JP2015178807A - Cylinder head of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide proper cooling performance according to the operation state of an engine, regarding the cylinder head of the engine.SOLUTION: In a cylinder head 1 of an engine having a plurality of cylinders 3, a cooling water passage is formed around an exhaust port 6 for discharging exhaust discharged from the cylinders 3, and cooling water inside the cooling water passage is circulated along a row direction L of the cylinders 3. Also, exhaust flow passages are made confluent into one at the downstream end of the exhaust port 6 to provide an exhaust confluence part 6C, and the exhaust confluence part is arranged at a position of being offset on the downstream side of the cooling water passage with respect to a center C of the engine in the row direction L of the cylinders 3.

Description

  The present invention relates to a cylinder head of an engine having a plurality of cylinders.

  2. Description of the Related Art Conventionally, a cylinder head and an exhaust manifold are integrally formed so that a plurality of exhaust ports connected to an engine combustion chamber merge in the cylinder head. Such a cylinder head is likely to be heated to exhaust heat as compared to a cylinder head provided separately. Thus, it has been proposed to improve cooling performance by circulating engine cooling water around the exhaust port. Specifically, it has been proposed to form a shape in which the peripheral surface of the exhaust port is surrounded by a water jacket, or to form the shape of the water jacket so that the flow of engine cooling water meanders (Patent Document 1,). 2).

Japanese Patent No. 4426343 Japanese Patent No. 4098712

However, the conventional cylinder head with a built-in manifold has a problem that it is difficult to set the cooling performance because the cooling performance required for the water jacket varies depending on the operating state of the engine.
One of the objects of the present invention has been developed in view of the above-described problems, and is to provide a cylinder head that can acquire an appropriate cooling performance according to the operating state of the engine. The present invention is not limited to this purpose, and is a function and effect derived from each configuration shown in the embodiments for carrying out the invention described later, and other effects of the present invention are to obtain a function and effect that cannot be obtained by conventional techniques. Can be positioned.

  (1) An engine cylinder head disclosed herein is a cylinder head of an engine having a plurality of cylinders, and is formed around an exhaust port for exhausting exhaust exhausted from the cylinder, and around the exhaust port. A cooling water passage provided so that the cooling water flows through the inside of the cylinder along the direction in which the cylinders are arranged. A plurality of exhaust passages are gathered together at the downstream end of the exhaust port, and the exhaust gathering portion is disposed at a position offset from the center of the engine to the downstream side of the cooling water passage in the row direction. Is provided.

(2) Preferably, the length of the exhaust passage from the rear cylinder of the engine to the exhaust collecting portion is shorter than the length of the exhaust passage from the front cylinder of the engine to the exhaust collecting portion.
In addition, it is preferable that the cooling water flows in the cooling water passage from the front side to the rear side of the engine. In this case, it is preferable that the exhaust collecting portion is disposed on the rear side with respect to the center of the engine.

  (3) The cooling water passage has a shape that merges after branching from the outer cooling water channel and an outer cooling water channel arranged along a manifold located on the outer surface side of the cylinder head, and It is preferable to have an inner cooling water channel disposed on the inner side of the cylinder head along the water channel.

  Appropriate cooling performance according to the operating state of the engine can be obtained.

It is a perspective view which illustrates the cylinder head of the engine concerning one embodiment. It is a typical longitudinal section of an engine. It is a horizontal sectional view showing the shape of the exhaust port in the cylinder head. (A) is a horizontal sectional view of the upper water jacket, (B) is a horizontal sectional view of the lower water jacket.

  An engine cylinder head applied to a vehicle will be described with reference to the drawings. Note that the embodiment described below is merely an example, and there is no intention to exclude various modifications and technical applications that are not explicitly described in the following embodiment. Each configuration of the present embodiment can be implemented with various modifications without departing from the spirit of the present embodiment, and can be selected or combined as necessary.

[1. Engine configuration]
The cylinder head 1 of this embodiment is attached to a cylinder block 2 of a water-cooled multi-cylinder engine 10. A plurality of cylinder bores 3 are arranged in a row inside the engine 10. The example shown in FIG. 1 is an engine 10 of three cylinders (# 1, # 2, # 3 in order from the front side) in which three cylinders 3 are arranged in series. Hereinafter, the arrangement direction of the cylinders 3 is represented by a symbol L.

