EP2173997B1 - Internal combustion engine having a plurality of cylinders - Google Patents

Abstract

Internal combustion engine having a plurality of cylinders which are combined to form at least two cylinder banks (B1, B2), wherein fuel can be injected by means of injectors (I1-I8) into combustion chambers of the cylinders, and wherein the injectors (I1-I8) are connected in each case to one of at least two high-pressure rails (R1, R2), wherein the injectors (I1-I8) of one cylinder bank (B1, B2) are connected to different high-pressure rails (R1, R2).

Description

State of the art

The present invention relates to an internal combustion engine having a plurality of cylinders, which are combined to form at least two cylinder banks, according to the preambles of the independent claims.

To reduce mechanical vibrations, a so-called unequal firing sequence is used, in particular in the case of V-engines. This means that the two cylinder banks do not alternate continuously with respect to the cylinder order. On the one hand, this results in two successive firings at a bank, on the other hand, there is a longer break at this bank when two consecutive firings take place at the second cylinder bank.

From the DE 197 12 135 For example, there is known a fuel injection system for an internal combustion engine which includes a number of fuel injectors fueled by a high pressure pump via a common supply line and high pressure lines leading to each of the fuel injectors. High-pressure accumulators are provided in the high-pressure lines. The diameter of the high-pressure lines leading from the common supply line to the high-pressure accumulators is dimensioned such that the spray quantity difference of the fuel injectors assumes a minimum.

Common rail systems are known for gasoline and diesel engines. In some applications, it makes sense, especially in diesel engines, to use two high-pressure pumps instead of one high-pressure pump, since, for example, the available pump capacity of a high-pressure pump alone is insufficient for the entire high-pressure quantity requirement. This is for example for smaller marine diesel engines the case derived from diesel engine series from the commercial vehicle sector. The ship's diesel engine has a higher specific power than the design for the commercial vehicle sector, so that the delivery of the high-pressure pump must be greater. In order to still be able to use commercially available components, in such a case in the prior art instead of a motor-wide common rail system with a high-pressure pump, a solution with two high-pressure pumps, each covering the high-pressure volume requirements of a cylinder bank used. Alternatively, the high-pressure quantity requirement of the two high-pressure rails or cylinder banks is covered by a common high-pressure pump, which has at least two hydraulically separate conveying elements, which are each hydraulically connected to a high-pressure rail. If an unequal ignition sequence is used in such an engine concept, this can lead to undesirably high pressure fluctuations in the two high-pressure trails.

Disclosure of the invention

An object of the invention is therefore to provide a device with which the pressure fluctuations in the individual high pressure rails can be reduced.

This problem is solved by an internal combustion engine having a plurality of cylinders, which are combined to form at least two cylinder banks, this can be in particular a V-engine, wherein fuel can be injected by means of injectors into combustion chambers of the cylinder and wherein the injectors each with one of at least two high-pressure trails are connected, wherein the injectors of a cylinder bank are connected to different high-pressure trails. Instead of a bank-wise assignment of the injectors to a high-pressure rail, the assignment of injectors of a cylinder bank to different high-pressure trails takes place.

The internal combustion engine comprises a first and a second cylinder bank and a first and second high-pressure rail, wherein some cylinders of the first cylinder bank with the first high-pressure rail and some cylinders of the first cylinder bank with the second high-pressure rail and some cylinders of the second cylinder bank with the first high-pressure rail and some cylinders second cylinder bank are connected to the second high-pressure rail. As a result, a uniform injection sequence of high-pressure trails is effected at an unequal firing order.

It is preferably provided that the high-pressure quantity requirement of the high-pressure rails is covered in each case by a separate high-pressure pump or by separate high-pressure elements of a high-pressure pump, which are each hydraulically connected to one of the high-pressure rails, wherein the high-pressure rails are hydraulically connected to one another. The hydraulic connection allows pressure equalization between the high pressure rails, reducing pressure fluctuations.

The hydraulic connection of the high-pressure rails preferably comprises a throttle. The restrictor limits the flow rate of the hydraulic connection and dampens hydraulic vibrations caused by changing pressure differences and thus changing directions of flow.

