JP4946768B2 - Parking brake system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new pressing device of a duo-servo type drum brake contained in a parking brake system. <P>SOLUTION: The direction of torque applied to a wheel is predicted in a stopping state of a vehicle. A shoe pressing rod 56 is moved to the left when the predicted direction of the torque is the forward rotating direction P and pressing force is applied to a brake shoe 40a to be a primary shoe when the torque is applied. The force in the circumferential direction applied to the brake shoe 40a is transmitted to a brake shoe 40b through an adjuster and makes contact with an anchor 36. Consequently, movement in the circumferential direction of the pair of brake shoes 40a, 40b is restrained when the predicted torque is actually applied after a parking brake works, and it is possible to restrain lowering of braking force. As such, in the duo-servo type drum brake, the pressing device imparting pressure force to the primary shoe out of the pair of brake shoes 40a, 40b is new. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a pressing device that presses a brake shoe against a rotating drum in a parking brake system including a duo-servo type drum brake.

In the duo-servo type parking brake described in Patent Documents 1 to 3, when the cable is pulled, the pair of brake shoes are pressed against the rotating drum via the brake lever and the strut, and the parking brake is operated.
An electric parking parking brake system including a duo-servo type drum brake described in Patent Document 4 includes (a) an electric motor, (b) a pair of slide members, and (c) a pair of the slide members and the electric motor. A motion conversion mechanism that is provided between the pair of slide members and converts the rotation of the electric motor into linear motions in opposite directions of the pair of slide members; and (d) the pair of slides by operating the electric motor according to the parking brake operation command. A pressing device is provided that includes a motor control unit that applies a pressing force to both of the pair of brake shoes to cause the parking brake to act by advancing the members in opposite directions.
An electric parking parking brake system including a duo-servo type drum brake described in Patent Document 5 is engaged with (a) an electric motor, (b) an eccentric cam, and (c) an outer peripheral surface of the eccentric cam. A pair of slide members, and (c) actuating an electric motor in response to a parking brake operation command to rotate the eccentric cam and moving the pair of slide members in opposite directions to each of the pair of brake shoes. A pressing device including a motor control unit that applies a pressing force and applies a parking brake.
JP-A-10-110758 JP 2001-165207 A JP-A-10-103391 JP 2001-82517 A JP 2006-336868 A

  An object of the present invention is to provide a novel pressing device provided in a parking brake system including a duo servo type drum brake.

