JPH04321747A - Internal combustion engine - Google Patents

Abstract

PURPOSE:To enhance the exhaust purifying performance by increasing the exhaust temperature at the time of engine starting and warming-up while, on the other hand, the merit of the stratified combustion engine is kept effective. CONSTITUTION:When, at the time of engine starting and warming-up, the temperature of a cooling water detected by a water temperature sensor 55 is below a prescribed value, since the fuel injection starting timing is advanced by fuel injection timing control means 61, the fuel is substantially uniformly distributed within a combustion chamber 23. On the other hand, since the amount of sucked air is decreased or increased in accordance with the increase or decrease in the number of idle revolutions and in addition the injecting amount of fuel is similarly decreased or increased by fuel injection amount control means 62, the fuel combustion is uniformly conducted as in an ordinary engine. Resultantly, the exhaust temperature becomes higher than in the case of a stratified combustion whereby the exhaust purifying performance of a catalyst at the time of engine starting and warming-up is enhanced. Excess of the cooling-water temperature over a prescribed value causes change-over from the uniform combustion to the stratified combustion. This makes effective the merit of the stratified combustion engine as it is.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine having a fuel injection device and a catalyst.

0002

2. Description of the Related Art A stratified combustion engine is known in which fuel partially injected into a combustion chamber near a spark plug is ignited and burned in a stratified manner. In such a stratified combustion engine, fuel is partially injected near the spark plug and ignited, so less fuel (
That is, the stratified combustion engine can perform stable combustion at low engine speeds, and is suitable for engines that require a low idle speed, such as automobile engines.

By the way, in such a stratified combustion engine, in order to reliably burn partially injected fuel, it is necessary to reliably supply fresh air to the location where the fuel has been injected. However, because it is difficult to reliably supply fresh air to certain areas, stratified combustion engines are operated with excess air compared to normal engines, and their exhaust temperature is lower than that of normal engines. Become.

0004

[Problems to be Solved by the Invention] Incidentally, in order for a catalyst for exhaust purification to work effectively, a temperature above a certain level (activation temperature) is required, but in a stratified combustion engine, as mentioned above, In addition, since the exhaust temperature is lower than that of a normal engine, there is a problem in that the exhaust purification performance is low, especially during startup and warm-up when the exhaust temperature is low.

The present invention has been made in view of the above problems, and its purpose is to improve exhaust purification performance by increasing the exhaust temperature at startup and warm-up while making full use of the advantages of a stratified combustion engine. An object of the present invention is to provide an internal combustion engine that can achieve the following goals.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a fuel injection device that injects fuel near a spark plug in a combustion chamber, and an internal combustion engine having a catalyst provided in an exhaust pipe. a temperature sensor that detects the temperature, a fuel injection timing control means that controls the fuel injection start timing of the fuel injection device, a fuel injection amount control device that controls the fuel injection amount of the fuel injection device, and an intake air control that controls the amount of intake air. means is provided, and in an idling state, when the engine temperature detected by the temperature sensor is below a predetermined value, the fuel injection timing control means advances the fuel injection start timing compared to when the engine temperature is above the predetermined value. At the same time, the intake air control means decreases or increases the amount of intake air in accordance with the vertical movement of the idle rotation speed, and at the same time, the fuel injection amount control means decreases or increases the fuel injection amount.
In the idling state, if the engine temperature detected by the temperature sensor is above a predetermined value, the fuel injection timing control means retards the fuel injection start timing compared to when the engine temperature is below the predetermined value. The present invention is characterized in that the fuel injection amount control means decreases or increases the fuel injection amount in accordance with the vertical movement of the rotational speed.

[0007]

[Operation] According to the present invention, in an idling state,
When the engine temperature detected by the temperature sensor is below a predetermined value, that is, during startup and warm-up, the fuel injection timing control means advances the fuel injection start timing compared to when the engine temperature is above the predetermined value. As a result, the fuel is distributed approximately uniformly within the combustion chamber. Here, the intake air amount is decreased or increased by the intake air control means in accordance with the vertical movement of the idle speed, and the fuel injection amount is decreased or increased by the fuel injection amount control means, so that the fuel is the same as in a normal engine. It burns evenly. As a result, the exhaust gas temperature is higher than that in the case of stratified combustion, and the exhaust purification performance of the catalyst is enhanced even during startup and warm-up.

