WO2007107397A1

WO2007107397A1 - Fuel injection valves for internal combustion engines

Info

Publication number: WO2007107397A1
Application number: PCT/EP2007/050775
Authority: WO
Inventors: Rolf-Juergen Giersch; Bernd Dittus
Original assignee: Robert Bosch Gmbh
Priority date: 2006-03-21
Filing date: 2007-01-26
Publication date: 2007-09-27
Also published as: EP1999363A1; ATE467756T1; EP1999363B1; DE502007003735D1; DE102006012842A1

Abstract

Fuel injection valve having a valve body (1) in which a bore (3) with a valve needle (7) arranged therein is formed. The valve needle (7) interacts with a valve seat (4), formed in the valve body (1), in such a way that at least one injection opening (10; 10') can be opened or closed as a result. Arranged in the bore (3) is a valve pin (5) which defines together with the valve needle (7) a first control space (25) which can be filled with fuel, wherein the fuel pressure in the first control space (25) acts on the valve needle (7) in such a way that the latter is pressed against the valve seat (4). Formed in the valve pin (5) is a longitudinal passage (22) leading to a second control space (27) in which a variable pressure can be set.

Description

description

title

Fuel injection valves for internal combustion engines

The invention relates to a fuel injection valve for internal combustion engines, as it is preferably used for the direct injection of fuel into the combustion chamber of self-igniting internal combustion engines.

State of the art

Injectors for the direct injection of fuel into the combustion chamber of internal combustion engines are known for a long time. Thus, published patent application DE 100 24 703 A1 shows such an injection valve as is used in so-called common-rail injection systems. The injector includes a valve needle longitudinally disposed in a valve body which, by its longitudinal movement, controls the opening and closing of at least one injection port by cooperating with a valve seat. The movement of the valve needle is controlled by a control valve, wherein the valve needle moving forces are generated hydraulically. Disadvantage of these fuel injection valves is on the one hand, the large moving mass, since the Ventilna- del, which includes the entire length of the injection nozzle, is relatively long and therefore heavy.

The resulting inertia makes it very difficult to carry out successive injection processes very quickly. On the other hand occurs at ever higher injection pressures the problem that the valve needle must be moved with very large forces in order to achieve the fast opening and closing operations. As a result, the valve needle settles hard on the valve seat, which can lead to wear and premature failure of the injection valve there, especially if in the course of further technical development ever higher injection pressures, which are well above 2000 bar, are controlled. European Patent Application EP 967 382 A2 discloses an injection valve in which the valve needle contains a smaller valve needle which opens and closes at least part of the injection openings. By means of this smaller valve needle, which is preferably arranged in a longitudinal bore of the larger valve needle, at least certain operating states can be controlled quickly by the small valve needle. In addition, a clean centering of the actual valve needle in the region of the valve seat is achieved via the smaller valve needle, so that a uniform injection is made possible by all Einspritzöffhungen.

However, the known fuel injection valve has the disadvantage that an independent control of the small valve needle is not possible. This makes fast activation difficult, as is the case for multiple injections, i. H. a subdivided into several injections fuel injection is necessary. In addition, the known fuel injection valve has the disadvantage that at ever higher pressure surrounding the nozzle needle, significant elastic deformation of the valve body occur.

This increases the leakage gap and results in more fuel being pumped into the fuel return, necessitating additional pumping of the high pressure pump, which compresses the fuel and provides it to the injector.

Advantages of the invention

Disclosure of the invention

The fuel injection valve according to the invention with the characterizing features of claim 1 has the advantage over that rapid control of

Injection can occur at low leakage, even at a pressure that is well above the currently achievable 2000 bar. For this purpose, a valve pin is arranged in the bore of the valve body, on which a valve needle is guided. A first control chamber is located within the valve pin, wherein the first control chamber is connected to a second control chamber through a connection formed in the valve pin. Of the

Pressure in the second control chamber is adjustable, preferably via a control valve, so that the pressure in the first control chamber can be changed very quickly. Due to the low moving mass, the valve needle can very quickly open or close the injection openings, whereby very rapid successive injections are made possible. Since there are no leakage gaps in the high-pressure area, the result is also high Here injection pressures no impairment of the function of the fuel injection valve according to the invention.

By the dependent claims advantageous developments of the subject invention are possible. In a first advantageous embodiment, the valve pin essentially has a hollow cylindrical shape, so that the connection between the two control chambers is formed by a longitudinal channel in the valve pin. The valve pin is preferably supported on the valve needle via a closing spring, so that the valve needle is pressed against the valve seat by the spring force. As a result, the Einspritzöffhungen remain closed even when the fuel injection valve is not operated. The valve pin can also advantageously be supported by a compression spring on a stationary stop, so that it is mounted between the closing spring on the one hand and the compression spring on the other. This facilitates easy assembly and disassembly of the fuel injection valve and allows to manufacture in the longitudinal direction with relatively large tolerances.

