JPH0583730B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a stratified air charge engine.

(Prior art) Conventionally, for the purpose of improving the fuel efficiency and emission performance of an engine, 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 this part A stratified air charge engine that achieves lean combustion as a whole by enriching the air-fuel ratio of the fuel and performing stratified combustion with improved ignitability is disclosed, for example, in JP-A-49-62807 and JP-A-49.
- It is publicly known as seen in No. 128109.

In the above-mentioned stratified air supply engine, the ignition fuel supplied around the ignition device is constant regardless of the load, and at the same time the ignition fuel is supplied, distributed fuel is supplied in an amount corresponding to the load. In this engine, since the exhaust gas temperature tends to be low, there is a problem that the catalyst device provided in the exhaust passage becomes overcooled, resulting in insufficient exhaust purification performance.

In other words, in stratified combustion, fuel efficiency is improved by achieving lean combustion, and pumping loss is reduced by increasing the opening of the throttle valve, but the amount of intake air is large. As the cooling performance increases, the exhaust temperature decreases. For example, during deceleration, there is almost no fuel supplied, so only low-temperature air passes through the catalyst device in the exhaust passage, bringing the catalyst into a supercooled state. When resuming the reaction purification associated with fuel supply, the catalyst device Since the temperature is low and the catalyst is not activated and does not reach the reaction temperature, there is a problem that sufficient purification performance is not obtained and emission properties are deteriorated.

(Object of the Invention) Therefore, in view of the above circumstances, the present invention performs stratified combustion in which fuel is unevenly distributed and supplied around the ignition device at least at low load times, and at the same time, in high load regions, the fuel is distributed throughout the combustion chamber. The purpose of the present invention is to provide a stratified air supply engine that achieves good stratified combustion and uniform combustion by uniformly combusting the air supplied with air, prevents overcooling of the catalyst device, and improves exhaust purification performance. It is.

(Structure of the Invention) The stratified air supply engine of the present invention includes a fuel supply means for supplying fuel for output control corresponding to the load into a combustion chamber, an ignition device disposed in the combustion chamber, and an opening area of an intake passage. It is equipped with an intake throttle means that controls the air flow without being mechanically linked to the access operation, a catalyst device disposed in the exhaust passage, and an exhaust temperature detection means that detects the temperature of the exhaust system.At least when the load is low, the fuel By supplying fuel unevenly distributed around the ignition device from the supply means and igniting it, stratified combustion is performed, and the intake throttle means increases the opening area of the intake passage in comparison to the amount of fuel to produce lean fuel. On the other hand, when the load is high, fuel is supplied dispersedly into the combustion chamber and ignited to achieve uniform combustion. When the air pressure decreases below, the intake air throttle means reduces the opening area of the intake passage to reduce the amount of intake air.

(Effect of the invention) In a low load range, the fuel supply means supplies fuel unevenly distributed around the ignition device in the combustion chamber to perform stratified combustion, and the intake throttle means supplies fuel unevenly distributed around the ignition device in the combustion chamber. This increases the opening area of the intake passage and performs lean combustion to improve fuel efficiency, while at the same time, in high-load operating ranges, the fuel supplied by the fuel supply means is dispersed for uniform combustion to reduce smoke generation. Good high-output operation can be ensured without any problems.

In addition, when the exhaust temperature is low, the intake air restrictor narrows the intake passage to reduce the amount of intake air, suppressing overcooling of the catalyst due to a large amount of intake air, and raising the catalyst temperature early when the catalyst reaction starts. This can be activated to ensure good exhaust purification performance.

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

Embodiment 1 This embodiment is shown in FIGS. 1 to 5, and shows an example in which the fuel supply means is composed of a first fuel supply means for stratification and a second fuel supply means for dispersion.

