JP2016050567A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine capable of suppressing the occurrence of surge in a turbocompressor without providing a swirler in an intake passage.SOLUTION: An internal combustion engine comprises: a turbocharger which has a turbine 11 provided in an exhaust passage 14 and has a turbocompressor 3 driven by the turbine 11 to turbocharge intake air and provided in an intake passage 13; a centrifugal electric compressor 1 which includes an impeller disposed upstream of the turbocompressor 3 in the intake passage 13 and an electric motor 16 driving the impeller, and which turbocharges the intake air by causing the electric motor 16 to drive the impeller so that a rotation direction of the impeller in a view from an impeller intake air inflow direction is identical to a rotation direction of the turbocompressor 3; a bypass passage 15 communicating the intake passage 13 upstream of the electric compressor 1 with the intake passage between the electric compressor and the turbocompressor; and a control unit, and the control unit controls the electric compressor 1 to be driven when it is predicted that surge occurs to the turbocompressor 3.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an internal combustion engine.

  2. Description of the Related Art Conventionally, there is known an internal combustion engine including a turbocharger that uses exhaust gas to rotate a turbo compressor provided in an intake passage to compress intake air. For example, Patent Document 1 discloses an internal combustion engine in which swirl vanes are installed in an intake passage upstream of a turbo compressor. By installing swirl vanes, swirl flow can be generated in the intake air introduced into the turbo compressor. Thereby, the angle of attack with respect to the intake air of the impeller of the turbo compressor can be reduced. As a result, the occurrence of surge in the turbo compressor can be suppressed.

JP 2010-090806 A JP 2010-185314 A Japanese Patent Laying-Open No. 2005-201092 JP 2008-0775549 A

  However, if the above-described swirl vanes are provided in the intake passage, the cost of parts increases. Furthermore, the swirl vane has an intake resistance in an operation region where no surge occurs. For this reason, pressure loss in the intake passage may increase, and fuel consumption may be reduced.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an internal combustion engine that can suppress occurrence of a surge in a turbo compressor without providing swirl vanes in an intake passage. .

In order to achieve the above object, a first invention is an internal combustion engine,
A turbocharger having a turbine that operates by exhaust energy of an internal combustion engine in an exhaust passage, and a turbo compressor that is driven by the turbine and that supercharges intake air in the intake passage;
An impeller disposed in the intake passage upstream of the turbo compressor, and an electric motor that drives the impeller, wherein the rotation direction of the impeller as viewed from the direction of intake air flow into the impeller is the rotation direction of the turbo compressor A centrifugal electric compressor that supercharges intake air by driving the impeller by the electric motor to be the same;
A bypass passage communicating the intake passage upstream of the electric compressor and the intake passage between the electric compressor and the turbo compressor;
A bypass valve provided in the bypass passage for opening and closing the bypass passage;
A control device for controlling the electric compressor and the bypass valve;
The controller is
When the bypass valve is fully open and when it is predicted that a surge will occur in the turbo compressor when the electric compressor is stopped, the electric compressor is driven.

A second invention is an internal combustion engine for achieving the above object,
A turbocharger having a turbine that operates by exhaust energy of an internal combustion engine in an exhaust passage, and a turbo compressor that is driven by the turbine and that supercharges intake air in the intake passage;
An impeller disposed in the intake passage upstream of the turbo compressor; and an electric motor that drives the impeller. A centrifugal electric compressor that supercharges intake air by driving the impeller by the electric motor to be the same;
A bypass passage communicating the intake passage upstream of the electric compressor and the intake passage between the electric compressor and the turbo compressor;
A bypass valve provided in the bypass passage for opening and closing the bypass passage;
A control device for controlling the electric compressor and the bypass valve;
The controller is
When it is predicted that a surge will occur in the turbo compressor when the bypass valve is fully open and the electric compressor is stopped, the electric compressor is idled by intake air and the opening of the bypass valve is reduced. It is characterized by.

  According to the present invention, in the operation region where no surge is generated, the intake air having the swirl flow in the same rotation direction as that of the turbo compressor can be flowed into the turbo compressor without providing the swirl vanes that serve as the intake air resistance. For this reason, the angle of attack with respect to the intake of the impeller of the turbo compressor can be reduced. As a result, the occurrence of surge in the turbo compressor can be suppressed.

1 is a diagram illustrating a configuration of a system according to a first embodiment. It is a figure explaining the flow of the intake air in an electric compressor. It is sectional drawing of an electric compressor. It is a figure showing a mode that the intake air compressed by the electric compressor is supplied to a turbo compressor. It is a figure for demonstrating how intake air hits the impeller of the rotating turbo compressor. 3 is a flowchart showing a routine representing specific contents of surge suppression control according to the first embodiment. 6 is a flowchart showing a routine representing specific contents of surge suppression control according to the second embodiment.

