JP2014101810A - Breather system of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a breather system of an internal combustion engine, capable of suitably returning a blow-by gas to an intake side and sucking fresh air into the internal combustion engine, and further keeping the average internal pressure of the internal combustion engine negative pressure, with a simple configuration.SOLUTION: A breather system 1 of an internal combustion engine includes: a breather passage 41 for returning a blow-by gas from an upper part of the internal combustion engine 10 to an intake passage 21 of the internal combustion engine 10; a one-way valve 42: a fresh air suction passage 51 for supplying fresh air from the intake passage 21 into a crankcase 18b; a one-way valve 52; and an orifice 53 provided on the fresh air suction passage 51. The one-way valve 42 opens when an internal pressure of the crankcase 18b is positive pressure. The one-way valve 52 opens when the internal pressure of the crankcase 18b is negative pressure. A flow rate of fresh air in the fresh air suction passage 51 is set to be smaller than a flow rate of the blow-by gas in the breather passage 41.

Description

  The present invention relates to a breather system for an internal combustion engine that returns blow-by gas of the internal combustion engine to an intake side.

  2. Description of the Related Art Conventionally, in an internal combustion engine such as a vehicle, a system is known in which blow-by gas discharged from the internal combustion engine is returned to the intake side of the internal combustion engine to reburn unburned gas (see Patent Documents 1 and 2).

  The system described in Patent Document 1 has a passage for returning blow-by gas to the intake passage of the internal combustion engine, and a passage for branching from the intake passage and sucking fresh air into the internal combustion engine, and providing a PCV valve in these passages. The PCV valve is controlled to open and close in accordance with the internal pressure of the internal combustion engine.

  The system described in Patent Document 2 has a passage for returning blow-by gas to the intake passage of the internal combustion engine, and a passage that branches from the intake passage and draws fresh air into the internal combustion engine. / Valve that opens and closes by detecting negative pressure is being used.

Japanese Utility Model Publication 2-64727 Japanese Utility Model Publication No. 60-170019

  The system described in Patent Document 1 is used for a four-cylinder internal combustion engine. However, when such a system is applied to a single-cylinder or a 360-degree crank type two-cylinder small internal combustion engine, Since the internal pressure of the internal combustion engine greatly fluctuates in the rotational range, the frequency of opening and closing the PCV valve increases, and the flow rate of blow-by gas that is returned to the intake side at low speed, high speed, etc. Variations in the flow rate may occur.

  Further, in a single cylinder or a 360-degree crank type two-cylinder small internal combustion engine, the average internal pressure of the internal combustion engine may become a positive pressure. The system described in Patent Document 2 detects the positive / negative pressure of the intake passage and opens and closes the valve. Therefore, when such a system is applied to a single cylinder or a 360 degree crank type two-cylinder small internal combustion engine, The valve may not open and function. These internal combustion engines may be equipped with a supercharger. However, if the amount of intake air by the compressor increases when the internal combustion engine rotates at a high speed, the average internal pressure will increase to the positive pressure side, and the pressure in the oil pan will increase. The compressor also acts as the same pressure and oil leakage occurs from the turbocharger, which may deteriorate combustion efficiency or generate white smoke. Furthermore, when the pressure in the crank chamber becomes high, there is a risk of deteriorating the seal of the internal combustion engine.

  The present invention has been made in view of these problems, and with a simple configuration, ventilation is preferably performed by returning blow-by gas to the intake side or sucking fresh air into the internal combustion engine. An internal combustion engine breather system capable of preventing an increase in friction due to an increase in the amount of unburned gas and suppressing an excessive increase in the average internal pressure of the internal combustion engine, and preferably maintaining the average internal pressure at a negative pressure The task is to do.

