JP2002047940A - Supercharging pressure control method of turbo- supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remedy the inconvenience that overshoot is produced, and an operating sense of an accelerator pedal is different from an actual driving sense due to opening control of a waste gate valve so as to make a supercharging pressure a target supercharging pressure at all times in a partial load zone, when carrying out feedback control of the supercharging pressure by a turbo supercharger. SOLUTION: In the turbo supercharger for supercharging an intake air by using exhaust gas of an engine provided with a throttle valve 13, pressure required for opening and closing control of a waste gate valve 7 of the tube supercharger, is controlled with a control valve so as to obtain a target supercharging pressure set in accordance with a number of rotations of the engine. A limiting value of a control variable for controlling an opening of a control valve is set so that the supercharging pressure is less than the target supercharging pressure in a zone where at least the opening degree of a throttle valve 13 is in a middle opening degree.

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 a turbocharger for controlling a supercharging pressure of a turbocharger to a target supercharging pressure.

[0002]

2. Description of the Related Art Conventionally, in a turbocharger in which a turbine is rotated by using exhaust gas of an engine and a compressor is driven by the rotation of the turbine to supercharge intake air,
In order to control the supercharging pressure, a wastegate valve that bypasses part of the exhaust gas introduced into the turbine without introducing it to the turbine is provided, and the supercharging pressure is targeted by opening and closing the wastegate valve. 2. Description of the Related Art There has been known an apparatus which performs feedback control on a pressure, that is, a target supercharging pressure, to prevent an excessive increase in the supercharging pressure, and perform control so that a torque corresponding to an engine speed is generated. The opening and closing control of the waste gate valve is such that the supercharging pressure is guided to a diaphragm type actuator, and the waste gate valve is driven by this actuator. The actuator is controlled by a control valve capable of introducing a supercharging pressure into the diaphragm chamber and opening the diaphragm chamber to the atmosphere independently of the supercharging pressure introduced into the engine. The control valve is controlled by a duty ratio of a control voltage set based on a difference between a target boost pressure and an actual boost pressure. Therefore, by fully opening the control valve, that is, controlling the duty ratio to 100%, the diaphragm chamber is depressurized to near the atmospheric pressure and the wastegate valve is closed. Conversely, by controlling at a predetermined duty ratio, the diaphragm chamber is opened. Is a pressure lower than the actual supercharging pressure but higher than the atmospheric pressure, and the wastegate valve is opened. In this way, the opening degree of the wastegate valve is controlled, and the feedback control is performed so that the supercharging pressure becomes the target supercharging pressure.

[0003] In order to adopt such a configuration,
For example, as disclosed in Japanese Patent Application Laid-Open No. Sho 62-113828, a target supercharging pressure is determined from the engine speed and the throttle opening and feedback control of the supercharging pressure is performed. The turbocharger controls the turbocharging pressure based on the engine rotation speed and the accelerator opening to control the supercharging pressure.

[0004]

However, in the former invention, since the control upper limit of the control valve for controlling the wastegate valve is not set by the throttle opening, the throttle opening is rapidly changed. In this case, the response of the control is low, and it may be difficult to control the supercharging pressure as required. For the same reason, control responsiveness was low even in the latter invention.

[0005] By the way, in order to improve the responsiveness of the control, it is sufficient to increase the supercharging pressure quickly to the target supercharging pressure. However, if the control for rapidly increasing the supercharging pressure is performed, This may cause a so-called overshoot, which rises above the target boost pressure. In view of such circumstances, in the above-described control of the supercharging pressure, the upper limit value of the duty ratio of the control voltage signal of the control valve is controlled in order to prevent overshoot of the control with respect to the target supercharging pressure at the time of transition. That is, the upper limit duty ratio is set. The upper limit duty ratio is set only when the throttle valve in which the throttle fully open switch is operated is fully opened, and is not set when the throttle valve is not fully opened, that is, in a so-called partial load state of the engine.

