JP2010007818A - Brake device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake device capable of detecting a pad contact position without giving uncomfortable feeling to a driver. <P>SOLUTION: A pad contact point is detected when the prescribed time passes after a detection signal from a wheel speed sensor shows the following relationship, wheel speed=0 km/h, (step S11; Yes), and it is determined that thrust of an electric caliper exceeds a prescribed value (step S12; Yes), that is, during stopping and braking of the vehicle. The uncomfortable feeling in creeping which is given to the driver in the conventional technique for detecting the pad contact position in stopping and non-braking of the vehicle can be prevented, pad contact point detection can be executed, and unnecessary sense of anxiety can be prevented from being imparted to the driver. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a brake device used in a vehicle such as an automobile.

Japanese Patent Application Laid-Open No. 2004-228688 discloses a brake device used in an automobile, which detects a pad contact position while the vehicle is stopped and not braked.
The brake device disclosed in Patent Document 1 detects the pad contact position while the vehicle is stopped and not braked.
JP 2000-055094 A

  Since the brake device disclosed in Patent Document 1 detects a pad contact position (pad contact point) while the vehicle is stopped and is not braked, it is erroneously determined that the vehicle is stopped during extremely low speed traveling such as creep traveling in a traffic jam or the like. May cause the pad contact position to be detected. In this case, since a slight braking force is applied to detect the pad contact position, the driver feels uncomfortable due to the deceleration at that time.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a brake device that can detect a pad contact position without causing a driver to feel uncomfortable.

  The invention of the present application is characterized in that the pad contact position is detected while the vehicle is stopped and during braking.

  According to the invention of the present application, the pad contact position is detected by the contact position detecting means during braking, so the pad contact position is not detected during extremely low speed traveling such as creep traveling, so that the pad does not feel uncomfortable to the driver. The contact position can be detected.

Hereinafter, a brake device according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.
FIG. 1 is a diagram schematically showing a brake device 1 according to an embodiment of the present invention. FIG. 2 is a control (hereinafter referred to as pad contact point detection) for the pad contact point detection (detection of the contact position between the disc rotor and the brake pad) of the control device 2 (contact position detection means) used in the brake device 1 of FIG. It is a flowchart which shows the arithmetic processing content including control.

  In FIG. 1, the brake device 1 includes an electric caliper 3 and the control device 2 including an electric caliper controller 4 and a vehicle controller 5. Four electric calipers 3 are provided corresponding to the four wheels (left and right front and rear wheels) of the vehicle. The electric caliper controller 4 is provided corresponding to each of the four electric calipers 3, and each is connected to the vehicle controller 5. In FIG. 1, four electric calipers 3 and four electric caliper controllers 4 are shown as one representative.

The electric caliper 3 includes a cylinder 7, a piston 8, a motor 9, a resolver 10 serving as position detection means, a rotation / linear motion conversion mechanism 11, a speed reduction mechanism 12, and a PKB mechanism 14. (Not shown). Brake pads (hereinafter referred to as pads appropriately) 17 and 17 are attached to the carrier 16, and the pads 17 and 17 generate a braking force with the disc rotor 18 sandwiched by the thrust of the piston 8 as the motor 9 is driven. .
A stroke simulator 20 is connected to the brake pedal 19 provided in the vehicle so that the brake pedal 19 generates a stroke having a magnitude corresponding to the operating force of the brake pedal 19. A brake operation amount sensor 21 is provided at a connection portion between the brake pedal 19 and the stroke simulator 20 so as to detect an operation amount (brake operation amount) of the brake pedal 19.
The vehicle further includes a wheel speed sensor 22, an inclination sensor 23, and an accelerator sensor 24.

The vehicle controller 5 is connected to a brake operation amount sensor 21, a wheel speed sensor 22, a tilt sensor 23, an accelerator sensor 24, and four electric caliper controllers 4. A battery (BATT) 26 is connected to the vehicle controller 5 via an ignition switch (IGN SW) 25, and power is supplied from the battery 26 when the ignition switch 25 is turned on. .
The vehicle controller 5 determines the thrust command value based on the detection data of the brake operation amount sensor 21 based on the operation of the brake pedal 19 by the driver.
The electric caliper controller 4 receives power supply from the battery 26, receives a thrust command value from the vehicle controller 5 via a communication medium such as CAN communication, and outputs a signal output from the resolver 10 based on the thrust command value. Based on the (resolver signal), the amount of rotation of the motor 9 is controlled by an electric current, and the piston 8 is pushed out (generates a piston thrust) via the speed reduction mechanism 12 and the rotation / linear motion conversion mechanism 11 to generate a braking force. That is, the brake force (brake force by the driver operation) is generated by the control performed by the electric caliper controller 4 in response to the driver's brake operation (depressing the brake pedal 19). In the present embodiment, the motor 9, the speed reduction mechanism 12, and the rotation / linear motion conversion mechanism 11 constitute an actuator.

