Monoblock engine

Abstract

To prevent knocking by promoting heat radiation from a piston while holding temperature holding performance by a block-side cooling water jacket, in a main body block of a monoblock-type engine.SOLUTION: A cylinder head 2 and a cylinder block 1 are integrally cast, and a cylinder 6 is formed between a cylinder bore 4 and a block-side cooling water jacket 5. The cylinder 6 is integrally connected to the cylinder head 2, the block-side cooling water jacket 5 communicates with a lower-stage head-side cooling water jacket 19 of the cylinder head 2, and cooling water is sent to an intake-side portion 19a of the lower-stage head-side cooling water jacket 19. An outside face (an inside face of the lower-stage head-side cooling water jacket 19) of the cylinder 6 is formed into a downward-narrowing tapered shape. Since the cylinder 6 is thinned downward, heat radiation from the piston is excellent. By this constitution, knocking resulting from an excessive rise of a temperature of the piston 17 can be prevented.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a monoblock engine in which a cylinder head and a cylinder block are integrated into a main body block, and is characterized in particular by the cooling structure of the cylinder block.

[0002] In reciprocating engines such as gasoline engines and diesel engines, a cooling water jacket is formed around the cylinder to cool the cylinder and piston. In order to prevent overcooling while adequately cooling the upper part of the cylinder to suppress knocking, a spacer is placed in the cooling water jacket so that the cooling water flows mainly through the upper part of the cooling water jacket (for example, Patent Document 1).

[0003] Patent Document 1 describes a typical engine in which the cylinder head and cylinder block are constructed as separate components, and a gasket is interposed between the cylinder head and the cylinder block, so the flow of heat is independent between the cylinder head and the cylinder block.

[0004] And when the heat is transferred from the cylinder to the cylinder head or a spacer is placed in the cooling water jacket to concentrate the cooling water flow in the upper part of the cooling water jacket, the cooling water does not move in the parts of the cooling water jacket other than the upper part (middle and lower parts) and keeps the cylinder warm, which results in raising the temperature of the oil and reducing the friction between the piston rings and the inner surface of the cylinder (inner surface of the cylinder bore), thus contributing to improved fuel efficiency.

[0005] On the other hand, the upper part of the cylinder is cooled intensively by the cooling water, which improves the cooling performance of the air-fuel mixture and suppresses knocking. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2013-189872 A Summary of the Invention [Problem to be solved by the invention]

[0007] As in Patent Document 1, arranging a spacer in the cooling water jacket of the cylinder block suppresses the sliding resistance of the piston and knocking, but there is a concern that knocking may occur due to a rise in temperature of the piston. That is, when a spacer is arranged in the cooling water jacket of the cylinder block, the parts of the cylinder except for the upper part are kept warm, but the heat dissipation from the piston decreases, so heat is trapped in the piston, and there is a concern that the piston may overheat and cause knocking.

[0008] On the other hand, integrating the cylinder head and cylinder block to form a main body block has many advantages, such as simplifying the structure. However, with the monoblock method, it is not possible to insert a spacer into the cooling water jacket of the cylinder block, so a structure must be devised that performs the same function as a spacer in terms of preventing knocking and suppressing the sliding resistance of the pistons.

[0009] In this case, it is necessary to take into account the following characteristics of a monoblock engine: since the cylinders and the cylinder head are integrated, heat is transferred between the cylinder head and the cylinders; and since the cooling water jacket of the cylinder block and the cooling water jacket of the cylinder head are connected, heat is transferred between the cooling water of the cylinder head and the cooling water of the cylinder block.

[0010] The present invention was made against this background, and aims to disclose an improved technology for the main body block of a monoblock engine that not only achieves the same effect as placing a spacer in the cooling water jacket of the cylinder block, but also improves piston cooling and suppresses knocking. [Means for solving the problem]

[0011] The present invention focuses on the monoblock structure in which the cylinder head and the cylinder block are integrated, and has been completed in order to make effective use of this monoblock structure.

