JP5556500B2 - Vehicle control apparatus and method - Google Patents

Description

  The present invention relates to a vehicle control technology including a vehicle height adjustment mechanism.

  In general, a vehicle having a function of adjusting a stroke amount of a suspension device of each wheel in accordance with a road surface state and traveling characteristics is known. In such a vehicle, it is possible to control the vehicle behavior by changing the stroke amount during driving or braking of the vehicle.

  For example, a technique for suppressing a yaw moment that deflects a vehicle that occurs during braking of the vehicle is known. Patent Document 1 discloses a motion control device that corrects vehicle deflection caused by braking of the vehicle due to left-right asymmetry inherent in the structure of the vehicle.

  Further, as a technique for reducing the influence of a change in the toe angle in the suspension device, Patent Document 2 discloses a characteristic of a toe angle change in a vehicle suspension so that the change in the toe angle associated with the vertical movement of the tire relative to the vehicle body is canceled out. Is disclosed. In Patent Document 3, when the difference between the left and right heights of the left and right steered wheels is greater than or equal to a predetermined value, each wheel in a direction in which the yaw motion of the vehicle caused by the change in the toe angle due to the suspension stroke of the left and right steered wheels decreases. A driving force control device for correcting the driving force is disclosed.

JP 2008-037259 A Japanese Patent Laid-Open No. 08-034221 JP 2007-043837 A

  In the technique of the above-mentioned Patent Document 1, the steering angle, the left and right braking force, and the like are controlled in order to generate a yaw moment in a direction that suppresses deflection at the time of straight braking caused by left-right asymmetry of the vehicle. Therefore, it is necessary to have a configuration such as a steering device that can be steered independently of the steering of the vehicle driver and a braking device that applies a braking force difference between the left and right wheels of the vehicle, which increases the complexity and cost of the structure. There is a problem of end.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a technique for suppressing deflection that occurs during straight braking of a vehicle using a vehicle height adjustment function of the vehicle.

  One embodiment of the present invention is a vehicle control device. The apparatus includes a suspension installed for each wheel and configured to be able to adjust a stroke amount, a braking state detection unit that detects a braking state during vehicle braking, a steering detection unit that detects a steering amount of the vehicle, and the steering A straight braking determination unit that determines whether or not the vehicle is traveling straight based on a detection value of the detection unit, and that determines whether or not the vehicle is braked based on a detection value of the braking state detection unit; and the straight braking determination unit When it is determined that the vehicle is braked when traveling straight, a deflection amount predicting means for predicting a deflection amount generated in the vehicle body due to left-right asymmetry of the vehicle, and a stroke amount of the suspension so as to reduce the predicted deflection And stroke adjusting means for changing.

  According to this aspect, the amount of deflection that will occur in the vehicle body during braking is predicted, and the stroke amount of the suspension device of each wheel is adjusted in a direction to reduce this amount. As a result, the steering angle of the suspension device changes, and braking deflection generated in the vehicle body is suppressed.

  The stroke adjusting means may reduce the deflection by using a yaw moment generated by a left-right difference in toe angle based on the stroke adjustment of the suspension.

  The deflection amount predicting means may predict the deflection amount from the center of gravity and deceleration of the vehicle body. Moreover, you may further provide the gravity center estimation means which estimates the gravity center of a vehicle body based on the grounding load concerning each wheel.

  Another aspect of the present invention is a vehicle control method that suppresses deflection of a vehicle during straight braking in a vehicle including a suspension that is installed for each wheel and configured to be able to adjust a stroke amount. This method detects a braking state at the time of vehicle braking, detects a steering amount of the vehicle, determines whether or not the vehicle is traveling straight based on the detected steering amount, and brakes the vehicle based on the detected braking state. The suspension so as to predict the amount of deflection generated in the vehicle body due to the left-right asymmetry of the vehicle and reduce the predicted deflection when it is determined that the vehicle is braked when going straight ahead. Including changing the stroke amount.

  ADVANTAGE OF THE INVENTION According to this invention, in the vehicle provided with the vehicle height adjustment mechanism, the deflection | deviation at the time of the rectilinear braking resulting from the left-right asymmetry of a vehicle can be suppressed.

