WO2002075140A1

WO2002075140A1 - Method for operating an internal combustion engine using a fuel apportioning system

Info

Publication number: WO2002075140A1
Application number: PCT/DE2001/004921
Authority: WO
Inventors: Klaus Joos; Jens Wolber; Thomas Frenz; Markus Amler; Hansjoerg Bochum
Original assignee: Robert Bosch Gmbh
Priority date: 2001-03-16
Filing date: 2001-12-22
Publication date: 2002-09-26
Also published as: EP1377736B1; DE50104445D1; EP1377736A1; ES2231569T3; DE10112702A1

Abstract

The invention relates to a method for operating an internal combustion engine (1) using a fuel apportioning system (11), whereby fuel is transported from a fuel reservoir (12) to a low pressure region (ND) of the fuel apportioning system (11) by means of a pre-supply pump (13), and from the low pressure region (ND) to a high pressure region (HD) of the fuel apportioning system (11) by means of a high pressure pump (14). Fuel situated in the high pressure region (HD) at an injection pressure (p r) is injected at least indirectly into a combustion chamber (4) of the internal combustion engine (1), by means of at least one injection valve (9). The injection pressure (p r) is regulated. At least one pilot control underlies the regulation of the injection pressure (p r) in order to improve the dynamics of the regulation of the injection pressure (p r), a pilot control variable (y) being determined using at least one characteristic diagram (K1, K2) in accordance with an operating point of the internal combustion engine (1).

Description

Method for operating an internal combustion engine with a fuel metering system

The present invention relates to a method for operating an internal combustion engine with a fuel metering system. In the method, fuel is fed from a prefeed pump

Fuel reservoir in a low pressure area of the fuel metering system and promoted by a high pressure pump from the low pressure area into a high pressure area of the fuel metering system. In the high pressure region with an injection pressure, fuel is injected at least indirectly into a combustion chamber of the internal combustion engine via at least one injection valve. The injection pressure is regulated.

The invention also relates to a computer program that can run on a computing device, in particular on a microprocessor.

Furthermore, the present invention relates to a memory element for a control unit of a fuel metering system of an internal combustion engine. The memory element is designed in particular as a read-only memory, as a random access memory or as a flash memory. A computer program is stored on the memory element and can be run on a computing device, in particular on a microprocessor. The invention also relates to a control device for a fuel metering system of an internal combustion engine. The fuel metering system has a prefeed pump for conveying fuel from a fuel reservoir in a low pressure area of the fuel metering system and a high pressure pump for conveying fuel from the low pressure area into a high pressure area of the fuel metering system. Furthermore, the fuel metering system comprises at least one injection valve for at least indirectly injecting fuel present in the high pressure region with an injection pressure into a combustion chamber of the internal combustion engine. The control unit regulates the injection pressure.

Finally, the present invention relates to a fuel metering system for an internal combustion engine. The fuel metering system has a prefeed pump for conveying fuel from a fuel reservoir into a low pressure area of the fuel metering system and a high pressure pump for conveying fuel from the low pressure area into a high pressure area of the fuel metering system. Furthermore, the fuel metering system comprises at least one injection valve for at least indirectly injecting fuel present in the high pressure region with an injection pressure into a combustion chamber of the internal combustion engine and a control unit for regulating the injection pressure.

State of the art

Fuel metering systems of the type mentioned inject the fuel either indirectly through an air intake pipe of the internal combustion engine into a combustion chamber of the internal combustion engine or directly into a combustion chamber of the internal combustion engine. Systems for the direct injection of fuel into combustion chambers of an internal combustion engine are For example, for the fuel supply of internal combustion engines with gasoline direct injection (BDE) known from the prior art. Such a fuel metering system has a pre-feed pump usually designed as an electric fuel pump (EKP), which pumps fuel from a fuel reservoir into a low-pressure area of the fuel metering system. At least one high-pressure pump of the fuel metering system delivers fuel from the low-pressure area into a high-pressure accumulator, which is arranged in a high-pressure area of the fuel metering system.

