The invention relates to an injection valve. Injection valves conventionally have a valve housing in which, for example, an actuator for controlling a servo valve is provided. The servo valve sets a pressure in a control chamber. Furthermore, the injection valve has a nozzle body which has a sealing seat and injection holes. A recess in which a nozzle needle is guided is made in the nozzle body. The nozzle needle is moved as a function of the pressure in the control chamber.
The recess has a pressure chamber which is connected to a fuel line of the housing. Since a fuel is guided at high pressure in the fuel line, particularly in the case of diesel injection valves, a sealing point is produced between the housing and the nozzle body. The sealing point is preferably sealed by the nozzle body being pressed against the housing. A clamping nut is provided for this purpose, said nut being connected to a thread of the housing and prestressing the nozzle body against the housing. The prestressing of the nozzle body requires large prestressing forces particularly at a high fuel pressure. The prestressing force has to be transmitted by the clamping nut to the nozzle body via an optimized geometry. For this purpose, it is known to form a bearing surface on the nozzle body, which surface is of conical design and tapers in the direction of the tip of the nozzle body.
At the same time, the clamping nut has a conical bearing surface which tapers in the direction of the tip of the nozzle body. A defined differential angle is made between the bearing surface of the nozzle body and the bearing surface of the clamping nut in order to ensure a defined surface pressure. At a very large prestressing force it has been shown that the action of force perpendicular with respect to the longitudinal direction of the nozzle body is relatively large and therefore produces an expansion of the clamping nut in the radial direction. Damage to the clamping nut may occur as a consequence.
The object of the invention is to provide an injection valve in which an optimized transmission of the prestressing force to the nozzle body is achieved.
The injection valve according to an embodiment of the invention has an optimized transmission of force between the clamping nut and the nozzle body. The optimized transmission of force is achieved by the surface with which the clamping nut rests on the nozzle body being enlarged. The enlarged surface is achieved by a curved shape which is formed either on the clamping nut or on the nozzle body. Owing to the curved shape, instead of a linear contact between the nozzle body and the clamping nut contact in the form of a ring surface is ensured.
The injection valve according to an embodiment has the advantage that the force for prestressing the nozzle body is transmitted via a transmission element. The transmission element permits a lower loading of the clamping nut in the radial direction.
The bearing surface which rests on the curved bearing surface preferably has a conical surface. The conical surface is preferably arranged at an angle of 40° and 60° with respect to the central axis of the injection valve. The pairing of the curved bearing surface with the planar conical surface provides a cost-effective embodiment.
In a preferred embodiment, the clamping nut has a concave partially spherical surface and the nozzle body has a convex surface. By means of this embodiment, an improved surface contact between the clamping nut and the nozzle body is achieved.
The curved bearing surface preferably has a convex surface. The radius of the convex surface lies preferably in the range from 20 to 60 mm.
In order to support the pressure chamber of the nozzle body, the curved surface is preferably arranged at the height of the pressure chamber, so that the line of action of the prestressing force passes through the pressure chamber. In this manner, at the same time as the nozzle body is pressed against the housing, the pressure chamber is supported from the outside, so that a high compressive strength of the nozzle body is achieved.
An optimum support in terms of pressure of the pressure chamber is achieved by the curved bearing surface being arranged at the height of the center of the pressure chamber.
The clamping nut preferably has a ring part which merges into a sleeve part. The sleeve part is arranged perpendicular with respect to the longitudinal axis of the injection valve. A first bearing surface is arranged on the ring part. In addition, a transmission element is provided which transmits the radial component of the prestressing force of the nozzle body into a virtually axial component which engages on the ring part. The transmission of the radial prestressing force to the ring part of the clamping nut makes it possible to make the sleeve part relatively thin. An overall small diameter of the injection valve is made possible by means of a thin sleeve part.
The transmission element preferably has in cross section the shape of a wedge with a third and fourth bearing surface, the third and fourth bearing surfaces being aligned at an angle of less than 90° with respect to each other.
The transmission element is preferably designed in the form of a ring which enables the prestressing force to be transmitted in a manner distributed uniformly around the circumference of the nozzle body.
The transmission element preferably bears against the ring part of the clamping nut, the surface pairing being arranged at an angle of approximately 90° with respect to the central axis of the injection valve. At the same time, a second surface pairing, which is arranged between the transmission element and the nozzle body, has an angle of 20° to 40° with respect to the central axis of the injection valve.
