JP2005531718A - Method for operating an internal combustion engine, computer program, control and / or regulating device and internal combustion engine - Google Patents

Abstract

The internal combustion engine described here is operated by a fuel system, where the amount of fuel reaching the combustion chamber depends on the drive control of the piezoelectric actuator of the injection valve. The drive control energy (dU2) for this piezoelectric actuator is supplied by a buffer accumulator. In order to be able to monitor the function of this drive control, it is proposed that the potential difference (dU1) of the buffer accumulator generated during the drive control of the piezoelectric actuator is at least occasionally determined at least roughly and the potential difference is at least 1 Used for comparison with two boundary values (76, 80).

Description

DESCRIPTION The present invention first relates to a method of operating an internal combustion engine, where the amount of fuel reaching the combustion chamber depends on the drive control of the piezoelectric actuator of the injection valve, the drive control energy of which is supplied by a buffer accumulator.

  Such a method is known from EP 1 138 917 A1. Here, a fuel injection system for an internal combustion engine including a piezoelectric actuator is described. The amount of fuel to be injected is controlled by this piezoelectric actuator. This control is performed by charging and discharging the piezoelectric actuator by the driver circuit. Charging causes the piezoelectric actuator to stretch and move the valve element coupled to it. At the time of discharge, the piezoelectric actuator contracts as before.

  Energy for charging the piezoelectric actuator is supplied by a buffer capacitor. This buffer capacitor is recharged by a direct current source. The energy flowing out of the piezoelectric actuator when it is discharged is returned to this buffer capacitor.

  The object of the present invention is to develop a method of the type mentioned at the outset so that the correct functioning of the injection system can be monitored easily and reliably.

  This problem is solved in a method of the type mentioned at the outset, at least sometimes and at least roughly, to determine the potential difference of the buffer accumulator that occurs during the drive control of the piezoelectric actuator and to use this potential difference for comparison with at least one boundary value. It is solved by.

Advantages of the Invention The present invention allows the correct functioning of a fuel injection system to be monitored permanently and without additional cost. This is done by monitoring drive control, i.e. monitoring charge / discharge of the piezoelectric actuator. Here, the piezoelectric actuator is a central portion of the fuel injection system. This is because the amount of fuel reaching the combustion chamber is finally adjusted by this piezoelectric actuator. That is, its correct function has an important meaning for the whole fuel injection system.

  The idea underlying the present invention is that the operation of the piezoelectric actuator can be monitored very well by detecting the electrical energy transmitted to or extracted from the piezoelectric actuator during drive control. On the other hand, the basis for this is that, unlike a magnetic actuator, for example, a piezoelectric actuator is driven and controlled only to actually change its length, whereas in the steady state of this piezoelectric actuator, This means that no electrical energy flows. Typically, the piezoelectric actuator is supplied with electrical energy to extend its length, and the stored electrical energy is taken out to contract its length.

  The electrical energy supplied to the piezoelectric actuator for operation is provided by a buffer accumulator and is returned to the buffer accumulator when the piezoelectric actuator is operated accordingly. Typically, the buffer accumulator is a buffer capacitor. By detecting the electric charge of the buffer accumulator before and after the drive control of the piezoelectric actuator, the energy actually supplied to the piezoelectric actuator or the electric energy actually taken out from the piezoelectric actuator can be determined with good accuracy. . Next, the obtained electric energy is compared with a target value or a boundary value. This allows the function of the piezoelectric actuator to be evaluated quickly, easily and during operation of the fuel injection system.

  Advantageous developments of the invention are described in the dependent claims.

  In a first development, the electric energy charged in the buffer accumulator is determined during the time when the potential of the buffer accumulator is determined, and the charge actually exchanged between the piezoelectric actuator and the buffer accumulator is determined. When considering this electrical energy. In general, the buffer accumulator is powered by a DC / DC converter. This DC / DC converter charges or recharges the buffer accumulator during the time between measurements. Therefore, the charge that is actually output to the piezoelectric actuator or the charge that flows back from here is sometimes converted by a DC / DC converter when determining the potential difference of the buffer accumulator generated by driving and controlling the piezoelectric actuator. Considering the electric energy passed through the buffer accumulator, it can be obtained with higher accuracy.

  For this purpose, a specific embodiment proposes to add or subtract the energy for charging the buffer accumulator to the potential difference, and to add this subtraction result or subtraction result to at least one boundary value. It is to be used for comparison.

  A simple programming technique is to estimate the energy charged in the buffer accumulator on the basis of a characteristic map, where the characteristic map is calculated between two potentials of the buffer accumulator. Memorize time and feed current.

