JPH05276799A - Voltage controller for ac generator in vehicle - Google Patents

Abstract

PURPOSE:To provide a voltage controller for AC generator in vehicle in which initial exciting current is limited and radio noise is suppressed. CONSTITUTION:An oscillation circuit 8 for limiting initial exciting current delivers an oscillation signal to a switching means 6 for driving an exciting coil 3 and turns the switching means 6 ON/OFF thus limiting the initial exciting current. A Darlington transistor 61 is employed in the switching means 6 and the oscillation circuit 8 sets the frequency fC of oscillation signal to be fed to the Darlington transistor 61 in a range of 20-150Hz thus suppressing radio noise in medium wave band.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage control device for a vehicle alternator, and more particularly to a voltage control device for reducing radio noise generated by a voltage surge from the generator.

[0002]

2. Description of the Related Art In an AC alternator for an automobile, a method is mainly adopted in which an initial exciting current is supplied from a battery and the generator rotates with the rotation of an engine to raise a voltage. However, at this time, there is a disadvantage that the battery is discharged in a short time if the engine is left unstarted while the key switch is turned on due to a driver's mistake. Therefore, as a method of suppressing the discharge of the battery, there are the following two methods disclosed in JP-A-54-140112. The first method is to connect a resistor in series with the exciting coil to limit the initial exciting current to the minimum amount necessary for rising.The second method is to provide an oscillation circuit for limiting the initial exciting current. This is a method in which this oscillation circuit applies an oscillation signal to a switching means for driving a current excitation coil to perform intermittent control to limit the initial excitation current.

[0003]

Each of the above methods has the following problems.

The first method requires a power resistor of about 10 W, which causes a loss due to heat generation, has a complicated structure, and has a low assembling property.

The second method has a small loss due to heat generation and does not cause a problem of assembling, but has a problem that noise is likely to be generated in a radio or the like due to a voltage surge when the switching means turns on and off the exciting current. ..

An object of the present invention is to provide a voltage control device for a vehicle alternator, which limits initial exciting current and suppresses generation of radio noise.

[0007]

To achieve the above object, the present invention provides an armature coil, an exciting coil, a rectifier for rectifying an AC output of the armature coil, and an exciting current of the exciting coil. Switching means, a battery charged by the DC output of the rectifier, voltage detection means for controlling the switching means according to the output of the rectifier or the voltage of the battery, and the operation of the generator reaches a predetermined state. Power generation detection means for detecting the occurrence of the occurrence and a detection control for intermittently controlling the switching means by applying an oscillation signal to the switching means from the time when the key switch is turned on to the time when the detection signal is generated. In the voltage control device for a vehicle AC generator, the intermittent control means provides an oscillation signal to the switching means. To set the frequency in the range from 20Hz to 150Hz.

Preferably, the switching means is a Darlington transistor, or a MOS-FE.
It may be T.

[0009]

In the present invention constructed as above, the oscillation frequency given by the interrupt control means to the switching means provided in the oscillation means for limiting the initial excitation current is 20 Hz to 150 H.
By setting in the range of z, the initial exciting current can be limited while suppressing the generation of radio noise.

[0010]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 is a circuit diagram showing an outline of an automotive alternator and a voltage control device therefor, which is composed of a generator 1, a voltage control device 5, a key switch 11, and a battery 12. The generator 1 includes an armature coil 2 that generates an induced voltage due to rotation, an excitation coil 3 for initial excitation, and a full-wave rectifier 4 that rectifies the three-phase alternating current generated by the armature coil 2. .. The voltage control device 5 includes a switching means 6 for intermittently controlling the exciting coil 3, a voltage detection circuit 7 for detecting an output voltage of the full-wave rectifier 4 or a charging voltage on the battery 12 side, and an ignition terminal IG when a key switch 11 is turned on. An oscillation circuit 8 that oscillates when power is supplied to the generator 1, a power generation detection circuit 9 that detects the one-phase voltage of the generator 1, a voltage detection circuit 7, an oscillation circuit 8 and an output from the power generation detection circuit 9 An intermittent control circuit 10 for controlling the operation of the switching means 6 is provided.

FIG. 2 shows a voltage control device 5 according to an embodiment of the present invention.
3 is a circuit diagram showing the configuration of FIG. The switching means 6 is a Darlington transistor 61, and the exciting coil 3 and the back-wheel electromotive force absorbing flywheel diode 21 are connected to the collector side thereof. The other end of the exciting coil 3 is connected to the output terminal A of the full-wave rectifier 4, and is also connected to the other end of the flywheel diode 21. The base of the Darlington transistor 61 is connected to the ignition terminal IG and the key switch 11 via the resistor 22.

