WO2017029076A1

WO2017029076A1 - Fuel injector

Info

Publication number: WO2017029076A1
Application number: PCT/EP2016/067664
Authority: WO
Inventors: Heinrich Werger
Original assignee: Robert Bosch Gmbh
Priority date: 2015-08-20
Filing date: 2016-07-25
Publication date: 2017-02-23
Also published as: DE102015215943A1

Abstract

The invention relates to a fuel injector (1) for injecting fuel into the combustion chamber of an internal combustion engine, wherein the fuel injector (1) comprises an injector body (2) and a nozzle body (5). The injector body (2) and the nozzle body (5) are clamped together via a nozzle clamping nut (6). A pressure chamber (8) is formed in the nozzle body (5), which can be supplied with pressurised fuel via a supply bore (13) A nozzle needle (7) that releases or closes at least one injection opening (9) is arranged in the pressure chamber (8) such that it can move longitudinally. Cooling channels (30) through which coolant can flow are formed in the nozzle clamping nut (6) for cooling the nozzle body (5), wherein the cooling channels (30) comprise a coolant supply (31) and a coolant return (32).

Description

description

fuel injector

State of the art

The invention relates to a fuel injector according to the preamble of

Claim 1.

A fuel injector for injecting fuel into the combustion chamber of an internal combustion engine according to the preamble of claim 1 is known from

EP1781931 B1. The known fuel injector comprises a

Injector body and a nozzle body. The injector body and the nozzle body are clamped together by a nozzle lock nut. In the nozzle body, a pressure chamber is formed, which is supplied via an inlet bore with pressurized fuel. An at least one injection opening releasing or closing longitudinally movable nozzle needle is arranged to be longitudinally movable in the pressure chamber.

Furthermore, the known fuel injector in the nozzle body formed on cooling channels. These cooling channels are used to cool the nozzle body and nozzle needle, especially in the combustion chamber facing areas.

The formation of the cooling channels in the nozzle body leads to a reduction in the strength of the nozzle body and thus its life. Furthermore, it is not possible to convert existing fuel injectors without active cooling simply on versions with cooling channels.

Disclosure of the invention In contrast, reduce the cooling channels of the invention

Fuel injector, the strength of the nozzle body not. In addition, active cooling can be easily retrofitted in conventional fuel injectors.

This includes a nozzle body. In the nozzle body, a pressure chamber is formed, which is supplied via an inlet bore with pressurized fuel. A nozzle needle releasing or closing at least one injection opening is arranged longitudinally movably in the pressure space. A cooling sleeve is arranged surrounding the nozzle body. In the cooling sleeve can be flowed through with coolant through cooling channels for cooling the nozzle body.

Preferably, the cooling sleeve with its cooling channels surrounds the nozzle body in the radial direction at its end facing the combustion chamber. As a result, the cooling of the nozzle body takes place very close to the combustion chamber. Due to the design of the cooling channels in the cooling sleeve, the strength of the nozzle body is not reduced. Preferably, the cooling sleeve is not subjected to high pressure, so that the structural weakening by the cooling channels has no adverse effect on their life.

Furthermore, it is possible to retrofit conventional fuel injectors without active cooling with a corresponding cooling sleeve, so that an active cooling is retrofitted. The further design of the fuel! The injector does not have to be changed or not changed significantly.

In preferred embodiments, the cooling sleeve also has the function of

Nozzle clamping nut and braces the nozzle body with other components of the injector, for example with an injector body.

Advantageously, the cooling channels comprise a coolant inlet and a coolant return. As a result, a controlled flow is achieved in the cooling channels.

In an advantageous development, the cooling sleeve at its end facing the combustion chamber on an outer body and an inner body, wherein the cooling channels at least partially between the outer body and the Inner body are formed. By means of this at least two-part embodiment of the cooling sleeve, the cooling channels can be manufactured comparatively easily. Nevertheless, even a complex flow geometry can be produced. Preferably, the outer body and inner body are then connected to each other by means of brazing media-tight.

