JP2005315118A - Cylinder block cooling structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling structure for a cylinder block capable of uniform cooling.
A cooling structure 1 of a cylinder block has partition plates 22, a recess 21 is provided between the partition plates 22, and a running water shielding plate 24 is located at one end of the recess 21. Yes. The cooling water introduced from the direction indicated by the arrow 100 flows from the lower bore 10L through the recess 21 to the upper bore 10H as indicated by the arrow 103.
[Selection] Figure 4

Description

  The present invention relates to a cooling structure for a cylinder block, and in particular to provide a cooling structure for a cylinder block that can cool the cylinder block uniformly.

Conventionally, the cooling structure of a cylinder block is disclosed by Unexamined-Japanese-Patent No. 2000-345838 (patent document 1), for example.
JP 2000-345838 A

  In the prior art, a partition member is provided for partitioning the cooling water to flow in a separate system of a high flow rate region and a low flow rate region at a predetermined length in the axial direction of a cylinder block provided with a water jacket around the cylinder bore. In this technique, the passage cross-sectional area of the high flow rate region is constant, and a temperature difference occurs between the upstream side and the downstream side. In order to solve this problem, since the sectional area of the partition member is changed between the upstream side and the downstream side, it is necessary to incline, the bore corresponding hole of the partition member becomes an ellipse, and the processing management of the partition member increases. was there.

  Accordingly, the present invention has been made to solve the above-described problems, and an object thereof is to provide a cylinder block cooling structure capable of uniform cooling.

  A cylinder block cooling structure according to the present invention includes a cylinder block having a water jacket portion for cooling a cylinder wall of an internal combustion engine, and a partition plate which is inserted into the water jacket portion and is formed to partition the upper and lower sides. Between the cylinders, there is provided a recess that becomes a through-passage that penetrates vertically. A running water shielding plate is located on the partition plate.

  In the cooling structure of the cylinder block configured as described above, the flow velocity of the cooling medium can be improved by the recess serving as the through passage. As a result, the cooling efficiency around the combustion chamber is improved, and uniform cooling is possible.

  Preferably, the running water shielding plate is located at one end of the recess.

  Preferably, each cylinder has first and second recesses, and the areas of the first and second recesses are equal or different. In this case, the area of the concave portion can be set according to the necessary portion for each cylinder, and appropriate cooling can be realized for each cylinder.

  Preferably, it has a cylindrical body that is integrally formed with the partition plate and extends toward the lower end of the bore, the thickness of the cylinder varies depending on the cylinder part, and the cylinder is in contact with the outer wall of the water jacket portion. In this case, the lower part of the bore can be covered with the cylindrical body, and overcooling at the lower part can be suppressed.

  More preferably, the partition plate and the cylindrical body are integrally formed of a resin body. In this case, the partition plate and the cylindrical body can be formed integrally with the resin, so that the manufacturing cost can be reduced.

  Preferably, the partition plate is located at least one half of the stroke from the upper end of the bore. In this case, overcooling at the lower part can be suppressed.

  More preferably, the inlet of the cooling medium to the water jacket portion is provided below the partition plate. In this case, the cooling rate of the upper part of the partition plate can be improved.

  According to the present invention, it is possible to provide a cylinder block cooling structure that enables uniform cooling.

  Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a schematic perspective view showing a cooling structure of a cylinder block according to the first embodiment of the present invention. FIG. 2 is a diagram for explaining the flow of the cooling water. Referring to FIGS. 1 and 2, in cylinder block cooling structure 1 according to the first embodiment of the present invention, cylinder block 10 and cylinder head 30 are cooled by cooling water. A cylinder liner assembly 11 having a plurality of bore regions 111, 112, 113 and 114 is provided inside the cylinder block 10, and the cylinder liner assembly 11 is surrounded by a water jacket portion 12. A cylinder head 30 is placed on the cylinder block 10, and devices such as cams and valves are accommodated in the cylinder head 30.

  The cylinder liner assembly 11 extends in the longitudinal direction from the front side 10f to the rear side 10r of the engine, and a plurality of bore regions 111, 112, 113, 114 are arranged along the longitudinal direction. In the bore regions 111, 112, 113, 114, heat is generated by the combustion of the fuel, and it is necessary to remove this heat. Therefore, cooling water as a cooling medium is used, and heat is removed by flowing this cooling water around the cylinder liner assembly 11.

