JP6580960B2 - Electric braking device for vehicle - Google Patents

Description

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

  Patent Document 1 includes a “brake squeal detecting means for detecting a brake squeal of a wheel in order to effectively suppress brake squeal in a vehicle brake hydraulic pressure control device. It is described that the brake noise is suppressed by changing the distribution of the brake fluid pressure.

  By the way, brake squeal is a phenomenon in which vibration is generated due to a frictional force generated between a brake pad and a brake disk. Specifically, fine vibrations are generated due to non-uniform contact when the brake pads contact the brake disc, and this causes self-excited vibrations. This self-excited vibration is affected not only by the brake disc body but also by the brake caliper and the suspension member. For this reason, brake noise in various frequency bands and vibration modes occurs.

  In the device described in Patent Document 1, the brake fluid pressure is changed as a countermeasure after the occurrence of the brake squeal. On the other hand, what suppresses a certain specific brake squeal among various types is not desired without suppressing all brake squeals. In addition, the apparatus described in Patent Document 1 is premised on the provision of brake squeal detection means for detecting the brake squeal of the wheel, but a simple configuration that does not use the detection means is required.

Japanese Unexamined Patent Publication No. 09-2221013

  An object of the present invention is to provide an electric braking device for a vehicle that can suppress brake noise with a simple configuration.

  An electric braking device (EBR) for a vehicle for solving the above problems includes an operation amount sensor (BPA) for obtaining an operation amount (Bpa) of a braking operation member (BP) by a vehicle driver, wheels of the vehicle, The friction member (MSB) presses the rotating member (KTB) that rotates integrally with the electric motor (MTR) to drive the actuator (BRK) that applies braking torque to the wheel, and the operation amount ( Based on Bpa), a target value (Fbt) of the pressing force, which is a force with which the friction member (MSB) presses the rotating member (KTB), is calculated, and the target value (Fbt) and the actual value of the pressing force ( And a controller (CTL) for controlling the electric motor (MTR) so that Fba) matches.

  In the electric braking device (EBR) for the vehicle, the controller (CTL) has at least one vibration characteristic of the rotating member (KTB), the friction member (MSB), and the actuator (BRK). Accordingly, the target value (Fbt) is kept constant as the operation amount (Bpa) increases so as to avoid the region of the pressing force in which the predicted brake squeal occurs, and the operation amount (Bpa) is predetermined. When the value (bp1, bp3, bp5) is reached, the target value (Fbt) is calculated based on a squeal avoidance characteristic (CHf, CHr) that increases the target value (Fbt) stepwise. ing.

  Brake squeal is caused by minute frictional force fluctuations that occur on the contact surface between the rotating member (KTB) and the friction member (MSB). The components of the rotating member (KTB) such as a brake disk and actuator (BRK) (for example, brake caliper) ) And resonate. The ease of occurrence of brake squeal (probability of occurrence) is determined by the vibration characteristics (eg, natural vibration) of each member (brake caliper, etc.), rotating member (KTB), and friction member (MSB) constituting the actuator (BRK) Characteristic and can be predicted analytically and experimentally based on the natural frequency and the natural mode. According to the above configuration, the squeal avoidance characteristics (CHf, CHr) make it possible to avoid the region of the pressing force where the occurrence of the brake squeal is predicted. Can be prevented.

  In the electric braking device (EBR) for the vehicle, the controller (CTL) determines whether or not the squeal avoidance characteristics (CHf, CHr) are necessary based on the driving state (Vxa, dBp, Sfp) of the vehicle. When it is determined that the squeal avoidance characteristic (CHf, CHr) is necessary, the target value (Fbt) is calculated based on the squeal avoidance characteristic (CHf, CHr), and the squeal avoidance characteristic ( When it is determined that (CHf, CHr) is unnecessary, the target value (Fbt) monotonously increases as the manipulated variable (Bpa) increases, unlike the squeal avoidance characteristics (CHf, CHr). The target value (Fbt) is calculated based on the normal characteristics (CNf, CNr).

  In the squeal avoidance characteristics (CHf, CHr), there is a region where the target value (Fbt) of the pressing force is kept constant even when the operation amount Bpa is increased. The necessity of the squeal avoidance characteristics (CHf, CHr) is determined based on the driving state (Vxa, dBp, Sfp) of the vehicle, and the squeal avoidance characteristics (CHf, CHr) only when the probability of occurrence of brake squeal is high. Based on this, the target value (Fbt) of the pressing force is calculated. With this configuration, brake squeal is reduced, and a sense of discomfort to the driver can be suppressed.

  Furthermore, in the electric braking device (EBR) for the vehicle, the predetermined values (bp1, bp3, bp5) are specified values that are larger than the play value (bp0) corresponding to the play of the brake operation member (BP). (Bp1) is included. The squeal avoidance characteristic (CHr) corresponding to the rear wheel of the vehicle maintains the target value (Fbt) at zero even when the operation amount (Bpa) increases from zero to exceed the play value (bp0). When the manipulated variable (Bpa) reaches the specified value (bp1), the target value (Fbt) is set to increase stepwise from zero.

  At the initial stage of braking (when the braking force is low), brake noise is likely to occur. In addition, in the initial stage of braking, changes in vehicle deceleration are unlikely to lead to a sense of discomfort to the driver. Further, the influence of the rear wheel braking force on the braking force of the entire vehicle is smaller than the braking force of the front wheels. The squeal avoidance characteristic CHr corresponding to the rear wheel of the vehicle can effectively suppress brake squeal in a region where the pressing force generated at a high frequency is low, and can suppress a sense of discomfort to the driver.

The whole block diagram for demonstrating the electric braking device of the vehicle of 1st Embodiment. Schematic of the rotation member for demonstrating the example of a brake squeal. Schematic for demonstrating a wheel side electronic control unit. (A), (b), (c) is a time series diagram for demonstrating the action | operation of the electric braking device of a vehicle. The whole block diagram for demonstrating the electric braking device of the vehicle of 2nd Embodiment.

(First embodiment)
Hereinafter, a first embodiment of an electric braking device for a vehicle will be described with reference to the drawings.

<Overall Configuration of Electric Braking Device EBR for Vehicle>
FIG. 1 is an overall configuration diagram of an electric braking device EBR for a vehicle. A vehicle including the electric braking device EBR includes a braking operation member BP, an operation amount acquisition unit BPA, a wheel speed acquisition unit VWA, a vehicle body side electronic control unit ECB, a braking unit BRK, and a communication line SGL. The operation amount acquisition means BPA, the vehicle body side electronic control unit ECB, the braking means BRK, and the communication line SGL are constituent elements of the electric braking device EBR.

  The braking operation member (for example, a brake pedal) BP is a member that is operated by the driver to decelerate and stop the vehicle. When the braking operation member BP is being operated, the braking torque of the wheel is adjusted by the braking means BRK. As a result, braking force is generated on the wheels, and the traveling vehicle is decelerated. 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 (operation amount sensor) BPA, a sensor (pressure sensor) for detecting the pressure of the master cylinder, a sensor (stepping force sensor) for detecting the operation force of the braking operation member BP, and an operation displacement of the braking operation member BP At least one of the sensors (stroke sensors) for detecting the above is employed. Therefore, the 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 operation amount Bpa is input to the vehicle body side electronic control unit ECB.

