JP2015044547A - Electrically-driven control device of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrically-driven control device of a vehicle which reduces a load of data communication performed between the car body side and the wheel side and can easily secure responsibility of an electric motor.SOLUTION: In an electrically-driven control device of a vehicle, a pressing member PSN presses a friction member MSB against a rotation member KTB fastened to a wheel by utilizing a driving torque of an electric motor MTR and, thereby, generates a brake torque to the wheel. Actual state gaining means FBA, PSA, MKA disposed on the wheel WHL side gain an actual value (actual pressing state) of the pressing state of the pressing member. Target state calculation means TRG disposed on the car body side of the vehicle calculates a target value (target pressing state) of the pressing state based on an operation amount of the brake operation member BP by means of a driver. A signal expressing the target pressing state is transmitted from the target state calculation means TRG to driving means DRV disposed on the wheel side via a bus SCB. The driving means DRV controls the electric motor based on the target pressing state and the actual pressing state.

Description

  The present invention relates to an electric braking device for a vehicle.

  In Patent Document 1, for the purpose of “reducing the cost of the bent cable and providing an inexpensive brake device”, “a drive control device for controlling the electric motor is attached to the wheel side where the electric motor is installed; "Communication with a vehicle motion control device installed on the vehicle body side of the vehicle is performed by bidirectional multiplex communication". Specifically, “From the drive control device (on the wheel side), the operating state of the actuator such as motor rotation angle, piston thrust, braking force, motor temperature, wheel speed, tire air pressure, pad wear state, etc. Information is sent to the motion control device (on the vehicle body side), which is based on the signals transmitted from the pedal sensor, the driving state detection device, and the drive control device described above. The target braking force is calculated, and a digital signal corresponding to the calculated target braking force is transmitted to the drive control device (on the wheel side). The motor of the actuator is controlled so as to achieve the target braking force, and at this time, the drive control device (on the wheel side) feeds back signals from the rotation angle sensor, thrust sensor, and braking force sensor to control the braking force. Bets have been described.

  As described above, in the device described in Patent Document 1, a plurality of various signals (signals such as the operating state of the actuator) from the wheel side drive control device (drive means) are converted into the vehicle body side motion control device (target state calculation means). ). The target braking force calculated by the vehicle body side motion control device is returned to the wheel side drive control device. That is, a large amount of communication data is exchanged in the reciprocating direction between the vehicle body side target state calculation means and the wheel side drive means, thereby controlling the electric motor.

  For the purpose of cost reduction, serial communication (communication in which data is transmitted serially bit by bit in one communication path) is adopted as a communication method between the target state calculation means and the drive means. When a large amount of communication data (various signals) is exchanged in the reciprocating direction as described above, the communication cycle (the time interval required for transmitting and receiving each signal) becomes long. Therefore, the problem that it becomes difficult to ensure the responsiveness of an electric motor may arise.

Japanese Patent No. 4154883

  The present invention has been made to cope with the above-described problem, and an object of the present invention is to reduce the load of data communication performed between the vehicle body side and the wheel side and to ensure the responsiveness of the electric motor. An electric braking device is provided.

  An electric braking device for a vehicle according to the present invention includes a rotating member (KTB) fixed to a vehicle wheel (WHL), an electric motor (MTR) provided on the wheel (WHL) side, and the rotating member (KTB). ) To generate a braking torque on the wheel (WHL) and the friction member (MSB) to the rotating member (KTB) using the driving torque of the electric motor (MTR). An operation amount acquisition means (BPA) for acquiring an operation amount (Bpa) of a braking operation member (BP) operated by a driver of the vehicle, and a wheel (WHL) Actual state acquisition means (FBA, PSA, MKA) provided on the side for acquiring the actual value of the pressing state of the pressing member (PSN) as the actual pressing state (Fba, Psa, Mka); DY) side, a target state calculation means (TRG) that calculates a target value of the pressing state as a target pressing state (Fbt, Pst, Mkt) based on the operation amount (Bpa), and the wheel (WHL) ) Side driving means (DRV) for controlling the electric motor (MTR) based on the target pressing state (Fbt, Pst, Mkt) and the actual pressing state (Fba, Psa, Mka), A bus (SCB) for transmitting a signal representing the target pressing state (Fbt, Pst, Mkt) from the target state calculating means (TRG) to the driving means (DRV).

  Here, the bus (SCB) may be a serial bus. The serial bus is a communication path through which data is sequentially transmitted bit by bit through one communication path (communication line).

  According to this, as in Patent Document 1, signals representing the target pressing states Fbt and Pst calculated by the vehicle body side target state calculation means TRG are transmitted to the wheel side drive means DRV via the bus SCB. On the other hand, unlike the above-mentioned patent document 1, signals representing the actual pressing states Fba (Fbc) and Psa (Psc) acquired by the wheel-side actual state acquisition means FBA and PSA are transmitted via the bus SCB. It is not transmitted to the target state calculation means TRG (that is, the electronic control unit ECU). In other words, in controlling the electric motor MTR, communication data need not be exchanged between the vehicle body side and the wheel side in the reciprocating direction, and only transmission of communication data from the vehicle body side to the wheel side is required. The

  Therefore, compared with the case where communication data is exchanged between the vehicle body side and the wheel side in a reciprocating direction, the load of data communication performed between the vehicle body side and the wheel side is reduced, and the response of the electric motor MTR Sex can be secured. As a result, even when a serial bus is adopted as the bus SCB and serial communication is adopted as a communication method between the vehicle body side and the wheel side, the target pressing states Fbt and Pst are expressed with a relatively short communication cycle. A signal can be transmitted from the vehicle body side to the wheel side. For this reason, the control cycle of the electric motor MTR does not become long, and the responsiveness of the electric motor MTR can be ensured.

  In the electric braking device, the driving means (DRV) is configured such that when the driver of the vehicle is operating the braking operation member (BP), the pressing member (PSN) as the target pressing state Based on the target pressing force (Fbt) that is a target value of pressing force and the actual pressing force (Fba) that is the actual value of the pressing force of the pressing member (PSN) as the actual pressing state, the electric motor ( MTR), and when the driver of the vehicle is not operating the braking operation member (BP), a target position that is a target value of the position of the pressing member (PSN) as the target pressing state The electric motor (MTR) is controlled based on (Pst, Mkt) and an actual position (Psa, Mka) that is an actual value of the position of the pressing member (PSN) as the actual pressing state. To be done It is preferred.

  As the pressing state of the pressing member, typically, the pressing force of the pressing member PSN and the position of the pressing member PSN can be assumed. Therefore, in controlling the electric motor MTR, pressing force feedback control of the pressing member and position feedback of the pressing member can be executed. If these two feedback controls are performed simultaneously, control interference may occur. In this regard, according to the above configuration, the pressing force feedback control is executed when the braking operation member BP is operated, and the position feedback control is executed when the braking operation member BP is not operated. Accordingly, since these two feedback controls are not executed simultaneously, no control interference can occur.

  The determination as to whether or not the braking operation member is operated can be made based on the braking operation amount (Bpa) (when Bpa ≧ bp0 is satisfied, the determination is “There is an operation”, and Bpa <bp0 is satisfied). In the case of “no operation”). Further, when the brake pedal BP is provided with a stop switch, it can also be performed based on the detection signal (“ON” or “OFF” signal) of this switch (the detection signal of the switch is “ON”). ”Determination of“ with operation ”,“ determination of “no operation” when “OFF”).

  In the electric braking apparatus, the electric motor MTR may be a brush motor. In a motor with a brush, a magnet is provided on a stator (stator), and a coil is provided on a rotor (rotor). Since the weight of the rotor is large, the motor with brush has a large moment of inertia compared with the brushless motor. Due to the presence of such moment of inertia, when a brushed motor is employed, there is a concern about the responsiveness at the time of motor startup. In the electric braking device, as described above, the load of data communication performed between the vehicle body side and the wheel side can be reduced. Accordingly, even when serial communication is adopted as a communication method between the vehicle body side and the wheel side, and a brush motor is adopted as the electric motor MTR, the response of the electric motor MTR can be sufficiently ensured.

  In the electric braking device, the driving means (DRV) is configured to determine whether the friction member (MSB) is in contact with the rotating member (KTB) based on the actual pressing state (Fba, Psa, Mka). Is preferably configured to determine a reference position (pzr) that is a position of the pressing member (PSN) corresponding to.

  In general, in the electric braking device, it is preferable that so-called “retraction control” is performed in order to reduce a loss related to dragging of a friction member (for example, a brake pad) MSB. “Retraction control” refers to adjusting the contact state of the screw inside the power conversion means NJB that converts the rotational motion of the electric motor MTR into the linear motion of the pressing member PSN, and maintaining the lubrication state of the screw properly. During non-braking, a slight gap is provided between the friction member MSB and the rotating member (for example, a brake disk) KTB to reduce power loss due to friction. The friction member (eg, brake pad) MSB wears with use. For this reason, in the “retraction control”, it is important to determine the position (reference position (also referred to as zero point) pzr) of the pressing member PSN corresponding to the boundary of whether or not the friction member MSB and the rotating member KTB are in contact with each other. .

  In the above configuration, the signals representing the actual pressing states Fba and Psa acquired on the wheel side are not transmitted to the vehicle body side (particularly, the ECU) via the bus SCB, but are transmitted to the wheel side driving means DRV. Thus, the reference position pzr is determined. For this reason, the communication load of the bus SCB does not increase for the determination of the reference position pzr. Therefore, the responsiveness of the electric motor MTR does not deteriorate for determining the reference position pzr.

  The electric braking device includes power conversion means (NJB) that converts the rotational motion of the electric motor (MTR) into linear motion of the pressing member (PSN), and the power conversion means (NJB) is a trapezoidal screw (MNJ). , ONJ) and grease (GRS), and the target state calculation means (TRG) is configured so that the pressing member is operated when the driver of the vehicle is not operating the braking operation member (BP). The target position (Pst, Mkt) is calculated so that (PSN) moves in a direction away from the rotating member (KTB) and then moves in a direction approaching the rotating member (KTB). Is preferred.

  When the trapezoidal screw (feed screw) lubricated by the grease GRS is employed as the power conversion means NJB, in order to maintain the efficiency of the power conversion means NJB, “retraction control” for updating the grease GRS in the flank of the trapezoidal screw is performed. It is preferred that it be implemented. In the above configuration, when the braking operation member BP is not operated by the driver, the pressing member PSN moves away from the rotating member KTB and then moves closer to the rotating member KTB by “retraction control”. To do. By this “pulling back control”, the contact state of the trapezoidal screw is changed, and the grease GRS in the flank gap can be moved. As a result, the grease GRS present in the trapezoidal screw flank can be appropriately updated.

1 is an overall configuration diagram of an electric braking device for a vehicle according to an embodiment of the present invention. It is a functional block diagram for demonstrating the target calculating means TRG and the drive means DRV which are connected via a serial bus. It is a functional block diagram for demonstrating the drive means DRV. It is a functional block diagram for demonstrating the correction | amendment calculation block HSI. It is a figure which shows the time series pattern of "pullback control" memorize | stored in control pattern memory | storage block PTN. It is a figure which shows embodiment of the braking means BRK. It is a figure for demonstrating a power conversion member. It is a figure for demonstrating the movement of the grease by "withdrawal control."

  Hereinafter, an electric braking device for a vehicle according to an embodiment of the present invention will be described with reference to the drawings.

<Overall Configuration of Electric Brake Device for Vehicle according to Embodiment of the Present Invention>
FIG. 1 shows a state where an electric braking device according to an embodiment of the present invention is mounted on a vehicle. The electric braking device generates a braking force on the wheel by applying a braking torque to the wheel according to an operation amount of a braking operation member (for example, a brake pedal) by the driver, and decelerates the traveling vehicle.