  Specifically, cooling water is supplied from the water pump 300 as indicated by an arrow 100. The cooling water passes around the cylinder liner assembly 11 as indicated by an arrow 101, flows upward along the water jacket partition plate 20, and enters the cylinder head 30. Cooling water flows in the cylinder head 30 as indicated by an arrow 102, and this cooling water is sent to the radiator.

  Referring to FIG. 2, the cylinder block 10 has a bore upper part 10H and a bore lower part 10L. A plurality of bore regions 111, 112, 113, 114 are provided in the cylinder block 10, and a partition plate 22 that is a part of the water jacket partition plate 20 around the cylindrical bore regions 111, 112, 113, 114. Is provided. The partition plate 22 partitions the lower bore portion 10L and the upper bore portion 10H, and a running water shielding plate 24 is disposed at the end of the partition plate 22. The running water is blocked by the running water shielding plate 24.

  A recess 21 as a notch is provided next to the running water shielding plate 24, and cooling water flows in the recess 21 from the lower bore 10L toward the upper bore 10H. A cylinder head 30 is placed on the cylinder block 10, and the cylinder head 30 is connected to the radiator 60. The radiator 60 can discharge the heat of the cooling water to the outside, and has an effect as a heat exchanger. The radiator 60 is connected to the water pump 300 via a thermostat 63. A part of the cooling water of the cylinder head 30 is supplied to the throttle body 61 and the heater 62.

  Next, the flow of cooling water will be described with reference to FIG. Cooling water supplied from the water pump 300 toward the cylinder block 10 in the direction indicated by the arrow 100 enters the lower bore portion 10L. Here, the air flows to the bore upper part 10H side through the recess 21, and the cylinder liner assembly 11 is cooled in the bore upper part 10H. The cooling water that has finished cooling the cylinder liner assembly 11 flows in the direction indicated by the arrow 101 and reaches the cylinder head 30. In the cylinder head 30, the cooling water flowing in the direction indicated by the arrow 102 in the predetermined passage cools the cam in the cylinder head 30, exits the cylinder head 30, and flows to the radiator 60. In the radiator 60, the cooling water is cooled by the traveling wind, and the cooling water dissipates the heat absorbed in the cylinder block 10 and the cylinder head 30 to the outside. Thus, the cooling water having a low temperature enters the thermostat 63 and is supplied to the water pump 300 again.

  A part of the cooling water of the cylinder head 30 is supplied to the throttle body 61. Furthermore, another part is supplied to the heater 62.

  FIG. 3 is a plan view of the cooling structure of the cylinder block according to the first embodiment of the present invention. Referring to FIG. 3, in cylinder block cooling structure 1 according to the first embodiment of the present invention, cylinder block 10 is cooled by cooling water as a cooling medium. The cylinder block 10 includes a cylinder liner assembly 11, a groove-shaped water jacket portion 12 surrounding the cylinder liner assembly 11, and a cylinder block base portion 13 surrounding the water jacket portion 12.

  The cylinder liner assembly 11 has four bore regions 111, 112, 113, 114, and has a structure in which an iron alloy surrounding each of the bore regions 111, 112, 113, 114 is surrounded by aluminum. The cylinder liner assembly 11 is surrounded by a water jacket portion 12 for flowing a cooling medium. The water jacket portion 12 has a concave shape and a shape along the cylinder liner assembly 11. The cylinder block base portion 13 is an engine block body and is made of an aluminum alloy.

  The cylinder block base portion 13 is provided with a cooling water inlet 115 as an inlet for the cooling medium. A gasket (not shown) is provided so as to cover the cylinder block base portion 13, and a gasket hole 41 serving as a cooling medium passage is formed in the gasket. The cylinder head 30 is placed on the gasket, and a passage that connects to the gasket hole 41 is provided in the cylinder head 30. The cooling medium passes through the passage so that the cylinder head 30 can be cooled. it can.

  The water jacket partition plate 20 is fitted to the water jacket portion 12 and contacts the cylinder liner assembly 11 and the cylinder block base portion 13. The water jacket partition plate 20 is fitted to the water jacket portion 12, is connected to the bowl-shaped partition plate 22, and the partition plate 22, and extends from the lower portion to the upper portion of the bore regions 111, 112, 113, 114. It comprises a body 23 and a flowing water shielding plate 24 that contacts both the cylindrical body 23 and the partition plate 22 and extends in the longitudinal direction. A region where the partition plate 22 is not formed is the recess 21.

