DE10229394A1 - Method, computer program, control and / or regulating device for operating an internal combustion engine, and internal combustion engine - Google Patents

Abstract

An internal combustion engine works with a fuel system in which a quantity of fuel entering a combustion chamber depends on the activation of a piezo actuator of an injection valve. The control energy (dU2) for the piezo actuator is provided by a buffer memory. In order to be able to monitor the function of the control, it is proposed that at least at times the potential difference (dU1) of the buffer memory that results when the piezo actuator is activated is at least approximately determined and used for a comparison with at least one limit value (76, 80).

Description

The invention initially relates to a Method for operating an internal combustion engine, in which an in amount of fuel entering a combustion chamber from a control of a piezo actuator of an injection valve, the control energy of a buffer memory is provided.

Such a method is known from the EP 1 138 917 A1 known. In this, a fuel injection system of an internal combustion engine is described, which comprises a piezo actuator. It controls the amount of fuel to be injected. This is done by charging and discharging the piezo actuator using a driver circuit. When loading, the piezo actuator expands and moves a valve element coupled to it. When unloading, the piezo actuator shortens again.

The energy to charge the piezo actuator is provided by a buffer capacitor. This is from recharged from a DC power source. The at a discharge of the Piezo actuator flowing out of this Energy is fed back into the buffer capacitor.

Object of the present invention it is therefore to further develop a method of the type mentioned at the beginning, that safe and easy monitoring the correct function of the injection system is possible.

This task is done in a process of the type mentioned in that at least temporarily the potential difference that results when the piezo actuator is activated of the buffer memory at least roughly determined and for a comparison is used with at least one limit.

Advantages of invention

With the present invention the correct functioning of the fuel injection system permanently and monitored without additional effort become. This is done by monitoring the control, So loading and unloading, the piezo actuator. With the piezo actuator is a central part of the fuel injection system, because with it ultimately the amount of fuel entering the combustion chamber set. So its correct function is for the entire fuel injection system of central importance.

The idea lies in the invention based on the fact that the operation of the piezo actuator is monitored very well can be that the electrical energy is recorded, which at a Transfer control to the piezo actuator or is delivered by him. The basis for this is again that a piezo actuator, unlike a magnetic actuator, for example, only for the actual change in length is controlled, whereas in the stationary state of the piezo actuator none electrical energy flows. Usually becomes the piezo actuator for an increase in his Length electrical Energy supplied and for a shortening its length an electrical energy stored in it is dissipated again.

The electrical energy that the Piezo actuator for one actuation supplied is provided by and in a buffer memory The buffer memory is activated when the piezo actuator is actuated accordingly electrical energy returned. Usually the buffer memory is a buffer capacitor. By the electrical charge of the buffer memory before and after one Control of the piezo actuator can be detected with good accuracy the piezo actuator actually supplied or the electrical actually discharged by it Energy can be determined. The determined electrical energy is then compared with a target or limit value. In this way is a quick assessment of the functionality of the piezo actuator and simple and during operation of the fuel injection system possible.

Advantageous further developments of Invention are in subclaims specified.

In a first training it says that a electrical energy with which the buffer storage between the times the determination of its potential is loaded, determined and at identifying one actually electrical exchanged between piezo actuator and buffer memory Cargo considered becomes. Generally, the buffer memory is powered by a DC / DC converter fed. This DC / DC converter is charging the buffer memory in the time between measurements if necessary. The actually on electrical energy delivered or returned by this piezo actuator can therefore with even higher Accuracy can be determined when determining the from the Control of the piezo actuator resulting potential difference Buffer memory that may have flowed from the DC / DC converter into the buffer memory electrical energy is taken into account.

This will be done in a concrete form suggested that the energy with which the buffer memory is loaded is added to or subtracted from the potential difference. and the addition result or the subtraction result for the comparison with which at least one limit value is used.

Programming is easy to implement a process in which the energy with which the buffer storage is loaded is estimated on the basis of a map in which a feed current and a period between the two determinations of the potential of the Buffer memory is fed.

