Injector sleeve

Abstract

An injector sleeve adapted to be mounted in a cylinder head of an internal combustion engine, where the injector sleeve comprises a tapered inner surface which constitutes a sealing surface for an injector, where the hardness of the tapered inner surface is higher than the hardness of the outer surface of the injector sleeve. The injector sleeve is produced in a cold forming process. The advantage of the invention is that the injector sleeve is provided with a sealing surface for an injector which is harder than the outer surface of the injector sleeve. In this way, a sealing surface for an injector having small tolerances is obtained without further machining, where the outer surface may be turned to the desired dimensions.

Claims

1. A cold forming process for producing an injector sleeve adapted to be mounted in a cylinder head of an internal combustion engine, having a nozzle portion, a mid portion and an upper portion, where the mid portion comprises a tapered inner surface which constitutes a sealing surface for an injector, wherein the hardness of the tapered inner surface is higher than the hardness of the outer surface of the injector sleeve.

2. Method for producing an injector sleeve from a stainless steel material, comprising the step of forming at least one inner surface of the injector sleeve by using a cold forming process.

3. Method according to claim 2, where the at least one inner surface constitutes a sealing surface adapted to bear against an injector.

4. Method according to claim 2, where the inner of the injector sleeve is shaped in two consecutive cold firming steps.

5. Method according to claim 2, comprising forming at least one inner surface of injector sleeve to its final shape using a cold forming process.

6. Method according to claim 5, comprising forming another portion of the injector sleeve to its final shape by machining after the cold forming process.

7. Method for producing an injector sleeve where at least one inner surface thereof constitutes a sealing surface adapted to bear against an injector, comprising the step of forming the at least one inner surface of the injector sleeve by using a cold forming process such that a hardness of the scaling surface is at least 350 HK.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The invention will be described in greater detail in the following, with reference to the attached drawing, where

(2) FIG. 1 shows a cut view of an injector sleeve according to the invention,

(3) FIG. 2 shows a detail of the injector sleeve according to FIG. 1, and

(4) FIG. 3 shows a cut view of an injector sleeve according to the invention with an injector mounted in a cylinder head.

MODES FOR CARRYING OUT THE INVENTION

(5) The embodiments of the invention with further developments described in the following are to be regarded only as examples and are in no way to limit the scope of the protection provided by the patent claims.

(6) FIGS. 1 and 2 shows an injector sleeve 1 according to the invention for the use in an internal combustion engine. The injector sleeve is circular with a centre axis 20 and comprises a lower nozzle portion 2, a mid portion 3 and an upper portion 4. The outer surface of the injector sleeve is denoted 5 and the inner surface is denoted 24. The upper portion is provided with an upper surface 6 which may be used when pushing the injector sleeve into the cylinder head. The upper portion further comprises an upper annular protrusion 7 and a lower annular protrusion 9 which extends outwards from the outer surface and which forms a groove 8 in between them. The groove 8 is adapted to hold a sealing ring 30 that will provide an upper seal between the injector sleeve and the coolant channel in the cylinder head. The upper portion comprises a side wall 10 and a shoulder 11 that connects the upper portion 4 with the mid portion 3. The inner part of the shoulder is provided with a knee 23 that can also be used as contact surface when pushing the injector sleeve into the cylinder head. The diameter of the mid portion of the injector sleeve is reduced compared with the upper portion.

(7) The mid portion 3 comprises a cylindrical portion 12 having an inner surface 22 and a tapered portion 13 having a tapered, conical sealing surface 21. The conical sealing surface 21 is adapted to provide the sealing surface between the injector and the injector sleeve. If the tolerances of the sealing surface are small enough and the hardness of this sealing surface is high enough, no external sealing means are necessary. An injector can thus be removed from the injector sleeve and reinserted in the injector sleeve without the need to replace the injector sleeve or any sealing means, such as sealing rings. The sealing surface is therefore produced with very high precision and is also provided with a very hard surface. In order to obtain such a sealing surface, the injector sleeve is produced in a cold forming process. The material is preferably a stainless steel material. In this way, a roundness of the sealing surface that is below 10 micrometers can be obtained, and a surface finish of the sealing surface that is below 1 micrometer can be obtained. The roundness is obtained by using the minimum zone circle definition, the surface finish is evaluated according to the R.sub.zDIN-definition.

(8) The hardness of the tapered sealing surface is preferably at least 10% higher than the hardness of the material at a distance d into the material. The distance is defined as a plane 26 that is parallel to the sealing surface 21 and is positioned with a distance d from the sealing surface, where d is 0.5 mm in the shown example. At a distance of about 1.0 mm into the material, the hardness of the material is approximately the same as the hardness of the outer surface of the injector sleeve.

