JP6238647B2 - Electric booster - Google Patents

Description

  The present invention relates to an electric booster that is incorporated in a brake device of a vehicle such as an automobile and generates a brake fluid pressure with a master cylinder using an electric motor.

  As a booster incorporated in a brake device, for example, as described in Patent Document 1, an electric booster using an electric motor as a boost source is known. The electric booster described in Patent Document 1 includes an input piston that moves forward and backward by operation of a brake pedal, a booster piston that is arranged to be relatively movable with respect to the input piston, and a rotation-linear motion conversion that moves the booster piston back and forth. A mechanism and an electric motor for applying a rotational force to the rotation-linear motion conversion mechanism. Then, the brake fluid pressure is generated in the pressure chamber of the master cylinder by the input thrust applied to the input piston from the brake pedal via the input rod and the booster thrust applied from the electric motor to the booster piston.

  In this electric booster, a booster piston (linear motion part of the rotation-linear motion conversion mechanism) is provided with a return spring (coil spring), and when the electric motor is not energized, the booster piston is initialized by the spring force of the return spring. It tries to return to the position.

JP 2010-23594 A

  However, in the above-described Patent Document 1, when the return spring expands and contracts with the movement of the linear motion member of the ball-screw mechanism, torque about the axis is applied to the linear motion member according to the winding direction of the coil spring. Works. When the linear motion member is returned to the initial position by the return spring, a gap may be formed between the linear motion member and the rotation preventing member due to the torque from the return spring. In this state, when the ball-screw mechanism starts to operate from the initial position, the linear motion member rotates together with the rotating member and generates a hitting sound by contacting the detent.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an electric booster that suppresses the generation of a hitting sound at the start of braking.

In order to solve the above-described problems, the present invention provides an electric motor provided in a housing , and a rotation-linear motion conversion mechanism that converts the rotational motion of the rotary member driven by the electric motor into linear motion of the linear motion member. A non-rotating stop formed on the housing to engage the concave and convex portions with the linear motion member to restrict rotation of the linear motion member about an axis, and a compression coil spring that urges the linear motion member in a backward direction. return comprises a spring, and in the electric booster generates a brake fluid pressure in the master cylinder to promote the piston by the linear motion member, said return spring, during forward before Symbol translation member the winding direction of its The linear motion member is caused to abut on the rotation stopper in the rotational direction when the linear motion member is retracted , so as to coincide with the rotational direction of the rotational member .

  According to the electric booster according to the present invention, it is possible to suppress the occurrence of hitting sound at the start of braking.

1 is a longitudinal sectional view of an electric booster according to an embodiment of the present invention. It is a disassembled perspective view of the electric booster shown in FIG. It is a perspective view of the return spring of the electric booster shown in FIG. It is a figure which shows the state of the clearance gap between the guide groove of the screw shaft of the ball screw mechanism of the electric booster shown in FIG. It is a graph which shows the relationship between the stroke of the screw shaft of the ball screw mechanism of the electric booster shown in FIG. 1, and the torque which acts on a screw shaft.

Hereinafter, an embodiment of the present invention will be described in detail based on the drawings.
As shown in FIGS. 1 and 2, an electric booster 1 according to this embodiment is a booster that uses an electric motor as a drive source, and is located in front of a housing 4 that houses an actuator 3 that is a booster. A tandem-type master cylinder 2 is connected to a portion (left side in FIG. 1), and a reservoir 5 (only part of which is shown in FIG. 1) is disposed on the upper portion of the master cylinder 2. The housing 4 has a rear cover 4B fitted to the opening side of the substantially bottomed cylindrical front housing 4A, is coupled to the front housing 4A by a plurality of bolts 4C, and houses the actuator 3 therein. A flat mounting seat surface 7 is formed on the rear cover 4B of the housing 4. From the center of the mounting seat surface 7, it is concentric with the master cylinder 2 and rearward (right side in FIG. 1), that is, the master cylinder. A cylindrical portion 8 protruding in a direction away from 2 is provided. The electric booster 1 is disposed in the engine room in a state where the cylindrical part 8 extends through the dash panel (not shown) that is a partition wall between the engine room and the vehicle compartment of the vehicle and extends into the vehicle interior. The mounting seat surface 7 is brought into contact with the dash panel, and is fixed to the dash panel by a plurality of stud bolts 7A (shown only in FIG. 2) fixed to the mounting seat surface 7.

