JP4013816B2 - Control device for supercharger with electric motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a supercharger with an electric motor that controls a supercharger with an electric motor disposed on an intake passage of an internal combustion engine mounted on a vehicle.
[0002]
[Prior art]
Attempts to obtain a high output (or low fuel consumption) by providing a supercharger driven by an electric motor on the intake passage of the engine and supercharging by the supercharger have been known for a long time. [Patent Document 1] also describes an internal combustion engine as described above. In the internal combustion engine described in [Patent Document 1], an electric motor (motor) is incorporated in a rotating shaft of a turbine / compressor of a turbo unit. In the internal combustion engine described in [Patent Document 1], the turbo lag after the start is eliminated by starting supercharging by the motor in advance before the vehicle starts, and the transmission is made neutral by making the transmission neutral. Reduces burden and prevents unexpected start of driving due to creep.
[0003]
[Patent Document 1]
JP-A-4-8640 [0004]
[Problems to be solved by the invention]
In the internal combustion engine described in [Patent Document 1], as described above, supercharging is performed in advance by an electric motor in order to eliminate the turbo lag when the vehicle is stopped, but in this way, a subsequent increase in output is predicted at low speeds. If supercharging is performed in advance using an electric motor, there is a risk of overcharging (hereinafter referred to as supercharging). Accordingly, an object of the present invention is to provide a control device for a supercharger with an electric motor that can perform supercharging smoothly while preventing excessive supercharging.
[0005]
[Means for Solving the Problems]
The control device for a supercharger with an electric motor according to claim 1 is provided with a supercharger disposed on an intake passage of an internal combustion engine mounted on a vehicle and driven by the electric motor, and a supercharging pressure by controlling the electric motor. A supercharging pressure control means for controlling the vehicle speed and a speed detection means for detecting the speed of the vehicle. The supercharging pressure control means is provided in the motor when the vehicle speed detected by the speed detection means is equal to or less than a predetermined value. The electric power to be applied is limited to a predetermined electric power or less , and the target rotational speed of the motor is set in the rotational speed region where the rate of change of the supercharging pressure with respect to the rotational speed of the electric motor is a predetermined value or less. Thus, the electric power applied to the electric motor is determined .
[0007]
According to a second aspect of the present invention, in the control device for a supercharger with electric motor according to the first aspect , the supercharging pressure control means sets the target rotational speed of the electric motor to be lower as the EGR amount is larger, and the set target It is characterized in that the electric power applied to the electric motor is determined so as to be the rotational speed.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the control device of the present invention will be described below. An engine 1 having a control device of the present embodiment is shown in FIG.
[0009]
Note that the term “supercharging pressure” is sometimes used as a term indicating a differential pressure with respect to atmospheric pressure. On the other hand, the term “supercharging pressure” may be used as a term indicating absolute pressure in the intake pipe. In the following, when it is necessary to divide and explain the two, the explanation will be made so that the point is clear. For example, when supercharging pressure control is performed based on the output of a pressure sensor that detects the pressure in the intake pipe, if this pressure sensor is a sensor that detects a differential pressure with respect to atmospheric pressure, the supercharging pressure control is “as a difference with respect to atmospheric pressure”. It is easy to control based on the “supercharging pressure”, and if the pressure sensor detects the absolute pressure, the supercharging pressure control is controlled based on the “intake pressure as the absolute pressure”. Is easy.
[0010]
The engine 1 described in the present embodiment is a multi-cylinder engine, but only one cylinder is shown in FIG. 1 as a sectional view. The engine 1 is a type of engine in which fuel is injected into a cylinder 3 by an injector 2. The engine 1 is a so-called lean burn engine and can also perform stratified combustion. A larger amount of intake air can be supercharged by a supercharger 20 and a turbocharger 11 by an electric motor 20a, which will be described later, so that not only high output but also low fuel consumption can be realized.
