Vehicle brake device

Abstract

The relationship between the torque of the electric motor (60) and the braking force generated by the electric brakes (81-84) has hysteresis characteristics. When the torque increases, the braking force increases along the positive efficiency line, and when the torque decreases, the braking force decreases along the reverse efficiency line. A prediction unit (45) of a torque command calculation unit (40) predicts a change in the current and later required braking force. The operating point adjuster (46) stores a maximum torque on a positive efficiency line and a minimum torque on a reverse efficiency line corresponding to the held braking force. An operation point adjuster (46) adjusts an operation point at which the braking force is maintained in an adjustment region (Za) between the minimum torque and the maximum torque on the basis of prediction information from the prediction unit (45). A torque command calculation unit (40) calculates a torque command value (Trq *) of the motor (60) at the operating point adjusted by the operating point adjuster (46).

Description

[0001] Cross-reference to related applications

[0002] This application is based on Japanese application No. 2022-139250 filed on September 1, 2022, and the contents thereof are cited herein. Technical Field

[0003] The present invention relates to a braking device for a vehicle. Background Art

[0004] In the past, the following technology is known: in an electric brake device of 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, the drive of the motor is controlled so that the magnitude of the pressing force reaches a target value. For example, in the electric brake device disclosed in Patent Document 1, the motor control device controls the driving current of the motor based on the magnitude of the pressing force detected by the load sensor. The relationship between the motor torque and the pressing force has a hysteresis characteristic. When the pressing force is applied to the brake disc and maintained, the motor control device increases the torque of the motor along the positive efficiency line until the pressing force rises to a specified value greater than the target value, and then reduces the torque of the motor along the reverse efficiency line until the pressing force is reduced to the target value.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 6080682

[0008] In this specification, the vertical axis of the hysteresis graph is described as "the relevant amount of the braking force". In Patent Document 1, the pressing force detected by the load sensor is equivalent to the actual braking force as the braking force actually output by the electric brake. In addition, the load command value in Patent Document 1 is equivalent to the required braking force. In the prior art of Patent Document 1, by moving the operating point from the positive efficiency line to the reverse efficiency line and maintaining the braking force, the current of the drive motor can be reduced while maintaining the braking force.

[0009] Patent Document 1 describes the action of increasing the braking force and then maintaining it, but does not describe the action of reducing the braking force and then maintaining it, or the action of switching the braking force from reduction to increase. In the action of reducing the braking force and then maintaining it, it is estimated that the braking force is maintained at the action point on the inverse efficiency line in terms of trend. When switching from the holding action at the action point on the inverse efficiency line to the braking force increasing action, a torque change equivalent to the width between the positive efficiency line and the inverse efficiency line is required, and there is a problem of response delay. Summary of the invention

[0010] An object of the present invention is to provide a vehicle brake device capable of adjusting a balance between a current reduction effect in braking force holding and responsiveness when switching from a holding operation to a braking force increasing operation.

[0011] The vehicle brake device of the present invention is mounted on a vehicle having a plurality of electric brakes provided on each wheel. The plurality of electric brakes convert torque output by a motor into linear motion force through a direct-acting mechanism and press the corresponding wheels to generate braking force.

[0012] The vehicle braking device includes a braking force control unit, which includes a torque command calculation unit and a current command calculation unit, and controls the braking force generated by each electric brake. The torque command calculation unit calculates a torque command value of the motor based on the required braking force indicated from the outside. The current command calculation unit calculates a current command value for energizing the motor based on the torque command value.

[0013] The relationship between the torque of the motor and the braking force generated by the electric brake has the following hysteresis characteristics: when the torque increases, the braking force increases along the positive efficiency line, when the torque decreases from the turning value where the increase turns to the decrease to the holding critical value, the braking force remains constant, and when the torque decreases from the holding critical value, the braking force decreases along the reverse efficiency line.

[0014] The torque command calculation unit includes a prediction unit and an operating point adjuster. The prediction unit predicts changes in the required braking force from now on.

[0015] The operating point adjuster stores the maximum torque on the positive efficiency line and the minimum torque on the reverse efficiency line corresponding to the maintained braking force, and adjusts the operating point to maintain the braking force in the adjustment area between the minimum torque and the maximum torque based on the prediction information of the prediction unit. The torque command calculation unit calculates the torque command value of the motor at the operating point adjusted by the operating point adjuster.

