JP2012132343A - Piston cooling device for internal-combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston cooling device in which a cooling effect of a piston can be improved when a high load is applied and the heat loss of the piston can be reduced when a low load is applied by using a simple and low-cost means.SOLUTION: A ring-shaped cooling cavity 26 is arranged inside a piston head 14a and a plurality of passages 42 for both of a lubricant and a blow-by gas are connected radially to the cooling cavity 26 in the peripheral direction. The other end of each of the plurality of passages 42 for both of the lubricant and the blow-by gas is communicated with the upper half area of an oil ring groove 25. The lubricant r flows on the wall 12 of a cylinder from the cooling cavity 26 and passing through the lower area of the passage 42 for both of the lubricant and the blow-by gas. Meanwhile, the blow-by gas g from a combustion chamber 16 intrudes into a space s between the wall 12 of the cylinder and the outside wall of the piston head, passes through the passage 42 for both of the lubricant and the blow-by gas and flows in the cooling cavity 26. Since the lubricant r and the blow-by gas g form a gas-liquid two-phase flow, the cooling effect of the piston head 14a can be improved.

Description

  The present invention relates to a piston cooling method and a cooling device that are suitable for use in an internal combustion engine such as a small diesel engine.

  In an internal combustion engine, a large heat load is applied to a piston, particularly a piston head. Depending on the heat load, the piston may become extremely hot and may melt. Therefore, conventionally, a technique for cooling the piston by forming a cooling cavity inside the piston head and circulating lubricating oil in the cooling cavity is conventionally known.

  Patent Document 1 discloses a cooling means provided with such a cooling cavity. The cooling means includes a lubricating oil supply hole and a lubricating oil discharge hole that are open in the piston inner space and connected to the cooling cavity, and an oil ring groove and a lubricating oil introduction hole that communicates with the cooling cavity. Yes. A lubricating oil injection nozzle that injects the lubricating oil pumped from the lubricating oil pump toward the openings of the lubricating oil supply hole and the lubricating oil discharge hole is disposed below the cooling cavity.

  By connecting the lubricating oil introduction hole to the oil ring groove in the circumferential tangent direction of the piston, the lubricating oil scraped by the oil ring is introduced into the cooling cavity at a speed in the circumferential direction of the piston. The lubricating oil having this speed merges with the lubricating oil in the cooling cavity to improve the flow of the lubricating oil in the cooling cavity, thereby improving the cooling effect.

  Next, the cooling means disclosed in Patent Document 2 will be described with reference to FIGS. 4 and 5, the piston head 104 slides inside the cylinder wall 102. On the side surface of the piston head 104, there are compression rings 110 and 112 that act as a seal for reducing blow-by gas that escapes from the combustion chamber 106, and an oil ring 114 that prevents leakage of lubricating oil in each ring groove. Contained.

  A ring-shaped cooling cavity 116 is provided inside the piston head 104, and a lubricating oil supply path 118 and a lubricating oil discharge path 120 each having an opening in the lower piston inner space 108 communicate with the cooling cavity 116. is doing. A lubricating oil injection nozzle (not shown) that injects the lubricating oil toward the lubricating oil supply path 118 is provided directly below the lubricating oil supply path 118. The lubricating oil supply path 118 and the oil ring groove 114 a communicate with each other through the first communication hole 122, and the lubricating oil discharge path 120 and the oil ring groove 114 a communicate with each other through the second communication hole 124. The first communication hole 122 and the second communication hole 124 form acute angles α and β with respect to the vertical direction (piston sliding direction), respectively.

  In such a configuration, the lubricating oil r is supplied from the lubricating oil supply path 118 to the cooling cavity 116 by the lubricating oil injection nozzle. On the other hand, blow-by gas g enters the first communication hole 122 from the combustion chamber 106 through the joint of the compression rings 110 and 112. The blow-by gas g acts to introduce the lubricating oil r in the lubricating oil supply path 118 into the cooling cavity 116. Similarly, the blow-by gas g that has passed through the second communication hole 124 acts to discharge the lubricating oil r in the lubricating oil discharge path 120 to the piston inner space 108. Thereby, the circulation amount of the lubricating oil r in the cooling cavity 116 is increased, and the cooling effect of the piston is improved.

