Exhaust valve and filtration device

Abstract

To remove bubbles by using an air vent structure of a small and simple constitution.SOLUTION: An exhaust valve provided in a plate-like part provided near an upper end of a filtration device installed in a tank in which oil is stored includes a rod-like part inserted into an air vent hole formed in the plate-like part, a first stopper provided at an upper end of the rod-like part, and a second stopper provided at a lower end of the rod-like part. The second stopper and the rod-shaped portion integrally constitute a moving member, and the moving member is formed so as to float on the oil. A hollow portion in which one end of the rod-shaped portion is provided is formed in the first stopper. The rod-shaped portion is movable between a position at which the first stopper abuts against the air vent hole to close the air vent hole and a position at which the moving member abuts against the air vent hole.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an exhaust valve and a filtering device. [Background technology]

[0002] Patent Document 1 discloses a suction strainer in which an air vent hole is formed in an upper plate that covers the entire upper end of an approximately cylindrical filtering section formed by folding a thin plate into a pleated shape, and a movable member is provided that can move between a position that blocks the air vent hole and a position that opens the air vent hole. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6830987 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the invention described in Patent Document 1, depending on the operating conditions of the device, there is a risk that oil will spray out from the air vent hole when the air vent hole is open.

[0005] The present invention has been made in view of the above circumstances, and has an object to provide an exhaust valve and a filter device that can prevent oil from spraying out from the air vent hole. [Means for solving the problem]

[0006] In order to solve the above problems, the valve device of the present invention is, for example, an exhaust valve provided on a plate-shaped portion provided near the upper end of a filtering device installed in a tank in which oil is stored, and comprises a rod-shaped portion inserted into an air vent hole formed in the plate-shaped portion, a first stopper provided at the upper end of the rod-shaped portion, and a second stopper provided at the lower end of the rod-shaped portion, the second stopper and the rod-shaped portion being integrated to form a movable member, the movable member being formed to float on oil, the first stopper having a hollow portion in which one end of the rod-shaped portion is provided, and the rod-shaped portion being movable between a position where the first stopper abuts against the air vent hole to block the air vent hole, and a position where the second stopper abuts against the air vent hole.

[0007] Furthermore, the filtering device according to the present invention is, for example, a filtering device installed in a tank in which oil is stored, and comprises a cylindrical filtering section, a plate-shaped section covering the entire upper end of the filtering section and having an air vent hole formed therein, and an exhaust valve inserted into the air vent hole, wherein the exhaust valve has a rod-shaped section inserted into the air vent hole, a first stopper provided at the upper end of the rod-shaped section, and a second stopper provided at the lower end of the rod-shaped section, the second stopper and the rod-shaped section being integrated to form a movable member, the movable member being formed to float on oil, the first stopper having a hollow section in which one end of the rod-shaped section is provided, and the exhaust valve is movable between a position where the first stopper abuts against the air vent hole to block the air vent hole, and a position where the second stopper abuts against the air vent hole.

[0008] The valve device or filtration device according to the present invention comprises a rod-shaped portion that is inserted into an air vent hole formed in the plate-shaped portion, a first stopper provided at the upper end of the rod-shaped portion, and a second stopper that floats on oil and is provided at the lower end of the rod-shaped portion, and is movable between a position where the first stopper abuts against the air vent hole to block it, and a position where the second stopper abuts against the air vent hole. In this way, by the movable member abutting against the air vent hole, the second stopper is positioned below the air vent hole, making it possible to prevent oil from spraying out of the air vent hole.

[0009] The first stopper and the second stopper may be made of different materials, which allows the first moving member to be made of rubber or metal.

[0010] The first stopper may have a hollow portion in which one end of the rod-shaped portion is provided. This reduces the weight of the first stopper and makes it easier to assemble the first stopper and the rod-shaped portion. This configuration is particularly effective when the first stopper is made of a heavy material such as rubber or metal.

[0011] The first stopper may be made of an elastically deformable material, whereby the first stopper is elastically deformed by external pressure and comes into close contact with the upper plate, thereby providing excellent sealing properties.

[0012] The second stopper can come into contact with the air vent hole, and may have a spherical, spherical-notched, spherical-frustum, conical, or conical-frustum portion. This makes it easier for the second stopper to block the circular air vent hole and to prevent oil from spraying out. In particular, even if the oil level is tilted due to tilting of the device, the second stopper can block the air vent hole.

[0013] The second stopper may have a main body portion having a side surface in the shape of a truncated cone, a truncated pyramid, or a column, and a recess may be formed in the lower end surface of the second stopper, whereby air accumulates in the recess, making it easier for the exhaust valve to separate from the plate-shaped portion, and thereby facilitating the release of air.

[0014] The shape of the side surface of the recess may be substantially similar to the shape of the side surface of the main body, and the width of the recess at the lower end of the second stopper may be 0.8 times or more the width of the main body, thereby increasing the size of the recess and allowing more air to be stored in the recess.

[0015] The connecting member may have a hole that connects the hollow portion of the filtering unit to the outside of the filtering unit, and the hole may be provided with a relief valve that is disposed inside the cover. In this way, the cover blocks the unfiltered hydraulic oil and air that flow out when the relief valve opens, and the air that has accumulated inside the cover can be discharged by the exhaust valve. This makes it possible to prevent air mixed in with the hydraulic oil from being sucked into the hydraulic pump. [Effects of the Invention]

[0016] According to the present invention, it is possible to prevent oil from spraying out from the air vent hole. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram showing an outline of a tank 100 in which a suction strainer 1 and an exhaust valve 2 are provided according to one embodiment of the present invention. [Figure 2] 1 is a diagram showing an outline of a suction strainer 1. FIG. [Figure 3] FIG. 2 is a cross-sectional view showing an outline of an exhaust valve 2. [Figure 4] 1A and 1B are diagrams showing an outline of a first stopper 21, in which (A) is a perspective view and (B) is a cross-sectional view. [Figure 5] 1A and 1B are diagrams showing an outline of a moving member 24, in which (A) is a perspective view, (B) is a plan view, and (C) is a cross-sectional view taken along the line AA of (B). [Figure 6] FIG. 2 is a diagram schematically illustrating a state in which the exhaust valve 2 is positioned at the upper end. [Figure 7] FIG. 2 is a diagram schematically illustrating a state in which the exhaust valve 2 is positioned at the lower end. [Figure 8] 10A to 10C are diagrams showing an outline of a first stopper 21A according to a modified example, in which (A) is a perspective view, (B) is a plan view, and (C) is a cross-sectional view. [Figure 9] 10A, 10B, and 10C are diagrams showing an outline of a first stopper 21B according to a modified example, in which (A) is a perspective view, (B) is a plan view, and (C) is a cross-sectional view. [Figure 10] 10A to 10C are diagrams showing an outline of a first stopper 21C according to a modified example, in which (A) is a perspective view, (B) is a plan view, and (C) is a cross-sectional view. [Figure 11] 10A to 10C are diagrams showing an outline of a first stopper 21D according to a modified example, in which (A) is a perspective view, (B) is a plan view, and (C) is a cross-sectional view. [Figure 12] 10A, 10B, and 10C are diagrams showing an outline of a moving member 24A having a second stopper 22A according to a modified example, in which (A) is a perspective view, (B) is a plan view, and (C) is a cross-sectional view. [Figure 13] 10A, 10B, and 10C are diagrams showing an outline of a moving member 24B having a second stopper 22B according to a modified example, in which (A) is a perspective view, (B) is a plan view, and (C) is a cross-sectional view. [Figure 14] FIG. 2 is a cross-sectional view showing an outline of an exhaust valve 2A. [Figure 15] FIG. 10 is a diagram schematically showing a state in which a first moving member 21E is positioned at the upper end. [Figure 16] 10 is a diagram schematically showing a state in which a second stopper 22C is positioned at the upper end. FIG. [Figure 17] FIG. 1 is a diagram illustrating an outline of a return filter 1A. [Figure 18] 1A and 1B are diagrams showing an outline of a return filter 1A, in which (A) is a plan view and (B) is a perspective view of a main part. [Figure 19] 1A and 1B are diagrams showing an outline of an exhaust valve 2B, in which (A) is a cross-sectional view and (B) is a side view. [Figure 20] 1A and 1B are diagrams showing an outline of an exhaust valve 2C, in which (A) is a cross-sectional view and (B) is a side view. [Figure 21]1A and 1B are diagrams showing an outline of an exhaust valve 2D, in which (A) is a cross-sectional view and (B) is a side view. [Figure 22] 1A and 1B are diagrams showing an outline of an exhaust valve 2E, in which (A) is a cross-sectional view and (B) is a side view. [Figure 23] 1A and 1B are diagrams showing an outline of an exhaust valve 2F, in which (A) is a cross-sectional view and (B) is a side view. [Figure 24] This is a diagram showing an outline of a moving member 24G that the exhaust valve has, where (A) is a plan view, (B) is a front view, (C) is a bottom view, (D) is a perspective view, and (E) is a side view. [Figure 25] This is a diagram showing an outline of the moving member 24H of the exhaust valve, where (A) is a plan view, (B) is a front view, (C) is a bottom view, (D) is an oblique view, and (E) is a side view. [Figure 26] FIG. 1 is a diagram illustrating an outline of a return filter 1B. [Figure 27] FIG. 1 is a diagram illustrating an outline of a return filter 1C. DETAILED DESCRIPTION OF THE INVENTION

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a filtering device installed in a tank that stores oil, or an exhaust valve provided in the filtering device.

