JP2020026240A - Brake system for vehicle - Google Patents

Abstract

To provide a brake system for a vehicle including a novel function using a periodic fluctuation of a pressing force to a disc rotor of a brake pad.SOLUTION: A brake system for a vehicle has a brake device provided with a sensor for detecting the pressing force W, and has a function of estimating wheel speed vbased on periodic fluctuation (T) of the pressing force detected by the sensor. The period of the fluctuation of the pressing force coincides with a rotational period of the wheel, and even when any control such as ABS control based on the vehicle speed is executed with the function to estimate the wheel speed, and a defect occurs that some wheel speed sensors cannot detect the wheel speed, it is possible to execute the control using the vehicle speed estimated based on the periodical fluctuation of the pressing force.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a vehicle brake system including a brake device that applies a braking force to a wheel by pressing a brake pad against a disk rotor that rotates with the wheel.

  As described in the following patent document, in a brake device, a pressing force, which is a force for pressing a brake pad against a disk rotor, fluctuates. In the brake device described in the following patent document, a disc An actuator for pressing a brake pad against the rotor is controlled.

JP 2011-173521 A

  The inventor of the present application has found that while controlling the actuator to apply a certain braking force to the wheels during the development of the brake device, the above-described variation in the pressing force is periodic. The present invention is based on the knowledge, and an object of the present invention is to provide a vehicle brake system having a novel function using a periodic variation of a pressing force.

In order to solve the above problems, a vehicle brake system according to the present invention includes:
(a) a disk rotor that rotates with the wheel, (b) a brake pad pressed against the disk rotor, and (c) an actuator that presses the brake pad against the disk rotor to apply a braking force to the wheel. A braking device,
A controller having a braking force control unit that controls a braking force generated by the brake device by controlling a pressing force that is a force that the actuator presses the brake pad against the disk rotor. hand,
The brake device has a sensor for detecting the pressing force,
The controller may include a wheel speed estimating unit that estimates a wheel speed based on a periodic change in the pressing force detected by the sensor.

  According to the knowledge of the inventor of the present application, the cycle of the fluctuation of the pressing force coincides with the rotation cycle of the wheel. That is, in short, if the wheel makes one rotation due to the inclination of the disk rotor or the like, the pressing force fluctuates slightly for one cycle. Therefore, it is possible to estimate the wheel speed based on the cycle of the change in the pressing force. As described above, the vehicle brake system of the present invention has a wheel speed estimating function that depends on the cycle of the pressing force, and the function executes, for example, some control based on the wheel speed. Even in the case where a failure such that the wheel speed cannot be detected by the wheel speed sensor occurs, it is possible to execute the control using the wheel speed estimated as described above.

1 is a partial sectional view showing a vehicle brake system according to an embodiment. It is a sectional view showing the actuator of the brake device which constitutes the brake system for vehicles of an example. FIG. 3 is a supplementary diagram for explaining a piston urging mechanism of the actuator shown in FIG. 2. FIG. 3 is a cross-sectional view of the actuator shown in FIG. 2 in a cross section different from that of FIG. 2 for explaining a piston retraction inhibiting mechanism of the actuator. When the braking force is applied to the wheel by the brake device, which is a graph showing changes with time of the value and the wheel speed v _W axial force W.

  The brake device in the vehicle brake system of the present invention may be a hydraulic brake device or a so-called electric brake device. As the actuator, in the case of a hydraulic brake device, for example, a device including a wheel cylinder may be adopted.In the case of an electric brake device, for example, an electric motor as a drive source, a retractable piston, and an electric An operation conversion mechanism for converting the rotation operation of the motor into the forward / backward movement of the piston may be provided, and the brake pad may be pressed against the disk rotor by the forward movement of the piston.

