JP2017210180A - Brake control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust a specification of a brake member around a wheel thermally, by using map information of a navigation device, and reduces a size of whole brake device.SOLUTION: A brake control device comprises: an operation amount sensor for detecting an operation amount of a brake operation member on a vehicle which has a navigation device comprising a position detection part for detecting a vehicle position, and a storage part including gradient information of a road on the periphery of the vehicle; front wheel/rear wheel actuators for generating front wheel/rear wheel brake force by pressing a friction member to rotation members which rotate with the front wheels and rear wheels; and a controller for controlling the front wheel/rear wheel actuators, on the basis of the operation amount. The controller reduces a ratio of the rear wheel brake force to a total brake force acting the vehicle, when a determination result is an affirmative result, according to the determination result of whether or not, there is a downhill over a prescribed distance on a front road, determined on the basis of the vehicle position and gradient information, compared with a case when the determination result is not the affirmative result.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a braking control device for a vehicle.

  Patent Document 1 describes “braking force distribution control in which the distribution of braking force is changed in order to meet the demand for braking performance at high braking loads without increasing the size of the vehicle braking device”. Yes. Specifically, “determination means for determining whether or not a high braking load state is based on the interval and the number of times of the braking execution processing, and the front and rear of the vehicle when the determination that the high braking load state is made” In the high braking load state, a braking execution process requesting a braking force exceeding a predetermined braking force and a drive execution process requesting a driving force exceeding a predetermined driving force are alternately performed in a high braking load state. The change in the braking force distribution of the front and rear wheels is detected as a reduction in the braking force of the front wheels, and is detected when the braking execution process is executed more than a predetermined number of times at a braking execution interval shorter than a predetermined time. "This is done by increasing the braking force of the rear wheels."

  The braking control device described in Patent Document 1 states that “the thermal capacity of the braking device on the rear wheel side is relatively large compared to the front wheel side. When the braking load is relatively high, the braking device is increased in size by temporarily executing the braking force distribution control so that the rear wheel braking device compensates for the lack of braking capacity or braking performance of the front wheel braking device. This makes it possible to achieve the braking performance or the braking capacity required at the time of high braking load. For this reason, in the brake control device disclosed in Patent Document 1, specifically, “when a traveling pattern in which rapid acceleration and rapid deceleration are repeated is executed and it is determined that the braking load is increased, first, the braking control device is relatively high. In order to reduce the braking load of the front wheel braking device operated by the braking force, the front and rear wheel braking force distribution is changed to be biased toward the rear wheel to prevent the front wheel braking device from falling into an overheated state. Thereafter, when the braking load is not sufficiently reduced even by such a change in distribution, control is performed such that the increase in the load on the braking device is suppressed by lowering the gear position of the transmission.

  From a thermal point of view in the braking control device, it is necessary to consider not only a traveling pattern in which rapid acceleration and rapid deceleration are repeated, but also situations in various braking operations. That is, in various braking operation situations, what is required for the front wheel and rear wheel braking devices may conflict. Specifically, there are a case where a strong braking force is generated in a short time during sudden braking from a high speed traveling and a case where a relatively low braking force is generated over a long time on a downhill road or the like. For a strong braking operation in a short time, a relatively high heat capacity is required for the braking device for the front wheels. On the other hand, a long braking operation requires a relatively high heat capacity relative to the rear wheel braking device. The heat capacity of the braking device can be increased by increasing the thickness of the brake disc and increasing the size of the brake caliper. However, these changes are not preferable from the viewpoint of reducing the size and weight of the apparatus.

  By the way, the present applicant has developed what uses the map information of a navigation apparatus as described in Patent Document 2. Specifically, in the device described in Patent Document 2, “a vehicle stabilization control device that achieves understeer suppression control that can effectively decelerate the vehicle when it is predicted that the vehicle cannot stably pass the curve” Therefore, “It is determined that the vehicle can stably pass the curve before and after entering the curve based on the curve shape based on the map information of the navigation device and the current vehicle speed. Is set to a large value (default value), and the braking force of each wheel is distributed so that the yaw characteristics of the vehicle are emphasized. On the other hand, if it is determined that the vehicle cannot properly pass the curve, the threshold value is adjusted to a relatively small value, and the vehicle The second characteristic that the braking force of each wheel are distributed so fast characteristics are emphasized are selected. "The present invention is based on the observed 該知.

JP 2011-156983 A JP 2010-105453 A

  An object of the present invention is to provide a braking control device capable of independently controlling braking force between at least a front wheel and a rear wheel of a vehicle. It is to provide what can be reduced in size as a whole braking device by thermally optimizing the specifications of the disk.

  A vehicle braking control apparatus according to the present invention includes a position detection unit (PVH) that detects a position (Pvh) of a vehicle, and a storage unit (KMP) that includes gradient information (Kmp) of a road around the vehicle. In a vehicle including a navigation device (NVS), an operation amount sensor (BPA) for detecting an operation amount (Bpa) of a braking operation member (BP) of the vehicle and a front wheel (WHf *) of the vehicle rotate together. A front wheel actuator (CAf *) that presses the friction member (MSB) against the front wheel rotating member (KTf *) to generate a front wheel braking force (Fbf *) on the front wheel (WHf *), and a rear wheel ( The rear wheel that presses the friction member (MSB) against the rear wheel rotating member (KTr *) that rotates integrally with WHr *) to generate the rear wheel braking force (Fbr *) on the rear wheel (WHr *). Actuator (CAr *) and the manipulated variable (Bpa) Based on, the front wheel actuator (CAf *), and provided with a controller (ECU) which controls the rear wheel actuator (CAr *).

  In the vehicle braking control apparatus according to the present invention, the controller (ECU) is configured based on the position of the vehicle (Pvh) and the gradient information (Kmp). Whether or not the road has a downhill for a predetermined distance (shd) (for example, a downhill that is longer than the predetermined distance shd and the average value of the downward gradient Kmp is larger than the predetermined value kmx). According to the determination result (“YES” or “NO”), when the determination result is affirmed (in the case of “YES”), the determination result is negative (in the case of “NO”). In comparison, the rear wheel braking force (Fbr *) distribution ratio (Hbn) to the total braking force (Fbf * + Fbr *) acting on the vehicle is reduced.

  The situation where a relatively low braking force is continuously generated on a downhill road for a long time (long-term, low-load braking state) is not a load state that generates the maximum braking force of the wheel, but the rear wheel braking member Is difficult to cool. Accordingly, a relatively high heat capacity is required for the braking device for the rear wheels in order to cope with a long-term low-load braking state. Further, in this traveling situation, the center of gravity of the vehicle is slightly shifted from the rear wheel side to the front wheel side, and the vertical force of the rear wheels is reduced compared to when traveling on a horizontal road.

  According to the above configuration, when there is a downhill that is longer than the predetermined distance shd and whose average downward slope is larger than the predetermined value kmx in front of the vehicle, there is a high probability that a long-term low-load state will occur. Is changed by decreasing the ratio Hbn of the rear wheel braking force Fbr *. Relatively, the braking force Fbr * of the rear wheel is weakened, and the braking force Fbf * by the front wheel braking device having a sufficient heat capacity is increased. For this reason, in various braking operations, the heat capacities of the braking devices for the front wheels and the rear wheels are optimized by the braking force distribution control, so that the entire braking control device can be reduced in size and weight.

  Further, by changing the braking force distribution, the front / rear distribution of the braking force corresponding to the axial load fluctuation caused by the slope of the slope can be achieved. In particular, when the slope is bent downward (especially a hairpin curve), it is required that the lateral force of the rear wheel be ensured. However, since the rear wheel braking force ratio Hbn is reduced, sufficient rear wheel lateral force is required. Power can be ensured and vehicle stability can be maintained.

1 is an overall configuration diagram showing an embodiment of a braking control device according to the present invention. It is a fragmentary sectional view for demonstrating a pressure adjustment unit. It is a functional block diagram for demonstrating the process in an electronic control unit. It is a circuit diagram for demonstrating an electric motor and its drive circuit. It is a flowchart for demonstrating the 1st process example in a long-term low load state. It is a flowchart for demonstrating the 2nd process example in a long-term low load state.

<Symbols of components and subscripts at the end of the symbols>
An embodiment of a vehicle braking control apparatus according to the present invention will be described with reference to the drawings. In the following description, constituent members, arithmetic processing, signals, and values having the same symbols, such as “ECU”, have the same function. Further, a suffix (“fr” or the like) added to the end of each symbol is a comprehensive symbol indicating which wheel it relates to. Specifically, “fr” indicates the right front wheel, “fl” indicates the left front wheel, “rr” indicates the right rear wheel, and “rl” indicates the left rear wheel. For example, in each wheel cylinder, they are expressed as a right front wheel wheel cylinder WCfr, a left front wheel wheel cylinder WCfl, a right rear wheel wheel cylinder WCrr, and a left rear wheel wheel cylinder WCrl.

