Intake system of internal combustion engine with supercharger

An intake system of an internal combustion engine with a supercharger includes: a negative pressure control valve which is disposed in the upstream side than an intake side supercharger in an intake passage; a first external gas introduction passage which introduces a single external gas made of blow-by gas, at a part of the intake passage which is on the upstream side of the intake side supercharger and on the downstream side of the negative pressure control valve; and a fresh air introduction passage which introduces fresh air to an internal combustion engine main body from the upstream side of the negative pressure control valve.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Application 2015-206255, filed on Oct. 20, 2015, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to an intake system of an internal combustion engine with a supercharger.

BACKGROUND DISCUSSION

In the related art, an intake system of an internal combustion engine with a supercharger is known (for example, refer to US2014/0318514A (Reference 1)).

The above-described Reference 1 discloses a ventilation system (intake system of an internal combustion engine with a supercharger) in an internal combustion engine with a turbocharger (supercharger). In the ventilation system in the internal combustion engine, an intake passage in which a throttle valve (negative pressure control valve), a compressor (intake side supercharger), an air cooler, a throttle valve, and an intake manifold, are disposed in this order, is connected to an internal combustion engine main body. In addition, an exhaust passage in which an exhaust manifold, an exhaust turbine, and an exhaust processing device (catalyst device) are disposed in this order, is connected to the internal combustion engine main body. In addition, in a state where a blow-by passage derived from a crankcase and an EGR gas passage derived from the exhaust passage merge into one external gas passage, the external gas passage is connected between the throttle valve and the compressor. In addition, the upstream side of the throttle valve and the crankcase communicate with each other via a fresh air introduction passage. Accordingly, while operating the internal combustion engine, a mixed gas of blow-by gas (non-combusted air-fuel mixture including combusted gas) and EGR gas (exhaust gas) is introduced to the exhaust passage by using a negative pressure which is generated at a connection part of the external gas passage as intake gas is throttled by the throttle valve, and the fresh air is supplied to the crankcase via the fresh air introduction passage.

However, in the ventilation system in the internal combustion engine described in the above-described Reference 1, since the blow-by gas passage and the EGR gas passage are connected between the throttle valve and the compressor in the intake passage in a state where the blow-by passage and the EGR gas passage merge into one external gas passage, moisture or particulate materials included in the EGR gas, and oil components included in the blow-by gas, are mixed with each other, and deposits (sediments) are more likely to be generated. In addition, as the deposits (sediments) are deposited on an inner wall of the one external gas passage, a probability that the external gas passage will block increases. Therefore, there is a problem that a sufficient ventilation performance of the internal combustion engine main body cannot be obtained.

SUMMARY

Thus, a need exists for an intake system of an internal combustion engine with a supercharger which is not suspectable to the drawback mentioned above.

An intake system of an internal combustion engine with a supercharger according to an aspect of this disclosure includes: a negative pressure control valve which is disposed in the upstream side than an intake side supercharger in an intake passage; a first external gas introduction passage which introduces a single external gas made of blow-by gas, at a part of the intake passage which is on the upstream side of the intake side supercharger and on the downstream side of the negative pressure control valve; and a fresh air introduction passage which introduces fresh air to an internal combustion engine main body from the upstream side of the negative pressure control valve.

DETAILED DESCRIPTION

Hereinafter, the embodiments of this disclosure will be describe based on the drawings.

First Embodiment

First, with reference toFIGS. 1 to 6, a configuration of an engine100according to a first embodiment of this disclosure will be described.

Schematic Configuration of Engine with Supercharger

As illustrated inFIG. 1, the engine100(an example of an internal combustion engine with a supercharger) for a vehicle (automobile) according to the first embodiment of this disclosure includes an engine main body10(internal combustion engine main body). The engine main body10includes: a cylinder block1in which a plurality of cylinders (cylinders1a) are formed; a cylinder head2which is fastened to an upper part of the cylinder block1; a crankcase3which is fastened to a lower part of the cylinder block1; and a head cover2awhich covers the cylinder head2. In addition, an intake passage30and an exhaust passage40are connected to the engine main body10. As a piston4reciprocates in the cylinder block1, one cycle of suction, compression, expansion (combustion), and exhaust is continuously repeated, and a crank shaft5is rotated.

In the cylinder head2, an intake valve6and an exhaust valve7which are periodically open and closed by the rotation of a cam shaft, and an ignition plug8, are incorporated. The cylinder head2includes a combustion chamber9, an intake port11which sends inhaled air to the combustion chamber9, and an exhaust port12which discharges exhaust gas. In addition, on the inside of the cylinder head2, a fresh air communication path13which communicates with a space between the cylinder head2and the head cover2a, and the crankcase3, is provided.

In addition, the engine100made of a gasoline engine is provided with an exhaust turbine driving type supercharger (turbocharger)20. In other words, in the supercharger20, a turbine wheel21and a compressor wheel22(intake side supercharger) which are connected to a turbine shaft23, are accommodated to be rotatable in a housing20a. In addition, in the supercharger20, the turbine wheel21is connected to the downstream side of an exhaust manifold41, and the compressor wheel22is connected to the intake passage30which is on the upstream side of an intercooler33. In the supercharger20, the turbine wheel21is rotated by an exhaust gas flow, and the compressor wheel22is rotated. Accordingly, the intake gas which is suctioned to the compressor wheel22becomes compressed air, and is supplied to the cylinder1a. In the engine100, since a larger amount of air is supplied to the cylinder1a, and charging efficiency increases compared to a non-supercharged engine with the same exhaust amount, an engine output increases.

