JP7553377B2 - Internal combustion engine - Google Patents

Description

This invention relates to an internal combustion engine, and is particularly characterized by its ability to improve the cooling of the areas between the bores of the cylinder block.

An internal combustion engine has a cylinder block and a cylinder head fixed to its upper surface, and the cylinder block has a water jacket formed to surround the group of cylinder bores for cooling. The problem here is that the degree of temperature rise in the cylinders varies depending on the location, and therefore simply running cooling water through the water jacket of the cylinder block can result in insufficient or overcooling of the cylinder block.

In particular, the inter-bore area of the cylinder block is prone to insufficient cooling because it is sandwiched between two cylinder bores and receives a large amount of heat. As a result, many ideas have been proposed to improve the cooling performance of the inter-bore area.

As an example, Patent Document 1 discloses that when providing an inter-bore cooling hole (drill path) between the bores that connects the water jacket of the cylinder block and the water jacket of the cylinder head, the inter-bore cooling hole is connected to the upper water jacket, which has a lower pressure among the upper and lower water jackets formed in the cylinder head, and the flow of cooling water is improved by utilizing the pressure difference. Therefore, in Patent Document 1, the cooling water flows from the water jacket of the cylinder block to the upper water jacket of the cylinder head.

JP 2002-168147 A

Patent Document 1 is an improvement technology for the so-called drill path, but there is a problem in that even if the flow rate is increased, it is difficult to cool the entire inter-bore area evenly using only the drill path. In addition, in Patent Document 1, the cooling water is sent from the water jacket of the cylinder block to the water jacket of the cylinder head, but in recent internal combustion engines, the water supply to the water jacket of the cylinder block is somewhat restricted, so it is possible that a strong water flow cannot be made to flow through the inter-bore cooling hole.

The present invention was made to improve this current situation, and aims to provide technology that can accurately cool the area between the bores.

The present invention relates to
"It has a cylinder block and a cylinder head fixed to the upper surface of the block.
The cylinder block has a plurality of cylinder bores arranged in the crankshaft direction with a bore-to-bore portion interposed therebetween, and a water jacket is formed so as to surround the group of cylinder bores. A slit is formed in the bore-to-bore portion, the slit having an upward opening so as to divide the bore-to-bore portion in two in the crankshaft direction.
The cylinder head is provided with a discharge passage for ejecting cooling water from a water jacket formed in the cylinder head toward the slit between the bores .
This is the basic configuration.

In the above basic configuration,
"The discharge passages are provided on both the intake side and the exhaust side, sandwiching the bore portion, and the two discharge passages are set in an inverted V-shape when viewed from the crankshaft axis direction so as to face toward locations away from each other on the bottom surface of the slit."
The structure is as follows.

As in Patent Document 1, it is common to form two water jackets, one above the other, on a cylinder head, but in the present invention, it is preferable for the discharge passage to communicate with the lower water jacket, which has a higher pressure.

In the present invention, the bore area is divided into two by a slit, so the bore area can be cooled evenly by passing water through the slit. However, the water jacket of the cylinder head flows at high pressure even when the engine is cold, so a strong water flow can be ejected from the discharge passage toward the slit. This improves the cooling of the bore area.

As a result, excessive heating of the air-fuel mixture can be prevented, which helps to prevent knocking. In addition, the cylinder bore can be kept highly round, which contributes to improved fuel economy by reducing piston friction, and reduced oil consumption by reducing blow-by gas.

By providing discharge passages on both the intake side and the exhaust side as in the present invention , the cooling performance of the inter-bore portion can be further improved. Also, in the present invention , the cooling water ejected from the discharge passage on the intake side and the cooling water ejected from the discharge passage on the exhaust side are reflected at the bottom surface of the slit and change direction upward while colliding with each other, so that two vortex currents are generated inside the slit. This significantly improves the contact of the cooling water with the inner surface of the slit, further improving the cooling performance of the inter-bore portion.

FIG. 2 is a plan view of the cylinder block according to the embodiment. FIG. FIG. 2 is a cross-sectional view taken along line III-III of FIG. FIG. 11 is a plan view of a cylinder block showing another example of a discharge passage.