  The pressing force detected by the pressing force sensor can be called a pressing load. The pressing force sensor detects the pressing force not by the pressing force itself, but by detecting the reaction force acting on the brake pad from the disk rotor by pressing the brake pad against the disk rotor, that is, the pressing reaction force. It may be. As the pressing force sensor, in the case of the hydraulic brake device, a sensor that detects the pressing force by detecting the pressure of the working fluid supplied to the wheel cylinder, that is, the wheel cylinder pressure can be employed. . In the case of the electric brake device, when the operation conversion mechanism includes a screw mechanism, for example, the pressing force is detected by detecting an axial force acting on a male screw rod having a male screw. Such a thing can be adopted.

  The periodic fluctuation of the pressing force is not limited to a simple vibration as long as the fluctuation is one rotation of the disk rotor, that is, one rotation of the wheel. For example, when the periodic fluctuation of the pressing force is caused by the inclination of the disk rotor, it becomes a simple vibration, but, for example, when it is caused by the difference depending on the position of the thickness of the disk rotor. It is conceivable that a plurality of local maximum values and local minimum values exist in one cycle, and such a variation is one mode of the periodic variation.

  The estimated wheel speed may be the rotational angular speed of the wheel, or the peripheral speed of the wheel, that is, the peripheral speed of the contact surface of the tire. The control using the estimated wheel speed is not particularly limited, and is not limited to being used only in a situation where a separate wheel speed sensor is provided and the sensor has failed. The estimation of the wheel speed in the present invention cannot be executed unless the vehicle brake device is generating a braking force. In view of this, it is desirable that the control using the estimated wheel speed is a control executed in a state where the braking force is being generated. Specifically, for example, ABS control (anti-lock control, anti-skid control) performed by detecting the locked state of the wheel based on the wheel speed is suitable.

  Hereinafter, as a specific embodiment of the present invention, a vehicle brake system of an example will be described in detail with reference to the drawings. The present invention can be embodied in various forms with various changes and improvements based on the knowledge of those skilled in the art, in addition to the following examples.

[A] Overall Configuration of Vehicle Brake System of Embodiment As shown in FIG. 1, a vehicle brake system of the embodiment (hereinafter, may be simply referred to as “brake system”) is a so-called electric brake device. 2 and an electronic control unit (hereinafter, sometimes referred to as “ECU”) 4 as a controller that controls the brake device 2.

  The brake device 2 includes a brake caliper 12 (hereinafter, may be simply abbreviated as “caliper 12”) for holding the actuator 10, a disk rotor 14 as a rotating body that rotates together with wheels, and a pair of brake pads (hereinafter, referred to as a “brake pad”). 16a and 16b).

  The caliper 12 moves in the axial direction (left-right direction in the figure) to a mount (not shown) provided on a carrier (not shown) for rotatably holding the wheel so as to straddle the disk rotor 14. It is kept possible. The pads 16a and 16b are held by the mount so as to sandwich the disk rotor 14 in a state where the movement in the axial direction is allowed. Each of the pads 16a and 16b includes a friction member 26 located on the side that comes into contact with the disk rotor 14, and a backup plate 28 that supports the friction member 26. To be pressed against.

  For convenience, if the left side in the figure is described as the front and the right side as the rear, the pad 16a on the front side is supported by the claw 32 which is the front end of the caliper body 30. The actuator 10 is held in a rear portion of the caliper body 30 so that the housing 40 of the actuator 10 is fixed. The actuator 10 has a piston 42 that advances and retreats with respect to the housing 40, and the piston 42 is moved forward so that a front end portion, more specifically, a front end portion of the pad 16b, specifically, the backup plate 28 of the pad 16b, Engage with. Then, the pair of pads 16a and 16b sandwich the disk rotor 14 as the piston 42 further advances in the engaged state. In other words, the pads 16a and 16b are pressed against the disk rotor 14. By this pressing, a braking force against the rotation of the wheels depending on the frictional force between the disk rotor 14 and the friction member 26, that is, a braking force for decelerating and stopping the vehicle is generated.

  The actuator 10 may be employed as a component of a caliper in which one of the brake pads is fixed to the front end of the piston, in other words, fixedly engages, and the other is fixed to the claw portion of the caliper body. It is possible.

