CN112664282B

CN112664282B - Control method for variable turbocharger

Info

Publication number: CN112664282B
Application number: CN201910977664.6A
Authority: CN
Inventors: 邓大伟; 郑有能
Original assignee: SAIC General Motors Corp Ltd; Pan Asia Technical Automotive Center Co Ltd
Current assignee: SAIC General Motors Corp Ltd; Pan Asia Technical Automotive Center Co Ltd
Priority date: 2019-10-15
Filing date: 2019-10-15
Publication date: 2023-02-21
Anticipated expiration: 2039-10-15
Also published as: CN112664282A

Abstract

The present application provides a control method for a variable turbocharger, which is used for a gasoline engine. The method comprises the following steps: 1) Determining a boost pressure control deviation from the turbocharger boost pressure and a boost pressure target value; 2) Outputting an actuator position control signal from the boost pressure control offset; 3) Determining a VGT flow set value and an exhaust pressure set value from the boost pressure target value and the intake air flow rate; 4) Determining a preset position value of a VGT actuator according to a VGT flow set value and an exhaust pressure set value; 5) Determining an actuator position target value according to the actuator position control signal and the VGT actuator position preset value; and 6) adjusting the opening of the VGT nozzle ring by the VGT actuator according to the actuator position target value. The control method for the variable turbocharger has the advantages of simplicity, reliability, easiness in implementation and the like, and can be applied to a gasoline engine and improve the operation efficiency of the gasoline engine.

Description

Control method for variable turbocharger

Technical Field

The present application relates to the field of vehicle control, and more particularly, to a control method for a variable turbocharger for a gasoline engine, which is intended to selectively control the opening degree of the variable turbocharger on the gasoline engine.

Background

Turbocharging technology has been applied to automotive gasoline engines to meet future fuel consumption regulations. With the further increase in the pressure of fuel consumption indicators, more and more gasoline engines begin to adopt new combustion cycle modes such as miller cycle and lean burn. However, the above circulation methods all require more air intake of the engine to maintain the original power performance, which requires significantly increasing the boost ratio, but the conventional exhaust gas release valve turbocharger has low overall efficiency due to large amount of air release at high speed, and increasing the boost ratio causes the lift of the back pressure before the vortex, which causes unsmooth exhaust or increases the amount of residual exhaust gas in the cylinder, which leads to combustion deterioration and even increased knocking tendency, and limits the performance improvement.

Variable Geometry Turbocharger (VGT) regulates turbine flow through a continuously Variable nozzle ring mechanism without flow resistance and exhaust energy losses caused by bleed valves, and thus has a higher overall efficiency in the high velocity region. Variable turbochargers typically have a nozzle ring mechanism placed in front of the turbine wheel, and the cross-sectional area of the gas flow inlet before entering the wheel can be changed by adjusting the angle of the nozzle ring, so as to achieve a continuously variable turbine cross-section. Although variable turbochargers have been implemented on engines using diesel fuel, the exhaust gas temperature in engines using gasoline is significantly higher (e.g., by about 100 degrees) than in engines using diesel fuel, and thus existing gasoline engines are not typically equipped with variable turbochargers.

In recent years, with the progress of high temperature resistant material technology and the reduction of cost, the development of a variable turbocharger for a gasoline engine capable of withstanding exhaust temperatures of 950 degrees or more has been advanced, and research on a control method of the variable turbocharger for the gasoline engine is urgently needed.

Disclosure of Invention

An object of an aspect of the present application is to provide a control method for a variable turbocharger that aims to provide effective control of a variable turbocharger of a gasoline engine.

The purpose of the application is realized by the following technical scheme:

a control method for a variable turbocharger for a gasoline engine, comprising the steps of:

1) Determining a boost pressure control deviation from the turbocharger boost pressure and a boost pressure target value;

2) Outputting an actuator position control signal from the boost pressure control offset;

3) Determining a VGT flow set value and an exhaust pressure set value from the boost pressure target value and the intake air flow;

4) Determining a preset position value of a VGT actuator according to a VGT flow set value and an exhaust pressure set value;

5) Determining an actuator position target value according to the actuator position control signal and the VGT actuator position preset value; and

6) And adjusting the opening of the VGT nozzle ring by the VGT actuator according to the actuator position target value.

In the above control method for a variable turbocharger, optionally, the boost pressure target value is determined by a manifold pressure preset value.

In the control method for a variable turbocharger described above, optionally, in step 2), the actuator position control signal is generated by a boost pressure PID controller.

