WO2019081116A1

WO2019081116A1 - Injector

Info

Publication number: WO2019081116A1
Application number: PCT/EP2018/074297
Authority: WO
Inventors: Dietmar Uhlmann; Benedikt Leibssle
Original assignee: Robert Bosch Gmbh
Priority date: 2017-10-23
Filing date: 2018-09-10
Publication date: 2019-05-02
Also published as: DE102017218869A1; DE112018003404A5; CN111263854A

Abstract

The invention relates to an injector (1) for dosing a liquid and a gaseous fuel, with an injector body (2) in which an outer nozzle needle (4) is arranged so as to be longitudinally movable, the outer nozzle needle (4) opening and closing at least one injection opening (10) by means of its axial movement so as to dose a gaseous fuel. The outer nozzle needle (4) is guided in a guide portion (30) of a guide bore (3) of the injector body (2), with a throttle gap (28) remaining between the guide portion (30) and the guide bore (3). A longitudinal bore (5) is also formed in the outer nozzle needle (4) and can be filled with fuel under an injection pressure. A longitudinally movable inner nozzle needle (6) is arranged in the longitudinal bore (5). The inner nozzle needle (6) cooperates with an inner nozzle seat (16) in order to open and close at least one injection opening (17). A gas chamber (12) is formed in the injector body (2), which gas chamber can be filled with gaseous fuel under an injection pressure and surrounds the outer nozzle needle (4) adjacently to the guide bore (3). The throttle gap (28) opens out into the gas chamber (12). In addition, a pressure chamber (33) is formed in the injector body (2) and can be filled with liquid fuel via a fluid channel (20). The pressure chamber (33) is arranged here adjacently to the throttle gap (28) by means of a wall (34).

Description

description

title

injector

The invention relates to an injector for metering a liquid and a gaseous fuel into a combustion chamber of an internal combustion engine according to the preamble of claim 1.

State of the art

From DE 10 2014 225 167 A1 an injector is known, with both liquid and gaseous fuel in a combustion chamber of a

Internal combustion engine can be metered. The injector has an outer nozzle needle which cooperates with an outer nozzle seat for opening and closing of injection openings. Furthermore, the injector has an inner nozzle needle which cooperates with an inner sealing seat for opening and closing of injection openings. The inner nozzle needle is received in the outer nozzle needle. Liquid and gaseous fuel can be metered independently of each other into the combustion chamber of the internal combustion engine. The outer nozzle needle is guided in a longitudinal bore of the injector body, so that a throttle gap is formed between the outer nozzle needle and the longitudinal bore. This is necessary to ensure a longitudinal movement of the outer nozzle needle. In this case, the throttle gap opens at one end in the gas-filled pressure chamber and at the other end it is exposed to the pressure of the liquid fuel, since the liquid fuel through the outer

Nozzle needle must be passed through, in which the inner nozzle needle is arranged. This creates a connection between the gaseous and the liquid fuel via the throttle gap. As long as both fuels with approximately the same pressure in the injector pending, there is virtually no flow over the throttle gap, so that a mixture of the two

Fuels are not taking place. Only a minor mixing is irrelevant for the operation of the injector in most cases. _Λ

However, if an operation of the injector with only liquid fuel desired, the liquid fuel can penetrate through the throttle gap in the pressure space of the gaseous fuel, since the necessary back pressure for the liquid fuel is no longer present. By filling this

Pressure chamber with liquid fuel can lead to uncontrolled combustion in the combustion chamber when the gas injection is restarted and, in addition, to engine damage or the emission of pollutants. Advantages of the invention

In contrast, the injector according to the invention has the advantage that operation of the injector with exclusively liquid fuel is possible even over a relatively long period of time without any difficulty in restarting the gas injection.

