JP2008179296A - Engine start controller for parallel hybrid vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine start controller of a parallel hybrid vehicle, which can appropriately restart an engine according to a traveling state, so that the traveling performance is improved. <P>SOLUTION: An electric motor 3 is connected to the output shaft of an engine 1, and the engine 1 is started with the power of the electric motor 3. When the vehicle is traveling by the electric motor, the controller 100 inhibits the start of the engine by the electric motor in the case of engine start inhibiting conditions that are judged when the slip rate of a driving wheel becomes excessive. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an engine start control device for a parallel hybrid vehicle provided with a plurality of types of power sources, and more particularly to an engine start control device for a parallel hybrid vehicle suitable for restart during traveling.

  As a parallel hybrid vehicle provided with two power sources of an engine and an electric motor, for example, those described in Patent Document 1, Patent Document 2, and the like are known. Such a parallel hybrid vehicle starts the engine with the power of the electric motor for traveling.

JP 2005-168081 A Japanese Patent Laid-Open No. 7-17419

  When starting an engine while a vehicle with an electric motor connected to the output shaft of the engine is running on the electric motor, the engine is controlled appropriately by increasing the torque of the electric motor. The output torque is unstable and fluctuates greatly. This fluctuating torque is amplified by the transmission and the final reduction gear (differential gear), and acts on the road surface as fluctuating driving force. For example, if the road friction coefficient is high such as dry asphalt road surface and the engine is not turning at high G, the fluctuation driving force at engine start will be within the friction circle of the driving wheel, but this fluctuation driving force will cause a shock in the front-rear direction. There is little that disturbs yaw stability.

  However, if the road surface friction coefficient is a little lower, such as wet asphalt road surface, or if the road surface friction coefficient is lower, such as a snowy road surface, the front and rear force margin of the drive wheel friction circle is small. The fluctuation driving force exceeds the friction circle, and the slip ratio of the driving wheel becomes excessive. As a result, the driving wheel enters a non-linear region and the friction circle becomes small, so that there is a problem that the lateral force is extremely reduced and the yaw stability is disturbed. The front-wheel drive vehicle suddenly has strong understeer, and the rear-wheel drive vehicle suddenly has strong oversteer.

  In addition, when the vehicle is driven by the electric motor and steered largely left and right, for example, by avoiding obstacles, the lateral force becomes excessive and the tire reaches a non-linear region and enters a limit state. When the engine is started in such a situation, there is a problem that the slip ratio of the drive wheels becomes excessive and there is a high possibility that the vehicle will deviate from the lane or out of the road.

  An object of the present invention is to provide an engine start control device for a parallel hybrid vehicle that can perform an appropriate engine restart according to the traveling state and has improved traveling performance.

(1) In order to achieve the above object, the present invention is used in a parallel hybrid vehicle in which an electric motor is connected to an output shaft of an internal combustion engine and the internal combustion engine can be started by the power of the electric motor. When the vehicle is running with the electric motor, the start control device for the parallel hybrid vehicle starts the internal combustion engine with the electric motor, and determines that the slip ratio of the drive wheels is excessive. In the start prohibition condition, control means for prohibiting the start of the internal combustion engine by the electric motor is provided.
With this configuration, the engine can be restarted appropriately according to the running state, and the running performance can be improved.

  (2) In the above (1), preferably, the engine start prohibition condition in the control means acts on the drive wheel due to a torque fluctuation when the internal combustion engine is started when the internal combustion engine is started. This is a case where it is determined that the resultant force of the longitudinal force acting on the driving wheel and the lateral force acting on the driving wheel exceeds a threshold value set inside the friction circle of the driving wheel.

  (3) In the above (1), preferably, the engine start prohibition condition in the control means acts on the drive wheel due to a torque fluctuation when the internal combustion engine is started when the internal combustion engine is started. This is a case where it is determined that the longitudinal force to be exceeded exceeds a threshold set inside the marginal longitudinal force of the drive wheel.

  (4) In the above (1), preferably, the engine start prohibition condition in the control means is that the front-rear force acting on the drive wheel by the electric motor and the drive wheel when the internal combustion engine is started. This is a case where it is determined that the resultant force with the acting lateral force exceeds a threshold value set inside the friction circle of the drive wheel.

