Control device for internal combustion engines

Abstract

To provide a control device of an internal combustion engine capable of improving the followability of supercharging pressure.SOLUTION: A control device of an internal combustion engine includes an acquisition part for acquiring the number of rotations of a supercharger, and a supercharging pressure control part for controlling supercharging pressure of the supercharger on the basis of the number of rotations.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a control device for an internal combustion engine.

Background Art

[0002] A supercharger for supercharging the air introduced into an internal combustion engine is known (for example, Patent Document 1, etc.).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The supercharging pressure is controlled by adjusting the opening degree of a wastegate valve (WGV) and controlling the flow rate of exhaust gas to the turbine of the supercharger. However, the followability of the actual supercharging pressure with respect to the target value of the supercharging pressure may be poor. Therefore, an object is to provide a control device for an internal combustion engine capable of improving the followability of the supercharging pressure.

Means for Solving the Problems

[0005] The above object can be achieved by a control device for an internal combustion engine including an acquisition unit that acquires the rotational speed of a supercharger, and a supercharging pressure control unit that controls the supercharging pressure of the supercharger based on the rotational speed.

[0006] The supercharging pressure control unit may control the supercharging pressure so that the difference between the rotational speed and the target value of the rotational speed becomes small.

[0007] The exhaust passage is provided with a turbine and a valve for the supercharger. The smaller the opening of the valve, the more exhaust gas is introduced into the turbine and the higher the boost pressure. The larger the opening of the valve, the less exhaust gas is introduced into the turbine and the lower the boost pressure. The boost pressure control unit may control the boost pressure by controlling the opening of the valve based on the rotational speed.

[0008] The boost pressure control unit may set a first amount based on the target value of the boost pressure, set a second amount based on the rotational speed, and control the opening degree of the valve based on the first amount and the second amount. [Effects of the Invention]

[0009] This invention provides a control device for internal combustion engines that can improve the responsiveness of boost pressure. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram illustrating an engine system according to an embodiment. [Figure 2] Figure 2 is a flowchart illustrating the processes performed by the ECU. [Figure 3] Figure 3 is an example of a time chart. [Modes for carrying out the invention]

[0011] The control device for the internal combustion engine of this embodiment will now be described with reference to the drawings. Figure 1 is a schematic diagram illustrating an engine system 100 according to the embodiment. The engine system 100 includes an internal combustion engine 10, a supercharger 20, and an ECU (Electronic Control Unit) 40.

[0012] The internal combustion engine 10 is a gasoline engine or a diesel engine, etc., which burns fuel to generate power. The internal combustion engine 10 is connected to an intake passage 12 and an exhaust passage 14. The supercharger 20 has a shaft 21, a compressor 22, and a turbine 24. The compressor 22 and the turbine 24 are connected by the shaft 21.

[0013] The intake passage 12 is equipped with, in order from upstream, an airflow meter 30, a compressor 22, a pressure sensor 33, and a throttle valve 32. A bypass passage 16 is connected to the intake passage 12. The bypass passage 16 is a passage that bypasses the compressor 22. The bypass passage 16 connects a position in the intake passage 12 upstream of the compressor 22 to a position downstream of the compressor 22 and upstream of the pressure sensor 33. An air bypass valve 36 is provided in the bypass passage 16. A rotational speed sensor 34 is provided near the compressor 22.

[0014] A turbine 24 is provided in the exhaust passage 14. A bypass passage 18 is connected to the exhaust passage 14. The bypass passage 18 is a passage that bypasses the turbine 24 and connects a position upstream of the turbine 24 to a position downstream of the turbine 24 in the exhaust passage 14. A wastegate valve (WGV) 38 is provided in the bypass passage 18. The air bypass valve 36 and WGV 38 are, for example, solenoid valves and are controlled by electrical signals.

[0015] The airflow meter 30 detects the airflow rate in the intake passage 12. The throttle valve 32 adjusts the airflow rate. When the throttle valve 32 is opened, the airflow rate increases. When it is opened, the airflow rate decreases. The pressure sensor 33 detects the pressure downstream of the compressor 22 in the intake passage 12. When the supercharger 20 is driven, the pressure sensor 33 detects the pressure of the supercharged air (supercharge pressure). The accelerator pedal position sensor 31 detects the accelerator pedal position. When the occupant presses down on the accelerator pedal (not shown), the accelerator pedal position increases.