Means and effects for solving the problem

The parking brake system according to claim 1 includes: (i) a non-rotating body; (ii) a rotating drum that rotates with a vehicle wheel; and an inner peripheral surface is a friction surface; and (iii) an inner periphery of the rotating drum. A pair of brake shoes having a friction material on the outer peripheral surface, and (iv) an anchor member fixed to the non-rotating body between one end portions of the pair of brake shoes, and (v) the The ends of the pair of brake shoes opposite to the side where the anchor member is provided are connected to each other, and the circumferential force applied to one of the pair of brake shoes is transmitted as the input of the other brake shoe. A duo-servo type drum brake comprising: a transmission member that vibrates; and (vi) a pressing device that is provided on the one end side of the pair of brake shoes and presses the friction material of the pair of brake shoes against the inner peripheral surface of the drum Including parking A rake system, wherein the pressing device includes (a) an electric drive source and (b) at least one action member that directly acts on each of the pair of brake shoes, and the at least one action member. A pressing mechanism that selectively applies a pressing force to one of the pair of brake shoes that acts on one of the action members, and (c) the pressing mechanism. By predicting the direction of torque applied to the wheels in a stopped state of the vehicle and controlling the electric drive source based on the prediction, the torque of the pair of brake shoes is applied to the one action member. A pressing force control unit that applies the pressing force to what becomes the primary shoe when added is included.
In the parking brake system described in this section, it is assumed that the direction of the torque applied to the wheel is predicted after the parking brake is applied (that is, during the operation of the parking brake), and that the torque is applied when the brake is applied. In this case, the pressing force is applied only to the primary shoe (hereinafter simply referred to as the primary shoe).
Regardless of whether the torque is in the forward rotation direction or the reverse rotation direction, the action member directly acts on the primary shoe and applies a pressing force by the electric drive source. The action member does not apply a pressing force to the secondary shoe (hereinafter simply referred to as the secondary shoe). In this braking action state (a state where the pressing force is not controlled by the electric drive source), even if the predicted torque is actually applied, the secondary shoe is already in contact with the anchor member. The movement of the secondary shoe in the circumferential direction is suppressed, and a decrease in braking force is suppressed.
As described above, the duo-servo type drum brake pressing device included in the parking brake system described in this section applies the pressing force only to the one that becomes the primary shoe when the rotational torque is applied to the wheels when the vehicle is stopped. Such a pressing device is not described in any of Patent Documents 1 to 5, and is novel.
On the other hand, Patent Documents 4 and 5 describe a pressing device that applies a pressing force to both of a pair of brake shoes by an electric actuator. In this parking brake, which of the pair of brake shoes moves is not uniquely determined, and if a torque is applied during the operation of the parking brake, the pair of brake shoes may be rotated in the direction of the torque. Yes, the secondary shoe comes into contact with one of the slide members, and a large force is applied to the slide member. On the other hand, in the parking brake system described in this section, since the secondary shoe is in contact with the anchor member, the anchor member receives the force in the circumferential direction and is not received by the action member. As a result, the action member can be reduced in strength, and the pressing device can be downsized and the cost can be reduced. Or since the frequency with which big force is applied to an action member can be made low, the lifetime of an action member can be lengthened.
When the vehicle is stopped, the direction of the torque applied to the wheels can be predicted based on the inclination of the road surface on which the vehicle is stopped and the shift position of the transmission. The vehicle is stopped by the operation of the service brake, the parking brake is then applied, and the service brake is often released after the parking brake is applied. When the service brake is released, torque due to gravity is applied to the wheels, or drive torque from the vehicle drive source is applied.
The direction of the torque predicted to be applied to the wheels when the vehicle is stopped can be acquired based on the direction of the inclination of the road surface on which the vehicle is stopped. The inclination direction of the road surface is detected by an inclination detection device. When the vehicle is stopped on the uphill, it is predicted that torque in the reverse rotation direction is applied, and when the vehicle is stopped on the downhill, torque in the forward rotation direction is applied. The inclination detection device can also be considered as an attitude detection device that detects the inclination of the vehicle in the front-rear direction. The tilt detection device may include a longitudinal acceleration sensor, and may further include a vehicle height sensor.
Further, the parking brake may be operated even when the vehicle drive source is in an operating state and the shift position is at a position other than parking. In that case, if the shift position is at a position other than neutral, the direction of torque predicted to be applied to the wheel based on the shift position can be acquired. When the shift position is a position for instructing forward movement, it is predicted that torque in the forward rotation direction is applied, and when it is in a position for instructing reverse movement, torque in the reverse rotation direction is predicted to be applied.
In the pressing mechanism, the number of action members may be one or two. When there is one action member, the one action member acts on both of the pair of brake shoes. When there are two action members, one of the action members acts on one of the pair of brake shoes, and the other of the action members acts on the other brake shoe. When there are two action members, one electric drive source may be provided in common for the two action members, or may be provided corresponding to the two action members, respectively.
The action member can be a rod (also referred to as a slide member or a piston), a cam, a rotation lever, or the like. The cam and the rotation lever may function as a motion conversion mechanism. In this case, both the cam and the rotation lever and an action member (for example, a rod) may be provided. The components of the action member and the motion conversion mechanism are rigid bodies, and it can be considered that they do not have flexibility like a cable.
The electric drive source can be an electric motor or an electrically deformable member having a piezoelectric element or the like. When the electric drive source is an electric motor and the action member is linearly movable such as a rod, a motion conversion mechanism is provided that converts the rotation of the electric motor into a linear motion and transmits it to the action member. It is usually done. The motion conversion mechanism can also be considered as a driving force transmission mechanism. When the electric drive source is an electrically deformable member, it is desirable to provide it for each action member.
Hereinafter, specific modes of the pressing device will be described.
In the parking brake system according to claim 3, the electric drive source includes one electric motor, and the pressing mechanism includes (a) one action member that acts on each of the pair of brake shoes, and (b) A movement conversion mechanism that converts rotation of the electric motor into linear movement of the one action member, and the pressing force control unit controls the rotation direction of the one electric motor to move the action member. A motor control unit for controlling the direction is included.
When the electric motor is rotated in one direction, the action member advances toward one of the pair of brake shoes and acts on one of the brake shoes to give a pressing force. When rotated in the opposite direction, the action member advances toward the other of the pair of brake shoes and acts on the other brake shoe to give a pressing force.
Therefore, by controlling the rotation direction of the electric motor, it is possible to selectively apply the pressing member to any one of the pair of brake shoes to apply the pressing force.
The parking brake system according to claim 4, wherein the motion conversion mechanism is held in (a) a housing and (b) the housing so as not to be relatively movable and relatively rotatable in the axial direction, and the first screw portion. And (c) a second screw member that is held by the housing so as to be relatively movable in the axial direction and includes a second screw portion that is screwed with the first screw portion. The first screw member is rotated by the electric motor, and the second screw member is movable integrally with the one action member.
When the first screw member is rotated with the rotation of the electric motor, the second screw member is linearly moved in the axial direction. Then, the action member is moved with the movement of the second screw member in the axial direction. For example, the first screw portion can be provided on the inner peripheral surface of the first screw member, and the second screw portion can be provided on the outer peripheral surface of the second screw member.
The motion conversion mechanism includes: (a) a housing; (b) a pinion held in the housing so as not to be relatively movable in the axial direction and relatively rotatable; and (c) held in the housing so as to be relatively movable in the axial direction. It is also possible to include a rack, wherein the pinion is rotatably provided as the electric motor rotates, and the rack is provided so as to be movable integrally with the one action member.
6. The parking brake system according to claim 5, wherein the electric drive source includes one electric motor, and the pressing mechanism is (a) two action members that directly act on each of the pair of brake shoes, respectively. And (b) (i) a cam rotated by the electric motor and acting on each of the two action members, and (ii) each of the two action members rotated by the rotation of the electric motor. A movement converting mechanism including any one of the levers acting on the lever, and the pressing force control unit controls one of the two acting members by controlling the rotation direction of the one electric motor. A motor control unit that selectively moves is included.
When the cam is rotated in one direction by the rotation of the electric motor in one direction, one of the two action members moves forward toward one brake shoe and acts on one brake shoe, thereby reducing the pressing force. Add. When the cam is rotated in the reverse direction by the reverse rotation of the electric motor, the other action member acts on the other brake shoe and applies a pressing force.
Similarly, when the lever is rotated in one direction by rotating the electric motor in one direction, one action member moves forward toward one brake shoe and acts to apply a pressing force. When the lever is rotated in the reverse direction by the reverse rotation of the electric motor, the other action member acts on the other brake shoe to apply a pressing force.
The cam may be in contact with the other action member while acting on one action member, but no pressing force is applied to the other action member.
In the parking brake system according to claim 6, the electric drive source includes one electric motor, and the pressing mechanism is (i) rotated by the electric motor and acting on each of the pair of brake shoes. One of a cam and (ii) a lever that is rotated by the electric motor and acts on each of the pair of brake shoes is included as the one action member, and the pressing force control unit includes the one force By controlling the rotation direction of the electric motor, a motor control unit that selectively applies a pressing force to any one of the pair of brake shoes is included.
In the parking brake system described in this section, the cam and the lever are acting members, and in the working state, the cam surface and the engaging portion of the lever act directly on the brake shoe. Since a dedicated action member is not necessary, the number of parts of the pressing device can be reduced accordingly.
Further, as described in claim 7, it is desirable that the pressing device is provided with a holding mechanism that holds the friction material pressing force even when electric power is not supplied to the electric drive source. For example, (i) the motion conversion mechanism has a function as a holding mechanism, (ii) the electric drive source has a function as a holding mechanism, (iii) the motion conversion mechanism, A holding mechanism can be provided separately from the drive source. When the electric drive source is an electric motor, the holding mechanism may or may not be provided coaxially with the output shaft of the electric motor.
(i) When the motion conversion mechanism has a function as a holding mechanism, when the motion conversion mechanism is a screw mechanism, the screw has a small lead angle or a trapezoidal screw, etc. Is applicable. (ii) When the electric drive source has a function as a holding mechanism, when the electric drive source has an electric motor and a speed reducer, the speed reducer shall have a gear mechanism having irreversible characteristics. Can do. The gear mechanism having irreversible characteristics may include a worm gear, a planetary gear, or a harmonic drive (registered trademark). A gear mechanism having non-reversible characteristics has a reverse efficiency (when an external force is applied to the electric drive source, the motor force necessary to prevent the electric motor from being rotated by the external force is divided by the external force. It can also be called a gear mechanism whose value is 0. The electric motor included in the electric drive source can be an ultrasonic motor.
For example, it is desirable to include (a) a worm rotated by the electric motor and (b) a worm wheel connected to the working rod via the motion conversion mechanism. .
Further, the pressing mechanism is provided in the vicinity of the anchor-side end portions of the pair of brake shoes. Therefore, it is desirable that the main body of the pressing mechanism be fixedly provided on the anchor member, or that the anchor member be the main body of the pressing mechanism as described in claim 9. If the anchor member is the main body of the pressing mechanism, there is an advantage that it is not necessary to separately provide a housing for the pressing device.
Further, the pressing force control unit can operate the electric drive source in accordance with an operation command for the parking brake. Duo servo type drum brakes are often used as parking brakes.
The parking brake system according to claim 11 includes: (a) a non-rotating body; (b) a rotating drum that rotates with a vehicle wheel; and an inner peripheral surface is a friction surface; and (c) an inner periphery of the rotating drum. A pair of brake shoes disposed on the outer peripheral surface and having a friction material on the outer peripheral surface; (d) an anchor member fixed to the non-rotating body between one end portions of the pair of brake shoes; The ends of the pair of brake shoes opposite to the side where the anchor member is provided are connected to each other, and the circumferential force applied to one of the pair of brake shoes is transmitted as the input of the other brake shoe. A duo-servo type drum brake comprising: a transmission member configured to transmit; and (f) a pressing device that is provided on the one end side of the pair of brake shoes and presses the friction material of the pair of brake shoes against the inner peripheral surface of the drum Including parking A rk in system, the pressing apparatus, (a) an electromagnetic drive source, (b) has an axial direction moving member which acts on one of a predetermined one of said pair of brake shoes, the axial direction moving member the, by acting on one of the brake shoes said predetermined by the electromagnetic drive source, and a pressing mechanism that applies a pressing force on one of the brake shoes, not power is supplied to the (c) said electromagnetic drive source state And a holding mechanism for holding a friction material pressing force which is a pressing force of the friction material against the friction surface .
In the parking brake system described in this section, in the duo-servo type drum brake, a pressing force is applied only to one brake shoe determined in advance by the advance of the axial movement member. As a result, the parking brake is applied. The axially moving member has, for example, a rod shape and does not have flexibility, and is moved linearly. It is not a flexible cable or a lever that can be rotated.
When torque is applied during parking brake operation when the vehicle is stopped, if one of the brake shoes is the primary shoe, the secondary shoe is in contact with the anchor member. The decrease can be satisfactorily suppressed. When one of the brake shoes is a secondary shoe, the primary shoe is in contact with the axially moving member, so that a reduction in braking force can be suppressed.
In addition, in the duo-servo type drum brake described in this section, if one brake shoe becomes a primary shoe when a torque in the forward rotation direction is applied to the wheel, the drum brake can be used during forward traveling of the vehicle. There is an advantage that a large braking force can be applied when the is operated. In this case, since a large force is not applied to the axially moving member, the strength of the axially moving member can be reduced and a large braking force can be applied.
In any of Patent Documents 1 to 5, as described in claim 7 of the present application, in the duo servo type drum brake included in the parking brake system, one of the predetermined ones is determined by advancing the axial movement member. There is no description of a pressing device that applies a pressing force only to the brake shoe, and the pressing device according to claim 7 of the present application is novel.
In addition, the technical features described in any one of claims 1 to 10 can be adopted in the parking brake system described in claim 11.

