JP2017198132A - Cylinder block - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylinder block capable of controlling a cooling efficiency at a communication passage between the cylinder bores and appropriately cooling between the cylinder bores.SOLUTION: This invention relates to a cylinder block 10 provided with a communication passage 22 arranged at an inter-bore wall part 17. The communication passage 22 has an inlet opening part 23 opened to a water jacket at one end and an outlet opening part 24 at the other end, the communication passage is arranged to cross a center of the inter-bore wall part 17 under being inclined in respect to the cylinder bore axial direction in such a way that cooling water at a water jacket may be flowed from the inlet opening part 23 toward the outlet opening part 24. The outlet opening part 24 is positioned near a top deck surface rather than the inlet opening part 23 in a depth direction of the water jacket. The inlet opening part 23 is opened at a deeper position than that of the bottom part of the head bolt hole 16. The communication passage 22 is formed in such a way that an inner diameter of the outlet side passage 34 adjacent to the outlet opening part 24 is made small as compared with that of the inlet side passage adjacent to the inlet opening part 23.SELECTED DRAWING: Figure 2

Description

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

  For example, Patent Document 1 discloses a cylinder block of a multi-cylinder internal combustion engine provided with a communication path that allows cooling water flowing through a water jacket to pass between adjacent cylinder bores. In the cylinder block disclosed in Patent Document 1, a communication path is provided between adjacent cylinder bores to reach the water jacket in the cylinder block obliquely downward from the upper surface of the cylinder block. The communication path is formed in a stepped manner in which the inner diameter of the upper end is larger than the inner diameter of the lower end, and the length of the upper end of the communication path is such that the thickness between the cylinder bores around the joint with the lower end is around the lower end. It is determined to be equal to the thickness between the cylinder bores.

  Therefore, in the cylinder block of Patent Document 1, even if the thickness between adjacent cylinder bores is small, a communication path having an inner diameter at the upper end larger than the inner diameter at the lower end is provided between the cylinder bores. The thickness between the cylinder bores around the part is made equal. In the cylinder block of Patent Document 1, a necessary thickness is secured to suppress a decrease in rigidity, and a contact area with the cooling water is increased to improve a cooling effect between the cylinder bores.

JP-A-61-112768

  In recent years, there is a demand to increase the engine displacement while reducing the size and weight of the engine as a whole, and the thickness between adjacent cylinder bores tends to be reduced. When the communication path of Patent Document 1 is formed in a cylinder block in which the wall between the bores between adjacent cylinder bores is formed thin, the length of the upper end of the large diameter communicating with the cylinder head is shortened, and the lower end of the small diameter is It will extend from the lower end of the water jacket to near the top dead center of the piston. Therefore, if an attempt is made to control the vicinity of the top dead center of the piston to the target temperature at the bore wall between the cylinder bores, the other portions will be excessively cooled, and the fuel efficiency and performance of the engine may be reduced. .

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a cylinder block capable of appropriately cooling the space between the cylinder bores by controlling the cooling efficiency of the communication path between the cylinder bores. .

  In order to solve the above-described problems, the present invention provides a plurality of cylinder bores arranged in a straight line, a water jacket provided around the cylinder bores for flowing cooling water, and the water A cylinder block comprising: a plurality of head bolt holes provided around the jacket; and a communication passage provided in a wall portion between the bores between adjacent cylinder bores and communicating with the water jacket among the plurality of cylinder bores. The communication path includes an inlet opening that opens to the water jacket at one end and an outlet opening at the other end, and the cooling water of the water jacket is directed from the inlet opening toward the outlet opening. The outlet opening is provided across the center of the wall portion between the bores in an inclined state with respect to the cylinder bore axial direction so as to flow. Is located closer to the top deck surface than the inlet opening in the depth direction of the water jacket, and the inlet opening is deeper than the bottom of the head bolt hole in the depth direction of the water jacket. The communication passage is formed so that an inner diameter of the outlet side passage adjacent to the outlet opening is smaller than an inner diameter of the inlet side passage adjacent to the inlet opening. Cylinder block.

