Automatic transmission fluid filter

The automatic transmission fluid filter includes a plastic upper case having an outlet port, a plastic lower case having an inlet port, and a filter element including a filter medium and a plastic holder frame holding the periphery of the filter medium and held between the upper case and lower case, at least one of the upper case and lower case including a pair of joint portions respectively joined to opposite walls a of the holder frame, and a connecting wall connecting the pair of joint portions and having a circular arc longitudinal cross section protruding outward of one case.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 of Japanese Application No. 2010-101471 filed on Apr. 26, 2010, the disclosure of which is expressly incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an automatic transmission fluid filter, and more particularly to an aesthetically pleasing automatic transmission fluid filter designed to be able to have improved case rigidity and fabrication properties as well as to be able to reduce pressure loss during use of the filter.

2. Description of Related Art

A commonly known conventional automatic transmission filter includes, for example as shown inFIG. 10, an upper case102having an outlet port102a, a lower case103having an inlet port103a, and a filter element106including a filter medium104and a holder frame105holding the periphery of the filter medium104and held between both cases102and103. A plurality of ribs107are formed to extend in the width direction of the case on inner surfaces of both cases102and103so as to enhance the case rigidity. These ribs107prevent deformation of the case toward the filter element due to suction negative pressure and a consequent increase in pressure loss, which will lead to performance deterioration. Japanese Patent Application Laid-Open No. 8-24532 discloses a fluid filter with an upper case and a lower case formed with ribs on their inner surfaces for preventing deformation of the filter medium.

However, with the conventional automatic transmission fluid filter mentioned above, sink marks easily occur during the case molding process because of the plurality of internally formed ribs107of the cases102and103, resulting in poor outer appearance. The case appearance is significantly deteriorated, in particular, when a case that is transparent or translucent is joined with the holder frame by laser welding. The ribs also cause an increase in the amount of use of resin which leads to a higher production cost. Another problem was that the ribs have a large impact on the flow properties of a fluid flowing through the filter chamber during use, causing an increase in pressure loss.

SUMMARY OF THE INVENTION

The embodiments of the present invention are provided to address the problems with the conventional technology above. An advantage of the embodiments of the present invention is to provide an aesthetically pleasing automatic transmission fluid filter designed to be able to have improved case rigidity and fabrication properties as well as to be able to reduce pressure loss during use of the filter.

One aspect of the present embodiments provides an automatic transmission fluid filter including a plastic upper case having an outlet port; a plastic lower case having an inlet port; and a filter element including a filter medium and a plastic holder frame holding a peripheral part of the filter medium and held between the upper case and the lower case, wherein at least one of the upper case and the lower case including a pair of joint portions respectively joined to opposite walls of the holder frame, and a connecting wall connecting the pair of joint portions and having a circular arc longitudinal cross section protruding outward of one case.

In a further aspect, the pair of joint portions respectively include a first lateral wall having an outer end joined to the wall of the holder frame and extending laterally inward of the one case, a vertical wall standing from an inner end of the first lateral wall, and a second lateral wall extending laterally inward of the one case from a standing distal end of the vertical wall, outer ends of the connecting wall being connected to inner ends of the second lateral walls.

In a further aspect, the pair of joint portions respectively include a first lateral wall having an outer end joined to the wall of the holder frame and extending laterally inward of the one case, and a vertical wall standing from an inner end of the first lateral wall, outer ends of the connecting wall being connected to standing distal ends of the vertical walls.

In a further aspect, the one case is made of a laser transmitting resin while the holder frame is made of a laser absorbing resin, and the joint portions are joined to the walls of the holder frame by laser welding.

In the automatic transmission fluid filter according to the present embodiments, at least one of the cases includes a pair of joint portions respectively joined to the opposite walls of the holder frame, and a connecting wall connecting the pair of joint portions and having a circular arc longitudinal cross section protruding outward of one case, so that the cases need not be provided with any ribs on the inner surfaces and yet can have enhanced rigidity due to the connecting wall having a circular arc longitudinal cross section. The cases have a substantially uniform wall thickness so that resin flowability during the case molding process is improved, as well as the amount of use of resin can be reduced, i.e., the case fabrication properties can be improved. Also, the fluid inside the cases will have better flow properties during the use of the filter so that the pressure loss can be reduced. Further, the cases have a good appearance.

