JPH108937A - Crank chamber ventilating structure for four-cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device which improves all the time ventilating efficiency of a crank chamber in a wide operation range and effectively prevents carrying out of oil from the crank chamber due to excessive ventilation of the crank chamber, in a crank chamber ventilating structure for a four-cycle engine. SOLUTION: The upstream of a throttle valve 9 in an intake passage 8 and a crank chamber 4 are communicated by first passages 11, 13 arranged so as to pass through an oil separator 12 in a cylinder head side, and the downstream of the throttle valve in the intake passage and the crank chamber are communicated by a second passage 15 passing through an oil separator 14 in a cylinder block side and provided on its way with an opening/closing valve 16 closed in accordance with an opening of the throttle valve. This second passage, between the oil separator in the cylinder block side and the opening/ closing valve, is communicated with the first passage by a bypass passage 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a crankcase ventilation structure for reducing blow-by gas in a four-cycle engine.

[0002]

2. Description of the Related Art In a four-stroke engine, blow-by gas leaking from a combustion chamber side to a crank chamber through a space between an inner wall of a cylinder and a piston ring is reduced to intake air passing through an intake passage and recombusted in the combustion chamber. For this reason, it has conventionally been common practice to communicate the crank chamber with an intake passage upstream of the throttle valve so as to pass through an oil separator provided on the cylinder head side in the middle of the crank chamber.

Further, in a four-stroke engine having such a blow-by gas reducing structure, as shown in FIG.
In addition to the first passage (passage 11, oil separator 12, passage 13) that communicates with the upstream side, the crank chamber 4
A second passage (oil separator 12, passage 15) that connects the crank chamber 4 with the intake passage 8 downstream of the throttle valve 9 so as to pass through an oil separator 14 provided on the cylinder block side so as to be adjacent to the cylinder block. It has been conventionally considered to provide an automatic opening / closing valve 16 which is closed in accordance with the opening degree of the throttle valve 9 in the middle of the second passage (in the passage 15).

In such a case, the throttle valve 9
When the valve is fully opened, the opening / closing valve 16 is closed.
Passage (passage 11, oil separator 12, passage 13)
Only through the movement of the piston 3 does the crankcase 4
(The gas including the blow-by gas) is discharged into the intake passage 8 and the gas (the intake air) is sucked into the crank chamber 4 from the intake passage 8 while opening and closing when the throttle valve 9 including the partial time is closed. Valve 16 is opened,
Due to the pressure difference between the upstream side and the downstream side of the throttle valve 8 and the movement of the piston 3, the first passage (passage 1)
1, the gas is sucked into the crank chamber 4 via the oil separator 12, the passage 13), and the gas is discharged from the crank chamber 4 to the intake passage 8 via the second passage (the oil separator 12, the passage 15). .

[0005]

By the way, in the four-stroke engine having the first passage and the second passage provided between the crank chamber and the intake passage as described above, at the time of low / medium speed load in which the throttle valve is closed. From the intake passage upstream of the throttle valve to the first passage, the crank chamber,
Since the gas continuously flows through the second passage in the intake passage downstream of the throttle valve, ventilation of the crank chamber is performed well.

However, in this case, when the throttle valve is largely closed and the opening / closing valve is widely opened, the flow of gas flowing from the crank chamber to the second passage becomes too strong, so that the crank chamber rotates with the rotation of the crank arm. The lubricating oil scattered through the cylinder block passes through the oil separator on the cylinder block side together with the gas flowing out from the second passage, and a large amount of oil is taken out to the intake passage.

On the other hand, when the throttle valve is almost fully opened and the on-off valve is largely closed, almost no gas flows into the second passage, so that in the case of a conventional general blow-by gas reducing structure having no second passage. In comparison, the ventilation efficiency of the crankcase is hardly improved.

[0008]

According to the present invention, in order to solve the above-mentioned problems, as described in the above-mentioned claim 1, the upstream side of the intake passage from the throttle valve and the crank chamber are provided. The oil separator is provided on the cylinder head side and is communicated with a first passage in which the oil separator is provided in the middle, and the crank chamber is located downstream of the throttle valve in the intake passage and the crank chamber. A four-stroke engine in which an open / close valve closed in accordance with the opening of the throttle valve is communicated by a second passage provided in the middle thereof so as to pass through an oil separator provided on the cylinder block side adjacent to A second passage is provided between the oil separator on the cylinder block side and the on-off valve by a bypass passage. And it is characterized in that the threaded through road and communication.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a four-stroke engine crankcase ventilation structure according to an embodiment of the present invention.

FIGS. 1 and 2 schematically show a four-stroke engine according to an embodiment of the present invention. FIG. 1 shows a state in which a throttle valve is substantially fully opened, and FIG. This shows the state when the throttle valve is closed including when it is partial.

Although not shown, the four-stroke engine 1 has a cylinder head cover, a cylinder head, a cylinder block, and a crankcase, the main body of which is formed in a combustion chamber top wall recessed on the lower surface of the cylinder head. A port and an exhaust port are respectively opened, an intake valve is installed at a combustion chamber opening of an intake port, an exhaust valve is installed at a combustion chamber opening of an exhaust port, and an intake passage extending from an air cleaner is provided at the intake port. An exhaust passage connected to a port and having a catalyst and a muffler is connected to the exhaust port.

As shown in the figure, a piston 3 is slidably fitted in a cylinder hole 2 penetrated through a cylinder block of the engine 1, and is defined by a lower portion of the cylinder block and a crankcase. Crank chamber 4
Is rotatably supported by a crankshaft 5. The piston pin 3 a of the piston 3 and the arm 5 of the crankshaft 5
The crank pin 5 b connecting the ends of the “a” is connected via a connecting rod 6.

