JP6405855B2 - Brake control device for vehicle - Google Patents

Description

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

  In Patent Document 1, “a pressurizing mechanism that is driven by an electric motor and pressurizes braking fluid in a wheel cylinder of a vehicle” and “a first fluid path that connects the pressurizing mechanism and the wheel cylinder” are disclosed. A pressure adjusting means (hydraulic pressure modulator) that is interposed in the middle and adjusts the pressure of the brake fluid (brake fluid pressure) in the wheel cylinder ”,“ the operation amount of the brake operation member, and the wheel speed of the vehicle ” Based on the above, there is known a vehicle braking control device including a pressurizing mechanism and a control means for controlling a pressure adjusting means.

In this apparatus, the “pressurizing mechanism” includes a “piston driven in the axial direction by an electric motor”. This piston has a "first fluid chamber formed inside the pressurizing mechanism and connected to the first fluid path" and a "fluid path leading to a reservoir formed inside the pressurizing mechanism and storing braking fluid". And a “second fluid chamber connected”. When this piston moves in the first direction in the axial direction (the direction toward the first fluid chamber), the volume of the first fluid chamber is reduced and the output pressure of the pressurizing mechanism (regulated with the pressurizing mechanism in the first fluid path). When the piston moves in the second direction (the direction toward the second fluid chamber), the volume of the first fluid chamber increases and the output pressure of the pressurizing mechanism increases. Decrease. Based on the operation amount of the braking operation member, the output pressure of the pressurizing mechanism is controlled by adjusting the position of the piston in the axial direction by controlling the electric motor.

  Further, in this device, anti-skid control for suppressing the lock of the wheel is executed by controlling the pressure adjusting means based on the wheel speed. While the anti-skid control is being executed, while the brake fluid pressure increasing mode is selected, the brake fluid pressure increases by controlling the pressure adjusting means and supplying the brake fluid from the pressurizing mechanism to the wheel cylinder. . While the brake fluid pressure reducing mode is selected, the brake fluid pressure is reduced by controlling the pressure adjusting means to discharge the brake fluid from the wheel cylinder to the reservoir. Regarding the pressure adjusting means, the “type in which the brake fluid is discharged to the reservoir in the pressure reducing mode” is also referred to as “discharge type”. The “discharge type” pressure adjusting means does not require a pump / motor and can be easily downsized.

  Incidentally, as described above, in the configuration in which the “discharge type” pressure adjusting means is employed, the brake fluid is discharged from the wheel cylinder to the reservoir in the pressure reducing mode during the execution of the anti-skid control, and after the pressure reducing mode, In the pressure-increasing mode selected subsequently, the brake fluid is replenished from the pressurizing mechanism to the wheel cylinder by the piston of the pressurizing mechanism moving in the first direction. In other words, each time the pressure increasing mode is executed, the piston of the pressurizing mechanism advances in the first direction. Therefore, when the anti-skid control is continued for a relatively long time (for example, when the anti-skid control is started at a relatively high vehicle speed on a road surface having a low road friction coefficient), the decompression mode and the pressure increase are performed. When the mode and the mode are repeatedly executed repeatedly (therefore, the pressure increasing mode is executed many times), the situation in which the position of the piston reaches the movable limit in the first direction (so-called piston bottoming) occurs. May occur. In order to properly execute anti-skid control over a relatively long time, it is anxious to reduce the possibility of such piston bottoming.

JP 2012-131263 A

  The present invention has been made to cope with the above-described problems, and the object thereof is to include a “pressurizing mechanism driven by an electric motor” and a “discharge type pressure adjusting means (hydraulic pressure modulator)”. An object of the present invention is to provide a braking control device for a vehicle, which is less likely to cause bottoming of a piston of a pressurizing mechanism even when anti-skid control is performed for a relatively long time.

  The braking control device according to the present invention includes the same “the pressurizing mechanism (KAK) including the piston (KPS)”, “the discharge-type pressure regulating means (hydraulic pressure modulator) (MJR)”, and , “The control means (CTL)”. The piston (KPS) driven by the electric motor (MTR) partitions the first fluid chamber (Rkc) and the second fluid chamber (Rrs).

The braking control device according to the present invention is characterized in that the pressurizing mechanism (KAK) is configured so that “when the piston (KPS) moves in the first direction on the first fluid chamber (Rkc) side in the axial direction, the first The brake fluid is not allowed to move from one fluid chamber (Rkc) to the second fluid chamber (Rrs), and the piston (KPS) is a second fluid chamber (Rrs) side second in the axial direction. A seal member (GCP) that allows movement of braking fluid from the second fluid chamber (Rrs) to the first fluid chamber (Rkc) when moving in the direction, and the control means (CTL) but while the pressure reduction mode during the execution of the anti-skid control is selected, by moving the piston (KPS) in the second direction by controlling the electric motor (MTR), the reservoir ( The brake fluid from SV) (BFL) said second fluid chamber (Rrs) and the sealing member (the via GCP) first fluid chamber (points that are configured to return to Rkc), in.

  Generally, in the pressure reduction mode, the pressure adjusting means is controlled to “a state where the pressure mechanism (KAK) and the wheel cylinder (WC) are shut off and the wheel cylinder (WC) and the reservoir (RSV) are in communication”. Therefore, even if the piston (KPS) is moved in the second direction in the decompression mode, the braking hydraulic pressure (the hydraulic pressure of the wheel cylinder (WC)) is not affected at all. In addition, when the piston (KPS) moves in the second direction by the seal member (GCP) having the above-described configuration, the second fluid chamber (Rrs) to the first fluid chamber (Rkc) (accordingly, the reservoir (RSV) ) To the first fluid path). Therefore, even in the decompression mode (that is, the state where the pressurization mechanism (KAK) and the wheel cylinder (WC) are disconnected), the piston (KPS) is moved in the second direction by the operation of the seal member (GCP). You can move on.

  The above characteristics are based on such knowledge. According to the above feature, in the decompression mode, the piston (KPS) is returned to the second direction (that is, the direction toward the initial position). That is, every time the pressure increasing mode is executed, the piston (KPS) advances in the first direction, while when the pressure reducing mode is executed, the piston (KPS) is returned to the direction toward the initial position. Therefore, even if the anti-skid control is continued for a relatively long time (thus, even if the pressure reduction mode and the pressure increase mode are repeatedly executed alternately and repeatedly), bottoming of the piston (KPS) can be suppressed. .

1 is an overall configuration diagram of a vehicle including an embodiment of a braking control device according to the present invention. It is a functional block diagram for demonstrating the process by the control means CTL shown in FIG. It is a fragmentary sectional view of pressurization mechanism KAK shown in FIG. It is the figure which showed the structure of the pressure regulation means MJR shown in FIG. It is a functional block diagram for demonstrating the process in the pressurization control block KAC shown in FIG. It is the 1st time chart which showed an example of the operation by the embodiment shown in FIG. It is the 2nd time chart which showed an example of the action | operation by embodiment shown in FIG.

<Configuration>
An overall configuration of a vehicle including an embodiment of a braking control device according to the present invention will be described with reference to FIG. Hereinafter, in the description of each drawing, the members / mechanisms having the same symbol are the same, and therefore, repeated description may be omitted.

  The vehicle includes a braking operation member BP, an operation amount acquisition unit BPA, an emergency state acquisition unit JQA, a wheel cylinder WC, a master cylinder MCL, a stroke simulator SSM, a pressurization mechanism KAK, a pressure adjustment unit MJR, an electronic control unit ECU, a fluid path HKJ, HJW, HMW, HRK, and solenoid valves VMC, VSS, VKC are provided.

  The braking operation member (for example, brake pedal) BP is a member that the driver operates to decelerate the vehicle. By operating the braking operation member BP, the braking torque of the wheel WH is adjusted, and a braking force is generated on each wheel. A rotating member (for example, a brake disc) KTB is fixed to the wheel WH. The wheel WH is provided with a wheel cylinder WC. By increasing the brake hydraulic pressure in the wheel cylinder WC, the friction member (for example, brake pad) MSB is pressed against the rotating member KTB. A braking torque is generated in the wheel WH by the frictional force generated at this time.

