EP3298260B1 - Injection system for an internal combustion engine and internal combustion engine having such an injection system - Google Patents

Description

The invention relates to an injection system for an internal combustion engine and an internal combustion engine with such an injection system.

From the not previously published German patent application DE 10 2014 213 648.2 A method for operating an internal combustion engine with an injection system is known in which a pressure control valve is controlled in a first operating mode of a protective mode to regulate a high pressure in a high pressure accumulator, the pressure control valve being opened permanently in a second operating mode of the protective mode to prevent an impermissibly high pressure increase to prevent in the high pressure accumulator. For comparatively small internal combustion engines with a low nominal output and / or with a relatively small number of combustion chambers, this configuration can be implemented in a functional, simple and cost-effective manner. However, it is disadvantageous that the design can only be scaled to a limited extent or with considerable effort and high costs. Larger internal combustion engines with a higher nominal output and / or a larger number of combustion chambers require the possibility of being able to cut off larger amounts of fuel in the event of a fault than smaller internal combustion engines with a lower nominal output and / or a smaller number of combustion chambers. If, therefore, a corresponding control and safety function is to be established in a larger internal combustion engine, a pressure control valve is required, which is designed to control correspondingly higher amounts of fuel. Such pressure regulating valves are, however, custom-made products that can only be manufactured in small series, so that they are comparatively expensive. In addition, different pressure regulating valves would be required for internal combustion engines with different rated outputs and / or different numbers of combustion chambers, which would also increase the logistical costs. There are further examples of injection systems in which a plurality of pressure regulating valves are arranged. DE 10 2005 059830 discloses an injection system wherein a pressure regulating valve is installed between each injection valve and the high pressure accumulator. According to DE 10 2009 051390 each side of the internal combustion engine designed as a V-engine is designed with its own injection system, each of which includes a pressure control valve.

The invention is based on the object of creating an injection system for an internal combustion engine and an internal combustion engine with such an injection system, the disadvantages mentioned not occurring.

The object is achieved by creating the subjects of the independent claims. Advantageous refinements result from the subclaims.

The object is achieved in particular by creating an injection system for an internal combustion engine which has at least one injector and at least one high-pressure accumulator, which is in fluid connection on the one hand with the at least one injector and on the other hand via a high-pressure pump with a fuel reservoir, the high-pressure pump being a suction throttle as Pressure actuator is assigned. The injection system also has at least two pressure regulating valves, via which the high-pressure accumulator can be brought into fluid connection, preferably fluidly connected, with the fuel reservoir. Because the injection system has at least two pressure regulating valves, protective and / or regulating functions achieved via the pressure regulating valves can be represented by more than one pressure regulating valve, so that an increased volume flow can be controlled from the high-pressure accumulator without having to scale the individual pressure regulating valves used . Rather, scaling can take place via the number of pressure control valves used. The individual pressure regulating valves can thus be installed as inexpensive mass-produced parts, which saves logistical costs, and the individual pressure regulating valves themselves are inexpensive. There is then also no need to keep different pressure control valves for different internal combustion engines; rather, larger internal combustion engines can be equipped with a larger number of pressure control valves than smaller internal combustion engines.

The suction throttle is preferably arranged on a low-pressure side of the high-pressure pump, so it is a low-pressure-side suction throttle that is assigned to the high-pressure pump. The suction throttle is accordingly arranged in particular upstream of the high-pressure pump. A low-pressure pump, by means of which fuel can be conveyed from the fuel reservoir to the high-pressure pump, is preferably also arranged upstream of the high-pressure pump. In this case, the suction throttle is preferably arranged fluidically between the low-pressure pump and the high-pressure pump. It is possible for the suction throttle to be formed integrally with the high-pressure pump.

The at least two pressure regulating valves are preferably arranged fluidically parallel to one another, with both - in parallel connection - the high-pressure accumulator with the fuel reservoir connect. If two identical pressure regulating valves are used - in particular with an identical nominal flow rate - a double volume flow can be diverted from the high pressure accumulator into the fuel reservoir via the pressure regulating valves, compared to an embodiment in which only one pressure regulating valve is provided.

The injection system is preferably free of a mechanical pressure relief valve, so it does not have a mechanical pressure relief valve. A mechanical pressure relief valve can be dispensed with, since a corresponding protective function - as will be explained in the following - can be provided by the at least two pressure regulating valves. The costs otherwise associated with a mechanical pressure relief valve can thus be saved.

The injection system preferably has a high pressure sensor, via which a high pressure in the high pressure accumulator can be detected. The high pressure sensor is preferably arranged on the high pressure accumulator. However, it is also possible to measure the high pressure in the injection system at a different point, in which case the high pressure measured at another point can be used to infer the pressure in the high-pressure accumulator, or the high pressure measured at another point is used to control the injection system can be.

The high-pressure accumulator is preferably designed as a common high-pressure accumulator with which a plurality of injectors are in fluid connection. Such a high-pressure accumulator is also referred to as a rail, the injection system preferably being designed as a common rail injection system.

The injection system is characterized by a control device which is operatively connected to the suction throttle and the at least two pressure control valves and preferably to the at least one injector. The injection system, in particular the control unit, is set up to regulate a high pressure in the high pressure accumulator during normal operation by activating the suction throttle as a pressure actuator. In normal operation, at least one first pressure regulating valve of the at least two pressure regulating valves is preferably activated to generate a high-pressure disturbance variable.

The injection system, in particular the control unit, is also set up to control the high pressure in the high pressure accumulator in a first operating mode of a protective mode by controlling to regulate at least one first pressure control valve of the at least two pressure control valves as a pressure actuator. The injection system, in particular the control unit, is also set up to, in a second operating mode of the protective mode, at least one second pressure regulating valve of the at least two pressure regulating valves, the at least one second pressure regulating valve being different from the at least one first pressure regulating valve, in addition to the at least one first pressure regulating valve as To control the pressure actuator to regulate the high pressure in the high pressure accumulator.

In normal operation, a conventional control of the high pressure via the suction throttle is provided, with a high pressure disturbance variable preferably being generated at the same time by means of at least one first pressure control valve by diverting fuel from the high pressure accumulator into the fuel reservoir via the at least one first pressure control valve. Such a control strategy is, for example, from the German patent specification DE 10 2009 031 529 B3 known. A constant leakage is simulated by means of the high-pressure disturbance variable, which increases the stability of the high-pressure control in the low-load range.

In the first operating mode of the protective operation, however, the high pressure in the high pressure accumulator is regulated by means of at least one first pressure regulating valve. This makes it possible that even in the event of a failure of a regulation via the suction throttle - in particular if the suction throttle itself fails as a pressure actuator, for example due to a cable break, forgetting to plug in the suction throttle connector, jamming or twisting of the suction throttle, or another error or defect - A regulation of the high pressure is still possible, namely by means of the at least one first pressure control valve. On the one hand, the injection system can thus be protected from impermissibly high high pressure, and on the other hand, periodic fluctuations in the high pressure are avoided. Rather, this is regulated to a setpoint value by activating the at least one first pressure regulating valve, so that there is no deterioration in the emissions behavior of the internal combustion engine.

However, operating situations can arise in which the at least one first pressure regulating valve is no longer sufficient for functioning high pressure regulation, so that the high pressure continues to rise despite activation of the at least one first pressure regulating valve. It is then possible in the second operating mode of the protective operation to switch on the at least one second pressure regulating valve, so that now the at least one first pressure regulating valve and the at least one second pressure regulating valve are controlled jointly as pressure actuators for regulating the high pressure. In this way, in particular, larger discharge quantities are achieved, so that efficient and reliable pressure regulation is possible even when there is a greater need for discharge.

In normal operation, the high pressure is preferably regulated by controlling the suction throttle as a pressure actuator in a first high pressure control circuit. In the first operating mode of the protective mode, the high pressure is preferably regulated by activating the at least one first pressure regulating valve in a second high pressure regulating circuit, which is different from the first high pressure regulating circuit. This enables a separation of the two control loops and their specific coordination to the control of the suction throttle on the one hand and the at least one first pressure regulating valve on the other hand.

If the at least one first pressure regulating valve and the at least one second pressure regulating valve differ - in particular in their nominal flow rates - it is possible that the at least one second pressure regulating valve is controlled by a third high pressure control circuit in the second operating mode of protective operation. However, it is preferred to use matching first and second pressure regulating valves - at least with regard to their characteristic values, in particular to a nominal flow rate - in which case it is then preferably provided that in the second operating mode of the protective operation the at least one first pressure regulating valve and the at least one second pressure regulating valve from the same, second high-pressure control circuit can be controlled. In this case, however, separate flow regulators can preferably be provided for energizing the various pressure regulating valves.

In a preferred exemplary embodiment of the injection system, it is provided that in normal operation only one of the pressure regulating valves, in particular precisely one and only one first pressure regulating valve, is activated to generate the high-pressure disturbance variable. The at least one further pressure regulating valve is then preferably closed or is driven into a closed state. However, it is also possible that in normal operation more than one first pressure control valve is activated to generate the high pressure disturbance variable, it being possible in particular that a subset of the total pressure control valves present is activated to produce a high pressure disturbance variable. Finally, it is also possible for all existing pressure control valves to be activated to generate a high-pressure disturbance variable. This can be a choice of the amount of actually controlled pressure control valves for the generation of the high pressure disturbance variable are selected in particular as a function of pressure.

In the first operating mode of the protective operation, only one and precisely one first pressure regulating valve is preferably activated as a pressure actuator. Other pressure regulating valves are preferably closed or are controlled in a closed state. Alternatively, it is possible that a subset of the existing pressure regulating valves, in particular more than a first pressure regulating valve, are activated as first pressure regulating valves and pressure actuators. However, at least one pressure regulating valve preferably remains in the first operating mode, which as a second pressure regulating valve is not activated as a pressure actuator, but is closed or is activated in a closed state.

This at least one remaining second pressure control valve is switched on in the second operating mode of the protective mode, that is to say controlled as a further pressure actuator. It is possible that precisely one second pressure control valve is switched on in the second operating mode. Alternatively, it is possible that a subset, in particular more than a second pressure regulating valve, are switched on as pressure actuators. Preferably, all remaining pressure regulating valves which are not already activated as first pressure regulating valves and pressure actuators in the first operating mode are additionally activated as pressure actuators and second pressure regulating valves in the second operating mode. It is possible here for a number of connected, second pressure control valves to be selected as a function of the pressure. In particular, a number of second pressure control valves are switched on as a function of pressure.

An exemplary embodiment of the injection system is preferred which is characterized in that a normal function is set for the at least one first pressure regulating valve in normal operation, in which the at least one first pressure regulating valve is controlled as a function of a set volume flow. In normal operation, the normal function provides an operating mode for the first pressure regulating valve in which the latter generates a high-pressure disturbance variable by diverting fuel from the high-pressure accumulator into the fuel reservoir.

