JP2009001151A - Brake control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly secure a clearance between a friction member and a braking member. <P>SOLUTION: This brake control device 1 is constituted for controlling an electric brake device for generating braking force by pressing a friction pad 16 to a disc rotor D by supplying an electric current to an electric motor 30. The brake control device 1 has an ECU 20 for operating the electric motor 30 based on a detecting result from a turning angle sensor 93 for detecting an operation quantity of the electric motor 30. The ECU 20 selectively switches ordinary return control for controlling a driving quantity of the electric motor 30 based on the detecting result of the turning angle sensor 93 when controlling to a separating state from a state of pressing the friction pad 16 to the disc rotor D and abnormal time return control for controlling the driving quantity of the electric motor 30 by time from when a current value of an input current supplied to the electric motor 30 becomes a predetermined value or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a brake control device, and more particularly to a control device for an electric brake.

  2. Description of the Related Art Conventionally, an electric brake device that generates a driving force by an actuator such as an electric motor and generates a braking force by the driving force is known. When controlling an electric brake, the load sensor is used to detect the load pressing a friction member such as a brake shoe, or the rotation angle sensor is used to detect the operating amount of the electric motor. Thus, the driving amount of the brake shoe or the like is determined (see Patent Documents 1 and 2).

JP 2000-71974 A JP 2003-287066 A

  However, when the load sensor or the rotation angle sensor described above breaks down electrically or mechanically, feedback control performed based on the detection result becomes impossible, and when the friction member is separated from the braking member such as a disk rotor, It becomes difficult to return accurately. Therefore, there is a problem that the clearance between the braking member and the friction member when the brake is not applied does not follow the set period until the failed sensor is repaired.

  Therefore, an object of the present invention is to provide a brake control device that can appropriately secure a clearance between a friction member and a braking member even when there is an abnormality in a sensor such as a load sensor or a rotation angle sensor.

  In order to solve the above-described problems, the present invention provides a brake control device that controls an electric brake device that generates a braking force by pressing a friction member against a braking member by supplying an electric current to the actuator. The controller has a control unit that operates the actuator based on a detection result from a detection unit that detects an operation amount, and the control unit controls the state in which the friction member is pressed from the braking member to a state in which the actuator is separated. In doing so, the first control for controlling the drive amount of the actuator based on the detection result of the detection unit, and the time from when the current value of the input current supplied to the actuator becomes a predetermined value or less, The second control for controlling the driving amount of the actuator is selectively switched.

According to such a brake control apparatus, not only the first control is performed based on the operation amount of the actuator detected by the detection unit, but also the second control that controls the actuator based on the input current input to the actuator. Control can also be performed by appropriately switching. Therefore, when the friction member is controlled to be separated from the braking member, the set clearance can be ensured even when the detection unit fails. In addition, the timing which switches 1st control and 2nd control can diagnose the abnormality of a detection part so that it may mention later, and when abnormality is detected, 2nd control can also be used.
The detection unit may directly detect the operation of the actuator, or may detect the operation of a portion that moves in accordance with the operation of the actuator.

  In the brake control device described above, the control unit stores in advance a correspondence relationship between a current value supplied to the actuator and a load that presses the friction member against the braking member, and refers to the correspondence relationship. The actuator can be operated based on the input current.

  In this brake control device, it is desirable that the time in the second control is increased as the load when the friction member is pressed against the braking member is increased.

  Generally, when a braking force is generated by pressing the friction member against the braking member, the larger the load, the more likely the friction member or the braking member will sag, and it will take some time to return to the original shape. . Therefore, when the time from when the current value of the input current becomes equal to or less than the predetermined value in the second control is made constant, after generating a large braking force, the friction member is restored when the sag is restored. There is a possibility that the clearance of the braking member becomes small. Therefore, the friction member and the braking member can be increased by increasing the time, that is, the time for moving the friction member in the direction opposite to the direction in which the friction member is pressed against the braking member, as the load when the friction member is pressed against the braking member is increased. The clearance can be set to an appropriate amount.

  In the brake control device described above, the actuator is, for example, an electric motor.

  The brake control device described above preferably includes a diagnosis unit that diagnoses an abnormality of the detection unit, and the control unit preferably executes the second control when the abnormality is detected by the diagnosis unit. .

  With this configuration, the second control can be executed only when an abnormality is detected by the diagnosis unit, and the clearance between the braking member and the friction member can be ensured as accurately as possible.

