JP7206936B2 - Cooling structure of multi-cylinder engine - Google Patents

Description

The present invention includes an engine body including a cylinder block in which a plurality of cylinders arranged in a line is formed, the cylinder block is provided with a block outer peripheral wall surrounding cylinder bore walls of the plurality of cylinders, and the block outer peripheral wall and the The present invention relates to a cooling structure for a multi-cylinder engine in which a water jacket through which coolant flows is defined between the cylinder bore walls of a plurality of cylinders.

2. Description of the Related Art In an engine, a water jacket is formed in the engine body so as to surround the wall of the cylinder bore, and the engine body is cooled by circulating coolant in the water jacket. Also, there is known a structure in which a spacer surrounding a cylinder bore wall is housed in a water jacket, and the spacer partitions the coolant flow path in the water jacket.

For example, Patent Literature 1 discloses a structure in which a spacer is accommodated in a water jacket so that the coolant flows only through the upper portion of the water jacket. Specifically, in the structure of Patent Document 1, a cooling liquid introduction portion for introducing cooling liquid into the water jacket is formed on the outer peripheral wall of the cylinder block, and the spacer has an upper portion close to the outer peripheral wall of the cylinder block and a lower portion. An opening is formed in the upper part of the spacer so as to be close to the cylinder liner and introduces the cooling liquid introduced from the cooling liquid introduction part into the inside of the water jacket spacer. According to the structure of Patent Document 1, the upper portion of the cylinder liner is effectively cooled.

JP 2015-190403 A

Since the combustion chamber in which the air-fuel mixture is combusted is formed in the upper portion of the cylinder bore wall or above the cylinder bore wall, the temperature in the upper portion of the cylinder bore wall tends to be higher than that in the lower portion in the vertical direction. From this, it can be said that according to the structure of Patent Document 1, the cylinder bore wall can be effectively cooled in the vertical direction. However, the temperature of the cylinder bore wall also becomes uneven in the circumferential direction. Specifically, the connecting portion of the cylinder bore wall of each cylinder tends to be heated to a higher temperature than other portions due to the application of combustion energy from the combustion chambers of two adjacent cylinders. Therefore, it is desirable to effectively cool the connecting portion of the cylinder bore wall, and in this respect, the structure of Patent Document 1 has room for improvement.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cooling structure for a multi-cylinder engine that can cool the cylinder bore walls more effectively.

In order to solve the above-mentioned problems, the present invention includes an engine body including a cylinder block in which a plurality of cylinders arranged in a line is formed, and the cylinder block is provided with a block outer peripheral wall surrounding the cylinder bore walls of the plurality of cylinders. A cooling structure for a multi-cylinder engine in which a water jacket through which coolant flows is defined between the outer peripheral wall of the block and the cylinder bore walls of the plurality of cylinders, wherein the inside of the cylinder block is filled with the coolant. A water jacket through which the coolant is circulated and a cooling liquid introduction portion for introducing the cooling liquid into the water jacket are formed,
The water jacket accommodates a spacer including a peripheral wall surrounding cylinder bore walls of a plurality of cylinders. At least a portion of the peripheral wall includes a first peripheral wall forming an upper portion thereof, a stepped portion projecting from the lower end of the first peripheral wall toward the cylinder side, and a cylinder of the stepped portion. a second peripheral wall extending downward from a side end of the first peripheral wall, the portion of the first peripheral wall facing the connection portion of the cylinder bore wall of each cylinder being a bore-to-bore corresponding portion, and centered between the adjacent bore-to-bore corresponding portions; When the positioned first peripheral wall is defined as a bore center corresponding portion, the stepped portion protrudes from the bore center corresponding portion toward the cylinder by the amount of projection of the portion that projects toward the cylinder side from the bore center corresponding portion. The curvature of the portion of the first peripheral wall extending from the bore-to-bore corresponding portion toward the side opposite to the cylinder is smaller than the curvature of the bore center corresponding portion. It is characterized by being formed as follows.

According to the present invention, the upper portion of at least a part of the water jacket has a relatively large flow passage area on the inner peripheral side of the peripheral wall due to the first peripheral wall, the cylinder bore wall, and the stepped portion (the second peripheral wall and the cylinder bore wall, A passageway is formed (compared to a passageway that is formed). Therefore, most of the coolant introduced into the water jacket can flow through this passage and come into contact with the upper portion of the cylinder bore wall, effectively cooling the upper portion of the cylinder bore wall, which tends to become hot due to its proximity to the combustion chamber. can be done.

Moreover, in the present invention, the amount of projection of the portion of the stepped portion that faces the connecting portion of the cylinder bore wall can be kept small. Therefore, at the connecting portion of the cylinder bore, the first peripheral wall is arranged at a position closer to the cylinder bore so that the cooling liquid can pass through while appropriately securing the minimum clearance between the second peripheral wall and the cylinder bore wall, and by extension, the minimum clearance between the spacer member and the cylinder bore wall. It is possible to bring the position to be closer to the cylinder bore wall. Therefore, it is possible to effectively lower the temperature of the connecting portion of the cylinder bore wall, which is particularly prone to high temperature.

Further, according to the present invention , the flow direction of the coolant can be directed to the cylinder side in the bore-to-bore corresponding portion, so that the coolant and the connecting portion of the cylinder bore can be brought into contact with each other more reliably. Therefore, the connecting portion of the cylinder bore can be cooled more effectively.

In the above configuration, preferably, the spacer includes a vertically extending reinforcing rib projecting from an outer peripheral surface of the bore-to-bore corresponding portion .

According to this configuration, it is possible to prevent deformation, damage, etc. of the bore-to-bore corresponding portion while reducing the separation distance between the bore-to-bore corresponding portion and the cylinder bore wall. Specifically, when the clearance is reduced, the flow velocity of the coolant passing through the bore-to-bore corresponding portion and the cylinder bore wall increases, and the pressure applied from the coolant to the bore-to-bore corresponding portion increases. There is a risk of deformation, etc. On the other hand, by providing the reinforcing ribs, the rigidity of the corresponding portion between the bores can be increased, and the deformation and the like of the portion can be suppressed.

In the above configuration, preferably, the amount of protrusion of the stepped portion from the first peripheral wall toward the cylinder side gradually decreases from the bore center corresponding portion toward the bore-to-bore corresponding portion .

According to this configuration, it is possible to smoothly flow the coolant toward the corresponding portion between the bores.

As described above, according to the present invention, the cylinder bore wall can be cooled more effectively.

1 is a schematic diagram showing the overall configuration of an engine system according to an embodiment of the present invention; FIG. Fig. 2 is a schematic perspective view of the surroundings of the engine body as viewed from the exhaust side; Fig. 2 is a schematic perspective view of the surroundings of the engine body as viewed from the intake side; FIG. 4 is a schematic perspective view showing a cylinder block and spacers; It is a schematic top view of a cylinder block. FIG. 4 is a top view of the cylinder block in which spacers are accommodated; FIG. 7 is a schematic cross-sectional view taken along line VII-VII of FIG. 6; FIG. 7 is a schematic cross-sectional view taken along line VIII-VIII of FIG. 6; FIG. 4 is a schematic perspective view of a spacer; FIG. 4 is a side view of the exhaust side of the spacer; It is a side view of the intake side of a spacer. FIG. 11 is a schematic cross-sectional view of the spacer taken along line XII-XII of FIG. 10; FIG. 13 is a schematic cross-sectional view of the spacer taken along line XIII-XIII of FIG. 12; FIG. 8 is a schematic cross-sectional view of the spacer taken along line XIV-XIV in FIG. 7; FIG. 8 is a schematic cross-sectional view of the spacer along line XV-XV of FIG. 7; Fig. 2 is a schematic side view showing an enlarged vicinity of a coolant introduction portion of a cylinder block; 11 is a schematic cross-sectional view of the spacer along line XVII-XVII of FIG. 10; FIG. FIG. 4 is a diagram schematically showing the flow of cooling liquid in the upper portion of the water jacket; FIG. 4 is a diagram schematically showing the flow of cooling liquid in the lower portion of the water jacket; It is the figure which expanded and showed the center peripheral wall 130 periphery in FIG.

A cooling structure for a multi-cylinder engine according to an embodiment of the present invention will be described below with reference to the drawings.

(1) Overall Configuration FIG. 1 is a schematic diagram showing a preferred embodiment of an engine system to which the cooling structure of the present invention is applied. The engine system 100 includes an engine body 1, a water pump 60, a radiator (RAD) 61, an ATF warmer (ATF/W) 62, an oil cooler (O/C) 63, and an EGR cooler (EGR/C) 64. and a heater 65 .

As shown in FIG. 1, the engine body 1 is an in-line four-cylinder four-cycle engine having four substantially cylindrical cylinders 2 arranged in a predetermined direction. The engine body 1 is mounted on a vehicle as a drive source for wheels. The engine body 1 includes a cylinder block 3 in which cylinders 2 are formed, and a cylinder head 4 that is fastened to the cylinder block 3 while covering the upper surface of the cylinder block 3 . A piston (not shown) is fitted in the cylinder 2 so as to be vertically movable. In this embodiment, self-ignition combustion in which the air-fuel mixture self-ignites is performed in at least a part of the operating range. Note that FIG. 1 shows the cylinder block 3 and the cylinder head 4 in a separated state.

