WO2012052264A1

WO2012052264A1 - Method for operating an internal combustion engine

Info

Publication number: WO2012052264A1
Application number: PCT/EP2011/066857
Authority: WO
Inventors: David Vitre
Original assignee: Robert Bosch Gmbh
Priority date: 2010-10-21
Filing date: 2011-09-28
Publication date: 2012-04-26
Also published as: DE102011005592A1; CN103201486A; CN103201486B; EP2630355A1

Abstract

The invention relates to a method for operating an internal combustion engine. Fuel is supplied from a fuel tank (9) to a high pressure accumulator (13) via a presupply pump (5), a metering unit (14) and a high pressure pump (3). The presupply pump (5) can be switched on to supply fuel. A pressure signal (22) of a pressure in the high pressure accumulator (13) is detected. An error of the metering unit (14) is detected. The metering unit (14) is essentially opened. A duration is detected as a function of the detected pressure signal (22). A point in time is detected as a function of the detected pressure signal (22). The presupply pump (5) is switched on for the duration at the point in time.

Description

Description title

Method for operating an internal combustion engine Prior art

The invention relates to a method for operating an internal combustion engine according to the preamble of claim 1.

In the event of a failure or operational restriction of a component of an internal combustion engine, it is known to use so-called 'limp home' methods which maintain the operation of the internal combustion engine under certain restrictions, such as reduced torque, thus increasing the overall availability of the motor vehicle.

It is known from EP 0 780 559 B1 that, in the event of a defect in the area of pressure regulation, the fuel pressure can be controlled and / or regulated by influencing the fuel flow in the low-pressure area

Limited operation of the internal combustion engine can be ensured.

Furthermore, a metering unit for a high-pressure pump is known, which may have an electrical or mechanical fault. Usually, the internal combustion engine is turned off in such an error, whereby no further travel is possible.

Also, a prefeed pump for delivering fuel from a

Fuel tank known, which is usually not continuously adjustable.

Disclosure of the invention The problem underlying the invention is solved by a method according to claim 1. Advantageous developments are specified in subclaims. For the invention important features can be further found in the following description and in the drawings, the features both alone and in different combinations for the

Invention may be important, without being explicitly referred to again.

The method makes it possible despite an error of the metering unit

To influence fuel pressure in a high pressure accumulator so that controlled injections can be performed. In a moderate driving behavior thus an accuracy of the injection quantity can be achieved such that a problem-free driving on a faulty

Metering unit is possible. The faulty metering unit is here in

Essentially open. This means that the fuel pressure in one

High-pressure accumulator is not too high and not too low, but moves within certain limits. Overall, a shutdown of the internal combustion engine is thus prevented due to a faulty metering unit and allows driving on. This increases the availability of the

Internal combustion engine and the associated motor vehicle.

In an advantageous embodiment of the method, the determined pressure signal falls below a first pressure value at a time. The first pressure value is less than a desired pressure value. This advantageously ensures that the prefeed pump is switched on to prevent too low a pressure.

In a further advantageous embodiment of the method, the

Time duration for the next switching on the feed pump increases when the determined pressure signal does not exceed a second pressure value. The second pressure value is greater than the desired pressure value. By extending the

Switch-on time of the prefeed pump is advantageously achieved that too low a pressure is prevented and thus injections of fuel can be carried out continuously. In a further advantageous embodiment of the method, the

Time for the next turn on the feed pump reduced when the detected pressure signal exceeds a third pressure value. The third pressure value is greater than the second pressure value. By reducing the switch-on time of the prefeed pump, an excessively high pressure is advantageously prevented in this case.

In a further advantageous embodiment of the method, the

Time duration for the next switching on the feed pump is not changed when the determined pressure signal exceeds the second pressure value and does not exceed the third pressure value. This embodiment advantageously makes it possible to advantageously maintain an achieved pressure curve

In a further advantageous embodiment of the method, a further period of time is started at the time and the prefeed pump is switched on at the end of the further period of time. As a result, it is not necessary to wait for the first pressure value to fall below the first pressure value, but the pre-feed pump is switched on after the expiry of the further period of time and thus a further decrease in the pressure is prevented.

