JPS633127B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a blow-by gas recirculation system for an engine, which is equipped with a supercharger and an air flow meter having a flap in an intake passage.

2. Description of the Related Art In general, engines for automobiles and the like are provided with a device that recirculates blow-by gas from the crankcase to an intake passage in order to prevent air pollution.

Conventionally, when a blow-by gas recirculation device is installed in a supercharged engine, as shown in Japanese Utility Model Application Publication No. 169464/1983, a first air recirculation system is used to connect the intake passage downstream of the throttle valve and the crankcase via the PCV valve. (the second blow-by hose as referred to in the above publication); and a second communication passage (the first blow-by hose as referred to in the above publication) that connects the intake passage upstream of the throttle valve and the supercharger to the crankcase. A structure is known in which this is provided. With this structure, when the PCV valve opens during low-load operation, blow-by gas in the crankcase is sucked into the intake passage downstream of the throttle valve through the first communication passage, and at the same time, for ventilation purposes. 2nd above
Air is supplied into the crankcase from the communication passage. In addition, when the supercharger is operating under high load, the PCV valve closes and as the pressure inside the crankcase increases, blow-by gas flows into the second
It is designed to be sent to the intake passage through the communication passage. Therefore, the second communication path is used both for ventilation during low-load operation and for blow-by gas distribution during high-load operation.

By the way, if an air flow meter for the fuel injection device is installed upstream of the throttle valve and supercharger, the above ventilation needs to be performed using air measured by the air flow meter, so the above As shown in the above publication, the second communication passage was connected to the intake passage downstream of the air flow meter. However, in commonly used air flow meters with flaps, the flaps act as intake resistance, and the intake passage between the air flow meter and the supercharger remains under negative pressure even during high-load operation. During operation, blow-by gas in the crankcase is excessively drawn into the intake passage through the second communication passage. Therefore, there is a problem in that engine lubricating oil mixes with the blow-by gas and flows out into the intake passage in large quantities, resulting in an increase in oil consumption.

In addition, in the device disclosed in the above publication, a bypass passage that bypasses the PCV valve, a reed valve, etc. are provided in the first communication passage, so that a part of the blow-by gas also flows to the first communication passage during high-load operation. However, even with this structure, the contamination of the supercharger with the above-mentioned oil can only be reduced, but the amount of oil consumed cannot be reduced.

In view of these circumstances, the present invention satisfies the condition of ventilating the inside of the crankcase with air measured by an air flow meter during low-load operation, while also preventing oil from entering the intake passage during blow-by gas recirculation during high-load operation. The present invention provides a blow-by gas recirculation device for a supercharged engine that can prevent oil leakage and reduce oil consumption.

Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

In the figure, 1 is an engine cylinder, 2 is a piston, and 3 is a crankcase. The crankcase 3 communicates with a cylinder head cover 4, and an oil pan 5 is attached to the lower end of the crankcase 3. Reference numeral 6 denotes an intake passage, in which a throttle valve 7 and a supercharger 8 are provided, and an air cleaner 9 is provided upstream of these.
An air flow meter 10 having a flap 10a is provided downstream of the flap 10a. The amount of fuel injected from the fuel injection valve 11 is controlled in accordance with the intake air flow rate detected by the air flow meter 10.

In the example shown in the figure, the supercharger 8 has an exhaust passage 1
The blower 8 is interlocked with the turbine 8b arranged at the
A rotating turbo supercharger is used, and the maximum supercharging pressure is controlled by a waste gate passage 13 and a waste gate valve 14. However, a vane type supercharger driven by a crankshaft or the like may be used as the supercharger. Further, although the positional relationship between the throttle valve 7 and the supercharger 8 is not limited in the present invention, the supercharger 8 is usually arranged upstream of the throttle valve 7.

In this engine, a blow-by gas recirculation device includes a first communication passage 15 that communicates the intake passage 6 downstream of the throttle valve 7 and the crankcase 3 via the PCV valve 16, and a first communication passage 15 that opens during low-load operation. a second communication passage 17 that communicates the intake passage 6 upstream of the throttle valve 7 and downstream of the air flow meter 10 with the crankcase 3 via the on-off valve 21;
and the above-mentioned on-off valve 21 that opens during high-load operation.
intake passage 6 upstream of air flow meter 10 via
and a third communication path 1 that communicates with the crankcase 3.
8 is provided.