Alternatively, it is also possible that loading of the buffer memory for determining the buffer memory is deactivated. This is possible from time to time if the buffer memory has a sufficiently high capacity. In this case, for example, programming of a map can be dispensed with, and accurate results are nevertheless achieved.

It is particularly preferred if then when the potential difference of the piezo actuator is equal to or larger than is a first limit value, an error entry corresponding to a short circuit and / or an action corresponding to a short circuit is initiated becomes. This is based on the idea that in the event of a short circuit additionally a current via the respective short circuit path to the charging or discharging current flows. Therefore discharges the buffer memory or the piezo actuator is stronger than in the normal case, and the difference between the recorded potentials is then at least the same or greater than the first limit. With this method, therefore, not only one Malfunction recognized per se, but the malfunction is also qualified become.

In further training, it is proposed that then when the potential difference of the piezo actuator is equal to or less than the first limit and equal to or less than is a second limit value, an error entry corresponding to a load drop takes place and / or an action corresponding to a drop in load is initiated becomes. With the method according to the invention is the distinction between different causes of errors possible what considerable advantages with regard to those to be taken in the event of an error activities Has.

The invention is based on that in the event of a load drop when the piezo actuator is activated ultimately no current flows, so that the voltage of the buffer memory is not or at least not changed significantly. The difference between the two recorded potentials of the buffer memory (before or after triggering the piezo actuator) is therefore below this limit.

The invention also relates to a computer program, which to carry out of the above method is suitable when it is executed on a computer. It is particularly preferred if the computer program on a Memory, in particular stored on a flash memory.

Object of the present invention is also a tax and / or regulator for operating an internal combustion engine. This will be special preferred if it comprises a memory on which a computer program according to one of the claims 8 or 9 is stored.

Furthermore, the present concerns Invention an internal combustion engine, which is a control and / or regulating device of the above Kind includes.

drawing

Below is a particularly preferred one embodiment of the present invention with reference to the accompanying Drawing explained in detail. The drawing shows:

1 a schematic representation of a fuel system with a plurality of injection valves designed according to a first embodiment;

2 a partial section through one of the injectors of 1 ;

3 a structural diagram of a method for operating the fuel system of 1 ;

4 a the structure picture of 3 corresponding flowchart; and

5 a section through another embodiment of an injection valve.

description of the embodiment

In 1 a fuel system bears the overall reference number 10 , It includes a fuel tank 12 , from which an electric fuel pump 14 the fuel to a high pressure fuel pump 16 promotes. This feeds a fuel manifold 18 ("Rail") in which the fuel is stored under high pressure.

To the fuel rail 18 are multiple fuel injectors 20 connected. They inject the fuel directly into combustion chambers 22 an internal combustion engine (not shown further). The fuel injectors are operated by a control unit 24 driven.

The construction of a fuel injector 20 is in 2 shown. Thereafter, the fuel injector includes 20 a housing 26 with a blind hole step bore 28 , At the top is a piezo actuator 30 arranged with a piston 32 connected is. The piston 32 limits a work space 34 of a hydraulic converter. A piston is also part of the hydraulic converter 36 that with a spherical valve element 38 connected is. The piston 36 has a smaller diameter than the piston 32 and is tightly guided in the housing.

The valve element 38 works with an in 2 upper valve seat 40 and with an in 2 lower valve seat 42 together. The valve seats 40 and 42 delimit a cavity in some areas 44 that has a throttle (without reference number) with a control room 46 connected is.

This is in turn via a throttle (without reference number) and a pressure line 47 with the fuel rail 18 connected. The control room 46 is in 2 down from a valve needle 48 limited. A channel 50 connects the fuel rail 18 with one in the area of the lower end of the valve needle 48 existing pressure space (not visible).

The fuel injector 20 works as follows: The piezo actuator can be operated via a device which is explained in more detail below 30 loaded and unloaded. The longitudinal extension of the piezo actuator is in the unloaded state 30 shorter than when loaded. The state with the shorter longitudinal extension is hereinafter referred to as "short" for the sake of simplicity, and the state with maximum longitudinal extension is hereinafter referred to as "long" for the sake of simplicity.

