JP7047333B2 - Vehicle electric braking device - Google Patents

Description

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

As described in Patent Document 1, the applicant stated, "Even if the reverse rotation drive of the electric motor becomes impossible, the output shaft of the electric motor is intended to return the piston to the initial position. It is equipped with a rotating shaft supported in the case of the energy storage mechanism (return mechanism) so that it can rotate integrally with the rotating shaft. When the shaft rotates in the reverse direction, the elastic energy stored in the spiral spring is released to apply the rotational torque of the reverse rotation to the rotating shaft. " The return mechanism of this electric braking device is provided between one end of a spiral spring (elastic body) and the housing, and when the rotation axis is rotated forward with a torque less than the first predetermined value, the elastic body housing. A torque limiter is provided that regulates relative rotation and allows relative rotation of the elastic body with respect to the housing when it is rotated forward with a torque equal to or higher than the first predetermined value. It is desired that the torque limiter has a simple structure and can be set as a value having a large return torque.

In order to solve the above problems, the applicant has developed a device (return mechanism) as shown in Patent Document 2. For example, in the device of Patent Document 2, "the return mechanism has a spiral spring whose one end is locked to a rotating shaft driven by an electric motor and a restraining surface extended in the radial outer direction of the spiral spring. The other end of the spiral spring is formed of a housing formed by a first valley fold portion, a first bend portion, and a ridge, which are valley-folded with respect to the outer peripheral surface in order of proximity to the one end. When the folded second bent portion is formed and the electric motor is rotated in the forward rotation direction, which is the direction in which the friction member is brought closer to the rotating member, the first bent portion presses the restraining surface, and the spiral spring presses the swirl spring. A return torque in the reverse direction is applied to the electric motor. The housing passes through the contact portion between the restraining surface and the first bent portion, and with respect to the tangent surface formed by the tangent line of the arc centered on the axis of the rotating shaft. It has a pressure receiving surface that is inclined inward in the radius of the spiral spring, and the outer peripheral surface between the first bent portion and the second bent portion is pressed against the pressure receiving surface. " The return mechanism needs further improvement.

Japanese Unexamined Patent Publication No. 2013-024389 Japanese Patent Application No. 2016-242964

It is an object of the present invention to provide a return mechanism that is applied to an electric braking device of a vehicle and employs a spiral spring in which a torque limiter operates appropriately.

The vehicle electric braking device according to the present invention includes an electric motor (MT) that presses a friction member (MS) against a rotating member (KT) that rotates integrally with a vehicle wheel (WH), and the electric motor (MT). With a return mechanism (MD) that generates a return torque (Tq) in the direction in which the friction member (MS) separates from the rotating member (KT) with respect to the electric motor (MT) when the electric motor (MT) is not energized. , Equipped with.

In the electric braking device of the vehicle according to the present invention, the return mechanism (MD) is "one end (Cz) is locked to a rotating shaft (SI, SO) driven by the electric motor (MT). , A part of the portion extending from the other end (Ca) opposite to the one end (Cz) to the one end (Cz) except for the other end (Ca) is bent. A housing (HG) having a "swirl spring (SU) having a formed restraint portion (Pk)" and a flat restraining surface (Mk) that houses the spiral spring (SU) and comes into contact with the restraint portion (Pk). ) And. The other end (Ca) is the axis (Mz) with respect to the extension surface (Mz) obtained by extending the restraining surface (Mk) so as to approach the axis (Ji, Jo) of the rotating shaft (SI, SO). It is configured to be located on the opposite side of Ji, Jo).

The spiral spring SU is bent so as to have a small radius and is assembled to the housing HG. Therefore, in addition to the elastic force Fs of the spiral spring SU, the force (bending force) Fm due to the bending of the spiral spring SU acts on the restraint portion Pk. According to the above configuration, since the bending force Fm acts on the restraint portion Pk in the radial outer direction Ds, proper operation of the return mechanism MD can be ensured as a torque limiter.

It is an overall block diagram of the electric braking device DB of the vehicle which concerns on this invention. It is sectional drawing for demonstrating the return mechanism MD. It is a characteristic figure for demonstrating the operation of the return mechanism MD. It is sectional drawing for demonstrating the stop part Aa (particularly, the stop surface Mk) of the return mechanism MD. It is a schematic diagram for demonstrating the restraint part Pk of a spiral spring SU. It is sectional drawing for demonstrating the position of the outer end Ca of a spiral spring SU. It is sectional drawing for demonstrating action and effect.

<Overall configuration of the electric braking device DB of the vehicle according to the present invention>
The electric braking device DB according to the embodiment of the present invention will be described with reference to the overall configuration diagram of FIG. In the following description, the components, arithmetic processing, signals, characteristics, and values with the same symbol exhibit the same function. Therefore, duplicate explanations may be omitted.

The vehicle equipped with the electric braking device DB is provided with a braking operation member BP, an operation amount sensor BA, a switch SP for a parking brake, a vehicle body side controller ECU, a braking actuator BR, and a communication line SG. Further, each wheel WH of the vehicle is provided with a brake caliper CP, a rotating member KT, 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 with respect to the wheel WH is adjusted, and a braking force is generated on the wheel WH. Specifically, a rotating member (for example, a brake disc) KT is fixed to the wheel WH of the vehicle, and a brake caliper CP is arranged so as to sandwich the rotating member KT. Then, in the brake caliper (simply also referred to as "caliper") CP, two friction members (for example, brake pads) MS are pressed against the rotating member KT by the power of the electric motor MT. Since the rotating member KT and the wheel WH are fixed so as to rotate integrally, a braking torque is applied to the wheel WH by the frictional force generated at this time, and as a result, a braking force is generated.

An operation amount sensor BA is provided so as to detect the operation amount Ba of the braking operation member BP by the driver. As the braking operation amount sensor BA, at least one of a pressure sensor that detects the pressure of the master cylinder, an operating force sensor that detects the operating force of the braking operating member BP, and an operating displacement sensor that detects the operating displacement of the braking operation member BP. One is adopted. The detected braking operation amount Ba is input to the vehicle body side controller ECU.

A switch for a parking brake (simply referred to as a "parking switch") SP is provided on the operation panel of the dashboard of the vehicle. The parking switch SP is an on / off type switch and indicates whether or not the parking brake is necessary. When the parking brake is required, an on signal is output as a signal (parking signal) Sp of the parking switch SP. On the other hand, if the parking brake is not required, the parking signal Sp is turned off. The parking signal Sp is input to the vehicle body side controller ECU.

A vehicle body side controller (also referred to as "vehicle body side electronic control unit") ECU is provided on the vehicle body of the vehicle. The vehicle body side controller ECU includes a target pressing force calculation block FT and a parking pressing force calculation block FP.