In a further advantageous embodiment of the invention, the valve pin is supported at its valve seat side end with a contact surface on the valve seat, so that it is held stationary by the compression spring. In this case, the valve pin preferably has openings through which the fuel can flow from a pressure chamber surrounding the valve pin in the direction of the injection openings.

In a further advantageous embodiment, it is also possible that a further sleeve is provided, which is likewise arranged in the bore of the valve body and which surrounds the valve pin and the valve needle. The sleeve is guided in this case in the bore and also ensures a guide of the valve pin and the valve needle, wherein the first control chamber between the valve pin and the valve needle is formed and is bounded radially outward by the sleeve. The sleeve has valve seat near also openings through which fuel can flow to the Einspritzöffhungen. Through the sleeve both the valve pin and the valve needle are very accurate with respect to the

Longitudinal axis of the valve body out, so that the injection takes place in accordance symmetrically.

In a further advantageous embodiment, the valve pin has a receptacle into which a pressure piston protrudes. The pressure piston limits together with the would take the second control chamber, which is connected via a longitudinal channel within the valve pin with the first control chamber. The pressure piston can be moved, for example via a piezoelectric actuator, so that the movement of the valve needle can be controlled directly above the piezo actuator. This design, in which the control of the valve needle is installed in the valve body, can be very compact injectors construct that take into account the constant need for component reduction.

drawing

In the drawing, various embodiments of the inventive fuel injection valve are shown. It shows:

1 shows a longitudinal section through a fuel injection valve according to the invention, FIG. 1a shows a cross section through the fuel injection valve shown in FIG. 1 along the line A-A, FIG.

FIG. 2 is a longitudinal sectional view of a further exemplary embodiment of a fuel injection valve according to the invention;

Figure 2a shows a cross section along the line A-A and

FIG. 2b shows an alternative construction of the injection valve shown in FIG. 2, only the region facing away from the valve seat being illustrated,

FIG. 3,

Figure 4 and Figure 5 show further embodiments, which are each shown in longitudinal section and Figure 6 shows a last embodiment in which in addition a piezoelectric actuator is shown, which is part of the entire injection valve.

Description of the embodiments

1 shows a erfmdungsgemäßes fuel injection valve is shown in longitudinal section. The fuel injection valve comprises a valve body 1, which is braced in the installed position against a holding body, not shown in the drawing. The valve body 1 has a bore 3 which is delimited at its combustion chamber end by a conical valve seat 4. The conical valve seat 4 terminates in a blind hole 6, wherein at least one Einspritzöffhung 10, 10 'either from the blind hole 6 o- which emanates from the conical valve seat 4 and opens in installation position of the fuel injection valve in the combustion chamber of the internal combustion engine. In the bore 3, a valve pin 5 is arranged longitudinally displaceable, wherein between the wall of the bore 3 and the valve pin 5, a pressure chamber 8 is formed which can be filled with fuel under high pressure. The valve pin 5 is guided in a middle section 105 in the bore 3: FIG. 1a shows a cross section through the fuel injection valve shown in FIG. 1 along the line AA. The valve pin 5 has in the middle guide portion 105 recesses 16 in the form of longitudinal grooves, so that here four guide surfaces 17 are formed on the outside of the valve pin 5, which bear against the wall of the bore 3. Through the recesses 16, a sufficiently large flow cross-section is formed through which fuel can flow unthrottled in the direction of the injection openings 10.

At the valve seat side end of the valve pin 5 is in a guide section 14, which is reduced in diameter. On the guide portion 14, a valve needle 7 is guided, which has a corresponding receptacle 15 which receives the guide portion 14 of the valve pin 5. The valve needle 7 has a substantially conical valve sealing surface 11, with which it rests on the valve seat 4 and thereby separates the pressure chamber 8 from the Einspritzöffhungen 10 when it rests against the valve seat 4. The valve needle 7 is clamped by a closing spring 12 against the valve pin 5, wherein the closing spring 12 surrounds the guide portion 14 of the valve pin 5.

