JP5212287B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine having a plurality of cylinders.

  An internal combustion engine forms an engine body by fastening a cylinder block and a cylinder head stacked on one end in the height direction thereof, and houses a plurality of cylinders serving as heat sources along the cylinder arrangement direction. . The left and right sides of the plurality of cylinders are cooled by a refrigerant passage on the cylinder block side, and the combustion chamber ceilings of the plurality of cylinders are cooled by a refrigerant passage on the cylinder head side.

By the way, a multi-cylinder internal combustion engine, for example, a two-cylinder engine in which a main part of an existing three-cylinder engine is used as it is so that one of a plurality of cylinders functions as a balancer cylinder that optimizes rotation balance. It is possible to share the main part of the engine body.
For example, of the three cylinders of a three-cylinder engine, two cylinders are combustion cylinders that generate rotational output in the combustion stroke, and the rotation balance is appropriate by eliminating the fuel supply system of the other cylinder and repeating compression and expansion. An example of an internal combustion engine using a balancer cylinder that achieves the above is disclosed in Japanese Patent Laid-Open No. 11-229889.

  Here, by setting the opening / closing timing of the intake / exhaust valve to an opening / closing timing equivalent to 4 cycles or 2 cycles, the timing of compression and expansion of the balancer cylinder is performed once or twice for two rotations of the crankshaft, and the output torque Disclosed is a technology that suppresses the variation of the image quality and ensures quietness.

Japanese Patent Laid-Open No. 11-229889

By the way, when the two cylinders of the three cylinders of the three-cylinder engine are combustion cylinders and the other one is a balancer cylinder as in the internal combustion engine of Patent Document 1, the engine body side is an existing three cylinder. Since the structure of the main part of the engine is used as it is, the following problems arise.
That is, when a two-cylinder engine having a balancer cylinder is formed by using the main part of an existing three-cylinder engine as it is, two combustion cylinders of the three cylinders form a heat source, while other One balancer cylinder is not a heat source. Nevertheless, the balancer cylinder is cooled by the refrigerant passages on the cylinder block side and the cylinder head side in the same manner as the other two combustion cylinders.

Thus, although the heat source is relatively few as two cylinders, the cooling water flowing through the refrigerant passages covering the portion facing the balancer cylinder continues to be wasted, resulting in this, The warm-up performance of a two-cylinder engine having a balancer cylinder will deteriorate.
Moreover, since the two cylinders that form the heat generation source are constantly cooled by a relatively large amount of cooling water for three cylinders, there is a problem in that the cooling loss increases.

  The present invention has been made based on the above-described problems, and an object of the present invention is to provide a cooling function for a portion of the refrigerant passage on the cylinder head side facing the balancer cylinder in a multi-cylinder engine having a balancer cylinder. An object of the present invention is to provide an internal combustion engine that is capable of suppressing cooling loss and improving warm-up performance.

The invention of claim 1 of the present application is fastened to the cylinder block having a plurality of cylinders arranged along the cylinder arrangement direction, a crankshaft rotating by receiving power from the plurality of cylinders, and the cylinder block. In an internal combustion engine having a cylinder head in which a refrigerant passage for flowing refrigerant in a cylinder arrangement direction is formed, the plurality of cylinders are a combustion cylinder that performs a cycle operation including a combustion stroke, and a balancer cylinder that performs a cycle operation that does not include a combustion stroke. The refrigerant passage of the cylinder head is formed such that a cross-sectional area of a portion facing the balancer cylinder is smaller than a cross-sectional area of a portion facing the combustion cylinder, and the plurality of cylinders include a piston, a cylinder, and a cylinder. A volume chamber constituted by a head, and a ceiling wall of the volume chamber of the balancer cylinder in the cylinder head is the combustion Formed to the ceiling wall of the volume chamber of the cylinder protrudes into the coolant passage, characterized in that.