In addition, the engine100is provided with an intake system50including the intake passage30. The intake system50has a role of returning blow-by gas (an example of the single external gas) which leaks to the inside of the crankcase3from the combustion chamber9through a void between the piston4and the cylinder1a, to the intake passage30, a role of ventilating the inside of the crankcase3by supplying fresh air diverged from the intake passage30to the engine main body10, and a role of introducing (recirculating) EGR gas (an example of another external gas different from the blow-by gas) of a part of the exhaust gas exhausted to the outside from the combustion chamber9, to the cylinder1a.

Configuration of Intake Passage and Exhaust Passage

In the intake passage30, toward the intake port11from an air intake port30a, the compressor wheel22, the intercooler33, a throttle valve34(an example of a throttle valve), and an intake manifold35, are connected to each other in this order in an air cleaner31, a negative pressure control valve32, the supercharger20. In addition, an opening area of the intake passage30when the throttle valve34is rotated to the completely closed side, is smaller than an opening area of the intake passage30when the negative pressure control valve32is rotated to the completely closed side. Here, the air intake port30awhich is on the upstream side of the air cleaner31having an atmospheric pressure is a position A, a part which is on the downstream side of the air cleaner31and on the upstream side of the negative pressure control valve32is a position B, and a part which is on the downstream side of the negative pressure control valve32and on the upstream side of the compressor wheel22is a position C.

The air cleaner31has a role of decreasing intake noise by removing dust in the intake gas. The negative pressure control valve32has a role of generating a pressure difference between the upstream side (position B) and the downstream side (position C) of the negative pressure control valve32by throttling a section of the intake passage as a valve body92is rotated. In this case, a pressure of the position C decreases to be lower than that of the position B. The intercooler33has a role of cooling the inhaled air compressed by the compressor wheel22. The throttle valve34has a role of controlling the inhaled air amount. The intake manifold35includes an intake tube group (not illustrated) which is branched at a surge tank and on the downstream side thereof, and the downstream side of the intake tube group is connected to the intake port11.

In the exhaust passage40, toward a muffler (not illustrated) from the exhaust port12, the exhaust manifold41which gathers the exhaust gas discharged from the combustion chamber9, the turbine wheel21in the supercharger20, and a catalyst device (catalyst converter)42are connected in this order.

In addition, in the first embodiment, as illustrated inFIG. 1, the intake system50including the intake passage30is provided with a blow-by gas passage51(an example of a first external gas introduction passage), a fresh air introduction passage61, and an EGR gas passage71(an example of a second external gas introduction passage) which are provided separately from one another.

Specific Configuration of Intake System

The blow-by gas passage51communicates with the position C of the intake passage30which is on the upstream side of the compressor wheel22and on the downstream side of the negative pressure control valve32, and the crankcase3in the engine main body10, and has a role of introducing the blow-by gas from the crankcase3to the intake passage30at the position C. In addition, an oil separator52which separates oil mist in the blow-by gas is connected to the engine main body10. In the oil separator52, non-combusted air-fuel mixture and the oil mist are separated from each other, and the separated liquid oil returns to the crankcase3. In addition, at an output portion of the oil separator52, a check valve53which prevents a counter flow of the blow-by gas after the separation of the oil which flows in the arrow U direction, is provided.

The fresh air introduction passage61communicates with the position B of the intake passage30which is on the upstream side of the negative pressure control valve32and on the downstream side of the air cleaner31, and the head cover2ain the engine main body10, and has role of branching and introducing the fresh air to the head cover2afrom the position B. In addition, in the fresh air introduction passage61, a check valve63for preventing a counter flow of the fresh air which flows in the arrow V direction, is provided.

The EGR gas passage71is provided separately from the blow-by gas passage51, and communicates with a position D of the exhaust passage40which is on the downstream side of the turbine wheel21and on the upstream side of the catalyst converter42, and the position C of the intake passage30which is on the upstream side of the compressor wheel22and on the downstream side of the negative pressure control valve32. Accordingly, the EGR gas passage71has a role of introducing the EGR gas which flows in the arrow W direction to the intake passage30from the position C. The EGR gas passage71includes an EGR cooler72which cools the exhaust gas, and an EGR control valve73which adjusts the introduction amount (EGR ratio) of the exhaust gas after the cooling.

Therefore, in the engine100, at the position C which is on the downstream side of the negative pressure control valve32, each of the blow-by gas and the EGR gas is introduced to the intake passage30. In addition, by providing the intake system50, opening degree adjustment of the negative pressure control valve32is performed in accordance with an operation state of the engine100, and the ventilation of the engine main body10(crankcase3) is performed.

For example, in a case where a rotation speed and a load of the engine100is relatively small (low), and the supercharger20does not achieve the function thereof, the negative pressure control valve32is closed only by a predetermined opening degree. In other words, by a throttling operation of the negative pressure control valve32when the engine100is in an idling state or is operated by a low (intermediate) rotation and a low (intermediate) load, a differential pressure is generated between the upstream (position B) and the downstream side (position C) of the negative pressure control valve32. In other words, the pressure of the position C decreases to be lower than that of the position B, and due to a suction force of the negative pressure generated at the position C, the blow-by gas from the crankcase3is introduced to the intake passage30via the blow-by gas passage51. In addition, since an inner pressure of the crankcase3is maintained to be in a state of a negative pressure which is slightly lower than the atmospheric pressure (positive pressure), the fresh air after passing the air cleaner31of which the pressure is close to the atmospheric pressure, is supplied into the head cover2avia the fresh air introduction passage61from the position B, and is introduced to the crankcase3via the fresh air communication path13. In addition, in a state where the rotation speed of the supercharger20is low, by the negative pressure in the crankcase3, the fresh air is also supplied to the head cover2a.

