CN111094091B - Electric booster - Google Patents

Abstract

The invention provides an electric booster which is easy to manufacture and has improved carrying performance on a vehicle. The electric booster (1) is provided with: an input pinion (55) that rotates in response to the movement of the input lever (50) and the input rack (51); an electric motor (67) driven in accordance with the rotation of the input pinion (55); an output pinion (83) which receives the rotation of the pinion (55) and the rotation from the electric motor (67) and rotates the output pinion (83) by transmitting the rotation to one receiving section (91) arranged along the rotation direction of the electric motor (67) or the rotation direction of the input pinion (55); an output rod (108) and an output rack (105), and the rotation of the output pinion (83) is transmitted to the output rod (108) and the output rack (105) to move the primary piston (7) of the master cylinder (2). Thus, the electric booster (1) is easy to manufacture and has improved mountability on a vehicle.

Description

Electric booster

Technical Field

The present invention relates to an electric booster which is incorporated in a brake device of a vehicle such as an automobile and which generates a brake hydraulic pressure in a master cylinder by an electric motor.

Background

As a conventional electric booster, for example, an electric booster described in patent document 1 includes: an input member that moves in accordance with an operation of a brake pedal; an input piston connected to the input member, a tip end portion of the input piston being disposed in a brake fluid chamber of the master pump; and a ball screw mechanism to which rotation from the electric motor is transmitted to press a piston of the master pump. In this electric booster, the axis of the input member and the axis of the ball screw mechanism are disposed on the same axis, and the axial direction of the input member and the axial direction of the output shaft of the electric motor are disposed in parallel.

Further, the brake control device described in patent document 2 includes: an input member connected to a brake pedal; an output member connected to the input member and connected to the master pump; a worm gear mechanism and a ball screw mechanism, which transmit the driving force of the electric motor to the output member. In this brake control device, the axis of the input member and the axis of the output member are disposed on the same axis, and the axial direction of the output shaft of the electric motor and the axial direction of the output member are disposed so as to be orthogonal to each other. In this brake control device, the electric motor is disposed at a position shifted by 90 ° in the circumferential direction of the master cylinder with respect to the position of the reservoir tank.

However, in the electric booster (brake control device) of the above-described patent documents 1 and 2, the electric booster is large in the axial direction and the radial direction of the master pump, and the mountability thereof on a vehicle may be lowered. In the above-described electric booster, in order to provide a through hole for inserting the input member in the screw shaft in the ball screw mechanism, in more detail, the processing cost of the through hole increases, and the outer diameter of the screw shaft needs to be increased, which makes it difficult to avoid an increase in size.

In the electric booster described in patent document 3, a brake pedal is coupled to a sun gear of a planetary gear mechanism, and an electric motor is coupled to a ring gear of the planetary gear mechanism. The output rod is connected to the carrier and the piston of the master pump. When the brake pedal is operated to rotate the sun gear, the pinion rotates and revolves, the carrier rotates to advance the output rod, the piston is pressed to generate hydraulic pressure in the master pump, and the electric motor is controlled according to the rotation of the sun gear to rotate the ring gear so as to follow the sun gear, thereby applying a rotational servo force of the electric motor to the rotation of the carrier.

However, in the electric booster of patent document 3, when a failure occurs in the electric motor, the controller, or the like, a stroke required for the output rod cannot be ensured, and a required brake fluid pressure may not be ensured.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-124344

Patent document 2: japanese patent laid-open publication No. 2016-

Patent document 3: japanese patent laid-open publication No. 2011-93472

Disclosure of Invention

Problems to be solved by the invention

As described above, in the electric servo units of patent documents 1 to 3, there is a possibility that problems may occur in terms of mountability on a vehicle and manufacturing.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an electric booster which is easy to manufacture and has improved mountability on a vehicle.

Means for solving the problems

In order to solve the above problem, a first aspect of the present invention provides an electric booster including: an input member that rotates in response to an operation of the input shaft member; an electric motor that is driven in accordance with rotation of the input member; an output member that rotates when the rotation of the input member and the rotation from the electric motor are transmitted to one receiving portion disposed opposite to the rotation direction of the electric motor or the rotation direction of the input member; an output shaft member, rotation of which is transmitted to the output shaft member to move a piston of a master cylinder.

In addition, a second aspect of the present invention provides an electric power assist device including: an input member that rotates in response to an operation of the input shaft member; an electric motor that is driven in accordance with rotation of the input member; an auxiliary member to which rotation of the electric motor is transmitted; an output member that rotates in a rotational direction of the auxiliary member or a rotational direction of the input member by receiving rotation of the input member and rotation of the auxiliary member in a plane; an output shaft member to which rotation of the output shaft member is transmitted to move a piston of a master cylinder;

when the output member is rotated only by the rotation of the input member, the auxiliary member is separated from the input member and the output member in the rotational direction.

Further, a third aspect of the present invention provides an electric power assist device, comprising: an input member that rotates in accordance with a linear motion of the input shaft member; an electric motor that is driven in accordance with a linear motion of the input shaft member; an auxiliary member that is coupled to a rotating shaft of the electric motor and rotates in the same direction as the electric motor and the input member by driving the electric motor; an output member to which the rotation of the input member and the rotation of the auxiliary member are transmitted together, and which rotates in the same direction as the input member and the auxiliary member; and an output shaft member that moves linearly in accordance with rotation of the output member and moves a piston of the master cylinder.

