JP2001159369A - Engine cooling structure - Google Patents

Abstract

(57) [Problem] To provide a cooling structure for an engine in which a water jacket is formed in a cylinder block so as to surround an outer periphery of a cylinder bore, without increasing machining costs.
By giving an appropriate temperature distribution to the cylinder wall, friction loss generated in the sliding portion with the piston is minimized. A plurality of ribs (17) extending parallel to a cylinder axis are formed on a wall surface of a water jacket (16) formed on a cylinder block (11) on a cylinder bore (12) side. The rib 17 includes an upper rib 17a located on the piston top dead center side and a lower rib 17b located on the piston bottom dead center side,
The height Ht of the upper rib 17a is substantially constant in the cylinder axis direction, and the height Hb of the lower rib 17b increases from the piston top dead center side to the piston bottom dead center side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine cooling structure for providing an appropriate temperature distribution to a cylinder wall of an engine in order to reduce frictional resistance of a piston.

[0002]

2. Description of the Related Art In recent years, in order to improve engine output and fuel efficiency, the cooling capacity around the combustion chamber and the upper part of the cylinder liner has been increased to suppress knocking, and the overcooling of the lower part of the cylinder liner has been prevented to reduce piston friction. Cooling circuits and water jackets that reduce resistance have been proposed.

For example, Japanese Patent Application Laid-Open No. 1-227850 discloses that a groove-shaped circulation chamber through which cooling water circulates is formed on an outer peripheral surface of an upper portion (top dead center side) of a cylinder liner held inside a cylinder block. By increasing the cooling capacity, it is possible to prevent seizure of the piston, prevent gas leakage and suppress knocking, and provide a convection chamber in which cooling water naturally convects on the outer peripheral surface of the lower part (bottom dead center side) of the cylinder liner. Patent Document 1 discloses a technique for preventing frictional resistance of a piston by preventing overcooling.

[0004]

However, the structure disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 1-227850 requires machining of the outer peripheral surface of the cylinder liner to form a circulation chamber and a convection chamber. There is a problem that the cost increases. In order to reduce the frictional resistance of the piston, it is desirable to lower the cooling capacity of the lower part of the cylinder liner toward the bottom dead center of the piston. Since the area is constant in the cylinder axis direction, the cooling capacity of the lower part of the cylinder liner cannot be changed in the cylinder axis direction, and it has been difficult to sufficiently exert the effect of reducing the frictional resistance of the piston.

The present invention has been made in view of the above-described circumstances, and provides an appropriate temperature distribution to a cylinder wall to minimize a friction loss generated in a sliding portion with a piston without increasing a processing cost. The purpose is to suppress.

[0006]

According to the present invention, there is provided a cooling structure for an engine in which a water jacket is formed in a cylinder block so as to surround an outer periphery of a cylinder bore. The water jacket is provided with a number of ribs extending in the cylinder axis direction on a wall surface on a cylinder bore side of the water jacket, wherein the ribs include an upper rib located on a piston top dead center side and a lower rib located on a piston bottom dead center side. The height of the rib is substantially constant in the cylinder axis direction, and the height of the lower rib is higher than the height of the upper rib, and increases from the piston top dead center side to the piston bottom dead center side. A featured engine cooling structure is proposed.

According to the above configuration, the height of the lower rib provided at the lower part of the water jacket is made higher than the height of the upper rib provided at the upper part, so that the amount of cooling water flowing through the lower part of the water jacket is reduced by the cooling water flowing through the upper part. The lower cylinder wall temperature can be raised by making the cooling effect of the lower part of the cylinder wall lower than the cooling effect of the upper part by making it smaller than the water amount. As a result, the oil film temperature on the bottom dead center side of the cylinder wall is raised as much as possible within the proper range to reduce viscosity, reduce frictional force, improve engine output, reduce fuel consumption, and reduce lubricating oil consumption. Can be saved. Further, since the ribs are formed on the cylinder block, there is no need to machine a circulation chamber or a convection chamber for supplying cooling water to the outer peripheral surface of the cylinder liner, thereby reducing the processing cost. Moreover, since the height of the lower rib increases from the piston top dead center side to the piston bottom dead center side, the cooling effect of the lower part of the cylinder wall becomes lower toward the bottom dead center side, and an appropriate temperature distribution is applied to the cylinder wall. Thus, the effect of reducing the frictional resistance of the piston can be further enhanced.

