How to remove oil from cleaning fluid

Abstract

Provided is a method for removing oil from a washing liquid that enables efficient removal of fine oil from a washing liquid by using a general-purpose filter element for separating out foreign matter.　A plurality of annular protrusions 22d are formed on an outer peripheral surface 22a of a filter element 22 along substantially the entire axial-direction length of the filter element 22, whereby numerous small eddies 40 are formed in annular trenches 22e between the annual protrusions 22d. The eddies 40 are produced by the Coanda effect, whereby the washing liquid flows along the annular trenches 22e due to the viscosity of the washing liquid. Because the eddies 40 have negative pressure, fine oil 41, which is lighter than water, is separated out from water and trapped by fibers in the filter element 22, which is oleophilic.

Description

[Technical Field]

[0001] The present invention relates to a method for removing oil from a cleaning liquid, and more particularly to a method for removing oil from a cleaning liquid that can remove fine oil particles from a cleaning liquid used to clean machined parts and the like. [Background technology]

[0002] Machine parts require the removal of cuttings, grinding debris, and other debris generated during machining and other processes. Oil-based and water-soluble cleaning solutions are known for this purpose. Water-soluble cleaning solutions are often used because they are non-flammable and non-explosive. Various cleaning methods and devices have been proposed for this purpose, including immersion in the cleaning solution, spray cleaning with the cleaning solution, and air injection cleaning. It is preferable that this water-soluble cleaning solution contain as little oil as possible. This is because oil adheres to the lipophilic object being cleaned, and if this oil contains fine lipophilic foreign matter, the cleaning effect will be reduced. For this reason, oil-water separation filters that remove oil from the cleaning solution have also been proposed (e.g., Patent Document 1 and Patent Document 2). These oil-water separation filters use inorganic powders, inorganic fibers, etc. to break down the oil and have a special layered filter structure.

[0003] On the other hand, although not for removing oil from cleaning fluid, a fuel filter has also been proposed in which annular sponge filter plates of different diameters and widths are stacked as a fuel filter body to increase the filtering area (Patent Document 3). These cylindrical fuel filters filter the fuel by directing the fuel in the radial direction of the fuel filter. The present applicant also proposed a filter device for a liquid storage device equipped with a cylindrical filter element (Patent Document 4). This filter element uses a nonwoven fabric made of highly lipophilic materials such as polypropylene (PP) or polyurethane (PU). This filter device for a liquid storage device mainly uses an oil skimmer to remove oil from the cleaning fluid. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-156104 [Patent Document 2] Japanese Patent Publication No. 2020-138195 [Patent Document 3] Jikko No. 37-22688 [Patent Document 4] Utility Model Registration No. 3182493 Summary of the Invention [Problem to be solved by the invention]

[0005] Nonwoven fabrics such as polypropylene are known to have high oil absorption due to their lipophilicity, but they are unable to effectively remove trace amounts of oil when water and fine oil particles (oil droplets) are thoroughly mixed. For this reason, filters with high oil removal performance, such as those described in Patent Documents 1 and 2, are recommended, but these filters must have special structures and components. Furthermore, safely disposing of these filters, which have special structures and components, without placing a burden on the environment, is not simple and costly. The fuel filter described in Patent Document 3 filters fuel by flowing it radially through the filter body, but is unable to remove fine oil particles in the cleaning solution. Furthermore, the filtering device described in Patent Document 4 uses an oil skimmer to remove oil from the cleaning solution. This filtering device flows the cleaning solution axially around the outer periphery of the filter element to remove foreign matter such as chips and prevent clogging. In other words, the purpose of removing oil is not to use the filter element; instead, the oil is removed using a separately installed oil skimmer. This oil skimmer can remove oil floating in the cleaning liquid, but it cannot remove minute oil particles in the cleaning liquid. The present invention solves the above problems and the following problems. An object of the present invention is to provide a method for removing oil from a cleaning liquid, which can efficiently remove fine oil particles from the cleaning liquid using a general-purpose filter element for separating foreign matter. Another object of the present invention is to provide a method for removing oil from a cleaning solution that can efficiently remove fine oil particles from the cleaning solution without using a special filtration device dedicated to oil-water separation. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention employs the following means. That is, the method for removing oil from a cleaning liquid of the first invention comprises a cleaning liquid storage tank which is a container for storing cleaning liquid to be supplied to a cleaning part to perform a predetermined cleaning operation, a supply pump provided in the cleaning liquid storage tank for sucking up the cleaning liquid stored in the cleaning liquid storage tank and discharging it from a discharge port to supply the cleaning liquid to the cleaning part, a filter device provided adjacent to the cleaning liquid storage tank, and a hollow, cylindrical filter element built into the filter device and communicating with the filter element for filtering the cleaning liquid, A plurality of annular projections are formed on the outer peripheral surface of the filter element. 、 The cleaning liquid supplied from the supply pump is directed in a direction parallel to the cylindrical axis of the filter element and The aforementioned The cleaning liquid flows only along the outer peripheral surface, and oil in the cleaning liquid is captured by the filter element.

