JP7809336B2 - Coolant Circulation Device - Google Patents

Description

The present invention relates to a coolant circulation device.

BACKGROUND ART Conventionally, grinding machines have been widely used that grind the surface of an object to be processed (a so-called workpiece) supported on a support table using a grinding tool such as a rotating grindstone (see, for example, Patent Document 1).
The grinding machine described in Patent Document 1 has a supply section that supplies coolant to a section where a workpiece is machined using a grinding tool (hereinafter referred to as the machining section), and a recovery section that recovers the coolant after it has been used in machining in the machining section.

The supply unit has a tank that stores coolant, a pump that pumps out the coolant from the tank, and a supply path that connects the tank to the machining part. When the grinding machine performs grinding, the supply unit pumps out the coolant from the tank using the pump, supplying the coolant to the machining part via the supply path.

The recovery section has a recovery path that connects the outer edge of the support base to the tank. Coolant used in processing with the grinding tool flows into the recovery path, for example by trickling down the support base. This recovery path collects the coolant and returns it to the tank.

Patent No. 6557759

In the above-mentioned grinding machine, the coolant that flows into the recovery path after being used for processing by the grinding tool contains sludge. As a result, the coolant flows through the recovery path while still containing sludge.

The amount of coolant flowing through the recovery path is determined by the amount of coolant required to process the workpiece in the processing area. As a result, the flow rate and flow speed of the coolant at each part of the recovery path are not always sufficient to flush the sludge contained in the coolant downstream. If the amount and speed of the coolant flowing through the recovery path is insufficient, some of the sludge contained in the coolant will remain and accumulate in the recovery path. In this case, the cumbersome task of regularly cleaning (removing) the sludge that has accumulated in the recovery path becomes necessary.

To prevent sludge from building up in the recovery path, it may be possible to increase the amount of coolant supplied to the machining area by the supply unit. However, this would result in an increase in the size of the components of the coolant circulation system, such as the pump that pressurizes the coolant.

Various aspects of a coolant circulation device for solving the above problems will be described below.
[Aspect 1] A coolant circulation device is applied to a grinding machine that uses a grinding tool to grind a workpiece supported on a support table, and includes a tank that stores coolant, a pump that pressure-feeds the coolant in the tank, a first supply unit that supplies the coolant pressure-feed by the pump to a processing portion of the grinding machine when grinding is performed by the grinding machine, and a recovery unit that recovers the coolant after being used in processing at the processing portion into the tank, wherein the recovery unit extends along the outer edge of the support table in a gutter-like manner into which the coolant flows, and a recovery path whose downstream end in the flow direction is connected to the tank, and the coolant circulation device includes an injection valve that injects the coolant toward the downstream side inside the recovery path, a second supply unit that supplies the coolant pressurized by the pump to the injection valve, and a control unit that controls the operation of the second supply unit so that the amount of coolant supplied by the second supply unit when the grinding process is stopped is greater than the amount of coolant supplied by the second supply unit when the grinding process is being performed.

With the above configuration, when the grinding machine is performing grinding, the coolant supplied to the processing portion of the grinding machine by the first supply unit flows into the recovery path, causing the coolant to flow continuously inside the recovery path. As a result, sludge contained in the coolant can be flushed downstream along with the coolant inside the recovery path.

In addition, when the grinding machine is stopped from performing grinding, the coolant is sprayed downstream from an injection valve installed in the recovery path. Therefore, if sludge has accumulated at the bottom of the recovery path, the sludge can be washed away and removed by the coolant sprayed from the injection valve. This prevents sludge from building up in the recovery path.

In the above configuration, when grinding processing is stopped, the first supply unit stops supplying coolant to the processing area. Therefore, at this time, the pump has a surplus in its pumping capacity (coolant supply capacity). With the above configuration, when grinding processing is stopped, the second supply unit can supply coolant to the injection valve by utilizing the surplus in the pump's pumping capacity. Therefore, even though a configuration is adopted in which coolant is injected from the injection valve when grinding processing is stopped, the resulting increase in the pump's pumping capacity can be prevented. This prevents the coolant circulation device from becoming larger.

[Aspect 2] The coolant circulation device described in [Aspect 1], wherein the recovery unit is provided between the recovery path and the tank and has a magnetic separator that attracts magnetic powder contained in the coolant by magnetic force, and the magnetic separator is connected to the downstream end of the recovery path in such a way that the interior of the magnetic separator and the downstream end of the recovery path form a single container.

