JPS6030437A - Stratified charging engine - Google Patents

Abstract

PURPOSE:To enable the combustion of an engine to be switched corresponding to a condition of the outside air, by detecting a switching point between the stratified combustion and the uniform combustion by the signal of an exhaust sensor, which detects a rate of excess air, so as to switch the combustion by a stratified fuel supply means and a dispersed fuel supply means. CONSTITUTION:When a supply amount of fuel is controlled, a control means 16, in low and intermediate loads below the first preset level by a load detecting means 17, fully opens a throttle valve 14 so as to hold an intake air amount to a fixed level and supplies only stratified fuel by a fuel supply means 11, performing stratified combustion with a large rate lambda of air. Then the control means 16, if it reaches a point A above a predetermined load, starts supply of dispersed fuel by a fuel supply means 13, and if it further reaches a point B, decreases the stratified fuel, transferring the combustion from the stratified combustion to uniform combustion. Setting this point A below the rate lambda of air of an ignition limit while the point B above the rate lambda of air, in which a smoke is started to be generated, the optimum rate lambda of excess air for the switching point A is detected by the signal of an exhaust sensor 18. In this way, the combustion can be most suitably switched even if the temperature rises and the density of air changes due to high ground moving and/or supercharging.

Description

[Detailed description of the invention] (Industrial application field) BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stratified air charge engine.

(Prior art) Conventionally, in commonly used engines with a throttle valve, the throttle valve, which is linked to the accelerator operation, listens to the intake passage and adjusts the amount of air-fuel mixture (filling amount) supplied to the combustion chamber. I am trying to control the engine output. However, in the above-mentioned engine with a throttle valve, a large intake negative pressure is generated due to the throttle operation of the throttle valve, which causes a pumping loss and has a problem of deteriorating fuel efficiency.

Additionally, if you try to operate with a mixture as lean as possible for the purpose of improving fuel efficiency and emissions, there is a limit to the air-fuel ratio of the mixture that can be ignited, and overall lean combustion cannot be realized. In contrast, stratified combustion is implemented in which only the fuel necessary for ignition out of the fuel supplied to the combustion chamber according to the load is unevenly distributed near the ignition device, and the air-fuel ratio in this area is enriched to improve ignitability. A stratified air charge engine that can realize lean combustion as a whole by doing so is disclosed in, for example, Japanese Patent Application Laid-Open No. 49-62807N.
, is well known as seen in Japanese Patent Application Laid-Open No. 128109/1983.

However, in the above-mentioned known stratified air supply engine, the ignition fuel supplied around the ignition device is constant regardless of the load, and the supply of this ignition fuel and the distributed fuel at the time of R71 according to the load are arranged. This is what we do,
In the low load range, which is the normal operation range, the supply of the above-mentioned dispersed fuel is small, and the air-fuel ratio of the fuel dispersed throughout the combustion chamber, other than the ignition fuel that is unevenly distributed near the ignition load, exceeds the flammability limit. I am in a very bad condition. Therefore, this overly dispersed fuel will not ignite and burn and will be left in the dry pile, reducing fuel efficiency and mission performance. Therefore, at such low loads, the throttle valve is throttled to reduce the amount of intake air, and the dispersed fuel is The air-fuel ratio of the fuel is increased to a state where combustion is possible. As described above, since the throttle valve is still required to ensure the combustion of the dispersed fuel, the pumping loss due to the closing operation of the throttle valve is still large.

(Object of the Invention) Therefore, in view of the above circumstances, the present invention has been devised to perform stratified combustion with improved ignitability by unevenly distributing one fuel around the ignition device by the first fuel supply means in the low load range, and In the load range, the second fuel supply means distributes the fuel throughout the combustion chamber for uniform combustion, reducing pumping loss and further improving fuel efficiency.Moreover, the timing of switching from stratified combustion to uniform combustion can be changed at various times. Set accurately according to conditions,
It is an object of the present invention to provide a stratified air charge engine that performs the switching at an appropriate time.

In other words, if the output is controlled by making the fuel supply richer in response to an increase in load, or if the air density changes due to factors such as a rise in temperature, a drop in atmospheric pressure due to movement to high altitudes, or an increase in pressure due to supercharging, Even if the fuel supply period is the same, the excess air ratio α (air-fuel ratio) varies. Performing stratified combustion when the excess air ratio is small (dense) may result in the generation of smoke due to a decrease in air utilization, while uniform combustion when the excess air ratio is large (thin) may result in poor ignitability. If this switching point is set depending on the load, it will not be possible to overcome the above-mentioned J: outside air conditions, and problems such as the occurrence of air leakage will occur. The present invention aims to improve this point as well.