[0011]
The engine 1 can perform stratified combustion by injecting fuel into a recess formed in the upper surface of the piston 4 during the compression stroke, and can also perform normal homogeneous combustion by intake stroke injection. An intake valve 8 opens and closes the inside of the cylinder 3 and the intake passage 5. The exhaust gas after combustion is exhausted to the exhaust passage 6. An exhaust valve 9 opens and closes the inside of the cylinder 3 and the exhaust passage 6. On the intake passage 5, an air cleaner 10, an air flow meter 27, a supercharger 20, a turbo unit 11, an intercooler 12, a throttle valve 13, and the like are arranged from the upstream side.
[0012]
The air cleaner 10 is a filter that removes dust and dirt in the intake air. The air flow meter 27 of this embodiment is of a hot wire type and detects the amount of intake air as a mass flow rate. The supercharger 20 is electrically driven by a built-in electric motor (motor) 20a. A compressor wheel is directly connected to the output shaft of the motor 20a. The motor 20 a of the supercharger 20 is connected to the battery 22 via the controller 21. The controller 21 controls the drive power of the motor 20a by controlling the power supplied to the motor 20a. The rotation speed of the motor 20a (that is, the rotation speed of the compressor wheel) can be detected by the controller 21.
[0013]
A bypass path 24 is provided so as to bypass the upstream side and the downstream side of the supercharger 20. A valve 25 for adjusting the amount of intake air passing through the bypass path 24 is disposed on the bypass path 24. The valve 25 is electrically driven to arbitrarily adjust the air flow rate through the bypass path 24. When the supercharger 20 is not operating, the supercharger 20 acts as an intake resistance, so that the bypass 25 is opened by the valve 25 to avoid the supercharger 20 becoming an intake resistance. To do. On the contrary, when the supercharger 20 is operated, the bypass path 24 is blocked by the valve 25 in order to prevent the intake air supercharged by the supercharger 20 from flowing back through the bypass path 24.
[0014]
The turbo unit 11 is disposed between the intake passage 5 and the exhaust passage 6 and performs supercharging. That is, in the engine 1 of this embodiment, supercharging can be performed by the supercharger 20 and the turbo unit 11 that are arranged in series. The turbo unit 11 has a variable nozzle mechanism 11a as a variable geometry mechanism. The variable nozzle mechanism 11a is controlled by an ECU 16 described later. On the downstream side of the turbo unit 11, an air-cooled intercooler 12 that lowers the temperature of the intake air whose temperature has increased due to an increase in pressure due to supercharging of the turbocharger 20 or the turbo unit 11 is disposed. The temperature of the intake air is lowered by the intercooler 12 to improve the filling efficiency.
[0015]
A throttle valve 13 that adjusts the amount of intake air is disposed downstream of the intercooler 12. The throttle valve 13 of the present embodiment is a so-called electronically controlled throttle valve, and an operation amount of the accelerator pedal 14 is detected by an accelerator positioning sensor 15, and the ECU 16 detects the throttle valve 13 based on this detection result and other information amounts. Is determined. The throttle valve 13 is opened and closed by a throttle motor 17 that is provided in association therewith. Further, a throttle positioning sensor 18 that detects the opening degree of the throttle valve 13 is also provided.
[0016]
A pressure sensor 19 for detecting the pressure (supercharging pressure / intake pressure) in the intake passage 5 is also provided on the downstream side of the throttle valve 13. These sensors 15, 18, 19, and 27 are connected to the ECU 16, and the detection results are sent to the ECU 16. The ECU 16 is an electronic control unit that includes a CPU, a ROM, a RAM, and the like. The ECU 16 is connected to the injector 2, the spark plug 7, the valve 25, the air flow meter 27, the controller 21, the battery 22, and the like, which are controlled by signals from the ECU 16, or are in a state (in the battery 22). If so, the charge state) is monitored.
[0017]
The motor 20 a of the supercharger 20 described above is also connected to the ECU 16 via the controller 21 and is controlled by the ECU 16 and the controller 21. Since the ECU 16 and the controller 21 can control the supercharging pressure by controlling the electric motor 20a, they function as supercharging pressure control means here. In the present embodiment, the supercharging pressure control is performed using the intake air amount as the operation state of the engine 1. Since the amount of intake air is detected by the air flow meter 27, the air flow meter functions as an operating state detection means here. Further, as will be described in detail later, a supercharging pressure upper limit that can be supercharged is set by the ECU 16 based on the detected intake air amount. That is, in the present embodiment, the ECU 16 also functions as an upper limit setting unit.
