JP2008248815A - Valve for adjusting recirculation quantity of blow-by gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely recirculate blow-by gas during start and during heavy load operation of an internal combustion engine in the internal combustion engine recirculating blow-by gas generated in a crankcase to an intake pipe. <P>SOLUTION: A plate 220 constructing a PCV (Positive Crankcase Ventilation) valve 200 is provided between a recirculation channel 122A and a recirculation channel 122b of blow-by gas. Overlapping area of an opening part 224 provided on a flat surface part 222 of the plate 220 and the recirculation channels 122A, 122B becomes the maximum (refer to Fig.3(A)) when pressure in an upstream chamber is roughly equal to pressure in a downstream chamber 216, and becomes smaller (refer to Fig.3(B)) when pressure in the downstream chamber 216 is lower than pressure in the upstream chamber 214. The upstream chamber 214 is connected to an upstream side of the electronic throttle valve in an intake pipe. The downstream chamber 216 is connected to a downstream side of the electronic throttle valve in the intake pipe. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for returning blow-by gas generated in an engine crankcase to an intake pipe, and more particularly to a valve for adjusting a return amount of blow-by gas.

  In general, an engine mounted on a vehicle returns to the intake pipe without releasing the gas (hereinafter also referred to as blow-by gas) from the gap between the cylinder and piston of the engine into the crankcase into the atmosphere. A blow-by gas reduction device is provided for recombustion. The technique regarding such a blow-by gas reduction apparatus is disclosed by Unexamined-Japanese-Patent No. 2005-240605 (patent document 1) and Unexamined-Japanese-Patent No. 3-112508 (patent document 2), for example.

  Patent Document 1 discloses a PCV (Positive Crankcase Ventilation) valve that smoothens the flow of blow-by gas in the metering unit and suppresses the deposition and deposition of blow-by gas on the metering unit and the spring. The PCV valve is provided in a blow bus gas passage that communicates the crankcase side of the engine with the intake manifold side. This PCV valve is formed so as to penetrate into the body, and a blow-by gas inlet is provided on the crankcase side, a body passage provided on the intake manifold side, and the intake manifold side relative to the crankcase side. A valve body that moves in the body passage to open the blow-by gas inlet when the negative pressure is large, a metering passage surface formed by a part of the body in the middle of the body passage, and a valve body And a weighing unit formed with the weighing surface. A curved surface having an upstream end at the center opposite to the axis of the body passage is formed in a cross section in the axial direction of the measurement passage surface on the body side.

  According to the PCV valve disclosed in Patent Document 1, since the upstream side of the metering passage surface is formed into a curved surface, the flow resistance of the blow-by gas in the metering section is smaller than that of the rectangular one, and the blow-by gas is absorbed in the body. Flows smoothly through the passage. Therefore, it can suppress that the sludge in blow-by gas adheres and accumulates on a measurement part, a spring, etc.

  Patent Document 2 discloses a blow-by gas recirculation device that can ensure excellent engine output without increasing consumption of engine oil. This recirculation device is attached to the intake pipe to recirculate the blowby gas in the crankcase into the intake pipe of the engine, and has a blowby gas recirculation pipe provided with a blowby gas outlet on the downstream pipe wall with respect to the intake flow, A dynamic pressure chamber formed at a downstream portion adjacent to the blow-by gas outlet in the blow-by gas return pipe and having a dynamic pressure inlet substantially opposite to the intake flow, and a blow-by gas passage and the dynamic pressure chamber in the blow-by gas return pipe are partitioned. And a piston member that is slidably attached to the partition wall that reduces the opening area of the blow-by gas outlet by raising the pressure receiving head in the blow-by gas passage. The pressure receiving area of the pressure receiving head in the blow-by gas passage of the piston member is formed larger than the pressure receiving area of the pressure receiving head in the dynamic pressure chamber of the piston member.

