Braking control device

Abstract

To provide a braking control device that can control braking accurately.SOLUTION: A brake ECU 50 controls an electric brake device 10. The electric brake device 10 comprises a brake disc 15, a brake pad 25 and a motor 40. A control part 60 of the brake ECU 50 comprises a driving control part 61, a state quantity obtaining part 62, and a backlash amount setting part 64. The driving control part 61 controls driving of the motor 40. The state quantity obtaining part 62 obtains a state quantity relating to braking control of the electric brake device 10. When releasing braking force, the backlash amount setting part 64 drives the motor 40 in a retreating direction from a gap original point Ps and then drives the motor in an advancing direction by a distance corresponding to a backlash amount G2, so as to set the backlash amount G2 which is used for gap control of securing a gap between the brake disc 15 and the brake pad 25 while pushing backlash to the advancing direction in a non-braking state, in accordance with a state quantity.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a brake control device. [Background technology]

[0002] Conventionally, electric disc brake devices have been known. For example, in Patent Document 1, when braking is released, the piston is rotated to a retreated position beyond the initial position where a desired pad clearance is created, and then the piston is rotated forward by a predetermined angle to the initial position. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-55093 A Summary of the Invention [Problem to be solved by the invention]

[0004] The amount of backlash in an electric brake device is the sum of the gaps between various components, including the backlash of the ball screw that constitutes the rotary-linear motion conversion mechanism, and may deviate from the design value due to pad wear and temperature.

[0005] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a braking control device capable of controlling braking with high accuracy. [Means for solving the problem]

[0006] The braking control device of the present invention controls a braking device (10), which includes a brake disc (15), a brake pad (25), and an actuator (40). The brake disc rotates integrally with the wheel. The brake pad generates a braking force by clamping the brake disc. The actuator generates a driving force that moves the brake pad in a forward direction, which is a direction in which the brake pad is pressed against the brake disc, or in a backward direction, which is a direction in which the brake pad is separated from the brake disc.

[0007] The braking control device includes a drive control unit (61), a state quantity acquisition unit (62), and a backlash amount setting unit (64). The drive control unit controls the drive of the actuator. The state quantity acquisition unit acquires state quantities related to braking control of the braking device. The backlash amount setting unit sets, in accordance with the state quantities, a backlash amount used in gap control for securing a gap between the brake disc and the brake pad with the backlash reduced on the forward side in a non-braking state by driving the actuator in the backward direction from a reference position and then in the forward direction by an amount equal to the backlash amount when the braking force is released. This makes it possible to perform braking control with high accuracy. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 illustrates an electric brake device according to an embodiment. [Diagram 2] FIG. 1 is a plan view of an electric brake device according to an embodiment. [Diagram 3] 4 is a flowchart illustrating a braking control process according to an embodiment. [Figure 4] 4 is a time chart illustrating a braking control process according to an embodiment. [Diagram 5] 4 is a flowchart illustrating a backlash estimation process according to an embodiment. [Figure 6] 5 is a flowchart illustrating a backlash estimation continuation determination process according to an embodiment. [Figure 7] 5 is a time chart illustrating a backlash estimation process according to an embodiment. [Figure 8] 5 is a time chart illustrating a backlash estimation process according to an embodiment. [Figure 9] 5 is a time chart illustrating a backlash estimation process according to an embodiment. [Figure 10] 10 is a flowchart illustrating a backlash estimation process according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (One embodiment) A braking control device according to the present invention will be described below with reference to the drawings. A braking control device according to an embodiment is shown in Figs. 1 to 8. The cross-sectional view in Fig. 1 corresponds to the cross section taken along line II in Fig. 2. As shown in Figs. 1 and 2, an electric brake device 10 includes a brake disc 15, a braking force generating unit 20, a motor 40 which is an actuator that generates power to drive the braking force generating unit 20, and a brake ECU 50 which serves as a braking control device, and is mounted on a vehicle (not shown). The brake disc 15 is provided on an axle (not shown) and rotates integrally with the wheel.

[0010] The braking force generating unit 20 has a caliper 21, a piston 23, brake pads 25, and a linear motion conversion mechanism 30. The caliper 21 is held by a mounting 27 via a slide pin 28. The piston 23 is provided slidably within a cylinder 22 provided in the caliper 21.