[0018]
On the other hand, an exhaust purification catalyst 23 for purifying exhaust gas is attached on the exhaust passage 6 downstream of the turbo unit 11. A crank positioning sensor 26 that detects the rotational position of the crankshaft is attached in the vicinity of the crankshaft of the engine 1. The crank positioning sensor 26 can also detect the engine speed from the position of the crank position.
[0019]
Further, an EGR (Exhaust Gas Recirculation) passage 28 for recirculating the exhaust gas from the exhaust passage 6 (upstream of the turbo unit 11) to the intake passage 5 (surge tank portion formed downstream of the pressure sensor 19) is arranged. It is installed. An EGR valve 29 for adjusting the exhaust gas recirculation amount (EGR amount) is mounted on the EGR passage 28. The opening degree (DUTY ratio) control of the EGR valve 25 is also performed by the ECU 16 described above. Although not shown, an EGR cooler that cools the EGR gas by using the cooling water of the engine 1 is provided between the EGR valve 29 and the surge tank of the intake passage 5.
[0020]
In the present embodiment, when the vehicle speed is equal to or less than a predetermined value, particularly when the vehicle is stopped or traveling at a low speed, the power applied to the motor 20a is limited to be equal to or less than the predetermined power. In this way, supercharging can be prevented while eliminating the turbo lag after the vehicle starts. Here, the target rotational speed of the motor 20a is set in a rotational speed region where the rate of change of the supercharging pressure with respect to the rotational speed of the motor 20a is equal to or less than a predetermined value, and the power applied to the motor 20a is determined so as to be the target rotational speed. Is done. At this time, the target rotational speed of the motor 20a is set lower as the EGR amount increases.
[0021]
Flow charts for this control are shown in FIGS. First, it is determined whether or not the supercharging condition using the supercharger 20 (motor 20a) is satisfied (step 200). The start / maintenance condition mentioned here is a condition in which it is possible to determine that the output increase is necessary or that the output increase is predicted. The start / maintenance condition is a determination condition for starting if the supercharging by the motor 20a has not been started, and a determination condition for maintaining the supercharging by the motor 20a if it has already started. If step 200 is negative, supercharging using the supercharger 20 is not performed and the flowcharts of FIGS. 2 and 3 are exited.
[0022]
On the other hand, when step 200 is affirmed and it is determined that supercharging by the supercharger 20 (motor 20a) is necessary, first, based on the accelerator opening, engine speed, and engine load, the target supercharging pressure Pt and The target fresh air amount Gat is determined by the ECU 16 (step 205). The accelerator opening is detected by an accelerator positioning sensor 15. The engine speed is detected by a crank positioning sensor 26. The engine load is calculated based on the intake air amount detected by the air flow meter 27 and the throttle opening detected by the throttle positioning sensor 18.
[0023]
The gas supplied to the cylinder 3 is composed of air newly sucked from the atmosphere (fresh air) and exhaust gas recirculated by the EGR mechanism. The target fresh air amount Gat is a target of this new air amount. In order for the engine 1 to obtain a certain output, the amount of air necessary for the combustion is required as fresh air. Next, the vehicle speed V is detected (step 210). The vehicle speed V is calculated (detected) by the ECU 16 based on a detection result of a vehicle speed sensor (not shown) attached to each wheel. Then, it is determined whether or not the detected vehicle speed V exceeds a predetermined value (step 215).
[0024]
If the vehicle speed V exceeds the predetermined value, the target rotational speed of the motor 20a is determined based on the target boost pressure Pt and the target fresh air amount Gat determined in step 205 as usual (step 220). On the other hand, if the vehicle speed V is equal to or lower than the predetermined value, the target rotational speed is limited to determine the target rotational speed of the motor 20a (step 220). As will be described later, limiting the target rotational speed of the motor 20a limits the amount of power applied to the motor 20a (limits it to a predetermined power or lower).
