JP2009254077A - Drive force control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress noise of collision in an engagement portion of a concave and convex portions of a transmission device which is transmitted from a drive force source to tires. <P>SOLUTION: The drive force control device obtains an alternately changing vibration torque while using a request torque transmitted from the drive force source to the tires as a reference, transmits the vibration torque from the drive force source to the tires and controls a friction coefficient between the tires and a road surface, wherein a power transmission device for transmitting torque by a mating force between the determining and convex portions is provided on the torque transmission passage. The drive force control device is provided with: a determining means for determining whether the request torque is in a drive region or a regenerative region, and whether or not the vibration torque moves forward and backward between the drive region and the regenerative region (step S4); and a correcting means for correcting the vibration torque so that the vibration torque can be generated in the same region as that of the request torque when the determining means has determined that the request torque is in either the drive region or the regenerative region and the drive torque moves forward and backward between the drive region and the regenerative region (steps S5, S6). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a driving force control device capable of controlling a friction coefficient between a tire and a road surface when transmitting torque from a driving force source of a vehicle to the tire.

  Generally, a driving force source is mounted on a vehicle, and torque of the driving force source is transmitted to a tire, so that a driving force is generated between the tire and a road surface. Here, even if the torque transmitted from the driving force source to the tire is the same and the rotation speed of the tire is the same, the driving force also changes when the friction coefficient changes between the tire and the road surface. Thus, the behavior of the vehicle changes depending on the coefficient of friction between the tire and the road surface. On the other hand, paying attention to the relationship between the friction coefficient between the tire and the road surface and the torque characteristics transmitted to the tire, the friction coefficient between the tire and the road surface is arbitrarily determined by vibrating the torque transmitted to the tire. A technique for controlling is described in Patent Document 1.

  In the vehicle control device described in Patent Document 1, an electric motor that drives each wheel of the vehicle is provided, and the electric motor is driven and driven according to a motor torque command value for obtaining a required driving torque. Be controlled. In normal control, the driving torque of each wheel or electric motor is detected, and feedback control is performed so that the detected driving torque becomes a motor torque command value. Further, in addition to the above-described normal control, it is described that a minute vibration is applied to the tire by superimposing a minute vibration signal on the drive signal of the electric motor to control the frictional force of the tire. For example, by controlling the amplitude, frequency, and phase of the minute vibrations of torque applied to the tire and arbitrarily adjusting the friction coefficient between the tire and the road surface, the running performance and behavior of the vehicle are stabilized. ing.

Republished patent WO02 / 000463

  By the way, a gear transmission device, a winding transmission device, a friction transmission device, a traction transmission device, and the like are provided in the power transmission path from the driving force source of the vehicle to the tire. Among these, the gear transmission device is a rotating element. Since there is no slippage between them, there is an advantage that power loss is small. However, in a vehicle in which a gear transmission is provided in the power transmission path from the electric motor to the tire, as described in Patent Document 1, control for giving a minute vibration to the torque transmitted from the electric motor to the tire is performed. When the torque of the electric motor is vibrated so as to extend over both the drive side and the regeneration side, there is a possibility that a tooth contact noise caused by backlash occurs at the meshing portion of the gears.

  The present invention has been made paying attention to the technical problem described above. When the torque transmitted from the driving force source to the tire is vibrated, a collision sound is generated at the engaging portion between the concave portion and the convex portion of the transmission device. It is an object of the present invention to provide a driving force control device that can suppress the occurrence.

  In order to achieve the above object, the invention of claim 1 includes a tire that contacts a road surface and a driving force source that generates torque to be transmitted to the tire, and the driving force source transmits the tire to the tire. By obtaining a required torque, obtaining a vibration torque that changes alternately with the required torque as a reference, and transmitting the vibration torque from the driving force source to the tire, the friction coefficient between the tire and the road surface is controlled. In the driving force control device, a transmission device that transmits torque by meshing between the concave portion and the convex portion is provided in a torque transmission path from the driving force source to the tire, and the required torque is transmitted to the driving region or the regeneration. Determination means for determining whether or not the vibration torque alternately moves between the drive area and the regeneration area in any one of the areas; Is generated in the same region as the required torque when it is determined that the vibration torque alternates between the drive region and the regeneration region. As described above, a correction means for correcting the vibration torque is provided.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect, the correction means removes a part of the vibration torque in a region different from the region where the required torque is present, so that the vibration torque becomes the required value. Means for correcting the vibration torque to occur in the same region as the torque, the work of the vibration torque in the phase including the removed portion of the vibration torque, and the removed phase of the vibration torque And a means for correcting the vibration torque so that the difference between the work of the vibration torque in the opposite phase is relatively small.