  Further, a suffix (“f *” or “r *”) added to the end of each symbol indicates which wheel (ie, front wheel or rear wheel) before and after the vehicle. Specifically, “f *” is a comprehensive symbol indicating the front wheel, and “r *” is a comprehensive symbol indicating the rear wheel. Therefore, the subscript “f *” is a generic term for “fr” and “fl”, and the subscript “r *” is a generic term for “rr” and “rl”. For example, the right front wheel wheel cylinder WCfr and the left front wheel wheel cylinder WCfl are represented as a front wheel wheel cylinder WCf *. Further, the right rear wheel wheel cylinder WCrr and the left rear wheel wheel cylinder WCrl are represented as a rear wheel wheel cylinder WCr *.

<Embodiment of Braking Control Device According to the Present Invention>
A vehicle including an embodiment of a braking control device according to the present invention will be described with reference to the overall configuration diagram of FIG. The vehicle includes a navigation device NVS, a communication bus CMB, a braking operation member BP, an operation amount acquisition means BPA, an electronic control unit ECU, a tandem master cylinder (also simply referred to as a master cylinder) MCL, a master cylinder shut-off valve VMf *, VMr *. (Simply referred to as “VM”), stroke simulator (simply referred to as “simulator”) SSM, simulator cutoff valve VSM, master cylinder fluid path HMf *, HMr * (simply also referred to as “HM”), wheel cylinder fluid path HWf *, HWr * (simply referred to as “HW”), simulator fluid path HSM, and pressure adjustment units CAf *, CAr * (simply referred to as pressure regulating units, also referred to as “CA”).

  Further, each wheel WHfr, WHfl, WHrr, WHrl (simply referred to as “WH”) of the vehicle has brake calipers CPfr, CPfl, CPrr, CPrl (simply referred to as calipers, also referred to as “CP”), Wheel cylinders WCfr, WCfl, WCrr, WCrl (also simply referred to as “WC”) and rotating members KTfr, KTfl, KTrr, KTrl (also simply referred to as “KT”) are provided.

  The navigation device NVS electronically displays the current position of the vehicle (own vehicle position) and provides route guidance to the destination set by the driver. The navigation device NVS includes a processing unit PRC, a vehicle position detection unit PVH, a yaw rate gyro GYR, an input unit INP, a storage unit KMP, and a display unit (display) MNT. The navigation device NVS is electrically connected to the electronic control unit ECU of the braking control device via a communication bus CMB (wired communication). Note that the communication bus CMB may be wireless communication.

  In the processing unit PRC of the navigation device NVS, signals from the vehicle position detection unit PVH, the yaw rate gyro GYR, the input unit INP, and the storage unit KMP are comprehensively processed. Then, the information processing result (vehicle position display, route guidance) related to the navigation function is displayed on the display unit MNT. An operation input related to the navigation function such as destination setting is performed by the driver via the input unit INP.

  In the vehicle position detection unit PVH, one of well-known methods is adopted to detect the current position Pvh of the vehicle. For example, a positioning signal from an artificial satellite is used to detect the position (latitude, longitude, etc.) Pvh of the vehicle. This is detection of the position of the vehicle using a so-called global positioning system (GPS). There is an error in GPS positioning, and radio waves from GPS cannot be received in a tunnel or the like. For this reason, the self-contained navigation by at least one of the signal of the yaw rate gyro GYR and the wheel speed sensor is used in combination with the GPS.

  The storage unit KMP of the navigation device NVS contains map information (map data) including detailed road information. In addition to the road map, the storage unit KMP stores various information such as road gradient information (uphill / downhill) Kmp, road elevation (undulation) Hmp, and information on the curve radius Rmp.

  The relative position Pvh of the vehicle with respect to the road is acquired from the detection result of the vehicle position detection unit PVH and the map information of the road in the storage unit KMP. Specifically, the vehicle position detection unit PVH detects the current vehicle position (latitude, longitude, etc.) Pvh on coordinates fixed to the earth. Furthermore, after the initial position of the vehicle is determined by the vehicle position detection unit PVH, the relative position of the vehicle from the initial position is sequentially updated based on information obtained from the yaw rate gyro GYR, wheel speed sensor, and the like. Thus, the current vehicle position Pvh is supplementarily estimated.

  The road map information stored in the storage unit KMP stores road positions (longitude and latitude). Therefore, the vehicle position Pvh relative to the road is specified by collating the current vehicle position Pvh and the position of the road in the map information. The current position Pvh of the vehicle and the gradient information (uphill / downhill gradient) Kmp around the vehicle are input from the navigation device NVS to the electronic control unit (controller) ECU via the communication bus CMB. For example, a controller area network (CAN) is employed as the communication bus CMB.

  The braking operation member (for example, brake pedal) BP is a member that the driver operates to decelerate the vehicle. By operating the braking operation member BP, the braking torque of the wheel WH is adjusted, and a braking force is generated on the wheel WH. Specifically, a rotating member (for example, a brake disc) KT is fixed to the vehicle wheel WH. The caliper CP is arranged so as to sandwich the rotating member KT. The caliper CP is provided with a wheel cylinder WC. By increasing the pressure (hydraulic pressure) of the brake fluid in the wheel cylinder WC, the friction member (for example, brake pad) MSB is pressed against the rotating member KT. Since the rotating member KT and the wheel WH are fixed so as to rotate together, a braking torque (braking force) is generated on the wheel WH by the frictional force generated at this time.

  The operation amount acquisition means (operation amount sensor) BPA is provided in the braking operation member BP. The operation amount acquisition means BPA acquires (detects) an operation amount (braking operation amount) Bpa of the braking operation member BP by the driver. Specifically, as the operation amount acquisition means BPA, the hydraulic pressure sensor PM1 that detects the pressure Pm1 of the master cylinder MCL, the operation displacement sensor SBP that detects the operation displacement Sbp of the braking operation member BP, and the operation of the braking operation member BP At least one of operation force sensors (not shown) for detecting force is employed. That is, the operation amount acquisition means BPA is a general term for the master cylinder hydraulic pressure sensor PM1, the operation displacement sensor SBP, and the operation force sensor. Therefore, the brake operation amount Bpa is determined based on at least one of the hydraulic pressure Pm1 of the master cylinder MCL, the operation displacement Sbp of the brake operation member BP, and the operation force of the brake operation member BP. The operation amount Bpa is input to an electronic control unit (also referred to as a controller) ECU.

  Based on the braking operation amount Bpa, the electronic control unit (controller) ECU is an electric motor of front wheels, rear wheel pressure adjustment units CAf *, CAr * (corresponding to front wheels, rear wheel actuators, and simply expressed as “CA”). MTf *, MTr * (simply expressed as “MT”), simulator cutoff valve VSM, and master cylinder cutoff valves VMf *, VMr * (simply expressed as “VM”) are controlled. A control algorithm for controlling the electric motor MT, the simulator cutoff valve VSM, and the master cylinder cutoff valve VM is programmed in the microprocessor of the controller ECU, and signals for controlling these are calculated.

  Specifically, the controller ECU outputs a drive signal Vsm for opening the simulator cutoff valve VSM when the manipulated variable Bpa is equal to or greater than a predetermined value (play equivalent value) bp0, and the master cylinder cutoff valve VM. Drive signals Vmf * and Vmr * (simply referred to as “Vm”) that output the closed position (generic name of VMf * and VMr *) are output. As a result, the master cylinder MCL is brought into communication with the simulator SSM, and the control cylinders SCf * and SCr * (also simply referred to as “SC”) of the pressure adjusting unit CA are brought into communication with the wheel cylinder WC. Accordingly, the hydraulic pressure in the wheel cylinder WC is controlled by the pressure adjusting unit CA (generic name for CAf * and CAr *).

  The master cylinder MCL is mechanically connected to the braking operation member BP via a piston rod. By the master cylinder MCL, the operation force (brake pedal depression force) of the brake operation member BP is converted into hydraulic pressure. Master cylinder fluid paths HMf * and HMr * (also simply referred to as “HM”) are fluidly connected to the master cylinder MCL. When the brake operation member BP is operated, the brake fluid (brake fluid) is discharged (pressure fed) from the master cylinder MCL to the master cylinder fluid passage HM. Here, the master cylinder fluid path HM (generic name for HMf * and HMr *) is a fluid path (for example, a brake pipe) from the master cylinder MCL to the master cylinder shut-off valve VM.