The normal function is preferably also set for the at least one first pressure regulating valve in the first operating mode and in the second operating mode of the protective operation, so that the pressure regulating valve is activated as a function of a setpoint volume flow. This is true in the second operating mode of the protective operation preferably also for the at least one second pressure control valve. The normal operation on the one hand and the first and second operating mode of the protective operation on the other hand preferably differ in this case in the way in which the target volume flow for controlling the pressure regulating valves is calculated:
In normal operation, the set volume flow is preferably calculated from a static and a dynamic set volume flow. The static setpoint volume flow is in turn preferably calculated as a function of a setpoint injection quantity and a speed of the internal combustion engine using a setpoint volume flow characteristic map. In the case of a torque-oriented structure, a target torque or a target load requirement can also be used instead of the target injection quantity. A constant leakage is simulated via the static target volume flow, in that the fuel is only diverted in a low-load range and in small quantities. The advantage here is that neither a significant increase in the fuel temperature nor a significant reduction in the efficiency of the internal combustion engine occur. By simulating a constant leakage for the injection system via at least one pressure control valve, the stability of the high pressure control circuit is increased in the low load range, which can be recognized, for example, from the fact that the high pressure remains approximately constant in overrun mode. The dynamic setpoint volume flow is calculated using a dynamic correction as a function of a setpoint high pressure and the actual high pressure - or a dynamic rail pressure defined in more detail below - or the control deviation derived therefrom. If the control deviation is negative, for example in the case of a load shedding of the internal combustion engine, the static target volume flow is corrected via the dynamic target volume flow. Otherwise, in particular in the case of a positive control deviation, there is no change in the static setpoint volume flow. An increase in pressure in the high pressure is counteracted via the dynamic setpoint volume flow, with the advantage that the system's settling time can be further improved.

This procedure is detailed in the German patent specifications DE 10 2009 031 529 B3 and particularly DE 10 2009 031 527 B3 described. In normal operation, the at least one first pressure regulating valve is controlled with the aid of the set volume flow in such a way that it increases the stability of the high pressure control circuit by simulating a constant leak and improves the regulation time of the injection system by means of the correction via the dynamic set volume flow.

In contrast, in the first and second operating modes of the protective mode, the set volume flow is preferably calculated in the second high-pressure control circuit, in particular by a pressure control valve pressure regulator. In this case, the set volume flow represents a manipulated variable of the second high pressure control circuit and is used to directly regulate the high pressure.

A control mimic is preferably provided for the pressure regulating valves, which has the setpoint volume flow as an input variable. It is then preferably by means of a - possibly virtual - switch when switching from normal operation to the first operating mode and / or to the second operating mode of the protective operation from the calculation of the target volume flow as the resulting volume flow from the static and dynamic target volume flow the calculation in the second high pressure control loop. The integral part of the pressure regulating valve pressure regulator of the second high-pressure regulating circuit is preferably initialized when switching with the resulting target volume flow calculated last before switching, so that a smooth, smooth switchover takes place.

An exemplary embodiment of the injection system is also preferred which is characterized in that the injection system, in particular the control unit, is set up to permanently open the at least one first pressure control valve and the at least one second pressure control valve in a third operating mode of the protective mode. This means in particular that a large, preferably a maximum, volume flow of fuel from the high-pressure accumulator is continuously diverted into the fuel reservoir via the pressure regulating valves. It means in particular that the pressure regulating valves are activated in the protective mode in the direction of maximum opening. Particularly preferably, the pressure regulating valves are opened to the maximum extent in the third operating mode of the protective mode. Depending on whether the pressure regulating valves are designed to be normally open or normally closed, a large, preferably maximum control current is preferably selected, or a small or no control current. The fuel volume flow actually passing through the pressure regulating valves depends on the high pressure in the high pressure accumulator, the term “maximum fuel volume flow” referring to the fact that the pressure regulating valves are open as far as possible. In this case, an impermissibly high high pressure in the high pressure accumulator is not only temporarily but permanently reduced quickly and reliably, so that the injection system is effectively and reliably protected. This functionality makes it possible to dispense with a mechanical pressure relief valve, so that installation space and costs can be saved.

The term "permanent" means in particular that the pressure control valves in the third operating mode are no longer controlled with a time-varying control signal, but rather continuously with a constant control signal, which results in a predetermined opening of the pressure control valves, preferably a maximum opening. It can be the case that the control signal is selected to be constant at zero when the pressure regulating valves are designed to be open when de-energized.

In the third operating mode of the protective mode, all pressure regulating valves are preferably opened permanently and, in particular, to the maximum extent. But it is also possible that only a subset of the existing pressure control valves are opened permanently and preferably to the maximum extent. A number of the pressure regulating valves that are permanently and preferably maximally open can be selected, in particular as a function of the pressure.

An exemplary embodiment of the injection system is preferred which is characterized in that the injection system, in particular the control unit, is set up to switch - in particular from normal operation - to the first operating mode of protective operation when the high pressure reaches or exceeds a first pressure limit value, or if a defect in the suction throttle is detected. The first pressure limit value is in particular selected such that reaching or exceeding it is an indication that pressure regulation of the high pressure via the suction throttle is no longer possible. This can in particular be an indication of a defect in the suction throttle. However, it is also possible that a defect in the suction throttle is recognized without the high pressure first reaching or exceeding the first pressure limit value. In this case, too, pressure control via the suction throttle is no longer possible. It therefore makes sense to switch to the first operating mode of the protective mode and then to regulate the high pressure by activating the at least one first pressure regulating valve as a pressure actuator.

Alternatively or in addition, it is preferably provided that, in particular from the first operating mode, a switch is made to the second operating mode when the high pressure reaches or exceeds a second pressure limit value. Reaching or exceeding the second pressure limit value is an indication that an activation of the at least one first Pressure regulating valve for pressure regulation is no longer sufficient, so that the second operating mode is advantageously selected, in which the at least one second pressure regulating valve is additionally activated as a pressure actuator for regulating the high pressure.

Alternatively or additionally, it is preferably provided that - in particular from the second operating mode - a switch is made to the third operating mode when the high pressure reaches or exceeds a third pressure limit value, or when a defect in a high pressure sensor is detected. Reaching or exceeding the third pressure limit value serves as an indication that an impermissibly high pressure is being reached in the high-pressure accumulator, which endangers the operational safety of the injection system and in particular of the high-pressure accumulator, with particular fear of damage to the injection system, especially the high-pressure accumulator. If a defect in the high pressure sensor is detected, it can in principle no longer be guaranteed that the high pressure is reliably regulated and in particular remains in a permissible range. It is therefore sensible in both cases to select the third operating mode and preferably to permanently control a maximum volume flow of fuel from the high-pressure accumulator into the fuel reservoir via the pressure regulating valves. This ensures safe and reliable protection for the injection system in the event of an impermissibly high pressure increase and / or failure of the high pressure sensor. For this reason in particular, a mechanical pressure relief valve can be dispensed with.

The third pressure limit value is preferably selected to be greater than the second pressure limit value. The third pressure limit value is preferably selected to be greater than the first pressure limit value. The second pressure limit value is preferably selected to be greater than the first pressure limit value. The second pressure limit value is particularly preferably selected to be greater than the first pressure limit value, the third pressure limit value being selected to be greater than the second pressure limit value.

By setting the first operating mode when the high pressure reaches or exceeds the first pressure limit value, it is ensured that this operating mode is always activated - and preferably only then - when there is a malfunction in the first high pressure control circuit. For this purpose, the first pressure limit value is preferably selected such that it is higher than a highest pressure value for the high pressure that is typically realized in error-free operation of the injection system.

In one exemplary embodiment of the injection system, it is possible, for example, for the high pressure to be regulated to a value of 2200 bar during operation. A pressure reserve is provided for any pressure fluctuations up to 2300 bar. In this case, the first pressure limit value is preferably selected to be 2400 bar in order to avoid the first operating mode being activated without a malfunction of the first high-pressure control circuit or the suction throttle being present. However, if such a malfunction occurs - for example a cable break in the intake throttle connector, jamming of the intake throttle, twisting of the same, or forgetting to plug in the intake throttle connector - the high pressure can rise above the intended reserve level, especially in a higher speed range of the internal combustion engine, especially when the intake throttle is designed to be normally open. In this case, the high pressure reaches or exceeds the first pressure limit value, and the at least one first pressure regulating valve takes over the control of the high pressure. In spite of the failure of the first high-pressure control circuit, stable control of the high pressure is still possible, so that there is no deterioration in the emission behavior of the internal combustion engine, while at the same time the engine is reliably protected from an impermissible increase in the high pressure.

The third pressure limit value can be, for example, 2500 bar. This can in particular correspond to a pressure at which a mechanical pressure relief valve would be designed for opening. Its function is now preferably completely simulated by the pressure regulating valves.

As already stated, the second pressure limit value is preferably selected between the first pressure limit value and the third pressure limit value.

Overall, the following picture emerges: If the first high-pressure control circuit and / or the suction throttle fails and the high pressure in the high-pressure accumulator rises as a result, this is initially in a range between the first pressure limit value and the second pressure limit value by the at least a first pressure regulating valve regulated in the first operating mode. If this is no longer sufficient for regulation and the second pressure limit value is reached or exceeded, the at least one second pressure regulating valve is switched on for regulating pressure in the second operating mode. By regulating the pressure by means of the pressure regulating valves, stable operation of the internal combustion engine with good emission values can also be made possible. This is especially the case in a low up Medium speed range in which, due to the low to medium speed of the high pressure pump itself, a fully open suction throttle is used to deliver a quantity of fuel that can still be controlled from the fuel reservoir into the high pressure accumulator by means of regulation via the pressure regulating valves. However, if the high pressure in the high pressure accumulator rises to an impermissibly high level above the third pressure limit value, for example in a high speed range of the internal combustion engine, pressure control via the pressure control valves is no longer possible. Rather, these are then opened as completely as possible in the third operating mode, so that a large, preferably maximum, fuel volume flow can be diverted into the fuel reservoir. This corresponds to the functionality of otherwise provided mechanical pressure relief valves.

It is possible that the first operating mode, the second operating mode and the third operating mode are run through sequentially one after the other, with the first operating mode being implemented, for example, when a defect occurs in the first high-pressure control circuit at an initially low speed of the internal combustion engine, with a further increase the speed then the second operating mode and finally the third operating mode is realized. However, it is also possible that the high pressure in the high pressure accumulator suddenly rises above the second or the third pressure limit value, in which case the first operating mode and / or the second operating mode is / are virtually skipped, the second or the third operating mode being rather immediately is realized.

For comparison with the pressure limit values, a dynamic rail pressure is preferably used, which results from filtering the high pressure measured by means of a high pressure sensor, in particular with a comparatively short time constant. Alternatively, it is also possible to compare the measured high pressure directly with the pressure limit values. On the other hand, filtering has the advantage that overshoots above the pressure limit values - albeit rarely occurring - do not lead directly to a switching of the operating modes.

In one embodiment, a manipulated variable for the pressure regulating valves is limited in the first and / or in the second operating mode as a function of the high pressure. This has the advantage that a pressure regulating valve is not opened further than it is at all most sensible for a given high pressure

Downshift is necessary. In this way, overriding the pressure control valve can be avoided. To

Limitation of the manipulated variable is preferably based on a characteristic curve through which a maximum volume flow of the pressure regulating valve is stored as a function of the high pressure.

When switching from normal operation to the first operating mode of protective operation, in one embodiment an integrating component of a pressure regulator of the second high-pressure control circuit, which is provided for activating the pressure regulating valve, is initialized with an activation value which, in normal operation, is immediately prior to switching to the Protection mode was used to control the pressure control valve. In this way, a smooth, trouble-free and continuous transition in the pressure control between control by the first high pressure control circuit in normal operation and control by the second high pressure control circuit in protection mode is ensured. In particular, this prevents jumps from occurring in the high pressure, which would lead to unstable operation of the internal combustion engine.

