WO2014000968A1

WO2014000968A1 - Fuel-injection valve for internal combustion engines

Info

Publication number: WO2014000968A1
Application number: PCT/EP2013/060200
Authority: WO
Inventors: Hans-Peter ZEITLHOFER; Roland Mitter
Original assignee: Robert Bosch Gmbh
Priority date: 2012-06-27
Filing date: 2013-05-16
Publication date: 2014-01-03
Also published as: EP2867519A1; EP2867519B1; DE102012210953A1

Abstract

The invention concerns a fuel-injection valve for internal combustion engines, with a housing (2), in which is formed a pressure chamber (6) from which at least one injection opening (8) proceeds. Disposed in the pressure chamber (6) is a valve needle (10), of which the longitudinal movement opens and closes the at least one injection opening (8). Remaining at least in sections between the valve needle (10) and the wall of the pressure chamber (6) is an annular space which can be filled with fuel at high pressure and through which fuel can flow in the direction of the injection openings (8). The valve needle (10) is guided by a guide section (14) formed in the pressure chamber (6). In the region of the guide section (14), the valve needle (10) comprises an elongate bore (15), through which fuel can flow from the part of the pressure chamber (6) upstream of the guide section (14) into the downstream part of the pressure chamber (6), a throttling point (16) being formed inside the elongate bore (15).

Description

Description title

Fuel injection valve for internal combustion engines

The invention relates to a fuel injection valve, as it is preferably used for the injection of fuel directly into combustion chambers of internal combustion engines use, preferably of those that operate on the principle of auto-ignition.

State of the art

For injection of fuel injection valves are known which inject fuel under high pressure into combustion chambers. The injection of the fuel is done by one or more injection ports under very high pressure, which may be up to 2500 bar, to achieve a fine atomization of the fuel. As a result, the fuel together with the compressed air in the combustion chamber forms an ignitable mixture which burns spontaneously or externally ignited.

To control the injection, the injectors usually have a valve needle, which is arranged longitudinally displaceable in the housing of a fuel injection valve. The valve needle is mounted longitudinally movable in a pressure chamber and surrounded by fuel under high pressure. As a result of its longitudinal movement, the valve needle opens or closes one or more injection openings through which the fuel finally reaches the combustion chamber of the internal combustion engine. This movement of the valve needle must be carried out very quickly and accurately to exactly the amount of fuel required at the desired time in to introduce the combustion chamber. Such a fuel injection valve is known for example from the published patent application DE 36 24 476 AI.

In order to guide the valve needle in the pressure chamber, this has at least one guide section, with which the valve needle is guided in the radial direction. But it can also be provided several guide sections. In order to bring the fuel between the wall of the pressure chamber and the valve needle through to the injection openings, an annular space is provided between the valve needle and the wall of the pressure chamber, through which the fuel flows to the injection openings. In the area of the guide section, ie where the valve needle is guided in the pressure chamber, special precautions must be taken to allow a throttle-free flow of the fuel. Here, for example, bevels on the valve needle are known, which allow a flow of fuel despite the leadership of the valve needle within the bore. Moreover, from DE 36 24 476 AI known to direct the fuel through an oblique bore which is formed in the valve needle and extends in the region of the guide portion.

In general, it should be avoided that the fuel pressure on its way through the pressure chamber significantly loses pressure by passing bottlenecks to have the full injection pressure at the injection ports for the best possible atomization of the fuel. In some injectors, however, a targeted reduction of the fuel pressure is desired and necessary for the function. Thus, from the document DE 10 2007 032 741 AI a fuel injection valve is known in which a throttle collar is formed on the valve needle, so that the fuel is throttled at its flow through the pressure chamber in the direction of the injection openings at this point and thereby loses some pressure , This is necessary to allow a safe closing of the valve needle, which is otherwise largely pressure balanced in the longitudinal direction. Disclosure of the invention

Object of the present invention is to pass the fuel Ström on the one hand to the leadership of the valve needle and on the other hand in a controlled manner to achieve throttling of the fuel flow to achieve a pressure difference between the upstream and downstream of a guide portion formed part of the pressure chamber, in which the valve needle is arranged. For this purpose, the valve needle of the fuel injection valve is arranged in the pressure chamber so that it closes and opens at least one injection opening by its longitudinal movement, can be introduced through the fuel into a combustion chamber of an internal combustion engine. In this case, at least in sections remains between the valve needle and the wall of the pressure chamber, an annular space, can flow through the fuel at high pressure in the direction of the injection openings. The valve needle has at the level of the guide portion has a longitudinal bore through which fuel from the upstream of the guide portion formed part of the pressure chamber in the downstream of the guide portion formed part of the pressure chamber can flow, wherein within the longitudinal bore, a throttle point is formed, throttled at the fuel ström and the pressure is reduced.