The high-pressure accumulator is designed, for example, as a distributor rail of a common rail (CR) fuel metering system. Injection valves branch off from the high-pressure accumulator and can be used to inject fuel from the high-pressure accumulator into the combustion chambers of the internal combustion engine with the injection pressure prevailing there (rail pressure).

The injection valves are controlled by a control unit of the internal combustion engine. The control unit also has the task of regulating the injection pressure prevailing in the high-pressure accumulator via a pressure control circuit. An increase in the injection pressure can be achieved by suitably controlling the high-pressure pump, that is to say by increasing the fuel supply to the high-pressure accumulator. A reduction in the injection pressure can be achieved by suitably actuating a control valve (pressure control valve) branching off from the high pressure accumulator, i.e. by increasing the fuel flow from the high pressure accumulator, or by actuating another control valve (quantity control valve) by means of which the delivery rate of the high pressure pump can be reduced. A pressure sensor is arranged in the high-pressure accumulator for detecting the injection pressure prevailing in the high-pressure accumulator. A fuel metering system of the type mentioned and a method for operating an internal combustion engine with a fuel metering system of the type mentioned are known, for example, from DE 195 39 885 AI. Reference is expressly made to this document. The injection pressure in the high-pressure range is regulated in the known fuel metering system by a suitable control of a pressure control valve. The regulation of the injection pressure is quite precise, but it exhibits inadequate dynamics in particular with load and speed dynamics, ie with strong fluctuations in the injection pressure (for example due to a sudden full load operation of the internal combustion engine). With load and speed dynamics, there are relatively high pressure deviations between the actual value and the target value.

The invention has for its object to improve the dynamic behavior of a fuel metering system of an internal combustion engine.

To achieve this object, the invention proposes, based on the method for operating an internal combustion engine of the type mentioned at the outset, that at least one pilot control is subordinate to the regulation of the injection pressure, a pilot control variable being determined with the aid of at least one characteristic diagram as a function of an operating point of the internal combustion engine ,

Advantages of the invention

The pilot control is subordinate to the regulation of the injection pressure. Both the pilot control and the regulation of the injection pressure actuate a control valve (pressure control valve, quantity control valve) assigned to a high pressure pump. In the case of high-pressure pumps driven independently of the internal combustion engine, for example at electrically driven high-pressure pumps, in which the delivery rate of the high-pressure pump can be varied via the pump speed, it is conceivable that the pilot control and the control actuate an electric drive motor of the high-pressure pump.

The pilot control performs a first control of the injection pressure as a function of the operating point of the internal combustion engine. The superimposed regulation of the injection pressure then regulates this controlled value to a more precise value. The subordinate pilot control already leads the actual value of the injection pressure very precisely to a target value. The higher-level control then only has to correct a relatively small control difference. As a result, the actual value of the injection pressure can be regulated to the target value particularly quickly. The pilot control subordinate to the regulation of the injection pressure can therefore significantly improve the dynamic behavior of the fuel metering system.

The relatively low dynamics of the control of the injection pressure in the event of load or speed fluctuations can be significantly improved by using a subordinate pilot control. The pilot control can be used to reduce pressure deviations in load or speed dynamics in a regulated fuel metering system. In addition, emergency operation of the internal combustion engine is possible because, if the control fails (for example due to a defective pressure sensor), the fuel metering system can also be operated with reduced accuracy of the injection pressure by the pilot control, depending on the quality of the pilot control. The pilot control also provides an additional diagnostic option. The control difference between a pilot control variable at the output of the pilot control and the target value of the A statement about the functionality of a high pressure circuit can be derived.