A parking brake system including a duo servo type drum brake according to an embodiment of the present invention will be described in detail with reference to the drawings.
In FIG. 1, reference numerals 14 and 16 indicate left and right rear wheels, and reference numerals 18 and 20 indicate drum brakes provided on the wheels 14 and 16, respectively. As shown in FIG. 2, the drum brakes 18 and 20 are duo-servo type drum brakes and act as parking brakes. Hereinafter, the drum brakes 18 and 20 may be referred to as parking brakes as necessary.
In FIG. 2, reference numeral 22 denotes a brake disc, reference numeral 23 denotes a caliper, and the brake disc 22 and the caliper 23 together constitute a disc brake 24 as a service brake. The drum brakes as the parking brakes 18 and 20 are provided on the inner peripheral side of the brake disc 22 and are drum-in disc brakes in this embodiment. The drum brakes 18 and 20 have the same structure.

  Each of the drum brakes 18 and 20 includes a backing plate 30 as a non-rotating body attached to a vehicle body (not shown), and a drum (rotating drum) 34 that has a friction surface 32 on its inner peripheral surface and rotates with the wheel 14. ing. An anchor member 36 and an adjuster 38 serving as a transmission member are provided at two locations separated from each other in the diameter direction of the backing plate 30. The anchor member 36 is fixed to the backing plate 30 and the adjuster 38 is a floating type. A pair of brake shoes 40 a and 40 b each having an arc shape are attached between the anchor member 36 and the adjuster 38 so as to face the inner peripheral surface of the drum 34. The pair of brake shoes 40a and 40b are attached to the backing plate 30 so as to be movable along the surfaces thereof by shoe hold-down devices 42a and 42b. The through hole provided in the center of the backing plate 30 is for allowing the axle shaft (not shown) to pass therethrough.

  The pair of brake shoes 40a and 40b are operatively connected to each other by an adjuster 38, and each other end abuts against the anchor member 36 and is rotatably supported. One end portions of the pair of brake shoes 40a and 40b are urged toward the adjuster 38 by an adjuster spring 44, and the other end portions are urged toward the anchor member 36 by a return spring 45. . Brake linings 46a and 46b as friction materials are held on the outer peripheral surfaces of the brake shoes 40a and 40b, and the pair of brake linings 46a and 46b are brought into contact with the friction surface 32 of the drum 34. A frictional force is generated between 46 b and the drum 34. The adjuster 38 is operated to adjust the gap between the pair of brake linings 46a, 46b and the drum 34 according to the wear of the pair of brake shoes 40a, 40b. The adjuster 38 functions as a transmission member that transmits one circumferential force of the pair of brake shoes 40a and 40b to the other brake shoe.

As shown in FIGS. 3 and 4, the pressing device 50 includes an electric motor 52 as an electric drive source, a motion conversion mechanism 54, a shoe pressing rod 56 as one action member, and a holding mechanism 58. The rotation of the electric motor 52 is converted into a linear motion by the motion conversion mechanism 54 and transmitted to the shoe pressing rod 56. The shoe pressing rod 56 does not have flexibility like a cable, but is a rigid body. The drum brake in this embodiment does not include a lever and is not operated by a cable.
As shown in FIG. 3, the motion conversion mechanism 54 includes a housing 60, a screw member 64 held in the housing 60 via a pair of bearings 66 so as to be relatively rotatable, and an axial direction on the inner peripheral side of the screw member 64. And a shoe pressing rod 56 held so as to be relatively movable. A first screw portion (female screw portion) 70 is formed on the inner peripheral surface of the screw member 64. On the other hand, a second screw portion (male screw portion) 72 is formed on the outer peripheral surface of the intermediate portion of the shoe pressing rod 56 and is screwed with the first screw portion 70 of the screw member 64. Shoe engaging portions 74 a and 74 b are provided at both ends of the shoe pressing rod 56. The shoe engaging portions 74 a and 74 b are shaped so as to sandwich the webs 76 a and b of the brake shoes 40 a and b, respectively, and function as detents for the shoe pressing rod 56. The size and shape of the shoe engaging portions 74a, 74b is such that the web 76a, b can be sandwiched from both sides even when the shoe pressing rod 56 is moved rightward or leftward in FIG. It is made into a shape (the size and shape are such that the webs 76a, b will not come off even if moved).
In the present embodiment, the screw member 64 corresponds to the first screw member, and the shoe pressing rod 56 corresponds to the second screw member. The shoe pressing rod 56 and the second screw member are integrally formed.

