circulating a liquid having a cooling action in the spindle head and cooling or heating the circulating fluid to adjust the supply liquid temperature, and a temperature of a spindle portion in the spindle head. Temperature detector for detecting the temperature, a second temperature detector for detecting the temperature of the machine body of the machine tool separated from the spindle, and a temperature for the spindle detected by the first and second temperature detectors. And a control temperature command means for issuing a temperature control command to the liquid temperature control supply device so that the temperature difference between the body temperature and the body temperature is constant,
Storage means for presetting and storing the supply liquid temperature of the liquid temperature adjusting and supplying device in correspondence with the processing conditions that cause the heat generation amount of the spindle to change, and the liquid temperature adjusting supply when the processing conditions are changed. Liquid temperature adjusting and supplying means for issuing a command to the liquid temperature adjusting and supplying device so that the supply liquid temperature of the vessel becomes the set temperature stored in the storing means, and the adjusting temperature commanding means when the processing conditions are changed. Is stopped for a predetermined time to issue a command from the set liquid temperature command means to the liquid temperature adjustment supply device, and after the predetermined time has elapsed, the command from the set liquid temperature command means is stopped to set the adjusted temperature. A spindle temperature control device for a machine tool, comprising: switching means adapted to issue a command from a command means to the liquid temperature adjusting and supplying device. 6. The first temperature detector detects the return liquid temperature of the circulating liquid from the spindle head to the liquid temperature adjusting and supplying device as the temperature of the spindle portion in the spindle head. 5. A spindle temperature control device for a machine tool according to claim 5. 7. The machine tool according to claim 5, wherein the second temperature detector detects a base temperature of the machine tool as a machine body temperature of the machine tool. Spindle temperature control device. 8. The storage device according to claim 5, wherein the storage means is capable of parametrically inputting the supply liquid temperature of the liquid temperature adjusting supply device which is preset and stored. Machine tool spindle temperature control device. 9. The method according to claim 5, wherein the switching means is capable of parametrically inputting a time for stopping the command to the liquid temperature adjusting and supplying device of the adjusting temperature commanding device. A spindle temperature control device for a machine tool according to item 1. 10. The liquid temperature adjusting feeder stops the supply of the circulating fluid to the spindle head while the spindle is stopped, and circulates the circulating fluid to the spindle head while the spindle is rotating. The spindle temperature control device for a machine tool according to claim 5, further comprising a valve. 11. The spindle temperature control device for a machine tool according to claim 5, wherein the machining condition is a rotational speed of the spindle.