Internal combustion engine piston

Abstract

To provide a piston of an internal combustion engine which can be efficiently cooled by water in a cooling channel.SOLUTION: A piston of an internal combustion engine includes a crown part 13 facing a combustion chamber 14 of the internal combustion engine. The interior of the crown part 13 is formed with a cooling channel 22, a first passage 23, and a second passage 24. The first passage 23 extends from an outer peripheral surface of the crown part 13 to the cooling channel 22 and is open in the cooling channel 22. The second passage 24 is open in the cooling channel 22 and connected to a crank chamber 15 of the internal combustion engine. The second passage 24 has: an inlet 24a connected to the cooling channel 22; and an outlet 24b connected to the crank chamber 15. At least one of the inlet 24a and the outlet 24b of the second passage 24 is located above an opening of the first passage 23 leading to the cooling channel 22.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a piston for an internal combustion engine. [Background technology]

[0002] As shown in Patent Document 1, the piston of an internal combustion engine has a crown portion that faces a combustion chamber. When the internal combustion engine is running, the piston reciprocates within the cylinder, repeating an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke of the internal combustion engine.

[0003] A ring groove is formed in the outer peripheral surface of the piston crown so as to extend in the circumferential direction. A piston ring is housed in the ring groove. This piston ring contacts the inner peripheral surface of the cylinder of the internal combustion engine to seal between the combustion chamber and the crankcase of the internal combustion engine. A cooling channel is formed inside the crown. A fluid for cooling the piston is flowed into this cooling channel.

[0004] A first passage is formed in the crown of the piston. The first passage extends from the outer circumferential surface of the crown to the cooling channel and opens into the cooling channel. An opening is formed in the crown, connecting the cooling channel to the crankcase of the internal combustion engine. The interior of this opening is a second passage. The second passage opens into the cooling channel and is connected to the crankcase of the internal combustion engine.

[0005] The internal combustion engine is equipped with an oil jet that discharges oil from the crankcase toward the piston crown. The oil discharged from the oil jet flows into the cooling channel via the second passage in the piston crown, thereby cooling the piston. Furthermore, the oil in the cooling channel is supplied between the outer surface of the piston crown and the inner surface of the cylinder via the first passage. This oil lubricates the piston ring and the inner surface of the cylinder. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-38414 Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, some fuels for internal combustion engines, such as hydrogen, produce a large amount of water when burned. When using such fuels, it is possible to use the water produced as the fuel burns in the combustion chamber to cool the piston. Specifically, by stopping the supply of oil to the cooling channel via the second passage by the oil jet, the water produced when the fuel burns in the combustion chamber is forced into the cooling channel via the first passage as the piston reciprocates.

[0008] However, in the piston of Patent Document 1, depending on the position of the second passage in the crown, water flowing from the first passage into the cooling channel immediately flows out of the second passage into the crankcase. This makes it difficult to retain the water in the cooling channel. As a result, the piston cannot be efficiently cooled by the water in the cooling channel. [Means for solving the problem]

[0009] The means for solving the above problems and their effects will be described below. A piston for an internal combustion engine that solves the above problem includes a crown portion facing a combustion chamber of the internal combustion engine. A cooling channel, a first passage, and a second passage are formed inside the crown portion. The first passage extends from the outer peripheral surface of the crown portion to the cooling channel and opens into the cooling channel. The second passage opens into the cooling channel and also opens into a crankcase of the internal combustion engine. The second passage has an inlet that opens into the cooling channel and an outlet that opens into the crankcase. At least one of the inlet and outlet of the second passage is located above the opening of the first passage into the cooling channel.

[0010] According to the above configuration, water generated by the combustion of fuel in the combustion chamber flows into the cooling channel through the first passage. Because at least one of the inlet and outlet of the second passage is located above the opening of the first passage to the cooling channel, the water flowing into the cooling channel is prevented from immediately flowing out into the crankcase of the internal combustion engine through the second passage. This allows the water to be retained within the cooling channel. Because water has a higher specific heat capacity than oil, the piston can be efficiently cooled by the water.

[0011] The internal combustion engine may include an oil jet that discharges oil from the crank chamber toward the crown of the piston, and the piston of the internal combustion engine may have an outlet of the second passage that opens toward the crank chamber in a direction that does not oppose the direction in which the oil is discharged from the oil jet.