In advantageous alternative embodiments, the cooling sleeve can also be made in one piece and the cooling channels are made for example by rapid prototyping or 3D printing.

In advantageous developments is between the outer body and the

Inner body formed over the circumference of the cooling sleeve with a flow-through coolant annulus. Preferably, the annulus connects the

Coolant inlet with the coolant return. Through the annulus, the cooling of the nozzle body takes place over its entire circumference at its end facing the combustion chamber. This cooling is particularly effective because the combustion chamber side is the hottest area of the nozzle body. Because such a relatively large amount of heat is dissipated from the tip of the nozzle body, thereby also indirectly the tip of the nozzle needle is effectively cooled.

In advantageous embodiments, the cooling channels, for example the

Coolant inlet and the coolant return, in each case a kidney-shaped flow cross section in the region between the outer body and the inner body. As a result, any tolerances between the inner body and outer body and possibly other components can be compensated without the

Affecting mass flow of the coolant through the cooling channels.

In advantageous developments of the invention is on the cooling sleeve a

Wärmeleitfläche formed. The heat-conducting surface contacts the nozzle body, preferably the end of the nozzle body facing the combustion chamber. The contacting is preferably carried out in the radial direction. This generates a heat flow from the comparatively very hot tip of the nozzle body via the heat-conducting surface into the cooling sleeve. In the cooling sleeve, the heat is dissipated again by the active cooling in the cooling channels. The Temperatures of the nozzle body and also nozzle needle, in particular at their ends facing the combustion chamber, are thereby effectively cooled.

In advantageous embodiments, the fuel injector has a water sleeve. The fuel inlet and the fuel return are at least partially in the

Water sleeve formed. The water sleeve is an attachment to the

Fuel injector. The cooling channels are so at least partially taken from the stress critical components and laid in the water sleeve instead. Preferably, the cooling sleeve comprises several components,

For example, a main body of the cooling sleeve and inner and outer body.

The main body can simultaneously as a nozzle retaining nut of the

Fuel injector act. Due to the multi-part design of the cooling sleeve of the main body can be advantageously designed without cooling channels; the cooling channels run through the water sleeve and from there through the inner and outer body. Retrofitting conventional uncooled

Fuel injectors with active cooling is particularly simple in these embodiments. Inner and outer body together form one

Heat protection sleeve, which is advantageously in contact with the nozzle body - for example, via the heat conduction surface - and thus from the

temperature-critical areas of the nozzle body and nozzle needle a large

Dissipates heat.

In advantageous developments, the water sleeve is clamped media-tight with the interposition of a sealing element with the cooling sleeve. As a result, the cooling channels between water sleeve and cooling channels in a simple way

Sealed environment. In preferred embodiments, the sealing element is arranged between the water sleeve and the outer body of the cooling sleeve. The bracing itself can be done for example by a press fit or a screw.

Advantageously, at least two elongated holes are formed in the sealing element: a first slot arranged in the coolant inlet and a second slot disposed in the coolant return. As a result, the formation of the cooling channels in the sealing element in a simple manner. The slots have a comparatively large Flow cross section, so that no throttling of the coolant flow takes place at them.

In advantageous embodiments, the fuel injector has an injector body. Furthermore, the cooling sleeve is designed as a nozzle retaining nut and braces the injector, optionally with the interposition of other components, against the nozzle body. Thus, the cooling sleeve on the one hand has the function of an active cooling for the nozzle body and the other one

Verschraubungsfunktion.

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:

1 shows a longitudinal section through a fuel injector according to the prior art,

2 schematically shows a fuel injector according to the invention, wherein only the essential areas are shown,

3 shows the section A-A of Figure 2,

Fig. 4 shows a further embodiment of the invention

Fuel! in longitudinal section, with only the essential areas being shown,

5 shows the section B-B of Figure 4,

Fig. 6 shows yet another embodiment of the invention

Fuel! in longitudinal section, with only the essential areas being shown,

Fig. 7, the sealing element of the embodiment of Figure 6 in

Perspective view. The same elements or elements with the same function are provided in the figures with the same reference numerals.

