JPH1169741A - Ac three-phase generator for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the ripple voltage and the noise incident thereto while suppressing increase in the size and weight of a generator and to suppress claw-pole resonance noise of a generator. SOLUTION: Neutral 14 of a three-phase armature winding 1 is connected only with any one of the high or low output end 34, 35 of a three-phase full- wave rectifier 3 through a neutral current rectifying element 14. More specifically, one of a pair of neutral diodes is eliminated in a conventional generator with neutral diode. According to the structure, the ripple voltage and the noise incident thereto are reduced while suppressing increase in the size and weight of the generator. Furthermore, claw-pole resonance noise of the generator can be suppressed and one neutral diode can be eliminated from a generator provided with neutral diodes on the opposite sides.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a three-phase AC generator for a vehicle having a three-phase full-wave rectifier.

[0002]

2. Description of the Related Art For example, Japanese Patent Laying-Open No. 58-218873 discloses a three-phase full-wave rectifier for full-wave rectifying a three-phase AC voltage output from each output terminal of a star-connected three-phase armature winding. In a three-phase AC generator for a vehicle having a rectifying element for neutral point current rectification between a high output terminal and a low output terminal of a three-phase full-wave rectifier and a neutral point of a three-phase armature winding, A three-phase AC generator for a vehicle (hereinafter also referred to as a generator with a neutral diode) connected by a neutral diode is disclosed.

[0003] This generator with a neutral point diode uses only a three-phase full-wave rectifier and does not use a neutral point diode. (Hereinafter also referred to as ")", the ripple current component can be output through the neutral diode, so that the ripple voltage component superimposed on the output DC voltage increases to some extent, but the output current can be improved without increasing the size of the generator. It is an excellent feature and is now widely used.

[0004]

In recent years, it has been desired to improve vehicle quietness. However, it has been found that when the generator with the neutral diode is used under a certain range of engine speed, the electric load, particularly the noise of a motor mounted on a vehicle, may be significantly increased.

[0005] This problem is solved when a neutral diodeless generator is used in place of the neutral diode generator, and is considered to be caused by the ripple voltage of the neutral diode generator. In other words, it has been found that this is due to a resonance phenomenon between a fundamental frequency component of a ripple voltage during a certain rotation of the generator and a combined impedance from the generator to the motor.

In order to reduce the noise caused by the ripple voltage, it is of course possible to employ the original neutral point diodeless generator. However, due to the recent increase in the electric load for vehicles, the maximum output of the three-phase AC generator for vehicles has to be increased, and in order to secure the necessary output with the neutral point diodeless generator, the generator size, A considerable increase in weight and cost were required.

On the other hand, when a neutral diodeless generator is used, the claw-shaped magnetic pole of the generator resonates,
It has been confirmed that the amount of noise generation sharply increases in a certain high-speed rotation range. Although the detailed reason why the claw-shaped magnetic pole resonance occurs only in the neutral diodeless generator is unknown, the inventors have found that the ripple voltage generated from the neutral diodeless generator as a whole is Is believed to be due to the fact that the ripple voltage contains high frequency components (in peak or squared integral values) that are less than generators with neutral point diodes but that cause the claw poles to magnetically resonate.

Therefore, conventionally, when a neutral point diodeless generator is employed, the possibility of generating claw-shaped magnetic pole noise of the generator increases, and the size and weight of the generator increase. There has been a problem that an increase in ripple voltage using a generator with a diode and the occurrence or possibility of motor noise due to this increase. The present invention has been made in view of these problems, and while suppressing an increase in the size and weight of the generator, reducing the ripple voltage and the noise caused thereby, and reducing the claw-shaped magnetic pole resonance noise of the generator. Deterrence is an issue to be solved.

