JP2010019246A - Piston cooling structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide piston cooling structure capable of easily securing structure for injecting oil into a piston. <P>SOLUTION: This piston cooling structure is provided for cooling the piston sliding in cylinder bores 1a and 1b formed in a crankcase by oil injected from an oil injection device 20, and formed with a through-hole 15 forming a bearing 2b on an inter-bore wall 2 between the cylinder bores 1a and 1b and penetrating in the axial direction of a crankshaft through the inter-bore wall 2 and a vertical through-hole 16 penetrating in the vertical direction up to the through-hole 15 from the bearing 2b, and constituted so that the oil injection device 20 is stored in the vertical through-hole 16 so that injection parts 20a and 20b face the through-hole 15, and can inject the oil toward the piston in both side cylinder bores 1a and 1b from the injection parts 20a and 20b. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a piston cooling structure that cools and lubricates a piston by injecting lubricating oil toward the piston.

Conventionally, as disclosed in Patent Document 1, this type of piston cooling structure has been proposed that cools and lubricates a piston by injecting oil from an oil jet toward the back side of the piston. .
In this piston cooling structure, only the oil injection hole that penetrates from the inner peripheral surface of the crank bearing of the cylinder block to the inner wall surface of the cylinder bore is formed as an oil jet. The design freedom is high. Moreover, if the oil injection holes are formed toward both adjacent cylinder bores, oil can be injected toward the adjacent pistons at a time.
Japanese Utility Model Publication No. 6-14005

  However, in such a piston cooling structure, the oil injection hole must be machined obliquely toward the cylinder bore, and the workability is not necessarily good, and when the oil injection hole is formed toward both adjacent cylinder bores, the machining is further performed. It was not good.

One object of the present invention is to simply secure a structure for injecting a cooling medium onto a piston, and the following means are adopted in order to achieve at least a part of the object.
The present invention is a piston cooling structure that cools a piston that slides in a cylinder bore formed in a crankcase by a cooling medium injected from a cooling medium injection device, and the crankcase constitutes a part of the cylinder bore And a bore wall formed with a bearing portion capable of rotatably supporting the crankshaft. The bore wall has a through-hole penetrating in the axial direction of the crankshaft, and from the bearing portion to the through-hole. A vertical through hole penetrating in the vertical direction is formed, and the cooling medium injection device is accommodated in the vertical through hole so that the injection unit faces the through hole, and is directed from the injection unit toward the piston. The gist is that the cooling medium is jetted.

  According to the piston cooling structure of the present invention, the vertical through hole penetrating in the vertical direction is formed in the through hole formed through the bore wall from the bearing portion that rotatably supports the crankshaft, and the injection portion faces the through hole. As described above, the cooling medium injection device is accommodated in the vertical through hole, and the cooling medium is injected from the injection unit toward the piston. Therefore, it is not necessary to obliquely machine the cooling medium injection hole for injecting the cooling medium toward the piston from the bearing portion. As a result, a structure for injecting the cooling medium onto the piston can be easily ensured.

In the piston cooling structure of the present invention, at least a part of the through hole is formed to open to the sliding surface of the cylinder bore so as to suppress an increase in pressure in the crank chamber when the piston is lowered. It can also be formed as a ventilation hole.
In this case, since the vent hole formed for suppressing the pumping loss when the piston descends is used as the through hole, it is not necessary to separately form the through hole.

Further, in the piston cooling structure of the present invention, the cylinder bore has a first cylinder bore and a second cylinder bore across the bore wall, and the piston is a first piston that slides in the first cylinder bore. A second piston that slides in the second cylinder bore, and the cooling medium injection device is configured such that the injection unit is capable of injecting the cooling medium in at least two directions. When accommodated, the cooling medium may be injected toward the first piston and the cooling medium may be injected toward the second piston.
If it carries out like this, two pistons can be cooled with one cooling medium injection device. As a result, the number of parts can be reduced.