If the piezo actuator 30 the valve element is in its short or long state 38 at the valve seat 40 or at the valve seat 42 , In both cases the fuel line stops 18 via the pressure line 47 in the control room 46 transferred hydraulic pressure to the valve needle 48 in their closed position. Therefore, fuel cannot come from the fuel injector 20 escape.

However, if the piezo actuator 30 is actuated so that it moves either from its short to the long or from the long to the short position, the valve element lies 38 neither on the valve seat 40 still on the valve seat 42 on. This leads to a pressure drop in the control room 46 and ultimately a pressure difference between the upper end and the lower end of the valve needle 48 , As a result, the valve needle moves in 2 up and gives the way for the fuel from the channel 50 free. Fuel can thus come from the fuel injector 20 in the corresponding combustion chamber 22 escape.

The control of the piezo actuator 30 is done by an electronic circuit 52 , of which some components in 2 are shown. A voltage source 54 provides a DC voltage, which in a DC / DC converter 56 is converted according to the respective requirements. With that of the DC / DC converter 56 provided electrical energy becomes a capacitor 58 loaded. This acts as a buffer memory for the piezo actuator 30 electrical energy to be supplied or to be discharged from it. Via a charging switch 60 and a discharge switch 62 can the capacitor 58 with the piezo actuator 30 get connected. The one in the condenser 58 stored electrical charge is from a measuring circuit 64 detected.

The charging switch is in the idle state 60 and the discharge switch 62 both open, so there is no current between the piezo actuator 30 and buffer capacitor 58 , To the piezo actuator 30 To move from its short state to the long state, it must be charged electrically. For this the charging switch 60 closed. The discharge switch 62 remains open. Thus current flows from the buffer capacitor 58 to the piezo actuator 30 , As soon as the piezo actuator 30 has reached the desired end position, the charging switch remains 60 opened again.

Around. the piezo actuator 30 Moving from the long to the short position has to be done in the piezo actuator 30 existing electrical charge can be discharged again. This is done with the charging switch open 30 , the discharge switch 62 closed. The one in the piezo actuator 30 stored electrical charge is in this way in the capacitor 58 recycled.

It is understood that the charge switch and the discharge switch 62 are usually not constantly closed during an actuation, but are only closed briefly and then opened again, the charge state of the piezo actuator then 30 detected and if necessary the charging switch 60 or the discharge switch 62 is closed again briefly. This process is repeated until the piezo actuator 30 has taken up the desired load or has released the load again. The details are in the EP 1 138 917 A1 to which express reference is hereby made.

To control the piezo actuator 30 To be able to monitor is accordingly in the 3 and 4 illustrated procedure: From the measuring circuit 64 becomes the state of charge of the buffer capacitor 58 before activation (reference number 66 ) and after activation (reference number 68 ) detected. The term "control" can be used to charge the piezo actuator 30 and a corresponding discharge of the buffer memory 58 or unloading the piezo actuator 30 and a corresponding charging of the buffer capacitor 58 be understood. The difference dU1 between the measured values before and after the activation is formed in 70.

In 72, a correction value is added to the difference dU1 determined in 70. This correction value is based on a map 74 determines in which on the one hand the time between the two measurements (reference symbol 66 and 68 ) and on the other hand that from the DC / DC converter to the buffer capacitor 58 flowed off electricity is fed. Coming out of the block 72 The resulting potential difference dU2 thus corresponds to that actually from the buffer capacitor 58 to the piezo actuator 30 flowed off or from the piezo actuator 30 to the buffer capacitor 58 returned energy. Through the map 74 is namely taken into account that in the period between the detection of the potential of the buffer capacitor 58 before a control and the potential after a control, the buffer capacitor 58 is reloaded by the DC / DC converter 56.