(Structure of the Invention) The stratified air supply engine of the present invention includes a first fuel supply means for supplying fuel around the ignition device in the combustion chamber, and a second fuel supply means for distributing fuel into the combustion chamber, The control means that receives the output signal of the exhaust sensor that detects the excess air ratio from the exhaust gas concentration uses this signal to set the switching point between stratified combustion and uniform combustion, and when the load is low below the switching point, the control means does not increase the load. Accordingly, the amount of fuel supplied from the first fuel supply means is increased, and when this switching point is exceeded, the amount of fuel supplied from the second fuel supply means is decreased. The present invention is characterized in that the fuel supply is started, and the supply amount is increased as the load increases, thereby making a transition from stratified combustion to uniform combustion.

(Effect of the invention) The switching point between the stratified combustion region and the uniform combustion region is detected by an exhaust sensor that detects the excess air ratio from the exhaust gas concentration,
By switching between the first fuel supply means and the second fuel supply means in accordance with this, the above-mentioned switching point is set at the optimal point in response to fluctuations in outside air conditions such as temperature and atmospheric pressure, or the presence or absence of supercharging. It is possible to accurately switch between stratified combustion and uniform combustion at a time when smoke or output decrease does not occur.

Therefore, in the low/medium load range, which is the normal operating range below the switching point, the first fuel supply means for stratification supplies an amount of fuel corresponding to the load around the ignition device in the combustion chamber to perform stratified combustion. By keeping the amount of intake air constant in this operating range, in addition to improving fuel efficiency through stratified combustion,
Bumping loss is reduced to further improve fuel efficiency. On the other hand, in a high-load operation range exceeding the switching point, the stratified fuel supply by the first fuel supply means is reduced, and the second fuel supply means starts supplying dispersed fuel to change stratified combustion to uniform combustion. It is possible to ensure good high-output operation without the generation of smoke.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

In the engine shown in FIG. 1, 1 is a combustion chamber formed above a piston 2, 3 is an intake passage for introducing intake air into the combustion chamber 1, and 4 is an exhaust passage for introducing exhaust gas from the combustion chamber 1. , 5 is an intake valve, 6 is an exhaust valve, and 7 is a catalyst device installed in the exhaust passage 4, respectively.

In the combustion chamber 1, an ignition device 8 using a spark plug is disposed, and a stratified fuel injection nozzle 9 for supplying fuel around the ignition device @8 is disposed. A fuel injection pump 10 is connected to constitute a first fuel supply means 11.

-h1 The intake passage 3 is provided with a second fuel supply means 13 including a dispersion fuel injection nozzle 12 for distributing fuel into the combustion chamber 1, and downstream of the dispersion fuel injection nozzle 12. A throttle valve 14 is provided, and this throttle valve 1
4 is provided with an actuator 15 (not linked to accelerator operation) that opens and closes the opening and closing operation.

As shown in FIG. 2, the downstream portion of the intake passage 3 is curved to introduce the intake air from the tangential direction of the combustion chamber 1 and generate a swirl S along the circumferential direction within the combustion chamber 1. This swirl causes the ignited fuel ignited by the device 8 consisting of the stratified fuel injection nozzle 9 of the first fuel supply means 11 to be sufficiently mixed with air, and the flame is transferred to the combustion chamber 1. Spread it throughout,
The entire injected fuel is sufficiently combusted.

The fuel injection pump 10 of the first fuel supply means 11, the second
The operation of the actuator 15 of the dispersing fuel injection nozzle 12 and the throttle valve 14 of the fuel supply means 13 is controlled by the control means 16.
controlled by

The control means 16 receives a load signal from a load detection means 17 which detects and overrides the required load of the engine by, for example, an accelerator sensor, and an oxygen concentration/sensor installed in the exhaust passage 4 which detects an excess air ratio λ from the exhaust gas concentration. An engine rotation sensor receives an air-fuel ratio signal from an exhaust sensor 18 such as an engine rotation sensor.

- 19, a water temperature signal from the water temperature sensor 20, etc., and control the fuel injection amount eIJ and fuel injection timing from the stratification fuel injection nozzle 9, and the fuel injection m from the dispersion fuel injection nozzle 12, respectively. At the same time, the closing timing of the throttle valve 14 is set to li! I III.

