JP2001353640A - Filtering device having back washing function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dispense with exchange of a filter. SOLUTION: This filtering device comprises a filtering tank partitioned into inner and outer tanks with cylindrical filters 2 comprising a wedge wire or a laminated wire mesh and a reservoir of filtered cutting fluid. Inner tanks of the reserving tank and the filtering tank are inter-communicated, and a means for pressing the cutting fluid from the user cutting fluid tank only during filtering is connected to the outer tank of the filtering tank. A means for flowing excessive cutting fluid overflowing from the reservoir to the filtered cutting fluid tank only during filtering is connected to the reservoir, and a means for supplying compressed air only during back wash is connected to the reservoir to press the cutting fluid reserved in the reservoir into the inner tank of the filtering tank. A means for discharging the cutting fluid to the used cutting fluid tank only during back flow cleaning is connected to the outer tank of the filtering tank, to enable, permanent use of the filter 2 and highly accurate filtering.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filtration device provided with a backwashing function for a coolant tank of a machine tool such as a lathe and a machining center.

[0002]

2. Description of the Related Art Conventionally, in a machine tool of this type, a cutting fluid used for machining a workpiece is poured together with chips into a chip conveyor, and is conveyed to a coolant tank outside the machine by the conveyor. In the coolant tank, the partition plate separates the tank into a pollution tank, an overflow tank, and a cleaning tank. As described above, the chips and the cutting fluid conveyed from the chip conveyor first flow into the pollution tank, where the cutting fluid flows there. The chips inside settle down, and the cutting fluid in the upper layer is separated by flowing into the overflow liquid tank by overflow. Uncut chips are floating in the cutting fluid in the overflow tank, and this cutting fluid is separated from the chips by the filtration device installed in the overflow tank, and the filtered cutting fluid is sent to the cleaning tank. It is stored and reused as cutting fluid for machine tools by a cutting fluid supply device. The filtration device is configured to rotate a wire mesh-shaped drum placed sideways in the overflow tank, and to separate cutting chips by flowing cutting fluid from the outside to the inside of the drum. Is equipped with a backwashing function that periodically removes chips attached to the outside of the drum by ejecting the cutting fluid from the cleaning tank to prevent clogging of the drum.

[0003]

However, the coolant tank is designed to be as compact as possible, and it is necessary to spray a large amount of cutting fluid in the cleaning tank onto the drum during backwashing. Sufficient supply was not possible, and in this case, the operation of the machine tool had to be stopped, which reduced the working efficiency. Further, in the above-mentioned filtering device, since a wire mesh-shaped drum is used, the mesh is coarse and filtration cannot be performed sufficiently. Therefore, a machine tool which employs a filtering device equipped with a paper filter instead of this is also available. Can be seen. This filtration device filters the cutting fluid pumped from the overflow tank to the outside with a paper filter, and the filtered cutting fluid flows out to the cleaning tank.If this filter is clogged, the filter is replaced frequently. However, the operation is extremely troublesome and time-consuming, and the unnecessary filter has to be treated as industrial waste, so that there is a problem that the running cost of the filter rises.

[0004]

DISCLOSURE OF THE INVENTION In view of the above problems, the present invention provides a cylindrical filter or a laminated wire mesh in which slits are arranged in an outer peripheral surface and a flow path from a hollow portion to a slit is formed in a tapered shape. A filter having a porous structure formed in a cylindrical shape, a filtration tank partitioned into inner and outer tanks, and a storage tank for filtered cutting fluid are provided, and the storage tank and the inner tank of the filtration tank communicate with each other. A means for press-fitting the cutting fluid from the used cutting fluid tank only at the time of filtration is connected to the outer tank of the filtration tank, and a means for discharging excess cutting fluid flowing from the storage tank to the filtered cutting fluid tank only at the time of filtration is provided. A means for supplying compressed air only at the time of backwashing is connected to the storage tank so that the cutting fluid stored in the storage tank is press-fitted into the inner tank of the filtration tank. use By connecting the means for discharging the cutting fluid to the outer tank of the filtration tank, the filter can be used permanently and high-precision filtration can be performed, and the cutting required for backwashing outside the coolant tank can be performed. The above problem is solved by storing a liquid to enable backwashing without stopping operation of a machine tool.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. 1 is a machine tool coolant tank CT
The main body 1 is composed of a filtration tank 5 partitioned into inner and outer tanks 3 and 4 with a cylindrical filter 2 and an inner and outer tank 8 with a cylindrical body 7 provided with a communication port 6. , 9 and a storage tank 10 for the filtered cutting fluid C.