  Around the cylinder 3, a water jacket 4 (cooling water passage) dug into a curved surface along the cylindrical surface 3B is formed. The water jacket 4 is continuously formed not only inside the cylinder block 2 but also inside the cylinder head 1, and cools the entire engine 10. The upper part of the water jacket 4 is opened at the upper surface of the cylinder block 2 and communicates with water jackets 4, 4A, 4B formed on the cylinder head 1 side. Thereby, the outer peripheral part of the exhaust port 6 is also cooled by the engine coolant.

  As shown in FIG. 2, a recess is formed on the lower surface of the cylinder head 1 as a ceiling surface 3A (ceiling surface of the combustion chamber), and an exhaust port 6 is connected to each combustion chamber. The exhaust port 6 is a multi-branch type exhaust passage that functions as an exhaust system manifold (multi-branch pipe). In the present embodiment, a turbocharger 35 and a catalyst device 36 are connected to the downstream side of the exhaust port 6 (see FIG. 1). The operating efficiency of these devices 35 and 36 is improved by raising the exhaust gas temperature after starting the engine 10 at an early stage.

[2. Exhaust port]
As shown in FIG. 3, the upstream end of the exhaust port 6 has a shape branched into six and is connected to each exhaust valve hole 12. On the other hand, the downstream end of the exhaust port 6 has a shape in which individual passages are integrated into one inside the cylinder head 1. The narrowest passage connected to the exhaust valve hole 12 (the branch pipe located at the most upstream side of the exhaust port 6) is referred to as a small passage 6A. The cross-sectional area S ₁ of one small passage 6A is set to be larger than the opening area of one exhaust valve hole 12. Further, the pair of small passages 6A connected to the same cylinder 3 merge at a position relatively close to the exhaust valve hole 12 to form an intermediate passage 6B (a branch pipe located at an intermediate portion of the exhaust port 6).

Sectional area S ₂ of the middle passage. 6B, the exhaust resistance is a so as not to two of the cross-sectional area 2S ₁ or more small passages 6A increases. Further, on the downstream side, an exhaust collecting portion 6C in which a plurality of middle passages 6B are gathered into one is provided. The order in which the middle passage 6B is merged is arbitrary. For example, after the middle passage 6B connected to the # 1 cylinder and the middle passage 6B connected to the # 2 cylinder are assembled (downstream from the junction) ) Merge the middle passage 6B connected to the # 3 cylinder.

  A crotch portion 16 is formed in a portion sandwiched between the middle passages 6B on the upstream side of the exhaust collecting portion 6C. In FIG. 3, the triangular portion sandwiched between the exhaust flow from the # 1 cylinder and the exhaust flow from the # 2 cylinder is the crotch portion 16A, and the exhaust flow from the # 2 cylinder and the exhaust flow from the # 3 cylinder The part sandwiched between the crotch parts 16B. These crotch portions 16A (between # 1 and # 2) and 16B (between # 2 and # 3) project substantially equally toward the outside of the cylinder head 1. A straight line connecting the tips of the crotch portions 16A and 16B in a top view is substantially parallel to the cylinder row direction L. Further, as indicated by a broken line in FIG. 3, the R portion (curved surface portion) of the front side wall of the outlet (exhaust port 18) of the exhaust collecting portion 6C is provided on the extended surface of the side wall surface of the # 2 cylinder of the crotch portion 16A. It is done. As a result, the flow of exhaust from the # 2 cylinder to the exhaust collecting portion 6C becomes smooth, and the flow path resistance decreases.

  Here, among the imaginary lines extending horizontally through the center of the # 2 cylinder, the line perpendicular to the cylinder row direction L is referred to as “the center line C of the engine 10”. As shown in FIG. 3, the exhaust collecting portion 6 </ b> C is disposed at a position offset from the center line C to the rear side of the engine 10. The offset direction of the exhaust collecting portion 6C with respect to the center line C is a direction toward the downstream side of the engine coolant. That is, the exhaust collecting portion 6 </ b> C is provided so as to be biased in the direction in which the temperature of the engine cooling water at the time of cold start of the engine 10 is high. Similarly, a single opening (hereinafter referred to as an exhaust port 18) serving as a downstream end of the exhaust collecting portion 6C is also provided at a position offset from the center line C to the rear side.

