JP5690132B2 - Engine ventilation system - Google Patents

Description

  The present invention relates to a ventilation system for a supercharged engine such as a turbocharger, and more particularly to a positive crankcase ventilation system (PCV system) that forms part of a blow-by gas processing system.

  For example, as described in Patent Document 1, a PCV system in a naturally aspirated or non-supercharged engine has a position downstream of a throttle valve in an intake manifold that is an intake passage and a crank chamber (crankcase) of the engine. A blow-by gas reduction passage that communicates with the crank chamber, a fresh air introduction passage that communicates a position upstream of the throttle valve in the intake manifold and the crank chamber, and a PCV valve provided in the blow-by gas reduction passage. ing.

  When the engine is under low load, the internal pressure of the engine becomes negative due to the action of the PCV valve, so that fresh air is introduced into the crankcase through the fresh air introduction passage, and at the same time, blow-by gas is fresh air in the crankcase. Are mixed with each other and led to a position downstream of the throttle valve in the intake manifold through the PCV valve. By ventilating the crankcase in this way, deterioration of the engine oil in the crankcase is suppressed.

  On the other hand, when the engine is heavily loaded, the negative pressure in the intake manifold is reduced (approaching the positive pressure), and the amount of blow-by gas discharged through the PCV valve is less than the amount of blow-by gas generated from the engine itself. Become. As a result, the blow-by gas in the crankcase is also discharged through the fresh air introduction passage and no new air is introduced into the crank case, so the engine oil in the crank case is deteriorated by the blow-by gas.

  Such a configuration is basically the same in, for example, a turbocharged engine using a turbocharger. In particular, in the case of a supercharged engine, the engine is low in comparison with a naturally aspirated or non-supercharged engine. Since the pressure in the intake manifold increases due to the supercharging pressure even under load, there are more operating areas where fresh air is not introduced into the crankcase, and as a result, the engine oil in the crankcase is more susceptible to deterioration by blow-by gas. There was a problem of becoming.

  Therefore, as described in Patent Document 2, the present inventors provided an orifice for introducing fresh air in the PCV valve of the supercharged engine, and the boost pressure, which is the pressure in the intake passage, became positive. In this case, an engine ventilation system was previously proposed in which fresh air was introduced into the crank chamber through a PCV valve to suppress deterioration of engine oil in the crank chamber.

JP 2007-16664 A JP 2010-112178 A

  However, in the technique described in Patent Document 2, when the boost pressure becomes a positive pressure, the fresh air is introduced into the crank chamber from the position downstream of the throttle valve in the intake passage through the PCV valve. Although the ventilation efficiency of the room will be improved, the flow rate of fresh air introduced into the crank chamber is not actively controlled, and there is still room for improvement.

  The present invention has been made paying attention to such problems, and particularly in a supercharged engine, when the boost pressure in the intake passage is a positive pressure, the engine operating state is changed according to the operating state of the engine. The object is to provide an engine ventilation system in which a suitable amount of fresh air is introduced into the crankcase.

  According to the first aspect of the present invention, there is provided a blow-by gas reduction passage that connects a position downstream of the throttle valve in the intake passage of the supercharged engine and the crank chamber of the engine, and an upstream of the throttle valve in the intake passage. A fresh air introduction passage that communicates the side position with the crank chamber, and a blow-by gas reduction passage, and the intake air pressure is increased when the boost pressure downstream of the throttle valve in the intake passage is negative. PCV valve for controlling the flow rate of blow-by gas toward the passage side, and when the boost pressure in the downstream side of the throttle valve in the intake passage becomes positive, the downstream side of the throttle valve in the intake passage Fresh air flow rate control means for introducing fresh air from the position into the crank chamber, and the fresh air flow rate control means includes the intake passage. Among them, fresh air is introduced into the crank chamber in an intermediate load operation region where the boost pressure downstream of the throttle valve is positive and lower than a predetermined set pressure, while the intake passage is more than the throttle valve. In the high load operation region where the boost pressure at the downstream position is equal to or higher than the set pressure, the introduction of fresh air from the downstream side of the throttle valve in the intake passage to the crank chamber is stopped, or the flow rate of the fresh air Is at least smaller than the maximum flow rate in the medium load operation region.

  According to the first aspect of the present invention, when fresh air is introduced into the crank chamber from the downstream side of the throttle valve in the intake passage, the amount of fresh air supplied to the engine is reduced accordingly. It was made based on the knowledge. That is, in the medium load operation region, fresh air is introduced into the crank chamber from the downstream side of the throttle valve in the intake passage, so that the crank chamber is actively ventilated while high output is required for the engine. In the high load operation region, the introduction of fresh air into the crank chamber from the downstream side of the throttle valve in the intake passage is stopped, or in order to suppress a decrease in the amount of fresh air supplied to the engine. The flow rate of fresh air is set to be smaller than at least the maximum flow rate in the medium load operation region.

  In this case, as in the second aspect of the invention, a variable orifice that functions as the fresh air flow control means is provided in the blow-by gas reduction passage, and functions as the fresh air flow control means in the high load operation region. It is desirable for the simplification of the structure that the flow path cross-sectional area of the variable orifice is at least smaller than the flow path cross-sectional area in the medium load operation region.

  Specifically, as in the invention described in claim 3, the PCV valve is a variable that functions as the new air flow rate control means separately from the variable orifice for blowby gas flow rate control that is the original function of the PCV valve. It is good to have an orifice.

  On the other hand, a variable orifice functioning as the fresh air flow control means is arranged in parallel with the PCV valve as in the invention described in claim 4 and functions as the fresh air flow control means in the high load operation region. You may make it make the flow-path cross-sectional area of a variable orifice smaller than the flow-path cross-sectional area in the said medium load operation area | region at least.

  Further, as in the fifth aspect of the invention, in the high load operation region, the variable orifice functioning as the fresh air flow rate control means is more often closed in the high load operation region. This is desirable for supplying fresh air to the engine.

  As in the invention of claim 6, in the medium load operation region, the flow rate of fresh air from the downstream side of the throttle valve to the crank chamber in the intake passage is constant, and in the high load operation region, If the flow rate of fresh air from the downstream side of the throttle valve in the intake passage to the crank chamber is equal to the flow rate in the medium load operation region, a certain amount or more is passed through at least a part of the blow-by gas reduction passage. Since no fresh air is introduced into the crank chamber, the amount of fresh air flowing into the engine (the amount of air) does not decrease when the engine is heavily loaded.

  According to the first aspect of the present invention, in the medium load operation region, a relatively large amount of fresh air is introduced into the crank chamber with emphasis on ventilation of the crank chamber, while in the high load operation region, engine output is increased. By supplying more fresh air to the engine with an emphasis on the above, it is possible to suppress a decrease in engine output in the high load operation region while suppressing deterioration of engine oil in the crank chamber.

  In addition, according to the invention described in claim 2, since fresh air is introduced into the crank chamber using an existing passage, it is advantageous in terms of simplification of the structure.

  Furthermore, according to the invention described in claim 3, the intended purpose can be achieved by making a slight improvement to the existing PCV valve, which is further advantageous in terms of simplification of the structure. .

  On the other hand, according to the invention described in claim 4, the variable orifice functioning as the fresh air flow rate control means is provided separately from the PCV valve, and the flow rate of fresh air introduced into the crank chamber is controlled by the variable orifice. Therefore, the flow rate of fresh air introduced into the crank chamber can be controlled with higher accuracy and stability.

  According to the invention described in claim 5, the engine output reduction in the high load operation region can be more effectively suppressed by stopping the introduction of fresh air into the crank chamber in the high load operation region. .

