JP4304491B2 - Engine cooling structure - Google Patents

Description

  The present invention relates to a cooling structure for an engine that cools a cylinder with water jacket cooling water formed around the cylinder.

  A water jacket is formed around the cylinder of the engine, and a cylinder block, a cylinder head, a piston in the cylinder, and the like are cooled by cooling water flowing in the water jacket, and these are maintained at an appropriate temperature.

  By the way, the temperature of the inner wall of the cylinder block forming the cylinder is likely to become high due to the high-temperature combustion gas at the portion located above the piston during the combustion stroke, and a temperature difference due to the position tends to occur. Such a temperature difference becomes a factor of deformation of the cylinder, which leads to an increase in oil consumption or an increase in friction. Therefore, it is desirable that the temperature of the cylinder block inner wall be as uniform as possible at each position.

Conventionally, in order to reduce the temperature difference in the vertical direction on the inner wall of the cylinder block, there is one in which the heat capacity is larger in the lower part than in the upper part. For example, in the cylinder block disclosed in Patent Document 1, the cylinder liner cast on the inner wall of the cylinder block is made thicker from the upper side to the lower side, so that the heat capacity of the inner wall of the cylinder block is reduced toward the upper side. .
JP 2000-64902 A

  Thus, by making the heat capacity of the inner wall of the cylinder block smaller toward the upper side, it is possible to effectively increase the cooling effect and effectively suppress the temperature rise of the portion that tends to become higher in the vertical direction of the inner wall of the cylinder block. .

  However, in the water jacket, the cooling water flowing through the inner peripheral side, that is, the portion close to the inner wall of the cylinder block has a large cooling effect, whereas the cooling water flowing through the outer peripheral side has a low contribution to the cylinder cooling effect. However, in the above-described conventional technology, no consideration is given in this respect, and the improvement of the water jacket cooling performance, that is, the uniformization of the temperature of the inner wall of the cylinder block, is naturally limited.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an engine cooling structure that can effectively cool the vicinity of the combustion chamber and make the temperature of the cylinder block inner wall uniform. It is to provide.

In the following, means for achieving the above object and its effects are described.
(1) The invention according to claim 1 is an engine cooling structure in which a cylinder liner is cooled by cooling water flowing through a water jacket, and the cylinder liner is integrally formed with an upper deck that supports a cylinder head. The upper deck forms the upper wall of the water jacket, and the bottom surface on the water jacket side is in the cylinder axial direction between the outer bottom surface which is the outer portion in the cylinder radial direction and the inner bottom surface in the cylinder radial direction. The outer bottom surface has a cylinder head side in the cylinder axial direction as a top portion and the opposite side to the bottom portion in the cylinder axial direction than the inner bottom surface. The water jacket is provided on the bottom side, and the water jacket is positioned between the outer bottom surface and the inner bottom surface in the cylinder axial direction. It is summarized in that the flow path cross-sectional area of the cylinder radially inwardly due to a difference in is intended to be set larger than the flow path cross-sectional area of the cylinder radially outwardly.

According to the said structure, the flow volume of the cooling water which flows into the cylinder block inner wall side which forms a cylinder can be increased. Therefore, it is possible to effectively cool the portion constituting the upper part of the cylinder where the combustion gas is in direct contact with the combustion gas during the combustion stroke, that is, the upper part of the inner wall of the cylinder block. Uniformity can be achieved. In order to increase the cooling water flow rate and further improve the cooling efficiency, the flow rate of the water jacket is gradually or gradually increased from the inner peripheral side to the outer peripheral side so as not to disturb the flux. It is desirable to change the road cross-sectional area.
Moreover, according to the said structure, in the upper part of a water jacket, the flow-path cross-sectional area can be narrowed toward the outer peripheral side, and the cooling water distribution which flows into an inner peripheral side can be increased. As a result, the upper part of the inner wall of the cylinder block can be cooled more effectively, and the temperature of the inner wall of the cylinder block can be made more uniform.
Moreover, according to the said structure, since the outer deck side becomes thicker than the inner peripheral side of a cylinder, the rigidity of the outer peripheral side part can be improved. As a result, the upper deck is deformed at the time of fastening with the head bolt, and the cylinder block pressed by the upper deck falls into the inside thereof, thereby suppressing the deformation of the cylinder and improving the sealing performance between the cylinder and the gasket. Will be able to. In particular, when the cylinder block adopts a structure in which its cylinder liner and upper deck are formed separately from other parts, the rigidity of the inner wall of the cylinder block largely depends on the rigidity of the upper deck, so the effect is more remarkable. It becomes.

