Intake and exhaust system

Abstract

To reduce a shock of an engine.SOLUTION: An intake / exhaust system 1 comprises: a supercharger 15 having a compressor 15a and a turbine 15b; an electric compressor 16 arranged at a downstream side with respect to the compressor 15a out of an intake / exhaust flow passage 12; an intake bypass path 12b for connecting an upstream side with respect to the electric compressor 16 and a downstream side with respect to the electric compressor 16 out of the intake / exhaust flow passage 12; a flow passage control valve (switching valve 22) for switching a state that intake air can circulate in the intake bypass path 12b, and a state that the circulation of the intake air in the intake bypass path 12b is blocked; a discharge bypass path 14 connected to a downstream side with respect to the compressor 15a, and an upstream side with respect to the electric compressor 16 out of the intake / exhaust flow passage 12, or an upstream side with respect to the flow passage control valve (switching valve 22) out of the intake bypass path 12b, and communicating with an exhaust port 13a; and a flow rate adjustment valve 41 arranged at the discharge bypass path 14.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an intake and exhaust system. [Background technology]

[0002] Some engine intake and exhaust systems include an electric compressor in addition to a supercharger having a compressor and a turbine (see, for example, Patent Document 1). The electric compressor is provided downstream of the compressor in the intake flow path. For example, in a vehicle equipped with such an intake and exhaust system, the electric compressor can be used to quickly increase the supercharging pressure (i.e., the pressure of the intake air drawn into the engine) when starting, etc., thereby improving torque responsiveness. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6222175 Summary of the Invention [Problem to be solved by the invention]

[0004] In an intake and exhaust system equipped with an electric compressor, the pressure of the intake air discharged from the turbocharger compressor and the flow rate of the intake air flowing into the electric compressor gradually increase while the electric compressor is operating. Here, it is assumed that the flow rate of the intake air flowing into the electric compressor exceeds a permissible value (i.e., the upper limit of the permissible range) before the pressure of the intake air discharged from the turbocharger compressor reaches the pressure of the intake air discharged from the electric compressor, causing the electric compressor to stop. In this case, a sudden and large change in the supercharging pressure may cause a sudden and large change in the torque of the engine, which may cause a shock.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide an intake and exhaust system capable of reducing engine shock. [Means for solving the problem]

[0006] In order to solve the above problems, an intake and exhaust system according to one embodiment of the present invention includes a compressor provided in an intake flow path connected to an engine, and a turbocharger having a turbine provided in an exhaust flow path connected to the engine, an electric compressor provided in the intake flow path downstream of the compressor, an intake bypass path connecting the intake flow path upstream of the electric compressor and the intake bypass path downstream of the electric compressor, a flow path control valve that switches between a state in which intake air can flow through the intake bypass path and a state in which the flow of intake air in the intake bypass path is blocked, an exhaust bypass path connected to the intake flow path downstream of the compressor and upstream of the electric compressor, or the intake bypass path upstream of the flow path control valve, and communicating with an exhaust port, and a flow rate adjustment valve provided in the exhaust bypass path. Effect of the Invention

[0007] According to the present invention, it is possible to reduce engine shock. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing a schematic configuration of an intake and exhaust system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram showing an example of a functional configuration of a control device according to an embodiment of the present invention. [Diagram 3] 5 is a flowchart showing an example of a flow of processing performed by a control device according to the embodiment of the present invention. [Figure 4] 5 is a diagram showing a state in which intake air flows through an intake bypass passage in the intake and exhaust system according to the embodiment of the present invention. FIG. [Diagram 5] 2 is a diagram showing a state in which intake air flows through an electric compressor in the intake and exhaust system according to the embodiment of the present invention. FIG. [Figure 6] FIG. 4 is a diagram showing an example of transitions of various state quantities in the embodiment of the present invention. [Figure 7] FIG. 13 is a schematic diagram showing a schematic configuration of an intake and exhaust system according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The dimensions, materials, and other specific values ​​shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid repeated explanations, and elements not directly related to the present invention are not shown.

[0010] <Intake and exhaust system configuration> The configuration of an intake and exhaust system 1 according to an embodiment of the present invention will be described with reference to FIGS.

[0011] Fig. 1 is a schematic diagram showing a schematic configuration of an intake and exhaust system 1. The intake and exhaust system 1 is mounted on a vehicle 100. As shown in Fig. 1, the intake and exhaust system 1 includes an engine 11, an intake passage 12, an exhaust passage 13, an exhaust bypass passage 14, a supercharger 15, an electric compressor 16, and a control device 17. The supercharger 15 has a compressor 15a and a turbine 15b. The compressor 15a and the turbine 15b are connected via a shaft and rotate integrally.