1 shows a fuel injector 1 for injecting fuel into the combustion chamber of an internal combustion engine in longitudinal section, as is known from the prior art.

The known fuel injector 1 comprises an injector body 2, a

Valve body 3, an intermediate plate 4 and a nozzle body 5. All these components are held together by a nozzle lock nut 6. The nozzle body 5 in this case contains a nozzle needle 7, which in an im

Nozzle body 5 formed pressure chamber 8 is arranged longitudinally displaceable. During an opening movement of the nozzle needle 7, fuel is injected via a plurality of injection openings 9 formed in the nozzle body 5 into the combustion chamber of the internal combustion engine.

At the nozzle needle 7, a collar is visible, on which a compression spring 10 is supported. The other end of the compression spring 10 is supported on a control sleeve 1 1, which in turn rests against the underside of the intermediate plate 4. The control sleeve 1 1 defines with the upper, the injection openings 9 opposite end face of the nozzle needle 7 and the underside of the intermediate plate 4 a control chamber 12. The pressure prevailing in the control chamber 12 pressure is decisive for the control of the longitudinal movement of the nozzle needle 7.

In the fuel injector 1, an inlet bore 13 is formed. About the

Zulaufbohrung 13, the fuel pressure on the one hand in the pressure chamber 8 is effective, where he exerts a force in the opening direction of the nozzle needle 7 via a pressure shoulder of the nozzle needle 7. On the other hand, this fuel pressure acts on a trained in the control sleeve 1 1 inlet throttle 15 in the control chamber 12 and holds, supported by the force of the compression spring 10, the nozzle needle 7 in their

Closed position.

When an electromagnet 16 is subsequently actuated, a magnet armature 17 and a valve needle 18 connected to the magnet armature 17 are lifted off by a valve seat 19 formed on the valve body 3. The fuel off the control chamber 12 can flow in this way through an opening formed in the intermediate plate 4 outlet throttle 20 via the valve seat 19 in a drain passage 21. The lowering of the hydraulic force in this way on the upper end face of the nozzle needle 7 leads to an opening of the nozzle needle 7. The fuel from the pressure chamber 8 thus passes through the injection openings 9 into the combustion chamber.

As soon as the electromagnet 16 is switched off, the magnet armature 17 is pressed in the direction of the valve seat 19 by the force of a further compression spring 22, so that the valve needle 18 is pressed against the valve seat 19. In this way, the drainage path of the fuel via the outlet throttle 20 and the valve seat 19 is blocked. About the inlet throttle 15 is in the control room 12 again

Fuel pressure built up, whereby the hydraulic closing force is increased. As a result, the nozzle needle 7 is moved in the direction of the injection openings 9 and closes them. The injection process is then completed.

In order to cool the components in the region of the combustion chamber, cooling passages 30 are in valve body 3, intermediate plate 4 and nozzle body 5 of the known

Fuel injector 1 is formed. Thus, especially the tip of the nozzle needle 7 and the nozzle body 5 can be cooled. In the sectional view of Figure 1, the cooling channels 30 are partially in the inlet bore 13. However, this is only due to the sectional view, in the embodiments, the cooling channels 30 are separated from the inlet bore 13.

The cooling channels 30 of the known fuel! However, injectors 1 reduce the strength of the nozzle body 5, so that according to the invention, the cooling channels 30 are formed outside of the nozzle body 5.