(2) The invention according to claim 2 is the engine cooling structure according to claim 1, wherein the engine includes a first divided body including the cylinder liner and the upper deck, and a cylinder liner. A second divided body including an outer wall surrounding the outer periphery is formed separately, and the water jacket is formed between the outer peripheral surface of the cylinder liner and the inner peripheral surface of the outer wall It is the gist.

(3) The invention according to claim 3 is the engine cooling structure according to claim 2, wherein the upper deck has a deck inner portion which is a portion on the inner side in the cylinder radial direction and a cylinder radial outer side connected thereto. The deck inner portion is connected to the cylinder liner, and the deck outer portion is supported by the top surface of the outer wall. There is a summary.

(4) The invention according to claim 4 is the engine cooling structure according to claim 3, wherein the inside of the deck forms an upper wall of the water jacket, and the outside of the deck is The gist is that the whole is supported by the top surface of the outer wall.
  (5) The invention according to claim 5 is characterized in that, in the engine cooling structure according to claim 4, the outer peripheral surface of the inner side of the deck is in contact with the inner peripheral surface of the outer wall.
  (6) The invention according to claim 6 is the engine cooling structure according to any one of claims 2 to 5, wherein the inner bottom surface of the upper wall of the water jacket is the innermost in the cylinder radial direction. The gist is that the portion is located on the top side in the cylinder axial direction from the top surface of the outer wall.

(7) The invention according to claim 7 is the engine cooling structure according to any one of claims 1 to 6, wherein the bottom surface of the upper wall of the water jacket extends from the cylinder radial direction inside to the cylinder radial direction outside. The gist is to incline from the top side in the cylinder axial direction toward the bottom side in the cylinder axial direction as it goes to.

According to the said structure, it can suppress that disorder arises in the flux of the cooling water which flows through a water jacket upper part, and can suppress the fall of the flow rate resulting from this. As a result, the upper part of the cylinder block inner wall can be cooled more effectively.

(8) According to an eighth aspect of the present invention, in the engine cooling structure according to the first to seventh aspects, the thickness of the cylinder liner increases from the top in the cylinder axial direction toward the bottom in the cylinder axial direction. The water jacket is configured such that the flow passage cross-sectional area on the bottom side in the cylinder axial direction is set smaller than the flow cross-sectional area on the top side in the cylinder axial direction through the setting of the thickness of the cylinder liner. It is the gist.

According to the above configuration, since the heat capacity of the inner wall of the cylinder block is larger on the lower side than on the upper side, the temperature difference in the vertical direction is reduced. Moreover, the flow passage cross-sectional area is narrowed toward the lower side of the water jacket depending on the thickness, so that the cooling water distribution at the upper part of the water jacket can be increased. As a result, the upper part of the inner wall of the cylinder block can be cooled more effectively Will be able to.

(9) The invention according to claim 9 is characterized in that, in the engine cooling structure according to any one of claims 1 to 8, the upper deck supports the cylinder head through the entire top surface thereof.

Hereinafter, an embodiment in which the present invention is embodied in an in-line 4-cylinder water-cooled engine will be described with reference to the drawings.
FIG. 1 is a perspective view of a main body portion of an engine 1 according to the present embodiment. As shown in the figure, the engine 1 includes a cylinder head 2 and a cylinder block 3, and the cylinder head 2 is fixed to the cylinder block 3 via a gasket 4. A head cover is attached above the cylinder head 2, and an oil pan is attached below the cylinder block 3.