  The master cylinder 2 includes a cylinder body 2A having a substantially bottomed cylindrical shape, and the front of the cylinder body 2A is inserted by the stud bolt 6A and the nut 6B of the front housing 4A in a state where the opening side of the cylinder body 2A is inserted into the opening of the bottom portion of the front housing 4A. It is coupled to the housing 4A.

  A bottomed cylinder bore 12 is formed in the cylinder body 2A of the master cylinder 2. A substantially cylindrical primary piston 10 whose front end is formed in a cup shape is inserted as a piston driven by the actuator 3 on the opening side of the cylinder bore 12. A cup-shaped secondary piston 11 is inserted on the bottom side of the cylinder bore 12. The rear end portion of the primary piston 10 projects from the opening of the master cylinder 2 into the housing 4 and extends into the cylindrical portion 8 of the rear cover 4B. In the cylinder body 2 </ b> A, a primary chamber 16 is formed between the cylinder bore 12, the primary piston 10 and the secondary piston 11, and a secondary chamber 17 is formed between the bottom of the cylinder bore 12 and the secondary piston 11. . The primary chamber 16 and the secondary chamber 17 are each a two-line hydraulic circuit for supplying hydraulic pressure to the brake caliper of each wheel via a hydraulic port (not shown) formed in the cylinder body 2A. (Not shown).

  In addition, reservoir ports 20 and 21 for connecting the primary chamber 16 and the secondary chamber 17 to the reservoir 5 are formed in the cylinder body 2A. On the inner peripheral surface of the cylinder bore 12 of the cylinder body 2A, annular seal grooves 22a, 22b and 23a, 23b are formed with a predetermined axial interval. Seal members 22A, 22B and 23A, 23B are disposed in the annular seal grooves 22a, 22b and 23a, 23b, respectively. The seal members 22A, 22B and 23A, 23B are connected to the cylinder bore 12 and the primary piston 10 respectively. And the secondary piston 11 are sealed. The two seal members 22A and 22B are arranged with the reservoir port 20 sandwiched along the axial direction. When the primary piston 10 is in the non-braking position shown in FIG. 1, the primary chamber 16 communicates with the reservoir port 20 via a port 24 provided on the side wall of the primary piston 10. When the primary piston 10 moves forward from the non-braking position, the primary chamber 16 is blocked from the reservoir port 20 by the seal member 22A. Further, the two seal members 23A and 23B are arranged with the reservoir port 21 interposed therebetween in the axial direction. When the secondary piston 11 is in the non-braking position shown in FIG. 1, the secondary chamber 17 communicates with the reservoir port 21 via a port 25 provided on the side wall of the secondary piston 11. When the secondary piston 11 moves forward from the non-braking position, the secondary chamber 17 is blocked from the reservoir port 21 by the seal member 23A.

  A spring assembly 26 is interposed between the primary piston 10 and the secondary piston 11 in the primary chamber 16, and a compression coil spring is provided between the bottom of the master cylinder 2 in the secondary chamber 17 and the secondary piston 11. A certain return spring 27 is interposed. The spring assembly 26 is held in a predetermined compression state by a retainer 29 in which a compression coil spring 28 can expand and contract, and can be compressed against the spring force. In the primary piston 10, a cylindrical spacer 51 is interposed between the retainer 29 and the intermediate wall 30 of the primary piston 10.