[0009]

According to the first aspect of the present invention, the neutral point of the three-phase armature winding is only one of the higher output terminal and the lower output terminal of the three-phase full-wave rectifier. Is connected to a rectifying element for neutral point current rectification. That is, in this means, one of the pair of neutral point diodes is omitted in the conventional generator with a neutral point diode. Hereinafter, the generator of this configuration having a neutral diode only on one side is also referred to as a generator with a neutral diode on one side, and a generator with a neutral diode on both sides has a neutral diode to distinguish it. Also called a generator.

In this manner, it is possible to reduce the ripple voltage and the noise caused by the ripple voltage while suppressing the increase in the size and weight of the generator, and also to suppress the claw-shaped magnetic pole resonance noise of the generator. Hereinafter, this will be described in more detail.
First, comparing the ripple voltage (especially the PP value or the squared integral value), the ripple voltage of the generator with one-sided neutral point diode of this configuration is smaller than that of the generator with two-sided neutral point diode. Larger than the neutral diodeless generator, which is the expected result.

However, it has been found that the waveform of the ripple voltage of the generator with the one-sided neutral diode is greatly different from that of the generator with the two-sided neutral diode. That is, the ripple voltage waveform output from the generator with the neutral diode on both sides has a very large fundamental frequency component, which is a function of the number of poles of the generator and the number of revolutions thereof. When the resonance frequency of the impedance of (2) approaches the fundamental frequency, there is a possibility that a large resonance noise is generated.

On the other hand, the ripple voltage waveform of the generator with one-sided neutral point diode has a smaller PP value and the squared integral value (corresponding to ripple power) than that of the generator with two-sided neutral point diode. In addition, the peak of every other peak of the ripple voltage waveform is small, so that the ripple voltage or the ripple power has a wide frequency (particularly, 2 to 5).
It was found that the waveform was dispersed in (double frequency component). For this reason, in a generator with a one-sided neutral diode, the ripple voltage concentrates on a certain frequency component (fundamental frequency component) as in a generator with a two-sided neutral diode. It has been found that the problem that large motor electromagnetic noise occurs in the approaching rotational speed region can be suppressed.

Next, comparing the maximum output current value, it is obvious that the maximum output current value of the generator with one-sided neutral point diode of this configuration is smaller than that of the generator with two-sided neutral point diode. Is the expected result,
Contrary to expectations, the amount of the drop was much smaller than expected (half the difference between the maximum output current of the generator with a two-sided neutral diode and the maximum output current of the neutral diodeless generator).

Regarding this result, the present inventors have found that the generator with one-sided neutral point diode has a larger neutral point potential fluctuation amount than the generator with one-sided neutral point diode.
It is estimated that this is because the amount of current output through the neutral point diode increases by that amount. Therefore, if a generator with a one-sided neutral diode is adopted, the ripple voltage can be reduced without significantly increasing its size and weight, and more specifically, the ripple voltage concentrated on a specific frequency component can be reduced. It is possible to realize a favorable effect and a reduction in resonance electromagnetic noise of a motor as an electric load.

Next, a comparison of the claw-shaped magnetic pole resonance noise of the generator shows that the claw-shaped magnetic pole resonance that conventionally occurred in the neutral diodeless generator and did not occur in the generator with the neutral diode on both sides is as follows. From the experiments, it was found that this configuration did not occur even in the generator with one-sided neutral diode. The reason why the claw-shaped magnetic pole resonance of the generator occurs only in this neutral point diodeless generator is that the ripple voltage generated from the neutral point diodeless generator is neutral on both sides when viewed from the peak value or the square integral value. Although the frequency is much less than a generator with a point diode or a generator with a one-sided neutral diode, a high frequency component that causes the claw-shaped magnetic pole to resonate magnetically (the number of The present inventors presume that the noise ripple voltage is included when the claw-shaped magnetic pole resonance occurs due to the large claw-shaped magnetic pole resonance.

In the generator with the one-sided neutral diode of the present configuration, the ripple voltage waveform of the generator with the two-sided neutral diode and the unique ripple voltage intermediate between that of the neutral-point diodeless generator. Since the waveform becomes a waveform, the ripple power is more concentrated than the neutral point diodeless generator on the fundamental frequency component or low-order harmonic component, and the power (square integral value) is concentrated. It is presumed that the high frequency component is conversely smaller than that of the neutral point diodeless generator, thereby suppressing the claw-shaped magnetic pole resonance noise.