  However, cooling the piston is effective because it can reduce the heat load of the piston at high loads, but is not preferable at low loads because it increases the heat loss of the piston and deteriorates fuel consumption. Therefore, it is necessary to adjust the flow rate of the lubricating oil for cooling between high load and low load. However, there is a question about the reliability and responsiveness of the adjustment mechanism using an electrical control device in a high temperature environment.

  Patent Document 3 discloses a cooling cavity provided inside a piston head, a lubricating oil injection nozzle that injects lubricating oil toward the cooling space, and a lubricating oil supply in which the lubricating oil injection nozzle is mounted at the tip. A piston cooling mechanism including a pipe and a lubricating oil pump provided in the lubricating oil supply pipe is disclosed. This lubricating oil pump is a mechanical pump, and is driven directly by a crankshaft or driven by transmitting the rotation of the crankshaft via a chain, a sprocket, or the like (paragraph [0053 of Patent Document 3). ]reference).

Japanese Utility Model Publication No. 1-142548 Japanese Laid-Open Patent Publication No. 10-184449 JP 2006-29127 A

  The piston cooling means disclosed in Patent Document 1 and Patent Document 2 cannot obtain a cooling effect higher than the heat transfer coefficient of the lubricating oil with respect to the abnormally high temperature that occurs during high loads. In the cooling means of Patent Document 2, the first communication hole 122 is connected to the inner side surface of the oil ring groove 114a. Therefore, when the blow-by gas g is directed to the first communication hole 122, there is a question as to whether or not the oil ring 114 becomes an obstacle and can exert the effect of increasing the circulation amount of the lubricating oil by the blow-by gas g. In addition, when the lubricating oil is directed from the first communication hole 122 toward the cylinder wall 102, the oil ring 114 may be in the way and hinder the lubrication of the cylinder wall 102.

  In the cooling means disclosed in Patent Document 3, since the lubricating oil pump is interlocked with the crankshaft, the rotational speed of the crankshaft is restricted. Therefore, it is not possible to obtain a sufficient cooling effect of the piston against the abnormally high temperature at the time of high load.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the prior art, and it is an object of the present invention to improve the piston cooling effect at a high load and reduce the heat loss of the piston at a low load by simple and low-cost means.

  In order to achieve such an object, the piston cooling method for an internal combustion engine according to the present invention supplies a lubricating oil from a lubricating oil injection nozzle to a cooling space provided in a piston head and having a communication hole opened downward to cool the piston. In the piston cooling method for an internal combustion engine, the first step of introducing blow-by gas into the oil ring groove from the compression ring joint by dynamic pressure of the blow-by gas when the internal combustion engine is under high load, and reaching the oil ring groove A second step of cooling the piston by introducing the blowby gas into the cooling space from the lubricating oil connecting the cooling space and the upper half region of the oil ring groove and the blowby gas combined passage. is there.

  In the method of the present invention, at high load, blow-by gas enters the oil ring groove from the combustion chamber, and further blow-by gas enters the lubricating oil and blow-by gas combined passage from the upper half region of the oil ring groove to enter the cooling space. Reach. The blow-by gas is cooled when it passes between the cylinder wall and the piston outer wall, and the cooled blow-by gas reaches the cooling space, thereby adding the cooling effect of the blow-by gas in addition to the cooling effect of the lubricating oil. Therefore, the piston cooling effect can be improved.

The piston cooling effect is reduced because the amount of blow-by gas entering the oil ring groove is small when the piston is not required to be cooled and the fuel consumption rate is likely to deteriorate due to heat loss. Therefore, the heat loss of the piston can be reduced.
According to the method of the present invention, the cooling effect of the piston can be improved without providing a special driving device, operating part or electrical control device, so there is no risk of abnormality or failure of the driving device or operating part, and the reliability Can be secured, and a simple and low-cost means can be realized.

