JPS5851231B2 - Vehicle battery charging status detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a state-of-charge detection device for a vehicle battery, and particularly to a state-of-charge detection device for detecting full charge of a vehicle battery.

Vehicle batteries form the power source for the ignition circuit of the internal combustion engine and other electrical systems, and must hold a sufficient amount of current to supply these loads.

As the engine rotates, charging current is sequentially supplied to the battery from the alternator to maintain current supply to the load.

If the amount of charge to the battery is insufficient, the operation of the electrical system will be impaired, resulting in problems such as difficulty in starting with a starter.

Furthermore, if the charged state of the battery is not maintained, there are disadvantages such as wear and tear on the electrodes or electrolyte of the battery itself.

In order to prevent such problems, the battery must be properly charged by the alternator.

However, if charging current is constantly supplied to the battery from the alternator, the battery may be overcharged, resulting in disadvantages such as the electrolyte being reduced due to water decomposition or other factors.

In order to maintain an appropriate state of charge in a typical vehicle battery, a voltage regulator controls the amount of power generated by an alternator.

However, the conventional voltage regulator simply controls the excitation circuit of the alternator using only the terminal voltage of the battery, and cannot directly detect the amount of charge of the battery.

Devices that detect the amount of electrolyte or its specific gravity are known as conventional battery monitors.

These devices allowed the vehicle driver to know the state of charge of the battery and make adjustments as necessary, such as reducing the load or changing the vehicle's driving conditions, or charging the battery.

However, this conventional detection device cannot always accurately detect the state of the battery; for example, it cannot distinguish between cases where the electrolyte is insufficient due to leakage and cases where the electrolyte is insufficient due to overcharging. Furthermore, the specific gravity of the electrolytic solution is affected by temperature, and furthermore, there is a drawback that accurate state detection is impossible due to differences in the specific gravity distribution inside the battery.The present invention was made in view of the above-mentioned conventional problems. The purpose is to provide an improved state of charge detection device that can accurately detect the state of charge of a battery, particularly full charge.

In order to achieve the above object, the present invention is characterized in that the voltage at the excitation terminal of the alternator is monitored and a pulse-like signal generated at the excitation terminal of the alternator is detected when the battery is fully charged.

Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a typical vehicle charging and discharging system.

A charging current is supplied to the battery 10 from the B terminal of the alternator 12, and a consumed current is supplied from the battery 10 to the load 14.

The terminal voltage of the battery 10 is detected by the voltage regulator 18 via the ignition key switch 16,
Voltage regulator 18 supplies an excitation signal to alternator 12 from its excitation terminal F.

The amount of power generated by the alternator 12 changes according to the excitation voltage applied from the excitation terminal F, so that the battery 10 can be charged in an optimal state.

As is clear from FIG. 1, the amount of power generated by the alternator 12 is determined by the excitation terminal
Controlled by voltage.

FIG. 2 shows a typical change in excitation terminal voltage.

The excitation terminal voltage is maintained at approximately the battery terminal voltage B until the terminal voltage of the battery 10 reaches a predetermined voltage.

In FIG. 2, at time t2, the battery 10 is almost fully charged, the pressure contact of the voltage regulator 18 is activated, and the excitation terminal voltage drops to M. Thereafter, the excitation terminal voltage moves intermittently between B and M.

At time t3, the required amount of charge to the battery 10 further decreases, and when overcharging approaches, the excitation terminal voltage decreases to ground potential E, and thereafter alternates between voltage B and voltage B until t4.

Further, after t4, the battery 10 requires only a small amount of charge, and a signal as shown in the figure is obtained between the voltages M and E.

As described above, it is clear that the excitation terminal voltage outputs an intermittent pulse-like output signal as shown in FIG. 2 when the battery 10 is fully charged.

Figure 3 shows a state in which the excitation terminal voltage in Figure 2 has been smoothed, and a sudden voltage drop can be seen at time t1, which is when the engine starts, but this is because the battery terminal voltage decreases due to current consumption in the starter motor. It shows that.

The present invention utilizes the fact that full charge of the battery 10 is detected by a pulse signal output to the excitation terminal voltage of the alternator, as shown in FIGS. 2 and 3, to accurately detect the battery condition. This is a characteristic feature.

FIG. 4 shows a first embodiment of the present invention, in which an alternator 1
The battery includes a full charge detection circuit 20 connected to the excitation terminal F of No. 2 and a display device 22.

The full charge detection circuit 20 includes an f-v converter (frequency-voltage converter) 24, which converts the pulsed signal of the excitation terminal shown in FIG. 2 into a DC voltage.

The output of the f-v converter 24 is connected to one input terminal of a comparator 26, and the other input terminal of the comparator 26 is supplied with a reference voltage from a reference voltage generation circuit 28.

The output of the comparator 26 is connected to the display device 22.
2 in the vehicle interior, it becomes possible for the vehicle driver to always know the state of the battery.

The f-v converter 24 does not provide an output between tl and 12 in FIG. 2, and in the illustrated embodiment,
During this time, the comparator 26 outputs a display signal to the display device 22.

Therefore, when the battery is uncharged, the display device 2
For example, an indicator lamp or the like constituting part 2 is turned on, and the driver knows that the battery is currently being charged.

At this time, the driver can take measures as necessary, such as selectively reducing the load or increasing the engine speed to increase the amount of power generated by the alternator.