It is a mimetic diagram of a four-wheeled vehicle provided with a vehicle control device concerning one embodiment of the present invention. It is a schematic diagram for demonstrating the principle which the deflection | deviation of a vehicle generate | occur | produces at the time of braking. It is a functional block diagram which shows the structure of a vehicle control apparatus. It is a schematic diagram for demonstrating the principle by which deflection | deviation is suppressed by the vehicle control apparatus. (A)-(d) is a graph explaining the change of the stroke amount at the time of control in each wheel. It is a flowchart of the control which suppresses the deflection | deviation of a vehicle.

  FIG. 1 is a schematic diagram of a four-wheel vehicle 10 including a vehicle control device according to an embodiment of the present invention. The vehicle 10 includes wheels including a left front wheel FL, a right front wheel FR, a left rear wheel RL, and a right rear wheel RR. In FIG. 1, the suspension device is shown in a plan view for the sake of simplicity. However, in an actual vehicle, for example, a knuckle, a tie rod, and an upper arm are arranged in an appropriate space arrangement to exhibit the function of the suspension device. In combination with other parts such as a lower arm in a known manner.

  Between the vehicle body 12 of the vehicle 10 and each wheel FL, FR, RL, RR, an air suspension device 16 configured by combining an air spring and an absorber is provided. By filling compressed air in an air chamber (not shown) formed so as to surround an absorber (not shown), the compressed air in the air chamber acts as a spring. By elastically supporting the wheel by the air spring, it is possible to prevent the impact of the wheel from being directly transmitted to the vehicle body 12. Further, by changing the volume of the air chamber, the vehicle height, that is, the distance between the wheel and the vehicle body can be adjusted for each wheel. The absorber generates a damping force between the sprung and unsprung parts of the vehicle.

  In the vicinity of each wheel FL, FR, RL, RR, a stroke sensor 106 for measuring the stroke amount of the absorber constituting the corresponding air suspension device 16 is arranged. The detection signal of the stroke sensor 106 is sent to an electronic control device 100 (hereinafter referred to as “ECU 100”) provided in the vehicle body 12.

  In some embodiments, a ground load sensor (not shown) for detecting the wheel ground load is incorporated into the air suspension 16 of each wheel. Instead of providing the ground load sensor, the ground load of the wheel may be calculated by multiplying the stroke amount detected by the stroke sensor 106 by the spring constant of the air spring.

  The wheel speed sensor 104 is installed in the vicinity of each wheel FL, FR, RL, RR or in the vicinity of any one of the wheels, detects the number of rotations of the wheel, and transmits it to the ECU 100. The steering wheel 18 is provided with a steering angle sensor 102, which detects the steering angle of the steering wheel and transmits it to the ECU 100.

  A brake torque sensor 110 is also installed on the vehicle body. For example, the brake torque sensor 110 detects the amount of depression of the brake pedal by the driver, and transmits the brake torque corresponding to the amount of depression to the ECU 100. In the present embodiment, it is assumed that the depression amount of the brake pedal and the brake torque are within a substantially linear range.

  The air chamber of the air suspension device 16 communicates with the air supply line 190. In the middle of the air supply line 190, air pressure control valves 140 are provided corresponding to the respective wheels. The pneumatic control valve 140 is electrically connected to the ECU 100 and can be switched between a valve open state and a valve closed state in accordance with a signal from the ECU 100. As a result, air can be supplied into the air chamber 20 of the air suspension 16 via the air supply line 190, or air can be discharged from the inside.

  The vehicle body 12 is provided with an air tank 166 for accumulating compressed air and supplying air to the air chamber via an air supply line 190. In FIG. 1, one air tank 166 is drawn for each of the front wheels and the rear wheels, but only one air tank may be provided in the vehicle body, or an air tank may be provided for each wheel. The air tank 166 is maintained at 700 to 800 kPa, for example, by sending compressed air from a compressor (not shown). The compressor receives power from a motor (not shown) and takes in air from the outside to generate compressed air.

  FIG. 2 is a schematic diagram for explaining a mechanism in which deflection occurs during straight braking of the vehicle. If the vehicle structure is a symmetrical vehicle, the vehicle should not deflect during straight braking unless there is an external factor that deflects the vehicle. However, in reality, the mounting positions of various devices mounted on the vehicle are not symmetrical, and passengers and luggage are often loaded in a biased manner, so the vehicle weight distribution is rarely symmetrical. . That is, the center of gravity is shifted to the left or right from the center of the vehicle. If equal braking torque is applied to the left and right wheels while the center of gravity is shifted to the left or right, a moment in the yaw direction is generated around the center of gravity of the vehicle body, so that the vehicle is deflected even during straight braking.