  According to the sixth aspect of the present invention, when the boost pressure downstream of the throttle valve is positive, fresh air introduced into the crankcase from the position downstream of the throttle valve is introduced. Since the amount does not exceed a certain amount, ventilation efficiency can be improved and deterioration of engine oil in the crank chamber can be suppressed without causing a decrease in engine output.

The figure which shows the 1st Embodiment of this invention, and is a figure which shows the flow of blow-by gas and the fresh air at the time of low load driving | operation of an engine. The figure which shows the flow of blow-by gas and the fresh air at the time of medium load driving | operation of an engine in FIG. The figure which shows the flow of blow-by gas and the fresh air at the time of high-load operation of an engine in FIG. The figure which shows the detail of the PCV valve | bulb in FIGS. The characteristic view which shows the relationship between the boost pressure of the intake system in FIGS. 1-3, and the flow volume of blow-by gas and fresh air. FIG. 5 is an enlarged view of a main part showing an operation state of the fresh air flow control orifice shown in FIG. 4, and (a) and (b) show an operation state of the fresh air flow control orifice in the medium load operation region shown in FIG. 5. FIG. 6C is a diagram showing an operating state of the fresh air flow control orifice in the high load operation region shown in FIG. The figure which shows the 2nd Embodiment of this invention, and is a figure which shows the flow of blow-by gas and the fresh air at the time of low load operation of an engine. In FIG. 7, the figure which shows the flow of blow-by gas and the fresh air at the time of engine medium load driving | operation. In FIG. 7, the figure which shows the flow of blow-by gas and the fresh air at the time of engine high load driving | operation. The figure which shows the detail of the PCV valve | bulb in FIGS. The figure which shows the detail of the fresh air flow control valve in FIGS. The figure which shows the 3rd Embodiment of this invention, and is a figure which shows the flow of blow-by gas and the fresh air at the time of low load operation of an engine. The figure which shows the detail of the PCV valve | bulb in 4th Embodiment. The perspective view of only the valve body of the PCV valve in FIG. The characteristic view which shows the relationship between the boost pressure of the intake system in 4th Embodiment, and the flow volume of blow-by gas and fresh air. FIG. 15 is an enlarged view of a main part showing the operating state of the fresh air flow control orifice shown in FIG. 13, and FIGS. FIG. 6C is a diagram showing an operating state of the fresh air flow control orifice in the high load operation region shown in FIG. The perspective view of only the valve body of the PCV valve in other embodiments. The perspective view of only the valve body of the PCV valve in a reference example . FIG. 18 is a characteristic diagram showing the relationship between the boost pressure of the intake system and the flow rates of blow-by gas and fresh air when the PCV valve having the valve body shown in FIG. 17 is applied in the fourth embodiment. Characteristic diagram showing the relationship between the flow rate of the boost pressure and the blow-by gas and fresh air in the intake system definitive Reference Example. The figure which shows the detail of the fresh air flow control valve in 5th Embodiment. The figure which shows the detail of the fresh air flow control valve in a reference example .

  1 to 6 are views showing a first preferred embodiment of the ventilation system according to the present invention. In particular, FIG. 1 shows the flow of blow-by gas and fresh air during low-load operation of the engine, and FIG. FIG. 3 shows the flow of blow-by gas and fresh air during high-load operation of the engine.

  In FIG. 1, a single cylinder of a supercharged in-line multi-cylinder engine is shown as an engine 1 for convenience, and an intake system 2 as an intake passage thereof has an air cleaner 3, an air flow meter 4, A compressor impeller 5b, an intercooler 6, and a throttle valve 7 of a turbocharger 5 that is a supercharger are provided. On the other hand, a turbine impeller 5 a of a turbocharger 5 is interposed in the exhaust system 8 of the engine 1.

  As is well known, the intake air is compressed (supercharged) through the air cleaner 3 and the air flow meter 4 by the compressor impeller 5b of the turbocharger 5 driven by the exhaust from the engine 1, and then the intercooler 6 in the subsequent stage. Then, the flow rate is adjusted by the throttle valve 7 and then introduced into the combustion chamber of the engine 1. A part of the exhaust from the engine 1 is returned to the intake system 2 side through the EGR cooler 9.

  A blow-by gas reduction passage 10 is provided in the intake system 2 so as to communicate with a position downstream of the throttle valve 7 and the crank chamber 1a of the engine 1, and a position upstream of the throttle valve 7 in the intake system 2 is provided. Here, a fresh air introduction passage 11 is provided in the intake system 2 for communicating the upstream side position of the compressor impeller 5b of the turbocharger 5 with the crank chamber 1a of the engine 1.

  The blow-by gas reduction passage 10 includes a PCV valve 12 and an oil mist separator 13 arranged in series so that the PCV valve 12 is on the throttle valve 7 side. A mist separator 14 is interposed. Both oil mist separators 13 and 14 are provided separately from the engine 1 and connected by a hose or the like, or provided integrally with the rocker cover (cylinder head cover) of the engine 1. There is also.

  Further, the PCV valve 12 is provided with a crank chamber as described later, separately from the blow-by gas flow control orifice 15 that controls the original flow control function of the PCV valve 12, that is, the function of controlling the flow of blow-by gas toward the intake system 2 side. A fresh air flow control orifice 16 for controlling the flow rate of fresh air toward the 1a side is provided as fresh air flow control means. That is, the blow-by gas flow control orifice 15 functions as a variable orifice for blow-by gas flow control, while the fresh air flow control orifice 16 functions as a variable orifice for new air flow control. The fresh air flow control orifice 16 is provided in series on the oil mist separator 13 side of the blow-by gas flow control orifice 15.

  FIG. 4 shows details of the PCV valve 12. This PCV valve 12 has a hollow valve body (casing or housing) 17 having a stepped cylindrical shape on both the inner and outer peripheral surfaces, and a spool type valve element 22 slidably inserted therein. The valve body main body 18 having a substantially bottomed cylindrical shape and the substantially cylindrical cover 19 connected to the opening of the valve body main body 18 are divided into two in the axial direction. A first port 20, which is an opening of the cover 19 on the side opposite to the valve body main body 18, is formed on the bottom wall of the valve body main body 18 on the downstream side of the throttle valve 7 in the intake system 2. 21 is connected to the oil mist separator 13 side (crank chamber 1a side).

  A flange portion 23 is formed at the axial center portion of the valve body 22, and a first compression coil spring 26 is interposed between the flange portion 23 and the cover 19, and the flange portion 23 and the valve body main body 18. A second compression coil spring 27 is interposed between the bottom wall and the bottom wall. The distal ends of both compression coil springs 26 and 27 are spaced apart from the thickness of the flange portion 23, and when the flange portion 23 is seated on one of the compression coil springs 26 and 27, 27 is set so that a gap G is formed between the other 27 and the flange portion 23. In this way, by providing a so-called play in the valve body 22 so that only one of the compression coil springs 26 and 7 has an elastic force acting on the valve body 22, the valve body 22 operates stably. I have to.

  In addition, a first throat portion 19 a is formed with a stepped portion at the opening of the cover 19 on the valve body main body 18 side, while a portion of the valve body 22 on the first port 20 side with respect to the flange portion 23. Is formed as a tapered blow-by gas measuring section 24 having a diameter increasing toward the flange section 23 side. When the boost pressure on the intake system 2 side is negative, the valve body 16 pulled by the negative pressure is slid relative to the valve body 17, and the boost pressure and the first compression coil spring 26 are The valve element 22 is stationary at a position where the elastic force is balanced. That is, when the first throat portion 19a and the blow-by gas measuring portion 24 move relative to each other according to the magnitude of the negative pressure, the opening degree between them and the flow rate of the blow-by gas flowing through the PCV valve 12 are continuously increased. It will be variably controlled. In other words, the gap formed between the first throat portion 19a and the blow-by gas metering portion 24 functions as the blow-by gas flow control orifice 15 described above.

