GB2307005A

GB2307005A - Control of timing in an i.c. engine fuel supply, eg injection, system

Info

Publication number: GB2307005A
Application number: GB9623093A
Authority: GB
Inventors: Peter Lutz; Peter Schmitz
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1995-11-10
Filing date: 1996-11-05
Publication date: 1997-05-14
Anticipated expiration: 2016-11-05
Also published as: GB9623093D0; GB2307005B; DE19541927B4; JPH09170479A; DE19541927A1

Description

1 r f 113 - 1 - 2307005 CONTROL OF SETTING MEANS IN AN ENGINE FUEL SUPPLY

SYSTEM The present invention relates to a method of and control means for controlling and/or regulation of an internal combustion engine, in particular control of setting means in a fuel supply system.

A method and control means for this purpose are described in, for example, DE-OS 42 42 252. This method and control means are for control of a fueladmetering equipment of, in particular, a diesel engine. In that case there is control of the drive of an injection adjuster which influences the conveying rate of the fuel admetering. For this purpose, an engine control device presets a signal which indicates the desired start of the conveying referred to the engine crankshaft position. A second control unit then controls a setting element in dependence on the angular setting of the engine camshaft. A regulator for control of an injection adjuster is also described in DE-OS 43 08 541.

As long as a specific angular setting of the camshaft is consistently associated with each angular setting of the crankshaft, accurate fuel admetering is possible with this form of drive control. However$ such an association is not possible in certain operational states, since fluctuations in the angular relationship of the crankshaft and camshaft arise due to the relatively imprecise coupling between crankshaft and camshaft. Due to these fluctuations, there is no fixed relationship between the angular settings of the crankshaft and the camshaft, which results in inaccuracy in the fuel admetering.

There is therefore a need for a method and control means which may, allow improvement in the accuracy of the fuel admetering, in part-lcular the setting of the fuel conveying start, especially by compensation for n, S-, the imprecise association of crankshaft and camshaft.

According to a first aspect of the present invention there is provided a method for the control of fuel-admetering equipment, especially for a diesel engine, with setting means for influencing the start of fuel conveying, wherein a regulation deviation is ascertainable starting out from a target value for the conveying start and an actual value for the conveying start, wherein a regulator, starting from the regulating deviation, presets a setting magnitude for action on the setting means, characterised in that a time magnitude for the target value of the conveying start is determinable with reference to a reference instant and that a correction magnitude, which takes into consideration the deviation between angular magnitudes referred to the camshaft and to the crankshaft. is presettable starting from the deviation between the instant at which the actual conveying start is recognised and the time magnitude for the target value of the conveying start. Preferably, the time magnitude for the target value of the conveying start is determinable starting out from Tnp"angular magnitude for the target value of the start of injection. 20 For preference, the angular magnitude for the target value of conveying start is presettable in dependence on operating characteristic magnitudes. In one preferred embodiment, the correction magnitude is feedable as regulating magnitude to a regulator which processes the conveying start as time magnitude. In another embodiment, the angular magnitude for the target value of conveying start is correctable by means of the correction magnitude and the corrected angular magnitude for the target value of (7) conveying start is feedable as regulating magnitude to a regulator which processes the start of conveying as angular magnitude.

According to a second aspect of the present invention there is provided control means for the control of fuel-admetering equipment, especially for a diesel engine, with setting means for influencing the start of fuel conveying, wherein a regulation deviation is ascertainable starting from a target value for conveying start and an actual value for conveying start, and with a regulator which, starting from the regulating deviation, presets a setting magnitude for action on the setting means, characterised in that means are provided which determine a time magnitude for the target value of conveying start with reference to a reference instant and preset a correction magnitude, which takes into consideration the deviation between angular magnitudes referred to the camshaft and the crankshaft, starting from the deviation between the instant at which the actual conveying start is recognised and the time magnitude for the target value of the conveying start.

