Coolant tank

Abstract

To provide a coolant tank that can discharge both of sludges and floating oil, which are contained in a coolant in a tank, with good efficiency.SOLUTION: A coolant tank comprises: a vertical type tank body; a first discharge port which discharges a coolant so as to revolve the same below the tank body; a second discharge port which opens toward an inner side of the tank body with respect to the first discharge port below the tank body, and discharges the coolant; an exhaust port provided at a bottom surface central part of the tank body; an oil skimmer which has a suction part floating in a liquid surface central part of the tank body, sucks oil contents separated from the coolant and floating toward a liquid surface from the suction part and collects the same; and a flow rate control part which controls a coolant discharge flow rate from each discharge port. The flow rate control part controls the coolant discharge flow rate so that a coolant revolution flow generated at a lower part in the tank body reaches a liquid surface peripheral part while decreasing the flow rate thereof toward an upper part in the tank body.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a coolant tank provided in a coolant circulation path of a machine tool.

Background Art

[0002] When machining a workpiece in a machine tool, chips are generated. If a large amount of chips accumulate inside the machine, it becomes difficult to continue machining. For this reason, conventionally, an operator has periodically stopped the operation of the machine tool and taken measures such as removing chips using an air blow. However, such manual removal of chips reduces the operating efficiency of the machine tool.

[0003] Therefore, in recent years, a system has been proposed in which a camera is installed inside the machine, the position of the chips is specified by analyzing the captured image, and the chips are automatically removed by discharging coolant toward the specified position (see Patent Document 1). A nozzle for discharging coolant is installed inside the machine. By changing the direction of this nozzle, the discharge direction of the coolant can be controlled.

[0004] A coolant tank for temporarily storing the coolant discharged from inside the machine is provided in the coolant circulation path of the machine tool. Since the coolant discharged from inside the machine contains sludge such as swarf, it is necessary to discharge it before the sludge solidifies inside the tank and remove it outside the tank.

[0005] Therefore, attempts have been made to use a vertical tank as the coolant tank, generate a swirling flow inside the tank, collect the sludge at the center of the bottom surface while discharging the coolant, remove the sludge with a filter outside the tank, and then supply it back inside the machine (see Patent Document 2). In such a system, in reality, sludge tends to accumulate also at positions away from the center of the bottom surface of the coolant tank. For this reason, while generating a swirling flow of the coolant inside the tank, the generation of stagnation at the center of the bottom surface is reduced so that the sludge can be efficiently discharged.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent No. 6887033 [Patent Document 2] International Publication No. 2023 / 021700 [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] By the way, the coolant contains lubricating oil (machine oil) in addition to sludge. When an upright tank as described above is adopted, components of lubricating oil with a specific gravity smaller than that of the coolant float to the liquid surface of the tank (this component is also called "floating oil"). Therefore, in order to maintain the cleanliness of the coolant in the tank, it is necessary to recover these floating oils. In this regard, measures such as floating an oil skimmer on the liquid surface to recover the floating oil are taken. However, since the floating oil is dispersed at the upper part of the tank and spreads over the entire liquid surface, there is room for improvement in that efficient recovery is difficult. [Means for Solving the Problems]

[0008] One aspect of the present invention is a coolant tank provided in a coolant circulation path of a machine tool. This coolant tank includes a vertical tank body for temporarily storing the coolant discharged from inside the machine tool, a first discharge port provided at the lower part of the tank body for discharging the coolant discharged from inside the machine tool so as to swirl along the inner peripheral surface of the tank body, a second discharge port provided at the lower part of the tank body and opening toward the inside of the tank body rather than the first discharge port for discharging the coolant discharged from inside the machine tool, a discharge port provided at the central part of the bottom surface of the tank body where the swirling center of the coolant is located for discharging the coolant toward the inside of the machine tool, an oil skimmer having a suction part floating at the central part of the liquid level of the tank body for sucking and collecting the oil separated from the coolant and floating toward the liquid level from the suction part, and a flow rate control part for controlling the discharge flow rate of the coolant from each discharge port. The flow rate control part controls the discharge flow rate of the coolant so that the swirling flow of the coolant generated in the lower part of the tank body reaches the peripheral part of the liquid level while reducing the flow rate toward the upper part of the tank body.

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a coolant tank capable of efficiently discharging both sludge and floating oil contained in the coolant in the tank.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

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Figure 13

Embodiments for Carrying Out the Invention

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view showing the appearance of a machine tool according to the embodiment. The machine tool 1 is configured as a complex processing machine that processes a workpiece into a desired shape while appropriately replacing tools. A processing chamber 2 is provided inside the device housing (inside the machine). In the processing chamber 2, a processing device for processing the workpiece is provided. On the side surface of the device housing, an operation panel 4 for operating the processing device is provided.

[0012] The machine tool 1 is provided with a coolant supply device 5 for supplying coolant to the processing chamber 2. In the coolant circulation path of the coolant supply device 5, coolant tanks (primary tank 6, secondary tank 8) for temporarily storing the coolant discharged from the processing chamber 2 are provided. The primary tank 6 is installed below the processing chamber 2, and the secondary tank 8 is installed behind the processing chamber 2. In this embodiment, the secondary tank 8 is a vertical tank, and while generating a swirling flow of the coolant in the tank, the generation of stagnation is reduced at the lower part of the tank. On the other hand, at the upper part of the tank, the swirling flow of the coolant is extended to the liquid surface peripheral part, and at the same time, it is controlled so that stagnation can occur at the central part of the liquid surface. Thereby, both the sludge and the floating oil contained in the coolant are efficiently collected, and a structure that can be discharged is adopted. Details thereof will be described below.

[0013] Figure 2 is a hardware configuration diagram of the machine tool 1. The machine tool 1 includes an information processing device 100, a machining control device 102, a machining device 104, a tool changer 106, a tool storage unit 108, and an imaging unit 110. The machining control device 102 functions as a numerical control unit and outputs a control signal to the machining device 104 according to a machining program (NC program). The machining device 104 moves a tool spindle (a "spindle unit" described later) according to an instruction from the machining control device 102 to machine a workpiece.

[0014] In addition to a mechanism for driving the spindle, the machining device 104 is provided with a coolant supply device 5 for supplying coolant to the machining chamber 2. The coolant is used as cutting oil for removing heat and lubricating the tool and the workpiece during machining, but is also used as a cleaning liquid for removing chips scattered in the machining chamber 2. The coolant supply device 5 is configured by arranging a coolant tank 112, a coolant discharge unit 114, a pump 116, a control valve 118, and a cyclone filter 120 in a coolant circulation path.

[0015] The coolant tank 112 is a tank for storing coolant and includes a primary tank 6 and a secondary tank 8. The coolant discharge unit 114 is a "discharge device" including a nozzle for discharging coolant into the machining chamber 2 and an actuator for driving the nozzle. The coolant circulates by driving the pump 116 and is supplied to the coolant discharge unit 114. The control valve 118 includes a plurality of on-off valves described later and switches the coolant flow path. The cyclone filter 120 is a centrifugal filter capable of centrifugally separating and collecting sludge from the coolant flowing through the coolant circulation path (details will be described later). The coolant supply device 5 further includes an oil skimmer 180. The oil skimmer 180 sucks and collects oil (floating oil) separated from the coolant and floating toward the liquid surface in the secondary tank 8 (details will be described later).