In the engine shown in FIG. 1, 1 is a combustion chamber formed above a piston 2, 3 is an intake passage that introduces intake air into the combustion chamber 1, 4 is an exhaust passage that leads out exhaust gas from the combustion chamber 1; Reference numeral 5 indicates an intake valve, 6 an exhaust valve, and 7 a catalyst device interposed in the exhaust passage 4, respectively.

The combustion chamber 1 is provided with an ignition device 8 using a spark plug, and a stratified fuel injection nozzle 9 for supplying fuel around the ignition device 8. The fuel injection pump 10 is connected to the first fuel supply means 11.
is configured.

On the other hand, a second fuel supply means 13 is interposed in the intake passage 3 and includes a dispersion fuel injection nozzle 12 for distributing fuel into the combustion chamber 1 . Further, a throttle valve 14 is disposed downstream of this dispersion fuel injection nozzle 12, and an actuator 15 (not linked to accelerator operation) for opening and closing the throttle valve 14 is disposed in the intake passage. An intake throttle means 21 is configured to control the opening area of No. 3 to regulate the amount of intake air.

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. is formed in the swirl port, and due to this swirl, the first combustion supply means 11
The ignition fuel supplied from the stratified fuel injection nozzle 9 and ignited by the ignition device 8 is sufficiently mixed with air, and the flame is propagated throughout the combustion chamber 1, so that the entire injected fuel is sufficiently combusted. be.

Fuel injection pump 1 of the first fuel supply means 11
0, the operation of the dispersing fuel injection nozzle 12 of the second fuel supply means 13 and the actuator 15 of the intake throttle means 21 is controlled by the control means 16.

The control means 16 receives a load signal from a load detection means 17 that detects the required load of the engine using, for example, an accelerator sensor, and receives a load signal from a load detection means 17 that detects the required load of the engine by using, for example, an accelerator sensor. Exhaust temperature detection means 1 detected by a sensor
temperature signal from 8, intake pressure signal from intake pressure sensor 19, and engine rotation sensor 20.
receives the engine rotation signal etc. from the stratification fuel injection nozzle 9, controls the fuel injection amount and fuel injection timing from the stratification fuel injection nozzle 9, and the fuel injection amount from the dispersion fuel injection nozzle 12, and also controls the closing operation timing of the throttle valve 14. It is something to control.

The control means 16 operates the intake throttle means 21 to close the throttle valve 14 and throttle the opening area of the intake passage 3 when the exhaust temperature is low, below a set value, in response to a detection signal from the exhaust temperature detection means 18. This reduces the amount of air.

Further, the control means 16 performs fuel supply amount control corresponding to the load by receiving a signal from the load detection means 17, and in the normal operating range in the low/medium load range below the set load, the second fuel supply means 13 controls the amount of distributed fuel. The supply is stopped, stratified fuel is supplied by the first fuel supply means 11 to perform stratified combustion, and the supply amount is increased as the load increases, and when the set load is exceeded, the supply amount of the stratified fuel is decreased. It is. on the other hand,
The distributed fuel by the second fuel supply means 13 starts to be supplied at a load equal to or higher than the above-mentioned set load, and compensates for the decrease in the amount of stratified fuel by the first fuel supply means 11, and also increases the total supply amount as the load increases. This is to increase the supply amount of dispersion fuel 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 engine load is performed as shown in FIG. This figure 3 shows the fluctuation of the fuel supply amount Q with respect to the fluctuation of the load, together with the fluctuation of the excess air ratio λ.
The throttle valve 14 is basically fully open and the amount of intake air is constant, and when the load increases, the fuel supply amount Q is increased to reduce the excess air ratio λ, that is, the air-fuel ratio is enriched to control the output. is set up to do so. In the fuel supply amount Q, the fuel in region I is
The fuel is supplied from the fuel supply means 11, and the fuel in the area is supplied from the second fuel supply means 13. The supply of stratified fuel by the first fuel supply means 11 increases as the load increases below the set load at point A, while when the set load exceeds point A, the supply of fuel from the first fuel supply means 11 decreases. However, when the load is high beyond 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 distributed fuel by the second fuel supply means 13 starts at a load equal to or higher than the set load at point A,
When the load increases from this, the first fuel supply means 11
This will compensate for the decrease in the supply of stratified fuel due to this, and will also supply increased fuel in response to the overall increase in load.

