JPH0432949B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The invention relates to a fuel injection nozzle for an internal combustion engine, comprising a valve needle loaded by a closing spring and opening in the direction of fuel flow. The valve needle is connected to a piston forming a damping chamber filled with fuel, the damping chamber being connected to the main flow of fuel only via a throttle channel during the opening stroke of the valve needle. Regarding.

PRIOR ART In the case of injection nozzles of the type mentioned above, the opening movement of the valve needle, over at least a partial stroke, causes fuel to flow into a damping chamber which is simply throttled and enlarged or from a damping chamber which is contracted. It is designed to be delayed or attenuated by being able to flow out. Provision is made that during the closing stroke of the valve needle, the valve needle is quickly returned to the closed position without being actuated by the damping element. In the case of the injection nozzle of the above-mentioned type, which is shown in German patent application no. This is achieved in such a way that the follow-up connection is interrupted during the return stroke of the valve needle and returns the piston to its starting position under the action of its own return spring. The damping chamber is formed by a blind bore in the nozzle holder, in which the piston is slidably mounted with a defined radial play. In such an arrangement, the piston requires additional space in the axial direction of the injection nozzle due to the additional elements and the return spring. The compliant connection between the valve needle and the piston is
The piston must have a sufficiently large play in the radial direction so that it does not get clamped on the inner wall of the bore of the nozzle holder and does not prevent the valve needle from working properly. Moreover, connections by follow-up connections will cause wear.

OBJECT OF THE INVENTION It is an object of the invention to improve the known fuel injection nozzle so that the elements forming the damping chamber are no longer tightened in the radial direction and a simple and space-saving construction is obtained. It is to do so.

Means for Solving the Problems The means of the present invention taken to solve the above-mentioned problems is such that the damping chamber is formed in a cap inserted into the piston, and the cap is inserted into the piston toward the injection opening at the latest. After the pre-stroke, it has a wall section which is supported on the casing and is displaceable against the force of the spring back to the other side.

Effects of the invention The advantage obtained by the invention is that the cap forming the damping chamber is centered radially directly on the piston, so that there is a gap between the cap and the surrounding wall of the nozzle holder. It is possible to have a suitably large radial play, and this ensures that clamping between the cap and the nozzle holder is avoided. Therefore, the piston is at least integrally connected with a support disk which serves for the engagement of the closing spring, or if no additional damping is to be obtained by means of inertial forces.
For example, it can also be formed by the valve needle itself or by the end section of the valve needle remote from the injection opening. In these cases, a follow-up connection between the valve needle and the piston with a special part for forming the piston is omitted. By virtue of the cap accommodated in the space of the pressure chamber, volume displacements and fuel pressure increases that affect the delivery flow are eliminated by piston action.

Advantageous embodiments and improvements of the device according to the invention are possible by means of the measures specified in the dependent claims.

For example, this is particularly simple if the cap as a whole is pressed against the end face of the piston by means of a return spring. Valve needle 26
During the return stroke, the entire cap is pushed back from the piston via the fuel cushion in the damping chamber, and the return spring acting on the cap at this time and thereafter pushes the fuel quantity that entered the damping chamber during the opening stroke out of the damping chamber again. put out. This process continues until the opening stroke of the valve needle begins, so that the spring force of the return spring acting on the cap is designed to be correspondingly weaker.

According to a further advantageous embodiment, the wall section of the cap that is displaced against a spring force forms a valve member, which valve member is located in a damping chamber relative to the rigid wall section with the valve opening. can be opened and slid outwards, so that the closing force is hardly affected during the return stroke of the valve needle.

Furthermore, the valve member is formed by the entire bottom of the cap, which bottom is adapted to be lifted against a spring force from the ring-shaped peripheral wall portion of the cap.

According to a further advantageous embodiment, the throttle channel leading into the damping chamber is formed in a simple manner by radial play between the piston and the overlapping part of the cap. In another embodiment, the cap has an aperture opening into the damping chamber;
The throttle hole is provided, for example, in the bottom of the cap.

In order to limit the damped partial stroke of the valve needle, the cap preferably has at least one transverse slot of a predetermined depth in its peripheral wall section. With the piston in the closed position of the valve needle,
The axial extent of the transverse slot defines the length of the partial stroke that is damped when the valve opens. Such a control function can also be achieved through horizontal holes in the cap. The transverse slots ensure only an unrestricted flow of fuel in the pressure chamber.

