CN111058969A

CN111058969A - Fuel injector, method for operating a fuel injector

Info

Publication number: CN111058969A
Application number: CN201910986215.8A
Authority: CN
Inventors: M·卡茨; B·莱布斯勒; J·韦斯内尔
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2018-10-17
Filing date: 2019-10-17
Publication date: 2020-04-24
Anticipated expiration: 2039-10-17
Also published as: CN111058969B; DE102018217723A1

Abstract

The invention relates to a fuel injector (1) for injecting gaseous fuel into a combustion chamber of an internal combustion engine, comprising at least one nozzle needle (2) that can be moved back and forth for releasing and closing at least one injection opening, wherein the nozzle needle (2) delimits a control chamber (3) that can be acted upon by a hydraulic pressure medium, preferably liquid fuel, via an inflow throttle (4). According to the invention, the inflow restrictor (4) has a variable restrictor cross-sectional area (A) for dynamically controlling the inflow of hydraulic pressure medium into the control chamber (3)_Z) And having a piston (6) which can be moved back and forth for actuating the release and closure of the throttle cross-sectionProduct (A)_Z) The actuator (5). The invention further relates to a method for operating a fuel injector (1).

Description

Fuel injector and method for operating a fuel injector

Technical Field

The present invention relates to a fuel injector for injecting a gaseous fuel, such as Natural Gas (NG), into a combustion chamber of an internal combustion engine.

The fuel injector may be configured as a single fuel injector or as a dual fuel injector. In the case of a dual fuel injector, the fuel injector may be used to blow in or inject two different fuels, such as a gaseous fuel and a liquid fuel. The gaseous fuel can be ignited, for example, by means of a liquid fuel. This applies in particular when diesel fuel is used as liquid fuel.

The invention further relates to a method for operating such a fuel injector.

Background

In the combustion of gaseous fuels, higher and higher injection pressures are achieved in order to meet the requirements such as those set for the combustion of diesel fuels at full load. However, high injection pressures lead to injection rates which are too high under partial load conditions of the internal combustion engine and which are often accompanied by undesirable noise generation and/or increased emissions when implemented. This should be avoided.

As a solution, a pressure regulating valve for regulating the gas pressure can be provided on a storage container for the gaseous fuel, via which storage container at least one fuel injector can be supplied with the gaseous fuel. However, the gas pressure regulation by such a pressure regulating device proceeds very slowly due to the high compressibility of the gaseous fuel. Furthermore, a large control flow is generated, which can be lost, since it cannot be either led back into the gas tank or supplied for combustion because of the low pressure level. The generated control flow cannot be discharged to the environment due to a large warming tendency (global warming).

Disclosure of Invention

The object on which the invention is based is therefore to specify a fuel injector for injecting gaseous fuel, which enables dynamic formation of the injection rate, in particular in relation to the operating point, while the gas pressure remains the same high.

In order to solve this task, a fuel injector for injecting a gaseous fuel into a combustion chamber of an internal combustion engine is proposed. Furthermore, a method for operating a fuel injector is specified. Advantageous embodiments of the invention are evident from the respective preferred embodiments.

The proposed fuel injector for injecting gaseous fuel into a combustion chamber of an internal combustion engine comprises at least one reciprocatable nozzle needle for releasing and closing at least one injection opening. The nozzle needle delimits a control chamber which can be acted upon by a hydraulic pressure medium, preferably liquid fuel, via an inflow restrictor. According to the invention, the inflow restrictor has a variable throttle cross-sectional area for dynamically controlling the inflow of hydraulic pressure medium into the control chamber and an actuator for actuating the piston, which is movable back and forth, for releasing and closing the throttle cross-sectional area.

By actuating the actuator, the position of the piston can be varied in a targeted manner such that the throttle cross-sectional area of the inflow throttle is increased or decreased. Accordingly, the flow rate through the inflow restriction may change and thus the inflow of hydraulic pressure medium into the control chamber may change. If the inflow of hydraulic pressure medium increases during the injection process, the control pressure in the control chamber drops more slowly, which results in the nozzle needle being braked and the speed of the nozzle needle when opening being reduced.