According to the recirculation device disclosed in Patent Document 2, a dynamic pressure chamber is provided in an intake pipe downstream of the blow-by gas recirculation pipe, and a positive pressure based on an intake air flow rate generated in the dynamic pressure chamber and a blow-by gas pressure in the blow-by gas recirculation pipe. The piston member is displaced by the pressure difference between the blow-by gas and the opening area of the blow-by gas outlet is controlled and the blow-by gas pressure is adjusted by the displacement of the pressure receiving head of the piston member in the blow-by gas passage. When the intake flow velocity increases, the positive pressure based on the intake flow velocity generated in the dynamic pressure chamber becomes higher than the blowby gas pressure in the blowby gas recirculation pipe, so that the piston member rises and the opening area of the blowby gas outlet decreases. Therefore, the flow rate of blow-by gas is limited. As a result, at the time of a high load at which the intake air flow rate increases, the amount of oil contained and discharged in the blow-by gas is reduced, so that an increase in oil consumption can be reliably prevented.
JP-A-2005-240605 Japanese Utility Model Publication No. 3-112508

  However, in the PCV valve disclosed in Patent Document 1, the blow-by gas inlet is blocked by the valve body when the negative pressures on the crankcase side and the intake manifold side become substantially equal. In such a state at the time of high load, blow-by gas generated in large quantities at the time of high load cannot be recirculated to the intake pipe side. Further, when the engine is stopped, the pressure on the crankcase side and the pressure on the intake manifold side become the atmospheric pressure and become equal, so that the blow-by gas inlet is shut off. For this reason, if the engine is stopped for a long time in cold weather, the water mixed in the blow-by gas and adhering to the valve body freezes with the inlet shut off, and the valve body moves in the direction to open the inlet. It may not be possible. In this case, even if the engine is started, the blow-by gas cannot be recirculated to the intake pipe side until the moisture adhering to the valve body is thawed.

  Further, in the recirculation device disclosed in Patent Document 2, when the intake flow velocity increases, the opening area of the blow-by gas outlet gradually decreases, and when the intake flow velocity exceeds a predetermined value, the blow-by gas outlet is shut off. For this reason, blow-by gas may not be recirculated to the intake pipe side when the intake flow velocity is high and the load is high.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an internal combustion engine that recirculates blow-by gas generated in a crankcase to an intake pipe in a blow-by state when the internal combustion engine is under a high load and a start. It is to provide a valve that can reliably recirculate gas.

  A valve according to a first aspect of the present invention includes a crankcase, an intake pipe, a throttle valve that is provided in the intake pipe and controls the amount of intake air supplied to the internal combustion engine, and a blow-by gas generated in the crankcase is used as a throttle valve for the intake pipe. In an internal combustion engine provided with a reflux path for refluxing further downstream, the amount of blow-by gas reflux is adjusted. This valve is provided in a return path, a first member that moves according to a difference between a pressure upstream of the throttle valve and a pressure downstream of the throttle valve, and the first member moves along with the movement of the first member. And a second member that changes the flow path area of the reflux path. When the upstream pressure and the downstream pressure are substantially equal, the second member changes the flow path area so as not to block the reflux path.

  According to the first invention, the internal combustion engine that recirculates the blow-by gas generated in the crankcase to the intake pipe is provided with a valve that adjusts the recirculation amount of the blow-by gas. The valve includes a first member and a second member. When the internal combustion engine is at a high load, the throttle valve is substantially fully opened, and the pressure on the upstream side and the pressure on the downstream side of the throttle valve are substantially equal. When the first member moves in response to the upstream pressure and the downstream pressure being substantially equal, the second member does not block the return path as the first member moves. Change the channel area. Therefore, the blowby gas can be reliably recirculated at the time of high load where a large amount of blowby gas is generated. Further, when the internal combustion engine is stopped, the throttle valve is substantially fully closed. However, the pressure on the upstream side and the pressure on the downstream side of the throttle valve are both atmospheric pressures, and the difference therebetween is eliminated. Therefore, as in the case of high load, the second member changes the flow path area so as not to block the reflux path. Thus, for example, even when the first member and the second member are frozen while the internal combustion engine is stopped, the reflux path is not blocked. Therefore, blow-by gas can be reliably recirculated when the internal combustion engine is started. As a result, in the internal combustion engine that recirculates the blow-by gas generated in the crankcase to the intake pipe, it is possible to provide a valve that can reliably recirculate the blow-by gas when the internal combustion engine is under a high load and at the start.

  In the valve according to the second invention, in addition to the configuration of the first invention, the second member is a flat plate. The plate is provided so as to be movable in a direction substantially perpendicular to the axial direction of the return path in accordance with the movement of the first member, and a plane portion that divides the return path into the crankcase side and the intake pipe side; And an opening that overlaps the reflux path when the upstream pressure and the downstream pressure are substantially equal.