  On the other hand, the second port 21 formed in the valve body 18 is formed in a tapered shape having a gradually increasing diameter toward the oil mist separator 13, while the second port of the valve body 22 is more than the flange portion 23. The portion on the 21 side is formed as a substantially stepped columnar fresh air metering portion 25 that gradually increases in diameter toward the flange portion 23 side.

  The fresh air measurement unit 25 is formed at the base of the fresh air measurement unit 25, and has a large diameter portion 25a having a diameter larger than the second throat portion 18a, which is the minimum diameter portion of the second port 21, and a large diameter portion 25a. An intermediate diameter portion 25b that is formed adjacent to the opposite flange portion 23 side and has a smaller diameter than the second throat portion 18a, and a small diameter portion that is formed at the tip of the fresh air measuring portion 25 and has a smaller diameter than the intermediate diameter portion 25b. 25c and a taper portion 25d formed between the medium diameter portion 25b and the small diameter portion 25c and gradually becoming smaller in diameter toward the small diameter portion 25c.

  When the boost pressure on the intake system 2 side is positive, the valve body 16 pressed by the positive pressure slides and displaces with respect to the valve body 17, and the boost pressure and the second compression coil spring 27 The valve body is stationary at a position balanced with the elastic force. That is, when the second throat portion 18a and the fresh air measuring portion 25 move relative to each other according to the magnitude of the positive pressure, the opening degree between them and the flow rate of fresh air flowing through the PCV valve 12 are continuously increased. It will be variably controlled. In other words, the gap formed between the second throat portion 18a and the fresh air metering portion 25 functions as the fresh air flow control orifice 16 described above.

  FIG. 5 is a graph showing the relationship between the boost pressure downstream of the throttle valve 7 in the intake system 2 and the flow rate of blow-by gas, etc., where A represents the amount of blow-by gas generated, and B represents the blow-by gas reduction. A flow rate characteristic of blow-by gas or the like in the oil mist separator 13 on the passage 10 side, and a symbol C indicate a flow characteristic of the blow-by gas or the like in the oil mist separator 14 on the fresh air introduction passage 11 side. In FIG. 5, the right side where the boost pressure is negative and the degree thereof is large is the low load side, and on the contrary, the left side where the boost pressure is positive and the degree is large is the high load side. Further, regarding the flow rate characteristics of blow-by gas and the like indicated by symbols B and C, the flow of blow-by gas from the crank chamber 1a side to the intake system 2 side is set to “positive (+)”, and the intake system 2 side to the crank chamber 1a side. The flow of fresh air going to is considered “negative (−)”.

  Since the PCV valve 12 is arranged in series with the oil mist separator 13 in the blow-by gas reduction passage 10 shown in FIG. 1, the boost pressure-flow rate characteristic of the PCV valve 12 by both flow rate control orifices 15, 16 is obtained. Is adjusted in advance so as to be substantially the same as the characteristic indicated by symbol B in FIG.

  According to the ventilation system configured in this way, as shown in FIGS. 1 and 5, when the boost pressure is negative and the degree of the negative pressure is large, that is, in the low-load operation region A1 shown in FIG. In the region on the right side of the figure, the valve body 22 of the PCV valve 12 shown in FIG. 4 is largely pulled in the left direction of the figure, and the flow passage cross-sectional area (opening) at the blow-by gas flow control orifice 15 is relatively small. Become. Accordingly, in the right load region of the low load operation region A1 in FIG. 5, the flow rate of blow-by gas discharged (reduced) to the intake system 2 side through the oil mist separator 13 and the PCV valve 12 in FIG. 1 is relatively small. In addition, the blow-by gas generation amount itself indicated by the symbol A in FIG. 5 is also small compared to other regions. At this time, the opening degree of the fresh air flow control orifice 16 becomes maximum.

  In this case, since the blow-by gas flow rate of the code B discharged to the intake system 2 side through the blow-by gas reduction passage 10 is larger than the blow-by gas generation amount shown by the code A in FIG. As shown, fresh air having a difference in flow rate between the two is introduced into the crank chamber 1 a through the fresh air introduction passage 11. As described above, the blow-by gas is discharged from the crank chamber 1a to the intake system 2 side through the blow-by gas reduction passage 10 and the fresh air is introduced into the crank chamber 1a through the new-air introduction passage 11, so that the crank chamber 1a is ventilated. Will be.

  Further, when the engine load increases from that state and the boost pressure gradually approaches positive pressure, the valve body 22 of the PCV valve 12 in FIG. 4 slides to the right as compared with the previous case, and the blow-by gas flow control orifice 15 is larger than the previous case. As a result, the blow-by gas flow rate indicated by symbol B discharged to the intake system 2 side through the blow-by gas reduction passage 10 and the fresh air flow rate indicated by symbol C introduced into the crank chamber 1a through the fresh air introduction passage 11 are increased. Become.

  Further, in the state immediately before the positive pressure where the boost pressure approaches the positive pressure as much as possible, the blow-by gas flow rate of the code B discharged to the intake system 2 side through the oil mist separator 13 and the PCV valve 12 in the blow-by gas reduction passage 10 is the code A. The amount of blow-by gas generated becomes smaller, and eventually the blow-by gas is exhausted from the fresh air introduction passage 11 as shown in FIG.

  When the load on the engine 1 further increases and the boost pressure in FIG. 5 changes to a positive pressure due to the supercharging pressure of the turbocharger 5 shown in FIG. 1, the valve body 22 of the PCV valve 12 shown in FIG. As shown in FIG. 2, the fresh air that has flowed into the blow-by gas reduction passage 10 from the downstream side of the throttle valve 7 by the boost pressure is slid to the right in FIG. After being measured by the fresh air flow control orifice 16, the air flows back to the crank chamber 1 a through the oil mist separator 13. At the same time, the blow-by gas generated in the engine 1 mixes with fresh air in the crank chamber 1a, and is discharged to the upstream side of the throttle valve 7 in the intake system 2 through the fresh air introduction passage 11, thereby ventilating the crank chamber 1a. . In other words, when the boost pressure is positive, the opening degree of the blow-by gas flow control orifice 15 is maximized, and the new air flow control orifice 16 in the PCV valve 12 has a new opening at the oil mist separator 13 on the blow-by gas reduction passage 10 side. Qi flow is controlled.

  As a result, in the medium load operation region A2 where the boost pressure in FIG. 5 is positive and smaller than the predetermined set pressure P1, the gas flow rate on the blow-by gas reduction passage 10 side indicated by symbol B is “negative (−)”. ”. At this time, the flow rate of the blowby gas discharged to the upstream side of the throttle valve 7 in the intake system 2 through the fresh air introduction passage 11 is equal to the blowby gas generation amount indicated by the symbol A in FIG. Since the amount of the fresh air flow on the 10 side is added, the blow-by gas flow rate on the fresh air introduction passage 11 side indicated by symbol C exceeds the blow-by gas generation amount of symbol A.

  6 (a) to 6 (c) are enlarged views of main parts showing the operating state of the PCV valve 12 when the boost pressure downstream of the throttle valve 7 in the intake system 2 is positive. In the middle load operation region A2 in FIG. 5, in the region where the degree of positive pressure is relatively small, as shown in FIGS. 6 (a) and 6 (b), the valve element 22 moves to the right side in the diagram as the boost pressure increases. The flow passage cross-sectional area of the fresh air flow control orifice 16 is gradually reduced by the taper portion 25d of the fresh air metering portion 25, but the fresh air on the blow-by gas reduction passage 10 side indicated by B in FIG. Is gradually increased under the influence of the increase in the boost pressure, and eventually reaches the maximum flow rate Q in the medium load operation region A2.