  In the brake control device described above, the actuator is an electric motor, the detection unit is a rotation angle sensor that detects a rotation amount of the electric motor, and the control unit is a rotation detected by the rotation angle sensor. The driving amount can be determined based on the amount.

  According to the present invention, when the friction member is controlled to be separated from the state in which the friction member is pressed against the braking member, the second control for controlling the drive amount of the actuator based on the input current input to the actuator is performed, and the friction is performed. A clearance between the member and the braking member can be appropriately ensured.

Next, a first embodiment of the present invention will be described in detail with reference to the drawings as appropriate.
In the drawings to be referred to, FIG. 1 is a schematic configuration diagram of a brake control device according to an embodiment of the present invention, and FIG. 2 is a sectional view of an electric brake controlled by the brake control device according to an embodiment of the present invention. is there.

  As shown in FIG. 1, the brake control device 1 is a device that controls the electric brake device 10 that generates a braking force by pressing the friction pad 16 against the disc rotor D by supplying a current to the electric motor 30. The brake control device 1 includes an electric motor 30 that is an example of an actuator, a pedal sensor 91 that detects an operation state of the brake pedal P, and a rotation angle as an example of a detection unit that detects a rotation angle as an operation amount of the electric motor 30. It comprises a sensor 93 and an ECU (electronic control unit) 20 mounted on the vehicle. In the ECU 20, a current detection unit 94 that detects a current (input current Im) input to the electric motor 30 is provided.

  The ECU 20 is an example of a control unit, and drives the electric motor 30 by determining a driving amount or an input current Im of the electric motor 30 based on detection values of the pedal sensor 91, the rotation angle sensor 93, and the current detection unit 94. Thus, an electric brake is realized. Although not shown, the ECU 20 includes a CPU and a storage device, and outputs a signal for controlling the electric motor 30 in accordance with the input of each sensor described above by executing a program stored in the storage device.

  The pedal sensor 91 detects an operation state of the brake pedal P. Examples of the detection state include an amount of depression of the brake pedal P, a depression load, and the like. If necessary, all of these are detected. A plurality of sensors may be provided, or only one sensor may be provided to detect only a part of them.

Next, the mechanical configuration of the electric brake device 10 will be described with reference to FIG.
The electric brake device 10 is a device that presses a friction pad 16 as an example of a friction member from both sides against a disc rotor D as an example of a braking member provided in a wheel W of a vehicle. In the caliper body 11, the electric brake device 10 transmits a coil 15 constituting a part of the electric motor 30, a ball screw mechanism 12 driven by the electric motor 30, and a rotational driving force of the electric motor 30 to the ball screw mechanism 12. The reduction gear mechanism 14 is provided.

  The caliper body 11 includes an action portion 11a disposed on the back surface of the friction pad 16 on one side (the vehicle inner side) with the disc rotor D interposed therebetween, and a reaction portion 11b disposed on the back surface of the friction pad 16 on the other side (the vehicle outer side). The bridge portion 11c connects the action portion 11a and the reaction portion 11b. The action part 11a is formed in a cylindrical shape, and each of the components described above is disposed therein.

  The coil 15 is fixed to the inner peripheral surface of the action portion 11 a of the caliper body 11 and functions as a stator of the electric motor 30 when electric power is supplied from the ECU 20.

  The reduction gear mechanism 14 includes a cylindrical portion 14a disposed inside the coil 15 and a gear mechanism portion 14b disposed on one of the cylindrical portions 14a (the vehicle inner side). A plurality of magnets 15 a are fixed to the outer peripheral surface of the cylindrical portion 14 a so as to face the coil 15, whereby the cylindrical portion 14 a functions as a rotor of the electric motor 30. Although details of the gear mechanism portion 14b are omitted, a planetary gear is provided and has a substantially triangular shape in a side view. An output gear 14c is provided inside the gear mechanism portion 14b.

  A rotation angle sensor 93 is disposed on the inner surface of the action portion 11a of the caliper body 11 and outside the vehicle of the gear mechanism portion 14b. The rotation angle sensor 93 detects the rotation angle of the electric motor 30 by detecting the apex portion of the above-described gear mechanism portion 14b in the side view triangle.

  The ball screw mechanism 12 includes a screw shaft 12a and a nut 12b that is screwed into the screw shaft 12a. The nut 12 b is rotatably supported by the action part 11 a of the caliper body 11 via a bearing 19. And the input gear 12c is provided in the outer periphery inside the vehicle of the nut 12b. The input gear 12c meshes with the output gear 14c of the reduction gear mechanism 14 described above.