In addition, the electric caliper controller 4 receives the input of the thrust command value from the vehicle controller 5 even when the driver does not perform a brake operation, and based on the thrust command value, the brake force (the braking force based on the command of the vehicle controller 5). ) Can be generated.
As an example of receiving an input of a thrust command value from the vehicle controller 5 without a driver's brake operation, there is a case where an auto hold operation such as a parking brake operation (PKB operation) or a slope start assist function is performed. In this case, the braking force can be generated based on the thrust command value from the vehicle controller 5 even when the driver does not perform the braking operation.

The PKB operation is executed as follows.
That is, the electric caliper controller 4 controls the rotation amount of the motor 9 with current based on the resolver signal based on the PKB drive command from the vehicle controller 5, and via the speed reduction mechanism 12 and the rotation / linear motion conversion mechanism 11. The piston 8 is pushed out (a piston thrust is generated) so as to obtain a thrust required for the PKB, and a braking force is generated. After the piston thrust reaches the thrust value required for the PKB, the PKB mechanism 14 is driven so that the latch gear (not shown) attached to the rotating shaft of the motor 9 can be engaged with the latch gear. The provided claw (not shown) is engaged to restrain the rotation of the motor 9 in the direction of lowering the thrust (in other words, the PKB operation function is exhibited).

  The electric caliper controller 4 performs PKB release control as follows. That is, once the motor 9 is rotated in the thrust increasing direction, the engagement between the pawl and the latch gear is disengaged, so that the electric caliper controller 4 controls the rotation amount of the motor 9 with current based on the signal from the resolver 10. Then, the piston 8 is returned to the pad clearance initial position (PKB release operation is completed).

  The control device 2 (the vehicle controller 5 and the electric caliper controller 4) has the functions described above (brake force generation control by driver operation, brake force generation control based on commands from the vehicle controller 5, PKB operation control, PKB release control, etc.). In addition, the initial braking force is applied in the control (hereinafter, appropriately referred to as pad contact point detection control) for the pad contact point detection operation (hereinafter, appropriately referred to as pad contact point detection operation) described in the next column (A). Wheel setting processing is performed.

(A) Initial braking force setting wheel settings:
In the pad contact point detection control, at least one wheel is applied with a braking force by PKB (in this case, the wheel to which the braking force is applied is referred to as a braking force application wheel at the time of detection control for the sake of convenience). (One wheel to be subjected to pad contact point detection control is hereinafter referred to as a target wheel as appropriate). In this case, as described above, the braking force application wheels at the time of detection control are at least one wheel, and may be two wheels, three wheels, and one wheel.
When there are two braking force application wheels during detection control, two rear wheels (rear left and right wheels), two front wheels (front left and right wheels), two left wheels (left front and rear wheels), and two right wheels (front right and left wheels). Wheel) one of two pairs of diagonal wheels (a left front wheel and a right rear wheel, a right front wheel and a left rear wheel) (here, for the sake of convenience, the left front wheel and the right rear wheel) and two pairs of pairs Of the square wheels, the other may be the right front wheel and the left rear wheel. In the case of three detection control braking force application wheels, braking force is applied to the remaining three wheels of the four wheels other than the target wheel to perform the pad contact point detection control.
Also, what wheels initial detection control braking force applying wheel including the number (for convenience,. That initially the braking force application wheel) for either a are predetermined. In the present embodiment, the initial braking force application wheels are two rear wheels.
Further, when the pad contact point detection control is performed for one target wheel, the pad contact point detection control is performed for a new target wheel instead of the detection target wheel (target wheel). However, regardless of the braking force application wheels at the time of detection control, all four wheels are set as target wheels. In this embodiment, the initial target wheel is the rear left wheel, and the target wheel is changed in the order of rear right wheel → front left wheel → front right wheel, and the pad contact point detection is performed for the corresponding wheel in this order. Operation is performed.