The voltage detection circuit 7 is composed of resistors 71 and 72 for dividing the voltage of the B terminal, a constant voltage diode 73 for judging whether the divided voltage is present or not, and a transistor 74, and an input terminal after the engine is started. The voltage of B, that is, the charging voltage of the battery 12 is adjusted to a predetermined voltage.

The oscillator circuit 8 includes a comparator 81, a Zener diode 82, a resistor 83, a capacitor 84,
It is composed of constant current sources 85 and 86 and a transistor 87. The operating principle of this oscillator circuit will be described below. When the capacitor 84 is charged, current flows from the constant current sources 85 and 86 and the terminal voltage of the capacitor 84 rises. When the terminal voltage further rises and exceeds the voltage of the Zener diode 82, the output level of the comparator becomes HI, the transistor 87 is turned on to form a triangular wave generating circuit of the resistor 83 and the capacitor 84, and the capacitor 84 is formed with these time constants. Discharge from. In this way, charge and discharge are repeatedly oscillated.

The power generation detection circuit 9 includes a smoothing circuit composed of resistors 91 and 92 and a capacitor 93, and a transistor 94.
When the one-phase voltage of the generator 1 reaches a constant value, the transistor 94 is turned on.

The on / off control circuit 10 is composed of a transistor 101 and a base resistor 102, and the transistor 101 of the on / off control circuit 10 is turned on / off by an oscillation signal of the oscillation circuit 8.

The present embodiment has the above configuration, and its operation will be described below.

When the driver turns on the key switch 12 to supply power to the ignition terminal IG, the oscillation signal of the oscillation circuit 8 causes the transistor 101 of the interruption control circuit 10 to be intermittent. As a result, the Darlington transistor 61 operates intermittently to conduct at a constant rate, and an exciting current according to this conducting ratio flows through the exciting coil 3. The average value of the exciting current at this time is such that the frequency fC of the on / off control pulse is 20 Hz to 1 so that the generator 1 can be started up.
The capacitor 84 and the resistor 83 are set so as to be 50 Hz.

The engine is started by the starter and the generator 1
When the number of revolutions increases and reaches a certain number, the exciting current causes the output voltage of the generator 1 to rise. As a result, the transistor 94 of the power generation detection circuit 9 is turned on and the transistor 101 is forcibly cut off, so that the oscillation signal of the oscillation circuit 8 is not transmitted to the base of the Darlington transistor 61, and the initial excitation is completed. Therefore,
After that, the Darlington transistor 61 performs a normal voltage adjusting operation by the voltage detecting circuit 7. That is, the resistance 71,
Depending on the settings of 72 and constant voltage diode 73, output terminal B
When the transistor 74 is configured to conduct when the voltage reaches a predetermined value, for example, 14.4 V, the exciting coil 3 is excited when the detected voltage is equal to or lower than the predetermined value, and is not excited when the detected voltage is equal to or higher than the predetermined value. As a result, the voltage at the output terminal B has a predetermined value of 14.
Adjusted to 4V.

The configuration and operation of the device in this embodiment are as described above. The main part of this embodiment is that the frequency fC of the on / off control pulse of the oscillation circuit 8 for intermittently operating the Darlington transistor 61 is In the settings. This frequency setting will be described below with reference to FIGS. The states of the currents flowing through the transistor 61 and the exciting coil 3 during the initial excitation are shown in FIGS. 3A and 3B, respectively.
Darlington transistor 61 conductive state, that is, ON
When the state time is t1 and the non-conducting state, that is, the OFF state time is t2, the frequency of the on / off control pulse is fC.
= 1 / (t1 + t2) The frequency characteristics of the generated noise distribution differ depending on what value the frequency fC of the on / off control pulse is set to.

FIG. 4 shows the frequency (FFT) analysis of the noise level at the output terminal B at the time of initial excitation, and shows the results when the frequency fC of the on / off control pulse is 100 Hz and 200 Hz. Noise frequency fR in the medium wave band = 6 in the range of 500 KHz to 1600 KHz
Noise of a level of 0 to 70 dBμ / V occurs.