[0011] The piston 23 is formed in a generally cylindrical shape with a bottom that opens toward the motor 40. Hereinafter, the position where the piston 23 is farthest from the brake disc 15 side is referred to as the initial position Pi, and the stroke amount from the initial position Pi is referred to as the piston stroke ST. Also, the direction in which the piston 23 approaches the brake disc 15 is referred to as the forward direction, and the direction in which the piston 23 moves away from the brake disc 15 is referred to as the backward direction.

[0012] A pair of brake pads 25 are provided on both sides of the brake disc 15. Hereinafter, the side facing the piston 23 is referred to as an inner pad 251, and the side held by the caliper 21 is referred to as an outer pad 252. The brake pad surface, which is the surface of the brake pad 25 that comes into contact with the brake disc 15, is made of a friction material, and generates a frictional force according to the brake pressure. This frictional force decelerates the rotation of the brake disc 15.

[0013] The linear motion conversion mechanism 30 is a screw mechanism having a rotating member 31, a pressing element 32, and the like. The rotating member 31 has a first shaft portion 311, a second shaft portion 312, and a flange portion 313. The first shaft portion 311 is rotatably supported by the caliper 21, and is rotationally driven by the motor 40. A male thread is formed on the second shaft portion 312. A thrust bearing 315 is provided between the flange portion 313 and the caliper 21.

[0014] The pressing member 32 is formed in a substantially cylindrical shape, and is a linear motion member provided axially movable inside the radial direction of the piston 23. An internal thread that meshes with the external thread of the second shaft portion 312 is formed on the inner circumferential surface of the pressing member 32.

[0015] The motor 40 is driven in response to the depression amount of a brake pedal (not shown) or the like, to rotate the rotating member 31. A reducer (not shown) or the like may be provided between the motor 40 and the rotating member 31. The motor 40 is provided with a rotation angle sensor 42 that detects the rotation angle. The amount of rotation of the motor 40 is calculated using the detection value of the rotation angle sensor 42, and the piston stroke ST can be calculated by converting it into a gear ratio. In other words, the amount of rotation of the motor 40 and the piston stroke ST are mutually convertible values, and the rotation angle sensor 42 can be regarded as a "stroke sensor." Note that a separate sensor that directly detects the piston stroke ST may be provided.

[0016] When the motor 40 is rotated in the forward direction, the presser 32 is advanced toward the bottom side of the piston 23, causing the piston 23 to press the inner pad 251, and the inner pad 251 moves toward the brake disc 15. When the inner clearance CL1 becomes 0 and the inner pad 251 and the brake disc 15 are in contact with each other, the piston 23 is further pressed, and the caliper 21 is driven to the left in the drawing. When the outer clearance CL2 becomes 0 and the outer pad 252 and the brake disc 15 are in contact with each other, the brake pad 25 holds the brake disc 15. When the motor 40 is further rotated in the forward direction, the brake pressing force increases.

[0017] Furthermore, when the motor 40 is rotated in the reverse direction, the pressing member 32 moves in a direction away from the bottom of the piston 23, whereby the pressure applied by the piston 23 to the brake pad 25 is released and the brake pad 25 and the brake disc 15 are separated from each other.

[0018] The reference position is the position where the brake pads 25 clamp the brake disc 15 and brake pressure begins to be generated. When the brakes are not applied, gap control is performed to stop the brake pads 25 at a position with a predetermined gap from the reference position. By performing gap control, responsiveness until frictional force is generated when the brakes are applied is ensured, and dragging when the brakes are not applied is suppressed. The reference position can also be considered as the origin of gap control. Hereinafter, the reference position in gap control is referred to as the gap origin Ps as appropriate.

[0019] The brake ECU 50 includes a drive circuit 51, a current sensor 52, and a control unit 60. The drive circuit 51 includes a switching element (not shown) that switches the current supplied to the motor 40. The current sensor 52 detects the motor current supplied to the motor 40.

[0020] The control unit 60 is mainly composed of a microcomputer and includes a CPU, ROM, RAM, I / O, and bus lines connecting these components (all not shown). Each process in the control unit 60 may be software processing in which the CPU executes a program stored in advance in a substantial memory device (i.e., a readable non-transitory tangible recording medium) such as a ROM, or may be hardware processing in which a dedicated electronic circuit is used.

