Vehicle braking system

Abstract

To provide a braking device for a vehicle which reduces a deviation from requested brake force when increasing brake force and holding the brake force and secures a reduction effect of a motor drive current.SOLUTION: A torque command calculation unit includes a position controller which calculates a torque command value so as to bring an actual position detected by a position sensor close to a position command value. The torque command calculation unit changes the torque command value sequentially from first to the fourth steps when increasing actual brake force and holding the actual brake force to requested brake force. The first step performs increase operation. The second step performs excess operation of increasing torque of a motor until the actual brake force reaches target excess brake force. The third step performs holding operation of reducing the torque of the motor while keeping the brake force in the time of termination of the excess operation. The fourth step performs returning operation of reducing the torque of the motor along a reverse efficiency line until the actual brake force reaches the requested brake force. The torque command calculation unit executes position control by the position controller in at least the second step.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a braking device for a vehicle. [Background technology]

[0002] Conventionally, in an electric brake device for a vehicle in which the relationship between the torque of the motor and the pressing force applied to the brake disc from the motion conversion mechanism has a hysteresis characteristic, a technique is known for controlling the drive of the motor so that the magnitude of the pressing force reaches a target value.

[0003] For example, in the electric brake device disclosed in Patent Document 1, a motor control device controls the motor drive current based on the magnitude of the pressing force detected by a load sensor. The relationship between the motor torque and the pressing force has a hysteresis characteristic. When a pressing force is applied to the brake disc and maintained, this motor control device increases the motor torque until the magnitude of the pressing force detected by the load sensor reaches a predetermined value greater than a target value, and then controls the motor drive current so as to decrease the motor torque until the magnitude of the pressing force detected by the load sensor reaches the target value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6080682 Summary of the Invention [Problem to be solved by the invention]

[0005] In this specification, "pressing force" is referred to as "load." Braking force correlates with load, and the required braking force is reflected in the load command value. When the braking force is increasing, the operation of increasing the motor torque along the normal efficiency line until the braking force reaches the required braking force is called the "increase operation." The operation of increasing the motor torque along the normal efficiency line until the braking force reaches a value that is a predetermined excess amount greater than the required braking force is called the "excess operation." The operation of reducing the motor torque while maintaining the braking force at the end of the excess operation is called the "holding operation." After the holding operation, the operation of reducing the motor torque along the inverse efficiency line until the braking force reaches the required braking force is called the "return operation."

[0006] To minimize the discrepancy between the required braking force reflected in the load command value and the braking force during the holding operation, it is preferable to set the offset value during the over-operation as small as possible. However, because load sensors generally have low accuracy, the prior art of Patent Document 1 requires that the braking force be changed by an offset value equal to or greater than the resolution of the load sensor during the over-operation. This increases the discrepancy between the actual braking force and the required braking force during the holding operation, which can lead to a deterioration in the brake feel.

[0007] Furthermore, if the pads or discs deform due to temperature changes, the operating point may not change even though the load is changing. In this case, the motor drive current may not be reduced sufficiently.

[0008] The present invention has been created in consideration of the above points, and its object is to provide a vehicle braking device that reduces the deviation from the required braking force when the braking force is increased and maintained, and ensures the effect of reducing the motor drive current. [Means for solving the problem]

[0009] The present invention In one aspect The vehicle braking device is mounted on a vehicle (900) having a plurality of electric brakes (81-84) provided on each wheel, which convert the torque output by a motor (60) into linear force by a linear motion mechanism (85) and press the torque against the corresponding wheel (91-94) to generate a braking force.

[0010] The vehicle braking system includes a braking force control unit (400) that includes a torque command calculation unit (40) and a current command calculation unit (50) and controls the braking force generated by each electric brake. The torque command calculation unit calculates a torque command value for the motor based on a required braking force commanded from an external source. The current command calculation unit calculates a current command value for supplying current to the motor based on the torque command value.

[0011] The electric brake is a load sensor (71) for detecting an actual load (F) which is a braking load actually applied to the wheel; and Position sensors (72, 73) are provided to detect the actual rotation angle of the motor or the actual position (θ, X) which is the actual stroke of the linear motion mechanism.

[0012] The relationship between the motor torque and the braking force generated by the electric brake has a hysteresis characteristic in which, as the torque increases, the braking force increases along the positive efficiency line, as the torque decreases from the turning value where the torque changes from increasing to decreasing to the holding critical value, the braking force is maintained constant, and as the torque decreases from the holding critical value, the braking force decreases along the inverse efficiency line.