  The wheel cylinder WC is provided with wheel cylinder pressure acquisition means PWA, and the wheel cylinder pressure Pwa is acquired (detected). The wheel WH is provided with wheel speed acquisition means VWA, and the wheel speed Vwa is acquired. The wheel cylinder pressure Pwa and the wheel speed Vwa are transmitted to the electronic control unit ECU.

  The braking operation member BP is provided with an operation amount acquisition means BPA. The operation amount acquisition means BPA acquires (detects) an operation amount (braking operation amount) Bpa of the braking operation member BP by the driver. As the operation amount acquisition means BPA, a sensor (master cylinder pressure acquisition means) PMC that detects the pressure of the master cylinder MCL, an operation force of the braking operation member BP, and / or a sensor that detects the displacement amount (brake pedal depression force sensor, brake A pedal displacement sensor) is employed. Therefore, the braking operation amount Bpa is calculated based on at least one of the master cylinder pressure Pmc, the brake pedal depression force, and the brake pedal displacement. The braking operation amount Bpa is input to the electronic control unit ECU.

  The pressurizing mechanism KAK includes a pressurizing piston KPS, a pressurizing cylinder KCL, a power transmission mechanism DDB, and an electric motor MTR. The pressurizing mechanism KAK is driven by the power of the electric motor MTR and increases the pressure of the wheel cylinder WC.

  The pressure piston KPS and the pressure cylinder KCL are combined to form one piston / cylinder. Specifically, a fluid chamber Rkc (see FIG. 3 described later) is formed (compartment) by the pressurizing piston KPS and the pressurizing cylinder KCL. The pressure piston KPS is moved (reciprocated in the central axis direction of the KCL) by the linear power converted from the rotational power of the electric motor MTR. The fluid chamber Rkc is filled with the brake fluid BFL, and the reciprocating motion causes the brake fluid BFL to move between the pressure cylinder KCL and the wheel cylinder WC. As a result, the pressure of the brake fluid BFL in the wheel cylinder WC is adjusted (increase / decrease).

  The pressurizing mechanism KAK is connected to the wheel cylinder WC via the electromagnetic valve VKC. In order to detect the pressure (output pressure) Pca generated by the pressurizing mechanism KAK, an output pressure acquiring means (pressure sensor) PCA is provided in the middle of the fluid path from the pressurizing mechanism KAK to the pressure adjusting means MJR. .

  The pressure mechanism KAK is provided with a piston position acquisition means (position sensor) PPS for acquiring (detecting) the position Pps of the pressure piston KPS. As the piston position acquisition unit PPS, the rotation angle Mka of the electric motor MTR acquired by the rotation angle acquisition unit MKA can be adopted.

  In the pressurization mechanism KAK, the rotational power (output torque) of the electric motor MTR is transmitted to the pressurization piston KPS via the power transmission mechanism DDB. Specifically, the power transmission mechanism DDB includes a reduction gear GSK and a rotation / linear motion conversion mechanism (screw member) NJB. The rotational power of the electric motor MTR is input to the speed reducer GSK, and this rotational power is decelerated and output from the speed reducer GSK. Then, the rotational power from the speed reducer GSK is converted into linear power by the screw member NJB and transmitted to the pressurizing piston KPS.

  The electric motor MTR is provided with a rotation angle acquisition means MKA, and the rotation angle Mka (for example, rotor position) of the MTR is acquired (detected). The position (displacement) Pps of the pressure piston KPS can be acquired (calculated) based on the motor rotation angle Mka and the specifications of the power transmission mechanism DDB.

  The electronic control unit ECU controls the pressurizing mechanism KAK (specifically, the electric motor MTR), the electromagnetic valves VMC, VSS, VKC, and the pressure adjusting means MJR. The electronic control unit ECU is provided with a control means CTL for controlling the pressurizing mechanism KAK and the like. The control means CTL is a control algorithm and is programmed in a microcomputer in the electronic control unit ECU.

  The master cylinder (also referred to as a brake master cylinder) MCL converts the operation force (brake pedal depression force) of the brake operation member BP, which is transmitted via the push rod PRD, into hydraulic pressure, and supplies the brake fluid BFL to the wheel wheel cylinder WC. Pump. The brake fluid BFL is replenished from the reservoir (also referred to as master reservoir) RSV to the master cylinder MCL via the pipe HRK. That is, when the braking operation member BP is not operated, the master cylinder MCL communicates with the master reservoir RSV via the fluid pipe HRK. Master cylinder MCL is connected to wheel cylinder WC by fluid piping HMW. In other words, the pipe HMW is a fluid pipe that connects the master cylinder MCL and the wheel cylinder WC.

  A simulator (also referred to as a stroke simulator) SSM is provided to generate an operation force on the braking operation member BP. For example, the simulator SSM is provided with a piston and an elastic body (for example, a compression spring). The braking fluid BFL is moved from the master cylinder MCL into the simulator SSM, and the piston is pushed by the flowing braking fluid BFL. A force is applied to the piston in a direction that prevents the inflow of the brake fluid by the elastic body. An operating force (for example, a brake pedal depression force) when the braking operation member BP is operated is formed by the elastic body.

  The fluid paths HKJ and HJW are fluid paths that connect the pressurizing mechanism KAK (particularly, the pressurizing cylinder KCL) and the wheel cylinder WC via a pressure regulating means (hydraulic modulator) MJR. The pipe HKJ is a fluid pipe that connects the pressurizing mechanism KAK (particularly, the pressurizing cylinder KCL) and the pressure regulating means MJR. The pipe HJW is a fluid pipe that connects the pressure adjusting means MJR and the wheel cylinder WC.

  The solenoid valve VKC is provided in the middle of the pipe HKJ, and switches between the HKJ communication / sever communication state. The electromagnetic valve VKC is a 2-port 2-position electromagnetic valve, and is also referred to as a “pressurizing mechanism cutoff valve”. The pressurization mechanism cutoff valve VKC is driven by a signal Skc formed by the control means CTL. Specifically, the VKC is brought into a communication state (open position) when the appropriate state of the device is affirmed by the diagnostic processing block SND in the CTL (during proper diagnosis), and the appropriate state of the device is denied. In the case (during improper diagnosis), the communication state is closed (closed position).

  The solenoid valve VMC is provided in the middle of the pipe HMW, and switches the HMW communication / sever communication state. The electromagnetic valve VMC is a 2-port 2-position electromagnetic valve, and is also referred to as a “master cylinder cutoff valve”. The master cylinder cutoff valve VMC is driven by a signal Smc formed by the control means CTL. Specifically, the VMC is brought into a non-communication state (closed position) when the appropriate state of the device is affirmed (during proper diagnosis) by the diagnostic processing block SND in the CTL, and the appropriate state of the device is denied. If it is detected (due to inappropriate diagnosis), the communication state (open position) is set. Accordingly, the wheel cylinder WC is connected only to the pressurizing mechanism KAK (pressurizing cylinder KCL) when appropriate, and is connected only to the master cylinder MCL when inappropriate.

  The solenoid valve VSS is provided in a path connecting the master cylinder MCL and the simulator SSM. The electromagnetic valve VSS is a 2-port 2-position electromagnetic valve, and is also referred to as a “simulator shut-off valve”. The simulator cutoff valve VSS is driven by a signal Sss formed by the control means CTL. Specifically, when the appropriate state of the device is affirmed by the diagnostic processing block SND in the CTL (at the time of proper diagnosis), the VSS is brought into a communication state (open position) and the appropriate state of the device is denied. In the case (during improper diagnosis), the communication state is closed (closed position). Therefore, when appropriate, the simulator SSM functions as a reaction force generation mechanism for the braking operation member BP. However, at the time of improper diagnosis, the simulator SSM does not consume the brake fluid BFL, and all the brake fluid amount from the master cylinder MCL is moved to the wheel cylinder WC.

  The pressure adjusting means (hydraulic pressure modulator) MJR adjusts the pressure in the wheel cylinder WC of each wheel independently of the operation of the braking operation member BP by the driver. The MJR is an actuator for executing so-called brake control such as anti-skid control. The pressure adjusting means MJR is configured by a solenoid valve (solenoid) SOL.