In an advantageous embodiment of the invention, the valve needle is modular and consists of a first valve needle part and a second valve needle part, between which a throttle piece is arranged. The longitudinal bore is formed by two formed in the valve needle parts blind holes, which are connected via a throttle formed in the throttle body. Thereby, a throttle connection is formed in a simple manner, which causes a pressure difference between the upstream and downstream of the guide portion located portion of the pressure chamber when a fuel injection occurs and the fuel in the longitudinal bore is in motion.

The connection of the longitudinal bore with the pressure chamber is formed in an advantageous embodiment of the invention by recesses in the valve needle, in particular by slot-shaped recesses, of which several may be formed distributed over the circumference of the valve needle. Such recesses ensure an unthrottled fuel ström in the longitudinal bore, without affecting the mechanical stability of the valve needle.

In a further advantageous embodiment, one of the connections or also both connections of the longitudinal bore with the pressure chamber is formed by a plurality of filter bores formed in the valve needle. These filter bores retain dirt particles, which can enter the injector with the flow of fuel and cause malfunctions there. The filter bores are formed in such a number and with such a diameter that they on the one hand have a good filtering effect, but on the other hand, the flow of fuel in the longitudinal bore or from the longitudinal bore in the pressure chamber or only insignificantly throttle, so that the throttling of the fuel flow and so that the pressure difference is caused exclusively by the throttle point in the throttle piece.

The filter bores are preferably formed as radially extending bores having a diameter of preferably 100 to 300 μηη. This

Diameter range allows to achieve the desired effect with a manageable number of throttle bores.

Further advantages and advantageous embodiments of the invention are the description and the drawings can be removed.

drawings

In the drawings, embodiments of the fuel injection valve according to the invention are shown. It shows

1 shows a schematic representation of a longitudinal section through an inventive fuel injection valve with the essential components connected,

Figure 2 is an enlarged view of the valve body arranged therein

Valve needle of a first embodiment and Figure 3 in the same representation as Figure 2 shows a further embodiment.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS In FIG. 1, a fuel injection valve 1 according to the invention is shown schematically in FIG

Longitudinal section shown. The fuel injection valve 1 comprises a housing 2, which comprises a holding body 4 and a valve body 5, which bear against each other with their respective end faces. The holding body 4 and the valve body 5 are pressed against each other by a device, not shown in the drawing, so that fuel from the interior of the housing 2 can not escape to the outside, so there is a liquid-tight connection between the two parts of the housing 2. In the holding body 4 and in the valve body 5, a pressure chamber 6 is formed which can be filled with fuel under high pressure. In the pressure chamber 6, a valve needle 10 is arranged longitudinally displaceable, which has a sealing surface 11 at its end facing the combustion chamber, which has a substantially conical shape and cooperates with a formed in the valve body 5 valve seat 12. If the valve needle 10 with the sealing surface 11 on the valve seat 12, so one or more injection ports 8, which are formed in the valve body 5, sealed against the pressure chamber 6. On the other hand, if the valve needle 10 lifts away from the valve seat 12, a connection is established between the valve needle 12 and the valve needle 12

Opened sealing surface 11 and the valve seat 12, can flow through the fuel from the pressure chamber 6 to the injection openings 8. The fuel, when the fuel insp scritz valve is installed in an internal combustion engine, passes through the injection openings 8 in a combustion chamber of the internal combustion engine.

The valve needle 10 extends into the holding body 4 and, at the end facing the valve seat, the valve needle 10 is guided in a sleeve 22 which, together with the valve seat facing away from the end of the valve needle 10 and a throttle plate 30, delimits a control chamber 26. The sleeve 22 is thereby pressed by a spring 25 against the throttle plate 30, wherein the spring 25 is arranged under pressure bias and is supported with its other end to a shoulder 24 which is formed on the valve needle 10. The control of the longitudinal movement of the valve needle 10 in the pressure chamber 6 is effected by an alternating pressure in the control chamber 26. For this purpose, a flow restrictor 41 is formed in the throttle plate 30, which can be connected via a control valve 32 and a drain line 34 to a fuel tank 40 in which only a low pressure, preferably ambient pressure prevails. The control valve 32 is preferably an electromagnetic valve, which can be opened or closed by applying a corresponding control current. The filling of the control chamber 26 via a likewise formed in the throttle plate 30 inlet throttle 42, which is connected via a high pressure line 35 to a high pressure accumulator 36. The high-pressure accumulator 36 contains fuel under high pressure, with which the fuel is ultimately to be introduced into the combustion chamber, and in turn is supplied from the fuel tank 40 via a high-pressure pump 37 with compressed fuel. With the high-pressure accumulator 36 a plurality of injectors 1 may be connected, which are each connected via high-pressure lines 35 to the high-pressure accumulator 36.

