KR20020081425A - Method for operating an internal combustion engine - Google Patents

Abstract

The present invention relates to a method of operating an engine, in particular a direct injection engine. According to the invention, the opening time t_i of the injection valve 10 is calculated according to the accumulator pressure p_r formed in the accumulator 8, and fuel is accumulated through the at least one pump 3, 7. And fuel is injected from the accumulator 8 through the injection valve 10 into the combustion chamber.

In order to measure as accurately as possible the amount of fuel injected, especially when the pressure fluctuations in the accumulator pressure p_r are very severe, the expected pressure value p_r_est is calculated from at least two measured pressure values and the slope of the accumulator pressure progress curve ( It is proposed to be used for the calculation of the opening time t_i of the injection valve 10 as the accumulator pressure p_r formed in the accumulator 8 when the value of dp_r_syn exceeds the preset threshold.

Description

How the engine works {METHOD FOR OPERATING AN INTERNAL COMBUSTION ENGINE}

Engines and methods of the kind mentioned at the outset are known from German patent 195 48 278. This patent describes a method for regulating the accumulator pressure in the accumulator of a common rail injection system (CR System). In this CR system, the opening time of the injection valve is calculated according to the amount of fuel injected and the accumulator pressure formed in the accumulator. Since the flow rate of the fuel passing through the injection valve is determined by the accumulator pressure, the accumulator pressure formed in the accumulator should be used in the calculation of the opening time. The accumulator pressure is measured synchronously with respect to the speed of rotation. The pressure regulation is within a defined time domain. The accumulator pressure, measured synchronously with respect to the speed of rotation for pressure regulation, is scanned synchronously with time.

In the method of operating the engine according to the prior art, there is a disadvantage that the opening time of the injection valve is not calculated based on the pressure of the accumulator formed in the accumulator at the time of injection but according to the pressure value measured before injection. In the static operating state where the change in accumulator pressure over time is small, the magnitude of the measured pressure value does not significantly affect the calculated opening time of the injection valve. However, in the dynamic pressure progression of accumulator pressure, there can be a relatively large difference between the pressure value measured before injection and the pressure value actually formed in the accumulator during injection, which is used in the calculation of the opening time. At dynamic pressure increase, the accumulator pressure during injection is higher than the previously measured pressure value. This results in that the flow rate through the injection valve and the fuel mass finally injected into the combustion chamber are also actually calculated larger. That is, excess fuel is supplied to the engine at the switching stage. Correspondingly when the dynamic pressure is reduced, too little fuel is supplied to the engine in the switching stage.

In later published German Patent No. 198 57 971, the opening time of the injection valve is not calculated by the pressure value measured before injection, but is based on at least two measured pressure values, in more detail. It is known that the expected pressure value is calculated at the start of the injection, which is then used based on the calculation of the opening time of the injection valve.

The invention particularly relates to an engine, in which fuel is supplied to at least one pump to the accumulator and injected from the accumulator to the combustion chamber through the injection valve, the opening time of the injection valve being calculated according to the accumulator pressure formed in the accumulator. It relates to a method of operating an injection engine. The present invention also provides an accumulator, at least one pump for supplying fuel to the accumulator, a combustion chamber, an injection valve for injecting fuel from the accumulator to the combustion chamber, and an injection according to the accumulator pressure formed in the accumulator. It relates to an engine, in particular a direct injection engine, incorporating a control device for calculating the opening time of the valve. The present invention also relates to a control device for such an engine.

Other features, applicability, and advantages of the invention are set forth in the following description of the embodiments of the invention shown in the drawings. All features described or illustrated are, individually or in any combination, form the subject of the invention, regardless of the abstract form or citation relationship in the claims, or regardless of the form or representational form in the text or figures. .

1 is a fuel supply system of an engine according to the present invention.

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

3 is a dynamic pressure progression curve of accumulator pressure in the accumulator of the engine.

It is an object of the present invention to reduce the error of fuel mass injected from the engine into the combustion chamber, thereby improving the fuel consumption, emission profile and noise generation of the engine.