In an advantageous development of the method, the time duration for the next switching on of the prefeed pump is increased if the ascertained pressure signal o does not rise above the first pressure value within the further time duration. Thus, the pre-feed pump is turned on for a longer time and too low pressure is thus additionally counteracted.

In an advantageous development of the method, the further time duration is approximately 5 times a low-point time duration, wherein the low-point time period extends from the time to an expected low point of the determined pressure, and wherein the low-point time period consists of a weighted average value is determined. As a result, the further time period is advantageously selected so that it can be detected whether the course of the determined pressure signal behaves as desired and increases or whether the profile of the determined pressure continuously moves in a low range. If the determined pressure is in the low range, it is advantageously possible to counteract and injections can be carried out. 5 Other features, applications and advantages of the invention

result from the following description of exemplary embodiments of the invention, which are illustrated in the figures of the drawing. All described or illustrated features alone or in any combination form the subject matter of the invention, regardless of their

Summary in the claims or their dependency and regardless of their formulation or representation in the description or in the drawing. There are for functionally equivalent sizes in all figures, even with different embodiments, the same reference numerals

used.

Hereinafter, exemplary embodiments of the invention will be explained with reference to the drawings. In the drawing show:

Figure 1 is a simplified diagram of a fuel injection system of a

Internal combustion engine;

Figure 2 is a schematic block diagram with a unit for

Activation of a prefeed pump;

Figures 3a-3d are each a schematic diagram with a time course of a detected pressure signal and a time course of a control signal for the prefeed pump.

FIG. 3e shows a schematic diagram for determining a time duration.

Figure 1 shows a fuel injection system 1 of an internal combustion engine in a much simplified representation. A fuel tank 9 is connected via a suction line 4, a prefeed pump 5 and a low-pressure line 7 with a (not explained in detail) high-pressure pump 3. In a not shown

Embodiment, the prefeed pump 5 may also be arranged in the fuel tank 9, wherein the suction line 4 is not present accordingly. The prefeed pump 5 can be designed in particular as an electric fuel pump. The prefeed pump 5 is supplied with an actuating signal 26. To the high-pressure pump 3, a high-pressure accumulator 13 ("common rail") is connected via a high-pressure line 1 1. A metering unit 14 - hereinafter referred to as ZME - with an actuating device 15 is arranged hydraulically in the course of the low-pressure line 7 between the prefeed pump 5 and the high-pressure pump 3. Other elements, such as valves of the high-pressure pump 3, are not shown in the figure 1. It is understood that the ZME 14 may be formed as a unit together with the high-pressure pump 3. For example, an intake valve of the high pressure pump 3 may be forcibly opened by the ZME 14.

During operation of the fuel injection system 1, the prefeed pump 5 promotes fuel from the fuel tank 9 into the low pressure line 7 and the

High-pressure pump 3 conveys the fuel into the high-pressure accumulator 13. The ZME 14 determines the quantity of fuel supplied to the high-pressure pump 3.

A measurement of the pressure within the high pressure accumulator 13 is made by a pressure sensor 16 to the high pressure accumulator 13. A value measured by this pressure sensor 16 is referred to as a pressure signal 22

designated.

The ZME 14 is supplied with a control signal 28. About the control signal 28, the opening of the ZME 14 can be influenced. The ZME 14 generates an error signal 24. The error signal 24 can be used to determine whether an error of the ZME 14 exists. On the other hand can be determined by the error signal 24, whether an electrical fault or a mechanical error of the ZME 14 is present. An error of the ZME 14 can also be determined by a combination of further parameters. For example, an electrical fault exists when the ZME 14, e.g. through a disconnected plug, is no longer supplied with energy. In the event of an electrical fault, the ZME 14 usually transitions to an open state, so that fuel is conveyed unhindered from the prefeed pump 5 to the high-pressure pump 3. In the event of a mechanical fault, the ZME 14 may be fully open, fully closed or partially open.