In addition, even when the supercharging (the throttle valve34is in a completely opened state) in which the rotation speed and the load of the engine100is relatively large (high) and the supercharger20achieves the function thereof, the negative pressure control valve32is closed only by a predetermined opening degree. In other words, the pressure of the position C becomes lower than that of the position B when viewed from the negative pressure control valve32, and due to the negative pressure generated at the position C, the blow-by gas from the engine main body10(crankcase3) is introduced to the intake passage30via the blow-by gas passage51. In addition, the fresh air after passing the air cleaner31of which the pressure is close to the atmospheric pressure, is introduced to the crankcase3which maintains a negative pressure via the fresh air introduction passage61from the position B. In this manner, in the entire operation region in the engine100, the negative pressure is generated (the opening degree decreases) at a part (position C) of the intake passage30which is on the upstream side of the compressor wheel22and on the downstream side of the negative pressure control valve32.

In addition, as a controlling configuration of the intake system50, as illustrated inFIG. 2, an opening degree sensor81which detects the opening degree of the negative pressure control valve32, a flow rate sensor82which detects a blow-by gas flow rate, a flow rate sensor83which detects an EGR gas flow rate, a motor93which drives the negative pressure control valve32, and the EGR control valve73(refer toFIG. 1), are electrically connected to an ECU (control portion)80which supervises control of the engine100.

In the ECU80, opening degree information from an accelerator opening degree sensor, rotation speed information of the engine100, information from an O2sensor (oxygen sensor) provided in the exhaust passage40, and information on a fuel injection amount, are input. The ECU80performs predetermined determination based on the information, and performs control of adjusting the opening degree of the negative pressure control valve32and the opening degree of the EGR control valve73while operating the engine100by driving the motor93. In addition, the introduction of the EGR gas is determined by the opening degree control of the EGR control valve73. In other words, even when the negative pressure is generated at the position C by the throttling operation of the negative pressure control valve32, in a case where the EGR control valve73is completely closed based on the operation state of the engine100, the EGR gas is not introduced to the intake passage30.

In addition, the negative pressure control valve32is provided with a valve body91, a butterfly type valve body92which has a rotating shaft92aand is accommodated in the valve body91, and the above-described motor93and the opening degree sensor81. In addition, in a case where the negative pressure control valve32is closed only by a predetermined opening degree, a negative pressure region Q (hatching region) in which the negative pressure (suction force) is the highest is generated on the downstream side of the negative pressure control valve32.

Here, in the first embodiment, in the valve body91, an opening51ato which the blow-by gas is introduced, and an opening71ato which the EGR gas is introduced, are provided. The openings51aand71aare disposed on an inner wall of the valve body91which corresponds to the negative pressure region Q. The opening51ais positioned on an inner wall91a(refer toFIG. 1) on a ceiling side of the valve body91, and the opening71ais positioned on an inner wall91b(refer toFIG. 1) on a bottom part side of the valve body91. Accordingly, the blow-by gas introduced from the position C is introduced to the intake passage30from the negative pressure region Q generated on the downstream side of the negative pressure control valve32, and the EGR gas is also introduced to the intake passage30from the negative pressure region Q generated on the downstream side of the negative pressure control valve32.

Operation Contents of Negative Pressure Control Valve in Operation State of Engine

Next, with reference toFIG. 3, contents of the operation control of the negative pressure control valve32(refer toFIG. 1) in a series of operation modes in which the engine100(refer toFIG. 1) in a stopped state is started to be operated, the vehicle travels only by a predetermined distance, and then, the vehicle is stopped, will be described.

First, in a state where the engine is stopped (period from time t0to time t1), the negative pressure control valve32is maintained to be in a completely open state based on the command of the ECU80(refer toFIG. 2). In addition, according to an ignition ON state (time t1) by the operation of an occupant, the negative pressure control valve32is changed to a completely closed state based on a command of the ECU80. After this, the negative pressure control valve32moves to an opening degree control state together with the engine start at time t2. In other words, the opening degree of the negative pressure control valve32is controlled (increases and decreases) to follow variation in engine rotation speed (amount of inhaled air) according to the travel of the vehicle. In addition, accordingly, since the pressure difference (differential pressure) is generated between the upstream side and the downstream side of the negative pressure control valve32, the blow-by gas (and the EGR gas) is introduced to the intake passage30(refer to FIG. 1) at the position C, and the ventilation in the crankcase3(refer toFIG. 1) is performed.

Here, the vehicle accelerates from time t2to time t3. In this case, as illustrated in four graphs on a left side inFIG. 4, based on a start of increase in accelerator opening degree at time t21, the opening degree of the throttle valve34(refer toFIG. 1) increases at time t23. Therefore, the engine100is moved from a low load state to a high load state. At this time, in the first embodiment, the opening degree of the negative pressure control valve32increases at a timing of time t22which is earlier than that of the throttle valve34. Accordingly, when the intake amount increases when the vehicle accelerates, the opening degree of the negative pressure control valve32increases before the opening degree of the throttle valve34increases. After this, in a case where the acceleration is stopped at time t24, the increase in opening degree of the throttle valve34is stopped at time t26, but the opening degree control is performed so that the increase in opening degree of the negative pressure control valve32is stopped at a timing of time t25, which is earlier than time t26.