The operation of the brake device 1 including the control device 2 will be described below based on the flowchart of FIG. 2 showing the control contents executed by the control device 2.
In the brake device 1, in the pad contact point detection control, as shown in FIG. 2, first, the detection signal from the wheel speed sensor 22 indicates wheel speed = 0 km / h, and this state has elapsed for a predetermined time ( It is determined whether or not the wheel speed has reached 0 km / h and a predetermined time has passed (step S11).
In step S11, “Wheel speed = 0 km / h” is used in the determination process. Instead, “Wheel speed is less than a predetermined value (wheel speed <predetermined value)” is used as a new step. Also good. In addition, when adopting a new step using “the wheel speed is less than a predetermined value (wheel speed <predetermined value)” in the determination process in this way, in the new step, the “detection signal from the wheel speed sensor 22 is detected. It is determined whether or not a predetermined time has elapsed since the wheel speed is smaller than a predetermined value. ).

Next, it is determined whether or not the thrust of the electric caliper 3 exceeds a predetermined value (step S12). If NO is determined in step S12, the pad contact point detection control is stopped (proceeds to END in FIG. 2).
YES in step S12, that is, the detection signal from the wheel speed sensor 22 is a wheel speed = 0 km / h and a predetermined time has elapsed (YES in step S11), and the thrust of the electric caliper 3 exceeds a predetermined value Is determined (YES in step S12), it is determined that the braking force is generated (during braking) in a state where the vehicle is stopped (stopped). When it is determined that the vehicle is stopped and the braking force is generated (a state where the braking force is generated) as described above, the pad contact point detection control including the following steps proceeds.

  In the brake force generation state, thrust is generated based on a command from the vehicle controller 5 when thrust is generated by the driver's operation of the brake pedal 19 and when the driver's brake pedal 19 is not operated. It is generated in each of two cases. As described above, when it is determined that the vehicle is stopped and the braking force is generated, the pad contact point detection control is advanced. In either case, the control of the electric caliper controller 4 is performed. Based on the above, the thrust of the target wheel is reduced.

As described above, in the present embodiment, the initial control force application wheels are two rear wheels, and in step S13 following the YES determination process in step S12, compared to the thrust command value (thrust during stopping). It is determined whether or not it exceeds 1/2 of the maximum thrust (brake force that can be generated by one wheel). If it is determined YES in step S13 (that is, the vehicle is stopped with only two rear wheels, and the stopping thrust is held at 1/2 or more of the brake force that can be generated with one wheel), The pad contact point detection control is stopped (the process after step S14 is not performed, and the process proceeds to END in FIG. 2).
The reason why the pad contact point detection operation is not performed is based on the following reason. That is, in the case described above (for example, when the vehicle is stopped only with the two rear wheels and more than half of the thrust that can be generated with the electric caliper 3 of each wheel is generated), the initial pad contact Even if the braking force of the other wheel (in this case, the rear right wheel) other than the target wheel of the point detection operation (in this embodiment, the initial target wheel is the rear left wheel) is increased to the maximum thrust, This is to prevent the braking force of the entire vehicle from decreasing, and this situation is prevented.

If it is determined as NO in step S13 (the thrust while the vehicle is stopped is not held at 1/2 or more of the brake force that can be generated on one wheel), it is different from the target wheel (initially, the rear left wheel in this embodiment). The thrust of the other wheel (rear right wheel) is increased, the vehicle is stopped, and a system capable of detecting the pad contact point with respect to the target wheel (rear left wheel) is established (step S14). In step S14, the braking force application wheels at the time of detection control are two rear wheels. Initially, one of the two rear wheels is a target wheel (initially, the left rear wheel in this embodiment), and the other wheel (rear) When a braking force is applied to the right wheel), a double braking force is applied to the other wheel (rear right wheel) in order to maintain the stop.
Subsequent to step S14, the thrust of the target wheel (the wheel targeted for detection of the pad contact point) is released (step S15), and the pad contact point detection operation proceeds.