  FIG. 2 is a schematic diagram of the vehicle 10 when the right-hand drive vehicle has one driver. In this case, the center of gravity G is located on the right side of the center line C of the vehicle body. Assume that the braking force applied to the left and right wheels is equal when the brake is applied (ie, D1 = D2 = D3 = D4). Since the yaw moment applied to the center of gravity is represented by the product of the distance of each wheel FL, FR, RL, RR from the center of gravity and the braking force, when the center of gravity G is to the right, A clockwise moment M is generated. Therefore, the vehicle body is deflected in the left direction BL in the figure.

  In this embodiment, in order to suppress this deflection, the stroke amount of the suspension is controlled to be different between the left and right wheels during straight braking. As a result, the steering amount of the left and right wheels acts in a direction to reduce the deflection generated in the vehicle body, and as a result, the vehicle body deflection is suppressed.

  FIG. 3 is a functional block diagram showing a configuration of a part (hereinafter referred to as “vehicle control device 150”) involved in vehicle control according to the present embodiment of the ECU 100. Each block shown here can be realized in hardware by an element and a mechanical device including a computer CPU and memory, and in software by a computer program or the like. It is drawn as a functional block to be realized. Therefore, those skilled in the art will understand that these functional blocks can be realized in various forms by a combination of hardware and software.

  The vehicle control device 150 includes a detection value acquisition unit 120, a straight braking determination unit 121, a deflection prediction unit 122, and a stroke adjustment unit 126.

  The detection value acquisition unit 120 receives various detection values from various sensors installed in the vehicle. The detected value includes a stroke amount detected by the stroke sensor 106, a wheel speed detected by the wheel speed sensor 104, a steering angle detected by the steering angle sensor 102, a pedal depression amount detected by the brake torque sensor 110, and the like. Is included.

  The straight braking determination unit 121 determines whether or not the vehicle 10 is in a straight braking state based on the detection value acquired by the detection value acquisition unit 120. Specifically, when the steering angle is within a predetermined angle range (for example, −5 degrees to +5 degrees), it is determined that the vehicle 10 is traveling straight, and the brake pedal is depressed more than a predetermined amount in this state. That is, when the brake torque is greater than or equal to a predetermined value, it is determined that the vehicle is in the straight braking state.

  The deflection prediction unit 122 estimates the direction and magnitude of the deflection generated in the vehicle body due to the left-right asymmetry of the vehicle when the straight-ahead braking determination unit 121 determines that the vehicle is braked when traveling straight. The deflection prediction unit 122 includes a centroid estimation unit 123 and a deflection amount estimation unit 124.

  The center of gravity estimation unit 123 estimates the position of the center of gravity of the vehicle body 12. When a load sensor is installed on the vehicle body 12, the position of the center of gravity of the vehicle body can be estimated from the distribution of the ground load of each wheel. When a load sensor is not set on the vehicle body 12, the center of gravity position is estimated after calculating the ground load of each wheel by multiplying the stroke amount detected by the stroke sensor 106 by a predetermined spring constant. The position of the center of gravity is related to the value of the yaw moment generated in each wheel during braking. The center of gravity position may be a fixed value.

  The deflection amount estimation unit 124 is generated in the vehicle body during straight braking based on the center of gravity of the vehicle body obtained by the center of gravity estimation unit 123, the vehicle speed detected by the wheel speed sensor 104, and the brake torque detected by the brake torque sensor 110. Estimate the direction and magnitude of the deflection that would be.

  The deflection amount estimation unit 124 calculates the deceleration of the vehicle from the vehicle speed and the brake torque. Then, the deflection amount estimation unit 124 refers to the deflection amount map in which the magnitude of the deflection generated in the vehicle body is uniquely determined for each combination of the calculated deceleration and the center of gravity of the vehicle body. The amount of deflection to be estimated is estimated. Note that the direction of deflection may be expressed by the sign of the amount of deflection in the map, or the deflection amount estimation unit 124 determines depending on whether the center of gravity is on the left or right side with respect to the center line of the vehicle body. Also good. The deflection amount map can be created by measuring or calculating the deflection of the vehicle when a combination of parameters is given for each vehicle or for each vehicle type based on a test or simulation with an actual vehicle.