By receiving 15 of the valve needle 7 and the guide portion 14 of the valve pin 5, a first control chamber 25 is limited, which is connected via a formed in the valve pin 5 longitudinal channel 22 with a second control chamber 27. This is delimited by the valve seat facing away from the end of the valve pin 5 and a pressure sleeve 18, wherein the pressure sleeve 18 surrounds the valve pin 5 at its valve seat facing away from the end. The pressure sleeve 18 is pressed against the not shown in the figure 1 holding body via a compression spring 20, which is supported on a connected to the valve pin 5 support ring 13. Characterized the valve pin 5 is pressed in the direction of the valve seat 4, while it is acted upon by the closing spring 12 in the opposite direction at the same time.

In order for the pressure to continue as quickly as possible from the second control chamber 27 into the first control chamber 25, the volume of the two control chambers 25, 27 and the volume must be of the longitudinal channel 22 should be as small as possible. Since the diameter of the longitudinal channel 22 due to production must have a certain minimum cross-section, it can be provided that a filling pin 31 is arranged in the longitudinal channel 22. Over the thickness and the length of the filler pin 31 so the volume can be optimally adjusted.

The operation of the fuel injection valve is as follows: In the pressure chamber 8, a predetermined high fuel pressure is maintained, which is provided for example in a so-called common rail. By a separate connection or by leakage gaps, such as between the valve pin 5 and the pressure sleeve 18, prevails in the second control chamber 27 and via the longitudinal channel 22 in the first control chamber 25, the same high fuel pressure as in the pressure chamber 8. If an injection takes place, then the over a control device, for example a control valve, which is accommodated in the holding body, not shown in the drawing, set a lower pressure in the second control chamber 27. As a result of the pressure drop in the second control chamber 27, the pressure in the first control chamber 25 decreases virtually instantaneously, since both are present

Control spaces 25, 27 are hydraulically connected to each other via the longitudinal channel 22. This causes a drop in the hydraulic force to the valve needle 7, which experiences a closing force in the direction of the valve seat 4 by the pressure in the first control chamber 25. By pressurizing a portion of the valve sealing surface 11, the valve needle 7 now lifts off the valve seat 4, so that fuel from the pressure chamber 8 between the valve sealing surface 11 and the valve seat 4 flows through to the injection openings 10 and is injected from there into the combustion chamber. As a result of subsequent pressure increase in the second control chamber 27, the pressure in the first control chamber 25 also rises again, and the valve needle 7 slides back into its closed position, ie. in contact with the valve seat 4.

FIG. 2 shows a second exemplary embodiment of the fuel injection valve according to the invention. The valve needle 7 is here, apart from the conical valve sealing surface 11, designed as a compact cylinder and thus not guided on the valve pin 5. The first control chamber 25 is formed between the valve needle 7 and the valve seat facing end face of the valve pin 5. In the bore 3, a sleeve 30 is additionally arranged in this embodiment, which surrounds both the valve pin 5 and the pressure sleeve 18 and the valve needle 7 and rests with a contact surface 37 on the valve seat 4. The sleeve 30 is fixedly disposed in the bore 3 and has recesses 16 through which - also in the embodiment of Figure 1 - guide surfaces 17 are formed with which the sleeve 30 on the wall of the bore. 3 is applied. Facing the valve seat, the sleeve 30 is surrounded by the pressure chamber 8, which is also filled with fuel under high pressure. In order to allow the inflow of fuel to the injection openings 10, a plurality of openings 32 are arranged on the sleeve 30, which are designed slot-shaped and provide a sufficient flow cross-section available. FIG. 2a shows a cross section along the line AA of FIG

Figure 2, through which the arrangement of the pressure sleeve 18 in the sleeve 30 is clear. The operation of this fuel injection valve is identical to the operation of the injection valve shown in Figure 1, so that a description of the function can be omitted here.

Figure 2b shows an alternative embodiment of the valve seat facing away from the end of the injection valve of Figure 2, wherein only the essential components are shown here. Instead of the pressure sleeve 18, a pressure piece 34 is provided here, which has a longitudinal bore 36. Between the pressure piece 34 and the valve pin 5, a gap 29 is formed in which the compression spring 20 is arranged, which presses the pressure piece 34 against the holding body, not shown, and at the same time the valve pin 5 in the direction of the valve needle 7. Thus, a series circuit the second control chamber 27, the intermediate space 29 and the first control chamber 25, which are each connected via a longitudinal bore 36 and a longitudinal channel 22 in the valve pin 5 and in the pressure piece 34 with each other. By this configuration, other damping properties arise, in particular, when the valve pin 5 performs a slight movement in the opening stroke of the valve needle 7.