Here, the invention of claim 2 of the present application is fastened to the cylinder block having a plurality of cylinders arranged along the cylinder arrangement direction, a crankshaft rotating by receiving power from the plurality of cylinders, and the cylinder block. In an internal combustion engine having a cylinder head in which a refrigerant passage for flowing refrigerant in a cylinder arrangement direction is formed, the plurality of cylinders are a combustion cylinder that performs a cycle operation including a combustion stroke, and a balancer cylinder that performs a cycle operation that does not include a combustion stroke. The refrigerant passage of the cylinder head is formed such that a flow passage cross-sectional area of a portion facing the balancer cylinder is smaller than a flow passage cross-sectional area of a portion facing the combustion cylinder, and the volume of the balancer cylinder in the cylinder head A cylindrical wall portion that communicates between the ceiling wall of the chamber and the wall portion of the cam chamber facing the ceiling wall of the volume chamber across the refrigerant passage. And disposed medium passage, characterized in that.

  The invention according to claim 3 of the present application is the internal combustion engine according to claim 1, wherein the cam facing the ceiling wall of the volume chamber of the balancer cylinder in the cylinder head and the ceiling wall of the volume chamber sandwiching the refrigerant passage. A cylindrical wall portion communicating with the wall surface portion of the chamber is disposed in the refrigerant passage.

  Here, in the invention of claim 4 of the present application, in the internal combustion engine according to claim 1, 2, or 3, three of the plurality of cylinders are arranged along the cylinder arrangement direction, and the first and third cylinders in the cylinder arrangement direction are provided. The combustion cylinder is characterized in that a second cylinder is formed as a balancer cylinder.

According to the first aspect of the present invention, the flow passage cross-sectional area of the refrigerant passage in the portion facing the balancer cylinder that does not require cooling is not formed and the refrigerant passage capacity of the cylinder head is suppressed. Therefore, the cooling loss can be reduced, the warm-up performance can be improved, and the engine weight can be reduced. In particular, the ceiling wall of the volume chamber of the balancer cylinder is formed so as to protrude relatively large into the refrigerant passage, and the volume chamber can be enlarged. Therefore, the balancer weight can be easily optimized by increasing the weight of the balancer piston.

In the invention of claim 2, the flow passage cross-sectional area of the refrigerant passage in the portion facing the balancer cylinder that does not require cooling is not formed and the refrigerant passage capacity of the cylinder head is suppressed. Therefore, the cooling loss can be reduced, the warm-up performance can be improved, and the engine weight can be reduced. In particular, by disposing a cylindrical wall portion that communicates the volume chamber of the balancer cylinder and the cam chamber in the cylinder head, energy loss during the compression or expansion stroke of the balancer cylinder can be suppressed. Further, the capacity of the refrigerant passage of the cylinder head can be reduced by relatively increasing the outer shape of the cylindrical wall portion disposed in the refrigerant passage, so that the cooling loss can be reduced, the warm-up performance is improved, and the engine Weight reduction can be achieved.

According to the third aspect of the present invention, since the volume chamber can be expanded, the balancer weight can be easily optimized by increasing the weight of the balancer piston. Further, by disposing a cylindrical wall portion that communicates the volume chamber of the balancer cylinder and the cam chamber in the cylinder head, energy loss during the compression or expansion stroke of the balancer cylinder can be suppressed. Further, the capacity of the refrigerant passage of the cylinder head can be reduced by relatively increasing the outer shape of the cylindrical wall portion disposed in the refrigerant passage, so that the cooling loss can be reduced, the warm-up performance is improved, and the engine Weight reduction can be achieved.

  In the invention of claim 4, since the balancer cylinder is disposed between the first and third combustion cylinders in the cylinder arrangement direction, the maximum value of the torsion torque generated in the crankshaft can be kept relatively low, and the durability Can be improved.

It is a principal part side sectional view of an internal-combustion engine as one embodiment of the present invention. FIG. 2 is a plan sectional view of a cylinder head portion of the internal combustion engine of FIG. 1. It is shape explanatory drawing of the refrigerant path in the cylinder head of the internal combustion engine of FIG. 1, and is a top view equivalent to the shape of a core. FIG. 2 is a side view corresponding to the shape of a core in the cylinder head of the internal combustion engine of FIG. 1 and a shape explanatory diagram of a refrigerant passage in the cylinder block. FIG. 6 is a partially cutaway cross-sectional view showing a modification of the refrigerant passage on the cylinder block side of the internal combustion engine of FIG. 1. FIG. 2 is an output torque change characteristic diagram according to a crank angle change of the internal combustion engine of FIG. 1. FIG. 2 is a stroke explanatory diagram corresponding to a change in crank angle of each cylinder of the internal combustion engine of FIG. 1. It is principal part side sectional drawing of the internal combustion engine as other embodiment of this invention.