[0012] The engine 11 is, for example, a spark-ignition internal combustion engine (that is, a gasoline engine). The engine 11 has a plurality of cylinders. A piston is slidably provided inside each cylinder, and a combustion chamber is defined by the piston. Each cylinder is provided with a fuel injection valve that injects fuel toward the combustion chamber. A mixture containing air and fuel is formed in the combustion chamber, and the mixture is burned by ignition of an ignition plug provided toward the combustion chamber. This causes the piston to perform a linear reciprocating motion, and power is transmitted to a crankshaft connected to the piston of each cylinder.

[0013] Each combustion chamber of the engine 11 communicates with an intake passage 12 via an intake port, and communicates with an exhaust passage 13 via an exhaust port. Each cylinder is provided with an intake valve capable of opening and closing the intake port, and an exhaust valve capable of opening and closing the exhaust port. By driving the intake valve and exhaust valve, air (i.e., intake air) is supplied to the combustion chamber, and exhaust gas is discharged from the combustion chamber.

[0014] The intake flow path 12 is connected to the engine 11, and is a flow path through which air (i.e., intake air) supplied to a combustion chamber of the engine 11 flows. An intake port 12a is provided at an upstream end of the intake flow path 12, through which outside air is taken in from outside the vehicle 100. An air filter 21 is provided in the intake flow path 12 downstream of the intake port 12a. The air filter 21 removes foreign matter contained in the air flowing through the intake flow path 12. A compressor 15a of the turbocharger 15 is provided in the intake flow path 12 downstream of the air filter 21. The compressor 15a compresses air and discharges it downstream. An electric compressor 16 is provided in the intake flow path 12 downstream of the compressor 15a. The electric compressor 16 is driven by electricity, compresses air, and discharges it downstream.

[0015] The intake air flow path 12 is connected by an intake air bypass path 12b between the upstream side of the electric compressor 16 and the downstream side of the electric compressor 16. That is, the intake air flow path 12 branches into the intake air bypass path 12b and a flow path toward the electric compressor 16, upstream of the electric compressor 16. A switching valve 22 is provided at the branch point of the intake air flow path 12 between the intake air bypass path 12b and the flow path toward the electric compressor 16. The switching valve 22 switches the supply destination (i.e., the downstream destination) of the intake air sent from the upstream side.

[0016] The switching valve 22 switches the supply destination of the intake air between the intake bypass passage 12b and the electric compressor 16. When the supply destination of the intake air is the intake bypass passage 12b, the intake air discharged from the compressor 15a of the turbocharger 15 flows through the intake bypass passage 12b without passing through the electric compressor 16. That is, the intake air is allowed to flow through the intake bypass passage 12b. On the other hand, when the supply destination of the intake air is the electric compressor 16, the intake air discharged from the compressor 15a of the turbocharger 15 flows through the electric compressor 16 without passing through the intake bypass passage 12b. That is, the flow of the intake air through the intake bypass passage 12b is blocked.

[0017] In this way, the switching valve 22 corresponds to an example of a flow path control valve according to the present invention (i.e., a valve that switches between a state in which intake air can flow through the intake bypass passage 12b and a state in which the flow of intake air through the intake bypass passage 12b is blocked). However, as will be described later, the flow path control valve according to the present invention is not limited to the switching valve 22.

[0018] An intercooler 23 is provided in the intake passage 12 downstream of the electric compressor 16. The intake air flowing through the intercooler 23 is cooled by exchanging heat with air outside the intercooler 23. An intake manifold (not shown) is provided in the intake passage 12 downstream of the intercooler 23. The intake manifold branches out toward each cylinder of the engine 11 and is connected to the intake port of each cylinder.

[0019] In the intake passage 12, outside air (i.e., intake air) is taken in from an intake port 12a as shown by a white arrow. The taken in intake air passes through an air filter 21, and then passes through a compressor 15a of the turbocharger 15. The intake air then passes through an electric compressor 16 or an intake bypass passage 12b, and then passes through an intercooler 23 before being sent to the engine 11. A switching valve 22 switches whether the intake air passes through the electric compressor 16 or the intake bypass passage 12b.