[0012] That is, the monoblock engine of the present invention is as follows: In the basic configuration in which "a cylinder head and a cylinder block are integrated into a main body block, a cylinder bore opening downward, and a block side cooling water jacket surrounding the upper part of the cylinder bore from the outside and communicating with a head side cooling water jacket provided on the cylinder head are formed, and the area between the cylinder bore and the block side cooling water jacket forms a cylinder," "The cylinder The outer surface exposed to the block side cooling water jacket is tapered downward at a constant angle over the entire height, and the portion of the cylinder corresponding to the block side cooling water jacket is formed to have an uneven thickness such that the thickness decreases at a constant rate from the upper end to the lower end, The outer peripheral surface of the block-side cooling water jacket on the side opposite to the cylinder is formed parallel to the axis of the cylinder bore, and the groove width of the block-side cooling water jacket is formed to be unequal, expanding at a constant rate from the upper end to the lower end. " This is the structure.

[0013] The present invention can be developed in various ways. For example, in claim 2, " The taper angle of the outer surface of the cylinder relative to the axis of the cylinder bore is approximately 5 degrees. " The following configuration is adopted. Effect of the Invention

[0014] Most of the heat from the piston is transferred to the inner surface of the cylinder through the piston ring, but in the present invention, the cylinder is thick at the top and thin at the bottom, so that heat exchange from the piston to the cooling water can be promoted even at the bottom of the block-side cooling water jacket. In this case, since the cylinder is integrally connected to the cylinder head, there is no problem in terms of strength even if the bottom of the cylinder is thinned. Therefore, in the present invention, it is possible to reduce the sliding resistance of the piston ring while preventing excessive heating of the piston and a decrease in the strength of the cylinder, and also to prevent or significantly suppress knocking.

[0015] The upper part of the cylinder becomes hot due to the heat of the combustion gas, but in the present invention, since the block side cooling water jacket and the head side cooling water jacket are connected, even if the upper part of the cylinder is thick, heat exchange from the upper part of the cylinder to the cooling water is vigorous, and the upper part of the cylinder can be cooled appropriately. Therefore, it has the same effect as if a spacer was installed. Also, since the upper part of the cylinder is thick, it has excellent strength against explosions.

[0016] It has been proposed to stop the flow of cooling water during cold start to promote the warming of the engine and cooling water. In the present invention, however, the cross-sectional area of ​​the lower part of the block-side cooling water jacket can be made large, so that even in a control mode in which the flow of cooling water is stopped during cold start, there is an advantage in that the amount of heat stored in the cooling water can be increased and the heat retention of the cylinders can be improved.

[0017] In addition, the engine of the present invention is a monoblock type, and the cylinder head and cylinder are connected as a single unit. Therefore, if there is a temperature difference between the top of the cylinder and the bottom of the cylinder head, heat will flow from one to the other, acting to eliminate the temperature difference. However, because the top of the cylinder is thick and has a large amount of heat storage, this smooths out the temperature change and prevents the occurrence of thermal strain.

[0018] In addition, claims 1 The outer surface of the cylinder (the inner surface of the block-side cooling water jacket) is tapered as shown in the figure. By doing so, Since the temperature change becomes gradual, the concentration of thermal stress in a specific portion can be prevented, the circularity of the cylinder can be maintained, and durability can be improved.

[0019] In addition, the outer periphery of the cooling water jacket on the block side is formed parallel to the axis of the cylinder bore, and the outer surface of the cylinder is formed tapered. By doing The cross-sectional area of ​​the block-side cooling water jacket decreases from bottom to top, and the upper end is constricted, so that even if the cooling water rises in temperature and tries to rise, the upward movement is suppressed. Therefore, it has an excellent effect of keeping the cylinder warm. [Brief description of the drawings]

[0020] [Figure 1] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Next, an embodiment of the present invention will be described with reference to the drawings. This embodiment is applied to a multi-cylinder (e.g., three-cylinder) internal combustion engine for a vehicle (automobile). In the following, the terms front-rear and left-right are used to specify directions, but the front-rear direction is the crankshaft direction, and the left-right direction is a direction perpendicular to the crankshaft and cylinder bore axes. Regarding front and rear, the side where the timing chain is arranged is the front, and the side where the transmission is arranged is the rear.

[0022] (1) Structure Description The engine has, as its basic element, a monoblock main body block 3 in which a cylinder block 1 and a cylinder head 2 are integrated, and a crankcase (not shown) is fixed to the underside of the cylinder block 1 by a group of bolts.

[0023] The cylinder block 1 is formed with a group of cylinder bores 4 that open downward and a block-side cooling water jacket 5 that surrounds the group of cylinder bores 4. The space between the cylinder bores 4 and the block-side cooling water jacket 5 forms a cylinder 6. Naturally, the upper end of the cylinder 6 is integrally connected to the cylinder head 2.

