JP6209815B2 - Cylinder head cooling structure - Google Patents

Description

  The present invention relates to a cooling structure for a cylinder head of an internal combustion engine.

  As a cooling structure of the cylinder head, in the one described in Patent Document 1, a water jacket through which cooling water flows, a lower water jacket, and an upper water jacket disposed above the lower water jacket, The upper and lower two-layer structure is formed, and a communication hole that communicates the two is formed through the partition wall that partitions the two.

JP 2003-184644 A

  If the flow of the cooling water between the upper water jacket and the lower water jacket stagnate, the temperature difference between the two becomes large, which may reduce the cooling efficiency. Specifically, since the temperature of the lower water jacket close to the combustion chamber tends to be higher than the temperature of the upper water jacket, if the temperature difference between the two increases, the cooling performance around the combustion chamber may decrease. is there.

  Therefore, the present invention promotes cooling water flow (convection) from the lower water jacket to the upper water jacket through the communication hole, and reduces the temperature difference between the upper water jacket and the lower water jacket, thereby improving the cooling performance. It is an object of the present invention to provide a novel cylinder head cooling structure that can be improved.

  In the cylinder head cooling structure according to the present invention, a water jacket through which cooling water flows has a lower water jacket and an upper and lower two-layer structure having an upper water jacket formed above the lower water jacket. I am doing. Moreover, it has a partition wall part which partitions an upper water jacket and a lower water jacket up and down, and the communicating hole which connects an upper water jacket and a lower water jacket is penetrated and formed in this partition wall part. A pair of inclined wall portions that are inclined obliquely upward toward the communication hole are formed on both sides of the communication hole in the partition wall portion so as to promote convection of the cooling water.

  During engine operation, the coolant temperature in the lower water jacket close to the combustion chamber of the lower water jacket and the upper water jacket tends to rise, and due to the temperature difference between them, the upper water jacket passes through the communication hole. A flow of cooling water toward the water jacket, that is, convection occurs.

  Here, in the present invention, by providing the partition wall portion with the inclined wall portion inclined obliquely upward toward the communication hole, the flow of the cooling water from the lower water jacket toward the communication hole along the inclined wall portion. Is promoted. That is, the inclined wall portion functions as a guide wall portion that guides the cooling water in the lower water jacket to the communication hole, and the convection is promoted.

  As described above, according to the present invention, the flow of cooling water from the lower water jacket to the upper water jacket through the communication hole is promoted, the temperature difference between the lower water jacket and the upper water jacket is reduced, and heat exchange performance is achieved. Can be improved.

Sectional drawing which follows the EE line of FIG. 2 which shows the cylinder head to which the cooling structure which concerns on one Example of this invention was applied. The top view which shows the said cylinder head. Sectional drawing which follows the AA line of FIG. 2 which shows the said cylinder head. Sectional drawing which follows the BB line of FIG. 2 which shows the said cylinder head. The side view which shows the said cylinder head. The side view which follows the CC line of FIG. 5 which shows the said cylinder head. The side view which follows the DD line | wire of FIG. 5 which shows the said cylinder head.

  Hereinafter, the present invention will be described with reference to illustrated embodiments. The cylinder head 10 is integrally cast of a metal material such as an aluminum alloy or cast iron, has a substantially box shape that opens upward, and is substantially long in the cylinder row direction and the crankshaft direction L1. It has a rectangular parallelepiped shape. The cylinder head 10 has a head cover (not shown) fixed to the mounting flange portion 11 at the upper peripheral edge and is fixed to a cylinder block (not shown) at the lower peripheral edge.

  As shown also in FIGS. 3 and 4, combustion chambers 13 of a plurality of (three in this example) cylinders are provided on the lower surface side of the lower wall portion 12 of the cylinder head 10 fixed to the upper surface of the cylinder block. They are arranged along the direction L1. Each combustion chamber 13 has a pent roof type recessed upward. Each combustion chamber 13 communicates with a pair of intake ports 14 and a pair of exhaust ports 15. As shown in FIGS. 5 and 6, with respect to the intake ports 14, a pair of intake ports 14 of the respective cylinders are joined in the middle and opened to the intake side wall, that is, a total of three intake ports on the intake side wall. The port 14 is open. On the other hand, with respect to the exhaust port 15, all the exhaust ports 15 merge in the middle and open to the side wall on the exhaust side. That is, only one exhaust port 15 is opened on the side wall on the exhaust side. The port shape is not limited to the structure of this embodiment, and for example, the exhaust port and the intake port may have the same structure.