  A breather system for an internal combustion engine according to the present invention includes a breather passage for returning blow-by gas from an upper portion of the internal combustion engine to an intake passage of the internal combustion engine, and the breather passage. A one-way valve that allows only the flow to the intake passage, a fresh air intake passage that branches from the intake passage and supplies fresh air from the intake passage into the crankcase of the internal combustion engine, and the fresh air intake A one-way valve provided in the passage for allowing only fresh air to flow from the intake passage into the crankcase; and an orifice provided in the fresh air intake passage; The one-way valve provided is opened when the internal pressure of the crankcase is positive, and the one-way valve provided in the fresh air intake passage is the internal pressure of the crankcase. The valve is opened when the pressure is negative, and the flow rate of the fresh air through the orifice of the fresh air intake passage is set to be smaller than the flow rate of the blow-by gas in the breather passage. .

  According to such a configuration, the breather passage for returning blow-by gas to the intake passage and the fresh air intake passage for supplying fresh air into the crankcase are provided separately, and each is provided with a one-way valve. The control of the valve is unnecessary, and the blow-by gas can be suitably returned to the intake side with a simple configuration. Also, compared to a breather system that sucks blow-by gas inside the internal combustion engine due to negative pressure generated downstream of the throttle valve, the internal pressure of the internal combustion engine fluctuates greatly in all rotational regions of the internal combustion engine. When applied to a single cylinder or a 360-degree crank type two-cylinder small internal combustion engine, blow-by gas is pushed out from the breather passage when the internal pressure of the internal combustion engine increases, so there is no negative pressure in the intake pipe at high rotation speed. However, since the scavenging action can be expected, it is possible to suppress the pressure inside the crankcase from becoming excessive. In addition, ventilation can be performed even at low rotation and low load where negative pressure is generated in the intake pipe, high scavenging ability is obtained in all rotation ranges of the internal combustion engine, and increase in the average internal pressure of the crankcase is suppressed, which is preferable Can be kept at negative pressure. Further, since the breather passage is connected to the upper part of the internal combustion engine and the fresh air intake passage is connected to the crankcase of the internal combustion engine, the flow path of the blow-by gas and the fresh air is separated to improve ventilation. In addition, the fresh air intake passage is provided with an orifice, and the flow rate of fresh air in the fresh air intake passage is set to be smaller than the flow rate of blow-by gas in the breather passage. The average value can be suppressed to atmospheric pressure or lower, and deterioration of combustion efficiency and generation of white smoke can be prevented.

  The connection portion between the fresh air intake passage and the intake passage may be provided upstream of the connection portion between the breather passage and the intake passage.

  According to such a configuration, since the connection portion between the fresh air intake passage and the intake passage is provided upstream of the connection portion between the breather passage and the intake passage, the crank is connected via the fresh air intake passage. It is possible to prevent blow-by gas from being mixed into fresh air sucked into the case.

  The breather system of the internal combustion engine may include an oil separator that separates oil contained in the blow-by gas from an upper part of the internal combustion engine, and the breather passage may be connected to the oil separator.

  According to such a configuration, oil can be preferably separated from blow-by gas.

  The breather system for an internal combustion engine according to the present invention includes a breather passage for returning blow-by gas from an upper portion of the internal combustion engine to an intake passage of the internal combustion engine, the breather passage, and an upper portion of the blow-by gas of the internal combustion engine. A one-way valve that allows only flow from the intake passage to the intake passage, a fresh air intake passage that branches from the intake passage and supplies fresh air from the intake passage into the crankcase of the internal combustion engine, and the new An orifice provided in the air intake passage, and the one-way valve provided in the breather passage opens when the internal pressure of the crankcase is positive, and the one of the fresh air intake passages The flow rate of the fresh air through the orifice is set to be smaller than the flow rate of the blow-by gas in the breather passage.

  According to such a configuration, the one-way valve for the new intake passage is eliminated and only the orifice is used, so that the pressure in the crankcase is rapidly increased or increased for a long time as at the time of high rotation of the internal combustion engine. In this case, the pressure in the crankcase can be released from the two systems, and the increase in the crankcase pressure can be suppressed. In addition, if the one-way valve and orifice are provided close to the internal combustion engine main body, the sticking of the one-way valve and the obstruction of the orifice due to freezing of condensation inside the pipe, which has been a problem with conventional blow-by gas pipes, are prevented. can do.