[0013] The torque command calculation unit is The device includes a load controller (43), a position controller (46), and a switching determination unit (47). The load controller converts the actual load detected by the load sensor into a load command value (F * The torque command value is calculated so that the position controller approaches the The actual position detected by the position sensor is converted into the position command value (θ * , X * ) and calculate the torque command value so that it approaches The switching determination unit determines switching between load control by the load controller and position control by the position controller. When increasing the actual braking force, which is the braking force actually output by the electric brake, and maintaining it at the required braking force, the torque command calculation unit changes the torque command value in the order of a first process, a second process, a third process, and a fourth process.

[0014] In the first step, an "increase operation" is performed to increase the motor torque along the normal efficiency line until the actual braking force reaches the required braking force. In the second step, an "excess operation" is performed to increase the motor torque along the normal efficiency line following the first step until the actual braking force reaches a target excess braking force that is a predetermined excess amount greater than the required braking force. In the third step, a "maintenance operation" is performed to reduce the motor torque while maintaining the braking force at the end of the excess operation. In the fourth step, a "return operation" is performed to reduce the motor torque along the inverse efficiency line until the actual braking force reaches the required braking force.

[0015] The switching determination unit is configured to calculate a torque command value according to each of the first to fourth processes, and determines whether to switch between the load control and the position control. The torque command calculation unit is load control is executed in the first process, and when the process shifts from the first process to the second process, the switch determination unit switches from load control to position control; At least in the second step, position control is performed by the position controller.

[0016] In this invention, by performing position control using a high-precision position sensor during the excess operation of the second process, the difference between the actual braking force and the required braking force during the holding operation can be reduced, preventing a deterioration in the feeling. Furthermore, even if a load change occurs due to a temperature change or the like, the position of the motor and linear motion mechanism can be directly detected by the position sensor, so the motor drive current can be reduced until the operating point changes reliably. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a configuration diagram of a vehicle on which the vehicle braking devices of the first to third embodiments are mounted. [Figure 2] FIG. 2 is a block diagram illustrating braking force control of electric brakes corresponding to each wheel. [Figure 3] (a) Schematic diagram of an electric brake pad, (b) Characteristics diagram of pad load and pad position. [Figure 4] FIG. 10 is a diagram showing braking force control in load control according to a comparative example. [Figure 5] FIG. 2 is a block diagram of a torque command calculation unit according to the first and second embodiments. [Figure 6] 5A and 5B are diagrams illustrating switching between load control and position control according to the first embodiment. [Figure 7]FIG. 10 is a diagram showing switching between load control and position control according to a modification of the first embodiment. [Figure 8] FIG. 10 is a diagram showing switching between load control and position control according to the second embodiment. [Figure 9] FIG. 10 is a block diagram of a torque command calculation unit according to a third embodiment. [Figure 10] FIG. 11 is a diagram showing braking force control in position control according to the third embodiment. [Figure 11] 10 is a flowchart of an operation changeover when a required braking force is increased. [Figure 12] 10 is a flowchart of a position command calculation. DETAILED DESCRIPTION OF THE INVENTION

[0018] Vehicle braking devices according to multiple embodiments of the present invention will be described with reference to the drawings. Substantially identical components in multiple embodiments will be assigned the same reference numerals, and descriptions thereof will be omitted. The following first to third embodiments will be collectively referred to as "the present embodiment." The vehicle braking device of the present embodiment is mounted on a vehicle in which multiple electric brakes are provided on each wheel, converting torque output by a motor into linear force using a linear motion mechanism and pressing the torque against the corresponding wheel to generate braking force. The vehicle braking device includes a braking force control unit that controls the braking force generated by each electric brake.

[0019] [Vehicle configuration] The configuration of a vehicle 900 and electric brakes 81-84 equipped with a vehicle braking device 30 of this embodiment will be described with reference to Figures 1 to 3(b). As shown in Figure 1, the vehicle 900 is a four-wheel vehicle having two rows of left and right pairs of wheels 91, 92, 93, 94 in the longitudinal direction. The front left and right wheels 91, 92 are labeled "FL, FR," and the rear left and right wheels 93, 94 are labeled "RL, RR." A plurality of (four in this example) electric brakes 81, 82, 83, 84 are provided corresponding to each wheel 91, 92, 93, 94. Hereinafter, four consecutive reference numerals will be abbreviated, such as "wheels 91-94" and "electric brakes 81-84."