[0007] The method for removing oil from a cleaning solution according to the second aspect of the present invention is the method for removing oil from a cleaning solution according to the first aspect of the present invention, wherein the filter element is The aforementioned The nonwoven fabric is characterized by having a fiber density gradient in which the void ratio decreases from the outer peripheral surface toward the inner peripheral surface. The method for removing oil from a cleaning solution according to the third aspect of the present invention is 1 or 2 The cleaning liquid reservoir device stores the cleaning liquid in the filter element only when the cleaning operation is suspended. The aforementioned It is characterized by flowing only along the outer circumferential surface.

[0008] In the method for removing oil from a cleaning solution according to the fourth aspect of the present invention,3 wherein the cleaning liquid storage device comprises a first circulation circuit (24) for communicating the discharge port of the supply pump with an inlet of the filter device (20), a second circulation circuit (25) for supplying the second-filtered cleaning liquid from the outlet of the filter device (20) to the cleaning part, a first on-off valve (26) provided in the second circulation circuit (25) for opening and closing the second circulation circuit (25), a drain port (21d) provided in the filter device (20) for discharging the cleaning liquid in the filter device (20) to the outside of the filter device (20), a drain circuit (27) for returning the cleaning liquid from the drain port (21d) of the filter device (20) to the cleaning liquid storage tank, and a second on-off valve (28) provided in the drain circuit (27) for opening and closing the drain circuit (27), The oil is trapped by the filter element by closing the first on-off valve (26) and opening the second on-off valve (26), so that the cleaning liquid penetrates the inner periphery of the filter device (20) and the filter element. The aforementioned The filter element is characterized in that the oil is removed by flowing through the space between the outer surface and the oil-repellent fiber of the filter element. [Effects of the Invention]

[0010] The method for removing oil from cleaning fluid of the present invention can efficiently remove fine oil particles from cleaning fluid using a general-purpose filter element for separating foreign matter, thereby reducing manufacturing costs and running costs and enabling the filter element to be disposed of safely and in an environmentally friendly manner. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a front view of a cleaning liquid storage device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a plan view of the cleaning liquid reservoir device of FIG. [Figure 3] FIG. 3 is a left side view of FIG. [Figure 4]FIG. 4 is a diagram for explaining the operation of the cleaning liquid reservoir device of FIG. 1, and is an explanatory diagram that schematically shows a state in which cleaning liquid is being sprayed onto the area to be cleaned. [Figure 5] FIG. 5 is a diagram for explaining the operation of the cleaning liquid reservoir device of FIG. 1, and is an explanatory diagram that schematically shows a state in which oil in the cleaning liquid is captured by the filter element. [Figure 6] FIG. 6 is an enlarged vertical cross-sectional view of the filter element of FIG. 5, schematically illustrating a state in which the filter element captures oil in the cleaning liquid. [Figure 7] FIG. 7 is an enlarged vertical cross-sectional view of a filter element according to a second embodiment of the present invention, illustrating a state in which the filter element captures oil in a cleaning liquid. DETAILED DESCRIPTION OF THE INVENTION

