JPS60163745A - Horn circuit - Google Patents

Abstract

PURPOSE:To make short warning sounds as desired which are effective as a countermeasure for noises by turning on a field-effect transistor when a touch switch is on to drive a relay circuit and thereby to sound a horn through a horn switch. CONSTITUTION:When a head touches a touch member of a touch switch TS, a gate G of a FET (field-effect transistor) Q1 receives the voltage from a secondary battery E1 divided between resistances R7, R6 and a resistance (several hundred KOMEGA) inherent to the hand on the basis of a node between resistances R4 and R5. Then, the FET Q1 held in cut-off state is turned on to pass the current to resistances R2, R3 in a relay circuit 3, and a transistor Q2 is turned on to close a switch 2a of a relay Re2. This causes a horn switch 1a of a relay Re1 to be closed and a horn H to which power is supplied through a battery B on board is operated to make a warning sound.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a horn circuit for driving a horn attached to an automobile or the like as an alarm generating means.

Conventionally, horns installed in automobiles and other vehicles as a means of generating a warning sound consist of a relay that passes a large current through a horn switch that is connected in series with the vehicle battery, and the switch that controls the excitation circuit of this relay is turned on. It was making a sound.

However, in the conventional horn circuit as described above, the switch that has a mechanically movable part used to turn on the excitation circuit of the relay has a movable part of a metal piece that is normally biased by a coil spring and in a non-contact state. Due to the structure in which the movable contact contacts the fixed contact during operation, it is not easy to make the movable contact momentarily contact the fixed contact against the biasing force of the coil spring to generate a short warning sound, and the contact may deteriorate over time. When it gets dirty, the conductivity deteriorates, and in some cases the alarm may not sound.

The present invention was made in view of the above-mentioned circumstances, and an object of the present invention is to provide a horn circuit that can generate a short warning sound at a desired time, which is useful as a noise countermeasure, and that does not cause malfunction.

This invention includes a relay circuit that turns on a horn switch,
A secondary battery that is charged by an in-vehicle battery, a pair of touch switches that are attached to a suitable position on the steering wheel and one of which is connected to the secondary battery, and the other of the touch switches are connected to the gate, both of which are connected to the secondary battery. A touch switch, characterized in that it is provided with a field effect transistor (hereinafter simply referred to as FET) to which a bias voltage is directly supplied, which is normally set to a cut-off state, and which is turned on when the switch is turned on to drive the relay circuit. The horn sounds only while the hand is in contact with the touch part.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

The figure is a circuit diagram of a horn circuit that is a specific embodiment of the present invention.

In the figure, the horn H is connected to 1 through the horn switch 1a.
Connected to 2V vehicle battery B.

Horn switch 1a is a contact point of relay Rel, and I
The excitation circuit of relay Rel that operates at A is relay R, which will be described later.
On/off control is performed by turning on/off the switch 2a, which is a contact point of e2.

In addition, the voltage of the vehicle battery B is applied to the secondary battery E1, which is a nickel cadmium battery with a rating of 1.2V, via the excitation coil of the relay Rel and the resistor R1 that regulates the charging current.
．． Guided by E2. Secondary battery El connected in series,
A relay circuit 3 that turns on and off the excitation circuit of the relay Rel is connected to both ends of E2. The relay circuit 3 is
It is composed of a relay Re2, a transistor Q2 for forming an excitation circuit for the relay Re2, and bias resistors R2 and R3. Resistor R3 of relay circuit 3
is FETQ that controls on/off of transistor Q2.
The drain D of I is connected.

A secondary battery E2 is connected to the source S of FETQI,
Bias voltage is supplied directly. FETQ
One terminal of a pair of touch switches TS is connected to the gate 1-G of I through a resistor 1 for short-circuit protection, and a high resistor R6 for biasing is also connected.

The other terminal of the touch switch TS receives voltage supply from the secondary battery E1.

FETQI is always supplied with a direct bias voltage from the secondary battery E2, but is set to a cut-off state during normal times when the touch switch TS is not turned on. FET
The reason why bias supply of Q'l is performed by the secondary battery E2 is to suppress fluctuations in bias voltage due to temperature changes and accurately control FET Ql over a wide temperature range. In other words, the bias of FETQI can be obtained by passing current through a Zener diode and using its Zener voltage, but since semiconductors have a narrow stable temperature range, the bias voltage fluctuates due to changes in ambient temperature, which can cause malfunction of the entire device. There are drawbacks to it. In addition, touch switch TS
The reason why FETQI is used as the input element is to enable high input impedance. That is,
This is to ensure that the relay circuit 3 can be turned on even if the short-circuit impedance of the touch switch TS is as high as a human hand.