Magnetic separators typically have a magnetic attraction section and a storage section where coolant accumulates. When the magnetic separator is in use, the attraction section is immersed in the coolant that has accumulated in the storage section. This allows magnetic powder (including sludge) in the coolant to be attracted to the attraction section and removed.

With the above configuration, the downstream end of the recovery path can be used as a reservoir where coolant accumulates. Therefore, compared to using a magnetic separator with a reservoir, the magnetic separator can be made smaller by the amount that part of the recovery path can be used as the reservoir. This allows for a more compact coolant circulation device.

[Aspect 3] The coolant circulation device according to [Aspect 2], wherein the injection valve is provided at a downstream end of the recovery path in a portion where the coolant accumulates.
When the grinding operation by the grinding machine is stopped, the supply of coolant to the processing area is also stopped. Simply stopping the supply of coolant causes sludge contained in the coolant to settle and accumulate at the downstream end of the trough-shaped recovery path, specifically the area where the coolant accumulates. For this reason, the area where coolant accumulates at the downstream end of the recovery path can be said to be an area where sludge easily accumulates.

With the above configuration, an injection valve is provided that injects coolant into areas where sludge is likely to accumulate when grinding operations are stopped. Therefore, by flushing away the sludge with the coolant injected from the injection valve, it is possible to effectively prevent sludge from accumulating at the bottom of the trough-shaped recovery path.

[Aspect 4] The coolant circulation device according to [Aspect 3], wherein the injection valve is provided at the upstream end in the flow direction of the portion where the coolant accumulates.
According to the above configuration, the coolant injected from the injection valve can wash away sludge from the entire portion where the coolant accumulates at the downstream end of the recovery path.

[Aspect 5] A coolant circulation device as described in [Aspect 3] or [Aspect 4], wherein the portion where the coolant accumulates has a corner that bends and extends in the flow direction, and the injection valve is provided at the corner.

These corners are areas where turbulence is likely to occur in the coolant flow, making them areas where sludge is likely to accumulate. With the above configuration, injection valves are installed in these corners, effectively preventing sludge from accumulating in these areas.

[Aspect 6] A coolant circulation device according to any one of [Aspects 3] to [Aspect 5], wherein the injection valve is configured to inject the coolant toward the connection between the recovery path and the magnetic separator.

According to the above configuration, the momentum of the coolant injected from the injection valve can be used to send the coolant containing sludge into the magnetic separator.
[Aspect 7] A coolant circulation device described in any one of [Aspect 1] to [Aspect 6], wherein the control unit stops the supply of the coolant to the injection valve by the second supply unit when the grinding process is being performed.

With the above configuration, when the grinding machine is performing grinding, the supply of coolant to the injection valve by the second supply unit is stopped, allowing the entire pump's pumping capacity to be used for the first pumping unit to supply coolant to the machining area. This allows a pump with lower pumping capacity to be used when performing grinding, compared to when coolant is injected from the injection valve. This prevents the pump from becoming larger, and ultimately prevents the coolant circulation device from becoming larger.

This invention makes it possible to prevent the coolant circulation device from becoming too large while also reducing the accumulation of sludge in the coolant recovery path.

1 is a schematic configuration diagram of a grinding machine to which a coolant circulation device according to an embodiment is applied; FIG. 2 is a schematic configuration diagram of the coolant circulation device of the embodiment. FIG. 2 is a perspective view of a recovery path and a magnetic separator according to the embodiment. FIG. 2 is a plan view of a recovery path and a magnetic separator according to the embodiment. FIG. 2 is a side cross-sectional view of the magnetic separator of the embodiment. FIG. 4 is a side cross-sectional view of a third passage and a magnetic separator in the embodiment. 4 is a flowchart showing an execution mode of an operation control process according to the embodiment;

An embodiment of the coolant circulation device will be described below.
First, a grinding machine to which the coolant circulation device of this embodiment is applied will be described.
As shown in Figure 1, the grinding machine 10 has a support table 11. The support table 11 has a rectangular outer edge in a plan view. A work table 12 is provided on top of the support table 11. The work table 12 is capable of reciprocating relative to the support table 11 in the longitudinal direction X of the support table 11. When a workpiece (hereinafter referred to as workpiece W) is machined by this grinding machine 10, the workpiece W is supported on the work table 12.

The grinding machine 10 has a processing head 13. A rotary grinding wheel 14 is attached to the processing head 13 as a grinding tool. The processing head 13 is capable of reciprocating movement in the vertical direction Y relative to the support base 11. The processing head 13 is also capable of reciprocating movement in the width direction Z of the support base 11 relative to the support base 11.

