JP2016048060A - Piston cooling structure of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston cooling structure of an internal combustion engine which can cool a piston over a wide range.SOLUTION: An internal combustion engine comprises an injection nozzle 60 which injects a lubricant to a piston rear face 22. One region which is obtained by dividing a plane including a piston center axis PC and parallel with a piston axis PPC, and the piston rear face 22 by using a cross line crossing with the piston rear face 22 is set as a third region RK3, and the other region is set as a fourth region RK4. Then, a salient part 26 which guides the lubricant colliding with the third region RK3 so as to progress toward the fourth region RK4 while a piston 20 moves between a lower dead point and an upper dead point is arranged at the piston rear face 22.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a structure for cooling a piston of an internal combustion engine.

In order to cool a piston of an internal combustion engine, a cooling structure that injects lubricating oil toward the back side of the top surface of the piston is known.
For example, in the internal combustion engine described in Patent Document 1, a cooling channel serving as a cooling oil passage is provided inside the piston. Then, the oil for cooling is supplied into the cooling channel by injecting the oil from below the piston toward the oil inlet of the cooling channel.

JP 2007-278220 A

  By the way, in the cooling structure described in the above-mentioned document 1, since the cooling channel is formed in the vicinity of the outer periphery of the piston, it is not possible to sufficiently cool the central portion of the piston where the heat is easily trapped and the temperature is relatively high. For example, there is a possibility that the amount of deformation of the piston becomes large and the sliding resistance in the cylinder becomes large.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a piston cooling structure for an internal combustion engine capable of cooling the entire central portion of the piston.

  A piston cooling structure for an internal combustion engine that solves the above problem includes an injection nozzle that injects a cooling fluid onto the back surface of a piston surrounded by a pair of connecting walls that connect an intake side skirt portion and an exhaust side skirt portion. Then, one region obtained by dividing the back surface into two at the intersection line between the plane including the central axis of the piston and perpendicular to the piston pin axis and the back surface is defined as a first region, and the other region is defined as a second region. . In addition, one region obtained by dividing the back surface into two at the intersection line between the plane including the central axis of the piston and parallel to the piston pin axis and the back surface is defined as a third region, and the other region is defined as a fourth region. . When each region is defined in this manner, when the piston is at the bottom dead center, the cooling fluid collides with the first region on the third region side, and when the piston is at the top dead center, the third region The injection direction of the injection nozzle is set so that the cooling fluid collides with the second region on the side. Then, on the back surface of the piston, while the piston moves between the bottom dead center and the top dead center, the cooling fluid that collides with the third region side is guided to the fourth region side. A guiding part is provided.

  According to this configuration, when the piston is at bottom dead center, the cooling fluid collides with the first region on the third region side, and when the piston is on top dead center, The injection direction of the injection nozzle is set so that the cooling fluid collides with the second region. Therefore, in the third region, that is, one region in which the back surface of the piston is divided into two at the intersection line between the plane including the central axis of the piston and parallel to the piston pin axis and the back surface of the piston, the setting of the injection direction is used. Cooling with a cooling fluid is performed.

  In addition, a guiding portion is provided for guiding the cooling fluid that has collided with the third region side toward the fourth region side while the piston moves between the bottom dead center and the top dead center. Yes. Therefore, in the fourth region, that is, the other region in which the back surface of the piston is divided into two at the intersection line between the plane including the central axis of the piston and parallel to the piston pin axis and the back surface of the piston, such a guide portion is provided. Therefore, cooling with the cooling fluid is performed.

  Thus, according to the same configuration, the position where the cooling fluid hits on the back surface of the piston changes according to the position of the piston in the cylinder, and the flow direction of the cooling fluid hitting the back surface of the piston is changed by the guiding portion. As a result, the cooling fluid is supplied to the entire central portion of the back surface of the piston, whereby the entire central portion of the piston can be cooled.

  In the piston cooling structure, it is preferable that the guide portion is constituted by a protrusion or a recess protruding from the back surface of the piston. According to these configurations, since the flow direction of the cooling fluid can be changed by the protrusions and the recesses, the cooling fluid that has collided with the third region side is guided toward the fourth region side. It becomes possible.