The adjustability of the throttle cross-sectional area of the inflow throttle enables an operating-point-dependent formation of the injection rate, in particular a load-dependent formation. Furthermore, the adjustment can be carried out dynamically, in particular independently of the gas pressure and independently of the pressure medium supply pressure, by means of the actuator provided. That is, not only the gas pressure but also the pressure medium supply pressure can be kept constant. A gas pressure control or gas pressure control device on the storage container for the gaseous fuel can thus be dispensed with. Furthermore, the gas supply pressure level can be set so high that maximum needle dynamics are achieved for a steep blowing rate at full load, which is then kept at a high level or flattened for optimum consumption.

For example, the following needle speed profile, which can be divided into four sections (the so-called "lift" profile), can be realized during the injection process: a) a fast first opening, b) a slow further opening, for example for bridging the ignition delay, c) a fast opening again in order to blow in a residual gas quantity at a high rate, and d) a fast closing of the nozzle needle. To achieve this, only different actuator characteristics are required.

Since the piston, which is movable to and fro, controls the flow of hydraulic pressure medium through the inflow restrictor, the pressure medium supply pressure acts on the piston. In order to achieve a pressure equalization and to make the piston insensitive to pressure fluctuations, it is proposed that the piston has at least one pressure equalization opening which extends therethrough, so that the same pressure, in particular the pressure medium supply pressure, acts on both sides of the piston. Thus, the piston is pressure balanced.

In one embodiment of the invention, it is provided that the piston is prestressed against a stop defining the end position by means of the spring force of a spring. The end position can be, for example, an initial position in which the piston is in the beginning of the injection process and in which the piston partially or completely closes off the throttle cross-sectional area of the inflow throttle. If the throttle cross-sectional area is completely closed, an initially very high needle speed can be achieved during opening, since initially no pressure medium flows into the control chamber via the inflow throttle, so that the control pressure acting on the nozzle needle in the closing direction drops very quickly.

Advantageously, the piston is guided in the sleeve. The individual sleeves enable an optimization of the material pairing, so that the guidance of the piston is improved. At least one opening for forming a variable throttle cross-sectional area of the inflow throttle is preferably formed in the sleeve. Thus, the separate sleeve also facilitates the modulation, resulting in a smaller tolerance in the inflow restriction. Preferably, at least one opening of the sleeve is formed in the region of a circumferential annular groove arranged on the outer circumferential side, through which the at least one opening communicates with an inflow channel into the control chamber. The annular groove allows the sleeve to be inserted in any desired angular position, in particular without it being necessary to establish a coincidence of at least one opening with the inflow channel into the control chamber. In this way assembly is simplified. Furthermore, the plurality of openings can be distributed over the circumference of the sleeve, so that the circumferential direction is fully utilized and the installation space requirement in the longitudinal direction of the sleeve is reduced. The annular groove may have any cross section, for example a circular or angular cross section.

The at least one opening provided in the sleeve to form the variable throttle cross-sectional area of the inflow throttle can be configured, for example, as a radial bore. If a plurality of radial bores are provided, these are preferably arranged one after the other in the direction of movement of the piston. If the piston moves relative to the sleeve, the number of radial holes that are released increases or decreases. In the case of a multi-row arrangement, the radial bores of adjacent rows can be arranged offset from one another in the direction of movement of the piston in order to achieve a continuous change in the throttle cross-sectional area and thus a continuous change in the flow through the inflow throttle.

Alternatively, a plurality of radial bores for forming the throttle cross-sectional area may also be arranged helically. In this way, a continuous increase or decrease of the throttle cross-sectional area of the inflow throttle can also be achieved.

Furthermore, the at least one opening of the sleeve can be formed by at least one slit having a width which remains the same or varies in the direction of movement of the piston. By means of the gap, the width of which varies in the direction of movement of the piston, a non-linear increase or decrease of the throttle cross-sectional area can in turn be achieved.

The sleeve is preferably inserted into a bore, wherein this may relate in particular to a bore in a body component of the fuel injector, for example a nozzle body. In this case, the sleeve may be pressed or screwed into the bore. To determine the insertion depth, the sleeve can be supported by a collar on the shoulder of the bore. In this way the assembly is further simplified.

The actuator provided for actuating the piston which can be moved back and forth is preferably embodied as an electric actuator, an electromagnetic actuator or a piezoelectric actuator. In particular, the actuator may be a magnetic actuator or a piezoelectric actuator (Piezoaktor). In the case of a magnetic actuator, the actuator preferably has an annular electromagnetic coil for acting on a piston which can be moved back and forth, which in this case preferably simultaneously assumes the function of an armature. The electromagnetic coil can surround the piston at least in sections, so that a magnetic actuator is realized which operates according to the inserted armature (Tauchanker) principle. In this way, the installation space requirement in the axial direction can be minimized.