  A flat pad pressing plate 16a for attaching the friction pad 16 is connected to the tip of the screw shaft 12a. The screw shaft 12a moves so as to advance and retreat in the axial direction by the rotation of the nut 12b.

  With the above configuration, an outline of the operation of the electric brake device 10 will be described. When the coil portion 15 is guided with a predetermined voltage pattern and the cylindrical portion 14a of the reduction gear mechanism 14 is rotated, the rotation speed is increased by the gear mechanism portion 14b. After being decelerated, the rotation is transmitted to the nut 12b by the meshing of the output gear 14c and the input gear 12c. Then, the rotation of the nut 12b causes the screw shaft 12a to move forward and backward in the axial direction thereof, to feed the friction pad 16 against the disk rotor D, or to return the friction pad 16 away from the disk rotor D. Can be made.

Next, a functional configuration of the brake control device 1 according to the embodiment will be described with reference to FIG. FIG. 3 is a functional block diagram of the brake control device according to the embodiment.
The ECU 20, which is an example of a control unit, applies a necessary current to the electric motor 30 in order to generate a braking force by pressing the friction pad 16 against the disk rotor D. Therefore, the ECU 20 includes a target load calculation unit 21a, a stroke-load calculation unit 21b, a current-load calculation unit 21c, a difference calculation unit 22, a load control unit 23, a motor driver 24, and a storage unit 29. ing.

The storage unit 29 stores a target clearance CL, a stroke-load map 29a, and an input current-load map 29b.
Since the target clearance CL is stopped in a state where a predetermined amount of clearance between the friction pad 16 and the disk rotor D (hereinafter referred to as “pad clearance”) is secured in the normal return control, the friction pad 16 moves away from the disk rotor D. This is data that stores the return amount of the friction pad 16 from the immediately preceding state.

As shown in FIG. 4, the stroke-load map 29 a is data indicating the correspondence between the stroke ST corresponding to the position of the friction pad 16 and the load F pressing the friction pad 16 against the disk rotor D. As a matter of course, the load F increases as the stroke ST increases. When the stroke ST is small, the friction pad 16 does not come into contact with the disk rotor D, so the load F becomes 0. When the contact starts, the load F gradually increases.
The stroke-load map 29a can be created with high accuracy by storing a large number of relations between the stroke ST obtained by the rotation angle sensor 93 and the load F obtained by actual measurement at this time.

As shown in FIG. 5, the input current-load map 29 b shows the relationship between the current input to the electric motor 30, that is, the current that actually flows, and the load F that presses the friction pad 16 against the disk rotor D. Data.
Since the input current Im increases in accordance with the load applied to the electric motor 30, the relationship between the input current Im and the load F is substantially proportional except for a range where the input current Im is low.

  The target load calculation unit 21a is a part that receives a detection value from the pedal sensor 91 and calculates a target load Ft that presses the friction pad 16 against the disc rotor D. For this reason, the target load calculation unit 21a outputs, for example, a target load Ft proportional to the depression load of the brake pedal P, or corrects to increase the target load Ft when the operation speed of the brake pedal P is fast. The target load Ft is determined. As this determination method, a conventionally known method can be arbitrarily used, and conditions and rules for realizing this determination method are stored in the storage unit 29.

The stroke-load calculation unit 21b calculates a stroke corresponding to the position of the friction pad based on the rotation angle Δθ acquired by the rotation angle sensor 93, and calculates an estimated load Fst from this stroke with reference to the stroke-load map 29a. It is the part to calculate.
The estimated load Fst is output to the difference calculation unit 22 and the current-load calculation unit 21c.

  The current-load calculation unit 21c is a part that calculates the estimated current Imh with reference to the input current-load map 29b based on the estimated load Fst. The estimated load Imh is output to the diagnosis unit 27.

  The difference calculation unit 22 is a part that calculates a difference between the target load Ft output from the target load calculation unit 21a and the estimated load Fst output from the stroke-load calculation unit 21b and outputs a load difference ΔF. This load difference ΔF is output to the load control unit 23.

