Electric machine lubrication system

An electric drive for a transmission having a housing, a pump drive, and a primary sump configured to hold oil and operatively connected to a vehicle engine. The electric drive includes an oil-cooled electric generator electrically connected to an oil-cooled electric motor by an inverter. The electric generator includes a generator oil output operatively connected to and configured to deliver a flow of oil to a secondary sump located in the housing. The electric motor includes a motor oil output operatively connected to and configured to deliver a flow to the secondary sump. The secondary sump is separate from the primary sump, wherein the oil from the secondary sump is pumped back into the lubrication circuit of the transmission. The secondary sump includes a feature to allow overflow to drain to the primary sump.

FIELD OF THE DISCLOSURE

The present invention generally relates to an electric machine for a transmission of a work vehicle, and more particularly to a lubrication system including an electric machine of a transmission work vehicle.

BACKGROUND

Work vehicles are configured to perform a wide variety of tasks for use such as construction vehicles, forestry vehicles, lawn maintenance vehicles, as well as on-road vehicles such as those used to plow snow, spread salt, or vehicles with towing capability. Additionally, work vehicles include agricultural vehicles, such as a tractor or a self-propelled combine-harvester, which include a prime mover that generates power to perform work. In the case of a tractor, for instance, the prime mover is often a diesel engine that generates power from a supply of diesel fuel. The diesel engine drives a transmission which moves wheels or treads to propel the tractor across a field. Tractors often include a power takeoff (PTO) which includes a shaft coupled to the transmission and driven by the engine to provide mechanical power to a work implement being pulled or pushed through a field by the tractor.

The PTO that extends from the tractor to the implement is directly coupled to the implement to drive an operation being performed by the implement. In different embodiments, the implements include a spreader, a rotary mower, a rotary tiller, and other types of implements. The implement receives rotary power from the PTO to drive the operation of the particular implement to which the tractor is connected.

Work vehicles are made to incorporate different types of transmissions based on cost as well as intended applications of the work vehicle. Transmissions includes both manual transmission and automatic transmissions. Automatic transmissions includes what is known as a “conventional” transmission, that shifts between discrete individual gears, and a continuously variable transmission (CVT) that changes gears through a continuous range of gear ratios. A subset of a CVT is known as an infinitely variable transmission (IVT). In CVTs and particularly IVTs, the transmission can include a motor used to control the speed of the transmission. The motor, due to the work it performs can become excessively hot during operation and requires a cooling system. Known cooling systems, however, can be insufficient to provide proper cooling. What is needed therefore is an apparatus configured to provide sufficient cooling during operation of the transmission.

SUMMARY

Electric machines require substantial cooling flow to optimize power density. A traditional approach to this would be sizing a lubrication pump to provide sufficient cooling flow to the electric machine and then allowing the cooling flow to drain to the primary sump. The present disclosure describes a method and apparatus for draining the electric machine flow to a secondary sump, where the fluid is then pumped back into the lubrication circuit either before or after an oil cooler. The secondary sump has an overflow feature to allow overflow to drain to the primary sump. Doing this, minimizes the need to increase the size of the main lubrication pump.

In one embodiment there is provided an electric drive for a transmission operatively connected to a vehicle engine. The electric drive includes an oil-cooled electric generator and an oil cooled electric motor. The electric generator includes an input drive configured to be driven by the engine, an electrical output configured to provide generator electrical power, and a generator oil output configured to deliver a flow of oil from the electrical generator. The oil-cooled electric motor includes a motor input, a motor driver configured to provide a mechanical power, and a motor oil output configured to deliver a flow of oil from the electric motor. A housing includes a first aperture operatively connected to the generator oil output and a second aperture operatively connected to the motor output, wherein the housing includes a chamber, operatively connected to the first aperture and to the second aperture, and a chamber output operatively connected to a pump drive, wherein the pump drive is configured to drive one or more pumps.

In one example of this embodiment, the electric drive includes an inverter having an inverter electrical input and an inverter electrical output, wherein the inverter converts the generator electrical power to inverter electrical power, and the inverter electrical output is operatively connected to the electric motor to provide inverter electrical power to the electric motor. In a second example, the electric motor includes a drive shaft configured to be operatively connected to the transmission, wherein a rotational speed of the drive shaft provides a speed control for the transmission. In a third example, the housing defines a cavity in which the chamber is located, wherein the chamber defines a primary sump and the cavity defines a secondary sump. In a fourth example, the housing includes an interior wall and an exterior wall, and further comprises a cover fixedly connected to the interior wall to define the secondary sump.

