EP1526268B1 - Method for controlling the common rail pressure in an internal combustion engine - Google Patents

Description

The invention relates to a method for regulating the pressure in a fuel reservoir of an internal combustion engine, in particular a common rail system. Moreover, the invention relates to a computer program and an apparatus for carrying out this method.

State of the art

From the prior art, for example from the DE 199 16 100 A1 Such a method and apparatus are basically known. More specifically, this document teaches to provide at least first and second control circuits for regulating the pressure in a fuel tank. In a first control mode, only the first control loop is used to regulate the pressure, wherein the pressure in the fuel accumulator is controlled by suitable control of a high pressure pump as a pressure control means. Alternatively, a second control mode is provided in which the pressure control takes place with the aid of the second control circuit via a pressure control valve, which acts directly on the fuel tank. Depending on the operating condition of the internal combustion engine is either the first or second control mode used for pressure control. Thus, for example, a switching process takes place from the first to the second control mode when certain values for the rotational speed or the fuel quantity to be injected are exceeded in a specific operating state of the internal combustion engine. For the complementary switching from the second to the first control mode also suitable criteria are defined.

WO 03/046357 A1 describes a method for controlling an internal combustion engine, in which a controlled system for regulating the rail pressure at a detected faulty rail pressure sensor separated and transferred to a controlled emergency operation. During the transition phase to controlled emergency operation, the control deviation is specified by a transition function.
Based on this prior art, it is therefore an object of the invention to develop a known method for regulating the pressure in a fuel storage of an internal combustion engine and a known computer program and a known device for performing this method such that the course of the rail pressure during a switching between two different control modes are not disturbed in an unacceptable way.

This object is achieved by the method claimed in claim 1. This method is characterized in that for carrying out the switching operation involved in the switching control loops are opened by their control devices are controlled instead of the previous input signal for preferably preferably each switching individually predetermined Umschalteingangssignalen, which are designed so that the control devices in the desired manner from a current operating state defined by the current control mode to one by the future control mode defined future operating state.

This claimed procedure for performing a switching from a current control mode to a future control mode has the advantage that undesirable disturbances of the rail pressure during the switching operation are avoided. According to the invention, this takes place in such a way that the control circuits involved in the switching operation are continuously transferred from their activated or deactivated operating state during the current control mode into their new activated or deactivated operating state during the future control mode by the switching input signal.

Advantages of the invention

To realize this homogeneous switching operation according to the invention, the switching input signal advantageously represents individually suitable control values for each switching cycle.

Advantageously, in particular, a control loop, which changes in the context of a switching from an activated to a deactivated operating state or vice versa, opened to perform the switching, that is, the control loop is separated for the duration of the switching operation. As already mentioned, the control device of the separated control loop is then no longer operated with the input signal but with the switching input signal, wherein the control value represented by the switching input signal is at least approximately adapted to the last control error supplied to the control device. In this way, a smoother as possible or more homogeneous Transition from the current control mode into the switching process ensured.

Advantageously, the switching control signal is formed from the predetermined control values and a rail pressure deviation applied thereto. This rail pressure deviation causes a correction of the fixed predetermined control values with respect to a current pressure situation in the fuel tank 200, wherein depending on the magnitude and sign of this pressure deviation, the speed at which the pressure in the fuel tank 200 is controlled, in view of the current there Drucksituaticn positive being affected. The connection of the rail pressure control deviation also causes the pressure deviation caused by the switching process in the fuel storage 200 to be kept as low as possible.

The transitions between steady-state control operation and switching operation are further smoothed or homogenized in both directions by monitoring a shift in the operating point caused by the switching input signal during at least that control device which switches from an activated to a deactivated operating state during the switching process reversed changes. It is then advantageous for homogenization purposes, if the transition from the switching operation in the future control mode is actually only carried out by disconnecting the switching input signal and clamping the usual input signal to the regulator device, if at least the monitored control device provided her for the future control mode activated or has reached deactivated operating state. in the With regard to a transition from a first to a second control mode, in each case only a different control loop is activated, it is advantageous in terms of harmonization of the transition, if not immediately from the first to the second or from the second to the first control mode is switched instead, but from the current first or second control mode first to the third control mode and from there to the second or first control mode is switched.

