GB2143381A

GB2143381A - Hall signal generator for producing trigger pulses for ignition operations in an internal combustion engine

Info

Publication number: GB2143381A
Application number: GB08413073A
Authority: GB
Inventors: Harry Kaiser
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1983-07-09
Filing date: 1984-05-22
Publication date: 1985-02-06
Also published as: JPS6036780A; GB8413073D0; DE3324816A1; GB2143381B

Abstract

A Hall signal generator for producing trigger pulses (26) for ignition operations in an internal combustion engine comprises a Hall element (19), a permanent magnet (18) and a masking rotor (17) which is made from soft iron and which has mask portions (23) which are separated from one another by gaps (22) and which are movable through a gap between the permanent magnet (18) and the Hall element (19). In accordance with the invention, the number of mask portions (23) is an integral multiple of the number of cylinders of the internal combustion engine, the pulses (25) produced thereby being reduced to the required number of trigger pulses by means of a frequency divider (24). Consequently, the flow of current in the primary winding (5) of the ignition coil (6) always extends over constant angular portions of the masking rotor (16). <IMAGE>

Description

SPECIFICATION Hall signal generator for producing trigger pulses for ignition operations in an internal combustion engine The invention relates to a Hall signal generatorfor producing trigger pulses for ignition operations in an internal combustion engine.

A signal generator is already known (in accordance with ref: BOSCH Technical Reports 5 - 1974 5/6, page 233), in which magnetic screening portions of a screening rotor are movable through a gap between a permanent magnet and a Hall element.

The number of screening portions is equal to the number of cylinders of the internal combustion engine. As soon as one of the screening portions arrives between the permanent magnet and the Hall element, a flow of current is established in the primary winding of an ignition coil and hence ignition energy is stored for the next ignition operation. When this screening portion leaves the gap between the permanent magnet and the Hall generator, the current fed by way of the primary winding of the ignition coil is interrupted and a high-voltage pulse is induced in the secondary winding of the ignition coil and cause a spark-over (ignition spark) at one of the spark plugs connected to the secondary winding. The cycle which has just been described recommences when the following screening portion arrives between the magnet and the Hall generator.

It has now been found that the angular distance between the leading edges of two successive screening portions is adequately constant over the entire circumference of the masking rotor, whereas the individual screening portions and the spaces separating them extend over angular ranges which differ from one another to a considerable extent as a result of manufacturing tolerances. Consequently, the angular distances over which the flow of current or the interruption of current in or through the primary winding respectively extends differ from one another to a considerable extent, and, in the case of a high engine speed, can mean that the amount of ignition energy stored is not always sufficient for an effective ignition spark.

It is an object of the present invention to provide a Hall signal generator which substantially overcomes the above-mentioned disadvantages.

In accordance with the present invention, there is provided a Hall signal generator for producing trigger pulses for ignition operations in an internal combustion engine, comprising a Hall element, a permanent magnet, and a screening rotor which has screening portions made from soft iron and separated from one another by spaces, the screening portions being movable through a gap between the permanent magnet and the Hall element, and a frequency divider connected to the Hall element, the number of screening portions being an integral multiple of the number of cylinders of the internal combustion engine, whereby the pulses produced by the Hall element are reduced to the required number of trigger pulses.

The invention will now be described further hereinafter, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a circuit diagram of an ignition system having a signal generator in accordance with the invention, and Figure 2 shows the construction of a masking rotor forming part of such a signal generator.

Figure 1 shows the circuit arrangement of an ignition system which is intended to form part of an internal combustion engine (not illustrated) of a motor vehicle (also not illustrated). This ignition system is fed from a direct current source 1 which may be the battery of the motor vehicle. A lead 2 is connected between the negative pole of the current source 1 and earth, and a supply lead 4 incorporating an operating switch (ignition switch) 3 is connected to the positive pole. The supply lead 4 is the starting point for a circuit branch which first leads by way of the primary winding 5 of an ignition coil 6 and then to the earth lead 2 by way of an electronic switch 7.

In the preferred case, the electronic switch 7 is a transistor 8.

One terminal of the secondary winding 9 of the ignition coil 6 is connected to the lead between the primary winding 5 and the electronic switch 7, and the other terminal of the secondary winding is connected to an electrode (rotor arm) 10 which is rotatable by the internal combustion engine and which is part of an ignition distributor 11 and can be moved past four fixed electrodes 12 which are spaced at equal angular distances apart. Each of the four fixed electrodes 12 is connected to the earth lead2bywayofoneoffoursparkplugs 13.

