JPS6263128A - Fuel controller for engine - Google Patents

Abstract

PURPOSE:To aim at improvement in fuel consumption and reduction in NOx content, by performing optimum control over a control valve according to engine load, in case of device which has a low load swirl port and a high load port and installs the control valve in this high load port. CONSTITUTION:An end part at the downstream side of a suction passage 5 is partitioned off into a high load port 12 large in a passage section area and a low load swirl port 13 small in the passage section area by a partition wall 11, and a control valve 14 is installed in this high load port 12. This control valve 14 is opened or closed by an actuator 19 being controlled by a control unit 15. And, this control unit 15 inputs detection signals (a), (b) and (d) of suction pressure, engine speed, accelerator opening, etc., and at a low load range, opens or closes the control valve 14, and sets an air-cuel ratio to the lean side, while after a throttle valve 8 comes to full-open with an increase in engine load, it is so constituted as to open the control valve 14 by degrees and to control the air-fuel ratio to the rich side after the full open of the said valve 14.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a fuel control device for an engine, in particular, a fuel control device for an engine, which has a swirl port for low load and a port for high load at the downstream end of an intake passage. This invention relates to a fuel control system for an engine equipped with a IIJ all valve at a port.

(Prior art) In general, in engines, in order to improve fuel efficiency and exhaust performance, the air-fuel ratio is variably controlled according to the operating range, as shown in Japanese Patent Laid-Open No. 57-210137, for example. However, in the low load range where the amount of intake air is small and the fuel is not well vaporized and atomized, the air-fuel ratio cannot be made sufficiently lean, and therefore the fuel efficiency is affected. could not be improved.

Therefore, in recent years, the downstream end of the intake passage has been replaced with a high-load port with a large flow passage cross-sectional area and a flow passage cross-sectional area formed so that the intake air inflow direction is offset from the center of the combustion chamber. A control valve is provided at the high load port, and the control valve is configured to close when the load is in a low load region and open when the load is in a high load region. A new intake device has been proposed. In other words, according to this intake system, in a low load region, intake air is introduced only from the low load port and a swirl of intake air is generated in the combustion chamber, resulting in good vaporization and atomization of the fuel and mixing with the intake air. This makes it possible to make the air-fuel ratio lean, and in high-load regions, sufficient intake air is introduced into the combustion chamber from both the low-load and high-load ports, so the required engine output can be maintained. It is guaranteed.

By the way, in such an intake system, the opening/closing operation of the control valve is such that when the engine load reaches a predetermined load when transitioning from a low load region to a high load region, the valve immediately changes from a fully open state to a fully open state. It is customary to do so. Therefore, when the control valve is in a fully closed state, that is, in a region where the load is lower than the predetermined load shown in FIG. Although it is possible to set the air-fuel ratio to a lean state, the swirl disappears in the higher load range than the above-mentioned predetermined load, so the air-fuel ratio should be set at a large rate of change as the load increases, as shown by You will have to make it rich. In other words, even if the engine load shifts to a higher load than the predetermined load, if you make effective use of the swirl to the extent possible in relation to the intake air amount, you can make the air-fuel ratio leaner by that amount. Although it is possible, as mentioned above, if the control valve is fully opened at the same time as the predetermined load is exceeded to the high load side, effective use of such swirl cannot be achieved.
This means that the air-fuel ratio must be unnecessarily rich.

(Object of the Invention) The present invention deals with the above-mentioned actual situation regarding the fuel control device of an engine, and provides a swirl port for low load and a port for high load at the downstream end of the intake passage. In a configuration in which a high-load port is equipped with a control valve, by optimally controlling the opening degree of the control valve according to the engine load,
To set an air-fuel ratio as lean over as wide an operating range as possible by making maximum use of intake swirl not only in a low load range but also in a medium load range. The purpose of this is to improve fuel efficiency, reduce NOx, etc. while ensuring the required engine output.

(Structure of the Invention) In order to achieve the above object, the engine fuel control device according to the present invention is characterized by having the following structure.

That is, in a configuration in which a low-load swirl port and a high-load port are provided at the downstream end of the intake passage, a control valve is provided at the high-load port, and a throttle valve is provided on the upstream side of both ports. , a control means is provided for controlling the opening degree and air-fuel ratio of the control valve according to the engine load. This control means maintains the control valve in a fully open state and sets the air-fuel ratio to a lean state at least in a low load region of the engine, and the throttle valve becomes fully open or substantially fully open as the engine load increases. Then, the opening degree of the control valve is gradually increased.

Then, after the control valve is fully open or approximately fully open, the air-fuel ratio is gradually made richer.