Effects of the invention

The electric booster of the present invention can be easily manufactured and can be mounted on a vehicle with improved mountability.

Drawings

Fig. 1 is a perspective view of an electric booster according to the present embodiment.

Fig. 2 is a perspective view of the electric booster of the present embodiment.

Fig. 3 is a schematic cross-sectional view of the electric power assist device of the present embodiment, showing only a part of the gear housing.

Fig. 4 is an exploded perspective view of the electric booster of the present embodiment.

Fig. 5 is a sectional view taken along line B-B of fig. 3.

Fig. 6 is a sectional view taken along line a-a of fig. 3.

Detailed Description

Next, the electric booster 1 according to the present embodiment will be described in detail with reference to fig. 1 to 6. As shown in fig. 1, an electric booster 1 according to the present embodiment has a structure in which a tandem type master cylinder 2 is coupled. In the following description, the master cylinder 2 side is referred to as the front side, and the brake pedal 40 side is referred to as the rear side. In addition to fig. 3, the brake pedal 40 is not shown.

First, the master cylinder 2 will be described in detail with reference to fig. 3.

The rear portion of the master pump 2 is inserted through a third opening 46 provided in the lower portion of the gear housing 41 and is coupled to the front wall portion of the gear housing 41 of the electric booster 1. A reservoir tank 3 for supplying brake fluid to the master cylinder 2 is mounted on the upper portion of the master cylinder 2. In the master cylinder 2, a bottomed pump chamber 4 is formed. A primary piston 7 is disposed on the opening portion side of the pump chamber 4. The front part of the primary piston 7 is disposed in the pump chamber 4 of the master pump 2. The rear portion of the primary piston 7 extends from the pump chamber 4 into the gear housing 41 via the third opening portion 46 of the gear housing 41.

The front and rear portions of the primary piston 7 are formed into cup shapes, and the entire piston is formed into an H-shaped cross section. A spherical recess 11 is formed in the rear surface of an intermediate wall 10 provided substantially at the center in the axial direction of the primary piston 7. A spherical surface 110 of an output rod 108 of the electric booster 1 described later is abutted on the spherical recess 11. A cup-shaped secondary piston 8 is arranged on the bottom side of the pump chamber 4. Further, in the pump chamber 4 of the master pump 2, a primary chamber 13 is formed between the primary piston 7 and the secondary piston 8, and a secondary chamber 14 is formed between the bottom of the pump chamber 4 and the secondary piston 8.

The primary chamber 13 and the secondary chamber 14 of the master pump 2 communicate with a hydraulic control unit (not shown) from two hydraulic ports 16 and 16 (see fig. 1) of the master pump 2, respectively, via two master pump assembly (アクチュエーション, actuation) lines (not shown). The hydraulic control unit is connected to the wheel cylinders (not shown) of the respective wheels via four-system base assembly (ファンデーション, foundation) lines (not shown). The brake fluid pressure generated by the master pump 2 or the fluid pressure control unit is supplied to the slave pumps of the respective wheels to generate braking force.

The master cylinder 2 is provided with tank ports 18 and 19 for connecting the primary chamber 13 and the secondary chamber 14 to the tank 3, respectively. On the inner circumferential surface of the pump chamber 4, annular piston seals 20, 21, 22, and 23 that abut against the primary piston 7 and the secondary piston 8 are arranged at predetermined intervals in the axial direction so as to divide the interior of the pump chamber 4 into the primary chamber 13 and the secondary chamber 14. The piston seals 20, 21 are disposed so as to sandwich a tank port 18 (rear side) in the axial direction. When the primary piston 7 is in the non-braking position shown in fig. 3, the primary chamber 13 communicates with the reservoir port 18 via a piston port 25 provided in the side wall of the primary piston 7. When the primary piston 7 advances from the non-braking position and the piston port 25 reaches a piston seal 21 (front side), the primary chamber 13 is blocked from the tank port 18 by the piston seal 21, and hydraulic pressure is generated.

Similarly, the remaining two piston seals 22 and 23 are disposed so as to sandwich the other reservoir port 19 (front side) in the axial direction. When the secondary piston 8 is in the non-braking position shown in figure 3, the secondary chamber 14 communicates with the reservoir port 19 via a piston port 26 provided in a side wall of the secondary piston 8. When the secondary piston 8 advances from the non-braking position and the piston port 26 reaches a piston seal 23 (front side), the secondary chamber 14 is blocked from the tank port 19 by the piston seal 23 to generate hydraulic pressure.

A compression spring 28 is interposed between the primary piston 7 and the secondary piston 8. The primary piston 7 and the secondary piston 8 are urged in a direction to be separated from each other by a compression spring 28. Inside the compression spring 28, a telescopic member 29 is disposed to be telescopic within a certain range. The telescopic member 29 is composed of a holder guide 30 that abuts against the intermediate wall 10 of the primary piston 7, and a holder rod 31 whose tip abuts against the secondary piston 8 and is movable in the axial direction in the holder guide 30.

