GB2173601A

GB2173601A - Ignition monitoring equipment

Info

Publication number: GB2173601A
Application number: GB08527803A
Authority: GB
Inventors: Russell Colin Richings; Alan Hoy
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1985-04-12
Filing date: 1985-11-11
Publication date: 1986-10-15
Also published as: GB8509386D0; GB2173601B; GB8527803D0

Abstract

Ignition monitoring equipment comprises a light emitting diode 22 adapted to be connected in series 14,16 with a high tension lead of the ignition circuit and arranged to produce a pulse of light for each spark pulse in the ignition circuit. A transient suppressor 26 is connected in parallel with the diode 22 to protect it from the high voltage spark pulses in the ignition circuit. Also connected are a series resistor 25, a parallel resistor 28 and a parallel Schottkey diode 30, the latter giving protection against reverse voltages. An optic fibre 36 conveys light pulses to an opto-electrical converter 38 which provides electrical signals for test or measurement purposes. <IMAGE>

Description

SPECIFICATION Ignition spark transducer This invention relates to motor vehicle ignition monitoring equipment connected to a transducer for providing a signal for each electrical spark generating pulse in the ignition circuit of an internal combustion engine. Such test equipment is used in service bays to set the correct spark timing, and may also find application in engine control systems.

The transducers used in such equipment must operate without reducing the spark or affecting the timing and without causing additional radio frequency interference.

It is usual to employ as a transducer in such an application an inductive loop passing around one of the ignition leads but the problem encountered with such a transducer is that the wire lead connecting the transducer to the monitoring equipment may sometimes pick up spurious voltages or in the case of a breakdown of insulation in the vicinity of the lead can cause the high ignition voltages to be applied to the monitoring equipment to cause possible damage to the equipment and shock to the system operator.

The invention seeks to provide a simple transducer er which mitigates the above problems and can be connected quickly and easily with an ignition circuit.

According to the present invention, there is provided an ignition monitoring equipment connected to a spark transducer which in use is connected series with the ignition circuit of an internal con bus- tion engine and serves to provide with a signal coincident with each spark, wherein the transducer is an electro-optical transducer connected by an optic fibre to the monitoring equipment and the monitoring equipment includes an opto-electrical transducer for converting light transmitted by the optic fibre into electrical signals, the electro-optical transducer comprising a light emitting diode and a transient suppressor connected in parallel with the light-emitting diode, the transient suppressor providing a path for each electrical spark generating pulse and limiting the voltage across the light emitting diode.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which; Figure 1 is a circuit diagram of an electro-optical transducer, Figure 2 is a rear view of the transducer, and Figure 3 is a side view of the transducer.

An ignition spark transducer 10 comprises a hollow PTFE housing 12 having a male H.T. connector 14 at the lower end adapted to fit the H.T. socket connecter of an ignition coil in the ignition circuit of an internal combustion engine. An. H.T. socket connector 16 is mounted in the upper end of the housing 12 and is adapted to receive the H.T. king lead which would normally be inserted in the ignition coil.

The male H.T. connector 14 is retained by nut 18 and the H.T. socket 16 is retained by nut 20.

A light emitting diode 22 is secured in an aperture in one side of the housing 12 by nut 24, and terminals are connected to the H.T. connectors 14 and 16 in series with a 200 ohm resistor 25, as shown in the circuit diagram of Figure 1.

A surge transient suppressor 26, a 1 Kohm resistor 28, and a Schottkey diode 30, are connected in parallel with the light emitting diode.

The polarity of the components is as shown in Figure 1 for a negative earth electrical system. A transducer for a positive earth system has the connections to the ignition coil and the king lead reversed.

The components 25, 26, 28 and 30 are preferably encapsulated in a silicone compound. The housing is closed, except for a window (now shown) for emission of light from the light emitting diode 22, by a sleeve 34. An optic fibre 36 is arranged in the vicinity of the light emitting diode 22 and leads to the monitoring equipment where an opto-electrical transducer, represented in Figure 1 by a photo-diode 38, converts the pulses of light into electrical signals to be used in setting up the spark timing.

