JPS5947532B2 - Storage battery charging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a storage battery charging device that controls the output voltage of an alternator driven by, for example, an internal combustion engine to a predetermined value and charges a storage battery with this voltage. .

First, a conventional device of this type is shown in FIG. 1 and will be explained.

In FIG. 1, reference numeral 1 denotes an alternating current generator installed in a vehicle (not shown) and driven by an internal combustion engine (not shown), with an armature coil 101 and a field coil 102 connected in a three-phase star shape.
2 is a full-wave rectifier that rectifies the AC output of the generator 1, and 201, 202, and 203 are first and second rectifiers, respectively.
These are second and third rectified output ends. 3 is a voltage regulator that controls the output voltage of the generator 1 to a predetermined value, and is composed of the following parts.

That is, 301 is a surge absorbing diode connected to both ends of the field coil 102, 302 is a transistor that is a switching element that controls the field current of the field coil 102, and 30
3 is a base resistor provided in the base circuit of this transistor 302, 304 is a transistor that controls on/off of the transistor 302, 305 detects the output voltage of the generator 1, and when this output voltage reaches a predetermined value or more, Zener diode, 306, 3, constituting the energized detection element
0T is a resistance consisting of a temperature compensation thermistor connected in series to each output terminal of the generator 1, and 4 is a first output terminal 201.
5 is a resistor connected between the second output terminal 202 and the key switch 6 connected to the storage battery 4, and T is connected across the resistor 5. It is a charging indicator light. The operation of the conventional device configured in this way will be explained.

First, when the key switch 6 is closed when starting the internal combustion engine, a base current is supplied from the storage battery 4 to the transistor 302 via the key switch 6, the resistor 5, and 303, and the transistor 302 becomes conductive.
A field current is supplied from the storage battery 4 to the field coil 102 through 02, and a field magnetomotive force is generated. At this time, since a potential difference is generated across the resistor 5, the charge indicator light 2 lights up to indicate the uncharged state of the storage battery 4. When the engine is started in this state, the generator 1 is driven, and an alternating current output is induced in the armature coil 101 according to the rotation speed, and this output is full-wave rectified by the full-wave rectifier 2. Here, when the rectified output voltage is below a predetermined value, that is, since the voltage dividing point potential of the voltage dividing circuit constituted by the resistors 306 and 301 is still low, the Zener diode 305 maintains a non-conducting state. When the rotational speed of the generator 1 further increases and the output voltage accordingly exceeds a predetermined value, the potential at the voltage dividing point of the voltage dividing circuit also increases, thereby causing the zener diode 305 to conduct. A base current flows to the transistor 304 through the inner diode 305, and the transistor 304 becomes conductive.
If this transistor 304 conducts, the transistor 304 becomes conductive.
02 becomes non-conductive, cuts off the field current of the field coil 102, and lowers the output voltage of the generator 1. When this output voltage drops to a predetermined value, the zener diode 305
, the transistor 304 becomes non-conductive, the transistor 302 becomes conductive, and the field coil 102 is energized, so that the output voltage of the generator 1 rises again. By repeating the above-described operations, the output voltage of the generator 1 is controlled to a predetermined value, and the storage battery 4 is charged to the predetermined voltage using this controlled voltage.

On the other hand, the charging indicator light 1 is connected to the second rectified output end 202 of the generator 1.
When the output voltage of each reaches a value equal to the power supply voltage value of the storage battery 4, the light goes out due to a decrease in the potential difference across the resistor 5, and the storage battery 4
Displays charging status. However, in the conventional device described above, external factors other than the storage battery charging device, such as
The generator 1, rectifier 2, and voltage regulator 3 are designed to continue producing the maximum output possible, regardless of engine overheating, overload, short circuit, local heat generation, etc.

Therefore, in the abnormal conditions described above, thermal runaway occurs due to each self-heating, causing thermal damage. Destroy the weakest point. Semiconductors are generally the weakest parts thermally, and defects in the market are concentrated in the rectifier 2, diode 301, transistors 302, 304, and zener diode 305. In addition, in order to create a storage battery charging device that can withstand thermal runaway even under the above abnormal conditions, it is necessary to use semiconductors that have extremely high heat resistance.Semiconductors with high heat resistance are difficult to manufacture and have poor reliability. becomes expensive. The present invention provides an excellent storage battery charging device that eliminates the above-mentioned drawbacks.

