WO2009086997A1

WO2009086997A1 - Fuel injection valve

Info

Publication number: WO2009086997A1
Application number: PCT/EP2008/066708
Authority: WO
Inventors: Cetin Irmak
Original assignee: Robert Bosch Gmbh
Priority date: 2008-01-10
Filing date: 2008-12-03
Publication date: 2009-07-16
Also published as: DE102008003851A1; CN101910607A; EP2232045B1; EP2232045A1

Abstract

A fuel injection valve (1) is preferably configured as an injector for fuel injection systems of air-compressing, self-igniting internal combustion engines. The fuel injection valve (1) comprises a piezoelectric actuator (2) and a valve needle (14) that can be directly actuated by the actuator (2). Further, a throttle plate (7) is provided with an intake throttle (8) and an outlet throttle (24) which feed into a control space (9). The control space (9) is delimited by a front surface (13) of the valve needle (14) and a first side (10) of the throttle plate (7). Further, in order to control the outlet throttle (24), a valve sleeve (21) is provided at a second side (11) of the throttle plate (7) facing away from the first side (10) of the throttle plate (7), said sleeve being actuatable by the actuator (2) against a spring force of a first spring element (40) for release of the outlet throttle (24), wherein the actuator (2) can be actuated against a spring force of a second spring element (41). Upon release of the outlet throttle (24), the pressure in the control space (9) drops such that the valve needle (14) is actuated.

Description

description

title

Fuel injector

State of the art

The invention relates to a fuel injection valve with a piezoelectric actuator. Specifically, the invention relates to the field of injectors for fuel injection systems of air compressing, self-igniting internal combustion engines.

From DE 103 26 259 Al an injector for fuel injection systems of internal combustion engines, in particular direct injection diesel engines is known. Here, a arranged in an injector piezoelectric actuator is provided, which is held on first spring means on the one hand with the injector body and on the other hand with a sleeve-like booster piston in abutment. Furthermore, a nozzle body connected to the injector body and having a nozzle discharge opening is provided, in which a graduated nozzle needle is guided in an axially displaceable manner. In addition, second spring means are arranged within the booster piston, which hold the nozzle needle in the closed position together with the injection pressure acting on the back of the nozzle needle. A control chamber formed at a nozzle needle-side end of the booster piston communicates with a fuel supply under injection pressure one

Leak gap in connection, wherein the nozzle needle is acted upon by the fuel located in the control chamber in the opening direction. As a result, a control of the nozzle needle can be achieved by the piezoelectric actuator.

The known from DE 103 26 259 Al injector has the disadvantage that gaseous components, in particular air, which may be provided in the field of the booster piston, for example, when starting the engine affect the performance, at least for a certain start time. This can lead to problems when starting the internal combustion engine, especially after longer periods.

Disclosure of the invention

Advantages of the invention

The fuel injection valve according to the invention with the features of claim 1 has the advantage that a reliable operation is possible even in a start-up phase or after longer periods. Specifically, the reliability of the fuel injection valve and thus an internal combustion engine having such a fuel injection valve can be improved.

The measures listed in the dependent claims advantageous refinements of the fuel injection valve specified in claim 1 are possible.

It is advantageous that the valve sleeve has a support cap and that the actuator within the valve sleeve is arranged and supported from the inside to the support cap. Thereby, a compact configuration is possible, wherein the actuator can be axially aligned with respect to an axis of the fuel injection valve.

Further, it is advantageous that a valve piece is provided, which rests against the second side of the throttle plate, and that the valve piece is partially surrounded circumferentially of the valve sleeve. It is also advantageous that between the valve piece and the valve sleeve, an annular second control chamber is formed, in which the extended through the valve piece outlet throttle opens. By actuating the valve sleeve by means of the piezoelectric actuator, a partial or complete connection of the second control chamber with an actuator chamber, in which the valve sleeve surrounded with the actuator, take place, so that the outlet throttle is partially or completely released. This reduces the pressure in the control chamber, which acts on the end face of the valve needle, which has an actuation of the valve needle and thus a spraying of fuel from the fuel injection valve result.

Moreover, it is advantageous that the second spring element is arranged together with the piezoelectric actuator within the valve sleeve, wherein the second spring element is supported on the one hand on the valve piece and on the other hand rests at least indirectly on the actuator. Temperature and thus length changes of components of the fuel injection valve can be compensated by the first spring element and the second spring element. Further, it is advantageous that the second spring element is configured relatively hard, while the first spring element is configured relatively soft, that is, that a Spring constant of the first spring element smaller, in particular significantly smaller, is as a spring constant of the second spring element. As a result, lifting losses are kept as low as possible with respect to an actuation of the piezoelectric actuator, since a compression of the second spring element can mean a stroke loss of the actuator. The stroke of the piezoelectric actuator thereby at least essentially causes a compression of the first spring element.

The spring elements are preferably designed as a tube springs, whereby in particular an axially symmetric deflection and an axially symmetrical application of force of the spring elements is achieved. Furthermore, the valve sleeve is preferably provided with one or more holes which form openings to connect the interior of the valve sleeve with the actuator chamber, so that the exchange of a medium, in particular an escape of gaseous components, especially air, is possible.