  According to the present invention, compared with the inlet side passage adjacent to the inlet opening of the communication passage, the flow rate of the cooling water in the outlet side passage adjacent to the outlet opening is increased to cool the outlet side passage of the communication passage. Control is performed to increase efficiency. The amount of heat exchanged between the cooling water flowing through the communication passage and the bore wall around the upper end of the cylinder bore adjacent to the piston top dead center is compared with the bore wall around the lower end of the cylinder bore adjacent to the piston bottom dead center. It is getting bigger. Therefore, by controlling the cooling efficiency of the communication passage, the bore wall around the inlet passage adjacent to the outlet passage adjacent to the communication passage outlet opening and the inlet passage adjacent to the inlet passage adjacent to the communication passage inlet opening. The wall portion between the bores can be appropriately cooled so that the temperature difference with the portion is reduced.

In the above cylinder block, at least the outlet passage may have a tapered shape in which an inner diameter decreases toward the outlet opening.
In this case, due to the cooling effect of the cooling water flowing through the communication passage, at least the temperature of the wall portion between the bores around the outlet side passage can be made substantially constant.

Further, in the above cylinder block, the cylinder block has an external opening that opens to the outside of the cylinder block and a connection opening that opens to the water jacket, and is a through passage formed coaxially with the communication path. It is good also as a structure provided with the sealing member which prevents the leakage of the cooling water which flows through the water jacket to the outside of the cylinder block.
In this case, it is possible to prevent the cooling water flowing through the water jacket from leaking out of the cylinder block with a simple configuration using a plug.

In the above cylinder block, the inlet-side passage has a first inner diameter and extends from the inlet opening toward the top deck surface side.
The outlet side passage has a second inner diameter smaller than the first inner diameter and extends from the outlet opening toward the water jacket side and is connected to the inlet side passage.
A step portion may be formed at a connection portion between the inlet-side passage and the outlet-side passage.
In this case, the communication path can be easily formed as compared with a configuration in which the entire communication path is formed in a tapered shape with a smaller inner diameter as it goes from the inlet opening to the outlet opening.

  The present invention can provide a cylinder block that can appropriately cool the space between the cylinder bores by controlling the cooling efficiency of the communication path between the cylinder bores.

It is a top view which shows the cylinder block which concerns on embodiment of this invention. It is the sectional view on the AA line of FIG. 1 which shows the cylinder block concerning embodiment of this invention. It is a graph which shows the relationship between the internal diameter of the communicating path of this invention, and the stress which the wall part between bores receives. It is a graph which shows the relationship between the internal diameter of the exit opening part of the communicating path of this invention, the amount of exchange heat of a cooling water, and a bore wall part. It is a graph which shows the relationship between the distance from the top deck surface of this invention, and the temperature of the wall part between bores. It is sectional drawing which shows the cylinder block which concerns on the modification 1 of this invention. It is sectional drawing which shows the cylinder block which concerns on the modification 2 of this invention. It is sectional drawing which shows the cylinder block which concerns on the modification 3 of this invention.

Hereinafter, the cylinder block concerning this embodiment is explained based on a drawing.
In the present embodiment, an example of a cylinder block in which cylinder cylinder walls between adjacent cylinder bores are integrated in an in-line four-cylinder internal combustion engine.

  A cylinder block 10 of the present embodiment shown in FIGS. 1 and 2 is provided with four cylinder bores 12 arranged in a straight line, a cylinder cylinder wall 11 defining the cylinder bore 12, and a cooling cylinder provided around the cylinder cylinder wall 11. And a water jacket 13 for flowing water.

  The upper side of FIG. 2 is the upper side of the cylinder block 10, and the lower side of FIG. 2 is the lower side of the cylinder block 10. As shown in FIG. 2, the cylinder block 10 includes a head surface 14 as a top deck surface (upper surface) and an outer peripheral wall 15 as a side surface.

