JPH0571767B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a stratified air charge engine that directs fuel towards a spark plug of the engine.

(Prior art) In conventional general spark ignition engines (gasoline engines), the amount of intake air is adjusted using a throttle valve, and the amount of fuel is supplied in accordance with the amount of intake air to maintain uniformity with the air. The mixture is mixed and ignited by a spark plug in the combustion chamber.
As a means to improve the output and fuel efficiency of such an engine, for example, as seen in Japanese Utility Model Application Publication No. 54-56006, compressed air is supplied into the combustion chamber during the compression stroke to promote swirling flow, thereby increasing the combustion speed. There are known products that increase the

By the way, at least when the engine is under low load,
If an air-fuel mixture with an ignitable air-fuel ratio exists near the spark plug, sufficient combustion is possible and the engine can be operated even if the fuel is lean in other parts of the combustion chamber. Focusing on these points, the Japanese Patent Laid-Open Publication No.
As disclosed in Japanese Patent No. 49-62807, a so-called stratified air supply engine is known in which fuel is injected toward a spark plug at a predetermined timing corresponding to the ignition timing. According to this engine, lean combustion is possible as long as fuel that provides the required air-fuel ratio is supplied near the spark plug, and since there is no problem even if excessive air is supplied, the throttle valve opening is adjusted at low load. can be increased or the throttle valve can be omitted, thereby reducing pumping loss at low loads. As a result, it becomes possible to significantly improve fuel efficiency.

In such a stratified air supply engine in which fuel is injected toward the spark plug, it is desired to promote atomization and vaporization of the fuel as much as possible in order to improve ignition performance during low loads. Furthermore, there is a problem in that fuel vaporization and atomization tend to deteriorate particularly when the engine temperature is low.

(Object of the Invention) In view of the above circumstances, the present invention provides a stratified air supply engine that injects fuel toward a spark plug at least at a predetermined timing under low load, by actively atomizing the fuel. The purpose is to improve ignitability through appropriate atomization and vaporization, particularly in accordance with the amount of fuel injected.

(Structure of the Invention) The stratified air supply engine of the present invention includes a fuel injection valve disposed toward a spark plug of the engine, an air injection valve that mixes air into the injected fuel from the fuel injection valve, and an engine. A load detection means for detecting the state, a crank angle detection means for detecting the crank angle of the engine, a temperature detection means for detecting the engine temperature, and receiving the outputs of the load detection means and the crank angle detection means, A fuel control means for controlling the fuel injection valve to inject fuel at a predetermined time from the latter half of the intake stroke to a predetermined time of the compression stroke when under load; an air control means for controlling the air injection valve so as to increase the amount of air to be injected when the engine temperature is lower than a predetermined value; It was established. The fuel injection valve and the air injection valve may be provided in the combustion chamber, or may be provided in the intake port near the combustion chamber, as long as the above requirements are satisfied.

(Example) Fig. 1 schematically shows an example in which the present invention is applied to a 4-cylinder 4-cycle engine, and Fig. 2 shows the specific structure of the combustion chamber portion and its vicinity of this engine. . In these figures, 1 is the engine body, 2 is the intake pipe 3 and the intake manifold 4.
5 is an air cleaner provided upstream of the intake passage 2, and 6 is an exhaust manifold. In the embodiment shown in the figure, a primary intake passage 8 is provided for each combustion chamber 7 of each cylinder of the engine body 1.
and a secondary intake passage 9 are provided in the intake manifold 4, and the secondary intake passage 9 is provided with a swirl control valve 10 for adjusting the opening degree of this passage 9. The operation of the swirl control valve 10 is controlled by a control unit 40, which will be described later, via an actuator 11.