  According to the second invention, the return path is divided into the crankcase side and the intake pipe side by the flat portion of the plate. When the first member moves in response to the upstream pressure and the downstream pressure being substantially equal, the plate moves in a direction substantially perpendicular to the axial direction of the reflux path, and is provided on the flat portion of the plate. The open part overlaps the reflux path. Therefore, the blow-by gas can be recirculated through the opening at the time of high load and start-up of the internal combustion engine in which the upstream pressure and the downstream pressure are substantially equal.

  In the valve according to the third invention, in addition to the configuration of the first invention, the second member has a pressure downstream of the upstream pressure when the upstream pressure and the downstream pressure are substantially equal. As compared with the case where the flow rate is small, the flow path area is changed.

  According to the third invention, the pressure on the upstream side and the pressure on the downstream side of the throttle valve are substantially equal at the time of high load. On the other hand, when the load is low, the throttle valve opening is small and the air in the intake pipe is supplied to the internal combustion engine, so the negative pressure on the downstream side (internal combustion engine side) of the throttle valve increases. That is, at the time of low load, the pressure on the downstream side becomes smaller than the pressure on the upstream side. When the upstream pressure and the downstream pressure are substantially equal, the second member increases the flow path area as compared to the case where the upstream pressure is smaller than the downstream pressure. As a result, the flow path area is increased when the load is high compared to when the load is low. Therefore, a larger amount of blow-by gas generated at a high load can be recirculated than at a low load.

  In the valve according to the fourth invention, in addition to the configuration of the third invention, the second member is a flat plate. The plate is provided so as to be movable in a direction substantially perpendicular to the axial direction of the return path in accordance with the movement of the first member, and a plane portion that divides the return path into the crankcase side and the intake pipe side; When the upstream pressure and the downstream pressure are substantially equal, the opening provided so as to increase the area overlapping the return path compared to the case where the downstream pressure is smaller than the upstream pressure. Including.

  According to the fourth invention, the reflux path is divided into the crankcase side and the intake pipe side by the flat portion of the plate. When the first member moves in response to the upstream pressure and the downstream pressure being substantially equal, the plate moves in a direction substantially perpendicular to the axial direction of the reflux path, and is provided on the flat portion of the plate. The area overlapping the opening and the reflux path increases. Therefore, a larger amount of blow-by gas generated at a high load can be recirculated than at a low load.

  In the valve according to the fifth invention, in addition to the configuration of the first invention, the second member flows so as not to block the reflux path when the upstream pressure and the downstream pressure are substantially equal. In addition to changing the path area, the flow path area is changed so as to block the return path when the pressure on the downstream side is larger than the pressure on the upstream side.

  According to the fifth invention, the second member changes the flow path area so as not to block the reflux path when the upstream pressure and the downstream pressure are substantially equal. Therefore, blow-by gas can be reliably recirculated at the time of high load and start-up of the internal combustion engine. Further, the second member blocks the reflux path when the downstream pressure is larger than the upstream pressure. Therefore, when a phenomenon occurs in which the air-fuel mixture supplied to the combustion chamber of the internal combustion engine returns to the intake pipe and burns (hereinafter also referred to as a backfire phenomenon), the pressure on the downstream side becomes larger than the pressure on the upstream side, The reflux path is blocked by the second member. Thereby, when a backfire phenomenon arises, it can suppress that a flame spreads through the return path to the crankcase side.

  In the valve according to the sixth invention, in addition to the structure of the fifth invention, the second member is a flat plate. The plate is provided so as to be movable in a direction substantially perpendicular to the axial direction of the return path in accordance with the movement of the first member, and a plane portion that divides the return path into the crankcase side and the intake pipe side; And an opening that overlaps with the reflux path when the upstream pressure and the downstream pressure are substantially equal, and that does not overlap with the reflux path when the downstream pressure is greater than the upstream pressure.

  According to the sixth invention, the opening overlaps with the reflux path when the upstream pressure and the downstream pressure are substantially equal. Therefore, the blow-by gas can be recirculated through the opening at the time of high load and start of the internal combustion engine. Further, the opening does not overlap the reflux path when the pressure on the downstream side is larger than the pressure on the upstream side. Therefore, when the backfire phenomenon occurs, it is possible to suppress the flame from spreading to the crankcase side through the reflux path at the flat portion of the plate.

  In the valve according to the seventh invention, in addition to the configuration of any one of the first to sixth inventions, the first member is in contact with a chamber whose one surface is connected upstream of the throttle valve, This is a piston member provided so that the surface of the cylinder is in contact with a chamber connected downstream of the throttle valve.

