JP2894048B2 - Supercharging pressure control method for internal combustion engine with turbocharger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a supercharging pressure of an internal combustion engine having a turbocharger.

[0002]

2. Description of the Related Art A turbocharger compressor is provided in an intake passage, and the compressor is driven by a turbine rotating by exhaust gas from the engine to compress intake air and supply the compressed air to the engine. Feeding devices are well known. If the supercharging pressure applied by the turbocharger is too high, knocking will occur or problems will occur in durability.Therefore, a bypass passage that bypasses the turbine is provided, and a wastegate is provided in this passage to reduce the supercharging pressure. The wastegate is opened accordingly to prevent the boost pressure from rising above a predetermined pressure.

[0003] By the way, in an internal combustion engine equipped with a conventional turbocharger, when the output is controlled, the turbocharger is not directly linked to the accelerator operation.
The engine output changes according to the following process. If you want to increase the engine output, depressing the accelerator petal increases the intake air volume and the exhaust pressure,
As a result, the turbine speed increases and the boost pressure increases,
As a result, the output is increased. If you want to reduce the engine output, operate the accelerator petal in reverse and follow the reverse process.

[0004]

In the conventional output control method as described above, that is, the control method of the supercharging pressure, there is no particular problem when the output is largely changed. If it is decreased, a response delay or an overresponse occurs, and it is difficult to accurately control the boost pressure or output.
For example, in a situation where delicate output control is required during cornering, the conventional boost pressure control method does not match the driver's intention with the actual output response, and the driving feeling, that is, the drivability is poor. Was.

The present invention has been made in order to solve such a problem, and performs fine adjustment of the engine output accurately and with good responsiveness in an engine operation region where a large output is required. It is an object of the present invention to provide a method for controlling a supercharging pressure of an internal combustion engine provided with a turbocharger.

[0006]

According to the present invention, there is provided, in accordance with the present invention, a wastegate having a wastegate, which is opened in response to a supercharging pressure, and which emits exhaust gas from an engine. A turbocharger that controls the supercharging pressure to a predetermined pressure or less by discharging part of the air to the atmosphere without passing through the turbine, and operating the accelerator petal to open the throttle valve disposed in the middle of the intake passage And controlling the engine output by controlling the engine output. When the accelerator is operated to a predetermined operation amount, the throttle valve is opened to a substantially full open position, and the accelerator petal is controlled to the predetermined operation amount. The accelerator pedal can be operated further to the stepping side, and the operation amount of the accelerator petal and the engine speed are detected. When the accelerator petal is operated at the predetermined operation amount or more, the detected accelerator pedal is detected. A turbocharger, wherein a target supercharging pressure is set according to an operation amount of a rupetal and an engine speed, and a supercharging pressure is controlled to a target supercharging pressure by adjusting a valve opening of the wastegate. There is provided a method for controlling a supercharging pressure of an internal combustion engine, comprising:

[0007]

In the operation region where a large engine output is required, when it is desired to slightly adjust the output, a target boost pressure is set according to the operation amount of the accelerator pedal and the engine speed, and the valve opening of the wastegate is adjusted. In order to adjust and control the supercharging pressure to the target supercharging pressure, the supercharging pressure is directly controlled by opening and closing the wastegate.

[0008]

An embodiment of the present invention will be described below with reference to the accompanying drawings. First, a schematic configuration of an internal combustion engine to which the method of the present invention is applied will be described with reference to FIGS. Reference numeral E indicates a multi-cylinder internal combustion engine, for example, a four-cylinder engine, and reference numeral 2 indicates an intake passage connected to an intake port of each cylinder. An air cleaner 6 is attached to the open end of the intake passage 2 on the atmosphere side, and a Karman vortex airflow sensor 13 is attached. The airflow sensor 13 is electrically connected to an input side of an electronic control unit (ECU) 20 to be described later, and generates a Karman vortex generation period signal f.
Is supplied to the ECU 20. A throttle valve 7 is disposed in the intake passage 2, and a surge tank 2 a is disposed in the intake passage 2 between the throttle valve 7 and the engine E. Injection valves 8 are respectively disposed immediately upstream of the intake valves 4, and each of the injection valves 8 is connected to the ECU 20 and driven by a drive signal from the ECU 20. Reference numeral 3 denotes an exhaust passage connected to the exhaust port of each cylinder, and a three-way catalyst 9 for purifying harmful gas components such as unburned hydrocarbons and nitrogen oxides in the exhaust gas is provided in the exhaust passage 3. Have been.

