JP2004100545A - Oil jet for cooling piston of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply sufficient amount of engine oil to the piston by making an inner diameter of an injection port of the oil jet proper and improve a cooling efficiency of a piston in an oil jet for cooling the piston of an internal combustion engine. <P>SOLUTION: The inner diameter d of the injection port 34c of the oil jet 34 is set so that the Reynolds number of an oil injection may be in the range of 2,000-5,000 and an oil injection acquiring rate of an oil inlet 32 reaches a prescribed value, i.e. 70% or more. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an oil jet for cooling a piston of an internal combustion engine, which cools the piston by spraying engine oil on the back surface of the top of the piston of the internal combustion engine.
[0002]
[Prior art]
In a general engine, a plurality of cylinders are formed in an engine main body, and a piston is slidably fitted in each cylinder up and down. A combustion chamber is formed by the engine main body and the piston. An intake port and an exhaust port are connected to the combustion chamber, and front ends of the intake valve and the exhaust valve face each port, so that the combustion chamber and each port can be opened and closed. A crankshaft is rotatably disposed below the engine body, and an eccentric portion of the crankshaft and a piston are connected by a connecting rod.
[0003]
When the engine is under a high load, the piston becomes hot and thermally expands, which may hinder proper operation.In addition, if the piston is kept at a high temperature for a long time, thermal deterioration may occur. Need to cool this piston. Conventionally, an oil jet is provided at a lower portion of an engine body, and engine oil is blown from an oil jet toward a back surface of a top portion of an operating piston to cool the piston. In this case, an annular cooling space is provided inside the piston, and the engine oil injected from the oil jet enters the cooling space from the inlet and is discharged from the outlet to cool the piston. .
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 10-077833
[Problems to be solved by the invention]
However, there is a demand for further improving the cooling efficiency of the piston by increasing the output of the engine. In this case, it is conceivable to increase the cooling efficiency of the piston by increasing the injection amount of oil injected from the oil jet to the piston, but this increases the driving force of the oil pump and deteriorates fuel efficiency. Problem. Also, what affects the cooling efficiency of the piston is not the amount of oil injected from the oil jet, but the amount of oil entering the cooling space inside the piston. That is, if the amount of oil injected from the oil jet is simply increased, the injected oil diffuses in a fan shape and does not properly reach the inlet of the cooling space. The amount of oil going in has hardly increased.
[0006]
Further, in Patent Document 1 described above, a plurality of base passages at the tip end of the oil jet are formed, and the inner diameter and the interval are set to predetermined values. In this case, by narrowing the base passage at the tip of the oil jet, it is possible to prevent the injected oil from diffusing in a fan shape as a laminar flow. However, when the base passage at the tip of the oil jet is narrowed in this way, foreign matters contained in the oil may be blocked in the base passage, and the injection resistance of the oil may be insufficient to secure a sufficient injection amount. There is.
[0007]
The present invention has been made to solve such a problem, and an internal combustion engine in which a sufficient amount of engine oil is supplied to a piston by setting an injection hole of an oil jet to an appropriate inner diameter to improve the cooling efficiency of the piston. It is an object of the present invention to provide a piston cooling oil jet.
[0008]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided an oil jet for cooling a piston of an internal combustion engine according to the first aspect of the present invention, wherein the engine oil is injected into an oil jet that cools the piston of the internal combustion engine by blowing the engine oil on the back surface of the top of the piston. A single injection port is formed, and the inner diameter of the injection port is set so that the injection oil Reynolds number is in the range of 2000 to 5000.
[0009]
Further, in the oil jet for cooling a piston of an internal combustion engine according to the second aspect of the present invention, in the oil jet for cooling by blowing engine oil on the back surface of the top of the piston of the internal combustion engine, the piston has an annular oil inlet and an oil outlet. A cooling space is provided, a single injection port for injecting engine oil is formed, and the inner diameter of the injection port is set so that the injection rate of the injection oil at the oil inlet becomes a predetermined value or more.