The four cylinders 2 formed in the cylinder block 3 are hereinafter referred to as a first cylinder 2a, a second cylinder 2b, a third cylinder 2c, and a fourth cylinder 2d in order from the right side of FIG. Further, the direction in which the cylinders 2 are arranged, that is, the direction in which the cylinders are arranged is called the front-rear direction, and the side of the first cylinder 2a is called the front, and the side of the fourth cylinder 2d is called the rear. In FIG. 1, the cylinder head 4 is shown so as to face in the opposite direction to the cylinder block 3 in the front-rear direction. In the cylinder head 4, an intake port (not shown) for introducing intake air into the cylinder 2 and an exhaust port (not shown) for discharging exhaust gas from the cylinder 2 are arranged across the central axis of the cylinder 2. , are formed separately on one side and the other side in the width direction of the engine body 1 orthogonal to the cylinder arrangement direction. Hereinafter, the width direction of the engine body 1 is referred to as the lateral direction, the side on which the intake port is formed is referred to as the intake side or left, and the opposite side is referred to as the exhaust side or right. In FIG. 1 and the like, "EX" indicates the exhaust side, and "IN" indicates the intake side.

The water pump 60 is a device that discharges coolant for cooling the engine body 1 . A water jacket 20 through which a coolant can flow is formed in the cylinder block 3 , and a water pump 60 introduces the coolant into the water jacket 20 .

Specifically, the cylinder block 3 is provided with a block outer peripheral wall 10 surrounding the cylinder bore walls 2e of the four cylinders 2, and a water jacket 20 is provided between the block outer peripheral wall 10 and the cylinder bore walls 2e of the cylinders 2. are partitioned. The block outer peripheral wall 10 is formed with a cooling liquid introduction portion 15 that opens to the outer peripheral surface thereof and communicates with the water jacket 20 . The water pump 60 is fixed to the cylinder block 3 so as to communicate with the cooling fluid introduction portion 15 , and the cooling fluid discharged from the water pump 60 is introduced into the water jacket 20 via the cooling fluid introduction portion 15 .

The radiator 61 is a device for cooling the cooling liquid, and cools the cooling liquid circulating inside by the running wind of the vehicle, a cooling fan, or the like.

The ATF warmer 62 is a device for warming ATF (ATF: automatic transmission fluid), which is hydraulic fluid of the automatic transmission 9 (see FIG. 2). In other words, in this embodiment, the automatic transmission 9 is connected to the engine body 1 to transmit the rotation of the engine body 1 to a shaft connected to an axle or the like and to convert the rotation speed, and the ATF warmer 62 is automatically Warm the ATF in the transmission 9. The ATF warmer 62 is formed with passages through which the ATF and the cooling liquid respectively flow, and the ATF is heated by heat exchange between the ATF and the cooling liquid flowing through the respective passages in the ATF warmer 62 .

The oil cooler 63 is a device for cooling engine oil, which is lubricating oil for lubricating each part of the engine body 1 . The oil cooler 63 is formed with passages through which the engine oil and the cooling liquid respectively flow, and the engine oil is cooled by heat exchange between the engine oil and the cooling liquid flowing through the respective passages in the oil cooler 63. be.

The EGR cooler 64 is a device for cooling EGR gas. That is, in this embodiment, an exhaust passage (not shown) and an intake passage (not shown) connected to the engine body 1 are connected to the engine body 1 in order to introduce part of the exhaust gas discharged from the engine body 1 into the engine body 1. A communicating EGR passage (not shown) is provided, and the EGR cooler 64 is provided in this EGR passage. The EGR cooler 64 cools EGR gas, which is gas flowing through the exhaust that is recirculated to the intake air (intake introduced into the engine body 1) through the EGR passage. The EGR cooler 64 is formed with passages through which the EGR gas and the cooling liquid respectively flow, and the EGR gas is cooled by heat exchange between the EGR gas and the cooling liquid flowing through the respective passages in the EGR cooler 64. .

The heater 65 is a heating (air-conditioning) heater for introducing warm air into the passenger compartment or the like. The heater 65 is formed with passages through which air and cooling liquid respectively flow, and the air is heated by heat exchange between the air and the cooling liquid flowing through the respective passages in the heater 65 .

As described above, the coolant cools the engine body 1 and exchanges heat with the target fluid in each device. A plurality of passages are provided for circulating the liquid. Specifically, the engine system 100 circulates the coolant between the main passage L10 that circulates the coolant between the water pump 60 and the radiator 61, and between the water pump 60 and the ATF warmer 62 and the oil cooler 63. A first sub-passage L20 and a second sub-passage L30 for circulating coolant between the water pump 60 and the EGR cooler 64 and heater 65 are provided.

The main passage L10 includes a coolant introduction portion 15, a water jacket 20, a first head-side jacket 4a formed in the cylinder head 4, a radiator introduction passage L11 connecting the first head-side jacket 4a and the radiator 61, and a radiator 61 and the water. A radiator lead-out passage L12 that connects with the pump 60 is included.

The first head-side jacket 4a is a passage formed inside the cylinder head 4 and extending in the front-rear direction. The first head-side jacket 4 a is formed so as to pass near the center of each cylinder 2 . The rear end portion of the first head-side jacket 4a and the rear end portion of the water jacket 20 communicate vertically. The first head-side jacket 4a opens on the intake-side side surface of the front end portion of the cylinder head 4, and the radiator introduction passage L11 is connected to this opening 4c (hereinafter referred to as the first head-side lead-out portion 4c). .

In the main passage L10, the coolant discharged from the water pump 60 flows into the water jacket 20 through the coolant introduction portion 15, and enters the first head-side jacket 4a from the rear end of the water jacket 20. After that, it flows into the radiator introduction passage L11 through the first head-side lead-out portion 4c. Thereafter, the coolant is cooled by the radiator 61 and returns to the water pump 60 again through the radiator lead-out passage L12.

A main opening/closing device TS1 for opening and closing the radiator lead-out passage L12 is provided in the radiator lead-out passage L12. The main switchgear TS1 includes a thermostat and an on-off valve. When the temperature of the coolant flowing through the radiator lead-out passage L12 is below a predetermined temperature, the on-off valve of the main opening/closing device TS1 is closed, and the flow of the coolant through the radiator lead-out passage L12 and the main passage L10 is stopped. On the other hand, when the temperature of the coolant flowing through the radiator lead-out passage L12 is equal to or higher than the predetermined temperature, the on-off valve of the main opening/closing device TS1 is opened, allowing the coolant to flow through the radiator lead-out passage L12 and the main passage L10. . This predetermined temperature is set to about 95° C., for example. In this embodiment, the predetermined temperature is changed based on a command from a PCM (Power Control Module) provided in the vehicle. The PCM is a device for controlling each part of the engine system 100, and as is well known, is a microprocessor composed of CPU, ROM, RAM and the like.

The first auxiliary passage L20 is an ATF warmer introduction passage connecting the coolant introduction portion 15, the water jacket 20, the first block side lead-out portion 16 formed in the cylinder block 3, and the first block side lead-out portion 16 and the ATF warmer 62. L21 includes an ATF warmer lead-out passage L22 connecting the ATF warmer 62 and the oil cooler 63, and an oil cooler lead-out passage L23 connecting the oil cooler 63 and the water pump 60.

In the first auxiliary passage L20, the cooling liquid discharged from the water pump 60 flows through the cooling liquid introduction portion 15 into the water jacket 20, and then is discharged from the first block side discharge portion 16 to the ATF warmer introduction passage L21. be done. After the coolant flows into the ATF warmer 62 to heat the ATF, it flows into the oil cooler 63 through the ATF warmer lead-out passage L22. The coolant whose temperature has been lowered by heating the ATF cools the oil in the oil cooler 63 and then returns to the water pump 60 through the oil cooler lead-out passage L23.

The ATF warmer introduction passage L21 is provided with a first auxiliary opening/closing device TS2 for opening and closing the ATF warmer introduction passage L21. The first auxiliary switchgear TS2 includes a thermostat and an on-off valve. When the temperature of the cooling liquid flowing through the ATF warmer introduction passage L21 is lower than the predetermined temperature, the opening/closing valve of the first auxiliary opening/closing device TS2 is closed, and the cooling liquid in the ATF warmer introduction passage L21 and the first auxiliary passage L20 is reduced. Distribution stops. On the other hand, when the temperature of the coolant flowing through the ATF warmer introduction passage L21 is equal to or higher than the predetermined temperature, the opening/closing valve of the first auxiliary opening/closing device TS2 is opened to cool the ATF warmer introduction passage L21 and the first auxiliary passage L20. Liquid can flow. This predetermined temperature is set to about 65° C., for example.

The second auxiliary passage L30 is an EGR cooler introduction passage that connects the coolant introduction portion 15, the water jacket 20, the second block side lead-out portion 17 formed in the cylinder block 3, the second block side lead-out portion 17, and the EGR cooler 64. L31, an EGR cooler lead-out passage L32 connecting the EGR cooler 64 and the heater 65, a heater lead-out passage L33 connecting the second head side jacket 4b formed in the cylinder head 4 and the heater 65, the second head side jacket 4b and the water pump. 60 is included.

