JPH0480207B2 - - 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. However, when the engine is running at high speeds, it is difficult to distribute the fuel unevenly around the ignition device, as it is at low speeds, and ignitability and combustibility are reduced.
There are problems that adversely affect output performance and emission performance.

In other words, in stratified combustion, fuel efficiency is improved by achieving lean combustion at low and medium loads, and the opening of the throttle valve is increased to reduce pumping loss. However, when the engine is operating at high speeds, the amount of intake air increases and its flow velocity increases, so the fuel is unevenly distributed around the ignition device, especially when the amount of fuel supplied is small, such as when the load is low. Because the supplied fuel disperses quickly and to a large extent, a sufficient stratified state is not maintained when ignited by the ignition device, making stratification incomplete and difficult, resulting in reduced ignitability and combustibility. .

(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. This ensures good stratified combustion and uniform combustion, as well as ensuring good stratified combustion at low engine speeds, while improving ignitability and combustibility at high engine speeds. The object of the present invention is to provide a stratified intake engine that achieves good output performance and emission performance.

(Structure of the Invention) The stratified air supply engine of the present invention includes a fuel supply means for supplying fuel around an ignition device in a combustion chamber, and an intake throttle means for controlling the opening area of an intake passage. This system performs stratified combustion by supplying fuel unevenly distributed around the ignition device from the supply means and igniting it, while at high loads it performs uniform combustion by supplying fuel distributed within the combustion chamber and igniting it. When the engine speed increases in the stratified combustion region, the opening area of the intake passage by the intake throttle means is made smaller than when the engine speed is low, thereby reducing the amount of intake air and enriching the air-fuel ratio. That is.

(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, improving fuel efficiency through lean combustion, while improving fuel efficiency. In the load operation range, the fuel supplied by the fuel supply means is dispersed to perform uniform combustion, and it is possible to ensure good high-output operation without generating smoke.

Furthermore, when the engine is running at high speeds in the region where stratified combustion is performed, the intake air throttle means reduces the amount of intake air compared to when the engine is running at low speeds, making the air-fuel ratio richer, ensuring reliable ignition and combustibility. Therefore, good exhaust purification performance can be obtained.

(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 6, and shows an example in which the fuel supply means is composed of a first fuel supply means for stratification and a second combustion 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 installed 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 the dispersion fuel injection nozzle 12, and an actuator 15 (not linked to accelerator operation) for opening and closing the throttle valve 14 is installed in the intake passage. An intake throttle means 20 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 fuel 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 dispersion fuel injection nozzle 12 of the second fuel supply means 13 and the actuator 15 of the intake throttle means 20 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 a detection signal from an engine rotation sensor 18 that detects the engine rotation speed, and also receives a detection signal from a water temperature sensor 19. receives the water temperature 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, the fuel injection amount from the dispersion fuel injection nozzle 12, etc., and controls the closing timing of the throttle valve 14. It is something to do.

The fuel supply amount control corresponding to the load by the control means 16 receives a signal from the load detection means 17, and the distributed fuel supply by the first fuel supply means 13 is stopped in the normal operation range in the low/medium load range below the set load. However, 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. 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, to compensate for the decrease in the amount of stratified fuel by the first fuel supply means 11, and to supply the entire amount as the load increases. The amount of fuel for dispersion increases so that the amount of fuel for dispersion increases, thereby shifting 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 established 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.

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.

On the other hand, from the relationship between the engine speed and the load, as shown in FIG. A uniform fuel region H is set in which the fuel is dispersed, and
An intake throttle area G in which the throttle valve 14 is throttled by the intake throttle means 20 is set on the side of the stratified combustion area F from the boundary (A curve) of the uniform fuel area H. In addition, in a region where the engine speed is high, the above-mentioned curve A is set to decrease so that uniform combustion is performed from a low load region.

FIG. 5 illustrates the opening degree of the throttle valve 14 with respect to fluctuations in engine speed under a constant load condition. In FIG. N
Throttle valve 14 near the area where the engine speed is high
is narrowed down to reduce the opening area to regulate the amount of intake air, and is set to be fully open in the low rotation range.

Note that the control of the intake throttle means 20 with respect to the load by the control means 16 is basically based on the throttle valve 14.
Non-throttle operation is performed with the engine fully open, and the opening degree is reduced during engine startup and deceleration to reduce intake air, for example.

