JP3105402B2 - Supercharging pressure control method - 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 in an automobile engine or the like in which intake air is supercharged by a turbocharger.

[0002]

2. Description of the Related Art In a turbocharger of an automobile engine, a wastegate valve is provided in a bypass passage of an exhaust turbine, and the opening and closing of the wastegate valve is controlled in accordance with an actual supercharging pressure. It is controlled so that a predetermined target supercharging pressure set according to the engine speed is obtained. Specifically, the supercharging pressure is guided to a diaphragm type actuator, and the waste gate valve is opened / closed by this actuator, and an opening / closing control valve capable of opening the diaphragm chamber of the actuator to the atmosphere is provided. The open / close control valve is opened / closed by feedback-controlling the duty ratio of the voltage applied to the open / close control valve in accordance with the difference between the target boost pressure and the actual boost pressure set according to the number, and the wastegate valve is opened The degree is controlled (see Japanese Patent Application Laid-Open No. 4-76224).

At the time of the feedback control, when an excessive duty ratio is given as a result of a calculation based on a difference between a target boost pressure and an actual boost pressure, if the duty ratio is controlled as it is, the boost pressure rapidly increases. There is a problem that the engine may be damaged due to a large overshoot. Therefore, conventionally, as shown in FIG. 4, an upper limit guard value is set for the value of the duty ratio to be controlled, and even if a higher duty ratio is obtained as a result of the calculation, control is performed with the upper limit guard value.

[0004]

By the way, in a steady operation state, a target supercharging pressure is given corresponding to the engine speed, and a required duty ratio for giving the target supercharging pressure corresponds to the engine speed. Given. As shown in FIG. 4, the required duty ratio has a characteristic that the engine speed is high in a low speed range, low in a middle speed range, and high in a high speed range.
As shown by the broken line in FIG. 4, it is set to a constant value regardless of the engine speed.

Therefore, at a low engine speed A, the difference between the required duty ratio and the upper guard value is small, so that the correction is insufficient and the control delay is increased. At the speed B, since the difference between the required duty ratio and the upper limit guard value is large, even if the upper limit guard value is provided, there is a possibility that overshoot may occur due to the control with the large duty ratio of the calculation result during transition. was there.

The present invention has been made in view of the above-mentioned problems, and has as its object to provide a supercharging pressure control method capable of ensuring high controllability without causing overshoot or control delay.

[0007]

SUMMARY OF THE INVENTION A supercharging pressure control method according to the present invention is to perform feedback control of the opening of a wastegate valve that bypasses an exhaust turbine of a turbocharger by a duty ratio of a voltage applied to an on / off control valve. In the supercharging pressure control method for controlling the supercharging pressure, the upper limit guard value of the duty ratio at the time of feedback control is
A supercharging pressure control method for setting an appropriate high value from a required duty ratio defined in correspondence with an engine rotation speed during a steady operation, wherein the value of the required duty ratio at a predetermined engine rotation speed is set in an actual operation state. Learning is performed, and an upper limit guard value at each engine speed is calculated from the learned value and a preset map.

[0008]

According to the present invention, the upper limit guard value of the duty ratio at the time of feedback control is set to a value that is appropriately higher than the required duty ratio defined in accordance with the engine speed during steady operation. Even in the rotation range, the duty ratio can be controlled in a control range having an appropriate margin for the required duty ratio, so that the control range is too wide, causing an overshoot at the time of transition or the control range being too narrow. High controllability can be ensured without causing a control delay due to insufficient correction.

Further, an actual required duty ratio is learned at a predetermined engine rotation speed, and an upper limit guard value at each engine rotation speed is calculated from the learned value and a map set in advance, thereby obtaining an individual difference for each engine. An appropriate upper limit guard value can be set without being affected by a pressure difference between a highland and a flat ground or a change with time, and high controllability can be secured with high reliability.

[0010]

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

First, the overall configuration of the supercharging pressure control device will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes a turbocharger of an automobile engine, which includes an exhaust turbine 3 disposed in an exhaust passage 2 and driven by exhaust gas energy, and a compressor 4 driven by the exhaust turbine 3. I have. The compressor 4 is disposed in the intake passage 5, compresses 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 and 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 waste gate valve 10
Is provided. The boost 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 is moved in accordance with the displacement of the operating rod 11b according to the boost pressure.
By opening 0 and bypassing a part of the exhaust gas, the supercharging pressure can be maintained constant.

One end of the pressure introducing passage 12 is connected to the air cleaner 6, and the other end of a pressure release passage 13 provided with an on-off control valve (VSV) 14 on the way is connected to the pressure introducing passage 12. 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 such that the opening degree is controlled by the duty ratio of the applied voltage, and the electronic control unit (ECU) 15 controls the duty ratio of the applied voltage to the opening / closing control valve 14. 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, an engine An engine rotation speed signal c from a speed sensor for detecting a rotation speed (NE) and a water temperature signal d from a water temperature sensor
Is entered.