≪Two lines of fluid path (configuration of front and rear piping) ≫
Two fluid paths will be described with reference to the hydraulic circuit. A path (fluid path) through which the brake fluid is moved between the master cylinder MCL and the four wheel cylinders WC includes two systems. One system is a “front wheel system”, and a first master cylinder chamber (also referred to as a first pressurizing chamber) Rm1 of the master cylinder MCL and a front wheel cylinder WCf * (generic name for WCfr and WCfl) are fluidly connected. . The other system is a “rear wheel system”, and the second master cylinder chamber (also referred to as second pressurizing chamber) Rm2 of the master cylinder MCL and the rear wheel cylinder WCR * (generic name for WCrr and WCrl) are fluidly connected. Is done. As the hydraulic circuit, a so-called front / rear piping configuration is employed. The configuration related to the front wheels and the configuration related to the rear wheels are basically the same. Therefore, the configuration of the fluid passage Hf * related to the front wheel will be described.

  The front wheel fluid passage Hf * connecting the first pressurizing chamber Rm1 of the master cylinder MCL and the front wheel cylinder WCf * is provided with a pressure adjustment unit (also referred to as a pressure adjustment unit) CAf * for the front wheels. That is, the pressure adjusting unit CAf * is interposed in the middle of the front wheel fluid path Hf *. Here, the front wheel master cylinder fluid passage HMf * is from the first pressurizing chamber Rm1 of the front wheel fluid passage Hf * to the front wheel master cylinder shutoff valve VMf *, and the wheel from the front wheel master cylinder shutoff valve VMf * of the front wheel fluid passage Hf *. Up to the cylinder WCf * is the front wheel cylinder fluid passage HWf *.

  The front wheel pressure adjustment unit CAf * (corresponding to the front wheel actuator) is composed of a front wheel control cylinder SCf * and a front wheel electric motor MTf *. When a braking operation is performed by the driver and when automatic pressurization is required, the fluid connection between the master cylinder MCL and the wheel cylinder WCf * is cut off (non-communication state) by the VMf *. Then, the hydraulic pressure of the wheel cylinder WCf * is adjusted (increased, held, or decreased) by the pressure adjustment unit CAf *. The hydraulic pressure (actual control hydraulic pressure) Pcf * adjusted by the front wheel pressure adjusting unit CAf * is acquired (detected) by the front wheel control hydraulic pressure sensor PCf *.

  The front wheel fluid passage Hf * includes a master cylinder fluid passage (braking pipe) HMf * from the master cylinder MCL to the master cylinder shut-off valve VMf *, and a wheel cylinder fluid passage (braking) from the master cylinder shut-off valve VMf * to the wheel cylinder WCf *. Piping) It is formed with HWf *. The master cylinder fluid pressure sensor PM1 is provided in the master cylinder fluid passage HMf * so as to detect the fluid pressure (master cylinder fluid pressure) Pm1 in the pressurizing chamber Rm1.

  A front wheel hydraulic unit HUf * is interposed in the front wheel cylinder fluid passage HWf *. Further, in the wheel cylinder fluid path HWf *, the control hydraulic pressure Pcf * of the pressure adjustment unit CAf * (particularly in the control cylinder SCf *) is detected between the pressure adjustment unit CAf * and the hydraulic pressure unit HUf *. Thus, a control hydraulic pressure sensor PCf * for the front wheels is provided.

  The front wheel hydraulic unit (also referred to as a modulator) HUf * is composed of a pressure increasing valve and a pressure reducing valve. When performing wheel slip control such as anti-skid control and vehicle stabilization control, the hydraulic pressure of the front wheel wheel cylinder WCf * Are controlled individually and independently.

  A stroke simulator (also simply referred to as a simulator) SSM is provided to generate an operating force on the braking operation member BP. A simulator cutoff valve (also simply referred to as a cutoff valve) VSM is provided between the hydraulic chamber in the master cylinder MCL and the simulator SSM. The cutoff valve VSM is a two-position electromagnetic valve having an open position and a closed position. When the shut-off valve VSM is in the open position, the master cylinder MCL and the simulator SSM are in communication with each other, and when the shut-off valve VSM is in the closed position, the master cylinder MCL and the simulator SSM are in shut-off state (not in communication). ) The shutoff valve VSM is controlled by a drive signal Vsm from the controller ECU. As the shutoff valve VSM, a normally closed electromagnetic valve (NC valve) can be adopted.

  Inside the simulator SSM, a piston and an elastic body (for example, a compression spring) are provided. Therefore, when the braking operation member BP is operated, the braking fluid is moved from the master cylinder MCL (pressurizing chamber Rm1) to the simulator SSM, and the piston is pushed by the flowing braking fluid. A force is applied to the piston in a direction to prevent the inflow of the brake fluid by the elastic body. By this elastic body, an operation force (for example, a brake pedal depression force) when the brake operation member BP is operated is formed.

  Next, the configuration related to the rear wheel fluid passage Hr * will be briefly described. As described above, the configuration related to the front wheel fluid passage Hf * and the configuration related to the rear wheel fluid passage Hr * are basically the same. Therefore, “Rm1” becomes “Rm2”, “WHf *” becomes “WHr *”, “HMf *” becomes “HMr *”, “HWf *” becomes “HWr *”, and “HUf *” becomes “HUf *”. HURr *, “CAf * (front wheel actuator)” corresponds to “CAr * (rear wheel actuator)”, “PCf * (front wheel sensor)” corresponds to “PCr * (rear wheel sensor)”, respectively. Yes. That is, in the description of the components related to the fluid path Hf * for the front wheel, the “front wheel” is replaced with the “rear wheel”, and the symbol suffix “f *” is replaced with “r *”. This corresponds to the description of the components related to the fluid path Hr *. In the configuration related to the rear wheel fluid path Hr *, the simulator and the master cylinder hydraulic pressure sensor are omitted. However, these may be provided in the rear wheel fluid passage Hr * as well as the front wheel fluid passage Hf *. The fluid circuit has been described above.

  A brake caliper (simply referred to as a caliper) CP is provided on the wheel WH, applies a braking torque to the wheel WH, and generates a braking force. A floating caliper can be adopted as the caliper CP. The caliper CP is configured to sandwich a rotating member (for example, a brake disc) KT via two friction members (for example, a brake pad) MSB. A wheel cylinder WC is provided in the caliper CP. By adjusting the hydraulic pressure in the wheel cylinder WC, the piston in the wheel cylinder WC is moved (advanced or retracted) with respect to the rotating member KT. By this movement of the piston, the friction member MSB is pressed against the rotating member KT, and a frictional force is generated.

  FIG. 1 illustrates the configuration of a disc-type braking device (disc brake). In this case, the friction member MSB is a brake pad, and the rotating member KT is a brake disk. Instead of the disc type braking device, a drum type braking device (drum brake) may be employed. In the case of a drum brake, a brake drum is employed instead of the caliper CP. The friction member MSB is a brake shoe, and the rotating member KT is a brake drum.

<Pressure adjustment unit (actuator) CA>
With reference to the partial cross-sectional view of FIG. 2, the pressure adjustment unit CAf * for front wheels (corresponding to the front wheel actuator) will be described. Since the rear wheel pressure adjustment unit CAr * (corresponding to the rear wheel actuator) has the same configuration as the front wheel pressure adjustment unit CAf *, description thereof will be omitted. The subscript “f *” replaced with the subscript “r *” corresponds to the description of the pressure adjustment unit CAr * for the rear wheel.

  The front wheel pressure adjustment unit CAf * is connected to a fluid path (for example, a brake pipe) HWf * between the electromagnetic valve VMf * and the wheel cylinder WCf *, and is driven by an electric motor MTf *. The pressure adjustment unit CAf * includes a reduction gear GSK, a rotation / linear motion conversion mechanism (screw mechanism) NJK, a pressing member PSH, a control piston SPS, a control cylinder SCf *, and a return spring SPR.

  The reduction gear GSK is composed of a small diameter gear SKH and a large diameter gear DKH. The rotational power of the electric motor MTf * is decelerated by the reduction gear GSK and transmitted to the screw mechanism NJK. Specifically, the small diameter gear SKH is fixed to the output shaft of the electric motor MTf *. The large-diameter gear DKH is engaged with the small-diameter gear SKH, and the large-diameter gear DKH and the bolt member BLT are fixed so that the rotational shaft of the large-diameter gear DKH coincides with the rotational shaft of the bolt member BLT of the screw mechanism NJK. .

  By the screw mechanism NJK, the rotational power of the speed reducer GSK is converted into linear power of the control piston SPS. Specifically, the bolt member BLT of the screw mechanism NJK is fixed coaxially with the large-diameter gear DKH, and the nut member NUT that is screwed with the bolt member BLT is moved. A pressing member PSH is fixed to the nut member NUT. By pressing the control piston SPS, the pressing member PSH is converted into linear power (forward power or reverse power) of the control piston SPS. Here, since the rotational movement of the nut member NUT is restrained by the key member KYB, the nut member NUT is moved in the direction of the rotational axis (the central axis of the SPS) Jsc of the large-diameter gear DKH and presses the control piston SPS. .