The transient suppressor is a PN silicon device which has been developed for connection across the voltage supply lines to integrated circuits or other voltage sensitive circuits to protect those circuits against surges in voltage. Above a certain characteristic voltage, typically in the range 6 to 20 volts the transient suppressor switches from a relatively high resistance to a low resistance with a very fast response time of (less than 1 x 10.12 seconds). In the present circuit the transient suppressor is used to pass the high spark voltage without significant degradation and to provide a signal at the characteristic voltage of the compressor device.

In operation, each spark pulse generated by the coil creates a high voltage across the connectors 14 and 16 of the transducer, with the coil going negative compared to the kind lead. This turns on the light emitting diode 22 which remains on for the duration of the spark. The suppressor 26 provides a low resistance as soon as the voltage exceeds a predetermined value, typically 18 volts. The suppressor thus protects the light emitting diode 22 from excessive voltage and provides a low resistance path for the current directly ensuring that the transducer has negligible effect on the spark.

The first diode 30 protects the circuit against reverse voltages. The optic fibre 36 transmits pulses of light emitted by the diode 22 to the opto-electrical transducer 38 in the monitoring equipment, where the resulting signal is used to set up the spark timing.

1. An ignition monitoring equipment connected to a sparktransducerwhich in use is connected series with the ignition circuit of an internal conbustion engine and serves to provide with a signal coincident with each spark, wherein the transducer is an electro-optical transducer connected by an optic fibre to the monitoring equipment and the monitoring equipment includes an opto-electrical transducer for converting light transmitted by the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Ignition spark transducer This invention relates to motor vehicle ignition monitoring equipment connected to a transducer for providing a signal for each electrical spark generating pulse in the ignition circuit of an internal combustion engine. Such test equipment is used in service bays to set the correct spark timing, and may also find application in engine control systems. The transducers used in such equipment must operate without reducing the spark or affecting the timing and without causing additional radio frequency interference. It is usual to employ as a transducer in such an application an inductive loop passing around one of the ignition leads but the problem encountered with such a transducer is that the wire lead connecting the transducer to the monitoring equipment may sometimes pick up spurious voltages or in the case of a breakdown of insulation in the vicinity of the lead can cause the high ignition voltages to be applied to the monitoring equipment to cause possible damage to the equipment and shock to the system operator. The invention seeks to provide a simple transducer er which mitigates the above problems and can be connected quickly and easily with an ignition circuit. According to the present invention, there is provided an ignition monitoring equipment connected to a spark transducer which in use is connected series with the ignition circuit of an internal con bus- tion engine and serves to provide with a signal coincident with each spark, wherein the transducer is an electro-optical transducer connected by an optic fibre to the monitoring equipment and the monitoring equipment includes an opto-electrical transducer for converting light transmitted by the optic fibre into electrical signals, the electro-optical transducer comprising a light emitting diode and a transient suppressor connected in parallel with the light-emitting diode, the transient suppressor providing a path for each electrical spark generating pulse and limiting the voltage across the light emitting diode. The invention will now be described further, by way of example, with reference to the accompanying drawings, in which; Figure 1 is a circuit diagram of an electro-optical transducer, Figure 2 is a rear view of the transducer, and Figure 3 is a side view of the transducer. An ignition spark transducer 10 comprises a hollow PTFE housing 12 having a male H.T. connector 14 at the lower end adapted to fit the H.T. socket connecter of an ignition coil in the ignition circuit of an internal combustion engine. An. H.T. socket connector 16 is mounted in the upper end of the housing 12 and is adapted to receive the H.T. king lead which would normally be inserted in the ignition coil. The male H.T. connector 14 is retained by nut 18 and the H.T. socket 16 is retained by nut 20. A light emitting diode 22 is secured in an aperture in one side of the housing 12 by nut 24, and terminals are connected to the H.T. connectors 14 and 16 in series with a 200 ohm resistor 25, as shown in the circuit diagram of Figure 1. A surge transient suppressor 26, a 1 Kohm resistor 28, and a Schottkey diode 30, are connected in parallel with the light emitting diode. The polarity of the components is as shown in Figure 1 for a negative earth electrical system. A transducer for a positive earth system has the connections to the ignition coil and the king lead reversed. The components 25, 26, 28 and 30 are preferably encapsulated in a silicone compound. The housing is closed, except for a window (now shown) for emission of light from the light emitting diode 22, by a sleeve 34. An optic fibre 36 is arranged in the vicinity of the light emitting diode 22 and leads to the monitoring equipment where an opto-electrical transducer, represented in Figure 1 by a photo-diode 38, converts the pulses of light into electrical signals to be used in setting up the spark timing. The transient suppressor is a PN silicon device which has been developed for connection across the voltage supply lines to integrated circuits or other voltage sensitive circuits to protect those circuits against surges in voltage. Above a certain characteristic voltage, typically in the range 6 to 20 volts the transient suppressor switches from a relatively high resistance to a low resistance with a very fast response time of (less than 1 x 10.12 seconds). In the present circuit the transient suppressor is used to pass the high spark voltage without significant degradation and to provide a signal at the characteristic voltage of the compressor device. In operation, each spark pulse generated by the coil creates a high voltage across the connectors 14 and 16 of the transducer, with the coil going negative compared to the kind lead. This turns on the light emitting diode 22 which remains on for the duration of the spark. The suppressor 26 provides a low resistance as soon as the voltage exceeds a predetermined value, typically 18 volts. The suppressor thus protects the light emitting diode 22 from excessive voltage and provides a low resistance path for the current directly ensuring that the transducer has negligible effect on the spark. The first diode 30 protects the circuit against reverse voltages. The optic fibre 36 transmits pulses of light emitted by the diode 22 to the opto-electrical transducer 38 in the monitoring equipment, where the resulting signal is used to set up the spark timing. CLAIMS

