CN111058969B

CN111058969B - Fuel injector, method for operating a fuel injector

Info

Publication number: CN111058969B
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: 2023-07-07
Anticipated expiration: 2039-10-17
Also published as: DE102018217723A1; CN111058969A

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 reciprocable 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 a liquid fuel, via an inflow restriction (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 a piston (6) for actuating the back and forth movement to release and close the throttle cross-sectional area (A _Z ) Is provided with an actuator (5). The invention also relates to a method for operating a fuel injector (1).

Description

Fuel injector, 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. Gaseous fuels can be ignited, for example, by means of liquid fuels. This applies in particular to the case where 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, increasingly higher blowing pressures are achieved in order to meet requirements such as those imposed on the combustion of diesel fuel at full load. However, high blowing pressures lead to blowing rates which are too high at partial loads of the internal combustion engine and which often accompany 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 at least one fuel injector can be supplied with the gaseous fuel. However, the gas pressure regulation by such pressure regulating means proceeds very slowly due to the high compressibility of the gaseous fuel. Furthermore, a large control flow is produced, which is lost because it can neither be led back into the gas tank nor supplied for combustion due to the low pressure level. The resulting control flow cannot be discharged to the environment due to a large warming tendency (global warming).

Disclosure of Invention

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

In order to solve this task, a fuel injector for blowing gaseous fuel into a combustion chamber of an internal combustion engine is proposed. Furthermore, a method for operating a fuel injector is provided. Advantageous embodiments of the invention can be seen from the various preferred embodiments.

The proposed fuel injector for injecting gaseous fuel into a combustion chamber of an internal combustion engine comprises at least one reciprocable 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 a liquid fuel, via an inflow restrictor. According to the invention, the inflow restrictor has a variable restrictor cross-sectional area for dynamically controlling the inflow of hydraulic pressure medium into the control chamber and an actuator for actuating the back and forth movable piston to release and close the restrictor cross-sectional area.

By actuating the actuator, the position of the piston can be changed in a targeted manner, so that the throttle cross-sectional area of the inflow throttle is increased or decreased. Accordingly, the flow rate through the inflow restrictor 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 being reduced when it is opened.

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

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

Since the back and forth movable piston controls the flow rate of the hydraulic pressure medium flowing into the throttle portion, the pressure medium supply pressure acts on the piston. In order to achieve pressure equalization and to make the piston insensitive to pressure fluctuations, it is proposed that the piston has at least one pressure equalization opening running through, 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 proposed that the piston is preloaded against a stop defining the end position by the spring force of the spring. The end position may be, for example, an initial position in which the piston is in at the beginning of the injection process and in which the piston partially or completely closes 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 when opening, since initially no pressure medium flows into the control chamber via the inflow throttle, so that the control pressure applied to the nozzle needle in the closing direction drops very rapidly.

Advantageously, the piston is guided in a sleeve. The separate sleeve enables an optimization of the material pairing, so that the guiding 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. The separate sleeve thus also facilitates the coordination, so that the inflow restriction has a smaller tolerance. 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 sleeve can be inserted into any angular position by means of the annular groove, in particular without having to establish a coincidence of at least one opening with the inflow channel into the control chamber. In this way, the assembly is simplified. Furthermore, a plurality of openings may be distributed over the circumference of the sleeve, so that the circumferential direction is fully utilized and the installation space requirement along the longitudinal direction of the sleeve is reduced. The annular groove may have any cross-section, such as a circular or angular cross-section.

The at least one opening provided in the sleeve for the purpose of forming a 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 as continuous a change as possible in the throttle cross-sectional area and thus in the flow rate 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 which varies in the direction of movement of the piston. By means of the slit, 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 be achieved.

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

The actuator provided for actuating the piston that 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 (piezo actuator). In the case of a magnetic actuator, the latter 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 the armature. The electromagnetic coil can surround the piston at least in sections, so that a magnetic actuator is realized which operates according to the principle of the plug-in armature (Tauchanker). In this way, the installation space requirement in the axial direction can be minimized.

For the purpose of providing energy and/or signal information, the actuator may have its own pin, via which it is electrically conductively connected or at least electrically conductively connectable to the control unit. In the control unit, an adjusting structure can be stored, which enables dynamic actuation of the actuator, for example actuation in relation to an operating point, in particular in relation to a load, in order to adjust the flow through the inflow restriction. Preferably, two additional pins that are assigned to the actuator are added to the four pins that typically already exist for conventional dual fuel injectors.