  As the screw mechanism NJK, a “sliding screw” such as a trapezoidal screw is employed. Further, as the screw mechanism NJK, a “rolling screw” such as a ball screw can be adopted.

  The control piston SPS is inserted into the cylindrical hole of the control cylinder SCf *, and a combination of the piston and the cylinder is formed. A seal member PSL is provided on the outer periphery of the control piston SPS. The seal member PSL seals between the outer periphery (outer wall) of the control piston SPS and the inner hole (inner wall) of the control cylinder SCf *. A pressure regulating chamber Rca defined by the control cylinder SCf * and the control piston SPS is formed.

  The pressure regulating chamber Rca in the control cylinder SCf * is connected to a fluid path (braking pipe) HWf * via a pressure regulating hole Asc. When the control piston SPS is moved (forward or backward) in the direction of the central axis (the central axis of the control cylinder bore) Jsc, the volume of the pressure regulating chamber Rca changes. At this time, the electromagnetic valve VMf * is closed by the drive signal Vmf *. Therefore, the brake fluid is not moved in the direction of the master cylinder MCL (pressurizing chamber Rm1), but is moved toward the wheel cylinder WCf *.

  When the electric motor MTf * is rotationally driven in the forward rotation direction, the control piston SPS moves forward in the direction of the central axis Jsc so that the volume of the pressure regulating chamber Rca is reduced. Accordingly, the brake fluid is pushed out from the control cylinder SCf * to the wheel cylinder WCf *. By this movement of the brake fluid, the pressing force of the friction member MSB against the rotating member KTf * is increased, and the braking torque of the wheel WHf * is increased.

  Conversely, when the electric motor MTf * is rotationally driven in the reverse direction, the control piston SPS moves in the backward direction so that the volume of the pressure regulating chamber Rca increases. Accordingly, the brake fluid is returned from the wheel cylinder WCf * toward the control cylinder SCf *. Due to this movement of the braking fluid, the pressing force of the friction member MSB against the rotating member KTf * is reduced, and the braking torque of the wheel WHf * is reduced.

  A control hydraulic pressure sensor PCf * (front wheel sensor) is provided so as to detect the hydraulic pressure Pcf * (front wheel output) in the pressure regulating chamber Rca. The actual control fluid pressure Pcf *, which is the detection result of the control fluid pressure sensor PCf *, is input to the controller ECU. A hydraulic unit HUf * is interposed in the wheel cylinder fluid path HWf *. The hydraulic pressure unit HUf * includes a pressure increasing valve and a pressure reducing valve, and independently controls the hydraulic pressure of the front wheel cylinder WCf * when it is necessary to execute wheel slip control (such as anti-skid control).

  The pressure adjustment unit CAf * is provided with a return spring (elastic body) SPR. When the energization of the electric motor MTf * is stopped by the return spring SPR, the control piston SPS is pressed against the stopper Stp. The position where the control piston SPS contacts the stopper Stp is the initial position (position corresponding to zero braking hydraulic pressure).

<Processing in electronic control unit (controller)>
Processing in the controller (electronic control unit) ECU will be described with reference to the functional block diagram of FIG. Here, an example in which brushless motors are employed as the electric motors MTf * and MTr * will be described.

  Similar to the description of other parts, members (components) and the like having the same symbols, such as “MCL”, have the same function. In addition, the suffix attached to the end of the symbol of each component indicates which wheel of the four wheels corresponds to. The subscript is that “fr” corresponds to “right front wheel”, “fl” corresponds to “left front wheel”, “rr” corresponds to “right rear wheel”, and “rl” corresponds to “left rear wheel”. Each expresses. Further, a suffix (“f *” or “r *”) added to the end of each symbol indicates which wheel (ie, front wheel or rear wheel) before and after the vehicle. Specifically, “f *” indicates the front wheel and “r *” indicates the rear wheel. Therefore, the subscript “f *” is a generic term for “fr” and “fl”, and the subscript “r *” is a generic term for “rr” and “rl”.

  The controller ECU controls the output of the electric motor MT (generic name for MTf * and MTr *) based on the operation amount Bpa. The controller ECU includes a target hydraulic pressure calculation block PCT, a long-term low-load state determination block CHK, an instruction energization amount calculation block ISJ, a hydraulic pressure feedback control block PFB, a target energization amount calculation block IMT, and a drive circuit DRV. .

  In the target hydraulic pressure calculation block PCT, front and rear wheel target hydraulic pressures Ptf * and Ptr * (also simply referred to as “Pt”) are calculated based on the braking operation amount Bpa. Here, the target hydraulic pressure Pt is a target value of the braking hydraulic pressure generated by the pressure adjustment unit CA. The result (rear wheel distribution ratio) Hbn of the long-term low load state determination block CHK is reflected in the calculation characteristic (calculation map) for calculating the target hydraulic pressure Pt.

  In the long-term low-load state determination block CHK, the rear wheel ratio Hbn in braking force distribution is determined based on the current vehicle position Pvh, road gradient information Kmp, and braking operation amount Bpa. The braking force distribution is a value representing the braking force of each axle as a ratio to the total braking force of all the axles of the vehicle. Therefore, the rear wheel distribution ratio Hbn is the ratio of the rear wheel braking force Fbr * to the total braking force (the sum of the front wheel braking force Fbf * and the rear wheel braking force Fbr *) acting on the entire vehicle. For example, it is expressed as “Hbn = Fbr * / (Fbf * + Fbr *) = 0.4”.

  The rear wheel distribution ratio Hbn can be set such that its value decreases as the front wheel braking force Fbf * increases. That is, when the front wheel braking force Fbf * is the X axis and the rear wheel braking force Fbr * is the Y axis, the change characteristic of the rear wheel distribution ratio Hbn is set as a “convex upward” characteristic. This is because the vertical force (load) of the front wheels increases and the vertical force of the rear wheels decreases due to the deceleration of the vehicle. Therefore, in the description of the embodiment, when discussing the magnitude relationship of the rear wheel distribution ratio Hbn, a situation in which the vehicle is at a predetermined deceleration is defined. For example, a situation where the vehicle deceleration is 0.5G may be employed. In this case, in a situation where the vehicle is decelerated at 0.5 G by the total braking force, the ratio Hbn is the ratio of the rear wheel braking force to the total braking force. Therefore, decreasing the rear wheel distribution ratio Hbn has the same meaning as increasing the distribution ratio of the front wheel braking force.

  In the long-term low load state determination block CHK, first, based on the vehicle position Pvh, the road information Kmp including the downward slope, and the braking operation amount Bpa, whether or not it is in the long-term low load state is generated. It is judged including the high probability. Here, the “long-term low load state” is a state in which the friction member MSB is within a predetermined range for a long time on the rear wheel rotation member KTr * (that is, not a load state that generates the maximum braking force of the wheel, The caliper CP or the like is continuously pressed in a low load state). Based on the determination result, the rear wheel distribution ratio Hbn is adjusted. A detailed determination method in the long-term low-load state determination block CHK will be described later.

  When it is determined that the low-load state is in the long term, the target hydraulic pressure calculation block PCT is instructed to decrease the rear wheel distribution ratio Hbn, compared to the case where it is not determined that the low-load state is in the long term. Is done. For example, if it is not determined from the long-term low-load state determination block CHK that the long-term low-load state is present, the target hydraulic pressure calculation block PCT instructs to adopt the calculation characteristics CPfo and CPro as the rear wheel distribution ratio Hbn. Signal is output. When it is determined that the engine is in a low load state for a long time, a signal instructing the adoption of the calculation characteristics CPfc and CPrc is output as the ratio Hbn in the target hydraulic pressure calculation block PCT. Here, the calculation characteristics CPfc and CPrc are characteristics in which the rear wheel distribution ratio Hbn is reduced compared to the calculation characteristics CPfo and CPro.

  If it is not determined in the long-term low load state determination block CHK that the long-term low load state is present, the target hydraulic pressure calculation block PCT uses the target hydraulic pressure calculation characteristics CPfo and CPro (solid line characteristics) to determine the braking operation amount. In the range where Bpa is “0 (zero)” (corresponding to the case where the braking operation is not performed) and less than the predetermined value bp0, the target hydraulic pressure Pt (Ptf *, Ptr *) is calculated to be “0”. The When the operation amount Bpa is equal to or greater than the predetermined value bp0, the target hydraulic pressure Pt is calculated so as to monotonously increase from “0” as the operation amount Bpa increases. Here, the predetermined value bp0 is a value (play equivalent value) corresponding to “play” of the braking operation member BP.

