EP1117930B1 - Method for electronically trimming an injector - Google Patents

Abstract

The invention relates to a method for electronically trimming at least one fluid injection pump. According to said method, a control module of an electronic control device detects a control signal which is corrected in accordance with the operation of the injection pump and preferably also a control signal which is corrected in accordance with the operation of the engine. Said control signal(s) is/are used to actuate the fluid injection pump. The inventive method also uses a fluid injection pump which operates according to the energy accumulation principle. The characteristic output of said fluid injection pump is identical or at least substantially approximative to a polynomial of at least the third degree. According to the inventive method, the parameters for a standard polynomial of at least the third degree are detected, stored and used to detect the required amount of fluid injection.

Description

The invention relates to a method for electronic minimization until eliminating nominal power deviations (trimming) a fluid injection device, in particular a fuel injection device, primarily a fuel injector with several injection pumps of an internal combustion engine.

For operating a fuel injection device for a Internal combustion engine it is known to generate a control signal which causes an injection pump at a certain time and as precisely as possible within a certain period of time Injecting fuel into an engine cylinder, which the Engine needs to perform a required, predetermined job to provide.

The control signal is calculated in an electronic control module and generated and sent to the electronic and / or electrical Devices of the injection device or the injection pump forwarded where it corresponds to the control signal Ejection of e.g. Fuel initiated and can run.

The generation of the control signal is complex and includes in usually a special tax strategy. Be taken into account a variety of influencing factors, e.g. engine operation based, related to the engine environment, fuel type and / or fuel condition are. Data are usually used for these influencing factors determined by sensors and delivered to the control module. For example, the engine speed, the crankshaft position, the engine coolant temperature, the engine exhaust pressure, the throttle position, the outside temperature, air pressure, or the like detected at a certain point in time, fed to the control module and processed or offset in the form of data in the control module, The calculation results in a factor with which a in the control module for the engine, the nominal power of the engine corresponding control signal proportional to the quantity multiplied becomes.

It is also known that e.g. the construction, the operating condition and the operating conditions of the injection pumps Significantly influence the time and duration of the spraying, in particular, injection pumps of identical design different Perform and a different Have spray behavior.

Known solutions to this problem are described in DE 195 20 037 A1 described, which is indicated as another new solution, determine the spray characteristics of each injection pump individually by measuring the spraying behavior of a large number of operating conditions and operating conditions and adaptation of the Control signal based on the measured data.

The individual injection pumps are used to substantiate this idea into certain trim categories of similar deviations divided and a matching factor for each category Control signal set.

However, it has been found that such categorized Trim factors caused by the injection pump Do not reduce deviations from the nominal power sufficiently.

When designing injection pumps, one strives e.g. to select the size and type of the components and the spatial shape in such a way that the injection pump has a linear spray behavior different spraying quantities and spraying times which has the different nominal powers of an engine correspond so that the respective control signal adjustment factor is easy to determine. Small amounts of fuel required with a correspondingly short period of time and larger or large quantities with a correspondingly longer or longer period hosed, the spraying quantity / spray duration ratio should correspond to a straight line in a diagram.

This effort to linearize the flow characteristic usually requires over-dimensioning of the components and / or the use of relatively expensive functional parts. moreover the oversized design requires considerably more electrical Operating power.

EP 391 573 A2 becomes a method and a device for the so-called "closed-loop" injection quantity control method in which the relationship between the basic injection pulse width and injection quantity based on an experimentally determined Polynomial is calculated.

Here, a piston displacement of the pump by means of sensors converted into a signal, which is the amount of fuel injected represents. This signal is used as a feedback signal for a "closed loop PID" which uses the injected amount compared with the required amount and for the next injection an adapted drive pulse for the injector delivers the error size of the hosed amount compared to the amount needed.

A disadvantage of this type of injection control is that the change in the delivery rate of the injection system only on the Let the injection process follow that follows the injection process, at which the error was found.

The object of the invention is a method for electronic Trimming an injector to create that without consuming constructional measures regarding the injection pump more precise adjustment of the control signal due to the injection pump the nominal injection power initiated by the control signal enables.

This object is solved by the features of claim 1. Advantageous developments of the invention are set out in the subclaims characterized.

The selection of the injection pump type is essential. used becomes an electromagnetically operated injection pump, which according to the energy storage principle works and for example in the WO 92/14925 and WO 93/18297.

