Oil Filter For Continuously Variable Transmission

Abstract

A filter configured to replace an original filter disposed in a cavity in a transmission, increases fluid flow rate through the filter. An example filter includes a bottom structure configured to mate with the bottom portion of the cavity, and the bottom structure defines an outlet through which oil passes from the cavity to the outlet of the housing. The filter also includes a filter media having a bottom portion and an opposite top portion, the bottom portion being coupled to the bottom structure of the filter. In the example filter system, the outer diameter of the bottom portion of the filter media is greater than the outer diameter of the top portion of the filter media.

Claims

1. A transmission oil filter system comprising: a transmission housing having an interior wall defining a substantially cylindrical cavity and a fluid outlet, said cavity having a top portion and a bottom portion, said cavity being adapted to receive an oil filter, said fluid outlet being disposed at said bottom portion of said cavity to provide a passage through which oil exits said cavity; a cover removably attached to said transmission housing over said top portion of said cavity, said cover defining a fluid inlet through which oil enters said top portion of said cavity; a filter removably disposed in said cavity, said filter comprising a bottom structure configured to mate with said bottom portion of said cavity, said bottom structure defining an outlet through which oil passes from said cavity to said outlet of said housing, and a filter media having a bottom portion and an opposite top portion, said bottom portion being coupled to said bottom structure of said filter, and wherein said bottom portion of said filter media has an outer diameter; said top portion of said filter has an outer diameter; and said outer diameter of said bottom portion of said filter media is greater than said outer diameter of said top portion of said filter media.

2. The transmission oil filter system of claim 1, wherein: said filter further includes a top structure coupled to said top portion of said filter media, and said filter further includes a rigid frame coupled between said bottom structure and said top structure, and said rigid frame is pervious to the passage of oil therethrough.

3. The transmission oil filter system of claim 2, wherein said filter media is tapered from said bottom portion of said filter media to said top portion of said filter media.

4. The transmission oil filter system of claim 3, wherein: said filter media is formed from a pliable material; said pliable material is folded into a corrugated configuration; and said pliable material is disposed in a conical configuration.

5. The transmission oil filter system of claim 2, wherein said bottom portion of said filter media is configured into a first cylinder having a first diameter; said top portion of said filter media is configured into a second cylinder having a second diameter; and said first diameter is greater than said second diameter.

6. The transmission oil filter system of claim 5, wherein said bottom portion of said filter media is formed from a first section of pliable material that is folded into a corrugated configuration, and said top portion of said filter media is formed from a second section of pliable material that is folded into corrugated configuration.

7. The transmission oil filter system of claim 6, wherein said filter further includes an annular plate having a top side, a bottom side, and an aperture passing through said top side of said annular plate and said bottom side of said annular plate, a top of said bottom portion of said filter media is bonded to said bottom side of said annular plate; and a bottom of said top portion of said filter media is bonded to said top side of said annular plate.

8. The transmission oil filter system of claim 1, wherein said filter media is a rigid, porous structure.

9. The transmission oil filter system of claim 1, wherein: said bottom structure of said filter includes a radial outer surface; said radial outer surface of said bottom structure defines a channel; said filter further includes a resilient gasket seated in said channel; said interior wall defining said bottom portion of said cylindrical cavity is adapted to urge against said resilient gasket to form a fluid barrier between said bottom structure of said filter and said interior wall of said housing defining said cylindrical cavity.

10. The transmission oil filter system of claim 1, wherein said housing is a continuously variable transmission housing.

11. A method for installing a transmission filter, said method comprising: providing a transmission having a transmission housing having an interior wall defining a substantially cylindrical cavity and a fluid outlet, said cavity having a top portion and a bottom portion, said cavity being configured to receive an oil filter, said fluid outlet being disposed at said bottom portion of said cavity to provide a passage through which oil exits said cavity, a cover removably attached to said transmission housing over said top portion of said cavity, said cover defining a fluid inlet through which oil enters said top portion of said cavity, a first filter removably disposed in said cavity, said filter having a bottom portion and a top portion; providing a second filter having a bottom portion and a top portion, said bottom portion of said second filter including a bottom structure adapted to mate with said bottom portion of said cavity, said top portion of said second filter having a diameter less than the diameter of said top portion of said first filter; removing said cover from said housing; removing said first filter from said cavity; installing said second filter in said cavity; and reattaching said cover to said transmission housing over said cavity.

