Prime-mover dynamo plants – Electric control – Engine control
Reexamination Certificate
1997-10-27
2001-08-21
Enad, Elvin (Department: 2834)
Prime-mover dynamo plants
Electric control
Engine control
C290S04000F, C290S04000F, C290S04000F, C290S04000F, C290S04000F
Reexamination Certificate
active
06278195
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an engine controller, a power output apparatus, and methods of controlling an engine and the power output apparatus. More specifically the present invention pertains to a technique of stopping the operation of an engine in a system including the engine for outputting power through combustion of a fuel and a motor connected to an output shaft of the engine via a damper as well as to a technique of stopping the operation of an engine in a power output apparatus for outputting power to a drive shaft.
DESCRIPTION OF THE RELATED ART
Known power output apparatuses for carrying out torque conversion of power output from an engine and outputting the converted power to a drive shaft include a combination of a fluid-based torque converter with a transmission. In such a power output apparatus, the torque converter is disposed between an output shaft of the engine and a rotating shaft linked with the transmission, and transmits the power between the rotating shaft and the output shaft through a flow of the sealed fluid. Since the torque converter transmits the power through a flow of the fluid, there is a slip between the output shaft and the rotating shaft, which leads to an energy loss corresponding to the slip. The energy loss is expressed as the product of the revolving speed difference between the rotating shaft and the output shaft and the torque transmitted to the output shaft, and is consumed as heat.
In a vehicle with such a power output apparatus mounted thereon as its power source, at the time when there is a large slip between the rotating shaft and the output shaft, that is, when a significantly large power is required, for example, at the time of starting the vehicle or running the vehicle on an upward slope at a low speed, a large energy loss in the torque converter undesirably lowers the energy efficiency. Even in a stationary driving state, the efficiency of power transmission by the torque converter is not 100%, and the fuel consumption rate in the conventional power output apparatus is thereby lower than that in a manual transmission.
In order to solve such problems, the applicants have proposed a system that does not include the fluid-based torque converter but has an engine, a planetary gear unit as three shaft-type power input/output means, a generator, a motor, and a battery and outputs the power from the motor to the drive shaft by utilizing the power output from the engine or electric power stored in the battery (JAPANESE PATENT LAYING-OPEN GAZETTE No. 50-30223). In this reference, however, there is no description of the control procedure when the operation of the engine is stopped.
In this power output apparatus, the output shaft of the engine and the rotating shaft of the motor are mechanically linked with each other by the three shaft-type power input/output means, and thus mechanically constitute one vibrating system. When the engine is an internal combustion engine, for example, a torque variation due to a gas explosion or reciprocating motions of the piston in the internal combustion engine causes torsional vibrations on the output shaft of the internal combustion engine and the rotating shaft of the motor. When the natural frequency of the shaft coincides with the forcible frequency, a resonance occurs. This may result in a foreign noise from the three shaft-type power input/output means and even in a fatigue destruction of the shaft in some cases. Such a resonance occurs in many cases at a revolving speed lower than the minimum of an operable revolving speed range of the engine, although it depends upon the type of the engine and the structure of the three shaft-type power input/output means.
The resonance of the torsional vibrations that may occur in the system at the time of stopping the operation of the engine is observed not only in the power output apparatus but in any driving system, wherein the output shaft of the engine and the rotating shaft of the motor are mechanically linked with each other. The primary countermeasure against these troubles is that the output shaft of the engine and the rotating shaft of the motor are mechanically linked with each other via a damper. The dampers having a significant effect on reduction of the amplitude of the torsional vibrations, however, require a special damping mechanism. This increases the required number of parts and makes the damper undesirably bulky. The small-sized simply-structured dampers, on the other hand, have little effects.
The motor is generally under the PI control. In the procedure of outputting a torque from the motor to the output shaft of the engine and thereby positively stopping the operation of the engine, the I term (integral term) may result in undershooting the output shaft of the engine, which causes a vibration of the whole driving system. When the driving system is mounted, for example, on a vehicle, the vibration due to undershooting is transmitted to the vehicle body and makes the driver uncomfortable.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a power output apparatus for outputting power from an engine to a drive shaft with a high efficiency, as well as a method of controlling such a power output apparatus.
Another object of the present invention is to provide a control technique of stopping the operation of an engine in a power output apparatus, which includes the engine, three shaft-type power input/output means, and two motors.
Still another object of the invention is to provide a power output apparatus which can prevent a resonance of torsional vibrations that may occur in the system when the operation of the engine is stopped, as well as to provide a method of controlling such a power output apparatus.
In the process of applying a torque from the motor to the output shaft of the engine to stop the operation of the engine, the control procedure of the motor may cause the revolving speed of the output shaft of the engine to undershoot and become smaller than zero. This may result in undesirable vibrations of the whole power output apparatus. In case that the power output apparatus is mounted on a vehicle, for example, the vibrations due to the undershoot are transmitted to the vehicle body and makes the driver uncomfortable.
This problem, that is, the resonance of torsional vibrations that may occur in the system in the course of stopping the operation of the engine, is not restricted to the power output apparatus, but arises in any driving system wherein the output shaft of the engine and the rotating shaft of the motor are mechanically connected to each other. The primary countermeasure against this problem is that the output shaft of the engine and the rotating shaft of the motor are mechanically linked with each other via a damper. The dampers having a significant effect on reduction of the amplitude of the torsional vibrations, however, require a special damping mechanism. This increases the required number of parts and makes the damper undesirably bulky. The small-sized simply-structured dampers, on the other hand, have little effects.
This problem is found not only in the structure that directly outputs power but in the structure of series hybrid that has a motor and a generator directly connected to each other and obtains a torque by the motor driven by means of the electric power generated by the generator while the vehicle is on a run.
A further object of the present invention is thus to provide a power output apparatus that prevents resonance of torsional vibrations which may occur in a system in the course of stopping the operation of an engine, as well as a method of controlling such a power output apparatus.
Another object of the present invention is accordingly to reduce vibrations that may occur in the course of stopping the operation of an engine.
Still another object of the present invention is thus to provide an engine controller that prevents resonance of torsional vibrations which may occur in a system in the course of stopping the operation of an engine, irrespecti
Kanai Hiroshi
Kotani Takeshi
Sasaki Shoichi
Takaoka Toshifumi
Yamaguchi Katsuhiko
Enad Elvin
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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