In order to realize this object, the present invention is based on the method of operation of an engine of the kind mentioned at the beginning, the expected pressure value is calculated from at least two measured pressure values, and the inclination value of the accumulator pressure progress curve is preset. If the threshold value is exceeded, it is proposed to be used for calculating the opening time of the injection valve as the accumulator pressure formed in the accumulator.

In other words, according to the invention, it is proposed to calculate the opening time of the injection valve in a known manner from the measured accumulator pressure value, in a dynamic operating state where the static operating state of the engine and the accumulator pressure only change slowly over time. .

If the accumulator pressure changes abruptly, that is, if the slope value of the accumulator pressure progression curve exceeds a preset threshold, then the most recent pressure value expected during the injection time, rather than the pressure value measured before the injection, is determined by the injection valve. Used to calculate the open time. The expected pressure value is calculated from at least two measured pressure values. The dynamic pressure change of the accumulator pressure can also be used through the present invention. Correspondingly, the opening time of the injection valve can be calculated and the fuel mass injected into the combustion chamber can be accurately metered even with dynamic pressure changes. The method according to the invention contributes to the improvement of fuel consumption, noise level and emission pattern of the engine.

As already mentioned, if the slope of the accumulator pressure progression curve exceeds the preset threshold, that is, if the accumulator pressure progression curve exceeds a certain dynamic state, the predicted pressure value is used only for calculating the opening time of the injection valve. This slope reflects the direction of the maximum pressure change of the accumulator pressure. The slope value reflects the maximum pressure change.

According to a preferred embodiment of the present invention, it is proposed that the average accumulator pressure between the injection start point and the end point is indicated via the predicted pressure value. This average accumulator pressure may be a value between the accumulator pressure at the injection start point and the accumulator pressure at the injection end point. It is preferable that this average accumulator pressure is exactly the median of the accumulator pressure at the injection start point and the accumulator pressure at the injection end point. As an alternative method, the average accumulator pressure is the accumulator pressure formed at a point exactly centered between the injection start point and the injection end point. This significantly reduces the error in fuel mass injected into the combustion chamber.

According to a preferred embodiment of the present invention, it is proposed that a compensation function is determined via the measured pressure value and the predicted pressure value is calculated by this compensation function. The first-compensated polynomial is preferably determined through the measured pressure value. Substituting the expected injection start point or the time point between the injection start point and the injection end point in the compensation function or the compensation polynomial gives a relatively accurate expected pressure value for the injection start point or between the injection start point and the injection end point. You can get it. The first-compensated polynomial can be determined from two measured pressure values with low memory capacity without long computational time and provides an expected pressure value with sufficient accuracy.

According to another embodiment of the invention, it is proposed that the measured pressure value is calculated via a plurality of injection cycles. In this way, short-term pressure fluctuations in the accumulator can be measured, which allows very stable operation of the engine.

If the pressure in the accumulator increases rapidly, the opening time of the injection valve calculated by the method according to the invention is shorter than the opening time calculated on the basis of the pressure value measured before the injection point. Likewise, if the pressure decreases rapidly, the opening time calculated by the method according to the invention is longer than the opening time calculated on the basis of the pressure value measured before the injection point. In particular, if the pressure fluctuation is very severe in the accumulator, on the one hand the deviation between the opening time calculated by the method according to the invention and on the other hand the opening time calculated on the basis of the pressure value measured before the injection point is In order to avoid becoming too large, in another embodiment according to the invention, the predicted pressure value is the accumulator pressure formed in the accumulator, which is multiplied by the reduction factor less than 1 to the expected pressure value before being used in the calculation of the opening time of the injection valve. Is proposed.

The method according to the invention has a very important meaning that it is implemented in the form of a control member which is mounted on an engine, in particular a control device of a direct injection engine. In this case, a program executable on the computing device of the control device, in particular a microprocessor, suitable for the execution of the method according to the invention is stored in the control member. In this case the invention is embodied via a program stored on the control member, so that the control member provided with this program represents the method according to the invention in which a suitable program is used for execution. In particular, an electrical storage medium such as, for example, read-only memory (ROM) or flash memory can be used as the control member.

