WO2011154229A1

WO2011154229A1 - Method for operating an internal combustion engine

Info

Publication number: WO2011154229A1
Application number: PCT/EP2011/058046
Authority: WO
Inventors: Christian Alexander Muennich; Till Wokoeck; Tobias Hillenbrand
Original assignee: Robert Bosch Gmbh
Priority date: 2010-06-09
Filing date: 2011-05-18
Publication date: 2011-12-15
Also published as: CN102918243B; DE102010029840A1; EP2580455A1; CN102918243A; DE102010029840B4

Abstract

A method for operating an internal combustion engine, in particular for avoiding undesired pressure deviations, is described. A setpoint value (108) of a pressure is determined as a function of a driver's request. An actual value (1 10) of the pressure is compared with the setpoint value (108) of the pressure. An actuation signal (106) which results therefrom is fed to a controlled section (44). The actual value (1 10) of the pressure is determined from the controlled section (44). A change in the driver's request is detected. A pressure correction value (104) is determined as a consequence of the change in the driver's request. The actuation signal (108) is changed as a function of the pressure correction value (104).

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 to operate an internal combustion engine pressures must be regulated. Examples are the regulation of a fuel pressure in a high-pressure accumulator of the internal combustion engine or the boost pressure in an intake pipe after a compressor and before entering the

Internal combustion engine.

It is also known that over or underpressure of the pressure can occur in the abovementioned regulations, the overshoot or undershoot of the pressure being considered as unintentional pressure deviations. It is also known that a hydraulically induced delayed closing of a

High pressure pump can lead to unwanted pressure deviations.

Disclosure of the invention

The problem underlying the invention is solved by a method according to claim 1. Advantageous developments are specified in subclaims. 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 a pressure correction value from the driver's request. A control signal will depend on the

Pressure correction value changed. From the driver's request can be quickly and easily closed to changes in the operating conditions of the engine and appropriate measures can be taken to prevent unwanted pressure variations.

A possible, unwanted pressure deviation predicament is the

Pressure correction value used to change the control signal. Any delays caused by hydraulic processes in the high-pressure pump are thus advantageously bypassed and an undesired pressure deviation can be avoided. Accordingly, a load on the components of

Reduced internal combustion engine and thus increases the life of the components as well as the entire internal combustion engine. Likewise, there are acoustic advantages, as a quieter operating noise of the

Internal combustion engine at load transitions results.

In an advantageous embodiment, an accelerator pedal gradient is used to determine a change in the driver's request. From the

Accelerator gradient can be easily and quickly on the

Close driver request and it can, for example, immediately recognize an upcoming load transition.

In an advantageous embodiment, the accelerator gradient is compared with a threshold value. If the threshold is exceeded, the

Pressure correction value determined. This will be an easy way to

Evaluation of the driver's request created that requires little computing capacity. In an advantageous embodiment of the method, the

Pressure correction value activated at a first time, wherein the first time corresponds to a threshold exceeded by the driver's request. Advantageously, therefore, immediately after the determination of a certain

Driver's request to be started with a measure to prevent an unwanted pressure deviation. In a further advantageous embodiment of the method, the

Pressure correction value is activated only at a second time, which is after the first time. By this second time can more

Operating parameters, such as physical properties of

Controlled system and the operating state of the internal combustion engine, to avoid an unwanted pressure deviation are taken into account.

In a further advantageous embodiment of the method, the second time and a third time at which the pressure correction value is deactivated depend on a rotational speed of the internal combustion engine. Since it is possible to deduce the characteristic of the expected deviation of the pressure from the rotational speed of the internal combustion engine, the rotational speed is the starting point for the determination of the times. Thus, the unwanted pressure deviation in direct dependence on the operating state, represented by the

Speed, be prevented.

In a further advantageous embodiment of the method, the

Activation and / or deactivation of the pressure correction value carried out according to a ramp function. This ensures that a raw value of the pressure correction value is not applied abruptly. A jump in the

Pressure correction value would result in undershot or overshoot of the pressure, which can be avoided by the ramp function.