According to this configuration, in a low load region of the engine, the control valve is fully opened and intake air is introduced into the combustion chamber only from the low load swirl port, so that swirl is not generated within the combustion chamber. This improves the mixing performance of fuel and intake air. Therefore, in this low load region, the required output performance can be obtained even if the air-fuel ratio is set to lean. When the throttle valve becomes fully open or almost fully open as the engine load increases (the throttle valve opens fully when the accelerator pedal is opened midway), the system is designed to compensate for the lack of intake air volume against the further increasing load. The control valve starts to open, but in that case, the control valve is not immediately fully opened, but the opening degree of the valve is gradually increased by the operation of the control means, so that The amount of intake air is increased while taking advantage of the swirl created by introducing the intake air from the low-load swirl bows 1 to 1. In other words, from the time the control valve starts opening until the valve becomes fully open (medium load region), the swirl is utilized to the maximum extent possible in relation to the intake air amount. This makes it possible to maintain the air-fuel ratio in a lean state even in this medium load region.

(Effects of the Invention) As described above, the engine fuel control device according to the present invention has a low-load swirl port and a high-load port, and the high-load port is provided with a control valve. In the configuration, the control valve is kept fully open at least in a low load region of the engine, and in a region above a predetermined load (
Since the opening degree of the control valve is gradually increased in the medium load region, not only will the air-fuel ratio become leaner due to the use of swirl in the low load region, but it will also lead to insufficient intake air in the medium load region. Instead, the swirl is utilized to the maximum extent to achieve a lean air-fuel ratio. This improves fuel efficiency, especially in this medium load range, and reduces N.

As for the generation of ×, the deterioration of driving performance, etc. is effectively suppressed.

(Example) Embodiments of the present invention shown in the figures will be described below.

As shown in FIG. 1, an intake passage 5 and an exhaust passage 6 are connected to the combustion chamber 2 of the engine 1 via intake and exhaust valves 3.4, and the intake passage 5 is connected to an accelerator from the upstream side. A throttle valve 8 linked to a pedal 7, a surge tank 9, and a fuel injection nozzle 10 are provided. Here, the downstream end of the intake passage 5 is partitioned by a partition wall 11 into a high-load port 12 having a large passage cross-sectional area and a low-load swirl port 13 having a small passage cross-sectional area. The load port 12 is equipped with a control valve 14 that opens and closes the port 12 . Further, the low-load swirl port 13 is formed so that the inflow direction of the intake air is offset from the center of the combustion chamber 2, and the intake air introduced into the combustion chamber 2 from the port 13 causes a swirl. It is designed to generate.

On the other hand, this engine 1 is equipped with a control unit 15 that controls the amount of fuel injected from the fuel injection nozzle 10. This control unit 1
5 detects a boost pressure signal a outputted from a boost pressure sensor 16 which is basically provided on the downstream side of the surge tank 9 in the intake passage 5 and detects boost pressure (intake pressure), and the engine rotation speed. Engine rotation sensor 1
inputs the rotational speed signal output from 7, and sets the fuel injection amount so that the air-fuel ratio becomes a predetermined value based on the boost pressure and engine rotational speed indicated by these signals a and b, This injection amount is output to the fuel injection nozzle 10 as a fuel injection signal C. The control unit 15 also receives an accelerator opening signal d from an accelerator opening sensor 18 that detects the amount of depression of the accelerator pedal 7 linked to the throttle valve 8, that is, the accelerator opening, and the signal d indicates It is determined whether the engine 1 is in an acceleration state based on the accelerator opening degree, and whether the engine load is in a low, medium, or high load region based on the boost pressure indicated by the boost pressure signal a. Based on these determination results, the opening/closing control of the control valve 14 provided at the high-load port 12 of the intake passage 5 and the air-fuel ratio are controlled. That is, when the boost pressure indicated by the boost pressure signal a is below a predetermined pressure, in other words, when the engine load is in a low load region, the control unit 15 causes the actuator 19 that drives the control valve 14 to control the valve 14. A valve control signal e is output to close the valve 14 to keep the valve 14 fully open, and the intake air whose flow rate is adjusted by the throttle valve 8 is sent to the low-load port 13.
It is introduced into the combustion chamber 2 only from the inside. Also, at this time, the fuel injection nozzle 1 is operated so that the air-fuel ratio of the air-fuel mixture in the combustion chamber 2 is maintained in a lean state (for example, air-fuel ratio≧22).
Controls the fuel injection amount from 0. On the other hand, when the boost pressure indicated by the boost pressure signal a is higher than the predetermined pressure, that is, when the engine load is in the medium load region or high load region (at this time, the throttle valve 8 is already fully open). ), the control unit 15 outputs a valve control signal e to the actuator 19 to open the control valve 14, thereby opening the valve 14 and opening the intake passage 5.
Both ports 12 and 13 are used for high load and low load intake.
The fuel is introduced into the combustion chamber 2 from above.

