JP2990019B2 - 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 supercharging pressure control method for an automobile engine or the like in which intake air is supercharged by a turbocharger, and more particularly to an improvement in skip control during acceleration.

[0002]

2. Description of the Related Art In a turbocharger for 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 a supercharging pressure. It is controlled so that a predetermined target supercharging pressure set according to the number 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 of the open / close control valve is performed by feedback-controlling the duty ratio of the voltage applied to the open / close control valve according to the target supercharging pressure given by the number and the actual supercharging pressure. It is configured to control.

In the above configuration, as shown in FIG.
During acceleration, the opening / closing control valve is fully opened, the wastegate valve is fully closed, and the actual feedback control is started after the intake pipe internal pressure (supercharging pressure) PM reaches the target supercharging pressure PMT. There is no problem in the case of gentle acceleration as shown by the broken line, but in the case of rapid acceleration as shown by the solid line, the overshoot of the supercharging pressure becomes large as shown by the hatched line due to control delay, and the engine is damaged. There was a problem that might come.

Therefore, as shown in FIG. 7, when reaching the target boost pressure PMT or its vicinity during acceleration, the duty ratio of the voltage applied to the on / off control valve is reduced by a predetermined amount in a skip manner to open the on / off control valve. There has also been proposed a configuration in which the control is shifted to the feedback control after the control is performed. However, in this case, good results are shown in the case of rapid acceleration as shown by the solid line, but in the case of gentle acceleration as shown by the broken line, the supercharged pressure has a step S
Then, there is a problem that a feeling of breathing appears at the end of acceleration and drivability deteriorates.

In order to further solve such a problem, Japanese Unexamined Patent Publication No. 4-76224 discloses a method of controlling the opening and closing of the cylinder when the difference between the current supercharging pressure and the target supercharging pressure becomes smaller than a predetermined value. After performing the skip control to skip the valve duty ratio in a skip manner, shift to the feedback control, and variably set the amount of change in the duty ratio during the skip control in accordance with the amount of change in the supercharging pressure. What has been proposed.

[0006]

However, the control method disclosed in the above publication can effectively prevent a large overshoot at the time of rapid acceleration and a feeling of breathing at the time of gentle acceleration, but the amount of decrease in the duty ratio is large. Since it is determined by the amount of change in the supercharging pressure, if the convergence value of the supercharging pressure and the corresponding duty ratio takes various values depending on the engine speed, an overshoot or an undershoot will also occur.

FIG. 8 and FIG. 9 will be described in more detail.
As shown in the figure, in the normal state of WOT (throttle valve is opened at a predetermined angle or more), the intake pipe internal pressure (supercharging pressure) is determined in accordance with the engine rotational speed, and the duty ratio converging to the intake pipe internal pressure is determined. I have. Therefore, when accelerating from the fully closed throttle to the WOT steady state, when the engine rotation speed is A, the duty ratio DA corresponding to the corresponding target value is high, and therefore, as shown in FIG. And an undershoot occurs. Conversely, when the engine speed is B, the duty ratio DB, which is the corresponding target value, is low.
As shown in FIG. 9B, the skip amount becomes relatively small, and overshoot occurs. When the engine speed is C, the corresponding target value duty ratio DC is in the middle. As shown in FIG. 9 (c), since the skip destination substantially corresponds to the duty ratio that gives the intake pipe internal pressure at that rotational speed, the intake pipe internal pressure is quickly and stably controlled to the target intake pressure. Thus, a control state as shown in FIG. 9 (c) is required in all engine speed ranges.

In view of such a conventional problem, the present invention provides a supercharging pressure control method capable of promptly and smoothly transitioning to feedback control without any overshoot or undershoot in all engine speed ranges after acceleration. The purpose is to provide.