The filter 2 is formed by winding a wedge wire W made of metal and having a substantially wedge-shaped cross section in a coil shape with its flat portion on the outside and a triangular mountain-shaped protrusion on the inside, as shown in FIG. It is formed in a cylindrical shape. In the filter 2, fine slits S are provided between adjacent wedge wires W, and the slits S are arranged in the vertical direction of the filter 2. Further, since the wedge wire W is formed by winding the coil as described above, the flow path L from the hollow portion 2a of the filter 2 to the slit S is configured to be tapered. See FIG. 6). In FIG. 6,
Reference numeral 2b denotes a ring constituting the upper and lower surfaces of the filter 2, and the ring 2b is welded to the end of the wedge wire W. 2c is a wedge wire W installed between the rings 2b.
It is a supporting rod.

[0007] In addition to the above-mentioned filter 2, a filter shown in Figs. The filter 2 has a porous structure by forming a laminated wire mesh N into a cylindrical shape.
Above and below, a ring 2b is welded to maintain the cylindrical shape of the filter 2. The filter 2 in the illustrated example is 5
It is composed of wire nettings N1 to N5 in which layers are plain woven, and is superposed and sintered integrally so that the meshes are separated from each other by the wire nettings N1 to N5 of each layer. The wire mesh N2 of the second layer from the outside of the filter 2 has the finest mesh, and the wire meshes N1, N3 of the first layer and the third layer from the outside sandwiching the wire mesh N2 are the same as or the same as the two-layer wire mesh N2. With a slightly larger mesh, the single-layer wire mesh N1 protects the two-layer wire mesh N2 from chips and under high pressure, and the three-layer wire mesh N3 similarly protects the two-layer wire mesh N2 and the four-layer and five-layer wire mesh N
4. It is configured to achieve the effect of dividing the pressure fluid into N5. Further, the four-layer and five-layer wire meshes N4 and N5 are both made of a mesh for reinforcement and relatively larger than the other wire meshes N1 to N3, and the four-layer wire mesh N4 is rotated by 90 degrees to rotate the other wire meshes N1 to N3. , N5 and the direction of the fold are phased by 90 degrees. In addition, the wire meshes N1 to N5 of each layer are formed so as to prevent misalignment even under a high pressure by fusing the intersections of the vertical and horizontal wires constituting the wire meshes. Since N1 to N5 are laminated, they have a strength such that they do not deform even under the pressure of the cutting fluid C during filtration and backwashing.

[0008] The filtration tank 5 and the storage tank 10 are each provided with an upper cover at the upper and lower ports of a cylindrical casing 11 having the same volume.
The lower lid 13 and the lower lid 13 are joined in an airtight manner by a ring packing 14. The upper lid 12 is provided with right-angle channels 15 and 16 communicating with the inner tanks 3 and 8 and the outer tanks 2 and 9 respectively. The channel 15 is
An inner tank communication port 17 provided on the center axis of the bottom of the upper lid 12, and a pipe connection port 18 provided on one side of the upper lid 12 are communicated,
At the bottom of the upper lid 12, an annular support groove 19 for fitting and supporting the upper end of the filter 2 is provided around the inner tank communication port 17, and a central portion of the upper part of the upper lid 12 communicates with the flow path 15. A through hole 20 is provided. The flow path 16 has an outer tank communication port 21 disposed adjacent to the inner tank joint port 17 at the bottom of the upper lid 12,
A separate pipe connection port 22 provided on the other side of the top cover 12 (the above-described pipe connection port 18 and the left-right symmetric portion) is formed to communicate with each other. A separate pipe connection port 23 communicating with the flow path 16 is provided.