A compression spring 33 is sandwiched between the bottom of the pump chamber 4 and the secondary piston 8. The compression spring 33 urges the bottom of the pump chamber 4 and the secondary piston 8 in a direction to separate from each other. Inside the compression spring 33, a telescopic member 34 is disposed to be telescopic within a certain range. The expansion/contraction member 34 includes a holder guide 35 having a front end abutting on the bottom of the pump chamber 4, and a holder rod 36 having a rear end abutting on the secondary piston 8 and being movable in the axial direction in the holder guide 35.

Next, the electric booster 1 of the present embodiment to which the above-described master pump 2 is connected will be described in detail with reference to fig. 1 to 6.

As shown in fig. 3 and 4, the electric booster 1 of the present embodiment includes: an input rod 50 that moves in the axial direction in accordance with an operation of the brake pedal 40, an input rack 51 coupled to the input rod 50, an input pinion 55 that rotates in accordance with a linear motion of the input rack 51, an electric motor 67 that is driven in accordance with the linear motion of the input rod 50 and the input rack 51, an output pinion 83 that rotates in the same direction to which the rotation of the input pinion 55 and the rotation from the electric motor 67 are transmitted, an output rack 105 that moves in a linear motion in accordance with the rotation of the output pinion 83, an output rod 108 that is coupled to the output rack 105 and presses the primary piston 7 of the master pump 2, and a gear housing 41 that houses the input rack 51 including the input rod 50, the input pinion 55, the output pinion 83, the output rack 105 including the output rod 108, and the like.

The gear housing 41 accommodates components such as the input pinion 55, the input rack 51, the output pinion 83, and the output rack 105. A cylindrical portion 42 is integrally provided on the rear surface of the gear housing 41 so as to project rearward from the upper portion of the rear surface. The cylindrical portion 42 communicates with the inside of the gear housing 41. A first opening 43 having a substantially circular shape penetrating in the vertical direction is formed substantially over the entire upper wall portion of the gear housing 41. The input pinion 55 and the output pinion 83 including the rotation shaft 69 of the electric motor 67 are accommodated in the gear housing 41 through the first opening 43. A motor case 71 that houses the electric motor 67 is connected to the upper wall surface of the gear case 41 around the first opening 43. A second opening 44 (see also fig. 5) having a substantially circular shape and penetrating in the front-rear direction is formed in the front wall portion of the gear housing 41 at an upper portion of the front wall portion. The input rod 50 and the input rack 51 are accommodated in the gear housing 41 through the second opening 44. The second opening 44 is closed by a cover 45.

A third opening 46 penetrating in the front-rear direction is formed in a lower portion of the front wall portion of the gear housing 41. The output rod 108 and the output rack 105 are accommodated in the gear housing 41 through the third opening 46. Further, the rear part of the primary piston 7 of the master cylinder 2 is disposed in the gear housing 41 through the third opening 46, and the rear part of the master cylinder 2 is inserted into the third opening 46 and fixed by a bolt. A support rod 48 for supporting an output pinion portion 85 of an output pinion 83, which will be described later, via a needle bearing 73C is provided in the gear housing 41 so as to protrude upward from the bottom surface thereof.

Referring also to fig. 1 and 2, the mounting plate 112 is fixed to the rear surface of the gear housing 41 by a plurality of mounting bolts 114 (three in the present embodiment). The mounting plate 112 is formed in a substantially rectangular shape. A substantially circular opening 113 penetrates a substantially central portion of the attachment plate 112. The attachment plate 112 is fixed to the gear housing 41 in a state where the cylindrical portion 42 of the gear housing 41 is inserted through the opening 113. The plurality of stud bolts 115 are inserted through and attached to four corners of the mounting plate 112. The electric booster 1 is configured such that the input rod 50 extending from the cylindrical portion 42 of the gear housing 41 is disposed in an engine compartment of the vehicle in a state of protruding into the vehicle compartment from an instrument panel (not shown) that is a partition wall between the engine compartment and the vehicle compartment, and is fixed to the instrument panel using a plurality of stud bolts 115.

As shown in fig. 3 and 4, the input rod 50 extends in the same direction as the axial direction of the master pump 2. The input rod 50 is a shaft different from the master cylinder 2, and is disposed above the master cylinder 2. The input rod 50 is inserted into the cylindrical portion 42 of the gear housing 41. The input rod 50 is supported in the gear housing 41 so as to be movable in the axial direction. An ear mount 60 is connected to a rear end portion of the input rod 50. The input rod 50 is coupled to the brake pedal 40 via an ear mount 60. Thus, the input rod 50 is linearly moved in the axial direction by operating the brake pedal 40. A return compression spring (not shown) for biasing the input lever 50 to an initial position is coupled to the input lever 50. The tip end portion of the input rod 50 is disposed in the gear housing 41. An input rack 51 is integrally connected to a distal end portion of the input rod 50.

