JPH0874588A - Supercharging control method - Google Patents

Abstract

PURPOSE: To secure high controllability without entailing any overshoot and control delay by setting the upper limit guard value of a control duty ratio in a proper manner. CONSTITUTION: In this supercharging control method which feedback-controls the opening of a waste gate valve 10 bypassing an exhaust turbine 3 of a turbocharger 1 by means of a duty ratio of impressed voltage to an on-off control valve 14, an upper limit guard value of the duty ratio in time of feedback control is properly set to a high value from a desired duty ratio to be prescribed in response to engine speed. As for the upper limited guard value, the desired duty ratio in time of a state when the target supercharging and the actual supercharging are almost accorded with each other in the specified engine speed NE is learned, and then it is operated from the learnt value and a preset map.

Description

Detailed Description of the Invention

[0001]

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

[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. It is configured to control the degree (see Japanese Patent Laid-Open No. 4-76224).

During the feedback control, when an excessive duty ratio is given as a result of the calculation based on the difference between the target boost pressure and the actual boost pressure, if the duty ratio is controlled as it is, the boost pressure rises sharply. 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 to the value of the duty ratio to be controlled, and even if a duty ratio higher than that is obtained as a result of the calculation, the upper limit guard value is used for control.

[0004]

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

Therefore, at the engine speed A in the low speed range, the difference between the required duty ratio and the upper limit guard value is small, so that there is a problem that the correction delay becomes insufficient and the control delay becomes large, while the engine speed in the medium speed range is increased. At speed B, the difference between the required duty ratio and the upper limit guard value is large, so that even if the upper limit guard value is provided, there is a risk that over-shoot may occur due to the control with the duty ratio having a large calculation result during the transition. was there.

In view of such conventional problems, an object of the present invention is to provide a supercharging pressure control method capable of ensuring high controllability without causing overshoot or control delay.

[0007]

According to the supercharging pressure control method of the present invention, the opening of a waste gate valve that bypasses the exhaust turbine of a turbocharger is feedback-controlled by the duty ratio of the voltage applied to the on-off control valve. In the boost pressure control method for controlling the boost pressure, the upper limit guard value of the duty ratio during feedback control is
It is characterized in that it is set to an appropriately high value from the required duty ratio specified in correspondence with the engine rotation speed during steady operation.

Preferably, the value of the required duty ratio at a predetermined engine speed is learned in an actual operating state, and the upper limit guard value at each engine speed is calculated from the learned value and a preset map.

[0009]

According to the present invention, the upper limit guard value of the duty ratio during feedback control is set to a value that is appropriately higher than the required duty ratio defined in correspondence to the engine speed during steady operation. Even in the rotation range, it is possible to control the duty ratio within a control range that has an appropriate margin for the required duty ratio. High controllability can be secured without causing a control delay due to insufficient correction.

Further, 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 preset map to obtain the individual difference for each engine. It is possible to set an appropriate upper limit guard value without being affected by the atmospheric pressure difference between the highland and the flatland, the change over time, and the like, and it is possible to secure high controllability with high reliability.

[0011]

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 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 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 introduction passage 12 is connected to the other end of a pressure relief passage 13 having one end connected to the air cleaner 6 and an opening / closing control valve (VSV) 14 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.

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 is set corresponding to the engine speed, and the opening / closing control valve 14 is set according to the difference between the target supercharging pressure and the actual supercharging pressure.
By controlling the duty ratio of the applied voltage with respect to, the feedback control is performed so that the boost pressure matches the target boost pressure. Further, during acceleration when the throttle valve 7 shifts from fully closed to a steady state, the opening / closing control valve 1
The applied voltage to No. 4 is controlled to 100% duty ratio or maximum duty ratio, the open / close control valve 14 is fully opened and the waste gate valve 10 is fully closed, and the boost pressure is increased and set corresponding to the engine speed. When the difference from the target boost pressure is within a certain value, skip control is performed to set the duty ratio low once to prevent overshoot if necessary, and then the duty ratio change amount falls within an appropriate range. The set normal feedback control is performed.

In the feedback control of the supercharging pressure, when an excessive duty ratio is given as a result of the calculation by the difference between the target supercharging pressure and the actual supercharging pressure, if the duty ratio is controlled as it is, Since the pressure suddenly rises and a large overshoot occurs, the upper limit guard value of the duty ratio set to prevent this will be described with reference to FIGS.
Will be described with reference to.

In FIG. 2, the required duty ratio for giving the target supercharging pressure, which is determined corresponding to the engine speed in the steady operation state, is shown by a virtual line. This standard required duty ratio has characteristics that it is high in the low speed region of the engine rotation speed, low in the medium speed region, and high in the high speed region. The upper limit guard value of the duty ratio control is set to an appropriately high value from this required duty ratio, as indicated by the broken line.

As described above, since the upper limit guard value of the duty ratio during the feedback control is set to a value that is appropriately higher than the required duty ratio defined corresponding to the engine rotation speed during steady operation, which rotation range The duty ratio can be controlled in a control range with an adequate margin for the required duty ratio, and the control range is too wide and overshoot occurs during a transition, or the control range is too narrow and correction is insufficient. High controllability can be secured without causing a control delay.

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

In the map of FIG. 3, the required duty ratio in the operating condition of the reference engine is actually obtained or assumed, and then an appropriately high value is set as the upper limit guard value, and then the predetermined engine rotation speed as the learning point is obtained. The characteristic value for each engine rotation 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 the upper limit guard value that almost properly corresponds to the 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 preset map, whereby the waste gate valve 10 is calculated. And characteristic difference of actuator 11 and pressure introduction passage 1
It is possible to set an appropriate upper limit guard value without being affected by individual differences of each engine such as the difference of distribution resistance of 2, etc., atmospheric pressure difference between highland and flatland, and changes over time, and secure high controllability with high reliability. can do.

[0022]

As described above, according to the supercharging pressure control method of the present invention, the upper limit guard value of the duty ratio during the feedback control is determined 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 that has an adequate margin for the required duty ratio in any rotation range, and the control range is too wide and will be exceeded during transients. High controllability can be secured without causing a chute or causing a control delay due to insufficient correction due to a narrow control range.

Further, by learning the actual required duty ratio at a predetermined engine rotation speed and calculating the upper limit guard value at each engine rotation speed from the learned value and a preset map, the individual difference for each engine and It is possible to easily set an appropriate upper limit guard value without being affected by a pressure difference between a highland and a flatland, a change with time, and the like, and it is possible to secure high controllability with high reliability.

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

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

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

Claims (2)

[Claims] 1. A supercharging pressure control method for controlling supercharging pressure by feedback-controlling an opening of a wastegate valve that bypasses an exhaust turbine of a turbocharger according to a duty ratio of a voltage applied to an on-off control valve. A supercharging pressure control method, wherein an upper limit guard value of a duty ratio during control is set to a value that is appropriately higher than a required duty ratio defined corresponding to an engine speed during steady operation. 2. A value of a required duty ratio at a predetermined engine speed is learned in an actual operating state, and an upper limit guard value at each engine speed is calculated from the learned value and a preset map. The supercharging pressure control method according to claim 1.