  1 and 2 show an internal combustion engine (hereinafter simply referred to as engine A1) as an embodiment of the present invention.

Engine A1 is a 4-cycle gasoline engine. The engine main body 1 of the engine A1 employs an in-line three-cylinder cylinder layout, and uses the engine main body 1 that is almost the same as an in-line three-cylinder normal engine. In the engine body 1, the first and third cylinders in the cylinder arrangement direction are set as the combustion cylinders P1, and the second cylinder is set as the balancer cylinder Pb.
Of the three cylinders, two cylinders at the front and rear ends are set as combustion cylinders P1 and P2 that generate rotational output in the combustion stroke, and one intermediate cylinder is set as a balancer cylinder Pb, and is formed in the engine 1 that outputs power by substantially two cylinders. Has been.

Here, the cylinder block 2 constituting the main part of the engine main body 1 has substantially the same configuration as that of an in-line three-cylinder normal engine, and three cylinders C are arranged in series along the cylinder arrangement direction. A water jacket wj is provided as a refrigerant passage around the front, rear, left and right of these three cylinders C. At a plurality of positions at the upper end of these water jackets (refrigerant passages) wj, communication paths communicating with a water jacket (refrigerant passage) wj on the cylinder head 8 side described later are formed.
The water jacket wj of the cylinder block 2 causes cooling water to flow along the left and right sides in the cylinder arrangement direction, thereby cooling the front and rear combustion cylinders P1 and P2 serving as a heat source and the intermediate balancer cylinder Pb. ing.

  Note that the portion of the water jacket wj of the cylinder block 2 facing the balancer cylinder Pb merely functions as a cooling water flow path, and does not require a cooling function, and can reduce the cross-sectional area of the flow path. desirable. However, in order to reduce the cost, the engine body 1 of the 1000cc normal engine of the inline three cylinders is shared as it is. However, depending on the case, the cooling water capacity is reduced in the portion of the water jacket wj facing the balancer cylinder Pb. For the purpose, as shown in FIG. 5, a hollow bulge M1 is attached as a retrofit, thereby forming a flow passage cross-sectional area Ss1 that is throttled to reduce the cooling water capacity and improve the engine warm-up performance. You may plan.

  A crankshaft 9 is pivotally attached to the lower part of the cylinder block 2 in the cylinder arrangement direction X, and the crankshaft 9 and the piston 11 of each cylinder C are connected by a crank mechanism. Here, from the pistons 11 of the front and rear combustion cylinders P1 and P2, the pressing force generated in the combustion stroke is converted into a rotational force by the crank mechanism and transmitted to the crankshaft 9, and to the piston 11m of the balancer cylinder Pb from the crankshaft 9. The rotational force is converted into a vertical displacement via a crank mechanism and transmitted, and the volume of the variable volume chamber (volume chamber) 12 of the balancer cylinder Pb is increased or decreased.

Here, the first and third cylinders in the cylinder arrangement direction are formed as combustion cylinders P1 that perform cycle operation including a combustion stroke, and the second cylinder is formed as a balancer cylinder Pb that performs cycle operation that does not include a combustion stroke. Thus, since the balancer cylinder Pb is arranged between the first and third combustion cylinders P1 and P2 in the cylinder arrangement direction, the maximum value of the torsion torque generated in the crankshaft 9 can be kept relatively low. In this case, the weight of the piston 11m of the balancer cylinder Pb is particularly greater than the weight of the pistons 11 of the front and rear combustion cylinders P1 and P2. For example, the top wall of the piston 11m of the balancer cylinder Pb (shown as the thickness t1 in FIG. 1) is formed relatively large. At this time, a bottom wall 16 on the cylinder head 8 side, which will be described later, facing the variable volume chamber 12 is formed to protrude toward the water jacket wj from the bottom walls 16 on the front and rear combustion cylinders P1, P2 side (projecting upward in FIG. 1). That is, it is formed by enlarging the volume of the variable volume chamber 12. For this reason, the thickness t1 of the top wall 111 of the piston 11 can be increased relatively easily, and the weight can be easily increased.
Moreover, the piston pin 15 is not hollow like the piston pins 15 of the front and rear combustion cylinders P1, P2, but is formed as a solid pin. The weight of the balancer cylinder Pb is set so that the weight of the piston 11m of the balancer cylinder Pb becomes equal to the total weight of both the pistons 11 of the front and rear combustion cylinders P1 and P2 as a result of these weight increase measures. Thereby, the piston 11 of the balancer cylinder Pb can exhibit a function as a reciprocating balancer.