  The electromagnetic valve SOL is composed of a combination of a pressure increasing valve ZAB and a pressure reducing valve GAB. When the pressure of the wheel cylinder WC is decreased, the pressure increasing valve ZAB is set to the closed position and the pressure reducing valve GAB is set to the open position. Thereby, the inflow of the brake fluid BFL from the pressurizing mechanism KAK into the pressure adjusting means MJR is blocked, and the brake fluid BFL in the wheel cylinder WC is moved to the reservoir RSV via the pipe HMR. That is, the pressure adjusting means (hydraulic modulator) MJR is a so-called discharge type.

  When the pressure of the wheel cylinder WC is increased, the pressure increasing valve ZAB is set to the open position and the pressure reducing valve GAB is set to the closed position. Then, the brake fluid BFL is moved into the WC from the pressurizing mechanism KAK.

  The emergency state quantity JqA acquires the emergency state quantity Jqa. The emergency state quantity acquisition means JQA includes a collision avoidance block VXS and a departure avoidance block VXR. The emergency state quantity Jqa is a state quantity that represents the emergency state of the vehicle. As the magnitude (absolute value) of the emergency state quantity Jqa is larger, the emergency state of the vehicle is higher. For example, the emergency state quantity Jqa can be acquired via the communication bus CAN.

  When the emergency state of the vehicle is a possibility of a collision with an obstacle ahead of the vehicle, the collision avoidance block VXS uses the collision avoidance vehicle speed (target value) Vxs as the emergency state amount Jqa and the speed of the host vehicle ( The deviation ΔVxs from the actual value) Vxa is calculated. Here, the target value Vxs is a target vehicle speed for avoiding a collision with an obstacle. The collision avoidance vehicle speed Vxs is calculated based on the distance between the obstacle and the host vehicle and the relative speed. The distance between the obstacle and the host vehicle and the relative speed are acquired by a known method (laser sensor, camera image, etc.). When the possibility of a collision with a front obstacle is high, the emergency state quantity Jqa (deviation ΔVxs) is a relatively large value.

  When the emergency state of the vehicle is likely to deviate from a traveling path (for example, a curve) in front of the vehicle, an appropriate vehicle speed (target value) Vxr as the emergency state amount Jqa and the actual vehicle in the departure avoidance block VXR A deviation ΔVxr from the speed Vxa is calculated. For example, the target value Vxr is a target vehicle speed for passing stably without departing from the curve. The appropriate vehicle speed Vxr is calculated based on the curve radius R. The curve radius R is acquired by a known method (navigation device, camera video, etc.). When the possibility that the vehicle deviates from the forward curve is high, the emergency state quantity Jqa (deviation ΔVxr) is set to a relatively large value.

<Processing of control means>
Next, processing in the control unit CTL will be described with reference to the functional block diagram of FIG. The control means CTL includes a diagnostic processing block SND, a pressurization control block KAC, and an anti-skid control block ASC. The control means CTL is a control algorithm and is programmed in a microcomputer in the electronic control unit ECU.

  The diagnostic processing block SND diagnoses the suitability of the operating state of the entire apparatus. For example, the suitability of the operating state of the electric motor MTR is used for the power supply state (for example, supply voltage) to the electric motor MTR, the operating state of the electronic control unit ECU that drives the electric motor MTR, and the control of the electric motor MTR. Diagnosis is made based on at least one of the operating states of an acquisition means (such as MKA) that acquires the state quantity to be performed.

  The diagnosis processing block SND includes an initial diagnosis block SHK and an operation monitoring block KNC. The diagnostic processing block SND is a control algorithm and is programmed in a microcomputer in the electronic control unit ECU. In the initial diagnosis block SHK, an initial diagnosis (so-called initial check) before the operation of the braking device is started. In the operation monitoring block KNC, the operation of the entire system is constantly monitored and diagnosed.

  In the initial diagnosis block SHK, the state of power supply to the braking control device, diagnosis of the electronic control unit ECU itself (for example, memory diagnosis), electric motor MTR, bridge circuit, energization amount acquisition means IMA, rotation angle acquisition means MKA, solenoid valve (VMC etc.) and at least one diagnosis (operation check) of the hydraulic pressure acquisition means (PMC etc.) is executed. Here, the bridge circuit is an electric circuit for driving the electric motor MTR. The bridge circuit is provided with energization amount acquisition means IMA (for example, a current sensor) for acquiring an energization amount (actual value) Ima to the electric motor MTR.

  In the initial diagnosis block SHK, specifically, when the voltage supplied to the electronic control unit ECU transitions from a state below the predetermined voltage v10 to a state above the predetermined voltage v10 (when the control device is started), the initial diagnosis block SHK Based on the diagnostic trigger signal, at least one initial check of the above functions is executed. For example, the trigger signal is determined based on a signal received from the communication bus CAN.

  In the initial diagnosis (initial check), a driving signal for diagnosis is transmitted from the initial diagnosis block SHK toward the bridge circuit and each solenoid valve. As a result, at least one change among the acquisition results (detection results of each sensor) of the energization amount acquisition means IMA, the rotation angle acquisition means MKA, and the hydraulic pressure acquisition means (PMC, etc.) is an initial diagnosis block. Received by SHK. Based on the reception result, at least one of a bridge circuit (that is, a switching element), an electric motor MTR, a solenoid valve, an energization amount acquisition unit IMA, a rotation angle acquisition unit MKA, and a hydraulic pressure acquisition unit PMC, PCA, PWA. It is diagnosed whether one function is in a state where it can operate normally. If there is any inconvenience in the function (operation), a signal indicating an inappropriate state is output and a preset action (for example, notification to the driver and restriction or stop of the operation) is performed. .

  Similarly, in the operation monitoring block KNC, the power supply state to the braking control device, the bridge circuit (that is, the switching element), the electric motor MTR, the electromagnetic valve, the energization amount acquisition unit IMA, the rotation angle acquisition unit MKA, and the hydraulic pressure It is diagnosed whether or not at least one function of the acquisition means is in a state where it can operate normally. Diagnosis of these components is performed based on a comparison between the target value of the electric motor MTR and the electromagnetic valve and the result (actual value). Specifically, the appropriate state is determined when the deviation between the target value and the actual value is less than a predetermined value set in advance, and the inappropriate state is determined when the deviation is equal to or greater than the predetermined value. When an unsuitable state exists in the function of each component (MTR, etc.), a signal indicating the unsuitable state is output and a preset action (for example, to the driver) Notification and operation restriction or stop).

  When all of the initial diagnosis block SHK and the operation monitoring block KNC determine “appropriate”, the diagnosis processing block SND determines “appropriate state”. The case where the appropriate state is determined is referred to as “at the time of appropriate diagnosis”. On the other hand, when at least one of the initial diagnosis block SHK and the operation monitoring block KNC determines “inappropriate (deny appropriate state)”, the diagnosis processing block SND determines “inappropriate state”. . The case where the inappropriate state is determined is referred to as “during inappropriate diagnosis”.

  From the diagnosis processing block SND, signals (drive signals) for driving the electromagnetic valves VMC, VSS, VKC are transmitted to the drive means DRV. Specifically, as the drive signal Smc of the electromagnetic valve VMC, the VMC is brought into a non-communication state (closed position) when it is judged appropriate, and the VMC is brought into a communication state (open position) when it is inappropriate. It is transmitted from the block SND to the driving means DRV.

  The drive signal Sss for the solenoid valve VSS is set to a communication state (open position) when judged appropriate, and to a non-communication state (closed position) when judged inappropriate, from the diagnostic processing block SND to the drive means DRV. Sent to. Similarly, the drive signal Skc of the electromagnetic valve VKC is set to the communication state (open position) when judged appropriate, and is set to the non-communication state (closed position) when judged inappropriate, from the diagnostic processing block SND to the drive means DRV. Sent to.