[0016] The information processing apparatus 100 includes an operation panel 4 and outputs a control command to the processing control apparatus 102 based on the operator's operation input. The information processing apparatus 100 also controls the screen displayed on the monitor of the operation panel 4 in response to the operator's operation input. The tool storage unit 108 stores tools. The tool changer 106 corresponds to a so-called ATC (Automatic Tool Changer), and takes out a tool from the tool storage unit 108 and exchanges it with the tool on the tool spindle according to the exchange instruction from the processing control apparatus 102.

[0017] The information processing apparatus 100 includes a flow rate control unit 101. The flow rate control unit 101 controls the pump 116 and the control valve 118. Thereby, the discharge amount of the coolant in the coolant tank 112 is adjusted, and the discharge amount of the coolant from the coolant discharge unit 114 is adjusted.

[0018] The imaging unit 110 is, for example, a camera equipped with an imaging element such as a CCD or a CMOS, and images an imaging area set in the processing chamber 2. As the "imaging area", an area where the presence of chips generated by the processing of the workpiece is assumed is set in advance. The angle of view of the camera is set so that the distribution and deposition status of chips can be grasped in a wide range in the processing chamber 2. The imaging unit 110 outputs the captured image to the information processing apparatus 100.

[0019] FIG. 3 is a perspective view showing the configuration in the processing chamber 2. FIG. 3(A) shows the state as viewed from obliquely above, and FIG. 3(B) shows the state as viewed from obliquely below. As shown in FIG. 3(A), the processing chamber 2 is surrounded by four side surfaces, and on one of the side surfaces, the spindle unit 10 is provided so as to be movable vertically and horizontally. The spindle unit 10 has a horizontal rotation axis, and a tool T is coaxially attached to the tip. The side surface facing the spindle unit 10 in the axial direction has a swing door 12. A support plate 14 extends horizontally from the swing door 12. The swing door 12 is a door that can rotate about a vertical axis.

[0020] A table 16 is provided below the support plate 14. A pallet 18 is detachably attached to the table 16, and a workpiece is placed and fixed on the pallet 18. By preparing a plurality of pallets 18 with the workpieces fixed thereon, the workpieces can be changed by exchanging the pallets 18, and time efficiency can be achieved.

[0021] The table 16 is movable in the axial direction of the spindle unit 10 and can also rotate in the horizontal plane. By rotationally driving the table 16, the workpiece on the pallet 18 can be rotated. By linearly driving the table 16, the workpiece approaches or separates from the tool T. That is, by controlling the rotation and movement of the table 16 and the movement of the spindle unit 10, the workpiece can be machined into a desired shape.

[0022] When the table 16 is at the position farthest from the spindle unit 10, the support plate 14 fits with the pallet 18. By rotating the swing door 12 in this state, the support plate 14 separates the pallet 18 from the table 16 and rotates integrally with the pallet 18. Thereby, the pallet 18 on which the machining of the workpiece has been completed is carried out of the machining chamber 2, and the pallet 18 on which the workpiece to be machined next is fixed can be carried into the machining chamber 2.

[0023] Below the table 16 and the spindle unit 10, a chip conveyor 20 for conveying chips outside the machining chamber 2 is provided. The table 16 moves above the chip conveyor 20. A shooter 22 is provided below the table 16. The shooter 22 guides the chips flowing from above by washing onto the chip conveyor 20.

[0024] The bottom surfaces located on both sides of the table 16 in the processing chamber 2 are inclined surfaces 24, which are inclined downward toward the shooter 22 so that the chips scattered during processing can easily flow to the shooter 22. Below the processing chamber 2, a primary tank 6 is arranged, and the coolant that has finished flowing the chips from inside the machine flows into and is collected by the chip conveyor 20 installed in the primary tank 6. Then, the coolant that has passed through the drum filter 44 in the chip conveyor 20 flows into the primary tank 6 and is temporarily stored (details will be described later).

[0025] As shown in FIG. 3(B), nozzles 28 for supplying coolant are installed at predetermined positions on the ceiling and side surfaces of the processing chamber 2. The nozzle 28 constitutes a coolant discharge portion 114 and is connected to the secondary tank 8 via a pipe (not shown) (details will be described later). The nozzle 28 is configured to be rotatable three-dimensionally. By rotating the nozzle 28, the discharge direction of the coolant can be controlled. By specifying the orientation of the nozzle 28, the coolant can be discharged toward the target in the processing chamber 2. The chips generated by the machining of the workpiece are washed away by the coolant and carried out of the processing chamber 2 by the chip conveyor 20.

[0026] Also, above the processing chamber 2, a plurality of cameras 30 for imaging the inside of the processing chamber 2 from above are installed. The camera 30 constitutes an imaging unit 110, images the machining state of the workpiece by the tool T, and images the chips generated by the machining (see FIG. 2). The imaging unit 110 outputs the captured image to the information processing device 100.

[0027] Each component of the information processing apparatus 100 is realized by hardware including an arithmetic unit such as a CPU (Central Processing Unit) and various computer processors, a storage device such as a memory and a storage, and a wired or wireless communication line connecting them, and software stored in the storage device and supplying processing instructions to the arithmetic unit. The computer program may be composed of a device driver, an operating system, various application programs located in upper layers thereof, and a library providing common functions to these programs.

[0028] When cleaning control inside the machine is performed by the coolant, the information processing apparatus 100 sets a target position for discharging the coolant based on the captured image acquired from the imaging unit 110. Then, an output is made to the processing control device 102 to issue a discharge command for the coolant directed to the target position. This discharge command includes information specifying the position for discharging the coolant (such as information specifying the discharge path). The processing control device 102 drives the coolant discharge unit 114 in response to this discharge command and controls the discharge of the coolant.

[0029] The spindle unit 10 is a so-called through spindle coolant device and holds a tool T in which an internal passage 32 for discharging the coolant is formed. At the tip of the tool T, a discharge port 34 is provided which forms one end of the internal passage 32 and discharges the coolant. The spindle unit 10 is formed with a communication passage 36 (see FIG. 3) that communicates the internal passage 32 of the tool T with the coolant circulation path. By discharging the coolant from the tip of the tool T during machining, it is possible to improve machining accuracy, shorten machining time, extend the life of the tool, and improve chip discharge performance. The spindle unit 10 to which the tool T is attached functions as the "first discharge unit".

[0030] FIG. 4 is a diagram schematically showing the configuration of the coolant supply device 5. The coolant supply device 5 has a coolant circulation path connecting the processing chamber 2, the primary tank 6, and the secondary tank 8 with piping or the like. In the processing chamber 2, a spindle unit 10 capable of discharging coolant and a plurality of nozzles 28 are provided. In the present embodiment, a nozzle 28a is disposed on the top surface of the processing chamber 2. Further, a nozzle 28b is disposed on the first side surface where the spindle unit 10 is provided, and a nozzle 28c is disposed on the second side surface facing the first side surface. These nozzles 28 are nozzles for internal cleaning and function as the "second discharge portion".

