JPH0678726B2 - Blow-by control device for alcohol fuel engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a blow-by control device for an alcohol fuel engine.

(Prior art) Recently, research and development of alcohol fuel engine using alcohol (methanol) as fuel for the purpose of reducing urban exhaust pollution such as NOx and diversifying transportation fuel (gasoline substitute).
Development is starting to take place.

The structure itself of such an alcohol fuel engine is similar to that of a normal gasoline engine,
Basically, there is no difference (for example, JP-A-58-1061).
(See Japanese Patent No. 47).

Also in the case of the alcohol fuel engine, a blow-by gas processing device for returning the blow-by gas to the intake passage of the engine and re-combusting in the engine combustion chamber is provided from the viewpoint of exhaust pollution prevention (countermeasures against unburned HC). There is something. This blow-by gas treatment device is generally constructed so as to communicate with the intake upstream side of the intake passage from the crankcase, cylinder head portion, etc. of the engine.

(Problems to be Solved by the Invention) However, in the alcohol fuel engine, since the alcohol as a fuel has a lower boiling point than that of gasoline and the component composition is relatively pure, There are different circumstances, and the following special problems occur especially when the engine is warming up.

That is, even in an alcohol-fueled engine, when the engine is cold, the air-fuel mixture state is maintained at a particularly high concentration. In that case, when the engine warms up and the oil temperature in the oil pan reaches the boiling point of alcohol, A large amount of alcohol contained in the oil evaporates at once and the blow-by gas having a high alcohol concentration is rapidly returned to the intake air.

As a result, the air-fuel mixture concentration (air-fuel ratio) in the engine combustion chamber suddenly becomes rich, and the combustion state becomes unstable. Especially in the idling state, the engine speed decreases,
There is a problem that causes an engine stall.

(Means for Solving Problems) The present invention has been made for the purpose of solving the above-mentioned problems, and is a blow-by method in which alcohol is used as fuel and blow-by gas generated on the engine body side is returned to the intake passage side. In an alcohol fueled engine equipped with a gas treatment device, an evaporation state detecting means for detecting an evaporation state of alcohol on the engine body side in a warm-up state of the engine, and an operation in accordance with a detection output of the evaporation state detecting means, Flow rate control means for controlling the flow rate of blow-by gas recirculated from the engine body side to the intake passage side is provided.

(Operation) According to the above means, the blow-by gas containing the evaporated alcohol gas generated when the engine is warmed up can be recirculated to the engine combustion chamber after the flow rate is arbitrarily controlled according to the operating state of the engine. Even if a large amount of alcohol evaporates as the machine progresses, they will not be supplied to the engine combustion chamber at once. As a result, the combustion state becomes stable, and it is possible to prevent the engine speed from decreasing and the engine stall from occurring even during idling.

(Embodiment) FIG. 1 shows a blow-by control device for an alcohol fuel engine according to a first embodiment of the present invention.

In FIG. 1, reference numeral 1 is an alcohol fuel engine (hereinafter, simply referred to as an engine). The engine 1 includes a cylinder block 2, a cylinder head 3 integrated on an upper portion of the cylinder block 2, and a cylinder head. 3 is composed of a cylinder head cover 3a capped on the upper portion of the cylinder block 3, and an oil pan 4 attached to the lower crankcase 5 of the cylinder block 2 from below. An intake valve 41 is attached to the cylinder head 3. An intake port 40 provided and an exhaust port 50 provided with an exhaust valve 51 are formed respectively. An intake pipe 8 connected to the air cleaner 11 via a carburetor 10 is connected to the intake port 40 via an intake manifold, and an exhaust pipe 9 is connected to the exhaust port 50 via an exhaust manifold. .

In the figure, reference numeral 60 is a piston fitted to the cylinder portion in the cylinder block 2, 61 is a crankshaft housed in the crankcase, and the piston 60
Is supported by the crankshaft 61 via a piston rod 62 and a crankpin 63. Also, reference numeral 70
Is an oil temperature sensor, such as a thermistor, for detecting the oil temperature of the engine oil provided in the oil passage of the cylinder block 2. The detection signal is input to the engine control unit 30, which will be described in detail later.

On the other hand, reference numeral 16 is a ventilation tube for leading out blow-by gas, which is provided at the upper end of a side portion of the crankcase 5 so as to communicate with the inside of the crankcase 5. The ventilation tube 16 is provided with a three-way solenoid valve 21. The first blow-by gas passage 22 and the second blow-by gas passage 23
It is designed to be able to selectively communicate with. The other end of the first blow-by gas passage 22 communicates with the intake passage 8a in the intake pipe 8, and a flow control valve 25 operated by the intake negative pressure of the intake passage 8a in the intake pipe 8 is provided in the middle thereof. It is provided.

The flow control valve 25 has a diaphragm inside the body case.
25a defines upper and lower chambers, and a negative pressure introduction path 27 is provided on the upper chamber side.
The partition wall 25c having the valve hole 9 on the lower chamber side is fitted and the valve body 25b for opening or closing the valve hole 9 is supported by the diaphragm 25a. It is configured. Further, the diaphragm 25a is
The coil spring 25d compressed to the upper chamber side always urges the valve body 25 in a direction to open the valve body at a predetermined pressure.
This urging pressure is appropriately set so that the flow rate of blow-by gas described later can be adjusted in relation to the intake negative pressure.

On the other hand, the second blow-by gas passage 23 is directly connected to the intake passage 8a downstream of the carburetor 10.