The second head-side jacket 4b is a passage formed inside the cylinder head 4 and extending in the front-rear direction. The second head-side jacket 4b is located closer to the exhaust side than the first head-side jacket 4a and passes around the exhaust port of each cylinder 2. As shown in FIG. The second head-side jacket 4b opens at the rear end of the exhaust-side side surface of the cylinder head 4, and the opening 4d (hereinafter referred to as the head-side introduction portion 4d) is connected to the heater lead-out passage L33. . The second head-side jacket 4b opens at the front end of the side surface of the cylinder head 4 on the exhaust side. It is connected.

In the second auxiliary passage L30, the coolant discharged from the water pump 60 flows through the coolant introduction portion 15 into the water jacket 20, and then from the first block side outlet portion 16 to the EGR cooler introduction passage L31. derived. The coolant then flows into the EGR cooler 64 to cool the EGR gas, and then flows into the heater 65 through the EGR cooler lead-out passage L32. The coolant heated by cooling the EGR gas heats the air by the heater 65, and then passes through the heater lead-out passage L33 and flows into the second head-side jacket 4b via the head-side introduction portion 4d. . The coolant cooled by heating the air with the heater 65 moves forward in the second head-side jacket 4b while cooling the cylinder head 4, and passes through the second head-side lead-out portion 4e and the head lead-out passage L34. Return to water pump 60 .

The head lead-out passage L34 is provided with a second auxiliary opening/closing device SV1 for opening and closing the head lead-out passage L34. The second auxiliary opening/closing device SV1 includes a solenoid valve that opens and closes the head lead-out passage L34. The degree of opening of this solenoid valve can be changed to fully closed, fully opened, and an intermediate degree of opening between fully closed and fully opened, and is changed by the PCM according to the operating state of the engine. When the solenoid valve closes, the cooling liquid stops flowing through the head lead-out passage L34 and the second sub-passage L30, and when the solenoid valve opens, the cooling liquid can flow through the head lead-out passage L34 and the second sub-passage L30. .

In this embodiment, the cylinder head 4 is provided with a communication passage 4f that connects the first head-side jacket 4a and the second head-side jacket 4b, and part of the cooling liquid in the first head-side jacket 4a is transferred to the first head-side jacket 4a. It is designed so that it can flow into the 2-head side jacket 4b.

Here, each passage L10, L20, L30 includes a water jacket 20. As shown in FIG. However, as will be described later, due to the spacer 30, the internal space of the water jacket 20 is divided into a passage forming part of the main passage L10, a passage forming part of the first sub-passage L20, and a second sub-passage L30. It is partitioned into a passage that constitutes a part of

(2) Structure Around Engine FIG. 2 is a schematic perspective view of the engine body 1 and its surroundings as seen from the exhaust side. FIG. 3 is a schematic perspective view of the engine body 1 and its surroundings viewed from the intake side. 4 is a schematic perspective view showing the cylinder block 3 and the spacer 30. FIG. FIG. 5 is a schematic top view of the cylinder block 3 when the spacer 30 is not accommodated in the water jacket 20. FIG.

In addition to a cylinder block 3 and a cylinder head 4 , the engine body 1 includes a head cover 6 provided above the cylinder head 4 for covering the camshaft and the like, various accessories 7 and an oil pan provided below the cylinder head 4 . Equipped with 5th grade. The automatic transmission 9 is arranged behind the cylinder block 3 . The radiator 61 is arranged on the intake side of the engine body 1 .

As shown in FIG. 5 and the like, the block outer peripheral wall 10 has a substantially rectangular parallelepiped shape. The block outer peripheral wall 10 includes an exhaust side wall 11 extending in the front-rear direction on the exhaust side and an intake side wall 11 extending substantially parallel to the exhaust side wall 11 on the intake side. 12, a front wall 13 extending in the left-right direction between the front end of the exhaust side wall 11 and the front end of the intake side wall 12, and a rear side wall extending in the left-right direction between the rear end of the exhaust side wall 11 and the rear end of the intake side wall 12. 14.

A plurality of bolt holes 19 are formed in the block outer wall 10 and open to the upper surface thereof. Head bolts for fastening the cylinder block 3 and the cylinder head 4 are screwed into these bolt holes 19 . The exhaust side wall 11 and the intake side wall 12 are formed with bulging portions 18 bulging toward the cylinders at the front end portion, the rear end portion, and the portion facing the portion between the adjacent cylinders 2 . , and a bolt hole 19 is formed in each of these bulging portions 18 .

As shown in FIG. 3, the water pump 60 is connected to the crankshaft via a belt 8a and a plurality of pulleys 8b, and is driven by the crankshaft, i.e., the engine, to discharge coolant. The water pump 60 is fixed to the front end portion of the exhaust side wall 11 , and the coolant introduction portion 15 is formed at the front end portion of the exhaust side wall 11 . As shown in FIG. 5 and the like, the cooling liquid introduction portion 15 is positioned forward of the center of the first cylinder 2a in the longitudinal direction, and is positioned closer to the intake side toward the front of the cylinder bore wall 2e of the first cylinder 2a. facing the curved portion.

As shown in FIG. 3, the first head-side lead-out portion 4c opens at the front end of the side surface of the cylinder head 4 on the intake side, and the radiator introduction passage L11 extends from the front end of the side surface of the cylinder head 4 on the intake side. It extends leftward toward the radiator 61 . The radiator lead-out passage L12 extends from the radiator 61 to the water pump 60 through the front of the engine body 1 . As shown in FIG. 2, the main opening/closing device TS1 is provided near the water pump 60. As shown in FIG.

As shown in FIGS. 3, 5, etc., the first block side lead-out portion 16 is formed in the intake side wall 12 . The first block side lead-out portion 16 is formed at a position facing the second cylinder 2b. The ATF warmer 62 is arranged close to the rear end of the intake side portion of the oil pan 5 . The ATF warmer introduction passage L21 extends from the first block side lead-out portion 16 to the ATF warmer 62 along the side surface of the engine body 1 on the intake side. As shown in FIG. 2, the oil cooler 63 is fixed to the lower part of the side surface of the cylinder block 3 on the exhaust side. The ATF warmer lead-out passage L22 extends from the ATF warmer 62 to the oil cooler 63 under the oil pan 5 . The oil cooler lead-out passage L23 extends obliquely upward and forward from the oil cooler 63 and is connected to the water pump 60 at its upper end.

As shown in FIGS. 2, 5, etc., the second block side lead-out portion 17 is formed in the exhaust side wall 11 . The second block side lead-out portion 17 is formed at a position facing the fourth cylinder 2d. The EGR cooler 64 is arranged behind the cylinder block 3 so as to extend left and right. The EGR cooler introduction passage L31 extends from the second block side lead-out portion 17 so as to wrap around the EGR cooler 64 and is connected to the lower surface of the EGR cooler 64 . The EGR cooler lead-out passage L32 extends upward from the EGR cooler 64 . Although illustration of the heater 65 is omitted in FIG. 2 , the EGR cooler lead-out passage L32 extends to the heater 65 . The head-side introduction portion 4d opens at the rear end of the side surface of the cylinder head 4 on the exhaust side, and the heater lead-out passage L33 extends from the heater 65 to the rear end of the side surface of the cylinder head 4 on the exhaust side. The second head-side lead-out portion 4 e opens at the front end of the side surface of the cylinder head 4 on the exhaust side. The head lead-out passage L34 extends rightward from the front end portion of the side surface on the exhaust side of the cylinder head 4 and then extends downward, and is connected to the water pump 60 at its lower end. The second auxiliary opening/closing device SV1 is provided in the middle portion in the vertical direction of the head lead-out passage L34.

(3) Detailed Structures of Spacer and Water Jacket Detailed structures of the spacer 30 and the water jacket 20 will be described.

FIG. 6 corresponds to FIG. 5 and is a schematic top view of the cylinder block 3 with the spacers 30 housed in the water jacket 20. As shown in FIG. FIG. 7 is a schematic cross-sectional view taken along line VII--VII of FIG. FIG. 8 is a schematic cross-sectional view along line VIII-VIII of FIG. FIG. 9 is a schematic perspective view of the spacer 30. FIG. 10 is a side view of the spacer 30 on the exhaust side, and FIG. 11 is a side view of the spacer 30 on the intake side. FIG. 12 is a schematic cross-sectional view of spacer 30 taken along line XII-XII of FIG. FIG. 13 is a schematic cross-sectional view of spacer 30 along line XIII-XIII of FIG. FIG. 14 is a schematic cross-sectional view along line XIV-XIV in FIG. FIG. 15 is a schematic cross-sectional view along line XV-XV of FIG.

The spacer 30 is housed inside the water jacket 20 in contact with the bottom surface of the water jacket 20 . The spacer 30 is made of, for example, a material (eg, synthetic resin) having a lower thermal conductivity than the material of the cylinder block 3 (eg, aluminum alloy).