  Further, at a position immediately before the set pressure P1 at which the flow rate of fresh air on the blow-by gas reduction passage 10 side indicated by the symbol B in FIG. 5 exceeds the maximum flow rate Q and the boost pressure approaches the preset pressure P1 as much as possible, FIG. The step portion 25e between the large diameter portion 25a and the medium diameter portion 25b in the fresh air measuring portion 25 shown in (b) of FIG. The road cross-sectional area is further reduced. As a result, the flow rate of fresh air on the blow-by gas reduction passage 10 side indicated by symbol B in FIG. 5 and the flow rate of blow-by gas on the fresh air introduction passage 11 side indicated by symbol C in FIG. Along with this, it gradually becomes smaller.

  When the boost pressure reaches the set pressure P1, as shown in FIG. 6C, the stepped portion 25e of the fresh air measuring portion 25 is seated on the bottom wall of the valve body 17, and the fresh air flow control orifice 16 is Fully closed state. Accordingly, as shown in FIG. 3 in addition to FIG. 5, in the high load operation region A3 where the boost pressure is equal to or higher than the set pressure P1, the flow rate of fresh air on the blow-by gas reduction passage 10 side indicated by reference symbol B is almost zero or Thus, the fresh air introduced into the crank chamber 1a is supplied to the engine 1 in the medium load operation region A2. At this time, the flow rate of blow-by gas on the fresh air introduction passage 11 side indicated by reference numeral C in FIG.

  Therefore, according to the present embodiment, in the middle load operation region A2 of FIG. 5, the ventilation of the crank chamber 1a is emphasized, and fresh air is actively introduced into the crank chamber 1a through the blow-by gas reduction passage 10, while the engine In the high load operation region A3 where higher output is required, the introduction of fresh air into the crank chamber 1a through the blow-by gas reduction passage 10 is stopped in order to supply more fresh air to the engine 1. While suppressing the deterioration of the engine oil due to the engine 1, it is possible to prevent the output of the engine 1 from decreasing in the high load operation region A3. The set pressure P1 may be set as appropriate in consideration of the balance between the engine output and the ventilation efficiency of the crank chamber 1a.

  Further, in the first embodiment, as shown in FIG. 5, fresh air is introduced into the crank chamber 1a through the blow-by gas reduction passage 10 in the high load operation region A3 where the boost pressure exceeds the set pressure P1. The flow rate of fresh air introduced into the crank chamber 1a in the high load operation region A3 does not necessarily have to be substantially zero or extremely small, but is at least greater than the maximum flow rate Q in the medium load operation region A2 in FIG. If it is set to be smaller, at least the output reduction of the engine 1 can be suppressed. However, when emphasizing the engine output in the high load operation region A3, it goes without saying that it is desirable to set the boost pressure-flow rate characteristic shown in FIG.

  FIGS. 7 to 11 are views showing a second embodiment of the ventilation system according to the present invention. In particular, FIG. 7 shows the flow of blow-by gas and fresh air during low-load operation of the engine, and FIG. FIG. 9 shows the flow of blow-by gas and fresh air during high-load operation of the engine. 7-9, the same code | symbol is attached | subjected to the part which is common in previous FIGS. 1-3.

  In the second embodiment, a PCV valve 28 that controls only the amount of blow-by gas discharged from the crank chamber 1a to the intake system 2 side is employed instead of the PCV valve 12 in the first embodiment described above. A fresh air flow control valve 29 for controlling the amount of fresh air introduced from the intake system 2 side into the crank chamber 1a is provided in parallel with the PCV valve 28. That is, the blow-by gas reduction passage 10 branches or merges from the downstream side position of the throttle valve 7 in the intake system 2 as in the first embodiment described above, but the bypass branches or merges from the equivalent position. Unlike the first embodiment described above, a passage 30 is provided, a fresh air flow control valve 29 is provided in the bypass passage 30, and the other end of the bypass passage 30 is connected to the oil mist separator 13. Yes. The boost pressure-flow rate characteristics of the PCV valve 28 and the fresh air flow rate control valve 29 are adjusted in advance so as to be substantially the same as the characteristic indicated by the symbol B shown in FIG.

  FIG. 10 shows details of the PCV valve 28. This PCV valve 28 has a so-called two-piece valve body 31 that is substantially the same as the PCV valve 28 in the first embodiment described above, in which a spool-type valve body 36 is slidably inserted. The first port 34 on the cover 32 side of the body 31 is connected to the downstream side of the throttle valve 7 in the intake system 2, and the second port 35 on the valve body body 33 side of the valve body 31 is connected to the oil mist separator 13 side. become.

  The valve body 36 includes a flange portion 37 formed at an end portion of the valve body 36 on the second port 35 side, and a tapered blow-by gas measuring portion 38 protruding from the flange portion 37 toward the first port 34 side. Are urged toward the second port 35 by a compression coil spring 39 interposed between the flange portion 37 and the cover 32. And the throat part 32a formed in the blow-by gas measurement part 38 of the said valve body 36 and the cover 32 is formed as the thing equivalent to 1st Embodiment mentioned above, Between the 1st mentioned above between them. The blow-by gas flow rate control orifice 40 equivalent to the embodiment is formed.

  That is, when the boost pressure on the intake system 2 side is negative, the valve body 36 is slid to a position where the boost pressure and the biasing force of the compression coil spring 39 are balanced, and the blow-by gas flow control orifice 40 is opened. Therefore, the flow rate of the blow-by gas flowing toward the intake system 2 is variably controlled. On the other hand, when the boost pressure on the intake system side is positive, the second port 35 is closed by the flange portion 37 of the valve body 36 seated on the bottom wall of the valve body main body 33, and the PCV valve 28 is It will be closed.

  FIG. 11 shows the details of the fresh air flow control valve 29. This new air flow control valve 29 is a valve body 41 slidably inserted in a so-called two-piece valve body 41 similar to the PCV valve 28. The first port 44 is connected to the downstream side of the throttle valve 7 in the intake system 2, and the second port 45 on the valve body main body 43 side of the valve body 41 is connected to the oil mist separator 13 side.

  The valve body 46 includes a flange portion 47 formed at an end portion of the valve body 46 on the first port 44 side, and a substantially stepped columnar fresh air metering projecting from the flange portion 47 toward the second port 45 side. 48, and is biased toward the first port 44 by a compression coil spring 49 interposed between the flange 47 and the bottom wall of the valve body main body 43. The fresh air metering portion 48 of the valve body 46 is formed in the same manner as the first embodiment described above with the large-diameter portion 48a, the medium-diameter portion 48b, the small-diameter portion 48c, and the tapered portion 48d. The throat portion 43a, which is the minimum diameter portion of the 2-port 45, is also formed as an equivalent to the first embodiment described above, and a fresh air flow rate equivalent to the first embodiment described above is formed between them. A control orifice 50 is formed.

  That is, when the boost pressure on the intake system 2 side is a negative pressure, the second port 45 is closed by the flange portion 47 of the valve body 46 seated on the bottom wall portion 42a of the cover 42, and the fresh air flow control is performed. The valve 29 is closed. On the other hand, when the boost pressure on the intake system 2 side is positive, the valve body 46 is slid to a position where the boost pressure and the biasing force of the compression coil spring 49 are balanced, and the fresh air flow control orifice 50 The opening, and thus the flow rate of fresh air flowing toward the oil mist separator 13 side is variably controlled. When the boost pressure of the intake system is equal to or higher than the set pressure P1 shown in FIG. 5, the stepped portion 48e between the large diameter portion 48a and the medium diameter portion 48b of the fresh air measuring portion 48 is the valve body main body 43. It is the same as that of the first embodiment described above that the second port 45 is closed by being seated on the bottom wall.