[0024] The block side cooling water jacket 5 has a loop shape surrounding the group of cylinder bores 4, with an inter-bore portion 7 being formed between adjacent cylinder bores 4, and the block side cooling water jacket 5 extends toward the inter-bore portion 7.

[0025] A recess (combustion chamber) 8 that opens toward the cylinder bore 4 is formed in the cylinder head 2, and a pair of intake ports 9 and exhaust ports 10, one at the front and one at the rear, open from both the left and right sides of the recess 8. The end of the intake port 9 is opened and closed by an intake valve 11, and the beginning of the intake port 20 is opened and closed by an exhaust valve 12. The valves 11, 12 are urged in the closing direction by a spring 13.

[0026] A pair of front and rear intake ports 9 are each opened separately on the intake side (not shown) of the cylinder head 2, and an intake manifold is fixed to the intake side of the cylinder head 2. On the other hand, each pair of exhaust ports 20 communicates with a collecting passage 14, which opens from one exhaust outlet 15 on the exhaust side of the cylinder head 2. A catalyst case or an exhaust turbocharger is connected to the exhaust outlet 15. An electrode of an ignition plug 16 is exposed in the recess 8.

[0027] A piston 17 is slidably fitted in the cylinder bore 4, and the piston 17 is in sliding contact with the inner surface of the cylinder 6 (the inner surface of the cylinder bore 4) via a piston ring 18 (a compression ring and an oil ring).

[0028] The cylinder head 2 is formed with a lower-stage head-side cooling water jacket 19 and an upper-stage head-side cooling water jacket 20. The lower-stage head-side cooling water jacket 19 has an intake side portion 19a, a center portion (upper portion of the bore) 19b, and an exhaust side portion 19c that are continuously connected. The upper-stage head-side cooling water jacket 20 is formed only on the exhaust side, but can be formed to extend to the intake side portion and upper portion of the bore as well. The center portion 19b extends in the front-rear direction by approximately the width of the cylinder bore 4.

[0029] The intake side portion of the block side cooling water jacket 5 is integrally connected to the intake side portion 19a of the lower-stage head side cooling water jacket 19. On the other hand, the exhaust side portion of the block side cooling water jacket 5 is integrally connected to the exhaust side portion 19c and the center portion 19b of the lower-stage head side cooling water jacket 19. In Fig. 1, the intake side portion 19a and the center portion 19b of the lower-stage head side cooling water jacket 19 are separate, but the two are connected at, for example, the inter-bore portion 7.

[0030] The outer peripheral surface 6a of the cylinder 6 (or the inner peripheral surface of the block-side cooling water jacket 5) is formed into a tapered surface that decreases in diameter downward over the entire circumference of the block-side cooling water jacket 5, thereby reducing the thickness of the cylinder 6. Throughout its height The cross-sectional area of ​​the lower-stage head-side cooling water jacket 19 decreases at a constant rate from top to bottom. The outer peripheral surface 5a of the block-side cooling water jacket 5 is parallel to the axis of the cylinder bore 4. Therefore, the cross-sectional area of ​​the lower-stage head-side cooling water jacket 19 expands at a constant rate from top to bottom, forming a downward bulge. With respect to the axis of the cylinder bore 4 The taper angle is generally set to about 5 degrees, with 3 to 7 degrees being preferable.

[0031] (2) Summary In the above configuration, as indicated by the dashed dotted line, the cooling water inlet 21 is located in the block side cooling water jacket 5, for example, at a portion between the first and second cylinder bores 4 from the front, and the cooling water is sent from here to the block side cooling water jacket 5 and discharged from the rear end of the cylinder head 2. The rear end of the exhaust side portion 19c of the lower-stage head side cooling water jacket 19 and the rear end of the upper-stage head side cooling water jacket 20 are in communication with each other, and the cooling water is discharged from this rear end.

[0032] Since the cross-sectional area of ​​the cylinder 6 gradually decreases from top to bottom, the heat of the piston 17 is transferred to the cooling water via the piston ring 18 and the cylinder 6, and the heat transfer improves toward the bottom of the cylinder 6, which promotes heat exchange from the piston 17 to the cooling water in the block-side cooling water jacket 5. As a result, the piston 17 is prevented from excessively increasing in temperature, and the occurrence of knocking can be suppressed.