The spacer 30 includes a peripheral wall 31 that surrounds the entire outer periphery of the cylinder bore wall 2e of each cylinder 2 and divides the inner space of the water jacket 20 into a cylinder side and a non-cylinder side. The cylinder bore wall 2e and the peripheral wall 31 of the spacer 30 extend along each cylinder 2 in a substantially arc shape when viewed from above. The cylinder bore walls 2e of the adjacent cylinders 2 are connected to each other, and the cylinder bore walls 2e and the peripheral wall 31 are formed by connecting four circles that slightly overlap when viewed from above, and have a shape in which the overlapping portions are removed. there is Hereinafter, the connecting portion between the cylinder bore walls 2e of the adjacent cylinders 2 will be referred to as a bore-to-bore portion 2f. The peripheral wall 31 has approximately the same height as the depth of the water jacket 20 . Along with this, almost the entire water jacket 20 is partitioned into a cylinder side and a non-cylinder side by a peripheral wall 31 .

The peripheral wall 31 facing the cylinder bore wall 2e of the first cylinder 2a is formed with a pair of first guide portions 38 formed of through holes passing through the peripheral wall 31 . These first guide portions 38 face each other in the left-right direction. Each first guide portion 38 faces the rear portion of the first cylinder 2a and extends from a position behind the center of the first cylinder 2a to a position slightly ahead of the rear end of the first cylinder 2 in the longitudinal direction. extended.

A pair of second guide portions 39, which are through holes passing through the peripheral wall 31, are also formed in the peripheral wall 31 facing the cylinder bore wall 2e of the fourth cylinder 2d. These second guide portions 39 face the vicinity of the center of the fourth cylinder 2d and face each other in the left-right direction. Each second guide portion 39 extends in the longitudinal direction from an intermediate position between the center of the fourth cylinder 2d and the front end of the fourth cylinder 2d to an intermediate position between the center and the rear end of the fourth cylinder 2d. The space on the cylinder side of the peripheral wall 31 and the space on the side opposite to the cylinder communicate with each other through these guide portions 38 and 39 .

Hereinafter, the intake-side first guide portion 38 will be referred to as an intake-side first guide portion 38i, the exhaust-side first guide portion 38 as an exhaust-side first guide portion 38e, and the intake-side second guide portion 38e. 39 is referred to as an intake side second guide portion 39i, and the exhaust side second guide portion 39 is referred to as an exhaust side second guide portion 39e.

(dividing wall)
The spacer 30 has a dividing wall 35 that vertically divides the peripheral wall 31 . The partition wall 35 divides the peripheral wall 31 into an upper peripheral wall 32 located on the upper side and a lower peripheral wall 33 located on the lower side over the entire circumference.

The dividing wall 35 is composed of an intermediate flange 35a and a step portion 35b.

Specifically, the peripheral wall 31 is formed with an intermediate flange 35a projecting from a vertical intermediate position of the peripheral wall 31 toward the side opposite to the cylinder. The intermediate flange 35 a is formed over the entire circumference of the peripheral wall 31 . As shown in FIGS. 7 and 8, the intermediate flange 35a protrudes to the vicinity of the block outer peripheral wall 10. As shown in FIGS. As a result, the space between the peripheral wall 31 and the block outer peripheral wall 10, that is, the space on the outer peripheral side of the peripheral wall 31 in the water jacket 20, is generally above and below the intermediate flange 35a over the entire circumference of the peripheral wall 31. It is partitioned into the space of

In addition, the lower portion of the peripheral wall 31 from the rear end of the first guide portion 38 to the front end of the second guide portion 39 is positioned closer to the cylinder than the upper portion on both the intake side and the exhaust side. A stepped portion 35b projecting from the lower end of the upper portion toward the cylinder side is formed at the intermediate position in the vertical direction of this portion. The intermediate flange 35a and the stepped portion 35b are provided at the same height position. The peripheral wall 31 is partitioned into an upper peripheral wall 32 and a lower peripheral wall 33 by the portion 35b. Below, a portion of the peripheral wall 31 from the rear end of the first intake-side guide portion 38i to the front end of the second intake-side guide portion 39i and the rear end of the first exhaust-side guide portion 38e to the second exhaust-side guide portion 38e will be described as appropriate. A portion up to the front end of the portion 39e is collectively referred to as a central peripheral wall 130. As shown in FIG. The upper peripheral wall 32 of the central peripheral wall 130, i.e., the portion above the dividing wall 35 of the central peripheral wall 130, corresponds to the "first peripheral wall" in the claims. The portion below the dividing wall 35 corresponds to the "second peripheral wall" in the claims.

As shown in FIG. 7 and the like, the stepped portion 35b protrudes to the vicinity of the cylinder bore wall 2e. Therefore, the space between the central peripheral wall 130 and the cylinder bore wall 2e, that is, the space on the inner peripheral side of the central peripheral wall 130 in the water jacket 20 is the space above the stepped portion 35b over the entire circumference of the central peripheral wall 130. It is divided into a space on the lower side.

The intermediate flange 35a and the stepped portion 35b are connected to each of the guide portions 38 and 39, and form the lower surfaces of the guide portions 38 and 39, respectively. That is, the guide portions 38 and 39 are formed in the upper peripheral wall 32 that constitutes a portion of the peripheral wall 31 above the intermediate flange 35a and the stepped portion 35b, and open upward from the intermediate flange 35a and the stepped portion 35b. ing.

A portion of the peripheral wall 31 in front of the front end of the first guide portion 38, that is, a portion extending through the front end of the peripheral wall 31 to the front end of the first intake-side guide portion 38i and the front end of the first exhaust-side guide portion 38e (hereinafter referred to as The stepped portion 35b is not formed in the front side peripheral wall 140), and in the front side peripheral wall 140, the peripheral wall 31 is divided into the upper side peripheral wall 32 and the lower side peripheral wall 33 only by the intermediate flange 35a. ing. That is, the inner peripheral surface of this portion is not divided vertically, but only the outer peripheral surface is vertically divided by the intermediate flange 35a. As a result, as shown in FIG. 8, in the area where the front side peripheral wall 140 is provided, the space between the cylinder bore wall 2e and the peripheral wall 31, that is, the space on the inner peripheral side of the peripheral wall 31 is not divided vertically, Only the space between the block outer peripheral wall 10, that is, the space on the outer peripheral side of the peripheral wall 31 is divided vertically by the intermediate flange 35a.

Similarly, the portion of the peripheral wall 31 on the rear side from the rear end of the second guide portion 38, that is, the rear end of the intake side second guide portion 39i and the rear end of the exhaust side second guide portion 39e passing through the rear end of the peripheral wall 31 A portion (hereinafter referred to as rear side peripheral wall 150 as appropriate) extending over the edge of the rear side portion 35b is also not formed with a stepped portion 35b. and a lower peripheral wall 33 . Also in the area where the rear side peripheral wall 150 is provided, the space between the cylinder bore wall 2e and the peripheral wall 31, that is, the space on the inner peripheral side of the peripheral wall 31 is not vertically partitioned, and the space between the peripheral wall 31 and the block outer peripheral wall 10 is not vertically partitioned. Only the space in between, that is, the space on the outer peripheral side of the peripheral wall 31 is vertically partitioned by the intermediate flange 35a.

Here, as shown in FIG. 15, the lower peripheral wall 33 is close to the cylinder bore wall 2e over its entire circumference. Specifically, over the entire circumference of the peripheral wall 31, the clearance between the lower peripheral wall 33 and the block outer peripheral wall 10 is larger than the clearance between the lower peripheral wall 33 and the cylinder bore wall 2e. Along with this, in the lower portion of the water jacket 20 (the space below the dividing wall 35), a passage having a flow area larger than that on the cylinder side is formed on the side opposite to the cylinder.

On the other hand, as shown in FIG. 14, the upper peripheral wall 32 of the central peripheral wall 130 is adjacent to the block peripheral wall 10, and the upper peripheral walls 32 of the front peripheral wall 140 and the rear peripheral wall 150 are adjacent to the cylinder bore wall 2e. Specifically, the gap between the upper peripheral wall 32 of the front peripheral wall 140 and the block outer peripheral wall 10 is larger than the gap between the upper peripheral wall 32 of the front peripheral wall 140 and the cylinder bore wall 2e. The dimension of the gap with the block outer peripheral wall 10 is larger than the dimension of the gap between the upper peripheral wall 32 of the rear side peripheral wall 150 and the cylinder bore wall 2e. On the other hand, the clearance dimension between the upper peripheral wall 32 of the central peripheral wall 130 and the block outer peripheral wall 10 is smaller than the clearance dimension between the upper peripheral wall 32 of the central peripheral wall 130 and the cylinder bore wall 2e. Along with this, in the region where the front side peripheral wall 140 and the rear side peripheral wall 150 are provided in the upper portion of the water jacket 20 (the space above the dividing wall 35), the flow passage area is larger on the non-cylinder side than on the cylinder side. A passage is formed, and in the region of the upper portion of the water jacket 20 where the central peripheral wall 130 is provided, a passage having a larger flow area is formed on the cylinder side than on the anti-cylinder side.

Here, the central peripheral wall 130 extends from the rear portion of the first cylinder 2a to the front portion of the fourth cylinder 2d, and each bore-to-bore portion 2f of the cylinder bore wall 2e faces the central peripheral wall 130. As shown in FIG. As a result, in the region of the water jacket 20 facing the upper portion of each bore-to-bore portion 2f, a passage having a larger flow area is formed on the cylinder side than on the counter-cylinder side.