  When it is determined in the long-term low-load state determination block CHK that the long-term low-load state is present, the target hydraulic pressure calculation block PCT determines the front wheels, the target hydraulic pressure based on the calculation characteristics CPfc and CPrc (characteristics of the broken line). Rear wheel target hydraulic pressures Ptf * and Ptr * are determined. In the characteristic CPfc, the front wheel target hydraulic pressure Ptf * is calculated to be larger for the same operation amount Bpa than in the characteristic CPfo. On the contrary, in the characteristic CPrc, the rear wheel target hydraulic pressure Ptr * is calculated to be smaller than the characteristic CPro with respect to the same operation amount Bpa. Therefore, in the result (hydraulic pressure target value) Pt calculated based on the characteristics CPfc and CPrc, the rear wheel distribution ratio Hbn is smaller than the calculation result Pt based on the characteristics CPfo and CPro. Here, even if the calculation result Pt is based on the characteristics CPfc and CPrc and the calculation result Pt is based on the characteristics CPfo and CPro, as long as the operation amount Bpa is the same, the total braking force as a vehicle (result, vehicle Are the same).

  In the case of the calculation characteristics CPfc and CPrc, as in the calculation characteristics CPfo and CPro, the target hydraulic pressure Pt is “in the range where the braking operation amount Bpa is not less than“ 0 (zero) ”and less than the predetermined value bp0 (play equivalent value). When the manipulated variable Bpa is equal to or greater than the predetermined value bp0, the target hydraulic pressure Pt is computed so as to monotonically increase from “0” as the manipulated variable Bpa increases.

  It should be noted that the relationship between the wheel cylinder hydraulic pressure and the wheel braking force includes the friction coefficient between the friction member MSB and the rotating member KT, the pressure receiving area of the wheel cylinder WC, and the effective braking radius in the positional relationship between the friction member MSB and the rotating member KT. (The position where the MSB presses the KT) and the radius of the wheel (tire) are associated one-to-one. In other words, the braking force generated by the wheel can be converted from the wheel cylinder hydraulic pressure based on the brake device and the specifications of the wheel.

  In the command energization amount calculation block ISJ, the electric motor that drives the pressure adjustment unit CA based on the target hydraulic pressure Pt (that is, Ptf *, Ptr *) and preset calculation characteristics (calculation maps) CIsa and CIsb. MT front and rear wheel command energization amounts Isf * and Isr * (also simply referred to as “Is”) are calculated. The command energization amount Is is a target value of the energization amount for controlling the electric motor MT. The calculation map for the command energization amount is composed of two characteristics CIsa and CIsb in consideration of the influence of hysteresis by the power transmission mechanism (GSK, NJK, etc.).

  Here, the “energization amount” is a state amount (state variable) for controlling the output torque of the electric motor MT. Since the electric motor MT outputs a torque substantially proportional to the current, the current target value of the electric motor MT can be used as the target value of the energization amount (target energization amount). Further, if the supply voltage to the electric motor MT is increased, the current is increased as a result, so that the supply voltage value can be used as the target energization amount. Further, since the supply voltage value can be adjusted by the duty ratio in the pulse width modulation, this duty ratio (ratio of energization time in one cycle) can be used as the energization amount.

  In the hydraulic pressure feedback control block PFB, the target values (target hydraulic pressures) Ptf * and Ptr * and the detected hydraulic pressure values (actual hydraulic pressures) Pcf * and Pcr * (simply Based on these, the compensation energization amounts Iff * and Ifr * (also simply referred to as “If”) of the electric motors MTf * and MTr * are calculated. Since only a control based on the command energization amount Is generates a hydraulic pressure error, the hydraulic pressure feedback control block PFB compensates for this error. The hydraulic pressure feedback control block PFB includes a comparison calculation and a hydraulic pressure compensation energization amount calculation block IPF.

  By the comparison calculation, the target value Pt of the hydraulic pressure and the detected value Pc are compared. Here, the actual hydraulic pressure values Pcf * (corresponding to the front wheel output) and Pcr * (corresponding to the rear wheel output) are obtained (detected) by the control hydraulic pressure sensors PCf * (front wheel sensor) and PCr * (rear wheel sensor). ) Is a detected value of hydraulic pressure (discharge fluid pressure). Here, the front wheel and rear wheel control hydraulic pressure sensors PCf * and PCr * are also simply expressed as “PC”. In the comparison calculation, deviations (hydraulic pressure deviations) ePf * and ePr * (simply expressed as “eP”) between the target hydraulic pressure Pt and the control hydraulic pressure Pc are calculated. The hydraulic pressure deviation eP (control variable) is input to the hydraulic pressure compensation energization amount calculation block IPF.

  The hydraulic pressure compensation energization amount calculation block IPF includes a proportional element block, a differential element block, and an integral element block, and so-called PID control is performed. In the proportional element block, the hydraulic pressure deviation eP is multiplied by the proportional gain Kp to calculate the proportional element of the hydraulic pressure deviation eP. In the differential element block, the hydraulic pressure deviation eP is differentiated, and this is multiplied by the differential gain Kd to calculate the differential element of the hydraulic pressure deviation eP. In the integral element block, the hydraulic pressure deviation eP is integrated, and this is multiplied by the integral gain Ki to calculate the integral element of the hydraulic pressure deviation eP. Then, by adding the proportional element, the differential element, and the integral element, the front wheel and rear wheel hydraulic pressure compensation energization amounts Iff * and Ifr * (also simply expressed as “If”) are calculated. That is, in the hydraulic pressure compensation energization amount calculation block IPF, based on the comparison result eP between the target hydraulic pressure Pt and the control hydraulic pressure Pc, the actual control hydraulic pressure (detected value) Pc is the target hydraulic pressure (target value) of the hydraulic pressure. ) Feedback control based on the hydraulic pressure is executed so as to coincide with Pt (that is, the deviation eP approaches “0 (zero)”).

  In the target energization amount calculation block IMT, the final target value of the energization amount, the front wheel and rear wheel target energization amounts Itf * and Itr * (also simply expressed as “It”) is calculated. The target energization amount It is calculated based on the command energization amount (target value) Is and the compensation energization amount (compensation value) If. Specifically, the compensation energization amount If is added to the command energization amount Is, and the sum thereof is calculated as the target energization amount It (ie, It = Is + If).

  In the target energization amount calculation block IMT, the sign (value sign) of the target energization amount It (Itf *, Itr *) is based on the direction in which the electric motor MT should rotate (that is, the increase / decrease direction of the hydraulic pressure). It is determined. Further, the target energization amount It is calculated based on the rotational power to be output from the electric motor MT (that is, the amount of increase / decrease of the hydraulic pressure). Specifically, when the brake hydraulic pressure is increased (the forward direction of the control piston SPS), the sign of the target energization amount It is calculated as a positive sign (It> 0), and the electric motor MT is driven in the forward direction. Is done. On the other hand, when the brake fluid pressure is decreased (reverse direction of the control piston SPS), the sign of the target energization amount It is determined to be a negative sign (It <0), and the electric motor MT is driven in the reverse direction. Furthermore, the output torque (rotational power) of the electric motor MT is controlled to increase as the absolute value of the target energization amount It increases, and the output torque is controlled to decrease as the absolute value of the target energization amount It decreases. .

<3-phase brushless motor and its drive circuit (example of 3-phase brushless motor)>
With reference to the circuit diagram of FIG. 4, a three-phase brushless motor having three coils (windings) of a U-phase coil CLU, a V-phase coil CLV, and a W-phase coil CLW is employed as the electric motor MT. An example will be described.

  The drive circuit DRV is an electric circuit that drives the electric motor MT, and corresponds to a part of the controller ECU. The drive circuit DRV includes a switching control unit SWT, a three-phase bridge circuit (also simply referred to as a bridge circuit) BRG, and a stabilization circuit LPF. The bridge circuit BRG is formed by six switching elements (power transistors) SUX, SUZ, SVX, SVZ, SWX, SWZ (also referred to as “SUX to SWZ”). The bridge circuit BRG is driven based on the drive signals Sux, Suz, Svx, Svz, Swx, Swz (also referred to as “Sux to Swz”) of each phase from the switching control unit SWT in the drive circuit DRV, and the electric motor MT Output is adjusted.

  In the drive circuit DRV, drive signals Sux to Swz for performing pulse width modulation on the switching elements SUX to SWZ are calculated based on the front wheel and rear wheel target energization amounts Itf * and Itr *. The front and rear wheel electric motors MTf * and MTr * have front wheel and rear wheel rotation angle sensors MKf * and MKr so as to detect the front wheel and rear wheel rotation angles Mkf * and Mkr * (also simply referred to as “Mk”). * (Simply written as “MK”) is provided.

