JP2002095177A - Alternating current generator for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost AC generator for vehicles. SOLUTION: The AC generator for vehicles is provided with a rotor having a field coil 21, a stator having armature coils 32, a rectifier unit 6, and a voltage controller 7 which comprises a voltage lowering circuit 71 and an excitation control circuit 72. The lowering circuit 71 lowers a high-voltage output of 42 V generated by the rectifier unit 6, and generates a low-voltage output of 14 V. This low-voltage output is taken out to the outside through a low-voltage output terminal 62, and is applied to the excitation circuit 72. The excitation circuit 72 intermittently applies the low voltage of 14 V applied from the lowering circuit 71 to the field coil 21, controls its exciting current, and adjusts the terminal voltage of a battery connected to the output terminal 62 to a specified value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alternator for a vehicle which is mounted on a passenger car, a truck or the like and is used for charging a battery.

[0002]

2. Description of the Related Art A general automotive alternator has an output voltage of about 14 V, and a field winding provided on a rotor usually has a voltage of 3 V.
The number of turns is about 00 to 500 times, and
This is very large compared to the number of turns of ~ 8. In particular, the number of turns of the field winding of the vehicular alternator that generates high voltage with an output voltage of about 42 V depends on the field winding used in the vehicular alternator with an output voltage of about 14 V. The number of turns is several times larger than the number of turns.

[0003] Some electric loads used in vehicles, for example, electric bulbs, need to be connected to a low-voltage power supply because a high voltage of 42 V shortens the life of the filament. For this reason, even when a vehicle AC generator having an output voltage of 42 V is provided, a method of reducing the output voltage using a DC-DC converter and applying the voltage to some electric loads is used. Has been adopted,
A voltage of about 14 V similar to that of a general automotive alternator is applied.

[0004]

By the way, as described above, the number of turns of the field winding of the vehicle alternator having a high output voltage is the same as that of a normal vehicle alternator having an output voltage of about 14V. Since the number of windings is extremely large compared to the number of windings, it takes a lot of time to manufacture this field winding, even if it is wound at a high speed with a winding machine, thus reducing manufacturing costs. There was a problem that it was difficult.

Further, it is necessary to provide a DC-DC converter separately from a vehicle generator. However, since the DC-DC converter is generally expensive, there is a problem that the cost of parts increases.

The present invention has been made in view of the above points, and an object of the present invention is to provide an automotive alternator capable of reducing costs.

[0007]

In order to solve the above-mentioned problems, an automotive alternator according to the present invention includes a rotor, a stator, a rectifier, and a voltage controller. The output voltage is controlled by applying a reduced voltage of the output voltage of the rectifier to the field winding of the rotor. Since the output voltage is stepped down and applied to the field winding, an appropriate excitation current can be realized with the field winding having a small number of turns. This makes it possible to reduce the manufacturing time and manufacturing cost when manufacturing the field winding.

Further, the above-mentioned voltage controller includes a step-down circuit for generating a voltage obtained by stepping down the output voltage, and an excitation control circuit which applies the stepped-down voltage to the field winding to flow an excitation current. It is desirable to take out the voltage generated by the step-down circuit as a low output voltage. By taking out and using the voltage obtained by stepping down the output voltage to be applied to the field winding, it is not necessary to provide a separate DC-DC converter for a part of the electric load, thereby enabling cost reduction. Become.

Further, it is desirable that the above-mentioned step-down circuit generates a low output voltage by performing pulse width modulation on the output voltage of the rectifier. As a result, the output voltage of the rectifier can be efficiently converted to a low output voltage, and the loss that occurs during this conversion can be minimized.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vehicle AC generator according to an embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an AC generator 1 for a vehicle according to an embodiment.
FIG. 3 is a diagram showing the configuration of FIG. FIG. 2 is a diagram showing a circuit configuration of the automotive alternator 1 of the present embodiment.

As shown in FIGS. 1 and 2, an automotive alternator 1 of the present embodiment includes a rotor 2, a stator 3, a frame 4, a brush device 5, a rectifier 6, and a voltage controller 7. It is configured.

The rotor 2 has a field winding 21 formed by winding an insulated copper wire in a cylindrical and concentric manner, and two field windings 21 that sandwich the field winding 21 along both sides of a rotation shaft 22. Field iron cores 23 and 24 are provided. In the vicinity of the end of the rotating shaft 22 on the side opposite to the pulley, two slip rings 25 and 26 respectively provided at both ends of the field winding 21 are provided. The excitation current is supplied to the winding 21.

The stator 3 includes a stator core 31 and a three-phase armature winding 32 wound around a plurality of slots having openings on the inner peripheral side of the stator core 31. The armature winding 32 is configured by commonly connecting one end of each of the X-phase, Y-phase, and Z-phase windings, and the common connection end serves as a neutral point.

The frame 4 houses the rotor 2 and the stator 3 described above. The rotor 2 is supported so as to be rotatable about a rotation shaft 21, and the field iron core of the rotor 2. The stator 3 arranged outside of 23 and 24 via a predetermined gap is fixed.