When grinding using the grinding machine 10, the processing head 13 is first moved in the width direction Z and the up-down direction Y. This puts the grinding machine 10 in a state where the grinding wheel 14 can be brought into contact with the desired position on the processing surface of the workpiece W. Then, in this state, the grinding wheel 14 is rotated, and the work table 12 and workpiece W are moved back and forth in the longitudinal direction X. This causes the processing surface of the workpiece W to be ground.

Next, the coolant circulation device 20 of this embodiment will be described.
As shown in FIG. 2, the coolant circulation device 20 of this embodiment includes a tank 21, a pump 22, a first supply unit 23, a recovery unit 24, a second supply unit 25, and an electronic control device 26.

The tank 21 stores a coolant C. The pump 22 pumps the coolant C from the tank 21. The operation of the pump 22 is controlled by an electronic control unit 26.
(1st supply section)
The first supply unit 23 is for supplying the coolant C pressure-fed by the pump 22 to the processing part (specifically, the processing head 13) of the grinding machine 10 when the grinding process is being performed by the grinding machine 10. The first supply unit 23 has a first supply path 231 and a first switching valve 232.

The first supply path 231 is composed of a hose, piping, etc. The first supply path 231 is a path through which the coolant C passes. The first supply path 231 extends in a manner that connects the output port of the pump 22 with the machining head 13. The coolant C discharged from the pump 22 is supplied to the machining head 13 via this first supply path 231.

An electromagnetically driven on-off valve is used as the first switching valve 232. Operation of the first switching valve 232 is controlled by the electronic control unit 26. The first switching valve 232 is located midway along the first supply path 231. When the first switching valve 232 is opened, the discharge port of the pump 22 is connected to the machining head 13. This allows coolant C to be supplied from the pump 22 to the machining head 13. On the other hand, when the first switching valve 232 is closed, communication between the discharge port of the pump 22 and the machining head 13 is blocked. This prevents coolant C from being supplied from the pump 22 to the machining head 13.

(Collection Department)
The recovery unit 24 recovers the coolant C after it has been used in machining in the machining head 13 into the tank 21. The recovery unit 24 has a recovery path 241, a magnetic separator 242, and a filter unit 243.

The recovery path 241 is shaped like a gutter into which the coolant C flows. As shown in Figures 1 and 2, the recovery path 241 extends below the support base 11 along the outer edge of the support base 11, covering the sides and bottom of the support base 11. The downstream end of the recovery path 241 in the flow direction of the coolant C (hereinafter simply referred to as the downstream side) is connected to the tank 21 (specifically, the magnetic separator 242).

As shown in Figures 3 and 4, the recovery path 241 extends in a U-shape in plan view. Specifically, the recovery path 241 has a first path 31, a second path 32, and a third path 33. The first path 31 extends in the longitudinal direction X along the outer edge of one side (upper side in Figure 4) in the width direction Z of the support base 11 (see Figure 2). The second path 32 extends in the longitudinal direction X along the outer edge of the other side (lower side in Figure 4) of the support base 11 in the width direction Z. The third path 33 connects the ends of the first path 31 and the second path 32 on one side (left side in Figure 4) in the longitudinal direction X, and extends in the width direction Z along the outer edge of one side (left side in Figure 4) of the support base 11 in the longitudinal direction X.

The recovery path 241 has a first path 2411 and a second path 2412 as paths through which the coolant C flows.
The first path 2411 is composed of the first path 31 and the third path 33. The end of the first path 31 farther from the third path 33 in the longitudinal direction X (the right side in FIG. 4 ) corresponds to the upstream-most portion of the first path 2411 in the flow direction. The connection between the first path 31 and the third path 33 corresponds to the intermediate portion of the first path 2411 in the flow direction. The end of the third path 33 farther from the first path 31 in the width direction Z corresponds to the downstream-most portion of the first path 2411. Each portion of the first path 2411 is inclined downward toward the downstream side in the flow direction of the coolant C. Each portion of the first path 2411 has a cross-sectional shape that narrows toward the bottom.

The second path 2412 is formed by the second passage 32. The end of the second path 32 farthest from the third path 33 in the longitudinal direction X (right side in Figure 4) corresponds to the most upstream portion of the second path 2412. The end of the second path 32 closest to the third path 33 in the longitudinal direction X corresponds to the most downstream portion of the second path 2412. Each portion of the second path 2412 is inclined downward toward the downstream side in the flow direction of the coolant C. Each portion of the second path 2412 also has a cross-sectional shape that narrows toward the bottom.