  In the second embodiment configured as described above, in the low load operation region A1 of FIG. 5 in which the boost pressure on the intake system 2 side is negative, the fresh air flow control valve 29 is used as shown in FIG. While the bypass passage 30 is blocked, the flow rate of blow-by gas discharged to the intake system 2 side is controlled by the PCV valve 28, and the blow-by gas recirculation passage 10 exhibits its original function.

  In the middle load operation region A2 in FIG. 5 where the boost pressure on the intake system 2 side is positive and lower than the set pressure P1, the blow-by gas recirculation passage 10 is blocked by the PCV valve 28 as shown in FIG. At the same time, the fresh air measured by the fresh air flow control valve 29 is introduced into the crank chamber 1 a through the bypass passage 30. Thereby, the crank chamber 1a is actively ventilated.

  Further, in the high load operation region A3 of FIG. 5 where the boost pressure on the intake system 2 side is equal to or higher than the set pressure P1, the bypass passage 30 is also shut off by the fresh air flow control valve 29 as shown in FIG. A lot of fresh air will be supplied. Thereby, the output fall of the engine 1 is prevented.

  Therefore, according to the second embodiment, the function similar to that of the first embodiment described above is exhibited, and when the boost pressure on the intake system 2 side is positive, the crank chamber Since the fresh air flow control valve 29 for controlling the flow rate of fresh air introduced into 1a is provided separately from the PCV valve 28, the flow rate of fresh air introduced into the crank chamber 1a can be controlled with higher accuracy and stability. There are benefits.

  FIG. 12 shows a modification of the above-described second embodiment, and shows the flow of blow-by gas and fresh air at the time of low load as in FIG.

  In this modification, the bypass passage 51 having the fresh air flow control valve 29 is directly connected to the crank chamber 1 a of the engine 1 instead of the oil mist separator 13.

  Therefore, it goes without saying that the same function as that of the second embodiment described above is also exhibited in this case.

  A fourth embodiment of the present invention will be described with reference to FIGS. In addition, this 4th Embodiment is applied to the ventilation system of FIGS. 1-3 shown in the 1st Embodiment mentioned above, Specifically, 1st Embodiment mentioned above is specifically, applied. In the embodiment, instead of the PCV valve 12 described above, a PCV valve 80 having a characteristic different from that of the PCV valve 12 is interposed.

FIG. 13 shows details of the PCV valve 80 according to the fourth embodiment.
In addition, about the component same as the PCV valve | bulb 12, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

  The PCV valve 80 has substantially the same configuration as the PCV valve 12 described above. However, as shown in FIG. 14, the fresh air metering portion 81 of the valve body 22 is formed at the root of the fresh air metering portion 81. The second port portion 21 is formed adjacent to the large-diameter portion 81a having a larger diameter than the second throat portion 18a, which is the minimum diameter portion of the second port 21, and the opposite-flange portion 23 side of the large-diameter portion 81a. A tapered portion 81b whose outer diameter gradually becomes smaller toward the side, a small diameter portion 81c formed at the tip of the fresh air measuring portion 81 and having a smaller diameter than the tapered portion 81b, and between the large diameter portion 81a and the tapered portion 81b. 81d, and a stepped portion 81e formed between the tapered portion 81b and the small diameter portion 81c.

  When the boost pressure on the intake system 2 side is positive, the valve body 22 pressed by the positive pressure slides and displaces with respect to the valve body 17, and the boost pressure and the second compression coil spring 27 The valve body is stationary at a position balanced with the elastic force.

  When the fresh air measuring portion 81 is formed as shown in FIG. 14, the boost pressure on the downstream side of the throttle valve 7 in the intake system 2 is switched to a positive pressure, and the valve body 22 is changed as the boost pressure increases. When the stepped portion 81d is slid and seated on the bottom wall of the valve body main body 18, the fresh air flow control orifice 16 is fully closed. In the PCV valve 80, the gap formed between the second throat portion 18a and the fresh air metering portion 81 functions as the above-described fresh air flow control orifice 16.

  FIG. 15 is a graph showing the relationship between the boost pressure on the downstream side of the throttle valve 7 in the intake system 2 and the flow rate of blow-by gas, etc., when the PCV valve 80 is applied to the ventilation system of FIGS. Symbol A is the amount of blow-by gas generated, Symbol B is the flow characteristics of blow-by gas in the oil mist separator 13 on the blow-by gas reduction passage 10 side, and Symbol C is the oil mist separator on the fresh air introduction passage 11 side. 14 shows the flow characteristics of blow-by gas and the like at 14 respectively. In FIG. 15, as in FIG. 5 described above, the right side where the boost pressure is negative and the degree thereof is large is the low load side, and conversely, the left side where the boost pressure is positive and the degree thereof is large. It is on the high load side. As for the flow rate characteristics of the blow-by gas indicated by reference characters B and C, the flow of blow-by gas from the crank chamber 1a side to the intake system 2 side is set to “positive (+)” as in FIG. The flow of fresh air from the system 2 side toward the crank chamber 1a side is defined as “negative (−)”.

Since the PCV valve 80 is arranged in series with the oil mist separator 13 in the blow-by gas reduction passage 10, the fourth pressure boosting flow rate characteristic of the PCV valve 80 by both flow rate control orifices 15 and 16 is the fourth characteristic. In the embodiment, the adjustment is made in advance so as to be substantially the same as the characteristic indicated by the symbol B in FIG. More specifically, in the operation range where the boost pressure downstream of the throttle valve 7 in the intake system 2 is positive, in the middle load operation region, fresh air flowing into the blow-by gas reduction passage 10 from the downstream side of the throttle valve 7 is shown. the amount is constant regardless of the boost pressure, so that the amount of fresh air flowing from the throttle valve 7 downstream to the blow-by gas returning passage 10 is substantially zero or very small in the high-load operation region, the fresh air metering unit 8 1 Is set.

  Also in the fourth embodiment as described above, in the low load operation region A1 shown in FIG. 15, the flow path cross-sectional area (opening degree) in the blow-by gas flow control orifice 15 increases as the negative pressure of the boost pressure increases. Relatively small. Accordingly, in the region on the right side in the low load operation region A1 of FIG. 15, the flow rate of blow-by gas discharged (reduced) to the intake system 2 side through the oil mist separator 13 and the PCV valve 80 becomes relatively small. The blow-by gas generation amount itself indicated by symbol A in FIG. 15 is also small compared to other regions. At this time, the opening degree of the fresh air flow control orifice 16 becomes maximum.

  Also in this case, since the blow-by gas flow rate of the symbol B discharged to the intake system 2 side through the blow-by gas reduction passage 10 is larger than the blow-by gas generation amount indicated by the symbol A in FIG. As shown, fresh air having a difference in flow rate between the two is introduced into the crank chamber 1 a through the fresh air introduction passage 11. As described above, the blow-by gas is discharged from the crank chamber 1a to the intake system 2 side through the blow-by gas reduction passage 10 and the fresh air is introduced into the crank chamber 1a through the new-air introduction passage 11, so that the crank chamber 1a is ventilated. Will be.

  In addition, when the engine load increases from that state and the boost pressure gradually approaches positive pressure, the valve body 22 of the PCV valve 80 in FIG. 13 slides to the right as compared with the previous case, and the blow-by gas flow control orifice 15 is larger than the previous case. As a result, the blow-by gas flow rate indicated by symbol B discharged to the intake system 2 side through the blow-by gas reduction passage 10 and the fresh air flow rate indicated by symbol C introduced into the crank chamber 1a through the fresh air introduction passage 11 are increased. Become.