2 schematically shows a fuel injector according to the invention, wherein only the essential areas are shown. A cooling sleeve 6 is as

Düsenspannmutter executed and braces the injector body 2 with the nozzle body 5; optionally, further components are arranged between these two components, for example a valve plate and / or a

Throttle plate. The longitudinally movably arranged in the nozzle body 5 nozzle needle 7 is not visible in the illustration of Figure 2. According to the invention, the cooling channels 30 in the cooling sleeve 6 or in the embodiment of FIG. Düsenspannmutter 6 formed or limited by this, wherein the

Cooling channels 30 include a coolant inlet 31 and a coolant return 32. The coolant inlet 31 and the coolant return 32 can be embodied, for example, as bores which run essentially in the direction of the longitudinal axis of the fuel injector 1. Depending on the requirement or operating situation, a coolant can flow through the cooling channels 30 in order to cool the fuel injector 1, especially in the region of the nozzle needle tip. The cooling channels 30 may have a connection to the cooling sleeve 6, as shown by way of example in FIG. 2 for the coolant inlet 31, or also by the cooling sleeve 6 in FIG

Injector 2 are continued, as exemplified for the coolant return 32.

At its end facing the combustion chamber, the cooling sleeve 6 has a collar 61, against which the contact with the nozzle body 5 bears with the injector body 2 for clamping. The collar 61 is made extended and the combustion chamber side covers a nozzle shaft 51 of the nozzle body 5 for the most part. The collar 61 or the entire cooling sleeve 6 may be designed in several parts, so that the cooling channels 30 can be made easier in the region of the nozzle shaft 51.

In the embodiment of Figure 2, the collar 61 is made in two parts and includes an outer body 62 and an inner body 63. Areas of

Cooling channels 30 are designed so that both the coolant inlet 31 and the coolant return 32 are at least partially formed between the outer body 62 and the inner body 63 and are limited by this. The outer body 62 and the inner body 63 are connected together by brazing, for example, such that the cooling channels 30 to the environment

are sealed media-tight.

Advantageously, the cooling sleeve 6 has a heat-conducting surface 64, which contacts the nozzle body 5 and thus guides the heat energy introduced from the combustion chamber into the nozzle body 5 via the heat-conducting surface 64 to the cooling sleeve 6 and dissipates it through the cooling channels 30. In the embodiment of Figure 2, the heat-conducting surface 64 is formed as a cylindrical inner surface on the inner body 63. The inner body 63 thus also has the function of a Heat protection sleeve to selectively dissipate heat energy from the nozzle shaft 51 and the tip of the nozzle needle 7.

At the combustion chamber facing the end of the fuel injector 1, an annular space 65 is formed between the outer body 62 and the inner body 63, which extends over the entire circumference of the inner body 63. The annular space 65 is part of the cooling channels 30 and is arranged in the flow direction of the coolant between the coolant inlet 31 and the coolant return 32. By way of example, a ring arrow 66 is shown, which the

Coolant flow in the annular space 65 schematically represents.

Air gaps 71, 72 between the nozzle body 5 and the cooling sleeve 6 are preferably formed with increasing distance from the combustion chamber. As a result, further thermal bridges between the nozzle body 5 and the cooling sleeve 6 are avoided, since these additional thermal bridges would result in an increased heat flow through the nozzle body 5 and thus the effectiveness of the

Would reduce heat conduction 64.

Furthermore, the outer body 62 and the inner body 63 are advantageously arranged in the cooling sleeve 6, that they largely outside the

Force flow of the biasing force between injector body 2 and nozzle body 5 are; As a result, the strength of outer body 62 and inner body 63 is not affected by the biasing force. The course of injection of the fuel! Njektors 1 can in the inventive

Embodiments of an electromagnet, as shown in the prior art in Figure 1, or by any other control devices, such as a piezoelectric actuator, are controlled. 3 shows the section A-A of Figure 2: In this embodiment, the

Coolant inlet 31 and the coolant return 32 in the form of a semi-circular recess in the outer body 62, while the outer wall of the

Inner body 63 has a cylindrical shape. This is a very easy to manufacture form of coolant inlet 31 and coolant return 32. The air gap 71 between the nozzle shaft 51 and the inner body 63 serves the thermal

Separation of these two components in this area. In alternative embodiments, it is also possible to produce the cooling sleeve 6 in one piece, so that the division into inner body 63 and outer body 62 is omitted. This can be done, for example, by means of "rapid prototyping" or 3D printing.