  According to the first aspect of the present invention, the required torque to be transmitted from the driving force source to the tire is obtained, and the frictional coefficient between the tire and the road surface is generated by generating the vibration torque that alternately changes with the required torque as a boundary. Can be controlled. Also, it is determined that the required torque transmitted from the driving force source to the tire is in either the driving region or the regenerative region, and the vibration torque changes alternately, that is, the driving region and the regenerative region alternate. If so, the vibration torque is corrected so that the vibration torque is in the same region as the required torque. Therefore, it can suppress that the recessed part and convex part of a transmission collide and a collision sound arises.

  According to the invention of claim 2, by removing a part of the change in the vibration torque in a region different from the region where the required torque exists, all of the vibration torque is generated in the same region as the required torque. Correct the vibration torque. More specifically, a part of the torque of the vibration torque and a work amount of the vibration torque in a phase where a part of the torque to be added to or subtracted from the required torque is removed and a part of the vibration torque are removed. The vibration torque is corrected so that the difference from the work of the vibration torque in the phase opposite to the phase becomes relatively small. Therefore, it is possible to prevent the vehicle from inadvertently accelerating or decelerating due to the vibration of the torque transmitted to the tire.

  The driving force source in the present invention is a power generation device connected to a tire so as to be able to transmit power. Examples of the driving force source include an electric motor, an engine, and a hydraulic motor. The electric motor is a rotating device that converts electric energy into kinetic energy, and the torque of the electric motor can be controlled by controlling the current value of the electric power supplied to the electric motor. As the electric motor, a motor / generator having a function of converting kinetic energy into electric energy can be used. The engine is a power unit that converts thermal energy when fuel is burned into kinetic energy, and an internal combustion engine such as a gasoline engine, a diesel engine, or an LPG engine can be used as the engine. These engines can control the output torque by controlling the intake air amount and the fuel injection amount. Further, the gasoline engine and the LPG engine can control the output torque by controlling the ignition timing. The hydraulic motor is a fluid machine that converts the fluid energy of oil into the kinetic energy of the rotor, and a rotary hydraulic motor such as a gear motor, a vane motor, or a screw motor can be used as the hydraulic motor. In the hydraulic motor, the output torque of the rotor can be controlled by controlling the oil pressure of oil that gives kinetic energy to the rotor.

  In the transmission device according to the present invention, backlash, that is, a circumferential gap or play is inevitably formed between the concave portion and the convex portion. The transmission device according to the present invention includes a gear transmission that transmits torque by the meshing force between the gears. As a power transmission device using this gear transmission, a transmission that can change the ratio of the input rotation speed and the output rotation speed, a reduction gear that cannot change the ratio of the input rotation speed and the output rotation speed, A transfer that distributes power to the front and rear wheels, a differential that allows a difference in rotational speed between the left and right wheels, and the like are included. Examples of the transmission include a planetary gear type transmission, a selection gear type transmission, a constant mesh transmission, and the like. Further, the transmission device according to the present invention includes a spline coupling provided at a connection portion between the output shaft and the propulsion shaft of the transmission, that is, a mechanism for transmitting torque by meshing the inner teeth with the outer teeth. The drive region in this invention includes the meaning of a region that applies torque that promotes the rotation of the tire, and the regeneration region includes the meaning of a region that applies torque (braking force) that inhibits rotation of the tire to the tire. . In the present invention, that the difference between work amounts is relatively small means a relative magnitude relationship, and there is no need to have a reference value for determining whether the difference is small or large.