[0025]
In this case, the upper limit of the rotational speed is determined, and the target rotational speed may be determined based on the target boost pressure Pt and the target fresh air amount Gat within a range not exceeding the upper limit. When the upper limit is exceeded, a predetermined fixed target rotational speed may be used. At this time, as shown in FIG. 4, the target rotational speed is limited within a region where the supercharging pressure sensitivity is low. The graph of FIG. 4 shows the relationship between the rotation speed of the compressor wheel (that is, equal to the rotation speed of the motor 20a) and the supercharging pressure, and the compressor operating line shows an increase in the compressor rotation speed as shown in the figure. In contrast, the boost pressure rises exponentially.
[0026]
For this reason, on the side where the compressor speed is low, there is a region where the change in the supercharging pressure is slow with respect to the change in the compressor speed. The above-described low supercharging pressure sensitivity means this region, that is, the rate of change of the supercharging pressure with respect to the rotation speed of the motor 20a (here, equal to the rotation speed of the compressor wheel) is low. That is, limiting the target rotational speed of the motor 20a to a range where the change in the supercharging pressure is small with respect to the rotational speed of the motor 20a makes the power applied to the motor 20a less than or equal to a predetermined power.
[0027]
Thereafter, it is further determined whether or not the exhaust gas recirculation by EGR is possible (step 230). If there is no room for inhaling the target fresh air amount Gat described above, exhaust gas recirculation by EGR cannot be performed because the fresh air amount is reduced when EGR is performed. However, when exhaust gas recirculation by EGR is possible, exhaust gas recirculation by EGR is performed to improve exhaust emission performance and fuel efficiency. When exhaust gas recirculation by EGR is possible, that is, when step 230 is affirmed, the amount of electric power to be applied to the motor 20a is determined based on the target rotational speed described above, taking the EGR amount into consideration (step). 235).
[0028]
The EGR amount is calculated by another routine. In the present embodiment, at this time, the target rotational speed determined in step 220 or step 225 is corrected (set) so that the target rotational speed of the motor 20a decreases as the EGR amount increases. The amount of electric power that can be applied to the motor 20a is determined based on the target rotational speed that is corrected in consideration of the EGR amount. When the applied power amount is determined, the motor 20a is driven based on the applied power amount, and supercharging by the supercharger 20 is performed (step 240). After step 240, the actual fresh air amount Ga is detected by the air flow meter 27 (step 245), and it is determined whether or not the detected fresh air amount Ga reaches the target fresh air amount Gat (step 250). .
[0029]
When the fresh air amount Ga has not reached the target fresh air amount Gat, that is, when step 250 is denied, the EGR valve 29 is controlled to reduce the exhaust gas recirculation amount by EGR, and the opening degree of the variable nozzle mechanism 11a. (Step 255). In this way, the amount of fresh air is increased, and supercharging by the turbo unit 11 is promoted in order to eliminate the turbo lag that occurs when the amount of fresh air is small (the amount of EGR is large). Reduce. On the other hand, when the fresh air amount Ga has reached the target fresh air amount Gat, that is, when step 250 is affirmed, the EGR valve 29 is controlled to increase the exhaust gas recirculation amount by EGR and the variable nozzle mechanism 11a. The opening is opened (step 260). By doing in this way, the amount of fresh air can be reduced, the amount of EGR can be secured, and the fuel consumption can be improved.
[0030]
If step 230 is negative, that is, if exhaust gas recirculation by EGR cannot be performed, the amount of electric power applied to the motor 20a is determined based on the target rotational speed described above (step 265), and the determined application is determined. Based on the amount of electric power, the motor 20a is driven to perform supercharging by the supercharger 20 (step 270). After step 255, step 260 or step 270, the actual boost pressure P is detected by the pressure sensor 19 (step 275), and it is determined whether or not the detected boost pressure P has reached the target boost pressure Pt described above. Determination is made (step 280).
[0031]
If the supercharging pressure P has reached the target supercharging pressure Pt, that is, if step 280 is affirmed, the current state is further within the region where the target supercharging pressure Pt can be achieved without driving the motor 20a. It is determined whether or not there is (step 285). If the current state is within the region where the target supercharging pressure Pt can be achieved without driving the motor 20a, the driving of the motor 20a is stopped and the supercharging by the supercharger 20 is finished (step 290).
