JP2005061243A - Supercharger for internal combustion engine - Google Patents

Abstract

To provide a supercharging device in which an electric supercharger does not become an intake resistance in an intake passage when a turbocharger rotates at a high speed, and an intake passage is secured even when the electric supercharger is stopped.
A turbocharger 3 driven by exhaust gas of an engine 14, an electric supercharger 23 interposed in an intake passage 6 downstream of the turbocharger 3 and driven by an electric motor 16, an electric supercharger A bypass passage 30 that bypasses the machine 23 and communicates an upstream side and a downstream side intake passage of the electric supercharger 23, and a bypass valve 9 provided in the vicinity of a junction 31 between the intake passage of the bypass passage 30; The bypass valve 9 and the electric supercharger 23 are controlled in association with each other, and the bypass valve 9 is closed after the electric supercharger starts driving. The bypass valve 9 is closed while the pressure upstream of the electric supercharger 23 is lower than the downstream pressure. The bypass valve control means 19 which controls to open the bypass valve 9 when the supercharging pressure upstream of the electric supercharger 23 becomes substantially equal to the downstream supercharging pressure is provided.
[Selection] Figure 1

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a supercharging device for an internal combustion engine, and more particularly to a supercharging device having a supercharger driven by an electric motor.
[0002]
[Prior art]
As a technique for improving engine output, a turbocharger that is driven by engine exhaust gas and pressurizes intake air is known. However, the turbocharger has a problem that turbocharging cannot be performed in a low engine speed range and a so-called turbo lag in which supercharging is delayed.
[0003]
Therefore, in order to compensate for the drawbacks of the turbocharger described above, Patent Document 1 discloses a technique for installing an electric supercharger that is driven by an electric motor in addition to the turbocharger.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-21573
[Problems to be solved by the present invention]
However, in Patent Document 1, when an electric supercharger is provided downstream of the turbocharger, an intake passage that bypasses the electric supercharger is not provided. When the supercharging pressure due to is exceeded, the electric supercharger becomes an intake resistance, and when the electric supercharger is stopped, the electric supercharger closes the intake passage.
[0006]
Therefore, in the present invention, when the supercharging pressure by the turbocharger exceeds the supercharging pressure by the electric supercharger or when the electric supercharger stops, the electric supercharger becomes an intake resistance in the intake passage, and the intake air An object of the present invention is to provide a supercharging device that is excellent in transient response of supercharging while preventing the passage from being blocked.
[0007]
[Means for Solving the Problems]
A turbocharger for an internal combustion engine according to the present invention includes a turbocharger that is driven by engine exhaust gas, an electric supercharger that is interposed in an intake passage downstream of the turbocharger and is driven by an electric motor, A bypass passage that bypasses the electric supercharger and connects the intake passage on the upstream side and the downstream side of the electric supercharger, a bypass valve that is provided in the vicinity of the junction of the intake passage of the bypass passage, and The bypass valve and the electric supercharger are controlled in association with each other, and the bypass valve is closed after the electric supercharger starts driving, and the bypass valve is closed while the pressure upstream of the electric supercharger is lower than the downstream pressure. And a bypass valve control means for controlling to open the bypass valve when the supercharging pressure upstream of the electric supercharger becomes substantially equal to the downstream supercharging pressure.
[0008]
[Action / Effect]
According to the present invention, the bypass passage for bypassing the electric supercharger provided downstream of the turbocharger and the bypass valve for opening and closing the bypass passage are provided, and the electric supercharger and the bypass valve are controlled in association with each other. The necessary and sufficient amount of air can be supplied to the engine through the bypass passage even when the electric supercharger is stopped or when the turbocharging efficiency of the turbocharger is increased.
[0009]
In addition, since the bypass valve is provided in the bypass passage near the junction of the bypass passage and the intake passage, the intake volume from the electric supercharger to the engine when the bypass valve is closed is small. The transient response of supercharging is improved.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0011]
FIG. 1 is a view showing a system of the present invention mounted on a vehicle, wherein 14 is an engine, and 3 is a turbocharger driven by exhaust gas of the engine 14.