In a fifth example, the interior wall of the housing includes a rib and the cover is fixedly connected to the rib to define the secondary sump. In a sixth example, the rib and the cover define an opening, wherein the opening is configured to provide for the release of oil from the generator oil output and motor oil output into the cavity. In a seventh example, the rib and the cover define a substantially fluid tight seal configured to direct the generator oil output and the motor oil output to a collection location of the secondary sump. In an eighth example, the electric drive includes a conduit operatively connected to the secondary sump at the collection location, wherein the conduit is configured to direct the collected oil from the sump.

In another embodiment there is provided a work vehicle including an engine, a transmission operatively connected to the engine, wherein the transmission includes a housing having a first aperture, a second aperture, and a chamber. An electric drive is operatively connected to the housing and includes an oil-cooled electric generator and an oil cooled electric motor. The electric generator includes an input drive configured to be driven by the engine, an electrical output configured to provide generator electrical power, and a generator oil output configured to deliver a flow of oil from the electric generator. The oil-cooled electric motor includes a motor input, a motor driver configured to provide mechanical power, and a motor oil output configured to deliver a flow of oil from the electric motor; wherein the first aperture is operatively connected to the generator oil output and the second aperture is operatively connected to the motor output. The chamber is operatively connected to the first aperture and to the second aperture, and a chamber output is operatively connected to a pump drive, wherein the pump drive is configured to drive one or more pumps.

In one example of this embodiment, the electric drive includes an inverter having an inverter electrical input and an inverter electrical output, wherein the inverter converts the generator electrical power to inverter electrical power and the inverter electrical output is operatively connected to the electric motor to provide inverter electrical power to the electric motor. In a second example, the electric motor includes a drive shaft configured to be operatively connected to the transmission, wherein a rotational speed of the drive shaft provides a speed control for the transmission. In a third example, the housing defines a cavity in which the chamber is located, wherein the chamber defines a primary sump and the cavity defines a secondary sump. In a fourth example, the housing includes an interior wall and an exterior wall, and further comprises a cover fixedly connected to the interior wall to define the secondary sump.

In a fifth example, the interior wall of the housing includes a rib and the cover is fixedly connected to the rib to define the secondary sump. In a sixth example, the rib and the cover define an opening, wherein the opening is configured to provide for the release of oil from the generator oil output and motor oil output into the cavity. In a seventh example, the rib and the cover define a substantially fluid tight seal configured to direct the generator oil output and the motor oil output to a collection location of the secondary sump. In an eighth example, the electric drive includes a conduit operatively connected to the secondary sump at the collection location, wherein the conduit is configured to direct the collected oil from the sump.

In a further embodiment there is provided a method for controlling the speed of an infinitely variable transmission having a housing, a pump drive, and a primary sump configured to hold oil. The method includes: providing an oil cooled electric generator operatively connected to the housing and an oil cooled motor operatively connected to the housing, the electric generator having a generator oil output configured to deliver a flow of oil from the electric generator to the housing and an electrical output operatively connected to the oil cooled motor, the oil-cooled electric motor having a motor oil output configured to deliver a flow of oil from the electric motor and a drive shaft extending into the housing; connecting the generator oil output to a first aperture of the housing and connecting the motor oil output to a second aperture of the housing; providing a chamber within the housing operatively connected to the first aperture and to the second aperture, the chamber including a chamber output operatively connected to the pump drive; delivering a flow of oil into the chamber from the first aperture and the second aperture, wherein the delivered flow of oil is separated from primary sump; and controlling the speed of the drive shaft to control the speed of the infinitely variable transmission.

In one example of this embodiment, the method further includes releasing a portion of the oil from the chamber into the primary sump during operation of the infinitely variable transmission.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of the novel invention, reference will now be made to the embodiments described herein and illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the novel invention is thereby intended, such alterations and further modifications in the illustrated devices and methods, and such further applications of the principles of the novel invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the novel invention relates.