  In the recess 21, the upper portion and the lower portion of the water jacket portion 12 are connected, and the lower cooling water flows upward through the recess 21. The area of the recess 21 increases as the distance from the cooling water inlet 115 increases. As a result, the area of the recess 21 closest to the cooling water inlet 115 is the smallest, and the area of the recess 21 farthest from the cooling water inlet 115 is increased. In the vicinity of the cooling water inlet 115, since the temperature of the cooling water is low, the cooling capacity by the cooling water is high. For this reason, the area of the recess 21 is reduced and the flow rate is suppressed to prevent overcooling.

  On the other hand, in the portion far from the cooling water inlet 115, the cooling water has already cooled the other portions and absorbed heat, so that the temperature becomes high. Therefore, the cooling capacity by the cooling water is smaller than that near the cooling water inlet 115. As a result, the cooling capacity is secured by increasing the flow rate, and active cooling is aimed at. The area of the recess 21 is not limited to the above-described tendency, and may be changed so as to match the target cooling efficiency. The partition plate 22 is in contact with the water jacket portion inner wall 12i and the water jacket portion outer wall 12t, and has a function of blocking the flow of the cooling water in the vertical direction. The partition plate 22 is formed in an arc shape, and a part thereof is notched to constitute the recess 21. A gasket hole 41 is provided above the partition 22, and the gasket hole 41 is connected to the cylinder head 30, and the cooling water flowing on the partition plate 22 passes through the gasket hole 41 toward the cylinder head 30 as indicated by an arrow 101. Flowing.

  The flow of the cooling water in the cylinder block 10 will be described. The cooling water inlet 115 is upstream of the flow, the gasket hole 41 is downstream of the flow, and the cooling water flows from the upstream toward the downstream. Cooling water that flows in the direction indicated by the arrow 100 from the cooling water inlet 115 enters the water jacket portion 12, contacts the cylinder liner assembly 11, and further flows upward through the recess 21. Thereafter, the cooling water flows in the circumferential direction along the partition plate 22 and then escapes upward through the gasket holes 41.

  In this embodiment, cooling water is introduced from the air supply side 10i of the cylinder block 10, and this cooling water is divided into two-handed flow toward the front side 10f and the rear side 10r, and further toward the exhaust side 10e. Although the flow is shown, it is not limited to this cooling water flow. For example, a cooling water is introduced from the front side 10f, and the cooling water is divided into two parts, an air supply side 10i and an exhaust side 10e, and further merged and discharged at the rear side 10r. A cooling system may be adopted in which cooling water is introduced from the side 10r, divided into an air supply side 10i and an exhaust side 10e, merged at the front side 10f, and discharged to the outside.

  FIG. 4 is a perspective view of the cylinder liner assembly and the water jacket partition plate. Referring to FIG. 4, the cylinder liner assembly 11 has a shape in which a plurality of cylinders are connected, and is arranged so that the respective axes are parallel to each other. The cylinder liner assembly 11 is kept warm by being covered with the water jacket partition plate 20. Specifically, the lower bore portion 10 </ b> L is covered with the water jacket partition plate 20, and the upper bore portion 10 </ b> H is not covered with the water jacket partition plate 20. The upper bore portion 10H is exposed from the water jacket partition plate 20, and is actively cooled.

  A cylindrical body 23 is provided below the water jacket partition plate 20, and the cylindrical body 23 has a shape along the cylinder liner assembly 11 and is disposed so as to be in contact with the cylinder liner assembly 11. Thereby, the lower bore 10L is kept warm by the cylindrical body 23. A partition plate 22 is attached to the upper surface of the cylindrical body 23, and the partition plate 22 extends in a curved manner so as to come into contact with the water jacket portion inner wall 12 i that is the outer peripheral surface of the cylinder liner assembly 11. The partition plate 22 has a function of adjusting the flow of the cooling water, and the cooling water flows along the partition plate 22 as indicated by an arrow 103.

