JP7319104B2 - Cylinder head of multi-cylinder internal combustion engine - Google Patents

Description

The present invention relates to a cylinder head for a multi-cylinder internal combustion engine.

A multi-cylinder internal combustion engine comprises a cylinder block in which a plurality of cylinders are arranged in the direction of the crankshaft axis, a cylinder head fixed on the upper surface thereof with head bolts, a head cover fixed on the upper surface of the cylinder head, the cylinder block and and a front cover (chain case) that is overlapped and fixed to the front surface of the cylinder head.

Since the cylinder head receives the most heat during operation, the cylinder head tends to thermally expand the most, resulting in problems caused by the difference in the amount of thermal expansion between the cylinder head and the cylinder block. .

For example, there is a problem that a bending force acts on the front cover because the cylinder head thermally expands more than the cylinder block in the direction of the crank axis. It is disclosed that the difference in thermal expansion between the cylinder block and the cylinder head is absorbed by interposing a liquid gasket between the cylinder block and the cylinder head.

JP-A-8-151955

As described above, the cylinder head thermally expands more than the cylinder block, but the lower portion of the cylinder head receives more heat than the upper portion. It is easy for the phenomenon to warp. Also, when looking at the exhaust side and the intake side, there is a phenomenon that the exhaust side undergoes a large amount of thermal expansion. Therefore, the cylinder head tends to warp and deform so that the front and rear corners on the exhaust side are the highest away from the cylinder block. present.

Therefore, in addition to metal gaskets, liquid gaskets are also provided on the mating surfaces of the cylinder block and cylinder head to ensure a good seal even if the cylinder head warps and deforms. When high-load driving such as high-speed driving or climbing a hill is performed, the lower part of the cylinder head near the cylinder block is rapidly heated, causing the cylinder head to warp significantly. However, there have been cases where the sealing performance cannot be ensured.

An object of the present invention is to improve such a situation.

The claimed invention is
" Equipped with multiple exhaust ports corresponding to multiple cylinders, an exhaust side upper cooling water jacket covering the exhaust ports from above, and a group of head bolts for fixing to the upper surface of the cylinder block,
A cylinder head of a multi -cylinder internal combustion engine, wherein one or more exhaust outlets communicating with the exhaust ports are opened on an exhaust side surface, and the exhaust outlets are connected to an exhaust passage,
A heating passage, which promotes thermal expansion of a portion above the exhaust port in the direction of the crankshaft axis by the heat of the exhaust gas, extends from the middle portion of the exhaust port to above the exhaust-side upper cooling water jacket. The end of the heating passage and the exhaust passage are connected by a bypass passage provided with a switching valve.”
It is configured.

In the present invention, the upper surface of the cylinder block means the surface of the cylinder block located on the opposite side of the crankshaft. , in the case of an internal combustion engine with a large slant, it may not always be vertically upward. The same applies to the portion above the exhaust port.

In the present invention, the portion to be heated (heated portion) may be one, or may be a plurality of portions separated in the axial direction of the crankshaft. Furthermore, the heated portion may extend in the axial direction of the crankshaft.

Furthermore, the warping phenomenon of the cylinder head appears conspicuously in a high-load operation state during warm-up operation, and the warpage phenomenon decreases when the cylinder head is warmed up as a whole. It is also possible to switch the exhaust gas flow by means of a valve so that the exhaust gas flows only in the operating state.

In the present invention, the heated portion of the cylinder head above the exhaust port is heated by the exhaust gas passing through the heating passage , thereby suppressing the difference in thermal expansion between the lower portion and the upper portion of the cylinder head. Therefore, it is possible to prevent or greatly suppress the warp deformation of the cylinder head. As a result, it is possible to prevent problems such as leakage of exhaust gas or seepage of oil due to excessive gaps between the cylinder head and the cylinder block.

In addition, since exhaust gas is used as a heat source, there is no problem of reduced fuel consumption, which occurs in the case of heating with an electric heater, for example. Rather, since the heated portion of the cylinder head is positioned near the valve gear chamber, the temperature of the oil is accelerated by the heating means, which contributes to the improvement of fuel efficiency through the reduction of mechanical loss. Further, in the present invention, since the high-temperature exhaust gas is used for heating, the responsiveness of the heating of the upper part of the cylinder head is also excellent, so that the warp deformation suppressing effect can be ensured.

FIG. 2 is a schematic side view of the first embodiment viewed from a direction perpendicular to the exhaust side surface; FIG. 2 is a longitudinal sectional view taken along the line II-II of FIG. 1; (A) is a longitudinal sectional view of a first reference example , and (B) is a side view of a second reference example .