The input rack 51 is housed in the gear housing 41 through the second opening 44 of the gear housing 41 in a state where the front end portion of the input rod 50 is integrally connected to the rear end portion of the input rack 51. The input rack 51 is supported in the gear housing 41 so as to be movable in the axial direction of the input rod 50. The input rack 51 is formed in a block shape elongated in the axial direction of the input rod 50. The input rack 51 has one surface on the input pinion 55 side formed as a vertical surface, and the other surface on the opposite side to the surface formed as a convex curved surface protruding outward. Referring also to fig. 5, a rack gear portion 52, in which an input pinion 55 is engaged with one surface of the input rack 51, is formed along the axial direction of the input rod 50. The input lever 50 including the input rack 51 corresponds to an input shaft member. A stroke sensor 54 is disposed so as to face the other surface of the input rack 51. The travel distance of the input rod 50 and the input rack 51 is measured by the stroke sensor 54. The stroke sensor 54 is mounted on a wall portion of the gear housing 41.

The input pinion 55 meshes with the rack gear portion 52 of the input rack 51, and rotates in accordance with the linear motion of the input rod 50 and the input rack 51. The input pinion 55 corresponds to an input member. The input pinion 55 is accommodated in the gear housing 41 through the first opening 43 of the gear housing 41. The input pinion 55 is rotatably supported in the gear housing 41. The input pinion 55 is formed in a cylindrical shape. The axial direction of the input pinion 55 is orthogonal to the axial direction of the input rod 50. The input pinion 55 includes an input pinion portion 57 and an input coupling portion 58 integrally formed downward from the input pinion portion 57. The input pinion portion 57 meshes with the rack gear portion 52 of the input rack 51. An input flange 62 is integrally connected to the outer peripheral surface of the input coupling portion 58 so as not to rotate relative thereto.

The input flange 62 includes: an input-side flange portion 64 formed in an annular shape having a diameter larger than that of the input pinion portion 57 of the input pinion 55, and an input-side pressing portion 65 provided at a lower end of the input-side flange portion 64 so as to be perpendicular downward from a part of the input-side flange portion 64 in the circumferential direction. The input flange 62 is connected to the input pinion 55 so as to be relatively non-rotatable, such that an inner peripheral surface of the input side flange portion 64 is spline-connected to an outer peripheral surface of the input connection portion 58 of the input pinion 55. The outer diameter of the input-side flange portion 64 substantially matches the inner diameter of an outer cylindrical portion 88 of an output rotating portion 84 of an output pinion 83 described later.

Referring also to fig. 6, the input side pressing portion 65 is formed in an arc shape having a predetermined thickness. The outer peripheral surface of the input side pressing portion 65 is formed in an arc shape continuous from the outer peripheral surface of the input side flange portion 64, and is formed so as to abut against an inner peripheral surface of an outer cylindrical portion 88 of an output rotating portion 84 of an output pinion 83 described later. The input side pressing portion 65 is formed to have a circumferential length smaller than a circumferential distance between a receiving portion 91 of the output rotating portion 84 of the output pinion 83 and a restricting projection 92, which will be described later. The thickness of the input side pressing portion 65 is formed to be substantially the same as the projection amount of a regulating projection 92 of the output rotating portion 84 of the output pinion 83 described later. Of the circumferential end surfaces of the input side pressing portion 65, an end surface on the receiving portion 91 side of the output rotation portion 84 of the output pinion 83 described later functions as an input surface 66.

The electric motor 67 is driven in accordance with the linear motion of the input rod 50 and the input rack 51. The electric motor 67 is disposed above the gear housing 41 and in parallel with the reservoir tank 3 in the axial direction of the master pump 2. In other words, the electric motor 67 is located behind the reservoir tank 3. The electric motor 67 is housed in a cylindrical motor case 71 having a top surface portion. The lower end surface of the motor case 71 is coupled to the upper end surface around the first opening 43 of the gear case 41. A so-called coaxial speed reducer 70, which is a drum speed reducer, is coupled to an output shaft 68 of the electric motor 67. The rotating shaft 69 extends from the coaxial speed reducer 70. The rotation shaft 69 is disposed in the gear housing 41 through the first opening 43 of the gear housing 41. The axial direction of the rotary shaft 69 is orthogonal to the axial directions of the master pump 2 and the input rod 50. The rotary shaft 69 is relatively rotatably inserted through the input pinion 55 in the gear housing 41 via a needle bearing 73A. An auxiliary flange 75 is connected to the outer peripheral surface of the rotary shaft 69 at a position below the input pinion 55 so as not to be relatively rotatable. The distal end of the rotating shaft 69 is supported via a needle bearing 73B in a relatively rotatable manner inside an inner cylindrical portion 87 of an output rotating portion 84 of an output pinion 83 described later.

The auxiliary flange 75 corresponds to an auxiliary member. The auxiliary flange 75 includes: an auxiliary side flange portion 78 formed in an annular shape having a smaller diameter than the input side flange portion 64 of the input flange 62, and an auxiliary side pressing portion 79 provided vertically downward from a part of a circumferential direction of a lower end of the auxiliary side flange portion 78. The auxiliary flange 75 is connected to the rotary shaft 69 so as not to be relatively rotatable, such that an inner peripheral surface of the auxiliary side flange 78 is spline-coupled to, for example, an outer peripheral surface of the lower portion of the input pinion 55 via the rotary shaft 69. Referring also to fig. 6, the auxiliary-side pressing portion 79 is formed in an arc shape having a predetermined thickness.