[0032]
On the other hand, even when the supercharging pressure P has not reached the target supercharging pressure Pt (when step 280 is denied), or even when the supercharging pressure P has reached the target supercharging pressure Pt, the current state is the motor. If it is within the region where the target supercharging pressure Pt can be achieved unless 20a is driven (when step 285 is denied), it is determined whether or not a condition for stopping supercharging by the supercharger 20 is satisfied. Determination is made (step 295). If the stop condition is satisfied, the driving of the motor 20a is stopped, and the supercharging by the supercharger 20 is finished (step 290). If the stop condition is not met, the flow of FIG. 2 and FIG.
[0033]
As described above, when the vehicle speed V is equal to or lower than the predetermined value, the rotational speed of the motor 20a is limited (that is, the applied power is limited), so that a high boost pressure is required when the vehicle speed V is equal to or lower than the predetermined value. When this is not the case, it is possible to effectively prevent the supercharging pressure from becoming too high (ie, supercharging).
[0034]
In the above-described embodiment, the rotation speed of the motor 20a is limited to the above-described region where the boost pressure sensitivity is low (that is, the applied power is limited). The supercharging pressure does not change greatly with respect to the change in the rotational speed of the motor 20a, that is, the target rotational speed of the motor 20a is set in a region where the vehicle behavior is not significantly changed, and the motor is set to the set target rotational speed. By determining the electric power to be applied to 20a, it is possible to prevent the supercharging from being suppressed and adversely affect the vehicle behavior.
[0035]
Furthermore, in the above-described embodiment, the target rotational speed of the motor 20a is set to be lower as the EGR amount is larger. In this way, when the amount of EGR is large, the supercharging effect is limited to ensure the effect of EGR, and the exhaust emission performance can be further improved.
[0036]
In the above-described embodiment, the power applied to the motor 20a is limited to a predetermined power or less even during vehicle travel such as during low speed travel, but only when it is determined that the vehicle is stopped, the power applied to the motor 20a is limited. The power may be limited to a predetermined power or less. In this case, when the vehicle is stopped, supercharging by the supercharger 20 is started in advance in order to improve acceleration after starting (pre-assist). In this case, in order to prevent supercharging, the applied power to the motor 20a is limited to a predetermined power or less. A flowchart in this case is shown in FIG.
[0037]
First, it is determined whether or not the pre-assist start condition described above is satisfied (step 500). The pre-assist start condition is a condition for considering that the vehicle is stopped but is supposed to start immediately. For example, one of the pre-assist conditions is a case where the vehicle is stopped and the state where the brake pedal is depressed is changed to a situation where the vehicle is not depressed. The pre-assist condition may be a case where the gear is shifted from the neutral state to the connected state (forward) while the vehicle is stopped. Here, it is determined here that the vehicle is stopped (that is, the vehicle speed can be regarded as 0). If step 500 is negative, the process exits the flowchart of FIG.
[0038]
On the other hand, when step 500 is affirmed and the pre-assist condition is satisfied, the target rotational speed of the motor 20a is determined (step 505). This target rotational speed is limited to the above-described region where the supercharging sensitivity is low in FIG. Even within this region, it may be determined as a predetermined fixed target rotational speed, or may be determined according to the operating state of the engine 1. When the target rotational speed is determined, it is determined whether or not it is an EGR possible region (step 510). This step itself is the same as step 230 described above.
[0039]
If step 510 is affirmed, that is, if exhaust gas recirculation by EGR is possible and is implemented, the target rotational speed determined in step 505 is corrected to the low rotational side (step 515). In the present embodiment, at this time, the target rotational speed is corrected so that the target rotational speed of the motor 20a decreases as the EGR amount increases. Based on the corrected target rotational speed, the amount of electric power applied to the motor 20a is determined (step 520). On the other hand, if step 510 is negative, that is, if exhaust gas recirculation by EGR is not performed, the amount of electric power applied to the motor 20a is determined based on the target rotational speed determined in step 505 (step 505). 520).