[0019] First Embodiment Fig. 1 is a diagram showing an outline of a tank 100 that is one embodiment of the present invention and that is provided therein with a suction strainer 1 and an exhaust valve 2. Fig. 1 shows the main parts of the tank 100 in a see-through manner.

[0020] The tank 100 is installed in a work machine (for example, a hydraulic device) not shown, and is a tank for storing hydraulic oil provided in a hydraulic circuit for supplying hydraulic oil to the hydraulic device. In the hydraulic circuit, the hydraulic oil passes through the hydraulic device and is introduced into the tank 100. The tank 100 has, for example, a box-shaped tank body 101, which is hollow inside.

[0021] In this embodiment, hydraulic oil is stored in tank 100, but the oil stored in the tank is not limited to hydraulic oil.

[0022] Inside the tank body 101, a suction strainer 1 provided with an exhaust valve 2 and a return filter 110 are mainly provided.

[0023] An inlet 101a is formed on the side of the tank body 101, allowing hydraulic oil to flow into the inside of the tank body 101. The hydraulic oil that flows in from the inlet 101a is guided to a return filter 110. The hydraulic oil is filtered by the return filter 110 and stored in the tank 100.

[0024] Furthermore, openings 101b and 101c are formed on an upper end surface 101f of the tank body 101 to be used for maintenance of the suction strainer 1 and the return filter 110. A lid 102 is attached to the opening 101b, and a lid 103 is attached to the opening 101c.

[0025] Bolt insertion holes are formed in the peripheral edges of the lid bodies 102 and 103. The lid bodies 102 and 103 are fastened to the tank body 101 by threading bolts 105 inserted into the bolt insertion holes into bolt holes (not shown) in the tank body 101.

[0026] An outlet 101d is formed near the bottom end of the tank body 101 (in this embodiment, at a position on the side of the tank body 101 close to the bottom surface 101g) to allow the hydraulic oil in the tank body 101 to flow out to a hydraulic pump (not shown). A suction pipe 104 connected to the suction port of the hydraulic pump (not shown) from the outside of the tank body 101 is inserted into the outlet 101d.

[0027] A suction strainer 1 is provided above the outlet 101d (inside the tank body 101) to prevent foreign matter from entering the suction pipe 104. The hydraulic oil stored in the tank 100 is sucked into a hydraulic pump (not shown), flows out into the suction pipe 104 through the suction strainer 1, and is then supplied to the hydraulic device again.

[0028] 1, as long as the outlet 101d is located near the bottom end of the tank body 101. For example, the outlet 101d may be formed on the bottom surface of the tank body 101.

[0029] A partition plate 101e is provided on the bottom surface of the tank body 101 to separate a space where the suction strainer 1 is provided from a space where the return filter 110 is provided. Note that the partition plate 101e is not essential.

[0030] Fig. 2 is a schematic diagram of a suction strainer 1 (corresponding to the filtration device of the present invention). Fig. 2 shows a partial cross section (however, hatching indicating a cross section is omitted). The suction strainer 1 mainly has a strainer portion 10 and an exhaust valve 2. The strainer portion 10 is provided with a rod portion 30.

[0031] The strainer portion 10 is a cylindrical member and is placed above the outlet 101d (see FIG. 1). The strainer portion 10 mainly includes a filter medium 11, an inner cylinder 12, and plates 15 and 16.

[0032] The inner cylinder 12 is a hollow cylindrical member having openings at both ends, and is made of a highly corrosion-resistant material (for example, stainless steel or resin). Holes are formed in the inner cylinder 12 over almost the entire area, through which hydraulic oil passes.

[0033] A filter material 11 is provided on the outside of the inner tube 12. The filter material 11 and the inner tube 12 correspond to the filtering section of the present invention. The height of the filter material 11 is approximately the same as the height of the inner tube 12. The filter material 11 is formed by folding a sheet-like thin plate with holes formed over almost the entire area into a pleated shape, connecting both ends of the folded thin plate, and rolling it into a cylindrical shape. In this embodiment, the filter material 11 is formed from a metal (e.g., stainless steel) mesh with fine wires woven into a mesh, but filter paper made of synthetic resin, paper, etc. may also be used. The filter material 11 is for filtering hydraulic oil.

[0034] The form of the filter medium 11 is not limited to this, and for example, the filter medium 11 may be one or more thin sheets such as wire mesh that are stacked and rolled into a cylindrical shape.

[0035] Plate 15 is provided at one end of filter medium 11 and inner cylinder 12, and plate 16 is provided at the other end. Plates 15 and 16 are disk-shaped or cylindrical members with a bottom, and are made of resin or metal.

[0036] Plates 15 and 16 are provided so as to cover the ends (openings) of filter medium 11 and inner cylinder 12. In other words, plates 15 and 16 sandwich filter medium 11 and inner cylinder 12 therebetween.

[0037] The plate 15 covers the entire upper end of the filter medium 11 and the inner cylinder 12, and has a surface 15a (corresponding to the plate-like portion of the present invention) that is approximately perpendicular to the axis ax of the filter medium 11. The surface 15a is provided at the upper end of the suction strainer 1. An air vent hole 20 is formed in the surface 15a. An exhaust valve 2 is also provided on the surface 15a. The exhaust valve 2 will be described in detail later.

[0038] The plate 16 is formed with a cylindrical fitting portion 16a that covers the entire lower end of the filter medium 11 and the inner cylinder 12 and is fitted onto the outlet 101d. A seal member 17 is provided on the inner peripheral surface of the fitting portion 16a to prevent hydraulic oil from entering the strainer portion 10 from between the plate 16 and the outlet 101d.

[0039] The rod section 30 mainly has a rod 31 and an attachment section 32. The rod 31 is disposed in a position extending upward from the strainer section 10. The upper end of the rod 31 is provided with an attachment section 32 that is attached to an attachment section (not shown) formed on the back surface of the lid body 103.

[0040] A spring (not shown) is provided in a contracted state inside the mounting portion 32. When the suction strainer 1 is provided inside the tank body 101, the spring biases the rod 31, i.e., the strainer portion 10, downward (in the -z direction).

[0041] By removing the cover 103 from the tank body 101 and pulling the upper end of the rod 31, the suction strainer 1 can be pulled out from the tank body 101 during maintenance or the like.

[0042] Next, we will explain the exhaust valve 2. Fig. 3 is a cross-sectional view showing an outline of the exhaust valve 2. The exhaust valve 2 mainly has a first stopper 21, a second stopper 22, and a rod-shaped portion 23.

[0043] The rod-shaped portion 23 is a member that is inserted into the air vent hole 20. The first stopper 21 is provided at the upper end of the rod-shaped portion 23, and the second stopper 22 is provided at the lower end of the rod-shaped portion 23. The second stopper 22 and the rod-shaped portion 23 are integral, and the second stopper 22 and the rod-shaped portion 23 form a moving member 24. By providing the moving member 24 to the first stopper 21, the exhaust valve 2 is formed.

[0044] 4A and 4B are diagrams showing an outline of first stopper 21, with (A) being a perspective view and (B) being a cross-sectional view. First stopper 21 is cylindrical and has a hollow portion 21a formed therein. Hollow portion 21a has hole 21b and hole 21c that connects hole 21b to the outside of first stopper 21. Diameter d1 of hole 21b is larger than diameter d2 of hole 21c.

[0045] First stopper 21 has a disk shape (or a cylindrical shape) with a diameter d3 larger than the diameter D (see FIG. 3) of air vent hole 20 so that it can close air vent hole 20. First stopper 21 is made of an elastically deformable material. Examples of elastically deformable materials include rubber and soft resin. In this embodiment, first stopper 21 is made of nitrile rubber (NBR).

[0046] 5 is a diagram showing an outline of the moving member 24, where (A) is a perspective view, (B) is a plan view (viewed from the +z direction), and (C) is a cross-sectional view taken along line AA of (B). The moving member 24 is made of a material whose specific gravity is smaller than that of oil so that it floats on oil.

[0047] The second stopper 22 has a spherical main body 22a and a flat portion 22b formed by cutting the upper end surface of the main body 22a along a flat surface. The flat portion 22b is not essential for the second stopper 22. If the second stopper 22 does not have the flat portion 22b, the second stopper 22 will be spherical.

[0048] The rod-shaped portion 23 protrudes from the upper end (here, the flat portion 22b) of the second stopper 22. The rod-shaped portion 23 has two rod-shaped portions 23a and a connecting portion 23b provided at one end of the rod-shaped portions 23a (here, the end not provided at the second stopper 22).