[0021] The control unit 60 has, as functional blocks, a drive control unit 61, a state quantity acquisition unit 62, a reference position setting unit 63, a backlash amount ("BL amount" in the figure) setting unit 64, and an implementation determination unit 65. The drive control unit 61 controls the drive of the motor 40. The state quantity acquisition unit 62 acquires state quantities related to braking control in the electric brake device 10. In this embodiment, the motor current and the motor rotation angle are acquired as the state quantities.

[0022] The reference position setting unit 63 sets the gap origin Ps. The backlash amount setting unit 64 sets the backlash amount G2 based on the detection value of the current sensor 52. The setting of the backlash amount G2 will be described later. The implementation determination unit 65 determines whether or not it is necessary to update the gap origin Ps and the backlash amount G2.

[0023] The braking control process of this embodiment will be described with reference to the flowchart of Fig. 3. This process is executed by the control unit 60 at a predetermined cycle. In S101, the control unit 60 judges whether or not there is a brake actuation command from the driver, a driving support system, or the like. If it is judged that there is no brake actuation command (S101: NO), the process from S102 onwards is skipped. If it is judged that there is a brake actuation command (S101: YES), the process proceeds to S102.

[0024] In S102, the implementation determination unit 65 determines whether or not to update the gap origin Ps. When there is a temperature change in the motor 40, such as when the IG is on or during continuous operation, the origin is updated. Also, when there is a large vibration of the vehicle, such as when driving on a rough road, the origin is not updated even if it is necessary. If it is determined that the origin is not to be updated (S102: NO), the process proceeds to S108. If it is determined that the origin is to be updated (S102: YES), the process proceeds to S103.

[0025] In S103, the control unit 60 performs constant voltage control of the motor 40, and detects a state in which the motor rotation speed is constant, that is, a state in which no further increase in rotation speed is expected, as the no-load state. The motor rotation speed in the no-load state is defined as the no-load rotation speed Nnl, and the motor current value is defined as the no-load current value Inl. In the following calculations, a value that has been subjected to noise reduction processing using a low-pass filter or the like is used as the no-load current value Inl.

[0026] In addition, in the constant voltage control, the "state in which no further increase in motor rotation speed is expected" means that the motor 40 outputs a motor torque equivalent to the sliding resistance of the caliper 21, etc., and although this state is not strictly an unloaded state, this state is referred to as an "unloaded state" in this specification.

[0027] In S104, the reference position setting unit 63 sets the origin determination threshold Ith based on the no-load current value Inl (see formula (1)). Ci in formula (1) is an adjustment value (e.g., 0.1) and is set to a value capable of absorbing output variations due to sensor noise and vehicle body vibration so that the position where the brake pressure increases can be stably detected. Note that, instead of multiplying the no-load current value Inl by (1+Ci) as an adjustment coefficient, the origin determination threshold Ith may be set by adding the adjustment value to the no-load current value Inl.

[0028] Ith = Inl × (1 + Ci) (1)

[0029] In S105, the reference position setting unit 63 judges whether the motor current Im exceeds the origin determination threshold Ith. If it is judged that the motor current Im does not exceed the origin determination threshold Ith (S105: NO), this judgment process is repeated. If it is judged that the motor current Im exceeds the origin determination threshold Ith (S105: YES), the process proceeds to S106.

[0030] In S106, the reference position setting unit 63 determines whether the motor rotation speed has decreased from the no-load rotation speed Nnl. If it is determined that the motor rotation speed has not decreased (S106: NO), the process returns to S105. If it is determined that the motor rotation speed has decreased (S106: YES), the process proceeds to S107. In S107, the control unit 60 sets the current piston stroke ST as the gap origin Ps.

[0031] In S108, the control unit 60 judges whether the brake pressure has reached the command value from the driver or the driving assistance system and the brake operation has been completed. The brake pressure can be detected, for example, by a load sensor (not shown). If it is determined that the brake operation has not been completed (S108: NO), the brake operation is continued so that the brake pressure reaches the command value. If it is determined that the brake operation has been completed (S108: YES), the process proceeds to S109 and the current brake operation state is maintained.

