JP2003528243A - Driving method of internal combustion engine - Google Patents

Abstract

(57) [Summary] The present invention relates to a method for driving an internal combustion engine, and particularly to a method for driving a direct injection internal combustion engine. In this internal combustion engine, at least one pump (3, 7) conveys fuel to an accumulator (8), from which it is injected into a combustion chamber via an injection valve (10). Here, the opening duration (t_i) of the injection valve (10) is calculated depending on the accumulated pressure (P_r) in the accumulator (8). The following is proposed so that the fuel amount can be obtained as accurately as possible when the pressure fluctuation of the accumulated pressure (P_r) is strong. That is, when the absolute value of the gradient (dp_r_syn) of the accumulated pressure characteristic exceeds a predetermined threshold value, an estimated pressure value (P_r_est) is calculated from at least two measured pressure values, and the estimated pressure value is stored in the accumulator (8). It is proposed to use as the accumulated pressure (P_r) for the calculation of the opening duration (t_i) of the injection valve (10).

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION In the present invention, at least one pump conveys fuel to an accumulator and injects fuel from this accumulator into a combustion chamber via an injection valve, where the duration of opening of the injection valve is the accumulator. The present invention relates to a method for driving an internal combustion engine, for example, a direct injection internal combustion engine, which is calculated depending on the accumulated pressure in the internal combustion engine. The present invention also relates to an internal combustion engine having the following elements, for example, a direct injection internal combustion engine. That is, a pressure accumulator, at least one pump that conveys fuel to the pressure accumulator, a combustion chamber, an injection valve that injects fuel from the pressure accumulator to the combustion chamber, and the opening duration of the injection valve to the accumulated pressure in the accumulator. An internal combustion engine, for example a direct-injection internal combustion engine, with a control device which calculates dependently.

[0002]   Finally, the invention also relates to a control device for an internal combustion engine of this kind.

A method and an internal combustion engine of the type mentioned at the outset are described in German Patent 195
It is known from the US Pat. No. 48278, which shows a method for controlling the accumulated pressure of a common rail injection system (CR system). In this type of CR system, the opening duration of the injection valve is calculated depending on the amount of fuel to be injected and the accumulated pressure in the pressure accumulator. The accumulated pressure in the accumulator should influence the open duration calculation. This is because the flow rate through the injection valve depends on the accumulated pressure. The accumulated pressure is detected in synchronization with the rotation speed. Pressure control is performed at fixed time intervals. In order to control the pressure, the accumulated pressure detected in synchronization with the rotation speed is sampled in time.

The drive methods for internal combustion engines known from the prior art have the following drawbacks. That is, the opening duration of the injection valve is calculated not by the accumulated pressure in the pressure accumulator at the time of injection but by the pressure value measured before injection. In a static drive, where the stored pressure changes only slightly over time, the age of the measured pressure value does not significantly affect the calculation of the injection valve opening duration. However, when the pressure characteristic of the stored pressure is dynamic, there is a relatively large difference between the pre-injection measured pressure value used to calculate the open duration and the actual pressure value present in the accumulator during injection. Occurs. If the pressure rises dynamically, the accumulated pressure during injection will be higher than the previously measured pressure value. As a result, the flow rate through the injection valve, and thus the amount of fuel injected into the combustion chamber, actually increases from the calculation. That is, the internal combustion engine shifts to the rich state. If the pressure drops correspondingly, the internal combustion engine goes into a lean state.

The following is known from the subsequently published German patent DE 198 57 971: That is, the opening duration of the injection valve is not calculated based on the pressure value measured before injection, but based on at least two measured pressure values, the pressure value after that, specifically, the estimated pressure at the time of injection start A value is obtained and this estimated pressure value is used as a basis for calculating the opening duration of the injection valve.

[0006] The object of the present invention is to reduce the error of the fuel quantity injected into the combustion chamber in an internal combustion engine, thereby improving the exhaust gas characteristics, the noise generation and the fuel consumption of the internal combustion engine.

