JP4358669B2 - Method for controlling an injection system of an internal combustion engine having at least two injection elements and apparatus for controlling an injection system of an internal combustion engine having at least two injection elements - Google Patents

Description

  The present invention relates to a method for controlling an injection system of an internal combustion engine having at least two injection elements and to an apparatus for controlling an injection system of an internal combustion engine having at least two injection elements.

  In particular, in the current high-pressure fuel injection system of a self-igniting internal combustion engine, the total amount of fuel injected into the combustion chamber of the internal combustion engine using an injection valve (injector) is divided into a plurality of partial injections each time. These partial injections often follow one another at very short time intervals, and most consist of one or more pilot injections applied in time prior to the original main injection. A widely known injection system described in DE 100 02 270 C1 is the so-called “common rail injection system”, in which the fuel is fed into the high-pressure reservoir (rail) before the fuel is supplied to the individual injectors. Temporarily stored.

  The multi-stage partial injection described above achieves an improved mixture treatment, and thus, in particular, reduces the exhaust gas emissions of the internal combustion engine, reduces the generation of noise during combustion, and improves the output of the internal combustion engine.

  In the partial injection described above, the accuracy of each injection amount is extremely important. At the same time, however, each injection using the above-mentioned injector contacts the rail in the injector itself, as well as a short and rapid change in fuel pressure from the rail in the pipeline located in the injection system to the corresponding injector. It is known to mean a short and rapid change in fuel pressure from the high pressure connection to the needle valve of the injector. Such a rapid change in pressure for a short period of time acts on the fuel pressure wave which preferably occurs between the rail and the injector after the control of the injector. This pressure wave, in particular, undesirably fluctuates the amount of fuel to be injected each time. On the contrary, this pressure wave effect increases further as the stroke frequency of the nozzle needle of the injector increases, so that a high-speed piezoelectric wave, particularly as an injection actuator, is used. It will become even more important to take this pressure wave into account in future injection systems where a regulator of the formula will be used for the nozzle needle in each injector.

In the known approach for minimizing the effects of the pressure waves described above, the effects of the pressure waves are surveyed on the examination table when outside the driving mode of the vehicle with the internal combustion engine described here (so-called “offline”). This survey result is then taken into account, for example, when the operating parameters of the internal combustion engine or the vehicle are adjusted in advance. However, the model on which the pressure wave due to the partial injection is considered in considering the time-dependent effects of each partial injection is very complex. That is, the model includes a plurality of operating parameters such as injection quantity, fuel pressure that is currently dominant in the rail, fuel temperature, or pipe geometry of the entire injection system. These operating parameters are taken into account in the parameterization of the pressure wave measurement carried out in the so-called “offline” described above. The pressure wave correction itself is performed by appropriately changing the control time of the injector, and the correction obtained collectively for the entire injector is applied to each individual injector. With this correction, the effect of pressure waves on injection is reduced from about +/− 4 mm ³ to about +/− 1 to 2 mm ³ .

Inflexible corrections, however, because relatively large deviations in the injection volume occur and / or as soon as the quantity is equalized by the injector's inherent control time, the amplitude of the triggered pressure fluctuation can increase significantly. In the above-described pressure wave correction using the function, the air-fuel mixture process is newly deteriorated, so that finally the noise during emission and combustion is increased. In other words, the fact that the difference in the injection amount is relatively large deviates significantly from the respective target values at the end of the injection. The pressure wave that is triggered each time when the injection is completed dominates the pressure fluctuations that occur as a whole, and as a result, a significant injection error occurs in the correction controlled as described above.
DE 100 02 270 C1

  The object of the present invention is to provide a method and a device as described at the outset in order to realize the aforesaid pressure wave correction which is improved in comparison with the prior art, in particular in the aforesaid operating situation of an internal combustion engine.

  The problem is that, with respect to the method, collective pressure wave correction is performed on at least two injection elements, a first correction function is obtained, individual characteristic quantities of at least two injection elements are detected, Converting a correction function into a second correction function using the detected individual characteristic quantities of at least two injection elements, and pressure wave correcting the control of the at least two injection elements using the second correction function. Means for performing a collective pressure wave correction on at least two injection elements to determine a first correction function, and means for detecting individual characteristic quantities of at least two injection elements. Means for converting the control of the at least two injection elements into a second correction function for pressure wave correction using the detected individual characteristic quantities of the at least two injection elements. It is resolved by Rukoto.