[B] Configuration of Actuator As shown in FIG. 2, the actuator 10 includes, in addition to the housing 40 and the piston 42 described above, an electric motor 44 as a drive source, and a reduction mechanism 46 for reducing the rotation of the electric motor 44. An input shaft 48 that is rotated by the rotation of the electric motor 44 decelerated through the speed reduction mechanism 46, and an operation conversion mechanism 50 that converts the rotation operation of the input shaft 48 into an advance / retreat operation (forward / backward operation) of the piston 42. And so on. In the following description, for the sake of convenience, the left side of the figure is referred to as the front, and the right side is referred to as the rear.

  The piston 42 is configured to include a piston head 52 and an output cylinder 54 which is a hollow cylinder of the piston 42, while the electric motor 44 has a cylindrical rotation drive shaft 56. I have. In detail, the rotation drive shaft 56, the output cylinder 54, and the input shaft 48 are so arranged that the output cylinder 54 and the input shaft 48 are coaxial with each other inside the rotation drive shaft 56. The axes are arranged such that the axes become an axis L which is a common axis. As a result, the present actuator 10 is made compact.

  The rotation drive shaft 56 is held by the housing 40 via a radial bearing 58 so as to be rotatable and immovable in the axial direction (the direction in which the axis L extends, which is the horizontal direction in the drawing). The electric motor 44 is configured to include a magnet 60 disposed on one circumference on the outer circumference of the rotary drive shaft 56 and a coil 62 fixed to the inner circumference of the housing 40 so as to surround the magnet 60. I have.

  The reduction mechanism 46 includes a hollow sun gear 64 fixedly attached to the rear end of the rotary drive shaft 56, a ring gear 66 fixed to the housing 40, and a sun gear 64 meshed with both the sun gear 64 and the ring gear 66. And a plurality of planetary gears 68 (only one is shown in the figure) orbiting around the planetary gears. Each of the plurality of planetary gears 68 is rotatably held by a flange 70 as a carrier. The input shaft 48 is formed by screwing a front shaft 72 forming a front part and a rear shaft 74 forming a rear part, and the flange 70 is formed by the front shaft 72 and the rear shaft. By being sandwiched and fixed between the input shaft 48 and the front shaft 72, the input shaft 48 rotates integrally with the front shaft 72 and the rear shaft 74. The rotation of the rotary drive shaft 56, that is, the rotation of the electric motor 44, is transmitted as the rotation of the input shaft 48 at a reduced speed via the speed reduction mechanism 46 configured as described above. Incidentally, the input shaft 48 is supported by the housing 40 via the flange 70, the thrust bearing 76, and the support plate 78 so as to be rotatable and immovable in the axial direction.

  A male screw 80 is formed on the outer periphery of the front shaft 72 of the input shaft 48, while a female screw 82 that is screwed with the male screw 80 is formed inside the output cylinder 54. That is, the input shaft 48 on which the male screw 80 is formed is a rotatable member rotatable by the rotation of the electric motor 44, and the output cylinder 54 on which the female screw 82 is formed is capable of moving forward and backward to move the piston 42 forward and backward. The motion conversion mechanism 50 functions as a linear motion member, and includes the input shaft 48 and the output cylinder 54. Incidentally, in the present actuator 10, the linear motion member and the piston can be considered to be integrated.

  The male screw 80 and the female screw 82 employ a trapezoidal screw as a relatively high-strength screw. Between the male screw 80 and the female screw 82, the operation of the motion conversion mechanism 50, that is, the operation of the actuator 10 Grease for smooth operation is interposed as a lubricant. The actuator 10 employs a motion conversion mechanism in which a male screw is formed in the rotating member and a female screw is formed in the direct acting member. However, a female screw is formed in the rotating member, and a male screw is formed in the direct acting member. It is also possible to configure the actuator by employing the motion conversion mechanism described above.