As another solution to the object of the present invention, on the basis of an engine of the kind mentioned at the outset, the control device calculates an expected pressure value from at least two measured pressure values, and the slope value of the accumulator pressure progress curve is pre-set. It is proposed to use this expected pressure value as the accumulator pressure formed in the accumulator if the set threshold value is exceeded.

According to a preferred embodiment of the present invention, it is proposed that the accumulator is formed as a high pressure accumulator of a common rail fuel injection system and the injection valve is formed as a high pressure injection valve. In engines with common rail injection systems in particular, it is preferable that the opening time of the high pressure injection valve is calculated by the expected pressure value representing the accumulator pressure during injection during dynamic pressure fluctuations.

As a solution to the object of the invention, on the basis of a control device of the kind mentioned at the outset, the control device calculates an expected pressure value from at least two measured pressure values, and the slope of the accumulator pressure progress curve is preset. When the threshold value is exceeded, it is proposed to use this expected pressure value as the accumulator pressure formed in the accumulator.

In Fig. 1, the entire fuel supply system of an engine according to the present invention including a high pressure injection device is indicated by reference numeral " 1 ". The fuel supply system 1 is also called a common rail system.

Reference numeral 2 denotes a fuel storage tank connected with the feed pump 3. The fuel reaches the metering valve 5 from the feed pump 3 via the conduit 4. The conduit 4 is connected with the fuel storage tank 2 via a low pressure limiting valve 6. The metering valve 5 is connected to the high pressure accumulator 8 via a high pressure pump 7. The high pressure accumulator 8 is formed as a high pressure accumulator pipe (rail). The high pressure accumulator 8 is connected to the high pressure injection valve 10 (so-called injector) through the fuel pipe 9. The high pressure accumulator 8 is connected with the fuel storage tank 2 via a pressure limiting valve 11. The metering valve 5 can be adjusted by the coil 12.

The region of the fuel injection system 1 between the outlet of the high pressure pump 7 and the inlet of the pressure limiting valve 11 is indicated as a high pressure region. The pressure in this high pressure region is measured by the sensor 13. The area of the fuel supply system 1 between the fuel storage tank 2 and the high pressure pump 7 is designated as a low pressure area.

Reference numeral 14 denotes a control device of the engine, which also controls the fuel supply system 1. The control device 14 provides a control signal A to the high pressure injection valve 10 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 plurality of output signals n of the other sensors 15, for example the speed sensor, are evaluated.

The control device 14 includes a filter 16, to which the output signal P_r of the pressure sensor 13 is supplied. The filter 13 provides the filtered pressure value P_r of the pressure sensor 13 to the flow calculator 17 and the addition integrator 18. The second inlet of the addition integrator 18 is provided with an output signal P_soll of the target value setting device 19. This target value setting device processes the output signal n of the other sensor 15 and the output signal Q_n of the flow rate calculator 17.

The flow rate calculation device 17 provides a control signal A to the high pressure injection valve 10 and a signal Q_n to the target value setting device 19, which signals the amount of fuel injected into the combustion chamber of the engine. Indicates. The output signal of the addition integrator 18 is provided to the pressure regulator 20, which in turn controls the coil 12 of the metering valve 5.

The operation manner of the fuel supply device 1 is as follows. The fuel is first supplied from the fuel storage tank 2 by the primary feed pump 3. When the pressure in the low pressure region exceeds the allowable value, the low pressure limiting valve 6 is opened, and the connection between the outlet of the primary feed pump 3 and the fuel storage tank 2 is opened.

The high pressure supply pump 7 supplies fuel from the low pressure region to the high pressure region. The high pressure pump 7 builds a high pressure in the high pressure accumulator 8. Further, in the fuel supply system used for the engine of the external ignition type, the pressure value in the high-pressure accumulator 8 reaches about 30 bar to 200 bar, and in the self-ignition engine, the pressure value reaches about 1000 bar to 2000 bar. The high pressure fuel may be supplied to the combustion chamber from each cylinder of the engine through the high pressure injection valve 10.