In the above-described control method for a variable turbocharger, optionally, in step 3), the VGT flow set value and the exhaust pressure set value are generated by a turbocharger model.

In the above control method for a variable turbocharger, optionally, in step 4), the VGT actuator position preset value is generated by a VGT nozzle ring opening model.

In the above control method for a variable turbocharger, optionally, the VGT actuator includes a position sensor to sense the opening degree of the nozzle ring of the VGT, so that the opening degree adjustment is performed by closed-loop control.

In the control method for a variable turbocharger described above, optionally, the variable turbocharger includes a variable nozzle ring mechanism made of a material capable of withstanding a temperature of at least 950 degrees celsius.

In the above control method for a variable turbocharger, optionally, the VGT nozzle ring opening degree includes a first region, a second region, a third region, and a fourth region determined according to the engine speed and the engine torque.

In the control method for a variable turbocharger described above, optionally, in the first region, the nozzle ring opening of the VGT is 100%; in the second area, the opening of the VGT nozzle ring is 30-60%; in the third area, the opening degree of the VGT nozzle ring is 20 percent; and in the fourth area, the opening degree of the nozzle ring of the VGT is 70-80%.

In the above control method for a variable turbocharger, optionally, the first region covers an entire range of the engine speed and a low torque range of the engine torque; the third region covers a low speed range of the engine speed and a high torque range of the engine torque; the fourth region covers a high speed range of the engine speed and a high torque range of the engine torque; the second region covers other operating ranges of engine speed and engine torque.

The control method for the variable turbocharger has the advantages of simplicity, reliability, easiness in implementation and the like, and can be applied to a gasoline engine and improve the operation efficiency of the gasoline engine.

Drawings

The present application will now be described in further detail with reference to the accompanying drawings and preferred embodiments. Those skilled in the art will appreciate that the drawings are designed solely for the purposes of illustrating preferred embodiments and that, accordingly, should not be taken as limiting the scope of the present application. Furthermore, unless specifically indicated, the drawings are intended to show the composition or construction of the objects only. The drawings may contain exaggerated displays and are not fully to scale.

FIG. 1 is a system schematic of a variable turbocharger for a gasoline engine.

Fig. 2 is a schematic view of the structure of the electronic actuator in the embodiment shown in fig. 1.

Fig. 3 is a schematic diagram of the working range of the embodiment shown in fig. 2.

FIG. 4 is a schematic diagram of the use strategy of the embodiment shown in FIG. 1.

Fig. 5 is a schematic diagram of the closed loop control logic of the embodiment shown in fig. 2.

Detailed Description

Hereinafter, preferred embodiments of the present application will be described in detail with reference to the accompanying drawings. Those skilled in the art will appreciate that these descriptions are merely illustrative, exemplary, and should not be construed as limiting the scope of the application.

It is noted that the terms top, bottom, upwardly, downwardly and the like are defined herein with respect to the drawings. Directions and orientations are relative concepts and can vary according to different locations and different states of use. These and other orientation or direction terms should not be construed as limiting.

Furthermore, it should be pointed out that for any single technical feature described or implied in the embodiments or any single technical feature shown or implied in the figures, it is still possible to combine these technical features (or their equivalents) to obtain other embodiments not directly mentioned herein.

It should be noted that in different drawings, the same reference numerals denote the same or substantially the same components.

FIG. 1 is a system schematic of a variable turbocharger for a gasoline engine. In the illustrated embodiment, solid arrows a represent fresh air or outside air drawn into the gasoline engine system, and dotted arrows B represent exhaust gas or high-temperature exhaust gas discharged after combustion of the gasoline engine. As shown, the outside air a first enters through the intake system or intake 100, passing through the compressor 121 of the turbocharger 120, the intercooler 130, the throttle 140, the manifold 150, the gasoline engine block 160, the turbine 122 of the turbocharger 120, and the catalyst 170 in that order.

Specifically, the outside air a is compressed by the compressor wheel 121 in the turbocharger 120, and the compressor wheel 121 is driven by the turbine wheel 122, and the turbine wheel 122 is driven by the exhaust gas B. For the sake of clarity, the general structure of the turbocharger 120 is only schematically shown in fig. 1. Other structures not specifically shown will be known to those skilled in the art from a knowledge of the turbocharger structure. In one embodiment of the present application, the turbocharger 120 is a variable turbocharger, with a variable nozzle ring mechanism and electronic actuators not specifically shown. A variable nozzle ring mechanism may be provided before the inlet of the turbine 122 to adjust the flow rate and velocity of the exhaust gas B used to drive the turbine 122.

