JP2010112178A - Ventilation system for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ventilation system capable of suppressing the deterioration of engine oil within a crankcase, in a supercharged engine. <P>SOLUTION: This ventilation system, as a positive crankcase ventilation system for an engine 1 with a turbocharger 5, includes a blowby gas recirculation passage 10, a fresh air introduction passage 11 and a PCV valve 12 with an orifice 24. While blowby gas is recirculated to an intake system 2 side through the blowby gas recirculation passage 10 during a low load, fresh air is introduced to the crankcase 1a through the fresh air introduction passage 11. When boost pressure in the intake system 2 becomes positive pressure, while blowby gas is recirculated to the intake system 2 side through the fresh air introduction passage 11, fresh air is introduced through the blowby gas recirculation passage 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a ventilation system for a supercharged engine using a turbocharger or the like, and particularly focuses on improving the ventilation rate of a positive crankcase ventilation system (PCV system) that constitutes a part of a blow-by gas processing system. Technology.

  A PCV system in a naturally aspirated or non-supercharged engine is known as described in, for example, Japanese Patent Application Laid-Open No. 2003-259542. The intake manifold, which is an intake passage, has a position downstream of the throttle valve and a crank chamber (crank) of the engine. A blow-by gas reduction passage that communicates with the case), a fresh air introduction passage that communicates a position upstream of the throttle valve in the intake manifold with the crank chamber, and a PCV valve provided in the blow-by gas reduction passage. I have.

  When the engine is under a 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 provided in the rocker cover etc. It mixes with fresh air in the clan case, and is guided to a position downstream of the throttle valve in the intake manifold via the PCV valve. Further, when the engine is heavily loaded, blow-by gas in the crankcase is also discharged through the fresh air introduction passage, and the blow-by gas is guided to a position upstream of the throttle valve in the intake manifold.

Such a configuration is basically the same in, for example, a turbocharged engine using a turbocharger, and a PCV system in the supercharged engine is disclosed in Patent Document 2.
JP 2007-16664 A JP 2003-184532 A

  In the conventional ventilation system, the boost pressure becomes large (approaching the positive pressure) at the time of high engine load as described above. Therefore, the blow-by gas discharged through the PCV valve is a blow-by gas generated from the engine itself. Less than the amount. As a result, ventilation in the crankcase becomes slow, and engine oil is degraded by blow-by gas.

  Especially in the case of a supercharged engine, the boost pressure becomes higher and positive pressure due to the supercharging pressure even when the engine is under a low load compared to a naturally aspirated or non-supercharged engine. The operation region where fresh air is not introduced into the case increases, and as a result, the engine oil in the crankcase is more easily deteriorated by blow-by gas, which is not preferable.

  The present invention has been made paying attention to such a problem, and an object of the present invention is to provide a ventilation system capable of suppressing deterioration of engine oil in a crankcase particularly in a supercharged engine.

  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 communicating the side position with the crank chamber, and a PCV valve provided in the blow-by gas reduction passage, and a boost pressure at a position downstream of the throttle valve in the intake passage is provided. When positive pressure is reached, fresh air is introduced into the crank chamber through at least a part of the blow-by gas reduction passage.

  In this case, as described in claim 2, when the boost pressure at a position downstream of the throttle valve in the intake passage becomes a positive pressure, the crank chamber is passed through the blow-by gas reduction passage including the PCV valve. It is desirable for the simplification of the structure that fresh air is introduced.

  More specifically, as described in claim 3, the PCV valve is provided with an orifice for introducing fresh air when the boost pressure becomes a positive pressure, in addition to the original flow rate control function of the PCV valve. It shall be.

  Alternatively, as described in claim 4, when the boost pressure at a position downstream of the throttle valve in the intake passage becomes a positive pressure, the crank chamber is newly introduced through a check valve in parallel with the PCV valve. It is assumed that qi is introduced.

  According to the first aspect of the present invention, since fresh air is reliably introduced into the crank chamber even when the boost pressure becomes positive, the ventilation efficiency is improved, and the engine oil in the crankcase is improved. Can be prevented.

  Particularly, according to the invention described in claim 2, since fresh air is introduced using the existing passage, it is advantageous in terms of simplification of the structure.

  Further, according to the invention described in claim 3, there is an advantage that the intended object can be achieved by adding a slight improvement to the existing PCV valve.

  According to the fourth aspect of the present invention, there is an advantage that fresh air can be introduced into the crank chamber more reliably and stably by providing the check valve separately from the PCV valve.

  1 to 5 are views showing a more specific first embodiment of the ventilation system according to the present invention. In particular, FIG. 1 shows the flow of blowbar gas and fresh air when the engine is under low load. Shows the flow of blowbar gas and fresh air at high engine loads.