  The load control unit 23 is a part that realizes feedback control by determining the direction and amount of driving the electric motor 30 based on the load difference ΔF and outputting the drive amount to the motor driver 24. For example, if the load difference ΔF is a positive value, the estimated load Fst is insufficient for the target load Ft, so it is determined that the friction pad 16 is sent (pressed) toward the disk rotor D by a predetermined amount, and the motor The direction and a predetermined amount are output to the driver 24. On the contrary, when the load difference ΔF is a negative value, the estimated load Fst is higher than the target load Ft, so that it is determined that the friction pad 16 is returned from the disk rotor D by a predetermined amount. Note that the predetermined amount of feeding or returning the friction pad 16 may be changed according to the magnitude of the load difference ΔF.

  The motor driver 24 is a part that drives the electric motor 30 by supplying a current to the electric motor 30 based on a command from the load control unit 23. A shunt resistor (not shown) is provided in the motor driver 24. The current detector 94 can detect the value of the current flowing through the electric motor 30 by looking at the voltage drop across the shunt resistor.

Further, when the ECU 20 controls the friction pad 16 from the state in which the friction pad 16 is pressed against the disk rotor D to the separated state, the normal return control that controls the drive amount of the electric motor 30 based on the detection result of the rotation angle sensor 93. (First control) and an abnormal time return control (second control) for controlling the drive amount of the actuator by the time TM from the time point when the current value of the input current Im supplied to the electric motor 30 becomes a predetermined value or less. ) And selectively switch.
For this reason, the ECU 20 includes a normal return control unit 25, an abnormality return control unit 26, a diagnosis unit 27, and a timer 28.

The normal return control unit 25 controls the drive amount of the electric motor 30 based on the detection result of the rotation angle sensor 93 when controlling the friction pad 16 from the state in which the friction pad 16 is pressed against the disk rotor D to the separated state. It is. When the friction pad 16 is returned from the disk rotor D, while the friction pad 16 is pressed against the disk rotor D, the electric motor 30 is rotated back to the load threshold Fth immediately before the estimated load Fst becomes almost zero. . For this reason, the normal return control unit 25 outputs the drive amount of the electric motor 30 to the motor driver 24.
When the estimated load Fst becomes smaller than the load threshold Fth, it can be determined that the pressing state of the friction pad 16 and the disk rotor D has disappeared. Here, this state is referred to as “contact point CP”. Thereafter, a drive amount command is output to the motor driver 24 so that the friction pad 16 is moved backward by the target clearance CL stored in advance in the electric motor 30. Therefore, the normal return control unit 25 acquires the rotation angle Δθ detected by the rotation angle sensor 93, calculates the return stroke RST from the contact point CP, and performs feedback control until the return stroke RST reaches the target clearance CL.

When the rotation angle sensor 93 fails, the abnormal time return control unit 26 controls the input current supplied to the electric motor 30 when controlling the friction pad 16 from being pressed against the disk rotor D. This is a part for controlling the drive amount of the actuator by the time TM from the time when the current value of Im becomes equal to or less than a predetermined value.
When the rotation angle sensor 93 fails, the load F can be grasped by referring to the input current Im. Therefore, referring to the detection value from the current detection unit 94, a drive amount instruction is output to the motor driver 24 so as to drive the electric motor 30 to the return side until the current threshold Imth corresponding to the load threshold Fth, and feedback control is performed. To do.
When the input current Im detected by the current detection unit 94 becomes equal to or less than the current threshold Imth, the abnormality return control unit 26 starts the timer 28 and starts measuring the time TM. Then, the drive amount is output to the motor driver 24 so that the friction pad 16 is moved to the return side at a constant speed until the time TM counted by the timer 28 becomes larger than the predetermined threshold value Tth.

  The threshold value Tth is desirably set larger as the load F when the friction pad 16 is pressed against the disk rotor D is larger. That is, the relationship between the load F and the threshold value Tth as shown in FIG. The threshold value Tth in FIG. 6 increases as the immediately preceding brake load F increases. When the abnormality return control unit 26 performs the return control, the threshold value Tth is determined with reference to the map of FIG. 6 based on the estimated load Fst in the immediately preceding brake, and the contact point CP is determined for the time of the threshold value Tth. The friction pad 16 may be returned from the front. By doing so, even if the friction pad 16 and other parts are temporarily sunk due to a large brake load, a large pad clearance is secured, and an appropriate pad clearance is obtained when the sag is recovered. Can do.