Further, the variable geometry turbocharger is provided with a turbine housing, an intermediate housing, a pressure housing, and the like. In one embodiment of the present application, the turbine housing is made of stainless steel, the intermediate housing is made of gray cast iron, and the pressure housing is made of cast aluminum alloy. The variable nozzle ring mechanism and the turbine housing may be made of materials capable of withstanding operating temperatures of at least 950 degrees celsius in order to withstand the high temperatures and pressures that may be carried by the exhaust gas B of the gasoline engine 130.

According to an embodiment of the present application, a boost pressure sensor 101 is provided between intercooler 130 and throttle valve 140, and a manifold pressure sensor 102 is provided in manifold 150. These sensors are configured to sense the pressure of gas a on the line and provide the pressure data to a vehicle control unit, engine control module, or other control device for the desired use.

Fig. 2 is a schematic structural diagram of an electronic actuator in the embodiment shown in fig. 1. The electronic actuator 200 includes a motor 210, a VGT actuator position sensor 220, and a PCB 230. The motor 210 is connected to a power source, not shown, through a motor positive connection 211 and a motor negative connection 212 so as to obtain power supply. The motor 210 also adjusts the position of the VGT actuator, that is, the opening degree of the variable nozzle ring mechanism, through the output shaft 213. The VGT actuator position sensor 220 may be disposed on the PCB 230 and configured to sense a state of the output shaft 213, thereby indirectly sensing a position of the VGT actuator and an opening degree of the variable nozzle ring mechanism. The result of the VGT actuator position sensor 220 is output by an output voltage 221 and optionally provided to a vehicle control unit, engine control module, or other control device. Further, the PCB board 230 is also electrically attached to a power supply 231 and a ground line 232 in order to provide power supply and safe operation capability. In one embodiment of the present application, the motor 210 may be a direct current motor. In another embodiment of the present application, the electronic actuator 200 further comprises a housing.

Fig. 3 is a schematic diagram of the operating range of the embodiment shown in fig. 2. The abscissa in fig. 3 represents the opening degree of the variable nozzle ring mechanism of the VGT, and the ordinate represents the output voltage of the VGT actuator position sensor 220. On the vertical axis, 5% of the maximum value of the output voltage of the VGT actuator position sensor 220 corresponds to the mechanical down-stop, 95% of the maximum value corresponds to the mechanical up-stop, 20% of the maximum value corresponds to the calibrated down-stop, and 80% of the maximum value corresponds to the calibrated up-stop. The lower calibration endpoint and the upper calibration endpoint correspond to the minimum flow opening and the maximum flow opening of the VGT actuator on the horizontal axis respectively. The actual VGT actuator operating range is in the 60% interval between the upper nominal and lower nominal downtimes. The region between the mechanical top dead center and the calibration top dead center and between the mechanical lower extreme point and the calibration lower extreme point is a reserved interval and is used for accommodating an error range caused by mechanical abrasion.

FIG. 4 is a schematic diagram of the use strategy of the embodiment shown in FIG. 1. The strategy for using the VGT actuator at different values of gasoline engine speed and gasoline engine output torque is shown in fig. 4 by way of example. The rotational speed of the gasoline engine is expressed in rpm, and the output torque of the gasoline engine is expressed in nm. The values of gasoline engine speed and gasoline engine output torque illustrated are exemplary only and may have different values for different models of engines. However, the strategy shown in FIG. 4 may be varied depending on the specific circumstances of different engines, and such variations are readily made by those skilled in the art in light of the teachings herein.

It is readily understood that there is an approximate upper limit between the rotational speed and the output torque of the gasoline engine, i.e., the boundary line at the top of

regions

2, 3 and 4 in fig. 4. Below this boundary line, it is possible for the gasoline engine to operate at different speeds and matching torques, thereby accommodating different disclosures.