  Wheel speed acquisition means (wheel speed sensor) VWA is provided for each wheel of the vehicle. The wheel speed acquisition means VWA acquires (detects) the rotation speed of the wheel as the wheel speed Vwa. Specifically, a gear-like sensor rotor that rotates integrally with the wheel is provided coaxially with the wheel, and the wheel speed acquisition means VWA is installed on the outer periphery of the sensor rotor with a minute gap. The wheel speed acquisition means VWA is composed of a coil and a magnetic pole, and the wheel speed Vwa of the wheel is detected based on a change in magnetic flux passing through the coil. The wheel speed Vwa is input to the vehicle body side electronic control unit ECB.

<Brake squeal>
Before describing the processing in the vehicle body side electronic control unit ECB, the brake noise will be described with reference to FIGS. 1 and 2. “Brake squeal” is a vibration source caused by contact between the rotating member (brake disc) KTB and the friction member (brake pad) MSB, and resonates with the members (parts) constituting the braking device and the vehicle body. This is a phenomenon caused by There are various types of brake squeal, but examples include squeal noise (easily generated when a low-speed vehicle is stopped with low pedaling force), glow sound (easily generated when the brake pedal is released at the time of starting, etc.) ), Hum (prone to occur when starting at very low speed), rumble (may occur during normal braking), and the like.

  Next, the generation mechanism of the brake squeal will be described. On the contact surface between the rotating member KTB and the friction member MSB, a frictional force is generated by sliding, and a minute fluctuation (stick-slip phenomenon) is always generated. The frictional force fluctuation resonates with members around the sliding portion (for example, the rotating member KTB and the friction member MSB), and self-excited vibration is generated. Factors causing the frictional force fluctuation include the vibration form of the braking device including the rotating member KTB, the physical properties of the friction member MSB (for example, the speed dependency of the friction member MSB, the wear state of the friction member MSB), and the thermal deformation of the constituent members. It is done.

  An example of self-excited vibration is mode coupling. In the mode coupling, resonance is generated when the natural frequencies of two or more natural modes are close to each other. For example, when the natural frequency of a certain natural mode of the brake disk (rotating member KTB) is close to the natural frequency of a certain natural mode of the brake caliper, the circumferential direction (in-plane direction) of the brake disk (rotating member KTB) This is a case where the natural frequency of the natural mode approximates the natural frequency of the natural mode in the axial direction (perpendicular direction) (see FIG. 2). In addition, the eigenmode has a plurality of modes in one member. For example, even with a brake disk (rotating member KTB) alone, there are several to several tens of eigenmodes.

  The vibration characteristics (natural vibration characteristics) of the braking device including the rotating member KTB can be analyzed in advance based on the shape, material, and restraint state (a form in which each member is fixed). The analysis for obtaining the natural vibration characteristic is generally called mode analysis (or eigenvalue analysis). As the natural vibration characteristic, a natural mode and a natural frequency are used. The eigenmode is a shape (that is, how vibration appears) in which an object (member) can be freely deformed in a given restraint state. For example, the distribution of vibration amplitude nodes and antinode positions is the eigenmode. The natural frequency is the degree of repetition of the natural mode per unit time. For example, the natural frequency is a frequency when an object is freely vibrated.

  Furthermore, a mode damping ratio can be adopted as the natural vibration characteristic. The mode damping ratio is a value indicating the convergence of vibration when free vibration is performed.In the case of free vibration, the larger the mode damping ratio in the time domain, the faster the convergence.In the frequency domain, the larger the mode damping ratio, the larger the amplitude. Get smaller. Further, the amplitude at the time of resonance decreases as the mode damping ratio increases. The mode damping ratio can be calculated based on, for example, complex eigenvalue analysis.

  As described above, the ease of occurrence of the brake squeal (occurrence probability) depends on the vibration of each member (brake caliper CRP, etc.), the rotary member KTB, and the friction member MSB constituting the braking means (actuator) BRK. It can be predicted based on characteristics (eg, natural vibration characteristics). Of the brake squeals caused by the vibration characteristics of the braking means BRK and the like, a high probability of occurrence can be confirmed in advance in an experiment.

≪Car body side electronic control unit ECB≫
The vehicle body side electronic control unit ECB will be described with reference to FIG. The vehicle body side electronic control unit ECB is provided in the vehicle body of the vehicle. The vehicle body side electronic control unit ECB includes an electric circuit including a processor and is fixed to the vehicle body. The vehicle body side electronic control unit ECB includes a target pressing force calculation block FBT, a vehicle body speed calculation block VXA, an operation speed calculation block DBP, a determination block HNT, and a vehicle body side communication unit CMB. The target pressing force calculation block FBT, the vehicle body speed calculation block VXA, the operation speed calculation block DBP, the determination block HNT, and the vehicle body side communication unit CMB are control algorithms and are programmed in the processor of the vehicle body side electronic control unit ECB. . Here, the vehicle body side electronic control unit ECB corresponds to a part of the control means (controller) CTL.

  In the target pressing force calculation block FBT, the target pressing force Fbt is calculated based on the operation amount Bpa. Here, the target pressing force Fbt 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. The target pressing force Fbt is based on the operation amount Bpa, the calculation characteristics (calculation map) CNf, CHf corresponding to the preset front wheels of the vehicle, and the calculation characteristics CNr, CHr corresponding to the preset rear wheels of the vehicle. Is calculated. Here, the calculation characteristics CNf and CNr are calculation characteristics corresponding to a case where avoidance of brake squeal described later is not performed. The calculation characteristics CNf and CNr are hereinafter referred to as “normal characteristics”. The calculation characteristics CHf and CHr are calculation characteristics corresponding to the case where the avoidance of brake squeal is performed. The calculation characteristics CHf and CHr are hereinafter referred to as “squeal avoidance characteristics”.

  First, calculation of the target pressing force Fbt based on the normal characteristics CNf and CNr will be described. The front wheel target pressing force Fbt is calculated based on a normal characteristic CNf of the front wheel indicated by a broken line in FIG. 1 and an operation amount Bpa. The normal characteristic CNf of the front wheels is a calculation map set in advance in the vehicle body side electronic control unit ECB. The front wheel target pressing force Fbt is calculated to be zero when the operation amount Bpa ranges from zero to the value bp0, and when the operation amount Bpa exceeds the value bp0, the target pressing force Fbt is calculated to increase monotonously as the operation amount Bpa increases. The Here, the value bp0 is a value corresponding to “play (the amount of operation that can be freely moved between the components)” of the braking operation member BP, and this value bp0 is hereinafter referred to as “play value”.