[0012] [First embodiment of cleaning liquid storage device] A cleaning liquid storage device according to a first embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a front view of the cleaning liquid storage device according to the first embodiment of the present invention, and FIG. 2 is a plan view of the cleaning liquid storage device of FIG. 1. FIG. 3 is a left side view of FIG. 1, and FIG. 4 is a diagram for explaining the operation of the cleaning liquid storage device of FIG. 1, which is an explanatory diagram showing a state in which cleaning liquid is sprayed onto a cleaning area. FIG. 5 is a diagram for explaining the operation of the cleaning liquid storage device of FIG. 1, which is an explanatory diagram showing a state in which oil in the cleaning liquid is captured by a filter element. FIG. 6 is an enlarged vertical cross-sectional view of the filter element of FIG. 5, which is a diagram showing a state in which the filter element captures oil in the cleaning liquid. The cleaning liquid in the embodiment of the present invention is a cleaning liquid that is sprayed from a nozzle or the like or immersed in the object to be cleaned in a cleaning device.

[0013] As shown in FIGS. 1 to 5, a cleaning liquid storage device 1 according to a first embodiment of the present invention comprises a cage-shaped filter element 14, a filter device 20, a filter element 22 housed within the filter device 20, a first on-off valve 26, a second on-off valve 28, and the like. A cleaning liquid storage tank 10 is provided above an oil pan 30 installed on the floor. The oil pan 30 is intended to prevent cleaning liquid from spilling onto the floor and soiling it, for example, when replacing the cleaning liquid with new liquid. The cleaning liquid storage tank 10 is a container with rounded corners on the inside when viewed from above, and stores cleaning liquid. A lid 31 is provided on top of the cleaning liquid storage tank 10. This lid 31 is divided into sections of a predetermined size and is used to cover the opening at the top of the cleaning liquid storage tank 10, preventing foreign matter such as dirt and dust from entering the cleaning liquid storage tank 10.

[0014] A filter bucket 13 is disposed above the cleaning liquid storage tank 10. A basket-shaped filter element 14 is disposed within the filter bucket 13. This basket-shaped filter element 14 is, for example, a nylon mesh basket or a paper filter basket. This basket-shaped filter element 14 receives the dirty cleaning liquid and performs primary filtration of cutting powder and other contaminants when the dirty cleaning liquid returns to the cleaning liquid storage tank 10 after cleaning machine parts and the like in the cleaning device. It also receives and performs primary filtration of the dirty cleaning liquid after cleaning the filter element 22 of the filter device 20 (described below). This primary filtration allows the cleaning liquid to be filtered to a level that can be sucked by the supply pump 11. The foreign matter collected in the basket-shaped filter element 14 is removed when a predetermined amount of foreign matter has accumulated or at predetermined intervals, and then disposed of by an operator.

[0015] The cover 31 is provided with a supply pump 11. The supply pump 11 sucks up the cleaning liquid stored in the cleaning liquid storage tank 10 through a suction port and discharges the cleaning liquid from a discharge port. A filter device 20 is provided above the oil pan 30, adjacent to the cleaning liquid storage tank 10. The cover 31 is also provided with an agitation pump 12 for agitating the cleaning liquid in the cleaning liquid storage tank 10. By providing this agitation pump 12 and agitating the cleaning liquid, the liquid temperature of the cleaning liquid is made uniform and foreign matter mixed in the cleaning liquid storage tank 10 is less likely to settle, making it easier to capture the foreign matter with the cage-shaped filter element 14 when the filter element 22 is cleaned.