A turbocharger TC compressor C is disposed in the intake passage 2 between the throttle valve 7 and the air cleaner 6, and a turbocharger TC turbine is disposed in the exhaust passage 3 between the engine E and the three-way catalyst 9. T is provided. The compressor C and the turbine T are connected by a drive shaft. A bypass passage 3a is provided in the turbocharger TC so as to bypass the turbine T. The bypass passage 3a is opened and closed by a waste gate 5, and a bypass passage 3a in which a part of exhaust gas from the engine E is opened. From the exhaust passage 3 on the atmosphere side.

The waste gate 5 has an actuator 20
Is driven to open. The actuator 20 is of a pressure-responsive type that opens and closes the waste gate 5 according to the supercharging pressure, and has a pressure chamber 2 defined by a diaphragm 20a.
0b communicates with the surge tank 2a via the conduit 21. The push rod 2 is attached to the diaphragm 20a.
The push rod 20d and the link mechanism transmit the displacement of the diaphragm 20a to the wastegate 5. The diaphragm 20a is constantly urged by a spring 20c in a direction to close the wastegate 5.

When the diaphragm pressing force due to the pressure (control pressure) in the pressure chamber 20b exceeds the spring force of the spring 20c, the diaphragm 20a is displaced and the waste gate 5 is opened.
The control pressure of the pressure chamber 20b can be controlled by performing duty control on an electromagnetic valve 23 described later. Pipe line 2
A stop 21a is provided in the middle of the stop 1.
One end of a pipe 22 is connected to a pipe 21 on the side of the actuator 20 from 1a. The other end of the pipe 22 is connected to the air cleaner 6. Then, the throttle 2 is also placed in the pipe line 22.
An electromagnetic valve 23 is disposed in the conduit 22 between the throttle 22a and the branch point described above. Solenoid valve 23
Is a normally-closed type, and the valve body 23a of the solenoid valve 23 opens when the solenoid 23b is urged to release the pressure in the pressure chamber 20b to the air cleaner 6. The solenoid valve 23 is connected to the ECU 20
, And is duty-controlled by a drive signal supplied from the ECU 20, and adjusts the pressure of the pressure chamber 20b according to the duty ratio.

As shown in FIG. 3, the throttle valve 7 of this embodiment is connected to an accelerator petal 25 by a wire 26. One end of the wire 26 rotates integrally with a rotation shaft of the throttle valve 7. The other end is connected to the accelerator petal 25 via a spring 26a. Therefore, the throttle valve 7 is opened according to the amount of depression (operation amount) θ of the accelerator petal 25, but is controlled by a spring 26a interposed between the wire 26 and the accelerator petal 25 as shown in FIG. It has valve opening characteristics. That is, when the accelerator pedal 25 is depressed, the throttle opening changes (for example, linearly) in accordance with the accelerator opening θ, and furthermore, when the accelerator petal 25 is further depressed, the accelerator opening θ becomes a predetermined operation value θtc (for example, 45 ° if full opening is 90 °)
Is reached, the throttle valve 7 is substantially fully opened (100
%). The accelerator pedal 25 is configured to be able to be further depressed to the fully opened position (90 °) from the above-mentioned predetermined operation value θtc while holding the throttle valve 7 at the fully opened position. The accelerator pedal 25 is provided with an accelerator opening sensor 16 for detecting the accelerator opening θ, and this sensor 16 is electrically connected to the input side of the ECU 20 to detect the detected accelerator opening θ.
20.

