DE102005005547A1 - Control for pump jet unit in involves setting the injection parameters, closing the first control valve and opening second control valve - Google Patents

Abstract

The pump jet unit control process is for an engine with a pump element (1), an injection jet (7), first control valve (27), and second control valve (31) between the pump element and a fuel return line (25). The injection parameters are opening pressure, injection start and/or injection duration. The first control valve is closed before injection begins to enable the required injection pressure to build up. The second control valve is opened at beginning of injection, and closed at end of injection.

Description

The The invention relates to a method for driving a pump-nozzle unit or a pump-line-nozzle unit an internal combustion engine, with a pump element, with an injection nozzle, with a first control valve, wherein with the first control valve a hydraulic connection between a fuel inlet on the one hand and the pump element and the injector on the other hand and arranged with an intermediate pump element and a fuel return second control valve.

in the In the context of the invention, the following will be referred to only as the unit injector (PDE). spoken, although always a pump-line-nozzle unit (PLDE) is meant. The main difference between a PDE fuel injection system and A PLDE fuel injection system is that with a PDE the pump element and the associated injector in the immediate spatial Close to each other are arranged while in a PLDE between the pump element and the hinspritzdüse a spatial Distance may be present, which is bridged by a high pressure line.

at the method according to the invention is envisaged that in a first step, the required Injection parameters, in particular opening pressure, start of injection and injection duration, an injection depending on the operating point the internal combustion engine are determined that in a second step closed the first control valve before the start of the injection is, so that until the beginning of the injection, the desired opening pressure builds that in a further step, the second control valve opened at the beginning of the injection will, and that eventually the second control valve closed to complete the injection becomes.

Advantages of invention

By the closing of the first control valve, the buildup of pressure in the PDE begins during the delivery stroke the piston of the pump element. As the pump elements usually driven by a cam, in turn, directly to the crankshaft the internal combustion engine is coupled, depends on the pressure build-up in the PDE among other things from the speed of the internal combustion engine, but also from the crank angle to which the first control valve is closed will, off. The latter connection is justified by the fact that the speed at which the piston moves in the pump element directly depends on the shape of the cam.

Under consideration these relationships and knowing the hydraulic behavior of the PDE can increase the pressure in the pump element and in the injector after closing the first Control valve are calculated.

If now the second control valve is opened, the pressure in the control chamber of the pump-nozzle unit drops, so that the injection nozzle opens and the injection begins. The opening pressure corresponds to the pressure, the after closing the first control valve and before the opening of the second control valve in the PDE.

In In other words, the bigger the one Time interval between closing the first control valve and the opening of the second control valve is, the bigger it is the opening pressure, the for the injection available stands. Since the pressure increase in the PDE after closing the first control valve also depends on the speed of the internal combustion engine can this relation also in degrees crank angles of the crankshaft or camshaft which drives the PDE. Which one preference given to the aforementioned types of representation in individual cases is easy to decide by a professional.

By the closing of the second control valve, the pressure in the control chamber of the injection nozzle increases again so that the injector is closed. In other words, by opening and closing the second control valve, the injection duration is set, while the time interval between the closing of the first control valve and opening the second control valve, the opening pressure is determined. This means that by the method according to the invention for driving a pump-nozzle unit both the opening pressure as well as the injection duration independently with high Accuracy and flexibility can be controlled. these can be used to ensure good emission and consumption behavior an internal combustion engine, according to the inventive method is accessed. The complex relationships between Speed, operating point of the internal combustion engine, load request and more, are advantageously stored in maps, so that in a simple way by accessing these maps of the right time to close of the first control valve and to open the second control valve can be determined. The same applies, of course for the Shut down the second control valve.

The inventive method can both for a main injection and / or a pilot injection and / or at least a post-injection can be used.

Thereby Is it possible, the opening pressure both the pilot injections, the main injection as well as the post injections independently to choose from each other within a combustion cycle.

In Advantageous development of the method according to the invention can also be provided be that the main injection divided into several sub-injections and that the first control valve before the first partial injection is closed and that the first control valve after completion of the last partial injection opened becomes. This means nothing else than that the number of drive operations for the first Control valve is reduced and also the partial injections a main injection to an adjustable pressure level.

In Further development of the method according to the invention becomes the completion of each pilot injection, each main injection, Each partial injection and each post-injection closed the second control valve.

As already mentioned, is the time interval between the closing of the first control valve and opening of the second control valve used to the desired opening pressure adjust.

alternative to the method described above, the second control valve be controlled before the first control valve. In this case No pressure is built up in the control room and only the force is effective the closing spring on the nozzle needle. In this operating mode opens the injector only when the first control valve has been closed and the pressure in the pump element, the closing force exceeds the closing spring. In this mode, the minimum opening pressure is reached. These Mode is particularly advantageous at low speeds to a cheap one noise to reach.