The nozzle ring opening degree of the VGT or the opening degree of the variable nozzle ring mechanism includes a first region 1, a second region 2, a third region 3, and a fourth region 4 determined according to the engine speed and the engine torque. In the first area, the opening degree of the nozzle ring of the VGT is 100 percent; in the second area, the opening of the VGT nozzle ring is 30-60%; in the third area, the opening degree of the VGT nozzle ring is 20 percent; and in the fourth area, the opening degree of the nozzle ring of the VGT is 70-80%. The first region 1 is intended to cover the entire range of engine speeds and the low torque range of engine torques. For example, in the illustrated embodiment, the first region includes a range of torque substantially below 80Nm and rotational speeds in the range of 1000 to 6000 rpm. Providing 100% opening at the first region is advantageous for reducing pumping losses and enables exhaust energy to reach the catalyst quickly at cold start for light-off. The third region 3 covers a low speed range of the engine speed and a high torque range of the engine torque. For example, the third zone 3 includes a zone having a rotational speed of about 1200-2200rpm and a torque in the range of 120-175 Nm. The third zone 3 is located below the borderline and above the second zone 2. Providing a smaller opening in the third region 3 is advantageous for meeting performance requirements. The fourth region 4 covers a high speed range of the engine speed and a high torque range of the engine torque. For example, the fourth region includes a region where the rotational speed is approximately 3500 to 6000rpm and the torque is in the range of 130 to 175 Nm. The fourth zone 4 is located below the borderline and above the second zone 2. Providing a medium degree of opening in the fourth region 4 is advantageous for meeting the power demand. The second region 2 covers other operating ranges of engine speed and engine torque. The second region 2 includes a range surrounded by the boundary line, the first region 1, the third region 3, and the fourth region 4. The use of the intermediate opening degree in the second region 2 is advantageous in that the variable turbocharger can be operated at a higher efficiency in a wide intermediate load region.

It should be appreciated that the terms "low speed," "high speed," "low torque," and "high torque" as referred to herein may have different values for particular operating conditions of a particular engine. Those skilled in the art will readily be able to determine specific values for different engines based on actual engine specifications and operating conditions. This application is intended to cover such modifications and variations.

Fig. 5 is a schematic diagram of the closed loop control logic of the embodiment shown in fig. 2. The entire variable turbocharger control apparatus includes the actuator 100 and the controller 300. The actuator 100 includes a VGT actuator or motor 210, a VGT actuator position sensor 220, a VGT nozzle ring or variable nozzle ring mechanism 123, a turbocharger 120, a boost pressure sensor 101, and the like, as described above. The relationship between the boost pressure sensor 101 and the turbocharger 120 is realized by intake air or outside air a.

Controller 300 is configured to obtain a manifold pressure preset value input 301 and an intake air flow input 302, and may also obtain other parameters or data related to vehicle and engine operation from a vehicle control unit, engine control module, or other control device. In the illustrated embodiment, the controller 300 includes: a boost pressure target value calculation module 310, a boost pressure control deviation calculation module 311, a boost pressure PID controller 312, a turbocharger model calculation module 320, a VGT nozzle ring opening model calculation module 330, an actuator position target calculation module 313, a VGT actuator PID controller 340, and the like.

The boost pressure target value calculation module 310 is configured to calculate a boost pressure target value based on the manifold pressure preset value input 301 and provide the boost pressure target value to the boost pressure control deviation calculation module 311 and the turbocharger model calculation module 320.

The boost pressure control deviation calculation module 311 is configured to calculate a boost pressure control deviation from the boost pressure target value and the actual boost pressure sensed from the boost pressure sensor 101 and provide the boost pressure control deviation to the boost pressure PID controller 312. In one embodiment of the present application, the boost pressure control deviation may be obtained by subtracting the actual boost pressure from the boost pressure target value.

Boost pressure PID controller 312 is configured to calculate an actuator position control signal based on the boost pressure control deviation and provide the actuator position control signal to actuator position target calculation module 313. During the calculation, the boost pressure PID controller 312 may appropriately employ PID control, thereby improving stability and continuity of the control result.

The turbocharger model calculation module 320 includes a mathematical model for a turbocharger, and calculates a VGT flow set value and an exhaust pressure set value from a boost pressure target value and an intake air flow rate, and then supplies the VGT flow set value and the exhaust pressure set value to the VGT nozzle ring opening model calculation module 330.

The VGT nozzle ring opening model calculation module 330 calculates an actuator position preset based on the VGT flow set value and the exhaust pressure set value and provides the actuator position preset to the actuator position target calculation module 313.

The actuator position target calculation module 313 calculates an actuator position target value based on the actuator position control signal and the actuator position preset value and provides the actuator position target value to the VGT actuator PID controller 340. In one embodiment of the subject application, the actuator position target calculation module 313 calculates the actuator position target value by adding the actuator position control signal and the actuator position preset value.

The VGT actuator PID controller 340 sends a control signal to the motor 210 and also performs closed loop control by the position of the VGT actuator sensed by the VGT actuator position sensor 220. In the calculation and control process, the VGT actuator PID controller 340 may appropriately employ PID control, thereby improving stability and continuity of the control result.