[0012]
An air flow meter (AFM) 1 for measuring an intake air amount Qa taken from an air cleaner (not shown) is installed in the intake passage 2 upstream of the turbocharger 3.
[0013]
The intake passage 6 downstream of the turbocharger 3 is provided with an electric supercharger 23 that performs supercharging by driving the compressor 4 by a drive motor 16. Further, the intake passage 6 bypasses the electric supercharger 23. And a bypass passage 30 connecting the intake passage 10 downstream from the electric supercharger 23, and a bypass valve 9 for opening and closing the bypass passage 30 is interposed.
[0014]
The electric supercharger 23 used in the present embodiment is a Roots type positive displacement supercharger, and air cannot pass through the compressor 4 when the electric supercharger 23 is stopped. Air is bypassed through the passage 30.
[0015]
The bypass valve 9 interposed in the bypass passage 30 is provided as close as possible to the junction 31 between the intake passage 10 and the bypass passage 30 in order to reduce the bypass passage volume downstream of the bypass valve 9 when the valve is closed. In addition, the first intercooler 7a is disposed upstream of the branch portion 32 of the intake passage 6 with the bypass passage 30.
[0016]
Further, the second intercooler 7b is provided downstream of the electric supercharger 23 and upstream of the merging portion 31, and pressure sensors 22 and 24 for detecting the passage pressure are provided upstream and downstream of the bypass valve 9, respectively.
[0017]
The electric supercharger 23 is driven by the motor controller 18 supplying the electric power of the battery 17 to the electric motor 16 based on a signal from the ECM 19, so that the rotational speed does not depend on the rotational speed of the engine 14 and is supercharged. The time until the pressure increases is shorter than that of the turbocharger 3.
[0018]
Therefore, taking advantage of this characteristic, the turbocharging of the turbocharger 3 is increased in a situation where the engine 14 is in a low rotation range or in a situation where the turbocharger 3 cannot perform supercharging, such as a turbo lag in which supercharging is delayed. The electric supercharger 23 is operated in order to cover up to supercharging.
[0019]
A control unit (ECM) 19 is provided to control the electric supercharger 23 and the bypass valve 9. When there is a request for acceleration of the vehicle, the ECM 19 operates the electric supercharger 23 and opens and closes the bypass valve 9 for a few seconds, for example, while there is a turbo lag by the turbocharger 3 in the early stage of acceleration. Supercharge so that the pressure connection is smooth.
[0020]
In the ECM 19, the rotation speed of the compressor 4 detected by the rotation speed sensor 20 disposed in the vicinity of the rotation shaft 23 a connecting the compressor 4 and the motor 16 of the electric supercharger 23 and the acceleration request detected by the acceleration request detection means 12. Are read as the rotation speed detection signal Nc and the acceleration request detection signal Th, respectively.
[0021]
The acceleration request detection means 12 detects the opening degree (or accelerator opening degree) of the throttle valve 12 interposed in the intake passage 10, and when the opening degree of the throttle valve 12 exceeds a predetermined threshold, the vehicle It is determined that the state is an acceleration request state, and an acceleration request detection signal Th is sent to the ECM 19. However, the threshold value is a constant value or a value determined so as to increase gradually according to the engine speed.
[0022]
When the acceleration request signal Th is read into the ECM 19, the ECM 19 sends a drive command to the electric motor 16. At this time, the bypass valve 9 remains open. If acceleration continues as it is, the rotational speed N of the electric motor 16 increases, and the air amount Qa sucked by the engine 14 and the air amount Qs passing through the compressor 4 become equal. At this time, the amount of air flowing through the bypass passage 30 is zero. The ECM 19 detects this state and closes the bypass valve 9. If the bypass valve 9 is opened as it is, the pressure in the intake passage 10 downstream of the electric supercharger 23 becomes higher than the upstream pressure, and the air flows back through the bypass passage 30, so that the air supplied to the engine 14 This is because there is less.