12. The method of claim 11, wherein: said second filter includes a filter media having a top portion and a bottom portion; said top portion of said second filter includes a top structure attached to said top portion of said filter media; said second filter further includes a rigid frame coupled between said bottom structure and said top structure, and said rigid frame facilitates the passage of oil therethrough.

13. The method of claim 12, wherein said filter media is tapered to narrow from said bottom portion of said filter media to said top portion of said filter media.

14. The method of claim 13, wherein: said filter media is formed from a pliable material; said pliable material is folded into a corrugated configuration; and said pliable material is shaped in a conical configuration.

15. The method of claim 12, wherein said bottom portion of said filter media is configured into a first cylinder having a first diameter; said top portion of said filter media is configured into a second cylinder having a second diameter; and said first diameter is greater than said second diameter.

16. The method of claim 15, wherein said bottom portion of said filter media is formed from a first section of pliable material that is folded into a corrugated configuration, and said top portion of said filter media is formed from a second section of pliable material that is folded into corrugated configuration.

17. The method of claim 16, wherein said second filter further includes an annular plate having a top side, a bottom side, and an aperture passing through said top side of said annular plate and said bottom side of said annular plate; a top of said bottom portion of said filter media is bonded to said bottom side of said annular plate; and a bottom of said top portion of said filter media is bonded to said top side of said annular plate.

18. The method of claim 11, wherein said second filter includes a filter media, said filter media being a rigid, porous structure.

19. The method of claim 11, wherein: said bottom structure of said second filter includes a radial outer surface; said radial outer surface of said bottom structure defines a channel; said second filter further includes a resilient gasket seated in said channel; said interior wall defining said bottom portion of said cylindrical cavity is adapted to urge against said resilient gasket to form a fluid barrier between said bottom structure of said second filter and said interior wall of said housing defining said cylindrical cavity.

20. The method of claim 11, wherein said transmission is a continuously variable transmission.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention is described with reference to the following drawings, wherein like reference numbers denote substantially similar elements:

[0020] FIG. 1 shows a cross-sectional view of a prior art transmission filter disposed in a transmission cavity;

[0021] FIG. 2 shows a cross-sectional view of an improved transmission filter disposed in the transmission cavity of FIG. 1;

[0022] FIG. 3 shows a cross-sectional view of another improved transmission filter disposed in the transmission cavity of FIG. 1;

[0023] FIG. 4 shows a cross-sectional view of another improved transmission filter disposed in the transmission cavity of FIG. 1;

[0024] FIG. 5 shows a cross-sectional view of yet another improved transmission filter disposed in the transmission cavity of FIG. 1;

[0025] FIG. 6 shows a cross-sectional view of yet another improved transmission filter disposed in the transmission cavity of FIG. 1; and

[0026] FIG. 7 is a flowchart summarizing a method for installing a transmission filter.

DETAILED DESCRIPTION

[0027] The present invention overcomes the problems associated with the prior art, by providing a transmission filter system that alleviates premature filter failure. In the following description, numerous specific details are set forth (e.g., structural materials, filter media materials, etc.) in order to provide a thorough understanding of the invention. Those skilled in the art will recognize, however, that the invention may be practiced apart from these specific details. In other instances, details of well-known filter manufacturing practices (e.g., molding, assembly, bonding, etc.) and components have been omitted, so as not to unnecessarily obscure the present invention.

[0028] In view of the prior art CVT filter shortcomings, the inventor has developed a novel transmission filter having a substantially longer life without sacrificing filtration performance. Upon detailed analysis of prior art system 100 of FIG. 1, the inventor has found that there are various flow impeding characteristics of filter 106 that contribute to its poor performance. Such characteristics contribute to major pressure losses, minor pressure losses, and pressure losses due to the flow impedance of media 118. These irreversible losses accumulate along the fluid path around and through filter 106. That is,

[00001]$P_{\mathrm{loss}}=P_{\mathrm{minor}}+P_{\mathrm{major}}+P_{\mathrm{media}\mathrm{loss}}$

where, [0029] P.sub.loss is the total irreversible pressure loss, [0030] P.sub.minor are minor irreversible pressure losses and are calculated by