Next, embodiments of the present invention will be described based on the drawings. In the following, the terms front-rear and left-right are used to specify the direction, but the front-rear direction is the direction of the crankshaft, with the side on which the timing chain is arranged as the front, and the side where the transmission is arranged as the rear. . Just to make sure, the directions are clearly shown in FIG.

The left-right direction is a direction perpendicular to the crank axis and the cylinder axis. The vertical direction is the direction of the cylinder axis and does not necessarily coincide with the vertical direction. However, although the internal combustion engine of this embodiment is slanted at a slight angle so that the exhaust side is tilted forward, it is basically of a vertical type.

(1).Basic structure of the embodiment
This embodiment is applied to a three-cylinder internal combustion engine for automobiles. Therefore, as shown in FIG. 1, the internal combustion engine comprises a cylinder block 1 in which three cylinders 2 are formed, a cylinder head 3 fixed to the upper surface of the cylinder block 1, and a cylinder straddling the front surfaces of the cylinder block 1 and the cylinder head 3. and a head cover 5 fixed to the upper surfaces of the cylinder head 3 and the front cover 4 in an overlapping manner.

A roof-shaped combustion chamber 6 is formed on the lower surface of the cylinder head 3 in correspondence with each cylinder 2. Each combustion chamber 6 includes a group of intake ports (not shown) opened on the intake side surface and an exhaust port. A group of exhaust ports 8 (see FIG. 2) in pairs open to the side 7 are open. The exhaust port 8 communicates with an exhaust collective passage 9 formed inside the cylinder head 3, and one exhaust outlet 10 communicating with the exhaust collective passage 9 opens in the exhaust side surface 7 of the cylinder head 3. there is

The exhaust outlet 10 opens into a mounting seat 11 formed on the exhaust side surface 7 of the cylinder head 3, and an elbow-shaped exhaust joint pipe 12 forming an exhaust passage is fixed to the mounting seat 11 by flange joining. A catalyst case (not shown) is connected to the exhaust joint pipe 12 .

It is also possible to fix an exhaust turbocharger to the mounting seat 11 . When the exhaust turbocharger is fixed, the catalyst case is connected to the outlet of the exhaust turbocharger. If it is positioned in the front-rear intermediate portion, the catalyst case will protrude behind the cylinder block 1 .

Therefore, in this embodiment, the exhaust outlet 10 is shifted forward so that the catalyst case does not protrude behind the cylinder block 1 even when an exhaust turbocharger is installed. there is

As shown in FIG. 2, inside the cylinder head 3, two-layer exhaust-side cooling water jackets 13 and 14 are arranged as cooling means so as to sandwich the exhaust port 8 and the exhaust collecting passage 9 from above and below; Intake-side cooling water jackets 15 located above and below (or the other of) groups of intake ports are formed. In FIG. 2, reference numeral 16 denotes a center cooling water jacket, reference numeral 17 denotes a cam shaft bearing portion, and reference numeral 18 denotes an exhaust valve arrangement passage.

(2). Heating Means In this embodiment, a heating passage 19 extending upward from one exhaust port 8 is formed in the vicinity of the exhaust outlet 10 as a heating means . The heating passage 19 extends upward from the middle of the exhaust port 8 to reach above the exhaust-side upper cooling water jacket 13 and opens to the exhaust side surface 7 at a position slightly below the longitudinal side wall 20 of the cylinder head 3 . . Therefore, the cylinder head 3 is heated at the front-rear middle portion above the exhaust port 8 and the exhaust-side upper cooling water jacket 13 .

The outlet of the heating passage 19 and the exhaust joint pipe 12 are connected by a bypass pipe 21, and the bypass pipe 21 is provided with an electromagnetic switching valve 22 or the like. The switching valve 22 is controlled by an ECU (engine control unit). Since the exhaust joint pipe 12 is positioned upstream of the catalyst case, the exhaust gas that has passed through the heating passage 19 is returned to a portion of the exhaust passage upstream of the catalyst case. Although the heating passage 19 of the embodiment is formed by casting, it can also be formed by drilling.

Now, since the lower part of the cylinder head 3 is strongly heated by the exhaust gas, the difference in the amount of thermal expansion caused by the temperature difference between the upper part and the lower part causes a A phenomenon occurs in which the lower surface warps upward. In particular, when a high-load operation such as climbing a hill is performed during warm-up, the temperature difference between the upper portion and the lower portion of the cylinder head 3 increases, and warping deformation becomes conspicuous. As a result, even a liquid gasket may not be able to follow, resulting in a poor sealing state.