  According to the seventh invention, the first member is in contact with the chamber connected on one side upstream of the throttle valve, and in contact with the chamber connected on the other side downstream of the throttle valve. It is the provided piston member. Therefore, the piston member can be directly moved by the difference between the pressure upstream of the throttle valve and the pressure downstream.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  With reference to FIG. 1, engine 100 on which the PCV device according to the present embodiment is mounted will be described. As shown in FIG. 1, the engine 100 mainly includes a crankcase 102, a cylinder 104, a piston 106, an intake valve 108, an exhaust valve 110, an intake pipe 112, an exhaust pipe 114, and a cylinder head 116. It consists of.

  The intake pipe 112 is provided with an electronic throttle valve 118. The electronic throttle valve 118 adjusts the amount of intake air supplied to the engine 100, and the adjusted amount of intake air is supplied from the intake valve 108 to the combustion chamber inside the engine 100 through the intake pipe 112. Fuel is combusted by the supplied intake air, and combustion gas is discharged to the outside of the engine 100 via the exhaust valve 110 and the exhaust pipe 114.

  The blow-by gas is a mixed gas that leaks into the crankcase 102 from the gap between the piston ring and the cylinder 104. Blow-by gas contains a large amount of hydrocarbons and moisture and is strongly acidic, so if it is too much, it will cause deterioration of engine oil and rust inside the engine. Moreover, since hydrocarbons are contained, it is not good for the environment to discharge to the atmosphere as it is.

  Therefore, the inside of the crankcase 102 and the inside of the cylinder head 116 are communicated. Further, the inside of the cylinder head 116 is communicated with the upstream side of the electronic throttle valve 118 in the intake pipe 112 (hereinafter also referred to as the upstream side of the intake pipe 112) by a pipe 124, and from the electronic throttle valve 118 in the intake pipe 112. It communicates with the downstream side (hereinafter also referred to as the downstream side of the intake pipe 112) and the reflux paths 122A and 122B. It should be noted that the inside of the cylinder head 116 may be directly communicated with the upstream side of the intake pipe 112 and the inside of the crankcase 102 by the pipe 124.

  The arrows shown in FIG. 1 indicate the flow of blow-by gas and fresh air. When intake air is supplied to the engine 100, the negative pressure on the downstream side of the intake pipe 112 increases. Therefore, fresh air is introduced into the cylinder head 116 from the upstream side of the intake pipe 112 through the pipe 124. As a result, the blow-by gas in the crankcase 102 flows into the cylinder head 116, and the fresh air introduced through the conduit 124 is mixed with the blow-by gas in the cylinder head 116, and flows through the reflux paths 122A and 122B. It flows and returns to the downstream side of the intake pipe 112.

  A PCV valve 200 is provided between the reflux path 122A and the reflux path 122B. The PCV valve 200 adjusts the amount of blow-by gas recirculated to the downstream side of the intake pipe 112. The PCV valve 200 includes a piston part 210, a plate 220, a spring 230, an upstream connection pipe 240, and a downstream connection pipe 250.

  The piston part 210 includes a piston 212, an upstream chamber 214, and a downstream chamber 216. The piston 212 is provided inside the cylinder of the piston portion 210 such that one surface of the piston 212 is in contact with the upstream chamber 214 and the other surface is in contact with the downstream chamber 216. The upstream chamber 214 is connected to the upstream side of the intake pipe 112 by an upstream connection pipe 240. The downstream chamber 216 is connected to the downstream side of the intake pipe 112 by a downstream connection pipe 250.

  The plate 220 is a flat plate having one end connected to the piston 212. The plate 220 is provided so as to be movable between the reflux path 122A and the reflux path 122B in a direction substantially perpendicular to the axial direction of the reflux paths 122A and 122B as the piston 212 moves. The plate 220 will be described in detail later.

  One end of the spring 230 is connected to the piston 212. The other end of the spring 230 is connected to the wall surface of the downstream chamber 216. The spring 230 is not limited to being provided in the downstream chamber 216, and may be provided in the upstream chamber 214.

  With reference to FIG. 2 and FIG. 3, the plate 220 which comprises the PCV valve | bulb 200 is demonstrated. 2 and 3 are cross-sectional views taken along the line 2-2 in FIG.

  As shown in FIG. 2, the flat portion 222 of the plate 220 is provided with an opening 224. The opening 224 is provided such that the area overlapping with the reflux paths 122A and 122B changes as the piston 212 moves.