[0031] The central portion of the bottom surface of the processing chamber 2 is open toward the chip conveyor 20. The chip conveyor 20 is configured by housing a pair of endless chains 42, a drum filter 44, and a drive mechanism 46 in a hollow housing 40. The drive mechanism 46 includes a plurality of sprockets around which the endless chain 42 is wound. One of the plurality of sprockets, a sprocket 48, is rotationally driven by a motor (not shown), and a sprocket 50 is provided integrally with the drum filter 44. Between the pair of endless chains 42, scraping plates (not shown) are provided at predetermined intervals in the longitudinal direction of the endless chain 42, and the scraping plates are configured to rotate inside the housing 40 by the rotation of the sprocket 50. The drum filter 44 is a drum-shaped filter having a filtering function and is configured to capture foreign substances contained in the coolant. The endless chain 42 is driven by the rotation of the sprocket 48, and the drum filter 44 also rotates.

[0032] One end side of the housing 40 extends obliquely upward, and a chip discharge portion 52 is provided at its tip. The endless chain 42 is provided so as to reach the chip discharge portion 52. A chip bucket (not shown) for collecting chips is installed directly below the chip discharge portion 52.

[0033] The primary tank 6 is installed so as to accommodate the housing 40 from below. The primary tank 6 is a rectangular container in plan view with an open upper end and is sufficiently larger than the housing 40 in plan view. An outlet 54 for discharging the coolant to the primary tank 6 is provided on the side surface of the housing 40. The outlet 54 communicates with the inside of the drum filter 44.

[0034] The chips discharged from the machining chamber 2 are conveyed to the chip discharge section 52 by the endless chain 42. The chips are discharged by the chip discharge section 52 and collected in the chip bucket. On the other hand, the coolant that has washed away the chips in the machining chamber 2 is introduced into the housing 40 and guided into the rotating drum filter 44. This coolant is filtered by passing through the surface of the drum filter 44. At this time, relatively large foreign matters such as chips contained in the coolant are captured by the drum filter 44. The filtered coolant is discharged into the primary tank 6 through the outlet 54.

[0035] The primary tank 6 is connected to the secondary tank 8 via a pipe 60. The pipe 60 is routed above the primary tank 6, branches into a first pipe 62 and a second pipe 64 at a branch point P1, and is inserted so as to hang down into the primary tank 6. A pump 116a, a check valve 68, and an on-off valve 70 are provided in the pipe 60 from its upstream side. The on-off valve 70 is a solenoid-driven solenoid valve in this embodiment, but may be a motor-driven motor valve.

[0036] The upstream end of the pipe 60 serves as a suction port 72 for the coolant. A mesh-like filter 73 is provided in the primary tank 6 so as to surround the suction port 72. The filter 73 prevents or suppresses the intrusion of foreign matters from the primary tank 6 into the suction port 72. By opening the on-off valve 70 and driving the pump 116a, the coolant can be pumped up from the primary tank 6 and introduced into the secondary tank 8. The check valve 68 prevents the backflow of the coolant in the pipe 60.

[0037] A discharge port 74 (first discharge port) is provided at the center of the bottom surface of the secondary tank 8, and one end of a pipe 76 is connected thereto. The other end of the pipe 76 communicates with the communication passage 36 of the main shaft unit 10. The flow path in the pipe 76 functions as the "first flow path" and guides the coolant discharged from the discharge port 74 to the main shaft unit 10. The pipe 76 is provided with an on-off valve 78, a pump 116b, a cyclone filter 120, a pump 116c, a check valve 86, and an on-off valve 88 in this order from the upstream side.

[0038] The cyclone filter 120 is a centrifugal filter capable of centrifugally separating and collecting sludge from the coolant discharged from the secondary tank 8. The on-off valves 78 and 88 are electromagnetic valves in this embodiment, but may be electric valves. By opening the on-off valves 78 and 88 and driving the pumps 116b and 116c, the coolant can be supplied to the main shaft unit 10. The check valve 86 prevents the reverse flow of the coolant in the pipe 76.

[0039] A branch point P2 is provided between the cyclone filter 120 and the pump 116c in the pipe 76, and a pipe 90 branches off. The tip of the pipe 90 opens into the primary tank 6. The pipe 90 is provided with an on-off valve 92. The on-off valve 92 is an electromagnetic valve in this embodiment, but may be an electric valve. By opening the on-off valve 92, a part of the coolant led out from the secondary tank 8 to the pipe 76 can be returned to the primary tank 6 through the pipe 90.

[0040] In addition, a discharge port 94 (second discharge port) is provided at the peripheral edge of the secondary tank 8, and one end of a pipe 96 is connected thereto. The other end of the pipe 96 is connected to a nozzle 28c. An on-off valve 91 and a pump 116d are provided in the pipe 96 from the upstream side. An on-off valve 98c is provided at the other end of the pipe 96 (upstream side of the nozzle 28c). Branch points P3 and P4 are provided on the downstream side of the pump 116d in the pipe 96, and pipes 95 and 97 branch off. The tip of the pipe 97 is connected to a nozzle 28a. An on-off valve 98a is provided in the pipe 97. The tip of the pipe 95 is connected to a nozzle 28b. An on-off valve 98b is provided in the pipe 95. The flow path in the pipe 96 functions as the "second flow path" and guides the coolant discharged from the discharge port 94 to the nozzle 28.

[0041] By opening the on-off valve 91 and driving the pump 116d, the coolant can be supplied from the secondary tank 8 to the nozzle 28. By opening the on-off valve 98a, the coolant can be discharged from the nozzle 28a, and by opening the on-off valve 98b, the coolant can be discharged from the nozzle 28b. By opening the on-off valve 98c, the coolant can be discharged from the nozzle 28c. At that time, by setting the orientation of each nozzle 28, the discharge position of the coolant in the processing chamber 2 can be controlled.

[0042] In the above configuration, the coolant discharged from the main shaft unit 10 and the nozzle 28 is guided from the bottom of the processing chamber 2 to the chip conveyor 20, filtered by the drum filter 44, and then temporarily stored in the primary tank 6. The coolant in the primary tank 6 is pumped up by the pump 116a and introduced into the secondary tank 8 for temporary storage. In the secondary tank 8, a swirling flow of the coolant is generated (details will be described later). Due to this swirling flow, the sludge contained in the coolant is concentrated at the central part (near the center) of the bottom surface of the secondary tank 8. Therefore, the concentration of the sludge in the secondary tank 8 is relatively high at the central part of the bottom surface and relatively low at the peripheral part (near the periphery).

[0043] The coolant in the secondary tank 8 is discharged separately into two systems: a pipe 76 connected to the discharge port 74 at the center of the bottom surface and a pipe 96 connected to the discharge port 94 at the peripheral edge of the bottom surface, and is supplied to the machining chamber 2. The coolant discharged into the pipe 76 is guided to the cyclone filter 120 by the power of the pump 116b. After the sludge is centrifugally separated and removed, it is guided to the spindle unit 10 by the power of the pump 116c. Then, it is discharged from the discharge port 34 of the tool T. The coolant discharged from the tool T is guided again from the bottom of the machining chamber 2 to the chip conveyor 20. Thus, in the coolant supply device 5, a coolant circulation path (first circulation path) including the flow path of the pipe 76 is formed.