Therefore, in this embodiment, during warm-up operation, the switching valve 22 is opened to allow part of the exhaust gas to flow into the heating passage 19, thereby heating the portion above the exhaust port 8. FIG. Then, the amount of thermal expansion of the portion of the cylinder head 3 above the exhaust port 8 increases, thereby reducing the difference in the amount of thermal expansion in the direction of the crankshaft axis between the upper portion and the lower portion of the cylinder head 3, thereby preventing warp deformation. can be reduced. As a result, the gap between the cylinder head 3 and the cylinder block 1 can be maintained within a range that can be sealed by the liquid gasket, thereby ensuring high sealing performance.

In this embodiment, the heating passage 19 is provided at only one location, but it is also possible to provide it at a plurality of locations separated in the crankshaft direction, such as providing at three locations corresponding to each cylinder. , the difference in the amount of thermal expansion between the upper portion and the lower portion of the cylinder head 3 can be further reduced. When the heating passages 19 are formed at a plurality of locations, the bypass pipes 21 may be combined into one and connected to the exhaust joint pipe 12, and the switching valve 22 may be provided at the combined portion.

Furthermore, as another mode, it is possible to form the heating passage 19 in a state of being elongated in the direction of the crank axis. The effect is even better. Also, the heating passage 19 can be provided at a plurality of locations with different heights.

The switching valve 22 may be interlocked with a load sensor so that it opens during warm-up when the cooling water temperature is lower than a set value and when a load greater than a preset value is applied. , may be set to open simultaneously with operation.

(3) .Reference example
In the first reference example shown in FIG. 3A, a heat pipe 23 in which a heat exchange medium is enclosed is used as a heating means. That is, the heat pipe 23 is configured so that the heat exchange medium can circulate inside between one end 23a and the other end 23b, and the one end 23a is connected to the exhaust joint pipe 12 via the holder 24. , the other end 23b is connected to the upper portion of the cylinder head 3 (for example, the longitudinal side wall 20).

Since the temperature of the upper part of the cylinder head 3 does not rise, the heat exchange medium receives heat from the exhaust joint pipe 12 and moves toward the cylinder head 3. , the heat is radiated to the cylinder head 3 at the other end 23b and returned to the one end 23a. can be made smaller.

As in the reference example , if a cylindrical holder 24 is used as a means for connecting the exhaust joint pipe 12 and the heat pipe 23, the amount of heat transfer from the exhaust joint pipe 12 to the heat pipe 23 can be increased, which is suitable. 3A, the heat transfer amount from the exhaust joint pipe 12 to the heat pipe 23 is also increased by projecting one end portion 23a of the heat pipe 23 into the exhaust joint pipe 12. can.

When the temperature difference between the one end 23a and the other end 23b of the heat pipe 23 decreases, the circulation speed of the medium decreases, and when the temperature difference disappears, the medium stops circulating. Therefore, heating of the cylinder head 3 can be automatically stopped or suppressed without providing the switching valve 22 .

FIG. 3B shows a second reference example which is a modification of the first reference example . In this example, one heat pipe 23 connected to the exhaust joint pipe 12 is branched into three. , are connected to the cylinder head 3 at three locations. When heating a plurality of locations of the cylinder head 3 with the heat pipes 23, the heat pipes 23 may be used individually instead of the branching method.

Although the embodiments of the present invention have been described above, the present invention can be embodied in various other ways. For example, the present invention can also be applied to a type in which an exhaust outlet is opened corresponding to each cylinder on the side of the exhaust, and the exhaust gas is collected in the exhaust manifold. In this case, the bypass pipe may be connected to the exhaust manifold or to the upper portion of the catalyst case.
If the exhaust turbocharger is connected to the exhaust side, the bypass pipe or heat pipe may be connected to the turbine housing that constitutes the exhaust turbocharger.

The present invention can be embodied in a cylinder head. Therefore, it can be used industrially.

1 cylinder block 2 cylinders (cylinder bores)
3 Cylinder head 7 Exhaust side surface 8 Exhaust port 9 Exhaust collective passage 10 Exhaust outlet 12 Exhaust joint pipe 19 Heating passage constituting heating means 21 Bypass pipe constituting heating means 22 Switching valve

Claims (1)

Equipped with a plurality of exhaust ports corresponding to a plurality of cylinders, an exhaust side upper cooling water jacket covering the exhaust ports from above, and a group of head bolts for fixing to the upper surface of the cylinder block,
A cylinder head of a multi -cylinder internal combustion engine, wherein one or more exhaust outlets communicating with the exhaust ports are opened on an exhaust side surface, and the exhaust outlets are connected to an exhaust passage,
A heating passage, which promotes thermal expansion of a portion above the exhaust port in the direction of the crankshaft axis by the heat of the exhaust gas, extends from the middle portion of the exhaust port to above the exhaust-side upper cooling water jacket. The exhaust passage is connected to the end of the heating passage by a bypass passage having a switching valve.
Cylinder head of a multi-cylinder internal combustion engine.

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