In the piston cooling structure of the present invention, the cylinder bore is arranged in parallel with the first cylinder bore, the second cylinder bore, the third cylinder bore, and the fourth cylinder bore in order from one to the other in the axial direction of the crankshaft. The bore wall includes a first bore wall between the first cylinder bore and the second cylinder bore, and a second bore wall between the third cylinder bore and the fourth cylinder bore, The cooling medium ejecting device may be accommodated in the vertical through hole formed in the wall between the first bores and the vertical through hole formed in the wall between the second bores, respectively. .
In this way, in the case of a four-cylinder engine, the piston can be reliably cooled with the minimum number of cooling medium injection devices. That is, in a 4-cylinder engine, a counterweight may be required between the second cylinder bore and the third cylinder bore of the crankshaft. In this case, the bore wall between the second cylinder bore and the third cylinder bore is required. If the coolant injection device is disposed in the vertical through hole formed in the cylinder, the coolant may not hit the piston sliding in the second cylinder bore and the third cylinder bore due to the counterweight. Such problems are caused by accommodating in the vertical through hole formed in the bore wall between the cylinder bore and the second cylinder bore and the vertical through hole formed in the bore wall between the third cylinder bore and the fourth cylinder bore, respectively. Can be avoided.

Further, in the piston cooling structure of the present invention, the crankshaft is rotatably journaled on the bearing portion via a bearing member, and a bearing surface formed between the bearing member and the journal portion. A lubricating oil passage capable of supplying lubricating oil is formed, and the bearing member is formed with a feeding passage capable of supplying the lubricating oil supplied to the bearing surface to the coolant injection device, The cooling medium injection device may inject the lubricating oil supplied from the supply path toward the piston.
If it carries out like this, the supply circuit of the cooling medium of a cooling medium injection apparatus can be ensured simply.

The present invention also provides a piston cooling structure for cooling a piston sliding in a cylinder bore formed in a crankcase by a cooling medium injected from a cooling medium injection device, wherein the crankcase is a part of the cylinder bore. And a bore wall formed with a bearing portion capable of rotatably supporting the crankshaft, the bore wall having a through-hole penetrating in the axial direction of the crankshaft, the bearing portion and the through-hole. A communication hole is formed to communicate with the hole in the axial direction of the cylinder bore, and the cooling medium injection device is accommodated in the communication hole so that the injection unit faces the through hole, and The cooling medium may be jetted toward the piston.
In this way, a communication hole is formed to connect the bearing portion for rotatably supporting the crankshaft and the through hole formed through the bore wall in the axial direction of the cylinder bore so that the injection portion faces the through hole. The cooling medium injection device is accommodated in the hole, and the cooling medium is injected from the injection unit toward the piston. Therefore, it is not necessary to obliquely machine the cooling medium injection hole for injecting the cooling medium toward the piston from the bearing portion. As a result, a structure for injecting the cooling medium onto the piston can be easily ensured.

In the piston cooling structure of the present invention, at least a part of the through hole is formed to open to the sliding surface of the cylinder bore, and an increase in the pressure in the crank chamber is suppressed when the piston is lowered. It can also be formed as a ventilation hole for the purpose.
In this case, since the vent hole formed for suppressing the pumping loss when the piston descends is used as the through hole, it is not necessary to separately form the through hole.

Further, in the piston cooling structure of the present invention, the cylinder bore has a first cylinder bore and a second cylinder bore across the bore wall, and the piston is a first piston that slides in the first cylinder bore. And a second piston that slides in the second cylinder bore, and the cooling medium injection device is configured such that the injection unit is configured to be able to inject the cooling medium in at least two directions, and is accommodated in the communication hole. In this case, the cooling medium may be injected toward the first piston and the cooling medium may be injected toward the second piston.
If it carries out like this, two pistons can be cooled with one cooling medium injection device. As a result, the number of parts can be reduced.

