Patent Application
20210372343
The present invention relates to an internal combustion engine, and, more particularly, to an injection system.
The invention relates to a method for operating an injection system of an internal combustion ending, an injection system for an internal combustion engine, and an internal combustion engine including such an injection system.
Injection systems and methods to operate same are known for example from DE 10 2014 213 648 B3 and DE 10 2015 209 377 B4.
An injection system of the type described herein includes at least one injector which is designed in particular to supply fuel into a combustion chamber of an internal combustion engine; and a high pressure accumulator which, on the one hand is connected fluidically with the at least one injector and on the other hand via a high pressure pump with a fuel reservoir. In this manner, propellant, or fuel—wherein these terms are used synonymously—can be moved by way of the high pressure pump out of the fuel reservoir into the high pressure accumulator. A low pressure side suction throttle is allocated to the high pressure pump. The suction throttle can in particular be actuated as a first pressure regulating element and is arranged in fluidic connection between the fuel reservoir and the high pressure accumulator, optionally upstream from the high pressure pump. The flow rate of the high pressure pump can thus be influenced via the suction throttle, as can at the same time the pressure in the high pressure accumulator. In addition, the injection system includes at least one high pressure side pressure control valve, via which the high pressure accumulator is fluidically connected with the fuel reservoir—in particular parallel to the flow path created by the high pressure pump. Fuel can thus be diverted from the high-pressure accumulator into the fuel reservoir via the pressure valve.
In the fluidic connection between the fuel reservoir and the high pressure accumulator a fuel filter can be provided which serves to filter water out of the fuel. However, at the same time air is thereby filtered from the fuel which can accumulate in the flow path to the high pressure accumulator, so that an air column forms. The air can again be pumped together with the fuel via the high pressure pump into the high pressure accumulator, where it can lead to undesirable pressure oscillations. It is thereby in particular possible that due to these undesirable oscillations, the high pressure in the high pressure accumulator exceeds a first pressure limit value.
Within the scope of a method for operating an injection system it is provided that the high pressure in the high pressure accumulator is regulated in normal operation by way of actuation of the low pressure side suction throttle, whereby the high pressure is regulated in a first operating mode of a safety operation by way of actuation of at least one high pressure side pressure control valve. Switching over from normal operation into the first operating mode of the safety operation occurs if the high pressure reaches or exceeds the first limit value. Since this represents a safety mechanism, it is typically provided that safety operation is maintained until the internal combustion engine including the injection system is shut off. If there is no actual error present and the first limit value was exceeded only momentarily due to undesirable pressure oscillations, continued regulating of the pressure via the first pressure control valve is proven disadvantageous, in particular since the fuel in this operating mode is excessively heated, causing the efficiency of the internal combustion engine to drop and emissions to increase.
What is needed in the art is to create a method for operating an injection system, an injection system for an internal combustion engine, and an internal combustion engine including such an injection system where the aforementioned disadvantages do not occur.
The present invention provides, in the scope of a method for operating an injection system, switching from the first operating mode of safety operation into normal operation occurs if, starting from above a pressure value, in particular the first pressure target value, the high pressure reaches or falls short of the target pressure value, wherein the target pressure value is lower than the first limit pressure value. In this manner a return of the injection system from safety operation into normal operation is made possible before the internal combustion engine is shut off, in other words, during running operation of the internal combustion engine. The fact that the high pressure again reaches or falls short of the pressure target value from above same, in particular when starting from first pressure limit value, indicates that no technical problem or defect of the injection system persists permanently, but instead that exceeding the first pressure limit is based on a temporary non-critical occurrence, for example an undesirable high pressure oscillation, so that safety operation can be safely exited in order to return to normal operation. Disadvantages resulting in particular from the operation of the injection system in safety operation—such as impermissible heating of the fuel—can thereby be avoided. In particular, in the case of high pressure oscillations which are due to air in the injection system, the latter changes only briefly into safety operation and—in particular if the air is removed from the high pressure accumulator due to deactivation of the pressure control valve—can subsequently return to normal operation wherein the high pressure is regulated by way of the suction throttle as the first pressure regulating element. Thus, unnecessary heating of the fuel and unnecessary load on the pressure valve are avoided. The lifespan of the internal combustion engine is extended, and the efficiency is improved. Moreover, emissions are reduced.
The pressure target value is in particular a high pressure value to which the high pressure in the high pressure accumulator is regulated according to requirements.
In the first operating mode of the safety operation, the at least one pressure control valve is actuated, in particular as second pressure regulating element in order to regulate the high pressure.
In normal operation a high pressure disturbance value is produced by way of the at least one pressure control valve in order to stabilize the high pressure control.
The high pressure accumulator can be designed in the embodiment of a common high pressure accumulator with which a plurality of injectors are fluidically connected. Such a high pressure accumulator is also referred to as a rail, whereas the injection system can be designed as a common rail injection system.
For comparison with the first pressure limit value a dynamic rail pressure can be used which results from a filtration of the high pressure, measured by way of a high pressure sensor, in particular with a comparable short time constant. Alternatively it is also possible to compare the measured high pressure directly with the first pressure limit value. In contrast, filtering has the advantage, that brief overshoots above the first pressure limit value do not directly result in switching into the first operating mode of the safety operation.