[0016] Depending on the vehicle state, the responsiveness in switching from the holding action to the increasing action may be prioritized over the current reduction in the braking force holding. In this case, when the prediction unit predicts that the braking force is required to increase from the current to the predicted time, the operating point adjuster maintains the braking force at an operating point on the positive efficiency line side compared to the operating point boundary in the increase prediction in the adjustment area. This reduces the response delay when switching from the holding action to the increasing action of the braking force. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other objects, features and advantages of the present invention will become more apparent through the following detailed description with reference to the accompanying drawings.

[0018] Figure 1 is a structural diagram of a vehicle equipped with a vehicle braking device according to an embodiment.

[0019] Figure 2 This is the braking force control block diagram of the electric brake corresponding to each wheel.

[0020] Figure 3A is a schematic diagram of the electric brake pad,

[0021] Figure 3B is a characteristic diagram of pad load and pad position,

[0022] Figure 4 is a graph showing the hysteresis characteristics of the motor torque and braking force.

[0023] Figure 5 is a block diagram of a torque command operation unit according to one embodiment.

[0024] Figure 6 is a diagram illustrating the calculation of the maximum torque and the minimum torque.

[0025] Figure 7 1 is a diagram for explaining the setting of the operating point boundary and the adjustment of the operating point when predicting an increase, maintaining, and decreasing the required braking force.

[0026] Figure 8 is a diagram showing an example of changes in the boundary coefficient corresponding to the electric brake temperature and the vehicle speed.

[0027] Fig. 9 This is a flowchart of the process of adjusting the operating point. DETAILED DESCRIPTION

[0028] A vehicle braking device according to one embodiment is described with reference to the accompanying drawings. The vehicle braking device of this embodiment is mounted on a vehicle having a plurality of electric brakes provided on each wheel, wherein the plurality of electric brakes convert the torque output by the motor into a linear motion force through a direct-acting mechanism and press the corresponding wheels to generate a braking force. The vehicle braking device includes a braking force control unit that controls the braking force generated by each electric brake.

[0029] [Vehicle structure]

[0030] Reference Figure 1 Figure 3B Next, the structures of the vehicle 900 and the electric brakes 81 to 84 equipped with the vehicle brake device 30 of this embodiment will be described. Figure 1 As shown, vehicle 900 is a four-wheeled vehicle having two rows of left and right paired wheels 91, 92, 93, 94 in the front-rear direction. The front left and right wheels 91, 92 are denoted as "FL, FR", and the rear left and right wheels 93, 94 are denoted as "RL, RR".

[0031] A plurality of (four in this example) electric brakes 81, 82, 83, 84 are provided corresponding to the wheels 91, 92, 93, 94. Hereinafter, four consecutive symbols are omitted and described as "wheels 91-94" and "electric brakes 81-84". The same is true for the symbols "electric brake temperatures Temp1-Temp4".

[0032] The vehicle brake 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 indicated from the outside. The required braking force is indicated by a brake operation of the driver, a brake signal from a driving assistance device, or the like.

[0033] The braking force control unit 400 of this embodiment obtains the vehicle speed V from the vehicle speed sensor 97 and obtains the electric brake temperatures Temp1-Temp4 from each electric brake 81-84. The electric brake temperatures Temp1-Temp4 are detected by, for example, a temperature sensor. Alternatively, when the influence of the outside air temperature, the waste heat of the vehicle, etc. is the same for each electric brake 81-84, the electric brake temperatures Temp1-Temp4 may be calculated based on the accumulated power values ​​of each electric brake 81-84.

[0034] In addition, the braking force control unit 400 of the present embodiment obtains information related to the automatic driving from the automatic driving controller 200. For example, the automatic driving controller 200 notifies that the slope of the downhill slope ahead is becoming steeper, gentler, or is about to turn to an uphill slope, or notifies that the vehicle is stopped due to waiting for a traffic light, while braking on a downhill slope. As described later, the braking force control unit 400 predicts changes in the required braking force from now on based on the automatic driving information from the automatic driving controller 200, other cameras, map information, etc.

[0035] In this embodiment, the control structures of the electric brakes 81-84 are the same. Figure 2 In the figure, the control structure of the electric brake by the braking force control unit 400 is shown by taking any one of the electric brakes 81 to 84 as an example.