[0010]
Further, in the oil jet for cooling a piston of an internal combustion engine according to the third aspect of the present invention, in the oil jet for cooling by spraying engine oil on the back surface of the top of the piston of the internal combustion engine, the annular oil jet has an oil inlet and an oil outlet on the piston. A cooling space is provided, and a single injection port for injecting engine oil is formed. The inner diameter of this injection port is adjusted so that the injection oil Reynolds number is in the range of 2000 to 5000, and the injection rate of the injection oil at the oil inlet is a predetermined value. It is set so that it becomes above.
[0011]
Therefore, a single injection port for injecting engine oil is formed, and the inner diameter of the injection port is set to a range of 2000 to 5000 for the injection oil Reynolds number, or the injection oil capture rate at the oil inlet is set to a predetermined value or more. Thus, a sufficient amount of engine oil can be supplied to the piston, and the cooling efficiency of the piston can be improved.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0013]
1 is a cross-sectional view of an oil jet for cooling a piston of an internal combustion engine according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view of a main part of an engine equipped with the oil jet of the present embodiment, and FIG. FIG. 4 is a graph showing the trapped oil amount with respect to the oil amount, FIG. 4 is a graph showing the trapped ratio with respect to the injected oil Reynolds number, and FIG.
[0014]
In the engine equipped with the oil jet of the present embodiment, as shown in FIG. 2, a cylinder head 12 is bolted on a cylinder block 11, and a piston 14 is provided in a cylinder 13 in the cylinder block 11. Fits up and down freely. A combustion chamber 15 is formed by the cylinder block 11, the cylinder head 12, and the piston 14. The combustion chamber 15 is connected to an intake port 16 and an exhaust port 17, and the intake port 16 and the exhaust port 17 are connected to an intake valve 18 and an exhaust port. The front end of the valve 19 faces so that the combustion chamber 15 and the ports 16 and 17 can be opened and closed. A crankshaft 20 is rotatably supported below the cylinder block 11, and an eccentric portion 21 of the crankshaft 20 and the piston 14 are connected by a connecting rod 22.
[0015]
An intake camshaft 23 and an exhaust camshaft 24 are rotatably supported on the upper portion of the cylinder head 12, and an intake cam 25 and an exhaust cam 26 having a predetermined lift amount for each cylinder are integrally formed. The intake cam 25 and the exhaust cam 26 push down the intake valve 18 and the exhaust valve 19 so that the combustion chamber 15 can communicate with the intake port 16 and the exhaust port 17. Further, the cylinder head 12 is provided with an ignition plug 27 whose tip faces the combustion chamber 15 and an injector (not shown) for injecting fuel into the intake port 16.
[0016]
The above-mentioned piston 14 is formed with an annular cooling space 31 located at the top thereof and having an annular shape, and an oil inlet 32 and an oil outlet 33 which are open downward from the cooling space 31. The oil inlet 32 and the oil outlet 33 are located substantially 180 degrees in the circumferential direction. An oil jet 34 is mounted on the cylinder block 11 below the piston 14 so as to face the oil inlet 32. The oil jet 34 can communicate with a main gallery 35 formed in the cylinder block 11 via an open / close valve (not shown).
[0017]
Therefore, when the oil supply pressure becomes equal to or higher than a predetermined value (for example, ^{2 to 4} kg / cm ² ) by the oil pump driven by the engine, the opening / closing valve is opened, and the engine oil of the main gallery 35 passes through the opening / closing valve to the oil jet 34. The engine oil is supplied and injected from the oil jet 34 toward the oil inlet 32 of the piston 14. Then, the engine oil injected from the oil jet 34 is captured by the cooling space 31 from the oil inlet 32 and is discharged from the oil outlet 33 after cooling the piston 14.
[0018]
In the oil jet 34 of the present embodiment, as shown in FIG. 1, a narrowed portion 34b whose leading end is narrowed is formed in an oil passage 34a communicating with the main gallery 35, and the narrowed portion 34b has a predetermined length. Injections 34c parallel to each other by L are continuously formed. Then, the inner diameter d of the injection port 34c is set such that the injection oil Reynolds number is in the range of 2000 to 5000, and the injection oil capture rate at the oil inlet 32 is equal to or more than a predetermined value (for example, 70%). You have set.