[0044] Although the internal passage 32 provided in the tool T is narrow, since the coolant from which the sludge has been removed by the cyclone filter 120 is supplied, problems such as blockage of the flow path by the sludge are less likely to occur. On the other hand, regarding the sludge itself, since the sludge concentrated at the center of the bottom surface of the secondary tank 8 is actively guided to the cyclone filter 120, the recovery efficiency can be improved.

[0045] On the other hand, the coolant discharged into the pipe 96 is guided to each nozzle 28 by the power of the pump 116d and discharged into the machining chamber 2. The coolant discharged from the nozzle 28 is guided again from the bottom of the machining chamber 2 to the chip conveyor 20. Thus, in the coolant supply device 5, a coolant circulation path (second circulation path) including the flow path of the pipe 96 is further formed. Since the concentration of sludge in the coolant discharged from the pipe 96 is low, the amount of sludge guided to the nozzle 28 is also small. In addition, since the discharge port of the nozzle 28 is sufficiently larger than the discharge port 34 of the tool T, problems such as blockage of the flow path by the sludge are less likely to occur.

[0046] As described above, in the present embodiment, a cyclone filter 120 (centrifugal filter), which is generally expensive, is provided in the coolant circulation path via the spindle unit 10 (thru-spindle coolant device), that is, the first circulation path where high cleanliness is required for the coolant. On the other hand, a centrifugal filter is not provided in the coolant circulation path via the nozzle 28, that is, the second circulation path where high cleanliness is not required for the coolant as much as in the thru-spindle coolant device. Thereby, the cost of the entire coolant supply device 5 can be suppressed.

[0047] An oil skimmer 180 is installed in the secondary tank 8. In addition to sludge, the coolant contains lubricating oil (machine oil), and the oil component with a specific gravity smaller than that of the coolant becomes floating oil and accumulates on the upper part of the secondary tank 8. Therefore, in the present embodiment, a float-type oil skimmer 180 is provided in the secondary tank 8. The oil skimmer 180 has a suction part 182 that floats so as to follow the liquid level of the coolant, and sucks and collects the floating oil that has been separated from the coolant and floats toward the liquid level from the suction part 182. This floating oil is led to a coalescer 184 (oil-water separator) via a pipe 186. The coalescer 184 aggregates the oil component of the floating oil and discharges it to a waste oil box (not shown).

[0048] Next, the specific structure of the secondary tank 8 (coolant tank) will be described. FIGS. 5 to 7 are diagrams showing the structure of the secondary tank 8. FIG. 5 is a perspective view seen from above, and FIG. 6 is a front view. FIG. 7 is a cross-sectional view taken along the line A-A in FIG. 6. For convenience of explanation, FIG. 5 shows a state where the upper surface and the front surface of the secondary tank 8 are open. FIG. 6 shows a state where the front surface of the secondary tank 8 is open.

[0049] As shown in FIGS. 5 and 6, the secondary tank 8 includes a vertical tank body 150 for temporarily storing a coolant, and a first pipe 62 and a second pipe 64 provided so as to hang down from above the tank body 150. The tank body 150 has a hollow rectangular parallelepiped shape that is rectangular in plan view and rectangular in side view, and reinforcing ribs 152a, 152b, and 152c are provided at the upper, central, and lower portions of its inner wall surface. Each rib projects inward on the inner peripheral surface of the tank body 150. Legs 154 are provided so as to support the bottom surface of the tank body 150 from below.

[0050] As also shown in FIG. 7, a common pipe 61 connected to the above-described pipe 60 (the upstream pipe extending from the primary tank 6) extends horizontally from the upper side surface of the tank body 150 into the interior. The common pipe 61 extends from near the right side surface of the tank body 150 from the back to the front, and branches into a first pipe 62 and a second pipe 64 with its tip as a branch point P1. The first pipe 62 has a bent pipe portion 62a that bends backward from the branch point P1 and extends substantially horizontally along the right side surface and the back surface, and a straight pipe portion 62b that hangs down from the tip of the bent pipe portion 62a toward the bottom surface of the tank body 150. The first pipe 62, the second pipe 64, and the common pipe 61 are arranged so as to be close to the inner peripheral surface of the tank body 150 so as not to interfere with the suction portion 182 of the oil skimmer 180.

[0051] Returning to FIG. 6, a discharge pipe portion 62c is provided at the lower end of the straight pipe portion 62b. The first pipe 62 is fixed to the rib 152b by a fixing bracket 160 and is stably supported.

[0052] On the other hand, the second pipe 64 has a straight pipe portion 64b that hangs down from the branch point P1, and a discharge pipe portion 64c is provided at the lower end of the straight pipe portion 64b. The second pipe 64 is fixed to the rib 152b by a fixing bracket 162 and is stably supported. The straight pipe portion 62b of the first pipe 62 and the straight pipe portion 64b of the second pipe 64 are arranged at diagonal positions in the tank body 150 (see FIG. 7). A discharge port 74 is provided at the central portion of the bottom surface of the tank body 150, and a discharge port 94 is provided at the peripheral edge portion of the bottom surface.

[0053] The tank body 150 has a vertical tank structure that is larger in the height direction than in width and depth. Specifically, the tank body 150 has a height that is 1.5 times or more its lateral width. The discharge pipe portion 62c of the first pipe 62 and the discharge pipe portion 64c of the second pipe 64 each have a coolant discharge port supplied by the pipe 60, and by adjusting the directions of these discharge ports, a swirling flow of coolant is generated within the tank body 150. Each discharge pipe portion is disposed at a position at a predetermined height h1 from the bottom surface 156 of the tank body 150, and each discharge port is located in the lower part of the tank body 150 and is spaced apart from the bottom surface of the tank body 150. The swirling flow will be formed in the lower part within the tank body 150.

[0054] In this embodiment, each discharge port is positioned at a height that is 1 / 4 or less of the height h0 of the tank body 150. However, in order to form a swirling flow in the lower part within the tank body 150, it is preferably positioned at a height that is at least 1 / 2 or less of the height h0 of the tank body 150.

[0055] While the first pipe 62 has a bent pipe portion 62a and a straight pipe portion 62b, the second pipe 64 has only a straight pipe portion 64b. For this reason, the lengths of the first pipe 62 and the second pipe 64 with respect to the branch point P1 are different. The first pipe 62 is longer than the second pipe 64. For this reason, an imbalance due to a difference in flow resistance occurs between the flow of coolant discharged from the discharge port of the first pipe 62 and the flow of coolant discharged from the discharge port of the second pipe 64, and this imbalance may contribute to the occurrence of stagnation in the tank body 150. In this regard, the bifurcated pipe structure provided in the first pipe 62 will reduce the occurrence of such stagnation (details will be described later).

[0056] In the central portion of the bottom surface of the tank body 150, a guide portion 185 for guiding the suction portion 182 of the oil skimmer 180 in the vertical direction is erected. The guide portion 185 includes three elongated guide members 185a. The guide member 185a has a height that is higher than the upper limit height (upper limit height hmax) of the liquid level set in the tank body 150. The three guide members 185a are erected so as to surround the discharge port 74 and are arranged at equal intervals around the axis of the discharge port 74.

