Coolant systems and machine tools

Abstract

The present invention relates to: a coolant apparatus that is configured to suppress temperature rise of a coolant; and a machine tool having the coolant apparatus mounted thereon. The coolant apparatus has: a coolant tank which can store therein a coolant supplied into a machining chamber for workpiece machining; a coolant pump which supplies used coolant in the coolant tank into the machining chamber; an intra-tank temperature sensor which measures the temperature of the coolant in the coolant tank; and a control device which, on the basis of a measurement value obtained by the intra-tank temperature sensor, regulates the revolving speed of a pump motor that drives the coolant pump.

Description

Technical Field

[0001] The present invention relates to a coolant device for suppressing the influence of temperature rise of coolant used for cooling and cleaning in workpiece machining, and to a machine tool provided with the coolant device. Background Art

[0002] In machine tools, coolant is used not only to reduce machining heat but also to provide lubrication and flush chips away from machining sites. After being used, the coolant is returned to the coolant tank and supplied back into the machining chamber by a coolant pump. As coolant that is repeatedly used absorbs heat from the coolant pump which generates heat during continuous operation, its temperature gradually increases, which would adversely affect workpiece machining if left unaddressed. For example, heat from the coolant injected into the machining chamber is transferred to the drive units, and the slight thermal deformation caused thereby affects the machining of workpieces that require high precision.

[0003] Patent Document 1 below discloses a machine tool that adjusts the temperature of repeatedly used coolant. The coolant tank of the machine tool is provided with a temperature adjustment tank for storing coolant from which chips and the like have been removed via a filter, and a temperature adjustment device is connected to the temperature adjustment tank. The temperature adjustment device suppresses the temperature rise of the coolant, and is configured to circulate the cooled coolant between itself and the temperature adjustment tank. Prior Art Documents Patent Documents

[0004] Patent Document 1 International Publication WO2017-122288 Patent Document 2 Japanese Unexamined Patent Publication No. 2016-97485 Summary of the Invention Problems to be Solved by the Invention

[0005] However, depending on the machining process of the workpiece, strict control of the coolant temperature may not be required. In such cases, installing an expensive temperature control device would be unnecessarily costly. On the other hand, if no temperature control is performed, the coolant temperature will rise, which could lead to a decrease in machining accuracy if left unchecked. Therefore, it is necessary to suppress the rise in coolant temperature that would affect machining. Thus, there is a need to suppress the rise in coolant temperature to a certain extent without incurring significant costs, in order to maintain the machining accuracy of the workpiece.

[0006] Therefore, the present invention aims to solve these problems by providing a coolant system equipped with a configuration that suppresses the temperature rise of the coolant, and a machine tool equipped with the coolant system. [Means for solving the problem]

[0007] A coolant system according to one aspect of the present invention includes a coolant tank for storing coolant supplied to a machining chamber where workpieces are machined, a coolant pump for supplying used coolant from the coolant tank to the machining chamber, and a tank temperature sensor for measuring the temperature of the coolant in the coolant tank. A temperature sensor for the drive unit measures the temperature of a column that supports a drive device for positioning a tool within the machining chamber, The system includes a control device that adjusts the rotational speed of the pump motor that drives the coolant pump based on the measurement value of the tank temperature sensor. Furthermore, the control device adjusts the rotational speed of the pump motor when the measured values ​​from the tank temperature sensor and the drive unit temperature sensor exceed predetermined temperatures set in advance. .

[0008] A machine tool in another aspect of the present invention includes a machining device for performing predetermined machining on a workpiece with a tool in a machining chamber, a coolant device for repeatedly supplying used coolant, which has flowed from the machining chamber and accumulated in a coolant tank, back to the machining chamber by a coolant pump, and a tank temperature sensor for measuring the temperature of the coolant in the coolant tank. and a temperature sensor for the drive unit that measures the temperature of the column supporting the drive unit that positions the tool within the machining chamber. A tank temperature sensor is provided. and the temperature sensor for the drive unit and Measurement values When the temperature exceeds the predetermined temperature set in advance for each deviceThe system includes a control device that adjusts the rotational speed of the pump motor that drives the coolant pump. [Effects of the Invention]