  The primary piston 10 is formed in a substantially cylindrical shape as a whole, and includes an intermediate wall 30 in the center in the axial direction. A guide bore 31 is formed in the intermediate wall 30 so as to penetrate in the axial direction. A small-diameter front end of a stepped input piston 32 having a step 32A is slidably and liquid-tightly inserted into the guide bore 31. The input piston 32 and the guide bore 31 are sealed with a seal 55.

  The intermediate portion of the primary piston 10 extending into the front housing 4A is inserted into a cylindrical spring receiving member 70 that fits into the opening at the bottom of the front housing 4A, and this spring receiving member 70 extends along the axial direction. It is slidably guided. The spring receiving member 70 is fixed to the front housing 4A and the master cylinder 2 by fitting an outer flange portion 71 formed at one end thereof to the opening at the bottom of the front housing 4A, and is connected to the cylinder bore 12 of the master cylinder 2. doing. The spring receiving member 70 seals between the primary piston 10 by a seal member 72 attached to the inner periphery of the rear end. The opening 12A of the cylinder bore 12 provided with the seal groove 22b and the seal member 22B of the master cylinder 2 is protruded radially inward, and the spring receiving member 70 is provided so that the axial length of the support portion of the primary piston 10 is increased. By increasing the length, the inclination of the primary piston 10 with respect to the cylinder bore 12 is suppressed.

  An input rod 34 is inserted into the cylindrical portion 8 of the rear cover 4B and the rear portion of the primary piston 10. The front end portion of the input rod 34 inserted into the rear portion of the primary piston 10 is connected to the rear end portion of the input piston 32. The connecting portion between the input rod 34 and the primary piston 10 forms a ball joint so that the inclination of the input rod 34 with respect to the primary piston 10 can be allowed to some extent. The rear end side of the input rod 34 extends from the cylindrical portion 8 to the outside, and a brake pedal (not shown) is connected to the rear end portion of the input rod 34 extending to the outside via a clevis 56. Yes. A hook-shaped stopper portion 90 is formed at an intermediate portion inserted into the cylindrical portion 8 of the input rod 34.

  At the rear end of the cylindrical portion 8 of the rear cover 4 </ b> C, a detent 39 is formed that extends radially inward toward the input rod 34 inserted into the cylindrical portion 8. The rotation stopper 39 is inserted into a guide groove 47B formed along the axial direction at a cylindrical rear end portion of a screw shaft 47 of a ball screw mechanism 41 described later. Then, when the stopper portion 90 of the input rod 34 abuts against the detent 39, the retracted position of the input rod 34 is defined.

  An annular spring receiver 35 is attached to the rear end portion of the primary piston 10. The primary piston 10 is biased in the backward direction by a return spring 36 that is a compression coil spring interposed between the rear end portion of the spring receiving member 70 and the spring receiver 35. The input piston 32 is compressed by springs 37 and 38, which are compression coil springs interposed between the intermediate piston 30 between the primary piston 10 and the spring support 35, respectively. And is held elastically in a neutral position where the spring force balances.

  The actuator 3 accommodated in the housing 4 includes an electric motor 40 and a ball screw mechanism 41 that is a rotation-linear motion conversion mechanism that converts the rotation of the electric motor 40 into linear motion and applies thrust to the primary piston 10. ing. The electric motor 40 is a permanent magnet embedded synchronous motor, and is disposed so as to face the stator 42 having a plurality of coils fixed to the rear step portion of the bottom of the front housing 4A, and the inner peripheral surface of the stator 42. And a plurality of permanent magnets 45A inserted in the rotor 45 and arranged along the circumferential direction. The rotor 45 is fixed to the outer peripheral portion of a nut member 46 that is a rotating member of the ball screw mechanism 41. The nut member 46 extends in the axial direction from the vicinity of the bottom of the front housing 4A to the vicinity of the rear cover 4B, and both ends thereof are rotatably supported by the front housing 4A and the rear cover 4B by bearings 43 and 44. The electric motor 40 may be a synchronous motor in which permanent magnets are arranged on the surface or inside of the rotor 45, or another type of motor such as an induction motor.