[0016] 4, 5, etc., the filter device 20 has two functions: it performs secondary filtration (microfiltration) of foreign matter in the cleaning liquid and removes traces of oil from the cleaning liquid. The filter device 20 is composed of a filter device main body 21 that forms the housing of the filter device 20, a filter element 22 built into the filter device main body 21, a partition wall 23 located below the filter element 22 and dividing the filter device 20 into a first chamber 20A and a second chamber 20B, and an upper cover 21e that covers the opening at the top of the filter device main body 21. The filter device main body 21 is provided with an inlet 21b located at the bottom for introducing the primarily filtered cleaning liquid into the first chamber 20A containing the filter element 22, and an outlet 21c located at the top for discharging the clean cleaning liquid that has been secondarily filtered (microfiltered) from the second chamber 20B. The upper cover 21e of the filter device main body 21 is provided with a drain port 21d for discharging the dirty cleaning liquid, which has been used to clean the filter element 22 and remove traces of oil, from the first chamber 20A to the outside of the filter device 20. Note that, although this embodiment has been described as a filter device 20 configured such that the second chamber 20B is provided below the first chamber 20A, a filter device configured such that the second chamber 20B is provided above the first chamber 20A may also be used.

[0017] A first circulation circuit 24 is provided between the supply pump 11 and the filter device 20 to communicate the discharge port of the supply pump 11 with the inlet 21b of the filter device 20 and to circulate the cleaning liquid so that the cleaning liquid discharged by the supply pump 11 can be sent to the filter device 20 (see FIGS. 4 and 5). The cleaning liquid discharged from the supply pump 11 flows through the first circulation circuit 24 and into the filter device 20. When removing fine oil, the filter element 22 causes the cleaning liquid that has flowed in from the inlet 21b to flow in a direction parallel to the axis of the filter element 22 and along the cylindrical outer circumferential surface, causing the filter element 22 to capture traces of oil in the cleaning liquid and discharge it from the drain port 21d. During cleaning of machine parts, etc., the filter element 22 causes the primarily filtered cleaning liquid that flows in from the inlet 21b to flow in the radial direction of the filter element 22, performs secondary filtration (microfiltration) of foreign matter, and discharges the clean cleaning liquid from the outlet 21c. A plurality of filter elements 22 (for example, seven) are provided in the filter device main body 21.

[0018] As shown in Figure 6, filter element 22 is made of a lipophilic nonwoven fabric such as polypropylene, has a fiber density gradient in which the porosity decreases from outer peripheral surface 22a to inner peripheral surface 22c (radially), and has a predetermined filtration accuracy (the particle size of the particles to be captured by the filter, expressed in microns). Furthermore, multiple annular protrusions 22d are formed at equal intervals on outer peripheral surface 22a of filter element 22 over substantially the entire length of filter element 22 in the axial direction (see Figure 6). Various methods for manufacturing filter element 22 from nonwoven fabric are known and are not part of the gist of the present invention, so a detailed description will not be given.

[0019] Normally (during cleaning), the filter element 22 filters the cleaning liquid by allowing only clean liquid components to pass through while blocking foreign matter contained in the cleaning liquid as the cleaning liquid passes (radially) from the outer peripheral surface 22a to the inner peripheral surface 22c. The cleaning liquid that has undergone secondary filtration (microfiltration) by the filter element 22 flows into the second chamber 20B from the end 22b of the filter element 22, which protrudes toward the second chamber 20B (see FIG. 4). The filter element 22 in this embodiment has a filtration accuracy of, for example, 10 microns. If higher filtration accuracy is desired, it can be 5 microns, 3 microns, or the like.

[0020] A second flow circuit 25 is provided between the outlet 21c of the filter device main body 21 and a cleaning area Wa of a cleaning device (not shown). A first on-off valve 26 is provided in the second flow circuit 25. In this embodiment, the first on-off valve 26 is an electromagnetic valve, and the second flow circuit 25 is closed by energizing one solenoid 26a and de-energizing the other solenoid 26b. In other words, the second flow circuit 25 is blocked at the position of the first on-off valve 26, and cleaning liquid is not delivered to the cleaning device. On the other hand, the second flow circuit 25 is opened by energizing the other solenoid 26b and de-energizing one solenoid 26a. In other words, the first on-off valve 26 in the second flow circuit 25 is opened, and clean cleaning liquid is delivered to the cleaning device and sprayed from a cleaning nozzle (not shown).

