JP2597220B2 - Cooling system for siamese-type cylinder of water-cooled multi-cylinder engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cooling device for a siamese-type cylinder of a water-cooled multi-cylinder engine, and in particular, to enhance the cooling performance of an upper portion of a continuous wall portion in which cylinder bodies are continuous. By doing
The present invention relates to a cooling device for a siamese-type cylinder of a water-cooled multi-cylinder engine that can reduce the overall length of the engine while preventing a piston ring stick.

<Prior Art> Conventionally, as a water-cooled multi-cylinder engine, for example, as shown in FIG. 4, a plurality of cylinder bodies 104a and 104b are continuously formed in a water jacket 103 of a cylinder block 102, and each cylinder body Some include so-called siamese-type cylinders 104 in which cylinder liners 105a and 105b are fitted inside 104a and 104b, respectively.

In this Siamiz type cylinder 104, the cylinder body 104a
In order to increase the cooling efficiency of the continuous wall portion 104c where the continuous wall portions 104b are continuous, a water jacket 10 is provided on the continuous wall portion 104c.
The cooling fluid passage 106 communicating with 3 is formed, and the water jacket is formed.
The cooling water circulating through the cooling passage 103 cools the continuous wall portion 104c and the cylinder liners 105a and 105b while flowing through the cooling liquid passage 106.

<Problems to be Solved by the Invention> In this conventional water-cooled multi-cylinder engine having a siamese-type cylinder, in order to prevent water leakage from the coolant passage 106 to the clan room 111, a cylinder liner 105a is provided in the coolant passage 106.
The outer surface of 105b cannot be exposed and the cooling liquid passage 106
And the cylinder liners 105a and 105b must be separated by a part of the continuous wall portion 104c which is thicker than the minimum thickness required for strength.

Therefore, if the inner diameter of the cylinder is increased in order to obtain a large output, the cooling liquid passage 106 formed in the continuous wall portion 104c becomes narrow, and the cooling efficiency is reduced.
2. Casting becomes difficult. In extreme cases, the continuous wall 104
There is no room for forming the cooling liquid passage 106 in c, and the continuous wall portion
Insufficient cooling of 104c and each cylinder liner 105a / 105b causes piston ring stick, especially top ring
The stick 108 may be generated, or the continuous wall portion 104c may have a particularly high temperature, and the thermal distortion of the cylinder 104 may increase.

Therefore, in order to prevent the occurrence of a ring stick, a keystone-type piston ring in which a ring stick is unlikely to be used is used for the top ring 108, or a sufficiently large coolant is provided in the continuous wall portion 104c by increasing the interval between cylinders. Road
Attempts have been made to form 106.

However, when a keystone type piston ring is used, there is a disadvantage that blow-by gas increases.

In addition, when the space between the cylinders is increased to form a sufficiently large coolant passage 106 in the continuous wall portion 104c, the entire length of the engine 1 becomes longer, and the Siamiz type, which is originally intended to reduce the overall length of the engine 1, is formed. The meaning of forming the cylinder 104 is lost.

On the other hand, in most cases, the ring stick occurs on the top ring 108, and it has been found that the ring stick can be almost completely prevented by efficiently cooling the portions of the cylinder liners 5a and 5b where the top ring 108 reciprocates.

The present invention has been made in view of the above circumstances,
A siamese-type cylinder cooling system for a water-cooled multi-cylinder engine that can reduce the overall length of the engine while preventing the piston ring stick by improving the cooling performance of the upper part of the cylinder liner and reduce the thermal distortion of the cylinder. It is intended to provide.

<Means for Solving the Problems> The present invention relates to, for example, FIG. 1 and FIG.
As shown in the figure, a plurality of cylinder bodies 4a and 4b adjacent to each other in a water jacket 3 of a cylinder block 2 of a water-cooled multi-cylinder engine 1 are connected to form a siamese cylinder 4, and each cylinder body 4a and 4b Assuming a cooling device for a Siamese-type cylinder of a water-cooled multi-cylinder engine, in which the cylinder liners 5a and 5b are fitted, and a cooling fluid passage 6 is formed above the continuous wall portion 4c where the cylinder bodies 4a and 4b are continuous. I have.