[0057] The suction part 182 includes a suction nozzle 190 provided at the center and a plurality of floats 192 radially provided on the outer peripheral surface of the suction nozzle 190. In the present embodiment, in a plan view, three floats 192 are provided at intervals of 120 degrees around the suction nozzle 190 (see FIG. 7). The inscribed circle of the three guide members 185a is configured to be slightly larger than the outer diameter circle of the suction nozzle 190. The suction part 182 is supported in such a manner that the base end portions of the respective floats 192 are sandwiched between two adjacent guide members 185a. With such a configuration, the guide part 185 can guide the suction part 182 in the vertical direction while keeping the suction part 182 at the center of the liquid level in the tank body 150.

[0058] A pump 116b is provided below the bottom of the tank body 150 (inside the leg part 154). Since the structure, function, etc. of the pump 116b are publicly known as described in the above Patent Document 2, the description thereof will be omitted.

[0059] In the present embodiment, the discharge pipe part 62c of the first pipe 62 has a bifurcated structure, that is, it has two discharge ports, so that the discharge directions of the coolant from the respective discharge ports are made different. Thereby, while generating a swirling flow by the discharge from one discharge port, the generation of stagnation is avoided or reduced by the discharge from the other discharge port. Hereinafter, first, the structure of the first pipe 62 will be described, and then the function due to the structure will be described.

[0060] FIGS. 8 and 9 are diagrams showing the configuration of the discharge pipe part 62c. FIG. 8(A) is a perspective view, FIG. 8(B) is a front view, and FIG. 8(C) is a plan view. FIG. 9(A) is a cross-sectional view taken along the line A-A of FIG. 8(B), FIG. 9(B) is a cross-sectional view taken along the line B-B of FIG. 8(B), and FIG. 9(C) is a cross-sectional view taken along the line C-C of FIG. 8(C).

[0061] As shown in FIGS. 8(A) to 8(C), the discharge pipe portion 62c has a bottomed cylindrical shape and includes a pipe body 164 connected to the lower end of the first pipe 62, and branch pipe portions 166 and 168 that branch into two from the pipe body 164. The discharge pipe portion 62c can be obtained, for example, by additive manufacturing using metal or resin, injection molding of a resin material, or die casting of a metal material. The upper end opening of the pipe body 164 and the lower end opening of the straight pipe portion 62b are coaxially connected. In the present embodiment, the first pipe 62 is installed in the tank body 150 such that the straight pipe portion 62b extends in the vertical direction (see FIG. 6). Therefore, when the discharge pipe portion 62c is assembled to the straight pipe portion 62b, the axis L of the pipe body 164 extends in the vertical direction.

[0062] The branch pipe portions 166 and 168 are provided so as to project horizontally and slightly downward from the lower portion of the pipe body 164. The branch pipe portion 166 has a discharge port 166a, and the branch pipe portion 168 has a discharge port 168a. The discharge port 166a functions as the "first discharge port", and the discharge port 168a functions as the "second discharge port". That is, the discharge pipe portion 62c has one coolant inlet and two coolant discharge ports, and the first discharge port and the second discharge port are integrally provided. The discharge ports 166a and 168a open downward at an angle with respect to the horizontal plane H.

[0063] As shown in FIGS. 9(A) to 9(C), the flow path 166b of the branch pipe portion 166 and the flow path 168b of the branch pipe portion 168 communicate with each other at the lower portion of the pipe body 164. The flow path 166b and the flow path 168b form an angle θ in a plan view (FIG. 9(B)). In the present embodiment, the angle θ is an acute angle (θ < 90 degrees), but it is not limited to this, and can be appropriately set from the viewpoints of promoting the generation of a swirling flow and reducing stagnation.

[0064] The discharge port 166a opens downward at an angle θ1 with respect to the horizontal plane H (FIG. 9(A)). On the other hand, the discharge port 168a opens downward at an angle θ2 with respect to the horizontal plane H (FIG. 9(C)). In the present embodiment, these angles are made the same (θ1 = θ2), but they may be different in a modified example.

[0065] The discharge ports 166a and 168a discharge the coolant flowing through the first pipe 62 into the tank body 150. By adjusting the directions in which these discharge ports open, that is, the discharge directions of the coolant from each discharge port, the generation state of the swirling flow generated in the tank body 150 can be maintained well. That is, by optimizing the direction of the discharge port 166a, the generation of the swirling flow can be promoted. On the other hand, by optimizing the direction of the discharge port 168a, the generation of stagnation during the generation of the swirling flow can be reduced.

[0066] Note that, unlike the discharge pipe portion 62c, the discharge pipe portion 64c does not branch and does not have a bifurcated structure (see FIG. 6). Specifically, the discharge pipe portion 64c has a structure in which the branch pipe portion 168 is eliminated and the discharge port 166a of the branch pipe portion 166 is made larger in the discharge pipe portion 62c shown in FIG. 8(a), but the detailed description thereof is omitted.

[0067] FIG. 10 is a cross-sectional view taken along the line B-B of FIG. 6. The tank body 150 is a rectangular tank including four flat inner surfaces, and the discharge ports 166a and 168a of the first pipe 62 are arranged close to one inner surface. The discharge port 169 of the second pipe 64 is arranged close to another inner surface. The discharge port 169 functions as the "third discharge port".

[0068] More specifically, curved guide portions 170 are provided at the four corners (corner portions) at the lower part of the tank body 150 (see FIG. 6). The guide portions 170 are provided so as to be smoothly connected to the four inner surfaces (flat surfaces) of the tank body 150 in a plan view. The guide portions 170 have a size (height) including the discharge ports of the discharge pipe portion 62c and the discharge pipe portion 64c in the height direction. As a result, the tank body 150 has a corner portion with an R-shaped (curved surface shape) inner peripheral surface at the height position of each discharge port. The guide portions 170 guide the coolant flowing through the lower part of the tank body 150 in the inner peripheral direction, and promote the generation and maintenance of the swirling flow of the coolant. The discharge port 74 is provided at the center of the bottom surface of the tank body 150 where the swirling center of the coolant is located.

[0069] The discharge pipe portion 62c is disposed near one corner of the tank body 150 and inside the guide portion 170. More specifically, the discharge pipe portion 62c is disposed near the connection portion between the curved surface of the guide portion 170 and the flat inner surface of the tank body 150. On the other hand, the discharge pipe portion 64c is disposed at a position substantially symmetric to the discharge pipe portion 62c with respect to the center of the tank body 150, that is, at a position diagonal to the discharge pipe portion 62c in the tank body 150. The discharge pipe portion 64c is also located inside the guide portion 170.

[0070] The two-dot chain arrows in the figure indicate the directions in which the respective discharge ports open in plan view, that is, the discharge directions of the coolant at the respective discharge ports. The one-dot chain line in the figure indicates the direction parallel to the inner surfaces (flat inner surfaces 150a, 150b) of the tank body 150 respectively located near the downstream sides of the discharge pipe portions 62c, 64c.