  The pressurization control block KAC includes a braking operation amount Bpa, an emergency state amount Jqa, an anti-skid control drive signal (such as a signal for MJR) Sas, a piston position Pps, an output pressure (pressure generated by KAK) Pca, and WC. Pressure (wheel cylinder pressure) Pwa is input. In the pressurization control block KAC, the target energization amount Imt of the electric motor MTR that drives the pressurization mechanism KAK is calculated based on these signals. Here, the target energization amount Imt is a target value of the energization amount for controlling the electric motor MTR. Imt is transmitted to the drive means DRV to control the electric motor MTR. A method for calculating Imt will be described later.

  In the anti-skid control block ASC, known anti-skid control is executed based on the wheel speed Vwa. Specifically, the wheel slip amount Slp is calculated in the anti-skid control block ASC. The slip amount Slp is calculated based on at least one of the wheel slip speed Vsl and the wheel deceleration dVw. Here, the wheel slip speed Vsl is calculated based on the deviation between the vehicle speed (body speed) Vxa and the wheel speed Vwa. The wheel deceleration dVw is calculated by differentiating the wheel speed Vwa. When the slip amount Slp is less than the predetermined amount sp0, the anti-skid control is not started, and when the slip amount Slp is greater than or equal to the predetermined amount sp0, the execution of the anti-skid control is started. The anti-skid control is configured by two control modes of “a pressure increasing mode” for increasing the pressure (WC pressure) of the wheel cylinder WC and “a pressure reducing mode” for decreasing the WC pressure.

  In the anti-skid control block ASC, a drive signal (anti-skid control signal) Sas for controlling the electromagnetic valve SOL in the pressure adjusting means MJR is calculated based on the wheel slip amount Slp. Here, the electromagnetic valve SOL is configured by a combination of a pressure increasing valve ZAB and a pressure reducing valve GAB. When the wheel slip amount Slp increases, the anti-skid control signal Sas is determined so as to decrease the WC pressure. That is, in the pressure reducing mode, a signal Sas is calculated which sets the pressure increasing valve ZAB of the electromagnetic valve SOL to the closed position and the SOL pressure reducing valve GAB to the open position. On the other hand, when the wheel slip amount Slp decreases (recovers), the anti-skid control signal Sas is determined so as to increase the WC pressure. In the pressure increasing mode, the signal Sas for controlling the duty of the pressure increasing valve ZAB of the SOL with the pressure reducing valve GAB of the electromagnetic valve SOL closed is calculated. Specifically, in the duty control in the pressure increasing mode, the open position and the closed position of the pressure increasing valve ZAB are repeatedly instructed so that the WC pressure is not increased rapidly. When the wheel slip amount Slp is maintained at a predetermined value, the time during which the pressure increasing valve ZAB is in the open position is shortened in the duty control in the pressure increasing mode, so that the WC pressure is maintained substantially constant.

  The anti-skid control signal Sas is transmitted to the driving unit DRV and the pressurization control block KAC. The signal Sas transmitted to the pressurization control block KAC can be replaced by the control flag FLa. The control flag FLa includes information indicating that the anti-skid control is being executed and the pressure adjustment instruction state in the anti-skid control (whether it is a pressure increase mode instruction or a pressure reduction mode instruction). ing.

  In the control mode of the anti-skid control, a “holding mode” for maintaining the WC pressure constant may be provided. Specifically, after the pressure reducing mode, the holding mode is formed, and the pressure increasing mode is started after the wheel slip amount Slp is recovered. In the holding mode of the anti-skid control, a signal Sas that closes the pressure increasing valve ZAB and the pressure reducing valve GAB of the electromagnetic valve SOL is calculated.

  The solenoid valve VKC is provided in the middle of the pipe HKJ, and switches between HKJ communication / sever communication based on the drive signal Skc. Specifically, when the appropriate state of the device is affirmed (when appropriate) by the diagnostic processing block SND in the CTL, the VKC is brought into a communication state (open position) and the appropriate state of the device is denied. When (inappropriate), it is in a non-communication state (closed position).

  The electromagnetic valve VMC is provided in the middle of the pipe HMW, and switches the HMW communication / sever communication state based on the drive signal Smc. Specifically, the VMC is brought into a non-communication state (closed position) when the appropriate state of the device is affirmed (during the appropriate state) by the diagnostic processing block SND in the CTL, and the appropriate state of the device is denied. In the case of failure (in an inappropriate state), the communication state (open position) is set. Accordingly, the wheel cylinder WC is connected only to the pressurizing mechanism KAK (pressurizing cylinder KCL) when appropriate, and is connected only to the master cylinder MCL when inappropriate.

  The solenoid valve VSS is provided in a path connecting the master cylinder MCL and the simulator SSM, and switches the communication / sever communication state between the MCL and the SSM based on the drive signal Sss. Specifically, when the appropriate state of the device is affirmed (in the appropriate state) by the diagnostic processing block SND in the CTL, the VSS is brought into a communication state (open position), and the appropriate state of the device is denied. In a case (in an inappropriate state), the communication state is closed (closed position). Therefore, the simulator SSM functions when appropriate. However, in an inappropriate state, the simulator SSM does not consume the brake fluid BFL, and the entire amount of the brake fluid BFL from the master cylinder MCL is moved to the wheel cylinder WC.

  The drive means (drive circuit) DRV drives the electric motor (MTR, etc.) and the electromagnetic valve (VKC, etc.) based on a signal (Imt etc.) from the control means CTL. The drive means DRV is configured in the electronic control unit ECU. Further, the driving means DRV can be incorporated in each element (MTR, VKC, etc.).

  The drive means (drive circuit) DRV drives the electric motor MTR based on the target energization amount Imt from the pressurization control block KAC (particularly, the target energization amount calculation block IMT). Specifically, in the DRV, a bridge circuit (motor driver circuit) is formed by a plurality of switching elements (for example, MOS-FETs) in order to drive the MTR. Based on the target energization amount Imt, energization / non-energization of these switching elements is switched, and the MTR is rotationally driven. The bridge circuit of the driving unit DRV is provided with an energization amount acquisition unit IMA that detects an energization amount Ima to the MTR.

  The drive means (drive circuit) DRV drives the electromagnetic valves VKC, VMC, VSS based on the signals Skc, Smc, Sss from the diagnostic processing block SND. Specifically, a solenoid driver for driving an electromagnetic valve (VKC or the like) is provided in the driving means DRV, and this energization / non-energization is switched to drive the electromagnetic valve.

  Similarly to the above, the drive means DRV drives the electromagnetic valves (the pressure increasing valve ZAB and the pressure reducing valve GAB) SOL in the pressure adjusting means MJR based on the drive signal Sas from the anti-skid control block ASC.

<Pressure mechanism KAK>
Next, the pressurizing mechanism KAK will be described with reference to the partial cross-sectional view of FIG. The pressurizing mechanism KAK adjusts the hydraulic pressure of the wheel cylinder WC based on the braking operation amount Bpa. The pressurizing mechanism KAK includes an electric motor MTR, a power transmission mechanism DDB, a pressurizing cylinder KCL, a pressurizing piston KPS, and a return spring DSB.

  The electric motor MTR is controlled by the electronic control unit ECU, and generates power for adjusting the hydraulic pressures of the four wheel cylinders WC. As the electric motor MTR, a motor with a brush or a brushless motor can be adopted. The electric motor MTR is provided with rotation angle acquisition means MKA for acquiring the position (rotation angle) Mka of the rotor (rotor) with respect to the stator (stator). In the rotation direction of the electric motor MTR, the forward rotation direction Fwd corresponds to the direction in which the hydraulic pressure (WC pressure) of the wheel cylinder WC increases (that is, the direction in which the braking torque increases), and the reverse rotation direction Rvs This corresponds to the direction in which the hydraulic pressure of the cylinder WC decreases (that is, the direction in which the braking torque decreases).

  The power transmission mechanism DDB converts the output (rotational power) of the electric motor MTR into linear power of the pressure piston KPS and transmits it. The power transmission mechanism DDB includes a reduction gear GSK and a screw member NJB.