[0020] The intake passage 12 is provided with a flow rate sensor 24, a first pressure sensor 25, and a second pressure sensor 26. The flow rate sensor 24 detects the flow rate of the intake air discharged from the compressor 15a. The flow rate sensor 24 is installed, for example, downstream of the compressor 15a and upstream of the switching valve 22 in the intake passage 12. The first pressure sensor 25 detects the pressure of the intake air discharged from the compressor 15a. The first pressure sensor 25 is installed, for example, downstream of the compressor 15a and upstream of the switching valve 22 in the intake passage 12. The second pressure sensor 26 detects the pressure of the intake air discharged from the electric compressor 16. The second pressure sensor 26 is installed, for example, downstream of the electric compressor 16 and upstream of the intercooler 23 in the intake passage 12.

[0021] The exhaust flow passage 13 is connected to the engine 11, and is a flow passage through which the exhaust gas discharged from the combustion chamber of the engine 11 flows. An exhaust port 13a through which the exhaust gas is discharged to the outside of the vehicle 100 is provided at the downstream end of the exhaust flow passage 13. An exhaust manifold (not shown) is provided in the exhaust flow passage 13. The exhaust manifold branches toward each cylinder of the engine 11 and is connected to the exhaust port of each cylinder. A turbine 15b of the supercharger 15 is provided downstream of the exhaust manifold in the exhaust flow passage 13. The turbine 15b converts the kinetic energy of the fluid into rotational energy. When the turbine 15b is rotated by the exhaust gas flowing through the turbine 15b, the rotational power is transmitted to the compressor 15a via a shaft, and the compressor 15a rotates. A catalyst 31 is provided downstream of the turbine 15b in the exhaust flow passage 13. The catalyst 31 purifies harmful components in the exhaust gas into harmless components. The catalyst 31 includes, for example, a three-way catalyst.

[0022] In the exhaust flow path 13, the exhaust gas discharged from the engine 11 passes through the turbine 15b of the turbocharger 15, then passes through the catalyst 31, and is discharged from the exhaust port 13a, as indicated by the white arrow.

[0023] The exhaust bypass passage 14 is connected to the intake passage 12 downstream of the compressor 15a and upstream of the electric compressor 16, and communicates with the exhaust port 13a of the exhaust passage 13. In the example of FIG. 1, the upstream end of the exhaust bypass passage 14 is connected to the intake passage 12 downstream of the compressor 15a and upstream of the switching valve 22. The downstream end of the exhaust bypass passage 14 is connected to the exhaust passage 13 downstream of the catalyst 31. In other words, the exhaust bypass passage 14 connects the intake passage 12 and the exhaust passage 13, bypassing the electric compressor 16 and the engine 11. However, as described later, the connection position of the upstream end of the exhaust bypass passage 14 and the connection position of the downstream end of the exhaust bypass passage 14 are not limited to the example of FIG. 1.

[0024] The exhaust bypass passage 14 is provided with a flow rate adjustment valve 41. The flow rate adjustment valve 41 adjusts the flow rate of the intake air flowing from the intake passage 12 to the exhaust bypass passage 14. The flow rate of the intake air flowing from the intake passage 12 to the exhaust bypass passage 14 changes depending on the opening degree of the flow rate adjustment valve 41. By adjusting the flow rate of the intake air flowing from the intake passage 12 to the exhaust bypass passage 14, the flow rate of the intake air flowing in the intake passage 12 downstream of the connection part with the exhaust bypass passage 14 is adjusted.

[0025] The vehicle 100 is provided with an accelerator opening sensor 51. The accelerator opening sensor 51 detects an accelerator opening corresponding to an amount of accelerator operation by a driver.

[0026] The control device 17 includes a CPU (Central Processing Unit) which is an arithmetic processing device, a ROM (Read Only Memory) which is a memory element that stores programs and arithmetic parameters used by the CPU, and a RAM (Random Access Memory) which is a memory element that temporarily stores parameters that change appropriately during execution of the CPU.

[0027] The control device 17 communicates with each device (e.g., the electric compressor 16, the switching valve 22, the flow rate sensor 24, the first pressure sensor 25, the second pressure sensor 26, the flow rate adjustment valve 41, the accelerator position sensor 51, etc.) mounted on the vehicle 100. The communication between the control device 17 and each device is realized, for example, by using CAN (Controller Area Network) communication.

[0028] Fig. 2 is a block diagram showing an example of a functional configuration of the control device 17. For example, as shown in Fig. 2, the control device 17 includes an acquisition unit 17a and a control unit 17b.

[0029] The acquiring unit 17a acquires various information used in the processing performed by the control unit 17b, and outputs the information to the control unit 17b. For example, the acquiring unit 17a acquires information from the flow rate sensor 24, the first pressure sensor 25, the second pressure sensor 26, and the accelerator position sensor 51.

