Return filter

A return filter is provided in a tank, for removing bubbles from hydraulic oil before returning the hydraulic oil to the tank. A vortex forming portion that includes a spiral-shaped blade member is provided in an outflow portion that has a substantially cylindrical shape and communicates with a hollow portion of a filter element. Thus, a vortex forms in the hydraulic oil flowing through the outflow portion and bubbles contained in the hydraulic oil are collected.

TECHNICAL FIELD

The present invention relates to a return filter.

BACKGROUND ART

Patent Document 1 discloses a hydraulic oil tank that includes a return port provided in an upper portion of the hydraulic oil tank. This return port is configured to return hydraulic oil from a cylinder side via a bubble removing device provided outside the hydraulic oil tank. The hydraulic oil returned from this return port is passed through a filter and housed in the hydraulic oil tank.

CITATION LIST

Patent Document

Patent Document 1: JP 2004-11873 A

Nevertheless, in the invention described in Patent Document 1, the problem arises that the bubble removing device needs to be separately provided outside the liquid tank. Further, when the hydraulic oil passes through the filter (hereinafter, referred to as a “return filter”) provided in the tank, bubbles may be produced in the hydraulic oil.

In light of the above, an object of the present invention is to provide a return filter capable of removing bubbles contained in hydraulic oil.

SUMMARY OF INVENTION

A return filter according to one or more embodiments of the present invention serves as, for example, a return filter provided in a tank. Such a return filter includes a filter element including a filtration member having a substantially cylindrical shape, a filter case having a bottomed substantially cylindrical shape and provided with the filtration member therein, an inflow portion configured to allow an inflow of oil and to communicate with a space between the filter case and the filter element, an outflow portion having a substantially cylindrical shape and provided to a bottom surface of the filter case, the outflow portion being configured to communicate with a hollow portion of the filter element, and a vortex forming portion including a blade member having a spiral shape and provided in the outflow portion.

According to one or more embodiments of the present invention, in the returning filter, the vortex forming portion that includes a blade member having a spiral shape is provided in the outflow portion that has a substantially cylindrical shape and communicates with the hollow portion of the filter element. This configuration allows the hydraulic oil flowing through the outflow portion to produce a vortex. As a result, the bubbles contained in the hydraulic oil are collected along an axis of the vortex, making it possible to remove the bubbles contained in the hydraulic oil when the hydraulic oil passes through the filtration member and the like in the return filter.

Here, the vortex forming portion may include a tubular portion having a substantially cylindrical shape with a covered upper end, the tubular portion being formed extending along an axis of the blade member at a substantial center of the vortex forming portion. The blade member may include, on a lower side thereof, a passage that crosses the blade member in a radial direction. The tubular portion and the outflow portion may each include a hole that communicates with the passage. This configuration allows the bubbles collected along the axis of the vortex to be released outside the return filter.

Here, the return filter may further include an outflow pipe that protrudes downward from a bottom surface of the filter case and is configured to communicate with the outflow portion. A lower end of the outflow pipe may be covered by a lower end surface having a substantially truncated cone shape that increases in height and decreases in width toward a center, and a side surface of the outflow pipe in a vicinity of the lower end surface may include a plurality of holes. This configuration causes a flow of the hydraulic oil to change to a direction substantially orthogonal to the axis, allowing the hydraulic oil to flow out horizontally.

Here, the return filter may further include a lid configured to cover an upper end of the filter case, a valve provided to the lid and configured to open and close depending on a difference in a pressure on an outer side of the filtration member and a pressure on an inner side of the filtration member, and a bypass strainer configured to allow passage of the oil after passing through the valve and including a frame having an inner peripheral surface to which the valve is fitted. In such a return filter, the filter element further includes an upper plate that covers an upper end of the filtration member, and the upper plate and the frame are integrated with each other. This configuration causes the upper plate and the bypass strainer to be integrated with each other, making it possible to reduce the size of the filter element.

According to one or more embodiments of the present invention, bubbles can be removed.

DESCRIPTION OF EMBODIMENTS

Below, detailed description of embodiments of the present invention will be given with reference to the drawings.

FIG. 1is a diagram illustrating an overview of a hydraulic oil tank100provided, therein, with a return filter1according to an embodiment of the present invention. InFIG. 1, main parts of the hydraulic oil tank100are illustrated from a perspective view.