In order to realize the energy supply and/or the signal information, the actuator can have its own pin, via which it is electrically conductively connected or at least can be electrically conductively connected to the controller. In the control device, a control structure can be stored which enables dynamic actuation of the actuator, for example, actuation as a function of the operating point, in particular as a function of the load, in order to control the flow through the inflow restrictor. Preferably, two further pins assigned to the actuator are added to the usually already existing four pins of a conventional dual fuel injector.

Alternatively, it is provided that the actuator is connected to an actuator of a control valve of the fuel injector via a current control device in order to realize the energy supply and/or the signal information. In this way, additional connections in the form of pins can be dispensed with. The connection can be realized, for example, by means of a so-called "Chip on injector integrated Chip". The actuation of the control valve is usually carried out by means of a controller. The control can also be used to control the actuator of the inflow restriction. For this purpose, the controller can use different holding current levels (Haltetromovitauau) depending on the load point.

Furthermore, a method for operating a fuel injector is proposed, which comprises at least one reciprocatable nozzle needle for releasing and closing at least one injection opening for injecting a gaseous fuel into a combustion chamber of an internal combustion engine. In order to control the reciprocating movement of the nozzle needle, a control pressure acting on the nozzle needle in the control chamber is varied. For this purpose, the control chamber is charged with a hydraulic pressure medium, preferably liquid fuel, via an inflow throttle and is discharged via an outflow throttle as a function of the switching position of the control valve. According to the invention, the inflow of hydraulic pressure medium into the control chamber is dynamically controlled by means of a variable throttle cross-sectional area of the inflow throttle during the injection process, and a piston that can be moved back and forth is used for the control. The back-and-forth movement of the piston is controlled by means of an actuator associated with the piston.

The proposed method can be used in particular for operating the fuel injector according to the invention, since it comprises a correspondingly configured inflow restrictor with a separate actuator for dynamically controlling the flow through the inflow restrictor during an injection cycle. The same advantages can therefore also be achieved with the aid of the method. In particular, a dynamic formation of the injection rate of the fuel injector, preferably a formation dependent on the operating point, in particular a formation dependent on the load, can be achieved with a constant, in particular maximum, gas pressure.

The required regulating energy and/or signal information for the actuator of the inflow restriction can be provided externally or internally. For example, the actuator may be attached to an external controller by additional pins. Alternatively, the actuator can be connected to the actuator of the control valve of the fuel injector via an integrated current regulator in such a way that the required regulating energy/signal information is generated directly in the fuel injector, for example by means of a "Chip on injector" solution.

Drawings

The invention is explained in more detail below with reference to the drawings. The figures show:

figure 1 is a schematic longitudinal section through a first inflow restriction of a fuel injector according to the invention with a variable restriction cross-sectional area,

figure 2 is a schematic longitudinal section through a second inflow restriction of a fuel injector of the invention with a variable restriction cross-sectional area,

fig. 3 is a diagram of the needle travel course and the throttle cross section of the inflow throttle with respect to the injection cycle time.

Detailed Description

Fig. 1 shows a fuel injector 1 according to the invention for injecting gaseous fuel into a combustion chamber of an internal combustion engine. The fuel injector 1 comprises a nozzle needle 2 which is received in a nozzle body 23 so as to be movable to and fro and which delimits a control chamber 3 on the end side, which can be charged with a hydraulic pressure medium, for example liquid fuel. By means of the reciprocating movement of the nozzle needle 2, an insufflation opening (not shown) formed in the nozzle body 23 can be released or closed. The reciprocating movement of the nozzle needle 2 is controlled by a control pressure in the control chamber 3. For this purpose, depending on the switching position of the control valve 20, the control chamber 3 can communicate with the low-pressure region 22 via the outflow throttle 21. Thus, the control chamber 3 can be relieved or the control pressure in the control chamber 3 can be reduced by the outflow throttle 21. The control chamber 3 is filled with hydraulic pressure medium via an inflow restrictor 4, which inflow restrictor 4 is connected or can be connected to the control chamber 3 via an inflow channel 13.

At full load of the internal combustion engine, it is necessary to achieve a high injection rate. For this purpose, the nozzle needle 2 must be opened as quickly as possible. In this case, the blowing rate has a comparatively steep rise. Conversely, at part load it is desirable that the injection rate initially rise smoothly to promote a slow and low noise start of combustion.