Next, the vehicle decelerates. In this case, as illustrated in four graphs on a right side inFIG. 4, the opening degree of the throttle valve34decreases at time t32based on the start of decrease in opening degree of the accelerator at time t31. Therefore, the engine100is moved from a high load state to a low load state. At this time, in the first embodiment, the opening degree of the negative pressure control valve32decreases at a timing of time t33which is later than that when the opening degree of the throttle valve34decreases. Accordingly, when the intake amount decreases when the vehicle decelerates, the decrease in the opening degree of the negative pressure control valve32is more delayed than the decrease in the opening degree of the throttle valve34. In addition, in a case where the deceleration is stopped at time t34, the decrease in opening degree of the throttle valve34is also stopped at time t35, but the opening degree control is performed so that the decrease in opening degree of the negative pressure control valve32is stopped at a timing of time t36being more delayed than time t35.

In addition, while the vehicle travels, in a case where the vehicle is temporarily stopped due to waiting for a traffic light or the like, the engine100at an idling rotation speed is temporarily stopped based on the command of the ECU80. In a state where the idling is stopped, as illustrated in four graphs on a left side inFIG. 5, the opening degree of the throttle valve34increases at a timing of time t29immediately before the engine100is stopped at time t3, and the opening degree of the negative pressure control valve32decreases. In addition, after the vehicle travels only by a predetermined distance, the vehicle decelerates and is stopped. In addition, in a case where the engine100is in an ignition OFF state by the operation of the occupant in a state where the idling rotation speed is achieved, as illustrated in four graphs on a right side inFIG. 5, the opening degree of the throttle valve34increases at a timing of time t49immediately before the engine100is stopped at time t5, and the opening degree of the negative pressure control valve32decreases. In other words, when the engine100is stopped when the idling is stopped, and when the engine100is stopped when the ignition is OFF, the flow rate (flow velocity) of the blow-by gas which is introduced to the intake passage30(position C), instantaneously increases.

In addition, a distribution state of the inner pressure of the intake passage30in a state S1(refer toFIG. 4) of the intake passage30at the idling rotation speed and in a state S2(refer toFIG. 4) of the intake passage30immediately before the above-described engine100is actually stopped, will be described with reference toFIG. 6.

As illustrated inFIG. 6, in the state S1, since the rotation speed is maintained as the idling rotation speed, while the opening degree of the throttle valve34mainly decreases, the opening degree of the negative pressure control valve32does not decrease to that extent. Therefore, a state where the pressure difference (differential pressure) between before and after the throttle valve34is relatively large, and the pressure difference (differential pressure) between before and after the negative pressure control valve32is relatively small, is achieved. In addition, pressure loss from the downstream side of the air cleaner31to an inlet of the intake manifold35, is obtained as total pressure loss P. In addition, in the state S2(timing of time t29or time t39inFIG. 4) immediately before the engine100changes to the state where the idling is stopped (or a state of being completely stopped), the opening degree of the throttle valve34increases, and the opening degree of the negative pressure control valve32decreases. Therefore, although being instantaneous, a state where the pressure difference between before and after the throttle valve34is relatively small, and the pressure difference between before and after the negative pressure control valve32is relatively large, is achieved. However, the total pressure loss P is maintained to be the same value as that of a case of state S2and state S1. In the step S2, while maintaining the total pressure loss P, the pressure difference (suction force) at the position C (refer toFIG. 1) increases since the opening degree of the negative pressure control valve32instantaneously decreases, and the introduction amount of the blow-by gas instantaneously increases. The intake system50which is mounted on the engine100according to the first embodiment, is configured as described above.

Effects of First Embodiment

In the first embodiment, the following effects can be obtained.

In the first embodiment, as described above, at the position C of the intake passage30which is on the upstream side of the compressor wheel22and on the downstream side of the negative pressure control valve32, the blow-by gas passage51which introduces the single blow-by gas, is provided. Accordingly, since it is possible to introduce (return) only the blow-by gas which is not mixed with the EGR gas or the like to the intake passage30via the blow-by gas passage51by using the negative pressure by the negative pressure control valve32, deposits (sediments) which are generated when a plural types of external gas are mixed with each other are not generated on the inner wall of the blow-by gas passage51. Therefore, since it is possible to introduce the blow-by gas without blocking the blow-by gas passage51, it is possible to obtain a sufficient ventilation performance of the engine main body10.

In addition, in the first embodiment, the blow-by gas passage51which introduces the single blow-by gas to the position C of the intake passage30which is on the upstream side of the compressor wheel22and on the downstream side of the negative pressure control valve32, and the fresh air introduction passage61which introduces the fresh air to the head cover2afrom the position B which is on the upstream side of the negative pressure control valve32, are provided. Accordingly, at the same time when the blow-by gas is introduced (returns) to the intake passage30from the engine main body10via the blow-by gas passage51, it is possible to supply the fresh air which is on the upstream side of the negative pressure control valve32to the crankcase3via the fresh air introduction passage61. Accordingly, since it is possible to reliably perform replacement of the fresh air and the blow-by gas in the engine main body10, it is possible to achieve a sufficient ventilation performance with respect to the engine main body10.

In addition, in the first embodiment, the EGR gas passage71which introduces the EGR gas to the position C of the intake passage30which is on the upstream side of the compressor wheel22and on the downstream side of the negative pressure control valve32, and the blow-by gas passage51, are provided separately from each other. Accordingly, since it is possible to independently introduce (return) the EGR gas to the intake passage30via the EGR gas passage71, it is also possible to suppress generation of the deposits caused by the mixing of the blow-by gas with other gas on the inner wall of the EGR gas passage71. Accordingly, since it is possible to operate the engine100by effectively using not only the blow-by gas but also the EGR gas, it is possible to maintain a high quality of the engine100.