In this case, the injector for dosing a liquid and a gaseous fuel to an injector, in which an outer nozzle needle

is arranged longitudinally movable. The outer nozzle needle opens and closes by its axial movement at least one injection port for metering a gaseous fuel and is in a guide portion of a

Guide bore of the injector body is guided. Furthermore, a throttle gap remains between the guide portion and the guide bore. In the outer nozzle needle, a longitudinal bore is formed, which can be filled with fuel under an injection pressure and in which an inner nozzle needle is arranged longitudinally movable. The inner nozzle needle cooperates with an inner nozzle seat for opening and closing at least one injection opening. In addition, a gas space is formed in the injector, which can be filled with gaseous fuel under a Eindüsdruck and surrounding the outer nozzle needle adjacent to the guide bore. The

Throttling gap opens into the gas space. In addition, a pressure chamber is formed in the injector, which is filled via a fluid channel with liquid fuel and which is adjacent to a wall of the throttle gap.

Through the throttle gap is an inevitable connection between the gas-filled gas space and the liquid fuel within the injector "

given. If, for example, a pressure gradient arises from the area filled with liquid fuel into the gas space, liquid fuel enters the gas space filled with gas. As a result, the throttle gap is additional

widened. By forming a pressure chamber in the injector body, this expansion can be prevented. The pressure chamber also fills with liquid fuel via the at least one inlet opening, which reduces the throttle gap and thus minimizes mixing of liquid and gaseous fuel.

In a first advantageous development of the invention, it is provided that the wall of the pressure chamber is elastically deformable by the pressure of the liquid fuel. Advantageously, the expansion of the wall of the pressure chamber in the direction of the outer nozzle needle completely closes the throttle gap at maximum injection pressure in the longitudinal bore and at ambient pressure in the gas space and fixes the outer nozzle needle by means of the wall in the guide bore. Thus, the connection, namely the throttle gap, between the liquid and the gaseous fuel is completely closed, so that the gas space is completely sealed even with prolonged operation with only liquid fuel. In addition, a fixation of the outer nozzle needle in the simple manner

Guide bore possible, the inner nozzle needle can be continued without problems. Thus, the operation of the injector for metering liquid fuel can be kept intact without major design changes, even if the gas pressure of the gaseous fuel unexpectedly collapses.

In a further embodiment of the invention, it is advantageously provided that the pressure chamber is toroidal and is advantageously produced by means of additive manufacturing in the injector body. Thus, in a simple constructive manner, the wall of the pressure chamber influence the size of the

Take throttle gaps and influence these.

In an advantageous embodiment, it is provided that the injector body is formed as a hollow cylinder and at the periphery of a uniform number of inlet openings of the pressure chamber is arranged. Thus, a uniform filling and emptying of the pressure chamber can be achieved with liquid fuel. In a further advantageous embodiment, the pressure chamber is formed with respect to the axial extent of the throttle gap in the injector body in one of the at least one Eindüsöffnung opposite region of the throttle gap. Thus, the entry of the liquid fuel immediately after entering the

Throttle gap can be minimized.

In an advantageous embodiment, it is provided that the outer nozzle needle, with its end remote from the at least one injection opening, delimits an outer control space which can be filled with liquid fuel so that a hydraulic closing force can be exerted on the outer nozzle needle in the axial direction. Thus, the closing force is hydraulically controllable in a known and simple manner and so the longitudinal movement of the outer nozzle needle. In the same way advantageously limits the inner nozzle needle with its at least one injection opening facing away from an inner end

Control chamber, which can be filled with liquid fuel, so that a hydraulic closing force on the inner nozzle needle is exercisable.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings.

These show in:

Fig. 1 is a schematic representation of an injector according to the invention for metering a liquid and a gaseous fuel in

Longitudinal section

2 shows an enlarged detail of the injector according to the invention from FIG. 1 in the region I in longitudinal section, FIG.

Fig. 3a shows an enlarged detail II of FIG. 2 before the filling of

Pressure chamber with liquid fuel in longitudinal section,

FIG. 3b shows the enlarged detail II from FIG. 2 in longitudinal section after the filling of the pressure chamber with liquid fuel in longitudinal section, FIG. an enlarged section of the injector according to the invention of FIG. 2 in area III in longitudinal section.

