JPH0571773B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system for an engine equipped with an intake air recirculation mechanism for reducing pumping loss.

(Prior art) When the throttle valve is tightened, intake resistance increases, pumping loss occurs, and fuel efficiency worsens. This problem occurs particularly in the low engine load range, and various proposals have been made to deal with this problem. One method is to perform intake air recirculation. For example, in Japanese Patent Application Laid-Open No. 168041/1986, a recirculation passage is provided to recirculate a part of the intake air once introduced into the combustion chamber, and the intake air is returned to this passage. An engine has been disclosed that includes an intake air recirculation mechanism that controls the amount of intake air by controlling the flow rate, thereby maintaining an appropriate idle speed.

(Problems to be solved) However, with this disclosed engine, the problem of pumping loss during idling operation can be solved, but in that case, if you try to control the entire load range with only the amount of intake recirculation, Unless the closing timing of the recirculation valve is delayed until close to top dead center, the required recirculation amount during idling cannot be obtained.
On the other hand, in that case, in a high load range, even if the reflux control valve is fully closed, the amount of leakage from the reflux control valve increases, and a sufficient filling amount may not be obtained. In this case, a variable timing mechanism may be provided in the intake recirculation valve, but the structure becomes complicated and becomes a factor in increasing costs. Furthermore, the constant negative pressure state in the intake passage created by throttling the throttle valve is necessary for the operation of a brake booster or a negative pressure actuator, and is simply caused by pumping due to the intake throttling. Merely reducing the loss will cause other problems in the functionality of the device.

(Means for solving the above problems) The present invention has been constructed in view of the above circumstances, and the intake device of the present invention includes an intake passage that introduces intake air into the combustion chamber from an intake port that opens into the combustion chamber. a reflux passage that recirculates a portion of the intake air introduced into the combustion chamber from a reflux port that opens into the combustion chamber; a reflux valve that is provided to open and close the reflux port and closes later than the intake port; The engine includes a throttle valve provided in the intake passage to control the amount of intake air flowing through the intake passage, and a recirculation control valve provided in the recirculation passage to control the amount of intake air recirculation.

According to the present invention, when the engine is operating at low load, the throttle valve is set to a predetermined initial opening and the recirculation control valve controls the amount of intake air, and during high load operation, the recirculation control valve is fully closed. The intake air filling amount is controlled by the throttle valve, and the torque generated by the engine when the throttle valve is initially opened matches the torque generated by the engine when the recirculation control valve is fully closed. It is characterized in that an initial opening degree is set. That is, in the present invention, control of the intake air filling amount is switched from control by the recirculation control valve to control by the throttle valve when the engine load increases to a constant load state. In this case, the torque generated by the engine is
It is configured to change smoothly regardless of the switching of the control means.