In addition, in the first embodiment, in the entire operation region in the engine100, the negative pressure control valve32is configured so that the negative pressure is generated (the opening degree decreases) at the position C of the intake passage30which is on the upstream side of the compressor wheel22and on the downstream side of the negative pressure control valve32. Accordingly, it is possible to reliably perform ventilation in the crankcase3in a region having a wide width in which the rotation speed of the engine100ranges from a low rotation speed zone including an idling rotation zone to a high rotation speed zone and the load of the engine100ranges from no-load or a low load to a high load. At this time, since it is possible to always form a flow of the blow-by gas toward the position C of the intake passage30from the crankcase in the blow-by gas passage51by the throttling operation of the negative pressure control valve32, it is possible to effectively prevent a pressure of the inside of the crankcase3in which the blow-by gas is generated, from becoming a positive pressure. Accordingly, it is also possible to easily prevent leakage of engine oil to the outside of the crankcase3.

In addition, in the first embodiment, the blow-by gas is introduced to the intake passage30from the negative pressure region Q generated on the downstream side of the negative pressure control valve32via the blow-by gas passage51. Accordingly, it is possible to reliably take the blow-by gas into the intake passage30from the negative pressure region Q generated on the downstream side of the negative pressure control valve32in which the negative pressure generated due to the operation of decreasing the opening degree of the negative pressure control valve32is the highest. Therefore, it is possible to maintain a high ventilation performance of the engine main body10.

In addition, in the first embodiment, in a configuration in which the opening area of the intake passage30when the throttle valve34is the completely closed side is smaller than the opening area of the intake passage30when the negative pressure control valve32is the completely closed side, when the engine100moves from the low load state to the high load state, the opening degree of the negative pressure control valve32increases before the opening degree of the throttle valve34increases, and when the engine100moves from the high load state to the low load state, the opening degree of the negative pressure control valve32decreases after the opening degree of the throttle valve34decreases. Accordingly, when the intake amount increases when the vehicle accelerates, since the opening degree of the negative pressure control valve32increases before the opening degree of the throttle valve34increases, it is possible to suppress the increase in intake amount in a case where the opening degree of the negative pressure control valve32does not increase in advance, and a substantial increase in the differential pressure between before and after the negative pressure control valve32. Accordingly, it is possible to suppress the increase in introduction amount of the blow-by gas caused by the increase in the differential pressure between before and after the negative pressure control valve32. In addition, when the vehicle decelerates, under a situation in which the opening degree of the throttle valve34decreases, the intake amount decreases, and the pressure difference between before and after the negative pressure control valve32decreases, since the decrease in opening degree of the negative pressure control valve32is delayed than the decrease in the opening degree of the throttle valve34decreases, it is possible to suppress the substantial increase in differential pressure between before and after the negative pressure control valve32in a case where the decrease in the opening degree of the negative pressure control valve32is not delayed in a state of a smaller intake amount. Accordingly, it is possible to allow the increase in the differential pressure between before and after the negative pressure control valve32to be slow, and in this case, it is also possible to suppress a useless increase in intake amount of the blow-by gas.

In addition, in the first embodiment, immediately before the engine100is stopped, the opening degree of the throttle valve34increases, and the opening degree of the negative pressure control valve32decreases. Accordingly, since the opening degree of the negative pressure control valve32decreases while the opening degree of the throttle valve34increases, it is possible to stabilize the intake amount in an idling rotation state immediately before the rotation of the engine100is stopped without changing the total pressure loss of the intake passage30. In addition, it is possible to instantaneously increase the pressure difference between before and after the negative pressure control valve32by decreasing the opening degree of the negative pressure control valve32. Accordingly, since it is possible to instantaneously increase the flow velocity of the blow-by gas immediately before the operation of the engine100is stopped, blocking of the oil separator52which separates the oil mist included in the blow-by gas due to liquid oil or other foreign materials generated after oil separation can be avoided.

In addition, in the first embodiment, the fresh air introduction passage61is configured to communicate with the position A of the intake passage30which is on the upstream side of the negative pressure control valve32and on the downstream side of the air cleaner31, and the head cover2a. Accordingly, it is possible to remove the dust, and to reliably introduce the fresh air of which the pressure is close to the atmospheric pressure (positive pressure) to the engine main body10(crankcase3).

Second Embodiment

Next, with reference toFIGS. 1, 7, and 8, a second embodiment will be described. In the second embodiment, an example in which an intake system250is configured by using a negative pressure control valve232having a structure different from that of the above-described first embodiment, will be described.

In the intake system250which is employed in an engine200(internal combustion engine with a supercharger) in the second embodiment of this disclosure, the negative pressure control valve232is used. As illustrated inFIG. 7, the negative pressure control valve232is provided with an introduction portion251ato which the blow-by gas is introduced, and an introduction portion271ato which the EGR gas is introduced. The introduction portion251apenetrates an inner wall91con one side (X1side) of the valve body91in the X-shaft direction, extends in parallel to the rotating shaft92a, and reaches a position near the center of the negative pressure region Q. Similarly, the introduction portion271apenetrates an inner wall91don the other side (X2side) of the valve body91in the X-shaft direction, extends in parallel to the rotating shaft92a, and reaches the position near the center of the negative pressure region Q. In addition, in the introduction portion251a, two circular openings251bwhich are open toward the downstream side in the negative pressure region Q, are formed, and in the introduction portion271a, two circular openings271bwhich are open toward the downstream side in the negative pressure region Q, are formed.