  At this time, the lubricating oil and blow-by gas may be mixed to form a gas-liquid two-phase flow. A heat-transfer coefficient increases by becoming a gas-liquid two-phase flow. The gas-liquid two-phase flow passes through the lubricating oil and blow-by gas combined passage and the cooling space, so that the piston cooling effect can be enhanced.

  The piston cooling device for an internal combustion engine of the present invention that can be directly used for carrying out the method of the present invention includes a cooling space provided inside a piston head, and a lubricating oil injection nozzle that injects lubricating oil toward the cooling space. An internal combustion engine piston cooling device comprising a lubricating oil supply passage connected to the lubricating oil injection nozzle and a lubricating oil pump provided in the lubricating oil supply passage, is provided radially around the cooling space. A plurality of lubricating oil and blow-by gas combined passages that communicate the cooling space with the upper half region of the oil ring groove are provided.

  In the device of the present invention, since the lubricating oil and blow-by gas combined passage is connected to the upper half region of the oil ring groove, the lubricating oil passing through the lower region of the lubricating oil and blow-by gas combined passage does not become an obstacle, Blow-by gas can smoothly enter the lubricating oil and blow-by gas passage. Then, the lubricating oil and the blow-by gas are mixed together to form a gas-liquid two-phase flow having a large heat transfer coefficient. The gas-liquid two-phase flow flows in the lubricating oil and blow-by gas combined passage and the cooling space, whereby the piston cooling effect can be improved.

  Further, as described above, the cooling effect of the piston is reduced because the amount of blow-by gas entering the oil ring groove is small at the time of low load where the cooling of the piston is unnecessary and the fuel consumption rate is likely to deteriorate due to heat loss. Therefore, the heat loss of the piston can be reduced.

  According to the method of the present invention, in the piston cooling method for an internal combustion engine, the piston is cooled by supplying the lubricating oil from the lubricating oil injection nozzle to the cooling space provided in the piston head and having a communication hole opened downward. The first step of introducing the blow-by gas into the oil ring groove from the joint of the compression ring by the dynamic pressure of the blow-by gas when the internal combustion engine is at a high load, and the blow-by gas that has reached the oil ring groove, The second step of cooling the piston by introducing it into the cooling space from the lubricating oil and blow-by gas combined passage connecting the upper half region of the groove and synergistic effect of the lubricating oil and blow-by gas at high load Thus, the piston cooling effect can be improved and the heat loss of the piston can be reduced at low load. In addition, this can be realized by simple and low-cost means.

  According to the device of the present invention, the cooling space provided in the piston head, the lubricating oil injection nozzle for injecting the lubricating oil toward the cooling space, and the lubricating oil supply connected to the lubricating oil injection nozzle In the piston cooling device for an internal combustion engine provided with a passage and a lubricating oil pump provided in the lubricating oil supply passage, the cooling space and the upper half region of the oil ring groove are provided radially around the cooling space. Since a plurality of lubricating oil and blow-by gas combined passages that communicate with each other are provided, the same effects as those of the present invention can be obtained.

It is front view sectional drawing of the piston head which concerns on one Embodiment of this invention apparatus. It is a top view sectional view of the piston head concerning the embodiment. It is a partially expanded sectional view of FIG. It is front sectional drawing (left half) which shows the piston cooling device of the conventional internal combustion engine. It is front sectional drawing (right half) which shows the piston cooling device of the conventional internal combustion engine.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.

  An embodiment of the device of the present invention will be described with reference to FIGS. 1 and 2 show a piston cooling device 10 of the present embodiment. Inside the cylinder wall 12, the piston 14 is connected to the connecting rod 38 and the crankshaft 40, and slides with the explosive force of the combustion chamber 16. As a result, a shaft output is generated on the crankshaft 40. Ring grooves 20a and 22a are formed on the side surface of the piston head 14a. The first compression ring 20 is attached to the ring groove 20a, and the second compression ring 22 is attached to the ring groove 22a.