As shown in FIG. 4, a partition wall 34 is provided inside the recovery path 241 at the connection between the second path 32 and the third path 33, separating the second path 32 and the third path 33. This partition wall 34 prevents interference between the flow of coolant C in the first path 2411 and the flow of coolant C in the second path 2412.

(Magnetic separator)
The magnetic separator 242 uses magnetic force to attract magnetic powder (such as sludge) contained in the coolant C. As shown in Fig. 2, the magnetic separator 242 is provided between the recovery path 241 and the tank 21. The magnetic separator 242 removes sludge contained in the coolant C before the coolant C returns to the tank 21.

As shown in FIGS. 5 and 6, the magnetic separator 242 includes a case 40, an adsorption section 41, a squeezing roller 43, and a scraping section 44.
The case 40 has an inlet 401. The inlet 401 is connected to downstream ends of the recovery paths 241 (specifically, the first path 2411 and the second path 2412). The coolant C flows from the recovery path 241 into the case 40 via the inlet 401. Specifically, the interior of the magnetic separator 242 and the downstream end of the first path 2411 are integrated into a single container, and the magnetic separator 242 (specifically, the inlet 401 of the case 40) is connected to the downstream end of the first path 2411. Furthermore, the interior of the magnetic separator 242 and the downstream end of the second path 2412 are integrated into a single container, and the magnetic separator 242 (specifically, the inlet 401 of the case 40) is connected to the downstream end of the second path 2412. The coolant circulation device 20 of this embodiment is configured so that the coolant C accumulates in the container-shaped portion, specifically, in the downstream end of the recovery path 241 and inside the case 40 of the magnetic separator 242. The case 40 also has an outlet 402. The coolant C flows out from this outlet 402.

The attraction part 41 is disposed inside the case 40. The attraction part 41 incorporates a permanent magnet. The attraction part 41 is cylindrical. The attraction part 41 is rotatable around the axis of the cylindrical shape. When in use, the attraction part 41 is driven to rotate by a motor (not shown). A portion of the attraction part 41 is immersed in the coolant C. Therefore, the attraction part 41 attracts sludge contained in the coolant C.

The squeezing roller 43 is disposed inside the case 40. The squeezing roller 43 is cylindrical. The axis of the squeezing roller 43 and the axis of the suction portion 41 extend parallel to each other. The squeezing roller 43 is disposed so that its outer surface contacts the outer surface of the suction portion 41. In the magnetic separator 242, the squeezing roller 43 rotates together with the suction portion 41, squeezing out the coolant C adhering to the suction portion 41 at the contact point between the suction portion 41 and the squeezing roller 43.

The scraping portion 44 is used to scrape off sludge adhering to the outer surface of the adsorption portion 41. The scraping portion 44 is fixed to the case 40. The scraping portion 44 extends from the inside to the outside of the case 40. The scraping portion 44 has a scraping plate 441 and a guide portion 442. The scraping plate 441 forms the tip portion of the scraping portion 44 inside the case 40. The tip of the scraping plate 441 is flat. The tip of the scraping plate 441 faces the outer surface of the adsorption portion 41. The guide portion 442 forms the part of the scraping portion 44 on the outer side of the case 40. The guide portion 442 extends from the inside to the outside of the case 40 with a U-shaped cross section. In the magnetic separator 242, as the adsorption portion 41 rotates, sludge adhering to the outer surface of the adsorption portion 41 is scraped off by the scraping plate 441 of the scraping portion 44. The sludge scraped off by the scraping plate 441 is guided by the guide portion 442 of the scraping portion 44 and discharged outside the case 40.

The filter section 243 has filter paper. As shown in FIG. 2, the filter section 243 is located downstream of the magnetic separator 242. After passing through the magnetic separator 242, the coolant C passes through the filter section 243. This filter section 243 removes sludge contained in the coolant C, i.e., sludge that cannot be completely removed by the magnetic separator 242. In this embodiment, the coolant C that passes through the filter section 243 is returned to the tank 21.

(Second supply section)
The second supply unit 25 is for supplying the coolant C pressure-fed by the pump 22 to the injection valves 51 to 54 provided in the recovery path 241. The second supply unit 25 has a second supply path 251 and a second switching valve 252.

The second supply path 251 is composed of a hose, piping, etc. The second supply path 251 is a path through which the coolant C passes. The second supply path 251 extends in a manner that connects the discharge port of the pump 22 with each of the injection valves 51 to 54. The coolant C pressurized by the pump 22 is supplied to each of the injection valves 51 to 54 via this second supply path 251.

