Oil pump anti-wear plate for transfer case and method of use

A replacement oil pump plate for attachment to an original equipment manufacture oil pump within a transfer case for elimination of mechanical wear by replacing the abrasive aluminum tabs formed on the oil pump with low-friction plastic tabs is disclosed. The present plastic tab design redistributes the surface-to-surface contact between the magnesium transfer case and the aluminum pump tabs away from the original wear points so that any necessary weld repairs to the transfer case will not be disturbed. The present replacement pump plate is provided in a kit format including a pump plate, machine screws, plastic tabs, and installation instructions. The present invention also describes a method of installing the pump plate kit on the original equipment manufacture oil pump subassembly.

BACKGROUND OF INVENTION

The present invention relates to automotive four-wheel drive systems and, more particularly, to an oil pump anti-wear plate for the repair of transfer cases utilized in four-wheel drive vehicles of various manufacturers.

Presently there are many types of four-wheel drive systems. For purposes of this application the term “four-wheel-drive system” will be understood to define an automotive drive system for providing power to all four wheels on a part-time basis (i.e. four-wheel-drive can be switched ON and OFF manually).

The transfer case assembly or so-called transfer case100(FIG. 1) in such a part-time, four-wheel-drive system functions to lock the front-axle driveshaft to the rear-axle driveshaft so that all four wheels are forced to turn at the same speed. In the four-wheel-drive operating mode the vehicle is provided with substantially increased torque at the wheels to handle steep terrain and low-traction situations.

Currently many original equipment manufacturers utilize NEW VENTURE GEAR series136,236,246,261or263transfer cases (hereinafter “the subject transfer cases”) in their four-wheel drive vehicles. Such transfer cases are commercially available from New Venture Gear Manufacturing GmbH, Roitzsch, Germany. In the subject transfer cases100an oil pump120is typically installed within a magnesium housing125(FIG. 2) that is utilized for weight reduction. The transfer case100is attached to the aft end of the transmission. The output shaft of the transmission (not shown) engages a mating internal spline130within the oil pump120, which generates hydraulic pressure to a clutch pack in the transfer case100to initiate four-wheel-drive operation.

In the construction of the subject transfer cases, internal pockets140are formed on the interior surface of the magnesium housing125(FIG. 2), which are designed to receive integral anti-rotation lugs155formed on the aluminum oil pump120to secure it in position. Because a small amount of movement of the oil pump120is necessary to keep the pump centered on the transmission output shaft, a concentrated area of surface-to-surface contact occurs as at145and results in mechanical fretting between the lugs155and the magnesium housing125eventually causing the lugs to wear through the softer magnesium housing and resulting in oil leakage from the transfer case100.

Thus, the present oil pump anti-wear plate and method of use has been developed to resolve this problem and other shortcomings of the prior art.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides an oil pump anti-wear plate that is attached to the original equipment manufacture (hereinafter “OEM”) oil pump cover within the transfer case of a four-wheel-drive vehicle. The present anti-wear plate eliminates damage to the magnesium housing of the transfer case caused by mechanical fretting of the aluminum lugs formed on the oil pump against the softer magnesium housing.

Advantageously, the present anti-wear plate redistributes the surface-to-surface contact between the magnesium housing and the pump lugs away from the original wear points by the installation of low-friction plastic inserts on the present anti-wear plate so that any mechanical fretting is eliminated. Further, the plastic inserts ensure that any necessary weld repairs to the transfer case for preventing leakage will not be disturbed.

The present oil pump anti-wear plate is provided in a kit format including an anti-wear plate, machine screws, low-friction plastic inserts, and installation instructions. The present invention also provides a method of installing the anti-wear plate on the OEM oil pump to salvage the expensive magnesium housing.

Other features and technical advantages of the present invention will become apparent from a study of the following description and the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Prior to describing the present invention in detail, it may be beneficial to briefly review the structure and function of a prior art transfer case assembly, indicated generally at100and illustrated inFIG. 1. The transfer case assembly or transfer case100in a part-time, four-wheel-drive system functions to lock the front-axle driveshaft to the rear-axle driveshaft so that all four wheels are forced to turn at the same speed. The subject transfer case assemblies100, which are utilized in part-time, four-wheel-drive systems, comprise a magnesium housing125containing a rear-axle output shaft126and a front-axle output shaft127, a planetary gear set105, a clutch pack110, a drive chain115, an oil pump120to actuate the clutch pack, and an electric motor135to shift the vehicle into four-wheel-drive operation. When shifted into four-wheel-drive, the vehicle is provided with substantially increased torque at the wheels to handle steep terrain and low-traction situations.

