EP1568874A2 - Method and apparatus for controlling the volume flow in a fuel injection system of an internal combustion engine - Google Patents

Abstract

In today's Common Rail injection systems, which are formed with a high-pressure control valve (PCV) and a volume flow control valve (VCV), the problem arises that often the adapted valve position of the volume flow control valve (VCV) is faulty. This is usually due to the fact that the valve position is controlled as a function of the rail pressure only via a one-dimensional adaptation map. This can result in undesirable ambiguities that can lead to fuel injection with shortages. To solve this problem, it is proposed according to the invention to use a two-dimensional adaptation map for adapting the valve position and thus the volume flow, wherein the adaptation values for the valve position are predetermined by the adaptation map as a function of two operating parameters of the internal combustion engine.

Description

The invention is based on a method or of a device for controlling the volume flow in one Common rail injection system of an internal combustion engine according to the independent claims 1 and 8. It is already known that in injection systems where the fuel injected directly into a cylinder of an internal combustion engine is, the rail pressure by Absteuerung in the high pressure area is controlled by a pressure control valve. The load point dependent Volume flow, however, is a flow control valve controlled. The controller is designed in this way that the high pressure pump as possible only the current Need for fuel supplies. With this approach should be achieved, on the one hand the power consumption of High pressure pump is kept low. On the other hand, too the fuel return amount and thereby in the low pressure range introduced amount of heat minimized.

To control the flow control valve is a two-dimensional Pre-control map used that of the injection quantity and the engine speed is performed. In this pilot control map The injection quantity and the engine speed are a measure for the current volume flow requirement of a particular Load for the internal combustion engine corresponds. Due to component variations it is additionally required a map with adaptation values for the control of the volume flow control valve provided. In particular, since the volume flow demand due to wear-induced higher internal leaks increase the lifetime of the system. The previously used Adaption map is only dependent on the rail pressure. Thus, in addition to the pilot control map, the one-dimensional Adaptation map for controlling the volume flow control valve used.

Returns the pilot control map (eg due to wear-related higher volume flow requirement) too low values, is due the behavior of the rail pressure regulator (high positive control deviation, since the amount to maintain the pressure is not sufficient) an adaptation of the volume flow control valve driving value triggered until the amount is sufficient again.

This adaptation value has hitherto been dependent on the rail pressure stored and at every load point that with this Pressure is used, used. The flow control valve is thus always with the pre-control value plus the adaptation value controlled.

However, the assignment of the load point and the rail pressure is not unique. One and the same pressure is at different Used load points. This can lead to a Load point of the adaptation value is used without reason because of this load point the same rail pressure is driven, as on another load point where the adaptation took place.

The consequence is that, for example, instead of the correct Adaption value a wrong, too high adaptation value from the Characteristic read out and thus provided too much fuel becomes. The pressure-dependent control thus leads into the mentioned cases to promote a wrong amount of fuel.

The invention is based on the object, the control of the Volume flow control valve to improve so that only possible the required amount of fuel is provided. These Task is with the features of the independent claims 1 and 8 solved.

In the method according to the invention for controlling the load point-dependent Volume flow in a fuel injection system an internal combustion engine with the characterizing Characteristics of the independent claims 1 and 8 the advantage in that for determining the valve position of the volume flow control valve in addition to the pilot control map uses a two-dimensional adaptation map becomes. It is regarded as particularly advantageous that in the two-dimensional adaptation map, the adaptation values for the volume flow control valve as a function of given two operating parameters of the internal combustion engine become.

By the measures listed in the dependent claims are advantageous developments and improvements of in the independent claims 1 and 8 given. As special Advantageously, it is considered that in the adaptation map the adaptation values for the valve position as a function of two of the following four operating parameters injection quantity, Engine torque, engine speed and load formed can be. With these possible two-way combinations of operating parameters result in adaptation values, which are adapted to the respective load point.

A particularly favorable solution is also seen in that the adaptation values are stored in an adaptation map, this is the adaptation value as a function of the two operating parameters Engine speed and injection quantity reflects. Because with these two operating parameters can be a one-to-one Adaptation value for the flow control valve pretend.

It is further provided, both in the pilot control map, as well as in the adaptation map the same operating parameters to use for the axes of the map. This procedure simplifies the control of the volume flow control valve, since the two operating parameters already be used for the pilot control map and thus a match given the load points.

Since not always stored in the adaptation map Values corresponding to the current load point are provided, that between two stored, neighboring values the adaptation map is interpolated.

Preferably, a linear interpolation of the adaptation values performed using the known algorithms can be.

In a further preferred embodiment, the values become the adoption map during operation of the injection system customized. Preferably, the values of the Adaptation map changed when the control variable of the controller the pressure regulating valve over a fixed threshold or below.

The device is advantageously in a diesel, Gasoline or gas engine applicable.