[0023]
The air amount Qa taken in by the engine 14 is detected by the air flow meter 1.
[0024]
The amount of air Qs passing through the electric supercharger 23 is determined approximately by the following equation (1) according to the rotational speed N of the electric motor 16.
[0025]
Qs = conversion coefficient A × compressor rotational speed N (1)
Conversion coefficient A: The bypass valve 9 is completely closed at the moment when the amount of air Qa sucked by the engine 14 such as the amount of air sent out by the compressor 4 per rotation coincides with the amount of air passing through the electric supercharger 23. It is ideal to be. If the rotational speed of the electric motor 16 at this time is the target rotational speed NT, the bypass valve 9 may be closed at the moment when the electric motor 16 reaches the target rotational speed NT.
[0026]
However, a certain delay time T occurs after the valve closing signal is input to the bypass valve 9 until it is completely closed. Therefore, the ECM 19 sends a command signal in consideration of the delay time T to the bypass valve 9.
Further, when the bypass valve 9 is closed and supercharging is performed by the electric supercharger 23, when the rotational speed of the turbocharger 3 increases and the pressures upstream and downstream of the electric supercharger 23 become substantially equal, The bypass valve 9 is opened and the electric supercharger 23 is stopped. This is because when the rotational speed of the turbocharger 3 is further increased, the amount of air pumped by the turbocharger 3 becomes larger than the amount of air pumped by the electric supercharger 23, and the electric supercharger 23 Because it becomes.
[0027]
FIG. 2 shows a control flow of this embodiment performed by the ECM 19.
[0028]
In step S100, it is determined whether or not the vehicle is accelerating.
[0029]
When it is accelerating, it progresses to step S101 and it is determined whether the electric supercharger 23 is operating.
[0030]
If it is determined in step S101 that the electric supercharger 23 is in operation, the process proceeds to step S105, where it is determined whether the bypass valve 9 is open.
[0031]
If the electric supercharger 23 is stopped in step S101, the process proceeds to step S102 and the electric supercharger 23 is operated.
[0032]
If it is determined in step S105 that the bypass valve 9 is open, the process proceeds to step S106, and the target rotational speed NT of the electric supercharger 23 described above is obtained from the engine intake air amount Qa. When the bypass valve 9 is closed, the process proceeds to step S110 described later.
[0033]
In step S107, a predicted rotational speed NF after the lapse of the delay time T is obtained according to a flow described later, and the process proceeds to step S108.
[0034]
The control performed by the ECM 19 in step S107 will be described using the flowchart shown in FIG.
[0035]
In step S201, the current rotation speed N of the electric motor 16 detected by the rotation sensor 20 provided near the shaft 23a of the electric supercharger 23 is read.
[0036]
In step S202, the actual rotational speed increase ΔN of the electric motor 16 is read from the detection value of the rotation sensor 20.
[0037]
In step S203, the current value I and voltage value V of the electric motor 16 are read.
[0038]
In step S204, a table of predicted rotation increases shown in FIG. 4 is searched to determine a rotation speed ΔNMAP that increases during the delay time T. In the table of FIG. 4, the predicted rotation increase value decreases as the rotation speed N increases. As can be seen from the characteristic diagram of a general motor shown in FIG. 5, since the motor has a characteristic that the torque decreases as the rotational speed increases, the rotational speed that increases in a certain time decreases as the rotational speed increases. Because it becomes.
[0039]
In step S205, taking into consideration that the rotation increase speed of the electric motor 16 changes due to a change in load applied to the electric motor 16, deterioration with time, or the like, the actual rotation increase actual speed ΔN is sequentially detected, and from this detection value, a predicted rotation increase value ΔNMAP is detected. Is corrected to ΔN1.
[0040]
In step S206, considering that the rotation increase speed of the electric motor 16 varies with the current value I, the rotation increase predicted value ΔN1 obtained in step S205 is corrected using the detected current value I to be ΔN2.
