JP3933078B2 - Supercharger for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an engine provided with a supercharger, and more particularly to a control device that has a bypass passage that bypasses the supercharger and switches these intake paths in accordance with operating conditions.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a technique using a supercharger such as a turbocharger is known as a method for improving engine torque.
[0003]
A turbocharger comprising a supercharger driven by an electric motor, a bypass passage that bypasses the supercharger, and a bypass valve that adjusts the opening degree of the bypass passage, when the required load increases due to acceleration or the like Patent Document 1 discloses a supercharging system that closes a bypass passage, performs supercharging by a supercharger, and supplies intake air to the engine through the bypass passage during normal operation.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-280145
[Problems to be solved by the present invention]
However, in the system described in Patent Document 1, it is necessary to provide a throttle valve for adjusting the amount of intake air supplied to the engine in addition to the bypass valve. Therefore, there are two valves in the intake passage, and there are problems of increased intake resistance, increased cost, and complicated control.
[0006]
Accordingly, an object of the present invention is to reduce intake resistance and cost, and to prevent complicated control of intake passage switching and intake air amount adjustment.
[0007]
[Means for Solving the Problems]
The supercharger of the present invention includes a positive displacement supercharger driven by an electric motor in an intake passage, and has an inlet upstream and an outlet downstream of the electric supercharger. A bypass passage that bypasses the intake passage and communicates with the intake passage, an on-off valve that makes the opening degree of the bypass passage variable, a required output detection means that detects a required output of the engine, and a required intake air amount based on the required output Required intake air amount calculating means for determining the required intake air amount by driving the on-off valve and the electric supercharger, and rotation of the electric supercharger when the engine is at a predetermined low load. Rotation lock means forbidden .
[0008]
[Action / Effect]
According to the present invention, since the on-off valve interposed in the bypass passage serves both as the opening adjustment function and the throttle function of the bypass passage, the cost is reduced as compared with the supercharging device including the opening adjustment valve and the throttle valve. In addition, the intake resistance in the intake passage can be reduced. In addition, since the rotation of the electric supercharger is locked during low load operation, the intake air flow due to the rotation of the electric supercharger can be prevented and the intake air amount can be accurately controlled.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0010]
FIG. 1 is a diagram showing the system configuration of this embodiment. Reference numeral 23 is an engine, and 3 is a turbocharger driven by exhaust of the engine 23.
[0011]
The turbocharger 3 includes a compressor 4, a turbine 5, and a shaft 6 that connects them. When the turbine 5 is rotated by exhaust of the engine 23, the compressor 4 that is connected to the turbine 5 via the shaft 6 is The air that has been rotated and passed through the air flow meter 1 provided in the intake passage 2 upstream of the turbocharger 3 is pumped to the intake passage 7 downstream.
[0012]
An intake air passage 7 downstream of the turbocharger 3 is provided with an intercooler 8 that cools the intake air that has been compressed by the turbocharger 3 and has reached a high temperature.
[0013]
The intake passage 7 is branched into an intake passage 10 and a bypass passage 11 at a branch point 9 downstream of the intercooler 8, and the intake passage 10 becomes hot after passing through the electric supercharger 16 and the electric supercharger 16. An intercooler 20 that cools the intake air is provided.
[0014]
The electric supercharger 16 used in the present embodiment is a positive displacement supercharger, and includes a compressor 17 and an electric motor 18 connected to the compressor 17 via a shaft 19. The electric motor 18 receives a motor controller 26 from a power source 27. It is driven by the electric power supplied through it. The electric motor 18 has a power generation function and can recover the rotation of the compressor 17 as electric power. A rotation speed sensor 29 is provided in the vicinity of the shaft 19 to detect the rotation speed of the electric supercharger 16.
[0015]
The bypass passage 11 is provided with an opening / closing valve 12 for adjusting the opening degree of the bypass passage 11, a pressure sensor 13 for detecting the pressure upstream of the opening / closing valve 12, and a pressure sensor 14 for detecting the downstream pressure. Detection values of the pressure sensors 13 and 14 are read into a control unit (ECU) 25.
[0016]
The intake passage 10 and the bypass passage 11 merge at a junction 15 downstream of the intercooler 20 and downstream of the on-off valve 12 to form an intake passage 21 and are connected to an intake manifold 22 of the engine 23.