[0009] According to the above configuration, during workpiece machining in the machining chamber, coolant is supplied to lubricate the machining point and wash away chips. This coolant flows into a coolant tank and is stored there, and then repeatedly supplied back into the machining chamber by a coolant pump. As the coolant gradually heats up, it begins to affect the machining process. Therefore, the coolant temperature in the coolant tank is measured by a tank temperature sensor, and the control device adjusts the rotation speed of the pump motor based on the measured value. This suppresses the heat generated by the coolant pump, thereby also suppressing the rise in coolant temperature. [Brief explanation of the drawing]

[0010] [Figure 1] This is a side view of the internal structure of one embodiment of a machine tool. [Figure 2] This is a perspective view showing the coolant tank. [Figure 3] This is a simplified circuit diagram showing one embodiment of a coolant system. [Figure 4] This is a block diagram representing the control system of a machine tool. [Figure 5] This is a flowchart diagram for executing the pump operation switching program. [Figure 6] This is a line graph showing the temperature change of the coolant as measured by a temperature sensor inside the tank. [Modes for carrying out the invention]

[0011] A coolant system according to the present invention and an embodiment of a machine tool equipped with the coolant system will be described below with reference to the drawings. Figure 1 is a side view of the internal structure of an embodiment of a machine tool. The coolant system according to the present invention can be used with various machine tools, and the machine tool 1 shown in Figure 1 is an NC lathe, which is one example. The machine tool 1 is mounted on a movable bed 14 equipped with wheels and is configured to move in the front-rear direction (Z-axis direction) along rails 13 laid on the upper surface of the base 3. The movable bed 14 is equipped with various drive devices such as a spindle unit 5, and the drive of the various drive devices is controlled by a control device 6 mounted at the rear of the machine body.

[0012] The spindle unit 5 is equipped with a spindle chuck 11 on a rotatable spindle, and rotates the gripped workpiece W using a spindle motor. The machine tool 1 is equipped with a turret unit 7 for selecting a tool from a plurality of tools that is suitable for workpiece processing. The turret unit 7 has a tool post 12 to which multiple tools are attached, and selects and positions the tool to be used for processing by swivel indexing. The drive devices that move the tool to the processing position of the workpiece W are a Z-axis drive device 8 that moves the tool in the Z-axis direction, which is the front-to-back direction of the machine body, and an X-axis drive device 9 that moves the tool in the X-axis direction, which is the up-and-down direction of the machine body.

[0013] In machine tool 1, the workpiece W is gripped in the spindle chuck 11 by transfer with an automatic workpiece transfer machine (not shown), and rotation is applied by the drive of the spindle unit 5. In the turret unit 7, the tool to be used for machining the workpiece W is selected by swivel indexing. Then, the tool, along with the turret unit 7, moves in the machining direction by the drive of the Z-axis drive unit 8 and the X-axis drive unit 9, and the predetermined machining is performed on the workpiece W. After machining the workpiece W, the machined workpiece W is replaced with a new workpiece W in the spindle chuck 11, and the automatic machining of workpiece W is repeated.

[0014] In the machine tool 1, a coolant tank 15 is provided below a processing chamber 10 where machining is performed, and chips and the like generated by machining a workpiece W are washed away by coolant and stored in the coolant tank 15. Here, FIG. 2 is a perspective view showing the coolant tank 15. A chip conveyor 18 is incorporated inside the coolant tank 15, and an input port 19 opened so as to be positioned at the bottom of the processing chamber 10 is formed. Chips generated by machining are washed away by the coolant supplied into the processing chamber 10, enter from the input port 19 together with the coolant, and are stored in a storage tank of the chip conveyor 18. Then, by driving the chip conveyor 18, only the chips are conveyed out of the machine, and discharged and recovered to an external recovery box.

[0015] The machine tool 1 is provided with a coolant device so that coolant can be used repeatedly. In the coolant device, a coolant pump 16 pumps up the coolant stored in the coolant tank 15 and feeds it back to the processing chamber 10. For example, in the storage tank of the chip conveyor 18, a drain opening closed by a punched metal with fine pores or the like is formed, and the coolant flowing out from the drain opening is stored in the coolant tank 15. Then, the used coolant is filtered and repeatedly supplied back to the processing chamber 10.

[0016] FIG. 3 is a schematic circuit diagram showing such a coolant device in a simplified manner. In the coolant device 2, a cylindrical strainer 17 is provided on the suction port side of the coolant pump 16, and a pipe 28 is connected to the secondary side. Specifically, as shown in FIG. 2, a pump chamber surrounded by a side wall 22 is formed at a corner of the coolant tank 15, and the coolant pump 16 provided with the strainer 17 is installed therein. A suction window 23 fitted with a mesh plate is formed in the side wall 22, and the structure is configured such that the coolant in the coolant tank 15 is drawn into the pump chamber 21 and then sucked up by driving the coolant pump 16.