An electromagnetically driven on-off valve is used as the second selector valve 252. Operation of the second selector valve 252 is controlled by the electronic control unit 26. The second selector valve 252 is located midway along the second supply path 251. When the second selector valve 252 is opened, the discharge port of the pump 22 is connected to each of the injection valves 51 to 54. This allows the supply of coolant C from the pump 22 to each of the injection valves 51 to 54. On the other hand, when the second selector valve 252 is closed, the connection between the discharge port of the pump 22 and each of the injection valves 51 to 54 is cut off. This prevents the supply of coolant C from the pump 22 to each of the injection valves 51 to 54.

(injection valve)
2 to 4, each of the injection valves 51 to 54 is provided in a manner that injects the coolant C downstream inside the recovery path 241. By injecting the coolant C from each of the injection valves 51 to 54, it is possible to flush the coolant C containing sludge downstream and to flush downstream the sludge that has accumulated at the bottom of the recovery path 241. This makes it possible to prevent sludge from accumulating in the recovery path 241.

Two first injection valves 51 are provided in the recovery path 241. One first injection valve 51 is provided at the upstream end (right side in Figure 4) of the first path 2411, and one first injection valve 51 is provided at the upstream end of the second path 2412. The first injection valves 51 are provided in a portion of the recovery path 241 where coolant C does not accumulate.

Two second injection valves 52, one third injection valve 53, and one fourth injection valve 54 are provided in the reservoir 244 (shown by dotted hatching in Figure 2), which is the portion of the recovery path 241 where the coolant C accumulates.

When the grinding operation by the grinding machine 10 is stopped, the supply of coolant C to the processing head 13 is also stopped. Simply stopping the supply of coolant C causes sludge contained in the coolant C to settle and accumulate at the downstream end of the trough-shaped recovery path 241, specifically in the reservoir 244 where the coolant C accumulates (the portion to the left of the dashed line L in Figure 4). For this reason, the reservoir 244 of the recovery path 241 can be said to be a portion where sludge tends to accumulate. In this embodiment, injection valves 52-54 are provided in the reservoir 244, where sludge tends to accumulate when grinding operation is stopped. Therefore, by flushing out the sludge with the coolant C sprayed from these injection valves 52-54, it is possible to prevent sludge from accumulating at the bottom of the trough-shaped recovery path 241.

One second injection valve 52 is provided at the upstream end (right side in Figure 4) of the reservoir 244 of the first path 2411, and one at the upstream end of the reservoir 244 of the second path 2412. This allows coolant C to be sprayed from the second injection valve 52 onto almost the entire reservoir 244 of the first path 2411. Furthermore, coolant C can be sprayed from the second injection valve 52 onto almost the entire reservoir 244 of the second path 2412. Therefore, according to this embodiment, the coolant C sprayed from the second injection valve 52 can flush sludge downstream throughout the entire reservoir 244 of the recovery path 241.

The third injection valve 53 is provided at the connection between the first passage 31 and the third passage 33, specifically at the portion that bends and extends in the flow direction of the coolant C (hereinafter referred to as the corner 245). Among the reservoir 244 of the recovery path 241, the corner 245 is a portion where turbulence is likely to occur in the flow of the coolant C, and therefore is a portion where sludge contained in the coolant C is likely to accumulate. According to this embodiment, the coolant C injected from the third injection valve 53 can wash away sludge that accumulates in the corner 245. This effectively prevents sludge from accumulating in the corner 245.

The fourth injection valve 54 is provided at a central position in the width direction Z of the third passage 33. The fourth injection valve 54 is provided in a manner that injects coolant C toward the inlet 401 of the magnetic separator 242, in other words, toward the connecting portion between the recovery path 241 and the magnetic separator 242. According to this embodiment, the momentum of the coolant C injected from the fourth injection valve 54 can be used to send the coolant C containing sludge into the interior of the magnetic separator 242.

(Electronic control device)
The electronic control device 26 has an arithmetic processing unit 261 consisting of one or more processors, and a storage unit 262 that stores various data related to the operation control of various devices. The storage unit 262 stores programs that cause the arithmetic processing unit 261 to execute various processes related to the operation control of the pump 22, the first selector valve 232, and the second selector valve 252. The arithmetic processing unit 261 executes the programs to execute various processes related to the operation control of the pump 22, the first selector valve 232, and the second selector valve 252. In this embodiment, the electronic control device 26 executes processes related to the operation control of the coolant circulation device 20 (operation control processes). In this embodiment, the electronic control device 26 corresponds to a control unit.

