JPH022456B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention forms a supercharging port in addition to a main intake port in a combustion chamber, and supplies air pressurized by a supercharger after the end of the intake stroke. The present invention relates to an engine supercharging device that supplies a combustion chamber from a supercharging port.

(Prior art) Conventionally, in addition to the main intake port that naturally takes in intake air using the engine's intake negative pressure, a supercharging port that supplies pressurized air from a supercharger at least during the compression stroke has been provided. Intake is performed by natural intake and supercharging by a supercharger, and a relatively small capacity supercharger is used to improve charging efficiency, while ensuring natural intake from the main intake port is not obstructed as much as possible. A technique is known that enables supercharging to be carried out (see Japanese Utility Model Application Publication No. 58-96017).

However, in an engine equipped with a supercharging device such as the one described above, when an injection valve is installed in the main intake port to inject fuel, the amount of fuel injected increases at high loads and high rotations, and the fuel injection time becomes longer. It is something that exists. In this way, at the end of the intake stroke when the fuel injected into the main intake port is flowing into the combustion chamber, when the timing valve opens and supercharging is performed from the supercharging port, this supercharging air causes the main intake air to flow into the combustion chamber. Since blowback occurs at the port, and the amount of blowback also fluctuates depending on changes in boost pressure, etc.
Fluctuations in the air-fuel ratio may occur, which may adversely affect drivability.

In other words, when the fuel injected into the main intake port is flowing into the combustion chamber, supercharging from the supercharging port is started, and the high pressure supercharging air from this supercharging port acts on the main intake port. As a result, the rich air-fuel mixture containing the injected fuel cannot flow into the combustion chamber from the main intake port, and is pushed back inward, preventing the predetermined amount of fuel from being supplied to the combustion chamber. The air-fuel ratio fluctuates.

In particular, in multi-cylinder engines that inject fuel to all cylinders simultaneously, the above phenomenon is likely to occur because the fuel injection period overlaps with the supercharging period.

(Object of the Invention) In view of the above circumstances, the present invention is designed to complete fuel injection into the main intake port before supercharging from the supercharging port starts and blowback occurs at the main intake port. It is an object of the present invention to provide an engine supercharging device that suppresses fluctuations in air-fuel ratio due to pushback of injected fuel even in the rotation range.

(Structure of the Invention) The supercharging device of the present invention has a main intake port that performs natural intake, and a supercharging port that is equipped with a supercharger and supplies supercharging air from the end of the intake stroke to the compression stroke. The invention is characterized in that the injection of fuel into the main intake port by the injection valve is controlled by a control device so that the combustion injection is completed at the latest by the start time of supercharging from the supercharging port. .

(Effects of the Invention) According to the present invention, during the supercharging period in which supercharging air is supplied from the supercharging port at the end of the intake stroke, fuel injection to the main intake port is performed at the latest until the start of the supercharging period. As a result, even under high load and high speed, supercharging from the supercharging port starts after the fuel injected into the main intake port flows into the combustion chamber. It can prevent blowback during spraying. Therefore, the rich fuel before flowing into the combustion chamber is not pushed back into the main intake port, suppressing fluctuations in the air-fuel ratio, improving combustion stability, and ensuring good drivability.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an engine equipped with a supercharging device, FIG. 2 is a block diagram of a control device for a four-cylinder engine, and FIG. 3 is an explanatory diagram showing the operation of the control device.
FIG. 4 is a time chart showing the relationship between the supercharging period and the fuel injection period.

The reciprocating engine E is one in which a crankshaft 4 is rotationally driven via a connecting rod 3 by the reciprocating motion of a piston 2 within a cylinder 1, and a combustion chamber 5 defined by the cylinder 1 and the piston 2. A main intake port 6, a supercharging port 7, and an exhaust port 8 are provided in the upper part of the engine.

