WO2011160900A1

WO2011160900A1 - Fuel injection device comprising a hydraulic coupler

Info

Publication number: WO2011160900A1
Application number: PCT/EP2011/058127
Authority: WO
Inventors: Peter Baumgartner
Original assignee: Robert Bosch Gmbh
Priority date: 2010-06-23
Filing date: 2011-05-19
Publication date: 2011-12-29
Also published as: DE102010030383A1

Abstract

The invention relates to a fuel injection device of an internal combustion engine, comprising a movably guided valve element (2), which is composed of multiple parts and integrated in a housing (3) and a nozzle body (4) and which comprises a control piston (8) and a nozzle needle (9), which, within a high-pressure chamber (33), are connected via a hydraulic coupler (10). The control piston (8) associated with a control chamber (26) can be connected via a selector valve (6) to a high-pressure connection (5) or a low-pressure connection (7). Depending on a switching position of the selector valve (6), the nozzle needle (9) lifts off a valve seat (41) to inject fuel or closes the valve seat (41). The hydraulic coupler (10) comprises a guide body (12), consisting of a base disk (11) that is braced in a hydraulically sealing manner between the housing (3) and the nozzle body (4) and has a central opening (13), in which the nozzle needle (9) and the control piston (8) are guided via a respective guide collar (14, 15). The hydraulic coupler (10) forms a first annular chamber (20), which is bounded by the base disc (11), the guide collar (14), the control surface (22) and a separate sliding sleeve (17) of the control piston (8). A second annular chamber (21) connected to the first annular chamber (20) at least via a leakage gap (32) is bounded by the base disk (11), including the immediately associated guide bushing (16), as well as a control surface (23) and the guide collar (15) of the nozzle needle (9).

Description

description

title

Fuel injection device with hydraulic coupler prior art

The invention relates to a fuel injection device, also referred to as a fuel injector, for an internal combustion engine, having a valve element which is constructed in several parts and integrated in a housing and a nozzle body. The valve element comprises a control piston and a nozzle needle. These components, the control piston and the nozzle needle, are connected within a high-pressure chamber via a hydraulic coupler. The control piston communicates with a control chamber, which can be controlled by a control valve, connected to a low pressure or return system. Depending on a switching position of the switching valve, a fuel injection takes place via an outlet opening in that the nozzle needle lifts off from a valve seat or causes a closure of the nozzle needle.

State of the art

Fuel injection devices are generally known, with which a diesel or gasoline fuel is injected directly into a combustion chamber of an internal combustion engine. For this purpose, a valve element is arranged in a housing, which in the region of a fuel outlet opening has a pressure surface acting overall in the opening direction of the valve element. At the opposite end of the valve element acting in the closing direction control surface is present, which limits a control chamber. In these devices, hydraulic vibrations between the common rail formed as a high-pressure accumulator and the injection device can occur. Such vibrations have an adverse effect on the course of injection, in particular in the case of multiple injection, and on the wear of the nozzle needle or the injector. To counteract these pressure oscillations, it is known from DE 10 2006 026 877 A1 to provide within the housing an additional storage volume which damps vibrations.

A generic fuel injection device is known from WO 2007/098975 A1. In this stroke-controlled injection device, a control chamber, which interacts with a control or coupler piston via a control surface, is actuated by a control valve. The control piston is guided at the end remote from the control chamber in a guide element and supported directly on the nozzle needle inserted in a nozzle needle within a coupler space of the guide member. With the fuel injection device closed, a high fuel pressure provided by a common rail is present in a region of the pressure surface acting in the opening direction and in the closing direction of the control surface. In order to open the valve element or the nozzle needle, the pressure applied to the control surface is lowered until the hydraulic force resultant acting in the opening direction exceeds the force acting on the pressure surface in the closing direction in order to bring about opening of the nozzle needle.

Object of the present invention is to provide a comparison with known devices improved fuel injector, which is constructed as possible optimized component and easy to install.

This object is achieved by a fuel injection device having the features of claim 1. Further advantageous embodiments of the invention are the subject of the dependent claims.