In the piston cooling structure of the present invention, the cylinder bore is arranged in parallel with the first cylinder bore, the second cylinder bore, the third cylinder bore, and the fourth cylinder bore in order from one to the other in the axial direction of the crankshaft. The bore wall includes a first bore wall between the first cylinder bore and the second cylinder bore, and a second bore wall between the third cylinder bore and the fourth cylinder bore, The cooling medium injection device may be accommodated in the communication hole formed in the first bore wall and the communication hole formed in the second bore wall.
In this way, in the case of a four-cylinder in-line engine, the piston can be reliably cooled with the minimum number of cooling medium injection devices. That is, in a 4-cylinder in-line engine, a counterweight may be required between the second cylinder bore and the third cylinder bore of the crankshaft. In this case, the distance between the bores between the second cylinder bore and the third cylinder bore If the coolant injection device is disposed in the communication hole formed in the wall, the coolant may not hit the piston sliding in the second cylinder bore and the third cylinder bore due to the counterweight. These problems can be avoided by accommodating in the communication hole formed in the bore wall between the cylinder bore and the second cylinder bore and the communication hole formed in the bore wall between the third cylinder bore and the fourth cylinder bore. it can.

Further, in the piston cooling structure of the present invention, the crankshaft is rotatably journaled on the bearing portion via a bearing member, and a bearing surface formed between the bearing member and the journal portion. A lubricating oil passage capable of supplying lubricating oil is formed, and the bearing member is formed with a feeding passage capable of supplying the lubricating oil supplied to the bearing surface to the coolant injection device, The cooling medium injection device may inject the lubricating oil supplied from the supply path toward the piston.
If it carries out like this, the supply circuit of the cooling medium of a cooling medium injection apparatus can be ensured simply.

Next, the best mode for carrying out the present invention will be described using examples.
FIG. 1 is a longitudinal sectional view of a crankcase of a four-cylinder in-line engine, and FIG. 2 is an enlarged view of portions between bore walls 2 and 4.
As shown in FIG. 1, a crankshaft 6 is rotatably provided in the crankcase 1. The cylinder bore 1a, the second cylinder bore 1b, and the third cylinder bore 1b are arranged in the axial direction of the crankshaft 6 from the left side to the right side in the drawing. No. 1 cylinder bore 1c and No. 4 cylinder bore 1d are juxtaposed, and in each cylinder bore 1a, 1b, 1c, 1d, a first connected to the crankshaft 6 via connecting rods 8a, 8b, 8c, 8d. A piston 7a, a second piston 7b, a third piston 7c, and a fourth piston 7d are provided so as to be slidable in the vertical direction.

In this example, oil injection devices 20 and 20 are provided on the bore wall 2 between the first cylinder bore 1a and the second cylinder bore 1b, and on the bore wall 4 between the third cylinder bore 1c and the fourth cylinder bore 1d, respectively. .
As shown in FIG. 2, the lower end side of the bore walls 2, 3, 4 is a thick base portion 2 a, 3 a, 4 a. A through hole 15 penetrating in the axial direction of the crankshaft 6 and communicating from the first cylinder bore 1a to the fourth cylinder bore 1d is formed through the upper portions of the base portions 2a, 3a, 4a. The through hole 15 is formed as a vent hole for suppressing an increase in pressure in the crank chamber S when the first piston 7a, the second piston 7b, the third piston 7c, and the fourth piston 7d are lowered. Is.

Also, substantially semicircular bearings 2b, 3b, 4b are formed on the lower ends of the bases 2a, 3a, 4a, and the crankshaft 6 is connected to the bearings 2b, 3b, 4b via a bearing member 5. The journal portion 6a is rotatably supported.
The bearing caps 13, 13, and 13 are fitted into the lower ends of the bearing members 5, 5, and 5 from the lower side, respectively. Of the bearing portions 2b, 3b, 4b, the bearing portions 2b, 4b are formed with vertical through holes 16 penetrating in the vertical direction up to the through holes 15.

An oil pan 9 is provided on the bottom side of the crankcase 1, and oil is stored in the oil pan 9. A strainer 10 is disposed in the oil pan 9, and the strainer 10 is rotated by the rotation of the oil pump 11. The oil in the oil pan 9 is sucked up and supplied to the bearing members 5, 5, 5 and the oil injection devices 20, 20, and from the oil injection devices 20, 20 to the pistons 7a, 7b, 7c, 7d. It is comprised so that oil may be ejected toward.
In FIG. 1, reference numeral 12 denotes a flywheel provided on the crankshaft 6 outside the crankcase 1.

