HYBRID VEHICLE WITH A COMBINATION ELECTRIC MACHINE AND A TORQUE CONVERTER

A propulsion system for an electric vehicle including an internal combustion engine and an electric machine disposed in a transmission housing that is attached to the engine. An engine vibration damper is disposed between the engine and the electric machine. A torque converter connects the engine to the turbine shaft and is disposed in the housing radially inboard of the windings of the electric machine. A turbine shaft connected to the electric machine is configured to transfer torque from the engine and the electric machine through the turbine shaft to a planetary gear set connected to the turbine shaft. A disconnect clutch is operatively connected between the engine and the electric machine and is disposed in the housing radially inboard the windings of the electric machine and is connected to the turbine shaft.

TECHNICAL FIELD

This disclosure relates to a driveline for a hybrid vehicle that includes an internal combustion engine and an electric propulsion electric machine that are configured to be selectively or jointly engaged with a transmission.

BACKGROUND

Hybrid vehicles include both an internal combustion engine and an electric machine that jointly or alternatively function to propel the vehicle. The electric machine may be used to propel the vehicle provided there is enough stored energy in the propulsion battery to power the electric machine. The internal combustion engine may provide torque to propel the vehicle when the battery is depleted, when there is insufficient torque provided by the electric machine, or to charge the battery with a regenerative braking system.

In some hybrid vehicles, the internal combustion engine, electric machine and transmission are separate assemblies that each have a separate housing. The separate assemblies are stacked and assembled. Stacking the assemblies requires considerable space within the vehicle and adds weight. Added weight reduces energy efficiency and vehicle range.

Heat created by the electric machine makes it necessary to cool the electric machine. The electric machine is housed in a relatively inaccessible location which makes cooling the electric machine a challenge. Coolant circulation systems have been proposed to cool the electric machine, but such systems add cost and weight to the vehicle.

Prior art electric machines included one damper between the internal combustion engine and the electric machine and a second damper between the electric machine and the torque converter. The second damper added weight and increased the space requirements for the vehicle's propulsion system.

This disclosure is directed to solving the above problems and other problems as summarized below.

SUMMARY

According to one aspect of this disclosure, a propulsion system for an electric vehicle is disclosed that comprises an engine having an input shaft, an electric machine having windings is disposed in a housing that is attached to the engine. An engine vibration damper is disposed between the engine and the electric machine. A torque converter is disposed in the housing and connects the electric machine and the engine to a turbine shaft connected to a turbine of the torque converter to transfer torque from the engine and the electric machine through the turbine shaft. A planetary gear set is disposed in the housing and is configured to receive torque from the turbine shaft. A disconnect clutch is operatively connected between the engine and the torque converter. The disconnect clutch is at least partially disposed in the housing radially inboard relative to the windings and is configured to selectively transfer torque from the input shaft to the torque converter.

According to another aspect of this disclosure, the propulsion system may further comprise a torque converter clutch disposed radially inside the windings of the electric machine that connects the torque converter housing to the turbine shaft. When the torque converter clutch is disengaged torque is provided through the torque converter to the turbine shaft. When the torque converter clutch is engaged the torque converter is bypassed and locks the torque converter housing to the turbine shaft.

The turbine shaft may define three axial channels, wherein a first axial channel supplies fluid to a torque converter clutch piston, a second axial channel supplies fluid to a disconnect clutch piston, and a third axial channel supplies fluid to a balance dam of the torque converter clutch and a balance dam of the disconnect clutch. The propulsion system may include an off-axis electric pump that provides the fluid under pressure to a valve body and supplies the fluid to the first axial channel, the second axial channel, and the third axial channel through a plurality of axially spaced channels defined in a front support wall of the housing. The off-axis electric pump provides sufficient fluid under pressure to fully engage the disconnect clutch.

The propulsion system may further comprise a valve body, an off-axis pump, a torque converter-in port, and a torque converter-out port. The valve body receives fluid from the off-axis pump and supplies the fluid to the torque converter-in port and receives fluid from torque converter-out port.

The electric machine and the torque converter are located directly adjacent to each other and are not separated by a vibration damper.