  Next, an embodiment of the present invention will be described with reference to the drawings. The vehicle 1 shown in FIG. 2 has four wheels, specifically, a right front wheel 2, a left front wheel 3, a right rear wheel 4, and a left rear wheel 5. Each wheel is configured by attaching a tire 7 to the wheel 6 and having an electric motor 8 disposed inside the wheel 6, that is, an in-wheel motor type wheel. The electric motor 8 is a motor generator that has both a power running (driving) function for converting electrical energy into kinetic energy and a regeneration function for converting kinetic energy into electrical energy. That is, the power running control is to operate the electric motor 8 as an electric motor, and the regeneration control is to operate the electric motor 8 as a generator. A speed reducer 9 is disposed in the power transmission path from the electric motor 8 to the wheel 6. The reduction gear 9 has a configuration in which the output rotation speed is lower than the input rotation speed. As the reduction gear 9, for example, a constantly meshing gear transmission mechanism can be used.

  As described above, the vehicle 1 shown in FIG. 2 is a four-wheel drive vehicle capable of independently controlling the torque transmitted to the tire 7 of each wheel. The electric motor 8, the speed reducer 9, and the wheels are supported by the vehicle body via a suspension device. This suspension device is a known device having a shock absorber, a spring and the like. Furthermore, a power source 13 is provided on the vehicle body. As the power source 13, a secondary battery that can be discharged and charged, for example, a battery or a capacitor can be used. Furthermore, in addition to the secondary battery, a fuel cell can also be used. The power source 13 and each electric motor 8 are connected by an electric circuit having an inverter (not shown).

  A braking device is provided for controlling the braking force applied to each wheel. The braking device includes a rotor that rotates integrally with the wheel 7, a disk caliper that sandwiches the rotor, a wheel cylinder 10 that operates the disk caliper, and an actuator 11 that controls the hydraulic pressure of the wheel cylinder 10. The wheel cylinder 10 is provided for each wheel, and the actuator 11 is provided on the vehicle body. Further, a steering device 12 is provided for controlling the steering angle of each wheel, particularly the front wheel. The steering device 12 has a known structure including a steering wheel provided in a room, a tie rod provided below the vehicle body, a gear box that converts a rotation operation of the steering wheel into an operating force of the tie rod, and the like. Furthermore, an electronic control device 14 for controlling the braking device and the electric motor 8 is provided. The electronic control device 14 includes an operation state of an accelerator pedal, an operation state of a brake pedal, a vehicle speed, a rotation speed of each wheel, an electric motor. A signal of a sensor or a switch for detecting the number of rotations, torque, and the like is input. The electronic control device 14 outputs vibrations for controlling the rotation speed and torque of the electric motor 8, signals for controlling the hydraulic pressure of the wheel cylinder 10, and the like.

  The vehicle 1 shown in FIG. 2 includes an anti-lock brake system, a traction control system, and the like as functions for controlling running performance. These systems control the frictional force of the tire 7 so as to stabilize the vehicle body by maximizing the frictional force of the tire 7. For example, the cornering force is sufficiently large and the braking force is large. The target slip ratio is calculated, and the hydraulic control of the wheel cylinder 10 of the braking device, the rotational speed and torque of the electric motor 8 are controlled so that the actual slip ratio of the tire 7 approaches the target slip ratio. The steering performance, power performance, braking performance, turning performance, etc. of the vehicle 1 are to be ensured. In order to perform such control, the electronic control unit 14 stores a map and data representing the relationship between the slip ratio of the tire 7 and the friction coefficient between the tire 7 and the road surface. Based on this, the hydraulic pressure of the wheel cylinder 10 and the torque and rotation speed of the electric motor 8 are controlled.

On the other hand, the correspondence relationship between the slip ratio of the tire 7 and the friction coefficient between the tire 7 and the road surface varies depending on the road surface condition. It is also known that the friction coefficient between the tire 7 and the road surface can be arbitrarily adjusted by changing the torque transmitted to the tire 7, that is, by giving vibration to the torque. Specifically, when the torque of the electric motor 8 applied to the tire 7 is vibrated, the friction coefficient between the tire 7 and the road surface is arbitrarily adjusted by controlling the amplitude, frequency, phase, etc. of the vibration. It is known. This principle is described in the republished patent WO02 / 000463. For example, a friction model using a rubber block instead of the tire 7 can be expressed by the following vibration equation (1).