The oil injection device 20 includes an upper member 21, a lower member 22 assembled to the upper member 21, and a spring 24 and a ball 23 accommodated in an internal space 200 formed by the upper member 21 and the lower member 22. It is accommodated in the vertical through hole 16. The upper member 21 has a conical convex portion 21a whose upper end protrudes in a conical shape upward in FIG. 2, and the conical convex portion 21a is inclined obliquely upward and downward on the left and right sides in FIG. A first oil injection hole 20a and a second oil injection hole 20b are formed. The lower member 22 is formed with a small hole 22a penetrating the bottom surface to communicate the internal space 200 with the outside.
By such first oil injection hole 20a and second oil injection hole 20b, oil can be simultaneously injected toward the first piston 7a and the second piston 7b, or the third piston 7c and the fourth piston 7d. .

FIG. 3 is an exploded perspective view schematically showing the configuration of the lubricating oil passage formed in the crankshaft 6 and the bearing member 5, and FIG. 4 shows the configuration of the oil supply circuit for supplying oil to the oil injection device 20. It is sectional drawing which shows an outline.
As shown in FIG. 3, the bearing member 5 is divided into an upper bearing member 5a and a lower bearing member 5b, and a bearing surface P is formed on the inner peripheral side of the upper bearing member 5a and the lower bearing member 5b. Yes. Engagement flanges 51a and 51b are integrally formed on both axial ends of the outer peripheral side of the upper bearing member 5a and the lower bearing member 5b, and the upper bearing member is interposed via the flanges 51a and 51b. 2, 5a can be attached so as to sandwich the base portions 2a, 3a and 4a of the bore walls 2, 3 and 4 so that the bore walls 2, 3 and 4 can be attached even when receiving axial thrust force. It is comprised so that it may not slip | deviate from 4 base part 2a, 3a, 4a.
An oil groove 52 is formed in a concave shape along the inner periphery of the bearing surface P at the axially central portion of the bearing surface P of the upper bearing member 5a, and the oil groove 52 penetrates in two locations in the radial direction. A first supply passage 53 and a second supply passage 54 are formed.

In the state where the upper bearing member 5a is attached to the bearing portions 2b, 3b, 4b of the base portions 2a, 3a, 4a of the bore walls 2, 3, 4, it corresponds to the first supply passage 53 as shown in FIG. An oil passage 18 is formed in the base 2a, 3a, 4a of the bore wall 2, 3, 4 at the position, and a main gallery 17 formed in the axial direction of the crankshaft 6 is formed in the oil passage 18. It is communicated. The vertical through hole 16 is formed at a position corresponding to the second supply path 54.
The main gallery 17 is supplied with oil from the oil pump 11.

As shown in FIG. 3, an opening 6d is formed in the journal portion 6a of the crankshaft 6, and the bearings of the connecting rods 8a, 8b, 8c, 8d of the pistons 7a, 7b, 7c, 7d are on the outside. An opening 6d is also formed in the crankpin 6b of the crankshaft 6 to be fitted, and a lubricating oil passage 6e for communicating between the opening 6d of the journal portion 6a and the opening 6d of the crankpin 6b is formed inside the crankshaft 6. Has been.
In the figure, 6c is a counterweight formed between the journal portion 6a and the crank pin 6b.

Next, the operation in such a structure will be described.
When the engine is started, the oil in the oil pan 9 is sucked up by the operation of the oil pump 11, and the oil passes through the main gallery 17 and from the oil passage 18 through the first supply passage 53 to the oil groove of the upper bearing member 5a. The oil flowing into the oil groove 52 lubricates between the bearing surface P of the bearing member 5 and the journal portion 6a of the crankshaft 6 by the oil flowing into the oil groove 52. Further, the oil passes through the lubricating oil passage 6e in the crankshaft 6 from the opening 6d, flows out from the opening 6d of the crankpin 6b, and the outer periphery of the crankpin 6b and the connecting rods 8a, Lubricate between the bearings (not shown) of 8b, 8c and 8d.