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 that the friction member MS pushes the rotating member KT, and is calculated based on the braking operation amount Ba and the preset calculation map Zft. In the calculation characteristic Zft, the target pressing force Ft is calculated to be "0" in the range where the operation amount Ba is "0" or more and less than the predetermined value bo, and when the operation amount Ba is the predetermined value bo or more, the operation amount Ba increases. It is calculated so as to monotonically increase from "0". Here, the predetermined value bo is a preset constant corresponding to the play of the braking operation member BP. The target pressing force Ft is transmitted to the wheel side controller ECW via the communication line SG.

In the parking push pressure calculation block FP, the parking push pressure Fp is calculated based on the parking signal Sp. Similar to the target pressing force Ft, the parking pressing force Fp is the target value of the pressing force of the friction member MS with respect to the rotating member KT. The parking pressing force Fp is calculated based on the parking signal Sp and the preset time-series calculation map Zfp. In the calculation characteristic Zfp, the time point at which the parking signal Sp transitions from the off state to the on state is set to "0" in the time T. That is, starting from "T = 0", the parking pressing force Fp is increased from "0" to a predetermined value fp at a predetermined time gradient df with the passage of time T. Here, the predetermined value fp is a preset constant, which is an extremely large value as compared with the pressing force generated by a normal braking operation so that the stopped state of the vehicle is maintained even on a slope. In the calculation characteristic Zfp, the parking pressing force Fp is reduced to "0" after the state of "Fp = fp" is maintained for a predetermined time tp (predetermined value set in advance). Since the rotational movement of the electric motor MT is constrained by the lock mechanism before the parking pressing force Fp is reduced toward "0", the actual pressing force Fa is maintained at a predetermined value fp. The parking pressing force Fp is transmitted to the wheel side controller ECW via the communication line SG.

The braking actuator BR (also simply referred to as "actuator") will be described.
The actuator BR presses the friction member (brake pad) MS against the rotating member (brake disc) KT. The frictional force generated at this time causes the actuator BR to apply braking torque to the wheel WH to generate braking force. As the actuator BR, a so-called floating disc brake configuration is exemplified. The braking actuator BR includes a caliper CP, a pressing piston PN, an electric motor MT, a rotation angle sensor MA, a speed reducer GS, an input shaft SI, an output shaft SO, a screw member NJ, a pressing pressure sensor FA, a wheel side controller ECW, and a return. It is composed of a mechanism MD.

The caliper CP is configured to sandwich the (brake disc) KT via the two friction members (brake pad) MS. Inside the caliper CP, the pressing piston (simply also referred to as the "piston") PN is moved (advanced or retracted) with respect to the rotating member KT. Due to the movement of the piston PN, the friction member MS is pressed against the rotating member KT to generate a frictional force. The movement of the piston PN is performed by the power of the electric motor MT. Specifically, an input shaft SI is fixed to the output shaft of the electric motor MT, and rotates integrally with the rotation axis Ji as the center. That is, the output (rotational force) of the electric motor MT is input to the input shaft SI.

The input shaft SI is a rotary shaft member (rotary shaft) that rotates around the rotary axis Ji. A small diameter gear is fixed to the input shaft SI. This small-diameter gear is meshed with the large-diameter gear to form a speed reducer GS. The output shaft SO is fixed to the large-diameter gear. The output shaft SO is a rotary shaft member (rotary shaft) that rotates around the rotary axis Jo. The power of the electric motor MT is transmitted from the input shaft SI to the output shaft SO via the reducer GS. The rotational power (torque) of the output shaft SO is converted into linear power (thrust in the central axis direction of the piston PN coaxial with the rotation axis Jo) by the screw member NJ. By this linear power (thrust), the piston PN is moved forward or backward with respect to the rotating member KT. By moving the piston PN, the force (pushing pressure) that the friction member MS pushes the rotating member KT is adjusted. Since the rotating member KT is fixed to the wheel, a frictional force is generated between the friction member MS and the rotating member KT, and the braking force of the wheel is adjusted.

The electric motor MT is a power source for moving the piston PN. For example, in the rotation direction of the electric motor MT, the forward rotation direction Ra corresponds to the direction in which the friction member MS approaches the rotation member KT. That is, the forward rotation direction Ra corresponds to the direction in which the piston PN advances, the pressing force increases, and the braking torque increases. Further, the reverse direction Rb of the electric motor MT corresponds to the direction in which the friction member MS moves away from the rotating member KT. That is, the reverse direction Rb corresponds to the direction in which the piston PN retracts, the pressing force decreases, and the braking torque decreases.

For example, a brushless motor is adopted as the electric motor MT. The electric motor MT is provided with a rotation angle sensor MA so as to detect the position (that is, the rotation angle) Ma of the rotor (rotor) of the electric motor MT. The brushless motor MT is driven based on the rotation angle Ma. Further, a pressing pressure sensor FA is provided so that the piston PN detects the force (actual pressing pressure) Fa that actually pushes the friction member MS. The detected actual rotation angle Ma and actual pushing pressure Fa are input to the wheel side controller ECW.

The wheel-side controller ECW is an electric circuit that drives the electric motor MT. The wheel-side controller ECW drives the electric motor MT based on the target, the parking push pressure Ft, Fp, the actual push pressure Fa, and the rotation angle Ma, and controls its output (rotational speed and torque). The target, parking pressing force Ft, and Fp are transmitted from the vehicle body side controller ECU to the wheel side controller ECW via the communication line SG. The wheel-side controller ECW (also referred to as “wheel-side electronic control unit”) is arranged (fixed) inside the caliper CP, and includes a microprocessor MP and a drive circuit DR.

The microprocessor MP includes various arithmetic processes. The drive circuit DR includes a bridge circuit composed of a plurality of switching elements. In the microprocessor MP of the controller ECW, a drive signal for controlling each switching element for driving the electric motor MT is calculated. Then, in the bridge circuit of the drive circuit DR, the energization state of each switching element is switched based on the drive signal, and the output of the electric motor MT is adjusted.

Specifically, the switching element is controlled so that the actual pressing force Fa (detected value of the pressing force sensor FA) matches the target, the parking pressing force Ft, and Fp. For example, a brushless motor is adopted as the electric motor MT. The brushless motor MT is driven based on the rotation angle Ma (detected value of the rotation angle sensor MA). Therefore, the electric motor MT is controlled based on the rotation angle Ma and the pressing force Fa. The electric power to the vehicle body side controller ECU and the wheel side controller ECW (including the electric motor MT) is supplied via the power line by the storage battery provided on the vehicle body side of the vehicle and the generator.