The length of the exhaust passage from each of the cylinders # 1 to # 3 to the exhaust collecting portion 6C is the longest on the front side of the engine 10 and shorter on the rear side. For example, as shown in FIG. 3, the passage length L ₁ from the # 1 cylinder to the outlet (exhaust port 18) of the exhaust collecting portion 6C, the passage length L ₂ from the # 2 cylinder to the outlet of the exhaust collecting portion 6C, # magnitude relation pathlength _{L 3} from three cylinders to the outlet of the exhaust collector 6C _is a _{L 1> L 2> L 3} . That is, the length of the exhaust passage is formed so as to be shortened at a portion where the engine coolant becomes high temperature.

[3. Water jacket]
As shown in FIGS. 4A and 4B, the cylinder head 1 is provided with two cooling water passages on the inner side and the outer side in a top view, and layers are formed on the upper side and the lower side of the exhaust port 6. Provided. Reference numeral 25 in FIG. 4B corresponds to a cooling water inlet to which cooling water is supplied from the water pump side, and reference numeral 26 corresponds to a cooling water outlet. Further, the thin broken line in the figure corresponds to the contour of the overhanging portion 14 of the cylinder head 1 and the exhaust port 6, and the two-dot chain line corresponds to the contour of the ceiling surface 3 </ b> A of the cylinder 3.

  The upper water jacket 4A is provided with an outer cooling water channel 23A and an inner cooling water channel 24A. These cooling water passages 23 </ b> A and 24 </ b> A both communicate with a water jacket 4 formed in the cylinder block 2. The overall shape of the outer cooling water passage 23 </ b> A and the inner cooling water passage 24 </ b> A is a semi-disc shape that is disposed substantially parallel to the upper surface 14 </ b> A of the overhanging portion 14 along the upper surface of the exhaust port 6.

  The outer cooling water passage 23A is arranged on the upper surface side along the exhaust passages of the # 1 cylinder and the # 3 cylinder. The arrangement shape of the outer cooling water passage 23 </ b> A is a semicircular arc when the engine 10 is viewed from above. As shown by a black arrow in FIG. 4A, the engine coolant flow direction is upstream on the front side (# 1 cylinder side) of the engine 10 and downstream on the rear side (# 3 cylinder side). .

  The inner cooling water passage 24A is a cooling water passage arranged on the inner side of the outer cooling water passage 23A, and is arranged on the upper surface side mainly along the exhaust port 6 through which the exhaust from the # 2 cylinder flows. The arrangement shape of the inner cooling water passage 24A is a semicircular arc shape smaller than the outer cooling water passage 23A in a top view of the engine 10, and the downstream side is a common flow passage with the outer cooling water passage 23A. As shown in FIG. 4A, the inner cooling water passage 24A branches from the outer cooling water passage 23A in the vicinity of the # 1 cylinder, and then joins the outer cooling water passage 23A above the middle passage 6B connected to the # 3 cylinder. To do. The engine coolant flow direction is upstream on the # 2 cylinder side and downstream on the # 3 cylinder side.

  Between the outer cooling water passage 23A and the inner cooling water passage 24A, an island portion 29A through which engine cooling water does not flow and a connection cooling water passage 28A that connects them are provided. The connection cooling water channel 28A is arranged at a position adjacent to the crotch portion 16 where the branch pipes of the exhaust port 6 join in the vertical direction.

  The lower water jacket 4B is also provided with an outer cooling water channel 23B and an inner cooling water channel 24B. The outer cooling water passage 23B is a cooling water passage located on the outer surface side of the overhanging portion 14, and is disposed on the lower surface side along the exhaust passages of the # 1 cylinder and the # 3 cylinder. The arrangement shape of the outer cooling water passage 23B is a semicircular arc shape when the engine 10 is viewed from above, similarly to the outer cooling water passage 23A. Thus, the exhaust port 6 is sandwiched from above and below by the pair of outer cooling water channels 23A and 23B. The flow direction of the engine cooling water is upstream on the front side (# 1 cylinder side) of the engine 10 and downstream on the rear side (# 3 cylinder side).