Furthermore, each of the four spark plugs 13 is disposed in one of four cylinders 14 of an internal combustion engine 15. For the sake of simplicity, the four cylinders 14 of the internal combustion engine 15 are indicated only symbolically by broken lines.

Finally, the ignition system has an associated Hall signal generator 16 which essentially comprises a soft iron screening rotor 17, a permanent magnet 18 and a Hall element 19, the Hall element 19 forming an integrated circuit together with a Schmitt trigger 20 connected to the output of the Hall element and a control transistor 21 connected to the output of the Schmitt trigger 20, the integrated circuit being a structural component of the signal generator 16. The screening rotor 17, whose possible construction is shown in Figure 2, comprises magnetic-screening portions 23 which are separated by spaces 22 and which are movable through the gap between the permanent magnet 18 and the Hall element 19, namely in the direction of rotation indicated by the arrow R in the present case.The number of screening portions 23 is an integral multiple of the number of cylinders 14 of the internal combustion engine 15, the number of screening portions 23 in the illustrated embodiment being twice the number of the cylinders 14 of the internal combustion engine 15.

The output of the control transistor 21 is connected to the input of a frequency divider 24 which reduces the pulses 25, produced by the signal generator 16, to the number of trigger pulses 26 required for triggering the ignition operations. The trigger pulses 26 made available at the output of the frequency divider 24 are fed to the control input of the electronic switch 7, the electronic switch 7 being conductive during the pulse duration t1 and being non-conductive during the duration t2 of the pulse interval.

In conjunction with the signal generator 16, the ignition system which has just been described operates in the following manner: As soon as the operating switch 3 is closed, and the internal combustion engine is put into operation, the spark plugs 13 ignite the fuel/air mixture compressed in the cylinders 14, the ignition sequence being determined by the ignition distributor 11.

Ignition occurs each time the flow of current through the primary winding 5 is interrupted by the electronic switch 8 at the end of the pulse duration to. A high-voltage pulse is then produced in the secondarywinding 9 and causes an electrical spark-over (ignition spark) at one of the spark plugs 13.

The signal generator 16 is then set (possibly with the use of a position sensor), such that a respective leading edge of one of the screening portions 23 entering between the magnet 18 and the Hall element 19 provides for the commencement of the pulse duration t1 and thus for the switching-on of the electronic switch 8 and flow of current then established in the primary winding 5. In the same way, one of the leading edges of one of the screening portions 23 entering between the permanent magnet 18 and Hall element 19 ensures that the pulse duration t1 is terminated and the pulse interval t2 is commenced, with the result that the electronic switch 8 interrupts the current flowing through the primary winding 5 and the high-voltage pulse, thereby appearing in the secondary winding 9, causes an electrical spark-over at a spark plug 13.

When manufacturing the screening rotor 17, it has been found that it is possible to achieve over its entire periphery equal angular distances between two leading and trailing edges of two successive screening portions 23, although it is different to realise an arrangement in which the individual screening portions 23 and the spaces 22 located therebetween extend over equal angular sections. It can be seen from this that the trigger pulses 26 can also extend over constant angular ranges (relative to the screening rotor 17), this not being the case when the screening portions 23 and the spaces 22 are used directly to form the trigger pulses 26.

In the simplest case, the frequency divider 24 may be a Tflip-flop.

It will be appreciated that, when required, it is also possible to use the edges of the screening portions 23, emerging from the gap between the permanent magnet 18 and the Hall element 19, for the purpose of forming the trigger pulses 26.

Claims

1. A Hall signal generatorfor producing trigger pulses for ignition operations in an internal combustion engine, comprising a Hall element, a permanent magnet, and a screening rotor which has screening portions made from soft iron and separated from one another by spaces, the screening portions being movable through a gap between the permanent magnet and the Hall element, and a frequency divider connected to the Hall element, the number of screening portions being an integral multiple of the number of cylinders of the internal combustion engine, whereby the pulses produced by the Hall element are reduced to the required number of trigger pulses.

2. A signal generator as claimed in claim 1, in which the frequency divider comprises a flip-flop.

3. A Hall signal generator substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.