It is possible that the injection system includes exactly one high pressure side pressure control valve. Alternatively it is however also possible that the injection system includes a plurality of high pressure side pressure control valves and that, in an optional design it includes exactly two high pressure side pressure control valves. It is therein possible that, in the first operating mode of the safety operation a plurality of high pressure side pressure control valves, in particular both high pressure side pressure control valves, are actuated as pressure regulating elements in order to regulate the high pressure in the high pressure accumulator. According to an optional arrangement it is provided that the first operating mode of the safety operation is divided into a first operating mode range of the first operating mode in which precisely one first high pressure side pressure control valve is actuated as a pressure regulating element in order to regulate the high pressure, wherein via at least one other high pressure side pressure control valve a high pressure disturbance variable can be generated to stabilize regulation. In a second operating mode range of the first operating mode at least one second pressure control valve of the plurality of pressure control valves is actuated in addition to the first pressure control valve as a pressure regulating element, in order to regulate the high pressure in the high pressure accumulator. Pressure based switching can occur between the first operating mode range and the second operating mode range. It is optional to change from the first operating mode range to the second operating mode range if the high pressure reaches or exceeds an operating mode range change pressure limit value that is greater than the first pressure limit value. In this way the at least one second pressure control valve can be used for regulating, if control via the first pressure control valve is no longer sufficient in order to control the high pressure, in particular because sufficient fuel cannot be removed from the high pressure accumulator.
According to a further development of the present invention it is provided that an integral part for a high pressure controller that is designed for actuation of the suction throttle for regulating the high pressure during normal operation is initialized with an integral initial value, when switching over from first operating mode of safety operation into normal operation. The integral initial value is thereby determined as a leakage value of the injection system, depending on a current operating point of the internal combustion engine. Thus, it is advantageously ensured that the suction throttle is suitably controlled by the high pressure regulator immediately after switching over to normal operation, in particular in such a way that an operating point dependent leakage of the injection system can be compensated for by delivering an adjusted amount of fuel into the high pressure accumulator. Otherwise, due to the interruption of the high pressure control by the high pressure regulator in the first mode of safety operation, there would be a risk that the regulator would actuate the suction throttle in an inappropriate way immediately after switching to normal operation, so that either too little or too much fuel would be moved into the high-pressure accumulator.
An operating point of the internal combustion engine in this case is understood to be in particular a pair of values of a current speed of the internal combustion engine, as well as a value determining the current performance of the internal combustion engine, in particular a current torque, a current performance, or a current injection volume of fuel. It is thereby apparent that the current fuel leakage from the high pressure accumulator is dependent on the one hand from the speed and on the other hand from the current performance since these are the primary values which determine how much fuel flows out of the high pressure accumulator.
According to a further embodiment of the present invention, the integral initial value is determined by reading out a leakage value from a leakage characteristics diagram of the internal combustion engine depending the current operating point. This provides an especially simple method of determining the leakage value. According to one embodiment it is possible to use the leakage value as the leakage characteristic value. In particular it is possible to use the leakage value directly as the integral initial value for initialization of the high pressure regulator. No further calculation steps are necessary in this case, so that the method is especially simple. Alternatively, it is possible that the leakage value is offset by at least one control factor to obtain the leakage characteristic value. This makes it possible to additionally influence the control behavior of the high pressure regulator, in particular to influence a transient oscillation of the high pressure on the pressure target value. The control factor can be chosen to be less than 1, in particular 0.8, in order to cause the high pressure to undershoot the pressure setpoint when switching from the first mode of safety operation to normal operation and thus to ensure a robust transition to high pressure control by way of the suction throttle as a pressure regulating element.
According to a further development of the present invention it is provided that a constant characteristics diagram is used as the leakage characteristics diagram. The leakage characteristics diagram can thus be assigned data once in an especially simple manner. The leakage characteristics diagram can be provided with data received in bench tests. Alternatively or in addition the leakage characteristics diagram is updated during operation of the injection system. In this way it is advantageously possible to keep the leakage characteristics diagram always up to date and thus to adapt it in particular to changed operating conditions of the internal combustion engine, for example to aging effects or similar situations. During normal operation the leakage characteristics diagram i can be provided with current data as the leakage values of the integral part of the high pressure regulator. For this, values of the integral part can be used from stationary operating points of the internal combustion engine. The integral part of the high pressure regulator in stationary operation corresponds herein at least substantially to the current leakage of the injection system and is thus especially suitable for parameterizing of the leakage characteristics diagram. It also clearly simplifies use of the leakage characteristics diagram within the scope of the herein suggested method, if values of the integral part are stored in same and which can then be used again easily to initialize the integral part for the high pressure regulator, in other words can be used as integral initial values. It is thereby possible that the current integral parts are offset with at least one factor before being stored in the leakage characteristics diagram, in particular to compensate for possible effects which occur in subsequent application of factors on the leakage values after they have been read out from the leakage characteristics diagram. The leakage characteristics diagram can be provided data of filtered values of the current integral part. This advantageously allows for filtering out brief fluctuations; in this respect a low-pass filtering is applied.