The potential difference dU2 is in a first comparator 76 fed in, in which the potential difference dU2 is compared with an upper threshold value. If the potential difference dU2 lies above this upper threshold value, this means that there is more current between the buffer capacitor 58 and the piezo actuator 30 flowed in or out than is normally expected. This is an indication of a short circuit, because in this case, in addition to the normal charging current, a current also flows via the corresponding short circuit path. It then takes place corresponding error entry or an action (e.g. switching off the control of individual cylinders or the entire system). The corresponding block carries in 1 the reference number 78 ,

The potential difference dU2 is also in a second comparator 80 fed in and compared there with a lower threshold value. If the potential difference dU2 is smaller than the lower threshold value, this is an indication of a load drop. In this case, namely, when the piezo actuator is actuated 30 no current from the capacitor 58 to the piezo actuator 30 or back, the voltage of the buffer capacitor 58 So does not change, or at least not significantly. A corresponding error entry and a corresponding action (block 82 ).

In 5 Another embodiment of an injection valve is shown. Elements and areas that have equivalent functions to elements of the 2 have shown the same reference numerals and are not described again in detail.

In contrast to the injection valve from 2 is that of 5 not double, but simply switching. This means that the the valve element 38 only in a switch position on a valve seat 40 is applied. If it is from the valve seat 40 takes off, it fluidically blocks a high pressure area 47 and the cavity 44 lying bypass channel 84 (this state is in 5 ) Shown. So it drops over a low pressure duct 88 the pressure in the cavity 44 and, via a throttle channel 86 , also in the control room 46 , resulting in a corresponding opening movement of the valve needle 48 leads.

If the valve element 38 back into contact with the valve seat 40 comes, the connection of the cavity 44 with the low pressure area 88 interrupted again, and the bypass line 84 will be released again. This increases the pressure in the cavity 44 back to high pressure level (area 47 ). Filling the control room 46 at high pressure level takes place relatively quickly on the one hand through the throttle channel 86 between cavity 44 and control room 46 and on the other hand through a fluidic between high pressure area 47 and control room 46 arranged throttle channel 90 ,

Claims (11)

Method for operating an internal combustion engine, in which a 22 ) amount of fuel coming from a control ( 67 ) of a piezo actuator ( 30 ) of an injection valve ( 20 ) whose control energy (dU2) depends on a buffer memory ( 58 ) provided; characterized in that at least at times which, when activated ( 67 ) of the piezo actuator ( 30 ) resulting potential difference (dUl) of the buffer memory ( 58 ) at least roughly determined ( 70 . 72 ) and is used for a comparison with at least one limit value ( 76 . 80 ). Method according to one of the preceding claims, characterized in that an electrical energy with which the buffer memory ( 58 ) between the times of determining its potential, is determined and when determining an actually between piezo actuator ( 30 ) and buffer memory ( 58 ) exchanged charge (dU2) is taken into account ( 72 ). A method according to claim 2, characterized in that the energy with which the buffer memory ( 58 ) is added to the detected potential difference (dUl) or subtracted from it ( 72 ) and the addition result (dU2) or the subtraction result for the comparison ( 76 . 80 ) with which at least one limit value is used. Method according to one of claims 2 or 3, characterized in that the energy with which the buffer memory ( 58 ) is loaded using a map ( 74 ) is estimated in which a feed current and a time period between the two determinations of the potential of the buffer store ( 58 ) is fed. A method according to claim 1, characterized in that a Loading the buffer memory for the determination of the potential difference of the buffer memory deactivated becomes. Method according to one of the preceding claims, characterized in that when the potential difference (dU2) of the piezo actuator ( 30 ) is equal to or greater than a first limit value, an error entry corresponding to a short circuit is made and / or a corresponding action is initiated ( 78 ). A method according to claim 6, characterized in that when the potential difference (dU2) of the piezo actuator ( 30 ) the same as or less than the first limit value and the same as or less than a second limit value, an error entry corresponding to a load drop occurs and / or a corresponding action is initiated ( 82 ). Computer program, characterized in that it is used to carry out the Method according to one of the preceding claims is suitable if it is based on running on a computer becomes. Computer program according to claim 8, characterized in that it is stored on a memory, in particular on a flash memory is. Control and / or regulating device ( 24 ) for support ben an internal combustion engine, characterized in that it comprises a memory on which a computer program according to one of claims 8 or 9 is stored. Internal combustion engine according to claim 10, characterized in that it is a control and / or regulating device ( 24 ) according to claim 10.