JPH0861104A - Excessive supercharging preventing method in supercharging pressure control - Google Patents

Abstract

PURPOSE: To positively prevent supercharging leading to the damage of the engine by interrupting the fuel supply, and prevent lowering of the drivability due to the interruption of the fuel supply as for as possible. CONSTITUTION: A first upper limit of supercharging pressure, beyond which the engine may be damaged, is set (#2), and a second upper limit of supercharging pressure is set between a target supercharging pressure and the first upper limit of supercharging (#5). When the supercharging pressure exceeds the first upper limit of supercharging pressure and when the supercharging pressure between the first and second upper limits of supercharging pressure is continuously maintained for over a fixed time the fuel supply is interrupted (#4).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to supercharging pressure control in an automobile engine or the like in which intake air is supercharged by a turbocharger, and more particularly to a method for preventing supercharging.

[0002]

2. Description of the Related Art A turbocharger for an automobile engine is provided with a wastegate valve in a bypass passage of its exhaust turbine, and by controlling the opening / closing of this wastegate valve according to the actual supercharging pressure, the supercharging pressure is increased. It is controlled so as to attain a predetermined target boost pressure set according to the engine speed. Specifically, supercharging pressure is guided to a diaphragm type actuator, and this actuator drives the wastegate valve to open and close, and an opening and closing control valve that can open the diaphragm chamber of the actuator to the atmosphere is used to rotate the engine. The open / close control valve is opened / closed by feedback control of the duty ratio of the applied voltage to the open / close control valve according to the difference between the target boost pressure set according to the number and the actual boost pressure, and the wastegate valve is opened. Is configured to control the degree.

In such supercharging pressure control, if the supercharging pressure cannot be controlled due to, for example, a failure of the wastegate valve, the supercharging pressure may rise abnormally and the engine may be damaged. In order to prevent such a danger, conventionally, when the intake pipe internal pressure exceeds a certain set value, the fuel supply is cut to prevent supercharging. Explaining with reference to FIG. 4, a target supercharging pressure is set in correspondence with the engine speed NE, and the intake gate internal pressure (supercharging pressure) PM is set to the target supercharging pressure so that the wastegate valve is controlled. The opening is controlled, and the supercharging prevention fuel cut area is set in the supercharging pressure area that is appropriately higher than the target supercharging pressure, and as soon as the supercharging pressure enters this supercharging prevention fuel cut area. I try to cut the fuel.

[0004]

However, as shown in FIG. 5, when the boost pressure rises rapidly such as during rapid acceleration, the intake pipe internal pressure (supercharging pressure) PM becomes the target boost pressure PMT.
If the target supercharging pressure PMT and the fuel cut supercharging pressure PMC are close to each other, a fuel cut will occur that exceeds the fuel cut supercharging pressure PMC during the overshoot. However, there is a problem that drivability is significantly deteriorated because the output torque of the engine sharply decreases.

On the other hand, if the fuel cut supercharging pressure PMC is raised in order to eliminate such a problem, there is a problem that the fuel cut may not work and the engine may be damaged at the time of actual failure.

In Japanese Patent Laid-Open No. 61-265331, first and second pressure values higher than the target supercharging pressure are set, and the supercharging pressure is lowered when the first pressure value is exceeded. A method is disclosed in which the fuel cut is performed when the second pressure value which is higher than the first pressure value and which is set higher than the first pressure value and decreased in accordance with an increase in the intake air amount is exceeded. Overshoot can be suppressed and the risk of engine damage can be reliably prevented, but since the set pressure for fuel cut is one step, the problem similar to the above-mentioned conventional problem remains.

In view of the above conventional problems, the present invention can reliably prevent supercharging that would damage the engine by fuel cut, and prevent deterioration of drivability due to fuel cut as much as possible. An object of the present invention is to provide a method of preventing supercharging in supercharging pressure control that can be performed.

[0008]

The supercharging prevention method in supercharging pressure control according to the present invention sets a first upper limit supercharging pressure which may cause engine damage when the supercharging pressure exceeds its value. And the second upper limit between the target boost pressure and the first upper limit boost pressure.
The upper limit of the supercharging pressure is set, and when the supercharging pressure exceeds the first upper limit of supercharging pressure and when the supercharging pressure between the first and second upper limit of supercharging pressure continues for a certain time or more, It is characterized by cutting the supply.