[00002]$\begin{array}{cc}{P}_{\mathrm{minor}}=K.Math.\frac{V^2}{2g}& \left(1\right)\end{array}$ [0031] and, [0032] P.sub.major are major irreversible pressure losses calculated by

[00003]$\begin{array}{cc}{P}_{\mathrm{major}}=\frac{\mathrm{fL}}{D}.Math.\frac{V^2}{2g}& \left(2\right)\end{array}$ [0033] and, [0034] P.sub.media loss are irreversible pressure losses that occur as the oil passes through media 118
where, [0035] P=fluid pressure g=acceleration of gravity [0036] K=loss coefficient f=friction factor of the fluid path walls [0037] =fluid density L=fluid path length [0038] V=fluid velocity D=distance between walls bounding fluid path

[0039] Consider the flow path from point-a in inlet 114 to point-h inside filter 106. First, as the oil from inlet 114 impacts the top of first end structure 122, it is redirected 90 degrees at point-b, thereby resulting in a first minor loss represented by

[00004]$P_{\mathrm{minor}\left(b\right)}=K_{90}.Math.\frac{V_b^2}{2g}$

where, [0040] K.sub.90 is the loss coefficient for a 90 degree turn in the fluid path.

[0041] Next, as oil from point-b moves to point-c, a first major pressure loss occurs and is represented by

[00005]$P_{\mathrm{major}\left(c\right)}=\frac{\mathrm{fL}}{D}.Math.\frac{V_c^2}{2g}=\frac{f_1.Math.d_2}{d_1}.Math.\frac{V_c^2}{2g}$

where [0042] f.sub.1 is the friction factor between the walls of cover 102 and first end structure 122.

[0043] Then, at point-d, the oil impacts the inside wall of cavity 110 and takes another 90 degree turn, thereby resulting in a second minor loss represented by

[00006]$P_{\mathrm{minor}\left(d\right)}=K_{90}.Math.\frac{V_d^2}{2g}$

[0044] Next, as oil from point-d moves to point-f, a second major pressure loss occurs and is represented by

[00007]$P_{\mathrm{minor}\left(e\right)}=\frac{\mathrm{fL}}{D}.Math.\frac{V_e^2}{2g}=\frac{f_2.Math.d_4}{d_3}.Math.\frac{V_e^2}{2g}$

where, [0045] f.sub.2 is the friction factor between the interior walls of cavity 110 and first end structure 122.

[0046] Then, at point-f, the oil takes another 90 degree turn before entering media 118, thereby resulting in a second minor loss represented by

[00008]$P_{\mathrm{minor}\left(f\right)}=K_{90}.Math.\frac{V_f^2}{2g}.$

[0047] From this it can be seen that the total irreversible pressure loss along the fluid path between point-a and point-h can be represented by

[00009]$P_{\mathrm{loss}}=.Math.P_{\mathrm{minor}}+.Math.P_{\mathrm{major}}$$P_{\mathrm{loss}}=P_{\mathrm{minor}\left(b\right)}+P_{\mathrm{minor}\left(d\right)}+P_{\mathrm{minor}\left(f\right)}+P_{\mathrm{major}\left(c\right)}+P_{\mathrm{major}\left(e\right)}$$P_{\mathrm{loss}}=K_{90}.Math.\frac{V_b^2}{2g}+K_{90}.Math.\frac{V_d^2}{2g}+K_{90}.Math.\frac{V_f^2}{2g}+\frac{f_1.Math.d_2}{d_1}.Math.\frac{V_c^2}{2g}+\frac{f_2.Math.d_4}{d_3}.Math.\frac{V_e^2}{2g}$

[0048] After rigorous testing of the prior art system 100, the inventor has found that such losses cause the hosting transmission to fail prematurely. In particular, the prior art design provides sufficient fluid flow for a new transmission, but not for a transmission that has been broken in.

[0049] To address the inadequate fluid flow, the inventor has developed a novel replacement CVT filter system 200, which is shown in a cross-sectional side view in FIG. 2. System 200 includes a filter 202 disposed in cavity 110 of housing 104 to filter transmission oil 112. Filter 202 includes a bottom structure 204, a gasket 206, a frame 208, a top structure 210, and a filter media 212.

