GB2256963A

GB2256963A - Electric horn

Info

Publication number: GB2256963A
Application number: GB9211757A
Authority: GB
Inventors: Young-Seog Kim
Original assignee: Mando Machinery Corp
Current assignee: Mando Machinery Corp
Priority date: 1991-06-08
Filing date: 1992-06-03
Publication date: 1992-12-23
Anticipated expiration: 2012-06-03
Also published as: JPH06324683A; JP2955904B2; DE4218621A1; DE4218621C2; GB2256963B; GB9211757D0

Description

0g, ELECTRIC HORN The present invention relates to an electric horn

employed in a vehicle; and more particularly, to an improved horn capable of minimizing or removing an electric arc produced between the mechanical contacts in a horn actuating circuitry during the operation of the horn.

In general, an electric horn for use in a vehicle Includes a horn actuating circuitry having mechanical contacts arranged therein. Specifically, a typical electric horn has an interrupter connected serially in circuit with a coil of an electromagnet. Therefore, electric arc may be produced at the interface between the contacts of the interrupter especially when a high current, e.g., 5 amperes, flows through the serial connection of the interrupter and the coil of the electromagnet. Such an arcing condition induces an electromagnetic interference that may disturb or interfere with radio reception and affect adversely on the operation of other electronic control circuits in the same vehicle. Furthermore, such electric arc may result in burning- out or fusingdown of the contacts. This requires use of an expensive and high durability material in constructing the interrupter.

Accordingly, there have been proposed electric horns for suppresing such electric arc. For example, U.S. Patent No. 4,568,995 discloses an electromagnetic interference suppression device for suppressing electric arcing between the mechanical contacts of a vehicle horn actuating circuit. However, such device has a disadvantage in that there is not provided means for controlling an electric current to be supplied to the contacts at an appropriate level. Therefore, it has limited effeitiveness in reducing the electric arc occuring at the mechanical contacts.

In Japanese Laid-Open Patent Publication No. 86-200045, there is provided an electric alarm capable of diminishing electric arc produced between the contacts of an interrupter during the operation of the alarm. However, in this device, since a horn actuating switch is connected serially incircuit with a coil of an electromagnet, a large quantity of current flows through the horn actuating switch, thereby creating an electric arcing condition at the interface between the contacts of the horn actuating switch.

on the other hand, in order to remove the electric arc across the contacts of the horn actuating switch, a horn relay may be used to channel a small quantity of current through the horn actuating switch. However, such addition of a horn relay results in a rather complicated structure of a horn device and a relatively high manufacturing cost. Furthermore, since the electromagnet is situated near the foremost of a vehicle while the horn relay is located near the horn acuating switch which is positioned within a steering wheel, a lengthy conductor is required to connect the electromagnet with the horn actuating switch. As a result, the - 3 conductor acts as a source of an electromagnetic inteference which frequently occurs from a high frequency signal, e.g., 400Hz of 5 amperes, flowing therethrough, thereby disturbing or interfering with other electronic controls.

Accordingly, it is an aim of the present invention to provide an improved electric horn employed in a vehicle, which can remove or minimize an electric arc produced between the mechanical contacts of a horn actuating switch during the operation of the horn.

It is another aim of the present invention to provide an improved electric horn capable of producing soft sounds.

According to the present invention there is 11 provided an electric horn which comprises:

a diaphragm held at its peripheral portion in a housing of the horn and having an armature attached to a middle portion thereof; an electromagnet having a coil and disposed adjacent to the armature in an opposed relationship with each other for causing the armature to move down under an action of a magnetic field produced by an energising current flowing through said coil; an electronic contactless switch connected to the coil for interrupting the energising current supply to the coil of the electromagnet; a normally-closed interrupter located near the armature and connected to a control input of the contactless switch for turning ON and OFF the contactless switch, the interrupter having a fixed contact and.a movable contact, the movable contact engaging the armature so as to open the interrupter by the downward movement of the armature; a current limiting resistor connected serially with the interrupter; and a horn actuating switch connected serially in circuit with the interrupter. A capacitor is connected in parallel with the horn actuating switch for enabling the turning ON and OFF cycle of the contactless switch to be repeated in a given period of time during which the electric current flowing through the coil of the electromagnet is gradually reduced in its level.

Embodiments of theinvention will be described, by way of example only, with reference to the following drawings in which like numbers refer to like parts in different views, and in which:

Fig. 1 shows an embodiment of a preferred electric horn in accordance with the present invention. Fig. 2 shows'another embodiment of an electric horn in accordance with this invention.

Referring now to Fig. 1, there is shown an electric horn according to. a'preferred embodiment of the present invention, which comprises a diaphragm 10 firmly held at its peripheral portion in a housing of the harn(not shown), an armature 12 attached to a middle portion of the diaphragm 10, and an electromagnet 14 having a coil 16 and located opposite the armature 12 for drawing down the armature 12 when it is energised.

The coil 16 serves to energise the electromagnet 14. One end of the coil 16 is connected to the positive terminal of a battery 18; while the negative terminal of the battery 18 is grounded. The emitter of a PNP transistor 20 is connected to the other end of the coil 16 of the electromagnet 14. The collector of the transistor 20 is connected to ground and the base of the transistor 20 is connected, through a current limiting resistor 22, to a movable contact 26 of a normally-closed interrupter 24 positioned adjacent to the armature 12. The movable contact 26 is engaged with the armature 12.