In the construction of the subject transfer cases, a generally cylindrical recess150with radially extending pockets140is formed on the interior surface of the magnesium housing125(FIG. 2), which conforms to the contour of cover122of the oil pump120to secure it in position. Cover122includes a plurality of radially projecting, anti-rotation lugs155integrally formed thereon, which are received in the mating pockets140. A plurality of threaded holes124is formed within cover122to attach the cover to the body of the oil pump120.

Because a small amount of eccentric movement of the oil pump120is necessary to keep the pump centered on the transmission output shaft, concentrated areas of surface-to-surface contact occur as at145resulting in mechanical fretting between the lugs155and the magnesium housing125. Such fretting action eventually causes the cast aluminum lugs155to wear through the softer magnesium housing125, which results in oil leakage and eventual malfunction of the transfer case100.

The present invention provides an oil pump anti-wear plate for the subject transfer cases to resolve this problem and will now be described. With further reference to the drawings, there is shown therein an oil pump anti-wear plate in accordance with the present invention, indicated generally at10and illustrated inFIGS. 3 and 4. Anti-wear plate10is a generally ring-shaped structure having a radial gap14that is fabricated from aluminum or other suitable material. Anti-wear plate10includes a plurality of integral mounting tabs15which are configured to receive low-friction inserts20(FIG. 7) thereon.

Referring toFIG. 5mounting tabs15are located at the same angular orientation and substantially the same radial dimension “R” as lugs155on the OEM cover122. In addition, tabs15are offset from the center plane of plate member12by a dimension “X” which is approximately equivalent to the thickness of the OEM cover122. Anti-wear plate10also includes an array of mounting holes24which are located in predetermined positions in coaxial alignment with threaded holes124in the pump cover122after installation.

With reference toFIGS. 6A-6Cthere is shown a low-friction insert in accordance with the present invention, indicated generally at20. Inserts20are fabricated from a high operating temperature, ultra high molecular weight (UHMW) polyethylene plastic such as TIVAR, or other plastic material having physical and chemical properties suitable for this purpose. It can be seen that inserts20are generally C-shaped in configuration and are designed to be installed on tabs15, which are integrally formed on pump plate10as most clearly shown inFIG. 7. More particularly, a pair of opposed protuberances20a,20bformed on insert20are configured to engage mating detents15a,15bformed in tabs15. Undercut relief zones20c,20dimpart resiliency to inserts20to enable the inserts to be manually snapped in place and retained in position on tabs15. In one embodiment of the present invention, a pair of such inserts20is installed on each tab15in side-by-side relation (FIG. 9).

Thus, it will be appreciated by those skilled in the art that the mounting tabs15with inserts20installed thereon are designed to provide the function of the OEM aluminum lugs155with the advantage of a low coefficient of friction and, thus, no abrasive effect on the magnesium housing125. In addition, inserts20redistribute the surface-to-surface contact with the magnesium housing125away from the original wear points so that any mechanical fretting is eliminated. Further, any necessary weld repairs to the magnesium housing125for preventing leakage will not be disturbed.

In a method of using the present invention, the oil pump120is initially removed from the transfer case100. Next, the oil pump120is disassembled by removing the OEM machine screws (not shown) from the pump cover122and the machine screws are discarded. Thereafter, the threaded machine screw holes124are drilled through using an 11/64 inch or slightly larger drill bit to remove the threads forming a plurality of modified mounting holes124′ (FIG. 8) in cover122′. Next, using a hacksaw or other suitable tool cut off the OEM lugs155and then grind or file the remnants of the lugs until blended with the peripheral contour of the cover122′ of the modified pump120′ as shown inFIG. 8.

Next, the modified pump120′ is reassembled (i.e. without machine screws initially) and the pump plate10including inserts20installed thereon is positioned on the modified cover122′ such that mounting holes24are aligned with the modified mounting holes124′ in the cover and gap14is radially oriented with pump outlet16as shown inFIG. 9. Thereafter, new machine screws17of a predetermined size are installed from the bottom side of the pump120′ extending through cover122′ and anti-wear plate10. Finally, a washer18and mating nut19provided in the present kit are attached to the new machine screws17to complete the installation.

Although not specifically illustrated in the drawings, it should be understood that additional equipment and structural components will be provided as necessary and that all of the components described above are arranged and supported in an appropriate fashion to form a complete and operative Oil Pump Anti-Wear Plate for Transfer Case and Method of Use incorporating features of the present invention.

Moreover, although illustrative embodiments of the invention have been described, a latitude of modification, change, and substitution is intended in the foregoing disclosure, and in certain instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of invention.