WO2004003365A1

WO2004003365A1 - Method, computer programme, and control or regulation device for the operation of an internal combustion engine

Info

Publication number: WO2004003365A1
Application number: PCT/DE2003/001762
Authority: WO
Inventors: Johannes-Joerg Rueger; Udo Schulz
Original assignee: Robert Bosch Gmbh
Priority date: 2002-06-29
Filing date: 2003-05-30
Publication date: 2004-01-08
Also published as: JP2005531718A; EP1520092A1; DE10229394A1

Abstract

An internal combustion engine operates with a fuel system in which the amount of fuel reaching a combustion chamber depends on an operation of a piezo actuator in an injection valve. The operation energy (dU2) for the piezo actuator is produced from a buffer store. According to the invention, the function of the operation can be monitored whereby the potential difference (dU1, 70) of the buffer store resulting on an operation of the piezoactuator is at least periodically approximately determined and used for a comparison with at least one threshold value (76, 80).

Description

METHOD, COMPUTER PROGRAM, CONTROL AND / OR REGULATING DEVICE FOR OPERATING A BR ENNKRAFTMAS CHINE

0

5

description

The invention initially relates to a method for operating an internal combustion engine, in which an amount of fuel entering a combustion chamber depends on the activation of a piezo actuator of an injection valve, the activation energy of which is provided 5 by a buffer store.

Such a method is known from EP 1 138 917 AI. In this, a fuel injection system of an internal combustion engine is described, which comprises a piezo actuator 0. 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. The piezo actuator shortens again when it is 5 discharged. The energy for charging the piezo actuator is provided by a buffer capacitor. This is recharged from a direct current source. The energy flowing out of the piezo actuator when it is discharged is fed back into the buffer capacitor.

The object of the present invention is therefore to develop a method of the type mentioned at the outset so that safe and simple monitoring of the correct functioning of the injection system is possible.

In a method of the type mentioned at the outset, this object is achieved in that, at least at times, the result of actuating the piezo actuator

Potential difference of the buffer memory is at least approximately determined and used for a comparison with at least one limit value.

Advantages of the invention

With the present invention, the correct function of the fuel injection system can be monitored continuously and without additional effort. This is done by monitoring the control, i.e. the charging and discharging, of the piezo actuator. The piezo actuator is a central part of the fuel injection system, because it ultimately adjusts the amount of fuel entering the combustion chamber. Its correct functioning is therefore of central importance for the entire fuel injection system.

The invention is based on the idea that the operation of the piezo actuator can be monitored very well in that the electrical energy, which is at a control is transmitted to the piezo actuator or is emitted by it. Again, the basis for this is that, unlike a magnetic actuator, for example, a piezo actuator is only actuated for the actual length change, whereas no electrical energy flows when the piezo actuator is stationary, usually electrical energy is supplied to the piezo actuator to increase its length and for one Shortening its length dissipates electrical energy stored in it again.

The electrical energy that is supplied to the piezo actuator for actuation is provided by a buffer store, and the electrical energy is returned to this buffer store when the piezo actuator is actuated accordingly, usually the buffer store is a buffer capacitor. By detecting the electrical charge of the buffer memory before and after actuation of the piezo actuator, the electrical energy actually supplied to the piezo actuator or actually discharged by it can be determined with good accuracy. The determined electrical energy is then compared with a target or limit value. In this way, an evaluation of the functionality of the piezo actuator is possible quickly and easily and during the operation of the fuel injection system.

Advantageous developments of the invention are specified in subclaims.

In a first development, it is stated that an electrical energy with which the buffer store is charged between the times of determining its potential is determined and taken into account when determining an electrical charge that is actually exchanged between the piezo actuator and the buffer store. In general the buffer memory is fed by a DC / DC converter. This DC / DC converter may reload the buffer memory between measurements. The electrical energy actually delivered to or returned from the piezo actuator can therefore be determined with even greater accuracy if, when determining the potential difference in the buffer store resulting from the control of the piezo actuator, the electrical energy that may have flowed from the DC / DC converter into the buffer store is taken into account.