  These compression rings are attached to the ring grooves 20a and 22a in a state where a tension that presses the cylinder wall 12 is applied. And it acts as a seal for reducing the blow-by gas g entering the gap s between the cylinder wall 12 and the piston outer surface from the combustion chamber 16. An oil ring groove 25 is formed below the ring groove 22a, and an oil ring 24 is attached to the oil ring groove 25. The oil ring 24 has a role of adjusting the film thickness of the lubricating oil adhering to the cylinder wall 12.

  In particular, as clearly shown in FIG. 2, a cooling cavity 26 having a ring shape is provided inside the piston head 14. A lubricating oil supply path 28 and a lubricating oil discharge path 30 are connected to the cooling cavity 26 at a position 180 degrees apart in the piston circumferential direction. The lubricating oil supply path 28 and the lubricating oil discharge path 30 are arranged downward and have openings 28 a and 30 a that open to the lower piston inner space 18. In the circumferential direction of the cooling cavity 26, eight lubricating oil and blow-by gas combined passages 42 are radially connected at equal intervals.

  The first compression ring 20 and the second compression ring 22 are formed with a mating port 44, and the blow-by gas g enters the oil ring groove side from the mating port 44. During operation of the piston head 14, the abutment 44 moves in the circumferential direction of the piston 14. Therefore, at the time of manufacture, it does not make much sense to determine the position of the mating port 44 in the circumferential direction of the piston.

  A lubricating oil injection nozzle 36 that injects the lubricating oil toward the lubricating oil supply path 28 is provided directly below the lubricating oil supply path 28. Since the piston 14 moves between the top dead center and the bottom dead center, the direction and shape of the lubricating oil injection nozzle 36 and the position of the opening 28a of the lubricating oil supply passage 28 are appropriately determined in consideration of this point. Set.

  The lubricating oil injection nozzle 36 is attached to the tip of the lubricating oil supply pipe 32, and the lubricating oil supply pipe 32 is provided with a lubricating oil pump 34. The high-pressure lubricating oil r is sent to the lubricating oil supply pipe 32 by the lubricating oil pump 34 and is injected from the lubricating oil injection nozzle 36 toward the opening 28 a of the lubricating oil supply path 28. Thus, the lubricating oil r is supplied from the opening 28 a through the lubricating oil supply path 28 to the cooling cavity 26.

  As shown in FIG. 3, the lubricating oil and blow-by gas combined passage 42 is open to the upper surface 25a of the oil ring groove 25, the cylinder wall 12 and the outer wall of the piston head 14a. In some cases, the opening of the lubricating oil and blow-by gas combined passage 42 may reach the upper portion of the side surface 25b of the oil ring groove 25 or the piston outer wall above the oil ring groove 25.

  In such a configuration, the lubricating oil r is injected by the lubricating oil injection nozzle 36 toward the opening 28 a of the lubricating oil supply path 28 and supplied from the lubricating oil supply path 28 to the cooling cavity 26. As shown in FIG. 3, the lubricating oil r supplied to the cooling cavity 26 passes through the lower space of the lubricating oil and blow-by gas combined passage 42 and enters the gap s between the cylinder wall 12 and the outer wall of the piston 14. Supplied and used for lubrication of the gap s.

  On the other hand, when the internal combustion engine is at a high load, the pressure of the combustion gas in the combustion chamber 16 increases, so that the flow rate of the blow-by gas g entering the gap s from the combustion chamber 16 increases. The blow-by gas g is cooled while passing through the gap s, passes through the joint 44 of the first compression ring 20 and the second compression ring 22, and reaches the oil ring groove 25. Usually, the oil ring 24 is in a position in contact with the lower surface 24c of the oil ring groove 25, so that the blow-by gas g that has reached the oil ring groove 25 passes through the space above the lubricating oil and blow-by gas combined passage 42 for cooling. It is possible to enter the cavity 26 smoothly.

