JP2932694B2 - Rectifier for automotive alternator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectifier for a three-phase AC generator for a vehicle.

[0002]

2. Description of the Related Art A conventional three-phase full-wave rectifier in which a diode is bridge-connected is used as a rectifier of an automotive alternator. This was performed by controlling the field current of an alternator (hereinafter referred to as an alternator).

[0003] In addition, for battery charging and the like, the SCR
A three-phase full-wave rectifier in which (thyristors) are bridge-connected is used.

[0004]

However, the three-phase full-wave rectifier of the diode bridge type has a problem that the rectification efficiency is not good. Hereinafter, this problem will be described in detail. Each diode is originally 2π / 3 with a different phase
(Rad) should be conducted, but in reality, π (rad) is conducted by the action of the leakage reactance except for the extremely low-speed rotation (low frequency) region. as a result,
As shown in FIG. 8, at time t1, the -z voltage is connected in parallel with the -x voltage at the output terminal of the three-phase full-wave rectifier, although a y-x spectral voltage should be generated. As a result, the DC output voltage Edc is reduced as shown by the solid line in FIG. 8, and the DC output voltage is lost only in the hatched portion.

On the other hand, the rectifier of the vehicle alternator of the SCR bridge type needs to add an arc extinguishing circuit for turning off, and has poor high-speed response. Therefore, it has not been advisable to employ the SCR for the high-speed intermittent operation of a high reactance load in a rectifier of an automotive alternator whose frequency during high-speed operation is much higher than the commercial frequency.

Further, recently, a technique for absorbing torque pulsation of a vehicle engine by generating and electrically switching an alternator has been proposed. However, in order to actually realize such a technique, a plurality of diode bridges are required. A complicated high-speed switching control circuit including a plurality of transistors is required. The present invention has been made to solve such a problem, and while improving the rectification efficiency,
It is an object of the present invention to provide a rectifier for a vehicle AC generator that can realize a power generation and a motor switching control of a three-phase AC generator with a simple circuit.

[0007]

According to the present invention, there is provided a rectifier for three-phase full-wave rectification of a three-phase AC voltage output from an automotive alternator, wherein a plurality of transistors are connected in a three-phase bridge. A three-phase full-wave rectifier capable of interrupting the current of each coil of the generator, only one of the plurality of positive-side transistors (2a, 2b, 2c) of the three-phase full-wave rectifier, and the three-phase full-wave rectifier And a control unit for sequentially turning on and off each of the plurality of transistors so that only one of the plurality of negative-side transistors (2d, 2e, 2f) conducts. In a preferred aspect, the control unit switches the plurality of transistors on and off corresponding to a cross point of two phase voltages to be switched. In a preferred aspect, the control unit includes a pulse width modulation type voltage control circuit for controlling the magnitude of the output DC voltage. In a preferred aspect, the voltage control circuit is characterized in that a carrier frequency of the pulse width modulation is set to an audible frequency or higher. In a preferred aspect, the control unit sets the conduction period of the plurality of transistors to 2π / 3.
It is characterized by the following settings.

Here, as the transistor, a bipolar transistor (BPT), an insulated gate transistor (IGFET, MOS FET), a junction gate transistor (JFET), an insulated gate bipolar transistor (IGBT) or the like can be adopted. Each phase coil of the generator may be star-connected or delta-connected.

[0009]

The three-phase full-wave rectifier of the rectifier of the automotive alternator according to the present invention comprises a plurality of transistors connected in a three-phase bridge. The control unit interrupts each transistor at a timing when the coils of the generator are not connected in parallel. That is, only one of the plurality of positive-side transistors (2a, 2b, 2c) of the three-phase full-wave rectifier and one of the plurality of negative-side transistors (2d, 2e, 2f) of the three-phase full-wave rectifier. These transistors are sequentially intermittently controlled so that only one of them becomes conductive. By doing so, the rectification efficiency can be improved and the magnitude of the output DC voltage can be increased.

That is, the two coils of the generator are connected in parallel by the action of the leakage reactance, so that almost no average voltage of both coils is output from both ends thereof. As a result, the output DC voltage is reduced. It does not drop. Further, as compared with the rectifier of the vehicle alternator of the SCR bridge type, an arc extinguishing circuit is not required and the high-speed response is improved, so that it is possible to cope with high-speed intermittent operation at the time of high-speed operation.

Further, by switching between the power generation operation of the generator and the electric operation together with the charging of the battery and the driving of the vehicle electric load, the torque pulsation of the vehicle engine can be absorbed without increasing the circuit scale of the three-phase full-wave rectifier. Becomes Further, according to the present invention, since the output DC voltage can be controlled by switching control of the transistor, the field magnetic flux of the generator can be generated by the permanent magnet, and the configuration of the generator can be simplified or brushless. Can be realized.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment. In this device, transistors 2a to 2f are connected in a three-phase bridge, and each phase coil (armature coil) 1x, 1y, 1
a three-phase full-wave rectifier 2 for three-phase full-wave rectification of the three-phase AC voltages x, y, z received from z, and a control unit 3 for switching the respective transistors 2a to 2f of the three-phase full-wave rectifier 2 at different phases. And

Each of the transistors 2a to 2f is constituted by an IGBT (insulated gate bipolar transistor). One end of the three-phase full-wave rectifier 2 is grounded, and the other end is a high-level power supply of the battery 4 and the electric load 5 for the vehicle. Connected to the end. The control unit 3 receives the phase voltage x output from the phase coil 1x and detects the frequency and phase thereof, and according to the detected frequency and phase, each of the transistors 2a to 2f
2 is a circuit for controlling the conduction of, for example, has a configuration as shown in FIG.