Embodiment 1 FIG.
[System configuration]
FIG. 1 is a diagram showing the configuration of the system according to the first embodiment. FIG. 1 shows an engine body 8. An intake manifold 7 and an exhaust manifold 9 are attached to the engine body 8. An intake passage 13 is connected to the intake manifold 7. An exhaust passage 14 is connected to the exhaust manifold 9.

  In the intake passage 13, an electric compressor 1, a turbo compressor 3, and an intercooler 4 are provided in order from the upstream. The turbo compressor 3 is a device that constitutes a turbocharger that compresses intake air using exhaust gas. The electric compressor 1 includes an impeller stored in a casing and an electric motor 16 that rotates the impeller. The electric compressor 1 is a device that compresses intake air by driving an electric motor 16 by electricity to rotate an impeller. The electric compressor 1 is provided for the purpose of compensating for the supercharging pressure when the turbo lag of the turbocharger is generated, and assisting supercharging during rapid acceleration.

  Here, the electric compressor 1 and the turbo compressor 3 are installed in series in the intake passage 13. Furthermore, the electric compressor 1 is installed so that the rotation direction of the impeller viewed from the intake air inflow direction to the impeller of the electric compressor 1 is the same as the rotation direction of the turbo compressor 3.

  Further, a bypass passage 15 that connects the intake passage 13 upstream of the electric compressor 1 and the intake passage 13 between the electric compressor 1 and the turbo compressor 3 is connected to the intake passage 13. The bypass passage 15 is provided with a bypass valve 2 for opening and closing the bypass passage 15.

  The exhaust passage 14 is provided with a turbine 11 that is a device constituting a turbocharger. As the exhaust gas passes through the turbine 11, the turbine 11 rotates, and the turbo compressor 3 rotates in conjunction with the rotation.

  A supercharging pressure sensor 5 and an air flow meter 6 are provided in the intake passage 13 between the intercooler 4 and the engine body 8.

  The system configuration of the first embodiment includes an ECU 100 (Electronic Control Unit) as a control device that controls the operating state of the engine body 8. A supercharging pressure sensor 5 and an air flow meter 6 are connected to the input side of the ECU 100. The ECU 100 detects the supercharging pressure in the intake passage 13 from the signal output from the supercharging pressure sensor 5. The ECU 100 detects the intake air flow rate from the signal output from the air flow meter 6.

  An actuator such as the electric compressor 1 and the bypass valve 2 is connected to the output side of the ECU 100. The ECU 100 outputs a signal to the electric compressor 1 to operate the electric compressor 1. The ECU 100 outputs a signal to the bypass valve 2 to adjust the opening degree of the bypass valve 2.

  By the way, when the pressure ratio (downstream pressure / upstream pressure) between the upstream side and the downstream side of the turbo compressor 3 becomes too high, a surge in which the intake air flows backward occurs. The surge can be prevented by reducing the angle of attack of the turbo compressor 3 with respect to the intake of the impeller. This is because by reducing the angle of attack, the intake air flows along the impeller, and the intake air is less likely to be separated from the impeller.

  Thus, in the first embodiment, when the surge occurs in the turbo compressor 3, the electric compressor 1 is driven to cause a swirl flow in the intake air. Thus, the angle of attack of the impeller with respect to the intake air is reduced, and the occurrence of surge in the turbo compressor 3 is suppressed. Hereinafter, the swirl flow generated by the electric compressor 1 will be described with reference to FIGS. 2, 3, 4, and 5.

[Intake swirl flow by electric compressor]
FIG. 2 is a diagram for explaining the flow of intake air in the electric compressor 1. FIG. 2 shows the electric compressor 1. An impeller (not shown) of the electric compressor 1 is accommodated in the casing 30. An annular scroll 34 is provided outside the casing 30 in the radial direction.

  FIG. 2 shows a state in which intake air flows from the central portion of the electric compressor 1. The intake air flowing into the electric compressor 1 is compressed by the impeller in the electric compressor 1. The compressed intake air is introduced into the scroll 34 of the electric compressor 1 and becomes a swirling flow in the scroll 34. This swirling flow is indicated by an arrow indicated by a symbol K in FIG.

  FIG. 3 is a cross-sectional view of the electric compressor 1. FIG. 3 shows the impeller 32 of the electric compressor 1. The arrow indicated by the symbol K in FIG. 3 shows a state in which the intake air turns into a swirl flow in the scroll 34 of the electric compressor 1, similarly to the arrow indicated by the symbol K in FIG. 2.