  Following step S15, it is determined whether or not the position of the piston 8 (piston position) has reached the currently recognized pad contact point (hereinafter referred to as the pad contact point current value as appropriate) (step S16). If NO is determined here, the process returns to step S15. If YES is determined in step S16, the electric caliper controller 4 returns (retracts) the piston 8 by a predetermined amount in the reducing direction, and sets the pad 17 and the disc rotor 18 so that the clearance between the pad 17 and the disk rotor 18 is not completely in contact (step S17). . Thereafter, the piston 8 is propelled (moved forward) in the direction of increasing force, and the gap between the pad 17 and the disk rotor 18 is reduced (step S18). While the piston 8 is propelled in the direction of increasing force, it is determined whether or not the current value of the motor 9 (motor current value) exceeds a predetermined value (step S19). If NO is determined in step S19, the process returns to step S18. If YES is determined in step S19, the piston position at the time of the determination is recognized as the position where the pad 17 and the disk rotor 18 are in contact with each other, and the position returned in that direction by a predetermined amount is set as a new pad contact point. The pad contact point is set as a pad contact point update value (step S20). In step S19, in the determination process, it is determined whether or not the motor current value exceeds a predetermined value. Instead, whether or not the motor current change amount in the increasing direction exceeds a predetermined value. May be used in the determination process.

  By obtaining a new pad contact point update value for the target wheel (initially, the left rear wheel in the present embodiment) in step S20, after executing the processing of step S21 described later, the target wheel (this implementation) In the embodiment, the pad contact point current value initially targeted for the rear left wheel is replaced with the pad contact point update value targeted for the target wheel (initially, the rear left wheel in this embodiment), and the control of the electric brake thereafter. As described above, the pad contact point detection operation for one target wheel is completed, the process returns to the main routine (not shown), and the pad contact point detection operation for the remaining three wheels is described above. It is executed according to the contents. Note that in the pad contact point detection operation for the front two wheels, the braking force is applied to the rear two wheels, so that the processing of step S13 and step S14 is not performed, and the process proceeds from step S12 to step S15.

  In step S21, the pad contact point current value is compared with the pad contact point update value, and a value of a predetermined ratio (for example, 1 / pad contact point update value) − (pad contact point current value)) is compared. Update processing is performed so that the value is reflected in increments of 10). By executing this step S21, the pad 17 and the disc rotor 18 during traveling are prevented from being dragged. That is, when the pad contact point is performed while the temperature of the pad 17 immediately after braking is increasing, or when the pad 17 is subjected to uneven wear, the accuracy of the pad contact point detection is reduced. There is a possibility that dragging occurs if no action is taken. On the other hand, by executing step S21, the accuracy of the pad contact point detection is prevented from being lowered and the occurrence of dragging is avoided.

  In the present embodiment, the pad contact point is detected when the vehicle is stopped and the braking force is generated (steps S11 to S13), that is, during braking while the vehicle is stopped. For this reason, as in the above-described prior art, the pad without causing a sense of incongruity to the driver caused during extremely low speed traveling such as creep traveling when the pad contact point detection is performed while the vehicle is stopped and not braked. The contact point detection operation can be executed, and the driver can drive the vehicle without feeling uneasy. In addition, since the pad contact position is detected sequentially for each wheel, the pad contact position can be detected without causing a change in braking force and without causing a driver feeling uncomfortable.

  In the above embodiment, the pad contact point detection operation is performed with the vehicle stopped, but for stopping the vehicle, a braking force may be applied to one of the three wheels other than the target wheel as described above, You may adjust so that braking force may be given to two wheels or three wheels.

  Moreover, you may perform the pad contact point detection control of the said embodiment at the time of parking, such as when it is in the P range of an automatic mission during PKB operation. When the operation is executed during the PKB operation, the thrust of the target wheel is reduced after the PKB release operation is performed once, and can be executed according to the example of the above embodiment.

Moreover, in the said embodiment, in order to implement pad contact point detection operation in the state where the vehicle stopped reliably, any one of the conditions shown in the following items (a) to (f) while the vehicle is stopped If the condition is satisfied, the pad contact point detection operation may be performed after the PKB is activated.
(A) When a thrust command is generated again based on the operation of the brake pedal 19 of the driver (b) When the opening of the driver's seat is detected while the ignition switch 25 is on (c) The ignition from the opening of the driver's seat door (D) When the shift range is in the P position while the ignition switch 25 is ON (e) When the ignition switch 25 is ON When off is detected from the state (f) When parking is completed by the automatic parking support system

  In the above-described embodiment, the target wheel is changed in the order of rear left wheel → rear right wheel → front left wheel → front right wheel. However, this order is not limited to this, and the rear right wheel → rear It may be changed to other order such as left wheel → front left wheel → front right wheel or front left wheel → front right wheel → rear left wheel → rear right wheel.