FIG. 1is an elevational side view of an agricultural vehicle, and more particularly a tractor10, including a frame12supported on a pair of front wheels14and a set of rear wheels16. While wheels are described in the embodiments, other ground engaging traction devices including tracks are contemplated. An operator cab18is mounted on the frame12and contains various controls for the vehicle10so as to be within the reach of a seated or standing operator. In one aspect, these controls may include a steering device, such as a steering wheel20. A prime mover22, such as an engine, is mounted on the frame12beneath a housing24and supplies power for driven components of the tractor10. The engine22, for example, is configured to drive a transmission (not shown), which is coupled to drive the wheels at various selected speeds and either in forward or reverse directions. In different embodiments, the front wheels, the rear wheels, or all of the wheels are driven in an all-wheel drive mode to move the tractor10.

While the described embodiments are discussed with reference to a tractor, in addition to agricultural vehicles, other work vehicles are contemplated including construction vehicles, forestry vehicles, lawn maintenance vehicles, as well as on-road vehicles such as those used to plow snow, spread salt, or vehicles with towing capability.

The cab18defines an operator workstation26, which is supported by the frame12. The cab18also encloses a seat28for seating the operator. The operator workstation26, in different embodiments, includes one or more of an operator user interface30including, but not limited to, a joystick, an accelerator pedal, and a power take-off (PTO) control device for turning on or off the PTO. Pedals for a brake and a clutch are also located in the cabin18, but are not shown.

FIG. 2is a rear perspective view of an electric machine lubrication system50mounted to a transmission housing52, also known as a manifold, which is configured to fluidically cooperate with an oil cooled electrical generator54and an oil cooled motor56. While the term oil is used herein, cooling fluid and fluid are also contemplated. The transmission housing is configured to be mounted to the transmission of the vehicle10and includes an aperture through which a power take off (PTO) shaft57extends as would be understood by one skilled in the art. The transmission housing52is illustrated as positioned on the transmission such that a bottom portion58of the housing, as illustrated inFIG. 2is located closest to ground and the side portions of the housing extend generally vertically from the bottom portion58. Each of the oil cooled electrical generator54and the oil cooled motor56are fixedly coupled to the transmission housing52at an upper portion of the housing.

The generator54includes an electrical connector60and the motor56includes an electrical connector62. An electrical inverter64is coupled to the connectors60and62such that power generated by the generator54is transmitted through the connector60to the inverter64. The inverter64converts the generator power to a motor power sufficient to power the oil cooled motor56. In other embodiments, the electrical generator directly generates a correct motor power to power the motor56, and the inverter64is not needed. In other embodiments, an inverter is located in either the generator54or the motor56and only a cable extends from the generator54to the motor56.

Each of the generator54and the motor56are oil cooled devices and receive oil from oil located in pressurized passages of the housing52. The cavity65includes a primary sump66, which is generally located in the cavity65toward the bottom58of the housing52. During operation of the transmission, oil collects in the primary sump66to a generally predefined level due to the effects of gravity.

During operation of the transmission, the cavity65is not completely filled with oil. Pressurized passages located in the housing52provide a sufficient amount of oil to lubricate the generator54and the motor62to provide for cooling of both. The generator54includes a gear driven drive shaft70which is driven by the engine. The motor56includes a drive shaft operatively connected to the transmission.

The transmission housing52receives pressurized oil from a lubrication pump that is part of the lubrication system50. The housing52includes a multitude of fluid passages to deliver the oil to supply ports of the generator52and the motor54. The oil enters into the generator54from one of the fluid paths located in the housing52and flows through the generator54and out of the generator to a rear drain tube72as seen inFIG. 2.

In one embodiment, about half of the oil provided to the generator52drains from the rear drain tube72and the remaining amount of oil drains from an open face of the generator52, through cavities in the manifold and rear cover to a secondary sump80which also receives oil from the rear drain tube72. Similarly oil enters into the motor56by fluid passages located in the housing52in the same fashion as oil enters the generator54. About half the oil flows through the motor56and out of the motor to a rear drain tube74. The remaining amount enters the secondary sump80from an open face of the motor56. Other amounts of oil are contemplated.

Each of the rear drain tubes72and74extends from their respective devices and are coupled respectively to the housing52at a first connection76and a second connection77. The motor56includes the drive shaft75which is operatively connected to the transmission. The rotational speed of the shaft75controls the speed of the transmission as would be understood by one skilled in the art. The rotational speed of the shaft is commanded in different embodiments by the operator or by a semi-autonomous control systems of the vehicle. Using the commanded speed, the transmission selects a mode of operation and an electric motor speed to achieve the commanded speed.