That is, the control unit 3 shapes the waveform of the phase voltage x to form a pulse signal having the same period, and shapes the pulse signal to form a reference pulse signal having a duty ratio of 0.5. A pulse signal having a frequency three times the frequency of the pulse signal and a duty ratio of 0.5% is formed, and the pulse signal having the triple frequency and the opposite phase pulse signal are used to generate a phase of 2π / 3 each. Form six different pulse signals, which are applied to the gates of the transistors 2a to 2f. The switching of each of the transistors 2a to 2f is performed at a cross point of two phase voltages to be switched.

As a result, only one of the transistors 2a to 2c and one of the transistors 2d to 2f are always in a conductive state, so that the output voltage Edc of the three-phase full-wave rectifier 2 is equal to the seventh voltage.
The waveform shown in the figure is obtained, the rectification loss is reduced, and the power generation efficiency is improved. Further, since the rotational angular velocity of the vehicular internal combustion engine fluctuates in each explosion / compression step, when the torque of the internal combustion engine falls below the average value in synchronization with the periodic fluctuation of the torque fluctuation, the control unit 3 activates each transistor. If the engine is shut off, the torque consumed by the alternator 1 decreases, so that the output torque of the engine increases and the torque fluctuation decreases.

Since the IGBT is suitable for high-capacity and high-speed operation, the IGBT has particularly good controllability. The output of the magnetic pulsating torque detector provided on the stator core is used as a signal to activate electromagnetic torque fluctuations that cause magnetic noise. Control becomes possible. Note that the conduction period of each transistor may be 2π / 3 or less. By setting it to 2π / 3 or less, the highest average current voltage can be output.

In this device, a permanent magnet is used for the rotor field 6. The magnitude of the DC voltage to be output can be controlled by providing a PWM (pulse width modulation) type voltage control circuit in the control unit 3 (see FIG. 4). Can be. Since the carrier frequency of the PWM control is selected to be higher than the audible frequency, there is no problem in noise. The voltage control circuit is provided after the phase voltage synthesizing circuit instead of FIG.
M control may be performed.

Further, in this embodiment, a reactor 7 is connected in series to the high-order output terminal of the three-phase full-wave rectifier 2 to form a series-wound coil that excites the field so as to strengthen the field magnetic flux. Further, the current interrupted by the IGBT is smoothed by the reactor 7 when flowing to the output current system, and the ripple is reduced. FIG. 5 shows a third embodiment.

This device is composed of transistors 2a to 2a shown in FIG.
2f and the transistors 2g to 2m are individually connected in the reverse direction, and the intermittent operation of the transistors 2a to 2m is separately controlled. In this case, by controlling the phase of each pulse signal output from the control unit 2, the alternator 1 can operate as a generator and a starting motor as is well known.

Of course, when operating as a generator, the transistors 2a to 2f are turned on at predetermined phases, and the transistors 2g to 2m are turned off. On the other hand, when operating as a starting motor, transistors 2g to 2g
m in a predetermined phase, and the transistors 2a-2
Block f. Incidentally, also when operating as a starting motor, the transistors 2g to 2m are switched every 2π / 3.

FIG. 6 shows a fourth embodiment. This device is
N-channel MOSFE as transistors 2a to 2f
T is used, and backflow prevention diodes 6a, 6b and 6c are provided between each branch of the bridge and the ground to improve rectification.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a rectifier for a vehicle AC generator according to the present invention.

FIG. 2 is a block diagram of a control unit shown in FIG. 1;

FIG. 3 is a circuit diagram of a second embodiment.

FIG. 4 is a block diagram of a control unit shown in FIG. 3;

FIG. 5 is a circuit diagram showing still another embodiment of the rectifier of the automotive alternator according to the present invention.

FIG. 6 is a circuit diagram showing still another embodiment of the rectifier of the automotive alternator according to the present invention.

FIG. 7 is a waveform diagram of a three-phase full-wave rectified voltage output from the apparatus of FIG.

FIG. 8 is a waveform diagram of a three-phase full-wave rectified voltage output from a conventional diode bridge type three-phase full-wave rectifier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Alternator 2 Three-phase full-wave rectifier 3 Control part

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Masato Hanai 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-4-138030 (JP, A) JP-A-2- 7834 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) H02J 7/14-7/24 H02M 7/219

Claims (5)

(57) [Claims] 1. A rectifier for three-phase full-wave rectification of a three-phase AC voltage output from a vehicular AC generator, comprising: a plurality of transistors connected in a three-phase bridge; A three-phase full-wave rectifier that can be shut off, and a plurality of positive-side transistors (2
a, 2b, 2c) and a plurality of negative side transistors (2d, 2e, 2c) of the three-phase full-wave rectifier.
f) a control unit for sequentially turning on and off each of the plurality of transistors so that only one of the transistors is conducted. 2. A rectifier for a three-phase AC generator for a vehicle according to claim 1, wherein said control unit switches said plurality of transistors on and off in accordance with a cross point of two phase voltages to be switched. . 3. A three-phase AC power generator for a vehicle according to claim 1, wherein said control unit includes a voltage control circuit of a pulse width modulation type for controlling the magnitude of an output DC voltage. Rectifier of the machine. 4. The rectifier of a three-phase AC generator for a vehicle according to claim 3, wherein said voltage control circuit sets a carrier frequency of the pulse width modulation to be equal to or higher than an audible frequency. 5. The three-phase AC generator for a vehicle according to claim 1, wherein said control unit sets the conduction period of said plurality of transistors to 2π / 3 or less. Rectifier.