[0030] The control unit 17b controls the operation of each device in the intake and exhaust system 1. For example, the control unit 17b includes an electric compressor control unit 17b1, a switching valve control unit 17b2, and a flow rate adjustment valve 17b3.

[0031] The electric compressor control unit 17b1 controls the electric compressor 16. Specifically, the electric compressor control unit 17b1 operates or stops the electric compressor 16 by controlling the power supply to the electric compressor 16. In addition, the electric compressor control unit 17b1 controls the rotation speed of the electric compressor 16 by controlling the current supplied to the electric compressor 16.

[0032] The switching valve control unit 17b2 controls the switching valve 22. Specifically, the switching valve control unit 17b2 drives the switching valve 22 to switch the intake air path, which is the path of the intake air in the intake flow passage 12. In other words, the switching valve control unit 17b2 switches between a state in which the intake air can flow through the intake bypass path 12b and a state in which the intake air can flow through the electric compressor 16.

[0033] The flow rate adjustment valve 17b3 controls the flow rate adjustment valve 41. Specifically, the flow rate adjustment valve 17b3 controls the opening degree of the flow rate adjustment valve 41 to control the flow rate of the intake air flowing from the intake air flow path 12 to the exhaust bypass path 14. This controls the flow rate of the intake air flowing in the intake air flow path 12 downstream of the connection portion with the exhaust bypass path 14.

[0034] The functions of the control device 17 according to the present embodiment may be divided among multiple control devices, or multiple functions may be realized by one control device. When the functions of the control device 17 are divided among multiple control devices, the multiple control devices may be connected to each other via a communication bus such as a CAN.

[0035] As described above, in the intake and exhaust system 1, the electric compressor 16 is provided downstream of the compressor 15a in the intake flow path 12. This makes it possible to quickly increase the boost pressure (i.e., the pressure of the intake air drawn into the engine 11) when the vehicle 100 starts, etc., thereby improving the torque responsiveness. Here, in this embodiment, the exhaust bypass path 14 is connected to the intake flow path 12, and a flow rate adjustment valve 41 is provided in the exhaust bypass path 14. This makes it possible to reduce shock to the engine 11.

[0036] <Operation of the intake and exhaust system> Next, the operation of the intake and exhaust system 1 according to the embodiment of the present invention will be described with reference to FIGS.

[0037] Fig. 3 is a flowchart showing an example of the flow of processing performed by the control device 17. The control flow shown in Fig. 3 starts in a state in which the switching valve 22 is controlled so that the intake air can flow through the intake bypass passage 12b, and is repeatedly started after the control flow ends.

[0038] FIG. 4 is a diagram showing a state in which intake air flows through the intake bypass passage 12b in the intake and exhaust system 1. In FIG. 4, the flow of intake air is indicated by white arrows. When the switching valve 22 is controlled so that the intake air can flow through the intake bypass passage 12b, as shown in FIG. 4, the intake air discharged from the compressor 15a passes through the intake bypass passage 12b without being sent to the electric compressor 16. Thereafter, the intake air passes through the intercooler 23 and is sent to the engine 11. In this case, the electric compressor 16 is stopped. Also, the flow rate control valve 41 is closed, and the intake air does not flow from the intake passage 12 to the exhaust bypass passage 14.

[0039] 3 is started, first, in step S101, the control unit 17b determines whether or not the accelerator opening is greater than a threshold value. The threshold value is set to a value that allows the determination of whether or not it is necessary to rapidly increase the supercharging pressure by using the electric compressor 16.

[0040] When it is determined that the accelerator opening is equal to or less than the threshold (step S101 / NO), the control unit 17b determines that it is not necessary to rapidly increase the boost pressure by using the electric compressor 16, and ends the control flow shown in Fig. 3. On the other hand, when it is determined that the accelerator opening is greater than the threshold (step S101 / YES), the control unit 17b determines that it is necessary to rapidly increase the boost pressure by using the electric compressor 16, and proceeds to step S102.

[0041] If the determination in step S101 is YES, in step S102, the control unit 17b controls the switching valve 22 so that the intake air flows through the electric compressor 16 (that is, so that the flow of the intake air through the intake bypass passage 12b is blocked). Next, in step S103, the control unit 17b operates the electric compressor 16.