  As an alternative, it is also possible to deactivate the charging of the buffer accumulator in order to determine the potential difference of the buffer accumulator. This may be possible if the buffer accumulator has a sufficiently large capacity. In this case, for example, the characteristic map programming can be omitted, and an accurate result can still be obtained.

  It is particularly advantageous when an error corresponding to a short circuit is made and / or an action corresponding to a short circuit is activated if the potential difference of the piezoelectric actuator is equal to or greater than the first boundary value. It is. The basis of this is the idea that in addition to the charging or discharging current, a current flows through each short-circuit path in the event of a short circuit. Therefore, the buffer accumulator or the piezoelectric actuator discharges more than usual, and in this case, the detected potential difference is at least equal to or greater than the first boundary value. That is, according to this method, not only the function error itself is identified, but also the error of this function can be evaluated.

  For this purpose, the development suggests that if the piezoelectric actuator potential difference is equal to or less than the first boundary value and equal to or less than the second boundary value, the load drop ( An error entry corresponding to (Lastabfall) is made and / or an action corresponding to a load drop is triggered. That is, different error causes can be distinguished by the method of the present invention. This is very advantageous in terms of the measures to be taken in case of an error.

  In this case, the premise of the present invention is that the current of the piezoelectric actuator does not flow when the piezoelectric actuator is driven and controlled when the load is reduced, so that the voltage of the buffer accumulator does not change or at least does not change greatly. is there. Therefore, the difference between the two potentials of the detected buffer storage (before or after the drive control of the piezoelectric actuator) is below this boundary value.

  The invention also relates to a computer program, which is an advantageous computer program for carrying out the above method when it is executed on a computer. It is particularly advantageous here if the computer program is stored in a storage device, for example a flash memory.

  The present invention is also directed to a control and / or adjustment device for operating an internal combustion engine. It is particularly advantageous here if the device comprises a storage device, in which the program according to claim 8 or 9 is stored.

  The invention further relates to an internal combustion engine, which includes a control and / or regulation device of the type described above.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, particularly advantageous embodiments of the invention will be described in detail with reference to the accompanying drawings. In this drawing,
FIG. 1 shows a schematic view of a fuel system having a plurality of injection valves configured according to the first embodiment,
FIG. 2 shows a partial cross-sectional view of one of the injection valves of FIG.
FIG. 3 shows a block diagram of a method for operating the fuel system of FIG.
FIG. 4 shows a flow diagram corresponding to the block diagram of FIG.
FIG. 5 shows a cross-sectional view of another embodiment of the injection valve.

DESCRIPTION OF THE EMBODIMENTS In FIG. 1, reference numeral 10 is attached to the whole fuel system. The fuel system includes a fuel tank 12, from which fuel is conveyed to a high pressure fuel pump 16 by an electric fuel pump 14. The high pressure fuel pump supplies fuel to a fuel storage line 18 (“rail” Rail), where the fuel is stored at a high pressure.

  A plurality of fuel injection valves 20 are connected to the fuel storage line 18. These directly inject fuel into the combustion chamber 22 of the internal combustion engine (not shown any further). The fuel injection valve is driven and controlled by a control and / or adjustment device 24.

  The structure of the fuel injection valve 20 is shown in FIG. According to this, the fuel injection valve 20 includes a casing 26 having a Sackloch-Stufenbohrung 28. A piezoelectric actuator 30 is disposed at the upper end of the piezoelectric actuator 30 and is connected to the piston 32. The piston 32 delimits the working chamber 34 of the hydraulic transducer. The piston 36 also forms part of this hydraulic transducer, which is connected to a spherical valve element 38. The piston 36 has a smaller diameter than the piston 32 and is closely guided in the casing.

  The valve element 38 cooperates with the upper valve seat 40 in FIG. 2 and the lower valve seat 42 in FIG. The valve seats 40 and 42 partition the space 44 in an area, and this space is connected to the control chamber 46 via a throttle (no reference numeral).

  The control chamber itself is connected to the fuel storage line 18 via a throttle (no reference sign) and a pressure line 47. The control chamber 46 is partitioned by a valve needle 48 downward in FIG. The channel 50 connects the fuel storage line 18 and a pressure chamber (not visible) provided in the lower end region of the valve needle 48.

The fuel injection valve 20 operates as follows. That is,
The piezoelectric actuator 30 can be charged and discharged again via a device described in more detail later. In the discharged state, the length of the piezoelectric actuator 30 is shorter than that in the charged state. The state having a relatively short length is hereinafter referred to as “short” for simplicity, and the state having the maximum length is hereinafter referred to as “long” for simplicity.

