JPH0571325A - Lubricant return structure of internal combustion engine - Google Patents

Abstract

PURPOSE:To let lubricant being supplied to gear flow smoothly into a lubricant outflow port, in an internal combustion engine which is equipped with a pair of gears engaging with each other for driving a cam shaft for an exhaust valve and a cam shaft for an intake valve. CONSTITUTION:A pair of gears 78 and 80, which engage with each other for driving a cam shaft 70 for an exhaust valves and a cam shaft 72 for an intake valve, are arranged in a housing 76. The gears 78 and 80 are rotated to shift downward at the engaging parts. Concerning the first gear 78, a lubricant outflow port 82 is made in the peripheral part of the bottom wall of the housing 76 positioned on the opposite side to the second gear 80. Air is drawn in the direction of an oil outflow port 82 from between both gears 78 and 80 below the engaging parts by arranging the constitution such that the interval between the peripheral section of the first gear 78 and the surface of a floor member 86 facing each other may be smaller than the interval between the peripheral section of the second gear 80 and the bottom wall member of the housing 76 facing each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricating oil return structure for an internal combustion engine.

[0002]

2. Description of the Related Art A pair of gears meshing with each other for driving an exhaust valve camshaft and an intake valve camshaft is provided, each gear is arranged in a housing, and both gears are arranged above a lower wall surface of the housing. A lubricating oil return structure for an internal combustion engine is known in which lubricating oil outlet holes are formed immediately below the gears and are spaced apart from each other (Japanese Utility Model Publication No. 2-905).
(See Japanese Patent Publication No. 1).

In an internal combustion engine having a pair of gears meshing with each other for driving the exhaust valve camshaft and the intake valve camshaft, the gears mesh with each other in order to smoothly mesh the pair of gears. A large amount of lubricating oil is supplied to the parts. If a large amount of lubricating oil supplied to the meshing parts of the gears does not flow out smoothly from the lubricating oil outflow hole and accumulates in the housing, the lubricating oil receives heat from the engine body and is heated. There is a problem that the temperature of the lubricating oil rises and the lubricating oil deteriorates. The lubricating oil supplied to the meshing portion is atomized and scattered by being stirred by the tooth surface of the rotating gear. If the lubricating oil that has been atomized and scattered in this way remains in the housing,
The atomized lubricating oil mixes into the blow-by gas reducing passage, resulting in an increase in the amount of lubricating oil consumed. As described above, when a large amount of lubricating oil supplied to the meshing portion of the gear is accumulated in the housing, various problems occur.

In order to solve these problems, in the above-described lubricating oil return structure for an internal combustion engine, a lubricating oil outflow hole is formed immediately below the gear, and the lubricating oil is supplied to the meshing portion by the air flow generated by the rotation of the pair of gears. A large amount of lubricating oil is smoothly introduced into the lubricating oil outflow hole.

[0005]

By the way, in order to put a large amount of lubricating oil supplied to the meshing portion of a pair of gears on the air flow and smoothly introduce it into the lubricating oil outflow hole, the air generated by the rotation of the gears should be used. It is most effective that the flow is directed between the gears below the meshing portion toward the lubricating oil outflow hole. However, in the above-mentioned lubricating oil return structure of the internal combustion engine, there is no suggestion of the existence region of the air flow and the flow direction of the air flow.

[0006]

In order to solve the above problems, according to the present invention, a pair of gears meshing with each other for driving the exhaust valve camshaft and the intake valve camshaft are provided. Each gear is rotated so as to move downward at the meshing portion, each gear is arranged in the housing, and both gears are arranged above the lower wall surface of the housing with a space therebetween. A lubricating oil outflow hole is formed on the peripheral part of the lower wall surface of the housing located on the opposite side, and one gear located on the lubricating oil outflow hole side draws air in the direction of the lubricating oil outflow hole between both gears below the meshing part. It has an air intake function.

[0007]

The air intake function of one gear located on the lubricating oil outflow hole side draws air in the direction of the lubricating oil outflow hole from between the two gears below the meshing portion. The lubricating oil supplied to the meshing portion of the gear is smoothly guided into the lubricating oil outflow hole by this air flow.