According to a further development of the present invention it is to be verified whether the suction throttle is defective before switching from the first operating mode of the safety operation into normal operation. Switching into normal operation occurs then only when no suction throttle defect is detected, or—in other words—if it is determined that the suction throttle can function properly. This advantageously avoids that switching into normal operation possibly occurred, even though a defect is present and that there is no assurance that the high pressure during normal operation is in fact being controlled. Thus, switching into normal operation occurs advantageously only if it has been effectively ensured that the suction throttle for control of the high pressure during normal operation can be actuated. Thus, damage to the internal combustion engine can be avoided.
In the first operating mode of the safety operation the suction throttle can be continuously open.
According to a further development of the present invention it is provided that switching into a second operating mode of the safety operation occurs when the high pressure exceeds a second pressure limit value, wherein in the second operating mode of the safety operation the at least one pressure control valve and the suction throttle are continuously open. The second pressure limit value is in particular greater than the first pressure limit value and can be greater than the operating mode change pressure limit value. In the second operating mode of the safety operation it is ensured that, in the event of the pressure being too high in the high pressure accumulator, a sufficient amount of fuel can permanently be removed from the high pressure accumulator by way of permanently opening the at least one pressure control valve. In order to protect the injection system and the internal combustion engine from excessively high pressure, control of the high pressure is thus being dispensed with. At the same time, the suction throttle is permanently opened in order to ensure that also in the medium performance range and at low load points of the internal combustion engine—when the high pressure pump operates at low speed—sufficient fuel is delivered into the high pressure accumulator, so that the operation of the internal combustion engine is not interrupted by insufficient fuel delivery. Due to the permanent leakage out of the high pressure accumulator via the permanently opened pressure control valve it could otherwise cause a deficiency in fuel supply to the combustion chambers, so that the internal combustion engine would eventually stall. The second operating mode of safety operation represents in particular a safety function which is to ensure an as defect-free continued operation of the internal combustion engine as possible in an emergency operation mode, in particular in order to provide a so-called limp-home function. Notably, the at least one pressure control valve can herein fulfil the function of a pressure relief valve, so that a mechanical pressure relief valve can advantageously be dispensed with.
According to one embodiment it is possible that the pressure control valve and/or the suction throttle are actively permanently opened, in other words are controlled in a permanently open condition. According to an alternative embodiment it is possible, that the pressure control valve and/or the suction throttle are passively permanently opened. This is possible in particular, if at least one of these elements is designed to be open when not energized. In this case the corresponding element is optionally not actuated, so that it is permanently open, particularly completely open. It is also possible that the at least one pressure control valve is designed to be closed when not energized and not under pressure, however, to be open without current, but when under pressure. This means that the pressure control system in a condition where it is not energized and not under pressure is closed, but wherein it opens in the deenergized condition at a predetermined limit opening pressure value. In this case the pressure control valve can be permanently open in the second operating mode of safety operation without actuation since the high pressure in the high pressure accumulator maintains it in the open position. Moreover, in a start operation of the internal combustion engine the pressure control valve can—when sufficient high pressure is not yet built up in the high pressure accumulator—be closed when deenergized, which enables faster pressure build-up, without having to actively actuate the pressure control valve in a closed condition. Actuation of the pressure control valve under pressure causes closing of the pressure control valve.
One embodiment of the method is optional which is characterized in that a normal function is established in normal operation for the pressure control valve, wherein the pressure control valve is actuated as a function of a target flow. In normal operation, the normal function provides an operating mode for the pressure control valve wherein the latter creates the high pressure disturbance value in that it moves fuel out of the high pressure accumulator into the fuel reservoir.
Optionally, the normal function is set for the pressure control valve also in first operating mode of safety operation, so that the pressure control valve is actuated depending on a target volume flow. Normal operation on the one hand and first operating mode of the safety range on the other hand differ in this case in the manner in which the target volume flow for actuation of the pressure control valve is calculated.
In normal operation, the target volume flow can be calculated from a statistic and a dynamic target volume flow. The statistic target volume flow in turn can be calculated depending on a target injection volume and a speed of the internal combustion engine, via a target volume flow characteristics diagram. In a torque-oriented structure a target torque or a target performance can be used in place of the target-injection volume. A constant leakage is reproduced via the statistic target volume flow, in that the fuel is only removed in a low load range and only in a small amount. It is therein advantageous that no significant increase in the fuel temperature and no significant reduction of the efficiency of the internal combustion engine occur. By reproducing a constant leakage for the injection system via the pressure control valve, the stability of high pressure regulating is increased in the low load range. This can be recognized for example in that the high pressure in thrust mode remains approximately constant. The dynamic target volume flow is calculated via a dynamic correction as a function of a target high pressure and an actual high pressure, or respectively from the therefrom derived control deviation. If the control deviation is negative, for example in the event of load shedding of the internal combustion engine the statistic target volume flow is corrected via the dynamic target volume flow. Otherwise, in particular with a positive control deviation no change occurs in the statistic target volume flow. A pressure increase of the high pressure is countered via the dynamic target volume flow, with the advantage that the settling time of the system can again be improved.
The procedure is described in detail in the German patent document DE 10 2009 031 529 B3.
In the first operating mode of safety operation the target volume flow is calculated by a pressure control valve pressure regulator for controlling the high pressure. In this case the target volume flow represents a manipulated variable for regulating the high pressure.