  Note that, as the normal characteristic CNf of the front wheel, a normal characteristic CNj in which a jump-in characteristic described below is considered may be employed. A jump-in characteristic (also called a jumping characteristic) increases the assisting force stepwise from zero so that the output can be increased with a small operating force (brake pedal depression force) in a booster (eg, negative pressure booster). To do. Accordingly, as a normal characteristic of the front wheels, as shown by a one-dot chain line in FIG. 1, in the range where the operation amount Bpa is from zero to the play value bp0, the target pressing force Fbt is zero and the operation amount Bpa becomes the play value bp0. In this case, a characteristic (normal characteristic CNj) in which the target pressing force Fbt increases from zero to the value fbj stepwise can be employed. Here, the value fbj is referred to as a “jump-in value”. Even in the normal characteristic CNj in which the jump-in characteristic is taken into account, the front wheel target pressing force Fbt is monotonously increased from the jump-in value fbj as the operation amount Bpa increases from the play value bp0.

  The rear wheel target pressing force Fbt is calculated based on the normal characteristic (calculation map) CNr of the rear wheel set in advance and indicated by the broken line in FIG. 1, and the operation amount Bpa. The rear wheel target pressing force Fbt is also calculated to be zero when the operation amount Bpa is in the range from zero to the play value bp0, and when the operation amount Bpa exceeds the play value bp0, it increases monotonously as the operation amount Bpa increases. Is calculated.

  Next, calculation of the target pressing force Fbt based on the squeal avoidance characteristics CHf and CHr will be described. As described above, some brake squeals can be predicted in advance by vibration analysis based on vibration characteristics determined by the shape, material, fixed form, and the like of the rotating member KTB, the friction member MSB, and the braking means BRK. The squeal avoidance characteristics CHf and CHr are set in advance so as to avoid a pressing force region (squeal region) where occurrence of a brake squeal is predicted.

The front wheel target pressing force Fbt is calculated based on the operation amount Bpa and the front wheel squeal avoidance characteristic (calculation map) CHf. Specifically, the target pressing force Fbt of the front wheel is determined as in (1) to (5) below.
(1) When the operation amount Bpa is “less than the play value bp0”, the target pressing force Fbt of the front wheels is calculated to be zero.
(2) In the range where the operation amount Bpa is “more than the play value bp0 and less than the value bp4”, the front wheel target pressing force Fbt is calculated so as to monotonously increase to the value fb4 as the operation amount Bpa increases.
(3) In the range where the manipulated variable Bpa is “value bp4 or more and less than value bp5”, the target pressing force Fbt of the front wheels is kept constant at the value fb4.
(4) When the increasing operation amount Bpa reaches “value bp5”, the front wheel target pressing force Fbt is increased stepwise from the value fb4 to the value fb5.
(5) When the operation amount Bpa is “value bp5 or more”, the front wheel target pressing force Fbt is monotonously increased from the value fb5 as the operation amount Bpa increases.

  In the front wheel squeal avoidance characteristic CHf, the range in which the value of the target pressing force Fbt is “value fb4 or more and less than value fb5” corresponds to a squeal region (a region where a brake squeal predicted by vibration analysis is likely to occur). Therefore, in order to avoid the squealing region, when the operation amount Bpa is not less than the value bp4 and less than the value bp5, the target pressing force Fbt of the front wheel is calculated to be a constant value fb4, and when it deviates from the squealing region ( When the increasing operation amount Bpa reaches the value bp5), the front wheel target pressing force Fbt is increased stepwise from the value fb4 to the value fb5. Note that the values bp4 and bp5 of the operation amount Bpa are preset predetermined values corresponding to the values fb4 and fb5 of the target pressing force Fbt of the front wheels.

  Note that the squeal avoidance characteristic CHj in which the jump-in characteristic is considered may be adopted as the front wheel squeal avoidance characteristic, similarly to the normal characteristic CNj. That is, in the squeal avoidance characteristic CHj in which the jump-in characteristic is taken into consideration, as shown by a one-dot chain line in FIG. 1, the operation amount Bpa is the play value bp0, and the front wheel target pressing force Fbt is the jump-in value stepwise from zero. Increased to fbj. Even in this case, in order to avoid the above-described squealing region, when the operation amount Bpa is equal to or greater than the value bp4 and less than the value bp5, the target pressing force Fbt of the front wheel is constant and the operation amount Bpa matches the value bp5. The target pressing force Fbt of the front wheel is increased stepwise.

The rear wheel target pressing force Fbt is calculated based on the operation amount Bpa and the rear wheel squeal avoidance characteristic (calculation map) CHr. Specifically, the target pressing force Fbt of the rear wheel is determined as in (1) to (5) below.
(1) When the operation amount Bpa is “less than value bp1,” the rear wheel target pressing force Fbt is calculated to be zero. Here, the value bp1 is a value larger than the play value bp0 and is referred to as a “specified value”.
(2) When the increasing operation amount Bpa reaches “value bp1,” the rear wheel target pressing force Fbt is increased stepwise from zero to the value fb1.
(3) In the range where the operation amount Bpa is “more than value bp1 and less than value bp2”, the rear wheel target pressing force Fbt is monotonously increased from the value fb1 as the operation amount Bpa increases.
(4) In the range where the operation amount Bpa is “more than value bp2 and less than value bp3”, the rear wheel target pressing force Fbt is maintained constant at the value fb2.
(5) When the increasing operation amount Bpa reaches “value bp3”, the rear wheel target pressing force Fbt is increased stepwise from the value fb2 to the value fb3.
(6) When the operation amount Bpa is “value bp3 or more”, the rear wheel target pressing force Fbt is monotonously increased from the value fb3 as the operation amount Bpa increases.

  In the rear wheel squeal avoidance characteristic CHr, a range in which the value of the target pressing force Fbt is “zero or more and less than the value fb1” and a range in which “the value is greater than or equal to the value fb2 and less than the value fb3” correspond to the squeal region. Therefore, in order to avoid the squealing region, in the range where the operation amount Bpa is less than the value bp1 which is larger than the play value bp0, even if the operation amount Bpa increases, the rear wheel target pressing force Fbt is held at zero. When it deviates from the squealing region (when the increasing operation amount Bpa reaches the value bp1), the rear wheel target pressing force Fbt is increased stepwise from zero to the value fb1. In the range where the operation amount Bpa is not less than the value bp2 and less than the value bp3, the target pressing force Fbt of the rear wheel is calculated to a constant value fb2, and when the operation amount Bpa is out of the squealing region (the increasing operation amount Bpa is a value). When reaching bp3), the rear wheel target pressing force Fbt is increased stepwise from the value fb2 to the value fb3. Note that the values bp1, bp2, and bp3 of the operation amount Bpa are predetermined values that correspond to the values fb1, fb2, and fb3 of the target pressing force Fbt of the rear wheels, respectively. Of the values bp1, bp2, and bp3 that are the predetermined values, the value bp1 corresponds to a preset specified value.