The return mechanism MD is provided on the input shaft SI (corresponding to the “rotary shaft”). When the energization of the electric motor MT is stopped by the return mechanism MD, the pressing contact between the friction member MS and the rotating member KT is released (that is, the actual pressing force Fa is returned toward "0". ). Specifically, when the electric motor MT is driven in the forward rotation direction Ra, elastic energy is stored in the return mechanism MD. Due to this elastic energy, the electric motor MT is rotated in the reverse direction Rb in the non-energized state of the electric motor MT. As a result, the piston PN is moved in the retracting direction, and the friction member MS is moved in the direction away from the rotating member KT. Therefore, even when the electric power is not supplied to the electric motor MT, the pressing state between the friction member MS and the rotating member KT is released by the return mechanism MD.

<Return mechanism MD>
The return mechanism MD will be described with reference to the cross-sectional view of FIG. The return mechanism MD rotates the electric motor MT in the reverse direction Rb, and a return torque Tq is generated so that the friction member (brake pad) MS is separated from the rotating member (brake disc) KT. When the energization of the electric motor MT is stopped by this return torque Tq, the pressing piston PN is returned to at least the initial position. Here, in the initial position of the piston PN, the gap between the rotating member KT and the friction member MS is approximately "0 (zero)", and when the friction member MS moves away from the rotating member KT, the pressing state thereof is changed. It corresponds to the position where it is released for the first time. Therefore, in the initial position, the pressing force Fa of the friction member MS with respect to the rotating member KT is “0”.

The return operation of the piston PN to the initial position is necessary as a fail-safe function even when the power supply to the electric braking device DB is stopped (including when the power source fails). Therefore, the return of the piston PN to the initial position is mechanically achieved by the elastic energy stored inside the return mechanism MD. Further, the initial position of the piston PN changes due to the wear of the friction member MS. Specifically, as the amount of wear of the friction member MS increases, the initial position of the piston PN is sequentially moved in the forward direction (direction approaching the rotating member KT). A wear compensation mechanism is required for the return mechanism MD so that the stored elastic energy of the return mechanism MD is maintained substantially constant regardless of the amount of wear of the friction member MS.

The return mechanism MD is provided on the input shaft SI (corresponding to the “rotary shaft”). The input shaft SI is fixed to the electric motor MT so as to rotate integrally with the output shaft of the electric motor MT. The return mechanism MD is composed of a spiral spring (elastic body) SU and a housing HG. The spiral spring SU is a mechanical element in which a highly elastic strip-shaped material is spirally wound. In the spiral spring SU, a force (elastic force) that tries to return the wound state to its original state is used. The spiral spring is also called a "spring". The housing HG is a member for accommodating the spiral spring SU. The housing HG is provided with a recess (recess) so as to accommodate the spiral spring SU. Further, the end portion of the spiral spring SU is locked at the side surface (stopping surface) Mk of the concave portion, and the spiral spring SU generates an elastic force (spring force) Fs.

A hooking portion Pz is formed at the inner end (corresponding to "one end") Cz of the spiral spring SU and is fixed to the input shaft SI. For example, in the spiral shape of the spiral spring SU, the hooking portion Pz is formed by bending the inner end Cz (a portion close to) so as to be rolled inward of the spiral shape. Specifically, the hooking portion Pz is formed by winding the portion of one end Cz in a mountain fold with respect to the outer peripheral surface Ms of the spiral spring SU at a right angle in the strip-shaped longitudinal direction. A notch having a semicircular cross section is provided on the outer peripheral portion of the input shaft SI so that the hooking portion Pz of the spiral spring SU is hooked. The engagement portion Pz of the spiral spring SU is fixed by engaging with the notch portion of the input shaft SI in a directional manner.

In the state where the spiral spring SU is not wound (that is, when "Tq = 0"), the hooking portion Pz is inserted (fitted) into the notch portion of the input shaft SI. When the input shaft SI is rotated in the forward rotation direction Ra by the electric motor MT, the hooking portion Pz of one end Cz is hooked on the notch portion of the input shaft SI. That is, the hooking portion Pz is fixed by receiving a force from the notch portion from the state where it is simply fitted in the notch portion. Therefore, as the input shaft SI rotates, the spiral spring SU is sequentially wound up, and its elastic energy is increased.

On the other hand, when the input shaft SI is rotated in the reverse direction Rb in a state where the spiral spring SU is not wound at all, the hooking portion Pz is disengaged from the notch portion of the input shaft SI. Therefore, the input shaft SI runs idle with respect to the hooking portion Pz. As described above, when the spiral spring SU is not wound, the hooking portion Pz and the notch portion are said to be "engaged in the forward rotation direction Ra but not in the reverse rotation direction Rb". , Has directionality.

In the longitudinal direction of the band-shaped spiral spring SU, the restraint portion Pk is formed at a portion close to the outer end (corresponding to the "other end") Ca located on the opposite side of the inner end Cz. The restraint portion Pk is a portion for restraining the relative movement with respect to the housing HG in the portion near the outer end Ca. The restraint portion Pk is formed by being bent a plurality of times at a right angle to the longitudinal direction of the spiral spring SU (that is, parallel to the rotation axis Ji of the input shaft SI). That is, in the spiral type cylindrical shape of the spiral spring SU, the folding lines of the plurality of bent portions are along the generatrix of the column. Specifically, in the order closer to the inner end Cz (the order farther from the outer end Ca), valley folds (referred to as "first bending portion Cl") and mountain folds ("second bending") with respect to the outer peripheral surface Ms, respectively. The restraint portion Pk is formed by being folded (referred to as a portion Cm) and a mountain fold (referred to as a “third bent portion Cn”). Here, in the cross-sectional shape of the spiral spring SU, the triangle Cl-Cm-Cn having the bent portion as the apex is called "constraint triangle Tk (in the three-dimensional shape, the restraint triangular prism)". In the spiral spring SU, in order to stably form the restraint triangle Tk, the portion closer to the outer end Ca than the third bent portion Cn is the outer peripheral surface Ms of the spiral spring SU and the inner peripheral surface Mu (outer peripheral surface Ms). It is configured to be sandwiched between (the back side of) and. Here, the area between the outer end Ca and the third bent portion Cn is referred to as a "folded portion Po".

The housing HG has bottomed recesses Aa, Ab, and Ap, and is a member for accommodating the spiral spring SU. Here, the recesses Aa and Ab are for restraining the restraining portion Pk, and are referred to as "stopping portions". Further, the recess Ap is for accommodating the spiral spring SU, and is referred to as a "storage unit". A through hole for the input shaft SI is provided in the bottom portion of the housing HG (particularly, the bottom portion of the storage portion Ap). The input shaft SI engaged with the tip of the output shaft of the electric motor MT is supported by the bush and penetrates a through hole provided at the bottom of the storage portion Ap. That is, the input shaft SI is attached to the housing HG in a rotatable state. The recesses Aa, Ab, and Ap are closed (covered) by the closing member to form a space for accommodating the spiral spring SU.