  The ball screw mechanism 41 is a nut member 46 and a linear motion member that is inserted into the nut member 46 and the cylindrical portion 8 of the housing 4, is movable along the axial direction, and is supported so as not to rotate around the axis. A hollow screw shaft 47. The inner peripheral surface of the nut member 46 and the outer peripheral surface of the screw shaft 47 which are the opposing surfaces form spiral grooves 46A and 47A, respectively. A plurality of balls 48 are loaded together with grease between the spiral grooves 46A and 47A. The screw shaft 47 is engaged with a guide groove 47B formed in the axial direction at a rear end portion protruding rearward from the cylindrical portion 8 with a rotation stop 39 formed on the cylindrical portion 8 of the rear housing 4B. It is supported so as to be movable in the axial direction and not to rotate around the axis. With this configuration, the ball screw mechanism 41 is configured such that the screw shaft 47 moves in the axial direction when the ball 48 rolls along the spiral grooves 46A and 47A as the nut member 46 rotates. . The ball screw mechanism 41 can mutually convert rotation and linear motion between the nut member 46 and the screw shaft 47, that is, the rotation of the nut member 46 is converted into the linear motion of the screw shaft 47 as described above. The linear motion of the screw shaft 47 can be converted into the rotation of the nut member 46. A cylindrical cover member 76 that covers the outer periphery of the screw shaft 47 is attached to the rear end portion of the cylindrical portion 8 of the rear housing 4B.

  In the above example, the rotational motion of the rotor 45 of the electric motor 40 is directly transmitted to the nut member 46 of the ball screw mechanism 41. However, a planetary gear mechanism, between the electric motor 40 and the ball screw mechanism 41, The rotation of the electric motor 40 may be reduced and transmitted to the ball screw mechanism 41 via a known reduction mechanism such as a differential reduction mechanism. In addition, the central axis of the rotor 45 of the electric motor 40 and the ball screw mechanism 41 is coaxial, but this is not limiting, and both the central axis of the electric motor and the central axis of the ball screw mechanism 41 are parallel to each other. In this case, the rotor of the electric motor and the ball screw mechanism are configured to transmit the rotational force by a transmission member such as a belt or a plurality of gears. Further, both may be arranged so that the central axis of the electric motor and the central axis of the ball screw mechanism 41 are perpendicular to each other. In this case, the rotor of the electric motor and the ball screw mechanism are connected by a worm gear or a bevel gear. Configure to communicate.

  The screw shaft 47 of the ball screw mechanism 41 is urged in the backward direction by the spring force of the return spring 49 that is a compression taper coil spring interposed between the outer flange portion 71 of the spring receiving member 70. The screw shaft 47 has its rear end portion in contact with a detent 39 provided on the cylindrical portion 8 of the rear cover 4B, thereby defining a retracted position. The rear end portion of the primary piston 10 is inserted into the screw shaft 47, and the flange-shaped contact formed on the outer peripheral portion of the spring receiver 35 is brought into contact with the annular step portion 50 formed on the inner peripheral portion of the screw shaft 47. The part 80 abuts via a shim 81 to define the retracted position of the primary piston 10 with respect to the screw shaft 47. Thereby, the primary piston 10 is pushed by the stepped portion 50 by the advancement of the screw shaft 47 and moves forward together with the screw shaft 47, and can be moved away from the stepped portion 50 independently. As shown in FIG. 1, the non-braking position of the primary piston 10 is defined by the stepped portion 50 of the screw shaft 47 that is in contact with the detent 39, and the maximum of the primary piston 10 and the spring assembly 26 in the non-braking position. The retracted position of the secondary piston 11, that is, the non-braking position is defined by the length.