Such injection pumps basically work due to the system not linear, which is why their selection was not immediately obvious. While it is not impossible to use a linear construction To ensure spray characteristics, however, would Adverse measures described above in a particularly exaggerated manner Dimensions required compared to other injection pump types.

The injection pumps used according to the invention, the following are also referred to as energy storage injection pumps, can be structurally set up so that their injection characteristics as close as possible to at least a third curve Degrees follows. The spray characteristics of most known System storage injection pumps follow from the system approximates a curve of third or higher degree, so that this Pumps do not need any structural changes. In the cases in for whom a structural change is to be striven for is enough usually e.g. off, the acceleration distance of the armature of the Extend pump for storing kinetic energy or shorten and / or the saturation behavior of the electromagnet of the electromagnetic drive of the injection pump adapt. These measures are so simple and require just such a small effort that they are almost ins Weight drop. These measures also favor usability of the full performance potential of the pumps and thus their efficiency in terms of both the delivery rate and with regard to the manufacturing effort for the respective application.

Within the scope of the method according to the invention, the spray characteristics of each individual manufactured injection pump are determined under normal conditions (e.g. at 20 ° C and normal atmospheric pressure), whereby measured values of the so-called flow curve or delivery characteristic curve are determined and processed in sufficient numbers, for example in the form of a signal duration / spray quantity diagram , The function is calculated from the measured values, which corresponds to the curve of the third or higher degree which can be determined from the measured values. The function for the third degree curve, which is generally known as: Y = A + B ₁ X + B ₂ X ² + B ₃ X ³ , contains the parameters A, B ₁ , B ₂ , B ₃ , with which the individual curve third degree of the injection pump individually recorded with the parameters is clearly defined. Y is the control signal duration to be determined and X is the amount of fluid to be sprayed.

The four parameters are stored electronically and if necessary e.g. linked to a serial number of the injection pump, electronically managed and represent the exact mathematical description of each point on the funding curve this individual injection pump. The electronic Control module of the electronic control system uses the If necessary, these parameters and calculate that for these individual Pump required switch-on duration signal for exact achievement of the requested injection quantity.

The four parameters are expediently known per se Marked detectable on or on the injection pump and accompany the injection pump until it is used and when it is used Use.

The measurement of a delivery curve of the injection pump is expedient due to time constraints on a limited number of individual measurements limited. However, each individual measurement can only be done with of finite accuracy, which results in that the measuring points correspond to the deviation tolerance Scatter the measuring device around the actual curve. A mathematically performed determination of the polynomial course not only interpolates between measurement errors and decreases their size but it also automatically leads to a non-linear Interpolation between the individual measuring points. This guaranteed according to the invention with a minimum of effort Maximum achievable precision in the reproduction of the injection quantity by means of an electrical signal duration.

When installing injection pumps, e.g. on an engine the parameters of each injection pump in a memory of the electronic control and the respective injection pump assigned.

As usual, the engine is driven by a map in which the quantity of fuel to be injected or an engine-specific correction value proportional to it is stored as a function of speed, load and some other commonly used engine operating parameters. To more precisely obtain the respective programmed nominal injection amount, the processor of the control is calculated also in particular before each injection operation for the system-specific trimming a necessary for the respective injection pump electrical drive signal Y. To this end, the required fuel amount X according to the equation Y = A + B ₁ X + B ₂ X ² + B ₃ X ³ and the numerical values for parameters A, B ₁ , B ₂ and B _{3 of} the corresponding injection pump are used.

To slow the necessary computing speed of the processor hold, an alternative method is provided according to the invention. The funding characteristics are shown each time the Motors recalculated once and digitally in a deferred Memory stored. Reading out memory data takes a long time less processor power than complex arithmetic operations. Even if a high storage capacity for finely resolved Characteristic curves can be selected, the total cost of these processes can be kept lower by the simpler processor.

As already described above, an electronic engine control recognizes usually also relevant for engine operation changing environmental influences such as Temperature and pressure of the sucked in air and adjusts the injection quantity at the engine specific Correct these conditions. Usually will the corrections as a percentage change in the Map entered control variables made before these to Injection pump system are forwarded. For the influences which directly affect the engine and its work process, are therefore the stored injection quantities or the addition proportional sizes with a corresponding factor larger or multiplied less than 1 to reflect the current environmental conditions adapt.