According to the invention described in claim 2,
In addition to the structure of claim 1, an engine cooling structure is proposed, wherein the thickness of the cylinder block sandwiched between the cylinder bore and the water jacket is large on the intake side and small on the exhaust side.

According to the above configuration, the thickness of the cylinder block sandwiched between the cylinder bore and the water jacket is increased on the intake side which is not easily affected by the combustion heat, so that the cooling effect of the cooling water is reduced and the combustion heat is reduced. Since the cooling effect is increased by reducing the cooling water on the exhaust side, which is easily affected, the temperature on the intake side and the exhaust side of the cylinder wall can be made uniform, and the frictional resistance of the piston can be further reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on embodiments of the present invention shown in the accompanying drawings.

1 to 6 show an embodiment of the present invention. FIG. 1 is a plan view of a cylinder block of an engine, and FIG.
FIG. 3 is a cross-sectional view taken along the line 2-2 in FIG. 1, FIG. 3 is a perspective view in which the outer wall of the water jacket of the cylinder block is cut away,
3 is a sectional view taken along line 4-4 in FIG. 3, FIG. 5 is a sectional view taken along line 5-5 in FIG. 3, and FIG. 6 is a view showing the relationship between cylinder wall temperature and frictional force.

As shown in FIGS. 1 and 2, a cylinder block 11 made of an aluminum alloy of a water-cooled four-cylinder engine is provided.
An outer wall body 14 for casting a siamese-type cylinder liner 13 defining four cylinder bores 12, and a crankcase 15 integrally connected to a lower portion of the outer wall body 14.
A water jacket 16 surrounding the outer periphery of the cylinder liner 13 and having an upper end opening to the deck surface 11 a of the cylinder block 11 is formed inside the outer wall body 14.

3 to 5, a plurality of ribs 17 extending parallel to the cylinder axis L are provided on the inner wall surface of the water jacket 16, that is, the wall surface on the side of the cylinder bores 12 in the radial direction. Protrude outward. Each of the ribs 17 linearly connects an upper rib 17a located on the piston top dead center side and a lower rib 17b located on the piston bottom dead center side from the intermediate portion. Upper rib 1
The height Ht of 7a is substantially constant in the direction of the cylinder axis L,
The height Hb of the lower rib 17b is higher than the height Ht of the upper rib 17a at the upper end thereof, and further higher toward the lower end.

Therefore, the radial width of the water jacket 16 in the portion where the rib 17 does not exist is the same as the width Wt1 on the top dead center side and the width Wb1 on the bottom dead center side. On the other hand, the radial width of the water jacket 16 in the portion where the rib 17 is present is the upper rib 1
The width Wt2 on the top dead center side corresponding to 7a and the width Wb2 on the bottom dead center side corresponding to the lower rib 17b are different. Specifically, the width Wt2 on the top dead center side is constant in the direction of the cylinder axis L, the width Wb2 on the bottom dead center side is smaller than the width Wt2 on the top dead center side, and gradually decreases from the upper end to the lower end. are doing.

As shown in FIG. 2, the thicknesses of the cylinder block 11 and the cylinder liner 13 sandwiched between the water jacket 16 and the cylinder bore 12 are different between the intake side and the exhaust side of the cylinder block 11. That is, the thickness Ti on the intake side is thicker than the thickness To on the exhaust side. Since the thickness of the cylinder liner 13 is constant in the circumferential direction, the water jacket 16
And cylinder block 11 between cylinder liner 13
Has a difference corresponding to the difference between Ti and To on the intake side and the exhaust side.

FIG. 6 shows the cylinder wall temperature Tt,
The relationship between Tb (temperature of the cylinder wall 13a) and the frictional force between the piston and the cylinder wall 13a is shown. Although the piston speed is slow above the cylinder liner 13,
An increase in the piston thrust load due to the combustion pressure makes it difficult to form an oil film, and the frictional force is minimized when the upper cylinder wall temperature Tt is relatively low.