In a further advantageous embodiment of the method, a further activation after activation of the pressure correction value by a debounce time is not performed. As a result, it can be advantageously avoided that an admission of the pressure correction value takes place several times. Thus, an adverse effect on the pressure can be avoided. In a further advantageous embodiment, a control difference, which is formed from the actual value and the desired value of the pressure, with the

Pressure correction value linked and applied to a controller. The controller generates the actuating signal. The method accordingly advantageously intervenes to a limited extent in an existing controller structure. This can be avoided that an application of the customer must be changed because the pressure correction value is fed directly to the controller. Likewise, a must Feedforward control, for example in the form of a Juckeldämpfers, not be adjusted.

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 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. 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;

Figure 2 is a schematic block diagram for determining a

Pressure correction value;

FIG. 3 shows a schematic block diagram of a controller structure for

Applying the pressure correction value; and

Figure 4 is a schematic diagram in two sections, each with deactivated and activated pressure correction value.

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 actuator 15 is hydraulically in the course of the low pressure line 7 between the prefeed pump 5 and the high pressure pump 3 is arranged. 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 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 delivers the fuel into the high pressure accumulator 13. The ZME 14 determines the high pressure pump 3 supplied fuel quantity.

A measurement of the pressure within the high pressure accumulator 13 is made by a pressure sensor, not shown, to the high pressure accumulator 13th

performed. A value measured by this pressure sensor is referred to as the actual value of the pressure and later identified by the reference numeral 1 10.

The ZME 14 is acted upon by a control signal 106. In accordance with the actuating signal 106, the ZME 14 supplies fuel to the high-pressure pump 3. The actuating signal 106 is usually determined by a control unit, not shown.

FIG. 2 shows a schematic block diagram 20 for determining a

Pressure correction value 104. From a driver's request, an accelerator gradient 100 is determined and fed to a comparator 26 together with a threshold value 124. The driver's request essentially corresponds to the position of the accelerator pedal of the motor vehicle to be actuated by a driver. From this driver's request, the accelerator gradient 100 is derived, for example as a percentage of an accelerator pedal travel per unit time. The accelerator gradient 100 is then compared to the threshold 124 in the comparator 26.

A first activation signal 134 has a first level, which corresponds to an activation when the accelerator gradient 100 exceeds the threshold value 124, that is, when the position of the accelerator pedal changes greatly. The first activation signal 134 has a second level which is one Deactivation corresponds to when the accelerator gradient 100 is less than the threshold value 124. A transition from the first to the second level is referred to as triggering. The first activation signal 134 is a

Activation unit 32 is supplied.

In addition to the first activation signal 134, the activation unit 32 is acted upon by a debounce time 126, a correction time 128 and a waiting time 132. The correction time 128 is determined by means of a characteristic curve 22 from a rotational speed 122 of the internal combustion engine. The waiting time 132 is determined by means of a characteristic curve 24 from the rotational speed 122.

The activation unit 32 generates a second activation signal 136. The second activation signal 136, like the first activation signal 134, has a first and second level. The second activation signal 136 is generated based on the first activation signal 134.

The activation unit 32 ensures that a multiple triggering of the second activation signal 136 by the first activation signal 134 during the debounce time 126 is prevented. For example, a jerky, desired by the driver load reduction to a bouncing of the

Accelerator gradient 100 and thus lead to a multiple triggering of the first activation signal 134. Accordingly, the debounce time 126 avoids multiple triggering of the second activation signal 136. After the triggering of the first activation signal 134 and the following

Expiration of the waiting time 132, the second activation signal 136 is triggered. After the triggering of the second activation signal 136, the second

Activation signal 136 for the correction time 128 is maintained at its first level and returns to the second level after the correction time 128.

A ramp function unit 34 is supplied with the second activation signal 136, a zero signal 141, a raw pressure correction value 142 and ramp parameter 138. The ramp function unit 34 generates the pressure correction value 104. The zero signal 141 corresponds to a zero level of the pressure correction value 104, usually a value of zero. The raw pressure correction value 142 is derived from a map 28 of an injection quantity 102 and the rotational speed 122 determined. The ramp parameters 138 are used for ramping in and out of the pressure correction value 104.