In the vibration equation (1), Fn is a vertical load in which the rubber block contacts the road surface, and μ · Fn is a friction force (μ is a friction coefficient of the road surface) acting on the rubber block sliding in a certain direction. Yes, m is the mass of the rubber block, k is the spring constant between the rubber block and the road surface, c is the damping coefficient of the rubber block, and ω 0 is the resonance frequency of the rubber block. By solving this vibration equation (1), the ratio μre1 between the frictional force that does not give minute vibration to the rubber block and the frictional force that gives minute vibration to the rubber block is obtained by the following equation (2).

  From the above two formulas, it is understood that the friction coefficient between the tire 7 and the road surface can be arbitrarily adjusted by applying vibration in the front-rear direction of the tire 7 to be controlled. The ratio μre1 depends on the frequency ω of the minute vibration to be applied, and the value of the ratio μre1 tends to decrease as the frequency ω approaches the resonance frequency ω0. In addition, it is possible to relatively increase the value of the ratio μre1 by applying vibration with a frequency higher than the resonance frequency ω0 by frequency modulation. Further, by applying a vibration torque in the rotational direction of the tire 7, the relationship between the friction coefficient and the slip ratio in the front-rear direction of the tire 7 tends to increase as the slip ratio increases. This is known, and is also described in the republished patent WO 02/000463.

  In this embodiment, in order to estimate whether or not the actual friction coefficient has reached the target friction coefficient, the electronic control unit 14 stores a map and data indicating the relationship between the slip ratio and the friction coefficient. And while estimating the slip ratio of the tire 7, an actual friction coefficient can be estimated from a map and data. Note that the slip ratio of each tire 7 can be estimated based on a signal from a sensor that detects the rotational speed of each wheel, and an estimation method thereof is disclosed in JP-A-2002-274356, JP-A-6-258196, and the like. Since it is well-known as described in the above, a detailed description is omitted. Thus, by vibrating the torque transmitted to the tire 7, it is possible to adjust the friction coefficient in the front-rear direction between the tire 7 and the road surface. In addition, when the case where the vibration torque is given is compared with the case where the vibration torque is not given, if the slip ratio in the front-rear direction is the same, the case where the vibration torque is given is compared to the case where the vibration torque is not given, It is known that the friction coefficient in the front-rear direction of the tire 7 is reduced. This is described in the republished patent WO02 / 000463.

  Incidentally, a speed reducer 9 is disposed in a power transmission path from the electric motor 8 to the tire 7. In the speed reducer 9, backlash is inevitably formed at the meshing portion of the gears. Therefore, when the torque transmitted from the electric motor 8 to the tire 7 vibrates and the torque of the electric motor 8 is switched from the drive side to the regeneration side, and when the torque is switched from the regeneration side to the drive side, the meshing portion of the gears is engaged. There was a possibility that impact sound would be generated due to collision between teeth. Here, the drive side means that the electric motor 8 is power-running controlled, and the regeneration side means that the electric motor 8 is regeneratively controlled.

  In this embodiment, when vibration is applied to the torque transmitted from the electric motor 8 to the tire 7, in order to suppress the occurrence of impact sound due to the collision between the teeth at the meshing portion of the gears, FIG. The flowchart is executed. The flowchart of FIG. 1 is an example in which torque is vibrated in the front-rear direction of the tire 7 while the vehicle 1 is traveling. First, it is determined whether or not a condition for starting vibration of torque transmitted to the tire 7 is established (step S1). For example, in order to adjust the coefficient of friction between the tire 7 and the road surface, if a switch for selecting whether or not to start torque vibration is provided according to the driver's intention, based on the operation state of the switch The determination in step S1 can be made. If a negative determination is made in step S1, the process returns to the start without performing any special control.

  On the other hand, if a positive determination is made in step S1, the vibration torque gain G and the vibration torque frequency F are determined (step S2). The processing in step S2 will be described with reference to the waveform diagram of FIG. FIG. 3 shows waveforms of required torque and vibration torque. In this embodiment, the required driving force is obtained using the vehicle speed and the accelerator opening as parameters, and processing for obtaining the required torque to be output from the electric motor 8 is performed based on the required driving force. As described above, the data and map for obtaining the required torque are stored in the electronic control unit 14. Then, a predetermined torque is added to the required torque, and the predetermined torque is subtracted from the required torque to obtain a torque that fluctuates around the required torque, that is, a vibration torque.