Examples of the method and embodiments of the control means will now be more particularly described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a schematic diagram of an engine fuel supply system with control means embodying the invention; Fig. 2 is a block diagram of injection start control means embodying the invention; Fig. 3 is a diagram showing different signals, entered as a function of time, arising in performance of a method exemplifying the invention; n, Fig. 4 is a block diagram of a developed form of control means embodying the invention; and Fig. 5 is a block diagram of a further developed form of control means embodying the invention.

Referring now to the drawings, Fig. 1 shows engine fuel-admetering equipment comprising a fuel pump 100, which consists of different components and is arranged in the vicinity of an internal combustion engine 90. In a low-pressure part 110, fuel is disposed under a relatively low pressure, which is maintained by a fuel-conveying pump (not shown). The fuel passes into a high-pressure part 120 by way of an electromagnetic valve 115. The high-pressure part is driven by a pump drive shaft 130 by way of a fuel conveying start adjuster. In the highpressure part 120, the fuel is pressurised to the pressure required for the injection. 15 The rotational speed of the drive 130 is detected by means of a sensor 135. This rotational speed substantially corresponds to the rotational speed of the engine camshaft. The sensor 135 scans markings on an increment wheel 136, which is arranged on the engine - camshaft or on the pump drive shaft 130. The drive shaft 130 is driven by means of a 20 drive 137, which is shown in dashed lines, from the crankshaft 152 of the engine. The drive 13 is preferably a toothed belt. A segment wheel 156, the markings of which are scanned by a sensor 155, is arranged at the crankshaft. The output signal of the rotational speed sensor 135 is supplied to 25 a pump control unit 140. The unit 140 acts on an electromagnetic valve 115, as well as on a fuel conveying start adjuster 125, by drive control signals.

n, In a particularly advantageous arrangement, the pump control unit consists of two separate components. The actual pump control unit 140 is then connected by way of appropriate connecting means 142 with an engine control unit 150 as well as with the different sensors and possibly further control units. Preferably, the connecting means 142 is provided by a bus system.

The unit 150. processes the parameters specific to the engine and delivers appropriate signals to the unit 140 by way of the connecting means 142.. Thus, for example, the angular setting of the camshaft and/or crankshaft at which the conveying of fuel is to start is transmitted as a digital magnitude. Further, preferably digital, signals indicate the desired quantity of conveying and the desired angle of the start of conveying referred to the camshaft.

The pump control unit 140 translates these signals into corresponding drive control signals for action on the valve 115 and the adjuster 125. In addition, a signal which identifies a preferred setting of the crankshaft is transmitted.

Sensors 145, which are connected with the pump control unit 140, detect data specific to the pump, for example the setting of the pump drive shaft 130. The data specific to the engine, as well as further operating parameters such as temperature and pressure values, are detected by means of sensors 152 and fed to the engine control unit 150 for processing. An accelerator pedal setting transmitter 160 supplies a signal indicating the intention of the driver of a vehicle fitted with the engine to the engine control unit 150.

The mechanical components of the fuel pump 100 basically correspond with those of the fuel pump described in Fig. 1 of DE-05 35 40 313.

n, \ ---1 The operation of this equipment in conjunction with the control means, in particular the pump control unit, embodying the invention is, however, different. Through drive control of the valve 115, the start of fuel conveying and also the end of fuel conveying are determined by this equipment. These magnitudes are referred by the pump control to the angular setting of the camshaft. The valve 115 can be regarded as a first setting means for the determination of the start and end of conveying. The conveying start adjuster 125, which in the case of the state of the art serves for the setting of the conveying start, is here used for displacement of the pump drive shaft relative to the crankshaft.

The conveying start adjuster 125 can be regarded as a second setting means.

In order to achieve combustion which is lower in noxious constituents and has good efficiency, the start of injection must take place at a certain setting of the crankshaft in dependence on different operating states, which are identified by signals supplied by the engine control 150 to the pump control 140.

