JPH0417767Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a forced ventilation system (hereinafter referred to as a PCV system) for an engine equipped with a supercharger.

[Conventional technology]

In an engine equipped with a turbocharger, if the boost pressure increases abnormally, such as during deceleration when the throttle valve closes, surging may occur, damaging the compressor or bearings, or causing abnormal noise in the intake system. may occur. To prevent this, some turbochargers are equipped with a bypass pipe that connects the upstream and downstream sides of the turbocharger and a bypass valve that opens and closes the bypass pipe.

On the other hand, engines with turbochargers
As disclosed in Japanese Utility Model Application No. 60-61425, the PCV device includes a first blow-by pipe that communicates a ventilation case formed in the head cover of the engine with the downstream side of the throttle valve;
It is known to have a second blow-by pipe that communicates the ventilation case with the upstream side of the compressor, and an orifice is provided in the blow-by pipe. The orifice of the first blow-by pipe is for preventing a large amount of high-pressure air from flowing into the ventilation case during supercharging.

[Problem that the invention attempts to solve]

In order to improve the responsiveness of the surging prevention effect, it is desirable that the bypass pipe of the supercharger connects the upstream and downstream sides of the compressor over the shortest distance, that is, opens just before the compressor. on the other hand,
The second blowby pipe of the PCV system has the function of recirculating the blowby gas in the ventilation case from the upstream side of the compressor to the combustion chamber of the engine when the throttle valve is fully open, making it easier to guide the blowby gas. In order to do this second
It is desirable that the blow-by pipe also be opened just before the compressor where the flow velocity is high. However, space is required around the compressor for these pipes, and space must also be secured to mount the bypass valve, which poses a problem in that it imposes certain restrictions on downsizing the engine room. Furthermore, since the first blow-by pipe has the orifice as described above, there is a problem in that a sufficient scavenging effect cannot be obtained when blow-by gas in the ventilation case is scavenged toward the throttle valve side.

[Means for solving problems]

In order to solve the above problems, this invention
The PCV device connects the second blow-by pipe to a bypass valve provided in the bypass pipe, and is provided with a flow rate control means that restricts only the flow from the bypass pipe to the ventilation case, and the bypass valve is When the pressure on the downstream side of the throttle valve is positive, the upstream side of the supercharger and the second blow-by pipe are communicated, and when the pressure on the downstream side of the throttle valve is a negative pressure that is greater than a predetermined value, the bypass pipe is communicated and bypassed. The tube and the second blow-by tube are configured to communicate with each other.

〔Example〕

The present invention will be explained below with reference to the illustrated embodiments.

FIG. 1 shows an embodiment of the present invention. A piston 12 is slidably accommodated in a cylinder bore 11 formed in a cylinder block 10, and a combustion chamber 13 is formed above the piston 12. An intake port 15 and an exhaust port 16, which are formed in the cylinder head 14 and open to the combustion chamber 13, are opened and closed by an intake valve 17 and an exhaust valve 18, respectively. Head cover 19 that covers the cylinder head 14
A ventilation case 20 is formed inside,
Blow-by gas is this ventilation case 2
It is designed to be temporarily held within 0.

The turbocharger 21 includes a compressor 22, a turbine 23, and a shaft 24 that connects them.
The turbines 23 are arranged within the exhaust passages 26, respectively. The turbine 23 is rotationally driven by the exhaust gas flowing in the exhaust passage 26, which rotates the compressor 22, thereby supercharging the amount of intake air.

The upstream and downstream sides of the compressor 22 are connected by a bypass pipe 30, and a bypass valve 31 consisting of a three-way valve is provided in the middle of the bypass pipe 30. The first port 31a of the bypass valve 31 opens on the upstream side of the compressor 22, and the second port 31b opens on the upstream side of the compressor 22.
opens downstream of the compressor 22. on the other hand,
The downstream side of the throttle valve 32 located downstream of the compressor 22 and the ventilation case 20 communicate with each other through a first blow-by pipe 33, and an orifice 34 is formed in the first blow-by pipe 33. Further, the ventilation case 20 and the third port 31c of the bypass valve 31 are communicated through a second blow-by pipe 35, and a pressure transmission valve mechanism 36 is provided in the middle of the second blow-by pipe 35. The pressure transmission valve mechanism 36 includes a check valve 37 that prevents flow from the bypass pipe 30 to the ventilation case 20 and an orifice 38 .