In order to solve this problem, the invention proposes the following based on the method of driving an internal combustion engine of the type described at the beginning. That is, when the absolute value with respect to the gradient of the accumulated pressure characteristic exceeds a predetermined threshold value, an estimated pressure value is calculated from at least two measured pressure values, and the estimated pressure value is used as accumulated pressure in the accumulator to open the injection valve. It is proposed to use it for calculating duration.

In other words, according to the present invention, in the static drive of the internal combustion engine and the dynamic drive in which the accumulated pressure changes only slowly over a period of time, the opening duration of the injection valve is measured by a method known per se. It is proposed to calculate based on the accumulated pressure value.

In the present invention, when the accumulated pressure changes relatively quickly, that is, when the absolute value for the gradient of the accumulated pressure characteristic exceeds a predetermined threshold value, the present invention is relatively old when calculating the opening duration of the injection valve. , The current estimated pressure value is used for the injection duration rather than the pre-injection measured pressure value. The estimated pressure value is calculated based on at least two measured pressure values. Dynamic pressure changes of the stored pressure are also taken into account by the invention.
The appropriate opening duration of the injection valve can be calculated and the amount of fuel to be injected into the combustion chamber can be metered very accurately even when the pressure changes dynamically. The method according to the invention improves exhaust emission characteristics, noise levels and fuel consumption of internal combustion engines.

As described above, the estimated pressure value is obtained only when the gradient of the accumulated pressure characteristic exceeds a predetermined threshold value, that is, when the accumulated pressure characteristic becomes dynamic to a certain degree or more, the opening duration of the injection valve. Used in the calculation of. The gradient shows the direction of the strongest pressure change of the accumulated pressure. The absolute value of the gradient represents the absolute value of the maximum pressure change.

In a further advantageous development of the invention, the following is proposed. That is, it is proposed that the estimated pressure value represents the intermediate accumulated pressure between the start and the end of injection. This intermediate accumulated pressure may be a value between the accumulated pressure at the start of injection and the accumulated pressure at the end of injection. Advantageously, it is the central pressure between the pressure at the beginning of injection and the pressure at the end of injection. Alternatively, the intermediate stored pressure is the stored pressure in the pressure accumulator at the very middle point between the start and the end of injection. This makes it possible to extremely effectively reduce an error in the amount of fuel injected into the combustion chamber.

In an advantageous configuration of the invention, the following is proposed. That is, it is proposed that the adjustment function is determined by the measured pressure value and the estimated pressure value is calculated based on this adjustment function. A first-order adjusting polynomial is preferably defined by the measured pressure value. By substituting the predicted injection start into this adjustment function or adjustment polynomial, a relatively accurate estimated pressure value at the injection start time can be obtained. Further, by substituting the time points existing between the injection start and the injection end, a relatively accurate estimated pressure value at the time points between the injection start and the injection end can be obtained. The first-order adjusting polynomial does not use long calculation times and requires little memory space and is defined by two measured pressure values. Furthermore, the first-order adjusting polynomial provides an estimated pressure value with sufficient accuracy.

In another advantageous development, the following is proposed. That is, it is proposed to detect the measured pressure value over a plurality of injection cycles. In this way, pressure fluctuations in the pressure accumulator can be detected for a short time, and the internal combustion engine can be driven extremely smoothly.

If the pressure rises dynamically in the accumulator, the opening duration of the injection valve calculated by the method of the invention is shorter than the opening duration calculated on the basis of the measured pressure value before injection. Similarly, if the pressure drops dynamically, the opening duration of the injection valve calculated by the method of the invention is longer than the opening duration calculated on the basis of the measured pressure value before injection. Especially when the pressure fluctuation in the accumulator is very strong, the difference between the opening duration calculated by the method of the present invention and the opening duration calculated based on the measured pressure value before injection should not be too large. In order to achieve this, the following is further proposed in an advantageous embodiment of the invention. That is, it is proposed to multiply the estimated pressure value by a reduction coefficient smaller than 1 and then use this estimated pressure value as the accumulated pressure in the accumulator for the calculation of the injection valve opening duration.