1. An ignition monitoring equipment connected to a sparktransducerwhich in use is connected series with the ignition circuit of an internal conbustion engine and serves to provide with a signal coincident with each spark, wherein the transducer is an electro-optical transducer connected by an optic fibre to the monitoring equipment and the monitoring equipment includes an opto-electrical transducer for converting light transmitted by the optic fibre into electrical signals, the electro-optical transducer comprising a light emitting diode and a transient suppressor connected in parallel with the light-emitting diode, the transient suppressor providing a path for each electrical spark generating pulse and limiting the voltage across the light emitting diode.

2. An ignition monitoring equipment as claimed in Claim 1, wherein the electro-optical transducer comprises a fast diode connected in parallel with the light emitting diode and the suppressor and arranged to provide a low resistance to any reverse voltage in the ignition current and thereby protect the light emitting diode from each reverse voltage.

3. An ignition monitoring equipment as claimed in Claim 1 or 2, wherein the electro-optical transducer further comprises a resistor connected in parallel with the suppressor.

4. An ignition monitoring equipment as claimed in any one of the preceding claims, wherein the electro-optical transducer further comprises a resistor connected in series with the light emitting diode.

5. An ignition monitoring equipment as claimed in any one of the preceding claims, wherein the electro-optical transducer comprises a housing having an electrical connector at one end adapted to fit into the H.T. terminal of a coil of the ignition current and an electrical connector at the other end adapted to receive a distributor lead of the ignition current, the suppressor and the light emitting diode being connected between the terminals with the housing and the light emitting diode being positioned to emit said pulses of light through a window in the side of the housing.

6. An ignition monitoring equipment having a spark transducer substantially as herein before described with reference to and as illustrated in the accompanying drawings.