Further, the oil that has flowed into the oil groove 52 of the upper shaft member 5 a also flows into the vertical through holes 16 of the base portions 2 a and 4 a of the bore walls 2 and 4 from the second supply path 54. The oil that has flowed into the vertical through hole 16 flows into a small hole 22 a formed in the lower member 22 of the oil injection device 20, and hydraulic pressure acts on the ball 23 accommodated in the internal space 200 of the oil injection device 20. When the oil pressure acting on the ball 23 reaches a predetermined oil pressure, the oil flowing into the small hole 22a pushes the ball 23 vertically upward against the spring force of the spring 24 housed in the internal space 200, The air flows into the internal space 200 and is ejected from the first oil injection hole 20a and the second oil injection hole 20b formed in the conical convex portion 21a of the upper member 21 into the cylinder bores 1a, 1b, 1c and 1d obliquely upward. Is done. That is, oil is ejected toward the back surface of each piston 7a, 7b, 7c, 7d. Thus, cooling and lubrication of the pistons 7a, 7b, 7c, and 7d are simultaneously performed.
Thus, oil can be used efficiently by operating the oil injection device 20 for the first time when the oil pressure becomes equal to or higher than a predetermined oil pressure. That is, by injecting oil only during high load operation of the engine that requires cooling of the pistons 7a, 7b, 7c, and 7d, during low load operation of the engine that does not require much cooling of the pistons 7a, 7b, 7c, and 7d. By not injecting oil, the use of oil can be made more efficient.

In this example, a vertical through hole 16 is formed in the base portions 2a and 4a of the bore walls 2 and 4 so as to penetrate the bearing portions 2b and 4b to the through hole 15 in the vertical direction. Since the oil injection device 20 capable of injecting obliquely upward is housed and arranged, it is not necessary to obliquely process the oil injection hole from the bearing portion into the cylinder bore as in the prior art, and each piston 7a, 7b, 7c, 7d A structure for injecting oil for cooling and lubrication can be easily secured. Further, since the vent hole formed for suppressing the pumping loss when the pistons 7a, 7b, 7c and 7d are lowered is used as the through hole 15, it is not necessary to form the through hole 15 separately.
Further, the oil injection device 20 has two oil injection holes 20a and 20b so that the two oil injection holes 20a and 20b face the adjacent two pistons 7a and 7b or the adjacent two pistons 7c and 7d. Since it is accommodated in the vertical through-hole 16, the two pistons 7a, 7b or the pistons 7c, 7d can be simultaneously cooled and lubricated by one oil injection device 20. As a result, the number of parts can be reduced.

  In the four-cylinder in-line engine as in this example, a counterweight 6c may be required between the second cylinder bore 1b and the third cylinder bore 1c of the crankshaft 6. In this case, the second cylinder bore 1b and When a vertical through hole 16 penetrating from the bearing portion 3b to the through hole 15 is formed in the bore wall 3 between the third cylinder bore 1c and the oil injection device 20 is disposed in the vertical through hole 16, the counter There is a case where the oil does not hit the pistons 7b and 7c sliding in the second cylinder bore 1b and the third cylinder bore 1c due to the weight 6c. However, in this example, the oil injection device 20 is provided between the vertical through hole 16 formed in the bore wall 2 between the first cylinder bore 1a and the second cylinder bore 1b, and between the third cylinder bore 1c and the fourth cylinder bore 1d. Since these are accommodated and arranged in the vertical through holes 16 formed in the inter-bore wall 4, such a problem can be avoided.

  In the embodiment, the two oil injection holes of the first oil injection hole 20a and the second oil injection hole 20b are provided in the conical convex portion 21a of the upper member 21 of the oil injection device 20, but the oil injection Three, four, or more holes may be provided.

  In the embodiment, the oil injection device 20 includes an upper member 21, a lower member 22 assembled to the upper member 21, a spring 24 and a ball 23 housed in an internal space 200 formed by the upper member 21 and the lower member 22. The oil is not injected unless the oil pressure acting on the ball 23 becomes equal to or higher than a predetermined oil pressure. However, the oil injection device 20 may not include the spring 24 and the ball 23. That is, the oil injection device 20 has a cone-shaped convex part in which two oil injection holes are formed, and a substantially cylindrical member in which a bottomed communication hole communicating with the two oil injection holes is formed upward from the bottom surface. It does not matter as a configuration.