  The stroke adjustment unit 126 adjusts the stroke amount of the suspension device of each wheel in order to reduce the influence of the deflection predicted by the deflection prediction unit 122. Specifically, the stroke adjusting unit 126 suppresses deflection by using a yaw moment generated in the vehicle body due to a left-right difference in toe angle due to a change in the stroke amount of the suspension device.

  The stroke adjustment unit 126 includes a stroke amount calculation unit 128 and a valve control unit 130. The stroke amount calculation unit 128 calculates a stroke amount to be generated in the suspension device of each wheel. The calculation of the stroke amount may be performed, for example, by inputting the direction and magnitude of the deflection obtained by the deflection amount estimation unit 124 into a calculation formula set in advance based on the geometry of the air suspension device. . Alternatively, the stroke amount of each wheel may be obtained with reference to a stroke amount map in which the stroke amount to be realized by the suspension device of each wheel is uniquely determined with respect to the combination of the deflection direction and the magnitude. This stroke amount map measures or calculates the stroke amount of each wheel suspension device required to reduce the influence of braking deflection based on actual vehicle tests or simulations for each vehicle or vehicle type. Can be created.

  The valve control unit 130 controls the opening degree, time, and the like of the pneumatic control valve that communicates with each air chamber so that the stroke amount calculated by the stroke amount calculation unit 128 is generated in the air suspension device of each wheel. Since it is well known to adjust the stroke amount of the air suspension device by opening and closing the valve, a detailed description thereof will be omitted.

  The operation of the vehicle control device 150 will be described. When the straight braking determination unit 121 determines that there is a brake input with almost no steering input by the steering wheel, the deflection prediction unit 122 is generated in the vehicle body based on the center of gravity of the vehicle body, the magnitude of the braking force, the vehicle speed, and the like. Predict the direction and magnitude of the braking deflection. The stroke adjustment unit 126 calculates the stroke amount of the air suspension device of each wheel necessary for suppressing the predicted braking deflection, and the air control valve leading to the air chamber is realized so that the calculated stroke amount is realized. Adjust the opening / closing amount. As a result, the steering angle of the suspension device changes, and braking deflection generated in the vehicle body is suppressed.

  FIG. 4 is a schematic diagram for explaining the principle of suppressing the deflection caused by the left-right asymmetry of the vehicle in the vehicle control device according to the present embodiment. As in FIG. Shown when braking. In the wheels FL, FR, RL, and RR in the figure, the dotted line indicates the direction of each wheel during non-control, and the solid line indicates the direction of each wheel during control.

  Since the load moves to the front wheel side when the vehicle 10 is braked, the suspension device on the front wheel side strokes on the bounce side, and the suspension device on the rear wheel side strokes on the rebound side. The stroke amount depends on the load and the spring constant of the suspension. Under normal circumstances, there is no significant difference in the load movement during braking between the left and right wheels, and the suspension device of the vehicle has the same spring constant between the left and right wheels. Therefore, when the vehicle is braked, the stroke amounts in the left and right wheel suspension devices are substantially equal.

  Generally, a suspension device has a structure in which a wheel steers when a stroke is displaced. This amount of steering is determined geometrically by the geometry of the suspension. In a normal vehicle, the suspension device is designed to be toe-in when bound and toe-out when rebound. Therefore, when the vehicle 10 of FIG. 4 performs straight braking, the front wheels FL and FR steer in the toe-in direction and the rear wheels RL and RR steer in the toe-out direction. The dotted line in FIG. 4 shows this state.