According to another aspect of this disclosure, a transmission is disclosed for a hybrid electric vehicle having an engine. The transmission comprise a transmission housing operatively connected to an input shaft from the engine. An electric machine is disposed in the transmission housing and connected to a torque converter. The electric machine includes a stator and a rotor that includes a plurality of windings. A torque converter is disposed in the transmission housing and includes a turbine, an impeller, and a stator. The torque converter hydrostatically connects the impeller to the turbine of the torque converter to transfer torque from the engine to a turbine shaft. A planetary gear set is disposed in the transmission housing and is configured to receive torque from the turbine shaft. A torque converter clutch is provided between the torque converter housing and the turbine shaft. The torque converter clutch is disposed in the transmission housing radially inboard relative to the windings of the electric machine. The torque converter clutch is configured to bypass the torque converter and provide torque from the torque converter housing to the turbine shaft.

According to another aspect of this disclosure, a combination electric machine and torque converter assembly is disclosed for a hybrid vehicle including an engine. The combination includes a housing, an electric machine disposed in the housing that includes a stator and a rotor. A torque converter is disposed in the housing and is operatively connected to the electric machine to receive torque from the engine. The torque converter has a disconnect clutch that is engaged to receive torque from an engine and provide torque to a turbine shaft. The disconnect clutch is disposed in the housing at a location radially inside the rotor of the electric machine.

As an alternative, a torque converter clutch may be disposed in the housing radially inside the windings of the rotor. The torque converter clutch functions to lock a torque converter housing to the turbine shaft bypassing the torque converter.

The above aspects of this disclosure and other aspects will be described below with reference to the attached drawings.

DETAILED DESCRIPTION

As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure could be incorporated in particular applications or implementations.

Referring toFIG. 1, a propulsion system10for a hybrid vehicle12is illustrated that includes an electric machine14for propelling the vehicle12, an internal combustion engine (“ICE”)16, a torque converter18, a multi-speed planetary gear set20, a valve body22, and an off-axis transmission fluid pump24. Power is provided to the electric machine14through a power electronics module26from a propulsion battery28. The propulsion battery28may include a plug-in charging station30including a power source, such as the electrical power grid (not shown) and electrical vehicle supply equipment (“EVSE”). If the vehicle12is a plug-in hybrid, a charge port32and a power converter34may be provided to charge the battery28.

Referring toFIG. 2, the ICE16is of conventional design and may be a gasoline or diesel engine. The ICE16is configured to be attached to the propulsion system10with an input shaft35that is selectively connected to the torque converter18by a disconnect clutch36(hereinafter a “KO clutch”). When the KO clutch36is engaged, torque from the ICE16is provided to the torque converter housing37which is connected to the impeller38of the torque converter18. The impeller38drives the turbine40of the torque converter18through the TC stator42that multiplies the torque for better acceleration.

The electric machine14includes a rotor44that is connected to the housing37of the torque converter18and a stator46of the electric machine14. The electric machine14may propel the vehicle12(shown inFIG. 1) independently, in conjunction with the ICE16, or the ICE16may propel the vehicle12independently.

A housing48encloses the electric machine14and torque converter18. A damper54is disposed between the ICE16and the housing48to dampen vibrations from the ICE16. According to one aspect of this disclosure, no damper is provided between the electric machine14and the torque converter18. Elimination of the damper as previously provided in the prior art allows parts of the torque converter18to be disposed radially inside the electric machine14to reduce the overall length of the propulsion system10.

The ICE16provides torque through the input shaft35to the KO clutch36. The KO clutch36is engaged to provide torque to the torque converter18and is released to interrupt or limit the torque provided by the ICE16to the torque converter18. The KO clutch36includes a clutch pack39that includes clutch plates and friction material that connect the ICE16input shaft35to the torque converter18. The KO clutch36includes a KO piston78and a KO balance dam76. The KO clutch36is controlled by automatic transmission fluid (hereinafter “ATF”) pressurized by an off-axis pump24and controlled by a computer-controlled valve body22.

Referring toFIGS. 2 and 3, ATF is provided through channels66in a front support68of the portion of the housing48enclosing the gear set20. The channels66provide fluid to the turbine shaft72. The channels66include a torque converter in channel66A, a torque converter out channel66B, a TC clutch piston channel66C, a KO clutch piston channel66D, and a balance dam channel66E. Two channels66F and66G are in fluid flow communication through the turbine shaft72(shown inFIG. 5) to the gear set20as will be described below. The gear set20, as illustrated, is of conventional design and includes a plurality of planetary gear sets.