Instead of carrying out the pilot control in a relatively complex manner from basic physical equations as a mathematical model of the high-pressure pump, it is proposed according to the invention to determine a pilot control variable of the pilot control using characteristic maps. The pilot control variable can be determined from the characteristic diagrams as a function of the operating point of the internal combustion engine. The measured values stored in the characteristic diagrams can be determined empirically in a simple manner on a test bench. All the effects that affect the injection pressure are taken into account in the recorded measured values.

Depending on an operating point of the internal combustion engine, values are stored in the or each characteristic map, from which a pilot control variable of the pilot control can be determined either directly or indirectly by mathematically linking the individual values.

According to an advantageous development of the present invention, it is proposed that the pilot control variable be determined as a function of the current injection pressure prevailing in the high pressure range. It is also proposed that the pilot control variable be determined as a function of the speed of the high-pressure pump. This is directly related to the delivery rate of the pump. Finally, it is proposed that the pilot control variable be determined as a function of the fuel flow required by the internal combustion engine. It has been shown that the current injection pressure, the speed of the high pressure pump and the fuel flow required by the internal combustion engine are the main influencing variables on the injection pressure prevailing in the high pressure range. From the injection pressure and the pump speed, the quantity of fuel delivered by the high-pressure pump and a target delivery flow can be determined from the required fuel flow and the acute injection pressure.

According to a preferred embodiment of the present invention, it is proposed that a control variable for the high-pressure pump be determined as the pilot control variable based on a straight line equation above the fuel flow required by the internal combustion engine, the gain and the offset of the straight line equation using characteristic maps as a function of the operating point the internal combustion engine can be determined. According to the invention, it has thus been recognized that the pump control variable can be represented as a straight line equation over the fuel flow required by the internal combustion engine. The gain and the offset of the straight line equation depend on the operating point of the internal combustion engine and can be determined using characteristic maps.

The gain of the straight line equation is advantageously determined with the aid of a first map as a function of the speed of the high-pressure pump and the current injection pressure. The parameter calculated by a control unit of the internal combustion engine for the current fuel requirement of the internal combustion engine is multiplied by the first map in which the gain of the straight line equation is stored as a function of the speed of the high pressure pump and the injection pressure.

According to a further preferred embodiment of the present invention, it is proposed that the offset of the straight line equation be determined with the aid of a second map as a function of the speed of the high-pressure pump and the current injection pressure. The value determined by means of the first map is converted from a second map as a function of the speed of the high-pressure pump and the injection pressure determined offset of the straight line equation in the current operating point of the internal combustion engine added. The result of the straight line equation with the values (gain and offset) resulting with the aid of the first map and the second map represents a good approximation to the true control variable. The control difference, which then has to be corrected by the higher-level control of the injection pressure, is very small, so that the control has a particularly high dynamic.

Under certain circumstances, voltage compensation and / or temperature compensation of the pilot control variable may be necessary. Therefore, according to another advantageous development of the present invention, it is proposed that the determined pilot control variable be corrected as a function of a supply voltage of a motor vehicle battery and / or of the outside temperature. A correction variable is advantageously also determined with the aid of characteristic diagrams as a function of voltage or as a function of temperature. The correction variable is, for example, a correction factor by which the input control variable determined with the aid of the first characteristic diagram and the second characteristic diagram is multiplied.

The value of the pilot control variable determined with the aid of the first characteristic diagram and the second characteristic diagram represents a static component. In the case of strong load or speed fluctuations, however, relatively slow settling processes can be observed, which the pilot control should also take into account, ie accelerate. For this reason, it is proposed according to a further preferred embodiment of the invention that a dynamic portion is added to the static portion of the determined pilot control variable by which triggers an overshoot of the pilot control variable when the injection pressure, the speed and / or the fuel flow change. Due to the brief overshoot of the pilot control variable, the transient processes can be significantly accelerated, particularly in the case of strong load or speed fluctuations, which leads to a particularly high dynamic of the fuel metering system. The dynamic component is advantageously determined with the aid of a differentiating transmission element, which preferably has a DTI behavior. The differentiated transmission element can, for example, always determine an additional correction value when there is a change in the required fuel flow, the speed of the high-pressure pump or the current injection pressure and take this into account when calculating the pilot control variable.