The brush device 5 has brushes 51 and 52. By pressing these brushes 51 and 52 against slip rings 25 and 26 provided on the rotating shaft 22,
The above-described excitation current is supplied.

The rectifier 6 is a three-phase full-wave rectifier circuit for converting an AC output induced in the three-phase armature winding 32 into a DC output. The rectifier 6 includes three anode-side diodes connected in common to the anode. , And three diodes on the positive electrode side to which the cathode is connected in common. The cathodes of the three diodes on the positive electrode side described above are connected to the high voltage output terminal 61.
It is connected to the.

The voltage controller 7 controls the output voltage of the vehicle alternator 1 by controlling the exciting current of the field winding 21. In the present embodiment, the output voltage is controlled to about 42V. The voltage controller 7 has a step-down circuit 71, an excitation control circuit 72, and a flywheel diode 73.

The step-down circuit 71 has a duty ratio of 33% for an output voltage of about 42 V appearing at the high voltage output terminal 6.
Is a switching circuit that performs PWM (Pulse Width Modulation) control, and generates a low voltage of 14 V by reducing the output voltage (42 V) to １ ／ by this PWM control. The output terminal of the step-down circuit 71 is connected to the excitation control circuit 72 and also to the low voltage output terminal 62.

The excitation control circuit 72 controls the output voltage by adjusting the excitation current by interrupting the operation of applying the voltage (14 V) generated by the step-down circuit 71 to the field winding 21. Specifically, the excitation control circuit 72 has a function of detecting a terminal voltage of a battery (not shown) connected to the low-voltage output terminal 62, and compares the detected terminal voltage with a predetermined adjustment voltage set value. And a function of controlling the duty ratio of the voltage applied from the step-down circuit 71 to the field winding 21 according to the comparison result. These functions provided in the excitation control circuit 72 are basically the same as the functions of the voltage controller of the automotive alternator having the output voltage of 14V.

As described above, the excitation control circuit 72 included in the voltage controller 7 of the present embodiment controls the excitation current of the field winding 21 so that the terminal voltage of the battery becomes a predetermined adjustment voltage set value. With this control, the high voltage output terminal 6
An output voltage of 1 to 42 V can be obtained, and an output voltage of 14 V can be obtained from the low voltage output terminal 62. Therefore, DC-
Without a DC converter, the low voltage output terminal 62
Output power can be directly supplied to some electric loads that require low-voltage driving, and the cost of parts can be reduced.

The excitation control circuit 72 in the voltage controller 7
The low voltage (14) generated by the step-down circuit 71
V) is applied, and this voltage is applied to the field winding 21. Therefore, compared to the conventional field winding in which a high voltage (42V) is directly applied to the field winding, Therefore, the number of turns of the field winding 21 of the present embodiment can be significantly reduced,
Manufacturing time can be reduced by shortening the time required for the winding process. For example, assuming that the same ampere-turn as that of a field winding used in a conventional vehicular alternator with an output voltage of 42 V is realized, the number of turns is approximately 900, and the number of turns is approximately 300, which is 1/3. Can be reduced.

In this embodiment, since the voltage of 42 V is reduced to 14 V by performing PWM control by the voltage lowering circuit 71, it is possible to suppress the occurrence of loss at the time of voltage reduction.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention. For example, in the above embodiment, 42V
Although a high voltage output and a low voltage output of 14 V are obtained, the combination is arbitrary, and the value of one or both output voltages may be changed. In this case,
The duty ratio of the PWM control in the step-down circuit 71 may be adjusted to the voltage ratio between the low voltage output and the high voltage output.

When the low voltage output is not always necessary, the low voltage output terminal is omitted and the high voltage output terminal 6
Only one may be formed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a vehicle alternator according to an embodiment.

FIG. 2 is a diagram showing a circuit configuration of the vehicle alternator shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vehicle alternator 2 Rotor 3 Stator 5 Brush device 6 Rectifier 7 Voltage controller 21 Field winding 32 Armature winding 61 High voltage output terminal 62 Low voltage output terminal 71 Step-down circuit 72 Excitation control circuit

Claims (3)

[Claims] 1. A rotor having a field winding, a stator having an armature winding, a rectifier for converting an AC output of the armature winding into a DC, and a voltage obtained by reducing an output voltage of the rectifier. And a voltage controller that controls the output voltage by applying a voltage to the field winding. 2. The field winding according to claim 1, wherein the voltage controller includes: a step-down circuit that generates a voltage obtained by stepping down an output voltage of the rectifier; and a voltage generated by the step-down circuit. And an excitation control circuit for supplying an excitation current to the AC generator, wherein the voltage generated by the step-down circuit is taken out as a low output voltage. 3. The automotive alternator according to claim 2, wherein the step-down circuit generates the low output voltage by performing pulse width modulation on an output voltage of the rectifier.