Elements with the same function are in the figures with the same

Reference numbers provided.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT FIG. 1 shows a longitudinal section of an injector 1 according to the invention, wherein only the essential regions of the injector 1 are shown. The injector 1 finds

Application in a combustion chamber of an internal combustion engine for the operation of two different fuels, on the one hand liquid fuel, preferably diesel, and on the other hand gaseous fuel, which are alternately or additive fed into the combustion chamber of the internal combustion engine.

The injector 1 has an injector body 2 with a valve seat body 9, wherein a guide bore 3 is formed in the injector body 2. In this guide bore 3, a piston-shaped outer nozzle needle 4 is arranged longitudinally movable. The outer nozzle needle 4 is in a guide portion 30 in the

Guided bore 3, wherein in this guide section 30 a

Throttle gap 28 is formed. Furthermore, the outer nozzle needle 4 has an outer nozzle needle tip 7, which is arranged with an outer nozzle seat 8 for opening and closing several in the valve seat body 9

Eindüsöffnungen 10 cooperates. The injector 2 limits together with an opposite end of the injection openings 10 36 of the outer nozzle needle 4 to an outer control chamber 25, in which an outer

Nozzle needle spring 1 1 is arranged. This outer nozzle needle spring 1 1 acts on the outer nozzle needle 4 with a force in the direction of the outer nozzle seat eighth

The outer nozzle needle 4 has a substantially cylindrical

Longitudinal bore 5, in which a piston-shaped inner nozzle needle. 6

is arranged longitudinally movable. With an inner nozzle needle tip 15, the inner nozzle needle 6 acts on a formed on the outer nozzle needle 4 inner

Nozzle seat 16 for opening and closing a plurality of injection openings 17 together. The injection openings 17 are downstream of the inner "

Nozzle seat 16 also formed in the outer nozzle needle 4. The injector 2 limits together with an injection openings 10 opposite end 37 of the inner nozzle needle 6 an inner

Control chamber 35 in which an inner nozzle needle spring 18 is arranged. The inner nozzle needle spring 18 acts on the inner nozzle needle 6 with a force in the direction of the injection openings 17.

In the injector body 2, a gas space 12 is formed, which can be filled via a gas channel 13 formed obliquely in the valve body 2 by means of a gas line 14 with gaseous fuel. Furthermore limits the longitudinal bore

5 in the outer nozzle needle 4 an inner pressure chamber 19. This inner pressure chamber 19 is connected via a formed in the outer nozzle needle 4 and the injector body 2 transverse bore 38 with a fluid passage 20. The fluid channel 20 is connected to a fluid line 21, so that the inner

Pressure chamber 19 can be filled with liquid fuel.

The injector 1 further comprises two independently controllable valve elements 22a, 22b, which comprise, for example, electromagnetic, hydraulic or mechanical actuators 23a, 23b. The first valve element 22a is connected to the fluid line by means of a first control line 24a

21 and the outer control chamber 25 connected. The second valve element 22b is connected to the fluid line 21 and the inner control chamber 35 by means of a second control line 24b. The second control line 24b is via a further in the outer nozzle needle 4 and the injector body. 2

trained transverse bore 39 connected to the fluid line 21. In the first

Control line 24a, a first control line throttle 27a and a second control line throttle 27b are also arranged, which limit the inflow of liquid fuel in the control lines 24a, 24b or prevent mutual interference of the control function by the two valve elements 42a, 42b. The two valve elements 42a, 22b are to that with a

Return line 26 connected.

Furthermore, a toroidal pressure chamber 33 is formed in the injector body 2, which is connected via at least one inlet opening 32 with the transverse bore 38. The pressure chamber 33 has an elastic deformable wall 34 with a rim facing the throttle gap 28. _

FIG. 2 shows an enlarged detail of the injector 1 according to the invention from FIG. 1 in the region I in longitudinal section. The pressure chamber 33 is arranged in a region A which is located in an upper region of the throttle gap 28 facing the valve elements 22a, 22b.

