JPH04191433A - Combustion control device for engine - Google Patents

Abstract

PURPOSE:To precisely detect and judge the fuel property while ensuring the combustion improving effect and ensure a satisfactory running property by detecting and judging the fuel property on the basis of the combustion state of an engine, and limiting the combustive property improving operation until the fuel property is detected after starting the engine. CONSTITUTION:A throttle valve 8 is provided in a collective intake passage 4b on the upper stream side of an intake passage 4, and a shutter valve 9 is disposed in the independent intake passage 4a of each cylinder 2 on the lower stream side from it. The shutter valve 9 throttles the flow of the suction air, when closed, to generate a turbulent flow around a fuel injection valve 14, whereby the evaporation and atomization of the injected fuel is promoted to improve the combustive property. The opening and closing control of the shutter valve 9 (operation control of a solenoid valve 10) is conducted according to the operating state by a controller 15. In this case, in the controller 15, the fuel property (volatility) is detected and judged from the fluctuation of engine rotating speed at the time of starting the engine. At the time of the detecting and judging operation of the fuel property, the closing operation of the shutter valve 9 is limited.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine combustion control device that detects fuel properties such as fuel volatility.

(Prior art) In recent years, engine fuels, especially gasoline, have become commercially available with low volatility, and when fuels with different fuel properties are supplied to an engine and combusted, various control characteristics have to be adjusted using this type of fuel. It is necessary to make corrections in response to changes in fuel properties.

In other words, when a heavy fuel with low volatility is supplied, the various control characteristics that were previously set for normal fuel will reduce fuel vaporization and fog, especially during cold driving when the engine temperature is low. This results in poor running performance. On the other hand, if fuel properties such as fuel volatility are detected and judged, the fuel increase during cold operation can be corrected to increase by a predetermined amount based on the detected fuel properties, thereby improving running performance. It becomes possible to improve.

Therefore, in order to detect and judge the fuel properties such as the volatility of the fuel, for example, Japanese Patent Application Laid-Open No. 62-288333,
As seen in the publication, based on the fact that heavy fuel and normal fuel have different combustion speeds, that is, pressure rises during combustion in the cylinder, the fuel properties are detected and determined based on the in-cylinder pressure detected by a pressure sensor. Techniques for this are well known.

On the other hand, in order to improve fuel economy and emissions in engines, techniques have been adopted to improve combustibility by promoting fuel atomization by increasing intake flow velocity. When optimizing combustion and speeding up combustion by improving the combustibility of the engine, the improvement is particularly carried out in the low rotation and low load region where combustibility decreases.

(Problem to be Solved by the Invention) However, in an engine in which the combustibility improvement function is activated as described above, the basic detection signal corresponding to the combustion state for determining the fuel properties is There is a problem that good detection judgment cannot be performed due to the influence of enhanced control.

That is, when determining fuel properties, the detection signal that serves as a criterion for engine rotational speed fluctuations related to changes in combustion conditions based on differences in fuel properties is determined by the detection signal of the combustion improvement means that promotes fuel atomization, etc. Fluctuations occur under the influence of improved combustibility due to operation, and the amount of fluctuation in the detection signal corresponding to differences in fuel properties decreases, making detection judgment difficult and decreasing detection accuracy.

Therefore, in view of the above circumstances, the present invention is designed to accurately detect and judge fuel properties while ensuring a combustion improvement effect through combustibility improvement control, and to ensure good running performance in response to changes in volatility. The object of the present invention is to provide a combustion control device for an engine.

(Means for Solving the Problems) In order to achieve the above object, the engine combustion control device of the present invention includes a combustion improving means for improving the combustibility of the engine. A fuel property detecting means for detecting and determining fuel properties; and a regulating means for restricting the combustibility improving operation by the combustion improving means until the fuel properties are detected by the fuel property detecting means after the engine is started. This is what I did.

The combustion improvement means includes a control valve that reduces the area of the intake passage in a low intake air region and improves combustibility by increasing the intake flow velocity, and another that generates turbulence in the intake air relative to the injected fuel in a low load and low rotation region. There are some known methods such as those that promote vaporization and atomization by increasing the air-fuel mixture, those that promote vaporization and atomization by increasing the flow velocity by narrowing the air-fuel mixture, and those that improve combustibility by strengthening swirl in the low intake region. techniques can be adopted.

Further, the fuel property detection means detects and judges signals related to fluctuations in combustion state corresponding to changes in fuel properties based on fluctuations in engine speed after a cold start, and signals detected from fluctuations in combustion pressure. A sensor that detects a change in the detection signal of an air-fuel ratio sensor is adopted.

