CN114076052A

CN114076052A - Gas injector with multiple valve needles

Info

Publication number: CN114076052A
Application number: CN202110920339.3A
Authority: CN
Inventors: M·米勒; M·伯厄
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2020-08-11
Filing date: 2021-08-11
Publication date: 2022-02-22
Also published as: DE102020210145A1; KR20220020224A

Abstract

The invention relates to a gas injector for injecting gas into a combustion chamber of an internal combustion engine, in particular directly, comprising an electromagnetic actuator (2) having an armature (20), an inner pole (21) and a coil (22), comprising at least two outwardly opening valve needles (31, 32, 33), wherein each valve needle releases and closes a through-flow opening of a gas path on a valve seat (90), and comprising a resetting device (10) which is provided for resetting the valve needles (31, 32, 33) into their initial position.

Description

Gas injector with multiple valve needles

Technical Field

The invention relates to a gas injector for injecting gaseous fuels, in particular hydrogen or natural gas or the like, having improved injection properties. The gas injector is designed in particular for direct injection into a combustion chamber of an internal combustion engine.

Background

Many different configurations of gas injectors are known from the prior art. The gas injectors which are injected directly into the combustion chamber are usually designed as outwardly opening injectors, since this type of injector design is expedient since the high combustion pressure in the combustion chamber assists the opening valve needle during the closing process. Compared to injectors for liquid fuels, such as gasoline injectors, gas injectors have a significantly larger valve seat cross section based on gaseous media. Only then can gaseous fuel be injected into the combustion chamber in sufficient quantity.

A further problem area in gas injectors is that, due to the fact that the medium is a gaseous medium, it cannot be lubricated by the medium itself, as is the case, for example, in fuel injectors that inject gasoline or diesel. This causes excessive wear during operation compared to fuel injectors for liquid fuels.

Disclosure of Invention

In contrast, the gas injector according to the invention for injecting gaseous fuel has the following advantages: in particular in the case of direct injection engines, space problems at the internal combustion engine can be avoided, since the gas injector according to the invention can be embodied smaller at its tip. Furthermore, the valve seat load of the gas injector can be significantly reduced at the valve seat. Furthermore, the force requirement for opening the injector is reduced, so that in the case of an electromagnetic actuator, the electromagnet can be significantly reduced in its size and power. This results in the advantage of high costs for the production of the gas injector. This is achieved according to the invention by: the gas injector has an electromagnetic actuator with an armature, an inner pole and a coil and at least two valve needles. Each of the valve needles releases and closes a through-flow opening of the gas path at the respective valve seat. A resetting device is also provided, which is provided for resetting the valve needle into its closed initial position again and closing the gas path at the valve seat. The invention thus provides for a plurality of valve needles, whereby the individual diameter of the respective valve seats can be reduced. Thereby, the force requirement necessary for opening the gas injector can be reduced. Furthermore, the smaller valve seat in terms of diameter makes it possible in particular to realize a smaller valve disk of the valve needle, so that the structural size at the tip of the gas injector is reduced. The space requirement necessary for the gas injector at its tip is thereby reduced, so that the gas injector is particularly suitable for direct injection applications in which the gas is injected directly into the combustion chamber of the internal combustion engine. The actuation of a plurality of valve needles by a common actuator therefore results in a gas injector with a relatively low number of components. In this case, the valve needles are embodied as outwardly opening valve needles, so that when the gas injector is opened, the gas pressure provides an additional opening force component.

The preferred embodiments show preferred embodiments of the invention.

Preferably, an actuating unit is provided which is arranged between the armature and the valve needles and transmits the movement of the armature to the valve needles. The actuating unit enables a greater degree of freedom in the design of the gas injector.

Preferably, the gas injector comprises exactly two valve needles or exactly three valve needles. In particular, exactly three valve needles are preferably provided. In this case, the three valve needles are arranged offset by 120 ° at the same distance from one another. The gas injector may also have more than three valve needles, in particular exactly four or exactly five or exactly six valve needles.

The gas injector preferably actuates a plurality of valve needles simultaneously. Thereby, a common behavior of the gas injector at injection can be achieved. Alternatively, the electromagnetic actuator operates the plurality of valve needles differently in time. Thereby, a plurality of valve needles can be opened and closed in a staggered manner. For example, the valve needles are of different lengths, wherein the valve needles are operated by one component with a surface-type contact area. Alternatively, the actuating unit has special projecting shoulders or regions, which are each assigned to a valve needle. The opening characteristics of the plurality of valve needles are defined in terms of the projection length of the area of the projection. Therefore, the staged injection of the fuel gas can be achieved. However, even with only one valve needle open or only two valve needles open, a small injection rate can be achieved.