[0017]
In addition to the above detection values, the ECU 25 reads the detection values of the accelerator opening sensor 30 and the engine speed sensor 31. The ECU 25 determines whether or not there is an acceleration request from the detected value of the accelerator opening sensor 30, and drives the electric supercharger 16 based on the detected values of the engine speed sensor 31, the speed sensor 29, the pressure sensors 13, 14 and the like. And the opening / closing of the on-off valve 12 is controlled. The determination of the acceleration request is made by creating a table in which the predetermined value is determined for each engine speed, and searching based on the detection value of the engine speed sensor 31. In order to simplify the control, a method may be used in which a threshold value corresponding to a predetermined accelerator opening is provided in advance and compared with a detection value of the accelerator opening sensor 30.
[0018]
In the present embodiment, the intake air amount is adjusted by associating and controlling the on-off valve 12 and the electric supercharger 16 without providing the throttle valve provided for adjusting the intake air amount in the conventional engine. As a result, the present system can prevent an increase in intake resistance in the intake path.
[0019]
FIG. 2 shows a flowchart of control of the electric supercharger 16 and the bypass valve 12 executed by the ECU 25.
[0020]
In step S100, it is determined whether or not there is an acceleration request exceeding a predetermined required output based on the accelerator opening or the like. The predetermined required output is an output that requires supercharging by the electric supercharger 16.
[0021]
If there is a predetermined acceleration request, the electric supercharger 16 is driven in step S101 and the process proceeds to step S102. In step S102, the subroutine shown in FIG. 5 is executed to control the intake air amount.
[0022]
In step S301 in FIG. 5, the on-off valve 12 is fully closed, and the air supplied to the engine 23 is controlled by controlling the rotational speed of the electric supercharger 16 according to the required intake air amount obtained from the accelerator opening degree in step S302. Adjust the amount. Since the electric supercharger used in the present embodiment is a positive displacement type, the amount of air pumped per rotation is constant, and the amount of air can be adjusted by controlling the number of rotations.
[0023]
If there is no acceleration request in step S100, the process proceeds to step S103, and the electric supercharger 16 is not driven (OFF), and in step S104, the electric motor is rotated by the accelerator opening, the intake air amount, and the intake negative pressure of the engine 23. The opening degree of the on-off valve 12 is determined according to the rotational speed of the supercharger 16, and the process proceeds to step S105. The required intake air amount of the engine 23, that is, the target intake air amount, is calculated by the ECU 25 based on the accelerator opening and the engine speed in principle, and the actual intake air amount measured by the air flow meter 1 is the target intake air amount. The opening degree of the on-off valve 12 through which the air amount obtained by subtracting the air amount passing through the electric supercharger 16 from the actual intake air amount is determined so as to coincide with the amount.
[0024]
In step S105, it is determined whether or not the opening degree of the on-off valve 12 determined in step S104 is equal to or less than a predetermined opening degree. The predetermined opening used here will be described with reference to FIG.
[0025]
FIG. 4 is a table of engine speed and engine torque, and a solid line B represents the engine torque when the on-off valve 12 is fully open. In the present embodiment, when the torque of the engine 23 is equal to or less than the predetermined torque indicated by the solid line A (region C indicated by the oblique lines), the rotation of the electric supercharger 16 is prohibited (locked), and the engine torque is determined to be the predetermined torque. Let the opening degree of the on-off valve 12 when it becomes (solid line A) be a predetermined opening degree.
[0026]
If it is less than the predetermined opening, the process proceeds to step S106, and the rotation of the electric supercharger 16 is locked according to a subroutine to be described later. If it is equal to or greater than the predetermined opening, the process proceeds to step S107.
[0027]
In step S107, the electric supercharger 16 is freely rotated, and the air supplied to the engine 23 is controlled by controlling the opening degree of the on-off valve 12 in accordance with the rotational speed of the electric supercharger 16 rotated by the suction negative pressure of the engine 23. Adjust the amount.
[0028]
Here, the rotation lock of the electric supercharger 16 performed in step S106 will be described with reference to FIG.