  A resolver 60 that is a rotational position sensor that detects the rotational position of the rotor 45 of the electric motor 40 is provided in the housing 4. The resolver 60 includes a resolver rotor 60A fixed to the outer peripheral portion on the rear side of the nut member 46, and a resolver stator 60B attached to the rear cover 4B so as to face the resolver rotor 60A, and the rotation of the rotor 45 is based on these relative displacements. Detect position.

  A movable spring support 83 is provided at the rear end of the screw shaft 47 so as to be movable in the axial direction along the guide groove 47B. The movable spring receiver 83 has a retracted position (see FIG. 1) defined by the cover member 76. A reaction force spring 84, which is a compression coil spring, is interposed between the rotation stopper 39 and the movable spring receiver 83. When the input rod 34 moves forward by a predetermined distance with respect to the cover member 76, that is, the cylindrical portion 8 (housing 4), the clevis 56 comes into contact with the movable spring receiver 83 and the input rod 34 further moves forward. The reaction force spring 84 is compressed, and the spring force is applied to the advance of the input rod 34 as a reaction force.

  The electric booster 1 is provided with a controller C which is a microprocessor-based electronic control device. The controller C includes a stroke sensor (not shown) for detecting the displacement of the brake pedal, that is, the displacement of the input piston 32 and the input rod 34, a current sensor (not shown) for detecting the current supplied to the electric motor 40, Various sensors such as a hydraulic pressure sensor (not shown) for detecting the hydraulic pressure in the primary chamber 16 and the secondary chamber 17 and an in-vehicle controller (not shown) are connected. The electric booster 1 operates by controlling the rotation of the electric motor 40 by these controllers based on the detection signals from the various sensors described above.

Next, the relationship between the operation direction of the ball screw mechanism 41 and the winding direction of the return spring 49 will be described.
In the ball screw mechanism 41, spiral grooves 46A and 47B are formed so that the screw shaft 47 moves forward when the nut member 46 rotates to the left (left when viewed from the rear of the electric booster, hereinafter the same). . The winding direction of the return spring 49, which is a coil spring, is left-handed. In general, when the coil spring expands and contracts, the end portion slightly rotates around the axis, and the rotation direction depends on the winding direction of the coil spring. When the left-handed return spring 49 is compressed by the advancement of the screw shaft 47 caused by the left rotation of the nut member 46 of the ball screw mechanism 41 and then compressed by the retraction of the screw shaft 47 caused by the right rotation of the nut member 46, The end abutting against the shaft 47 rotates to the left and tries to rotate the screw shaft 47 to the left.

The operation of the present embodiment configured as described above will be described.
When the input piston 32 is moved forward via the input rod 34 by operating the brake pedal, the displacement of the input piston 32 is detected by the stroke sensor, and the operation of the electric motor 40 is controlled by the controller based on the displacement of the input piston 32. The primary piston 10 is pressed by the step portion 50 of the screw shaft 47 of the ball screw mechanism 41 via the shim 81 and the spring receiver 35, and the primary piston 10 is advanced to follow the displacement of the input piston 32. Thereby, a hydraulic pressure is generated in the primary chamber 16, and this hydraulic pressure is transmitted to the secondary chamber 17 via the secondary piston 11. In this way, the brake hydraulic pressure generated in the master cylinder 2 is supplied to the brake caliper of each wheel via the hydraulic pressure port to generate a braking force. When the operation of the brake pedal is released, the input piston 32, the primary piston 10 and the secondary piston 11 are retracted, the brake fluid pressure in the master cylinder 2 is reduced, and the braking force is released.