In that case, when the rate of change over time of the accelerator opening indicated by the accelerator opening signal d is greater than zero, that is, when the engine 1 is in an accelerating state, the opening of the control valve 14 is as follows:
It is gradually increased as the boost pressure increases, and the air-fuel ratio of the air-fuel mixture at this time is also gradually changed to a rich state at a small rate of change.

Then, from the drive amount of the actuator 19, the control valve 1
Until it is detected that the control valve 14 is fully open based on the valve opening signal f from the control valve opening sensor 20 that detects the opening of the control valve 14, the control valve 14 is not opened as described above. At the same time, the air-fuel ratio is controlled to be gradually rich at a small rate of change, and after the control valve 14 is fully open, the air-fuel ratio is increased as the boost pressure increases. Control is performed to make it rich at a large rate of change. still,
When the rate of change in the accelerator opening indicated by the accelerator opening signal d is larger than a predetermined value, that is, when the engine 1 is rapidly accelerating, the air-fuel ratio is corrected to the rich side according to the rate of change in the accelerator opening at this time. It's about to be controlled.

Next, the control valve 1 in this control unit 15
The opening/closing control operation and the air-fuel ratio control operation of No. 4 will be explained according to the flowchart of FIG.

When the engine 1 is started, the control unit 15
First, step x1 in the flowchart is executed to obtain the accelerator opening A indicated by the accelerator opening signal d from the accelerator opening sensor 18, the engine rotation speed N indicated by the rotation speed signal from the engine rotation sensor 17, Read the boost pressure P indicated by the boost pressure signal a from the boost pressure sensor 16 and the opening degree θ of the control valve 14 indicated by the valve opening signal f from the control valve opening sensor 20, and execute step x2. Then, the rate of change α in the accelerator opening is calculated using the formula α-(A-A')/A, (A': previous accelerator opening). And step X3. When it is determined that the rate of change α of the accelerator opening is less than or equal to the predetermined value α0 and greater than or equal to 0 according to X4, that is, the operating state of the engine 1 is not a sudden acceleration state but a normal acceleration state,
The control unit 15 executes step x5 so that the boost pressure P read in step x1 is the predetermined pressure Po.
As a result, the boost pressure P
is less than the predetermined pressure Po, step x6 is executed. In other words, the opening degree θ of the control valve 14 is set according to the engine speed N and the boost pressure P, and a signal corresponding to this opening degree θ is output as the valve control signal e to one actuator that drives the control valve 14. At the same time, fuel injection 11
F is set according to the engine speed N and boost pressure P in the same manner as above, and a signal corresponding to this injection fitF is outputted to the fuel injection nozzle 10 as a fuel injection signal C. In that case, the predetermined pressure PO, which was used as a criterion when executing step x5, is determined by the fact that the opening degree of the throttle valve 8 gradually increases as indicated by the symbol X, as shown in FIG. 3 (I>). This is the boost pressure when the valve 8 is fully open, and in the low load region until the actual boost pressure P reaches this predetermined pressure PO, the opening degree θ of the control valve 14 is set in step x6. is O, and the control valve 14 is kept fully open as shown by the symbol x1 in FIG. 3(n).As a result, the intake air guided to the downstream side of the intake passage 5 is It is introduced into the combustion chamber 2 only from the swirl port 13, and a swirl is generated in the combustion chamber 2.The generation of this swirl improves the mixing performance of the intake air and fuel, so that the above-mentioned step It becomes possible to reduce the fuel injection amount F set in step 6, and the air-fuel ratio is in a lean state (for example, the air-fuel ratio is 22 or higher) as shown by the symbol x 2 in Fig. 3 (1). will be maintained.