A primary intake port 13 communicating with the primary intake passage 8, a secondary intake port 14 communicating with the secondary intake passage 9, and an exhaust port 15 are opened in the combustion chamber 7 of each cylinder, and these ports 13, Primary side intake valves 16 are respectively opened and closed at predetermined timings by valve operating mechanisms (not shown) at openings 14 and 15;
A secondary intake valve 17 and an exhaust valve 18 are provided. Further, within the combustion chamber 7, a spark plug 20 is provided, and a fuel injection valve 21 and an air injection valve 22 are also provided. Above fuel injection valve 2
1 is provided facing the spark plug 20. Furthermore, the air injection valve 22 is disposed close to the fuel injection valve 21 and oriented in a predetermined direction so that the injected air mixes with the injected fuel from the fuel injection valve 21. In addition, in FIG. 1, for convenience of drawing, the arrangement of the fuel injection valve 21 and the air injection valve 22 is shown only for the rightmost cylinder, but the arrangement of the fuel injection valve 21 and the air injection valve 22 is similarly shown for the other cylinders. 22 are arranged.

The fuel injection valve 21 is connected to a fuel injection pump 23. This fuel injection pump 23 is driven by the crankshaft 27 of the engine via a timing belt 24 and pulleys 25, 26, and supplies fuel to the fuel injection valves 21 of each cylinder for injection, and starts the injection. The structure allows the timing and injection end timing to be adjusted according to electrical control signals. The air injection valve 22 is connected to an air pump 30 via an air reservoir 29, and the air pump 30 is driven by the crankshaft 27 via a belt 31 and pulleys 32, 33. In the figure, an air return passage 34 is provided between the air reservoir 29 and the air pump 30 in order to promote pressure rise in the air reservoir 29 when the engine is started, and the air return passage 34 is opened and closed when the engine is started. A recycle valve 35 is provided. 36 is a check valve provided in the air introduction passage 37 to the air pump 30, and 38 is a relief valve provided in the air relief passage 39.

Further, 40 is a control unit for various controls, for example, as shown in FIG. 3, a control unit 41 using a microcomputer and various converters 42
Contains ~47. The control unit 41 receives an accelerator opening signal from an accelerator opening sensor 51 via an A/D converter 42, and also receives an F/V (frequency-voltage) converter 43 and an A/D converter from a crank angle sensor 52. An engine speed signal is inputted via the /D converter 44, and the load condition is detected based on this accelerator opening degree and the engine speed, and a crank angle signal is inputted from the crank angle sensor 52. . Further, the smoke sensor 5 detects the occurrence of smoke so that the air injection amount is corrected when the engine temperature is low, and in the embodiment, the air injection amount is further corrected when smoke occurs.
3 and a water temperature sensor (temperature detection means for detecting engine temperature) 54 that detects, for example, cooling water temperature as a temperature related to the engine temperature, a smoke signal and a water temperature signal are transmitted via A/D converters 45 and 46, respectively. is input to the control section 41.
Furthermore, a pressure sensor 55 detects the pressure inside the air reservoir 29 for control at the time of starting which will be described later.
A pressure signal provided from the A/D converter 47 and a start signal as an interrupt signal provided from the start sensor 56 are also input to the control section 41 . The control section 4
1 functions as a fuel control means to control fuel injection from the fuel injection valve 21, an air control means to control air injection from the air injection valve 22, and a water temperature corresponding to the engine temperature is set to a predetermined value. It has a function as an air correction means that increases and corrects the air injection amount in the following cases (and when smoke occurs), and directly controls the operation of the fuel injection pump 23 and the opening/closing operation of the air injection valve 22. . Also,
The actuator 11 of the swirl control valve 10 and the recycle valve 35 are also controlled by the control section 41.
It is controlled by.

In the control valve 41, fuel and air injection start times and injection end times under various operating conditions are stored in advance as a data map.
Based on this map, the fuel injection timing and injection amount are set so that the fuel is injected in the latter half of the intake stroke or the compression stroke at least when the load is low, and the fuel injection amount is controlled according to the load. The air injection timing and injection amount are set so that the air is injected in synchronization with the timing and the air injection amount increases as the fuel injection amount increases. For example, the map is created so that the timing is controlled according to the characteristics shown in FIG. That is, in FIG. 4, Fs and Fe represent the fuel injection start timing and injection end time, respectively, As and Ae represent the air injection start time and injection end time, respectively, and I represents the ignition timing. As shown in this figure, in the low load region, fuel is injected in the latter half of the compression stroke, and when the injection ends.
Fe and Ae are made to almost match ignition timing I. The fuel injection start timing Fs is set so that as the load increases, the fuel injection period is lengthened to increase the fuel injection amount. In addition, in this region, the air injection end timing Ae
The air injection amount is made to correspond to the fuel injection amount by making it coincide with the fuel injection end time Fe and by making the air injection start time As almost correspond to the fuel injection start time Fs. Note that control at high loads is not limited by the present invention, but at high loads when the fuel injection amount is increased, there is no need for stratified air supply; rather, in order to increase the air utilization rate and improve the output, it is necessary to increase the fuel supply. It is preferable to ignite the fuel in a dispersed state, and in this case, air injection for the purpose of atomizing or vaporizing the fuel is not necessary. For this reason, in the illustrated characteristics, when the load increases to a certain extent, the injection timing of fuel and air is advanced, and in the high load region, injection is performed in the first half of the intake stroke, and the amount of air injection is reduced.