  When the hydraulic pressure is generated, a part of the hydraulic pressure in the primary chamber 16 is received by the input piston 32, and the reaction force is fed back to the brake pedal via the input rod 34. Thereby, a desired braking force can be generated with a predetermined boost ratio. Then, by adjusting the relative position between the input piston 32 and the primary piston 10 that follows the input piston 32, the spring force of the springs 37 and 38 is applied to the input piston 32, and the reaction force against the input rod 34 is adjusted. The boost ratio can be adjusted. At this time, the boost ratio is increased by adjusting the position of the primary piston 10 forward with respect to the input piston 32, and the boost ratio is decreased by adjusting backward. Then, the controller controls the rotation of the electric motor 40 according to the state of the vehicle based on the detection signals of various sensors, so that the boost control, the brake assist control, the inter-vehicle stability control, the inter-vehicle control, the regenerative cooperative control. Brake control such as can be executed.

  When the output of the electric motor 40 reaches the maximum and reaches a full load state where the forward movement of the primary piston 10 stops, the clevis 56 comes into contact with the movable spring receiver 83. When the brake pedal is further depressed from this full load state, the reaction force spring 84 is compressed, and the spring force is applied to the brake pedal as a reaction force. As a result, a decrease in the pedal reaction force due to the stop of the primary piston 10 can be compensated, and the uncomfortable feeling to the driver is reduced.

  When the operation of the brake pedal is released and the screw shaft 47 of the ball screw mechanism 41 is retracted, the left-handed return spring 49 is rotated slightly to the left with the end abutting against the screw shaft 47 as the screw spring 47 extends. Try to rotate the shaft 47 to the left. As a result, when no power is applied to the nut member 46 of the ball screw mechanism 41 when the driving force of the electric motor 40 is not applied, the screw shaft 47 is rotated to the left by the torque from the return spring 49 as shown in FIG. And it stops in the state which contact | abutted to one side of the detent 39. Thereafter, when the electric motor 40 is energized and the nut member 46 of the ball screw mechanism 41 is driven to rotate counterclockwise, the screw shaft 47 attempts to rotate counterclockwise as the nut member 46 rotates. In addition, since it is in contact with one side of the rotation stopper 39 in the left rotation direction (see FIG. 4A), a hitting sound due to contact with the rotation stopper 39 is not generated. Then, by the left rotation of the nut member 46, the screw shaft 47 advances while the return spring 49 compresses to propel the primary piston 10 and generate the brake fluid pressure in the master cylinder 2. In this way, it is possible to prevent the occurrence of a hitting sound when starting braking.

  Here, assuming that the return spring 49 is right-handed, when the operation of the brake pedal is released, the torque from the return spring 49 tries to rotate the screw shaft 47 to the right. As a result, when no power is applied to the nut member 46 of the ball screw mechanism 41 when the driving force of the electric motor 40 does not act, the screw shaft 47 rotates to the right by the torque from the return spring 49 as shown in FIG. Then, it stops in a state where it abuts against the other side of the rotation stopper 39, and a gap C is formed between one side of the rotation stopper 39. Thereafter, when the electric motor 40 is energized and the nut member 46 of the ball screw mechanism 41 is driven and rotated counterclockwise, the screw shaft 47 attempts to rotate counterclockwise as the nut member 46 rotates. When the torque that acts on the screw shaft 47 from the nut member 46 exceeds the torque that acts on the screw shaft 47 from the return spring 49, the screw shaft 47 rotates to the left by the gap C, and the other of the detent 39 Touching the side (see FIG. 4A), a hitting sound is generated.

  The relationship between the stroke of the screw shaft 47 of the ball screw mechanism 41 at the start of braking of the electric booster 1 and the torque acting on the screw shaft 47 will be described with reference to FIG. In FIG. 5, the counterclockwise torque is positive, and in the electric booster 1 (return spring 49 is left-handed) of the present embodiment, the torque acting on the screw shaft 47 from the return spring 49 is indicated by a solid line (1). The sum of the torque applied to the screw shaft 47 from the nut member 46 is indicated by a solid line (2). When the return spring 49 is a right-handed winding, the torque applied to the screw shaft 47 from the return spring 49 is indicated by a solid line ( 3) The sum obtained by adding the torque acting on the screw shaft from the nut member 46 to this torque is shown by a solid line (4).