Control means embodying the invention is illustrated schematically in the block diagram of Fig. 2. The internal combustion engine, which receives fuel from the fuel pump 100, is again denoted by 90. An injection adjuster in the pump for setting the start of fuel conveying or the end of fuel injection can be driven by means of an injection adjuster drive control 220.

An output signal P of a regulator 230 is passed by way of a first switch 225 to the injection adjuster drive control 220. An output signal D of a junction 240 is led by way of a second switch 235 to the regulator 230. The output signal SBD of a junction 245 is applied to one input of 7 - the junction 240. One input to the junction 245 is the output signal SBI of a needle movement sensor 205, which is preferably arranged at the engine. The output signal SBS of a target value presetter 250 represents the second input of the junction or addition point 245.

The drive control 220 can be acted on alternatively by an output signal PMAX of a maximum value presetter 232 or an input signal PMIN of a minimum value presetter 234 by means of the first switch 225. The regulator 230 can be acted on by an output signal of an initialising module 265 by means of the second switch 235.

An output signal SBIM of a model 260 is present at the second input of the junction 240 by way of a third switch 262. The model 260 is acted on at least by the output signal SBI of the needle movement sensor 205 and the actual setting magnitude PI. In the simplest example, the model is a PT1 member or an integrator. However, the model can be realised by means of an observer or an appropriate computing program.

The output signal of the junction 245 is also applied to the initialising module 265 and, by way of a fourth switch 275, to a switching module 270. The switching module 270 can be selectably acted on by the output signal from the junction 240 by way of the switch 275.

The switching module 270 controls the switches 235 and 225 by appropriate drive control signals.

The switches are usually in the positions drawn by solid lines. In this case, the equipment operates as follows: Starting from the comparison between the target value SBS, which is preset by the target value presetter 250, and the actual value SBI for the start of injection, the regulator 230 determines a signal P for action on the injection setter drive control 220. The regulator 230 preferably has proportional- 0 integral behaviour, but other forms of regulator are possible.

The signal P is an adjusting angle. This adjusting angle is realised by the injection adjuster drive control 220 preferably through drive control of an electromagnetic valve at a keying ratio. The pressure in the injection adjuster can be influenced by means of this valve. The injection adjuster assumes a certain position in dependence on the pressure and injection begins at different instants in dependence on the position of the adjuster. The exact instant of the start of the injection can be detected by, for example, the needle movement sensor 205.

The thus detected actual value SBI in respect of injection start is compared with the target value SBS and fed to the regulator 230.

If the comparison reveals a large deviation (M), which is the case particularly when the target value SBS changes greatly, the injection adjuster needs a certain time until it has reached the new target value.

To allow for this, the deviation valve 5BD is fed to the module 270. If the module recognises that the deviation SBD is greater than an upper threshold value or smaller than a lower threshold value, the second switch 235 is transferred into its position drawn in dashed lines.

In addition, according to whether the deviation S8D falls below a lower threshold value or rises above an upper threshold value, the switch 225 is moved into its upper or into its lower setting. In this case, the drive control 220 is acted on by the maximum value PMAX or the minimum value PMIN. This has the consequence that the injection adjuster and thereby the actual value very rapidly assume the new value. In effect, if the deviation 5BD lies outside the range defined by two threshold values the regulator 230 is switched off and a maximum value or a minimum value is preset for the setting magnitude. When the deviation is within the defined range, the regulator 230 is active. It is possible for several ranges to be defined, with different values being chosen in the different ranges. 5 When the regulator is switched off, i.e. when the switches 235 and 225 are switched over, the integral component of the regulator is frozen. This means that the output magnitude P of the regulator is stored. When the regulator is switched on again, i.e. when the switch 225 is transferred back into its position shown by a solid line, the switch 235 10 is returned into its original position with some delay. In place of the regulator 230, a regulator with preferably proportional-integral-differential behaviour can be used. In this embodiment, the output signal of the junction 245 is fed as input magnitude to the regulator. 15 Fig. 3 shows different magnitudes entered as a function of time or angular setting of the crankshaft. The start of fuel conveying, which is the instant after which the conveying of fuel is possible, is denoted by FB. This instant can be recognised, for example, by monitoring the reaction of the electromagnetic valve current. The time instant at which the start of conveying takes place is denoted by 7B and the angular setting of the crankshaft on the start of conveying is denoted by WFB.