In a specific embodiment, it is proposed that the energy with which the buffer store is loaded be added to or subtracted from the potential difference and the result of the addition or subtraction is used for the comparison with the at least one limit value.

In terms of programming, it is easy to implement a method in which the energy with which the buffer store is loaded is estimated on the basis of a map into which a feed current and a time period between the two determinations of the potential of the buffer store are fed.

As an alternative to this, it is also possible for loading the buffer memory to be deactivated for determining the buffer memory. 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 the potential difference of the piezo actuator is equal to or greater than is a first limit value, an error entry corresponding to a short circuit is made and / or an action corresponding to a short circuit is initiated. This is based on the idea that in the event of a short circuit, in addition to the charging or discharging current, a current also flows via the respective short circuit path. The buffer store or the piezo actuator therefore discharges more than in the normal case, and the difference between the detected potentials is then at least equal to or greater than the first limit value. With this method, not only can a malfunction per se be recognized, but the malfunction can also be qualified.

In a further development, it is proposed that if the potential difference of the piezo actuator is equal to or less than the first limit value and equal to or less than a second limit value, an error entry corresponding to a load drop occurs and / or an action corresponding to a load drop is initiated. With the method according to the invention, it is therefore possible to differentiate between different causes of errors, which has considerable advantages with regard to the measures to be taken in the event of an error.

The invention is based on the fact that one

Lastly, no load flows when the piezo actuator is activated, so that the voltage of the buffer memory does not change, or at least does not change significantly. The difference between the two recorded potentials of the buffer memory (before or after one

Control of the piezo actuator) is therefore below this limit.

The invention also relates to a computer program which is suitable for carrying out the above method if it is running on a computer. It is particularly preferred if the computer program is stored on a memory, in particular on a flash memory.

The present invention also relates to a control and / or control device for operating an internal combustion engine. This is particularly preferred if it comprises a memory on which a computer program according to one of claims 8 or 9 is stored.

Furthermore, the present invention relates to an internal combustion engine, which comprises a control and / or regulating device of the above type.

drawing

A particularly preferred exemplary embodiment of the present invention is explained in detail below with reference to the accompanying drawing. The drawing shows:

Figure 1 is a schematic representation of a

Fuel system with several injection valves designed according to a first embodiment;

FIG. 2 shows a partial section through one of the injection valves of FIG. 1;

FIG. 3 shows a structural diagram of a method for operating the fuel system from FIG. 1;

FIG. 4 shows a flow diagram corresponding to the structural diagram of FIG. 3; and

Figure 5 shows a section through another embodiment -a fuel injector.

Description of the embodiment

In Fig. 1, a fuel system as a whole carries that

Reference numeral 10. It comprises a fuel tank 12, from which an electric fuel pump 14 delivers the fuel to a high-pressure fuel pump 16. This feeds a fuel rail 18 ("rail"), in which the fuel is stored under high pressure.

A plurality of fuel injection valves 20 are connected to the fuel rail 18. They inject the fuel directly into combustion chambers 22 of an internal combustion engine (not shown further). The fuel injection valves are controlled by a control and regulating device 24.

The structure of a fuel injection valve 20 is shown in FIG. 2. Thereafter, the fuel injection valve 20 comprises a housing 26 with a blind hole 28. At its upper end there is a piezo actuator 30 which is connected to a piston 32. The piston 32 delimits a working space 34 of a hydraulic converter. Part of the hydraulic converter is also a piston 36 which is connected to a spherical valve element 38. The piston 36 has a smaller diameter than the piston 32 and is tightly guided in the housing.

The valve element 38 cooperates with an upper valve seat 40 in FIG. 2 and with a lower valve seat 42 in FIG. 2. The valve seats 40 and 42 partially delimit a cavity 44 which is connected to a control chamber 46 via a throttle (without reference number). This is in turn connected via a throttle (without reference number) and a pressure line 47 to the fuel collecting line 18. The control chamber 46 is delimited at the bottom in FIG. 2 by a valve needle 48. A channel 50 connects the fuel collecting line 18 to a pressure chamber (not visible) present in the area of the lower end of the valve needle 48.

