WO2001038723A1

WO2001038723A1 - Fuel injection valve for internal combustion engines

Info

Publication number: WO2001038723A1
Application number: PCT/DE2000/003798
Authority: WO
Inventors: Werner Wagner; Siegfried Ruthardt; Holger Rapp
Original assignee: Robert Bosch Gmbh
Priority date: 1999-11-19
Filing date: 2000-10-27
Publication date: 2001-05-31
Also published as: DE19955663A1

Abstract

The invention relates to a fuel injection valve with a valve member (5) that can be longitudinally displaced in a bore (7) against a closing force. Said valve member is guided in a combustion-chamber remote zone in the bore (7) and merges into a zone that is smaller in diameter in direction of the combustion chamber. Said latter zone and the wall of the bore (7) define a pressure chamber (20) between them that is filled with fuel. At the combustion-chamber end of the valve member (5) a valve stem (24) is configured that interacts with a valve seat (22) disposed at the end of the bore (7), thereby controlling at least one injection opening (28). The valve member (5) is provided with a blind bore (60) that extends coaxially relative to its longitudinal axis. Said blind bore is open towards the end facing away from the valve-seat and a pressure pin (4) projects into said bore, said pressure pin resting on the end of the blind bore (60) that is configured as a support surface (62). The pressure pin (4) projects over the combustion-chamber remote end of the valve member (5) and transmits the closing force to the valve member (5) so that said valve member, when brought out of axis with the bore (7), is subjected to less wear and has a more even injection behavior due to the reduction of tilting moments.

Description

Fuel injection valve for internal combustion engines

State of the art

The invention is based on a fuel injection valve for internal combustion engines according to the preamble of claim 1. Such a fuel injection valve is known from published application DE 196 11 884. A bore is formed in a valve body, in which a piston-shaped valve member, which is axially movable against a closing force, is arranged. By tapering the valve member towards the combustion chamber, one or more pressure surfaces are formed on the valve member, which are arranged in the pressure chamber and to which a force can be exerted by filling the pressure chamber with fuel under high pressure, which acts counter to the closing force.

The closing force is applied at the end of the valve member facing away from the combustion chamber and ideally acts exactly in the axis of symmetry of the valve member. Faults and irregularities can, however, lead to a / deviation of the valve element from the ideal central position. This is possible in particular on the valve seat, which is far away from the guided section of the valve member. Since the closing force is applied far away from the valve seat, there is a relatively large, tilting movement in the event of a deflection

Moment on the valve member, which promotes further teaching. If a plurality of injection openings distributed over the circumference are arranged in the valve seat, then an asymmetrical injection occurs due to the axis adjustment of the valve member. it at a relatively large, tipping moment on the valve member during a teaching, which promotes further teaching. If a plurality of injection openings distributed over the circumference are arranged in the valve seat, asymmetrical injection occurs as a result of the axis adjustment of the valve member, which has a disadvantageous effect on the combustion process.

Advantages of the invention

The fuel injection valve according to the invention for internal combustion engines with the characterizing features of claim 1 has the advantage that the closing force is exerted on the valve member near the valve sealing surface on the valve member, whereby the tilting moment of the closing force on the valve member is significantly reduced. The valve member has a bore which is coaxial with the axis of the valve member and which is open at its end remote from the combustion chamber. A push pin protrudes into this blind bore, which is supported at the end of the blind bore and which is acted upon by the closing force at its end facing away from the combustion chamber. Due to the introduction of the closing force near the valve sealing surface, there is only a slight tilting moment due to the closing force when the valve member on the valve seat is adjusted. The better centering of the valve member achieved in this way leads to a uniform injection pattern with a plurality of injection openings and to less wear in the region of the guided section of the valve member.

In an advantageous embodiment of the object of the invention, a support surface forming the bottom surface of the blind bore is essentially conical and the tip of the pressure pin is in contact with the support surface comes, has a spherical shape. As a result, the end of the pressure pin on the valve seat side is automatically centered in the blind bore and the closing force is exerted precisely on the valve member in the axial direction.

In a further advantageous embodiment, an annular gap is formed between the pressure pin and the wall of the blind bore. With this play, the closing force on the valve member can be exactly in the axial direction even when the valve member is slightly deflected or deformed

Center point of the support surface of the blind bore.

