JP2005214153A - Intake air amount control device for internal combustion engine and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an intake air amount control method for an internal combustion engine for securing an optimum intake air amount (new air intake amount) depending on the operated condition of the interral combustion engine by suitably controlling a VNT variable blade angle and an EGR valve angle while considering both of them, to provide its method. <P>SOLUTION: The intake air amount (new air intake amount) control device A is provided for the internal combustion engine (an automobile engine 1 for example) having a variable blade turbocharger (VNT 2) and the exhaust recirculation device (an EGR system 6). It comprises operated condition detecting means (an engine speed detecting means 20 for detecting an engine speed and a fuel injection amount calculating block 30) for detecting the operated condition of the internal combustion engine 1 and a control means (a control unit 10) for determining the angle (VNT variable blade angle) of the variable blade in the variable blade turbocharger (VNT 2) and the valve opening (EGR valve opening) of an exhaust recirculation valve (EGR valve Ve) in accordance with the detection results of the operated condition detecting means 20, 30. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for controlling the amount of air taken into an internal combustion engine such as an automobile engine. More specifically, the present invention relates to a technique for controlling the intake air amount in an internal combustion engine having a variable blade turbocharger (VNT) and an exhaust gas recirculation system (EGR).

  In an internal combustion engine (for example, an automobile engine), a turbocharger (turbocharger) that is driven by a turbine that is rotated by exhaust gas and that controls the supercharging ratio by changing the angle of the turbine blades (so-called VNT) ) Is already known (see, for example, Patent Document 1).

  In addition, in order to lower the combustion temperature in the cylinder and suppress the exhaust amount of NOx in the exhaust gas, the valve opening degree of the exhaust gas recirculation valve (EGR valve) is adjusted, and the exhaust gas flow rate (EGR amount) to the intake air Alternatively, an exhaust gas recirculation system (EGR) that controls a fresh air intake amount is also known (see, for example, Patent Document 2).

In recent years, cars equipped with both VNT and EGR have appeared.
Here, both VNT and EGR directly act on fresh air intake of the engine, and the angle of the variable blade in VNT and the valve opening of the EGR valve in EGR are the air supplied to the engine (not exhaust gas) Directly affects the supply of fresh air. Therefore, if the VNT variable blade angle and / or the EGR valve opening are not appropriate, it becomes difficult to realize an optimum fresh air intake amount corresponding to the operating state of the engine, and the engine performance can be improved. Absent.

Both the VNT variable blade angle and the EGR valve opening are controlled by open loop control (hereinafter, “OPEN LOOP”) in which one numerical value is determined from the engine speed and the fuel supply amount (for example, fuel injection amount). Also, feedback control (hereinafter referred to as “CLOSED LOOP”) for controlling the VNT variable blade angle or the EGR valve opening so that the fresh air intake amount of the engine approaches the target value is used in combination.
In the control of the VNT variable blade angle and / or the control of the EGR valve opening, depending on whether the OPEN LOOP or the CLOSED LOOP is determined, the determination of the fresh air intake amount of the engine has a great influence. become.

As for the VNT variable blade angle and the EGR valve opening, whether the control is set to OPEN LOOP or CLOSED LOOP is determined by the operating state of the engine.
Here, as described above, the VNT variable blade angle and the EGR valve opening are both control parameters that greatly affect the amount of fresh air supplied to the engine (fresh air intake amount). If the amount is optimally controlled, it should be determined whether the control mode is OPEN LOOP or CLOSED LOOP while taking into account the relative relationship between the VNT variable blade angle and the EGR valve opening. is there.

However, in the conventional technique, the control of the VNT variable blade angle and the control of the EGR valve opening are performed independently, and the VNT variable is also used to determine whether the control mode is OPEN LOOP or CLOSED LOOP. The blade angle and the EGR valve opening were determined independently.
For this reason, it has been difficult to say that the fresh air intake amount of the engine is optimally controlled. Moreover, since the amount of air flowing into the engine changes when both control factors change, stable engine operation is difficult.
JP 2002-147246 A JP 2001-182602 A

  The present invention has been proposed in view of the above-mentioned problems of the prior art, and while considering both the VNT variable blade angle and the EGR valve opening, both are suitably coordinated to control the operating state of the internal combustion engine. It is an object of the present invention to provide an intake air amount control device and control method for an internal combustion engine that can secure an optimal intake air amount (fresh air intake amount) according to the above.