  As shown in FIGS. 1 and 2, the cylinder bore 12 is a cylindrical space that opens upward from the head surface 14 and has an axis extending in the vertical direction. The four cylinder bores 12 are arranged in a straight line. Yes. Further, the cylinder block 10 includes a plurality of substantially cylindrical head bolt holes 16 that open to the head surface 14 and extend in the vertical direction. The head bolt holes 16 are provided on both sides of the juxtaposed direction between adjacent cylinder bores 12. The cylinder block 10 is fastened to a cylinder head (not shown) by a head bolt (not shown) inserted through the head bolt hole 16 and abuts against the cylinder head on the head surface 14.

  The cylinder cylindrical wall 11 between the adjacent cylinder bores 12 is integrated to form an inter-bore wall portion 17. The water jacket 13 is provided in the head surface 14 so as to surround the four cylinder bores 12. The head bolt hole 16 is provided around the water jacket 13. The cylinder block 10 includes a water inlet 18 at one end in the direction in which the four cylinder bores 12 are juxtaposed. The water inlet 18 is connected to a water pump (not shown) installed outside the cylinder block 10, extends along the direction in which the cylinder bores 12 of the cylinder block 10 are juxtaposed, and is connected to the water jacket 13 for cooling. Water is allowed to flow into the cylinder block 10.

  The cylinder head is provided in the vicinity of the water inlet 18 of the cylinder block 10, is connected to the water jacket 13, and includes a water outlet 29 that allows cooling water to flow from the cylinder block 10 into the cylinder head. The water jacket 13 includes an outward path 20 and a return path 21 extending in a wave shape along the periphery of the four cylinder bores 12 on both sides of the juxtaposed direction of the four cylinder bores 12. The forward path 20 and the backward path 21 are connected at both ends of the four cylinder bores 12 in the cylinder block 10 in the juxtaposed direction. The forward path 20 is connected to the water inlet path 18, and the return path 21 is connected to the water outlet path 29 of the cylinder head.

  As shown in FIG. 1, the bore wall 17 of the cylinder block 10 is provided between the forward path 20 and the return path 21 across the center of the bore wall 17 in an inclined state with respect to the axial direction of the cylinder bore 12. Further, a communication path 22 having a circular shape in cross section is provided. The communication path 22 communicates with the water jacket 13, and as shown in FIG. 2, an inlet opening 23 that opens to the forward path 20 of the water jacket 13 at one end, and an outlet opening 24 that opens at the head surface 14 at the other end. Is provided. In the present embodiment, the outlet opening 24 is not connected to the return path 21.

  In the communication path 22, the inlet opening 23 is opened at a position deeper than the bottom of the head bolt hole 16 in the depth direction of the water jacket 13, and the outlet opening 24 is an inlet opening in the depth direction of the water jacket 13. It is located above the side closer to the head surface 14 than 23. The communication path 22 includes a first communication path 35 as an inlet-side path adjacent to the inlet opening 23 and a second communication path 36 as an outlet-side path adjacent to the outlet opening 24. The inner diameter of the communication path 22 is smaller than the inner diameter of the first communication path 35, and the inner diameter of the communication path 22 is formed in a tapered shape that continuously decreases from the inlet opening 23 toward the outlet opening 24.

  Further, a through-hole 25 having a circular cross section extending in a direction perpendicular to the juxtaposed direction of the cylinder bores 12 is provided between the forward passage 20 and the outer peripheral wall 15 in the inter-bore wall portion 17 of the cylinder block 10. Yes. The through passage 25 includes a connection opening 28 that opens to the forward path 20 at one end, and an external opening 26 that opens to the outside of the cylinder block 10 at the outer peripheral wall 15 of the cylinder block 10 at the other end. The through passage 25 is located above the connection opening 28 on the side closer to the head surface 14 than the external opening 26 in the depth direction of the water jacket 13, and upward from the external opening 26 toward the connection opening 28. Tilt. The through passage 25 is coaxial with the communication passage 22 and has a constant inner diameter. The external opening 26 opens at a position deeper than the bottom of the head bolt hole 16 in the depth direction of the water jacket 13. A plug 27 as a sealing member for preventing leakage of the cooling water flowing through the water jacket 13 to the outside of the cylinder block 10 is fitted into the through passage 25.