The invention also relates to a computer program which is suitable for executing the method according to the invention if it runs on a computing device, in particular on a microprocessor. It is particularly preferred if the computer program is stored on a memory element, in particular on a flash memory. The computer program represents the invention in the same way as the method is suitable for executing it.

Of particular importance is the implementation of the method according to the invention in the form of a storage element which is provided for a control unit of a fuel metering system of an internal combustion engine. In this case, a computer program is stored on the memory element, which is executable on a computing device, in particular on a microprocessor, and is suitable for executing the method according to the invention. In this case, the invention is implemented by a computer program stored on the memory element, so that this the memory element provided with the computer program represents the invention in the same way as the method for the execution of which the computer program is suitable. In particular, an electrical storage medium can be used as the storage element, for example a read-only memory, a random access memory or a flash memory.

As a further solution to the problem of the present invention, starting from the control device for a fuel measuring system of an internal combustion engine of the type mentioned at the outset, it is proposed that the control device have at least one pilot control subordinate to the regulation of the injection pressure and a pilot control variable with the aid of at least one map as a function of determined an operating point of the internal combustion engine.

According to an advantageous development of the present invention, it is proposed that the control device have means for executing the method according to the invention.

As yet another solution to the object of the present invention, it is proposed, starting from the fuel metering system for an internal combustion engine of the type mentioned at the outset, that the fuel metering system has at least one pilot control subordinate to the regulation of the injection pressure and a pilot control variable with the aid of a characteristic diagram as a function of an operating point Internal combustion engine determined.

According to an advantageous development of the present invention, it is proposed that the fuel metering system have means for carrying out the method according to the invention.

drawings Further features, possible applications and advantages of the invention result from the following description of exemplary embodiments of the invention, which are shown in the drawing. All of the features described or illustrated form individually or in any way. Combination of the subject of the invention, regardless of their summary in the claims or their relationship and regardless of their wording or representation in the description or in the drawing. Show it:

Figure 1 with an internal combustion engine. a fuel metering system according to the invention;

FIG. 2 shows a block diagram for determining a pilot control variable of a pilot control of the injection pressure according to the present invention;

FIG. 3 shows a block diagram for determining a dynamic portion of the input control variable; and

Figure 4 is a block diagram for determining a static portion of the input variable.

Description of the embodiments

FIG. 1 shows a direct-injection internal combustion engine 1 of a motor vehicle, in which the piston 2 can be moved back and forth in a cylinder 3. The cylinder 3 is provided with a combustion chamber 4, which i.a. is limited by the piston 2, an inlet valve 5 and an outlet valve 6. An intake pipe 7 is coupled to the inlet valve 5 and an exhaust pipe 8 is coupled to the outlet valve 6.

In the area of the inlet valve 5 and the outlet valve 6, an injection valve 9 and a spark plug 10 protrude in the Combustion chamber 4. Fuel can be injected into combustion chamber 4 via injection valve 9. Fuel can be ignited with the combustion chamber 4 using the spark plug 10. The piston 2 is caused by the combustion of the fuel in the combustion chamber 4 in a back and forth movement, which is transmitted to a crankshaft, not shown, and exerts a torque on this.

The internal combustion engine 1 has a fuel metering system 11, by means of which the fuel to be injected into the combustion chamber 4 via the injection valve 9 is metered. The fuel metering system 11 has one

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-H P 0 N ß k -H ü> a k rß -k 4-J 4-J k φ TS rH EH tn a υ ß O ß ω rß rß? EU ß EU 4J -H w Φ P k £ Φ J-J w rH CQ W k Ti -H CQ ß CO co CQ! -H <u