A worm gear 58 as a holding mechanism is provided between the electric motor 52 and the motion conversion mechanism 54. The worm gear 58 includes a worm 80 and a worm wheel 82. The worm 80 is provided rotatably on the output shaft 83 of the electric motor 52. On the inner peripheral side of the worm wheel 82, a screw member 64 is held so as to be integrally rotatable via a key 84, and the worm wheel 82 is held by the housing 60 in a state where relative movement in the axial direction is prevented. The As a result, in the motion conversion mechanism 54, the axial movement of the screw member 64 is also prevented, and the rotation of the screw member 64 is converted into the axial movement of the shoe pressing rod 56.
Even when a large force is applied to the shoe pressing rod 56 in a state where no electric current is supplied to the electric motor 52 by the worm gear 58, the electric motor 52 is prevented from rotating by the force. The worm gear 58 also functions as a speed reducer.
The housing 60 is fixedly held by the anchor member 36, and pressing force sensors 94 and 96 are attached to opposing surfaces 90 and 92 of the anchor member 36 that face the surface orthogonal to the axial direction of the housing 60, respectively. It is done. The pressing force sensors 94 and 96 are pressure-sensitive sensors, and the pressing force sensor 94 detects the pressing force applied to the brake shoe 40b by the shoe pressing rod 56 (strictly speaking, the reaction force of the pressing force). The pressing force sensor 96 detects the pressing force applied by the shoe pressing rod 56 to the brake shoe 40a.
The housing 60 and the anchor member 36 can be composed of a plurality of members.

In this embodiment, the electric motor 52 is controlled by a command from an electric parking brake ECU (PKBECU) 200 as shown in FIG. The parking brake ECU 200 is mainly composed of a computer, and includes an input / output unit 202, an execution unit 204, a storage unit 206, and the like. The input / output unit 202 includes pressing force sensors 94 and 96, an ammeter 210 that detects a current flowing through the electric motor 52, a rotation speed sensor 212 that detects the rotation speed of the electric motor 52, and a parking brake switch (hereinafter simply referred to as parking). 214 and the like) are connected, and the electric motor 52 is connected via the drive circuit 216.
The electric parking brake ECU 200 is connected via a CAN (Car Area Network) 218 to other computers provided in the vehicle, such as a slip control ECU (VSCUCU) 220, an engine / transmission ECU (ETC ECU) 222, and the like. The slip control ECU 220 is connected to a longitudinal acceleration sensor 226 and the like as a tilt detection device, and the engine / transmission ECU 222 is connected to a shift position sensor 228 and the like, and information such as the longitudinal acceleration and the shift position is stored in the slip control ECU 220 and the engine. -It supplies to parking brake ECU200 via transmission ECU222, CAN218. The longitudinal acceleration sensor 226 includes two detection units that detect acceleration in a direction inclined by 45 ° with respect to the front-rear direction of the vehicle, and the acceleration in the front-rear direction of the vehicle based on the detection values by these two detection units. Is acquired. Therefore, even if an abnormality occurs in one of the two detection units, it is possible to acquire acceleration in the front-rear direction by the other.

The pressing force sensor can be attached to the portion of the shoe engaging portion 74a, 74b of the shoe pressing rod 56 that contacts the brake shoes 40a, b. In that case, the pressing force applied to the brake shoes 40a, 40b is directly detected. In particular, when the housing 60 is provided integrally with the anchor member 36, it is desirable to attach it to the shoe engaging portions 74a and 74b.
Alternatively, the anchor member 36 may be attached to a portion that contacts the brake shoes 40a, 40b. In this case, the pressing force obtained by the servo effect can also be detected.

When the parking switch 214 instructs the operation of the parking brakes 18 and 20 (hereinafter, the operation of the parking brakes 18 and 20 may be referred to as “lock”), the parking switch 214 is referred to as the release. In some cases, the switch is operated, for example, and may include a lock-side operation unit and a release-side operation unit. When the lock-side operation unit is operated (hereinafter abbreviated as the case where the lock instruction operation is performed), there is a lock request, and when the release-side operation unit is operated (hereinafter, the release instruction operation is performed). (Abbreviated as “Case”) is a release request.
The shift position sensor 228 may detect the position of the shift operation member or may detect the shift position of the transmission.

The operation of the parking brake system configured as described above will be described.
When the parking brakes 18 and 20 are not in operation, the shoe pressing rod 56 is in the neutral position shown in the figure. In the neutral position, the brake shoes 40a, b slightly contact or do not contact the shoe engaging portions 74a, b.
When the lock instruction operation of the parking brake switch 214 is performed, the electric motor 52 is operated and the parking brakes 18 and 20 are operated. In that case, the direction of torque predicted to be applied to the wheels 14 and 16 is acquired during the operation (after operation) of the parking brakes 18 and 20. When the predicted torque is applied, the shoe becomes a primary shoe (when the pair of brake shoes 40a and 40b are moved along the inner peripheral surface of the rotary drum 34 by the torque, the anchor member 36 The shoe pressing rod 56 is moved forward toward a shoe opposite to the shoe abutting on the shoe (hereinafter simply referred to as a primary shoe). The shoe pressing rod 56 acts directly on the primary shoe (in direct contact with the primary shoe) and applies a pressing force. In the neutral position, even if the brake shoe 40 is not in contact with the shoe pressing rod 56, it is brought into a state where it can be reliably contacted and act directly by being advanced.
For example, when it is acquired that the predicted direction of the torque is the forward rotation direction P, the shoe pressing rod 56 is moved leftward in FIG. 3, and a pressing force is applied to the brake shoe 40a. A circumferential force acting on the brake shoe 40 a is transmitted to the brake shoe 40 b by the adjuster 38, and the brake shoe 40 b is pressed against the anchor member 36.
When the predicted direction of the torque is the backward rotation direction Q, the shoe pressing rod 56 is moved to the right in FIG. 3, and a pressing force is applied to the brake shoe 40b. The pressing force applied to the brake shoe 40b is transmitted to the brake shoe 40a via the adjuster 38, and the brake shoe 40a is pressed against the anchor member 36.