[0021] The filter device 20 can remove foreign matter from the cleaning liquid by passing the cleaning liquid from the outer peripheral surface 22a to the inner peripheral surface 22c of the filter element 22, but it cannot fully remove fine oil particles from the cleaning liquid. As the fine oil particles in the cleaning liquid increase and adhere to the lipophilic objects being cleaned, the cleaning effectiveness decreases if fine foreign matter is contained in the oil. Therefore, the cleaning liquid storage device 1 is equipped with a function for cleaning the filter element 22 and removing the fine oil particles. Specifically, when the filter device 20 performs secondary filtration (microfiltration) for a predetermined period of time, foreign matter adheres to the outer peripheral surface 22a of the filter element 22, causing clogging of the filter element 22. Clogging of the filter element 22 hinders the passage and inflow of cleaning liquid from the outer peripheral surface 22a to the inner peripheral surface 22c, resulting in an insufficient amount of cleaning liquid being delivered to the cleaning device and a decrease in cleaning performance. For this reason, a drain circuit 27 is provided between the drain port 21d of the upper cover 21e of the filter device 20 and the cleaning liquid storage tank 10. A second opening / closing valve 28 is provided midway along the drain circuit 27.

[0022] In this embodiment, the second on-off valve 28 is a solenoid valve, and the drain circuit 27 is closed by energizing one solenoid 28a and de-energizing the other solenoid 28b. In other words, the drain circuit 27 is blocked, and the cleaning liquid in the filter device main body 21 does not return to the cleaning liquid storage tank 10 via the drain circuit 27. On the other hand, the drain circuit 27 is opened by energizing the other solenoid 28b and de-energizing the one solenoid 28a. In other words, the drain circuit 27 is opened, and the cleaning liquid in the filter device main body 21 can return to the cleaning liquid storage tank 10 via the drain circuit 27. The first on-off valve 26 and the second on-off valve 28 are controlled by a control device (not shown). For example, a changeover switch for switching between "cleaning" and "oil removal" may be provided on an operation panel (not shown), and by selecting this changeover switch, the first on-off valve 26 and the second on-off valve 28 may be controlled by a control device. Note that in the description of this embodiment, the first on-off valve and the second on-off valve are described as solenoid valves, but they may also be manual first on-off valves and second on-off valves.

[0023] The cleaning liquid storage tank 10 is provided with a level gauge 17 for indicating the level of the stored cleaning liquid (see FIG. 1). This type of level gauge 17 is a float-type level gauge that indicates the level of the liquid by the up and down movement of a stainless steel float 17a floating on the liquid surface. This level gauge 17 is designed to detect when the liquid level reaches an upper or lower limit position and emit a signal. For example, the lower limit position is set at a position a predetermined amount higher than the top surface of the cleaning liquid heater 18.

[0024] The cleaning liquid storage tank 10 is also provided with a temperature measuring element 19 for measuring the temperature of the stored cleaning liquid. The cleaning liquid storage tank 10 is also provided with a cleaning liquid heater (liquid heater) 18 for maintaining the cleaning liquid at a predetermined temperature. The cleaning liquid heater 18 in this embodiment is a stainless steel heater with an anti-dry-burn function. That is, the cleaning liquid in the cleaning liquid storage tank 10 is kept liquid within a predetermined temperature range by the cleaning liquid heater 18 being controlled by a control device (not shown) based on the temperature data measured by the temperature measuring element 19.