For such a four-stroke engine 1, a crankcase 4 having an oil pan 7 at a lower portion thereof.
The crank chamber 4 and the oil separator 12 are connected to each other through the oil separator 12 provided integrally with the cylinder head cover to communicate with the upstream side of the throttle valve 9 in the intake passage 8 from the air cleaner to the intake port. A passage 11 communicating with the oil separator 12 and a passage 13 communicating the oil separator 12 with the intake passage 8 on the upstream side of the throttle valve 9 are provided as first passages in which the oil separator 12 is disposed in the middle.

An oil separator 14 is provided in the cylinder block adjacent to the crank chamber 4, and a passage 15 for communicating the oil separator 14 with the intake passage 8 downstream of the throttle valve 9 is opened and closed midway. The oil passage 14 is provided with a valve 16, and the interior of the crank chamber 4 is opened / closed by the oil separator 14 and the passage 15 through an opening / closing valve 16.
The intake passage 8 communicates with the downstream side of the throttle valve 9.

The opening / closing valve 16 is controlled in accordance with the opening of the throttle valve 9 so that the passage 15 is fully closed when the throttle valve 9 is fully opened, and the passage 15 is opened as the throttle valve 9 is closed. It is.

Further, as described above, the first passage (passage 1)
1, an oil separator 12, a passage 13) and a second passage (oil separator 14, a passage 15).
For the cycle engine 1, in the present embodiment, a passage 15 between the oil separator 14 and the on-off valve 16 in the second passage, and an oil separator 12 on the cylinder head side (cylinder head cover) located in the middle of the first passage. Over the bypass passage 1 so that they can communicate with each other.
7 are provided.

According to the four-stroke engine 1 of this embodiment in which the bypass passage 17 is provided as described above, when the throttle valve 9 is fully opened, the open / close valve 16 is closed, and as shown in FIG. The gas in the crank chamber 4 containing the gas flows from the oil separator 14 to the passage 1.
Although it is not discharged to the downstream side of the throttle valve 9 of the intake passage 8 through the passage 5, the piston 3 moves to some extent from the oil separator 14 on the cylinder block side to the bypass passage 17 through the passage 15 3, the ventilation efficiency of the crank chamber 4 is improved.

On the other hand, when the throttle valve 9 is closed, the opening / closing valve 16 is opened accordingly, and as shown in FIG. 2, the pressure difference between the upstream side and the downstream side of the throttle valve 9 in the intake passage 8 and the piston 3 Movement of the intake passage 8
From the upstream side of the throttle valve 9 through the first passage (passage 13, oil separator 12, passage 11), gas is sucked into the crank chamber 4 and gas containing blow-by gas in the crank chamber 4 Is continuously discharged to the downstream side of the throttle valve 9 in the intake passage 8 through the second passage (oil separator 14, passage 15), so that the ventilation of the crank chamber 4 is performed well.

Moreover, at the same time, the passage 1 of the first passage
Since the gas flows from the oil separator 3 and the oil separator 12 through the bypass passage 17 to the downstream side of the oil separator 14 in the second passage, the flow of the gas flowing from the crank chamber 4 through the oil separator 14 to the second passage is strong. It does not become too much (for example, the intake passage 8
When 25% of the gas discharged downstream of the throttle valve 9 flows through the bypass passage 17, the gas discharged from the crank chamber 4 through the oil separator 14 is reduced to 75% of the normal value.) , Crank arm 5a
Lubricating oil scattered in the crank chamber 4 along with the rotation of the cylinder does not pass through the oil separator 14 and is taken out to the intake passage 8 side in a large amount.

Although the embodiment of the present invention has been described above, the present invention can also be realized by connecting the bypass passage 17 to the passage 13 without connecting to the oil separator 12 on the side of the first passage. It is needless to say that the present invention is not limited to the specific structure as shown in the above embodiment, for example, it can be implemented.

[0021]

According to the crankcase ventilation structure for a four-stroke engine of the present invention as described above, the ventilation efficiency of the crankcase can be constantly improved in a wide operating range from full opening to full closing of the throttle valve. In addition to this, it is possible to effectively prevent the oil from being taken out of the crank chamber due to too strong ventilation of the crank chamber.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a state in which a throttle valve is fully opened in one embodiment of a crankcase ventilation structure of a four-cycle engine of the present invention.

FIG. 2 is a schematic explanatory view showing a state when the throttle valve of the embodiment shown in FIG. 1 is closed.

FIG. 3 is a schematic explanatory view showing a conventional crankcase ventilation structure of a four-cycle engine.

[Description of Signs] 1 4-cycle engine 4 Crank chamber 8 Intake passage 9 Throttle valve 11 Passage (first passage) 12 Oil separator (on cylinder head side) 13 Passage (first passage) 14 Oil separator (on cylinder block side) 15 passage (second passage) 16 on-off valve 17 bypass passage

Claims (1)

[Claims] An upstream side of a throttle valve of an intake passage and a crank chamber are communicated with each other by a first passage in which an oil separator is provided in the middle so as to pass through an oil separator provided on a cylinder head side. The opening / closing valve is closed according to the opening of the throttle valve so that the downstream side of the throttle valve of the intake passage and the crank chamber pass through an oil separator provided on the cylinder block side adjacent to the crank chamber. In the four-stroke engine, the second passage is communicated with the first passage by a bypass passage between the oil separator on the cylinder block side and the opening / closing valve. A crankcase ventilation structure for a four-stroke engine.