  A breather system for an internal combustion engine is provided at a connection portion between a first oil separator that separates oil contained in the blow-by gas from an upper part of the internal combustion engine and a crankcase of the fresh air intake passage. A second oil separator that separates oil contained in the blow-by gas flowing through the air intake passage, and the breather passage may be connected to the first oil separator.

  According to such a configuration, by eliminating the one-way valve for the fresh air intake passage, unburned gas in the crankcase is prevented from being released to the outside, and can be reliably and cleanly operated even in cold weather. A breather system can be provided.

  A breather system for an internal combustion engine according to the present invention includes a breather passage for returning blowby gas from a crankcase of the internal combustion engine to an intake passage of the internal combustion engine, the breather passage, and the breather gas from the crankcase of the blowby gas. A one-way valve that allows only flow to the intake passage, a fresh air intake passage that branches from the intake passage and supplies fresh air from the intake passage to the upper part of the internal combustion engine, and a fresh air intake passage. An orifice provided in an upper part of the internal combustion engine, and the one-way valve provided in the breather passage opens when the internal pressure of the crankcase is positive, and the orifice in the fresh air intake passage The flow rate of the fresh air is set so as to be smaller than the flow rate of the blow-by gas in the breather passage.

  According to such a configuration, it is possible to directly cope with pressure fluctuations in the crankcase by forming the breather passage connected to the crankcase side.

  The internal combustion engine may be a single-cylinder or two-cylinder small internal combustion engine.

  According to such a configuration, in a single-cylinder or two-cylinder small internal combustion engine, the internal pressure fluctuation in the crankcase during operation is large, and the average internal pressure is more than 3 cylinders. Therefore, according to the present invention, it is possible to prevent the average internal pressure inside the crankcase from increasing, improve the scavenging performance, and reduce the friction.

  According to the present invention, ventilation is performed by suitably returning the blow-by gas to the intake side or sucking fresh air into the internal combustion engine with a simple configuration, and the unburned gas inside the internal combustion engine increases to increase the friction. In addition, the excessive increase in the average internal pressure of the internal combustion engine can be suppressed, and preferably the average internal pressure can be kept at a negative pressure.

1 is a diagram schematically showing a breather system for an internal combustion engine according to a first embodiment of the present invention. (A) is a top view which shows an example of an internal combustion engine and an oil separator, (b) is X1 arrow sectional drawing of (a). (A) is X2 arrow sectional drawing of FIG.2 (b), (b) is X3 arrow sectional drawing of FIG.2 (b). It is a schematic diagram for demonstrating operation | movement of the breather system of the internal combustion engine which concerns on 1st embodiment, (a) is a figure which shows operation | movement at the time of piston lowering, (b) is a figure which shows the operation at the time of piston raising. is there. It is a figure which shows typically the breather system of the internal combustion engine which concerns on 2nd embodiment of this invention. It is a schematic diagram for demonstrating operation | movement of the breather system of the internal combustion engine which concerns on 2nd embodiment, (a) is a figure which shows operation | movement at the time of piston lowering, (b) is a figure which shows operation | movement at the time of piston raising. is there. It is a figure which shows typically the breather system of the internal combustion engine which concerns on 3rd embodiment of this invention. It is a schematic diagram for demonstrating operation | movement of the breather system of the internal combustion engine which concerns on 3rd embodiment, (a) is a figure which shows operation | movement at the time of piston lowering, (b) is a figure which shows the operation at the time of piston raising. is there. It is a top view which shows the other example of an internal combustion engine and an oil separator. (A) is X4 arrow sectional drawing of FIG. 9, (b) is X5 arrow sectional drawing of FIG.

  The embodiment of the present invention will be described in detail with reference to FIGS. 1 to 6 by taking as an example the case where the breather system for an internal combustion engine of the present invention is applied to a single cylinder or a 360-degree crank type two-cylinder small-sized internal combustion engine for a vehicle. explain. In the description, the same elements are denoted by the same reference numerals, and redundant description is omitted. Moreover, when explaining a direction, it demonstrates based on the front-back, left-right and up-down in the state in which the internal combustion engine E was installed in the vehicle. Note that “up and down in the cylinder axis direction” means that the upper side is the upper side and the lower side is the lower side with respect to the cylinder orthogonal plane that is a plane orthogonal to the cylinder axis.