When the throttle valve is not fully opened and the engine is operating under a partial load, the duty ratio required for the control valve is set to make the supercharging pressure at that time the target supercharging pressure. Is close to 100%, so the wastegate valve is closed and the turbocharger operates to constantly increase the boost pressure. As a result,
Since the supercharging pressure will be increased with a small amount of exhaust gas, the turbocharger will be used in an operation region where the turbo efficiency is poor, and the intake shaft temperature will increase, and the rotating shaft and bearing of the turbocharger will increase. Otherwise, such problems as overheating of the parts such as the back of the gasket, and deterioration of the durability of the turbine will occur. In addition, since the supercharging pressure acts so as to constantly increase, the torque of the engine rapidly increases with respect to the accelerator pedal depression, and the torque greatly increases even with a slight change in the accelerator pedal depression. It fluctuated. When the torque fluctuates in this manner, driving becomes jerky and drivability is reduced.

An object of the present invention is to solve such a problem.

[0008]

In order to achieve the above object, the present invention takes the following measures. That is, the present invention relates to a turbocharger that supercharges intake air by using exhaust gas of an engine having a throttle valve so that a target supercharging pressure set according to the engine speed is obtained. A supercharging pressure control method for a turbocharger in which a control valve controls a pressure required for opening and closing the wastegate valve, wherein the supercharging pressure is set to a target supercharging at least in a region where the throttle valve is in a middle opening degree. It is characterized in that a control value limit value for controlling the opening of the control valve so as to be less than the pressure is set.

With such a configuration, when the opening of the throttle valve is in the middle range, the limit value of the control amount of the control valve is set to be less than the target supercharging pressure.
Even if the control amount of the control valve is increased or decreased, it is regulated by the set limit value. As described above, the control amount of the control valve is regulated by the limit value, so that the supercharging pressure increases beyond the target supercharging pressure even when the control is performed by setting the control valve to a value corresponding to the target supercharging pressure. It is possible to prevent that. Moreover, when controlling the control amount of the control valve so that the target boost pressure is attained, the control amount is only regulated by the limit value, and therefore, compared to the control in which the control amount is changed according to the operation state. Control can be simplified.

In order to balance the operating feeling of the throttle valve with the operating state of the engine, the control value limit value is
It is preferable to set so that the supercharging pressure increases as the opening of the throttle valve increases.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described.
This will be described with reference to the drawings.

A turbocharger 1, which is a turbocharger schematically shown in FIG. 1, is mounted on a four-cylinder engine for an automobile, for example. This turbocharger 1
Is provided with an exhaust turbine 2 that rotates by the energy of exhaust gas discharged from the engine, that is, an exhaust pressure, and a compressor 3 driven by the exhaust turbine 2. The compressor 3 is introduced into an intake passage 5 through an air cleaner 4. Air can be compressed by the compressor 3 and supplied to the engine. A bypass passage 6 is provided for the exhaust turbine 2, and a waste gate valve 7 is opened and closed by a diaphragm type actuator 8 in the bypass passage 6. The inner diameter of the bypass passage 6 is 0.6 to less than the wheel diameter of the exhaust turbine 2.
It is formed so as to have an inner diameter of 1.0 times.

The actuator 8 has a diaphragm chamber 8a which is urged rearward by a pressure adjusting spring (not shown), and the pressure of air introduced into the diaphragm chamber 8a is regulated by the pressure adjusting spring. When the value exceeds a predetermined value, the diaphragm 8a is displaced and the operating rod 8c is operated to protrude forward. Further, the wastegate valve 7 is configured to be opened by the advance of the operating rod 8c. The diaphragm chamber 8b communicates with the compressor downstream side 5a of the intake passage 5 via the pressure guiding passage 9. A depressurizing passage 10 branched from the middle of the pressure guiding passage 9 is communicated with the inside of the air cleaner 4, and an on-off control valve (VSV) 11 is provided in the middle of the depressurizing passage 10.
Is interposed.