The first and second restraining portions Aa and Ab of the housing HG are located in the radial outer direction Ds about the rotation axis Ji of the input shaft SI with respect to the accommodating portion Ap, and are provided so as to be continuous with the accommodating portion Ap. Has been done. Since the spiral spring SU is a highly elastic material wound in a spiral shape, it tends to spread outward. Therefore, the restraint portion Pk (that is, the restraint triangle Tk) is usually housed (fitted) inside the first restraint portion Aa or the second restraint portion Ab.

Inside the first and second restraining portions Aa and Ab of the housing HG, a surface extending parallel to the rotation axis Ji of the input shaft SI and extending in the direction away from the axis Ji (radius outer direction) Ds ("stopping"). A surface Mk ") is formed. The restraining surface Mk is continuous with the inner peripheral surface Mp (cylindrical surface parallel to the axis Ji) of the accommodating portion Ap. Therefore, the first and second restraining portions Aa and Ab and the storage portion Ap form one space. When the input shaft SI is rotated in the forward rotation direction Ra by the electric motor MT, the second bent portion Cm of the restraint portion Pk is pressed against the restraining surface Mk. As a result, the restraint portion Pk is fixed (locked) by receiving a force from the restraint surface Mk from the state where it is merely fitted to the first and second restraint portions (recessed portions) Aa and Ab. That is, the restraint portion Pk (particularly, the second bent portion Cm), which is a portion near the outer end Ca, is pressed against the restraining surface Mk, and the movement of the restraint portion Pk in the normal rotation direction Ra is restrained. As a result, as the input shaft SI rotates in the forward rotation direction Ra, the spiral spring SU is wound up and the return torque Tq is increased.

When the spiral spring SU is sequentially wound, the elastic energy stored in the spiral spring SU increases, and the elastic force Fs (return spring) causes the spiral spring SU to rotate the input shaft SI in the reverse direction Rb. Force) is generated. When the return torque Tq in the reverse direction Rb is applied to the input shaft SI by the elastic force Fs and the electric motor MT is not energized, the friction member MS is moved in the direction away from the rotating member KT (backward direction). ..

A pressure receiving surface Mj forming an angle of 50 to 100 degrees with respect to the restraining surface Mk is formed on the restraining portions Aa and Ab. The restraint portion Pk (that is, the restraint triangle Tk) comes into contact with the restraint surface Mk at the second bent portion Cm (point P). That is, the spiral spring SU receives the reaction force Fr of the elastic force Fs from the restraining surface Mk at the second bending portion Cm. In order to avoid local concentration of force, the elastic force Fs is a force in which the outer peripheral surface Ms (referred to as “pressing surface Mo”) between the second bending portion Cm and the third bending portion Cn comes into contact with the pressure receiving surface Mj. Supported by. That is, since the pressing surface Mo comes into surface contact with the pressure receiving surface Mj, the shape of the restraint triangle Tk can be maintained.

When the input shaft SI is further rotated in the normal rotation direction Ra and the spiral spring SU is wound up, the gap between the inner peripheral surface Mu and the outer peripheral surface Ms decreases, and gradually becomes the inner peripheral surface Mu and the outer peripheral surface Ms. Will be in close contact. By this winding tightening, the spiral spring SU tries to reduce the diameter. Therefore, the restraint portion Pk is pulled in the direction (inward radius) Du approaching the rotation axis Ji. When the winding state of the spiral spring SU reaches a predetermined state, the restraining portion Pk begins to slide on the restraining surface Mk in the radial inward direction Du, and is separated from the restraining surface Mk. The return torque Tq at the time (instantaneous) when the contact between the restraint portion Pk (particularly, the second bending portion Cm) and the restraint surface Mk is released is referred to as "upper limit torque q3". In the return mechanism MD, the torque limiter function is achieved by utilizing the radius reducing action of the spiral spring SU. Here, the "torque limiter" is a device in which the connection state is released and the torque transmission is cut off when an overload state occurs, and is also referred to as a "safety clutch".

The return mechanism MD may be installed on any of the rotating shafts from the electric motor MT to the piston PN. For example, the return mechanism MD may be provided on the piston PN and the output shaft SO (rotary axis Jo) coaxial with the screw member NJ. Alternatively, an intermediate shaft is provided between the input shaft SI and the output shaft SO, and the return mechanism MD is provided on the intermediate shaft. The rotation axis in this case is the rotation axis of the intermediate shaft. Regardless of which rotating shaft the return mechanism MD is provided with, the same effect as described above can be obtained.

<Relationship between rotation angle and torque in return mechanism MD>
The operation of the return mechanism MD will be described with reference to the characteristic diagram of FIG. This characteristic diagram shows the relationship between the rotation angle Ma of the electric motor MT (that is, the rotation angle of the input shaft SI) and the return torque Tq. Since the return torque Tq is generated by the elastic force Fs, the return torque Tq corresponds to the elastic force Fs.

The friction member MS and the piston PN are not fixed so as to move together. Therefore, in the forward movement of the piston PN, the piston PN pushes the back plate portion of the friction member MS, and both move together. On the other hand, in the backward movement of the piston PN, both move together until the initial position where the friction member MS receives a force from the rotating member KT. However, when the piston PN is returned beyond the initial position, the piston PN and the friction member MS are separated from each other. In the state where the piston PN and the friction member MS are separated, the gap between the friction member MS and the rotary member KT is widened by the runout of the rotary member KT or the like.

When the rotation angle Ma is "0", the piston PN is located at the rear end position farthest from the rotating member KT. At "Ma = 0", the spiral spring SU is not wound up and the elastic force Fs is not generated (that is, "Tq = 0").

The state in which the friction member MS is new and is not worn at all is shown by the characteristic Za of the solid line. In the state of "Ma = m0, Tq = 0" in the characteristic Za, the hooking portion Pz is housed in the notch portion of the input shaft SI. At this time, the restraint portion Pk is housed in the first restraint portion Aa or the second restraint portion Ab. In this state, when the electric motor MT is rotated in the reverse direction Rb, the hooking portion Pz comes off the notch portion, and the input shaft SI idles with respect to the spiral spring SU. Even when the hooking portion Pz is out of the notch portion, when the electric motor MT is rotated in the forward rotation direction Ra, the hooking portion Pz is immediately locked to the notch portion. Further, when the restraint portion Pk is outside the restraint portions Aa and Ab, the spiral spring SU tends to expand in the radial inner direction Du, so that the restraint portion Pk is caused by the rotation of the forward rotation direction Ra of the electric motor MT. , Enter the restraining parts Aa and Ab.