Furthermore, it is advantageous if the cap is placed on the side of the injection opening.
It is supported by the casing via a preloaded support spring. By suitably specifying the support spring with respect to the damping coefficient, the damping effect can be limited in dependence on the pressure. This is desired in most cases in the high speed range of the internal combustion engine, so that the return spring can return the cap to its starting position before the start of the next injection process.

A return spring for the cap engages a cage slidably supported between two stops fixed to the casing, in which the cap and a preloaded support spring are received. This makes it easier to assemble the parts.

Furthermore, the cap is open to the damping chamber and has a throttle valve controlled by the fuel pressure difference between the outside and inside of the damping chamber.
The damping effect can be limited depending on the pressure. The closing spring of the throttle valve can be arranged either outside or inside the damping chamber.

It is furthermore advantageous if the cap is provided with a flange, on which a return spring formed as a helical spring engages. In this case, the return spring extends over part of the cap and the piston, so that no space in the axial direction of the injection nozzle is required for this part of the return spring.

According to a further advantageous embodiment, the piston is integrally connected to the valve needle or is formed by the valve needle itself. In most cases, however, the piston is advantageously connected in one piece with a support element for the closing spring of the valve needle.

Example The invention will be explained below with reference to the exemplary embodiments shown.

The injection nozzle in FIG. 1 has a nozzle body 10, which is fastened to a nozzle holder 14 by a cap nut 12. A sleeve 16 is provided between the nozzle body 10 and the nozzle holder 14.
is arranged, the sleeve having an inwardly directed shoulder 18 which separates a chamber 20 from a larger diameter chamber 22 in the inner chamber of the injection nozzle. A valve seat 24 is formed in the nozzle body 10 and a valve needle 26 is slidably mounted thereon, the sealing cone 27 of which is pressed towards the valve seat 24 by a closing spring 28. There is. The closing spring 28 is supported on the nozzle body 10 and engages via a flange part 30 in a support disk 32 which is itself supported on a shoulder 34 of the valve needle 26 .

A suction hole 36 is formed in the nozzle holder 14 and opens into the chamber 20 which is connected to the chamber 22 via a through hole 38 surrounded by the shoulder 18 . From the chamber 22, a bore 40 formed in the nozzle body 10 opens into an annular chamber 42, which is located between the central bore wall of the nozzle body 10 and a section 44 of the valve needle 26 of reduced diameter. It is formed and reaches directly in front of the valve seat 24. In the illustrated closed position, there is a distance hg between the flange part 30 and the nozzle body 10, which distance hg corresponds to the entire stroke of the valve needle 26. The valve needle 26 is slid outwardly in the opening direction by the fuel pressure against the closing spring 28 until the flange part 30 abuts the nozzle body 10 . When the valve is closed, the closing spring 28 returns the valve needle 26 inwardly to the closed position shown.

A projection 46 designed as a damping piston is connected to the shoulder 34 of the valve needle 26;
The protrusion passes through the through hole 38 and projects into the chamber 20. The diameter of the piston-like projection 46 corresponds to the guide diameter of the valve needle 26. A cap 48 is mounted on the protrusion 46 and is attached to the bottom 5.
0, a peripheral wall 52 and a flange 54. Engaged in the cap 48 is a return spring 56 which surrounds the peripheral wall 52 and urges the flange 54 towards the shoulder 18 of the sleeve 16.

A transverse slot 58 is formed in the flange 54 of the cap 48 and in the region of the peripheral wall 52 connected thereto, through which the fuel flows into the valve needle opening chamber from the chambers 20 to 22.
In the illustrated closed position of the valve needle 26, a damping chamber 60 is formed between the end face of the projection 46 and the bottom 50 of the cap 48, which damping chamber 60
6 and the circumferential wall 52 of the cap 48, it is throttled and connected to the fuel outflow passage. In the illustrated closed position, the projection 46 extends axially beyond the transverse slot 58 of the cap 48 by a distance hv, which distance corresponds to the damped front stroke of the valve needle 26 described below.