The opening / closing control valve 11 operates a valve body (not shown) to be opened / closed by an electromagnetic actuator, and applies a control voltage signal having a duty ratio DBST for determining an opening time length to the electromagnetic actuator. The opening is controlled to an opening corresponding to the duty ratio DBST. That is, the opening / closing control valve 11 is duty-controlled by the electronic control unit 12 to feedback-control the opening of the wastegate valve 7.

The electronic control unit 12 comprises a microcomputer system having a central processing unit (not shown), a memory, an input interface, and an output interface. The input interface includes at least a throttle valve 13 linked to the accelerator pedal.
A signal a output from the throttle sensor 14 for detecting the opening degree of the air, a supercharging pressure signal b output from the pressure sensor 16 for detecting the pressure in the surge tank 15, and the intake air in the surge tank 15 Temperature sensor 21 for detecting temperature
, A cylinder discrimination signal G1, a crank angle reference position signal G2, an engine speed signal c, and an engine cooling water temperature output from a cam position sensor 17 for detecting a rotation state of the engine. A water temperature signal d output from a water temperature sensor 18 for detecting
A vehicle speed signal e or the like output from a vehicle speed sensor 19 for detecting the vehicle speed is input. A drive control voltage signal (pulse voltage) is supplied from the output interface to the electromagnetic actuator of the opening / closing control valve 11.

The electronic control unit 12 has a program for controlling the fuel injection amount based on the output signals from the various sensors. The electronic control unit 12
The pressure required for opening and closing control of the wastegate valve 7 is controlled by the opening and closing control valve 11 so that the target supercharging pressure set according to the engine speed NE is obtained, and at least the opening degree of the throttle valve 13 is set to the middle. The opening / closing control valve 11 is controlled so that the supercharging pressure becomes lower than the target supercharging pressure in the opening range.
There is a built-in supercharging pressure control program configured to set an upper limit value that is a limit value of a control amount for controlling the opening degree.

In order to set the duty ratio DBST of the control voltage signal of the open / close control valve 11, the engine speed NE and the throttle valve 13
The upper limit value DMMAX set on the basis of the opening degree of the throttle, ie, the throttle opening degree TA, is stored in the two-dimensional table TDM
Saved as MAX. This two-dimensional table TDM
MAX includes the throttle opening TA and the engine speed NE.
The upper limit value DMMAX is set for the representative value. The upper limit value DMMAX is set so as to increase as the throttle opening TA increases in the partial load range, that is, when the throttle opening TA of the throttle valve 13 is a medium opening. Also, this upper limit value DM
MAX is set so that the supercharging pressure becomes lower than the target supercharging pressure when the opening / closing control valve 11 is controlled using this value. In this embodiment, as in the prior art, the upper limit value DMM at the middle opening degree according to the engine speed NE when the throttle opening degree TA is substantially fully opened.
An upper limit value DMMAX different from AX is set.

A schematic control procedure in the supercharging pressure control program is shown in FIGS.

In this control program, the opening / closing control valve 11 controls the actual supercharging pressure (hereinafter referred to as the actual supercharging pressure) PM
The feedback control is performed so that the TPB becomes the target supercharging pressure PMT, and the fully closed control is performed when the operation state does not satisfy the condition of the feedback control. Feedback control is executed when the following conditions are satisfied. That is, the pressure sensor 16 and the water temperature sensor 18 after the start, in which the cooling water temperature of the engine is within a predetermined range, for example, a range defined by a temperature for determining completion of warm-up and a temperature in a high load state. The engine is operated under the conditions that the normal state is maintained for a predetermined time, the traction fuel is not cut off when the running is hindered due to excessive torque, and the fuel supply is not being cut. When there is a state, feedback control is performed. On the other hand, if one of the above conditions is not met,
Execute the fully closed control.