Alternatively or additionally, it is preferred that a standstill function is set for the pressure regulating valves in the third operating mode of the protective mode, the pressure regulating valves not being activated in the standstill function. This is particularly the case when a pressure control valve is used which is open when de-energized. The fact that the pressure regulating valves are then not activated in the standstill function, i.e. not energized, results in a maximum opening of the same, so that a maximum fuel volume flow is diverted from the high-pressure accumulator into the fuel reservoir via the pressure regulating valves. In this way, the pressure regulating valves can completely take over the functionality of an otherwise provided mechanical pressure relief valve, so that the mechanical pressure relief valve can be dispensed with. The currentless open design of the pressure regulating valves has the advantage that they reliably open completely even when they are no longer supplied with current due to a defect.

A transition from the normal function to the standstill function is preferably carried out when the high pressure, in particular the dynamic rail pressure, reaches or exceeds the third pressure limit value, or when a defect in the high pressure sensor is detected. If the high pressure sensor is defective, the high pressure can no longer be regulated, and it is also no longer possible to detect an impermissibly high pressure in the high pressure accumulator. For safety reasons, the standstill function for the Pressure control valves are set so that they open to the maximum and thus bring the injection system into a safe state, which corresponds to a state in which the mechanical pressure relief valve would be open in the prior art. An inadmissible increase in high pressure can then no longer occur. The standstill function is preferably also set on the basis of the normal function when a standstill of the internal combustion engine is determined. In particular, if the speed of the internal combustion engine falls below a predetermined value for a predetermined time, a standstill of the internal combustion engine is recognized and the standstill function for the pressure regulating valves is set. This is particularly the case when the internal combustion engine is switched off. A transition between the standstill function and the normal function occurs when the internal combustion engine is started, preferably when it is determined that the internal combustion engine is running, with the high pressure simultaneously exceeding a starting pressure value. A certain minimum pressure build-up therefore preferably takes place in the high-pressure accumulator before a pressure regulating valve is activated in the normal function for generating the high-pressure disturbance variable. The fact that the internal combustion engine is running can preferably be recognized by the fact that a predetermined limit speed is exceeded for a predetermined time.

An exemplary embodiment of the injection system is also preferred which is characterized in that the injection system, in particular the control unit, is set up to move the suction throttle to a permanently open position in at least one of the three operating modes of the protective operation, in particular in the third operating mode of the protective operation head for. Because of the pressure control valves that are opened as much as possible in the third operating mode, it is possible that the pressure in the high-pressure accumulator drops sharply. While it is then still possible in a high speed range of the internal combustion engine to nevertheless provide sufficient high pressure to operate the internal combustion engine, if the suction throttle is not sufficiently open in a medium or low speed range, the high pressure in the high pressure accumulator can drop so sharply that no longer enough fuel can be injected through the injectors. The internal combustion engine is stalled in such a case. In order to avoid this, the suction throttle is permanently opened in the third operating mode in a kind of emergency operation, in particular controlled to a permanently open operation, in order to ensure that enough fuel can still be pumped into the high-pressure accumulator in the medium and low speed range of the internal combustion engine. in order to be able to maintain operation of the internal combustion engine. A suction throttle is preferably used, which is de-energized is open. In the third operating mode, the suction throttle is therefore preferably controlled with a current that is small compared to its maximum closing current, for example 0.5 A, or not at all, that is to say not energized. In the case in which it is not energized, it is open to the maximum.

As an alternative or in addition, the suction throttle is opened permanently in the first and / or in the second operating mode of the protective mode, preferably controlled for a permanently open mode, in particular not supplied with current or only with a small current. This prevents double, simultaneous regulation of the high pressure on the one hand via the pressure control valves and on the other hand via the suction throttle, especially in a case in which the first or second operating mode is activated by an overshoot of the high pressure with an intact suction throttle.

The control device is preferably set up to filter the measured high pressure, in particular for filtering with a first, longer time constant in order to calculate an actual high pressure to be used within the scope of the pressure control, and for filtering the measured high pressure with a second, shorter time constant, by one to calculate dynamic rail pressure, which is compared in particular with the pressure limit values.

An exemplary embodiment of the injection system is preferred which is characterized in that at least one of the at least two pressure regulating valves is designed to be normally open. Particularly preferably, all pressure regulating valves are designed to be normally open. This embodiment has the advantage that a normally open pressure regulating valve opens to the maximum extent in the event that it is not activated or energized, which enables particularly safe and reliable operation, especially when a mechanical pressure relief valve is dispensed with. An impermissible increase in the high pressure in the high pressure accumulator can then also be avoided if it is not possible to energize the pressure regulating valve due to a technical error.

Alternatively or additionally, it is possible for at least one pressure control valve of the at least two pressure control valves to be designed to be closed without pressure and without current. In particular, it is possible for all pressure regulating valves to be designed to be closed without pressure and without current. Such a pressure regulating valve is designed such that it is closed when the pressure prevailing in the high-pressure accumulator, that is to say the rail pressure, is less than a predetermined one Opening pressure value. The high pressure is applied to an inlet of the pressure control valve when this is properly mounted on the injection system. The pressure control valve opens when the pressure applied on the inlet side reaches or exceeds the opening pressure value in the de-energized state. If the pressure regulating valve is therefore depressurized and de-energized on the input side, it is biased into a closed state, for example by means of a mechanical biasing element. If the pressure on the inlet side reaches or exceeds the opening pressure value, and if the pressure control valve is not energized, it is opened - preferably against the force of the pretensioning element - so that it is open without current at the opening pressure value and higher inlet pressures. If the pressure control valve is energized in this state, it closes depending on the current with which it is controlled. It is closed to the maximum when it is controlled with a predetermined, maximum current value. If it is no longer supplied with current or if the current supply fails, it opens again completely, whereby it closes when the pressure on the inlet side falls below the opening pressure value.

The opening pressure value is preferably selected such that it is lower than a high pressure which is minimally reached in normal control operation of the injection system. In particular, in the specific example mentioned above in connection with the operating modes of protective operation, it is possible for the opening pressure value to be 850 bar. In this case, the starting pressure value at which there is a transition from the standstill function of the pressure regulating valve to the normal function when the internal combustion engine is started is also preferably selected such that it is approximately of the order of magnitude of the opening pressure value, whereby it is preferably selected to be somewhat lower in order to ensure that the pressure control valve is activated in any case as soon as it opens by reaching or exceeding the opening pressure value. Tolerances of the pressure regulating valve can also be taken into account here. For example, it can be that the starting pressure value is selected to be 600 bar.

The following functionality results: If the internal combustion engine is at a standstill and the high pressure in the high pressure accumulator has consequently fallen below the opening pressure value, the pressure regulating valve is arranged in its standstill function and is therefore de-energized and unpressurized. It is therefore closed. If the internal combustion engine now starts, the closed pressure control valve initially enables a rapid and reliable pressure build-up in the high-pressure accumulator, since no fuel is diverted into the fuel reservoir via the pressure control valve. Typically, the high pressure now reaches the high pressure accumulator first the starting pressure value, whereby a transition from the standstill function to the normal function takes place, the pressure control valve being activated as a result. In this case, however, it is typically still closed because the opening pressure value has not yet been reached. The high pressure in the high pressure accumulator continues to rise and finally also exceeds the opening pressure value, the pressure regulating valve then opening and - in the absence of activation - would also be open without current. By energizing and appropriately activating the pressure regulating valve, it is now possible to influence its degree of opening and, in particular, to close it further by applying a greater amount of current or to open it further by applying less current. If there is a transition to the standstill function again in the third operating mode of the protective operation, the pressure control valve is no longer activated, in which case, at the moment of the transition, a high pressure prevails that is greater than the third pressure limit value, i.e. in particular much greater than the opening pressure value. In this state, the pressure regulating valve is therefore open without current and, due to the lack of activation, controls a maximum volume flow of fuel from the high-pressure accumulator into the fuel reservoir, so that it safely and reliably fulfills its protective function. This makes it possible to do without a mechanical pressure relief valve. The pressure control valve only closes again when the high pressure drops below the opening pressure value. In this way, reliable operation of the injection system is achieved, and there is no longer any risk of damage or impermissibly high pressure.

An exemplary embodiment of the injection system is also preferred, which is characterized in that the injection system, in particular the control unit, is set up to generate a first control signal and a second control signal, and to alternate between the at least one first pressure control valve and the at least one second pressure control valve to be controlled with the first control signal and the second control signal. In particular, it is provided that at a first point in time the at least one first pressure control valve is controlled with the first control signal, the at least one second pressure control valve being controlled simultaneously with the second control signal, with the at least one first pressure control valve being controlled with the second control signal at a second time is controlled, at the same time the at least one second pressure control valve is controlled with the first control signal. This embodiment has the advantage that the various pressure regulating valves can be used to full capacity. This applies in particular to a case in which only one of the pressure regulating valves is activated, so that one of the activation signals is active and the other is permanently inactive. Without alternating activation, only one of the pressure regulating valves would now be permanently activated and thus loaded, while the other pressure regulating valve would not be used. By alternating activation, it can also be ensured in such a case that a uniform utilization of the pressure regulating valves is ensured, so that their maintenance and replacement times can be homogenized and, overall, longer maintenance intervals can be realized. Even in a case in which both the first control signal and the second control signal are active, any differences that may still exist in the control signals are evened out and distributed homogeneously to the various pressure regulating valves through alternating control. It is of course possible for the control device to be set up to generate more than two control signals, in particular for more than two pressure regulating valves. It is possible here for the different control signals to be assigned to the different pressure regulating valves alternately, in particular cyclically, in different ways.

A regulator for energizing the pressure regulating valve is preferably provided for each pressure regulating valve, the regulators also being assigned alternately to the various pressure regulating valves. In particular, the currents detected at the pressure regulating valves are also switched over so that they can be detected by the correct, currently responsible controllers and used for regulation.

The control signals are preferably only switched over to the various pressure regulating valves when the internal combustion engine is at a standstill. Otherwise, there may be short-term malfunctions in the operation of the internal combustion engine.

The control signals are preferably switched over after a predetermined operating time of the injection system has elapsed, in particular after a predetermined number of operating hours has elapsed. For example, a switchover can take place after 5000 operating hours. If, after the predetermined number of operating hours has elapsed, it is determined that the internal combustion engine is not at a standstill, the next standstill of the internal combustion engine is preferably waited for before a switchover takes place.

An exemplary embodiment of the injection system is also preferred which is characterized in that the injection system is free of a mechanical pressure relief valve. In particular, the injection valve does not have a mechanical pressure relief valve. To a mechanical overpressure valve can be dispensed with because a protective function of the injection system against impermissibly high pressures can be represented safely and efficiently via the pressure control valves. In this way, costs and installation space associated with a mechanical pressure relief valve can be saved.

The object is also achieved by creating an internal combustion engine which has an injection system according to one of the exemplary embodiments described above. In connection with the internal combustion engine, the advantages that have already been explained in connection with the injection system are realized.

The control device is preferably designed as an engine control unit (ECU) of the internal combustion engine. Alternatively, however, it is also possible for a separate control unit to be used specifically for controlling the injection system.

The injection system preferably has a plurality of injectors, with exactly one and only one high-pressure accumulator, or alternatively two high-pressure accumulators - for V-engines - or also three high-pressure accumulators - for W-engines - or possibly another configuration of high-pressure accumulators for one another configuration of combustion chambers of the internal combustion engine, wherein the various injectors are fluidly connected to the high-pressure accumulator (s). In particular, a plurality of injectors are each connected to a common high-pressure accumulator. The common high-pressure accumulator (s) is / are in this case designed as a so-called common bar, in particular as a rail, the injection system preferably being designed as a common rail injection system.