[0041]
In step S207, considering that the rotation speed of the electric motor 16 varies depending on the voltage value V, the predicted rotation increase value ΔN2 obtained in step S206 is corrected to ΔN3 using the detected voltage value V.
[0042]
In step S208, the predicted rotation speed after the delay time T is obtained by adding the estimated increase value ΔNE obtained by integrating the rotation increase speed ΔN3 obtained in the above and the delay time T to the rotation speed N of the electric motor 16 read in step S201. Find NF.
[0043]
The predicted rotational speed NF is obtained as described above, and the process proceeds to step S108 in FIG.
[0044]
Although correction is performed in steps S205 to S207, it is not always necessary to perform all corrections, and only one or two of them may be used.
[0045]
In step S108, it is determined whether or not the predicted rotational speed NF is equal to or higher than the target rotational speed NT. If the predicted rotational speed NF matches or exceeds the target rotational speed NT, the process proceeds to step S109, and the bypass valve Close 9 If the predicted rotational speed NF is lower than the target rotational speed NT, the process returns to step S100 with the bypass valve 9 open.
[0046]
When the bypass valve 9 is closed in step S105, the process proceeds to step S110, and the upstream pressure P1 and the downstream pressure P2 of the electric supercharger 23 are compared.
[0047]
If the upstream pressure P1 is equal to or higher than the downstream pressure P2, the bypass valve 9 is opened in step S111, and the electric supercharger 23 is stopped in step S112.
[0048]
When the upstream pressure P1 is lower than the downstream pressure P2, supercharging by the electric supercharger 23 is continued as it is.
[0049]
If the vehicle is not accelerating in step S100, the bypass valve 9 is opened in step S103, and the electric supercharger 23 is stopped in step S104.
[0050]
FIG. 6 shows a time chart during the valve closing operation of the above control.
[0051]
The ECM 19 issues a motor drive command at the moment (t = t0) when the opening of the throttle valve 12 exceeds the threshold value set as the acceleration required opening.
[0052]
The electric motor 16 starts driving and the rotational speed N increases, and the predicted rotational speed NF also increases accordingly. When the predicted rotational speed NF reaches the target rotational speed NT when t = t1, the ECM 19 issues a valve closing command to the bypass valve 9.
[0053]
The bypass valve 9 that has received the valve closing command starts the valve closing operation, but the fully closed state is t = t2. The time from t1 to t2 is the delay time T. During the delay time T, the rotation speed of the electric motor 16 continues to increase and reaches the target rotation speed NT at the time t = t2.
[0054]
FIG. 7 shows a time chart of the valve opening operation of the bypass valve 9.
[0055]
At the moment (t = t0) when the opening of the throttle valve 12 exceeds the threshold set as the acceleration required opening, the ECM 19 issues a motor drive command.
[0056]
As the electric motor 16 is turned on, the bypass valve 9 is closed at the timing described above, and both the upstream and downstream pressures increase.
[0057]
As described above, since the rotational speed of the electric supercharger 23 is faster than that of the turbocharger 3, the speed of increase of the downstream pressure P2 is faster than that of the upstream pressure P1. The rotational speed of the electric motor 16 reaches the limit at t01, but the engine rotational speed further increases and the intake air amount increases, so the downstream pressure P2 starts to decrease.
[0058]
On the other hand, the rotational speed of the turbocharger 3 increases as the engine rotational speed increases, so the upstream pressure P1 continues to increase.
[0059]
When the upstream side pressure and the downstream side pressure become equal at t02, the bypass valve 9 is opened and the electric motor 16 is stopped. However, since the turbocharger 3 performs supercharging, the pressure in the intake passage Continues to rise.
