JP2022026496A - Electrically-driven braking device of vehicle - Google Patents

Abstract

To make two spring members holding a ball equally loaded at non-braking in an electrically-driven braking device which adopts a non-circulation type ball screw mechanism.SOLUTION: An electrically-driven braking device adjusts braking force of wheels by controlling, with an electric motor, pressing force of a friction member against a rotary member fixed to the wheel. The electrically-driven braking device comprises: a ball screw mechanism which converts rotational power of the electric motor into linear power of the friction member; and a controller which increases the pressing force in normal driving of the electric motor and reduces the pressing force in reverse driving of the electric motor. In the electrically-driven braking device, the ball screw mechanism includes a ball line whose both ends are held by two spring members. In a case where a rotation angle of the electric motor becomes equal to or greater than a prescribed angle in a period from a start to an end of electric conduction to the electric motor, the controller changes a rotation angle in a reverse direction further with respect to a reference angle shifting from a state where the pressing force is generated when driving the electric motor in the reverse direction, into a state where the pressing force is not generated.SELECTED DRAWING: Figure 5

Description

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

The applicant has a patent for the purpose of "providing a rotation / linear motion conversion mechanism (screw mechanism) of an electric braking device of a vehicle that can maintain a good lubrication state for a long period of time". We are developing an electric braking device for vehicles as described in Document 1. In the device of Patent Document 1, "the rotary motion of the electric motor is converted into the linear motion of the pressing piston that presses the friction member by the screw mechanism. A lubricant is stored in the gap of the screw mechanism. Control means. Rotates the electric motor in the forward rotation direction when the pressing force is increased, and rotates the electric motor in the reverse direction when the pressing force is decreased. When the pressing force is decreased, the rotation angle of the electric motor The rigidity value Gcp, which is the amount of change in the pressing force with respect to the amount of change in the Rotate the electric motor in the reverse direction until t5. "

Patent Document 2 states that "the ball screw device 22 is used as a female screw groove 33 and a stopper for the purpose of providing an inexpensive ball screw device that does not require high dimensional machining accuracy for machining a recess that receives a spring member. A ball nut 30 including recesses 60 and 70 and a screw shaft 28 including a male screw groove 34 are provided. A ball row L is interposed in a raceway K formed between the female screw groove 33 and the male screw groove 34. Coil springs 51 and 52 as spring members are interposed between the balls 29 of the ends La and Lb of L and the recesses 60 and 70 as stoppers. The coil springs 51 and 52 make at least one circumference of the track path K. It has a minute length. " Further, Patent Document 1 describes that the ball screw device is applied to a braking device (also referred to as an "electric braking device") using an electric motor as a drive source.

It is assumed that the non-circulating ball screw mechanism as described in Patent Document 2 is applied to the electric braking device as described in Patent Document 1. In the thread mechanism NJ, the ball BL has a spiral shape formed by a male thread groove (also referred to as “shaft thread groove”) Ms of the shaft member SF and a female thread groove (also referred to as “nut thread groove”) Mn of the nut member NT. It is arranged in a row in the thread groove of. Aggregates of ball BLs (referred to as "ball rows") BLs formed in a ball groove and arranged in a row are two spring members SA and SB at both ends Ea and Eb inside the nut thread groove Mn. Held by.

When the braking operation is performed on the electric braking device DS, one side of the two spring members SA and SB is contracted and the other side is extended. The amount of deformation of the spring members SA and SB depends on the relative displacement between the shaft member SF and the nut member NT due to the braking operation. In normal braking operation, the relative displacement between the shaft member SF and the nut member NT is not so large, so the amount of deformation is relatively small. However, when the friction member MS is suddenly worn or the like, the relative displacement becomes extremely large, and the amount of deformation of the spring members SA and SB becomes large. Since friction exists between the ball BL and the threaded grooves Ms and Mn, it becomes difficult for the ball BL to move smoothly in the threaded groove when the amount of deformation increases. As a result, a situation may occur in which the load states of the two spring members SA and SB are not even when the brakes are not applied. This situation is not preferred with respect to the durability of the electric braking device.

JP-A-2014-142044 Japanese Unexamined Patent Publication No. 2016-037981

An object of the present invention is to provide an electric braking device for a vehicle in which a non-circulating ball screw mechanism is adopted, in which the load states of two spring members holding the ball during non-braking can be equalized. ..
Is.

The vehicle electric braking device according to the present invention controls the pressing force (Fa) of the friction member (MS) against the rotating member (KT) fixed to the wheel (WH) of the vehicle by an electric motor (MT). A ball screw mechanism (NJ) that adjusts the braking force (Fx) of the wheel (WH) and converts the rotational power of the electric motor (MT) into the linear power of the friction member (MS), and the above. By driving the electric motor (MT) in the forward rotation direction (Da), the pressing force (Fa) is increased, and the electric motor (MT) is rotated in the reverse direction (Db) opposite to the normal rotation direction (Da). A controller (ECU) that reduces the pressing force (Fa) by driving the wheel is provided.

In the electric braking device for a vehicle according to the present invention, the ball screw mechanism (NJ) includes ball rows (BLs) in which both ends (Ea, Eb) are held by two spring members (SA, SB). It is composed. Then, in the period from the start to the end of energization of the electric motor (MT), the rotation angle (Ka) of the electric motor (MT) of the controller (ECU) becomes a predetermined angle (kx) or more. In the case, it is further than the reference angle (km) that transitions from the state in which the pressing force (Fa) is generated to the state in which the pressing force (Fa) is not generated when the electric motor (MT) is driven in the reverse direction (Db). The angle of rotation (Ka) is changed in the reverse direction (Db). Further, the controller (ECU) changes the rotation angle (Ka) to the reference angle (km) after changing the rotation angle (Ka) from the reference angle (ko) to the reverse direction (Db). return.

According to the above configuration, since the ball train BLs are forcibly moved in the thread groove, the first and second spring members that hold the ball train BLs during non-braking (that is, after the braking operation is completed). The load of SA and SB (that is, the amount of deformation) is made uniform. This can improve the durability of the electric braking device DS.

It is a schematic diagram for demonstrating the 1st Embodiment of the electric braking device DS. It is a schematic diagram for demonstrating the non-circulation type ball screw mechanism NJ. It is a flow diagram for demonstrating the processing of a reference angle calculation. It is a flow diagram for demonstrating the process of equalization control. It is a time series diagram for demonstrating the operation of equalization control. It is the schematic for demonstrating the 2nd Embodiment of the electric braking device DS.

Hereinafter, embodiments of the electric braking device for vehicles according to the present invention will be described with reference to the drawings.

<Symbols of components, subscripts at the end of symbols>
In the following description, components, elements, signals, etc. with the same symbol, such as "MT", have the same function. The subscripts "1" and "2" (particularly in FIG. 6) added to the end of the symbols relating to the two braking systems are comprehensive symbols indicating which system they are related to, and "1" is a comprehensive symbol. One braking system (also referred to as "first braking system BK1") and "2" indicate the other braking system (also referred to as "second braking system BK2"). The subscripts "1" and "2" may be omitted. When the subscripts "1" and "2" are omitted, the symbols represent generic names. For example, "CW1" is a wheel cylinder related to the first braking system BK1, and "CW2" is a wheel cylinder related to the second braking system BK2. And, "CW" is a general term for wheel cylinders.

<Direction of exercise / movement>
Next, the directions of movement / movement of the shaft member SF, the nut member NT, the rotating member KT, the friction member MS, and the electric motor MT will be described. When the friction member MS is moved in the direction (referred to as "forward direction") toward the rotating member KT, the pressing force Fa, which is the force with which the friction member MS is pressed against the rotating member KT, is increased, and the braking force Fx is increased. Will be done. On the contrary, when the friction member MS is moved to Hb in the direction away from the rotating member KT (the direction opposite to the forward direction Ha, which is referred to as the “backward direction”), the pressing force Fa is reduced and the braking force Fx is reduced. Will be done. The movement of the friction member MS is realized by the relative displacement of the shaft member SF and the nut member NT in the screw mechanism NJ. For example, when the shaft member SF is fixed, the nut member NT is moved in the forward direction Ha, so that the friction member MS is moved in the forward direction Ha and the nut member NT is moved in the backward direction Hb. The friction member MS is moved in the receding direction Hb. Here, the movement of the forward direction Ha corresponds to the forward rotation direction Da of the electric motor MT, and the movement of the backward direction Hb corresponds to the reverse rotation direction Db opposite to the normal rotation direction Da of the electric motor MT. That is, when the electric motor MT is rotationally driven in the forward rotation direction Da, the nut member NT is moved in the forward direction Ha, and the friction member MS is moved in the forward direction Ha. As a result, the pressing force Fa is increased and the braking force Fx is increased. On the contrary, when the electric motor MT is rotationally driven in the reverse direction Db, the nut member NT is moved in the backward direction Hb, and the friction member MS is moved in the backward direction Hb. As a result, the pressing force Fa is reduced and the braking force Fx is reduced.