[0049] The rod-shaped portion 23a is a part of a cylinder, and the diameter d4 of this cylinder is smaller than the hole diameter D of the air vent hole 20 (see Figure 3). The rod-shaped portion 23a is formed by forming a slot 23e along the longitudinal direction of the cylinder. The slot 23e is formed by cutting out the center of a cylindrical member along its central axis. By cutting out a large portion of the cylinder to form the slot 23e, the thickness t of the rod-shaped portion 23a becomes thinner, making it easier to deform in a direction that narrows the diameter. The connecting portion 23b has a protrusion 23d that protrudes outward in the circumferential direction.

[0050] Returning to the explanation of Figure 3, rod-shaped portion 23a is deformed with a finger or the like to move protrusion 23d toward center line ax2, whereby protrusion 23d passes through air vent hole 20 and hole 21c. Then, rod-shaped portion 23a is returned to its original state with protrusion 23d inserted into hole 21b, whereby rod-shaped portion 23 is provided in hollow portion 21a. Protrusion 23d comes into contact with surface 21d (see Figure 4(B)), whereby moving member 24 is assembled to first stopper 21 so that rod-shaped portion 23 does not come out of hollow portion 21a.

[0051] The rod-shaped portion 23a is inserted into the air vent hole 20. As a result, the exhaust valve 2 is attached to the surface 15a of the plate 15, and the rod-shaped portion 23a is able to slide inside the air vent hole 20. In other words, the exhaust valve 2 is able to move between a position where the first stopper 21 abuts against the air vent hole 20 to close the air vent hole 20, and a position where the second stopper 22 abuts against the air vent hole 20 to close the air vent hole 20.

[0052] The entire exhaust valve 2 needs to float due to the buoyancy acting on the second stopper 22. Furthermore, if the entire second stopper 22 is immersed in oil when the exhaust valve 2 floats, it may not be possible to expect the effect of preventing oil from spraying out of the air vent hole 20. For this reason, it is desirable to set the weight of the exhaust valve 2 so that it is balanced with at least a portion of the second stopper 22 exposed above the oil surface.

[0053] Next, we will explain the functions of the suction strainer 1 and exhaust valve 2 configured as above. First, the suction strainer 1 is attached to the tank body 101 in which hydraulic oil is stored. The rod 31 is held so that the attachment part 32 is positioned upward (+z direction), and the suction strainer 1 is pushed downward (-z direction).

[0054] Because the upper end of the strainer portion 10 is covered by the plate 15, when the suction strainer 1 is attached to the inside of the tank body 101, air accumulates inside the inner tube 12, i.e., below the plate 15. The air accumulated below the plate 15 pushes the exhaust valve 2 up in the +z direction through the air vent hole 20. As a result, as shown in FIG. 3, the air vent hole 20 opens, and the air accumulated below the plate 15 is released from inside the strainer portion 10 into the tank body 101. This sets the suction strainer 1 in the tank body 101, allowing the suction strainer 1 to perform its function.

[0055] When hydraulic oil stored in the tank body 101 is sucked by a hydraulic pump (not shown), it is sucked from the outside of the filter medium 11 into the inside of the strainer portion 10 of the suction strainer 1. Dust and other particles are removed from the hydraulic oil by the filter medium 11, and the oil flows into the inside of the inner tube 12. The oil that has flowed into the inside of the inner tube 12 flows out of the strainer portion 10 from below.

[0056] When hydraulic oil is sucked into the strainer section 10 from the outside of the filter medium 11, air bubbles contained in the hydraulic oil are also sucked into the strainer section 10 along with the hydraulic oil. The air bubbles sucked into the strainer section 10 grow larger and rise, and when a certain amount of air accumulates below the plate 15, the internal pressure of the suction strainer 1 (the pressure in the space S1 (see FIG. 2) surrounded by the inner tube 12 and the plates 15 and 16) becomes higher than the external pressure (the pressure in the space S2 (see FIG. 1) outside the suction strainer 1 and inside the tank body 101), and the exhaust valve 2 is pushed up in the +z direction. As a result, as shown in FIG. 3, the air vent hole 20 opens, and the air accumulated below the plate 15 is released from inside the strainer section 10 into the tank body 101.

[0057] When hydraulic oil flows into the inner cylinder 12 and the oil level S rises inside the inner cylinder 12, the second stopper 22 rises along with the oil level. FIG. 6 is a schematic diagram showing the state in which the exhaust valve 2 is pushed up in the +z direction by the hydraulic oil (the exhaust valve 2 is positioned at the upper end). The second stopper 22 is made of a material whose specific gravity is smaller than that of the oil and floats on the hydraulic oil. Therefore, the second stopper 22, i.e., the exhaust valve 2, rises along with the oil level S, and eventually the second stopper 22 comes into contact with the air vent hole 20, blocking it. This prevents hydraulic oil from escaping from the air vent hole 20. The second stopper 22, i.e., the main body 22a, is spherical and easily blocks the circular air vent hole 20.

[0058] After that, when the device is stopped and the flow of hydraulic oil stops, the internal pressure of the suction strainer 1 gradually decreases. Then, when the internal pressure of the suction strainer 1 becomes equal to or lower than the external pressure, the exhaust valve 2 moves in the -z direction.

[0059] FIG. 7 is a schematic diagram showing the state in which the exhaust valve 2 has moved in the −z direction (the exhaust valve 2 is located at the bottom end) after the device has stopped. Space S1 is filled with hydraulic oil, and the second stopper 22 is subjected to buoyancy. However, because the internal pressure of the suction strainer 1 is equal to or lower than the external pressure, the exhaust valve 2 is moved in the −z direction by the external pressure. As a result, the first stopper 21 abuts against the air vent hole 20, blocking the air vent hole 20, and air and hydraulic oil do not flow from space S2 into space S1 through the air vent hole 20. Furthermore, because the first stopper 21 is elastically deformable, the first stopper 21 is elastically deformed when the exhaust valve 2 is pressed in the −z direction by external pressure, and the first stopper 21 exhibits excellent sealing properties.

[0060] According to this embodiment, the exhaust valve 2 has a first stopper 21 and a second stopper 22, and the second stopper 22 is formed from a material whose specific gravity is less than that of oil. Therefore, when the space S1 is filled with hydraulic oil, the second stopper 22 blocks the air vent hole 20, thereby preventing the hydraulic oil from spraying out of the air vent hole 20.

[0061] Furthermore, according to this embodiment, by making second stopper 22, i.e., main body portion 22a, spherical, it becomes easier to block circular air vent hole 20 and to prevent hydraulic oil from spraying out. For example, even if the oil level is tilted due to tilting of the device or the like when exhaust valve 2 is rising, exhaust valve 2 can block air vent hole 20. Furthermore, even if the central axis of air vent hole 20 and the central axis of exhaust valve 2 are misaligned when exhaust valve 2 is rising, spherical main body portion 22a can come into contact with air vent hole 20 to correct the misalignment of the central axes.

[0062] Furthermore, according to this embodiment, the first stopper 21 and the moving member 24 are assembled into one exhaust valve 2, which is then simply provided on the plate 15, so that the exhaust valve 2 can have a simple configuration.

[0063] Furthermore, according to the present embodiment, the exhaust valve 2 is formed by assembling the first stopper 21 and the moving member 24, so the first stopper 21 and the second stopper 22 can be formed from different materials. This allows for freedom in the material from which the first stopper 21 is formed, and the first stopper 21 can be formed from a material that is elastically deformable. By making the first stopper 21 elastically deformable, the first stopper 21 exhibits excellent sealing properties, making it possible to prevent hydraulic oil from spurting out from the air vent hole 20.

[0064] In the present embodiment, first stopper 21 has a disk shape with a chamfered upper edge, but the shape of first stopper 21 is not limited to this. Figures 8 to 11 are diagrams showing outlines of first stoppers 21A to 21D according to modified examples. In Figures 8 to 11, (A) is a perspective view, (B) is a plan view, and (C) is a cross-sectional view.

[0065] 8 and 9, first stoppers 21A and 21B may be disk-shaped. The diameter of first stoppers 21A and 21B is optional, and may be approximately twice the diameter of air vent hole 20, as in first stopper 21B.

[0066] 10, a tapered surface 21e with a gradually decreasing diameter may be formed on the sealing surface on the lower side (second stopper 22 side) of first stopper 21C. Tapered surface 21e may be a flat surface (C surface) or a curved surface (R surface). In first stopper 21C, tapered surface 21e is a curved surface that convex outward. This makes it easier for tapered surface 21e to block circular air vent hole 20.

[0067] 11, first stopper 21D may be suction cup-shaped. First stopper 21D has funnel-shaped sealing surface 21f and is hollow inside. Therefore, sealing surface 21f can be easily deformed, and sealing surface 21f can be tightly attached to surface 15a (see FIG. 2, etc.), thereby reliably closing air vent hole 20.

[0068] In addition, in the present embodiment, the second stopper 22 has the spherical main body portion 22a, but the second stopper 22 may have a configuration other than the main body portion 22a. For example, the main body portion 22a may be provided with a disk-shaped flange portion. That is, it is sufficient that the second stopper 22 has the spherical main body portion 22a.

[0069] In addition, in this embodiment, the main body portion 22a is spherical, but the shape of the main end portion (second stopper) is not limited to this. Figures 12 and 13 are diagrams showing the outline of moving members 24A and 24B having second stoppers 22A and 22B according to modified examples. In Figures 12 and 13, (A) is a perspective view, (B) is a plan view, and (C) is a cross-sectional view.