The embodiment shown in FIG. 2 will be described below.

In Fig. 2, 308 is the Zener diode 3 for voltage regulation.
05 is a Zener diode for temperature detection connected in parallel, 8 is an overtemperature detector installed at a location of the rectifier 2 or voltage regulator 3 that is prone to thermal runaway, 801 is a resistor, 8 is a
02 is a temperature detection element whose resistance value increases rapidly when the set temperature is reached. This overtemperature detector 8, the Zener diode type, the transistors 302, 304, etc. described above constitute a protection circuit in the event of a temperature rise.The operation of the embodiment device configured as above will be explained.

First, when the temperature at the location where the overtemperature detector 8 is installed is normal, the resistance of the temperature detection element 802 is a low value, so the potential at the voltage dividing point with the resistor 801 is low, and the temperature detection zener Diode 308 is cut off.

Therefore, the voltage regulator 3 operates similarly to the conventional device shown in FIG. 1 to control the output voltage of the generator 1 to a predetermined value, and charges the storage battery 4 with this controlled voltage. In addition, the charging indicator light T also operates normally. Next, if the temperature at which the overtemperature detector 8 is attached rises above the preset temperature due to some external factor, the resistance value of the temperature detection element 802 will rapidly increase, and the resistance value of the temperature detection element 802 will rise rapidly. The potential at the dividing point increases, and the temperature detection Zener diode 308 becomes conductive.

Then, transistor 304 becomes conductive, and transistor 3
02 is cut off, the field current flowing through the field coil 102 is cut off, the field magnetomotive force disappears, and the generator 1 stops producing output. Therefore, since neither the rectifier 2 nor the voltage regulator 3 outputs an output, self-heating due to the output current is eliminated.
The temperature of the entire storage battery charging device decreases. When this temperature falls below the set temperature, the temperature detection element 802 returns to its original low resistance value, and the temperature detection zener diode 3
08 is cut off, voltage regulator 3 operates normally, and generator 1
also operates normally, and the rectifier 2 outputs a normal rectified output. By repeating this process, the temperature at the location where the overtemperature detector 8 of the storage battery charging device is attached can be lowered to below the set temperature, thereby preventing thermal damage.

In addition, the overtemperature detector 8 may be activated due to an external factor other than the storage battery charging device.
The temperature at the location where the is installed reaches or exceeds the set temperature,
Even when the outputs of the generator 1, rectifier 2, and voltage regulator 3 are cut off, if the temperature does not fall below the set temperature, the cut-off state is continued to prevent additional heat generation due to self-heating. As can be understood from the above explanation, the number of overtemperature detectors 8 does not have to be one, and the number of overtemperature detectors 8 is attached to multiple temperature-sensitive parts, and the number of overtemperature detectors 8 is connected in parallel to the Zener diode 305 for voltage detection. By adding a Zener diode for temperature detection, it is possible to cut off the output of the generator 1, rectifier 2, and voltage regulator 3 no matter which part is overheated, thereby preventing damage due to thermal runaway. . As described above, the present invention detects overtemperature of the rectifier 2, voltage regulator 3, or their parts of the storage battery charging device, and reduces or cuts off the field current of the generator 1. By preventing the temperature of the device 3 or its parts from exceeding the set temperature, the heat resistance of the thermally weakest parts, such as semiconductors, can be lowered, and the temperature will be lowered only at normal temperatures. The device can be designed according to the specifications, and an inexpensive and highly reliable storage battery charging device can be provided.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram showing a conventional device, and FIG. 2 is an electric circuit diagram showing an embodiment of the present invention.

Claims (1)

[Claims] 1. A storage battery that is charged via a rectifier by the output of an alternating current generator having a field coil, and a voltage regulator that controls the output voltage of the generator to be constant by controlling the current of the field coil. The storage battery charging device is equipped with at least one temperature detection element, and when the temperature of the rectifier and voltage regulator or their parts rises above a preset temperature, a current flows through the field coil. A storage battery charging device characterized by being provided with a protection circuit that controls the output of the generator to reduce or cut off the output of the generator.