In addition, as illustrated inFIG. 8, the introduction portion251aand the introduction portion271aare provided at height positions H2at which the shaft centers have the same height in a state of opposing each other in the X-shaft direction. In addition, a state where the valve body92of the negative pressure control valve232is completely closed is illustrated by a solid line, and a state of being completely open is illustrated by a broken line. In addition, in a case where the valve body92is controlled to be entirely open, the valve body92is also configured to control the opening degree having a predetermined angle α with respect to a line segment150(illustrated by a one-dot chain line) that extends in the intake flow direction from the shaft center (height position H1). In other words, since the angle α is provided even in the completely open state, the negative pressure control valve232is configured so that the negative pressure region Q is generated on the downstream side of the valve body92, and the introduction portion251aand the introduction portion271aare disposed in the negative pressure region Q.

In addition, in a state where a tip end part in the intake downstream direction on a lower surface (rear surface)92cof the valve body92abuts against an outer side surfaces of the introduction portions251aand271a, a distance L (Z-shaft direction) to the height position H2of the introduction portion251a(271a) with respect to the height position H1of the rotating shaft92a, is determined so that the angle α which is slightly upward from the intake flow direction is provided in the valve body92. Therefore, the introduction portions251aand271aalso perform a role of a stopper in a case where the valve body92is completely open. Accordingly, the blow-by gas which is introduced from the position C is introduced to the intake passage30from the negative pressure region Q generated on the downstream side of the negative pressure control valve232. Similarly, the EGR gas is also introduced to the intake passage30from the negative pressure region Q generated on the downstream side of the negative pressure control valve232.

In addition, in the second embodiment, as the control content of the negative pressure control valve232in the intake system250, other than the operation region in which the engine200is in a high load state and is from the intermediate rotation speed zone to the high rotation speed zone, the opening degree of the negative pressure control valve232decreases so that the negative pressure is generated at a part (position C) of the intake passage30which is on the upstream side of the compressor wheel22and on the downstream side of the negative pressure control valve232. This is different from that in the first embodiment.

Accordingly, in the second embodiment, while performing the ventilation of the engine main body10(crankcase3) in a regular region other than the operation region which is in the high load state and is from the intermediate rotation speed zone to the high rotation speed zone, in the operation region which is in the high load state and is from the intermediate rotation speed zone to the high rotation speed zone, the ventilation of the engine main body10is temporarily stopped, the intake amount of the fresh air to the cylinder1a(refer toFIG. 1) instantaneously increases (is supercharged), and the output reliability of the engine200is prioritized. In addition, other configurations in the second embodiment are similar to those of the above-described first embodiment.

Effects of Second Embodiment

In the second embodiment, as described above, other than the operation region which is in the high load state and is from the intermediate rotation speed zone to the high rotation speed zone in the engine200, the negative pressure control valve232is configured so that the negative pressure is generated at the position C of the intake passage30which is on the upstream side of the compressor wheel22and on the downstream side of the negative pressure control valve232. Accordingly, while the ventilation of the engine main body10is performed in the regular region other than the operation region which is in the high load state and is from the intermediate rotation speed zone to the high rotation speed zone, in the operation region which is in the high load state and is from the intermediate rotation speed zone to the high rotation speed zone, it is possible to temporarily stop the ventilation of the engine main body10, to instantaneously increase (supercharge) the intake amount of the fresh air to the cylinder1a, and to prioritize output reliability of the engine200. Accordingly, while obtaining a ventilation performance in the regular region, it is possible to obtain the engine200which can achieve the highest output in a high level.

In addition, in the second embodiment, the introduction portion251ato which the blow-by gas is introduced penetrates the inner wall91cof the valve body91, extends in parallel to the rotating shaft92a, and is disposed in the negative pressure region Q, and the introduction portion271ato which the EGR gas is introduced penetrates the inner wall91dof the valve body91, extends in parallel to the rotating shaft92a, and is disposed in the negative pressure region Q. In this manner, the introduction portion251aand the introduction portion271aconfigure the negative pressure control valve232. Accordingly, it is possible to reliably take the blow-by gas and the EGR gas into the intake passage30from the negative pressure region Q generated on the downstream side of the negative pressure control valve232in which the negative pressure (suction force) generated due to the opening degree decreasing operation by the negative pressure control valve232is the highest. In addition, other effects of the second embodiment are similar to those of the above-described first embodiment.

Modification Example

It is considered that the embodiments disclosed here are examples and are not restrictive from all of the viewpoint. The range of this disclosure is illustrated not by the description of the above-described embodiments but by the range of the appended claims, and further, includes all of the modifications (modification examples) within the meaning and range that are equivalent to the range of the appended claims.

For example, in the above-described first and second embodiments, this disclosure is employed in the intake system50of the engine100provided with the exhaust turbine driving type supercharger20, but this disclosure is not limited thereto. In other words, this disclosure may be employed in the intake system of the engine provided with a supercharger which is driven by a driving force of the crank shaft5.

In addition, in the above-described first and second embodiments, the EGR gas passage71is provided in the intake system50(250), but this disclosure is not limited thereto. In other words, the intake system of the internal combustion engine with a supercharger may be configured so that only the blow-by gas is introduced to the intake passage30from the position C which is on the downstream side of the negative pressure control valve32and on the upstream side of the compressor wheel22.

In addition, in the above-described first embodiment, the openings51aand71aof the blow-by gas and the EGR gas are provided on the inner wall of the valve body91which is on the downstream side of the negative pressure control valve32, and in the above-described second embodiment, the introduction portions251aand271awhich extend to the negative pressure region Q from the inner wall of the valve body91on the downstream side of the negative pressure control valve232are provided, but this disclosure is not limited thereto. For example, a hollow flow path (the blow-by gas passage51and/or the EGR gas passage71) may be provided in the rotating shaft92awhich rotates the valve body92, and an opening which is open to the negative pressure region Q may be formed in the rotating shaft92a.