Finally, it is advantageous that during the third control mode, while both control circuits are activated to control the pressure in the fuel storage, the control devices of the two control circuits are each fed with an input signal which not only the control loop associated with the control error, but also the represents a control deviation assigned to each other control loop.

The above object of the invention is further achieved by a device and a computer program for carrying out the method according to the invention. The advantages of these solutions correspond to the advantages mentioned above with reference to the claimed method.

Further advantageous embodiments of the method and the device are the subject of the dependent claims.

drawings

Figur 1

den schematischen Aufbau einer erfindungsgemäßen Vorrichtung; und

Figur 2

den schematischen Aufbau einer Management-Regeleinrichtung als Bestandteil der erfindungsgemäßen Vorrichtung

zeigt.The description is a total of two figures attached, wherein

FIG. 1

the schematic structure of a device according to the invention; and

FIG. 2

the schematic structure of a management control device as part of the device according to the invention

shows.

Description of the embodiments

The invention will be described below in the form of various embodiments with reference to FIGS FIGS. 1 and 2 described in detail.

FIG. 1 shows the structure of the inventive device 100 for regulating the pressure in a fuel tank 200 of an internal combustion engine (not shown here) according to the invention. The fuel accumulator is in particular a so-called common rail.

The device comprises a first control loop 110 with a first subtraction device 112 for providing a control deviation r1, a first control device 114 and a throttle valve 116 as an actuator. This first control circuit regulates via the throttle valve 116, the high-pressure pump 210 supplied Kraftstcffmenge. The first control circuit ensures that precisely the amount of fuel which is predetermined via a setpoint signal S _{M-setpoint of} the subtraction unit 112 is supplied to the high-pressure pump 210 via the throttle valve 116. For this purpose, the difference formation device 112 performs a constant comparison between the desired fuel quantity requested by the desired quantity signal S _{M-desired and} the flow rate through the throttle valve 116 actually provided and represented by the is-quantity signal S _M-ist actual fuel quantity and outputs a possibly detected difference r1 between the target and the actual amount as a quantity deviation. This quantity deviation r1 is output to the control device 114 during steady-state operation of the first control loop as a control deviation in the form of an input signal e1. As a special feature in the first control loop, it should be noted that the amount of fuel actually metered in by the throttle valve 116 in accordance with FIG. 1 is not detected with the aid of a flow meter at the output of the throttle valve 116, but instead that the controlled variable at the output of the first control device 114 is evaluated as a representative of the actual set amount of fuel actually set. Due to a physically unique association between this control variable and the actual set amount of fuel this tap is according to FIG. 1 equally effective as a direct determination of the flow rate.

As just described, the first control circuit 110 initially controls only the fuel quantity supplied to the high-pressure pump 210. However, the high-pressure pump 210 is connected to the fuel storage 200 via a fuel line 220. The control of the amount of fuel supplied to the fuel reservoir 200 by means of the first control circuit can therefore indirectly also control the pressure in the fuel accumulator.

In addition to the first control loop, the device 100 according to FIG FIG. 1 Furthermore, a second control circuit 120. This includes a second difference formation device 122, which a possible deviation between a predetermined target pressure, represented by a signal S _{D target} and that of one. Pressure sensor 230 measured actual pressure in the fuel reservoir 200, represented by a signal S _D-actual detected. The second control circuit 120 further comprises a second control device 124 which receives the pressure deviation r2 detected by the second subtraction device 122 during stationary control operation in the form of an input signal e2 and controls a pressure control valve 126 in response to this pressure deviation r2 which is directly dependent on the pressure in Fuel tank 200 acts. In contrast to the first control loop, the second control circuit therefore carries out a direct regulation of the pressure in the fuel accumulator.