  In the piston cooling structure, the collision position between the back surface of the piston and the cooling fluid changes between the first region and the second region while the piston moves between the bottom dead center and the top dead center. Preferably, the injection direction of the injection nozzle is set, and the guide portion is provided on the locus of the collision position that changes as the piston moves.

  According to this configuration, since the guide portion is provided on the locus where the collision position between the back surface of the piston and the cooling fluid changes, the cooling fluid that collides with the back surface of the piston can be reliably applied to the guide portion. it can.

  In the above-described piston cooling structure, it is preferable that the injection direction of the injection nozzle be inclined in two axial directions, ie, a direction parallel to the piston pin axis and a direction intersecting with the parallel direction.

  According to this configuration, since the injection direction of the injection nozzle is inclined in a direction parallel to the piston pin axis, the back surface of the piston is moved while the piston moves between the bottom dead center and the top dead center. And the cooling fluid collide with each other from the first region to the second region. Therefore, when the piston is at the bottom dead center, the cooling fluid is caused to collide with the first area on the third area side. When the piston is on the top dead center, the inside of the second area on the third area side is It is also possible to make the cooling fluid collide with.

  Moreover, according to the same structure, the injection direction of the injection nozzle is also inclined in the direction intersecting with the direction parallel to the piston pin axis. Therefore, the cooling fluid that collides with the back surface of the piston easily flows from the third region to the fourth region, and can further promote the above-described operation and effect of the guiding portion.

The schematic diagram which shows the cross-sectional structure perpendicular | vertical with respect to a piston pin axis | shaft about the cylinder periphery and piston of an internal combustion engine to which the piston cooling structure was applied. The schematic diagram which shows the cylinder periphery and sectional structure of a piston along the 2-2 line of FIG. The schematic diagram which shows the back surface of a piston. The schematic diagram which shows the back surface of a piston. The schematic diagram which shows the back surface of a piston. The schematic diagram which shows the flow of the lubricating oil in the back surface of a piston. The schematic diagram which shows the back surface of the piston in other embodiment. FIG. 8 is a sectional view of the piston taken along line 8-8 in FIG. 7. The schematic diagram of the back surface of the piston for showing the injection direction of the lubricating oil in other embodiment.

Hereinafter, an embodiment of a piston cooling structure for an internal combustion engine will be described with reference to FIGS.
As shown in FIG. 1, a piston 20 is housed in a cylinder 10 of an internal combustion engine so as to be movable up and down. On the outer periphery of the piston 20, there is provided an intake side skirt portion 27 extending from the top surface 21 to the lower side of the cylinder 10 and disposed on the intake port side of the internal combustion engine. Similarly, on the outer periphery of the piston 20, there is provided an exhaust side skirt portion 29 that extends from the top surface 21 below the cylinder 10 and is disposed on the exhaust port side of the internal combustion engine.

  A plurality of piston rings 30 are assembled on the outer periphery of the piston 20. Further, a cylindrical piston pin 40 is inserted into the piston 20, and the small diameter end side of the connecting rod 50 is assembled to the outer periphery of the piston pin 40.

  Hereinafter, in the cylindrical piston 20 having the circular top surface 21, the central axis of the cylindrical shape is referred to as “piston central axis PC”. The central axis of the piston pin 40 is referred to as “piston pin axis PPC”. Further, as shown in FIGS. 1, 3, 6, 7, and 9, the diameter direction of the piston 20 and the direction perpendicular to the piston pin axis PPC is referred to as the “X direction”, and the piston central axis PC One X direction is called “X1 direction” and the other X direction is called “X2 direction”. As shown in FIGS. 2, 3, 6, 7, 8, and 9, the diameter direction of the piston 20 and parallel to the piston pin axis PPC is referred to as the “Y direction”. With respect to the central axis PC, one Y direction is referred to as “Y1 direction” and the other Y direction is referred to as “Y2 direction”.

  Below the cylinder 10, there is provided an injection nozzle 60 that injects the lubricating oil J as a cooling fluid toward the piston back surface 22 that is the back surface of the top surface 21. The injection nozzle 60 is connected to an oil pan 61 in which lubricating oil is stored via an oil gallery and an oil pump 62.