Alternatively or in addition it is can be that for the pressure control valve in the second operating mode of safety operation a standstill function is set, wherein the pressure control valve is not actuated in the standstill function. This is the case in particular, when a pressure control valve is used which is open in a deactivated state or closed in a deactivated and pressure-free state. Due to the fact that the pressure control valve is then not actuated in the standstill function, in other words, that is not energized, a maximum opening of the latter results—possibly due to the high pressure applied at the input side—so that a maximum fuel volume flow is moved from the high pressure accumulator into the fuel reservoir via the pressure control valve. In this way, the pressure control valve can completely assume the functionality of an otherwise provided mechanical pressure relief valve, so that provision of the mechanical relief valve can be dispensed with. The deenergized open or pressure free and deenergized closed design of the pressure control valve has the advantage therein that it reliably opens completely even if it is no longer energized due to a defect.
A transition from normal function into standstill function can be carried out if the high pressure, in particular the dynamic rail pressure, exceeds the second pressure limit value, or when a defect in the high pressure sensor has been detected. If the high pressure sensor is defective the high pressure can no longer be regulated, and it is also no longer possible to recognize an impermissible high pressure in the high pressure accumulator. Therefore, the standstill function for the pressure control valve is established for safety reasons, so that the latter opens to a maximum, thus bringing the injection system into a safe condition that is consistent with a condition in which otherwise the mechanical pressure relief valve would open. An impermissible increase in the high pressure can thus no longer occur. The standstill function can be established based on the normal function even if a standstill of the internal combustion engine is detected. A standstill of the internal combustion engine is detected and the standstill function for the pressure control valve is set, especially if the speed of the internal combustion engine drops for a predetermined time below a predetermined value. This is the case especially if the internal combustion engine is shut off. A transition between the standstill function and the normal function occurs at a start of the internal combustion engine, such as when it is detected that the internal combustion engine is running, whereby at the same time the high pressure exceeds a start pressure value. Hence, a certain minimum pressure build up can occur initially in the high pressure accumulator before the pressure control valve is actuated in normal function to produce the high pressure disturbance value. That the internal combustion engine is running can be detected in that a predetermined speed limit is exceeded over a predetermined time period.
According to a further development of the invention it is provided that only from the first operating mode of the safety operation switching occurs back into normal operation. This means in particular that no switching occurs from the second operating mode of the safety operation back into normal operation. This accounts for the idea that the second pressure limit value can be selected such that it is exceeded by the high pressure only if in fact a serious defect is present in the injection system, so that subsequently a return into normal operation can no longer be justified. Accordingly, it is additionally optionally provided that no switching occurs from the second operating mode of safety operation into the first operating mode of safety operation. The second operating mode of the safety operation thus remains advantageously unchanged until the internal combustion engine is shut off, and optionally thereafter until it is signaled or confirmed in a suitable manner that the defect on the injection system has been removed, for example by operating a switch, an electronic input or by a similar action.
The present invention also provides an injection system for an internal combustion engine is, which includes at least one injector and a high pressure accumulator, which on the one hand is fluidically connected with the at least one injector and on the other hand is fluidically connected via a high pressure pump with a fuel reservoir, wherein a suction throttle is allocated to the high pressure pump as a first pressure regulating element. In addition, the injection system also includes at least one pressure control valve through which the high pressure accumulator is fluidically connected with the fuel reservoir. In addition, the injection system also includes a control unit that is operatively connected with the at least one injector, the suction throttle and the at least one pressure control valve—in each case for actuation of them. The control unit is arranged to carry out s method of the present invention or a method according to one of the previously described embodiments. Advantages result in particular in connection with the injection system, which have already been discussed in connection with the method.
The control unit can be designed as an engine control unit (ECU) of the internal combustion engine. Alternatively it is however also possible, that a separate control unit is provided specifically to carry out the method.
Upstream from the high pressure pump and the suction throttle, a low pressure pump can be arranged, to deliver fuel from the fuel reservoir to the suction throttle and the high pressure pump.
On the high pressure accumulator a pressure sensor can be located which is arranged to detect a high pressure in the high pressure accumulator and which is operatively connected with the control unit, so that the high pressure can be registered in the control unit. The control unit can be arranged to filter the measured high pressure, in particular for filtration with a first, longer time constant to calculate an actual high pressure that is to be used within the frame of the pressure control and can be arranged for filtration of the measured high pressure with a second, shorter time constant, in order to calculate the dynamic rail pressure.
According to one optional embodiment, the injection system includes precisely one pressure control valve.
According to another optional embodiment the injection system includes a plurality of pressure control valves, such as precisely two pressure control valves, wherein the high pressure accumulator is fluidically connected via each of the pressure control valves—optionally fluidically connected parallel to one another—with the fuel reservoir.
The at least one pressure control valve can be designed in a deenergized open manner. This design has the advantage that the pressure control valve in a case when it is not actuated or energized opens to a maximum, which ensures an especially safe and reliable operation, in particular when a mechanical pressure relief valve has been dispensed with. An impermissible rise in the high pressure in the high pressure accumulator can be avoided, even when energizing of the pressure control valve is not possible due to a technical defect.