By using an energy storage injection pump, whose Funding characteristic under normal curve conditions third degree or approximately a curve of third or higher Degree follows, it is surprisingly possible to some significant changing influences on the injection pump or to an injection system equipped with several injection pumps, which influence the delivery rate of the injection pump, by correcting the control signal very precisely and without any special Consider effort (system-specific trimming). This Influences are e.g. different temperatures in the fuel, different temperatures at the injector, different Battery voltages, different driver output signals.

It was surprisingly found that the most relevant influences only a shift of a normal conveying characteristic curve corresponding to a curve of third or higher degree cause without the characteristic curve itself their individual form is changed. The respective one relevant influence-based shift of the funding characteristic runs two-dimensionally, namely in the X and Y directions, which leads to The consequence is that a usual correction with only one factor is not is possible. Rather, this is system-specific according to the invention Trimming with two calculation values per type of influence, from which surprisingly high trim accuracy results.

According to the invention, as in the determination of the standard funding characteristic under normal conditions, characteristic curves through measurement e.g. the delivery rate at some certain different States of an influence type determined and e.g. the four parameters of the respective corresponding third degree curve. A factor is then mathematically determined for each parameter, which its individual change among the different States of the relevant type of influence. These factors are stored in the same way and that Control module provided. For example, in in this context, the characteristic curves and their third curve Degree corresponding parameters for certain different Temperatures (states) of the nozzle temperature (type of influence), certain different voltages (states) of the supply voltage (Type of influence), certain different currents (States) of the driver output signals (influence type), certain different temperatures (states) of the fuel temperature (Type of influence), certain different density values (States) of the fuel density (influence type) determined.

According to a simplified embodiment of the invention Procedures are used for the shifts in the funding curve certain different states of an influence type ΔX- and ΔY values determined instead of the polynomial or curve parameters and saved and made available to the control module. This procedure reduces the memory data and the computing power to be provided to a considerable extent.

In both cases, an arithmetic operation is provided in the control module, a corresponding linear one for intermediate states Interpolation takes place between either the parameters, if these are stored, or in the event that ΔX or ΔY values are stored between the stored ΔX and ΔY values.

The inventive selection of a curve third or higher Degree for the delivery curve of an injection pump has been surprising Way that most influencing factors or Types of influence are also shifted according to an X-Y Behave third or higher degree curve. With linearized Injection elements can do linearization for the standard characteristic curves be achieved, the different types of influence but do not cause a parallel shift or otherwise easily detectable displacement of the straight line; rather, they show different types Waveforms on so that their capture and use a very large electronic effort for correction values requires.

According to a further special embodiment of the invention is used in the case of stored ΔX and ΔY values uses an arithmetic operation for control signal generation, after which the environmental influences relevant for engine operation taking into account the fuel signal proportional control signal value (engine-specific correction) the corresponding Point on the funding curve corresponding to normal conditions (Normal polynomial or normal characteristic) e.g. third degree of Injection pump determined and then the ΔX value of the individualized, a previously determined state of a Injection pump trim correction according to the type of influence Addition or subtraction is assigned. With the so obtained Control signal value X is the Y value of the control module Third degree polynomial is calculated, which is shifted by the value ΔX is. Then the ΔX value is obtained by adding or subtracting assigned, resulting in a point on a corresponding two-dimensional shift, but in the course third degree coincidence correction polynomial, where a signal duration results from this point, which is below the relevant state of the type of influence for the required injection quantity the individualized injection pump required is.

This condition-corrected signal duration is determined through the simplest and quickest for microprocessors Operation, namely the addition or subtraction of two Values. The choice of the type of influence to be corrected is arbitrary, the respective correction is equally simple. It can according to the number of influencing factors to be corrected correspondingly many assignments made at the same time become.

It is also expedient to provide the tolerances that are inevitable in the manufacture of the electrical power stage occur correct. It is not a question of a size that varies with changing environmental conditions; but their influence on the funding curve has - as in surprising Way could be determined - also two-dimensional shifting Effect on the norm polynomial and can therefore be also correct a pair of values ΔX and ΔY as described above.

The procedure for determining and storing this correction variable is as follows:

After completion, each motor control becomes an electrical one Functional test, at which reactive loads instead of Injection pumps can be connected to the output channels. The Current rise curve of a single current pulse is on each Channel recorded and mathematically formed the integral below. This integral corresponds to the electrical performed Job. Does the measured integral value deviate from a given one If the target size decreases, a corresponding pair of addition or subtraction values is created selected, assigned to the relevant output channel and stored in the control. Independent of Each output channel is given the later controlled injection element the correction for his characteristic shortcoming or its excess of electrical work.