  A power source (storage battery) BBD is provided (fixed) to the vehicle body BDY. The power supply BBD supplies electric power to the electronic control unit ECU and the braking means (brake actuator) BRK. Further, an alternator ALT is provided on the vehicle body BDY. The vehicle body power supply BBD is charged by the alternator ALT.

  An electronic control unit ECU is provided (fixed) on the vehicle body BDY. In the electronic control unit ECU, drive signals (target values) Fbt and Pst of the electric motor MTR are calculated based on the braking operation amount Bpa and transmitted to the drive means (electric circuit for driving the MTR) DRV via the serial communication bus SCB. Is done. Electric power for driving the electric motor MTR is supplied from a power supply BBD provided in the vehicle body to the DRV via the ECU and the vehicle body power line PBD.

  The driving means DRV is provided (fixed) inside the caliper CPR. The drive means DRV is a drive circuit (electric circuit) for driving the electric motor MTR, and includes a control means CTL, a bridge circuit HBR composed of switching elements (for example, MOS-FETs), and a noise reduction circuit NIZ. (IND etc.). In the control means CTL programmed in the CPU (processor) in the DRV, based on the drive signal of the MTR (for example, the target pressing force Fbt, the target position Pst) obtained through the SCB and the electric power obtained through the PBD. Thus, the switching element is driven, and the rotational direction and rotational power of the MTR are controlled.

  Power line communication in which the power line PBD is also used as a serial communication bus (communication line) SCB can be employed. In this case, the SCB is integrated into the PBD (that is, the SCB is omitted), and the electric motor drive signal is superimposed on the PBD and transmitted to the DRV. Here, the power line communication is also referred to as power line communication (PLC), and is a communication system that performs high-speed data communication using the power supply wiring PBD.

  One side of the suspension arm (for example, the upper arm UAM, the lower arm LAM) is attached to the vehicle body BDY of the vehicle, and the other side is attached to the knuckle NKL. The coil spring SPR and the shock absorber SHA are attached to a suspension arm or a knuckle NKL. The wheel WHL is suspended from the vehicle body BDY by the coil spring SPR and the shock absorber SHA. The suspension arm, SPR, NKL, and SHA are members constituting a known suspension device.

  The hub bearing unit HBU is fixed to the knuckle NKL. The wheel WHL is supported by a hub bearing in the hub bearing unit HBU. A rotating member (brake disc) KTB is fixed to the wheel WHL, and the KTB is rotated integrally with the WHL (that is, the rotating shaft of the KTB and the rotating shaft of the WHL are coaxial).

  The mounting bracket MTB is fixed to the knuckle NKL by fastening members (for example, bolts) TK1 and TK2 (not shown). A caliper CPR is attached to the MTB via slide pins GD1, GD2 (not shown). The brake caliper CPR is a floating caliper and is configured to sandwich a rotating member (brake disk) KTB via two friction members (brake pads) MSB. Specifically, the slide pins GD1 and GD2 are fixed to the mounting bracket MTB, and the pressing member (piston) PSN in the caliper CRP is slid by the electric motor MTR along the GD1 and GD2 toward the rotating member KTB. .

<Overall configuration of electronic control unit ECU, power supply BBD, and braking means BRK>
As shown in FIG. 2, a vehicle including the electric braking device includes a braking operation member BP, an electronic control unit ECU, a power source (storage battery or the like) BBD, and a braking means (brake actuator) BRK. Here, the ECU and BRK are connected by a serial communication bus (signal line) SCB and a power supply line (power line) PBD via an ECU side connector CNB and a BRK side connector CNC, and a drive signal of the MTR. And electric power is supplied.

  The braking operation member (for example, brake pedal) BP is a member that the driver operates to decelerate the vehicle. Based on the operation amount of BP, the braking means (brake actuator) BRK adjusts the braking torque of the wheel WHL, the braking force is generated on the wheel WHL, and the running vehicle is decelerated.

  The braking operation member BP is provided with a braking operation amount acquisition means BPA. The operation amount (braking operation amount) Bpa of the braking operation member BP by the driver is acquired (detected) by the braking operation amount acquisition means BPA. As a braking operation amount acquisition means BPA, a sensor (pressure sensor) for detecting the pressure of a master cylinder (not shown), an operation force of the braking operation member BP, and / or a sensor for detecting a displacement amount (a brake pedal depression force sensor, Brake pedal stroke sensor) is adopted. Accordingly, the braking operation amount Bpa is calculated based on at least one of the master cylinder pressure, the brake pedal depression force, and the brake pedal stroke. The braking operation amount Bpa is input to the electronic control unit ECU. Bpa is calculated or acquired by another electronic control unit, and the calculated value (signal) can be transmitted to the ECU via the communication bus.

  Electric power is supplied from the power supply BBD fixed to the vehicle body BDY to the electronic control unit ECU provided on the vehicle body side and the braking means BRK (particularly, the drive circuit DRV) provided on the wheel side. A rechargeable secondary battery (also referred to as a storage battery or a rechargeable battery) may be employed as the power supply BBD. Here, the secondary battery is one of batteries (chemical battery) that converts chemical energy of a substance into direct-current power by a chemical reaction, and can store electricity by charging and can be used repeatedly. Specifically, in the secondary battery, the internal chemical energy is converted into electrical energy during the discharge process, and the electric energy is converted into chemical energy by flowing current in the opposite direction to that during discharge, and the energy is stored. Is done. The power source BBD is charged by an alternator (generator) ALT when the amount of stored electricity (accumulated energy) decreases.

  The electronic control unit ECU outputs target values (drive signals) Fbt and Pst for driving the electric motor MTR to the drive means DRV. In addition, electric power for driving the MTR is supplied to the DRV via the ECU. Specifically, the ECU is provided with a connector CNB, and the serial communication bus SCB and the vehicle body power line PBD are connected to the driving means DRV via the CNB. Then, target values (target pressing states) Fbt and Pst are calculated by target calculation means TRG programmed in the electronic control unit ECU, and Fbt and Pst are transmitted to the DRV through the SCB. Further, electric power (current) from the vehicle body power supply BBD is supplied to the drive means DRV through the vehicle body power line PBD via the ECU.

[Target calculation means TRG]
Target calculation means (corresponding to target state calculation means) TRG for calculating the target pressing state Fbt (target pressing force) and Pst (target position) of the braking means BRK is programmed in a CPU (processor) in the electronic control unit ECU. Has been.

  The target calculation means TRG is a control algorithm, and includes an instruction pressing force calculation block FBS, an anti-skid control block ABS, a traction control block TCS, a vehicle stabilization control block ESC, a target pressing force calculation block FBT, and a pullback control block HMC. Consists of. The target state calculation means TRG is fixed to the vehicle body BDY of the vehicle, and calculates a target pressing force Fbt and a target position Pst (for example, Mkt) as a target pressing state based on the braking operation amount Bpa.

  In the command pressure calculation block FBS, the command pressure Fbs of each wheel WHL is calculated based on the braking operation amount Bpa and the command pressure calculation characteristic (calculation map) CHfb set in advance. The command pressing force Fbs is a target value of the pressing force that is a force with which the friction member (brake pad) MSB presses the rotating member (brake disc) KTB in the electric braking means BRK.

  In the anti-skid control block ABS, a target pressing force Fabs for executing a known anti-skid control is calculated based on an acquisition result (wheel speed) of a wheel speed acquisition means (not shown). The That is, the anti-skid control target pressing force Fabs is a target value of the pressing force for preventing wheel lock.

  In the traction control block TCS, a target pressing force Ftcs for executing known traction control (Traction Control) is calculated based on an acquisition result (wheel speed) of a wheel speed acquisition means (not shown). That is, the traction control target pressing force Ftcs is a target value of the pressing force for suppressing wheel spin (overspeed).

  In the vehicle stabilization control block ESC, based on the acquisition result (yaw rate) of the vehicle behavior acquisition means (for example, yaw rate sensor, not shown), a target push for executing the well-known vehicle stabilization control (Vehicle Stability Control) is performed. The pressure Fesc is calculated. That is, the vehicle stabilization control target pressing force Fesc is a target value of the pressing force for suppressing excessive vehicle understeer and / or oversteer.

  In the target pressing force calculation block FBT, the final target pressing force Fbs, the anti-skid control target pressing force Fabs, the traction control target pressing force Ftcs, and the vehicle stabilization control target pressing force Fesc are used. The pressure Fbt is calculated. Specifically, one of Fabs, Ftcs, and Fesc is selected, Fbs is corrected by the selected one, and Fbt is calculated. The selection order of Fabs, Ftcs, and Fesc is determined based on the running state of the vehicle and the state of the wheels. Note that Ftsc is not calculated when the corresponding wheel is not a drive wheel (when not connected to the drive train).

  In the pullback control block HMC, a target position Pst for performing the screw pullback operation is calculated based on the braking operation amount Bpa. Here, the screw pullback operation is performed in the power conversion member (screw member) NJB “contact state (in the case of a trapezoidal screw, a flank contact state, and in the case of a ball screw, a contact state between a ball and a groove). "Is adjusted. In the pull-back control block HMC, when the braking operation is not performed (that is, when Bpa = 0), the screw (that is, the pressing member PSN) is pulled back by the reverse rotation of the electric motor MTR. The target position Pst of the pressing member PSN is based on the position (contact start position) where the contact between the friction member MSB and the rotating member KTB is started (reference position pzr described later).

  The pullback control block HMC includes a control pattern storage block PTN. In the control pattern storage block PTN, “to which contact state the screw member NJB is pulled back” is stored as a plurality of control patterns. Here, the control pattern is a reference model of the target position Pst of the pressing member PSN associated with the passage of time.

  First, the contact state of the screw and each pullback control pattern will be described. In the contact state of the screw, the friction member MSB is in contact with the rotating member KTB and the pressing member PSN receives a force from the friction member MSB (that is, the pressing force Fba is generated, hereinafter, “ (Referred to as “pressing contact state”), the friction member MSB and the rotating member KTB just start to be separated and the contact portion of the screw is free (that is, the screw does not transmit any power at all, hereinafter “ A state that is different from that in the pressing contact state, and a state in which the pressing member PSN moves away from the rotating member KTB (hereinafter referred to as a “retracting contact state”), There are three states.

  Accordingly, at least a “contact release pattern” in which a free contact state is achieved, a “contact switching pattern” in which at least a pull back contact state is achieved, and a “limit pull back pattern” in which a screw is pulled back to the screw engagement limit. There are three control patterns (normative models) with different pullback amounts. The following summarizes the transition of the screw contact state and the outline of the control pattern for each control pattern.

<Contact release pattern>
In the contact release pattern, the screw contact state transitions from the press contact state to the free contact state. In the contact release pattern, the screw is pulled back until the contact (contact) of the first contact portion of the screw is released and the first contact portion becomes free. Specifically, it is pulled back to the first pull-back position (predetermined value) ps1. Thereafter, the screw is moved to the standby position psb during non-braking. Here, the standby position psb is the position of the screw (that is, PSN) when the driver is not operating the braking operation member (when not braking). During non-braking, the PSN standby position psb is set so that the MSB can wait at a position slightly away from the KTB in order to suppress dragging of the MSB.

《Abutment switching pattern》
In the contact switching pattern, the contact state of the screw changes from the free contact state to the pull back contact state (starting from the press contact state). In the contact switching pattern, the screw is pulled back through the free contact state until a portion (second contact portion) different from the pressed contact state contacts. In the case of a trapezoidal screw, the flank (pressure-side flank during pressing, which is the first flank) on the opposite side to the flank abutting in the pressing-abutted state (play-side flank during pressing, the second flank) Is pulled back until it comes into contact. Specifically, it is pulled back to the second pull back position (predetermined value) ps2. Thereafter, the screw (that is, PSN) is moved to the standby position psb at the time of non-braking (for example, when Bpa = 0).