  FIG. 4 is a diagram illustrating a state where the intake air compressed by the electric compressor 1 is supplied to the turbo compressor 3. The solid arrows in FIG. 4 indicate the intake air that has passed through the electric compressor 1 and turned into a swirling flow. The solid-line arrows in FIG. 4 become more horizontal as the swirl flow is stronger. A symbol X in FIG. 4 indicates an impeller of the turbo compressor 3. The impeller of the turbo compressor 3 rotates in the direction of the dashed-dotted arrow.

  FIG. 4 shows a state in which the swirling flow strikes the impeller of the rotating turbo compressor 3 in absolute coordinates. Here, in order to express the swirl flow that hits the impeller of the turbo compressor 3 that is actually rotating, it is necessary to express the swirl flow in relative coordinates as viewed from the impeller of the turbo compressor 3. Hereinafter, the swirl flow impinging on the impeller of the turbo compressor 3 will be described with reference to FIG.

  FIG. 5 is a view for explaining how the intake air hits the impeller of the rotating turbo compressor 3. A solid arrow indicated by a symbol A indicates a flow when the intake air compressed by the electric compressor 1 flows into the turbo compressor 3. Here, since the impeller of the turbo compressor 3 is rotating, the relative inflow angle of the intake air is as indicated by a solid arrow indicated by a symbol B.

  5 indicates the flow of intake air that has flowed into the turbo compressor 3 without being compressed by the electric compressor 1. Further, the relative inflow angle of the intake air is as shown by a broken-line arrow indicated by a symbol B '.

  As shown in FIG. 5, when the intake air flowing into the turbo compressor 3 does not turn (broken line arrow B ′), the intake air flowing in the same direction as the impeller of the turbo compressor 3 (solid line arrow). In B), the angle of attack of the impeller with respect to the intake air becomes small. For this reason, if the electric compressor 1 and the turbo compressor 3 according to the first embodiment are arranged, it is possible to suppress the separation of the intake air from the impeller blade surface and suppress the occurrence of a surge in the turbo compressor 3.

  Here, the electric compressor 1 can be operated at an arbitrary timing regardless of the operating state of the engine. For this reason, if the surge in the turbo compressor 3 is predicted and control for operating the electric compressor 1 is performed, an appropriate surge countermeasure can be realized. In the first embodiment, such control is performed as surge suppression control. Hereinafter, specific control contents of the surge suppression control in the first embodiment will be described with reference to FIG.

[Surge suppression control]
FIG. 6 is a flowchart showing a routine representing specific contents of surge suppression control according to the first embodiment. The ECU 100 has a memory for storing this routine. The ECU 100 has a processor for executing the stored routine.

  First, the ECU 100 determines whether or not the electric compressor 1 is stopped and the bypass valve 2 is fully opened (S100). This is because there is no need to execute surge suppression control when the electric compressor 1 is operating, and when the bypass valve 2 is closed, the effect described in the surge suppression control of the second embodiment is already obtained. Because. If the ECU 100 determines that the electric compressor 1 is stopped and the bypass valve 2 is not fully opened, the ECU 100 ends this routine. In S100, it is determined whether or not the bypass valve 2 is fully open. The full open here is an opening that is set as the maximum opening in terms of control.

  On the other hand, when it is determined in S100 that the electric compressor 1 is stopped and the bypass valve 2 is fully open, the ECU 100 predicts whether or not a surge occurs in the turbo compressor 3 (S102). Specifically, the ECU 100 generates a surge in the turbo compressor 3 based on the relationship between the supercharging pressure detected from the supercharging pressure sensor 5 and its change speed and the intake flow rate detected from the air flow meter 6 and its change speed. Predict. Alternatively, the ECU 100 predicts the occurrence of a surge based on the target boost pressure and the target intake air flow determined by the torque requested by the driver. When it is predicted that no surge will occur in the turbo compressor 3, the ECU 100 ends this routine.

  On the other hand, when the ECU 100 predicts that a surge in the turbo compressor 3 will occur in S102, the ECU 100 operates the electric compressor 1 (S104). Here, the rotational speed and the driving time of the electric compressor 1 are set to the rotational speed and the driving time at which a sufficient swirling flow is obtained by a test in advance.

  Next, the ECU 100 adjusts the opening degree of the bypass valve 2 and the opening degree of the waste gate valve (WGV) so as to reach the target supercharging pressure (S106). Here, when the supercharging pressure can be set to the target supercharging pressure only by the wastegate valve, only the wastegate valve may be adjusted without adjusting the opening degree of the bypass valve 2. Thereafter, this routine ends.