When the rotation angle Ma is increased in the forward rotation direction Ra while both the hooking portion Pz and the restraint portion Pk are constrained, the spiral spring SU causes the return torque Tq (reverse direction Rb centered on the rotation axis Ji). Rotational force) begins to be generated. In the characteristic Za, the return torque Tq starts increasing from "0" at an angle m0.

In the return mechanism MD, it is necessary to pull the piston PN back to at least the initial position (the position where the friction member MS does not press the rotating member KT and the pressing force Fa is “0”). Therefore, even if an error is included in the return mechanism MD, at a predetermined angle (initial angle) m1 of the rotation angle Ma corresponding to the initial position, the pullback of the piston PN can be surely achieved. A predetermined torque (initial torque) q1 is set to be generated (see point A). In other words, at the initial position of the piston PN, the initial torque q1 in the reverse direction Rb acts on the electric motor MT by the return mechanism MD.

When the rotation angle Ma is further increased and the spiral spring SU is sequentially wound up, the return torque Tq increases accordingly. The characteristic Za is set so that the return torque Tq changes only slightly in the vicinity of "Ma = m1" even if the rotation angle Ma changes. Therefore, even if the friction member MS is worn and the initial position of the piston PN changes, the return torque Tq is substantially constant at the initial position of the piston PN. On the other hand, in the region where the rotation angle Ma is large, the return torque Tq has a characteristic of "convex downward" with respect to the rotation angle Ma. Therefore, for a slight increase in the angle of rotation Ma, the return torque Tq greatly increases (see points B and C).

When the friction member MS is new (that is, when the amount of wear is "0"), the state in which the parking pressing force Fp is increased to a predetermined value fp by the parking brake corresponds to the point B. As the amount of wear of the friction member MS gradually increases, the operating point corresponding to "Fp = fp" changes from the point B toward the point C along the characteristic Za. That is, when the amount of wear of the friction member MS is large, the rotation angle Ma for securing the predetermined pressing force fp increases and the return torque is increased as compared with the case where the amount of wear of the friction member MS is small. Tq increases. In order to keep the elastic energy stored in the spiral spring SU substantially constant, the torque limiter operates in the return mechanism MD. The operation is referred to as a "relocking operation". The relocking operation is performed when the parking brake is activated.

When the operating point corresponding to the predetermined pressing force fp of the parking brake reaches the point C, the relocking operation occurs. When the return torque Tq tries to exceed a predetermined value (upper limit torque) q3, slip occurs between the restraint portion Pk and the restraint surface Mk, and the restraint portion Pk cannot be locked by the restraint surface Mk. By the relocking operation, the return torque Tq generated during the parking brake is reduced, and the return torque Tq is not generated when the upper limit torque q3 is exceeded. Here, the upper limit torque q3 is set in advance based on the characteristics (spring constant, etc.) and shape (length, plate thickness, etc.) of the spiral spring SU, and the shapes of the recesses Aa, Ab (particularly, the restraining surface Mk). Will be done.

After the locked state of the restraint portion Pk by the restraint surface Mk of the first restraint portion Aa is released, the restraint portion Pk is locked again by the restraint surface Mk of the second restraint portion Ab. At this time, the characteristic Za is changed to the characteristic Zb shown by the broken line. That is, the return torque Tq is not reduced to "0", and the state of the point C is changed to the state of the point E. The value q2 is referred to as the "relocking torque". In the characteristic Zb after the relocking operation, the angle at which the return torque Tq starts to increase from "0" is changed from the angle m0 to the angle m5, and the initial angle corresponding to the initial position is changed from the angle m1 to the angle m6. Will be done. That is, the initial torque q1 is generated at the initial angle m6. Then, the operating point corresponding to "Fp = fp" is changed from the point B to the point E. Further, when the amount of wear of the friction member MS increases, the same operation as described above is repeated. That is, the operating point corresponding to the predetermined pressing force fp of the parking brake increases from the point E to the point F. Then, when the return torque Tq reaches the upper limit torque q3, the relocking operation occurs again, and the characteristic Zb is changed to the new characteristic. By the relocking operation, the relationship between the rotation angle Ma and the return torque Tq is appropriately updated, and the function of the torque limiter is achieved.

<Stopping parts Aa, Ab of return mechanism MD>
The details of the restraining portions Aa and Ab of the return mechanism MD will be described with reference to the cross-sectional view of FIG. The first restraint portion Aa and the second restraint portion Ab are point-symmetrical (when rotated 180 degrees about the axis line Ji) with respect to the rotation axis Ji of the input shaft SI in the cross section of the return mechanism MD. Matching figure).

Each line will be described in a cross section perpendicular to the rotation axis Ji of the input shaft SI.
In the state where the restraining portion Pk is most expanded outward in the restraining portion Aa (for example, when the spiral spring SU is wound after the hooking portion Pz is removed from the notch portion), the restraining portion is formed at the point P. The second bent portion Cm of Pk comes into contact with the restraining surface Mk. That is, the point P is the contact point between the restraining surface Mk and the restraining portion Pk, which is the farthest from the axis Ji. The straight line connecting the axis Ji and the point P is called "normal line Lh".

Each surface inside the restraint portion Aa will be described.
Each surface inside the restraint portion Aa is continuous with the inner peripheral surface Mp (cylindrical surface parallel to the rotation axis Ji) inside the storage portion Ap, and forms one space (chamber) for accommodating the spiral spring SU. .. The plane including the axis Ji and the normal Lh is referred to as "normal plane Mh". The normal surface Mh includes a contact portion between the restraint portion Pk and the restraint surface Mk (that is, a straight line passing through the point P and parallel to the axis Ji) and the axis Ji.

The spiral spring SU has a cylindrical spiral shape centered on the rotation axis Ji of the input shaft SI. In the state of being assembled to the return mechanism MD, the longitudinal direction of the spiral spring SU is perpendicular (perpendicular) to the rotation axis Ji. A restraint portion Pk is formed in the vicinity of the outer end (other end) Ca of the spiral spring SU. In the circular spiral shape of the spiral spring SU, the radial outer direction Ds is a direction away from the rotation axis Ji. On the other hand, the inner radius direction Du is a direction approaching the rotation axis Ji (center). Strictly speaking, the radial direction is the direction on the normal line Lh, but in the following description, the radial directions Ds and Du represent directions with respect to the rotation axis Ji.

In the cross section of the recess of the housing HG, the inside of the circle (indicated by the alternate long and short dash line) centered on the axis Ji is the storage portion Ap. The storage portion Ap is a recess having a substantially cylindrical inner wall (circumferential surface) Mp, and a spiral spring SU (cylindrical spiral portion of the spiral spring SU excluding the restraint portion Pk) is stored inside the recess. The restraint portion Aa is a recess located outside the storage portion Ap (that is, outside the circle of the alternate long and short dash line) in the cross-sectional view of the recess. A restraining surface Mk and a pressure receiving surface Mj are formed inside the restraining portion Aa, and the restraining portion Pk (the portion of the restraining triangle Tk) of the spiral spring SU is housed. When the restraining portion Pk (particularly, the second bending portion Cm) abuts on the restraining surface Mk, the rotation of the spiral spring SU in the forward rotation direction Ra is stopped, and the portion of the outer end Ca is locked. The inner peripheral surface Mp, the restraining surface Mk, and the pressure receiving surface Mj are connected surfaces, and one space is formed by these surfaces.