The at least one pressure control valve can be designed in a pressure free and deenergized closed manner. It can be designed such that, with a pressure applied at the input side it is closed up to a predetermined limit opening pressure value, whereby it opens when the pressure at the input side in deenergized condition reaches or exceeds the limit opening pressure value. This results in particular in the advantages already discussed in the context of the method.
According to a further development of the present invention it is provided that the injection system does not include a mechanical pressure relief valve. As already discussed in the context of the method, its function can more advantageously be assumed by the at least one pressure control valve in the second operating mode of the safety operation.
The present invention also provides an internal combustion engine which includes the inventive injection system or an injection system according to one of the previously described design examples. The advantages that were already discussed in the context of the injection system and the method result in particular in connection with the internal combustion engine.
The internal combustion engine can have a plurality of—such as identical—combustion chambers. At least one injector of the injection system can be allocated to each combustion chamber in order to deliver fuel into the combustion chamber. The injection system thus has at least as many injectors as the internal combustion engine has combustion chambers; according to an optional embodiment in particular there are exactly as many, wherein it is however also possible that two or more injectors respectively are allocated to each combustion chamber. The combustion engine can in particular have four, six, eight, ten, twelve, fourteen, sixteen, eighteen or twenty combustion chambers. However, another, in particular smaller or greater number of combustion chambers is also possible. The internal combustion engine can be designed as a piston engine. The internal combustion engine can be designed as a diesel engine.
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
Referring now to the drawings, and more particularly to
Injection system 3 does not have a mechanical pressure relief valve which is conventionally provided, and which connects high pressure accumulator 13 with fuel reservoir 7. The mechanical pressure relief valve can be dispensed with since its function can be completely assumed by pressure control valve 19.
The operating mode of internal combustion engine 1 is determined by an electronic control unit 21, which can be designed as engine control unit of internal combustion engine 1, in particular as a so-called engine control unit (ECU). Electronic control unit 21 includes the usual components of a microcomputer system—for example a microprocessor, I/O modules, buffer, and memory modules (EEPROM, RAM). Operating data which is relevant for the operation of internal combustion engine 1 are stored in the memory modules in characteristics diagrams/characteristics curves. Based on these, electronic control unit 21 calculates output values from input values. The following input values are shown in an exemplary manner in
As illustrated in
Injection system 3 herein includes additionally a second, in particular electrically controllable pressure control valve 20, via which high pressure accumulator 13 is also fluidically connected with fuel reservoir 7. The two pressure control valves 19, 20 are thus connected in particular fluidically parallel to one another. Via second pressure control valve 20 a fuel volume flow can also be defined which can be moved out of high pressure accumulator 13 into fuel reservoir 7. This fuel volume flow is identified in
It is possible that injection system 3 has more than two pressure control valves 19, 20.
In contrast to
If second pressure control valve 20 is added, optionally only the following changes occur in the method which is described below for precisely one pressure control valve 19: second pressure control valve 20 is controlled in a normal operation and in a first operating mode range of a first operating mode of a safety operation to produce the high pressure disturbance variable. In a second operating mode range of the first operating mode of the safety operation, second pressure control valve 20 can be actuated for pressure regulating in addition to first pressure control valve 19, in particular by way of a pressure control valve-pressure regulator. In a second operating mode of the safety operation, second pressure control valve 20 is also optionally permanently open. On the basis of the following explanation in connection with first pressure control valve 19 as the only pressure control valve, this functionality is not difficult to implement. Furthermore, a corresponding use of a second pressure control valve is disclosed in German patent document DE 10 2015 209 377 B4.
For the sake of simplicity, the following will discuss the functionality of injection system 1 of the embodiment illustrated in
A second switching element 29 is provided, which is designed to switch the actuation of pressure control valve 19 from a normal function into a standstill function and back. Second switching element 29 is herein controlled depending on a second logic signal SIG2 or respectively depending on a value of a corresponding variable. Second switching element 29 can be designed as a virtual, in particular software-based, switching element which switches as a function of a value of a variable, designed in particular as a flag between normal function and standstill function. Alternatively it is however also possible that the second switching element is designed as a real switch, for example as a relay which switches depending on a signal value of an electric signal. In the herein concretely illustrated embodiment, second logic signal SIG2 corresponds to a time conditions variable which can assume values 1 for a first condition and 2 for a second condition. The normal function for the pressure control valve is herein set when second logic signal SIG2 assumes value 2, wherein the standstill function is set, when second logic signal SIG2 assumes value 1. Of course, a deviating definition of second logic signal SIG2 is possible, in particular in such a way that a corresponding variable can assume values 0 and 1.
First, actuation of pressure control valve 19 during normal operation, as well as in set normal function will be described. A first computation element 31 is provided which issues a calculated target-volume flow VS,ber as an output value, wherein the current speed n1, the target injection volume Qs, the target high pressure pS, the dynamic rail pressure pdyn and the actual high pressure pI are input into first computation element 31 as input values. The functionality of first computation element 31 is described in detail in German patent documents DE 10 2009 031 528 B3 and DE 10 2009 031 527 B3. It is shown in particular that in a low load range, for example when idling internal combustion engine 1, a positive value is calculated for a statistic target volume flow, whereas outside a low load range a statistic target volume flow of 0 is calculated. The statistic target volume flow can be corrected by adding up a dynamic target volume flow which for its part is calculated by a dynamic correction, depending on the target high pressure pS, the actual high pressure pI and the dynamic rail pressure pdyn. The calculated target volume flow VS,ber is the sum of the statistic target volume flow and the dynamic target volume flow. In this respect, the calculated target volume flow VS,ber is a resulting target volume flow.