  The reduction gear GSK reduces the rotational speed of the power of the electric motor MTR and outputs it to the screw member NJB. That is, the rotational output (torque) of the electric motor MTR is increased according to the reduction ratio of the reduction gear GSK and transmitted to the screw member NJB as rotational force (torque). For example, the reduction gear GSK is configured by a small diameter gear SKH and a large diameter gear DKH.

  As the reduction gear GSK, a wrapping transmission mechanism using a belt can be employed instead of the gear transmission mechanism. In this case, instead of the large diameter gear DKH and the small diameter gear SKH, a set of a large diameter pulley and a small diameter pulley is employed. By employing the belt transmission mechanism, the distance between the two axes can be increased and the reduction ratio can be set large. As a result, a high rotation / small torque type electric motor is adopted as the electric motor MTR, and the apparatus can be miniaturized. In addition, gear rattling noise and the like can be avoided, and the quietness of the apparatus can be improved.

  The screw member NJB of the power transmission mechanism DDB is a member (rotation / linear motion conversion mechanism) that converts rotational power into linear power. The screw member NJB includes a nut member NUT and a bolt member BLT. The bolt member BLT is fixed coaxially (axis Jkc) to the large-diameter gear DKH. Key grooves are formed in the outer peripheral portion of the nut member NUT and the inner peripheral portion of the pressure cylinder KCL. When the key member KYB is fitted in the key groove, the nut member NUT is restricted from rotating around the central axis Jkc, but linear movement in the direction of the central axis Jkc (longitudinal direction of the key groove) is allowed. Is done. The pressure piston KPS is moved relative to the pressure cylinder KCL by the linear motion of the nut member NUT.

  The screw member NJB has reversibility (has reverse efficiency) and can transmit power in both directions. That is, when the pressure in the wheel cylinder WC is increased (when the braking torque is increased), power is transmitted from the electric motor MTR to the pressure piston KPS through the screw member NJB. Conversely, when the pressure in the wheel cylinder WC is reduced (when the braking torque is reduced), power is transmitted from the pressure piston KPS to the electric motor MTR via the screw member NJB (at this time, the reverse Efficiency is greater than “0”).

  The screw member 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) output from the reduction gear GSK is transmitted as linear power (thrust) of the pressurizing piston KPS through the screw member NJB (ONJ and MNJ).

  Instead of the sliding screw, a rolling screw (such as a ball screw) in which power is transmitted by “rolling” may be employed as 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. As the rotation / linear motion conversion mechanism of the power transmission mechanism DDB, a conversion mechanism such as a ball ramp member, a rotation wedge member, a rack & pinion member, or the like can be employed instead of the screw member NJB.

  Similar to the structure of the master cylinder MCL, the inside of the pressure cylinder KCL is partitioned into a fluid chamber Rkc (corresponding to the first fluid chamber) by the pressure piston KPS. The fluid chamber Rkc communicates with the master reservoir RSV through the relief port PRK and the fluid piping HRK when the generation of the braking torque is unnecessary (for example, when the braking operation member BP is not operated).

  When the braking torque of the wheel is increased, the electric motor MTR is driven in the normal rotation direction Fwd, whereby the nut member NUT pushes the pressurizing piston KPS and the KPS is moved. A primary seal (a cup-shaped rubber seal for contacting the inner peripheral portion of the pressure cylinder KCL and holding the hydraulic pressure) GCP is provided on the outer peripheral portion of the pressure piston KPS. As the pressure piston KPS is moved in the forward direction (leftward in FIG. 3) in the pressure cylinder KCL, the relief port PRK is closed by the primary seal (cup seal) GCP, and the fluid chamber Rkc The communication state with the reservoir RSV is hindered (becomes a non-communication state).

  Further, when the pressurizing piston KPS is moved in the forward direction, the volume of the fluid chamber Rkc is reduced, and the brake fluid (brake fluid) BFL is discharged from the fluid chamber Rkc toward the four-wheel wheel cylinder WC. The hydraulic pressure in the wheel cylinder WC is increased. That is, the brake fluid BFL is pumped from the output port PKJ of the fluid chamber Rkc to the fluid pipe HKJ. Here, the forward direction of the pressurizing piston KPS is a direction in which the volume of the fluid chamber Rkc is reduced, and corresponds to the forward rotation direction Fwd of the electric motor MTR.

  When the braking torque of the wheel is reduced, the electric motor MTR is driven in the reverse direction Rvs, and the pressurizing piston KPS is moved in the reverse direction (the direction opposite to the forward direction and rightward in FIG. 3). , And return to the original position (the initial position where the fluid chamber Rkc communicates with the reservoir RSV). By the movement of the pressurizing piston KPS, the volume of the fluid chamber Rkc is increased, the brake fluid BFL is returned from the wheel cylinder WC into the pressurizing cylinder KCL, and the hydraulic pressure of the wheel cylinder WC is decreased. Here, the reverse direction of the pressurizing piston KPS is a direction in which the volume of the fluid chamber Rkc is increased, and corresponds to the reverse rotation direction Rvs of the electric motor MTR.

  The pressurizing mechanism KAK is provided with a return spring DSB so as to return the pressurizing piston KPS to an initial position (a position where the fluid chamber Rkc and the reservoir RSV communicate with each other). Even when energization of the electric motor MTR is stopped by the return spring DSB, the pressure piston KPS can be returned to the initial position (zero point).

  In addition, a reservoir connection chamber Rrs (corresponding to a second fluid chamber), which is partitioned by a pressure piston KPS, a primary seal GCP, and a secondary seal GCS, is formed inside the pressure cylinder KCL. Here, the primary seal GCP and the secondary seal GCS are seal members having a cup shape. The reservoir connection chamber Rrs is connected to the reservoir RSV via the reservoir port PRR and the pipe HRK. Therefore, the inside of the reservoir connection chamber Rrs is always at atmospheric pressure.

  The sealing performance of the primary seal GCP depends on the moving direction of the pressurizing piston KPS. When the pressurizing piston KPS is moved in the forward direction (left direction in FIG. 3), the cup seal GCP has a sealing function (function to prevent liquid from leaking) and increases the hydraulic pressure of the wheel cylinder WC. . On the other hand, when the pressurizing piston KPS is moved in the backward direction (the right direction in FIG. 3, the direction opposite to the forward direction in the central axis direction of the KPS), fluid is supplied from the reservoir connection chamber Rrs (that is, the reservoir RSV). The movement of the brake fluid BFL can be allowed inside the chamber Rkc via the lip portion of the primary seal GCP.

  On the other hand, the sealing function of the secondary seal GCS is exhibited without depending on the moving direction of the pressurizing piston KPS. Therefore, the brake fluid BFL does not leak to the screw member NJB side from the fluid chamber Rkc and the reservoir connection chamber Rrs.

<Pressure adjusting means MJR>
Next, an embodiment of the pressure adjusting means MJR will be described with reference to FIG. The configuration of FIG. 4 is a configuration in which the pressure reduction of the wheel cylinder pressure is performed by opening the master reservoir RSV, and the re-pressure increase is performed by the pressurization mechanism KAK. Yes.

  The pressure adjusting means (hydraulic pressure modulator) MJR adjusts the pressure (WC pressure) in the wheel cylinder WC of each wheel independently of the operation of the braking operation member BP by the driver. The pressure adjusting means MJR is an actuator for performing so-called brake control such as anti-skid control.

  When the slip amount Slp of the wheel increases and exceeds the threshold value, the anti-skid control pressure reduction mode is executed. Specifically, the pressure increasing valve ZAB is brought into a non-communication state, the pressure reducing valve GAB is brought into a communication state, and the brake fluid BFL in the wheel cylinder WC is moved to the master reservoir RSV via the pipe HMR, whereby the wheel The pressure in the cylinder WC (WC pressure) is reduced. On the other hand, when the slip amount Slp decreases and becomes smaller than the threshold value, the anti-skid control pressure increasing mode is executed. Specifically, the pressure increasing valve ZAB is brought into a communicating state, the pressure reducing valve GAB is brought into a non-communicating state, and the braking fluid BFL is moved from the pressurizing mechanism KAK into the wheel cylinder WC, whereby the WC pressure is increased. The

  When the pressure (WC pressure) of the wheel cylinder WC is increased (when the anti-skid control pressure increasing mode is executed), the pressure increasing valve ZAB is duty-controlled. Specifically, the time change amount of the WC pressure is moderated by periodically repeating the communication state and the non-communication state of the pressure increasing valve ZAB. Since the sudden increase of the WC pressure is suppressed by the duty control of the pressure increasing valve ZAB, an increase in the locking tendency of the wheel WH can be prevented.