If the pair of joint portions are formed to respectively include a first lateral wall, a vertical wall, and a second lateral wall, and the outer ends of the connecting wall are connected to the inner ends of the second lateral walls, the stress locally applied on the cases by the vertical walls can be dispersed and the points of stress can be distanced from the first lateral walls, whereby the rigidity (in particular, joint strength) of the cases can be further improved. Since the first lateral walls can be joined to the walls of the holder frame in a state in which the first lateral walls and second lateral walls are pressed down with jigs, the case fabrication properties can be further improved. When the first lateral walls and the second lateral walls are pressed down with the jigs, the first lateral walls can conform to the walls of the holder frame due to flexure of the vertical walls, which contributes to a further improvement in the case fabrication properties.

If the pair of joint portions are formed to respectively include a first lateral wall and a vertical wall, and the outer ends of the connecting wall are connected to the distal ends of the vertical walls, the stress locally applied on the cases by the vertical walls can be dispersed and the points of stress can be distanced from the first lateral walls, whereby the rigidity (in particular, joint strength) of the cases can be further improved.

If one of the cases is made of a laser transmitting resin, while the holder frame is made of a laser absorbing resin, and the joint portions are joined to the walls of the holder frame by laser welding, the case can be easily joined to the holder frame and can have a good appearance even though a transparent or translucent material is employed for the case.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The automatic transmission fluid filter according to the present embodiments includes a plastic upper case (2) having an outlet port, a plastic lower case (3) having an inlet port, and a filter element (6) including a filter medium (4) and a plastic holder frame (5) holding the periphery of the filter medium and held between the upper case and lower case. The automatic transmission fluid filter is characterized in that at least one of the upper case and lower case includes a pair of joint portions (8,10) respectively joined to opposite walls (5a) of the holder frame, and a connecting wall (7,17) connecting the pair of joint portions and having a circular arc longitudinal cross section protruding outward of one case (see, for example,FIG. 3etc.).

The automatic transmission fluid filter according to the present embodiments may include, for example, the following three forms: [1] The pair of joint portions respectively include a first lateral wall (8a,10a) having an outer end joined to the wall of the holder frame and extending laterally inward of the one case, a vertical wall (8b,10b) standing from an inner end of the first lateral wall, and a second lateral wall (8c,10c) extending laterally inward of the one case from a standing distal end of the vertical wall, outer ends of the connecting wall being connected to inner ends of the second lateral walls (see, for example,FIG. 3, etc.). [2] The pair of joint portions respectively include a first lateral wall (8a′) having an outer end joined to the wall of the holder frame and extending laterally inward of the one case, and a vertical wall (8b′) standing from an inner end of the first lateral wall, outer ends of the connecting wall being connected to standing distal ends of the vertical walls (see, for example,FIG. 6, etc.). [3] The pair of joint portions respectively include a first lateral wall (8a″) having an outer end joined to the wall of the holder frame and extending laterally inward of the one case, outer ends of the connecting wall being connected to inner ends of the first lateral walls (see, for example,FIG. 7, etc.).

The automatic transmission fluid filter according to the present embodiments may include a form, for example, in which one case is made of a laser transmitting resin while the holder frame is made of a laser absorbing resin, and the joint portions are joined to the walls of the holder frame by laser welding. In this case, the form [1] described above is particularly preferable, since the first lateral wall of one case and the holder frame can be readily and reliably joined together by irradiating a laser beam (L) from one case toward the wall of the holder frame through a gap between jigs (15a,15b) pressing down the first lateral wall and second lateral wall (see, for example,FIG. 5, etc.).

The automatic transmission fluid filter according to the present embodiments may include a form, for example, in which the connecting wall has a radius of curvature (R) of from 50 to 300 mm (preferably from 100 to 200 mm, in particular from 130 to 180 mm) (see, for example,FIG. 5, etc.). Thereby the case can have improved rigidity, and a minimum necessary space inside so as to prevent deterioration of the flow properties of the fluid.

The automatic transmission fluid filter according to the present embodiments may include a form, for example, in which the one case is formed substantially rectangular in plan view, while the connecting wall is formed to have a circular arc surface with an axis center in the longitudinal direction of the one case (for example, seeFIG. 4, etc.). Thereby the case can have improved rigidity, and prevent deterioration of the flow properties of the fluid flowing in the longitudinal direction inside the case.

