JP2018012432A - Braking control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a braking control device for a vehicle that has a simple configuration and enables prompt supply of braking fluid to a wheel cylinder and improvement of braking torque increase responsiveness.SOLUTION: A braking control device increases hydraulic pressure of a wheel cylinder WC by using an electric motor MTR controlled based on an operation amount Bpa of a braking operation member BP of a vehicle to apply braking force to a wheel WH. The braking control device includes: a pressurization unit KAU having an accumulator ACC that is in fluid connection with the wheel cylinder WC via an on-off valve VAC and driven by the electric motor MTR; and a controller ECU for controlling the on-off valve VAC on the basis of the operation amount Bpa. The controller ECU calculates an operation speed dBp on the basis of the operation amount Bpa, maintains the on-off valve VAC at a closing position without change when the operation speed dBp is less than a predetermined speed dbz, and changes the on-off valve VAC from the closing position to an opening position when the operation speed dBp exceeds the predetermined speed dbz.SELECTED DRAWING: Figure 1

Description

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

  Patent Document 1 states that, for the purpose of “suppressing the response delay of the actual brake hydraulic pressure”, “the changing speed of the target brake hydraulic pressure BPt1 with respect to the first hydraulic pressure generating means (motor drive cylinder 13) is a predetermined value or more. At least one of the three conditions when the deviation ΔBP between the target brake hydraulic pressure BPt1 and the actual brake hydraulic pressure BPa is equal to or greater than a predetermined value and when the target brake hydraulic pressure BPt1 is equal to or greater than the predetermined value. Is established, the second hydraulic pressure controller (26a) drives the second hydraulic pressure generating means (the VSA device 26) so that the actual brake fluid pressure BPa approaches the target brake fluid pressure BPt1, thereby the actual brake fluid. It improves the responsiveness of the pressure BPa ".

  In the device described in Patent Document 1, two devices, a motor drive cylinder and a VSA device, are driven simultaneously in order to improve the response of actual braking fluid pressure. However, since both devices are driven by the electric motor, the rising speed of the rotation of the electric motor is limited due to the influence of the moment of inertia and the like.

  By the way, the actual response of the brake fluid pressure depends on the gap between the rotating member (brake disc) and the friction member (brake pad) (called a brake gap), the elastic deformation (compression deformation) of the friction member, and the like. Therefore, in order to improve the response of the brake fluid pressure (and consequently the brake torque), a relatively low-pressure brake fluid is supplied at the beginning of braking so as to close the brake gap and start elastic deformation of the friction member. Is effective. For this reason, what has a simple structure and can supply brake fluid quickly to a wheel cylinder is desired.

Japanese Unexamined Patent Publication No. 2015-110361

  An object of the present invention is to provide a simple configuration that can quickly supply a brake fluid to a wheel cylinder and improve an increase response of braking torque.

  The vehicle braking control apparatus according to the present invention increases the hydraulic pressure of the wheel cylinder (WC) by the electric motor (MTR) controlled based on the operation amount (Bpa) of the braking operation member (BP) of the vehicle, A braking force is applied to the wheel (WH). A vehicle braking control device includes an accumulator (ACC) fluidly connected to the wheel cylinder (WC) via an on-off valve (VAC), and a pressure unit (KAU) driven by the electric motor (MTR). And a controller (ECU) for controlling the on-off valve (VAC) based on the operation amount (Bpa).

  In the vehicle braking control apparatus according to the present invention, the controller (ECU) calculates an operation speed (dBp) based on the operation amount (Bpa), and the operation speed (dBp) is less than a predetermined speed (dbz). In some cases, the on-off valve (VAC) is maintained in the closed position, and when the operating speed (dBp) exceeds the predetermined speed (dbz), the on-off valve (VAC) is opened from the closed position to the open position. Change to

  In the vehicle braking control apparatus according to the present invention, the controller (ECU) opens the open / close valve (VAC) when the operation amount (Bpa) is “0 (zero)”, and the electric motor (MTR) Therefore, the accumulator (ACC) is accumulated.

  According to the above configuration, at the initial stage of the braking operation, the accumulator ACC supplies a relatively low-pressure braking fluid to the wheel cylinder WC (referred to as “pressurizing assist control”). As a result of the pressurization assist control, the clearance between the rotary member KT and the friction member MS is instantly reduced, and the elastic deformation of the friction member is started, so that the response of the brake fluid pressure increase is improved. Further, the pressure assist control by the accumulator ACC is not executed when the operation speed dBp of the braking operation member BP is less than the predetermined speed dbz, and is executed when the operation speed dBp exceeds the predetermined speed dbz. That is, appropriate pressurization assist control can be performed only when the response of the brake fluid pressure increase is required.

  Further, the accumulator ACC is accumulated by the pressurizing unit KAU when “Bpa = 0” (referred to as “accumulation control”). The on-off valve VAC has a slight leakage and may not accumulate pressure for a long time. For this reason, in accumulator ACC, the case where the fluid pressure required for gap filling etc. is not ensured may arise. When the brake operation member BP is not operated, pressure accumulation is performed in the accumulator ACC by the pressure accumulation control, and the necessary hydraulic pressure can be constantly maintained.