  When the pressure in the upstream chamber 214 and the pressure in the downstream chamber 216 are substantially equal, the piston 212 is held at the center of the cylinder of the piston portion 210 by the elastic force of the spring 230 as shown in FIG. At this time, as shown in FIG. 3A, the area where the opening 224 and the reflux paths 122A and 122B overlap (the hatched portion in FIG. 3) is maximized.

  When the pressure in the downstream chamber 216 is smaller than the pressure in the upstream chamber 214, a force having a magnitude corresponding to the pressure difference between the upstream chamber 214 and the downstream chamber 216 acts on the piston 212 in the left direction of the drawing. For this reason, as shown in FIG. 3B, the piston 212 moves to the left side of the drawing to a position where the force corresponding to the pressure difference and the elastic force of the spring 230 are balanced. At this time, as shown in FIG. 3B, the area where the opening 224 and the reflux paths 122A and 122B overlap is smaller than when the pressure in the upstream chamber 214 and the pressure in the downstream chamber 216 are equal.

  When the pressure in the downstream chamber 216 is larger than the pressure in the upstream chamber 214, a force having a magnitude corresponding to the pressure difference between the upstream chamber 214 and the downstream chamber 216 acts on the piston 212 in the right direction of the drawing. Therefore, as shown in FIG. 3C, the piston 212 moves to the right side of the drawing to a position where the force corresponding to the pressure difference and the elastic force of the spring 230 are balanced. At this time, as shown in FIG. 3C, the opening 224 and the reflux paths 122A and 122B do not overlap.

  An operation of the PCV valve 200 according to the present embodiment based on the above structure will be described.

  When the engine 100 is under a low load, the opening of the electronic throttle valve 118 is small and air is supplied from the intake pipe 112 to the engine 100, so that the negative pressure upstream of the intake pipe 112 increases. Therefore, the pressure in the downstream chamber 216 becomes smaller than the pressure in the upstream chamber 214, and the piston 212 moves to the left side of the drawing to the position shown in FIG. At this time, the blow-by gas flows from the recirculation path 122A to the recirculation path 122B through a portion where the opening 224 and the recirculation paths 122A and 122B overlap (the hatched portion in FIG. 5B), and upstream of the intake pipe 112. Refluxed to the side.

  When the engine 100 is at a high load, the electronic throttle valve 118 is substantially fully opened, and the negative pressure of the entire intake pipe 112 (the upstream side of the intake pipe 112 and the downstream side of the intake pipe 112) increases. Therefore, the pressure in the upstream chamber 214 and the pressure in the downstream chamber 216 become substantially equal, and the piston 212 is held at the center of the cylinder of the piston portion 210 as shown in FIG. At this time, the area where the opening 224 and the reflux paths 122A and 122B overlap (the hatched portion in FIG. 3A) is the maximum value, which is larger than when the load is low. Thereby, the blow-by gas generated in a large amount at high load can be recirculated more than at low load.

  Further, when the engine 100 is stopped, the electronic throttle valve 118 is substantially fully closed. However, the pressure on the upstream side of the intake pipe 112 and the pressure on the downstream side of the intake pipe 112 are both atmospheric pressures, and the difference between the two. Will disappear. Therefore, the area where the opening 224 and the reflux paths 122A and 122B overlap is the maximum value as in the case of high load (see the hatched portion in FIG. 3A). Thus, for example, even if the piston 212 and the plate 220 are frozen while the engine 100 is stopped, the reflux path 122A and the reflux path 122B are not blocked. Therefore, blow-by gas can be reliably recirculated when engine 100 is started.

  Further, when a backfire phenomenon occurs in engine 100, the air-fuel mixture supplied to the combustion chamber of engine 100 returns to intake pipe 112 and burns. Thereby, the pressure on the downstream side of the intake pipe 112 close to the engine 100 instantaneously becomes larger than the pressure on the upstream side of the intake pipe 112. Therefore, the pressure in the downstream chamber 216 becomes larger than the pressure in the upstream chamber 214, and the piston 212 moves to the right side of the drawing to the position shown in FIG. At this time, as shown in FIG. 3C, the opening 224 and the reflux paths 122A and 122B do not overlap, and the reflux path 122A and the reflux path 122B are blocked. Therefore, when a backfire phenomenon occurs, it is possible to prevent the flame from spreading through the reflux paths 122A and 122B and into the cylinder head 116 and the crankcase 102.