The operation of the injector 1 is as follows:

Fig. 1 shows the injector 1 in a closed position. The valve elements 22a, 22b with their actuators 23a, 23b are closed, so that due to the supply of liquid fuel from the fluid line 21 in the control lines 24a, 24b, a high fuel pressure prevails on liquid fuel. The inner nozzle seat 16 and the outer nozzle seat 8 are each closed so that no liquid fuel or gaseous fuel can escape via the injection openings 17 or the injection openings 10 into the combustion chamber of the internal combustion engine.

When the first actuating device 23a of the first valve element 22a is actuated, liquid fuel can escape from the outer control chamber 25 via the first control line 24a and the valve element 22a into the return line 26. Thus, the hydraulic pressure in the outer control chamber 25 is reduced to the outer nozzle needle 4, so that the outer nozzle needle 4 moves against the force of the outer nozzle needle spring 1 1 in the direction of the first valve element 22a. The outer nozzle needle tip 7 lifts off from the outer nozzle seat 8 and releases the injection openings 10, so that gaseous fuel from the gas space 12 into the combustion chamber of the

Internal combustion engine can occur. In the same way, the second nozzle needle 6 can be controlled so that the inner nozzle seat 16 is released and liquid fuel from the inner pressure chamber over the

Injection openings 17 can be injected into the combustion chamber of the internal combustion engine. Depending on the control of the first valve element 22a and the second valve element 22b so the fuel pressure and thus the hydraulic closing force both in the inner control chamber 35 and in the outer control chamber 25 can be adjusted, the pressure in both control chambers 25, 35 independently adjustable is.

Typically, such injectors are operated by first introducing a firing amount of liquid fuel into a combustion chamber "

and then a larger amount of gaseous fuel, which provides most of the energy. Upon actuation of the first valve element 22a, the fuel pressure in the inner control chamber 35 is lowered, so that the inner nozzle needle 6 lifts against the closing force of the inner nozzle needle spring 18 in the axial direction of the inner nozzle seat 16 due to the lowered fuel pressure in the inner control chamber 35 and releases it. Thus, liquid fuel enters the combustion chamber from the injection openings 17. By pressing the first valve element 22a again, the inner nozzle needle 4 closes the injection openings 17 again. At the same time or with a short time interval, the second valve element 22b is actuated, so that the

Fuel pressure in the outer control chamber 25 decreases. In the same way as before, the outer nozzle needle 4 releases the outer nozzle seat 8. Thus, gaseous fuel can escape from the injection openings 10. This is ignited by the previously ignited liquid fuel quantity, so that combustion takes place in the combustion chamber. To end the injection process, the second

Valve element 22b operated again.

Between the transverse bore 38 and thus the fluid channel 20 and the gas space 12 is given via the throttle gap 28 on the guide portion 30 a connection. Thus, in principle, a connection between the transverse bore 38 filled with liquid fuel and the gas space 12 filled with gaseous fuel is present. This allows a flow of liquid fuel into the gas space 12 or a flow of gaseous fuel from the gas space 12 in the direction of the transverse bore 38. Both currents are only slightly harmless to the operation of the injector 1. As long as the pressure in the transverse bore 38 and are approximately equal in the gas space 12,

for example, each 500 bar, there is only a slight mixing or no mixing of the liquid and the gaseous fuel. However, if only a very small pressure is present in the gas space 12 than that of the liquid fuel within the injector 1, then a pressure gradient occurs within the throttle gap 28, ie, starting from the transverse bore 38, the pressure in the throttle gap 28 decreases continuously until pressure In the gas space 12. Thus, as shown in Fig.3a as a section II from Fig.2, via the throttle gap 28 liquid fuel enters the gas space 12 and simultaneously expands the throttle gap 28. _Λ

Liquid fuel from the transverse bore 38 enters the pressure chamber 33 via the inlet opening 32 so that it also fills with liquid fuel and the pressure in the pressure chamber 33 corresponds to that in the transverse bore 38. As a result, the wall 34 of the pressure chamber 33 in the direction of

Throttle gap 28 elastically deformed until at maximum pressure in the

Transverse bore 38 and ambient pressure in the gas space 12, the throttle gap 28 completely closes, as shown in Figure 3b. At the same time, the outer nozzle needle 4 is fixed in the guide bore 3 by the widened wall 34 of the pressure chamber 33, if no injection of gaseous fuel into the combustion chamber of the internal combustion engine he follows.

