GB2356710A

GB2356710A - Recognition of engine cylinder work state

Info

Publication number: GB2356710A
Application number: GB0023218A
Authority: GB
Inventors: Holger Loof; Markus Panzer; Thilo Jahn
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1999-10-02
Filing date: 2000-09-21
Publication date: 2001-05-30
Anticipated expiration: 2020-09-21
Also published as: GB2356710B; JP2001140691A; DE19947764A1; GB0023218D0; FR2799241B1; FR2799241A1

Description

2356710 RECOGNITION OF ENGINE CYLINDER WORK STATE The present invention

relates to a method of and equipment for recognising the work state or work cycle of a cylinder of a six cylinder or twelve cylinder engine.

Recognition of the work state of a specific cylinder is necessary in different kinds of control or regulation of internal combustion engines, especially of the ignition and/or injection in a four-stroke engine. A transmitter which responds to a mark applied to the or a camshaft of the engine is usually provided for that purpose. However, since the angular accuracy of transmitters of that kind is usually inadequate due to the mechanical play that is present, this transmitter signal is additionally linked with a signal of a rotational speed transmitter, which responds to marks of a transmitter wheel rotating with the crankshaft. US-PS 3 592 178 discloses an electronic ignition system in which, for regulation of ignition angle and cylinder recognition, which corresponds with work cycle recognition, a transmitter wheel rotating synchronously with a distributor arm of the ignition distributor is used. One transmitter is provided for continuous rotational angle information and a further transmitter is provided for cylinder recognition.

A method of recognising the work cycle of an internal combustion engine is described in WO 97/05971, in which recognition is possible of the instantaneous work cycle of a cylinder by comparison of a signal synchronous with crankshaft angle and a signal modulated by the combustion processes of the engine.

In summary, it can be said that it is usual in conventional cylinder recognition systems to use two transmitters. In that case, one rotational speed transmitter is frequently arranged on the crankshaft and a further one on the camshaft of the engine. In a four-stroke engine, two crankshaft revolutions or one camshaft revolution are necessary for one cylinder cycle. In a fault-free case, therefore, the cylinder association of the crankshaft revolution signal is undertaken with the assistance of the signal of the camshaft.

If, however, the rotational speed transmitter of the camshaft cuts out or fails, it proves very complicated in conventional systems to establish the exact work state of, for example, the first cylinder. Establishing the work state of the first cylinder is, however, necessary after a 2 restarting of the engine in order to make possible a further operation of the system.

There is thus a need for means of recognising, in simpler manner by comparison with conventional systems, of the work state of a cylinder, especially the first cylinder, of a six cylinder or twelve cylinder internal combustion engine.

According to a first aspect of the present invention there is provided a method of recognising the work state or work cycle of a cylinder of a six or twelve cylinder internal combustion engine, wherein a transmitter coupled with a crankshaft of the internal combustion engine issues for each crankshaft revolution a transmitter signal which can be associated with the work state of the first or fourth or the first or seventh cylinder, characterised in that a drivable conveying pump coupled with the crankshaft or synchronised with the crankshaft, especially a conveying pump of a common rail injection system, is operated in a first work state at a cycle speed corresponding with the cylinder number and in a second work state at a cycle rate corresponding with half the cylinder number.

According to a second aspect of the invention there is provided equipment for recognising the work state or work cycle of a cylinder of a six or twelve cylinder internal combustion engine, with a transmitter which is coupled with a crankshaft of the engine and which issues for each crankshaft revolution a transmitter signal which can be associated with the work state of the first or fourth or the first or seventh cylinder, characterised in that a drivable conveying pump coupled with the crankshaft or synchronised with the crankshaft, especially a conveying pump of a common rail injection system, is operated in a first work state at a cycle speed corresponding with the cylinder number and in a second work state at a cycle rate corresponding with half the cylinder number.

In the case of, in particular, an engine constructed with a common rail injection system the work state or work cycle of the first cylinder of a cylinder cycle can be established in more simple manner by a method exemplifying or equipment embodying the present invention. Use is made of the fact that in, for example, common rail systems a synchronisation occurs or can be set between the work cycle of the respective cylinder and pump cycle rate of a common rail high pressure pump. By means of selective drive control of the pump, for example, a logical interlinking of the pressure signal, which originates from the pump, with a gate array synchronisation signal from a crankshaft transmitter can then be 3 carried out for establishing the work cycle of the first cylinder.

Preferably, the conveying pump is a double ram pump, which is operated with two rams for the first work state and with one ram for the second work state. A pump control of that kind can be performed by way of, for example, suitable software, by means of which one pump half can be selectably switched off. For example, it can be ensured by way of a coded plug connection that the pump is controlled or switched off in such a manner that in the work cycle of the first cylinder a pressure maximum arises in a pressure chamber, especially the distributor link of a common rail system, associated with the conveying pump. Since the pressure build-up is at a maximum only for each second cylinder, pressure troughs occur between the respective cylinders. Thus, in the case of conveying with only one ram a maximum pressure can be produced in the work cycle of cylinder 1 of a six cylinder engine and a minimum pressure can be produced in the work cycle of cylinder 4, so that the work states of the first and fourth cylinders are distinguishable from one another. If the conveying pump were to produce a pressure maximum per cylinder, the work state of the cylinder I would not be distinguishable from that of the cylinder 4. As a corresponding rotational speed signal is provided by the crankshaft in each work cycle or work state of the first and fourth cylinder (gate array synch ronisation), the work state specifically of the first cylinder is determinable by means of logical intedinking of the pressure signal and the rotational speed signal of the crankshaft, i.e. if a pressure maximum is present in the case of a gate array synchronisation, the work state of the first cylinder I is positively recognised.