Further, the opening degree of the swirl control valve 10 under various load conditions is stored in advance in the control section 41 as a data map, and the swirl control valve 10 is closed when the load is low, and when the load is high, the swirl is adjusted to the corresponding opening degree. The above map is created so that the control valve 10 opens. Also, depending on the state of smoke generation and cooling water temperature, the timing of the start of air injection is determined.
A correction coefficient for correcting the air injection amount by correcting As or end time Ae is also set in advance. For example, when correcting the air injection start timing As, as shown in FIG. 5
As shown in Figure B, the correction coefficient according to the cooling water temperature T
Ts is set to 1 when the cooling water temperature T is 50°C or higher, and is decreased below that.

The control executed by the control unit 40 is shown in flowcharts as shown in FIGS. 6 and 7.

In the main routine shown in FIG. 6, first, detection signals of accelerator opening A and engine speed R, which determine the load condition, are input (step X ₁ );
Based on this signal, each fuel and air injection start timing is determined according to the load condition at that time from a map that has been set in advance to give the characteristics shown in Figure 4 above.
As, Fs and each injection end time Ae, Fe are calculated (steps X ₂ and X ₃ ). Furthermore, the smoke S and cooling water temperature T detection signals are input, and corresponding correction coefficients Ss and Ts are determined, and these correction coefficients Ss and Ts are multiplied by the air injection start timing As (step ₄ ~ _X7 ). Next, after repeatedly inputting the detection signal of the crank angle θ and waiting for the crank angle θ to reach the injection start timings As and Fs,
Control is performed to start injection of fuel and air (steps _X8 to _X10 ). Subsequently, after repeatedly inputting the detection signal of the crank angle θ and waiting for the crank angle θ to reach the injection end timings Ae and Fe, control is performed to end the injection of fuel and air (steps X ₁₁ to _X3 ). Further, the opening degree (S valve opening degree) S ₀ of the swirl control valve 10 is calculated according to the accelerator opening degree A and the engine rotation speed R, and a control signal giving this opening degree S ₀ is sent to the actuator 11. (steps _X14 , _X15 ). After that, the process returns to step _X1 and the above flow is repeated.

With such control, during low load, fuel is injected from the fuel injection valve 21 toward the spark plug 20 at a predetermined time in the latter half of the compression stroke, and the fuel is mainly supplied to the vicinity of the spark plug and to other parts of the combustion chamber 7. Ignition occurs when the fuel is lean in some areas. Therefore, even with a small amount of fuel, ignition and combustion are possible, and the engine can be operated. In addition, in this case, there is no problem even if excessive air is supplied from the primary intake passage 8 to the combustion chamber 7, so the throttle valve is omitted in the figure so that the intake air from the primary intake passage 8 is not restricted. This reduces pumping loss. When fuel is injected toward the spark plug 20 in this way, air is injected from the air injection valve 22 at the same time, and this air mixes with the injected fuel to actively atomize and vaporize the fuel. will be held. In particular, since the air injection amount is controlled in accordance with the fuel injection amount, atomization and vaporization of the fuel are appropriately promoted within a range where the fuel is not dispersed too much, and ignitability is improved.

On the other hand, when the load is high, the fuel injection amount is increased, fuel is injected in the first half of the intake stroke, and the swirl control valve 10 is opened to create a swirl in the combustion chamber 7 by intake air from the secondary intake passage 9. Since the fuel is increased, ignition is performed after the fuel is sufficiently diffused into the combustion chamber 7.