(distribution wall)
A distribution wall 36 is provided on the outer peripheral surface of the peripheral wall 31 on the exhaust side, and extends vertically and protrudes toward the side opposite to the cylinder (that is, protrudes toward the block outer peripheral wall 10). As shown in FIG. 9 and the like, the distribution wall 36 is located on the front side of the exhaust-side first guide portion 38e. In this embodiment, the distribution wall 36 is positioned slightly forward of the center of the first cylinder 2a in the longitudinal direction. The intermediate flange 35a extends in the circumferential direction of the peripheral wall 31 so as to divide the distribution wall 36 into upper and lower parts. The distribution wall 36 includes an upper distribution wall 36a extending upward from the intermediate flange 35a and an upper distribution wall 36a extending downward from the intermediate flange 35a. and a lower distribution wall 36b.

FIG. 16 is an enlarged view of the front end portion of the cylinder block 3 on the exhaust side. As shown in FIG. 16, the distribution wall 36 and the cooling liquid introduction portion 15 are opposed to each other, and when viewed from the outside of the cooling liquid introduction portion 15, the distribution wall 36 is located at an intermediate position of the cooling liquid introduction portion 15 in the front-rear direction. It extends vertically. A portion of the intermediate flange 35 a that faces the coolant introduction portion 15 is located between the lower end and the upper end of the coolant introduction portion 15 . Accordingly, the space between the opening of the cooling liquid introduction portion 15 on the block outer peripheral wall 10 side and the peripheral wall 31 is defined by a first inflow portion A1 located above the intermediate flange 35a and in front of the upper distribution wall 36a, A second inlet A2 located above the intermediate flange 35a and behind the upper distribution wall 36a, a third inlet A3 located below the intermediate flange 35a and in front of the lower distribution wall 36b, and below the intermediate flange 35a. It is also divided into four spaces with the fourth inflow part A4 located behind the lower distribution wall 36b.

The area of each of the inflow portions A1 to A4 when the peripheral wall 31 is viewed through the cooling liquid introduction portion 15, more specifically, the opening edge of the cooling liquid introduction portion 15 on the block outer peripheral wall side, the intermediate flange 35a and the distribution wall 36 opposite to the cylinder Each area defined by the side edges is set as follows. The area of the first inflow portion A1 and the area of the second inflow portion A2 are set substantially equal. The areas of these first and second inflow portions A1 and A2 are made larger than the areas of the third and fourth inflow portions A3 and A4. The area of the third inflow portion A3 is made smaller than the area of the fourth inflow portion A4. For example, the area of the third inflow portion A3 is set to approximately half the area of the fourth inflow portion A4.

(Details of central wall)
20 is an enlarged view of the periphery of the central peripheral wall 130 in FIG. 12. FIG.

As described above, the peripheral wall 31 extends along the cylinder 2 in a substantially arcuate shape when viewed from above. The central peripheral wall 130 extends from a position forward of the rear end of the first cylinder 2a to a position rearward of the front end of the fourth cylinder 2d. Along with this, the upper peripheral wall 32 of the central peripheral wall 130 includes bore-to-bore corresponding portions 139 that face the three bore-to-bore portions 2f, respectively, and bulges forward and rearward from the bore-to-bore corresponding portions 139 toward the side opposite to the cylinder. It is composed of a part that curves into A portion of the central peripheral wall 130 extending between the bore-to-bore corresponding portions 139 has a substantially semicircular shape when viewed from above, and hereinafter, this portion will be referred to as a curved portion 132 as appropriate.

As described above, the curved portion 132 has a substantially semicircular shape as a whole, but the curvature in the circumferential direction is not constant, and the portion closer to the bore-to-bore corresponding portion 139 has a greater curvature than the portion farther away ( small radius of curvature).

Specifically, in the present embodiment, the curved portion 132 is generally composed of a first portion 133, a pair of second portions 134, and a pair of third portions 135 having different curvatures.

The first portion 133 is a portion extending forward and rearward from a bore center corresponding portion 133c that is a portion located in the center of the adjacent bore corresponding portions 139 . The first portion 133 has an arc shape when viewed from above. Specifically, the first portion 133 extends along a circle whose center is located on a plane passing through the centers of the opposing cylinders 2 and extending in the left-right direction.

The third portion 135 is a portion extending from each bore-to-bore corresponding portion 139 . The third portion 135 also has an arc shape when viewed from above. Specifically, the third portion 135 extending forward from the bore-to-bore corresponding portion 139 extends along a circle whose center is positioned forward and toward the cylinder side of the third portion 135, and extends rearward from the bore-to-bore corresponding portion 139. The extending third portion 135 extends along a circle whose center is located on the rear side and the cylinder side of the third portion 135 . The curvature of the third portion 135 is set to a value larger than the curvature of the first portion 133 .

The second portion 134 is a portion extending over the end of the first portion 133 and the end of the third portion 135 . In this embodiment, the second portion 134 extends linearly when viewed from above. That is, the second portion 134 extending forward from the third portion 135 extending forward from the bore-to-bore corresponding portion 139 extends in a straight line so as to be located on the opposite side of the cylinder toward the front side, and extends rearward from the bore-to-bore corresponding portion 139 . A second portion 134 extending rearward from the third portion 135 extends in a straight line so as to be located on the side opposite to the cylinder toward the rear side. The curvature of the second portion 134 is 0 because it is a straight line.

Thus, in the present embodiment, the curvature of the third portion 135 of the curved portion 132 is the largest, and the bore-to-bore corresponding portion 139 is configured to protrude further toward the cylinder 2 side.

Further, in the portion between the bore-to-bore corresponding portions 139, the amount of protrusion of the stepped portion 35b toward the cylinder side is d1 from the bore-to-bore corresponding portion 139, and d2 from the center bore-to-corresponding portion 133c. is smaller than

In the present embodiment, as shown in FIG. 20, in the portion between the bore corresponding portions 139, the amount of protrusion of the stepped portion 35b toward the cylinder 2 side is from the bore center corresponding portion 133c toward the bore corresponding portion 139. is gradually decreasing. Accordingly, in the present embodiment, the separation distance from the cylinder-side end of the stepped portion 35 b , that is, the cylinder-side end face of the peripheral wall 31 to the upper peripheral wall 32 is the shortest at the bore-to-bore corresponding portion 139 . That is, in the present embodiment, as described above, the upper peripheral wall 32 of the central peripheral wall 130 is configured such that the curvature decreases toward the bore-to-bore corresponding portion 139, while the lower peripheral wall 33 of the central peripheral wall 130 has a lower curvature. The curvature of the portion between the corresponding portions 139 is substantially constant.

A portion of the central peripheral wall 130 surrounding the first cylinder 2a is interrupted in the middle of the curved portion 132 described above. Specifically, the third portion 135 configured as described above extends forward from the bore-to-bore corresponding portion 139 facing the bore-to-bore portion 2f of the first cylinder 2a and the second cylinder 2b. A second portion 134 configured as described above extends forward from 135 . A portion of the first portion 133 configured as described above extends forward from the second portion 134 . Further, the portion of the central peripheral wall 130 surrounding the fourth cylinder 2 d is interrupted in the middle of the second portion 134 . Specifically, the third portion 135 configured as described above extends rearward from the inter-bore corresponding portion 139 facing the inter-bore portion 2f of the third cylinder 2b and the fourth cylinder 2d. A portion of the second portion 134 configured as described above extends rearward from 135 .

(rib)
As shown in FIGS. 12 and 13, the inner peripheral surface of the peripheral wall 31 is provided with a plurality of ribs protruding toward the cylinder.

The peripheral wall 31 is provided with a pair of vertically extending ribs 51a to 51d facing each other across the center of the cylinder 2 for each of the cylinders 2a to 2d. That is, the peripheral wall 31 is provided with a pair of left and right ribs 51 on a plane extending in the left-right direction through the centers of the cylinders 2a to 2d. 13 is a view showing the inner peripheral surface of the peripheral wall 31 on the intake side, and the inner peripheral surface on the exhaust side of the peripheral wall 31 is not shown. The ribs 51a to 51d on the intake side and the ribs 51a to 51d on the exhaust side paired with the ribs 51a to 51d have the same structure.

A pair of left and right first ribs 51 a provided on a plane extending in the left-right direction through the center of the first cylinder 2 a extends from the upper end to the lower end of the front side peripheral wall 140 .

The second rib 51b, the third rib 51c, and the fourth rib 51d, which are the ribs corresponding to the second cylinder 2b, the third cylinder 2c, and the fourth cylinder 2d, respectively, extend downward from the upper end of the lower peripheral wall 33. there is In this embodiment, the second to fourth ribs 51b to 51c extend from the upper end to the lower end of the lower peripheral wall 33, and the fourth rib 51d corresponding to the fourth cylinder 2d extends from the lower edge of the second guide portion 39. extends downward from the

The peripheral wall 31 is also provided with vertically extending ribs 51 at its front and rear ends. That is, the fifth rib 51e is provided at the front end of the peripheral wall 31 (front side peripheral wall 140) surrounding the first cylinder 2a, and the sixth rib 51e is provided at the rear end of the peripheral wall 31 (rear side peripheral wall 150) surrounding the fourth cylinder 2d. A rib 51f is provided. As shown in FIGS. 17, 12, etc., which are cross-sectional views taken along line XVII-XVII of FIG.

(flange)
The spacer 30 has a plurality of flanges in addition to the intermediate flange 35a.