[0019]
That is, the graph shown in FIG. 3 shows the amount of captured oil captured from the oil inlet 32 into the cooling space 31 with respect to the amount of engine oil injected from the oil jet 34. From this graph, it can be seen that even if the amount of injected oil increases, the amount of trapped oil does not increase in proportion, but remains substantially constant at a predetermined amount of trapped oil. In fact, the trapping rate of engine oil is about 70%. It can be seen that it is sufficient to secure a capture rate of 70% or more.
[0020]
On the other hand, the trapping rate of the engine oil is related to the injected oil Reynolds number Re. The graph shown in FIG. 4 shows the trapping ratio with respect to the Reynolds number Re of the jet oil. From this graph, it can be seen that the trapping rate decreases as the oil Reynolds number Re increases. By taking into account the above-described range of the engine oil trapping rate of 70% or more to this graph, it is found that the injection oil Reynolds number Re is 5000 or less is appropriate. As described above, when the oil supply pressure becomes equal to or higher than a predetermined value, the opening / closing valve is opened and the engine oil of the main gallery 35 is supplied to the oil jet 34 and is injected from the injection port 34c. The Reynolds number Re is approximately 2000. Therefore, the appropriate range of the oil Reynolds number Re can be set to 2000 to 5000.
[0021]
This can be seen from the graph of FIG. The graph of FIG. 5 is a graph showing the oil spread angle with respect to the oil Reynolds number. It can be seen that the oil spread angle increases as the oil Reynolds number increases. Is greater than 5000, the oil spread angle becomes 10 (deg) or more, and the engine oil cannot be properly injected into the oil inlet 32.
[0022]
The oil Reynolds number Re can be obtained by the following equation.
Re = (V · d) / ν
V represents the flow rate of the oil at the injection port 34c, and ν represents the kinematic viscosity of the engine oil.
[0023]
Accordingly, although the kinematic viscosity ν of the engine oil changes according to the temperature of the engine oil (the kinematic viscosity ν decreases as the temperature of the engine oil increases), it can be set as a substantially constant constant. Since the oil flow velocity V is set by the oil supply pressure and the inner diameter d, the oil flow velocity V is adjusted according to the inner diameter d of the injection port 34c and the oil supply pressure so that the oil Reynolds number Re becomes an appropriate value (2000 to 5000). What is necessary is just to set the injection oil flow velocity V to an appropriate value.
[0024]
Although the oil Reynolds number Re is desirably set to a value as small as possible within an appropriate range (2000 to 5000) in terms of the oil spread angle and the trapping rate, as described above, the engine performance is taken into consideration. It is desirable to set it to an appropriate value in order to secure the minimum required amount of fuel oil.
[0025]
As described above, according to the oil jet for cooling the piston of the internal combustion engine of the first embodiment, the inner diameter d of the injection port 34c of the oil jet 34 is set so that the injection oil Reynolds number is in the range of 2000 to 5000. At a predetermined value (for example, 70%) or more. Therefore, a sufficient amount of engine oil can be supplied to the piston 14 by the oil jet 34, so that the cooling efficiency of the piston 14 can be improved and the driving force of the oil pump is increased in order to increase the injection amount of the engine oil. Therefore, it is possible to prevent fuel consumption from deteriorating.
[0026]
FIG. 6 shows a cross section of a main part of an engine equipped with an oil jet according to a second embodiment of the present invention, and FIG. 7 shows a cross section taken along line VII-VII of FIG. Note that members having the same functions as those described in the above-described embodiment are denoted by the same reference numerals, and redundant description will be omitted.
[0027]
In the second embodiment, as shown in FIGS. 6 and 7, two oil inlets 32 are formed in the cooling space 31 of the piston 14 so as to be substantially 180 degrees in the circumferential direction and two oil outlets 33 are formed. The oil inlet 32 and the oil outlet 33 are disposed so as to be substantially 90 degrees apart from each other in the circumferential direction. Two oil jets 34 are mounted on the cylinder block 11 below the piston 14 so as to face the oil inlets 32.