  2A and 2B are views showing a perspective structure and a side structure of the cylinder block 3, respectively. As shown in the figure, the cylinder block 3 is formed with four cylinders 5 at the top and a crankcase 6 at the bottom. A crankshaft is rotatably supported on the crankcase 6 by a bearing (not shown). An upper deck 7 on which the cylinder head 2 is placed is provided on the top of the cylinder block 3.

  FIG. 3 is an exploded perspective view of the cylinder block 3. As shown in the figure, the cylinder block 3 according to the present embodiment is divided and formed at a middle portion between the upper deck 7 and the crankcase 6 with a portion serving as a water jacket formed around the cylinder as a boundary. . Specifically, an inner peripheral block 10 in which the cylinder block inner wall 8 constituting the cylinder-side peripheral wall of the water jacket and the upper deck 7 are integrally formed, a cylinder outer wall 12 constituting the outer peripheral wall of the water jacket, and the crank The case 6 is divided into an outer peripheral block 15 formed integrally. The cylinder block 3 is formed by assembling the inner peripheral block 10 and the outer peripheral block 15 together.

  4A and 4B are views showing a perspective structure and a side structure of the inner peripheral block 10, respectively. As shown in the figure, the cylinder block inner wall 8 is formed in a shape in which four circular pipes serving as cylinder liners of each cylinder are continuously connected, and the cylinder 5 is formed by the inner peripheral surface 23 of each cylinder. The peripheral wall surface is configured. And the outer peripheral surface 24 of each cylindrical body comprises the wall surface by the side of the cylinder of a water jacket by the inner peripheral block 10 being assembled | attached to the outer peripheral block 15. FIG. The upper deck 7 is formed at the upper end 8 a of the cylinder block inner wall 8.

  5A and 5B are views showing a perspective structure and a side structure of the outer peripheral block 15, respectively. As shown in the figure, a cylinder outer wall 12 is formed on an upper portion of the crankcase 6 so as to protrude upward. When the outer peripheral block 15 is assembled with the inner peripheral block 10, the cylinder outer wall 12 has an inner peripheral surface 25 facing the outer peripheral surface 24 of the cylinder block inner wall 8, that is, an outer peripheral wall of the water jacket. It is formed in a substantially annular shape. The top surface of the cylinder outer wall 12 serves as a receiving surface 12a against which the upper deck 7 of the inner peripheral block 10 comes into contact.

  6 is a cross-sectional view of the cylinder block 3 taken along line VII-VII in a state where the cylinder head 2 and the cylinder block 3 are assembled (see FIG. 1). As shown in the figure, the inner peripheral block 10 has its inner cylinder block wall 8 inserted inside the outer cylinder wall 12 (see FIG. 3), and the end of the upper deck 7 contacts the receiving surface 12a of the outer cylinder wall 12. In this way, the outer peripheral block 15 is assembled. The inner peripheral block 10 is fixed to the outer peripheral block 15 by the cylinder head 2 and the cylinder outer wall 12 being fastened by a head bolt 27 and the upper deck 7 being fixed to the cylinder outer wall 12. .

  A water jacket 30 is defined around the cylinder by the outer peripheral surface 24 of the cylinder block inner wall 8, the inner peripheral surface 25 of the cylinder outer wall 12, and the lower surface 7a of the upper deck 7. That is, in the present embodiment, the upper deck 7 is an upper wall that partitions the upper portion of the water jacket 30.

Next, the cooling structure of the cylinder block in this embodiment is demonstrated.
FIG. 7 is a schematic view of a cylinder block cross section around the water jacket. Note that the thickness of the cylinder block inner wall and the upper deck in the figure are exaggerated for easy understanding.

  As shown in the figure, in this embodiment, the cylinder block inner wall 8 is thicker on the lower side than on the upper side, that is, the thickness d2 of the lower end 8b is larger than the thickness d1 of the upper end 8a. Is formed. Specifically, the thickness is configured to gradually increase from the upper side to the lower side.