  (5) In the above (1), preferably, when the vehicle is running on the electric motor, the control means is the internal combustion engine when the tire has already entered a non-linear region and is in a limit state. Is prohibited.

  (6) In the above (1), preferably, the control means permits the start of the internal combustion engine only in a straight traveling state when the amount of charge of the battery is reduced even when it is determined that the start is prohibited. Is.

  According to the present invention, an appropriate engine can be restarted according to the traveling state, and traveling performance can be improved.

Hereinafter, the configuration and operation of an engine start control device for a parallel hybrid vehicle according to an embodiment of the present invention will be described with reference to FIGS.
First, the configuration of a parallel hybrid vehicle equipped with an engine start control device for a parallel hybrid vehicle according to the present embodiment will be described with reference to FIG.
FIG. 1 is an overall configuration diagram showing a configuration of a parallel hybrid vehicle equipped with an engine start control device for a parallel hybrid vehicle according to an embodiment of the present invention.

  The parallel hybrid vehicle shown in FIG. 1 is a rear wheel drive vehicle in which an engine and a transmission are placed vertically.

  The parallel hybrid vehicle includes an engine (internal combustion engine) 1 that is a first drive source, an electric motor 3, a clutch 6, a transmission 2, a rear differential 14, a rear drive shaft 15, a rear wheel 16, and a propeller. The shaft 17 is provided, and the drive device of the whole vehicle is comprised by these.

  The engine 1 is a power device such as a gasoline engine or a diesel engine. The transmission 2 is a transmission such as a manual transmission or an automatic transmission, and is not particularly limited.

  The electric motor 3 can use a synchronous motor, for example, and is configured to have both a function as an electric motor and a function as a generator. Furthermore, a power storage device (not shown) such as a battery is electrically connected to the electric motor 3 via an inverter (not shown). And by controlling this inverter, the output torque or regenerative torque of the electric motor 3 can be adjusted appropriately.

  The clutch 6 can engage and disengage the engine 1 and the transmission 2. The clutch 6 only needs to have a friction element, and the shape and method are not limited. Further, the clutch 6 may be omitted if the transmission 2 includes a torque converter or a clutch.

  The engine start control device for controlling the start of the engine 1 includes a longitudinal acceleration sensor 50, a lateral acceleration sensor 51, a handle angle sensor 52, a yaw rate sensor 53, a front wheel speed sensor 54, and a rear wheel speed sensor. 55, a control device 100, a battery storage amount calculation device 101, a road surface friction coefficient detection device 102, and a limit state detection device 103. Signals from the sensors 50, 51, 52, 53, 54, 55 and the devices 101, 102, 103 are input to the control device 100. Further, the control device 100 outputs a control signal to the engine 1, the electric motor 3, and the clutch 6.

  In this parallel hybrid vehicle, the control device 100 controls the driving torque driven by the electric motor 3 when starting. The driving torque of the electric motor 3 is changed by the transmission 2 and transmitted to the rear wheel 16 via the propeller shaft 17 -rear differential 14 -rear drive shaft 15 to drive the rear wheel 16.

  When the vehicle speed reaches a predetermined vehicle speed (for example, 30 km / h), the control device 100 engages the clutch 6, transmits the torque of the electric motor 3 to the engine 1, injects fuel into the engine 1, and ignites The engine 1 is started by controlling the timing. As the vehicle speed, for example, the front wheel speed that is a non-driven wheel detected by the front wheel speed sensor 54 is used.

  When the engine 1 is started, the driving torque of the engine 1 is controlled by the control device 100. The driving torque of the engine 1 and the torque of the electric motor 3 are shifted by the transmission 2 and transmitted to the rear wheel 16 via the propeller shaft 17 -rear differential 14 -rear drive shaft 15 to drive the rear wheel 16.

  Thereafter, when the vehicle speed reaches a second predetermined vehicle speed (for example, 60 km / h), the driving of the electric motor 3 is stopped and the rear wheel 16 is driven only by the driving torque of the engine 1.

  Further, at the time of deceleration or the like, the electric motor 3 is driven by the rotational force of the rear wheel 16, and the electric power generated when the electric motor 3 operates as a generator is stored in the battery.