<Overall Configuration of Electric Braking Device for Vehicles According to the Present Invention>
An embodiment of the electric braking device DS of the vehicle will be described with reference to the overall configuration diagram of FIG. The vehicle equipped with the electric braking device DS includes a braking operation member BP, a rotating member KT, a brake caliper CP, and a friction member MS.

The braking operation member (for example, the brake pedal) BP is a member operated by the driver to decelerate the vehicle. By operating the braking operation member BP, the braking torque of the wheel WH is adjusted, and the braking force Fx is generated on the wheel WH. Specifically, the wheel WH of the vehicle is provided with a rotating member KT (for example, a brake disc). The rotating member KT is fixed so as to rotate integrally with the wheel WH. A brake caliper CP is provided so as to sandwich the rotating member KT. In the brake caliper (also simply referred to as "caliper") CP, two (pair) friction member (eg, brake pad) MSs are pressed against the rotating member KT by the power of the electric motor MT. Braking torque (resulting in braking force Fx) is generated in the wheel WH by the frictional force generated at this time. For example, a floating caliper is adopted as the caliper CP.

The electric braking device DS includes a braking operation amount sensor BA, a braking actuator AC, and a controller ECU.

The braking operation member (brake pedal) BP is provided with a braking operation amount sensor BA. The braking operation amount sensor BA acquires (detects) the operation amount (braking operation amount) Ba of the braking operation member BP by the driver. As the braking operation amount sensor BA, a sensor (pressure sensor PM) that detects the pressure (master cylinder hydraulic pressure) Pm of the master cylinder CM, a sensor (treading force sensor FP) that detects the operating force Fp of the braking operation member BP, and braking. At least one of the sensors (stroke sensor SP) that detects the operation displacement Sp of the operation member BP is adopted. That is, the braking operation amount Ba is calculated based on at least one of the master cylinder hydraulic pressure Pm, the operating force Fp of the braking operation member BP, and the operation displacement Sp of the braking operation member BP. The braking operation amount Ba is input to the controller ECU.

≪Brake actuator AC≫
The friction member MS (brake pad) is pressed against the rotating member KT (brake disc) that rotates integrally with the wheel WH by the braking actuator (simply also referred to as “actuator”) AC. The frictional force generated at this time applies braking torque to the wheels WH, generates braking force Fx, and decelerates the running vehicle.

The actuator AC is fixed to the brake caliper CP. The actuator AC is composed of a pressing piston PN, an electric motor MT, a speed reducer GS, a screw mechanism NJ, a rotation angle sensor KA, and a pressing pressure sensor FA.

A pressing piston (simply also referred to as a "piston") PN is provided inside the caliper CP so that it can move with respect to the rotating member KT (brake disc). The pressing piston PN is linearly moved by the power (torque output) of the electric motor MT. That is, the electric motor MT is a power source for driving (moving) the pressing piston PN. For example, as the electric motor MT, a brushed motor or a blessingless motor is adopted.

The movement of the pressing piston PN presses the friction member MS, and the pressing state of the friction member MS against the rotating member KT (that is, the pressing force Fa) is adjusted. That is, the pressing piston PN is a moving member that presses the friction member MS against the rotating member KT to generate a braking force Fx on the wheel WH of the vehicle. Specifically, when the electric motor MT is rotated in the forward rotation direction Da, the pressing piston PN is moved in the forward direction Ha, the friction member MS is moved in the forward direction Ha, and the pressing force Fa is increased. Further, when the electric motor MT is rotated in the reverse direction Db, the pressing piston PN is moved in the backward direction Hb, the friction member MS is moved in the backward direction Hb, and the pressing force Fa is reduced.

The output (rotational power around the axis) of the electric motor MT is transmitted to the pressing piston PN via the speed reducer GS and the screw mechanism NJ. Specifically, the power of the electric motor MT is decelerated by the speed reducer GS. Then, the rotational power of the electric motor MT is converted into linear power of the piston PN (thrust in the central axis direction of the piston PN) by the screw mechanism NJ.

In the screw mechanism NJ, the shaft member SF and the nut member NT are meshed with each other via a plurality of balls BL (for example, steel balls). That is, the screw mechanism NJ is a ball screw mechanism. For example, the rotational power of the electric motor MT is transmitted as the rotational power of the shaft member SF. At this time, the nut member NT is prevented from rotating by a key mechanism, a spline mechanism, or the like. The nut member NT does not rotate around its central axis and can only move in the direction along the central axis. As a result, the rotational power of the shaft member SF is converted into the linear power of the nut member NT. Since the nut member NT is arranged so as to press the pressing piston PN, the rotational power of the electric motor MT is converted into the linear power of the friction member MS via the screw mechanism NJ.

In the power transmission of the screw mechanism NJ, the above configuration may be reversed. That is, the rotational power of the electric motor MT is transmitted as the rotational power of the nut member NT. Further, the shaft member SF is detented and is moved only in the direction along the central axis. As a result, the rotational power of the nut member NT is converted into the linear power of the shaft member SF. The shaft member SF is arranged so as to press the pressing piston PN, and the rotational power of the electric motor MT is converted into the linear power of the friction member MS via the screw mechanism NJ.

In any case, the rotational power of the electric motor MT is transmitted as the linear power of the pressing piston PN via the screw mechanism NJ. As a result, the friction member MS is moved with respect to the rotating member KT, and a pressing force Fa with respect to the rotating member KT is generated and adjusted. That is, the ball screw mechanism NJ converts the rotational power of the electric motor MT into the linear power of the friction member MS, and the pressing force Fa is adjusted. Then, the braking force Fx of the wheel WH is generated and adjusted according to the frictional force between the friction member MS and the rotating member KT generated by the pressing force Fa.

In the rotation direction of the electric motor MT, the normal rotation direction Da is the approach direction (forward direction Ha) of the pressing piston PN (resulting in the friction member MS) with respect to the rotating member KT, the pressing force Fa increases, and the braking force Fx increases. Corresponds to (direction). The reverse direction Db opposite to the normal rotation direction Da is the direction of separation of the pressing piston PN or the like with respect to the rotating member KT (the backward direction Hb opposite to the forward direction Ha), the pressing force Fa decreases, and the braking force Fx decreases. Corresponds to the direction of

The electric motor MT is provided with a rotation angle sensor KA. The rotation angle sensor KA detects the position (for example, rotation angle) Ka of the rotor (rotor) of the electric motor MT. The detected actual rotation angle Ka is input to the controller ECU. For example, the rotation angle sensor KA is built in the electric motor MT. As the rotation angle sensor KA, Hall IC type and resolver type sensors are adopted.

The actuator AC is provided with a push pressure sensor FA. The pressing force sensor FA detects the force (pressing pressure) Fa on which the pressing piston PN pushes the friction member MS. The detected actual pressing force Fa is input to the controller ECU. For example, the push pressure sensor FA is provided in the power transmission path between the speed reducer GS and the screw mechanism NJ.

≪Controller ECU≫
The electric braking device DS (particularly, the braking actuator AC) is controlled by a controller (also referred to as an "electronic control unit") ECU. Specifically, the electric motor MT is driven by the controller ECU. The controller ECU includes an electric circuit board on which a microprocessor and the like are mounted, and a drive circuit DR that energizes the electric motor MT. The control algorithm for driving the electric motor MT is programmed in the microprocessor. The controller ECU is connected to another controller so that signals (detected values, calculated values, etc.) can be transmitted and received via the communication bus BS.

The controller ECU is composed of a target push pressure calculation block FT, an indicated energization amount calculation block IS, a push pressure feedback control block IF, a target energization amount calculation block IT, and a drive circuit DR.

In the target pressing force calculation block FT, the target pressing force Ft is calculated based on the braking operation amount Ba. The target pressing force Ft is a target value of the force (pressing pressure) Fa that the friction member MS pushes the rotating member KT. The target pressing force Ft is calculated based on the braking operation amount Ba and the preset calculation map Zft. Specifically, according to the calculation map Zft, the target pressing force Ft is calculated to be “0” in the range from “0” to the value bo in the operation amount Ba. Then, when the manipulated variable Ba exceeds the value bo, the target pressing force Ft is calculated to monotonically increase as the manipulated variable Ba increases. The value bo is a preset predetermined value (constant) corresponding to the "play (free movement between the components)" of the braking operation member BP.