Disclosure of the invention

According to the invention, a hydraulic coupler with a guide body is provided for a fuel injection device, which comprises a hydraulically tightly clamped between the housing and the nozzle body base disk. In the base disk, a central opening is integrated to guide the nozzle needle and the control piston or the coupler piston, in each of which a guide collar of the nozzle needle and the control piston engage in a form-fitting manner. The structural design also provides that the hydraulic coupler comprises a first annulus, which differs from the base disc, the guide collar, a control surface and a separate sliding sleeve of the control piston is limited. A second annular space of the hydraulic coupler, which is connected via at least one leakage gap with the first annular space is bounded by the base disk, including directly associated guide bushing and a control surface and the guide collar of the nozzle needle. The guide bush connected in one piece with the base disk comprises an inner diameter which is larger than the central opening for the guide collar and encloses the nozzle needle on the outside with limited lengths.

By integrated in the base disc opening for guiding the control piston and the nozzle needle accounts for previously known solutions various components, such as an additional disc or spring, which advantageously adjusts a component-optimized structure of the hydraulic coupler. In addition, the invention provides a simplified component and space-optimized design, which leads to a cost-effective production of the valve element. In addition, components of previous devices can advantageously be used to implement the present invention. Due to the reduced component circumference and the strained directly between the housing and the nozzle body base plate also simplifies the assembly. Thus, a significant cost advantage can be realized by the fuel injection device according to the invention.

The hydraulic coupler, for realizing a path translation and reversal of the direction of travel, according to the invention, also includes the advantages of previous solutions, such as a centric, leak-free, function-enhancing high-pressure volume. This results in advantages in terms of manufacturing, such as the simple introduction of the central opening in the base disk. Furthermore, the strength of the hydraulic valve element improves due to elimination of critical intersections of high pressure bores, which has an advantageous effect on the function and life of the fuel injector. The fuel injection device according to the invention is further characterized by a high efficiency, as compared to previous devices between the valve element and the housing leaks no longer occur. The structure according to the invention, in particular the guide body of the hydraulic coupler, allows a simplified adaptation or compensation of manufacturing tolerances, which advantageously improve the injector function. The two-chamber coupler according to the invention provides an increased internal storage volume which prevents the occurrence of adverse hydraulic oscillations between the fuel injector and the high pressure port, a common rail. These vibrations or pressure waves have a negative influence on the course of injection, in particular in the case of multiple injections and the wear of the nozzle needle on the valve seat. In addition, the accuracy of the injection quantity increases with multiple injections. The hydraulic coupler of two separate components of the valve element increases the degree of freedom in the design of the fuel injection device. The valve element is preferably designed with an almost matching pressure surface and control surface in order to be able to realize pressure equalization with correspondingly high dynamics.

According to a preferred embodiment, a separate, linearly displaceable, the control piston enclosing sliding sleeve or control sleeve is provided to form the second annular space of the hydraulic coupler. The control sleeve enclosing the sliding sleeve is acted upon by a spring means, in particular a compression spring and is non-positively and sealed supported by a sealing seat on the base disc of the guide body. To optimize the function of the sliding sleeve is provided that the biasing force of the applied spring means is tuned to a defined pressure level in the annulus. As a result, the sliding sleeve can additionally perform a switching function in that the sliding sleeve lifts off from the sealing seat when the overpressure in the first annular space of the hydraulic coupler is greater than the pressure in the high-pressure space. For this purpose, the sliding sleeve on the inside comprises a radially stepped portion which is widened relative to the control piston and which has an annular hydraulic

forms actable control surface.

As a measure to prevent skewing in the installed state, the sliding sleeve is largely guided centrally on a guide section axially spaced from the end faces of the sliding sleeve on the control piston. The sliding sleeve has added to the guide section an enlarged inner diameter. This measure ensures a production-related tolerance compensation and ensures a closed annular abutment of the sliding sleeve on the sealing seat of the base plate, to achieve an effective seal. According to a further embodiment of the invention it is provided that the hydraulically effective pressure and / or control surfaces of the valve element are dimensioned differently. Thus, for example, the response of the hydraulic coupler or the operation of the valve element can be directly influenced, for example, to realize a different actuating speed between the control piston and the nozzle needle. For this purpose, it makes sense to interpret the hydraulically effective control surfaces of the annular spaces of the hydraulic coupler deviating from each other. The size of these annular spaces is determined directly by the diameter of the control piston and the nozzle needle. Furthermore, the volume size of the annular spaces of the hydraulic coupler of the length and the

Diameter of the guide collars of the control piston and the nozzle needle determined.