[0042] Fig. 5 is a diagram showing a state in which intake air flows through the electric compressor 16 in the intake and exhaust system 1. In Fig. 5, similar to Fig. 4, the flow of intake air is indicated by outline arrows. When the switching valve 22 is controlled so that the intake air can flow through the electric compressor 16, as shown in Fig. 5, the intake air discharged from the compressor 15a is sent to the electric compressor 16 without being sent to the intake bypass passage 12b. Then, the intake air compressed and discharged by the electric compressor 16 passes through the intercooler 23 and is sent to the engine 11.

[0043] 3, in step S104, the control unit 17b controls the opening degree of the flow rate adjustment valve 41 based on the flow rate of the intake air flowing into the electric compressor 16 (hereinafter, also referred to as the intake air inflow rate). As the intake air inflow rate, for example, the detection result of the flow rate sensor 24 is used.

[0044] In step S104, the control unit 17b controls the opening degree of the flow rate adjustment valve 41 so that the intake air inflow rate is maintained at or below a reference flow rate. The reference flow rate is set according to the allowable value of the intake air inflow rate (i.e., the upper limit of the allowable range of the intake air inflow rate at which the electric compressor 16 can operate normally). The reference flow rate is set to a value slightly smaller than the allowable value of the intake air inflow rate, for example.

[0045] As described above, when the electric compressor 16 is in operation, the flow rate control valve 41 is appropriately opened, so that the intake air flows from the intake passage 12 to the exhaust bypass passage 14, as shown by the dashed white arrow in Fig. 5. For example, when the intake air inflow rate reaches the reference flow rate or exceeds the reference flow rate, the control unit 17b opens the flow rate control valve 41. Then, by controlling the opening degree of the flow rate control valve 41, the flow rate of the intake air flowing from the intake passage 12 to the exhaust bypass passage 14 is adjusted, and the intake air inflow rate is maintained at or below the reference flow rate.

[0046] 3, in step S105, the control unit 17b determines whether or not the pressure of the intake air discharged from the compressor 15a (hereinafter also referred to as the compressor outlet pressure) has exceeded the pressure of the intake air discharged from the electric compressor 16 (hereinafter also referred to as the electric compressor outlet pressure). As the compressor outlet pressure, for example, the detection result of the first pressure sensor 25 is used. As the electric compressor outlet pressure, for example, the detection result of the second pressure sensor 26 is used.

[0047] If it is determined that the compressor outlet pressure does not exceed the electric compressor outlet pressure (step S105 / NO), the process returns to step S104. On the other hand, if it is determined that the compressor outlet pressure exceeds the electric compressor outlet pressure (step S105 / YES), the process proceeds to step S106.

[0048] If the determination in step S105 is YES, in step S106, the control unit 17b stops the electric compressor 16. Next, in step S107, the control unit 17b closes the flow rate adjustment valve 41. Next, in step S108, the control unit 17b controls the switching valve 22 so that the intake air flows through the intake bypass passage 12b (i.e., so that the intake air can flow through the intake bypass passage 12b), and the control flow shown in Fig. 3 ends. As a result, the intake path in the intake flow passage 12 returns from the state in Fig. 5 to the state in Fig. 4.

[0049] 6 is a diagram showing an example of the transition of various state quantities in this embodiment. In FIG. 6, the various state quantities are the switching state of the intake path, the operating state of the electric compressor 16, the opening degree [%] of the flow rate control valve 41, the intake air inflow amount [m 3 / s], boost pressure [kPa], engine torque [Nm], and acceleration of the vehicle 100 [m / s 2 The switching state of the intake path is the electric compressor path, which corresponds to the state of the intake path in the intake flow passage 12 shown in Fig. 5. The switching state of the intake path is the intake bypass path, which corresponds to the state of the intake path in the intake flow passage 12 shown in Fig. 4.

[0050] In the example shown in FIG. 6, the vehicle 100 is stopped before time T1. Therefore, the electric compressor 16 is stopped, and the switching state of the intake path is the intake bypass path (i.e., the state of FIG. 4). In addition, the flow rate control valve 41 is closed. Then, at time T1, the accelerator is operated and the vehicle 100 starts moving. Here, at time T1, the accelerator opening exceeds a threshold value, and the switching valve 22 is controlled so that the intake air flows through the electric compressor 16. As a result, the switching state of the intake path is switched to the electric compressor path (i.e., the state of FIG. 5). Then, at time T1, the electric compressor 16 operates. As a result, the boost pressure increases after time T1, and the engine torque increases. Therefore, the acceleration of the vehicle 100 also increases.