[0012] According to the above configuration, oil discharged from the oil jet can be prevented from entering the cooling channel via the second passage. Therefore, oil that has entered the cooling channel can be prevented from causing water in the cooling channel to flow into the crankcase via the second passage. If oil that has entered the cooling channel causes water in the cooling channel to flow into the crankcase, the oil will accumulate in the cooling channel. Because oil has a lower specific heat than water, if the oil accumulates in the cooling channel, the cooling performance of the piston will decrease. This can be prevented.

[0013] In the piston of the internal combustion engine, it is conceivable that the opening direction of the outlet of the second passage relative to the crank chamber is perpendicular to the discharge direction of oil from the oil jet.

[0014] With this configuration, the opening direction of the outlet of the second passage relative to the crank chamber is perpendicular to the direction in which oil is discharged from the oil jet, thereby effectively preventing the oil from entering the Cougarin channel via the second passage.

[0015] Some internal combustion engines are equipped with an oil jet that discharges oil from the crankcase toward the crown of the piston, and it is conceivable that the oil discharged from the oil jet hits a position of the piston crown that corresponds to the cooling channel.

[0016] According to this configuration, when oil discharged from the oil jet strikes a position in the crown portion corresponding to the cooling channel, the water in the cooling channel is cooled by the oil. This allows the piston to be effectively cooled by the water in the cooling channel. Therefore, the amount of oil discharged from the oil jet can be kept small to achieve the water cooling required to cool the piston. As a result, the energy loss of the internal combustion engine caused by discharging oil from the oil jet can be kept small, and the deterioration of fuel efficiency of the internal combustion engine due to the discharge of oil from the oil jet can be suppressed.

[0017] In the piston of the internal combustion engine, a plurality of ring grooves are formed at intervals on the outer peripheral surface of the crown portion from the combustion chamber side to the crank chamber side, and a piston ring that contacts the inner peripheral surface of a cylinder in the internal combustion engine is housed in each of the plurality of ring grooves. It is considered that the first passage opens at a location between the outer peripheral surface of the crown portion and the inner peripheral surface of the cylinder, between the piston ring closest to the combustion chamber and the piston ring adjacent to that piston ring.

[0018] In an internal combustion engine, if gas leaks from the combustion chamber between the outer circumferential surface of the piston crown and the inner circumferential surface of the cylinder, between the piston ring closest to the combustion chamber and the piston ring next to that piston ring, the pressure at that location may increase. In this case, as the pressure at that location approaches the pressure inside the combustion chamber, the force acting on the piston ring closest to the combustion chamber due to the pressure difference decreases. As a result, the piston ring, which is pressed against the inner wall of the ring groove by this force, becomes more likely to move within the ring groove, causing the piston ring's position within the ring groove to become unstable. This unstable position of the piston ring can lead to wear on the piston ring and the inner circumferential surface of the cylinder, and an increase in the amount of blow-by gas flowing from the combustion chamber into the crankcase.

[0019] However, with the above configuration, because the first passage is open at the location, the volume of the location is increased by the amount of the first passage. As a result, even if gas in the combustion chamber leaks to the location, the pressure at the location is less likely to increase, and the pressure at the location is less likely to approach the pressure inside the combustion chamber. As a result, the force acting on the piston ring closest to the combustion chamber due to the pressure difference is prevented from becoming smaller, and the position of the piston ring in the ring groove is prevented from becoming unstable due to the reduced force. Therefore, wear on the piston ring and the inner circumferential surface of the cylinder, as well as an increase in the amount of blow-by gas flowing from the combustion chamber into the crankcase, which would otherwise be caused by the piston ring becoming unstable, are prevented. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic diagram showing a piston and its surroundings in an internal combustion engine. [Figure 2] 1 is a graph showing the relationship between piston temperature and piston strength. [Figure 3] 2 is a cross-sectional view showing a portion of the piston in FIG. 1 surrounded by a dashed line. [Figure 4] FIG. 4 is an enlarged cross-sectional view showing a top ring and a ring groove in the piston of FIG. 3. [Figure 5] FIG. 10 is a cross-sectional view showing another example of a first passage formed in the crown portion of the piston. [Figure 6] FIG. 10 is a cross-sectional view showing another example of a first passage formed in the crown portion of the piston. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, one embodiment of a piston for an internal combustion engine will be described with reference to FIGS. As shown in FIG. 1, a piston 11 of an internal combustion engine is disposed within a cylinder 12 of the engine. The piston 11 has a crown 13. The crown 13 faces a combustion chamber 14 of the engine. The internal combustion engine is driven by the combustion of fuel within the combustion chamber 14. The fuel used for the internal combustion engine is one that produces a large amount of water upon combustion, such as hydrogen. When the internal combustion engine is running, the piston 11 reciprocates within the cylinder 12 of the engine. As the piston 11 reciprocates, the engine repeats an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. An oil jet 26 is provided in a crank chamber 15 of the internal combustion engine, which discharges oil from the crank chamber 15 toward the crown 13 of the piston 11 as shown by the arrow.