  Thus, in the squeal avoidance characteristics CHf and CHr, there is a region where the target pressing force Fbt is kept constant even when the operation amount Bpa is increased. For this reason, in order not to give the driver a sense of incongruity, the stepwise increase amount in the target pressing force Fbt is determined in advance so that the change in the deceleration to the vehicle is small. Specifically, the value fb1, the difference hfb between the value fb2 and the value fb3, and the difference hfc between the value fb4 and the value fb5 correspond to the braking force to such a degree that a change in vehicle deceleration is hardly felt by the driver. Can be set to a value. Note that the brake squeal suppression performance by the squeal avoidance characteristics CHf and CHr and the uncomfortable feeling to the driver are in a trade-off relationship.

  Therefore, the use of the squeal avoidance characteristics CHf and CHr can be selectively performed according to the driving state of the vehicle. Specifically, the target pressing force calculation block FBT is provided with two characteristics of normal characteristics CNf and CNr and squeal avoidance characteristics CHf and CHr. Then, in the determination block HNT, it is determined whether or not the noise avoidance characteristics CHf and CHr are necessary based on the driving state of the vehicle. That is, it is determined whether or not the probability of occurrence of brake squeal is high in the driving state of the vehicle. When the determination block HNT determines that the squeal avoidance characteristics CHf and CHr are necessary (that is, the probability of occurrence of brake squeal is high), the squeal avoidance characteristics CHf and CHr are employed for calculating the target pressing force Fbt. The On the other hand, when the determination block HNT determines that the squeal avoidance characteristics CHf and CHr are unnecessary (that is, the probability of occurrence of brake squeal is low), the normal characteristics CNf and CNr are used for calculating the target pressing force Fbt. It is done.

  For example, whether or not the squeal avoidance characteristics CHf and CHr are necessary is determined based on at least one of the vehicle body speed Vxa, the operation speed dBp of the braking operation member BP, and the shift position Sfp of the transmission. Hereinafter, each example will be described.

  In the vehicle body speed calculation block VXA, the vehicle body speed Vxa is calculated by a known method based on the wheel speed Vwa of each wheel. For example, among the wheel speeds Vwa of four wheels, the fastest one can be set as the vehicle body speed Vxa. Here, the wheel speed Vwa is detected by wheel speed acquisition means VWA provided on each wheel.

  In the determination block HNT, based on the vehicle body speed Vxa, it is determined whether or not the vehicle body speed Vxa is less than the predetermined vehicle speed vx0. As a result, the determination signal Hnt is determined. The determination signal Hnt is input to the target pressing force calculation block FBT. When the determination signal Hnt is an affirmative signal that “the vehicle body speed Vxa is less than the predetermined vehicle speed vx0”, the squeal avoidance characteristics CHf and CHr are employed in the target pressing force calculation block FBT, The target pressing force Fbt of each rear wheel is calculated. On the other hand, when the vehicle body speed Vxa is equal to or higher than the predetermined vehicle speed vx0 and the determination signal Hnt is a signal that denies that “the vehicle body speed Vxa is less than the predetermined vehicle speed vx0”, in the target pressing force calculation block FBT, The normal characteristics CNf and CNr are employed to calculate the target pressing force Fbt for each of the front and rear wheels. Thus, when the vehicle body speed Vxa is equal to or higher than the predetermined vehicle speed vx0, the squeal avoidance characteristics CHf and CHr are not adopted. When the vehicle body speed Vxa is high, the brake squeal is noticeable due to the running sound (wind noise, tire noise, etc.). Due to not.

  In the operation speed calculation block DBP, the operation speed dBp of the braking operation member BP is calculated. Specifically, the operation amount Bpa is differentiated with respect to time, and the change amount of the operation amount Bpa with respect to time is calculated as the operation speed dBp.

  In the determination block HNT, based on the operation speed dBp, it is determined whether or not the operation speed dBp is less than the predetermined operation speed db0. As a result, the determination signal Hnt is determined. The determination signal Hnt is input to the target pressing force calculation block FBT as in the case of the vehicle body speed Vxa. When the determination signal Hnt is an affirmative signal that “the operation speed dBp is less than the predetermined operation speed db0”, the squeal avoidance characteristics CHf and CHr are adopted in the target pressing force calculation block FBT, and the front wheels The target pressing force Fbt of each rear wheel is calculated. On the other hand, when the operation speed dBp is equal to or higher than the predetermined operation speed db0 and the determination signal Hnt is a signal that denies that “the operation speed dBp is less than the predetermined operation speed db0”, the target pressing force calculation block FBT is notified. Thus, the normal characteristics CNf and CNr are employed to calculate the target pressing force Fbt for each of the front wheels and the rear wheels. Thus, when the operation speed dBp is equal to or higher than the predetermined operation speed db0, the noise avoidance characteristics CHf and CHr are not adopted. When the operation speed dBp of the braking operation member BP is high, the target pressing force Fbt increases or decreases. This is due to passing through the squealing region in an instant.

  In the determination block HNT, based on the shift position Sfp of the transmission by the driver's operation of the shift lever SL, it is determined whether or not the shift position Sfp is reverse. The shift position Sfp is acquired (detected) by the shift position acquisition means (shift position sensor) SFP and is input to the vehicle body side electronic control unit ECB. Also, the shift position Sfp can be acquired from another electronic control unit (for example, an electronic control unit for an automatic transmission) via a communication bus.

  When the determination signal Hnt from the determination block HNT is a signal that affirms that “the shift position Sfp is backward”, the squeal avoidance characteristics CHf and CHr are adopted in the target pressing force calculation block FBT, The target pressing force Fbt for each of the front and rear wheels is calculated. On the other hand, when the shift position Sfp instructs to move forward, and the determination signal Hnt is a signal that denies that “the shift position Sfp is backward,” the normal characteristics CNf, CNr in the target pressing force calculation block FBT. Is employed to calculate the target pressing force Fbt for each of the front and rear wheels. The reason why the noise avoidance characteristics CHf and CHr are employed only when the shift position Sfp instructs to reverse is that the vehicle is in an extremely low speed when the vehicle is reverse and the brake noise is likely to occur. .

  The target pressing force Fbt for each of the front and rear wheels calculated by the target pressing force calculation block FBT is output to the vehicle body side communication unit CMB. The vehicle body side communication unit CMB is connected to the communication line SGL, and exchanges data with the wheel side communication unit CMW of the wheel side electronic control unit ECW. The vehicle body side electronic control unit ECB has been described above.

≪Braking means (actuator) BRK≫
Next, the braking means BRK will be described. The braking means BRK is a brake actuator, and is provided on each of the four front, rear, left and right wheels in the vehicle. The braking means BRK gives the wheel a braking torque corresponding to the frictional force generated by pressing the friction member MSB against the rotating member KTB rotating integrally with the wheel. As a result, braking force is generated on the wheels, and the running vehicle decelerates.

  As the braking means BRK, a so-called disc type braking device (disc brake) is exemplified. In this case, the friction member MSB is a brake pad, and the rotating member KTB is a brake disc. The braking means BRK may be a drum type braking device (drum brake). In the case of a drum brake, the friction member MSB is a brake shoe, and the rotating member KTB is a brake drum.