In addition, in the above-described first embodiment, the openings51aand71aare provided on the inner wall of the valve body91which corresponds to the negative pressure region Q, and in the above-described second embodiment, the introduction portions251aand271aare provided in the negative pressure region Q, but this disclosure is not limited thereto. An introduction port (introduction portion) of blow-by gas and the EGR gas may be provided in the vicinity of the negative pressure region Q, and may be configured to introduce the blow-by gas and the EGR gas to the intake passage30by using the suction force of the negative pressure region Q.

In addition, in the above-described second embodiment, the introduction portions251aand271aare respectively provided, but this disclosure is not limited thereto. For example, one introduction tube which penetrates the negative pressure region Q which is along the rotating shaft92aand on the downstream side thereof may be provided, and by dividing the center part of the introduction tube, the introduction portion251amay be formed the X1side, and the introduction portion271amay be formed on the X2side.

In addition, in the above-described second embodiment, the opening251b(271b) is formed in the introduction portion251a(271a) to have a circular shape, but this disclosure is not limited thereto. The opening which introduces the external gas may be formed in a nozzle shape, or may be formed in a slit shape (elongated shape). In addition, two openings251b(271b) are provided, but this disclosure is not limited thereto. The number of openings may be one, or may be three. In addition, the introduction portion251aand the introduction portion271amay have different number of openings from each other.

In addition, in the above-described first and second embodiments, this disclosure is employed in the intake system50(250) which is mounted in the vehicle (automobile) provided with the engine100(200) configured of a gasoline engine, but this disclosure is not limited thereto. In other words, other than the gasoline engine, this disclosure can be employed in a diesel engine and a gas engine with a supercharger.

An intake system of an internal combustion engine with a supercharger according to an aspect of this disclosure includes: a negative pressure control valve which is disposed in the upstream side than an intake side supercharger in an intake passage; a first external gas introduction passage which introduces a single external gas made of blow-by gas, at a part of the intake passage which is on the upstream side of the intake side supercharger and on the downstream side of the negative pressure control valve; and a fresh air introduction passage which introduces fresh air to an internal combustion engine main body from the upstream side of the negative pressure control valve.

In the intake system of an internal combustion engine with a supercharger according to the aspect of this disclosure, as described above, the first external gas introduction passage which introduces the single external gas made of blow-by gas, is provided at a part of the intake passage which is on the upstream side of the intake side supercharger and on the downstream side of the negative pressure control valve. Accordingly, since it is possible to introduce (return) only the blow-by gas which is not mixed with another external gas (EGR gas or the like) to the intake passage by using the negative pressure due to the negative pressure control valve via the first external gas introduction passage, deposits (sediments) which are generated when plural types of external gas are mixed with each other, are not generated on the inner wall of the first external gas introduction passage. Therefore, since it is possible to introduce the blow-by gas without blocking the first external gas introduction passage, it is possible to obtain a sufficient ventilation performance of the internal combustion engine main body.

In addition, in the intake system of an internal combustion engine with a supercharger according to the aspect of this disclosure, the first external gas introduction passage which introduces the single external gas made of blow-by gas, and the fresh air introduction passage which introduces the fresh air to the internal combustion engine main body from the upstream side of the negative pressure control valve, are provided at a part of the intake passage which is on the upstream side of the intake side supercharger and on the downstream side of the negative pressure control valve. Accordingly, at the same time as when the blow-by gas from the internal combustion engine main body is introduced (returned) to the intake passage via the first external gas introduction passage, it is possible to supply the fresh air which is on the upstream side of the negative pressure control valve to the internal combustion engine main body via the fresh air introduction passage. According to this, since it is possible to reliably replace the fresh air and the blow-by gas with each other in the internal combustion engine main body, it is possible to achieve a more sufficient ventilation performance with respect to the internal combustion engine main body.

It is preferable that the intake system of an internal combustion engine with a supercharger according to the aspect of this disclosure further includes a second external gas introduction passage which is provided separately from the first external gas introduction passage, and introduces another external gas different from the blow-by gas to the part of the intake passage which is on the upstream side of the intake side supercharger and on the downstream side of the negative pressure control valve.

In this configuration, since it is possible to introduce (return) external gases separately from the blow-by gas to the intake passage via the second external gas introduction passage separately from the blow-by gas, it is possible to suppress generation of deposits caused by the mixing of the blow-by gas with the external gases on the inner wall of the second external gas introduction passage. Accordingly, since it is possible to operate the internal combustion engine with a supercharger by effectively using not only the blow-by gas but also the another external gas, it is possible to maintain a high quality of the internal combustion engine with a supercharger.

In the intake system of an internal combustion engine with a supercharger according to the aspect of this disclosure, it is preferable that the negative pressure control valve decreases an opening degree to allow a negative pressure to be generated at the part of the intake passage which is on the upstream side of the intake side supercharger and on the downstream side of the negative pressure control valve, in all of the operation regions.

In this configuration, it is possible to reliably perform ventilation of the internal combustion engine in a region having a wide width in which a rotation speed (engine rotation speed) of the internal combustion engine with a supercharger ranges from a low rotation speed zone including an idling rotation zone to a high rotation speed zone and a load (engine load) of the internal combustion engine with a supercharger ranges from no-load or a low load to a high load. At this time, since it is possible to always form a flow of the blow-by gas toward the intake passage from the internal combustion engine main body in the first external gas introduction path by a throttling operation of the negative pressure control valve, it is possible to effectively prevent a pressure of the inside of the internal combustion engine main body in which the blow-by gas is generated, from becoming a positive pressure. Accordingly, it is also possible to easily prevent leakage of engine oil to the outside of the internal combustion engine main body (crankcase).

