WO2008055724A1

WO2008055724A1 - Injector for injecting fuel

Info

Publication number: WO2008055724A1
Application number: PCT/EP2007/059530
Authority: WO
Inventors: Nadja Eisenmenger; Hans-Christoph Magel
Original assignee: Robert Bosch Gmbh
Priority date: 2006-11-10
Filing date: 2007-09-11
Publication date: 2008-05-15
Also published as: ATE535704T1; CN101535625B; CN101535625A; EP2092187A1; EP2092187B1; DE102006053128A1

Abstract

The invention relates to an injector for injecting fuel into a combustion chamber of an internal combustion engine, comprising an injector housing, an upper housing part (25) and a center housing part (29), wherein an injection valve member, which opens or closes at least one injection opening, is activated via a control valve (1). The control valve (1) comprises a tappet (9), allowing a connection from a control chamber into a fuel return line to be opened or closed. A bore (15) is provided in the tappet (9), wherein a guiding pin (17) is received in this bore, is radially displaceable in relation to the injector housing (25, 39) and encloses a valve chamber (29) together with the wall of the bore (15) in the tappet (9). Said valve chamber is hydraulically connected with the control chamber. The guiding pin (17) is pressed against a contact surface by the pressure prevailing in the valve chamber (29), thus aligning the tappet (9).

Description

description

title

Injector for injecting fuel

State of the art

The invention relates to an injector for injecting fuel in a combustion chamber of an internal combustion engine according to the preamble of claim 1.

For the introduction of fuel into direct-injection, self-igniting internal combustion engines, increasingly hub-controlled high-pressure accumulator injection systems (common rail systems) are being used. The stroke-controlled high-pressure accumulator injection system allows the injection pressure to be adapted to the load and speed of the internal combustion engine.

Usually, fuel injectors are used in the stroke-controlled high-pressure accumulator injection systems, which are operated with 2/2-way control valves. Through the 2/2-control valve, a control chamber with a fuel supply, is supplied through the fuel at system pressure fuel supplied, or connected to a fuel return in the low pressure range. This allows the pressure in the control room to be set to system pressure or to return pressure. The pressure prevailing in the control chamber acts on a control piston, which in turn is connected to an injection valve member. At high pressure in the control chamber so the injection valve member is placed in his seat and the injection openings are closed. At low pressure in the control chamber, the injection valve member lifts from its seat and fuel is injected into the internal combustion engine.

In order to reduce the emissions of the internal combustion engine and to achieve high specific powers, it is necessary to inject the fuel with ever higher injection pressure into the combustion chamber of the internal combustion engine. Due to the ever-increasing demanded injection pressure, the requirements for the 2/2 control valve also change. In currently used control valves, the connection from the control chamber is closed in the fuel return by a spherical closure element. This is against the pressure in the control room via a pressure piece, an anchor bolt and a spring in his seat posed. To open the control valve, the anchor bolt is raised against the spring force by means of a magnetic circuit. Since a larger spring force is required with increasing injection pressure to close the control valve, a larger magnetic force must also be applied to open the control valve. At injection pressures of more than 1800 bar, however, this principle known from the prior art can only be maintained under difficult conditions.

Disclosure of the invention

Advantages of the invention

In an inventively designed injector for injecting fuel into a combustion chamber of an internal combustion engine with an injector, in which an injection valve member which releases or closes at least one injection port is controlled via a control valve, the control valve comprises a valve stem, with which a connection from a control chamber is releasable or closable in a fuel return. In the valve stem, a bore is formed, in which a guide pin is received, which surrounds a valve space which is hydraulically connected to the control chamber with the wall of the bore in the valve stem, wherein the guide pin by the pressure prevailing in the valve space against a bearing surface is pressed, whereby the valve stem is aligned.

In control valves for fuel injectors, as known from the prior art, the valve stem or the armature of the solenoid valve is guided over fixedly connected to the fuel injector guide components. It is necessary to integrate the armature guide in the magnetic recording, resulting in a complicated structure and expensive component. Advantage of the injector according to the invention over this known from the prior art injector is that the guide pin is pressed due to the high injection pressure with a large force from the valve chamber against a stop surface. This force can be used as a contact pressure for the guide pin. The guide pin is held in this position. In order for the valve stem to be aligned via the guide pin, the guide pin is preferably aligned at right angles over the contact surface in the case of a flat seat. In contrast, in the case of a ball seat, it is preferable for the guide pin to be radially displaceable into a position in which the valve tappet is aligned with the seat. Thus, it is not necessary to manufacture the guide pin and the magnet holder from a component. The division of magnet holder and guide pin results in simple, easy-to-manufacture components. The production cost is thus reduced. In a first embodiment, the guide pin is placed against the injector housing by the pressure prevailing in the valve space and thereby held in position. Alternatively, however, it is also possible that at least one further component is received between the guide pin and the injector housing, wherein the guide pin is placed against the further component. The further component is provided, for example, by this pressure force and possibly a spring force against the injector. However, the further component can also be formed integrally with the injector housing and form, for example, a part of the magnet assembly.