The fuel injection valve 20 operates as follows: The piezo actuator 30 can be charged and discharged again via a device which will be explained in more detail below.

In the unloaded state, the longitudinal extent of the

Piezo actuator 30 shorter than when loaded. The state with the shorter longitudinal extension is subsequently referred to as "short" for the sake of simplicity, and the state with the maximum

For the sake of simplicity, longitudinal extension as

called "long".

When the piezo actuator 30 is in its short or long state, the valve element 38 is seated on the valve seat 40 or on the valve seat 42. In both cases, the hydraulic pressure transmitted from the fuel manifold 18 via the pressure line 47 into the control chamber 46 holds the valve needle 48 in their closed position. Therefore, fuel cannot leak from the fuel injection valve 20.

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, this is because

Valve element 38 neither on the valve seat 40 nor on the valve seat 42. This leads to a pressure drop in the control chamber 46 and ultimately to a pressure difference between the upper end and the lower end of the valve needle 48. As a result, the valve needle in FIG. 2 moves upwards and gives clear the way for the fuel from channel 50. Fuel can thus exit the fuel injection valve 20 into the corresponding combustion chamber 22.

The control of the piezo actuator 30 is carried out by an electronic circuit 52, some components of which are shown in FIG. 2. A voltage source 54 provides a DC voltage which is converted in a DC / DC converter 56 in accordance with the respective requirements. A capacitor 58 is charged with the electrical energy provided by the DC / DC converter 56. This acts as a buffer store for the electrical energy to be supplied to or removed from the piezo actuator 30. The capacitor 58 can be connected to the capacitor 58 via a charging switch 60 and a discharge switch 62

Piezo actuator 30 are connected. The electrical charge stored in the capacitor 58 is detected by a measuring circuit 64.

In the idle state, the charging switch 60 and

Discharge switch 62 both open, so there is no current flowing between the piezo actuator 30 and the buffer capacitor 58. In order to bring the piezo actuator 30 from its short state to the long state, it must be charged electrically. For this purpose, the charging switch 60 is closed. The

Discharge switch 62 remains open. Current therefore 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 lacquer switch 60 remains open again.

In order to move the piezo actuator 30 from the long to the short position, the electrical charge present in the piezo actuator 30 must be discharged again. For this purpose, the discharge switch 62 is closed when the charging switch 30 is open. The electrical stored in the piezo actuator 30 Charge is returned to the capacitor 5c in this way.

It goes without saying that the charge switch and the discharge switch 62 are usually not constantly closed during an actuation, but are only closed for a short time and then opened again, the charge state of the piezo actuator 30 then being detected and, if appropriate, the charge switch 60 and the discharge switch 62 again is closed briefly. This process is repeated until the piezo actuator 30 has picked up the desired charge or has released the charge again. The details of this are described in EP 1 138 917 AI, to which reference is hereby expressly made.

In order to be able to monitor the activation of the piezo actuator 30, the procedure shown in FIGS. 3 and 4 is followed: the measuring circuit 64 determines the state of charge of the buffer capacitor 58 before activation (reference number 66) and after activation

(Reference numeral 68) detected. The term “control” can be understood here to mean charging the piezo actuator 30 and correspondingly discharging the buffer store 58 or also discharging the piezo actuator 30 and correspondingly charging the buffer capacitor 58. The difference between the measured values before and after the activation is formed in 70.

In 72, a correction value is added to the difference clU1 determined in 70. This correction value is determined on the basis of a characteristic curve 74, into which the time between the two measurements (reference numerals 66 and 68) and the current which has flowed from the DC / DC converter to the buffer compensator 58 are fed in. The potential difference dU2 resulting from block 72 thus corresponds to the energy which has actually flowed from the buffer capacitor 58 to the piezo actuator 30 or which has flowed back from the piezo actuator 30 to the buffer connector 58. The characteristic map 74 takes into account that the buffer capacitor 58 is recharged by the DC / DC converter 56 in the time period which lies between the detection of the potential of the buffer capacitor 58 before activation and the potential after activation.