As a result, according to the generator with a one-sided neutral point diode of this configuration, the ripple voltage can be reduced without increasing the size and weight of the generator, and more specifically, the ripple voltage concentrated on a specific frequency component can be reduced. Therefore, it is possible to achieve a favorable effect on the battery and a reduction in resonance electromagnetic noise of the motor which is an electric load, and furthermore, a reduction in claw-shaped magnetic pole resonance noise, a generator with a neutral diode on both sides. It is possible to reduce the number of components for one neutral point diode.

According to a second aspect of the present invention, there is provided the vehicle three-phase AC generator according to the first aspect, further comprising a rectifying element for neutral point current rectification together with a rectifying element constituting the three-phase full-wave rectifier. Are housed in the air passage of the cooling fan in the housing of the generator, i.e. in the passage of the air flow generated by the cooling fan. With this configuration, the following operation and effect can be obtained.

In a generator with a neutral diode on both sides, a total of eight rectifying elements must be accommodated in this air passage for cooling the generator. It suffices to house the rectifying elements. Although the required space of the rectifying element itself is not so large, the cooling fin structure becomes complicated and large due to the necessity of cooling. It is not impossible to adopt a mounting cooling structure that does not require cooling fins, but in that case, the location of each rectifying element in the air passage to apply sufficient cooling airflow to the rectifying element, that is, the neutral diode. Is a problem.

In this configuration, since the number of rectifying elements requiring cooling can be reduced, the rectifying elements in the air passage can be freely placed in the air passage, and the cooling performance is improved.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the following examples. (Embodiment) FIG. 1 is a partially cutaway axial sectional view of a vehicle three-phase AC generator of this embodiment, and FIG. 2 is a circuit diagram thereof.
This will be described with reference to FIG.

The three-phase AC generator for a vehicle has a star-connected three-phase armature winding 1 composed of armature windings 11 to 13 and an exciting coil 2. The output terminals of the armature windings 11 to 13 are The three-phase full-wave rectifier (three-phase full-wave rectifier) 3 is connected to each AC terminal (connection point) 31 to 33, and the high output terminal 34 and the low output terminal 35 of the three-phase full-wave rectifier 3 are connected to both ends of the battery 4. To the blower motor 6 through the switch 5. The three-phase full-wave rectifier 3 is formed by connecting six junction diodes in a three-phase bridge, and performs full-wave rectification of a three-phase AC voltage. The exciting coil 2 is excited by the exciting current supplied from the regulator 7 to generate a magnetic flux, and causes the three-phase armature winding 1 to generate a three-phase AC voltage. Reference numeral 71 denotes a common-emitter transistor for PWM-controlling an exciting current supplied to the exciting coil, and 72 denotes a flywheel diode. The regulator 7 has the same configuration as that of the conventional regulator, and controls the exciting current by intermittently controlling the transistor 71 in accordance with the level of the voltage (B voltage) of the battery 4, whereby the armature windings 11 to 13 are controlled. Is controlled so that the voltage B becomes a predetermined level. Since this control operation is well known, further description is omitted.

This embodiment is particularly characterized in that the neutral point 14 of the three-phase armature winding 1 and the lower output terminal 35 of the three-phase full-wave rectifier 3 are connected by the neutral point diode 8. The neutral diode 8 comprises a silicon diode, the anode of which is connected to the lower output 35 and the cathode of which is connected to the neutral 14. In FIG.
Reference numeral 91 denotes a claw-shaped magnetic pole, and reference numeral 10 denotes a housing of a three-phase AC generator for a vehicle.