[0032] In S110, the control unit 60 judges whether or not there is a brake release request from the driver or the driving support system. If it is judged that there is no brake release request (S110: NO), the process returns to S109 and the current brake operation state is continued. If it is judged that there is a brake release request (S110: YES), the process proceeds to S111.

[0033] In S111, the drive control unit 61 performs gap control to move the brake pad 25 back from the gap origin Ps to a position with a predetermined gap amount G1. In the gap control, first, reverse rotation control is performed to rotate the motor 40 in the reverse direction.

[0034] In S112, the control unit 60 judges whether the piston stroke ST has reached the retracted position. The retracted position is a position that is moved back from the gap origin Ps by a predetermined gap amount G1 and backlash amount G2. If it is judged that the piston stroke ST has not reached the retracted position (S112: NO), the process returns to S111 and the reverse rotation control continues. If it is judged that the piston stroke ST has reached the retracted position (S112: YES), the process proceeds to S113.

[0035] In S113, the control unit 60 performs forward direction control to rotate the motor 40 in the forward direction. In S114, the control unit 60 judges whether the gap control is completed. Here, it is judged that the gap control is completed when the motor 40 rotates forward from the reverse position by the backlash amount G2. If it is judged that the gap control is not completed (S114: NO), the process returns to S113 and the forward rotation control continues. If it is judged that the gap control is completed (S114: YES), the process proceeds to S115, the motor 40 is stopped, and the brake control is ended.

[0036] The brake control process of this embodiment will be described with reference to the time chart of Fig. 4. In Fig. 4, the horizontal axis represents a common time axis, and from the top, the brake pressure, motor rotation speed, motor current, piston stroke, and brake drag force are shown.

[0037] When a brake activation command is issued at time x10, current begins to be applied to the motor 40. At startup, the motor rotation speed is zero, so an excessively large current flows temporarily, but as the motor rotation speed increases, the current value decreases by an amount equal to the back electromotive current. In the case of constant voltage control, which is voltage control with a fixed pattern, the motor rotation speed increases and stabilizes until the motor torque and the load torque acting on the motor 40 are balanced. This state is detected as a no-load state, and the origin determination threshold value Ith is calculated based on the no-load current value Inl (see equation (1)).

[0038] At time x11, the brake pad 25 and the brake disc 15 come into contact with each other, and when the piston 23 is further pressed from the state where there is no gap between them, the vertical load between the brake pad 25 and the brake disc 15 increases, and the brake drag force increases due to friction on the contact surface between the brake pad 25 and the brake disc 15. In addition, the motor rotation speed decreases, and the motor current increases.

[0039] At time x12, an increase in the current value and a decrease in the rotation speed are detected, and when the motor current reaches the origin determination threshold Ith, the piston stroke position at this time is set as the gap origin Ps. At time x13, when the brake pressure reaches the designated value, the current operating state is maintained.

[0040] At time x14, when a brake release request is input, the motor 40 is rotated in the reverse direction, reducing the brake pressure. At time x15, when the piston stroke ST returns to the retracted position, the reverse rotation control is switched to forward rotation control, and the motor 40 is rotated forward by the backlash amount G2. At time x16, when the rotation from the retracted position by the backlash amount G2 is completed, the power supply to the motor 40 is turned off, and the brake release control is terminated. At this time, the piston stroke ST is at a position separated by a predetermined gap amount G1 from the gap origin Ps, and the backlash is closed on the forward side. This makes it possible to both avoid drag and improve the next control responsiveness.

[0041] Incidentally, the backlash amount G2 is not only the backlash in the screw mechanism of the rotating member 31 and the presser 32, but also the total of gaps at multiple locations, such as the gap between the piston 23 and the presser 32, the gap between the brake pad 25 and a shim (not shown), and the gap between the contact portion of the brake pad 25 with the piston 23 or the caliper 21 due to the inclination of the brake pad 25, and the backlash amount G2 varies depending on the amount of pad wear and temperature. Therefore, it is difficult to calculate the actual backlash amount G2 from the design value.

[0042] In the gap control when the brake is released, if the set backlash amount G2 is smaller than the actual amount, a predetermined gap amount cannot be secured between the brake disc 15, and dragging may occur. Also, if the set backlash amount G2 is larger than the actual amount, the piston 23 is returned more than the predetermined gap amount G1, and responsiveness may deteriorate at the time of the next brake control.