The potential difference dU2 is fed into a first comparator 76, in which the potential difference dü2 is compared with an upper threshold value. If the potential difference dU2 is above this upper threshold value, this means that more current has flowed in and out between the buffer capacitor 58 and the piezo actuator 30 than is to be expected in the normal case. This is an indication of a short circuit, because in this case a current flows in addition to the normal charging current via the corresponding short circuit path. A corresponding error entry or an action then takes place (for example, switching off the activation of individual cylinders or the entire system). The corresponding block has the reference symbol 78 in FIG. 1.

The potential difference dU2 is also fed into a second comparator 80 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, when the piezo actuator 30 is actuated, no current flows from the capacitor 58 to the piezo actuator 30 or back, so the voltage of the buffer capacitor 58 does not change, or at least does not change significantly. A corresponding error entry and a corresponding action then take place (block 82). A further embodiment of an injection valve is shown in FIG. Elements and areas which have functions equivalent to elements of the injection valve shown in FIG. 2 have the same reference numerals and are not described again in detail.

In contrast to the injection valve of Figure 2, that of Figure 5 is not double, but single-switching. This means that the valve element 38 only bears against a valve seat 40 in one switching position. When it lifts off the valve seat 40, it blocks a bypass duct 84 fluidly located between a high-pressure region 47 and the cavity 44 (this state is shown in FIG. 5). The pressure in the cavity 44 and, via a throttle channel 86, also in the control chamber 46 thus decrease via a low-pressure channel 88, which leads to a corresponding opening movement of the valve needle 48.

When the valve element 38 comes into contact with the valve seat 40 again, the connection of the cavity 44 to the low-pressure region 88 is interrupted again and the bypass line 84 is released again. As a result, the pressure in the cavity 44 rises again to the high pressure level (area 47). The control chamber 46 is filled comparatively quickly on the high pressure level, on the one hand, through the throttle duct 86 between the cavity 44 and the control chamber 46 and, on the other hand, through a throttle duct 90 arranged fluidically between the high pressure region 47 and the control chamber 46.

Claims

Expectations

1. Method for operating an internal combustion engine, in which a fuel quantity entering a combustion chamber (22) depends on a control (67) of a piezo actuator (30) of an injection valve (20), the control energy (dU2) of which is provided by a buffer store (58) , characterized in that at least occasionally the potential difference (clül) of the buffer memory (58) which results when the piezo actuator (30) is activated (70, 72) and is used for a comparison with at least one limit value ( 76, 80).

2. The method according to any one of the preceding claims, characterized in that an electrical energy with which the buffer store (58) is charged between the times of determining its potential is determined and in the determination of an actually between the piezo actuator (30) and the buffer store (58 ) exchanged charge (dU2) is taken into account (72).

3. The method according to claim 2, characterized in that the energy with which the buffer store (58) is loaded is added to the detected potential difference (clül) or subtracted from it (72) and the addition result (dU2) or the subtraction result is used for the comparison (76, 80) with the at least one limit value.

4. The method according to any one of claims 2 or 3, characterized in that the energy with which the

Buffer memory (58) is loaded, is estimated using a Kεnnfeld (74), into which a supply current and a period between the two determinations of the potential of the buffer memory (58) is fed.

5. The method according to claim 1, characterized in that a loading of the buffer memory for determining the potential difference of the buffer memory is deactivated.

6. The method according to any 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 occurs and / or a corresponding action is initiated (78).

7. The method according to claim 6, characterized in that when the potential difference (dU2) of

Piezo actuator (30) is equal to or less than the first limit value and equal to or less than a second limit value, an error entry corresponding to a load drop is made and / or a corresponding action is initiated (82).

8. Computer program, characterized in that it is suitable for performing the method according to one of the preceding claims when it is executed on a computer.

9. Computer program according to claim 8, characterized in that it is stored on a memory, in particular on a flash memory.

10. Control and / or regulating device (24) for operating an internal combustion engine, characterized in that it is a

Includes memory on which a computer program according to one of claims 8 or 9 is stored.

11. Internal combustion engine according to claim 10, characterized in that it comprises a control and / or regulating device (24) according to claim 10.