[0040]
By doing in this way, the supercharging at the time of a pre-assist can be suppressed by restrict | limiting the rotation speed of the motor 20a at the time of a vehicle stop (vehicle speed is below predetermined value 0). In particular, by limiting the rotation speed of the motor 20a within the low supercharging sensitivity region in FIG. 4, it is possible to reliably prevent adverse effects due to supercharging while improving the vehicle motion performance after the vehicle starts. Further, the exhaust emission performance can be further improved by lowering the target rotational speed of the motor 20a as the EGR amount increases.
[0041]
In addition, this invention is not limited to embodiment mentioned above. For example, in the embodiment shown in FIG. 1 described above, a turbocharger 20 with a motor 20 a is provided on the upstream side separately from the turbo unit 11. However, the present invention can be applied to a supercharger equipped with an electric motor (motor). As shown in FIG. 6, the turbo unit 11 includes an electric motor (motor) 11b. Can also be applied. The embodiment shown in FIG. 6 has substantially the same configuration as that shown in FIG. 1 except for the arrangement of the motor 11b (and that the supercharger 20 is not provided). Are denoted by the same reference numerals, and detailed description thereof is omitted.
[0042]
In the embodiment shown in FIG. 6, the motor 11 b is incorporated so that the rotating shaft of the turbine / compressor wheel of the turbo unit 11 becomes the output shaft. Even in this case, since the relationship between the applied power to the motor 20a and the supercharging effect changes, the various control maps will differ, but basically the control shown in the flowcharts of FIGS. Can be performed as well.
[0043]
【The invention's effect】
According to the control device for a supercharger with an electric motor of the present invention, by limiting the electric power applied to the electric motor when the vehicle speed is equal to or lower than a predetermined value, the supercharging under the situation where the vehicle speed is equal to or lower than the predetermined value is performed. It can be effectively prevented.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a configuration of an internal combustion engine (engine) having an embodiment of a control device of the present invention.
FIG. 2 is a flowchart (first half) of supercharging pressure control according to an embodiment of the control device of the present invention.
FIG. 3 is a flowchart (second half) of supercharging pressure control according to an embodiment of the control device of the present invention.
FIG. 4 is a graph showing the relationship between compressor wheel rotation speed (= motor rotation speed) and supercharging pressure.
FIG. 5 is a flowchart of supercharging pressure control according to an embodiment of the control device of the present invention (during pre-assist when stopped).
FIG. 6 is a configuration diagram showing a configuration of an internal combustion engine (engine) having another embodiment of the control device of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Injector, 3 ... Cylinder, 4 ... Piston, 5 ... Intake passage, 6 ... Exhaust passage, 7 ... Spark plug, 8 ... Intake valve, 9 ... Exhaust valve, 10 ... Air cleaner, 11 ... Turbo unit, DESCRIPTION OF SYMBOLS 11a ... Variable nozzle mechanism, 12 ... Intercooler, 13 ... Throttle valve, 14 ... Accelerator pedal, 15 ... Accelerator positioning sensor, 16 ... ECU, 17 ... Throttle motor, 18 ... Throttle positioning sensor, 19 ... Pressure sensor, 20 ... Supercharging , 20a ... motor (electric motor), 21 ... controller, 22 ... battery, 23 ... exhaust purification catalyst, 24 ... bypass passage, 25 ... valve, 26 ... crank positioning sensor, 27 ... air flow meter, 28 ... EGR passage, 29 ... EGR valve.

Claims (2)

A turbocharger disposed on an intake passage of an internal combustion engine mounted on the vehicle and driven by an electric motor; a supercharging pressure control means for controlling the electric motor to control a supercharging pressure; and a speed of the vehicle Speed detecting means for detecting,
The boost pressure control means, said speed vehicle speed detected by the detecting means to limit the power applied to the electric motor at a predetermined power less than in the case of less than a predetermined value, and the boost pressure to the rotational speed of the electric motor And setting the target rotational speed of the electric motor in a rotational speed region where the change rate of the motor is equal to or less than a predetermined value, and determining the electric power to be applied to the electric motor so as to be the set target rotational speed Machine control device. The boost pressure control means, according to claim 1, EGR amount as set the motor low target rotation speed of the large, and determines the electric power applied to the motor so that the target rotational speed set The control apparatus of the supercharger with an electric motor as described in 2.

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