In the intake system of an internal combustion engine with a supercharger according to the aspect of this disclosure, it is preferable that the negative pressure control valve decreases an opening degree to allow a negative pressure to be generated at the part of the intake passage which is on the upstream side of the intake side supercharger and on the downstream side of the negative pressure control valve, except for an operation region which is in a high load state and is from an intermediate rotation speed zone to a high rotation speed zone.

In this configuration, while performing ventilation of the internal combustion engine main body in a regular region other than the operation region which is in the high load state and is from the intermediate rotation speed zone to the high rotation speed zone, in the operation region which is in the high load state and is from the intermediate rotation speed zone to the high rotation speed zone, it is possible to temporarily stop the ventilation of the internal combustion engine main body, to instantaneously increase (supercharge) an intake amount of the fresh air to a cylinder, and to prioritize output reliability of the internal combustion engine with a supercharger. Accordingly, while obtaining a ventilation performance in the regular region, it is possible to obtain an internal combustion engine with a supercharger which can achieve the highest output in a high level.

In the intake system of an internal combustion engine with a supercharger according to the aspect of this disclosure, it is preferable that the single external gas made of the blow-by gas is introduced to the intake passage from a negative pressure region generated on the downstream side of the negative pressure control valve and the vicinity thereof via the first external gas introduction passage.

In this configuration, it is possible to reliably take the blow-by gas into the intake passage from the negative pressure region generated on the downstream side of the negative pressure control valve in which the negative pressure (suction force) generated due to an opening degree decreasing operation (throttling operation) of the negative pressure control valve is the highest, and the vicinity thereof. Therefore, it is possible to maintain a high ventilation performance of the internal combustion engine main body.

It is preferable that the intake system of an internal combustion engine with a supercharger according to the aspect of this disclosure further includes a throttle valve which is disposed in the downstream side than the intake side supercharger in the intake passage, an opening area of the intake passage when the throttle valve is rotated to the completely closed side is smaller than an opening area of the intake passage when the negative control valve is rotated to the completely closed side, and when moving from a low load state to a high load state, the opening degree of the negative pressure control valve increases before the opening degree of the throttle valve increases, and when moving from a high load state to a low load state, the opening degree of the negative pressure control valve decreases after the opening of the throttle valve decreases.

In this configuration, when the intake amount increases when a vehicle in which the internal combustion engine moves from a low load state to a high load state accelerates, or the like, since the opening degree of the negative pressure control valve increases before the opening degree of the throttle valve increases, it is possible to suppress a substantial increase in pressure difference (differential pressure) between before and after the negative pressure control valve, which occurs along with an increase in the intake amount in a case where the opening degree of the negative pressure control valve does not increase in advance. Accordingly, it is possible to suppress a useless increase in introduction amount of the blow-by gas caused by the increase in the differential pressure between before and after the negative pressure control valve. In addition, when a vehicle in which the internal combustion engine moves from a high load state to a low load state decelerates, or the like, in a situation in which the opening degree of the throttle valve decreases, the intake amount decreases, and a pressure difference between before and after the negative pressure control valve decreases, since the decrease in the opening degree of the negative pressure control valve is delayed with respect to the decrease in opening degree of the throttle valve, it is possible to suppress a substantial increase in differential pressure between before and after the negative pressure control valve, which occurs in a case where the decrease in the opening degree of the negative pressure control valve is not delayed in a state of a smaller intake amount. Accordingly, it is possible to allow the increase in differential pressure between before and after the negative pressure control valve to be slow. Therefore, in this case, it is also possible to suppress a useless increase in intake amount of the blow-by gas.

It is preferable that the intake system of an internal combustion engine with a supercharger according to the aspect of this disclosure further includes a throttle valve which is disposed in the downstream side than the intake side supercharger in the intake passage, the opening area of the intake passage when the throttle valve is rotated to the completely closed side is smaller than an opening area of the intake passage when the negative control valve is rotated to the completely closed side, and immediately before an operation of the internal combustion main body is stopped, the opening degree of the negative pressure control valve decreases as the opening degree of the throttle valve increases.

In this configuration, since the opening degree of the negative pressure control valve decreases while the opening degree of the throttle valve increases, it is possible to stabilize the intake amount in an idling rotation state immediately before the operation of the internal combustion engine main body is stopped without changing the total pressure loss of the intake passage. In addition, it is possible to instantaneously increase the pressure difference between before and after the negative pressure control valve by decreasing the opening degree of the negative pressure control valve. Accordingly, since it is possible to instantaneously increase a flow velocity of the blow-by gas immediately before the operation of the internal combustion engine main body is stopped, blocking of an oil separator which separates oil mist included in the blow-by gas due to liquid oil generated after oil separation or other foreign materials can be avoided.

In addition, in the specification, in the intake system of an internal combustion engine with a supercharger, the following configuration can also be considered.

That is, in the intake system of an internal combustion engine with a supercharger according to the aspect of this disclosure, the fresh air introduction passage communicates with a part of the intake passage which is on the upstream side of the negative pressure control valve and on the downstream side of an air cleaner, and the internal combustion engine main body.

In addition, in the intake system of an internal combustion engine with a supercharger according to the aspect of this disclosure, in which the blow-by gas is introduced to the intake passage from the negative pressure region and the vicinity thereof, the first external gas introduction passage includes an external gas introduction portion in which the single external gas made of the blow-by gas is mixed with intake gas penetrating a wall surface of the intake passage and extending to the negative pressure region.