Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1983-04-07
1984-11-13
Miller, J. D.
Electrical generator or motor structure
Dynamoelectric
Rotary
310 60R, 310 68D, H02K 906, H02K 4724
Patent
active
044828306
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an electric generator for a vehicle having an increased cooling airflow obtained by increasing the number of rotations of the cooling fan in order to improve the ability to cool the electric generator.
BACKGROUND ART
Electric generators for vehicles have rotors generally driven by the vehicle engine, and a cooling fan for the electric generator is fixed to this rotor. The airflow from the cooling fan is increased in proportion to the rotational speed. A low rate of electric generation has been unobtainable because a sufficient airflow for cooling the generator cannot be obtained in a region in which the speed of rotation of the engine is low (and therefore in a region of low speed of the electric generator). By raising the ratio of the speed of the electric generator to that of the engine, the airflow can be increased in a low speed region but the cooling fan becomes too noisy to be practical in the high speed region.
As a method of reducing the noise of a cooling fan in a region of high speed of rotation, there are proposed electromagnetic couplings, as disclosed in Japanese laid-open utility model application No. 109,808/1975, but the airflow in the low speed region cannot be increased because the rotary magnetic field is imparted by the rotor of the electric generator.
A conventional device of the type referred to will be described with respect to FIGS. 1 and 2. First in FIG. 1 a stator 1 having a three-phase armature winding wound thereon has mounted therein a rotor 2 having a field winding wound thereon which is opposed to the stator across a minute gap in the diametrical direction. A rotary shaft 21 is fixed to this rotor, a pulley 3 is fixed to this rotary shaft, a cooling fan 5 is fixed to the rotary shaft integral with this pulley, a bracket 6 is provided for journalling rotary shaft 21 through a bearing 4, a voltage regulator 9 is provided for holding the output voltage from armature winding 15 constant, and rectifier 10 is provided for rectifying the AC output induced in the armature winding.
As well known, in the conventional device constructed in this way, upon starting the engine, the rotary shaft 21 is driven to rotate the rotor 2. Thus a three-phase AC voltage is induced in the armature winding and that AC voltage is rectified through rectifier 10 and supplied to a battery or a load not shown. Also the output voltage from the armature winding is held at a constant magnitude by means of the voltage regulator.
Also since the cooling fan 5 is rotated with the rotor 2, a cooling airflow is caused to pass through the electric generator to cool it.
However, conventional cooling fan 5 has been disadvantageous in that the airflow is small in the low speed region of the engine and in the high speed region of the engine, the airflow is sufficient but it becomes too noisy.
A conventional device for eliminating this disadvantage is shown in FIG. 2. In FIG. 2 a permanent magnet 51 is provided which functions as an inductor for an electromagnetic coupling and which has adjacent magnetic poles on the perimeter of a circle which are different in polarity from each other, the magnet being fixed to said cooling fan 5. A magnetic plate 8 is mounted on pulley 3 opposed to permanent magnet 51 across a minute gap in the diametrical direction and serves as an induced member for the electromagnetic coupling.
The cooling fan 5 in this conventional example is caused to be freely rotated independently of the rotary shaft 21 and the rotational speed is constant when the torque of the electromagnetic coupling, composed of the permanent magnet 51 forming a rotary magnetic field, with the magnetic plate 8 fixed to the rotor shaft 21, is in accord with the torque due to the air pressure of the cooling fan. This conventional arrangement produces an improvement in the noise of the cooling fan 5 in the high speed region but the airflow from the cooling fan 5 in the low speed range does not increase as compared with the conventional arrangement shown in FIG. 1. Thus it does not re
REFERENCES:
patent: 2586452 (1952-02-01), Aske
patent: 2613240 (1952-10-01), Robinson
patent: 2827855 (1958-03-01), Rankin
patent: 3142772 (1964-07-01), Jones
patent: 3586938 (1971-06-01), LeGall
patent: 3670190 (1972-06-01), Goebel
patent: 4164852 (1979-08-01), Anzalone
Iwaki Yoshiyuki
Matsumoto Akio
Miller J. D.
Mitsubishi Denki & Kabushiki Kaisha
Rebsch D. L.
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