The motor 210 adjusts the VGT nozzle ring or variable nozzle ring mechanism 123 to vary the VGT flow and exhaust pressure of the turbocharger 120, thereby affecting the boost pressure of the intake air or ambient air a, the change in boost pressure being sensed by the boost pressure sensor 101 and provided to the controller 300.

To summarize, the above provides a control method for a variable turbocharger, optionally for a gasoline engine, comprising the steps of:

1) Determining a boost pressure control deviation from a turbocharger boost pressure and a boost pressure target value, wherein the boost pressure target value may be determined from a manifold pressure preset value;

2) Outputting an actuator position control signal from the boost pressure control offset, wherein the actuator position control signal may be generated by a boost pressure PID controller;

3) Determining a VGT flow set value and an exhaust pressure set value from the boost pressure target value and the intake air flow, wherein the VGT flow set value and the exhaust pressure set value may be generated by a turbocharger model;

4) Determining a VGT actuator position preset value from the VGT flow set value and the exhaust pressure set value, wherein the VGT actuator position preset value can be generated by a VGT nozzle ring opening model;

6) The opening degree of the VGT nozzle ring is adjusted by the VGT actuator according to the actuator position target value, wherein the VGT actuator can comprise a position sensor for sensing the opening degree of the VGT nozzle ring, so that the opening degree adjustment is carried out through closed-loop control.

In the above embodiments, each module may be implemented by a separate device, or the functions of two or more modules may be implemented by a single device.

By adopting the control method for the variable turbocharger disclosed by the application, the variable turbocharger can be installed, controlled and used on the gasoline engine, so that the combustion and running efficiency of the gasoline engine is improved, and the energy consumption ratio and the user experience of a vehicle are effectively improved.

The present specification discloses the present application with reference to the accompanying drawings. One skilled in the art will be able to practice the present application, including making and using any devices or systems, selecting appropriate materials, and using any combination of methods. The scope of the present application is defined by the claims and encompasses other examples that occur to those skilled in the art. Such other examples should be considered within the scope defined by the claims, as long as they include structural elements that do not differ from the literal language of the claims, or equivalent structural elements.

Claims

1. A control method for a variable turbocharger for a gasoline engine, characterized by comprising the steps of:

3) Determining a VGT flow set value and an exhaust pressure set value from the boost pressure target value and intake air flow rate;

4) Determining a VGT actuator position preset value from the VGT flow set value and the exhaust pressure set value;

5) Determining an actuator position target value from the actuator position control signal and the VGT actuator position preset value; and

6) And adjusting the opening of the VGT nozzle ring by a VGT actuator according to the actuator position target value.

2. The control method for a variable turbocharger according to claim 1, wherein the boost pressure target value is determined by a manifold pressure preset value.

3. The control method for a variable turbocharger according to claim 1, characterized in that in step 2), the actuator position control signal is generated by a boost pressure PID controller.

4. The control method for a variable turbocharger according to claim 1, wherein in step 3), the VGT flow set value and the exhaust pressure set value are generated by a turbocharger model.

5. The control method for a variable turbocharger according to claim 1, wherein in step 4), the VGT actuator position preset value is generated by a VGT nozzle ring opening model.

6. The control method for a variable turbocharger of claim 1, wherein the VGT actuator comprises a position sensor to sense an opening of a nozzle ring of the VGT, whereby the opening adjustment is made by closed-loop control.

7. The control method for a variable turbocharger according to claim 1, characterized in that the variable turbocharger includes a variable nozzle ring mechanism made of a material capable of withstanding a temperature of at least 950 degrees celsius.

8. The control method for a variable turbocharger according to claim 1, wherein the VGT nozzle ring opening comprises a first region, a second region, a third region, and a fourth region determined according to an engine speed and an engine torque.

9. The control method for a variable turbocharger according to claim 8, wherein in the first region, the VGT nozzle ring opening is 100%; in the second area, the opening degree of the VGT nozzle ring is 30% -60%; in the third area, the opening degree of the VGT nozzle ring is 20%; and in the fourth area, the opening degree of the VGT nozzle ring is 70-80%.

10. The control method for a variable turbocharger according to claim 9, characterized in that the first region covers an entire range of engine rotational speed and a low torque range of engine torque; the third region covers a low speed range of engine speed and a high torque range of engine torque; the fourth region covers a high speed range of engine speed and a high torque range of engine torque; the second region covers other operating ranges of engine speed and engine torque.