The touch switch TS is a switch that is attached to a suitable position on the steering wheel of an automobile, and when a person's hand touches the touch part, a closed circuit is formed through the hand.

In the above configuration, under normal conditions, that is, when the horn H is not sounding, the touch part of the touch switch TS is in an insulated state, and no gate voltage is applied to the gate G of FET QI, so that FET Ql is It is in a cut-off state. When FETQl is in the cutoff state, the relay circuit 3 is in the off state, so the switch 2a, which is the contact point of the relay Re2, is open. Further, at this time, a weak charging current is supplied to the secondary batteries El and E2 from the vehicle battery B via the excitation coil of the relay Rel and the resistor R1. At this weak charging current, the relay Rel
Since the operating current is IA, the excitation coil will not operate and the horn switch 1a will not close.

Next, touch the touch part of the touch switch TS with your hand,
The state in which the horn H is sounding the alarm will be explained.

When a human hand touches the touch part of the touch switch TS, the resistance of the human hand is about several tens of ohms, so the FET Ql
The gate G is based on the connection point between resistors R4 and R5,
The voltage of the secondary battery E1 divided by resistors R7 and R6 and several hundred Ω is applied. When a gate voltage is applied to FETQI, FETQI, which was in a cutoff state, is turned on. By turning on FETQI, the resistance R of relay circuit 3
2, current flows through R3, turning on transistor Q2.

When transistor Q2 is turned on and an excitation circuit for relay Re2 is formed, switch 2a, which is a contact point of relay Re2,
closes. When the switch 2a is closed, the excitation circuit of the relay Rel is supplied with the operating current of IA from the on-vehicle battery 7 battery B, and the horn switch 1a, which is the contact point of the relay Rel, is
Also close. When the horn switch 1a is turned on, the horn H
The voltage of 12V car battery B is supplied to the horn H.
generates an alarm. That is, while the hand is in contact with the touch part of the touch switch TS, the horn H continues to generate the alarm sound due to the above operation. If you want to shorten the alarm sound generated by horn H as a noise countermeasure, you can shorten the contact time of your hand with the touch part of touch switch TS, and relay R
It can be shortened within the allowable response range of e1 and Re2.

In the embodiments shown above, the horn switch is configured with a relay in order to pass a large current through the horn, but the horn switch can also be made into a non-contact switch using well-known techniques.

As described above, according to the present invention, there is provided a relay circuit for turning on a horn switch, a secondary battery that is charged by an on-board battery, and a pair of touch switches that are attached to appropriate positions on a steering wheel and one of which is connected to the secondary battery. , the other end of the touch switch is connected to the gate, and a bias voltage is directly supplied by the secondary battery, and the FET is normally set to the cassette off state and turns on when the touch switch is on to drive the relay circuit. Therefore, the horn can sound reliably just by touching the touch part of the touch switch with a high impedance human hand, and
From the standpoint of noise control, there is an advantage in that the time for generating the alarm can be shortened by simply shortening the contact time of the hand brought into contact with the touch part. Furthermore, the FET is supplied with bias voltage directly from a secondary battery, and the touch switch has no mechanical moving parts, so it can operate accurately over a wide temperature range and there is no risk of malfunction over time. has advantages.

[Brief explanation of the drawing]

The figure is a circuit diagram of a horn circuit that is a specific embodiment of the present invention. H-bone, B-vehicle battery, El, R2-secondary battery, 1a-horn switch, TS-touch switch, Ql-FET (field effect transistor) 3-relay circuit. Applicant Kuroi Electric Co., Ltd. Agent Patent Attorney Hisao Komori

Claims (1)

[Claims] A horn circuit that connects a horn switch to an on-vehicle battery and turns on the horn switch to sound an alarm, comprising: a relay circuit that turns on the horn switch; and a secondary battery that is charged by the on-board battery. A battery, a pair of touch switches attached to a suitable position on the handle, one of which is connected to the secondary battery, and the other of the touch switches is connected to the gate and a bias voltage is directly supplied by the secondary battery, and normally and a field-effect transistor that is set to a negative power off state when the touch switch is turned on and drives the relay circuit when the touch switch is turned on.