  When the piezoelectric actuator 30 is in a short or long state, the valve element 38 is seated on the valve seat 40 or the valve seat 42. In any case, the valve needle 48 is held in its closed position by the hydraulic pressure transmitted from the fuel storage line 18 to the control chamber 46 via the pressure line 47. Therefore, fuel does not exit from the fuel injection valve 20.

  However, when the piezoelectric actuator 30 is driven and controlled to move from its short position to its long position, or from its long position to its short position, the valve element 38 is neither at the valve seat 40 nor at the valve seat 42. As a result, a pressure drop occurs in the control chamber 46, and a pressure difference is finally generated between the upper end portion and the lower end portion of the valve needle 48. As a result, the valve needle of FIG. 2 moves up and opens a passage for fuel from channel 50. As a result, fuel can exit from the fuel injection valve 20 to the corresponding combustion chamber 22.

  The drive control of the piezoelectric actuator 30 is performed by an electronic circuit 52, and a few components of this electronic circuit are shown in FIG. The voltage source 54 supplies a direct current voltage, which is converted by the DC / DC converter 56 according to each request. The capacitor 58 is charged by the electric energy supplied from the DC / DC converter 56. This capacitor acts as a buffer accumulator for the electrical energy to be supplied to or taken from the piezoelectric actuator 30. The capacitor 58 and the piezoelectric actuator 30 can be connected via the charge switch 60 and the discharge switch 62. The charge stored in the capacitor 58 is detected by the measurement circuit 64.

  In the stationary state, both the charge switch 60 and the discharge switch 62 are open, so that no current flows between the piezoelectric actuator 30 and the buffer accumulator 58. In order to change the piezoelectric actuator 30 from its short state to its long state, the piezoelectric actuator must be charged. For this reason, the charge switch 60 is closed. The discharge switch 62 remains open. As a result, a current flows from the buffer capacitor 58 to the piezoelectric actuator 30. As soon as the piezoelectric actuator 30 reaches the desired final state, the charging switch 60 remains open again.

  In order to move the piezoelectric actuator 30 from a long position to a short position, the electric charge in the piezoelectric actuator 30 must be taken out again. For this purpose, the charge switch 30 is opened and the discharge switch 62 is closed. The charge accumulated in the piezoelectric actuator 30 is thereby returned to the capacitor 58.

  It will be apparent that the charge and discharge switches 62 described above are normally not temporarily closed during operation, but are temporarily closed and then reopened. At this time, the state of charge of the piezoelectric actuator 30 is detected, and in some cases, the charge switch 60 or the discharge switch 62 is temporarily closed once again. This process is repeated until the piezoelectric actuator 30 receives the desired charge or the charge is removed again. Details on this are given in EP 1 138 917 A1. This is clearly quoted here.

  In order to be able to monitor the drive control of the piezoelectric actuator 30, the method shown in FIGS. That is, the measurement circuit 64 detects the state of charge of the buffer capacitor 58 before drive control (reference numeral 66) and after drive control (reference numeral 68). Here, “driving control” is understood to mean the charging of the piezoelectric actuator 30 and the corresponding discharge of the buffer storage 58, or the discharging of the piezoelectric actuator 30 and the corresponding charging of the buffer storage 58. be able to. At reference numeral 70, a difference dU1 between the measured values before and after the drive control is formed.

  At reference numeral 72, the correction value is added to the difference dU1 determined at reference numeral 70. This correction value is determined based on the characteristic map 74. This characteristic map on the one hand stores the time between the two measurements (reference numerals 66 and 68) and on the other hand the current flowing out of the DC / DC converter into the buffer capacitor 58. Therefore, the potential difference dU2 obtained from the block 72 corresponds to the energy actually flowing from the buffer capacitor 58 to the piezoelectric actuator 30 or the energy flowing back from the piezoelectric actuator 30 to the buffer accumulator 58. That is, the following is considered by the characteristic map 74. That is, it is considered that the buffer capacitor 58 is recharged by the DC / DC converter 56 during the time between the potential detection of the buffer capacitor 58 before the drive control and the potential detection after the drive control.

  The potential difference dU2 is supplied to the first comparator 76, where the potential difference dU2 is compared with the upper threshold value. If the potential difference dU2 is greater than or equal to this upper threshold value, this means that more current is expected to flow out or flow in between the buffer capacitor 58 and the piezoelectric actuator 30 than in the normal case. This is a sign for a short circuit. This is because in this case, in addition to the normal charging current, further current flows through the corresponding short-circuit path. In this case, a corresponding error entry or action (for example, the drive control of individual cylinders or the entire system is shut off) is performed. Corresponding blocks in FIG.