When the vehicle is stopped, the direction of the torque applied to the wheels 14 and 16 can be predicted based on the slope of the road surface on which the vehicle is stopped and the shift position of the transmission. The vehicle is stopped by the operation of the service brake 24, and then the parking brakes 18 and 20 are applied, and the service brake 24 is often released after the parking brakes 18 and 20 are applied. When the service brake 24 is released, torque due to gravity is applied to the wheels, or drive torque from the vehicle drive source is applied.
When the vehicle is stopped on an inclined road surface, as shown in FIG. 8, when the longitudinal acceleration G, the gravitational acceleration g, and the inclination angle θ are set, the equation G = g · sin θ
Is established. Therefore, based on the longitudinal acceleration G, the inclination angle θ (size, direction) can be acquired. From the above formula, when the acceleration direction is the forward direction (G> 0), the vehicle is stopped on the downhill (sin θ> 0, θ> 0), and the acceleration direction is the backward direction (G <0). ), It is understood that the vehicle stops on an uphill (sin θ <0, θ <0). When the road on which the vehicle is stopped is an uphill, when the service brake 24 is released, it is predicted that the torque in the backward rotation direction Q will act on the wheels 14 and 16, and in the case of a downhill The torque in the forward rotation direction P is expected to act. Further, when the absolute value of the inclination angle θ is acquired based on the longitudinal acceleration G, and the road surface is inclined when the absolute value of the inclination angle θ is larger than a predetermined set value, it is equal to or less than the set value. It can be assumed that the vehicle is stopped on a substantially horizontal road surface.
Even when the vehicle drive source is in an operating state and the shift position is at a position other than parking, the parking brakes 18 and 20 may be acted upon by a lock instruction operation of the parking switch 214. In that case, if the shift position is at a position other than neutral, the direction of torque predicted to be applied to the wheel based on the shift position can be acquired. When the shift position is a position for instructing forward movement (for example, drive position, 1st position, 2nd position, etc.), the torque in the forward rotational direction P is applied when the service brake 24 is released, and the position for instructing reverse movement In the case of (for example, reverse position), it is predicted that torque in the reverse rotation direction Q is applied.
In this embodiment, when the road surface on which the vehicle is stopped is inclined, the direction of the torque is predicted based on the direction of the inclination, and the road surface on which the vehicle is stopped is almost horizontal. The direction of the torque is predicted based on the direction of the driving torque.
Note that the predicted torque direction can also be acquired based on both the magnitude of the road surface inclination angle, the direction and the magnitude of the driving torque, and the direction.

In this embodiment, the parking brake control program represented by the flowchart of FIG. 5 is executed at predetermined time intervals. In step 1 (hereinafter abbreviated as S1. The same applies to the other steps), it is determined whether or not the parking switch 214 has been operated. Is determined. In the case of a lock instruction, in S 3 and 4, as described above, the inclination direction is acquired based on the detection value by the longitudinal acceleration sensor 226, and the driving torque direction is determined based on the detection result by the shift position sensor 228. To be acquired. In S5, the direction of torque applied when the service brake 24 is released is predicted, and the rotation direction of the electric motor 52, that is, the movement direction of the shoe pressing rod 56 is determined.
In S6, the supply current to the electric motor 52 is controlled, and the parking brakes 18 and 20 are operated. The shoe pressing rod 56 is moved, and a pressing force is applied to the primary shoe.
On the other hand, if it is not a lock instruction but a release instruction, the determination in S2 is NO, and the parking brakes 18 and 20 are released by controlling the current supplied to the electric motor 52 in S7. The shoe pressing rod 56 is returned to the neutral position.

The execution of the brake operation in S6 is shown in the flowchart of FIG.
In this embodiment, the magnitude of the pressing force applied when the brake is operated is a predetermined set value (target pressing force), and the electric motor 52 is operated so that the actual pressing force becomes the target pressing force. It is done. Since a predetermined relationship is established between the pressing force and the brake force that can be output (the force applied between the road surface and the tire), if the pressing force is the target pressing force, a desired magnitude is obtained. The brake force is obtained. Further, when the electric motor 52 is a DC motor or the like, when the pressing force is large, the load applied to the electric motor 52 becomes larger than when the pressing force is small, and the value of the flowing current increases. A predetermined relationship is established between the current flowing through the electric motor 52 and the pressing force. When the current value is determined, the pressing force is determined. From this, it can be assumed that the pressing force reaches the target pressing force when the current flowing through the electric motor 52 reaches the target current value.
In S31, a start command for rotating the electric motor 52 in the direction determined in S5 is output. In S32, the rotational speed of the electric motor 52 is detected (the count value of the rotational speed counter is read). In S33, the current value is detected. In S34, whether the current value has reached a predetermined target current value. It is determined whether or not. Before reaching the target current value, the determination in S34 is NO, and S32 and 33 are repeatedly executed. The rotation speed is detected and the current value is detected. When the current value reaches the target current value, the electric motor 52 is stopped and the supply current is set to 0 in S35. In S36, the rotational speed of the electric motor 52 from the neutral position to the operating position is stored.
The shoe pressing rod 56 acts on the primary shoe and applies a pressing force. In this state, even if the supply current to the electric motor 52 is zero, the holding mechanism 58 prevents the electric motor 52 from rotating, and the friction material pressing force is held.
Further, in this state (in a state where the friction material pressing force is held by the holding mechanism 58), even if the predicted torque is actually applied, the secondary shoe is already in contact with the anchor member 36. The movement of the brake shoes 40a and 40b along the inner peripheral surface of the rotary drum 34 can be suppressed, and the reduction in brake force can be suppressed.
Further, since the secondary shoe is in contact with the anchor member 36, a large force is hardly applied to the shoe pressing rod 56. Therefore, the strength of the shoe pressing rod 56 can be reduced, the cost can be reduced, and the pressing device 50 can be downsized. Alternatively, even if a large force is applied to the shoe pressing rod 56 via the brake shoe 40, the number of times is reduced. Therefore, the life of the shoe pressing rod 56 can be extended.

The execution of brake release in S7 is shown in the flowchart of FIG.
In S51, a start command for rotating the electric motor 52 in the direction opposite to that in the operation of S6 is output. In S52, the rotational speed is detected (the count value of the rotational speed counter is read). The number of rotations detected in S52 is the number of rotations in the direction opposite to that when the brake of the electric motor 52 is operated. If the detected number of revolutions is the same as the number of revolutions at the time of brake operation, it is understood that the shoe pressing rod 56 has been returned to the neutral position.
In S53, it is determined whether or not the rotational speed in the reverse direction is equal to the rotational speed stored in S36. If the rotational speed is smaller than the stored rotational speed, S52 and 53 are repeatedly executed to be equal to the stored value. When it becomes, determination of S53 becomes YES and rotation of the electric motor 52 is stopped in S54. Thereby, the shoe pressing rod 56 is returned to the neutral position. The return spring 45 reduces the diameter of the pair of brake shoes 40a and 40b and releases the brake.