On the input side of the ECU 20, in addition to the above-described sensors, a pressure sensor 11, which is attached to the surge tank 2a and detects intake pressure, ie, a supercharging pressure, is attached to the surge tank 2a and detects intake air temperature. A temperature sensor 12, a throttle opening sensor 14 for detecting a valve opening (θ) of the throttle valve 7, an idle switch 15 for detecting a fully closed position of the throttle valve 7, and a turbocharger rotation speed for detecting a rotation speed of the turbocharger TC. Sensor 17,
An engine speed sensor 18 for detecting a predetermined crank angle position (for example, a top dead center position of an intake stroke) of each cylinder, and an engine coolant temperature (Tw) sensor 1 attached to a cylinder block of the engine 10 for detecting an engine coolant temperature Tw.
9 and sensors for detecting other engine operating parameter values such as battery voltage and atmospheric pressure are electrically connected.

The ECU 20 calculates the amount of fuel supplied to the engine E in accordance with the engine operating state detected by the various sensors described above, and calculates the amount of fuel corresponding to the calculated value to the fuel injection valve 8.
And controls the supercharging pressure as described later. These fuel supply control and supercharging pressure control are based on EC
It is executed by a central processing unit (CPU) built in U20. The ECU 20 includes, in addition to the above-described central processing unit,
A storage device for storing a control program, a control variable value, an operation value, and the like, an input / output device for receiving a signal value from a sensor, and outputting a drive signal to the fuel injection valve 8 and the solenoid valve 23, and the like are provided.

Next, a control procedure of the supercharging pressure according to the present invention will be described with reference to a flowchart shown in FIG. First,
The ECU 20 determines whether or not the accelerator opening θ detected by the accelerator opening sensor 16 is equal to or greater than a predetermined operation value θtc (45 °) (step S10). If the result of this determination is negative (No), the routine proceeds to step S18, where normal supercharging pressure control is executed. In this normal supercharging pressure control, the throttle valve 7 is opened and closed in accordance with the depression amount (accelerator opening) θ of the accelerator petal 25, and the intake air amount is increased or decreased. At this time, the ECU 20 sets the duty ratio Dt of the solenoid valve 23 to 0, and does not operate the solenoid valve 23. Therefore, the pressure in the surge tank 2a, that is, the supercharging pressure, is constantly guided to the pressure chamber 20b of the actuator 20, and the supercharging pressure is the pressure of the diaphragm caused by the supercharging pressure. Until a predetermined upper pressure that overcomes the force is reached, the actuator 20 does not operate and the wastegate 5 remains closed. When the supercharging pressure reaches the above-mentioned predetermined upper limit, the actuator 20 operates to open the wastegate 5, so that the supercharging pressure does not exceed the predetermined upper limit. This predetermined upper limit is, for example,
It is set to a relatively low value such as 50 mmHgG.

If the determination result of step S10 is affirmative (Ye
In the case of s), the process proceeds to step S12, and in accordance with the accelerator opening degree θ and the engine speed Ne, the target supercharging pressure P is obtained from the target supercharging pressure map previously stored in the above-mentioned storage device.
Set tc. The following table shows target boost pressure values Ptc stored in the target boost pressure map, and these values are experimentally set in consideration of occurrence of engine knock and durability. In setting the target supercharging pressure Ptc, four map values near the detected values of the accelerator opening θ and the engine speed Ne are read from the map, and the accelerator opening θ and the engine speed Ne are determined by a known interpolation method. If the target boost pressure value corresponding to the detected value is set, the target boost pressure Ptc can be set to change continuously.

[0017]

[Table 1]

Next, the supercharging pressure Pt is read from the pressure sensor 11 (step S14), and the absolute value of the deviation between the supercharging pressure Pt and the target supercharging pressure Ptc set as described above is set to a predetermined value ΔP
It is determined whether it is larger than ts (step S16).
This determination is to determine whether the supercharging pressure Pt can be regarded as the same value as the target supercharging pressure Ptc, and the predetermined value ΔPts is set to a very small value. If the supercharging pressure Pt is substantially equal to the target supercharging pressure Ptc, the ECU 20 ends the routine without changing the duty ratio Dt (step S20). In this case, the ECU 20 controls the duty of the solenoid valve 23 using the duty ratio Dt set last time, so that the valve opening of the wastegate 5 is constant and the supercharging pressure is also kept constant.