(Description of Embodiment) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Referring to FIG. 1, the engine E of this example is:
It is a four-cylinder in-line engine, and an intake port 5 is opened in the combustion chamber 2 of each cylinder 1, which communicates with a branch intake passage 4 branched from a surge tank 3.
An air cleaner 7 is provided at the upstream end of the intake passage 6 extending upstream from the surge tank 3, and an air flow meter 8 is provided downstream of the air cleaner 7. Furthermore, a throttle valve 9 is provided downstream of the air flow meter 8, and an injector 10 for injecting fuel is installed near the combustion chamber 2 of each branch intake passage 4. A bypass passage 11 that bypasses the throttle valve 9 is connected to the intake passage 6, and a bypass valve 12 that controls the amount of bypass intake air flowing through the passage 11 is provided in the bypass passage 11. Further, the combustion chamber 2 is connected to the combustion chamber 2 through the intake passage 4.
A recirculation passage 13 that recirculates a part of the intake air introduced into the
is connected to the reflux port 1, and the passage 13 is connected to the reflux port 1.
It opens into the combustion chamber 2 at 4. A reflux control valve 15 for controlling the amount of reflux from each cylinder 1 is installed in the reflux passage 13 . These recirculation passages 13 are connected to communicate with each other, so that the intake air recirculated from each cylinder 1 is again sent to any other cylinder 1 during the intake stroke. Furthermore, in the combustion chamber 2,
The exhaust port 17 of the exhaust passage 16 is open.
Three ports opening into the combustion chamber 2, that is, an intake port 5, a reflux port 14, and an exhaust port 17, are combined with an intake valve 18, a reflux valve 19, and an exhaust valve 20, respectively, and these ports are operated at a predetermined timing. It is designed to open and close with. In this case, the recirculation valve 19 has an opening/closing timing that is slightly delayed from the intake valve 20, as shown in FIG. The throttle valve 9 is connected to a throttle servo motor 21a, and its opening degree is controlled by the motor. The throttle valve 9 is connected to the accelerator pedal 21 via the throttle servo motor 21a, and when the amount of depression of the accelerator pedal exceeds a predetermined value, it begins to open and the amount of depression increases. The opening degree increases accordingly. Further, the reflux control valve 15 is connected to a control motor 22 which is also a servo motor, and its opening degree is adjusted according to the operation of the control motor 22, thereby controlling the reflux amount. It is becoming possible to do this. In this example, as described above, the intake air amount is controlled by the throttle valve 9 and the bypass valve 12, and the recirculation amount is controlled by the recirculation control valve 15. In order to control the operations of the bypass valve 12 and the reflux control 15, in this example, a controller 23 preferably constituted by a microcomputer is provided. The controller 23 includes an air flow meter 8 that measures the amount of intake air, a throttle opening sensor 24 that detects the opening of the throttle valve 9, and a reflux valve opening sensor 15a that detects the opening of the reflux control valve. A pressure sensor 25 that detects the intake pressure downstream of the throttle valve 9 in the intake passage 6, and a water temperature sensor 2 that is attached to the engine E and detects the engine cooling water temperature.
6, and an O ₂ sensor 27 that detects the oxygen concentration in exhaust gas.Furthermore, a signal from a rotation speed sensor 28 that detects the engine rotation speed is input. The controller 23 calculates these input signals and outputs control signals to the throttle servo motor 21a and the recirculation control valve 15 to control the intake air amount and recirculation amount, and also outputs a command signal to the injector 10. The output is used to control the fuel injection amount.

Below, regarding the control of the intake air amount and recirculation amount in this example,
This will be explained with reference to FIGS. 3 and 4.

FIG. 3 is a flowchart for controlling the intake air amount and recirculation amount in this example. Controller 23
initializes the memory before starting control. Next, necessary data such as engine cooling water temperature, accelerator opening, and engine speed are read, and based on these data, a target intake air amount Q _a corresponding to the accelerator opening is calculated.
Then, it is determined from the engine load state whether the current operating state is in the range where the recirculation amount is controlled by the recirculation control valve 15 or the range where the intake air amount is controlled by the throttle valve 9. , issues a control command to the reflux control valve control motor 22 or the throttle servo motor 21a. In this case, the current operating state of the reflux control valve 15
If the control range is within the control range, as shown in FIG. 4, the recirculation valve opening calculation module calculates the recirculation control opening θ _R corresponding to the target intake air amount Q _a .
After setting the opening θ _T of the throttle valve 9 to the initial opening, the recirculation control valve opening sensors 27, 1
The control motor 22 is operated to reach the target opening θ _R according to the difference between the opening θ RR and the actual opening θ _RR of the recirculation control valve 15 from the opening 5a. In this example, the initial opening degree of the throttle valve 9 is set to θ _IN , and by keeping the bypass valve 12 open, the initial opening degree of the throttle valve 9 can be substantially obtained at θ _IN . It's summery. Further, when the operating state of the engine is within a range in which intake air amount control should be performed by controlling the opening degree of the throttle valve 9, the controller 23 uses the throttle valve opening calculation module to calculate the target throttle amount corresponding to the target intake air amount _Qa. Calculate the opening degree θ _T. In this case, the opening θ _R of the recirculation control valve 15 is set to 0, and according to the difference between the actual throttle opening θ _TR from the throttle valve opening sensor 24 and the target throttle opening θ _T ,
The throttle servo motor 21a is operated so that the throttle opening becomes the target throttle opening _θT . Furthermore, although not shown in the flowchart, the controller 23 calculates the fuel injection amount Q _f corresponding to the intake air amount θ _a , and adds correction by various modules shown in FIG. 4 to the injector 10. Outputs injection command signal.

