JPH0476223A - Supercharging pressure control method for turbocharger - Google Patents

Abstract

PURPOSE:To enhance drivability by skippingly controlling an opening/closing control valve for controlling an actuator for opening or closing a waste gate valve if a difference between a target supercharging pressure and an actual supercharging pressure is smaller than a value determined on the basis of a supercharging pressure. CONSTITUTION:In a turbocharger 1, a waste gate valve 7 is provided on a bypass passage 6 disposed with respect to an exhaust turbine 2, and is opened or closed by an actuator 8. The actuator 8 opens the waste gate valve 7 via an operating rod 8c in the case where an air pressure inside a diaphragm chamber 8b regulated by an opening/closing control valve 11 exceeds a predetermined value specified by a pressure regulating spring. In duty-controlling the opening/ closing control valve 11 by means of an ECU 12, a duty ratio is skippingly changed up to a set value on the way if a difference between a target supercharging pressure and an actual supercharging pressure is smaller than a value determined on the basis of a supercharging pressure, and then, the duty ratio is gradually changed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling boost pressure of a turbocharger that can be suitably adopted in automobiles and the like.

[Prior Art] In a turbocharger installed in an automobile engine, a diaphragm-type actuator is actuated by boost pressure, and this actuation opens a wastegate valve in an exhaust bypass passage installed in parallel with an exhaust turbine. Generally, the boost pressure is prevented from rising above a set pressure. However, with just this, there is a problem that as the engine rotation approaches the maximum speed (as the engine speed approaches the maximum speed), the charging efficiency of the air supply decreases, and the output torque tends to decrease.

Therefore, an opening/closing control valve is provided that intermittently opens the diaphragm chamber of the actuator to the atmosphere, and the duty ratio of the opening/closing operation of this opening/closing control valve is changed by feedback control based on the detection result of the boost pressure. Some are designed to converge the pressure to a required target boost pressure.

However, with this kind of feedback control, when the accelerator pedal is suddenly pressed for sudden acceleration, overshoot occurs due to control delay, and the boost pressure temporarily decreases. may greatly exceed the target boost pressure. Therefore, there is a problem that the durability of the turbocharger and the engine is adversely affected.

In order to solve the above problems, as a prior art of the present invention, for example, as shown in Japanese Patent Laid-Open No. 153523/1983, when sudden acceleration of the engine is detected, feedback control is temporarily activated. Some systems improve control followability by stopping the engine and controlling the boost pressure to open. In addition, as shown in Fig. 8, if the difference between the target boost pressure and the actual boost pressure PM is larger than the judgment value Pi, the on-off control valve is adjusted to the maximum duty ratio, max.
control so that the supercharging pressure PM can rise quickly, and if the difference is smaller than the judgment value Pi, in other words, the supercharging pressure PM becomes smaller than the judgment value Pi from the target supercharging pressure. If the pressure exceeds the subtracted pressure, the duty ratio is skipped to an intermediate set value up to t, and then the duty ratio is gradually changed based on the actual supercharging pressure detection result. In some systems, the boost pressure PM is controlled to converge to the target boost pressure.

[Problem to be Solved by the Invention] However, in such a configuration, since the duty ratio jump setting value t and the judgment value Pi are each constant, if the gear position of the transmission differs, The amount of overshoot of boost pressure changes significantly. That is, the rate of increase in supercharging pressure during acceleration is largely influenced by the gear position of the transmission. For example, as shown in Fig. 9, when acceleration is performed with the transmission operated in 2nd 2nd gear, the rate of increase in supercharging pressure PM is large, and the transmission is operated in 3rd gear. When acceleration is performed in , the rate of increase in supercharging pressure PM becomes smaller than in the above case. For this reason, if the set value t and the judgment value Pi are each constant, when the transmission is suddenly accelerated at the second 2nd position, a control delay of the supercharging pressure PM will occur, resulting in overstrain. The amount becomes larger. Further, when the transmission is accelerated in the third Bth position, even if the supercharging pressure PM is similarly adjusted, the amount of overshoot becomes smaller due to a decrease in the rate of increase in the supercharging pressure PM. As a result, drivability deteriorates and the turbocharger and engine are adversely affected.