Short description of the drawing

Preferred embodiments of the invention are explained in more detail in the following description with reference to the accompanying drawings. It shows:

Fig. 1 is a fuel injection valve with a piezoelectric actuator in a schematic

Sectional view according to an embodiment of the invention.

Embodiments of the invention

Fig. 1 shows a fuel injection valve 1 with a piezoelectric actuator 2 according to an embodiment of the invention. The

Fuel injection valve 1 can serve in particular as an injector for fuel injection systems of air-compressing, self-igniting internal combustion engines. A preferred use of the fuel injection valve 1 is for a fuel injection system with a common rail, the diesel fuel under high pressure leads to a plurality of fuel injection valves 1. However, the fuel injection valve 1 according to the invention is also suitable for other applications.

The fuel injection valve 1 has a valve housing 3. In the valve housing 3, a high-pressure bore 4 is designed, can be guided through the high-pressure fuel in a fuel chamber 5 in the interior of the valve housing 3. A section 6 of the high-pressure bore 4 leads through a throttle plate 7, which is connected in a suitable manner to the valve housing 3. From the high-pressure bore 4 branches off an inlet throttle 8, which is configured in the throttle plate 7. The inlet throttle 8 carries fuel into a control chamber 9 which is delimited by a first side 10 of the throttle plate 7, a control chamber sleeve 12 and an end face 13 of a valve needle 14. In the initial state is thus in the control chamber 9 under high pressure fuel, so that the valve needle 14 is pressed in the direction of a valve seat body 15. On the valve seat body 15, a valve seat surface 16 is formed, which cooperates with the valve needle 14 to form a sealing seat.

Within the valve housing 3, an actuator chamber 20 is also formed. The actuator chamber 20 is located on one of the first side 10 facing away from the second side 11 of the Throttle plate 7. In the actuator chamber 20, a valve sleeve 21 and a valve member 22 are arranged, wherein the valve member 22 is located directly on the second side 11 of the throttle plate 7. In the valve piece 22, a bore portion 23 is formed, which extends an outlet throttle 24 formed in the throttle plate 7. The outlet throttle 24 thereby connects the control chamber 9 with an annular second control chamber 25, which is formed between the valve member 22 and the valve sleeve 21. In this embodiment, an annular groove is formed on a cylinder jacket-shaped outer side 26 of the valve piece 22 for the design of the second control chamber 25. Furthermore, the valve piece 22 has a shoulder 27, which forms a valve seat with respect to the valve sleeve 21, so that in the initial position shown in FIG. 1, the second control chamber 25 is separated from the rest of the actuator chamber 20.

The actuator chamber 20 is connected via a return bore 28 to a tank of the fuel injection system, so that there is a relatively low pressure at the return bore 28. Thus, the fuel provided in the actuator chamber 20 is under low pressure. However, the second control chamber 25 is in the starting position under high pressure.

The valve sleeve 21 has an inner space 30, which is bounded on the one hand by the valve piece 22 and on the other hand by a support cap 31 of the valve sleeve 21 and circumferentially by a wall 32 of the valve sleeve 21. In the valve sleeve 21 bores 33, 34 are provided, so that a connection between the interior 30 of the valve sleeve 21 and the actuator chamber 20 is made. Specifically, the bore 34 forms an opening 35 in the valve piece 22, via which a balance between the inner space 30 of the valve sleeve 21 and the Actuator 20 exists.

In the actuator chamber 20, a first spring element 40 is also arranged, which is designed as a tube spring. The first spring element 40 is supported on the one hand on the valve housing 3 and on the other hand on the support cap 31 of the valve sleeve 21. The first spring element 40 has a certain prestress, so that the valve sleeve 21 is pressed against the shoulder 27 of the valve piece 22, so that the valve seat formed between the valve piece 22 and the valve sleeve 21 is closed.

Further, in the inner space 30 of the valve sleeve 21, the piezoelectric actuator 2 and a second spring element 41 are arranged. In this case, the piezoelectric actuator 2 is supported on the support cap 31 of the valve sleeve 21, while the second spring element 41 is supported on the one hand on the valve member 22 and on the other hand rests against the piezoelectric actuator 2. The second spring element 41 has a certain bias, so that the piezoelectric actuator 2 is biased.