[0036] Each electric brake 81-84 includes a motor 60, a direct-acting mechanism 85, and a brake caliper 86. The motor 60 is, for example, a permanent magnet three-phase brushless motor, and outputs torque by a driving current supplied from the braking force control unit 400. The direct-acting mechanism 85 is an actuator that decelerates the output rotation of the motor 60 and converts it into a linear motion. The rotation angle θ of the motor 60 is proportional to the stroke X of the direct-acting mechanism 85. In this way, each electric brake 81-84 converts the torque output by the motor 60 into a linear motion force through the direct-acting mechanism 85, and presses the corresponding wheels 91-94 to generate a braking force.

[0037] The output torque of the motor 60 actuates the pad 87 of the brake caliper 86 via the direct-acting mechanism 85. The pad 87 is moved and pressed against the disk 88 of each wheel 91 to 94, thereby generating a braking force due to friction. In addition, the pad 87 is separated from the disk 88 to release the braking force.

[0038] Reference Figure 3A , Figure 3B , yes Figure 2 The characteristics of the pad 87 of the electric brake 81-81 shown in part IIIa are supplemented. Figure 3A As shown, the pad 87 has a spring-like characteristic, and the pressing force Fd generated by the direct-acting mechanism 85 and the reaction force Fr corresponding to the strain amount act in opposite directions to each other. Figure 3B As shown in FIG. 1 , the pad position X based on the stroke of the direct-acting mechanism 85 is approximately proportional to the pad load F. If the pad position changes by ΔX according to the change Δθ in the rotation angle of the motor 60, the pad load changes by ΔF. Figure 3B In the equation, the symbol "ΔF" represents the change in load. Figure 5 The “ΔF” used below, which indicates a load deviation between a load command value and an actual load, has different meanings.

[0039] Back to Figure 2 The braking force control unit 400 includes a torque command calculation unit 40, a current command calculation unit 50, and an inverter 55. The torque command calculation unit 40 calculates a torque command value Trq* of the motor 60 based on the required braking force indicated from the outside. The current command calculation unit 50 calculates a current command value I* for energizing the motor 60 based on the torque command value.

[0040] The inverter 55 converts the DC power of the battery 15 into AC power, and supplies the AC power corresponding to the current command value I* to the motor 60. In addition, the detailed structure of the current feedback from the current command calculation unit 50 to the inverter 55 is omitted. The inverter 55 performs a switching operation according to a switching signal generated by PWM control or the like by a general motor control technology.

[0041] In a basic embodiment, the electric brakes 81-84 are provided with a load sensor 71, which detects an actual load F as a braking load actually pressed on the wheels 91-94. The actual load F detected by the load sensor 71 is input to the torque command calculation unit 40. The torque command calculation unit 40 performs load control so that the actual load F approaches the load command value calculated based on the required braking force, and calculates the torque command value Trq*. In the description of one embodiment, the structure in which the torque command calculation unit 40 performs load control is assumed.

[0042] However, the electric brakes 81 to 84 of other embodiments may also include an angle sensor 72 shown by a dashed line or a stroke sensor 73 shown by a dashed double line. The angle sensor 72 detects an actual angle θ as an actual rotation angle of the motor 60. The stroke sensor 73 detects an actual stroke X as an actual stroke of the linear motion mechanism 85.

[0043] The angle sensor 72 and the stroke sensor 73 are collectively referred to as "position sensors", and the actual angle θ and the actual stroke X are collectively referred to as "actual positions". The actual positions θ and X detected by the position sensors 72 and 73 are input to the torque command calculation unit 40. The torque command calculation unit 40 may perform position control in place of load control or in addition to load control so that the actual positions θ and X are close to the position command value based on the required braking force calculation, and calculate the torque command value Trq*.

[0044] Next, refer to Figure 4 The relationship between the motor torque and the braking force in the electric brake of this structure is described. The braking force is related to the brake pad load. Hereinafter, the "torque" referred to as the torque output by the motor 60 and the "load" referred to as the pressing load applied by the pad 87 are described. Figure 4 This corresponds to FIG. 10 of Patent Document 1 (Japanese Patent No. 6080682).

[0045] 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 from increasing to decreasing to the holding threshold value Tcr, the braking force remains constant. When the torque decreases from the holding threshold value Tcr, the braking force decreases along the reverse efficiency line.