  As described above, according to the PCV valve according to the present embodiment, the flow area of the return path of the blow-by gas is changed by the plate that moves in accordance with the pressure on the upstream side and the pressure on the downstream side of the throttle valve. . When the pressure on the upstream side and the pressure on the downstream side of the throttle valve are substantially equal, the plate is moved so as not to block the reflux path. As a result, the blow-by gas can be reliably recirculated at a high load when a large amount of blow-by gas is generated. For example, even when the plate is frozen when the engine is stopped, the blow-by gas can be reliably It can be refluxed.

  In addition, the shape of the opening part 224 of the plate 220 mounted in the PCV valve | bulb which concerns on this invention is not limited to the shape shown in FIG. 2 and FIG. For example, as shown in FIG. 4, an opening 1224 having a smaller area overlapping with the reflux paths 122 </ b> A and 122 </ b> B at low load may be used.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure which shows the structure of the engine by which the PCV valve which concerns on embodiment of this invention is mounted. It is sectional drawing (the 1) of the PCV valve | bulb which concerns on embodiment of this invention. It is sectional drawing (the 2) of the PCV valve | bulb which concerns on embodiment of this invention. It is sectional drawing (the 3) of the PCV valve | bulb which concerns on embodiment of this invention.

Explanation of symbols

  100 Engine, 102 Crankcase, 104 Cylinder, 106 Piston, 108 Intake valve, 110 Exhaust valve, 112 Intake pipe, 114 Exhaust pipe, 116 Cylinder head, 118 Electronic throttle valve, 122A, 122B Return path, 124 pipe line, 200 PCV Valve, 210 Piston part, 212 Piston, 214 Upstream chamber, 216 Downstream chamber, 220 Plate, 222 Planar part, 224, 1224 Opening part, 230 Spring, 240 Upstream connection pipe, 250 Downstream connection pipe.

Claims (7)

A crankcase, an intake pipe, a throttle valve that is provided in the intake pipe and controls the amount of intake air supplied to the internal combustion engine, and blow-by gas generated in the crankcase is further downstream than the throttle valve in the intake pipe. In an internal combustion engine provided with a reflux path for reflux, a valve for adjusting a reflux amount of the blow-by gas,
A first member that moves in accordance with a difference between a pressure upstream of the throttle valve and a pressure downstream of the throttle valve;
A second member that is provided in the return path and changes the flow path area of the return path in accordance with the movement of the first member;
The second member is a valve that changes the flow path area so as not to block the reflux path when the upstream pressure and the downstream pressure are substantially equal. The second member is a flat plate,
The plate is
A plane part that is provided so as to be movable in a direction substantially perpendicular to the axial direction of the return path as the first member moves, and that divides the return path into the crankcase side and the intake pipe side;
2. The valve according to claim 1, further comprising: an opening that is provided in the flat portion and overlaps the reflux path when the upstream pressure and the downstream pressure are substantially equal.   The second member increases the flow path area when the upstream pressure and the downstream pressure are substantially equal as compared to when the downstream pressure is smaller than the upstream pressure. The valve according to claim 1, wherein The second member is a flat plate,
The plate is
A plane part that is provided so as to be movable in a direction substantially perpendicular to the axial direction of the return path as the first member moves, and that divides the return path into the crankcase side and the intake pipe side;
When the pressure on the upstream side and the pressure on the downstream side are substantially equal to each other, the area overlapping the return path is increased compared to the case where the pressure on the downstream side is smaller than the pressure on the upstream side. The valve according to claim 3, further comprising an opening provided to do so.   In addition to changing the flow path area so as not to block the return path when the upstream pressure and the downstream pressure are substantially equal, the second member is configured to change the upstream pressure. The valve according to claim 1, wherein when the pressure on the downstream side is larger, the flow passage area is changed so as to block the reflux path. The second member is a flat plate,
The plate is
A plane part that is provided so as to be movable in a direction substantially perpendicular to the axial direction of the return path as the first member moves, and that divides the return path into the crankcase side and the intake pipe side;
It is provided in the flat portion and overlaps with the reflux path when the upstream pressure and the downstream pressure are substantially equal, and overlaps with the reflux path when the downstream pressure is larger than the upstream pressure. The valve according to claim 5, comprising a non-opening opening.   The first member is a piston provided such that one surface is in contact with a chamber connected upstream of the throttle valve and the other surface is in contact with a chamber connected downstream of the throttle valve. The valve according to claim 1, which is a member.

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