1 is an overall configuration diagram of a vehicle equipped with a vehicle braking control device according to the present invention. It is a functional block diagram for demonstrating the process in a controller. It is a flowchart for demonstrating pressurization assistance control. It is a flowchart for demonstrating pressure accumulation control.

<Overall Configuration of Brake Control Device for Vehicle according to the Present Invention>
A braking control device BCS according to the present invention will be described with reference to the overall configuration diagram of FIG. In the following description, constituent members, calculation processes, signals, characteristics, and values to which the same symbols are attached serve the same function. Therefore, duplicate description may be omitted.

  For vehicles equipped with the braking control device BCS, the braking operation member BP, the braking operation amount sensor BPA, the controller ECU, the master cylinder MC, the stroke simulator SSM, the simulator cutoff valve VSM, the pressurizing unit KAU, the switching valve VKR, the master cylinder piping HMC , A wheel cylinder pipe HWC and a pressure cylinder pipe HKC are provided. Furthermore, each wheel WH of the vehicle is provided with a brake caliper CP, a wheel cylinder WC, a rotating member KT, and a friction member MS.

  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. Brake caliper CP is arranged so as to sandwich rotating member KT. A brake caliper (also simply referred to as a caliper) CP is provided with a wheel cylinder WC. By adjusting (increasing or decreasing) the hydraulic pressure in the wheel cylinder WC of the caliper CP, 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 (for example, brake pad) MS is pressed against the rotating member KT, and a pressing force is generated. The rotating member KT and the wheel WH are fixed via a fixed shaft DS. For this reason, braking torque (braking force) is generated in the wheel WH by the frictional force generated by the pressing force.

  When the brake operation member BP is not operated, the friction member MS and the rotation member KT have a slight gap (“brake gap”) due to the elasticity of the cup seal in the wheel cylinder WC, the rotational vibration of the rotation member KT, and the like. It is maintained in the state with. For this reason, in the initial stage in which the brake operation member BP is operated, first, the flow rate of the brake fluid is required to close the brake gap. Since the brake gap is generated by the cup seal elasticity or the like, the hydraulic pressure of the brake fluid necessary to fill the gap is extremely low. Furthermore, after the friction member MS comes into contact with the rotating member KT, the flow rate of the brake fluid is also required to make the surface unevenness of the friction member MS uniform (that is, to slightly compress and deform). Similarly, the hydraulic pressure required for compressive deformation is also low.

  A braking operation amount sensor (also simply referred to as an operation amount sensor) BPA is provided on the braking operation member BP. The operation amount sensor BPA detects an operation amount (braking operation amount) Bpa of the braking operation member BP by the driver. Specifically, as the operation amount sensor BPA, a hydraulic pressure sensor that detects the pressure of the master cylinder MC, an operation displacement sensor that detects the operation displacement of the braking operation member BP, and an operation that detects the operation force of the braking operation member BP. At least one of the force sensors is employed. That is, the operation amount sensor BPA is a general term for the master cylinder hydraulic pressure sensor, the operation displacement sensor, and the operation force sensor. Accordingly, the brake operation amount Bpa is determined based on at least one of the hydraulic pressure of the master cylinder MC, the operation displacement of the brake operation member BP, and the operation force of the brake operation member BP. The operation amount Bpa is input to the controller ECU.

  The controller (electronic control unit) ECU includes an electric circuit board on which a microprocessor and the like are mounted, and a control algorithm programmed in the microprocessor. The controller ECU controls the pressurizing unit KAU, the shutoff valve VSM, the switching valve VKR, and the on-off valve VAC based on the braking operation amount Bpa. Specifically, based on a programmed control algorithm, signals (Su1 and the like) for controlling the electric motor MTR, the shutoff valve VSM, the switching valve VKR, and the on-off valve VAC are calculated and output from the controller ECU.

  The controller ECU outputs a drive signal Vsm that opens the shut-off valve VSM when the operation amount Bpa is equal to or greater than the predetermined value bp0, and the switching valve VKR switches between the pressurizing cylinder pipe HKC and the wheel cylinder pipe HWC. A drive signal Vkr for setting the communication state is output to each electromagnetic valve VSM, VKR. In this case, the master cylinder MC is in communication with the simulator SSM, and the pressure cylinder KCL is in communication with the wheel cylinder WC.

  The controller ECU calculates a drive signal (such as Su1) for driving the electric motor MTR based on the operation amount Bpa, the rotation angle Mka, and the pressing force Fpa (hydraulic pressure of the pressurizing cylinder KCL), and a drive circuit Output to DRV. Here, the braking operation amount Bpa is detected by the braking operation amount sensor BPA, the actual rotation angle Mka is detected by the rotation angle sensor MKA, and the actual pressing force Fpa is detected by the pressing force sensor FPA. The pressure of the brake fluid in the wheel cylinder WC is controlled (maintained, increased, or decreased) by the pressurizing unit KAU driven by the electric motor MTR.