In the indicated energization amount calculation block IS, the indicated energization amount Is is calculated based on the target pressing force Ft and the preset calculation map Zis. The indicated energization amount Is is a target value of the energization amount to the electric motor MT for achieving the target pressing force Ft. The "energized amount" is a state quantity (variable) for controlling the output torque of the electric motor MT. Since the electric motor MT outputs a torque substantially proportional to the current, the current value of the electric motor MT is used as the energization amount. Further, if the supply voltage to the electric motor MT is increased, the current value is increased as a result, so that the supply voltage value can be used as the energization amount. Further, since the supply voltage value may be adjusted by the duty ratio in the pulse width modulation, this duty ratio may be used as the energization amount. In the indicated energization amount calculation block IS, the indicated energization amount Is is calculated so as to increase in accordance with the increase in the target pressing force Ft according to the calculation map Zis. In the calculation map Zis of the indicated energization amount Is, the hysteresis of the braking actuator AC is taken into consideration.

In the pressing force feedback control block IF, the compensation energization amount If is calculated based on the target pressing force (target value) Ft and the actual pressing force (detected value) Fa. The indicated energization amount Is is calculated as a value corresponding to the target pressing force Ft, but there is an error between the target pressing force Ft and the actual pressing force (detected value of the pressing force sensor FA) Fa due to the efficiency fluctuation of the braking actuator AC. May occur. The compensated energization amount If is for reducing (compensating) this error. Specifically, in the pressing force feedback control block IF, first, the deviation (pressing pressure deviation) hF between the target pressing force Ft and the actual pressing force Fa is calculated. Then, it is calculated so that the compensation energization amount If becomes larger as the pressing force deviation hF becomes larger. The compensation energization amount If is controlled so that the actual value Fa of the pressing force (detected value of the pressing force sensor FA) matches the target value Ft of the pressing force.

In the target energization amount calculation block IT, the target energization amount It, which is the final target value of the energization amount (for example, supply current) for the electric motor MT, is calculated. In the target energization amount calculation block IT, the indicated energization amount Is is adjusted by the compensating energization amount If, and the target energization amount It is calculated. Specifically, the compensated energization amount If is added to the indicated energization amount Is, and the target energization amount It is calculated (that is, "It = Is + If").

In the drive circuit DR, the electric motor MT is energized based on the target energization amount It. In the drive circuit DR, a bridge circuit is formed by switching elements (power semiconductor devices such as MOS-FETs and IGBTs). The electric motor MT is driven by controlling the amount of electricity supplied to the electric motor MT via the bridge circuit. The drive circuit DR is provided with an energization amount sensor IA that detects an actual energization amount Ia of the electric motor MT. For example, a current sensor is adopted as the energization amount sensor IA, and the supply current Ia to the electric motor MT is detected.

The rotation direction (normal rotation direction Da or reverse rotation direction Db) of the electric motor MT is determined based on the sign (positive or negative of the value) of the energization amount (that is, the target energization amount It). The magnitude of the output (rotational power) of the electric motor MT is controlled based on the magnitude of the energization amount. For example, when the sign of the target energization amount It is a positive sign (+) (It> 0), the electric motor MT is driven in the forward rotation direction Da (increase direction of the pressing force Fa), and the target energization amount It When the sign is a negative sign (−) (It <0), the electric motor MT is driven in the reverse direction Db (decrease direction of the pressing force Fa). The larger the absolute value of the target energization amount It is, the larger the output torque of the electric motor MT is, and the smaller the absolute value of the target energization amount It is, the smaller the output torque is.

In the drive circuit DR, an instruction value (target value) for performing pulse width modulation is calculated based on the target energization amount It. For example, the duty ratio of the pulse width (the ratio of the pulse width in the ON state to the period in the periodic pulse wave) is determined based on the target energization amount It and the preset calculation map. Based on the duty ratio (target value), the switching element constituting the bridge circuit is driven, and the electric motor MT is energized. Further, in the drive circuit DR, so-called current feedback control is executed. The deviation hI (energization amount deviation) between the detection value (for example, the actual current value) Ia of the energization amount sensor IA and the target energization amount It is calculated, and the duty ratio is set so that the deviation hI approaches "0". It will be corrected (fine-tuned).

In the controller ECU, in the non-circulation type ball screw mechanism NJ, the reference angle calculation block KO, so that the load states of the two spring members SA and SB holding the plurality of ball BLs are evenly distributed during the non-braking operation. And the equalization control block IE is included.

In the reference angle calculation block KO, the reference angle ko (including the reference angle km after rapid wear described later) is calculated based on the actual pressing force Fa, the actual rotation angle Ka, and a known method. The "reference angle" is from the state in which the pressing force Fa is generated (that is, the state of "Fa> 0") when the electric motor MT is driven in the reverse direction Db (during the reverse operation of the electric motor MT). This is the rotation angle Ka when the state in which the pressing force Fa is no longer generated (that is, the pressing force Fa is substantially “0 (zero)”) is entered. In the braking operation, when the electric motor MT is driven in the reverse direction Db while the rotation angle Ka is larger than the reference angle, the friction member MS is moved in the direction away from the rotation member KT (backward direction) Hb, which is generated. The pressing force Fa is gradually reduced. Then, when the rotation angle Ka reaches the reference angle, the friction member MS does not press the rotation member KT, and “Fa≈0 (a state in which the friction member MS and the rotation member KT rub against each other with no load)”. Further, when the electric motor MT is driven in the reverse direction Db, the friction member MS and the pressing piston PN are separated, and the state of "Fa≈0" is maintained. In other words, the reference angle is the rotation angle Ka at the time of transition from the state in which the friction member MS and the pressing piston PN are in contact to the state in which they are not in contact with each other.

As will be described later, the position of the reference angle changes (that is, is displaced) according to the wear of the friction member MS. In particular, in a situation where rapid wear occurs, the displacement of the reference angle is large before the start of the braking operation and after the rapid wear occurs. In the following description, when it is necessary to distinguish the reference angle, they are referred to separately as "reference angle ko before wear" and "reference angle km after wear". When it is not necessary to distinguish, the reference angle ko is a general term including the reference angle km.

In the equalization control block IE, the pull-back energization amount IE is calculated based on the rotation angle Ka. The pull-back energization amount Ie forcibly moves the ball rows BLs (rows of a plurality of ball BLs arranged without gaps in the nut thread groove Mn) to change the load state of the first and second spring members SA and SB. This is the target value of the amount of electricity to be equalized. Specifically, "the rotation angle Ka became equal to or greater than the first predetermined angle kx during the period from the start to the end of energization of the electric motor MT (that is, during a series of braking operations)". Under the conditions, the occurrence of rapid wear is determined. Here, the first predetermined angle kx is a predetermined value (constant) set with reference to the reference angle ko before wear. For example, the predetermined angle kx is determined by adding a predetermined value hx (a preset positive sign constant) to the reference angle ko (that is, “kx = ko + hx”). Then, when rapid wear occurs, a negative sign (-) occurs when the electric motor MT is driven in the reverse direction Db (particularly, when the rotation angle Ka is returned to the reference angle km after rapid wear). The pull-back energization amount Ie is calculated. The rotation angle Ka of the electric motor MT is further changed in the reverse direction Db from the reference angle km by the pull-back energization amount Ie. The operation is referred to as a "pull-back operation".

During a series of braking operations (also referred to as "one braking"), a state in which the rotation angle Ka becomes a predetermined angle kx or more (that is, the occurrence of rapid wear) is stored. Then, when the situation occurs, the pressing piston PN is further pulled back from the position [km] corresponding to the reference angle km in the backward direction Hb. Here, in the component member (shaft member SF or nut member NT) of the pressing piston PN and the screw mechanism NJ that presses the piston PN, the position [ko] ([km] corresponding to the reference angle ko (km). ) Is also called the "initial position". Since the specifications (reduction ratio, lead, etc.) are known to the speed reducer GS and the screw mechanism NJ, the positional relationship between the reference angle and the initial position is uniquely determined.