<Processing in pressurization control block KAC>
Next, processing in the pressurization control block KAC will be described with reference to the functional block diagram of FIG. 5 and the time charts of FIGS. The pressurization control block KAC includes an instruction pressure calculation block PCS, a target pressure calculation block PCT, and a target energization amount calculation block IMT.

  In the command hydraulic pressure calculation block PCS, the command pressure Pcs is calculated based on the braking operation amount Bpa and the calculation characteristics (calculation map) CHpc. Here, the command pressure Pcs is a target value of the brake fluid pressure (output pressure) generated by the pressurizing mechanism KAK. Specifically, in the calculation characteristic CHpc, the command pressure Pcs is calculated to be “0” in the range where the operation amount Bpa is “0 (zero)” (corresponding to the case where no braking operation is performed) and less than the predetermined value bp0. When the manipulated variable Bpa is equal to or greater than the predetermined value bp0, the command pressure Pcs is calculated so as to simply increase from “0”.

  Further, in order to automatically decelerate the vehicle when the driver does not recognize the emergency state of the vehicle, the command pressure Pcs is calculated based on the emergency state amount Jqa (a state variable expressing the emergency state of the vehicle). Can be done. Also in this case, as in the case of the braking operation amount Bpa, the command pressure Pcs is calculated to be “0” in the range where the emergency state amount Jqa is greater than or equal to “0 (zero)” and less than the predetermined value bp0, and Jqa is the predetermined value. At bp0 or higher, the command pressure Pcs is calculated so as to simply increase from “0”.

  In the target pressure calculation block PCT, various adjustments are made to the command pressure Pcs, and the target pressure Pct that is the final target value of the output pressure of the pressurizing mechanism KAK is calculated. The target pressure calculation block PCT includes a pressure feedback calculation block AFB, a pressure limit control block ASG, and a pullback control block HMC. Note that the pressure limit control block ASG and the pullback control block HMC function only during execution of the anti-skid control.

  In the pressure feedback calculation block AFB, so-called feedback control is executed based on the deviation ΔPc between the command pressure (target value) Pcs and the output pressure (actual value) Pca in the pressurizing mechanism KAK, and the target pressure Pct is calculated. The Here, the actual value Pca is acquired (detected) by the pressure acquisition means PCA. When the anti-skid control is not executed, the command pressure Pcs is adjusted by the deviation ΔPc, and the final target pressure Pct is determined.

  In the pressure limit control block ASG, the increase in the output pressure Pca of the KAK is limited so that the output pressure Pca of the pressurizing means KAK (that is, the supply pressure to the MJR) is necessary and sufficient in the execution of the anti-skid control. The “pressure limit control” is executed. The pressure limit control will be described with reference to the time chart of FIG.

  In the example shown in FIG. 6, the braking operation by the driver is started at time t0, and the WC pressure is gradually increased. At time t1, the wheel slip amount Slp exceeds the anti-skid control threshold value sp0, and anti-skid control is started. That is, the anti-skid control decompression mode is executed at time t1. In the pressure limit control block ASG, the hydraulic pressure (actual value of the output pressure) Pca at the time point when the anti-skid control is started (that is, t1) is stored as a value pab (reference pressure). Further, in the pressure limit control block ASG, the limit pressure pac is determined based on the reference pressure pab. Specifically, a predetermined pressure (predetermined predetermined value) pm1 is added to the reference pressure pab to determine the limit pressure pac (that is, pac = pad + pm1).

  After time t1, the braking operation amount Bpa is increased by the driver's operation, but the target pressure Pct is limited to the value pac (limit pressure). Specifically, the target pressure Pct (as a result, the actual pressure Pca) reaches the limit pressure pac at time t2, and the pressure limit control (output pressure limit control) of the pressurizing mechanism KAK starts. This is because the anti-skid control is started when the WC pressure reaches a state corresponding to the maximum friction between the wheel and the road surface, and therefore the WC pressure does not increase even if the target pressure Pct is further increased. It depends.

  When the wheel cylinder pressure (WC pressure) reaches the maximum frictional condition on the road surface, the wheels begin to tend to lock. The WC pressure at this time is referred to as “lock pressure”. Even if the output pressure (target value) Pct of the pressurizing mechanism KAK is instructed to be larger than the lock pressure according to the operation amount Bpa of the braking operation member BP, the WC pressure is limited by the anti-skid control. When the output pressure of the pressurization mechanism is increased more than necessary, the difference between the output pressure and the lock pressure (referred to as “differential pressure”) increases, and the execution of stable anti-skid control is hindered. Can occur. By the pressure limiting control, the output pressure of the pressurizing mechanism KAK is limited to the minimum necessary with respect to the lock pressure, and the differential pressure is appropriately maintained, so that stable anti-skid control can be executed.

  When the anti-skid control is started, the WC pressure is first reduced by the pressure adjusting means MJR driven by the anti-skid control block ASC. Thereafter, the WC pressure is repeatedly increased and decreased based on a change in the slip amount Slp of the wheel.

  The braking operation amount Bpa is kept constant from time t3 to t4 by the driver. Thereafter, when the driver steps on the braking operation member BP and the maintained Bpa (value bac) increases beyond the predetermined amount ba2, the pressure limit control is terminated, and the target pressure Pct is indicated. The pressure is increased to Pcs. Specifically, the holding state (value bac) of the braking operation member BP is stored in the pressure limit control block ASG, and a value obtained by adding the predetermined value ba2 to the value bac is set as the release value bap (threshold value). Is done. Then, at time t5 when the braking operation amount Bpa exceeds the release value bap, the pressure restriction control is released (terminated). At the end of the control, in order to suppress a sudden change in the target pressure Pct (that is, Pca), a limit can be provided to the increasing slope of Pct (a change amount with respect to time). That is, the target pressure Pct is gradually increased toward the command pressure Pcs.

  In the pull back control block HMC, pull back control of the pressure piston KPS is executed. When the discharge type pressure adjusting means MJR is employed, the brake fluid BFL is discharged to the master reservoir RSV in the reduced pressure state of the anti-skid control. The re-pressurization state in the anti-skid control is performed by replenishing the brake fluid BFL from the pressurizing mechanism KAK. Therefore, when the anti-skid control is continued for a relatively long time (for example, when the anti-skid control is started at a relatively high vehicle speed on a road surface having a low road surface friction coefficient), the pressurizing mechanism KAK Since the piston KPS gradually moves forward (moves in the direction of the central axis), there may be a concern about the bottoming of the pressurizing piston KPS (reaching the KPS stroke limit).

  In the pull-back control block HMC, in order to avoid the above bottoming, the pressure piston KPS is pulled back toward the initial position (zero point position) corresponding to the non-braking state without affecting the performance of the anti-skid control. It is. That is, what the pressure piston KPS moves in the reverse direction during execution of the anti-skid control is referred to as “retraction control”. The pull back control will be described with reference to the time chart of FIG.

  In the example shown in FIG. 7, the anti-skid control is being executed, and the pressure adjustment means MJR repeatedly increases / decreases the pressure Pwa in the wheel cylinder WC. Specifically, when the anti-skid control is in the pressure reduction mode, execution of the pull-back control is started. In this regard, pullback control is executed in the configuration described in Japanese Patent Application Laid-Open No. 2003-31463 (hydraulic pressure holding period in which the anti-skid control is in the pressure increasing mode (the pressure increasing valve closing period in which opening and closing are alternately repeated). Greatly different).