[0050] Bottom structure 204 is an annular, rigid structure formed from plastic but may also be formed from any other suitable material such as, for example, metal. Bottom structure 204 defines an aperture 214, a channel 216, and a recess 218. Aperture 214 provides a passage through which filtered oil 112 exits filter 202. Channel 216 extends completely around the radial outer surface of structure 204 and provides a seat for gasket 206. Recess 218 is a cylindrical recess formed on the top surface of bottom structure 204 and is configured to seat the bottom end of filter media 212.

[0051] Gasket 206 is a resilient O-ring that is seated in channel 216 to provide a fluid barrier between the interior walls of cavity 110 and bottom structure 204.

[0052] Frame 208 is a rigid structure that is fixed to bottom structure 204 and top structure 210 to provide structural support therebetween. Furthermore, frame 208 provides structural support to filter media 212, which can lose some of its rigidity when it becomes saturated with oil. Frame 208 also includes a plurality of apertures 220, which provide passages through which filtered oil enters the interior of filter 202. In this example, frame 208 is substantially conical but may alternately be cylindrical or any other useful shape.

[0053] Top structure 210 is an annular, rigid structure formed from plastic but may also be formed from any other suitable material such as, for example, metal. Top structure 210 defines a cylindrical recess 222, which is formed on the bottom surface of structure 210 and configured to receive the top end of filter media 212. Bottom structure 204, frame 208, and top structure 210 may be integral parts of a single monolithic structure formed, for example, by injection molding plastic. Alternately, they may be individual parts bonded together by some suitable means (e.g., glue, thermal weld, etc.) to form a single rigid body.

[0054] Filter media 212 filters transmission oil passing therethrough. In this example, filter media 212 is formed from a section of thin, pliable material that is folded into a corrugated (e.g., fan-fold) configuration and disposed about frame 208 in a conical configuration (e.g., compressed more at the top than at the bottom). The bottom and top ends of filter media 212 are bonded to bottom structure 204 and top structure 210, respectively, by and adhesive 224, to prevent unfiltered oil from bypassing filter media 212.

[0055] As compared to prior art filter 106, filter 202 (in combination with cavity 110) presents a much lower resistance to oil flow therethrough, because irreversible major and minor pressure losses are substantially reduced. This can be seen by analyzing such losses along the flow path of oil 112 as it moves from inlet 114 to outlet 116. That is, such losses are represented by

[00010]$P_{\mathrm{loss}}=.Math.P_{\mathrm{minor}}+.Math.P_{\mathrm{major}}$

[0056] Consider the flow path from point-a in inlet 114 to point-h in filter 202. First, as the oil from inlet 114 impacts the top surface of structure 204, it is redirected 90 degrees at point-b, thereby resulting in a first minor loss P.sub.minor(b) represented by

[00011]$P_{\mathrm{minor}\left(b\right)}=K_{90}.Math.\frac{V_b^2}{2g}$

[0057] Such loss is approximately the same for both filters 106 and 202 at point-b because both have approximately the same loss coefficient K.sub.90, fluid density , fluid velocity V.sub.b, and gravity g.

[0058] Next, as oil from point-b moves to point-c in filter 202, a first major pressure loss occurs and is represented by

[00012]$P_{\mathrm{major}\left(c\right)}=\frac{\mathrm{fL}}{D}.Math.\frac{V_c^2}{2g}=\frac{f_1.Math.d_2}{d_1}.Math.\frac{V_c^2}{2g}$

[0059] Because d.sub.1 for filter 202 is greater than d.sub.1 (headspace) for filter 106, d.sub.2 for filter 202 is less than d.sub.2 for filter 106, and V.sub.c for filter 202 is less than V.sub.c for filter 106, the overall P.sub.major(c) for filter 202 is less than the P.sub.major(c) for filter 106. Of course, friction factor f.sub.1 and gravity g are the same values in both filters 202 and 106.

[0060] Then, at point-d, the oil impacts the inside wall of cavity 110 and takes another 90 degree turn in filter 202, thereby resulting in a second minor loss represented by

[00013]$P_{\mathrm{minor}\left(d\right)}=K_{90}.Math.\frac{V_d^2}{2g}$

[0061] Although loss coefficient K.sub.90, fluid density , and gravity g are the same values for both filters 202 and 106, V.sub.d for filter 202 is less than V.sub.d for filter 106. This is because the flow path height d.sub.1 for filter 202 is greater than the flow path height d.sub.1 for filter 106. As a result, P.sub.minor(d) for filter 202 is less than P.sub.minor(d) for filter 106.