The lower cover 13 is provided with a screw hole 24 at the center thereof, and a disc-shaped bottom plate 25 on which the filter 2 or the tubular body 7 is placed is disposed above the screw hole 24. Bottom plate 25
Are supported by a plurality of legs 26 projecting upward from the inner peripheral edge of the lower lid 13. At the center of the bottom plate 25, a shaft 27 is erected vertically upward, and the shaft 27 has a male threaded portion 28 provided at the tip thereof protrudes through the through hole 20 of the upper lid 12, and the male threaded portion is formed on the upper lid 12.
By fastening 28 with a lock nut 29, the casing 11 is sandwiched between the upper lid 12 and the lower lid 13, and the filter 2 or the tubular body 7 is sandwiched and integrated between the support groove 19 and the bottom plate 25. In the filtration tank 5, the inner and outer tanks 3 and 4, which are defined by the filter 2 in the casing 11, communicate with the flow paths 15 and 16, respectively. In the storage tank 10, the inner and outer tanks 8, 9 defined by the cylindrical body 7 in the casing 11 communicate with the flow paths 15, 16, respectively, and a communication port 6 provided in a lower part of the side wall of the cylindrical body 7. Accordingly, the inner and outer tanks 8 and 9 communicate with each other, and the closing cap 30 is screwed into the screw hole 24 of the lower lid 13 in an airtight manner. The upper lid 12 hermetically closes the through hole 20 by a ring packing 31 interposed between the lock nut 29 and the upper lid 12 between the upper and lower ends of the filter 2 or the cylindrical body 7 and the support groove 19 and the bottom plate 25. The ring packing
Sealed with 32. In the filtration tank 5,
A barrel-shaped coil spring 33 whose inner diameter and the outermost diameter of the filter 2 substantially match each other is externally fitted and fixed to the upper part of the shaft 27 corresponding to the upper part of the filter 2.
The filter 2 erected on the bottom plate 25 is positioned by the barrel-shaped coil spring 33 so as to be arranged on the concentric circle of the shaft 27, and when the upper lid 12 is covered with the casing 11, the upper end of the filter 2 is placed in the support groove 19. Is designed to easily respond.

The filtration tank 5 and the storage tank 10 are air-tightly screwed with nipples 34 at the pipe joints 18 of the respective flow paths 15, and the inner tanks 3, 8 of the tanks 5, 10 are connected by piping. I have.
In addition, a check valve 36 for preventing backflow from the filtration tank 5 is connected to the piping connection port 22 of the flow path 16 of the filtration tank 5 via a separate nipple 35. The check valve 36 is connected to the discharge side of a coolant pump 37 via a series of piping paths. In the filtration tank 5, a measuring part of a pressure gauge 38 is screwed in a gas-tight manner to a pipe joint 23 communicating with the flow path 16 and connected to the outer tank 4. It is made to confirm. The suction side of the pump 37 is a used cutting fluid tank DC in which a coolant tank CT is defined by a partition plate.
T (hereinafter referred to as sludge tank DCT). An outer tank 4 provided at the bottom (lower lid) 13 of the filtration tank 5
(Screw hole) 24 is connected to the sludge tank DCT via a valve 39 such as an electromagnetic valve or an electric valve.

The pipe joint 22 of the passage 16 of the storage tank 10
, A separate valve 40 such as an electromagnetic valve or an electric valve is connected via a separate nipple 35a, and the valve 40 is a filtered cutting fluid tank formed by partitioning a coolant tank CT with a partition plate through a series of piping paths. A pipe is connected to a CCT (hereinafter, referred to as a cleaning tank CCT). In the storage tank 10, a separate valve 41 such as an electromagnetic valve or an electric valve is connected to the pipe joint 23 communicating with the flow path 16, and the valve 41 is compressed by an air compressor or the like via a series of pipe paths. The pipe is connected to the air supply source AP. Here, the compressed air supply source AP
May be configured as a check valve for preventing backflow from the storage tank 10. In the present embodiment, the filtration tank 5 and the storage tank 10 have the same volume, but the storage tank 10 may have a larger volume than the filtration tank 5.

Next, another embodiment will be described with reference to FIGS. This filtration device is a modification of the main body 1,
The same or corresponding parts as those described above are denoted by the same reference numerals and description thereof will be omitted. The main body 1 is formed by partitioning a substantially cylindrical closed tank 42 into an upper layer and a lower layer, forming an upper layer as a storage tank 10 for the filtered cutting fluid C, and using a filter 2 in the lower layer to form inner and outer tanks 3, 4.
The filtration tank 5 is formed into a compartment, and the inner tank 3 of the filtration tank 5 communicates with the storage tank 10. A flange 43 is protruded from the outer peripheral edge of the upper opening of the closed tank 42, and a disk-shaped sealing lid 44 is placed on the flange 43, and this is bolted to the flange 43. O-ring 45 is arranged in the circular groove engraved at the joint part with
The upper mouth of 42 is airtightly closed.