On the other hand, if the decision result in the step S16 is negative, the process proceeds to a step S22, in which a duty ratio Dt according to a deviation (= Pt-Ptc) between the supercharging pressure Pt and the target supercharging pressure Ptc is set. To end the routine. In this case, the method of setting the duty ratio Dt is not particularly limited.
Various known methods can be applied. When the supercharging pressure Pt is larger than the target supercharging pressure Ptc, the duty ratio Dt is set smaller than the previous value. With this duty ratio Dt, the solenoid valve 23
, The control pressure leaking from the pressure chamber 20b of the actuator 20 via the solenoid valve 23 decreases, and the actuator 20 operates the wastegate 5 to the open side. For this reason, the supercharging pressure Pt decreases toward the target supercharging pressure Ptc. On the other hand, the supercharging pressure Pt is equal to the target supercharging pressure Ptc.
If smaller, the duty ratio Dt is set larger than the previous value, the control pressure leaking from the pressure chamber 20b of the actuator 20 via the solenoid valve 23 increases, and the actuator 20 closes the waste gate 5 to the closing side. Activate. For this reason, the supercharging pressure Pt increases toward the target supercharging pressure Ptc.

In the above embodiment, the waste gate 5
Was driven to open by a pressure-responsive actuator 20,
The actuator for opening the waste gate 5 is not limited to this.

[0021]

As is apparent from the above description, according to the method for controlling the supercharging pressure of the internal combustion engine provided with the turbocharger of the present invention, the throttle valve is substantially fully opened when the accelerator is operated to a predetermined operation amount. At the same time
The accelerator petal can be operated further on the stepping side than the operation amount, the operation amount of the accelerator petal and the engine speed are detected, and when the accelerator petal is operated at or above the operation amount, the detected operation amount of the accelerator petal is The target boost pressure is set according to the engine speed, and the valve opening of the wastegate is adjusted to control the boost pressure to the target boost pressure. Is directly controlled, the response speed becomes extremely fast, and an over-response state is not caused, and a slight output adjustment intended by the driver can be accurately performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the method of the present invention is applied.

FIG. 2 is a diagram showing details of a supercharging pressure control device of the turbocharger TC shown in FIG. 1;

FIG. 3 is a view showing details of a valve opening mechanism of a throttle valve 7 shown in FIG. 1;

FIG. 4 is a graph showing a relationship between an accelerator opening and a throttle opening.

FIG. 5 is an electronic control unit (ECU) 20 for controlling the supercharging pressure.
FIG. 3 is a block diagram showing the configuration of FIG.

FIG. 6 is a flowchart showing a control procedure of supercharging pressure control executed by the electronic control unit 20.

[Explanation of symbols]

 C Compressor E Internal combustion engine T Turbine TC Turbocharger 5 Wastegate 7 Throttle valve 11 Pressure sensor 16 Accelerator opening sensor 18 Engine speed sensor 20 Actuator 23 Solenoid valve 25 Accelerator

Claims (1)

(57) [Claims] A waste gate is provided, and the waste gate is opened in response to a supercharging pressure, and a part of exhaust gas from an engine is discharged to the atmosphere side without passing through a turbine to reduce the supercharging pressure. Equipped with a turbocharger that controls to a predetermined pressure or less,
A supercharging pressure control method for an internal combustion engine in which an accelerator petal is operated to adjust a valve opening of a throttle valve disposed in the middle of an intake passage to control an engine output. The valve is opened to a substantially fully open position, and the accelerator petal can be operated further on the stepping side than the predetermined operation amount. The operation amount of the accelerator petal and the engine speed are detected, and the accelerator petal is set to the predetermined operation amount. When operated as described above, the target supercharging pressure is set according to the detected operation amount of the accelerator petal and the engine speed, and the supercharging pressure is adjusted to the target supercharging pressure by adjusting the valve opening of the wastegate. A supercharging pressure control method for an internal combustion engine provided with a turbocharger, characterized by performing control.