  The master cylinder MC is mechanically connected to the brake operation member BP via the brake rod BRD. The master cylinder MC converts the operation force (brake pedal depression force) of the brake operation member BP into the pressure of the brake fluid. When the master cylinder pipe HMC is connected to the master cylinder MC and the brake operation member BP is operated, the brake fluid is discharged (pressure-fed) from the master cylinder MC to the master cylinder pipe HMC. The master cylinder pipe HMC is a fluid path that connects the master cylinder MC and the switching valve VKR.

  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 referred to simply as a cutoff valve) VSM is provided between the hydraulic chamber in the master cylinder MC 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 MC 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 MC 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. The braking fluid is moved from the master cylinder MC to the simulator SSM, and the piston is pushed by the flowing braking fluid. A force is applied to the piston in a direction that prevents the inflow of the brake fluid by the elastic body. An operating force (for example, a brake pedal depression force) when the braking operation member BP is operated is formed by the elastic body.

≪Pressure unit KAU≫
The pressurizing unit KAU discharges (pressurizes) the brake fluid to the pressurizing cylinder pipe HKC using the electric motor MTR as a power source. And with this pressure, the pressurizing unit KAU presses (presses) the friction member MS against the rotating member KT, and applies braking torque (braking force) to the wheel WH. In other words, the pressurizing unit KAU generates a force (pressing force) for pressing the friction member MS against the rotating member KT by the electric motor MTR.

  The pressure unit KAU includes an electric motor MTR, a drive circuit DRV, a power transmission mechanism DDK, a pressure rod KRD, a pressure cylinder KCL, a pressure piston PKC, and a pressure sensor FPA.

  The electric motor MTR is a power source for the pressurization cylinder KCL to adjust the pressure of the brake fluid in the wheel cylinder WC (pressurization, decompression, etc.). For example, a three-phase brushless motor is employed as the electric motor MTR. The electric motor MTR has three coils CLU, CLV, and CLW, and is driven by the drive circuit DRV. The electric motor MTR is provided with a rotation angle sensor MKA that detects a rotor position (rotation angle) Mka of the electric motor MTR. The rotation angle Mka is input to the controller ECU.

  The drive circuit DRV is an electric circuit board on which a switching element (power semiconductor device) for driving the electric motor MTR is mounted. Specifically, a three-phase bridge circuit is formed in the drive circuit DRV, and the energization state to the electric motor MTR is controlled based on the drive signal (Su1 or the like). The drive circuit DRV is provided with an energization amount sensor (for example, a current sensor) IMA that detects an actual energization amount Ima (generic name of each phase) to the electric motor MTR. The energization amount (detection value) Ima of each phase is input to the controller ECU.

  The power transmission mechanism DDK decelerates the rotational power of the electric motor MTR, converts it into linear power, and outputs it to the pressure rod KRD. Specifically, the power transmission mechanism DDK is provided with a speed reducer (not shown), and the rotational power from the electric motor MTR is decelerated and output to a screw member (not shown). Then, the rotational power is converted into the linear power of the pressure rod KRD by the screw member. That is, the power transmission mechanism DDK is a rotation / linear motion conversion mechanism.

  A pressure piston PKC is fixed to the pressure rod KRD. The pressure piston PKC is inserted into the inner hole of the pressure cylinder KCL to form a combination of the piston and the cylinder. Specifically, a sealing member (not shown) is provided on the outer periphery of the pressurizing piston PKC, and liquid tightness is ensured between the pressurizing cylinder KCL and the inner hole (inner wall). That is, a pressure chamber Rkc that is partitioned by the pressure cylinder KCL and the pressure piston PKC and filled with the brake fluid is formed.

  In the pressure cylinder KCL, the volume of the pressure chamber Rkc is changed by moving the pressure piston PKC in the central axis direction. Due to this volume change, the brake fluid is moved between the pressure cylinder KCL and the wheel cylinder WC via the brake pipes (fluid paths) HKC and HWC. The hydraulic pressure in the wheel cylinder WC is adjusted by taking in and out the brake fluid from the pressure cylinder KCL, and as a result, the force (pressing force) by which the friction member MS presses the rotating member KT is adjusted.

  For example, as the pressing force sensor FPA, a hydraulic pressure sensor that detects the hydraulic pressure Fpa of the pressurizing chamber Rkc is built in the pressurizing unit KAU (particularly, the pressurizing cylinder KCL). A hydraulic pressure sensor (corresponding to a pressing force sensor) FPA is fixed to the pressurizing cylinder KCL and integrally configured as a pressurizing unit KAU. The detection value Fpa of the pressing force (that is, the hydraulic pressure in the pressurizing chamber Rkc) is input to the controller ECU.

  The pressurizing unit KAU includes an accumulator ACC and an accumulator on / off valve (also simply referred to as an on / off valve) VAC. The accumulator ACC is accumulated when the braking operation member BP is not operated. When the operation speed dBp of the braking operation member BP is fast, the pressurization of the wheel cylinder WC is assisted by the hydraulic pressure in the accumulator ACC. Specifically, the operation speed dBp is calculated based on the operation amount Bpa. When the operation speed dBp is less than the predetermined speed dbz, the on-off valve VAC is set to the closed position. When the operation speed dBp is satisfied to be equal to or higher than the predetermined speed dbz, the on-off valve VAC is changed from the closed position to the open position. As a result, the brake fluid stored in the accumulator ACC is moved toward the wheel cylinder WC. The on-off valve VAC is changed from the open position to the closed position after continuing a predetermined time tka (referred to as “auxiliary time”).