However, in step x5 above, the boost pressure P reaches the predetermined pressure Po.
If it is determined that the above is the case, the control;
The unit 15 executes step x7 to determine whether or not the opening degree θ of the control valve 14 is equal to the maximum opening degree Omax. executes step x8. That is, a predetermined amount of minute opening lθ is added to the opening degree θ of the control valve 14 read in step x1 above, and this added value is set as the new opening degree θ of the control valve 14. A signal corresponding to the opening degree θ is output to the actuator 19 as a valve control signal e. As a result, as shown by the symbol y1 in FIG. 3 (II), the control valve 14
The opening degree θ is gradually increased. Therefore, in this region, the intake air guided to the downstream side of the intake passage 5 is introduced into the combustion chamber 2 from the low-load swirl port 13, and some intake air is also combusted from the high-load port 12. It is introduced into the chamber 2. In this case, the flow rate of the intake air introduced from the high-load port 12 is not suddenly increased, but is gradually increased at a relatively small rate of change as the opening degree of the control valve 14 increases. Swirl port 13 for low load
The swirl generated in the combustion chamber by the intake air introduced from the combustion chamber is not immediately extinguished, but maintains its effect until the control valve 14 is fully open.
In addition, by introducing intake air from the high-load port 12 as well, the insufficient amount of intake air in this region is compensated for. As a result, while ensuring sufficient engine output, the effect of the swirl makes it possible to maintain the air-fuel ratio in a lean state as shown by the symbol y2 in FIG. 3 (I[[). , the air-fuel ratio becomes slightly richer gradually as the intake air increases). Therefore, conventionally
When the control valve 14 is switched from the fully open state to the fully open state within this region, as shown in FIG. Compared to this, the fuel efficiency in this medium load range is improved, and the deterioration of drivability due to the generated acid of NOx is effectively suppressed.

Further, when it is determined that the opening degree θ of the control valve 14 is the maximum opening degree θmaX in the above step x7 in the flowchart, that is, when the control valve 14 is in the fully open state, the control unit 15 performs the step ×9 determines whether the previous fuel injection ff1F' is equal to the maximum value F wax, and also determines whether the injection amount F' is equal to the maximum value F wax
Until it becomes equal to , the opening degree θ of the control valve 14 is set to the maximum opening degree θWaX by executing step Then, a predetermined injection ff1AF is added to the previous fuel injection IF', and after setting this added value as a new fuel injection IF, it is output as a fuel injection signal C to the fuel injection nozzle 10. Therefore, in the high-load side region where the boost pressure P is higher than the predetermined pressure P1 on the high-pressure side, the air-fuel ratio is enriched at a relatively large rate of change, as shown by the symbol z2 in FIG. 3 (III). It turns out. Then, when the previous fuel injection IF' reaches the maximum value F wax in step x9, the control unit 15 maintains the fuel injection IF at the maximum value F max by executing step x11. .

If it is determined in step x4 that the engine 1 is not in an accelerating state, the control unit 15 executes step x6 to adjust the opening degree θ of the control valve 14 and the fuel injection IF at that time. The desired opening degree 0 and injection IF are set according to the engine speed N and boost pressure P, and if it is determined in step x3 that the engine 1 is in a rapid acceleration state, step x12 is performed. Then, the opening degree θ of the control valve 14 and the fuel injection tJJIF are corrected to the increasing side according to the engine speed N, boost pressure P, and rate of change α of the accelerator opening degree, so that the output necessary for rapid acceleration is increased. make sure you get it. Here, in the above embodiment, the control valve 14 starts its opening operation after the throttle valve 8 is fully open, and the air-fuel ratio is changed by a relatively large amount when the control valve 14 is fully open. However, the opening operation of the control valve is started before the throttle valve 8 is fully opened, and the opening operation of the control valve is started before the throttle valve 8 is fully opened.
The air-fuel ratio may be shifted to the rich side before the l1l valve 14 is fully opened, and the torque shock at the time of switching may be reduced by overlapping the respective operating timings.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the fuel control device according to the present invention, in which FIG. 1 is an overall configuration diagram, FIG. 2 is a flowchart showing the operation, and FIG. 3 (1). (n) and (I[[) are a control characteristic diagram of the throttle opening degree, a control characteristic diagram of the control valve opening degree, and a control characteristic diagram of the air-fuel ratio, respectively. Further, FIG. 4 is a conventional air-fuel ratio control characteristic diagram. DESCRIPTION OF SYMBOLS 1... Engine, 5... Intake passage, 8... Throttle valve, 11... Partition wall, 12... Port for high load, 13... Swirl port for low load, 14...
Control valve, 15...control means (control unit)
, θ...Opening degree of the control valve.

Claims (1)

[Claims] (1) The downstream end of the intake passage is divided into a low-load swirl port and a high-load port by a partition wall, and the high-load port is equipped with a control valve, and a throttle valve is installed on the upstream side of both ports. In the installed engine, at least in a low load range, the control valve is kept fully closed and the air-fuel ratio is set to lean, and as the engine load increases, the throttle valve is fully opened or substantially fully open. After the control valve is fully open, the control valve gradually increases the opening degree of the control valve from the fully closed state, and after the control valve is fully open or approximately fully open, the air-fuel ratio is controlled to be rich. Fuel control device for the engine.