[0008] When the engine temperature reaches a predetermined value or higher due to completion of warm-up, etc., the fuel injection start timing is retarded compared to when the engine temperature is below the predetermined value, and the vertical fluctuation of the idle speed is Accordingly, the fuel injection amount is decreased or increased by the fuel injection amount control means, so the combustion is switched from uniform combustion to stratified combustion, and stable idling is performed at low rotation speeds, allowing the original benefits of the stratified combustion engine to be utilized. It will be done.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the overall configuration of an internal combustion engine according to the present invention, FIG. 2 is a sectional view of the main parts of the engine, and FIG. 3 is a sectional view of a fuel injection device.

First, the overall structure of the internal combustion engine according to the present invention will be explained based on FIG. A piston 3 is slidably fitted into each of the cylinders 2 . . . , and each piston 3 is connected to a crankshaft 5 via a connecting rod 4 . A part of the rotational power of the crankshaft 5 is transmitted to the air compressor 6 and the auxiliary machine 7 to drive these air compressor 6 and the auxiliary machine 7, and the rest of the rotational power of the crankshaft 5 is transmitted via the clutch 8. The signal is transmitted to the transmission 9 and used to drive the travel drive system.

By the way, as shown in FIG. 2, a scavenging port 10 and an exhaust port 11 are formed for each cylinder in the cylinder body 1, and an intake manifold 14 is connected to an intake port 13 that opens into the crank chamber 12. connected. The intake manifold 14 is provided with a reed valve 15 for each cylinder, and a flow rate sensor 16 is provided at the gathering portion of the intake manifold 14, as shown in FIG. Also, the flow rate sensor 16 of the intake manifold 14
As shown in FIG. 2, a main passage 17 and a bypass passage 18 are formed downstream of the main passage 1.
7. The bypass passage 18 has large and small main throttle valves 19,
A sub-throttle valve 20 is provided respectively. The main throttle valve 19 is connected to an accelerator pedal (not shown), and the sub-throttle valve 20 constitutes an intake control means, which is driven to open and close by a servo motor 21 during idling when the main throttle valve 19 is closed. to adjust the amount of intake air when idling.

Further, a combustion chamber 23 is formed for each cylinder in the cylinder head 22 attached to the upper part of the cylinder body 1 of the engine. A fuel injection device 30 is attached to inject fuel at appropriate timing. Furthermore, the cylinder head 22 is provided with a spark plug 24 for each cylinder.
are screwed on, and the discharge portion of each spark plug 24 faces the combustion chamber 23 (see FIG. 2).

By the way, as shown in FIG. 1, the fuel in the fuel tank 50 is supplied to the fuel injection device 30 after passing through a filter 51 and being pressurized by a fuel pump 52. 6
Compressed air that has been pressurized is supplied. The surplus fuel and compressed air that are not injected into each cylinder are discharged from the fuel injection device 30 through the pressure regulator 54 to the fuel tank 50 and an exhaust pipe (not shown), respectively. still,
As will be described later, the fuel injection device 30 injects fuel into the combustion chamber 23 of each cylinder, but the fuel injection start timing is controlled by the fuel injection timing control means 61, and the fuel injection amount is controlled by the fuel injection amount control means 62 ( (see Figure 1). Although not shown, the exhaust pipe is provided with a catalyst for purifying exhaust gas.

Further, in FIG. 1, 60 is a controller, which collects engine operating information, that is, the cooling water temperature detected by the water temperature sensor 55, and the rotation sensor 56.
The engine speed detected by the flow rate sensor 16
intake air amount detected by the throttle valve 19,
the fuel injection timing control means 61 based on the opening degree of 20;
Fuel injection amount control means 62, pressure regulator 54
and sends a control signal to the servo motor 21.

The configuration of the fuel injection device 30 will now be explained based on FIG. 3.