  With reference to the solid lines (1) and (2), in the electric booster 1 of this embodiment, when the stroke is 0, only the counterclockwise (positive) torque from the return spring 49 is applied to the screw shaft 47. Works. In this state, the screw shaft 47 rotates counterclockwise by the torque from the return spring 49 and the guide groove 47B of the screw shaft 47 is in contact with one side of the detent 39 as shown in FIG. . When the stroke increases, the rotation of the nut member 46 driven by the electric motor 40 increases the counterclockwise (positive) torque acting on the screw shaft 47 from the nut member 46, and the return spring 49 is compressed by the compression of the return spring 49. The counterclockwise (positive) torque acting on the screw shaft 47 also increases. In the stroke S1, hydraulic pressure is generated in the master cylinder 2 by the advance of the primary piston 10, and the torque from the nut member 46 is rapidly increased by the reaction force. In this case, the torque acting on the screw shaft 47 is always counterclockwise (positive), and the guide groove 47B of the screw shaft 47 is always in contact with one side of the rotation stopper 39. No hitting sound is generated by contact with the stop 39.

  On the other hand, when the return spring 49 is right-handed, referring to the solid lines (3) and (4), when the stroke is 0, only the right-turn (negative) torque from the return spring 49 is applied to the screw shaft 47. Works. In this state, the screw shaft 47 is rotated to the right by the torque from the return spring 49 and the guide groove 47B is in contact with the other side of the detent 39 as shown in FIG. When the stroke increases, the rotation of the nut member 46 driven by the electric motor 40 increases the counterclockwise (positive) torque acting on the screw shaft 47 from the nut member 46, and the return spring 49 is compressed by the compression of the return spring 49. As a result, the clockwise (negative) torque acting on the screw shaft also increases. In the stroke S1, hydraulic pressure is generated in the master cylinder 2 by the advance of the primary piston 10, and the torque from the nut member 46 is rapidly increased by the reaction force. At the stroke S2, the counterclockwise (positive) torque from the nut member 46 exceeds the counterclockwise (negative) torque from the return spring 49, and the screw shaft 47 starts to rotate left together with the nut member 46. At the stroke S3, The guide groove 47B of the screw shaft 47 abuts against one side of the detent 39 to generate a hitting sound.

  In the above embodiment, when the rotation direction of the nut member 46 when the screw shaft 47 of the ball screw mechanism 41 advances is clockwise, the same effect as above can be obtained by setting the winding direction of the return spring 49 to the right. Can be obtained. The winding direction of the return spring 49 may be matched with the rotational direction of the screw shaft 47 when moving forward.

  DESCRIPTION OF SYMBOLS 1 ... Electric booster, 2 ... Master cylinder, 10 ... Primary piston (piston), 39 ... Anti-rotation, 40 ... Electric motor, 39 ... Anti-rotation, 41 ... Ball screw mechanism (rotation-linear motion conversion mechanism), 46 ... Nut member (opening member), 47 ... screw shaft (linear motion member), 49 ... return spring (return spring)

Claims (1)

An electric motor provided in the housing ;
A rotation-linear motion conversion mechanism that converts the rotational motion of the rotating member driven by the electric motor into the linear motion of the linear motion member;
A detent formed on the housing to engage the concave and convex portions with the linear motion member to restrict rotation of the linear motion member about its axis;
A return spring that is a compression coil spring that biases the linear motion member in the backward direction,
In the electric booster that propels the piston by the linear motion member and generates the brake fluid pressure in the master cylinder,
Said return spring, the winding direction of its match the rotational direction of said rotary member during forward movement of the front Symbol translation member, the straight to the direction of rotation relative to said detent when said linear member is retracted An electric booster characterized by contacting a moving member .

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