Furthermore, the gas injector preferably comprises a guide member for guiding the valve needles, which guide member has a plurality of guide openings, wherein one guide opening is penetrated by each of the valve needles. Preferably, the guide openings each have two circular openings which merge into one another and have different diameters. Here, the circular opening with the larger diameter serves for introducing the valve needle into the guide member, while the circular opening with the smaller diameter serves as a retaining element for the valve needle. The guiding is effected on the outer circumference of the guide member. Furthermore, the valve needles preferably have a second guide region at their end pointing towards the valve seat. In this way, a reliable guidance of the valve needles at the two valve needle regions can be achieved.

Furthermore, the guide member preferably has additional notches on the outer circumference for the gas to flow through. This ensures that a sufficient amount of gas can flow away through the guide element when the gas injector is open.

Furthermore, it is preferred that the valve needles each have a constriction which is arranged in the guide member in the assembled state. The diameter of the constriction can be selected to correspond to the diameter of the smaller circular opening, so that the valve needle is reliably held in the smaller circular opening of the guide member. The guide member is guided on the outer periphery or in the region of the outer periphery in the interior of the valve housing or the like.

According to a particularly preferred embodiment of the invention, the actuating unit has a closed lubricant chamber which is filled with lubricant and in which the armature is arranged. Here, a flexible sealing element, in particular a bellows (Balg) or the like, seals the lubricant chamber from the gas path inside the gas injector. The service life of the gas injector can be significantly extended by providing a lubricant chamber filled with lubricant. In the lubricant chamber, a movable armature of an electromagnetic actuator is arranged, at which the greatest wear in operation generally occurs.

Furthermore, a braking device is preferably arranged in the lubricant chamber, which braking device is provided for braking the closing element during the resetting of the valve needle. Wear at the valve seat can thereby be reduced, since the stop of the valve needle at the valve body seat can be reduced by braking the valve needle during the resetting process. The braking device makes it possible to reduce the impulse when the valve needle impacts on the valve body, in particular because the valve seat is generally very dry and in a hot combustion chamber atmosphere.

Preferably, the braking means comprises a brake pin and a resilient braking element, such as a spring or a resilient member. During the resetting process, the brake pin can be operatively connected to the armature and/or the valve needle, so that the armature impacts on the brake pin before it actually comes to a stop and moves the brake pin against the force of the spring element, as a result of which damping of the armature during the resetting process can be achieved. In particular, the return speed of the armature is reduced. This is additionally assisted by an additional mass acceleration provided by the braking device. In addition, further braking is achieved by the displacement of lubricant between the armature and the brake pin. The speed of return of the valve needle can also be further reduced by friction of the guide element or the like with the brake pin. All this reduces the impact force of the armature on the stop, so that the service life of the armature can be further extended.

The braking means also brakes the valve needle immediately before it hits the valve seat. This reduces wear at that location.

In particular, a brake guide element is preferably arranged on the brake pin, which brake guide element ensures a stable movement of the brake pin. Furthermore, friction can additionally be generated by the braking guide element during the resetting of the valve needle, which friction additionally provides a damping function.

Preferably, as lubricant, an oil with a constant viscosity at different temperatures is used, in particular a mineral oil is added. Alternatively, liquid fuels, in particular diesel or gasoline, are used. Further alternatively, grease is used as the lubricant.

Preferably, the flexible sealing element is a single-layer or multi-layer bellows. The bellows is preferably made of metal or alternatively of plastic. Preferably, the bellows is fastened with one end directly to the closing element and with the other end to a housing component of the gas injector. For example, in the case of metal bellows, this fixing can be achieved by means of a weld seam.

Alternatively, the flexible sealing element is a membrane. The film may be single-layered or multi-layered and is fixed to the respective component, for example by laser welding, for sealing the lubricant cell.

Preferably, the gas path of the gaseous fuel is arranged in a region between a valve housing of the gas injector and an actuator housing of the gas injector. Thereby, the actuator can be arranged in the housing and at least partially preassembled as an assembly. In this way, the lubricant chamber can also be arranged in a relatively simple manner in the interior of the actuator housing.