Open / close control valve 1 in feedback control
The duty ratio DBST of one control voltage signal is determined by the procedure shown in FIG. In FIG. 2, first, in step S1, the actual boost pressure PMTPB is reduced to the target boost pressure PMT.
Is determined to be within a predetermined pressure range centered on.
The predetermined pressure range is a predetermined value KDPM from the target supercharging pressure PMT.
T is defined as the lower limit, and the target boost pressure PMT is set to a predetermined value K.
The upper limit is set to the value obtained by adding DPMT. In step S1, when the actual supercharging pressure PMTPB is within a predetermined pressure range, it sets the current duty ratio DBST _n the previous duty ratio DBST _n-1. Conversely, if the actual boost pressure PMTPB is out of the predetermined pressure range in step S1, the process proceeds to step S3, where the actual boost pressure P
Based on MTPB and target boost pressure PMT, duty ratio DBST is determined by PID control.

In step S4, it is determined whether or not the duty ratio DBST obtained this time is equal to or smaller than the upper limit duty ratio DBSTMAX. If it is equal to or smaller than the upper limit, the process proceeds to step S5. In step S5, the duty ratio DBST is set to the lower limit guard value K.
It is determined whether or not DOUTMIN is greater than or equal to DOUTMIN. If it is less than DOUTMIN, the process proceeds to step S7. If it is greater than DOUTMIN, the duty ratio DBST is set to the value obtained in step S3I, and the current process ends. This lower guard value KDOUTM
IN is set corresponding to a state where the open / close control valve 11 is mechanically fully closed. Since the duty ratio DBST exceeds the upper limit duty ratio DBSTMAX in step S6, the duty ratio DBST is set to the upper limit duty ratio DBSTMAX. Step S7
Then, the duty ratio DBST is set to the lower limit guard value KDOUT
Since it is determined that the duty ratio is less than MIN, the duty ratio DBST is set to the lower limit guard value KDOUTMIN, and the current process is terminated.

As described above, the duty ratio DBS when the open / close control valve 11 is feedback-controlled.
T is that the actual supercharging pressure PMTPB is within a predetermined pressure range,
Moreover, the previously set duty ratio DBST _n-1 is _equal to the upper limit duty ratio DBSTMAX and the lower limit guard value KDOUT.
If the value is between MIN and MIN, the value is adopted to maintain the previously set duty ratio DBST _n-1 (step S1 → S2). On the other hand, if the actual supercharging pressure PMTPB is out of the predetermined pressure range, the duty ratio DBST calculated based on the target supercharging pressure and the actual supercharging pressure is calculated by PI
D control is performed to calculate the duty ratio DBST (step S1 → S3). The thus obtained duty ratio D
If BST is a value between the upper limit duty ratio DBSTMAX and the lower limit guard value KDOUTMIN, the value is adopted (step S4 → S5 → end), otherwise,
That is, when the obtained duty ratio DBST is higher than the upper limit duty ratio DBSTMAX, the upper limit duty ratio DBSTMAX is reduced (step S6 → end), and when the obtained duty ratio DBST is lower than the lower limit guard value KDOUTMIN, the lower limit guard value KDOUTMIN is changed (step S6). S7 → End) is adopted.

Accordingly, the supercharging pressure is always maintained in the vicinity including the target supercharging pressure by the feedback control. Further, even in an operation state in which the supercharging pressure exceeds the target supercharging pressure and overshoots, the upper limit duty ratio DB set so that the supercharging pressure becomes lower than the target supercharging pressure.
Since the duty ratio DBST is regulated by STMAX, it is possible to prevent the supercharging pressure from becoming larger than the target supercharging pressure and causing a large torque change.