  An intake air amount control device for an internal combustion engine according to the present invention includes an intake air amount (fresh air intake) of an internal combustion engine (for example, an automobile engine 1) having a variable blade turbocharger (VNT2) and an exhaust gas recirculation device (EGR system 6). Amount) In the control device (A), a rotational speed detecting means for detecting the rotational speed of the internal combustion engine (1) (for example, a rotational speed detecting means 20 for detecting the rotational speed of the engine) and the internal combustion engine (1) Injection quantity (for example, fuel injection quantity) calculating step (30) for detecting the amount of fuel supplied, and variable blade turbo based on the detection results of the rotational speed detection means (20) and the fuel injection quantity calculating step (30) Control means (control unit 10) for determining the angle of the variable blade (VNT variable blade angle) in the charger (VNT2) and the valve opening (EGR valve opening) of the exhaust gas recirculation valve (EGR valve Ve). The control means (10) controls the operating state of the internal combustion engine (1), controls the angle of the variable blades (VNT2) and the valve opening degree (of the EGR valve Ve). The first region (E1) to be an open loop control (OPEN LOOP) for determining one numerical value from the fuel injection amount and the control of the angle of the variable blade is set to one numerical value from the internal combustion engine speed and the fuel injection amount. Open loop control to be determined (OPEN LOOP) and control of the valve opening to feedback control (CLOSED LOOP) to control the intake air amount (fresh air intake amount) of the internal combustion engine (1) to approach the target value. The control of the second region (E2) and the angle of the variable blade is a feedback control (CLOSED LOOP) for controlling the intake air amount of the internal combustion engine (1) to approach the target value. A third region (E3) in which the valve opening is controlled by an open loop control (OPEN LOOP) for determining one numerical value from the internal combustion engine speed and the fuel injection amount; Control for classifying the valve opening degree into any one of the four areas, the fourth area (E4), which is feedback control (CLOSED) for controlling the intake air amount of the internal combustion engine to approach the target value. (Claim 1).

  Here, the first region (E1) is a region where the rotational speed of the internal combustion engine (1) is low or the fuel injection amount is small, and the third (E3) region is a region where the fuel injection amount is large. The fourth region (E4) is a region where the internal combustion engine speed is neither high nor low and the fuel injection amount is relatively small, and the second region (E2) is preferably another operating region. (Claim 2).

  The control means (control unit 10) includes the number of revolutions of the internal combustion engine, the injection amount of fuel supplied to the internal combustion engine (that is, the operating state of the internal combustion engine), and the four regions (E1 to E4) described above. It is preferable to have storage means (for example, a database) for storing the relative relationship (for example, characteristic curve or map).

  An intake air amount control method for an internal combustion engine of the present invention includes an intake air amount (fresh air intake amount) of an internal combustion engine (for example, an automobile engine 1) having a variable blade turbocharger (VNT2) and an exhaust gas recirculation device (EGR). In the control method, the rotational speed detection step (S1) for detecting the rotational speed of the internal combustion engine (1) (by the rotational speed detection means 20) and the internal combustion engine (1) (by the fuel injection amount calculation step 30) are supplied. A fuel injection amount calculation step (S1) for detecting a fuel supply amount (for example, a fuel injection amount), and an internal combustion engine operation state determination for determining the operation state of the internal combustion engine based on the detection results of the rotation speed detection step and the fuel injection amount calculation step. Including a step (S2) and a control step (3) for controlling the angle of the variable blade and the valve opening, wherein the control step (3) is an internal combustion engine determined in an internal combustion engine operating state determination step. Engine operating conditions A first region (E1) in which the control of the angle of the variable blade and the control of the valve opening are set to open loop control (OPEN LOOP) for determining one numerical value from the internal combustion engine speed and the fuel injection amount; The variable blade angle is controlled by open loop control (OPEN LOOP) that determines one numerical value from the internal combustion engine speed and the fuel injection amount, and the valve opening control is controlled by the intake air amount of the internal combustion engine approaching the target value. Feedback control for controlling the angle of the variable blades so that the intake air amount of the internal combustion engine (1) approaches the target value (second region (E2) to be feedback controlled (CLOSED LOOP) and Open loop control (OPEN LOOP) that determines one numerical value from the internal combustion engine speed and the fuel injection amount. The third region (E3) to be controlled and feedback control (CLOSED LOOP) for controlling the angle of the variable blade and the control of the valve opening so that the intake air amount of the internal combustion engine (1) approaches the target value. The fourth region (E4) is classified into any one of the four regions (claim 4).