Next, the operation of the engine start control device for the parallel hybrid vehicle according to the present embodiment will be described with reference to FIGS.
FIG. 2 is a flowchart showing the operation of the engine start control device for the parallel hybrid vehicle according to the embodiment of the present invention. 3 to 5 are operation explanatory views of the engine start control device of the parallel hybrid vehicle according to one embodiment of the present invention.

  In step S10 of FIG. 2, the control device 100 determines whether or not the motor is running. If the motor is not running, the process ends. If the motor is running, the process proceeds to step S20.

  In step S10, the control device 100 determines whether there is a start request. For example, when the vehicle speed using the front wheel speed detected by the front wheel speed sensor 54 reaches a predetermined vehicle speed (for example, 30 km / h), it is determined that there is a start request. If there is no start request, the process ends. If there is a start request, the process proceeds to step S30.

  In step S30, control device 100 determines whether or not the vehicle is traveling straight ahead. Whether or not the vehicle is traveling straight, for example, the steering wheel angle detected by the steering wheel angle sensor 52, the lateral acceleration detected by the lateral acceleration sensor 51, and the yaw rate detected by the yaw rate sensor 53 are relatively small. This can be determined by being within the threshold. If it is determined that the vehicle is traveling straight, the process proceeds to step S40. If it is determined that the vehicle is not traveling straight (turning), the process proceeds to step S80.

  Hereinafter, control during straight traveling will be described. If the vehicle is traveling straight, it is determined in step S40 whether the straight start prohibition condition is satisfied. When the straight start prohibition condition is satisfied, the engine 1 is prohibited from starting in step S60 after the determination in step S50. If the straight start prohibition condition is not satisfied, the engine 1 is started in step S70. Details of the start prohibition condition for straight traveling will be described in detail below.

  First, FIG. 3 (A) shows the load distribution between the front and rear wheels of a front and rear two-wheel model with one left and right wheel. FIG. 3B shows the friction circle of FIG.

  FIG. 4 shows the yaw moment around the center of gravity in the front and rear two-wheel model.

First, the operation principle will be described with reference to FIG. Car weight is W, front axle weight is Wf, rear axle weight is Wr, distance between axles is L, distance between front axle and center of gravity is Lf, distance between rear axle and center of gravity is Lr, vehicle body center of gravity is Hg, road friction coefficient Is μ and the road surface gradient is θ, the front axle weight Wf and the rear axle weight Wr are

Wf = W · (Lr / L) −W · (Hg / L) · sin θ = W / L · (Lr−Hg · sin θ) (1)

Wr = W · (Lr / L) + W · (Hg / L) · sin θ = W / L · (Lr + Hg · sin θ) (2)

It becomes.

The diameter Ff of the friction circle on the front shaft and the diameter Fr of the friction circle on the rear shaft are

Ff = μ · Wf = μ · W / L · (Lr−Hg · sin θ) (3)

Fr = μ · Wr = μ · W / L · (Lr + Hg · sin θ) (4)

It becomes.

For example, as shown in the following formula (5), the road surface gradient is obtained from the difference between the current torque Fx, the acceleration Fx / W obtained from the vehicle weight W, and the acceleration Gx obtained from the longitudinal acceleration sensor.

sin ⁻¹ θ = Gx− (Fx / W) (5)

As required. The current torque Fx is obtained from a drive torque command value from the control device 100 to the electric motor 3.

Next, a specific example of control during straight traveling will be described. If it is determined in step S30 that the vehicle is traveling straight, the lateral force can be ignored.
(First straight-line engine start prohibition condition)
When the value obtained by adding the fluctuation torque Fx_st at the time of starting the engine to the rear wheel torque Fx_m by the motor exceeds the threshold value Fr_th that is smaller than the friction circle of the driving wheel (the following expression (6)), the engine 1 is started. Is prohibited.

Fx_m + Fx_st> Fr_th (6)

The threshold value Fr_th is smaller than the diameter Fr of the friction circle on the rear shaft.
(Second straight running engine start prohibition condition)
Or, when the fluctuation torque Fx_st at the time of starting the engine exceeds the marginal torque obtained by subtracting the rear wheel torque Fx_m by the motor at this time from the threshold value Fr_th that is smaller than the friction circle (the following formula (7)) ,

Fx_st> Fx_m−Fr_th (7)

The starting of the engine 1 is prohibited.
(Third straight running engine start prohibition condition)
Alternatively, when the rear wheel torque Fx_m by the motor exceeds a threshold value Fr_th that is smaller than the friction circle of the driving wheel (the following equation (8)),

Fx_m> Fr_th (8)

The starting of the engine 1 is prohibited.