  Based on the target energization amount It and the rotation angle Mk (generic name for Mkf * and Mkr *), the energization amount target values Iut, Ivt and Iwt of each phase (U phase, V phase and W phase) are calculated. . Based on the target energization amounts Iut, Ivt, Iwt of each phase, the duty ratio of the pulse width of each phase (ratio of on-time to one cycle) Dut, Dvt, Dwt is determined. Based on the duty ratio (target values) Dut, Dvt, Dwt, whether each of the switching elements SUX to SWZ constituting the bridge circuit BRG is turned on (energized state) or turned off (non-energized state) Drive signals Sux to Swz are calculated. The bridge circuit BRG of the drive circuit DRV is driven by the drive signals Sux to Swz.

  The energization or non-energization states of the six switching elements SUX to SWZ are individually controlled by the six drive signals Sux to Swz. Here, the larger the duty ratio, the longer the energization time per unit time in each switching element, and the larger the current flows through the coil. As a result, the rotational power of the electric motor MT is increased.

  The drive circuit DRV includes an energization amount acquisition unit (for example, a current sensor) IMA for each phase, and acquires (detects) an actual energization amount (generic name of each phase) Ima. So-called current feedback control is executed so that the detected value (actual current value) Ima of each phase matches the target values Iut, Ivt, and Iwt. Specifically, the duty ratios Dut, Dvt, Dwt are corrected (finely adjusted) based on the deviations between the actual energization amounts Ima and the target energization amounts Iut, Ivt, Iwt. With this current feedback control, highly accurate motor control can be achieved.

  The drive circuit DRV is supplied with power from a power source (storage battery BAT, generator ALT). In order to reduce fluctuations in the supplied power (voltage), the drive circuit DRV is provided with a stabilization circuit LPF. The stabilization circuit LPF is configured by a combination of at least one capacitor (capacitor) and at least one inductor (coil), and is a so-called LC circuit.

  As the electric motor MT, a brush motor (simply referred to as a brush motor) may be employed instead of the brushless motor. In this case, an H bridge circuit formed by four switching elements (power transistors) is used as the bridge circuit BRG. In other words, in the brush motor bridge circuit BRG, one of the three phases of the brushless motor is omitted. As in the case of the brushless motor, the electric motor MT is provided with a rotation angle sensor MK, and the drive circuit DRV is provided with a stabilization circuit LPF. Furthermore, the drive circuit DRV is provided with an energization amount sensor IMA.

<First processing example in long-term low-load state determination block>
A first processing example in the long-term low-load state determination block CHK will be described with reference to the flowchart of FIG. Here, the “long-term low load state” means that the situation in which the friction member MSB presses the rotating member KTr * of the rear wheel (the situation within the predetermined pressing range sfh) has already been continued for a predetermined long time. Or a high probability that the state will occur in the future. This braking state is not a load state that generates the maximum braking force of the wheels. However, since the relatively low braking load state continues for a long time, the braking members (CP, MSB, etc.) around the rear wheels are difficult to be cooled in the long-term low load state. Therefore, the rear wheel braking member (suspension part) is one of the thermally severe load conditions.

  First, in step S100, initial setting is executed. In the process of step S100, the rear wheel distribution ratio Hbn is set to a preset initial value hbo. For example, the initial value hbo can be set as a characteristic approximate to the ideal braking force distribution CRso (see block B160). The ideal braking force distribution is a braking force distribution in which the front and rear wheels are simultaneously locked even on road surfaces having different friction coefficients, and the vehicle braking force is maximized. In other words, in the ideal braking force distribution, the braking force is distributed along the dynamic load distribution of each wheel (the wheel load considering the acceleration acting on the vehicle body). Since the dynamic load distribution is determined by the vehicle specifications, the ideal braking force distribution can be set in advance based on the specifications. For example, the characteristic CRso corresponds to the calculation characteristics CPfo and CPro (see FIG. 3). At this time, the dynamic load variation is taken into consideration, and the characteristic CPfo is set to “convex downward” and the characteristic CPro is set to “convex upward”.

  In consideration of vehicle stability during turning braking, the initial value hbo can be set as a characteristic that follows the ideal braking force distribution CRso but slightly leaves a margin in the rear wheel braking force Fbr *. The distribution characteristic in this case has a shape (intermediate characteristic between characteristic CRso and characteristic CHbn) in which the ideal braking force distribution CRso is reduced in the direction of the rear wheel braking force Fbr *.

  In step S101, the vehicle position Pvh and the road gradient information Kmp are read. Next, in step S102, based on the vehicle position Pvh and the gradient information (particularly the gradient of the downhill road) Kmp, “downhill longer than the predetermined distance shd ahead of the road on which the vehicle is currently traveling” It is determined whether or not there is. This determination is referred to as “downhill determination”. In the downhill determination, it is not necessary that the downward gradient is continuous. For example, “whether or not the average value of the downward gradient is larger than the predetermined gradient kmx (predetermined predetermined value) over a predetermined distance shd”. (That is, whether the road ahead of the vehicle is a downhill having a predetermined gradient kmx when viewed as a whole) is determined.

  If the downhill determination is affirmed in step S102, the probability that a long-term low-load state will occur is high. If the determination in step S102 is affirmative (if “YES”), the process proceeds to step S110. On the other hand, when there is no downhill having a certain slope in front of the vehicle and the downhill determination in step S102 is negative (in the case of “NO”), the process returns to step S101.

  In step S110, the braking operation amount Bpa is read. Next, in step S120, based on the operation amount Bpa, it is determined whether or not the operation amount Bpa is greater than or equal to the lower value bpx. Here, the lower value bpx is a predetermined value (threshold value) used for determination, and is set in advance. If “Bpa ≧ bpx” and step S120 is affirmative (“YES”), the process proceeds to step S130. On the other hand, if “Bpa <bpx” and step S120 is negative (“NO”), the process returns to step S110.

  In step S130, based on the braking operation amount Bpa, it is determined whether or not the operation amount Bpa is less than the upper value bpz. Here, the upper value bpz is a predetermined value (threshold value) used for determination, and is set in advance as a value larger than the lower value bpx. If “Bpa <bpz” and step S130 is positive (“YES”), the process proceeds to step S140. On the other hand, if “Bpa ≧ bpz” and step S130 is negative (“NO”), the process returns to step S110.

  When the conditions of steps S120 and S130 are satisfied (that is, when “bpx ≦ Bpa <bpz” and in a low load braking state), time counting is started by timer processing in step S140. Here, the time point at which the determination in step S130 is satisfied for the first time (that is, the calculation cycle in which step S130 transitions from negative determination to positive determination) is set as the starting point of time (T = 0), and the elapsed time from this starting point Tkz is determined.

  In step S150, it is determined whether or not “elapsed time Tkz is equal to or longer than predetermined time tfx”. Here, the predetermined time tfx is a predetermined value (threshold value) used for determination, and is set in advance. If “Tkz ≧ tfx” and step S150 is affirmative (“YES”), the process proceeds to step S160. On the other hand, if “Tkz <tfx” and step S150 is negative (“NO”), the process returns to step S110.

  When the state of “bpx ≦ Bpa <bpz” is continued for a predetermined time tfx, the ratio Hbn is decreased from the initial value hbo and changed to the lower limit value (predetermined predetermined value) hbq in step S160. Is done. For example, the ratio Hbn is reduced from the initial value hbo to the lower limit value hbq so that the ideal braking force distribution characteristic CRso shown in the block B160 becomes the distribution characteristic CHbn in which the rear wheel braking force distribution is further reduced. Here, the initial ratio hbo corresponds to the calculation characteristics CPfo and CPro, and the calculation characteristics after the ratio Hbn is decreased and changed to the lower limit value hbq correspond to the characteristics CPfc and CPrc (see FIG. 3).

  Before the processing of step S160 is performed, the front wheel and rear wheel braking forces Fbf * and Fbr * are set to “point P: hbo = fro / (ffo + fro)” as indicated by the characteristic CRso of the block B160 (blowing part). It has been decided. When the process of step S160 is executed, the front wheel and rear wheel braking forces Fbf * and Fbr * are changed to “point Q: hbq = frq / (ffq + frq)” as indicated by the characteristic CHbn of the block B160.

  Accordingly, when the rear wheel distribution ratio Hbn is changed from the initial value hbo to the lower limit value hbq, the calculation characteristic of the target hydraulic pressure Pt is changed from the characteristic CRso to the characteristic CHbn. As a result, the front wheel braking force Fbf * and the rear wheel braking force Fbr * are relatively adjusted. That is, the front wheel braking force Fbf * is increased from the value ffo to the value ffq, and the rear wheel braking force Fbr * is decreased from the value fro to the value frq. This adjustment of the braking force is smoothly increased / decreased so as not to give the driver a sense of incongruity (for example, a discontinuity in the vehicle deceleration).