  Inside the outer cooling water passage 23B, an inner cooling water passage 24B is disposed along the exhaust port 6 through which the exhaust from the # 2 cylinder flows. Similar to the inner cooling water channel 24A, the inner cooling water channel 24B is arranged in a semicircular shape smaller than the outer cooling water channel 23A in the top view of the engine 10, and the downstream side is a common channel with the outer cooling water channel 23B. . As a result, the exhaust port 6 is sandwiched from above and below by the pair of inner cooling water channels 24A and 24B. The engine coolant flow direction is upstream on the # 2 cylinder side and downstream on the # 3 cylinder side.

Between the outer cooling water passage 23B and the inner cooling water passage 24B, there are provided an island portion 29B through which engine cooling water does not flow and a connection cooling water passage 28B that connects both of them. The connection cooling water channel 28B is disposed adjacent to the crotch portion 16 where the branch pipe of the exhaust port 6 joins in the vertical direction.
A thermostat that opens and closes a passage connected to a radiator (not shown) according to the temperature of the engine coolant is provided at an inlet portion where the coolant flows into the engine 10. When the engine 10 is started in a cold state, the engine coolant is returned to the coolant inlet 25 of the engine 10 without passing through the radiator. On the other hand, in the warm state, the thermostat is opened, and the engine coolant passes through the radiator and is returned to the coolant inlet 25 of the engine 10 in a cooled state.

[4. Action, effect]
(1) While the engine 10 is warming up, a thermostat (not shown) is closed, and the engine coolant does not pass through the radiator. Therefore, the temperature of the engine cooling water flowing through the cylinder head 1 circulates while raising the temperature under the influence of heat generated in the cylinder 3 and the exhaust port 6 of the engine 10. The cooling water temperature of the engine cooling water in the cylinder head 1 becomes the highest after absorbing the heat generated in the cylinder 3 and the exhaust port 6, is returned to the cooling water inlet 25, and the heat of the cylinder 3 and the exhaust port 6 is again increased. Absorbed and fed to the cooling water outlet 26. When the engine 10 is cold-started, the temperature of the engine coolant in the cylinder head 1 rises on the coolant outlet 26 side, and the isothermal line increases from the downstream side to the upstream side as time elapses after the engine 10 is started. Move towards the side.

  In consideration of such temperature characteristics of the engine cooling water, in the cylinder head 1 described above, the position of the exhaust collecting portion 6C in the cylinder row direction L is offset to the downstream side of the engine cooling water from the center line C. Is set. As a result, exhaust can be collected in the cylinder head 1 at a position where the coolant temperature is relatively high, and the exhaust heat exhausted from the engine 10 through the exhaust port 6 is not lost to the cylinder head 1. Discharged. Therefore, a decrease in the exhaust temperature of the exhaust collecting portion 6C during the warm-up of the engine 10 can be suppressed, and an appropriate cooling performance corresponding to the operating state of the engine 10 can be obtained.

  In addition, for example, during the warm-up of the engine 10, the catalyst device 36 disposed on the exhaust downstream side of the exhaust collecting portion 6C can be activated quickly, and the exhaust purification performance of the catalyst device 36 can be improved. Can do. Or the reduction | decrease of the volume of the exhaust gas which flows into the turbocharger 35 on an exhaust passage can be suppressed, and the supercharging efficiency by the turbocharger 35 can be improved.

(2) In the cylinder head 1 described above, the exhaust port 6 is set so that the distances L ₁ , L ₂ , L ₃ from the cylinders # 1 to # 3 to the exhaust collecting portion 6C satisfy L ₁ > L ₂ > L _3. Is formed. That is, the distance of the portion where heat is exchanged between the exhaust and the cooling water (in other words, the area of the portion where heat is transferred) is large on the # 1 cylinder side and small on the # 3 cylinder side. On the other hand, since the cooling water in the water jacket 4 flows from the # 1 cylinder side to the # 3 cylinder side, the cooling water temperature at the cold start is slightly lower on the # 1 cylinder side and slightly higher on the # 3 cylinder side. Become. By disposing the exhaust collecting portion 6C on the side where the cooling water temperature becomes high, the temperature rise of the cooling water at the time of cold start can be promoted, and the warm-up time of the engine 10 can be shortened.