An example of the method and embodiment of the equipment of the present invention will now be more particularly described by way of the accompanying drawing, the single figure of which is a signal diagram illustrating the principle of a method exemplifying the invention for a six cylinder internal combustion engine.

Referring now to the drawing there is shown in the first line a signal G originating from a transmitter which responds to a mark applied to a transmitter wheel rotating synchronously with the crankshaft of a six cylinder internal combustion engine. The signal G thus corresponds to a pulse train formed by a sequence of individual pulses which are triggered in each complete revolution of the transmitter wheel or crankshaft.

In the second line of the figure there is shown the pressure arising in a distributor link of a 4 common rail storage fuel injection system for two different operating states. The pressure of the system is produced by means of a double ram pump, which is known per se and therefore is not further explained. The normal operating state of a double ram pump can be characterised by means of the curve 1 represented as a dashed line; during one cylinder cycle, i.e. running through the work cycles or work states of all six cylinders, a corresponding number of pressure maxima and pressure minima occur. Denoted by BDC are the respective bottom dead centres of the cylinders. It can be recognised that on the basis of a logical linking of the signals G and 1 a distinction of the work states of the first and the fourth cylinders (which are associated with an identical angular position of the crankshaft) is not possible.

In the method exemplifying the invention, however, during a second operating state of the conveying pump a pressure course can be produced as indicated by means of the curve 2 represented as a solid line. Through operating a double ram pump with only one ram a pressure course curve is obtained which has only one pressure maximum with respect to each second cylinder. For a six cylinder engine this means that with appropriate setting of the partial operation of the conveying pump a pressure maximum arises in the work state of the first cylinder and a pressure minimum arises in the work state of the fourth cylinder. Through logical linking of the curve 2 with the signal G the work state of cylinder 1 becomes clearly recognisable, i.e. clearly distinguishable from the work state of cylinder 4.

As the individual cylinders of the engine are in a fixed phase relationship to one another the corresponding work cycle of any desired cylinder can similarly be established by simple angle additions, which is a known procedure as such and which, for simplification of the illustration, is not further explained.

The method according to the invention is usable with advantage particularly when a rotational speed transmitter associated with a camshaft falls. However, it is equally possible to use the method in ordinary manner, i.e. for the normal operation of a motor vehicle which does not have a camshaft transmitter. For this purpose it is, for example, possible after starting of the engine to intentionally switch off one pump half of the double ram pump in order to achieve a clear angle association of the work states of the individual cylinders merely on the basis of the pressure signal then obtained and a crankshaft transmitter signal. After carrying out this clear association, the double ram pump can then be switched over to double ram operation.

The method has been described and illustrated on the basis of a six cylinder engine, but is usable in analogous manner for a twelve cylinder engine, wherein in this case a differentiation of the first and the seventh cylinders is carried out.

6

Claims

1 A method of recognising the work state of a cylinder of a six or twelve cylinder engine equipped with a fuel conveying pump controllable to provide different conveying rates, comprising the steps of producing a signal synchronous with engine crankshaft rotation and indicative of the work state of two separate cylinders of the engine, controlling the pump for operation selectably at a first rate corresponding with the number of cylinders of the engine to produce a first pressure course and at a second rate corresponding with half the number of cylinders of the engine to produce a second pressure course and correlating the signal and the second pressure course to distinguish between said two cylinders.

2. A method as claimed in claim 1', wherein the pump is the pump of a common rail fuel injection system.

3. A method as claimed in claim I or claim 2, wherein the pump is a double ram pump and is controllable to operate with both rams to provide the first rate and with one of the rams to provide the second rate.

4. A method as claimed in any one of the preceding claims, wherein said two cylinders are the first and fourth cylinders of a six cylinder engine or first and seventh cylinders of a twelve cylinder engine.

5. A method as claimed in claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.

6. Equipment for recognising the work state of a cylinder of a six or twelve cylinder engine equipped with a fuel conveying pump controllable to provide different conveying rates, comprising means for producing a signal synchronous with engine crankshaft rotation and indicative of the work state of two separate cylinders of the engine, controlling the pump for operation selectably at a first rate corresponding with the number of cylinders of the engine to produce a first pressure course and at a second rate corresponding with half the number of cylinders of the engine to produce a second pressure course and correlating the signal and the second pressure course to distinguish between said two cylinders.

7 7. Equipment as claimed in claim 6, wherein the pump is the pump of a common rail fuel injection system.

8. Equipment as claimed in claim 6 or claim 7, wherein the pump is a double ram pump and is controllable to operate with both rams to provide the first rate and with one of the rams to provide the second rate.

9. Equipment as claimed in any one of claims 6 to 8, wherein said two cylinders are the first and fourth cylinders of a six cylinder engine or first and seventh cylinders of a twelve cylinder engine.

10. Equipment substantially as hereinbefore described with reference to the accompanying drawings.