Alternatively, it is proposed that the actuator is connected to the actuator of the control valve of the fuel injector by means of a current control device in order to achieve the energy supply and/or signal information. In this way, additional connectors in the form of pins can be dispensed with. The connection can be realized, for example, by means of a so-called "injector integrated Chip (Chip on Injektor)". Manipulation of the control valve is typically performed by means of a controller. The controller may also be used to operate an actuator flowing into the restriction. For this purpose, the controller may use different holding current levels (haltestimoniveau) depending on the load point.

Furthermore, a method for operating a fuel injector is proposed, which comprises at least one reciprocable nozzle needle for releasing and closing at least one injection opening for injecting gaseous fuel into a combustion chamber of an internal combustion engine. In order to control the reciprocating movement of the nozzle needle, the control pressure acting on the nozzle needle in the control chamber is changed. For this purpose, the control chamber is acted upon by a hydraulic pressure medium, preferably liquid fuel, via the inflow throttle, and is relieved via the outflow throttle, depending on 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 the 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. In this case, 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 of 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 thus be achieved with the aid of the method. In particular, a dynamic formation of the injection rate of the fuel injector, preferably a formation that is dependent on the operating point, in particular a formation that is dependent on the load, can be achieved with a constant, in particular maximum, gas pressure.

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

Drawings

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

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

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

fig. 3 shows the needle travel profile and the throttle cross section of the inflow throttle with respect to the injection cycle time.

Detailed Description

The inventive fuel injector 1 for blowing gaseous fuel into the combustion chamber of an internal combustion engine is known in part from fig. 1. The fuel injector 1 comprises a nozzle needle 2 which is received in a reciprocatingly movable manner in a nozzle body 23 and which delimits a control chamber 3 on the end side, which can be acted upon by a hydraulic pressure medium, for example liquid fuel. By the reciprocating movement of the nozzle needle 2, an insufflation opening (not shown) configured 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 outflow throttle 21 enables an unloading of the control chamber 3 or a control pressure drop in the control chamber 3. The control chamber 3 is filled with hydraulic pressure medium via the inflow restrictor 4, which inflow restrictor 4 is or can be connected to the control chamber 3 via the inflow channel 13.

At full load of the internal combustion engine, a high blow-in rate needs to be achieved. For this purpose, the nozzle needle 2 must be opened as quickly as possible. In this case, the blowing rate has a relatively steep rise. In contrast, it is desirable at partial load that the injection rate initially rise smoothly in order to promote slow and low noise combustion initiation.

To achieve the above, the present invention is shown in fig. 1The inflow restrictor 4 of the fuel injector 1 has a variable or adjustable restrictor cross-sectional area a _Z . By variable throttle cross-sectional area A _Z The inflow of the hydraulic pressure medium in 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 at partial load so that the control pressure drops less quickly and the nozzle needle 2 opens less quickly than at full load. In this way, a load-dependent blow-in rate build-up can be achieved.

In order to release and close the throttle cross-sectional area A of the inflow throttle element 4 _Z The inflow restrictor has a back-and-forth movable piston 6, which forms a control edge 24 at 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 electromagnetic 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, a magnetic field is formed, the magnetic force of which acts on the piston 6 by: the piston moves against the spring force of the spring 8 in the direction of the pole piece 28. In this case, the piston 6 releases a larger throttle cross-sectional area a _Z So that the flow rate through the inflow restrictor 4 increases. If the energization of the solenoid 31 is completed, the spring 8 resets the piston 6 so that the piston 6 at least partially closes the throttle cross-sectional area a _Z So 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 during the injection process, in particular independently of the gas pressure, so that the gas pressure can be kept constant and high.

Since the piston 6 is currently penetrated by the pressure balance hole 7, a 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 requirements can be reduced.

The spring force of the spring 8 is also currently used to pre-load the piston 6 against a stop 9The stops define the end position, in particular the initial position of the piston 6. In this position, the piston 6 completely closes the throttle cross-sectional area a of the inflow throttle 4 _Z . If the control chamber 3 is unloaded 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. As the inflow restrictor 4 opens, the rapid control pressure drop can be stopped by the addition of the inflow pressure medium and the nozzle needle 2 is braked, so that in the further course of the opening stroke of the nozzle needle 2 opens less rapidly. In this way, an opening stroke of the nozzle needle can be achieved, which has a "lift" -course or can be divided into four sections. The corresponding course is shown, for example, in fig. 3, wherein curve a is the possible course under full load and curve a' is the possible course under partial load. Corresponding throttle cross-sectional area A _Z Given by curve B or B'. Curve a″ shows the course obtained when the inflow via the inflow restriction 4 is greater than the outflow via the outflow restriction 21. The corresponding throttle cross-sectional area is given by curve B ".