[0046] In the prior art of Patent Document 1, the torque of the motor is increased until the magnitude of the load detected by the load sensor reaches "a value greater than the target value F* by a predetermined offset value dF". Thereafter, the drive current of the motor is controlled so that the torque of the motor is reduced until the magnitude of the load detected by the load sensor reaches the target value F*. The load F, i.e., the braking force, is maintained during the process of reducing the torque of the motor.

[0047] The action of increasing the torque and braking force along the positive efficiency line is defined as an "increasing action", the action of maintaining the braking force at any action point between the positive efficiency line and the reverse efficiency line is defined as a "maintaining action", and the action of reducing the torque and braking force along the reverse efficiency line is defined as a "reducing action".

[0048] In the prior art of Patent Document 1, when switching from the holding action at the action point on the reverse efficiency line to the braking force increasing action, a torque change equivalent to the width between the positive efficiency line and the reverse efficiency line is required, and there is a problem of response delay. Therefore, the purpose of the vehicle brake device 30 of this embodiment is to be able to adjust the balance between the current reduction effect in the braking force holding and the responsiveness when switching from the holding action to the braking force increasing action according to the vehicle state, etc.

[0049] (One embodiment)

[0050] Figure 5 A block diagram of the torque command calculation unit 40 according to one embodiment is shown. The torque command calculation unit 40 includes a load command calculation unit 41 , a load deviation calculator 42 , a prediction unit 45 , an operating point adjuster 46 , and a load controller 48 .

[0051] The load command calculation unit 41 calculates a load command value F* based on the required braking force. The load deviation calculator 42 calculates a load deviation ΔF (=F*−F) between the actual load F detected by the load sensor 71 and the load command value F*, and outputs the calculated value to the load controller 48 .

[0052] The prediction unit 45 obtains the current required braking force and the automatic driving information from the automatic driving controller 200 and other camera and map information, and predicts the change of the required braking force from now on. The prediction unit 45 notifies the operating point adjuster 46 of the prediction information related to the change of the required braking force from now on.

[0053] For example, the following situation is assumed: while the vehicle is driving down a slope by automatic driving while maintaining the braking force at a constant deceleration, information is notified based on camera images and map information that the road ahead is a downhill slope with a steeper slope than the downhill slope currently being driven. In this case, the braking force needs to be increased in order to maintain the deceleration constant. Therefore, the prediction unit 45 predicts that the required braking force will increase from now on.

[0054] On the contrary, when the vehicle is driving downhill by automatic driving while maintaining the braking force at a constant deceleration and the information that the road ahead is a downhill or uphill slope with a gentler slope than the current driving location is notified, the prediction unit 45 predicts that the braking force required from now on will decrease. In addition, when the vehicle ahead is decelerating in a car equipped with ACC (adaptive cruise control), the prediction unit 45 predicts that the braking force required from now on will increase. When the brake is released and a small movement is performed just before stopping, the prediction unit 45 predicts that the braking force required from now on will decrease.

[0055] The configuration is not limited to the configuration example in which the prediction unit 45 predicts the change in the required braking force based on the vehicle behavior information obtained from the outside, and may be configured as follows: the prediction unit 45 receives the result of the prediction of the change in the required braking force performed by the automatic driving controller 200, etc., and issues an instruction to the action point adjuster 46.

[0056] The operating point adjuster 46 obtains the actual load F, the load deviation ΔF, the electric brake temperature Temp1-Temp4, and the vehicle speed V. Based on the actual load F and the load deviation ΔF, the current operating point on the map and the direction of increase or decrease of the braking force are estimated. In addition, the operating point adjuster 46 obtains the automatic driving information, other cameras, map information, etc. from the automatic driving controller 200.

[0057] The operating point adjuster 46 sets Figure 4 The torque-braking force relationship shown is stored as a map. When the braking force is being maintained, the action point adjuster 46 stores the maximum torque on the positive efficiency line and the minimum torque on the reverse efficiency line corresponding to the maintained braking force based on the map. In addition, the action point adjuster 46 adjusts the action point for maintaining the braking force in the adjustment area between the minimum torque and the maximum torque based on the prediction information of the prediction unit 45. For example, when the prediction unit 45 predicts that the braking force required from now on will increase, the action point adjuster 46 shifts the action point to the positive efficiency line side. For details on the function of the action point adjuster 46, refer to Figure 6 to Figure 9 This will be described later.