Alternatively, the gas path of the gaseous fuel is configured to pass through a region of the electromagnetic actuator, in particular through a coil chamber in which a coil of the electromagnetic actuator is arranged. Thereby, a separate actuator housing for the electromagnetic actuator can be dispensed with. Particularly preferably, the electrical contact means passes through the gas path of the gaseous fuel. This reduces the complexity of the gas injector in particular. It should be noted that the electrical contact means through the gas chamber must obviously be sealed at the surface (nach au β en hin).

Furthermore, it is preferred that a filter is arranged in the gas path for the gaseous fuel in order to filter out solid particles present in the gaseous fuel, if necessary, or in order to filter out solid particles resulting from production or from assembly.

It is also preferred that the gas injector is pressure balanced. The force for opening the gas injector by means of the electromagnetic actuator is thus independent of the gas pressure. Therefore, the time during which the injector is opened after the start of energization and closed after the end of energization is also independent of the gas pressure. This in turn allows operation with different gas pressures. The gas pressure can be reduced in the case of a small desired injection quantity, and increased in the case of a large desired injection quantity.

Preferably, the return is effected by means of a single common return spring. It is also possible that each individual valve needle is loaded by its own return spring. In the case of a pressure equalization of the injector, in the closed state of the gas injector, in particular no pressure is generated on the valve needle by the gaseous fuel, so that the loading of the valve needle can be significantly reduced.

Drawings

Hereinafter, embodiments of the present invention are described in detail with reference to the accompanying drawings. In the attached drawings:

FIG. 1: a schematic cross-sectional view of a gas injector according to a first embodiment of the invention;

FIG. 2: a schematic perspective view from the outside of the gas injector of fig. 1;

FIG. 3: FIG. 1 is an enlarged schematic partial cross-sectional view of the gas injector;

FIG. 4: a schematic top view of a guide member of the gas injector of fig. 1;

FIG. 5: an enlarged schematic partial cross-sectional view of a gas injector according to a second embodiment of the invention;

FIG. 6: an enlarged schematic partial cross-sectional view of a gas injector according to a third embodiment of the invention, an

FIG. 7: a schematic partial cross-sectional view of a gas injector according to a fourth embodiment of the invention.

Detailed Description

Hereinafter, a gas injector 1 according to a first preferred embodiment of the present invention will be described in detail with reference to fig. 1 to 4.

As can be seen from fig. 1, a gas injector 1 for introducing gaseous fuel comprises an electromagnetic actuator 2 which actuates three valve needles by means of an actuating unit 3. As can be seen from fig. 2, a first valve needle 31, a second valve needle 32 and a third valve needle 33 are provided. The three valve needles are arranged at intervals of 120 ° in the circumferential direction.

The three valve needles 31, 32, 33 are outwardly open valve needles and, as can be seen from fig. 2, each have a valve disk. The diameters of the valve disks of the valve needles 31, 32, 33 are equal in each case.

The electromagnetic actuator 2 comprises an armature 20, which is in contact with three valve needles 31, 32, 33 by means of an armature pin 24 and an armature sleeve 25. The armature sleeve 25 has an axial contact surface 25a which contacts the three valve needles 31, 32, 33.

The electromagnetic actuator 2 further comprises an inner pole 21, a coil 22 and a magnetic housing 23 providing magnetic feedback to the electromagnetic actuator.

Fig. 1 shows the closed state of the gas injector 1, in which the sealing seat 90 in the valve body 9 is closed by the three valve needles 31, 32, 33.

Furthermore, the gas injector 1 comprises a body 7 through which the gaseous fuel to be injected is supplied. A valve housing 8 is fixed to the main body 7. An inner pole 21 is fastened to the valve housing 8 and a valve body 9, which receives three valve needles 31, 32, 33, is fastened to the inner pole 21.

Furthermore, the gas injector 1 comprises a spring element 61 and an intermediate piece 60, which presses an armature with an armature pin against the valve needle with a low force. The total restoring force is thus derived from the difference in force from the lower restoring element 10 and the elastic element 61.

As can be further seen from fig. 1, the gas path for the gaseous fuel to be injected runs through the interior of the main body 7 and the magnet housing 23, through the brake guide element 62 and the opening 20a in the armature 20 into the interior region of the valve body 9.