[0017] The fuel injection device 30 is connected to the cylinder head 22.
a housing 31 fixed to the housing 31 and an injection port 3 of an injection space 32 formed in the housing 31 into the combustion chamber 23;
It is configured to include a valve mechanism 33 that opens and closes 2a, an injector 34 that supplies fuel to the injection space 32, and an air rail 35 that supplies compressed air to the injection space 32.

An injector 34 is provided in the housing 31.
A fuel supply path 3 for guiding fuel from the injection space 32 to the injection space 32
6 and an air supply path 37 for guiding compressed air from the air compressor 6 (see FIG. 1) to the injection space 32.

Further, the valve mechanism 33 has a main valve 38 housed in the injection space 32, and the main valve 38 is biased by a leaf spring 39 and a spring 40 in the direction of closing the injection port 32a. has been done.

Next, the operation of this internal combustion engine will be explained with reference to FIGS. 4 to 7. In addition, FIG. 4 is a flow chart showing the transition of the combustion state of the engine, FIG. 5 is a chart showing the target idle speed of the engine with respect to the cooling water temperature, FIG. 6 is a timing chart showing the fuel injection start timing and fuel injection period, and FIG. Figures a), (b), and (c) are diagrams showing changes over time in the engine speed, catalyst temperature, and hydrocarbon (HC) content in exhaust gas after engine startup.

When the engine is started, it is determined whether the operating state is warm-up (idling) or not (step 1 in FIG. 4), and if the engine is running under load immediately after starting the engine, the engine is in the normal stratified state. The combustion cycle is made closer to the air cycle to improve thermal efficiency at partial loads and reduce air pollution. That is, the high-pressure fuel and compressed air supplied to the fuel injection device 30 are guided to the injection space 32 via the fuel supply path 36 and the air supply path 37 shown in FIG. When the solenoid 41 is energized for an appropriate time at an appropriate timing under the control of the control unit 62, the main valve 38 is opened for a predetermined period of time, and the fuel introduced into the injection space 32 is transferred together with compressed air from the injection port 32a to the combustion chamber 23. The mixture is atomized by being injected, and a rich air-fuel mixture is partially formed near the discharge part of the spark plug 24 in the combustion chamber 23.

On the other hand, the crank chamber 12 passes through the reed valve 15.
The fresh air sucked into the engine is first compressed by the descending piston 3, and then introduced into the combustion chamber 23 through the scavenging port 10 and compressed together with the air-fuel mixture. Then, the rich mixture is ignited and combusted by the spark plug 24,
Once a flame is generated within the combustion chamber 23, combustion spreads throughout the combustion chamber 23, and stratified combustion of the air-fuel mixture is performed in the combustion chamber 23. By the way, when warming up the engine, the controller 60 adjusts the cooling water temperature T detected by the water temperature sensor 55.
is below a predetermined value T0 (for example, 40°C) (step 2 in FIG. 4), and if the cooling water temperature T is below a predetermined value T0 (T≦T0), the combustion state of the engine is made uniform. If the value is higher than a predetermined value T0 (T>T0), the combustion state of the engine is controlled to be stratified combustion (steps 11 to 15 in FIG. 4).

That is, the cooling water temperature T is below the predetermined value T0 (T≦
T0), first, the engine's target idle speed A for the cooling water temperature T at that time is the curve A in FIG.
(Step 3 in FIG. 4), and the main throttle valve 19 shown in FIG. 2 is fully closed (Step 4 in FIG. 4).
While the intake air amount is throttled, the fuel injection timing t1 (see FIG. 6) is advanced by the fuel injection timing control means 61 (step 5 in FIG. 4).