  The braking means (actuator) BRK includes a brake caliper (also simply referred to as a caliper) CRP, a pressing member PSN, an electric motor MTR, a rotation angle acquisition means MKA, a reduction gear GSK, an output member SFO, a screw member NJB, and a pressing force acquisition means FBA. And the wheel side electronic control unit ECW.

  A floating caliper can be adopted as the caliper CRP. The caliper CRP is configured to sandwich a rotating member (brake disc) KTB via two friction members (brake pads) MSB. Inside the caliper CRP, the pressing member (brake piston) PSN moves (advances or retracts) with respect to the rotating member KTB.

  By the movement of the pressing member PSN, the friction member MSB is pressed against the rotating member KTB, and a frictional force is generated. The movement of the pressing member PSN is performed by the power of the electric motor MTR. Specifically, the output (rotational force around the shaft) of the electric motor MTR is transmitted to the output member SFO via the reduction gear GSK. Then, the rotational power (torque) of the output member SFO is converted into linear power (axial thrust of the pressing member PSN) by the screw member NJB and transmitted to the pressing member PSN. As a result, the pressing member PSN is moved with respect to the rotating member KTB. By the movement of the pressing member PSN, the force (pressing force) by which the friction member MSB presses the rotating member KTB is adjusted. Since the rotating member KTB is fixed to the wheel, a frictional force is generated between the friction member MSB and the rotating member KTB, and the braking torque of the wheel is adjusted.

  The electric motor MTR is a power source for driving (moving) the pressing member PSN. For example, a motor with a brush or a brushless motor may be employed as the electric motor MTR. 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 rotation angle acquisition means (for example, rotation angle sensor) MKA acquires (detects) the rotation angle Mka of the rotor (rotor) of the electric motor MTR. The detected rotation angle Mka is input to the wheel side electronic control unit ECW (specifically, the processor in the wheel side electronic control unit ECW).

  The pressing force acquisition means (for example, a pressing force sensor) FBA acquires (detects) a force (actual pressing force) Fba that the pressing member PSN presses the friction member MSB. The detected actual pressing force (actual pressing force) Fba is input to the wheel side electronic control unit ECW (specifically, the processor in the wheel side electronic control unit ECW). For example, the pressing force acquisition unit FBA is provided between the output member SFO and the caliper CRP.

  The wheel side electronic control unit ECW is an electric circuit that drives the electric motor MTR. The wheel-side electronic control unit ECW drives the electric motor MTR based on the target pressing force Fbt and controls its output. Here, the target pressing force Fbt is transmitted from the vehicle body side electronic control unit ECB to the wheel side electronic control unit ECW via a communication line (also referred to as a signal line) SGL. The wheel side electronic control unit ECW is disposed (fixed) inside the caliper CRP.

  The wheel side electronic control unit ECW includes a wheel side communication unit CMW, a wheel side calculation unit ENW, and a drive unit DRV. The wheel side communication unit CMW is connected to the communication line SGL, and exchanges data signals with the vehicle body side communication unit CMB of the vehicle body side electronic control unit ECB. The vehicle body side communication unit CMB, the communication line SGL, and the wheel side communication unit CMW are collectively referred to as “communication means TSN” (see FIG. 3).

  As shown in FIG. 3, the wheel side calculation unit ENW calculates drive signals Sw1 to Sw4 for controlling the switching elements SW1 to SW4 for driving the electric motor MTR. The drive unit (drive circuit) DRV is configured as a bridge circuit HBR including switching elements SW1 to SW4. In the bridge circuit HBR, the energization states of the switching elements SW1 to SW4 are switched based on the drive signals Sw1 to Sw4. By this switching, the electric motor MTR is rotationally driven and its output is adjusted. The braking means BRK has been described above.

  As shown in FIGS. 1 and 3, the communication line SGL is a communication means between the vehicle body side electronic control unit ECB and the wheel side electronic control unit ECW, and corresponds to a part of the control means CTL. Data signals are transmitted (received / transmitted) between the vehicle body side electronic control unit ECB and the wheel side electronic control unit ECW by the communication line SGL. A serial communication bus is adopted as the communication line SGL. The serial communication bus is a bus that transmits data one bit at a time in one communication path. For example, a CAN bus is adopted as a serial communication bus.

<Wheel-side electronic control unit ECW>
The wheel side electronic control unit ECW will be described with reference to the schematic diagram of FIG. Here, the wheel side electronic control unit ECW corresponds to a part of the control means (controller) CTL.

  The wheel-side electronic control unit ECW adjusts the energization state (finally the magnitude and direction of the current) to the electric motor MTR based on the target pressing force Fbt received from the vehicle body-side electronic control unit ECB. Controls MTR output and rotation direction. The wheel-side electronic control unit ECW includes a wheel-side communication unit CMW, a wheel-side calculation unit ENW, and a drive unit DRV.

≪Wheel side communication unit CMW≫
The wheel side communication unit CMW is a part of the communication means TSN, and is connected to the vehicle body side communication unit CMB of the vehicle body side electronic control unit ECB via the communication line SGL. Here, a serial communication bus (for example, CAN communication) is employed as the communication line SGL. The target pressing force Fbt is transmitted (transmitted) from the vehicle body side electronic control unit ECB to the wheel side electronic control unit ECW (in particular, from the vehicle body side communication unit CMB to the wheel side communication unit CMW) via the communication line SGL. Further, in the vehicle body side communication unit CMB and the wheel side communication unit CMW, error detection is performed on a data signal (such as the target pressing force Fbt) that is received and transmitted.

≪Wheel side calculation unit ENW≫
The wheel side calculation unit ENW is a control algorithm and is programmed in a processor in the wheel side electronic control unit ECW. The wheel side calculation unit ENW includes an instruction energization amount calculation block IST, a pressing force feedback control block FBC, a target energization amount calculation block IMT, a pulse width modulation block PWM, and a switching control block SWT.

  The command energization amount calculation block IST calculates the command energization amount Ist based on the target pressing force Fbt and preset calculation characteristics (calculation maps) CHs1 and CHs2. The command energization amount Ist is a target value of the energization amount to the electric motor MTR for achieving the target pressing force Fbt. The calculation map of the command energization amount Ist is composed of two calculation characteristics CHs1 and CHs2 in consideration of the hysteresis of the braking means BRK.

  The energization amount to the electric motor MTR 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 the pulse width modulation, this duty ratio can be used as the energization amount.

  The pressing force feedback control block FBC calculates the feedback energization amount Ibt based on the target pressing force (target value) Fbt and the actual pressing force (actual value) Fba. Specifically, first, a pressing force deviation eFb that is a deviation between the target pressing force Fbt and the actual pressing force Fba is calculated. In the feedback energization amount calculation block IBT, the feedback energization amount Ibt is calculated by PID control based on the pressing force deviation eFb. Although the command energization amount Ist is calculated as a value corresponding to the target pressing force Fbt, there may be an error between the target pressing force Fbt and the actual pressing force Fba due to the efficiency variation of the braking means BRK. Therefore, the feedback energization amount Ibt is determined so as to reduce this error. That is, the actual pressing force Fba that is the actual value of the pressing force (the detected value of the pressing force acquisition means FBA) is controlled to coincide with the target pressing force Fbt that is the target value of the pressing force.