[0008]

1 to 5 show a case where the present invention is applied to a two-cylinder internal combustion engine. Note that FIG. 5 is a schematic diagram showing the engine cooling water passage structure. 2 to 5, 1a is the first cylinder, 1b is the second cylinder, 3 is a cylinder block, 5
Is a piston that reciprocates in the cylinder block 3, and 7 is a cylinder head fixed on the cylinder block 3. A pair of air supply valves 12 are arranged on one side of the inner wall surface of the cylinder head 7 of each cylinder 1a, 1b.
Three exhaust valves 14 are arranged on the other side of the inner wall surface. An ignition plug 16 is arranged at the center of the inner wall surface of the cylinder head 7, and a fuel injection valve (not shown) is arranged at the peripheral portion of the inner wall surface of the cylinder head 7 located on the side of the pair of air supply valves 12. An air supply port 18 is formed in the cylinder head 7 for the air supply valve 12, and an exhaust port 2 is formed for the exhaust valve 14.
0 is formed.

The exhaust valve 14 of each cylinder 1a, 1b is controlled to be opened and closed by an exhaust valve drive cam (not shown) formed on the exhaust valve cam shaft 70. On the other hand, the air supply valve 12 is controlled to be opened / closed by an air supply valve drive cam (not shown) formed on the air supply valve cam shaft 72. As shown in FIG. 1, a cylinder head cover 74 is fixed on the cylinder head 7, and a housing 76 is formed by a part of the cylinder head 7 and a part of the cylinder head cover 74. The exhaust valve camshaft 70 and the air supply valve camshaft 72 are arranged in the housing 76.

As shown in FIG. 1, the first gear 78 is fixed on the exhaust valve camshaft 70, and the second gear 80 is fixed on the intake valve camshaft 72. 78 and 80 mesh with each other. The pair of gears 78 and 80 are arranged in the housing 76, and the pair of gears 78 and 80 are arranged above the lower wall surface of the housing 76, that is, the upper wall surface of the cylinder head 7 with a space therebetween. .. The exhaust valve camshaft 70 is driven by an engine through a pulley and a belt (not shown), and the rotation of the exhaust valve camshaft 70 is transmitted to the intake valve camshaft 72 by a pair of gears 78 and 80 meshing with each other. It The gears 78 and 80 are shown in FIG.
In FIG. 5, the meshing portion is rotated so as to move downward as indicated by arrows A and B. A scissors gear is used as the second gear 80.

A lubricating oil outflow hole 82 is formed on the lower wall surface of the housing 76 located on the side opposite to the second gear 80 with respect to the first gear 78, that is, on the upper wall surface of the cylinder head 7. The lubricating oil outflow hole 82 is formed by a lubricating oil outflow pipe 84 mounted in the cylinder head 7, and the lubricating oil outflow pipe 84 penetrates through a first cooling water passage 42 described later.

As shown in FIG. 1, on the upper wall surface of the cylinder head 7 below the first gear 78, a floor extending from the peripheral edge of the lubricating oil outflow hole 82 to the vicinity of the position directly below the meshing portion of the pair of gears 78, 80. The face member 86 is arranged. The floor surface member 86 is inclined at an angle θ with respect to the horizontal plane,
That is, the height of the floor surface member 86 gradually decreases from the lower side of the meshing portion of the pair of gears 78, 80 toward the peripheral edge side of the lubricating oil outflow hole 82. Further, as can be seen from FIG. 1, the outer peripheral surface portion of the first gear 78 and the floor surface member 86 facing each other.
The distance between the second gear 8 and the surface portion of the second gear 8 facing each other.
It is smaller than the distance between the outer peripheral surface portion of 0 and the upper wall surface portion of the cylinder head 7.