When time t2 in FIG. 2 is reached, a pulse-like signal is generated at the excitation terminal of the alternator 12, and the f-v converter 24 supplies an output signal proportional to the frequency of the pulse signal to the comparator 26, and this DC voltage is When the value exceeds the reference voltage of the reference voltage generation circuit 28, the display on the display device 22 is stopped.

As a result, the display lamps of the display device 22 go out, and the driver knows that the battery is fully charged.

FIG. 5 shows a second embodiment of the present invention, in which a pulsed signal at the excitation terminal F is detected by a low-pass filter 34 consisting of a resistor 30 and a capacitor 32, and the output of this low-pass filter 34 is detected by a resistor 36 and a variable resistor. The voltage is divided by a voltage dividing circuit 40 consisting of 38 and supplied to the base of a transistor 42.

A display lamp 44 is connected to the collector of the transistor 42 in series with a resistor 46, and when the signal from the voltage dividing circuit 40 reaches a predetermined value, the transistor 42 is turned on and the display lamp 44 is turned on.

According to this second embodiment, when the battery is continuously charged and the excitation terminal F is maintained at approximately the battery voltage, the transistor 42 is continuously turned on, the indicator lamp 44 is lit, and the excitation terminal F is maintained at approximately the battery voltage. It is understood that when a pulse signal is supplied to , the base potential of the transistor 42 decreases and the transistor 42 is turned off, and as a result, the indicator lamp 44 is turned off when the battery is fully charged.

FIG. 6 shows a third embodiment of the present invention, in which full charge can be detected by counting the pulse signals of the excitation terminal with a counter.

A signal voltage-divided by a resistor 48 and an adjustment resistor 50 connected to the excitation terminal F is applied to a Nandt gate 52, and its output is applied to a counter 54.

The output of the counter 54 is connected via an inverter 56 to a light emitting diode 58 forming a display device, and is also fed back to the Nandt gate 52.

In the initial state, the output of the inverter 56 is at the H level, and the excitation terminal voltage is also at the H level, which is close to the battery voltage, so that the Nant gate 52 outputs an L level signal.

It is understood that as long as there is no change in the output of the counter 54 thereafter, the output of the Nandt gate 52 depends only on the excitation terminal voltage, and its polarity is reversed.

This state is shown in the time chart of FIG.

Waveform 101 in FIG. 7 shows the excitation terminal voltage, and waveform 1
02 indicates the output of the Nandt gate 52, and it is understood that the polarities are opposite to each other.

When the battery reaches full charge, the Nandt gate 52 outputs an inverted pulse of the excitation terminal output, and the counter 54 counts the number of pulses.

Now, if the counter is a hexadecimal ripple counter, when the 8th pulse rises, the counter 54 outputs an output 103, and as a result, the output 104 of the impark 56 becomes L level and the light emitting diode 58 turns off.

Furthermore, the L level signal of the inverter 56 is applied to the Nant gate 52.
After that, the output of the Nant gate 52 is held at H level.

In the illustrated embodiment, since the light emitting diode 58 is used as a display device, the display can be directly controlled by the output of the inverter 56 without using a drive circuit consisting of a transistor or the like.

Further, in this embodiment, full charge is detected when the count value of the counter 54 exceeds a predetermined value, but this may prevent malfunctions due to noise contamination or short-term changes in excitation terminal voltage due to engine surging. can be prevented.

Of course, the count value of the counter 54 can be set arbitrarily.

FIG. 8 shows still another fourth embodiment of the present invention.
The configuration is almost the same as that of the embodiment, and the same constituent members are given the same reference numerals and explanations will be omitted.

The fourth embodiment is characterized in that a monostable multi-circuit 60 is activated by the output of the counter 54, and a predetermined short-time display is performed when the battery is fully charged.

FIG. 9 shows waveforms at various parts in FIG. 8.

As is clear from FIG. 9, the output of the counter 54 causes the monostable multicircuit 60 to go to H level for a short period of time as indicated by the signal 105, turning on the transistor 66 connected through the resistor 62, 64, and turning on the lamp 68. and activates the buzzer 70.

The time constant of the multi-circuit 60 is determined by the resistor 72 and capacitor 74.
Determined by

As explained above, according to the present invention, it is possible to reliably display the battery status to the driver by detecting pulse-like voltage changes occurring at the excitation terminal of the alternator, and to accurately display the charging status with an extremely simple circuit configuration. It becomes possible to detect.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the charging/discharging system of a typical vehicle, Figure 2 is a characteristic diagram showing changes in the excitation terminal voltage in Figure 1, and Figure 3 shows the smoothed excitation terminal voltage in Figure 2. FIG. 4 is a block diagram showing a first preferred embodiment of the detection device according to the present invention, FIG. 5 is a circuit diagram showing a second embodiment of the present invention, and FIG. FIG. 7 is a circuit diagram showing the third embodiment, FIG. 7 is a time chart of the third embodiment, FIG. 8 is a circuit diagram showing the fourth embodiment of the present invention, and FIG. 9 is a time chart of the fourth embodiment. 10... Battery, 12... Alternator, 20... Full charge detection circuit, 22...
...Display device, F...Excitation terminal.

Claims (1)

[Claims] 1. A full charge detection circuit that is connected to an excitation terminal of an alternator and detects a pulse-like voltage change at the excitation terminal, and a display device that displays the state of charge of the battery based on the output of the full charge detection circuit. 1. A state of charge detection device for a vehicle battery, characterized in that a pulse signal output to an excitation terminal of an alternator indicates that the battery is fully charged.