[0062] Next, as oil from point-d moves to point-f in filter 202, a second major pressure loss occurs and is represented by

[00014]$P_{\mathrm{major}\left(e\right)}=\frac{\mathrm{fL}}{D}.Math.\frac{V_e^2}{2g}=\frac{f_2.Math.d_4}{d_3}.Math.\frac{V_e^2}{2g}$

[0063] Because d.sub.3 for filter 202 is greater than d.sub.3 for filter 106, d.sub.4 for filter 202 is less than d.sub.4 for filter 106, and V.sub.e for filter 202 is less than V.sub.e for filter 106, the overall P.sub.major(e) for filter 202 is less than the P.sub.major(e) for filter 106. Of course, friction factor f.sub.2 and gravity g are the same values in both filters 202 and 106.

[0064] Finally, at point-f in filter 202, the oil takes an approximate 45 degree turn before entering media 212, thereby resulting in a second minor loss represented by

[00015]$P_{\mathrm{minor}\left(f\right)}=K_{60}.Math.\frac{V_f^2}{2g}$

[0065] Because filter media 212 is pitched at an angle (e.g. 60 degrees), the oil requires less redirection and suffers less of an irreversible pressure loss. That is, K.sub.60 for filter 202 is less than K.sub.90 for filter 106.

[0066] In summary, it is shown that P.sub.major(c), P.sub.minor(d), P.sub.major(e), and P.sub.minor(f) are all less in filter 202, as compared to prior art filter 106. As a result, the overall irreversible pressure losses caused by filter 202 are much less than those caused by filter 106. Through experimentation, the inventor has found that by replacing prior art filter 106 with filter 202, the hosting transmission no longer exhibited the symptoms of bucking and jerking.

[0067] Another way of thinking about the improvement provided by filter 202, as compared to prior art filter 106, is that the cross sectional area of the fluid flow path is expanded at different points by the geometry of filter 202, and, for a constant supply pressure, a bigger pipe delivers more fluid. Above top structure 210, the cross sectional area of the fluid path is essentially the side surface area of a right circular cylinder of height d.sub.1 (i.e., 2rd.sub.1). Because d1 for filter 202 is much larger than d1 for the prior art filter 106, the cross sectional area of the fluid flow path (for any given radius (r)) is much larger for filter 202. Similarly, adjacent top structure 210 (e.g., at point-e), the cross sectional area of the fluid flow path is an annulus. Without doing the math, it should be readily apparent that the annular area surrounding top structure 210 (FIG. 2) is significantly greater than the annular area surrounding first structure 122 of filter 106.

[0068] FIG. 3 shows a cross-sectional view of a transmission oil filter system 300, according to another embodiment of the invention. System 300 includes a filter 302 disposed in cavity 110 of housing 104 to filter transmission oil 112. Filter 302 includes a bottom structure 304, a gasket 306, a frame 308, a top structure 310, a first media portion 312, an intermediate plate 314, and a second media portion 316.

[0069] Structure 304 is an annular, rigid structure formed from plastic but may also be formed from any other suitable material such as, for example, metal. Structure 304 defines an aperture 318, a channel 320, and a recess 322. Aperture 318 provides a passage through which filtered oil 112 exits filter 302. Channel 320 extends completely around the radial outer surface of structure 304 to seat gasket 306. Recess 322 is a cylindrical recess formed on the top surface of structure 304 to seat the bottom end of first media portion 312. As indicated by the thick black line, the bottom end of first media portion 312 is adhered to the top surface of structure 304.

[0070] Gasket 306 is a resilient O-ring that is seated in channel 320 to provide a fluid barrier between the interior walls of cavity 110 and structure 304.

[0071] Frame 308 is a rigid structure that is fixed to structures 304 and 310 to provide structural support therebetween. Furthermore, frame 308 provides structural support to first media portion 312 and second media portion 316. Frame 308 also includes a plurality of apertures 324, which provide passages through which filtered oil enters the interior of filter 302. In this example, frame 308 is substantially cylindrical.