[0043] Therefore, in this embodiment, the backlash amount G2 is estimated based on the behavior of the motor current when the brake is applied. The backlash estimation process will be described based on the flowchart of FIG. 5. In S201, the control unit 60 judges whether or not there is a backlash amount update request. For example, when there is a risk of the backlash amount fluctuating due to a motor overload state or a change in the running environment temperature, the backlash amount is updated. This may be determined based on a command from a higher-level ECU or the like. If it is judged that there is no backlash amount update request (S201: NO), the process from S202 onwards is skipped. If it is judged that there is a backlash update request (S201: YES), the process proceeds to S202.

[0044] In S202, the control unit 60 judges whether the vehicle is stopped or not. If it is judged that the vehicle is not stopped (S202: NO), the process from S203 onwards is skipped and the backlash amount G2 is not updated. If it is judged that the vehicle is stopped (S202: YES), the process proceeds to S203. Note that the subsequent processes are performed, for example, one wheel at a time, on the premise that the vehicle is kept stopped by the parking brake or braking force on the wheels not subjected to backlash estimation. Also, if the vehicle transitions to a running state during the process from S203 onwards, the process related to the update of the backlash amount G2 is interrupted. Details will be described later.

[0045] In S203, the control unit 60 performs braking by rotating the motor 40 in the forward direction from a state in which the motor is spaced apart to an extent that at least a no-load energization period is ensured, acquires a state quantity as a reference, and sets the behavior of the acquired state quantity as a reference operation. In this embodiment, the transition of the motor current over time is acquired as the state quantity and set as the reference operation.

[0046] In S204, the control unit 60 determines whether the brake pressure of the brake pad 25 has reached the target value. It is determined whether the brake pressure has reached the target value. If it is determined that the brake pressure has not reached the target value (S204: NO), the brake operation and acquisition of the state quantity are continued. Note that the acquisition of the state quantity may be canceled after the value of the period required to update the backlash amount G2 is acquired. If it is determined that the brake pressure has reached the target value (S204: YES), the process proceeds to S205.

[0047] In S205, the control unit 60 rotates the motor 40 in the reverse direction to release the brake. In S206, the control unit 60 judges whether the gap control is completed or not. If it is judged that the gap control is not completed (S206: NO), the gap control is continued. If it is judged that the gap control is completed (S206: YES), the process proceeds to S207.

[0048] In S207, the control unit 60 rotates the motor 40 in the forward direction to start the detection operation. Here, the motor 40 is driven in the same manner as in S203, and the transition of the motor current over time is acquired as a state quantity for determination. The behavior of the acquired state quantity is regarded as the detection operation.

[0049] In S208, the control unit 60 judges whether or not the detection of the current rise behavior is completed. Here, as the detection operation, at least the value until the motor current exceeds the origin determination threshold Ith is necessary for comparison with the reference operation, so for example, when a predetermined time has passed since the motor current exceeded the origin determination threshold Ith, the detection of the current rise behavior is judged to be completed. If it is judged that the detection of the current rise behavior is not completed (S208: NO), the forward rotation drive of the motor 40 and the acquisition of the state quantity are continued. If it is judged that the detection of the current rise behavior is completed (S208: YES), the process proceeds to S209. Hereinafter, the range from the completion of the gap control to the completion of the detection of the current rise behavior is referred to as the current rise region.

[0050] In S209, the backlash amount setting unit 64 judges whether the reference operation and the detection operation match in the current rising region. In comparing the reference operation and the detection operation, it is not necessary to judge whether they match completely, and if the waveforms showing the transition of the motor current relative to the motor rotation amount in the current rising region are roughly the same, the reference operation and the detection operation are deemed to match. If it is judged that the reference operation and the detection operation match (S209: YES), the process proceeds to S211. If it is judged that the reference operation and the detection operation do not match (S209: NO), the process proceeds to S210.

[0051] If the backlash amount G2 used in the gap control in S205 is smaller than the actual value, the motor current will rise again before the no-load state is reached, and so the amount will not match the state amount during comparative operation. Therefore, in S210, the backlash amount setting unit 64 adjusts the value to increase the backlash amount G2.