  The target energization amount calculation block IMT calculates a target energization amount Imt that is a final target value for the electric motor MTR. In the target energization amount calculation block IMT, the instruction energization amount Ist is adjusted by the feedback energization amount Ibt, and the target energization amount Imt is calculated. Specifically, the feedback energization amount Ibt is added to the command energization amount Ist, and the target energization amount Imt is calculated.

  The direction of rotation of the electric motor MTR is determined based on the sign (the sign of the value) of the target energization amount Imt, and the output (rotational power) of the electric motor MTR is controlled based on the magnitude of 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 normal rotation direction (increase direction of the pressing force), and the sign of the target energization amount Imt is In the case of a negative sign (Imt <0), the electric motor MTR is driven in the reverse direction (decreasing direction of the pressing force). Further, the output torque of the electric motor MTR is controlled to increase as the absolute value of the target energization amount Imt increases, and the output torque of the electric motor MTR is controlled to decrease as the absolute value of the target energization amount Imt decreases. .

  The pulse width modulation block PWM calculates an instruction value (target value) for performing pulse width modulation based on the target energization amount Imt. Specifically, the pulse width modulation block PWM is based on the target energization amount Imt and a preset characteristic (computation map), and the duty ratio Dut of the pulse width (in the periodic pulse wave, the on-state for the cycle is set. Determine the pulse width ratio of the state). In addition, the pulse width modulation block PWM determines the rotation direction of the electric motor MTR based on the sign (positive sign or negative sign) of the target energization amount Imt. 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, in the pulse width modulation block PWM, the rotation direction of the electric motor MTR and the energization amount to the electric motor MTR (that is, the electric motor MTR). Output).

  Further, in the pulse width modulation block PWM, so-called current feedback control can be executed. In this case, the detected value of the energization amount acquisition means IMA, that is, the motor current Ima flowing through the electric motor MTR is input to the pulse width modulation block PWM. The duty ratio Dut is corrected (finely adjusted) based on the deviation eIm between the target energization amount Imt, which is the target value of the motor current, and the actual energization amount (= motor current Ima). With this current feedback control, highly accurate motor control can be achieved.

  The switching control block SWT outputs drive signals Sw1 to Sw4 to the switching elements SW1 to SW4 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. The larger the duty ratio Dut, the longer the energization time per unit time, and the larger current flows through the electric motor MTR.

≪Driver DRV≫
The drive unit DRV is an electric circuit for driving the electric motor MTR. The drive unit (drive circuit) DRV includes a bridge circuit HBR and energization amount acquisition means IMA. FIG. 3 shows, as an example, a drive unit 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 bridge circuit HBR can control the rotation direction (forward rotation direction or reverse rotation direction) of the electric motor by changing the energization direction to the electric motor with a single power supply without requiring a bidirectional power supply. Circuit. The bridge circuit HBR includes switching elements SW1 to SW4. The switching elements SW1 to SW4 are elements that can turn on (energize) / off (non-energize) a part of the electric circuit. The switching elements SW1 to SW4 are driven by drive signals Sw1 to Sw4 from the wheel side calculation unit ENW. The rotation direction and output torque of the electric motor MTR are adjusted by switching the energization / non-energization states of the respective switching elements. For example, a MOS-FET or IGBT is employed as the switching element.

  When the electric motor MTR is driven in the forward direction, the switching elements SW1 and SW4 are energized (on state), and the switching elements SW2 and SW3 are deenergized (off state). On the other hand, when the electric motor MTR is driven in the reverse direction, the switching elements SW1 and SW4 are turned off (off state), and the switching elements SW2 and SW3 are turned on (on state).

  An energization amount acquisition means (for example, a current sensor) IMA for the electric motor is provided in the bridge circuit HBR. The energization amount acquisition unit IMA acquires a motor current Ima that is an energization amount of the electric motor MTR. For example, a current value that actually flows through the electric motor MTR can be detected by the motor current sensor as the motor current Ima.

  A motor with a brush (also referred to as a brush motor) is employed as the electric motor MTR. The electric motor MTR is provided with a rotation angle acquisition means (rotation angle sensor) MKA that acquires (detects) the rotation angle (actual value) Mka of the rotor. The rotation angle Mka is input to the wheel side electronic control unit ECW.

  As the electric motor MTR, a brushless motor may be employed instead of the brush motor. The brushless motor has a structure in which the rotor (rotor) is a permanent magnet and the stator (stator) is a winding circuit (electromagnet), and the rotation angle acquisition means MKA detects the rotation angle Mka of the rotor. By switching the switching element in accordance with Mka, the supply current is commutated.

  When a brushless motor is employed, the bridge circuit HBR is configured by six switching elements. As in the case of the motor with brush, the energization state / non-energization state of the switching element is controlled based on the duty ratio Dut. Based on the actual rotor rotation angle Mka, the six switching elements constituting the three-phase bridge circuit are controlled. The direction of the coil energization amount of the U-phase, V-phase, and W-phase of the bridge circuit (that is, the excitation direction) is sequentially switched by the switching element to drive the electric motor 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.

  The pressing force acquisition means (pressing force sensor) FBA acquires (detects) an actual pressing force Fba that is a force by which the pressing member PSN presses the friction member MSB. The pressing force acquisition means FBA is provided between the screw member NJB and the caliper CRP. For example, when the pressing force acquisition unit FBA is fixed to the caliper CRP, the pressing force acquisition unit FBA acquires the reaction force (reaction) received by the pressing member PSN from the friction member MSB as the actual pressing force Fba. The actual pressing force (actual value) Fba is input to the wheel side electronic control unit ECW (particularly, the pressing force feedback control block FBC).

  The storage battery BAT and the generator ALT are provided on the vehicle body side of the vehicle. The storage battery BAT and the generator ALT supply power to the vehicle body side electronic control unit ECB and the wheel side electronic control unit ECW via the power line PWL. That is, power to the electric motor MTR is supplied by the storage battery BAT or the like.

<Time-series operation of electric braking device EBR>
With reference to the time series diagrams of FIGS. 4A, 4B, and 4C, the operation of the electric braking device EBR employing the squeal avoidance characteristics CHf (or CHj) and CHr will be described. The operation of the electric braking device EBR is controlled by the control means CTL (the vehicle body side electronic control unit ECB, the wheel side electronic control unit ECW, and the communication line SGL). In the time-series diagram shown in FIG. 4A, the driver starts the braking operation at time t0, and then the operation amount Bpa is gradually increased and held constant at time t7. Is assumed. In the time series diagrams shown in FIGS. 4B and 4C, the target pressing force Fbt of the front wheel and the rear wheel corresponding to the operation amount Bpa is plotted. Further, since the actual pressing force Fba is controlled by the control means CTL so as to coincide with the target pressing force Fbt, the actual pressing force Fba plotted in FIGS. 4B and 4C together with the target pressing force Fbt. Is overlapped with the target pressing force Fbt.