[0020] The vehicle braking device 30 includes a braking force control unit 400. The braking force control unit 400 controls the braking force generated by each electric brake 81-84 based on a required braking force commanded from an external device. The required braking force is commanded by the driver's brake operation, a braking signal from a driving assistance device, or the like. At least a portion of position sensor signals θ, X that detect the operating position of the motor or linear motion mechanism that constitutes each electric brake 81-84, and a load sensor signal F that detects the pressing load of the brake pad, are input to the braking force control unit 400. Details of the sensor signals θ, X, and F will be described later with reference to FIG. 2. Which sensor signals are input to the braking force control unit 400 varies depending on the embodiment.

[0021] In this embodiment, the control configuration of each of the electric brakes 81-84 is the same. Ki The control configuration is illustrated.

[0022] Each of the electric brakes 81-84 includes a motor 60, a linear motion mechanism 85, and a caliper 86. The motor 60 is configured, for example, as a permanent magnet three-phase brushless motor, and outputs torque in response to a drive current supplied from a braking force control unit 400. The linear motion mechanism 85 is an actuator that converts the output rotation of the motor 60 into linear motion while decelerating. The rotation angle θ of the motor 60 is proportional to the stroke X of the linear motion mechanism 85. In this way, each of the electric brakes 81-84 converts the torque output by the motor 60 into linear force by the linear motion mechanism 85, and presses the torque against the corresponding wheel 91-94 to generate a braking force.

[0023] The output torque of the motor 60 operates the pads 87 of the caliper 86 via the linear motion mechanism 85. The pads 87 move and are pressed against the disks 88 of the wheels 91-94, generating a braking force due to friction. When the pads 87 move away from the disks 88, the braking force is released.

[0024] 3(a) and (b), the characteristics of the pad 87 of the electric brake 81-81 shown in part IIIa of FIG. 2 will be further described. As shown in FIG. 3(a), the pad 87 has spring-like characteristics, and a pressing force Fd by the linear motion mechanism 85 and a reaction force Fr corresponding to the amount of strain act in opposite directions. As shown in FIG. 3(b), the pad position X based on the stroke of the linear motion mechanism 85 is approximately proportional to the pad load F. If the pad position changes by ΔX due to a change Δθ in the rotation angle of the motor 60, the pad load changes by ΔF.

[0025] Returning to Fig. 2, braking force control unit 400 includes a torque command calculation unit 40, a current command calculation unit 50, and an inverter 55. Torque command calculation unit 40 calculates a torque command value for motor 60 based on a required braking force commanded from the outside. Current command calculation unit 50 calculates a current command value to be supplied to motor 60 based on the torque command value.

[0026] The inverter 55 converts the DC power of the battery 15 into AC power, and supplies the AC power according to the current command value to the motor 60. Note that a detailed description of the configuration from the current command calculation unit 50 to the inverter 55 will be omitted. Using a general motor control technique, the inverter 55 performs a switching operation according to a switching signal, for example, by PWM control.

[0027] The electric brakes 81-84 are also equipped with at least one of an angle sensor 72 indicated by a solid line and a stroke sensor 73 indicated by a two-dot chain line. The angle sensor 72 detects an actual angle θ, which is the actual rotation angle of the motor 60. The stroke sensor 73 detects an actual stroke X, which is the actual stroke of the linear motion mechanism 85. The stroke sensor 73 may detect a change in position of a moving part of the linear motion mechanism 85, or may detect a change in position of a pad 87.

[0028] The angle sensor 72 and the stroke sensor 73 are collectively referred to as the "position sensor." The position sensors 72, 73 are composed of, for example, Hall elements or magnetic resistance elements, and are capable of detecting position with relatively high accuracy. The actual angle θ and actual stroke X are collectively referred to as the "actual position." The actual positions θ and X detected by the position sensors 72, 73 are input to the torque command calculation unit 40. In this embodiment, a configuration mainly including the angle sensor 72 is assumed, and the following description will use only the symbols for the "position sensor 72" and the "actual position θ." A configuration including the stroke sensor 73 will be described in other embodiments.

[0029] In the first and second embodiments, the electric brakes 81-84 further include a load sensor 71 indicated by a dashed line. The load sensor 71 detects an actual load F, which is the braking load that is actually applied to the wheels 91-94. The load sensor 71 is configured, for example, with a load cell or the like, and has lower detection accuracy than the position sensor 72. The actual load F detected by the load sensor 71 is input to the torque command calculation unit 40. In the third embodiment, the electric brakes 81-84 do not include a load sensor 71 in the first place, or the actual load F detected by the load sensor 71 is not used for calculations by the torque command calculation unit 40.

[0030] Next, the relationship between motor torque and braking force in an electric brake of this configuration will be explained with reference to FIG. 4. Braking force correlates with brake pad load. Hereinafter, "torque" simply refers to the torque output by motor 60, and "load" simply refers to the pressing load by pad 87. FIG. 4 corresponds to FIG. 10 in Patent Document 1 (Japanese Patent No. 6080682), and is treated as a comparative example in this specification for reasons that will be described later.