<First embodiment>
FIG. 1 is a diagram schematically showing a breather system for an internal combustion engine according to a first embodiment of the present invention. As shown in FIG. 1, an internal combustion engine breather system 1A (hereinafter simply referred to as a breather system 1A) according to a first embodiment of the present invention includes an internal combustion engine 10, an intake system 20, an oil separator 30, A breather system 40A and a fresh air inhalation system 50A are provided.

  The internal combustion engine 10 is a power source installed in a vehicle, and an oil pan 11, a cylinder block 12, a cylinder head 13, and a cylinder cover 14 are stacked in order from the bottom. Inside the internal combustion engine 10, a piston 15, a connecting rod 16, and a crank 17 are provided. Inside the internal combustion engine 10, a combustion chamber 18 a is formed above the piston 15, and a crankcase 18 b is formed below the piston 15. A valve operating chamber 18c is formed above the combustion chamber 18a. Part of the gas generated in the combustion chamber 18a flows out to the crankcase 18b through the gap between the cylinder block 12 and the piston 15 as blow-by gas, and via a communication path connecting the crankcase 18b and the valve operating chamber 18c. It flows out to the valve operating chamber 18c. The oil stored in the oil pan 11 circulates in the internal combustion engine 10 as lubricating oil, but a part of the oil is contained in the blow-by gas and discharged outside the internal combustion engine 10.

  The intake system 20 draws fresh air into the internal combustion engine 10 and includes an intake passage 21 that is a pipe through which fresh air flows, and an air cleaner that is provided in the intake passage 21 to adsorb and remove dust contained in the fresh air. 22.

  The oil separator 30 is provided on the upper part of the internal combustion engine 10 and separates oil from blow-by gas from the internal combustion engine 10. The separated oil is returned to the oil pan 11 through an oil passage 36 including a pipe, a hose and the like. The oil separator 30 will be described later in detail.

  The breather system 40A includes a breather passage 41 that is a hose that returns blow-by gas, from which oil has been separated by the oil separator 30, to the intake passage 21, and a breather gas that is provided in the breather passage 41 and flows from the oil separator 30 to the intake passage 21. A one-way valve 42 that allows only The one-way valve 42 is a mechanical check valve that is normally closed and does not need to be controlled, and opens when the crankcase 18b has a positive pressure. The one-way valve 42 is provided in the vicinity of the main body of the internal combustion engine 10, and the one-way valve 42 is prevented from sticking when the internal combustion engine 10 is cold.

  The fresh air intake system 50A branches from the intake passage 21 and supplies fresh air from the intake passage 21 to a crankcase 18b formed in the cylinder block 12 of the internal combustion engine 10. And a one-way valve 52 that is provided in the fresh air intake passage 51 and allows only fresh air to flow into the crankcase 18b from the intake passage 21. The one-way valve 52 is a mechanical check valve that is normally closed and does not require control, and opens when the inside of the crankcase 18b becomes negative pressure. The one-way valve 52 is provided in the vicinity of the main body of the internal combustion engine 10, and the one-way valve 42 is prevented from sticking when the internal combustion engine 10 is cold.

  Further, the fresh air intake system 50A includes an orifice 53 provided in the fresh air intake passage 51, and the flow rate of fresh air in the fresh air intake passage 51 is smaller than the flow rate of blow-by gas in the breather passage 41. It is set to be. In the present embodiment, the orifice 53 is formed integrally with a joint that connects the fresh air intake passage 51 and the intake passage 21.

<Oil separator>
As shown in FIGS. 2 and 3, the oil separator 30 </ b> A as an example of the oil separator 30 is separate from the cylinder head 13 and the head cover 14, and includes a bottom plate portion 31, a middle plate portion 32, and a lid portion 33. And comprising.