[0009]

According to the present invention, as soon as the supercharging pressure exceeds the first upper limit supercharging pressure, the fuel supply is cut off, whereby the risk of engine damage due to supercharging can be reliably prevented, and the supercharging pressure can be prevented. Is between the second upper limit supercharging pressure and the first upper limit supercharging pressure, the duration is measured, and if it continues for a certain time or longer, the fuel supply is cut because the engine may be damaged. Secondly due to overshoot, etc.
When the upper limit supercharging pressure is only exceeded, the fuel supply is not cut off, and therefore the drivability is not deteriorated due to the cutoff of the fuel supply. Thus, it is possible to reliably prevent supercharging that would damage the engine and prevent deterioration of drivability due to fuel cut as much as possible.

[0010]

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

First, the overall structure of the supercharging pressure control device will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes a turbocharger for an automobile engine, which includes an exhaust turbine 3 arranged in an exhaust passage 2 and driven by energy of exhaust gas, and a compressor 4 driven by the exhaust turbine 3. There is. The compressor 4 is arranged in the intake passage 5, compresses the air introduced from the air cleaner 6, and supplies the compressed air to the engine through the throttle valve 7 and the surge tank 8.

A bypass passage 9 is provided for the exhaust turbine 3, and a waste gate valve 10 for opening / closing the bypass passage 9 to control the flow rate of exhaust gas introduced into the exhaust turbine 3 is provided. A diaphragm type actuator 11 for opening and closing the wastegate valve 10.
Is provided. The supercharging pressure on the downstream side of the compressor 4 is introduced into the diaphragm chamber 11a of the actuator 11 through the pressure introducing passage 12, and the waste gate valve 1 corresponding to the displacement amount of the operating rod 11b corresponding to the supercharging pressure.
By opening 0 to bypass a part of the exhaust gas, the supercharging pressure can be maintained constant.

The pressure introducing passage 12 is connected to the air cleaner 6 at one end thereof, and is connected to the other end of a pressure relief passage 13 in which an opening / closing control valve (VSV) 14 is disposed midway. By controlling the opening degree, the supercharging pressure introduced into the diaphragm chamber 11a is controlled, and the opening degree of the waste gate valve 10 is controlled so that the set supercharging pressure can be varied. The opening / closing control valve 14 is configured so that its opening degree is controlled by the duty ratio of the applied voltage, and the duty ratio of the applied voltage to the opening / closing control valve 14 is controlled by the electronic control unit (ECU) 15. It is configured. The electronic control unit 15 includes a throttle opening signal a from a throttle sensor that detects the opening of the throttle valve 7, an intake pipe internal pressure signal b from a pressure sensor that detects the intake pipe internal pressure in the surge tank 8, and an engine Engine rotation speed signal c from the speed sensor that detects the rotation speed (NE) and water temperature signal d from the water temperature sensor
Has been entered. Also, an electronic control unit (ECU)
15 is also configured to control an injector 16 that supplies fuel to the combustion chamber.

In the above configuration, the electronic control unit (EC
In controlling the supercharging pressure by U), first, the throttle opening signal a, the intake pipe internal pressure signal b, the engine rotation speed signal c,
When the water temperature signal d is read, the throttle valve 7 is opened by a predetermined angle or more, and the water temperature is within a predetermined temperature range, the supercharging pressure control is started. In the supercharging pressure control, a target supercharging pressure PMT is set according to the engine speed, and the duty of the applied voltage to the opening / closing control valve 14 is set according to the difference between the target supercharging pressure PMT and the actual supercharging pressure PM. By controlling the ratio, feedback control is performed so that the supercharging pressure PM matches the target supercharging pressure PMT. Also,
At the time of acceleration when the throttle valve 7 shifts from fully closed to a steady state, the applied voltage to the opening / closing control valve 14 is set to 10
By controlling the duty ratio to 0% or the maximum duty ratio, the opening / closing control valve 14 is fully opened to completely close the wastegate valve 10, and the boost pressure is increased to set the target supercharging corresponding to the engine speed. When the difference from the pressure PMT is within a certain value, skip control is performed to temporarily set the duty ratio low in order to prevent overshoot as necessary, and then the change amount of the duty ratio is set to an appropriate range. Feedback control is performed.