Next, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, the terms front-rear and left-right are used to specify directions, with the front-rear direction being the crank axis direction and the left-right direction being the direction perpendicular to the crank axis and the cylinder bore axis. Regarding front and rear, the side where the timing chain is located is referred to as the front, and the side where the transmission is located is referred to as the rear. The directions are clearly shown in Figure 1.

(1). Basic Structure This embodiment is applied to an automotive gasoline internal combustion engine, which includes a cylinder block 1, a cylinder head 3 (see Figure 2) fixed to its upper surface via a gasket 2, and a front cover (timing chain cover) 4 secured to the side surfaces of the cylinder block 1 and cylinder head 3.

The internal combustion engine of this embodiment has three cylinders, and the cylinder block 1 has three cylinder bores 5 formed in the crankshaft direction, and a loop-shaped water jacket 6 that surrounds the group of cylinder bores 5. Therefore, the group of cylinder bores 5 and the water jacket 6 form three cylinders 7, and adjacent cylinders 7 are integrated via the bore gap 8.

A water supply passage 9 is formed in the cylinder block 1 on the intake side of the water jacket 6, and extends long in the crankshaft direction (along the group of cylinders 7). The water supply passage 9 is in the form of a groove that opens upward, and is closed by the gasket 2 to form a passage.

The front end of the water supply passage 9 is connected to an inlet 10. The inlet 10 is located below the top surface of the cylinder block 1 and opens to the intake side. Cooling water is pumped into the inlet 10 from a water pump (not shown). Therefore, the water pump is fixed to the intake side of the cylinder block 1. The water pump is electrically driven.

From the water supply passage 9, cooling water is sent toward a lower water jacket 11 (see FIG. 3) formed in the cylinder head 3. As shown in simplified form in FIG. 1 with cross-hatching and in solid lines in FIG. 2, a communication passage 12 is formed on the underside of the cylinder head 3 to send cooling water to the lower water jacket 11. The communication passage 12 opens into the water supply passage 9 by drilling holes in the gasket 2, and two are formed at the front and rear of each cylinder 7.

Although not shown in the figure, the cylinder head 3 is formed with a lower water jacket 11 consisting of an intake-side lower jacket located below the intake ports, a lower center jacket located generally above the group of cylinder bores 5 and extending in the crankshaft direction, and an exhaust-side lower jacket located below the group of exhaust ports. In addition, an upper water jacket is formed above the lower water jacket 11.

The cooling water for the cylinder block is sent to the lower water jacket 11 through the communication passage 12, and then sent to the upper water jacket from the lower center jacket that constitutes the lower water jacket 11. Therefore, the lower water jacket 11 is at a higher pressure than the upper water jacket.

The reference number 13 in Figures 2 and 3 indicates a head bolt, and the reference number 14 in Figure 2 indicates a downward hole formed as a remnant of a foot provided to support the core during casting. In addition, in Figure 2, the reference number 2a indicates the combustion chamber (recess), the reference number 2b indicates the end of the intake port, the reference number 2c indicates the beginning of the exhaust port, and the reference number 2d indicates the plug hole in which the ignition plug is located.

(2) Cylinder Cooling Means By forming the water supply passage 9 in the cylinder block 1, a wall portion 15 is formed in the cylinder block 1, sandwiched between the water jacket 6 and the water supply passage 9. Furthermore, lower discharge passages 16 that traverse the water jacket 6 and spray cooling water toward the cylinders 7 are formed in portions of the wall portion 15 located to the left and right of the center of each cylinder 7 (or cylinder bore 5) in a plan view.

The lower discharge passage 16 is formed as a groove (slit) with a cross-sectional shape of a semicircle or a square that opens upward, and is sealed with a gasket 2 to form a tunnel. The water jacket 6 may be of equal depth over its entire length, or the depth may change smoothly, for example, being shallowest on the side of the center of the cylinder 7 and deepest on the side of the bore section 8.

In the cylinder block 1, the cooling water that is sprayed from each lower discharge passage 16 to cool the cylinders flows through the water jacket 6 from the intake side to the exhaust side, and is discharged into the lower water jacket 11 of the cylinder head 3 through a connecting passage (not shown). Therefore, the cooling water sprayed toward the central cylinder 7 passes by the sides of the cylinders 7 at both the front and rear ends and heads toward the exhaust side.