In a further advantageous embodiment, the closing force is exerted on the pressure pin by a closing spring. This allows the subject of the invention to be applied to nozzle holder combinations in which the opening stroke of the valve member takes place against the force of one or more closing springs which, individually or in combination, generate the closing force.

In a further advantageous embodiment, the closing force is exerted on the pressure pin via a pressure piston which can be moved by a hydraulic force. This configuration allows the subject of the invention to be used in particular in fuel injection systems which operate on the common rail principle.

In a further advantageous embodiment, the pressure pin at the end facing away from the valve member merges into a pressure pin head which is guided in a bore. This results in an exact centering of the pressure pin at the end facing away from the valve member, and thus when the valve member is readjusted, which means that the pressure pin is readjusted. This is accompanied by an additional driving moment on the valve member towards the central axis of the bore.

Further advantages and advantageous embodiments of the subject matter of the invention can be found in the drawing, the description and the claims.

drawing

Two embodiments of a fuel injection valve according to the invention are shown in the drawing and explained in more detail in the following description. 1 shows a longitudinal section through a fuel injection valve according to the invention, FIG. 2 shows a longitudinal section through another fuel injection valve according to the invention, FIG. 3 shows an enlarged view of the valve member from FIG. 1 or FIG. 2, FIG. 4 shows an enlarged view of FIG. 1 in the area of the push pin head, FIG 5 a further embodiment of the push pin head and in FIGS. 6, 7, 8 and 9 different designs of the transition from the pressure piston to the push pin head are shown.

Description of the embodiments

1 shows a longitudinal section through a fuel injection valve to which the subject matter of the invention is applied. In the following, the structure is first explained and then the mode of operation is explained.

A bore 7 is formed in the valve body 1, the end of which faces the combustion chamber has a valve seat 22 in which at least one injection opening 28 is formed. A piston-shaped valve member 5 is arranged in the bore 7. net, which is stepped in diameter and is subdivided into a section facing away from the combustion chamber and having a larger diameter, which is guided in the bore 7, and a section facing the combustion chamber and having a smaller diameter. A pressure chamber 20 is formed between the wall of the bore 7 and the section of the valve member 5 which is smaller in diameter and can be filled with fuel under high pressure via an inlet channel 26. At the transition of the two valve member sections, a pressure shoulder 6 is formed, which is arranged in the pressure chamber 20 and to which a force is exerted in the axial direction on the valve member 5 by the fuel pressure in the pressure chamber 20. At the end of the valve member 5 on the combustion chamber side, an essentially conical valve sealing surface 24 is formed, which cooperates with the valve seat 22 and closes the injection opening 28 against the pressure chamber 20 in the closed position of the valve member 5.

The valve body 1 is clamped with a clamping nut 8 against a valve holding body 2 in which a spring chamber 19 is formed coaxially with the valve member 5. The valve member 5 is connected to a pressure pin head 18 which is arranged in the spring chamber 19 and is movable in the axial direction in the spring chamber 19. A piston-shaped pressure piston 3 adjoins the valve pin 5 facing away from the valve member 5, said piston being arranged so as to be axially movable in a receiving bore 10 formed in the valve holding body 2 and the end facing the combustion chamber comes into contact with the pressure pin head 18. Since the pressure piston 3 is made smaller in diameter than the pressure pin head 18, an annular shoulder remains on the pressure pin head 18, between which and the end of the spring chamber 19 facing away from the combustion chamber there is a pretensioned closing spring 16 which acts on the pressure pin head 18 in the closing direction of the valve member 5 , The end of the pressure piston 3 facing away from the combustion chamber and the receiving bore 10 delimit a valve control chamber 41 which is connected via an inlet throttle 39 to the inlet 26 and via an outlet throttle 37 to a relief chamber 11 formed in the valve holding body 2. An essentially rotationally symmetrical magnet armature 12 is arranged in the relief chamber 11, and a valve ball 35 is arranged at the end on the combustion chamber side thereof. The magnet armature 12 is acted upon by the force of a closing spring 30 arranged at the end of the relief chamber 11 facing away from the combustion chamber in the direction of the valve member 5, whereby the valve ball 35 is pressed onto the opening of the outlet throttle 37 and the valve control chamber 41 is closed against the relief chamber 11. The relief chamber 11 is connected via a drain channel 32 to a drain line, not shown in the drawing, via which fuel can flow out of the relief chamber 11. In the area of the relief chamber 11 facing away from the combustion chamber, an electromagnet 14 is arranged, which by energizing can exert a magnetic force on the magnet armature 12 against the force of the closing spring 30.