In the closed state of the fuel injection valve 1, the valve needle 10 is pressed by the pressure in the control chamber 26 and the consequent hydraulic force in the direction of the valve seat 12. Although the spring 25 presses the valve needle 10 also in the direction of the valve seat 12, but this force plays only a minor role in relation to the large hydraulic forces. Since the valve needle 10 rests with its sealing surface 11 on the valve seat 12, parts of the valve sealing surface are not acted upon by the pressure of the pressure chamber 6, so that there is an excess of force in the direction of the valve seat 12, which is due to the hydraulic forces. The control valve 32 is in its closed position, so that the drain line 34 is interrupted.

To move the valve needle 10 in the pressure chamber 6, the control valve 32 is opened, so that the control chamber 26 via the outlet throttle 41 and the

Leakage oil line 34 is connected to the fuel tank 40. As a result, the pressure in the control chamber 26 decreases, wherein the outlet throttle 41 and the inlet throttle 42 are dimensioned so that when the control valve 32 is open more fuel the control chamber 26 drains, as over the inlet throttle 42 flows in the same period. Due to the hydraulic forces on the valve needle 10, in particular within the valve body 5, now results in a resultant force on the valve needle 10, which is directed away from the valve seat 12 and the valve needle 10 spends in its open position. The valve needle 10 lifts off from the valve seat 12 and releases the injection openings 8, so that fuel is ejected from the pressure chamber 6 via the injection openings 8. To terminate the injection, the control valve 32 is closed again, so that in the control chamber 26 again a high fuel pressure setting, which urges the valve needle 10 with a closing force in the direction of the valve seat 12 and pushes back into its closed position.

The remaining between the valve needle 10 and the wall of the pressure chamber 6 space serves as a fuel line, can flow through the fuel through the pressure chamber 6 to the injection openings 8. For the arrangement of the valve needle 10 exactly in the middle of the pressure chamber 6, a guide portion 14 is formed in the valve body 5, in which the valve needle 10 is guided. The space remaining between the valve needle 10 and the guide section 14 is so small that, on the one hand, a certain lubricating film remains between the valve needle 10 and the wall of the pressure chamber 6 in order to permit movement of the valve needle 10, which, on the other hand, is so narrow, that fuel can flow through this residual gap in the direction of the injection openings 8 only to a very small extent, so that only a leakage flow is possible. So that fuel from the upstream of the guide portion 14 located

Area of the pressure chamber 6 can flow into the downstream part of the pressure chamber 6, a longitudinal bore 15 is formed in the valve needle 10, which extends at the height of the guide portion 14, as shown enlarged in Figure 2 again. The longitudinal bore 15 is formed in that the valve needle 10 consists of two valve needle parts 110, 210, between which a throttle piece 20 is arranged. The first valve needle part 110 is arranged in the valve body 5, while the second valve needle part 210 is arranged in the holding body 4. Both valve needle parts 110, 210 abut with their end faces on the throttle piece 20 and are firmly connected to this, for example by a weld or solder joint. The longitudinal bore 15 is formed by a first blind bore 115 and a second blind bore 215, which are introduced in the first valve needle part 110 and in the second valve needle part 210. The throttle piece 20 has a central longitudinal bore, in which a throttle point 16 is formed in the form of a constriction

In order to allow the flow of fuel through the longitudinal bore 15, in the first valve needle part 110 and in the second valve needle part 210 in each case one or more connections 17, 18 are formed. The first connection 17 in the first valve needle part 110 is formed here as a slot-shaped recess, the second connection 18 in the second valve needle part 210 in the form of an oblique bore. However, each of the connections 17, 18 may be formed as an oblique bore or slot-shaped recess. It is also possible for a plurality of connections 17, 18 to be distributed over the circumference of the valve needle 10. The compounds 17, 18 are designed so that the fuel can flow unrestricted in the longitudinal bore 15, so that the pressure reduction occurs almost exclusively at the throttle point 16.