The hydraulic oil tank100is installed in a work machine (a hydraulic apparatus, for example, not illustrated), and is disposed inside a hydraulic circuit of hydraulic oil supplied to the hydraulic apparatus and is configured to store the hydraulic oil. The hydraulic oil tank100includes a tank main body101having a box shape, for example, and this tank main body101has a hollow interior. The tank main body101primarily includes the return filter1and a suction strainer110.

In the hydraulic circuit, the hydraulic oil passes through the hydraulic apparatus and is introduced into the hydraulic oil tank100.

An inflow port101aconfigured to allow the hydraulic oil to flow into the tank main body101is formed on a side surface of the tank main body101. The hydraulic oil that has entered through the inflow port101ais introduced into the return filter1. The hydraulic oil is filtered by the return filter1and is stored in the hydraulic oil tank100.

Openings101b,101cused for maintenance of the return filter1, the suction strainer110, and the like are formed at an upper end portion of the tank main body101. The return filter1is attached to the opening101b. Further, a lid103is attached to the opening101c.

Bolt insertion holes are formed in peripheral edge portions of lids11,103. Bolts105inserted through the bolt insertion holes are screwed into bolt holes (not illustrated) of the tank main body101, thereby tightening the lids11,103to the tank main body101.

An outflow port101dthat allows the hydraulic oil inside the tank main body101to flow out to a hydraulic pump (not illustrated) is formed in a vicinity of a lower end portion of the tank main body101(on a side surface of the tank main body101near a bottom surface in the present embodiment). A suction pipe104that leads to a suction port of the hydraulic pump (not illustrated) is fitted into the outflow port101dfrom an outer side of the tank main body101.

To prevent foreign matter from entering the suction pipe104, the suction strainer110is provided on an upper side of the outflow port101d(inner side of the tank main body101). The hydraulic oil stored in the hydraulic oil tank100is suctioned into the hydraulic pump (not illustrated), flows out to the suction pipe104via the suction strainer110, and is supplied once again to the hydraulic apparatus.

A partition plate101ethat defines a space where the suction strainer110is provided and a space where the return filter1is provided is provided to the bottom surface of the tank main body101. Note that the partition plate101eis not necessarily required.

FIG. 2is a side view illustrating an overview of the return filter1. Further,FIG. 3is a cross-sectional view illustrating an overview of the return filter1(note that hatching indicating a cross section is omitted).

The return filter1mainly includes a filter case10, an inflow portion20, a filter element30, an outflow portion40, and a vortex producing portion50.

The filter case10is a member having a bottomed substantially cylindrical shape, and is formed from a metal. The lid11is provided to the filter case10so as to cover an upper end of the filter case10.

A valve12is provided to the lid11. The valve12is configured to open and close depending on a difference between a pressure between the filter case10and the filter element30(on an outer side of the filter element30), and a pressure on the inner side of the filter element30. An outer peripheral surface of the valve12is fitted to an inner peripheral surface of a bypass strainer13through which the hydraulic oil passes after passing through the valve12.

The inflow portion20includes an inflow pipe21inserted into the inflow port101a. The hydraulic oil flows into the inflow pipe21. The hydraulic oil that has flowed from the inflow pipe21is introduced into a space between the filter case10and the filter element30.

The filter element30is a member having a substantially cylindrical shape provided in the filter case10. An upper end of the filter element30is formed by the lid11and a lower end is formed by the outflow portion40, which causes the filter element30to be held in the filter case10.

The filter element30mainly includes an inner tube31, an outer tube32, a filtration member33, and plates34,35.

The inner tube31and the outer tube32are members that have substantially hollow cylindrical shapes and include openings at both ends. The inner tube31and the outer tube32are formed from a material (stainless steel, for example) having high corrosion resistance. Holes through which the hydraulic oil passes are formed substantially in an entire region of the inner tube31and the outer tube32. Note that the inner tube31and the outer tube32may be formed from a resin. Further, the outer tube32is not necessarily required.

The filtration member33is provided between the inner tube31and the outer tube32. The filtration member33has a substantially cylindrical shape and a thickness in a radial direction. A height of the filtration member33is substantially the same as a height of the inner tube31and the outer tube32.

