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 gap 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 gap amount setting part 64 drives the motor 40 in a retreating direction from a gap original point Ps so as to set a gap target value Gt relating to a retreat amount from the gap original point Ps, in gap control of securing a gap between the brake disc 15 and the brake pad 25 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] 2. Description of the Related Art Electric brake devices are known in the art. For example, in Patent Document 1, when braking ends, the brake pads are separated from the disc rotor in accordance with the amount of thermal deformation of the disc rotor caused by braking. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-32868 A Summary of the Invention [Problem to be solved by the invention]

[0004] In controlling the gap that is created when the electric brake is released, the appropriate gap changes due to factors other than the temperature of the disc rotor.

[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 gap amount setting unit (64). The drive control unit controls driving of the actuator. The state quantity acquisition unit acquires state quantities related to braking control of the braking device. When releasing the braking force, the gap amount setting unit sets a gap target value related to the amount of retraction from a reference position in accordance with the state quantities in gap control that ensures a gap between the brake disc and the brake pad in a non-braking state by driving the actuator in a retracting direction from a reference position. This makes it possible to perform braking control with high accuracy. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing an electric brake device according to a first embodiment. [Diagram 2] FIG. 1 is a plan view of an electric brake device according to a first embodiment. [Diagram 3] 4 is a flowchart illustrating a braking control process according to the first embodiment. [Figure 4] FIG. 2 is a bottom view showing a state of the electric brake device during braking according to the first embodiment. [Diagram 5] FIG. 2 is a schematic diagram showing a state of a brake pad during braking according to the first embodiment. [Figure 6] FIG. 2 is a bottom view showing a state of the electric brake device according to the first embodiment when the brake is released. [Figure 7] FIG. 4 is a schematic diagram showing a state of the brake pads when the brake is released according to the first embodiment. [Figure 8] FIG. 4 is an explanatory diagram showing the relationship between a piston stroke and a brake pressing force according to the first embodiment. [Figure 9] 4 is a time chart illustrating a braking control process according to the first embodiment. [Figure 10] 10 is a time chart illustrating a braking control process according to a second embodiment. [Figure 11] 13 is a time chart illustrating a braking control process according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (First 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 9. 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 includes 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. 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 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 gap amount 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 state quantities acquired include a motor current, a motor rotation angle, and a brake pressing force detected by a load sensor (not shown). The brake pressing force may be calculated from the motor current, etc., instead of the load sensor.

[0022] A reference position setting unit 63 sets a gap origin Ps. A gap amount setting unit 64 sets a gap target value Gt, which is a target value of the amount of retreat from the gap origin Ps (hereinafter, "gap amount G1"), so as to reduce drag when not braking and ensure responsiveness when braking when the brake is released. An implementation determination unit 65 determines whether or not the gap origin Ps and the gap target value Gt need to be updated.

[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 determines whether or not there is a brake release request from the driver or the driving assistance system. If it is determined 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 determined that there is a brake release request (S110: YES), the process proceeds to S111. In S111, the gap amount setting unit 64 sets the gap target value Gt. The gap target value Gt may be set while the brake is being held.

[0033] In S112, the drive control unit 61 performs gap control to retract the brake pad 25 to a position with a gap of the gap amount G1 from the gap origin Ps. In S113, the control unit 60 judges whether the gap control is completed or not. If it is judged that the gap control is not completed (S113: NO), the process returns to S112 and the gap control is continued. If it is judged that the gap control is completed (S113: YES), the process proceeds to S114, the motor 40 is stopped, and the brake control is ended.

[0034] The wear state of the brake pad 25 will be described with reference to Fig. 4 to Fig. 8. In Fig. 5 and Fig. 7, (a) shows a case where the wear is relatively small, and (b) shows a case where the wear is relatively large. In Fig. 7, the inclination angle of the caliper 21 when the brake is released is θ, the contact point between the brake pad 25 and the brake disc 15 just before they separate is P, and the distances between the center of the brake pad 25 and the brake disc 15 at that time are L1 and L2.

[0035] 4 and 5, when the brake is applied, the caliper 21 is driven to reduce the gap, so the inclination of the caliper 21 decreases to match the shape of the brake pad 25. On the other hand, when the brake is released, the caliper 21 inclines by the amount of the gap of the slide pin 28 depending on the center of gravity of the caliper 21 and the drag direction, as shown in FIG.