[0031] The relationship between the torque of the motor 60 and the braking force generated by the electric brakes 81-84 has a hysteresis characteristic. When the torque increases, the braking force increases along the positive efficiency line. When the torque decreases from the turning value Tconv, where the torque starts to decrease, to the holding critical value Tcr, the braking force is maintained constant. When the torque decreases from the holding critical value Tcr, the braking force decreases along the inverse efficiency line.

[0032] On the vertical axis, "Fhold" is the target value of the load, and "dF" is the offset value. "Fex (=Fhold+dF)" is the "predetermined value greater than the target value," which is the target value plus the offset value. In the prior art of Patent Document 1, the motor torque is increased until the magnitude of the load detected by the load sensor reaches the "predetermined value Fex greater than the target value." After that, the motor drive current is controlled to reduce the motor torque until the magnitude of the load detected by the load sensor reaches the target value.

[0033] The braking force actually output by the electric brakes 61-64 is called the "actual braking force." When the actual braking force is increased to the required braking force and maintained, the terms 1 to 4 representing the hysteresis changes in the torque and braking force are defined. (1) to (4) in Figure 4 correspond to the first to fourth processes.

[0034] In the first step, an "increasing operation" is performed to increase the torque of the motor 60 along the positive efficiency line until the actual braking force reaches the required braking force. In the second step, following the first step, an "exceeding operation" is performed to increase the torque of the motor 60 along the positive efficiency line until the actual braking force reaches a target excess braking force that is larger than the required braking force by a predetermined excess amount. In the third step, a "maintaining operation" is performed to reduce the torque of the motor 60 while maintaining the braking force at the end of the exceeding operation. In the fourth step, a "returning operation" is performed to reduce the torque of the motor 60 along the inverse efficiency line until the actual braking force reaches the required braking force.

[0035] 4, the outlined block arrows attached to the first to fourth processes indicate load control based on the actual load F detected by the load sensor 71. In other words, in the comparative example corresponding to the prior art of Patent Document 1, load control is performed in all of the first to fourth processes.

[0036] However, because the load sensor 71 generally has low accuracy, in the comparative example, it is necessary to change the braking force by an amount equivalent to the offset value dF, which is greater than the resolution of the load sensor 71, during excessive braking. This can increase the difference between the required braking force and the maintained braking force, potentially resulting in a worsening of the braking feel. Furthermore, if the pads 87 or discs 88 are deformed due to temperature changes or other factors, the operating point may not change despite a change in the load. In this case, the effect of reducing the drive current of the motor 60 may not be sufficient.

[0037] Therefore, the vehicle brake device 30 of this embodiment aims to reduce the deviation from the required braking force when increasing and maintaining the braking force, and to ensure the effect of reducing the motor drive current. The torque command calculation unit 40 of each embodiment changes the torque command value in the order of a first process, a second process, a third process, and a fourth process when increasing the actual braking force to the required braking force and maintaining it. The torque command calculation unit 40 calculates the torque command value by position control based on the actual position θ detected by the position sensor 72 at least in the second process.

[0038] Next, the detailed configuration of each embodiment will be described. The torque command calculation units of the first and second embodiments are distinguished by being assigned the reference numeral "401", and the torque command calculation unit of the third embodiment is distinguished by being assigned the reference numeral "403".

[0039] (First and second embodiments) The first and second embodiments will be described with reference to Figures 5 to 8. In the first and second embodiments, as the first to fourth processes are performed, a switch is made between load control based on the actual load F detected by the load sensor 71 and position control based on the actual position θ detected by the position sensor 72.

[0040] 5 shows a block diagram of the torque command calculation unit 401 according to the first and second embodiments. The torque command calculation unit 401 includes a load command calculation unit 41, a load deviation calculator 42, a load controller 43, a position command calculation unit 44, a position deviation calculator 45, a position controller 46, a switching determination unit 47, and a switch 48.

[0041] The load command calculation unit 41 calculates a load command value F based on the required braking force. * The load deviation calculator 42 calculates the actual load F detected by the load sensor 71 and the load command value F * Load deviation ΔF (= |F * The load controller 43 calculates the load deviation ΔF so as to approach zero, that is, the actual load F and the load command value F. * The torque command value is calculated so as to approach

[0042] The position command calculation unit 44 calculates a position command value θ based on the required braking force by a method to be described later or as shown by the broken line. * The position deviation calculator 45 calculates the actual position θ detected by the position sensor 72 and the position command value θ * Position deviation Δθ(=|θ * The position controller 46 calculates the position deviation Δθ so as to approach zero, that is, the actual position θ in relation to the position command value θ * The torque command value is calculated so as to approach

[0043] The switching determination unit 47 is configured to calculate a torque command value for the motor 60 according to each of the first to fourth processes, and determines whether to switch between the load control by the load controller 43 and the position control by the position controller 46.