[0025] Furthermore, the cleaning liquid storage tank 10 is provided with an oil skimmer 15, which is a floating matter removal device for removing floating matter, oil, etc., which are foreign matter with a light specific gravity that floats or floats in the cleaning liquid. This oil skimmer 15 attaches floating matter that has floated in the cleaning liquid in the cleaning liquid storage tank 10 to a metal belt 15a, removes it to the top of the cleaning liquid storage tank 10, scrapes off the adhering floating matter, etc., and collects it in a floating matter collection container 16.

[0026] The operation of this cleaning liquid storage device 1 will now be described. Figure 4 is an explanatory diagram that shows a state in which cleaning liquid is being sprayed onto the cleaning area, and Figure 5 is an explanatory diagram that shows a state in which the filter element is being cleaned and fine oil is being removed. When performing cleaning work using clean cleaning liquid that has been secondarily filtered (microfiltered) through the filter device 20 of the cleaning liquid storage device 1, for example, the changeover switch on the operation panel (not shown) is set to "cleaning" and the "start" button switch is pressed. The control device (not shown) opens the first on-off valve 26, closes the second on-off valve 28, and starts the supply pump 11.

[0027] As shown in FIG. 4, during cleaning of a machine part or the like, the pump pressure of the supply pump 11 causes the primarily filtered cleaning liquid supplied to the first circulation circuit 24 to flow in the direction of arrow f1 within the first circulation circuit 24, in the directions of arrows f2, f3, and f4 within the filter device 20, and in the directions of arrows f5 and f6 within the second circulation circuit 25, and is then supplied to the cleaning area Wa (see FIG. 4). Specifically, as the primarily filtered cleaning liquid passes and flows from the outer peripheral surface 22a of the filter element 22 to the inner peripheral surface 22c in the radial direction of arrow f3, secondary filtration (microfiltration) of the cleaning liquid occurs. In the cleaning device, the cleaning liquid is sprayed from a cleaning nozzle or the like to clean the cleaning area Wa of the object to be cleaned (not shown). The contaminated cleaning liquid flows through a return path (not shown), undergoes primary filtration via the filter bucket 13 and the cage-shaped filter element 14 within the filter bucket 13, and is then returned to the cleaning liquid storage tank 10. In this way, the clean cleaning liquid that has been secondarily filtered (microfiltered) by the filter device 20 is sprayed from the cleaning nozzle onto the cleaning area Wa without coming into contact with the outside air, and the cleaning work is carried out. To stop the cleaning work, press the "Stop" button switch on the operation panel.

[0028] To clean the filter element 22 and remove fine oil particles (oil droplets), for example, the selector switch on the operation panel (not shown) is set to "oil removal" and the "start" button is pressed. The control device (not shown) closes the first on-off valve 26, opens the second on-off valve 28, and starts the supply pump 11. As shown in FIG. 5 , the cleaning liquid supplied by the supply pump 11 flows in the direction of arrow f1 through the first distribution circuit 24, in the directions of arrows f2 and f10 through the filter device 20, and in the directions of arrows f11 and f12 through the drain circuit 27, thereby cleaning the filter element 22 and removing fine oil particles. That is, the cleaning liquid flows in the direction of arrow f10 through the space between the inner periphery 21a of the filter device main body 21 and the outer periphery 22a of the filter element 22, cleaning the filter element 22 and removing fine oil particles. To stop cleaning the filter element and removing fine oil, press the "Stop" button on the control panel.