  The cylinder head 10 is provided with a plug hole 16 for attaching a spark plug for each cylinder. The plug hole 16 has a cylindrical shape whose lower end is opened near the top of the combustion chamber 13 so as to support the spark plug in a posture facing the top of the combustion chamber 13. In addition, as shown in FIG. 2, a partition wall portion 17 extending in the head width direction L <b> 3 across each plug hole 16 is provided. A halved bearing surface 18 for rotatably supporting two camshafts that drive the intake valve and the exhaust valve is formed on the upper surface of each partition wall portion 17.

  The cylinder head 10 is formed with a water jacket 20 that is a space through which cooling water flows. The water jacket 20 has a structure divided into two layers with respect to the cylinder axial direction L2 along the vertical direction and the vertical direction of the in-vehicle mounting posture, that is, the lower water jacket 21 and the lower water jacket 21 than the lower water jacket 21. An upper and lower two-layer structure having an upper water jacket 22 positioned above is formed.

  The lower water jacket 21 and the upper water jacket 22 are partitioned by a partition wall portion 23 having a predetermined thickness. The lower water jacket 21 is formed between the lower wall portion 12 constituting the lower surface of the cylinder head 10 and the partition wall portion 23 with respect to the cylinder axial direction L2. The upper water jacket 22 is formed between the partition wall portion 23 and the upper wall portion 24 disposed above the partition wall portion 23. An intake valve, an exhaust valve, and the like are disposed in a space above the upper wall portion 24.

  A communication hole 25 that allows the upper water jacket 22 and the lower water jacket 21 to communicate with each other is formed through the partition wall portion 23. Note that a through hole 26 is formed in the upper wall portion 24 so as to be coaxial with the communication hole 25 during casting so that the communication hole 25 is integrally formed during casting. Since this through hole 26 is unnecessary after casting, it is closed by a cap 27. As shown in FIG. 4, the communication holes 25 are provided between the combustion chambers 13 of adjacent cylinders, that is, a total of two central portions between the cylinders in the crankshaft direction L1.

  As shown in FIG. 1, each communication hole 25 is formed at the center of the cylinder head 10 with respect to the head width direction L3 orthogonal to both the crankshaft direction L1 and the cylinder shaft direction L2. The partition wall 23 is formed with a pair of inclined wall portions 28 that are inclined obliquely upward toward the central portion where the communication hole 25 is formed on both sides of the communication hole 25 in the head width direction L3. That is, the inclined wall portion 28 is formed in a shape protruding upward in the head width direction L3 with the central portion where the communication hole 25 is formed as a top portion. The inclined wall portion 28 is inclined so that the center (communication hole 25) becomes higher with respect to the horizontal direction even in the vehicle-mounted state, and the inclination angle is set to 15 degrees or more.

  As shown in FIG. 3, auxiliary communication for communicating the upper water jacket 22 and the lower water jacket 21 is provided at both ends in the crankshaft direction L1 of the partition wall portion 23 in which the communication hole 25 is not provided. A hole 29 is formed through.

  In a normal engine operation state, cooling water circulated through the lower cylinder block by the electric oil pump 2 (see FIG. 1) driven and controlled by the control unit 1 is formed through the lower wall portion 12 of the cylinder head 10. The water is introduced into the water jacket 20 of the cylinder head 10 through the cooling water inlet 30, more specifically, into the lower water jacket 21, and circulates in the water jacket 20. As described above, the cooling water inlet 30 is formed in the lower water jacket 21 of the lower water jacket 21 and the upper water jacket 22 in the upper and lower two-layer structure, and the cooling water is introduced into the lower water jacket 21. Therefore, the cooling water is actively circulated to the lower water jacket 21 side to effectively cool the vicinity of the combustion chamber 13 that is likely to become high temperature.

  On the other hand, in the cold state in which the warm-up operation is performed, such as immediately after the engine is started, the electric water pump 2 is stopped despite the internal combustion engine being operated, and the cooling water in the water jacket 20 is increased. By promoting the temperature, the temperature rise of the engine oil flowing in the oil passage disposed in the vicinity of the water jacket 20 is promoted, and consequently the warm-up of the internal combustion engine is promoted, and the warm-up operation is completed in a short period of time. Because of that.