[0029]
FIG. 3 shows a control subroutine performed in step S105. In step S201, it is determined whether or not the rotational speed of the electric supercharger 16 is equal to or lower than a predetermined rotational speed. If the rotational speed is equal to or lower than the predetermined rotational speed, the process proceeds to step S202. In step S202, the motor controller 26 applies a current in the opposite phase to that when the electric supercharger 16 is driven to the electric motor 18, and brakes the rotation of the electric supercharger 16 due to the suction negative pressure (reverse phase braking mode). In step S203, the rotation of the electric supercharger 16 is locked, and the amount of air supplied to the engine 23 is adjusted only by opening control of the on-off valve 12.
[0030]
If the rotational speed of the electric supercharger 16 is larger than the predetermined rotational speed in step S201, the process proceeds to step S204, where the electric motor 18 is caused to function as a generator and the rotational energy of the electric supercharger 16 is recovered as electric power (regenerative braking). Mode), returning to step S201 again and repeating the above control. When the rotational speed of the electric supercharger 16 decreases to a predetermined rotational speed, the process proceeds to step S202, and the reverse phase braking mode is set.
[0031]
Thereby, even when the rotational speed of the electric supercharger 16 is high, it is not necessary to flow a large negative phase current, and the rotational energy of the electric supercharger 16 until the rotational speed is decreased to a predetermined rotational speed can be recovered as electric power.
[0032]
As described above, in the present embodiment, the on-off valve 12 combines the switching of the intake path and the control of the amount of air supplied to the engine 23, so that only one valve is required in the intake path, reducing the intake resistance and cost. Can be reduced.
[0033]
When the electric supercharger 16 is stopped and the on-off valve 12 is below a predetermined opening, that is, when the engine 23 is operating at a low load, the rotation of the electric supercharger 16 is locked, so that inflow of intake air due to rotation of the electric supercharger 16 is prevented In addition, the intake air amount can be accurately controlled.
[0034]
When the rotation of the electric supercharger 16 is locked, if it is higher than the predetermined rotation number, the regenerative braking mode is switched to lower the rotation number, so that energy can be recovered and the rotation can be locked. It is also possible to reduce the negative phase current.
[0035]
Since there is no intake resistance in the intake passage 21 from the on-off valve 12 to the intake manifold 22, it is possible to improve the transient response of supercharging if the distance from the on-off valve 12 to the intake manifold 22 is made as short as possible. It is.
[0036]
Since the intercooler 8 is provided downstream of the turbocharger 3 and upstream of the branching point 9 and the intercooler 20 is provided downstream of the electric supercharger 16 and upstream of the junction 15, the electric supercharger 16 is driven when the electric supercharger 16 is driven. It is possible to increase the oxygen density of the air supplied to the engine 23 and obtain high torque by cooling the air passing through the machine 16 with the enter cooler 8 and cooling with the intercooler 20 even after passing through the electric supercharger 16. It is. Further, when the electric supercharger 16 is stopped, the air after passing through the turbocharger 3 is cooled by the intercooler 8 and does not pass through the intercooler 20, so that pressure loss due to passing through the intercooler 20 can be prevented.
[0037]
As shown in the system configuration diagram of FIG. 7, the intercooler 8 is provided in the intake passage 7 downstream of the branch point 9 and upstream of the electric supercharger 16, and the intercooler 20 is provided in the intake passage 21 downstream of the junction 15. Even if provided, the cooling effect is the same.
[0038]
Further, the method of locking the rotation of the electric supercharger 16 is not limited to the method of applying a reverse-phase current to the electric motor 18 described above, and is engaged with a mechanical locking means, for example, the shaft 19 so that the shaft 19 cannot be rotated. A method using a fixing device is also conceivable.
[0039]
A second embodiment will be described with reference to FIG.
[0040]
FIG. 8 shows the system configuration of the second embodiment. The only difference from the first embodiment is the arrangement of the intercoolers 8 and 20. In this embodiment, the intercooler 8 is arranged in the intake passage 7 downstream of the turbocharger 3 and upstream of the branch point 9. An intercooler 20 is disposed in the downstream intake passage 21.
[0041]
As a result, in this embodiment, the intake air passes through the intercoolers 8 and 20 regardless of whether the electric supercharger 16 is driven or stopped. Therefore, even when the cooling performance equivalent to that of the first embodiment is ensured, each intercooler Can be miniaturized, and the degree of freedom of in-vehicle layout increases.