The set load at point A is set to a load state such that the excess air ratio λ at that point is less than the excess air ratio λ, which is the ignition limit that allows ignition even in a homogeneous mixture, and the load at point B is set at that point. The load condition is set such that the excess air ratio λ at the time becomes equal to or higher than the excess air ratio λ at which the air utilization rate decreases and smoke starts to occur due to stratified combustion.

Therefore, below the above-mentioned 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 B, fuel is distributed and supplied throughout the combustion chamber 1. In the uniform combustion region, A-B
The region between is the transition region from the stratified combustion region to the uniform combustion region.

Also, the switching point A from stratified combustion to uniform combustion
The point is set to vary according to the intake pressure detected by the intake pressure sensor 19, and is set to shift to the low load side when the intake pressure, that is, the intake air density decreases.

Note that the timing at which the second fuel supply means 13 starts supplying the distributed fuel is not made to coincide with the set load point A at which the supply of stratified fuel by the first fuel supply means 11 is reduced, but rather to match the successive loads near this point A. The supply may be started in the state.

In addition, the switching between the stratified fuel supply by the first fuel supply means 11 and the distributed fuel supply by the second fuel supply means 13 is performed by gradually decreasing and increasing as described above, and also by changing the setting load between point A and point B. It may be possible to switch it on and off in a load state between.

Next, FIG. 4 shows the injection timing (injection start timing) and ignition timing of stratified fuel by the first fuel supply means 11 in response to load fluctuations, and stratification is performed below the set load at point A. In this region, the injection timing is set a predetermined amount earlier than the ignition timing near compression top dead center, and ignition is performed with the injected fuel effectively unevenly distributed around the ignition device 8. As we move beyond point A to the area where point B is decentralized,
The injection timing is advanced to perform injection at an earlier stage, thereby reducing uneven distribution of the fuel injected from the first fuel supply means 11 and dispersing it throughout the combustion chamber 1. Additionally, during extremely low load conditions such as during idling, the fuel injection timing and ignition timing are slightly advanced to improve stability.

On the other hand, the control means 16 controls the opening and closing of the throttle valve 14 of the intake throttle means 21 as shown in FIG.
Basically, non-throttle operation is performed with the throttle valve 14 fully open, and the opening degree is reduced during engine startup, deceleration, etc. to reduce the amount of intake air. In addition, when the exhaust temperature is low, as shown by the chain line in Figure 5, the valve is throttled in the low and medium load range, and as the load decreases, the opening is made smaller and the amount of intake air is reduced. .

Therefore, according to the stratified air charge engine of the above embodiment, in the normal operating range at low and medium loads below the set load point A, stratified combustion is performed to obtain good ignitability, and lean combustion is made possible to improve fuel efficiency. At the same time, in this stratified region, the intake air amount is kept constant without closing the throttle valve 14, and the output is controlled by the fuel supply amount by the first fuel supply means 11. Pumping loss associated with the throttling operation of the valve 14 can be significantly reduced, and fuel efficiency is further improved.

In addition, in the high-load operation range exceeding the set load point A mentioned above, the system shifts from stratified combustion to uniform combustion to increase the air utilization rate and perform high-output operation without smoke generation. It provides good driving performance and improves fuel efficiency by reducing pumping loss.

Further, when the exhaust gas temperature is low, the intake air throttle means 21 closes the throttle valve 14 to reduce the amount of intake air, thereby reducing the amount of air flowing through the catalyst device 7, thereby preventing the catalyst device 7 from being overcooled. At this time, as the intake pressure decreases due to the closing operation of the throttle valve 14, the switching point A from stratified combustion to uniform combustion shifts to the low load side, and homogeneous combustion is performed from the low load state, and the exhaust gas The catalyst temperature is made to rise quickly as the temperature rises.