The abovementioned geometries ensure an improved transmission of the prestressing force.
The invention will be explained in greater detail below with reference to the figures, in which:
The nozzle body 3 has a first section 19 which is of cylindrical design and bears with a pressure surface 20 against the housing 2. The first section 19 merges via a second bearing surface 10 into a second section 21 which is likewise of cylindrical design. The second section 20 has a smaller diameter than the first section 19.
The nozzle body 3 has a recess 23 which is arranged symmetrically with respect to the central axis 18 and has a widened area which constitutes a pressure chamber 5. The recess 23 serves as a fuel accumulator. A nozzle needle which is assigned at its tip to a sealing seat in the nozzle body is placed in the recess 23. The nozzle needle 6 is guided in the region of the first section 19 in the recess 23. Furthermore, injection holes which are in connection with the pressure chamber 5 and are arranged below the sealing seat are made in the nozzle body 3. If the nozzle needle 6 bears against the sealing seat, then there is no connection between the pressure chamber 5 and the injection holes. If the nozzle needle is lifted off the sealing seat, then the fuel which is present in the pressure chamber 5 can pass laterally past the nozzle needle 6 to the injection holes, and an injection takes place.
The second bearing surface 10 is designed as a conical surface which tapers from the first section 19 in the direction of the second section 21. The second bearing surface 10 is preferably at a third angle c with respect to the central axis of symmetry 18. The third angle c lies in the range of from 10° to 70°, preferably between 40° and 60°.
The nozzle body 3 is encircled by a clamping nut 1 which has a ring part 8 which merges into a sleeve part 7. The ring part 8 is arranged in the region of the second section 21. The sleeve part 7 is guided as far as the housing 2 along the second bearing surface 10 and the first section 19. The sleeve part 7 is screwed to the housing 2 via a thread 14. The ring part 8 has a first bearing surface 9 which is arranged at a second angle b with respect to the central axis of symmetry 18. The second angle b preferably lies in the region of 90°. The first bearing surface 9 faces the second bearing surface 10. The transmission element 4, which is preferably designed in the form of a ring, is arranged between the clamping nut 1 and the nozzle body 3. The cross section of the transmission element 4 essentially has a triangular shape, a third bearing surface 11 of the transmission element 4 being assigned to the first bearing surface 9, and a fourth bearing surface 12 of the transmission element 4 being assigned to the second bearing surface 10. The transmission element 4 has an outer surface 22 which essentially constitutes a cylindrical surface which is arranged essentially parallel to the inner surface of the sleeve part 7. A defined gap 13 is provided between the outer surface 22 of the transmission element 4 and the inner surface of the sleeve part 7.
The first and the third bearing surface 9, 11 and the second and the fourth bearing surface 10, 12 constitute a first and a second surface pairing, respectively. The first bearing surface 9 is preferably arranged virtually parallel to the third bearing surface 11, and the second bearing surface 10 is preferably arranged virtually parallel to the fourth bearing surface 12. A differential angle a is usually provided between the first and third bearing surfaces 9, 11 and the second and fourth bearing surfaces 10, 12.
The transmission element 4 has, in the form of a ring, a partially wedge-shaped inner recess which corresponds essentially to the conical shape of the second bearing surface 10. The radius of the inner recess of the transmission element 4 is matched to the conical shape of the second bearing surface 10 in such a manner that the entire fourth bearing surface 12 of the transmission element 4 rests on the second bearing surface 10 of the nozzle body 3.
The clamping nut 1 is screwed to the housing 2 via the thread 14, so that the transmission element 4 is pressed by the first bearing surface 9 in the direction of the first section 19. In the process, the fourth bearing surface 12 of the transmission element 4 comes into contact with the second bearing surface 10 of the nozzle body 3, a transmission of force between the ring part 8 and the second bearing surface 10 taking place. By means of the defined gap 13 it is ensured that radial forces are not transmitted to the sleeve part 7 of the clamping nut 1. This permits a relatively narrow design of the sleeve part 7, as a result of which an injection valve having a small cross section is made possible.