[0052] In S211, which is entered when the state quantity for judgment and the state quantity for comparison match in the current rise region, the backlash amount setting unit 64 judges whether the no-load current supply time Xnl is greater than the no-load holding judgment threshold Xth in the detection operation. If the no-load state is long, the responsiveness deteriorates, so the no-load holding judgment threshold Xth is set within a value that allows the response time from the brake operation command to the arrival of the brake pressing force command value that allows the vehicle to exert sufficient braking force to be completed in an arbitrary time. If it is determined that the no-load current supply time Xnl is greater than the no-load holding judgment threshold Xth (S211: YES), the process proceeds to S212.

[0053] If the no-load current application time Xnl is greater than the no-load hold determination threshold value Xth, the backlash is returned more than the actual backlash amount G2 in the gap control, and if a braking request is received again during reverse movement in the gap control, the responsiveness will deteriorate. Therefore, in S212, the backlash amount setting unit 64 adjusts the value so that the backlash amount G2 becomes smaller. In S213, since the set backlash amount G2 is a value corresponding to the actual backlash, the backlash amount setting unit 64 holds the set value.

[0054] After the adjustment of the backlash amount G2 is completed, the system transitions to a desired control state. For example, to release the brake, the system returns the gap amount G1 and the backlash amount G2 from the gap origin Ps, and turns off the power supply to the motor 40. Also, when there is a brake operation request, for example, to adjust the backlash amount for another wheel, the system controls the drive of the motor 40 so as to achieve the target brake pressure.

[0055] The backlash estimation continuation determination process will be described with reference to the flowchart of Fig. 6. This process is executed by the control unit 60 at a predetermined cycle. In S251, the control unit 60 determines whether or not the backlash estimation process is in progress. If it is determined that the backlash estimation process is not in progress (S251: NO), the process from S252 onwards is skipped. If it is determined that the backlash estimation process is in progress (S251: YES), the process proceeds to S252.

[0056] In S252, the control unit 60 judges whether the vehicle has transitioned from a stopped state to a running state due to an acceleration command or the like. If it is judged that the vehicle has not transitioned to a running state (S252: NO), that is, if the vehicle is still stopped, the control unit 60 proceeds to S253 and continues the backlash estimation process. If it is judged that the vehicle has transitioned to a running state (S252: YES), the control unit 60 proceeds to S253 and interrupts the backlash estimation process.

[0057] In S254, the control unit 60 drives the motor 40 by gap control using the currently set value so that the brake pad 25 is positioned at a predetermined gap amount G1 from the gap origin Ps. After the gap control is completed, the motor 40 is stopped.

[0058] The backlash estimation process of this embodiment will be described based on the time charts of Figures 7 to 9. In Figures 7 to 9, the horizontal axis is a common motor rotation amount, and from the top, the sensor output of the current sensor 52, the brake pressing force, and the brake drag force are shown. Also, the dashed line indicates the reference operation, the dashed line indicates the release operation under gap control, and the solid line indicates the detection operation. For the sake of explanation, Figures 7 to 9 show that the reference brake operation is performed from the initial position Pi, but it may be performed from a position further forward than the initial position Pi as long as it is a position retreated from the gap origin Ps to an extent that the no-load state period can be sufficiently secured.

[0059] 7 shows the behavior when the set backlash amount G2 is insufficient. As shown by the dashed line, the motor 40 is driven from the initial position Pi to a rotational position Pt where the brake pressure is the target value by the reference brake operation. When the brake pressure reaches the target value, the motor 40 is rotated in the reverse direction as shown by the two-dot chain line to perform gap control, and the rotational position of the motor 40 is returned from the gap origin Ps to a return position Pa by the gap amount G1 and the currently set backlash amount G2. In addition, from the return position Pa, the motor 40 is rotated in the forward direction again, and the motor 40 is driven to a position Pc where the rising behavior of the motor current is completed.

[0060] If the set backlash amount G2 is insufficient, the amount of return from the gap origin Ps is insufficient, and the motor current changes from decreasing to increasing without passing through a no-load current flow. Therefore, as shown by the dashed circle, the behavior of the state quantity (here, the motor current) at the time of current rise does not match between the reference operation and the detected operation. In such a case, the backlash amount G2 is corrected to the increasing side. The correction amount may be determined based on the detected state quantity, or may be a fixed value. The same applies when correcting to the decreasing side.