The manner in which the operation control process is executed will be described below.
7, when the grinding machine 10 is performing grinding (step S1: YES), the first supply unit 23 supplies the coolant C to the machining head 13 (step S2). At this time, the second supply unit 25 stops supplying the coolant C to the injection valves 51 to 54. Specifically, with the pump 22 operating, the first selector valve 232 is opened and the second selector valve 252 is closed.

In this embodiment, when the grinding machine 10 is performing grinding, the coolant C supplied to the processing head 13 by the first supply unit 23 flows into the recovery path 241. As a result, the coolant C flows continuously inside the recovery path 241. Therefore, inside the recovery path 241, the sludge contained in the coolant C can flow downstream together with the coolant C.

Furthermore, in this embodiment, when the grinding machine 10 is performing grinding, the supply of coolant C by the second supply unit 25 to the injection valves 51-54 is stopped. At this time, the pumping capacity (coolant C supply capacity) of the pump 22 is not used to supply coolant C to each injection valve 51-54 by the second supply unit 25. Therefore, all of the pumping capacity of the pump 22 can be used to supply coolant C to the machining head 13 by the first supply unit 23. This makes it possible to use a pump 22 with lower pumping capacity compared to when coolant C is injected from the injection valves 51-54, even when the grinding machine 10 is performing grinding. This prevents the pump 22, and therefore the coolant circulation device 20, from becoming larger.

On the other hand, when grinding by the grinding machine 10 is stopped (step S1: NO), the supply of coolant C to the machining head 13 by the first supply unit 23 is stopped (step S3). At this time, the supply of coolant C to each injection valve 51-54 by the second supply unit 25 is started. Specifically, with the pump 22 operating, the first selector valve 232 is closed and the second selector valve 252 is opened.

In this embodiment, when grinding by the grinding machine 10 is stopped, coolant C is sprayed downstream from the injection valves 51-54 provided in the recovery path 241. Therefore, if sludge has accumulated at the bottom of the recovery path 241, the sludge can be washed away and removed by the coolant C sprayed from the injection valves 51-54. This makes it possible to prevent sludge from building up in the recovery path 241.

Furthermore, in this embodiment, even when grinding processing by the grinding machine 10 is stopped, the circulation of coolant C continues in the circulation path formed by the recovery path 241, magnetic separator 242, filter unit 243, and tank 21. Therefore, compared to when the circulation of coolant C is stopped in conjunction with the stopping of grinding processing by the grinding machine 10, the period during which coolant C passes through the magnetic separator 242 and filter unit 243 can be extended. Furthermore, the total amount of coolant C passing through the magnetic separator 242 and filter unit 243 can also be increased. This allows sludge contained in the coolant C to be thoroughly removed, thereby keeping the coolant C clean.

Furthermore, in this embodiment, when the grinding operation by the grinding machine 10 is stopped, the supply of coolant C to the machining head 13 by the first supply unit 23 is stopped. Therefore, at this time, the pump 22 has a surplus in its pumping capacity. According to this embodiment, when the grinding operation is stopped, the second supply unit 25 can supply coolant C to the injection valves 51-54 by utilizing the surplus in the pumping capacity of the pump 22. Therefore, although a configuration is adopted in which coolant C is injected from the injection valves 51-54 when the grinding operation is stopped, an increase in the pumping capacity of the pump 22 due to this can be prevented. This prevents the pump 22, and therefore the coolant circulation device 20, from becoming larger.

According to this embodiment, sludge accumulation in the recovery path 241 is suppressed, thereby reducing the need for tedious maintenance work such as periodically cleaning sludge accumulated in the recovery path 241. Furthermore, because the size of the pump 22 is suppressed, the coolant circulation device 20 can be operated with reduced energy consumption.

According to this embodiment, the following effects can be obtained.
(1) When the grinding machine 10 is performing grinding, the supply of coolant C to the injection valves 51 to 54 by the second supply unit 25 is stopped. When the grinding machine 10 is not performing grinding, the second supply unit 25 continues to supply coolant C to the injection valves 51 to 54. This makes it possible to prevent the coolant circulation device 20 from becoming larger and to prevent sludge from accumulating in the recovery path 241.

(2) A magnetic separator 242 is provided between the recovery path 241 and the tank 21. The interior of the magnetic separator 242 and the downstream end of the recovery path 241 form a single integrated container, and the magnetic separator 242 is connected to the downstream end of the recovery path 241.