The fuel injector works as follows: Fuel is introduced into the inlet channel 26 under high pressure via a fuel inlet system, not shown in the drawing, and a certain pressure level in the inlet channel 26 is thereby maintained. If the electromagnet 14 is not energized, the magnet armature 12 is pressed by the force of the closing spring 30 with the valve ball 35 against the opening of the outlet throttle 37. As a result, the valve control chamber 41 is closed against the relief chamber 11, so that because of the inlet throttle 39 in the valve control chamber 41 the fuel pressure is the same as in the inlet channel 26 and in the pressure chamber 20. Since the diameter of the pressure piston 3 is larger than the diameter of the guided section of the valve member 5, exceeds the hydraulic force on the the end face 43 of the pressure piston 3 which delimits the valve control chamber 41 and faces away from the combustion chamber, the hydraulic force on the pressure shoulder 6 and the valve sealing surface 24. The pressure piston 3 is thereby pressed towards the combustion chamber and presses the valve member 5 with the valve sealing surface 24 against the

Valve seat 22, whereby the injection opening 28 is closed. The opening of the fuel injection valve is initiated by energizing the electromagnet 14 and thereby moving the magnet armature 12 in the axial direction away from the combustion chamber towards the electromagnet 14 until it hits a stop formed in the region of the electromagnet 14 and not shown in the drawing comes to the plant. The valve ball 35 is thus lifted from the opening of the outlet throttle 37 and fuel can flow from the valve control chamber 41 into the relief chamber 11. The flow resistances of the outlet throttle 37 and the inlet throttle 39 are dimensioned such that pressure equalization to the inlet channel 26 cannot take place immediately. As a result, the pressure in the valve control chamber 41 drops below the pressure in the inlet channel 26 and the force on the end face 43 of the chamber remote from the combustion chamber

Pressure piston 3 drops accordingly and becomes smaller than that on the pressure shoulder 6 and the valve sealing surface 24. The valve member 5 experiences a resultant force in the axial direction away from the combustion chamber and the valve sealing surface 24 lifts off the valve seat 22 and connects the pressure chamber 20 to the combustion chamber. This opening stroke movement is continued until the end face 43 of the pressure piston 3 facing away from the combustion chamber, which serves as a stop surface, comes to rest against the end of the receiving bore 10 facing away from the combustion chamber.

The closing of the fuel injection valve is initiated in that the electromagnet 14 is no longer energized and the magnet armature 12 presses the valve ball 35 onto the opening of the outlet throttle 37 by the force of the closing spring 30. Since there is no drain from the valve control chamber 41 in the Relief chamber 11 can take place, the pressure in the valve control chamber 41 adjusts to the pressure in the inlet channel 26 via the inlet throttle 39. Due to the above-described ratios of the diameter of the pressure piston 3 and the valve member 5, the hydraulic force on the end face 43 of the pressure piston 3 again predominates, so that the pressure piston 3 and thus also the valve member 5 are moved in the direction of the combustion chamber and thereby stop the injection process. The closing spring 16 only serves to seal the fuel injection valve in the non-operating state. The closing spring 16 is of secondary importance for the actual opening and closing movement of the valve member 5.