It is preferably provided that each of the high-pressure rails is pressurized by a high-pressure pump or by separate high-pressure elements of a high-pressure pump, which are hydraulically connected to one of the high-pressure rails, and the fuel pressure of a high-pressure rail is regulated and the fuel pressure of the other high-pressure rail is precontrolled. As a result, a chaotic behavior of the control, which can be caused by the hydraulic connection can be reduced or avoided.

Each of the high pressure rails is preferably pressurized by a high pressure pump or by separate high pressure elements of a high pressure pump hydraulically connected to one of the high pressure rails, and the fuel pressure of a high pressure rail is controlled by a regulator comprising at least a proportional and an integral portion the fuel pressure of the other high-pressure rails is regulated by means of a regulator comprising only a proportional and no integrating component. This variant also reduces or avoids the aforementioned chaotic behavior of the pressure control.

Brief description of the drawings

Fig. 1

eine Skizze einer Einspritzanlage einer Brennkraftmaschine;

Fig. 2

eine Skizze einer Einspritz- bzw. Zündreihenfolge des Beispiels gemäß Fig. 1;

Fig. 3

eine Prinzipskizze zur Verdeutlichung von Druckschwankungen des Drucks im Hochdruckrail ;

Fig. 4

eine Skizze eines Beispiels einer Regelung bzw. Steuerung;

Fig. 5

eine Skizze eines zweiten Beispiels einer Regelung;

Fig. 6

eine Skizze eines erfindungsgemäßen Ausführungsbeispiels einer Einspritzanlage einer Brennkraftmaschine.

Fig. 7

eine Skizze einer Einspritz- bzw. Zündreihenfolge des Ausführungsbeispiels gemäß Fig. 6.

Hereinafter, an embodiment of the present invention will be explained in more detail with reference to the accompanying drawings. Showing:

Fig. 1

a sketch of an injection system of an internal combustion engine;

Fig. 2

a sketch of an injection or firing order of the example according to Fig. 1 ;

Fig. 3

a schematic diagram to illustrate pressure fluctuations of the pressure in the high pressure rail;

Fig. 4

a sketch of an example of a controller or control;

Fig. 5

a sketch of a second example of a scheme;

Fig. 6

a sketch of an embodiment according to the invention an injection system of an internal combustion engine.

Fig. 7

a sketch of an injection or firing order of the embodiment according to Fig. 6 ,

Embodiments of the invention

Fig. 1 shows a sketch of an injection system of an internal combustion engine in a greatly simplified representation. Shown is a rough sketch of an injection system 1 of an eight-cylinder diesel engine. It is assumed here by an 8-cylinder internal combustion engine with a cylinder arrangement in V-shape, wherein the cylinders each form a row of cylinders a cylinder bank B1 and B2. The cylinders, pistons, exhaust valves and the like of the internal combustion engine are in the sketch of Fig. 1 not shown, the cylinders are referred only by the respective injectors, these are referred to here as I1 to I8. The injectors I1 to I4 belong to the first cylinder bank B1, the injectors I5 to I8 belong to the second cylinder bank B2. The injectors I1 to I8 each include an injection valve that can be electrically opened and closed by a piezoelectric or magnetic actuator. The electrical opening and closing of the injectors of the injectors I1 to I8 via control units, these are referred to here as S1 and S2, which electrically control the injectors I1-I8. The injectors I1 to I4 are controlled by the controller S1, the injectors I5 to I8 are controlled by the controller S2. The injectors are each connected to a known high-pressure rail R1 or R2. The injectors I1 to I4 are connected to the high-pressure rail R1, and the injectors I5 to I8 are connected to the high-pressure rail R2. The high-pressure rail R1 is acted upon by a high-pressure pump P1 with fuel pressure, the high-pressure rail R2 is acted upon by a high-pressure pump P2 with fuel pressure. The high-pressure pumps P1 and P2 can either be supplied with fuel by separate low-pressure pumps or by a common low-pressure pump. These and other elements of the fuel supply system such as filters, valves and the like are known per se for a common rail system and here not shown. Effectively, therefore, two independent common-rail injection systems are provided for each cylinder bank. One of the control units is operated as a master, the other as a slave. Alternatively, the control can also be done by a common control unit. The pressure in the high-pressure rail R1 is measured by a first pressure sensor RDS1 and transmitted to the control unit S1, according to the pressure in the high-pressure rail R2 is measured via a second pressure sensor RDS2 and transmitted to the control unit S2. The high-pressure rails R1 and R2 are hydraulically connected to each other with a connecting line 2. Within the connecting line 2, a throttle 3 is arranged. The choke can as shown in the illustration Fig. 1 may be a throttle valve with constant constriction, but may also be a throttle valve that is adjustable. In this case, there is an electromechanical adjustment, which is controlled for example by one of the control units S1 or S2 or an extra control.