The outer peripheral surface of the auxiliary-side pressing portion 79 is formed in an arc shape continuous from the outer peripheral surface of the auxiliary-side flange portion 78, and is formed so as to abut against the inner peripheral surface of the input-side pressing portion 65 of the input flange 62. The inner circumferential surface of the auxiliary-side pressing portion 79 is formed in an arc shape that abuts against the outer circumferential surface of an inner cylindrical portion 87 of an output rotating portion 84 of an output pinion 83, which will be described later. Both circumferential end surfaces of the auxiliary side pressing portion 79 are formed to have a circumferential length that matches both circumferential end surfaces of the input side pressing portion 65 of the input flange 62. The thickness of the auxiliary side pressing portion 79 is formed to be able to pass between a regulating protrusion 92 of an output rotating portion 84 of an output pinion 83 described later and the outer peripheral surface of the inner cylindrical portion 87. Of the circumferential end surfaces of the auxiliary-side pressing portion 79, an end surface on the receiving portion 91 side of the output rotating portion 84 of the output pinion 83, which will be described later, functions as an auxiliary surface 81. The area of the auxiliary surface 81 of the auxiliary side pressing portion 79 of the auxiliary flange 75 is set larger than the area of the input surface 66 of the input side pressing portion 65 of the input flange 62.

An output pinion 83 is housed in the gear housing 41, and rotation from the input pinion 55 and rotation from the electric motor 67 are transmitted to the output pinion 83, so that the output pinion 83 rotates. The output pinion 83 corresponds to an output member. The output pinion 83 is disposed in the gear housing 41 through the second opening 44 of the gear housing 41. The output pinion 83 is rotatably supported in the gear housing 41. The output pinion 83 includes: a double-cylindrical output rotating portion 84 having a bottom and rotatably supported by the gear housing 41 via a ball bearing 86, and a cylindrical output pinion portion 85 integrally connected concentrically to the bottom surface of the output rotating portion 84.

The output rotating portion 84 is formed to have a larger diameter than the output pinion portion 85. Referring also to fig. 6, the output rotation portion 84 includes: an inner cylindrical portion 87, an outer cylindrical portion 88 concentrically arranged with an interval from the outside of the inner cylindrical portion 87, and a disc-shaped bottom portion 89 closing the lower end openings of the inner cylindrical portion 87 and the outer cylindrical portion 88. An annular space 90 is formed between the inner cylindrical portion 87 and the outer cylindrical portion 88. A receiving portion 91 that divides the annular space 90 into two chambers is provided between the inner cylindrical portion 87 and the outer cylindrical portion 88. The restricting projection 92 is formed at a position separated from the receiving portion 91 by a predetermined range in the clockwise direction in fig. 6. The restricting projection 92 projects from the inner wall surface of the outer cylindrical portion 88 toward the annular space 90. In the receiving portion 91, a surface on the restricting projection 92 side functions as a receiving surface 93.

In the output rotating portion 84, a gap is provided between the distal end portion of the regulating protrusion 92 in the radial direction and the outer peripheral surface of the inner cylindrical portion 87 to such an extent that the auxiliary side pressing portion 79 of the auxiliary flange 75 can pass therethrough. Between the receiving portion 91 and the regulating protrusion portion 92 of the output rotating portion 84 of the output pinion 83, the input side pressing portion 65 of the input flange 62 and the auxiliary side pressing portion 79 of the auxiliary flange 75 are arranged in radial contact. The input side pressing portion 65 of the input flange 62 is disposed on the outer cylindrical portion 88 side of the output rotating portion 84, and the auxiliary side pressing portion 79 of the auxiliary flange 75 is disposed on the inner cylindrical portion 87 side of the output rotating portion 84. A reaction plate 98 is disposed between the input side pressing portion 65 and the auxiliary side pressing portion 79 and the receiving portion 91 of the output rotating portion 84. Specifically, the reaction plate 98 is disposed so as to abut on substantially the entire area of the receiving surface 93 of the receiving portion 91 of the output rotating portion 84.

The input surface 66 of the input side pressing portion 65 of the input flange 62 and the auxiliary surface 81 of the auxiliary side pressing portion 79 of the auxiliary flange 75 are respectively abutted on substantially the entire surface of the reaction plate 98 on the side of the restriction protrusion 92. The reaction plate 98 is made of an elastic body such as rubber. The reaction plate 98 is formed in a substantially rectangular plate shape. The reaction plate 98 is formed such that the thickness thereof gradually increases from the inner cylindrical portion 87 toward the outer cylindrical portion 88. The area of the auxiliary surface 81 of the auxiliary side pressing portion 79 of the auxiliary flange 75 in contact with the reaction plate 98 is larger than the area of the input surface 66 of the input side pressing portion 65 of the input flange 62 in contact with the reaction plate 98.