In Figure 3, another embodiment is shown in longitudinal section. The valve pin 5 is here, as in the embodiment shown in Figure 1, by

Guide surfaces 17 guided in the bore 3. Between the pressure sleeve 18 and the valve pin 5, a compression spring is arranged here, which presses the valve pin 5 with a contact surface 19 against the valve seat 4. In order to allow the fuel flow to the injection openings 10, openings 32 'are here provided, which are similar to the openings 32 in the sleeve 30 of the embodiment of Figure 2 are executed. The

Valve needle 7, the valve sealing surface 11 faces away from a piston-shaped end 21, with which it is guided in a receptacle 24 in the valve pin 5. Between a collar 33 and a shoulder in the receptacle 24, the closing spring 12 is arranged, which presses the valve needle 7 against the valve seat 4. The first control chamber 25 is formed by the end face of the piston-shaped end 21 and by the base of the receptacle 24th limited and is also connected here by the longitudinal channel 22 with the second control chamber 27. The operation is also identical to that of the preceding exemplary embodiments, in which case a further pressure surface 35 is formed by the annular collar 33 on the valve needle 7, which causes an additional hydraulic force to the valve needle 7 in Öffhungsrichtung. Unlike the previous embodiments, the valve pin 5 does not move here and remains stationary during the entire injection.

4 shows a further exemplary embodiment is shown, wherein here the same representation as in Figure 3 was selected. The two exemplary embodiments differ only in that the valve needle 7 terminates here in a pin 23 which is arranged in the receptacle 24 and through which a valve needle 7, a shoulder is formed, against which the closing spring 12 is applied. The valve needle 7 is guided in the receptacle 24, wherein a hydraulic Öffhungskraft results only in that a part of the sealing surface 11 is acted upon by the fuel pressure of the pressure chamber 8.

In the embodiment shown in Figure 5, which is also shown in longitudinal section, the valve pin 5 has no guide surfaces 17, but a cylindrical outer shape and an outer diameter which is significantly smaller than the inner diameter of the bore 3. To the pressure pin 5 in To center the bore 3, a guide plate 38 is provided which rests against a shoulder 41 on the pressure pin 5. Between the guide plate 38 and the pressure sleeve 18, the compression spring 20 is arranged, which presses against the shoulder 41 against the shoulder 41. In the guide plate 38 a plurality of passages 39 are provided, so that the fuel can flow unthrottled through the pressure chamber 8 in the direction of the injection openings. When Öffhungshubbe- movement of the valve needle 7, only the valve needle 7 is moved while the pressure pin 5 stationary in the bore 3 remains.

6 shows a further embodiment is shown, in which in addition to the valve body 1 nor a drive device, shown here in the form of a piezoelectric actuator 40, which is usually arranged in the holding body. The valve pin 5 has a receptacle 24, in which the valve needle 7 - as in previous embodiments - is guided. In addition, the valve pin 5 on its opposite side on a further receptacle 26 in which a pressure piston 42 is guided, wherein the second control chamber 27 through the pressure piston 42 and through the wall of the second receptacle 26 is limited. Between the pressure piston 42 and the valve pin 5, the compression spring 20 is arranged, which pushes the pressure piston 42 away from the valve pin 5.

The pressure piston 42 is connected directly to the piezoelectric actuator 40, so that by a corresponding energization of the piezoelectric actuator 40 is a longitudinal movement of the pressure piston 42 through which the volume of the second control chamber 27 is variable, so that either fuel displaced from the second control chamber 27 or via leakage gaps between the wall of the second receptacle 26 and the pressure piston 42 in the second control chamber 27 is promoted. At the beginning of the injection, the piezoelectric actuator 40 is shortened. The second control chamber 27 is the same as the first control chamber 25 and the longitudinal channel 22 via

Leakage column, the z. B. are formed between the pressure piston 42 and the second receptacle 26, connected to the pressure chamber 8 and thus filled with fuel under pressure. The piezoelectric actuator 40 is in its maximum deflection position, so that the volume of the second control chamber 27 and the first control chamber 25 is as small as possible. If an injection takes place, then the piezoelectric actuator 40 is shortened, so that the

Retracting piston 42. This increases the volume of the second control chamber 27, as a result of which the pressure in the first control chamber 25 drops rapidly, wherein a throttle 28 can be provided to avoid pressure oscillations and to control the pressure drop in the longitudinal channel 22 over time. Due to the pressure drop in the first control chamber 25 and the concomitant decrease in the hydraulic closing force on the valve needle 7, this is the fuel pressure in the pressure chamber 8 in its open position, d. H. pushed away from the valve seat 4, so that the Einspritzöffhungen 10 are released. To end the injection, the piezoelectric actuator 40 is extended again, so that the pressure builds up again in the control chambers 25, 27 and presses the valve needle 7 back into its closed position. About the leakage column then finds one

Pressure equalization between the pressure chamber 8 and the control chambers 25, 27 instead.

