Interrelated power delivery controls – including engine control – Plural engines – Electric engine
Reexamination Certificate
1999-07-15
2001-01-23
Marmor, Charles A (Department: 3681)
Interrelated power delivery controls, including engine control
Plural engines
Electric engine
C477S003000, C180S065230, C192S085060, C192S083000
Reexamination Certificate
active
06176808
ABSTRACT:
TECHNICAL FIELD
The invention relates to hybrid vehicle drivelines with an internal combustion engine and an electric motor providing torque input to transmission gearing.
BACKGROUND OF THE INVENTION
In a typical automotive vehicle driveline, it is common practice to include a hydrokinetic torque converter. The impeller of the torque converter receives engine torque and the turbine of the torque converter transfers torque to the torque input element of multiple-ratio gearing of the transmission.
The presence of the torque converter in the torque flow path introduces hydrokinetic power losses, particularly during startup of the vehicle, as the torque converter fluid in the converter torus circuit is accelerated and decelerated. These losses are manifested in heat loss to the hydrokinetic fluid, which requires a heat exchanger to maintain an acceptable hydrokinetic fluid temperature.
Attempts have been made to eliminate the power losses inherent in a powertrain having an internal combustion engine and a torque converter automatic transmission by replacing the engine with an electric motor, the power output element of the motor being connected to the torque input element of the transmission. Such driveline arrangements, however, do not take advantage of the superior performance of an internal combustion engine in an automotive vehicle. Further, they require the presence of an on-board electric voltage source.
Attempts to combine the advantages of an internal combustion engine with an electric motor drive have been made in hybrid vehicle arrangements, but the engine is required in such known designs to operate throughout a large speed range including startup speeds and to operate at idle speed while the vehicle is at rest.
BRIEF DESCRIPTION OF THE INVENTION
The transmission and control system of the invention is particularly adapted for use with a hybrid electric vehicle including an internal combustion engine and a multiple-ratio transmission gearing arrangement wherein provision is made for significantly improving fuel economy and reducing undesirable exhaust gas emissions from the engine.
It is an objective to provide an improved hybrid electric vehicle transmission and control system which would permit the internal combustion engine to be deactivated when the vehicle is at rest. The improved driveline of the invention includes an induction motor that is useful to provide added launch performance, which permits the multiple-ratio transmission to operate throughout a desired ratio range without the necessity for using a hydrokinetic torque converter between the engine and the input element of the transmission gearing.
It is also an objective of the invention to use an induction motor in a hybrid vehicle driveline, when the motor is not required for rapid vehicle startup, to function as an alternator.
The absence of a hydrokinetic torque converter from the hybrid electric vehicle driveline of the invention does not result in undesirable torsional vibration since the induction motor situated between the engine and the transmission may function as a vibration damping structure as well as a means for effecting shift quality improvement.
During vehicle coast-down, regenerative braking is achieved by the induction motor, thereby further improving the fuel economy.
The engine idle and launch speed control are provided by modulating the forward clutch engagement with a closed-loop electronic controller. The forward clutch may be located in the transmission structure itself or it may be an independent clutch located in the torque flow path between the engine and the input element of the gearing. The clutch, regardless of whether it is an integral element of the transmission gearing or is a stand-alone clutch on the torque output side of the engine, may be used to disconnect the engine from the induction motor during regenerative braking.
The clutch also disconnects the engine from the torque flow path when the engine is required to operate at low throttle and during operation of the vehicle at low speed when only the induction motor may be used to propel the vehicle. It is at this time that the internal combustion engine is most inefficient. Thus, by disconnecting the engine, the engine may be reserved for operation in the speed range at which it is most efficient as the induction motor supplies the driving torque.
The clutch may be used also to rapidly restart the engine when the vehicle is moving by using the vehicle momentum since the engine is connected mechanically through the clutch to the gearing.
The torque output of the induction motor can be optimized by maintaining the engine speed at a lower level than that which would be the case with a conventional automatic transmission with a torque converter. The launch performance is improved compared to a driveline with a converter transmission since the output torque at the traction wheels increases more rapidly during launch of the vehicle when the electric motor is used for launch purposes.
The presence of the induction motor in the driveline makes it possible to improve shift quality during a speed ratio upshift. For example, it is necessary during an upshift to disengage one friction element as the other is engaged. Torque builds up in one friction element during a so-called torque phase, which occurs at the beginning of the upshift. Normally, line pressure is increased quickly at the beginning of the torque phase in order to reduce the time interval required to accomplish a shift. Just prior to the completion of the torque phase, the line pressure is reduced so that the subsequent inertia phase of the shift can be initiated. The inertia phase is accompanied by a change in the rotary speed of rotating elements as the oncoming clutch becomes activated.
In order to reduce the so-called “torque hole” that occurs during the torque phase of an upshift prior to the initiation of the inertia phase, the induction motor can be used to supply a temporary torque boost so that the net torque at the traction wheels remains relatively constant. This improves shift quality.
When the vehicle is at rest and the engine is shut down, it is necessary to have the forward clutches in the transmission applied. On launch, the operator moves the throttle to the advanced position. The launch torque of the electric motor then moves the vehicle, thereby permitting the engine to be restarted. This procedure makes it necessary for the forward clutches to be applied. This is accomplished in the driveline of the present invention by using an auxiliary electric pump system to provide a threshold pressure to the transmission clutches when the engine is inactive. As hydraulic pressure increases following restarting of the engine, the pump is turned off.
The invention further comprises a clutch on the torque output side of the engine. It is normally applied with a spring force so that, on engine startup, hydraulic flow at the output of the transmission pump is reduced. The clutch need not be stroked before it is pressurized.
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Brown Larry Thomas
Kraska Marvin Paul
Ortmann Walter Joseph
Ford Global Technologies Inc.
Marmor Charles A
McKenzie Frank G.
Parekh Ankur
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