Planetary gear transmission systems or components – Input from independent power sources – Including electric motor input
Reexamination Certificate
1999-12-16
2001-07-10
Marmor, Charles A (Department: 3681)
Planetary gear transmission systems or components
Input from independent power sources
Including electric motor input
C192S003280
Reexamination Certificate
active
06258001
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
1. Field of the Invention
The present invention relates to a drive train connecting an engine and a motor in a vehicle, and more specifically to a hybrid vehicle drive train having a motor integrated with an automatic transmission, including a hydraulic transmission such as a torque converter, into a single unit.
2. Related Art
Japanese Patent Application No. HEI 9-215270, Japanese Patent Application No. HEI 5-30605 and Japanese Patent Application No. HEI 5-024447 all disclose parallel type hybrid vehicle drive trains. This type of hybrid vehicle drive train is provided with a motor/generator in an automatic transmission having a torque converter. The driving force of the motor/generator during start and acceleration of the vehicle assists the driving force of the engine. The motor/generator also functions as a generator to assist the engine brake effect when driving down a hill and also regenerates braking energy, thereby improving gas mileage and reducing the amount of discharged exhaust gas.
In the drive train disclosed by HEI 9-215270, a motor housing which houses a motor/generator is interposed between an engine housing and a transmission housing which also houses a torque converter. In the drive train disclosed by HEI 5-30605, a motor/generator is provided between a pump impeller and a turbine runner of the torque converter. In the drive train disclosed by HEI 5-024447, a motor/generator is provided between an element extending from the torque converter to the output shaft via an automatic transmission unit and a case which houses the drive system. More specifically, the motor/generator is provided between the torque converter and the automatic transmission unit or on the side behind the transmission.
When the motor/generator is provided between an internal combustion engine and a torque converter, as in HEI 9-215270, the overall length of the unit including the transmission and the engine increases by the axial length of the motor/generator, creating a problem of mounting in a vehicle. Decreasing the axial length of the motor/generator in order to limit the overall length is a possibility; however, since the output torque of the motor (generator) is defined by the length of the rotor and the stator, it is difficult to shorten the overall length while maintaining the required output torque of the motor. Also, when the rotor is directly connected to the crankshaft, the precision of centering of the crankshaft directly affects the precision of centering of the rotor. Therefore, with the rotor it is necessary to set an air gap sufficient only to allow for the amount of eccentricity following the vibrations deriving from combustion. As a result, the efficiency of the motor/generator decreases requiring a proportional increase in capacity (size) of the motor/generator.
When a motor/generator is arranged axially intermediate a front cover of a torque converter and a turbine, as in HEI 5-30605, the axial length increases by the length of the motor/generator just as mentioned above. Furthermore, the precision of centering of the crankshaft directly affects the precision of support of the rotor because the front cover is directly connected to the crankshaft. In addition, the stator which is fixed to the pump impeller and the rotor which is fixed to the turbine runner shift relative to one another in the axial direction due to expansion or contraction of the torque converter from changes in the charge pressure and centrifugal pressure thereof, resulting in an equivalent drop in efficiency of the motor. Therefore, a larger motor/generator is needed in order to achieve the required output to compensate for the efficiency drop. In addition, when aligned radially with a torque converter, the motor/generator extends beyond the outer diameter of the torque converter. This results in an increase in the overall radial dimension which makes it difficult to ensure minimum freeboard and complicates mounting in a vehicle. In this case, ensuring the output torque of the motor (generator) is relatively easy since the diameter of the motor/generator is greatly increased. However, since the diameter of the torque converter is fixed according to the output torque of the engine, the diameter of the motor/generator arranged radially outward of the torque converter cannot be made smaller.
Further, in the design of HEI 5-024447 it is difficult to increase the diameter of the motor/generator, and therefore difficult to ensure the output torque of the motor (generator) within a limited space, i.e. the space between the torque converter and the automatic transmission or on the side behind the automatic transmission. In addition, since the motor/generator is connected to the engine via the torque converter or further, via the automatic transmission unit it is difficult to start the engine by the motor/generator, and therefore, an additional motor for starting the engine becomes necessary.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a vehicle drive unit which allows for smaller axial and radial dimensions. A second object of the present invention is to provide a hybrid vehicle drive train which supports the motor with high precision independent of centering precision of the engine crankshaft and independent of deformation of the hydraulic transmission. A third object is to increase the efficiency of the motor and enable the motor to be made smaller.
To achieve the foregoing objects, the present invention provides a vehicle drive train including an engine, a first transmission unit and a second transmission interposed between a crankshaft of the engine and an input shaft of the first transmission unit. The hybrid vehicle drive train also includes a lock-up clutch and a motor having a stator and a rotor, wherein the rotor is directly connected to an output element of the engine for rotation therewith in forward and reverse directions. The hybrid vehicle drive train has the lock-up clutch located between the engine and the second transmission unit. The lock-up clutch has a diameter smaller than the outer diameter of the second transmission unit and the motor is arranged axially overlapping and radially outward of the outer circumference of the lock-up clutch. By such a design, the invention ensures mountability in a vehicle. In addition, capacity of the second transmission is ensured because the motor is arranged radially outward of the lock-up clutch and between the engine and the second transmission. Furthermore, the motor is arranged so as to ensure mounting capability with adequate freeboard. Output torque of the motor is ensured and starting performance of the engine and drive performance of the vehicle are improved.
Preferably, the lock-up clutch is a multiple disc clutch. Because the lock-up clutch is a multiple disc clutch it provides sufficient torque capacity, despite the fact that it has a small diameter, so that the motor can be arranged on the outer diameter side of the lock-up clutch, i.e., radially outward of the lock-up clutch.
The lock-up clutch is preferably connected to a damper having coil springs spaced around its circumference. This damper is arranged axially overlapping on the inner circumference of the friction plates of the lock-up clutch. Since the damper does not require its own axial space, the overall length of the drive train need not be increased to accommodate same.
The second transmission unit is preferably a hydraulic transmission, for example a torque converter which includes a turbine runner, a pump impeller, and a stator, and which increases torque when starting the vehicle in motion under power of the motor only. The hydraulic transmission may have a front cover which covers the turbine runner and the lock-up clutch and which connects the pump impeller, the crankshaft, and the rotor of the motor. The front cover has an axially extending portion in the center thereof, which defines a small diameter portion of the housing of the second transmission unit. The motor is arranged radially outward
Amano Masaya
Hasebe Masahiro
Nakamura Seiji
Omote Kenji
Shinohara Keiichi
Aisin Aw Co. Ltd.
Ho Ha
Lorusso & Loud
Marmor Charles A
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