Prime-mover dynamo plants – Electric control – Engine control
Reexamination Certificate
2001-12-19
2004-03-30
Nguyen, Tran (Department: 2834)
Prime-mover dynamo plants
Electric control
Engine control
C290S04000F, C290S04000F, C290S04000F, C290S04000F, C290S04000F, C322S014000, C322S016000
Reexamination Certificate
active
06713888
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to a type of rotary electrical device of the type known as a synchronous machine, and in particular to a synchronous machine for use in a vehicle motor-generator apparatus that is controllable for selectively performing electric motor and electric power generation functions.
2. Description of Prior Art
There have been proposals made in the prior art to use a synchronous machine of the type having a field winding in a motor-generator apparatus of a vehicle which is driven by an internal combustion engine (referred to in the following simply as the engine), so that a single rotary electrical device can be employed as a motor for the purpose of starting the engine and also as a generator (driven from the engine) for supplying electric power for charging the vehicle battery while the engine is running. Alternatively, such a vehicle motor-generator apparatus could also be utilized to provide electrically driven motive power when required, in the case of a hybrid type of motor vehicle.
However with such an apparatus, a worst-case operating condition occurs when the engine is halted immediately after the vehicle motor-generator apparatus has been running in a condition in which it is generate a substantial level of electric power (so that the synchronous machine is at a high temperature), and the engine is then restarted shortly after having been halted, so that a high level of current must be passed through the field winding of the synchronous machine under a condition of low speed of rotation. As a result, the maximum allowable temperature of the field winding may be exceeded, so that insulation breakdown or deterioration may occur. Such a condition may occur relatively frequently for example when the vehicle operates in an “idling halt” mode, whereby the engine is halted automatically under certain conditions.
It is necessary to design such a vehicle motor-generator apparatus such that the maximum allowable temperature of the field winding will not be exceeded even under the worst-case condition described above, when operating under the maximum anticipated ambient temperature. For that reason, it has been necessary for the size and weight of the synchronous machine used in such a vehicle motor-generator apparatus to be substantially greater than that of a conventional vehicle generator, having only an electric power generating function.
However it is undesirable to have to design such a vehicle motor-generator apparatus on the basis of thermal conditions which occur when the apparatus must supply a large amount of torque during a very short time interval, for the purpose of starting the vehicle engine, since in that case the thermal capacity of the vehicle motor-generator apparatus will be greatly in excess of that which is necessary during the majority of the time that the apparatus is operated, i.e., the configuration of the synchronous machine of the vehicle motor-generator apparatus will be excessively large and heavy.
Furthermore an important parameter of such a vehicle motor-generator apparatus is the time interval which must elapse, after the vehicle engine has been halted, between the issuance of an “engine start” command to the control section of the vehicle motor-generator apparatus (i.e., when the ignition switch of the vehicle is actuated) and the time point at which the engine then actually is started. In the prior art, the problem exists that the field winding of the synchronous machine of the vehicle motor-generator apparatus has a substantial amount of inductance, so that a significant amount of time is required for current build-up to occur in the field winding to achieve sufficient torque to initiate engine starting, and this increases the amount of time required to effect starting of the engine.
One objective of the present invention therefore is to provide a vehicle motor-generator apparatus whereby the size and weight of the synchronous machine used in the vehicle motor-generator apparatus can be reduced by comparison with the prior art, while a further objective is to reduce the amount of time required to perform engine starting, by such a vehicle motor-generator apparatus.
Moreover, in Japanese patent HEI 8-214470 a field winding type of synchronous machine is described whereby a phase-advanced AC current, supplied from a power inverter (i.e., a DC-AC and AC-DC converter), is caused to flow in the armature winding of the synchronous machine when the synchronous machine operates to generate electric power. This enables a higher level of generated electric power to be attained when the synchronous machine is driven at a low speed of rotation, by comparison with a conventional type of vehicle generator apparatus which applies only DC rectification to the AC output voltage from the synchronous machine.
Furthermore, such a method can also enable increased efficiency of electric power generation to be achieved when the synchronous machine is driven at a high speed of rotation, by utilizing field control.
However in the prior art it has been necessary to provide such devices as power MOS transistors as switching elements, for supplying the phase-advanced current to the armature winding of the synchronous machine. As a result, the circuit cost becomes higher than in the case of an apparatus which uses only diode rectifiers. Furthermore due to the use of phase-advanced current supply to the armature winding of the synchronous machine, a lowering of efficiency occurs because of increased resistive losses in the armature winding and increased generation of heat, so that the requirements for cooling the armature winding become more stringent.
Furthermore in Japanese patent HEI 10-30463, a synchronous machine is disclosed which is of the type having a field winding and having permanent magnets embedded in the rotor, whereby the effective magnetic flux in the rotor can be controlled such as to eliminate the need to produce a weak flow of current in the armature winding when the synchronous machine is operated at a high speed of rotation, i.e., a flow of current for the purpose of preventing an excessively high level of voltage being generated due to the magnetic fields of the permanent magnets under such a condition of high speed of rotation. Furthermore, with that synchronous machine, even if armature current control becomes ineffective when the synchronous machine is operated at a high speed of rotation, the magnetic flux of the permanent magnets is shunted in such a way that high stability is ensured. That type of synchronous machine will be referred to in the following as a combination permanent magnet and field winding synchronous machine of magnetic shunt type.
However with such a prior art combination permanent magnet and field winding synchronous machine of magnetic shunt type, since the magnetic circuit is complex, there is a high degree of magnetic reluctance in the magnetic circuit, so that the device becomes large in scale in relation to its electric power generating capability.
It is therefore another objective of the present invention to overcome the above disadvantage, by providing a combination permanent magnet and field winding synchronous machine of magnetic shunt type, for use in a vehicle motor-generator apparatus, which maintains a high degree of suppression of the adverse effects of magnetic flux during operation at a high speed of rotation, while the levels of generated torque and output power are increased in relation to the size of the machine. The suitability of such a synchronous machine for use in a vehicle motor-generator apparatus can thereby be increased.
SUMMARY OF THE INVENTION
With the present invention, the various objectives summarized above are attained as follows.
According to a first aspect, the invention provides a vehicle motor-generator apparatus comprising a field winding type of synchronous machine, an AC-to-DC and DC-to-AC power converter which converts the DC voltage of a battery of the vehicle to an AC voltage, to thereby supply an AC armature cu
Cuevas Pedro J.
Denso Corporation
Nguyen Tran
LandOfFree
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