[0033] In this embodiment, the cooling water flows into the intake side portion 19a of the lower head side cooling water jacket 19, so in the block side cooling water jacket 5, the flow of the cooling water becomes worse the further down it goes. Therefore, the heat retention performance of the cylinder 6 provided by the cooling water becomes higher the further down it goes. However, since the cylinder 6 becomes thinner the further down it goes, this has an excellent effect of preventing excessive heating of the piston 17 while maintaining high heat retention performance of the cylinder 6.

[0034] Since the cylinder 6 becomes thicker toward the top, the heat transfer of the cylinder 6 becomes worse toward the top, but since the upper end of the block side cooling water jacket 5 communicates with the lower-stage head side cooling water jacket 19, the cooling water hits the upper part of the cylinder 6 strongly and in large quantity at the upper part of the block side cooling water jacket 5, and therefore the upper part of the cylinder 6 can be cooled accurately. Therefore, it is possible to prevent the intake air from being heated by the upper part of the cylinder 6, which would induce knocking.

[0035] The cylinder 6 is integrated with the cylinder head 2 and therefore has excellent strength. The cylinder 6 is thicker at the upper portion where the explosive force acts strongly, which is particularly advantageous in terms of strength.

[0036] When the cylinder 6 and the cylinder head 2 are integrated, heat is transferred when there is a temperature difference between the cylinder head 2 and the cylinder 6. In this case, the cylinder head 2 becomes hot on the exhaust side, so that a temperature difference is also likely to occur in the cylinder 6 between the exhaust side and the intake side.

[0037] Regarding this point, in this embodiment, the communication area between the intake side portion 19a and the bore upper portion 19b of the lower-stage head side cooling water jacket 19 is reduced on the intake side to suppress cooling of the cylinder 6, while on the exhaust side, the bore upper portion 19b and the exhaust side portion 19c of the lower-stage head side cooling water jacket 19 are communicated with the block side cooling water jacket 5 to improve the cooling performance of the upper portion of the cylinder 6. Therefore, the temperature difference between the intake side and the exhaust side in the upper portion of the cylinder 6 is reduced as much as possible to prevent the occurrence of distortion due to heat. This point is also one of the major advantages of this embodiment.

[0038] It is also possible to send cooling water from the block-side cooling water jacket 5 toward the lower-stage head-side cooling water jacket 19. In this case, since the upper end of the block-side cooling water jacket 5 is narrowed, when the cooling water is caused to rise from the block-side cooling water jacket 5 on the exhaust side to the lower-stage head-side cooling water jacket 19 on the exhaust side, the cooling water can be made to hit the vicinity of the exhaust port 10 with an increased flow rate, and therefore the periphery of the exhaust port, which becomes hot, can be thoroughly cooled.

[0039] N The outer peripheral surface 6a of the cylinder 6 has an uneven thickness in the vertical direction, but has a uniform thickness in the circumferential direction.

[0040] The present invention can be embodied in various ways other than the illustrated embodiment. Ba, B The depth of the lock side cooling water jacket can be set arbitrarily. [Industrial Applicability]

[0041] The present invention can be embodied in a monoblock engine, and therefore has industrial applicability. [Explanation of symbols]

[0042] 1 Cylinder block 2. Cylinder head 3 Body block 4 Cylinder bore 5 Block side cooling water jacket 6-cylinder 6a Outer surface of cylinder 9 Intake port 10 Exhaust port 17 Piston 18 Piston rings 19 Lower head side cooling water jacket 20 Upper head side cooling water jacket

Claims

1. A monoblock engine in which a cylinder head and a cylinder block are integrated into a main body block, a cylinder bore opening downward, and a block side cooling water jacket surrounding an upper portion of the cylinder bore from the outside and communicating with a head side cooling water jacket provided on the cylinder head are formed, and a portion between the cylinder bore and the block side cooling water jacket forms a cylinder, The outer surface of the cylinder exposed to the block side cooling water jacket is tapered downward at a constant angle over the entire height, and the portion of the cylinder corresponding to the block side cooling water jacket is formed to have an uneven thickness such that the thickness decreases at a constant rate from the upper end to the lower end. The outer peripheral surface of the block side cooling water jacket on the opposite side to the cylinder is formed parallel to the axis of the cylinder bore, and the groove width of the block side cooling water jacket is formed to be unequal, expanding at a constant rate from the upper end to the lower end. Monoblock engine.

2. The taper angle of the outer surface of the cylinder relative to the axis of the cylinder bore is approximately 5 degrees.

2. A monoblock engine according to claim 1.

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