Internal-combustion engines – Particular piston and enclosing cylinder construction – Cylinder head
Reexamination Certificate
2001-03-01
2002-05-07
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Particular piston and enclosing cylinder construction
Cylinder head
C123S193300
Reexamination Certificate
active
06382167
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a monoblock cylinder head for a water-cooling type engine, and in particular to a monoblock cylinder head that does not form a clearance, through which non-combustion gas can enter, between the head and a piston in a joining inner circumferential surface of an upper end portion of a cylinder wall portion to a cylinder head ceiling portion.
2. Description of the Related Art
A monoblock cylinder head is frequently used for an aircraft engine.
To manufacture an engine main body, in general, as shown in
FIG. 3
, a cylinder block
40
and a cylinder head
41
are joined to each other by bolts with a cylinder gasket
42
interposed there between, thereby constructing an engine main body
43
. In the drawing, reference numeral
44
denotes a head cover, and reference numeral
45
denotes an oil pan.
A monoblock cylinder head is formed from a cylinder block cylinder portion and a cylinder head by integrated molding using a casting die. The monoblock cylinder head can dispense with a plurality of bolt boss portions, bolts and a head gasket corresponding thereto, which are, otherwise required in a case where the cylinder block cylinder portion and the cylinder head are separated and thus joined to each other. Consequently, the monoblock can reduce the weight of the engine main body, and, for this reason, is frequently used, in particular, for an aircraft engine.
As shown in
FIG. 4
, in the monoblock cylinder head
46
of this type, a stress concentration acts on a joining portion
52
between a cylinder head ceiling portion
49
and a cylinder wall portion
48
, which is caused due to combustion pressure applied to the cylinder head ceiling portion
49
and the upper portion of the cylinder wall portion
48
. To relax this stress concentration, an annular groove portion
57
having a predetermined radius of curvature is formed circumferentially in an inner circumferential surface of the joining portion
52
of the monoblock cylinder head
46
.
In a case where the joining portion
52
is formed to have the predetermined radius of curvature, even if a piston
53
reaches an upper dead point in the upper end portion of a cylinder
55
as shown in
FIG. 5
, an annular space portion
56
is formed along the inner circumferential surface of the cylinder
55
between a piston circumferential surface portion
54
and the inner circumferential surface portion of the annular groove portion
57
. Consequently, non-combustion gas enters into this annular space portion
56
, so that it causes disadvantages decreasing the combustion efficiency, the fuel consumption efficiency and the exhaust emission.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a monoblock cylinder head, which can relax stress concentration caused by generated combustion load on a joining portion between a cylinder head ceiling portion and a cylinder upper end portion, and which can develop the combustion efficiency to improve the fuel consumption efficiency as well as improve the exhaust emission.
To attain the object as noted above, according to the present invention, there is provided amonoblock cylinder head for an engine, in which a cylinder upper end portion and a cylinder head ceiling portion are formed integrally, the monoblock cylinder head comprising an annular groove portion, having such a radius of curvature as to be capable of supporting load generated by combustion in a combustion chamber within a cylinder, that is circumferentially provided in an inner circumferential surface of a joining portion of an upper end portion of a cylinder wall portion to the cylinder head ceiling portion, and an engagement member, having an inner circumferential surface portion capable of forming substantially the same plane as a cylinder interior surface, that is engaged with the annular groove portion.
Accordingly, in the present invention, since the engagement member is engaged with the annular groove portion, and the inner circumferential surface portion of this engagement member forms substantially the same plane as the cylinder interior surface, the upper end portion of the cylinder wall portion and the cylinder head ceiling portion are jointed to each other continuously and substantially perpendicularly.
For this reason, even if a piston is arrived at an upper dead point, there is formed no space portion in the joining portion of the upper end portion of the cylinder wall portion to the cylinder head ceiling portion, unlikely to the conventional monoblock cylinder head. Consequently, it is possible to prevent problems encountered in the prior art, in which the non-combustion gas enters into the space portion so that it causes to lower the combustion efficiency to lower the fuel consumption efficiency and to lower the exhaust emission.
The construction of the monoblock cylinder head according to the present invention is effectively applied, in particular, to a so-called liner-less type monoblock cylinder head different from a type in which, after a monoblock cylinder head is formed by integrated molding, a separate cylinder liner is inserted into a cylinder.
That is, in a case where a monoblock cylinder head is cast to have an annular groove portion having a predetermined radius of curvature in an inner circumferential surface portion of a joining portion of a cylinder side wall to a cylinder head ceiling portion, and then a separate cylinder liner is insertion disposed within the cylinder so that the cylinder has the liner, the annular groove portion is covered by the cylinder liner during a honing process, and accordingly similarly to the construction of the present invention, the cylinder head ceiling portion and the cylinder wall portion are joined to each other continuously and substantially perpendicularly.
However, the construction of the monoblock cylinder head according to the present invention is effectively applied to a so-called liner-less type monoblock cylinder head in which such a separate cylinder liner is not disposed within the cylinder.
Since the annular groove portion, having such a radius of curvature as to be capable of supporting load generated by combustion in the combustion chamber within the cylinder, is circumferentially provided in the inner circumferential surface of the joining portion of the upper end portion of the cylinder wall portion to the cylinder head ceiling portion, it is possible to relax the stress concentration caused on the joining portion of the upper end portion of the cylinder wall portion to the cylinder head ceiling portion when the combustion load is generated.
In the present invention, the engagement member is annular, and is fitted to substantially the entire circumference of the annular groove portion.
Accordingly, in the present invention, since the engagement member is fitted to the entire circumference of the annular groove portion, the presence of the space portion can be eliminated over the entire circumference.
In the present invention, the annular engagement member is formed to have a radius of curvature slightly larger than that of a cylinder inner circumferential surface portion, and is partly cut, so that the engagement member is engaged with the annular groove portion by an enlarging biasing force.
Accordingly, in the present invention, after the honing process is carried out for the cylinder head inner circumferential surface, the engagement member is deformed so that its inner diameter is reduced, and then inserted from the lower portion of the cylinder into the cylinder to be fitted into the annular groove portion, and thereafter engaged with the annular groove portion by enlarging the engagement member.
Consequently, the manufacture of the monoblock cylinder head that can improve the combustion efficiency to improve the fuel consumption efficiency and improve the exhaust emission, can be performed easily.
Further, in the present invention, the joining portion of the upper end portion of the cylinder wall portion to the cylinder head ceil
McMahon Marguerite
Toyota Jidosha & Kabushiki Kaisha
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