  The bottom plate portion 31 is fixed to the head cover 14 with a bolt or the like, and has a communication hole 31a that communicates with the blow-by gas discharge hole 14a of the head cover 14 and a circular shape in plan view that is erected upward so as to surround the insertion hole 31a. An inner wall portion 31b and an outer wall portion 31c erected upward so as to surround the inner wall portion 31b are provided. An oil chamber 31d is formed between the inner wall portion 31b and the outer wall portion 31c. A mounting hole 31e is formed in the oil chamber 31d, and an oil passage 36 is formed in the mounting hole 31e. A joint 34 connected so as to be able to distribute oil is attached.

  The middle plate portion 32 is provided on the bottom plate portion 31, and includes an insertion hole 32a through which an edge portion of the communication hole 31a is inserted, and a plurality of oil dropping holes 32b.

  The lid portion 33 is provided on the middle plate portion 32, and includes a maze wall portion 33a that is erected downward and forms a maze. The lid portion 33 is formed with an attachment hole, and a joint 35 connected to the breather passage 41 so as to allow gas flow is attached to the attachment hole. The joint 35 is connected to the most downstream side of the labyrinth 33a so that gas can flow.

  The blow-by gas of the internal combustion engine 10 is introduced into the oil separator 30A through the blow-by gas discharge hole 14a. The blow-by gas is introduced into the maze through the communication hole 31a and flows through the maze. In the middle of the maze, there are a plurality of oil drop holes 32 b, and the oil separated from the blow-by gas falls from the oil drop holes 32 b to the oil chamber 31 d, circulates through the oil passage 36 via the joint 34, and goes to the oil pan 11. Returned. The blow-by gas from which the oil has been separated flows through the breather passage 41 via the joint 35 and is returned to the intake passage 21.

<Operation of breather system>
As shown in FIG. 4A, when the piston of the internal combustion engine 10 descends, the pressure in the crankcase 18b of the internal combustion engine 10 increases, so the pressure of blow-by gas discharged from the internal combustion engine 10 also increases, and the crankcase When the pressure in 18b changes from negative pressure to positive pressure, blow-by gas pushes open the one-way valve 41 of the breather system 40A and flows out into the intake passage 21. Here, the one-way valve 52 of the fresh air intake system 50A is closed because the pressure in the crankcase 18b increases from negative pressure to positive pressure, and fresh air is supplied to the cylinder via the fresh air intake system 50A. There is no suction into the block 12 (in the crankcase 18b).

  On the other hand, as shown in FIG. 4 (b), when the piston of the internal combustion engine 10 rises, the pressure in the crankcase 18b of the internal combustion engine 10 decreases from positive pressure to negative pressure, thereby causing a one-way valve for the fresh air intake system 50A. 52 is opened, and fresh air is sucked into the cylinder block 12 (in the crankcase 18b) through the fresh air intake passage 51. Here, the one-way valve 42 of the breather system 40A is closed because the pressure in the crankcase 18b decreases from positive pressure to negative pressure, and blow-by gas is returned to the intake passage 21 through the breather system 40A. It will never be.

A breather system 1A according to an embodiment of the present invention is provided with a breather passage 41 for returning blow-by gas to the intake passage 21 and a fresh air intake passage 51 for supplying fresh air into the internal combustion engine 10, which are provided separately. Since the directional valve is provided, it is not necessary to control the valve, and the blow-by gas can be suitably returned to the intake side with a simple configuration.
Further, even when applied to the single cylinder or 360-degree crank type two-cylinder internal combustion engine 10 in which the internal pressure of the cylinder case 18b greatly fluctuates in the entire rotational region of the internal combustion engine 10, the internal combustion engine 10 is high in the entire rotational region. While scavenging ability and fresh air introduction ability are obtained, it is possible to prevent the average internal pressure of the crankcase 18b from excessively increasing to the positive pressure side, and preferably keep the average internal pressure at a negative pressure.
Also, since the breather passage 41 is connected to the upper part of the internal combustion engine 10 and the fresh air intake passage 51 is connected to the crankcase 18b of the internal combustion engine 10, the flow path of blow-by gas and fresh air is separated and ventilated. Improves.
Further, the fresh air intake passage 51 is provided with an orifice 53, and the flow rate of fresh air in the fresh air intake passage 51 is set to be smaller than the flow rate of blow-by gas in the breather passage 41. The average value of the internal pressure of the crankcase 18b can be suppressed to an atmospheric pressure or lower, and deterioration of combustion efficiency and generation of white smoke can be prevented.
Further, since the connection portion between the fresh air intake passage 51 and the intake passage 21 is provided upstream of the connection portion between the breather passage 41 and the intake passage 21, the crankcase is connected via the fresh air intake passage 51. It is possible to prevent blow-by gas from being mixed into the fresh air sucked into 18b.