Note that the second fuel supply means 13 uses a fuel injection method using the dispersion fuel injection nozzle 12,
A vaporizer may be used to supply dispersed fuel to the intake passage 3.

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; Similarly to 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. In that case, the second fuel supply means 13
The injection timing of the dispersed fuel directly supplied to the
earlier than the fuel injection timing by the fuel supply means 11,
The injection is set to be completed between the intake stroke and the early stage of the compression stroke, and the fuel supplied by the second fuel supply means 13 is mixed with the intake air and uniformly dispersed in the combustion chamber 1, thereby achieving uniform combustion. This is what you get.

Embodiment 2 This embodiment is shown in FIGS. 6 to 9, and is an example in which the fuel supply means is constituted by one fuel injection nozzle provided in the intake passage.

In the engine shown in FIGS. 6 and 7,
22 is a primary intake passage that opens to the primary intake port 23 of the combustion chamber 1, and 24 is the secondary intake port 25.
26 is an exhaust port 27
28 is a primary intake valve, 29 is a secondary intake valve, 30 is an exhaust valve, and 8 is an ignition device using a spark plug.

The downstream portion of the primary intake passage 22 is located in the combustion chamber 1.
The swirl port is provided at the swirl port that forms a swirl, and the upstream side merges with the secondary intake passage 24, and the amount of intake air is regulated by the operation of the intake throttle means 21 by the throttle valve 14. A swirl control valve 31 is interposed.

Further, a fuel injection nozzle 32 is disposed in the primary intake passage 22, which injects fuel from the valve gap toward the vicinity of the ignition device 8 in the combustion chamber 1 when the primary intake valve 28 is opened. A fuel supply means 33 is configured.

The fuel supply means 33 and the intake throttle means 21
In this case, the amount of fuel injected from the fuel injection nozzle 32, the injection timing, and the opening degree of the throttle valve 14 are controlled by the same control means (not shown) as in the previous example. The fuel supply means 33 controls the output by increasing the amount of fuel supplied according to the load, and switches between stratified combustion and uniform combustion by controlling the injection timing.

That is, the fuel injection timing is performed as shown in FIG. 8, where S indicates the injection start timing and E indicates the injection end timing. The fuel injection timing in the stratified load region below the set load, which corresponds to point A in FIG. Fuel flows into the combustion chamber 1 through the opening gap of the valve 28 and is supplied so as to be unevenly distributed around the ignition device 8, and even when the piston 2 rises in the compression stroke, the fuel is distributed unevenly in the upper part of the combustion chamber 1. This is to perform stratified combustion. At this time, the end of fuel injection is set at a fixed time, the start of injection is made earlier, and the amount of injection is increased as the load increases.

In addition, when the set load at point A is exceeded, the injection timing is greatly advanced to make it earlier, and when the load exceeds point B, the end of injection is kept constant and the start of injection is advanced to respond to the increase in load. This increases the injection amount, and by supplying fuel from the beginning of the intake stroke, the fuel that has flowed into the combustion chamber 1 is dispersed throughout the combustion chamber 1 by the flow of intake air, resulting in uniform combustion. .

The switching point A from stratified combustion to uniform combustion is
As in the previous example, it is set to shift to the low load side as the intake pressure decreases.

Note that the swirl control valve 31 installed in the secondary intake passage 24 opens from the set point A to supply intake air from the secondary intake passage 24 as well, and replaces the intake air supplied by the primary intake passage 22. This prevents the swirl strength from becoming excessive, suppresses the occurrence of combustion noise and knocking caused by an abnormal increase in combustion speed, and also reduces intake resistance and improves intake efficiency.