When the rotation angle Ka becomes less than the second predetermined angle kz after the pull-back operation is performed, the pull-back energization amount Ie is increased, and the electric motor MT is driven in the forward rotation direction Da. Then, the rotation angle Ka that has been changed in the reverse direction Db with respect to the reference angle km is returned to the reference angle km. Here, the second predetermined angle kz is a predetermined value (constant) set with reference to the reference angle km after wear. For example, the predetermined angle kz is determined by subtracting a predetermined value hz (a preset plus sign constant) from the reference angle km (that is, "kz = km-hz"). By increasing the angle of rotation Ka, the pressing piston PN is returned to the initial position [km] after wear.

The drive control of the electric motor MT as described above is called "equalization control". Since the ball train BLs in the nut thread groove Mn are forcibly moved by the equalization control, the first step is performed during non-braking (that is, after the braking operation is completed) after abnormal wear such as rapid wear occurs. , The load (that is, the amount of deformation) of the second spring members SA and SB is made uniform. As a result, the durability of the electric braking device DS is improved.

<Non-circulation type ball screw mechanism NJ>
The ball screw mechanism NJ will be described with reference to the schematic diagram of FIG. The ball screw mechanism NJ is a non-circulation type. The non-circulating type ball screw mechanism NJ is composed of a shaft member SF, a nut member NT, and ball rows BLs (a large number of balls BL arranged in a row in a thread groove). Specifically, in the screw mechanism NJ, male thread grooves (also referred to as "shaft thread grooves") Ms are spirally provided on the outer peripheral portion of the shaft member SF. Further, a female thread groove (also referred to as “nut thread groove”) Mn is spirally provided in the inner peripheral portion of the nut member NT. The shaft thread groove Ms and the nut thread groove Mn are formed (processed) so as to mesh with each other via a ball BL (for example, a steel ball). The balls BL are arranged without gaps so as to form a row in the thread groove composed of the shaft thread groove Ms and the nut thread groove Mn. That is, the ball rows BLs are arranged in the ball groove. The two ends (first end and second end) Ea and Eb of the ball rows BLs arranged in a row are two spring members (first and second spring members) inside the nut thread groove Mn. It is held by SA and SB.

For example, in the screw mechanism NJ, the rotational power of the electric motor MT is input to the shaft member SF, and the linear power is output from the detented nut member NT. On the contrary, the rotational power of the electric motor MT may be input to the nut member NT, and the linear power may be output from the detented shaft member SF. In any case, since the rotating member KT and the brake caliper CP are fixed to the wheel WH, the relative displacement between the shaft member SF and the nut member NT corresponds to the relative displacement between the friction member MS and the rotating member KT. do. Therefore, the pressing force Fa corresponds to the relative displacement (relative positional relationship) between the shaft member SF and the nut member NT in the direction of the central axis Js (which is also the rotation axis) of the shaft member SF and the nut member NT. Is adjusted. Hereinafter, a configuration in which linear power is output from the nut member NT and the pressing piston PN (finally, the friction member MS) is pushed by the nut member NT will be described as an example.

FIG. 2A shows the relative positional relationship between the shaft member SF and the nut member NT during braking operation. In FIG. 2A, the upper side of the central axis Js of the shaft member SF and the nut member NT (indicated by the symbol (A)) indicates that the braking state is appropriate (also referred to as “normal braking”). The lower side of the central axis Js (indicated by the symbol (B)) represents a state in which the friction member MS is rapidly worn (also referred to as “abnormal braking”). In FIG. 2A, the state (1) is a state in which the friction member MS is substantially new and has not been worn over time, and the state (2) is a state in which the amount of wear of the friction member MS has increased due to aged wear. , Represent each. Further, the state (3) of FIG. 2A represents a state in which abrupt wear occurs in one braking operation in the friction member MS that has not been worn over time.

FIG. 2B shows a nut thread groove Mn formed spirally around the central axis Js at the inner peripheral portion of the nut member NT and extended in a straight line for convenience. Inside the nut thread groove Mn, both ends Ea and Eb of the ball train BLs are held by the first and second spring members SA and SB. In FIG. 2B, the first stage represents the non-braking time, the second stage represents the normal braking time, and the third and fourth stages represent the abnormal braking time, respectively. Hereinafter, the deformed states of the first and second spring members SA and SB in each state will be described.

[Α] During non-braking When the electric braking device DS is not braking (that is, the electric motor MT is not energized), the rotation angle Ka (rotor position) of the electric motor MT is the reference angle ko. The nut member NT is at the position (initial position) [ko] corresponding to the reference angle ko. At this time, the first and second end portions Ea and Eb (also both ends of the ball train BLs) of the first and second spring members SA and SB are at the positions pa and pb, and the first and second spring members SA. , SB have the same amount of deformation and are compressed (see the first stage of FIG. 2B). Here, the reference angle ko is the rotation angle Ka when the generated pressing force Fa transitions to a state in which it does not occur during the reverse operation of the electric motor MT, and is in contact with the friction member MS. It is also the rotation angle Ka when the pressing piston PN separates from the friction member MS.

[Β] During normal braking (during braking without rapid wear, which is one of the abnormal wear phenomena)
During normal braking, the electric motor MT is rotationally driven, and the rotation angle Ka is displaced from the reference angle ko to the angle kp. As a result, the nut member NT is moved from the initial position [ko] corresponding to the reference angle ko to the position [kp] corresponding to the angle kp (the position separated by the distance Lp from the initial position [ko]) (state). (1)). Here, the distance Lp depends on the amount of deformation caused by the brake caliper CP generated during braking and the rigidity (spring constant) of the friction member MS. The ball train BLs are moved by the movement of the nut member NT. Specifically, the first end portion Ea (one end portion of the ball train BLs) of the first spring member SA is moved from the position pa to the position qa, and the first spring member SA is contracted as compared with the non-braking time. On the other hand, the second end portion Eb (the other end portion of the ball train BLs) of the second spring member SB is moved from the position pb to the position qb, and the second spring member SB is extended as compared with the non-braking state. Therefore, the amount of deformation (compression amount) of the first spring member SA is larger than the amount of deformation of the second spring member SB (see the second stage of FIG. 2B).

As the friction member MS wears over time, the initial position (position corresponding to the reference angle ko) [ko] is gradually moved to the forward direction Ha. Specifically, the initial position [ko] is displaced in the forward direction Ha according to the wear amount (dimension decrease amount in the thickness direction of the friction member MS) Lm of the friction member MS. When the normal braking operation is performed in this state, the rotation angle Ka is displaced from the reference angle ko to the angle kq. As a result, the nut member NT is moved from the initial position [ko] to the position [kq] corresponding to the angle kq (the position separated by the distance Lq from the initial position [ko]) (see state (2)). .. Here, the distance Lq depends on the amount of deformation of the brake caliper CP and the friction member MS generated during braking. When the friction member MS is worn over time, the thickness dimension of the friction member MS becomes smaller, so that the rigidity (spring constant) of the friction member MS is increased. Therefore, even if the degree of braking operation is the same, the displacement of the nut member NT becomes smaller (that is, “Lq <Lp”) as compared with the state where the aging wear is small.

As in the case where the amount of wear is small, the movement of the nut member NT causes the first end Ea of the first spring member SA to move from the position pa to the position qa, and the first spring member SA is compared when not braking. And shrink. On the other hand, the second end portion Eb of the second spring member SB is moved from the position pb to the position qb, and the second spring member SB is extended as compared with the non-braking state. Therefore, the amount of deformation (compression amount) of the first spring member SA is larger than the amount of deformation of the second spring member SB (see the second stage of FIG. 2B).

[Γ] During abnormal braking (during braking where rapid wear occurs in one braking)
A case where rapid wear occurs in a state where the friction member MS has not been worn over time will be described as an example. For example, "rapid wear" may occur due to brake fade. Specifically, when braking is continued on a downhill or the like, rubber, resin, etc., which are materials for friction members (for example, brake pads), exceed their heat resistant temperatures, are thermally decomposed, and are gasified. Then, the gas enters between the friction member and the rotating member (for example, the rotating member), and a gas film is formed. This gas film acts like a lubricant and reduces the coefficient of friction. The phenomenon is "brake fade phenomenon (simply also referred to as" fade ")". When a fade occurs, the material of the friction member (particularly, the base material, for example, a phenol resin which is a thermosetting resin) is decomposed and becomes brittle. At this time, in addition to the decrease in the coefficient of friction, sudden wear (for example, wear of about several mm in one braking operation) may occur. The wear is referred to as "fade wear".