  The injection direction of the injection nozzle 60 is inclined in a direction intersecting with a direction parallel to the piston pin axis PPC. For example, the injection direction of the injection nozzle 60 is set to a line segment SL parallel to the central axis of the cylinder 10 on a plane that intersects the direction parallel to the piston pin axis PPC (such as on a plane orthogonal to the piston pin axis). On the other hand, it is set to be inclined toward the piston central axis PC by the first angle θA. Therefore, as shown by the solid line in FIG. 1, the collision position A where the piston back surface 22 and the lubricating oil J collide when the position of the piston 20 is at the bottom dead center, and the two-dot chain line in FIG. As shown, the collision position B where the piston back surface 22 and the lubricating oil J collide with each other when the position of the piston 20 is at the top dead center is different. More specifically, the collision position of the lubricating oil J changes in a direction closer to the piston center axis PC in the X direction as the position of the piston 20 approaches the top dead center.

As shown in FIG. 2, the piston back surface 22 is provided with a pair of connecting walls 23 extending so as to expand downward of the cylinder 10.
As shown in FIG. 3, the connecting wall 23 is a wall portion that connects the intake side skirt portion 27 and the exhaust side skirt portion 29. In the present embodiment, the above-described cooling lubricant J is injected and supplied from the injection nozzle 60 to the piston back surface 22 surrounded by the pair of connecting walls 23.

  As shown in FIG. 2, the injection direction of the injection nozzle 60 is also inclined in a direction parallel to the piston pin axis PPC. For example, as shown in FIG. 2, the injection direction of the injection nozzle 60 is a second angle θB with respect to a line segment SL parallel to the central axis of the cylinder 10 on a plane parallel to the piston pin axis PPC. It is set so as to incline toward the piston center axis PC by the amount. Therefore, as shown by the solid line in FIG. 2, the collision position A where the piston back surface 22 collides with the lubricating oil J when the position of the piston 20 is at the bottom dead center, and the two-dot chain line in FIG. As shown, the collision position B where the piston back surface 22 and the lubricating oil J collide with each other when the position of the piston 20 is at the top dead center is different. More specifically, the collision position of the lubricating oil J changes from the Y1 direction to the Y2 direction as the position of the piston 20 approaches the top dead center.

As shown in FIG. 3, the pair of connecting walls 23 are provided with pin bosses 24 in which insertion holes 25 for inserting the piston pins 40 are formed.
Further, as described above, the collision position A of the lubricating oil J when the position of the piston 20 is at the bottom dead center and the collision position of the lubricating oil J when the position of the piston 20 is at the top dead center. Unlike B, the closer the position of the piston 20 approaches top dead center, the more the collision position of the lubricating oil J changes in the direction of approaching the piston center axis PC in the X direction of the piston 20. Further, as the position of the piston 20 approaches the top dead center, the collision position of the lubricating oil J changes from the Y1 direction to the Y2 direction. Therefore, while the position of the piston 20 changes between the bottom dead center and the top dead center, the collision position of the lubricating oil J changes continuously, and as shown by a two-dot chain line in FIG. The trajectory of the collision position of the oil J changes obliquely with respect to the diameter direction of the piston 20 parallel to the piston pin axis PPC.

On the locus of the collision position of the lubricating oil J, a protrusion 26 protruding from the piston back surface 22 is provided.
As shown in FIG. 3 and FIG. 2, the protrusion 26 is formed in a plate shape, and the side surface in the longitudinal direction is a guide surface 26a that changes the flow direction of the lubricating oil J supplied to the piston back surface 22. It has become. Further, the protrusion 26 is on the locus of the collision position of the lubricating oil J, and the position of the piston 20 is the position of the intermediate point P2 between the top dead center P3 and the bottom dead center P1 shown in FIG. At the collision position of the lubricating oil J.

Next, the operation of this embodiment will be described with reference to FIGS.
As shown in FIG. 4, the piston back surface 22 is divided into two regions at a line segment K <b> 1 that includes the piston center axis PC and is perpendicular to the piston pin axis PPC and the line of intersection of the piston back surface 22. A region closer to the injection nozzle 60 is a first region RK1, and the other region is a second region RK2.