  The present invention is based on the fact that the pressure wave correction for each injector is individually performed using the injector-specific amplitude modulation of the correction data obtained collectively for all the injectors. In other words, it is proposed to perform collective pressure wave correction in the first order approximation, and to individually adapt the correction data obtained at that time to the respective injectors using appropriate amplitude modulation in the second order approximation. The

  In an advantageous embodiment according to the invention, first a pressure wave correction is performed collectively for all the injectors of the injection system, and based on this a first correction function expressed for the whole injector is determined. An appropriate sensor or engine controller provides the characteristic or operating quantity specific to the injector. As the specific injector characteristic quantity, the outflow throttle / inflow throttle outflow / inflow adjustment ratio or the injector injection nozzle opening pressure is preferably taken into account.

  Alternatively, the actual amount compensation adjustment of each individual injector can be performed in a manner known per se, and the resulting compensation adjustment data specific to the injector is used as the characteristic amount specific to the injector as described above. can do.

  In another embodiment, additionally, the detected injector-specific characteristic quantity is normalized, and an injector-specific value for the aforementioned amplitude modulation of the first correction function is calculated from the normalized correction quantity. . Based on the first correction function, an amplitude-modulated correction function for each injector is calculated individually, and finally, the pressure wave correction of the control time of each injector can be performed using this correction function.

  The correction data of the aforementioned correction function calculated individually for each injector is preferably transmitted in the form of a control code to the engine controller, which in this embodiment performs the aforementioned pressure wave correction. carry out.

  The invention further relates to a device for controlling the injection system in particular in the manner described above, which in an advantageous embodiment provides a control signal for determining the amount of fuel to be injected under the influence of the pressure wave of the partial injection. Means for dependently, means for performing collective pressure wave correction on at least two injection elements to determine a collective correction function, means for detecting individual characteristic quantities of at least two injection elements, Means for performing amplitude modulation of the collective correction function using the detected individual characteristic quantities of at least two injection elements.

The method and the device according to the invention achieve individual corrections for each injector of the injection quantity characteristic in a multistage partial injection which is continuous in time, in particular independently of the dominant pressure wave amplitude. Even when the pressure fluctuation is large, accurate and effective pressure wave correction can be realized, and with this pressure wave correction, a very small injection amount tolerance can be realized. The operating characteristics of the internal combustion engine, such as combustion noise, are also optimized. With the configuration according to the present invention, the variation in the injection amount as described at the beginning can be further reduced from 1-2 mm ³ to 0.5-1 mm ³ .

  The present invention can advantageously be used with the aforementioned advantages in a common rail injection system operating with a high speed piezoelectric adjustment element, and also in post injection and pilot injection applied continuously in time, It can also be used in individual post-injections applied correspondingly.

  The invention is explained in more detail below on the basis of examples and with reference to the drawings, in order to clarify further characteristics, features and advantages of the invention.

  FIG. 1 shows the components of a high-pressure fuel injection system, which is an example of a common rail system, required for understanding the present invention. The fuel reserve tank is indicated with reference symbol 1. The fuel reserve tank 1 is connected to a second filter 15 via a first filter 5 and a feed pump 10 in order to supply fuel. Starting from the second filter 15, the fuel reaches the high-pressure pump 25 via a pipe line. The connection pipe between the second filter 15 and the high pressure pump 25 is further connected to the fuel reserve tank 1 via a connection pipe having a low pressure limiting valve 45. The high pressure pump 25 is connected to the rail 30. The rail 30 is referred to as a (high pressure) tank and is also connected to various injectors 31 through a fuel pipe in a pressure-guided manner. The rail 30 can be connected to the fuel reserve tank 1 via a pressure discharge valve or a relief valve 35. The pressure relief valve 35 can be controlled using a coil 36.

  The conduit between the outflow side of the high pressure pump 25 and the inflow side of the pressure discharge valve is referred to as a “high pressure region”. In this region, the fuel is in a high pressure state. The pressure in the high pressure region is detected using the sensor 40. On the other hand, the pipe line between the fuel reserve tank 1 and the high pressure pump 25 is referred to as a “low pressure region”.

  The control unit 60 applies a control signal AP to the high-pressure pump 25, a control signal A to the injector 31 and / or a control signal AV to the pressure exhaust valve 35. The controller 60 processes various signals of various sensors 65 that characterize the operating state of the internal combustion engine and / or the vehicle driven by the internal combustion engine. Such an operating state is, for example, the rotational speed N of the internal combustion engine.

  The injection system shown in FIG. 1 operates as follows: The fuel present in the fuel reserve tank 1 is supplied through a first filter and a second filter 15 using a feed pump 10. When the pressure in the low pressure region increases to an unacceptably high value, the low pressure limiting valve 45 is opened, and the connection between the discharge side of the feed pump 10 and the reserve tank 1 is released.