The internal combustion engine is preferably designed as a reciprocating piston engine. It is possible that the internal combustion engine is set up to drive a passenger car, a truck or a utility vehicle. In a preferred embodiment, the internal combustion engine is used to drive particularly heavy land or water vehicles, for example mining vehicles, trains, the internal combustion engine being used in a locomotive or a railcar, or ships. It is also possible to use the internal combustion engine to drive a vehicle used for defense, for example a tank. An embodiment of the internal combustion engine is preferably also stationary, for example for stationary energy supply in emergency power mode, Continuous load operation or peak load operation used, the internal combustion engine in this case preferably driving a generator. Stationary use of the internal combustion engine to drive auxiliary units, for example fire pumps on drilling rigs, is also possible. It is also possible to use the internal combustion engine in the field of conveying fossil raw materials and, in particular, fuels, for example oil and / or gas. It is also possible to use the internal combustion engine in the industrial sector or in the construction sector, for example in a construction or construction machine, for example in a crane or an excavator. The internal combustion engine is preferably designed as a diesel engine, as a gasoline engine, as a gas engine for operation with natural gas, biogas, special gas or another suitable gas. In particular, if the internal combustion engine is designed as a gas engine, it is suitable for use in a block-type thermal power station for stationary energy generation.

An exemplary embodiment of the internal combustion engine is preferred in which it is designed as a large engine. The internal combustion engine preferably has eight combustion chambers or more, in particular ten combustion chambers, twelve combustion chambers, fourteen combustion chambers, sixteen combustion chambers, eighteen combustion chambers or twenty combustion chambers. An internal combustion engine which is designed as a reciprocating piston engine with twenty cylinders is particularly preferred.

The design of the injection system proposed here makes it possible in particular to install the same pressure regulating valves for a multitude of different internal combustion engines with a multitude of different configurations and numbers of cylinders, a number of built-in pressure regulating valves only being scaled with the size of the internal combustion engine.

Figur 1

eine schematische Darstellung eines Ausführungsbeispiels einer Brennkraftmaschine mit einem Einspritzsystem;

Figur 2

eine erste schematische Detaildarstellung einer Ansteuerung des Einspritzsystems;

Figur 3

eine zweite schematische Detaildarstellung einer Ansteuerung des Einspritzsystems;

Figur 4

eine dritte schematische Detaildarstellung einer Ansteuerung des Einspritzsystems;

Figur 5

eine vierte schematische Detaildarstellung einer Ansteuerung des Einspritzsystems;

Figur 6

eine fünfte schematische Detaildarstellung einer Ansteuerung des Einspritzsystems;

Figur 7

eine sechste schematische Detaildarstellung einer Ansteuerung des Einspritzsystems;

Figur 8

eine siebte schematische Detaildarstellung einer Ansteuerung des Einspritzsystems, und

Figur 9

eine achte schematische Detaildarstellung einer Ansteuerung des Einspritzsystems.

The invention is explained in more detail below with reference to the drawing. Show:

Figure 1

a schematic representation of an embodiment of an internal combustion engine with an injection system;

Figure 2

a first schematic detailed representation of a control of the injection system;

Figure 3

a second schematic detailed representation of a control of the injection system;

Figure 4

a third schematic detailed representation of a control of the injection system;

Figure 5

a fourth schematic detailed representation of a control of the injection system;

Figure 6

a fifth schematic detailed representation of a control of the injection system;

Figure 7

a sixth schematic detailed representation of a control of the injection system;

Figure 8

a seventh schematic detailed representation of a control of the injection system, and

Figure 9

an eighth schematic detailed representation of a control of the injection system.

Fig. 1 shows a schematic representation of an exemplary embodiment of an internal combustion engine 1 which has an injection system 3. This is preferably designed as a common rail injection system. It has a low-pressure pump 5 for delivering fuel from a fuel reservoir 7, an adjustable, low-pressure-side suction throttle 9 for influencing a volume flow of fuel flowing through it, a high-pressure pump 11 for delivering the fuel under pressure increase into a high-pressure accumulator 13, and the high-pressure accumulator 13 for storing the fuel , and a plurality of injectors 15 for injecting the fuel into combustion chambers 16 of the internal combustion engine 1. It is optional It is possible that the injection system 3 is also designed with individual stores, in which case, for example, an individual store 17 is integrated into the injector 15 as an additional buffer volume. A first, in particular electrically controllable pressure control valve 19 is provided, via which the high-pressure accumulator 13 is fluidly connected to the fuel reservoir 7. The position of the first pressure regulating valve 19 defines a fuel volume flow which is diverted from the high-pressure accumulator 13 into the fuel reservoir 7. This fuel volume flow is shown in Figure 1 as well as in the following text with VDRV1 and represents a high pressure disturbance of the injection system 3.

The injection system 3 has a second, in particular electrically controllable, pressure regulating valve 20, via which the high-pressure accumulator 13 is also fluidly connected to the fuel reservoir 7. The two pressure regulating valves 19, 20 are accordingly arranged in particular fluidically parallel to one another. A fuel volume flow can also be defined via the second pressure regulating valve 20, which fuel volume flow can be diverted from the high-pressure accumulator 13 into the fuel reservoir 7. This fuel volume flow is shown in Figure 1 as well as in the following text referred to as VDRV2.

The injection system 3 does not have a mechanical pressure relief valve, which is conventionally provided according to the prior art and then connects the high-pressure accumulator 13 to the fuel reservoir 7. According to the invention, the mechanical pressure relief valve can be dispensed with, since its function is completely taken over by the pressure regulating valves 19, 20.

It is possible for the injection system 3 to have more than two pressure regulating valves 19, 20. For the sake of simpler representation, however, the mode of operation of the injection system 1 according to the invention is explained in the following on the basis of the exemplary embodiment shown here, which has exactly two pressure regulating valves 19, 20.

The mode of operation of the internal combustion engine 1 is determined by an electronic control unit 21, which is preferably designed as an engine control unit of the internal combustion engine 1, namely as a so-called engine control unit (ECU). The electronic control unit 21 contains the usual components of a microcomputer system, for example a microprocessor, I / O modules, buffers and memory modules (EEPROM, RAM). The operating data relevant to the operation of the internal combustion engine 1 are stored in the memory modules applied in maps / characteristic curves. The electronic control unit 21 uses this to calculate output variables from input variables. In Figure 1 The following input variables are shown as examples: a measured, still unfiltered high pressure p, which prevails in the high pressure accumulator 13 and is measured by means of a high pressure sensor 23, a current engine speed n _I , a signal FP for the output specification by an operator of the internal combustion engine 1, and an input variable E. Further sensor signals are preferably combined under input variable E, for example a charge air pressure of an exhaust gas turbocharger. In an injection system 3 with individual accumulators 17, an individual accumulator pressure p _{E is} preferably an additional input variable of control unit 21.

In Figure 1 The output variables of the electronic control unit 21 include, for example, a signal PWMSD for controlling the suction throttle 9 as a pressure actuator, a signal ve for controlling the injectors 15 - which in particular specifies a start and / or an end of injection or also an injection duration - and a first signal PWMDRV1 for control a first pressure regulating valve of the two pressure regulating valves 19, 20, and a second signal PWMDRV2 for controlling a second pressure regulating valve of the two pressure regulating valves 19, 20 is shown. As will be explained below, the in Figure 1 The illustrated assignment of the first signal PWMDRV1 to the first pressure regulating valve 19 and the second signal PWMDRV2 to the second pressure regulating valve 20 are not fixed for all times, rather the pressure regulating valves 19, 20 are preferably controlled alternately with the signals PWMDRV1, PWMDRV2. The signals PWMDRV1, PWMDRV2 are preferably pulse-width modulated signals via which the position of a pressure regulating valve 19, 20 and thus the volume flow VDRV1, VDRV2 assigned to the pressure regulating valve 19, 20 can be defined. In Figure 1 an output variable A is also shown, which is representative of further actuating signals for controlling and / or regulating the internal combustion engine 1, for example for an actuating signal for activating a second exhaust gas turbocharger during register charging.

Fig. 2 shows a first schematic representation of an embodiment of a method which is considered an example and does not belong to the invention. In the following, the method of operation of the method under control of only one of the pressure regulating valves 19, 20 is first explained, with the functionality then being explained in a next step, which is added by adding a further pressure regulating valve 20, 19.

A first high-pressure control circuit 25 is provided, via which, in normal operation of the injection system 3, the high pressure in the high-pressure accumulator 13 is controlled by means of the suction throttle 9 as a pressure actuator. The first high pressure control circuit 25 is in connection with Figure 9 explained in more detail where it is shown in detail. The first high-pressure control circuit 25 has a setpoint high pressure p _s for the injection system 3 as an input variable. This is preferably read out from a characteristic map as a function of the speed n _{I of} the internal combustion engine 1, a load or torque request on the internal combustion engine 1 and / or as a function of further variables, in particular for a correction. Further input variables of the first high-pressure control circuit 25 are, in particular, the speed n _{I of} the internal combustion engine 1 as well as a setpoint injection quantity Q _s - in particular also read from a characteristic map. As an output variable, the first high pressure control circuit 25 has, in particular, the high pressure p measured by the high pressure sensor 23, which is preferably subjected to a first filtering with a larger time constant in order to determine _{an actual high pressure p I} is subjected to a smaller time constant in order to calculate _{a dynamic rail pressure p dyn.} These two pressure values p _I , p _dyn represent further output variables of the first high-pressure control circuit 25.

In Figure 2 In particular, the control of a first pressure control valve of the two pressure control valves 19, 20, for example the control of the first pressure control valve 19, is shown. A first switching element 27 is preferably provided with which it is possible to switch between normal operation and a first operating mode of protective operation as a function of a first logic signal SIG1. The switching element 27 is preferably implemented entirely on an electronic or software level. The functionality described below is preferably switched over as a function of a value of a variable corresponding to the first logic signal SIG1, which is in particular designed as a so-called flag and can assume the values “true” or “false”. Alternatively, however, it is of course also possible for the switching element 27 to be designed as a real switch, for example as a relay. This switch can then be switched, for example, as a function of a level of an electrical signal. In the embodiment specifically illustrated here, normal operation is set when the first logic signal SIG1 has the value “false”. In contrast, the operating mode of protective operation is set when the first logical signal SIG1 has the value "true".

A second switching element 29 is provided, which is set up to switch the first control signal PWMDRV1 between two modes, wherein in particular a pressure control valve 19, 20 controlled by the first control signal PWMDRV1 can be switched from a normal function to a standstill function and back. The second switching element 29 is controlled as a function of a second logic signal Z or the value of a corresponding variable. The second switching element 29 can be configured as a virtual, in particular software-based, switching element which switches between the normal function and the standstill function as a function of the value of a variable configured in particular as a flag. Alternatively, however, it is also possible for the second switching element to be designed as a real switch, for example as a relay, which switches as a function of a signal value of an electrical signal. In the specific embodiment shown here, the second logic signal Z corresponds to a state variable which can assume the values 1 for a first state and 2 for a second state. The normal function for the activated pressure regulating valve 19, 20 is set here when the second logic signal Z assumes the value 2, the standstill function being set when the second logic signal Z assumes the value 1. It goes without saying that a different definition of the second logic signal Z is possible, in particular such that a corresponding variable can assume the values 0 and 1.