When rapid wear (fade wear) occurs during braking operation, the electric motor MT rotates including the amount of deformation due to the rigidity of the brake caliper CP and the like, as well as the amount corresponding to the amount of wear of the friction member MS. Need to be driven. Therefore, at the time of abnormal braking, the rotation angle Ka is displaced from the reference angle ko to the angle kr. As a result, the nut member NT is moved from the initial position [ko] to the position [kr] corresponding to the angle kr (see state (3)). As described above, the distance from the initial position [ko] to the position [kr] is an amount obtained by adding the amount of wear of the friction member MS to the amount of deformation of the brake caliper CP or the like that occurs during braking. The ball train BLs are moved by the movement of the nut member NT. Specifically, the first end Ea of the first spring member SA is moved from the position pa to the position ra, and the second end Eb of the second spring member SB is moved from the position pb to the position rb. The amount of deformation (compression amount) of the first and second spring members SA and SB is extremely large as compared with the case of normal braking (see FIG. 2B, third stage).

After the braking operation including the abnormal braking is completed, the rotation angle Ka of the electric motor MT is returned toward the reference angle ko. However, since the friction member MS is worn and its thickness dimension is reduced, the reference angle ko before wear is changed to the reference angle km after wear. Then, the nut member NT is returned to the initial position [km] after wear, which corresponds to the reference angle km after wear. The distance Ln between the initial position [ko] before wear and the initial position [km] after wear is the amount of wear (decrease in thickness dimension) of the friction member MS generated during abnormal braking.

When the nut member NT is returned to the initial position [km] after wear, the first end portion Ea of the first spring member SA is moved from the position ra to the position ta, and the second end portion Eb of the second spring member SB. Is moved from position rb to position tb. At this time, even if the nut member NT is in the initial position [km], the deformation amount (compression amount) of the first spring member SA is larger than the deformation amount of the second spring member SB. That is, the load states of the first and second spring members SA and SB are not equalized even if they are returned to the initial position [km] due to rapid wear (see the fourth stage of FIG. 2B).

Since there is friction between the ball BL and the threaded grooves Ms and Mn, the ball row BLs are difficult to roll easily, and the first and second spring members SA and SB are caught in the threaded groove. Is a concern. In particular, when the amount of deformation of the first and second spring members SA and SB increases, the probability of catching the first and second spring members SA and SB increases. When the first and second spring members SA and SB are caught, the ball trains BLs are not smoothly moved in the thread groove, and the elastic forces of the first and second spring members SA and SB cause the first and second spring members SA and SB to move smoothly. It becomes difficult to return to the positions pa and pb where the load states of the spring members SA and SB are equal. In addition, when rapid wear occurs, the reference angle is changed (change from angle ko to angle km), so that the loads of the first and second spring members SA and SB are non-uniform at the reference angle km. In other words, the ball rows BLs are offset in the thread groove.

In the electric braking device DS, from the viewpoint of durability, it is desirable that the situation is avoided and the load states of the two spring members SA and SB become uniform during non-braking. It should be noted that such a problem is peculiar to the non-circulating ball screw and cannot occur in the circulating ball screw (see, for example, Japanese Patent Application Laid-Open No. 2006-242237).

<Processing of reference angle calculation block KO>
The processing of the reference angle calculation block KO will be described with reference to the flow chart of FIG. In the reference angle calculation block KO, when the electric motor MT is operated (driven) in the reverse direction Db, the reference angle ko including the reference angle km after wear is calculated and stored. Here, the reference angles ko and km change from the state in which the pressing force Fa is generated to the state in which the pressing force Fa is not generated (that is, “Fa≈0”), and the friction member MS and the rotating member KT have no load. It is the rotation angle Ka in the state transition that changes to the state of rubbing with each other. The pressing piston PN is configured to push the friction member MS, but is not fixed to the friction member MS. Therefore, the reference angles ko and km can be said to be the rotation angle Ka at the time when the pressing piston PN that was in contact with the friction member MS is separated from the friction member MS.

In step S110, various signals including the pressing force Fa (detection value of the pressing force sensor FA) and the rotation angle Ka of the electric motor (MT) (detection value of the rotation angle sensor KA) are read.

In step S120, "whether or not the electric motor MT is operating in the reverse direction Db" is determined based on the change in the rotation angle Ka. For example, the time change amount dK of the rotation angle Ka (for example, the change amount of the current value with respect to the previous value in the calculation cycle) is calculated. When the rotation angle Ka increases and the change amount dK has a plus sign (+), it is determined that the electric motor MT is operating in the normal rotation direction Da. In this case, step S120 is denied and processing is returned to step S110. On the other hand, when the rotation angle Ka decreases and the change amount dK has a negative sign (−), it is determined that the electric motor MT is operating in the reverse direction Db. In this case, step S120 is affirmed and processing proceeds to step S130.

In step S130, the reference angle ko (including the reference angle km) is determined when the rotation angle Ka changes in the reverse direction Db based on the pressing force Fa, the rotation angle Ka, and a known calculation method. .. For example, as known calculation methods for determining the reference angle ko, JP-A-2000-018294, JP-A-2001-2254711, JP-A-2004-124950, JP-A-2014-177206, and JP-A-2014. The method described in at least one of 177207 is employed.

For example, in step S130, the amount of decrease in the pressing force Fa with respect to the amount of decrease in the angle of rotation Ka is calculated as the amount of change (inclination) Cp. That is, the inclination Cp is a value obtained by dividing the amount of decrease in the pressing force Fa by the amount of decrease in the angle of rotation Ka. Then, the reference angle ko is determined based on the rotation angle Ka when the inclination Cp is less than the predetermined amount cp. Further, the reference angle ko may be calculated based on the rotation angle Ka (value kz) when the pressing force Fa is less than the predetermined force fz. Here, the predetermined force fz is a predetermined value (constant) set in advance.

In step S140, the reference angle ko determined in step S130 is stored. The stored reference angle ko is used for equalization control.

<Processing of equalization control>
The process of equalization control will be described with reference to the flow chart of FIG. The equalization control forcibly moves the ball train BLs when the rotation angle Ka (rotor position) of the electric motor MT is returned to the reference angles ko and km when rapid wear occurs during one braking. , The purpose is to equalize the loads of the first and second spring members SA and SB of the non-circulating ball screw mechanism NJ.

In step S210, various signals including the rotation angle Ka, the pressing force Fa, the operation amount Ba, the target pressing force Ft, the indicated energizing amount Is, the target energizing amount It, the actual energizing amount Ia, and the like are read.

In step S220, it is determined whether or not the operation of the electric motor MT is a normal rotation operation (referred to as “normal rotation determination”). Here, "operation of the electric motor MT" is a state in which the electric motor MT is energized and driven. For the operation of the electric motor MT, the electric motor MT is driven in the forward direction Ha so that the pressing force Fa is increased, and the electric motor MT is moved in the backward direction Hb so that the pressing force Fa is decreased. There is a "reverse operation" driven by the electric motor MT and a "holding operation" in which the rotation of the electric motor MT is stopped so that the pressing force Fa is kept constant. The determination of the operating state of these electric motors MT is performed based on the detected values such as the rotation angle Ka and the actual energization amount Ia. Further, since the rotation angle Ka, the actual energization amount Ia, etc. are control results based on the target value (including the operation amount Ba) corresponding to the operation amount Ba, the state amount from the operation amount Ba to the rotation angle Ka ( The operating state of the electric motor MT may be determined based on the control variable). For example, the state quantity corresponds to a braking operation amount Ba, a target pressing force Ft, an indicated energization amount Is, a target energization amount It, an actual energization amount Ia, an actual rotation angle Ka, and the like (see FIG. 1).

When the electric motor MT is rotating in the normal direction, step S220 is affirmed, and the process proceeds to step S230. On the other hand, when the electric motor MT is in the holding operation or the reverse operation, step S220 is denied and the process proceeds to step S250.

In step S230, "whether or not the rotation angle Ka is equal to or greater than the predetermined angle kx" is determined based on the rotation angle Ka. Here, the predetermined angle kx (first predetermined angle) is a threshold value for determining execution of equalization control, and is a predetermined value (constant) set in advance. If “Ka ≧ kx” and step S230 is affirmed, the process proceeds to step S240. On the other hand, if "Ka <kx" and step S230 is denied, the process is returned to step S210.

In step S240, the control flag FL is set to "1". Here, the control flag FL is for instructing the necessity of equalization control. In the control flag FL, "0" indicates that "equalization control is not required", and "1" indicates that "equalization control is required". That is, when "FL = 0", the equalization control (pull-back process described later) when the electric motor MT is reverse-operated is not executed. On the other hand, when "FL = 1", equalization control is executed when the electric motor MT is reverse-operated. In other words, the control flag FL memorizes the occurrence of "Ka ≧ kx" (that is, the occurrence of rapid wear) during one braking (the period from the start to the end of energization of the electric motor MT). Will be done. Then, when the state occurs, equalization control is executed. The control flag FL is set to "0" as an initial value.