  The high pressure pump 25 supplies the fuel Q1 from the low pressure region to the high pressure region. The high pressure pump 25 creates a very high pressure in the rail 30. In the usual case, a maximum pressure value of 30 to 100 bar is achieved in an injection system for an externally ignited internal combustion engine and a maximum pressure value of 1000 to 2000 bar is achieved in a self-ignited internal combustion engine. Therefore, the fuel can be metered into individual combustion chambers (cylinders) of the internal combustion engine using the injector 31 at a high pressure.

  A pressure P in the rail or in the entire high pressure region is detected using the sensor 40. The controllable high pressure pump 25 and / or pressure relief valve 35 is used to adjust the pressure in the high pressure region.

  An electric fuel pump is usually used as the feed pump 10. It is also possible to use a plurality of supply pumps connected in parallel, especially for the relatively high supply required for commercial vehicles.

  FIG. 2 shows an enlarged cross-sectional view of a piezoelectrically operated injection valve (injector) 101 clarified from DE 100 02 270 C1. The injection valve 101 has a piezoelectric unit 104 for operating a valve member 103 that is movable in the axial direction in a hole 113 of a valve body 107. The injection valve 101 further includes an adjustment piston 109 that is in contact with the piezoelectric unit 104 and an operation piston 114 that is in contact with the valve closing member 115. Between the pistons 109 and 114, a hydraulic chamber 116 that operates as a hydraulic converter is disposed. Valve closure member 115 cooperates with at least one valve seat 118, 119 to separate low pressure region 120 from high pressure region 121. The electronic control unit 112, which is merely suggested schematically, provides a control voltage for the piezoelectric unit 104 and also depends on the pressure level generated in each case in the high pressure region 121. In the high pressure region 121 of the injection valve 101, an outflow throttle 130 and an inflow throttle 131 are additionally arranged. The outflow / inflow adjustment ratio of these two throttles 130 and 131 is adjusted by using the control valve 132.

  FIG. 3 shows a typical control signal profile for the injector shown in FIG. 2 in the case of main injection 200 and pilot injection 205 preceding in time. The five signal paths shown represent various temporal control states, in which the temporal interval between the two control signals 200, 205 is stepwise as can be seen from top to bottom in the figure. It is reduced to the minimum value Δtmin. It is assumed that the time interval Δtstart caused by the application is selected so that the pressure wave in the rail caused by pilot injection is weakened again until the main injection 200 is controlled. The corresponding value is known in advance as an empirical value. Furthermore, the time difference Δtmin between the injection times shown at the bottom corresponds to a minimum time interval, at which time the pressure wave caused by the pilot injection 205 already has a measurable change in operating characteristic. It is premised on that it leads to a torque change of the internal combustion engine.

  The two injections shown in FIG. 3 are merely used for illustration purposes, so that the method and apparatus according to the present invention can be used accordingly for the temporal application of multiple injections. It is understood that, of course, individual pilot injections that are adjacent in time can also be influenced in the manner described here on the basis of pressure waves.

  The pressure wave effect described above can be explained as follows based on FIG. If the pilot injection (VE) 205 is sufficiently spaced in time from the main injection (HE) 200, that is, if there is an interval Δtstart, the pressure wave triggered by the pilot injection 205 is already generated by the main injection 200. It is weakened and therefore no longer affects the amount of fuel injected in the main injection. This time interval depends substantially on the current rail pressure present in the rail, for example based on the wave velocity depending on the pressure, as is known. A suitable output value empirically determined for Δtstrat is> 2 ms. Although the start of control of the main injection remains constant, the pilot injection is brought closer to the main injection in time, so that the aforementioned time interval changes, especially in the area of the nozzle needle at the time of opening and the nozzle needle Since the pressure is high based on the location where the pressure wave is peaked or low based on the location where the wave is trough, The injection amount is affected. This produces an amount of effect or torque effect that can be detected using, for example, an engine speed signal. Alternatively, the effect of the quantity can also be detected in a known manner by controlling the λ sensor or λ sensor.

  In FIG. 4a, a typical pressure wave profile p_Injektor in the region of the injector of the common rail injection system shown in FIG. 1 is plotted over time t. A pilot injection that is applied in time to the main injection (or possibly a pilot injection) results in two components: a primary pressure fluctuation 320 and a secondary pressure fluctuation 330. Based on the output pressure p_Rail generated inside the rail, the primary pressure fluctuation 320 is caused by the opening of the switching valve 103 shown in FIG. 2 at the time 315 (t1), and by the outflow throttle / inflow throttle adjustment ratio of the throttle check valve. Induced. On the other hand, the secondary pressure fluctuation is caused by the opening of the nozzle needle at time t2 and the closing of the nozzle needle at time t3. Based on the closure of the nozzle needle at time t3, an additional short pressure overshoot 325 occurs here.