[0058] The load controller 48 calculates the torque command value Trq* so that the load deviation ΔF is substantially close to zero, that is, the actual load F is close to the load command value F*. The load controller 48 also calculates the torque command value Trq* at the operating point adjusted by the operating point adjuster 46 while the braking force is maintained.

[0059] Reference Figure 6 The storage of the maximum torque Trq_max and the minimum torque Trq_min and the calculation of the hysteresis width W_hys by the operating point adjuster 46 will be described. Figure 6 In the torque-braking force map, the white circle on the positive efficiency line represents the maximum torque Trq_max, and the shaded circle on the negative efficiency line represents the minimum torque Trq_min. The operating point adjuster 46 stores the maximum torque Trq_max and the minimum torque Trq_min corresponding to each load command value F*.

[0060] For example, in the manufacturing process, at the time of the first action, the operating point adjuster 46 changes the torque relative to the load command value F* as "0→maximum torque→0", and stores the maximum torque Trq_max and the minimum torque Trq_min. The mapping may be appropriately updated each time the power is turned on, each operation, etc. In addition, in the case of a holding action in which the load command value F* is returned after an over-action as in the prior art of patent document 1, the operating point adjuster 46 may also store the torque value at the start of the over-action and at the end of the return action. In this case, it is not necessary to maintain the entire mapping, which is efficient.

[0061] The torque width from the minimum torque Trq_min to the maximum torque Trq_max is defined as “hysteresis width W_hys”. The thick line portion between the minimum torque Trq_min and the maximum torque Trq_max is the adjustment region Za for maintaining the operating point of the braking force. The operating point adjuster 46 adjusts the operating point for maintaining the braking force in the adjustment region Za based on the prediction information of the prediction unit 45.

[0062] Next, refer to Figure 7 , Figure 8 , the adjustment of the operating point in the braking force holding action is described. In the following description, "the operating point close to the positive efficiency line" includes "the operating point on the positive efficiency line", and "the operating point close to the reverse efficiency line" includes "the operating point on the reverse efficiency line". "Reducing the response delay" includes "making the response delay zero". The operating point adjuster 46 identifies the change in the required braking force within the predicted time specified after the current time based on the prediction information of the prediction unit 45.

[0063] The case where it is predicted that the braking force is required to increase from the current time to the predicted time and the operation is switched from the holding operation to the increasing operation is referred to as "increase prediction time". In the increase prediction time, the operating point adjuster 46 holds the braking force at an operating point close to the positive efficiency line, thereby reducing the current reduction effect during holding, but can reduce the response delay when switching to the increasing operation.

[0064] On the other hand, the case where it is predicted that the required braking force will decrease from the current time to the predicted time and the holding action is switched to the reducing action is referred to as "reduction prediction time". In the reduction prediction time, the operating point adjuster 46 holds the braking force at an operating point close to the inverse efficiency line, thereby appropriately ensuring the current reducing effect during holding and reducing the response delay when switching to the reducing action.

[0065] The case where the required braking force is predicted to be maintained from now to a predicted time or longer is referred to as “maintaining prediction time.” Even in the maintaining prediction time, the operating point adjuster 46 maintains the braking force at an operating point close to the inverse efficiency line, thereby appropriately ensuring the current reduction effect during maintaining.

[0066] For example, the operating point adjuster 46 is configured by Figure 7 The structure shown is used to specifically adjust the operating point. The operating point adjuster 46 sets the operating point boundary OBi when the prediction is increased, the operating point boundary OBh when the prediction is maintained, and the operating point boundary OBd when the prediction is reduced in the adjustment area Za. The operating point boundaries OBi, OBh, and OBd are expressed as follows using the minimum torque Trq_min corresponding to the load command value F*, the hysteresis width W_hys, and the boundary coefficients α, β, and γ (0≤α≤1, 0≤β≤1, 0≤γ≤1). When the boundary coefficients α, β, and γ are 0, the operating point is set on the inverse efficiency line, and when the boundary coefficients α, β, and γ are 1, the operating point is set on the positive efficiency line.

[0067] OBi=Trq_min+α×W_hys

[0068] OBh=Trq_min+β×W_hys

[0069] OBd=Trq_min+γ×W_hys

[0070] exist Figure 7 In FIG. 1 , each operating point boundary OBi, OBh, and OBd is represented by an image with α>0.5, β≈0.5, and γ<0.5. The operating point adjuster 46 can reduce the response delay when switching to the increasing operation by maintaining the braking force at the operating point on the positive efficiency line side compared to the operating point boundary OBi when increasing the prediction. In addition, the operating point adjuster 46 can appropriately ensure the current reduction effect by maintaining the braking force at the operating point on the reverse efficiency line side compared to the respective operating point boundaries OBh and OBd when maintaining the prediction and reducing the prediction.