  When the engine start prohibition condition is satisfied in step S40 of FIG. 2, the process proceeds to step S50, and it is determined whether or not the battery storage amount is small. The battery power storage amount is obtained by the battery power storage amount calculation device 101. When the battery storage amount is small, the process proceeds to step S70, and the engine 1 start process is executed. When the battery storage amount is not small, the process proceeds to step S60, and the engine 1 start prohibition process is executed.

  That is, when the amount of charge of the battery is small, traveling by the electric motor 3 is not maintained, so that it is necessary to shift to traveling by the engine 1 even if the yaw stability is somewhat disturbed. Therefore, the storage amount calculation device 101 detects the storage amount of the storage device, and when the storage amount is smaller than the threshold value, the engine start is permitted. At this time, since the vehicle is traveling straight, even if the friction circle is exceeded, the yaw change is small, and the yaw stability does not extremely decrease. At this time, traction control by braking may be performed so that the slip rate does not become excessive.

  Next, control during turning will be described. If it is determined in step S30 in FIG. 2 that the vehicle is not traveling straight (turning), it is determined in step S80 whether the yaw stability has decreased. If the yaw stability has not deteriorated, it is determined in step S90 whether or not the turning start prohibition condition is satisfied. If the turning start prohibition condition is satisfied, starting of the engine 1 is prohibited in step S100. When the turning start prohibition condition is not satisfied, the engine 1 is started in step S70. If it is determined in step S80 that the yaw stability has decreased, step S90 is passed, and in step S100, the start of the engine 1 is prohibited. The yaw stability will be described later with reference to FIG.

The front wheel lateral force Fyf and the rear wheel lateral force Fyr are expressed by the following equation (9):

Fyf + Fyr = Fy = W · Gy (9)

Can be represented.

Here, since the yaw moment Mz around the center of gravity can be regarded as 0 if the vehicle is turning at a lateral acceleration Gy in a state where there is no extreme understeer or oversteer, the following equation (10) is obtained:

Mz = Fyf · (Lf / L) −Fyr · (Lr / L) = 0 (10)

It is established.

By developing equation (10), the front wheel lateral force Fyf is

Fyf = W · Gy · (Lr / L) (11)

It becomes.

Also, the rear wheel lateral force Fyr is

Fyr = Fy−Fyf = W · Gy · (Lf / L) (12)

It is obtained as

Next, a specific example of control during turning will be described.
(First turning engine start prohibition condition)
When the resultant force of the front / rear force (Fx_m + Fx_st) obtained by adding the fluctuation torque Fx_st at the start of the engine to the rear wheel torque Fx_m by the motor and the rear wheel lateral force Fyr exceeds a threshold value Fr_th smaller than the friction circle of the rear wheel,

√ ((Fx_m + Fx_st) ² + Fyr ² )> Fr_th (13)

The starting of the engine 1 is prohibited.
(Second turn engine start prohibition condition)
Alternatively, when the fluctuation torque Fx_st at the time of starting the engine exceeds the marginal torque obtained by subtracting the rear wheel torque Fx_m by the motor from the threshold front / rear force Fxr_max obtained from the threshold value Fr_th and the rear wheel lateral force Fyr smaller than the friction circle ( In the following equation (16), the start of the engine 1 is prohibited.

First, the limit longitudinal force Fxr_max is obtained as an equation (15) from the following equation (14).

Fxr_max ² + Fyr ² = Fr_th ² (14)

Fxr_max = √ (Fr_th ² −Fyr ² ) (15)

further,
Fx_st> Fr_max−Fx_m = √ (Fr_th ² −Fyr ² ) −Fx_m (16)

As required.
(Third turning engine start prohibition condition)
Alternatively, when the resultant force of the rear wheel torque longitudinal force Fx_m and the rear wheel lateral force Fyr by the motor exceeds a threshold value Fr_th that is smaller than the rear wheel friction circle (the following equation (17)),

√ (Fx_m ² −Fyr ² )> Fx_st (17)

The starting of the engine 1 is prohibited.