The control means 16 controls the amount of fuel supplied by detecting the switching point between stratified combustion and uniform combustion in response to the detection signal from the exhaust gas suppressor 18, and also detecting the switching point between stratified combustion and uniform combustion by receiving the signal from the load detection means 17. In the normal operation range in the low/medium load range, the supply of distributed fuel to the second fuel supply means 13 is stopped, and stratified fuel is supplied by the first fuel supply means 11 to perform stratified combustion, so that the load increases. The supply amount is increased accordingly, and when the switching point is exceeded, the supply m of stratified fuel is decreased. On the other hand, the second fuel supply means 13 starts supplying the dispersed fuel above the switching point to compensate for the decrease in the amount of stratified fuel produced by the first fuel supply means 11, and the total supply amount increases as the load increases. The supply m of the dispersion fuel is increased so as to shift from stratified combustion to uniform combustion. At this time, the injection amount and number of injections for each injection are set in accordance with the engine rotation speed.

That is, the fuel supply amount control by the first fuel supply means 11 and the second fuel supply means 13 corresponding to the load of the engine is as follows.
This is done as shown in FIG. FIG. 3 shows the fluctuation of the fuel supply IQ with respect to the fluctuation of the load as well as the fluctuation of the excess air ratio λ.The throttle valve 14 is basically fully open and the intake air pressure is constant, and the In response to an increase in , the fuel supply mQ is increased to reduce the excess air ratio λ, that is, the air-fuel ratio is enriched to perform output control.

Fuel supply IMQk: Fuel in region (3) is supplied from the first fuel supply means 11, and fuel in region H is supplied from the second fuel supply means 13. First fuel supply means 11
The supply of stratified fuel increases as the load increases below negative vj, which corresponds to the switching point of point A determined by the signal of the exhaust sensor 18;
The fuel supply from the first fuel supply means 11 is reduced, and when the load exceeds point B, a small amount of fuel injection is continued in order to prevent the stratification fuel injection nozzle 9 from clogging with carbon and to prevent heating.

On the other hand, the supply of dispersed fuel by the second fuel supply means 13 starts at a switching point of point A or above, and when the load increases from this point on, it compensates for the decrease in the supply of stratified fuel by the first fuel supply means 11, and Overall, increased fuel is supplied in response to an increase in load.

The switching point of point A above is the excess air ratio λ being controlled at that point.
is set to a value that is less than the ignition limit excess air ratio λ that allows ignition even in a homogeneous mixture, and point B is set at a value such that the excess air ratio λ at that point is such that the air utilization rate decreases due to stratified combustion. The value is set so that the excess air ratio is 2 or more, at which smoke begins to occur. The curve of the excess air ratio λ changes as the air density changes, and the optimum excess air ratio λ for the switching point A is determined based on the output signal of the exhaust sensor 18 for this changed characteristic. It is something to detect.

Therefore, below the above point A, there is a stratified combustion region in which fuel is supplied unevenly around the ignition device 8 of the combustion chamber 1, and above point 8 there is a stratified combustion region in which fuel is distributed and supplied throughout the combustion chamber 1. In the combustion region, the region between Δ-B is a transition region from the stratified combustion region to the uniform combustion region.

Note that the start timing of the supply of distributed fuel by the second fuel supply means 13 is not made to coincide with the switching point A point at which the supply of stratified fuel by the first fuel supply means 11 is reduced, but rather, the timing of starting the supply of distributed fuel by the second fuel supply means 13 is determined based on the successive loads in the vicinity of this point A. Supply in state #[I 'lh J
All you have to do is make it so.

Moreover, the stratified fuel supply by the first fuel supply means 11 and the second
The switching of the distributed fuel II supply by the fuel supply means 13 is performed by gradually decreasing and increasing as described above, and also by switching on and off at the switching point in the load state between the set load point A and B point. It may be possible to switch.

Next, FIG. 4 shows that the first fuel supply means 1
1 indicates the ignition timing of the stratified fuel injection (injector start time 1!1). In the region where stratification is performed below the switching point of point A, the injection timing is the ignition timing near compression top dead center. The timing is set at a predetermined time interval, and ignition is performed with the injected fuel effectively unevenly distributed around the ignition device 8. Above A
As the point moves beyond point B to the region where point B is dispersed, the injection ++j period is advanced and injection is performed at an early stage C.
The uneven distribution of the fuel injected from the fuel supply means 11 is reduced and the fuel is dispersed throughout the combustion chamber 1. Also, at extremely low load such as during idling, fuel injection is 0, 1111.
J d3 J: The ignition timing has been advanced slightly to improve stability. In addition, in Fig. 4, the ignition timing is set to be approximately constant in response to load fluctuations, but this changes as the load increases.
It may also be changed to advance the ignition timing.

