JP2021004572A - Cylinder head of multicylinder internal combustion engine - Google Patents

Abstract

To suppress the warp deformation of a cylinder head caused by a difference of thermal expansion amounts of an upper part and a lower part without decreasing fuel consumption.SOLUTION: An exhaust port 8 corresponding to each cylinder is formed in a cylinder head 3, and an exhaust gas emitted to each exhaust port 8 is discharged to an exhaust joint pipe (or an exhaust turbo supercharger) from an exhaust outlet 10 via an exhaust emission aggregation passage 9. A heating passage 19 communicating with the exhaust port 8, and opened at an exhaust side face 7 of the cylinder head 3 is formed above the exhaust port 8. An outlet of the heating passage 19 and the exhaust joint pipe 12 are connected to each other by a bypass pipe 21, and a selector valve 22 is provided at the bypass pipe 21. At a warmup operation, by making an exhaust gas flow into the heating passage 19 by opening the selector valve 22, a difference between thermal expansion amounts of an upper part and a lower part of the cylinder head 3, thus suppressing the warp deformation of the cylinder head 3.SELECTED DRAWING: Figure 2

Description

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

A multi-cylinder internal combustion engine includes a cylinder block in which a plurality of cylinders are arranged side by side in the direction of the crank axis, a cylinder head fixed to the upper surface of the cylinder head with a head bolt, a head cover fixed to the upper surface of the cylinder head, and a cylinder block. It is equipped with a front cover (chain case) that is stacked and fixed to the front of the cylinder head.

Since the cylinder head receives the most heat during operation, the cylinder head tends to expand thermally most, which causes a problem 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 due to the cylinder head thermally expanding on the crank axis more than the cylinder block. Regarding this point, Patent Document 1 describes the mating surface between the cylinder head and the front cover. It is disclosed that the difference in thermal expansion between the cylinder block and the cylinder head is absorbed by interposing a liquid gasket.

Japanese Unexamined Patent Publication No. 8-151955

As described above, the cylinder head expands more thermally than the cylinder block, but since the cylinder head receives more heat at the lower part than at the upper part, the cylinder head is on the upper side due to thermal expansion when viewed from the direction orthogonal to the crank axis and the cylinder axis. The phenomenon of warping is likely to occur. Further, looking at the exhaust side and the intake side, there is a phenomenon that a large amount of thermal expansion occurs on the exhaust side. Therefore, the cylinder head tends to warp and deform so that the front and rear corners on the exhaust side are separated from the cylinder block at the highest level. Present.

Therefore, in addition to the metal gasket, a liquid gasket is also provided on the mating surface between the cylinder block and the cylinder head so that the sealing performance can be ensured even if the cylinder head is warped and deformed. When high-load operation such as high-speed driving or climbing is performed, the lower part of the cylinder head near the cylinder block is rapidly heated, so that the warp phenomenon of the cylinder head becomes noticeable and a liquid gasket is interposed. However, there were cases where the sealing property could not be ensured.

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

The present invention relates to a cylinder head in which a plurality of cylinders are fixed to the upper surface of a cylinder block formed by arranging them in the direction of the crank axis by head bolts.
"One or more exhaust outlets communicating with the exhaust port are opened on the exhaust side surface, and a heating means for promoting thermal expansion of a portion above the exhaust port in the direction of the crank axis due to the heat of the exhaust gas. Is provided "
It is configured as.

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

In the present invention, the exhaust gas is used as the heat source of the heating means, but includes both the case where the cylinder head is directly heated by the exhaust gas and the case where the cylinder head is indirectly heated via the heat exchange medium. Further, the heated portion (heated portion) may be one location, or may be a plurality of locations separated in the crank axis direction. Further, the heated portion may be in a form of extending long in the crank axis direction.

Furthermore, the warp phenomenon of the cylinder head is prominent in the high load operation state during warm-up operation, and the warp phenomenon decreases when the cylinder head is warmed as a whole. Therefore, only in the high load operation state during warm-up operation. It is also possible to switch the flow of exhaust gas with a valve so that the exhaust gas flows.

In the present invention, the difference in thermal expansion between the lower part and the upper part of the cylinder head can be suppressed by heating the heated portion of the cylinder head above the exhaust port by the heating means. Therefore, it is possible to prevent or significantly suppress the warp deformation of the cylinder head. As a result, an excessive gap is generated between the cylinder head and the cylinder block, and it is possible to prevent problems such as exhaust gas leakage and oil seepage.