  When the anti-skid control is in the pressure increasing mode, the pullback control is not executed, and the target pressure Pct is maintained at the value phb (for example, the limit pressure). At time u1, the anti-skid control pressure increase mode is changed to the pressure reduction mode. At this mode change time u1 (or immediately after), the pull-back control is started, and the target pressure Pct is changed to a value phc smaller than the value phb. Here, the value phc is a value larger by a predetermined value ph1 than the maximum pressure pha by the anti-skid control. Accordingly, the relationship among the maximum pressure pha during the execution of the anti-skid control, the pressure phc during the execution of the pull-back control of the pressurizing piston KPS, and the pressure phb during the non-execution of the KPS pull-back control is expressed as “pha <phc <phb It is.

  By the pull-back control, the pressure piston KPS is pulled back toward the initial position (zero point position, corresponding to Pct = 0). Accordingly, since the pressure increasing valve ZAB is in the closed position in the pressure reducing mode, the brake fluid BFL is transferred from the reservoir connection chamber Rrs (second fluid chamber) to the fluid chamber Rkc (first fluid chamber), and the primary seal GCP and the pressure cylinder. It is replenished through the gap (the tip of the lip) of the inner wall of the KCL. In the discharge type pressure adjusting means MJR, the brake fluid BFL is moved to the reservoir RSV when the WC pressure decreases. As a result of the pull-back operation of the pressurizing piston KPS, the brake fluid BFL moved (outflowed) to the reservoir RSV is returned from the second fluid chamber Rrs into the first fluid chamber Rkc via the primary seal GCP.

  At the time point u3 when the pressure reduction mode of the anti-skid control is changed to the pressure increase mode, the target pressure Pct is increased, and the returned pressure piston KPS starts to move in the forward direction. At this time, the increase gradient (increase amount with respect to time) dpc of the target pressure Pct (result Pca) is set larger than the increase gradient (time change amount) dpw of the pressure Pwa of the wheel cylinder WC (dpc> dpw). As a result, the WC pressure can be reliably increased in the increase mode of the anti-skid control.

  The increase in the target pressure Pct after pulling back the pressure piston KPS can be started before the anti-skid control increase mode is started (before switching from the pressure reduction mode to the pressure increase mode, for example). . This is because once the pressure piston KPS is pulled back, the brake fluid BFL is replenished into the pressure cylinder KCL (ie, Rkc).

  In the target energization amount calculation block IMT, the target energization amount Imt (the target value of the energization amount for controlling the MTR) of the electric motor MTR that drives the pressurizing mechanism KAK is calculated based on the target hydraulic pressure Pct and the like. 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 approximately proportional to the current, the current target value of the electric motor MTR can be used as the target value of the energization amount (target energization amount). Further, if the supply voltage to the electric motor MTR is increased, the current is increased as a result, so that the supply voltage value can be used as the target energization amount. Further, since the supply voltage value can be adjusted by the duty ratio in the pulse width modulation, this duty ratio (ratio of energization time in one cycle) can be used as the energization amount.

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

  In the target energization amount calculation block IMT, a target energization amount Imt of the electric motor MTR is calculated based on the target hydraulic pressure Pct and a preset calculation map. Since the output of the electric motor MTR increases as the energization amount increases, the calculation map is set so that the target energization amount Imt simply increases as the target pressure Pct increases. The target energization amount Imt is transmitted to the drive means (drive circuit) DRV.

  An example of the target energization amount Imt calculated in the pressure limit control will be described with reference to FIG. During the anti-skid control, the command pressure (target value) Pcs is limited to the target pressure (target value) Pct by pressure limit control. As a result, the target energization amount Imt is also limited (held at the limit value iac). That is, the target energization amount (target value) Imt is smaller than the command energization amount (target value) Ims calculated based on the command pressure Pcs. Further, the pressure limit control is stopped by the increase in the operation of the brake operation member BP by the driver, and is increased toward the command energization amount Ims.

  An example of the target energization amount Imt calculated in the pullback control will be described with reference to FIG. During the anti-skid control, the target pressure Pct is decreased by the pull-back control in the pressure-reducing mode of the anti-skid control (that is, when the pressure increasing valve ZAB is closed). As a result, the target energization amount Imt is decreased from the value ihb to the value ihc in FIG. Here, the value ihc corresponds to a value phc obtained by adding a predetermined value ph1 to the maximum pressure pha of the anti-skid control. When the pressurizing piston KPS is pulled back (moved in the backward direction) with the pressure increasing valve ZAB being closed, the fluid chamber Rkc becomes negative pressure, so that the brake fluid BFL is passed through the primary seal GCP. The reservoir connection chamber Rrs (that is, the reservoir RSV) is moved into the fluid chamber Rkc. As a result, the pressurizing mechanism KAK can be replenished with the brake fluid BFL during anti-skid control. The maximum pressure pha is the maximum value among the WC pressures that are increased and decreased during the series of anti-skid control (from the start to the end). The maximum pressure pha is stored in the memory of the ECU.

<Embodiment of Pressure Limit Control Block ASG>
In the pressure limiting control, during the execution of the anti-skid control, the output pressure Pca of the pressurizing mechanism KAK is maintained at a pressure suitable for the friction state between the traveling road surface and the wheels. Specifically, the hydraulic pressure value pac necessary and sufficient for generating the wheel lock is the hydraulic pressure (reference) when the anti-skid control is started (when the first pressure reduction by the control is started). Pressure) is determined based on pab (pac = pab + pm1, where value pm1 is a predetermined value set in advance)). Then, the target pressure Pct is adjusted so that the outlet hydraulic pressure of the pressurizing mechanism KAK (that is, the pressurizing cylinder KCL) is not increased above the limit pressure pac.

[Response when the vehicle is traveling on a μ-split road]
The pressurizing mechanism KAK increases the pressure with respect to the wheel cylinders WC of the left and right wheels of the vehicle. Therefore, when the left and right wheels of the vehicle are traveling on road surfaces with different friction coefficients (so-called μ split roads), the above limitation The pressure pac is determined based on the wheel having the higher friction coefficient. Specifically, of the right and left wheels of the vehicle, after the wheel cylinder WC of one side wheel is depressurized by the hydraulic pressure modulator MJR, the pressurizing mechanism KAK at the time when the wheel cylinder WC of the other side wheel is depressurized by the MJR. The hydraulic pressure pab is adopted as the reference pressure. Of the left and right wheels, the first pressure reduction of the anti-skid control is performed in the wheel cylinder WC of the one side wheel, but the pressure reduction is not performed in the wheel cylinder WC of the other side wheel. Restriction control is not executed (started). The pressure limit control is started when the pressure reduction is performed in both the wheel cylinders of the left and right wheels (that is, when the first pressure reduction mode of the anti-skid control is started). That is, when the vehicle is traveling on a μ-split road, the output of the pressurizing mechanism KAK at the time when the anti-skid control is started (at the time when the first pressure reduction is started by the control) on the wheel with higher road surface friction ( The hydraulic pressure value) is set to the hydraulic pressure pab.

  For example, when the wheel cylinder WC of at least one of the four wheels is not depressurized by the hydraulic pressure modulator MJR, execution of the pressure limit control may be prohibited. That is, the pressure limit control can be executed only when the anti-skid control is executed for all four wheels. Specifically, in each wheel, the maximum pressure at the time when the anti-skid control is started is set as the reference pressure pab, and the pressure limiting control of the pressurizing mechanism KAK is executed.

[Response to changes in road surface friction]
Next, a response to a case where the road surface friction coefficient changes in the pressure limit control will be described. Here, mention will be made particularly when the road surface friction changes from a low state to a high state. If the wheel slip Slp does not increase despite the pressure adjusting means (hydraulic pressure modulator) MJR being in a pressure increasing state (a state where the pressure increasing valve ZAB is in the open position), the pressure limiting control is terminated and held. The target energization amount Imt is increased while the increase gradient (change amount with respect to time) is limited toward the command energization amount Ims. Specifically, the pressure limit control is stopped when the wheel slip Slp remains below the predetermined value sl1 for a predetermined time ts1 from the time when the pressure increasing valve ZAB of the MJR is changed from the closed position to the open position. The This is because the Slp does not increase even in the pressure increase state (pressure increase mode) of the anti-skid control because the traveling road surface of the vehicle is changed from a low friction coefficient to a high friction coefficient.