  In addition, as shown in FIG. 5, in one region where the piston back surface 22 is divided into two at a line segment K <b> 2 indicating the intersection line between the plane including the piston center axis PC and parallel to the piston pin axis PPC and the piston back surface 22. A region closer to the injection nozzle 60 is a third region RK3, and the other region is a fourth region RK4.

  As shown in FIGS. 4 and 5, when the piston 20 is at the bottom dead center, the lubricating oil J collides with the collision position A, that is, the first region RK1 on the third region RK3 side, and the piston 20 is at the top dead center. The injection direction of the injection nozzle 60 is set so that the lubricating oil J collides with the collision position B, that is, the second region RK2 on the third region RK3 side. Therefore, as shown in FIG. 5, the piston back surface 22 is set to 2 in a third segment RK3, that is, a line segment K2 that is an intersection line between the piston back surface 22 and a plane that includes the piston central axis PC and is parallel to the piston pin axis PPC. One of the divided areas is cooled by the lubricating oil J by setting the injection direction of the injection nozzle 60.

  On the other hand, as shown in FIG. 6, the piston back surface 22 is separated by a line K 2 that is the intersection of the fourth region RK 4, that is, the plane including the piston central axis PC and parallel to the piston pin axis PPC, and the piston back surface 22. The other divided region is cooled by the induction of the lubricating oil J by the guide surface 26a of the protrusion 26 described above.

  That is, when the position of the piston 20 is between the bottom dead center P1 and the intermediate point P2, the flow direction of the lubricating oil J (illustrated by a two-dot chain line in FIG. 6) that has collided with the piston back surface 22 Is changed by the guide surface 26a of the protrusion 26, and the lubricating oil J that has collided with the third region RK3 is guided toward the fourth region RK4. Since the protrusion 26 functioning as a guiding portion for guiding the lubricating oil J is provided in this manner, the fourth region RK4 of the piston back surface 22 is cooled by the lubricating oil J induced by the protruding portion 26. Is done.

  In this way, by appropriately setting the injection direction of the injection nozzle 60 and providing the protrusion 26 on the piston back surface 22, the position where the lubricant oil J hits the piston back surface 22 depends on the position of the piston 20 in the cylinder 10. The flow direction of the lubricating oil J that hits the piston back surface 22 is changed by the protrusion 26. Therefore, even when one injection nozzle 60 is prepared for one piston 20, it is possible to supply the lubricating oil J to both the third region RK3 and the fourth region RK4. Lubricating oil J can be supplied to the entire central portion of the piston back surface 22. Therefore, the entire central portion of the piston 20 can be cooled.

  Since the entire central portion of the piston 20 can be cooled in this way, for example, the knocking resistance of the internal combustion engine is improved. Therefore, it becomes possible to set the advance angle limit of the ignition timing further to the advance angle side, and for example, the combustion efficiency of the internal combustion engine and the like are improved. In addition, since the entire central portion of the piston 20 can be cooled, deformation of the piston 20 due to heat as described above can be suppressed, and thereby an increase in sliding resistance of the piston 20 in the cylinder 10 can be suppressed. It becomes like this.

According to this embodiment described above, the following effects can be obtained.
(1) When the piston 20 is at the bottom dead center, the lubricating oil J collides with the first region RK1 on the third region RK3 side, and when the piston 20 is at the top dead center side, the third region RK3 side. The injection direction of the injection nozzle 60 is set so that the lubricating oil J collides with the second region RK2. Then, on the piston back surface 22, the lubricating oil J colliding with the third region RK3 side is directed toward the fourth region RK4 while the piston 20 moves between the bottom dead center and the top dead center. A protrusion 26 is provided which functions as a guide part for guiding the light to the surface. Therefore, the entire central portion of the piston 20 can be cooled.

  (2) Since the guide portion is configured by a protrusion 26 protruding from the piston back surface 22, and the flow direction of the lubricating oil J can be changed by the protrusion 26, the third region RK 3 It is possible to guide the lubricating oil J that has collided to the side toward the fourth region RK4.