The restraint surface Mk, which is one of the inner walls of the restraint portion Aa, extends from the contact portion (point P) between the restraint portion Pk and the restraint surface Mk in the inner radius direction Du so as to approach the axis Ji of the input shaft SI. Has been done. Specifically, as the restraint surface Mk approaches the axis Ji (that is, toward the inner radius direction Du), the portion (point P) farthest from the axis Ji on the restraint surface Mk with respect to the normal plane Mh. ) Slightly tilted in the normal rotation direction Ra (in the cross-sectional view, the normal Lh is tilted clockwise around the point P). In other words, the restraint surface Mk and the normal surface Mh intersect at a straight line at "a portion (point P) where the restraint portion Pk and the restraint surface Mk can be in contact with each other and are farthest from the axis Ji". Then, the restraint surface Mk is formed so that the distance between the restraint surface Mk and the normal plane Mh increases as the point P approaches the axis Ji. Here, the angle formed by the restraining surface Mk and the normal surface Mh is referred to as a "sliding angle β". Since the restraining surface Mk is provided with a sliding angle β, the surface Mz on which the restraining surface Mk is extended does not intersect with the rotation axis Ji. Here, the surface Mz is referred to as an "extended surface (extended line Lz in the cross section)".

When the input shaft SI is rotated in the forward rotation direction Ra and the spiral spring SU is wound, the spiral spring SU reduces its diameter. Therefore, the restraint portion Pk is pulled in the direction toward the axis Ji (inward radius direction Du). When the return torque Tq by the spiral spring SU reaches the upper limit torque q3, the restraint portion Pk begins to slide on the restraint surface Mk in the radial inward direction Du, and is instantly deviated from the restraint surface Mk. The movement of Du in the radial inward direction of the restraint portion Pk is blocked by the static friction force. As soon as the force of the spiral spring SU pulling the restraint portion Pk in the radial inward direction Du exceeds the static friction force, the restraint portion Pk is moved from the point P toward the point Q. This is because the coefficient of static friction (result, static friction force) is larger than the coefficient of dynamic friction (result, dynamic friction force). In addition, due to the characteristics of the friction coefficient, it is preferable that the restraining surface Mk is formed of a resin material.

The point Q is the point closest to the rotation axis Ji among the contact points between the restraint portion Pk and the restraint surface Mk. When the second bent portion Cm exceeds the point Q, the restraining portion Pk deviates from the restraining surface Mk and slides on the inner peripheral surface Mp of the storage portion Ap. Since the spiral spring SU is about to expand in the radial outer direction Ds, the restraint portion Pk slides over 180 degrees and then fits in the second restraint portion Ab. Then, again, the restraint portion Pk (particularly, the second bent portion Cm) and the restraint surface Mk of the second restraint portion Ab come into contact with each other, the restraint portion Pk is pressed against the restraint surface Mk, and the portion of the outer end Ca is pressed. Be restrained. A relocking operation is executed in which the restraining portion Pk is disengaged from the restraining surface Mk of the first restraining portion Aa and is locked to the restraining surface Mk of the second restraining portion Ab again. The relocking operation functions as a torque limiter, and the maximum elastic energy stored in the return mechanism MD is maintained substantially constant.

In the cross section of the return mechanism MD, the second bent portion Cm is on the restraining surface Mk from the point P (the contactable point farthest from the axis Ji) to the point Q (the contactable point closest to the axis Ji). It is locked at some position. For example, after the hooking portion Pz is removed from the notch portion, the restraining portion Pk is brought into the most expanded state, so that the restraining portion Pk is locked to the restraining surface Mk in the vicinity of the point P. On the other hand, when the re-locking operation occurs, it is performed instantaneously, so that the restraining portion Pk is locked to the restraining surface Mk near the central portion between the points P and Q.

Since the torque limiter function is achieved by utilizing the winding action of the spiral spring SU, the upper limit torque q3 can be suitably set even if the return torque Tq is large. Further, the restraining surface Mk is provided with a sliding angle β (an angle formed by the normal surface Mh and the extension surface Mz). Due to the sliding angle β, the elastic energy of the spiral spring SU decreases as the rotation axis Ji approaches from the point P, and the spring approaches a stable state. As a result, the contact portion Cm can be smoothly moved (relocking operation).

<Restriction part Pk of spiral spring SU>
The details of the restraining portion Pk of the spiral spring SU will be described with reference to the schematic diagram of FIG. The restraint portion Pk is formed by utilizing a part of the outer end Ca of the spiral spring SU, instead of adding a new member to the spiral spring SU. In the longitudinal direction of the ribbon-shaped spiral spring SU, the outer end (the other end) Ca is located on the opposite side of the inner end (one end on which the hooking portion Pz is formed) Cz. In the spiral spring SU, the restraint portion Pk is brought into contact with the restraining surface Mk, so that the portion of the outer end Ca (particularly, the contact portion Cm) is locked. The spiral spring SU is normally in a wound state, but the figure shows a state in which the outer end Ca portion is extended.

From the outer end Ca of the spiral spring SU, a portion extending over a predetermined length (a portion close to the outer end Ca) is bent multiple times perpendicularly to the longitudinal direction of the spiral spring SU, and the restraining portion Pk is formed. It is formed. Specifically, in the order in which the ribbon-shaped spiral spring SU is closer to the inner end Cz, the first bent portion Cl, the second bent portion Cm, and the third bent portion Cn have creases perpendicular to the longitudinal direction of the spiral spring SU (the creases are perpendicular to the longitudinal direction of the spiral spring SU. That is, it is curved so as to be parallel to the rotation axis Ji of the input shaft SI). The first bent portion Cl is valley-folded with respect to the outer peripheral surface Ms (it is mountain-folded with respect to the inner peripheral surface Mu, and the bent tip faces the outside of the cylinder). On the other hand, the second bent portion Cm and the third bent portion Cn are mountain-folded with respect to the outer peripheral surface Ms (valley-folded with respect to the inner peripheral surface Mu) in the spiral state of the spiral spring SU. The bent tip faces the inside of the cylinder). The restraint portion Pk is formed by bending molding at the first, second, and third bending portions Cl, Cm, and Cn. In the cross section of the return mechanism MD, the restraint triangle Tk is formed at the three corners (bent portions) Cl, Cm, and Cn. In the three-dimensional shape, the restraint portion Pk has a triangular prism shape in which the restraint triangle Tk has a cross-sectional shape perpendicular to the rotation axis Ji.