[0072] Top structure 310 is an annular, rigid structure formed from plastic but may also be formed from any other suitable material such as, for example, metal. Top structure 310 defines a cylindrical recess 326 formed on the bottom surface of top structure 310, which is configured to receive the top end of first media portion 312. Structure 304, frame 308, and structure 310 may be integral parts of a single monolithic structure formed, for example, by injection molding plastic. Alternately, they may be individual parts bonded together by some suitable means (e.g., glue, thermal weld, etc.) to form a single rigid body.

[0073] First media portion 312 filters transmission oil passing therethrough. In this example, first media portion 312 is formed from a section of thin, pliable material that is folded into a corrugated configuration and disposed about frame 308 in a cylindrical configuration. The bottom and top ends of first media portion 312 are bonded to structure 304 and plate 314, respectively, by an adhesive 328 to prevent unfiltered oil from bypassing first media portion 312.

[0074] Intermediate plate 314 is an annular disk-shaped structure bonded between first media portion 312 and second media portion 316 to prevent oil from bypassing therebetween.

[0075] Second media portion 316 filters transmission oil passing therethrough. In this example, second media portion 316 is formed from a second section of thin, pliable material that is folded into a corrugated configuration and disposed about frame 308 in a cylindrical configuration. The top and bottom ends of second media portion 316 are bonded to structure 310 and plate 314, respectively, by adhesive 328 to prevent unfiltered oil from bypassing second media portion 316.

[0076] As shown, the outer diameter of second media portion 316 is substantially less than the outer diameter of first media portion 312. As compared to prior art filter 106, filter 302 has a much lower resistance to oil flow therethrough because irreversible major and minor pressure losses are substantially reduced. This can be seen by analyzing such losses along the flow path of oil 112 as it moves from inlet 114 to outlet 116. That is, such losses are represented by

[00016]$P_{\mathrm{loss}}=.Math.P_{\mathrm{minor}}+.Math.P_{\mathrm{major}}$

[0077] Consider the flow path from point-a in inlet 114 to point-h in filter 302. First, as the oil from inlet 114 impacts the top surface of structure 310, it is redirected 90 degrees at point-b, thereby resulting in a first minor loss P.sub.minor(b) represented by

[00017]$P_{\mathrm{minor}\left(b\right)}=K_{90}.Math.\frac{V_b^2}{2g}$

[0078] Such loss is approximately the same for both filters 106 and 302 at point-b because both have approximately the same loss coefficient K.sub.90, fluid density , fluid velocity V.sub.b, and gravity g.

[0079] Next, as oil from point-b moves to point-c in filter 302, a first major pressure loss occurs and is represented by

[00018]$P_{\mathrm{major}\left(c\right)}=\frac{\mathrm{fL}}{D}.Math.\frac{V_c^2}{2g}=\frac{f_1.Math.d_2}{d_1}.Math.\frac{V_c^2}{2g}$

[0080] Because d.sub.1 for filter 302 is greater than d.sub.1 for filter 106, d.sub.2 for filter 302 is less than d.sub.2 for filter 106, and V.sub.c for filter 302 is less than V.sub.c for filter 106, the overall P.sub.major(c) for filter 302 is less than the P.sub.major(c) for filter 106. Of course, friction factor f.sub.1 and gravity g are the same values in both filters 302 and 106.

[0081] Then, at point-d, the oil impacts the inside wall of cavity 110 and takes another 90 degree downward turn in filter 302, thereby resulting in a second minor loss represented by

[00019]$P_{\mathrm{minor}\left(d\right)}=K_{90}.Math.\frac{V_d^2}{2g}$

[0082] Although loss coefficient K.sub.90, fluid density , and gravity g are the same values for both filters 302 and 106, V.sub.d for filter 302 is less than V.sub.d for filter 106. This is because the flow path height d.sub.1 for filter 302 is greater than the flow path height d.sub.1 for filter 106. As a result, P.sub.minor(d) for filter 302 is less than P.sub.minor(d) for filter 106.

[0083] Next, as oil from point-d moves to point-f in filter 302, a second major pressure loss occurs and is represented by

[00020]$P_{\mathrm{major}\left(e\right)}=\frac{\mathrm{fL}}{D}.Math.\frac{V_e^2}{2g}=\frac{f_2.Math.d_4}{d_3}.Math.\frac{V_e^2}{2g}$

[0084] Because d.sub.3 for filter 302 is greater than d.sub.3 for filter 106, d.sub.4 for filter 302 is less than d.sub.4 for filter 106, and V.sub.e for filter 302 is less than V.sub.e for filter 106, the overall P.sub.major(e) for filter 302 is less than the P.sub.major(e) for filter 106. Of course, friction factor f.sub.2 and gravity g are the same values in both filters 302 and 106.