First of all, the control of a first pressure regulating valve 19, 20 in normal operation and when the normal function is set will now be described. A first calculation element 31 is provided, which outputs a calculated target volume flow V _S.ber as an output variable, with the current speed n _I , the target injection _{quantity Q s} , the target high pressure p _s , the dynamic rail pressure p _dyn and the actual high pressure p _{I are included} . The functioning of the calculation element 31 is detailed in the German patents DE 10 2009 031 528 B3 and DE 10 2009 031 527 B3 described. It is shown in particular that in a low load range, for example when the internal combustion engine 1 is idling, a positive value for a static target volume flow is calculated, while in a normal operating range a static target volume flow of 0 is calculated. The static target volume flow is preferably corrected by adding up a dynamic target volume flow, which in turn is calculated via a dynamic correction as a function of the target high pressure p _s , the actual high pressure p _I and the dynamic rail pressure p _dyn . The calculated target volume flow V _{S, ber} is finally the sum of the static target volume flow and the dynamic target volume flow. It The calculated target volume flow V _S is a resultant target volume flow.

In normal operation, when the first logical signal SIG1 has the value “false”, the calculated setpoint volume flow V _{S, ber is transferred} to a pressure control valve map 33 as the setpoint volume flow V _S. The pressure control valve map 33 forms here - as in the German patent DE 10 2009 031 528 B3 described - an inverse characteristic of a pressure control valve 19, 20 used. In a preferred embodiment, the injection system has identical pressure regulating valves 19, 20, so that the same pressure regulating valve characteristics map 33 can be used for each of the pressure regulating valves 19, 20. As an alternative, however, it is also possible to use different pressure regulating valves 19, 20, in which case a pressure regulating valve characteristic map assigned separately to these is then used for each pressure regulating valve 19, 20. The output variable of the pressure control valve characteristic map 33 is a pressure control valve setpoint current I _s , the input variables are the setpoint volume flow rate V _{S to be} controlled and the actual high pressure p _I.

In an alternative embodiment of the method, which does not belong to the invention, it is also possible for the set volume flow V _S not to be calculated by means of the first calculation element 31, but rather to be specified as constant in normal operation.

The pressure regulating valve setpoint current is fed to a first current regulator 35, which has the task of regulating the current for controlling the pressure regulating valve 19, 20. Further input variables of the first current regulator 35 are, for example, a proportional _{coefficient kp I, DRV} and an ohmic resistance R _I , _{DRV of} the pressure regulating valve 19, 20. The output variable of the first current regulator 35 is a first setpoint voltage U _S for the pressure regulating valve 19, 20, which through With reference to an operating voltage U _{B, it is} converted into a duty cycle for the first, pulse-width modulated signal PWMDRV1 for controlling the pressure regulating valve 19, 20 in the usual manner and is supplied to this in the normal function, i.e. when the second logic signal Z has the value 2. To regulate the current, the current at the pressure control valve 19, 20 controlled by the first control signal PWMDRV1 is _{measured as the first current variable I R} , filtered in a first current filter 37 and the first filtered actual current I ₁ fed back to the current regulator 35.

As already indicated, the switch-on duration is in the form of the first, pulse-width-modulated control signal PWMDRV1 for controlling a pressure control valve 19, 20 in itself Taken as usual, calculated from the first setpoint voltage U _S and the operating voltage U _{B according to the following equation:} $$\mathrm{PWMDRV}1=\left({\mathrm{U}}_{\mathrm{S.}}/{\mathrm{U}}_{\mathrm{B.}}\right)\times 100.$$

In this way, in normal operation, a high pressure disturbance variable, namely the controlled set volume flow V _S , is generated via one of the pressure regulating valves 19, 20.

If the first logic signal SIG1 assumes the value “true”, the first switching element 27 switches from normal operation to protective operation. The conditions under which this is the case is discussed in connection with Figure 3 explained. With regard to the control of the pressure regulating valve 19, 20, there is no difference in the first and second operating mode of the protective mode, as here, too, the pressure regulating valve 19, 20 is _{controlled with the target volume flow V S} , at least as long as the normal function is set by the switching element 29 . In this respect, in Figure 2 to the right of the switching element 27, no change to the explanations given above. The set volume flow V _S is calculated differently in the first and second operating mode of the protective operation than in the normal operation, namely via a second high-pressure control circuit 39.

In this case, the set volume flow rate V _S is set identically to a limited output _{volume flow rate V R} from a pressure regulating valve pressure regulator 41 - with the exception of a factor f _DRV which will be explained below. This corresponds to the upper switching position of the first switching element 27. The pressure regulating valve pressure regulator 41 has as an input variable a high pressure control deviation e _p , which is calculated as the difference between the target high pressure p _s and the dynamic rail pressure p _dyn. Further input variables of the pressure regulating valve pressure regulator 41 are preferably a maximum volume flow V _max for the pressure regulating valve 19, 20, the set volume flow V _{S, ber} calculated in the first calculation element 31 and / or a proportional coefficient kp _DRV . The pressure regulating valve pressure regulator 41 is preferably implemented as a PI (DT ₁ ) algorithm, which is shown in Figure 7 is explained in more detail. In this case - as will be explained below - an integrating component (I component) at the point in time at which the first switching element 27 moves from its in Figure 2 is switched to its upper switching position, initialized _{with the calculated target volume flow V S, ber.} The I component of the pressure regulating valve pressure regulator 41 is limited at the top to the maximum volume flow V _max for the pressure regulating valve 19, 20. The maximum volume flow V _{max is} preferably - except for the factor f _DRV - an output variable of a two-dimensional characteristic curve 43, which has the maximum volume flow through the pressure regulating valve 19, 20 as a function of the high pressure, the characteristic curve 43 receiving _{the dynamic rail pressure p dyn as an input variable.} As already indicated, in this exemplary embodiment it is assumed that the pressure regulating valves 19, 20 are of identical design, so that an identical characteristic curve 43 can be used for both pressure regulating valves. However, it is also possible to use different pressure regulating valves 19, 20, in which case a separate characteristic curve 43 is used for each of the pressure regulating valves 19, 20. The direct output variable of the pressure control valve pressure regulator 41 is an unlimited volume flow V _U , which is limited in a limiting element 45 to the maximum volume flow V _max. The limiting element 45 finally outputs the limited setpoint volume flow V _R as an output variable. This is then - except for the below-mentioned factor f _DRV - the pressure regulating valve 19, 20 controlled as the target volumetric flow V _S by the desired volume flow V _S in the previously described manner is supplied to the pressure control valve characteristic diagram 33rd

In this way, a pressure regulating valve 19, 20 as a pressure actuator for regulating the high pressure in the high pressure accumulator 13 via the second high pressure control circuit 39 is activated in the first operating mode of the protective operation.

In the following, the mode of operation will now be explained, which is given by adding a second pressure regulating valve 20, 19.

As in connection with Figure 3 will be explained in more detail, the first logic signal SIG1 assumes the logic value "true" when the dynamic rail pressure p _dyn - for example as a result of a cable break in the suction throttle connector - reaches a first pressure limit value p _G1 . As a result, the first switching element 27 changes to the in FIG Figure 2 Upper switching position shown, so that the high pressure is now regulated with the aid of the second high pressure control circuit 39 and one of the pressure control valves 19, 20. As also in connection with Figure 3 will be explained below, a third logic signal SIG2 has the value "false" if the dynamic rail pressure p _dyn has not yet reached a second pressure limit value p _G2. A second pressure control valve setpoint current I _{S, 2} for a second pressure control valve 20, 19 is then read out from a second pressure control valve characteristic map 49, which has the actual high pressure p _I and the value zero for the setpoint volume flow as input variables. If the two pressure regulating valves 19, 20 are of identical design, the second is Pressure regulating valve characteristic map 49 is the same as the first pressure regulating valve characteristic map 33 and differs only with regard to the incoming setpoint volume flow set to zero. If different pressure regulating valves 19, 20 are used, the two pressure regulating valve characteristics maps 33, 49 can differ. Because the second pressure regulating valve characteristic map 49 has the value zero as the incoming set volume flow, the pressure regulating valve 19, 20 activated in this way is activated in such a way that it is completely closed, whereby it does not divert any fuel into the fuel reservoir 7. The high pressure is therefore regulated only with the aid of a pressure regulating valve 19, 20 until the dynamic rail pressure p _{dyn reaches} the second pressure limit value p _G2.

A fourth switching element 44 is provided which determines the value of the previously mentioned factor f _DRV . This fourth switching element 44 is also controlled as a function of the third logic signal SIG2, and takes its in Figure 2 shown lower switch position when the third logical signal SIG2 has the value "false" (false). In this case, the output variable of the characteristic curve 43 is multiplied by the factor 1. Correspondingly, the limited set volume flow V _R resulting from the limitation element 45 is divided by the factor 1.

If the dynamic rail pressure p _dyn rises and reaches or exceeds the second pressure limit value p _G2 , then the third logic signal SIG2 assumes the value “true”. This leads to the third switching element 47 and the fourth switching element 44 in their in Figure 2 Change upper switch position. If one first looks at the third switching element 47, it becomes apparent that as a result, the second pressure control valve setpoint current I _{S, 2} in the exemplary embodiment specifically illustrated here now becomes identical to the first pressure control valve setpoint current I _S , so that both pressure control valves 19, 20 as a result be applied with the same nominal current. This in turn presupposes that the two pressure regulating valves 19, 20 are of identical design, which corresponds to a preferred embodiment. It is of course possible, however, to apply separate setpoint currents, in particular those resulting from separate characteristic maps, to them if the pressure regulating valves 19, 20 differ.

Two identical pressure regulating valves 19, 20 can cut off twice the amount of fuel compared to a single pressure regulating valve 19, 20. For this reason, if one considers the fourth switching element 44, the factor f _DRV now assumes the value 2, as a result of which the maximum volume flow V _max resulting from the characteristic curve 43 is doubled. The limited one Volume flow V _R , which results from the limiting element 45, on the other hand, is divided by the factor f _DRV and thus now by two, since ultimately the resulting pressure control valve setpoint volume flow V _S corresponds in each case to a pressure control valve 19, 20 and in each case to the control of a pressure control valve 19, 20 serves. This procedure is also coordinated with the preferred embodiment, in which the two pressure control valves 19, 20 used are of identical design. If they are designed differently, on the other hand, different characteristic curves 43, different second high-pressure control circuits 39, and different pressure control valve characteristics maps 33, 49 are preferably used to control the different pressure control valves. If, on the other hand, more than two identically designed pressure control valves are provided, these can be completely analogous to the illustration in Figure 2 are controlled by a multiplication of the control elements shown there for each pressure control valve 19, 20, _{the number of pressure control valves used can be used as the factor f DRV} in the upper switching position of the fourth switching element 44.

The second pressure control valve setpoint current I _{S, 2} is the input variable of a second current controller 51, which is otherwise preferably designed exactly like the first current controller 35. The control mimics for generating the second control signal PWMDRV2 also correspond to those for generating the first control signal PWMDRV1, with a fifth switching element 53 being provided here for switching between the normal function and the standstill function, and with a second current _{filter 55 being provided for filtering a second, measured current I R, 2} , which has a second actual current I _{I as the output , 2} , which is fed to the second current regulator 51. The controller parameters of the second current controller 51 are preferably set in the same way as the corresponding parameters of the first current controller 35.