In the closed tank 42, pipe joints 22 and 23 project from the upper side wall under the flange 43 at symmetrical portions, and valves 40 and 41 are connected to the pipe joints 22 and 23, respectively. Then, one valve 40 is connected to the cleaning tank CCT by a pipe, and the other valve 41 is connected to the compressed air supply source AP by a pipe. Note that the valve 41 may be a check valve similar to the above. Further, in the closed tank 42, the pipe connection port 22,
Below the bottom 23, a bottomed cylindrical container 46 is arranged, and the container 46 has a flange 47 projecting from an outer peripheral edge of an upper opening thereof, and the flange 47 is attached to the inner wall of the closed tank 42. The sealing tank 42 is airtightly partitioned into the storage tank 10 and the filtration tank 5 by being engaged and mounted on an annular projection 48 provided on the storage tank 10. In the flange 47, an O-ring 49 is arranged in a circular groove formed in a joint portion with the projection 48, and the flange 47 is fixed to the projection 48 with bolts. The capacity of the storage tank 10 is equal to or larger than the capacity of the filtration tank 5. Reference numeral 50 denotes a tripod provided on the lower side of the closed tank 42 for standing on the tank, reference numeral 51 denotes a handle provided on the closed lid 44, and reference numeral 52 denotes a handle provided on the flange 47 of the container 46.

The bottom of the container 46 has a plurality (6 in the illustrated example).
Of the inner tank communication hole 17
The upper end of the filter 2 is fitted and supported by 19. Also, container
At the bottom center of 46, a shaft 27 is hung down, and the center of the bottom plate 25 is penetrated by a male screw 28 provided at the lower end of the shaft 27, and the male screw 28 is fastened by a lock nut 29, Container 46
And the bottom plate 25 sandwiches the filter 2.

The bottom plate 25 is provided with a circular concave portion 53 for positioning and mounting each filter 2 on the upper surface thereof.
A circular packing 54 and a circular plate 55 made of metal are laminated in order from the top. The circular plate 55, which is in contact with the upper end of the circular plate 53, is vertically adjusted by an adjusting bolt 56 screwed into the center of the circular concave portion 53 from the lower surface of the bottom plate 25. Are securely sandwiched between the bottom plate 25 and the bottom surface of the container 46. The bottom plate 25 is provided with a plurality of circulation ports 57 so as to ensure the fluidity of the cutting liquid C from the bottom plate 25 side.

A closed tank 42 corresponding to the filtration tank 5
A pipe connection port 22 is provided on the lower side wall of the
A check valve 36 is connected to 22 and the check valve 36 is connected to a sludge tank DCT via a pump 37. In addition, filtration tank 5
In the center of the bottom 13 of the (sealed tank 42), the outlet 24 of the outer tank 4
Project vertically downward, connect a valve 39 to the outlet 24,
The valve 39 is connected to the sludge tank DCT by piping. The pressure gauge 38 is attached to the outside of the lower side wall of the closed tank 42 so that the measurement part is disposed in the outer tank 4 of the filtration tank 5. In this embodiment, a plurality (6 in the illustrated example) is used.
In this case, one filter 2 (wedge wire type or laminated wire mesh type) may be used as long as it has the same filtering performance as the filter 2. .

Next, the operation of the filtration device having a backwashing function according to the present invention will be described with reference to FIGS. In the drawing, the flow of the fluid at the time of filtration is indicated by a solid arrow, and the flow of the fluid at the time of backwashing is indicated by a broken arrow. First, the case of filtering will be described. In such a state,
The valves 39 and 41 are closed, and the valve 40 is opened. Then, by operating the pump 37, the used cutting fluid C in the sludge tank DCT is injected into the outer tank 4 of the filtration tank 5 via the check valve 36. Due to the pressure of the pump 37, the cutting fluid C in the outer tub 4 is pressed into the filter 2 through the slit S or the mesh, and is filtered. At this time, chips in the cutting fluid C adhere to the surface of the filter 2 on the outer tank 4 side, and the clean cutting fluid C
Flows into the inner tank 3. In the apparatus shown in FIG. 4, the clean cutting fluid C in the inner tank 3 passes through the nipple 34 and is stored in the storage tank 3.
10 and the outer tank 9 through the communication port 6.
Also flows into Further, in the apparatus shown in FIG. 11, the clean cutting fluid C in the inner tank 3 flows into the storage tank 10 through the inner tank communication port 17. When the storage tank 10 is filled with the cutting liquid C, the excess cutting liquid C that overflows from the storage tank 10 flows out to the cleaning tank CCT via the valve 40.
When the valve 41 is a check valve, the cutting fluid C is supplied from the compression supply source A.
No backflow to P side.