FIG. 2 shows a second fuel injection valve to which the subject matter of the invention is applied. The valve body 1 is clamped against the valve holding body 2 with a clamping nut 8 with the interposition of an intermediate disk 56. The bore 7, the valve member 5 and the

Pressure chamber 20, as well as valve surface 22, valve seat 24 and injection openings 28, are designed in the same way as in the fuel injection valve shown in FIG. 1. The main differences are that the closing force is applied to the valve member 5 exclusively by a closing spring 54, the force of which is determined by the design, and that the injection process is controlled via the variable fuel pressure in the pressure chamber 20. The valve member 5 is connected to a spring plate 58, which is arranged in a spring chamber 52 formed in the valve holding body 2. The closing spring 54 is arranged under prestress between the spring plate 58 and the end of the spring chamber 52 facing away from the combustion chamber. Due to the force of the closing spring 54, the valve member 5 with the valve sealing surface 22 pressed against the valve seat 24. Magnetic or electrical control devices are not necessary with this fuel injection valve.

The fuel injection valve works as follows: The injection process is initiated by the fuel pressure in the inlet channel 26 increasing. This also increases the fuel pressure in the pressure chamber 20 and thus the hydraulic force on the pressure shoulder 6 or the valve sealing surface 24. If the resulting force in the axial direction on the valve member 5 exceeds the force of the closing spring 54, the valve member 5 lifts with the valve sealing surface 24 from the valve seat 22 and fuel is injected into the combustion chamber through the injection opening 28. The opening stroke movement of the valve member 5 continues until the valve member 5 comes to rest against a stop surface formed in the intermediate disk 56. The end of the injection process is initiated by the fact that the fuel pressure decreases in the inlet channel 26 and thus also in the pressure chamber 20. If the resulting force on the pressure shoulder 6 or the valve sealing surface 24 falls below the force of the closing spring 54, the valve member 5 is replaced by the force of the Closing spring 54 is moved toward valve seat 22 until valve sealing surface 24 abuts valve seat 22. The injection openings 28 are closed against the pressure chamber 20 and the injection process is ended.

FIG. 3 shows an enlarged illustration of the valve member 5 of the exemplary embodiment shown in FIG. 1 or in FIG. 2. The valve member 5 is constructed to be rotationally symmetrical and has a blind bore 60 which extends coaxially to its longitudinal axis and which extends from the end of the valve member 5 facing away from the combustion chamber into the half of the section of the valve which faces the combustion chamber and is smaller in diameter. limb 5 extends. The end of the blind bore 60 is designed as a support surface 62 which is essentially conical, the tip of the cone cone pointing towards the valve seat 22. The closing force on the valve member 5 is transmitted by a pressure pin 4 which connects to the pressure pin head mentioned in the exemplary embodiment in FIG. 1 or 2. Starting from the valve holding body 2 or the intermediate disk 56, the pressure pin 4 projects into the blind bore 60 and comes into contact with the support surface 62 with its end face, which is designed as a pressure surface 64 and faces the valve seat 22. The outer diameter of the pressure pin 4 is smaller than the inner diameter of the blind bore 60, so that an annular gap 66 is formed between the pressure pin 4 and the inner wall of the blind bore 60. The pressure surface 64 is spherical, so that in interaction with the conical support surface 62 results in a force centering the pressure pin 4 in the blind bore 60 on the pressure pin 4.

Since the force application point of the pressure pin 4 is very close to the valve sealing surface 24, when the valve member 5 is deflected, there is only a slight tilting moment due to the closing force with respect to the valve seat 22. This results in a more precise guidance of the valve member 5 in the bore 7 and a more precise positioning of the valve sealing surface 24 on the valve seat 22. It is a further advantage that the force application point of the pressure pin 4 faces the valve seat towards the guided section of the valve member 5. If, during the closing movement of the valve member 5 on the valve seat 22, the valve member 5 gets caught, which leads to a tilting of the valve member 5, a restoring moment is exerted by the force application point on the valve seat side, which centering the valve member 5 in hole 7 restored. this leads to a reduction in wear in the guided section of the valve member 5.

FIG. 4 and FIG. 5 show an enlarged illustration of the end of the pressure pin 4 on the combustion chamber side of the fuel injection valve shown in FIG. 1. The push pin 4 goes away from the combustion chamber into a push pin head

18, which is larger in diameter than the pressure pin 4. It is arranged in the spring chamber 19 and, in the exemplary embodiment shown in FIG. 4, has a smaller outer diameter than the diameter of the spring chamber 19. The pressure piston 3, which is also in the spring chamber

19 protrudes, with its end face 48 facing the valve member 5 comes to rest against the head face 47 of the pressure pin head 18 facing the pressure piston 3.