[0070] As shown in FIG. 12, the moving member 24A has a second stopper 22A and a rod-shaped portion 23. The second stopper 22A has a spherical main body 22c, a flat portion 22b formed by cutting the upper end surface of the main body 22c along a flat surface, and a flat portion 22d formed by cutting the lower end surface of the main body 22c along a flat surface. In other words, the main body 22c has a shape in which the lower half of the main body 22a is removed. Note that the flat portions 22b and 22d are not essential, and if the second stopper 22A does not have the flat portion 22b, it will have a hemispherical shape. Furthermore, the flat portion 22d may be provided with a disk-shaped flange portion having a diameter larger than that of the flat portion 22d.

[0071] If the diameter of the portion of the second stopper that contacts the air vent hole 20 gradually changes, the second stopper will more easily block the circular air vent hole 20, and the spraying of hydraulic oil will be more easily suppressed, just like second stopper 22 having spherical main body portion 22a. In other words, it is desirable for the second stopper to have a spherical, hemispherical, detangular, frustum-shaped, conical, or truncated conical portion. Here, a detangular shape refers to a shape obtained by cutting a sphere with one plane, and a truncated shape refers to a shape obtained by cutting a sphere with two parallel planes.

[0072] 13, the moving member 24B has a second stopper 22B and a rod-shaped portion 23. The second stopper 22B is flat. The diameter of the second stopper 22B may be equal to or greater than the diameter of the air vent hole 20.

[0073] In addition, in the present embodiment, the moving member 24 is provided to the first stopper 21 by inserting the protrusion 23d into the hole 21b, but the manner in which the moving member 24 is provided to the first stopper 21 is not limited to this. For example, the rod-shaped portion may be cylindrical, with a male thread formed on the outer circumferential surface and a female thread formed in the first stopper, and the rod-shaped portion may be provided to the first stopper by screwing these together.

[0074] In addition, in the present embodiment, the moving member 24 is configured by the rod-shaped portion 23 and the second stopper 22, but the rod-shaped portion 23 may be provided on the first stopper. In that case, the first stopper and the rod-shaped portion 23 may configure the moving member, which may be provided on the second stopper.

[0075] Furthermore, in this embodiment, second stopper 22 is formed from a material whose specific gravity is less than that of oil, but the material of second stopper 22 is not limited to this. The key is that second stopper 22 should float on oil. For example, the second stopper may be made of a material whose specific gravity is greater than that of oil, and a cavity may be formed inside the second stopper so that the second stopper floats on oil. In this case, too, it is desirable to set the weight of the exhaust valve so that it is balanced with at least a portion of the second stopper exposed above the oil surface.

[0076] <Second embodiment> In the first embodiment of the present invention, the exhaust valve 2 in which the first stopper 21 and the moving member 24 are assembled is used, but the form of the exhaust valve is not limited to this.

[0077] In the second embodiment of the present invention, the first stopper and the second stopper are not integrated. An exhaust valve 2A according to the second embodiment will be described below. Note that the same parts as those in the first embodiment are given the same reference numerals, and description thereof will be omitted.

[0078] The exhaust valve 2A, like the exhaust valve 2, is provided on the surface 15a of the plate 15 of the suction strainer 1. An air vent hole 20 is formed in the surface 15a, and the exhaust valve 2A opens and closes this air vent hole 20.

[0079] 14 is a cross-sectional view showing an outline of the exhaust valve 2 A. The exhaust valve 2 A mainly includes a first moving member 21 E, a second stopper 22 C, and a valve housing 25.

[0080] The first moving member 21E is made of resin or an elastically deformable material and has an upper stopper 21g provided at an upper end, a lower stopper 21h provided at a lower end, and a rod-shaped portion 21i connecting the upper stopper 21g and the lower stopper 21h.

[0081] The upper stopper 21g has a disk shape (or a cylindrical shape). The diameter of the upper stopper 21g is larger than the diameter of the air vent hole 20. The upper stopper 21g is provided at the upper end of the rod-shaped portion 21i, and when the first moving member 21E moves downward and the upper stopper 21g comes into contact with the air vent hole 20, the upper stopper 21g closes the air vent hole 20. Note that the shape of the upper stopper 21g is not limited to this and may be, for example, spherical.

[0082] In plan view (when viewed from the +z direction), rod-shaped portion 21i is smaller than air vent hole 20. Furthermore, in plan view, lower stopper 21h is larger than air vent hole 20. Therefore, first moving member 21E moves in the vertical direction (z direction) inside air vent hole 20, and upper stopper 21g and lower stopper 21h prevent first moving member 21E from slipping out of air vent hole 20.

[0083] Lower stopper 21h and rod-shaped portion 21i are deformable in a direction that reduces the diameter, and by pushing first moving member 21E into air vent hole 20 from above (+z side), rod-shaped portion 21i is inserted into air vent hole 20 and first moving member 21E is provided on surface 15a. First moving member 21E is movable between a position that blocks air vent hole 20 and a position that opens air vent hole 20.

[0084] The second stopper 22C is provided inside the valve housing 25. The second stopper 22C is spherical and formed so as to float on oil.

[0085] Valve housing 25 is provided below surface 15a of plate 15 so as to cover air vent hole 20. Valve housing 25 mainly has side surfaces 25a, a bottom surface 25b, and a partition plate 25c.

[0086] The side surface 25a is tubular (here, cylindrical), and a bottom surface 25b is provided near the lower end of the side surface 25a. Note that the shape of the side surface 25a is not limited to a cylindrical shape, and may be a hollow barrel shape or the like.

[0087] A hole 25d (corresponding to a first hole of the present invention) is formed in the bottom surface 25b. The diameter d6 of the hole 25d is smaller than the diameter d5 of the second stopper 22C.

[0088] The partition plate 25c divides the space formed by the side surface 25a and the bottom surface 25b into a lower space S3 into which the second stopper 22C is inserted and an upper space S4 in which the first moving member 21E is provided. The partition plate 25c is formed with a hole 25e (corresponding to the second hole of the present invention) that connects the lower space S3 and the upper space S4. The diameter d6 of the hole 25e is smaller than the diameter d4 of the second stopper 22C. The hole 25e is located above the hole 25d.

[0089] The partition plate 25c has a thickness that gradually decreases so that the height of the lower surface increases toward the hole 25e, but the shape of the partition plate 25c is not limited to this.

[0090] Since the second stopper 22C is inserted into the lower space S3, the second stopper 22C is movable between a position where the second stopper 22C blocks the hole 25d and a position where the second stopper 22C blocks the hole 25e.

[0091] The side surface 25a has a communication hole 25f formed therein, which communicates a space surrounded by the side surface 25a, the bottom surface 25b, and the partition plate 25c (lower space S3) with the space outside the valve housing 25 (space S1, see FIG. 2). The number of communication holes 25f may be one or more.

[0092] Next, the functions of the suction strainer 1 and exhaust valve 2A configured as described above will be explained. First, the suction strainer 1 is attached to the tank body 101 in which hydraulic oil is stored. When the suction strainer 1 is attached to the inside of the tank body 101, air that has accumulated below the plate 15 pushes up the first moving member 21E in the +z direction through the air vent hole 20.

[0093] 15 is a diagram schematically illustrating the state in which the first moving member 21E is pushed up in the +z direction. As indicated by the two-dot chain line in FIG. 15, air flows from the space S1 into the lower space S3 through the communication hole 25f and from the lower space S3 into the upper space S4 through the hole 25e, pushing up the first moving member 21E in the +z direction. As a result, the air vent hole 20 opens, and the air accumulated below the plate 15 is released from inside the strainer portion 10 (see FIG. 2, etc.) into the space S2 inside the tank body 101 (see FIG. 1, etc.). This allows the suction strainer 1 to be set in the tank body 101, enabling the suction strainer 1 to perform its function.

[0094] When the hydraulic oil stored in the tank body 101 is sucked by a hydraulic pump (not shown), dust and other particles are removed from the filter medium 11, and the hydraulic oil flows from the outside of the filter medium 11 into the inside of the inner tube 12. When the hydraulic oil is sucked from the outside of the filter medium 11 into the inside of the strainer section 10, air bubbles contained in the hydraulic oil are sucked into the inside of the strainer section 10 along with the hydraulic oil, and when the internal pressure of the suction strainer 1 becomes higher than the external pressure, as shown in FIG. 15 , the first movable member 21E is pushed up in the +z direction, opening the air vent hole 20, and the air that has accumulated below the plate 15 is released from inside the strainer section 10 into the tank body 101.

[0095] When hydraulic oil flows into the inner cylinder 12 and the oil level O rises inside the inner cylinder 12, the second stopper 22C rises along with the oil level O. FIG. 16 is a schematic diagram showing the second stopper 22C being pushed up in the +z direction by the hydraulic oil (the second stopper 22C is positioned at the upper end). The second stopper 22C is made of a material whose specific gravity is smaller than that of the oil and floats on the hydraulic oil. Therefore, the second stopper 22C rises along with the oil level, and eventually the second stopper 22C abuts against the partition plate 25c and blocks the hole 25e. This prevents the hydraulic oil from escaping from the hole 25e, i.e., the air vent hole 20. The second stopper 22C is spherical and easily blocks the circular hole 25e.