  A portion where the partition plate 22 is not formed is a concave portion 21, and the concave portion 21 serves as a passage through which cooling water flows from the lower bore portion 10L toward the upper bore portion 10H. That is, since the passage connecting the lower bore 10L and the upper bore 10H is only the recess 21, all the cooling water flows through the recess 21. Therefore, the flow rate of the cooling water for each cylinder can be adjusted by controlling the area of the recess 21. A running water shielding plate 24 is disposed at the end of the partition plate 22. The running water shielding plate 24 is disposed in the upper bore portion 10H and extends upward from the lower direction. The running water shielding plate 24 extends to the same position as the deck surface 10 d that is the upper end surface of the cylinder liner assembly 11. As a result, the cooling water cannot exceed the flowing water shielding plate 24 and flows to the cylinder head side. The partition plate 22 and the flowing water shielding plate 24 provided in the water jacket portion 12 constitute a cooling water passage, and the cooling water flows along this passage as indicated by an arrow 103.

  The lower bore 10L is kept warm by a cylindrical body 23 made of heat insulating resin and has a low flow velocity. The partition plate 22 is provided at 1/3 of the reciprocating stroke of the piston housed in the bore region 111. That is, the distance from the deck surface 10d to the partition plate 22 is 1/3 of the stroke. This number is not particularly limited, and can be appropriately changed according to the amount of heat generated by the engine, the necessity for cooling, and the like. The recess 21 is provided in a region between bores in the vicinity of adjacent bore regions. Thereby, the area between the bores where heat is likely to accumulate can be actively cooled with high-speed running water.

  FIG. 5 is a cross-sectional view taken along line VV in FIG. Referring to FIG. 5, a cylinder block 10 includes a cylinder liner assembly 11 located inside, a water jacket portion 12 as a coolant passage disposed so as to surround the cylinder liner assembly 11, and a water jacket. And a cylinder block base portion 13 that surrounds the portion 12 and faces the cylinder liner assembly 11. The cylinder liner assembly 11 has a water jacket portion inner wall 12i, and the water jacket portion inner wall 12i is in contact with cooling water 100W as a cooling medium.

  The water jacket portion 12 is a region provided between the cylinder liner assembly 11 and the cylinder block base portion 13 and has a bottom portion 12u. The cylinder liner assembly 11 and the cylinder block base 13 are connected to each other at the bottom 12u. The width of the water jacket portion 12 is not particularly limited, and the width (the distance between the water jacket portion inner wall 12i and the water jacket portion outer wall 12t may be configured to be substantially constant. 12 may be formed in a V shape.

  In this case, the water jacket portion inner wall 12i and the outer wall 12t facing the water jacket portion 12 have tapered surfaces. The cylinder block base portion 13 is made of an aluminum alloy and is configured by a method such as die casting. In addition, the material of the cylinder block base part 13 and the cylinder liner assembly 11 is not particularly limited, and may be made of cast iron as well as an aluminum alloy. The cylinder block base portion 13 serves as an engine block, and various accessories provided in the engine are attached.

  The cylinder block base portion 13 is provided with a cooling water inlet (not shown), and cooling water 100W from the water pump is introduced into the hole serving as the inlet. In addition, it is possible to use not only the cooling water 100W but also various fluids such as long life coolant and oil as the cooling medium.

  On the deck surface 10d that is the upper surface of the cylinder block 10, the water jacket portion 12 is exposed and is an open deck type. A gasket and a cylinder head are mounted on the deck surface 10d. The gasket functions to seal the cooling water 100W flowing through the water jacket portion 12.

  A water jacket partition plate 20 is inserted into the water jacket portion 12. The water jacket partition plate 20 has a shape along the water jacket portion 12 and surrounds the cylinder liner assembly 11. The material of the water jacket partition plate 20 is not particularly limited, and various materials such as a metal material such as iron and aluminum, an inorganic material, and a resin can be employed.

  The cylinder liner assembly 11 may be provided with a drill path as a through hole.

  The cylindrical body 23 of the water jacket partition plate 20 is in close contact with the inner wall 12i of the water jacket portion and plays a role of keeping the lower portion of the bore region 112 warm. As shown in FIG. 4, the cooling water introduced from the direction indicated by the arrow 100 first contacts the cylindrical body 23 and does not directly contact the cylinder liner assembly 11, so that the bore lower part 10 </ b> L is kept warm. The partition plate 22 extends in a direction orthogonal to the direction in which the cylindrical body 23 extends, contacts the water jacket inner wall 12i and the water jacket outer wall 12t, and partitions the upper bore portion 10H and the lower bore portion 10L.