《Limit pullback pattern》
In the limit pullback pattern, the contact state of the screw transitions from the free contact state (starting from the press contact state) to the pull back contact state. In the limit pull-back pattern, the screw is pulled back to the limit portion where the screw can be screwed through the state where the contact portion is switched. For example, in the screw member NJB, the screw is pulled back until the movement is limited by the stopper. Specifically, it is pulled back to the third pullback position (predetermined value) ps3. Thereafter, the screw (that is, PSN) is moved to the standby position psb at the time of non-braking (for example, when Bpa = 0).

  In the pullback control block HMC, any one of the three pullback control patterns (stored in advance in the PTN) is selected. The selection of the control pattern is determined based on at least one of the acceleration operation amount Apa, the shift shift position Spa, and the vehicle speed Vxa. The acceleration operation amount Apa is an operation amount of an acceleration operation member (accelerator pedal) AP (not shown), and is acquired (detected) by the acceleration operation amount acquisition means APA. For example, the stroke (displacement) of the acceleration operation member AP (not shown) is detected as the acceleration operation amount Apa by the acceleration operation amount acquisition means (stroke sensor) APA. The shift shift position Spa is a position of a shift shift member (shift lever) SP (not shown) (for example, a parking position, a forward position, a reverse position), and each shift position is acquired by the shift shift position acquisition means SPA ( Detected). The vehicle speed Vxa is acquired (detected) by the vehicle speed acquisition means VXA. Each wheel WHL is provided with a wheel speed acquisition means VWA, and the vehicle speed Vxa can be calculated based on the wheel speed (rotational speed) Vwa acquired by the VWA.

  Each control pattern is not selected when the braking operation amount Bpa increases or when the braking operation amount Bpa is greater than or equal to the predetermined operation amount bpa0. Any one of the control patterns is selected when the braking operation amount Bpa decreases and Bpa becomes less than the predetermined operation amount bpa0. The control pattern selection is performed based on at least one of the vehicle speed Vxa, the acceleration operation amount Apa, and the shift position Spa.

  When the acceleration operation amount Apa is greater than or equal to the first predetermined operation amount (predetermined predetermined value) ap1 (Apa ≧ ap1), the limit pullback pattern is selected, and the acceleration operation amount Apa is less than the first predetermined operation amount ap1. In addition, when the second predetermined operation amount (a predetermined value set in advance and smaller than ap1) ap2 or more (ap2 ≦ Apa <ap1), the contact switching pattern is selected, and the acceleration operation amount Apa is the second When the operation amount is less than the predetermined operation amount ap2 (Apa <ap2), the contact release pattern can be selected. When the acceleration operation amount Apa is large (that is, when the vehicle is rapidly accelerated), the probability of sudden braking is low, and therefore the limit pullback pattern can be selected. On the other hand, when the acceleration operation amount Apa is small (that is, when the vehicle is not rapidly accelerated), the contact release pattern can be selected in preparation for sudden braking by the driver.

  When the shift shift position (selector operating position) Spa of the transmission indicates a parking position (P range), a limit pullback pattern can be selected. This is because the vehicle is surely stopped when the shift position Spa indicates the P range.

  When the vehicle speed Vxa is equal to or higher than the first predetermined speed (predetermined predetermined value) vx1 (Vxa ≧ vx1), the contact release pattern is selected, the vehicle speed Vxa is less than the first predetermined speed vx1, and the first 2 When a predetermined speed (a predetermined value set in advance and smaller than vx1) vx2 or more (vx2 ≦ Vxa <vx1), the contact switching pattern is selected, and the vehicle speed Vxa is less than the second predetermined speed vx2. In the case (Vxa <vx2), a limit pullback pattern may be selected. The greater the pullback amount, the greater the effect of lubrication renewal. On the other hand, the smaller the pullback amount, the higher the braking torque response. For this reason, when the vehicle speed Vxa is small, a control pattern with a large pullback amount is selected, and when the vehicle speed Vxa is large, a control pattern with a small pullback amount is selected. As a result, the lubrication performance of the screw member NJB and the response of the braking torque can be compatible.

  By selecting each pullback control pattern, a transition pattern of the target position Pst with respect to time (a value of Pst that changes every moment) is determined. That is, the pattern of the target position Pst that changes in time series includes a contact release pattern (retraction operation to the first predetermined position ps1), a contact switching pattern (retraction operation to the second predetermined position ps2), and limit pullback. Any one of the patterns (retraction operation to the third predetermined position ps3) is determined. Based on the selected control pattern, the target position Pst of the pullback control in each calculation cycle (each control cycle) is sequentially output from the HMC. In each pull-back pattern, the position (screw position) of the pressing member PSN is finally moved to the standby position psb. Here, the standby position psb is set to a side where the predetermined position ps0 is pulled back from the reference position (PSN position zero point) pzr (that is, the side where PSN is away from KTB). Further, the standby position psb can be set to coincide with the reference position pzr.

  The target pressing force Fbt calculated in the target pressing force calculation block FBT and the target position Pst calculated in the pullback control calculation block HMC are transmitted to the communication module TMB. That is, the target pressing states (target values) Fbt and Pst calculated in the target state calculating means TRG are input to the TMB. The communication module TMB is an element (ECU side communication module) for performing serial communication provided in the electronic control unit ECU. The target pressing force (signal) Fbt and the target position (signal) Pst are supplied to the braking means BRK (specifically, the drive circuit DRV) fixed to the wheel via the ECU side connector CNB and the serial communication bus SCB. Sent.

  The communication bus (Communication Bus) is a common path (communication line) for exchanging control information (data, calculation results, etc.) between the means (each module). The communication bus is classified into a serial communication bus and a parallel communication bus according to the path. In the serial communication bus, one communication path (communication line) is used, and data is sequentially transferred. That is, in the serial communication bus, data is transmitted one bit at a time in series on one path. In a parallel communication bus (Parallel Communication Bus), a plurality of communication paths (parallel paths) are used, and data is transferred while synchronizing them. In the serial communication bus, 1-bit data is transmitted sequentially, whereas in a parallel communication bus with four paths (signal lines), for example, 4-bit information can be transmitted simultaneously. Synchronization is required. In the present invention, the serial communication bus SCB is employed for exchanging control information from the target (state) calculating means TRG to the driving means DRV.

  A CAN (Controller Area Network) bus may be employed as the serial communication bus SCB. The CAN communication is a serial communication standardized by ISO (International Organization for Standardization), and is adopted, for example, in a network for automobiles (in-vehicle network). A plurality of electronic control units ECUs are mounted on an automobile. Each ECU shares information (sensor signals, state variables, control calculation results, etc.) with other ECUs and is operated in cooperation. In CAN communication, each ECU can be communicated by a wiring with a small amount of information by being connected by two communication lines (CAN-H line, CAN-L line). Specifically, a signal is transmitted by voltage differential (balanced connection). Here, each ECU selects and reads only necessary data from data on CAN communication.

[Brake means BRK]
The brake means (brake actuator) BRK includes a brake caliper (floating caliper) CPR, a pressing member (brake piston) PSN, an electric motor (brush motor or brushless motor) MTR, a position acquisition means PSA (for example, a rotation angle detection means) MKA), reduction gear GSK, shaft member SFT, power conversion member (screw member) NJB, pressing force acquisition means FBA, and drive means (MTR drive circuit) DRV.

  The brake caliper CPR is a floating caliper and is configured to sandwich a rotating member (brake disk) KTB via two friction members (brake pads) MSB. Within the caliper CPR, the pressing member PSN is slid and moved forward or backward toward the rotating member KTB. In the caliper CPR, the keyway KYM is formed so as to extend in the direction of the rotation axis (shaft axis Jsf) of the shaft member SFT.

  The pressing member (brake piston) PSN presses the friction member MSB against the rotating member KTB to generate a frictional force. The key member KYA is fixed to the pressing member PSN. When the key member KYA is fitted into the key groove KYM, the pressing member PSN is restricted from rotating around the shaft axis, but linear movement in the direction of the shaft axis (longitudinal direction of the key groove KYM) is allowed. Is done.

  The electric motor MTR generates power for pressing the friction member MSB against the rotating member KTB. That is, the electric motor MTR drives the pressing member PSN. Specifically, the output of the electric motor MTR (rotational power around the motor shaft Jmt) is transmitted to the shaft member SFT via the reduction gear GSK, and the rotational power of the SFT (torque around the shaft axis Jsf) It is converted into linear power (thrust in the direction of the pressing shaft Jps) by the conversion member (for example, screw member) NJB and transmitted to the pressing member PSN. Then, the pressing member (brake piston) PSN is advanced or retracted toward the rotating member (brake disc) KTB. By the movement of the PSN, the force (pressing force) Fba that the friction member (brake pad) MSB presses the rotating member KTB is adjusted. Since the rotating member KTB is fixed to the wheel WHL, a frictional force is generated between the friction member MSB and the rotating member KTB, and the braking force is adjusted to the wheel WHL, for example, the traveling vehicle is decelerated. As the electric motor MTR, a motor with a brush or a brushless motor is employed.

  In the rotation direction of the electric motor MTR, the forward rotation direction corresponds to the direction in which the friction member MSB approaches the rotation member KTB (the direction in which the pressing force increases and the braking torque increases), and the reverse rotation direction corresponds to the friction member MSB. Corresponds to the direction away from the rotating member KTB (the direction in which the pressing force decreases and the braking torque decreases). The output of the electric motor MTR is determined based on the target energization amount Imt. Specifically, when the sign of the target energization amount Imt is a positive sign (Imt> 0), the electric motor MTR is driven in the forward rotation direction, and the sign of Imt is a negative sign (Imt <0). The electric motor MTR is driven in the reverse direction. Further, the rotational power of the electric motor MTR is determined based on the magnitude (absolute value) of the target energization amount Imt. That is, the larger the absolute value of the target energization amount Imt, the larger the output torque of the electric motor MTR, and the smaller the absolute value of the target energization amount Imt, the smaller the output torque.

  Screw position acquisition means (corresponding to actual state acquisition means, also simply referred to as position acquisition means) PSA acquires (detects) the actual position (actual value of the screw position) Psa of the screw as a signal representing the actual pressing state. To do. Since the screw member NJB is fixed to the pressing member PSN, the screw position is the same as the position of the pressing member PSN. Further, since the specifications of the braking means BRK (GSK gear ratio, NJB lead, etc.) are known values determined at the design stage, from the rotation angle of the electric motor MTR to the position of the pressing member PSN. The means for acquiring the state quantity relating to the position can be employed as the position acquiring means PSA. For example, the rotation angle acquisition means MKA of the electric motor MTR can be adopted as the position acquisition means PSA. The acquired (detected) actual position Psa (actual rotation angle Mka) is input to the drive means DRV (particularly, the CPU mounted on the DRV).

  The rotation angle acquisition means (rotation angle sensor) MKA acquires (detects) the rotation angle Mka of the rotor (rotor) of the electric motor MTR. The rotation angle acquisition means MKA is disposed inside the electric motor MTR and coaxially with the rotor and the commutator (that is, coaxial with the MTR and provided on the motor shaft Jmt).

  The reduction gear GSK reduces the rotational speed of the power of the electric motor MTR and outputs it to the shaft member SFT. That is, the rotational output (torque) of the MTR is increased according to the reduction ratio of the reduction gear GSK, and the rotational force (torque) of the shaft member SFT is obtained. For example, the GSK is composed of a small diameter gear SKH and a large diameter gear DKH. As GSK, instead of the gear transmission mechanism, a winding transmission mechanism such as a belt or a chain, or a friction transmission mechanism may be employed.