Figure 2 shows a schematic block diagram with a unit 20 for

Control of the prefeed pump 5. The unit 20, the pressure signal 22 and the error signal 24 are supplied. In a manner not shown, other variables, such as a speed of the internal combustion engine, the unit 20 are supplied. The unit 20 generates the control signal 26. In a manner not shown, the unit 20 can also generate the control signal 28. In the case of an error of the ZME 14, in particular in the case of a mechanical error, it can be determined via the analysis of the time profile of the pressure signal 22 whether the ZME 14 is sufficiently opened in order to convey fuel to the high-pressure pump 3 by means of the prefeed pump 5. If the increase in pressure in the case of a prefeed pump 5 that is switched on is not steep enough, it is possible to draw conclusions about a closed ZME 14. If the drop in pressure does not proceed steeply enough when the prefeed pump 5 is switched off, it is also possible to conclude that the ZME 14 is closed. The unit 20 is part of a control unit, not shown. The control unit, not shown, is part of the internal combustion engine, in particular for a motor vehicle.

Usually, the control signal 26 has two states. In the first state of the actuating signal 26, the prefeed pump 5 is switched on and delivers

Fuel from the fuel tank 9 to the ZME 14. In the second state of the control signal 26, the prefeed pump 5 is switched off, so that no fuel is conveyed from the fuel tank 9 by means of the prefeed pump 5 to the ZME 14.

The actuating signal 26 is formed substantially in response to the pressure signal 22 and the error signal 24.

FIG. 3 a shows a schematic diagram 30 a with a time profile of a determined pressure signal 22 a and a time profile of a

The pressure signal 22a corresponds to the pressure signal 22 from FIGS. 1 and 2. The control signal 26a corresponds to the control signal 26 from FIGS. 1 and 2. The times t1, t2, t3 are on a time axis t and t4 applied. On a

Pressure axis p are plotted a first pressure value pL, a target pressure value pS, a second pressure value pH1 and a third pressure value pH2. The pressure values pL, pH 1 and pH2 are determined as a function of the desired pressure value pS, more precisely with a respective offset to the desired pressure value pS. On a

State axis z has two states z0 and z1 plotted. The state zO corresponds to a switched-off prefeed pump 5 from FIG. 1. The state z1 corresponds to a switched-on prefeed pump 5 from FIG. 1.

The pressure signal 22a falls short of the first pressure value pL in a region A at the time t1. After the time t2, the pressure signal 22a changes from a falling course to a rising course. The pressure signal 22a rises above the second pressure value pH1. However, the pressure signal 22a does not exceed the third pressure value pH2. The pressure signal 22a changes into a falling course. The pressure signal 22a falls short of the first pressure value pL in a region B at the time t3. This starts after time t4

Pressure signal 22a rise again and exceeds the first pressure value pL.

The control signal 26a remains in state z0 until time t1, rises to state z1 at time t1, remains in state z1 until time t2, and returns to state z0 at time t2. The control signal 26a remains in state z0 until time t3, rises to state z1 at time t3, stays in state z1 until time t4, and returns to state z0 at time t4. The determined pressure signal 22a in each case falls short of the first pressure value pL at the times t1 and t3. The undershooting of the first pressure value pL causes the pressure signal 26a to be transferred from the state zO to the state z1. If, therefore, the determined pressure signal 22a drops below the first pressure value pL, the prefeed pump 5 of FIG. 1 is switched on.