The amount of fuel delivered in a unit of time is below among other things, a result of the pressure difference between the pressure inside the nozzle of the injection pump and outside of it taking into account the flow resistance of the nozzle. The means that especially with direct injection into the combustion chamber an internal combustion engine a dependency of the funded Fuel quantity from the back pressure or the position of the engine piston before top dead center at the time of injection consists. This dependency is particularly strong if, as with the energy storage injection pumps selected according to the invention the case, the output on a balance of power between magnetic force on the pump piston and all opposing forces based. For a well controllable According to the invention, direct injection is therefore also compensation of the pressure prevailing in the combustion chamber.

It has been shown that in the used according to the invention Injection pumps with different back pressures with increasing Back pressure to reduce a distortion of the delivery characteristic Flow rates with simultaneous shift to larger control signal time values occurs. This effect can be done mathematically describe by multiplying the abscissa value by a corresponding factor and an addition to the oridinate value. Here again, surprisingly, it is not necessary, the parameter values recorded in a standard state to change for the injection pump. The multiplication of the The abscissa value is carried out by the polynomial calculation and the ordinate is then added.

If the application of the injection system is one directly injected engine, this is usually the case with one Design for unthrottled or at least in partial load little throttled operation. An advantage of unthrottled or little throttled engines is the greatest possible independence the mixture formation of environmental influences in part-load operation. The The control method according to the invention therefore sees a programmable one Threshold in the engine map before which none Fuel quantity corrections more regarding air temperature and Air pressure can be carried out. To make a smooth transition between corrected and uncorrected map area achieve is an interpolation of the correction values to zero intended. This interpolation starts from another programmable Threshold that is above the former.

Fig. 1

ein Signaldauer/Einspritzmengen-Diagramm mit Förderkennlinien einer bestimmten Einspritzpumpe;

Fig. 2

ein Signaldauer/Einspritzmengen-Diagramm mit Förderkennlinien einer bestimmten Einspritzpumpe bei unterschiedlichen Gegendrücken.

Fig. 3

schematisch eine nach dem erfindungsgemäßen Verfahren arbeitende Steuerstrategie.

The method according to the invention can be seen by way of example from the drawing. Show it:

Fig. 1

a signal duration / injection quantity diagram with delivery characteristics of a specific injection pump;

Fig. 2

a signal duration / injection quantity diagram with delivery characteristics of a specific injection pump at different back pressures.

Fig. 3

schematically a control strategy working according to the inventive method.

In Fig. 1, the injection quantity V _e is plotted on the abscissa and the signal duration t _i on the ordinate. A standard delivery characteristic curve 1 is drawn in as a 3rd degree curve, the parameters of which are indicated in box 2 (flow curve under normal conditions). A correction curve 3 of the same shape with a ΔX / ΔY shift is shown above curve 1. Curve 3 of the third degree is a flow curve or delivery characteristic of the injection pump in a specific state of a specific type of influence, possible types of influence being listed, for example, in box 4. The correction according to the invention is based on the V _e value S, which has already been corrected for the engine operation and is proportional to the fuel quantity and which results from the nominal value from the engine-specific correction. To the lying on the standard polynomial 1, belonging to the V _e value S point T _1, the correction value is added .DELTA.X the injection operation correction. For the resulting coordinates of the point P in the diagram, the corresponding ΔX-shifted third-degree polynomial is calculated by the control module. The correction value ΔY is then added to the injection pump operating correction and a point T _{2 is} determined, which lies on the state-related X / Y-shifted third-degree polynomial 3, the parameters of which are indicated in box 5. The point T ₂ lying on the polynomial 3 represents a corresponding state-related corrected time period of t _i in ms for the injection of the required fuel quantity.

Fig. 2 illustrates the influence of a back pressure in the map diagram. Starting from the norm polynomial 1 of the third degree at atmospheric back pressure, the polynomials become third Grades 6 to 10 set at correspondingly higher back pressures. The position of these polynomials results in distortions, those with F * X and ΔY values, based on norm polynomial 1 mathematically can be grasped exactly. With the F * X and ΔY values a corresponding back pressure correction is made again only one multiplication and one addition or subtraction required.

The described invention is not based on the examples given limited. Further types of influence can be determined the third or polynomials shifted from the norm polynomial higher degree or correspondingly distorted third or polynomials higher degree. The invention can also be implemented if only approximate third or higher polynomials Degrees arise because then still the simple described Correction procedure is applicable.