During the filtration, the outer tank 4 of the filter 2
When a large amount of chips are attached to the surface on the side and the filtering function of the filter 2 is reduced, the amount of the cutting fluid C that permeates the filter 2 is reduced, and the pressure in the outer tub 4 rises above a normal value. Such a state is confirmed by the pressure gauge 38, and at this time, the filter 2 is backwashed with the clean cutting fluid C. In this cleaning, first, the pump 37 is stopped. Next, by opening the valves 39 and 41 and closing the valve 40 and operating the compressed air supply source AP, the compressed air passes through the valve 41, and in the apparatus shown in FIG. It flows into the tank 9 and, in the device shown in FIG. In addition, valve 41
Is a check valve, the compressed air automatically flows into the storage tank 10. And the storage tank
The pressure inside 10 increases, and the clean cutting fluid C stored in the storage tank 10 passes through the outer tank 9, the communication port 6, and the inner tank 8 in the apparatus shown in FIG. 4, and in the apparatus shown in FIG. , Storage tank 10
And through the inner tank communication port 17 into the inner tank 3 of the filtration tank 5. As a result, the pressurized fluid (cutting fluid) C is press-fitted from the inner tank 3 side of the filter 2 to the outer tank 4 side, and the filter 2
The chips attached to the slits S or the mesh on the outer tank 4 side are blown out to wash the filter 2. The chips spouted into the outer tank 4 of the filtration tank 5 are discharged together with the cutting fluid C from the outlet 24 through the valve 39 to the sludge tank DCT.
At this time, the cutting fluid C containing chips does not flow backward to the pump 37 by the check valve 36.

[0019]

In short, according to the present invention, since the cylindrical filter 2 in which the filtration tank 5 is divided into the inner and outer tanks 3 and 4 has the slits S arranged in the outer peripheral surface, the cutting fluid C passes through the slits S. As a result, the chips can be separated, and the filtration accuracy can be greatly improved as compared with the conventional coarse mesh wire drum. Also, the filter 2 is clogged with the chips attached to the surface by the filtration. Also has a strength that enables backwashing as compared with the conventional paper filter.
This eliminates the need for replacement and makes permanent use possible. This eliminates the conventional problem of treating industrial waste and greatly reduces the running cost of the filter 2. Also, since the cross section of the flow passage from the inner tank 3 side to the slit S is narrowed down to a tapered shape,
In the backwashing, the pressure of the cutting fluid C spouting from the slit S toward the outer tub 4 can be increased, and the chips attached to the gap can be removed at once from the outer peripheral surface of the filter 2 to be cleaned.

In the filter 2 having a porous structure in which the laminated wire mesh N is formed in a cylindrical shape, the wire meshes N1 to N
5, the mesh is separated from each other, and the mesh can be made finer, so that the filtration accuracy can be significantly improved as compared with the conventional product as described above. Since it has a strength that does not deform the shape even under the pressure of the cutting fluid C, it can be used repeatedly.