  FIG. 6 is a side view of the water jacket partition plate. FIG. 7 is a perspective view of the water jacket partition plate. Referring to FIGS. 6 and 7, cylindrical body 23 constituting water jacket partition plate 20 has a shape obtained by connecting a plurality of cylinders, and is disposed so as to surround a predetermined internal space. The cylinder liner assembly 11 is located in this internal space. The cylindrical body 23 is located in the lower bore portion 10L and keeps the lower portion of the cylinder liner assembly 11 warm. This prevents overcooling. A partition plate 22 is arranged on the cylindrical body 23.

  The partition plate 22 is disposed so as to extend in the lateral direction along the cylindrical body 23, and has a shape in which a part is notched. The notch is a recess 21, and the recess 21 is provided in the vicinity of the boundary between adjacent bore regions, and functions to improve the flow velocity in the region between the bores in the vicinity of this boundary. The recess 21 serves as a cooling water flow path from the lower bore 10L to the upper bore 10H. When comparing the plurality of recesses 21, the area of the recess 21 is small on the cooling water inlet side (the side closer to the portion indicated by the arrow 100), and the area of the recess 21 increases as the distance from the inlet increases. A running water shielding plate 24 is disposed adjacent to the recess 21. As shown in FIG. 6, the running water shielding plate 24 extends to the same height as the deck surface 10 d and has a function of preventing the cooling water from flowing beyond the running water shielding plate 24.

  The cylinder block cooling structure 1 according to the present invention as described above is inserted into the water jacket portion 12 and the cylinder block 10 having the water jacket portion 12 for cooling the cylinder liner assembly 11 as the cylinder wall of the internal combustion engine. And a partition plate 22 that is molded and partitions the upper and lower sides. A concave portion 21 serving as a through-passage passing through the upper and lower sides is provided between the cylinders, and a running water shielding plate 24 is located at one end of the concave portion 21. The areas of the plurality of recesses 21 are different from each other. A cylindrical body 23 extending integrally with the partition plate 22 toward the lower end of the bore is provided. The thickness of the cylindrical body 23 varies depending on the cylinder part, and the cylindrical body 23 is in contact with the inner wall 12i of the water jacket portion constituting the bore outer wall. To do.

  The partition plate 22 is located at least one half of the stroke above the deck surface 10d which is the upper end of the bore. That is, the distance from the deck surface 10d to the partition plate 22 is half or less of the stroke. The partition plate 22, the cylindrical body 23, and the running water shielding plate 24 are integrally formed of resin.

  FIG. 8 is a graph showing the relationship between the height of the bore region and the temperature in the cylinder block cooling structure according to the present invention. Referring to FIG. 8, a curve 501 shows the relationship between the height of the bore region and the temperature in the conventional cooling structure in which the water jacket partition plate is not provided. A curve 502 shows the relationship between the height of the bore region and the temperature in the cooling structure of the cylinder block using the water jacket partition plate without the partition plate 22. A curve 503 shows the relationship between the height of the bore region and the temperature in the cylinder block cooling structure shown in FIGS. Referring to FIG. 8, in the cylinder block cooling structure according to the present invention, the temperature of the bore region is substantially constant along the height of the bore region. This is because the effect of keeping the lower part of the bore warm and cooling the upper part of the bore is great. As indicated by a curve 501, in the conventional cooling structure of the cylinder block, the temperature at the lower part of the bore region is low and the temperature at the upper part (near the deck surface) is high. This is because cold cooling water is introduced into the lower part, the lower part is overcooled, and the upper part is not cooled much. As shown by the curve 502, the temperature distribution can be improved to some extent by inserting a water jacket partition, but it is not improved as much as the present invention.

  As described above, the cylinder block cooling structure according to the present invention enables uniform cooling. Moreover, in this invention, since the cylinder block 10 is manufactured by die casting, the degree of freedom of the shape of the water jacket portion 12 is dramatically improved. Further, the accuracy is improved with respect to the cylinder block made of cast metal. In addition, the manufacturing cost can be greatly reduced. This is because a core is not required and the water jacket partition plate 20 can be made of resin.