[0061] As shown in Fig. 8, when the set backlash amount G2 is appropriate, the behavior of the state quantity at the time of current rise coincides between the reference operation and the detection operation, as shown by the dashed circle. Also, since the no-load current application time Xnl (not shown in Fig. 8) is shorter than the no-load maintenance judgment threshold value Xth, it is judged that the set backlash amount G2 is appropriate. In this case, the backlash amount G2 is not updated, and the set value is maintained.

[0062] As shown in Fig. 9, when the set backlash amount G2 is larger than the actual amount, the behavior of the state quantity at the time of the rise of the current coincides between the reference operation and the detection operation, as shown by the dashed circle. Also, the return amount from the gap origin Ps becomes large, so the current-carrying section NL in the no-load state occurs. The no-load current-carrying time Xnl, which is the time to pass through the current-carrying section NL in the no-load state, is larger than the no-load holding judgment threshold value Xth, so the backlash amount G2 is corrected to the decreasing side.

[0063] In this embodiment, by comparing the reference operation with the detection operation, it is possible to set an appropriate backlash amount G2 according to the driving conditions, etc. This allows the electric brake device 10 to appropriately control the gap when the brake is released. Note that in Figs. 7 to 9, the range from the return position Pa to the rising behavior completion position Pc is the "current rising region", which corresponds to the "determination range".

[0064] As described above, the brake ECU 50 controls the electric braking device 10, which includes the brake disc 15, the brake pad 25, and the motor 40. The brake disc 15 rotates integrally with the wheel. The brake pad 25 generates a braking force by clamping the brake disc 15. The motor 40 generates a driving force to move the brake pad 25 in a forward direction, which is a direction in which the brake pad 25 is pressed against the brake disc 15, or in a backward direction, which is a direction in which the brake pad 25 is separated from the brake disc 15.

[0065] The control unit 60 of the brake ECU 50 includes a drive control unit 61, a state quantity acquisition unit 62, and a backlash amount setting unit 64. The drive control unit 61 controls the drive of the motor 40. The state quantity acquisition unit 62 acquires state quantities related to the braking control of the electric brake device 10.

[0066] The backlash amount setting unit 64 sets the backlash amount G2 used in gap control to ensure a gap between the brake disc 15 and the brake pad 25 in a state where the backlash is reduced to the forward side in a non-braking state by driving the motor 40 in the backward direction from the gap origin Ps, which is a reference position, and then driving the motor 40 in the forward direction by the amount of backlash G2, according to the state amount when the braking force is released. By making the backlash amount G2 variable according to the state amount, braking control can be performed with high precision. In detail, the backlash amount G2 is set according to the wear state and temperature of the brake pad 25, so that the gap control can be performed with high precision, and the occurrence of drag and variation in responsiveness can be reduced.

[0067] The state quantity includes the motor current that is passed through the motor 40. The backlash amount setting unit 64 adjusts the backlash amount G2 based on a comparison result between a reference operation, which is the behavior of the motor current when the motor 40 is driven in the forward direction from a state in which the brake disc 15 and the brake pad 25 are sufficiently separated, and a detection operation, which is the behavior of the actuator current when the actuator is driven in the forward direction from a position retreated from the reference position by the gap amount G1 and the set backlash amount G2. Note that the "state in which the brake disc 15 and the brake pad 25 are sufficiently separated" refers to a state in which the brake disc 15 and the brake pad 25 are retreated from the gap origin Ps by more than the sum of the maximum expected backlash amount G2 and the desired gap amount G1, and a period of no-load state is ensured.

[0068] In detail, when the reference operation and the detection operation in the judgment range including the gap origin Ps do not match, the backlash amount setting unit 64 adjusts the backlash amount G2 to the larger side. Also, when the reference operation and the detection operation in the judgment range match and the period during which the motor current does not change is greater than the no-load holding judgment threshold value Xth, the backlash amount setting unit 64 adjusts the backlash amount G2 to the smaller side. This allows the backlash amount G2 to be set appropriately.

[0069] The control unit 60 further includes an implementation determination unit 65 that determines whether or not the backlash amount G2 needs to be updated. The implementation determination unit 65 prohibits the update of the backlash amount G2 when the vehicle is traveling, and allows the update of the backlash amount G2 when the vehicle is stopped. This allows the backlash amount G2 to be updated with high accuracy.

