Electricity: single generator systems – Automatic control of generator or driving means – Antihunting or rate of change
Reexamination Certificate
2000-12-22
2002-07-30
Ponomarenko, Nicholas (Department: 2834)
Electricity: single generator systems
Automatic control of generator or driving means
Antihunting or rate of change
C322S029000, C322S059000
Reexamination Certificate
active
06426609
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
The present invention is related to Japanese patent application No. Hei. 11-367125, filed Dec. 24, 1999; 2000-81610, filed Mar. 23, 2000 the contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates to a motor vehicle alternator, and more particularly, to a motor vehicle alternator that prevents hunting of the rotational speed of the engine during idle state.
BACKGROUND OF THE INVENTION
A decrease in rotational speed (hereinafter referred to as an idle rotational speed) of a motor vehicle alternator during vehicle idle will cause torque generated by the engine to be reduced. For this reason, the alternator drive torque (hereinafter also referred to as load torque) viewed from the engine will in turn increase due to the connection of an electrical load. For example, a large amount of starting current of a compressor drive motor is used for air conditioning within the vehicle. This will result in a hunting phenomenon in which the idle rotational speed becomes unstable and fluctuates.
Hunting of the rotational speed of the engine can cause the battery voltage to fluctuate more significantly, leading to various abnormal conditions and presenting a difficulty in maintaining idle operation or the like.
To prevent hunting of motor vehicle alternators of this type, various techniques have been conventionally suggested which allow adjustment of the control voltage according to a change in rotational speed.
Japanese Unexamined Patent Publication No. 7111, published 1979, suggested that the control voltage of an alternator should be reduced according to the rate of change in speed (a differential value) during deceleration of the engine (for negative differential values of rotational speed of the engine). On the other hand, during engine acceleration (for positive differential values of rotational speed of the engine), the voltage should be increased according to the rate of change in speed (a differential value).
Japanese Unexamined Patent Publication No. 87636, published 1985, applied for by the present inventor suggested that the amount of generated electricity should be kept below a predetermined value for a certain time during which the idle rotational speed recovered from the point of an increase in electrical load.
Japanese Patent Publication No. 55040 of 1994 applied for by the present inventor suggested that the control voltage should be increased in proportion to the degree of acceleration while increasing the rotational speed of the engine (under acceleration), while being delayed for a predetermined time relative to an increase in rotational speed of the engine.
Japanese Unexamined Patent Publication No. 327199, published 1997, suggested that a target voltage should be set to a certain low value less than a steady state target voltage during engine acceleration. On the other hand, during deceleration of the engine, the target voltage should be set to a certain high value higher than the steady state target voltage.
However, the following problems have been found to occur even with the aforementioned various prior-art techniques. First, these anti-hunting techniques change the control voltage of a regulator according to a change in rotational speed of the engine. Thus, the change of the rotational speed of the engine is associated with the change of the control voltage irrespective of the condition of the electric circuitry comprising the battery, electrical loads, and the alternator. For this reason, the condition of the electric circuitry was not taken into account and therefore the techniques were without validity in some cases. For example, it was not easy to take corrective action appropriately when the battery voltage recovered earlier than expected during acceleration or when the voltage recovered slower than expected due to a deep discharge regardless of substantial completion of acceleration. Furthermore, it was necessary to add signals such as a battery voltage to control parameters in addition to the aforementioned rotational speed of the engine, thus making the circuit processing complicated.
Furthermore, the aforementioned various conventional techniques provided a sudden variation in output or in drive torque (load torque) of the alternator during transitions of the rotational speed of the engine. The transitions include a transition from a steady state mode to a deceleration mode, a transition from the deceleration mode to an acceleration mode, and a transition near the point of completion of the acceleration mode. Such a sudden change in output of the alternator would cause a sudden change in torque and thereby a shock. The change would also readily cause heavy current charging to or heavy current discharging from batteries upon generation of high output, leading to a drop in charging efficiency or an increase in loss of power distribution.
SUMMARY OF THE INVENTION
In a first aspect of the invention, the controller sets the control voltage to an acceleration control voltage higher than the battery voltage by a predetermined voltage difference &Dgr;V1, within a range of voltages higher than the battery voltage and less than the steady state control voltage, during a acceleration during low speeds with the rotational speed being equal to or less than a predetermined value and a rate of increase in the rotational speed being equal to or greater than a predetermined value. This control can be called a mode for supressing rates of increase in battery voltage or a charge supression mode. Control of this type may be executed prior to control which employs the steady state control voltage as a control voltage, thereby preferably realizing control.
That is, according to this control, the control voltage is set higher than the battery voltage by a predetermined voltage difference &Dgr;V1 in the recovery process of the rotational speed of the engine. In this process, the rotational speed of the engine and the battery voltage are decreased due to the connection of electrical loads, and the rotational speed of the engine is increased due to an increase in fuel injection provided subsequently by the engine control system. Also, the predetermined voltage difference &Dgr;V1 ranges from 0.1V to 0.15V, and may be kept at a constant value during acceleration during low speeds. Alternatively, for example, the difference may be increased from the earlier stage to the later stage of acceleration during low speeds.
In another aspect, the control voltage is further set to a deceleration control voltage lower than the battery voltage by a predetermined voltage difference &Dgr;V2. This is carried out after the rotational speed of the engine has decreased below a first predetermined rotational speed value N1 within a period of deceleration during low speeds immediately preceding the aforementioned acceleration during low speeds. The control of this type can be referred to as a battery voltage drop adjustment mode or a discharge suppression mode which means not more than the suppression of discharge of the battery. Moreover, the control is desirably executed prior to the control which employs the steady state control voltage as a control voltage.
The predetermined voltage difference &Dgr;V2 ranges from 0.01V to 0.1V, and may be kept at a constant value during deceleration during low speeds. Alternatively, for example, the difference may be increased being operatively associated with a decrease in rotational speed of the engine or a drop in battery voltage.
That is, this arrangement employs a gradual decrease in control voltage during deceleration. This is carried out at the later stage of during deceleration during low speeds in which a smaller amount of the alternator output and torque produced by the engine is provided. The control voltage is thereby maintained to prevent the battery from being discharged while the rotational speed of the engine has decreased slightly and allowable power generation capacity is available at the earlier stage of during deceleration during low speeds. When the rotati
Sada Takeshi
Tanaka Koji
Taniguchi Makoto
Denso Corporation
Oliff & Berridg,e PLC
Ponomarenko Nicholas
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