  Here, the first region (E1) is a region where the rotational speed of the internal combustion engine is low or the fuel injection amount is small, and the third region (E3) is a region where the fuel injection amount is large, Region 4 (E4) is a region where the internal combustion engine speed is neither high nor low, and the fuel injection amount is relatively small, and the second region (E2) is another operating region.

  According to the present embodiment having the configuration and the control method described above, in the control of the VNT (2) variable blade angle and / or the control of the EGR valve (Ve) opening degree, open control (OPEN LOOP) or feedback control ( CLOSED LOOP) can be accurately determined in accordance with the operating state.

In order to control by appropriately selecting whether to perform open control or feedback control in accordance with the driving situation, the fresh air intake amount of the internal combustion engine (engine 1) is appropriately determined.
That is, the engine (1) has a low rotational speed or a low fuel injection amount, in other words, a state where the engine load is extremely low, such as coasting while stopping or running (first area E1 in FIG. 2). ), Open-loop control (OPEN) with the target control value reduced to one point is selected for both EGR and VNT, and the engine load and vehicle speed (engine speed) change. In an operating state (second region E2 in FIG. 2), open control is selected for VNT and feedback control is selected for EGR, and fine control is performed. When the fuel injection amount is high and the load is high (third region E3 in FIG. 2), the open control is selected for EGR and the feedback control is selected for VNT regardless of the engine speed, and the engine load and vehicle speed change. For example, in an ordinary operating state with a relatively low load, feedback control is selected for both EGR control and VNT control.

Because of such control, especially on general roads where there are many changes in operating conditions, especially NOx reduction is achieved at a high level, and both improvement in fuel consumption and reduction of NOx can be achieved in the internal combustion engine (engine 1). .
Furthermore, when the load is relatively low and the engine speed is medium, the feedback control is selected for both EGR control and VNT control, enabling more detailed fuel saving and low NOx emissions. To do.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
In FIG. 1, an intake air amount control device A for an internal combustion engine according to an embodiment of the present invention is an exhaust equipped with a variable blade turbocharger (VNT; hereinafter, a variable blade turbocharger is abbreviated as VNT) 2 of the engine 1. It has a system 3, an intake system 5 equipped with an intercooler 4, and an EGR system 6 that recirculates part of the exhaust gas from the exhaust system to the intake system.

  The intake system 5 includes a first air duct 51 that connects the VNT 2 and the intercooler 4, and a second air duct 52 that connects the intercooler 4 and the intake manifold 7 of the engine 1.

  The EGR system 6 is equipped with an EGR cooler 63, and is provided with an exhaust manifold 8 of the engine 1 and a first EGR pipe 61 that connects the EGR cooler 63, and an EGR valve Ve that is an exhaust gas recirculation valve. A second ERG pipe 62 is provided to connect the merging portion 53 formed in the second air duct 52 of the intake system 5.

  The engine 1 is equipped with a control unit 10 for controlling the intake air amount of the engine, an engine rotation sensor 20, and a process 30 for calculating a fuel injection amount. The engine rotation sensor 20 and the flow meter 30 are Both are connected to the control unit 10 by an input signal line Li.

The VNT (variable blade turbocharger) 2 is provided with an actuator Vt for changing the angle of the variable blade according to a control signal of the control unit 10, and the actuator Vt is connected to the control unit 10 by a control signal line Lo.
The EGR valve is also configured such that the valve opening degree is controlled by a control signal from the control unit 10 and is connected to the control unit 10 by a control signal line Lo.

  The control unit 10 is connected to a database 40 as storage means. The database 40 includes a map showing the relationship between engine load, fuel injection amount and / or engine speed, and operation during EGR control. Map of variable blade angle of VNT to be controlled that matches the conditions (hereinafter, “Map of variable blade angle of VNT to be controlled that matches the operating conditions” is referred to as “VNT map”), when EGR control is not performed A VNT map, a VNT map when feeding back the EGR amount, a VNT map when feeding back the intake air flow rate, a map showing the relationship between the VNT variable blade angle and the supercharging ratio related to the intake air flow rate, and the like are stored. .