Further, since the exhaust gas is used as the heat source, the problem of fuel consumption reduction as in the case of heating with an electric heater does not occur. Rather, since the heated portion of the cylinder head is located near the valve chamber, the heating means promotes the temperature rise of the oil, which contributes to the improvement of fuel efficiency through the reduction of mechanical loss. Further, in the present invention, since heating is performed by using high-temperature exhaust gas, the responsiveness of heating of the upper part of the cylinder head is also excellent, and therefore, the effect of suppressing warpage deformation can be ensured.

It is a schematic side view which saw the 1st Embodiment from the direction orthogonal to the exhaust side surface. FIG. 1 is a vertical sectional view taken along the line II-II of FIG. (A) is a vertical sectional view of the second embodiment, and (B) is a side view of the third embodiment.

Next, an embodiment of the present invention will be described with reference to the drawings. In the following, the front-back and left-right words are used to specify the direction, but the front-back direction is the crank axis direction, and the side where the timing chain is arranged is the front and the side where the transmission is arranged is the back. .. To be on the safe side, the direction is clearly shown in Fig. 1.

The left-right direction is a direction orthogonal to the crank axis and the cylinder axis. The vertical direction is the cylinder axis direction and does not necessarily coincide with the vertical direction. However, although the internal combustion engine of the present embodiment is slanted by a slight angle so that the exhaust side tilts forward, it is basically a vertical type, and therefore the vertical direction may be regarded as a vertical direction.

(1). Basic structure of the first embodiment First, the first embodiment shown in FIGS. 1 and 2 will be described. This embodiment is applied to a 3-cylinder internal combustion engine for automobiles. Therefore, as shown in FIG. 1, the internal combustion engine straddles the cylinder block 1 in which the three cylinders 2 are formed, the cylinder head 3 fixed to the upper surface of the cylinder block 1, and the front surfaces of the cylinder block 1 and the cylinder head 3. It includes a front cover 4 which is stacked and arranged in a state of being stacked, and a head cover 5 which is stacked and fixed on the upper surfaces of the cylinder head 3 and the front cover 4.

A roof-shaped combustion chamber 6 is formed on the lower surface of the cylinder head 3 corresponding to each cylinder 2. In each combustion chamber 6, a group of intake ports (not shown) opened on the intake side surface and exhaust gas. A group of a pair of exhaust ports 8 (see FIG. 2) opened toward the side surface 7 is open. The exhaust port 8 communicates with an exhaust collecting passage 9 formed inside the cylinder head 3, and one exhaust outlet 10 communicating with the exhaust collecting passage 9 opens on the exhaust side surface 7 of the cylinder head 3. There is.

The exhaust outlet 10 is open to a mounting seat 11 formed on the exhaust side surface 7 of the cylinder head 3, and an elbow-shaped exhaust joint pipe 12 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 the exhaust turbocharger to the mounting seat 11. When fixing the exhaust turbocharger, the catalyst case is connected to the outlet of the exhaust turbocharger, but since the outlet of the exhaust turbocharger opens backward, the exhaust outlet 10 is assumed to be on the exhaust side surface 7. If it is located in the middle of the front and rear, the catalyst case protrudes behind the cylinder block 1.

Therefore, in the present embodiment, the exhaust outlet 10 is arranged so as to be shifted to the front side so that the catalyst case does not protrude behind the cylinder block 1 even when the exhaust turbocharger is attached. There is.

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

(2). Heating means In the present embodiment, as the heating means, a heating passage 19 is formed in the vicinity of the exhaust outlet 10 from one exhaust port 8 upward, and the heating passage 19 is the length of the cylinder head 3. It opens to the exhaust side surface 7 at a portion slightly below the side wall 20. Therefore, the front and rear half of the cylinder head 3 is heated at a portion above the exhaust port 8.

The outlet of the heating passage 19 and the exhaust joint pipe 12 are connected by a pipe bus 21, and the pipe bus 21 is provided with an electromagnetic type 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 located on the upstream side of the catalyst case, the exhaust gas that has passed through the heating passage 19 is returned to a portion of the exhaust passage on the upstream side of the catalyst case. Although the heating passage 19 of the embodiment is formed by casting, it can also be formed by drilling.

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 the exhaust side to be exaggerated as shown by the alternate long and short dash line in FIG. A phenomenon occurs in which the lower surface warps and deforms upward. In particular, when a high-load operation such as climbing a slope is performed during warm-up operation, the temperature difference between the upper part and the lower part of the cylinder head 3 becomes large and the warp deformation becomes remarkable, so that the gap due to the warp deformation becomes large. As a result, even a liquid gasket may not be able to follow and the seal may be in a defective state.