The above upper duty ratio DBSTMAX
Is calculated according to the procedure described below. In FIG. 3, first, in step S11, an upper limit value DMMAX set based on the throttle opening TA of the throttle valve 13 and the engine speed NE is added to the duty learning value DOUTM to calculate an upper limit duty ratio DBSTMAX.
The duty learning value DOUTM is a value obtained by learning the duty ratio DBST at a predetermined engine speed in a medium speed range, which is a stable operation range in which torque fluctuation is small. On the other hand, the upper limit value DMMAX is set in the table
To find the upper limit value DMMAX corresponding to the engine speed NE and the throttle opening TA at this time. The corresponding engine speed NE and throttle opening TA
If there is no such value, the value is obtained by interpolation calculation.

After calculating the upper limit duty ratio DBSTMAX, in step S12, the calculated upper limit duty ratio DBSTMAX is changed to the upper limit guard value KDOUTMAX.
It is determined whether or not it is below. If it exceeds, the process proceeds to step S13, and if it is below, the process proceeds to step S14. The upper limit guard value KDOUTMAX is set in accordance with a state in which the open / close control valve 11 is mechanically fully opened, and the upper limit duty ratio DBSTMAX is determined by the sum of the duty learning value DOUTM and the upper limit value DMMAX. Therefore, the opening / closing control valve 11 is set so as to prevent the duty ratio from becoming 100% or more and controlling the opening / closing control valve 11 to be opened more than its mechanical fully open state. The calculated upper limit duty ratio DBSTMAX is equal to the upper limit guard value KDOUT.
If the maximum duty ratio DBSTMAX is exceeded, the upper limit duty ratio DBSTMAX is set to the upper limit guard value K in step S13.
DOUTMAX is set, and this process ends. on the other hand,
If the calculated upper limit duty ratio DBSTMAX is equal to or smaller than the upper limit guard value KDOUTMAX, step S1 is performed.
In 4, it is determined whether or not the upper limit duty ratio DBSTMAX is equal to or larger than the lower limit guard value KDOUTMIN. If the upper limit duty ratio DBSTMAX is smaller than the lower limit guard value KDOUTMIN, the process proceeds to step S15. This processing ends. In step S15, since the calculated upper limit duty ratio DBSTMAX has not reached the lower limit guard value KDOUTMIN, the lower limit guard value KDOUTMIN is set as the upper limit duty ratio DBSTMAX.
Set.

In such a configuration, the open / close control valve 11
In the operation state in which the throttle valve 13 is in the middle opening degree, the duty ratio DBS
When T is set to the upper limit duty ratio DBSTMAX, the upper limit value DMMAX and the duty learning value D set by the engine speed NE and the throttle valve TA at this time are set.
Upper limit duty ratio DBSTM based on the total value with OUTM
AX is calculated. The calculated upper limit duty ratio DBSTMAX is equal to the upper limit guard value KDOUTMAX.
If the calculated upper limit duty ratio DBSTMAX is an intermediate value between the lower limit guard value KDOUTMIN and the lower limit guard value KDOUTMIN.
The opening / closing control valve 11 is not controlled with the duty ratio DBST having a large value.

Thus, even if the open / close control valve 11 is opened at the upper limit duty ratio DBSTMAX, the open / close control valve 11
The opening of the throttle valve 13 is small, and the pressure applied to the actuator 8 is small, and the waste gate valve 7 is opened according to the pressure.
The supercharging pressure decreases in accordance with A, and the torque is kept low. Also, the throttle opening degree TA of the throttle valve 13
Increases in the middle opening region, the upper limit duty ratio DBSTMAX increases accordingly, so that the opening of the opening / closing control valve 11 increases, and the waste gate valve 1
3 is closed, the boost pressure increases, and the torque increases. In addition, since the upper limit duty ratio DBST is set lower than the duty ratio for setting the target supercharging pressure, the supercharging pressure rises beyond the target supercharging pressure, and suddenly changes with the change of the throttle valve 13. The torque does not increase.