[0070] In the embodiment, the electric brake device 10 corresponds to the "brake device", the brake ECU 50 corresponds to the "brake control device", the motor 40 corresponds to the "actuator", the motor current corresponds to the "actuator current", the gap origin Ps corresponds to the "reference position", the origin judgment threshold Ith corresponds to the "judgment threshold", and the current rise region corresponds to the "judgment range".

[0071] (Other embodiments) In the above embodiment, the gap origin is set using the motor current and the motor rotation speed as the state quantity. In other embodiments, the gap origin may be set using parameters other than the motor current and the motor rotation speed. The same applies to the backlash amount.

[0072] In another embodiment, the backlash estimation process may be repeated until a predetermined value is obtained. In detail, as shown in Fig. 10, after the backlash amount is adjusted to the increasing or decreasing side in S210 or S211, the process returns to S203 and performs the state amount acquisition operation and the detection operation again. When the process proceeds to S213 and the set value is held, the backlash estimation process ends.

[0073] In the above embodiment, the actuator is a motor. In other embodiments, the actuator may be something other than a motor, such as a solenoid. Also, the configurations related to the braking force generating unit, the linear motion conversion mechanism, and the like may be different from those in the above embodiment.

[0074] In the present disclosure, the brake control device may be described as "a brake control device according to any one of items 1 to 4, further comprising an implementation determination unit (68) that determines whether or not the backlash amount needs to be updated, wherein the implementation determination unit prohibits updating of the backlash amount when the vehicle is traveling and allows updating of the backlash amount when the vehicle is stopped."

[0075] The control unit and the method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control unit and the method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described in the present disclosure may be realized by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. In addition, the computer program may be stored in a computer-readable non-transient tangible recording medium as instructions executed by a computer. As described above, the present invention is not limited to the above embodiment, and can be implemented in various forms within the scope of the invention. [Explanation of symbols]

[0076] 10. Electric brake device (braking device) 15 Brake disc 25 Brake pads 40 Motor (actuator) 50···Brake ECU (Brake Control Unit) 60...Control section 61 Drive control unit 62... State quantity acquisition unit 64 Backlash amount setting section

Claims

1. A brake disc (15) that rotates together with the wheel; A brake pad (25) that generates a braking force by clamping the brake disc; an actuator (40) that generates a driving force for moving the brake pad in a forward direction, which is a direction in which the brake pad is pressed against the brake disc, or in a backward direction, which is a direction in which the brake pad is separated from the brake disc; A braking control device for controlling a braking device (10) comprising: A drive control unit (61) for controlling the drive of the actuator; A state quantity acquisition unit (62) that acquires a state quantity related to braking control of the braking device; a backlash amount setting unit (64) that sets, in accordance with the state amount, the backlash amount used in gap control for securing a gap between the brake disc and the brake pad in a state where the backlash is reduced on the forward side in a non-braking state by driving the actuator in the backward direction from a reference position and then driving the actuator in the forward direction by an amount corresponding to a backlash amount when releasing the braking force; A braking control device comprising:

2. the state quantity includes an actuator current passed through the actuator, 2. The brake control device according to claim 1, wherein the backlash amount setting unit adjusts the amount of backlash based on a comparison result between a reference operation, which is the behavior of the actuator current when the actuator is driven in the forward direction from a state in which the brake disc and the brake pad are sufficiently separated, and a detection operation, which is the behavior of the actuator current when the actuator is driven in the forward direction from a position retreated from the reference position by a gap amount and the set backlash amount.

3. 3. The brake control device according to claim 2, wherein the backlash amount setting unit adjusts the backlash amount to a larger amount when it is determined that the reference motion and the detected motion do not match in a determination range including the reference position.

4. 4. The brake control device according to claim 2 or 3, wherein the backlash amount setting unit adjusts the backlash amount to a smaller side when it is determined that the reference operation and the detected operation in a determination range including the reference position match and the period during which the actuator current does not change is greater than a determination threshold value.

5. Further, an implementation determination unit (65) is provided for determining whether or not the backlash amount needs to be updated. The implementation determination unit is prohibiting updating of the backlash amount when the vehicle is running; 2. The brake control device according to claim 1, wherein the backlash amount is allowed to be updated when the vehicle is stopped.

Images