JP2724564B2 - Overvoltage alarm device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overvoltage warning device for warning that a voltage of a generator such as an alternator mounted on a vehicle has become excessive.

[0002]

2. Description of the Related Art As a power source of a vehicle, a battery and an alternator (generator) are usually mounted. The alternator is driven by the engine to generate power, supply power to various vehicle loads, and charge the battery.

[0003] Since the number of revolutions of the engine constantly changes depending on the operating condition of the vehicle, the voltage generated by the alternator is also changed.
It changes with it. However, since it is necessary to supply a predetermined voltage to the vehicle load, the alternator is provided with a regulator for controlling the field current and controlling the generated voltage to a predetermined value.

[0004] However, when an accident such as a short-circuit of the field coil to the vehicle body occurs, the regulator cannot control the field current, and the voltage generated by the alternator may become excessive. Then, an excessive current flows into the vehicle load and the battery, and if left as it is, an accident such as burning of the vehicle load or breakage of the battery will eventually occur.

In order to detect an overvoltage as soon as possible and avoid the above-described accident, it is necessary to take some measures. Conventionally, the detection depends on the driver's perception. There were many cases. That is, when an overvoltage occurs, the brightness of meters and various display lamps around the driver's seat increases, and the overvoltage is detected by the driver sensing the brightness.

As a conventional document concerning overvoltage of a vehicle power supply, there is, for example, Japanese Patent Application Laid-Open No. 2-197299.

[0007]

However, if the detection of overvoltage relies on the driver's perception, there is an individual difference in the degree of sensing, and the sensing may be delayed or overlooked. Or the battery may be damaged. An object of the present invention is to solve such a problem.

[0008]

In order to solve the above-mentioned problems, in the overvoltage alarm device of the present invention, a reset switch having a normally closed contact and a normally open contact is supplied through the normally closed contact. It is configured to include an overvoltage detection circuit that detects that the voltage has become overvoltage, and a capacitor that discharges electric charge through the normally open contact, so that the overvoltage detection circuit does not perform a detection operation for an instantaneous overvoltage. A holding circuit for holding an overvoltage detection state until the reset switch is reset, and a switch element of the holding circuit. An alarm circuit that issues an alarm when turned on is provided.

[0009]

[Operation] By using an overvoltage detection circuit that generates a detection signal when a voltage from an alternator or the like exceeds a predetermined value, overvoltage detection can be performed regardless of individual differences between drivers, and overlooked. Can also be prevented. By detecting the voltage to be detected after passing it through the time constant circuit, it is no longer possible to respond to an instantaneous excessive voltage that does not need to respond.

[0010] Further, once an overvoltage is detected, a holding circuit that keeps the ON state is provided, and power is supplied to the alarm circuit via the holding circuit. Therefore, it is possible to continue to output an alarm until the driver notices. Even if the driver releases the hold by the reset switch, if the malfunction is not caused, the alarm is issued again, so that it is possible to determine whether or not the malfunction has occurred.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing an overvoltage alarm device of the present invention. In FIG. 1, 1 to 4 are resistors, 5 and 6 are diodes, 7 is a Zener diode, 8 to 12 are resistors, 1
3 and 14 are transistors, 15 is a reset switch, 1
6, 17 are resistors, 18 is a buzzer, 19 and 20 are light emitting diodes, 21 is a resistor, 22 is a diode, 23 is a key switch, 24 is a load, 25 is a battery, 26 is a battery switch, 27 is an alternator, and 28 is a regulator. ,
29 is an overvoltage detection circuit, 30 is a time constant circuit, 31 is a capacitor, 32 is a holding circuit, and 33 is an alarm circuit.

The portion to the left of the boundary line XX is the overvoltage alarm device, and the portion to the right thereof is the vehicle wiring portion including the battery 25, the alternator 27, the load 24, and the like. The battery 25 and the alternator 27 constitute a power supply unit. The alternator 27 is driven by an engine (not shown) to generate power. The generated voltage is controlled to a constant voltage by the regulator 28. Battery 25 is
Connected to an alternator 27 via a battery switch 26.

When the key switch 23 is turned on, power is supplied from the battery 25 to the load 24. When the alternator 27 starts generating power, the battery 25 and the load 24 are mainly supplied from the alternator 27. The overvoltage alarm device of the present invention detects that the power supply voltage supplied to the load via the key switch 23 has become overvoltage.

First, an outline of the configuration of the overvoltage alarm device will be described. A main part of the overvoltage alarm device includes an overvoltage detection circuit 2 for detecting that the power supply voltage has become larger than a predetermined value.
9, an holding circuit 32 for holding the ON state when an overvoltage is detected, and an alarm circuit 33 for notifying that the overvoltage has been detected. The light emitting diode 20 is a power indicator for indicating that the power voltage is being applied.