FIG. 5 shows the ON / OFF frequency distribution characteristics of the noise level with the horizontal axis representing the ON / OFF frequency fC (KHz) in the case of fR = 500 KHz which is near the transmission frequency of the NHK radio. As shown in the figure, the noise level according to this embodiment using the Darlington transistor is 150.
The effect of noise reduction is great in the region where the on / off frequency fC is 150 Hz or less, because it sharply rises around Hz.
Therefore, the frequency fC of the on / off control pulse is set to 150
Noise reduction can be achieved by setting the capacitor 84 and the resistor 83 to be equal to or lower than Hz. However, at 20 Hz or less, the brightness of the lamps such as the charge lamp when the key switch 11 is turned on becomes a problem, so fC = 20 Hz to 150 Hz is considered to be appropriate as the applicable range of this embodiment.

According to this embodiment, the Darlington transistor 61 is provided as the switching means 6 for intermittently controlling the exciting coil 3, and the frequency fC of the on / off control pulse of the oscillation circuit 8 for intermittently operating the Darlington transistor 61 is set. Since it was set to 20Hz-150Hz,
The initial excitation current can be limited while suppressing the generation of radio noise.

Next, another embodiment of the switching means 6 will be described with reference to FIGS. In this embodiment, a MOS-FET is used as the switching means. 6 and 7 are circuit diagrams of the Darlington transistor 61 and the MOS-FET, respectively. The MOS-FET has the characteristic that the on / off speed is slower than that of the Darlington transistor 61. This characteristic is shown in FIG. 8 by the change in the voltage of the input terminal B and the change in the collector voltage or the drain voltage, with the voltage on the horizontal axis and the voltage on the vertical axis. As shown in the figure, M
The OS-FET has a smaller change in the B terminal voltage than the Darlington transistor 61, and has a slower change in the drain voltage with time. On the other hand, since the generation of noise increases as the voltage changes faster and the amount of change increases, the MOS-FET has a greater noise reduction effect than the Darlington transistor 61. MOS-
The noise reduction effect by the on / off frequency fC of the FET is shown in comparison with the Darlington transistor 61. fC = 2
The noise reduction effect at 0 Hz to 150 Hz is similar to the case of the Darlington transistor embodiment described above, but in the MOS-FET in the above application range, about 2 dBμ / V is further added as compared with the Darlington transistor.
The noise can be reduced to some extent.

According to the present embodiment, since the MOS-FET is used as the switching means 6 for intermittently controlling the exciting coil 3, the noise reducing effect is further enhanced.

[0026]

According to the present invention, since the oscillation frequency provided by the intermittent control circuit is set to 20 Hz to 150 Hz, the initial exciting current can be limited while suppressing the generation of radio noise.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an outline of a vehicle alternator and a voltage control device thereof.

FIG. 2 is a circuit diagram showing a configuration of a voltage control device according to an embodiment of the present invention.

FIG. 3 is a diagram showing a state of current flowing through a transistor and an exciting coil during initial excitation.

FIG. 4 is a FFT analysis waveform diagram of an output terminal at the time of initial excitation.

FIG. 5 is a diagram showing a noise level on / off frequency distribution characteristic.

FIG. 6 is a circuit diagram of a Darlington transistor.

FIG. 7 is a circuit diagram of a MOS-FET.

FIG. 8 is a diagram showing how the voltages of a MOS-FET and a Darlington transistor change with time.

FIG. 9 is a diagram showing a noise reduction effect in the case of an embodiment using a MOS-FET.

[Explanation of symbols]

 1 Generator 3 Excitation Coil 5 Voltage Control Device 6 Switching Means 61 Darlington Transistor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuo Ueno 2520 Takaba, Katsuta City, Ibaraki Prefecture Hitachi Ltd. Automotive Equipment Division

Claims (2)

[Claims] 1. An armature coil, an exciting coil, a rectifier for rectifying an AC output of the armature coil, a switching means for connecting and disconnecting an exciting current of the exciting coil, and a battery charged by a DC output of the rectifier. A voltage detection means for controlling the switching means according to the output of the rectifier or the voltage of the battery; and a power generation detection means for detecting that the operation of the generator has reached a predetermined state and generating a detection signal. In a voltage control device for a vehicle alternator, which has an intermittent control means for intermittently controlling the switching means by giving an oscillating signal to the switching means from the time when the key switch is turned on to the time when the detection signal is generated, The intermittent control means changes the frequency of the oscillation signal given to the switching means from 20 Hz to 150 Hz.
The voltage control device is characterized by being set within the range up to. 2. The voltage control device according to claim 1,
The voltage control device wherein the switching means is a Darlington transistor or a MOS-FET.