FIG. 4 shows a section III from FIG. 2, wherein a uniform number of inlet openings 32 of the pressure chamber 33 are arranged in the injector body 2 on its circumference. The inlet openings 32 are preferably formed as bores and have a throttling effect. The pressure chamber 33 is preferably manufactured using the manufacturing technology additive manufacturing.

When filled with liquid fuel pressure chamber 33, the wall thickness of the injector 2 between the wall 34 of the pressure chamber 33 and the throttle gap 28 in a range of values between 0.4 mm and 0.8 mm, preferably 0.6 mm.

Claims

claims

Injector (1) for dosing a liquid and a gaseous

Fuel with an injector body (2) in which an outer nozzle needle (4) is arranged longitudinally movable, the outer nozzle needle (4) by its axial movement at least one injection opening (10) for metering a gaseous fuel opens and closes and wherein the outer nozzle needle (4) in a guide portion (30) of a guide bore (3) of the injector body (2) is guided, wherein between the guide portion (30) and the guide bore (3) a

Throttle gap (28) remains, wherein in the outer nozzle needle (4) has a longitudinal bore (5) is formed, which with fuel under a

Injection pressure can be filled and in which longitudinal bore (5) an inner nozzle needle (6) is arranged longitudinally movable, wherein the inner

Nozzle needle (6) for opening and closing at least one

Injection opening (17) with an inner nozzle seat (16) cooperates, wherein in the injector body (2) a gas space (12) is formed which can be filled with gaseous fuel under a Eindüsdruck and the outer nozzle needle (4) adjacent to the guide bore ( 3), wherein the throttle gap (28) opens into the gas space (12), characterized in that in the injector body (2) a pressure chamber (33) is formed, which via a fluid channel (20) can be filled with liquid fuel and which Pressure chamber (33) with a wall (34) adjacent to the throttle gap (28).

Injector (1) according to claim 1, characterized in that the

Wall (34) of the pressure chamber (33) is elastically deformable by the pressure of the liquid fuel.

Injector (1) according to claim 2, characterized in that the

Widening of the wall (34) of the pressure chamber (33) in the direction of the outer nozzle needle (4) at maximum injection pressure in the

Longitudinal bore (5) and at ambient pressure in the gas space (12) the throttle gap (28) completely closes and fixes the outer nozzle needle (4) by means of the wall (34) in the guide bore (3). Injector (1) according to one of the preceding claims, characterized in that the pressure chamber (33) is toroidal.

Injector (1) according to one of the preceding claims, characterized in that the pressure chamber (33) in the injector body (2) is manufactured by means of additive manufacturing.

Injector (1) according to one of the preceding claims, characterized in that the injector body (2) is hollow-cylindrical in shape and on whose circumference a uniform number of inlet openings (32) of the pressure chamber (33) is arranged.

Injector (1) according to one of the preceding claims, characterized in that the pressure chamber (33) with respect to the axial extent of the throttle gap (28) in the injector body (2) in one of the at least one Eindüsöffnung (10) facing away region (A) of the throttle gap (28) is formed.

Injector (1) according to one of the preceding claims, characterized in that the outer nozzle needle (4) with its at least one Eindüsöffnung (10) facing away from the end (36) defines an outer control chamber (25) which can be filled with liquid fuel, so a hydraulic closing force can be exerted on the outer nozzle needle (4) in the axial direction.

Injector (1) according to one of the preceding claims, characterized in that the inner nozzle needle (6) with its at least one injection opening (17) facing away from end (37) defines an inner control chamber (35) which can be filled with liquid fuel, so a hydraulic closing force can be exerted on the inner nozzle needle (6).