The first and second control circuits 110, 120 can be operated both individually and simultaneously, that is to say in parallel. Thus, in a first control mode only the first control loop 110 and in a second control mode only the second control loop 120 is activated, while in a third control mode the first and the second control loop 110, 120 are activated simultaneously. The decision on which of the three rule modes mentioned the device according to FIG. 1 is operated takes place in response to a control mode signal S _R , which specifies a current or future control mode, in particular depending on a current operating state of the internal combustion engine. In FIG. 1 It can be seen that this control mode signal S _{R is} supplied to a control management device 130 in which, inter alia, preferably the two difference-forming devices 112 and 122 already mentioned are integrated.

This rule management device 130 is designed, the respective control devices 114, 124 of the two control loops 110, 120 in response to a respective to control desired, represented by the control mode signal S _R control mode.

FIG. 2 shows the structure of the rule management device 130 according to the invention. The input signals of this device 130 have been described with reference to FIG FIG. 1 mentioned; They are in FIG. 2 denoted by the same reference sign. It can be seen that the rule management device 130, in addition to the two differentiation devices 120, 122, also has a memory device 132 for storing and providing predetermined control values. These control values substantially shape the switching input signals u1, u2 for the controllers 114, 124 during a switching operation. Furthermore, the rule management device 130 comprises a first and a second switching device 134, 136 for generating the first and second input signals e1, e2 for the first and the second control device 114, 124 during stationary control operation in one of the three said control modes or for generating the switching input signal u1, u2 for at least one of the control devices 114, 124 during a switching process. Finally, the rule management device 130 comprises a control device 138 for controlling the memory device 132 and the switching devices 134, 136 in response to the control mode signal S _R via control signals St1, St2 and St3.

The functioning of in FIG. 2 illustrated rule management device 130 according to the invention will be described in detail below. In this case, a distinction is made between a stationary control operation of the device 100 in the three named control modes and between the possible transitional operations between these control modes.

For operation of the device 100 during a first control mode during which the pressure in the fuel reservoir 200 is controlled only by means of the first control loop 110, the control management device 130 operates as follows: In this case, the control device 138 controls the first switching device 134 via the first control signal St1 such that the switching device 134 forms the input signal e1 for the first control device 114 at its output in such a way that it represents the pressure deviation r2 provided by the second subtraction device 112. At the same time, the control device 138 controls the second switching device 136 via the control signal St2 in such a way that the switching device 136 generates the input signal e2 for the second control device 124 on the basis of predetermined control values. These control values are provided to the second switching device 136 by the memory device 132 after it has been informed by the third control signal St3 of the control device 138 which control values from which memory addresses within the memory device 132 are currently to be output to the second switching device 136. The control values in this case are preferably predetermined so that they keep the second control device 124 in an inactive, ie deactivated state. Alternatively, the control values may also cause a shutdown of the second control device, preferably in a standby mode.

In an operation of the device 100 during the second control mode, during which the pressure in the fuel reservoir 200 is controlled only by means of the second control loop 120, the rule management device 130 operates as follows. With her first and third control signal St1, St3, it controls the memory device 132 and the first switching device 134 in an analogous manner as the second switching device 136 during the operation described in the last paragraph in the first control mode. The first switching device 134 then generates an input signal e1 for the first control device 114 on the basis of suitable control values provided by the memory device 132. These control values are then designed such that they deactivate or switch off the first control device. When operating in the second control mode, the second switching device 136 is controlled by the second control signal St2 of the control device 138 such that it forms the input signal e2 for the second control device 124 from the pressure deviation r2 provided by the second subtraction device 122.

In the event that the device 100 is operated in the third control mode during which the pressure in the fuel reservoir 200 is regulated by means of both the first and second control circuits 110, 120, the rule management device 130 operates as follows. The control device 138 then controls the first switching device 134 via the first control signal St1 in such a way that it forms the input signal e1 for the first control device 114 on the basis of the quantity deviation r1 provided by the first subtraction device 112. At the same time, the control device controls the second switching device 136 via the second control signal St2 in such a way that the input signal e2 for the second control device 124 is formed on the basis of the pressure deviation r2 provided by the second subtraction device 122. Advantageously, however, the input signals do not become formed only on the basis of the mentioned, but with additional consideration of the other deviations r1, r2.