[0096] After that, when the device is stopped and the flow of hydraulic oil stops, the internal pressure of the suction strainer 1 gradually decreases. Then, when the internal pressure of the suction strainer 1 becomes equal to or lower than the external pressure, the first moving member 21E moves in the -z direction from the position indicated by the dotted line in Fig. 16 to the position indicated by the solid line. As a result, the first moving member 21E comes into contact with the air vent hole 20, and the upper stopper 21g blocks the air vent hole 20, preventing air and hydraulic oil from flowing from space S2 into space S1 through the air vent hole 20.

[0097] According to this embodiment, the exhaust valve 2A has a first moving member 21E and a second stopper 22C, and the second stopper 22C is formed from a material whose specific gravity is less than that of oil. Therefore, when the space S1 is filled with hydraulic oil, the second stopper 22C blocks the hole 25e, thereby preventing the hydraulic oil from spraying out of the air vent hole 20.

[0098] Furthermore, according to this embodiment, second stopper 22C is spherical, so it is easy to block circular hole 25e and prevent hydraulic oil from spraying out. For example, even if the oil level is tilted due to the tilt of the device when exhaust valve 2 is raised, second stopper 22C can block air vent hole 20.

[0099] In this embodiment, second stopper 22C is spherical, but the shape of second stopper 22C is not limited to this. To facilitate closing hole 25e, it is desirable that the portion of second stopper 22C that contacts hole 25e be a curved surface that is convex outward. That is, it is desirable that second stopper 22C have a spherical, spherical truncated, spherical frustum, conical, or conical frustum portion. For example, second stopper 22C may be bicone-shaped. Alternatively, second stopper 22C may be provided with a disk-shaped flange portion.

[0100] <Third embodiment> In the first embodiment of the present invention, the air vent hole 20 is provided on the surface 15a (corresponding to the plate-like portion of the present invention) of the suction strainer 1 (corresponding to the filtering device of the present invention), and the exhaust valve 2 is provided in this air vent hole 20, but the filtering device and the plate-like portion on which the exhaust valve is provided are not limited to this, and the shape of the exhaust valve is also not limited to this.

[0101] In the third embodiment of the present invention, an exhaust valve is provided on the return filter. The following describes the return filter 1A and the exhaust valve 2B, which are the filtering device according to the second embodiment. The same parts as those in the first embodiment are designated by the same reference numerals, and their description will be omitted.

[0102] Fig. 17 is a diagram showing an outline of a return filter 1A (corresponding to the filtering device of the present invention). Fig. 17 shows a cross section of a portion (however, hatching indicating a cross section is omitted). Fig. 18 is a diagram showing an outline of the return filter 1A, where (A) is a plan view and (B) is a perspective view of a main part.

[0103] The return filter 1A mainly includes a filter element 10A, a connecting member 14, a cover 18, a relief valve 40, and an exhaust valve 2B, although the relief valve 40 is not essential.

[0104] The filter element 10A is provided with a rod portion 30. The rod portion 30 connects the return filter 1A to a lid 102 provided on the upper end surface 101f of the tank body 101. The rod 31 is disposed in a position extending upward from the filter element 10A. An attachment portion 32 is provided at the upper end of the rod 31 and attached to an attachment portion 102a formed on the back surface of the lid 102. A spring 33 is provided inside the attachment portion 32 in a contracted state. When the return filter 1A is provided inside the tank body 101, the spring 33 biases the rod 31, i.e., the return filter 1A, downward (in the -z direction). The lower end of the return filter 1A is provided on the bottom surface 101g of the tank body 101, and the return filter 1A is fixed inside the tank body 101 by the spring 33.

[0105] The filter element 10A mainly comprises a filter medium 11A, an inner cylinder 12A, an upper plate 15A, and a lower plate 16A. The filter element is generally cylindrical. An inlet pipe 101h is provided on the bottom surface 101g and is located at the -z end of the filter element, i.e., on the lower plate 16A.

[0106] The filter medium 11A is cylindrical and serves to filter hydraulic oil. The filter medium 11A is formed, for example, by folding a sheet of filter paper into pleats, connecting both ends of the folded thin plate, and rolling it into a cylindrical shape. The filter paper is made of, for example, synthetic resin or paper, and the hydraulic oil is filtered as it passes through the filter paper.

[0107] The inner cylinder 12A is a cylindrical member having openings at both ends, and is made of a highly corrosion-resistant material (for example, stainless steel or resin). Holes are formed over almost the entire area of ​​the inner cylinder 12A, through which hydraulic oil passes.

[0108] A filter medium 11A is provided on the outside of the inner cylinder 12A. The height of the filter medium 11A is approximately the same as the height of the inner cylinder 12A. An outer cylinder having holes formed over almost the entire area through which the hydraulic oil passes may be provided on the outside of the filter medium 11A.

[0109] The upper plate 15A is provided at the upper (+z side) end of the filter material 11A and the inner tube 12A (corresponding to the filtration section of the present invention), and the lower plate 16A is provided at the lower (-z side) end of the filter material 11A and the inner tube 12A.

[0110] The upper plate 15A and the lower plate 16A are provided so as to cover the ends of the filter medium 11A and the inner cylinder 12. In other words, the upper plate 15A and the lower plate 16A sandwich the filter medium 11A and the inner cylinder 12A.

[0111] The upper plate 15A covers the entire upper ends of the filter medium 11A and the inner cylinder 12. The upper plate 15A also has a hollow portion 15b that connects the hollow portion (space S1) of the filter medium 11A and the inner cylinder 12 to the outside of the filter medium 11A and the inner cylinder 12 (space S5).

[0112] The upper plate 15A is provided with a connecting member 14. The connecting member 14 connects the filter element and the cover 18. The connecting member 14 mainly includes a plate-shaped member 14a and a holding member 14b.

[0113] The upper end of plate-shaped member 14a is attached to cover 18, and the lower end is attached to holding member 14b. The lower end of plate-shaped member 14a is attached to the upper end of holding member 14b, and plate-shaped member 14a is disposed in a position extending upward from holding member 14b. Cylindrical portion 14c of holding member 14b is provided inside hollow portion 15b of upper plate 15A. Cylindrical portion 14c is provided with hole 14d that connects the hollow portion of filter medium 11A and inner tube 12 with the outside of filter medium 11A and inner tube 12. A relief valve 40 is provided in hole 14d.

[0114] A sealing member 50 such as an O-ring is provided between the cylindrical portion 14c and the upper plate 15A, so that the holding member 14b and the upper plate 15A are fixed together so that hydraulic oil does not leak from between the holding member 14b and the upper plate 15A.

[0115] The relief valve 40 is provided in the holding member 14b. When the relief valve 40 is closed, the valve element of the relief valve 40 covers the hole 14d. When the pressure in the space S1 increases due to clogging of the filter medium 11A or the like, the valve element moves upward against the biasing force of the elastic member. As a result, the valve element moves away from the holding member 14b (valve seat), the relief valve 40 opens, and hydraulic oil can pass through the hole 14d. When the pressure in the space S1 decreases, the valve element moves downward due to the biasing force of the elastic member, and the valve element abuts against the holding member 14b.

[0116] The cover 18 is provided on the plate-like member 14a. The cover 18 mainly has a cylindrical portion 18a and a plate-like portion 18b provided on the cylindrical portion 18a. The cylindrical portion 18a is provided on the outside of the relief valve 40, the connecting member 14, the upper plate 15A, and a portion (near the upper end) of the filter medium 11A. Note that the cylindrical portion 18a may cover the entire upper plate 15A and the filter medium 11A.

[0117] The plate-shaped portion 18b is provided at the upper end of the cylindrical portion 18a so as to cover the hollow portion of the cylindrical portion 18a. That is, the plate-shaped portion 18b is provided at the upper end of the return filter 1A. Note that the plate-shaped portion 18b is not limited to being provided at the upper end of the cylindrical portion 18a (return filter 1A) as long as it is provided near the upper end of the cylindrical portion 18a (return filter 1A). For example, the upper end of the cylindrical portion 18a may be located slightly on the +z side of the plate-shaped portion 18b.

[0118] The plate-shaped portion 18b is fixed to the holding member 14b by bolts 19. In this way, the cover 18 is provided on the holding member 14b. However, the manner in which the cover 18 is provided on the holding member 14b is not limited to this.

[0119] The plate-shaped portion 18b is formed with an air vent hole 20. The plate-shaped portion 18b is also provided with an exhaust valve 2B.

[0120] 19A and 19B are diagrams showing an outline of the exhaust valve 2B, where (A) is a cross-sectional view (cross-sectional view taken along line HH in FIG. 18) and (B) is a side view. The exhaust valve 2B mainly has a first stopper 21F and a moving member 24C.

[0121] First stopper 21F has a cylindrical shape with a rounded chamfered upper end and has a hollow portion 21j formed therein. Hollow portion 21j has hole 21k and hole 21c that communicates with hole 21k and the outside of first stopper 21F. Diameter d1 of hole 21k is larger than diameter d2 of hole 21c.