  As described above, the vibration torque alternates between the phase higher than the required torque and the phase lower than the required torque at a predetermined cycle with the required torque as a boundary. The difference between the required torque and the vibration torque is the vibration torque gain G, and the frequency of the vibration period per unit time is the frequency F. The vibration period is a time from the request torque as a starting point, which is higher than the request torque, then lower than the request torque via the request torque, and thereafter returns to the request torque. In this embodiment, data and a map indicating the correspondence between the vehicle speed and the friction coefficient are stored in the electronic control unit 14, and the target friction coefficient is obtained from the vehicle speed. Next, a map and data for determining the vibration torque gain and frequency are stored in the electronic control unit 14 for each target friction coefficient. In step S2, the vibration torque gain and frequency are determined using this map and data. Desired.

  Subsequent to step S2, control for oscillating torque transmitted from the electric motor 8 to the tire 7 is started (step S3). The torque vibration of the tire 7 performed in step S3 has the characteristics obtained in step S2. Specifically, the torque value can be vibrated by controlling the current value of the electric power supplied to the electric motor 8. Following this step S3, it is determined whether or not the vibration torque is switched between the drive side and the regeneration side with zero Nm as a boundary (step S4). If the determination in step S4 is affirmative, the portion where the vibration torque crosses zero Nm, that is, the regeneration side torque is removed, and the vibration gain G ′ from the required torque to the remaining vibration torque is set to a predetermined value. While extracting every time t ′, the vibration gain G ′ and the predetermined time t ′ are stored in the electronic control unit 14 (step S5).

  The processing in step S5 will be described with reference to the vibration waveform in FIG. In FIG. 4, the accelerator pedal is depressed and the required torque is on the drive side. In addition, a portion of the vibration torque that is lower than the required torque alternates between the drive side and the regeneration side with zero Nm as a boundary. Therefore, the portion of the vibration torque exceeding zero Nm, specifically, the regeneration side torque is deleted. For this reason, a part of the vibration torque becomes zero Nm. Further, the vibration gain G ′ of the vibration torque less than the required torque is extracted at every predetermined time t ′ from the point A where the vibration torque is less than the required torque to the point B until the vibration torque returns to the required torque. Is done. Following this step S5, the portion where the vibration torque is higher than the required torque, that is, from point B to point C, is obtained by adding the vibration gain G ′ to the required torque at every predetermined time t ′. (Step S6) and return to the start. On the other hand, if a negative determination is made in step S4, the control for applying the vibration torque to the tire with the value obtained in step S2 is continued (step S7), and the process returns to the start.

  In the above description, an example in which the accelerator pedal is depressed and the required torque is on the drive side is described. However, in this control example, the accelerator pedal is returned and the electric motor 8 is operated. The present invention is also applicable to the case where the regeneration control is performed in the case where the required torque is on the regeneration side. In this case, in step S5, when the vibration torque fluctuates mainly on the regeneration side and the vibration torque is switched between the regeneration side and the drive side with zero Nm as a boundary, the drive side portion is cut. In step S5, the torque of the cut portion is controlled to zero Nm. Further, in step S5, the vibration gain G ′ is added every predetermined time t ′. Further, in step S6, in a portion where the vibration torque is lower than the required torque, the vibration torque is obtained by adding the vibration gain G ′ to the required torque at every predetermined time t ′. The map and data used in the above control example are obtained by storing values obtained by experiments or simulations in advance in the electronic control unit 14. An example of changing a part of the flowchart of FIG. 1 will be described. It is also possible to employ a routine that proceeds to step S4 after step S2 without performing step S3. In this case, torque vibration of the electric motor 8 may be started in step S5 or step S7.