To achieve this, the inflow restrictor 4 of the fuel injector 1 according to the invention shown in fig. 1 has a variable or adjustable restrictor cross-sectional area a_Z. By variable throttle cross-sectional area A_ZThe inflow of hydraulic pressure medium into the control chamber 3 and thus the control pressure in the control chamber 3 can be controlled in a targeted manner. For example, the inflow can be increased in the case of partial load, so that the control pressure drops less quickly and the nozzle needle 2 opens less quickly than in the case of full load. In this way, a load-dependent blow-in rate development can be achieved.

In order to release and close the throttle cross-sectional area A of the inflow throttle 4_ZThe inflow restrictor has a piston 6 which can be moved back and forth and which forms a control edge 24 on the end face. For actuating the piston 6, an actuator 5 is provided, which is currently embodied as a magnetic actuator. The magnetic actuator comprises an annular magnetic coil 31 which is separated from the magnetic sleeve 27 and the pole piece 28 by a built-in nonmagnetic ring 30. The magnetic sleeve 27 and the pole piece 28 cooperate with the nozzle body 23 to form a magnetic circuit 32. If the electromagnetic coil 31 is energized, thenA magnetic field whose magnetic force acts on the piston 6 by: the piston is moved in the direction of the pole piece 28 against the spring force of the spring 8. In this case, the piston 6 releases a relatively large throttle cross-sectional area a_ZSo that the flow rate passing through the inflow throttling part 4 is increased. If the current supply to the solenoid 31 is ended, the spring 8 resets the piston 6, so that the piston 6 at least partially closes off the throttle cross-sectional area A_ZSo that the flow through the inflow restriction 4 is reduced again. In this way, the movement of the nozzle needle 2 can be controlled dynamically, in particular independently of the gas pressure, during the injection process, so that the gas pressure can be kept constant and high.

Since the piston 6 is now penetrated by the pressure compensation bore 7, pressure medium supply pressure acts on both sides of the piston 6. The piston 6 is thus pressure-balanced, so that the spring force of the spring 8 and thus the adjusting force of the actuator 5 can be small. In this way, the installation space requirement can be reduced.

The spring force of the spring 8 is also used to pretension the piston 6 against a stop 9, which defines an end position, in particular an initial position of the piston 6. In this position, the piston 6 completely closes off the throttle cross-sectional area a of the inflow throttle 4_Z. If the control chamber 3 is relieved by the outflow throttle 21 with the inflow throttle 4 completely closed, the control pressure in the control chamber 3 drops very quickly, which results in the nozzle needle 2 also opening very quickly. With the opening of the inflow restrictor 4, the rapid control pressure drop can be stopped by replenishing the inflowing pressure medium and the nozzle needle 2 can be braked so that the nozzle needle 2 opens less quickly in the further course of the opening stroke of the nozzle needle. In this way, an opening stroke of the nozzle needle can be achieved, which has a "lift" -profile or can be divided into four sections. The corresponding course is shown, for example, in fig. 3, where curve a is a possible course in the case of full load and curve a' is a possible course in the case of partial load. Corresponding throttle cross-sectional area A_ZGiven by curve B or B'. Curve a "shows what is obtained when the inflow via the inflow restriction 4 is greater than the outflow via the outflow restriction 21And (4) moving towards. The corresponding throttle cross-sectional area is given by curve B ".

Fig. 1 shows a variable or adjustable throttle cross-sectional area a of the inflow throttle 4_ZThe openings 11 of the sleeve 10 form a passage, which is inserted into the bore 14 of the nozzle body 23. The openings 11 are currently embodied as single bores, which are arranged one behind the other in a plurality of rows. Alternatively, the slit may be selected or any other opening shape may be selected. The sleeve 10 has an annular groove 12 on the outer circumference side, through which the opening 11 communicates with the inflow channel 13, so that the opening 11 does not necessarily have to coincide with the inflow channel 13. In this way, the openings 11 can also be distributed over the circumference of the sleeve 10. The sleeve 10 now has a collar 15, by means of which it rests on a shoulder 16 of the bore 14, so that the insertion depth of the sleeve 10 is predefined. The annular rim 15 at the same time forms a stop 9 for the piston 6, wherein the piston 6 has an annular rim 26 which interacts with the annular rim 15 of the sleeve 10. Furthermore, the spring 8 is supported on the annular rim 26, in particular indirectly via an adjusting washer 25 for adjusting the spring preload on the annular rim 26.