Through the metering valve 5 the pressure in the high pressure region can be regulated. The metering valve 5 adjusts the supply amount of the high pressure pump 7 according to the voltage supplied to the coil 12 or the current passing through the coil 12.

Other actuators may be mounted to adjust the accumulator pressure p_r in the high pressure region. This is a supply regulated electric primary feed pump or pressure limiting valve, which can alternatively be used for the metering valve 5, which can also be controlled by a coil.

The control signal A for the high pressure injection valve 10 is determined according to the accumulator pressure p_r and the fuel amount Q_n injected. The amount of fuel injected is controlled through the opening time t_i of the high pressure injection valve 10. Since the flow rate of the open injection valve 10 is determined in accordance with the accumulator pressure p_r in the high pressure accumulator 8, this flow rate should be taken into account when calculating the opening time t_i. The output signal A is calculated at variable time intervals according to the number of revolutions. The time interval between each calculation time point is determined by the engine speed n. The calculation of the control signal for the metering valve 5 is calculated with a constant time pulse in the pressure regulator 20. This time pulse should be selected so that the pressure regulator 20 can react immediately to the changing target value P_soll and the new target value P_soll can be adjusted as quickly as possible.

According to the prior art, the opening time of the high pressure injection valve, ie the control signal A, is calculated directly from the measured pressure value p_r. Theoretically, the injection process can proceed at a relatively early time point (eg at 340 ° before the top dead center (OT) of the ignition stage), so that the calculated opening time of the high pressure injection valve 10 for injection should be Should already be provided. However, due to this, the opening time t_i calculated for the high pressure injection valve 10 at a relatively late injection (eg 240 ° before top dead center of the ignition stage) is based on the pressure value p_r measured a relatively long time ago. The result is calculated as.

The calculation of the opening time t_i of the high pressure injection valve 10 according to the relatively old, pre-measured pressure value p_r has little effect on the static operating state of the engine. However, the pressure in the high pressure accumulator 8 can fluctuate very quickly. Pressure fluctuations are generated on the one hand by injection and on the other by pressure build up in the high pressure region. The measured pressure value used in the calculation of the opening time t_i at this dynamic pressure fluctuation shows a partial difference from the accumulator pressure actually formed in the high pressure accumulator 8 at the injection point.

In order to measure the amount of fuel injected into the combustion chamber of the engine through the high pressure injection valve 10 as accurately as possible, according to the present invention, the high pressure is based on the expected pressure value of the accumulator pressure formed in the high pressure accumulator 8 at the time of injection. It is proposed to calculate the opening time t_i of the injection valve 10. 2 shows a flowchart of the method according to the invention. This method begins at functional block 30. In the next functional block 31, the accumulator pressure p_r_ist currently formed in the high pressure accumulator 8 is measured and stored in the storage device 32. In the function block 33, the old pressure value p_r_ist_alt previously measured from the storage device 32 is called. The function block 34 then forms a slope of the accumulator pressure progress curve dp_r_syn, in which the previous accumulator pressure value p_r_ist_alt is subtracted from the current accumulator pressure value p_r_ist. In the inquiry block 35, it is then checked whether the slope dp_r_syn value exceeds a preset threshold. If the accumulator pressure p_r in the high pressure accumulator 8 changes relatively quickly, the slope value of the accumulator pressure progression curve exceeds the preset threshold. In this case the expected pressure value p_r_est is calculated in the function block 36. In the function block 37, the opening time t_i of the high pressure injection valve 10 is calculated according to the expected pressure value p_r_est.

In this embodiment, the first compensation polynomial is determined from the two measured pressure values p_r and the expected pressure value p_r is calculated from the compensation straight line. As detailed in German Patent No. 198 57 971, hereby expressly cited, the expected pressure value p_r_est represents the accumulator pressure p_r at the start of injection. In this case, the expected pressure value p_r_est is calculated by the following equation (compare FIG. 3).

[Equation 1]

In the four-stroke engine, the following equation applies:

[Equation 2]

Here, w_esb_x represents the angle at the injection starting point.