4 shows a further embodiment of the invention

Fuel injector 1. In the embodiment of Figure 4, the cooling sleeve 6 is designed in three parts, with a main body 60, the inner body 63 and the outer body 62. The main body 60 includes the largest areas of the cooling sleeve 6 up to the collar 61 and has the function of

Nozzle clamping nut. The main body 60 braces the nozzle body 5 in the usual way with the injector body 2 via its collar 61.

In the area of the nozzle shaft 51, the inner body 63 and the outer body 62 are arranged, similar to the preceding embodiments. However, in the sectional plane B-B, a parting plane is formed between the main body 60 on the one hand and the inner and outer bodies 63, 62 on the other hand.

In the embodiment of Figure 4, the inner body 63 and the

Outer body 62 a heat protection sleeve, on the one hand over the

Wärmeleitfläche 64 is plugged or pressed onto the nozzle shaft 51 and on the other fixed or clamped on the biasing force or Pratzkraft between the collar 61 and a cylinder head 80 of the internal combustion engine.

FIG. 5 shows the section B-B of FIG. 4 in a preferred embodiment, wherein only the heat-protection sleeve 62, 63 is shown. The outer body 62 has in the region of the plane B-B, ie on its front side, kidney-shaped

Recesses 31 a, 32 a, which each form a volume expansion of the coolant inlet 31 and the coolant return 32. Thereby, the positioning of the heat insulating sleeve 62, 63 to the main body 60 of the cooling sleeve 6 is made more tolerant.

In alternative embodiments, the kidney-shaped recesses may also be formed in the inner body 63 or in the main body 60. Fig.6 shows yet another embodiment of the invention

Fuel injector 1. Also in the embodiment of Figure 6, the cooling sleeve 6 is designed in three parts, with a main body 60, the inner body 63 and the outer body 62, similar to the embodiment of FIG. The main body 60 thus again has the function of a nozzle retaining nut.

In addition, however, outside the fuel injector 1 is a water sleeve 85 with an inlet channel 86 formed therein and a non-illustrated

Drain channel arranged. The inlet channel 86 is part of the coolant inlet 31 and the outlet channel is part of the coolant return 32. Between the

Water sleeve 85 and the outer body 62 is a sealing element 90 is arranged therein with radially elongated holes 35, wherein the slots 35 are part of the coolant inlet 31 and the coolant return 32. In this embodiment, the cooling channels 30 are no longer through the

Main body 60 of the cooling sleeve 6, but by water sleeve 85, sealing member 90, outer body 62 and inner body 63. In the outer body 62 is a

Radial bore 34 is formed. Between outer body 62 and inner body 63, an axial bore 33 is formed. The coolant inlet 31 thus has in

Flow direction of the coolant to the inlet channel 85, at least one slot 35, the radial bore 34 and the axial bore 33 and then opens into the annular space 65th

The coolant return 32 is not explicitly drawn in FIG. 6, but runs analogously over the bores or cavities with the reference symbols 65, 33, 34,

35, 86.

In alternative embodiments, the cooling sleeve 6 can also be made in one or two parts, analogous to the previous embodiments, for example, the main body 60 and the inner body 63 are combined to form a component.

Fig. 7 shows the sealing element of the embodiment of Figure 6 in

perspective view. In this embodiment, four slots 35 are formed radially, with two slots in the coolant inlet 31 and in the Refrigerant return 32 are arranged. In alternative embodiments, however, any numbers and shapes of slots 35 are possible.