In normal operation, when first logic signal SIG1 indicates value “false”, the calculated target volume flow VS,ber is delivered to a pressure control valve characteristics diagram 33 as target volume flow VS. As described in the German patent document DE 10 2009 031 528 B3, pressure control valve characteristics diagram 33 shows an inverse characteristic of pressure control valve 19. Output value of this characteristics diagram is a pressure control valve target current IS; input values are the target volume flow VS that is to be removed and the actual high pressure pI.
Alternatively it is also possible that target volume flow VS is not calculated by way of computation element 31 but is specified constantly in normal operation.
Pressure control valve target current IS is supplied to a current regulator 35 whose task it is to regulate the current for actuation of pressure control valve 19. Additional input values of current regulator 35 are for example a proportional coefficient kpI, DRV and an ohmic resistor RI, DRV of pressure control valve 19. Output value of current regulator 35 is a target voltage US for pressure control valve 19 which, in reference to an operating voltage UB is converted in a customary manner into a duty cycle for pulse-width modulated signal PWMDRV for control of pressure control valve 19 and is supplied to the latter during normal function, that is, when second logic signal SIG2 shows value 2. To regulate the current, the current is measured at pressure control valve 19 as a current value IDRV, filtered in a first current filter 37 and again supplied to current regulator 35 as filtered actual current I1.
As already indicated, duty cycle PWMDRV of the pulse-width modulated signal for controlling pressure control valve 19 is in its own right calculated in a conventional manner according to the following equation from target voltage US and operating voltage UB:
PWMDRV=(US/UB)×100.
In this manner, a high pressure disturbance value, namely the moved target volume flow VS, is produced in normal operation via pressure control valve 19.
If first logic signal SIG1 accepts value “true”, first switching element 27 switches from normal operation into the first operating mode of safety operation. The conditions under which this is the case are discussed in connection with
In this case, target volume flow VS is identically set with a limited output volume flow VR of a pressure control valve-pressure regulator 41. This corresponds with the upper switching position of first switching element 27. Pressure control valve-pressure regulator 41 has as an input value of a high pressure control deviation ep, which is calculated as a difference of target high pressure pS and actual high pressure pI. Additional input values of pressure control valve-pressure regulator 41 can be a maximum volume flow Vmax for pressure control valve 19, the target volume flow VS,ber calculated in first computation element 31, and/or a proportional coefficient kpDRV. Pressure control valve-pressure regulator 41 can be designed as PI(DT1) algorithm. In the process, an integral part (I-part) is initialized with the calculated target volume flow VS,ber at the time when first switching element 27 is switched from its lower to its upper switching position as shown in
If dynamic rail pressure pdyn reaches or exceeds first pressure limit value pG1, the output of first comparator element 47 jumps from “false” to “true”. Thus, the output of first OR-function link 49 also jumps from “false” to “true”. Therefore however, the output of first AND-function link 51 also jumps from “false” to “true” so that the value of first logic signal SIG1 becomes “true”. This value is again fed to first OR-function link 49 which however does not change that the output of the latter remains “true”. Even a drop of dynamic rail pressure pdyn to below first pressure limit value pG1 can no longer change the truth value of first logic signal SIG1. It remains “true” until variable MS and thus also its rejection, changes its truth value, namely when internal combustion engine no longer runs.
This shows the following: Normal operation is realized as long as dynamic rail pressure pdyn is below limit value pG1. In this case, the target volume flow VS is identical to calculated target volume flow VS,ber, since first logic signal SIG1 accepts value “false” and switching element 27 is therefore arranged in its lower position in
In the first operating mode of the safety operation, pressure control valve 19 takes over the regulation of the high pressure via second high pressure control circuit 39.
It also becomes clear, that no return to normal operation out of first operation mode of the safety operation is possible with this method as long as internal combustion engine 1 is running. Undesirable, air-induced oscillations of the high pressure can thus lead inconveniently to the first operating mode of the safety operation to be set, without being able to exit it again once the high pressure has dropped.
Returning to
If however, second logic signal SIG2 indicates a value of 2, the normal function for pressure control valve 19 is set—as already explained—the latter being controlled by way of target volume flow VS and the therefrom calculated signal PWMDRV.
In
Only when a running operation of internal combustion engine 1 is detected and at the same time the actual high pressure pI exceeds a starting value pst, the normal function for pressure control valve 19 is set, and the standstill function is reset—along arrow P1. The normal function is reset, and the standstill function is set along arrow P2, if dynamic rail pressure pdyn exceeds a second pressure limit value pG2, or if a defect of a high pressure sensor—illustrated herein by a logic variable HDSD—is detected, or if it is detected that internal combustion engine 1 is stationary. Pressure control valve 19 is not actuated in the standstill function, whereas during normal function—as explained in connection with
The following functionality results: At the start of internal combustion engine 1, there is initially no high pressure in high pressure accumulator 13, and pressure control valve 19 is arranged in its standstill function, so that it is pressure-fee and deenergized, in other words closed. When running up internal combustion engine 1, a high pressure can quickly form in high pressure accumulator 13 which, at some time exceeds starting value pst. This is optionally lower than the limit opening pressure value of pressure control valve 19, so that initially the normal function is set for the latter before it opens. This ensures advantageously that pressure control valve 19 is actuated when it first opens. Since it is closed in a pressure-free manner it remains closed even during actuation, until the actual high pressure pI also exceeds the limit opening pressure value, wherein it then opens and is actuated in the normal function, specifically either in normal function or in the first operating mode of the safety operation.