[0071] like Figure 8 As shown, the operating point adjuster 46 may also change the boundary coefficients α, β, γ according to at least one of the electric brake temperature Temp and the vehicle speed V, and change the operating point boundaries OBi, OBh, OBd. Here, the electric brake temperature Temp is set as a representative value calculated as the maximum value and average value of each electric brake temperature Temp1-Temp4. Figure 8 Although a simple broken line characteristic is exemplified in FIG. 1 , a multi-step or curved characteristic may be used. In addition, a logic for determining the boundary coefficients α, β, and γ by mediating the dependency based on the electric brake temperature Temp and the dependency based on the vehicle speed V may be added.

[0072] In the high temperature region where the electric brake temperature Temp is higher than the critical value TempX, the requirement for reducing the heat generated by energizing the windings of the inverter 55 and the motor 60 to avoid failure of the components becomes higher than the switching responsiveness to the braking force increase operation. Therefore, it is preferable to reduce the boundary coefficients α, β, and γ to be close to 0.

[0073] On the other hand, in the high-speed area where the vehicle speed V is above the critical value VX, the influence caused by the switching delay to the braking force increase action is large, so it is required to give priority to improving the responsiveness compared to reducing the current in the maintenance. In particular, when increasing the prediction, it is preferred to increase the boundary coefficient α to close to 1 to minimize the response delay. If the prediction reliability is high when maintaining the prediction and when reducing the prediction, the boundary coefficients β and γ can also be set to constant regardless of the vehicle speed V as shown by the dotted line. However, it is also possible to prevent emergency braking that is contrary to the prediction and change the boundary coefficients β and γ significantly when the vehicle speed V is above the critical value VX.

[0074] Reference Fig. 9 The flowchart of FIG. 4 is used to explain the processing performed by the operating point adjuster 46. In the description of the flowchart, the symbol "S" means a step. In S1, the operating point adjuster 46 changes the operating point boundaries OBi, OBh, and OBd of the increase action, the hold action, and the decrease action according to the vehicle speed V or the electric brake temperature Temp. For example, the operating point adjuster 46 is as follows: Figure 8 As shown, the boundary coefficients α, β, and γ are changed according to the electric brake temperature Temp or the vehicle speed V. In addition, the operating point boundaries may be set to fixed values ​​regardless of the electric brake temperature Temp or the vehicle speed V.

[0075] In S2, the operating point adjuster 46 obtains the prediction information of the required braking force from the prediction unit 45. When the prediction unit 45 predicts that the required braking force will increase from the current time to the predicted time, it is determined as "yes" in S3. At this time, in S4, the operating point adjuster 46 maintains the braking force at the operating point on the positive efficiency line side compared to the operating point boundary OBi at the time of increase prediction in the adjustment area Za.

[0076] If the prediction unit 45 predicts that the required braking force will be maintained for a period of time longer than the predicted time, the determination in S5 is “Yes”. In this case, in S6, the operating point adjuster 46 maintains the braking force at an operating point in the adjustment area Za that is closer to the efficiency line than the operating point boundary OBh during the maintenance prediction.

[0077] If the prediction unit 45 predicts that the required braking force will decrease from now to the predicted time, the determination in S7 is “Yes”. In this case, in S8, the operating point adjuster 46 maintains the braking force at an operating point on the opposite efficiency line side of the operating point boundary OBd in the reduction prediction in the adjustment area Za.

[0078] As described above, the operating point adjuster 46 adjusts the operating point for maintaining the braking force based on the prediction information of the prediction unit 45. This makes it possible to appropriately adjust the balance between the current reduction effect in the braking force maintenance and the responsiveness when switching from the maintenance operation to the braking force increase operation.

[0079] (Other embodiments)

[0080] (a) The vehicle equipped with the vehicle brake device of the present invention is not limited to a four-wheeled vehicle having two rows of wheels in pairs in the front-rear direction of the vehicle, but may be a vehicle with six or more wheels having three or more rows of wheels in the front-rear direction of the vehicle. In addition, the vehicle brake device of the present invention may also be installed in a vehicle that does not have the automatic driving controller 200.