[0036] As shown in Fig. 7, the brake pad 25 of this embodiment is provided with a tapered portion 26 on the surface facing the brake disc 15. If the caliper 21 tilts in the same way when the brake is released, regardless of the state of wear, the contact point P immediately before separation will be located farther from the center position of the brake pad 25 as the amount of wear increases. Therefore, the distance between the center position of the brake pad 25 and the brake disc 15 immediately before the pads separate will be larger when the amount of wear is large compared to when the amount of wear is small. That is, L1 <L2である。

[0037] Therefore, when the amount of wear is large, drag will occur unless the brake pad 25 is retracted from the face-to-face contact state with the brake disc (see FIG. 5) by at least L2, which is larger than L1. That is, in order to prevent drag from occurring, the greater the amount of friction, the greater the gap target value Gt must be.

[0038] Figures 8(a) and 8(b) show the relationship between the piston stroke ST and the brake pressure applied by the brake pad 25, with Figure 8(a) showing the case when the pad is not worn and Figure 8(b) showing the case when the pad is worn. In Figures 8(a) and 8(b), the horizontal axis is the piston stroke ST and the vertical axis is the brake pressure, with the solid line indicating when the brake is applied and the two-dot chain line indicating when the brake is released.

[0039] As shown in FIG. 8(a) and FIG. 8(b), when the brake pad 25 is worn, the gradient of the brake pressure with respect to the piston stroke ST when the pressure is generated is larger than when the brake pad 25 is not worn. Therefore, a target correction value Ga is calculated based on the gradient Kw [kN / mm] of the brake pressure with respect to the current piston stroke ST and the gradient K0 [kN / mm] of the brake pressure with respect to the piston stroke ST in the initial state when the brake pad 25 is not worn (see formula (2)). In addition, a target gap value Gt is calculated using the target correction value Ga (formula (3)). In the formula, α is an arbitrary conversion coefficient (for example, 0.8), and G0 is an initial value of the gap amount when there is no wear. Since Kw≧K0, (Kw / K0)≧1.

[0040] Ga = α × {(Kw / K0)-1} (2) Gt = G0 + Ga (3)

[0041] The brake control process of this embodiment will be described with reference to the time chart of Fig. 9. In Fig. 9, the horizontal axis represents a common time axis, and from the top, motor current, motor rotation speed, piston stroke, and brake drag force are shown.

[0042] In FIG. 9, the left side of the page shows the behavior of the brake pads 25 when there is no wear. When a brake activation command is issued at time x10, current begins to be applied to the motor 40. At start-up, 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 equivalent to the back electromotive current. When controlling at a constant voltage, the motor rotation speed stabilizes in a no-load state. In addition, the origin determination threshold Ith is calculated based on the no-load current value Inl (see formula (1)).

[0043] When the brake pad 25 and the brake disc 15 come into contact with each other and there is no gap between them, the piston 23 is pressed further, increasing the vertical load between the brake pad 25 and the brake disc 15, and increasing the brake drag force due to friction on the contact surfaces between the brake pad 25 and the brake disc 15. In addition, the motor rotation speed decreases and the motor current increases.

[0044] At time x11, 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 x12, when the brake pressing force reaches the designated value, the current operating state is maintained.

[0045] At time x13, when a brake release request is input, the motor 40 is rotated in the reverse direction to reduce the brake pressure. At time x14, when the vehicle reaches a position retreated by the gap target value Gt from the set gap origin Ps, the power supply to the motor 40 is turned off and the brake release control is terminated.

[0046] The right side of the page shows behavior when the brake pad 25 is worn. When a brake actuation command is issued at time x20, current is started to be applied to the motor 40, and the gap origin Ps is set at time x21 when the motor current reaches the origin determination threshold Ith. When the brake pad 25 is worn, the brake pad 25 and the brake disc 15 come into contact on the forward direction side compared to when the brake pad 25 is not worn. Therefore, the gap origin Ps is set at a position shifted toward the forward direction side compared to when the brake pad 25 is not worn. When the brake pressure reaches the designated value at time x22, the current actuation state is maintained.

[0047] When a brake release request is input at time x23, the motor 40 is rotated in the reverse direction to reduce the brake pressure. When wear is large, the gap origin Ps is set shifted toward the forward direction, and in addition, as shown by the dashed line D, the caliper 21 tilts, causing large drag due to one-sided contact, so the gap target value Gt is made larger than when there is no wear. This makes it possible to appropriately suppress drag even when friction is large.