The shaft member SFT is a rotating shaft member and transmits the rotational power transmitted from the reduction gear GSK to the screw member NJB. The end of the shaft member SFT is processed into a spherical shape and functions as a universal joint. This universal joint compensates for the effect of PSN oscillation (oscillating motion) that occurs when the MSB slides.

  The power conversion member (screw member) NJB is a power conversion member that converts the rotational power of the shaft member SFT into linear power. That is, NJB is a rotation / linear motion conversion mechanism. For example, the NJB can be composed of a nut member NUT and a bolt member BLT. The screw member NJB has reversibility (has reverse efficiency) and can transmit power in both directions. That is, when the braking torque is increased (when the pressing force Fba is increased), power is transmitted from the shaft member SFT to the pressing member PSN through the screw member NJB. Conversely, when the braking torque is reduced (when the pressing force Fba is reduced), power is transmitted from the pressing member PSN to the shaft member SFT via the screw member NJB (reverse efficiency is less than “0”). large).

  A “feed screw” may be adopted as the power conversion member NJB. The NJB is configured by a sliding screw (such as a trapezoidal screw) that transmits power by “sliding”. In this case, the nut member NUT is provided with a female screw (inner screw) MNJ. The bolt member BLT is provided with a male screw (outer screw) ONJ and is screwed to the MNJ of the NUT. The rotational power (torque) transmitted from the shaft member SFT is transmitted as linear power (thrust) of the pressing member PSN via the screw member NJB (ONJ and MNJ). Further, instead of the above-described sliding screw, a rolling screw (such as a ball screw) in which power is transmitted by “rolling” may be employed for the screw member NJB. In this case, a ball groove is provided in the nut member and the bolt member. Power is transmitted through a ball (steel ball) fitted in the ball groove. In place of the screw member NJB, a conversion mechanism such as a ball ramp member, a rotary wedge member, a rack and pinion member, or the like may be employed as a power conversion member for converting a rotational motion into a linear motion.

  The pressing force acquisition means (corresponding to the actual state acquisition means) FBA acquires (detects) the reaction force (reaction) of the force (pressing force) Fba that the pressing member PSN presses the friction member MSB as a signal representing the actual pressing state. . A strain generating body is formed in the FBA, and the strain is detected by a strain detection element, and Fba is acquired. For example, as a strain detection element, a device using a change in electrical resistance (strain gauge), a device using ultrasonic waves, or the like can be used. The FBA is provided between the shaft member SFT and the caliper CPR, and is fixed to the caliper CRP. The acquired (detected) actual pressing force Fba is input to the driving means DRV (particularly, the CPU mounted on the DRV).

  The driving means DRV is fixed inside the caliper CPR, and drives and controls the electric motor MTR based on the target pressing force Fbt. The DRV includes a communication module TMC, a control unit CTL, a bridge circuit HBR, and the like.

[Connectors CNB, CNC, and wiring SCB, PBD]
A connector CNC is provided on the surface of the caliper CPR. From here, the drive power of the electric motor MTR and the drive signal (target pressing force Fbt) of the MTR are taken into the drive means DRV. The target signal Fbt is supplied to the BRK side connector (wheel side connector) CNC by the signal line SCB and the electric power by the vehicle body power line PBD, respectively.

  Similar to the drive means DRV, the connector CNB is provided in the electronic control unit ECU. A serial communication bus (signal line) SCB and a power line PBD are connected to the ECU via an ECU side connector (vehicle body side connector) CNB. That is, the electronic control unit ECU (vehicle body BDY is connected to the vehicle body BDY) via wiring (signal line SCB and power line PBD) relayed by the ECU side connector (vehicle body side connector) CNB and the BRK side connector (wheel side connector) CNC. Arrangement) and the drive circuit DRV (arranged on the wheel WHL). In other words, the serial communication bus SCB transmits an MTR drive signal (target pressing force Fbt) from the ECU to the DRV via the connectors CNB and CNC. The power line PBD supplies power for driving the electric motor MTR from the ECU to the DRV via the connectors CNB and CNC. As the PBD, a twisted pair cable (Twisted Pair Cable) formed by twisting two electric wires may be employed.

<Driving means DRV>
Next, the details of the drive means (drive circuit) DRV will be described with reference to FIG. The drive means DRV controls the energization state (the magnitude of the energization amount and the energization direction) to the electric motor MTR based on the target pressing states Fbt and Pst (Mkt), and the output of the MTR (for example, the braking means BRK is generated). Adjust the braking torque. FIG. 3 shows an example of drive means DRV in the case where a motor with a brush (also simply referred to as a brush motor) is employed as the electric motor MTR. The drive means DRV is composed of a communication module (DRV-side communication module) TMC, a control algorithm (control means CTL, etc.), and an electric circuit (bridge circuit HBR, etc.).

[Communication module TMC]
A communication module TMC is provided in the drive circuit DRV. The communication module TMC receives signals representing the target pressing states Fbt and Pst. The communication module (DRV side communication module) TMC is for realizing a serial communication function, like the ECU side communication module TMB. For example, in the case of a CAN bus, the communication modules TMB and TMC are configured by a transceiver IC and a CAN controller. The transceiver IC converts the signal into CAN-H and CAN-L differential signals, and passes the communication signal on the CAN bus. Specifically, in the communication modules TMB and TMC, at the time of reception, the differential voltage received from the serial communication bus SCB is converted into a digital signal by the transceiver IC, and is sent to the reception port (RX port) of the CAN controller inside the microcomputer. Sent. On the other hand, at the time of transmission, a digital signal is sent from the transmission port (TX port) of the controller to the transceiver, and this signal is converted into a differential voltage by the transceiver and then sent onto the SCB.

[Control means CTL]
Based on the target pressing force (one of the target pressing states) Fbt and the target position (the other of the target pressing states) Pst, the control means CTL controls the actual energization amount (finally, the electric motor MTR). Control the magnitude and direction of the current). The control means CTL is a control algorithm, which is programmed in a CPU (Central Processing Unit) mounted on the electric board of the drive circuit DRV. The CTL includes an instruction energization amount calculation block IST, a correction calculation block HSI, a pressing force feedback control block IFT, a position feedback control block IPT, an energization amount adjustment calculation block IMT, a pulse width modulation block PWM, and a switching control block SWT. Is done.

  The command energization amount calculation block IST is based on the target pressing force Fbt (target pressing state transmitted from the target state calculation means TRG) and preset command energization amount calculation characteristics (calculation maps) CHs1, CHs2. The command energization amount Ist is calculated. The command energization amount Ist is a target value of the energization amount to the electric motor MTR for the electric braking means BRK to achieve the target pressing force Fbt. The calculation map of Ist is composed of two characteristics CHs1 and CHs2 in consideration of the hysteresis of the electric braking means BRK. The characteristic CHs1 corresponds to the case where the pressing force is increased, and the characteristic CHs2 corresponds to the case where the pressing force is decreased. Therefore, compared with the characteristic CHs2, the characteristic CHs1 is set to output a relatively large command energization amount Ist.

  Here, the energization amount is a state amount (variable) for controlling the output torque of the electric motor MTR. Since the electric motor MTR outputs a torque substantially proportional to the current, the current target value of the electric motor MTR can be used as the target value of the 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. Furthermore, since the supply voltage value can be adjusted by the duty ratio in pulse width modulation (PWM), this duty ratio can be used as the energization amount.

  In the correction calculation block HSI, zero point correction of the pressing force acquisition unit FBA (for example, a pressing force sensor) and the position acquisition unit PSA (for example, the MTR rotation angle acquisition unit MKA) is performed. A signal from the FBA (pressing force Fba) and a signal from the PSA (actual position Psa) are input to the correction calculation block HSI, the zero point is corrected, and the corrected actual pressing force (corrected pressing force) is corrected. Pressure) Fbc and corrected actual position (corrected position) Psc are output. Here, in the case of the pressing force acquisition means FBA, the zero point represents a detection value (acquisition value) in a state where the pressing force (MSB is a force that presses KTB) is not actually generated. In the case of PSA, it represents a reference position pzr that is a boundary of whether or not a pressing force is generated between MSB and KTB (that is, whether MSB and KTB are in contact). Here, the deviation (deviation) from the zero point of the output value of the FBA is referred to as zero point drift. That is, the FBA zero point drift is a deviation (deviation from the value “0”) in a situation where no pressing force is actually generated.

  The pressing force feedback control block IFT calculates the pressing force feedback energization amount Ift based on the target pressing force (target pressing state) Fbt and the actual pressing force (actual pressing state after zero point correction) Fbc. Although the command energization amount Ist is calculated as a value corresponding to the target pressing force Fbt, there is an error (steady state) between the target pressing force Fbt and the actual pressing force (corrected pressing force) Fbc due to the fluctuation in the efficiency of the electric braking means BRK. Error) may occur. The pressing force feedback energization amount Ift is calculated based on a deviation (pressing force deviation) ΔFb between the target pressing force Fbt and the actual pressing force Fbc and a preset calculation characteristic (calculation map) CHf, and the above error is calculated. Decided to decrease. That is, the pressing force feedback control is not executed in the vehicle body side ECU, but is executed in the wheel side drive circuit DRV (specifically, in the CPU mounted on the DRV). Since the pressing force feedback control is completed in the driving means DRV, the communication load of the serial communication bus SCB can be suppressed. The actual pressing force Fbc is acquired (detected) by the pressing force acquisition means (actual state acquisition means) FBA.

  The position feedback control block IPT is based on the target position (target pressing state transmitted from the target state calculating means TRG) Pst and the actual position (actual pressing state after zero point correction) Psc. Is calculated. The position feedback energization amount Ipt is calculated so that the position of the screw (that is, the position of PSN) matches the target position Pst. Specifically, Ipt is calculated based on a deviation (position deviation) ΔPs between the target position Pst and the actual position (corrected position) Psc and a preset calculation characteristic (calculation map) CHp, and the deviation ΔPs is calculated. Decided to decrease. That is, the position feedback control is not executed in the vehicle body side ECU, but is executed in the wheel side drive circuit DRV (specifically, in the CPU mounted on the DRV). Since the position feedback control is completed in the drive means DRV, the communication load of the serial communication bus SCB can be suppressed. The actual position Psc is acquired (detected) by a position acquisition means (real state acquisition means) PSA (for example, an electric motor rotation angle acquisition means MKA).

  The energization amount adjustment calculation block IMT calculates a target energization amount Imt that is a final target value for the electric motor MTR. In the energization amount adjustment calculation block IMT, first, the command energization amount Ist is adjusted by the pressing force feedback energization amount Ift. Specifically, the feedback energization amount Ift is added to the command energization amount Ist, and this result is calculated as the target energization amount Ims (Ims = Ist + Ift). Further, the position feedback energization amount Ipt is transmitted from the position feedback control block IPT to the energization amount adjustment calculation block IMT. Then, one of Ims and Ipt is selected by the selection means SNT in the energization amount adjustment calculation block IMT. Specifically, when the braking operation is performed by the driver (for example, when Bpa> 0), the target energization amount Ims is adopted as the final target energization amount Imt. On the other hand, when the braking operation is not performed (for example, when Bpa = 0), the position feedback energization amount Ipt is output as the final position feedback energization amount Imt. Then, based on the sign (value sign) of the target energization amount Imt, the rotation direction of the electric motor MTR (forward rotation direction in which the pressing force increases or reverse rotation direction in which the pressing force decreases) is determined, and the target energization amount Imt. The output (rotational power) of the electric motor MTR is controlled based on the size of the motor. The presence / absence of the braking operation can be determined using the threshold value bp0 (a predetermined value larger than “0”). Specifically, “operated” is determined when the braking operation amount Bpa is equal to or greater than a predetermined value bp0, and “no operation” is determined when Bpa is less than bp0. Alternatively, the presence or absence of a braking operation can be determined based on a signal Stp provided with a stop switch (ON / OFF switch) provided on the braking operation member BP. Specifically, “operation present” is determined when Stp indicates an ON state, and “no operation” is determined when Stp indicates an OFF state.