  (3) While the piston 20 moves between the bottom dead center and the top dead center, the collision position between the piston back surface 22 and the lubricating oil J is between the first region RK1 and the second region RK2. The injection direction of the injection nozzle 60 is set so as to change. And the protrusion 26 which functions as a guidance | induction part is provided on the locus | trajectory of the collision position of the lubricating oil J which changes with the movement of piston 20. As shown in FIG. Therefore, the lubricating oil J that collides with the piston back surface 22 can be reliably applied to the protrusion 26.

  (4) The injection direction of the injection nozzle 60 is inclined in a biaxial direction, which is a direction parallel to the piston pin axis and a direction intersecting the parallel direction. Since the injection direction of the injection nozzle 60 is inclined in a direction parallel to the piston pin axis in this way, the piston 20 has a bottom dead center and a top dead center as shown in FIG. During the movement, the collision position between the piston back surface 22 and the lubricating oil J changes between the first region RK1 and the second region RK2. Accordingly, when the piston 20 is at the bottom dead center, the lubricating oil J collides with the first region RK1 on the third region RK3 side, and when the piston 20 is at the top dead center, the lubricant region J on the third region RK3 side. It is also possible to cause the lubricant J to collide with the second region RK2.

  Further, the injection direction of the injection nozzle 60 is also inclined in a direction intersecting with the direction parallel to the piston pin axis. Therefore, the lubricating oil J that collides with the piston back surface 22 easily flows in the direction from the third region RK3 to the fourth region RK4, as shown in FIG. The effect can be further promoted.

In addition, the said embodiment can also be changed and implemented as follows.
In the above embodiment, the protrusion 26 is provided as a guide for guiding the lubricating oil J that has collided with the third region RK3 toward the fourth region RK4. You may comprise a guidance part. For example, as a configuration that functions as such a guide portion, a recess 28 may be provided on the piston back surface 22. Such a modification is shown in FIG.

  As shown in FIG. 7, the collision position A of the lubricating oil J when the position of the piston 20 is at the bottom dead center, and the collision position of the lubricating oil J when the position of the piston 20 is at the top dead center. A concave portion 28 (shown by hatching in FIG. 7) is formed on the piston back surface 22 on the locus (shown by a two-dot chain line in FIG. 7) of the collision position of the lubricating oil J that changes with B.

  As shown in FIG. 8, the portion of the recess 28 that intersects the locus of the collision position of the lubricating oil J is cut vertically from the piston back surface 22 toward the top surface 21 of the piston. Similarly to the guide surface 26a of the protrusion 26, the guide surface 28a changes the flow direction of the lubricating oil J supplied to the piston back surface 22. Even in such a modified example, since the concave portion 28 has an action according to the protrusion 26, the effect according to the above embodiment can be obtained.

  In the above embodiment, the injection direction of the injection nozzle 60 is inclined in the biaxial direction, which is a direction parallel to the piston pin axis and a direction intersecting the same direction. In addition, the injection direction of the injection nozzle 60 may be inclined only in a direction parallel to the piston pin axis. That is, the first angle θA shown in FIG. 1 may be set to “0 °”.

  Even in this modification, as shown in FIG. 2 above, the injection direction of the injection nozzle 60 is parallel to the piston pin axis, and is a line segment SL parallel to the central axis of the cylinder 10. On the other hand, it is set to be inclined toward the piston central axis PC by the second angle θB. Therefore, as shown by the solid line in FIG. 2, the collision position A where the piston back surface 22 and the lubricating oil J collide when the position of the piston 20 is at the bottom dead center is shown in FIG. As indicated by the dotted line, the collision position B where the piston back surface 22 and the lubricating oil J collide with each other when the position of the piston 20 is at the top dead center is different. More specifically, the collision position of the lubricating oil J changes from the Y1 direction to the Y2 direction as the position of the piston 20 approaches the top dead center.

