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. A driving control part 61 controls driving of a motor 40. A state amount obtaining part 62 obtains a state amount relating to braking control by the electric brake device 10. When releasing braking force, a reference position setting part 63 drives an actuator in a retreating direction from a gap original point Ps as a reference position so as to set the gap original point Ps which is used for gap control of securing a gap between a brake disc 15 and a brake pad 25 in a non-braking state, on the basis of a state quantity. The reference position setting part 63 detects an unloaded state that is a state in which the state quantity remains stable in a period of time during which braking control is started and then the brake pad 25 contacts the brake disc 15, and sets, as the gap original point Ps, a piston stroke ST at the time when a change of the state quantity from the quantity in the unloaded state is detected.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Conventionally, there is known a control device for an electric brake. For example, in Patent Document 1, when a state in which a control current is larger than a maximum no-load current continues for a certain period of time, a load detection signal is turned ON. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2022 / 202243 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, when the output of the current sensor varies due to temperature changes such as brake overheating, the load detection point shifts, and the accuracy of detecting the initial position of the pad gap decreases.

[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 reference position setting unit 63. The drive control unit controls the drive of the actuator. The state quantity acquisition unit acquires state quantities related to the braking control of the braking device.

[0008] The reference position setting unit sets a reference position based on the state quantity to be used in gap control for ensuring a gap between the brake disc and the brake pad in a non-braking state by driving the actuator in the backward direction from the reference position when the braking force is released. The reference position setting unit detects a no-load state in which the state quantity is stable during the period from the start of braking control until the brake pad abuts against the brake disc, and sets the actuator position when a change in the state quantity from the no-load state is detected as the reference position. This allows for accurate braking control. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 illustrates an electric brake device according to an embodiment. [Diagram 2] 4 is a flowchart illustrating a braking control process according to an embodiment. [Diagram 3] 4 is a time chart illustrating a braking control process according to an embodiment. [Figure 4] FIG. 4 is an explanatory diagram showing a relationship between a piston stroke and a brake pressing force according to one embodiment. [Diagram 5] FIG. 4 is a characteristic diagram showing motor characteristics according to one embodiment. [Figure 6] 11 is a time chart illustrating a brake control process according to a reference example in which the origin determination threshold value is a fixed value. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (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 one embodiment is shown in Figs. 1 to 5. As shown in Fig. 1, 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.

[0011] 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 (not shown). The piston 23 is provided slidably within a cylinder 22 provided in the caliper 21.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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, and an implementation determination 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 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. The reference position setting unit 63 sets the gap origin Ps. The implementation determination unit 64 determines whether or not the gap origin Ps needs to be updated.

[0023] The braking control process of this embodiment will be described with reference to the flowchart of Fig. 2. 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 64 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 FIG. 4, the horizontal axis represents the piston stroke ST, and the vertical axis represents the brake pressure. The brake pressure will be described as roughly corresponding to the motor current. As shown by the arrow A, immediately after the brake pad 25 and the brake disc 15 come into contact with each other, the brake pressure increases gradually due to the play at the pad installation location and the inclination of the brake pad 25. When the partial contact state is resolved, the brake pad 25 is crushed and the brake pressure increases, so that the increase in the brake pressure relative to the stroke amount is large. In other words, the amount of change in the stroke relative to the increase in the brake pressure is small. In this embodiment, the adjustment value Ci is used to set a threshold value at a point where the amount of change in the piston stroke is relatively small, so that the deviation of the gap origin Ps is small even if the motor current varies.

[0032] Returning to FIG. 2, in S108, the control unit 60 determines whether the brake pressure has reached a 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.

[0033] 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.

[0034] In S111, the drive control unit 61 performs gap control to retract the brake pad 25 to a position with a predetermined gap amount G from the gap origin Ps. In S112, the control unit 60 judges whether the gap control is completed or not. If it is judged that the gap control is not completed (S112: NO), the process returns to S111 and the gap control is continued. If it is judged that the gap control is completed (S112: YES), the process proceeds to S113, the motor 40 is stopped, and the brake release is completed.

[0035] The brake control process of this embodiment will be described based on the time chart of Fig. 3. In Fig. 3, 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.

[0036] 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.

[0037] 5 is a motor characteristic diagram of the motor 40, with the horizontal axis representing torque and the vertical axis representing motor speed or motor current. If the torque that balances with the motor load due to piston sliding friction or the like is taken as balancing torque Tr, then the motor speed at this time is taken as no-load speed Nnl, and the current value is taken as no-load current value Inl. Based on the detected no-load current value Inl, an origin determination threshold Ith is calculated (see formula (1)).

[0038] 3, at time x11, the brake pad 25 and the brake disc 15 come into contact with each other, eliminating the gap, and the piston 23 is further pressed, increasing the brake pressing force, and the brake drag force increases 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.

[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 to reduce the brake pressure. At time x15, when the brake pad 25 returns to a position separated by a predetermined gap amount G from the gap origin Ps set by the gap control, the power supply to the motor 40 is turned off and the brake release control is terminated.

[0041] For example, there is a risk that the output of the current sensor 52 will vary due to overheating of the electric brake device 10, and if the origin determination threshold Ith is set to a fixed value, the piston stroke position at the time when the motor current exceeds the origin determination threshold Ith will shift, and the detection accuracy of the gap origin Ps will decrease.

[0042] Fig. 6 is a reference example in which the origin determination threshold Ith is a fixed value. In Fig. 6, the normal state is indicated by a solid line, and the behavior during the normal state is the same as that in Fig. 3. In addition, the case in which the output gain of the current sensor 52 is smaller than normal is indicated by a dashed line.

