The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2018-203083, filed Oct. 29, 2018. The contents of this application are incorporated herein by reference in their entirety.
The present disclosure relates to a cylinder head of an internal combustion engine, and more particularly, to a cylinder head including a pair of intake ports communicating with a common combustion chamber.
In a water-cooled internal combustion engine, a flow path for cooling water is formed in a cylinder head. By forming the flow path of the cooling water in the vicinity of an intake port and cooling the wall surface of the intake port, occurrence of knocking may be suppressed. Also, charging efficiency may be improved by decrease of intake air temperature. Further, when a pair of intake ports communicating with a common combustion chamber are provided in a cylinder head, cooling efficiency may be enhanced by flowing cooling water also between the intake ports.
JP 2000-329001 A discloses a configuration of a cylinder head for securing a flow rate of cooling water flowing between intake ports. In the cylinder head disclosed in JP 2000-329001 A, the interval between the openings of the intake ports is widened, and the opening diameter of the intake ports is set relatively smaller than that of a general four-valve type internal combustion engine.
However, if the opening diameter of the intake port is reduced, the amount of intake air is reduced and, as a result, efficiency and output may is reduced. Therefore, in the cylinder head disclosed in JP 2000-329001 A, the intake ports are formed as tangential ports having a small intake resistance in order to prevent the efficiency and the output from reducing. Also, in JP 2000-329001 A, the lift amount of intake valve is increased so that actual cross-sectional area of an intake passage is increased.
The configuration of the cylinder head disclosed in the above-mentioned document is not applicable to all internal combustion engines. Generally, in order to increase the intake air amount, opening diameter of intake port should be larger. However, when the opening diameter of the intake port is increased, the interval between the intake ports becomes narrow. As a result, it becomes difficult to secure the flow rate of cooling water flowing between the intake ports. In order to merely secure the flow rate of the cooling water, the space of flow path of the cooling water may be secured by reducing wall thickness of the port wall. However, it becomes difficult to secure the strength enough to withstand the explosive stress, the thermal stress, and the like from a combustion chamber.
The present disclosure has been conceived in consideration of the above-mentioned problems, and an object of an example in the present disclosure is to provide a cylinder head that secures a flow path for flowing cooling water between a pair of intake ports communicating with a common combustion chamber while maintaining an opening diameter and strength of the pair of the intake ports.
In a cylinder head according to an example of the present disclosure, a pair of intake ports communicating with the common combustion chamber are formed so that the wall thickness of the port walls on opposing sides is relatively small and the wall thickness of the port walls on reversing sides is relatively large. The opposing side is the side on which the port walls of the pair of the intake ports face each other. The reversing side is the side opposite to the opposing side. That is, the reversing side is the side on which the port walls of the pair of the intake ports face away from each other. An inter-ports flow path for flowing the cooling water is formed between the port walls on the opposing sides of the pair of the intake ports. According to the cylinder head configured as described above, the cross-sectional area of the inter-ports flow path is increased while maintaining the opening diameter of the intake port by making the wall thickness of the port wall on the side facing each other relatively thin. In addition, the strength of the intake port can be maintained by relatively increasing the wall thickness of the port walls on the sides facing away from each other.
One intake passage may bifurcates in the cylinder head to form a pair of intake ports. It is preferred to flow the cooling water into the gap between the crotch of the intake passage branched into the pair of the intake ports and the combustion chamber. According to the cylinder head of the example in the present disclosure, it is possible to form the inter-ports flow path having a large cross-sectional area in the gap between the crotch of the intake path and the combustion chamber.
The wall thickness of the each port wall of the pair of the intake ports may gradually increase from the opposing side to the reversing side. According to this configuration, it is possible to prevent stress concentration.
When the injector insertion hole communicating with the combustion chamber is located between the pair of the intake ports and the cylinder block mating surface, the wall thickness of the hole wall of the injector insertion hole on the side facing the pair of the intake ports may be thinner than the wall thickness of the hole wall on the side facing away from the pair of the intake ports. A communication passage for introducing the cooling water into the inter-ports flow path may be formed between the pair of the intake ports and the injector insertion hole. According to this configuration, it is possible to secure a flow path for flowing the cooling water in the inter-ports flow path.
As described above, according to the cylinder head of the example in the present disclosure, it is possible to secure the flow path for flowing the cooling water between the intake ports while maintaining the opening diameters and strengths of the pair of the intake ports communicating with the common combustion chamber.
Embodiments in the present disclosure will be described with reference to the drawings. However, the following embodiments exemplify apparatuses and methods for embodying the technical idea of the present disclosure.
The first embodiment in the present disclosure will be described with reference to the drawings.
In the cylinder head 2, four combustion chambers 4 for four cylinders are formed in line at equal intervals in the longitudinal direction. In the cylinder head 2, a pair of intake ports 11 and 12 opened to the combustion chamber 4 and a pair of exhaust ports 13 and 14 opened to the combustion chamber 4 are provided for each combustion chamber 4. An ellipse drawn by a dotted line in
The cylinder head 2 is provided with a spark plug insertion hole 15 for each combustion chamber 4, which vertically penetrates the cylinder head 2 and opens at the center of the combustion chamber 4. The circle of the spark plug insertion hole 15 drawn by a dotted line in
The cylinder head 2 includes a water jacket 6 through which cooling water flows. The water jacket 6 is formed inside the cylinder head 2 by using a core when the cylinder head 2 is cast. The shape of the core is the same as that of the water jacket 6 shown in
The water jacket 6 is composed of a combustion-chamber-side water jacket 6a for cooling the top portion of the combustion chamber 4 and its periphery, and an exhaust-side water jacket 6b for cooling the periphery of the exhaust ports 13 and 14. The intake ports 11 and 12 are cooled by the combustion-chamber-side water jacket 6a.
