JP3328745B2 - Valve timing control device for alcohol engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve timing control device for an alcohol engine.

[0002]

2. Description of the Related Art In an engine for an automobile or the like, as described in, for example, Japanese Patent Application Laid-Open No. Hei. Is being done. Since alcohol fuel is a single fuel and has a characteristic of low boiling point and good vaporization, the use of such an alcohol fuel provides better flammability compared to the use of gasoline fuel. The advantage is that the lean limit is also increased.

On the other hand, in a general gasoline engine,
There is also known a technique in which valve timing variable means is provided to increase the overlap period of the intake and exhaust valves, thereby improving fuel efficiency. That is, if the overlap period is increased in this manner, the internal EGR introduced into the combustion chamber increases, and the flammability deteriorates accordingly, so that the driver depresses the accelerator, thereby causing the throttle valve to operate. The negative pressure on the downstream side is reduced, so that the pumping loss can be reduced, and the effect of reducing fuel consumption can be obtained.

[0004]

By the way, in an engine using alcohol fuel, when an attempt is made to obtain an effect of reducing fuel consumption by using the above-described variable valve timing means, the alcohol fuel has good flammability and lean resistance. Due to the high combustion limit, even if the internal EGR is increased by increasing the overlap period of the intake / exhaust valves, the accelerator pedal is not depressed by the driver, so the pumping loss is not reduced and the fuel consumption reduction effect is sufficient. There is a problem that can not be obtained.

The present invention has been made in view of the above problems, and in an engine using alcohol fuel, fuel efficiency can be improved without deteriorating flammability by controlling valve timing. The purpose is to be.

[0006]

A valve timing control apparatus for an alcohol engine according to the present invention uses an alcohol-containing fuel and varies a valve timing overlap period between an intake valve and an exhaust valve. The present invention relates to a valve timing control device for an alcohol engine provided with an alcohol concentration detecting means for detecting an alcohol concentration in fuel, and an output of the alcohol concentration detecting means, as shown in FIG. It is at high, and further comprising a valve timing control means for controlling the valve timing varying means to increase the internal EGR amount by increasing the overlap period.

[0007]

In the present invention, the alcohol concentration in the fuel is detected by the alcohol concentration detecting means, and when the alcohol concentration is high, the overlap period of the intake / exhaust valve is made longer than when the alcohol concentration is low to increase the internal EGR amount. The valve timing is set. In this way, when the alcohol concentration is high, the internal EGR increases, and the combustion deteriorates. Therefore, the driver can sufficiently depress the accelerator, the negative pressure downstream of the throttle valve can be reduced, and the pumping loss can be reduced. It is reduced and the fuel efficiency is improved.

[0008]

Embodiments will be described below with reference to the drawings.

FIG. 2 is an overall system diagram of one embodiment of the present invention.

As shown in FIG. 1, in this embodiment,
An intake port 3 and an exhaust port 4 are opened in a combustion chamber 2 of the engine 1, and an intake valve 5 and an exhaust valve 6 for opening and closing these ports 3, 4 are provided. An ignition plug 7 is provided at the center of the combustion chamber 2. An intake passage 8 communicating with the intake port 3 is provided with an injector 9 for fuel injection, and an exhaust passage 10 communicating with the exhaust port 4 is provided with two catalytic converters 11 and 12 for purifying exhaust gas. Further, a heater-equipped O ₂ sensor 13 for detecting the oxygen concentration in the exhaust gas is provided at a position further upstream of the upstream catalytic converter 11.

A fuel passage 15 for guiding fuel from a fuel tank 14 is connected to the injector 9. Fuel tank 1
A fuel pump 16 is disposed in the fuel cell 4, and the fuel passage 15 is connected to a discharge side thereof. A methanol sensor 17 for detecting the concentration of methanol in the fuel is provided in the middle of the fuel passage 15. The fuel passage 15
A return passage 18 is connected to the fuel tank 14 and a pressure regulator 19 for adjusting the fuel pressure is provided at the connection.

The fuel injection control and ignition control of the engine 1 are performed by a control unit 20 composed of a microcomputer. Therefore, in addition to the methanol concentration signal from the methanol sensor 17 and the oxygen concentration signal from the O ₂ sensor 13, the control unit 20 receives an intake air amount signal from an air flow meter, an engine speed signal from an engine speed sensor, and a throttle signal. An idle switch signal or the like from an idle switch attached to the valve is input. As for the fuel injection amount of the engine 1, a basic injection amount is calculated based on the engine speed and the intake air amount, and various corrections based on the engine water temperature and the like and feedback correction based on the output of the O ₂ sensor 13 are added thereto. The igniter is controlled by an ignition signal corresponding to the engine speed and load.