Of particular importance is that the method of the invention is implemented in the form of control elements for a control device of an internal combustion engine, for example a direct injection internal combustion engine. A program is stored in this control element, which program is executed by a calculator of the control device, for example a microprocessor, and is suitable for carrying out the method of the invention. In such a case, the present invention is realized by the program stored in this control element.
Therefore, this control element provided with a program is an invention as well as the manner in which this program is suitable for implementation. Electrical storage media, for example read-only memories (ROMs) and flash memories, are used in particular as control elements.

As a further solution of the invention, the following is proposed based on an internal combustion engine of the type mentioned at the outset. That is, when the absolute value of the gradient of the accumulated pressure characteristic exceeds a predetermined threshold value, the control device calculates an estimated pressure value from at least two measured pressure values and uses this estimated pressure value as the accumulated pressure in the accumulator. Is proposed.

In an advantageous development of the invention, the following is proposed. That is, it is proposed that the pressure accumulator is configured as a high pressure accumulator of a common rail (CR) fuel injection system and the injection valve is configured as a high pressure injection valve. The following are particularly advantageous for internal combustion engines with a CR injection system. That is, when the pressure fluctuation of the accumulated pressure is dynamic,
It is advantageous to calculate the opening duration of the high-pressure injection valve based on the estimated pressure value. This estimated pressure value represents the accumulated pressure during injection.

Finally, as another solution to the problem of the present invention, the following is proposed based on the control device of the type described at the beginning. That is, when the absolute value of the gradient of the accumulated pressure characteristic exceeds a predetermined threshold value, the controller calculates an estimated pressure value from at least two measured pressure values, and uses this estimated pressure value as the accumulated pressure in the pressure accumulator. Suggest to use.

Drawings Further features, applications and advantages of the invention will become apparent from the following description of the illustrated embodiment of the invention. All described or illustrated features are themselves
Alternatively, any combination forms the symmetry of the invention. It does not depend on the summary of these features in the claims or on the interrelationship of these features, or on the way they are expressed in the description or the drawings.

[0020]   FIG. 1 shows a fuel supply system for an internal combustion engine according to the present invention.

FIG. 2 shows a flow chart of the method of the invention according to a preferred embodiment.

FIG. 3 is a graph showing a dynamic pressure characteristic of accumulated pressure in the pressure accumulator of the internal combustion engine.

In FIG. 1, a fuel supply system for an internal combustion engine according to the invention, which has a high-pressure injection part, is indicated generally by the reference numeral 1. This fuel supply system 1 is commonly referred to as a common rail (CR) fuel injection system.

Reference numeral 2 designates a fuel reservoir tank. This fuel reservoir tank is connected to the transfer pump 3. The fuel reaches the metering valve 5 from the carrier pump 3 via the conduit 4. The conduit 4 is connected to the fuel reservoir tank 2 via a low pressure limiting valve 6. The metering valve 5 is connected to a high pressure accumulator 8 via a high pressure pump 7. The high pressure accumulator 8 is configured as a conduit (rail) of the high pressure accumulator. The high pressure accumulator 8 is connected via a fuel conduit 9 to a high pressure injection valve 10 (so-called injector). The high pressure accumulator 8 is connected to the fuel reservoir tank 2 via a pressure limiting valve 11. The metering valve 5 is drive-controlled by the coil 12.

The region of the fuel supply system 1 between the outlet side of the high pressure pump 7 and the inlet side of the pressure limiting valve 11 is called the high pressure region. The pressure in the high pressure region is detected by the sensor 13. The region of the fuel supply system 1 between the fuel reservoir tank 2 and the high pressure pump 7 is called the low pressure region.

Reference numeral 14 designates a control system for an internal combustion engine. This control device also controls the fuel supply system 1. The control device 14 applies the drive control signal A to the high-pressure injection valve 10 and further drives and controls the coil 12 of the metering valve 5. For this purpose, the output signal P_r of the pressure sensor 13 and the different output signals n from the further sensor 15, for example the speed sensor, are evaluated.