Therefore, in the region where the throttle opening TA of the throttle valve 13 is medium, the opening of the wastegate valve 7 is controlled in a state substantially proportional to the throttle opening TA, and the supercharging pressure is controlled. In addition, the overshoot in which the supercharging pressure rises more than necessary can be suppressed. Therefore, it is possible to prevent the torque from fluctuating due to the excessive boost pressure, and the increase in the torque is substantially proportional to the throttle opening degree TA, in other words, substantially proportional to the operation feeling of the accelerator pedal. Operability can be improved, and easy-to-handle engine characteristics can be obtained. Moreover, since the supercharging pressure can be prevented from increasing excessively, a decrease in turbo efficiency due to an excessive increase in the supercharging pressure can be prevented. As a result, the temperature of the intake air can be reduced, the heat damage of components constituting the turbocharger can be reduced, and the durability of the turbine can be improved. Further, when executing the feedback control, the duty ratio DBST for setting the target supercharging pressure is set.
, The throttle opening TA is set as a parameter with respect to the upper limit value DMMAX of the duty ratio DBST instead of taking the throttle opening TA into consideration, so that the control of the opening / closing control valve 11, that is, the configuration of the control program is simplified. can do.

The present invention is not limited to the embodiment described above. In the above-described embodiment, the wastegate valve is configured to be closed when the open / close control valve is fully opened. Conversely, when the open / close control valve is fully closed, the wastegate valve is closed. May be configured to close. In this case, the limit value of the control amount of the opening / closing control valve is a lower limit value set based on the engine speed and the throttle opening of the throttle valve.

In addition, the configuration of each section is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[0031]

As described above, according to the present invention, when the opening of the throttle valve is in the middle range, the limit value of the control amount of the control valve is set to be less than the target supercharging pressure. Therefore, even if the control amount of the control valve is increased or decreased, the control value is regulated by the set limit value. Therefore, even if the control amount is set to a value corresponding to the target boost pressure and the control is performed, the target boost pressure is not increased. It is possible to prevent the supercharging pressure from rising. Moreover, when controlling the control amount of the control valve so that the target boost pressure is attained, the control amount is only regulated by the limit value, and therefore, compared to the control in which the control amount is changed according to the operation state. Control can be simplified.

If the limit value of the control amount is set so that the supercharging pressure increases as the opening of the throttle valve increases, the operating feeling of the throttle valve and the operating state of the engine, that is, the torque, can be improved. The characteristics can be balanced or substantially proportional, and the engine characteristics can be easily handled.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing the overall configuration of an embodiment of the present invention.

FIG. 2 is a flowchart schematically showing a control procedure of the embodiment.

FIG. 3 is a flowchart schematically showing a control procedure of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Turbocharger 2 ... Exhaust turbine 3 ... Compressor 7 ... Waste gate valve 11 ... Opening / closing control valve 12 ... Electronic control device 13 ... Throttle valve

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kenji Hayashi 2-1-1 Taoyuan, Ikeda-shi, Osaka Daihatsu Industry Co., Ltd. (72) Takahiro Ozaki 2-1-1 Taoyuan, Ikeda-shi, Osaka Daiha (72) Inventor Keiichi Yamaguchi 2-1-1 Taoyuan, Ikeda-shi, Osaka Daihatsu Industry F-term (reference) 3G005 EA04 EA16 FA01 FA04 FA06 GA03 GB28 GC05 GD09 GD14 GE01 HA19 JA06 JA12 JA13 JA23 JA39 JA51

Claims (2)

[Claims] In a turbocharger for supercharging intake air using exhaust gas of an engine having a throttle valve, a target supercharging pressure set according to an engine speed is provided.
A supercharging pressure control method for a turbocharger, wherein a pressure required for opening and closing control of a wastegate valve of a turbocharger is controlled by a control valve, wherein the supercharging pressure is at least in a region where a throttle valve is in a middle opening degree. A control amount limit value for controlling the opening of the control valve such that the pressure is less than a target supercharging pressure. 2. The turbocharger according to claim 1, wherein the control value is set so that the supercharging pressure increases as the opening of the throttle valve increases. Pressure control method.