  Thus, in the control example of FIG. 1, it is possible to avoid the vibration torque from going back and forth between the drive side and the regeneration side with zero Nm as a boundary. For this reason, with the reduction gear 9 from the electric motor 8 to the tire 7, it is possible to suppress the occurrence of impact noise at the meshing portion of the gears. Moreover, the vibration of the part (unsprung part) where the load is not supported by the spring of the suspension device can be suppressed. In addition, by applying a vibration torque in the front-rear direction of the tire 7 to adjust the friction coefficient, the characteristics of the friction coefficient in the lateral direction of the tire 7 can be adjusted. Specifically, if the slip ratio in the front-rear direction of the tire 7 is the same, the friction coefficient in the lateral direction of the tire 7 is greater when the vibration torque is applied than when the vibration torque is not applied. It is known to grow. This is described in the republished patent WO02 / 000463. Further, by performing the processing of step S5 and step S6, the work amount of the electric motor 8 from the point A to the point B is matched with the work amount of the electric motor 8 from the point B to the point C. be able to. Therefore, it is possible to suppress acceleration / deceleration in the front-rear direction while the vehicle 1 is traveling. In step S6, control is performed to relatively reduce the difference between the work amount of the electric motor 8 from the point A to the point B and the work amount of the electric motor 8 from the point B to the point C. You can also do it.

  Further, in the example shown in FIG. 4, the vibration torque has a sine wave shape, and the range on both sides including the inflection point of the vibration torque is adjusted to a substantially flat torque, as shown in FIG. Further, by gradually changing the vibration gain G ′, it is possible to obtain a vibration torque waveform without a flat portion. In the present invention, in addition to the power train of the so-called in-wheel motor type in which the electric motor 8 is arranged inside the wheel 7 of each wheel, the torque of the electric motor mounted on the vehicle body passes through the transmission device, The present invention can also be applied to a two-wheel drive vehicle configured to be transmitted to either the front wheel or the rear wheel. Furthermore, the present invention is also applicable to a four-wheel drive vehicle having a configuration in which the torque of the electric motor mounted on the vehicle body is transmitted to both the front wheels and the rear wheels via the transmission device.

  Here, the correspondence between the configuration described in this embodiment and the configuration of the present invention will be described. The tire 7 corresponds to the tire of the present invention, and the electric motor 8 corresponds to the driving force source of the present invention. The speed reducer 9 corresponds to the transmission device of the present invention. Further, the correspondence between the functional means shown in FIG. 1 and the configuration of the present invention will be explained. Step S4 corresponds to the determination means of the present invention, and steps S5 and S6 serve as the correction means of the present invention. Equivalent to. Further, a reference example of control for vibrating the torque transmitted to the tire 7 will be described. In this control, the vibration torque is controlled so as to alternate between the drive side and the regeneration side with respect to the required torque, and the work amount on the drive side and the work amount on the regeneration side are the same.

It is a flowchart which shows the example of control which can be performed with the driving force control apparatus of this invention. It is a conceptual diagram of the vehicle used as the object of the driving force control apparatus of this invention. It is a wave form diagram which shows the change of the torque transmitted to a tire by this invention. It is a wave form diagram which shows the example which correct | amends the torque transmitted to a tire by this invention. It is a wave form diagram which shows the other example which correct | amends the torque transmitted to a tire by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 7 ... Tire, 8 ... Electric motor, 9 ... Reduction gear, 14 ... Electronic control unit.

Claims (2)

A tire having contact with a road surface and a driving force source that generates torque to be transmitted to the tire are obtained. A required torque to be transmitted from the driving force source to the tire is obtained, and the torque changes alternately with reference to the required torque. In the driving force control device that determines the vibration torque and transmits the vibration torque from the driving force source to the tire to control the coefficient of friction between the tire and the road surface,
In the torque transmission path from the driving force source to the tire, there is provided a transmission device for transmitting torque by meshing between the concave portion and the convex portion,
Determination means for determining whether the required torque is in either the drive region or the regenerative region, and whether the vibration torque alternates between the drive region and the regenerative region;
When it is determined that the required torque is in either the drive region or the regenerative region, and the vibration torque alternates between the drive region and the regenerative region, the vibration torque is the same region as the required torque. A driving force control apparatus comprising: a correcting unit that corrects the vibration torque so as to generate the vibration torque. The correction means includes
Means for correcting the vibration torque so that the vibration torque is generated in the same region as the request torque by removing a part of the vibration torque in a region different from the region where the request torque is present;
The difference between the work of the vibration torque in the phase including the removed portion of the vibration torque and the work of the vibration torque in the phase opposite to the removed phase of the vibration torque is relatively small. The driving force control apparatus according to claim 1, further comprising means for correcting the vibration torque.

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