The arrangement of the components of Figure 6, the complete control of the valve needle 7 and thus the injection can be moved into the valve body 1, which must be provided in the holding body, only the piezoelectric actuator 40 with its electrical connections and the connection of the pressure chamber 8 with the high-pressure fuel source.

The exemplary embodiments shown moreover have the advantage that the valve needle 7 is made very small, so that the manufacturing costs can be reduced. This is particularly interesting if, to further increase the precision of relatively expensive Materials for the production of the valve needle 7 find use, such as stainless steels.

Claims

claims

1. Fuel injection valve for internal combustion engines with a valve body (1), in which a bore (3) is formed with a valve needle arranged therein (7), wherein the valve needle (7) so formed in the valve body (1) valve seat

(4) cooperates in that thereby at least one Einspritzöffhung (10; 10 ') can be opened or closed, and with a valve pin (5) which is also arranged in the bore (3) and which together with the valve needle (7) a limited first fuel chamber (25), which is filled with fuel, wherein the fuel pressure in the first control chamber (25) acts on the valve needle (7), that it is pressed against the valve seat (4), characterized in that in the valve pin (5) a longitudinal channel (22) to a second control chamber (27) is formed, in which a variable pressure is adjustable.

2. Fuel injection valve according to claim 1, characterized in that the valve pin (5) has substantially the shape of a hollow cylinder.

3. Fuel injection valve according to claim 2, characterized in that the valve pin (5) via a closing spring (12) on the valve needle (7) is supported, so that the valve needle (7) by the spring force against the valve seat (4) is pressed.

4. Fuel injection valve according to claim 3, characterized in that the valve pin (5) at its valve needle (7) facing away from the end via a compression spring (20) is supported stationary.

5. Fuel injection valve according to claim 4, characterized in that the valve pin (5) via the compression spring (20) on a pressure sleeve (18) is supported, which limits the second control chamber (27).

6. Fuel injection valve according to claim 2 or 3, characterized in that the

Valve needle (7) has a receptacle (15) into which the valve pin (5) with a Guide section (14) is immersed, so that the valve needle (7) in its movement to open and close the at least one Einspritzöffhung (10; 10 ') on the guide portion (14) is guided.

7. Fuel injection valve according to claim 2 or 3, characterized in that the valve pin (5) has a receptacle (24) at its valve needle (7) facing

End has, in which the valve needle (7) protrudes and thereby in their movement to open and close the at least one injection port (10, 10 ') in the receptacle (24) is guided.

8. Fuel injection valve according to claim 1 or 2, characterized in that the valve pin (5) at its valve needle (7) facing away from the end

Compressive spring (20) supports stationary and thereby with a contact surface (19) against the valve seat (4) is pressed.

9. Fuel injection valve according to claim 8, characterized in that in the valve pin (5) openings (32 ') are formed, via the fuel of the at least one Einspritzöffhung (10; 10') can flow when the valve needle (7) the at least one Einspritzöffhung (10; 10 ') releases.

10. Fuel injection valve according to claim 9, characterized in that on the valve needle (7) a pressure surface (35) is formed, which is acted upon by the fuel, which acts through the openings (32 ') of the valve pin (5), so that through the hydraulic force on the pressure surface (35) one of the valve seat (4) directed away

Force on the valve needle (7) acts.

11. Fuel injection valve according to claim 1, characterized in that the valve pin (5) by a sleeve (30) is surrounded, which rests with a contact surface (37) on the valve seat (4) and which limits the first control chamber (25) radially outward ,

12. Fuel injection valve according to claim 1, characterized in that the valve pin (5) valve seat facing away from a second receptacle (26) for a pressure piston (42), so that through the wall (26) of the second receptacle and the pressure piston (42) of the second Control room (27) is limited.

13. Fuel injection valve according to claim 12, characterized in that the pressure pin (5) by a drive device (40) is longitudinally movable so that by its longitudinal movement, the volume of the second control chamber (27) is variable.

14. Fuel injection valve according to claim 13, characterized in that the drive device is a piezoelectric actuator (40).

15. Fuel injection valve according to claim 12 or 13, characterized in that in the longitudinal channel (22) a throttle point (28) is provided.

16. Fuel injection valve according to one of the preceding claims, characterized in that the valve pin (5) in the bore (3) of the valve body (1) through

Guide surfaces (17) is centered, which bear against the wall of the bore (3).

17. Fuel injection valve according to claim 16, characterized in that on the valve pin (5) recesses (16) are formed through which a fuel flow to the at least one injection port (10; 10 ') is made possible.