On the other hand, since the piston speed is high in the middle portion of the cylinder liner 13, the drag resistance of the lubricating oil increases and the frictional force increases. Also cylinder liner 1
In the lower part of 3, the piston thrust load is small, so that the lower cylinder wall temperature Tb becomes easy to form an oil film up to a wall temperature higher than the top dead center side. Therefore, when the lubricating oil viscosity is further reduced, the frictional force is minimized. Become. From the above, it is possible to reduce the frictional force in the middle and lower portions of the cylinder liner 13 by increasing the lower cylinder wall temperature Tb. However, if the lower cylinder wall temperature Tb becomes too high, the oil film is cut, the sliding portion is damaged, and the cylinder liner 13 is thermally deformed, so that an operable limit wall temperature exists.

Next, the operation of the embodiment of the present invention having the above configuration will be described.

The cooling water supplied from the cooling water pump with the operation of the engine flows through the water jacket 16 of the cylinder block 11 and cools the cylinder liner 13. At this time, since the radial width Wt2 of the water jacket 16 is large at the upper part of the water jacket 16 where the upper rib 17a having the low height Ht is formed, the cooling water easily flows in the circumferential direction, and the cooling effect is enhanced. , The upper cylinder wall temperature Tt can be set lower. Thereby, the temperature of the oil film above the cylinder wall 13a (near the piston top dead center) can be appropriately maintained while preventing the engine from overheating and increasing the durability, and the frictional force can be reduced to reduce the friction loss. .

The lower portion of the water jacket 16 on which the lower rib 17b having a high height Hb is formed is connected to the lower rib 17b.
b, the radial width Wb2 of the water jacket 16 in the radial direction is reduced, so that the cooling water is less likely to flow in the circumferential direction and the cooling effect is reduced, and the cooling effect is reduced by the height Hb of the lower rib 17b. The lower the lower the water jacket 16 becomes, the higher the water jacket 16 becomes. The lower rib 17 having a high height Hb is also provided.
b reduces the amount of cooling water below the water jacket 16 and makes it difficult for the cooling water to flow in the space between the adjacent lower ribs 17b, 17b, so that the lower side of the water jacket 16 has a further cooling effect. Decrease.

As a result, the temperature of the lower part of the cylinder wall 13a (the middle part and the vicinity of the bottom dead center of the piston) can be made higher than in the prior art to reduce the viscosity of the oil film, and the sliding part of the piston and the cylinder wall 13a can be formed. It is possible to reduce the frictional force to reduce the frictional loss, to improve the output and to save the fuel consumption, and to reduce the oil film adhered to the cylinder wall 13a to reduce the consumption of the lubricating oil. it can.

Further, if the cross-sectional shape of the water jacket 16 is changed in the direction of the cylinder axis L by machining the circulation chamber and the convection chamber for flowing the cooling water on the outer peripheral surface of the cylinder liner 13, the processing cost of the cylinder liner 13 is increased. It will increase significantly. However, in this embodiment, since the ribs 17 are formed on the cylinder block 11 to change the cross-sectional shape of the water jacket 16 in the direction of the cylinder axis L, it is only necessary to change the shape of the core forming the water jacket 16. The purpose can be achieved, and the processing cost can be reduced.

Further, since the height Hb of the lower rib 17b is increased from the piston top dead center side to the piston bottom dead center side, the cooling effect of the water jacket 16 is reduced toward the bottom dead center side to reduce the cylinder wall. 13a can be given an appropriate temperature distribution, and the effect of reducing frictional resistance can be further enhanced.

Further, the thickness of the cylinder block 11 and the cylinder liner 13 interposed between the cylinder bore 12 and the water jacket 16 is increased on the intake side, which is hardly affected by the combustion heat, to reduce the cooling effect, thereby reducing the influence of the combustion heat. Since the cooling effect is increased by reducing the temperature on the exhaust side, which is easily received, the temperatures on the intake side and the exhaust side of the cylinder wall 12a can be made uniform, and the frictional resistance of the piston can be further reduced.