The start of the injection is denoted by SB. This instant is that at which the injection into the engine actually begins. This magnitude is usually detected by the nee.dle movement sensor. The time instant at which the injection start S8 occurs is denoted by TSB and the corresponding angular setting of the crankshaft by WSB.

The upper dead centre i s denoted by OT. The instant at which the crankshaft reaches its upper dead centre is denoted by TOT and the angular setting by WOT.

A reference pulse R is provided by a pulse wheel, which is scanned by the sensor 155, for each cylinder. The instant at which the reference pulse R occurs is denoted by TREF and the corresponding angular setting of the crankshaft by WREF.

The spacing between the reference pulse R and the upper dead centre OT is denoted by the angular magnitude AWREF and time magnitude ATREF. The spacing between the upper dead centre OT and the injection start SB is denoted 'by the angular magnitude by AWSB and time magnitude by ATSB. The spacing between the conveying start FB and the injection start SB, which corresponds to the shaft transmit time, is denoted by the angular magnitude &WWL and time magnitude &TWL. The shaft transit time AWL is the angle through which the crankshaft turns between conveying start and injection start. It is a measure of the spacing between the conveying start and the actual injection start.

The spacing between the reference pulse R and the conveying start FB is denoted by the time magnitude,&TFB and angular magnitude.&WFB.

The angular magnitudes &W and the time magnitudes AT can be mathematically converted from one to the other, in particular by the equation T = W. 6. N in which N is the rotational speed of the shaft (crankshaft, camshaft or pump drive shaft) to which the magnitude is related.

There is, however, the problem that the pump control can compute the different magnitudes merely referred to the camshaft. The position of 1 11 the crankshaft is known in the pump control only on the occurrence of the reference pulse R, which is transmitted by the engine control to the pump control. In the case of a rigid, defined coupling between the crankshaft and camshaft. no errors result. In the case of a loose, undefined coupling of the crankshaft and camshaft, no fixed relationship exists between angular magnitudes referred to the camshaft and the crankshaft. This error can be compensated for as described in the following.

Fig. 4 shows a block diagram of an embodiment in which the error is reduced by the drive control signals being referred not to the camshaft, but to the crankshaft. The output signal &WSBS of an injection start characteristic field 250, which processes the signals of different sensors 251, is applied to a junction 305, at the second input of which the angular magnitude AWREF is present, which is preset by a block 310. The output of the junction 305 gets to a further, first junction 315, at the second input of which the output signal AWL of a shaft transmit time characteristic field 310 is present. The signals of sensors 321 serve as input magnitudes for the shaft transit time characteristic field 310.

These are, for example, signals which characterise the quantity of fuel to be injected, start of conveying, rotational speed and temperatures.

The output signal &WFBS of the first junction 315 gets to a second junction 325, to the second input of which is applied the output signal NKW of a block 330, which processes the output signal of the sensor 155 as input magnitude. The output signal ATHS of the junction 325 is passed to a junction 335, at the second input of which the output signal ATFBI of a further comparison point 340 is present. The output signal TFBI of a BIP recognition stage 345 is fed with negative sign and the signal TREF, which indicates the instant of the reference pulse, is fed 0 with positive sign to the junction 340. The output si gnal of the comparison point 335 is fed to a regulator 300, which drives the injection adjuster 125. The regulator 300 can correspond with the regulator 230 illustrated in Fig. 2.