  In the embodiment, the vertical through hole 16 is a vent hole for suppressing an increase in pressure in the crank chamber S when the first piston 7a, the second piston 7b, the third piston 7c, and the fourth piston 7d are lowered. However, it is also possible to form a through hole different from the through hole 15 in the inter-bore walls 2 and 4 and connect the vertical through hole 16 to the through hole.

  In the embodiment, the oil injection device 20 is not disposed on the bore wall 3 between the second cylinder bore 1b and the third cylinder bore 1c, but the bore between the second cylinder bore 1b and the third cylinder bore 1c is not provided. The oil injection device 20 may be arranged by forming the vertical through-hole 16 in the intermediate wall 3. In this case, the first piston 7a is cooled and lubricated by the oil injection device 20 disposed on the bore wall 2 between the first cylinder bore 1a and the second cylinder bore 1b, and between the second cylinder bore 1b and the third cylinder bore 1c. The second and third pistons 7b and 7c are cooled and lubricated by the oil injection device 20 disposed on the bore wall 3 of the cylinder, and the oil injection device disposed on the bore wall 4 between the third cylinder bore 1c and the fourth cylinder bore 1d. 20 may be used to cool and lubricate the fourth piston 1d.

  In the embodiment, the oil groove 52 is formed in the upper bearing member 5 a of the bearing member 5, but the oil groove 52 may be formed in the journal portion 6 a of the crankshaft 6.

  In the embodiment, oil is supplied from the oil gallery 17 to the oil injection device 20 through the lubricating oil passage 6e in the crankshaft 6, the oil groove 52 of the upper bearing member 5a, and the second supply passage 54. The oil supply oil path to the oil injection device 20 may take any form, for example, one that supplies oil from the oil gallery 17 directly to the oil injection device 20.

  In the embodiment, a four-cylinder in-line engine is used. However, the number of cylinders may be any number such as a single cylinder, a two-cylinder in-line engine, a three-cylinder in-line engine, or an in-line engine having five or more cylinders. Moreover, not only an in-line engine but a V-type engine or a horizontally opposed engine may be used. In the case of a V-type engine or a horizontally opposed engine, the oil injection device 20 is accommodated in a communication hole that connects the bearing portions 2b, 4b and the through hole 15 in the axial direction of the cylinder bores 1a, 1b, 1c, 1d. What should I do?

  As mentioned above, although embodiment of this invention was described using the Example, this invention is not limited to such an Example, In the range which does not deviate from the summary of this invention, it can implement with a various form. Of course.

It is a longitudinal cross-sectional block diagram of an engine crankcase. It is a principal part expanded block diagram of the part of the wall between bores in FIG. It is a principal part disassembled perspective structure figure of a bearing member and a crankshaft. It is a side surface expanded block diagram of the state where the bearing member was attached to the bearing part of the wall between bores.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crankcase 1a 1st cylinder bore 1b 2nd cylinder bore 1c 3rd cylinder bore 1d 4th cylinder bore 2, 3, 4 Bore wall 2a, 4a Base part of bore wall 2b, 4b Bearing part 5 Bearing member 5a Upper bearing member 5b Lower bearing Member 6 Crankshaft 6a Journal portion 6b Crankpin 6c Counterweight 6d Opening 6e Lubricating oil passage 7a, 7b, 7c, 7d Piston 8a, 8d Connecting rod 9 Oil pan 11 Oil pump 13 Bearing cap 15 Through hole (vent hole)
16 Vertical through hole (receiving hole)
17 Oil gallery 18 Oil passage 20 Oil injection device 20a 1st oil injection hole (injection part)
20b 2nd oil injection hole (injection part)
21 Upper member 22 Lower member 22a Small hole 23 Ball 24 Spring 52 Oil groove 53 First supply path 54 Second supply path P Bearing surface

Claims (10)