The power supply voltage is applied to the overvoltage detection circuit 29 via the diode 22 and the reset switch 15. The diode 22 is for reverse connection protection. The terminal (+,-) of the overvoltage alarm device is inserted in order to prevent the circuit of the overvoltage alarm device from being destroyed even if a reverse voltage is applied by accidentally reversing the connection.

As will be described in detail later, the reset switch 15 is provided for determining (confirming) whether the overvoltage causes an accident or a transient overvoltage that does not cause the accident. The reset switch 15
Is a structure (normal ON momentary switch) having a normally closed contact 15-1 and a normally open contact 15-2,
The power supply voltage is supplied via the normally closed contact 15-1.

The power supply voltage is divided by resistors 1 to 3 and applied to a series circuit composed of a diode 5, a resistor 4, a Zener diode 7, and a base / emitter of a transistor 13. The division ratio is adjusted by the central resistor 2. When the divided voltage has a normal value, the Zener diode 7 and the transistor 13 are off.

(Overvoltage Detection Operation) When the divided voltage is larger than the sum of the voltage of the Zener diode 7, the base-emitter forward voltage drop of the transistor 13, and the forward voltage drop of the diode 5, the Zener diode 7 turns on. , The transistor 13 is also turned on. By this operation, an overvoltage is detected. Therefore, what value the voltage to be determined to be an overvoltage is set depends on what kind of Zener diode 7 is used as the Zener diode 7 or how the voltage dividing ratio is set by the resistor 2. Can be

When the transistor 13 is turned on, the base potential of the transistor 14 decreases, and the transistor 14 is turned on. When the transistor 14 is turned on, the current flowing there is shunted and flows through the path of the resistor 9 → the diode 6 → the resistor 4 → the Zener diode 7 → the base / emitter of the transistor 13.

With this current, the ON state of the transistor 13 (therefore, the ON state of the transistor 14) is maintained even if the value of the divided voltage becomes small. That is, once the transistor 14 is turned on, the on state is maintained. The hold is released only when the reset switch 1
5 is turned off, but for the operation at that time,
Will be described later.

The other current shunted by the transistor 14 flows to the alarm circuit 33, which sounds the buzzer 18 and turns on the light emitting diode 19 to notify the driver that an overvoltage has been detected.

The time constant circuit 30 also serves as the resistors 1 to 3 of the overvoltage detection circuit 29 and is composed of a capacitor 31 and this. This is provided to prevent the transistor 13 from being turned on when the power supply voltage becomes momentarily excessive due to a surge or the like. Since the instantaneous fluctuation is an AC component, it is bypassed by the capacitor 31.

The overvoltage alarm device operates as described above to detect overvoltage. However, the overvoltage alarm device sometimes malfunctions for some reason to give an alarm. Therefore, it is convenient to provide a means for confirming whether an overvoltage state has occurred or a malfunction has occurred. The reset switch 15 is provided as the means.

When an alarm is issued, the driver turns off the reset switch 15. Then, the normally closed contact 15-1 is turned off and the normally open contact 15-2 is turned on. Normally closed contact 15-
When 1 is turned off, the power supply voltage is cut off, the transistor 14 that has been turned off is turned off, and the alarm stops. When the normally open contact 15-2 is turned on, the electric charge of the capacitor 31 is discharged through the resistor 8.

When the reset switch 15 is returned to the original position, the power supply voltage is supplied again. If the power supply is really in an overvoltage state, an alarm should be issued again. There shouldn't be. Thus, it is possible to determine whether or not a malfunction has occurred.

[0026]

As described above, according to the overvoltage alarm device of the present invention, an overvoltage can be detected without relying on the driver's detection, and a vehicle load and a battery burnout accident can be reliably prevented. become able to. Further, it is possible to determine whether or not a malfunction has occurred even if an alarm is issued by a circuit for holding the overvoltage detection state and a reset switch for canceling the state.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overvoltage alarm device of the present invention.

[Explanation of symbols]

1-4 resistance, 5, 6 diode, 7 Zener diode, 8-12 resistance, 13, 14 transistor
15: reset switch, 16, 17: resistor, 18: buzzer, 19, 20: light emitting diode, 21: resistor, 22
... Diode, 23 ... Key switch, 24 ... Load, 25
... Battery, 26 ... Battery switch, 27 ... Alternator, 28 ... Regulator, 29 ... Overvoltage detection circuit, 3
0: time constant circuit, 31: capacitor, 32: holding circuit,
33… Alarm circuit

Claims (1)

(57) [Claims] 1. A reset switch having a normally closed contact and a normally open contact, an overvoltage detection circuit for detecting that a voltage supplied via the normally closed contact has become overvoltage, and the normally open contact A time constant circuit configured to prevent the overvoltage detection circuit from detecting the instantaneous excessive voltage, and a switch element that is turned on when the overvoltage is detected. Comprising a holding circuit that holds an overvoltage detection state until the reset switch is reset, and an alarm circuit that issues an alarm when a switch element of the holding circuit is turned on. Alarm device.