Further Advantages and advantageous embodiment of the invention are the following Drawing, the description and the claims can be removed. All features disclosed in the drawings, the description and the claims can be essential to the invention both individually and in any combination.

drawings

It demonstrate:

1 a schematic representation of a pump-nozzle unit;

2 the time course of an injection cycle; and

3 a section from 2 ,

description the embodiments

In 1 a pump-nozzle unit (PDE) according to the invention is shown schematically. A pump element 1 has a delivery room 3 on, its volume through an oscillating pump piston 5 periodically reduced and enlarged. An injector 7 consists inter alia of a housing 9 with a pressure room 11 , In the case 9 is a nozzle needle 13 taken up by a closing spring 15 against a nozzle needle seat 17 is pressed and so the injector 7 closes.

Above the nozzle needle 13 is a tax room 19 arranged by a control piston 21 is limited. The control piston 21 Can be integral with the nozzle needle 13 be formed or formed as a separate component. The force on the face of the control piston 21 and from the closing spring 15 on the nozzle needle 13 applied force n is greater than that in the opening direction of the pressure chamber 11 on the nozzle needle 13 acting force when the pressure in the pressure chamber 11 and in the control room 19 are the same size.

About high pressure lines 23 are the pump element 1 as well as the pressure room 11 and the control room 19 the injector 7 connected.

Between a fuel feed 25 and the high pressure line 23 is a first control valve 27 intended.

Between a fuel return 29 and the control room 19 is a second control valve 31 arranged. The first control valve 27 and the second control valve 31 can be operated via an unillustrated control unit.

In the high pressure line 23 which the control room 19 with the delivery room 3 of the pump element 1 connects, is an inlet throttle 33 while in the line between the control room 19 and the second control valve 31 an outlet throttle 35 is provided. The PDE according to the invention works as follows:
The second control valve 31 is normally closed.

During a delivery stroke of the pump piston 5 that is, when the volume of the delivery chamber 3 by the movement of the pump piston 5 reduced, finds no pressure build-up in the pressure room 11 and in the control room 19 instead, as long as the first control valve 27 is open. Once the first control valve 27 is closed and the second control valve 31 remains closed, builds in the pressure room 11 and in the control room 19 a pressure on.

Since the on the front side of the control piston 21 acting hydraulic force is greater than that on the pressure shoulder of the nozzle needle 13 from the one in the pressure room 11 force present fuel remains in this switching position, the nozzle needle 13 on the nozzle needle seat 17 and as a result the injector 7 closed.

If now the second control valve 31 is opened, finds a pressure reduction in the control room 19 instead, because the outlet throttle 33 the rapid subsequent flow of fuel from the pumping chamber 3 limited. On the other hand, the outlet throttle 35 so dimensioned that the fuel from the control room 19 fast enough into the fuel return 29 can drain and so a pressure reduction in the control room 19 takes place. As soon as the on the nozzle needle 13 in the opening direction acting hydraulic force, that in the pressure chamber 11 Exists fuel is greater than that of the control piston acting from that in the control room 19 force applied fuel, opens the nozzle needle 13 and the injection starts. The pressure in the pressure room 11 and in the control room 19 rises after closing the first control valve 27 always on. This means that only when the second control valve 31 is opened, no further pressure build-up takes place and it is injected fuel into the combustion chamber of the internal combustion engine, not shown. The time interval between the closing of the first control valve 27 and the opening of the second control valve can thus be used to control the opening pressure.

In 2 Several diagrams are shown above each other. In the top diagram is the energization of the first control valve 27 Plotted over time, while in the diagram below the energization of the second control valve 31 is shown. Below these are the pressure cycles DZ1, DZ2 and DZ3. A printing cycle begins as soon as a pressure build-up in the pressure chamber 11 and in the control room 19 takes place.

In the line below the injection durations are shown. The in 2 illustrated injection cycle is divided into three pressure cycles, namely a first pressure cycle DZ1, a second pressure cycle DZ2, consisting of a plurality of partial injections, and a third pressure cycle DZ3.

The partial injections TE _ji taking place in the pressure cycles are indicated as follows: The first index "j" corresponds to the number of the pressure cycle within which the partial injection takes place The second index "i" corresponds to the number of partial injection within a pressure cycle. For example, the first partial injection in the second pressure cycle is labeled TE ₂₁ .

At a time t ₁ , the first control valve 27 energized and as a result, the pressure build-up in the pressure chamber begins 11 and in the control room 19 , At a time t ₂ , the second control valve 31 driven. At time t ₃ is the second control valve 31 opened, so that the injection begins. The time interval .DELTA.t _1.3 is a measure of how much time for the pressure build-up in the pressure chamber 11 and in the control room 19 is available. This means nothing else than that by a suitable time-delayed control of initially the first control valve 27 and on the second control valve 31 the opening pressure can be controlled.