The illustrated injection nozzle operates as follows: Due to the increase in fuel pressure at the beginning of the injection stroke, the cap 48 cannot follow the movement of the valve needle 26, so that the damping chamber 60 and the chamber 20 are throttled. A pressure difference is created between them. In this case, the pressure rise in the damping chamber 60 and thus at the end face of the projection 46 or the valve needle 26 takes place more slowly than the pressure rise in the chamber 20, so that the movement of the valve needle 26 is the distance hv
, and is delayed or attenuated until the end face of the protrusion 46 reaches the range of the transverse slit 58. From this point on, the remaining stroke of the valve needle is carried out without damping until the flange part 30 impinges on the nozzle body 10.

In the first partial stroke hv, fuel is forced through the annular cap between the projection 46 and the peripheral wall 52 of the cap 48 into the damping chamber 60. During the closing movement of the valve needle 26, the cap 48 is pulled upwards via the inflowing fuel cushion in the damping chamber 60, in which case the restoring spring 56 resists only slightly compared to the considerably stronger closing spring 28. The spring force of the return spring 56 is such that the amount of fuel that has flowed into the damping chamber 60 remains in the damping chamber 6 with a residual amount remaining from the start of the closing stroke of the valve needle 26 to the start of the next opening stroke.
0 and the cap 48 is set to come into contact with the shoulder 18 again.

The cap 48 is centered on the valve needle 26 and has a considerable radial play with respect to the nozzle holder 14, so that the valve needle 26 can operate without being tightened. The return spring 56 for the cap 48 extends partially beyond the cap 48, so that in such an arrangement the element for partial damping of the opening stroke of the valve needle 26 is located in the injection nozzle. Requires little space in the axial direction.

The injection nozzle according to FIG. 2 substantially corresponds to the injection nozzle shown in FIG. 1, and identical parts are therefore provided with the same reference numerals. However, the cap 48 is provided with a throttle hole 62 in its bottom 50, by means of which the effect of the piston damping is controlled. Furthermore, the projection 46 of the valve needle 26 has a distance h ₁ relative to the shoulder 18 in the closed position of the valve needle 26, in contrast to the embodiment according to FIG. is displaced upwards. As a result, the element for damping the valve needle movement only acts after a prestroke of distance h ₁ , which is advantageous in many cases. Here, the cap 48 rests directly on the valve needle 26 or on its projection 46 in the illustrated starting position, so that the upper end of the projection 46 of the valve needle 26 is of spherical design; This facilitates displacement of fuel from the damping chamber 60.

In the embodiment according to FIGS. 1 and 2, the cap 48 forms a self-rigid member and is reciprocated as a whole by the valve needle 26 and the return spring 56. In the case of the injection nozzle according to FIG. 3, instead of a one-piece cap, there is provided a unit consisting of a ring member 64 and a flat valve member 66, said valve member being pressed against the ring member 64 by a return spring 68. is pressed against the upper end surface of. The ring member 64 is connected to the valve needle 26
The sleeve 16 rests on the shoulder 18 in the illustrated closed position and is provided with a small residual volume of the damping chamber 60 in this position. When the valve needle 26 moves in the opening direction, fuel is forced into the damping chamber 60 through the throttle hole 70 in the valve member 66 . In this case, a desired damped pressure increase is produced at the end face of the projection 46 of the valve needle 26. Valve needle 26 has partial stroke hv
, the end face of the projection 46 enters within the confines of the transverse slot 72 of the ring member 64, thereby terminating the damping action. On the return stroke of the valve needle 26, the valve member 66 is disengaged from the ring member 64, so that the previously forced fuel can again flow out of the damping chamber 60 with a residual volume remaining.

In the case of the injection nozzle according to FIG. 4, a damping piston 76 is provided, which has a socket 78 which serves as a support for the closing spring 28. A cap 80 is fitted onto the damping piston 76 and has a bottom 81.
is pressed towards the central projection 84 of the damping piston 76 by a return spring 82 . The cap 80 is likewise provided with a transverse slot 86 and is constructed of such length that it has a distance h ₁ from the shoulder 18 of the sleeve 16 in the illustrated closed position of the valve needle 26 . The opening and closing process of the valve takes place here in a similar manner as in the previous embodiment. By forming the damping piston 76 as a separate part from the valve needle 26, the diameter of the damping piston 76 is selected to be larger than the diameter of the valve needle 26, so that a damping effect can be achieved in the desired manner. is also controlled.