  Thereby, the cylinder block inner wall 8 has a smaller heat capacity on the upper side than the heat capacity on the lower side. In addition, the flow passage cross-sectional area of the water jacket 30 is narrowed toward the lower side due to its thickness, so that more cooling water is distributed to the upper side of the water jacket 30.

  Further, the water jacket 30 of the present embodiment is set so that the flow path cross-sectional area on the inner peripheral side is larger than the outer peripheral side. The “outer peripheral side (left side in FIG. 7)” and “inner peripheral side (right side in FIG. 7)” indicate the radial direction of the cylinder 5 (the same applies hereinafter).

  Specifically, the upper deck 7 constituting the upper wall above the water jacket 30 is thicker on the cylinder outer wall 12 side than the cylinder block inner wall 8 side, that is, on the cylinder outer wall 12 side than the thickness d3 on the cylinder block inner wall 8 side. The thickness d4 is formed to be large. As a result, the upper deck 7 is positioned downward, that is, on the water jacket 30 side as the outer peripheral portion thereof. Specifically, the lower surface 7a of the upper deck 7 is inclined downward toward the outer peripheral side.

  In other words, the water jacket 30 of the present embodiment is configured such that the cross-sectional area of the flow path becomes narrower toward the outer peripheral side in the upper part due to the thickness of the upper deck 7, and thereby the inner peripheral side, that is, the cylinder block inner wall 8. More cooling water is distributed to the side. The lower deck 7a of the upper deck 7 is inclined downward from the upper end 8a of the cylinder block inner wall 8 toward the cylinder outer wall 12 so that the flux at the upper part of the water jacket 30 is not disturbed. Further, by increasing the thickness of the upper deck 7 toward the outer peripheral side, the rigidity of the upper deck 7 is improved.

As described above, according to the present embodiment, the following features can be obtained.
(1) The upper deck 7 constituting the upper wall above the water jacket 30 has a larger thickness on the cylinder outer wall 12 side (thickness d4) than on the cylinder block inner wall 8 side (thickness d3). It forms so that it may be located in the lower part, ie, the water jacket 30 side, as the site | part.

  With such a configuration, the flow passage cross-sectional area on the outer periphery side of the water jacket 30 is narrowed so that more cooling water can be distributed to the inner periphery side, that is, the cylinder block inner wall 8 side forming the cylinder 5. Become. Therefore, it is possible to effectively cool the upper portion of the cylinder block inner wall 8 that constitutes the upper part of the cylinder that is heated by direct contact with the combustion gas during the combustion stroke, and the temperature of the cylinder block inner wall 8 is further increased. Uniformity can be achieved.

  Further, the rigidity of the upper deck 7 is improved by increasing the thickness of the upper deck 7. Therefore, it is possible to prevent the cylinder 5 from being deformed such that the upper deck 7 is deformed when the head bolt 27 is fastened, and the cylinder block inner wall 8 pressed against the upper deck 7 falls into the inside thereof. The sealing property between the gasket 4 can be improved. In particular, when a structure in which the cylinder block inner wall 8 (cylinder liner) and the upper deck 7 are formed separately from the other parts, such as the cylinder block 3 of the present embodiment, the rigidity of the cylinder block inner wall 8 is as follows. The effect becomes more prominent because it depends on the rigidity.

(2) The upper deck 7 is formed such that the lower surface 7a is inclined downward toward the outer peripheral side.
With such a configuration, it is possible to suppress the disturbance of the flow rate of the cooling water flowing through the upper portion of the water jacket 30 and to suppress the decrease in the flow velocity due to this. As a result, the upper part of the cylinder block inner wall 8 can be cooled more effectively.

(3) The cylinder block inner wall 8 is formed so that the lower side is thicker than the upper side, that is, the thickness d2 of the lower end 8b is larger than the thickness d1 of the upper end 8a.
With such a configuration, the heat capacity of the cylinder block inner wall 8 is larger on the lower side than on the upper side, and the temperature difference in the vertical direction is reduced. Moreover, the cooling water distribution of the upper part of the water jacket 30 can be increased by narrowing the channel cross-sectional area of the lower part of the water jacket 30 by the thickness. As a result, the upper part of the cylinder block inner wall 8 can be more effectively cooled.