Referring toFIGS. 2 and 4, the turbine shaft72defines a plurality of feeds74that extend axially through the shaft72. One of the feeds74A is in fluid flow communication with the TC piston60. A second feed74B is in fluid flow communication with the KO piston78. A third feed74C is in fluid flow communication with both the TC balance dam62and KO balance dam76. In one embodiment, the third feed74C also supplies ATF top lubricate the electric machine14. The turbine shaft72also includes two feeds74D and74E (shown inFIG. 5) that are in fluid flow communication with the gear set20.

Torque converter clutch56, or “TC clutch,” is engaged to transfer torque directly from the torque converter housing37to the turbine40and the turbine shaft72. The TC clutch56is engaged to improve efficiency by eliminating energy losses inherent in the torque converter18operation. Engaging the TC clutch56locks the torque converter housing37to the turbine shaft72.

The torque converter clutch56includes TC piston60in fluid communication with TC piston feed74A for actuating the TC clutch56. When the TC clutch56is actuated, the torque converter18is bypassed and torque from the ICE16is mechanically connected, or locked, by the TC clutch56to the turbine shaft72.

The balance dam feed74C is in fluid flow communication with both the torque converter balance dam62(hereinafter “TC balance dam”) and the KO balance dam76. Three or four cross-drilled holes82are defined by the turbine shaft72. The cross drilled holes82in the turbine shaft are open with the feed74A being open to the TC piston60, feed74B being open to the KO clutch piston78, and feed74C being open to balance dams62and76.

In one embodiment, a lubrication feed88receives ATF through the cross-drilled holes82and supplies ATF to a thrust bearing90disposed between the turbine shaft72and the input shaft35. The electric machine14includes magnets (not shown) in the rotor44that are heated as a result of electric machine14operation and require cooling. The thrust bearing90splashes the ATF outwardly to cool and lubricate the electric machine14. The balance dam feed74C provides fluid flow communication with the TC balance dam62, The KO balance dam76, and the lubrication feed88.

The TC piston60is actuated to apply the TC clutch56. When the TC clutch56is actuated, ATF is supplied through the TC piston feed74A and fluid in the TC balance dam62flows back to the feed74C. Similarly, when the KO clutch36is actuated, ATF is provided through the KO piston feed74B to the KO piston78and fluid in the KO balance dam76flows back to the feed74C.

Referring toFIG. 6, (shown inFIG. 5) the planetary gear sets20each include a sun gear20A about which planet gears20B rotate within a ring gear20D. A carrier20C connects the planet gears20B. The sun gears20A, ring gears20D and carriers20C are selectively locked to change the gear ratio as is well-known in the art.

The valve body22receives pressurized ATF from the pump24and selectively supplies ATF to clutches associated with the torque converter in-channel66A, the torque converter out-channel66B, the TC piston channel66C, the balance dam channel66E, and the two channels66F and66G that are in fluid flow communication with the planetary gear set20.

The KO clutch36is assembled radially inside the windings100of the stator42to reduce the overall length of the propulsion system10. The TC clutch56is assembled at least partially radially inside the windings92. In the illustrated example, the clutch pack58and balance dam62are disposed at a location radially inside the electric machine14. By eliminating a damper from between the electric machine14and the torque converter18, space is requirements are reduced by locating the KO clutch36and TC clutch56fully or partially radially inside the windings92of the electric machine14.

The propulsion system10has three modes of operation including a first mode—engine16only; a second mode—electric machine14only; and a third mode—with both the engine16and electric machine14providing torque to the turbine shaft72and planetary gear set20.

In the first mode of operation, the KO clutch36is engaged and torque from the ICE16is provided through the torque converter housing37to the torque converter18. The impeller38drives the turbine40through the TC stator42and provides torque to the turbine shaft72and planetary gear set20. When the TC clutch56is engaged, the torque converter housing37provides torque directly to the turbine shaft72and the planetary gear set20.

In the second mode of operation, torque from the electric machine14is provided to the turbine shaft72through the torque converter18.

In the third mode of operation, torque from the ICE16is provided to the torque converter housing37by engaging the KO clutch56while torque from the electric machine14is provided directly to the torque converter housing37. Torque from the torque converter housing37is provided to the turbine shaft72through the torque converter18.