Scavenge gear assembly for an oil pump of a vehicle

A gear assembly of a scavenge oil pump for a vehicle is provided. The assembly comprises a first pair of meshing gears comprising a first drive gear disposed about a drive shaft and a first slave gear disposed about a slave drive in parallel relationship with the drive shaft. The first drive gear and first slave gear are in rotational meshing cooperation. The assembly comprises a second pair of meshing gears comprising a second drive gear disposed about the drive shaft and a second slave gear disposed about the slave drive. The second drive gear and second slave gear are in rotational meshing cooperation. The second pair of meshing gears is disposed linearly adjacent to the first pair of meshing gears. The first pair and the second pair of meshing gears have about ⅜ of a tooth spacing relative to each other for torque transmission of scavenge oil.

INTRODUCTION

The present disclosure relates to gear assemblies for an oil pump and, more particularly, a scavenge gear assembly for a scavenge oil pump of a vehicle.

Pumps having meshing gears experience continual pressure pulses, horsepower loss, torque oscillation to the gear drive shaft, noise, vibration, and harshness. Pumps also experience increased scavenge backpressure which affects oil aeration. While current pumps achieve their intended purposes, there is a need for improvement to reduce pressure pulses, horsepower loss, torque oscillation to the gear drive shaft, noise, vibration, and harshness along with decreasing scavenge backpressure.

SUMMARY

According to several aspects, a scavenge gear assembly of a scavenge oil pump for a vehicle is provided. In one aspect, the scavenge gear assembly comprises a drive shaft and a slave drive or slave drive shaft in parallel relationship. The assembly further comprises a first pair of meshing gears comprising a first drive gear and a first slave gear identical to the first drive gear. The first drive gear is rotationally disposed about the drive shaft and the first slave gear is rotationally disposed about the slave drive shaft. The first drive gear and first slave gear are in rotational meshing cooperation for torque transmission. Each of the first drive gear and the first slave gear has teeth equally disposed thereabout.

In this aspect, the assembly comprises a second pair of meshing gears comprising a second drive gear and a second slave gear identical to the second drive gear. The second drive gear is rotationally disposed about the drive shaft and the second slave gear is rotationally disposed about the slave drive shaft. The second drive gear and second slave gear are in rotational meshing cooperation for torque transmission. The second pair of meshing gears is disposed linearly adjacent to the first pair of meshing gears. Each of the second drive gear and the second slave gear has teeth equally disposed thereabout.

The assembly further comprises a dividing plate disposed between the first and second pair of meshing gears. In this aspect, the first pair of meshing gears and the second pair of meshing gears have about ⅜ of a tooth spacing relative to each other for torque transmission of scavenge oil. In one embodiment, each of the first drive gear, the first slave gear, the second drive gear and the second slave gear has seven teeth disposed thereabout.

In one embodiment, the drive shaft comprises a first keyway formed thereon and a second keyway formed longitudinally adjacent the first keyway. the first drive gear is disposed on the first keyway and the second drive gear disposed on the second keyway such that the first and second drive gears are disposed longitudinally adjacent to each other. The first keyway of the drive shaft is angularly aligned with the apex of one tooth of the first drive gear and the second keyway of the drive shaft is angularly aligned with the apex of one tooth of the second drive gear.

In this embodiment, the first keyway and the second keyway of the drive shaft are longitudinally adjacent and angularly spaced about 19.29 degrees from each other to provide about ⅜ of a tooth spacing.

In another embodiment, each of the first drive gear, the first slave gear, the second drive gear and the second slave gear is a spur gear. In yet another embodiment, the assembly further comprises a first end plate disposed on the first pair of meshing gears and an opposing second end plate disposed on the second pair of meshing gears.

In another aspect, a scavenge gear assembly of a scavenge oil pump for a vehicle is provided. In this aspect, the gear assembly comprises a drive shaft and a slave drive shaft in parallel relationship. The assembly further comprises a first pair of meshing gears comprising a first drive gear and a first slave gear identical to the first drive gear. The first drive gear is rotationally disposed about the drive shaft and the first slave gear is rotationally disposed about the slave drive shaft. The first drive gear and first slave gear are in rotational meshing cooperation for torque transmission. Each of the first drive gear and the first slave gear has teeth equally disposed thereabout.

The assembly further comprises a second pair of meshing gears comprising a second drive gear and a second slave gear identical to the second drive gear. The second drive gear is rotationally disposed about the drive shaft and the second slave gear is rotationally disposed about the slave drive shaft. The second drive gear and second slave gear are in rotational meshing cooperation for torque transmission. The second pair of meshing gears is disposed linearly adjacent to the first pair of meshing gears. Each of the second drive gear and the second slave gear has teeth equally disposed thereabout.