[0051] During operation of the electric compressor 16, the opening degree of the flow rate control valve 41 is controlled so that the intake air inflow rate is maintained at or below the reference flow rate. In the example of FIG. 6, the intake air inflow rate increases after time T1, and reaches the reference flow rate at time T2. Therefore, the flow rate control valve 41 is opened at time T2, and the opening degree of the flow rate control valve 41 is controlled so that the intake air inflow rate is maintained at or below the reference flow rate after time T2. In the example of FIG. 6, since the intake air inflow rate is maintained at the reference flow rate after time T2, the boost pressure is almost maintained, and the engine torque is also almost maintained. In this way, by maintaining the intake air inflow rate at the reference flow rate, the boost pressure and the engine torque can be maintained as high as possible. Note that the acceleration of the vehicle 100 decreases after time T2.

[0052] After time T1 when the electric compressor 16 is operated, the intake air compressed and discharged by the electric compressor 16 is sent to the engine 11. Therefore, after time T1, the electric compressor outlet pressure corresponds to the supercharging pressure. Here, after time T1, the turbine 15b of the supercharger 15 is rotated by the exhaust air, so that the compressor 15a of the supercharger 15 is also rotated. As a result, the compressor outlet pressure gradually increases. Then, at time T3 after time T2, the compressor outlet pressure exceeds the electric compressor outlet pressure (i.e., the supercharging pressure), and the electric compressor 16 stops. Then, at time T3, the flow rate control valve 41 closes, and the switching state of the intake path is switched to the intake bypass path (i.e., the state of FIG. 4). After that, after time T3, the supercharging pressure and engine torque increase due to the supercharger 15, and the acceleration of the vehicle 100 also increases again.

[0053] However, unlike this embodiment, if the exhaust bypass passage 14 and the flow rate control valve 41 are not provided, the various state quantities change as shown by the dashed lines in FIG. 6. In the example shown by the dashed lines, after time T1 when the electric compressor 16 is operated, the intake air inflow reaches an allowable value before the compressor outlet pressure reaches the electric compressor outlet pressure (i.e., the boost pressure), and the electric compressor 16 stops. As a result, when the electric compressor 16 stops, as shown by the dashed lines, the boost pressure suddenly drops significantly, and the engine torque also suddenly drops significantly. This sudden and large change in engine torque causes a shock to the engine 11. That is, a large impact is caused to the vehicle 100.

[0054] On the other hand, in this embodiment, since the exhaust bypass passage 14 and the flow rate adjustment valve 41 are provided, the intake air inflow rate can be adjusted so as not to reach the allowable value, and the operating time of the electric compressor 16 can be extended. As a result, the electric compressor 16 can be stopped after the compressor outlet pressure has come closer to the electric compressor outlet pressure (in the example of FIG. 6, after the compressor outlet pressure has reached the electric compressor outlet pressure). Therefore, when the electric compressor 16 is stopped, a sudden large change in the supercharging pressure is suppressed, and a sudden large change in the engine torque is suppressed. Therefore, a shock to the engine 11 can be reduced.

[0055] Furthermore, in the example shown by the dashed line, the acceleration of the vehicle 100 also drops significantly with the drop in engine torque. On the other hand, in the present embodiment, the engine torque is prevented from changing significantly, and therefore the acceleration of the vehicle 100 is prevented from dropping significantly. Therefore, the acceleration performance of the vehicle 100 is improved.

[0056] In the above, an example in which the switching valve 22 is used as the flow path control valve according to the present invention has been described. However, the flow path control valve according to the present invention is not limited to the switching valve 22. For example, an opening and closing valve for opening and closing the intake bypass passage 12b may be used instead of the switching valve 22. The opening and closing valve is provided in the intake bypass passage 12b. For example, the opening and closing valve may be provided at the upstream end of the intake bypass passage 12b, at the downstream end of the intake bypass passage 12b, or between the upstream end and the downstream end of the intake bypass passage 12b. When the opening and closing valve is opened, the intake air is allowed to flow through the intake bypass passage 12b. When the opening and closing valve is closed, the flow of the intake air through the intake bypass passage 12b is blocked.

[0057] Also, in the above, an example has been described in which the opening degree of the flow rate adjustment valve 41 is controlled based on the intake air inflow rate. However, the control device 17 may control the opening degree of the flow rate adjustment valve 41 based on parameters other than the intake air inflow rate. For example, the control device 17 may control the opening degree of the flow rate adjustment valve 41 based on the concentration of nitrogen oxides (i.e., NOx) discharged from the exhaust port 13a of the exhaust flow path 13. Hereinafter, the concentration of discharged NOx is also referred to as the NOx emission concentration.