A method for manufacturing the cylinder block 10 having the above configuration will be described below.
The cylinder block 10 is formed with a water jacket 13 by, for example, aluminum casting. After the aluminum casting, the cylinder bore 12 and the head bolt hole 16 are processed in the cylinder block 10. Furthermore, the through passage 25 and the communication passage 22 are formed in the cylinder block 10 by drilling with a drill. The through passage 25 forms an external opening 26 in the outer peripheral wall 15 below the forward path 20 side of the cylinder block 10, forms a passage inclined upward from the external opening 26, and includes a connection opening 28 that opens in the forward path 20. Formed and provided. The communication path 22 forms an inlet opening 23 that opens to the forward path 20, forms a first communication path 35 and a second communication path 36 that incline upward from the inlet opening 23, and an outlet that opens to the head surface 14. An opening 24 is formed and provided. Then, the plug 27 is fitted into the through passage 25 from the external opening 26. Although a part of the through passage 25 is sealed with the plug 27, for example, a plug that seals from the external opening 26 to the connection opening 28 of the through passage 25 may be used.

The operation of the cylinder block 10 having the above configuration will be described below.
Relatively high-pressure cooling water sent out from a water pump arranged outside the cylinder block 10 flows into the cylinder block 10 from the water inlet 18 and flows through the water jacket 13. The cooling water flows in the direction indicated by the arrow in FIG. 1 through the forward path 20 of the water jacket 13 and flows in the direction indicated by the arrow in FIG.

  At this time, the cylinder cylinder wall 11 around the cylinder bore 12 whose temperature rises due to the combustion of fuel in the cylinder bore 12 is cooled by the cooling water flowing through the water jacket 13. Then, the cooling water flows into the cylinder head from the return path 21 of the water jacket 13 through the water discharge path 29 of the cylinder head. The cooling water flows through the inside of the cylinder head, and the cylinder head is cooled by the cooling water.

  Further, the cooling water that has flowed into the cylinder block 10 in a relatively high pressure state is gradually reduced in pressure due to a pressure loss caused by flowing through the water jacket 13. The cooling water flowing through the forward path 20 of the water jacket 13 has a higher pressure than the cooling water flowing from the return path 21 into the cylinder head. Therefore, due to the pressure difference between the cooling water in the forward path 20 and the cylinder head, a part of the cooling water flowing through the forward path 20 is directed from the inlet opening 23 toward the outlet opening 24 through the communication path 22 connected to the forward path 20. It flows upward as indicated by the arrow 2. At this time, the inter-bore wall portion 17 around the communication path 22 is cooled by the cooling water flowing through the communication path 22. Further, the cooling water flows from the outlet opening 24 provided on the head surface 14 into the cylinder head through the water discharge passage 29.

  FIG. 3 shows the relationship between the inner diameter of the communication path and the stress that the inter-bore wall portion 17 receives from adjacent bores. As can be seen from FIG. 3, as the inner diameter of the communication path increases, the stress applied to the inter-bore wall portion 17 increases in proportion to this. That is, when the inner diameter of the communication path is increased in order to increase the amount of cooling water flowing through the communication path, the stress received by the inter-bore wall portion 17 is increased. When the stress received from the adjacent bore exceeds the maximum stress P, the inter-bore wall portion 17 cannot maintain the rigidity of the inter-bore wall portion 17, so the inner diameter of the communication path is equal to or less than the maximum inner diameter R 1 where the stress becomes the maximum stress P. Set to 3 can be obtained by simulation or experiment. For example, when the minimum thickness of the wall portion between the bores is 6 mm, the maximum inner diameter R1 of the communication path is 3 mm.