A preferred design provides to use a control piston whose diameter exceeds the diameter of the nozzle needle. This measure causes a faster response of the control piston to the nozzle needle at the beginning of the fuel injection.

In a design of the hydraulic coupler, wherein the hydraulically actuated surface of the nozzle needle is smaller than the comparable surface of the control piston, the hydraulic coupler acts with open nozzle needle as a closing direction in the hydraulic spring, which assists a safe closing of the nozzle needle.

Another design criterion of the hydraulic coupler relates to the guided in the base disc guide collars, which are tailored, inter alia, to the component thickness of the base disc. The guide collar length exceeds the respective travel of the associated component by an amount that ensures safe guidance of the control piston and the nozzle needle in the opening of the base disc. In the case of travel paths that occur differently, it is advisable, for example, for a guide collar length of the control piston to exceed a guide collar length of the nozzle needle.

To optimize the function of the hydraulic coupler is further provided according to the invention that the central opening of the base disc of the guide body has at least one longitudinal groove. With this measure, there is an accelerated pressure and flow compensation of the hydraulic fluid of the spaced annular channels of the hydraulic coupler. In addition or as an alternative to a longitudinal groove, according to a further constructive concept of the invention, the nozzle needle engages with a guide collar designed as a polygonal profile in the central opening of the base disk. It is also advantageous to provide the guide collar of the control piston with a corresponding polygonal profile.

Due to the installation position of the base disk, two separate areas of the high-pressure chamber form. To achieve an unimpeded fluid loading of the nozzle needle pressure chamber, at least one fluid passage or a fluid channel is provided in the base disk. As a measure to influence the fluid flow, it is advisable to introduce a flow restrictor into each fluid passage of the base disk.

According to the inventive concept, the base disk of the guide body is clamped hydraulically tight between the housing and the nozzle body. In order to achieve a defined exact installation position of the guide body, the base disk is enclosed on the outside directly by a clamping nut which joins the housing and the nozzle, whereby no disadvantageous misalignment of the valve element occurs. To create an effective stroke limitation of the nozzle needle, the base disk within the second annular space forms a stroke stop, which advantageously surrounds the edge zone of the central opening. For targeted influence on the injection quantity, it is advisable to additionally introduce a travel of the nozzle needle limiting Hubeinstellstück.

Brief description of the drawings

An embodiment of the invention will be described below with reference to the drawings.

Show it:

1 shows a fuel injection device with hydraulic coupler, according to a preferred embodiment, 2 shows a detail "X" of the fuel injection device, according to Figure 1 in an enlarged view.

Embodiment of the invention

The injection device 1 according to Figure 1, which also as fuel! may be referred to, comprises a valve element 2, which is arranged displaceably in a housing 3 and in a nozzle body 4. A high-pressure pump not shown in FIG. 1 conveys the diesel or petrol fuel from a reservoir into a high-pressure connection 5, also referred to as a common rail, to which a plurality of injection devices 1 are connected, via which the fuel can be injected directly into associated combustion chambers of an internal combustion engine. Furthermore, the injection device 1 is connected via a switching valve 6 with a low pressure port 7 and a subsequent fuel reservoir. The valve element 2 comprises a guided in the housing 3, also referred to as a coupler piston control piston 8 and a nozzle needle 9, which are connected via a hydraulic coupler 10. The structure of the coupler 10 includes a guide body 12, consisting of a base plate 1 1 inserted between the housing 3 and the nozzle body 4, which is clamped hydraulically tight by means of a clamping nut 43. In a central opening 13 of the base disk 1 1, the control piston 8 and the nozzle needle 9 are each guided over a guide collar 14,15. The nozzle needle 9 is further guided in an integrally connected to the base disc 1 1 guide bush 16. A separate, the control piston 8 enclosing, acted upon by a spring means 18 sliding sleeve 17 is frictionally supported by a sealing seat 19 on the base plate 1 1.

