EP2638272A2

EP2638272A2 - Method for operating an internal combustion engine

Info

Publication number: EP2638272A2
Application number: EP11767726.0A
Authority: EP
Inventors: Markus Viereck
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2010-11-11
Filing date: 2011-10-12
Publication date: 2013-09-18
Also published as: DE102010043755A1; US9249753B2; CN103221667A; WO2012062522A3; CN103221667B; WO2012062522A2; DE102010043755B4; US20130304353A1

Abstract

The invention relates to a method for operating an internal combustion engine. The internal combustion engine comprises a high-pressure accumulator (13) and a low-pressure region (8). The high-pressure accumulator (13) and the low-pressure region (8) are connected via a pressure control valve (10). In the method, an open position of the pressure control valve (10) is dependent on an actuating pressure. A negative load change of the internal combustion engine is detected. The actuating pressure is reduced from an initial level to a low level at a point in time dependent on the detection of a negative load change.

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.

It is known that in order to operate an internal combustion engine with a high-pressure accumulator, the fuel pressure in the high-pressure accumulator must be regulated. Internal combustion engines are also known, which have a fuel-carrying connection between the high-pressure accumulator and a low-pressure region, which can be opened or closed via a pressure regulating valve.

In addition, it is known that the pressure control valve can be operated in a conventional mode, i. in a pressure control mode, operated purely controlled. The control is designed so that the pressure control valve always remains closed.

It is also known that overshoots of the pressure can occur in the above-mentioned controls or regulations, wherein the

Overshoots of the pressure are regarded as unwanted pressure deviations.

For example, negative load changes can turn into an unwanted one

Overshoot lead. DE 101 31 783 A1 discloses a method for

Stabilization of fuel pressure.

Disclosure of the invention

The problem underlying the invention is achieved by a method according to claim 1. Advantageous developments are in the Subclaims specified. Features which are important for the invention can also be found in the following description and in the drawings, wherein the features, both alone and in different combinations, can be important for the invention, without being explicitly referred to again.

The method advantageously generates depending on a

Detecting a negative load change a set pressure for the

Pressure control valve. By reducing the setting pressure of the pressure regulating valve from an initial level to a low level, an undesired positive pressure deviation can advantageously be avoided, since fuel flows off via the pressure regulating valve and the pressure within the high-pressure accumulator is thus reduced in a controlled manner.

The possible, unwanted positive pressure deviation presumably the setting pressure is changed so that any delays are bypassed by hydraulic processes in the high-pressure pump advantageous. Thus, the degradation of the pressure in the high pressure accumulator can be more accurately influenced and the pressure control can be supported. Accordingly, a load of the components of the internal combustion engine is reduced and thus increases the life of the components as well as the entire internal combustion engine. As a result, the components can be designed in such a way that they are not protected against unwanted positive pressure deviations. Likewise, there are acoustic benefits, since the process is a quieter

Operating noise of the internal combustion engine at negative load transitions results.

In an advantageous embodiment of the method, the injection quantity is reduced simultaneously with the reduction of the setting pressure. This advantageously allows continuation of the injections with a reduced amount of fuel, whereby fuel is saved while preventing an unwanted positive pressure deviation.

In an advantageous embodiment of the method, the set pressure lingers for a period of time from one time to another time at the low level and the set pressure returns to the next time in the vicinity of the initial level. This advantageously achieves that Pressure control valve is operated only during the specified period of time "overdriven". This causes an at least temporary opening of the pressure regulating valve, so that fuel can flow from the high-pressure accumulator into the low-pressure region and this pressure reduction prevents an undesired positive pressure deviation.

In an advantageous development of the method, the return of the setting pressure is carried out in the vicinity of the initial level in the form of a ramp function. The ramp function transfers a first input value into a second input value over a certain period of time. This can advantageously negative effects on the pressure control valve supplied current or voltage signal, which is generated by a signal converter or a current control can be prevented. In a further advantageous embodiment of the method, the actuator

Pressure after reduction into a sloping course over. Just by lowering the control pressure, it is possible that the

Pressure control valve opens. Due to the further sloping course is

ensures that the pressure control valve is operated so that no unwanted positive pressure deviations arise.

In a further advantageous embodiment of the method, the

Reduction of the control pressure generated by a unit, wherein the unit comprises a phase-raising D-member. Because the inductance of the

Pressure regulating valve delays its opening, the phase-raising D-

Link for the fact that the actuating pressure is essentially proportional to the

Change rate of an input difference is changed. The phase-raising D-member thus compensates in part for the delay through the inductance of the pressure control valve and thus ensures that the pressure control valve react faster and thus, an unwanted positive

Pressure deviation predisposed, can be opened faster.