[0042]
The control of the on-off valve 12 is basically the same as in the first embodiment, but the control performed in step S102 in FIG. 2 is different.
[0043]
FIG. 6 shows a flowchart of the control performed in step S102. When the electric supercharger is driven in step S101, the on-off valve 12 is fully closed after a predetermined time has elapsed in step S401. In step S402, the intake air amount is controlled by controlling the rotational speed of the electric supercharger 16.
[0044]
The predetermined time is determined by measuring in advance the time required for the electric supercharger 16 to reach a superchargeable rotational speed from the start of driving. If the open / close valve 12 is fully closed when the rotational speed of the electric supercharger 16 is not sufficiently high, the amount of air supplied to the engine 23 is drastically reduced and a shock due to torque fluctuation occurs. In the embodiment, air is also supplied from the bypass passage 11 until the rotational speed at which the electric supercharger 16 can be supercharged is reached, so that the aforementioned shock due to torque fluctuation can be prevented.
[0045]
As described above, in the present embodiment, in addition to the same effects as those of the first embodiment, the two intercoolers are arranged in series, so that the capacity of each intercooler can be reduced, and the degree of freedom of the layout in the vehicle increases. .
[0046]
When the acceleration request is detected and the electric supercharger 16 is driven, the on-off valve 12 is opened until the electric supercharger 16 reaches a revolving speed at which the electric supercharger 16 can be supercharged. It becomes possible to do.
[0047]
As shown in FIG. 9, the intercooler 8 is disposed in the bypass passage 11 upstream of the on-off valve 12 and downstream of the branching base point 9, and the intercooler 20 is intake air downstream of the electric supercharger 16 and upstream of the junction 15. When arranged in the passage 10, the intercooler 8 cools only the air that has passed through the turbocharger 3, and the intercooler 20 cools only the air that has passed through the electric supercharger 16, so each intercooler is downsized. This makes it possible to increase the degree of freedom of layout when mounted on a vehicle.
[0048]
A third embodiment will be described with reference to FIG.
[0049]
The configuration of the present embodiment is obtained by removing the turbocharger 3 and the intercooler 8 downstream of the turbocharger 3 from the configuration of the first embodiment, and the intake passage 2 is connected to the intake passage 10 downstream of the air flow meter 1. Branches to the bypass passage 11. The downstream of the branch point 9 has the same configuration as that of the first embodiment shown in FIG.
[0050]
The control of the electric supercharger 16 and the on-off valve 12 is basically the same as in the first embodiment. However, the subroutine executed in step S102 of FIG. 2 is as shown in FIG.
[0051]
In step S501 of FIG. 11, the air amount Qa passing through the air flow meter 1 and the air amount Qs passing through the intake passage 10 are read into the ECU 25.
[0052]
In step S502, the on-off valve 12 is fully closed when the air amount Qa passing through the air flow meter 1 and the air amount Qs passing through the intake passage 10 become equal. This is because when the amount of air Qa passing through the air flow meter 1 and the amount of air Qs passing through the intake passage 10 are equal, air does not flow through the bypass passage 11 and is supplied to the engine 23 even if the on-off valve 12 is fully closed. This is because the amount of air does not change and the occurrence of shock due to torque fluctuation can be prevented.
[0053]
In step S503, the rotational speed of the electric supercharger 16 is controlled according to the required intake air amount of the engine 23.
[0054]
As described above, in the present embodiment, similarly to the first embodiment, the on-off valve 12 combines the switching of the intake system path and the control of the amount of air supplied to the engine 23, so the number of valves in the intake path is one. It is possible to reduce intake resistance and cost.
[0055]
When the electric supercharger 16 is stopped and the on-off valve 12 is below a predetermined opening, that is, when the engine 23 is operating at a low load, the rotation of the electric supercharger 16 is locked, so that inflow of intake air due to rotation of the electric supercharger 16 is prevented it can.
[0056]
When the rotation of the electric supercharger 16 is locked, if the rotation speed is higher than the predetermined rotation speed, the regenerative braking mode is switched to lower the rotation speed, so that the energy can be recovered and the reverse for locking the rotation. The phase current can also be reduced.