[0029] As shown in Figure 6, the cleaning liquid supplied from the supply pump 11 flows only in a direction parallel to the cylindrical axis of the filter element 22 and along the cylindrical outer surface 22a. However, the outer surface 22a of the filter element 22 is formed with multiple annular protrusions 22d with rectangular cross-sections that are uneven in the axial direction along almost the entire length of the filter element 22 in the axial direction. This causes countless small vortices 40 to form in the annular grooves 22e between the annular protrusions 22d. These vortices 40 are created by the Coanda effect, in which the viscosity of the cleaning liquid causes the cleaning liquid to flow along the annular grooves 22e. Because the vortices 40 create negative pressure, fine oil particles 41, which are lighter than water, are separated from the water and captured by the lipophilic fibers of the filter element 22. The Coanda effect is known as a property in which a jet of viscous fluid is attracted to a nearby wall surface or behaves as if it is in continuous contact with a convex wall surface, and its occurrence is essentially unrelated to the dimensions of the wall or the convex shape (see U.S. Pat. No. 2,052,869). While the annular convex portion 22d in this embodiment has a rectangular cross-sectional shape, it may be a triangular, arc-shaped, or other annular convex portion as long as it creates turbulence in the cleaning liquid. Furthermore, the annular convex portion may be formed in a spiral shape on the outer periphery of the filter element 22.

[0030] At the same time, foreign matter adhering to the outer surface 22a of the filter element 22 is simultaneously separated. Larger particles are carried away with the cleaning fluid, while smaller particles and fine oil particles (oil droplets) are captured by the fibers. The contaminated cleaning fluid used to clean the filter element 22 flows through the drain circuit 27 (Figure 5), undergoes primary filtration through the filter bucket 13 and the cage-shaped filter element 14 within the filter bucket 13, and returns to the cleaning fluid storage tank 10. When the cleaning device is not performing cleaning operations, the first on-off valve 26 and the second on-off valve 28 can be switched to clean the filter element 22 and remove fine oil particles (oil droplets), thereby improving the operating rate of the cleaning device. The filter element 22 of the first embodiment of the present invention is made of inexpensive nonwoven fabric, such as polypropylene, and can efficiently remove fine oil particles from the cleaning fluid without the need for a specially designed filter device specifically designed for oil-water separation. This reduces manufacturing and running costs and enables the filter element 22 to be disposed of safely and environmentally.

[0031] [Second embodiment of cleaning liquid storage device] FIG. 7 is an enlarged longitudinal cross-sectional view of a filter element 220 according to a second embodiment of the present invention, illustrating the removal of oil from cleaning fluid by the filter element 220. As shown in FIG. 7, the outer peripheral surface 220a of the filter element 220 according to the second embodiment of the present invention does not have the annular protrusion 22d of the first embodiment. However, the filter element 220 is made of a lipophilic nonwoven fabric, such as a polypropylene-based fabric, and has a fiber density gradient in which the porosity decreases from the outer peripheral surface 220a to the inner peripheral surface 220c. In this example, three layers of filters with different densities and thicknesses are stacked. Therefore, when cleaning fluid supplied from the supply pump 11 flows parallel to the cylindrical axis of the filter element 220 and along the cylindrical outer peripheral surface 22a, countless small vortices 400 are generated in the gaps 22f of the outer peripheral surface 220a, where the fiber diameter is large and the porosity is high. These vortices 400 are generated by the Coanda effect, which causes the cleaning fluid to flow along the gaps 22f due to the viscosity of the cleaning fluid. The vortex flow 400 creates a negative pressure, so that fine oil particles 410, which are lighter than water, are separated from the water and captured by the fibers of the lipophilic filter element 220. Note that the lamination of multiple layers of nonwoven fabrics with different porosities is a well-known technique (for example, JP 2013-236985 A), and therefore the manufacturing method thereof will not be described in detail here.

[0032] Other Embodiments Although the present invention has been described above with reference to an embodiment, it is not limited to this embodiment. For example, in the above-described embodiment, the filter element is used for both filtering cleaning fluid by flowing the cleaning fluid from the outer peripheral surface 22a to the inner peripheral surface 22c and removing fine oil particles by flowing the cleaning fluid only along the cylindrical outer peripheral surface in a direction parallel to the axis of the filter element. However, the filter element may also be used solely for removing fine oil particles. Furthermore, the filter element shown in FIG. 7 uses three layers of fibers with different thicknesses to achieve a fiber density that decreases the porosity from the outer peripheral surface to the inner peripheral surface. However, given the objective of the present invention, which is to remove fine oil particles from cleaning fluid, the fibers constituting the filter element may be nonwoven or woven fabrics with continuously varying densities, rather than laminated, as long as they effectively generate vortex flows. Furthermore, fibers of uniform density and thickness may be used as long as they effectively generate vortex flows. [Explanation of symbols]