  The accumulator ACC supplies brake fluid for filling the brake gap and compressing the surface irregularities of the friction member MS. For this purpose, a high hydraulic pressure is not required, so the hydraulic pressure of the brake fluid stored in the accumulator ACC is not so high as to produce the maximum deceleration of the vehicle. That is, the hydraulic pressure corresponding to the filling of the brake gap and the compression of the surface unevenness of the friction member MS (referred to as “gap filling hydraulic pressure”) is set in advance. Then, the brake fluid is stored in the accumulator ACC at the gap filling fluid pressure paz.

  One of the important matters for improving the response to increase in braking torque (braking force of the wheel WH) during sudden braking is that the gap between the rotating member KT and the friction member MS (for example, the brake disc and the brake pad) Is quickly eliminated, and the elastic deformation of the friction member MS is accelerated so that the friction member MS is pressed against the rotating member KT. This is achieved by supplying a predetermined amount (predetermined volume) of a relatively low pressure brake fluid in the initial stage of braking. The brake fluid accumulated in the accumulator ACC is supplied to the wheel cylinder WC over an auxiliary time tka, which is a relatively short time, when the on-off valve VAC is changed to the open position. Before the pressurizing cylinder KCL discharges the brake fluid, the brake gap is closed by pressurization from the accumulator ACC. And since the elastic deformation of the friction member MS is instantly started, the response of the braking force can be improved. The pressurizing unit KAU has been described above.

  The switching valve VKR switches between “a state in which the wheel cylinder WC is connected to the master cylinder MC” and “a state in which the wheel cylinder WC is connected to the pressurizing cylinder KCL”. The switching valve VKR is controlled based on a drive signal Vkr from the controller ECU. Specifically, when the braking operation is not performed (when “Bpa <bp0”), the wheel cylinder pipe HWC is brought into communication with the master cylinder pipe HMC via the switching valve VKR and pressurized. The cylinder piping HKC is not communicated (blocked). Here, the wheel cylinder pipe HWC is a fluid path connected to the wheel cylinder WC. When a braking operation is performed (that is, when “Bpa ≧ bp0” is established), the switching valve VKR is excited based on the drive signal Vkr, the communication between the wheel cylinder pipe HWC and the master cylinder pipe HMC is cut off, and the wheel The cylinder pipe HWC and the pressure cylinder pipe HKC are brought into communication.

<Processing in controller ECU>
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 a brushless motor is employed as the electric motor MTR will be described. Note that, as described above, components having the same symbol, arithmetic processing, signals, characteristics, and values exhibit the same function.

  In the controller ECU, the electric motor MTR is driven and the electromagnetic valves VSM, VKR, and VAC are excited based on the operation amount Bpa of the braking operation member BP. A switching circuit SU1, SU2, SV1, SV2, SW1, SW2 (simply referred to as “SU1 to SW2”) forms a drive circuit DRV (three-phase bridge circuit). Driving of the electric motor MTR is executed by the drive circuit DRV. Specifically, signals Su1, Su2, Sv1, Sv2, Sw1, Sw2 (simply referred to as “Su1 to Sw2”) for driving the switching elements SU1 to SW2 are calculated by the controller ECU. The controller ECU determines signals Vsm, Vkr, and Vac for driving the electromagnetic valves VSM, VKR, and VAC.

  The controller ECU includes a target pressing force calculation block FPT, an instruction energization amount calculation block IMS, a pressing force feedback control block FFB, a target energization amount calculation block IMT, a switching control block SWT, a solenoid valve control block SLC, a pressurization auxiliary control block KAH, And it is comprised by the pressure accumulation control block CKA.

  In the target pressing force calculation block FPT, the target pressing force Fpt is calculated based on the braking operation amount Bpa and the calculation characteristic (calculation map) CFpt. Here, the target pressing force Fpt is a target value of the hydraulic pressure (corresponding to the pressing force) generated by the pressurizing unit KAU. Specifically, in the calculation characteristic CFpt, the target pressing force Fpt is calculated as “0 (zero)” in the range where the braking operation amount Bpa is greater than zero (corresponding to the case where the braking operation is not performed) and less than the predetermined value bp0. When the operation amount Bpa is equal to or greater than the predetermined value bp0, the target pressing force Fpt is calculated so as to monotonically increase from “0” as the operation amount Bpa increases. Here, the predetermined value bp0 is a value corresponding to “play” of the braking operation member BP.

  In the command energization amount calculation block IMS, based on the target pressing force Fpt and preset calculation characteristics (calculation maps) CIup and CIdw, the command energization amount Ims (electric motor) of the electric motor MTR that drives the pressurizing unit KAU The energization amount target value for controlling the MTR is calculated. The calculation map for the command energization amount Ims takes into consideration the influence of hysteresis due to the power transmission mechanism DDK or the like, and includes a characteristic CIup when the target pressing force Fpt increases and a characteristic CIdw when the target pressing force Fpt decreases. It consists of two characteristics.