When the guide pin is placed against the injector housing by the pressure prevailing in the valve space and thereby held in position, it is preferred that an extension is formed on the guide pin, which is provided with one side against the injector and on the other side as a compression spring executed spring element acts, which is received between the extension and the valve stem. Advantage of the spring element, which is received between the extension of the guide pin and the valve stem is that is pressed by the spring force, which is exerted by the spring element and acting on the extension of the guide pin, the guide pin with the extension against the injector. As a result, the force with which the guide pin is placed against the injector, even then large enough to hold the guide pin in position, when the pressure in the valve chamber drops to return pressure.

In a preferred embodiment, the control valve is magnet-actuated and an armature of the solenoid-operated control valve is formed on the valve stem. The fact that the armature is formed on the valve stem, the number of required components can be reduced. In addition, it is possible to build the injector compact. Also, by forming the armature on the valve lifter, the mass of the moving components is reduced, so that a faster opening and closing of the control valve is possible.

Preferably, an annular closure element is formed on the valve stem. The annular closing element is preferably configured such that the diameter of the bore in the valve tappet and the inner diameter of the annular closing element are approximately equal. Due to the approximately equal diameter of the valve tappet is pressure balanced. It is therefore not necessary to apply an additional force for closing the control valve, which counteracts the pressure force in the valve chamber. The smaller forces required mean that a faster opening and closing of the control valve is possible. The course of injection can be better adapted to the operating conditions of the internal combustion engine. -A-

The annular closing element on the valve tappet is designed, for example, as a sealing surface, which can be placed in a valve seat. The formation of the annular closing element as a sealing surface, the closing movement of the valve stem is damped and thus reduces wear. The valve seat into which the annular closure element is placed in order to close the control valve is designed, for example, as a flat seat, a conical seat or a ball seat. In a preferred embodiment, the annular closing element is a conical sealing surface and the valve seat is formed as a spherical surface. Advantage of this embodiment is that no increased parallelism requirements are placed on the contact surface of the guide pin and the valve seat. The spherical surface of the valve seat has a joint function, wherein the compensation of a possible axial offset takes place by radial displacement of the guide pin on its contact surface. In addition, the valve seat formed as a spherical surface also allows a liquid-tight closing of the control valve at an inclination of the valve piston against the injector.

Brief description of the drawings

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

Show it

1 shows a erfϊndungsgemäß trained control valve in a first embodiment,

2 shows a erfϊndungsgemäß trained control valve in a second embodiment,

3 shows a erfϊndungsgemäß trained control valve with cone / ball seat.

Embodiments of the invention

Figure 1 shows a erfϊndungsgemäß trained control valve in a first embodiment.

In an injector for injecting fuel into a combustion chamber of an internal combustion engine, an injection valve member, which releases or closes at least one injection opening, is actuated by means of a control valve 1. The control valve 1 is actuated by an actuator 3. In the embodiment shown here, the actuator 3 is a Magnetic actuator. This comprises a coil 5, which is accommodated in a magnetic core 7. Alternatively, it is also possible to use a different actuator, for example a piezoelectric actuator, instead of a magnetic actuator.

The control valve 1 further comprises a valve tappet 9, which in the embodiment illustrated here comprises an annular closing element 11. To close the control valve 1, the annular closing element 11 is placed in a valve seat 13. In the embodiment shown here, the valve seat 13 is a flat seat.

In the valve stem 9, a bore 15 is formed. In the bore 15, a guide pin 17 is received. The bore 15 acts simultaneously as a guide for the valve stem 9. The valve stem 9 is guided on the guide pin 17. By the leadership of the valve stem 9 on the guide pin 17 is avoided that the valve stem 9 is displaced radially to the injector 19 or tilted. On the guide pin 17 an extension 21 is formed, which rests with a surface 23 on an upper housing part 25 of the injector. On the guide pin 17, a step 27 is further formed, which acts as a stroke limiter for the valve tappet 9. By striking the step 27, the movement of the valve stem 9 is stopped.

The guide pin 17 and the bore 15 enclose a valve chamber 29. At the valve chamber 29, a channel 31 connects, which opens into a control chamber, not shown here. In the channel 31, a throttle element 33 is formed. Through the throttle element 33 a back pressure independent flow is ensured. This also ensures a back pressure-dependent control chamber pressure.