The filtration member32is formed by pleating a filter paper formed of a synthetic resin, paper, or the like, and connecting both ends of the pleated filter paper to form a cylindrical shape. As a result, the filtration member33is formed into a substantially cylindrical pleated shape. The filtration member33is configured to filter the hydraulic oil.

A plate34is provided to respective first ends of the outer tube32and the inner tube31and a plate35is provided to respective second ends. The plate34and the plate35are members having a substantially circular plate shape or a bottomed substantially cylindrical shape, and are formed from a resin or a metal.

The plate34and the plate35are provided so as to cover the ends (openings) of the inner tube31, the outer tube32, and the filtration member33. In other words, the plate34and the plate35sandwich the inner tube31, the outer tube32, and the filtration member33.

The plate34covers lower ends of the inner tube31, the outer tube32, and the filtration member33. An inner peripheral surface34aof the plate34is fitted to a fitting pipe41(described below) of the outflow portion40.

A sealing member61is provided to an inner peripheral surface of the plate34. The sealing member61is configured so that the hydraulic oil does not enter the fitting pipe41from between the plate34and the fitting pipe41.

The plate35covers the upper ends of the inner tube31, the outer tube32, and the filtration member33.FIG. 4is an enlarged partial view ofFIG. 3.

The bypass strainer13mainly includes a frame13ahaving a substantially cylindrical shape as a whole, and a filtration portion13bhaving a mesh shape stretched in a space of the frame13a.

The inner peripheral surface35aof the plate35is fitted to the outer peripheral surface13cof the bypass strainer13. Thus, the plate35and the bypass strainer13are integrated. As a result, the size of the return filter1can be reduced.

The plate35and the inner peripheral surface35bare fitted to an outer peripheral surface12aof the valve12. As a result, the filter element30and the bypass strainer13are attached to the valve12. Note that the outer peripheral surface12aof the valve12is fitted to an inner peripheral surface13dof the bypass strainer13.

A sealing member62is provided to a groove35cformed in an inner peripheral surface of the plate35. Thus, in a case that the inner peripheral surface35bis fitted to the outer peripheral surface12a, the hydraulic oil does not enter the bypass strainer13from the area between the valve12and the plate35.

The description will now return toFIG. 3. The outflow portion40has a substantially cylindrical shape as a whole, and mainly includes a fitting pipe41, an inner side pipe42, and an outflow pipe43.

The fitting pipe41is a member having a substantially cylindrical shape, and is provided in the filter case10. The inner peripheral surface34aof the plate34is fitted to an outer peripheral surface of the fitting pipe41. Thus, a hollow portion of the filter element30(a hollow portion of the inner tube31) and a hollow portion of the fitting pipe41are in communication.

The inner side pipe42is a member having a substantially cylindrical shape, and is provided in the filter case10. Further, the inner side pipe42is provided to the hollow portion of the fitting pipe41. Thus, the hydraulic oil after filtration that has entered the fitting pipe41flows out to the inner side pipe42.

The outflow pipe43is provided to a lower end of the inner side pipe42via the filter case10. The outflow pipe43is a member having a substantially cylindrical shape, and is provided protruding downward from the bottom surface10a(surface on the −z side) of the filter case10. The outflow pipe43communicates with the inner side pipe42via the opening10b.

Note that while the inner side pipe42is provided above the bottom surface of the filter case10and the outflow pipe43is provide below the bottom surface of the filter case10in the present embodiment, a configuration in which the outflow portion40is provided to the bottom surface of the filter case10is not limited to this embodiment. The outflow portion40need only to be provided to the bottom surface of the filter case10with an upper end in communication with the inner peripheral portion of the filter element30and a lower end surface protruding into the tank main body101.

A lower end of an outflow pipe43is covered by a lower end surface43ahaving a substantially truncated cone shape that increases in height and decreases in width toward the center. A plurality of holes43bare formed in a side surface of the outflow pipe, in a vicinity of the lower end surface43a. As a result, the hydraulic oil that has flowed downward (in the −z direction) through the outflow pipe43comes into contact with the lower end surface43a, thereby changing the flow to a direction substantially orthogonal to the z direction and causing the hydraulic oil to flow out from the holes43band into the tank main body101.

Further, the vortex producing portion50is provided to a hollow portion of the outflow pipe43.FIGS. 5 to 7are perspective views illustrating details of the vortex producing portion50. Note thatFIG. 6is a perspective view of a portion that is not visible.