In this embodiment, the assembly further comprises a dividing plate disposed between the first and second pair of meshing gears. The first pair of meshing gears and the second pair of meshing gears have a tooth spacing determined by an average of a sum of a first optimum for reducing pumping pulse and a second optimum for reducing meshing pulse. In this embodiment, the first optimum is represented by ½N and the second optimum is represented by ¼N, where N is the number of teeth per gear or pulsations per gear revolution.

In one embodiment, each of the first drive gear, the first slave gear, the second drive gear and the second slave gear has seven teeth disposed thereabout.

In another embodiment, the drive shaft comprises a first keyway formed thereon and a second keyway formed longitudinally adjacent the first keyway. The first drive gear is disposed on the first keyway and the second drive gear is disposed on the second keyway such that the first and second drive gears are disposed longitudinally adjacent to each other. Moreover, the first keyway of the drive shaft is angularly aligned with the apex of one tooth of the first drive gear and the second keyway of the drive shaft is radially aligned with the apex of one tooth of the second drive gear.

Furthermore, the first keyway and the second keyway of the drive shaft are angularly spaced about 19.29 degrees from each other to provide the tooth spacing of the average of the sum of the first optimum and the second optimum.

In another embodiment, each of the first drive gear, the first slave gear, the second drive gear and the second slave gear is a spur gear.

In yet another embodiment, the assembly further comprises a first end plate disposed on the first pair of meshing gears and an opposing second end plate disposed on the second pair of meshing gears.

In another aspect, a vehicle having a scavenge gear assembly for a scavenge oil pump is provided. In this aspect, the vehicle comprises a chassis and a body supported by the chassis. The body includes a motor compartment and an occupant zone. The motor compartment includes the scavenge gear assembly for the scavenge oil pump of the vehicle.

In this embodiment, the assembly comprises a drive shaft and a slave drive shaft in parallel relationship. The assembly further comprises a first pair of meshing gears comprising a first drive gear and a first slave gear identical to the first drive gear. The first drive gear is rotationally disposed about the drive shaft and the first slave gear is rotationally disposed about the slave drive shaft. The first drive gear and first slave gear are in rotational meshing cooperation for torque transmission. Each of the first drive gear and the first slave gear has teeth equally disposed thereabout.

In this embodiment, the assembly further comprises a second pair of meshing gears comprising a second drive gear and a second slave gear identical to the second drive gear. The second drive gear is rotationally disposed about the drive shaft and the second slave gear is rotationally disposed about the slave drive shaft. The second drive gear and second slave gear are in rotational meshing cooperation for torque transmission. The second pair of meshing gears is disposed linearly adjacent to the first pair of meshing gears. Each of the second drive gear and the second slave gear has teeth equally disposed thereabout. The assembly further comprises a dividing plate disposed between the first and second pair of meshing gears.

In another embodiment, the assembly further comprises first and second end plates. The first end plate is disposed on one end of a pump manifold or train and the other end plate is disposed on another end of the pump manifold.

In one embodiment, the first pair of meshing gears and the second pair of meshing gears have about ⅜ of a tooth spacing relative to each other for torque transmission of scavenge oil.

In one embodiment, the drive shaft comprises a first keyway formed thereon and a second keyway formed longitudinally adjacent the first keyway. The first drive gear is disposed on the first keyway and the second drive gear is disposed on the second keyway such that the first and second drive gears are disposed longitudinally adjacent to each other. The first keyway of the drive shaft is angularly aligned with the apex of one tooth of the first drive gear and the second keyway of the drive shaft is angularly aligned with the apex of one tooth of the second drive gear.

Furthermore, the first keyway and the second keyway of the drive shaft are angularly spaced about 19.29 degrees from each other to provide about ⅜ of a tooth spacing.

In another embodiment, each of the first drive gear, the first slave gear, the second drive gear and the second slave gear is a spur gear.

In yet another embodiment, the assembly further comprises a first end plate disposed on the first pair of meshing gears and an opposing second end plate disposed on the second pair of meshing gears.

DETAILED DESCRIPTION

FIG. 1Illustrates a scavenge gear assembly10for a scavenge oil pump12of a vehicle in accordance with one embodiment of the present disclosure. Preferably, the assembly10is connected to the pump by way of an intermediate shaft (not shown) and is housed in a casting or housing14in fluid communication with an engine block15of the vehicle.