The polynomials of higher degree than third degree are then always used when the measurement values for the norm polynomial are not exact enough to follow a third degree curve. It has shown, that in this case the measured values are usually higher on a curve Degrees. In any case, within the scope of the invention the higher degree curve can be determined, which the measured values on corresponds most precisely. A curve is preferably third Degree determined because compared to higher degree curves fewer parameters need to be set and saved.

Fig. 3 illustrates a control strategy according to the invention Method. The outlined fields with the asterisk indicate a multiplication and the outlined fields with the + sign indicate an addition or subtraction. On the left Side of Fig. 3 it can be seen that the basic map fuel delivers a signal value proportional to the amount of fuel, which Signal values of the motor-specific correction is multiplied. In the case of engine-specific correction - as is evident from the dashed field and the lined fields contained therein results - e.g. a threshold load, the air temperature and the air pressure taken into account in the usual way.

On the right side of Fig. 3 is the system specific trimming shown for an injection pump. In the dashed field are influence types in lined fields, due to which the polynomial is corrected. The location of the asterisk field and the position of the + fields in Fig. 3 with respect to the thickly drawn Signal duration cylinder 1 line indicates when which correction to Trimming is done. For example, regarding the influence type "cylinder counter pressure", that the multiplication in advance is carried out and only after the polynomial calculation of the ΔY value is added or subtracted.

Vertical thin arrow lines indicate that the corresponding Values for additional cylinders can be used.

The control strategy shown in FIG. 3 can of course be used also a different order of addition and subtraction provide for the types of influence, but it is essential that assumed a signal value proportional to the amount of fuel that already has the engine-specific corrections.

Claims (9)

1. Method for electronic trimming of at least one fluid injection pump, in which a control signal which is corrected for injection pump operation and, preferably, a control signal which is corrected for engine operation as well are determined by a control module of an electronic control device and are used for operation of the fluid injection pump,
   characterized in that

   a) a fluid injection pump is used which operates on the energy storage principle and whose feed characteristic follows an at least third-order polynomial identically or at least largely approximately;

   b) the parameters are determined and stored on a fuel-injection-pump specific basis in predetermined standard conditions for an at least third-order standard polynomial;

   c) at least one further at least third-order correction polynomial, which is specific for the type of influence, is determined for a specific type of influence acting on the fuel injection pump, and its parameters are stored, and

   d) the parameters of the standard polynomial and of the correction polynomial or polynomials are used for determining a corrected control signal for operation of the fuel injection pump.
2. Method according to Claim 1,
   characterized in that the correction polynomial which is specific for the type of influence is shifted in comparison to the standard polynomial X-Y, and preferably has the same shape.
3. Method according to Claim 1 and/or 2,
   characterized in that a control signal which is corrected for engine operation and is proportional to the fluid quantity is first of all calculated in the normal manner by the control module, and at least two control values for a type of influence are assigned by addition or subtraction to this control signal, which control values are calculated by the control module from the parameters of the standard polynomial and of the correction polynomial, from which a corrected control signal, which is proportional to the fluid quantity, results.
4. Method according to one or more of Claims 1 to 3,
   characterized in that one control value for a type influence is assigned by multiplication, and a further control value for this type of influence is assigned by addition or subtraction to the control signal which is corrected for engine operation and is proportional to the fluid quantity, which control values are calculated by the control module from the parameters of the standard polynomial and of the correction polynomial.
5. Method according to one or more of Claims 1 to 4,
   characterized in that the control module determines a time duration control signal for the corrected control signal.
6. Method according to one or more of Claims 1 to 5,
   characterized in that the control signal is produced by first of all using the ΔX values for the types of influence and then, after calculating the polynomials, using the ΔY values for these types of influence.
7. Method according to one or more of Claims 1 to 6,
   characterized in that when determining the standard feed characteristic in normal conditions, feed characteristics are determined by measuring the feed rate for a number of specific different states of a type of influence, and the parameters of the respective corresponding curve are defined.
8. Method according to one or more of Claims 1 to 7,
   characterized in that ΔX and ΔY values are defined and stored instead of the polynomial parameters for the shifts of the feed characteristic for specific different states of a type of influence.
9. Method according to Claim 8,
   characterized in that a computation operation is carried out in the control module, which carries out a corresponding linear interpolation for intermediate states between either the parameters, if these are stored, or between the stored ΔX and ΔY values in the situation where ΔX or ΔY values are stored.

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