For example, one end of the first communicating path 15 is connected to the surge tank 19 downstream of the throttle valve 7, and the other end is connected to the surge tank 19 downstream of the throttle valve 7.
It is connected to the cylinder head cover 4 via a PCV valve 16. The above PCV valve 16 is
During low-load operation without supercharging, the valve opens and the flow rate of blow-by gas is controlled according to the pressure difference between the crankcase 3 side and the intake passage 6 side, and during high-load operation with supercharging, the intake air It opens and closes in response to an increase in pressure on the passage 6 side, thereby blocking the first communication passage 15. In addition, the second communication path 17 and the third
The communication passages 18 are branched from passages 20 connected to the crankcase 3 or the cylinder head cover 4, and are connected to the respective predetermined positions of the intake passage 6, and the two communication passages 18 are connected to the above-mentioned branch points.
A two-way valve 21 that also serves as an on-off valve for valves 7 and 18 is provided. This valve 21 is, for example,
It is operated by a solenoid device 23 in response to a signal from an operation detection sensor 22 of the PCV valve 16. During low load operation when the PCV valve 16 is open, the second communication passage 17 is opened and the third communication passage 18 is closed as shown in the figure, and during high load operation when the PCV valve 16 is closed, the second The communication path 17 is closed and the third communication path 18 is opened.

An oil separator 24 may be provided in the third communication path 18 if necessary. In this case, the oil separated in the oil separator 24 is passed through the oil recovery path 25 to the oil pan 5.
Please make sure that it is collected by.

The operation of this blow-by gas recirculation device will be explained next.

During low load operation when supercharging is not performed, the above
When the PCV valve 16 is opened, the two-way valve 21 opens the second communication path 17 and closes the third communication path 18.
Therefore, as shown by arrows A and B in the figure, the blow-by gas in the crankcase 3 is sucked into the communication passage 6 downstream of the throttle valve 7 through the first communication passage 15, and the blow-by gas is sucked into the intake passage upstream of the throttle valve 7. 6 to 2nd
Air is sent into the crankcase 3 through the communication passage 17 to perform ventilation. In this case, since ventilation is performed using the air measured by the air flow meter 10, no error occurs in the detection of the intake air flow rate and the control of the fuel injection amount based on this.

Furthermore, during high-load operation in which supercharging is performed by the supercharger 8, the PCV valve 16 is closed, and the second communication passage 17 is closed and the third communication passage 18 is opened in a two-way state. Valve 21 is switched. Therefore, as shown by arrow C, blow-by gas flows out into the third communication passage 18 as the pressure inside the crankcase 3 increases, and the blow-by gas flows out into the third communication passage 18.
The air is then sent to the intake passage 6 upstream of the air flow meter 10. This suppresses engine lubricating oil from flowing into the intake system. In other words,
Conventionally, when blow-by gas is returned to the intake passage downstream of the air flow meter where negative pressure is created due to the intake resistance due to the flap of the air flow meter during high loads, the flow rate and flow velocity of the blow-by gas are large, so the lubrication The oil mixes with the blow-by gas in the form of a mist and flows out into the intake system. In this case, even if an oil separator is provided, the oil cannot be easily separated. On the other hand,
During high load operation, the first and second communication passages 15,
If the blow-by gas is recirculated into the intake passage 6 upstream of the air flow meter 10 through the third communication passage 18 provided separately from the air flow meter 17, the flow rate and flow velocity of the blow-by gas are reduced because this position is at almost atmospheric pressure. This will prevent oil from flowing out.

In addition, in this device, there is no practical problem even if the timing at which the PCV valve 16 is in the closed state and the timing at which the two-way valve 21 is switched are slightly different from each other.
Furthermore, since the air cleaner 9 causes almost no intake resistance, the connection point of the third communicating passage 18 to the intake passage 6 can be upstream or downstream of the air cleaner 9 as long as it is upstream of the air flow meter 10. good.

As described above, the device of the present invention satisfies the condition that during low-load operation, blow-by gas is recirculated and ventilated through the first and second communication paths, and ventilation is performed using air measured by an air flow meter. It satisfies me. Furthermore, during high-load operation, the blow-by gas is returned to the intake passage upstream of the air flow meter through the third communication path, which prevents lubricating oil from mixing with the blow-by gas and flowing out during high-load operation. , which can significantly reduce oil consumption.

[Brief explanation of the drawing]

The figure is a schematic diagram showing an embodiment of the device of the present invention. 3... Crank case, 6... Intake passage, 7... Throttle valve, 8... Supercharger, 10... Air flow meter, 15
...First communication path, 16...PCV valve, 17...Second communication path, 18...Third communication path, 21...Way valve (opening/closing valve).

Claims (1)

[Claims] 1. In an engine equipped with a throttle valve, a supercharger, and an air flow meter located upstream of these and having a flap in the intake passage, the intake passage downstream of the throttle valve communicates with the crankcase via the PCV valve. a second communication passage that communicates the intake passage upstream of the throttle valve and downstream of the air flow meter with the crankcase via an on-off valve that opens during low-load operating conditions; A blow-by gas recirculation device for a supercharged engine, characterized in that a third communication passage communicates an intake passage upstream of an air flow meter with a crankcase via an on-off valve that opens when the air flow meter opens.