[0048] 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.

[0049] The control unit 60 of the brake ECU 50 includes a drive control unit 61, a state quantity acquisition unit 62, and a gap 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.

[0050] When releasing the braking force, the gap amount setting unit 64 drives the motor 40 in the backward direction from the gap origin Ps to ensure a gap between the brake disc 15 and the brake pad 25 in a non-braking state, and sets a gap target value Gt relating to the amount of retreat from the gap origin Ps in accordance with a state quantity. By making the gap target value Gt variable in accordance with the state quantity, braking control with high accuracy is possible.

[0051] The gap amount setting unit 64 sets the gap target value Gt using a correction value calculated from a state quantity whose behavior changes according to the amount of wear of the brake pad 25. In this embodiment, the gradient Kw of the brake pressure with respect to the piston stroke ST is used as the state quantity whose behavior changes according to the amount of wear. This makes it possible to improve responsiveness and reduce dragging at the same time according to the wear state of the brake pad 25.

[0052] Second embodiment The second embodiment is shown in Fig. 10. For example, if the expansion coefficient of the brake pad 25 is larger than that of the caliper 21, the expansion due to the rise in temperature will be larger in the brake pad 25 than in the caliper 21, so in order to avoid dragging, it is desirable to set the target gap value Gt according to the brake temperature. Specifically, when the brake temperature is relatively high, the target gap value Gt is set larger than when the brake temperature is low.

[0053] The brake temperature may be calculated from the detection value of a temperature sensor installed in the electric brake device 10 or in the vicinity thereof, but when it is difficult to install a temperature sensor or when temperature information cannot be obtained, the brake temperature may be estimated from the braking time Xb and the brake pressure. Note that the braking time Xb is the holding time during which the desired brake pressure is maintained.

[0054] The brake control process of this embodiment will be described based on the time chart of Fig. 10. Fig. 10 shows an example of setting the gap target value Gt according to the braking time, with the left side of the page showing a case where the braking time Xb is short, and the right side showing a case where the braking time Xb is long. Here, it is assumed that there is no wear on the brake pads 25, and the process when the braking time Xb is short is generally similar to the left side of the page in the first embodiment, so the description will be omitted. Note that when the braking time Xb is relatively short, for example, shorter than the gap adjustment judgment time, it is not necessary to adjust the gap target value Gt.

[0055] An example of a case where the braking time Xb is relatively long, such as when traveling downhill, is shown on the right side of FIG. 10. The processing from time x30 to time x32 is the same as the processing from time x10 to time x12. When the brake pressure reaches the designated value at time x32, the applied state is maintained. When a brake release request is input at time x33, the brake temperature is estimated based on the braking time Xb and the brake pressure from time x32 to time x33. Then, based on the estimated brake temperature, a gap target value Gt is set and the motor 40 is rotated in the reverse direction. When the position is reached at time x34, where the brake is retreated by the gap target value Gt from the gap origin Ps, the power supply to the motor 40 is turned off and the brake release control is terminated.

[0056] After the brakes are released, the set target clearance value Gt is maintained, and if a brake activation command is issued promptly after time x34, the brake temperature is likely not to have dropped, so the target clearance value Gt adjusted during the previous braking is used.

[0057] Furthermore, when the non-braking state continues, as shown by the two-dot chain line, the target gap value Gt is gradually decreased according to the non-braking time within a range in which the value after gradual decrease does not fall below the gap amount G1 at low temperature. For example, the amount of cooling is estimated from the ambient temperature and the vehicle speed, and the target gap value Gt is gradually decreased based on the amount of cooling. Alternatively, the target gap value Gt may be gradually decreased by a time function or map calculation according to the non-braking time.

[0058] The state quantity includes a braking time, which is the time during which the brake pad 25 is held pressed against the brake disc 15 with a target pressing force. The gap amount setting unit 64 sets the gap target value Gt so that the amount of retraction increases as the braking time increases. This makes it possible to set the gap target value Gt according to the gap state due to temperature change without using the detection value of a temperature sensor, and thus allows appropriate gap control.