[0085] Finally, at point-f in filter 302, the oil takes an approximate 90 degree turn before entering media portion 316, thereby resulting in a second minor loss which is approximately the same loss encountered with filter 106.

[0086] In summary, it is shown that P.sub.major(c), P.sub.minor(d), and P.sub.major(e), are all less in filter 302 as compared to prior art filter 106. As a result, the overall irreversible pressure losses in filter 302 are much less than that of filter 106. Through experimentation, the inventor has found that by replacing prior art filter 106 with filter 302, the hosting transmission no longer exhibited the symptoms of bucking and jerking.

[0087] FIG. 4 shows a cross-sectional view of a system 400 according to an alternate embodiment of the invention. System 400 includes a filter 402 disposed in cavity 110 of housing 104 to filter transmission oil 112. Filter 402 includes a bottom structure 404, a gasket 406, a frame 408, a top structure 410, and a filter media 412.

[0088] Structure 404 is an annular, rigid structure formed from plastic but may also be formed from any other suitable material such as, for example, metal. Structure 404 defines an aperture 414, a channel 416, and a recess 418. Aperture 414 provides a passage through which filtered oil 112 exits filter 402. Channel 416 extends completely around the radial outer surface of structure 404 to seat gasket 406. Recess 418 is a cylindrical recess formed on the top surface of structure 404 to seat the bottom end of filter media 412.

[0089] Gasket 406 is a resilient O-ring that is seated in channel 416 to provide a fluid barrier between the interior walls of cavity 110 and structure 404.

[0090] Frame 408 is a rigid structure that is fixed to structures 404 and 410 to provide structural support therebetween. Furthermore, frame 408 provides structural support to filter media 412. Frame 408 also includes a plurality of apertures 420, which provide passages through which filtered oil enters the interior of filter 402. In this example, frame 408 is substantially cylindrical.

[0091] Structure 410 is an annular, rigid structure formed from plastic but may also be formed from any other suitable material such as, for example, metal. Structure 410 defines a cylindrical recess 422 formed on the bottom surface of structure 410 to receive the top end of filter media 412. Structure 404, frame 408, and structure 410 may be integral parts of a single monolithic structure formed, for example, by injection molding plastic. Alternately, they may be individual parts bonded together by some suitable means (e.g., glue, thermal weld, etc.) to form a single rigid body.

[0092] Filter media 412 filters transmission oil passing therethrough. In this example, filter media 412 is formed from a section of thin, pliable material that is folded into a corrugated configuration and disposed about frame 408 in a cylindrical configuration. The bottom and top ends of filter media 412 are bonded to structures 404 and 410, respectively, by and adhesive 424 to prevent unfiltered oil from bypassing filter media 412.

[0093] As shown, d.sub.1 and d.sub.3 with filter 402 are substantially larger than d.sub.1 and d.sub.3, respectively, with filter 106. As a result, the flow path between the interior walls of cavity 110 and the exterior surface of filter 106 are substantially less restricting to oil flow.

[0094] FIG. 5 shows a cross-sectional view of a system 500 according to an alternate embodiment of the invention. System 500 includes a filter 502 disposed in cavity 110 of housing 104 to filter transmission oil 112. Filter 502 includes a bottom structure 504, a gasket 506, a frame 508, a top structure 510, a first media portion 512, and a second media portion 514.

[0095] Structure 504 is an annular, rigid structure formed from plastic but may also be formed from any other suitable material such as, for example, metal. Structure 504 defines an aperture 516, a channel 518, and a recess 520. Aperture 516 provides a passage through which filtered oil 112 exits filter 502. Channel 518 extends completely around the radial outer surface of structure 504 to seat gasket 506. Recess 520 is a cylindrical recess formed on the top surface of structure 504 to seat the bottom end of first media portion 512.

[0096] Gasket 506 is a resilient O-ring that is seated in channel 518 to provide a fluid barrier between the interior walls of cavity 110 and bottom structure 504.