In step S250, it is determined whether or not the operation of the electric motor MT is a reverse operation. Similar to step S220, the reverse operation of the electric motor MT is determined based on the state quantity (control variable) from the manipulated variable Ba to the rotation angle Ka. If the electric motor MT is held and operated, step S250 is denied and processing is returned to step S210. On the other hand, when the electric motor MT is reverse-operated, step S250 is affirmed, and the process proceeds to step S260.

In step S260, "whether or not the control flag FL is" 1 "" is determined based on the control flag FL. If the rotation angle Ka is less than the predetermined angle kx before the electric motor MT is reverse-operated and “FL = 0”, step S260 is denied and the process is returned to step S210. .. On the other hand, if the rotation angle Ka becomes equal to or greater than the predetermined angle kx even once before the electric motor MT is reverse-operated and “FL = 1”, step S260 is affirmed and the process proceeds to step S260. ..

In step S270, "whether or not the rotation angle Ka is equal to or less than the reference angle km" is determined based on the rotation angle Ka. If "Ka> km" and the rotation angle Ka has not yet been returned to the reference angle km, step S270 is denied and the process is returned to step S210. On the other hand, if “Ka ≦ km” and step S270 is affirmed, the process proceeds to step S280.

In step S280, a pullback operation, which is part of the equalization control, is performed. In the pull-back operation, the pull-back energization amount Ie is calculated so that the rotation angle Ka is further displaced in the reverse direction Db from the reference angle km and then returned to the reference angle km. Here, the pull-back energization amount Ie is a target value of the energization amount in the equalization control (particularly, the pull-back operation). In the region of “Ka ≦ km”, the target pressing force Ft is “0”, so the pullback energization amount Ie is calculated as the target energization amount It (that is, “It = Ie”). In the pull-back operation, control is performed so that the actual energization amount Ia matches the pull-back energization amount Ie. Even if the ball train BLs in the nut thread groove Mn are forcibly moved by the pull-back operation of the equalization control and the first and second spring members SA and SB are caught, this is eliminated. Will be done. As a result, the load states of the first and second spring members SA and SB are made even during non-braking after the braking operation is completed, so that the durability of the electric braking device DS can be improved.

For example, in the pull-back operation, the rotation direction change (change in the drive direction of the electric motor MT) of the forward rotation direction Da and the reverse rotation direction Db of the rotation angle Ka may be repeated a plurality of times. That is, the rotation angle Ka is "displaced in the reverse direction Db from the reference angle km" → "then returns to the reference angle km" → "removes from the reference angle km to the reverse direction Db" → "then the reference angle km". The forward rotation operation and the reverse rotation operation of the electric motor MT are repeated in the order of "re-returning to". As a result, the catching of the first and second spring members SA and SB can be more effectively eliminated.

<Operation of equalization control>
The operation of equalization control will be described with reference to the time series diagram of FIG. FIG. 5A shows a case where equalization control is not executed during normal braking, and FIG. 5B shows a case where equalization control is executed during abnormal braking.

First, a case where equalization control is not executed will be described with reference to FIG. 5A. At the time point t0, the operation of the braking operation member BP is started. Before the time point t0, the control flag FL is set to "0" as an initial value.

At the time point t0, the operation of the braking operation member BP is started, and the operation amount Ba is increased. Accordingly, the target energization amount It is increased, energization to the electric motor MT is started, and the amount is increased. The time point t0 is the start time point of a series of braking operations (one braking). The rotation angle Ka is increased in the normal rotation direction Da as the energization amount It (target value) and Ia (actual value) increase. At this time, since the state of "Ka <kx" is maintained, the control flag FL remains "0 (a state in which equalization control is not required)". In the diagram relating to "It, Ia" in the second stage from the top of FIG. 5A, the actual energization amount Ia is controlled to match the target energization amount It by the energization amount feedback control. Therefore, the target value It and the detected value Ia overlap.

From the time point t1, the braking operation member BP is held, and the operation amount Ba is made constant at the value sa. Accordingly, the target energization amount It (resulting in the actual energization amount Ia) is reduced from the value ia to the value ib in consideration of the hysteresis of the actuator AC. Depending on the maintenance of the operation amount Ba, the rotation angle Ka is maintained at the value ka after the time point t1.

At the time point t2, the braking operation member BP is returned and the operation amount Ba is reduced. In the target energization amount It, the target energization amount It (as a result, the actual energization amount Ia) is rapidly reduced from the value ib to the value ic so as to compensate for the hysteresis of the actuator AC, and then is reduced. Accordingly, the rotation angle Ka is changed (decreased) in the reverse direction Db. After the time point t3, the target energization amount It of the negative sign (−) is indicated. This is to compensate for the friction loss of the power transmission function of the speed reducer GS, the screw mechanism NJ, and the like.

At the time point t4, the operation of the braking operation member BP is stopped, and the operation amount Ba is set to “0”. At the time point t4, the rotation angle Ka reaches the reference angle ko. As a result, the target energization amount It is set to "0", the energization to the electric motor MT is stopped, and the operation of the electric motor MT is stopped. The time point t4 is the end time point of a series of braking operations (one braking operation).

Next, the operation of equalization control will be described with reference to FIG. 5 (b). From the time point u0, the operation of the braking operation member BP is started, and the operation amount Ba is increased. Accordingly, the target energization amount It is increased, energization to the electric motor MT is started, and the energization amounts It and Ia are increased. In the diagram, the energization amounts It and Ia are the same. Time point u0 is the start time of a series of braking operations (one braking operation). The rotation angle Ka is increased in the normal rotation direction Da as the energization amounts It and Ia increase.

At the time point u1, the braking operation member BP is held, and the operation amount Ba is made constant at the value sa. Accordingly, the energization amounts It and Ia are reduced and maintained from the value ia to the value ib so as to compensate for the hysteresis of the actuator AC. Since the manipulated variable Ba is maintained constant, the rotation angle Ka is maintained at the value ka after the time point u1.

At time u2, fade wear occurs. Since the friction member MS wears rapidly, the energization amounts It and Ia are increased by the pressing force feedback control and the rotation angle Ka is increased so that the pressing force Fa corresponding to "Ba = sa" is generated from the time point u2. Will be done. Therefore, from the time point u2, the electric motor MT is operated in the forward rotation direction Da and the rotation angle Ka is increased even though the braking operation member BP is held and the operation amount Ba is kept constant. ..

At the time point u3, the rotation angle Ka becomes a predetermined angle (first predetermined angle) kx or more, and the condition of step S230 is satisfied. As a result, the control flag FL, which was maintained at "0" as the initial value, is changed to "1". That is, it is stored by the control flag FL that rapid wear occurs during the above braking (the period from the start to the end of energization of the electric motor MT) and the state of “Ka ≧ kx” occurs. The first predetermined angle kz is a predetermined value (constant) set in advance with reference to the reference angle ko before wear.

At the time point u4, the braking operation member BP is returned and the operation amount Ba is reduced. The hysteresis of the actuator AC is compensated, and the energization amounts It and Ia are rapidly reduced from the value id to the value ie and are reduced. In response to this, the electric motor MT is driven in the reverse direction Db, and the rotation angle Ka is reduced from the angle kd. The difference hm (displacement) between the angle ka and the angle kd corresponds to the amount of wear of the friction member MS.

At the time point u5, the operation of the braking operation member BP is completed, and the operation amount Ba is returned to "0". At the time point u5, the rotation angle Ka reaches the reference angle km after wear, and the condition of step S270 is affirmed. Here, the reference angle km after wear changes in the normal rotation direction Da by the displacement hm from the reference angle ko before wear. Since the condition of step S270 (that is, the actual rotation angle Ka becomes equal to or greater than the first predetermined angle kx during the period from the start to the end of energization of the electric motor MT) is already satisfied, the time point u5 At, equalization control (particularly, pullback operation) is started. In the pull-back operation, the target energization amount It (that is, the pull-back energization amount Ie) is maintained at the negative sign (−) value im corresponding to the drive of the reverse direction Db of the electric motor MT. By maintaining "It = im", the reverse drive of the electric motor MT is continued, and the rotation angle Ka is further displaced in the reverse direction Db from the reference angle km.