As shown inFIGS. 2 and 3, the scavenge gear assembly10comprises a drive shaft16and a slave drive or slave drive shaft18disposed adjacent and in parallel relationship with the drive shaft16. The assembly10further comprises a first pair of meshing gears20rotationally disposed about the drive shaft16and the slave drive18. The first pair of meshing gears20comprises a first drive gear22and a first slave gear24identical to the first drive gear22. As shown, the first drive gear22is rotationally disposed about the drive shaft16to thereby rotate about a longitudinal axis of the drive shaft16. Likewise, the first slave gear24is rotationally disposed about the slave drive18to thereby rotate about a longitudinal axis of the slave drive18. Moreover, the first drive gear22and first slave gear24rotate about their respective axis in rotational meshing cooperation for torque transmission. In this embodiment, each of the first drive gear22and the first slave gear24has teeth26,28equally formed thereabout.

In this aspect, the assembly10further comprises a second pair of meshing gears30rotationally disposed about the drive shaft16and the slave drive18. The second pair of meshing gears30comprises a second drive gear32and a second slave gear34identical to the second drive gear32. As shown, the second drive gear32is rotationally disposed about the drive shaft16to thereby rotate about the longitudinal axis of the drive shaft16and the second slave gear34is rotationally disposed about the slave drive18to thereby rotate about the longitudinal axis of the slave drive18. Moreover, the second drive gear32and the second slave gear34rotate about their respective axis in rotational meshing cooperation for torque transmission. In this embodiment, each of the second drive gear32and the second slave gear34has teeth36,38equally formed thereabout.

As shown, the second pair of meshing gears30is disposed linearly adjacent to the first pair of meshing gears20. That is, the second drive gear32is disposed linearly adjacent to the first drive gear22along the longitudinal axis of the drive shaft16. Moreover, the second slave gear34is disposed linearly adjacent to the second slave gear34along the longitudinal axis of the slave drive18. The assembly10further comprises a dividing plate42disposed between the first and second pair of meshing gears30.

In one embodiment, the first pair of meshing gears20and the second pair of meshing gears30have a timing or tooth spacing of about ⅜ of a tooth spacing (or ⅜N of a gear rotation) relative to each other for torque transmission of scavenge oil. In other words, the second pair of meshing gears30has about ⅜ of a tooth spacing relative to the first pair of meshing gears20. That is, the second drive gear32is rotated ⅜ of one tooth spacing about the drive shaft16relative to the first drive gear22, where one tooth spacing may be measured as angularly or radially from one tooth peak to an adjacent tooth peak of a gear.

The term “about” as used herein is known by those skilled in the art. Alternatively, the term “about” may be interpreted to mean+/−2 degree or +/−8% tooth spacing.

In another embodiment, the tooth spacing of the first and second drive gears22,32may be the average of a first optimum for reducing pumping pulsations and a second optimum for reducing meshing pulsations. When in motion, each gear has an unsteady pulsation or noise at the outer diameter of the gear. Such pulsation is related to the number of teeth (or a multiple thereof). For example, the first drive gear22(a first gear) has an unsteady pulsation at its outer diameter and related to its seven teeth26. In this example, to cancel out the unsteady pulsation, the second drive gear32(an adjacent gear) is timed to have its pulsations out of phase with the first drive gear22. A primary frequency of the pulsations may be represented by N pulsations per revolution or number of teeth per gear. Multiples of the frequency will also be present. Thus, the amount of revolutions made by the first drive gear22to generated one wavelength of the frequency will be 1/N revolutions. In this example, to maximize the cancellation of the frequency, the second drive gear32(the adjacent gear) is to be spaced by half of the wavelength, or ½N. Hence, the second drive gear32will be timed such that the teeth36are timed ½N revolutions from the first drive gear22.

Moreover, at a meshing area M of the gears, there are 2N meshing events that happen per revolution. As shown, each meshing event is created from a tooth peak P and a gear trough T between a pair of meshing gears, e.g., the first pair of meshing gears20. Each meshing event then happens every ½N of gear rotation, where a rotation is one full rotation. Thus, every ½N revolution generates one wavelength of frequency. In this example, for the adjacent gear (the second drive gear32) to generate a wave out of phase, the second drive gear32is timed ½ of this wavelength. Hence, the adjacent gear should be timed at ½*½N, which is ¼N. Therefore, the adjacent gear is timed a quarter of a gear tooth spacing from the first gear.