In addition, if fuel atomization and vaporization are insufficient, smoke will increase and the engine temperature (cooling water temperature) will increase.
When the fuel is low, the viscosity of the fuel becomes high and it becomes difficult to atomize and vaporize the fuel, but in these cases, the amount of air injected is increased by the correction in steps X ₄ to X ₇ , and the atomization and vaporization of the fuel are increased. This allows for better vaporization.

The interrupt routine shown in FIG. 7 is for controlling the startup, and is started by a signal from the start sensor 54, and first a pressure signal from the pressure sensor 53 is input (step Y ₁ ). ,
It is determined whether the pressure P is greater than or equal to the set value α (step Y ₂ ). If the pressure P is less than the set value α, the recycle valve 35 is controlled to repeatedly open and close (step Y ₃ ), thereby promoting a rise in pressure within the air reservoir 29. When the pressure P exceeds the set value α, the recycle valve 35 is closed, and starting fuel and air are injected (step
_Y4 ). Then, it is determined whether or not the starting has ended (step _Y5 ), and when the starting has ended, the process returns to the main routine shown in FIG. 5.

8 and 9 show another embodiment of the invention. In this embodiment, a fuel injection valve 21' and an air injection valve 22 are provided in the primary intake port 13, and in this case as well, the fuel injection valve 21' is arranged toward the spark plug 20 in the combustion chamber 7, and the air injection valve 22 is arranged to mix air into the injected fuel. Further, in this embodiment, the fuel injection valve 21'
Similar to the air injection valve 22, the control unit 40
In this case, the fuel injection valve 21' can be connected to a fuel injection pump (not shown) such as that used in ordinary gasoline engines. good.

When the injection valves 21' and 22 are installed in the intake port 13 in this way, it is necessary to inject the fuel before the intake valve 16 closes, so as shown in FIG. The injection start timings As, Fs and injection end timings Fe, Ae are set so that fuel and air are injected at the final stage, but apart from this point, the control device is configured in the same manner as in the first embodiment. has been done.

(Effects of the Invention) As described above, the present invention has the following advantages:
Fuel is injected toward the spark plug from the latter half of the intake stroke to a predetermined time in the compression stroke, and the injected fuel is mixed with air injected from the air injection valve, so that so-called stratified air supply results in lean combustion and Pumping loss can be reduced, fuel efficiency is improved, and fuel atomization and vaporization are promoted. In particular, as the fuel injection amount increases, the air injection amount also increases, and the air injection amount is increased to correct the tendency for vaporization and atomization to occur less easily when the engine temperature is low. The fuel is appropriately atomized and vaporized, and the ignitability and combustibility are significantly improved.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic diagram showing an embodiment of the present invention;
Figure 2 is an enlarged view of the combustion chamber and its vicinity, Figure 3 is a block diagram of the control system, Figure 4 is a characteristic diagram of fuel and air injection timing, and Figures 5A and B.
6 and 7 are flowcharts, FIG. 8 is an overall schematic diagram showing another embodiment, and FIG. 9 is a diagram corresponding to FIG. 2. , FIG. 10 is a diagram corresponding to FIG. 4 in the case of this embodiment. 20... Spark plug, 21, 21'... Fuel injection valve, 22... Air injection valve, 40... Control unit, 51... Accelerator opening sensor, 52... Crank angle sensor.

Claims (1)

[Claims] 1. A fuel injection valve disposed toward the spark plug of the engine, an air injection valve that injects air in a direction that interferes with the injected fuel from the fuel injection valve, and a load detection means that detects the load state of the engine. A crank angle detection means for detecting the crank angle of the engine, a temperature detection means for detecting the engine temperature, and the outputs of the load detection means and the crank angle detection means are received, and when the engine is under low load, from the second half of the intake stroke to the compression stroke. a fuel control means for controlling the fuel injection valve to inject fuel at a predetermined timing; and a fuel control means for injecting air in synchronization with the fuel injection and increasing the amount of air injection as the amount of fuel injection increases. A stratified feed system characterized by comprising: an air control means for controlling an air injection valve; and an air correction means for increasing the amount of air injection when the engine temperature is below a predetermined value in response to the output of the temperature detection means. Chi engine.