  (4) The upper deck 7 has a cylinder block inner wall 8 (cylinder liner) formed integrally. With such a configuration, the shape of the lower surface 7a of the upper deck 7 serving as the upper wall above the water jacket can be freely set by a normal casting method without performing special processing such as cutting. become.

In addition, you may change each said embodiment as follows.
In the present embodiment, the upper deck 7 constituting the upper wall above the water jacket 30 is formed so as to be positioned on the lower side as the outer peripheral portion thereof, so that the flow passage cross-sectional area of the water jacket 30 is set on the outer peripheral side. The inner circumference was set to be larger. However, the present invention is not limited to this, and the cylinder outer wall 12 may be formed so as to be positioned closer to the water jacket 30 toward the upper side, and the bottom wall of the water jacket 30 may be positioned closer to the water jacket 30 toward the outer peripheral side. You may form in.

  In the present embodiment, the cylinder block inner wall 8 is formed so that the lower side is thicker than the upper side, but this is not limiting, and as shown in FIG. It may be uniform.

  In the present embodiment, the upper deck 7 of the cylinder block 3 constitutes the upper wall that defines the upper portion of the water jacket 30, but as shown in FIG. 9, the upper wall is constituted by the cylinder head bottom portion 42. And you may form this cylinder head bottom part 42 so that the outer peripheral side may be located in the water jacket 30 side.

  With such a configuration, the shape of the cylinder head bottom 42 can be changed, and the cylinder block 3 can be diverted with a normal closed deck type with the water jacket 30 opened above, and its versatility. Can be increased.

  In the present embodiment, the thickness of the upper deck 7 is gradually increased from the cylinder block inner wall 8 side toward the cylinder outer wall 12 side, and the lower surface 7a of the upper deck 7 is formed so as to be inclined downward toward the outer peripheral side. However, the present invention is not limited to this, and the upper deck 7 only needs to be positioned closer to the water jacket 30 as the outer periphery thereof. The shape of the lower surface 7a is, for example, the upper deck 47a shown in FIG. There may be a step on the cylinder outer wall 12 side. Moreover, like the upper deck 47b shown in FIG. 11, it may be stepped from the cylinder block inner wall 8 side to the cylinder outer wall 12 side.

  In this embodiment, the thickness of the upper deck 7 is made larger on the cylinder outer wall 12 side (thickness d4) than on the cylinder block inner wall 8 side (thickness d3), so that the outer peripheral portion is lower, that is, on the water jacket 30 side. It was formed so that it might be located in. However, the present invention is not limited to this, and the basic thickness of the upper deck 57 shown in FIG. 12 is thick (thickness d4), and the inner peripheral portion is made thinner so that the flow path of the water jacket 30 is reduced. The cross-sectional area may be set so that the inner peripheral side is larger than the outer peripheral side. Further, as shown in the figure, the shape of the lower surface of the upper deck 57 may be formed such that a slope inclined downward toward the outer peripheral side is formed only on the inner peripheral side, and the outer peripheral side may be flat.

  In the present embodiment, the cylinder block 3 is divided into the inner peripheral block 10 in which the cylinder block inner wall 8 and the upper deck 7 are integrally formed, and the outer peripheral block 15 having the cylinder outer wall 12. However, the present invention is not limited to this, and the upper deck 7 may be formed integrally with the cylinder outer wall 12 and separately from the cylinder block inner wall 8, or may be formed separately from the cylinder block inner wall 8 and the cylinder outer wall 12.