The spacer 30 includes a second flange 42 that forms part of the upper opening edge of each second guide portion 39 and the upper peripheral wall 32 . Each second flange 42 extends from the front end of each second guide portion 39 to a position slightly rearward of the rear end. As shown in FIG. 6, each second flange 42 extends from the vicinity of the block outer peripheral wall 10 to the vicinity of the cylinder bore wall 2e in top view, and the block outer peripheral wall 10 and the cylinder bore in the region where each second guide portion 38 is formed. It covers almost the entire upper part of the gap with the wall 2e.

The spacer 30 includes a pair of first flanges 41 projecting from the upper ends of the portions of the upper peripheral wall 32 where the first guide portions 38 are formed, respectively, toward the side opposite to the cylinder. The first flange 41 extends over the entire first guide portion 38 in the front-rear direction. In other words, the first flange 41 extends across the rear edge of the front peripheral wall 140 and the front edge of the central peripheral wall 130 in the front-rear direction.

The spacer 30 includes a third flange 43 projecting from the upper end of the front peripheral wall 140 toward the side opposite to the cylinder. The third flange 43 extends from the same position as the rear end of the coolant introduction portion 15 in the front-rear direction to the front end of the intake-side first guide portion 38i around the front side.

The intake-side first flange 41 corresponding to the intake-side first guide portion 38i extends rearward continuously from the intake-side rear end portion of the third flange 43 . The first flange 41 on the exhaust side corresponding to the first guide portion 38e on the exhaust side extends rearward from a position slightly spaced rearward from the rear end portion of the third flange 43 on the exhaust side.

Thus, in the present embodiment, a flange projecting toward the side opposite to the cylinder is provided over substantially the entire circumference of the upper end of the peripheral wall 31 surrounding the first cylinder 2a. As shown in FIG. 6 and the like, the flanges (each of the first flange 41 and the third flange 43) extend to the vicinity of the block outer peripheral wall 10 as a whole. As a result, substantially the entire space above the space between the peripheral wall 31 surrounding the first cylinder 2a and the block outer peripheral wall 10, including the space between the front side peripheral wall 140 and the block outer peripheral wall 10, is formed by the flange. will be covered.

Here, as described above, the bulging portion 18 is formed at each front end portion of the exhaust side wall 11 and the intake side wall 12 . Correspondingly, in the present embodiment, the exhaust-side end of the front end of the third flange 43 corresponds to the bulging portion of the front end of the exhaust side wall 11 (hereinafter, appropriately referred to as the first exhaust-side bulge) when viewed from above. ) 18e so as to be recessed toward the cylinder side, and has a shape surrounding the exhaust-side first bulging portion 18e. The intake-side end of the front end of the third flange 43 extends along the bulging portion (hereinafter referred to as the intake-side first bulging portion) 18i at the front end of the intake side wall 12 when viewed from above. It is curved so as to be recessed to the side, and has a shape surrounding the intake-side first swelling portion 18i.

A plurality of regulating portions 43a that protrude upward are provided on the upper surface of the portion of the third flange 43 that is the front end portion of the third flange 43 and extends in the left-right direction along the front side wall 13 . These restricting portions 43a extend in the front-rear direction and are arranged parallel to each other in the left-right direction. The restricting portion 43a extends over the entire upper surface of the front end portion of the third flange 43 in the front-rear direction.

As shown in FIG. 9 and the like, the spacer 30 includes a fourth flange 44 that extends vertically and protrudes rearward from the rear end portion of the upper peripheral wall 32 . A fourth flange 44 extends from the upper end of the upper peripheral wall 32 to the intermediate flange 35a. As shown in FIG. 9 and the like, the spacer 30 includes a fifth flange 45 and a sixth flange 46 extending in the circumferential direction of the peripheral wall 31 and protruding from the lower end of the peripheral wall 31 and a portion slightly above the lower end of the peripheral wall 31 toward the anti-cylinder side. . These fifth and sixth flanges 45 and 46 are provided over the entire circumference of the peripheral wall 31 .

As shown in FIGS. 11, 15, etc., the spacer 30 includes a first restricting flange 47 protruding from the intake-side outer peripheral surface of the portion of the lower peripheral wall 33 surrounding the second cylinder 2b toward the side opposite to the cylinder. The first restricting flange 47 extends vertically across the intermediate flange 35 a and the fifth flange 46 . The first block side lead-out portion 16 is provided at a position facing the lower peripheral wall 33 . The first restricting flange 47 is provided rearward of the first block-side lead-out portion 16 .

As shown in FIGS. 10, 15, etc., the spacer 30 includes a second restricting flange 48 projecting from the outer peripheral surface of the portion of the lower peripheral wall 33 surrounding the fourth cylinder 2d on the exhaust side toward the side opposite to the cylinder. The second restricting flange 48 extends vertically across the intermediate flange 35 a and the fifth flange 45 . The second block side lead-out portion 17 is provided at a position facing the lower peripheral wall 33 . The second restricting flange 48 is provided behind the second block-side lead-out portion 17 .

As shown in FIGS. 9, 12, etc., the spacer 30 extends in the vertical direction at the portion of the upper peripheral wall 32 facing the inter-bore portion 2f, that is, the outer peripheral surface of the inter-bore corresponding portion 139. A reinforcing rib 52 protruding from the outer peripheral surface of the peripheral wall 32 toward the side opposite to the cylinder is provided. Each reinforcing rib 52 extends from near the upper end of the upper peripheral wall 32 to the intermediate flange 35a.

(4) Flow of Cooling Liquid in Water Jacket The flow of cooling liquid in the water jacket 20 will be described. 18 shows the flow in the upper space of the water jacket 20 (the space above the dividing wall 35 of the water jacket 20), and FIG. FIG. 2 is a diagram schematically showing the flow of the lower space).

The cooling liquid discharged from the water pump 60 is introduced into the water jacket 20 through the cooling liquid introduction portion 15 . At this time, the cooling liquid flows separately into the first to fourth inflow portions A1 to A4. The cooling liquid that has flowed into each of the inflow portions A1 to A4 flows as follows.

(Coolant that has flowed into the first inflow portion A1 and the second inflow portion A2)
The coolant that has flowed into the first inflow portion A1 defined above the intermediate flange 35a flows through the upper space of the water jacket 20. As shown in FIG.

The coolant that has flowed into the first inflow portion A1 first flows through the first inflow portion around the front side of the passage defined between the peripheral wall 31 above the intermediate flange 35a, that is, the upper peripheral wall 32, and the block outer peripheral wall 10. It passes through a portion extending from A1 to the intake side first guide portion 38i (hereinafter referred to as the first upper passage 21u as appropriate) and moves to the intake side first guide portion 38i.

In the intake-side first guide portion 38i, the intermediate flange 35a and the stepped portion 35b are connected. In a region behind the intake-side first guide portion 38i, the space on the inner peripheral side of the peripheral wall 31 is vertically partitioned by the stepped portion 35b. Above the stepped portion 35b in this region, the upper peripheral wall 32 of the central peripheral wall 130 defines a passage having a larger flow area on the cylinder side than on the anti-cylinder side. As a result, most of the cooling liquid that has reached the intake-side first guide portion 38i passes through the cylinder-side passage above the stepped portion 35b and having a large flow area, that is, the intake-side portion of the upper peripheral wall 32 of the central peripheral wall 130. and the cylinder bore wall 2e (hereinafter referred to as second upper passage 22u). Then, the coolant moves rearward through the second upper passage 22u to the intake side second guide portion 39i.

In the intake-side second guide portion 39i, the stepped portion 35b and the intermediate flange 35a are connected. In a region behind the intake-side second guide portion 39i, a space on the outer peripheral side of the peripheral wall 31 is divided vertically by the intermediate flange 35a. Further, above the intermediate flange 35a in this region, a passage having a flow area larger than that on the cylinder side is defined by the rear peripheral wall 150 on the side opposite to the cylinder. As a result, most of the coolant that has reached the intake-side second guide portion 39i passes through the non-cylinder-side passage above the intermediate flange 35a and having a large flow area, that is, the upper peripheral wall 32 of the rear peripheral wall 150 and the cylinder bore. It flows into a passage partitioned between itself and the wall 2e (hereinafter referred to as a third upper passage 23u as appropriate). The third upper passage 23u communicates with the first head-side jacket 4a, and the coolant that reaches the third upper passage 23u flows into the first head-side jacket 4a.

The coolant that has flowed into the second inflow portion A2 formed above the intermediate flange 35a also flows through the upper space of the water jacket 20. As shown in FIG.

The coolant that has flowed into the second inflow portion A2 first flows rearward from the second inflow portion A2 in the passage defined between the peripheral wall 31 above the intermediate flange 35a, that is, the upper peripheral wall 32, and the block outer peripheral wall 10. It passes through the extending portion (hereinafter referred to as the fourth upper passage 24u as appropriate) toward the exhaust-side first guide portion 38e.