The pulse width modulation block PWM is based on the pulse width modulation (PWM, Pulse) based on the target energization amount Imt.
The indicated value (target value) for performing Width Modulation is calculated. Specifically, the pulse width modulation block PWM determines the pulse width duty ratio Dut (ON / OFF time ratio) based on the target energization amount Imt and a preset characteristic (computation map). . In addition, the PWM determines the rotation direction of the MTR based on the sign of Imt (positive sign or negative sign). For example, the rotation direction of the electric motor MTR is set such that the forward rotation direction is a positive (plus) value and the reverse rotation direction is a negative (minus) value. Since the final output voltage is determined by the input voltage (power supply voltage) and the duty ratio Dut, the rotation direction of the MTR and the energization amount to the MTR (that is, the output of the MTR) are determined in PWM.

  In the pulse width modulation block PWM, so-called current feedback control can be executed. In this case, a detection value (actual current supply amount to the electric motor MTR, for example, an actual current value) Ima of the current supply amount acquisition unit IMA is input to the PWM. Then, the duty ratio Dut is corrected (finely adjusted) based on the deviation ΔIm between the target energization amount Imt and the actual energization amount Ima. With this current feedback control, highly accurate motor control can be achieved.

  The switching control block SWT outputs a drive signal to the switching elements (S1 to S4) constituting the bridge circuit HBR based on the duty ratio (target value) Dut. This drive signal indicates whether each switching element is energized or not energized. Specifically, when the electric motor MTR is driven in the forward rotation direction based on the duty ratio Dut, S1 and S4 are energized (ON state), and S2 and S3 are de-energized (OFF state) ) And the energization / non-energization states of S1 and S4 are switched in the energization time (energization cycle) corresponding to Dut. Similarly, when the MTR is driven in the reverse direction, S1 and S4 are controlled to be in a non-energized state (OFF state), and S2 and S3 are controlled to be in an energized state (ON state), and the energized state of S2 and S3 ( ON / OFF switching cycle) is adjusted based on the duty ratio Dut. As the Dut increases, the energization time per unit time is lengthened, and a larger current flows through the MTR. For example, when Dut = 100% is instructed, the corresponding switching element is always energized, and when Dut = 0% is instructed, it is in a non-energized state.

[Bridge circuit HBR and noise reduction circuit NIZ]
The switching elements S1 to S4 are elements that can turn on (energize) / off (non-energize) a part of the electric circuit. For example, a MOS-FET or IGBT is used as the switching element. A switching circuit S1 to S4 constitutes a bridge circuit HBR. Here, the bridge circuit can change the energization direction to the electric motor with a single power source without requiring a bidirectional power source, and can change the rotation direction (forward direction or reverse direction) of the electric motor. It is a circuit that can be controlled. This bridge circuit is also referred to as an H bridge circuit or a full bridge circuit. The switching elements S1 to S4 are driven by control means CTL (signal from SWT). By switching the energization / non-energization state of each switching element, the rotation direction (forward rotation direction, reverse rotation direction) and output torque (magnification amount) of the electric motor MTR are adjusted. Here, the forward rotation direction of the MTR is a rotation direction in which the MSB is brought closer to the KTB, the braking torque is increased, and the deceleration of the traveling vehicle is increased. The reverse rotation direction of the MTR is to pull the MSB away from the KTB. In the rotational direction, the braking torque is reduced and the deceleration of the running vehicle is reduced.

  When a large output is required for the electric motor MTR, a large current is passed through the switching elements S1 to S4. At this time, since heat is generated in the switching elements S1 to S4, a heat radiating plate (heat sink) can be provided in S1 to S4. Specifically, a metal plate (for example, an aluminum plate) with good thermal conductivity can be fixed to S1 to S4.

  The drive circuit DRV is provided with a noise reduction circuit (stabilization circuit) NIZ for stabilizing supply power (that is, reducing voltage fluctuation). The noise reduction circuit NIZ is a so-called LC circuit (also referred to as an LC filter), and includes a combination of at least one inductor (coil) IND and at least one capacitor (capacitor) CND. For example, as the NIZ, the first and second capacitors CND1, CND2 and the inductor IND are combined to form a low-pass filter (π-type filter). Specifically, the π-type low-pass filter is a so-called Chebyshev low-pass LC filter, which is a filter including two capacitors CND1 and CND2 parallel to the line and one series inductor. In general, an inductor is more expensive than a capacitor (capacitor). Therefore, by adopting a π-type filter, component costs are suppressed, and good performance can be obtained. Further, as the noise reduction filter NIZ, a T-type low-pass filter (configured by two series inductors and one parallel capacitor) may be employed instead of the π-type low-pass filter.

  The drive circuit DRV is provided with energization amount acquisition means (for example, a current sensor) IMA. The energization amount acquisition means IMA acquires (detects) an actual energization amount (for example, current that actually flows through the electric motor MTR) Ima to the electric motor MTR.

[Electric motor MTR]
As the electric motor MTR, a motor with a brush (also simply referred to as a brush motor) is employed. A motor with a brush is also called a commutator motor. In the electric motor, a current flowing through an armature (electromagnet by winding) is rotated by a mechanical commutator (commutator) CMT and a brush BLC. It is switched according to the phase. That is, the commutator CMT and the brush BLC constitute a mechanical rotation switch, and the current to the winding circuit is alternately inverted. In a motor with a brush, the stator (stator) side is constituted by a permanent magnet, and the rotor (rotor) side is constituted by a winding circuit (electromagnet). The brush BLC is in contact with the commutator CMT so that electric power is supplied to the winding circuit (rotor). The brush BLC is pressed against the commutator CMT by a spring (elastic body), and a current is commutated by rotating the CMT. In the MTR, there is provided rotation angle acquisition means MKA for acquiring (detecting) the rotor position (actual position, actual rotation angle) Mka.

  As the electric motor MTR, a brushless motor may be employed instead of the brush motor. The brushless motor is also referred to as a non-commutator motor (brushless direct current motor). In the electric motor, current is commutated by an electronic circuit instead of the mechanical commutator CMT of the brushed motor. . In a brushless motor, the rotor (rotor) is a permanent magnet and the stator (stator) is a winding circuit (electromagnet). The rotor rotation position (rotation angle) Mka is detected and switched according to Mka. The supply current is commutated by switching the elements. The rotor position Mka is detected by a rotation angle acquisition means MKA provided inside the electric motor MTR.

  When a brushless motor is employed, the bridge circuit HBR of the driving unit DRV is configured by six switching elements. As in the case of the motor with brush, the energization state / non-energization state of the switching elements constituting the bridge circuit HBR is controlled based on the duty ratio (target value) Dut determined by the pulse width modulation block PWM.

  In the brushless motor, the rotor position (rotation angle) Mka of the electric motor MTR is acquired by the rotation angle acquisition means MKA. In the switching control block SWT, the six switching elements constituting the three-phase bridge circuit are controlled based on the actual position Mka. The switching elements sequentially switch the direction of the energization amount of the U-phase, V-phase, and W-phase coils of the bridge circuit (that is, the excitation direction) to drive the MTR. The rotation direction (forward rotation or reverse rotation) of the brushless motor is determined by the relationship between the rotor and the excitation position.

<Correction calculation block HSI>
Next, an embodiment of the correction calculation block HSI will be described with reference to the functional block diagram of FIG. The correction calculation block HSI (control algorithm) is programmed in the drive means DRV. In the correction calculation block HSI, the zero position of the screw position acquisition means (that is, the position acquisition means of the pressing member and is also simply referred to as position acquisition means) PSA and the pressing force acquisition means FBA (for example, a pressing force sensor). Correction is performed. The zero point of the position acquisition means PSA is a reference position pzr corresponding to the boundary of whether or not a pressing force is generated between the MSB and KTB (that is, the boundary position of whether or not the MSB and KTB are in contact). is there. The reference position pzr is also a position at which the screw contact state switches from the press contact state to the free contact state when the pressing force Fba decreases (when the electric motor MTR is reversed). The zero point of the pressing force acquisition means FBA is a value representing a state where no pressing force (the MSB presses KTB) is actually generated. Here, the deviation (deviation, offset) from the zero point of the FBA is referred to as zero point drift. Since the specifications of BRK (GSK gear ratio, NJB lead, etc.) are known, rotation angle acquisition means (MTR rotation angle sensor) MKA can be employed as position acquisition means PSA.

  The correction calculation block HSI includes a position change amount calculation block PSH, a pressing force change amount calculation block FBH, a rigidity value calculation block GCQ, a candidate position / candidate force calculation block PFK, a reference position calculation block PZR, a position correction calculation block PSC, a correction pressing block. It consists of a pressure calculation block FZR and a pressing force correction calculation block FBC.

  In the position change amount calculation block PSH, the position change amount Psh is calculated based on the actual position Psa of the screw. Specifically, the past value of Psa (value in the past calculation cycle) psa [k] is stored, compared with the current value of Psa (value in the current calculation cycle) psa [g], and the deviation is Calculated as the position change amount Psh. That is, the position change amount Psh is calculated according to Psh = psa [k] −psa [g]. Here, the past value psa [k] is a calculated value one cycle or a plurality of cycles before the current (current) in the calculation cycle, and is a predetermined time from the current value (current value) psa [g]. (Predetermined value) This is the previous calculation value by th0. That is, in the calculation cycle, a predetermined cycle (a preset fixed value) elapses from the past value psa [k] to the current value psa [g].

  In the pressing force change amount calculation block FBH, the pressing force change amount Fbh is calculated based on the pressing force actual value Fba. Specifically, in each calculation cycle, the Fba past value fba [k] corresponding to the Psa past value psa [k] and the Fba current value fba [g] corresponding to the Psa current value psa [g]. Are compared, and the deviation is calculated as the pressing force change amount Fbh. That is, the pressing force change amount Fbh is calculated according to Fbh = fba [k] −fba [g]. psa [k] and fba [k] are values in the same calculation cycle, and psa [g] and fba [g] are values in the same calculation cycle.

  In the rigidity value calculation block GCQ, the rigidity value Gcq is calculated based on the position change amount Psh and the pressing force change amount Fbh. Specifically, the change amount Fbh of the pressing force with respect to the change amount Psh of the position is calculated as the stiffness value Gcq (= Fbh / Psh). The rigidity value Gcq is a value corresponding to the spring constant of the caliper CPR and the series spring of the friction member MSB. For this reason, the pressing force change amount (for example, the pressing force time change amount) Fbh is divided by the position change amount (for example, the position time change amount) Psh to calculate the stiffness value Gcq.

  In the candidate position / candidate force calculation block PFK, when the electric motor MTR is reversely rotated (that is, Bpa is decreased), the screw position is calculated based on the actual position Psa, the actual pressing force Fba, and the rigidity value Gcq. A position (reference position pzr) candidate (candidate position) Pkk serving as a reference for the position (rotation angle) and a candidate (candidate force fzr) Fkk for correcting the pressing force are calculated. Specifically, Psa and Fba at the time of transition from the state where the stiffness value Gcq is equal to or greater than the predetermined value gcqx (the state before one calculation cycle) to the state less than gcqx (the current calculation cycle) are the candidate positions Pkk. , And the candidate power Fkk, respectively. That is, in the calculation cycle of Gcq, the previous value (calculation value in the previous calculation cycle) gcq [g-1] is equal to or greater than gcqx, and the current value (calculation value in the current calculation cycle) gcq [g] Is less than gcqx, the current value psa [g] of the screw position (ie, PSN position) is calculated as the candidate position Pkk, and the current value fba [g] of the pressing force is calculated as the candidate force Fkk and stored. Is done. Therefore, the pressing force corresponding to the candidate position Pkk is stored as the candidate force Fkk.