  The diagnosis unit 27 is a part that diagnoses an abnormality of the rotation angle sensor 93. Therefore, the diagnosis unit 27 obtains the rotation angle Δθ from the rotation angle sensor 93 and calculates the position of the friction pad 16, that is, the stroke ST. Then, the estimated load Fst is calculated with reference to the stroke-load map 29a. On the other hand, the diagnosis unit 27 acquires the estimated current Imh and the actual current Im. When the difference between the estimated current Imh and the current Im exceeds a predetermined error threshold Eth, the rotation angle sensor 93 is diagnosed as abnormal.

  The operation of the brake control device 1 configured as described above will be described with reference to the flowcharts of FIGS. In the following, only the abnormality diagnosis of the rotation angle sensor 93 and the control on the return side of the friction pad 16 will be described. FIG. 7 is a flowchart showing the abnormality diagnosis and control mode determination processing, FIG. 8 is a flowchart of normal return control, and FIG. 9 is a flowchart of abnormality return control.

  As shown in FIG. 7, the brake control device 1 always diagnoses an abnormality in the rotation angle sensor 93. The ECU 20 acquires the rotation angle Δθ from the rotation angle sensor 93 (S101), and calculates the stroke ST that is the position of the friction pad 16 based on the rotation angle Δθ (S102). The calculation of the stroke ST can be performed, for example, by adding or subtracting the movement amount of the friction pad 16 according to the rotation angle Δθ of the electric motor 30 acquired this time to the previously calculated stroke ST.

  Based on the calculated stroke ST, the estimated load Fst is acquired with reference to the stroke-load map 29a (S103). On the other hand, with reference to the input current-load map 29b, the estimated current Imh is acquired based on the estimated load Fst (S104). Further, the input current Im is acquired from the current detection unit 94 (S105).

Next, it is determined whether or not the difference between the estimated current Imh obtained in step S104 and the input current Im is greater than a predetermined error threshold Eth (S106, Yes), and it is determined that the rotation angle sensor 93 is abnormal. (S108). Then, when the friction pad 16 is moved to the return side, the return control at the time of abnormality is performed (S300).
On the other hand, when the difference between the estimated current Imh obtained in step S104 and the input current Im is equal to or smaller than the predetermined error threshold Eth (S106, No), it is determined that the rotation angle sensor 93 is normal (S107), and the friction pad 16 is moved. When moving to the return side, normal return control (S200) is performed.

Next, the normal return control operation will be described.
As shown in FIG. 8, the ECU 20 obtains the target load Ft by the target load calculation unit 21a (S201). Then, the stroke-load calculation unit 21b calculates a stroke based on the rotation angle Δθ detected by the rotation angle sensor 93, and acquires the estimated load Fst with reference to the stroke-load map 29a (S202). Next, it is determined whether the estimated load Fst is equal to or less than a predetermined load threshold Fth (S203). When the estimated load Fst is larger than the load threshold Fth (S203, No), the electric motor 30 is rotationally controlled on the return side (S204), and the processing from step S201 is repeated.
On the other hand, when the estimated load Fst is less than or equal to the load threshold Fth (S203, Yes), the mutual pressing force between the friction pad 16 and the disk rotor D is nearly zero, and the friction pad 16 is at the contact point CP. Move to control to ensure pad clearance.

Therefore, the ECU 20 acquires the rotation angle Δθ (S205), and calculates the return stroke RST based on the rotation angle Δθ (S206). The return stroke RST here is the amount of movement of the friction pad 16 and the disk rotor D from the contact point CP to the return side. The return stroke RST can be calculated in the same manner as the stroke ST described above.
Then, the return stroke RST is compared with the target clearance CL previously stored in the storage unit 29. If the return stroke RST is equal to or less than the target clearance CL (No in S207), the pad clearance is not yet sufficient. Then, the electric motor 30 is rotationally controlled to the return side (S208), and the processing from step S204 is repeated.
On the other hand, when the return stroke RST is larger than the target clearance CL (S207, Yes), the processing is terminated because the predetermined target clearance CL has been secured.

Next, the operation of abnormality return control will be described.
As shown in FIG. 9, the ECU 20 acquires the input current Im from the current detection unit 94 (S301). Then, it is determined whether or not the input current Im is equal to or smaller than a predetermined current threshold Imth. If the input current Im is larger than the current threshold Imth (S302, No), the electric motor 30 is controlled to rotate to the return side (S303). Repeat the process.
On the other hand, if the input current Im is equal to or smaller than the current threshold Imth in step S302 (Yes), the process proceeds to control for securing the pad clearance, and the timer 28 is started (S304).
Then, the time TM is acquired (S305), and it is determined whether or not the time TM is larger than the threshold value Tth (S306). When the time TM is equal to or less than the threshold Tth (S306, No), the electric motor 30 is controlled to rotate back (S307), and the processing from step S305 is repeated.
On the other hand, when the time TM is larger than the threshold value Tth (S306, Yes), the target clearance CL is secured, and the process is terminated.