A piston cooling structure that cools a piston sliding in a cylinder bore formed in a crankcase by a cooling medium injected from a cooling medium injection device,
The crankcase includes a bore wall formed with a bearing portion that forms a part of the cylinder bore and can rotatably support the crankshaft.
The bore wall is formed with a through hole penetrating in the axial direction of the crankshaft and a vertical through hole penetrating in a vertical direction from the bearing portion to the through hole.
The cooling medium injection device is configured to be accommodated in the vertical through hole so that an injection unit faces the through hole, and to inject the cooling medium from the injection unit toward the piston. The through hole is formed so as to be at least partially opened to a sliding surface of the cylinder bore, and is formed as a vent hole for suppressing an increase in pressure in the crank chamber when the piston is lowered. 2. The piston cooling structure according to 1. The cylinder bore has a first cylinder bore and a second cylinder bore across the bore wall,
The piston has a first piston that slides in the first cylinder bore, and a second piston that slides in the second cylinder bore,
The cooling medium injection device is configured such that the injection unit is capable of injecting the cooling medium in at least two directions, and injects the cooling medium toward the first piston when accommodated in the vertical through hole. The piston cooling structure according to claim 1, wherein a cooling medium is injected toward the second piston. The cylinder bore is arranged in parallel with the first cylinder bore, the second cylinder bore, the third cylinder bore and the fourth cylinder bore in order from one to the other in the axial direction of the crankshaft.
The bore wall has a first bore wall between the first cylinder bore and the second cylinder bore, and a second bore wall between the third cylinder bore and the fourth cylinder bore,
The said cooling medium injection apparatus is respectively accommodated in the said vertical through-hole formed in the said 1st bore wall, and the said vertical through-hole formed in the said 2nd bore wall. Piston cooling structure. The crankshaft includes a journal portion rotatably supported on the bearing portion via a bearing member, and a lubricating oil passage capable of supplying lubricating oil to a bearing surface formed between the bearing member and the journal portion. And formed,
The bearing member is formed with a supply path capable of supplying the lubricating oil supplied to the bearing surface to the cooling medium injection device.
The piston cooling structure according to any one of claims 1 to 4, wherein the cooling medium injection device injects the lubricating oil supplied from the supply path toward the piston. A piston cooling structure that cools a piston sliding in a cylinder bore formed in a crankcase by a cooling medium injected from a cooling medium injection device,
The crankcase includes a bore wall formed with a bearing portion that forms a part of the cylinder bore and can rotatably support the crankshaft.
The bore wall is formed with a through hole penetrating in the axial direction of the crankshaft, and a communication hole connecting the bearing portion and the through hole in the axial direction of the cylinder bore,
The cooling medium injection device is a piston cooling structure in which the injection unit is accommodated in the communication hole so as to face the through hole, and the cooling medium is injected from the injection unit toward the piston. The through hole is formed so that at least a part thereof is opened to the sliding surface of the cylinder bore, and is formed as a vent hole for suppressing an increase in pressure in the crank chamber when the piston descends. Item 7. A piston cooling structure according to Item 6. The cylinder bore has a first cylinder bore and a second cylinder bore across the bore wall,
The piston has a first piston that slides in the first cylinder bore, and a second piston that slides in the second cylinder bore,
The cooling medium injection device is configured such that the injection unit is configured to be capable of injecting the cooling medium in at least two directions, and injects the cooling medium toward the first piston when accommodated in the communication hole. The piston cooling structure according to claim 6 or 7, wherein a cooling medium is injected toward the second piston. The cylinder bore is arranged in parallel with the first cylinder bore, the second cylinder bore, the third cylinder bore and the fourth cylinder bore in order from one to the other in the axial direction of the crankshaft.
The bore wall has a first bore wall between the first cylinder bore and the second cylinder bore, and a second bore wall between the third cylinder bore and the fourth cylinder bore,
The piston according to claim 8, wherein the cooling medium injection device is accommodated in the communication hole formed in the wall between the first bores and the communication hole formed in the wall between the second bores. Cooling structure. The crankshaft includes a journal portion rotatably supported on the bearing portion via a bearing member, and a lubricating oil passage capable of supplying lubricating oil to a bearing surface formed between the bearing member and the journal portion. And formed,
The bearing member is formed with a supply path capable of supplying the lubricating oil supplied to the bearing surface to the cooling medium injection device.
The piston cooling structure according to any one of claims 6 to 9, wherein the cooling medium injection device injects the lubricating oil supplied from the supply path toward the piston.

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