[0033] 1...Cleaning liquid storage device 10...Cleaning solution storage tank 11...Supply pump 12...Agitation pump 13...Filter bucket 14...Cage-shaped filter element 15...Floating matter removal device (oil skimmer) 15a...metal belt 16...Floating object collection container 17…Liquid level gauge 17a...Float 18...Liquid heater (cleaning liquid heater) 19...Temperature sensor 20...Filter device 20A...Room 1 20B...Second room 21...Filter device body 21a...Inner circumference 21b...Entrance section 21c...Exit part 21d...Drain opening 21e…Top lid 22, 220...Filter element 22a, 220a...outer surface 22b...end 22c, 220c…Inner peripheral surface 22d...Ring-shaped convex part 22e...Annular groove 22f…Void 23...Partition part 24…1st distribution circuit 25…Second distribution circuit 26...First shut-off valve 26a, 26b...Solenoid 27...Drain circuit 28...Second shut-off valve 28a, 28b...Solenoid 30...Oil pan 31...lid body 40, 400...vortex 41, 410...Oil Wa…Cleaning area

Claims

1. a cleaning liquid storage tank that is a container for storing a cleaning liquid to be supplied to a cleaning area for performing a predetermined cleaning operation; a supply pump provided in the cleaning liquid storage tank for sucking up the cleaning liquid stored in the cleaning liquid storage tank and discharging it from a discharge port to supply the cleaning liquid to the area to be cleaned; a filter device disposed adjacent to the cleaning liquid storage tank; a filter element that is built into the filter device and has a hollow, cylindrical shape and is used to filter the cleaning liquid; In a cleaning liquid storage device comprising: A plurality of annular protrusions are formed on the outer peripheral surface of the filter element, The cleaning liquid supplied from the supply pump is caused to flow in a direction parallel to the cylindrical axis of the filter element and only along the outer circumferential surface of the cylinder, thereby trapping oil in the cleaning liquid in the filter element. A method for removing oil from a cleaning solution.

2. The method for removing oil from a cleaning solution according to claim 1, The filter element is a nonwoven fabric having a fiber density gradient in which the porosity decreases from the outer peripheral surface toward the inner peripheral surface of the filter element. A method for removing oil from a cleaning solution.

3. The method for removing oil from a cleaning solution according to claim 1 or 2, The cleaning liquid reservoir allows the cleaning liquid to flow only along the outer circumferential surface of the filter element only when the cleaning operation is suspended. A method for removing oil from a cleaning solution.

4. The method for removing oil from a cleaning solution according to claim 3, The cleaning liquid storage device is a first flow circuit (24) for communicating the discharge port of the supply pump with the inlet of the filter device (20); a second circulation circuit (25) for supplying the secondarily filtered cleaning liquid from the outlet of the filter device (20) to the cleaning portion; a first on-off valve (26) provided in the second circulation circuit (25) for opening and closing the second circulation circuit (25); a drain port (21d) provided in the filter device (20) for discharging the cleaning liquid in the filter device (20) to the outside of the filter device (20); a drain circuit (27) for returning the cleaning liquid from the drain port (21d) of the filter device (20) to the cleaning liquid storage tank; a second on-off valve (28) provided in the drain circuit (27) for opening and closing the drain circuit (27); The capture of the oil by the filter element is By closing the first on-off valve (26) and opening the second on-off valve, the cleaning liquid flows through the space between the inner periphery of the filter device (20) and the outer periphery of the filter element, and the cleaning liquid is removed by the lipophilic fibers of the filter element. A method for removing oil from a cleaning solution.

Images