[0081] (b) In the above embodiment, the torque command calculation unit 40 calculates the torque command value Trq* by load control. However, in other embodiments, the torque command calculation unit 40 may calculate the torque command value Trq* by position control. In this case, the braking force is related to the position θ and X. Figure 4 , Figure 6 The position θ, X is used as the vertical axis of the corresponding hysteresis diagram.

[0082] (c) The operating point may not be adjusted using information on the electric brake temperature Temp or the vehicle speed V. For example, in areas where the electric brake temperature Temp is more affected by air temperature than by heat generated by energization, the air temperature may be considered as the electric brake temperature Temp.

[0083] The present invention is not limited to the above-described embodiments, and can be implemented in various forms within the scope of the present invention.

[0084] The braking force control unit and method thereof described in the present invention may be implemented by a dedicated computer as described below, which is provided by constituting a processor and a memory, and the processor is programmed to execute one or more functions embodied by a computer program. Alternatively, the braking force control unit and method thereof described in the present invention may also be implemented by a dedicated computer as described below, which is provided by constituting a processor by one or more dedicated hardware logic circuits. Alternatively, the braking force control unit and method thereof described in the present invention may also be implemented by one or more dedicated computers, which are composed of a combination of a processor and a memory programmed to execute one or more functions and a processor composed of one or more hardware logic circuits. In addition, the computer program may also be stored as an instruction executed by a computer in a non-transient tangible recording medium readable by a computer.

[0085] The present invention is described based on the embodiments. However, the present invention is not limited to the embodiments and structures. The present invention also includes various modifications and variations within the equivalent range. In addition, various combinations and modes, and even other combinations and modes that only include one element, more than one element, or less than one element in them, are also included in the scope and thought range of the present invention.

Claims

1. A vehicle brake device, mounted on a vehicle (900) having a plurality of electric brakes (81-84) on each wheel, wherein the plurality of electric brakes convert torque output by a motor (60) into linear motion force through a direct-acting mechanism (85), and press the corresponding wheels (91-94) to generate braking force, wherein the vehicle brake device is characterized in that: A braking force control unit (400) is provided, the braking force control unit including a torque command calculation unit (40) and a current command calculation unit (50), and controls the braking force generated by each of the electric brakes, the torque command calculation unit calculating a torque command value of the electric motor based on a required braking force indicated from the outside, and the current command calculation unit calculating a current command value for energizing the electric motor based on the torque command value. The relationship between the torque of the motor and the braking force generated by the electric brake has the following hysteresis characteristics: when the torque increases, the braking force increases along the positive efficiency line, when the torque decreases from the turning value from increase to decrease to the holding threshold value, the braking force remains constant, and when the torque decreases from the holding threshold value, the braking force decreases along the reverse efficiency line. The torque command calculation unit includes: a prediction unit (45) for predicting a change in the required braking force after the present time; and an operating point adjuster (46) which stores the maximum torque on the positive efficiency line and the minimum torque on the reverse efficiency line corresponding to the braking force to be maintained, and adjusts the operating point for maintaining the braking force in an adjustment region (Za) between the minimum torque and the maximum torque based on the prediction information of the prediction unit, The torque command calculation unit calculates a torque command value of the electric motor at the operating point adjusted by the operating point adjuster.

2. The vehicle braking device according to claim 1, characterized in that: When the prediction unit predicts that the required braking force will increase from the current time to the predicted time, The operating point adjuster maintains the braking force at an operating point on the positive efficiency line side relative to the operating point boundary (OBi) during increase prediction in the adjustment region.

3. The vehicle braking device according to claim 1, characterized in that: When the prediction unit predicts that the required braking force will be maintained from the current time to a predicted time or longer, The operating point adjuster maintains the braking force at an operating point on the opposite efficiency line side of the operating point boundary (OBh) at the time of maintaining prediction in the adjustment region.

4. The vehicle braking device according to claim 1, characterized in that: When the prediction unit predicts that the required braking force will decrease within a predicted time from the current time, The operating point adjuster maintains the braking force at an operating point on the opposite efficiency line side of the operating point boundary (OBd) during reduction prediction in the adjustment region.

5. The vehicle brake device according to any one of claims 2 to 4, characterized in that: The operating point adjuster changes the operating point boundary according to at least one of a temperature of the electric brake and a vehicle speed.

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