A horn actuating switch 30 is at its one end connected to a fixed contact 28 of the interrupter 24 which is arranged in an opposite relationship with respect to the movable contact 26. The other end of the horn actuating switch 30 is connected to ground. The horn actuating switch 30 is positioned within a steering wheel(not shown). Normallyopened contacts of the horn actuating switch 30 become closed when the horn actuating switch 30 is subjected to an external manual actuating pressure.

A capacitor 32 is connected in parallel with the horn actuating switch 30 and begins to charge at the time when the horn actuating switch 30 is opened.

In operation, closing of the horn actuating switch 30 causes an electric current to flow from the battery 18 to ground through the coil 16 of the electromagnet 14, the emitter-base of the PNP transistor 20, the current limiting resistor 22, the contacts 26, 28 of the interrupter 24, and the horn actuating switch 30, thereby turning ON the transistor 20.

When the transitor 20 is ON, a closed loop is formed by the battery 18, the coil 16 of the electromagnet 14 and the emittercollector of the transistor 20, thereby causing an energising current supplied to the coil 16 of the electromagnet 14.

Accordingly, a magnetic field is generated around the electromagnet 14 by the energising current flowing through the coil 16 of the electromagnet 14 to thereby move the armature 12 toward the electromagnet 14. Such movement of the armature 12 causes the movable contact 26 and the fixed contact 28 of the interrupter 24 to open, thereby turning OFF the transistor 20. This enables the electromagnet 14 to be de-energised; and, thus, allows the armature 12 to move up from the electromagnet 14 by the spring action of the diaphragm 10. Return of the armature 12 allows the contacts 26, 28 of the interrupter 24 to close again. The energising current it resupplied to the coil 16 and the cycle is repeated.

When the horn actuating switch 30 is opened, the capacitor 32 begins to charge. Charging of the capacitor 32 enables the turning ON and OFF cycle of the transistor 20 to be repeated in a given period of time. In this period, the exciting current flowing through the coil 16 of the electromagnet 14 is gradually reduced in its magnitude. As a result, the gradually reduced current will weaken the intensity of the vibration of the diaphragm, thereby providing gradually lowering sounds in its volume.

Fig. 2 shows another embodiment of the present invention wherein an NPN transistor 34 is used instead of the PNP transistor 20 of Fig. 1. The collector of the NPN transistor 34 is connected to the other end of the coil 16 of the electromagnet 14 and the emitter thereof is connected to ground.

In addition, the collector of a PNP transistor 36 is connected to the base of the NPN transistor 34 through a second current limiting resistor 38. The emitter of the PNP transistor 36 is connected to the movable contact 26 of the interrupter 24. The fixed contact 28 of the interrupter 24 is commonly connected to the positive terminal of the battery 18 and one end of the coil 16.. The base of the PNP transistor 36 is commonly connected to one end of the horn actuating switch 30 and the positive terminal of the capacitor 32 through the first current limiting resistor 22.

In operation, closing of the horn actuating switch 30 causes an electric current to flow from the battery 18 to ground through the interrupter 24, the emitter-base of the PNP transistor 36, the first current limitting resistor 22 and the horn actuating switch 30, thereby turning ON the PNP transistor 36. Therefore, the PNP transitor 36 turns ON the NPN transistor 34, thereby enabling the electromagnet 14 to be energised. As a result, the energisation of the electromagnet 14 causes the armature 12 to move down toward the electromagnet 14. The interrupter 24 is opened to turn OFF the PNP transistor 36 because of the downward movement of the armature 12, thereby turning OFF the NPN transistor 34. This causes the electromagnet 14 to be de-energised and the armature 12 to return at its original position by "the spring action of the diaphragm 10, thereby closing again the interrupter 24. As described in the first embodiment, after the horn s witch 30 is opened, such cycles are repeated by the capacitor 32 in a given period of time.

Although this invention has been shown and described with respect to the preferred embodiments, it will be apparent to those skilled in the art that certain changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.

Claims

1. An& electric horn for use in a vehicle, which comprises:

a diaphragm held at its peripheral portion in a housing of the horn and having an armature attached to a middle portion thereof; an electromagnet having a coil and disposed adjacent to the armature in an opposite relationship with each other for causing the armature to move downward under an action of a magnetic field produced by an energising current flowing through the coil; a first electronic contactless switch connected to the coil for interrupting the energising current supply to the coil of the electromagnet; a normally-closed interrupter located near the armature and connected to a control input of the contactless switch for turning ON and OFF the contactless switch, the interrupter having a fixed contact and a movable contact, said movable contact engaging the armature so as to open the interrupter by the downward movement of the armature; a first current limiting resistor connected serially with the interrupter; and a horn actuating switch connected serially in circuit with the interrupter.

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2. The electric horn of claim 1, wherein said first contactless switch is a PNP transistor; and the horn actuating switch is disposed between ground and the interrupter.

3. The electric horn of claim 1, further comprising a second electronic contactless switch connected between the interrupter and said first electronic contactless switch for coupling and decoupling said interrupter to and from the control input of said first electronic contactless switch.

4. The electric horn of claim 3, wherein said first contactless switch is an NPN transistor; said second contactless switch is a PNP transistor; said horn switch is connected between a control input of said second switch and ground; said first current limiting resistor is connected between the control input of said second switch and g-round; and a second current limiting resistor is connected between said second switch and the control input of said first switch.

5. The electric horn of any of the preceding claims, further comprising means, at the time of opening of the horn switch, for enabling the turning ON and OFF cycle of said contactless switch(es) to be repeated in a given period of time during which the energising current flowing through the coil is gradually reduced in its amplitude.

6. The electric horn of claim 5, wherein said enabling means is a capacitor connected in parallel with the horn switch.

7. An electric horn substantially as hereinbefore described with reference to the accompanying drawings.

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