[0071] That is, for the first pipe 62, the discharge port 166a opens toward the inner surface 150a of the tank body 150, while the discharge port 168a opens toward the side opposite to the inner surface 150a. As shown in the figure, with reference to the direction parallel to the inner surface 150a, the discharge port 166a opens in a direction forming an angle θ3 with respect to the inner surface 150a side, and the discharge port 168a opens in a direction forming an angle θ4 with respect to the side opposite to the inner surface 150a. In this embodiment, these angles are made the same (θ3 = θ4), but they may be different and can be appropriately set from the viewpoints of promoting the generation of swirling flow and reducing stagnation in the tank body 150.

[0072] On the other hand, for the second pipe 64, the discharge port 169 opens toward the inner surface 150b of the tank body 150. As shown in the figure, with reference to the direction parallel to the inner surface 150b, the discharge port 169 opens in a direction forming an angle θ5 with respect to the inner surface 150b side. In this embodiment, the angle θ3 of the discharge port 166a and the angle θ5 of the discharge port 169 are made the same (θ5 = θ3), but they may be different and can be appropriately set from the viewpoint of promoting the generation of swirling flow in the tank body 150.

[0073] Figs. 11 and 12 are diagrams schematically showing the principle of generating a swirling flow in the tank body 150. Fig. 11 shows a front view. Fig. 12 shows a plan view, Fig. 12(A) corresponds to Fig. 10, and Fig. 12(B) corresponds to Fig. 7. As described above, the discharge ports 166a, 168a of the first pipe 62 and the discharge port 169 of the second pipe 64 are arranged in the lower region of the tank body 150, and the discharge ports 166a, 169 are opened toward the adjacent inner surfaces 150a, 150b respectively (Figs. 11, 12(A)). Thereby, a swirling flow of the coolant can be generated at the lower part of the tank body 150. That is, the discharge ports 166a of the first pipe 62 and the discharge port 169 of the second pipe 64 constitute a "swirling flow generation structure" for swirling the coolant along the inner peripheral surface of the tank body 150.

[0074] However, through the verification by the inventor, it has been found that just opening the discharge ports 166a, 169 in this way, the swirling flow tends to be biased toward the inner peripheral surface side of the tank body 150 and cause stagnation inside. In that case, it is difficult to sufficiently collect the sludge at the center of the bottom surface of the tank body 150. In this regard, in the present embodiment, the first pipe 62 is further provided with a discharge port 168a to discharge a part of the coolant toward the inside of the tank body 150. Thereby, the bias of the swirling flow toward the inner peripheral surface side is broken to eliminate the stagnation, and a swirling flow can also be generated inside (the central part of the tank body 150). As a result, the sludge can be efficiently discharged from the discharge port 74 provided at the center of the bottom surface of the tank body 150.

[0075] In addition, by providing each discharge port in the lower region of the tank body 150, the swirling flow can be concentrated in the lower half of the tank body 150. Further, by directing each discharge port slightly downward, it becomes easier to generate a swirling flow below each discharge port, that is, over the bottom of the tank body 150. Specifically, combined with the suction action due to the discharge of the coolant from the discharge port 74, a swirling flow in the lower region of the tank body 150 becomes an inverted conical shape (inverted triangular shape in side view) or a mortar shape (a shape in which the swirling radius increases from bottom to top). In other words, the swirling radius becomes smaller toward the bottom, and the sludge tends to gather at the central part. That is, the sludge can be guided to the discharge port 74 provided at the center of the bottom surface, and the discharge efficiency of the sludge from the discharge port 74 can be improved.

[0076] On the premise of such a configuration, the flow rate control unit 101 drives the pump 116a (see FIG. 4), and controls the discharge amount of the coolant from each discharge port so that a swirling flow of the coolant is sufficiently formed in the lower part of the tank body 150, while the swirling flow becomes slower toward the upper liquid surface. The ribs 152c and 152b provided on the inner peripheral surface of the tank body 150 serve as resistance to the swirling flow transmitted from the lower part to the upper part of the tank body 150.

[0077] FIG. 13 is a diagram showing the movement of the floating oil according to the liquid level height of the coolant. FIG. 13(A) shows a state where the coolant is stored up to the upper limit height hmax, and FIG. 13(B) shows a state where the coolant is stored up to a height of half or less of the upper limit height hmax.

[0078] Normally, the coolant is stored in the coolant tank (secondary tank 8) up to the upper limit height hmax (FIG. 13(A)). When the coolant supply device 5 is driven in this state, if the circulation of the coolant is normal, the liquid level moves up and down near the upper limit height hmax.

[0079] The flow control unit 101 is configured to cause the swirling flow of the coolant generated at the lower part of the tank body 150 to reach the liquid surface peripheral part while reducing the flow rate toward the upper part of the tank body 150. More specifically, in a state where the coolant is stored in the tank body 150 up to the upper limit height hmax, the flow rate of the coolant at the liquid surface peripheral part is controlled so as to be 1 / 3 or less of the flow rate of the coolant at the height position of each discharge port.

[0080] The flow control unit 101 controls the discharge flow rate of the coolant such that the swirling flow of the coolant is formed from the swirling center to the inner peripheral surface at the lower part of the tank body 150 (FIG. 12(A)), while not being formed at the liquid surface central part at the upper limit height hmax of the tank body 150 (FIG. 12(B)). That is, at the upper limit height hmax, a gentle swirling flow is formed at the liquid surface peripheral part, but no swirling flow is formed at the liquid surface central part C.

[0081] Note that the “liquid surface central part C” mentioned here may be, for example, a region where the suction part 182 of the oil skimmer 180 is located (the inner region of the circumscribed circle of the float 192). “No swirling flow is formed at the liquid surface central part” means that the flow at the liquid surface central part C is stagnant, including not only a state where no swirling flow is formed at all, but also a very gentle and substantially unformed state.

[0082] At this time, as described above, a gentle swirling flow is formed at the liquid surface peripheral part, but the liquid surface central part is in a stagnant state. Since the floating oil Oc has a property of easily gathering in the stagnant region, it accumulates at the liquid surface central part (FIG. 13(A)). Therefore, it is efficiently sucked by the suction part 182 located at the liquid surface central part. That is, the floating oil Oc can be efficiently recovered and discharged by the oil skimmer 180.

[0083] On the other hand, assume that due to some factor, the circulation of the coolant cannot be maintained normally and the liquid level drops significantly below the upper limit height hmax (Fig. 13(B)). In this case, the swirling flow reaches the central part of the liquid surface, and the floating oil is dispersed and spreads over the entire liquid surface, making efficient recovery difficult. Therefore, when the liquid level is near the upper limit height hmax, the effect of the above-described coolant flow rate control (improvement in the recovery efficiency of the floating oil Oc) can be obtained.

[0084] As described above, the machine tool has been described based on the embodiment. In the present embodiment, at the lower part of the vertical coolant tank (secondary tank 8), discharge ports 166a and 169 that open toward the inner surface of the tank to generate a swirling flow of the coolant, and a discharge port 168a that opens toward the side opposite to the inner surface of the tank to reduce the generation of stagnation during the generation of the swirling flow are provided. That is, by discharging the coolant from the discharge ports 166a and 169 toward the inner surface, the generation of the swirling flow is promoted, while by discharging the coolant from the discharge port 168a toward the side opposite to the inner surface, the stagnation at the lower part of the tank is eliminated. On the other hand, at the upper part of the tank, the swirling flow of the coolant is made to reach the peripheral part of the liquid surface, and control is performed so that stagnation can occur at the central part of the liquid surface. Thereby, the sludge contained in the coolant in the tank can be concentrated at the central part of the bottom surface of the tank where the discharge port 74 is located, and the floating oil can be concentrated at the central part of the liquid surface where the suction part 182 is located. As a result, both the sludge and the floating oil contained in the coolant can be efficiently discharged.