[Effect of pressure limit control]
Even when the driver operates the braking operation member BP to an amount larger than the operation amount corresponding to the road surface friction, the output hydraulic pressure of the pressurizing mechanism KAK is limited, so that stable anti-skid control is executed. obtain. Furthermore, since the dependence of the hydraulic pressure characteristic on the operation amount of the braking operation member BP is reduced, the opening area of the throttle element (orifice etc.) built in the pressure adjusting means MJR can be expanded, so that the resistance of the element Can be reduced, and the responsiveness of the entire apparatus can be improved.

  When the braking operation member BP is stepped on by the driver, when the frictional state of the road surface changes, the restriction of the output hydraulic pressure of the pressurizing mechanism KAK is released, so that appropriate anti-skid control can be executed. . Furthermore, since the restriction is executed based on the anti-skid control on the wheel having the highest road surface friction on the μ split road, even when the road surface is in a non-uniform state, appropriate measures can be taken. .

<Embodiment of Pullback Control Block HMC>
In the discharge-type hydraulic pressure modulator MJR, when the hydraulic pressure of the wheel cylinder WC is reduced in the anti-skid control, the brake fluid BFL inside the WC is moved to the reservoir RSV. Specifically, the hydraulic pressure modulator MJR includes an on-off valve (pressure reducing valve) GAB disposed between WC and RSV, and when the hydraulic pressure of WC is decreased, the pressure reducing valve GAB is opened from the closed position. The brake fluid BFL is moved from the WC to the RSV via the pressure reducing valve GAB. For this reason, when the execution time of the anti-skid control is extended over a long period, the brake fluid BFL in the pressurizing mechanism KAK gradually decreases.

  When the anti-skid control is being performed and the hydraulic pressure modulator MJR is in the pressure reduction mode (that is, when the pressure increasing valve ZAB is in the closed position), the master reservoir RSV is retracted by retracting the pressure piston KPS. The brake fluid (brake fluid) BFL is replenished (inflowed) into the pressurizing mechanism KAK (fluid chamber Rkc partitioned by KCL and KPS). Here, intentionally retracting the pressure piston KPS to replenish the brake fluid to the pressure mechanism KAK is referred to as “retraction control”.

  The cup seal (primary seal) GCP of the pressure piston KPS has directionality in the sealing function. Specifically, in the axial movement of the pressurizing piston KPS, one direction that is the direction in which the brake fluid BFL is discharged from the fluid chamber Rkc toward the wheel cylinder WC (the forward direction of KPS, the volume of Rkc decreases). (Corresponding to the direction) exhibits a sealing function. On the other hand, when the pressure increasing valve ZAB is not in communication and the pressurizing piston KPS is moved in another direction (the reverse direction of KPS) that is opposite to the one direction, the brake fluid BFL is From the outside of the fluid chamber Rkc (reservoir connection chamber Rrs), it can be sucked into the inside of the KCL (fluid chamber Rkc) via its lip portion. Specifically, when the volume of the fluid chamber Rkc (first fluid chamber) is increased in a state where the pressure increasing valve ZAB is in the closed position, the pressure in the fluid chamber Rkc becomes negative pressure, so that the atmospheric pressure state is reached. The brake fluid BFL flows from the reservoir connection chamber Rrs (second fluid chamber) through the lip portion of the primary seal GCP. That is, the sealing performance of the primary seal GCP depends on the moving direction (forward or backward direction) of the pressure piston KPS. When all of the wheels (pressure adjustment target wheels) that are regulated by the pressurizing mechanism KAK are in a reduced pressure state in the anti-skid control (that is, when the pressure increasing valve ZAB is closed), the pressurizing piston KPS is The brake fluid BFL is moved from the reservoir RSV to the inside of the pressurizing mechanism KAK and replenished.

  Since the brake RS is replenished from the reservoir RSV to the pressurizing mechanism KAK by the pull-back control, the return pump HPJ and the pump HPJ are driven in the anti-skid control hydraulic pressure modulator MJR. The electric motor MTJ for doing so may be omitted.

  Position acquisition means PPS for acquiring the position (piston position) Pps of the pressure piston KPS may be provided. When the piston position Pps is within the predetermined distance px from the initial position (zero point) p0, the pullback control of the pressure piston KPS is not executed (the pullback control is prohibited). On the other hand, when the piston position Pps is away from the initial position p0 by a predetermined distance px, the pull-back control is permitted (a state in which the control can be executed when the condition is satisfied). When the retraction control is prohibited or permitted based on the position Pps of the pressurizing piston KPS, or when the brake fluid BFL needs to be replenished (for example, when executing control on a road surface with a low friction coefficient) The pull-back control can be performed only when the probability of bottoming is increased).

  MTR: electric motor, KAK: pressurizing mechanism, MJR: pressure adjusting means, BPA: operation amount acquiring means, VWA: wheel speed acquiring means, CTL: control means, KPS: piston, Rkc: first fluid chamber, Rrs: first 2 fluid chambers, GCP ... seal member, RSV ... reservoir

Claims (1)

A pressurizing mechanism that is driven by an electric motor and pressurizes a brake fluid in a wheel cylinder of the vehicle;
Pressure adjusting means that is interposed in the middle of the first fluid path that connects the pressurizing mechanism and the wheel cylinder, and that adjusts the brake fluid pressure that is the pressure of the brake fluid in the wheel cylinder;
An operation amount obtaining means for obtaining an operation amount of the braking operation member of the vehicle;
Wheel speed acquisition means for acquiring the wheel speed of the vehicle;
Control means for controlling the pressurizing mechanism and the pressure adjusting means based on the operation amount and the speed of the wheel;
A vehicle braking control device comprising:
The pressure mechanism is
A first fluid chamber formed in the pressurizing mechanism and connected to the first fluid path; and a fluid path connected to a reservoir formed in the pressurizing mechanism and storing a brake fluid. A piston that partitions the two fluid chambers and is driven in the axial direction by the electric motor;
When the piston moves in the first direction on the first fluid chamber side in the axial direction, the movement of the brake fluid from the first fluid chamber to the second fluid chamber is not allowed, and the piston is not in the shaft. A seal member that allows movement of the brake fluid from the second fluid chamber to the first fluid chamber when moving in the second direction on the second fluid chamber side in the direction;
The volume of the first fluid chamber is reduced by the movement of the piston in the first direction, and the pressure of the brake fluid between the pressurizing mechanism and the pressure regulating means in the first fluid path is An output pressure of the pressurizing mechanism is increased, and the volume of the first fluid chamber is increased by the movement of the piston in the second direction to decrease the output pressure of the pressurizing mechanism,
The pressure adjusting means is
A pressure reducing mode in which the wheel cylinder is communicated with the reservoir and the connection between the pressurizing mechanism and the wheel cylinder is disconnected; and the pressurizing mechanism and the wheel cylinder without communicating the wheel cylinder with the reservoir; Is configured to be able to realize the state of the pressure increasing mode to connect,
The control means includes
Based on the operation amount, the electric motor is controlled to adjust the position of the piston in the axial direction to control the output pressure of the pressurizing mechanism,
The control means includes
Based on the speed of the wheel, anti-skid control that suppresses the lock of the wheel is executed, and while the anti-skid control is being executed, the adjustment is performed while the brake fluid pressure increasing mode is selected. While the pressure means is controlled to be in the pressure increasing mode and the brake fluid is supplied from the pressurizing mechanism to the wheel cylinder, the brake fluid pressure is increased and the brake fluid pressure reducing mode is selected. Is configured to reduce the braking fluid pressure by controlling the pressure regulating means to the state of the decompression mode and discharging the braking fluid from the wheel cylinder to the reservoir,
The control means includes
While the pressure reducing mode is selected during execution of the anti-skid control, the braking fluid is discharged from the reservoir to the second fluid by controlling the electric motor and moving the piston in the second direction. A braking control device for a vehicle configured to return to the first fluid chamber via a chamber and the seal member .

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