The lubricating oil r and the blow-by gas g are mixed in the oil ring groove 25 and the lubricating oil and blow-by gas combined passage 42 to form a gas-liquid two-phase flow. This gas-liquid two-phase flow is stirred in the lubricating oil and blow-by gas combined passage 42 and the cooling cavity 26. This gas-liquid two-phase flow has an increased heat transfer coefficient, and the cooling capacity of the piston 14 is increased by being agitated.
At low loads where the piston 14 does not need to be cooled and heat loss due to the cooling action of the lubricating oil r is likely to deteriorate the fuel efficiency, the flow rate of the blow-by gas g is small, so the cooling capacity by the gas-liquid two-phase flow is reduced To do.

  As described above, according to the present embodiment, when the piston 14 needs to be cooled at a high load, the cooling effect of the piston 14 can be enhanced by the gas-liquid two-phase flow including the lubricating oil r and the blow-by gas g. The cooling effect of the piston 14 can be suppressed at a low load that does not require cooling. Therefore, it is possible to prevent the piston 14 from being melted at the time of high load, and the fuel efficiency is not deteriorated at the time of low load. In addition, in the present embodiment, since a special drive device or operating unit or control device for adjusting the cooling capacity is not required, it is possible to ensure reliability as in the past, and to realize this with simple and cost-effective means. .

  In FIG. 3, a two-dot chain line 46 indicates a connection position of the conventional lubricating oil supply path with respect to the oil ring groove 25. Conventionally, the lubricating oil supply path is connected to the side surface 25 b of the oil ring groove 25. At this connection position, the lubricating oil supply path is blocked by the oil ring 24, and the lubricating oil r and blow-by gas g cannot be smoothly distributed. Therefore, the cooling effect of the piston 14 cannot be enhanced.

  According to the present invention, in an internal combustion engine, with a simple and low-cost configuration, the piston cooling effect can be enhanced at high loads, and the heat loss of the pistons can be suppressed at low loads.

DESCRIPTION OF SYMBOLS 10 Piston cooling device 12,102 Cylinder wall 14,104 Piston 14a Piston head 16,106 Combustion chamber 18,108 Piston inner space 20 1st compression ring 20a, 22a Ring groove 22 2nd compression ring 24,114 Oil ring 25,114a Oil ring groove 25a Upper surface 25b Side surface 25c Lower surface 26, 116 Cooling cavity 28, 118 Lubricating oil supply path 28a, 30a Opening 30, 120 Lubricating oil discharge path 32 Lubricating oil supply pipe 34 Lubricating oil pump 36 Lubricating oil injection nozzle 38 Connecting rod 40 Crankshaft 42 Lubricating oil and blow-by gas combined passage 44 Abutment 46 Conventional lubricating oil supply passage 110, 112 Compression ring 122 First communication hole 124 Second communication hole g Blow-by gas r Lubricating oil

Claims (3)

In a piston cooling method for an internal combustion engine, the piston is cooled by supplying lubricating oil from a lubricating oil injection nozzle to a cooling space provided inside the piston head and having a communication hole opened downward.
A first step of introducing blow-by gas into the oil ring groove from the joint of the compression ring by dynamic pressure of the blow-by gas at a high load of the internal combustion engine;
A second step of cooling the piston by introducing the blow-by gas that has reached the oil ring groove into the cooling space from the lubricating oil and blow-by gas combined passage connecting the cooling space and the upper half region of the oil ring groove; A piston cooling method for an internal combustion engine.   In the second step, the blow-by gas introduced into the lubricating oil and blow-by gas combined passage is mixed with the lubricating oil, and the gas-liquid two-phase mixed with the lubricating oil and blow-by gas combined passage and the cooling space in the cooling space 2. The piston cooling method for an internal combustion engine according to claim 1, wherein a flow is formed. A cooling space provided inside the piston head; a lubricating oil injection nozzle that injects lubricating oil toward the cooling space; a lubricating oil supply path connected to the lubricating oil injection nozzle; and the lubricating oil supply path In a piston cooling device for an internal combustion engine provided with a provided lubricating oil pump,
A piston cooling apparatus for an internal combustion engine, wherein a plurality of lubricating oil and blow-by gas combined passages are provided radially around the cooling space and communicate with the cooling space and the upper half region of the oil ring groove. .

Images