  In the above embodiment, as described above, when the vehicle is stopped and braked, the contact position detecting means sequentially sets the pad contact point for each wheel (rear left wheel → rear right wheel → front left wheel → front right wheel). (In other words, the contact position between the disc rotor and the brake pad is detected sequentially for each wheel), but instead of this, (a) the left and right wheels are detected separately, (A) The front and rear wheels may be detected sequentially, or (c) the pair of wheels that are diagonal wheels may be detected sequentially.

Here, (a) detecting the left and right wheels sequentially, for example, for the rear left and right wheels, in the order of the rear left wheel and the rear right wheel (or in the order of the rear right wheel and the rear left wheel), pad The contact point is detected, and the front left and right wheels are similarly detected in the order of the front left wheel and the front right wheel (or the front right wheel and the front left wheel in this order).
In addition, (a) detecting the front and rear wheels sequentially, for example, for the left front and rear wheels, detects the pad contact point in the order of the left front wheel and the left rear wheel (or in the order of the left rear wheel and the left front wheel). Or, for the right front wheel, the detection of the pad contact point in the order of the right front wheel and the right rear wheel (or conversely the order of the right rear wheel and the right front wheel).
Further, (c) detecting sequentially for each pair of wheels that form a diagonal wheel means, for example, one of two pairs of diagonal wheels (a left front wheel and a right rear wheel, a right front wheel and a left rear wheel). For a pair of diagonal wheels (a left front wheel and a right rear wheel), a pad contact point is detected in the order of the left front wheel and the right rear wheel (or in the order of the right rear wheel and the left front wheel), or the other pair For the diagonal wheels (the right front wheel and the left rear wheel), the pad contact point is detected in the order of the right front wheel and the left rear wheel (or the order of the left rear wheel and the right front wheel on the contrary).

In the above embodiment, in step S11, it is determined whether or not the predetermined time has elapsed since the wheel speed is 0 km / h. Instead, “the wheel speed is less than a predetermined value and predetermined. It may be determined whether or not time has elapsed (wheel speed <predetermined value).
Moreover, in the said embodiment, although the case where an initial braking force provision wheel was made into two rear wheels was taken as an example, it is not restricted to this. For example, two front wheels, two left wheels, two right wheels, two diagonal wheels (one pair of diagonal wheels or the other pair of diagonal wheels), or four wheels It is good also considering three wheels except any one of these as an initial braking force provision wheel. In this case, after that, the braking force application wheel at the time of detection control may be appropriately changed according to the target wheel.

If the pad contact point detection is performed when the stop state is maintained on a hill or the like, the brake force of the wheel subject to the pad contact point detection operation is reduced, and thus the vehicle slides down in the above embodiment. there is a possibility. On the other hand, if the inclination of the currently stopped road surface is detected using the inclination sensor 23 based on the signal of the inclination sensor 23 and the vehicle is stopped at an inclination exceeding a predetermined value, the pad clearance pad While the contact point detection operation is being performed, the braking force of wheels other than the target wheel (the wheel that is performing the pad contact point detection operation) (hereinafter, for convenience, other wheels) is increased (see step S15). ) Can take measures. According to this measure, the pad contact point detection on a slope or the like can be performed safely without reducing the braking force of the entire vehicle and consequently without causing the vehicle to slip.
In addition, when the friction coefficient of the grounding road surface of the target wheel (the wheel that performs the pad contact point detection operation) is high and the friction coefficient of the grounding road surface of the other wheel is low, or when the load on both wheels is biased May not be able to keep the vehicle stopped even if the thrust of other wheels is increased. In order to prevent such a situation (possibility of not being able to keep the vehicle stopped), if the movement of the vehicle is detected during the pad contact point detection operation by monitoring the wheel speed change The pad contact point detection operation is immediately interrupted, and a treatment for returning to the thrust before starting the pad contact point detection operation is performed. By taking this measure, the occurrence of the above situation can be avoided and safety can be ensured.