The second switching element 29 and the fifth switching element 53 also show that the switch-on duration of the control signals PWMDRV1, PWMDRV2 in the standstill function is identical to 0%. In the normal function, on the other hand, the respective control signal PWMDRV1, PWMDRV2 is generated by the control mimic assigned to it, as has already been explained above.

The two control signals PWMDRV1, PWMDRV2 are fed to a switchover logic 57, which is described below in connection with the Figures 5 and 6 will be explained in more detail, the switchover logic 57 ensuring that the pressure control valves 19, 20 alternate with the Control signals PWMDRV1, PWMDRV2 are controlled. The measured current variables I _R , I _{R, 2 are} also taken from the switching logic 57, which ensures that they are always measured on the respective pressure control valves 19, 20 correctly assigned to the control signals PWMDRV1, PWMDRV2 in order to ensure a defined regulation of each of the To ensure pressure control valves 19, 20 via the flow regulator 35, 51.

Fig. 3 shows the conditions under which the first logic signal SIG1 and the third logic signal SIG2 each assume the values "true" and "false".

In the following, this is initially based on Figure 3a ) explained for the first logical signal SIG1. As long as the dynamic rail pressure p _dyn does not reach or exceed a first pressure limit value p _G1 , the output of a first comparator element 59 has the value “false”. When the internal combustion engine 1 is started, the value of the first logic signal SIG1 is initialized with "false". As a result, the result of a first ORing element 61 is also “false” as long as the output of the first comparator element 59 has the value “false”. The output of the first ORing element 61 is fed to an input of a first ORing element 63, the other input of which is fed a negative represented by a dash to a variable MS, the variable MS having the value "true" when the internal combustion engine 1 is at a standstill, and where it has the value "false" when the internal combustion engine 1 is running. When the internal combustion engine 1 is in operation, the value of the negative value of the variable MS is "true". Overall, it now appears that the output of the rounding element 63 and thus the value of the first logic signal SIG1 is “false” as long as the dynamic rail pressure p _dyn does not reach or exceed the first pressure limit value p _G1. If the dynamic rail pressure p _dyn reaches or exceeds the first pressure limit value p _GI , the output of the first comparator element 59 jumps from “false” to “true”. The output of the first ORing element 61 thus also jumps from “false” to “true”. If the internal combustion engine 1 is running, the output of the first rounding element 63 also jumps from “false” to “true”, so that the value of the first logic signal SIG1 becomes “true”. This value is fed back to the first ORing element 61, but this does not change the fact that its output remains "true". Even a drop in the dynamic rail pressure p _dyn below the first pressure limit value p _G1 can no longer change the truth value of the first logic signal SIG1. Rather, this remains "true" until the variable MS and thus also its negative change its truth value, namely when the internal combustion engine 1 is no longer running. This shows the following: Normal operation is implemented as long as dynamic Rail pressure p _dyn falls below the first pressure limit value p _G1 . In this case, the set volume flow rate V _{S is} identical to the calculated set volume flow rate V _{S, ber} . If the dynamic rail pressure p _dyn reaches or exceeds the first pressure limit value p _G1 , the first logic signal SIG1 assumes the value “true” and the first switching element 27 assumes its upper switching position. In this case, the set volume flow V _{S is} identical to the limited volume flow V _{R of} the second high-pressure control circuit 39, except for the factor F _DRV . This means that in normal operation a high pressure disturbance variable is generated by one of the pressure regulating valves 19, 20, wherein in the first operating mode of the protective operation the high pressure always when the dynamic rail pressure p _{dyn reaches} the first pressure limit value p _GI , then from the pressure regulating valve Pressure regulator 41 is regulated, and this until a standstill of the internal combustion engine 1 is recognized. In the first operating mode of the protective operation, at least one of the pressure control valves 19, 20 takes over the control of the high pressure via the second high pressure control circuit 39.

In Figure 3b ) the logic for switching the third logic signal SIG2 is shown. It can be seen that this corresponds completely to the logic for switching the first logic signal SIG1, the second pressure limit value p _{G2 being used} as the input variable _{only instead of the first pressure limit value p G1.} The corresponding logical switching components are here compared to Figure 3a ) are provided with a crossed reference symbol. Due to the completely identical mode of operation, the explanations apply to Figure 3a ) referenced. Analogously to the first logic signal SIG1, the following is shown for the second logic signal SIG2: This is "initialized" with the value "false" at the beginning of operation of the internal combustion engine 1, with its truth value changing to "true" when the dynamic rail pressure p _dyn reaches or exceeds the second pressure limit value p _G2 , whereupon the truth value of the third logic signal SIG2 remains “true” until a standstill of the internal combustion engine 1 is recognized.

Regarding Figure 2 shows that the second operating mode of the protective operation is activated when the third logical signal SIG2 changes its truth value from "false" to "true", in which case the previously inactive pressure control valve 20, 19 is switched on so that the high pressure of both Pressure control valves 19, 20 is regulated.

Coming back to Figure 2 The third operating mode of protective operation is also explained below: A switch is made to this when the second logic signal Z assumes the value 1. In this case, the second switching element 29 and also the fifth switching element 53 are in their in Figure 2 brought the upper switching position shown, thereby the standstill function for both pressure control valves 19, 20 is set. In this standstill function, the pressure regulating valves 19, 20 are no longer activated, that is to say the activation signals PWMDRV1, PWMDRV2 are set to zero. Since pressure regulating valves 19, 20 which are open when currentlessly open are preferably used at least under the inlet pressure, these now permanently control a maximum fuel volume flow from the high-pressure accumulator 13 into the fuel reservoir 7.

If, on the other hand, the second logic signal Z has the value 2, the normal function for the pressure regulating valves 19, 20 is set - as already explained - and these are set with their respective setpoint currents I _S , I _{S, 2} and the control signals PWMDRV1, PWMDRV2 calculated from them controlled.

Fig. 4 shows schematically a state transition diagram for the pressure control valves 19, 20 from the normal function to the standstill function and back. In this case, the pressure regulating valves 19, 20 are preferably designed so that they are designed to be closed without pressure and without current, whereby they are further preferably designed so that they are closed at a pressure applied on the input side up to an opening pressure value, whereby they open when the pressure applied on the input side Pressure in the de-energized state reaches or exceeds the opening pressure value. They are then open when de-energized under input pressure and can be activated in the direction of the closed state by energizing them. The opening pressure value can be, for example, 850 bar.

In Figure 4 the standstill function is symbolized by a first circle K1, the normal function being symbolized by a second circle K2 at the top right. A first arrow P1 represents a transition between the standstill function and the normal function, with a second arrow P2 representing a transition between the normal function and the standstill function. A third arrow P3 indicates an initialization of the internal combustion engine 1 after the start, the pressure regulating valves 19, 20 initially being initialized in the standstill function. Only when a running operation of the internal combustion engine 1 is recognized at the same time, and the actual high pressure p _I exceeds a predetermined starting value p _St , is the normal function set for the pressure regulating valves 19, 20 - along the arrow P1 - and the standstill function reset, in particular by the second logic signal Z changes its value from 1 to 2. The normal function is reset and the standstill function is set along the arrow P2 when the dynamic rail pressure p _dyn exceeds the third pressure limit value p _{exceeds G3} , or when a defect in a high-pressure sensor - represented here by a logic variable HDSD - is detected, or when it is detected that the internal combustion engine 1 is at a standstill. In the standstill function, in which the second logic signal Z again assumes the value 1, the pressure regulating valves 19, 20 are not activated, although they are in the normal function - as already in connection with Figure 2 explained - are controlled by means of the set currents I _S , I _{S, 2 assigned to them in each case.}

The following functionality now results: When the internal combustion engine 1 starts, there is initially no high pressure in the high pressure accumulator 13, and the pressure regulating valves 19, 20 are arranged in their standstill function so that they are depressurized and energized, i.e. closed. When the internal combustion engine 1 is running up, a high pressure can therefore quickly develop in the high-pressure accumulator, which at some point exceeds _{the starting value p St.} This is preferably lower than the opening pressure value of the pressure regulating valves 19, 20, so that the normal function is initially set for them before they open. This advantageously ensures that the pressure regulating valves 19, 20 are always activated when they open for the first time. Since they are closed without pressure, they remain closed under control until the actual high pressure p _I also exceeds the opening pressure value, in which case they open and are controlled in normal operation, namely either in normal operation or in the first operating mode of protective operation.

However, if one of the cases described above occurs, the standstill function for the pressure regulating valves 19, 20 is set again.

This is particularly the case when the dynamic rail pressure p _dyn exceeds the third pressure limit value p _G3 , which is preferably selected to be greater than the first pressure limit value p _G1 and the second pressure limit value p _G2 , and in particular has a value at which in a conventional embodiment of the injection system would open a mechanical pressure relief valve. Since the pressure regulating valves 19, 20 are normally open under pressure, they open completely in the standstill function in this case and thus safely and reliably fulfill the function of a pressure relief valve.

The transition from the normal function to the standstill function also takes place if a defect is detected in the high pressure sensor 23. If there is a defect here, the high pressure in the high pressure accumulator 13 can no longer be regulated. To the internal combustion engine 1 anyway To still be able to operate safely, the transition from the normal function to the standstill function is brought about for the pressure regulating valves 19, 20 so that they open and thus prevent an impermissible increase in the high pressure.

Furthermore, the transition from the normal function to the standstill function takes place in a case in which a standstill of the internal combustion engine 1 is determined. This corresponds to resetting the pressure regulating valves 19, 20, so that when the internal combustion engine 1 is restarted, the cycle described here can start again.

If the standstill function is set for the pressure regulating valves 19, 20 under pressure in the high-pressure accumulator 13, they are opened to the maximum and control a maximum volume flow from the high-pressure accumulator 13 into the fuel reservoir 7. This corresponds to a protective function for the internal combustion engine 1 and the injection system 3, this protective function in particular being able to replace the lack of a mechanical pressure relief valve.

It is important here that the pressure regulating valves 19, 20 have only two functional states, namely the standstill function and the normal function, these two functional states being fully sufficient to represent the entire relevant functionality of the pressure regulating valves 19, 20 including the protective function for replacing a mechanical pressure relief valve.

It can be seen that even after the second pressure limit value p _G2 has been exceeded, stable control of the high pressure by means of the pressure regulating valves is still possible, since the delivery capacity of the high pressure pump 11 is speed-dependent. This means that engine operating values, especially emission values, can still be complied with in this case. It is only in the higher speed range that the third pressure limit value p _G3 must be expected to be exceeded. In this case, the pressure regulating valves 19, 20 open completely, and a deterioration in the engine operating values, especially the emissions, must be expected. At least stable operation of the engine is then also guaranteed.

Even if the high pressure sensor 23 fails, stable engine operation is still possible, even if the engine operating values, in particular the emission values, may deteriorate in this case.

Because the second pressure limit value p _{G2 is} greater than the first pressure limit value p _G1 , it is avoided that both pressure regulating valves 19, 20 are simultaneously transferred from a closed to an open state. In this way, large pressure gradients, which could have a damaging effect on the injection system 3, are avoided.

As already indicated, the pressure regulating valves 19, 20 are alternately acted upon by the control signals PWMDRV1 and PWMDRV2. This means that one of the two pressure regulating valves 19, 20 is acted upon by the first control signal PWMDRV1 during a predetermined period of time, for example 5000 operating hours. At the same time, the other pressure regulating valve 20, 19 is acted upon by the second control signal PWMDRV2. Conversely, after the predetermined period of time has elapsed, one pressure control valve 19, 20 is acted upon with the second control signal PWMDRV2 and the other pressure control valve 20, 19 with the first control signal PWMDRV1 - again for the predetermined period of time. This is now in connection with the Figures 5 and 6 explained in more detail.