So far, the behavior of the rule management device 130 has been described for each stationary control operation in either the first, second or third control mode. Below is the behavior of the rule management device 130 according to the invention during a switching process in which is switched from a current control mode to a future desired control mode in response to the control mode signal S _R. To carry out this switching process, the rule management device 130 is designed to open the control circuits involved in a switching process by their control device 114, 124 no longer actuated as before in stationary control operation with the input signal e1 or e2, but instead with special switching input signal u1, u2 become. These switching input signals are designed such that the control devices 114, 124 are transferred in the desired manner from a current operating state defined by the current control mode, active or passive, into a future operating state defined by the future control mode, active or passive.

The switching input signals u1, u2 are basically based on suitably predetermined control values provided by the memory device 132. The control values are individually predetermined for each possible switching operation between two different control modes. At the in FIG. 2 the structure of the control means 130, the first and the second switching means 134, 136 are then controlled during a switching operation by the first and the second control signal St1, St2, that they generate the switching signals u1, u2 on the basis of suitable control values provided by the memory device 132. The memory device 132 is in turn instructed by the third control signal St3 accordingly.

In order to optimize the speed with which the pressure is to be changed or regulated during a switching process in the fuel reservoir 200, it is advantageous if the switching input signals u1, u2 are formed not only from the pure control values but instead from control values which have been subjected to the current pressure deviation r2 provided by the second subtraction device 122. Depending on the magnitude and sign of this pressure deviation, the switching input signals u1, u2 then deviate more or less strongly from the originally predetermined control values; In this way, not only the control speed is optimized in terms of the current pressure situation in the fuel storage, but it is also kept as low as possible caused by the switching pressure deviation.

The control device 138 may be designed as a state machine, which allows monitoring of the operating points of the control device 114, 124 during a switching operation.

In a switching operation from the third control mode, in which both control loops are active, to the first or second control mode, in which only one control loop is active, the procedure is as follows: First, both control loops 110, 120 are opened by not using them the input signals e1, e2, but instead be controlled with the switching Eihgangssignal u1, u2. It Then takes place a monitoring of the switching input points u1, u2 conditional shift of the operating points of the two control device 114, 124, in particular with regard to when the to be disabled in this switching control device leaves its previous effective workspace. When this time is reached, the hitherto active switching control device, the hitherto entered switching input signal u1, u2 is turned off. The associated control circuit is then closed again by the control device - instead of the switching input signal - with the predetermined for the selected future first or second control mode input signal e1, e2, which represents one of said control deviations, is controlled.

In parallel, the control device to be deactivated continues to be supplied with the changeover input signal until this control device has been deactivated due to the operating point shift. Alternatively, the control device to be deactivated can also simply be switched off.

• Sie steuert über eines der Steuersignal St1, St2 zunächst nur diejenige Umschalteinrichtung 134, 136 an, die der bei dem aktuellen Regelmodus deaktivierten, aber für den zukünftigen Regelmodus zu aktivierenden Regeleinrichtung 114, 124 zugeordnet ist. Die Ansteuerung erfolgt so, dass diese Umschalteinrichtung 134 oder 136 der zu aktivierenden Regeleinrichtung ein auf geeigneten, wiederum durch die Speichereinrichtung 132 bereitgestellten Steuerwerten basierendes Umschalt-Eingangssignal u1, u2 zuführt. Es wird dann vorzugsweise wiederum über die als Zustandsautomat ausgebildete Steuereinrichtung 138 eine Verschiebung des Arbeitspunktes bei der zu aktivierenden Regeleinrichtung überwacht, um festzustellen, wann diese Regeleinrichtung überhaupt wieder in einen wirksamen Arbeitsbereich eintritt. Der Zeitpunkt des Eintritts des Arbeitspunktes in den wirksamen Arbeitsbereich ist zu unterscheiden von einem anderen Zeitpunkt, wann der Arbeitspunkt der zu aktivierenden Regeleinrichtung einen durch den zukünftigen Regelmodus geprägten Betriebspunkt repräsentiert; zwischen beiden Zeitpunkten liegt üblicherweise ein zeitlicher Abstand.