<Second Embodiment>
Subsequently, the breather system according to the second embodiment of the present invention will be described focusing on differences from the breather system 1A according to the first embodiment.

  As shown in FIG. 5, the breather system 1B according to the second embodiment of the present invention includes a fresh air intake system 50B instead of the fresh air intake system 50A. The fresh air intake system 50B functions as a fresh air intake system when the piston of the internal combustion engine 10 is raised, and functions as a sub exhaust system when the piston of the internal combustion engine 10 is lowered.

  The fresh air intake system 50 </ b> B does not include the one-way valve 52 but further includes an oil separator (second oil separator) 54 and an oil passage 55.

  The oil separator 54 is provided in the cylinder block 12 of the internal combustion engine 10, and separates oil from blow-by gas from the internal combustion engine 10, similar to the oil separator (first oil separator) 30 described above. The oil separator 54 is integrally formed on the inner wall surface or the outer wall surface of the crankcase 18b. The oil separated by the oil separator 54 is returned to the oil pan 11 through an oil passage 55 composed of a pipe, a hose and the like.

  In the present embodiment, the orifice 53 is not a joint that connects the fresh air intake passage 51 and the intake passage 21 but a joint that connects the blow-by gas discharge side of the oil separator 54 and the fresh air intake passage 51. It is integrally formed. This is to prevent icing in the orifice 53 by providing the orifice 53 in the vicinity of the cylinder block 12 where the temperature becomes high.

<Operation of breather system>
As shown in FIG. 6A, when the piston of the internal combustion engine 10 descends, the pressure in the crankcase 18b of the internal combustion engine 10 increases, so the pressure of blow-by gas discharged from the internal combustion engine 10 also increases, and the crankcase When the pressure in 18b changes from a negative pressure to a positive pressure, blow-by gas pushes open the one-way valve 42 of the breather system 40A and flows out into the intake passage 21. Here, the fresh air intake system 50B functions as an auxiliary breather system that assists exhaust by the breather system 40A. That is, part of the blow-by gas discharged from the internal combustion engine 10 flows out to the intake passage 21 through the fresh air intake passage 51. Here, the flow rate of the blowby gas flowing out to the intake passage 21 via the fresh air intake passage 51 is smaller than the flow rate of the blowby gas flowing out to the intake passage 21 via the breather passage 41.

  On the other hand, as shown in FIG. 6B, when the piston of the internal combustion engine 10 is raised, fresh air is sucked into the cylinder block 12 (in the crankcase 18b) via the fresh air intake passage 51. Here, the one-way valve 42 of the breather system 40A is closed because the pressure in the crankcase 18b decreases from positive pressure to negative pressure, and blow-by gas is returned to the intake passage 21 through the breather system 40A. It will never be.

  The breather system 1B according to the second embodiment of the present invention is provided with a breather passage 41 for returning blow-by gas to the intake passage 21 and a fresh air intake passage 51 for supplying fresh air into the internal combustion engine 10, The breather passage 41 is provided with a one-way valve that opens when the pressure in the crankcase 18b increases, and the fresh air intake passage 51 is provided with an orifice 53 adjacent to the crankcase 18b. Is not necessary, and the blow-by gas is preferably returned to the intake side with a simple configuration, and fresh air can be introduced when negative pressure is generated in the crankcase 18b.

<Third embodiment>
Subsequently, a breather system according to a third embodiment of the present invention will be described focusing on differences from the breather system 1A according to the first embodiment.