The pre-feed pump 5 of FIG. 1, which is switched on at the time t1, is switched off at the time t2 after a time duration d (n) has elapsed. In a next cycle n + 1, where n denotes a previous cycle, a time duration d (n + 1) for the next switching on of the prefeed pump 5 of Figure 1 is selected equal to the time duration d (n), since the pressure signal 22a the second pressure value exceeds pH1 after the time t1 and before the time t3 and the pressure signal 22a does not exceed the third pressure value pH2 after the time t1 and before the time t3. Thus, the times t1, t2, etc. depend on the course of the pressure signal 22a. The value range of the durations d (n) and d (n + 1) is limited by a minimum value and a maximum value. A cycle usually starts when the pressure value pL is undershot by the pressure signal 22 or here 22a. In FIG. 3a, the cycle n begins with the pressure value pL falling below the pressure signal 22a in the region A at the time t1 and ends with the pressure value pL falling below the pressure signal 22a in the region B at the time t3. The cycle n + 1 starts when the pressure value pL is undershot by the pressure signal 22a in the region B at the time

In a manner not shown, an additional pressure value is provided below the first pressure value pL, wherein the additional pressure value is independent of other pressure values, such as the desired pressure value pS, and is constant. If the pressure signal 22 or 22a drops below this additional pressure value, then regardless of whether the prefeed pump 5 is switched on or off, i. irrespective of the state of the actuating signal 26 or 26a, the prefeed pump 5 is switched on, which corresponds to the state z1 of the actuating signal 26 or 26a. If the pressure signal 22 or 22a exceeds this additional pressure value, the previously deactivated process parts or the previously deactivated process are reactivated.

In a manner also not shown, a further pressure value is provided above the first pressure value pL, wherein the further pressure value is independent of the other pressure values, such as the desired pressure value pS, and is constant. If the pressure signal 22 or 22a exceeds the further pressure value, then regardless of whether the prefeed pump 5 is switched on or off, i. regardless of the state of the control signal 26 or 26 a, the

Pre-feed pump 5 is turned off, which the state zO of the control signal 26 or

26a corresponds. If the pressure signal 22 or 22a drops below this further pressure value, the previously deactivated process parts or the previously deactivated process are reactivated. FIG. 3b shows a schematic diagram 30b with a time profile of a determined pressure signal 22b and a time profile of a

Control signal 26b for the prefeed pump 5 of Figure 1. The pressure signal 22b corresponds to the pressure signal 22 of Figures 1 and 2. The control signal 26b corresponds to the control signal 26 of Figures 1 and 2.

Times t5, t6, t7, t8 and t9 are plotted on the time axis t. The pressure signal 22b falls below the first pressure value pL in the region A at the time t5. The pressure signal 22b continues to fall to rise again after time t6. The pressure signal 22b reaches a high point between the desired pressure value pS and the second pressure value pH1 and then begins to decrease again to fall below the first pressure value pL in the region B at the time t7. After the time t9, the pressure signal 22b rises again above the first pressure value pL. At the time t5, the actuating signal 26b rises from the state zO to the state z1. The actuating signal 26b lingers in the state z1 and returns to the state z0 at the time t6. Until the time t7, the control signal 26b remains in the state zO and jumps to the state z1 at the time t7. The control signal 26b remains in the state z1 until the time t9 and returns to the state z0 at the time t9.

Since the pressure signal 22b does not rise above the second pressure value pH 1 after the previous cycle n which starts at time t5 and before the drive cycle n + 1 starts at time t7, the time period d (n + 1) becomes the next Cycle n + 1 starting from the time duration d (n) from the previous cycle by one

Duration dind increased.

In a form that is not shown, the prefeed pump 5 from FIG. 1 can be switched on again at an earlier point in time, such as at time t7, which corresponds to a transition of the actuating signal 26b from the state zO to the state z1. This may be between reaching the high point of the pressure signal 22b and the beginning of the next cycle, i. between times t6 and t7, with the pressure signal 22b decreasing. Trigger for the renewed switching on the feed pump 5, for example, the expiration of a time period explained below, which runs from the time t5 be.