Furthermore, the magnetic sleeve 27 is supported on the annular rim 15 of the sleeve 10 by the snap-in edge 33(Bei β kante) in such a way that a sealing action is achieved in order to seal the pressure medium supply pressure acting on the inside against low pressure, the required sealing force can be applied, for example, by a cover 29 which closes the opening 14 outwards.

The actuator 5 shown in fig. 1, which flows into the throttle 4, has a first pin and a second pin 17, which lead out of the nozzle body 23 and enable the actuator 5 to be attached to an electric current supply and/or a control. The actuator 5 can therefore be supplied with the necessary control energy and/or signal information via the pin 17.

Alternatively, the actuator 5 can also be supplied with the control energy/signal information internally, as shown for example in fig. 2. The actuator 5 is connected via a current regulator 18 to a further actuator 19 for actuating a control valve 20 for switching the outflow throttle 21. The necessary signal information may be stored on a chip integrated into the fuel injector 1 (injector integrated chip).

Since the remainder of the fuel injector 1 of fig. 2 corresponds to the remainder of the fuel injector 1 of fig. 1, reference to the description of fig. 1 is to be avoided in order to avoid repetition.

Claims

1. A fuel injector (1) for injecting gaseous fuel into a combustion chamber of an internal combustion engine, comprising at least one reciprocatable nozzle needle (2) for releasing and closing at least one injection opening, wherein the nozzle needle (2) delimits a control chamber (3) which can be acted upon by a hydraulic pressure medium, preferably liquid fuel, via an inflow throttle (4), characterized in that the inflow throttle (4) has a variable throttle cross-sectional area (A)_Z) For dynamically controlling the inflow of hydraulic pressure medium into the control chamber (3), and the inflow throttle (4) having an actuator (5) for actuating a piston (6) that can be moved back and forth in order to release and close the throttle cross-sectional area (A)_Z)。

2. A fuel injector (1) as claimed in claim 1, characterized in that the piston (6) has at least one pressure compensation bore (7) passing through so that the same pressure, in particular the pressure medium supply pressure, acts on both sides of the piston (6).

3. A fuel injector (1) as claimed in claim 1 or 2, characterized in that the piston (6) is pretensioned against a stop (9) defining an end position by the spring force of a spring (8).

4. Fuel injector (1) as claimed in one of the preceding claims, characterized in that the piston (6) is guided in a sleeve (10) in which at least one opening (11) is formed for forming the variable throttle cross-sectional area (A) of the inflow throttle (4)_Z) Preferably, the at least one opening (11) of the sleeve (10) is formed in the region of a circumferential annular groove (12) arranged on the outer circumference, through which annular groove the at least one opening (11) opensAn inflow channel (13) into the control chamber (3).

5. A fuel injector (1) as claimed in claim 4, characterized in that the sleeve (10) is placed into a bore (14), wherein preferably the sleeve (10) is supported on a shoulder (16) of the bore (14) by a collar (15).

6. A fuel injector (1) as claimed in any one of the preceding claims, characterized in that the actuator (5) is embodied as an electric, electromagnetic or piezoelectric actuator (5).

7. A fuel injector (1) as claimed in any one of the preceding claims, wherein the actuator (5) is electrically conductively connected or connectable to a controller via its own pin (17).

8. A fuel injector (1) as claimed in any one of the preceding claims, characterized in that the actuator (5) is connected to an actuator (19) of a control valve (20) of the fuel injector (1) via a current regulating device (18).

9. Method for operating a fuel injector (1) comprising at least one nozzle needle (2) which can be moved back and forth for releasing and closing at least one injection opening for injecting gaseous fuel into a combustion chamber of an internal combustion engine, wherein, for controlling the back and forth movement of the nozzle needle (2), a control pressure acting on the nozzle needle (2) is varied in a control chamber (3) which is acted upon by a hydraulic pressure medium, preferably liquid fuel, via an inflow throttle (4) and is relieved via an outflow throttle (21) as a function of a switching position of a control valve (20), characterized in that a variable throttle cross-sectional area (A) is provided via the inflow throttle (4) during an injection process_Z) The inflow of the hydraulic pressure medium into the control chamber (3) is dynamically controlled, and a piston (6) that can be moved back and forth is used for the control, wherein the actuation of the piston (6) is assistedA device (5) for controlling the back and forth movement of the piston (6).