In the exhaust-side first guide portion 38e, the intermediate flange 35a and the stepped portion 35b are also connected. Further, in the area behind the first guide portion 38e on the exhaust side, the space on the inner peripheral side of the peripheral wall 31 is divided vertically by the stepped portion 35b, and in the upper space, the upper peripheral wall 32 of the central peripheral wall 130 divides the space on the cylinder side. A passage having a flow passage area larger than that on the counter-cylinder side is defined on the side. As with the intake side, most of the coolant that has reached the first guide portion 38e on the exhaust side is located above the stepped portion 35b and passes through the cylinder side passage having a large flow area, that is, the upper side of the central peripheral wall 130. It flows into a passage defined between the exhaust-side portion of the peripheral wall 32 and the cylinder bore wall 2e (hereinafter referred to as a fifth upper passage 25u as appropriate). Then, the cooling liquid moves rearward in the fifth upper passage 25u and reaches the exhaust-side second guide portion 39e. As with the intake side, most of the coolant that has reached the second guide portion 39e on the exhaust side flows into the third upper passage 23u, that is, the passage on the counter-cylinder side, which has a larger passage area than the cylinder side, After that, it flows into the first head-side jacket 4a.

The third upper passage 23u is divided into an intake side and an exhaust side by a fourth flange 44, and the cooling liquid flowing from the first inflow portion A1 flows into the first intake side portion of the third upper passage 23u. The coolant that has flowed into the head-side jacket 4a and has flowed from the second inflow portion A2 flows into the first head-side jacket 4a at the exhaust-side portion of the third upper passage 23u.

Thus, the coolant that has flowed into the first inflow portion A1 and the second inflow portion A2 passes through the passage along the upper peripheral wall 32, that is, the passage that is partitioned above the dividing wall 35 of the water jacket 20. The first to fifth upper passages 25u and the respective guide portions through which the cooling liquid that has flowed into the first inflow portion A1 and the second inflow portion A2 passes through the first head-side jacket 4a. 38 and 39 constitute the portion formed in the water jacket 20 of the main passage L10. In the following description, the inner space of the water jacket 20, which is defined above the dividing wall 35, is referred to as an upper passage 20u.

As described above, in the upper passage 20u, the coolant passes through the outer peripheral side of the peripheral wall 31 in the portion along the front side peripheral wall 140 and the rear side peripheral wall 150, and the cooling liquid flows in the inner peripheral side of the peripheral wall 31 in the portion along the central peripheral wall 130. It is designed to pass. As a result, the coolant does not directly contact the cylinder bore wall 2e in the front portion of the first cylinder 2a and the rear portion of the fourth cylinder 2d. The cooling liquid comes into direct contact with the upper portion of the cylinder bore wall 2e.

In this embodiment, the third flange 43, the first rib 51d, and the fifth rib 51e reliably prevent direct contact between the coolant and the cylinder bore wall 2e on the front side of the first cylinder 2a. .

Specifically, the flow direction of part of the cooling liquid that has flowed into the first and second inflow portions A1 and A2 is directed upward as it collides with the front side peripheral wall 140 that faces the inflow portions A1 and A2. On the other hand, in the present embodiment, as described above, the space between the coolant introduction portion 15 and the front peripheral wall 140 is covered with the third flange 43 above. Therefore, in the vicinity of the first and second inflow portions A1 and A2, the coolant is prevented from flowing over the upper end of the front side peripheral wall 140 to the inner peripheral side of the front side peripheral wall 140, and the coolant is prevented from flowing into the front side portion of the first cylinder 2a. Direct contact with the cylinder bore wall 2e is avoided.

In addition, in the first upper passage 21u along the front peripheral wall 140, the passage area is reduced by the first exhaust-side bulging portion 18e and the first intake-side bulging portion 18i. The speed of the cooling liquid that has vigorously flowed into the first inflow portion A1 is further increased when passing through the first swelling portions 18e and 18i. As a result, the flow of the cooling liquid becomes turbulent on the downstream side of the first bulging portions 18e and 18i, and the flow direction of some of the cooling liquid is upward. On the other hand, in the present embodiment, the space between the front side peripheral wall 140 and the block outer peripheral wall 10 is also covered with the third flange 43 on the downstream side of the first bulging portions 18e and 18i. . Therefore, the third flange 43 prevents the coolant from flowing over the upper end of the front peripheral wall 140 into the space closer to the cylinder than the front peripheral wall 140 .

Also, part of the coolant may move forward after passing through each first guide portion 38 and enter the gap between the front peripheral wall 140 and the cylinder bore wall 2e. In contrast, in the present embodiment, the inner peripheral surface of the front side peripheral wall 140 is divided in the peripheral direction by the first rib 51a and the fifth rib 51e. That is, the provision of the first rib 51a and the fifth rib 51e prevents the inner peripheral surface of the front side peripheral wall 140 from becoming a continuous peripheral surface. Therefore, the cooling liquid is prevented from flowing along the inner peripheral surface of the front side peripheral wall 140, and part of the cooling liquid that reaches the first guide portions 38 enters the inner peripheral side of the front side peripheral wall 140. is also avoided.

Further, in the present embodiment, the sixth rib 51f reliably avoids direct contact between the cylinder bore wall 2e in the rear portion of the fourth cylinder 2d and the coolant.

Specifically, the inner peripheral surface of the rear side peripheral wall 150 is divided by the sixth ribs 51f in the same manner as the fifth ribs 51e. This prevents the coolant from flowing along the inner peripheral surface of the rear peripheral wall 150 , and part of the coolant that has passed through the second guide portion 39 enters the inner peripheral side of the rear peripheral wall 150 . to avoid direct contact with the cylinder bore wall 2e of the fourth cylinder 2d.

In addition, in the present embodiment, the second to fourth ribs 51b to 51d prevent the coolant flowing through the second upper passage 22u and the fifth upper passage 25u from leaking below the stepped portion 35b. It's like

Specifically, if the inner peripheral surface of the lower peripheral wall 33 below the second upper passage 22u were to be continuous, a flow would be formed along this inner peripheral surface as indicated by the dashed line in FIG. Along with this flow, the coolant tends to leak downward from the second upper passage 22u. On the other hand, the lower peripheral wall 33 below the second upper passage 22u, that is, the inner peripheral surface of the lower peripheral wall 33 facing the second to fourth cylinders 2b to 2d is formed by the second to fourth ribs 51b to 51d. The division by 51d prevents the flow from being formed. Therefore, the coolant in the second upper passage 22u is prevented from leaking downward. Similarly, in the fifth upper passage 25u, the inner peripheral surface of the lower peripheral wall 33 below the fifth upper passage 25u is divided by the second to fourth ribs 51b to 51d on the exhaust side. Formation of a flow along the peripheral surface is prevented, and downward leakage of the cooling liquid flowing through the fifth upper passage 25u is avoided.

(Coolant that has flowed into the third inflow portion A3)
The coolant that has flowed into the third inflow portion A3 formed below the intermediate flange 35a flows through the lower space of the water jacket 20. As shown in FIG.

The cooling liquid that has flowed into the third inflow portion A3 passes through a passage defined between the peripheral wall 31 below the intermediate flange 35a, that is, the lower peripheral wall 33, and the block outer peripheral wall 10, and flows forward from the third inflow portion A3. , then turn around to the intake side. The coolant that has flowed into the intake side moves rearward through a passage defined between the lower peripheral wall 33 on the intake side and the block outer peripheral wall 10 . As described above, the first restricting flange 47 is provided on the intake-side side surface of the lower peripheral wall 33 behind the first block-side lead-out portion 16 . Therefore, the coolant is restricted from moving further rearward by the first restricting flange 47 and introduced into the first block side lead-out portion 16 . Then, the coolant is led out of the water jacket 20 through the first block side lead-out portion 16 .

In this way, the coolant that has flowed into the third inflow portion A3 is led out to the first block side lead-out portion 16, and is located between the lower side peripheral wall 33 and the block outer peripheral wall 10 and in the third inflow portion A3. A passage that is between the portion A3 and the first restricting flange 47 and that passes through the front side of the peripheral wall 31 (hereinafter referred to as a first lower passage 21d as appropriate) constitutes part of the first auxiliary passage L20.

(Fourth inflow part A3)
The coolant that has flowed into the fourth inflow portion A4 formed below the intermediate flange 35a flows through the lower space of the water jacket 20. As shown in FIG.

The cooling liquid that has flowed into the fourth inflow portion A4 moves rearward through a passage defined between the peripheral wall 31 below the intermediate flange 35a, that is, the lower peripheral wall 33, and the block outer peripheral wall 10. As shown in FIG. As described above, the second restricting flange 48 is provided on the exhaust-side side surface of the lower peripheral wall 33 at a position behind the second block-side lead-out portion 17 . Therefore, the cooling liquid is restricted from moving further rearward by the second restricting flange 48 and introduced into the second block side lead-out portion 17 . Then, the coolant is led out of the water jacket 20 through the second block side lead-out portion 17 .

In this way, the coolant that has flowed into the fourth inflow portion A4 is led out to the second block side lead-out portion 17, and is located between the lower peripheral wall 33 and the block outer peripheral wall 10 and in the fourth inflow port A4. A passage along the exhaust side of the peripheral wall 31 between the portion A4 and the second regulating flange 48 (hereinafter referred to as a second lower passage 22d) constitutes a part of the second auxiliary passage L20. .