Reference numeral 10 denotes a restoring element which is supported with one end on the valve body 9 and with the other end on the guide member 11. The guide member 11 can be seen in detail in fig. 4. The guide member 11 comprises three guide openings 12, wherein in each guide opening a valve needle of the valve needles passes through. The guide opening 12 is in principle of identical design and comprises a first circular opening 111 and a second circular opening 112. Here, the diameter of the first circular opening 111 is larger than the diameter of the second circular opening 112. As can be seen from fig. 4, the

circular openings

111, 112 merge into one another. Three guide surfaces 11a are formed on the outer circumference of the guide member 11.

In the assembled state, the three valve needles 31, 32, 33 are arranged with the constriction 13 in the second circular opening 112, respectively. However, for the assembly of these three valve needles a first circular opening 111 is required, through which the valve needle is first inserted and then arranged in a second circular opening 112 by means of the constriction 13 of the valve needle. This can be seen in detail in fig. 3.

As can be further seen from fig. 3, the valve needle also has a second guide region 14 adjacent to the sealing seat 90.

The guide member 11 also has a flattened portion 110 on its outer periphery 3 in order to provide a wider cross section for the gas to flow into the guide member 11. The valve needles 31, 32, 33 are therefore fixedly connected to the guide member 11 in the constriction 13, which guide member is, however, movably arranged inside the valve body 9. The

valve needle

31, 32, 33 is thus guided doubly at the guide member 11 by means of the guide surface 11a and at the second guide area 14. Thereby, a very reliable guidance of the valve needle can be achieved.

Therefore, to open the gas injector 1, the magnetic actuator 2 is moved, thereby attracting the armature 20 towards the inner pole 21. Since the armature 20 is fixedly connected to the armature pin 24, the armature movement is transmitted via the armature sleeve 25 to the three valve needles 31, 32, 33, whereby the opening process is carried out. Here, the three valve needles 31, 32, 33 open simultaneously.

After the injection is completed, the activation of the electromagnetic actuator 2 is terminated, so that the resetting element 10 resets the three valve needles 31, 32, 33 again into the closed position shown in fig. 1 by means of the guide member 11. In this case, the armature 20 is braked by the brake device 6 and in particular the brake spring 61.

In contrast to the prior art, the gas injector 1 according to the invention does not have only a single valve needle with a larger diameter, but a plurality of valve needles with a smaller diameter. It is thereby achieved that the tip of the gas injector 1, on which the sealing seat 90 is arranged, can be made smaller than in the prior art. The gas injector 1 is thus particularly suitable for injecting gaseous fuel directly into the combustion chamber of an internal combustion engine. Furthermore, if a higher combustion chamber pressure is applied to the valve needle, the valve seat load on the sealing seat 90 can be reduced, since the sum of the three small valve needle circle areas is smaller than one large valve needle circle area. Furthermore, the force requirement of the electromagnetic actuator 2 can also be reduced, so that the electromagnetic actuator 2 can be implemented significantly smaller and at lower cost than in the prior art.

A comparison of a gas injector with a single valve needle with the gas injector 1 of the present embodiment with three valve needles is shown by way of example in the following table in order to show the resulting advantages:

table:

as can be seen from the table, except for the tip outer diameter, which was reduced by 32%. The line pressure on the seal seat is also reduced by 58%. Thereby, a magnetic force reduced by 33% is obtained.

This clearly shows that the advantages of the gas injector 1 with multiple valve needles of the present invention enable a significant reduction in the size of the electromagnetic actuator compared to the prior art, thereby enabling a significant cost reduction of the gas injector of the present invention.

Fig. 5 and 6 show a second and a third embodiment of the invention, wherein identical or functionally identical components are denoted by the same reference numerals.

In this case, the second and third exemplary embodiments can each effect the opening of a plurality of valve needles in such a way that they do not open and do not close simultaneously. For this purpose, in the second exemplary embodiment, the second valve needle 32 is extended in the direction of the armature sleeve 25 by an extension region 32a, as shown in fig. 5. In the third exemplary embodiment in fig. 6, a shoulder 25b is provided on the armature bushing 25. In the case of the second and third exemplary embodiments, the second valve needle 32 is therefore actuated earlier than the first valve needle 31 and the third valve needle 33 (not shown). Accordingly, during the closing process, the second valve needle 32 closes later than the other two valve needles. In the case of a magnet which is partially excited, it is also possible to open only one second valve needle 32. Thus, a smaller injection rate of the fuel gas into the combustion chamber is obtained.

Thus, staged injection of the gas injector can be achieved in a simple manner. The opening and closing characteristics can be realized in a simple manner by changing the length of one or more valve needles or by providing one or more shoulders of different lengths on the armature sleeve 25. It should be noted that additional components having different axial lengths may also be provided between the valve needle and the armature sleeve. In other respects, the second and third embodiments correspond to the first embodiment, so that reference can be made to the description given there.