The second bearing surface 10 in the nozzle body 3 is preferably formed at the height at which a pressure chamber 5 is made in the nozzle body 3, so that the line of action of the prestressing force passes through the pressure chamber 5. The pressure chamber 5 is connected to the fuel line, so that fuel at high pressure is present in the pressure chamber 5. The provision of the pressure chamber 5 enables the nozzle body 3 to have a small wall thickness in the region of the pressure chamber 5, so that it is advantageous if a prestressing force is exerted from the outside on the nozzle body 3 in the region of the pressure chamber 5, which force counteracts the pressure in the pressure chamber 5. This prestressing force is exerted on the nozzle body 3 by the transmission element 4. In this manner, an optimum passing of the prestressing force to the wall of the pressure chamber 5 is achieved.
In this exemplary embodiment, the first bearing surface 9 is designed as a conical inner surface which tapers in the direction of the second section 21 of the nozzle body 3. The first bearing surface 9 is preferably arranged at a fourth angle d with respect to the central axis of symmetry 18. The fourth angle d lies in the range of from 10° to 70°, preferably in the range of from 40° to 60°.
The second bearing surface 10 is assigned to the first bearing surface 9 and bears directly against the first bearing surface 9 in a supporting region 25. The bearing region 25 extends over a certain length in the longitudinal direction of the nozzle body 3, so that a defined pressing of the ring surface between the clamping nut 1 and the nozzle body 3 is achieved. This surface pressure is achieved on account of the curved shape of the second bearing surface 10. The convex shape of the second bearing surface 10 means that it is not necessary to produce the first and the second bearing surface 9, 10 with a precisely set differential angle. Relatively large angular ranges are sufficient for optimum surface pressing. This permits a simple and cost-effective manufacturing of the injection valve.
In
The nozzle body 3 is designed corresponding to the nozzle body 3 from
The clamping nut 1 merges from a ring part 8 into a sleeve part 7 in a transitional region 26. The transitional region is designed in the form of an inner conical surface 9, so that the wall of the clamping nut 1 on the ring part 8 continuously decreases in size as far as the sleeve part 7. Since the clamping nut 1 is essentially in the form of a sleeve, the diameter of the inner recess of the clamping nut 1 has a smaller value in the region of the ring part 8 than the diameter of the inner recess of the clamping nut 1 in the region of the sleeve part 7. The nozzle body 3 and the housing 2 are placed into the inner recess of the clamping nut 1. It is essential that there is at least one curved bearing surface in a surface pairing between the clamping nut 1 and the nozzle body 3, so that a relatively wide ring surface is achieved as bearing region 25, with which the first and second bearing surfaces 9, 10 bear against each other and the prestressing force is transmitted. By means of the wide ring surfaces, the press-on force is provided over a relatively small surface pressure, so that both the clamping nut 1 and the nozzle body 3 are subject to relatively small stresses. This permits a thinner design of the wall of the clamping nut 1 and also a thinner design of the wall of the nozzle body 3.
An essential advantage of the embodiments of
The dome-like shape of the first bearing surface 9 and of the convex surface of the second bearing surface 10 enable optimum matching which permits the use of relatively small radii for the first and the second bearing surfaces 9, 10. The relatively small radii have the advantage that small radii can be checked precisely and re-measured. In this manner, a precise keeping to the predetermined radii is made possible during the production.
An essential advantage of the concave partially spherical surface is that the partially spherical surface and the assigned convex surface are simple to manufacture.
Number | Date | Country | Kind |
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100 18 663 | Apr 2000 | DE | national |
This application is a continuation of U.S. patent application Ser. No. 10/271,240 filed Oct. 14, 2002, now U.S. Pat. No. 6,799,748, which is a continuation of co-pending International Application No. PCT/DE01/01430 filed Apr. 11, 2001, which designates the United States, and claims priority to German application number DE 10018663.7 filed Apr. 14, 2000.
Number | Name | Date | Kind |
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4314670 | Walsh, Jr. | Feb 1982 | A |
6053432 | Stevens | Apr 2000 | A |
Number | Date | Country |
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2926382 | Jan 1980 | DE |
19508636 | Sep 1996 | DE |
19523243 | Jan 1997 | DE |
19523243 | Jan 1997 | DE |
19729843 | Jan 1999 | DE |
0890734 | May 1998 | EP |
Number | Date | Country | |
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20040217321 A1 | Nov 2004 | US |
Number | Date | Country | |
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Parent | 10271240 | Oct 2002 | US |
Child | 10854832 | US | |
Parent | PCT/DE01/01430 | Apr 2001 | US |
Child | 10271240 | US |