FIG. 3 c shows a schematic diagram 30 c with a time profile of a determined pressure signal 22 c and a time profile of a

Actuating signal 26c for the prefeed pump 5 of Figure 1. Times t10, t11, t12, t13 and t14 are plotted on the time axis t. The pressure signal 22c falls below the first pressure value pL in the region A at the time t10. The pressure signal 22c begins to rise again after the time t11 and reaches a high point above the third pressure value pH2. Thereafter, the pressure signal 22c drops and falls below the

Time t12 in the area B, the first pressure value pL. After time t14, the pressure signal 22c again exceeds the first pressure value pL.

The actuating signal 26c jumps from the state zO to the state z1 at the time t10. At the time t1 1, the control signal 26c jumps from the state z1 to the state z0. At the time t12, the control signal 26c jumps from the state zO to the state z1. At the time t13, the control signal 26c jumps from the state z1 to the state z0.

Since the pressure signal 22c rises above the third pressure value pH2 between times t10 and t12, for the next cycle n + 1, the time period d (n + 1) is reduced from the time duration d (n) of the previous cycle n by a duration dred ,

In addition, in a manner not shown, the time duration d (n + 1) can not be reduced when the pressure signal 22c exceeds the third pressure value pH2 a first time and then falls below again. If the time duration d (n + 1) has not been reduced during this first crossing, the procedure is as described above for a subsequent second exceeding of the third pressure value pH2.

In a further, not shown, form, the exceeding of the third pressure value pH 2 when the prefeed pump 5 of FIG. 1 is switched on causes the prefeed pump 5 to be switched off.

FIG. 3d shows a schematic diagram 30d with a time profile of a determined pressure signal 22d and a time profile of a

Actuating signal 26d for the prefeed pump 5 of Figure 1. Times t15, t16, t17, t18, t19, t20, t21, t22, t23, and t24 are plotted on the time axis t. The time t18 is generally referred to as additional time. The pressure signal 22d falls below the first pressure value pL in the region A at the time t15. At additional time t18 is the

Pressure signal 22d in a range C continues below the first pressure value pL. After the time t19, the pressure signal 22d rises, reaches a high point after the time t21 and before the time t22, and then drops to rise again after the time t24.

The control signal 26d rises from the state zO to the state z1 at the time t15. At time t16, the control signal 26d falls back from state z1 to state z0. At the additional time t18, the actuating signal 26d rises from the state zO to the state z1. At time t19, the actuating signal 26d falls back from state z1 to state z0. At the time t22, the actuating signal 26d rises from the state zO to the state z1. At the instant t24, the actuating signal 26d falls back from the state z1 to the state z0.

At time t15, a second time period del2 and a third time duration dell start to run. By way of example, the second time period del2 is essentially twice the third time duration d1. The determination of the third time duration d1c is explained below with reference to FIG. 3e. When the pressure signal 22d reaches the end of the second time period del2, i. until reaching the additional time t18, not the first pressure value pL, then on the one hand the

Control signal 26d from the state zO in the state z1 transferred, i. the prefeed pump 5 is turned on for the period of time d (n), and the time duration d (n + 1) for the next cycle n + 1 to be executed is increased from the time d (n) of the previous cycle n by a period dinc2. In a manner not shown, also at time t22, the third time period dell and the second time duration del2 start to run with the following subsequent steps above,

FIG. 3e shows a schematic diagram 30e for determining the third time duration d. Time points t25, t26, t27 and t28 are plotted on the time axis t.

The pressure signal 22e falls short of the first pressure value pL in the region A at the time t25. The pressure signal 22e continues to fall to rise again after time t26. At time t26, the pressure signal 22e is on a low point and then starts to rise again. The pressure signal 22e reaches a high point between the first pressure value pH2 and the second pressure value pH1 and then begins to decrease again to fall below the first pressure value pL in the region B at the time t27. After the time t28, the pressure signal 22e rises again above the first pressure value pL. At time t28, the pressure signal 22e is at a low point. A time del1 (n) starts at time t25 and ends at time t26. A time period del1 (n + 1) starts at time t27 and ends at time t28.