  In the above embodiment, the pad contact point detection operation is sequentially performed for each wheel. However, for example, when the stop time is short, the pad contact point detection operation is performed for all the wheels. It is likely that the pad contact point detection operation is interrupted before the operation is completed. In order to prevent this situation from occurring, if the pad contact point detection operation is interrupted, the pad contact point update value will be updated from the wheel that has not been updated in the previous operation in the next pad contact point detection operation. The contact point detection operation is started, and control is performed so that the pad contact point detection operation is performed on all wheels on average.

  Further, in the above embodiment, the pad contact point detection is performed when the vehicle is stopped and the brake is operating. However, when the vehicle is going down a relatively long mountain slope, the pad 17 is worn. Even if there is a vehicle, the frequency of stopping is low and there is a possibility that the pad contact point is not updated. In order to prevent such a situation (the possibility that the pad contact point update is not performed), the following measures are taken when the frequency of the pad contact point detection operation is low. That is, when the frequency of the pad contact point detection operation is low, the normal brake is controlled by temporarily closing the clearance between the pad 17 and the disk rotor 18. When the above-described pad contact point detection operation is performed, a highly accurate contact point can be detected, and the pad contact point update value is updated using the highly accurate contact point thus obtained. To do. By taking such a measure, it is possible to avoid the above situation (possibility that pad contact point update is not performed).

  Note that the above-described control for temporarily closing the clearance between the pad 17 and the disk rotor 18 is performed, for example, in the control of the electric caliper controller 4 with the magnitude of the brake force (for example, estimated from the vehicle speed, command thrust, motor current, etc.) and operation. When the value obtained by time integration (brake force / time integration value) exceeds a predetermined value, the piston 8 can be advanced in the thrust increasing direction by a preset piston driving amount.

It is sectional drawing which shows typically the brake device which concerns on one Embodiment of this invention with the control system. It is a flowchart which shows the content of arithmetic processing including the pad contact point detection of the control apparatus of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Brake device, 2 ... Control apparatus (contact position detection means), 8 ... Piston, 9 ... Motor (actuator), 10 ... Resolver (position detection means), 11 ... Rotation linear motion conversion mechanism (actuator), 12 ... Deceleration Mechanism (actuator), 17 ... brake pad (pad), 18 ... disc rotor.

Claims (8)

A disc rotor provided on each wheel of the vehicle, an actuator that linearly moves the piston along the axial direction of the disc rotor, a brake pad that is pressed by the linear motion of the piston and contacts the disc rotor, and the piston A brake having position detection means for detecting a piston position, which is a displacement of the position detection means, and contact position detection means for detecting a contact position between the disc rotor and the brake pad at the time of non-braking as a reference position of the position detection means In the device
A brake device that detects the contact position when the vehicle is stopped and during braking.   2. The brake device according to claim 1, wherein the contact position detection unit sequentially detects the contact position for each wheel or a pair of two wheels.   The brake device according to claim 2, wherein the contact position detection unit sequentially detects the contact position separately for left and right wheels.   The brake device according to claim 2, wherein the contact position detection unit sequentially detects the contact position for each pair of wheels serving as diagonal wheels.   The brake device according to claim 2, wherein the contact position detection unit sequentially detects the contact position separately for front and rear wheels.   3. The brake device according to claim 2, wherein when the contact position detection unit detects the contact position of one wheel or a pair of wheels, the braking force of another wheel is increased. A disc rotor provided on each wheel of the vehicle, an actuator that linearly moves the piston along the axial direction of the disc rotor, a brake pad that is pressed by the linear motion of the piston and contacts the disc rotor, and the piston A brake having position detection means for detecting a piston position, which is a displacement of the position detection means, and contact position detection means for detecting a contact position between the disc rotor and the brake pad at the time of non-braking as a reference position of the position detection means In the device
The brake device, wherein the contact position is detected when the vehicle is parked. A disc rotor provided on each wheel of the vehicle, an actuator that linearly moves the piston along the axial direction of the disc rotor, a brake pad that is pressed by the linear motion of the piston and contacts the disc rotor, and the piston A brake having position detection means for detecting a piston position, which is a displacement of the position detection means, and contact position detection means for detecting a contact position between the disc rotor and the brake pad at the time of non-braking as a reference position of the position detection means In the device
The brake device according to claim 1, wherein the contact position is sequentially detected by the contact position detection means for each wheel or a pair of two wheels.

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