  As can be understood from the above description, in the present actuator 10, the piston 42 is advanced and retracted by rotating the electric motor 44. The state shown in the figure is a state in which the piston 42 is located at the most rear end position in the movable range (hereinafter, may be referred to as a “set retreat end position”). When the motor 44 is rotated forward, the piston 42 advances, and the pads 16a, 16b are pressed against the disk rotor 14 with the front end of the piston 42 engaged with the pad 16b, as seen from FIG. Power is generated. Incidentally, the magnitude of the braking force is a magnitude corresponding to the current supplied to the electric motor 44. Thereafter, when the electric motor 44 is rotated in the reverse direction, the piston 42 retreats, the engagement between the piston 42 and the pad 16b is released, and no braking force is generated. It returns to the set retreat end position shown in FIG.

  As can be understood from the above description, the brake device 2 that is an electric brake device directly applies the force generated by the electric motor 44 to the brake pads 16a and 16b that are friction members without using a hydraulic fluid such as brake oil. By acting, the brake pads 16a and 16b are pressed against the disk rotor 14 which is a rotating body to generate a braking force. In short, it is configured to generate a braking force that directly depends on the force generated by the electric motor 44. The friction members 26 of the pads 16a and 16b can be considered as elastic bodies, and are elastically deformed by an amount corresponding to the generated braking force.

  In addition to the components described above, in the present actuator 10, a resolver 84 is provided as a motor rotation angle sensor for detecting the rotation angle of the electric motor 44. Based on the detection signal of the resolver 84, the position and the amount of movement of the piston 42 in the axial direction, more precisely, the rotational position of the input shaft 48 can be detected. An axial force sensor 86 (a load cell) for detecting a thrust force acting on the input shaft 48, that is, an axial force (axial load) is disposed between the support plate 78 and the thrust bearing 76. Has been established. As will be described in detail later, this axial force corresponds to the force (pressing force) of the piston 42 pressing the brake pad 16b against the disk rotor 14, and is determined by an axial force sensor 86 that functions as a sensor for detecting the pressing force. Based on this, it is possible to detect the braking force generated by the brake device 2.

  In the present actuator 10, the reverse efficiency of the motion conversion mechanism 50 is not so high as compared with the normal efficiency. That is, even when the force for retreating the piston 42 acts on the piston 42, the input shaft 48 does not easily rotate. Therefore, for example, when the supply of current to the electric motor 44 is cut off while the piston 42 is moving forward and a braking force is being generated, the piston 42 can be easily moved backward. Instead, it is expected that the state in which the braking force is being generated will continue. Assuming such a case, the present actuator 10 has a mechanism for urging the piston 42 in a direction of retreating by the elastic force exerted by the elastic body, more specifically, a rotational urging force (““ (Which can also be referred to as “rotation torque”) to the input shaft 48.

  More specifically, the piston urging mechanism 90 includes an outer race 92 fixed to the housing 40 and an inner race fixed to the rear shaft 74 of the input shaft 48 so as to rotate integrally therewith and arranged inside the outer race 92. 94 and a spiral spring (sometimes called a “spring spring” or “spring”) 96 as an elastic body disposed between portions of the outer ring 92 and the inner ring 94 that face each other. It is configured.

  The spiral spring 96 is hardly elastically deformed as shown in FIG. 3A in the state shown in FIG. 2, that is, in the state where the piston 42 is located at the above-described set retreat end position, It is in a state where almost no elastic force is generated. From this state, as the input shaft 48 is rotated by the electric motor 44 to advance the piston 42, as shown in FIG. 3B, the piston is gradually tightened to generate an elastic force. That is, the elastic force having a magnitude corresponding to the amount of advance of the piston 42 from the set retreat end position acts as an urging force against the advance of the piston 42, that is, acts as an urging force in the direction of retreating the piston 42. . In other words, the urging force acting on the input shaft 48 by the spiral spring 96 increases as the piston 42 advances. The piston 42 is easily retracted by such a rotational urging force. For example, the piston 42 cannot be retracted by the electric motor 44 while the piston 42 is moving forward and a braking force is being generated. In such a case, the piston 42 can be retracted.