[0059] After the gap control is completed, the gap amount setting unit 64 gradually decreases the target gap value Gt in accordance with the non-braking time during which the non-braking state continues. This makes it possible to appropriately set the target gap value Gt in accordance with the cooling state of the electric brake device 10.

[0060] Third embodiment The third embodiment is shown in Fig. 11. In Fig. 11, the horizontal axis represents a common time axis, and from the top, motor rotation speed, piston stroke, and brake drag force are shown. When a brake activation command is issued at time x40, power supply to the motor 40 begins. When the brake pressure reaches a designated value at time x42, the current activation state is maintained.

[0061] In this example, the actual response time Xr, which is the time from when the brake application starts until the brake pressure reaches the command value, is longer than the target response time Xt. In other words, when the brake application starts from position P1, which is the piston position before the brake application starts, the brake application does not reach position P2, where the brake pressure reaches the command value, within the target response time.

[0062] Therefore, the target gap value Gt is corrected so that the brake pressure reaches the command value within the target response time Xt. In detail, a correction amount As is calculated from the difference between the actual response time Xr and the target response time Xt and the no-load rotation speed Nnl, and the target gap value Gt is corrected to be smaller by the correction amount As.

[0063] At time x43, when a brake release request is input, the motor 40 is rotated in the reverse direction to reduce the brake pressure. At this time, gap control is performed using the corrected gap target value Gt. At time x44, when the vehicle reaches a position retreated by the corrected gap target value Gt from the gap origin Ps (not shown in FIG. 11), the power supply to the motor 40 is turned off and the brake release control is terminated.

[0064] Since the piston 23 is stopped on the forward side of the position P1 by the correction amount As, the responsiveness is improved. Note that, since drag occurs if the gap is too small, it is desirable to set the gap target value Gt taking into consideration the disk runout, temperature change, etc.

[0065] The state quantities include a response time, which is the time from the start of braking until the target braking force is reached, and a motor rotation speed. The motor rotation speed is a value that can be converted into a rotational angular velocity of the motor 40 and corresponds to the "actuator drive speed." When the response time is longer than the target response time, the gap amount setting unit 64 corrects the gap target value Gt based on the difference between the response time and the target response time, and the motor rotation speed from the start of braking until the target braking force is reached. This makes it possible to achieve both a reduction in drag and responsiveness.

[0066] 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 gap amount G1 corresponds to the "backward amount", and the motor rotation speed corresponds to the "driving speed".

[0067] (Other embodiments) In the above embodiment, the target gap value is set using the state quantities such as the gradient of the brake pressure force relative to the piston stroke, the braking time, the response time, and the motor rotation speed. In other embodiments, the state quantities used to set the target gap value may be parameters different from those in the above embodiment. Also, the target gap value may be set by combining a plurality of parameters or embodiments.

[0068] In another embodiment, in the gap control, reverse rotation control may be performed to retreat the rotor by an amount corresponding to the gap amount and the backlash amount, and then forward rotation control may be performed to advance the rotor by an amount corresponding to the backlash amount.

[0069] 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.

[0070] 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]

[0071] 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 Gap 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 gap amount setting unit (64) that, in a gap control for securing a gap between the brake disc and the brake pad in a non-braking state by driving the actuator in the retreat direction from a reference position when the braking force is released, sets a gap target value related to a retreat amount from the reference position in accordance with the state amount; A braking control device comprising:

2. the reference position is variable depending on an actuator current applied to the actuator, 2. The brake control device according to claim 1, wherein the gap amount setting unit uses a correction value calculated from the state quantity whose behavior changes depending on the amount of wear of the brake pad, and sets the gap target value so that the amount of retraction increases as the amount of wear increases.

3. the state quantity includes a braking time which is a time during which the brake pad is held in a state in which it is pressed against the brake disc with a target pressing force, 2. The brake control device according to claim 1, wherein the gap amount setting unit sets the target gap value such that the amount of retraction increases as the braking time increases.

4. 4. The brake control device according to claim 3, wherein the gap amount setting unit gradually reduces the target gap value in accordance with a non-braking time during which a non-braking state continues after the gap control is completed.

5. The state quantity includes a response time, which is a time from the start of braking until a target braking force is reached, and a drive speed of the actuator, 2. The brake control device according to claim 1, wherein, when the response time is longer than a target response time, the gap amount setting unit corrects the target gap value based on a difference between the response time and the target response time and on the driving speed from the start of braking to the time when the target braking force is reached.

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