Thus, the timing of the adjacent gear (e.g., the second drive gear32) from the first gear (e.g., the first drive gear22) may have two optimums for reducing each local pulsation. For reducing pumping pulse at the outer diameter of the gear, a first optimum may be represented by: ½ tooth spacing (or ½N). For reducing meshing pulse near the meshing area of gears, a second optimum may be represented by: ¼ tooth spacing (or ¼N). Hence, tooth spacing or an average of the first optimum and the second optimum may be represented by:

As depicted in the drawings, the assembly10comprises a plurality of sets or pairs of meshing gears rotationally disposed about the drive shaft16and the slave drive18for a multi-stage scavenge pump. For purposes of describing the present disclosure, only the first pair and the second pair of meshing gears will be discussed herein. However, it is to be understood that the assembly may comprise a plurality of sets of meshing gears for a multi-stage scavenge pump without departing from the spirit and scope of the present disclosure.

Referring toFIG. 4, the drive shaft16comprises a first keyway44formed thereon and a second keyway46formed longitudinally adjacent the first keyway44. The first drive gear22has a key matingly disposed in the first keyway44and the second drive gear32has a key matingly disposed in the second keyway46such that the first and second drive gears22,32are disposed longitudinally adjacent to each other with about a ⅜ of a tooth spacing relative to each other. In this example, the first keyway44is angularly aligned with the apex48of one tooth of the first drive gear22and the second keyway46is angularly aligned with the apex50of one tooth of the second drive gear32. It is to be understood that each of the first drive gear22and the second drive gear32is locked in orientation with its respective tooth apex by way of its key. That is, the key is matingly inserted in the keyway to thereby lock the gear in orientation with its respective apex. As a result, the first and second drive gears are locked in orientation and have about ⅜ of a tooth spacing relative to each other.

By way of example, the second keyway46is formed on the drive shaft16and angularly spaced about 19.29 degrees relative to the first keyway44to provide about ⅜ of a tooth spacing. In this example, the second keyway46has a tooth offset of about 0.38 tooth relative the first keyway44. However, it is to be understood that the first keyway44and the second keyway46may be angularly spaced at other degrees without departing from the spirit and scope of the present disclosure so long as the first pair of meshing gears20and the second pair of meshing gears30have about ⅜ of a tooth spacing. Accordingly, it is also appreciated that the first keyway44and the second keyway46may be tooth offset at other suitable values without departing from the spirit and scope of the present disclosure so long as the first pair of meshing gears20and the second pair of meshing gears30have about ⅜ of a tooth spacing.

In this example, each of the first and second drive gears22,32comprises seven teeth. In one embodiment, each of the first drive gear22, the first slave gear24, the second drive gear32and the second slave gear34has seven teeth disposed thereabout.

In another embodiment, the first drive gear22, the first slave gear24, the second drive gear32and the second slave gear34is a spur gear. In yet another embodiment, the assembly10further comprises a first end plate62disposed on an end pair of meshing gears (here, the first pair of meshing gears20) and an opposing second end plate64disposed on an opposing end of a pair of meshing gears (here, the second pair of meshing gears30).

It is to be understood that each pair of meshing gears is to be separated by dividing plates or end plates on each side thereof to thereby separate each pair of meshing gears from an adjacent or neighboring pair of meshing gears. For example, for the assembly10, a side plate is disposed between adjacent pairs of meshing gears. Moreover, an end plate or a dividing plate is disposed on each end of the assembly. Alternatively, the pairs or sets of meshing gears may be disposed in a housing that separates each set of gears without departing from the spirit and scope of the present disclosure.

FIG. 5is a graph of outlet pressure (absolute pressure, kPa vs. crankangle) of four pairs of identical meshing gears having seven teeth per gear and differing tooth spacing. The tooth spacing include zero of a tooth spacing, ¼ of a tooth spacing, ⅜ of a tooth spacing, and ½ of a tooth spacing. As shown, the meshing gears with ⅜ of a tooth spacing have the lowest outlet pressure, resulting in lower aeration.

FIG. 6is a graph of pressure amplitude changes (absolute pressure, kPa vs. crankangle) of four pairs of identical meshing gears having seven teeth per gear and differing tooth spacing. Data was taken at the widest area of a manifold. In this example, the tooth spacings include zero of a tooth spacing, ¼ of a tooth spacing, ⅜ of a tooth spacing, and ½ of a tooth spacing. As shown, the meshing gears having ⅜ of a tooth spacing is close to having the lowest pressure amplitude, resulting is reduced NVH (noise, vibration, harshness) impact risk.

FIG. 7is a graph comparing drive shaft16torque oscillation (amplitude, HP vs. frequency, Hz) of four pairs of identical meshing gears having seven teeth per gear and differing tooth spacing.FIG. 7depicts gear rotational orders: first order, second order, third order, fourth order, fifth order, sixth order, and seventh order. As an example, the gears with ⅜ of a tooth spacing shows to have the lowest horsepower (HP) at the fourth order, thereby resulting in a lower torque pulsation. A lower torque pulsation translates to an improved shaft fatigue life.