  The engine start prohibition conditions have been described above for each of the three cases of going straight and turning.

  Here, as understood from a comparison between the formula (6) and the formula (13), in the formula (13), the case where the rear wheel lateral force Fyr is 0 is the formula (6). Therefore, the expression (6) and the expression (13) include that “the resultant force of the longitudinal force acting on the driving wheel due to the torque fluctuation when the engine 1 is started and the lateral force acting on the driving wheel is “When the threshold value set inside the friction circle of the drive wheel is exceeded, engine start is prohibited”.

  Similarly, the expression (7) and the expression (15) are included as follows: “The longitudinal force acting on the driving wheel due to the torque fluctuation when the engine 1 is started is within the marginal longitudinal force of the driving wheel. “When the set threshold value is exceeded, engine start is prohibited”.

  The expression (8) and the expression (16) are included as follows: “The resultant force of the longitudinal force acting on the driving wheel by the electric motor when the engine 1 is started and the lateral force acting on the driving wheel is the driving wheel. The engine start is prohibited when the threshold value set inside the friction circle is exceeded.

  Next, the yaw stability in step S80 in FIG. 2 will be described with reference to FIG. When the electric motor 3 has already reached the non-linear region due to traveling by the electric motor 3 and is in the limit state, for example, as shown in FIG. If this occurs, the generated lateral acceleration becomes excessive, the tire generating force exceeds the friction circle, the tire reaches a non-linear region, and the yaw stability decreases.

  Therefore, when the limit state detection device 103 determines that the vehicle is in the limit state, the control device 100 prohibits the start of the engine 1 in step S80.

  The limit state detection method can be detected from the steering wheel angular velocity and the yaw rate change rate phase difference as described in, for example, Japanese Patent Application Laid-Open No. 7-17419.

Next, another configuration of the parallel hybrid vehicle equipped with the engine start control device for the parallel hybrid vehicle according to the present embodiment will be described with reference to FIG.
FIG. 6 is an overall configuration diagram showing another configuration of a parallel hybrid vehicle equipped with an engine start control device for a parallel hybrid vehicle according to an embodiment of the present invention.

  The parallel hybrid vehicle shown in FIG. 6 is a front-wheel drive vehicle in which an engine and a transmission are placed horizontally.

  The parallel hybrid vehicle includes an engine (internal combustion engine) 1 that is a first drive source, an electric motor 3, a clutch 6, a transmission 2, a front differential 11, a front drive shaft 12, and a front wheel 13. These constitute a drive device for the entire vehicle.

  The engine start control device for controlling the start of the engine 1 includes a longitudinal acceleration sensor 50, a lateral acceleration sensor 51, a handle angle sensor 52, a yaw rate sensor 53, a front wheel speed sensor 54, and a rear wheel speed sensor. 55, a control device 100, a battery storage amount calculation device 101, a road surface friction coefficient detection device 102, and a limit state detection device 103. Signals from the sensors 50, 51, 52, 53, 54, 55 and the devices 101, 102, 103 are input to the control device 100. Further, the control device 100 outputs a control signal to the engine 1, the electric motor 3, and the clutch 6.

  In this parallel hybrid vehicle, when starting, the control device 100 controls the torque that the electric motor 3 torques. The drive torque of the electric motor 3 is changed by the transmission 2 and transmitted to the front wheels 13 via the front differential 11 and the front drive shaft 12 to drive the rear wheels 16.

  When the vehicle speed reaches a predetermined vehicle speed (for example, 30 km / h), the control device 100 engages the clutch 6, transmits the torque of the electric motor 3 to the engine 1, injects fuel into the engine 1, and ignites The engine 1 is started by controlling the timing. As the vehicle speed, for example, a front wheel speed that is a non-driven wheel detected by the front wheel speed sensor 54 is used.

  When the engine 1 is started, the driving torque of the engine 1 is controlled by the control device 100. The driving torque of the engine 1 and the torque of the electric motor 3 are shifted by the transmission 2 and transmitted to the rear wheel 16 via the front differential 11 and the front drive shaft 12 to drive the front wheel 13.