The spring elements 40, 41 are preferably configured differently. Preferably, the first spring element 40 is soft, while the second spring element 41 is designed hard. That is, the first spring element 40 preferably has a smaller spring constant than the second spring element 41. Specifically, there is a relatively large difference in the spring constant of the spring elements 40, 41. This has the advantage that upon actuation of the piezoelectric actuator 2 of the Actuator 2 generated stroke at least substantially for shortening, that is, deflection, the first spring element 40 leads, while the second spring element 41 is not shortened as possible. As a result, the stroke of the piezoelectric actuator 2 is at least substantially used for opening the valve seat formed between the valve sleeve 21 and the shoulder 27 of the valve piece 22 in order to partially or completely release the second control chamber 25. Further, the first spring element 40 in the de-energized and thus unactuated state of the piezoelectric actuator 2, a higher spring force than the second spring element 41st

Upon actuation of the piezoelectric actuator 2, first, the second spring element 41 is shortened until the biasing force of the first spring element 40 is reached. Then, the first spring element 40 is compressed and thus shortened, so that the valve sleeve 21 is lifted from the valve seat formed on the shoulder 27. If then the spring force of the first spring element 40 is again greater than the spring force of the second spring element 41, the second spring element 41 is again compressed until it again exceeds the spring force of the first spring element 40. So the first spring element 40 is gradually compressed. Thus, therefore, the valve sleeve 21 is gradually raised. Thus, the second storage space 25 is opened to the actuator chamber 20, so that the outlet throttle 24 is released and the pressure of the fuel in the control chamber 9 decreases. The force effectively acting on the valve needle 14 is then executed to the control chamber 9, so that the valve needle 14 is lifted from its valve seat on the valve seat surface 16 and fuel from the fuel chamber 5 via the open sealing seat and the nozzle opening 42 is hosed.

By discharging the piezoelectric actuator 2 is the Fuel injection valve 1 closed again. In this case, carried by the first spring element 40, a provision of the valve sleeve 21 in the starting position shown in FIG. 1, in which the valve sleeve 21 rests again on the valve seat formed by the shoulder 27 of the valve member 22. In this case, the second control chamber 25 is closed, so that the pressure in the control chamber 9 rises again to the high pressure and an effective force for closing the valve needle 14 is generated in the starting position shown in FIG.

The fuel injection valve 1 has an axis 45. By the described embodiment, the piezoelectric actuator 2 with respect to the axis 45 of the fuel injection valve 1 can be centered. Furthermore, the spring elements 40, 41 can be aligned with respect to the axis 45, wherein a symmetrical force development of the spring elements 40, 41 is achieved by the design of the spring elements 40, 41 as a tube springs. This results in a compact design and high reliability of the fuel injection valve 1. Furthermore, gaseous components, in particular air, which are present in particular in a start phase of the fuel injection valve in the valve housing 3, can be removed in an advantageous manner. Specifically, when the fuel injection valve 1 is put into operation via the inlet throttle 8, first the control chamber 9 and thus also via the outlet throttle 24 the second control chamber 25 is filled with fuel under high pressure. Gaseous components are displaced from the control chambers 9, 25. As a result, the functionality of the fuel injection valve 1 is guaranteed from the beginning. Problems when starting the internal combustion engine are prevented. The invention is not limited to the described embodiments.

Claims

claims

1. Fuel injection valve (1), in particular injector for fuel injection systems of air-compressing, self-igniting internal combustion engines, with a piezoelectric actuator (2) and one of the actuator (2) indirectly actuable valve needle (14), characterized in that a throttle plate (7) with at least an outlet throttle (24) is provided, that a control chamber (9) is provided which is delimited by an end face (13) of the valve needle (14) and a first side (10) of the throttle plate (7), wherein the outlet throttle (24) associated with the control chamber (9), that for controlling the outlet throttle (24) on a side facing away from the first side (10) of the throttle plate (7) second side (11) of the throttle plate (7) is provided a valve sleeve (21) is actuatable by the actuator (2) for at least partially releasing the outlet throttle (24) against a spring force of a first spring element (40), and that the actuator (2) against a spring force of a second spring element ( 41) can be actuated.

2. Fuel injection valve according to claim 1, characterized in that the valve sleeve (21) has a support cap (31) and that the actuator (2) within the valve sleeve (21) is arranged and on the support cap (31) is supported.

3. Fuel injection valve according to claim 2, characterized in that a valve piece (22) is provided, which rests against the second side (11) of the throttle plate (7), and that the valve piece (22) is circumferentially at least partially surrounded by the valve sleeve (21).

4. Fuel injection valve according to claim 3, characterized in that between the valve piece (22) and the valve sleeve (21) an annular second control chamber (25) is formed, in which the through the valve piece (22) extended outlet throttle (24) opens.

5. Fuel injection valve according to claim 4, characterized in that the second spring element (41) within the valve sleeve (21) is arranged.

6. Fuel injection valve according to claim 5, characterized in that the second spring element (41) on the one hand on the valve piece (22) is supported and on the other hand at least indirectly applied to the actuator (2).

7. Fuel injection valve according to one of claims 1 to 6, characterized in that the first spring element (40) is designed as a tube spring and / or that the second spring element (41) is designed as a tube spring.

8. Fuel injection valve according to one of claims 1 to 7, characterized in that the valve sleeve (21) is arranged in an actuator chamber (20) and that the valve sleeve (21) has at least one opening (35), via which an interior (30) of the valve sleeve (21) with the actuator chamber (20). connected is.

9. Fuel injection valve according to one of claims 1 to 8, characterized in that the spring force of the first spring element (40) in the initial state is greater than the spring force of the second spring element (41).

10. Fuel injection valve according to one of claims 1 to 9, characterized in that a spring constant of the first spring element (40) is smaller than a spring constant of the second spring element (41).