  When the lock instruction operation of the parking switch 214 is detected while the vehicle is running, the direction of the torque actually applied to the wheels 14 and 16 when the brake is applied is acquired, and the pressing force is applied to the primary shoe. It is done.

  In the present embodiment, the motion converting mechanism 54, the shoe pressing rod 56, etc. constitute a pressing mechanism, and the portion for storing S1-6 of the parking brake control program represented by the flowchart of FIG. 5 of the parking brake ECU 200 is executed. The pressing force control unit is configured by, and the like, and the torque direction prediction unit is configured by a part for storing S3 and S5, a part for executing the part, and the like. The pressing force control unit is also a parking brake control unit and a motor control unit.

In the above embodiment, the counter that counts the number of rotations of the electric motor 52 counts in the same manner whether the shoe pressing rod 56 is advanced from the neutral position or returned to the neutral position. However, it is also possible to increase the count number when moving forward from the neutral position and decrease the count number when returning to the neutral position. In this case, in S53, it is determined whether or not the count value has reached 0 (the count number corresponding to the neutral position). Further, it is not necessary to count and store the number of rotations of the electric motor 52 when the brake is operated, and S32 and 36 are not required.
In the above embodiment, the current supplied to the electric motor 52 is controlled so that the current flowing through the electric motor 52 reaches a predetermined target current value when the brake is operated. The supply current may be controlled so that the detection values of the sensors 94 and 96 reach a predetermined target pressing force. When the brake is released, the electric motor 52 is rotated in the reverse direction until the value detected by the pressing force sensors 94 and 96 becomes substantially 0 (a size that can be regarded as being in the neutral position).
An example in that case is shown in FIGS. Steps that are the same as those in the embodiment shown in FIGS. 6 and 7 are given the same step numbers and description thereof is omitted.
At the time of brake operation, after the electric motor 52 is started, in S33a, the pressing force is detected by the pressing force sensor 96 (for example, when the shoe pressing rod 56 is moved leftward in FIG. 3), and S34a. It is determined whether or not the target pressing force has been reached. Before reaching the target pressing force, S33a and 34a are repeatedly executed. When the target pressing force is reached, the electric motor 52 is stopped in S35.
When the brake is released, after the electric motor 52 is started in the reverse direction, the pressing force is detected by the pressing force sensors 94 and 96 in S52a. In S53a, it is determined whether or not both detection values are substantially zero. Determined. It is determined whether or not the actual pressing force is equal to or less than a set value at which the pressing force can be regarded as 0. If both the detected values of the pressing force sensors 94 and 96 are equal to or less than the set value, neutrality is determined. Assuming that the electric motor 52 has been returned to the position, the electric motor 52 is stopped in S54.
In this case, if it is determined whether or not the neutral position is based only on the value detected by the pressing force sensor 96, it may be returned too much (the shoe pressing rod 56 goes too far to the right). On the other hand, based on the detection values of both the sensors 94 and 96 (so that the detection value of the pressing force sensor 94 does not exceed the set value), the shoe pressing rod 56 can be more reliably returned to the neutral position.

When the shoe pressing rod 56 is returned to the neutral position, it is in the neutral position when the value detected by the pressing force sensor 96 is equal to or less than the set value and the state equal to or less than the set value continues for the set time. Thus, the electric motor 52 can be stopped.
Further, a stroke sensor for detecting the stroke of the shoe pressing rod 56 may be provided so that the electric motor 52 can be operated so that the stroke reaches a target value. Furthermore, the structure of the pressing mechanism 50 is not limited to that in the above embodiment.
For example, if there is an installation space, the electric motor 52 can be provided on the same side as the side where the pressing mechanism of the backing plate 30 is provided. Moreover, the shape of the screw parts 70 and 72 is not limited. For example, it can be a shape with a small lead angle or a trapezoidal screw. In that case, the motion conversion mechanism can be provided with a holding function.

Further, the pressing device can have the structure shown in FIGS. The pressing device 300 includes a motion conversion mechanism 302 having a rack and pinion (spur gear) mechanism and a motor 304 with a speed reducer as an electric drive source, and a housing is provided integrally with the anchor member 36 (anchor member 36). Functions as a housing).
The motion conversion mechanism 302 includes a pinion 312 that can rotate integrally with the output shaft 310 of the motor 304 with a speed reducer, and a rack 314 that is screwed with the pinion 312, and the rack 314 is relative to the anchor member 36 in the axial direction. It is held movable. The rack 314 and the shoe pressing rod are integrally formed.
The motor 304 with a speed reducer includes an electric motor 320 and a speed reducer 322. The speed reducer 322 can be provided with a harmonic drive mechanism (registered trademark) or can be provided with a planetary gear mechanism and has a function as a holding mechanism. When a planetary gear mechanism is provided, it is often used in a state where the output shaft of the electric motor 320 is connected to the sun gear and the output shaft 310 of the motor 302 with a speed reducer is connected to the planetary gear (planet carrier). The planetary gear mechanism may be provided in a plurality of stages.
If the speed reducer 322 includes a harmonic drive mechanism, a planetary gear mechanism, and the like, a large force can be applied via the brake shoes 40a, b and the shoe pressing rod 314 when no electric current is supplied to the electric motor 320. Even if added, the electric motor 320 can be prevented from rotating.
In the present embodiment, since the anti-rotation mechanism is not indispensable, the shoe engaging portions 74a and 74b provided in the above embodiment are not indispensable.
In this embodiment, the movement converting mechanism 302, the shoe pressing rod 314 and the like constitute a pressing mechanism. The shoe pressing rod 314 is also a component of the motion conversion mechanism 302.

  The electric motor 320 can be an ultrasonic motor. In that case, the electric motor 320 has a holding function.

Further, the pressing device may have the structure shown in FIGS. The pressing device 350 includes a motion conversion mechanism 354 having an eccentric cam 352 and a pair of shoe pressing rods 360a and 360b.
A through hole 372 in the thickness direction (a direction perpendicular to the backing plate 30 and a direction parallel to the axle shaft) is formed in the anchor member 36, and the output of the motor 304 with a speed reducer is inserted into the through hole 372 via a bearing. The shaft 310 is held so as to be relatively rotatable. An eccentric cam 352 is rotatably held integrally with the output shaft 310, but the center C of the eccentric cam 352 is located at a distance d from the center axis M of the output shaft 310.
A pair of shoe pressing rods 360a and 360b are disposed opposite to the cam surface (the outer peripheral surface in the present embodiment) of the eccentric cam 356. The pair of shoe pressing rods 360a and 360b are held by the anchor member 36 so as to be relatively movable in the axial direction.