  The squeal avoidance characteristics CHf (or CHj) and CHr are vibration characteristics (for example, specific characteristics) of at least one of a rotating member (for example, a brake disc) KTB, a friction member (for example, a brake pad) MSB, and a braking means BRK. The frequency is set in advance analytically or experimentally based on the frequency and the natural mode. The squeal avoidance characteristics CHf (or CHj) and CHr are stored as a calculation map inside the control means CTL.

  At time t0, the braking operation by the driver is started and the operation amount Bpa starts to increase. However, in the “play” region of the braking operation member BP (a range where the operation amount Bpa is zero or more and a play value bp0 or less), the front wheel target pressing force Fbt and the rear wheel target pressing force Fbt are calculated to zero. Here, the play of the braking operation member BP is an operation amount in a range in which the braking operation does not affect the actual operation of the braking means BRK. At time t1, the operation amount Bpa matches the play value bp0, and then the operation amount Bpa further increases.

  From time t1 when the operation amount Bpa exceeds the play value bp0, the front wheel target pressing force Fbt calculated based on the front wheel squeal avoidance characteristic CHf is monotonously increased from zero. However, the rear wheel target pressing force Fbt calculated based on the rear wheel squeal avoidance characteristic CHr is maintained at zero. Then, when the operation amount Bpa reaches the value (specified value) bp1 at the time point t2, the rear wheel target pressing force Fbt is instantaneously increased from zero to the value fb1.

  In the rear wheel, the region where the actual pressing force Fba is from zero to the value fb1 corresponds to a squeal region where brake squeal is likely to occur. In addition, at the beginning of braking (when the braking force is small), changes in vehicle deceleration are unlikely to lead to a sense of discomfort to the driver. Further, the influence of the rear wheel braking force on the braking force of the entire vehicle is smaller than the braking force of the front wheels. Therefore, the squealing avoidance characteristic CHr of the rear wheels can effectively avoid the squealing region, prevent brake squealing, and suppress a sense of discomfort to the driver.

  After the time point t2, the target pressing force Fbt for the rear wheel monotonously increases from the value fb1 as the operation amount Bpa increases. When the rear wheel target pressing force Fbt (that is, the rear wheel actual pressing force Fba) enters the rear wheel squealing region at time t3, the rear wheel target pressing force Fbt is maintained at the value fb2. Further, at the time t4 when the operation amount Bpa is increased and the actual pressing force Fba of the rear wheel is out of the squealing region, the target pressing force Fbt of the rear wheel suddenly (instantly) changes from the value fb2 to the value fb3. After that, it is monotonously increased in accordance with the increase in the operation amount Bpa. At the time t7 when the operation amount Bpa is held at the value bp6, the rear wheel target pressing force Fbt is also held constant at the value fb6.

  When the front wheel target pressing force Fbt (that is, the front wheel actual pressing force Fba) enters the front wheel squealing region at time t5, the front wheel target pressing force Fbt is maintained at the value fb4. Further, when the operation amount Bpa is increased and the actual pressing force Fba of the front wheel deviates from the squealing region, the target pressing force Fbt of the front wheel is suddenly increased from the value fb4 to the value fb5 (instantaneously). Thereafter, it is monotonously increased in accordance with the increase in the operation amount Bpa. Similar to the rear wheel, at the time t7 when the operation amount Bpa is held at the value bp6, the target pressing force Fbt of the front wheel is also held constant at the value fb7.

  A jump-in characteristic as indicated by the alternate long and short dash line can be employed at the initial stage of braking of the target pressing force Fbt of the front wheel. The jump-in characteristic is a characteristic that is generally adopted for a booster (for example, a negative pressure booster). In the initial stage of braking corresponding to the play of the braking operation member BP, the braking force is instantaneously applied with a slight operating force. It is something to launch. In the jump-in characteristic of the target pressing force Fbt of the front wheel, based on the squeal avoidance characteristic CHj (see FIG. 1) in which the jump-in characteristic is taken into account, at the time t1 when the operation amount Bpa matches the play value bp0, The target pressing force Fbt is instantaneously increased from zero to the jump-in value fbj. Even in the squeal avoidance characteristic CHj in which the jump-in characteristic is considered, the target pressing force Fbt of the front wheel is maintained at the value fb4 while the operation amount Bpa is equal to or greater than the value bp4 and less than the value bp5.

In the rear wheel squeal avoidance characteristic CHr, the rear wheel target pressing force Fbt is maintained at zero until a value bp1 that is larger than the play value bp0. For this reason, the jump-in characteristic of the target pressing force Fbt of the front wheel not only assists the driver's operation characteristic but also has an effect of compensating for the deceleration of the vehicle. Note that the value fb1, the difference hfb (difference between the value fb3 and the value fb2), and the difference hfc (difference between the value fb5 and the value fb4) are reduced to the entire vehicle even if the target pressing force Fbt is instantaneously increased. It can be set to such an extent that it does not affect the speed change.
In the case where a so-called hydraulic actuator that adjusts the actual pushing force Fba of the wheel by the braking hydraulic pressure is provided for the wheel, an electric braking means (actuator) BRK is provided for the wheel. Compared with the case where it exists, the followability of the actual pressing force Fba with respect to the change of the target pressing force Fbt calculated using the squeal avoidance characteristics CHf and CHr is not good. Therefore, in such a hydraulic actuator, even if the target pressing force Fbt is maintained so as to avoid the squealing region where the brake squeal is likely to occur, the actual pressing force Fba enters the squealing region where the brake squeal is likely to occur. Sometimes. In this case, the brake squeal occurs even if the target pressing force Fbt is maintained. In this regard, by providing the electric braking means (actuator) BRK with respect to the wheels, the actual pressing force Fba is maintained by maintaining the target pressing force Fbt so as to avoid the squealing region where the brake squeal is likely to occur. This makes it difficult to enter a squeal area where brake squeal is likely to occur, and can suppress the occurrence of predictable brake squeal.
In the electric braking device EBR for a vehicle according to the first embodiment, when the operation amount Bpa of the braking operation member BP is increased, the rear wheel target pressing force Fbt, that is, the rear wheel braking force is maintained. And the period during which the front wheel target pressing force Fbt, that is, the front wheel braking force is maintained, does not overlap. In particular, in the initial stage of braking with a small operation amount Bpa, that is, during the period from the value bp0 to the value bp1, the braking force of the rear wheels is maintained as the operation amount Bpa increases, but the braking force of the front wheels increases. Is done. Accordingly, while the operation amount Bpa is increased, the vehicle deceleration can be increased even when the braking force of the rear wheel is maintained, so that the driver who operates the braking operation member BP feels uncomfortable. It becomes difficult to give.