The automatic transmission fluid filter according to the present embodiments may include a form, for example, in which the filter medium is formed in a pleated shape, and the holder frame includes a pair of first walls (5a) holding pleated edges (4a) of the filter medium and joined with the joint portions of the one case, and a pair of second walls (5b) continuous with these first walls and holding non-pleated edges (4b) of the filter medium, these first walls and second walls having a larger height (h2) than the pleats height (h1) of the filter medium (for example, seeFIG. 2, etc.). Thereby the filter medium can have a large filtering area and improved filtering efficiency.

EXAMPLE

The present invention will be hereinafter described more specifically by way of examples of embodiment using the drawings. The “automatic transmission fluid filter” according to the invention is herein exemplified as an oil filter.

(1) Structure of the Oil Filter

The oil filter1according to this example embodiment includes an upper case2made of a laser transmitting resin and having an outlet port2a, a lower case3made of a laser transmitting resin and having an inlet port3a, and a filter element6including a filter medium4and a holder frame5made of a laser absorbing resin, holding the periphery of the filter medium4and held between the upper case2and the lower case3, as shown inFIG. 1toFIG. 4. These upper case2and lower case3are respectively formed to be substantially rectangular in plan view.

The filter element6is integrally formed with the filter medium4and holder frame5by insertion molding. This filter medium4is formed substantially rectangular in plan view and in a pleated shape. The holder frame5includes a pair of first walls5aholding pleated edges4aof the filter medium4, and a pair of second walls5bcontinuous with these first walls5aand holding non-pleated edges4bof the filter medium4. These first walls5aand second walls5bhave a larger height h2than the pleats height h1of the filter medium4. These holder frame5, upper case2and lower case3form a filter chamber S of the oil filter1, as well as an outer surface (design surface).

The upper case2includes a pair of joint portions8respectively joined to the pair of first walls5a, a pair of joint portions9respectively joined to the pair of second walls5b, and a connecting wall7connecting these joint portions8and9and having a circular arc longitudinal cross section protruding outward (upward) of the upper case2, as shown inFIG. 2andFIG. 3. These joint portions8and9are continuous and in a stepped flange shape as a whole (seeFIG. 4). The connecting wall7is formed to have a circular arc surface having an axis center along a longitudinal direction of the upper case2, with a radius of curvature R (seeFIG. 5) of about 150 mm.

The joint portions8respectively include a first lateral wall8ahaving an outer end joined to an upper end face of the first wall5aof the holder frame5by laser welding and extending substantially horizontally inward (toward the center) of the upper case2, a vertical wall8bstanding from an inner end of this first lateral wall8a, and a second lateral wall8cextending substantially horizontally inward (toward the center) of the upper case2from a standing distal end of the vertical wall8b, as shown inFIG. 3. To an inner end of this second lateral wall8cis connected an outer end of the connecting wall7.

The joint portions9respectively include a first lateral wall9ahaving an outer end joined to an upper end face of the second wall5bof the holder frame5by laser welding and extending substantially horizontally inward (toward the center) of the upper case2, a vertical wall9bstanding from an inner end of this first lateral wall9a, and a second lateral wall9cextending substantially horizontally inward (toward the center) of the upper case2from a standing distal end of the vertical wall9b, as shown inFIG. 2. To an inner end of this second lateral wall9cis connected an outer end of the connecting wall7.

The lower case3includes a pair of joint portions10respectively joined to the pair of first walls5a, a pair of joint portions11respectively joined to the pair of second walls5b, and a connecting wall17connecting these pairs of joint portions10and11and having a circular arc longitudinal cross section protruding outward (downward) of the lower case3, as shown inFIG. 2andFIG. 3. These joint portions10and11are continuous and in a stepped flange shape as a whole. The connecting wall17is formed to have a circular arc surface having an axis center along a longitudinal direction of the lower case3, with a radius of curvature of about 150 mm.

The joint portions10respectively include a first lateral wall10ahaving an outer end joined to a lower end face of the first wall5aof the holder frame5by laser welding and extending substantially horizontally inward (toward the center) of the lower case3, a vertical wall10bstanding from an inner end of this first lateral wall10a, and a second lateral wall10cextending substantially horizontally inward (toward the center) of the lower case3from a standing distal end of the vertical wall10b, as shown inFIG. 3. To an inner end of this second lateral wall10cis connected an outer end of the connecting wall17.