Thereafter, when the vehicle speed reaches a second predetermined vehicle speed (for example, 60 km / h), the driving of the electric motor 3 is stopped and the front wheels 13 are driven only by the driving torque of the engine 1.

  Further, at the time of deceleration or the like, the electric motor 3 is driven by the rotational force of the front wheels 13, and the electric power generated when the electric motor 3 operates as a generator is stored in the battery.

As described above, according to the present embodiment, the parallel hybrid vehicle does not disturb the yaw stability of the vehicle when the engine is requested to start while the electric motor is running, and the engine is restarted appropriately according to the running state. This improves the running performance.

1 is an overall configuration diagram showing a configuration of a parallel hybrid vehicle equipped with an engine start control device for a parallel hybrid vehicle according to an embodiment of the present invention. It is a flowchart which shows operation | movement of the engine starting control apparatus of the parallel hybrid vehicle by one Embodiment of this invention. It is operation | movement explanatory drawing of the engine starting control apparatus of the parallel hybrid vehicle by one Embodiment of this invention. It is operation | movement explanatory drawing of the engine starting control apparatus of the parallel hybrid vehicle by one Embodiment of this invention. It is operation | movement explanatory drawing of the engine starting control apparatus of the parallel hybrid vehicle by one Embodiment of this invention. It is a whole block diagram which shows the other structure of the parallel hybrid vehicle carrying the engine start control apparatus of the parallel hybrid vehicle by one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Transmission 3 ... Electric motor 6 ... Clutch 11 ... Front differential 12 ... Front drive shaft 13 ... Front wheel 14 ... Rear differential 15 ... Rear drive shaft 16 ... Rear wheel, 17 ... Propeller shaft 50 ... Longitudinal acceleration sensor 51 ... Lateral acceleration sensor 52 ... steer angle sensor 53 ... yaw rate sensor 54 ... front wheel speed sensor 55 ... rear wheel speed sensor 100 ... control device 101 ... charge amount calculation device 102 ... road friction coefficient detection device 103 ... limit state detection device

Claims (6)

An electric motor is connected to the output shaft of the internal combustion engine, used for a parallel hybrid vehicle capable of starting the internal combustion engine with the power of the electric motor,
When the vehicle is running with the electric motor, a start control device for a parallel hybrid vehicle that starts the internal combustion engine with the electric motor,
A start control device for a parallel hybrid vehicle, comprising control means for prohibiting the start of the internal combustion engine by the electric motor when an engine start prohibition condition is determined in which the slip ratio of the drive wheel is determined to be excessive. In the start control device of the parallel hybrid vehicle according to claim 1,
The engine start prohibition condition in the control means is:
When attempting to start the internal combustion engine, the resultant force of the longitudinal force acting on the drive wheel and the lateral force acting on the drive wheel due to torque fluctuation when the internal combustion engine is started is the friction circle of the drive wheel. A start control device for a parallel hybrid vehicle, characterized in that it is determined that a threshold value set inside is exceeded. In the start control device of the parallel hybrid vehicle according to claim 1,
The engine start prohibition condition in the control means is:
When starting the internal combustion engine and the longitudinal force acting on the drive wheel due to torque fluctuation when the internal combustion engine is started exceeds a threshold set inside the marginal longitudinal force of the drive wheel A start control device for a parallel hybrid vehicle, characterized in that a determination is made. In the start control device of the parallel hybrid vehicle according to claim 1,
The engine start prohibition condition in the control means is:
When the internal combustion engine is started, the resultant force of the longitudinal force acting on the drive wheel by the electric motor and the lateral force acting on the drive wheel is set to a threshold value set inside the friction circle of the drive wheel A start control device for a parallel hybrid vehicle, characterized in that it is determined that it exceeds the limit. In the start control device of the parallel hybrid vehicle according to claim 1,
The parallel hybrid characterized in that the control means prohibits starting of the internal combustion engine when the vehicle is running with the electric motor and the tire is already in a non-linear region and is in a limit state. Vehicle start control device. In the start control device of the parallel hybrid vehicle according to claim 1,
Even if it is determined that the start is prohibited, the control means permits the start of the internal combustion engine only in a straight traveling state when the amount of charge of the battery is low, the start control device for a parallel hybrid vehicle characterized in that .

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