[0016] Air flows through the intake passage 12 and is introduced into the internal combustion engine 10. The air forms a fuel-air mixture in the combustion chamber of the internal combustion engine 10. Power is generated when this mixture burns. The exhaust gas generated by the combustion flows through the exhaust passage 14 and is discharged.

[0017] The exhaust gas blows onto the turbine 24, causing it to rotate. The compressor 22 is connected to the turbine 24 and therefore rotates together with it. As the compressor 22 rotates, air is supercharged. When the supercharged air is introduced into the internal combustion engine 10, the output of the internal combustion engine 10 increases. The rotation speed sensor 34 detects the rotation speed of the compressor 22 (the rotation speed of the supercharger 20, the turbo rotation speed).

[0018] A portion of the air bypasses from the downstream side to the upstream side of the compressor 22 and flows through the bypass passage 16. The larger the opening of the air bypass valve 36, the greater the airflow rate in the bypass passage 16. The amount of air supercharged by the compressor 22 decreases. The smaller the opening, the greater the airflow rate in the bypass passage 16. The amount of air supercharged increases.

[0019] A portion of the exhaust is bypassed from the upstream to the downstream side of the turbine 24 and flows through the bypass passage 18. The smaller the opening of WGV38, the lower the flow rate of exhaust in the bypass passage 18 and the higher the flow rate of exhaust introduced to the turbine 24. As the amount of exhaust blown onto the turbine 24 increases, the rotational speed of the supercharger 20 increases and the boost pressure rises. The larger the opening of WGV38, the higher the flow rate of exhaust in the bypass passage 18 and the lower the flow rate of exhaust introduced to the turbine 24. The rotational speed of the supercharger 20 decreases and the boost pressure decreases.

[0020] The ECU40 is a control unit equipped with a CPU (Central Processing Unit) and other arithmetic units, as well as memory devices such as RAM (Random Access Memory) and ROM (Read Only Memory). The ECU40 performs various control functions by executing programs stored in the ROM and other memory devices.

[0021] The ECU 40 acquires the air flow rate detected by the air flow meter 30 and detects the pressure detected by the pressure sensor 33. The ECU 40 acquires the accelerator opening detected by the accelerator opening sensor 31. The ECU 40 functions as an acquisition unit that acquires the rotational speed of the supercharger 20 detected by the rotational speed sensor 34. The ECU 40 acquires the target value (target rotational speed) of the rotational speed of the supercharger 20 and stores the target value. The ECU 40 controls the opening degree of the throttle valve 32 and the opening degree of the air bypass valve 36. The ECU 40 functions as a supercharging pressure control unit that controls the supercharging pressure by controlling the opening degree of the WGV 38.

[0022] The ECU 40 controls the opening degree of the WGV 38 using a control amount (first amount) and a compensation amount (second amount). The control amount is, for example, the duty ratio of voltage or current. The greater the control amount, the greater the force to reduce the opening degree of the WGV 38. The smaller the control amount, the greater the force to increase the opening degree of the WGV 38. The compensation amount is an amount for correcting the control amount. When the compensation amount is large, the force to reduce the opening degree increases. When the compensation amount is small, the force to increase the opening degree increases. The ECU 40 determines the compensation amount based on, for example, the difference between the rotational speed and the target rotational speed. When reducing the opening degree of the WGV 38, the control amount and the compensation amount are increased. When increasing the opening degree, the control amount and the compensation amount are decreased.

[0023] FIG. 2 is a flowchart illustrating the process executed by the ECU 40. The ECU 40 sets a target air amount and a target supercharging pressure based on the accelerator opening and the like (step S10). The target air amount is the target value of the air flow rate in the intake passage 12. The target supercharging pressure is the target value of the pressure of the air supercharged by the supercharger 20.

[0024] The ECU 40 sets a target rotational speed based on the target air amount and the like (step S12). The target rotational speed is the target value for the rotational speed of the supercharger 20. When the rotational speed reaches the target rotational speed, the supercharging pressure reaches the target supercharging pressure. The ECU 40 acquires the supercharging pressure from the pressure sensor 33 (step S14).