Next, the controller 60 determines whether the actual engine speed (idle speed) R deviates from the target idle speed A (step 6 in FIG. 4), and if there is no deviation (R=A), In this case, the intake air amount and fuel injection amount are not adjusted, and when the engine speed R is smaller than the target idle speed A (R<A), the opening degree of the sub-throttle valve 20 increases (as shown in FIG. 4). At step 7), the fuel injection amount is increased by the fuel injection period Δt1 (see FIG. 6) by the fuel injection amount control means 62 (step 8 in FIG. 4). Moreover, when the engine speed R is larger than the target idle speed A (R>A), the opening degree of the sub-throttle valve 20 is decreased (step 9 in FIG. 4), and
The fuel injection amount control means 62 shortens the fuel injection period Δt1 and reduces the fuel injection amount (step 8 in FIG. 4).
). In this case, in controlling the fuel injection amount by the fuel injection amount control means 62, the fuel injection start time t1 is kept constant, and the fuel injection period Δt1 is changed by changing the fuel injection end time, thereby controlling the fuel injection amount. The amount is being decreased or increased. Further, in this case, as shown in FIG. 6, fuel injection is started before the exhaust port 11 closes, but the fuel injected from the fuel injection device 30 into each combustion chamber 23 actually reaches the exhaust port 11. By selecting the fuel injection start timing t1 so that the exhaust port 11 closes before the exhaust port 11 closes, it is possible to prevent fuel from blowing through the exhaust port 11.

As described above, when the cooling water temperature T is below the predetermined value T0 (T≦T0), the fuel injection start timing t1 is advanced, so that the fuel is almost in the combustion chamber 23. Furthermore, the sub-throttle valve 20 is controlled to close or open according to the vertical movement of the engine speed R to decrease or increase the intake air amount, and the fuel injection amount is decreased or increased by the fuel injection amount control means 62. Therefore, the fuel supplied to each combustion chamber 23 is uniformly combusted as in a normal engine. In this way, when the fuel is burnt uniformly like in a normal engine during warm-up operation when the engine temperature is low, the exhaust temperature increases compared to the case of stratified combustion with excess air, and as shown in Figure 7 (
As shown by the solid line a in Fig. 7(c), the catalyst temperature rises quickly compared to the conventional temperature shown by the broken line b, and the time for the catalyst to start purifying the exhaust gas is brought forward, and as shown by the solid line c in Fig. 7(c). As shown, the content of hydrocarbons (HC) in the exhaust gas is reduced compared to the conventional one shown by the broken line d, and the exhaust purification performance of the catalyst is enhanced even when the engine is started and warmed up. .

On the other hand, if the cooling water temperature T becomes higher than the predetermined value T0 due to the uniform combustion described above, or if the cooling water temperature T already exceeds the predetermined value T0 at the time of starting the engine (T>
To), the fuel injection timing control means 61 determines the fuel injection start timing when the cooling water temperature T is below the predetermined value T0 (T
≦T0), and the fuel injection amount is decreased or increased by the fuel injection amount control means 62 in accordance with the vertical movement of the idle rotation speed R, and the combustion is switched from uniform combustion to stratified combustion (Fig. 4 steps 11-15).

That is, in this case as well, the target idle speed A of the engine is set based on curve B in FIG. 5, and the sub-throttle valve 20 shown in FIG. 2 is fully closed (step 11 in FIG. 4). The main throttle valve 19 is opened a small amount (step 12 in FIG. 4). Conversely, the main throttle valve 19 may be fully closed and the sub-throttle valve 20 may be slightly opened, or the sub-throttle valve 20 may be eliminated and the intake air amount may be controlled only by the main throttle valve 19. In this case, the amount of intake air can be increased compared to the case of uniform combustion.

In this stratified combustion region, the amount of deviation of the engine speed R from the target idle speed A |
The method of controlling the fuel injection amount differs depending on R-A|. That is, the controller 60 determines whether the engine rotation speed R deviates from the target idle rotation speed A (step 13 in FIG. 4), and if there is no deviation (|R-A|=0), the fuel is as shown in FIG. The fuel is injected for a period of Δt2 from time t2, and the fuel injection amount is kept constant. And the amount of deviation |
When R-A| is less than 40 rpm (0<|R-A|<4
0), as shown in FIG. 6, the fuel injection start timing t2 is kept constant, and the fuel injection periods Δt2' and Δt2'' are advanced or retarded by changing the fuel injection end timing (FIG. 4). Step 14), thereby decreasing or increasing the fuel injection amount. In addition, when the deviation amount |R-A| is 40 rpm or more (|R-A|≧40), the fuel injection period Δt3 is kept constant as shown in FIG. 6, and the fuel injection start timings t3, t
3' is retarded or advanced (step 15 in FIG. 4), the fuel injection amount is decreased or increased. In this case, even if the fuel injection period Δt3 is constant, the fuel injection start time t3
, t3', the cylinder internal pressure when the fuel is injected will differ; for example, if the fuel injection start timing is advanced, the fuel will be injected when the cylinder internal pressure is low and the differential pressure with the fuel pressure is large. Therefore, the fuel injection amount is increased.