Therefore, for example, the engine 1 is now in a warm-up operation state (before completion).
In the case of (1), since the intake amount is small and the intake negative pressure is also low, the diaphragm 25a of the flow control valve 25 is pushed by the coil spring 25d and the valve body 25b is pushed downward to open the valve hole 9. It is in a state. On the other hand, in this state, the three-way solenoid valve 21 is opened to the second blow-by gas passage 23 side by the control of the engine control unit 30. Therefore, a relatively small amount of blow-by gas BG containing the non-evaporated alcohol component supplied from the crankcase 5 and the cylinder head upper space 7 of the engine 1 passes through the second blow-by gas passage 23 and the intake passage downstream of the carburetor 10. Reflux directly into 8a.

Next, when it is detected by the oil temperature sensor 70 that the temperature of the oil flowing through the oil passage of the engine 1 has reached the boiling point temperature of alcohol of 65 ° C. upon completion of warm-up, the engine control unit 30 causes the three-way solenoid valve to operate. 21 is opened to the first blow-by gas passage 22 side, and blow-by gas from the engine is supplied into the intake passage 8a via the flow rate control valve 25. The blow-by gas supply control via the flow rate control valve 25 is performed only in the region where the oil temperature is between 65 ° C. and 75 ° C. by the control action of the engine control unit 30.

Therefore, in this state, as described above, when the oil temperature reaches 65 ° C., the alcohol fuel accumulated in the oil pan 4 starts to evaporate at once, but the flow rate control valve 25 accompanies the completion of warming up. By operating according to the negative pressure of the intake air, the flow rate is adjusted and limited, and then gradually returned to the intake passage 8a side. Therefore, a large amount of evaporated alcohol gas will not be recirculated to the intake passage 8a side at a time, the engine fuel state will be stable, and even if the engine shifts to the idle state, the engine rotation due to a sudden enrichment of the air-fuel ratio will occur. It is possible to prevent a decrease in number (rough idle) and engine stall before they occur.

In the first embodiment, the flow control of the blow-by gas by the flow control valve 25 is performed within the oil temperature range of 65 ° C to 75 ° C for the following reason.

That is, the boiling point (distillation point) of alcohol (methanol)
Since it is 65 ° C, there is no need to take evaporation measures below that, and on the other hand, it takes a certain time to consume the evaporated large amount of alcohol gas while adjusting the flow rate as described above. Time (control time) of the above oil temperature
This is because the temperature rising time up to 75 ° C was set. Therefore, it goes without saying that this time may be set separately using a timer.

Next, FIG. 2 shows a blow-by control device for an alcohol fuel engine according to a second embodiment of the present invention. In this embodiment, independent blow-by control is provided for the cylinder head upper space 6 side and the crankcase 5 side. It is an application example of the present invention having a gas passage (ventilation system). The system on the crankcase 5 side is exactly the same as that of the first embodiment, but a similar flow rate control valve 25 is also provided on the cylinder head 3 side to perform the same flow rate control as above. Reference numeral 7 indicates a blow-by gas lead-out buffer portion in the cylinder head upper space 6.

In each of the above embodiments, the flow rate control is performed on the basis of the increase in the oil temperature, but the alcohol evaporation state is detected by, for example, the pressure increase (evaporation pressure) in the crankcase, the alcohol gas concentration, and the blow-by gas. It is needless to say that the flow rate increase in the passage may be used as a reference for detection, and in other embodiments, the above various factors may be used instead of the oil temperature.

(Effects of the Invention) As described above, the present invention provides an alcohol fuel engine equipped with a blow-by gas processing device that uses alcohol as a fuel and recirculates blow-by gas generated on the engine body side to the intake passage side. In the warm-up state, the evaporation state detecting means for detecting the evaporation state of the alcohol on the engine body side, and the blow-by which is operated according to the detection output of the evaporation state detecting means and is recirculated from the engine body side to the intake passage side And a flow rate control means for controlling a gas flow rate.

Therefore, according to the present invention, the blow-by gas containing the evaporated alcohol gas generated during engine warm-up can be recirculated to the engine combustion chamber after the flow rate is arbitrarily controlled according to the operating state of the engine. Even if a large amount of alcohol evaporates with the progress, they are not supplied to the engine combustion chamber at once. As a result, the combustion state becomes stable, and it is possible to prevent the engine speed from decreasing and the engine stall from occurring even during idling.

[Brief description of drawings]

1 is a sectional view of a blow-by control device for an alcohol fuel engine according to a first embodiment of the present invention, and FIG. 2 is a sectional view of a blow-by control device for an alcohol fuel engine according to a second embodiment of the present invention. is there. 1 …… Alcohol fuel engine 2 …… Cylinder block 3 …… Cylinder head 3a …… Cylinder head cover 4 …… Oil pan 5 …… Crankcase 6 …… Cylinder head upper space 8 …… Intake pipe 10 …… Carburetor 11 …… Air cleaner 16 …… Crankcase ventilation tube 21 …… Three-way solenoid valve 22 …… First blow-by gas passage 23 …… Second blow-by gas passage 25 …… Flow control valve 29 …… Oil temperature sensor 30 …… Engine control unit

Claims (1)

[Claims] 1. An alcohol fuel engine equipped with a blow-by gas treatment device, which uses alcohol as a fuel, and causes blow-by gas generated on the engine body side to recirculate to the intake passage side, in a warm-up state of the engine. Evaporation state detection means for detecting the evaporation state of the, and flow rate control means for controlling the flow rate of blow-by gas which is operated according to the detection output of the evaporation state detection means and is recirculated from the engine body side to the intake passage side are provided. A blow-by control device for an alcohol fuel engine, which is characterized by the following.