[0025] The ECU40 sets the control amount based on the boost pressure, target rotational speed, and target air volume (step S16). The ECU40 calculates the control amount, for example, by PD control. That is, the ECU40 sets the control amount based on a polynomial that includes the boost pressure, target boost pressure, target air volume, and the value obtained by differentiating these. The ECU40 obtains the rotational speed from the rotational speed sensor 34 (step S18). The ECU40 sets the compensation amount based on the rotational speed and target rotational speed (step S20). The ECU40 sets the opening degree of the WGV38 based on the control amount and compensation amount (step S22). The ECU40 controls the WGV38 so that the set opening degree is achieved (step S24). This completes the process shown in Figure 2.

[0026] Figure 3 is an example of a time chart. From top to bottom, it shows the rotational speed of the supercharger 20, the boost pressure, the compensation amount for the WGV38 opening, the control amount for the WGV38, and the opening of the WGV38. The horizontal axis represents time. Figure 3 shows an example where the accelerator opening is increasing.

[0027] In Figure 3, the solid lines represent embodiments, and the dotted lines represent comparative examples. In the embodiments, the opening of WGV38 is controlled based on the rotational speed, as explained in Figure 2. In the comparative examples, the opening is controlled based on the boost pressure. R0 is the target rotational speed, and P0 is the target boost pressure. At time t1, the target rotational speed R0 and target boost pressure P0 increase, and then remain constant from time t2 onward.

[0028] In the comparative example, control is performed to make the boost pressure follow the target boost pressure P0. The opening degree of WGV38 is controlled based on the boost pressure. No compensation is used. The control amount and the opening degree of WGV38 change as shown by the dotted line. Around time t1, the opening degree of WGV38 decreases. As the opening degree decreases, the amount of exhaust introduced to the turbine 24 increases, and the boost pressure increases. The boost pressure rises in line with the target boost pressure P0, but it significantly exceeds the target boost pressure P0 (overshoot). As the opening degree of WGV38 increases, the amount of exhaust bypassing the turbine 24 increases. The boost pressure decreases. After time t4, the boost pressure falls below the target boost pressure P0 (undershoot). In the comparative example, the boost pressure tracking performance is poor. The rotational speed also tracks the target rotational speed R0 poorly.

[0029] In this embodiment, control is performed to make the rotational speed follow the target rotational speed R0. In other words, control is performed to reduce the difference between the rotational speed and the target rotational speed R0. The controlled amount and the opening of WGV38 change as shown by the solid line. Around time t1, the controlled amount increases and the opening of WGV38 decreases. As the opening decreases, the amount of exhaust gas introduced into the turbine 24 increases, and the rotational speed and boost pressure increase. The rotational speed increases in accordance with the target rotational speed R0. The boost pressure increases in accordance with the target boost pressure P0.

[0030] At time t3, the rotational speed increases to a value equal to the target rotational speed R0. The compensation amount is set to a value smaller than X0. The controlled amount is corrected by the compensation amount and becomes smaller than that of the comparative example. As the controlled amount decreases, the opening of WGV38 becomes larger than that of the comparative example. As the opening becomes larger, the amount of exhaust introduced into turbine 24 decreases, resulting in lower rotational speed and boost pressure. Overshoot of rotational speed is suppressed, and it approaches the target rotational speed R0.

[0031] At time t4, the rotational speed decreases to the target rotational speed R0. The compensation amount is set to a value greater than X0. The control amount increases, and the opening angle decreases. As the opening angle decreases, the amount of exhaust gas introduced to the turbine 24 increases, resulting in increased rotational speed and boost pressure. Rotational speed undershoot is suppressed, and the speed approaches the target rotational speed R0. Boost pressure overshoot and undershoot are also suppressed, and the boost pressure approaches the target boost pressure P0. The responsiveness of rotational speed and boost pressure is improved.

[0032] According to this embodiment, the ECU 40 controls the boost pressure based on the rotational speed of the supercharger 20. Compared to control based on boost pressure, control based on rotational speed improves the responsiveness of the boost pressure.

[0033] The ECU 40 determines the target rotational speed of the supercharger 20 and acquires the rotational speed (steps S12 and S18 in Figure 2). The ECU 40 controls the engine to minimize the difference between the current rotational speed and the target rotational speed R0, causing the rotational speed to follow the target rotational speed R0. By making the rotational speed follow the target rotational speed R0, the boost pressure also follows the target boost pressure P0. This improves the responsiveness of the boost pressure.