  As described above, according to the brake control device 1 of the present embodiment, when the rotation angle sensor 93 is normal, the friction pad 16 and the disk rotor D are pressed against each other based on the estimated load Fst. Control is performed, and immediately before the friction pad 16 and the disc rotor D are separated, the pad clearance is secured based on the detection value of the rotation angle sensor 93. For this reason, an accurate pad clearance can be ensured.

  Even if there is an abnormality in the rotation angle sensor 93, control is performed immediately before the friction pad 16 and the disc rotor D are separated based on the input current Im of the electric motor 30, and the input current Im is a current threshold value. After being equal to or less than Imth, the electric motor 30 is driven at a constant speed for a predetermined time (the same time as the threshold value Tth), whereby a pad clearance almost as set can be secured.

Therefore, according to the brake control device 1 of the present embodiment, even if the rotation angle sensor 93 is abnormal, it is possible to ensure the pad clearance appropriately.
Further, when the load F is large, if the predetermined threshold value Tth is increased, it is possible to ensure an appropriate pad clearance even if the friction pad 16 or other members sag.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be appropriately modified and implemented.
In the above embodiment, the present invention has been described by taking a disc brake as an example. However, the present invention can also be applied to a drum brake.
In the embodiment, the current detection unit 94 provided in the ECU 20 is used to detect the input current Im of the electric motor 30. However, a detection unit is provided by providing a current sensor between the motor driver 24 and the electric motor 30. It can also be used as
In the embodiment, the rotation angle sensor 93 is shown as a detection unit that detects the operation amount of the electric motor 30, but a load sensor that measures the pressing force of the disk rotor D may be separately provided as the detection unit.
Moreover, although the electric motor 30 was shown as an example of an actuator, if an actuator is an electric thing, it will not be restricted to an electric motor.

It is a schematic structure figure of a brake control device concerning an embodiment of the present invention. It is sectional drawing of the electric brake controlled by the brake control apparatus which concerns on embodiment of this invention. It is a functional block diagram of a brake control device concerning an embodiment. It is a figure which shows an example of a stroke-load map. It is a figure which shows an example of an input current-load map. . It is a figure which shows an example of the relationship between the load F and threshold value Tth. It is a flowchart which shows the process of diagnosis of abnormality and determination of a control mode. It is a flowchart of normal return control. It is a flowchart of abnormality return control.

Explanation of symbols

1 Brake control device F
DESCRIPTION OF SYMBOLS 10 Electric brake device 11 Caliper body 12 Ball screw mechanism 14 Reduction gear mechanism 15 Coil 15a Magnet 16 Friction pad 19 Bearing 20 ECU
30 Electric motor 91 Pedal sensor 93 Rotation angle sensor 94 Current detection part D Disc rotor P Brake pedal W Wheel

Claims (6)

A brake control device that controls an electric brake device that generates a braking force by pressing a friction member against a braking member by supplying current to an actuator,
A control unit that operates the actuator based on a detection result from a detection unit that detects an operation amount of the actuator;
The control unit controls a driving amount of the actuator based on a detection result of the detection unit when controlling the friction member from a state of pressing the friction member to a state of separating the friction member. A brake control device that selectively switches between the second control for controlling the driving amount of the actuator according to the time from the time when the current value of the input current supplied to the actuator becomes a predetermined value or less. .   The control unit stores in advance a correspondence relationship between a current value supplied to the actuator and a load that presses the friction member against the braking member, and refers to the correspondence relationship based on the input current. The brake control device according to claim 1, wherein the actuator is operated.   3. The brake control device according to claim 2, wherein the time in the second control is lengthened as the load when the friction member is pressed against the braking member is increased.   The brake control device according to any one of claims 1 to 3, wherein the actuator is an electric motor. A diagnostic unit for diagnosing an abnormality of the detection unit;
The brake control device according to any one of claims 1 to 4, wherein the control unit executes the second control when an abnormality is detected by the diagnosis unit. The detection unit is a rotation angle sensor that detects a rotation amount of the electric motor,
The brake control device according to claim 4, wherein the control unit determines the drive amount based on a rotation amount detected by the rotation angle sensor.

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