  Here, the “energization amount” is a state amount (state variable) for controlling the output torque of the electric motor MTR. Since the electric motor MTR outputs a torque approximately proportional to the current, the current target value of the electric motor MTR can be used as the target value of the energization amount (target energization amount). Further, if the supply voltage to the electric motor MTR 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 pressing force feedback control block FFB, the target value (for example, target hydraulic pressure) Fpt of the pressing force and the actual value (hydraulic pressure detection value) Fpa of the pressing force are set as control state variables, and based on these, the electric motor A compensation energization amount Ifp of MTR is calculated. Since an error occurs in the pressing force only by the control based on the command energization amount Ims, the pressing force feedback control block FFB compensates for this error. The pressing force feedback control block FFB includes a comparison calculation and a compensation energization amount calculation block IFP.

  By the comparison calculation, the target value Fpt of the pressing force is compared with the actual value Fpa. Here, the actual value Fpa of the pressing force is a detection value detected by a pressing force sensor FPA (for example, a hydraulic pressure sensor that detects the hydraulic pressure of the pressure cylinder KCL). In the comparison calculation, a deviation (pressing force deviation) eFp between the target pressing force (target value) Fpt and the actual pressing force (detected value) Fpa is calculated. The pressing force deviation eFp (which is a control variable and is “pressure” as a physical quantity) is input to the compensation energization amount calculation block IFP.

  The compensation energization amount calculation block IFP includes a proportional element block, a differential element block, and an integral element block. In the proportional element block, the proportional force Kp is multiplied by the pressing force deviation eFp to calculate the proportional element of the pressing force deviation eFp. In the differential element block, the pressing force deviation eFp is differentiated, and this is multiplied by the differential gain Kd to calculate the differential element of the pressing force deviation eFp. In the integral element block, the pressing force deviation eFp is integrated, and this is multiplied by an integral gain Ki to calculate an integral element of the pressing force deviation eFp. Then, the compensation energization amount Ifp is calculated by adding the proportional element, the differential element, and the integral element. That is, in the compensation energization amount calculation block IFP, the actual pressing force (detected value) Fpa is converted to the target pressing force (target value) Fpt based on the comparison result (the pressing force deviation eFp) between the target pressing force Fpt and the actual pressing force Fpa. So that the deviation eFp approaches “0 (zero)”, so-called PID control based on the pressing force is executed.

  In the target energization amount calculation block IMT, based on the command energization amount (target value) Ims, the compensation energization amount (compensation amount by the pressing force feedback control) Ifp, and the pressure accumulation energization amount Ick, a final target value of the energization amount is obtained. A certain target energization amount Imt is calculated. Specifically, the compensation energization amount Ifp and the pressure accumulation energization amount Ick are added to the command energization amount Ims, and the sum thereof is calculated as the target energization amount Imt (that is, Imt = Ims + Ifp + Ick). Here, the pressure accumulation energization amount Ick will be described later.

  In the target energization amount calculation block IMT, the sign (the sign of the value) of the target energization amount Imt is determined based on the direction in which the electric motor MTR should rotate (that is, the increase / decrease direction of the pressing force). Further, the target energization amount Imt is calculated based on the rotational power to be output from the electric motor MTR (that is, the amount of increase / decrease in the pressing force). Specifically, when increasing the braking pressure, the sign of the target energization amount Imt is calculated as a positive sign (Imt> 0), and the electric motor MTR is driven in the forward rotation direction. On the other hand, when decreasing the braking pressure, the sign of the target energization amount Imt is determined to be a negative sign (Imt <0), and the electric motor MTR is driven in the reverse direction. Furthermore, the output torque (rotational power) of the electric motor MTR is controlled to increase as the absolute value of the target energization amount Imt increases, and the output torque is controlled to decrease as the absolute value of the target energization amount Imt decreases. .

  In the switching control block SWT, drive signals Su1 to Sw2 for performing pulse width modulation on the switching elements SU1 to SW2 are calculated based on the target energization amount Imt. When the electric motor MTR is a brushless motor, the target value Imt (generic name of each phase) of the energization amount of each phase (U phase, V phase, W phase) is based on the target energization amount Imt and the rotation angle Mka. Calculated. Based on the target energization amount Imt of each phase, the duty ratio of the pulse width of each phase (ratio of on time with respect to one cycle) Dut is determined. Then, based on the duty ratio (target value) Dut, whether each of the switching elements SU1 to SW2 constituting the three-phase bridge circuit is turned on (energized state) or turned off (non-energized state) Drive signals Su1 to Sw2 are calculated. The drive signals Su1 to Sw2 are output to the drive circuit DRV.

  The energization or non-energization states of the six switching elements SU1 to SW2 are individually controlled by the six drive signals Su1 to Sw2. Here, as the duty ratio Dut (generic name of each phase) is larger, the energization time per unit time is lengthened in each switching element, and a larger current flows in the coil. Therefore, the rotational power of the electric motor MTR is increased.