[0043] When the origin determination threshold Ith is a fixed value, if the gain of the output of the current sensor 52 is smaller than normal, the gap origin Psx is set to a position shifted further forward than normal (time xa). Therefore, if the same gap control as normal is performed, the brake pad 25 will stop at time xb further forward than normal. If the brake drag force cannot be sufficiently reduced due to an insufficient return amount, this can cause deterioration of power consumption and pad wear.

[0044] Although not shown, when the gain of the current sensor 52 is larger than normal, the gap origin is set at a position shifted toward the backward direction from normal. Also, when the gain of the current sensor 52 is large and the no-load current value Inl is larger than the origin determination threshold value Ith (i.e., Inl>Ith), the origin is determined immediately after the inrush current is detected, so the return amount becomes larger than normal and responsiveness deteriorates.

[0045] In this embodiment, the origin determination threshold Ith is set based on the no-load current value Inl, which is the motor current in a no-load state, and the gap origin Ps is set. This makes it possible to appropriately set the gap origin Ps, which is the reference position for gap control, regardless of variations in the sensor output of the current sensor 52 due to temperature changes, etc.

[0046] 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.

[0047] The control unit 60 of the brake ECU 50 includes a drive control unit 61, a state quantity acquisition unit 62, and a reference position setting unit 63. 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. The reference position setting unit 63 sets, based on the state quantities, a gap origin Ps used in gap control for securing a gap between the brake disc 15 and the brake pad 25 in a non-braking state by driving the actuator in the backward direction from the gap origin Ps, which is a reference position, when releasing the braking force.

[0048] The reference position setting unit 63 detects an unloaded state in which the state quantity is stable during the period from the start of braking control until the brake pad 25 abuts against the brake disc 15, and sets the piston stroke ST when a change in the state quantity from the unloaded state is detected as the gap origin Ps. This enables accurate braking control. In detail, by detecting the relative change in the state quantity from the unloaded state, the gap origin Ps can be appropriately set even if the sensor value varies due to, for example, a temperature change, etc., so that the gap control can be performed accurately and the occurrence of drag and variation in responsiveness can be reduced.

[0049] The state quantity includes the motor current flowing through the motor 40. The reference position setting unit 63 sets an origin determination threshold Ith based on the motor current in an unloaded state, and when the motor current exceeds the origin determination threshold Ith, it determines that a change in the state quantity has been detected, and sets the piston stroke ST at this time as the gap origin Ps. By using the motor current as the state quantity, it is possible to distinguish between an unloaded state and a loaded state, and the gap origin Ps can be appropriately set even if the sensor value varies.

[0050] The actuator is the motor 40, and the state quantities include the motor current passed through the motor 40 and the rotational angular velocity of the motor 40. The rotational angular velocity is a value that can be converted from the motor rotation speed. The reference position setting unit 63 sets the piston stroke ST when both the motor current and the motor rotation speed change from the no-load state as the gap origin Ps. This makes it possible to avoid erroneously determining, as the reference position, a state in which the motor current temporarily increases, such as when the brake pad 25 temporarily contacts the brake disc due to vehicle body vibration or the like.

[0051] The drive control unit 61 controls the motor 40 with voltage control of a fixed pattern from the start of braking control until the gap origin Ps is set. By performing constant voltage control, the gap origin Ps can be stably detected.

[0052] The control unit 60 further includes an implementation determination unit 64 that determines whether or not the gap origin Ps needs to be updated. This allows the gap origin Ps to be updated appropriately. If it is determined that the no-load period is not available, the implementation determination unit 64 does not update the gap origin Ps. This makes it possible to prevent the gap origin Ps from being updated to an inappropriate value.

[0053] 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 piston stroke ST corresponds to the "actuator position".

[0054] (Other embodiments) In the above embodiment, the gap origin is set using the motor current and the motor rotation speed as the state quantities. In other embodiments, the gap origin may be set using parameters other than the motor current and the motor rotation speed.

[0055] 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.

[0056] In the present disclosure, the brake control device may be configured as "the brake control device described in any one of items 1 to 3, wherein the drive control unit controls the actuator with a fixed pattern of voltage control from the start of brake control until the reference position is set," or "the brake control device described in any one of items 1 to 4, further including an implementation determination unit (68) that determines whether or not the reference position needs to be updated."

[0057] 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]

[0058] 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 63...Reference position 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 reference position setting unit (63) that sets, based on the state quantity, the reference position used in gap control for ensuring a gap between the brake disc and the brake pad in a non-braking state by driving the actuator in the rearward direction from a reference position when releasing the braking force; and Equipped with The reference position setting unit detects an unloaded state in which the state quantity is stable during the period from the start of braking control to the time when the brake pad contacts the brake disc, and sets the position of the actuator when a change in the state quantity from the unloaded state is detected as the reference position.

2. the state quantity includes an actuator current passed through the actuator, 2. The brake control device according to claim 1, wherein the reference position setting unit sets a judgment threshold based on the actuator current in the no-load state, and sets the position of the actuator when the actuator current exceeds the judgment threshold as the reference position.

3. The actuator is a motor, the state quantities include a motor current supplied to the motor and a rotational angular velocity of the motor, 3. The brake control device according to claim 1, wherein the reference position setting unit sets the position of the actuator when both the motor current and the rotational angular velocity change from the no-load state as the reference position.

4. 3. The brake control device according to claim 1, wherein the drive control unit controls the actuator with voltage control of a fixed pattern from the start of brake control until the reference position is set.

5. 3. The brake control device according to claim 1, further comprising an implementation determination unit (64) that determines whether or not the reference position needs to be updated.

6. The brake control device according to claim 5 , wherein the execution determination unit does not update the reference position when it is determined that the period of time in the no-load state will not be obtained.

Images