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are illustrated in the figures of the drawing. All described or illustrated features form for themselves or in any Combination of the subject matter of the invention, regardless of theirs

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

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;

FIG. 2 shows a schematic block diagram for determining an actuator

pressure;

FIG. 3 shows a schematic block diagram for the alternative determination of the

Actuating-pressure; and

Figure 4 is a schematic diagram with three sections, each with different gradients of the setting pressure.

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. 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.

The high pressure accumulator 13 is associated with a pressure sensor 16 which generates an actual pressure 104. The actual pressure 104 is supplied to a control unit 12.

The high-pressure accumulator 13 is connected to the low-pressure line 7 via a pressure regulating valve 10, which is referred to below as PCV (Pressure Control Valve). This means that the high-pressure accumulator 13 with a

Low-pressure region 8 of the fuel injection system 1 is connected. The PCV 10 is supplied with a control signal 102, wherein the control signal 102 from the

Control unit 12 is generated.

When the PCV 10 is open, fuel from the high-pressure accumulator 13 can therefore flow into the low-pressure line 7 or into the low-pressure area due to the pressure difference between the high-pressure accumulator 13 and the low-pressure region 8

8 flow. In a manner not shown, the PCV 10 also with the fuel tank

9 or connected to the suction line 4.

FIG. 2 shows a schematic block diagram 20 for determining a setting pressure 108 for the actuating signal 102. The schematic block diagram 20 is part of the control device 12 from FIG. 1.

A signal 1 18 is supplied to a control unit 44. The control unit 44 detects a signal 1 12. The signal 112 is fed to a switch 24. The switch 24 is also a signal 1 14 is supplied. Via the signal 122, which is likewise supplied to the switch 24, it is determined which of the signals 1 12 and 114 is supplied as the setting pressure 108 to a signal converter 42. The signal converter 42 generates the actuating signal 102, which is supplied to the PCV 10 of FIG. The actuating pressure 108 thus influences the open position of the pressure regulating valve 10 of FIG. 1. The signal converter 42 may further include current and / or voltage controls and / or controls. The control unit 44 generates the signal 1 12 in such a way that when the signal 1 12 is forwarded as the actuating pressure 108 by the switch 24, the PCV 10 from FIG. 1 remains completely closed. The signal 1 18 may be, for example, a desired or actual pressure or the like.

The signals 1 14 and 122 are generated by a unit 22. In the illustrated state of the switch 24, the signal 114 as the actuating pressure 108 is the

Signal converter 42 supplied. The signal 122 and the signal 114 are formed depending on a negative load change of the internal combustion engine. For this purpose, the unit 22 is acted upon by a signal 126, wherein the signal 126 indicates a negative load change of the internal combustion engine.

The signal 114 is formed such that when forwarding the signal 1 14 as a control pressure 108, the PCV 10 opens and fuel from the

High-pressure accumulator 13 can flow into the low-pressure region 8. For this purpose, the signal 1 14 is usually brought to a lower value than the signal 1 12. The unit 22 may be acted upon in a manner not shown also with a speed, an injection amount or another variable with respect to the internal combustion engine to determine the signal 1 14 and / or the signal 122 in dependence on the corresponding size.

The signal 114 or the signal 122 may be based on a predictive

Print information to be determined. Other parameters such as the dead time of the high pressure pump, the high pressure volume, the

Compressibility of the fuel or the incoming and outgoing

Flow rates in the high-pressure accumulator 13 can be taken into account in this determination. For such a determination, the unit 22 is provided with inputs, not shown.

The signal 112 and the signal 114 are embodied, for example, as a pressure signal or actuating pressure or can be configured correspondingly in a current / voltage level for controlling the PCV 10.

In a manner not shown, the switch 24 may be configured such that when switching from the signal 1 12 to the signal 114 or when switching from the signal 114 to the signal 1 12 a ramp function is used, which ensures that the control pressure 108 is not increased or decreased abruptly from one level to another level.

FIG. 3 shows a schematic block diagram 30 for alternative determination of the setting pressure 108 for the actuating signal 102. The schematic block diagram 30 is part of the control device 12 from FIG. 1. The signal converter 42 and the control unit 44 from FIG.

Between the signal converter 42 and the control unit 44 is analogous to the switch 24, a switch 34. The switch 34 has the same

Functionality on how the switch 24. The switch 34, in addition to the signal 1 12 a signal 116 and a signal 124 is supplied.

The signals 1 16 and 124 are generated by a unit 32. Like the unit 22 of Figure 2, the unit 32 is applied to the signal 126. The unit 32 has a unit 36, wherein the unit 36 generates the signal 116 and is acted upon by a difference 128. The difference 128 is generated by subtracting an actual signal 105 from a desired signal 106 at a location 39. In a manner not shown, the difference 128 may also be generated by subtracting the desired signal 106 from the actual signal 105. The unit 36 includes a phase-raising D-member 38. The unit 36 may be a controller or a controller. The phase-raising D-gate 38 ensures that the signal 1 16 generated by the unit 36 is fast or jumpy

Changes to the difference 128 are responding. The unit 32 may be applied in a form not shown also with a speed, an injection amount or another variable with respect to the internal combustion engine to determine the signal 1 16 and / or the signal 124 in dependence on the corresponding size.