An interface78and an interface79located on an exterior of the housing52and are used to control transmission functions, as is understood by those skilled in the art. Another interface includes ports130,132, and134. One port is for supplying a control pressure flow from an external pump. A second port is for supplying a lube flow from a primary lubrication pump126(seeFIG. 7). A third port is a control line leaving the transmission for other vehicle functions. In other embodiments, a single fluid cooler or more than two fluid coolers are contemplated.

Apertures extending through the housing52deliver oil from each of the generators by generator drain tube72and motor drain tube74to a secondary sump80, as illustrated inFIG. 3. The secondary sump80is generally located in a central portion of the housing52and includes a cover or plate82that provides a wall to define the secondary sump80with the interior of the housing52. As further seen inFIG. 4, the oil located in the secondary sump flows by the force of gravity between the plate82and the interior of the housing toward the bottom58of the housing where it collects between the plate82and the housing52. A conduit84, also known as a jumper tube, transfers the collected oil from the secondary sump80to a pumping apparatus86, which in different embodiments includes one or more pumps including a scavenger pump and/or a recycle pump. A drive shaft88extends through the pumping apparatus86and in different embodiments is coupled to various implements for mechanically powering those implements. In one embodiment, the drive shaft88is coupled to a power take off shaft located at the front of the vehicle10.

FIG. 5illustrates cavity65of the housing52with the plate82removed. The housing52includes raised features90, such as ribs, extending from a back wall92of the housing52to define the secondary sump80in combination with the plate82. The features90extend from a gap94toward the bottom of the housing52. The features90in combination with the plate82direct fluid flow from an aperture96coupled to the motor drain tube74and direct fluid flow from an aperture98coupled to the generator drain tube72. The fluid flow from each of the apertures96and98toward the conduit84where it is delivered to the pump apparatus86. The rib90and the plate82combine to define a relatively fluid tight seal to keep oil from the generator and the motor within the cavity65.

The gap94between the back wall92and the plate82provides an opening to enable fluid to be expelled or release from the secondary sump80into the interior of the housing as necessary. For instance, under certain conditions where the flow of oil from the generator drain tube72and the motor drain tube74exceeds the capacity of the secondary sump80, fluid moves through the gap94and into the housing cavity65.

The secondary sump80, as further illustrated inFIG. 6, includes a bottom portion100, or collection location, where the fluid received through the apertures96and98collects. The conduit84includes an open end102that receives the fluid to movement through a tube84. The tube84is operatively connected to a pump apparatus housing106that includes an aperture108coupled to the tube104. The housing106includes a channel110configured to deliver the oil to the one or more pumps being driven by the pump apparatus86. A cover112(seeFIG. 5) has been removed to illustrate the interior of the housing106. The bottom portion of the secondary sump100does not include an aperture and consequently, fluid located in the secondary sump80does not enter into the primary sump66, unless the fluid escapes from the gap94.

FIG. 7illustrates a system flow diagram of the electric machine lubrication system50. The system50includes the primary sump66which is fluidically coupled to the secondary sump80resulting from fluid overflow at the overflow gap94. The primary sump66provides fluid for the transmission lubrication circuit which is provided to both the oil cooled generator54and to the oil cooled motor56. InFIG. 7, the labels MG1and MG2are used to indicate motor/generator. In different embodiments, reversed locations of the motor and generator are contemplated. In other embodiments, however, the two electronic machines (eMachines), the generator54and the motor56, are configured to provide both functions of electrical power generation and mechanical power generation.

Oil that has moved to the secondary sump80is delivered to a scavenger pump120and to a recycle pump122that are part of the pump apparatus86as described herein. The fluid pumped by each of the pumps120and122are provided to the fluid circuit where the fluid is cooled by an oil cooler124which is located external to the transmission. A cooler/lube pump126and an associated sump128are located externally to the transmission to provide fluid to various lubrication circuits as would be understood by one skilled in the art.

While exemplary embodiments incorporating the principles of the present disclosure have been described hereinabove, the present disclosure is not limited to the described embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the disclosure using its general principles. In addition, while the terms greater than and less than have been used in making comparison, it is understood that either of the less than or greater than determines can include the determination of being equal to a value. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this disclosure pertains and which fall within the limits of the appended claims.