Further, since the inner tank 3 of the filtration tank 5 and the storage tank 10 for the filtered cutting fluid C are communicated with each other, the cutting fluid C required for backwashing can be stored outside the cleaning tank CCT. Even if only the amount used by the machine can be stored, it is not necessary to stop the operation of the machine tool at the time of backwashing, and a sufficient amount of the cutting fluid C to regenerate the filtering function of the filter 2 during the operation. Filter 2 can be backwashed,
Therefore, an efficient machining operation by the machine tool becomes possible.
Further, by connecting a means (a check valve 36 and a pump 37) for injecting the cutting liquid C from the sludge tank DCT only at the time of filtration to the outer tank 4 of the filtration tank 5, the cutting liquid C containing chips can be removed. The cutting fluid C can be filtered by being pressed into the filter 2 from the tank 4 to separate the chips and the clean cutting fluid C containing no chips, and the cutting fluid C can flow into the storage tank 10. Also, the cleaning tank C is used only when the excess cutting fluid C overflowing from the storage tank 10 is filtered.
Since the means (valve 40) for flowing out to the CT is connected to the storage tank 10, an amount of the cutting fluid C necessary for backwashing can be stored in the storage tank 10, and the excess cutting fluid C is removed from the cleaning tank CCT.
And the cutting fluid C can be reused in the machine tool.
Also, since the means for supplying the compressed air only at the time of backflow cleaning (compressed air supply source AP) is connected to the storage tank 10, it is necessary for backflow cleaning stored in the storage tank 10 without using excessive cutting fluid C. The filter 2 can be backwashed with only a small amount of the cutting fluid C, and the cutting fluid C is pressed into the inner tank 3 of the filtration tank 5 so that the outer tank of the filter 2 can be pressurized by the pressure of the cutting fluid C. The chips attached to the surface on the fourth side can be wiped without leaving any, and the filtering function of the filter 2 can be regenerated.
Also, since the means (valve 39) for discharging the cutting fluid C to the sludge tank DCT only at the time of backwashing is connected to the outer tank 4 of the filtration tank 5, the washed chips together with the cutting fluid C are transferred to the sludge tank of the outer tank 4. Discharge to the DCT prevents the cutting fluid C from staying in the outer tub 4 and preventing the chips from adhering to the filter 2 and deteriorating the filtering function. Since C is not discarded, it is filtered again and used as cutting fluid C used in the machine tool, and the cutting fluid C can be circulated without waste.

Since a pressure gauge 38 for measuring the pressure in the outer tank 4 of the filtration tank 5 is provided in the filtration tank 5, it is necessary to confirm that the pressure in the outer tank 4 has risen above a normal value during filtration. As a result, the filtering function of the filter 2 is reduced, and it is possible to easily understand that it is time to perform backwashing, and the practical effect is extremely large.

[Brief description of the drawings]

FIG. 1 is a diagram showing a use state of a filtration device.

FIG. 2 is a sectional view of a main part of the filtration device.

FIG. 3 is an exploded perspective view.

FIG. 4 is a diagram showing the flow of fluid during filtration and backwashing.

FIG. 5 is a perspective view of a filter made of a wedge wire.

FIG. 6 is an enlarged sectional view of the filter.

FIG. 7 is a perspective view of a filter composed of a laminated wire mesh.

FIG. 8 is an enlarged sectional view of the filter.

FIG. 9 is a cross-sectional view showing a laminated state of a wire mesh of the filter.

FIG. 10 is a sectional view of a main part showing another embodiment.

FIG. 11 is a diagram showing the flow of fluid during filtration and backwashing.

FIG. 12 is an exploded perspective view.

[Explanation of symbols]

 2 Filter 2a Hollow part 3 Inner tank 4 Outer tank 5 Filtration tank 10 Storage tank 36 Check valve 37 Pump 38 Pressure gauge 39 Valve 40 Valve 41 Valve AP Compressed air supply source C Cutting fluid CCT Filtered cutting fluid tank DCT Used cutting Liquid tank L Flow path N Laminated wire mesh S Slit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 35/02 B01D 29/38 520C 35/02 E

Claims (3)

[Claims] 1. A filtration tank in which slits are arranged in an outer peripheral surface and a flow path from a hollow portion to a slit is formed in an inner and outer tank by a cylindrical filter having a tapered shape, and a storage of filtered cutting fluid is provided. A tank is provided, the storage tank communicates with the inner tank of the filtration tank, and a means for press-fitting the cutting fluid from the used cutting fluid tank only at the time of filtration is connected to the outer tank of the filtration tank, and overflow from the storage tank is provided. A means for discharging excess cutting fluid to the filtered cutting fluid tank only during filtration is connected to the storage tank, and a means for supplying compressed air only during backwashing is connected to the storage tank, and the cutting fluid stored in the storage tank is connected to the storage tank. And a means for discharging the cutting fluid to the used cutting fluid tank only at the time of backflow cleaning is connected to the outer tank of the filtration tank. Filtration device. 2. The filtering device according to claim 1, wherein the filter has a porous structure formed by forming a laminated metal mesh into a cylindrical shape. 3. The filtering device according to claim 1, wherein a pressure gauge for measuring the pressure inside the outer tank of the filtration tank is provided in the filtration tank.