  Further, in a state immediately before the positive pressure where the boost pressure approaches the positive pressure as much as possible, the blow-by gas flow rate of the code B discharged to the intake system 2 side through the oil mist separator 13 and the PCV valve 80 in the blow-by gas reduction passage 10 is represented by the code A. The amount of blow-by gas generated becomes smaller, and eventually the blow-by gas is exhausted from the fresh air introduction passage 11 as well.

  When the load on the engine 1 further increases and the boost pressure in FIG. 15 changes to a positive pressure, the valve body 22 of the PCV valve 80 shown in FIG. 13 receives the boost pressure and slides to the right in FIG. In the system 2, fresh air that has flowed into the blow-by gas reduction passage 10 from the downstream side of the throttle valve 7 by the boost pressure is measured by the fresh air flow control orifice 16 of the PCV valve 80, and then passed through the oil mist separator 13 to the crank chamber. It will flow back to the 1a side. At the same time, the blow-by gas generated in the engine 1 mixes with fresh air in the crank chamber 1a, and is discharged to the upstream side of the throttle valve 7 in the intake system 2 through the fresh air introduction passage 11, thereby ventilating the crank chamber 1a. . That is, also in this PCV valve 80, when the boost pressure is positive, the opening degree of the blow-by gas flow control orifice 15 is maximized, and the fresh air flow control orifice 16 in the PCV valve 80 has the blow-by gas reduction passage 10 side. The flow rate of fresh air in the oil mist separator 13 is controlled.

  Accordingly, the operation region in which the boost pressure in FIG. 15 is a positive pressure, that is, the medium pressure operation region A2 in which the boost pressure is a positive pressure and is smaller than the preset pressure P1, and the boost pressure is equal to or higher than the preset pressure P1 In the high-load operation region A3, the gas flow rate on the blow-by gas reduction passage 10 side indicated by the symbol B turns to “negative (−)”. At this time, the flow rate of the blow-by gas discharged to the upstream side of the throttle valve 7 in the intake system 2 through the fresh air introduction passage 11 is equal to the blow-by gas generation amount indicated by symbol A in FIG. Since the amount of the fresh air flow on the 10 side is added, the blow-by gas flow rate on the fresh air introduction passage 11 side indicated by symbol C exceeds the blow-by gas generation amount of symbol A.

FIGS. 16A to 16C are main part enlarged views showing the operating state of the PCV valve 80 when the boost pressure downstream of the throttle valve 7 in the intake system 2 is positive. The region of the load operating region A2 in Figure 1 5, as shown in FIG. 1-6 (a), (b), the valve body 22 with an increase in the boost pressure is slid to the right in the figure, the fresh air The flow passage cross-sectional area of the fresh air flow control orifice 16 is gradually reduced by the tapered portion 81b of the measuring portion 81. Here, in the fourth embodiment, when the boost pressure downstream of the throttle valve 7 in the intake system 2 is switched to the positive pressure, the blow-by gas indicated by the symbol B in FIG. The boost pressure-flow rate characteristic of the PCV valve 80 is such that the flow rate of fresh air on the reduction passage 10 side becomes a constant flow rate Q1 even if the boost pressure downstream of the throttle valve 7 in the intake system 2 increases. Is set.

  Then, at the position immediately before the set pressure P1 at which the boost pressure approaches the preset set pressure P1 as much as possible, as shown in FIG. 16B, the large-diameter portion 81a and the tapered portion 81b of the fresh air measuring portion 81 The stepped portion 81d therebetween approaches the bottom wall of the valve body main body 18, and the flow passage cross-sectional area of the fresh air flow control orifice 16 is further reduced. As a result, the flow rate of fresh air on the blow-by gas reduction passage 10 side indicated by symbol B in FIG. 15 and the flow rate of blow-by gas on the fresh air introduction passage 11 side indicated by symbol C in FIG. Along with this, it gradually becomes smaller.

  When the boost pressure reaches the set pressure P1, the stepped portion 81d of the fresh air measuring portion 81 is seated on the bottom wall of the valve body 17 as shown in FIG. Fully closed state. As a result, as shown in FIG. 15, in the high load operation region A3 where the boost pressure is equal to or higher than the set pressure P1, the flow rate of fresh air on the blow-by gas reduction passage 10 side indicated by reference symbol B becomes substantially zero or extremely small. In the medium load operation region A2, fresh air introduced into the crank chamber 1a is supplied to the engine 1. At this time, the flow rate of blow-by gas on the fresh air introduction passage 11 side indicated by reference numeral C in FIG. 15 is equal to the blow-by gas generation amount indicated by reference numeral A.

  According to the ventilation system in the fourth embodiment configured as described above, ventilation in the crank chamber 1a is emphasized in the medium load operation region, and a positive fixed amount Q1 is newly added to the crank chamber 1a through the blow-by gas reduction passage 10. On the other hand, in the high-load operation region of the engine, the fresh air is not substantially introduced into the crank chamber 1a through the blow-by gas reduction passage 10, thereby giving more importance to the engine output and supplying more fresh air to the engine. Can be supplied.

  When the PCV valve 80 is applied, the constant flow rate Q1 set in the medium load operation region A2 may be set as appropriate in consideration of the balance between the engine output and the ventilation efficiency of the crank chamber 1a.

  Moreover, the fresh air measurement part 81 of the valve body 22 in the PCV valve 80 in the fourth embodiment described above can also be configured as shown in FIGS. 17 and 18.

  In the example shown in FIG. 17, the fresh air measuring portion 91 of the valve body 22 has a diameter that increases toward the flange portion 23 side, and a first taper portion 91 a in which the distal end side on the second port portion 21 side is formed in a tapered shape. And a second taper 91b, and a stepped portion 91c formed between the first taper 91a and the second taper 91b. The first taper portion 91a is formed to have a larger diameter than the second taper portion 91b.

  When the fresh air measuring section 91 is formed as shown in FIG. 17, when the boost pressure downstream of the throttle valve 7 in the intake system 2 is switched to a positive pressure, the flow rate of fresh air flowing through the PCV valve is It is controlled so that it can be switched in two stages according to the load. In the PCV valve including the valve body 22 having the fresh air measuring portion 91, the gap formed between the second throat portion 18a and the fresh air measuring portion 91 functions as the above-described fresh air flow control orifice 16. become.

  FIG. 19 shows the boost pressure on the downstream side of the throttle valve 7 in the intake system 2 when the PCV valve including the valve body 22 having the fresh air measuring unit 91 is applied to the ventilation system of FIGS. It is the graph which showed the relationship with flow volume, such as blow-by gas.

  In the middle load operation region A2 of FIG. 19, the flow passage cross-sectional area of the fresh air flow control orifice 16 is gradually reduced by the second taper portion 91b of the fresh air metering portion 91 as the boost pressure increases. The boost pressure-flow rate characteristic of the PCV valve is set so that the fresh air on the blow-by gas reduction passage 10 side indicated by the symbol B has a constant flow rate Q1. Then, at the position immediately before the set pressure P1 at which the boost pressure approaches the preset set pressure P1 as much as possible, the stepped portion 91c approaches the bottom wall of the valve body main body 18, and the flow passage cross-sectional area of the fresh air flow control orifice 16 is increased. It gets smaller. As a result, the flow rate of fresh air on the blow-by gas reduction passage 10 side indicated by symbol B in FIG. 19 and the flow rate of blow-by gas on the fresh air introduction passage 11 side indicated by symbol C in FIG. Along with this, it gradually becomes smaller.