In a manner not shown, the unit 36 without a

phase-raising D-member 38 to be executed. However, the signal generated by unit 36 would then not respond to changes in difference 128 as quickly. This would be advantageous if the dynamization by the phase-raising D-member 38, depending on the system, is not necessary to achieve the desired pressure behavior. For example, the actual signal 105 may be the set pressure 108 and the set signal 106 may be a target set pressure.

Or the actual signal 105 is, for example, an actual volume flow through the PCV 10 and the desired signal 106 is a desired volume flow through the PCV 10, wherein a dead amount of the high-pressure pump 3 can be selectively removed. The actual volume flow can be measured or estimated from existing variables in the control unit. Or the actual signal 105 is, for example, the actual pressure 104 from FIG. 1 and FIG

Target signal 106 is a desired pressure.

Or the actual signal 105 is, for example, an actual pressure or an actual pressure gradient, wherein the actual pressure or the actual pressure gradient can be obtained from a predictive estimation. Accordingly, the desired signal

106 a corresponding desired pressure or target pressure gradient. This means that certain pressure levels lying in the future can be detected in advance and prevented by appropriate countermeasures. The difference 128 may be used by the unit 36, as long as the difference is a set pressure for the high pressure accumulator 13 and the actual pressure 104 to affect the closing process of the PCV. If too little pressure, that is to say a positive difference 128 when generating the difference 128 according to FIG. 3, is found, the difference 128 leads to a rapid closing. If too much pressure is detected, ie a negative difference 128, the difference leads to a slow closing.

Signal 1 16 and / or signal 124 of FIG. 3 or signal 1 14 and / or signal 122 of FIG. 2 can be determined on the basis of predictive pressure information. Other parameters such as the

Dead time of the high pressure pump, the high pressure volume, the

Compressibility of the fuel or the incoming and outgoing

Flow rates into the high-pressure accumulator 13 can be taken into account when determining the signal 1 16 and / or 124 or the signal 1 14 and / or the signal 122. For such a determination, the unit 32 or the

Unit 22 provided with corresponding inputs, not shown. FIG. 4 shows a schematic diagram 40 with three sections a, b and c, wherein in each case different courses of the setting pressure 108 are shown which influence the course of the actual pressure 104. A time axis t is shown, wherein two times t1 and t2 are plotted on the time axis t.

In the section a, the PCV 10 is closed. The section a thus corresponds to the forwarding of the signal 1 12 as a set pressure 108 in Figures 2 and 3. The control pressure 108 is only controlled in this case.

In section a, a desired pressure 106a drops from time t1. Before or at the time t1, a negative load change is detected, which makes a decreasing injection quantity necessary in the following. An actual pressure 104a does not follow the predetermined target pressure 106a, but begins to rise at the time t1 and approaches the flag again only after leaving the mark 100a

Course of the desired pressure 106a. The course of the actual pressure 104a in the marking 100a represents an undesired positive pressure deviation and thus a pressure overshoot. An injection quantity 110a which is discharged from the high-pressure accumulator 13 into cylinders of the

Internal combustion engine is injected, drops abruptly at time t1, so begins to decrease at time t1. The setting pressure 108a also drops from the time t1. However, the falling of the set pressure 108a does not necessarily cause the PCV 10 to open. The signal 122a remains constant and the signal 1 12 is forwarded as actuating pressure 108 by the switches 24 and 34, respectively.

In the sections b and c, the signals 1 14 and 1 16 are forwarded as actuating pressure 108. Thus, the PCV 10 is at least temporarily safely opened and it can flow fuel from the high pressure accumulator 13 in the low pressure region 8 of the internal combustion engine. The corresponding pressure reduction can be read in the curves of an actual pressure 104b and an actual pressure 104c.

In section b, a desired pressure 106b drops from time t1. The actual pressure 104b has a time-delayed waste compared to the target pressure 106b. In comparison with the section a, the actual pressure 104b in

Excerpt b in the mark 100b no or only a small unwanted positive pressure deviation. The injection amount 1 10b drops at time t1 abruptly or begins to decrease in a manner not shown near the time t1.

The control pressure 108b is at a point in time t1

Starting level. The control pressure 108b drops abruptly at time t1 and then is at a low level. The set pressure 108b abruptly increases again after the lapse of a period of time at time t2, to jump to the previous value of the course of the set pressure 108a, i. to return to the initial level, the current value of the signal 1 12. The

Initial level and the low level each covers a range of

Values, where the initial level is above the low level. The above time period between the times t1 and t2 is determined depending on the rotational speed of the internal combustion engine. The low level is determined depending on the speed of the internal combustion engine. Furthermore, the change in injection quantity and other factors can affect the low level.