Therefore, in the present embodiment, during the warm-up operation, a part of the exhaust gas is allowed to flow into the heating passage 19 by opening the switching valve 22, thereby heating the portion above the exhaust port 8. Then, the amount of thermal expansion of the portion of the cylinder head 3 above the exhaust port 8 increases, so that the difference in the amount of thermal expansion in the crank axis direction between the upper part and the lower part of the cylinder head 3 is reduced, and warpage deformation occurs. 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, and high sealing performance can be ensured.

In the present embodiment, the heating passages 19 are provided at only one place, but it is also possible to provide the heating passages at a plurality of places separated in the crank axis direction, such as at three places corresponding to each cylinder. The difference in the amount of thermal expansion between the upper part and the lower part of the cylinder head 3 can be further reduced. When the heating passages 19 are formed at a plurality of locations, the pipe bus pipes 21 may be bundled into one and connected to the exhaust joint pipe 12, and the switching valve 22 may be provided at the portion gathered into one.

Further, as another embodiment, the heating passage 19 can be formed in a state of extending long in the crank axis direction. In this case, the difference in thermal expansion between the upper part and the lower part can be further reduced, so that the warp deformation is suppressed. The effect is further improved. Further, the heating passages 19 can be provided at a plurality of locations by changing the height up and down.

The switching valve 22 may be set to open in conjunction with the load sensor during warm-up operation in which the cooling water temperature is lower than the set value and when a load larger than the preset value is applied. , May be set to open at the same time as driving.

(3). In another embodiment (A), a heat pipe 23 in which a heat exchange medium is sealed is used as the heating means. That is, in the heat pipe 23, the heat exchange medium can circulate between the one end portion 23a and the other end portion 23b inside, and the one end portion 23a is connected to the exhaust joint pipe 12 via the holder 24. The other end 23b is connected to the upper part of the cylinder head 3 (for example, the longitudinal side wall 20).

Then, while the temperature of the exhaust joint pipe 12 becomes high due to the operation of the engine, the temperature of the upper part of the cylinder head 3 does not rise, so that the heat exchange medium receives heat from the exhaust joint pipe 12 and moves toward the cylinder head 3. By repeating the circulation of radiating heat to the cylinder head 3 at the other end 23b and returning to the one end 23a, the upper portion of the cylinder head 3 is heated, and the difference in the amount of thermal expansion from the upper portion of the cylinder head 3 to the lower portion. Can be made smaller.

When the tubular holder 24 is used as the connecting means between the exhaust joint pipe 12 and the heat pipe 23 as in the embodiment, the amount of heat transferred from the exhaust joint pipe 12 to the heat pipe 23 can be increased, which is preferable. Further, as shown by a one-point chain line in FIG. 3A, the amount of heat transferred from the exhaust joint pipe 12 to the heat pipe 23 can be increased by projecting one end 23a of the heat pipe 23 into the exhaust joint pipe 12. it can.

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

FIG. 3B shows a modified example. In this example, one heat pipe 23 connected to the exhaust joint pipe 12 is branched into three, and each branch is divided into three cylinder heads 3. It is connected to the place. When a plurality of locations of the cylinder head 3 are heated by the heat pipes 23, the heat pipes 23 may be individually used instead of the branching method.

Although the embodiments of the present invention have been described above, the present invention can be embodied in various ways. For example, the present invention can also be applied to a type in which an exhaust outlet is opened on the exhaust side surface corresponding to each cylinder to collect exhaust gas in an exhaust manifold. In this case, the bypass pipe or heat pipe may be connected to the exhaust manifold or the upper part of the catalyst case. If an 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 invention of the present application can be embodied in a cylinder head. Therefore, it can be used industrially.

1 cylinder block 2 cylinders (cylinder bore)
3 Cylinder head 7 Exhaust side surface 8 Exhaust port 9 Exhaust collecting passage 10 Exhaust outlet 12 Exhaust joint pipe 19 Heating passage constituting the heating means 21 Bypass pipe constituting the heating means 22 Switching valve 23 Heat pipe constituting the heating means

Claims (1)

A cylinder head fixed by head bolts to the upper surface of a cylinder block in which a plurality of cylinders are arranged side by side in the crank axis direction.
One or more exhaust outlets communicating with the exhaust port are opened on the exhaust side surface, and a heating means for promoting thermal expansion of a portion above the exhaust port in the direction of the crank axis due to the heat of the exhaust gas is provided. Provided,
Cylinder head of a multi-cylinder internal combustion engine.

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