Fig. 5 shows a schematic representation of a logic for an alternating control of the pressure regulating valves 19, 20 on the basis of various diagrams. A first diagram 1) shows a time _{counter Z DRV} plotted against time t. A predetermined time period t _{DRV is} shown in curly brackets. The time counter Z _DRV has its maximum value, for example 5000 operating hours, at a first point in time t ₁ after the predetermined time period t _{DRV has elapsed.}

The second, middle diagram 2) shows the logical variable MS as a function of time t, this assuming the value 0 when the internal combustion engine 1 is running and the value 1 when the internal combustion engine 1 is at a standstill. Up to a second point in time t ₂ , the variable MS assumes the value 0, that is to say the internal combustion engine 1 is running. At the second point in time t ₂ , it assumes the value 1, so a standstill of the internal combustion engine 1 is recognized. The first, upper diagram shows that the time counter Z _{DRV is} now reset to 0. It then runs up to its maximum value again, which is then reached again at a third point in time t ₃ . There is no change in the time counter Z _DRV between the first point in time t ₁ and the second point in time t ₂ because it has reached its maximum value, although no standstill of the internal combustion engine 1 has yet been detected. At the third time t ₃ , the time counter Z _{DRV is} reset to the value 0 because the second Diagram showing a stopped engine. The time counter Z _{DRV is} then counted up again until it finally reaches its maximum value again at a fourth point in time t _4. Since the second diagram only shows a stopped engine at a fifth point in time t ₅ , the time counter is reset to the value 0 at the fifth point in time t _{5 in accordance with the first diagram.} The counter then runs up again to its maximum value, which it reaches again _{at a sixth point in time t 6.} The third, lower diagram 3) shows a fourth logic signal SIG4 plotted against time t. This fourth logic signal SIG4 indicates when a change in the assignment of the control signals PWMDRV1, PWMDRV2 to the corresponding pressure regulating valves 19, 20 should take place. This fourth logic signal SIG4 has the value 0 at time 0. Whenever the time counter Z _{DRV has reached} its maximum value and a stationary internal combustion engine 1 is simultaneously indicated by the logic signal MS, there is a change in the value of the fourth logic signal SIG4. This means that the signal SIG4 changes _{from the value 0 to the value 1 at the second time t 2,} from the value 1 to the value 0 at the third time t ₃ and from the value 0 again at the fifth time t ₅ changes the value 1. Overall, there is a change in the value of the fourth logic signal SIG4 and thus in the assignment of the control signals PWMDRV1, PWMDRV2 to the pressure regulating valves 19, 20 at these times.

Fig. 6 shows a function of the switchover logic 57 in a schematic representation. This has a sixth switching element 65 and a seventh switching element 67, which change their switching position as a function of the fourth logic signal SIG4. If the fourth logic signal SIG4 assumes the value 0, both switching elements 65, 67 are in their Figure 6 shown, upper switch position. The first control signal PWMDRV1 is thus assigned to the first pressure regulating valve 19, the second control signal PWMDRV2 being assigned to the second pressure regulating valve 20 at the same time. _{At the same time, the first measured current I R is} measured at the first pressure regulating valve 19, the second measured current I _{R, 2 being} measured at the second pressure regulating valve - which is possibly caused by additional physical switching elements, but is explained here together with the control signals for the sake of simplicity 20 is measured.

If the fourth logic signal SIG4 assumes the value 1, the switching elements 65, 67 change to their in Figure 6 shown, lower switch position. The first control signal PWMDRV1 is now assigned to the second pressure control valve 20, the second control signal PWMDRV2 being assigned to the first pressure control valve 19. At the same time, the first measured current variable I _R measured at the second pressure regulating valve 20, the second measured current variable I _{R, 2 being} measured at the first pressure regulating valve 19.

The switchover logic 57, depending on the fourth logic signal SIG4, causes the pressure regulating valves 19, 20 to be controlled alternately with the various control signals PWMDRV1, PWMDRV2, which at the same time ensures that the current regulators 35, 51 provided for this purpose each have the correct measured current variables I _R , I _{R, 2 are} supplied.

Fig. 7 shows a schematic representation of the pressure regulating valve pressure regulator 41, which is designed here as a PI (DT _{1) pressure regulator.} It can be seen that the output variable V _{U of} the pressure regulating valve pressure regulator 41 consists of three summed regulator components, namely a proportional component Ap, an integral component A _I , and a differential component A _DTI . These three components are added to one another in a summation point 69 to form the unlimited volume flow V _U. The proportional component A _{P represents the product of the control deviation e p} multiplied by the value -1 in a multiplication point 71 with the proportional _{coefficient kp DRV} . The integrating component A _I results from the sum of two summands. The first addend here is the current integral component A _{I delayed by one sampling step T a} . The second summand is the product of a gain factor r2 _DRV and the sum of the current control deviation e _p delayed by one sampling step - again multiplied by the factor −1 in the multiplication point 71. The sum of both summands is limited upwards to the maximum volume flow V _max in a limiting element 73. The gain factor r2 _DRV is calculated using the following formula, in which tn _{DRV is} an integral time: $$\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="imgf0002.png,imgf0004.png"\; state="\{\{state\}\}">r</figure-callout>}{2}_{\mathit{DRV}}=\frac{64{\mathit{kp}}_{\mathit{DRV}}{T}_a}{{\mathit{tn}}_{\mathit{DRV}}}.$$

The integrating component A _I depends on whether the dynamic rail pressure p _{dyn has reached} the first pressure limit value p _GI for the first time after the internal combustion engine 1 has started. If this is the case, the first logic signal SIG1 assumes the value "true" and an in Figure 7 The eighth switching element 75 shown changes into its lower switching position. In this switching position, the integrating component A _{I is} identical to the output signal of the limiting element 73, that is to say the integrating component A _I is limited to the maximum volume flow V _max . Becomes a standstill of the internal combustion engine 1 recognized, takes - as already in connection with Figure 3 explained - the first logic signal SIG1 the value "false", and the eighth switching element 75 changes to its upper switching position. In this case, the integrating component A _I is set to the calculated volume flow V _{S, ber} . The calculated target volume flow V _S thus represents the initialization value of the integrating component A _I in the event that the pressure regulating valve pressure regulator 41 is activated when the dynamic rail pressure p _dyn exceeds the first pressure limit value p _GI.

The calculation of the differential component A _DTI is in the lower part of Figure 7 shown. This proportion is the sum of two products. The first product results from a multiplication of the factor r4 _DRV by the differential component A _DTI delayed by one sampling step. The second product resulting from the multiplication of the factor r3 _DRV with the difference multiplied by the factor -1 deviation e _p and the deviation correspondingly delayed by one sampling step and multiplied by the factor -1 e _p.

The factor r3 _{DRV is} calculated using the following equation, in which tv _{DRV is} a derivative time and t1 _{DRV is} a delay time: $$\mathrm{<figure-callout\; id="3"\; label="r"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">r</figure-callout>}{3}_{\mathit{DRV}}=\frac{2{\mathit{kp}}_{\mathit{DRV}}{\mathit{tv}}_{\mathit{DRV}}}{2\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">t</figure-callout>}{1}_{\mathit{DRV}}+T_a}.$$

The factor r4 _{DRV is} calculated according to the following equation: $$r{\mathrm{4th}}_{\mathit{DRV}}=\frac{2\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">t</figure-callout>}{1}_{\mathit{DRV}}-T_a}{2\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">t</figure-callout>}{1}_{\mathit{DRV}}+T_a}.$$

It appears therefore that the gains r2 and r3 _{DRV DRV} of the proportional kp _DRV depend. The gain factor r2 _{DRV also} depends on _{the reset time tn DRV} , the gain _{factor r3 DRV} on the lead time tv _DRV and the delay time t1 _DRV . The gain factor r4 _{DRV also} depends on the delay time t1 _DRV .

Fig. 8 shows a schematic representation of a logic for calculating the value of a fifth logic signal SIG5, which is used to ensure that in the first and in the second operating mode of the protective operation, the suction throttle 9 is controlled to a permanently open operation. This approach is used in conjunction with Figure 9 explained in more detail. The The value of the fifth logic signal SIG5 results from a third rounding element 77, whose first input again receives the negation of the variable MS, the result of a previous calculation, which is explained in more detail below, entering the second input. The fifth logic signal SIG5 is initially initialized with the value "false" when the internal combustion engine 1 is started. The result of a third comparator element 81, in which it is checked whether the dynamic rail pressure p _{dyn is} greater than or equal to the third pressure limit value p _G3 , enters a first input of a third ORing element 79. The result of a comparison element 83 goes into the second input of the third ORing element 79, which checks whether the value of the logical variable HDSD, which indicates a sensor defect of the high pressure sensor 23, is equal to 1, in which case there is a sensor defect and there is none The sensor is defective if the value of the HDSD variable is 0. It can thus be seen that the output of the third ORing element 79 assumes the value “true” when at least one of the outputs of the third comparator element 81 or of the comparison element 83 assumes the value “true”. So that the output of the third ORing element 79 assumes the value "true", at least one of the following conditions must be met: The dynamic rail pressure p _dyn must have reached or exceeded the third pressure limit value p _G3 , and / or there must be a sensor defect in the high pressure sensor 23 have been determined so that the variable HDSD takes the value 1. If none of these conditions is met, the output of the third ORing element 79 has the value “false”.

The output of the third ORing element 79 goes into a first input of a fourth ORing element 85, whose second input receives the value of the fifth logic signal SIG5. Since this is originally initialized with the value “false”, the output of the fourth ORing element 85 has the value “false” until the output of the third ORing element 79 assumes the value “true”. If this is the case, the output of the fourth ORing element 85 also jumps to the value “true”. In this case, the value of the third rounding element 77 also jumps to true when the internal combustion engine 1 is running, so that the value of the fifth logic signal SIG5 also jumps to "true". Based on Figure 8 shows that the value of the fifth logic signal SIG5 remains "true" until a standstill of the internal combustion engine 1 is recognized, in which case the variable MS assumes the value "true" and thus its negative assumes the value "false".

If the suction throttle 9 is also to be opened permanently in the second and / or in the first operating mode of the protective operation - in particular by a double regulation of the high pressure via the To prevent suction throttle 9 and pressure regulating valves 19, 20 - this can be achieved by using the second pressure limit value p _G2 or the first pressure limit value p _G1 instead of the third pressure limit value p _G3 in the third comparator element 81 and comparing it with the dynamic rail pressure p _dyn becomes.

Fig. 9 shows a schematic representation of the first high-pressure control circuit 25 including a ninth switching element 87 to illustrate the permanently open operation of the suction throttle 9 in the first, second and / or third operating mode of the protective mode, with the ninth switching element 87 being controlled by the fifth logic signal SIG5 is received, its calculation in connection with Figure 8 has been described. It is possible for the ninth switching element 87 to be designed as a software switch, that is to say as a purely virtual switch. Alternatively, it is of course also possible for the ninth switching element 87 to be designed as a physical switch, for example as a relay.