  The aforementioned throttle check valve is used here to throttle the fuel flow to the injector. This throttle check valve restricts the flow in one direction in a known manner and allows free flow in the opposite direction. Depending on the mounting position of the check valve, the throttling effect can be performed during inflow or outflow. The conversion from the inflow control to the outflow control is performed, for example, by rotating the check valve 180 degrees about a predetermined axis.

  In FIG. 4b, a typical fuel quantity profile m_Einspr during injection is shown to explain the pressure wave correction according to the invention. In this graph, the instantaneous injection amount to the injector is plotted over the differential time t_diff. The differential time t_diff is here defined by the time interval between the falling edge of the injection amount course present in a rectangular shape and the rising edge of the corresponding rectangular injection quantity course following the injection amount course. A solid line 400 represents a collective average value of the injection amount of the whole injector obtained in a known manner. In contrast, the dashed line 405 and the dash-dot line 410 represent the quantity course scaled using the amplitude modulation described herein, and these quantity courses are directly used to correct the injection quantities of the two injectors. Based on. In this example, the volume course 405 has a reduced amplitude compared to the middle course 400 and the quantity course 410 has a correspondingly increased amplitude compared to the middle course 400, but these quantity courses are for illustrative purposes. It is just a representation.

  The intrinsic pressure wave correction of the individual injector control data or control signals is finally done by appropriately changing the control data in a known manner. FIG. 4b additionally shows an average line m_mittig for periodically changing quantity courses 405, 510 for illustration. For this value representing the quantity course unaffected by the aforementioned pressure wave, the variation curve shown has been pre-normalized so that the relative change with respect to this average line can be further taken into account. At time t′1, the quantity courses 405, 410 for the two injectors with respect to the mean line m_mittig represent a negative overshoot. Accordingly, the control time at this point should be corrected upward as indicated by arrow 415 for the injector corresponding to curve 410. Correspondingly, for the injector corresponding to curve 405, a substantially slight correction according to the present invention is made as indicated by arrow 420. If a correction based on overshoot at time t'2 having a sign opposite to that at time t'1 has to be performed, the characteristics at time t'2 are reversed. That is, in the case of the curve 410, correction according to the arrow 425 is performed, and in the case of the curve 405, substantially slight correction is also performed according to the arrow 430.

FIG. 5 shows a flowchart, on which the method according to the invention will be explained in more detail. For each injector of the injection system, which is only suggested here schematically, a collective pressure wave correction 500 is performed in step 500 in a manner known per se. This collective pressure wave correction provides a first (collective) correction function f _K for injectors that are controlled hypothetically and averagely with respect to the pressure wave, which correction function f _K is substantially It depends on the parameter injection mass Δm_Einspr and the control time Δt. This correction function is further normalized to an average injection amount m_mittig corresponding to a value not affected by the pressure wave in step 505 for further processing according to the embodiment. In step 510, the normalized correction function f _K , norm is intermediately stored in the control device of the internal combustion engine in the form of a correction matrix.

  In step 515, the characteristic amount specific to the injector is detected. Here, the actual amount compensation adjustment is also performed in a known manner, and the data generated at this time is used as the characteristic amount. Alternatively, the individual control data of the injector, the outflow throttle / inflow throttle adjustment ratio of each injector or the open pressure p_Offnung of the injection nozzle of each injector is used as such a characteristic quantity. The obtained raw data of the individual injector characteristic values is normalized to the aforementioned average value m_mittig in step 520 and transmitted to the aforementioned control device in the form of a control code in step 525. Intermediate storage. The normalized correction function value intermediately stored in the control device is preferably amplitude modulated or amplitude scaled using the detected individual injector characteristic quantities. Of course, it can be seen that the correction function can be changed in other ways using the aforementioned characteristic quantities, for example by weighted scaling.

In step 530, a constant or time-varying scaling factor is calculated in the controller based on the normalized injector characteristic transmitted data, and in step 535, the scaling factor is used to normalize each individual injector. is the correction function f _K scaling that is, thereby a new correction function f _{K, norm,} inj.-indiv occurs. Finally, in step 540, the above-described intrinsic pressure wave correction of the control data of each injector is performed using the new correction function f _K , norm, inj.-indiv.