[0122] The diameter d3 of first stopper 21F is larger than the diameter D of air vent hole 20 so that first stopper 21F can close air vent hole 20. Furthermore, first stopper 21F is made of an elastically deformable material. Examples of elastically deformable materials include rubber and soft resin. In this embodiment, first stopper 21F is made of nitrile rubber (NBR).

[0123] The moving member 24C is made of a material (e.g., resin) whose specific gravity is less than that of oil so that it floats on oil. The moving member 24C mainly has a second stopper 22D and a rod-shaped portion 23A. The second stopper 22D and the rod-shaped portion 23A integrally constitute the moving member 24C. In the present invention, the term "integrally constituted" is a concept that includes cases where they are integrally formed (molded, etc.) and cases where separately formed parts are integrated into a single part.

[0124] The second stopper 22D has a main body 22e and a lower end 22f. The main body 22e has a truncated cone-shaped side surface. The lower end 22f has a cylindrical side surface and is provided below the main body 22e. However, the lower end 22f is not essential.

[0125] A recess 22g is formed in the lower end surface of second stopper 22D. By providing recess 22g, air accumulates in recess 22g when exhaust valve 2B is used to release air, making it easier for exhaust valve 2B to move in the +z direction.

[0126] The shape of the side surface of the recess 22g is a truncated cone, and is similar (substantially similar) to the shape of the side surface of the main body 22e. Furthermore, at the lower end of the second stopper 22D, the diameter d4 (corresponding to the width of the present invention) of the recess 22g is 0.8 times or more the diameter d5 (corresponding to the width of the present invention) of the main body 22e. In this embodiment, the diameter d4 is 0.81 times the diameter d5.

[0127] As a result, recess 22g is made as large as possible, allowing a large amount of air to be stored in recess 22g. Note that "similar (substantially similar)" does not only refer to perfect similarity, but also includes a small degree of error. For example, even if the inclination angle of the side surface of recess 22g and the inclination angle of the side surface of main body 22e are identical, the term "similar (substantially similar)" as used herein is applicable even if there is an error of several degrees.

[0128] Rod-shaped portion 23A is provided above second stopper 22D. Rod-shaped portion 23A has columnar portion 23g provided on second stopper 22D, two rod-shaped rod-shaped portions 23f, and connecting portion 23b provided at one end of rod-shaped portion 23f (here, the end not provided on columnar portion 23g). Rod-shaped portion 23f protrudes from the upper end of columnar portion 23g.

[0129] Like rod-shaped portion 23a, rod-shaped portion 23f is a part of a cylinder, and the diameter of this cylinder is smaller than the hole diameter D of air vent hole 20. Rod-shaped portion 23f is formed by forming a slot along the longitudinal direction of the cylinder.

[0130] By deforming rod-shaped portion 23f with a finger or the like to move protrusion 23d toward center line ax2, protrusion 23d passes through air vent hole 20 and hole 21c. Then, by returning rod-shaped portion 23j to its original state with protrusion 23d inserted into hole 21k, rod-shaped portion 23A is provided in hollow portion 21j, and moving member 24C is assembled to first stopper 21F.

[0131] As a result, exhaust valve 2B is attached to plate-shaped portion 18b, and rod-shaped portion 23f is able to slide inside air vent hole 20. In other words, exhaust valve 2B is able to move between a position where first stopper 21F abuts against air vent hole 20 to block it, and a position where second stopper 22D abuts against air vent hole 20.

[0132] When rod-shaped portion 23f is positioned inside air vent hole 20, air is released from air vent hole 20. Since the side surface of main body portion 22e of second stopper 22D is frustoconical, when second stopper 22D abuts against air vent hole 20, main body portion 22e completely blocks air vent hole 20, preventing hydraulic oil from spraying out.

[0133] Next, the functions of the return filter 1A and exhaust valve 2B configured as described above will be described. When the engine of a construction machine or the like equipped with the return filter 1A is idling or running, as shown in Fig. 17, unfiltered hydraulic oil flows from an inlet pipe 101h provided on the bottom surface 101g into a space S1 surrounded by the inner cylinder 12A, upper plate 15A, and lower plate 16A. The hydraulic oil that flows into space S1 is filtered as it flows from the inside to the outside of the filter medium 11A, and then flows out into a space S2 outside the return filter 1A and inside the tank body 101, or into a space S5 outside the filter medium 11A and inner cylinder 12 and inside the cover 18 (see the arrows in Fig. 17).

[0134] Because cover 18 is provided on the outside of filter medium 11A, the hydraulic oil that has flowed into space S5 after filtration hits cover 18 and flows downward, and then flows out from the lower end of cylindrical portion 18a into space S2. The hydraulic oil that has flowed into space S2 is stored in tank body 101. The oil level S of the hydraulic oil stored in tank body 101 is located below the upper end of filter medium 11A and above the lower end of cover 18.

[0135] When the engine of the construction machine or the like provided with the return filter 1A is in operation, the amount of oil passing through the filter medium 11A is greater than the amount of oil flowing out from the lower end of the cylindrical portion 18a into the space S2.

[0136] Since space S5 is a space formed by being surrounded by cover 18, air accumulates in space S5 above the oil level S. When an amount of oil that is greater than the amount of oil that flows out from space S5 to space S2 flows into space S5 from space S1, the pressure in space S5 becomes higher than the pressure in space S2.

[0137] 19, the air that has accumulated in the upper part of space S5 pushes up exhaust valve 2B provided on plate-shaped portion 18b, causing first stopper 21F to move away from air vent hole 20, opening air vent hole 20, and allowing the air that has accumulated in the upper part of space S5 to flow out of space S5 into tank body 101. If air remains inside cover 18, there is a risk that the air will be entrained in the oil due to contact between the oil and the air, so by using exhaust valve 2B to exhaust the air to the outside of cover 18, it is possible to prevent air bubbles from being mixed into the oil.

[0138] When all the air accumulated in the upper part of the space S5 is discharged from the space S5 through the air vent hole 20, the entire space S5 is filled with hydraulic oil. As a result, all of the filter medium 11A can be used effectively for filtration.

[0139] Because recess 22g is provided on the lower end surface of second stopper 22D, air accumulates in recess 22g, reducing the specific gravity of exhaust valve 2B relative to oil. As a result, oil can more easily push up exhaust valve 2B in the +z direction. In addition, by enlarging recess 22g, more air can accumulate in recess 22g, making it easier for exhaust valve 2B to move in the +z direction.

[0140] Note that when first stopper 21F and second stopper 22D are away from air vent hole 20 and cylindrical portion 23g is positioned inside air vent hole 20, air vent hole 20 is always open. Therefore, some hydraulic oil flows out of space S5 through air vent hole 20, but the hydraulic oil stored in space S5 is filtered hydraulic oil, so there is no problem if it flows from space S5 to space S2 through air vent hole 20 and cover 18. Note that relief valve 40 may open for safety reasons when filter medium 11A becomes clogged or during a cold start, and in this case hydraulic oil that has not passed through filter medium 11A may be released into tank 100.

[0141] Returning to the explanation of FIG. 17 , when the engine of a construction machine or the like equipped with the return filter 1A stops or returns to an idling state, a large amount of hydraulic oil stops flowing into space S5, and the pressure in space S5 gradually drops to the pressure in space S2. Because the air vent hole 20 is open, air inside the tank body 101 flows into space S5 through the air vent hole 20 as the pressure in space S5 drops. When the pressure in space S5 becomes equal to the pressure in space S2, the exhaust valve 2B moves in the −z direction, and the first stopper 21F abuts against and blocks the air vent hole 20, preventing air and hydraulic oil from flowing into space S5 through the air vent hole 20. Furthermore, because the first stopper 21F is elastically deformable, the first stopper 21F elastically deforms, providing excellent sealing properties.

[0142] When the pressure in space S1 increases while the engine is running, the relief valve 40 opens to prevent damage to the return filter 1A. At that time, unfiltered hydraulic oil and air forcefully flow out from space S1 to space S5 through hole 14d. Because cover 18 is provided, the air that flows out of space S1 together with the hydraulic oil remains in space S5 without flowing into space S2. When the amount of air that has flowed into space S5 exceeds a certain amount, the air pushes up the exhaust valve 2B, and the air is discharged through air vent hole 20 to the top of the tank body 101. This prevents air mixed in with the hydraulic oil from being sucked into the hydraulic pump (not shown) via a suction strainer (not shown).

[0143] According to the present embodiment, first stopper 21F and moving member 24C are assembled into a single exhaust valve 2B, which is then simply provided on plate-shaped portion 18b, resulting in a simple configuration of exhaust valve 2. Furthermore, by arranging second stopper 22D below air vent hole 20, second stopper 22D closes air vent hole 20, preventing oil from spraying out of air vent hole 20. In particular, by forming the side surface of main body portion 22e of second stopper 22D into a truncated cone shape, main body portion 22e can reliably close air vent hole 20.

[0144] Furthermore, according to this embodiment, by providing an exhaust valve 2B on the plate-shaped portion 18b provided at the upper end of the return filter 1A, air accumulated inside the return filter 1A can be released to the outside of the return filter 1A, thereby preventing air mixed in with the hydraulic oil from being sucked into the downstream hydraulic pump.