  The drive circuit DRV is provided with an energization amount sensor (for example, a current sensor) IMA for each phase, and an actual energization amount Ima (a generic name for each phase) is detected. The detected value (for example, actual current value) Ima of each phase is input to the switching control block SWT. Then, so-called current feedback control is executed so that the detection value Ima of each phase matches the target value Imt. Specifically, in each phase, the duty ratio Dut is corrected (finely adjusted) based on the deviation between the actual energization amount Ima and the target energization amount Imt. With this current feedback control, highly accurate motor control can be achieved.

  In the solenoid valve control block SLC, drive signals Vsm, Vkr, and Vac for controlling the solenoid valves VSM, VKR, and VAC are calculated based on the operation amount Bpa. When the operation amount Bpa is less than the predetermined amount bp0 (particularly, when “Bpa = 0”), the drive signal Vsm is determined so that the simulator cutoff valve VSM is set to the open position in response to the non-braking operation ( For example, when the shutoff valve VSM is an NC valve, the drive signal Vsm indicates non-excitation). At the same time, in the case of “Bpa <bp0”, “the master cylinder MC and the wheel cylinder WC are communicated and the pressurizing cylinder KCL and the wheel cylinder WC are shut off (referred to as a non-excited state)”. A drive signal Vkr is calculated.

  The operation amount Bpa is increased and the time after the operation amount Bpa becomes equal to or greater than the predetermined amount bp0 corresponds to the time of braking operation, and at that time (braking operation start time), the shutoff valve VSM is changed from the closed position to the open position. Thus, the drive signal Vsm is determined. When the shutoff valve VSM is an NC valve, an excitation instruction is started as the drive signal Vsm at the start of the braking operation. Further, the drive signal Vkr is set so that “the master cylinder MC and the wheel cylinder WC are disconnected and the pressurizing cylinder KCL and the wheel cylinder WC are in communication (referred to as an excited state)” at the start of the braking operation. It is determined.

  In the electromagnetic valve control block SLC, drive signals Vkr and Vac for the switching valve VKR and the accumulator opening / closing valve VAC are determined so as to correspond to the pressurization assist control and the pressure accumulation control. The pressure assist control is to supply the brake fluid from the accumulator ACC to the wheel cylinder WC so as to improve the response of the increase of the braking torque in the initial stage of the braking operation. Further, the pressure accumulation control is for accumulating the accumulator ACC when the operation of the braking operation member BP is not performed (that is, the condition of “Bpa = 0”). Next, pressurization auxiliary control and pressure accumulation control will be described.

  In the pressure assist control block KAH, a signal (control flag) FLka indicating execution of the pressure assist control is determined. In the control flag FLka, “0 (zero)” indicates non-execution of pressurization assist control, and “1” indicates execution of pressurization assist control. Therefore, the time when the control flag FLka changes from “0 (non-execution)” to “1 (control execution)” is the start time of the pressure assist control.

  In the pressure assist control block KAH, the braking operation speed dBp is calculated based on the braking operation amount Bpa. Specifically, the operation amount Bpa is differentiated with respect to time, and the operation speed dBp is calculated. When the operation speed dBp is less than the predetermined speed dbz (that is, when the braking operation is not sudden), the pressure assist control is not executed. When the operation speed dBp becomes equal to or higher than the predetermined speed dbz (calculation cycle in which the sudden operation is determined), execution of the pressure assist control is started. When the pressurization assist control is started, “FLka = 1” is output to the solenoid valve control block SLC. The predetermined speed dbz is a preset threshold value (predetermined value).

  Driving so that the on-off valve VAC is changed from the closed position to the open position when the control flag FLka transits from “0 (control not executed)” to “1 (control executed)” in the solenoid valve control block SLC. A signal Vac is output. At the same time, the drive signal Vkr causes the changeover valve VKR to change from “the communication between the master cylinder MC and the wheel cylinder WC and the communication between the pressure cylinder KCL and the wheel cylinder WC” (de-energized state) to the “master cylinder”. The MC is switched to the non-communication between the wheel cylinder WC and the communication between the pressure cylinder KCL and the wheel cylinder WC (excitation state).

  As a result, before the brake fluid is discharged from the pressure cylinder KCL, the brake fluid is discharged from the accumulator ACC toward the wheel cylinder WC. By this movement of the brake fluid, the brake gap between the rotating member KT and the friction member MS is closed, and compression of the friction member MS is started. For this reason, the rising response of the braking torque is improved.

  In the pressure assist control block KAH, when the predetermined time tka has elapsed from the time point when the pressure assist control is started, the pressure assist control is terminated. With the end of the pressurization assist control, the on-off valve VAC is changed from the open position to the closed position. When a little time has elapsed from the start of braking, the electric motor MTR starts supplying braking fluid from the pressurizing cylinder KCL to the wheel cylinder WC. For this reason, the on-off valve VAC is closed to prevent the brake fluid from being consumed by the accumulator ACC. It should be noted that, in the passage of time when a sudden braking operation is performed, “operation start of the brake operation member BP” → “change of the on-off valve VAC to the open position” → “pressure cylinder KCL starts to discharge brake fluid” → The state transition is performed in the order of “change the on-off valve VAC to the closed position”. Accordingly, the predetermined time tka corresponds to a time during which no brake fluid is discharged from the pressurizing cylinder KCL after the start of the braking operation. The predetermined time tka is set in advance based on the specifications of the braking control device (for example, the performance of the MTR).