As shown in FIG. 13, the eccentric cam 356 is in a neutral position indicated by a solid line when the parking brakes 18 and 20 are not in operation. The center C ₀ of the eccentric cam 352 is located on the axial center line of the motion converting mechanism 354, and the distance between the center M and the retracted end faces 380a, b of the shoe pressing rods 360a, 360b is equal to each other. It is in.
When the predicted torque direction is the forward rotation direction P when the brake is operated, the eccentric cam 352 is rotated to the phase indicated by the broken line by the rotation of the motor 304 with a speed reducer (the center is C ₁ ). In position). The shoe pressing rod 360a is moved to the left and directly acts on the brake shoe 40a to apply a pressing force. In this case, the outer peripheral surface of the eccentric cam 352 may come into contact with the retreat end surface 380b of the shoe pressing rod 360b, but the shoe pressing rod 360b is not moved rightward, and the shoe pressing rod 360b is not moved to the brake shoe 40b. No pressing force is applied to the.
When the predicted direction of torque is the backward rotation direction Q, the motor 304 with a speed reducer is rotated in the reverse direction, and the eccentric cam 352 is rotated to the phase indicated by the alternate long and short dash line (center is the position of C ₂ ). It is done. The shoe pressing rod 360b is moved to the right, and a pressing force is applied to the brake shoe 40b.
When the brake is released, the eccentric cam 352 is returned to the neutral position shown by the solid line. The pair of brake shoes 40 a, b and shoe pressing rods 360 a, b are returned to the non-acting position (neutral position) by the return spring 45.
In this embodiment, since the output shaft 310 of the motor 304 with a speed reducer is attached through the through hole 372 formed in the anchor member 36, the brake shoes 40a and b side of the backing plate 30 are provided even if the space is small. In addition, a motion conversion mechanism 354 and the like can be installed.
In this embodiment, the pressing mechanism is constituted by the motion conversion mechanism 354, the shoe pressing rods 360a and 360b, the anchor 36, and the like. The motion conversion mechanism 354 includes a structure that holds the eccentric cam 352 and the shoe pressing rods 360a and 360b so as to be linearly movable in the axial direction.

In the above embodiment, the pair of shoe pressing rods 360a, 360b is not indispensable, and the outer circumferential surface of the eccentric cam 352 can directly act on the pair of brake shoes 40a, 40b to apply a pressing force.
In addition, it is not essential that the cam surface be an outer peripheral surface.

Further, the pressing device may have the structure shown in FIG. In this embodiment, the pressing device 400 includes a motion conversion mechanism 404 provided with a lever member 402. The lever member 402 is formed integrally with a sector gear (worm wheel) 406, and two shoe pressing rods 360 a and 360 b are disposed so as to face the front end portion 408. Further, the lever member 402 passes through the long holes 412 and 414 formed in the backing plate 30 and the anchor member 36 in the intermediate portion, and is opposite to the side on which the brake shoe 40 is disposed on the backing plate 30. , The lever support member 416 is rotatably held around the rotation center point R. The long holes 412 and 414 have a function as a guide portion of the lever member 402.
The sector gear 406 of the lever member 402 is screwed into a worm 418 that can rotate integrally with the output shaft 310 of the motor 304 with a speed reducer.
When the brake is operated, the lever member 402 is rotated by the rotation of the motor 304 with a speed reducer, whereby one of the shoe pressing rods 360a and 360b is selectively moved. When the lever member 402 is rotated counterclockwise in FIG. 15, the shoe pressing rod 360a is moved, and a pressing force is applied to the brake shoe 40a. When the lever member 402 is rotated clockwise, the shoe pressing rod 360b is moved, and a pressing force is applied to the brake shoe 40b.
When the brake is released, the lever member 402 is returned to the neutral position (posture) by the reverse rotation of the motor 304 with a speed reducer. The return spring 45 returns the pair of brake shoes 40a, 40b and shoe pressing rods 360a, 360b to the neutral position.
In this embodiment, the pressing mechanism is constituted by the motion conversion mechanism 404, the shoe pressing rods 360a and 360b, the anchor member 36, and the like.

Note that the shoe pressing rods 360a and 360b may be a single rod that can move integrally.
Further, the shoe pressing rods 360a, 360b are not indispensable, and a pressing force can be directly applied to the brake shoes 40a, b by the tip end portion 408 of the lever member 402.
Further, when the worm 418 and the sector gear 406 have irreversible characteristics, the worm 418 and the sector gear 406 function as a holding mechanism. In that case, the reduction gear 322 need not include a gear device having non-reciprocal characteristics. Also, the speed reducer itself is not essential.

Furthermore, the pressing device can have a structure shown in FIGS. In the pressing device 500, the shoe engaging portion 504 of the shoe pressing rod (axially moving member) 502 is provided at the end portion on the brake shoe 40a side, and is not provided at the end portion on the brake shoe 40b side. This structure is the same as the pressing device 50 shown in FIGS.
In this embodiment, the shoe pressing rod 502 does not act directly on the brake shoe 40b and does not apply a pressing force.
When the lock instruction operation of the parking switch 214 is detected, the shoe pressing rod 502 is moved to the left by the operation of the electric motor 52 without predicting the direction of torque. The shoe pressing rod 502 directly acts on (abuts) the brake shoe 40a and applies a pressing force. The force in the circumferential direction of the brake shoe 40a is transmitted to the brake shoe 40b via the adjuster 38, and the brake shoe 40b is pressed against the anchor member 36.
In this state, when a torque in the forward rotation direction P is applied, the secondary shoe 40b is in contact with the anchor member 36, so that the movement of the pair of brake shoes 40a, b in the circumferential direction is suppressed, and the brake The decrease in force can be satisfactorily suppressed. In addition, when torque in the reverse rotation direction Q is applied, the secondary shoe 40a is in contact with the shoe pressing rod 502, and thereby, a reduction in braking force can be suppressed.
Furthermore, the brake shoe 40a to which a pressing force is applied is a shoe that becomes a primary shoe when a torque is applied in the forward rotation direction P. Therefore, a large braking force can be applied when the parking brakes 18 and 20 are operated during traveling.
The pressing device in each of the above embodiments can be applied to the pressing device 500 in the present embodiment.

The brake system including the duo-servo type drum brake in each of the above embodiments can be applied to a service brake. For example, it is possible to apply an urging force to the primary shoe by operating an electric motor or the like in accordance with a service brake operation command.
Although a plurality of embodiments of the present invention have been described above, the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art in addition to the aspects described above.