[0017] Returning to FIG. 3, a pipe 28 connected to the coolant pump 16 extends toward the machining chamber 10, and a cleaning-side flow path 281 and a machining portion-side flow path 282 are formed, for example, by branching in the middle. The cleaning-side flow path 281 is a flow path that supplies coolant for flowing chips accumulated at the bottom of the machining chamber 10 to the input port 19, and the machining portion-side flow path 282 is a flow path for injecting coolant that lubricates and cools the machining point of a workpiece W and further flushes away chips. The machining portion-side flow path 282 is formed so as to pass through the tool post 12 of the turret device 7 to reach the machining point of the workpiece W.

[0018] The coolant device 2 of the present embodiment is provided with temperature sensors 25, 26 for measuring temperature changes related to coolant, and is connected to the control device 6. This configuration is for controlling the driving of the coolant pump 16 according to the measured values of the temperature sensors 25, 26, and a pump operation switching program is stored in the control device 6. The temperature sensor 25 is an in-tank temperature sensor disposed inside the coolant tank 15 and directly measures the temperature change of the coolant. Further, the temperature sensor 26 is attached to a column 29 that supports the Z-axis drive device 8 and the X-axis drive device 9, and is a drive portion temperature sensor for measuring temperature changes near the drive portion that are affected by the temperature of the coolant.

[0019] FIG. 4 is a block diagram showing a control system of the machine tool 1. The control device 6 of the machine tool 1 is mainly composed of a computer including a CPU 41, and storage devices such as a ROM 42, a RAM 43, and a non-volatile memory 44, and is connected to the coolant device 2, a spindle device 5, the turret device 7, the Z-axis drive device 8, the X-axis drive device 9, and the like via an I / O 45. As shown in FIG. 3, the coolant device 2 is configured such that the control device 6 drives and controls the pump motor 27 of the coolant pump 16 based on signals from the temperature sensors 25 and 26.

[0020] The drive motors of each device, such as the coolant device 2 and the spindle device 5, are connected via driver circuits 47. The driver circuit 47 of the coolant device 2 incorporates an inverter as a means of controlling the rotational speed of the pump motor 27, and the current of the pump motor 27 is controlled according to the command signal. In other words, the coolant device 2 of the machine tool 1 is configured to suppress the amount of heat generated by changing the rotational speed of the pump motor 27. Therefore, the control device 6 stores not only machining programs related to various machining processes, but also the pump operation switching program that drives and controls the pump motor 27 according to changes in the coolant temperature.

[0021] The coolant pump 16 generates heat during continuous operation, and the coolant, as it repeatedly passes through the coolant pump 16, absorbs heat and its temperature gradually rises. When the coolant is sprayed into the machining chamber 10, heat is transferred to the Z-axis drive unit 8 and the X-axis drive unit 9, among other components. For example, the Z-axis drive unit 8 and the X-axis drive unit 9 position the cutting edge of the tool relative to the workpiece W through the drive control of a servo motor using a ball screw. However, even slight changes in the dimensions of the screw shaft or other components due to heat can disrupt the extremely precise tool positioning control, reducing the machining accuracy of the workpiece.

[0022] Therefore, the pump operation switching program is configured to switch the rotation speed of the pump motor 27 depending on the situation in order to suppress the amount of heat generated by the coolant pump 16. In this embodiment, the operation of the coolant pump 16 can be switched in five stages depending on the situation of the machine tool 1. The situation for switching the operating speed of the coolant pump 16 (the rotation speed of the pump motor 27) is determined based on whether or not machining is being performed in the machine tool 1, the measured values ​​of the temperature sensors 25 and 26, etc.

[0023] Figure 5 is a flowchart for executing the pump operation switching program. First, the machine tool 1 starts operating its various components when the start switch is operated, and the coolant pump 16 in the coolant system 2 is also started by the pump motor 27. As a result, the coolant in the coolant tank 15 is drawn up by the coolant pump 16, pushed into the pipe 28, and sprayed into the machining chamber 10 through the cleaning side passage 281 and the machining side passage 282.