  The potential difference dU2 is also supplied to the second comparator 80, where it is compared with the lower threshold. If the potential difference dU2 is below the lower threshold, this is a sign for a load drop. That is, in this case, when the piezoelectric actuator 30 is driven and controlled, current does not flow from the capacitor 58 to the piezoelectric actuator 30 or vice versa, that is, the voltage of the buffer capacitor 58 does not change, or at least does not change significantly. In this case, a corresponding error entry and a corresponding action are performed (block 82).

  FIG. 5 shows another embodiment of the injection valve. Here, elements and regions having the same function as the elements of the injection valve shown in FIG. 2 have the same reference numerals and are not described in detail again.

  Unlike the injection valve of FIG. 2, the injection valve of FIG. 5 is not a double type but a simple switching type. That is, the valve element 38 fits the valve seat 40 only at one switching position. As the valve element lifts from the valve seat 40, it blocks the fluidic bypass channel 84 between the high pressure region 47 and the cavity 44 (this condition is shown in FIG. 5). This reduces the pressure in the cavity 44 via the low pressure channel 88 and also reduces the pressure in the control chamber 46 via the throttle channel 86 so that a corresponding opening movement of the valve needle 48 takes place.

  When the valve element 38 is fitted to the valve seat 40 again, the connection between the void 44 and the low pressure region 88 is interrupted again and the bypass line 84 is opened again. This again increases the pressure in the cavity 44 to a high pressure level (region 47). The filling of the control chamber 46 to the high pressure level was relatively quickly placed by the throttle channel 86 between the cavity 44 and the control chamber 46 and fluidly between the high pressure region 47 and the control chamber 46. This is done by the throttle channel 90.

1 is a schematic view of a fuel system having a plurality of injection valves configured according to a first embodiment. It is the fragmentary sectional view which cut | disconnected one of the injection valves of FIG. FIG. 2 is a block diagram of a method for operating the fuel system of FIG. 1. 4 is a flowchart corresponding to the configuration diagram of FIG. 3. It is sectional drawing which cut another embodiment of the injection valve.

Claims (11)

The amount of fuel reaching the combustion chamber (22) depends on the drive control (67) of the piezoelectric actuator (30) of the injection valve (20), and the drive control energy (dU2) of the piezoelectric actuator is stored in the buffer accumulator (58). In a method of operating an internal combustion engine, supplied by
A potential difference (dU1) of the buffer accumulator (58) generated during the drive control (67) of the piezoelectric actuator (30) is at least occasionally determined at least roughly (70, 72);
Using the potential difference for comparison with at least one boundary value (76, 80),
A method of operating an internal combustion engine. Determining the electrical energy charged to the buffer accumulator during the time of determining the potential of the buffer accumulator (58);
Taking into account the electrical energy in determining the charge (dU2) actually exchanged between the piezoelectric actuator (30) and the buffer accumulator (58) (72);
The method of claim 1. The energy for charging the buffer accumulator (58) must be added to the detected potential difference (dU1) or subtracted from the potential difference (72),
The addition result (dU2) or the subtraction result is used for comparison (76, 80) with at least one boundary value.
The method of claim 2. Estimating the energy charged in the buffer accumulator (58) based on the characteristic map (74);
The time between the calculation of two potentials of the buffer accumulator (58) and the feeding current are stored in the characteristic map.
The method according to claim 2 or 3. Deactivating charging of the buffer accumulator to determine the potential difference of the buffer accumulator;
The method of claim 1. If the potential difference (dU2) of the piezoelectric actuator (30) is equal to or greater than the first boundary value, an error entry corresponding to a short circuit is made and / or a corresponding action is activated (78 ),
6. A method according to any one of claims 1-5. If the potential difference (dU2) of the piezoelectric actuator (30) is equal to or smaller than the first boundary value and equal to or smaller than the second boundary value, an error corresponding to a load drop Make an entry and / or activate the corresponding action (82),
The method of claim 6. In a computer program,
When the computer program is executed on a computer, it is advantageous to carry out the method according to any one of claims 1 to 7,
Computer program. The computer program is stored in a storage device such as a flash memory,
The computer program according to claim 8. In a control and / or regulating device (24) for operating an internal combustion engine,
The device includes a storage device;
The computer program according to claim 8 or 9 is stored in the storage device.
Control and / or regulation device for operating an internal combustion engine. In internal combustion engines,
Internal combustion engine comprising a control and / or regulation device (24) according to claim 10.

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