It is a conceptual diagram which shows the whole parking brake system which is one Example of this invention. It is a top view of the drum brake contained in the said parking brake system. It is sectional drawing of the pressing apparatus of the said drum brake. It is AA sectional drawing of FIG. It is a flowchart showing the parking brake control program memorize | stored in the memory | storage part of electric parking brake ECU of the said parking brake system. It is a flowchart showing a part of the program (brake operation). It is a flowchart showing another part of the said program (brake release). It is a figure which shows the relationship between the inclination of the road surface and the longitudinal acceleration which the vehicle has stopped. It is a flowchart showing a part of another parking brake control program memorize | stored in the said memory | storage part (brake operation | movement). It is a flowchart showing another part of the parking brake control program (brake release). It is sectional drawing which shows notionally another pressing apparatus of the drum brake contained in the said parking brake system. It is BB sectional drawing of FIG. It is sectional drawing which shows notionally another pressing apparatus of the drum brake contained in the said parking brake system. It is DD sectional drawing of FIG. It is sectional drawing which shows notionally another pressing apparatus of the drum brake contained in the said parking brake system. It is sectional drawing which shows notionally another pressing apparatus of the drum brake contained in the said parking brake system. It is EE sectional drawing of FIG.

Explanation of symbols

  18, 20: Drum brake (parking brake) 30: Backing plate 36: Anchor member 40a, b: Brake shoe 50, 300, 350, 400, 500: Pressing device 52, 320: Electric motor 54, 302, 354, 402: Motion conversion mechanism 56, 360a, b, 502: Shoe pressing rod 58, 322: Holding mechanism 60: Housing 64: Screw member 74a, b: Shoe engaging portion 80: Worm 82: Worm wheel 94, 96: Pressing force sensor 200 : Parking brake ECU 210: Ammeter 212: Speed sensor 214: Parking switch 226: Longitudinal acceleration sensor 228: Shift position sensor 312: Pinion 314: Rack 322: Reducer 352: Eccentric cam 402: Lever member 406; Sector gears 412 and 414: long hole 418: worm

Claims (11)

A non-rotating body,
A rotating drum that rotates with the wheels of the vehicle and whose inner peripheral surface is a friction surface;
A pair of brake shoes disposed on the inner peripheral side of the rotating drum and having a friction material on the outer peripheral surface;
An anchor member fixed to the non-rotating body between one end portions of the pair of brake shoes,
The ends of the pair of brake shoes opposite to the side on which the anchor member is provided are connected to each other, and the circumferential force applied to one of the pair of brake shoes is used as an input to the other brake shoe. A transmission member for transmitting;
A parking brake system including a duo-servo type drum brake, which is provided on the one end side of the pair of brake shoes and includes a pressing device that presses the friction material of the pair of brake shoes against the inner peripheral surface of the drum; ,
The pressing device has (a) an electric drive source and (b) at least one action member that directly acts on each of the pair of brake shoes, and one of the at least one action members is provided. A pressing mechanism that is operated by the electric drive source to selectively apply a pressing force to one of the pair of brake shoes that acts on one of the action members; and (c) the vehicle in a stopped state. The direction of the torque applied to the wheel is predicted, and the electric drive source is controlled based on the prediction, so that when one of the pair of brake shoes is applied with the torque, the primary acting member is primary. A parking brake system comprising: a pressing force control unit that applies the pressing force to a shoe. The pressing force control unit is (a) an inclination detection device that detects an inclination direction of a road surface on which the vehicle is stopped, and (b) the road surface inclination direction detected by the inclination detection device based on the inclination direction of the road surface. The parking brake system according to claim 1, further comprising a torque direction prediction unit that predicts a direction of torque applied to the wheel. The electric drive source includes one electric motor, and the pressing mechanism includes (a) one action member that directly acts on each of the pair of brake shoes, and (b) rotation of the electric motor. A motor conversion unit that converts a linear motion of the member, and the pressing force control unit controls a rotation direction of the one electric motor, thereby controlling a moving direction of the one action member. The parking brake system according to claim 1 or 2 including. The motion conversion mechanism includes: (a) a housing; (b) a first screw member that is held in the housing so as not to be relatively movable and relatively rotatable in the axial direction; A second screw member that is held in the housing so as to be relatively movable in the axial direction and includes a second screw portion that is screwed with the first screw portion, the first screw member being driven by the electric motor The parking brake system according to claim 3, wherein the parking screw system is rotated and the second screw member is movable integrally with the one action member. The electric drive source includes one electric motor, and the pressing mechanism includes (a) two action members that directly act on each of the pair of brake shoes, and (b) (i) the electric motor. A motion including any one of a cam rotated and acting on each of the two action members; and (ii) a lever rotated by the rotation of the electric motor and acting on each of the two action members. And a pressing force control unit including a motor control unit that selectively moves one of the two action members by controlling a rotation direction of the one electric motor. The parking brake system according to 1 or 2. The electric drive source includes one electric motor, and the pressing mechanism is (i) a cam rotated by the electric motor and acting on each of the pair of brake shoes, and (ii) rotated by the electric motor. One of the levers acting on each of the pair of brake shoes is included as the one action member, and the pressing force control unit controls the rotation direction of the one electric motor, thereby The parking brake system according to claim 1, further comprising a motor control unit that selectively applies a pressing force to one of the pair of brake shoes. The pressing device includes a holding mechanism that holds a friction material pressing force that is a pressing force of the friction material against the friction surface in a state where electric power is not supplied to the electromagnetic drive source. Parking brake system described in 1. The electric drive source includes one electric motor;
The parking mechanism according to claim 7, wherein the holding mechanism includes: (a) a worm rotated by the electric motor; and (b) a worm wheel connected to the at least one action member via the motion conversion mechanism. Brake system.   The parking brake system according to any one of claims 1 to 8, wherein the anchor member constitutes a main body of the pressing mechanism.   The parking brake system according to any one of claims 1 to 9, wherein the pressing force control unit includes a parking brake control unit that operates the electric drive source in response to a parking brake operation command. A non-rotating body,
A rotating drum that rotates with the wheels of the vehicle and whose inner peripheral surface is a friction surface;
A pair of brake shoes disposed on the inner peripheral side of the rotating drum and having a friction material on the outer peripheral surface;
An anchor member fixed to the non-rotating body between one end portions of the pair of brake shoes,
The ends of the pair of brake shoes opposite to the side on which the anchor member is provided are connected to each other, and the circumferential force applied to one of the pair of brake shoes is used as an input to the other brake shoe. A transmission member for transmitting;
A parking brake system including a duo-servo type drum brake, which is provided on the one end side of the pair of brake shoes and includes a pressing device that presses the friction material of the pair of brake shoes against the inner peripheral surface of the drum; ,
The pressing device has (a) an electromagnetic drive source, and (b) an axially moving member that acts on a predetermined one of the pair of brake shoes, and the axially moving member is A pressing mechanism that applies a pressing force to the one brake shoe by acting on the one predetermined brake shoe by a source ; and (c) the friction material in a state where no electric power is supplied to the electromagnetic drive source. A parking brake system comprising: a holding mechanism for holding a friction material pressing force which is a pressing force against the friction surface .

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