(Functions and Effects) The above-mentioned combustion control device basically operates the combustion improvement means at low load and low rotation speeds where the combustibility of the engine decreases, and improves the combustibility of the engine by promoting fuel atomization, etc. This improves drivability, fuel efficiency, and emissions, and performs combustion improvement control such that the combustion improvement means is driven to a non-operating state in order to obtain high output under high load conditions.

On the other hand, the fuel properties are detected and determined by the fuel property detection means based on the fluctuations in the engine speed during cold starting, but after the engine is started, until the fuel properties are detected by the fuel property detection means, By restricting the combustibility improving operation by the combustion improving means by the regulating means, the amount of variation corresponding to the change in fuel properties in the detection signal related to the combustion state at the time of fuel property detection becomes large, and the detection judgment of the fuel properties increases. This can be done with high precision, and based on this detection, appropriate control can be performed in accordance with the fuel properties.

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

FIG. 1 and FIG. 2 show a schematic configuration of an engine to which a combustion control device is applied in one embodiment.

Four cylinders 2 are installed in the engine body 1, and each cylinder 2
An intake port 3 and an exhaust port 5 are opened in the intake port 3, and an independent intake passage 4 at the downstream end of the intake passage 4 is opened in the intake boat 3.
a are connected independently. Further, the upstream sides of the independent intake passages 4a of the respective cylinders 2 are gathered into one collective intake passage 4b.

A throttle valve 8 is disposed in the collective intake passage 4b on the upstream side of the intake passage 4, and a shutter valve 9 is disposed in the independent intake passage 4a of each cylinder 2 on the downstream side. . The shutter valves 9 for each cylinder 2 are fixed to a common valve shaft 9a and are opened and closed simultaneously for each cylinder.

The throttle valve 8 is opened and closed in conjunction with the accelerator operation, and the shutter valve 9 is opened and closed in a low-load, low-speed range according to the operating state by an actuator 12 that operates based on intake negative pressure.

That is, one end of the actuator 12 is connected to a negative pressure introduction passage 12a whose other end is connected to the intake passage 4a downstream of the shutter valve 9, and a three-way solenoid valve 10 is interposed in the middle of this negative pressure introduction passage 12a. The opening and closing of the shutter valve 9 is controlled by operating the solenoid valve 10.

The shutter valve 9 is set to open when negative intake pressure is introduced into the actuator 12. Further, a fuel injection valve 14 is disposed in each independent intake passage 4a of each cylinder 2 downstream of the shutter valve 9.

When the shutter valve 9 is in the closed state,
The shutter valve 9 restricts the flow of intake air to generate turbulence around the fuel injection valve 14, thereby forming a combustion improving means E that improves combustibility by promoting vaporization and atomization of the injected fuel. Opening/closing control of the shutter valve 9 (operation control of the solenoid valve 10) and fuel injection control of the fuel injection valve 14 are performed according to a control signal from a controller 15 according to the operating state.

The controller 15 includes:
A rotation signal from the rotation speed sensor 17 that detects the engine rotation speed, an engine water temperature signal from the water temperature sensor 18, a signal from the range sensor 19 that detects the N range of the transmission, and an idle switch that operates when the throttle valve 8 is fully closed. 20
, an intake air amount signal from the intake air amount sensor 6, and the like are respectively input.

Furthermore, the controller 15 has the function of a fuel property detecting means for detecting and determining fuel properties (volatility) from fluctuations in engine speed at the time of engine startup, and when the fuel property detecting means is in operation for detecting and determining, The shutter valve 9 constituting the improving means E has the function of a restricting means for restricting the closing operation so that the shutter valve 9 constituting the improving means E does not close and become in a state of improving combustibility.

In addition, in the fuel injection control by the controller 15, when the fuel property detecting means detects that the fuel used is heavy fuel at the time of starting the engine, the increase in the amount of fuel supplied during cold conditions (warm-up increase) is increased. However, it is configured to perform correction control to reduce the temperature as the engine water temperature rises.

Specifically, the fuel properties are determined by detecting changes in the engine rotational speed after a cold start, and a time chart thereof will be explained based on FIG. 3. In order to start the engine, when the starter motor is activated at point a and cranking begins, the engine speed begins to rise as shown in (B) and further increases as the fuel is ignited and reaches a complete explosion state.
After starting, the engine speed decreases and then changes to a speed that corresponds to the engine water temperature, throttle opening, etc.

Then, the time t during which the engine rotational speed in the reduced state decreased from a predetermined rotational speed Nc to Nd is measured, and this time t
However, with heavy fuel, the volatility of the fuel is lower than with normal fuel, and the air-fuel ratio is lean, so the drop time is short (decrease speed is fast <), and when the above measured time t is less than the set value to, heavy fuel It is determined that the supply of This results in
The fuel properties will be determined at point d, at which the engine speed has decreased to Nd.