In the output rotating portion 84 of the output pinion 83, the circumferential distance between the receiving portion 91 and the regulating projection 92 is configured to be slightly larger than the length obtained by adding the thickness of the portion of the reaction plate 98 that abuts against the input side pressing portion 65 to the circumferential length of the input side pressing portion 65 of the input pinion 55. When the input surface 66 of the input side pressing portion 65 of the input pinion 55 is disposed so as to abut against the reaction plate 98, a clearance S is provided between the restricting projection 92 and the circumferential end surface on the side opposite to the receiving surface 93 of the input side pressing portion 65. The input pinion 55 and the output pinion 83 are allowed to rotate relative to each other by an amount equivalent to the clearance S. In other words, relative rotation beyond the above-described clearance S is restricted in terms of the input pinion 55 and the output pinion 83. Rotation from the electric motor 67 (output shaft 68) is transmitted to the rotating shaft 69 via the coaxial speed reducer 70, and the distal end of the rotating shaft 69 is relatively rotatably supported via a needle bearing 73B in an inner cylindrical portion 87 of an output rotating portion 84 of the output pinion 83.

As shown in fig. 3, a substantially circular support recess 100 is recessed in the bottom surface of the disc-shaped bottom portion 89 of the output rotation portion 84. The upper end of the output pinion gear 85 is housed in the support recess 100, and the output pinion gear 85 and the output rotating portion 84 are integrally connected concentrically. The output pinion portion 85 is formed in a cylindrical shape. The output pinion portion 85 of the output pinion 83 has substantially the same outer diameter as the input pinion portion 57 of the input pinion 55. The axial lengths of the output pinion gear portion 85 of the output pinion 83 and the input pinion gear portion 57 of the input pinion 55 are also substantially the same. A support rod 48 projecting upward from the bottom surface in the gear housing 41 via a needle bearing 73C is inserted into the lower end of the output pinion portion 85. Thereby, the output pinion 83 is rotatably supported by the gear housing 41. The rotary shaft 69, the input pinion 55, and the output pinion 83 are concentrically disposed in the gear housing 41, and the rotation from the electric motor 67 (output shaft 68) is transmitted to the rotary shaft 69.

The output rack 105 meshes with the output pinion portion 85 of the output pinion 83. The output rack 105 is accommodated in the gear housing 41 through the third opening 46 of the gear housing 41. The output rack 105 is supported in the gear housing 41 so as to be movable in the axial direction of the output rod 108. Like the input rack 50, the output rack 105 is formed in a rectangular block shape that is long in the axial direction of an output rod 108 described later. The output rack 105 has one surface on the output pinion 83 side formed as a vertical surface, and the other surface on the opposite side to the surface formed as a convex curved surface protruding outward. A rack gear portion 106, in which the output pinion 83 is engaged with one surface of the output rack 105, is formed along the axial direction of the output rod 108. The output rack 105 is disposed at a lower position in the gear housing 41 with a space from the input rack 51. The vertical lengths of the output rack 105 and the input rack 51 are substantially the same. The lengths of the output rack 105 and the input rack 51 in the front-rear direction are also substantially the same.

The output rod 108 is integrally connected to the front end of the output rack 105. The output rod 108 is accommodated in the gear housing 41 through the third opening 46 of the gear housing 41 in a state where the rear end portion thereof is integrally coupled to the front end portion of the output rack 105. The output rod 108 is disposed extending toward the master pump 2 within the gear housing 41. The axial direction of the output rod 108 is the same as the axial direction of the input rod 50, and is parallel to each other. The output rod 108 is disposed on a different axis from the input rod 50, and more specifically, is disposed on the same axis as the master pump 2 at a position lower than the input rod 50. The output rod 108 including the output rack 105 corresponds to an output shaft member. The output rod 108 including the output rack 105 and the input rod 50 including the input rack 51 are arranged in parallel with each other. Further, the output rod 108 including the output rack 105 and a part of the input rod 50 including the input rack 51 are disposed to overlap in the axial direction. The front end surface of the output rod 108 is formed as a spherical surface 110. A sleeve 109 is provided on the outer peripheral surface of the output rod 108. The spherical surface 110 at the front end of the output rod 108 abuts against the spherical recess 11 provided in the rear surface of the intermediate wall 10 of the primary piston 7 of the master cylinder 2.

As shown in fig. 1 and 2, the controller 118 is disposed on the side in the front-rear direction with respect to the electric power assist apparatus 1. Specifically, the controller 118 is disposed on the side of the electric motor 67 (motor case 71) and the gear case 41. The controller 118 is connected to the upper end of the motor case 71 via the bracket 120 and the gear case 41. The controller 118 controls driving of the electric motor 67 based on detection signals from various sensors such as the stroke sensor 54 that detects the movement amounts of the input rod 50 and the input rack 51, a rotation angle detection unit (not shown) that detects the rotation angle of the output shaft 68 (the rotation shaft 69) of the electric motor 67, and a current sensor (not shown) that detects the current value supplied to the electric motor 67. By controlling the driving of the electric motor 67 by the controller 118, the output pinion gear portion 85 of the output pinion 83 is rotated via the rotary shaft 69 and the assist flange 75 to push the output rod 108, so that the brake fluid pressure can be generated in the primary chamber 13 and the secondary chamber 14 of the master pump 2 at a desired assist ratio.

Next, the operation of the electric booster 1 when energized will be described.