In the present invention, the following characteristic structure is added in order to achieve the above object on the premise of the cooling device for the Siamese type cylinder of the water-cooled multi-cylinder engine.

That is, the coolant passage 6 is cut off from the water jacket 3 and the cylinder liners 5a
The outer surface of 5b is exposed, and the cooling oil is forcibly circulated to the cooling liquid passage 6 through the cooling liquid supply passage 10, and cooling is performed in the vicinity of the center of the continuous wall portion 4c where the cylinder bodies 4a and 4b are continuous. The liquid supply path 10 is communicated with the cooling liquid path 6 so that the cooling oil flowing into the cooling liquid path 6 from the cooling liquid supply path 10 is diverted from the vicinity of the center of the continuous wall portion 4c to both sides thereof. It is characterized by having comprised in.

<Operation> In the present invention, the cooling fluid passage 6 provided above the continuous wall portion 4c is shut off from the water jacket 3, and the cooling oil is forced to circulate through the cooling fluid passage 6. The outer surface of the upper part of each of the cylinder liners 5a and 5b exposed to 6 is efficiently cooled by the cooling oil circulating in the cooling liquid passage 6.

Further, since the outer surfaces of the cylinder liners 5a and 5b are exposed to the coolant passage 6, the coolant passage 6 and the cylinder liners 5a and 5b are exposed.
There is no wall of the continuous wall 4c between the two, and the cylinder interval can be shortened.

In the present invention, the cooling liquid passage 6 may be formed only in the continuous wall portion 4c, but in particular, the cooling liquid passage 6 is formed in the upper part of each cylinder body 4a, 4b from the continuous wall portion 4c to the entire periphery of each cylinder liner 5a, 5b. In this case, the upper portions of the cylinder liners 5a and 5b can be efficiently cooled over the entire circumference, and
The temperature distribution at the upper part of 5a and 5b can be made uniform.

Furthermore, since the continuous wall portion 4c of the cylinder 4 has a large temperature drop with respect to other wall portions as much as it is not water-cooled, the cylinder 4 is liable to undergo thermal distortion. As the continuous wall portion 4c is cooled by the cooling oil passing through the cooling liquid passage 6, the temperature drop of each portion of the cylinder 4 is reduced, and the thermal distortion is reduced.

The cooling oil has a high cooling capacity because the temperature is still low in the upstream part of the cooling liquid passage 6, whereas the cooling capacity of the cylinder 4 gradually decreases as the temperature increases toward the downstream side. .

The cooling oil flowing from the coolant supply passage 10 into the coolant passage 6 is
The flow is diverted from the vicinity of the center of the continuous wall portion 4c to both sides thereof. Then, among the continuous wall portions 4c, the center portion of the wall having the highest temperature is cooled most strongly with the low-temperature cooling oil, whereas the temperature gradually increases toward both sides of the wall where the temperature gradually decreases. Cooling with rising cooling oil gradually weakens. For this reason, the temperature drop due to the cooling oil in the central portion of the continuous wall portion 4c due to the cooling oil becomes the largest, and the temperature difference between the central portion of the wall portion and both sides of the wall portion becomes small. In the case of (1), the temperature difference between the wall portions is small, and the thermal distortion is small.

<Embodiment> Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional plan view of a cooling device for a siamese-type cylinder of a water-cooled multi-cylinder engine according to one embodiment of the present invention, and FIG. 2 is a vertical sectional side view of the engine.

In this embodiment, the present invention is applied to a cooling device for a siamese cylinder of a two-cylinder overhead camshaft engine.
As shown in the figure, two cylinder bodies 4a and 4b adjacent to each other in a water jacket 3 of a cylinder block 2 of an engine 1 are continuously connected to each other to form a siamese cylinder 4.
Are formed, and cylinder liners 5a and 5b are fitted in the respective cylinder bodies 4a and 4b.