In the above configuration, the electronic control unit (EC
In controlling the supercharging pressure by U), first, a throttle opening signal a, an intake pipe internal pressure signal b, an engine rotation speed signal c,
When the water temperature signal d is read and the throttle valve 7 is opened by a predetermined angle or more and the water temperature is within a predetermined temperature range, the control enters the supercharging pressure control. In the supercharging pressure control, a target supercharging pressure is set in accordance with the engine speed, and an opening / closing control valve 14 is provided in accordance with a difference between the target supercharging pressure and the actual supercharging pressure.
By controlling the duty ratio of the applied voltage with respect to, feedback control is performed so that the supercharging pressure matches the target supercharging pressure. Also, during acceleration when the throttle valve 7 shifts from a fully closed state to a steady state, the open / close control valve 1
4 is controlled to a 100% duty ratio or a maximum duty ratio, the opening / closing control valve 14 is fully opened, the wastegate valve 10 is fully closed, and the boost pressure is increased and set according to the engine speed. When the difference from the target supercharging pressure is within a certain value, skip control is performed to set the duty ratio once lower to prevent overshoot, if necessary. The set normal feedback control is performed.

In the above-described feedback control of the supercharging pressure, when an excessive duty ratio is given by a calculation result based on a difference between a target supercharging pressure and an actual supercharging pressure, when the duty ratio is controlled as it is, the supercharging is performed. Since the pressure rises sharply and causes a large overshoot, the upper limit guard value of the duty ratio set to prevent this is shown in FIGS.
This will be described with reference to FIG.

In FIG. 2, the required duty ratio for providing the target boost pressure determined according to the engine speed in the steady operation state is indicated by a virtual line. The standard required duty ratio has a characteristic that it is high in a low engine speed range, low in a middle speed range, and high in a high speed range. The upper limit guard value of the duty ratio control is set to a value that is appropriately higher than the required duty ratio, as indicated by a broken line.

As described above, the upper limit guard value of the duty ratio at the time of the feedback control is set to a value that is appropriately higher than the required duty ratio defined corresponding to the engine speed during the steady operation. In this case, the duty ratio can be controlled in a control range having an appropriate margin for the required duty ratio, and the control range is too wide to cause an overshoot at the time of transition, or the control range is too narrow, resulting in insufficient correction. High controllability can be ensured without causing a control delay.

In the actual setting method of such an upper limit guard value, the duty ratio at a predetermined engine rotational speed G in a middle speed range where the duty ratio control is stable in the operating state of the engine is read as a learning value. this is,
This is the required duty ratio of the engine rotation speed G under the operating conditions of the engine. The upper limit guard value is calculated by adding the learned value to a characteristic value set for each engine speed by a map as shown in FIG. Further, the final upper limit guard value is set to a lower duty ratio of the final upper limit value, which is an upper limit value finally required for safe driving, and the calculated value.

The map shown in FIG. 3 is obtained by assuming or assuming a required duty ratio in a reference engine operating state, then setting an appropriately high value as an upper limit guard value, and then setting a predetermined engine rotation speed as a learning point. The characteristic value for each engine speed is set by subtracting the required duty ratio at the speed G. Therefore, by adding the characteristic value to the learning value that is different for each engine and each operating condition, it is possible to set an upper limit guard value that almost appropriately corresponds to an operating condition of an arbitrary engine.

As described above, the actual required duty ratio is learned at a predetermined engine speed, and the upper limit guard value at each engine speed is calculated from the learned value and a map set in advance. And the pressure introduction passage 1
(2) An appropriate upper guard value can be set without being affected by individual differences such as the flow resistance difference of each engine, pressure differences between highlands and flatlands, and changes over time, ensuring high controllability with high reliability. can do.

[0021]

According to the supercharging pressure control method of the present invention, as described above, the upper limit guard value of the duty ratio at the time of the feedback control is adjusted from the required duty ratio defined corresponding to the engine speed during the steady operation. Since it is set to an appropriately high value, it is possible to control the duty ratio in a control range with an appropriate margin for the required duty ratio in any rotation range, and the control range is too wide to exceed High controllability can be ensured without causing a shoot or a control delay due to insufficient correction because the control range is too narrow.

Further, by learning an actual required duty ratio at a predetermined engine speed and calculating an upper limit guard value at each engine speed from the learned value and a map set in advance, individual differences between engines can be obtained. An appropriate upper limit guard value can be easily set without being affected by a pressure difference or a change with time between a highland and a flat ground, and high controllability can be secured with high reliability.

[Brief description of the 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 an explanatory diagram of an upper limit guard value of a control duty ratio in the embodiment.

FIG. 3 is an explanatory diagram of a map for obtaining an upper limit guard value in the embodiment.

FIG. 4 is an explanatory diagram of an upper limit guard value of a control duty ratio in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Turbocharger 3 Exhaust turbine 9 Bypass passage 10 Wastegate valve 14 On-off control valve (VSV) 15 Electronic control unit (ECU)

Claims (1)

(57) [Claims] 1. A supercharging pressure control method for controlling a supercharging pressure by feedback-controlling an opening degree of a wastegate valve that bypasses an exhaust turbine of a turbocharger by a duty ratio of a voltage applied to an on / off control valve. The upper limit guard value of the duty ratio at the time of control is set to an appropriately higher value than the required duty ratio defined corresponding to the engine speed during steady operation.
This is a supercharging pressure control method, which is performed at a predetermined engine speed.
Learning of the required duty ratio value in the actual operation state,
From the learning value and the map set in advance, each engine speed
Calculate upper limit guard value in speed
Supercharging pressure control method.