The joint portions11respectively include a first lateral wall11ahaving an outer end joined to a lower end face of the second wall5bof the holder frame5by laser welding and extending substantially horizontally inward (toward the center) of the lower case3, a vertical wall11bstanding from an inner end of this first lateral wall11a, and a second lateral wall11cextending substantially horizontally inward (toward the center) of the lower case3from a standing distal end of the vertical wall11b, as shown inFIG. 2. To an inner end of this second lateral wall11cis connected an outer end of the connecting wall17.

(2) Method of Fabricating the Oil Filter

Next, a method of fabricating the oil filter1having the above structure will be described. As shown inFIG. 5, the joint portion8(9) of the upper case2is abutted on the upper end face of the wall5a(5b) of the holder frame5, and in this abutted state, the first lateral wall8a(9a) and second lateral wall8c(9c) of the upper case2are pressed down with jigs15aand15b. In this pressed state, a laser beam L is irradiated from above through a gap between the jigs15aand15bover the entire circumference of the upper case2. The laser beam L transmits the first lateral wall8a(9a) of the upper case2and reaches a projection18formed on the upper end face of the holder frame5. This projection18is melted, and so is the first lateral wall8a(9a) of the upper case2. Thus the first lateral wall8a(9a) of the upper case2is joined to the holder frame5by laser welding. The lower case3is joined to the holder frame5by laser welding in a similar manner as with the above-described upper case2.

The oil filter1is immersed in oil inside an oil pan13(seeFIG. 2) when used. The oil used on the automatic transmission side is accumulated inside the oil pan13, and this accumulated oil is made to flow into the filter chamber S from the inlet port3aand filtered by the filter medium4, as indicated by broken lines with arrows inFIG. 2andFIG. 3. Filtered oil flows out from the outlet port2aand returns to the automatic transmission side.

(3) Effects of the Example Embodiment

According to the oil filter1of this example embodiment, the cases2and3include pairs of joint portions8and10respectively joined to the opposite walls5aof the holder frame5, and connecting walls7and17connecting the pairs of joint portions8and10and having a circular arc longitudinal cross section protruding outward of the cases2and3, so that the cases2and3need not be provided with internal ribs and yet can have enhanced rigidity due to the connecting walls7and17having a circular arc longitudinal cross section. The cases2and3have a substantially uniform wall thickness so that resin flowability during the case molding process is improved, as well as the amount of use of resin can be reduced, i.e., the fabrication properties of the cases2and3are improved. Also, the fluid inside the cases2and3will have better flow properties during the use of the filter so that the pressure loss can be reduced. Further, the cases2and3have a good appearance.

In this example embodiment, the pairs of joint portions8and10are formed to respectively include first lateral walls8aand10a, vertical walls8band10b, and second lateral walls8cand10c, the outer ends of the connecting walls7and17being connected to the inner ends of the second lateral walls8cand10c. This way, the stress locally applied on the cases2and3by the vertical walls8band10bcan be dispersed and the points of stress can be distanced from the first lateral walls8aand10a, whereby the rigidity (in particular, joint strength) of the cases2and3can be further improved. Since the first lateral walls8aand10acan be joined to the walls5aof the holder frame5by laser welding, with the first lateral walls8aand10aand second lateral walls8cand10cbeing pressed down with jigs15aand15b, the case fabrication properties can be improved. In addition, when the first lateral walls8aand10aand second lateral walls8cand10care pressed down with the jigs15aand15b, the first lateral walls8aand10acan conform to the walls5aof the holder frame5due to flexure of the vertical walls8band10b, which contributes to a further improvement in the case fabrication properties.

In this example embodiment, the cases2and3are made of a laser transmitting resin, while the holder frame5is made of a laser absorbing resin, and the joint portions8and10are joined to the walls5aof the holder frame5by laser welding. Therefore the cases2and3can be easily joined to the holder frame5and can have a good appearance even though a transparent or translucent material is employed for the cases2and3.

In this example embodiment, the cases2and3are formed substantially rectangular in plan view, while the connecting walls7and17are formed in a circular arc surface having an axis center in the longitudinal direction of the cases2and3, so that the cases2and3can have enhanced rigidity, and prevent deterioration of the flow properties of fluid flowing in the longitudinal direction inside the cases2and3.