Figur 1

zeigt in schematischer Darstellung den Hochdruckteil eines Common Rail Einspritzsystems,

Figur 2

zeigt ein zweidimensionales Vorsteuerkennfeld nach dem Stand der Technik,

Figur 3

zeigt ein Ausführungsbeispiel der Erfindung mit einem zweidimensionales Adaptionskennfeld und

Figur 4

zeigt ein Blockschaltbild einer erfindungsgemäßen Vorrichtung.

An embodiment of the invention is illustrated in the drawing and is explained in more detail in the following drawings.

FIG. 1

shows a schematic representation of the high pressure part of a common rail injection system,

FIG. 2

shows a two-dimensional pilot control map according to the prior art,

FIG. 3

shows an embodiment of the invention with a two-dimensional adaptation map and

FIG. 4

shows a block diagram of a device according to the invention.

In Figure 1 is a schematic representation substantially the high pressure part of a common rail injection system shown, that for an internal combustion engine, for example a Diesel, gasoline or gas engine is usable. It shows the Components with which the fuel in the rail under high Pressure for the injectors is provided.

The fuel is first of a (not shown in Figure 1 Tank) via a fuel inlet A of a fuel priming pump 1 supplied. The fuel feed pump 1 is above its output with the input of a controllable Volume flow control valve VCV connected. For the regulation of the form is parallel to the fuel feed pump, a form control valve 5, over the excess fuel be returned to the low pressure area can. Furthermore, the output of the flow control valve VCV connected to a high-pressure pump 8, which in the rail a very high fuel pressure, depending on the application, for example 800 ... 2000 bar generated. To produce the high Rail pressure, the high-pressure pump 8 three displacement units 3 on. Furthermore, in the inlet area of the high-pressure pump 8 a flushing / lubricating valve 6 is installed over which the Fuel feed pump 1, the high-pressure pump 8 with fuel rinses and lubricates.

At the high pressure outlet of the high pressure pump 8 is a high pressure control valve PCV arranged. The high pressure control valve PCV regulates preferably by means of a PI controller, the high fuel pressure in the rail. On the output side, the high-pressure control valve PCV on Split filter 7 downstream to solid suspended particles in To filter out fuel before the fuel is over High pressure connection B to a downstream fuel storage supplied with connected injectors. In front the input of the high pressure control valve PCV is a branch for a fuel return C provided to excess Fuel returned to the low pressure area.

FIG. 2 shows a known two-dimensional pilot control map, that for controlling the volume flow control valve VCV use place.

In the representation of the pilot control map according to FIG. 2 are on the X-axis, the engine speed N and on the Y-axis the injection quantity MF (mass of fuel) is plotted. The pilot control value for the flow control valve VCV is then for a current speed N and a load-dependent predetermined Injection quantity MF on the Z-axis as percentage (% value) the pulse width modulated signal with which the flow control valve is controlled, readable. The pilot control value initially serves for the volume flow control valve VCV as a default value, which is still using an adaptation value can be adjusted to depend on the actual Parameters of the injection system an exact valve position to obtain.

Alternatively, the pilot value can also be stored as a table be. In the table are also dependent on the Engine speed N and the injection quantity MF, the characteristics as Percentage values from the maximum opening angle of the flow control valve VCV indicated.

The valve position of the volume flow control valve VCV is with Help of a pulse width modulation (PWM values) controlled. Around to achieve an adaptation of the valve position is used to determine of the PWM value for a current operating point Adaptation value from the adaptation map to the pilot control value of the pilot control map.

According to the invention, the adaptation map in Dependence of two operating parameters two-dimensional form.

FIG. 3 shows an exemplary embodiment of the invention Adaptation characteristic field. Here are the operating parameters Injection amount MF and the engine speed N used. The adaptation map owns - in this special case - the Same axes as the pilot control map of Figure 2. On the X-axis is the speed N and the Y-axis is the injection quantity MF applied. The adaptation value A can then open the Z axis as a percentage of the maximum opening angle of the Volume flow control valve VCV are read.

In an alternative embodiment of the invention is provided that the adaptation values in the adaptation map depend on each of two of the following operating parameters filed are: the injection quantity MF, the engine torque, the engine speed N and / or the load TQI. By two each of these Parameter can via the two-dimensional adaptation map an exact assignment of the adaptation value to the load of Internal combustion engine are produced. It is thus avoided that by an incorrect opening angle of the flow control valve VCV the high pressure pump too much or too little Fuel into the fuel storage of the internal combustion engine is encouraged. The control according to the invention is the same Advantageously, manufacturing tolerances of the individual Assemblies of the injection system of the internal combustion engine.

For the determination of the adaptation values is further provided that the values of the adaptation map are preferably be linearly interpolated. This can be done with a simple linear regression also determine intermediate values, so that the adaptation values are determined more accurately.

According to the invention, it is further provided that the adaptation values for the individual load points in the two-dimensional adaptation map be continuously adjusted so that an automatic adaptation for the flow control valve VCV yields. This results in an exact load point-dependent Adaptation to the toleranced components installed, which is also independent of their aging and wear works.