When this three-phase alternator for a vehicle is operated,
If the potential at the neutral point 14 of the three-phase armature winding 1 is going to fall below the ground potential by more than the forward voltage drop of the diode, this is prevented.
To 13 are generated, and the output current is increased. More generally, in a star-connected three-phase armature winding, the three-phase full-wave rectifier receives the vector sum voltage of the generated voltages of the two coils of the armature windings 11 to 13, so that the low rotation region However, in the high rotation region, the output leveling out reaches a plateau by an increase in the internal impedance due to the series connection of these two series coils. Therefore,
When this neutral point diode is connected, the problem of increasing the internal impedance due to the series connection of the impedances of the armature windings 11 to 13 as in the case of the Δ connection is alleviated, and the output is increased.

Hereinafter, the result of an experiment in the circuit of FIG. 2 will be described. FIG. 3 shows a ripple voltage waveform of a generator with a neutral diode on both sides, and FIG. 4 shows a ripple voltage waveform of a generator with a neutral diode on one side. I is blower-
V1 is the waveform of the motor drive current supplied to the motor 6, and V1 is the ripple voltage waveform at the high end of the blower motor 6.
Reference numeral 2 denotes a ripple voltage waveform at the high-order output terminal of the three-phase full-wave rectifier 3.

The specifications and experimental conditions of the three-phase AC generator for a vehicle are as follows. Ambient temperature 90 ° C, number of claw-shaped magnetic poles 12,
Excitation current 3A, generator rotation speed 4500 rpm, average power generation voltage 13.5V. However, the generator with one-sided neutral point diode had the same configuration as the generator with two-sided neutral point diode except that the high-side neutral point diode was omitted. (Ripple voltage) First, the ripple voltage is compared.

In the generator with neutral diodes on both sides shown in FIG. 3, the average output current is 50 A and the ripple current PP is
The value was 150 mA, V1 was 1.2 V, and V2 was 0.6 V. On the other hand, in the generator with one-sided neutral point diode shown in FIG. 4, the average output current is 50 A and the ripple current PP is
The value was 120 mA, V1 was 0.85 V, and V2 was 0.5 V.

A comparison between FIG. 3 and FIG. 4 shows that in the generator with one-sided neutral point diode, it is natural that the ripple voltage is small and that the peak voltage of every other peak of the ripple voltage waveform is small.
Therefore, the waveform is such that the ripple voltage or ripple power is dispersed over a wide frequency range (especially, 2 to 5 times the frequency component thereof). For this reason, in a generator with a one-sided neutral diode, the ripple voltage concentrates on a certain frequency component (fundamental frequency component) as in a generator with a two-sided neutral diode. The problem that large motor electromagnetic noise is generated in the approaching rotational speed region can be suppressed. (Maximum output current value) Next, a comparison is made for the maximum output current value.

FIG. 5 shows the relationship between the maximum output current and the generator speed of a generator with a neutral diode on both sides, a generator with a neutral diode on one side, and a diodeless generator with a neutral point. The neutral point diodeless generator had the same configuration except that a pair of neutral point diodes was omitted from the generator with neutral point diodes on both sides. It was found that a generator with a single-sided neutral diode can obtain a maximum output current value that is considerably larger than a maximum output current value between a generator with a double-sided neutral diode and a neutral-point diodeless generator. .

The present inventors have found that the generator with one-sided neutral point diode has a larger neutral point potential fluctuation amount than the generator with one-sided neutral point diode,
It is estimated that this is because the amount of current output through the neutral point diode increases by that amount. Therefore, if a generator with a one-sided neutral diode is adopted, the ripple voltage can be reduced without significantly increasing its size and weight, and more specifically, the ripple voltage concentrated on a specific frequency component can be reduced. It is possible to realize a favorable effect and a reduction in resonance electromagnetic noise of a motor as an electric load. (Claw-shaped magnetic pole resonance noise) Next, comparison will be made regarding claw-shaped magnetic pole resonance noise.