[0044] The switching determination unit 47 receives the load command value F * , load deviation ΔF, and in some embodiments, position deviation Δθ are input. * The fluctuation of the required braking force is grasped by the load command value F * When the fluctuation amount of is within a predetermined range and the load deviation ΔF is below the load deviation threshold, the actual load F in the load control is equal to the load command value F * When the position deviation Δθ falls below the position deviation threshold, it is determined that the actual position θ in the position control has reached the position command value θ * is judged to have been reached.

[0045] Switch 48 switches the torque command value output by torque command calculation unit 401 in response to a command from switching determination unit 47. In the configuration example shown in Fig. 5, switch 48 is provided on the output side of each of controllers 43, 46, but the configuration is not limited to this, and a switching function may be realized such that, for example, the operation of one of load controller 43 or position controller 46 is masked.

[0046] The timing at which the first process shifts to the second process is referred to as the "excess operation start timing." The load command calculation unit 41 converts the actual position θ acquired at the excess operation start timing notified by the switch 48 into a position command value θ * This position command value θ * is the initial position command value in the position control of the second step, which will be described in detail later with reference to the flowchart of FIG.

[0047] FIG. 6 shows switching between load control and position control according to the first embodiment. The hysteresis characteristics of torque and braking force are the same as those in the comparative example shown in FIG. 4. As indicated by the double vertical axis, in the first and second embodiments, the braking force is correlated with the load F and the position θ. In other words, the load F and the position θ are used doubly as parameters correlated with the braking force.

[0048] The load F corresponding to the required braking force is the target holding load Fhold, and the position θ corresponding to the required braking force is the target holding position θhold. Furthermore, the load F corresponding to the target excess braking force is the target excess load Fex (=Fhold+dF), which is larger than the target holding load Fhold by the load excess amount dF. The position θ corresponding to the target excess braking force is the target excess position θex (=θhold+dθ), which is larger than the target holding position θhold by the position excess amount dθ. Here, the magnitude of the position θ is defined according to the magnitude of the corresponding braking force. In other words, the larger the corresponding braking force, the larger the position θ.

[0049] 6 to 8, the outlined block arrows represent load control, and the hatched block arrows represent position control. In both the first and second embodiments, the torque command calculation unit 401 executes load control in the first process. In the first embodiment, the torque command calculation unit 401 executes position control in the second process, and executes load control in the third and fourth processes. When transitioning from the first process to the second process, the torque command calculation unit 401 switches from load control to position control by the switching determination unit 47.

[0050] Specifically, when the first process is shifted to the second process, the switch determination unit 47 commands the switch 48 to switch to position control if the load deviation ΔF falls below the load deviation threshold. The torque command calculation unit 401 stores the actual load F detected by the load sensor 71 at the timing of the start of the excessive operation when the first process is shifted to the second process as the target holding load Fhold. In the second process, the actual position θ is calculated as the position command value θ * The torque command value calculated by the position controller 46 so as to approximate

[0051] Furthermore, when transitioning from the second process to the third process, if the position deviation Δθ falls below the position deviation threshold, the switching determination unit 47 commands the switch 48 to switch to load control. In the third process, no active control is performed, and the torque naturally decreases from the positive efficiency line to the inverse efficiency line. When the torque command value decreases to the inverse efficiency line, transition is made to the fourth process while maintaining load control. In the fourth process, the torque command calculation unit 401 continues the return operation until the actual load F reaches the target holding load Fhold.

[0052] In the first embodiment, a highly accurate position sensor 72 is used in the overshoot operation of the second process, and position control can be performed by setting the position overshoot amount dθ as small as possible according to the resolution of the position sensor 72. Therefore, compared to the comparative example in which load control is performed in the second process, the difference between the actual braking force and the required braking force in the holding operation can be reduced, preventing a deterioration in the feeling. Furthermore, even if a load change occurs due to a temperature change or the like, the position of the motor 60 and the linear motion mechanism 85 is directly detected by the position sensor 72, so the motor drive current can be reduced until the operating point changes reliably.