Typically, the magnetic separator 242 has a magnetic attraction portion 41 and a storage portion (shown by a dashed line in Figure 5) in which the coolant C accumulates. When the magnetic separator 242 is in use, the attraction portion 41 is immersed in the coolant C accumulated in the storage portion. This causes the magnetic powder in the coolant C to be attracted to the attraction portion 41 and removed. According to this embodiment, the downstream end of the recovery path 241 can be used as a storage portion in which the coolant C accumulates. Therefore, compared to using a magnetic separator with a storage portion, the magnetic separator 242 can be made smaller by the amount that part of the recovery path 241 can be used as the storage portion, and this in turn allows for a more compact coolant circulation device 20.

(3) The second injection valve 52, third injection valve 53, and fourth injection valve 54 are provided in the reservoir 244 of the recovery path 241. With this configuration, the injection valves 52 to 54 can be provided in the reservoir 244, which is an area where sludge tends to accumulate when grinding processing is stopped. Therefore, by flushing out the sludge with the coolant C injected from the injection valves 52 to 54, it is possible to effectively prevent sludge from accumulating at the bottom of the trough-shaped recovery path 241.

(4) One second injection valve 52 is provided at the upstream end of the reservoir 244 of the first path 2411, and one at the upstream end of the reservoir 244 of the second path 2412. With this configuration, the coolant C injected from the second injection valve 52 can flush out sludge throughout the reservoir 244 of the recovery path 241.

(5) The third injection valve 53 is provided at the corner 245 of the recovery path 241. With this configuration, the coolant C injected from the third injection valve 53 can wash away sludge that accumulates at the corner 245. This effectively prevents sludge from accumulating at the corner 245.

(6) The fourth injection valve 54 is configured to inject coolant C toward the connection between the recovery path 241 and the magnetic separator 242. With this configuration, the momentum of the coolant C injected from the fourth injection valve 54 can be used to send the coolant C containing sludge into the interior of the magnetic separator 242.

(Example of change)
The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

- A single three-way valve may be provided in place of the first switching valve 232 and the second switching valve 252. In this case, the operation of the three-way valve can be controlled to be in either a first operating state in which the discharge port of the pump 22 is connected to the machining head 13, or a second operating state in which the discharge port of the pump 22 is connected to each of the injection valves 51 to 54.

The filter unit 243 may be omitted.
The partition wall 34 may be omitted.
When the grinding machine 10 is performing a grinding operation, the supply of coolant C to each of the injection valves 51-54 may not necessarily be stopped, and a small amount of coolant C may be supplied to all of the injection valves 51-54. Alternatively, when the grinding machine 10 is performing a grinding operation, a small amount of coolant C may be supplied to one (or more) of the injection valves 51-54. In short, the operation of the second supply unit 25 (more specifically, its components) may be controlled so that the amount of coolant C supplied by the second supply unit 25 when the grinding operation is stopped is greater than the amount of coolant C supplied by the second supply unit 25 when the grinding operation is stopped. With this configuration, when the grinding operation is stopped by the grinding machine 10, the second supply unit 25 can supply coolant C to the injection valves 51-54 by utilizing the surplus pumping capacity of the pump 22.

- One (or more) of the injection valves 51-54 may be omitted. It is also possible to install one (or more) new injection valves inside the recovery path 241.

- The second supply unit 25 may be configured to supply coolant C to each injection valve 51-54 only during the period (execution period) from when grinding by the grinding machine 10 is stopped until a predetermined time has elapsed. This configuration also makes it possible to prevent sludge from building up in the recovery path 241.

In the above configuration, the injection period of the injection valves 51-54 that will appropriately prevent sludge from accumulating in the recovery path 241 can be determined based on the results of experiments and simulations, and this injection period can be predetermined as the execution period.

Furthermore, in the above configuration, the operation of the second supply unit 25 can be controlled as follows. That is, the amount of coolant C supplied by the second supply unit 25 to each injection valve 51-54 when the grinding machine 10 is performing grinding is set to "VC1." The amount of coolant C supplied by the second supply unit 25 when the grinding machine 10 is not performing grinding and the second supply unit 25 is supplying coolant C to each injection valve 51-54 (during the execution period) is set to "VC2." The operation of the second supply unit 25 can then be controlled so that the supply amount VC2 is greater than the supply amount VC1.