The vortex producing portion50mainly includes a main body portion51, a flange portion52, a blade member53, a tubular portion54, and an air flow path55.

The main body portion51is a member having a substantially cylindrical shape, and is inserted into the outflow pipe43. The flange portion52for attaching the vortex producing portion50to the outflow pipe43and the filter case10is integrally formed with an upper end of the main body portion51.

As illustrated inFIG. 3, in a case that the flange portion52is provided on an inner side of the bottom surface10aof the filter case10so that the main body portion51protrudes downward, the main body portion51is inserted into the opening10bformed in the bottom surface10a. Further, the main body portion51inserted into the opening10bis also inserted into the outflow pipe43that communicates with the opening10b.

The description will now return toFIGS. 5 to 7. The blade members53having a spiral shape are formed on an inner peripheral surface of the main body portion51. Each of the blade members53is a member that produces a vortex in the hydraulic oil that flows into the outflow pipe43. The blade members53, having a spiral shape, allow the hydraulic oil that flows into the outflow pipe43to flow downward (in the −z direction) while swirling and forming a vortex, as indicated by the arrows inFIG. 3.

While four blade members53are provided in a circumferential direction in the present embodiment, the number of blade members53is not limited to four. For example, in a case that the blade members53having a fan shape in a planar view are used, the number of blade members53needs only to be two or greater. Further, the shape of the blade members53is not limited to the fan shape. For example, the blade member may be a single blade having a spiral shape continuously extending for 360 degrees or greater.

The tubular portion54is provided along an axis of the blade member53. The tubular portion54has a substantially cylindrical shape with an upper end thereof covered, and includes a space where the bubbles contained in the hydraulic oil accumulate (details described below).

The air flow path55that crosses in the radial direction is formed in the blade member53, on a surface on a lower side (−z side). While the air flow path55is a tubular member in the present embodiment, the shape of the air flow path55is not limited thereto. For example, a groove between two ribs formed on a back surface of the blade member53may serve as the air flow path. Further, the position and number of the air flow paths55are also not limited to such a configuration. For example, the air flow path55may be formed on each of the blade members53, or a plurality of the air flow paths55may be formed on one blade member53.

A hole51athat communicates with the air flow path55is formed in the main body portion51(refer toFIGS. 5 and 6). A hole (not illustrated) that communicates with the hole51ais formed in the outflow pipe43.

A hole54athat communicates with the air flow path55is formed in the tubular portion54(refer toFIG. 7). As a result, the air accumulated in the tubular portion54passes through the air flow path55, the hole51a, and the hole (not illustrated) formed in the outflow pipe43, and is released into the tank main body101.

Note that while the vortex producing portion50is provided in the outflow pipe43in the present embodiment, the vortex producing portion50need only to be provided to the outflow portion40, and thus may be provided to the fitting pipe41or the inner side pipe42. Further, while the outflow portion40and the vortex producing portion50are separately provided in the present embodiment, the vortex producing portion50may be formed in the outflow portion40. In a case that the vortex producing portion50is formed in the outflow portion40, at least the blade member53, the tubular portion54, and the air flow path55need to be formed.

Next, the functionality of the return filter1thus configured will be described. The arrows inFIG. 3indicate the flow of the hydraulic oil in the return filter1.

The hydraulic oil that has flowed into the inflow portion20is introduced into the space between the filter case10and the filter element30. The hydraulic oil flows from the outer side to the inner side of the filter element30, and the filtered hydraulic oil flows out to the inner side of the inner tube31.

The filtered hydraulic oil flows downward from the inner side of the inner tube31and through the inner sides of the fitting pipe41and the inner side pipe42, and is introduced into the vortex producing portion50.

The hydraulic oil introduced into the vortex producing portion50collides with the blade members53, changing the direction of flow. The blade members53, having a spiral shape, produce a spiral-shaped vortex in the hydraulic oil that has collided with the blade members53.

In a case that the hydraulic oil flows downward (in the −z direction) while swirling and forming a spiral-shaped vortex, the bubbles contained in the hydraulic oil are collected along the axis of the vortex (that is, the axis of the blade members53) by centrifugal force. In the vicinity of the axis of the vortex, the flow rate is near zero, and thus the bubbles collected along the axis collide with each other to increase in size. The bubbles that have grown to a certain size or larger move upward (in the +z direction) and accumulate in a space in a vicinity of an upper end of the tubular portion54.