  Specifically, the partition plate 22 that divides the water jacket portion 12 into upper and lower portions makes the flow passage cross-sectional area of the upper portion of the water jacket portion 12 smaller than the lower flow passage cross-sectional area, thereby increasing the flow velocity of the upper bore portion 10H Cooling efficiency can be improved.

  Further, by providing the recess 21 as the communication path in the area between the bores, the cooling efficiency of each of the bore areas 111 to 114 can be changed depending on the size of the recess, thereby improving the cooling efficiency. Further, by providing the concave portion 21, it is possible to suppress the flow velocity in the lower portion of the water jacket portion 12, increase the wall temperature in the lower portion, and reduce the friction.

(Embodiment 2)
FIG. 9 is a cross-sectional view of the cooling structure of the cylinder block according to the second embodiment of the present invention. The cross section shown in FIG. 9 corresponds to the cross section shown in FIG. Referring to FIG. 9, in the cylinder block cooling structure 1 according to the second embodiment of the present invention, the water jacket according to the first embodiment is that the water jacket partition plate 20 does not have a cylindrical body. Different from the partition plate 20. The water jacket partition plate 20 has a partition plate 22, which partitions the upper bore portion 10H and the lower bore portion 10L. Furthermore, as shown in FIG. 4, a recess 21 is provided between the partition plates 22, and a running water shielding plate 24 is disposed at the end of the recess 21. The shape obtained by removing the cylindrical body 23 from FIG. 4 is a perspective view of the water jacket partition plate 20. The cylinder block cooling structure 1 configured as described above according to the second embodiment has the same effects as the cylinder block cooling structure according to the first embodiment.

  Although the embodiment of the present invention has been described above, the embodiment shown here can be variously modified. First, the number of bore regions provided in one cylinder block 10 is not limited to the embodiment, and a single or a plurality of bore regions may be provided.

  Engines to which the present invention is applied include diesel engines and gasoline engines, and the present invention can be applied to various types of engines such as inline, V, W, and horizontally opposed types. Is possible.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be applied in the field of a cooling structure for a cylinder block of an internal combustion engine.

It is a typical perspective view which shows the cooling structure of the cylinder block according to Embodiment 1 of this invention. It is a figure shown in order to demonstrate the flow of a cooling water. It is a top view of the cooling structure of the cylinder block according to Embodiment 1 of this invention. It is a perspective view of a cylinder liner aggregate and a water jacket partition plate. It is sectional drawing along the VV line in FIG. It is a side view of a water jacket partition plate. It is a perspective view of a water jacket partition plate. It is a graph which shows the relationship between the height of a bore area | region and temperature in the cooling structure of the cylinder block according to this invention. It is sectional drawing of the cooling structure of the cylinder block according to Embodiment 2 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Cylinder block cooling structure, 10 Cylinder block, 11 Cylinder liner aggregate | assembly, 12 Water jacket part, 13 Cylinder block base part, 20 Water jacket partition plate, 21 Recessed part, 22 Partition plate, 23 Cylinder body, 24 Running water shielding board.

Claims (7)

A cylinder block having a water jacket portion for cooling a cylinder wall of the internal combustion engine;
A partition plate that is inserted into the water jacket portion and molded to partition the upper limit;
A recess is provided between the cylinders to form a through-passage that penetrates up and down,
A cooling structure for a cylinder block in which a running water shielding plate is located on the partition plate.   The cooling structure for a cylinder block according to claim 1, wherein the flowing water shielding plate is located at one end of the recess.   The cooling structure for a cylinder block according to claim 1 or 2, wherein the first and second recesses are provided between the cylinders, and the areas of the first and second recesses are the same or different.   A cylindrical body integrally formed with the partition plate and extending toward the lower end of the bore, the thickness of the cylindrical body varies depending on the cylinder part, and the cylindrical body is in contact with the outer wall of the water jacket portion. 4. The cylinder block cooling structure according to any one of items 3 to 3.   The cylinder block cooling structure according to claim 4, wherein the partition plate and the cylindrical body are integrally formed of a resin body.   The cylinder block cooling structure according to any one of claims 1 to 5, wherein the partition plate is located at least one half of a stroke from an upper end of the bore.   The cooling structure for a cylinder block according to claim 6, wherein the inlet of the cooling medium to the water jacket portion is located below the partition plate.

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