[0009]

SUMMARY OF THE INVENTION A boost pressure control method according to the present invention performs feedback control so as to control a boost pressure to a target value by opening / closing a wastegate valve of a turbocharger, and a wastegate valve during acceleration. Fully closed,
When the supercharging pressure reaches the target supercharging pressure or in the vicinity thereof, or when the difference therebetween becomes smaller than a predetermined value, the supercharging pressure shifts to feedback control after performing skip control for opening the waste gate valve in a predetermined amount in a skip manner. The control method is characterized in that the opening of the wastegate valve at the time of the skip control is set close to the opening at which the supercharging pressure determined in accordance with the engine rotation speed in a steady state is provided.

[0010]

According to the present invention, the skip destination during the skip control is set near the opening of the wastegate valve which gives the supercharging pressure which should be finally stabilized at the engine rotational speed. Thereafter, the feedback control can be promptly and smoothly shifted to the feedback control without any overshoot or undershoot in all engine speed regions.

[0011]

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

In FIG. 1, reference numeral 1 denotes a turbocharger of an automobile engine, which is disposed in an exhaust passage 2 and driven by the energy of exhaust gas, and a compressor 4 driven by the exhaust turbine 3. It has. The compressor 4 is disposed in the intake passage 5,
The air introduced from the air cleaner 6 is compressed and supplied 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 a 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.
It is configured such that the supercharging pressure can be maintained constant by opening 0 to bypass a part of the exhaust gas.

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. 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 A rotation speed signal c from a speed sensor for detecting a rotation speed (NE), a water temperature signal d from a water temperature sensor, and the like are input.

Next, the electronic control unit 1 having the above configuration
5 will be described with reference to FIG. Before entering the supercharging pressure control operation of FIG. 2, although not shown, a throttle opening signal a, an intake pipe internal pressure signal b, a rotation speed signal c, and a water temperature signal d are read in advance, and the throttle valve 7 is set to a predetermined angle. It is configured to open the above and to start the supercharging pressure control when the condition that the water temperature is within a predetermined temperature range is satisfied. First, in step # 1, it is determined whether or not a skip flag described later is set. If the flag is set, it means that the skip control has already been performed and the feedback control in step # 6 is immediately performed. Move to In the feedback control, when the difference between the actual supercharging pressure and the target supercharging pressure is large, such as during acceleration when the throttle valve 7 shifts from the fully closed state to the WOT steady state, the voltage applied to the on-off control valve 14 is increased by 100%. Control to% duty ratio or maximum duty ratio,
The opening / closing control valve 14 is fully opened and the waste gate valve 10
When the supercharging pressure rises and the difference from the target supercharging pressure set in accordance with the engine speed falls within a certain value, the duty ratio change amount is set to an appropriate range. It is configured to perform normal feedback control. On the other hand, if the skip flag has not been set, skip control has not been performed yet, and it is sequentially determined whether or not the skip control condition is satisfied. That is, in step # 2, it is determined whether or not the actual intake pipe internal pressure PM has reached a pressure lower by α from the target supercharging pressure PMT at the engine rotational speed.
The control then proceeds to step # 3 where the intake pipe internal pressure P at a certain elapsed time is reached.
It is determined whether the amount of change ΔPM of M is greater than β, and β
In the following cases, there is no need to perform skip control, so the flow proceeds to feedback control in step # 6, and if it is larger than β, the flow proceeds to skip control in step # 4. The skip control method will be described later. When the skip control is performed, the skip flag is set in step # 5, and the conditions for entering the supercharging pressure control are canceled and the steps # 2 and # are performed until the skip flag is reset until the skip flag is reset. Step # 3 without performing the judgment of # 3
The control operation shifts to the feedback control of No. 6 and returns to the main routine.

According to the above control method, during acceleration, FIG.
3A, when the current supercharging pressure PM reaches a pressure lower than the target supercharging pressure PMT by α, as indicated by hatching in FIG.
As shown in (b), it is determined whether or not the rise of the supercharging pressure is large, that is, whether or not the change amount ΔPM is larger than β, and as shown by a solid line in FIG. Can reliably prevent the occurrence of overshoot by performing skip control before reaching the target supercharging pressure PMT. Also, as shown by the broken line in FIG. When it is not necessary to perform the skip control, the undershoot can be prevented by performing the feedback control without performing the skip control.