When the brake pedal 40 is operated from a non-operated state of the brake pedal 40, that is, the brake pedal 40 is depressed, the input rack 51 advances together with the input rod 50 against the elastic force of the return compression spring. As the input lever 50 and the input rack 51 advance, the input pinion portion 57 of the input pinion 55 rotates, and the input surface 66 of the input side pressing portion 65 of the input flange 62 presses the reaction plate 98 in the rotation direction of the input pinion 55. When the input rod 50 and the input rack 51 move forward in accordance with the operation of the brake pedal 40, the stroke sensor 54 detects the movement amounts of the input rod 50 and the input rack 51, the rotation angle detection means detects the rotation angle of the output shaft 68 (the rotation shaft 69) of the electric motor 67, and the controller 118 controls the driving of the electric motor 67 based on the detection results and the like.

When the rotation shaft 69 starts to rotate by driving the electric motor 67, the rotation is transmitted to the auxiliary side pressing portion 79 of the auxiliary flange 75, and the auxiliary surface 81 of the auxiliary side pressing portion 79 presses the reaction plate 98 in the rotation direction of the rotation shaft 69. As a result, the thrust force from the input flange 62 (the input surface 66 of the input-side pressing portion 65) accompanying the operation of the brake pedal 40 and the thrust force from the auxiliary flange 75 (the auxiliary surface 81 of the auxiliary-side pressing portion 79) accompanying the driving of the electric motor 67 are transmitted to the receiving surface 93 of the receiving portion 91 of the output rotating portion 84 of the output pinion 83 via the reaction plate 98, and the output pinion 83 is rotated in the rotating direction of the input flange 62 and the auxiliary flange 75. Thereafter, the output rack 105 and the output rod 108 advance with the rotation of the output pinion 83, and thereby the primary piston 7 and the secondary piston 8 of the master cylinder 2 are pressed and advanced by the output rod 108. When the electric motor 67 is driven, the rotation direction of the rotation shaft 69, the rotation direction of the auxiliary flange 75 (the auxiliary side pressing portion 79), and the rotation direction of the output pinion 83 are the same.

Thereby, hydraulic pressures are generated in the primary chamber 13 and the secondary chamber 14 of the master pump 2, respectively, and the brake hydraulic pressures generated in the primary chamber 13 and the secondary chamber 14 are supplied to the slave pumps of the respective wheels via the hydraulic pressure control means, thereby generating braking forces by friction braking. When the hydraulic pressure is generated in the master cylinder 2, the hydraulic pressures of the primary chamber 13 and the secondary chamber 14 are received by the input surface 66 of the input-side pressing portion 65 of the input flange 62 via the reaction plate 98, and the reaction force obtained by adding the elastic force of the return compression spring to the reaction force caused by the hydraulic pressure is transmitted to the brake pedal 40 via the input rack 51 and the input rod 50.

Further, a ratio of a pressure receiving area of the input surface 66 of the input side pressing portion 65 of the input flange 62 to a pressure receiving area of the auxiliary surface 81 of the auxiliary side pressing portion 79 of the auxiliary flange 75, and a ratio of a distance from the input surface 66 of the input side pressing portion 65 to the rotation center to a distance from the auxiliary surface 81 of the auxiliary side pressing portion 79 to the rotation center, which are caused by the hydraulic pressure of the master pump 2, can be set to a boosting ratio (a ratio of the hydraulic pressure output of the brake pedal 40 to the operation input), and a desired braking force can be generated. In the present embodiment, since the pressure receiving area of the auxiliary surface 81 of the auxiliary flange 75 (the auxiliary side pressing portion 79) is larger than the pressure receiving area of the input surface 66 of the input flange 62 (the input side pressing portion 65), the ratio of the hydraulic pressure output to the operation input of the brake pedal 40 can be doubled, and a desired braking force can be generated.

Next, when the operation of the brake pedal 40 is released, that is, when the brake pedal 40 is released from being depressed, the output rack 105 is retracted by a reaction force due to the hydraulic pressure from the master pump 2 (the primary chamber 13 and the secondary chamber 14), the output pinion 83 rotates in the reverse direction, the input side pressing portion 65 of the input flange 62 is retracted toward the initial position, and the input pinion 55 is reversed, whereby the input rack 51 is retracted, and the input rod 50 is retracted to the initial position while being biased by the return compression spring. At the same time, the stroke detection device 7 detects the amount of retraction of the input rod 50 and the input rack 51, the rotation angle detection means detects the rotation angle of the output shaft 68 (the rotation shaft 69) of the electric motor 67, and the controller 118 controls the driving (reverse rotation) of the electric motor 67 based on the detection results, and transmits the reverse rotation to the auxiliary flange 75 so that the auxiliary side pressing portion 79 is retracted toward the initial position.

However, even when the auxiliary flange 75 is disabled by a failure or the like of the electric motor 67 or the controller 118, the input lever 50 and the input rack 51 move forward by the operation of the brake pedal 40, and the input surface 66 of the input side pressing portion 65 of the input flange 62 of the input pinion 55 presses the reaction plate 98. Then, the thrust force from the input flange 62 in accordance with the operation of the brake pedal 40 is transmitted to the receiving surface 93 of the receiving portion 91 of the output rotating portion 84 of the output pinion 83 via the reaction plate 98 to rotate the output pinion 83, whereby the primary piston 7 and the secondary piston 8 of the master cylinder 2 can be pushed and advanced by the output rod 108.