The opening degree of the throttle valve 14 in this embodiment is controlled as shown in FIG. In this example, the stratification of the fuel in the stratification region is lowered as the proportion of fuel being unevenly distributed around the ignition device 8 is lower than in the previous example, so the throttle valve 14 needs to be throttled to reduce the amount of intake air. However, compared to conventional carburetor engines, which control the output based on the amount of air-fuel mixture filling, as shown by the chain line, the throttle opening is small;
Pumping loss can be reduced.

When the exhaust gas temperature decreases, the throttle valve opening degree is reduced to the degree shown by the chain line to reduce the amount of intake air.

Therefore, in this embodiment as well, at low loads, lean combustion is performed by stratified combustion to improve fuel efficiency, while at high loads, homogeneous combustion allows high output operation without smoke generation. can.

In addition, when the exhaust temperature decreases, the intake air amount is reduced by reducing the opening area of the intake passage, and the catalyst device 7
In addition to preventing overcooling of the fuel, the transition to uniform combustion is brought forward, and the temperature is raised early at the start of the reaction to activate the catalyst.

In both of the above embodiments, the switching point from stratified combustion to uniform combustion is shifted to the low load side according to the intake pressure, and uniform combustion is performed early when the exhaust temperature is low. Alternatively, when the exhaust gas temperature decreases, the fuel injection timing may be advanced even under low load to obtain a tendency toward uniform combustion.

Furthermore, in both of the above embodiments, the amount of reduction in the amount of intake air by the intake air throttle means 21 is changed and adjusted according to the exhaust gas temperature, that is, the catalyst temperature, so that the amount of intake air is increased as the temperature rises. Good too.

[Brief explanation of the drawing]

1 to 5 show a first embodiment of the present invention, and FIG. 1 is a schematic configuration diagram of a stratified air intake engine;
Fig. 2 is a plan view schematically showing the combustion chamber, Fig. 3 is a characteristic diagram showing control of fuel supply amount with respect to load along with excess air ratio, and Fig. 4 is a diagram showing the control of fuel supply amount with respect to load.
A characteristic diagram showing the injection timing and ignition timing of the stratified fuel by the fuel supply means, FIG. 5 is a characteristic diagram showing the opening degree of the throttle valve with respect to load fluctuation, and FIGS. 6 to 9 show a second embodiment of the present invention. Fig. 6 is a bottom view showing a partial section of the cylinder head in a stratified air charge engine, Fig. 7 is a sectional view taken along the - line in Fig. 6, and Fig. 8 shows fuel injection timing control according to load. FIG. 9 is a characteristic diagram showing the opening degree control of the throttle valve with respect to the load. DESCRIPTION OF SYMBOLS 1... Combustion chamber, 3... Intake passage, 7... Catalyst device, 8... Ignition device, 9... Fuel injection nozzle for stratification, 10... Fuel injection pump, 11... First fuel supply means, 12 ...Fuel injection nozzle for dispersion, 13
...second fuel supply means, 14...throttle valve, 15...
...actuator, 16...control means, 17...
Load detection means, 18... Exhaust temperature detection means, 21
...Intake throttle means, 32...Fuel injection nozzle, 3
3...Fuel supply means.

Claims (1)

[Claims] 1. A fuel supply means that supplies fuel for output control in accordance with the load into the combustion chamber, an ignition device disposed within the combustion chamber, and a control system that controls the opening area of the intake passage without mechanically linking it to the accelerator operation. At least when the load is low, the fuel supply means distributes fuel unevenly around the ignition device. The fuel is supplied and ignited to perform stratified combustion, and the intake throttle means increases the opening area of the intake passage compared to the amount of fuel to perform lean combustion. At the time of high load, the fuel is dispersed within the combustion chamber. In the stratified air supply engine, which performs uniform combustion by supplying and igniting the exhaust gas, when the temperature of the exhaust system falls below a set value in response to an output from the exhaust temperature detecting means, the intake throttle means A stratified air intake engine characterized in that the opening area of the intake passage is reduced to reduce the amount of intake air.