  In the brake device 2, in the actuator 10, in order for the brake device to function as an electric parking brake, a piston retreat inhibition mechanism 100 that inhibits retraction of the piston 42 when the piston 42 is advanced is provided. ing.

  4, the ratchet teeth 102 are formed on the outer periphery of the flange 70, and the flange 70 is rotated by the rotation of the input shaft 48. Functions as a rotating gear. On the other hand, an electromagnetic solenoid (hereinafter may be simply referred to as “solenoid 106”) 106 which is an electromagnetic actuator is fixed to the housing 40 of the actuator 10 via a seat plate 104, and the solenoid 106 When an electric current is supplied to the solenoid 106, the locking rod 108 as a movable body is moved in the axial direction thereof, more specifically, in a direction approaching the flange 70. A guide sleeve 110 is attached to the seat plate 104, and the locking rod 108 is advanced and retracted while being guided by the guide sleeve 110. Incidentally, a notch 112 is formed in the housing 40 of the actuator 10, the guide sleeve 110 is present in the notch 112, and the tip of the locking rod 108 faces the inside of the housing 40. A compression coil spring (hereinafter sometimes abbreviated as “spring”) 114 is provided in the guide sleeve 110, and the spring 114 urges the locking rod 108 in a direction away from the flange 70. I have.

  A claw 116 is formed at the tip of the locking rod 108, and the claw 116 can be engaged with the ratchet teeth 102 of the flange 70. That is, the locking rod 108 functions as a pawl for locking the ratchet teeth 102 at the pawl 116 (it can be considered that the pawl is formed on the movable rod 108). FIGS. 2 and 4A show a state in which the locking rod 108 is located at a non-locking position where the ratchet teeth 102 cannot be locked, and FIG. In a state where the ratchet teeth 102 are located at a locking position where the ratchet teeth 102 can be locked, more specifically, a state where the pawl 116 of the locking rod 108 is hooked on the ratchet teeth 102, that is, the locking rod 108 is actually A state where the teeth 102 are locked is shown.

  In other words, the spring 114 constitutes a pawl biasing mechanism that biases the locking rod 108 in a direction in which the locking rod 108 moves from the locked position to the non-locked position. On the other hand, the solenoid 106 urges the locking rod 108 as a movable body toward the ratchet teeth 102 by supplying an electric current, thereby maintaining the locking rod 108 at the locking position against the urging force of the spring 114. It is supposed to constitute a maintenance device.

  As can be seen from the directions of the ratchet teeth 102 and the claws 116 of the locking rod 108, when the locking rod 108 is positioned at the locking position by supplying current to the solenoid 106, the piston 42 moves backward ( The rotation of the flange 70 in the direction of the black arrow shown in the drawing, which may be hereinafter referred to as the “reverse rotation direction”, is prohibited, but the direction in which the piston 42 moves forward (the direction of the white arrow shown in the drawing). In the following, rotation of the flange 70 in the “forward rotation direction” may be permitted. More specifically, the locking rod 108 is moved in a direction away from the center of the flange 70 while maintaining the state in which the pawl 116 is in contact with the ratchet teeth 102 by the urging force of the spring 114, and Rotation is allowed. Needless to say, such an operation is an operation of a general ratchet mechanism (one-way clutch mechanism) including a ratchet gear and a pawl. 100 prohibits the piston 42 from retreating. Incidentally, the “locking position” is not limited to the position where the locking rod 108 locks the ratchet teeth 102, but also when the locking rod 108 is urged toward the center of the flange 70 by the solenoid 106. The position in contact with the tooth 102 is also meant.

  In the state where the locking rod 108 locks the ratchet teeth 102, even if the supply of current to the solenoid 106 is cut off, the state in which the pawl 116 is hooked on the ratchet teeth 102 is maintained, and The locking rod 108 does not move to the non-locking position.