If the second activation signal 136 is at its second level for deactivation, the ramp function unit 34 selects the zero signal 141

Generation of the pressure correction value 104 from. Is the second one?

Activation signal 136 at its first level for activation, the ramp function unit 34 selects the raw pressure correction value 142 to generate the pressure correction value 104.

Since the pressure correction value 104 at the beginning of the triggering of the second activation signal 136 is at a value of the zero signal 141, that is at a zero level, one of the ramp parameters 138 is supplied to a first ramp function. The first ramp function ensures that the pressure correction value 104 does not jump from the zero level to the raw level.

Pressure correction value 142 increases or decreases, but over a period of time

is faded in or angefüllt. Usually this is the

Pressure correction value 104 is proportionally composed of the zero signal 141 and the raw pressure correction value 142, wherein the proportion in the first ramp function shifts over time to the raw pressure correction value 142. If the second activation signal 136 returns to its untripped state, there is a corresponding deceleration of the

Pressure correction value 104 instead. The beginning of the triggered state of the second activation signal 136 corresponds to an activation of the

Pressure correction value 104. The end of the triggered state of the second

Activation signal 136 corresponds to a deactivation of the pressure correction value 104.

FIG. 3 shows a schematic block diagram 40 of a controller structure for supplying the pressure correction value 104. The actual value 110 of the pressure is determined from a controlled system 44 formed essentially by the ZME 14, the actuating device 15, the high-pressure pump 3 and the high-pressure accumulator 13. The actual value 1 10 of the pressure is subtracted at a point 146 from a target value 108 of the pressure. The target value 108 is inter alia dependent on the driver's request, whereby the driver's request is reflected in the target value 108 with a time delay. The result of the subtraction at location 146 is a first control difference 143. At a point 148, the first

Control difference 143 and the pressure correction value 104 added, the

corresponding sum at the point 148 is a second control difference 144. The subtraction at location 146 as well as the addition at location 148 are also commonly referred to as linking. The second control difference 144 is applied to a controller 42. The controller 42 is usually a PI controller. The controller 42 generates the actuating signal 106. The actuating signal 106 is fed to the controlled system 44. The actuating signal 106 determines the degree of opening of the ZME 14.

FIG. 4 shows a schematic diagram in two cutouts 50a and 50b. The detail 50a shows the schematic diagram with deactivated

Pressure correction value 104. The detail 50b shows the schematic diagram with the pressure correction value 104 activated. Along a time axis t, times t0, t1, t2 and t3 are plotted. The time tO is generally referred to as the first time. The time t1 is generally referred to as the second time. The time t3 is generally referred to as the third time. The detail 50b shows an application of the block diagrams 20 and 40 of FIGS. 2 and 3 for avoiding a pressure overshoot in the high-pressure accumulator 13 as it is present in the cutout 50a and explained below.

In the cutout 50a, the accelerator gradient 100a drops sharply at time t0, stays at a low level, and returns to the previous level before time t2. This corresponds to a removal of the foot from

Accelerator, which means a transition to overrun. When the accelerator gradient 100a drops, the threshold value 124 is exceeded.

For the purpose of explanation, however, the function according to the schematic block diagram 20 of FIG. 2 is deactivated. Thus, despite the

Crossing the threshold 124 no activation signal 134a generated. The pressure correction value 104a is thus in the deactivated state, which corresponds to the zero signal 141 in FIG.

The injection amount 102a remains at a nearly same level until the time t2, and decreases in accordance with the transition to the coasting operation after the time t2. This corresponds to the usual procedures when using a conventional engine control unit. The control signal 106a remains at a nearly same level until time t2, and drops after time t2. The drop of the control signal 106a causes a reduction in the degree of opening of the ZME 14 of Figure 1.