As shown in FIG. 1 and FIG.
The cylinder body 4a, including the continuous wall portion 4c
Each cylinder liner 5a is located at the upper part of the top ring 4b, that is, at the upper part of the vertical stroke range of the top ring 8 externally fitted to the piston 7.
A cooling liquid passage 6 independent of the water jacket 3 is formed so as to surround the outer periphery of 5b. The outer surfaces of the cylinder liners 5a and 5b are exposed in the cooling liquid passage 6 over the entire circumference.

 Cooling oil is forcibly circulated through the cooling liquid passage 6.

Here, cooling oil circulating through a cooling oil system completely independent of a lubrication path for lubricating each part of the engine 1 may be forcedly circulated through the cooling liquid passage 6. In order to reduce the required oil amount of the entire engine 1, a part of the lubricating oil is circulated as cooling oil to the cooling liquid passage 6 through a cooling oil system branched from a lubrication path for lubricating each part of the engine 1. ing.

That is, the central crank bearing 9 is attached to the continuous wall portion 4c.
A cooling oil supply passage 10 communicating with a cooling fluid passage 6 is formed from an oil pan 12 provided below a crank room 11 by an oil pump 13 shown in FIG. A part of the lubricating oil supplied to 9 is supplied to the cooling liquid path 6 via the cooling oil supply path 10. In the vicinity of the center of the continuous wall portion 4c where the cylinder bodies 4a and 4b are continuous with each other, the coolant supply passage 10 is communicated with the coolant passage 6 so that the cooling oil flowing into the coolant passage 6 from the coolant supply passage 10 is removed. The flow is divided from the vicinity of the center of the continuous wall portion 4c to both sides thereof.

Further, an oil return path 14 communicating from the coolant passage 6 to the crank room 11 is formed in a wall portion of the cylinder body 4a, 4b opposite to the continuous wall portion 4c, so that the oil is supplied to the coolant passage 6. The cooling oil thus dropped is dropped onto the oil pan 12 via the oil return path 14.

A part of the cooling oil supplied to the cooling liquid passage 6 passes through a gap formed between each cylinder main body 4a, 4b and each cylinder liner 5a, 5b, passes through a crankcase 11, passes through an oil pan 12
To the cylinder liner 5a, 5b
Each of the cylinder liners 5a and 5b is cooled while falling along the outer surface of the cylinder.

Further, a radiator is connected to the water jacket 3 so that the cooling water is forcibly circulated between the radiator and the water jacket 3 by a water pump 15 shown in FIG.

In this embodiment, since the cooling oil circulating in the cooling liquid passage 6 directly contacts the outer surface of the upper part of the cylinder liners 5a and 5b, the cooling efficiency of the upper parts of the cylinder liners 5a and 5b increases, and for example, the cooling oil temperature decreases. When the temperature is about 110 ° C., the temperature of the top ring 8 is maintained at about 200 ° C. or less, so that the ring stick of the top ring 8 can be reliably prevented.

In addition, since the ring stick can be prevented in this manner, a ring that generates little blow-by gas, such as a tapered shape, an inside bevel shape, a plain shape, and an undercut shape, can be used as the top ring 8.

Further, since the outer surfaces of the cylinder liners 5a and 5b are exposed to the cooling fluid passage 6, and the continuous wall portions 4c between the cooling fluid passage 6 and the cylinder liners 5a and 5b are eliminated, the cylinder spacing is reduced. The thickness of each cylinder body 4a and 4b, including the continuous wall portion 4c, can be made as thin as possible in view of strength and casting technology, thereby shortening the overall length of the engine 1 to the minimum. it can.

In addition, a part of the cooling oil supplied from the cooling fluid passage 6 to the cooling fluid passage 6 is supplied to each of the cylinder bodies 4a and 4b and each of the cylinder liners.
The oil drops from the gap formed between the oil pan 5a and the oil pan 12 through the crankcase 11, and the cooling oil circulating through the cooling liquid passage 6 is pumped up from the oil pan 12 by the oil pump 13 and pressurized by cranking. Since it is a part of the lubricating oil supplied to the bearing part 9, there is no problem at all. On the contrary, each of the cylinder liners 5a and 5b can be cooled by a part of the cooling oil, and the cooling efficiency of each of the cylinder liners 5a and 5b is further improved. Can be enhanced.