The present invention aims to eliminate all of the above-mentioned problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention takes the following measures.

That is, the turbocharger supercharging pressure control method according to the present invention is configured such that the supercharging pressure can be adjusted by controlling the actuator that opens and closes the waste gate valve of the turbocharger by duty-controlling the opening/closing control valve. In advance, when the difference between the target boost pressure and the actual boost pressure becomes smaller than the determination value, the duty ratio of the opening/closing control valve is changed in a skip manner to an intermediate set value, and the duty ratio is changed. A turbocharger supercharging pressure control method that gradually changes the supercharging pressure based on the actual supercharging pressure detection result and performs feedback control of the supercharging pressure to a target supercharging pressure, wherein the determination value is used as the supercharging pressure It is characterized in that it changes in response to the amount of change in.

[Operation] According to such a configuration, if the difference between the target boost pressure and the actual boost pressure is large and exceeds the determination value, the opening/closing control valve is controlled with the maximum duty ratio. become. In this case, the actuator closes the wastegate valve to promote an increase in supercharging pressure. When the boost pressure increases and the difference becomes smaller than the determination value, the duty ratio is changed in a skip manner to an intermediate set value, and then the duty ratio is gradually changed. As a result, the amount of exhaust gas bypass is adjusted by the actuator, and the boost pressure is converged to the target boost pressure.

Additionally, if the amount of change in boost pressure is large, the above-mentioned judgment value will be changed to a large value, and the timing of boost pressure adjustment will be accelerated according to the rate of increase in boost pressure. It becomes possible to effectively suppress the overshoot of the boost pressure at Conversely, if the amount of change in boost pressure is small,
The determination value is changed to a small value, and the timing of adjusting the supercharging pressure is delayed in accordance with the rate of increase in the supercharging pressure.

[Example 1] An example of the present invention will be described below with reference to FIGS. 1 to 7.

In the figure, 1 is a turbocharger for an automobile engine.

The turbocharger 1 includes an exhaust turbine 2 that rotates with the energy of exhaust gas discharged from an engine, and a compressor 3 driven by the exhaust turbine 2. The turbocharger 1 is introduced into an intake passage 5 through an air cleaner 4. This air can be compressed by the compressor 3 and supplied to the engine. Further, a bypass passage 6 is provided for the exhaust turbine 2, a waste gate valve 7 is disposed in the bypass passage 6, and the waste gate valve 7 is opened and closed by a diaphragm type actuator 8.

The actuator 8 is formed by forming a sealed diaphragm chamber 8b on the back side of a diaphragm 8a that is biased rearward by a pressure regulating spring (not shown). When the pressure exceeds a predetermined value defined by the pressure regulating spring, the diaphragm 8a is deflected and the actuating rod 8C is operated to protrude forward. The waste gate valve 7 is configured to open when the actuating rod 8C moves forward. The diaphragm chamber 8b is
The compressor downstream side 5a of the intake passage 5 via the pressure passage 9
It is communicated with. Further, a pressure relief path 10 branched from the middle of this pressure guide path 9 is communicated with the inside of the air cleaner 4,
An on-off control valve VSV 11 is interposed in the middle of this pressure relief path 10.

The opening/closing control valve VSV 11 is configured such that a valve body (not shown) that opens and closes the pressure relief passage 10 is operated by an electromagnetic actuator, and is switched to the open position only while a driving voltage is applied to the electromagnetic actuator. It looks like this.