[0058] For example, when the electric compressor 16 is stopped and the intake path in the intake flow passage 12 is in the state shown in Fig. 4, if the NOx emission concentration exceeds the reference concentration, the control device 17 may open the flow rate control valve 41. This allows a portion of the intake air to be sent to the exhaust flow passage 13 via the exhaust bypass passage 14, thereby diluting the NOx emission concentration. In addition, the control device 17 may increase the opening of the flow rate control valve 41 as the NOx emission concentration increases. This allows the NOx emission concentration to be more appropriately diluted.

[0059] <Effects of the intake and exhaust system> Next, the effects of the intake and exhaust system 1 according to the embodiment of the present invention will be described.

[0060] The intake and exhaust system 1 according to this embodiment includes an exhaust bypass passage 14 and a flow rate control valve 41 provided in the exhaust bypass passage 14. This allows the intake air inflow rate (i.e., the flow rate of the intake air flowing into the electric compressor 16) to be adjusted by adjusting the flow rate of the intake air flowing from the intake air flow passage 12 to the exhaust bypass passage 14. Therefore, while the electric compressor 16 is operating, the intake air inflow rate can be adjusted so as not to reach the allowable value, and the operating time of the electric compressor 16 can be extended. Therefore, the electric compressor 16 can be stopped after the compressor outlet pressure becomes closer to the electric compressor outlet pressure. Therefore, a sudden large change in the supercharging pressure is suppressed, and a sudden large change in the engine torque is suppressed. Therefore, a shock to the engine 11 can be reduced.

[0061] In the example of FIG. 1 described above, the upstream end of the exhaust bypass passage 14 is connected to the intake passage 12 downstream of the compressor 15a and upstream of the switching valve 22. However, the upstream end of the exhaust bypass passage 14 may be connected to the intake passage 12 downstream of the switching valve 22 and upstream of the electric compressor 16. FIG. 7 is a schematic diagram showing a schematic configuration of an intake and exhaust system 1A according to a modified example. The intake and exhaust system 1A is mounted on a vehicle 100A. Unlike the intake and exhaust system 1 described above, the intake and exhaust system 1A uses an opening and closing valve 22A that opens and closes the intake bypass passage 12b as a flow path control valve instead of the switching valve 22. The opening and closing valve 22A is provided between the upstream end and the downstream end of the intake bypass passage 12b. Also, unlike the intake and exhaust system 1 described above, the upstream end of the exhaust bypass passage 14A is connected to the intake bypass passage 12b upstream of the opening and closing valve 22A. In this intake and exhaust system 1A as well, the same effects as those of the intake and exhaust system 1 described above can be achieved.

[0062] 1 described above, the downstream end of the exhaust bypass passage 14 is connected to the exhaust flow path 13 downstream of the catalyst 31. However, if there is another exhaust port (i.e., an opening that communicates with the external space of the vehicle 100 and can discharge gas) in addition to the exhaust port 13a of the exhaust flow path 13, the downstream end of the exhaust bypass passage 14 may communicate with the other exhaust port.

[0063] As described above, even if the connection position of the upstream end of the discharge bypass passage 14 and the connection position of the downstream end of the discharge bypass passage 14 are different from those in the example of Fig. 1, the same effect as in the example of Fig. 1 can be achieved. That is, the discharge bypass passage 14 only needs to be connected to the intake passage 12 downstream of the compressor 15a and upstream of the electric compressor 16, or to the intake bypass passage 12b upstream of the passage control valve, and communicate with the exhaust port.

[0064] Moreover, in the intake and exhaust system 1 according to this embodiment, it is preferable that the control device 17 operates the electric compressor 16 while controlling the flow path control valve (e.g., the switching valve 22) so that the flow of intake air in the intake bypass passage 12b is blocked, and controls the opening degree of the flow rate adjustment valve 41 based on the flow rate of the intake air flowing into the electric compressor 16 (i.e., the intake air inflow rate) while the electric compressor 16 is operating. This appropriately realizes the adjustment of the intake air inflow rate so as not to reach the allowable value while the electric compressor 16 is operating. Therefore, it is appropriately realized to extend the operating time of the electric compressor 16.

[0065] Furthermore, in the intake and exhaust system 1 according to this embodiment, it is preferable that the control device 17 controls the opening degree of the flow rate adjustment valve 41 so that the flow rate of the intake air flowing into the electric compressor 16 (i.e., the intake air inflow rate) is maintained at or below the reference flow rate while the electric compressor 16 is in operation. This makes it possible to more appropriately adjust the intake air inflow rate so that it does not reach the allowable value while the electric compressor 16 is in operation. Therefore, it is possible to more appropriately extend the operation time of the electric compressor 16.