(9) A hardness of the sealing surface that is harder than 350 HK and preferably harder than 380 HK is obtained at the same time in the cold forming process. The hardness of the material is here measured with the Knoop hardness test HK 0.5, which is defined by the ASTM D1474 standard. The hardness of the material will extend into the material from the sealing surface such that the section of the material having a hardness higher than 350 HK extends at least 0.5 mm into the material, at plane 26. In this way, the sealing surface will not deform when the injector is mounted, but will only deflect some.

(10) It is also possible to make the sealing surface 21 somewhat spherical with a relatively large radius, preferably larger than the radius of the injector sleeve. A spherical sealing surface 21 is of advantage for injectors having a conical cap nut with a planar contact surface.

(11) The advantage of the inventive injector sleeve is that such surface properties can be obtained without the need of machining and heat treatment. When the injector sleeve is cold formed, the interior of the injector sleeve is ready. The outer surface of the injector sleeve is however still raw and requires some machining before the final shape is obtained. The outer surface of the injector sleeve will not be as hard as the inner sealing surface, and a simple turning of the outer surface is enough to obtain the final shape. Since the injector sleeve will be fixedly mounted in the cylinder head, it is of advantage that the outer surface is not as hard as the inner sealing surface. The outer surface may thus deform some during the mounting. The hardness of the tapered sealing surface is preferably at least 10% higher than the hardness of the outer surface of the injector sleeve.

(12) The lower surface 14 of the mid portion is provided with one or more grooves 16. A viscous sealant is applied to the lower surface before the injector sleeve is mounted in the cylinder head, and the grooves will aid the sealing between the injector sleeve and the cylinder head, such that the sealing of the coolant channel is permeable.

(13) During the manufacture of the injector sleeve, the inner of the upper portion and the mid portion are formed to the final shape in the cold forming process. The injector sleeve also comprises a lower nozzle portion 2 with a cylindrical portion 15, having a smaller diameter than the mid portion. The nozzle portion receives its final shape in a later machining stage. The end region of the nozzle portion comprises a collar 25 having a tapered surface 17, a mid surface 18 and a tapered surface 19. The collar is adapted to be flared out in an opening of the cylinder head after the injector sleeve is mounted in the cylinder head. The injector sleeve is in this way secured in the axial direction without the use of any other fastening means. This will provide a gas tight sealing between the injector sleeve and the cylinder head for combustion gases from the combustion chamber.

(14) FIG. 3 shows a cut view of an injector sleeve 1 mounted in a cylinder head 27. The injector sleeve is pushed into the cylinder head with appropriate mounting tools, bearing on the upper surface 6 and/or the knee 23. A sealing ring 30 is provided in the groove 8 and a viscous sealing compound 31 is applied on the lower surface 14 before the injector sleeve is inserted. When the injector sleeve is inserted to the final position, the collar 25 is flared out against the opening surface 33 of the cylinder head. The injector sleeve is now fixedly mounted in the cylinder head and proper sealing is provided between the injector sleeve and the cylinder head, both for the coolant channel 28 and for the combustion chamber.

(15) The injector 29 is provided with a sealing surface 32 which is adapted to bear on the conical sealing surface 21 of the injector sleeve. The injector cap nut is thus also tapered with an angle that corresponds to the angle of the sealing surface 21. The sealing surface 32 of the injector is further spherical with a relatively large radius. The radius of the spherical sealing surface is preferably larger than the outer radius of the injector cap nut. With such a large radius, and with the deflection of the mounting surfaces 21 and 32 when the injector is mounted in the injector sleeve, a gas tight seal is provided between the injector and the injector sleeve that will withstand the pressure of the combustion chamber.

(16) Due to the spherical shape of the injector sealing surface, a circular, annular sealing area is created between the injector sealing surface 32 and the sealing surface 21 of the injector sleeve, where the injector bears on the injector sleeve. In the shown example, the diameter of the sealing area will be around 16 mm and the radius of the spherical injector sealing surface 32 is approximately 40 mm. These measures can of course eb varied depending on the type of injector.

(17) The inventive injector sleeve is suitable both for injectors used in a common rail configuration as well as for unit injectors.

(18) The invention is not to be regarded as being limited to the embodiments described above, a number of additional variants and modifications being possible within the scope of the subsequent patent claims.

REFERENCE SIGNS

(19) 1: Injector sleeve 2: Nozzle portion 3: Mid portion 4: Upper portion 5: Outer surface 6: Upper surface 7: Upper annular protrusion 8: Groove 9: Lower annular protrusion 10: Side wall 11: Shoulder 12: Cylindrical portion 13: Tapered portion 14: Lower surface 15: Cylindrical portion 16: Groove 17: Tapered surface 18: Contact surface 19: Tapered surface 20: Centre axis 21: Tapered sealing surface 22: Inner surface 23: Knee 24: Inner surface 25: Collar 26: Plane 27: Cylinder head 28: Coolant channel 29: Injector 30: O-ring 31: Sealing compound 32: Injector sealing surface 33: Opening surface