[0053] Furthermore, because the existing electric brakes 81-84 are equipped with the load sensor 71, changes to the existing design can be minimized by having the torque command calculation unit 401 switch the control so that position control is performed only in the second process and load control is performed in the first, third, and fourth processes. Furthermore, by using the same control for the third and fourth processes, it is possible to transition from the holding operation to the returning operation as the situation demands without determining the end of the holding operation.

[0054] FIG. 7 shows switching between load control and position control according to a modification of the first embodiment. In this modification, the torque command calculation unit 401 executes position control in the third process following the second process, and executes load control in the fourth process. In other words, switching from position control to load control occurs not when the excess operation transitions to the holding operation, but when the holding operation transitions to the return operation. In this modification, logic for determining the end of the holding operation needs to be added to the switching determination unit 47, but by performing position control in the second process, the same effects as in the first embodiment can be obtained.

[0055] 8 shows switching between load control and position control according to the second embodiment. In the second embodiment, the torque command calculation unit 401 executes position control in the third and fourth processes following the second process. As in the first embodiment, when transitioning from the first process to the second process, the torque command calculation unit 401 switches from load control to position control by the switching determination unit 47.

[0056] The torque command calculation unit 401 stores the actual position θ detected by the position sensor 72 at the timing of starting the excessive operation when the first process is changed to the second process as the target holding position θhold. In the second process, the actual position θ is calculated as the position command value θ * The torque command value calculated by the position controller 46 so as to approximate

[0057] When the actual position θ reaches the target overshoot position θex, the process shifts from the second process to the third process, where the torque decreases naturally from the positive efficiency line to the inverse efficiency line while maintaining the braking force at the end of the overshoot operation. When the torque command value decreases to the inverse efficiency line, the process shifts to the fourth process while maintaining position control. In the fourth process, the torque command calculation unit 401 continues the return operation until the actual position θ reaches the target hold position θhold.

[0058] In the second embodiment, by performing position control in the second process, the same effects as in the first embodiment can be obtained. Furthermore, position control can be performed with the same accuracy in the overshoot operation and the return operation for a small position overshoot amount dθ.

[0059] (Third embodiment) A third embodiment will be described with reference to Fig. 9 and Fig. 10. In the third embodiment, a torque command calculation unit 403 executes position control based on the actual position θ detected by the position sensor 72 throughout the first to fourth processes. Fig. 9 shows a block diagram of the torque command calculation unit 403 of the third embodiment. The torque command calculation unit 403 has a position command calculation unit 44, a position deviation calculator 45, and a position controller 46.

[0060] The position command calculation unit 44 calculates a position command value θ based on the required braking force. * In the configuration of Fig. 5, the required braking force is basically input to load command calculation unit 41, and may also be input to position command calculation unit 44. In contrast, in the configuration of Fig. 9, there is no load command calculation unit 41, so the required braking force is always input to position command calculation unit 44. The position deviation calculator 45 and the position controller 46 are the same as those in the configuration of Fig. 5, and therefore their explanation will be omitted.

[0061] The position deviation Δθ (=|θ * -θ|) is fed back to the position command calculation unit 44. When the position deviation Δθ falls below the position deviation threshold, the position command calculation unit 44 calculates the actual position θ in the position control in accordance with the position command value θ * is judged to have been reached.

[0062] FIG. 10 shows braking force control by position control according to the third embodiment. The hysteresis characteristics between torque and braking force are the same as those in the comparative example and the first and second embodiments. In the third embodiment, braking force correlates only with position θ. In FIG. 10, hatched block arrows represent position control. Torque command calculation unit 403 executes position control in the first process.

[0063] The torque command calculation unit 403 calculates a position command value θ corresponding to the actual position θ and the required braking force. * When the actual position θ reaches the target holding position θhold, the actual position θ detected by the position sensor 72 at the timing of the start of the excess operation that transitions from the first process to the second process is stored as the target holding position θhold. After that, position control continues up to the fourth process, as in the second embodiment.

[0064] In the third embodiment, by performing position control in the second process, the same effects as those of the first and second embodiments can be obtained. In addition, since logic for switching between load control and position control is not required, the configuration of the torque command calculation unit 403 can be simplified.

[0065] [Flowchart of braking force control according to this embodiment] Next, braking force control will be described comprehensively for the first to third embodiments with reference to the flowcharts of Figures 11 and 12. In the description of the flowcharts, the symbol "S" means step.

[0066] FIG. 11 shows the flow of switching operations when the required braking force increases. This flow applies to the first and second embodiments in which load control is performed in the first process. Considering the situations in which the first and second embodiments are effectively used, the case where the required braking force is decreasing is omitted from the premise. Therefore, the logic for determining whether the required braking force is increasing or decreasing is also omitted. However, in actual system design, it is necessary to design a flow that includes the case where the required braking force is decreasing.