A lubricating oil supply passage (not shown) is formed in the exhaust valve cam shaft 70 along the axial direction thereof, and an oil hole communicating with the lubricating oil supply passage is formed in the exhaust valve cam shaft 70. It is appropriately provided on the outer peripheral surface. Similarly, a lubricating oil supply passage is also formed in the air supply valve cam shaft 72 along the axial direction thereof, and an oil hole communicating with this lubricating oil supply passage is formed on the outer peripheral surface of the air supply valve cam shaft 72. Is appropriately drilled. Lubricating oil supplied from the oil holes of the exhaust valve camshaft 70 and the air supply valve camshaft 72 causes engagement between the pair of gears 78 and 80, the cam surface of the exhaust valve drive cam, and the air supply valve drive cam. The cam surface is lubricated. In particular, a large amount of lubricating oil is supplied to the meshing portions of the pair of gears 78 and 80 to ensure a smooth meshing action.

Next, the airflow generated in the housing 76 will be described with reference to FIG. Figure 1
When the first gear 78 is rotated in the direction indicated by the arrow A, the entire gap region C in which the distance between the outer peripheral surface portion of the first gear 78 and the surface portion of the floor surface member 86 facing each other is the smallest Of air is swept out to the left in FIG. 1 by the rotation of the teeth of the first gear 78. As a result, the pressure in the clearance region C decreases, so that air is drawn toward the clearance region C from between the gears 78, 80 below the meshing portion of the pair of gears 78, 80. Thus, the pair of gears 78, 80
An air flow drawn in toward the lubricating oil outflow hole 82 is generated between the gears 78 and 80 below the meshing part of the.

On the other hand, the distance between the outer peripheral surface portion of the second gear 80 facing each other and the upper wall surface portion of the cylinder head 7 is formed to be large. Therefore, when the second gear 80 is rotated in the direction shown by the arrow B, the second gears facing each other
The second gear 8 in the air in the gap area D formed between the outer peripheral surface portion of the gear 80 and the upper wall surface portion of the cylinder head 7.
Only the air portion located near 0 is swept to the right in FIG. 1 by the rotation of the teeth of the second gear 80. In this way, since only the air in the gap area D located near the second gear 80 is swept out, the pressure in the gap area D hardly decreases. Therefore, no airflow is drawn in between the gears 78, 80 below the meshing portion of the pair of gears 78, 80 in the gap region D direction.

Thus, a large amount of lubricating oil supplied to the pair of gears 78, 80 is drawn from between the gears 78, 80 below the meshing portion of the pair of gears 78, 80 toward the lubricating oil outflow hole 82. As shown in FIG.
_It is carried smoothly into the lubricating oil outflow hole 82 as indicated by ₁ , E ₂ and E ₃ . The lubricating oil supplied to the gears 78, 80 is agitated by the rotation of the teeth of the gears 78, 80 and atomized. Since the lubricating oil atomized in this way easily flows into the air flow, the lubricating oil is guided into the lubricating oil outflow hole 82 more smoothly. Further, since the floor surface member 86 is inclined at an angle θ with respect to the horizontal plane as described above, the lubricating oil adhering to the surface of the floor surface member 86 is also subjected to its own weight to cause the lubricating oil outflow hole 82.
It flows in smoothly. The lubricating oil that has flowed into the lubricating oil outflow hole 82 is returned to the oil pan (not shown) via the lubricating oil outflow passage 88 (see FIG. 4) formed in the cylinder block 3.

As described above, a large amount of lubricating oil supplied to the pair of gears 78 and 80 is smoothly discharged from the lubricating oil outflow hole 82 without accumulating in the housing 76. Therefore, the lubricating oil can be circulated well. Also,
The lubricating oil in the housing 76 is prevented from being deteriorated by receiving heat from the cylinder head 7. Further, since the lubricating oil in the housing 76 is prevented from entering the blow-by gas returning passage, it is possible to prevent the consumption amount of the lubricating oil from increasing.

Next, the cooling water passage structure will be described with reference to FIGS. 2 to 5. Referring to FIGS. 2 to 5, 3
0 is a radiator, 32 is a thermostat, and 34 is a water pump. The thermostat 32 connects the cooling water inlet passage 40 and the first cooling water passage 42 during warm operation, and closes the bypass passage 60 to cut off the communication between the in-head water jacket 54 and the first cooling water passage 42. .. On the other hand, during cold operation, the thermostat 32 blocks communication between the cooling water inlet passage 40 and the first cooling water passage 42, and opens the bypass passage 60 to connect the in-head water jacket 54 and the first cooling water passage 42. Communicate.