The folded portion Po is provided so that the shape of the restraint portion Pk (that is, the triangular prism shape including the restraint triangle Tk) is surely maintained. The folded-back portion Po is a portion closer to the outer end Ca than the third bent portion Cn (including the outer end Ca). The folded-back portion Po is sandwiched between the inner peripheral surface Mu and the outer peripheral surface Ms of the spiral spring SU. Specifically, the folded-back portion Po is the inner peripheral surface Mu of the portion of the spiral spring SU located on the outermost side in the state where the spiral spring SU is wound (the inner peripheral surface Mu of the portion farthest from the rotation axis Ji). , In the figure, it is extended straight) and the outer peripheral surface Ms of the portion of the spiral spring SU located on the second outer side (the outer peripheral surface Ms corresponding to the inner peripheral surface Mu, and in the figure, the radius Rs. It is a portion sandwiched between (shown in FIG. 2) and (see FIG. 2). When the spiral spring SU is wound, the inner peripheral surface Mu and the outer peripheral surface Ms are brought into close contact with each other, and the inner peripheral surface Mu and the portion of the folded-back portion Po sandwiched by the outer peripheral surface Ms are firmly fixed. Since the shape of the restraint triangle Tk is surely maintained by the folded-back portion Po, the restraint portion Pk functions appropriately as a structural portion in charge of the elastic force Fs.

As the cross-sectional shape of the restraint portion Pk by bending molding, a polygonal shape can be adopted instead of the triangular shape. For example, a quadrangle as shown by a broken line may be adopted. In this case, in addition to the corner portions Cn, Cm, and Cl, a bent portion Co that is perpendicular to the longitudinal direction of the spiral spring SU and is mountain-folded with respect to the outer peripheral surface Ms is formed. Even in this case, the folded-back portion Po is formed between the inner peripheral surface Mu and the outer peripheral surface Ms of the spiral spring SU. The folded portion Po firmly forms the polygonal shape of the restraining portion Pk.

Instead of the hooking portion Pz shown in FIG. 2, a portion in which the inner end Sz portion of the spiral spring SU is bent at an acute angle at the bending portion Cy may be adopted. The input shaft SI is formed with a notch having a V-shaped cross section so as to lock the hooking portion Pz. Similarly to the above, when the spiral spring SU is not wound up, the hooking portion Pz is simply fitted in the V-shaped notch. Then, when the input shaft SI is rotated in the forward rotation direction Ra, the hooking portion Pz is locked to the notch portion, the spiral spring SU is wound up, and the return torque Tq is increased.

<Position of outer end Ca of spiral spring SU>
The position of the outer end Ca of the spiral spring SU will be described with reference to the cross-sectional view of FIG. The state in which the restraint portion Pk is locked at the central portion of the restraint surface Mk and the return torque Tq in the reverse rotation direction Rb is acting around the axis Ji is shown. The point P is a portion on the restraint surface Mk where the second bent portion Cm and the restraint surface Mk can come into contact with each other and is farthest from the axis Ji. The point Q is a portion on the restraint surface Mk where the second bent portion Cm and the restraint surface Mk can come into contact with each other and is closest to the axis Ji. The restraint portion Pk (particularly, the second bent portion Cm) is in contact with the restraint surface Mk between the points P and Q.

The normal plane Mh is a plane including the axis Ji and the point P. The restraint surface Mk is a plane in which the normal surface Mh is tilted in the normal rotation direction Ra by the sliding angle β with the “straight line parallel to the axis line Ji including the point P” as the center. The extension surface Mz is a plane in which the restraint surface Mk is extended in a direction approaching the axis Ji. Therefore, the distance between the extension surface Mz (that is, the restraint surface Mk) and the restraint surface Mk increases as it approaches the axis Ji. Further, the extension surface Mz does not include the axis line Ji. That is, the axis Ji does not exist on the extension surface Mz, and the extension surface Mz and the axis Ji are separated by a predetermined distance.

In a state where the spiral spring SU is wound and the return torque Tq is generated, the outer end Ca of the spiral spring SU is located on the side opposite to the axis Ji with respect to the extension surface Mz. Dimensions (longitudinal length) are set. For example, in the above-mentioned winding state, the spiral spring SU generates a return torque Tq (that is, initial torque q1) corresponding to the initial position of the piston PN (the piston position where the actual pressing force Fa becomes “0”). (See Figure 3). The spiral spring SU (particularly, the folded-back portion Po) is bent so that its radius becomes smaller and assembled to the housing HG. Therefore, in addition to the elastic force Fs, a force (bending force) Fm caused by bending of the folded portion Po acts on the restraining portion Pk. Since the outer end Ca is on the side opposite to the axis Ji with respect to the extension surface Mz, the bending force Fm of the folded portion Po acts on the restraint portion Pk in the radial outer direction Ds. By winding the spiral spring SU, the restraining portion Pk tends to be moved in the radial inner direction Du, but since the bending force Fm acts on the radial outer direction Ds, it operates suitably as a torque limiter and reengages. Stopping can be done properly.

The dimension (length in the longitudinal direction) of the folded portion Po is set so that the outer end Ca is located on the side opposite to the restraining portion Pk with respect to the vertical surface My. Here, the vertical plane My is a plane perpendicular to the extension plane Mz and including the axis Ji. Since the outer end Ca is on the side opposite to the restraining portion Pk with respect to the vertical plane My, the folded portion Po can be set as long as possible. The restraint portion Pk is held by the frictional force generated when the folded portion Po is sandwiched between the outer peripheral surface Ms and the inner peripheral surface Mu. Since the distance at which the folded-back portion Po is gripped is sufficiently secured, the restraining portion Pk can be firmly formed.

<Action / effect>
The operation and effect of the electric braking device DB according to the present invention will be described with reference to the cross-sectional view of FIG. 7. The electric braking device DB includes an electric motor MT that presses the friction member MS against a rotating member KT that rotates integrally with the wheel WH of the vehicle, and an electric motor MT when the electric motor MT is not energized. Therefore, a return mechanism MD that generates a return torque Tq in the direction in which the friction member MS moves away from the rotating member KT is provided. The return mechanism MD includes a spiral spring SU and a housing HG for accommodating the spiral spring SU. The spiral spring SU is engaged with a rotary shaft SI driven by an electric motor MT at one end Cz thereof. Further, the spiral spring SU has a restraining portion Pk formed by bending the portion of the other end Ca located on the side opposite to the one end Cz. Then, the restraining portion Pk comes into contact with the restraining surface Mk of the housing HG.