FIG. 6 shows the relationship between the noise level and the number of revolutions of the generator with a neutral diode on both sides, the generator with a neutral diode on one side, and the diodeless generator with a neutral point. However, the measurement was performed at a position 30 cm horizontally away from the generator in the radial direction of the generator. As a result, there was no difference in the noise level between the generator with the neutral diode on both sides and the generator with the neutral diode on one side, but in the case of the diodeless generator with a neutral point, around 11,000 rpm (for example, 4500 rpm in the engine speed). (Near) a remarkable claw-shaped magnetic pole resonance noise occurred.

The inventors of the present invention consider that the ripple voltage generated from the neutral point diodeless generator can be expressed as a peak value or a squared integrated value. Although it is much less than a generator with a magnetic pole, a high frequency component that causes the claw-shaped magnetic pole to resonate magnetically (a harmonic component more than several times the fundamental frequency component of a generator with a neutral diode on both sides) is large. The present inventors presume that this is because noise ripple voltage is included when claw-shaped magnetic pole resonance occurs.

As described above, according to the generator with one-sided neutral point diode of this configuration, the ripple voltage can be reduced without significantly increasing the size and weight, and more specifically, the ripple voltage concentrated on a specific frequency component can be reduced. Therefore, it is possible to achieve a favorable effect on the battery and a reduction in resonance electromagnetic noise of the motor which is an electric load, and furthermore, a reduction in claw-shaped magnetic pole resonance noise, a generator with a neutral diode on both sides. The number of components can be reduced by one neutral point diode.

Further, in this embodiment, the three-phase full-wave rectifier 3
Together with the diode constituting the housing 1 of the generator.
The neutral point diode 8 is housed in the air passage of the cooling fan 100 in the area 0, particularly in the upstream side thereof. By doing so, a good cooling effect can be easily obtained. (Modification) In the above embodiment, a junction diode is used as each rectifier, but a MOS transistor or an IGBT may be used instead. In the above embodiment, the field magnetic flux is generated by the exciting coil.
It is good also as a structure which uses a permanent magnet together. Further, in the above embodiment, the element on the high side of the neutral point diode is omitted, but the element on the low side may of course be omitted.

[Brief description of the drawings]

FIG. 1 is a partially broken axial sectional view of a three-phase AC generator for a vehicle according to a first embodiment.

FIG. 2 is a circuit diagram of the three-phase AC generator for a vehicle in FIG. 1;

FIG. 3 is a ripple voltage waveform diagram of a generator with a neutral diode on both sides of a comparative example.

FIG. 4 is a ripple voltage waveform diagram of the generator with one-sided neutral point diode of the embodiment.

FIG. 5 is a characteristic diagram showing the relationship between the maximum output current and the generator speed of a generator with a neutral diode on both sides, a generator with a neutral diode on one side, and a diodeless generator with a neutral point.

FIG. 6 is a characteristic diagram showing the relationship between the noise level and the generator speed of a generator with a neutral diode on both sides, a generator with a neutral diode on one side, and a diodeless generator with a neutral point.

[Explanation of symbols]

1 is a three-phase armature winding, 2 is an exciting coil, 3 is a three-phase full-wave rectifier (three-phase full-wave rectifier), 4 is a battery, 6 is a blower motor, and 8 is rectification for neutral point current rectification. Element, 11 to 13
Is a three-phase armature coil of each phase armature coil, and 14 is a neutral point.

Claims (2)

[Claims] 1. A three-phase full-wave AC generator for a vehicle having a three-phase full-wave rectifier for full-wave rectifying a three-phase AC voltage output from each output terminal of a star-connected three-phase armature winding, The neutral point of the three-phase armature winding is connected to only one of the higher output terminal and the lower output terminal of the three-phase full-wave rectifier via a rectifying element for neutral point current rectification. A three-phase alternator for vehicles characterized by the following. 2. The three-phase alternating current generator for a vehicle according to claim 1, wherein the rectifying element for rectifying the neutral point current together with a rectifying element constituting the three-phase full-wave rectifier includes a housing for the generator. A three-phase AC generator for a vehicle, wherein the three-phase AC generator is housed in an air passage of a cooling fan in the vehicle.