For example, to determine the third time duration dell, the first one becomes

Determination, i. the time duration del1 (n), equated to the third time duration dell The time duration del1 (n + 1) from the following cycle n + 1 is weighted into the third time duration dell. A determined time period del1 (n + z) from a following cycle n + z is weighted into the third time period dell as weighted above. However, a first determination of the third duration dell can also be carried out by averaging two or more time periods del1 (n), del1 (n + 1), etc.

Claims

claims

1. A method for operating an internal combustion engine, wherein fuel from a fuel tank (9), via a prefeed pump (5) via a

Metering unit (14) and via a high-pressure pump (3) one

High-pressure accumulator (13) is supplied, wherein the prefeed pump (5) for delivering fuel is switched on, and wherein a pressure signal (22; 22a-22d) of a pressure in the high-pressure accumulator (13) is determined, characterized in that an error of the metering unit (14) it is determined that the metering unit (14) is substantially open, that a period of time (d (n); d (n + 1)) is determined as a function of the determined pressure signal (22; 22a-22d), and in that the prefeed pump (5) is switched on for the duration (d (n); d (n + 1)).

2. The method of claim 1, wherein a time (t1; t3; t5; t7; t10; t12; t15; t22) is determined as a function of the determined pressure signal (22; 22a-22d), and wherein the prefeed pump (5) at the time (t1; t3; t5; t7; t10; t12; t15; t22) for the period (d (n); d (n + 1)) is turned on.

3. The method of claim 1 or 2, wherein the determined pressure signal (22;

22a-22d) at the time (t1; t3; t5; t7; t10; t12; t15; t22) falls below a first pressure value (pL), wherein the first pressure value (pL) is less than a desired pressure value (pS).

4. The method according to any one of the preceding claims, wherein the time duration (d (n + 1)) for the next turn on the feed pump (5) is increased when the determined pressure signal (22b) does not exceed a second pressure value (pH 1) the second pressure value (pH 1) is greater than the setpoint pressure value (pS).

5. The method according to any one of the preceding claims, wherein the time duration (d (n + 1)) for the next switching on of the prefeed pump (5) is reduced, when the determined pressure signal (22c) exceeds a third pressure value (pH2), wherein the third pressure value (pH2) is greater than the second pressure value (pH1).

Method according to one of the preceding claims, wherein the time duration (d (n + 1)) for the next switching on of the prefeed pump (5) is not changed when the determined pressure signal (22a) exceeds the second pressure value (pH1) and the third pressure value ( pH2). 7. The method according to any one of the preceding claims, wherein a second

Time (del2) at the time (t1; t3; t5; t7; t10; t12; t15; t22) is started, wherein the prefeed pump (5) at the time (t1; t3; t5; t7; t10; t12; t15 t22) for the period (d (n); d (n + 1)) is turned on, and wherein the prefeed pump (5) at the expiration of the second period (del2) at an additional time (t18) for the period (d ( n)) is turned on when the detected pressure signal (22d) within the second period (del2) does not rise above the first pressure value (pL).

Method according to claim 7, wherein the time duration (d (n + 1)) for the next switching on of the prefeed pump (5) is increased after the expiration of the second time duration (del2), if the ascertained pressure signal (22d) within the second time duration (del2 ), and wherein the prefeed pump (5) for the period (d (n + 1)) for the next turn on the feed pump (5) is turned on when the detected pressure signal (22d) among the first pressure value (pL) drops.

Method according to one of claims 7 or 8, wherein the second time duration (del2) is set substantially twice as large as a third time duration (dell), wherein the third time duration (dell) from the time (t1; t3; t5; t7 t10; t12; t15; t22) until another time (t26, t28) of an expected low point of the detected pressure signal (22e) after the time (t1; t3; t5; t7; t10; t12; t15; t22), after that

Pressure signal (22 e) increases again.

Control device on which a method according to any one of claims 1 to 9 is executable. Internal combustion engine, in particular for a motor vehicle with control unit according to claim 10.