As mentioned above, when the cooling water temperature T becomes higher than the predetermined value T0 (T>T0), the combustion is switched from uniform combustion to stratified combustion, so that stable idling at low rotation speeds is achieved. This allows the original advantages of the stratified combustion engine to be utilized as is.

In the above embodiments, the cooling water temperature is particularly used as the engine temperature, but it goes without saying that the catalyst temperature may also be used as the engine temperature.

[0031]

As is clear from the above description, according to the present invention, in an internal combustion engine having a fuel injection device that injects fuel near a spark plug in a combustion chamber, and a catalyst provided in an exhaust pipe, engine temperature can be controlled. a temperature sensor that detects
A fuel injection timing control means for controlling the start timing of fuel injection by the fuel injection device, a fuel injection amount control means for controlling the fuel injection amount of the fuel injection device, and an intake air control means for controlling the amount of intake air are provided. When the engine temperature detected by the temperature sensor is below a predetermined value, the fuel injection timing control means advances the fuel injection start timing compared to when the engine temperature is above the predetermined value, and also advances the idle speed. In response to the vertical movement, the intake air control means decreases or increases the amount of intake air, and at the same time, the fuel injection amount control means decreases or increases the fuel injection amount. In this case, the fuel injection timing control means retards the fuel injection start timing compared to when the engine temperature is below a predetermined value, and the fuel injection amount control means retards the fuel injection start timing in accordance with the vertical fluctuation of the idle speed. Since the injection amount is decreased or increased, it is possible to take advantage of the advantages of a stratified combustion engine while increasing the exhaust gas temperature during startup and warm-up, thereby improving exhaust purification performance.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the overall configuration of a stratified combustion engine according to the present invention.

FIG. 2 is a sectional view of a main part of a stratified combustion engine according to the present invention.

FIG. 3 is a sectional view of the fuel injection device.

FIG. 4 is a flowchart showing changes in the combustion state of the engine.

FIG. 5 is a diagram showing the target idle speed of the engine with respect to the cooling water temperature.

FIG. 6 is a timing chart showing fuel injection start timing and fuel injection period.

FIGS. 7(a), (b), and (c) are diagrams showing changes over time in the engine speed, catalyst temperature, and hydrocarbon (HC) content in exhaust gas after engine startup; FIG.

[Explanation of symbols]

20 Sub-throttle valve (intake control means) 23
Combustion chamber 24 Spark plug 30 Fuel injection device 55 Water temperature sensor (temperature sensor) 60
Controller 61 Fuel injection timing control means 62
Fuel injection amount control means

Claims (1)

[Claims] Claim 1: In an internal combustion engine having a fuel injection device that injects fuel near a spark plug in a combustion chamber, and a catalyst provided in an exhaust pipe, a temperature sensor that detects engine temperature and a method for starting fuel injection by the fuel injection device. A fuel injection timing control means for controlling the timing, a fuel injection amount control means for controlling the fuel injection amount of the fuel injection device, and an intake air control means for controlling the intake air amount, and in an idling state,
When the engine temperature detected by the temperature sensor is below a predetermined value, the fuel injection timing control means advances the fuel injection start timing compared to when the engine temperature is above the predetermined value, and also increases or decreases the idle speed. At the same time, the intake air control means decreases or increases the amount of intake air, and the fuel injection amount control means decreases or increases the fuel injection amount depending on the engine speed. in case of,
The fuel injection timing control means retards the fuel injection start timing compared to when the engine temperature is below a predetermined value, and the fuel injection amount control means decreases or increases the fuel injection amount in accordance with the vertical movement of the idle speed. An internal combustion engine characterized in that it is configured to