As already explained, an input variable of the first high pressure control circuit 25 is the set high pressure p _S , which in this case is compared with the actual high pressure p _{I in order to calculate the control deviation e p.} This control deviation e _p is an input variable of a high pressure regulator 89, which is preferably designed as a PI (DT ₁ ) algorithm. Another input variable of the high pressure regulator 89 is preferably a proportional coefficient kp _SD . The output variable of the high-pressure regulator 89 is a fuel volume flow V _SD for the intake throttle 9, to which a target fuel consumption V _{Q is} added in an addition point 91. This target fuel consumption V _Q is calculated in a calculation element 93 as a function of the speed n _I and the target injection _{quantity Q S} and represents a disturbance variable in the first high pressure control circuit 25. As the sum of the output variable V _{SD of} the high pressure regulator 89 and the disturbance variable V _Q results in an unlimited target fuel volume flow V _{U, DS} . This is limited in a limiting element 95 as a function of the speed n _I to a maximum volume flow V _{max, SD} for the suction throttle 9. The output of the limiting element 95 results in a limited target fuel volume flow V _{S, SD} for the suction throttle 9, which is included as an input variable in a pump characteristic curve 97. This converts the limited target fuel volume flow V _{S, SD} into a characteristic suction throttle flow I _{KL, SD} .

If the ninth switching element 87 has the in Figure 9 shown, upper switching state, which is the case when the fifth logic signal SIG5 has the value "false", a suction throttle setpoint current I _{S , SD is set} equal to the characteristic suction throttle current I KL, SD. This Suction throttle setpoint current I _{S, SD} represents the input variable of a suction throttle flow regulator 99, which has the task of regulating the suction throttle flow through suction throttle 9. Another input variable of the suction throttle current regulator 99 is, inter alia, an actual suction throttle current I _{I, SD} . The output variable of the suction throttle current regulator 99 is a suction throttle setpoint voltage U _{S, SD} , which is finally converted in a calculation element 101 in a manner known per se into a duty cycle of a pulse-width modulated signal PWMSD for the suction throttle 9. The suction throttle 9 is controlled with this, the signal thus acting overall on a control path 103, which in particular has the suction throttle 9, the high-pressure pump 11, and the high-pressure accumulator 13. The suction throttle current is measured, _{resulting in a raw measured value I R, SD} which is filtered in a current filter 105. The current filter 105 is preferably designed as a PT ₁ filter. The output variable of this filter is the actual suction throttle current I _{I, SD} , which in turn is fed to the suction throttle current regulator 99.

The controlled variable of the first high pressure control circuit 25 is the high pressure in the high pressure accumulator 13. Raw values of this high pressure p are measured by the high pressure sensor 23 and filtered by a first high pressure filter element 107, which has the actual high pressure p _I as its output variable. In addition, the raw values of the high pressure p are filtered by a second high pressure filter element 109, the output variable of which is the dynamic rail pressure p _dyn . Both high-pressure filter elements are preferably implemented by a PT ₁ algorithm, a time constant of the first high-pressure filter element 107 being greater than a time constant of the second high-pressure filter element 109. In particular, the second high-pressure filter element 109 is a faster filter than the first High pressure filter element 107 is formed. The time constant of the second high pressure filter element 109 can also be identical to the value zero, so that the dynamic rail pressure p _dyn then corresponds to the measured raw values of the high pressure p or is identical to them. With the dynamic rail pressure p _{dyn, there} is thus a highly dynamic value for the high pressure, which is always required in particular when a rapid reaction to certain occurring events has to take place.

Output variables of the first high pressure control circuit 25 are therefore the filtered high pressure values p _I , p _{dyn in} addition to the unfiltered high pressure p.

If the fifth logic signal SIG5 assumes the value "true", the ninth switching element 87 switches to its in Figure 9 shown, lower switching position. In this case, the target suction throttle current is I _{S, SD is} no longer identical to the characteristic suction throttle current I _{KL, SD} , but rather is equated with a suction throttle emergency current I _{N, SD.} The suction throttle emergency current I _{N, SD} preferably has a predetermined, constant value, for example 0 A, in which case the suction throttle 9, which is preferably open when de-energized, is open to the maximum, or it has a small current value compared to a maximum closed position of the suction throttle 9, for example 0.5 A, so that the suction throttle 9 is not fully, but still largely open. In this case, the suction throttle emergency current I _{N, SD} and the associated opening of the suction throttle 9 reliably prevents the internal combustion engine 1 from stopping when it is operated in the third operating mode of protective operation with the pressure control valves 19, 20 open to the maximum. The opening of the intake throttle 9 has the effect that a sufficient amount of fuel can still be fed into the high-pressure accumulator 13 even in a medium to low speed range, so that the internal combustion engine 1 can be operated without stalling. In this way, in the first and / or second operating mode, a double regulation of the high pressure is prevented on the one hand via the suction throttle 9 and on the other hand via the pressure regulating valves 19, 20.

Overall, it has been shown that with the aid of the injection system 3 and the internal combustion engine 1 it is possible to carry out stable pressure regulation even when the first high-pressure control circuit 25 can no longer take over the pressure regulation, whereby, alternatively or additionally, a mechanical pressure relief valve can be saved, since its functionality is taken over by the pressure regulating valves 19, 20. In addition, it is shown that the injection system 3 can easily be scaled with regard to the size of an internal combustion engine 1 with which it is used, by adapting the number of pressure regulating valves 19, 20. Pressure regulating valves 19, 20 that can be produced at low cost, such as are known, for example, from automobile series production, can thus be used. If, for example, a cable break of a suction throttle connector occurs in the lower speed range, stable control of the high pressure by means of the pressure regulating valves 19, 20 is still possible _{in this area after the first or second pressure limit value p GI} , p _{G2 has been reached or exceeded, since the pumping capacity of the} High pressure pump is speed dependent. In this case, predetermined engine operating values, especially emission values, can still be complied with in this case. It is only in higher speed ranges that the third pressure limit value p _G3 must be expected to be exceeded. In this case, the pressure regulating valves 19, 20 open completely, and a deterioration in the engine operating values, especially the emissions, must be expected.

At least stable operation of the internal combustion engine 1 is then still guaranteed. Even if the high pressure sensor 23 fails, stable operation of the internal combustion engine 1 is possible, even if the operating values may deteriorate in this case.

The fact that the pressure regulating valves 19, 20 are not activated at the same time prevents the injection system 3 from being damaged by excessive high-pressure gradients. If there are more than two pressure regulating valves 19, 20, it is possible to set separate pressure limit values for connecting each of these pressure regulating valves 19, 20 or for connecting groups of these pressure regulating valves 19, 20, which can be staggered in size.

The pressure regulating valves 19, 20 are evenly utilized by alternate actuation.

Overall, the following mode of operation can also be seen for the internal combustion engine 1 or the injection system 3:
This includes at least two pressure regulating valves 19, 20, but no mechanical pressure relief valve. If the high pressure rises, for example as a result of a cable break in a suction throttle connector, and the dynamic rail pressure p _dyn reaches the first pressure limit value p _G1 , the second high pressure control circuit 39 takes over the control of the high pressure by activating one of the pressure control valves 19, 20. The other pressure regulating valve 20, 19 is activated in such a way that it remains closed.

If the dynamic rail pressure p _{dyn reaches or exceeds the second pressure limit value p G2} , which is preferably greater than the first pressure limit value p _G1 , while the internal combustion engine 1 is running, despite the activation of one pressure control valve 19, 20, the further pressure control valve 20, 19 is also used to control the High pressure activated. Both pressure regulating valves 19, 20 are preferably activated with the same setpoint current I _S , I _{S, 2} .

If the dynamic rail pressure p _dyn reaches or exceeds the third pressure limit value p _G3 , which is preferably greater than the first pressure limit value p _G1 and the second pressure limit value p _G2 , or if the high pressure sensor 23 fails, the pressure regulating valves 19, 20 are controlled so that open them reliably, permanently and preferably completely. In all cases, the suction throttle 9 is preferably activated at the same time in such a way that it is also in the fully open state is operated. The pressure regulating valves 19, 20 are controlled alternately at predeterminable time intervals. A change may only take place when the internal combustion engine 1 is at a standstill.

Claims (10)

1. Injection system (3) for an internal combustion engine (1), comprising

   - at least one injector (15), and comprising

   - a high-pressure accumulator (13), which is in a fluid connection both with the at least one injector (15) and, via a high-pressure pump (11), with a fuel reservoir (7), wherein

   - a suction throttle (9) is assigned to the high-pressure pump (11) as a pressure setting element, wherein

   - the injection system (3) has at least two pressure regulation valves (19, 20), via which the high-pressure accumulator (13) can be brought into a fluid connection with the fuel reservoir (7),
   characterised by a control device (21), which is operatively connected to the suction throttle (9) and to the at least two pressure regulation valves (19, 20), wherein the injection system (3) is configured so as,

   a) in a normal operation, to regulate a high pressure in the high-pressure accumulator (13) by actuating the suction throttle (9) as a pressure setting element, wherein preferably at least one first pressure regulation valve (19, 20) of the at least two pressure regulation valves (19, 20) being actuated to generate a high-pressure disturbance value; so as,

   b) in a first mode of a protective operation, to regulate the high pressure in the high-pressure accumulator (13) by actuating the at least one first pressure regulation valve (19, 20) as a pressure setting element; and so as,

   c) in a second mode of the protective operation, to actuate at least a second pressure regulation valve (20, 19) of the at least two pressure regulation valves (19, 20), which is different from the at least one first pressure regulation valve (19, 20), in addition to the at least one first pressure regulation valve (19, 20), as a pressure setting element to regulate the high pressure in the high-pressure accumulator (13).
2. Injection system (3) according to claim 1, characterised in that the injection system (3) is configured so as, in a third mode of the protective operation, to open the at least one first pressure regulation valve (19, 20) and the at least one second pressure regulation valve (20, 19) permanently.
3. Injection system (3) according to either of the preceding claims, characterised in that the injection system (3) is configured so as

   d) to switch into the first mode of the protective operation if the high pressure reaches or exceeds a first pressure threshold (p_G1) or if a defect in the suction throttle (9) is detected, and/or so as

   e) to switch into the second mode of the protective operation if the high pressure reaches or exceeds a second threshold (p_G2).
4. Injection system (3) according to either claim 2 or claim 3, characterised in that the injection system (3) is configured so as
   f) to switch into the third mode of the protective operation if the high pressure reaches or exceeds a third pressure threshold (p_G3) or if a defect in a high-pressure sensor (23) is detected.
5. Injection system (3) according to any of the preceding claims, characterised in that the injection system (3) is configured so as, in at least one mode of the protective operation, to actuate the suction throttle (9) into a permanently open position.
6. Injection system (3) according to any of the preceding claims, characterised in that at least one of the at least two pressure regulation valves (19, 20) is configured normally open.
7. Injection system (3) according to any of the preceding claims, characterised in that the injection system (3) is configured to generate a first actuation signal (PWMDRV1) and a second actuation signal (PWMDRV2) and so as to actuate the at least one first pressure regulation valve (19, 20) and the at least one second pressure regulation valve (20, 19) alternatingly with the first actuation signal (PWMDRV1) and the second actuation signal (PWMDRV2).
8. Injection system (3) according to any of the preceding claims, characterised in that the injection system (3) is free of a mechanical overpressure valve.
9. Internal combustion engine (1) comprising an injection system (3) according to any of claims 1 to 8.
10. Internal combustion engine (1) according to claim 9, characterised in that the internal combustion engine (1) is configured as a large engine, wherein the internal combustion engine has eight or more combustion chambers (16).

Images