Prime-mover dynamo plants – Electric control – Engine control
Reexamination Certificate
2000-01-18
2002-01-22
Ramirez, Nestor (Department: 2834)
Prime-mover dynamo plants
Electric control
Engine control
C290S017000, C290S021000
Reexamination Certificate
active
06340847
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power output apparatus including both an engine and a motor as the power source, as well as to a method of controlling such a power output apparatus. More specifically the invention pertains to a power output apparatus having a linkage mechanism that causes the motor to be linked with either one of an output shaft of the engine and a drive shaft.
2. Description of the Related Art
One of the recently proposed techniques is a hybrid vehicle with a power output apparatus mounted thereon, which includes both an engine and a motor as the power source (for example, JAPANESE PATENT LAID-OPEN GAZETTE No. 9-47094). A parallel hybrid vehicle is one of the hybrid vehicles. In the parallel hybrid vehicle, the power output apparatus mounted thereon causes part of the power output from the engine to be transmitted to a drive shaft via a power regulation unit and the residual part to be regenerated as electric power. The regenerated electric power may be accumulated in a battery or used to drive the motor, which is the power source other than the engine. The power output apparatus controls the power regulation unit and the motor in the course of transmission of the power and thereby enables the power output from the engine to be converted into an arbitrary combination of the revolving speed and the torque and output to the drive shaft. In the hybrid vehicle, the engine can thus be driven at a selected driving point having a high driving efficiency, irrespective of the required output to the drive shaft. Compared with the conventional vehicle having only the engine as the driving source, the hybrid vehicle desirably saves the resources and has reduced emissions.
The motor in the power output apparatus may be linked with either one of the drive shaft and an output shaft of the engine. In the arrangement of linking the motor with the drive shaft, the driving efficiency is improved in the under drive state where the revolving speed of the drive shaft is lower than the engine speed. In the arrangement of linking the motor with the output shaft of the engine, on the other hand, the driving efficiency is improved in the over drive state where the revolving speed of the drive shaft is higher than the engine speed. These characteristics are ascribed to the circulation of the power discussed below.
The process of power transmission when the motor is linked with the drive shaft is described with reference to
FIGS. 13 and 14
. In this example, an output shaft or crankshaft CS of an engine EG is linked with a drive shaft DS via a pair-rotor motor CM functioning as the power regulation unit, and an assist motor AM is connected with the drive shaft DS.
FIG. 13
shows a flow of power in the under drive condition that converts the power output from the engine EG to a combination of a lower revolving speed and a greater torque and causes the converted power to be output to the drive shaft DS. A power PU
1
output from the engine EG is transmitted as a power PU
2
having a lower revolving speed by the pair-rotor motor CM. There is a relative slide between two rotors in the pair-rotor motor CM, and electric power is generated according to a revolving speed difference between the two rotors. Part of the power PU
1
output from the engine EG is accordingly regenerated as an electric power EU
1
. The assist motor AM carries out the power operation with the regenerated electric power EU
1
to compensate for a deficiency of torque. A resulting power PU
3
output to the drive shaft DS accordingly has the required revolving speed and torque.
FIG. 14
shows a flow of power in the over drive condition that converts the power output from the engine EG to a combination of a higher revolving speed and a smaller torque and causes the converted power to be output to the drive shaft DS. The power PU
1
output from the engine EG is transmitted as a power PU
4
having a higher revolving speed by the pair-rotor motor CM, which carries out the power operation. The assist motor AM applies a load to compensate for a surplus of torque. A resulting power PU
5
output to the drive shaft DS accordingly has the required revolving speed and torque. The assist motor AM regenerates part of the power PU
4
as an electric power EU
2
, so as to apply the load. The regenerated electric power EU
2
is supplied to the pair-rotor motor CM.
In the under drive condition, the electric power regenerated by the pair-rotor motor CM positioned on the upstream is supplied to the assist motor AM positioned on the downstream in the course of transmitting the power output from the engine EG to the drive shaft DS. In the over drive condition, on the other hand, the electric power regenerated by the assist motor AM positioned on the downstream is supplied to the pair-rotor motor CM positioned on the upstream. The electric power supplied to the pair-rotor motor CM is again supplied as mechanical power to the assist motor AM positioned on the downstream. There is accordingly a power circulation &ggr;1 in the over drive condition as shown in FIG.
14
. The power circulation &ggr;1 reduces the percentage of the power effectively transmitted to the drive shaft DS to the power output from the engine EG, thereby lowering the driving efficiency of the hybrid vehicle.
The process of power transmission when the motor is linked with the output shaft of the engine is described with reference to
FIGS. 15 and 16
.
FIG. 15
shows a flow of power in the under drive condition, and
FIG. 16
shows a flow of power in the over drive condition. The phenomena observed under the condition of linkage of the motor with the output shaft are reverse to the phenomena under the condition of linkage of the motor with the drive shaft. In the under drive condition, an electric power EO
1
regenerated by the pair-rotor motor CM positioned on the downstream is supplied to the assist motor AM positioned on the upstream. In the over drive condition, on the other hand, an electric power EO
2
regenerated by the assist motor AM positioned on the upstream is supplied to the pair-rotor motor CM positioned on the downstream. There is accordingly a power circulation &ggr;2 in the under drive condition as shown in
FIG. 15
, in the case where the motor is linked with the output shaft of the engine. This lowers the driving efficiency of the hybrid vehicle.
By taking into account the above phenomena, a proposed hybrid vehicle has a power output apparatus mounted thereon, which enables the destination of linkage of the motor to be switched between the drive shaft and the output shaft of the engine (for example, the hybrid vehicle disclosed in JAPANESE PATENT LAID-OPEN GAZETTE No. 10-75501). The power output apparatus has a first clutch that allows engagement and disengagement between the motor and the output shaft of the engine and a second clutch that allows engagement and disengagement between the motor and the drive shaft. When the engine speed is higher than the revolving speed of the drive shaft, the first clutch disengages while the second clutch engages. This causes the motor to be linked with the drive shaft. When the engine speed is lower than the revolving speed of the drive shaft, on the contrary, the first clutch engages while the second clutch disengages. This causes the motor to be linked with the output shaft of the engine. This mechanism ensures the high driving efficiency both in the under drive condition and in the over drive condition.
In the proposed power output apparatus that changes the state of linkage of the motor, for the further improvement of the driving efficiency, the working point of the engine is set along a certain performance line where the highest efficiency of the engine attains, that is, the performance line attaining the optimum fuel consumption of the engine, both in the under drive condition and in the over drive condition.
In the under drive condition, it is accordingly required to raise the maximum load capacity of the motor and increase the maximum electric current of a
Kanamori Akihiko
Kawabata Yasutomo
Matsuhashi Shigeru
Takagi Nobuyoshi
Yamada Eiji
Gonzalez Julio C.
Oliff & Berridg,e PLC
Ramirez Nestor
Toyota Jidosha & Kabushiki Kaisha
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