[0022] FIG. 2 shows the relationship between the temperature of piston 11 and the strength of piston 11. As can be seen from FIG. 2, the lower the temperature of piston 11, the stronger the strength of piston 11. For example, in an internal combustion engine that uses hydrogen as fuel, abnormal combustion of fuel is likely to occur in combustion chamber 14, so it is desirable to improve the durability of piston 11 during such abnormal combustion. In order to improve the durability of piston 11 during abnormal combustion of fuel, it has been considered to increase the strength of piston 11 by keeping the temperature of piston 11 low.

[0023] <Structure for cooling the piston 11> Figure 3 shows an enlarged cross section of the area surrounded by the dashed line in the piston 11 in Figure 1. As can be seen from Figure 3, a plurality of ring grooves 16-18 are formed at intervals on the outer peripheral surface of the crown portion 13 of the piston 11, extending from the combustion chamber 14 toward the crank chamber 15. A top ring 19 is housed in the ring groove 16, a second ring 20 is housed in the ring groove 17, and an oil ring 21 is housed in the ring groove 18. The top ring 19, the second ring 20, and the oil ring 21 function as piston rings that contact the inner peripheral surface of the cylinder 12 in the internal combustion engine. These piston rings are positioned in the order of top ring 19, second ring 20, and oil ring 21, extending from the combustion chamber 14 toward the crank chamber 15.

[0024] A cooling channel 22, a first passage 23, and a second passage 24 are formed inside the crown portion 13 of the piston 11. The cooling channel 22 is a space that extends annularly around the center line of the piston 11, and is filled with a fluid for cooling the piston 11. Oil ejected from an oil jet 26 (FIG. 1) hits the position of the crown portion 13 corresponding to the cooling channel 22.

[0025] The first passage 23 extends from the outer peripheral surface of the crown portion 13 to the cooling channel 22 and opens within the cooling channel 22. More specifically, the first passage 23 opens at a position within the ring groove 17 closer to the top ring 19. As a result, the first passage 23 opens at a location between the outer peripheral surface of the crown portion 13 and the inner peripheral surface of the cylinder 12, between the top ring 19, which is the piston ring closest to the combustion chamber 14, and the second ring 20, which is the piston ring located next to the top ring 19.

[0026] The second passage 24 opens into the cooling channel 22 and is connected to the crank chamber 15. The second passage 24 has an inlet 24a connected to the cooling channel 22 and an outlet 24b connected to the crank chamber 15. At least one of the inlet 24a and the outlet 24b of the second passage 24 is located above the opening of the first passage 23 relative to the cooling channel 22, i.e., closer to the combustion chamber 14. In this example, both the inlet 24a and the outlet 24b of the second passage 24 are located above the opening of the first passage 23.

[0027] The opening direction of the outlet 24b of the second passage 24 relative to the crank chamber 15 is set to a direction that does not oppose the direction in which oil is discharged from the oil jet 26, i.e., the direction of the arrow in Figure 1. More specifically, the opening direction of the outlet 24b of the second passage 24 relative to the crank chamber 15 is set to a direction that is perpendicular to the direction in which oil is discharged from the oil jet 26.

