JP5202235B2 - Engine ventilation system - Google Patents

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 problems, 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.

This onset Ming, a blowby gas returning passage connecting the crank chamber downstream position and the engine the throttle valve of the intake passage supercharged engine, upstream position than the throttle valve of the intake passage above A fresh air introduction passage communicating with the crank chamber, and a PCV valve provided in the blow-by gas reduction passage and having a flow rate adjusting function, wherein the boost pressure at a position downstream of the throttle valve in the intake passage is provided. There when it becomes a positive pressure, characterized in that the fresh air in the crank chamber through a blow-by gas returning communication path including the PCV valve is adapted to be introduced.

In this case, the PCV valve includes a cylindrical valve body, one port formed at one end of the valve body and connected downstream of the throttle valve in the intake passage, and the other valve body. The other port connected to the crank chamber side is formed with a hole diameter smaller than the inner diameter near the other end of the valve body at the end, and a stepped portion at the axially central portion of the inner peripheral surface of the valve body And a throat portion formed in a slidable manner in the valve body, and is formed in a tapered shape so that the diameter gradually increases from one end side to the other end side of the valve body, and the slide A spool-type valve body that continuously changes the opening degree at the throat portion by displacement, and a compression valve that urges the valve body toward the other end side of the valve body. And a flange portion formed at a position near the other end of the valve body in the valve body, and projecting from the flange portion toward the other port side, and the valve body is located on the other end side of the valve body. When sliding to the stroke limit position, the valve body abuts against the vertical wall surface formed by the inner diameter near the other end of the valve body and the other port, and ensures a predetermined gap between the flange portion and the vertical wall surface. A plurality of protrusions that regulate the position of the valve body, and the valve body is formed as the maximum diameter portion of the valve body on the other end side of the valve body excluding the flange portion, and the valve body is a stroke on the other end side of the valve body. And a head portion that is positioned on the inner peripheral side of the other port and forms an orifice between the other port when it is slid to the limit position.

According to the onset bright, since the boost pressure is reliably fresh air in the crank chamber even when it becomes a positive pressure is introduced, improved ventilation efficiency, suppress degradation of engine oil in the crankcase In addition, since new air is introduced using the existing passage, it is advantageous in terms of simplification of the structure. In addition, there is an advantage that the intended purpose can be achieved with a slight modification 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 head portion 16a as the maximum diameter portion of the valve body 16 excluding the flange portion 21 to be described later. It will function as the orifice 24.

  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, etc., where symbol A represents the amount of blow-by gas generated and symbol B represents 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, PCV valve 12 in FIG. 3, while the valve body 16 is in the position of the figure, the introduction of fresh air into the crank chamber 1a side through between gap between the orifice 24 and the throat portion 20 and the valve body 16 Will be positively tolerated.

  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.

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.

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
15 ... Valve body
16 ... Valve
16a ... Head part
17 ... One port
18 ... the other port
19 ... Compression coil spring
20 ... Throat
21 ... Flange
22 ... Protrusions
23 ... Vertical wall
24 ... Orifice
G ... Gap

Claims (1)

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 and having a flow rate adjusting function;
With
If the boost pressure downstream position than the throttle valve of the intake passage becomes positive, looks like fresh air is introduced into the crank chamber through a blow-by gas returning communication path including the PCV valve And
Furthermore, the PCV valve is
A tubular valve body,
One port formed at one end of the valve body and connected downstream of the throttle valve in the intake passage;
The other end of the valve body is formed with a hole diameter smaller than the inner diameter near the other end of the valve body, and the other port connected to the crank chamber side;
A throat portion formed with a step portion in the central portion in the axial center direction of the inner peripheral surface of the valve body;
The valve body is slidably inserted into the valve body, and is formed in a tapered shape so that the diameter gradually increases from one end side to the other end side of the valve body. A spool-type valve body that continuously changes the degree,
A compression coil spring that biases the valve body toward the other end of the valve body;
A flange portion formed at a position near the other end of the valve body among the valve bodies;
When the valve body slides and displaces to the stroke limit position on the other end side of the valve body, it is formed in a vertical direction formed by the other port and the inner diameter near the other end of the valve body. A plurality of protrusions that abut against the wall surface and regulate the position of the valve body while ensuring a predetermined gap between the flange portion and the vertical wall surface;
It is formed as the maximum diameter part of the valve body on the other end side of the valve body excluding the flange, and when the valve body slides to the stroke limit position on the other end side of the valve body, the other port A head portion that is located on the inner peripheral side of the other and forms an orifice with the other port;
Engine ventilation system to have characterized Rukoto have.

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