In this example embodiment, the filter medium4is formed in a pleated shape, while the holder frame5is formed to include a pair of first walls5a, which hold pleated edges4aof the filter medium4and to which first lateral walls8aand10aof the cases2and3are joined, and a pair of second walls5bcontinuous with these first walls5aand holding non-pleated edges4bof the filter medium4. These first walls5aand second walls5bhave a larger height h2than the pleats height h1of the filter medium4. Therefore, the filter medium4can have a larger filter area and improved filtering efficiency.

The present invention is not limited to the above example embodiment and can be variously modified in accordance with the purposes and applications within the scope of the invention. Namely, while one form was described in the above example embodiment wherein the joint portions8and10of the cases2and3respectively include first lateral walls8aand10a, vertical walls8band10b, and second lateral walls8cand10c, the invention is not limited to this. For example, as shown inFIG. 6, as another design for the joint portion8′ of the case2(or case3), it may include a first lateral wall8a′ having an outer end joined to an upper end face of the first wall5aof the holder frame5by laser welding and extending substantially horizontally inward (toward the center) of the upper case2, and a vertical wall8b′ standing from an inner end of this first lateral wall8a′, the outer ends of the connecting wall7being connected to standing distal ends of the vertical walls8b′. Alternatively, for example as shown inFIG. 7, the joint portion8″ of the case2(or case3) may include a first lateral wall8a″ having an outer end joined to an upper end face of the first wall5aof the holder frame5by laser welding and extending substantially horizontally inward (toward the center) of the upper case2, the outer ends of the connecting wall7being connected to inner ends of the first lateral walls8a″.

In the above examples of embodiment, for example as shown inFIG. 8, the connecting wall7of the case2(or case3) may be formed with generally U-shaped corrugations21, or for example as shown inFIG. 9, the connecting wall7of the case2(or case3) may be formed with undulating ribs22, or the connecting wall7of the case2(or case3) may be formed with generally V-shaped corrugations. In the case with providing V-shaped corrugations, these corrugations should preferably be provided in a shape corresponding to the pleats of the filter medium4, so that the oil flow area between the filter medium4and the cases2and3will be substantially uniform.

While one form of the cases2and3was described in the above example embodiment wherein both cases have circular arc shaped connecting walls7and17, the invention is not limited to this. For example, one of the cases2and3may have a circular arc shaped connecting wall while the other case may have a flat connecting wall.

While the connecting walls7and17having one circular arc portion were shown in the above example embodiment, the invention is not limited to this. The connecting walls7,17may have a plurality of circular arc portions with different radii of curvature, for example, or may have a circular arc portion and a linear portion.

While the connecting walls7and17having a circular arc surface with an axis center in the longitudinal direction of the cases2and3were shown in the above example embodiment, the invention is not limited to this. The connecting walls may have a circular arc surface with an axis center in the direction of shorter sides of the cases2and3. Alternatively, the connecting walls may be in a dome shape protruding toward the center of the cases2and3.

While a tubular inlet port3awas illustrated in the above example embodiment, the invention is not limited to this, and the inlet port may be formed, for example, as a hole provided in the lower case3, for example. The inlet port3a, however, should preferably be tubular from a viewpoint of reducing air entrapment in the oil pan13.

While a pleated filter medium4was illustrated in the above example embodiment, the invention is not limited to this and the filter medium may be in the form of a sheet, corrugated, or bag-shaped. The material for the filter medium may be, for example, non-woven cloth, woven fabric, paper, and the like.

In the above example embodiment, laser welding was illustrated as one form of joining the cases2and3and the holder frame5. The invention is not limited to this and these parts may be joined together by any of vibration welding, ultrasonic welding, hot plate welding, or bonding with an adhesive or the like.

The invention is widely applicable as a technique for filtering fluid used in automatic transmissions such as a torque control type, CVT, and the like. More particularly, the invention can favorably be used as an automatic transmission fluid filter for automobiles, buses, trucks, as well as other vehicles including railroad vehicles such as locomotives and cars, construction vehicles, agricultural vehicles, industrial vehicles, and the like.

The present invention is not limited to the above-described embodiments, and various variations and modifications may be possible without departing from the scope of the present invention.