The desired value 108a and the actual value 1 10a of the pressure remain until the

Time t2 on a nearly the same level. After the time t2, the target value 108a of the pressure drops. After the time t2, the actual value 1 10a of the pressure does not follow the desired value 108a of the pressure. In the region of a marking 52a, the actual value 1 10a of the pressure has an overshoot. The overshoot represents an unwanted pressure deviation. The

Overshoot is characterized by an increase of the actual value 1 10a, whereby the target value 108a decreases. The actual value 1 10a of the pressure approaches the target value 108a again after reaching a maximum of the overshoot. Reason for the overshoot is the hydraulic delay of the closure of the high pressure pump 3 of Figure 1.

In the cut-out 50b, the accelerator gradient 100b drops sharply at time t0, stays at a lower level, and returns to the previous level before time t2. As in section 50a, so also in the

Section 50b of the accelerator gradient 100b the threshold 124th Im

In connection with the cutout 50b, the schematic block diagram 20 of FIG. 2 is not deactivated. Thus, due to the crossing of threshold 124 by accelerator gradient 100b, an enable signal 134 is generated, resulting in the output of a pressure correction value 104b.

The pressure correction value 104b is in the deactivated state before the time t0. After time t0, the pressure correction value 104b drops, moves below the previous level, and returns to the deactivated state only at time t3. The pressure correction value 104b is generated by the block diagram 20 of FIG. 2 and supplied to the controller structure there according to the block diagram 40 of FIG.

The injection amount 102b stays at a nearly equal level until the time t2, and falls after the time t2 in accordance with the transition to the coasting mode. The control signal 106b remains at an almost same level until the time t0 and drops off after the time t0. The drop in the control signal 106b causes a reduction in the degree of opening of the ZME 14 of Figure 1, whereby the high-pressure pump 3 is supplied less fuel per time.

The target value 108b of the pressure and the actual value 110b of the pressure are at an almost identical level before the time t2. After the time t2, the target value 108b of the pressure and the actual value 110b of the pressure fall off. The actual value 1 10b of the pressure points in an area of the marking

52b no overshoot, but follows the target value 108b of the pressure. The overshoot as in section 52b is avoided because the closure of the ZME 14 of Figure 1 is already initiated at the time tO. The cutout 50a as well as the cutout 50b show an operating situation of the

Internal combustion engine at a transition into overrun operation. When the pressure correction value 104a in section 50a is not activated, the hydraulically induced delayed closing time of the high-pressure pump 3 in FIG. 1 leads to the overshoot of the actual value 110a of the pressure in the marking 52a. This results from the fact that the transition into the overrun only by the falling

Target value 108b or the falling injection amount 102a can be detected and taken into account at the time t2.

In contrast, with the pressure correction value 104b activated, as shown in section 50b, the pushing operation is already detected at the time t0. As a result, immediately after the time t0, the actuating signal 106b can be changed in a suitable manner, which in turn means that the actual signal 110b of the pressure no longer has an overshoot. In the section 50b thus the transition of the internal combustion engine in the

This is equivalent to preventing the overshoot of the actual value 1 10a according to the mark 52a in the cutout 50a in the cutout 50b by means of the pressure correction value 104b Compensation of the actual value 1 10b performed in response to the driver's request. At the time t0, the accelerator gradient 100b and thus ultimately the driver's intention are evaluated in accordance with the block diagram 20 from FIG. 2 such that the determined pressure correction value 104b is fed to the control structure from FIG. According to FIG. 3, the first control difference 143 is linked by the pressure correction value 104b to a second control difference 144, which is supplied to the controller 42. The controller 42 in FIG. 3 determines the actuating signal 106b in accordance with the second control difference 144.

The drop of the control signal 106b during the thrust transition is brought forward by the active pressure correction value 104b from the time t2 in the cutout 50a to the time t0 in the cutout 50b. Accordingly, with the pressure correction value 104b activated, the ZME 14 closes sooner than when deactivated

Pressure correction value 104a. An earlier closing of the ZME 14 of Figure 1 has the consequence that an overshoot of the actual value 1 10a is avoided in the mark 52a and a course of the actual value 1 10b sets as in mark 52b.

The thrust transition can thus already be detected at the time t0 by the evaluation of the accelerator gradient 100 or 100b. As a result, closing of the ZME 14 in accordance with the actuating signal 106b can already be initiated at the time t0 and thus before the time t2.