  In the high load operation region A3 of FIG. 19 where the boost pressure is equal to or higher than the set pressure P1, the flow passage cross-sectional area of the fresh air flow control orifice 16 is gradually reduced by the first taper portion 91a as the boost pressure increases. However, the boost pressure-flow rate characteristic of the PCV valve is set so that the fresh air at the blow-by gas reduction passage 10 side indicated by the symbol B in FIG. 19 has a constant flow rate Q2. The constant flow rate Q2 in the high load operation region A3 is set smaller than the constant flow rate Q1 in the medium load operation region A2.

  Therefore, if a PCV valve having such a valve body 22 having the fresh air metering portion 91 is applied, even if the boost pressure downstream of the throttle valve 7 is positive, the high pressure of the engine 1 is high. Ventilation efficiency can be improved and deterioration of the engine oil in the crank chamber 1a can be suppressed without causing a decrease in the output of the engine 1 during load.

  In addition, when applying the PCV valve provided with the valve body 22 having the fresh air measuring unit 91, the constant flow rate Q1 set in the medium load operation region A2 and the constant flow rate Q2 set in the high load operation region A3 are: It may be set as appropriate in consideration of the balance between the engine output and the ventilation efficiency of the crank chamber 1a.

In the reference example shown in FIG. 18, the fresh air measuring portion 101 formed in the portion of the valve body 22 closer to the second port than the flange portion 23 increases in diameter toward the flange portion 23 side, and the second port The distal end side of the portion 21 is composed of a tapered portion 101a formed in a tapered shape and a columnar distal end portion 101b formed in the same diameter as the distal end of the tapered portion 101a.

  In the PCV valve including the valve body 22 having the fresh air measuring unit 101, the second throat portion 18a and the fresh air measuring unit 101 move relative to each other according to the magnitude of the positive pressure, thereby forming both of them. Although the opening degree is continuously variably controlled, the flow rate of fresh air flowing through the PCV valve is controlled to be constant regardless of the magnitude of the positive pressure. In the PCV valve including the valve body 22 having the fresh air metering unit 101, the gap formed between the second throat portion 18a and the fresh air metering unit 101 functions as the above-described fresh air flow control orifice 16. become.

  FIG. 20 shows the boost pressure on the downstream side of the throttle valve 7 in the intake system 2 when the PCV valve including the valve body 22 having the fresh air measuring unit 101 is applied to the ventilation system of FIGS. It is the graph which showed the relationship with flow volume, such as blow-by gas.

  In the medium load operation region A2 in FIG. 20, from the region where the degree of positive pressure is relatively small to the high load operation region A3 in FIG. 20, the fresh air is measured by the taper portion 101a of the fresh air measuring unit 101 as the boost pressure increases. The cross-sectional area of the flow control orifice 16 gradually decreases. Here, in the present embodiment, when the boost pressure downstream of the throttle valve 7 in the intake system 2 is switched to a positive pressure, the flow rate of fresh air on the blow-by gas reduction passage 10 side indicated by B in FIG. However, the boost pressure of the PCV valve provided with the valve body 22 having the fresh air measuring portion 101 so that the constant flow rate Q1 is obtained even if the boost pressure downstream of the throttle valve 7 in the intake system 2 increases. Flow characteristics are set.

  In the PCV valve having the valve body 22 having the fresh air metering portion 101 configured as described above, the flow of the fresh air flow control orifice 16 increases as the boost pressure at the downstream side of the throttle valve 7 becomes a positive pressure. Since the road cross-sectional area is small, the amount of fresh air introduced into the crank chamber 1a through the PCV valve is set to a constant flow rate Q1 even if the boost pressure downstream of the throttle valve 7 becomes a positive pressure. Is possible.

  In other words, even if the boost pressure at a position downstream of the throttle valve 7 becomes a positive pressure, the new pressure introduced into the crank chamber 1a through the PCV valve provided with the valve body 22 having the fresh air measuring portion 101. Qi can be a certain amount. That is, even when the boost pressure at the downstream side of the throttle valve 7 becomes a positive pressure when the engine 1 is at a high load, a certain amount or more of fresh air is not introduced into the crank chamber 1a through the PCV valve. When the engine 1 is heavily loaded, the amount of fresh air (air amount) flowing into the engine 1 does not decrease.

  Therefore, when the boost pressure downstream of the throttle valve 7 is positive, the engine 1 in the crank chamber 1a improves the ventilation efficiency without reducing the output of the engine 1 when the engine 1 is heavily loaded. Can be prevented.

  In addition, when applying the PCV valve provided with the valve body 22 having the fresh air measuring unit 101, the constant flow Q1 set in the medium load operation region A2 and the high load operation region A3 is the engine output and the crank chamber 1a. What is necessary is just to set suitably considering the balance with ventilation efficiency.

  FIG. 21 shows a fresh air flow control valve 130 used in the fifth embodiment of the ventilation system according to the present invention.

  In the fifth embodiment, instead of the PCV amount control valve 29 in the second embodiment described above, a fresh air flow rate control valve for controlling the amount of fresh air introduced from the intake system 2 side into the crank chamber 1a. 130 is provided in parallel with the PCV valve 28.

  The boost pressure-flow rate characteristics of the PCV valve 28 and the fresh air flow control valve 130 are the same as the characteristics of the PCV valve 80 in the fourth embodiment described above, that is, substantially the same as the characteristics of the symbol B shown in FIG. It has been adjusted in advance to be equivalent.

  FIG. 21 shows the details of the fresh air flow control valve 130. The fresh air flow control valve 130 is formed by inserting a spool-type valve body 146 in a so-called two-piece valve body 141 similar to the above-described fresh air flow control valve 29 so as to be slidable. The first port 144 on the cover 142 side is connected to the downstream side of the throttle valve 7 in the intake system 2, and the second port 145 on the valve body body 143 side of the valve body 141 is connected to the oil mist separator 13 side. .

  The valve body 146 includes a flange portion 147 formed at an end portion of the valve body 146 on the first port 144 side, and a substantially tapered fresh air measuring portion 148 protruding from the flange portion 147 toward the second port 145 side. And is urged toward the first port 144 by a compression coil spring 149 interposed between the flange portion 147 and the bottom wall of the valve body main body 143. And the fresh air measurement part 148 of the said valve body 146 is formed like the 4th Embodiment mentioned above with the large diameter part 148a, the taper part 148b, the small diameter part 148c, the step part 148d, and the step part 148e. In addition, the throat portion 143a, which is the minimum diameter portion of the second port 145, is also formed as the same as the above-described fourth embodiment, and between them, the above-described fourth embodiment and An equivalent fresh air flow control orifice 150 is formed.

  When the boost pressure on the intake system 2 side is negative, the second port 145 is closed by the flange portion 147 of the valve body 146 seating on the bottom wall portion 142a of the cover 142, and the fresh air flow control valve 130 is closed. Will close. On the other hand, when the boost pressure on the intake system 2 side is positive, the valve body 146 is slid to a position where the boost pressure and the urging force of the compression coil spring 149 are balanced. In the middle load operation region, the amount of fresh air flowing from the downstream side of the throttle valve 7 to the blow-by gas reduction passage 10 is constant regardless of the boost pressure, and in the high load operation region, the blow-by gas reduction passage from the downstream side of the throttle valve 7. The boost pressure-flow rate characteristic of the fresh air flow control valve 130 is set so that the amount of fresh air flowing into the air flow 10 is almost zero or extremely small.

  In the fifth embodiment configured as described above, in the low load operation region where the boost pressure on the intake system 2 side is negative, the bypass passage 30 is blocked by the fresh air flow control valve 130, while the intake system The flow rate of blow-by gas discharged to the second side is controlled by the PCV valve 28, and the blow-by gas recirculation passage 10 exhibits its original function.

