Internal-combustion engines – Particular piston and enclosing cylinder construction – Cylinder head
Reexamination Certificate
1999-06-04
2001-05-22
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Particular piston and enclosing cylinder construction
Cylinder head
C123S456000
Reexamination Certificate
active
06234135
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a cylinder head for mounting on, for example, a diesel engine, which cylinder head is provided with cavities for injection units for fuel into the engine and supply means for liquid fuel. Such cylinder heads have an elongated shape and are intended to be mounted on preferably the top side of an engine having several cylinders, e.g. six.
PRIOR ART
Engines which are driven by liquid fuel, e.g. diesel oil, usually include a plurality of cylinders which at a regulated rate shall be provided with fuel by an injection nozzle and sufficient air for the combustion and must have an outlet for the exhaust gases. These functions are usually collected in a cylinder head which is mounted as a cover on the cylinders. Since the cylinders stand in a row, the cylinder head will be elongated.
The cylinder head is mostly moulded with completed passages for air and exhaust gases and possibly cavities for the fuel injection units. These cavities may also be bored. However, something that is always necessary is to bore passages for supply of fuel to the cavities for the fuel injection units. These passages, of which there are two, normally have a diameter of approximately 9,5 millimetres and they must run at a certain, short distance from each other through the whole length of the cylinder head. The passages are bored usually from the ends of both short sides. Since fuel from these passages is to be forced into the fuel injection units, it is necessary to seal the passages both from each other and from the surroundings. Three surfaces which seal against O-rings have therefore been mounted on the injection unit, one below the lowermost passage, the second between the passages and the third above the uppermost passage.
One of the passages, preferably the lower one, is intended to feed fuel to the fuel injection units, whereas the second passage is intended for surplus fuel and to lead this in the opposite direction to that which the fuel has in the first passage and to maintain a certain pressure in the system. The pressure level is controlled by a valve mounted in connection to the second passage.
The amount of fuel which is to be injected into the engine is portioned out through the injection units. However, the total amount of these portions is much lower than the circulating amount, which is about four to eight times the total injected amount.
TECHNICAL PROBLEM
The space in the cylinder head is limited since it shall include both the inlet and the exhaust gas passages for the engine and also cooling passages. Two fuel passages will therefore result in the dimension of these and further passages having to be limited. The limited space does not allow for desired freedom for designing these.
As a result of the small dimension of the bores working difficulties will arise, since it is difficult to maintain a straight and accurate direction in a bore having a small diameter and a great length, usually in the order of 1 m. As a consequence of this, a high incidence of rejects of the cylinder heads will arise and a high level of process conducting will be required, which together will result in high production costs.
With two passages, four outlets in every injection cavity will also be obtained, which outlets (or inlets) must be deburred so that impurities in the form of burrs will not come out into the fuel and cause damage to the impurity-sensitive injection units. This deburring requires great attention, care and accuracy and has a negative influence on the production costs.
Various fuels which can be used in the engine are temperature-sensitive and the lubricating capability etc. is negatively influenced by a too high temperature, and leading to operational disturbances. The cooling liquid and the greasing oil in and around the cylinder head heat the fuel which is transported through the borings in the cylinder head and it is therefore of great importance that the heat transfer between the colder fuel and the surroundings will be as small as possible. With two passages each having a diameter of normally 9,5 mm and a length of 1 m a projected heat transfer surface of about 60 000 mm
2
will be obtained.
THE SOLUTION
According to the present invention, the above problems have been solved by means of an elongated cylinder head for mounting on, for example, a diesel engine having cavities for injection units and means for supplying liquid fuel, such as diesel oil, to these units, as well as the usual air and cooling passages, if required. The cylinder head is characterized by having only one longitudinal fuel passage for feeding of fuel to and removing of fuel from all injection units.
According to the invention, it is suitable that the fuel passage ends in one or both of the shorter sides of the elongated cylinder head.
According to the invention, one or more transverse passages for feeding or removing of fuel to or from the longitudinal passage may however be arranged at one or both of the ends of the longitudinal fuel passage.
According to the invention, a valve for controlling the pressure of the fuel in the longitudinal fuel passage may be arranged therein at the outlet end for the fuel or outside the passage.
Further, it is suitable, according to the invention, that the longitudinal fuel passage has a diameter of 10-15 mm.
According to the invention, only two surfaces for sealing against O-rings mounted on the injection units may be made in each cavity for the injection units, one above and one below the inlet and outlet openings for the longitudinal fuel passage.
REFERENCES:
patent: 5297524 (1994-03-01), Fransson et al.
patent: 5411001 (1995-05-01), Werner et al.
patent: 5692477 (1997-12-01), Berger et al.
patent: 5752486 (1998-05-01), Nakashima et al.
patent: 826 216 (1951-12-01), None
patent: 42 41 374 A1 (1994-06-01), None
patent: 468 719 (1993-03-01), None
Lerner David Littenberg Krumholz & Mentlik LLP
McMahon Marguerite
Volvo Lastvagnar AB
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