By performing the above control, as shown in FIG. 5, in a region where the engine load is low, the throttle valve 9 is maintained at the initial opening θ _IN , and the opening of the recirculation control valve 15 is maintained at the opening θ IN. It decreases in proportion to the increase in load. Therefore, as the load increases, the amount of recirculation decreases and the amount of intake air charged into the combustion chamber increases. Then, when the engine load reaches a predetermined value, the recirculation control valve 15 is fully closed, and when the load increases thereafter, the opening degree of the throttle valve 9 increases accordingly. As a result, the intake air amount increases and the intake air filling amount increases. And the reflux control valve 1
The configuration is such that there is no difference in the filling amount between when the throttle valve 5 is fully closed and when the throttle valve 9 is initially opened. Therefore, the intake air filling amount is determined by the reflux control valve 1.
5 and throttle valve 9, it increases continuously as the load increases. In this example, in order to set the actual initial opening degree θ _IN of the throttle valve 9, the bypass passage 11 and the bypass valve 12 are
However, it is not necessary to do so, and the initial opening degree may be ensured by setting the opening degree of the throttle valve to a predetermined opening degree.

(Effects of the Invention) According to the present invention, as described above, by controlling the recirculation amount by the recirculation control valve and controlling the intake air amount by the throttle valve, the engine can be operated in a wide range from the low load region to the high load region. The filling amount can be controlled smoothly. That is,
In low load areas, the recirculation amount can be controlled to reduce pumping loss while controlling the filling amount, and in high load areas, the throttle valve can be controlled to ensure sufficient intake air filling. . Furthermore, since the throttle valve 9 is provided, it is possible to create a constant negative pressure state at low loads.
Therefore, the operation of the brake booster and the negative pressure actuator will not be hindered.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic diagram of an engine according to an embodiment of the present invention, FIG. 2 is a characteristic diagram showing valve timing, and FIG. 3 is a flowchart showing an example of control according to the present invention. FIG. 4 is an operational system diagram of the controller, and FIG. 5 is a graph showing changes in the opening degrees of the recirculation control valve and the throttle valve. E... Engine, 1... Cylinder, 4, 6...
Intake passage, 9...Throttle valve, 10...Injector, 12...Bypass valve, 15...Recirculation control valve, 21a...Throttle servo motor, 22...
...control motor.

Claims (1)

[Claims] 1. An intake passage that introduces intake air into the combustion chamber from an intake port that opens into the combustion chamber, a reflux passage that refluxes a part of the intake air introduced into the combustion chamber from a reflux port that opens into the combustion chamber, and the reflux port that a reflux valve that is provided to open and close and closes later than the intake port; a throttle valve that is provided in the intake passage and controls the amount of intake air flowing through the intake passage; and a reflux valve that is provided in the reflux passage and controls the intake air reflux amount. When the engine is operating at low load, the throttle valve is set to a predetermined initial opening degree, and the recirculation control valve controls the amount of intake air, and during high load operation, the recirculation control valve is fully closed. The intake air filling amount is controlled by the throttle valve, and the initial opening is adjusted so that the engine generated torque at the initial opening of the throttle valve matches the engine generated torque when the recirculation control valve is fully closed. An engine intake system characterized by a set temperature.