Fig. 7 shows a gas injector 1 according to a fourth embodiment of the invention. Identical or functionally identical parts are also denoted by the same reference numerals as in the first embodiment.

The gas injector 1 of the fourth exemplary embodiment corresponds essentially to the gas injector of the first exemplary embodiment, wherein the gas injector of the fourth exemplary embodiment additionally comprises a closed lubricant chamber 4.

As can be seen from fig. 7, the lubricant chamber 4 is defined by the body 7, the magnetic housing 23, the brake guide element 62, the inner pole 21 and the flexible sealing element 5. The armature 20 is arranged in the interior of the lubricant chamber 4.

The lubricant chamber 4 is filled with a lubricant, for example a liquid fuel, such as gasoline or diesel oil, or grease or the like. Thereby, continuous lubrication of the armature 20 can be provided. The problem of the lack of lubrication of the moving parts in the case of gaseous fuel, which occurs in the prior art, is therefore compensated by the lubricant chamber in which the armature 20 is arranged.

Furthermore, the gas injector 1 comprises a braking device 6. The braking device 6 is arranged on the side of the armature 20 facing away from the valve needles 31, 32, 33. The detent device 6 comprises a detent pin 60, a detent spring 61 supported thereon and a detent guide element 62 which is fixedly arranged in the magnet housing 23. The brake pin 60 is in contact with the armature pin 24.

The lubricant chamber 4 also has the following advantages: when the gas injector 1 is closed, the resetting is additionally braked by the lubricant present in the lubricant chamber 4.

In the fourth embodiment, the flexible sealing element 5 is implemented as a metal bellows. It should be noted, however, that other flexible sealing elements, such as films or plastic bellows or the like, may also be provided. In other respects, this embodiment corresponds to the first embodiment, so that reference can be made to the description given there.

Claims

1. A gas injector for injecting a gas, in particular directly into a combustion chamber of an internal combustion engine, the gas injector comprising:

-an electromagnetic actuator (2) having an armature (20), an inner pole (21) and a coil (22);

-at least two outwardly opening valve needles (31, 32, 33), wherein each valve needle releases and closes a through-flow opening of a gas path on a valve seat (90); and

-a resetting device (10) arranged for resetting the valve needle (31, 32, 33) into an initial position of the valve needle.

2. The gas injector of claim 1, further comprising:

-an operating unit (3) which is arranged between the armature (20) and the valve needle (31, 32, 33) and which transmits the movement of the armature (20) to the valve needle (31, 32, 33).

3. A gas injector as claimed in claim 1 or 2, wherein the gas injector is provided with exactly two valve needles or exactly three valve needles or exactly four valve needles.

4. A gas injector as claimed in claim 2 or 3, wherein the valve needles (31, 32, 33) are operated simultaneously by means of the operating unit (3).

5. A gas injector as claimed in claim 2 or 3, wherein the valve needles (31, 32, 33) are manipulated temporally differently by the manipulation unit (3).

6. A gas injector as claimed in claim 5, wherein the valve needles (31, 32, 33) are of different lengths, or the actuating unit (3) has a shoulder projecting in the axial direction, by means of which one of the valve needles can be actuated.

7. A gas injector according to any one of the preceding claims, further comprising a guide member (11) having guide openings (12) for guiding the valve needle, wherein each guide opening is penetrated by one valve needle (31, 32, 33), respectively.

8. The gas injector as claimed in claim 7, wherein the guide openings (12) of the guide member (11) each have two circular openings (111, 112) which transition into one another and have different diameters.

9. A gas injector according to claim 7 or 8, wherein the resetting device (10) is supported on the guide member (11).

10. A gas injector according to any one of claims 7 to 9, wherein the guide member (11) has one or more flattened portions (110) on the outer periphery for gas to flow through.

11. A gas injector according to any one of claims 7 to 10, wherein the valve needles (31, 32, 33) each have a constriction (13) which is arranged in the guide member (11).

12. The gas injector according to any one of claims 2 to 11, wherein the operating unit (3) has a closed lubricant chamber (4) which is filled with lubricant and in which the armature (20) of the electromagnetic actuator (2) is arranged, wherein the lubricant chamber (4) comprises a flexible sealing element (5) which seals the lubricant chamber with respect to the gas path in the gas injector.