In all four embodiments, instead of the damping chamber 60 being controlled open via the transverse slits 58, 72, 86, the pressure is controlled by one or more additional holes in the caps 48, 80 or in the ring member 64. It is also possible to control the opening to the chamber 20.

In the case of the injection nozzle according to FIG. 5, a cap 90 is mounted on the projection 46 of the valve needle 26, which cap has a flange edge 92 at its upper end.
, and a support spring 94 is engaged with the flange edge. The cap 90 and the support spring 94 are
Shoulder 98 of nozzle holder 14 and sleeve 1
It is fixed in a cage 96 which is slidably supported with a large radial play in the chamber 20 between the shoulders 18 of 6 and 6. A return spring 100 acts on the cage 96, and the return spring 100 acts on the cage 96.
6 is pressed against the shoulder 18. Cage 96 includes wall holes 102, 104, 106, and 108 through which fuel passes from chamber 20 into through hole 38 and into chamber 22. The cap 90 is provided with a damping chamber 60, as in the previous embodiment, which is connected to the chamber 20 through a throttle hole 100.

The injection nozzle according to FIG. 5 operates as follows: At the beginning of the injection process, all parts assume the position shown in FIG. 5, in which the cage 96 rests against the shoulder 18. When the fuel pressure increases, the cap 90 is initially unable to follow the movement of the valve needle 26 due to the action of the support spring 94, and the fuel is delayed into the damping chamber 60 only through the narrow throttle hole 110. As a result, a pressure difference is created between the damping chamber 60 and the chamber 20. The greater the pressure difference, the faster the valve needle 26 is moved in the opening direction. The spring force of the support spring 94 is set such that in idling operation and in the intermediate speed range of the internal combustion engine the pressure difference does not overcome the preload of the support spring 94, so that the damping effect is effective over the entire needle stroke. It is. Depending on the case, the cap 90 can also be provided with several slots in accordance with the embodiment according to FIG. 1, so that in the case of large needle strokes there are limitations associated with the damping stroke.

In the upper speed range of the internal combustion engine, the pressure difference between chamber 20 and damping chamber 60 is increased to the extent that the preload of support spring 94 is overcome. Then support spring 9
4, the cap 90 follows the valve needle 26, so that the damping action is no longer any stronger. In short, by suitably selecting or adjusting the spring force of the support spring 94, the damping effect can be limited in a desired amount in relation to the pressure. During the closing stroke of the valve needle 26, the entire cage 96, including the cap 90 and the support spring 94, is first displaced upwardly while compressing the return spring 100. The spring force of the return spring 100 pushes the quantity of fuel that has entered the damping chamber 60 out of the damping chamber 60 from the beginning of the closing stroke of the valve needle until the beginning of the next opening stroke, until only a residual volume remains corresponding to the starting position shown. The cage 96 is again set to abut the shoulder 18.

In the case of the injection nozzle according to FIG. 6, a cap 120 is inserted into the projection 46 of the valve needle 26 and is pressed against the shoulder 18 of the sleeve 16 by a return spring 122. . Although not visible in the drawing, the cap 120 is formed with a wall penetration part located in the middle of the main flow path of the fuel, and the fuel reaches the through hole 38 and the chamber 22 from the chamber 20 through the wall penetration part. . A damping chamber 60 is provided in the cap 120 , which is connected to the chamber 20 via a throttle hole 124 and additionally a throttle valve 126 that opens toward the damping chamber 60 . The throttle valve 126 is a closing member 128
The closing member is pressed onto the seat by a leaf spring 130 arranged outside the damping chamber 60. The leaf spring 130 is designed and prestressed in such a way that the throttle valve 120 opens at a predetermined pressure difference and limits the damping action to a predetermined value. During the closing stroke of the valve needle 26, the throttle valve 126 is closed. The cap 120 is temporarily displaced upwards, as in the embodiment of FIGS. almost unstoppable.

The injection nozzle according to FIG. 7 operates in the same way as the injection nozzle according to FIG. 120. cap 120
Although it is not visible in the drawing, it has a wall penetration part, and the main flow of fuel passes through this wall penetration part. Throttle valve 1
32 has a closure member 136 that closes a relatively small hole 138 in the bottom of the cap 120, so that the closure spring 134 can be made very small and accommodated within a blind hole in the projection 46. can.