  The method described here can be realized either in the form of a circuit in the control device inherently provided for this purpose or in the form of a control code in the engine control device itself. Such a device comprises control means or calculation means, using which these first pressure wave corrections are first performed on the injection element to determine the first correction function described above. By means of suitable storage means, the first correction function can be intermediately stored in the aforementioned control device in the form of a correction matrix. Furthermore, sensor means for detecting individual characteristic quantities of the injection elements are provided. Alternatively, these characteristic quantities can be supplied from the engine control device itself as long as the above-described actual quantity compensation adjustment is based. Furthermore, calculation means or control means for converting the first correction function as described above using the detected characteristic amount is provided. Finally, the device includes calculation means or control means for correcting the control signal that determines the amount of fuel to be injected according to the injector.

1 is a schematic diagram of a common rail system known in the prior art. 1 is a partial schematic view in the longitudinal direction of a fuel injection valve for an internal combustion engine according to the prior art; FIG. In order to illustrate the pressure wave effect on which the present invention is based, an injection scheme known in the prior art with main injection and post injection based on corresponding control signals of the injection adjusting element. It is a typical pressure wave course in the common rail system shown in FIG. 2 is a typical fuel flow diagram for explaining pressure wave correction according to the present invention. It is a flowchart for further explaining the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Fuel reserve tank, 5 1st filter, 10 Feed pump, 15 2nd filter, 25 High pressure pump, 30 Rail, 31 Injector, 35 Pressure exhaust valve, 36 Coil, 40, 65 Sensor, 60 Control part

Claims (11)

A method for controlling an injection system of an internal combustion engine having at least two injection elements, comprising:
Dividing the fuel metering into a first partial injection and at least one second partial injection, the control signal determining the amount of fuel to be injected using the at least two injection elements is a pressure of the at least two partial injections In a method for controlling an injection system of an internal combustion engine having at least two injection elements, correcting depending on the influence of waves,
Performing a collective pressure wave correction on the at least two injection elements to determine a first correction function;
Detecting individual characteristic quantities of the at least two injection elements;
The first correction function is converted to a second correction function using the detected individual characteristic quantities of the at least two injection elements, and the second correction function is used to convert the first correction function of the at least two injection elements. A method for controlling an injection system of an internal combustion engine having at least two injection elements, characterized in that the control is pressure wave corrected.   The conversion of the first correction function to the second correction function using the detected individual characteristic quantities of the at least two ejection elements is performed by amplitude scaling or amplitude modulation of the first correction function. Item 2. The method according to Item 1.   The method according to claim 1, wherein the individual characteristic quantities of the at least two injection elements are formed based on actual amount compensation adjustments respectively performed for the at least two injection elements.   The individual characteristic quantities of the at least two injection elements are formed by an outflow throttle / inflow throttle adjustment ratio of the respective injection elements and / or by an opening pressure of an injection valve of the respective injection elements. The method of any one of these.   The method according to claim 1, wherein the first correction function is intermediately stored in the control device of the internal combustion engine in the form of a correction matrix.   The method according to claim 1, wherein the determined individual characteristic quantities of the at least two injection elements are transmitted to the control device of the internal combustion engine in the form of a control code. An apparatus for controlling an injection system of an internal combustion engine having at least two injection elements,
The fuel metering is divided into a first partial injection and at least one second partial injection;
Controlling an injection system of an internal combustion engine having at least two injection elements, provided with means for correcting a control signal for determining the amount of fuel to be injected depending on the influence of the pressure wave of the at least two partial injections In the device
Means for performing a collective pressure wave correction on the at least two injection elements to obtain a first correction function;
Means for detecting individual characteristic quantities of the at least two injection elements;
Means for converting the first correction function into a second correction function for pressure wave correction of control of the at least two injection elements by using the detected individual characteristic quantities of the at least two injection elements. An apparatus for controlling at least two injection elements having an injection system for an internal combustion engine, characterized in that   8. The apparatus of claim 7, wherein the means for converting the first correction function performs amplitude scaling or amplitude modulation of the first correction function.   9. An apparatus according to claim 7 or 8, wherein the means for detecting individual characteristic quantities of the at least two injection elements cooperate with means for performing an actual quantity compensation adjustment for the at least two injection elements.   The means for detecting the individual characteristic quantities of the at least two injection elements cooperates with means for supplying the outflow throttle / inflow throttle adjustment ratio of the respective injection elements and / or the opening pressure of the injection valves of the respective injection elements. A device according to claim 7 or 8.   11. The device according to claim 7, further comprising means for intermediately storing the first correction function in the form of a correction matrix in the control device of the internal combustion engine.

Images