The bubbles accumulated in the vicinity of the upper end of the tubular portion54flow through the hole54aand out to the air flow path55. The bubbles that have flowed out to the air flow path55flow through the hole51aand the like, and are released to the outside of the return filter1.

As a result, the hydraulic oil that has flowed downward while swirling and forming a vortex comes into contact with the lower end surface43a, thereby changing the flow to a direction substantially orthogonal to the z direction and causing the hydraulic oil to flow through the holes43band into the tank main body101. As a result, the hydraulic oil that has flowed through the outflow pipe43cannot vigorously collide with the bottom surface of the tank main body101.

According to the present embodiment, the bubbles contained in the hydraulic oil can be removed by the return filter1. This makes it possible to prevent defects that occur as a result of air being suctioned into the pump. The bubbles may also be prevented from bursting inside the hydraulic circuit or the like, which causes the temperature and the pressure of the hydraulic oil to temporarily increase to a significant degree and, as a result, the occurrence of part damage and the like.

Note that while bubbles are collected and removed by producing a vortex in the hydraulic oil by the vortex producing portion50in the present embodiment, the method of collecting the bubbles is not limited thereto. For example, the bubbles may be removed by filling the outflow pipe43with steel wool or the like.

Steel wool is obtained by processing an iron (stainless steel, for example) into fine, long fibers, and this steel wool can be bundled to form various shapes. The member formed by bundling the steel wool has a plurality of spaces formed in a surface and interior thereof. The bubbles contained in the hydraulic oil are captured in the spaces in the surface and the interior of the member formed by bundling the steel wool, and the captured bubbles are collected, causing the bubbles to grow. When the bubbles grow and become large in size, the bubbles separate from the steel wool and rise upward (in the +z direction).

Thus, the bubbles can be effectively removed even when the outflow pipe43is filled with a material having a plurality of fine spaces formed in the surface and interior thereof. Note that the material that fills the outflow pipe43is not limited to steel wool, and a sintered metal or a sponge, for example, may be used.

Further, the steel wool need not fill the outflow pipe43entirely, and only at least the hollow portion of the outflow portion40needs to be filled with the steel wool in a long narrow strip shape in the direction orthogonal to the axis (xy plane).

Further, while the outflow pipe43has a constant cross-sectional area in the present embodiment, the shape of the outflow pipe43is not limited thereto.FIG. 8illustrates an overview of a return filter2that uses an outflow pipe43A that forms a restricting portion43cthat gradually decreases a cross-sectional area of the pipe. The restricting portion43chas the effect of further strengthening the vortex of the hydraulic oil. Thus, the restricting portion43cis suitably provided to a position as close as possible to the vortex producing portion50, that is, the blade members53. Note that the position, length, taper angle, and the like of the restricting portion43care not limited to the illustrated configuration.

Embodiments of the invention have been described in detail with reference to the drawings; however, specific configurations are not limited to the embodiments, and changes in the design or the like are also included within a scope which does not depart from the gist of the invention. For example, the above examples have been explained in detail in order to facilitate understanding of the present invention and are not necessarily limited to examples provided with the entirety of the configuration described above. In addition, the configuration of an embodiment may be partially replaced with the configuration of a different embodiment, or the configuration of the different embodiment may be added to, deleted from, or replaced with the configuration of the embodiment.

Further, the term “substantially” in the present invention is not to be understood as merely being strictly the same, and is a concept that includes variations and modifications to an extent that does not result in loss in identity. For example, the term “substantially orthogonal” is not limited to being strictly orthogonal, and is a concept that includes variations of several degrees, for example. Further, simple expressions such as orthogonal, parallel, and identical are not to be understood as merely being strictly orthogonal, parallel, identical, and the like, and include being substantially parallel, substantially orthogonal, substantially matching, and the like.

Furthermore, the meaning of the term “vicinity” in the present invention includes a region of a range (which can be determined as desired) near a position serving as a reference. For example, the term “a vicinity of an end” refers to a region of a range near the end, and is a concept indicating that the end may or may not be included.

REFERENCE SIGNS LIST