  Note that, in the determinations in step S120 and step S130, the operation amount Bpa being in the region “bpx to bpz” corresponds to “within the predetermined pressing range sfh” in the description of the long-term low-load state. Further, in the determination in step S150, the predetermined time tfx corresponds to “predetermined long time” in the description of the long-term low-load state. In addition, a decrease in the rear wheel distribution ratio Hbn is synonymous with an increase in the distribution ratio of the front wheel braking force.

  In the long-term low-load state determination block CHK, first, based on the vehicle position Pvh and the gradient information Kmp, it is determined whether or not “the probability that a long-term low-load state will occur is high (referred to as“ probability determination ”)”. The When the probability determination is affirmed, based on the operation amount Bpa, it is determined “whether or not a long-term low-load state has actually occurred.” When the probability determination is negative, the operation amount Bpa Judgment by is not performed. The “long-term low load state” is a state in which the pressing state of the rear wheel rotation member KTr * of the friction member MSB is within the predetermined pressing range sfh and this pressing state is continued for a predetermined time. The long-term low-load state is not so severe with the braking member for the front wheel, but is a thermally severe condition for the braking member (CP, MSB, etc.) provided on the rear wheel.

  In the probability determination, first, the current position of the vehicle on the road map is determined based on the vehicle position Pvh. The road information in the storage unit KMP corresponding to the vehicle position Pvh (especially the gradient information Kmp) is referred to, “the vehicle is ahead of the vehicle and is longer than the predetermined distance shd and has an average downward gradient larger than the predetermined value kmx. It is determined whether there is a slope or not (that is, downhill determination). “There is a downhill in front of the vehicle that is longer than the predetermined distance shd and whose average downward slope is larger than the predetermined value kmx”. “The pressing state of the rear wheel rotating member KTr * of the friction member MSB is the predetermined pressure. It is in the range sfh and is associated with “a state in which this pressing state continues for a predetermined time”. This is because when the downhill determination is affirmed, there is a high probability that a long-term low-load state will occur.

  Then, after the downhill determination is affirmed, based on the operation amount Bpa, “whether or not a long-term low load state actually occurs” is determined. If it is not determined that a long-term low load condition has occurred, the initial value hbo is adopted. For example, as the initial value hbo, a so-called characteristic approximating ideal braking force distribution (calculation characteristic CRso) can be adopted. When the long-term low-load state is determined, the initial value hbo is changed and corrected so that the ratio Hbn of the rear wheel braking force Fbr * to the entire braking force of the vehicle decreases.

  In a relatively weak braking operation (long-term low-load braking state) over a long period of time, a relatively high heat capacity is required for the rear wheel braking device (CP, MSB, etc.). When such a braking state is likely to occur and actually occurs, the braking force of the rear wheel is weakened, and the braking force by the front wheel braking member having a sufficient heat capacity is increased. For this reason, in various braking operations, the heat capacities of the braking devices for the front wheels and the rear wheels are optimized by the braking force distribution control, so that the entire braking control device can be reduced in size and weight.

  In addition, when a strong braking force is applied in a short time during sudden braking from high speed traveling (short-term high-load braking state different from long-term low-load braking state), the rear wheel braking force initial distribution ratio hbo Is adopted. In this short-term, high-load braking state, vehicle stability (for example, a straight traveling state is maintained without being laterally deflected) is desired. In a short-term high-load braking state, a preset rear wheel braking force distribution ratio (initial value) hbo is always adopted, so that the stability of the vehicle can be ensured. Here, as the initial value hbo, a so-called characteristic approximate to ideal braking force distribution (calculation characteristic CRso) can be adopted.

  In the long-term low-load state determination block CHK, “whether or not it is a long-term low-load state” can be determined based on the detection result Pcr * (corresponding to the rear wheel output) instead of the operation amount Bpa. Further, the determination can be made based on the target value Ptr *. The target hydraulic pressure Ptr * is calculated based on the operation amount Bpa. Therefore, in the long-term low load state determination block CHK, based on at least one of the braking operation amount Bpa and the actual hydraulic pressure Pcr * (rear wheel output by the rear wheel actuator) of the rear wheel pressure adjustment unit CAr *, It is determined whether or not “long-term low load state”. Based on this determination result, the ratio Hbn is determined. Even when the target hydraulic pressure Ptr * and the actual hydraulic pressure Pcr * are adopted, the same effect as that in the case of the operation amount Bpa is obtained.

  When there is a long downhill in front of the vehicle, the driver does not use the friction brake (that is, does not operate the braking operation member BP), and uses the engine brake and regenerative brake well, and goes down the downhill. There is. The ratio Hbn is decreased under the condition “existence of a long downhill road” and “continuation of bpx ≦ Bpa <bpz”. For this reason, when the driver does not use the friction brake so much, the ratio Hbn is not changed. The ratio Hbn can be reduced in consideration of the driver's braking operation.

  In the long-term low load state determination block CHK, the processing from step S110 to step S150 can be omitted. A long-term low-load braking state is likely to occur in a situation where the slope gradually descends from a high altitude (that is, when a relatively low braking force is continuously generated on a downhill road for a long time). In addition, in this driving situation, the center of gravity of the vehicle is slightly shifted from the rear wheel side to the front wheel side, and the vertical force of the rear wheel is reduced. Therefore, if there is a downhill longer than the predetermined distance shd and the average downhill is greater than the predetermined value kmx in front of the vehicle, and it is highly likely that a long-term low-load state will occur, the operation amount The process of step S160 can be executed immediately without making a determination based on Bpa or the like.

  By the distribution correction in step S160, the rear wheel braking force Fbr * is relatively weakened and the front wheel braking force Fbf * is relatively increased. As a result, the front / rear distribution of the braking force corresponding to the axial load variation caused by the slope of the slope can be achieved. In the case of a downward slope spelling (especially a hairpin curve), it is required to ensure the lateral force of the rear wheel. In such a traveling state, since the ratio Hbn of the rear wheel braking force is reduced, a sufficient rear wheel lateral force can be ensured and the stability of the vehicle can be maintained.

  It should be noted that “whether or not the processing from step S110 to step S150 is adopted (referred to as“ determination of necessity of braking operation condition ”) is the curve information of the downhill road ahead of the vehicle (for example, the curve radius Rmp, the curve Number). Normally (ie, in the initial characteristics), the necessity determination is not performed, and at least one of “relatively large curve radius of downhill road” and “relatively small number of curves” is When satisfied, the necessity determination is performed. On the contrary, the necessity determination is not normally performed (that is, in the initial characteristic), among “the relatively small curve radius of the downhill road” and “the relatively large number of curves”. The necessity determination can be executed when at least one of the above is satisfied. When the curve radius is small and the number of curves is large, the stability of the vehicle is more demanded.

<Second processing example in long-term low-load state determination block>
A second processing example in the long-term low-load state determination block CHK will be described with reference to the flowchart of FIG. In the first processing example, the actual occurrence of a long-term low load state is determined based on the magnitude relationship of the operation amount Bpa and the like, but in the second processing example, the appearance frequency of the operation amount Bpa and the like is analyzed. The long-term low load state is determined.

  In step S200, the same initial setting as in step S100 is performed. That is, the rear wheel distribution ratio Hbn is set to a preset initial ratio hbo. For example, the initial value hbo can be set to a characteristic approximate to the ideal braking force distribution CRso, or to the intermediate characteristic along the ideal braking force distribution CRso and having a margin for the rear wheel braking force.

  Thereafter, similarly to the first processing example, the vehicle position Pvh and the road gradient information Kmp are read in step S201. Next, in step S202, based on the vehicle position Pvh and the gradient information (particularly the downward gradient) Kmp, “a downhill longer than the predetermined distance shd is ahead of the road on which the vehicle is currently traveling”. Or not (downhill determination) "is executed. For example, the presence of the downhill is determined according to “whether or not the average value of the down slope is larger than the predetermined slope (predetermined value) kmx over the predetermined distance shd”.

  If the downhill determination is affirmed in step S202, the long-term low load state is highly likely to occur. If the determination in step S202 is affirmative (if “YES”), the process proceeds to step S210. On the other hand, when there is no downhill in front of the vehicle and the downhill determination in step S202 is negative (in the case of “NO”), the process returns to step S201.

  In step S210, the operation amount Bpa in the current calculation cycle is read and stored. Next, in step S220, the operation amount Bpa (a plurality of data) stored in the past is read. The operation amount Bpa read out here is data in a series of braking operations (stored since the start of the current braking operation).