The hydraulic coupler 10 forms two at least via a leakage gap 32 connected annular spaces 20,21. A first annular space 20 is delimited by the base disk 11, the guide collar 14, a control surface 22 and the separate sliding sleeve 17 of the control piston 8. The second annular space 21 is limited by the base disk

1 1, the guide disc 16 directly associated with the base plate 1 1, which has a larger, the nozzle needle 9 limited enclosing inner diameter compared to the central opening 13 of the base disc 1 1. A further delimitation of the second annular space 21 is effected by a control surface 23 and the guide collar 15 of the nozzle needle 9. At the free end, the control piston 8 is guided with an enlarged piston diameter in a sleeve 25 assigned to an end body 24, which to confine a control room 26 together. When the switching valve 6 is de-energized and the nozzle needle 9 is closed according to FIG. 1, the high-pressure port 5 is connected via the channel 28 to an annular channel 29 and the switching valve 6. From the annular channel 29 of the system or rail pressure in a high-pressure chamber 33 and a supply throttle 30 is transmitted to the control chamber 26. Furthermore, the system pressure via a fluid passage 34 of the base disk 1 1 in a nozzle needle side portion of the high pressure chamber 33 and via a channel 35 in the pressure chamber 36 a. Due to unavoidable leaks through the leadership of the nozzle needle 9 in the sliding sleeve 16 and the control piston 8 in the guide bush 17 prevails in the annular spaces 20,21 of the coupler 10 of the system pressure. With closed nozzle needle

9, only a part of the pressure surface 36 in the region of the outlet openings 37a, 37b is acted upon by the rail pressure, thereby adjusts in a summation with the pressure surface 38 on the nozzle needle 9 in an opening direction acting hydraulic force, which is less than that in the closing direction a control surface 39 in the control chamber 26 of the control piston 8 acting force, which is supported by the force of a spring means 40.

After energizing the switching valve 6, which is designed as a 2/2-way valve, the connection to the high-pressure connection 5 is interrupted and a connection to the low-pressure connection 7 is established, connected to a pressure drop in the control chamber

26. The thereby adjusting pressure and force difference between the control surface 22 in the annular space 20 and the control surface 39 of the actuating piston 8 causes an actuating movement of the actuating piston 8 in the arrow direction, against the spring force of the spring means 40. The adjusting movement of the actuating piston 8 also interrupts the connection of the Control chamber 26 to the channel 28 and causes an increase in volume of the annular space

20, which reduces the hydraulic pressure in both annular spaces 20, 21 of the hydraulic coupler 10, which are connected via a leakage gap 32. The reduced pressure allows an adjustment, a lifting of the nozzle needle 9 from a sealing seat 41, whereby the acted upon by the hydraulic fluid pressure surface 46 of the nozzle needle 9 is increased, and thus supports the opening process of the nozzle needle 9 and a

Fuel injection through the outlet openings 37a, 37b to start in a combustion chamber of the internal combustion engine. To end the injection, the switching valve 6 is brought into the starting position, whereby the control chamber 26 and the high pressure chamber 33 are connected to the high pressure port 5. Due to the increase of the pressure in the control chamber 26 to the rail pressure of the control piston 8 is moved in the closing direction. FIG. 2 shows the detail "X" of the injection device 1 according to FIG. 1 on an enlarged scale and in particular clarifies the structure of the hydraulic coupler 10. To achieve a more rapid pressure and volume compensation between the annular spaces 20, 21, it closes in the base disk 1 1 integrated opening 13 for receiving the guide collars 14, 15 at least one longitudinal groove 42. Alternatively or in addition to the longitudinal groove 42, the guide collar 15 of the nozzle needle 9 is formed as a polygonal profile, for example as a square Diameter D _{2 of} the nozzle needle 9, which correspondingly differentiates the hydraulically actuated control surfaces 22, 23 of the annular spaces 20, 21. This design accelerates the response, the adjusting movement of the control piston 8 after energizing the switching valve 6. A stepped section 31 pointing to the sealing seat 19 , a radial step of the sliding sleeve 17 with the diameter R D ₃ forms a hydraulically loadable annular surface, which allows for pressure peaks occurring within the annular space 20, an overpressure against the Hochdruckdraum 33 lifting the sliding sleeve 17 of the base plate 1 1. In order to influence the fuel flow within the high-pressure space 33, a flow throttle 45 is integrated in the fluid passage 34 of the base disk 11. The diameter D _{4 of} the annular space 21 exceeds the diameter D _{2 of} the nozzle needle 9, and thus ensures an unimpeded adjusting movement of the nozzle needle 9 within the annular space 21st Furthermore, a stroke stop 44 is provided for the nozzle needle 9 within the annular space 21 on the base plate 1 1. The lengths Si and S _{2 of} the guide collars 14, 15 are different, which are chosen in coordination with the base plate thickness so that in all positions of the valve element 2, both the control piston 8 and the nozzle needle 9 in the base plate 1 1 is sufficiently performed.