  Since the braking fluid is discharged from the accumulator ACC by the pressurization assist control, the accumulator ACC needs to be accumulated for the next pressurization assist control. For this reason, in the pressure accumulation control, the accumulator ACC is accumulated to the gap filling hydraulic pressure paz based on the operation amount Bpa and the control flag FLka.

  In the pressure accumulation control block CKA, the pressure accumulation energization amount Ick and the drive signals Vkr and Vac are determined based on the operation amount Bpa and the control flag FLka. Here, the pressure accumulation energization amount Ick is a target value of the electric motor MTR for executing pressure accumulation control. The pressure accumulation control is executed when the operation of the braking operation member BP is not performed (that is, when the condition “Bpa = 0” is satisfied). Accordingly, the accumulated pressure energization amount Ick is input to the target energization amount calculation block IMT. However, when “Bpa = 0”, “Ims = 0, Ifp = 0”, “Imt = Ick” during execution of the accumulation pressure control. Is calculated. Details of the pressure accumulation control block CKA will be described later.

<Processing of auxiliary pressure control block>
With reference to the flowchart of FIG. 3, the process in the pressurization auxiliary control block KAH will be described. In order to improve the response of the rising of the braking torque (WH braking force) (increase from 0), the gap between the rotating member KT and the friction member MS is instantaneously filled, and the friction member MS is compressed and deformed. It is necessary to speed up. In the pressurization assist control, when the responsiveness is required (that is, when “dBp ≧ dbz”), braking fluid is supplied from the accumulator ACC to fill the gap.

  First, in step S110, the braking operation amount Bpa is read. Next, in step S120, the braking operation speed dBp is calculated based on the operation amount Bpa. Specifically, the operation amount Bpa is differentiated with respect to time, and the operation speed dBp is calculated.

  In step S130, “whether or not the operation speed dBp is equal to or higher than a predetermined speed dbz” is determined. Here, the predetermined speed dbz is a predetermined value set in advance as a threshold value for determination. If “dBp <dbz” and step S130 is negative (“NO”), the process returns to step S110. On the other hand, if “dBp ≧ dbz” and step S130 is positive (if “YES”), the process proceeds to step S140.

  In step S140, pressure assist control is executed. Specifically, for the first time, “FLka = 1” is output to the solenoid valve control block SLC when step S130 is satisfied (calculation cycle). In the electromagnetic valve control block SLC, a drive signal Vac for switching the open / close valve VAC from the closed position to the open position is determined in response to the state transition of the control flag FLka. At this time, on the basis of the operation amount Bpa, the switching valve VKR is in a state of “communication between the master cylinder MC and the wheel cylinder WC and no communication between the pressure cylinder KCL and the wheel cylinder WC” (de-energized state). The state is switched to the “non-communication between the master cylinder MC and the wheel cylinder WC and the communication between the pressure cylinder KCL and the wheel cylinder WC” (excitation state).

  The duration of the process in step S140 is counted. When the continuation time is equal to or longer than the predetermined time tka, the pressure assist control in step S140 is ended. This is to prevent the brake fluid in the accumulator ACC from moving and prevent the discharge fluid from the pressure cylinder KCL from being consumed by the accumulator ACC. Here, the predetermined time tka is a predetermined value set in advance and is a value corresponding to the time from the start of operation of the braking operation member BP to the start of discharge of the brake fluid from the pressure cylinder KCL.

<Processing of pressure accumulation control block>
With reference to the flowchart of FIG. 4, the process in the pressure accumulation control block CKA will be described. In the pressure assist control, the brake fluid is replenished from the accumulator ACC to the wheel cylinder WC. In the pressure accumulation control, the accumulator ACC is filled with the brake fluid. The pressure accumulation control is executed when the braking operation member BP is not operated.

  First, in step S210, the operation amount Bpa and the control flag FLka for the pressure assist control are read. Next, in step S220, based on the operation amount Bpa, it is determined whether or not the braking operation member BP is being operated. If “Bpa> 0” and step S220 is positive (if “YES”), the process returns to step S210. On the other hand, if “Bpa = 0” and step S220 is negative (“NO”), the process proceeds to step S230.

  In step S230, based on the control flag FLka, it is determined whether or not the auxiliary pressurization control has been executed during the previous braking operation. If step S230 is positive (if “YES”), the process proceeds to step S260. On the other hand, when step S230 is negative (when “NO”), the process proceeds to step S240.

  In step S240, an elapsed time Tck from the time when the previous pressure accumulation control is completed is calculated. Then, in step S250, “whether or not the elapsed time Tck is equal to or longer than the predetermined time tcz” is determined. If “Tck <tcz” and step S250 is negative (“NO”), the process returns to step S210. On the other hand, if “Tck ≧ tcz” and step S250 is positive (if “YES”), the process proceeds to step S260. Here, the predetermined time tcz is a threshold value set in advance for determination.