The one angular magnitude for the target value of the injection start &WSBS is filed as angular magnitude referred to the crankshaft in dependence on different operating characteristic magnitudes in the characteristic field 250. This target value is filed, for example in dependence on the quantity of fuel to be injected, rotational speed, and temperature and pressure values. The target value AWSBS indicates the angular difference between the desired injection start 5B and the upper dead centre OT.

The angular setting AWREF referred to the upper dead centre OT of the crankshaft on the occurrence of the reference pulse R is filed in block 310. By interlinking of the signal AWREF and the signal AWSBS at the junction 305 and by interlinking with the shaft transit time AWL at the junction 315, the magnitude AWFBS, which indicates the spacing between the reference pulse R and the conveying start FB as angular magnitude referred to the crankshaft, results at the output of the junction 315. The magnitude &WFBS corresponds with the time magnitude for the target value for conveying start. The target value for injection start is converted into a target value for conveying start by means of the shaft transit time AWL.

Starting from the signals of the sensor 155, the block 330 computes the rotational speed NKW of the crankshaft. The angular magnitude &WFBS for the target value is converted into the time magnitude &TFBS for the target value at the junction 325 by means of the rotational speed NKW of G the crankshaft. This magnitude is applied as target value to the junction 335.

At the second input of the junction 335, there is present the output signal ATFBI of the junction 340. At the one input thereof, the signal TFBI is present, which indicates the instant of the actual conveying start, and at the second input of which the signal TREF is present, which indicates the instant of the reference pulse. The junction compares the two magnitudes and provides the signal &TFBI at its output. The signal TFBI is issued by the BIP recognition 345.

The output signal of the crankshaft rotational speed sensor 155 serves as reference value TREF. The signal, which indicates the actual conveying start TFBI as time magnitude, is presented by the BIP recognition 345. The BIP recognition ascertains the instant at which the valve reaches the setting for which the admetering of fuel begins. This is possible, for example, by evaluation of the course of the current flowing through the valve. The signal TFBI corresponds with the actual value of conveying start as time magnitude.

The signal ATFBI, which indicates the actual time spacing between the reference pulse R and the actual conveying start FB, is present at the output of the junction 340. The target value ATHS and the actual value ATFBI for the spacing between the conveying start and the reference value R are compared at the point 335 and the deviation therebetween is fed to the regulator 300, which thus appropriately drives the injection adjuster 125 in dependence on the comparison result of actual conveying start (actual value of conveying start) and the desired conveying start (target value of conveying start).

According to the described embodiment, the target and actual values le, for conveying start are ascertained as time magnitudes relative to a reference pulse R synchronous with the crankshaft. The deviation between the actual value ATFBI and target value L7BS is fed directly to the regulator 300 for the injection adjuster. Preferably, a regulator with at least proportional-integral behaviour is used.

Correspondingly, the target and actual values can also be referred to a reference synchronous with time in place of the reference synchronous with the crankshaft.

A further embodiment is illustrated in Fig. 5. Different sensors 402 apply signals to a characteristic field 400. The field 400 applies a signal WFBS to one input of a junction 445. At the second input of the junction 445, the output signal of a junction 410 is present, to a first input of which is applied the output signal of the block 330 which processes the rotational speed signal of the sensor 155. Applied to the second input of the junction 410 is the output signal of a junction 415, at the first input of which the output signal &TFBI of the junction 340 is present with negative sign. The output signal,&TFBS of a block 420 is present with positive sign at the second input of the junction 415. The block 420 processes the signal WFBS of the characteristic field 400 as well as the output signal of the block 330.

This equipment operates as follows: A target value for the start of conveying is filed as an angular magnitude WFBS in the characteristic field 400 in dependence on different operating characteristic magnitudes, such as the quantity of fuel to.be injected, different temperature and/or pressure values and the rotational speed.

The time difference ATFBI between the instant TREF of the occurrence of the reference pulse R and the instant TFBI of the actual start of nl conveying is ascertained at the junction 340 in corresponding manner to Fi g. 4. This magnitude corresponds with the time spacing between the occurrence of the reference pulse R and the actual conveying start, which is ascertainable, for example, by means of the BIP recognition.