[0024] The coolant flows down through the machining chamber 10 and returns to the coolant tank 15, where it is circulated and pumped out again by the coolant pump 16. In the pump operation switching program, the workpiece machining status in the machine tool 1 is checked (S101), and if machining is to be performed on the workpiece W (S101:YES), then confirmation is performed based on the measurements of the temperature sensors 25 and 26. In this embodiment, of the two temperature sensors 25 and 26, the operation of the coolant pump 16 is switched based first on the measurement result of the temperature sensor 25 for the coolant.

[0025] Therefore, in the machine tool 1 where machining operations are performed on the workpiece W, it is checked whether the measurement value of the temperature sensor 25 exceeds the preset first switching temperature of the coolant (S102). If the coolant temperature has not risen and has not exceeded the first switching temperature (S102: NO), the drive control of the pump motor 27 corresponding to the normal output of the coolant pump 16 is performed (S103). In this embodiment, the rotation speed of the pump motor 27 when the coolant pump 16 is in normal operation is described as 100%.

[0026] When multiple workpieces are processed by the machine tool 1, the coolant pump 16 becomes hot over time, and the temperature of the coolant also rises. Therefore, if the measurement value of the temperature sensor 25 exceeds the first switching temperature (S102:YS), it is then checked whether the measurement value of the temperature sensor 26 exceeds the preset second switching temperature of the drive unit (S104). Specifically, it is checked whether the column 29 on which the Z-axis drive unit 8 and the like are mounted exceeds the preset second switching temperature (S104).

[0027] If the temperature does not exceed the second switching temperature (S104: NO), the pump motor 27 is operated at a reduced speed of 80% (S105). On the other hand, if the temperature exceeds the second switching temperature (S104: YES), the pump motor 27 is operated at a further reduced speed of 60% (S106). Here, Figure 6 is a line graph showing the temperature change of the coolant measured by the temperature sensor 25. The vertical axis shows the temperature of the coolant, and the horizontal axis shows the operating time of the coolant pump 16.

[0028] If the coolant pump 16 is running continuously, the coolant temperature tends to rise, as shown in the graph. The temperature indicated by the dashed line is the first switching temperature, and at point T1, the coolant temperature exceeds this limit. Therefore, the rotation speed of the pump motor 27 is reduced to 80% by the drive control in step S105 described above, which reduces the amount of heat generated by the coolant pump 16 and suppresses the rise in coolant temperature. However, heat still accumulates in the continuously running coolant pump 16, and the coolant temperature rises again.

[0029] If the temperature sensor 26 reading exceeds the second switching temperature (the temperature change graph is not shown), the drive control in step S106 reduces the rotation speed of the pump motor 27 to 60%. This reduces the amount of heat generated by the coolant pump 16, and the rise in coolant temperature at T2 is suppressed as shown in the graph in Figure 6. However, even in this case, heat accumulates in the coolant pump 16, which continues to operate, and the temperature rises again. However, by reducing the rotation speed of the pump motor 27 to 80% or 60%, it becomes possible to suppress the temperature rise while maintaining a certain amount of coolant discharge from the coolant pump 16.

[0030] Next, there will be periods when machine tool 1 is not processing workpiece W. For example, machine tool 1 forms a processing line with other machine tools, and workpiece W is automatically transported by an autoloader. Therefore, there may be waiting times when processing cannot be performed due to timing issues with other machine tools. Also, if a malfunction or other problem occurs before or after machine tool 1 in the processing line, processing will be suspended until repairs are completed. Conventionally, even when workpiece processing was not being performed, the coolant pump continued to operate normally.

[0031] In this embodiment, if the workpiece W is not processed for a certain period of time, the pump motor 27 is operated at a reduced rotational speed. Therefore, when the machine tool 1 is not in a state to process the workpiece W (S101: NO), the operation of the coolant pump 16 is switched to power-saving mode. This not only suppresses the heat generated by the coolant pump 16, as in steps S105 and S106, but also achieves a power-saving operation effect by reducing power consumption by lowering the rotational speed of the pump motor 27.

[0032] Therefore, if no machining command has been issued for machine tool 1 (S101: NO), a check is performed to see if there is a problem on the machining line (S107). If a malfunction or other problem occurs in another machine tool, the control device 6, upon receiving the stop command signal, determines whether to stop machining the workpiece (S107: YES), and further reduces the rotation speed of the pump motor 27 to 20% for low-speed operation (S108). Since repairs for malfunctions are expected to result in long downtimes, the rotation speed is reduced to the minimum to suppress heat generation in the coolant pump 16 and power consumption in the pump motor 27.