Next, regarding the above-described skip control method,
This will be described with reference to FIGS. As shown in FIG. 4, the intake pipe internal pressure PM has a fixed relationship with the engine rotational speed NE when the throttle opening is steady at a predetermined angle or more, and an opening / closing control valve for giving the intake pipe internal pressure PM. The duty ratio of the applied voltage to 15 also shows a certain correspondence. For example, when the engine speed is A, the duty ratio is high as DA, and when the engine speed increases to B, the duty ratio decreases as DB. However, to increase the engine speed to C, the duty ratio must be increased to DC. And a gentle v-shaped curve is drawn. Therefore, in the skip control, FIG.
As shown by a broken line, a value of the duty ratio slightly lower than the duty ratio corresponding to the engine rotation speed NE in the steady state is set as the skip destination duty ratio (skip request value).

By performing the skip control as described above, as shown in FIG.
In both cases B and C, it is possible to smoothly and promptly control the intake pipe pressure to an appropriate value without causing overshoot or undershoot due to the skip control. FIG. 5A shows a case where the engine speed NE is A, and FIG. 5B shows a case where the engine speed NE is B.
FIG. 5C shows the case where the engine speed NE is C,
Regardless of the engine speed, the intake pipe internal pressure is quickly controlled to an appropriate value. Therefore, there is no danger that the engine will be damaged due to the occurrence of overshoot, or a step will occur in the supercharging pressure due to the occurrence of undershoot, and drivability will not be degraded, and controllability will be improved.

The duty ratio of the skip destination in the skip control can be easily obtained during the control operation by mapping in advance and storing the duty ratio in correspondence with the engine rotational speed NE.

In the above-described embodiment, an example in which the supercharging pressure control is performed by the duty ratio control of the voltage applied to the on-off control valve has been described. However, it is only necessary to control the opening of the waste gate valve. However, the present invention is not limited to this.

[0021]

According to the supercharging pressure control method of the present invention, as described above, the wastegate valve which supplies the supercharging pressure to be finally stabilized at the engine speed at the skip destination during the skip control is provided. Since the opening is set near the opening, it is possible to shift to the feedback control promptly and smoothly without any overshoot or undershoot in all engine rotational speed regions after acceleration.

[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 a flowchart of a supercharging pressure control operation of the embodiment.

FIG. 3 is an explanatory diagram of a time change of an intake pipe internal pressure and a change amount thereof in the embodiment.

FIG. 4 is an explanatory diagram of a relationship among an engine rotation speed, an intake pipe internal pressure, a duty ratio, and a skip request value in the embodiment.

FIG. 5 is an explanatory diagram of a control state of intake pipe internal pressure by skip control at each engine rotation speed in the embodiment.

FIG. 6 is an explanatory diagram of a control state of an intake pipe internal pressure in a conventional example.

FIG. 7 is an explanatory diagram of a control state of an intake pipe internal pressure by a skip control of a conventional example.

FIG. 8 is an explanatory diagram of a relationship among an engine rotation speed, an intake pipe internal pressure, and a duty ratio.

FIG. 9 is an explanatory diagram of a control state of an intake pipe internal pressure by skip control at each engine rotation speed 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)

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F02B 37/00-37/14

Claims (1)

(57) [Claims] 1. A wastegate valve of a turbocharger is opened and closed to perform feedback control so as to keep a supercharging pressure at a target value, and at the time of acceleration, the wastegate valve is fully closed so that the supercharging pressure is equal to a target supercharging pressure or a target supercharging pressure. In the supercharging pressure control method in which the control reaches the vicinity thereof or when the difference between them becomes smaller than a predetermined value, the wastegate valve is skipped by a predetermined amount in a skip manner and then the feedback control is performed. A supercharging pressure control method characterized in that a gate valve opening is set near an opening that gives a supercharging pressure determined in accordance with an engine rotation speed in a steady state.