During the warm operation, the cooling water cooled by the radiator is supplied through the hose 38 and the cooling water inlet passage 40 into the first cooling water passage 42 formed below the exhaust port 20 of the cylinder 1a. It Next, the cooling water passes through the head block communication passage 44, the block internal passage 46, and the water pump inlet passage 48, and the water pump 34.
Be led to. Next, the cooling water discharged from the water pump 34 is sent into the in-block water jacket 50, and the cooling water flowing out of the in-block water jacket 50 flows into the in-head water jacket 54 through the water jacket communication passage 52, The cooling water flowing out from the inner water jacket 54 is guided to the radiator 30 via the cooling water outlet passage 56.

On the other hand, during the cold operation, the cooling water flowing out from the water jacket 54 in the head flows into the first cooling water passage 42 through the bypass passage 60, and the cooling water does not pass through the radiator 30 but flows into the engine. Circulates only within the body. As shown in FIGS. 1 and 2, the lubricating oil outflow pipe 84 passes through the inside of the first cooling water passage 42. Therefore, the lubricating oil flowing in the lubricating oil outflow hole 82 is the first
It is cooled by the cooling water flowing in the cooling water passage 42. Thus, the deterioration of the lubricating oil can be prevented more reliably.

Next, another embodiment will be described with reference to FIG. When the embodiment shown in FIG. 6 is compared with the embodiment shown in FIG. 1, in the embodiment shown in FIG. 6, a weir 90 is formed on the upper wall surface of the cylinder head 7 below the second gear 80 and faces each other. The distance between the outer peripheral surface of the second gear 80 and the surface of the cuff 90 is formed to be very small. Therefore, when the second gear 80 is rotated in the direction indicated by the arrow B, the second gear 80 is provided in the gap region F between the outer peripheral surface portion of the second gear 80 and the surface of the cuff 90 facing each other. Almost no air is swept out by the rotation of the teeth. Therefore, the pressure in the gap region F is hardly reduced, and therefore, the air flow drawn in the gap region F direction from between the gears 78, 80 below the meshing portion of the pair of gears 78, 80 is not generated. Thus, as in the case of the embodiment shown in FIG. 1, a large amount of lubricating oil supplied to the pair of gears 78, 80 is discharged from between the gears 78, 80 below the meshing portion of the pair of gears 78, 80. The airflow drawn toward the lubricating oil outflow hole 82 is smoothly carried into the lubricating oil outflow hole 82.

[0022]

The lubricating oil supplied to the pair of gears is
It is possible to smoothly flow into the lubricating oil outflow hole without accumulating in the housing.

[Brief description of drawings]

FIG. 1 is a view of a lubricating oil return structure for an internal combustion engine shown in FIG.
It is sectional drawing seen along the -I line.

FIG. 2 is a sectional view of the cylinder head taken along line II-II in FIG.

3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a schematic view showing a cooling water passage structure.

FIG. 6 is a sectional view similar to FIG. 1, showing another embodiment of the lubricating oil returning structure.

[Explanation of symbols]

 70 ... Exhaust valve camshaft 72 ... Air supply valve camshaft 76 ... Housing 78 ... First gear 80 ... Second gear 82 ... Lubricating oil outflow hole

Claims (1)

[Claims] 1. A pair of gears meshing with each other for driving an exhaust valve camshaft and an intake valve camshaft, each gear being rotated so as to move downward at a meshing portion. And the two gears are spaced apart from the lower wall surface of the housing upward, and a lubricating oil outflow hole is formed on the peripheral portion of the lower wall surface of the housing that is located opposite to the other gear with respect to one gear. A lubricating oil returning structure for an internal combustion engine, wherein the one gear located on the lubricating oil outflow hole side has an air intake function of injecting air in the direction of the lubricating oil outflow hole between both gears below the meshing portion.