  In the reference position calculation block PZR, the reference position pzr is determined based on the actual screw position Psa, the rigidity value Gcq, and the candidate position Pkk. Specifically, the reference position calculation block PZR monitors whether or not the stiffness value Gcq is less than a predetermined value gcqx (Gcq <gcqx) from the time when the candidate position Pkk is determined. When the state of “Gcq <gcqx” is continued beyond the displacement (gap equivalent value) skh corresponding to the gap of the power transmission member GSK or the like in Psa (that is, in the corresponding calculation cycle), the candidate position Pkk Is determined as the reference position pzr. However, if the state of “Gcq <gcqx” is not continued beyond the gap equivalent value (displacement) skh, Pkk is forgotten (reset) when Gcq becomes equal to or greater than gcqx.

  In the reference position calculation block PZR, the value at the previous braking is set as the reference position pzr until the reference position pzr is newly updated by the candidate position Pkk. Here, the clearance equivalent value skh is a value corresponding to a mechanical clearance in the BRK power transmission path (power transmission member from MTR to PSN), and is a threshold value set in advance as a design value.

  In the position correction calculation block PSC, Psa acquired by PSA is corrected by the reference position pzr, and a corrected screw position (corrected position) Psc is calculated. Psa at the time point set as the reference position pzr is set to the zero point, and the correction position Psc is calculated. In other words, at the screw position after correction (PSN position after correction) Psc, the reference position pzr, which is the boundary between whether the pressing force is generated between the MSB and KTB, is the position acquisition means (for example, the rotation angle). Sensor MKA) The zero point position of PSA.

  In the corrected pressing force calculation block FZR, the corrected pressing force fzr corresponding to the zero point drift of Fba acquired by the FBA is calculated based on the actual position Psa, the stiffness value Gcq, and the candidate force Fkk. Similar to the method of determining the reference position pzr, the actual pressing force Fba at the time of transition from the state where the stiffness value Gcq is equal to or greater than the predetermined value gcqx (the state before one computation cycle) to the state less than gcqx (the current computation cycle) is Is stored as a candidate force (candidate of corrected pressing force) Fkk, and when the state of “Gcq <gcqx” continues beyond the gap equivalent value skh in Psa, the candidate force Fkk is adopted as the corrected pressing force fzr. Is done. Therefore, the reference position pzr and the correction pressing force fzr are determined simultaneously (in the same calculation cycle). Therefore, the pressing force corresponding to the reference position pzr is determined as the corrected pressing force fzr. When the state of “Gcq <gcqx” is not continued beyond the gap equivalent value skh, the correction candidate force Fkk is temporarily forgotten (reset) when Gcq becomes equal to or greater than gcqx.

  In the pressing force correction calculation block FBC, the actual pressing force Fba is corrected based on the corrected pressing force fzr, and the corrected pressing force (corrected pressing force) Fbc is calculated. Since the corrected pressing force fzr corresponds to the zero point drift of the pressing force acquisition means FBA, error correction is performed by subtracting the corrected pressing force fzr from the actual pressing force Fba, and the corrected pressing force Fbc is calculated.

  Further, since there is a mutual relationship (proportional relationship when the speed of the electric motor is constant) between time and the displacement of the electric motor, the gap equivalent value is replaced with the displacement threshold value skh, A time threshold skt may be employed. That is, it is determined whether or not the state of “Gcq <gcqx” is continued beyond the time skt under the condition related to the gap equivalent value.

  When the rigidity value Gcq (corresponding to the spring constant of BRK) becomes less than the predetermined value gcqx, the reference position pzr is not immediately determined, but this state (Gcq <gcqx state) is the gap equivalent values skh, skt The reference position pzr is determined for the first time. For this reason, the reference position pzr can be accurately determined even if there is an ineffective displacement due to the gap between the power transmission members such as the speed reducer. Further, since the stiffness value (actual value) Gcq is calculated as the ratio of the pressing force change amount Fbh to the position change amount Psh, the influence of the error of the obtaining means (sensor) (particularly, the zero point drift of the FBA) is compensated. obtain. The gap (clearance) of the power transmission member is caused by, for example, a gear backlash, a joint gap, or a bearing gap. Furthermore, these gaps can be enlarged by aging. For this reason, the clearance equivalent values skh and skt can be values (predetermined predetermined values) that allow for the clearance of the power transmission member including aged wear.

  The “force” is detected by measuring the strain of the strain generating body (displacement that occurs when the force is received). In this distortion detection, drift (offset) of the detected value becomes a problem. The actual pressing force Fba at the candidate position Pkk is stored, and the zero point drift value fzr is determined based on the actual pressing force Fba at the time when the reference position pzr is determined when the gap equivalent value condition is satisfied. For this reason, compensation for the zero point drift of the FBA can be reliably performed.

  In the correction calculation block HSI, signals Psa and Fba from the acquisition means PSA and FBA are used to calculate the zero points pzr and fzr of each acquisition means. Since the correction calculation block HSI is programmed in the driving means DRV (particularly the processor), the signals (actual pressing states) Psa and Fba do not need to be transmitted to the electronic control unit ECU. That is, the zero point correction calculation of the actual state acquisition means FBA, PSA (MKA) is completed in the drive means DRV. For this reason, an increase in the communication load of the serial communication bus SCB can be suppressed.

<Time series pattern of pullback control>
Next, with reference to FIG. 5, the time series pattern of the pull back control stored in advance in the control pattern storage block PTN in the pull back control block HMC will be described. In each control pattern (transition of the target position Pst in time series), “to which contact state the screw member NJB is pulled back” is different. As the screw contact state, the MSB is in contact with the KTB and the PSN is receiving a force from the MSB (press contact state), the MSB and the KTB are just starting to leave, and the screw contact portion is free There are three states: (a free contact state) and a state where a part different from that in the press contact state contacts and the PSN moves away from the KTB (retraction contact state). Therefore, three control patterns are stored in the PTN.

  First, the “contact release pattern” for changing from the pressed contact state to the free contact state will be described. In the contact release pattern, the screw is pulled back until the contact of the first contact portion (first flank) of the screw is released and the first contact portion becomes free. Specifically, it is pulled back from the reference position pzr to the first pull-back position (predetermined value) ps1 at the speed of the pressing member PSN (time change of PSN position, predetermined value) dps1 (time point t1). Then, after being held for a predetermined time thj at the position ps1, the screw is moved to the standby position psb during non-braking at the screw speed (predetermined value) -dps2 (time point t3).

  The standby position psb is the position of the screw (that is, the pressing member PSN) when the driver is not operating the braking operation member (when not braking). During non-braking, the screw standby position psb is set so that the MSB can be held at a position slightly separated from the KTB (position separated from the reference position pzr by the value ps0) in order to suppress dragging of the MSB. Here, the value ps0 may be set to “zero”. In this case, the standby position psb matches the reference position pzr.

  Next, the “contact switching pattern” for changing from the free contact state to the pull back contact state (starting from the press contact state) will be described. In the contact switching pattern, the screw is pulled back through the free contact state until a portion (second contact portion) different from the pressed contact state contacts. In the case of a trapezoidal screw, the flank (pressure-side flank during pressing, which is the first flank) on the opposite side to the flank abutting in the pressing-abutted state (play-side flank during pressing, the second flank) Is pulled back until it comes into contact. Specifically, it is pulled back from the reference position pzr to the second pull-back position (predetermined value) ps2 at the speed of the pressing member PSN (time change of PSN position, predetermined value) dps1 (time point t4). Similarly, after being held for a predetermined time thj at the position ps2, the screw is moved to the standby position psb at a screw speed (predetermined value) −dps2 (time point t6).

  Finally, a description will be given of a “limit pull-back pattern” in which the transition from the free contact state to the pull-back contact state (starting from the press contact state) is made, and further, the screw is pulled back to the limit portion where the screw can be screwed. In the limit pull-back pattern, the screw is pulled back to the limit portion where the screw can be screwed through the state where the contact portion is switched. For example, in the screw member NJB, the screw is pulled back until the movement is limited by the stopper. Specifically, it is pulled back from the reference position pzr to the third pullback position (predetermined value) ps3 at the PSN speed (PSN position temporal change, predetermined value) dps1 (time t7). Similarly, after being held for a predetermined time thj at a position ps3 (for example, a stopper position), the screw is moved to the standby position psb at a screw speed (predetermined value) −dps2 (time point t9).

  In the pullback control, there is a trade-off between the pullback amount (distances from pzr to ps1, ps2, and ps3) and the lubrication state update allowance. In the contact switching pattern (corresponding to the position ps2) and the limit pullback pattern (corresponding to the position ps3) having a large pullback amount, the effect of updating the lubrication state is large, but braking is started during the pullback control. In some cases, it takes time until the braking torque is generated. On the contrary, in the contact release pattern (corresponding to the position ps1) with a small pullback amount, the effect of updating the lubrication state is limited. However, when braking is started during the pullback control, the braking torque is immediately increased. Can be generated. Since each pullback control pattern is selected according to the situation based on the acceleration operation amount Apa, the vehicle speed Vxa, and the like, the above trade-off can be satisfied.

<Embodiment of braking means BRK>
Next, an embodiment of the braking means (brake actuator) BRK will be described with reference to FIG. FIG. 6 corresponds to FIG. In FIG. 6, the electric motor MTR, the speed reducer GSK, the pressing member (brake piston) CPR and the like are the same as those in FIG.

  The input member INP is fixed to the output shaft of the reduction gear GSK (for example, the rotation shaft of the large diameter gear DKH). The input member INP contacts the shaft member SFT via the universal joint UNV. Specifically, a spherical surface (for example, a concave spherical surface) is formed at the end of the input member INP (the side opposite to the portion fixed to the GSK), and this end can function as a part of the universal joint UNV. .

  The pressing force acquisition means FBA is fixed to the caliper CPR, and acquires (detects) the reaction force (reaction) of the force (pressing force) Fba that the pressing member PSN presses the friction member MSB. The pressing force acquisition means FBA is provided in the input member INP and outputs Fba.

  A universal joint UNV is provided between the input member INP and the shaft member SFT. Specifically, a spherical member (a member having a concave spherical surface with a radius rq) QMB is provided between the input member INP and the shaft member SFT, and the end surface of the shaft member SFT has a spherical shape (a convex spherical shape with a radius rq). It is said. The shaft member SFT and the spherical member QMB slide to function as a universal joint UNV. The universal joint UNV transmits power by absorbing the eccentricity (axial deviation) between the axis Jin of the input member INP and the axis Jsf of the shaft member SFT. Note that the above-described shaft misalignment is caused by bending of the floating caliper CPR and uneven wear of the friction member MSB.

  The pressing member PSN slides in the caliper CPR in the axial direction of the PSN (Jsp direction, ie, the axial direction Jsf of the SFT), and presses the friction member MSB against the rotating member KTB. By the key member KYA and the key groove KYM, the movement of the pressing member PSN is performed in the shaft axis direction (longitudinal direction of the key groove KYM) with the rotational movement with respect to the caliper CPR limited. Since the eccentricity of Jin and Jsf is absorbed by the universal joint UNV, the shaft (shaft shaft) Jsf of the shaft member SFT and the shaft (pressing shaft) Jps of the pressing member PSN are coaxial.