[0028] When an internal combustion engine is running, water is produced as fuel is burned in the combustion chamber 14. This produced water becomes water vapor. As the piston 11 reciprocates, this water vapor passes between the top ring 19 and the inner peripheral surface of the cylinder 12 and enters the space between the top ring 19 and the second ring 20, which is between the outer peripheral surface of the crown 13 of the piston 11 and the inner peripheral surface of the cylinder 12.

[0029] Furthermore, the water vapor in the combustion chamber 14 also enters the above-mentioned area through the corner between the top ring 19 and the ring groove 16. The water vapor that enters the above-mentioned area is forced into the cooling channel 22 through the first passage 23. Inside the cooling channel 22, the water vapor turns into water and accumulates. This water cools the piston 11. The water in the cooling channel 22 can be discharged into the crankcase 15 of the internal combustion engine through the second passage 24. Therefore, excessive water does not accumulate inside the cooling channel 22.

[0030] Next, the function and effect of the piston of the internal combustion engine according to this embodiment will be described. (1) Both the inlet 24a and the outlet 24b of the second passage 24 in the crown 13 of the piston 11 are located above the opening of the first passage 23 to the cooling channel 22. This prevents water flowing into the cooling channel 22 from immediately flowing out into the crankcase 15 of the internal combustion engine via the second passage 24. In this way, water that has accumulated in the cooling channel 22 is less likely to flow into the crankcase 15 via the second passage 24, and the water can be retained within the cooling channel 22. Because water has a higher specific heat than oil, the piston 11 can be efficiently cooled by the water.

[0031] (2) The opening direction of the outlet 24b of the second passage 24 relative to the crank chamber 15 is a direction that does not oppose the direction in which oil is discharged from the oil jet 26, more specifically, a direction that is perpendicular to the direction in which oil is discharged. This prevents the oil discharged from the oil jet 26 from entering the cooling channel 22 via the second passage 24. Therefore, the oil that has entered the cooling channel 22 prevents water in the cooling channel 22 from flowing into the crank chamber 15 via the second passage 24. If the oil that has entered the cooling channel 22 causes water in the cooling channel 22 to flow into the crank chamber 15, the oil will accumulate in the cooling channel 22. Because oil has a lower specific heat than water, if the oil accumulates in the cooling channel 22, the cooling performance of the piston 11 will deteriorate. This can be prevented.

[0032] (3) Oil discharged from the oil jet 26 hits the crown 13 of the piston 11 at a position corresponding to the cooling channel 22. The water vapor flowing from the first passage 23 into the cooling channel 22 is cooled by the oil and efficiently turns into water. Furthermore, the water in the cooling channel 22 is cooled by the oil. This allows the piston 11 to be effectively cooled by the water in the cooling channel 22. Therefore, the amount of oil discharged from the oil jet 26 can be kept small to achieve the cooling of the water required to cool the piston 11. As a result, the energy loss of the internal combustion engine caused by discharging oil from the oil jet 26 can be kept small, and the deterioration of fuel efficiency of the internal combustion engine due to the discharge of oil from the oil jet 26 can be suppressed.

[0033] (4) In an internal combustion engine, if gas leaks from the combustion chamber 14 to a location between the top ring 19 and the second ring 20, between the outer circumferential surface of the piston crown 13 and the inner circumferential surface of the cylinder 12, the pressure at that location may increase. In this case, the pressure at that location approaches the pressure in the combustion chamber 14, and the force acting on the top ring 19 due to the pressure difference decreases. As a result, the top ring 19, which is pressed against the inner wall of the ring groove 16 by the force, becomes more likely to move within the ring groove 16, making the position of the top ring 19 unstable within the ring groove 16, as shown in FIG. 4 . This unstable position of the top ring 19 can cause wear on the top ring 19 and the inner circumferential surface of the cylinder 12 and increase the amount of blow-by gas flowing from the combustion chamber 14 into the crankcase 15.

[0034] However, the first passage 23 formed in the crown portion 13 of the piston 11 opens at a location between the outer peripheral surface of the crown portion 13 of the piston 11 and the inner peripheral surface of the cylinder 12, between the top ring 19 and the second ring 20. This increases the volume of the location by the amount of the first passage 23. Even if gas leaks to the location from the combustion chamber 14, the pressure at the location is less likely to increase, and the pressure at the location is less likely to approach the pressure within the combustion chamber 14. This prevents the force acting on the top ring 19 due to the pressure difference from decreasing, which in turn prevents the position of the top ring 19 in the ring groove 16 from becoming unstable. This prevents wear on the inner peripheral surfaces of the top ring 19 and the cylinder 12, and prevents an increase in the amount of blow-by gas flowing from the combustion chamber 14 into the crank chamber 15, which would otherwise be caused by an instability in the position of the top ring 19.