  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, In addition to a compressor impeller 5b and an intercooler 6 of a turbocharger 5 serving as a feeder, a throttle valve 7 is interposed. 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 recirculated 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 to communicate the position upstream of the compressor impeller 5b of the turbocharger 5 with the crank chamber 1a.

  A PCV valve 12 and an oil mist separator 13 are interposed in series in the blow-by gas reduction passage 10 so that the PCV valve 12 is on the throttle valve 7 side. A mist separator 14 is interposed. Further, in the PCV valve 12, an orifice 24 for introducing fresh air when the boost pressure that is the intake pressure of the intake system 2 becomes a positive pressure is described later, in addition to the flow control function inherent to the PCV valve 12. It is provided in series on the oil mist separator 13 side. Any of the oil mist separators 13 and 14 may be provided integrally with the rocker cover (cylinder head cover) in addition to the case where the oil mist separators 13 and 14 are provided independently of the engine 1 by a hose connection or the like.

  3 shows details of the PCV valve 12, and FIG. 4 shows details of the valve body 16 of the PCV valve 12. The PCV valve 12 is a hollow valve body having a stepped cylindrical shape on the inner and outer peripheral surfaces. A (casing or housing) 15 has a spool-type valve body 16 slidably inserted therein, and one port 17 of the valve body 15 is disposed downstream of the throttle valve 7 in the intake system 2 and on the opposite side (the other). Are connected to the crank chamber 1a side (oil mist separator 13 side). The valve body 16 is urged toward the other port 18 by a compression coil spring 19 interposed between the valve body 16 and the valve body 15. The valve body 15 is formed by screwing and connecting two pieces 15a and 15b divided into two in the longitudinal direction.

  A throat portion 20 is formed with a step portion at the central portion in the axial center direction on the inner peripheral surface of the valve body 15, while the outer periphery of the valve body 16 inserted into the inner periphery of the valve body 15 including the throat portion 20. The surface is formed as a tapered shape having a smoother curvature toward the end on the side opposite to the smaller diameter side closer to the end on the port 17 side and gradually increasing in diameter toward the end on the opposite side. It is. Therefore, when the boost pressure on the intake system 2 side is a negative pressure, the valve body 16 pulled by the negative pressure slides and displaces with respect to the valve body 15, and the boost pressure and the elasticity of the compression coil spring 19 are detected. The valve body 16 stops at a position where the force is balanced. That is, when the throat portion 20 and the valve body 16 move relative to each other according to the magnitude of the boost pressure, the opening degree between them and the flow rate of the blow-by gas flowing through the PCV valve 12 are continuously variably controlled. become. A predetermined gap is secured between the port 18 on the valve body 15 side and the largest diameter portion of the valve body 16 excluding the flange portion 21 described later, and this gap functions as the orifice 24. It will be.

  As shown in FIG. 4, a large-diameter flange portion 21 is formed on the end portion of the valve body 16 in the PCV valve 12 on the port 18 side of the valve body 15, as shown in FIG. 4. It functions as a spring seat (spring seat) for the compression coil spring 19 on the valve body 16 side. The flange portion 21 is formed with a plurality of cylindrical protrusion portions 22 protruding toward the port 18 side of the valve body 15 at equal pitches in the circumferential direction. By contacting the vertical wall surface 23 near the port 18 on the peripheral surface, the projection 22 itself functions as a stopper portion that regulates the position of the valve body 16 in the biasing direction by the compression coil spring 19.

  Even when the protrusion 22 on the valve body 16 side contacts the vertical wall surface 23 as described above, a gap corresponding to the height of the protrusion 22 between the flange portion 21 and the vertical wall surface 23, That is, a gap G having a predetermined size communicating with the orifice 24 is secured. Thereby, even if the valve body 16 is slid to the stroke limit position by the elastic force of the compression coil spring 19 and the protrusion 22 on the flange 21 side is seated on the vertical wall surface 23, not only the throat portion 20, A predetermined opening degree is also secured in the orifice 24 communicating with the gap G.

  FIG. 5 shows 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 or the like. Reference symbol A indicates the amount of blow-by gas generated, and reference symbol B indicates the blow-by gas reduction passage 10. The flow characteristic of blow-by gas and the like in the oil mist separator 13 on the side, and the symbol C indicate the flow characteristic of blow-by gas and the like in the oil mist separator 14 on the fresh air introduction passage 11 side. In FIG. 5, the left side where the boost pressure is negative and the degree thereof is large is the low load side, and on the contrary, the right side where the boost pressure is positive and the degree is large is the high load side.