(5) Functions, etc. As described above, in the present embodiment, the peripheral wall 31 and the dividing wall 35 allow the coolant to flow through the inner space of the water jacket 20. Each lower passage 21d, 22d located respectively is formed. In the central peripheral wall 130, the channel area between the upper peripheral wall 32 and the cylinder bore wall 2e is made larger than the channel area between the upper peripheral wall 32 and the block outer peripheral wall 10, so that the upper peripheral wall 32 and the cylinder bore wall 2e constitutes a part of the upper passage 20u, and the upper portions of the cylinder bore walls 2e of the second and third cylinders 2b and 2c and the upper portions of the inter-bore portions 2f and the coolant are in direct contact with each other. On the other hand, each of the lower passages 21d and 22d is configured so that the cylinder bore wall 2e of each cylinder 2 and the coolant do not come into direct contact with each other. Further, the upper passage 20u is configured so that the front portion of the first cylinder 2a and the rear portion of the fourth cylinder 2d do not come into direct contact with the coolant.

As a result, the cylinder bore walls 2e of the second and third cylinders 2b and 2c, which tend to become hot due to the presence of other cylinders on both sides, and the bore-to-bore portion 2f, which tends to become hot by receiving combustion energy from the two cylinders. The upper part, which is particularly prone to high temperatures due to its proximity to the combustion chamber, can be reliably cooled by direct contact with the coolant. Other portions that are likely to be maintained at a relatively low temperature, specifically, the front portion of the cylinder bore wall 2e of the first cylinder 2a, the rear portion of the cylinder bore wall 2e of the fourth cylinder 2d, and the cylinders 2a to 2d. It is possible to avoid excessive cooling of the lower portion of the cylinder bore wall 2e of , due to direct contact with the coolant. Therefore, the temperatures of the combustion chambers of the cylinders 2a to 2d can be adjusted to appropriate temperatures. In particular, in this embodiment, as described above, self-ignition combustion is performed in the combustion chamber. Therefore, if the cylinder bore wall 2e is cooled excessively, the temperature in the combustion chamber becomes too low, and there is a risk that the self-ignition combustion will not occur stably. On the other hand, as described above, by avoiding excessive cooling of the cylinder bore wall 2e, the stability of autoignition combustion can be enhanced.

Moreover, in the present embodiment, the projection amount of the portion of the stepped portion 35b that projects from the bore-to-bore corresponding portion 139 toward the cylinder side is smaller than the projection amount of the bore center corresponding portion 133c of the stepped portion 35b. It is formed to be

Therefore, in the portion facing the inter-bore portion 2f, an appropriate gap is provided between the lower peripheral wall 33 and the cylinder bore wall 2e to improve the mountability of the spacer 30 and the reliability of the spacer 30. It can be brought closer to the inter-bore portion 2f. Since the upper peripheral wall 32 can be brought closer to the inter-bore portion 2f, the contact between the inter-bore portion 2f, which tends to be particularly high in temperature, of the upper portion of the cylinder bore wall 2e and the cooling liquid is promoted, thereby lowering the temperature of the inter-bore portion 2f. can be effectively reduced. In addition, the flow velocity of the cooling liquid when passing through the inter-bore portion 2f can be increased, which also effectively reduces the temperature of the inter-bore portion 2f.

Further, in the present embodiment, in the upper peripheral wall 32 of the central peripheral wall 130, the curvature of the portion extending from the bore-to-bore corresponding portion 139 toward the side opposite to the cylinder, that is, the third portion 135 is greater than that of the bore center corresponding portion 133c and the curvature of the first portion. It is formed so as to be smaller than the curvature of 133 . Therefore, the flow direction of the coolant can be directed more towards the cylinder side in the bore-to-bore corresponding portion 139, and the contact between the coolant and the bore-to-bore portion 2f can be further promoted. Therefore, the inter-bore portion 2f can be cooled more effectively.

Further, in the present embodiment, the amount of protrusion of the stepped portion 35b toward the cylinder side gradually decreases from the bore center corresponding portion 133c toward the inter-bore corresponding portion 139. The flow area of the passage through which the cooling liquid flows is gradually reduced. Therefore, the coolant can smoothly flow from the bore center corresponding portion 133 c toward the inter-bore corresponding portion 139 . As a result, the cooling liquid can be appropriately flowed even in a portion having a small flow passage area between the bore-to-bore corresponding portion 139 and the bore-to-bore portion 2f.

Further, in the present embodiment, reinforcing ribs 52 extending in the vertical direction and protruding toward the side opposite to the cylinder are provided on portions of the upper peripheral wall 32 that face the respective bore-to-bore portions 2f. Therefore, by increasing the rigidity of each bore-to-bore corresponding portion 139, it is possible to suppress deformation or the like of each bore-to-bore corresponding portion 139 to which a high pressure is applied from the coolant due to the passage of the coolant at high speed, as described above.

(6) Modifications In the above embodiment, the case where self-ignition combustion is performed in the combustion chamber has been described, but the form of combustion performed in the combustion chamber is not limited to this. Also, the number of cylinders is not limited to the above.

1 Engine Body 2 Cylinder 2e Cylinder Bore Wall 3 Cylinder Block 10 Block Peripheral Wall 15 Cooling Fluid Inlet Portion 20 Water Jacket 30 Spacer 31 Peripheral Wall 35a Stepped Portion 52 Reinforcement Rib 60 Water Pump 130 Central Peripheral Wall 133c Bore Center Corresponding Portion 139 Inter-Bore Corresponding Portion

Claims (4)

An engine body including a cylinder block in which a plurality of cylinders arranged in a line is formed, wherein the cylinder block is provided with a block outer peripheral wall surrounding cylinder bore walls of the plurality of cylinders, and the block outer peripheral wall and the plurality of cylinders are separated from each other. A cooling structure for a multi-cylinder engine in which a water jacket through which coolant flows is defined between the cylinder bore wall and the
The cylinder block is formed with a water jacket in which a cooling liquid flows and a cooling liquid introduction portion for introducing the cooling liquid into the water jacket,
The water jacket accommodates a spacer including a peripheral wall surrounding cylinder bore walls of a plurality of cylinders,
The outer peripheral surface of the cylinder bore wall and the inner peripheral surface of the peripheral wall facing the outer peripheral surface are formed to extend in a substantially arc shape when viewed from the top for each cylinder,
At least a part of the peripheral wall includes a first peripheral wall constituting an upper portion thereof, a stepped portion projecting from a lower end of the first peripheral wall toward the cylinder side, and a second peripheral wall extending downward from an end portion of the stepped portion on the cylinder side. a peripheral wall;
When the portion of the first peripheral wall facing the connection portion of the cylinder bore wall of each cylinder is the bore-to-bore corresponding portion, and the first peripheral wall positioned at the center of the adjacent bore-to-bore corresponding portion is the bore center corresponding portion, The stepped portion is formed so that the projection amount of the portion projecting from the bore-to-bore corresponding portion toward the cylinder side is smaller than the projection amount of the portion projecting from the bore center corresponding portion toward the cylinder side,
A multi-cylinder engine , wherein the first peripheral wall is formed such that the curvature of the portion extending from the bore-to-bore corresponding portion toward the counter-cylinder side is smaller than the curvature of the central bore corresponding portion. cooling structure. In the cooling structure for a multi-cylinder engine according to claim 1 ,
The cooling structure for a multi-cylinder engine, wherein the spacer includes a vertically extending reinforcing rib projecting from an outer peripheral surface of the bore-to-bore corresponding portion. In the cooling structure for a multi-cylinder engine according to claim 1 or 2 ,
A cooling structure for a multi-cylinder engine, wherein a projection amount of the stepped portion from the first peripheral wall toward the cylinder side gradually decreases from the bore center corresponding portion toward the bore-to-bore corresponding portion. An engine body including a cylinder block in which a plurality of cylinders arranged in a line is formed, wherein the cylinder block is provided with a block outer peripheral wall surrounding cylinder bore walls of the plurality of cylinders, and the block outer peripheral wall and the plurality of cylinders are separated from each other. A cooling structure for a multi-cylinder engine in which a water jacket through which coolant flows is defined between the cylinder bore wall and the
The cylinder block is formed with a water jacket in which a cooling liquid flows and a cooling liquid introduction portion for introducing the cooling liquid into the water jacket,
The water jacket accommodates a spacer including a peripheral wall surrounding cylinder bore walls of a plurality of cylinders,
The outer peripheral surface of the cylinder bore wall and the inner peripheral surface of the peripheral wall facing the outer peripheral surface are formed to extend in a substantially arc shape when viewed from the top for each cylinder,
At least a part of the peripheral wall includes a first peripheral wall constituting an upper portion thereof, a stepped portion projecting from a lower end of the first peripheral wall toward the cylinder side, and a second peripheral wall extending downward from an end portion of the stepped portion on the cylinder side. a peripheral wall;
When the portion of the first peripheral wall facing the connection portion of the cylinder bore wall of each cylinder is the bore-to-bore corresponding portion, and the first peripheral wall positioned at the center of the adjacent bore-to-bore corresponding portion is the bore center corresponding portion, The stepped portion is formed so that the projection amount of the portion projecting from the bore-to-bore corresponding portion toward the cylinder side is smaller than the projection amount of the portion projecting from the bore center corresponding portion toward the cylinder side, A cooling structure for a multi-cylinder engine, wherein a projection amount of the stepped portion from the first peripheral wall toward the cylinder side gradually decreases from the bore center corresponding portion toward the bore-to-bore corresponding portion.

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