4-J 4J Φ -H φ ak Φ PP CQ rH in Φ k «. 4H CQ Di Φ φ u -k in rH CQ Ti φ k rß co TJ P a φ 1 Φ Φ ß ß -H -H 4-J Φ Φ ß in k TS A φ ^• vr ß co Φ ß rö k ß - H a 4-J ü XN Φ XP. 4P rß 4-1 P Φ N 3 k in TJ P ß Φ U rß Φ -k rH P rß 0- Φ TJ okk ü 4P 4-JO to Φ ü CQ X 4-1 ß Φ CQ tn P 4-1 TJ -H ü k J -P tn ü> tn ß φ PP -H CO P k co ß CO Φ k tn Φ 4-1 -k CQ 4P rö X XI ß rH CQ P CJ rö ß k

© m 1 Ti a φ> -ku £ k 4J 4J φ AH a ß JP rß rß k ß ε -k -k co TJ 4-J υ Φ rH -H rl ß rß CO in -ß Φ φ rß rß CO - -0 4H --P Φ 4H O k 3 k tn φ rö CH 4-1 rö to O 0 ß k rδ CQ rH ß ü ß ß υ Φ 4P k ß Ti k ß 4H 4H Ti φ X Φ rß Φ 4H CQ ß rß kkk rH -H 0 rH 0 rß O -H Φ o -H ß Φ Φ Φ -k Φ 0 -k 1 rQ UAP Φ. ß 4-1 Φ Φ Φ

CQ Φ> ^ rö CO X EU HS tu P rQ Ti rπ> rQ J in £ 4-1 B »i => CO = P 3 SH CQ QO>

first characteristic diagram Kl as a function of the speed n_HDP of the high pressure pump 14 and the current injection pressure p_r and multiplied by the fuel quantity rk required by the internal combustion engine 1. The offset b of the straight line equation is also determined with the aid of a second map K2 as a function of the speed n_HDP of the high-pressure pump 14 and the current injection pressure p_r. The sum of the offset b and the product of the gain a and the fuel quantity rk forms the stationary part y_stat.

Different values for the gain a of the straight line equation are stored in the first map K 1 depending on the operating point. Likewise, different values for the offset b of the straight line equation are stored in the second map K2 depending on the operating point. The values stored in the characteristic diagrams K1, K2 can be determined empirically in a simple manner, for example on a test bench. The advantage of empirically determined values is in particular that all disturbance variables that affect the injection pressure p_r are taken into account.

If desired, automotive battery voltage or temperature compensation can be provided. For example, it is conceivable to take into account a correction value for the stationary value y_stat, which is determined from a voltage or temperature-dependent characteristic diagram.

Claims

Expectations

1. Method for operating an internal combustion engine (1) with a fuel metering system (11), in which fuel from a prefeed pump (13) from a fuel reservoir (12) into a low-pressure area

(ND) of the fuel metering system (11) and from a high pressure pump (14) from the low pressure area (ND) to a high pressure area (HD) of the fuel metering system

(11) is conveyed and fuel present in the high pressure area (HD) with an injection pressure (p_r) is injected at least indirectly into a combustion chamber (4) of the internal combustion engine (1) via at least one injection valve (9), the injection pressure (p_r) being regulated , characterized in that the regulation of the injection pressure (p_r) is subordinate to at least one pilot control, a pilot control variable (y) using at least one characteristic diagram

(K1, K2) is determined as a function of an operating point of the internal combustion engine (1).

2. The method according to claim 1, characterized in that the pilot control variable (y) is determined as a function of the current injection pressure (p_r).

3. The method according to claim 1 or 2, characterized in that the pilot control variable (y) is determined as a function of the speed (n_HDP) of the high pressure pump (14).

4. The method according to any one of claims 1 to 3, characterized in that the pilot variable (y) is determined as a function of the fuel flow (rk) required by the internal combustion engine (1).