[0145] In this embodiment, since the recess 22g is provided to reduce the specific gravity of the exhaust valve 2B relative to the oil, it is not essential that the second stopper 22D be made of a material whose specific gravity is less than that of oil. In short, it is sufficient that the second stopper 22D is formed so that it floats on the oil. Also, in this embodiment, the first stopper 21 is made of rubber and the moving member 24C is made of resin, but the materials of the first stopper 21 and the moving member 24C are not limited to these. For example, the first stopper 21 and the moving member 24C may be made of rubber or resin.

[0146] In addition, in this embodiment, exhaust valve 2B having first stopper 21F and moving member 24C is used, but the configuration of the exhaust valve is not limited to this. Exhaust valves according to modifications will be described below. In the following explanation, explanations of parts that are the same as those of exhaust valve 2B will be omitted.

[0147] 20 to 23 are diagrams showing the outline of exhaust valves 2C, 2D, 2E, and 2F according to modified examples, in which (A) is a cross-sectional view and (B) is a side view.

[0148] The exhaust valve 2C shown in Figure 20 mainly includes a first stopper 21G and a moving member 24C. The first stopper 21G differs from the first stopper 21F in that it has a cylindrical shape without a rounded chamfer at the top end. The first stopper 21G has a hollow portion 21m formed therein. The hollow portion 21m has a hole 21l and a hole 21c that connects the hole 21l to the outside of the first stopper 21G. The diameter d1 of the hole 21l is larger than the diameter d2 of the hole 21c.

[0149] The first stopper 21G has a curved surface 21n formed near the bottom end, the diameter of which decreases as it approaches the bottom end. Therefore, the curved surface 21n easily blocks the circular air vent hole 20.

[0150] 21 mainly includes a first stopper 21F and a moving member 24D. The moving member 24D mainly includes a second stopper 22E and a rod-shaped portion 23B. The second stopper 22E and the rod-shaped portion 23B integrally form the moving member 24D.

[0151] Second stopper 22E (corresponding to the main body of the present invention) has a columnar side surface. A recess 22h is formed in the lower end surface of second stopper 22E. By providing recess 22h, air accumulates in recess 22h when exhaust valve 2B is used to release air, making it easier for exhaust valve 2B to move in the +z direction.

[0152] The shape of the side surface of recess 22h is substantially similar to the shape of the side surface of second stopper 22E, and the diameter d6 of recess 22h (corresponding to the width of the present invention) at the lower end of second stopper 22E is 0.8 times or more the diameter d7 (corresponding to the width of the present invention) of second stopper 22E. In this embodiment, diameter d6 is 0.82 times the diameter d7. As a result, the size of recess 22h can be increased, allowing more air to be stored in recess 22h. However, the shape and size of recess 22h are not limited to these.

[0153] The rod-shaped portion 23B differs from the rod-shaped portion 23A in that it does not have the columnar portion 23g, but is otherwise similar to the rod-shaped portion 23A.

[0154] 22 mainly includes a first stopper 21F and a moving member 24E. The moving member 24E mainly includes a second stopper 22F and a rod-shaped portion 23B. The second stopper 22F and the rod-shaped portion 23B integrally form the moving member 24E.

[0155] The second stopper 22F (corresponding to the main body of the present invention) has a columnar side surface similar to the second stopper 22E, but differs from the second stopper 22E in that it has an inclined portion 22i near the upper end. A recess 22j is formed in the lower end surface of the second stopper 22F. When air is released using the exhaust valve 2E, air accumulates in the recess 22j, making it easier for the exhaust valve 2E to move in the +z direction. However, the shape of the recess 22j is not limited to this.

[0156] 23 mainly includes a first stopper 21F and a moving member 24F. The moving member 24F mainly includes a second stopper 22G and a rod-shaped portion 23B. The second stopper 22G and the rod-shaped portion 23B integrally form the moving member 24F.

[0157] The second stopper 22G (corresponding to the main body of the present invention) has a columnar side surface similar to that of the second stopper 22E, but differs from the second stopper 22E in that it has a rounded, chamfered curved surface 22k near the upper end. A recess 22l is formed in the lower end surface of the second stopper 22G. When air is released using the exhaust valve 2E, air accumulates in the recess 22l, making it easier for the exhaust valve 2F to move in the +z direction. However, the shape of the recess 22l is not limited to this.

[0158] 24 and 25 are diagrams showing the outline of moving members 24G and 24H of the exhaust valve according to the modified example, where (A) is a plan view (viewed from above), (B) is a front view, (C) is a bottom view (viewed from below), (D) is a perspective view, and (E) is a side view. The moving members 24G and 24H can be attached to the first stoppers 21F and 21G, etc.

[0159] As shown in Figure 24, the moving member 24G mainly has a second stopper 22H and a rod-shaped portion 23A. The second stopper 22H and the rod-shaped portion 23A integrally constitute the moving member 24G. The second stopper 22H (corresponding to the main body of the present invention) has a truncated pyramidal side, in this case a quadrangular truncated pyramidal side. The second stopper 22H may have a rectangular cylindrical lower end provided at the lower end of the main body having a truncated pyramidal side.

[0160] A recess 22m is formed in the lower end surface of the second stopper 22H. By providing the recess 22m, air accumulates in the recess 22m, making it easier for the moving member 24G to move in the +z direction. Furthermore, in order to make the recess 22m as large as possible, the shape of the side surface of the recess 22m is a truncated quadrangular pyramid, that is, the shape of the side surface of the recess 22m is made substantially similar to the shape of the side surface of the second stopper 22H, and the width w1 of the recess 22m at the lower end of the second stopper 22H is made 0.8 times or more the width w2 of the second stopper 22H. However, the shape and size of the recess 22m are not limited to this.

[0161] As shown in Figure 25, the moving member 24H mainly has a second stopper 22I and a rod-shaped portion 23A. The second stopper 22I and the rod-shaped portion 23A integrally constitute the moving member 24H. The second stopper 22I (corresponding to the main body of the present invention) has a truncated pyramidal side, here a hexagonal truncated pyramidal side. The second stopper 22I may have a hexagonal cylindrical lower end at the lower end of the main body having a hexagonal truncated pyramidal side.

[0162] A recess 22n is formed in the lower end surface of the second stopper 22I. By providing the recess 22n, air accumulates in the recess 22n, making it easier for the moving member 24G to move in the +z direction. Furthermore, in order to make the recess 22n as large as possible, the shape of the side surface of the recess 22m is a hexagonal truncated pyramid, i.e., the shape of the side surface of the recess 22m is made substantially similar to the shape of the side surface of the second stopper 22I, and the width w3 of the recess 22n at the lower end of the second stopper 22I is made 0.8 times or more the width w4 of the second stopper 22I. However, the shape and size of the recess 22n are not limited to this.

[0163] <Fourth embodiment> In the third embodiment of the present invention, the exhaust valve 2B is provided in the return filter 1A (corresponding to the filtering device of the present invention), but the filtering device and the plate-like portion on which the exhaust valve is provided are not limited to this, and the shape of the exhaust valve is also not limited to this.

[0164] The fourth embodiment of the present invention is an embodiment in which an exhaust valve is provided on a return filter that does not have a cover. A return filter 1B and an exhaust valve 2G, which are filtration devices according to the fourth embodiment, will be described below. Note that the same parts as those in the first to third embodiments are given the same reference numerals, and descriptions thereof will be omitted.

[0165] Fig. 26 is a diagram showing an outline of a return filter 1B (corresponding to the filtering device of the present invention). Fig. 26 shows a partial cross section (however, hatching indicating a cross section is omitted). The return filter 1B may be provided with a rod portion 30.

[0166] The return filter 1B mainly includes a filter element 10B, a relief valve 40, and an exhaust valve 2G. Note that the return filter 1B can be provided with various types of exhaust valves, such as exhaust valves 2, 2A, and 2B, in addition to the exhaust valve 2G. The relief valve 40 is not essential.

[0167] The filter element 10B mainly comprises a filter medium 11A, an inner cylinder 12A, an upper plate 15B, and a lower plate 16A. The upper plate 15B is provided at the upper (+z side) ends of the filter medium 11A and the inner cylinder 12A (corresponding to the filtration section of the present invention) and covers the entire upper ends of the filter medium 11A and the inner cylinder 12A. The upper plate 15B has a plate-shaped portion 15c provided at the upper end of the return filter 1B. A relief valve 40 is provided on the plate-shaped portion 15c.

[0168] An air vent hole 20 is formed in the plate-shaped portion 15c. An exhaust valve 2G is provided in the air vent hole 20. The exhaust valve 2G mainly includes a first stopper 21F and a moving member 24I. The moving member 24I mainly includes a second stopper 22J and a rod-shaped portion 23A. The second stopper 22J and the rod-shaped portion 23A integrally form the moving member 24I. The second stopper 22J has a columnar side surface like the second stopper 22F, but is longer than the second stopper 22F. This enlarges the recess provided at the bottom end of the second stopper 22J, making it easier for oil to push up the exhaust valve 2G.