[0034] By suppressing engine speed overshoot and undershoot, boost pressure overshoot and undershoot are also suppressed. For example, during acceleration, the boost pressure rises to the target boost pressure P0 and maintains a position near P0. Since there is no need to limit the slope (rate of change) of the boost pressure, smooth acceleration is possible.

[0035] The ECU40 controls the boost pressure by controlling the opening of the WGV38 based on the rotational speed of the supercharger 20. A smaller opening increases the amount of exhaust introduced to the turbine 24, and thus the boost pressure rises. A larger opening decreases the amount of exhaust introduced to the turbine 24, and thus the boost pressure falls. By adjusting the opening based on the rotational speed, the responsiveness of the boost pressure is improved.

[0036] The ECU40 sets the control amount and compensation amount (steps S16 and S20). The control amount is determined based on the target boost pressure and target air volume. The compensation amount is determined based on the engine speed and target engine speed. The opening degree of the WGV38 is controlled based on the control amount and compensation amount. The control amount is corrected by the compensation amount. Based on the corrected control amount, the ECU40 controls the opening degree of the WGV38 (step S24). Since the compensation amount is determined based on the engine speed, the opening degree changes according to the engine speed. This improves the responsiveness of the boost pressure.

[0037] The ECU40 sets the control variable based on, for example, the boost pressure, target boost pressure, target air volume, and a value obtained by differentiating any of these. The boost pressure, target boost pressure, and target air volume may be multiplied by coefficients. In other words, the control variable is determined by PD control. In addition to PD control, the ECU40 may also set the control variable by performing PI control and PID control.

[0038] The ECU40 sets the compensation amount based on the difference between the current rotational speed and the target rotational speed R0. The larger the absolute value of the difference, the larger the absolute value of the compensation amount. The smaller the absolute value of the difference, the smaller the absolute value of the compensation amount. If the rotational speed is greater than the target rotational speed R0, the compensation amount is set so that the opening angle increases. If the rotational speed is less than the target rotational speed R0, the compensation amount is set so that the opening angle decreases. The compensation amount may also be set based on, for example, the change in rotational speed. If the absolute value of the change in rotational speed over time is greater than or equal to a certain value, the ECU40 sets the compensation amount. If the change is a positive value, the rotational speed is increasing. The compensation amount is set so that the opening angle increases. If the change is a negative value, the rotational speed is decreasing. The compensation amount is set so that the opening angle decreases.

[0039] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the invention as described in the claims. [Explanation of symbols]

[0040] 10 Internal combustion engine, 12 Intake passage, 14 Exhaust passage, 16, 18 Bypass passage, 20 Supercharger, 21 Shaft, 22 Compressor, 24 Turbine, 30 Airflow meter, 31 Accelerator position sensor, 32 Throttle valve, 33 Pressure sensor, 34 RPM sensor, 36 Air bypass valve, 38 Wastegate valve, 40 ECU, 100 Engine system

Claims

1. An acquisition unit that acquires the rotational speed of the supercharger, The system comprises a boost pressure control unit that controls the boost pressure of the supercharger based on the rotational speed, The supercharger has a compressor and a turbine connected to each other. The compressor supercharges the air introduced into the internal combustion engine. The turbine and valve of the supercharger are provided in the exhaust passage. The smaller the opening of the valve, the more exhaust gas is introduced into the turbine, and the higher the boost pressure. The larger the opening of the valve, the less exhaust gas is introduced into the turbine, and the lower the boost pressure. The acquisition unit acquires the rotational speed of the compressor. The supercharger pressure control unit controls the supercharger pressure by controlling the valve opening degree so that the difference between the rotational speed acquired by the acquisition unit and the target value of the rotational speed becomes small. The supercharge pressure control unit is a control device for an internal combustion engine that sets a first amount based on a target value of the supercharge pressure, sets a second amount based on the rotational speed, and controls the opening degree of the valve based on the first amount and the second amount.

2. The control device for an internal combustion engine according to claim 1, wherein the supercharger pressure control unit controls the supercharger pressure so that the difference between the rotational speed and the target value of the rotational speed becomes small.

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