  The cooling effect by the cooling water flowing through the communication path 22 is determined by the heat transfer coefficient between the cooling water and the inter-bore wall portion 17 in which the communication path 22 is formed. The heat transfer coefficient is an element that is influenced by the flow rate of the cooling water flowing through the communication path 22. When the inner diameter of the communication path 22 is reduced, the flow rate of the cooling water is increased, and when the flow rate of the cooling water is increased, the heat transfer coefficient is also increased. When the heat transfer coefficient between the cooling water and the bore wall portion 17 is large, the exchange heat quantity Q between the cooling water and the bore wall portion 17 becomes large.

  FIG. 4 is a diagram showing a relationship between the size of the inner diameter of the outlet opening and the exchange heat quantity Q between the cooling water flowing through the communication path and the bore wall 17 when the inlet opening of the communication path has an inner diameter R3. is there. As can be seen from FIG. 4, when the inner diameter of the outlet opening is reduced from R3, the flow rate of the cooling water flowing through the communication passage is increased, so that the exchange heat quantity Q is increased. When the inner diameter of the outlet opening becomes the inner diameter R2, the exchange heat quantity Q between the cooling water and the bore wall 17 is maximized. However, when the inner diameter of the communication path is smaller than the inner diameter R2, the wet area (surface area) of the communication path is remarkably reduced. Therefore, the exchange heat quantity Q between the cooling water and the bore wall 17 is less than the flow rate of the cooling water. It is affected by the size and decreases. The relationship of FIG. 4 can be obtained by simulation or experiment. For example, when the inner diameter R3 of the inlet opening is 3 mm, the inner diameter R2 of the outlet opening where the exchange heat quantity Q is the largest is 1 mm.

  Further, the temperature of the cylinder cylinder wall 11 around the cylinder bore 12 becomes higher as the part is closer to the cylinder head, that is, the part corresponding to the piston top dead center. When the temperature of the cylinder barrel wall 11 rises, the temperature of the lubricating oil supplied into the cylinder bore 12 also rises, and accordingly the viscosity of the lubricating oil decreases. However, if the temperature of the lubricating oil becomes too high, its viscosity will exceed the appropriate range of use, and oil consumption will increase. Therefore, the inter-bore wall portion 17 is a portion corresponding to the piston top dead center where the temperature is the highest, more specifically, a top ring located slightly below the head surface 14 when the piston is at the top dead center. In the corresponding part, it is necessary to make the viscosity of the lubricating oil not more than the upper limit temperature T1 at which it can be maintained in an appropriate use range. Further, when the temperature of the lubricating oil is lowered, the viscosity thereof is increased, and accordingly, the sliding resistance of the piston is increased and the fuel consumption is deteriorated. For this reason, the temperature of the inter-bore wall portion 17 needs to be equal to or higher than the lower limit temperature T2 at which the viscosity of the lubricating oil can be maintained in a normal use range.

  FIG. 5 shows the relationship between the distance from the head surface 14 of the cylinder block 10 and the temperature of the bore wall 17 in the case where the communication path is provided in the bore wall 17. A graph indicated by a solid line shows a case of the communication path 22 formed in a tapered shape in which the inner diameter of the present embodiment continuously decreases from the inlet opening 23 toward the outlet opening 24. As can be seen from FIG. 5, in this embodiment, since the shape of the communication path 22 is set so that the cooling efficiency becomes closer to the cylinder head side, the temperature of the bore wall portion 17 is set to the piston top dead center. The part shown in FIG. 2 that is the part corresponding to the point, that is the part corresponding to the piston bottom dead center, and the part D shown in FIG. 2 that is the part corresponding to the piston bottom dead center. Up to B, the temperature can be within the range of the upper limit temperature T1 and the lower limit temperature T2. Specifically, since the communication path 22 is formed in a tapered shape so that the inner diameter continuously decreases from the inlet opening 23 toward the outlet opening 24, the cooling water flowing through the communication path 22 is formed. The flow velocity is larger in the outlet side passage adjacent to the outlet opening 24 of the communication passage 22 than in the inlet side passage adjacent to the inlet opening 23 of the communication passage 22, and the coolant and the bore wall portion 17 flowing through the communication passage 22. The exchange heat quantity Q is made larger in the inter-bore wall portion 17 around the outlet-side passage of the communication passage 22 than in the inter-bore wall portion 17 around the inlet-side passage of the communication passage 22.