  (3) In the cylinder head 1 described above, the water jacket 4 is arranged in a planar shape along the exhaust port 6 and the exhaust collecting portion 6C. Further, the exhaust port 6 and the exhaust collecting portion 6C are sandwiched between the upper and lower water jackets 4A and 4B as shown in FIG. Thereby, the area of the part in which heat exchange is performed between the exhaust gas and the cooling water can be increased, and the warming effect of the cooling water at the time of cold start and the cooling effect at the time of warm can be enhanced.

(4) In the above cylinder head 1, as shown in FIG. 3, the flow passage area of the middle passage 6B is a two small passages 6A sectional area 2S ₁ or more, the extension of the # 2 side wall surface of the crotch portion 16A The R portion of the front side wall of the outlet (exhaust port 18) of the exhaust collecting portion 6C is provided on the surface. With such a structure, it is possible to maximize the area where the water jacket 4 and the exhaust collecting portion 6C overlap while rectifying the exhaust discharged from each cylinder. Therefore, the engine 10 can be appropriately cooled at the time of warm operation while the cooling water temperature is efficiently increased at the time of cold start.

  (5) The outer cooling water passages 23A and 23B are arranged in a semicircular arc when viewed from the top of the engine 10 along the exhaust passage connected to the # 1 cylinder and the # 3 cylinder. On the other hand, the inner cooling water passages 24A and 24B are arranged in a semicircular arc shape inside the outer cooling water passages 23A and 23B along the exhaust passage connected to the # 2 cylinder. With such a cooling water channel layout, it is possible to save the space of the water jacket 4 while increasing the cooling efficiency of the entire exhaust port 6. In addition, by providing two internal and external cooling water channels, each channel cross-sectional area can be reduced while securing a total channel cross-sectional area, and the flow rate of the cooling water can be increased. Thereby, the cooling efficiency around the exhaust port 6 built in the cylinder head 1 can be improved.

Further, the flow rate of the engine cooling water in each of the cooling water passages 23 and 24 is determined according to the cross-sectional area and the shape of each flow passage. From this, it is possible to individually set the flow velocity and flow rate in each of the cooling flow paths 23 and 24 of the two systems in consideration of the heat dissipation from the overhanging portion 14 and improve the cooling efficiency of the cylinder head 1. Can be made.
Moreover, since the heat dissipation to the outside of the cylinder head 1 is different between the outer surface side and the inner side of the cylinder head 1, the cooling capacity required for the water jacket 4 is also slightly different. On the other hand, in the cylinder head 1 described above, the water jacket 4 is provided separately for each of the outer surface side and the inner side of the cylinder head 1. Thereby, the cooling capacity suitable for each cooling water channel can be given, and the cooling performance of the engine 10 and its controllability can be improved.

  The cylinder head 1 can be applied to a multi-cylinder engine other than the in-line three-cylinder engine (for example, an in-line four-cylinder engine or a V-type six-cylinder engine). Alternatively, an engine in which one cylinder 3 is provided with one intake valve hole and one exhaust valve hole 12 may be used.

2 Cylinder block 4 Water jacket (cooling water passage)
6 Exhaust port 6C Exhaust collecting part C Center line

Claims (3)

A cylinder head of an engine having a plurality of cylinders,
An exhaust port for exhausting exhaust from the cylinder;
A cooling water passage formed around the exhaust port and provided so that cooling water flows along the direction in which the cylinders are arranged;
A plurality of exhaust passages gathered together at the downstream end of the exhaust port, and an exhaust gathering portion disposed at a position offset from the center of the engine to the downstream side of the cooling water passage in the row direction;
An engine cylinder head, comprising: The length of the exhaust passage from the rear cylinder of the engine to the exhaust collecting portion is shorter than the length of the exhaust passage from the front cylinder of the engine to the exhaust collecting portion. The cylinder head of the engine according to 1. The cooling water passage has an outer cooling water passage disposed along a manifold located on the outer surface side of the cylinder head, and a shape that merges after branching from the outer cooling water passage, along the outer cooling water passage. The engine cylinder head according to claim 1, further comprising an inner cooling water passage disposed on an inner side of the cylinder head.

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