The control device 14 has a filter 16, to which the output signal P_r of the pressure sensor 13 is supplied. The filter 16 includes a fuel amount calculation device 17 and an addition point 18
The filtered pressure value P_r of the pressure sensor 13 is applied to. Addition point 18
The output signal P_soll of the target value setting device 19 is applied to the second input side of. This target value setting device 19 is provided with the output signal n of another sensor 15 and the fuel amount calculation device 1.
7 output signal Q_n.

The fuel amount calculation device 17 applies the drive control signal A to the high pressure injection device 10 and applies the signal Q_n to the target value setting device 19. This signal Q_n corresponds to the amount of fuel to be injected into the combustion chamber of the internal combustion engine. The output signal of the addition point 18 is applied to the pressure control unit 20. The pressure control unit further controls the drive of the coil 12 of the metering valve 5.

The fuel supply system 1 operates as follows. First, fuel is transported from the fuel reservoir tank 2 by the transport pump 3. As soon as the pressure in the low pressure region increases to an unacceptably high level, the low pressure limiting valve 6 is opened and the output side of the transfer pump 3 and the fuel reservoir tank 2 are connected.

The high-pressure transfer pump 7 transfers the fuel from the low pressure region to the high pressure region. The high-pressure pump 7 forms a high pressure in the high-pressure accumulated pressure 8. Normally, in the fuel supply system for an external ignition type internal combustion engine, the pressure value in the high pressure accumulator 8 reaches about 30 to 200 bar. Further, in the self-ignition type internal combustion engine, the pressure value reaches about 1000 to 2000 bar. Through the high-pressure injection valve 10, the fuel is metered at high pressure into the individual combustion chambers in the cylinder of the internal combustion engine.

The pressure in the high pressure region is controlled by the metering valve 5. Depending on the voltage applied to the coil 12 or the current flowing through the coil 12, the metering valve 5 supplies the high-pressure pump 7 with different delivery rates.

Another actuator may be used to control the accumulated pressure P_r in the high pressure region. As an alternative to the metering valve 5, this is an electric transfer pump or pressure control valve with which the transfer rate can be adjusted. Here, this pressure control valve is drive-controlled by a coil.

The drive control signal A for the high-pressure injection valve 10 depends on the accumulated pressure P_r and the fuel amount Q_n to be injected. The amount of fuel to be injected is the open duration t of the high pressure injection valve 10.
Adjusted via _i. Since the flow rate through the opened injection valve 10 depends on the accumulated pressure P_r of the high-pressure accumulator 8, the accumulated pressure should influence the calculation of the opening duration t_i. The calculation of the drive control signal A is performed with a variable time interval depending on the rotation speed. The time interval between the individual calculations depends on the engine speed n of the internal combustion engine. The drive control signal A for the metering valve 5 is calculated by the time clock fixed by the pressure control unit 20. This time clock is selected as follows. That is, the pressure control unit 2
0 can immediately respond to a changing target value P_soll, and a new target value P_s
The ol is chosen to be adjusted as quickly as possible.

In the prior art, the opening duration of the high-pressure injection valve, ie the drive control signal A, is calculated directly from the measured pressure value P_r. Since the injection may theoretically already occur at a relatively early time (eg, 340 ° before the top dead center (OT) of the ignition phase), the calculated opening duration for the injection is 10 must already be delivered before such an early point. However, this will result in an open duration t_i of the high-pressure injection valve 10 calculated on the basis of a relatively old measured pressure value P_r if the injection is relatively slow (eg 240 ° before ignition OT).

The calculation of the opening duration t_i of the high-pressure injection valve 10, which is dependent on a relatively old, early measured pressure value P_r, has little influence on the static drive of the internal combustion engine. However, the pressure in the high pressure accumulator 8 fluctuates very strongly. The fluctuations in pressure are due on the one hand to the injection and, on the other hand, to the pressure generation in the high pressure region. With such dynamic pressure fluctuations, the measured pressure value used to calculate the opening duration t_i differs partly from the actual stored pressure in the high pressure accumulator 8 at the time of injection.