  The pressing member PSN has a cup shape. Specifically, the pressing member PSN has a cylindrical shape (cylinder shape), and has a shape in which one is closed and the other is open in the axial direction (Jps direction). A first tube portion (inner wall) Et1 is formed on the inner side (inner peripheral side) of the pressing member PSN. The first cylindrical portion Et1 has a smooth surface (that is, the surface is formed by an assembly of straight lines and has a generatrix), and is smooth. Here, when a curved surface is drawn by movement of a straight line, the straight line at each position is a generatrix of the curved surface.

  One end portion of the pressing member PSN is provided with a sealing wall (partition wall) Mp1, and the first cylindrical portion Et1 is closed (closed). The other end of the pressing member PSN (opposite side of the sealing wall Mp1) is an opening (one part of PSN) Kk1, and the first tube portion Et1 is in an open state.

  A bolt member BLT having a male screw ONJ is fixed to the pressing member PSN (specifically, the sealing wall Mp1). A storage chamber Hch is formed that is partitioned by the first cylindrical portion (inner wall of PSN) Et1, the sealing wall (partition wall of PSN) Mp1, the cap member (lid) CAP, and the second cylindrical portion (outer wall of SFT) Et2. . The interior of the storage chamber Hch is filled with grease GRS containing a solid lubricant without being mixed with gas. The locations where the grease GRS enters and exits from the storage chamber Hch are limited to the screw member NJB (particularly, the gap between the screws) and the cap member CAP (particularly, the gap between Et1 and Et2).

  The screw member NJB converts the rotational power of the shaft member SFT into linear power of the pressing member PSN (that is, a rotation / linear motion conversion member). The screw member NJB includes a bolt member BLT and a nut member NUT. The bolt member BLT is fixed to the sealing wall Mp1 of the pressing member PSN. A male thread (outer thread) ONJ is formed on the bolt member BLT. The nut member NUT is fixed to the shaft member SFT. A female screw (inner screw) MNJ is formed on the nut member NUT, and the female screw MNJ and the male screw ONJ are screwed together. Grease GRS is applied to the screw member NJB. Specifically, the gap between the male screw ONJ and the female screw MNJ is filled with grease GRS containing a solid lubricant by removing gas as much as possible.

  The shaft member SFT transmits the rotational power of the input member INP to the screw member NJB. A spherical surface (for example, a convex spherical surface) is provided at the end of the shaft member SFT that contacts the input member INP, and slidably contacts the spherical member QMB and functions as a part of the universal joint UNV.

  The shaft member SFT has a cup shape having a smaller diameter than the first cylindrical portion Et1 on the side opposite to the portion that contacts the input member INP. In the cup shape of the shaft member SFT, the second cylinder part Et2 is formed on the outer side, and the third cylinder part Et3 is formed on the inner side. The second cylindrical portion Et2 has a straight surface (that is, a bus bar) and is smooth. One end portion of the third cylinder portion Et3 is provided with a sealing wall Mp3 so that Et3 is closed. The other end (the opposite side of the sealing wall Mp3) of the third cylindrical portion Et3 is an opening (one part of SFT) Kk3, and Et3 is in an open state.

  The shaft member SFT is inserted inside the first cylindrical portion Et1 (for example, a PSN inner peripheral portion having a cylindrical shape) of the pressing member PSN. For this reason, the first cylinder portion Et1 of the pressing member PSN and the second cylinder portion Et2 of the shaft member SFT (for example, an SFT outer peripheral portion having a cylindrical shape) have an overlap portion (overlapping portion) Ovp. A nut member NUT having an internal thread MNJ is fixed to the third cylinder portion Et3. A closed space Hmp (isolated from the outside and closed) that is partitioned by the third cylindrical portion Et3 (for example, an SFT inner peripheral portion having a cylindrical shape), a sealed wall (SFT partition wall) Mp3, and a nut member NUT ) Is formed. The inside of the sealed chamber Hmp is filled with grease GRS without being mixed with gas (gas is removed as much as possible). The location where grease enters and exits from the sealed chamber is limited to the screw member NJB (particularly, the gap between the screws).

  The cap member CAP prevents the grease GRS from flowing out from the storage chamber Hch (for example, position Pb3) to the external position Pb4, and gas (air) is transferred from the external position Pb4 to the storage chamber Hch (for example, position Pb3). It is a lid (cap) for preventing inflow. Specifically, the cap member CAP has a disk shape with a hole in the center, and is in sliding contact with the first cylindrical portion Et1 at the outer peripheral portion thereof, and is in sliding contact with the second cylindrical portion Et2 at the inner peripheral portion thereof. The cap member CAP can move in the axial direction relative to the pressing member PSN and the shaft member SFT (linear movement in a direction parallel to the axis, and movement in the Jps direction and Jsf direction). is there. In addition, relative rotation about the axis with respect to at least one of the pressing member PSN and the shaft member SFT (rotational movement around the axis, around Jps and around at least one axis around Jsf) Relative rotational movement). Here, the axis Jps of the pressing member PSN and the axis Jsf of the shaft member SFT are the same.

  The reduction in the efficiency of the screw member NJB, which is a power conversion member, is largely due to the depletion (grease breakage) of the grease GRS. Specifically, the depletion of the grease GRS can occur when gas (air) enters the interface lubricated by the grease GRS. For this reason, grease GRS is filled in and around the screw member NJB, and these parts are separated (isolated) from the part (gas part) where gas (for example, air) exists, The lubrication state of the screw member NJB can be maintained well.

  A sealed chamber Hmp is formed at one end (position Pb1) of the screw member NJB, and the inside thereof is fully filled with grease GRS containing a solid lubricant. That is, a dead-end chamber (sealed chamber) Hmp partitioned by a wall is provided at one end of the screw member NJB, and the internal gas is removed as much as possible and is filled with the grease GRS. For this reason, gas does not flow in from the position Pb1 of one end of the screw member NJB. A storage chamber Hch is formed at the other end (position Pb2) of the screw member NJB, and the inside thereof is also filled with grease GRS. That is, even in the Hch, the gas is removed as much as possible to fill the GRS. The path through which the gas flows into the storage chamber Hch is from the opening Kk1, but the path is covered (closed) by the cap member CAP, and the inflow of gas from this portion is suppressed. . In this embodiment, the first cylindrical portion Et1 and the second cylindrical portion Et2 with which the cap member CAP is slidably contacted are formed so that the shape of the slidable contact surface (sliding surface) is a straight line (an assembly of straight lines). . Therefore, inflow of gas and outflow of grease GRS can be effectively prevented.

  Furthermore, in the pressing member PSN and the shaft member SFT, two cylindrical members having large and small cup shapes with different diameters are configured to face each other and overlap at the respective openings Kk1 and Kk3. . Therefore, a storage chamber Hch (a chamber filled with grease GRS) is formed at least over the overlap portion Ovp (internal space of the PSN). That is, the grease GRS exists from the end portion Pb2 of the screw member NJB to the vicinity of the portion Pb4 where the gas exists. By this overlap structure, the path from the screw member NJB (position Pb2) to the position Pb4 can be sufficiently secured without increasing the axial length of the entire BRK. Since the section filled with the grease GRS is set longer with respect to the screw member NJB, it is isolated from the gas part (position Pb4), so that the gas inflow to the screw member NJB can be effectively suppressed.

  In the screw shapes of the male screw ONJ and the female screw MNJ, a screw gap (mountain gap and flank gap) can be a flow path of the grease GRS. Due to the movement of the pressing member PSN (advance or retreat with respect to the rotating member), a volume change occurs in the sealed chamber Hmp. Specifically, when the pressing member PSN moves forward toward the rotating member KTB (when the pressing force Fba increases and the braking torque increases), the volume of the sealed chamber Hmp is the amount that the bolt member BLT moves forward. Only increase. Conversely, when the pressing member PSN is retracted from the rotating member KTB (when the pressing force Fba is decreased and the braking torque is decreased), the volume of the sealed chamber Hmp is decreased by the amount of the bolt member BLT being retracted. Since the screw member NJB and the sealed chamber Hmp are fully filled with the grease GRS (that is, no gas is mixed), the volume change is stored in the grease GRS through the gap of the screw member NJB. It can be absorbed by moving to the chamber Hch.

  One cause of the decrease in efficiency of the screw member NJB is that the same portion is always in contact with the solid lubricant contained in the grease GRS. Specifically, the contact part (that is, the power transmission part) of the solid lubricant in the grease GRS does not change, and the limited part always transmits power. The grease GRS in the screw member NJB is updated by the movement of the grease GRS, the solid lubricant is rotated, and the contact portion (power transmission portion) is changed, so that the lubrication state can be properly maintained.

  The universal joint UNV may be provided between the pressing member PSN and the shaft member SFT. However, when this configuration is adopted, the first cylindrical portion Et1 (a part of the pressing member PSN, an inner peripheral portion) and the second cylindrical portion Et2 (a part of the shaft member SFT, the outer peripheral portion). ) Is insufficient, the cap member CAP is inclined, and the movement of the cap member CAP in the axial direction can be hindered. On the other hand, in this embodiment, since the universal joint UNV is provided between the input member INP and the shaft member SFT, the parallelism between the first cylindrical portion Et1 and the second cylindrical portion Et2 is maintained, and the cap member CAP is maintained. Smooth sliding can be ensured.

<Screw member (power conversion member)>
Next, the details of the screw member NJB, which is a power conversion member, will be described with reference to FIG. NJB is a feed screw and includes a female screw MNJ and a male screw ONJ.

  FIG. 7A is for defining and describing the names of the respective parts in the screw member NJB. The shape of the female thread (inner thread) MNJ is composed of a female thread crest Ymn and a female thread trough (groove) Tmn. Specifically, it is composed of a female thread peak Scm, a female thread flank Fmn, and a female thread root Tzm. Similarly, the male thread (outer thread) ONJ has a male thread crest Yon and a male thread trough (groove) Ton. Specifically, it is constituted by a male thread crest Sco, a male thread flank Fon, and a male thread valley bottom Tzo. Here, the summits Scm and Sco are flat portions at the top of the crest of the screw, and the valley bottoms Tzm and Tzo are flat portions at the bottom of the trough of the screw. Franks Fmn and Fon are surfaces that connect the summits Scm and Sco to the valley bottoms Tzm and Tzo. Fmn and Fon are straight in the cross section including the rotation axis of the screw. Power is transmitted by pressure contact between the flank Fmn of the internal thread MNJ and the flank Fon of the external thread ONJ.

  FIG. 7B is for explaining a screwed state of the female screw MNJ and the male screw ONJ when the rotational motion is converted into a linear motion via the power conversion member NJB. Here, the rotational motion of the female screw MNJ (that is, the nut NUT) is converted into the linear motion of the external screw ONJ (bolt BLT). FIG. 7B shows that the female thread crest Ymn and the male thread trough Ton mesh with the female thread trough Tmn and the male thread crest Yon, and the female thread MNJ is the male thread ONJ. Is pressed (in the drawing, the female screw MNJ is pressing the male screw ONJ in the direction of the arrow). In the female thread MNJ and male thread ONJ, the flank on which the force is acting (the load receiving side) is called the pressure flank (Pressure Flank) and is the flank on the opposite side of the pressure flank. The flank on which no force is applied is referred to as a play flank.

  In the play side flank, the gap (distance on the pitch line) between the play side flank of the female screw MNJ and the play side flank of the male screw ONJ is referred to as a flank gap Cfk. The pitch line Pch is a virtual cylindrical bus (Generatrix) used to define the effective diameter of the screw. That is, it is a cylindrical bus line in which the width Wyo of the external thread is equal to the width Wym of the internal thread, and the internal thread valley width (external thread groove width) Wto and internal thread valley width (internal thread groove width). It can also be said that the width of the cylinder is equal to Wtm.