The main intake port 6, the supercharging port 7, and the exhaust port 8 are connected to an intake valve 9 whose opening/closing timing is controlled by a well-known timing cam (not shown) in synchronization with the rotation of the crankshaft 4 of the engine E, and a sub-intake valve. The valve 10 and the exhaust valve 11 are opened and closed at predetermined timings, respectively.

An intake passage 13 that communicates with an air cleaner 12 is connected to the main intake port 6 , and an injection valve 14 that injects fuel toward the main intake port 6 is disposed in this intake passage 13 . Interposed between the air cleaner 12 and the air cleaner 12, from the upstream side, are an air flow meter 15 that detects the amount of intake air, a throttle valve 16 that opens and closes depending on the load, and a surge tank 17 that retains air. This main intake port 6 is opened by an intake valve 9 during the intake stroke of the engine E, allowing intake air to be naturally drawn into the combustion chamber 5. Further, when the exhaust port 8 is opened by the exhaust valve 11, exhaust gas generated by combustion is discharged to the outside through the exhaust passage 20.

On the other hand, the supercharging port 7 is connected to a supercharging passage 18 whose upstream end communicates with the intake passage 13 downstream of the air flow meter 15 . In the middle of this supercharging passage 18, a supercharger 19 consisting of a vane type air pump that sucks air from the intake passage 13, pressurizes it, and then discharges it is installed. It is driven and supplies pressurized air to the supercharging port 7. The auxiliary intake valve 10 is opened and closed in synchronization with the crankshaft 4, and is opened and closed so as to perform supercharging between the end of the intake stroke when the main intake port 6 is closed by the intake valve 9 and the beginning of the compression stroke. The intake valve 9 closes with a delay of a set value from the intake valve 9.

In addition, in FIG. 1, 22 is a return passage communicating the discharge side and suction side of the supercharger 19, 23 is a relief valve interposed in the middle of the return passage 22,
24 is installed downstream of the supercharger 19 in the supercharging passage 18, and its opening and closing are controlled according to the engine load.
For example, the sub-throttle valve 24 is a sub-throttle valve that is opened in synchronization with the throttle valve 16 after it opens to a predetermined opening degree or more, and the sub-throttle valve 24 controls the amount of supercharging according to the load of the engine.

The fuel injection timing and injection amount (injection time) by the injection valve 14 are performed based on a control signal from a control device 25 (control unit). In addition to the intake air amount signal from the air flow meter 15, this control device 25 receives an engine rotation speed signal from a rotation speed sensor 26 that detects the engine rotation speed, and a crank angle sensor 27 that detects the crank angle of the crankshaft 4. The control device 25 calculates the fuel injection amount (injection time) and injection timing based on these signals, and outputs a control signal.

As shown in FIG. 2, the control device 25 receives an intake air amount signal from the air flow meter 15 and an engine rotation speed signal from the rotation speed sensor 26, and based on both signals, the injection time corresponding to one injection amount is determined. The injection time calculation circuit 28 is provided for setting the injection time calculation circuit 28, and the output signal of the injection time calculation circuit 28 is inputted to each timer circuit 29a to 29d for each cylinder.
In addition, the crank angle signal of the crank angle sensor 27 outputs a reference signal A every time the crankshaft 4 makes one revolution (360 degrees), and
Detects and outputs cylinder signal B every time it rotates (180°),
The reference signal A is input as the reset signal C to the counter 31 via the flip-flop circuit 30, while the cylinder signal B is output to the counter 31 and is counted in order in correspondence with each cylinder by this counter 31, so that each cylinder is counted in turn. Signals D to G are sequentially output to timer circuits 29a to 29d corresponding to the timer circuits 29a to 29d. Each of the timer circuits 29a to 29d outputs a control signal to the injection valves 14a to 14d for the corresponding cylinder for a period of time based on the signal from the injection time calculation circuit 28 when the signals D to G from the counter 31 are input.