[0097] Frame 508 is a rigid structure that is fixed to structures 504 and 510 to provide structural support therebetween. Furthermore, frame 508 provides structural support to second media portion 514. Frame 508 also includes a plurality of apertures 522, which provide passages through which filtered oil enters the interior of filter 502. In this example, frame 508 is substantially cylindrical.

[0098] Top structure 510 is an annular, rigid structure formed from plastic but may also be formed from any other suitable material such as, for example, metal. The bottom surface of top structure 510 defines a cylindrical recess 524 that receives the top end of second media portion 514. The top surface of top structure 510 defines a smaller cylindrical recess 526 that seats media portion 512. Top structure 510 further includes a set of apertures 528 through which oil filtered by media portion 512 enters into filter 502. In this example embodiment, more than two apertures 528 are arranged in a circular array, but only two of apertures 528 are visible in the cross-sectional view of FIG. 5. Apertures 528 reduce the overall resistance to oil flow through filter 502 by providing additional flow paths, thereby increasing the total cross-sectional area of the flow path through filter 502. Top structure 510, frame 508, and structure 504 may be integral parts of a single monolithic structure formed, for example, by injection molding plastic. Alternately, they may be individual parts bonded together by some suitable means (e.g., glue, thermal weld, etc.) to form a single rigid body.

[0099] Media portion 512 is formed from a section of thin, pliable material that is cut into a cylindrical disk shape. Media portion 512 is also seated and bonded into recess 526 to filter oil passing through apertures 528.

[0100] Media portion 514 filters transmission oil passing therethrough. In this example, media portion 512 is formed from a section of thin, pliable material that is folded into a corrugated configuration and disposed about frame 508 in a cylindrical configuration. The bottom and top ends of media portion 514 are bonded to structures 504 and 510, respectively, by and adhesive 530 to prevent unfiltered oil from bypassing media portion 514.

[0101] FIG. 6 shows a cross-sectional view of yet another alternate example system 600. System 600 includes a filter 602 disposed in cavity 110 of housing 104 to filter transmission oil 112 (represented by dark arrows). Filter 602 includes a bottom structure 604, a gasket 606, and a filter media 608.

[0102] Bottom structure 604 is an annular, rigid structure formed from plastic but may also be formed from any other suitable material such as, for example, metal. Bottom structure 604 defines an aperture 610, a channel 612, and a recess 614. Aperture 610 provides a passage through which filtered oil 112 exits filter 602. Channel 612 extends completely around the radial outer surface of bottom structure 604 to seat gasket 606. Recess 614 is a cylindrical recess formed on the top surface of bottom structure 604 to seat the bottom end of filter media 608.

[0103] Gasket 606 is a resilient O-ring that is seated in channel 612 to provide a fluid barrier between the interior walls of cavity 110 and structure 604.

[0104] Filter media 608 is a porous, rigid, monolithic member. The porosity of media 608 is such that media 608 is pervious to oil flow yet also collects small contaminants from oil passing therethrough. The bottom surface of media 608 is bonded to structure 604 via an adhesive 616.

[0105] FIG. 7 is a flowchart summarizing a method 700 of installing a transmission filter. In a first step 702, a transmission having a cylindrical cavity, a first oil filter disposed in the cavity, and a cover mounted to the transmission, over the cylindrical cavity, are provided. The first oil filter includes a bottom portion and an opposite top portion. The bottom portion of the first oil filter is configured to mate with the transmission. Then, in a second step 704, a second oil filter having a bottom portion configured to mate with the transmission and an opposite top portion that has a smaller diameter and/or height than the top portion of the first oil filter is provided. Next, in a third step 706, the cover is removed from the transmission. Then, in a fourth step 708, the first oil filter is removed from the cavity. Next, in a fifth step 710, the second oil filter is placed in the cavity. Finally, in a sixth step 712, the cover is mounted to the transmission, over the cavity.

[0106] The description of particular embodiments of the present invention is now complete. Many of the described features may be substituted, altered or omitted without departing from the scope of the invention. For example, alternate transmission types, may be substituted for the CVT. As another example, the described filter cavity may be non-cylindrical, so long as the replacement filter is sufficiently different from the original filter to increase oil flow therethrough. These and other deviations from the particular embodiments shown will be apparent to those skilled in the art, particularly in view of the foregoing disclosure.