  The operation and control method of the intake air amount control apparatus according to the present embodiment will be described below with reference to FIG.

  Intake air sucked from an air inlet (not shown) is supercharged by the energy of exhaust gas in the VNT 2, is pumped to the intercooler 4 by the first air duct 51, and is cooled in the intercooler 4, thereby further improving the oxygen filling efficiency. 2 is supplied into the cylinder 9 through the air duct 52 and the intake manifold 7.

On the other hand, most of the exhaust gas discharged from the exhaust manifold 8 flows into the VNT 2, but a part (recirculation exhaust gas: EGR) is sent to the EGR cooler 63 via the first EGR pipe 61.
The recirculated exhaust gas (EGR) cooled by the EGR cooler 63 is supplied through the second air duct 52 through the second EGR pipe 62 and is supplied into the second air duct 52 (fresh air). ), And then flows into the intake manifold 7 through the second air duct 52.

  In the control method of the intake air amount control device having the above-described configuration, the engine speed sensor 20 detects the number of revolutions of the engine 1, the flow meter 30 detects the fuel injection amount, and the engine operation is performed based on the detection results. The state is recognized as the following four operation states (four operation regions).

The four operation states (four operation regions) refer to regions indicated by E1, E2, E3, and E4 in FIG. 2 showing the fuel injection characteristics, for example.
That is, the first region E1 is a region where the rotational speed of the engine 1 is low or the fuel injection amount is small, in other words, a region where the engine load is extremely low such as coasting while stopping or running. is there. The second region E2 is a region in which the engine load and the vehicle speed (engine rotation speed) change, and includes driving on a general road and is in a driving state with a relatively high load.
The third region E3 is a region in an operating state at a high load with a large amount of fuel injection.
The fourth region E4 is a medium speed region, but is a region where the engine load and the vehicle speed (engine rotation speed) change, and the driving state is relatively low on a general road, for example.

The control unit 10 performs control of the angle of the variable vane of the VNT 2 and control of the valve opening of the EGR valve Ve according to the recognized operating state (the first to fourth regions E1 to E4 in FIG. 2). It is done by the method.
That is, referring to FIG. 3, in the first region E1, the VNT control and the EGR control are set to open loop control (OPEN) for determining one numerical value from the internal combustion engine speed and the fuel injection amount.
In the second region E2, the VNT control is set to open loop control (OPEN LOOP) for determining one numerical value from the engine speed and the fuel injection amount, and the EGR control is set to the intake air amount (fresh air intake amount) of the internal combustion engine. (I.e., not shown, for example, an actually measured fresh air amount that is an engine intake air amount measured by an air flow sensor interposed in the intake system 5 is obtained from the rotational speed and the injection amount 1. It is set to feedback control (CLOSED LOOP) in which the EGR valve opening is feedback-controlled so that one numerical value (target new air amount) is obtained.
In the third region E3, the VNT (variable blade) control is set to feedback control (CLOSED LOOP) for controlling the intake air amount (fresh air intake amount) of the internal combustion engine to approach the target value, and the EGR control is set to the engine speed. And an open loop control (OPEN LOOP) for determining one numerical value from the fuel injection amount.
In the fourth region E4, both VMT (variable blade) control and EGR control are set to feedback control (CLOSED LOOP) for controlling the intake air amount (fresh air intake amount) of the internal combustion engine to approach the target value. To control.

  Next, a method for controlling the intake air amount will be described with reference to FIG.

  First, in step S1, the engine speed is determined by the engine rotation sensor 20, and the fuel supply amount to the engine is determined by the fuel injection amount calculation step 30. Here, the fuel injection amount calculation means 30 is configured to calculate the fuel injection amount by an accelerator sensor, a boost sensor, and an air flow sensor.

  In the next step S2, the control unit 10 determines the four operating states shown in FIG. 2 based on the data relating to the detected engine speed, the data relating to the fuel injection amount, and a map (not shown) stored in the database 40. Which region of the regions (E1 to E4) belongs is determined, and the process proceeds to the next step S3.