In order to keep low due to the high fuel pressure in the valve space occurring leakage between the bore 15 and the guide pin 17, the bore 15 and the surface of the guide pin 17 are fitted to each other so that the bore 15 and the surface of the guide pin 17 act as a sealing surface ,

So that the valve tappet 9 can be moved by the actuator 3, an armature 35 is formed on the valve tappet 9 in the embodiment shown here. The stroke of the valve stem 9 is adjusted by an adjusting ring 37 which is received between the upper housing part 25 and a central housing part 39. The setting of the stroke takes place via the height h of the adjusting ring 37th

The upper housing part 25 and the middle housing part 39 are connected to each other by a clamping sleeve 41. For this purpose, the clamping sleeve 41 is located on a shoulder 43 at the top Housing part 25 and is screwed with a thread 45 on the central housing part. So that no fuel can escape at the injector along the connection of the upper housing part 25 and the middle housing part 39, a sealing ring 47 is received between the upper housing part 25 and the middle housing part 39.

The guide pin 17 is enclosed by a spring element 49. The spring element 49 is preferably designed as a compression spring coil spring. The spring element 49 is supported on one side on the valve tappet 9 and on the other side on the extension 21 of the guide pin 17. In order to adjust the spring force of the spring element 49, it is possible to position a shim 51 between the spring element and the extension 21. By the height of the dial 51, the bias of the spring element 49 is set.

Due to the spring force of the spring element 49, which acts on the extension 21 on the guide pin 17 via the adjustment disk 51, the guide pin 17 is pressed against the upper housing part 25. In addition, acts on the guide pin 17, a pressure force in the valve chamber 29. The pressure force is dependent on the pressure of the fuel, which prevails in the valve chamber 29. When the control valve 1 is closed, system pressure prevails in the valve chamber 29. When the control valve 1 is open, the pressure in the valve chamber drops, since the fuel then flows into the low-pressure region of the injection system. Thus, when the control valve 1 is open, the pressure force on the guide pin 17 also decreases. However, since the spring force of the spring element 49 continues to act on the guide pin 17 even when the control valve 1 is open, it is held in contact with the surface 23, whereby the valve tappet 9 is aligned with the valve seat 13.

To start an injection process, the coil 5 is energized. This forms a magnetic field around the coil, through which the armature 35 is attracted. The valve stem 9 with the armature formed thereon rises with the annular closing element 11 from the valve seat 13. A connection from the valve chamber 29 in the fuel return is released. The pressure in the valve chamber 29 drops. Due to the decreasing pressure in the valve chamber 29 fuel flows through the channel 31 with the throttle element 33 from the control chamber, not shown here. The pressure in the control room also decreases. Due to the decreasing pressure in the control chamber, the control piston is moved in the direction of the control chamber. The injection valve member rises from its seat and thus releases the at least one injection opening. Fuel is injected into the combustion chamber of the internal combustion engine. While the control valve 5 is open and so fuel from the control chamber 29 can flow into the low-pressure region, whereby the pressure in the valve chamber 29 decreases, and the force acting on the guide pin 17 compressive force decreases. However, since the spring member 49 exerts a spring force on the extension 21, the guide pin 17 is further pressed against the upper housing part 25 and thus held in position. In addition, the pressure in the valve chamber 29 does not decrease to the pressure in the low pressure range, since the control chamber, not shown here, is connected to the fuel inlet and so nachlauf flows continuously under system pressure fuel in the control chamber, which then via the channel 31 and the throttle element 33 in the valve chamber 29 flows.

To end the injection process, the energization of the coil 5 is terminated. The valve stem 9 is provided with the aid of the spring force of the spring element 49 with its annular closing element 11 in the valve seat 13. The connection from the valve chamber 29 in the low pressure region is closed. The fuel flowing into the control chamber leads to an increase in pressure in the control chamber and thus also in the valve chamber 29, which is hydraulically connected to the control chamber via the channel 31 and the throttle element 33. On the guide pin 17 again affects the pressure force of the fuel under system pressure. At the same time is moved by the higher pressure in the control chamber, the control piston in the direction of the injection valve member and the injection valve member is placed in its seat to close the at least one injection port.

FIG. 2 shows a control valve according to the invention designed in a second embodiment.