  The vehicle control device 150 according to the present embodiment controls the stroke amount of the suspension device of each wheel so that a clockwise yaw moment is generated in the vehicle body at the time of straight braking of the vehicle. In the case of a vehicle whose center of gravity is on the right side and deflected to the left as shown in FIG. In addition, the stroke amount is forcibly changed. Similarly, the stroke amount is forcibly changed in the direction of increasing the rebound (that is, increasing toe out) the suspension of the left rear wheel RL and in the direction of decreasing the rebound (that is, decreasing toe out) of the suspension of the right rear wheel RR. Arrows E1 to E4 in FIG. 4 indicate the direction and displacement amount of each wheel by the direction and length of the arrow. By changing the stroke amount, a right yaw moment is generated around the center of gravity G. This yaw moment bends the vehicle body to the right BR. As a result, the amount of deflection generated in the vehicle body can be suppressed because the force is offset by the leftward bending force generated due to the left-right asymmetry of the vehicle.

  FIGS. 5A to 5D are diagrams for explaining the stroke amount control for the suspension device of each wheel described with reference to FIG. 4 in more detail. 5 (a) to 5 (d) all relate to a vehicle whose center of gravity described in FIGS. 2 and 4 is on the right side.

  FIG. 5A is a graph showing the relationship between the stroke amount in the bounce direction and the ground contact load on the front wheels FL and FR. It is assumed that the relationship between the stroke amount during normal traveling and the ground load is represented by a solid line in the figure. The stroke adjustment unit 126 controls to increase the stroke amount in the bounce direction for the left front wheel FL and decrease the stroke amount in the bounce direction for the right front wheel FR during straight braking.

  FIG. 5B is a graph showing the relationship between the stroke amount in the bounce direction and the steer angle in the toe-in direction for the front wheels FL and FR. In the present embodiment, it is assumed that the stroke amount and the steer angle are in a linear relationship. As described above, the stroke adjusting unit 126 increases the stroke amount in the bounce direction for the left front wheel FL and decreases the stroke amount in the bounce direction for the right front wheel FR during straight braking. As a result, it can be seen that the steer angle in the toe direction of the left front wheel FL increases and the steer angle in the toe direction of the right front wheel FR decreases. Therefore, a rightward yaw moment is generated in the vehicle body, and left deflection can be suppressed.

  FIG. 5C is a graph showing the relationship between the stroke amount in the rebound direction and the ground contact load in the rear wheels RL and RR. The stroke adjustment unit 126 increases the stroke amount in the rebound direction for the left rear wheel RL (that is, decreases the stroke amount in the bounce direction) and decreases the stroke amount in the rebound direction for the right rear wheel RR during straight braking. To control.

  FIG. 5D is a graph showing the relationship between the stroke amount in the rebound direction and the steer angle in the toe-out direction at the rear wheels RL and RR. As described above, the stroke adjusting unit 126 increases the stroke amount in the rebound direction for the left rear wheel RL and decreases the stroke amount in the rebound direction for the right rear wheel RR as described above. As a result, it can be seen that the steering angle of the left rear wheel RL in the toe-out direction increases and the steering angle of the right rear wheel RR in the toe-out direction decreases. Therefore, a clockwise yaw moment is generated in the vehicle body, and left deflection can be suppressed.

  When the suspension characteristic is set to be toe-out when bound, the control may be reversed in the left-right direction.

  Further, when the vehicle is deflected to the right because the center of gravity is on the left side, the control may be reversed in the left-right direction.

  FIG. 6 is a flowchart of a deflection suppression process according to the present embodiment. First, the straight braking determination unit 121 determines whether or not the brake is stepped on when the vehicle goes straight (S10). That is, when the steering angle of the steering wheel is within a predetermined range, it is determined whether a brake torque greater than a predetermined value has been generated. If the brake is stepped on while the vehicle is turning, or if the brake torque is low even during straight travel (N in S10), it is not appropriate to execute the deflection suppression control, and thus this flow is terminated.

  When the brake is stepped on at a predetermined brake torque or higher when the vehicle is traveling straight (Y in S10), the center of gravity estimating unit 123 estimates the center of gravity position of the vehicle body based on the detection value of the ground load sensor or the stroke amount sensor (S12). Based on the center of gravity of the vehicle body, the vehicle speed, and the brake torque, the deflection amount estimation unit 124 estimates the direction and magnitude of the deflection that will be generated in the vehicle body by the current brake (S14).

  The stroke amount calculation unit 128 obtains the stroke amount to be achieved by the suspension device of each wheel in order to reduce the estimated braking deflection (S16). The valve control unit 130 controls the air valve that communicates with the air chamber of the suspension device of each wheel (S18).