Although the embodiments of the present invention have been described in detail above, various design changes can be made in the present invention without departing from the gist thereof.

For example, the engine of the embodiment has a siamese type cylinder liner 13, but the present invention is also applicable to an engine having an independent cylinder liner for each cylinder or an engine having no cylinder liner. can do.

[0027]

As described above, according to the first aspect of the present invention, the height of the lower rib provided at the lower portion of the water jacket is higher than the height of the upper rib provided at the upper portion. The amount of cooling water flowing in the lower part of the jacket is made smaller than the amount of cooling water flowing in the upper part, and the cooling effect of the lower part of the cylinder wall is made lower than that of the upper part, so that the lower cylinder wall temperature can be raised. As a result, the oil film temperature on the cylinder bottom dead center side of the cylinder wall is raised as much as possible within an appropriate range to reduce viscosity, reduce frictional force, improve engine output, reduce fuel consumption, and lubricating oil consumption. Can be saved. In addition, since the ribs are formed on the cylinder block, it is not necessary to machine a circulation chamber or a convection chamber for flowing cooling water on the outer peripheral surface of the cylinder liner, thereby reducing the processing cost. In addition, since the height of the lower rib increases from the piston top dead center side to the piston bottom dead center side, the cooling effect of the lower part of the cylinder wall becomes lower toward the bottom dead center side, and an appropriate temperature distribution is applied to the cylinder wall. Thus, the effect of reducing the frictional resistance of the piston can be further enhanced.

According to the invention described in claim 2,
The thickness of the cylinder block sandwiched between the cylinder bore and the water jacket is increased on the intake side, which is not easily affected by combustion heat, to reduce the cooling effect of cooling water, and on the exhaust side, which is easily affected by combustion heat, is reduced. As a result, the cooling effect of the cooling water is increased, so that the temperatures on the intake side and the exhaust side of the cylinder wall are made uniform, so that the frictional resistance of the piston can be further reduced.

[Brief description of the drawings]

FIG. 1 is a plan view of a cylinder block of an engine.

FIG. 2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is a perspective view of an outer wall portion of a water jacket of a cylinder block cut away.

FIG. 4 is a sectional view taken along line 4-4 in FIG. 3;

FIG. 5 is a sectional view taken along line 5-5 in FIG. 3;

FIG. 6 is a diagram showing the relationship between cylinder wall temperature and frictional force.

[Explanation of symbols]

11 Cylinder block 12 Cylinder bore 16 Water jacket 17 Rib 17a Upper rib 17b Lower rib L Cylinder axis Ht Height of upper rib Hb Height of lower rib Ti Thickness between cylinder bore and water jacket To Wall between cylinder bore and water jacket Thick

Continuing from the front page (72) Inventor Kazuhiro Yamamoto 1-4-1 Chuo, Wako-shi, Saitama Pref. Inside Honda R & D Co., Ltd. (72) Inventor Masakatsu Miya 1-4-1 Chuo, Wako-shi, Saitama Co., Ltd. Honda R & D F-term (reference) 3G024 AA21 AA26 AA33 BA06 CA05 DA17 EA01

Claims (2)

[Claims] An engine cooling structure in which a water jacket (16) is formed in a cylinder block (11) so as to surround an outer periphery of a cylinder bore (12), wherein a cylinder is provided on a wall surface of the water jacket (16) on a cylinder bore (12) side. A plurality of ribs (17) extending in the direction of the axis (L) are provided, the ribs (17) being an upper rib (17a) located at the piston top dead center side and a lower rib (17b) located at the piston bottom dead center side. The height (Ht) of the upper rib (17a) is substantially constant in the direction of the cylinder axis (L), and the height (Hb) of the lower rib (17b) is
Is higher than the height (Ht) of the upper rib (17a),
An engine cooling structure characterized by increasing from a piston top dead center side to a piston bottom dead center side. 2. The cooling of the engine according to claim 1, wherein the thickness (Ti, To) between the cylinder bore (12) and the water jacket (16) is large on the intake side and small on the exhaust side. Construction.