The opening/closing control valve VSV 11 is controlled by an electronic control unit ECU 1.
2, the opening/closing is controlled by duty. This electronic control unit ECU 12 is composed of a microcomputer unit equipped with a central processing unit (not shown), a memory, an input interface, and an output interface, and the input interface includes:
At least the signal a from the throttle sensor 14 for detecting the opening degree of the throttle valve 13 linked to the accelerator pedal and the supercharging pressure signal from the pressure sensor 16 for detecting the pressure in the surge tank 15, the engine rotation An engine rotation signal C indicating the engine cooling water temperature and a water temperature signal d corresponding to the engine cooling water temperature are respectively input.

From the output interface, the on-off control valve VSV
A driving pulse voltage is supplied to eleven electromagnetic actuators. Note that as the throttle sensor 14, a potentiometer or the like that converts the opening degree of the throttle valve 13 into an electrical signal is used. As the pressure sensor 16, for example, a pressure sensor whose electric capacity changes depending on the pressure difference between the upper and lower sides of a pair of diaphragms and which can obtain an electric signal proportional to the boost pressure is used. The engine rotation signal C is obtained, for example, by calculating the engine rotation speed based on the time interval of ignition pulses output from the ignition device. The water temperature signal d is
It is inputted from a water temperature sensor (not shown) that includes a built-in thermistor whose resistance value changes depending on the engine cooling water temperature.

Furthermore, the electronic control unit ECU 12 has a built-in program as schematically shown in FIG.

First, in step 51, various information such as a signal a from the throttle sensor 14, a boost pressure signal b from the pressure sensor 16, an engine rotation signal C1, and a water temperature signal d are input, and the process proceeds to step 52. In step 52, it is determined whether predetermined feedback execution conditions are satisfied, for example, whether the throttle valve 13 is at a predetermined angle (60' deg) or more, and whether the engine cooling water temperature is within a predetermined range. Each judgment is made, and the process proceeds to step 53 only if these execution conditions are satisfied. In step 53, a target supercharging pressure PMt corresponding to the engine rotational speed NE is determined based on a relational expression previously stored in the memory and a map as shown in FIG. 3, and the process proceeds to step 54. Step 5
In step 4, for example, the amount of change ΔPM in supercharging pressure PM is calculated from the value at the previous detection and the value at the latest detection, and step 55
Proceed to. In step 55, a determination value Pi corresponding to the amount of change ΔPM in supercharging pressure PM is determined based on the relational expression previously stored in the memory and a map as shown in FIG. 5, and the process proceeds to step 56. In step 56, it is determined whether the difference between the target supercharging pressure PMt and the actual supercharging pressure PM (PMt-PM) is smaller than the determination value Pi. If the difference (PMt-PM) is greater than the determination value Pi, the process proceeds to step 57; if it is smaller, the process proceeds to step 58.

In step 57, the duty ratio of the on-off control valve VSV 11 is set to the maximum value, max. In step 58, the duty ratio is changed in a skip manner to a value near the intermediate value (for example, 60%). Next, as shown in Fig. 4, the corrected duty ratio ΔD is determined based on the absolute value of the difference between the target supercharging pressure PMt and the actual supercharging pressure PM from the map stored in the memory in advance, and the corrected duty ratio ΔD is determined. The corrected duty ratio ΔD is sequentially added to the previous duty ratio, and the duty ratio of the pulse voltage applied to the on-off control valve vSVll is gradually changed in the direction in which the boost pressure PM approaches the target boost pressure PMt. go.

The above control is repeatedly executed while the engine is operating.

According to such a configuration, when the difference between the target supercharging pressure PMt and the actual supercharging pressure PM (PMt-PM) is larger than the judgment value Pi, the on-off control valve VSV 11 is set at a maximum duty ratio of max. (steps 51 to 57)
. In this case, a pulse voltage is continuously applied to the electromagnetic actuator of the opening/closing control valve VSV 11, and the wastegate valve 7 is closed by the actuator 8, so that the increase in supercharging pressure PM is promoted. The boost pressure PM increases and the difference (PMt-PM) becomes the judgment value Pi.
When the duty ratio becomes smaller, first, the duty ratio reaches its maximum value, m
After being changed in a skip-like manner from ax to an intermediate setting value to t, the duty ratio is gradually changed (steps 56-58). As a result, the actuator 8 adjusts the bypass amount of the exhaust gas, suppressing the rate of increase in supercharging pressure PM, and causing the supercharging pressure PM to gradually converge to the target supercharging pressure PMt.