  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-blow-by gas flow characteristics of the PCV valve 12 including the orifice 24 are as follows: It has been adjusted in advance so as to be substantially the same as the characteristic indicated by the symbol B in FIG.

  According to the ventilation system configured as described above, as shown in FIGS. 1 and 5, when the engine 1 is under a low load, that is, in the region P1 in FIG. 5, the pressure on the downstream side of the throttle valve 7 in the intake system 2 Since a certain intake pressure, that is, the boost pressure is a negative pressure and the degree of the negative pressure is large, in the PCV valve 12 shown in FIG. 3, the valve body 16 is moved in the left direction in FIG. The gap (opening) between the throat portion 20 and the valve body 16 becomes small due to being pulled greatly. Therefore, in the region P1 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. It is relatively small compared to other areas.

  In the area P1 of FIG. 5, the flow rate of the blow-by gas flow indicated by reference sign 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 rather than the amount of blow-by gas generated indicated by reference sign A. Therefore, the difference in flow rate between the two becomes the amount of fresh air introduced into the crank chamber 1a. Therefore, as shown in FIG. 1, the blow-by gas is 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, and then into the crank chamber 1 a through the fresh air introduction passage 11. Fresh air is introduced and the crank chamber 1a is ventilated.

  Here, since the fresh air introduced into the crank chamber 1a through the fresh air introduction passage 11 passes through the oil mist separator 14, the flow rate characteristic of the oil mist separator 14 indicated by symbol C is inherent in the region P1 of FIG. If it exists, it becomes “positive (+)”, but the flow rate of blow-by gas exhausted to the upstream side of the throttle valve 7 in the intake system 2 through the fresh air introduction passage 11 is set to “positive (+)” as will be described later. Therefore, the characteristic indicated by the symbol C is “negative (−)” in the region P1 of FIG.

  Further, in the region P2 of FIG. 5 where the load of the engine 1 becomes high, the boost pressure gradually approaches the positive pressure, so in the PCV valve 12 of FIG. The opening degree at the throat portion 20 is increased. Therefore, as the amount of blow-by gas generated indicated by reference A increases, the blow-by gas flow of reference B discharged to the intake system 2 side through the oil mist separator 13 and the PCV valve 12 of the blow-by gas reduction passage 10, and the fresh air introduction passage 11 The amount of fresh air introduced from will also increase.

  Then, at the position immediately before the positive pressure where the boost pressure in FIG. 5 approaches the positive pressure as much as possible, the blow-by gas flow rate of the symbol 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 amount of blow-by gas generated as indicated by symbol A is reduced, and at the same time, the amount of fresh air introduced as indicated by symbol C from the fresh air introduction passage 11 to the crank chamber 1a is also reduced. Eventually, as shown in FIG. Blow-by gas is also discharged from the introduction passage 11 to the upstream side of the throttle valve 7 in the intake system 2.

  In the region P3 where the load of the engine 1 is further increased and the boost pressure in FIG. 5 turns to a positive pressure due to the supercharging pressure of the turbocharger 5 shown in FIG. 1, the PCV valve 12 in FIG. Receives a boost pressure in addition to the elastic force of the compression coil spring 19 and slides and displaces to the right in the figure, and the protrusion 22 on the valve element 16 side is seated on the vertical wall surface 23 as shown in the figure. . In this state, the opening at the throat portion 20 is maximized, and an opening corresponding to the orifice 24 is secured on the port 18 side.

  Then, after the boost pressure has changed to a positive pressure, that is, in the region P3 of FIG. 5, as the blow-by gas generation amount indicated by the symbol A increases, the throttle in the intake system 2 passes through the fresh air introduction passage 11 including the oil mist separator 14. The blow-by gas flow rate (symbol C) discharged to the upstream side of the valve 7 rapidly increases, and the blow-by gas flow rate at the PCV valve 12 and the oil mist separator 13 on the blow-by gas reduction passage 10 side is “negative (−)”. "Will turn to the side.

  The fact that the gas flow rate on the blow-by gas reduction passage 10 side turns to the “negative (−)” side means that fresh air on the downstream side of the throttle valve 7 flows backward to the crank chamber 1 a side through the PCV valve 12 and the oil mist separator 13. This means that fresh air is being actively introduced to the crank chamber 1a side. That is, in the region P3 of FIG. 5, the blow-by gas discharge amount indicated by the symbol C through the fresh air introduction passage 11 is larger than the blow-by gas generation amount indicated by the symbol A, and the flow rate difference between them is the blow-by gas reduction passage 10. It will be the amount of fresh air introduced through. That is, the PCV valve 12 of FIG. 3 actively introduces fresh air to the crank chamber 1a side through the gaps between the orifice 24 and the throat portion 20 and the valve body 16 while the valve body 16 is in the position shown in FIG. Will be allowed.