[0066] In addition, in the intake and exhaust system 1 according to this embodiment, when the pressure of the intake air discharged from the compressor 15a (i.e., the compressor outlet pressure) exceeds the pressure of the intake air discharged from the electric compressor 16 (i.e., the electric compressor outlet pressure) during operation of the electric compressor 16, it is preferable that the control device 17 stops the electric compressor 16 and controls the flow path control valve (e.g., the switching valve 22) so that the intake air can flow through the intake bypass passage 12b. This appropriately reduces the change in the supercharging pressure when the electric compressor 16 is stopped. Therefore, it is appropriately reduced the change in the engine torque when the electric compressor 16 is stopped. Therefore, it is appropriately reduced the shock of the engine 11.

[0067] Moreover, in the intake and exhaust system 1 according to this embodiment, the downstream end of the exhaust bypass passage 14 is preferably connected to an exhaust port 13a provided in the exhaust flow path 13, and the control device 17 preferably controls the opening degree of the flow rate adjustment valve 41 based on the concentration of nitrogen oxides (i.e., the NOx emission concentration) exhausted from the exhaust port 13a of the exhaust flow path 13. This makes it possible to dilute the NOx emission concentration so that it does not become excessively high.

[0068] The above describes a preferred embodiment of the present invention with reference to the attached drawings. However, it goes without saying that the present invention is not limited to the above-described embodiment, and various modified or altered examples within the scope of the claims also fall within the technical scope of the present invention.

[0069] For example, the processes described herein using flowcharts do not necessarily have to be performed in the order shown in the flowcharts, and additional process steps may be employed or some process steps may be omitted. [Explanation of symbols]

[0070] 1. Intake and exhaust system 1A Intake and exhaust system 11 Engine 12 Intake passage 12a Air intake 12b Intake bypass passage 13 Exhaust flow path 13a Exhaust port 14 Discharge bypass 14A Exhaust bypass 15 Turbocharger 15a Compressor 15b Turbine 16 Electric Compressor 17 Control device 21 Air Filter 22 Switching valve (flow path control valve) 22A Opening and closing valve (flow control valve) 23 Intercooler 24 Flow Sensor 25 First pressure sensor 26 Second pressure sensor 31 Catalyst 41 Flow control valve 51 Accelerator opening sensor 100 vehicles 100A Vehicle

Claims

1. a turbocharger having a compressor provided in an intake passage connected to an engine and a turbine provided in an exhaust passage connected to the engine; an electric compressor provided in the intake passage downstream of the compressor; an intake bypass passage connecting an upstream side of the electric compressor and a downstream side of the electric compressor in the intake passage; a flow passage control valve that switches between a state in which the intake air can flow through the intake bypass passage and a state in which the intake air is blocked from flowing through the intake bypass passage; an exhaust bypass passage connected to an exhaust port, the exhaust bypass passage being connected to a downstream side of the compressor and an upstream side of the electric compressor in the intake passage, or the intake bypass passage being connected to a upstream side of the passage control valve; a flow rate control valve provided in the exhaust bypass passage; Equipped with Intake and exhaust system.

2. a control device for controlling the electric compressor, the flow passage control valve, and the flow rate adjustment valve; The control device includes: operating the electric compressor in a state in which the flow path control valve is controlled so that the flow of the intake air through the intake bypass path is blocked; controlling an opening degree of the flow rate regulating valve based on a flow rate of the intake air flowing into the electric compressor during operation of the electric compressor; The intake and exhaust system according to claim 1 .

3. the control device controls an opening degree of the flow rate regulating valve so that a flow rate of the intake air flowing into the electric compressor is maintained equal to or less than a reference flow rate while the electric compressor is in operation. The intake and exhaust system according to claim 2 .

4. When a pressure of the intake air discharged from the electric compressor exceeds a pressure of the intake air discharged from the electric compressor during operation of the electric compressor, the control device stops the electric compressor and controls the flow path control valve so that the intake air can flow through the intake bypass path. The intake and exhaust system according to claim 2 or 3.

5. a downstream end of the exhaust bypass passage communicates with an exhaust port provided in the exhaust passage; The control device controls an opening degree of the flow rate adjustment valve based on a concentration of nitrogen oxides discharged from the exhaust port of the exhaust flow path. The intake and exhaust system according to any one of claims 2 to 4.

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