[C] Configuration Related to Control The control in the brake system, that is, the control of the brake device 2 is executed by the ECU 4 described above. Referring to FIG. 1, the ECU 4 includes a computer (microcomputer) 120 including a CPU, a ROM, a RAM, and the like, and an inverter 122 that is a drive circuit of the electric motor 44 of the actuator 10. Have been.

  The computer 120 performs a predetermined process according to a predetermined program. In view of the content of the processing, it can be considered that the computer 120 is configured to include a predetermined functional unit for convenience. FIG. 1 is a functional block diagram of the ECU 4. Referring to FIG. 1, as important functional units, a braking force control unit 124, an ABS control unit 126, a wheel speed determination unit 128, and a dependence signal switching unit 130 are provided. Can be considered to have. These functional units will be described later in detail.

As signals necessary for controlling the braking force generated by the brake device 2, a signal about the rotation angle θ of the electric motor 44 detected by the resolver 84 and a signal about the axial force W detected by the axial force sensor 86 are output from the actuator 10. Is sent to the ECU 4, more specifically, to the braking force control unit 124. Further, in the present braking system is required information about the wheel speed v _W at the ABS control, in order to obtain the information, the wheel speed sensor 132 (called an electromagnetic pickup) is provided. The detection signal P from the wheel speed sensor 132 is also sent to the ECU 4.

Although described later in detail, the present braking system is that it is possible to estimate the wheel speed v _W by periodic variation of the axial force W. Therefore, the signal relating to the axial force W and the detection signal P from the wheel speed sensor 132 are sent to the dependent signal switching unit 130, and these signals are selectively transmitted to the wheel by the dependent signal switching unit 130. It is sent to the speed determining unit 128.

In the present brake system, the brake device 2 is provided with an ECU 4 that is a dedicated controller for the brake device 2. For example, the brake device 2 and the brake devices provided on the other wheels are integrated. A controller may be provided to control the operation.
[D] Control of brake device
i) Braking force control The ECU 4 performs braking force control as basic control of the brake device 2. The braking force control is a control performed by the braking force control unit 124, and is a control for causing the braking device 2 to generate a braking force according to a braking force request. More specifically, an operation amount δ of a brake pedal, which is a brake operation member, is input to the braking force control unit 124, and the braking force control unit 124 generates a braking force according to the operation amount δ. Next, a target axial force W ^* , which is a target axial force W, is determined. Then, the braking force control unit 124 supplies the electric power to the electric motor 44 according to a feedback control rule based on the axial force deviation ΔW (the deviation of the actual axial force W obtained by the detection of the axial force sensor 86 from the target axial force W ^* ). The current I is determined, and a command for the current I is sent to the inverter 122. The inverter 122 supplies the commanded current I to the electric motor 44 in consideration of the motor rotation angle θ. That is, the braking force control unit 124 controls the braking force generated by the brake device 2 by controlling the pressing force that is the force pressing the brake pads 16a and 16b against the disk rotor 14. Although detailed description is omitted here, actually, in the braking force control, control based on the position of the piston 42 obtained by the motor rotation angle θ is also performed. Also, in the case of a braking request from the automatic brake, a command regarding the braking force required of the brake device 2 is sent to the braking force control unit 124, and the braking force control unit 124 Control is performed to generate a braking force based on the command.