Bypass valve 31 is switched and driven by actuator 40 . Actuator 40 is Ciel 4
1, a diaphragm 42 is provided to form a pressure-changing chamber 43, and a spring 44 for biasing the diaphragm 42 is provided in the pressure-changing chamber 43.The diaphragm 42 is connected to the valve body of the bypass valve 31, and the pressure-changing chamber 43 The chamber 43 communicates with a portion of the intake passage 25 downstream of the throttle valve 32 via a connecting pipe 45. Therefore, when the throttle valve 32 opens and supercharging pressure, that is, positive pressure is generated by the turbocharger 21 on the downstream side thereof, the diaphragm 42 is biased by the spring 44 and is in the forward position, and the bypass valve 31 is in the first position.
and the third ports 31a and 31c are communicated with each other.
On the other hand, when the throttle valve 32 is closed and a large negative pressure is generated on the downstream side thereof, the diaphragm 42 is sucked by the negative pressure introduced into the variable pressure chamber 43 and is in the retracted position, and the bypass valve 31 is in the first and second positions. 2, and third ports 31a, 31b, and 31c.

FIG. 2 shows the structure of the bypass valve 31. The bypass valve 31 is supported by an air cleaner hose 46 that constitutes a portion of the intake passage 25 upstream of the compressor 22, and the first port 31a is connected to a hole 47 (bypass pipe 30 (first
(located on the upstream side of Figure)). The second port 31b faces perpendicularly to the first port 31a, and the third port 31c extends toward the opposite side of the first port 31a. An actuator 40 is disposed above the bypass valve 31.
0 is formed with a port 48 for connection to a communication pipe 45 (FIG. 1).

The device of this embodiment operates as follows.

When the opening degree of the throttle valve 32 falls below a predetermined value during deceleration, etc., and a large negative pressure is generated downstream of the throttle valve 32, this negative pressure is applied to the actuator 40.
The pressure is transmitted to the variable pressure chamber 43, thereby displacing the diaphragm 42 and switching the bypass valve 31. That is, the bypass valve 31 is connected to the bypass pipe 30
At the same time, the bypass pipe 30 is brought into communication with the second blow-by pipe 35. Therefore, the occurrence of surging around the compressor 22 is prevented, and air on the upstream side of the compressor 22 is routed from the first and third ports 31a and 31c to the second port.
Air is guided to the ventilation case 20 through the blow-by pipe 35, and the air downstream of the compressor 22 is passed through the second and third ports 31b and 3.
1c to the ventilation case 20 through the second blow-by pipe 35, and an appropriate amount of air is supplied into the ventilation case 20 by the pressure transmission mechanism 36, while the first blow-by gas pipe 3
3 to the downstream side of the throttle valve 32, a reliable scavenging action is performed.

On the other hand, when the opening degree of the throttle valve 32 is larger than a predetermined value, the pressure on the downstream side of the throttle valve 32 becomes positive pressure (supercharging pressure by the turbocharger 21),
This causes the diaphragm 4 of the actuator 40 to
2 is pushed forward by the spring 44, and the bypass valve 31 is switched. That is, the bypass valve 31
makes the first and third ports 31a and 31c communicate with each other, and closes the second port 31b.
Therefore, high-pressure air downstream of the throttle valve 32 is supplied to the ventilation case 20 through the first blow-by pipe 33, passes from the second blow-by pipe 35 through the third and first ports 31c, 31a, It flows back to the upstream side of the compressor 22. At this time, the check valve 37 of the pressure transmission valve mechanism 36 opens, so the flow rate of gas passing through the second blow-by pipe 35 becomes large, and the ventilation case 2
Sufficient scavenging action within 0 is performed.

[Effect of idea]

As described above, according to the present invention, since the second blow-by pipe is connected to the bypass pipe, the piping around the compressor is simplified, and space inside the engine can be saved. Also, blow-by gas in the ventilation case is reliably scavenged during both deceleration and supercharging.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an embodiment of the present invention;
The figure is a plan view showing the mounting structure of the bypass valve. 20... Ventilation case, 21... Turbocharger, 30... Bypass pipe,
31... Bypass valve, 32... Throttle valve, 3
3...first blow-by pipe, 35...second blow-by pipe, 36...pressure transmission valve mechanism (flow control means).

Claims (1)

[Claims for Utility Model Registration] 1. An engine with a supercharger that connects the upstream and downstream sides of a supercharger with a bypass pipe and is provided with a bypass valve that opens and closes the bypass pipe, which a first blow-by pipe that communicates the downstream side of the throttle valve located downstream of the engine with a ventilation case formed in the head cover of the engine; and a second blow-by pipe that connects the ventilation case and the bypass valve. , a flow rate control means for restricting only the flow from the bypass pipe to the ventilation case, and the bypass valve is configured to control the flow rate between the upstream side of the supercharger and the second side when the pressure on the downstream side of the throttle valve is positive pressure.
A supercharging characterized in that a blow-by pipe is brought into communication, and when the pressure on the downstream side of the throttle valve is a negative pressure greater than a predetermined value, the bypass pipe is brought into communication, and the bypass pipe and the second blow-by pipe are brought into communication with each other. Forced ventilation system for motorized engines. 2. Utility model registration claim 1, wherein the flow rate control means is a pressure transmission valve mechanism having a check valve and an orifice that prevent the flow from the bypass pipe to the ventilation case. forced ventilation system.