[0067] In S11, it is determined whether the first process (increasing operation) is in progress. If the answer is YES in S11, the actual braking force increases in S12. In S13, it is determined whether the load deviation ΔF is smaller than the load deviation threshold ΔFth1. If the answer is YES in S13, the process switches to the third process (maintaining operation) via the second process (exceeding operation) in S14.

[0068] If the result in S11 is NO, it is estimated that the third process (holding operation) is in progress. In the above embodiment, it is not assumed that the required braking force will suddenly change during the third process. However, in reality, the required braking force may suddenly change during the third process, and the load command value F * If we exclude the case of a sudden decrease from the premise that the required braking force increases, the load command value F * increases rapidly, and the actual load F and the load command value F * It is assumed that the load deviation ΔF between the load and the load changes suddenly. In S15, it is determined whether the load deviation ΔF is greater than the load deviation threshold value ΔFth2. If the answer is YES in S15, in S16, the third process (maintaining operation) is stopped and the process is switched to the first process (increasing operation).

[0069] 12 shows the flow of position command calculation by the position command calculation unit 44. In S21, the first process (increasing operation) is performed. In S22, it is determined whether the actual braking force has reached the required braking force and the process has shifted from the first process to the second process. If the result in S22 is YES, in S23, the actual position θ at the timing when the exceeding operation starts is stored as the target holding position θhold.

[0070] In S24, in the second process (excessive operation), the position command value θ *Specifically, the temporary position θtemp, which is larger than the target holding position θhold, is set as the position command value θ * The temporary position θtemp is increased before the actual position θ increases. * ) increases, the actual position θ increases accordingly.

[0071] In S25, it is determined whether the temporary position θtemp has reached the target excess position θex. If the answer is YES in S25, the process proceeds to the third process (holding operation) in S26. After S26, two steps, S27 or S28, can be selected.

[0072] In S27 corresponding to the first embodiment, the load control is switched to, and the load command value F * is set to the target holding load Fhold. In S28 corresponding to the second and third embodiments, the position command value θ * is changed to the target holding position θhold.

[0073] (Other embodiments) (a) The vehicle on which the vehicle braking device of the present invention is mounted is not limited to a four-wheel vehicle having two rows of left and right pairs of wheels in the longitudinal direction of the vehicle, but may also be a vehicle with six or more wheels having three or more rows of wheels in the longitudinal direction of the vehicle.

[0074] (b) In the above embodiment, it is assumed that the angle sensor 72 of the motor 60 is mainly used as the position sensor, but the stroke sensor 73 of the linear motion mechanism 85 may also be used as the position sensor. In this case, the position controller 46 adjusts the actual position X so that the position deviation ΔX approaches zero, that is, adjusts the actual position X to the position command value X * The torque command value is calculated so as to approach

[0075] The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention.

[0076] The braking force control unit and the method thereof described herein may be implemented by a special-purpose computer configured by configuring a processor and memory programmed to perform one or more functions embodied in a computer program. Alternatively, the braking force control unit and the method thereof described herein may be implemented by a special-purpose computer configured by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the braking force control unit and the method thereof described herein may be implemented by one or more special-purpose computers configured by combining a processor and memory programmed to perform one or more functions with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory tangible storage medium. [Explanation of symbols]

[0077] 30. Vehicle braking device, 400 Braking force control section, 40 (401, 403) Torque command calculation unit, 43: Load controller, 46: Position controller, 50...Current command calculation section, 60···motor, 72: Angle sensor (position sensor), 73: Stroke sensor (position sensor), 81-84 Electric brake, 85 Linear motion mechanism, 900···Vehicles, 91-94···Wheels.