FIG. 7A shows a case where the outer end Ca is located on the same side as the axis Ji with respect to the extension surface Mz. The folded portion Po of the spiral spring SU is bent and assembled to the housing HG. Therefore, the folded portion Po generates a bending force Fm with respect to the restraining surface Mk. The bending force Fm of the folded portion Po acts perpendicularly to the straight line (plane) connecting the outer end Ca indicated by the alternate long and short dash line and the second bent portion Cm. Therefore, the component force Fn of the bending force Fm acts on the restraining surface Mk in the radial inner direction Du. Due to this component force Fn, the restraining portion Pk of the spiral spring SU is likely to come off from the restraining surface Mk. That is, the return mechanism MD may not operate properly as a torque limiter.

On the other hand, FIG. 7B shows a case where the outer end Ca is located on the side opposite to the axis Ji with respect to the extension surface Mz. For example, it corresponds to the case where the force (pushing pressure) Fa for pressing the friction member MS against the rotating member KT is “0 (zero)” (that is, the initial position of the piston PN and the state of “Tq = q1”). Similar to the above, the bending force Fm of the folded portion Po acts perpendicularly to the straight line (plane) connecting the outer end Ca indicated by the alternate long and short dash line and the second bent portion Cm. The electric braking device DB according to the present invention is configured such that the other end Ca is located on the opposite side of the axis Ji with respect to the extension surface Mz in which the restraining surface Mk is extended so as to approach the axis Ji. Due to this geometric relationship, the component force Fn of the bending force Fm acts on the restraining surface Mk in the radial outer direction Ds. That is, the contact between the restraining portion Pk and the restraining surface Mk is difficult to be released by the component force Fn. As a result, the return mechanism MD can properly operate as a torque limiter.

The restraining surface Mk is provided with a sliding angle β so that the release of the restraining portion Pk is stabilized. Since the sliding angle β acts to facilitate the release of the restraint portion Pk, when the outer end Ca is on the same side as the axis Ji as shown in FIG. 7 (a), the restraint portion Pk is sufficiently locked. It may not be done. However, as shown in FIG. 7B, when the outer end Ca is on the opposite side of the axis Ji, the bending force Fm of the folded-back portion Po makes it difficult to release the restraint portion Pk, and the restraint portion Pk is locked. It can be achieved with certainty. Further, the dimensions of the spiral spring SU are set so that the outer end Ca is located on the side opposite to the restraining portion Pk with respect to the vertical plane My (a plane orthogonal to the extension plane Mz and including the rotation axis Ji). obtain. As a result, the length of the folded-back portion Po is sufficiently long, so that the formation of the restraint portion Pk can be made firm.

<Other embodiments>
Hereinafter, other embodiments will be described. Other embodiments also have the same effect as described above.
In the above embodiment, the return mechanism MD is provided on the input shaft SI. However, the return mechanism MD is installed in any of the rotating members from the electric motor MT to the piston PN. In other words, the return mechanism MD is provided on a rotary shaft (for example, an output shaft SO) that is rotationally driven by the electric motor MT. When the return mechanism MD is provided on the output shaft SO, "SI" is replaced with "SO" and "Ji" is replaced with "Jo".

In the above embodiment, the housing HG is provided with two portions, a first restraint portion Aa and a second restraint portion Ab, as a portion for locking the restraint portion Pk. However, the number of restraining portions may be one or more. For example, when the second restraint portion Ab is omitted, in the re-locking operation, the restraint portion Pk slides on the inner peripheral surface Mp of the storage portion Ap over 360 degrees, and then again to the first restraint portion Aa. Locked. Further, when the housing HG is provided with three restraining portions, the restraining portion Pk is re-locked after moving in the storage portion Ap by 120 degrees. That is, as the number of restraining portions increases, torque can be limited by the relocking operation in a narrower range. When the upper limit torque q3 is the same, the relocking point (for example, point E) approaches the point of the upper limit torque (for example, point C) as the number of stopping portions increases. Therefore, the relocking torque q2 is set to a larger value, and the change from the upper limit torque q3 to the relocking torque q2 when the relocking operation is performed is reduced. The difference between the angle corresponding to the relocking torque q2 (for example, the angle m2) and the angle corresponding to the upper limit torque q3 (for example, the angle m3) corresponds to the value obtained by dividing 360 degrees by the number of restraining portions. do. For example, when the housing HG is configured by the two restraints, the above angle difference is 180 degrees.

In the above embodiment, it is exemplified that the restraining surface Mk is formed of a resin material. However, the entire housing HG, including the closure member, can be made of resin material. Since the resin material has an appropriate coefficient of friction, stick slip is unlikely to occur at the contact portion (that is, the second bent portion Cm) between the restraining portion Pk and the restraining surface Mk. Therefore, an appropriate release of the excessive return torque Tq can be achieved. Further, since the actuator BR is provided on the wheel, it is affected by vibration due to the unevenness of the road surface. Since the vibration is also input in the directions of the rotation axes Ji and Jo, the bottom portion of the housing HG and the closed portion come into contact with the side surface of the spiral spring SU. By adopting a resin material for the housing HG, wear of the housing HG due to contact with the side surface of the spiral spring SU can be suppressed.

DB ... electric braking device, BP ... braking operation member, MS ... friction member, KT ... rotating member, MT ... electric motor, PN ... pressing piston, MD ... return mechanism, SU ... spiral spring, Ca ... outer end of spiral spring, Cz ... Inner end of spiral spring, HG ... Housing, Tq ... Return torque, Ra ... Forward rotation direction, Rb ... Reverse direction, SI ... Input shaft, Ji ... Input shaft rotation axis, SO ... Output shaft, Jo ... Output shaft Rotation axis, Pz ... Hooking part, Pk ... Restraining part, Mk ... Stopping surface, Mz ... Extension surface, My ... Vertical surface, Ms ... Swirl spring outer peripheral surface, Mu ... Swirl spring inner peripheral surface, Cl ... 1 Bent part, Cm ... 2nd bent part (contact part), Cl ... 3rd bent part, Po ... Folded part.

Claims (1)

An electric motor that presses the friction member against the rotating member that rotates integrally with the wheel of the vehicle,
A return mechanism that generates a return torque in the direction in which the friction member separates from the rotating member with respect to the electric motor when the electric motor is not energized.
It is an electric braking device of a vehicle equipped with
The return mechanism is
A portion of one end is engaged with a rotary shaft driven by the electric motor, and the other end of a portion extending from the other end opposite to the one end toward the one end for a predetermined length. A spiral spring with a restraining part formed by bending a part except for
A housing that houses the spiral spring and has a planar restraining surface that comes into contact with the restraint.
Including
The other end is an electric braking device for a vehicle, which is located on the side opposite to the axis of the extension surface obtained by extending the restraining surface so as to approach the axis of the rotating shaft.

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