If however, one of the previously described cases occurs, the standstill function is again set for pressure control valve 19.
This is the case in particular, if dynamic rail pressure pdyn exceeds second pressure limit value pG2, wherein this can be selected to be greater than first pressure limit value pG1 and has a value in particular where, in a conventional design of injection system 3 a mechanical pressure relief valve would open. Since pressure control valve 19 is open in a deenergized state under pressure, it opens in this case completely in standstill function and thus fulfills the function of a pressure relief valve safely and reliably.
The transition from normal function into the standstill function also occurs if a defect is detected in high pressure sensor 23. If a defect is present here, the high pressure in high pressure accumulator 13 can no longer be controlled. In order to still be able to operate internal combustion engine 1 in a safe manner, the transition from normal function into the standstill function for pressure control valve 19 is induced, so that it opens and thereby prevents an impermissible rise in the high pressure.
The transition from normal function into the standstill function moreover occurs in a situation where a standstill of internal combustion engine 1 is detected. This corresponds to a reset of pressure control valve 19, so that during a renewed start of internal combustion engine 1 the herein described cycle can again start anew.
If the standstill function is set under pressure in high pressure accumulator 13 for pressure control valve 19, the latter is open to maximum and moves a maximum volume flow out of high pressure accumulator 13 into fuel reservoir 7. This corresponds to a safety function for internal combustion engine 1 and injection system 3, wherein this safety function can in particular replace the absence of a mechanical pressure relief valve.
It is important herein that pressure control valve 19 only has two states, specifically the standstill function and the normal function, wherein these two states are completely sufficient to represent the entire relevant functionality of pressure control valve 19, including the safety function for substitution of a mechanical pressure relief valve.
The output of second OR-link 63 feeds into a first input of a third OR-link 69, into the second input of which the value of third logic signal SIG3 is fed. Since this is originally initialized with value “false”, the output of third OR-link 69 indicates the value “false” as long as the output of second OR-link 63 assumes value “true”. If this is the case, the output of third OR-link 69 also jumps to value “true”. In this case, the value of second AND-link 61 also jumps to “true” if internal combustion engine 1 is running, that is, if the rejection of variable MS has value 1, so that also the value of third logic signal SIG3 jumps to “true”. With
As already explained, the input value of high pressure control circuit 25 is the target high pressure pS which, for calculating of control deviation ep is compared with the actual high pressure pI. This control deviation ep is an input value of a high pressure regulator 73 that can be designed as a PI(DT1) algorithm and is discussed in further detail in connection with
If third switching element 71 indicates the upper switching state shown in
Output value of this filter is the actual suction throttle current II,SD which in turn is supplied to suction throttle current regulator 83.
The control variable of first high pressure control circuit 25 is the high pressure in high pressure accumulator 13. Raw values of said high pressure p are measured by high pressure sensor 23 and filtered by a first high pressure filter element 91, which has the actual high pressure pI as the output value. Furthermore, the raw values of high pressure p are filtered by a second high pressure filter element 93, the output value of which is dynamic rail pressure pdyn. Both filters can be implemented by a PT1-algorithm, wherein a time constant of first high pressure filter element 91 is greater than a time constant of second high pressure filter element 93. In particular, second high pressure filter element 93 is a faster filter than first high pressure filter element 91. The time constant of second high pressure filter element 93 can be identical with a zero value, so that then dynamic rail pressure pdyn corresponds to the measured raw values of high pressure p, or respectively, is identical with them. With dynamic rail pressure pdyn, a hydrodynamic value exists for the high pressure, which is advantageous in particular, if a faster reaction is desired for certain occurring events.
Output values of first high pressure control circuit 25 are thus the filtered high pressure values pI, Pdyn, in addition to unfiltered high pressure p.
If third logical signal SIG3 assumes value “true”, third switching element 71 switches into its lower switching position, as shown in
It becomes clear that a return from the second operating mode of safety operation into normal operation—and incidentally also into the first operating mode of safety operation—is not provided, as long as internal combustion engine 1 is running. A return into normal operation is possible only after turning off and restarting internal combustion engine 1, and optionally furthermore, only after confirmation that a possibly present defect has been eliminated.
In
Switching into the first operating mode of the safety operation occurs in particular, if the high pressure exceeds second pressure limit value pG2, wherein in the second operating mode of the safety operation, pressure control valve 19 and suction throttle 9 are permanently open.