  In such a balancer cylinder Pb, the piston 11m receives the rotational force from the crankshaft 9 and moves upward, thereby reducing the volume of the variable volume chamber 12 and performing a compression stroke. The piston 11 is moved downward to perform an expansion stroke by increasing the volume, so that a rotational force is applied to the crankshaft 9. In the case of repeating these compression and expansion strokes, there is no intake / exhaust of the air in the variable volume chamber 12 to the outside, and the rotational force of the crankshaft 9 enters and exits every one rotation (360 °).

  Here, the balancer cylinder Pb is arranged at a rotational position opposite to the other two combustion cylinders P1, P2 by 180 ° in crank angle (see FIG. 1). Further, as shown in FIGS. 6 and 7, when one of the two combustion cylinders P1 and P2 is in the explosion / expansion stroke and the other is in the suction stroke, the balancer cylinder Pb receives the rotational force and performs the compression stroke. Conversely, when one of the two combustion cylinders P1, P2 is in the exhaust stroke and the other is in the compression stroke, the balancer cylinder Pb performs the expansion stroke, thereby returning the rotational force to the crankshaft 9, and the two combustion cylinders P1, P2 It can be used for consumption of rotational force in the side compression and exhaust strokes.

  Therefore, the direction of the rotational force applied to the crankshaft 9 generated in the two combustion cylinders P1 and P2 in the explosion / expansion stroke and the rotational force applied to the crankshaft 9 generated in the expansion stroke of the balancer cylinder Pb are always in opposite directions. It becomes. By providing the balancer cylinder Pb in this way, the variation in the rotational force applied to the crankshaft 9 can be smoothed, and the engine can be kept quiet. In addition, since the balancer cylinder Pb is disposed between the first and third combustion cylinders P1 and P2 in the cylinder arrangement direction, that is, the balancer cylinder Pb is located at the center in the longitudinal direction of the crankshaft 9, and the combustion cylinder P1 is located on both sides thereof. , P2 is deployed. For this reason, the relative distance between the balancer cylinder Pb and the front and rear combustion cylinders P1 and P2 is relatively short, and the torsional displacement between the balancer cylinder Pb and the combustion cylinders P1 and P2 that perform reverse torsional displacement is kept relatively small. In this respect, durability can be improved.

  As shown in FIGS. 1 and 2, the cylinder head 8 fastened to the top of the cylinder block 2 is formed long in the cylinder arrangement direction X, and a bottom wall 16 that is superimposed on the upper end of the cylinder block 2 and the cylinder arrangement direction thereon. A water jacket wj formed long in X, an intermediate wall 23 on the water jacket wj, and a cam chamber 19 thereon are formed, and the outer periphery thereof is covered with an outer peripheral vertical wall 24. The upper portion of the cam chamber 19 is covered with a head cover 25 formed so that the peripheral edge overlaps the outer peripheral vertical wall 24, and is fastened together. The cam shaft 35 pivotally supported in the cam chamber 19 is connected to the crankshaft 9 via a belt-type rotation transmission system 36.

The bottom wall 16 of the cylinder head 8 is opposed to the combustion chamber 18 of the first combustion cylinder P1 along the cylinder arrangement direction X (ceiling wall), and is opposed to the variable volume chamber 12 of the balancer cylinder Pb (ceiling wall). The wall (ceiling wall) facing the combustion chamber 18 of the second combustion cylinder P2 is formed continuously in this order along the cylinder arrangement direction X.
A wall of the first and second combustion cylinders P1 and P2 facing the respective combustion chambers 18 is formed with a mounting hole 31 for a spark plug (not shown) at the center and a plug receiving cylinder upward from the mounting hole 31. 32 extends and the upper end passes through the water jacket (refrigerant passage) wj to reach the cam chamber 19 and faces the head cover 25.