[0033] Next, if the control device 6 has not received a stop command signal (S107: NO), it is simply a waiting time between machining operations, so it is checked whether or not the pre-set unmachined confirmation time (e.g., 30 seconds) has been exceeded (S109). The unmachined confirmation time is counted by a timer from the time machining of the previous workpiece W is completed. If it is within the unmachined confirmation time (S109: NO), control is performed according to the measured values ​​of the temperature sensors 25 and 26 mentioned above, and if machining of the next workpiece W begins during that time (S101: YES), the count value is reset to zero.

[0034] On the other hand, if the processing of the next workpiece W is not started and the unprocessed confirmation time has elapsed, the control device 6 determines that processing of workpiece W should be stopped (S109: YES), and the rotation speed of the pump motor 27 is reduced to 40% for low-speed operation (S110). The timer count value is then reset to zero. This is a standby state that allows the coolant flow rate to be restored immediately when processing starts, and even then the rotation speed is reduced to suppress heat generation in the coolant pump 16 and power consumption in the pump motor 27.

[0035] Therefore, according to this embodiment, the operating speed of the coolant pump 16 (the rotation speed of the pump motor 27) is switched based on the measured values ​​of the temperature sensors 25 and 26, making it possible to suppress the rise in coolant temperature as shown in the graph of Figure 6 (at T1 and T2). In addition, by lowering the rotation speed of the pump motor 27 when the machine tool 1 is not processing a workpiece, an energy-saving effect can be obtained by reducing power consumption. Furthermore, the rise in coolant temperature affected by the coolant pump 16 can also be suppressed. In this embodiment, the rotation speed of the pump motor 27 is changed in five stages depending on the situation, so the above effects can be obtained without reducing the function of the coolant ejected in the processing chamber 10.

[0036] Although one embodiment of the present invention has been described, the present invention is not limited thereto, and various modifications are possible without departing from its spirit. In the above embodiment, an NC lathe was given as an example of a machine tool, but other NC machining equipment such as machining centers, or manually operated machine tools, may also be used as long as they are equipped with the coolant device according to the present invention. In the above embodiment, the rotation speed of the pump motor 27 was adjusted according to the measurements of the temperature sensors 25 and 26, but the rotation speed may be adjusted in multiple stages according to the measurements of the temperature sensor 25, which measures the temperature of the coolant. The coolant system is not limited to one incorporating the chip conveyor described in the above embodiment, but may have various configurations. [Explanation of symbols]

[0037] 1...Machine tool 2...Coolant system 5...Spindle unit 6...Control unit 7...Turret unit 8...Z-axis drive unit 9...X-axis drive unit 15...Coolant tank 16...Coolant pump 25,26...Temperature sensor 27...Pump motor

Claims

1. A coolant tank in which coolant supplied to the machining chamber where workpieces are processed is stored, A coolant pump that supplies used coolant from the coolant tank to the machining chamber, A tank temperature sensor for measuring the temperature of the coolant in the coolant tank, A temperature sensor for the drive unit measures the temperature of a column that supports a drive device for positioning a tool within the machining chamber, A control device that adjusts the rotational speed of the pump motor that drives the coolant pump based on the measurement value of the tank temperature sensor, It has, The control device is a coolant system that adjusts the rotational speed of the pump motor when the measured values ​​from the tank temperature sensor and the drive unit temperature sensor exceed predetermined temperatures set in advance.

2. A machining apparatus for performing predetermined machining operations on a workpiece using a tool within a machining chamber, A coolant system that repeatedly supplies used coolant, which has flowed from the processing chamber and accumulated in a coolant tank, back to the processing chamber by a coolant pump, The coolant tank is provided with an internal tank temperature sensor for measuring the temperature of the coolant, and the machining chamber is provided with a drive unit temperature sensor for measuring the temperature of a column supporting a drive unit for positioning a tool. The control device adjusts the rotation speed of the pump motor that drives the coolant pump when the measured values ​​from the internal tank temperature sensor and the drive unit temperature sensor exceed predetermined temperatures set in advance. A machine tool having

3. The machine tool according to claim 2, wherein the control device drives and controls the processing device, and adjusts the rotational speed of the pump motor based on the determination that the processing device has stopped processing the workpiece.

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