[Brief explanation of drawings]

1, 2, 3, 4, 5, 6 and 7 are partial longitudinal sectional views showing different embodiments of the injection nozzle according to the invention. 10... Nozzle, 12... Bag nut, 14...
Nozzle holder, 16...sleeve, 18...shoulder, 20, 22...chamber, 24...valve seat, 26...
...Valve needle, 27...Seal cone, 28...
... Closing spring, 30 ... Flange part, 32 ... Support disk, 34 ... Shoulder, 36 ... Suction hole,
38...through hole, 40...hole, 42...annular chamber,
44...Division, 46...Protrusion, 48...Cap, 50...Bottom, 52...Peripheral wall, 54...Flange, 56...Return spring, 58...Horizontal slit, 6
0... Damping chamber, 62... Throttle hole, 64... Ring member, 66... Valve member, 68... Return spring, 70
... throttle hole, 72 ... horizontal slit, 76 ... damping piston, 78 ... socket, 80 ... cap, 81 ... bottom, 82 ... return spring, 84 ... protrusion, 86 ... horizontal slit, 90...cap,
92...flange edge, 94...support spring, 96...
...Cage, 98...Shoulder, 100...Return spring, 102, 104, 106, 108...Wall through hole, 110...Aperture hole, 120...Cap, 1
22...Return spring, 124, 126...Aperture hole,
128... Closing member, 130... Leaf spring, 132
... Throttle valve, 134 ... Closing spring, 136 ... Closing member, 138 ... Hole.

Claims (1)

[Scope of Claims] 1. A fuel injection nozzle for an internal combustion engine, comprising a valve needle loaded by a closing spring and opening in the direction of fuel flow, the valve needle comprising:
It is connected to a piston 46, 76 which forms a damping chamber 60 filled with fuel, said damping chamber being connected to the main flow of fuel only via a throttle channel during the opening stroke of the valve needle. , the damping chamber 60 is inserted into the cap 48, 64, 80, 90, 1, which is inserted into the piston 46, 76.
20, and the cap is formed at the latest in the pre-stroke h ₁ of the piston 46, 76 towards the injection opening side.
after which springs 56, 68, 82, 100, 12 are supported on the casing and returned to the other side.
Fuel injection nozzle for an internal combustion engine, characterized in that it has a wall section that is displaceable against a force of 2. 2. The cap 48, 80, 90, 120 is pressed as a whole by the return spring 56, 82, 100, 122 towards the end face of the piston 46, 76, and the displaceable wall section is 2. A fuel injection nozzle according to claim 1, wherein the fuel injection nozzle is formed by bottoms 50, 81. 3. The wall section of the cap that is displaced against the spring force forms a valve member 66, which opens the damping chamber 60 relative to the rigid wall section with the valve opening. 2. A fuel injection nozzle as claimed in claim 1, which is slidable in both directions. 4. The valve member 66 is formed by the entire bottom of the cap, which bottom is lifted against a spring force from a ring member 64 as a rigid wall section of the cap. Fuel injection nozzle as described. 5. Any one of claims 1 to 4, wherein the cap 48, 80 has at least one lateral slit 58, 72, 86 of a predetermined depth in the peripheral wall 52 and the ring member 64. Fuel injection nozzle as described in section. 6. The fuel injection nozzle according to any one of claims 1 to 3, wherein the cap 90 is supported by the casing via a preloaded support spring 94 toward the injection opening side. 7. A return spring 100 for the cap 90 engages in a cage 96 slidably mounted between shoulders 98, 18 formed as two stops fixed to the casing, in which 3. A fuel injection nozzle according to claim 2, in which a cap 90 and a preloaded support spring 94 are housed. 8. The cap 120 is open to the damping chamber 60 and has throttle valves 126, 132 that are controlled by the difference in fuel pressure between the outside and inside of the damping chamber 60. The fuel injection nozzle according to any one of items 1 to 7. 9. The cap 48 is provided with a flange 54,
3. A fuel injection nozzle as claimed in claim 2, in which a return spring 56 formed as a coil spring engages the flange. 10. The fuel injection nozzle according to claim 1, wherein the piston 46 is integrally connected to the valve needle 26 or is formed by the valve needle 26 itself. 11. Fuel injection nozzle according to one of the claims 1 to 9, in which the piston 76 is integrally connected with a support element 78 for the closing spring 28 of the valve needle 26.