Next, fuel cut control for preventing supercharging by the electronic control unit 15 will be described with reference to FIGS. 2 and 3. In FIG. 2, first, it is judged whether or not the intake pipe internal pressure (supercharging pressure) PM exceeds a first upper limit supercharging pressure KPM1 (step # 1).
Immediately after shifting to 4, the fuel supply from the injector 16 is stopped by the control signal from the electronic control unit (ECU),
Perform a fuel cut to prevent engine damage due to supercharging. That is, the first upper limit supercharging pressure KPM1 is set to a supercharging pressure that may cause damage to the engine promptly if a higher supercharging pressure is applied.

If the intake pipe internal pressure (supercharging pressure) PM does not exceed the first upper limit supercharging pressure KPM1, it is determined whether the intake pipe internal pressure (supercharging pressure) PM exceeds the second upper limit supercharging pressure KPM2. Is determined (step # 2), the second upper limit boost pressure K
If PM2 is not exceeded, there is no possibility of a supercharging state, so the routine proceeds to step # 5, where fuel cut is not executed and the normal operating state is maintained or returned to the normal operating state. On the other hand, when the intake pipe internal pressure (supercharging pressure) PM exceeds the second upper limit supercharging pressure KPM2, after the intake pipe internal pressure (supercharging pressure) PM exceeds the second upper limit supercharging pressure KPM2, T It is determined whether or not time (msec) or more has elapsed (step # 3), and if it has elapsed, the process proceeds to step # 4 to execute fuel cut and prevent engine damage. On the contrary, when the time T has not elapsed, the routine proceeds to step # 5 and the normal operating state is maintained. That is, the second upper limit supercharging pressure KPM1 is not likely to damage the engine even if the supercharging pressure is temporarily exceeded due to overshoot or the like. The boost pressure is set to be high.

Thus, as shown in FIG. 3, even if the supercharging pressure PM overshoots the target supercharging pressure PMT during acceleration and exceeds the second upper limit supercharging pressure KPM2, it continues to exceed it. If the time t is smaller than the constant time T,
The fuel cut is not executed, and therefore the drivability is not deteriorated. Of course, there is no danger of damaging the engine then. Further, when t becomes larger than T due to a failure of the wastegate valve 9 or the supercharging pressure PM exceeds the first upper limit supercharging pressure KPM1, the fuel cut is executed. It is possible to surely prevent the damage.

[0018]

As described above, according to the supercharging prevention method in the supercharging pressure control of the present invention, as soon as the supercharging pressure exceeds the first upper limit supercharging pressure, the fuel supply is cut off so that the supercharging is prevented. You can surely prevent the risk of engine damage due to supply,
Moreover, if the supercharging pressure continues for a certain period of time between the second upper limit supercharging pressure and the first upper limit supercharging pressure, the fuel supply is cut because the engine may be damaged, but due to overshoot, etc. When the second upper limit supercharging pressure is temporarily exceeded, the fuel supply is not cut, so that the drivability is not deteriorated due to the cut of the fuel supply, and therefore the supercharging that may damage the engine is reliably prevented. In addition, it is possible to prevent deterioration of drivability due to fuel cut as much as possible.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a supercharging pressure control device according to an embodiment of the present invention.

FIG. 2 is a flowchart of fuel cut control for preventing supercharging in the embodiment.

FIG. 3 is an explanatory diagram of a change state of a target supercharging pressure, a first upper limit supercharging pressure, a second upper limit supercharging pressure, and an intake pipe internal pressure in the embodiment.

FIG. 4 is an explanatory diagram of a relationship between a target supercharging pressure and a fuel cut region for preventing supercharging in a conventional example.

FIG. 5 is an explanatory diagram when a fuel cut is executed by overshoot in a conventional example.

[Explanation of symbols]

 1 Turbocharger 3 Exhaust Turbine 9 Bypass Passage 10 Wastegate Valve 14 Open / close Control Valve (VSV) 15 Electronic Control Unit (ECU) 16 Injector

Claims (1)

[Claims] 1. A first upper limit supercharging pressure which may cause engine damage when the supercharging pressure exceeds that value, and is set between the target supercharging pressure and the first upper limit supercharging pressure. When the second upper limit supercharging pressure is set and the supercharging pressure exceeds the first upper limit supercharging pressure, and when the supercharging pressure between the first and second upper limit supercharging pressures continues for a certain time or longer. A method of preventing supercharging in supercharging pressure control, characterized in that the fuel supply is cut off.