In Fig. 2 is the firing order and thus the injection order of the 8-cylinder internal combustion engine according to Fig. 1 shown. The crankshaft angle φ is represented by φ = 0 ° CA to φ = 720 ° CA. The firing order is plotted over the crankshaft angle and plotted graphically one above the other for easier understanding. The firing order here is 1, 5, 7, 2, 6, 3, 4, 8. The bank-wise representation shows that, for example, the cylinders 5 and 7 of the cylinder bank B2 and the cylinders 3 and 4 of the cylinder bank B1 with a relatively short Ignite distance of 1 / n * 720 ° KW (n = number of cylinders) one after the other and thus inject one after the other with this short distance.

Fig. 3 shows a schematic diagram to illustrate pressure fluctuations of the high pressure rail pressure PR in the two high pressure rails R1 and R2, here the example of the high pressure rail R1. How out Fig. 2 can be seen, there is, for example, between the injection and thus ignition of the cylinders 1 and 2, a relatively long break of 2 / n * 720 ° KW (n = number of cylinders), whereas the immediately consecutive ignition and injection of the cylinders 3 and 4 only has a relatively short pause of 1 / n * 720 ° CA (n = number of cylinders) between two injections. If no further measures are taken, then these very different times between two injections result in that the uninterrupted promotion the high-pressure pump during a relatively long injection pause, for example, between the cylinders 1 and 2, a pressure increase takes place at a relatively short time between two injections such as between the injections of the cylinders 3 and 4, a pressure drop, indicated by a line PR, takes place. The connecting line 2 between the two high-pressure rails R1 and R2 now ensures that the pressure fluctuations of the two high-pressure rails R1 and R2 are smoothed. Occurring pressure oscillations by reciprocating fuel are reduced by the throttle 3.

Due to the hydraulic connection between the high pressure rails R1 and R2, there is a mutual influence of the previously independent high pressure rail pressure control loops, which can unpredictable, even chaotic behavior, can result. This behavior can be countered by two different measures:

Firstly, one of the high-pressure pumps in an open loop (ie, a controller) can be controlled, the other high pressure pump is still controlled by a closed loop. The control of the high pressure pump controlled by an open loop is stored in a pilot control map in the control unit. Fig. 4 shows a sketch of such a scheme or control. In the upper area of the Fig. 4 the control circuit for the high-pressure rail R1 is shown, this includes a regulator RG1, whose output provides a control variable for the high-pressure pump P1. At the output of the high pressure pump P1 is the high pressure rail pressure PR1, which is measured by a pressure sensor RDS1 and is connected as an electrical signal to a the input of the regulator RG1 upstream subtractor with negative characters. At the other input of the subtractor, the setpoint rail pressure P1_S is applied as the reference variable with a positive sign. In this respect, this is a classic control loop. The high-pressure rail R2 does not include any control but is controlled on the basis of the desired value PR2_S of the high-pressure rail pressure via a controller S2, which determines a control variable for the high-pressure pump P2 on the basis of a characteristic diagram.

Alternatively, the high pressure rail pressures PR1 and PR2 of both high pressure rails R1 and R2 may be controlled as in FIG Fig. 5 shown. Both control circuits are therefore structured as the control circuit for the high pressure rail R1 in Fig. 4 , The controller RG1 in Fig. 5 for the high pressure rail R1 is a regulator with a proportional component and an integrating component, thus a PI controller. The regulator for the high pressure rail R2, in Fig. 5 referred to as RG 2, has only a proportional share, so it is a pure P-controller. The proportional component can react dynamically to existing system deviations in the short term. The integrating component responds with a time delay even to small deviations from the setpoint.