The control valve shown in Figure 2 differs from the control valve shown in Figure 1 by the formation of the guide pin 17th

In the embodiment shown here, a further component 53 is received between the guide pin 17 and the upper housing part 25. On the further component 53, the extension 21 is formed, against which the spring element 49 is supported. The guide pin 17 is provided with an end face 55 against the further component 53. The guide pin 17 is held by the pressure force acting in the valve chamber 29 on this, in its position. At the same time, the pressure force acting on the guide pin 17 is transmitted via the end face 55 to the further component 53. As a result, the further component 53 with the extension 21 is placed against the upper housing part 25. At the same time, the spring force of the spring element 49, which likewise sets this against the upper housing part 25, acts on the further component 53. In this way, the further component 53 is held in position. Due to the fact that the pressure in the valve chamber 29 is also open Control valve 1 does not drop to ambient pressure due to the fuel flowing over the control chamber and the channel 31, the guide pin 10 is held in its bearing on the further component 53 in the embodiment shown in Figure 2, whereby the valve stem 9 is aligned with the valve seat 13. Alternatively, it is possible that the further component 53 is formed integrally with the upper housing part 25.

Figure 3 shows an inventively designed control valve in a third embodiment.

The control valve 1 shown in Figure 3 differs from the embodiment shown in Figure 1 by the formation of the valve seat 13 and the annular closing element 11. In the embodiment shown in Figure 3, the annular closure member 11 is designed with a conical sealing surface. The valve seat 13 is designed as a spherical surface. Advantage of the ball-shaped valve seat 13 relative to a flat seat is that the valve seat 13, the sealing surface of the annular closure member 11 and the surface 23 of the extension 21, which rests against the upper housing part 25, need not be made exactly parallel to a liquid-tight closing allow the valve 1. Due to the design of the valve seat 13 as a spherical surface of this has a joint function. A liquid-tight closing is thus ensured even if the conical sealing surface of the annular closing element 11 is not formed exactly parallel. A possible axial offset of the guide pin 17 is compensated by radial displacement of the guide pin 17 on the surface 23.

In addition to the ball-shaped valve seat shown in FIG. 3 with a conically configured sealing surface on the annular closing element 11, it is also possible for the valve seat 13 and the annular closing element 11 to be formed as a flat seat. Alternatively, it is also possible for the valve seat 13 to be cone-shaped and the annular closing element 11 to be provided with a conical sealing surface, wherein the cone angles of the conical valve seat 13 and the conical sealing surface preferably have a difference in the range of 1 ° to 5 °, so that the surface pressure of the annular closure member 11 is concentrated in the conically shaped valve seat 13 on a line. Furthermore, however, it is also possible for the annular closing element 11 and the valve seat 13 to assume any geometry known and suitable to the person skilled in the art.

Claims

claims

An injector for injecting fuel into a combustion chamber of an internal combustion engine having an injector housing, an upper housing part (25) and a middle housing part (39), in which an injection valve member which releases or closes at least one injection opening, via a control valve (1) is controlled, wherein the control valve (1) comprises a valve stem (9) with which a connection from a control chamber in a fuel return is releasable or closable, characterized in that in the valve stem (9) has a bore (15) is formed in a guide pin (17) is received, which encloses with the wall of the bore (15) in the valve tappet (9) a valve space (29), which is hydraulically connected to the control chamber, wherein the guide pin (17) through which in the valve space ( 29) prevailing pressure against a contact surface is pressed, whereby the valve stem (9) is aligned.

2. An injector according to claim 1, characterized in that the guide pin (17) by the in the valve chamber (29) prevailing pressure against the upper housing part (25) and thereby held in position.

3. Injector according to claim 1, characterized in that between the guide pin (17) and the upper housing part (25) at least one further component (53) is received, wherein the guide pin (17) against the further component (53) is provided and by this pressure force, the further component (53) is placed against the upper housing part (25), whereby the further component (23) is held in its position.

4. An injector according to claim 1 or 2, characterized in that on the guide pin (17) an extension (21) is formed, which is provided with one side against the upper housing part (25) and on the other side of a designed as a compression spring spring element ( 49) which is received between the extension (21) and the valve piston (9).

5. An injector according to one of claims 1 to 4, characterized in that the control valve (1) is magnet-actuated and on the valve tappet (9) an armature (35) of the solenoid-operated control valve (1) is formed.

6. Injector according to one of claims 1 to 5, characterized in that on the valve tappet (9) an annular closing element (11) is formed.

7. An injector according to one of claims 1 to 5, characterized in that the diameter of the bore (15) in the valve tappet (9) and the inner diameter of the annular closing element (11) are approximately equal.

8. Injector according to claim 6 or 7, characterized in that the annular closing element (11) on the valve tappet (9) is designed as a sealing surface, which in a

Valve seat (13) can be placed.

9. Injector according to one of claims 6 to 8, characterized in that the valve seat (13) is designed as a flat seat, conical seat or ball seat.

10. Injector according to one of claims 6 to 9, characterized in that the annular closing element (11) has a conical sealing surface and the valve seat (13) is designed as a spherical surface.