[0060]
As described above, the predicted rotational speed NF is set in consideration of the increase in the rotational speed of the electric motor 16 during the delay time T from when the bypass valve 9 receives the valve closing command until the bypass valve 9 is fully closed. Since the valve closing command is issued when the predicted rotational speed NF reaches the target rotational speed NT, the bypass valve 9 is fully closed at the same time when the electric motor 16 reaches the target rotational speed, and the torque fluctuation at the time of closing the valve. Can be prevented.
[0061]
Since the predicted rotation increase value retrieved from the rotation increase predicted value table is corrected based on the actual rotation increase actual speed ΔN that is sequentially detected, the rotation increase speed changes due to a change in load applied to the motor 16 or deterioration with time. Also, an accurate predicted rotational speed NF can be obtained.
[0062]
Since the predicted rotation increase value retrieved from the rotation increase predicted value table is corrected based on the current value I and voltage value V of the motor 16, accurate prediction is possible even if the operating state, power generation state, battery capacity, etc. change. The rotational speed NF can be obtained.
[0063]
When the supercharging by the electric supercharger 23 is being performed with the bypass valve 9 closed, the turbocharger 3 is bypassed when the rotational speed of the turbocharger 3 becomes high and the pressures upstream and downstream of the electric supercharger 23 become substantially equal. Since the valve 9 is opened and the electric supercharger 23 is stopped, air is supplied to the engine 14 through the bypass passage, and the electric supercharger 23 can be prevented from becoming an intake resistance. Since the bypass valve 9 is opened when the upstream and downstream pressures are substantially equal, that is, when the bypass valve 9 is opened, almost no air flows. Therefore, when the bypass valve 9 is opened, the air flow in the intake passage suddenly increases. Will not change. Therefore, it is possible to prevent the occurrence of torque shock when the valve is opened.
[0064]
As described above, in the present embodiment, the following effects can be obtained.
[0065]
A bypass passage 30 parallel to the electric supercharger 23 and a bypass valve 9 for opening and closing the bypass passage 30 are provided. When the electric supercharger 23 is stopped without an acceleration request, and when the acceleration is requested, the turbocharger 3 Since the bypass valve 9 is opened in a state where the supercharging efficiency is increased, the required amount of air is supplied to the engine 14 through the bypass passage 30. That is, the electric supercharger 23 does not close the intake passage when stopped, and the electric supercharger 23 does not become an intake resistance when the turbocharger 3 is operating with high efficiency.
[0066]
Since the bypass valve 9 is provided in the vicinity of the merge portion 31 of the bypass passage 30, the volume between the bypass valve 9 and the merge portion 31 when the bypass valve 9 is closed is reduced. Thereby, since the intake volume from the electric supercharger 23 to the engine 14 can be reduced, the transient response when the electric supercharger 23 is driven is improved.
[0067]
Since the exhaust gas is not used to drive the electric supercharger 23 that performs supplementary supercharging until the supercharge of the turbocharger 3 rises, only the electric motor 16 is driven. There is almost no heat transfer. As a result, the temperature rise during driving of the electric motor 16 can be suppressed, so that the supercharging pressure of the turbocharger 3 does not increase easily on an uphill road, etc. Even when it has to be supplied, the electric supercharger 23 can be driven without stopping.
[0068]
By providing the intercooler 7a upstream of the branch portion 32 of the intake passage 6, the air that has been compressed by the turbocharger 3 and heated to high temperature can be improved by the intercooler 7a while improving the engine torque and reducing the knock. Since it is supplied to the electric supercharger 23 after being cooled, the amount of heat transferred from the compressor 4 of the electric supercharger 23 to the shaft 23a and the electric motor 16 is reduced, and the efficiency of the electric motor 16 can be improved.
As a result, the current value of the electric motor 16 is increased to improve the torque, and acceleration immediately after the acceleration request requested by the driver can be realized.
[0069]
Since the bypass valve 9, the turbocharger 3, and the electric supercharger 23 are controlled in association with each other, torque fluctuations and air-fuel ratio shifts caused by the ON / OFF of the electric supercharger 23 can be prevented, and the motor 16 is driven. Therefore, there is no shock associated with the clutch connection as in the conventional mechanical supercharger. Therefore, an unpleasant shock is not transmitted to the driver when acceleration is requested.