Regarding the detection and determination of the fuel properties described above, as shown in (A), the operation of the shutter valve 9 is such that the shutter valve 9, which was closed when the engine was stopped before point a, is used to determine the fuel properties from point a. The shutter valve 9 is opened until the point d is reached, and after the determination, the shutter valve 9 is controlled to be closed in order to improve the combustibility under low load conditions.

On the other hand, the fuel injection amount at the time of starting is as shown in (C).
Starting fuel set according to the engine water temperature is supplied from the start of cranking at point A until the start is completed at point B, and from point B, when starting is completed, the starting fuel is gradually reduced and transferred to warm-up increased fuel. If it is detected that the fuel is a heavy fuel with low volatility at 6 points, the amount of warm-up fuel is further increased according to the water temperature and gradually reduced as the warm-up progresses. It is.

The reason for determining fuel properties during a cold start is that the difference in fuel volatility becomes noticeable in low temperature regions, and in high temperature regions, vaporization is promoted by heating, resulting in a difference in volatility. This is because the based fluctuations are small and detection becomes difficult.

The processing of the controller 15 will be explained along the flowchart of FIG. This flowchart shows only the fuel property determination control, and after the control starts, step S1
It is determined whether or not it is a cold time when the engine water temperature is 50 degrees Celsius or less. Since the fuel properties are detected when the fuel is cold, step S2
Then, the shutter valve 9 is fully opened to prohibit the combustion improving operation and start the engine.

When the engine is started, it is determined in step S3 whether or not the N range is set, and further, in step S4, the idle switch 2 is
If it is 0 or on, it is determined whether the throttle valve 8 is fully closed or not, and it is determined whether the fuel property detection condition is satisfied.

Then, if the determinations in steps S3 and S4 are YES, and at the time of cold start in an idle no-load state, step S5
Then, it is determined whether or not the measured value t of the time taken for the engine speed to decrease from Nc to Nd is less than the set value to of heavy fuel.

If the determination in step S5 is YES, if heavy fuel is supplied and the volatility is low, the heavy fuel determination flag H is set to 1 in step S6. On the other hand, the determination in step S5 is N.
If the fuel is normal fuel at o, and if the fuel property detection conditions are not met, the heavy determination flag H is set at step S7.
After clearing to O, the prohibition of closing the shutter valve 9 is canceled in step S8, and the shutter valve 9 is controlled according to the operating state. That is, when the engine is in a low rotation and low load region, the shutter valve 9 is closed to improve combustion performance, and in other regions, it is opened.

Note that, depending on the setting of the heavy fuel determination flag H, an increase in the amount of heavy fuel is corrected in a fuel control routine (not shown).

As a result of the above-mentioned action, when the fuel property judgment conditions are met during a cold start, the closing operation of the shutter valve 9 is prohibited, and the closing operation promotes fuel atomization, improving combustibility and increasing engine speed. This makes it possible to accurately detect and determine changes in fuel properties (volatility) based on changes in the engine rotational speed decreasing characteristic.

In addition, in the above embodiment, heavy fuel is detected based on the rate of decrease in engine speed, but in the case of heavy fuel, the drop in engine speed after cold start is completed becomes large. Therefore, it may be determined that heavy fuel is being supplied when the engine rotational speed after the completion of starting has decreased below a reference value. Furthermore, since the combustion speed and the increase in combustion pressure are different for heavy fuels, the in-cylinder pressure may be detected and the fuel properties may be determined from its change characteristics. Furthermore, with heavy fuel, the amount of fuel actually supplied to the combustion chamber is small for the same amount of fuel supplied, resulting in a lean air-fuel ratio, so the lean detection signal of the air-fuel ratio sensor is longer than the predetermined value. In this case, it may be determined that heavy fuel is being supplied. Additionally, other known fuel property determination methods may be employed.

On the other hand, in the embodiment described above, when the engine is cold, the shutter valve 9 is operated to the fully open state at the same time as the engine starts. may be determined.

Next, FIG. 5 shows the overall configuration of an engine incorporating the combustion improvement means of another embodiment.

The engine body 1 of this example is equipped with four cylinders 2 similar to the previous example, each cylinder 2 has an intake port 3 and an exhaust port 5 opened, and the intake port 3 has an independent intake air at the downstream end of the intake passage 4. The passages 4a are each independently connected. Further, the upstream sides of the independent intake passages 4a of the respective cylinders 2 are combined into one collective intake passage 4b, and an air flow meter 6 for detecting the amount of intake air and an air cleaner 7 are interposed in the upstream part.