The perspective view of the main-body part of the engine in this embodiment. The figure which shows together (a) perspective structure and (b) side structure of a cylinder block. The exploded perspective view of the cylinder block. The figure which shows together (a) perspective structure and (b) side structure of the inner peripheral block which comprises the cylinder block. The figure which shows together (a) perspective structure and (b) side structure of the outer periphery block which comprises the cylinder block. Sectional drawing along the VII-VII line of FIG. The schematic diagram of the cylinder block cross section in the water jacket periphery. The schematic diagram of the cylinder block cross section in the water jacket periphery of another example. The schematic diagram of the cylinder block cross section in the water jacket periphery of another example. The schematic diagram of the cylinder block cross section in the water jacket periphery of another example. The schematic diagram of the cylinder block cross section in the water jacket periphery of another example. The schematic diagram of the cylinder block cross section in the water jacket periphery of another example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Cylinder head, 3 ... Cylinder block, 5 ... Cylinder, 7, 47a, 47b, 57 ... Upper deck, 7a ... Lower surface, 8, 38 ... Cylinder block inner wall, 8a ... Upper end part, 12 ... Cylinder block outer wall 30 ... Water jacket, 42 ... Cylinder head bottom, d1-d4 ... Thickness.

Claims (9)

  In the cooling structure of the engine that cools the cylinder liner with cooling water flowing through the water jacket,
  The cylinder liner is formed integrally with an upper deck that supports a cylinder head.
  The upper deck forms an upper wall of the water jacket, and a bottom surface on the water jacket side has a cylinder axial direction between an outer bottom surface that is an outer portion in the cylinder radial direction and an inner bottom surface in the cylinder radial direction. The positions are set to different positions,
  The outer bottom surface is provided closer to the cylinder axial direction bottom side than the inner bottom surface when the cylinder head side in the cylinder axial direction is the top and the opposite side is the bottom.
  The water jacket is set such that the cross-sectional area of the inner channel in the cylinder radial direction is larger than the cross-sectional area of the outer channel in the cylinder radial direction due to the difference in position between the outer bottom surface and the inner bottom surface in the cylinder axial direction. is there
  An engine cooling structure characterized by that.   The engine cooling structure according to claim 1,
  In the engine, a first divided body including the cylinder liner and the upper deck and a second divided body including an outer wall surrounding an outer periphery of the cylinder liner are separately formed. The water jacket is formed between the outer peripheral surface of the cylinder liner and the inner peripheral surface of the outer wall.
  An engine cooling structure characterized by that.   The engine cooling structure according to claim 2,
  The upper deck is composed of a deck inner portion which is a portion on the inner side in the cylinder radial direction and a deck outer portion which is a portion on the outer side in the cylinder radial direction connected thereto,
  The deck inner part is connected to the cylinder liner,
  The deck outer portion is supported by the top surface of the outer wall.
  An engine cooling structure characterized by that.   The engine cooling structure according to claim 3,
  The deck inner part forms the upper wall of the water jacket as a whole,
  The deck outer portion is entirely supported by the top surface of the outer wall.
  An engine cooling structure characterized by that.   The engine cooling structure according to claim 4,
  The outer peripheral surface of the inner side of the deck is in contact with the inner peripheral surface of the outer wall.
  An engine cooling structure characterized by that.   The engine cooling structure according to any one of claims 2 to 5,
  Of the inner bottom surface of the upper wall of the water jacket, the most inner portion in the cylinder radial direction is located closer to the top in the cylinder axial direction than the top surface of the outer wall.
  An engine cooling structure characterized by that.   The engine cooling structure according to any one of claims 1 to 6,
  The bottom surface of the upper wall of the water jacket is inclined from the top side in the cylinder axial direction to the bottom side in the cylinder axial direction from the inner side in the cylinder radial direction toward the outer side in the cylinder radial direction.
  An engine cooling structure characterized by that.   The engine cooling structure according to claim 1,
  The cylinder liner is formed in such a manner that its thickness increases from the cylinder axial direction top side toward the cylinder axial direction bottom side,
  The water jacket is configured such that the flow passage cross-sectional area on the bottom side in the cylinder axial direction is set smaller than the flow cross-sectional area on the top side in the cylinder axial direction through the setting of the thickness of the cylinder liner.
  An engine cooling structure characterized by that.   The engine cooling structure according to any one of claims 1 to 8,
  The upper deck supports the cylinder head throughout its top surface
  An engine cooling structure characterized by that.

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