The opening and closing timing of the intake valve 3 is controlled by a variable valve timing mechanism (not shown).
The switching is performed in stages, and the switching control is performed by the control unit 20.
That is, when the variable valve timing mechanism (VVT) is turned on, the opening / closing timing of the intake valve 3 is changed to the advanced side as shown by the broken line in FIG. 3, thereby increasing the overlap period of the intake and exhaust valves. Is done.

In this embodiment, the switching of the variable valve timing mechanism is controlled in accordance with the operating state of the engine and the concentration of methanol in the fuel. FIG.
The horizontal axis shows the engine speed (N), and the vertical axis shows the operating range of the variable valve timing mechanism (VVT) when the engine load (intake charge; Ce) is taken. As shown in the figure, at the time of idling, the intake air amount is small and the combustion stability is poor, so that the VVT is unconditionally turned off in consideration of the occurrence of engine stall due to the influence of the internal EGR, and the engine speed N during high rotation exceeding a predetermined rotational speed N _2, also turn off the VVT in the sense of increasing the intake air charging amount in the closing retard the intake valve. Then, at the time of partial load except at the time of idling and high rotation, the VVT is switched on / off according to the methanol concentration. That is, when the methanol concentration is high, the VVT is turned on to increase the overlap period of the intake and exhaust valves, thereby reducing pumping loss and improving fuel efficiency. On the other hand, when the methanol concentration is low, the VVT is turned off. To ensure the quality.

FIG. 5 shows the characteristics when the crank angle of the valve overlap is plotted on the horizontal axis, and the internal EGR rate (%) and the fuel consumption rate be (g / ps · h) are plotted on the vertical axis. is there. As shown in the drawing, the internal EGR rate increases as the valve overlap increases, whereas the fuel efficiency rate increases as the valve overlap increases and the internal EGR increases to obtain the same output as the throttle valve opening. , The characteristic is reduced. The hatched area on the curve indicating the internal EGR rate is E
An excess region of GR is shown, where M ₀ is M ₈₅ when the methanol concentration in the fuel is 0% (gasoline concentration 100%).
Indicates the case where the methanol concentration is 85%. As described above, the valve overlap can be increased as the methanol concentration increases. In the drawing, the broken line indicates whether the VVT is on or off.

Next, the above control of this embodiment will be described with reference to a flowchart shown in FIG. Here, S1 to S7
Is each step.

In the control according to this flowchart, the process is started. First, at S1, the engine speed, the intake air amount,
Reads various signals such as idle switch and alcohol (methanol) concentration. Next, in S2, it is checked whether the idle switch (IDSW) is off, that is, whether the throttle valve is open.

[0018] When referred to S2 is NO, that idle switch determination is on, go to S3, then see if the engine speed N is lower than the switching speed N ₁ of the VVT, when that low, VVT in S4
To end this flow.

Meanwhile, the term S2 determination is YES, that idle switch is off, and, when that N ≧ N ₁ is determined in S3 is then in S5 the engine speed N from the VVT switching rotational speed N ₂ Is high, and if it is high, the process also proceeds to S4 and VV
Turn off T.

If the determination in S5 is NO, that is, if N is N ₂
If so, it is next determined in S6 whether the methanol concentration FC is 50% or more. When the determination is NO, that is, when the determination is less than 50%, S
Go to 4 to turn off VVT, while YES, ie 5
If it is 0% or more, VVT is turned on in S7, and this flow ends.

[0021]

According to the present invention, the internal EGR amount is increased and the pumping loss is reduced when the alcohol concentration in the fuel is high, so that the fuel efficiency can be reduced without deteriorating the combustibility. Can be improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of the present invention.

FIG. 2 is an overall system diagram of an embodiment of the present invention.

FIG. 3 is a diagram showing valve timing in one embodiment of the present invention.

FIG. 4 is a diagram showing an operation range of a variable valve timing mechanism according to an embodiment of the present invention.

FIG. 5 is a diagram showing characteristics of an EGR rate and a fuel consumption rate with respect to a valve overlap in one embodiment of the present invention.

FIG. 6 is a flowchart for executing control according to an embodiment of the present invention;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 5 Intake valve 6 Exhaust valve 14 Fuel tank 17 Methanol sensor 20 Control unit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI F02D 45/00364 F02D 45 / 00364K

Claims (1)

(57) [Claims] 1. A valve timing control apparatus for an alcohol engine, comprising: a valve timing variable means for using an alcohol-containing fuel and varying an overlap period of valve timings of an intake valve and an exhaust valve, the valve timing control apparatus comprising: Alcohol concentration detection means for detecting the alcohol concentration, receiving the output of the alcohol concentration detection means,
When a high alcohol concentration, the valve timing control apparatus for an alcohol engine comprising the valve timing control means for controlling the valve timing varying means to increase the internal EGR amount by increasing the overlap period.