In order to obtain the fuel amount to be injected into the combustion chamber of the internal combustion engine via the high pressure injection valve 10 as accurately as possible, the present invention proposes the following. That is, it is proposed to calculate the opening duration t_i of the high-pressure injection valve 10 based on the estimated pressure value with respect to the accumulated pressure in the high-pressure accumulator 8 at the time of injection. A flow chart of the method according to the invention is shown in FIG. The method begins at function block 30. In the subsequent functional block 31, the accumulated pressure P_r_i in the high-pressure accumulator 8 at present.
st is measured and stored in the memory 32. In function block 33, the early measured old pressure value P_r_ist_alt is retrieved from the memory 32. Then, the functional block 34 forms the gradient of the accumulated pressure characteristic dp_r_syn. This is based on the current accumulated pressure value P_r_ist to the old accumulated pressure value P_r_ist_alt.
Is subtracted. Continuing, in inquiry block 35, the slope dp_
It is checked whether the absolute value of r_syn exceeds a predetermined threshold. When the accumulated pressure P_r_ist in the high-pressure accumulator 8 changes relatively quickly, the absolute value for the gradient of the accumulated pressure characteristic exceeds a predetermined threshold value. In such a case, the estimated pressure value P_r_
est is calculated at function block 36. The opening duration t_i of the high-pressure injection valve 10 is subsequently calculated in function block 37 as a function of this estimated pressure value P_r_est.

In this embodiment, the first-order adjustment polynomial is determined by the two measured pressure values P_r,
The estimated pressure value P_r_est is calculated based on the adjustment straight line. The estimated pressure value P_r_est may represent the accumulated pressure P_r at the start of injection. This is described in detail in DE 198 57 971 A1, which is hereby referred to. In this case, the estimated pressure value P_r_est is calculated based on the following formula (see FIG. 3).

[0038]

[Equation 1]

[0039] Here, the following equations apply to a 4-cycle internal combustion engine.

[0040]

[Equation 2]

[0041] w_esb_x is the angle at the start of injection.

In this embodiment, the estimated pressure value P_r_est represents the accumulated pressure P_r at the middle of injection, that is, at the angle w_esm_x between the start and the end of injection. In this case, the estimated pressure value P_r_est is calculated based on the following formula.

[0043]

[Equation 3]

[0044] Here, w_esm_x is the angle in the middle of the injection, and the following equation holds.

[0045]

[Equation 4]

[0046] Also, the following equation applies to a four-cycle internal combustion engine.

[0047]

[Equation 5]

Here, the rotational speed n of the internal combustion engine and the opening duration t_i corresponding to the injection duration are used.

If the absolute value for the gradient of the stored pressure characteristic is below a threshold, that is to say if the internal combustion engine is driven in the range of static drive, German patent DE 19548
In a manner known per se from 278, the opening duration t_i of the high-pressure injection valve 10 is calculated directly from the measured pressure value P_r_ist in function block 38. Finally, the calculated opening duration t_i of the high-pressure injection valve 10 is sent to the function block 39. The function block 40 ends the method of the present invention.

[Brief description of drawings]

[Figure 1]   1 is a diagram showing a fuel supply system for an internal combustion engine according to the present invention.

[Fig. 2]   3 is a flow chart of the method of the present invention according to an advantageous embodiment.

[Figure 3]   3 is a graph showing a dynamic pressure characteristic of accumulated pressure in a pressure accumulator of an internal combustion engine.