The program sequence illustrated in
If it is determined in step S1, that variable BM does not have value 2, the program sequence is continued in a second step S2 where it is verified whether dynamic rail pressure pdyn is greater than second pressure limit value pG2. If this is the case, the value of variable BM is set to 2 in a third step S3. Thus, switching into the second operating mode of safety operation occurs. The program sequence ends subsequently in twelfth step S12. The program sequence according to
If, in contrast it is determined in the second step S2, that dynamic rail pressure pdyn is not greater than second pressure limit value pG2, it is queried in a fourth step S4 whether variable BM has a value 1. If this is the case it is verified in a fifth step S5, whether suction throttle 9 is defective. If this is the case, the program sequence ends again in the twelfth step S12. If no defect on suction throttle 9 is detected in fifth step S5 the program sequence is continued in a sixth step S6 where it is determined if dynamic rail pressure pdyn is smaller than or equal to the target pressure value—or synonymously target high pressure—pS. If this is not the case, the program sequence ends in the twelfth step S12.
If, in contrast this is the case, the program sequence is continued in a seventh step S7, where a value 0 is assigned to variable BM, thus switching operation of injection system 3 back into normal operation. It is therefore, verified in particular prior to switching from first operation mode of the safety operation into normal operation, whether suction throttle 9 is defective, wherein switching into normal operation occurs only if suction throttle 9 is not defective.
In an eighth step S8 the integral part for high pressure controller 73 is initialized with an integral initial value Iinit, as explained in further detail in connection with
If it is determined in fourth step S4, that the value of variable BM is not equal to 1, the program sequence is continued in a ninth step S9 where it is verified whether dynamic rail pressure pdyn is greater than or equal to first pressure limit value pG1. If this is the case, the value of variable BM is set to 1 in an eleventh step S1l and thereby switched into the first operating mode of safety operation. If, in contrast the result of the query in the ninth step S9 is negative, the value of variable BM is set to 0 in tenth step S10. According to another embodiment, tenth step S10 can be omitted since, after querying in first step S1 and in fourth step S4 only value 0 remains as set for variable BM, thus not requiring a renewed setting of this value. Nevertheless, tenth step S10 can be provided in particular for safety and redundancy reasons. After eleventh step S11 or tenth step S10 respectively, the program sequence ends again in twelfth step S12.
The program sequence according to
Leakage characteristics diagram 95 can be assigned data and can then be used as a constant characteristics diagram. It is in particular also possible that leakage characteristics diagram 95 is provided with data of measured values for the integral part of high pressure regulator 73 from test bench trials on an optionally mint condition engine. Alternatively it is possible that leakage characteristics diagram 95 is updated during operation of injection system 3, wherein it can be assigned data of current values, optionally filtered values of the integral part of high pressure regulator 73 as leakage values, if necessary taking into account unit conversion factors.
Leakage characteristics diagram 95 can thus always be maintained in a current state and can in particular also consider ageing effects of injection system and/or internal combustion engine 1.
Thus, it also becomes clear from
If the value of variable BM is unequal to 0, integral part AI is set equal to integral initial value Iinit. Consequently this means that third operating mode switching element 103 switches over to integral initial value Iinit, when changing over from normal operation in particular into the first operating mode of the safety operation occurs. Since suction throttle 9 is not actuated in this case—compare
In
The calculation of differential part ADT1 is shown in the lower section of
Factor r3p is calculated according to the following equation in which tvp is a lead time and t1p is a delay time:
Factor r4p is calculated according to the following equation:
It is herein shown that amplification factors r2p and r3p depend on proportional coefficient kPSD. In addition, amplification factor r2p is dependent on reset time tnp; amplification factor r3p is dependent on lead time tvp and delay time t1p. Amplification factor r4p is also dependent on delay time t1p.
In this first operating mode of safety operation the high pressure is influenced through removal of fuel via pressure control valve 19 and can be regulated to target high pressure pS. By removal of fuel out of high pressure accumulator 13 a drop of high pressure occurs towards target high pressure pS until the latter is ultimately reached at a point in time t2 and is subsequently undershot. By reaching target high pressure pS from above, in other words from first pressure limit value pG1, the value of variable BM is again set to 0, thus switching over to normal operation, as can be seen from the lower diagram. Therefore, the high pressure is again regulated with by way of suction throttle 9. Because together with the fuel, air is also removed from high pressure accumulator 13, a stable transient oscillation of the high pressure to its target value occurs as a consequence, wherein in the illustrated case, at a third point in time t the high pressure has returned completely to target high pressure pS.
It has thus been advantageously achieved that internal combustion engine 1 in the event of high pressure oscillations which are caused by air in injection system 3 changes only briefly into the first operating mode of safety operation and subsequently, when the air has escaped from high pressure accumulator 13 due to actuation of pressure valve 19, returns to normal operation, wherein the high pressure is again regulated by suction throttle 9. This avoids unnecessary heating of the fuel and unnecessary load on pressure control valve 19, thus prolonging the long-term durability of internal combustion engine 1 and improving its efficiency.
While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2019 202 004.6 | Feb 2019 | DE | national |
This is a continuation of PCT application No. PCT/EP2020/053741, entitled “METHOD FOR OPERATING AN INJECTION SYSTEM OF AN INTERNAL COMBUSTION ENGINE, AN INJECTION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE, AND AN INTERNAL COMBUSTION ENGINE COMPRISING SUCH AN INJECTION SYSTEM”, filed Feb. 13, 2020, which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2020/053741 | Feb 2020 | US |
| Child | 17401984 | US |