The valve needle 10 is designed so that it is substantially balanced in force in the open state, ie, the hydraulic forces cancel each other in the longitudinal direction substantially against each other. Since the closing force exerted by the spring 25 on the valve needle 10 is not sufficient for a quick closing alone, the closing of the valve needle 10 must be hydraulically assisted, as too slow needle closing leads to increased pollutant emissions. For this purpose, a pressure difference between the upstream and downstream of the guide portion 14 located parts of the pressure chamber must be achieved because then the opening force on the valve needle 10 by the fuel pressure in the valve body 5 is lower than the closing force, by the hydraulic force within the control chamber 26 on the Valve needle 10 is exercised. The fuel flows to the injection openings 8 through the longitudinal bore 15 within the valve needle 10. By the throttle point 16 within the longitudinal bore 15 such a pressure difference is achieved, so that the pressure in the downstream of the Führungsab- Section 14 lying pressure chamber 6 is lower than upstream of the guide portion 14th

3 shows a further embodiment of the fuel injection valve according to the invention is shown, in which case - as in Figure 2 - only the valve body 5 is shown together with the valve needle 10. The valve needle 10 here also has a longitudinal bore 15, wherein the connection with the pressure chamber 6 upstream of the guide section 14 is formed by filter bores 19 which are introduced into the valve needle 10 in the radial direction. The filter holes 19 are dimensioned in number and diameter so that no or only a slight pressure reduction takes place at these filter holes 19 compared to the pressure reduction at the throttle point 16. The filter holes 21 are used to filter out particles in the fuel, which were not detected by the rule in the fuel injection system and the fuel insp scritz valve upstream filter so that they do not reach the injection ports 8.

The filter bores 19 are designed as radial bores and can be produced in various ways, for example by electro-sion or by a laser drilling process. The diameter of the filter bores 19 is preferably 100 to 300 μηη, depending on the viscosity of the fuel and depending on the number of filter bores 19, so that no or only one compared to the pressure reduction at the throttle point 16 low pressure reduction takes place.

Claims

claims

1. Injection fuel valve for internal combustion engines with a housing (2) in which a pressure chamber (6) is formed, from which at least one injection port (8) goes out, and with a in the pressure chamber (6) arranged valve needle (10) through their longitudinal movement which opens and closes at least one injection opening (8), wherein between the valve needle (10) and the wall of the pressure chamber (6) at least partially remains an annular space which can be filled with fuel under high pressure and by the fuel in the direction of the injection openings (8) is guided, and with a in the pressure chamber (6) formed guide portion (14) in which the valve needle (10) is guided, characterized in that the valve needle (10) in the region of the guide portion (14) has a longitudinal bore (15 ), through which fuel from the upstream of the guide portion (14) located part of the pressure chamber (6) in the downstream part of the pressure chamber (6) can flow, wob ei within the longitudinal bore (15) a throttle point (16) is formed.

2. fuel injection valve according to claim 1, characterized in that the longitudinal bore (15) upstream of the guide portion (14) through a first connection (17) and downstream of the guide portion (14) by a second connection (18) with the pressure chamber (6 ) connected is.

3. fuel injector valve according to claim 1 or 2, characterized in that the valve needle (10) is modular and has a first valve needle part (110) and a second valve needle part (210), between which a throttle piece (20) is arranged, the having the throttle point (16).

4. fuel injection valve according to claim 3, characterized in that the first valve needle part (110) has a first blind bore (115) and the second valve needle part (210) has a second blind bore (215) which are formed so that by connecting the two Valve needle parts (110, 210) under Interposed position of the throttle piece (20), the longitudinal bore (15) with the throttle point (16) is formed.

5. fuel injection valve according to claim 2, characterized in that the compounds (17, 18) are formed by recesses in the valve needle (10).

6. fuel injector valve according to claim 5, characterized in that the recesses (17; 18) are slot-shaped.

7. fuel injection valve according to claim 5 or 6, characterized in that a plurality of recesses (17; 18) are arranged distributed over the circumference of the valve needle (10).

8. fuel injector valve according to claim 2, characterized in that the first connection (17) between the longitudinal bore (15) and the pressure chamber (6) by a plurality of filter bores (19) is formed, which are formed in the valve needle (10).

9. fuel injection valve according to claim 8, characterized in that the filter bores (19) are formed as radial bores in the valve needle (10).

10. fuel injector valve according to claim 8 or 9, characterized in that the filter bores have a diameter of 100 to 300 μηη.

11. fuel injection valve according to claim 8, 9 or 10, characterized in that the filter bores (19) are formed in such a number and with such a diameter that the fuel flow from the pressure chamber (6) in the longitudinal bore (15) through the filter bores (19) is not or only slightly throttled.

12. fuel injector valve according to claim 1, characterized in that the first valve needle part (110), the second valve needle part (210) and the throttle piece (20) are fixedly connected to each other, preferably by a

Welding or soldering connection.

13. fuel injection valve according to claim 1, characterized in that between the wall of the pressure chamber and the valve needle in the region of the guide portion (14) has a thickness such that only one

Leakage flow is possible.