- The coolant circulation device according to the above embodiment can also be applied to a coolant circulation device of the type in which the recovery path extends in a square ring shape along the outer edge of the support base. The coolant circulation device according to the above embodiment can also be applied to a coolant circulation device of the type in which the recovery path extends in a C-shape along the outer edge of an elliptical (or circular) support base. The coolant circulation device according to the above embodiment can also be applied to a coolant circulation device of the type in which the recovery path extends in a ring shape along the outer edge of an elliptical (or circular) support base.

- The coolant circulation device according to the above embodiment can also be applied to coolant circulation devices that are designed so that coolant C does not accumulate at the downstream end of the recovery path, such as coolant circulation devices that use the magnetic separator with the storage section described above.

- The coolant circulation device according to the above embodiment can also be applied to coolant circulation devices that do not have a magnetic separator 242, such as a coolant circulation device that uses a cyclone separator instead of the magnetic separator 242.

REFERENCE SIGNS LIST 10 Grinding machine 11 Support stand 12 Work table 13 Machining head 14 Rotary grinding wheel 20 Coolant circulation device 21 Tank 22 Pump 23 First supply section 24 Recovery section 241 Recovery path 242 Magnetic separator 244 Reservoir section 245 Corner section 25 Second supply section 26 Electronic control device 51 First injection valve 52 Second injection valve 53 Third injection valve 54 Fourth injection valve

Claims (7)

A coolant circulation device adapted for use in a grinding machine that uses a grinding tool to grind a workpiece supported on a support table, the coolant circulation device comprising: a tank that stores coolant; a pump that pressure-feeds the coolant in the tank; a first supply unit that supplies the coolant pressure-feed by the pump to a processing portion of the grinding machine when grinding is performed by the grinding machine; and a recovery unit that recovers the coolant into the tank after it has been used in processing at the processing portion,
the recovery section extends along an outer edge of the support base in a gutter-like manner into which the coolant flows, and has a recovery path whose downstream end in a flow direction of the coolant is connected to the tank;
The coolant circulation device is
an injection valve that injects the coolant toward the downstream side inside the recovery path;
a second supply unit that supplies the coolant pressure-fed by the pump to the injection valve;
a control unit that controls the operation of the first supply unit and the second supply unit in such a manner that, during execution of the grinding process , the first supply unit executes the supply of the coolant to the processed portion and the second supply unit stops the supply of the coolant to the injection valve, and, when execution of the grinding process is stopped, the first supply unit stops the supply of the coolant to the processed portion and the second supply unit starts the supply of the coolant to the injection valve ,
The coolant circulation device , wherein the pump is a common pump used to pressure-feed the coolant in the first supply unit and to pressure-feed the coolant in the second supply unit . A coolant circulation device adapted for use in a grinding machine that uses a grinding tool to grind a workpiece supported on a support table, the coolant circulation device comprising: a tank that stores coolant; a pump that pressure-feeds the coolant in the tank; a first supply unit that supplies the coolant pressure-feed by the pump to a processing portion of the grinding machine when grinding is performed by the grinding machine; and a recovery unit that recovers the coolant into the tank after it has been used in processing at the processing portion,
the recovery section extends along an outer edge of the support base in a gutter-like manner into which the coolant flows, and has a recovery path whose downstream end in a flow direction of the coolant is connected to the tank;
The coolant circulation device is
an injection valve that injects the coolant toward the downstream side inside the recovery path;
a second supply unit that supplies the coolant pressure-fed by the pump to the injection valve;
a control unit that controls the operation of the second supply unit in such a manner that the amount of coolant supplied by the second supply unit when the grinding process is stopped is greater than the amount of coolant supplied by the second supply unit when the grinding process is being performed,
the recovery unit is provided between the recovery path and the tank, and includes a magnetic separator that attracts magnetic powder contained in the coolant by magnetic force;
The magnetic separator is a coolant circulation device connected to the downstream end of the recovery path in such a manner that the interior of the magnetic separator and the downstream end of the recovery path form a single container. The coolant circulation device according to claim 2 , wherein the injection valve is provided at a downstream end of the recovery path in a portion where the coolant accumulates. 4. The coolant circulation device according to claim 3, wherein the injection valve is provided at an upstream end in the flow direction of the portion where the coolant accumulates. the portion where the coolant accumulates has a corner portion that bends and extends in the flow direction,
The coolant circulation device according to claim 3 , wherein the injection valve is provided at the corner portion. The coolant circulation device according to claim 3 , wherein the injection valve is provided in a manner to inject the coolant toward a communication portion between the recovery path and the magnetic separator. The coolant circulation device according to any one of claims 2 to 6, wherein the control unit stops the supply of the coolant to the injection valve by the second supply unit during execution of the grinding process.