Field of the Invention
Exemplary embodiments of the present invention relate to an exhaust manifold for a vehicle which can prevent a crack from occurring on an end portion of an exhaust port due to high-temperature gas discharged from the exhaust manifold.
Description of Related Art
Recently, in order to apply a downsizing concept of a gasoline turbocharger, the use of an exhaust manifold-integrated cylinder head has showed a tendency to gradually increase, and especially, the exhaust manifold-integrated cylinder head has been widely used to improve the fuel efficiency in a high-speed high-load range.
Since the aforementioned exhaust manifold-integrated cylinder head includes a cylinder head and an exhaust manifold which are integrated with each other, the temperature of cooling water increased by the exhaust manifold additionally increases the temperature of a combustion chamber, so that it is possible to use a smaller amount of fuel than in the prior art, thereby improving the fuel efficiency in a high-speed high-load range.
However, since such an exhaust manifold is integrated with a cylinder head, the length of a runner is short, and exhaust energy is lost due to exhaust interference, so that a low-to-medium-speed performance is deteriorated.
In order to partially solve such a problem, a four-cylinder system is configured in a 4-2 type exhaust structure such that, among first, second, third and fourth runners 101, 102, 103 and 104, respectively, the first and fourth runners 101 and 104 are connected to each other, while the second and third runners 102 and 103 are connected to each other, as shown in FIG. 1, so as to form two exhaust ports at an end portion of an exhaust manifold. Such a structure is configured to increase the lengths of the runners and to reduce exhaust interference.
FIG. 2 is a cross-sectional view illustrating an exhaust port portion shown in FIG. 1, wherein a partition portion 105 is formed in a portion at which the two exhaust ports meet each other.
However, when such a partition portion 105 is continuously exposed to high-temperature exhaust gas, a crack occurs from an end portion 105-1 due to a limit of the property value of the exhaust manifold integrated with the cylinder head 100 and made of aluminum.
In order to solve such a problem, it may be considered to form a water jacket 106 at a position near to the partition portion. However, such a configuration cannot be achieved in the conventional mold structure because it is impossible to connect the water jacket lengthwise, and a 4-2 type exhaust structure cannot be formed due to limits in structure and shape on manufacturing the exhaust port at a position near to the water jacket.
In addition, the partition may be formed to be thicker than that in the prior art so as to improve the durability of the partition. However, in this case, the cross section area of the exhaust port is reduced to increase an exhaust resistance.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.