  In step S230, the appearance frequency is analyzed based on the time-series plural operation amounts Bpa. A plurality of data are classified based on the magnitude of the operation amount Bpa, and the frequency that occurs repeatedly is counted as the appearance frequency of the operation amount Bpa. Specifically, the appearance frequency (ratio of all analysis data) Hnd from a predetermined lower value bpx to a predetermined upper value bpz, which is indicated by a hatched bar graph, is calculated. Here, the range from the lower value bpx to the upper value bpz corresponds to the predetermined pressing range sfh. Therefore, the appearance frequency Hnd is a frequency that occurs within the predetermined pressing range sfh in the plurality of stored operation amounts Bpa.

  In step S240, “whether or not the appearance frequency Hnd is equal to or higher than the predetermined frequency hnx” is determined based on the analyzed frequency Hnd. Here, the predetermined frequency hnx is a predetermined value (threshold value) used for determination, and is set in advance. If “Hnd ≧ hnx” and step S240 is affirmed (“YES”), the process proceeds to step S250. On the other hand, if “Hnd <hnx” and step S240 is negative (“NO”), the process returns to step S210.

  Similar to the first processing example, in step S250, time counting is started by timer processing. Specifically, the time point at which the determination in step S240 is satisfied for the first time (that is, the calculation cycle in which step S240 transitions from a negative determination to an affirmative determination) is set as a time starting point (T = 0). The elapsed time Tkz is counted.

  In step S260, it is determined whether or not “elapsed time Tkz is equal to or longer than predetermined time tfx”. Here, the predetermined time tfx (corresponding to “predetermined long time” in the description of the long-term low load state) is a predetermined value (threshold value) used for determination, and is set in advance. If “Tkz ≧ tfx” and step S260 is affirmative (“YES”), the process proceeds to step S270. On the other hand, if “Tkz <tfx” and step S260 is negative (“NO”), the process returns to step S210.

  When the appearance frequency Hnd satisfying “bpx ≦ Bpa <bpz” is equal to or higher than the predetermined frequency hnx, the rear wheel distribution ratio Hbn decreases from the initial value hbo in step S270. And changed to the lower limit hbq (<hbo). For example, the rear wheel distribution ratio Hbn is changed from the initial value hbo to the initial value hbo so as to become the braking force distribution characteristic CHbn in which the rear wheel distribution is further reduced from the ideal braking force distribution characteristic CRso shown in the block B270. To a smaller value (a preset lower limit value) hbq.

  As described in block B160 of step S160, as shown in block B270 (blowing portion) of step S270, the front wheel braking force Fbf * is smoothly increased from the value ffo to the value ffq, and the rear wheel braking force Fbr *. Is smoothly reduced from value fro to value frq (transition from point P to point Q). That is, the rear wheel braking force Fbr * is relatively decreased, and the front wheel braking force Fbf * is relatively increased. Here, the initial value hbo corresponds to the calculation characteristics CPfo and CPro, and the calculation characteristics after the ratio Hbn is decreased and changed to the lower limit value hbq correspond to the characteristics CPfc and CPrc (see FIG. 3).

  Further, as shown by the calculation characteristic CHbp indicated by a broken line, the rear wheel distribution ratio Hbn can be determined to decrease as the appearance frequency Hnd of the predetermined range sfh increases. In this case, when the appearance frequency Hnd becomes equal to the predetermined frequency hnx, the rear wheel distribution ratio Hbn is rapidly decreased from the initial value hbo to a predetermined value (intermediate value) hbp set in advance. Then, the rear wheel distribution ratio Hbn is monotonously decreased from the intermediate value hbp to the lower limit value hbq as the frequency Hnd increases until the frequency Hnd reaches an upper limit value hnz that is greater than the predetermined frequency hnx (characteristics of step S270). (See CHbp).

  Similar to the first processing example, in the second processing example, instead of the appearance frequency Hnd of the operation amount Bpa, at least one of the target hydraulic pressure Ptr * (target value) and the actual hydraulic pressure Pcr * (detected value). Based on one appearance frequency Hnd, it is determined whether or not it is a low-load state for a long time. Since the target hydraulic pressure Ptr * is calculated based on the manipulated variable Bpa, in other words, based on at least one of the manipulated variable Bpa and the actual hydraulic pressure Pcr * (rear wheel output), A low load condition determination can be made.

  In addition, in the second processing example, the processing steps from step S240 to step S260 can be omitted. Therefore, after it is determined that there is a long downhill in front of the vehicle, the appearance frequency Hnd of the operation amount Bpa or the like is analyzed, and the rear wheel braking force ratio Hbn is reduced based on this frequency Hnd.

  The second processing example also has the same effect as the first processing example. That is, since the preset initial value hbo is adopted for the short-term high-load braking state, the stability of the vehicle can be ensured. In a situation where there is a probability of occurrence of a braking state with a low load for a long period of time, the rear wheel distribution ratio Hbn is reduced based on the frequency Hnd within the predetermined pressing range sfh. For this reason, the braking force Fbr * of the rear wheel is weakened, the braking force Fbf * by the front wheel braking device having a sufficient heat capacity is increased, the heat capacity is optimized, and the rear wheel load caused by the downhill gradient is increased. A braking force distribution corresponding to the decrease can be achieved.

  Further, when the probability of occurrence of a long-term low load state is high, the rear wheel braking force ratio Hbn decreases based on the appearance frequency Hnd regardless of whether or not the long-term low load state actually occurs. Can be done. Similar to the first processing example, in the second processing example, “whether or not the processing from step S240 to step S260 is adopted” is the curve information of the downhill road ahead of the vehicle (for example, the curve radius Rmp, Based on the number of curves).

<Other embodiments>
In the embodiment described with reference to FIG. 1 and the like, the hydraulic pressures of the four wheel cylinders WC are controlled by the two pressure adjusting units CA driven by the electric motor MT. However, what is required of the braking control device according to the present invention is that the distribution of the braking force can be changed between the front and rear wheels of the vehicle.

  Therefore, as a configuration of the braking control device, as described in JP-A-2015-71382, “the hydraulic pressure is generated by one electric motor and the braking force of each wheel is controlled by an electromagnetic valve”, As described in Japanese Unexamined Patent Application Publication No. 2010-13014, “the hydraulic pressure stored in the accumulator is adjusted by a solenoid valve and the braking force of each wheel is controlled”, described in Japanese Patent Application Laid-Open No. 2014-51197. Such as “the one in which the braking force is controlled by an electric braking actuator that does not use fluid” may be employed. Even when such a configuration of the braking control device is employed, the same effect as described above can be obtained by determining the long-term low load state and reducing the ratio Hbn. When an electric braking actuator that does not use fluid is employed, instead of the hydraulic pressure sensor PC, a pressing force sensor that detects the force with which the friction member MSB presses the rotating member KT is used as a front wheel or rear wheel sensor. Adopted.

  In the above description, the determination of “whether or not there is a downhill for a predetermined distance shd ahead of the host vehicle (downhill determination)” is obtained from the navigation device NVS via the communication bus CMB. This is performed by the controller ECU based on the position Pvh and the road gradient information Kmp. However, the downhill determination can be made not only in the controller ECU but also in the navigation device NVS (particularly, the processing unit PRC). In this case, the downhill determination result is transmitted to the controller ECU through the communication bus CMB.

  The downhill determination may be executed by both the controller ECU and the navigation device NVS. Only when these two determination results match and the two determination results match, the rear wheel distribution ratio Hbn is reduced. By comparing the two determination results, the robustness of the downhill determination can be improved.

BP ... braking operation member, BPA ... operation amount sensor, CA ... pressure adjusting unit (front wheel, rear wheel actuator), PC ... control hydraulic pressure sensor (front wheel, rear wheel sensor), MT ... electric motor, MK ... rotation angle sensor, ECU ... Controller, CP ... Caliper, KT ... Rotating member, MSB ... Friction member, NVS ... Navigation device, PVH ... Position detecting unit, KMP ... Storage unit, Pvh ... Vehicle position, Kmp ... Gradient information, Hbn ... Rear wheel control Power ratio.

Claims (1)

A position detector for detecting the position of the vehicle;
A storage unit including road gradient information around the vehicle;
In a vehicle provided with a navigation device having
An operation amount sensor for detecting an operation amount of the braking operation member of the vehicle;
A front wheel actuator that presses a friction member against a front wheel rotating member that rotates integrally with the front wheel of the vehicle to generate a front wheel braking force on the front wheel;
A rear wheel actuator that presses a friction member against a rear wheel rotating member that rotates integrally with the rear wheel of the vehicle to generate a rear wheel braking force on the rear wheel;
A controller for controlling the front wheel actuator and the rear wheel actuator based on the operation amount;
A vehicle brake control device comprising:
The controller is
According to the determination result of "whether or not there is a downhill for a predetermined distance on the road ahead of which the vehicle is traveling" made based on the position of the vehicle and the gradient information,
A vehicle configured to reduce the distribution ratio of the rear wheel braking force to the total braking force acting on the vehicle when the determination result is affirmed compared to when the determination result is negative Braking control device.