Claims

1. A vehicle braking device mounted on a vehicle (900) in which a plurality of electric brakes (81-84) are provided on each wheel, and the electric brakes (81-84) convert torque output by a motor (60) into linear force by a linear motion mechanism (85), and press the torque against the corresponding wheel (91-94) to generate a braking force, a braking force control unit (400) including a torque command calculation unit (40) that calculates a torque command value for the motor based on a required braking force commanded from an external source, and a current command calculation unit (50) that calculates a current command value to be supplied to the motor based on the torque command value, and that controls the braking force generated by each of the electric brakes; The electric brake includes a load sensor (71) that detects an actual load (F), which is a braking load that is actually pressed against the wheel, and position sensors (72, 73) that detect an actual rotation angle of the motor or an actual position (θ, X), which is an actual stroke of the linear motion mechanism, The relationship between the torque of the motor and the braking force generated in the electric brake has a hysteresis characteristic in which, when the torque increases, the braking force increases along a positive efficiency line, when the torque decreases from a turning value where the torque changes from increasing to decreasing to a holding critical value, the braking force is maintained constant, and when the torque decreases from the holding critical value, the braking force decreases along an inverse efficiency line; The torque command calculation unit (401) a load controller (43) that calculates the torque command value so that the actual load detected by the load sensor approaches a load command value (F*) calculated based on the required braking force; The actual position detected by the position sensor is converted into a position command value (θ ＊ , X ＊ a position controller (46) that calculates the torque command value so as to approach the a switching determination unit (47) that determines switching between load control by the load controller and position control by the position controller; and When the actual braking force, which is the braking force actually output by the electric brake, is increased and maintained at the required braking force, a first step of increasing the torque of the motor along the positive efficiency line until the actual braking force reaches the required braking force; a second step of performing an over-operation of increasing the torque of the motor along the normal efficiency line following the first step until the actual braking force reaches a target over-braking force that is larger than the required braking force by a predetermined over-operation amount; a third step of performing a holding operation in which the torque of the motor is reduced while the braking force at the end of the excessive operation is maintained; and a fourth step of performing a return operation to reduce the torque of the motor along the inverse efficiency line until the actual braking force reaches the required braking force; The torque command value is changed in the order of the switching determination unit is configured to calculate the torque command value in accordance with each of the first to fourth steps, and determines switching between the load control and the position control; The torque command calculation unit executes the load control in the first process, and when transitioning from the first process to the second process, the switching determination unit switches from the load control to the position control, and executes position control by the position controller at least in the second process.

2. The vehicle braking system according to claim 1 , wherein the torque command calculation unit executes the load control in the fourth step.

3. The vehicle braking system according to claim 1 , wherein the torque command calculation unit executes the position control in the fourth step.

4. The torque command calculation unit The actual load detected by the load sensor at the timing of starting the excessive operation when the first step is shifted to the second step is stored as a target holding load (Fhold); 3. The vehicle brake system according to claim 2, wherein in the fourth step, the returning operation is continued until the actual load reaches the target retained load.

5. The torque command calculation unit The actual position detected by the position sensor at the start timing of the excess operation when the first step is shifted to the second step is stored as a target holding position (θhold); 4. The vehicle brake system according to claim 3, wherein in the fourth step, the returning operation is continued until the actual position reaches the target holding position.

6. A vehicle braking device mounted on a vehicle (900) in which a plurality of electric brakes (81-84) are provided on each wheel, and the electric brakes (81-84) convert torque output by a motor (60) into linear force by a linear motion mechanism (85), and press the torque against the corresponding wheel (91-94) to generate a braking force, a braking force control unit (400) including a torque command calculation unit (40) that calculates a torque command value for the motor based on a required braking force commanded from an external source, and a current command calculation unit (50) that calculates a current command value to be supplied to the motor based on the torque command value, and that controls the braking force generated by each of the electric brakes; the electric brake includes position sensors (72, 73) for detecting an actual position (θ, X) which is an actual rotation angle of the motor or an actual stroke of the linear motion mechanism; The relationship between the torque of the motor and the braking force generated in the electric brake has a hysteresis characteristic in which, when the torque increases, the braking force increases along a positive efficiency line, when the torque decreases from a turning value where the torque changes from increasing to decreasing to a holding critical value, the braking force is maintained constant, and when the torque decreases from the holding critical value, the braking force decreases along an inverse efficiency line; The torque command calculation unit (403) The actual position detected by the position sensor is converted into a position command value (θ ＊ , X ＊ a position controller (46) that calculates the torque command value so as to approach When the actual braking force, which is the braking force actually output by the electric brake, is increased and maintained at the required braking force, a first step of increasing the torque of the motor along the positive efficiency line until the actual braking force reaches the required braking force; a second step of performing an over-operation of increasing the torque of the motor along the normal efficiency line following the first step until the actual braking force reaches a target over-braking force that is larger than the required braking force by a predetermined over-operation amount; a third step of performing a holding operation in which the torque of the motor is reduced while the braking force at the end of the excessive operation is maintained; and a fourth step of performing a return operation to reduce the torque of the motor along the inverse efficiency line until the actual braking force reaches the required braking force; The torque command value is changed in the order of performing position control by the position controller at least in the second step; The torque command calculation unit The actual position detected by the position sensor at the start timing of the excess operation when the first step is shifted to the second step is stored as a target holding position (θhold); In the fourth step, the returning operation is continued until the actual position reaches the target holding position.

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