In this embodiment, the expected pressure value p_r_est represents the accumulator pressure p_r at the central point of injection, that is, the angle w_esm_x which is the central point between the injection start point and the injection end point. In this case, the expected pressure value p_r_est is calculated by the following equation.

[Equation 3]

Here, w_esm_x, which is calculated by the following equation, is an angle at the center point of injection.

w_esm_x = w_esb_x + angle {0.5 * t_1}

In a four-stroke engine, the following equation applies:

Angle {0.5 * t_1} = 0.006

Here, (n) is the engine speed, (t_i) is the opening time corresponding to the injection time.

If the inclination value of the accumulator pressure progression curve is below the threshold, ie if the engine is operated in the static operating region, the opening of the high pressure injection valve 10 in the function block 38 in the manner known in German Patent No. 195 48 278. The time t_i is calculated directly from the measured pressure value p_r_ist. Subsequently the calculated opening time t_i of the high pressure injection valve 10 is output in the function block 39. At functional block 40 the method according to the invention ends.

Claims (10)

Fuel is supplied to the accumulator 8 through at least one pump 3, 7 and injected from the accumulator 8 to the combustion chamber through the injection valve 10, the opening time t_i of the injection valve 10. In a method of operating an engine, in particular a direct injection engine, which is calculated according to the accumulator pressure p_r formed in the accumulator 8, The accumulator formed in the accumulator 8 if the expected pressure value p_r_est is calculated from at least two measured pressure values p_r_ist and p_r_ist_alt and the slope (dp_r_syn) value of the accumulator pressure progress curve exceeds a preset threshold. Characterized in that it is used for the calculation of the opening time (t_i) of the injection valve (10) as the pressure (p_r). Method according to claim 1, characterized in that the estimated pressure value (p_r_est) indicates the average accumulator pressure (p_r) between the starting point of injection and the ending point of injection. Method according to claim 1 or 2, characterized in that the compensation function is determined via the measured pressure value and the expected pressure value (p_r_esr) is calculated by this compensation function. 4. The method of claim 3, wherein the first compensation polynomial is determined through measured pressure values. The method of claim 1, wherein the measured pressure value is measured through a plurality of injection cycles. The reduction according to any one of claims 1 to 5, wherein the expected pressure value is less than one before being used in the calculation of the opening time t_i of the injection valve 10 as the accumulator pressure formed in the accumulator 8. And the coefficient is multiplied by the expected pressure value p_r_est. Computing device of the control device 14, in particular a control device 14 of an engine, in particular a direct injection engine, which is executable on a microprocessor and which stores a program suitable for carrying out the method according to claim 1. Control elements, especially read-only memory (ROM) or flash memory. Accumulator 8, at least one pump 3, 7 for supplying fuel to the accumulator 8, a combustion chamber, and an injection valve 10 for injecting fuel from the accumulator 8 into the combustion chamber. And an engine, in particular a direct injection engine, comprising a control device 14 for calculating the opening time t_i of the injection valve 10 in accordance with the accumulator pressure p_r formed in the accumulator 8, The controller 14 calculates the expected pressure value p_r_est from at least two measured pressure values, and if the inclination value of the accumulator pressure progress curve exceeds a preset threshold, it is defined as the accumulator pressure formed in the accumulator 8. An engine characterized by using an expected pressure value p_r_est. 10. The engine according to claim 8, wherein the accumulator (8) is formed as a high pressure accumulator of a common rail (CR) fuel injection system, and the injection valve (10) is formed as a high pressure injection valve. Accumulator 8, at least one pump 3, 7 for supplying fuel to the accumulator 8, a combustion chamber, and an injection valve 10 for injecting fuel from the accumulator 8 into the combustion chamber. And a control device 14 for calculating an opening time t_i of the injection valve 10 according to the accumulator pressure p_r formed in the accumulator 8, in particular a control device for a direct injection engine ( 14), The controller 14 calculates the expected pressure value p_r_est from at least two measured pressure values, and if the inclination value of the accumulator pressure progress curve exceeds a preset threshold, it is defined as the accumulator pressure formed in the accumulator 8. A control device characterized in that the expected pressure value p_r_est is used.