A first control valve 28 is disposed in the collective intake passage 4b on the upstream side of the intake passage 4, and a second control valve 29 is disposed in the independent intake passage 4a of each cylinder 2 on the downstream side. It is set up. The second control valves 29 for each cylinder 2 are fixed to a common valve shaft 29a and are opened and closed simultaneously for each cylinder.

The first control valve 28 and the second control valve 29 are operated by actuators 31 and 32 equipped with position sensors.
Each one is opened and closed with separate characteristics.

Further, a second control valve 29 is provided downstream of the first control valve 28.
An upstream fuel injection valve 33 common to each cylinder is disposed in the collective intake passage 4b on the more upstream side, and a downstream fuel injection valve 34 is disposed in the independent intake passage 4a of each cylinder 2 downstream of the second control valve 29. is provided, and its fuel injection control is performed in response to a control signal from a controller 35 depending on the operating state.

The controller 35 includes:
Signals from various sensors similar to the previous example are input.

The fuel injection control by this controller 35 usually involves controlling the fuel injection amount determined according to the operating state by applying it to the upstream fuel injection valve 33.
The system performs synchronous injection at a predetermined timing from the beginning, and performs asynchronous injection from the downstream fuel injection valve 34 during transitions such as during acceleration to improve response.

On the other hand, the controller 35 controls the opening degrees of the first control valve 28 and the second control valve 29. At times, it is in a fully closed state, but in response to an increase in intake pressure or load, the opening degree increases rapidly during off-idle and becomes fully open. On the other hand, the second control valve 29 is fully closed when the load is extremely low, such as when idling or decelerating, and when the load increases, it opens to a predetermined opening depending on the degree of load to adjust the intake air amount. This is what we do.

In the closed state (low load state), the second control valve 29 promotes vaporization and atomization of the fuel injected from the upstream fuel injection valve 33 by the throttled second control valve 29. It constitutes a combustion improving means E for improving combustibility. In addition, as in the previous example, during the period in which the fuel property is detected and judged by the fuel property detection means that detects and judges the fuel property from the fluctuation of the engine speed during cold starting, the combustibility of the combustion improving means E is determined. Regulatory measures are in place to prohibit enhanced operation.

That is, when detecting the fuel properties, the second control valve 29 is opened or fuel is injected from the downstream fuel injection valve 34 to eliminate the fuel vaporization and atomization promotion function and stop the combustion improvement function. It is.

In addition, the heavy fuel determination routine, fuel correction, etc. are the same as in the previous example, and when the configuration in the drawings is the same, the same reference numerals are given and the explanation thereof will be omitted.

Further, as a combustion improving means other than the above-mentioned embodiment, for example, swirl control described in Japanese Patent Application Laid-Open No. 59-105929 may be used.

In other words, the intake passage near the intake port is separated into a low-speed intake passage with a small passage area and a high-speed intake passage with a larger passage area, and a shutter valve that closes in the high-load range is interposed in the high-speed intake passage. , when increasing the flow velocity of intake air from the low-speed intake passage in a low load region to generate a strong swirl to improve combustibility, the shutter valve should be controlled to open when detecting and judging fuel properties. It's a good thing.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an engine equipped with a combustion control device according to an embodiment of the present invention. FIG. 2 is a schematic diagram of the essential parts of the intake system of the same engine shown in plan. FIG. 3 is a fuel An explanatory diagram showing control characteristics at the time of property determination; FIG. 4 is a flow diagram of main parts for explaining the processing of the controller; FIG. 5 is a schematic configuration diagram of an engine equipped with a combustion control device in another embodiment. It is. ]... Engine body, 4... Intake passage, 8... Throttle valve, 9...
... Shutter valve, 10 ... Three-way solenoid valve, 12 ... Actuator, 14 ...
... Fuel injection valve, 15.35 ... Controller, 17 ... Rotation speed sensor, 28 ...
First control valve, 29...Second control valve, 32...
...Actuator, 33...Upstream fuel injection valve, 34...Downstream fuel injection valve, E...
Combustion improvement means. Figure 3 Figure 2 Figure 4

Claims (2)

[Claims] (1) In an engine combustion control device equipped with a combustion improving means for improving the combustibility of the engine, the fuel property detecting means detects and determines the fuel property based on a signal related to the combustion state of the engine; A combustion control device for an engine, comprising: a regulating means for restricting the combustion improving operation by the combustion improving means until the fuel properties are detected by the fuel property detecting means. (2) The combustion control device for an engine according to claim 1, wherein the combustion improving means is a control valve that reduces an intake passage area in a low intake air region.