In a switching operation from a current first or second control mode, in which only one control loop is active, to the third control mode, in which both control loops 110, 120 are active, the rule management device 130 proceeds as follows:

• Initially, via one of the control signals St1, St2, it only activates that switching device 134, 136 which is associated with the control device 114, 124 deactivated in the current control mode but to be activated for the future control mode. The control is carried out so that this switching means 134 or 136 of the control device to be activated on a suitable, in turn by the Memory controller 132 based control values supplied switching input signal u1, u2 supplies. In turn, it is then preferably monitored via the control device 138, which is designed as a state machine, to shift the operating point in the control device to be activated in order to determine when this control device will even reenter an effective working area. The time of entry of the working point into the effective working range is to be distinguished from another time when the operating point of the control device to be activated represents an operating point characterized by the future control mode; between the two times is usually a time interval.

As soon as it has been determined that the control device to be activated has entered the effective working range, that control device which is activated both in the current and in the future desired control mode and which is still controlled by the input signal e1, e2 of the current control mode, will also be actuated. cut off from this input signal and instead fed with the same switching input signal u1, u2 as the regulator to be activated. Both control devices are then supplied with the same switching input signal as long as possible, until both control devices have been converted into such an active operating state as is provided for the future desired control mode.

Switching operations from the first to the second control mode or vice versa are preferably not realized by a direct switching between these control modes. Such a direct switching disadvantageously would have severe disturbances of the rail pressure during the Switchover result. According to the invention it is therefore proposed to choose a detour via the third control mode in such switching operations. Specifically, this means that in a switching operation from the first to the second control mode first a Umschaltvcrgang from the first to the third and subsequent switching from the third to the second control mode should be done. Analogously, a switching process from the second control mode to the first control mode is realized by first switching over from the second to the third and subsequently from the third to the first control mode. These described switching operations involving the third control mode are preferably carried out as described above.

The control device 138 is designed such that, for each of the said switching operations, it appropriately controls the memory device 132 and the first and second switching devices 134, 136 via the control signals St1, St2 in order to implement in particular the switching input signals u1, u2 in a suitable manner.

The inventive method described is preferably realized in the form of a computer program. The computer program may optionally be stored together with other computer programs on a computer-readable medium. The data carrier may be a floppy disk, a compact disc or a so-called flash memory. The computer program stored on the data carrier can then be transferred or sold as a product to a customer. However, the computer program can also be transmitted without the aid of a data carrier via an electronic communication network, in particular the Internet, as a product to the customer.

Claims (14)

1. Method for controlling the pressure in a common rail (200) of an internal combustion engine, comprising the steps:

   a) steady-state operation of the pressure control in accordance with a current control mode in which at least a first control circuit for controlling the pressure is activated;

   b) carrying out a switch-over process for switching over the pressure control from the current control mode to a control mode which will be desired in the future, in response to a control mode signal (S_R); and

   c) steady-state operation of the pressure control according to the future control mode in which an at least second control circuit for controlling the pressure is activated;

   wherein during each steady-state operation of a control circuit a control device (114, 124) which is individually assigned to each control circuit is actuated with an input signal (e1, e2) which represents a control error;
   characterized in that on the basis of predetermined control values which are made available in a memory device (132) switch-over input signals (u1, u2) are determined individually for each switch-over process, and in that in order to carry out the switch-over process according to step b) the control circuits (110, 120) which are involved in the switch-over process are opened in that their control devices (114, 124) are actuated by means of the switch-over input signals (u1, u2) instead of with the previous input signal (e1, e2), and the control devices (114, 124) are switched over by means of the switch-over input signals (u1, u2) from a current operating state, defined by the current control mode, into a future operating state, which is defined by the future control mode and is therefore later compared to the current time.
2. Method according to Claim 1, characterized in that the switch-over input signals represent predetermined control values which are dimensioned individually depending on the desired switch-over process.
3. Method according to Claim 2, characterized in that the switch-over input signals represent predetermined constant control values.
4. Method according to Claim 2 or 3, characterized in that the switch-over signals take into account not only the control values but in each case also a current rail pressure error.
5. Method according to one of the preceding claims, characterized in that the transfer of the control devices (114, 124) from the current operating state into the future operating state is monitored on the basis of a shift of the working point of the respective control device (114, 124) which is caused by the switch-over input signals (u1, u2).
6. Method according to one of the preceding claims, characterized in that a first, a second and a third control mode are available alternatively, wherein in the first control mode only a first control circuit (110) is activated, in the second control mode only a second control circuit (120) is activated, and in the third control mode both the first and the second control circuit (110, 120) for controlling the pressure are activated.
7. Method according to Claim 6, characterized in that during a switch-over process from the third control mode to the first or second control mode the method has the following partial steps:

   b1.1) The opening of the first and of the second control circuit by actuating both the control device (114) which is to be deactivated within the scope of the switch-over process and the control device (124) which remains active within the scope of the switch-over process instead of with the input signals (e1, e2) from the current steady-state control mode with preferably the same switch-over input signals (u1, u2) which represent the predetermined control values;

   b1.2) Monitoring of the shifting, due to the switch-over input signals (u1, u2), of the working points of the two control devices (114, 124), and execution of the following steps if the control device which is to be deactivated leaves its previous effective working range:

   b1.3) Switching off the previous switch-over input signal (u1, u2) which represents the predefined control values, when the control circuit (110, 120) remains active, and closing this control circuit by actuating the control device thereof with a different input signal which is predefined according to method step c) and the selected future first or second control mode and which represents a control error;

   b1.4) Continuation of the actuation of the control device (114, 124) of the control circuit which is to be deactivated, with the switch-over input signal (u1, u2) until the control device (114, 124) thereof has been deactivated on the basis of the shifting of the working point; and during the method step c): Stopping of the deactivated control circuit in the deactivated state either by continued suitable actuation with the switch-over input signal (u1, u2) or by switching off this control circuit, preferably into a stand-by mode.
8. Method according to Claim 6, characterized in that a switch-over process according to method step b) from the current first or second control mode to the third control mode of the method has the following partial steps:

   b2.1) Actuation of the control device (114, 124) which was previously deactivated in the current control mode but is to be activated for the future control mode, with a suitable switch-over input signal (u1, u2);

   b2.2) Monitoring of the shifting, due to the actuation, of the working point of the control device of the control circuit which is to be activated, in order to determine when the previously deactivated control device enters an effective working range again;

   b2.3) Continuation of the actuation of the control device (u1, u2) which is to be activated with the switch-over signal (u1, u2) beyond the time of detection according to step b2.2) and simultaneous opening of the control circuit (110, 120), activated during the current control mode and the future control mode, by actuating the control device (114, 124) of said control circuit (110, 120) with preferably the same switch-over signal (u1, u2) as the control device which is to be activated, in each case until both control devices have been transferred into an active operating state, such as is provided for the third control mode which will be desired in future.
9. Method at least according to Claim 6, characterized in that a transition from the current first control mode to a future second control mode according to step b) comprises the following partial steps: execution of a switch-over process from the current first control mode to the third control mode according to Claims 1 and 8; and execution of a switch-over process from the third control mode to the future second control mode according to Claims 1 and 7.
10. Method at least according to Claim 6, characterized in that a transition from the current second control mode to a future first control mode according to step b) comprises the following partial steps:

    Execution of a switch-over process from the current second control mode to the third control mode according to Claims 1 and 8; and

    Execution of a switch-over process from the third control mode to the future first control mode according to Claims 1 and 7.
11. Method at least according to Claim 6, characterized in that during operation according to the third control mode the input signals (e1, e2) for both control devices (114, 124) each represent not only a control error which is assigned to the particular control circuit but also a control error which is assigned to the other control circuit.
12. Computer program for an open-loop and/or closed-loop control device, characterized in that said computer program is programmed to carry out a method according to one of Claims 1 to 11.
13. Device (100) for controlling the pressure in a common rail (200) of an internal combustion engine, characterized in that said device (100) has a memory on which a computer program according to Claim 12 is stored, and in that said device (100) is designed to carry out a computer program according to Claim 12.
14. Device (100) according to Claim 13, characterized in that the common rail (200) is a common rail system.

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