[0035] The above embodiment can be modified as follows, for example: The above embodiment and the following modifications can be combined and implemented within the scope of technical compatibility. 5, the first passage 23 may open at the center of the ring groove 17 in the direction of the center line of the piston 11. As a result, the first passage 23 opens at a location between the outer peripheral surface of the crown portion 13 and the inner peripheral surface of the cylinder 12, between the top ring 19, which is the piston ring closest to the combustion chamber 14, and the second ring 20, which is the piston ring located next to the top ring 19.

[0036] 6, the first passage 23 may open at a location between the ring groove 16 and the ring groove 17 on the outer peripheral surface of the crown portion 13. As a result, the first passage 23 opens at a location between the outer peripheral surface of the crown portion 13 and the inner peripheral surface of the cylinder 12, between the top ring 19, which is the piston ring closest to the combustion chamber 14, and the second ring 20, which is the piston ring located next to the top ring 19.

[0037] It is not necessary for the oil ejected from the oil jet 26 to hit the position of the crown 13 of the piston 11 corresponding to the cooling channel 22 . The opening direction of the outlet 24 b of the second passage 24 with respect to the crank chamber 15 does not necessarily have to be perpendicular to the direction in which oil is discharged from the oil jet 26 .

[0038] Of the inlet 24 a and outlet 24 b of the second passage 24 , only the inlet 24 a may be located above the opening of the first passage 23 to the cooling channel 22 . Of the inlet 24 a and the outlet 24 b of the second passage 24 , only the outlet 24 b may be located above the opening of the first passage 23 to the cooling channel 22 .

[0039] Although hydrogen is used as an example of fuel for an internal combustion engine, other fuels that produce a lot of water when burned may also be used. [Explanation of symbols]

[0040] 11...Piston 12...Cylinder 13...Crown 14...Combustion chamber 15...Crankcase 16...Ring groove 17...Ring groove 18...Ring groove 19...Top ring 20...Second Ring 21...Oil ring 22...Cooling channel 23…1st aisle 24…Second aisle 24a…Entrance 24b…Exit 26...Oil jet

Claims

1. a crown portion facing a combustion chamber of an internal combustion engine; A cooling channel, a first passage, and a second passage are formed inside the crown, the first passage extends from an outer peripheral surface of the crown to the cooling channel and opens into the cooling channel; The second passage is open to the cooling channel and to a crankcase of the internal combustion engine, the second passage has an inlet opening to the cooling channel and an outlet opening to the crankcase, At least one of an inlet and an outlet of the second passage is located above an opening of the first passage to the cooling channel; A plurality of ring grooves are formed at intervals on the outer peripheral surface of the crown portion from the combustion chamber side toward the crank chamber side, A piston ring that contacts the inner peripheral surface of a cylinder in an internal combustion engine is accommodated in each of the plurality of ring grooves, A piston for an internal combustion engine, wherein the first passage opens at a location between the outer peripheral surface of the crown portion and the inner peripheral surface of the cylinder, between the piston ring closest to the combustion chamber and the piston ring located adjacent to that piston ring.

2. the internal combustion engine is provided with an oil jet that discharges oil from the crank chamber toward the crown portion, 2. The piston for an internal combustion engine according to claim 1, wherein the opening direction of the outlet of the second passage relative to the crank chamber is not opposite to the direction in which oil is discharged from the oil jet.

3. 3. The piston for an internal combustion engine according to claim 2, wherein the opening direction of the outlet of the second passage relative to the crank chamber is perpendicular to the direction in which oil is discharged from the oil jet.

4. the internal combustion engine is provided with an oil jet that discharges oil from the crank chamber toward the crown portion, 2. The piston for an internal combustion engine according to claim 1, wherein the oil discharged from the oil jet hits a position of the crown portion corresponding to the cooling channel.

Images