(Second Embodiment)
Next, an electric braking device EBR for a vehicle according to a second embodiment will be described with reference to the overall configuration diagram of FIG. In the first embodiment, the braking torque of the four wheels (front and rear, left and right) of the vehicle is adjusted by the braking means (actuator) BRK. In the second embodiment, the braking torque of the front wheels is applied from the master cylinder MC. It is adjusted by the hydraulic pressure, and the braking torque of the rear wheel is adjusted by the braking means BRK. That is, in the second embodiment, a general hydraulic pressure system is adopted as a braking device for the front wheels, so that the squeal avoidance characteristic CHr is applied only to the rear wheels.

  The front wheel hydraulic system will be briefly described. The braking operation member BP is connected to the master cylinder MC via a booster (brake booster) BB. Here, the booster BB has the jump-in characteristic described above. The master cylinder MC is fluidly connected to the front wheel cylinder WC by a brake pipe HKN. When the brake operation member BP is operated, the brake fluid is discharged from the master cylinder MC toward the front wheel cylinder WC, and the hydraulic pressure in the wheel cylinder WC is increased. As a result, the brake piston in the caliper CRP presses the friction member MSB against the rotating member KTB. A braking torque is applied to the front wheels by the frictional force at this time.

  The rear wheel is provided with a brake means (actuator) BRK, and the friction member MSB is pressed against the rotating member KTB by the control means (controller) CTL including the rear wheel squeal avoidance characteristic CHr and the rear wheel normal characteristic CNr described above. The actual pressing force Fba, which is the applied force, is controlled. Specifically, the rear wheel target pressing force Fbt is determined based on the rear wheel squeal avoidance characteristic CHr or the rear wheel normal characteristic CNr, and the actual pressing force Fba is calculated as the rear wheel target pressing force Fbt. It is controlled by the control means CTL so as to match.

  Similarly to the first embodiment, in the second embodiment, the vehicle is in an operating state (for example, at least one of the vehicle speed Vxa, the operation speed dBp of BP, and the shift position Sfp of the transmission). Based on this, any one of the rear wheel squeal avoidance characteristic CHr and the rear wheel normal characteristic CNr is selectively adopted to calculate the rear wheel target pressing force Fbt.

  When the rear wheel squeal avoidance characteristic CHr is employed, the actual pressing force is kept constant over a predetermined range. However, in the deceleration of the vehicle, the degree of contribution of the rear wheel braking force is much smaller than the degree of contribution of the front wheel braking force. For this reason, even if the pressing force is limited to be constant over a predetermined range by the rear wheel squeal avoidance characteristic CHr, the influence on the deceleration of the vehicle is small. Therefore, the predictable brake noise of the rear wheel can be effectively suppressed by the configuration of the second embodiment, that is, the configuration in which the front wheel is a hydraulic braking system and the rear wheel is an electric braking system.

In the configuration of the second embodiment, in particular, in the rear wheel squeal avoidance characteristic CHr, “the target of the rear wheel even if the operation amount Bpa increases from zero to exceed the play value bp0 corresponding to the play of the braking operation member BP. The effect of “the characteristic of increasing the target pressing force Fbt of the rear wheel stepwise from zero” when the pressing force Fbt is maintained at zero and the operation amount Bpa becomes a value bp1 larger than the play value is great. This is because the brake noise of the rear wheels is likely to occur when the vehicle is creeping and a slight braking force is generated. Further, due to the jump-in characteristic of the booster, the front wheel braking force is increased stepwise at the value bp0. For this reason, even if it is a case where said rear-wheel characteristic is employ | adopted, in the deceleration of a vehicle, the discomfort to a driver | operator can be suppressed.
In addition, you may change each said embodiment into another embodiment as follows.
In each of the above embodiments, the vehicle speed Vxa is less than the predetermined vehicle speed vx0, the operation speed dBp of the braking operation member BP is less than the predetermined operation speed db0, and the shift position Sfp is all reverse. The target pressing force Fbt for each of the front wheels and the rear wheels is calculated based on the squeal avoidance characteristics CHf and CHr on the condition that the relationship is established. However, if the conditions for employing the squeal avoidance characteristics CHf and CHr include that the vehicle body speed Vxa is less than the predetermined vehicle speed vx0, the operation speed dBp of the braking operation member BP is less than the predetermined operation speed db0, and The shift position Sfp may not include the reverse movement. Moreover, if the conditions for adopting the squeal avoidance characteristics CHf and CHr include that the operation speed dBp of the braking operation member BP is less than the predetermined operation speed db0, the vehicle body speed Vxa is less than the predetermined vehicle speed vx0, and The shift position Sfp may not include the reverse movement. Further, if the conditions for adopting the squeal avoidance characteristics CHf and CHr include that the shift position Sfp is reverse, the operation speed dBp of the braking operation member BP is less than the predetermined operation speed db0, and the vehicle body speed. It may not include that Vxa is less than the predetermined vehicle speed vx0.

  BP ... braking operation member, BPA ... operation amount acquisition means (operation amount sensor), BRK ... braking means (actuator), EBR ... electric braking device, ECB ... vehicle body side electronic control unit, ECW ... wheel side electronic control unit, SGL ... Signal line, CTL ... control means (controller), MTR ... electric motor, Fbt ... target pressing force, KTB ... rotating member, MSB ... friction member, CHf ... front wheel squeal avoidance characteristic, CHr ... rear wheel squeal avoidance characteristic, CNf ... normal characteristics of front wheels, CNr ... normal characteristics of rear wheels.

Claims (2)

An operation amount sensor for acquiring an operation amount of a braking operation member by a vehicle driver;
An actuator that applies a braking torque to the wheel by pressing a rotating member that rotates integrally with the wheel of the vehicle by a friction member by driving an electric motor;
Based on the operation amount, a target value of a pressing force, which is a force with which the friction member presses the rotating member, is calculated, and the electric motor is controlled so that the target value matches the actual value of the pressing force. A controller,
In an electric braking device for a vehicle comprising:
The controller is
The target is increased according to an increase in the operation amount so as to avoid a region of the pressing force in which a brake squeal that is predicted according to vibration characteristics of at least one of the rotating member, the friction member, and the actuator is generated. Maintaining the value constant, and calculating the target value based on a squeal avoidance characteristic that increases the target value stepwise when the manipulated variable reaches a predetermined value ,
The predetermined value includes a specified value that is a value greater than an idle value corresponding to the idle play of the braking operation member,
The squeal avoidance characteristic corresponding to the rear wheel of the vehicle maintains the target value at zero even when the operation amount increases from zero to exceed the play value, and the operation amount reaches the specified value An electric braking device for a vehicle , wherein the target value is set to increase stepwise from zero . The electric braking device for a vehicle according to claim 1,
The controller is
Determining the necessity of the squeal avoidance characteristics based on the driving state of the vehicle;
When it is determined that the squeal avoidance characteristic is necessary, the target value is calculated based on the squeal avoidance characteristic,
When it is determined that the squeal avoidance characteristic is unnecessary, unlike the squeal avoidance characteristic, the target value is calculated based on a normal characteristic in which the target value increases monotonously as the manipulated variable increases. An electric braking device for a vehicle.

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