The signal 122b rises at time t1 and drops abruptly at time t2. According to the signal 122b, the signal 1 12 is selected as the actuating pressure 108 by the switch 24 or 34 before the time t1. According to the signal 122b, which corresponds to the signal 122 or 124 in FIGS. 2 or 3, between the times t1 and t2, the signal 1 14 or 1 16 is selected by the switches 24 and 34 as actuating pressure 108. According to the signal 122b, after

Time t2, the signal 1 12 from the switch 24 and 34 selected as a set pressure 108.

According to the course of the set pressure 108b, it is possible for the PCV 10 to briefly open to release enough fuel from the high-pressure accumulator 13, so that no or only a small positive pressure deviation of the actual pressure 104b compared to the mark 100a occurs.

In section c, a setpoint pressure 106c drops off after time t1. Likewise, the actual pressure 104c drops, but with a time delay to the target pressure 106c. In the marking 100c, the actual pressure 104c has no or only a small unwanted positive pressure deviation compared to the mark 100a. The

Injection amount 1 10c drops abruptly at time t1. The actuating pressure 108c falls abruptly at time t1 and then has a sloping course. Signal 122c jumps at time t1. Also, instead of the decreasing course of the setting pressure 108c, a constant value after the sudden drop may be substantially maintained.

According to the signal 122c, which corresponds to the signal 122 or 124 in FIGS. 2 or 3, the switch 24 or 34 selects the signal 1 12 for forwarding as setting pressure 108c before time t1. According to the signal 122c, the switch 24 or 34 selects the signal 114 or 116 after the time t1

Forwarding as actuating pressure 108c.

The course of the actuating pressure 108c has the consequence that the PCV 10 opens at least briefly so that fuel can flow from the high-pressure accumulator 13 into the low-pressure region 8 and an undesired positive

Pressure deviation, especially an unwanted positive deviation of the actual pressure 104a in the mark 100a, can be avoided or reduced.

The actuating signal 102 is usually a current or voltage signal. Signals 122, 124, 122a, 122b, and 122c are typically a digital signal, but may be used to perform ramping or ramping

Input signals of the switch 24 and 34 may be formed according to otherwise. Accordingly, the switch 24 or 34 may be formed to a Einrampung or Ausrampung.

The actual pressure 104a, 104b and 104c is generally referred to as an actual signal. The desired pressure 106a, 106b and 106c is generally referred to as a desired signal.

Claims

claims

1. A method for operating an internal combustion engine, wherein the

Internal combustion engine, a high-pressure accumulator (13) and a

Low pressure region (8), wherein the high-pressure accumulator (13) and the low-pressure region (8) via a pressure control valve (10) are connected, wherein an open position of the pressure control valve (10) by a set pressure (108) is dependent, and wherein a negative Load change of

Internal combustion engine is detected, characterized in that in

Depending on the detection of a negative load change the set pressure (108) at a time (t1) is reduced from an initial level to a low level.

2. The method of claim 1, wherein at almost the same time

Reduction of the setting pressure (108) an injection quantity (1 10) of the internal combustion engine is lowered.

3. The method of claim 1 or 2, wherein the setting pressure (108) for a

Period of time from the time (t1) to a further time (t2) dwells at the low level and the setting pressure (108) at the further time (t2) returns to the vicinity of the initial level.

A method according to any one of the preceding claims, wherein decreasing the set pressure (108) from the initial level to a low level and / or returning the set pressure (108) to the vicinity of

Output levels is performed in the form of a ramp function.

5. The method according to any one of the preceding claims, wherein the low level of the control pressure (108) is determined in dependence on a rotational speed of the internal combustion engine.

6. The method according to any one of the preceding claims, wherein the time is determined in dependence on the rotational speed of the internal combustion engine.

7. The method of claim 1, wherein the set pressure (108) after the

Reduction into a declining course, and where the

Absolute value of the gradient of the falling gradient is less than the absolute value of the gradient of the reduction.

8. The method according to any one of the preceding claims, wherein the

Reduction of the actuating pressure (108) by means of a unit (36) is generated, and wherein the unit (36) comprises a phase-raising D-member (38).

9. The method of claim 8, wherein the unit (36) a difference (128) is supplied, and wherein the difference (128) from a subtraction of an actual signal (105) from a desired signal (106) and from a Subtraction of a desired signal (106) is formed by an actual signal (104).

10. Control device on which a method according to any one of claims 1 to 9

is executable.

1 1. internal combustion engine, in particular for a motor vehicle with a

Control device according to claim 10.