  Further, as shown in FIG. 2, a pair of intake ports 33 are provided on the other side from the left and right sides from the opposing walls (ceiling walls) of the first and second combustion cylinders P 1 and P 2 to the combustion chambers 18. A pair of exhaust ports 34 are extended and formed in a state of protruding into the water jacket wj. That is, the cylindrical wall portion of each port protrudes into the water jacket wj (see FIG. 5), and is continuously curved between the opposing wall of each combustion chamber 18 and the left and right side wall portions of the outer peripheral vertical wall 24. Is done. On the other hand, the opening of the spark plug mounting hole 31 and the ports 33 and 34 is excluded from the wall facing the variable volume chamber 12 of the balancer cylinder Pb, that is, the ceiling wall of the balancer cylinder (see FIG. 2). Thus, the cylindrical wall portion of each port and the plug collecting cylinder are eliminated.

As shown in FIG. 2, such a water jacket wj on the upper side of the bottom wall 16 of the cylinder head 8 increases the cooling efficiency at the portions facing the first and second combustion cylinders P1 and P2 serving as heat generation sources. The water jacket wj has a relatively large channel cross-sectional area and a large channel width B1. On the other hand, a cooling function is not required at the portion facing the balancer cylinder Pb, and only a function as a flow path for smoothly flowing cooling water in the cylinder arrangement direction X is maintained as shown in FIGS. The central flow path rc is narrowed, and the reduction area E is formed larger than the front and rear flow paths. For this reason, the flow path width B2 of the central flow path rc is formed to be relatively small, thereby eliminating the cooling water required for useless cooling. 3 and 4 show a plan view and a side view corresponding to the outer shape of the core for forming the water jacket wj, that is, the shape of the cylinder head 8 with the water jacket wj extracted.
Here, as shown in FIG. 2, the water jacket wj of the cylinder head 8 has a flow passage cross-sectional area of the central flow passage rc facing the variable volume chamber 12 so that the inlet 4 before and after the water jacket wj of the cylinder head 8. Or the flow passage cross-sectional area of the outlet 5 is formed to be approximately the same size. As a result, the flow resistance of the cooling water circulation system as a whole is prevented from increasing due to the narrow central channel rc.

  As shown in FIGS. 1, 2, and 4, the water jacket wj of the cylinder head 8 and the upper end of the cylinder block 2 are communicated with each other by a plurality of vertical communication paths r. The first and second combustion cylinders P1 and P2 are dispersed and formed in a plurality of portions, and are excluded from the portions facing the balancer cylinder Pb. The cooling water of the water jacket wj on the cylinder head 8 side can flow into the water jacket wj of the cylinder block 2 through a part of the communication path r, and at the same time, the cooling water on the cylinder block 2 side passes through the other part of the communication path r. It is formed so as to return to the water jacket wj on the cylinder head 8 side.

  During the operation of the engine A1, the cooling water that the cooling water circulation system Rw flows reaches the inlet 4 of the engine body 1 and flows into the water jacket wj of the cylinder head 8 to relatively widen the flow path. The wall facing the combustion chamber 18 of the first combustion cylinder P1 and the intake / exhaust ports 6 and 7 (see FIG. 2) are cooled, and the flow path is narrowed to flow into the central flow path rc facing the balancer cylinder Pb. Then, the flow path is enlarged again on the downstream side, the opposing wall to the combustion chamber 18 of the second combustion cylinder P2 and the intake / exhaust ports 6 and 7 are cooled, and the flow path is narrowed on that to reach the outlet 5; It flows out to a discharge pipe (not shown).

  In parallel with this, as shown in FIG. 4, the cooling water branched from the inlet 4 of the cylinder head 8 passes through the vertical communication path r from the water jacket wj side of the cylinder head 8 and passes through the water in the cylinder block 2. It flows into the jacket wj. The coolant that has reached the water jacket wj of the cylinder block 2 flows from the outer peripheral side of the first combustion cylinder P1 to the outer peripheral side of the balancer cylinder Pb, and then flows to the outer periphery of the second combustion cylinder P2. It passes through the longitudinal communication path r from wj, returns to the water jacket wj side of the cylinder head 8, and flows out to a discharge pipe (not shown) through the outlet 5.