Fig. 6 shows an inventive embodiment of an injection system for an internal combustion engine having a plurality of cylinders. The presentation essentially corresponds to the representation in Fig. 1 , Accordingly, the designation of identical modules is the same. In contrast to the embodiment according to Fig. 1 Here is dispensed with the hydraulic connection between the two high-pressure rails R1 and R2. Instead, the assignment of high-pressure rail R1 to cylinder bank B1 and high-pressure rail R2 to cylinder bank B2 is canceled. The injectors of the cylinder bank 1, which are the injectors I1, I2, I3 and I4 are no longer associated with the high-pressure rail R1, instead, in the specific example of the ignition sequence 1, 5, 7, 2, 6, 3, 4, 8 mentioned above the injectors I1 and I4 assigned to the high-pressure rail R1, the injectors I2 and I3 are assigned to the high-pressure rail R2. Correspondingly, the injectors I5 and I8 of the second cylinder bank B2 are assigned to the high-pressure rail R2, the injectors I6 and I7 of the second cylinder bank B2 are assigned to the high-pressure rail R1. An alternative, likewise unequal ignition sequence can be counteracted by an alternative, suitable assignment of the injectors to the high-pressure rails R1 and R2 in the sense of the invention. Fig. 7 shows the injection order according to the representation of Fig. 2 , While in Fig. 2 the assignment between high pressure rail R1 and cylinder bank B1 and high pressure rail R2 and cylinder bank B2 is identical, this is in Fig. 7 not identical, instead, reference is made here only to the high-pressure rails R1 and R2. The high-pressure rail R1, the cylinders 1, 4, 6, 7 associated with the high-pressure rail R2, the cylinders 2, 3, 5 and 8 are assigned. How out Fig. 7 can be seen, the ignitions and thus the injections are each assigned alternately the high-pressure rails R1 and R2, so that here no different pause times between successive injections as in the embodiment according to Fig. 1 the case was, occurs.

Claims (4)

1. Internal combustion engine having a plurality of cylinders which are grouped to form at least two cylinder banks (B1, B2), wherein fuel can be injected by means of injectors (I1 - 18) into combustion chambers of the cylinders, and wherein the injectors (I1 - 18) are connected in each case to one of at least two high-pressure rails (R1, R2), and the injectors (I1 - I8) of one cylinder bank (B1, B2) are connected to different high-pressure rails (R1, R2), characterized in that the internal combustion engine comprises a first cylinder bank (B1) and a second cylinder bank (B2) and a first high-pressure rail (R1) and a second high-pressure rail (R2), wherein some cylinders of the first cylinder bank (B1) are connected to the first high-pressure rail (R1) and some cylinders of the first cylinder bank (B1) are connected to the second high-pressure rail (R2), and some cylinders of the second cylinder bank (B2) are connected to the first high-pressure rail (R1) and some cylinders of the second cylinder bank (B2) are connected to the second high-pressure rail (R2).
2. Internal combustion engine according to Claim 1, characterized in that the high-pressure demand of the at least two high-pressure rails (R1, R2) is covered in each case by a dedicated high-pressure pump.
3. Internal combustion engine according to one of the preceding claims, characterized in that each of the high-pressure rails (R1, R2) is charged with fuel pressure by one high-pressure pump (P1, P2) or by separate high-pressure elements of one high-pressure pump which are hydraulically connected to in each case one of the high-pressure rails, and the fuel pressure of one high-pressure rail is regulated and the fuel pressure of the other high-pressure rail is pilot-controlled.
4. Internal combustion engine according to one of the preceding claims, characterized in that each of the high-pressure rails (R1, R2) is charged with fuel pressure by a high-pressure pump (P1, P2), and the fuel pressure of one high-pressure rail is regulated by means of a regulator which comprises at least one proportional component and one integral component, and the fuel pressure of the other high-pressure rail is regulated by means of a regulator which comprises only a proportional component and no integral component.

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