Claims

claims

1 . Fuel injection device of an internal combustion engine, with a multi-part constructed, in a housing (3) and a nozzle body (4) integrated, slidably guided valve element (2) comprising a control piston (8) and a nozzle needle (9) within a high-pressure chamber (33) via a hydraulic

Coupler (10) are connected, wherein the control piston (8) cooperates with a control chamber (26) which is connectable via a switching valve (6) with a high pressure port (5) or a low pressure port (7) and depending on a switching position of the switching valve ( 6) the nozzle needle (9) lifts off from a valve seat (41) for fuel injection via an outlet opening (34a, 37b) or closes the valve seat (41),

characterized in that the hydraulic coupler (10) comprises a guide body (12) consisting of a between the housing (3) and the nozzle body (4) hydraulically tight braced base disc (1 1) with a central opening (13) in which the Nozzle needle (9) and the control piston (8) are each guided via a guide collar (14, 15) and the hydraulic coupler (10) comprises a first annular space (20) which extends from the base disk (11), the guide collar (14). , a control surface (22) and a separate sliding sleeve (17) of the control piston (8) is limited and a second, at least over a leakage gap (32) with the first annular space (20) connected annular space (21) of the base disc (1 1), including directly associated guide bushing (16), and a control surface (23) and the guide collar (15) of the nozzle needle (9) is limited.

2. Injection device according to claim 1,

characterized in that the separate linearly displaceable, the control piston

(8) enclosing sliding sleeve (17) of the hydraulic coupler (10) via a sealing seat (19) acted upon by a spring means (40) on the base disc (1 1) of the guide body (12) is supported.

3. Injection device according to claim 2,

characterized in that the sliding sleeve (17) at an overpressure in the first Annular space (20) relative to a pressure in the high pressure chamber (33) from the sealing seat (19) lifts, wherein the sliding sleeve (17) sealing seat side relative to the control piston (8) inside a stepped portion (31).

4. Injection device according to claim 2,

characterized in that the sliding sleeve (17) via a respective end face of the sliding sleeve (17) axially spaced guide portion (S ₃ ) on the control piston (8) is guided.

5. Injection device according to at least one of claims 1 to 4,

characterized in that the hydraulically effective pressure and / or control surfaces of the valve element (2) are dimensioned differently.

6. Injection device according to at least one of claims 1 to 5,

characterized in that to achieve deviating from each other designed hydraulically effective control surfaces (22, 23) of the hydraulic coupler (10) exceeds a diameter (D-ι) of the control piston (8) has a diameter (D ₂ ) of the nozzle needle (9).

7. Injection device according to at least one of claims 1 to 6,

characterized in that the guide collars (14, 15) with a length (S'i, S ₂ ) in the base disc (1 1) are performed, exceed the maximum travel of the nozzle needle (9) and the control piston (8).

8. Injection device according to at least one of claims 1 to 7,

characterized in that the central opening (13) of the base disc (1 1) of the guide body (12) at least one of the annular channels (20,21) of the hydraulic coupler (10) connecting longitudinal groove (42).

9. Injection device according to at least one of claims 1 to 8,

characterized in that the nozzle needle (9) and / or the control piston (8) engages with a cylindrical or formed as a polygonal profile guide collar (14, 15) in the opening (13) of the base disc (1 1).

10. Injection device according to at least one of claims 1 to 9,

characterized in that the base plate dividing the high-pressure chamber (33) Be (1 1) of the guide body (12) includes at least one Fluiddurchtntt (34) or fluid channel.

1 1. Injection device according to claim 10,

characterized in that a flow restrictor (45) is integrated in the fluid passage (34) of the base disc (11) of the guide body (12).

12. Injection device according to at least one of claims 1 to 1 1,

characterized in that the base disc (1 1) of the guide body (12) on the outside by a housing (3) and the nozzle body (4) together clamping nut (43) is enclosed.

13. Injection device according to at least one of claims 1 to 12,

characterized in that within the second annular space (21), the base disc (1 1) of the guide body forms a stroke stop (44) for the nozzle needle (9).