The operation of the fuel injector 1 according to the invention is as follows:

The opening and closing of the nozzle needle 7 of the fuel! Njektors 1 is controlled by means of a control valve or the electromagnet 16. If the

Control chamber 12 is relieved by the control valve, lifts the nozzle needle 7 from its seat and are the injection ports 9 free, so that fuel is injected under high pressure into the combustion chamber of the internal combustion engine.

The tip of the nozzle body 5 in the region of the injection openings 9 thus protrudes into the combustion chamber and is therefore exposed to very high temperatures. Also, the other components in the immediate vicinity to how

For example, the nozzle needle 7, experience very high temperatures. To reduce these temperatures or a high amount of heat from the

To dissipate the environment of the nozzle body 5, the fuel injector 1 has cooling channels 30. According to the invention, these cooling channels 30 are at least partially formed in the cooling sleeve 6 or limited by this.

Preferably, the cooling sleeve 6 at the same time has the function of a nozzle retaining nut. With the help of the flow through the cooling channels 30 by a suitable coolant, the temperatures at the components involved are reduced, which leads to an increase in the respective component life.

Furthermore, a fast fuel aging and subsequently a

Functional impairment due to deposit formation avoided.

The cooling sleeve 6 with the cooling channels 30 formed therein is also suitable as a retrofit kit for existing fuel injectors 1 without active cooling.

Claims

claims

1 . Fuel injector (1) for injecting fuel into the combustion chamber of an internal combustion engine, wherein the fuel! Injector (1) comprises a nozzle body (5), wherein in the nozzle body (5) a pressure chamber (8) is formed, which is supplied via an inlet bore (13) with pressurized fuel, one at least one injection opening (9) releasing or closing longitudinally movable nozzle needle (7) is arranged in the pressure chamber (8), wherein a cooling sleeve (6) is arranged surrounding the nozzle body (5),

characterized,

in that cooling channels (30) through which coolant can flow are provided in the cooling sleeve (6) for cooling the nozzle body (5).

2. Fuel injector (1) according to claim 1,

characterized,

that the cooling channels (30) a coolant inlet (31) and a

Include coolant return (32).

3. Fuel injector (1) according to claim 1 or 2,

characterized,

the cooling sleeve (6) has an outer body (62) and an inner body (63) at its end facing the combustion chamber, and in that the

Cooling channels (30) are at least partially formed between the outer body (62) and the inner body (63).

4. fuel injector (1) according to claim 3,

characterized,

in that an annular space (65) through which coolant can flow is formed between the outer body (62) and the inner body (63) over the circumference of the cooling sleeve (6).

5. Fuel injector (1) according to one of claims 3 or 4,

characterized, that the cooling channels (30) between the outer body (62) and the

Inner body (63) have kidney-shaped flow cross-sections.

Fuel injector (1) according to one of claims 1 to 5,

characterized,

a heat-conducting surface (64) is formed on the cooling sleeve (6), the heat-conducting surface (64) contacting the nozzle body (5), preferably at the end of the nozzle body (5) facing the combustion chamber.

Fuel injector (1) according to one of claims 2 to 6,

characterized,

the fuel injector (1) has a water sleeve (85), wherein the fuel inlet (31) and the fuel return (32) are partially in the

Water sleeve (85) are formed.

Fuel injector (1) according to claim 7,

characterized,

that the water sleeve (85) with the interposition of a sealing element (90) with the cooling sleeve (6) is clamped media-tight.

Fuel injector (1) according to claim 8,

characterized,

in that at least two slots (35) are formed in the sealing element (90), wherein the first slot (35) in the coolant inlet (31) and the second slot (35) in the coolant return (32) is arranged.

0. Fuel injector (1) according to one of claims 1 to 9,

characterized,

the fuel injector (1) has an injector body (2) and that the cooling sleeve (6) is designed as a nozzle retaining nut, wherein the injector body (2) and the nozzle body (5) are braced against one another by the cooling sleeve (6).