In step S3, the control unit 10 determines the operating state of the engine 1 determined in step S2, controls the angle of the variable blades of the VNT2 and the valve opening of the EGR valve Ve, and controls the engine speed and fuel injection amount. Open loop control (OPEN LOOP) to determine one numerical value from the first region E1 to open loop control (OPEN LOOP), variable blade angle control to determine one numerical value from the engine speed and fuel injection amount (OPEN LOOP) And a second region (E2) in which the control of the valve opening is set to feedback control (CLOSED LOOP) for controlling the intake air amount (fresh air intake amount) of the internal combustion engine to approach the target value, Feedback control (CLOSED) for controlling the angle so that the intake air amount (fresh air intake amount) of the internal combustion engine (1) approaches the target value LOOP) and a third region (E3) in which the valve opening is controlled by an open loop control (OPEN LOOP) for determining one numerical value from the engine speed and the fuel injection amount; 4 in a fourth region (E4) in which both the EGR valve opening are set to feedback control (CLOSED LOOP) for controlling the intake air amount (fresh air intake amount) of the internal combustion engine (1) to approach the target value. Classify into any one of the two areas.
That is, select the VNT angle, EGR valve opening control method (open loop control (OPEN LOOP) or feedback control (CLOSED LOOP)) corresponding to the region to which it belongs (based on the table in FIG. 3), The VNT angle and the opening degree of the EGR valve are controlled by the selected control method.
Here, the control of the VNT angle and the opening degree of the EGR valve are performed by known control software (method) regardless of OPEN LOOP and CLOSED LOOP. As a result, the amount of intake air to the engine 1 depends on the operating state. It is controlled as the most suitable value.

  In the next step S4, the control unit 10 determines whether or not to end the control (whether the operation has ended), and if it can be ended (YES in step S4), the control unit 10 ends the control as it is. On the other hand, if the control is not finished (operation is continued) (NO in step S4), the process proceeds to step S5, waits for a predetermined time (loop in S6), and if the predetermined time elapses (step S5). YES), the process returns to step S1, and step S1 and subsequent steps are repeated again.

  According to the present embodiment having the above-described configuration and control method, whether to perform open control (OPEN LOOP) or feedback control (CLOSED LOOP) in the control of the VNT variable blade angle and / or the control of the EGR valve opening. However, it can be determined accurately in accordance with the driving state.

In order to control by appropriately selecting whether to perform open control or feedback control in accordance with the driving situation, the fresh air intake amount of the internal combustion engine (engine) is appropriately determined.
That is, in a state where the engine load is extremely low (first area E1 in FIG. 2) such as coasting while stopping or traveling, open loop control (OPEN LOOP) in which the target control value is reduced to one point for both EGR and VNT. ) Is selected, the engine load and the vehicle speed (engine speed) change, and in operation with a relatively high load (second region E2 in FIG. 2), VNT is open control, and EGR is feedback control. Selected and finer control is performed. Further, during high load (third region E2 in FIG. 2), EGR is selected for open control and VNT is selected for feedback control regardless of the engine speed. Further, when the load is relatively low and the engine rotation speed is in the medium speed range (fourth region E4 in FIG. 2), feedback control is selected for both EGR control and VNT control.

  In this way, the control method is appropriately and finely selected according to the operating state, so that especially on general roads where the operating conditions change frequently, NOx reduction is achieved at a high level and fuel efficiency of the internal combustion engine (engine) is improved. And NOx reduction can both be achieved.

  Furthermore, when the load is relatively low and the engine speed is medium, the feedback control is selected for both EGR control and VNT control, enabling more detailed fuel saving and low NOx emissions. To do.

The illustrated embodiment is merely an example, and is not intended to limit the technical scope of the present invention.
For example, in the illustrated embodiment, a fuel flow meter is used as a means for detecting the fuel supply amount. However, a fuel supply amount may be calculated by processing a signal from a potentiometer provided in the accelerator pedal.

1 is a block diagram showing an entire intake air amount control device according to an embodiment of the present invention. In the embodiment of the present invention, the control characteristic diagram which divided the field where the control method of two sets of control of EGR control and VNT control changes into four fields. The table which matched the combination of control of EGR control and VNT control with four control fields in the embodiment of the present invention. The flowchart which shows the intake air amount control method in embodiment of this invention.