  The graph shown with the dashed-dotted line of FIG. 5 shows the case of the comparative example 1 made into the communicating path provided with a fixed internal diameter. In Comparative Example 1, the flow rate of the cooling water flowing through the communication path is constant, and the amount of heat exchanged between the cooling water flowing through the communication path and the wall portion between the bores is also constant. As can be seen from FIG. 5, the temperature of the inter-bore wall portion 17 is the same as that of the present embodiment in the portion A corresponding to the top dead center of the piston (a portion below the head surface 14 by the distance D1) as in Comparative Example 1. If the cooling efficiency of the communication path is set so that the temperature is between the upper limit temperature T1 and the lower limit temperature T2, the cooling efficiency of the communication path of Comparative Example 1 is constant from the inlet opening to the outlet opening. The portion B corresponding to the bottom dead center (the portion separated by the distance D2 from the head surface 14) is overcooled, and the temperature of the bore wall portion 17 becomes lower than the lower limit temperature T2.

  The graph shown with the dashed-two dotted line of FIG. 5 shows the case of the comparative example 2 made into the communicating path provided with a fixed internal diameter. In Comparative Example 2, the flow rate of the cooling water flowing through the communication path is constant, and the amount of heat exchanged between the cooling water flowing through the communication path and the wall portion between the bores is also constant. As can be seen from FIG. 5, the temperature of the bore wall portion 17 is the same as that of the present embodiment at the portion B corresponding to the piston bottom dead center as in Comparative Example 2 (the portion separated from the head surface 14 by the distance D2). If the cooling efficiency of the communication path is set so that the temperature is between the upper limit temperature T1 and the lower limit temperature T2, the cooling efficiency of the communication path of Comparative Example 2 is constant from the inlet opening to the outlet opening. The portion A corresponding to the top dead center (the portion separated from the head surface 14 by the distance D1) is insufficiently cooled, and the temperature of the inter-bore wall portion 17 becomes higher than the upper limit temperature T1.

In the present embodiment, the following operations and effects are achieved.
(1) The communication passage 22 is positioned on the side where the outlet opening 24 is closer to the head surface 14 than the inlet opening 23 in the depth direction of the water jacket 13, and the inlet opening 23 is in the depth direction of the water jacket 13. The head bolt hole 16 is formed so as to open deeper than the bottom of the head bolt hole 16. Furthermore, the inner diameter of the outlet side passage adjacent to the outlet opening 24 is made smaller than the inner diameter of the inlet side passage adjacent to the inlet opening 23. Therefore, compared with the inlet side passage adjacent to the inlet opening 23 of the communication passage 22, the cooling water flow rate in the outlet side passage adjacent to the outlet opening 24 is increased to cool the outlet side passage of the communication passage 22. Control is performed to increase efficiency. The amount of exchange heat Q of the cooling water flowing through the communication passage 22 and the bore wall portion 17 around the upper end of the cylinder bore 12 adjacent to the piston top dead center is the bore wall around the lower end of the cylinder bore 12 adjacent to the piston bottom dead center. It is larger than part 17. Therefore, by controlling the cooling efficiency of the communication passage 22, the inlet-side passage adjacent to the inter-bore wall portion 17 around the outlet-side passage adjacent to the outlet opening 24 of the communication passage 22 and the inlet opening 23 of the communication passage 22. The inter-bore wall portion 17 can be appropriately cooled so that the temperature difference with the surrounding inter-bore wall portion 17 is reduced. By appropriately cooling the inter-bore wall portion 17, deformation of the cylinder bore 12 can be suppressed, and power loss of the internal combustion engine due to friction between the piston housed in the cylinder bore 12 and the cylinder block 10 can be reduced. .