When the actual rotation angle Ka reaches the second predetermined angle kz at the time point u6, after that, the electric motor MT is driven in the forward rotation direction Da, and the rotation angle Ka is increased. Here, the second predetermined angle kz is a predetermined value (constant) set with reference to the reference angle km after wear. From the time point u6, the energization amounts It and Ia are increased, the electric motor MT is driven in the forward rotation direction Da, and the rotation angle Ka is returned toward the reference angle km. Then, at the time u7 when the rotation angle Ka reaches the reference angle km, the equalization control is terminated and the energization to the electric motor MT is stopped. At the time point u7, which is the end point of the equalization control, the control flag FL is reset from "1" to "0". Therefore, at the start of the next series of braking operations, the control flag FL is set to "FL = 0" as an initial value.

The operations from time points u5 to u7 correspond to the pull-back operation in step S280. By this pull-back operation, the ball train BLs are forcibly moved and the deviation of the ball train BLs is eliminated, so that the load states of the two spring members SA and SB are made substantially equal.

In the pull-back operation of the equalization control, the forward / reverse rotation of the electric motor MT may be repeated. In this case, the processes corresponding to the time points u5 to u7 are repeated a plurality of times. By repeated operation, equalization of the load state of the spring members SA and SB can be achieved more efficiently.

<Second Embodiment of Electric Braking Device DS>
A second embodiment of the electric braking device DS will be described with reference to the schematic diagram of FIG. In the electric braking device DS described with reference to FIG. 1, the power of the electric motor MT is mechanically and directly transmitted directly to the friction member MS without going through a power transmission medium such as a braking fluid BF, and the friction member MS causes the friction member MS. It was pressed by the rotating member KT. Instead of this, in the electric braking device DS according to the second embodiment, the power of the electric motor MT is transmitted to the friction member MS via the braking fluid BF, so that the friction member MS is transferred to the rotating member KT. Pressed. That is, in the second embodiment, the braking fluid BF is used as a power transmission medium to generate a braking force Fx.

As described above, the components, elements, signals and the like having the same symbol have the same function. The subscripts "1" and "2" added to the end of the symbols related to the two braking systems are comprehensive symbols, where "1" represents the first braking system BK1 and "2" represents the second braking system BK2. .. Here, the subscripts "1" and "2" may be omitted. When the subscripts "1" and "2" are omitted, the symbols represent generic names. Further, in the direction of movement / movement of the member, the forward direction Ha corresponds to the forward rotation direction Da, and these correspond to the direction in which the pressing force Fa increases. Further, the backward direction Hb opposite to the forward direction Ha corresponds to the reverse direction Db opposite to the forward rotation direction Da, and these correspond to the direction in which the pressing force Fa decreases.

In addition to the braking operation member BP, the rotating member KT, and the brake caliper CP, the vehicle equipped with the electric braking device DS is provided with a wheel cylinder CW, a master reservoir RV, and a master cylinder CM.

Similar to the first embodiment, in the electric braking device DS, a braking force Fx is generated on the wheel WH by using the electric motor MT as a power source based on the operation of the braking operation member BP (brake pedal). To. Specifically, a rotating member (brake disc) KT is fixed to the wheel WH of the vehicle, and a brake caliper CP is arranged so as to sandwich the rotating member KT.

The brake caliper CP is provided with a wheel cylinder CW. A piston is provided in the wheel cylinder CW. By this movement of the piston, the pressure (braking fluid pressure) Pw of the braking fluid BF in the wheel cylinder CW is increased. Then, the friction member (brake pad) MS is pressed against the rotating member KT by the pressing force Fa by the braking hydraulic pressure Pw. That is, when the braking fluid BF is used as a power transmission medium, the braking fluid pressure Pw is generated by the rotational power of the electric motor MT, and the braking fluid pressure Pw is transmitted as the pressing pressure Fa.

A master reservoir (also referred to as an "atmospheric pressure reservoir") RV is provided so as to replenish the brake fluid BF to the master cylinder CM. Brake fluid BF is stored inside the master reservoir RV.

The master cylinder CM is mechanically connected to the braking operation member BP via a brake rod RD or the like. As the master cylinder CM, a tandem type is adopted. The inside of the master cylinder CM is divided into two hydraulic chambers (first and second hydraulic chambers) Rm1 and Rm2 by two master pistons PH and PG.

The first hydraulic chamber Rm1 and the first wheel cylinder CW1 of the tandem type master cylinder CM are connected by the first connection path HS1. Further, the second hydraulic chamber Rm2 and the second wheel cylinder CW2 are connected by a second connection path HS2. One end of the first and second connection paths HS1 and HS2 is connected to the first and second hydraulic chambers Rm1 and Rm2 of the master cylinder CM. The other end of the first and second connection paths HS1 and HS2 is branched into two and connected to the first and second wheel cylinders CW1 and CW2.

≪Electric control device DS≫
The electric braking device DS includes a braking operation amount sensor BA, a stroke simulator SS, a simulator valve VS, a fluid unit HU, and a controller ECU.

The braking operation amount sensor BA detects the operation amount Ba of the braking operation member (brake pedal) BP by the driver. Specifically, as the braking operation amount sensor BA, the master cylinder hydraulic pressure sensor PM (= PM1, Pm2) that detects the hydraulic pressure (master cylinder hydraulic pressure) Pm (= Pm1, Pm2) in the hydraulic pressure chamber Rm of the master cylinder CM. PM2), an operation displacement sensor SP for detecting the operation displacement Sp of the braking operation member BP, and an operation force sensor FP for detecting the operation force Fp of the braking operation member BP are adopted.

A stroke simulator (simply also referred to as “simulator”) SS is provided to generate an operating force Fp on the braking operating member BP. A simulator valve VS is provided between the master cylinder CM (particularly, the second hydraulic chamber Rm2) and the simulator SS. The simulator valve VS is a normally closed solenoid valve (on / off valve) having an open position and a closed position. When the electric braking device DS is activated, the simulator valve VS is opened, and the master cylinder CM and the simulator SS are in a communicating state.

The fluid unit HU includes the first and second separation valves VM1, VM2, the first and second master cylinder hydraulic pressure sensors PM1 and PM2, the pressure regulating unit YC, the first and second communication valves VR1, VR2, the first and the first. 2 The brake fluid pressure sensors PW1 and PW2 are included. The fluid unit HU corresponds to the braking actuator AC described above.

The first and second separation valves VM1 and VM2 (= VM) are provided in the first and second connection paths HS1 and HS2 (= HS). The first and second separation valves VM1 and VM2 are normally open solenoid valves (on / off valves) having an open position and a closed position. When the electric braking device DS is started, the separation valve VM is closed and the master cylinder CM and the wheel cylinder CW are shut off (non-communication state).

On the side of the master cylinder CM of the separation valves VM1 and VM2, the first and second master cylinder liquids so as to detect the hydraulic pressures (master cylinder hydraulic pressures) Pm1 and Pm2 of the first and second hydraulic chambers Rm1 and Rm2. Pressure sensors PM1 and PM2 are provided. Since the first and second master cylinder hydraulic pressures Pm1 and Pm2 are substantially the same, any one of the first and second master cylinder hydraulic pressure sensors PM1 and PM2 can be omitted.

The pressure regulating unit YC is composed of an electric motor MT, a speed reducer GS, a non-circulating ball screw mechanism NJ, a pressure regulating piston PC, a pressure regulating cylinder CC, and a braking fluid pressure sensor PW (= PW1, PW2). ..

The rotational power of the electric motor MT is decelerated by the speed reducer GS and transmitted to the non-circulation type ball screw mechanism NJ. For example, a small diameter gear is fixed to the output shaft of the electric motor MT. The small-diameter gear is engaged with the large-diameter gear, and its rotating shaft is fixed to the shaft member SF of the screw mechanism NJ. The non-circulation type screw mechanism (rotational / linear motion conversion mechanism) NJ is composed of a shaft member SF, a nut member NT, and a ball train BLs. The non-circulating ball screw mechanism NJ converts the rotational power of the speed reducer GS into the linear power of the pressure regulating piston PC.

For example, in the screw mechanism NJ, the rotational power of the electric motor MT is input to the shaft member SF, and the linear power is output from the detented nut member NT. On the contrary, the rotational power of the electric motor MT may be input to the nut member NT, and the linear power may be output from the detented shaft member SF. In any case, the rotational power of the electric motor MT is converted into the linear power of the pressure regulating piston PC and output by the screw mechanism NJ.