Explanation of symbols

1 ... Engine 2 ... Variable wing turbocharger / VNT
3 ... Exhaust system
4 ... Intercooler
5 ... Intake system 6 ... EGR system 7 ... Intake manifold 8 ... Exhaust manifold 10 ... Control unit 20 ... Engine rotation sensor 30 ... Fuel flow meter 40 ... Database E1 ... First region E2 ... Second region E3 ... Third region Ve ... EGR valve Vt ... Actuator

Claims (5)

  In an intake air amount control device for an internal combustion engine having a variable blade turbocharger and an exhaust gas recirculation device, a rotational speed detection means for detecting the rotational speed of the internal combustion engine, a fuel injection amount supplied to the internal combustion engine, and a rotational speed Control means for determining the angle of the variable blade and the valve opening degree of the exhaust gas recirculation valve in the variable blade turbocharger based on the detection means and the fuel injection amount, and the control means indicates the operating state of the internal combustion engine, the variable blade A first region in which the control of the angle of the valve and the control of the valve opening are made open loop control for determining one numerical value from the engine speed and the fuel injection amount, and the control of the angle of the variable blades is made in the engine speed And a second area in which the control of the valve opening is a feedback control in which the intake air amount of the internal combustion engine approaches the target value. And the control of the angle of the variable blade is a feedback control for controlling the intake air amount of the internal combustion engine to approach a target value, and the control of the valve opening is a numerical value from the internal combustion engine speed and the fuel injection amount. A third region for open loop control to be determined, and fourth control for feedback angle control for controlling the angle of the variable blade and the valve opening so that the intake air amount of the internal combustion engine approaches a target value. An intake air amount control device for an internal combustion engine, which is configured to perform control to be classified into any one of the four regions.   The first region is a region where the rotational speed of the internal combustion engine is low or the fuel injection amount is small, the third region is a region where the fuel injection amount is large, and the fourth region is the rotational speed of the internal combustion engine. 2. The intake air amount control device for an internal combustion engine according to claim 1, wherein the fuel injection amount is neither high nor low and the fuel injection amount is relatively small, and the second region is another operation region.   The control means includes storage means for storing a relative relationship between the number of revolutions of the internal combustion engine of the internal combustion engine and the injection amount of fuel supplied to the internal combustion engine, and the above-described four regions. 2. The intake air amount control device for any one of the internal combustion engines.   In an intake air amount control method for an internal combustion engine having a variable blade turbocharger and an exhaust gas recirculation device, a rotational speed detection step for detecting the rotational speed of the internal combustion engine, and an injection amount calculation step for fuel supplied to the internal combustion engine; An internal combustion engine operation state determination step for determining an operation state of the internal combustion engine based on detection results of the rotational speed detection step and the fuel injection amount calculation step, and a control step for controlling the angle of the variable blade and the valve opening degree. The control step includes the operation state of the internal combustion engine determined in the internal combustion engine operation state determination step, the control of the angle of the variable blades and the control of the valve opening from the internal combustion engine speed and the fuel injection amount. A first region for open-loop control for determining a numerical value, and an open-loop control for determining one numerical value from an internal combustion engine speed and a fuel injection amount for controlling the angle of the variable blade, and the valve opening degree The second region is controlled so that the intake air amount of the internal combustion engine approaches the target value, and the control of the angle of the variable blade is controlled so that the intake air amount of the internal combustion engine approaches the target value. A third region in which feedback control is performed, and the control of the valve opening is an open loop control in which one numerical value is determined from the internal combustion engine speed and the fuel injection amount; and the angle control of the variable blade and the valve opening The intake air of the internal combustion engine is classified into any one of the four areas of the fourth area, which is feedback control that controls the intake air amount of the internal combustion engine to approach the target value. Quantity control method.   The first region is a region where the rotational speed of the internal combustion engine is low or the fuel injection amount is small, the third region is a region where the fuel injection amount is large, and the fourth region is the rotational speed of the internal combustion engine. 5. The intake air amount control method for an internal combustion engine according to claim 4, wherein the fuel injection amount is neither high nor low and the fuel injection amount is relatively small, and the second region is another operation region.

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