In principle, the same structure is shown in FIG. 5, only the push pin head 18 is guided in the spring chamber 19 here. The guidance of the push pin head 18 in the spring chamber 19 results in greater stability and a more exact centering of the push pin 4 at the end facing away from the combustion chamber. One or more recesses 45 are formed on the outer lateral surface of the pressure pin head 18, as a result of which the spring chamber 19 is connected to the bore 7. Leakage oil, which is pressed out of the pressure chamber 20 past the guided section of the valve member 5, can thereby flow into the spring chamber 19.

FIGS. 6 to 9 show different embodiments of the transition from the pressure piston 3 to the pressure pin head 18. In Figure 6, the end face 48 of the pressure piston 3 is ground flat, while the head surface 47 of the pressure pin head 18 has a concave shape. In Figure 7, the head surface 47 is also concave, but the end face 48 of the pressure piston 3 is convex. FIG. 8 shows both the head surface 47 of the push pin head 18 and the end face 48 of the pressure piston 3 is formed flat and they lie flat against one another. In the exemplary embodiment shown in FIG. 9, the top surface of the push pin head 18 is also flat, while the end surface 48 has a convex shape. In the embodiments of FIGS. 6, 7 and 9, there is a point-like contact between the pressure piston 3 and the pressure pin head 18. Depending on the requirements for the stability and the other requirements of the fuel injector, different force transmissions from the pressure piston 3 into the pressure pin can occur 4 can be selected.

Claims

Expectations

1. Fuel injection valve for internal combustion engines with a valve body (1) with a bore (7) formed therein, in which a piston-shaped, against a

Closing force by pressurizing a pressure surface (6, 24) longitudinally displaceable valve member (5) is arranged, which valve member (5) is designed stepped in the outside diameter, the larger section in the outside diameter being guided in the area of the bore (7) facing away from the combustion chamber and the smaller section Section is arranged in a pressure chamber (20) which can be filled with fuel and is formed between the wall of the bore (7) and the valve member (5), and with one at the end of the valve member (5) on the combustion chamber side

Valve sealing surface (24) which cooperates with a conical valve seat (22) formed on the combustion chamber end of the bore (7) and comes into contact with the fuel injector in the closed position under the action of the closing force, at least one injection opening (22) in the valve seat (22) 28) through which the pressure chamber (20) can be connected to the combustion chamber for fuel injection, characterized in that the valve member (5) has a blind bore (60) which is open at the end facing away from the valve seat and extends coaxially to the axis of the valve member (5). has a push pin (4) which is supported on the end of the blind bore (60) designed as a support surface (62) and through which push pin (4) the closing force can be transmitted to the valve member (5).

2. Fuel injection valve according to claim 1, characterized in that the blind bore (60) extends into the smaller diameter section of the valve member (5).

3. Fuel injection valve according to claim 2, characterized in that the blind bore (60) extends into the valve seat side half of the valve member (5).

4. Fuel injection valve according to claim 1, characterized in that the support surface (62) has a conical shape, the tip of the cone cone the valve seat

(22) faces.

5. Fuel injection valve according to one of the preceding claims, characterized in that the end of the pressure pin (4) formed on the valve seat facing pressure surface (64) is spherical.

6. Fuel injection valve according to claim 1, characterized in that an annular gap (66) is formed between the pressure pin (4) and the wall of the blind bore (60).

7. Fuel injection valve according to claim 1, characterized in that the closing force on at least one in the valve holding body (2) arranged closing spring (54) is exerted on the pressure pin (4).

8. Fuel injection valve according to claim 1, characterized in that a piston-shaped pressure piston (3) is arranged in the valve holding body (2), which comes into contact at least indirectly with the valve member (5) and which hydraulically moves the closing force on the valve member (5). exercises.

9. Fuel injection valve according to claim 8, characterized in that a pressure pin head (18) is formed on the end of the pressure pin facing away from the combustion chamber, on which the end of the pressure piston (3) facing the valve member (5) comes to rest.

0. Fuel injection valve according to claim 9, characterized in that the push pin head (18) is guided in a bore (17) formed in the valve holding body (2).