[Procedure for Amendment] Submission for translation of Article 34 Amendment of Patent Cooperation Treaty

[Submission date] October 4, 2001 (2001.10.4)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Contents of correction]

[Claims]

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02M 47/00 F02M 47/00 EF term (reference) 3G066 AB02 AC01 AC09 AD12 BA17 BA22 BA23 BA51 CA04U CB01 CB12 CC01 CD26 CD29 DA01 DC09 DC18 3G084 BA11 BA13 BA14 BA15 DA02 DA04 DA10 DA39 EA07 EA11 EC04 FA00 FA33 3G301 HA01 HA02 HA04 JA02 JA25 JA26 JA37 LB06 MA11 MA18 NA07 NA09 NC01 ND42 ND45 NE17 NE19 PB08Z PE01Z

Claims (10)

[Claims] 1. A method of driving an internal combustion engine, for example, a direct injection type internal combustion engine, wherein fuel is conveyed to a pressure accumulator (8) by at least one pump (3, 7), and the fuel is accumulated in the accumulator (8). ) From the injection valve (10) into the combustion chamber, and the open duration (t_i) of the injection valve (10) is calculated depending on the accumulated pressure (P_r) in the pressure accumulator (8). In the above method, at least two measured pressure values (P_r_ist, P_r_ist_) are obtained when the absolute value of the accumulated pressure characteristic gradient (dp_r_syn) exceeds a predetermined threshold value.
Alt) to calculate an estimated pressure value (P_r_est), and the pressure accumulator (8)
A method for driving an internal combustion engine, for example, a direct injection internal combustion engine, which is used as a stored pressure (P_r) in the calculation of an opening duration (t_i) of the injection valve (10). 2. The method according to claim 1, wherein the estimated pressure value (P_r_est) represents an intermediate accumulated pressure (P_r) between the start and the end of injection. 3. The method according to claim 1, wherein the adjustment function is defined by the measured pressure value, and the estimated pressure value (P_r_est) is calculated based on the adjustment function. 4. The method of claim 3, wherein a first order adjustment polynomial is defined by the measured pressure value. 5. The method according to claim 1, wherein the measured pressure value is detected over a plurality of injection cycles. 6. The estimated pressure value (P_r_est) is multiplied by a reduction coefficient smaller than 1, and then the estimated pressure value is used as the accumulated pressure in the pressure accumulator (8) for the duration of opening of the injection valve (10) ( Method according to any one of claims 1 to 5 for use in calculating t_i). 7. A control element, for example a read-only memory (ROM) or a flash memory, for a control device (14) of an internal combustion engine, for example a direct injection internal combustion engine, the control device being the computing device of the control device (14). A control element, characterized in that it is executed by, for example, a microprocessor and stores a program suitable for carrying out the method according to claims 1 to 6. 8. A pressure accumulator (8), at least one pump (3, 7) for conveying fuel to the pressure accumulator (8), a combustion chamber, and fuel from the pressure accumulator (8) to the combustion chamber. An internal combustion engine having an injection valve (10) for injecting fuel and a controller (14) for calculating the opening duration (t_i) of the injection valve (10) depending on the accumulated pressure (P_r) in the pressure accumulator (8) In the engine, when the absolute value of the gradient (dp_r_syn) of the accumulated pressure characteristic exceeds a predetermined threshold value, the control device (14) calculates an estimated pressure value (from at least two measured pressure values).
P_r_est) is calculated, and the estimated pressure value is used as the accumulated pressure in the pressure accumulator (8), for example, a direct injection internal combustion engine. 9. The pressure accumulator (8) as a high pressure accumulator of a common rail (CR) fuel injection system, and the injection valve (10) as a high pressure injection valve according to claim 8. Internal combustion engine. 10. Accumulator (8), at least one pump (3, 7) for delivering fuel to the accumulator (8), combustion chamber, fuel from the accumulator (8) to the combustion chamber. An internal combustion engine having an injection valve (10) for injecting fuel and a controller (14) for calculating the opening duration (t_i) of the injection valve (10) depending on the accumulated pressure (P_r) in the pressure accumulator (8) In a control device (14) for an engine, for example, a direct injection internal combustion engine, when the absolute value with respect to the gradient of the accumulated pressure characteristic exceeds a predetermined threshold value, the control device (14) estimates the pressure value from at least two measured pressure values ( P_r_est
) Is calculated, and the estimated pressure value (P_r_est) is used as the accumulated pressure in the pressure accumulator (8).