As described above, in the engine A1 of FIG. 1, the cooling water flowing through the water jackets wj on the cylinder block 2 side and the cylinder head 8 side is sideways and above the combustion chamber 18 of the first and second combustion cylinders P1 and P2. The cooling operation can be performed accurately by passing through each of the outer peripheral portions. In this case, the side of the variable volume portion 12 of the balancer cylinder Pb that is not the heat source is the same as the other portions, and the upper portion reliably reduces the cooling function and allows only the function as the cooling water flow path.
As described above, the flow passage cross-sectional area of the water jacket wj of the cylinder head 8 at the portion facing the balancer cylinder Pb that does not require cooling and that does not have a heat generation source is formed to be relatively small like the central flow passage rc. Unnecessary cooling operation can be suppressed and cooling loss can be reduced.

Furthermore, the volume of the water jacket wj on the cylinder head 8 side facing the balancer cylinder Pb is reduced to relatively reduce the cooling water capacity, so that the warm-up performance can be improved and the engine weight can be reduced.
Further, in this embodiment, the cooling water capacity is reduced only by narrowing the flow passage cross-sectional area of the water jacket wj of the cylinder head 8, and the cylinder block side of the engine of the conventional three-cylinder co-combustion cylinder is used. Since it is used, it can be easily shared and can be implemented at low cost.

FIG. 8 shows another embodiment of the present invention.
The engine A2 here is different from the engine A1 in FIG. 1 in the structure of the bottom wall 16a of the cylinder head 8a facing the balancer cylinder Pb, and the configuration of other parts is the same. The explanation of the overlapping part is omitted.
The engine body 1a of the engine A2 in FIG. 8 sequentially arranges a first combustion cylinder P1, a balancer cylinder Pb, and a second combustion cylinder P2 in series in the cylinder arrangement direction X. The bottom wall 16a of the cylinder head 8a of the engine A2 has a wall facing the combustion chamber 18 of the first combustion cylinder P1 along the cylinder arrangement direction X, a wall facing the variable volume chamber 12a of the balancer cylinder Pb, and a second wall. A wall facing the combustion chamber 18 of the combustion cylinder P2 is continuously formed along the cylinder arrangement direction X in this order.

In this case, the cylinder block 2 is formed in the same manner as the engine A1 in FIG. 1, and the cylinder head 8a on the cylinder block 2 is the same as the engine A1 in FIG. 1 except that the configuration of the bottom wall 16a and the intermediate wall 23a and the water jacket wj are different. Is formed.
Of the bottom wall 16a of the cylinder head 8, the opposing walls of the first and second combustion cylinders P1 and P2 to the combustion chamber 18 are formed in the same manner as the engine A1 in FIG. The wall facing the variable volume chamber 12a of the balancer cylinder Pb is connected to the opposite (upper) cam chamber 19 via the water jacket wj and the intermediate wall 23a facing the cam wall 19 via the cylindrical wall portion 28. .

Both the opposing wall of the variable volume chamber 12a connected to one end of the cylindrical wall portion 28 and the intermediate wall 23a connected to the other end are formed with openings m, and these openings m and the inner wall of the cylindrical wall portion 28 are passed through. The variable volume chamber 12 a communicates with the cam chamber 19. That is, the volume of the variable volume chamber 12 a is increased by the volume of the cam chamber 19.
Here, the inner diameter of the cylindrical wall portion 28 is formed to be larger than about half of the diameter of the variable volume chamber 12, so that the air flow when the volume of the variable volume chamber 12 fluctuates is not subjected to flow resistance. Formed.
Further, in the water jacket wj of the cylinder head 8a, the flow passage cross-sectional area of the portion facing the balancer cylinder Pb is reduced by the arrangement of the cylindrical wall portion 28, that is, the first and second combustion cylinders before and after the flow passage cross-sectional area. It is reduced from the cross-sectional area of the flow path at the part facing P1 and P2. Thus, useless cooling of the variable volume chamber 12 of the balancer cylinder Pb that is not a heat generation source can be eliminated, and cooling water corresponding to the volume of the cylindrical wall portion 28 is eliminated.