Next, FIG. 6 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. Beyond point A above
As the point shifts to a region where points are dispersed, the injection timing is advanced to perform injection at an earlier stage, thereby reducing uneven distribution of fuel injected from the first fuel supply means 11 and dispersing it throughout the fuel chamber 1. Let them do it. Additionally, during extremely low load conditions such as during idling, the fuel injection timing and ignition timing are slightly advanced to improve stability.

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.

Furthermore, even in the stratified combustion region below point A, when the engine speed is high, the intake throttle means 20 closes the throttle valve 14 to reduce the opening area of the intake passage 3, reducing the amount of intake air and reducing the air-fuel ratio. This ensures excellent ignitability and combustibility.

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. 7 to 11, 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. 7 and 8,
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 20 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 fuel 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 20
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. 9, 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. The fuel flows into the fuel chamber 1 through the opening gap of the primary intake valve 28 and is supplied unevenly around the ignition device 8, so that even when the piston 2 rises during the compression stroke, the fuel flows into the upper part of the combustion chamber 1. They are unevenly distributed 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 increased and advanced, 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 system increases the injection amount by supplying fuel from the beginning of the intake stroke to the combustion chamber 1.
The fuel flowing into the combustion chamber 1 is dispersed throughout the combustion chamber 1 by the flow of intake air, thereby achieving uniform combustion.

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 a conventional carburetor type engine as shown by the chain line in which the output is controlled by the air-fuel mixture filling amount, the throttle opening is small and pumping loss can be reduced.

In the high rotation state in the stratified combustion region F, that is, in the intake throttle region G in FIG. The fuel ratio is enriched, and the throttle valve opening for this rotational speed is controlled so that as the rotational speed increases, the opening area of the intake passage 3 decreases as shown in Fig. 11. do.

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.

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.

Furthermore, when the engine speed increases in the stratified combustion region, the air-fuel ratio is enriched by reducing the amount of intake air, thereby achieving good ignitability and combustibility.

[Brief explanation of drawings]

1 to 6 show a first embodiment of the present invention, and FIG. 1 is a schematic configuration diagram of a stratified air charge engine;
Figure 2 is a plan view schematically showing the combustion chamber, Figure 3 is a characteristic diagram showing the control of fuel supply amount with respect to load along with excess air ratio, and Figure 4 is a stratified combustion region with respect to fluctuations in engine speed and load. Figure 5 is a characteristic diagram showing the relationship between the uniform combustion area and the intake throttle area. Figure 5 is a characteristic diagram showing the relationship between engine speed and throttle valve opening when the load is constant. 1
Characteristic diagrams showing the injection timing and ignition timing of stratified fuel by the fuel supply means, FIGS. 7 to 11 show a second embodiment of the present invention, and FIG. 7 shows a part of the cylinder head in a stratified intake engine. 8 is a sectional view taken along the - line in FIG. 7, FIG. 9 is a characteristic diagram showing fuel injection timing control with respect to load, and FIG. 10 is a diagram showing throttle valve opening control with respect to load. The characteristic diagram shown in FIG. 11 is a characteristic diagram showing the relationship between the engine speed and the throttle valve opening when the load is kept constant. DESCRIPTION OF SYMBOLS 1... Combustion chamber, 3... Intake passage, 8... Ignition device, 9... Fuel injection nozzle for stratification, 10... Fuel injection pump, 11... First fuel supply means, 12...
...dispersion fuel injection nozzle, 13...second fuel supply means, 14...throttle valve, 15...actuator, 16...control means, 17...load detection means,
18...Engine rotation center, 20...Intake throttle means, 32...Fuel injection nozzle, 33...Fuel supply means.

Claims (1)

[Claims] 1. A fuel supply means for supplying fuel into the combustion chamber;
The combustion chamber is equipped with an ignition device disposed in a combustion chamber and an intake throttle means for controlling the opening area of the intake passage, and at least when the load is low, the fuel supply means supplies fuel unevenly distributed around the ignition device and ignites the combustion chamber. This is a stratified air supply engine that performs stratified combustion, and at high loads, disperses fuel into the combustion chamber and ignites it to achieve uniform combustion. The stratified intake system is characterized in that the intake throttle means is closed according to the engine speed so that the opening area of the intake passage is smaller than the opening area of the intake passage due to the intake throttle means at low engine speeds. Chi engine.