A slit 17 is formed in the bore section 8, which opens upward and divides it in half in the crankshaft direction. The slit 17 is formed by lowering a milling cutter. Therefore, the bottom surface 17a of the slit 17 has an arc shape that bulges downward (concave upward) when viewed from the crankshaft direction.

The upper discharge passage 18 is formed at the lower end of the cylinder head 3 on both the left and right sides of the slit 17. The upper discharge passage 18 is the discharge passage described in the claims, and is inclined with respect to the cylinder bore axis as viewed from the crankshaft axis direction so as to face the slit 17.

As shown in FIG. 3, the extension lines 18a of the left and right upper discharge passages 18 reach the bottom surface 17a of the slit 17, but the left and right upper discharge passages 18 form an inverted V-shape when viewed from the crankshaft axis direction, and the extension lines 18a of both upper discharge passages 18 do not intersect above the bottom surface 17a of the slit 17, and the intersection point between both extension lines 18a and the bottom surface 17a is some distance in the left-right direction from the left-right middle position of the slit 17.

The water flows ejected from both upper discharge passages 18 are reflected by the bottom surface 17a of the slit 17, collide with each other, and change direction upwards, then hit the gasket 2 and move away from each other. As a result, two vortex flows are generated in the slit 17. This dramatically improves the contact of the cooling water with the inner surface of the slit 17, and significantly improves heat exchange from the inner surface of the slit 17 to the cooling water.

And because most of the cooling water in the water supply passage 9 flows into the lower water jacket 11 of the cylinder head 3, the water pressure in the lower water jacket 11 is high as described above, and high-pressure cooling water is ejected from the upper discharge passage 18 into the slit 17. Therefore, the bore section 8 can be cooled accurately.

When the lower discharge passage 16 is provided in the cylinder block 1 as in the embodiment, the intake side portion of the upper end of each cylinder 7 is pinpoint-cooled, which has the advantage of suppressing excessive heating of the mixture during the intake stroke and suppressing knocking. It also contributes to maintaining the roundness of the cylinder bore 5.

In the above embodiment, the upper discharge passage 18 on the intake side and the upper discharge passage 18 on the exhaust side are aligned in a straight line in the left-right direction in a plan view, but in the modified example shown in FIG. 4, the orientation of the upper discharge passage 18 on the exhalation side and the upper discharge passage 18 on the exhaust side are changed, and both upper discharge passages 18 are arranged in a position where their extensions intersect. This configuration reliably prevents the backflow phenomenon in which the water flow ejected from one upper discharge passage 18 is reflected by the slit 17 and flows toward the other upper discharge passage 18.

Although the embodiment of the present invention has been described above, the present invention can be embodied in various other ways. For example, the target internal combustion engine is not limited to a three-cylinder engine, and the invention can also be applied to multi-cylinder internal combustion engines other than three cylinders.

The upper discharge passage may be formed on only one of the intake side or exhaust side. Whether it is formed on both sides or only on one side, it is possible to form multiple upper discharge passages on the intake side or exhaust side.

The present invention can be embodied in an internal combustion engine. Therefore, it can be used industrially.

REFERENCE SIGNS LIST 1 Cylinder block 3 Cylinder head 5 Cylinder bore 6 Water jacket 7 Cylinder 8 Interbore portion 9 Water supply passage 11 Lower water jacket 12 Communication passage 17 Slit 18 Upper discharge passage (discharge passage in claims)

Claims (1)

The engine has a cylinder block and a cylinder head fixed to the upper surface of the block.
The cylinder block has a plurality of cylinder bores arranged in the crankshaft direction with a bore-to-bore portion interposed therebetween, and a water jacket is formed so as to surround the group of cylinder bores. A slit is formed in the bore-to-bore portion, the slit having an upward opening so as to divide the bore-to-bore portion in two in the crankshaft direction.
an internal combustion engine, wherein the cylinder head is formed with a discharge passage for ejecting cooling water from a water jacket formed in the cylinder head toward a slit between the bores,
The discharge passages are provided on both the intake side and the exhaust side of the bore portion, and the two discharge passages are set in an inverted V-shape as viewed from the crankshaft axis direction so as to face toward positions spaced apart from each other on the bottom surface of the slit.
Internal combustion engine.

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