  As shown in FIG. 7, a breather system 1C according to a third embodiment of the present invention includes a breather system 40C and a fresh air suction system 50C in place of the breather system 40A and the fresh air suction system 50A, and an oil separator. 30 is not provided. The fresh air intake system 50C functions as a fresh air intake system when the piston of the internal combustion engine 10 is raised, and as a secondary exhaust system when the piston of the internal combustion engine 10 is lowered, like the fresh air intake system 50B according to the second embodiment. Function.

  The breather passage 41 of the breather system 40C is connected not to the upper part of the internal combustion engine 10, but to the crankcase 18b of the internal combustion engine 10, more specifically, to the gas-liquid separation chamber provided in the crankcase 18b.

  The fresh air intake system 50 </ b> C does not include the one-way valve 52. In the present embodiment, the fresh air intake passage 51 is connected to the upper portion of the internal combustion engine 10, and the orifice 53 is not a joint connecting the fresh air intake passage 51 and the intake passage 21, but a fresh air. A joint that connects the suction passage 51 and the upper part of the internal combustion engine 10 is formed integrally. This is to prevent icing in the orifice 53 by providing the orifice 53 in the vicinity of the internal combustion engine 10 where the temperature becomes high.

<Operation of breather system>
As shown in FIG. 8 (a), when the piston of the internal combustion engine 10 descends, the pressure in the crankcase 18b of the internal combustion engine 10 increases, so the pressure of the blow-by gas discharged from the internal combustion engine 10 also increases, and the crankcase When the pressure in 18b changes from a negative pressure to a positive pressure, blow-by gas pushes open the one-way valve 42 of the breather system 40C and flows out into the intake passage 21. Here, the fresh air intake system 50C functions as an auxiliary breather system that assists the exhaust by the breather system 40C. That is, part of the blow-by gas discharged from the internal combustion engine 10 flows out to the intake passage 21 through the fresh air intake passage 51. Here, the flow rate of the blowby gas flowing out to the intake passage 21 via the fresh air intake passage 51 is smaller than the flow rate of the blowby gas flowing out to the intake passage 21 via the breather passage 41.

  On the other hand, as shown in FIG. 8B, when the piston of the internal combustion engine 10 is raised, fresh air is drawn into the internal combustion engine 10 (in the valve operating chamber 18c) via the fresh air intake passage 51. Here, the one-way valve 42 of the breather system 40C is closed because the pressure in the crankcase 18b decreases from positive pressure to negative pressure, and blow-by gas is returned to the intake passage 21 through the breather system 40C. It will never be.

  The breather system 1C according to the third embodiment of the present invention is provided with a breather passage 41 for returning blow-by gas to the intake passage 21 and a fresh air intake passage 51 for supplying fresh air into the internal combustion engine 10, The breather passage 41 is provided with a one-way valve that opens when the pressure in the crankcase 18b increases, and the fresh air intake passage 51 is provided with an orifice 53 close to the upper part of the internal combustion engine 10, so that the valve Control is not required, and the blow-by gas is preferably returned to the intake side with a simple configuration, and fresh air can be introduced when negative pressure is generated in the crankcase 18b. Further, by forming the breather passage 41 by connecting it to the crankcase 18b side, it is possible to directly cope with pressure fluctuations in the crankcase 18b.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it can change suitably. The present invention is applicable not only to a single-cylinder or two-cylinder small internal combustion engine but also to a four-cylinder internal combustion engine. Further, an oil separator may be provided between the internal combustion engine 10 and the breather system 40C of the breather system 1C according to the third embodiment. For example, the oil separator 30 is not limited to the oil separator 30A described above. As shown in FIGS. 9 and 10, in an oil separator 30 </ b> D that is another example of the oil separator 30, the bottom plate portion 31 is configured integrally with the head cover 14.

  The oil separator 30 (30A, 30D) is separated by an intermediate plate portion 32 into an upper labyrinth through which blow-by gas circulates and a lower oil chamber 31d through which oil separated from the blow-by gas circulates. By doing in this way, the quantity of the oil which distribute | circulates the floor (middle board part 32) of a maze can be reduced, and the quantity of the oil contained in blowby gas can be reduced suitably.