  Grease GRS containing a solid lubricant is injected into the screw gap. The screw gap is represented by a portion indicated by abbcd-e-f-gh in the cross-sectional shape of the screw, and the crest gap Csm of the female screw MNJ, the crest gap Cso of the male screw ONJ, And it is formed in the flank gap Cfk. Here, the crest gap (also the crevice gap of the male thread) Csm of the female thread MNJ is a gap between the crest Scm of the female thread and the crest Tzo of the male thread. Specifically, in the cross-sectional shape of the female screw MNJ and male screw ONJ that are concentrically fitted to each other (cross-section including the screw rotation axes Jps and Jsf), the top of the female screw (surface that connects the flank on both sides of the screw thread). And a straight line connecting the bottom of the male thread (the surface connecting the flank on both sides of the thread groove). Similarly, a crest gap (also a crevice gap of a female thread) Cso of the external thread ONJ is a gap between a crest Sco of the external thread and a trough bottom Tzm of the internal thread. Specifically, in the cross-sectional shape of the female screw MNJ and the male screw ONJ that are concentrically fitted to each other (cross-section including the screw rotation axes Jps and Jsf), a straight line that connects the valley bottoms of the female screw and a straight line that connects the tops of the male screws It is a gap between. The flank gap Cfk is a gap between the flank Fmn of the internal thread MNJ and the flank Fon of the external thread ONJ.

  Since the volume change of the sealed chamber Hmp is generated in accordance with the movement (movement) of the pressing member PSN, the screw gap becomes a moving path of the grease GRS between the sealed chamber Hmp and the storage chamber Hch. Specifically, when the pressing force Fba is increased, the volume of the sealed chamber Hmp is increased, and when Fba is decreased, the volume of Hmp is decreased. Since the sealed chamber Hmp is filled with the grease GRS containing the solid lubricant, this volume change is absorbed by the grease GRS moving through the screw gap. In other words, when the volume of the sealed chamber Hmp decreases, the grease GRS in the sealed chamber Hmp is discharged to the screw member NJB. Conversely, when the volume of the sealed chamber Hmp increases, the grease GRS is sucked into the sealed chamber Hmp from the screw member NJB. Due to the movement of the grease GRS, the solid lubricant in the power conversion member is moved, and the lubrication state can be properly maintained.

  When the screw gaps (mountain gaps Csm, Cso and flank gap Cfk) serve as a flow path for the grease GRS, the flow resistance (viscosity resistance) of the grease GRS affects the efficiency of the braking means BRK. Therefore, the cross-sectional area of the screw gap is set based on the viscosity (consistency) of the grease GRS. And, in the no-load state (state where the pressing force is zero), the rotational power of the electric motor MTR necessary for the flow of the grease GRS (that is, the torque loss due to the movement of the grease GRS) is less than a predetermined value. The cross-sectional area of the screw gap can be determined. Here, the cross-sectional area of the screw gap is the total area of Csm, Cso, and Cfk in the cross section including the screw rotation axis (Jps, Jsf). In the example shown in FIG. It is the area of the part enclosed by a) thru | or (h).

  Since the part that converts the rotational power of the electric motor MTR into the pressing force is a screw flank, it is desirable that the grease GRS be moved with respect to the flank gap. In the thread shape of the thread member NJB, the thread groove (thread valley) width Wtm, Wto is the thread width Wym, in the thread pitch line Pch so that at least the flank gap Cfk becomes the grease GRS flow path. It is set larger (wider) than Wyo. The grease GRS is moved between the sealed chamber Hmp and the storage chamber Hch through this gap (flank gap Cfk). When the screw is screwed, a certain amount of backlash is required, but the flank gap Cfk can be set to a value larger than the standard backlash determined by the screw standard. Further, the flank gap Cfk (the distance between the line segment bc and the line segment fg) is the summit clearance Csm (the distance between the line segment cd and the line segment ef) of the female screw MNJ, and the summit gap Cso (line of the external thread ONJ). It is set to be larger (wider) than at least one of the distance ab and the line segment gh).

<Movement of grease GRS by pullback control>
Next, the movement of the grease GRS that occurs in the screw member NJB by pullback control will be described with reference to FIG. FIG. 8 corresponds to FIG. Accordingly, in FIG. 8, the same symbols as those in FIG. 6 are given to members that perform the same or equivalent functions as the members shown in FIG. 6.

  FIG. 8A shows a state where the actual position Psa of the screw (that is, the actual position of the pressing member PSN) matches the reference position pzr. By the pull back control, the actual position (actual position of the screw) Psa of the pressing member PSN is retracted to the position ps1, ps2, or ps3 (that is, moved away from the KTB). Finally, as shown in FIG. 8B, the actual position Psa is advanced from the position ps1, ps2, or ps3 to the standby position psb (that is, moved in a direction approaching KTB). . Here, the standby position psb is the position of the PSN at the time of non-braking, and is a position away from the reference position pzr by ps0 (a minute predetermined value). By maintaining the PSN at the standby position psb, it is possible to prevent dragging of the MSB during normal travel (a state where the MSB and KTB are in slight contact with each other and friction is generated).

  A bolt member BLT having a male screw ONJ is fixed inside the pressing member (piston) PSN having a cup shape (one shape is closed in the Jps axial direction and the other is open). The storage chamber Hch is formed by being partitioned by the inner periphery of the PSN and the partition, the cap member CAP, and the outer periphery of the SFT.

  The shaft member SFT that transmits rotational power to the screw member NJB has a cup shape (a shape in which one is closed and the other is open in the Jps axial direction). The SFT is inserted inside the PSN so that the opening of the PSN faces the opening of the SFT. That is, the inner peripheral portion of the pressing member PSN and the outer peripheral portion of the shaft member SFT are configured to overlap each other. A nut member NUT having a female screw MNJ is fixed inside the shaft member SFT, and the NUT is screwed with a screw ONJ of the bolt member BLT. The sealed chamber Hmp (a space that is isolated from the outside and closed) is partitioned by the inner peripheral portion of the SFT, the partition wall, the NUT, and the BLT.

  The screw member NJB, the storage chamber Hch, and the sealed chamber Hmp are filled with grease GRS containing a solid lubricant without gas being mixed therein (gas is removed as much as possible). That is, the inflow / outflow of the grease GRS from the storage chamber Hch is limited to the screw member NJB (particularly, the trapezoidal screw gap) and the gap between the cap member CAP and the PSN inner peripheral part (or SFT outer peripheral part). In addition, the entrance and exit of the grease from the sealed chamber Hmp is limited to the screw member NJB (particularly, the gap between the screws).

  Assume that the braking torque is gradually decreased (the vehicle deceleration is decreased). The electric motor MTR is rotated in the reverse direction, and the pressing member PSN is retracted from the rotating member KTB (moved toward the reference position pzr). In this case, the volume of the sealed chamber Hmp is reduced, but the grease GRS moves through the screw gap (from the position Pb1 toward the position Pb2) and flows out from the sealed chamber Hmp to the storage chamber Hch. Although the volume of the GRS in the Hch increases, the cap member CAP is moved in the direction away from the KTB (right direction), and this volume change is absorbed. When the PSN reaches the reference position pzr, the braking torque becomes zero.

  By the pull back control, as indicated by the arrow (1), the position of the pressing member PSN (that is, the screw position) is further pulled back from the reference position pzr (MSB starts to be separated from the KTB). When the pull back control based on the contact release pattern (return to the position ps1) is selected, the PSN position is retracted until the free contact state is achieved. Since the PSN position is returned to the free contact state, the first contact portion (first flank) that has been in contact begins to leave, and grease GRS enters here. For this reason, the lubrication of the screw member NJB can be improved.

  When the pull-back control based on the contact switching pattern (return to the position ps2) is selected, the PSN position is retracted from the free contact state to the pull-back contact state. Since the PSN position is returned to the retracting contact state, the portion that is in contact in the pressing contact state (the pressure side portion during pressing, for example, the first flank) is the portion on the opposite side (playing side when pressed) The part is pulled back until the second flank contacts. At this time, the first contact portions (first flank) are separated as much as possible and filled with grease GRS. Similarly, when the pull-back control based on the limit pull-back pattern (return to the position ps3) is selected, similarly, the first abutment portion (first flank) is isolated to the maximum, and this is filled with the grease GRS. .

  In the pull-back control, after reaching the final target positions ps1, ps2, and ps3, the positions are maintained for a predetermined time tsj. Thereafter, as indicated by the arrow (2), the electric motor MTR is rotated forward and the pressing member PSN is advanced toward the standby position psb. In this case, the volume of the sealed chamber Hmp is increased, but the grease GRS moves through the screw gap (from the position Pb2 toward the position Pb1) and flows into the sealed chamber Hmp from the storage chamber Hch. Although the volume of GRS in the Hch decreases, the cap member CAP is moved in the direction approaching KTB (left direction), and this volume change is absorbed.

  The efficiency reduction of the screw member NJB is caused by exhaustion of the grease GRS (grease breakage) and continuous contact of the same portion of the solid lubricant contained in the grease GRS. The depletion of grease GRS occurs when gas (air) enters the interface lubricated by the grease GRS. By forming Hmp and Hch, a portion (in the screw member NJB and its peripheral portion) filled with the grease GRS is moved away from a portion (gas portion) where gas (for example, air) exists. By being (isolated), the lubrication state of the screw member NJB can be maintained well. Moreover, the contact part (namely, power transmission part) of the solid lubricant in the grease GRS does not change, and the limited part always transmits power may occur because the GRS is not moved. The grease GRS in the screw member NJB is moved by the pull-back control (that is, the reverse movement of the PSN from the reference position pzr), so that the GRS is updated and the solid lubricant is rotated to The state is renewed, and the lubrication state can be properly maintained.

  During non-braking, the pressing member PSN is maintained at the standby position psb. The standby position psb exists in a direction away from the rotary member KTB by a distance ps0 from the reference position pzr. Therefore, there is a gap between the rotating member KTB and the friction member MSB during non-braking. As a result, MSB dragging (power loss due to friction with KTB) can be suppressed.

  MSB ... friction member, KTB ... rotating member, PSN ... pressing member, MTR ... electric motor, BPA ... operation amount acquisition means, FBA, PSA, MKA ... real state acquisition means, TRG ... target state calculation means, DRV ... drive means, SCB ... Bus

Claims (3)

A rotating member fixed to a vehicle wheel;
An electric motor provided on the wheel side;
A friction member that presses the rotating member to generate a braking torque on the wheel;
A pressing member that presses the friction member toward the rotating member using a driving torque of the electric motor;
An operation amount acquisition means for acquiring an operation amount of a braking operation member operated by a driver of the vehicle;
Real state acquisition means provided on the wheel side and acquiring an actual value of the pressing state of the pressing member as an actual pressing state;
A target state calculation means that is provided on the vehicle body side of the vehicle and calculates a target value of the pressing state as a target pressing state based on the operation amount;
Drive means provided on the wheel side, for controlling the electric motor based on the target pressing state and the actual pressing state;
A bus for transmitting a signal representing the target pressing state from the target state calculating means to the driving means;
An electric braking device for a vehicle, comprising: The electric braking device for a vehicle according to claim 1,
The electric braking device for a vehicle, wherein the bus is a serial bus. In the electric braking device for a vehicle according to claim 1 or 2,
The driving means includes
When the driver of the vehicle is operating the braking operation member, the target pressing force that is a target value of the pressing force of the pressing member as the target pressing state, and the actual pressing state, Controlling the electric motor based on an actual pressing force which is an actual value of the pressing force of the pressing member;
When the driver of the vehicle is not operating the braking operation member, the target position that is the target value of the position of the pressing member as the target pressing state, and the pressing as the actual pressing state An electric braking device for a vehicle configured to control the electric motor based on an actual position which is an actual value of a position of a member.

Images