[0169] When the engine of a construction machine or the like equipped with return filter 1B is idling or running, unfiltered hydraulic oil flows from an inlet pipe 101h (not shown in FIG. 26) provided on a bottom surface 101g (not shown in FIG. 26) into a space S1 surrounded by the inner cylinder 12A, upper plate 15B, and lower plate 16A. The hydraulic oil that flows into space S1 is filtered as it flows from the inside to the outside of filter material 11A, and then flows out of return filter 1B (see arrows in FIG. 26). When air accumulates in space S1, the air pushes up exhaust valve 2G, discharging the air to the outside of return filter 1B.

[0170] <Fifth embodiment> In the third and fourth embodiments of the present invention, the hydraulic oil is filtered by flowing from the inside to the outside of the filter medium 11A, but the direction in which the hydraulic oil flows is not limited to this.

[0171] In the fifth embodiment of the present invention, hydraulic oil is filtered by flowing through a filter medium from the outside to the inside. A return filter 1C, which is a filtering device according to the fifth embodiment, will be described below. Note that the same parts as those in the first to fourth embodiments are given the same reference numerals, and description thereof will be omitted.

[0172] Fig. 27 is a diagram showing an outline of a return filter 1C (corresponding to the filtering device of the present invention). Fig. 27 shows a part in cross section (however, hatching indicating a cross section is omitted). The return filter 1C may be provided with a rod portion 30.

[0173] The return filter 1C mainly includes a filter element 10C and an exhaust valve 2B. Note that the return filter 1C can be provided with various types of exhaust valves, such as an exhaust valve 2, in addition to the exhaust valve 2B.

[0174] The filter element 10C mainly comprises a filter medium 11A, an inner cylinder 12A, an upper plate 15C, and a lower plate 16A. The upper plate 15C is provided at the upper (+z side) ends of the filter medium 11A and the inner cylinder 12A (corresponding to the filtration section of the present invention) and covers the entire upper ends of the filter medium 11A and the inner cylinder 12A. The upper plate 15C has a plate-shaped portion 15d provided at the upper end of the return filter 1C. An air vent hole 20 is formed in the plate-shaped portion 15d. An exhaust valve 2B is provided in the air vent hole 20.

[0175] When the engine of a construction machine or the like equipped with the return filter 1C is idling or running, unfiltered hydraulic oil flows into the tank body 101 (not shown in FIG. 27), is filtered as it flows from the outside to the inside of the filter medium 11A, and flows into the space S1 surrounded by the inner cylinder 12A, the upper plate 15C, and the lower plate 16A. The filtered hydraulic oil flows out from a pipe (not shown in FIG. 27) provided on the lower plate 16A.

[0176] Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configurations are not limited to these embodiments, and design modifications within the scope of the gist of the present invention are also included. For example, the above examples have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add, delete, or replace other configurations to the configuration of one embodiment.

[0177] In the present invention, the term "substantially" does not only mean strictly identical, but also includes errors or deformations to the extent that identity is not lost. For example, "substantially perpendicular" is not limited to strictly perpendicular, but includes an error of, for example, several degrees. Furthermore, for example, when expressing orthogonal, parallel, coincident, etc., it includes not only strictly perpendicular, parallel, coincident, etc., but also substantially parallel, substantially perpendicular, substantially coincident, etc.

[0178] In addition, in the present invention, "vicinity" means including a certain range (which can be determined arbitrarily) near a reference position. For example, "near an end" is a concept indicating a certain range near the end, which may or may not include the end. [Explanation of symbols]

[0179] 1: Suction strainer 1A, 1B, 1C: Return filter 2, 2A, 2B, 2C, 2D, 2E, 2F, 2G: Exhaust valve 10: Strainer section 10A, 10B, 10C: Filter elements 11, 11A: Filter medium 12, 12A: Inner cylinder 14: Connecting member 14a: Plate-shaped member 14b: Holding member 14c: Cylindrical part 14d: Hole 15, 16: Plate 15A, 15B, 15C: Upper plate 15a: face 15b: Hollow part 15c, 15d: Plate-shaped parts 16A: Lower plate 16a: Fitting part 17: Sealing material 18: Cover 18a: Cylindrical part 18b: Plate-shaped part 19: Bolt 20: Air vent hole 21, 21A, 21B, 21C, 21D, 21F, 21G: First stopper 21E: First moving member 21a: Hollow part 21b, 21k, 21l: Hole 21c:hole 21d: face 21e: Tapered surface 21f: Sealing surface 21g: Upper stopper 21h: Lower stopper 21i: Rod-shaped part 21j, 21m: Hollow part 21n: Curved surface part 22, 22A, 22B, 22C, 22D, 22E, 22F, 22G, 22H, 22I, 22J: Second stopper 22a, 22e: Main body 22b, 22d: Flat part 22c: Main body 22f: Bottom end 22g, 22h: recess 22i: Inclined part 22j, 22l, 22m, 22n: recessed parts 22k: Curved part 23, 23A, 23B, 23a: Rod-shaped part 23b:Connection part 23d: Protrusion 23e: Slit 23f: Rod-shaped part 23g: Cylindrical part 23j: Rod-shaped part 24, 24A, 24B, 24C, 24D, 24F, 24G, 24H, 24I: Moving parts 25: Valve housing 25a: Side 25b: Bottom 25c: Divider 25d, 25e: hole 25f: Communication hole 30: Rod part 31: Rod 32: Mounting part 33: Spring 40: Relief valve 50: Sealing material 100: Hydraulic oil tank 101: Tank body 101a: Inlet 101b, 101c: Opening 101d: Outlet 101e: Partition 101f: Upper end surface 101g: Bottom 101h:Inflow pipe 102, 103: Lid 102a Mounting part 104: Suction pipe 105: Bolt 110: Return filter

Claims

1. An exhaust valve provided on a plate-shaped portion provided near the upper end of a filtering device installed in a tank in which oil is stored, a rod-shaped portion that is inserted into an air vent hole formed in the plate-shaped portion; a first stopper provided at an upper end of the rod-shaped portion; a second stopper provided at a lower end of the rod-shaped portion; Equipped with the second stopper and the rod-shaped portion integrally constitute a moving member, The moving member is formed to float on oil, The first stopper has a hollow portion in which one end of the rod-shaped portion is provided, The rod-shaped portion is movable between a position where the first stopper abuts against the air vent hole to close the air vent hole and a position where the second stopper abuts against the air vent hole. An exhaust valve characterized by:

2. The first stopper and the second stopper are formed of different materials.

2. The exhaust valve according to claim 1.

3. The first stopper is made of an elastically deformable material.

3. An exhaust valve according to claim 1 or 2.

4. The second stopper has a spherical, semi-spherical, semi-spherical, truncated spherical, conical, or truncated conical portion.

4. An exhaust valve according to claim 1.

5. the second stopper has a main body portion whose side surface is frustum-shaped, truncated pyramidal, or columnar, A recess is formed in the lower end surface of the second stopper.

4. An exhaust valve according to claim 1.

6. a shape of a side surface of the recess is substantially similar to a shape of a side surface of the main body portion; At the lower end of the second stopper, the width of the recess is 0.8 times or more the width of the main body.

6. The exhaust valve according to claim 5.

7. A filtering device installed in a tank in which oil is stored, A cylindrical filtration section; a plate-shaped portion covering the entire upper end of the filtration portion and having an air vent hole formed therein; an exhaust valve inserted into the air vent hole; Equipped with the exhaust valve includes a rod-shaped portion inserted into the air vent hole, a first stopper provided at an upper end of the rod-shaped portion, and a second stopper provided at a lower end of the rod-shaped portion, the second stopper and the rod-shaped portion integrally constitute a moving member, The moving member is formed to float on oil, The first stopper has a hollow portion in which one end of the rod-shaped portion is provided, The exhaust valve is movable between a position where the first stopper abuts against the air vent hole to close the air vent hole and a position where the second stopper abuts against the air vent hole. A filtration device characterized by:

8. A filtering device installed in a tank in which oil is stored, A cylindrical filtration section; an upper plate covering the entire upper end of the filtration unit; a connecting member provided on the upper plate and protruding upward from the upper plate; a cover provided on the connecting member, the cover being a cylindrical portion provided on the outside of at least a part of the filtering portion and the connecting member; and a plate-like portion provided near the upper end of the cylindrical portion, the plate-like portion covering the hollow portion of the cylindrical portion, the plate-like portion having an air vent hole; an exhaust valve inserted into the air vent hole; Equipped with the exhaust valve includes a rod-shaped portion inserted into the air vent hole, a first stopper provided at an upper end of the rod-shaped portion, and a second stopper provided at a lower end of the rod-shaped portion, the second stopper and the rod-shaped portion integrally constitute a moving member, The moving member is formed to float on oil, The first stopper has a hollow portion in which one end of the rod-shaped portion is provided, The exhaust valve is movable between a position where the first stopper abuts against the air vent hole to close the air vent hole and a position where the second stopper abuts against the air vent hole. A filtration device characterized by:

9. a hole is formed in the connecting member, the hole communicating the hollow portion of the filtering section with the outside of the filtering section; The hole is provided with a relief valve, The relief valve is disposed inside the cover.

9. The filtering device according to claim 8.

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