[0070]
Since exhaust gas is not used to drive the electric supercharger 23, there is no restriction on the positional relationship with the exhaust pipe, and the degree of freedom in layout is increased. Therefore, by shortening the path length from the electric supercharger 23 to the throttle valve 12 as much as possible, it is possible to improve the transient response when the electric supercharger 23 is in operation.
[0071]
Since exhaust gas is not used to drive the electric supercharger 23, it is not necessary to switch the exhaust path when the electric supercharger 23 is turned on and off, and the valve necessary for switching the pipe is only for the intake pipe. In FIG. 5, only the bypass valve 9 provided in the bypass passage 30 is provided. Thereby, it is possible to prevent the control associated with the bypass valve 9, the turbocharger 3, and the electric supercharger 23 from becoming complicated.
[0072]
A second embodiment will be described with reference to FIG.
[0073]
The difference between the present embodiment and the first embodiment is a place where the first intercooler 7 a is installed. In the present embodiment, the intercooler 7 a is installed upstream of the bypass valve 9 in the bypass passage 30. The opening / closing control of the bypass valve 9 and the drive control of the electric supercharger 23 are the same as in the first embodiment.
[0074]
With the above configuration, when the bypass valve 9 is closed and the electric supercharger 23 is driven during acceleration, the air pressurized by the turbocharger 3 is supplied to the electric supercharger 23 as it is. As a result, the pressure loss is reduced as compared with the case where the electric supercharger 23 is supplied after passing through the intercooler 7a, so that the transient response of supercharging during acceleration is improved.
[0075]
The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.
[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 flowchart of opening / closing control of the bypass valve according to the first embodiment.
FIG. 3 is a flowchart for obtaining a predicted rotation speed of the electric supercharger.
FIG. 4 is a table of predicted rotation rise values.
FIG. 5 is a characteristic diagram of a general electric motor.
FIG. 6 is a time chart during valve closing operation.
FIG. 7 is a time chart during valve opening operation.
FIG. 8 is a diagram illustrating a system according to a second embodiment.
[Explanation of symbols]
1 Air flow meter (AFM)
3 Turbocharger 4 Compressor 6 Intake passage 7a Intercooler (first intercooler)
7b Intercooler (second intercooler)
DESCRIPTION OF SYMBOLS 9 Bypass valve 10 Intake passage 12 Throttle valve 14 Engine 16 Electric motor 17 Battery 18 Motor controller 19 Control unit 20 Rotation speed sensor 22, 24 Pressure sensor 23 Electric supercharger 25 Opening / closing sensor 30 Bypass passage 31 Junction part 32 Branch part

Claims (4)

A turbocharger driven by engine exhaust,
An electric supercharger interposed in an intake passage downstream of the turbocharger and driven by an electric motor;
A bypass passage that bypasses the electric supercharger and communicates an upstream side and a downstream side intake passage of the electric supercharger;
A bypass valve provided in the vicinity of a merging portion on the downstream side of the bypass passage with the intake passage;
The bypass valve and the electric supercharger are controlled in association with each other, the bypass valve is closed after the electric supercharger starts driving, and the bypass valve is operated while the pressure upstream of the electric supercharger is lower than the downstream pressure. An internal combustion engine comprising: bypass valve control means for controlling to open the bypass valve when the supercharging pressure upstream of the electric supercharger is substantially equal to the downstream supercharging pressure while being closed. Engine supercharger. The supercharger for an internal combustion engine according to claim 1, wherein the first intercooler is provided in an intake passage downstream of the turbocharger and upstream of a branching portion with the bypass passage. The supercharger for an internal combustion engine according to claim 1, wherein a first intercooler is provided in the bypass passage. The supercharger for an internal combustion engine according to claim 2 or 3, wherein a second intercooler is provided downstream of the electric supercharger and upstream of a junction with the bypass passage.

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