  As shown in FIG. 9, in this modified example, if the above-described protrusion 26 is provided on the locus where the collision position of the lubricating oil J changes, as shown in FIG. Lubricating oil J that has collided with the third region RK3 is guided toward the fourth region RK4. Accordingly, it is possible to obtain the same effect as that of the protrusion 26 of the above embodiment. In place of the protrusion 26, the above-described recess 28 may be provided.

  In the embodiment and the modification thereof, when the piston 20 is at a position between the bottom dead center P1 and the intermediate point P2, the protrusion 26 and the recess 28 are used to move the third region RK3 to the fourth region. The lubricating oil J is guided to the region RK4. In addition, when the injection position of the injection nozzle 60 is changed and the piston 20 is at a position between the top dead center P3 and the intermediate point P2, the third region is utilized by using the protrusion 26 and the recess 28. The lubricating oil J may be guided from RK3 to the fourth region RK4. Even in this case, the piston 20 can be cooled over a wide range in the same manner as in the above-described embodiment and its modifications.

  As shown in FIG. 2 and FIG. 6, the protrusion 26 has the lubricating oil J when the position of the piston 20 is the middle point P2 between the top dead center P3 and the bottom dead center P1. Although provided at the collision position, the relationship between the position of the piston 20 and the position of the protrusion 26 can be changed as appropriate. For example, the protrusion 26 is provided at the collision position of the lubricating oil J when the position of the piston 20 is closer to the bottom dead center P1 than the intermediate point P2, or the position of the piston 20 is higher than the intermediate point P2. You may provide the protrusion 26 in the collision position of the lubricating oil J when it is near the dead center P3.

  The lubricating oil stored in the oil pan 61 is used as the cooling fluid for cooling the piston 20, but other cooling fluid suitable for cooling the piston 20 may be used.

  DESCRIPTION OF SYMBOLS 10 ... Cylinder, 20 ... Piston, 21 ... Top surface of (piston), 22 ... Piston back surface, 23 ... Connection wall, 24 ... Pin boss, 25 ... Insertion hole, 26 ... Projection part, 26a ... Guiding surface, 28 ... Recessed part, 28a ... guide surface, 30 ... piston ring, 40 ... piston pin, 50 ... connecting rod, 60 ... injection nozzle, 61 ... oil pan, 62 ... oil pump, 200 ... piston, 220 ... piston back surface, RK1 ... first region, RK2 ... second region, RK3 ... third region, RK4 ... fourth region, PC ... piston central axis, PPC ... piston pin shaft.

Claims (5)

A piston cooling structure for an internal combustion engine comprising an injection nozzle for injecting a cooling fluid onto the back surface of a piston surrounded by a pair of connecting walls connecting an intake side skirt portion and an exhaust side skirt portion,
One region obtained by dividing the back surface into two at the intersecting line of the back surface and the plane perpendicular to the piston pin axis including the central axis of the piston is a first region, and the other region is a second region,
When one region obtained by dividing the back surface into two at the intersection line of the plane including the central axis of the piston and parallel to the piston pin axis and the back surface is the third region, and the other region is the fourth region,
When the piston is at the bottom dead center, the cooling fluid collides with the first area on the third area side, and when the piston is at the top dead center, the cooling fluid is on the second area on the third area side. The injection direction of the injection nozzle is set so that the cooling fluid collides,
On the back surface, a guiding portion that guides the cooling fluid that has collided with the third region side toward the fourth region side while the piston moves between the bottom dead center and the top dead center. A piston cooling structure for an internal combustion engine, comprising: The piston cooling structure for an internal combustion engine according to claim 1, wherein the guide portion is configured by a protrusion protruding from the back surface. The piston cooling structure for an internal combustion engine according to claim 1, wherein the guide portion is configured by a recess formed on the back surface. While the piston moves between the bottom dead center and the top dead center, the injection nozzle so that the collision position between the back surface and the cooling fluid changes between the first region and the second region. The injection direction is set,
The piston cooling structure for an internal combustion engine according to any one of claims 1 to 3, wherein the guide portion is provided on a trajectory of the collision position that changes as the piston moves. The injection direction of the injection nozzle is inclined in a biaxial direction that is a direction parallel to the piston pin axis and a direction that intersects the parallel direction. Piston cooling structure for an internal combustion engine.