ii) ABS control The ABS control is a control executed by the ABS control unit 126, and is a control for reducing the braking force applied when the wheels are locked during a request for the braking force. The difference between the wheel speed v _W and the vehicle running speed (also referred to as “vehicle speed”) v _B is equal to or greater than the set difference. Is detected. Normally, the detection signal P of the wheel speed sensor 132 is input to the wheel speed determination unit 128 by the dependence signal switching unit 130, and the wheel speed determination unit 128 controls the brake device 2 based on the input detection signal P. wheels to impart power (hereinafter, sometimes referred to as "the wheel") to determine the wheel speed v _W of. The wheel speed v _W of the other wheel is sent to the ABS control unit 126, and the ABS control unit 126 compares the wheel speed v _W of the wheel determined by the wheel speed determination unit 128 with the wheel speed v _W of the other wheel. based on the wheel speed v _W, to determine the vehicle running speed v _B. Then, the vehicle running speed v _B was thus determined, based on the wheel speed v _W of the wheel, whether the wheel is locked or not. When the wheels are locked, the ABS control unit 126 issues a command to the braking force control unit 124 to loosen the braking force. The braking force control unit 124 determines a current I to be supplied to the electric motor 44 based on the command, and issues a command for the current I to the inverter 122.

iii) Estimation of Wheel Speed Based on Axial Force In a state where a braking force is applied to the wheel, the axial force sensor 86 detects an axial force W according to the braking force. When the wheel is rotating, the value of the detected axial force W undergoes some fluctuation. More specifically, for example, as extremely shown by a two-dot chain line in FIG. 1, the disk rotor 14 is slightly inclined, and the thickness of the disk rotor 14 is very small, but also circumferentially. It varies in. The value of the axial force W actually detected varies periodically with one rotation of the wheel due to the inclination of the disk rotor 14, the variation in the thickness, and the like.

Figure 5 is a graph showing approximate when a braking force of a certain magnitude is applied to the wheels, the change with time of the value and the wheel speed v _W axial force W. If described with reference to the graph from the time the braking force has been applied, the wheel speed v _W is gradually lowered with a gradient corresponding to the magnitude of the braking force. Then, the axial force W periodically fluctuates from the time when the braking force is applied, and the period of the fluctuation gradually becomes longer as the wheel speed decreases. Assuming that the outer diameter of the wheel, that is, the outer diameter of the ground contact surface of the tire is D and the cycle of the variation is T _n (n = 0, 1, 2,...), The wheel speed v _W is represented by the following equation. be able to.
v _W = π · D / T _n
According to the above equation, to detect the actual axial force W, if it monitors the period T _n of variation in the axial force W, it is the wheel speed v _W that can be estimated.

In the present brake system, when the wheel speed sensor 132 fails, the dependent signal switching unit 130 outputs a signal about the axial force W detected by the axial force sensor 86 instead of the detection signal P from the wheel speed sensor 132. , To the wheel speed determining unit 128. Then, the wheel speed determination unit 128, based on a signal axial force W, identifies the fluctuation period T _n axial force W, based on the identified change period T _n, estimating the wheel speed v _W. That is, the wheel speed determining unit 128 functions as a wheel speed estimating unit that estimates the wheel speed based on the periodic fluctuation of the pressing force detected by the sensor. As a result, the ABS control unit 126, even when the wheel speed sensor 132 is defective, based on the wheel speed v _W of the wheel estimated by the wheel speed determining unit 128, is to execute the ABS control It is possible.

2: Brake device 4: Electronic control unit (ECU) [controller] 10: Actuator 12: Brake caliper 14: Disc rotor 16a, 16b: Brake pad 42: Piston 44: Electric motor 46: Reduction mechanism 48: Input shaft 50: Operation Conversion mechanism 86: axial force sensor 120: computer 122: inverter [drive circuit] 124: braking force control unit 126: ABS control unit 128: wheel speed determination unit 130: dependence signal switching unit 132: wheel speed sensor W: axial force v _W : Wheel speed

Claims (1)

(a) a disk rotor that rotates with the wheel, (b) a brake pad pressed against the disk rotor, and (c) an actuator that presses the brake pad against the disk rotor to apply a braking force to the wheel. A braking device,
A controller having a braking force control unit that controls a braking force generated by the brake device by controlling a pressing force that is a force that the actuator presses the brake pad against the disk rotor. hand,
The brake device has a sensor for detecting the pressing force,
A brake system for a vehicle, wherein the controller has a wheel speed estimating unit that estimates a wheel speed based on a periodic change in the pressing force detected by the sensor.

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