  In step S260, pressure accumulation control is executed. Specifically, for the first time, when step S260 is satisfied (calculation cycle), the accumulated energization amount Ick is output to the target energization amount calculation block IMT, and “FLck = 1” is output to the solenoid valve control block SLC. Is output. Here, the pressure accumulation energization amount Ick is a target energization amount of the electric motor MTR for pressure accumulation control. The accumulator energization amount Ick is based on a preset time series pattern, and the starting point of the accumulator control is started, and the electric motor MTR is driven to rotate forward. Here, the time series pattern is set in advance so as to increase the hydraulic pressure in the accumulator ACC to the gap filling hydraulic pressure paz. Here, the clearance filling fluid pressure paz is a fluid pressure that is necessary and sufficient to close the brake clearance, and is a predetermined fluid pressure set in advance.

  In the electromagnetic valve control block SLC, a drive signal Vac for switching the on-off valve VAC from the closed position to the open position is determined in response to the transition of the control flag FLck from “0” to “1”. At the same time, the switching valve VKR is switched from the “communication between the master cylinder MC and the wheel cylinder WC and the communication between the pressure cylinder KCL and the wheel cylinder WC” (non-excited state) to the “master cylinder MC and wheel cylinder WC. The drive signal Vkr is output so as to be switched to a state (excitation state) in which the pressure cylinder KCL and the wheel cylinder WC are in communication with each other.

  The duration of the process in step S260 is counted. When the duration time is equal to or longer than the predetermined time tcz, the pressure accumulation control in step S260 is terminated. At the end of the pressure accumulation control, the on-off valve VAC is switched from the open position to the closed position. Further, the switching valve VKR is changed from the excited state to the non-excited state. Thereafter, the electric motor MTR is driven in reverse and returned to the initial position corresponding to “Bpa = 0”.

  There may be a slight leak in the on-off valve VAC. Therefore, the accumulator ACC is not kept in the pressure accumulation state for a long time, and the liquid pressure necessary for gap filling or the like may not be ensured. When the braking operation is not performed by the pressure accumulation control, pressure accumulation is performed in the accumulator ACC, and the necessary hydraulic pressure can be constantly maintained.

  An accumulator sensor PAC (pressure sensor) that detects the fluid pressure Pac in the accumulator ACC is provided, and accumulation control can be executed based on the accumulator fluid pressure Pac (see FIG. 1). Specifically, based on the accumulator hydraulic pressure Pac, “whether or not the accumulator hydraulic pressure Pac is equal to or higher than the gap filling hydraulic pressure (predetermined value) paz” is determined. In the case of “Pac ≧ paz”, the pressure accumulation control is not executed. On the other hand, in the case of “Pac <paz”, the pressure accumulation control is executed. Here, the gap filling fluid pressure paz is a threshold value for determination. Specifically, the hydraulic pressure corresponding to filling of the brake gap and compression of the surface unevenness of the friction member MS is set in advance. When the determination based on the accumulator hydraulic pressure Pac is employed, the processes of steps S240 and S250 can be omitted.

<Other embodiments>
Hereinafter, other embodiments will be described. In other embodiments, the same effects as described above are obtained. That is, in the initial stage of the braking operation (before the brake fluid is discharged from the pressurizing unit KCL), a relatively low pressure brake fluid is supplied from the accumulator ACC to the wheel cylinder WC. As a result, the friction member MS starts to be compressed and deformed, and the increase response of the braking torque is improved.

  In the above description, the configuration of the disc type braking device (disc brake) has been exemplified. In this case, the friction member MS 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 MS is a brake shoe, and the rotating member KT is a brake drum.

  As the electric motor MTR, 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. That is, in the bridge circuit of the brush motor, one of the three phases of the brushless motor is omitted. As in the case of the brushless motor, the electric motor MTR is provided with a rotation angle sensor MKA. Furthermore, the drive circuit DRV is provided with an energization amount sensor IMA.

BP ... Brake operation member, MTR ... Electric motor, KAU ... Pressure unit, ACC ... Accumulator, ECU ... Controller, VAC ... Open / close valve, BPA ... Operation amount sensor, FPA ... Pressure force sensor, Bpa ... Operation amount, dBp ... Operation speed.

Claims (2)

A braking control device for a vehicle that increases a hydraulic pressure of a wheel cylinder and applies a braking force to a wheel by an electric motor controlled based on an operation amount of a braking operation member of the vehicle,
A pressurizing unit having an accumulator fluidly connected to the wheel cylinder via an on-off valve and driven by the electric motor;
A controller for controlling the on-off valve based on the operation amount;
With
The controller is
Calculate the operation speed based on the operation amount,
If the operating speed is less than a predetermined speed, the on-off valve is maintained in the closed position,
A braking control device for a vehicle, wherein when the operation speed exceeds the predetermined speed, the on-off valve is changed from a closed position to an open position. The vehicle braking control device according to claim 1,
The controller is
A braking control device for a vehicle, wherein when the operation amount is zero, the on-off valve is opened and the accumulator is accumulated by the electric motor.