(2) Due to the cooling effect of the cooling water flowing through the communication passage 22, the temperature of the inter-bore wall portion 17 around the communication passage 22 can be made substantially constant from the inlet opening 23 to the outlet opening 24. Therefore, there is no variation in the viscosity of the lubricating oil that is affected by the temperature around the inter-bore wall portion 17, and the adjustment of the viscosity of the lubricating oil is facilitated. Therefore, it is possible to prevent the bore wall portion 17 around the outlet-side passage adjacent to the outlet opening 24 of the communication passage 22 from being excessively cooled, thereby reducing the cooling efficiency, and reducing the power loss of the internal combustion engine. Have been able to. Further, the oil is caused by the temperature of the lubricating oil flowing through the cylinder block 10 rising and the lubricating oil evaporating due to excessive heating of the inter-bore wall portion 17 around the outlet side passage adjacent to the outlet opening 24 of the communication passage 22. Consumption can be suppressed.

(3) The communication passage 22 extends from a position deeper than the bottom of the head bolt hole 16 of the bore wall portion 17 to the head surface 14, and the entire bore wall portion 17 is cooled by cooling water flowing through the communication passage 22. Can be cooled.

(4) The inlet opening 23 of the communication passage 22 opens at a position deeper than the bottom of the head bolt hole 16 in the depth direction of the water jacket 13. Therefore, by further drilling from the through passage 25, it is possible to easily form the communication passage 22 that is coaxial with the through passage 25 and is provided across the center of the inter-bore wall portion 17.

(5) A plug 27 as a sealing member is fitted in the through passage 25. Therefore, it is possible to prevent the cooling water flowing through the water jacket 13 from leaking out of the cylinder block 10 with a simple configuration using the plug 27.

(6) The communication path 22 is connected to the forward path 20 where the inlet opening 23 is connected to the water inlet 18 through which the cooling water flows from the outside of the cylinder block 10, and the outlet opening 24 is connected via the return path 21 and the water outlet 29. The forward path 20 is at a higher pressure than the inside of the cylinder head. Therefore, by utilizing the pressure difference between the forward path 20 and the inside of the cylinder head, the cooling water can be easily circulated from the inlet opening 23 toward the outlet opening 24.

  The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the gist of the invention. For example, the following modifications may be made.

In the above embodiment, the communication path is formed in a tapered shape whose inner diameter continuously decreases from the inlet opening toward the outlet opening. In particular, it is only necessary that the exchange heat amount of the cylinder tube wall around the cylinder bore adjacent to the piston top dead center, which becomes high in temperature, can be increased as compared with other portions. For example, as in Modification 1 shown in FIG. 6, the communication passage 30 is set to the first inner diameter, and the first communication portion 32 as the inlet-side passage adjacent to the inlet opening 31 is larger than the first inner diameter. The inner diameter may be set so as to be coaxial with a second communication portion 34 as an outlet side passage which is set to have two inner diameters and is adjacent to the outlet opening 33. In this case, the communication path 30 can be easily formed as compared with a configuration in which the entire communication path is formed in a tapered shape in which the inner diameter continuously decreases from the inlet opening toward the outlet opening.