Furthermore, the opening/closing control of the throttle valve 14 by the secondary means 16 is basically to return the throttle valve 14 to a fully open state to perform non-throttle operation. The closing operation timing of this throttle valve 14 is
For example, in order to enrich the air-fuel ratio at extremely low loads such as when starting or idling the engine, to obtain good startability and low speed rotation, or when the water temperature detected by the water temperature sensor 20 is lower than the set temperature or when the engine is cold, or when the catalyst In order to reduce the amount of intake air when the temperature of the device 7 is low to raise the temperature quickly, and to prevent a drop in catalyst temperature during deceleration when fuel supply is stopped and to improve engine braking performance. , are controlled to close the throttle valves 14, respectively.

Therefore, according to the stratified air charge engine of the above embodiment, in the normal operating range of low/medium loads below the switching point A, stratified combustion is achieved, and good youthfulness is achieved.
At the same time, in this stratified region, the intake air level is kept constant without closing the throttle valve 14, and the output is controlled by the fuel supply m by the first fuel supply means 11. By doing so, the pumping loss accompanying the throttling operation of the throttle valve 14 can be significantly reduced, and fuel efficiency is further improved.

In addition, in the high-load operation range beyond the switching point A, the system shifts from stratified combustion to uniform combustion to increase the air utilization rate and perform high-output operation without generating smoke.
Good driving performance can be achieved in all driving ranges, and fuel efficiency can be improved by reducing pumping losses.

Furthermore, by switching from stratified combustion to uniform combustion in accordance with the output signal of the exhaust sensor 18, when the air density decreases due to a rise in temperature or a drop in atmospheric pressure (when moving to high altitudes), etc. During supercharging, the switching point shifts to the low load side, while on the other hand, it switches when the switching point shifts to the high load side.This allows for good stratified combustion without smoke or a drop in output. Uniform combustion can be switched.

Note that the second fuel supply means 13 may supply dispersed fuel to the intake passage 3 using a carburetor instead of the fuel injection method using the dispersion fuel injection nozzle 12.
The combustion chamber 1 may be of a type in which the subchamber is tilted to the right.

Further, in the above embodiment, the dispersion fuel injection nozzle 12 of the second fuel supply means 13 is interposed in the middle of the intake passage 3; Like the stratified fuel injection nozzle 9 of the first fuel supply means 11, it may be arranged so as to open into the combustion chamber 1, and in that case, the second fuel supply means 13 directly supplies the fuel to the combustion chamber 1. The injection timing of the dispersed fuel is the same as the first one above.
It is set so that the injection is completed earlier than the fuel injection timing by the fuel supply means 11 and between the intake stroke and the early stage of the compression stroke, and the fuel supplied to the second fuel supply means 73 is mixed with the intake air and flows into the combustion chamber. so that it is evenly distributed within 1,
This ensures uniform combustion.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of a stratified air supply engine according to an embodiment of the present invention, Fig. 2 is a plan view schematically showing the combustion chamber, and Fig. 3 is a diagram showing the control of the amount of fuel supplied to the load with excess air. FIG. 4 is a characteristic diagram showing the injection timing and ignition timing of stratified fuel by the first fuel supply means with respect to load fluctuations. 1... Combustion chamber 3... Intake passage 8...
... Ignition device 9 ... Fuel injection nozzle for stratification 10 ... Fuel injection pump 11 ... 1st j15 fuel supply means 12 ...
・Distribution fuel injection nozzle 13... Second fuel supply means 16... Control means 17... Load detection means 18... Exhaust sensor

Claims (1)

[Claims] (1) A first fuel supply means for supplying fuel around the ignition device in the combustion chamber, and a second fuel supply means for dispersing the fuel into the combustion chamber.
It is equipped with a fuel supply means and an exhaust sensor that detects the excess air ratio from the exhaust gas concentration, and receives the signal from the exhaust sensor to set the switching point between stratified combustion and uniform combustion, and to reduce the load below the switching point. In the region, the amount of fuel supplied from the first fuel supply means is increased according to the increase in load, and when the switching point is exceeded, the amount of fuel supplied is decreased, while in the high load region near or above the switching point, the second fuel supply is increased. A stratified air supply engine characterized in that it is provided with control means for starting fuel supply from the means and increasing the amount of fuel supplied as the load increases.