  In the middle load operation region where the boost pressure on the intake system 2 side is positive, the blow-by gas recirculation passage 10 is shut off by the PCV valve 28 and the constant flow Q1 measured by the fresh air flow control valve 130 is renewed. The air is introduced into the crank chamber 1a through the bypass passage 30. Thereby, the crank chamber 1a is actively ventilated.

  In the high load operation region where the boost pressure on the intake system 2 side is positive, the blow-by gas recirculation passage 10 is blocked by the PCV valve 28 and the bypass passage 30 is also blocked by the fresh air flow control valve 130.

  Therefore, in the fifth embodiment, the same function as in each of the above-described embodiments is exhibited, and a fresh air flow rate control valve for controlling the flow rate of fresh air introduced into the downstream crank chamber 1a. Since 29 is provided separately from the PCV valve 28, there is an advantage that the flow rate of fresh air introduced into the crank chamber 1a can be controlled more accurately and stably. In particular, in the fifth embodiment, in the high load operation region where the boost pressure on the intake system 2 side is positive, the amount of fresh air flowing from the downstream side of the throttle valve 7 into the blow-by gas reduction passage 10 is almost zero or extremely low. Since it is made small, there is an advantage that more fresh air can be supplied to the engine with emphasis on the engine output in the high-load operation region of the engine.

In the fifth embodiment described above, a fresh air flow control valve 160 shown in FIG. 22 can be used instead of the fresh air flow control valve 130. FIG. 22 shows a fresh air flow control valve 160 of a reference example .

In this reference example , the boost pressure-flow rate characteristics of the PCV valve 28 and the fresh air flow control valve 160 are the same as those of the PCV valve including the valve body 22 having the fresh air measuring unit 101 described above, that is, in FIG. It has been adjusted in advance so as to be substantially the same as the characteristic of the symbol B shown.

  FIG. 22 shows the details of the fresh air flow control valve 160. The fresh air flow control valve 160 is formed by inserting a spool-type valve body 166 in a so-called two-piece structure valve body 161 similar to the above-described fresh air flow control valve 29 so as to be slidable. The first port 164 on the cover 162 side is connected to the downstream side of the throttle valve 7 in the intake system 2, and the second port 165 on the valve body body 163 side of the valve body 161 is connected to the oil mist separator 13 side. .

  The valve body 166 includes a flange portion 167 formed at an end portion of the valve body 166 on the first port 164 side, and a substantially tapered fresh air measuring portion 168 protruding from the flange portion 167 toward the second port 165 side. And urged toward the first port 164 side by a compression coil spring 169 interposed between the flange portion 167 and the bottom wall of the valve body main body 163. And the fresh air measurement part 168 of the said valve body 166 is formed similarly to the fresh air measurement part 101 of FIG. 18 mentioned above with the taper part 168a and the cylindrical small diameter part 168b. A fresh air flow control orifice 170 is formed between the fresh air measuring portion 168 and the throat portion 163a which is the minimum diameter portion of the second port 165.

  When the boost pressure on the intake system 2 side is negative, the second port 165 is closed by the flange portion 167 of the valve body 166 seating on the bottom wall portion 162 a of the cover 162, and the fresh air flow control valve 160. Will close. On the other hand, when the boost pressure on the intake system 2 side is a positive pressure, the valve body 166 slides to a position where the boost pressure and the urging force of the compression coil spring 169 are balanced, and new pressure increases as the boost pressure increases. Although the flow passage cross-sectional area of the air flow control orifice 150 is gradually reduced, the boost pressure of the fresh air flow control valve 160 is set so that the flow rate of fresh air flowing toward the oil mist separator 13 becomes a constant flow rate Q1. Flow characteristics are set.

In this reference example configured as described above, in the low load operation region where the boost pressure on the intake system 2 side is negative, the bypass passage 30 is blocked by the fresh air flow control valve 160, while on the intake system 2 side. The flow rate of the blow-by gas discharged is controlled by the PCV valve 28, and the blow-by gas recirculation passage 10 exhibits its original function.

  In the medium load operation region and the high load operation region where the boost pressure on the intake system 2 side is positive, the blow-by gas recirculation passage 10 is shut off by the PCV valve 28 and measured by the fresh air flow control valve 160. The fresh air having a constant flow rate Q1 is introduced into the crank chamber 1a through the bypass passage 30. Thereby, the crank chamber 1a is actively ventilated.

Therefore, also in this reference example , it is possible to obtain substantially the same operational effects as those of the fifth embodiment described above. Further, in this reference example , even in a high load operation region where the boost pressure on the intake system 2 side is positive, fresh air at a constant flow rate Q1 is supplied from the downstream side of the throttle valve 7 via the blow-by gas reduction passage 10 to the crank chamber. Since it is introduced into 1a, the ventilation efficiency at the time of high load can be improved and deterioration of the engine oil in the crank chamber 1a can be suppressed without causing a decrease in the output of the engine 1 at the time of high load.

Also in this reference example and the fifth embodiment, the fresh air flow control valves 160 and 130 may be connected so as to directly communicate with the crank chamber 1a of the engine 1 instead of the oil mist separator 13. .

DESCRIPTION OF SYMBOLS 1 ... Engine 1a ... Crank chamber 2 ... Intake system (intake passage)
5 ... Turbocharger (supercharger)
7 ... Throttle valve 10 ... Blow-by gas reduction passage 11 ... New air introduction passage 12 ... PCV valve 15 ... Blow-by gas flow control orifice (variable orifice for blow-by gas flow control)
16 ... New air flow control orifice (variable orifice functioning as a new air flow control means)
28 ... PCV valve 40 ... Blow-by gas flow control orifice (variable orifice for blow-by gas flow control)

Claims (5)

A blow-by gas reduction passage that communicates a position downstream of the throttle valve in the intake passage of the supercharged engine and the crank chamber of the engine;
A fresh air introduction passage communicating the position upstream of the throttle valve in the intake passage and the crank chamber;
A PCV valve that is provided in the blow-by gas reduction passage and controls the flow rate of the blow-by gas toward the intake passage when the boost pressure downstream of the throttle valve in the intake passage is negative.
A fresh air flow rate control that introduces fresh air into the crank chamber from a position downstream of the throttle valve in the intake passage when the boost pressure downstream of the throttle valve in the intake passage becomes a positive pressure. Means, and
The fresh air flow control means supplies fresh air to the crank chamber in an intermediate load operation region where the boost pressure downstream of the throttle valve in the intake passage is positive and lower than a predetermined set pressure. On the other hand, in the high load operation region where the boost pressure at the downstream side of the throttle valve is equal to or higher than the set pressure in the intake passage, a new passage from the downstream side of the throttle valve to the crank chamber is introduced in the intake passage. The engine ventilation system is characterized in that the introduction of the air is stopped, or the flow rate of the fresh air is made at least smaller than the maximum flow rate in the medium load operation region. A variable orifice functioning as the fresh air flow rate control means is provided in the blow-by gas reduction passage,
In the high load operation region, the flow passage cross-sectional area of the variable orifice functioning as the fresh air flow control means is at least smaller than the flow passage cross-sectional area in the medium load operation region, The engine ventilation system according to claim 1.   3. The PCV valve according to claim 2, wherein the PCV valve has a variable orifice that functions as the fresh air flow rate control means, in addition to the variable orifice for blow-by gas flow rate control, which is the original function of the PCV valve. Engine ventilation system. A variable orifice functioning as the fresh air flow control means is arranged in parallel with the PCV valve,
In the high load operation region, the flow passage cross-sectional area of the variable orifice functioning as the fresh air flow control means is at least smaller than the flow passage cross-sectional area in the medium load operation region, The engine ventilation system according to claim 1.   The engine ventilation system according to any one of claims 2 to 4, wherein the variable orifice functioning as the fresh air flow rate control means is closed in the high load operation region.

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