The situation illustrated in Figure 4 of a transition into the overrun operation is exemplary. The generation of the pressure correction value 104 or 104b and the corresponding application is also possible for a reverse case of a transition to an acceleration. In this case, undershoots of the actual value 110 of the pressure occur, which can be avoided by a pressure correction value 104 generated in accordance with FIG. 2, an application according to FIG. 3 and a premature increase in the degree of opening of the ZME 14 from FIG. Accordingly, the desire of the driver has to be one

Acceleration from the accelerator gradient 100 can be determined.

Another embodiment for preventing unwanted deviations of a pressure relates to influencing a boost pressure which is generated by a compressor. A charge of the internal combustion engine is done via a compressor. The compressor is supplied with a control signal, which is generated according to FIG. The compressor generates a pressure, the boost pressure, in a suction pipe which is connected to the inlet of the internal combustion engine. Also, this pressure is subject to changes, as previously

described be recognized before their occurrence by the evaluation of the driver's request or the accelerator gradient 100. If the threshold value 124 is exceeded or fallen short of by the accelerator gradient 100, the pressure correction value 104 is formed according to the block diagram 20 of FIG. 2, fed to a control structure according to the block diagram 40 of FIG. 3, thus avoiding a pressure undershoot or a pressure overshoot of the boost pressure.

Claims

claims

1 . Method for operating an internal combustion engine, in particular for

Avoiding unwanted pressure deviations, wherein a desired value (108) of a pressure in response to a driver's request is determined, wherein an actual value (1 10) of the pressure with the desired value (108) of the pressure is compared, one of them resulting control signal (106) is fed to a controlled system (44), and wherein from the controlled system (44) the actual value (1 10) of the pressure is determined, characterized in that a

Change in the driver's request is detected as a result of

Changing the driver's request, a pressure correction value (104) is determined, and that the actuating signal (106) in dependence on the

Pressure correction value (104) is changed.

2. The method according to claim 1, wherein the change of the driver's request corresponds to an accelerator pedal gradient (100; 100a; 100b), in particular one accelerator pedal travel per unit time.

3. The method according to claim 1 or 2, wherein the change of

Driver's request with a threshold (124) is compared, and wherein in response to exceeding the threshold (124) of the

Pressure correction value (104) is determined.

4. The method of claim 3, wherein the overshoot to a first

Time (tO) is detected, wherein the pressure correction value (104) in

Dependency of the overshoot is activated at the first time (to), and wherein the pressure correction value (104) is deactivated at a third time (t3).

5. The method according to claim 3, wherein the exceeding of the first

Time (tO) is detected, wherein the pressure correction value (104) in

Dependence of the excess at a second time (t1) after the first time (tO) is activated, and wherein the pressure correction value (104) is deactivated at the third time (t3).

6. The method of claim 4 or 5, wherein the second time (t2) and / or the third time (t3) depending on a speed (122) of

Internal combustion engine can be determined.

A method according to any one of claims 4 to 6, wherein the activation and / or deactivation of the pressure correction value (104) is performed according to a ramp function.

8. The method of claim 4, wherein a further activation of the pressure correction value is not carried out with the pressure correction value activated for a debounce time starting from the first time or the second time ,

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

Pressure correction value (104) depending on an injection quantity (102) and / or a rotational speed (122) is determined.

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

Pressure correction value (104) with a control difference (143) from the actual value (1 10) and the setpoint value (108) is linked, wherein the result of the linkage is applied to a controller (42), and wherein the controller (42) generates the control signal (106).

1 1. Method according to one of the preceding claims, wherein the control signal (106) of the regulator (42) of a metering unit (41) is acted upon, and wherein the pressure is a fuel pressure.

12. The method according to any one of the preceding claims, wherein the control signal (106) of the regulator (42) is applied to a compressor, and wherein the pressure is a boost pressure.

13. Control unit on which a method according to one of claims 1 to 12

is executable.

14. Internal combustion engine, in particular for a motor vehicle with a control device according to claim 13.