  As described above, according to the present embodiment, the direction and magnitude of the braking deflection that will occur in the vehicle body is predicted based on the center of gravity of the vehicle body, the brake torque, and the vehicle speed, and each wheel is reduced in the direction in which it is reduced. Adjust the stroke amount of the air suspension device. As a result, the steering angle of the suspension device changes, and braking deflection generated in the vehicle body is suppressed.

The present invention has been described based on the embodiments. These embodiments are merely examples, and modifications such as any combination of the embodiments, each component of the embodiment, and any combination of each processing process are also within the scope of the present invention. It will be understood by those skilled in the art.
The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added based on the knowledge of those skilled in the art. The configuration shown in each drawing is for explaining an example, and can be appropriately changed as long as the configuration can achieve the same function.

In the embodiment, it is described that the stroke amount of the four wheels of the vehicle is adjusted simultaneously. However, for example, the stroke amount may be adjusted only for the front wheels FL and FR or only for the rear wheels RL and RR. In this case, the amount of deflection suppression may be smaller than when all four wheels are adjusted.
Further, the stroke amount may be adjusted for one of the front wheels FL and FR and one of the rear wheels RL and RR, or the stroke amount may be adjusted for one wheel from each of the front and rear wheels. When adjusting the stroke amount of only one front wheel, for example, the left front wheel FL is controlled and the right front wheel FR is not controlled, thereby increasing the toe-in amount of the left front wheel and generating a right yaw moment. it can.

  In the embodiment, a vehicle including an air suspension device that adjusts the vehicle height according to the amount of compressed air has been described. However, the present invention can be applied to a vehicle including an arbitrary suspension device whose stroke amount can be changed by a signal from the ECU. The invention can be applied.

  FL left front wheel, FR right front wheel, RL left rear wheel, RR right rear wheel, 10 vehicle, 12 vehicle body, 16 air suspension, 18 steering wheel, 100 ECU, 102 steering angle sensor 104 wheel speed sensor, 106 stroke sensor, 110 brake Torque sensor, 120 detection value acquisition unit, 121 straight braking determination unit, 122 deflection prediction unit, 123 center of gravity estimation unit, 124 deflection amount estimation unit, 126 stroke adjustment unit, 128 stroke amount calculation unit, 130 valve control unit, 140 air pressure control Valve, 150 vehicle control device, 166 air tank, C vehicle center line, G vehicle center of gravity.

Claims (5)

A suspension that is installed for each wheel and is configured to be able to adjust the stroke amount,
Braking state detecting means for detecting a braking state during vehicle braking;
Steering detection means for detecting the steering amount of the vehicle;
Straight braking determination means for determining whether or not the vehicle is traveling straight based on a detection value of the steering detection means, and for determining whether or not the vehicle is braked based on a detection value of the braking state detection means;
A deflection amount predicting means for predicting a deflection amount generated in the vehicle body due to left-right asymmetry of the vehicle when it is determined by the straight braking determination means that the vehicle is braked when traveling straight;
By then changing the stroke of the pre-Symbol suspension changing the steering angle, a stroke adjusting means for reducing the predicted deflection,
A vehicle control device comprising:   The vehicle control device according to claim 1, wherein the stroke adjusting means reduces the deflection by using a yaw moment generated by a left-right difference in toe angle based on a stroke adjustment of the suspension.   The vehicle control apparatus according to claim 1, wherein the deflection amount predicting unit predicts the deflection amount based on a center of gravity and a deceleration of a vehicle body.   4. The vehicle control device according to claim 3, further comprising a center of gravity estimating means for estimating the center of gravity of the vehicle body based on a ground load applied to each wheel. In a vehicle including a suspension that is installed for each wheel and configured to be able to adjust a stroke amount, a vehicle control method that suppresses deflection of the vehicle during straight braking,
Detect the braking state during vehicle braking,
Detect the amount of steering of the vehicle,
Based on the detected steering amount, it is determined whether the vehicle is going straight ahead,
Determining whether the vehicle is braked based on the detected braking state;
When it is determined that the vehicle is braked when traveling straight ahead, the amount of deflection generated in the vehicle body due to the left-right asymmetry of the vehicle is predicted,
By changing the steering angle by changing the stroke amount before Symbol suspension, the vehicle control method comprising reducing the predicted deflection.

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