  By performing the control of the first embodiment, the intake air that has caused the swirling flow can be caused to flow into the turbo compressor 3. For this reason, the angle of attack of the turbo compressor 3 with respect to the intake of the impeller can be reduced. As a result, the occurrence of surge in the turbo compressor 3 can be suppressed.

Embodiment 2. FIG.
The second embodiment differs from the first embodiment in that, in surge suppression control, the opening degree of the bypass valve 2 is controlled rather than operating the electric compressor 1. Hereinafter, the surge suppression control of the second embodiment will be described.

  FIG. 7 is a flowchart showing a routine representing specific contents of surge suppression control according to the second embodiment. In addition, since S200 and S202 are the same processes as S100 and S102 of Embodiment 1, description is abbreviate | omitted.

  If the ECU 100 predicts that a surge will occur in the turbo compressor 3 in S202, the ECU 100 sets the electric compressor 1 in a state where it can idle by intake air (S204). Specifically, the ECU 100 does not energize the electric motor 16 of the electric compressor 1 so that the impeller 32 of the electric compressor 1 can idle by intake air. Furthermore, when the impeller 32 of the electric compressor 1 can be separated from the electric motor 16, they may be separated.

  Next, the ECU 100 closes the bypass valve 2 to a predetermined opening (S206). Specifically, the opening degree is determined based on a map set in advance in the ECU 100, and the bypass valve 2 is controlled to be fully closed or partially closed. More specifically, the higher the rotational speed of the turbo compressor 3, the lower the opening degree of the bypass valve 2. The map set in the ECU 100 is a map in which the opening degree of the bypass valve 2 and the rotation speed of the turbo compressor 3 are associated with each other. In this way, by closing the bypass valve 2 to a predetermined opening degree, the intake air flowing through the bypass passage 15 passes through the electric compressor 1. For this reason, the electric compressor 1 can be rotated by the flow of intake air. As a result, a swirling flow is generated in the scroll 34 of the electric compressor 1. In S206, the control for fully closing the bypass valve 2 has been described. However, the term "full close" here is not limited to the state in which the opening degree of the bypass valve 2 is 0%, but is set as the minimum opening degree for control. The opening degree may be sufficient.

  Next, the ECU 100 adjusts the opening degree of the waste gate valve (WGV) so as to reach the target supercharging pressure (S208). Thereafter, this routine ends.

  By performing the surge suppression control of the second embodiment, the intake air is introduced into the scroll 34 of the electric compressor 1 to cause a swirling flow, and then the intake air is caused to flow into the turbo compressor 3 as in the first embodiment. be able to. As a result, the occurrence of surge in the turbo compressor 3 can be suppressed.

DESCRIPTION OF SYMBOLS 1 Electric compressor 2 Bypass valve 3 Turbo compressor 5 Supercharging pressure sensor 6 Air flow meter 8 Engine main body 15 Bypass passage 100 ECU

Claims (2)

A turbocharger having a turbine that operates by exhaust energy of an internal combustion engine in an exhaust passage, and a turbo compressor that is driven by the turbine and that supercharges intake air in the intake passage;
An impeller disposed in the intake passage upstream of the turbo compressor; and an electric motor that drives the impeller. A centrifugal electric compressor that supercharges intake air by driving the impeller by the electric motor to be the same;
A bypass passage communicating the intake passage upstream of the electric compressor and the intake passage between the electric compressor and the turbo compressor;
A bypass valve provided in the bypass passage for opening and closing the bypass passage;
A control device for controlling the electric compressor and the bypass valve;
The controller is
An internal combustion engine that drives the electric compressor when it is predicted that a surge will occur in the turbo compressor when the bypass valve is fully open and the electric compressor is stopped. A turbocharger having a turbine that operates by exhaust energy of an internal combustion engine in an exhaust passage, and a turbo compressor that is driven by the turbine and that supercharges intake air in the intake passage;
An impeller disposed in the intake passage upstream of the turbo compressor, and an electric motor that drives the impeller, wherein the rotation direction of the impeller as viewed from the direction of intake air flow into the impeller is the rotation direction of the turbo compressor A centrifugal electric compressor that supercharges intake air by driving the impeller by the electric motor to be the same;
A bypass passage communicating the intake passage upstream of the electric compressor and the intake passage between the electric compressor and the turbo compressor;
A bypass valve provided in the bypass passage for opening and closing the bypass passage;
A control device for controlling the electric compressor and the bypass valve;
The controller is
When it is predicted that a surge will occur in the turbo compressor when the bypass valve is fully open and the electric compressor is stopped, the electric compressor is idled by intake air and the opening of the bypass valve is reduced. An internal combustion engine characterized by the above.

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