The variable or adjustable throttle cross-sectional area a of the inflow throttle element 4 shown in fig. 1 _Z Constituted by a plurality of openings 11 of the sleeve 10 which is placed in the holes 14 of the nozzle body 23. The openings 11 are currently embodied as single holes, which are arranged one after the other in rows. Alternatively, a slit or any other opening shape may be selected. The sleeve 10 has an annular groove 12 on the outer circumferential side, through which the opening 11 communicates with the inflow channel 13, so that the opening 11 does not have to coincide with the inflow channel 13. In this way, the openings 11 may also be distributed over the circumference of the sleeve 10. The sleeve 10 now has a collar 15, by means of which the sleeve is supported on a shoulder 16 of the bore 14, so that the insertion depth of the sleeve 10 is predefined. The collar 15 simultaneously forms the stop 9 for the piston 6, wherein the piston 6 has a collar 26 which cooperates with the collar 15 of the sleeve 10. The spring 8 is furthermore supported on the rim 26, in particular indirectly on the ring via a setting washer 25 for setting the spring preloadOn the edge 26.

Furthermore, the magnetic sleeve 27 is supported on the annular rim 15 of the sleeve 10 by the snap-in edge 33 (beiβkante) 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 aperture 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 a current supply and/or a control device. Thus, the actuator 5 can be supplied with the necessary regulation energy and/or signal information via the pin 17.

Alternatively, the actuator 5 may also be provided internally with adjustment energy/signal information, as shown for example in fig. 2. The actuator 5 is connected here via a current regulating device 18 to a further actuator 19, which is used to actuate 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 is made to the description of fig. 1 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 reciprocable 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 via an inflow restrictor (4), characterized in that the inflow restrictor (4) has a variable restrictor cross-sectional area (a _Z ) For dynamically controlling the inflow of hydraulic pressure medium into the control chamber (3), and the inflow restriction (4) has an actuator (5) for actuating a piston (6) movable back and forth to release and close the restriction cross-sectional area (A _Z )。

2. Fuel injector (1) according to claim 1, characterized in that the piston (6) has at least one pressure balancing hole (7) therethrough such that the same pressure is applied on both sides of the piston (6).

3. Fuel injector (1) according to claim 1 or 2, characterized in that the piston (6) is preloaded against a stop (9) defining a final position by the spring force of a spring (8).

4. Fuel injector (1) according to claim 1 or 2, 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 _Z )。

5. The fuel injector (1) according to claim 4, characterized in that the sleeve (10) is placed in a bore (14).

6. The fuel injector (1) according to claim 1 or 2, characterized in that the actuator (5) is embodied as an electric, electromagnetic or piezoelectric actuator (5).

7. The fuel injector (1) according to claim 1 or 2, characterized in that the actuator (5) is electrically conductively or conductively connected to the controller via its own pin (17).

8. The fuel injector (1) according to claim 1 or 2, characterized in that the actuator (5) is connected to an actuator (19) of a control valve (20) of the fuel injector (1) by means of a current regulating device (18).

9. The fuel injector (1) according to claim 1, characterized in that the hydraulic pressure medium is a liquid fuel.

10. The fuel injector (1) according to claim 2, characterized in that the pressure is a pressure medium supply pressure.

11. The fuel injector (1) according to claim 4, characterized in that the at least one opening (11) of the sleeve (10) is embodied in the region of a circumferential annular groove (12) arranged on the outer circumferential side, through which the at least one opening (11) communicates with an inflow channel (13) into the control chamber (3).

12. The fuel injector (1) according to claim 5, characterized in that the sleeve (10) is supported on a shoulder (16) of the bore (14) by a rim (15).

13. Method for operating a fuel injector (1) for injecting gaseous fuel into a combustion chamber of an internal combustion engine, comprising at least one reciprocable nozzle needle (2) for releasing and closing at least one injection opening, wherein for controlling the reciprocation 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 via an inflow throttle (4) and is relieved via an outflow throttle (21) in dependence on a switching position of a control valve (20), characterized in that a variable throttle cross-sectional area (A) is provided during an injection process by the inflow throttle (4) _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 back and forth movement of the piston (6) is controlled by means of an actuator (5) associated with the piston (6).

14. The method according to claim 13, wherein the hydraulic pressure medium is a liquid fuel.