For adaptation of the adaptation values of the adaptation characteristic field the controlled variable of the PI regulator of the pressure regulating valve of one Control unit monitored. Exceeds the controlled variable of the PI controller a set threshold, so will from the control unit a corresponding adaptation value in the adaptation map to the present operating point according to the parameters entered the axis of the adaptation map. He adaptation value is chosen so that when controlling the volume flow control valve VCV with the pilot value from the pilot control map and the adaptation value from the adaptation map so much fuel in the fuel tank is that the control variable of the PI controller again below the Threshold arrives. The adaptation value is for example at Exceeding or falling below the threshold for the controller value by a fixed value or a specified one Percentage reduced or increased.

Due to the optimal adaptation to the required fuel quantity Ensures that the low pressure system is insensitive is against the heat input via the fuel return system. The return system can therefore close, respectively be connected directly to the high-pressure pump, because the fuel is no longer heated.

Another advantage is also seen in the fact that the control quality in particular in injection methods with a multiple injection is improved, since the pressure fluctuations in the Rail due to wrong or unstable valve position be minimized.

Figure 4 shows an embodiment of the invention with a Device for controlling the load point-dependent volume flow in a common rail injection system. It has one program-controlled control unit 10, which with a program memory 11, a memory 12 for a first pilot control map for the pressure control valve and a second pilot control map for the flow control valve and with a memory 13 is connected to an adaptation map. The control unit 10 a program is running, which the connected Components fuel feed pump 1, high pressure pump 8, High pressure control valve PCV and the volume flow control valve VCV etc. regulates or controls. It is provided that a PI controller 9, the high-pressure control valve PCV after the predetermined first pilot control map regulates. In addition, the PI controller 9 connected to the controller 10 and reports the current Control value of the high-pressure control valve to the control unit 10. The controller 10 is connected to sensors that the operating parameters, in particular the rotational speed, the injection quantity, detect the engine torque and the load. The Volume flow control valve VCV is in its valve position by means of the second pilot control map and the two-dimensional map Adaptionskennfeldes controlled so that every current Last point as exactly as possible the required amount of fuel provided. Through this load point-dependent Control of the volume flow control valve VCV is in an advantageous Way that minimizes the fuel return amount and thus in particular a heating of the fuel in the Tank is avoided. Furthermore, it is achieved that the High pressure pump with a timing belt or a mechanical Clutch is driven, consumes less energy and thus reduces the power consumption of the high-pressure pump. The result is a high engine performance and / or a reduced Fuel consumption.

Claims (10)

Method for controlling the volume flow in a common rail injection system of an internal combustion engine, wherein the rail pressure is generated by means of a high pressure pump (8) and adjusted by a controllable high pressure control valve (PCV) in the rail and wherein the volume flow is determined by a valve position of a controllable volume flow control valve (VCV) , which is controlled by means of a pilot control map and an adaptation map as a function of an operating parameter of the internal combustion engine, characterized in that the adaptation map is formed two-dimensional, wherein in the adaptation map, the adaptation values for the valve position in accordance with two operating parameters of the internal combustion engine are predetermined. A method according to claim 1, characterized in that in the adaptation map, the adaptation values for the valve position are determined in dependence on two of the following operating parameters: the injection quantity (MF) of the fuel, the engine speed (N) and / or the motor torque or load (TQI). A method according to claim 1 or 2, characterized in that the adaptation values are stored in the adaptation map with the operating parameters engine speed (N) and injection quantity (MF). A method according to claim 3, characterized in that the adaptation map has the same parameter axes as the pilot control map. Method according to one of the preceding claims, characterized in that a current adaptation value is interpolated from adjacent values of the adaptation characteristic field. A method according to claim 5, characterized in that the interpolation is linear. Method according to one of Claims 1 to 6, characterized in that the adaptation values of the adaptation characteristic field are adapted as a function of the control value of the regulator (9) of the high-pressure control valve (PCV). Device for controlling the load-point-dependent volume flow in a common-rail injection system of an internal combustion engine, with a high-pressure pump (8), with a controllable high-pressure control valve (PCV), with a controllable volume flow control valve (VCV), with a program-controlled control unit (10) and with a memory (13 ) according to one of the preceding claims, characterized in that in the memory (13) a two-dimensional Adaptionskennfeldes for the flow control valve (VCV) is stored, and that the control unit, the valve position of the volume flow control valve (VCV) in response to a pilot control map and the adaptation map depending on two operating parameters of the internal combustion engine controls. Apparatus according to claim 8, characterized in that in the adaptation map, the adaptation values in dependence on the speed (N) of the internal combustion engine and the injection quantity (MF) are stored. Device according to one of claims 8 or 9, characterized in that the control unit (10) detects a control value of the regulator (9) of the high-pressure control valve (PCV) and decreases or increases the adaptation value in the adaptation map when it exceeds or falls below comparison thresholds.

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