Fastening an exhaust manifold to an engine cylinder head

Details Fastening an exhaust manifold to an engine cylinder head Fastening an exhaust manifold to an engine cylinder head

2000-04-26

2001-12-11

Denion, Thomas (Department: 3748)

Power plants

Internal combustion engine with treatment or handling of...

Common receiver having inlets from plural cylinder

C060S321000, C060S322000

Reexamination Certificate

active

06327854

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATIONS
Priority is claimed under 35 U.S.C. 119 with respect to German Patent Application 199 20 822.0-13 filed on May 6, 1999.
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to an arrangement for fastening an exhaust manifold on to the cylinder head of an internal combustion engine.
An exhaust manifold of the generic type is disclosed in DE 196 35 870 A, and a typical earlier fastening of the exhaust manifold to the cylinder head can be seen from DE 38 28 723 A.
To accommodate thermal growth or expansion of the exhaust manifold and inhibit warping, the manifold's flanges which are used to attach it to a cylinder head permit sliding movement of the manifold along the sealing surface with the engine, along either a seal member of the actual surface of the cylinder head itself. For this purpose, holes in the inlet flanges of the manifold are made larger than the diameters of the fasteners, either bolts or studs and nuts, and are designed as slots. However, the fasteners have to be tightened with a defined torque to extremely small tolerances, e.g. 16 Nm±1 Nm to both permit desired sliding movement and also adequate sealing. In an installation where several fasteners are installed in series for a given manifold, much time is expended to satisfy attach the manifold because the fasteners must be tightened in sequence and gradually using at least two torque settings for the installation tool. In addition to this difficulty, there is only a small degree of certainty of a proper reinstallation of a manifold after servicing in the workshop where such narrow tolerances likely cannot be achieved.
SUMMARY OF THE INVENTION
The object of the invention is to provide an apparatus and method of installation of an exhaust manifold without defining a very specific tightening torque but permitting desirable sliding movement of the manifold along the cylinder-head surface while still maintaining good sealing.
In the arrangement and proposal according to the subject invention, the fasteners in the form of nuts are threaded onto studs by means of commonly used tools until they engage spacer elements which is readily accomplished in a short period of time. The length dimension of the shank portion of the spacer element is determined such that, with a nut tightened on to the stud to the aforedescribed engaging extent, sliding movement of the manifold's flange is not prevented. Also, sealing is assured against a typical multi-layered gasket member which is positioned beneath the flange. The spacer element design does not permit the surface contact between the manifold and cylinder head to be excessive so as to inhibit thermal growth.
The spacer element may be in the form of a bushing which is inserted into the manifold's hole and with an internal diameter greater than the diameter of the stud with the result that the manifold flange is permitted to be displaced upon thermal expansion of the exhaust manifold. The end of the spacer element which is adjacent the nut fastener may be provided with a collar portion adapted to engage the exterior of the manifold. Alternatively, the nut itself may include a collar portion with the collar engaging the manifold flange outwardly of the spacer bushing. This spacer bushing may be produced, for example, as a cost-effective turned part, an extruded part, or a sintered metal formed part. In order to facilitate assembly in a plant, the spacer bushing may be connected to the flange in captive fashion, e.g. by adhesive bonding or lightly pressing in the associated hole.
It is also possible for the spacer bushing to be integral with the nut fastener, in which case the nut is designed as a collar nut and the collar portion engaging the manifold's flange portion.
Finally, it is also possible for the spacer element to be integral with the stud but with its diameter smaller than the flange's hole in order to allow the flange to be move in a slidingly manner. In this case, the nut might be designed as a collar nut, of which the collar portion engages the flange outside the spacer portion of the stud.


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