In the above embodiment, the communication path has a tapered shape in which the inner diameter continuously decreases from the inlet opening toward the outlet opening. In particular, it is only necessary that the exchange heat quantity Q of the bore wall around the cylinder bore adjacent to the piston top dead center, which becomes high in temperature, can be increased as compared with other parts, and the communication portion is at least on the outlet side adjacent to the outlet opening. The passage may have a tapered shape whose inner diameter continuously decreases toward the outlet opening. For example, as in Modification 2 shown in FIG. 7, the communication passage 40 is connected to the first communication portion 42 having a constant inner diameter as an inlet-side passage adjacent to the inlet opening 41 and the first communication portion 42. Even if it forms so that the 2nd communication part 44 as an exit side channel | path adjacent to the taper-shaped exit opening part 43 where an internal diameter becomes small toward the exit opening part 43 from the connection part with the 1st communication part 42 may be provided. good.

In the above embodiment, the communication path is formed by drilling so as to have a tapered shape in which the inner diameter decreases from the inlet opening toward the outlet opening. The communication path may be tapered. For example, as in Modification 3 shown in FIG. 8, the communication path 50 is formed to have a constant inner diameter by drilling, and then the collar 51 is provided in the communication path 50. By inserting, the communication passage 50 divides a first communication portion 53 as an entrance-side passage adjacent to the entrance opening 52 and a tapered space whose inner diameter becomes smaller toward the exit opening 54, thereby dividing the exit opening. You may form the 2nd communication part 55 as an exit side channel | path adjacent to the part 54. FIG.

In the above embodiment, the outlet opening of the communication path is formed on the head surface, but this is not restrictive. It is only necessary that the cooling water can flow from the inlet opening portion of the communication passage toward the outlet opening portion due to the pressure difference, and the outlet opening portion may be provided in the return path of the water jacket.

10 Cylinder block 12 Cylinder bore 13 Water jacket 14 Head surface (as top deck surface)
16 Head bolt hole 17 Bore wall portion 22, 30, 40, 50 Communication passage 23, 31, 41, 52 Inlet opening portion 24, 33, 43, 54 Outlet opening portion 25 Through passage 26 External opening portion 27 Plug (sealing) As a component)
28 connection opening 32, 42, 53 1st communication part (as an entrance side channel)
34, 44, 55 Second communication part (as outlet side passage)

Claims (4)

A plurality of cylinder bores arranged in a straight line;
A water jacket provided to surround the plurality of cylinder bores, and for flowing cooling water;
A plurality of head bolt holes provided around the water jacket;
Of the plurality of cylinder bores, a cylinder block provided with a communication passage provided on a wall between bores between adjacent cylinder bores and communicating with the water jacket,
The communication path includes an inlet opening that opens to the water jacket at one end and an outlet opening at the other end so that the cooling water of the water jacket flows from the inlet opening toward the outlet opening. It is provided across the center of the wall portion between the bores in an inclined state with respect to the cylinder bore axial direction,
The outlet opening is located closer to the top deck surface than the inlet opening in the depth direction of the water jacket;
The inlet opening is opened at a position deeper than the bottom of the head bolt hole in the depth direction of the water jacket;
The cylinder block, wherein the communication passage is formed so that an inner diameter of an outlet side passage adjacent to the outlet opening is smaller than an inner diameter of an inlet side passage adjacent to the inlet opening.   2. The cylinder block according to claim 1, wherein at least the outlet side passage of the communication passage is formed in a tapered shape whose inner diameter decreases toward the outlet opening. The cylinder block has an external opening that opens to the outside of the cylinder block and a connection opening that opens to the water jacket, and includes a through passage formed coaxially with the communication path,
The cylinder block according to claim 1, wherein a sealing member that prevents leakage of cooling water flowing through the water jacket to the outside of the cylinder block is provided in the through passage. The inlet side passage has a first inner diameter and extends from the inlet opening toward the top deck surface side,
The outlet side passage has a second inner diameter smaller than the first inner diameter and extends from the outlet opening toward the water jacket side and is connected to the inlet side passage.
The cylinder block according to any one of claims 1 to 3, wherein a step portion is formed at a connection portion between the inlet-side passage and the outlet-side passage.

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