<Effects of the Invention> As described above, in the present invention, the cooling fluid passage formed at the upper part of the continuous wall portion of the siamese cylinder is made independent of the water jacket, and the cooling oil is forcibly circulated. Since the outer surfaces of the respective cylinder liners are exposed, the respective cylinder liners can be efficiently cooled by the cooling oil circulating in the cooling liquid passage, and the generation of the ring stick can be prevented.

Also, by exposing the outer surface of each cylinder liner to the cooling fluid passage, the continuous wall between the cooling fluid passage and each cylinder liner is eliminated, thereby shortening the cylinder interval and shortening the overall length of the engine. be able to.

Furthermore, since the continuous wall portion 4c of the cylinder 4 has a large temperature drop with respect to other wall portions as much as it is not water-cooled, the cylinder 4 is liable to undergo thermal distortion. As the continuous wall portion 4c is cooled by the cooling oil passing through the cooling liquid passage 6, the temperature drop of each portion of the cylinder 4 is reduced, and the thermal distortion is reduced.

The cooling oil has a large cooling capacity because the temperature is still low in the upstream part of the cooling liquid passage 6, whereas the cooling capacity of the cylinder 4 gradually decreases as the temperature rises toward the downstream side. Go.

The cooling oil flowing from the coolant supply passage 10 into the coolant passage 6 is
The flow is diverted from the vicinity of the center of the continuous wall portion 4c to both sides thereof. Then, among the continuous wall portions 4c, the center portion of the wall having the highest temperature is cooled most strongly with the low-temperature cooling oil, whereas the temperature gradually increases toward both sides of the wall, where the temperature gradually decreases. Cooling with rising cooling oil gradually weakens. Therefore, the temperature of the continuous wall portion 4c at the center portion of the wall is greatly reduced by the cooling oil, and the temperature drop between the center portion of the inner wall and both sides of the inner wall is reduced. The temperature difference between the wall portions is reduced, and the thermal distortion is reduced.

[Brief description of the drawings]

1 and 2 show a cooling device for a siamese-type cylinder of a water-cooled multi-cylinder engine according to one embodiment of the present invention. FIG. 1 is a cross-sectional plan view, and FIG. is there. FIG. 3 is a longitudinal sectional side view of a cooling device for a conventional Siamese cylinder of a water-cooled multi-cylinder engine. 1 ... engine, 2 ... cylinder block, 3 ... water jacket, 4 ... siamese cylinder, 4a ...
Cylinder body, 4b …… Cylinder body, 4c …… Slave wall part, 5a …… Cylinder liner, 5b …… Cylinder liner, 6
…… Cooling fluid path.

Claims (1)

(57) [Claims] A siamese type cylinder (4) comprising a plurality of cylinder bodies (4a) and (4b) adjacent to each other in a water jacket (3) of a cylinder block (2) of a water-cooled multi-cylinder engine (1). And each cylinder liner (5a) is attached to each cylinder body (4a) and (4b).
a) Siamiz of a water-cooled multi-cylinder engine in which a coolant passage (6) is formed at the top of a continuous wall (4c) where cylinder bodies (4a) and (4b) are continuous with each other. In the cooling device for a cylindrical cylinder, the coolant passage (6) is shut off from the water jacket (3), and each cylinder liner (5) is inserted into the coolant passage (6).
a) The outer surface of (5b) is exposed, and the cooling oil is forcibly circulated through the cooling liquid supply path (10) to the cooling liquid path (6), so that the cylinder bodies (4a) and (4b) In the vicinity of the center of the continuous continuous wall portion (4c), the coolant supply passage (10) was communicated with the coolant passage (6), and flowed into the coolant passage (6) from the coolant supply passage (10). A cooling device for a siamese-type cylinder of a water-cooled multi-cylinder engine, wherein cooling oil is diverted from a portion near a center of a continuous wall portion (4c) to both sides thereof.