  When the electric water pump 2 is stopped during the operation of the engine as described above, the temperature difference between the lower water jacket 21 on the high temperature side and the upper water jacket 22 on the low temperature side is indicated by the arrows in FIGS. Thus, a flow of cooling water from the lower water jacket 21 having a high temperature toward the upper water jacket 22 having a low temperature, that is, convection occurs. Thus, the cooling water flowing into the upper water jacket 22 through the communication hole 25 is returned to the crankshaft direction of the lower water jacket 21 through the auxiliary communication holes 29 provided at both ends in the crankshaft direction L1. In this way, a series of cooling water flows (convection) circulating through the lower water jacket 21 and the upper water jacket 22 are generated despite the water pump 2 being stopped.

  In this embodiment, since the partition wall portion 23 is provided with the inclined wall portion 28 that is inclined upward toward the central communication hole 25, the inside of the lower water jacket 21 is formed along the inclined wall portion 28. The cooling water easily flows into the upper water jacket 22 through the communication hole 25. That is, the inclined wall portion 28 leads the cooling water in the lower water jacket 21 to the communication hole 25, and the convection is promoted.

  By promoting convection in this way, heat exchange between the aluminum alloy cylinder head 10 and the cooling water is promoted, and the temperature difference between the lower water jacket 21 and the upper water jacket 22 is suppressed, An excessive temperature rise of the lower water jacket 21 is suppressed. Here, when the temperature of the lower water jacket 21 is excessively increased, the warm-up promotion operation by stopping the water pump 2 is canceled and the water pump 2 is restarted so as to avoid overheating and excessive temperature increase of the component temperature. However, in this embodiment, by providing the inclined wall portion 28 to promote the convection, an excessive temperature rise of the lower water jacket 21 can be suppressed.

  Further, even in the normal engine operating state after the warm-up described above, the inclined wall portion 28 promotes the flow of the cooling water from the lower water jacket 21 to the upper water jacket 22 through the communication hole 25, so that the lower side The temperature difference between the water jacket 21 and the upper water jacket 22 can be reduced, and the heat exchange performance can be improved.

  As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes. For example, the present invention can be similarly applied to a cylinder head of another type of internal combustion engine such as an in-line four-cylinder internal combustion engine.

DESCRIPTION OF SYMBOLS 2 ... Water pump 10 ... Cylinder head 20 ... Water jacket 21 ... Lower water jacket 22 ... Upper water jacket 23 ... Partition wall part 25 ... Communication hole 28 ... Inclined wall part 29 ... Auxiliary communication hole

Claims (6)

The water jacket through which the cooling water flows has an upper and lower two-layer structure having a lower water jacket and an upper water jacket formed above the lower water jacket,
Having a partition wall portion for vertically dividing the upper water jacket and the lower water jacket,
In this partition wall portion, a communication hole that allows communication between the upper water jacket and the lower water jacket is formed through,
And, on both sides of the communication hole in the partition wall portion, a pair of inclined obliquely upward toward the communication hole so as to facilitate convection of the cooling water flowing from the lower water jacket into the upper water jacket through the communicating hole An inclined wall is formed ,
The communication hole is formed at the center in the head width direction,
The cooling structure for a cylinder head, wherein the inclined wall portion is formed in a shape protruding upward in the head width direction with a central portion where the communication hole is formed as a top portion .   2. The cylinder head according to claim 1, wherein the inclined wall portion is inclined obliquely upward toward the communication hole with respect to a head width direction orthogonal to both the crankshaft direction and the cylinder axis direction. Cooling structure.   The cylinder head cooling structure according to claim 1 or 2, wherein the communication hole is disposed between combustion chambers of two cylinders adjacent to each other in the crankshaft direction.   4. The cylinder head according to claim 3, wherein an auxiliary communication hole that communicates the upper water jacket and the lower water jacket is formed through the partition wall at both ends in the crankshaft direction. Cooling structure.   The cylinder according to any one of claims 1 to 4, wherein a cooling water inlet for introducing cooling water is formed in the lower water jacket among the upper water jacket and the lower water jacket. Head cooling structure.   6. The cooling structure for a cylinder head according to claim 1, wherein when the engine is cold, the electric water pump is stopped so as to promote warm-up of the internal combustion engine.

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