The combustion-chamber-side water jacket 6a includes a plurality of cooling water flow paths 20, 21, 22, and 23 extending from the intake side to the exhaust side for flowing cooling water from the cooling water inlets 25 and 26 to the exhaust-side water jacket 6b through the sides of the intake ports 11 and 12. The cooling water flow paths 20, 21, 22, and 23 include a inter-chambers flow path 21 passing between adjacent combustion chambers 4 and 4, end flow paths 22 and 23 passing between the each end of the cylinder head 2 and the outer combustion chamber 4, and an inter-ports flow path 20 passing between the pair of the intake ports 11 and 12 communicating with the common combustion chamber 4. However, the inter-ports flow path 20 is connected to the cooling water inlets 25 and 26 by communication passages 27 and 28 formed between the intake ports 11 and 12 and the injector insertion hole 16. Arrow lines extending from the cooling water inlets 25 and 26 in
Next, the water jacket 6, in particular, the combustion-chamber-side water jacket 6a, will be described in detail.
The cooling water flowing through the inter-ports flow path 20 lowers the wall surface temperature around the combustion chamber 4 and the intake ports 11 and 12, so that the increase of the compression end gas temperature is suppressed. Since the flow rate of the cooling water depends on the cross-sectional area of the inter-ports flow path 20, by making the cross-sectional area as large as possible, the increase of the compression end gas temperature is effectively suppressed. However, the shape and position of each wall surface 61-67 constituting the inter-ports flow path 20 are constrained, and the cross-sectional area of the inter-ports flow path 20 is not easily enlarged. For example, the position of the wall surface 61 which determines the height of the inter-ports flow path 20 is determined by the position of the crotch of the intake passage 10. A port injection injector (not shown) is attached to the crotch portion of the intake passage 10. Therefore, it is difficult to change the position of the wall surface 61 and increase the height of the inter-ports flow path 20 due to the constraint caused by the positional relationship between the port injection injector and the intake ports 11 and 12.
In the present embodiment, the cross-sectional area of the inter-ports flow path 20 is enlarged by enlarging the distance between the wall surfaces 62 and 63 corresponding to the outer wall surfaces of the port walls of the intake ports 11 and 12 among the wall surfaces 61 to 67 constituting the inter-ports flow path 20. More specifically, the distance between the wall surfaces 62 and 63 is increased by reducing the wall thickness of the port walls of the intake ports 11 and 12, as described below.
In the comparative example shown in
If the width of the inter-ports flow path 20 is simply made wider, the diameter of the intake ports 11 and 12 may be made smaller, or the wall thickness of the port walls 110 and 120 may be made thinner. However, in the former method, a decrease in intake air amount causes a decrease in efficiency and output. In the latter method, it becomes difficult to secure the strength of the intake ports 11 and 12 enough to withstand the explosive stress, the thermal stress, and the like from a combustion chamber 4.
With respect to such a problem, in the present embodiment, as described above, the wall thickness of the port walls 111 and 121 on the opposing sides is reduced, while the wall thickness of the port walls 112 and 122 on the reversing sides is increased. That is, instead of reducing the wall thickness in the whole port walls 110 and 120, the wall thickness of the portion related to the width of the inter-ports flow path 20 is reduced, and the wall thickness of the other portion is increased by an amount corresponding to the thinning of the portion. In addition, in the present embodiment, the wall thickness of the port walls 110 and 120 is gradually increased from the port walls 111 and 121 on the opposing sides to the port walls 112 and 122 on the reversing sides. The stress concentration can be prevented by gradually changing the wall thickness in the circumferential direction without forming a step in the wall thickness of the port walls 110 and 120.
The thinning of the wall thickness of the port walls 111 and 121 on the opposing sides has an effect that the cross-sectional area of the inter-ports flow path 20 can be increased while maintaining the opening diameters of the intake ports 11 and 12. Increasing the wall thickness of the port walls 112 and 122 on the reversing sides has the effect of maintaining the strength of the intake ports 11 and 12. That is, according to the present embodiment, it is possible to secure a flow path for flowing the cooling water between the intake ports 11 and 12 while maintaining the opening diameters and strengths of the intake ports 11 and 12.
Second embodiment in the present disclosure will be described with reference to the drawings.
As described in the first embodiment, the inter-ports flow path 20 is connected to the cooling water inlets 25 and 26 by the communication passages 27 and 28 formed between the intake ports 11 and 12 and the injector insertion hole 16. Therefore, the flow rate of the cooling water flowing through the inter-ports flow path 20 depends on the ease of flow of the cooling water in the communication passages 27 and 28.
As described with reference to
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Number | Date | Country |
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2000-329001 | Nov 2000 | JP |
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Number | Date | Country | |
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20200132013 A1 | Apr 2020 | US |