The pressure adjusting piston PC is inserted into the inner hole of the pressure adjusting cylinder CC to form the pressure adjusting chamber Rc. The pressure control chamber Rc is connected to the first and second connecting paths HS1 and HS2 via the first and second connecting paths HR1 and HR2. By moving the pressure adjusting piston PC, the volume of the pressure adjusting chamber Rc changes. At this time, since the first and second communication valves VR1 and VR2 are opened and the first and second separation valves VM1 and VM2 are closed, the braking fluid BF is the first and second hydraulic chambers Rm1. , Rm2 is not returned, but is moved with respect to the first and second wheel cylinders CW1 and CW2.

The pressure adjusting cylinder CC is connected to the master reservoir RV via the reservoir path HV. When the electric motor MT is not energized and the pressure adjusting piston PC is in its initial position (position corresponding to the reference angle ko) [ko], the pressure adjusting cylinder CC and the master reservoir RV are in a communicating state. , The pressure control chamber Rc is set to atmospheric pressure.

When the electric motor MT is rotationally driven in the forward rotation direction Da, the communication state between the pressure regulating chamber Rc and the master reservoir RV is cut off. Then, the volume of the pressure adjusting chamber Rc of the pressure adjusting cylinder CC is reduced, and the braking fluid pressure Pw is increased. On the other hand, when the electric motor MT is rotationally driven in the reverse direction Db, the volume of the pressure adjusting chamber Rc is increased, and the braking fluid BF is returned from the first and second wheel cylinders CW1 and CW2 to the pressure adjusting cylinder CC. As a result, the braking fluid pressure Pw is reduced. A return spring (elastic body) is provided in the pressure regulating chamber Rc, and when the energization of the electric motor MT is stopped, the pressure regulating piston PC is returned to its initial position.

The first and second connection paths HS1 and HS2 are provided with first and second braking fluid pressure sensors PW1 and PW2 so as to detect the first and second braking fluid pressures Pw1 and Pw2. Since the first and second braking fluid pressures Pw1 and Pw2 are substantially the same, one of the first and second braking hydraulic pressure sensors PW1 and PW2 may be omitted.

Between the fluid unit HU and the wheel cylinder CW, a hydraulic pressure modulator MJ is provided so that the braking hydraulic pressure Pw can be adjusted independently by each wheel cylinder CW such as anti-lock brake control. The hydraulic modulator MJ is composed of a set of a normally open type inlet valve and a normally closed type outlet valve for each wheel cylinder CW.

The controller (electronic control unit) ECU controls the electric motor MT, the solenoid valve VM, VR, VS, and the hydraulic modulator MJ (particularly, the inlet valve and the outlet valve). The controller ECU includes an electric circuit board on which a microprocessor and the like are mounted, and a control algorithm programmed in the microprocessor. The controller ECU is programmed with a process including the equalization control block IE and the like as in the first embodiment.

Also in the second embodiment, as in the first embodiment, equalization control is executed when the electric motor MT is driven in the reverse direction Db toward the reference angle ko. In the equalization control, when the rotation angle Ka of the electric motor MT is equal to or larger than the first predetermined angle kx (preset constant) in the period from the start to the end of energization of the electric motor MT. , This is stored in the control flag FL. Then, when the electric motor MT is driven in the reverse rotation direction Db (direction opposite to the normal rotation direction Da), the rotation angle Ka and the reference angle ko (braking fluid pressure Pw (that is, pressing force Fa)) are generated. The rotation angle is further changed to the reverse direction Db than the rotation angle Ka) corresponding to the state in which the state is not generated. After that, when the rotation angle Ka becomes less than the second predetermined angle kz, the electric motor MT is driven in the forward rotation direction Da, and the rotation angle Ka is returned to the reference angle ko again.

Also in the second embodiment, the above equalization control is executed at the time of rapid wear such that the state of “Ka ≧ kx” occurs. The equalization control has the same effect as that of the first embodiment. Specifically, since the amount of deformation of the first and second spring members SA and SB becomes large during rapid wear, the first and second spring members SA and SB are likely to be caught in the nut thread groove Mn and the like. Since the ball trains BLs are forcibly moved by the equalization control, the catching of the first and second spring members SA and SB can be eliminated.

Hereinafter, the differences from the electric braking device DS according to the first embodiment will be described.
[1] Initial position of pressure adjusting piston PC in wear [ko]
In the electric braking device DS according to the second embodiment, the braking fluid BF is supplied from the master reservoir RV when the pressure adjusting piston PC is located at the initial position [ko] even when the braking operation is not executed. Therefore, the movement (change) of the initial position [ko] in the forward direction Ha due to the wear (including aged wear and rapid wear) of the friction member MS as described with reference to FIG. 2 does not occur. That is, in the electric braking device DS according to the second embodiment, the initial position [ko] of the pressure adjusting piston PC is always the same position.

[2] Calculation of Reference Angle ko As described above, in the electric braking device DS according to the second embodiment, the initial position [ko] of the pressure regulating piston PC is always the same position, so refer to FIG. The operation of determining the reference angle as described is unnecessary. For example, a stopper for the pressure adjusting piston PC is provided in the pressure adjusting cylinder CC, and the position where the pressure adjusting piston PC abuts on the stopper is set as the initial position [ko]. When the pull-back operation is performed, the movement of the pressure adjusting piston PC in the backward direction Hb is blocked by the stopper. Therefore, in the pull-back operation of the second embodiment, the pressure adjusting piston PC and the screw mechanism NJ (nut member NT or shaft member SF) are separated from each other.

[3] External Leakage of Brake Fluid BF In the electric braking device DS according to the second embodiment, the braking fluid BF is used for power transmission of the electric motor MT, but the braking fluid BF leaks to the outside of the electric braking device DS. A phenomenon similar to rapid wear occurs when a situation (referred to as "external leakage") occurs. When the brake fluid BF leaks to the outside, the pressure adjusting piston PC continues to be moved in the forward direction Ha during one braking. In such a situation, the amount of deformation of the first and second spring members SA and SB may be excessive, as in the situation where the abnormal wear described with reference to FIG. 2 has occurred. In the electric braking device DS, equalization control is executed when the rotation angle Ka becomes a predetermined angle kx or more during one braking (the period from the start to the end of energization of the electric motor MT), so that the brake fluid BF Even in the situation where external leakage occurs, the same effect as when rapid wear occurs is obtained.

<Other embodiments>
In the above embodiment, a configuration in which a brake pad is used as the friction member MS and a brake disc is used as the rotating member KT (so-called disc type brake configuration) is exemplified. Instead of this, the above equalization control may be applied to a configuration in which a brake lining is used as the friction member MS and a brake drum is used as the rotating member KT (so-called drum type brake configuration). Even a drum type brake has the same effect as a disc type brake.

DS ... Electric braking device, WH ... Wheels, BP ... Braking operation member, CW ... Wheel cylinder, ECU ... Controller (electronic control unit), MS ... Friction member, KT ... Rotating member, NJ ... Non-circulating ball screw mechanism, SF ... Shaft member, NT ... Nut member, BL ... Ball, BLs ... Ball row, SA ... First spring member, SB ... Second spring member, Ms ... Shaft thread groove (male thread groove), Mn ... Nut thread groove (female thread groove) ), MT ... electric motor, KA ... rotation angle sensor, Ka ... rotation angle (detection value), ko ... reference angle before wear, [ko] ... initial position before wear (each member position corresponding to reference angle ko) , Km ... reference angle after wear, [km] ... initial position after wear (position of each member corresponding to reference angle km), FA ... push pressure sensor, Fa ... actual push pressure (detection value), PW ... braking Hydraulic pressure sensor, Pw ... Adjusting hydraulic pressure (detection value), PN ... Pressing piston, PC ... Pressure adjusting piston, BF ... Braking liquid.

Claims (2)

An electric braking device for a vehicle that adjusts the braking force of the wheels by controlling the pressing force of the friction member against the rotating member fixed to the wheels of the vehicle by an electric motor.
A ball screw mechanism that converts the rotational power of the electric motor into the linear power of the friction member,
A controller that drives the electric motor in the forward rotation direction to increase the pressing force and drives the electric motor in the reverse direction opposite to the normal rotation direction to decrease the pressing force.
Equipped with
The ball screw mechanism includes a ball train whose both ends are held by two spring members.
The controller
When the rotation angle of the electric motor becomes a predetermined angle or more in the period from the start to the end of energization of the electric motor, the pressing force is applied when the electric motor is driven in the reverse direction. An electric braking device for a vehicle that changes the rotation angle in the reverse direction further than a reference angle for transitioning from a state in which is generated to a state in which is not generated. In the electric braking device of the vehicle according to claim 1,
The controller
An electric braking device for a vehicle that returns the rotation angle to the reference angle after changing the rotation angle from the reference angle in the reverse direction.

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