[0028]
By providing the two oil jets 34 in this manner, it is possible to set the injection oil Reynolds number Re to a value as small as possible within an appropriate range (2000 to 5000) while securing the required oil injection amount. While improving the cooling efficiency of the engine 14, the engine oil pump can be optimized.
[0029]
In the above-described embodiment, a description has been given based on a gasoline engine that supplies fuel to the intake passage.However, the present invention is not limited to this. For all internal combustion engines such as a direct injection gasoline engine and a diesel engine, Can be applied.
[0030]
【The invention's effect】
As described in detail in the above embodiment, according to the piston cooling oil jet of the first aspect of the present invention, a single injection port for injecting engine oil is formed, and the inner diameter of this injection port is changed to the injection oil Reynolds. Since the number is set to be in the range of 2000 to 5000, it is possible to secure the injection oil capture rate at the oil inlet at a predetermined value or more, and to supply a sufficient amount of engine oil to the piston to cool the piston. Efficiency can be improved.
[0031]
According to the oil jet for cooling a piston of an internal combustion engine of the invention of claim 2, the piston is provided with an annular cooling space having an oil inlet and an oil outlet, and a single injection port for injecting engine oil is formed. Since the inner diameter of the injection port is set so that the oil capture rate at the oil inlet is equal to or higher than a predetermined value, a sufficient amount of engine oil can be supplied to the piston, and the cooling efficiency of the piston can be improved. it can.
[0032]
Further, according to the oil jet for cooling a piston of an internal combustion engine according to the third aspect of the invention, the piston is provided with an annular cooling space having an oil inlet and an oil outlet, and a single injection port for injecting engine oil is formed. Since the inner diameter of the injection port is set so that the injection oil Reynolds number is in the range of 2000 to 5000 and the injection rate of the injection oil at the oil inlet is equal to or higher than a predetermined value, a sufficient amount of engine oil is supplied to the piston. The cooling efficiency of the piston can be improved.
[Brief description of the drawings]
FIG. 1 is a sectional view of a piston cooling oil jet of an internal combustion engine according to a first embodiment of the present invention.
FIG. 2 is a sectional view of a main part of an engine equipped with the oil jet according to the embodiment.
FIG. 3 is a graph showing the amount of trapped oil with respect to the amount of oil injected from an oil jet.
FIG. 4 is a graph showing a trapping rate with respect to a fuel oil Reynolds number.
FIG. 5 is a graph showing a spray oil spread angle with respect to a spray oil Reynolds number.
FIG. 6 is a sectional view of a main part of an engine equipped with an oil jet according to a second embodiment of the present invention.
FIG. 7 is a sectional view taken along line VII-VII of FIG. 6;
[Explanation of symbols]
13 Cylinder 14 Piston 22 Connecting rod 31 Cooling space 32 Oil inlet 33 Oil outlet 34 Oil jet 34c Injector

Claims (3)

In an oil jet that cools by spraying engine oil on the back surface of the top of a piston of an internal combustion engine, a single injection port for injecting engine oil is formed, and the inner diameter of the injection port is set so that the oil Reynolds number is in the range of 2000 to 5000. An oil jet for cooling a piston of an internal combustion engine, wherein the oil jet is set to be as follows. In an oil jet for cooling by spraying engine oil on the back of the top of a piston of an internal combustion engine, the piston is provided with an annular cooling space having an oil inlet and an oil outlet, and a single injection port for injecting engine oil is provided. An oil jet for cooling a piston of an internal combustion engine, wherein an inner diameter of the injection port is set so that an injection oil capture rate at the oil inlet is equal to or higher than a predetermined value. In an oil jet for cooling by spraying engine oil on the back of the top of a piston of an internal combustion engine, the piston is provided with an annular cooling space having an oil inlet and an oil outlet, and a single injection port for injecting engine oil is provided. A piston for an internal combustion engine, wherein the inner diameter of the injection port is set so that the injection oil Reynolds number is in the range of 2000 to 5000 and the injection oil capture rate at the oil inlet is equal to or higher than a predetermined value. Oil jet for cooling.

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