Starting from the difference between the angular magnitudes WFBS for the target value for conveying start, which is derived from the characteristic field 400, and the known angular setting of the crankshaft

WREF on the occurrence of the reference pulse R, an angular magnitude results, which is converted into the time magnitude A7BS in the block 420 by means of the rotational speed NKW. This magnitude indicates the desired time spacing between the conveying start FB and the reference pulse R. The magnitude &TFBI is compared with the magnitude A7BS at the comparison point 415. The time deviation between the target value and the actual value for the time duration between the conveying start and the reference pulse R is present at the output of the junction 415. Starting from the deviation between the instant ATFBI, at which the actual conveying start is present, and the time magnitude &TFBS for the target value of conveying start, there is provided a correcting magnitude which takes into consideration the deviation between angular magnitudes referred to the camshaft and angular magnitudes referred to the crankshaft.

This time magnitude is converted into a corresponding angular magnitude at the junction 410 by means of the rotational speed value, which is provided by the block 330. The output magnitude of the junction 410 is a measure of the deviation of the crankshaft angle from the camshaft angle. The target value WFBS for conveying start is corrected by this comparison signal. The output signal of the junction 445 is applied to the junction 245 in Fig. 2 for correction of the output signal of the characteristic field 250.

According to the described embodiments, the target instant and the actual instant of the conveying start are determined relative to the reference mark R synchronous with the crankshaft. This deviation is superimposed as a correcting magnitude on the injection adjuster position regulator according to Fig. 2.

0

Claims

1. A method of controlling setting means in a fuel supply system of an engine, comprising the steps of determining, with respect to a reference instant, a time magnitude for a target value for the start of fuel conveying by the system, determining a time magnitude for the actual value of fuel conveying start, determining a correction magnitude in dependence on the difference between the determined magnitudes for the target and actual values of fuel conveying start, the correction magnitude taking into consideration any difference between engine crankshaft angle and engine camshaft angle, and determining a setting magnitude for the setting means in dependence on the difference between the target and actual values of fuel conveying start with use of the correction magnitude.

2. A method as claimed in claim 1, wherein the system is a fuel injection system and the method comprises the step of determining the magnitude for the target value of fuel conveying start in dependence on an angle magnitude for a target value for start of fuel injection by the system.

3. A method as claimed in claim 1 or claim 2, comprising the step of determining an angle magnitude for the target value of fuel conveying start in dependence on at least one engine operating parameter and determining the time magnitude for the target value for fuel conveying start on the determined angle magnitude for that target value.

0

4. A method as claimed in any one of the preceding claims, wherein the step of determining the setting magnitude comprises determining a time magnitude for fuel conveying start by way of regulating means having the correction magnitude as an input magnitude.

5. A method as claimed in any one of claims 1 to 3, wherein the step of determining the setting magnitude comprises correcting an angle magnitude for the target. value of fuel conveying start by the correction magnitude and determining an angle magnitude for fuel conveying start by way of regulating means having said corrected angle magnitude as an input magnitude.

6. A method as claimed in any one of the preceding claims, wherein the reference instant occurs when the engine crankshaft has a predetermined angular position.

7. A method substantially as hereinbefore described with reference to any one of the accompanying drawings.

8. Control means for controlling setting means in a fuel supply system of an engine, the control means comprising means for determining, with respect to a reference instant, a time magnitude for a target value for the start of fuel conveying by the system, determining a time magnitude for the actual value of fuel conveying start, determining a correction magnitude in dependence on the difference between the determined magnitudes for the target and actual values of fuel conveying start, the correction magnitude taking into consideration any difference between engine crankshaft angle and engine camshaft angle, and determining a setting magnitude for the setting means in dependence on the difference between the target and actual values of fuel conveying start with use of the correction magnitude.

9. Control means substantially as hereinbefore described with reference to any one of the accompanying drawings.