That is, the reference signal A and the cylinder signal B from the crank angle sensor 27 are output as pulse signals every 360° and 180° as shown in FIG. is converted by the flip-flop circuit 30 as shown in FIG. When these signals and the signal from the injection time calculation circuit 28 are output at the same time, control signals are output to each of the injection valves 14a to 14d, and as shown in FIG. 3D and When the G signal level rises to high, fuel injection starts,
Based on the signal from the injection time calculation circuit 28, injection is continued for a time T set by each timer circuit 29a to 29d, and a predetermined amount of fuel is injected according to the operating state.

Next, the operation of the above embodiment will be explained.
Based on the operation of the control device 25 as described above, fuel injection by the injection valve 14 is performed at the timing shown in FIG. 4 with respect to supercharging from the supercharging port 7.

The main intake port 6, which is opened and closed by the intake valve 9, opens near the intake top dead center TDC, as shown in I, and closes to the bottom dead center.
It closes after passing BDC, and natural intake occurs due to the negative intake pressure in the combustion chamber 5. In response to this intake stroke, the supercharging port 7, which is opened and closed by the auxiliary intake valve 10, opens at the end of the intake stroke, slightly before the main intake port 6 closes, and enters the compression stroke later than the main intake port 6, as shown in FIG. During this period, supercharging is performed. The end timing of this supercharging is actually determined by the pressurizing ability or capacity of the supercharger 19.

In contrast to these timings of natural intake and supercharging, fuel injection starts before or after the main intake port 6 opens, as shown in , and even when the fuel injection time is the longest, the auxiliary intake valve 10 The fuel injection is set to end before the opening timing, that is, before supercharging from the supercharging port 7 starts. Therefore, all of the fuel injected into the intake passage 13 is supplied to the combustion chamber 5 before the auxiliary intake valve 10 opens and supercharging starts. Even if blowback occurs in the main intake port 6 due to supercharging air when supercharging is started, the rich air-fuel mixture will not be pushed back like blowback during fuel injection, but instead will flow into the combustion chamber 5. Only a portion of the fuel that has entered and diffused is pushed back, and the fluctuation in the air-fuel ratio is small.

As described above, with respect to the supercharging period due to the action of the auxiliary intake valve 10 provided in the supercharging passage 18, the fuel injection period with the main intake port 6 open does not overlap with the supercharging period. This prevents blowback during fuel injection. Therefore, the fuel flowing into the combustion chamber 5 by natural suction action is not pushed back into the main intake port 6 by the supercharging air, and the discharge of the vane type supercharger 19 as in the above embodiment is prevented. Combustion stability is improved by suppressing fluctuations in the air-fuel ratio due to pulsations and fluctuations in supercharging pressure due to changes in supercharger rotation speed.

Note that the present invention is not limited to the above-mentioned embodiments, and for example, a timing valve may be provided in the supercharging passage and the supercharging period may be controlled by the valve. In this case, the opening of the timing valve may be controlled by the timing valve. It is sufficient to set the fuel injection to end by the specified time.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of an engine equipped with a supercharging device according to an embodiment of the present invention, Fig. 2 is a block diagram of a control device for a 4-cylinder engine, and Figs. 3 A to G
4 is an explanatory diagram showing the operation of the control device, and FIG. 4 is a time chart showing the relationship between the supercharging period and the fuel injection period. E...Engine, 4...Crankshaft, 5...Combustion chamber, 6...Main intake port, 7...Supercharging port,
9...Intake valve, 10...Sub-intake valve, 13...Intake passage, 14...Injection valve, 15...Air flow meter, 18...Supercharging passage, 19...Supercharger, 25...
…Control device.

Claims (1)

[Claims] 1 It has a main intake port that performs natural intake and a supercharging port that is equipped with a supercharger and supplies supercharging air, and when the engine is under high load, in addition to fresh air from the main intake passage, at least during the compression stroke, In an engine supercharging device that supplies supercharging air from a supply port, an injection valve for injecting fuel to the main intake port is provided, and the fuel injection from the injection valve is controlled so that the supercharging air is supplied from the supercharging port at the latest. A supercharging device for an engine, characterized in that it is equipped with a control device that controls the charging to be completed by the start time.