Further, when the amount of change ΔPM in the supercharging pressure PM is large, for example, when sudden acceleration is performed with the transmission being operated to 2nd 2nd, as shown in FIG.
i is changed to a large value, and the adjustment timing of supercharging pressure PM is accelerated in accordance with the rising speed of supercharging pressure PM.

As a result, the rate of increase in supercharging pressure PM during sudden acceleration is suppressed to around the target supercharging pressure PMt, and supercharging pressure P
The overshoot of M can be effectively suppressed.

Conversely, when the amount of change ΔPM in supercharging pressure PM is small, for example, when sudden acceleration is performed with the transmission being operated to 3rd, as shown in FIG.
is changed to a small value, and the adjustment timing of supercharging pressure PM is delayed in accordance with the rising speed of supercharging pressure PM. As a result, the supercharging pressure PM smoothly rises to around the target supercharging pressure PMt, and the rate of increase is suppressed in a region closer to the target supercharging pressure PMt, and overshoot of the supercharging pressure PM is suppressed. Ru.

Therefore, according to such a configuration, the opening/closing control valve VSV 11 is appropriately controlled in accordance with the amount of change in the boost pressure,
Since the actuator 8 that opens and closes the wastegate valve 7 can be controlled, overshoot of the supercharging pressure during rapid acceleration can be effectively suppressed without being affected by the gear position of the transmission. As a result, drivability in the entire rotation range can be improved at each gear position of the transmission, and overrun of the turbocharger 1 and strain on the engine can be effectively prevented.

In the above embodiment, the determination value of the supercharging pressure is set in correspondence with the second 2nd position and the third 3rd position of the transmission, but it may be set in correspondence with each gear position.

[Effects of the Invention] Since the present invention has the above-described configuration, the boost pressure can be controlled to an appropriate value according to the engine rotation, and the engine performance can be maintained at a high value in the entire rotation range. is possible. Moreover, since the boost pressure can be adjusted in response to the amount of change in boost pressure, it is possible to effectively prevent boost pressure overshoot during sudden acceleration without being affected by the gear position of the transmission. can be reduced. As a result, strain on the turbocharger and engine can be effectively prevented, and drivability in the entire rotation range can be improved.

[Brief explanation of drawings]

1 to 7 show one embodiment of the present invention, FIG. 1 is an explanatory diagram of the overall configuration, FIG. 2 is a flowchart diagram schematically showing the control procedure, and FIGS. 3 to 5 are control diagrams. 6 and 7 are diagrams illustrating the setting conditions of . FIG. 8 is a functional explanatory diagram corresponding to FIGS. 6 and 7 showing a conventional example, and FIG. 9 is an operational explanatory diagram showing defects in the conventional example. 1...Turbocharger 2...Exhaust turbine 3...Compressor 6...Bypass passage 7...Wastegate valve 8...Actuator 11...Opening/closing control valve 12...Electronic control device

Claims (1)

[Claims] By controlling the duty of the opening/closing control valve, the actuator that opens and closes the waste gate valve of the turbocharger is controlled to adjust the boost pressure, and the difference between the target boost pressure and the actual boost pressure is When the difference becomes smaller than the judgment value, the duty ratio of the opening/closing control valve is changed in a skip manner to an intermediate set value, and the duty ratio is gradually changed based on the actual boost pressure detection result to prevent overload. A turbocharger boost pressure control method that performs feedback control of boost pressure to a target boost pressure,
A supercharging pressure control method for a turbocharger, characterized in that the determination value is changed in accordance with an amount of change in supercharging pressure.