5. The method according to any one of claims 2 to 4, characterized in that as the pilot control variable (y) a control variable for the high pressure pump (14) using a straight line equation (y = a-rk + b) above that of the internal combustion engine (1) required fuel flow (rk) is determined, the gain (a) and the offset

(b) the straight line equation can be determined using characteristic maps (K1, K2) as a function of the operating point of the internal combustion engine (1).

6. The method according to claim 5, characterized in that the gain (a) of the straight line equation is determined with the aid of a first map (Kl) as a function of the speed (n_HDP) of the high-pressure pump (14) and the current injection pressure (p__r).

7. The method according to claim 5 or 6, characterized in that the offset (b) of the straight line equation is determined with the aid of a second map (K2) as a function of the speed (n_HDP) of the high pressure pump (14) and the current injection pressure (p_r) ,

8. The method according to any one of claims 2 to 7, characterized in that the determined pilot variable (y) is corrected as a function of a supply voltage of a motor vehicle battery and / or from the outside temperature.

9. A method according to claim 8, characterized in that a correction variable is determined with the aid of characteristic diagrams depending on the voltage or temperature.

10. The method according to any one of claims 1 to 9, characterized in that a dynamic component (y_dyn) is added to the determined pilot control variable (y_stat), by which when there is a change in the injection pressure (p_r), the speed (n_HDP) and / or of the fuel flow (rk) an overshoot of the pilot variable (y) is triggered.

11. The method according to claim 10, characterized in that the dynamic component (y_dyn) is determined with the aid of a differentiating transmission element (DTl), which preferably has a DTl behavior.

12. Computer program, which is executable on a computing device, in particular on a microprocessor (26), characterized in that the computer program is suitable for executing a method according to one of claims 1 to 11 when it runs on the computing device.

13. Computer program according to claim 12, characterized in that the computer program is stored on a memory element, in particular on a flash memory (27).

14. Storage element, in particular read-only memory, random access memory or flash memory (27), for a control unit (22) of a fuel metering system (11) of an internal combustion engine (1), on which a computer program is stored that is stored on a computing device, in particular on a microprocessor (26), is executable and suitable for executing a method according to one of claims 1 to 11.

15. Control device (22) for a fuel metering system (11) of an internal combustion engine (1), the

Fuel metering system (11) a pre-feed pump (13) for delivering fuel from a fuel tank (12) in a low pressure (ND) area of the

Fuel metering system (11), a high-pressure pump (14) for conveying fuel from the low-pressure area (ND) into a high-pressure area (HD) of the fuel metering system

(11) and at least one injection valve (9) for at least indirectly injecting fuel present in the high pressure region (HD) with an injection pressure (p_r) into a combustion chamber (4) of the internal combustion engine (1), the control unit (22) having the injection pressure (p_r) regulates, characterized in that the control device (22) has at least one control subordinate to the regulation of the injection pressure (p_r) and a pilot control variable

(y) with the aid of at least one map (K1, K2) as a function of an operating point of the internal combustion engine

(I) determined.

16. Control device (22) according to claim 15, characterized in that the control device (22) has means for performing a method according to one of claims 2 to 11.

17. Fuel metering system (11) for an internal combustion engine (1), the fuel metering system

(II) a pre-feed pump (13) for delivering fuel from a fuel reservoir (12) to a low pressure area (ND) of the fuel metering system (11), a high pressure pump (14) for delivering fuel from the low pressure area (ND) to a high pressure area ( HD) of the fuel metering system (11), at least one injection valve (9) for at least indirectly injecting in the high pressure area (HD) with an injection pressure

(p_r) fuel present in a combustion chamber (4) of the internal combustion engine (1) and a control unit (22) for regulating the injection pressure (p_r), characterized in that the fuel metering system (11) has at least one for regulating the injection pressure (p_r) has subordinate pilot control and a pilot control variable (y) with the help of at least one map (Kl, K2) in

Determined as a function of an operating point of the internal combustion engine (1).

18. Fuel metering system (11) according to claim 17, characterized in that the fuel metering system (11) has means for carrying out a method according to one of claims 2 to 11.