  As shown in FIGS. 10 (a) and 10 (b), as the internal combustion engine 10 is tilted backward, the oil separator 30 (30A, 30D) is also tilted backward at an angle θ. 30 (30A, 30D) is connected to the rear portion, and no rib is formed in the oil chamber 31d of the bottom plate portion 31, so that the oil discharge performance is improved.

  Moreover, since the cross-sectional area of the joint 34 is set larger than the total cross-sectional area of the plurality of oil dropping holes 32b, the oil can be suitably discharged.

  Further, when the oil level of the oil pan 11 fluctuates due to turning of the vehicle in which the internal combustion engine 10 is installed, fluctuations in the gas pressure in the oil passage 36 and the intake passage 21 can be suitably suppressed.

1A, 1B, 1C Internal combustion engine breather system 10 Internal combustion engine 18b Crankcase 21 Intake passage 41 Breather passage 42 One-way valve 51 Fresh air intake passage 52 One-way valve 53 Orifice

Claims (7)

A breather passage for returning blow-by gas from the top of the internal combustion engine to the intake passage of the internal combustion engine;
A one-way valve provided in the breather passage and allowing only the flow of the blow-by gas from the upper part of the internal combustion engine to the intake passage;
A fresh air intake passage that branches from the intake passage and supplies fresh air from the intake passage into the crankcase of the internal combustion engine;
A one-way valve provided in the fresh air intake passage and allowing only the flow of the fresh air from the intake passage into the crankcase;
An orifice provided in the fresh air intake passage;
With
The one-way valve provided in the breather passage opens when the internal pressure of the crankcase is positive,
The one-way valve provided in the fresh air intake passage opens when the internal pressure of the crankcase is negative,
A breather system for an internal combustion engine, wherein a flow rate of the fresh air through the orifice of the fresh air intake passage is set to be smaller than a flow rate of the blow-by gas in the breather passage. 2. The internal combustion engine according to claim 1, wherein a connection portion between the fresh air intake passage and the intake passage is provided upstream of a connection portion between the breather passage and the intake passage. Breather system. An oil separator for separating oil contained in the blow-by gas from the upper part of the internal combustion engine;
The breather system for an internal combustion engine according to claim 1 or 2, wherein the breather passage is connected to the oil separator. A breather passage for returning blow-by gas from the top of the internal combustion engine to the intake passage of the internal combustion engine;
A one-way valve provided in the breather passage and allowing only the flow of the blow-by gas from the upper part of the internal combustion engine to the intake passage;
A fresh air intake passage that branches from the intake passage and supplies fresh air from the intake passage into the crankcase of the internal combustion engine;
An orifice provided in the fresh air intake passage;
With
The one-way valve provided in the breather passage opens when the internal pressure of the crankcase is positive,
A breather system for an internal combustion engine, wherein a flow rate of the fresh air through the orifice of the fresh air intake passage is set to be smaller than a flow rate of the blow-by gas in the breather passage. A first oil separator for separating oil contained in the blow-by gas from the upper part of the internal combustion engine;
A second oil separator that is provided at a connection portion of the fresh air intake passage with a crankcase and separates oil contained in blow-by gas flowing through the fresh air intake passage;
With
The breather system for an internal combustion engine according to claim 4, wherein the breather passage is connected to the first oil separator. A breather passage for returning blow-by gas from the crankcase of the internal combustion engine to the intake passage of the internal combustion engine;
A one-way valve provided in the breather passage and allowing only the flow of the blow-by gas from the crankcase to the intake passage;
A fresh air intake passage that branches from the intake passage and supplies fresh air from the intake passage to the upper part of the internal combustion engine;
An orifice provided above the internal combustion engine of the fresh air intake passage;
With
The one-way valve provided in the breather passage opens when the internal pressure of the crankcase is positive,
A breather system for an internal combustion engine, wherein a flow rate of the fresh air through the orifice of the fresh air intake passage is set to be smaller than a flow rate of the blow-by gas in the breather passage. The breather system for an internal combustion engine according to any one of claims 1 to 6, wherein the internal combustion engine is a single-cylinder or two-cylinder small-sized internal combustion engine.

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