  Therefore, as shown in FIG. 5, even in the region P3 after the boost pressure has changed to a positive pressure, it is possible to actively introduce fresh air into the crank chamber 1a and perform ventilation. The ventilation rate of the crank chamber 1a is greatly improved, and deterioration of engine oil due to blow-by gas can be suppressed.

  Here, in the first embodiment, the function of the orifice 24 is provided in the PCV valve 12 as shown in FIG. 3, but the conventionally known PCV valve and the orifice member are independent from each other. The same function can be achieved even if they are provided in series. However, the structure of FIG. 3 is more desirable in terms of reducing the number of parts and simplifying the structure.

  6 and 7 show a second embodiment of the present invention, and the same reference numerals are given to the parts common to FIGS. That is, FIG. 6 shows the flow of blow bar gas and fresh air when the engine is under low load, and FIG. 7 shows the flow of blow bar gas and fresh air when the engine is under high load.

  In the second embodiment, a conventionally known PCV valve 25 is employed in place of the PCV valve 12 shown in FIGS. 1, 2, and 3, and a check valve 27 is interposed in parallel with the PCV valve 25. is there. The conventionally known PCV valve 25 is a type that does not have the function of the orifice 24 in the structure of FIG.

  That is, as shown in FIG. 6, the blow-by gas reduction passage 10 is branched or joined to the downstream position of the throttle valve 7 in the intake system 2, but the bypass passage 26 is branched or joined from the equivalent position. The bypass passage 26 is provided with a check valve 27 and the other end of the bypass passage 26 is connected to the oil mist separator 13.

  According to the second embodiment, as shown in FIG. 6, when the engine is under a low load, the boost pressure on the intake system 2 side is a negative pressure, so the oil mist separator 13 and the PCV valve 25 are The blow-by gas recirculation passage 10 having the function exhibits the original function, and the bypass passage 26 having the check valve 27 does not function at all.

  On the other hand, as shown in FIG. 7, when the load on the engine 1 increases and the boost pressure on the intake system 2 side becomes positive, the check valve 27 in the bypass passage 26 opens, and the orifice in the PCV valve 12 in FIG. As in FIG. 24, the check valve 27 positively allows the introduction of fresh air, and as a result, the same function as that of the first embodiment is exhibited in the second embodiment. become.

  FIG. 8 shows a third embodiment of the present invention, and shows the flow of blow bar gas and fresh air at the time of low engine load similar to FIG.

  In the third embodiment, as shown in FIG. 8, a bypass passage 26 having a check valve 27 is directly connected to the crank chamber 1 a of the engine 1 instead of the oil mist separator 13.

  Also in this case, it goes without saying that the same function as in the second embodiment is exhibited.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the 1st Embodiment of this invention, and is structure explanatory drawing which shows the flow of blow bar gas and fresh air at the time of low engine load. FIG. 2 is a configuration explanatory view showing the flow of blow bar gas and fresh air when the engine is at a high load in FIG. 1. The expanded sectional view which shows the detail of the PCV valve | bulb in FIG. 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 an intake system in FIGS. The figure which shows the 2nd Embodiment of this invention, and is a structure explanatory drawing which shows the flow of blow bar gas and the fresh air at the time of the low load of an engine. FIG. 7 is a configuration explanatory diagram showing the flow of blow bar gas and fresh air when the engine is under high load. The figure which shows the 3rd Embodiment of this invention, and is a structure explanatory drawing which shows the flow of blow bar gas and the fresh air at the time of the low load of an engine.

Explanation of symbols

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 24 ... Orifice 26 ... Bypass passage 27 ... Check valve

Claims (4)

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 provided in the blow-by gas reduction passage;
With
When the boost pressure downstream of the throttle valve in the intake passage becomes a positive pressure, fresh air is introduced into the crank chamber through at least a part of the blow-by gas reduction passage. Features an engine ventilation system.   When the boost pressure downstream of the throttle valve in the intake passage becomes a positive pressure, fresh air is introduced into the crank chamber through the blow-by gas reduction passage including the PCV valve. The engine ventilation system according to claim 1, wherein the engine ventilation system is an engine ventilation system.   3. The engine according to claim 2, wherein the PCV valve is provided with an orifice for introducing fresh air when the boost pressure becomes a positive pressure, in addition to the flow rate control function inherent to the PCV valve. Ventilation system.   When the boost pressure downstream of the throttle valve in the intake passage becomes positive, fresh air is introduced into the crank chamber through a check valve in parallel with the PCV valve. The engine ventilation system according to claim 1.

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