At time t ₄ , the second control valve 31 closed again and the injection finished. The first pressure cycle DZ1 begins at time t ₂ and ends between t ₄ and t ₅ when the first control valve 27 is again de-energized.

At time t ₅ , the first control valve 27 closed again and it begins again a pressure build-up in the pressure chamber 11 and in the control room 19 , In 2 is the beginning of the energization of the first control valve 27 denoted by t ₅ .

At time t ₆ , the second control valve 31 energized again so that it is open at time t ₇ . This means that at time t _7, the first partial injection TE _{21 of} the second pressure cycle DZ2 begins. At time t ₈ , the second control valve 31 closed, so that the partial injection TE _{21 is} terminated. This process is repeated two more times during the second pressure cycle, so that the second pressure cycle DZ2 in total consists of the partial injections TE ₂₁ , TE ₂₂ and TE ₂₃ . In the case of the third printing cycle DZ3, the same process is repeated in principle as in the first printing cycle DZ1.

In 3 the second print cycle DZ2 is slightly enlarged and shown in more detail. In this case, the time t ₅ is entered so that at this time, the first control valve 27 closed is.

In principle, however, it is possible both to start the activation of the first control valve 27 and the second control valve 31 taking into account the switching times of these valves to calculate or directly calculate the time at which the first control valve 27 and the second control valve 31 has reached its switching positions.

In connection with the second print cycle lus DZ2 is advised that the first control valve 27 is closed only once, so that during the entire injection cycle, consisting of the first pressure cycle DZ1, second pressure cycle DZ2 and third pressure cycle DZ3, the first control valve 27 only three times closed and opened, while the second control valve 31 a total of five times open and closed.

The partial injections of a pressure cycle are coupled together. Thus, for example, in the second pressure cycle DZ2 for a partial injection TE _2i the delivery start and the opening pressure can be specified, while in the other partial injections only one parameter is freely selectable. In the illustrated example, the partial injection TE _{22 has} the highest priority, since it provides the largest contribution to the torque generation. As a result, the delivery start and the opening pressure are specified in this partial injection. For the partial injections TE ₂₁ and TE ₂₃ either the start of delivery or the opening pressure are prioritized. If the opening pressure is to be prioritized for these partial injections, then this can be done by the appropriate choice of the distance to partial injection TE ₂₂ .

Claims (12)

Method for controlling a pump-nozzle unit (PDE) or a pump-line-nozzle unit (PLDE) of an internal combustion engine with a pump element ( 1 ), with an injection nozzle ( 7 ), with a first control valve ( 27 ) and with an between pump element ( 1 ) and a fuel return ( 25 ) arranged second control valve ( 31 ) characterized by the following method steps: - determining injection parameters, in particular opening pressure, start of injection and / or injection duration; an injection in dependence on the operating point of the internal combustion engine, - closing the first control valve ( 27 ) before the beginning of the injection, so that the desired opening pressure is built up until the beginning of the injection (DZ1, DZ2, DZ3), - opening of the second control valve ( 31 ) at the beginning of the injection (DZ1, DZ2, TE, DZ3) and closing the second control valve ( 31 ) to complete the injection. Method according to claim 1, characterized in that that the injection includes several pressure cycles ((DZ1, DZ2, DZ3).). Method according to one of claims 1 or 2, characterized in that the pressure cycles (DZ1, DZ2, DZ3) a plurality of partial injections (TE _ji ) have, and that the first control valve ( 27 ) is closed before the first partial _injection (TE _j1 ), and that the first control valve ( 27 ) is opened after completion of the last partial injection. Method according to one of the preceding claims, characterized in that at the beginning of each partial injection (TE _ji ) the second control valve ( 31 ) is opened. Method according to one of the preceding claims, characterized in that for the termination of each partial injection (TE _ji ) the second control valve ( 31 ) is closed. Method according to one of the preceding claims, characterized in that the time interval between the closing of the first control valve ( 27 ) and the opening of the second control valve ( 31 ) is selected so that the desired opening pressure is established. Method according to one of claims 3 to 6, characterized in that for a partial injection (TE ₂₂ ) the start of delivery and the opening pressure are freely selected and for the other partial injections (TE ₂₁ , TE ₂₃ ) the start of delivery or the opening pressure is chosen freely. A method according to claim 7, characterized in that for another partial injection (TE ₂₁ , TE ₂₃ ), the opening pressure by the distance to the partial injection (TE ₂₂ ) are freely selected at the start of delivery and opening pressure is set. Method according to one of claims 1 or 2, characterized in that the second control valve ( 31 ) is opened before the first control valve ( 27 ) is closed. Computer program, characterized in that it works according to one of the preceding methods. Computer program according to claim 11, characterized that it can be stored on a storage medium. control unit for controlling a fuel injection system of an internal combustion engine, characterized in that it according to one of the methods of the claims 1 to 9 works.