[0057]
Similarly to the second embodiment, when the acceleration request is detected and the electric supercharger 16 is driven, the on-off valve 12 is opened until the electric supercharger 16 reaches a rotation speed at which supercharging is possible. Thus, it is possible to prevent a shock due to torque fluctuation of the engine 23.
[0058]
In addition, this invention is not necessarily limited to said embodiment, It cannot be overemphasized that a various change can be made within the range of the technical idea as described in a claim.
[Brief description of the drawings]
FIG. 1 is a diagram showing a system configuration of a first embodiment of the present invention.
FIG. 2 is a control flowchart of the electric supercharger and the bypass valve according to the first embodiment.
FIG. 3 is a flowchart of rotation lock control of the electric supercharger according to the first embodiment.
FIG. 4 is a diagram illustrating a rotation lock region of the electric supercharger.
FIG. 5 is a control subroutine at the start of driving the electric supercharger according to the first embodiment.
FIG. 6 is a control subroutine at the start of driving the electric supercharger according to the second embodiment.
FIG. 7 is a system configuration diagram in which the arrangement of the intercoolers of the first embodiment is different.
FIG. 8 is a diagram illustrating a system configuration of a second embodiment.
FIG. 9 is a system configuration diagram in which the arrangement of the intercoolers of the second embodiment is different.
FIG. 10 is a diagram illustrating a system configuration of a third embodiment.
FIG. 11 is a control subroutine at the start of driving the electric supercharger according to the third embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Airflow meter 2 Intake passage 3 Turbocharger 4 Turbocharger compressor 5 Turbine 6 Shaft 7 Intake passage 8 Intercooler 9 Branch point 10 Intake passage 11 Bypass passage 12 On-off valve 13 Pressure sensor (upstream side)
14 Pressure sensor (downstream side)
15 Junction 16 Electric supercharger 17 Electric supercharger compressor 18 Electric motor 19 Shaft 20 Intercooler 21 Intake passage 22 Intake manifold 23 Engine 24 Exhaust manifold 25 Control unit (ECU)
26 Motor controller 27 Power supply 28 Exhaust passage 29 Rotational speed sensor 30 Accelerator opening sensor 31 Engine speed sensor

Claims (7)

A positive displacement electric supercharger driven by an electric motor is interposed in the intake passage,
A bypass passage having an inlet upstream of the electric supercharger and an outlet downstream, and bypassing the electric supercharger and communicating the intake passage;
An on-off valve that makes the opening of the bypass passage variable;
Requested output detecting means for detecting the requested output of the engine;
A required intake air amount calculating means for obtaining a required intake air amount based on the required output;
Control means for controlling the required intake air amount by driving the on-off valve and the electric supercharger;
Rotation lock means for prohibiting rotation of the electric supercharger when the engine is at a predetermined low load;
A supercharging device for an internal combustion engine, comprising: The control device drives the electric supercharger when the acceleration request exceeds a predetermined required output of the engine and fully closes the on-off valve, and drives the electric supercharger when a non-acceleration request other than the acceleration request is made. The supercharging device for an internal combustion engine according to claim 1, wherein the on-off valve is driven to control the required intake air amount. The supercharging device for an internal combustion engine according to claim 2, wherein the control means fully closes the on-off valve after a predetermined time has elapsed after driving the electric supercharger at the time of the acceleration request. When the non-acceleration request is made, the control means controls the opening / closing valve so that the total amount of air passing through the electric supercharger and the amount of air passing through the opening / closing valve becomes a target intake air amount determined according to the required output. The supercharging device for an internal combustion engine according to claim 2, wherein the opening degree is controlled. The supercharging device for an internal combustion engine according to claim 4 , wherein the rotation lock unit prohibits rotation of the electric supercharger by causing a reverse phase current to flow through the electric motor. The electric supercharger has a regenerative power generation function, and the rotation lock means regeneratively brakes until the electric motor is reduced to a predetermined rotation speed, and locks the rotation by supplying a reverse phase current when the rotation speed is lower than the predetermined rotation speed. The supercharging device for an internal combustion engine according to claim 5 . The supercharger for an internal combustion engine according to any one of claims 1 to 6 , wherein a turbocharger is disposed in an intake passage upstream from an inlet of the bypass passage.

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