[0085] By integrally forming the discharge port 166a and the discharge port 168a, the manufacturing cost of the coolant discharge part in the pipe can also be reduced. The discharge pipe part 62c including the discharge ports 166a and 168a can be manufactured by injection molding of a resin material or die casting of a metal material. By assembling the discharge pipe part 62c to the lower end of the straight pipe part 62b, the first pipe 62 can be easily realized.

[0086] Also, as shown in Fig. 11, taking advantage of the fact that the secondary tank 8 is a large vertical tank in the height direction, by arranging each discharge port at the lower part of the tank, a swirling flow is intensively formed in the lower region of the tank body 150. That is, since substantially no swirling flow is formed in the upper region of the tank body 150, the oil skimmer 180 floating on the liquid surface can stably recover the oil content contained in the coolant. That is, sludge having a specific gravity greater than that of the coolant is actively discharged from the lower discharge port 74, and oil having a specific gravity smaller than that of the coolant is actively recovered by the 180 arranged on the upper liquid surface. Thereby, it becomes easier to keep the coolant clean as a whole.

[0087] In this embodiment, the first pipe 62 and the second pipe 64 are suspended from above the tank body 150, and each discharge port is provided at the lower end thereof. Further, the coolant is discharged with each discharge port directed slightly downward. Thereby, not only can a swirling flow be generated in the lower region of the tank body 150, but also it becomes difficult for each pipe to inhibit the flow of the coolant in the lower region. As a result, the formation of the swirling flow can be stabilized. Also, by suspending each pipe from above, backflow from the tank body 150 to the pipe can be prevented.

[0088] Also, as shown in Fig. 4, in this embodiment, a cyclone filter 120 (centrifugal separation filter), which is generally expensive, is provided in the coolant circulation path passing through the main shaft unit 10, that is, the circulation path where a high cleanliness is required for the coolant. On the other hand, a centrifugal separation filter is not provided in the coolant circulation path passing through the nozzle 28, that is, the circulation path where a high cleanliness is not required for the coolant as much as in the through spindle coolant device. By limitedly providing the centrifugal separation filter, the manufacturing cost of the coolant supply device can be suppressed.

[0089] Rather, from the perspective of supplying a coolant with high cleanliness, it is natural to consider supplying the coolant discharged from the bottom peripheral portion where the sludge has a low concentration in the secondary tank 8 to the spindle unit 10. However, in the present embodiment, the coolant discharged from the central portion of the bottom surface where the sludge has a high concentration is deliberately supplied to the spindle unit 10. Although this may seem contradictory at first glance, by passing the coolant with a high sludge concentration through the cyclone filter 120, a coolant with high cleanliness can be supplied to the spindle unit 10. Further, by guiding the coolant containing a large amount of sludge to the cyclone filter 120, as a result, the sludge in the secondary tank 8 can be efficiently recovered and removed.

[0090] In addition, for applications that do not require high cleanliness, such as in-machine cleaning by the nozzle 28, the coolant is discharged from the vicinity of the peripheral portion where sludge is less likely to accumulate in the vertical tank. Therefore, it is easy to sufficiently secure the coolant supply amount required not only for the machining applications of the machine tool but also for chip flushing for automation. Further, since a centrifugal filter is not provided in the coolant circulation path that does not pass through the spindle unit 10, the residence time required for sludge separation is reduced, so that the coolant flow rate that can be supplied per unit time can also be increased. Therefore, even if the number of locations and the amount of coolant discharged further increase due to demands for automation, etc., it is easy to cope with them.

[0091] [Modification Example] In the above embodiment, the machine tool 1 has been described as a multi-tasking machine, but it may be a turning center or a machining center.

[0092] In the above embodiment, the machining chamber 2 has been exemplified as the inside of the machine tool. In a modification example, the coolant may be discharged and circulated in a pallet exchange chamber or other inside of the machine tool. In that case, the same system and coolant tank as in the above embodiment may be adopted for the coolant circulation path. The pallet exchange chamber is a space for exchanging pallets with workpieces attached.

[0093] In the above-described embodiment, as shown in FIG. 5, the first pipe 62 and the second pipe 64 are suspended from above the tank body 150, and a coolant discharge port is provided at the lower end of each pipe. In a modified example, each pipe may be provided so as to protrude from the bottom of the tank body, and a discharge port may be provided at the upper part thereof. Alternatively, each pipe may be provided so as to protrude from the side part of the tank body, and a discharge port may be provided at the tip end thereof. However, the direction in which each discharge pipe opens is the same as that in the above-described embodiment.

[0094] In the above-described embodiment, the first pipe 62 and the second pipe 64 are provided at diagonal positions in the tank body 150. Then, the first pipe 62 has a bifurcated structure, and a discharge port 166a (first discharge port) and a discharge port 168a (second discharge port) are provided, and a single discharge port 169 is provided in the second pipe 64. In a modified example, both the first pipe 62 and the second pipe 64 may have a bifurcated structure, and a first discharge port and a second discharge port may be provided. In that case, for the second pipe 64 as well, it is preferable that the first discharge port opens toward the inner surface of the tank body, while the second discharge port opens toward the side opposite to the inner surface. Thereby, it may be possible to further reduce the generation of stagnation associated with the swirling flow.

[0095] In the above-described embodiment, a configuration in which the first pipe 62 has a bifurcated structure and a discharge port 166a (first discharge port) and a discharge port 168a (second discharge port) are provided is illustrated. In a modified example, the first discharge port that opens toward the inner surface of the tank body and the second discharge port that opens toward the side opposite to the inner surface may be configured to be displaced in the height direction of the first pipe 62.

[0096] In the above embodiment, a configuration in which the discharge port 166a (first discharge port) and the discharge port 168a (second discharge port) are integrally provided in the first pipe 62 was illustrated. In a modified example, a configuration may be adopted in which a first discharge port that opens toward the inner surface of the tank body and a second discharge port that opens toward the side opposite to the inner surface are respectively provided in separate pipes. Further, when the discharge port 166a and the discharge port 168a are integrally provided in the first pipe 62, it may be other than the bifurcated structure formed by the manufacturing method shown in the above embodiment. For example, it may be bifurcated into two branches by a pipe joint, and a discharge port forming member for adjusting the opening diameter or the like may be attached to the pipe joint.

[0097] In the above embodiment, a configuration in which discharge ports of the pipes are provided at two diagonal positions in the tank body 150 to promote the generation of a swirling flow was illustrated. In a modified example, a discharge port of the pipe may be provided at one or both of the remaining two corners of the tank body 150 to further promote the generation of a swirling flow. Also in that case, a first discharge port that opens toward the inner surface of the tank body and a second discharge port that opens toward the side opposite to the inner surface may be provided.