In the engine A2 shown in FIG. 8, the cooling water flowing through the water jackets wj on the cylinder block 2 side and the cylinder head 8 side is located on the side and upper sides of the combustion chambers 18a of the first and second combustion cylinders P1 and P2. Cooling can be performed accurately by passing through the part. Further, the side of the variable volume portion 21 of the balancer cylinder Pb which is not a heat source is cooled in the same manner as other portions, and the upper portion reduces the cooling water capacity by disposing the cylindrical wall portion 28, thereby reducing the cooling function. Fluidized.
As described above, since the flow passage cross-sectional area of the water jacket wj of the cylinder head 8 is relatively small at the portion facing the balancer cylinder Pb that has no heat source and does not require cooling, useless cooling operation can be suppressed. The cooling loss can be reduced. Furthermore, since the volume of the portion facing the balancer cylinder Pb is reduced by providing the cylindrical wall portion 28, the cooling water capacity as the water jacket wj of the cylinder head 8 can be reduced, so that the warm-up performance is improved and the engine weight is reduced. Can be achieved.
Furthermore, in this case, the cylindrical wall portion 28 can contribute to increasing the rigidity of the intermediate wall 23, and the cooling water capacity can be easily reduced by increasing the inner diameter of the cylindrical wall portion 28.

DESCRIPTION OF SYMBOLS 1 Engine main body 2 Cylinder block 8 Cylinder head 9 Crankshaft 12 Variable volume chamber 28 Cylindrical wall part wj Water jacket (refrigerant passage)
A1, A2 engine (internal combustion engine)
P1, P2 Combustion cylinder Pb Balancer cylinder X Cylinder arrangement direction

Claims (4)

A cylinder block having a plurality of cylinders arranged along the cylinder arrangement direction;
A crankshaft that rotates by receiving power from the plurality of cylinders;
In an internal combustion engine comprising a cylinder head fastened to the cylinder block and formed with a refrigerant passage through which refrigerant flows in the cylinder arrangement direction,
The plurality of cylinders include a combustion cylinder that performs cycle operation including a combustion stroke, and a balancer cylinder that performs cycle operation that does not include a combustion stroke,
The refrigerant passage of the cylinder head is formed such that a flow passage cross-sectional area of a portion facing the balancer cylinder is smaller than a flow passage cross-sectional area of a portion facing the combustion cylinder ,
The plurality of cylinders includes a volume chamber composed of a piston, a cylinder, and a cylinder head,
An internal combustion engine characterized in that a ceiling wall of a volume chamber of the balancer cylinder in the cylinder head is formed so as to protrude from the ceiling wall of the volume chamber of the combustion cylinder into the refrigerant passage . A cylinder block having a plurality of cylinders arranged along the cylinder arrangement direction;
A crankshaft that rotates by receiving power from the plurality of cylinders;
In an internal combustion engine comprising a cylinder head fastened to the cylinder block and formed with a refrigerant passage through which refrigerant flows in the cylinder arrangement direction,
The plurality of cylinders include a combustion cylinder that performs cycle operation including a combustion stroke, and a balancer cylinder that performs cycle operation that does not include a combustion stroke,
The refrigerant passage of the cylinder head is formed such that a flow passage cross-sectional area of a portion facing the balancer cylinder is smaller than a flow passage cross-sectional area of a portion facing the combustion cylinder,
A cylindrical wall portion is provided in the refrigerant passage that communicates the ceiling wall of the volume chamber of the balancer cylinder in the cylinder head and the wall surface portion of the cam chamber facing the ceiling wall of the volume chamber across the refrigerant passage. the internal combustion engine, characterized in that. The internal combustion engine according to claim 1,
A cylindrical wall portion that communicates between the ceiling wall of the volume chamber of the balancer cylinder in the cylinder head and the wall portion of the cam chamber that faces the ceiling wall of the volume chamber across the refrigerant passage is disposed in the refrigerant passage. An internal combustion engine characterized by that. The internal combustion engine according to claim 1, 2, or 3,
3. The internal combustion engine according to claim 1, wherein three cylinders are arranged along a cylinder arrangement direction, and the first and third cylinders in the cylinder arrangement direction are formed as combustion cylinders and the second cylinder is formed as a balancer cylinder.

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