[0098] In the above embodiment, a configuration in which, in the first pipe 62, a discharge port 166a (first discharge port) that opens toward the inner surface of the tank body 150 and a discharge port 168a (second discharge port) that opens toward the side opposite to the inner surface are provided was illustrated. In a modified example, a configuration in which the second discharge port opens in a direction parallel to the inner surface may be adopted. Alternatively, a configuration in which the second discharge port opens toward the inner surface of the tank body in the same manner as the first discharge port, but opens more toward the inside of the tank body than the first discharge port may be adopted.

[0099] In the above-described embodiment, from the viewpoint of efficiently collecting sludge by utilizing a swirling flow, a configuration is exemplified in which a discharge port 74 (first discharge port) is provided at the center of the bottom surface in the tank body 150, and a discharge port 94 (second discharge port) is provided at the peripheral edge of the bottom surface. When the radius of the swirling flow at the bottom of the tank body 150 is small, depending on the swirling radius of the coolant at the bottom, the discharge port 94 (second discharge port) may be provided inside the peripheral edge of the bottom surface. That is, the first discharge port may be provided at the aggregation location where the sludge contained in the coolant is collected by the swirling flow of the coolant, and the second discharge port may be provided at a location separated from the aggregation location.

[0100] In the above-described embodiment, a cyclone filter 120 (centrifugal separation filter) is provided in the pipe 76 (first flow path), while a configuration is exemplified in which no filter is provided in the pipe 96 (second flow path). In a modified example, a filter that can be realized at a lower cost than a centrifugal separation filter, such as a filtration filter having a porous body or a mesh structure, may be provided in the pipe 96.

[0101] In the above-described embodiment, a rectangular tank in a plan view is exemplified as the tank body 150, but a rectangular tank in a polygonal shape in a plan view may also be used. Alternatively, a cylindrical tank in a circular shape in a plan view may also be used. Also in that case, it is preferable to provide a first discharge port that opens toward the inner peripheral surface of the tank body and a second discharge port that opens toward the inside of the tank body (opposite side to the inner peripheral surface) rather than the inner peripheral surface.

[0102] Note that the present invention is not limited to the above-described embodiment and modified example, and components can be modified and embodied without departing from the gist. Various inventions may be formed by appropriately combining a plurality of components disclosed in the above-described embodiment and modified example. Also, some components may be deleted from all the components shown in the above-described embodiment and modified example.

Explanation of Reference Numerals

[0103] 1 Machine tool, 2 Processing chamber, 5 Coolant supply device, 6 Primary tank, 8 Secondary tank, 10 Spindle unit, 18 Pallet, 20 Chip conveyor, 22 Shooter, 28 Nozzle, 30 Camera, 32 Internal passage, 34 Discharge port, 36 Communication passage, 40 Housing, 42 Endless chain, 44 Drum filter, 46 Drive mechanism, 52 Chip discharge section, 54 Discharge port, 60 Pipe, 62 First pipe, 62c Discharge pipe section, 64 Second pipe, 64c Discharge pipe section, 68 Check valve, 70 On-off valve, 72 Suction port, 73 Filter, 74 Discharge port, 76 Pipe, 78 On-off valve, 86 Check valve, 88 On-off valve, 90 Pipe, 91 On-off valve, 92 On-off valve, 94 Discharge port, 95 Pipe, 96 Pipe, 97 Pipe, 98a On-off valve, 98b On-off valve, 98c On-off valve, 100 Information processing device, 101 Flow control section, 102 Processing control device, 104 Processing device, 112 Coolant tank, 114 Coolant discharge section, 116 Pump, 118 Control valve, 120 Cyclone filter, 150 Tank body, 150a Inner surface, 150b Inner surface, 152b Rib, 152c Rib, 156 Bottom surface, 164 Pipe body, 166 Branch pipe section, 166a Discharge port, 168 Branch pipe section, 168a Discharge port, 169 Discharge port, 170 Guide section, 180 Oil skimmer, 182 Suction section, 185 Guide section, 190 Suction nozzle, 192 Float, Oc Floating oil, T Tool.

Claims

1. A coolant tank provided in a coolant circulation path of a machine tool, comprising: a vertical tank body for temporarily storing the coolant discharged from inside the machine tool; a first discharge port provided at a lower part of the tank body for discharging the coolant discharged from inside the machine tool so as to swirl along the inner peripheral surface of the tank body; a second discharge port provided at a lower part of the tank body, opening toward the inside of the tank body rather than the first discharge port, for discharging the coolant discharged from inside the machine tool; a discharge port provided at the center of the bottom surface of the tank body where the swirling center of the coolant is located, for discharging the coolant toward the inside of the machine; an oil skimmer having a suction part floating at the center of the liquid level of the tank body, for sucking and collecting the oil separated from the coolant and floating toward the liquid level from the suction part; a flow rate control part for controlling the discharge flow rate of the coolant from each discharge port; and comprising wherein the flow rate control part controls the discharge flow rate of the coolant such that the swirling flow of the coolant generated in the lower part of the tank body reaches the peripheral edge of the liquid level while reducing the flow rate toward the upper part of the tank body. A coolant tank.

2. The flow rate control part controls the discharge flow rate of the coolant such that the swirling flow of the coolant is formed from the swirling center to the inner peripheral surface in the lower part of the tank body, but is not formed at the center of the liquid level of the tank body. The coolant tank according to claim 1.

3. The flow rate control part controls the discharge flow rate of the coolant such that, in a state where the coolant is stored up to the upper limit height set in the tank body, the flow rate of the coolant at the peripheral edge of the liquid level is 1 / 3 or less of the flow rate of the coolant at the height position of each discharge port. The coolant tank according to claim 1 or 2.

4. Ribs protruding inward are provided at a position higher than each discharge port on the inner peripheral surface of the tank body. The coolant tank according to claim 1 or 2, wherein the ribs serve as a resistance to the swirling flow transmitted from the lower part to the upper part of the tank body.

5. The coolant tank according to claim 1 or 2, further comprising a guide part for guiding the suction part in the vertical direction so as to keep the suction part at the center of the liquid level of the tank body.

6. The tank body has a height that is 1.5 times or more the lateral width of the tank body. The coolant tank according to claim 1 or 2.

7. The coolant tank according to claim 1 or 2, wherein the first discharge port and the second discharge port each open downward at an angle with respect to the horizontal plane.

8. It is provided on the downstream side of a primary tank that stores the coolant discharged from inside the machine, and is configured as a secondary tank into which the coolant pumped up from the primary tank is introduced. It includes a pipe for introducing the coolant from the primary tank into the tank body. The pipe is connected to an upstream pipe extending from the primary tank and a common pipe extending from the upper side surface of the tank body into the interior, a first pipe and a second pipe that branch off from the common pipe and are provided so as to hang down from the upper part to the lower region inside the tank body, and includes the first discharge port and the second discharge port are provided at the lower end of the first pipe, a third discharge port is provided at the lower end of the second pipe, the third discharge port opens toward the inner peripheral surface so as to swirl the coolant along the inner peripheral surface of the tank body on the side opposite to the first discharge port with respect to the swirling center of the coolant. The coolant tank according to claim 5, wherein the common pipe, the first pipe, and the second pipe are arranged close to the inner peripheral surface of the tank body so as not to interfere with the suction part of the oil skimmer.

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