At this time, since the auxiliary-side pressing portion 79 of the auxiliary flange 75 is configured to be able to pass between the regulating protrusion 92 of the output rotating portion 84 of the output pinion 83 and the outer peripheral surface of the inner cylindrical portion 87, even when the output rotating portion 84 of the output pinion 83 rotates due to the rotation of the input flange 62 of the input pinion 55 in a state where the auxiliary-side pressing portion 79 of the auxiliary flange 75 is stopped, the auxiliary-side pressing portion 79 of the auxiliary flange 75 does not interfere with the regulating protrusion 92 of the output rotating portion 84 of the output pinion 83, the output pinion 83 can continue to rotate without hindrance, and the auxiliary-side pressing portion 79 of the auxiliary flange 75 gradually separates from the output pinion 83 and the input pinion 55 in the rotational direction. Then, the output rack 105 and the output rod 108 move forward along with the rotation of the output pinion 83, and thereby the primary piston 7 and the secondary piston 8 of the master cylinder 2 move forward, and the master cylinder 2 can generate hydraulic pressure, and the braking function can be maintained. As described above, in the electric booster 1 of the present embodiment, even when the electric motor 67 or the controller 118 fails, the stroke required for the output rod 108 can be ensured.

In the electric booster 1 of the present embodiment, the restriction protrusion 92 is provided on the output rotating portion 84 of the output pinion 83, thereby restricting the relative rotation of the input pinion 55 and the output pinion 83 beyond the clearance S. Thus, for example, when the master pump 2 generates hydraulic pressure only by driving the electric motor 67, rotation from the electric motor 67 (output shaft 68) is transmitted to the rotating shaft 69, rotation of the auxiliary side pressing portion 79 of the auxiliary flange 75 only by the rotation of the rotating shaft 69 is transmitted to the reaction plate 98, and thrust force from the auxiliary flange 75 (the auxiliary surface 81 of the auxiliary side pressing portion 79) only with the driving of the electric motor 67 is transmitted to the receiving surface 93 of the receiving portion 91 of the output rotating portion 84 of the output pinion 83 via the reaction plate 98, and the output pinion 83 is rotated.

At this time, the input side pressing portion 65 of the input flange 62 rotates together with the output pinion 83 so as to be pressed by the regulating projection portion 92 of the output rotating portion 84 of the output pinion 83, that is, the relative rotation of the input pinion 55 with respect to the output pinion 83 exceeding the clearance S is regulated, and therefore, the input pinion 55 also rotates in the same direction so as to follow the output pinion 83. As a result, the input rod 50 and the input rack 51 are advanced, and the brake pedal 40 is rotated about the fulcrum even if a depression force is not applied to the brake pedal 40.

On the other hand, in the electric booster 1 according to the other embodiment, the output rotation portion 84 of the output pinion 83 is not provided with the restriction projection 92, and the input pinion 55 and the output pinion 83 are configured to be relatively rotatable. Thus, for example, when the master pump 2 generates hydraulic pressure only by driving the electric motor 67, rotation from the electric motor 67 (output shaft 68) is transmitted to the rotating shaft 69, rotation of the auxiliary side pressing portion 79 of the auxiliary flange 75 only by the rotation of the rotating shaft 69 is transmitted to the reaction plate 98, and thrust force from the auxiliary flange 75 (the auxiliary surface 81 of the auxiliary side pressing portion 79) only with the driving of the electric motor 67 is transmitted to the receiving surface 93 of the receiving portion 91 of the output rotating portion 84 of the output pinion 83 via the reaction plate 98, and the output pinion 83 is rotated. At this time, since the input pinion 55 and the output pinion 83 are configured to be relatively rotatable, the input pinion 55 does not rotate together with the rotation of the output pinion 83, and as a result, the input lever 50, the input rack 51, and the brake pedal 40 do not operate.

As described above, the electric booster 1 of the present embodiment includes: an input pinion 55, the input pinion 55 rotating in response to the operation of the input lever 50 and the input rack 51; an electric motor 67 for driving the electric motor 67 in response to rotation of the input pinion 55; an output pinion 83 that rotates when the rotation of the input pinion 55 and the rotation from the electric motor 67 are transmitted to one receiving portion 91 disposed opposite to the rotation direction of the electric motor 67 or the rotation direction of the input pinion 55; the rotation of the output pinion 83 is transmitted to the output rack 105 and the output rod 108, and the primary and secondary pistons of the master cylinder 2 are moved.

Thus, the electric booster 1 can be reduced in size in the axial direction and the radial direction of the master pump 2, and can be mounted on a vehicle with improved mountability. Further, since the electric booster 1 does not employ a ball screw mechanism as in the conventional electric booster, the electric booster can be manufactured easily while suppressing the processing cost of the components. In the electric booster 1, even when the assist flange 75 cannot be operated due to a failure or the like of the electric motor 67 or the controller 118, the movement amount of the output rod 108 required to generate a desired hydraulic pressure in the master pump 2 can be secured.

In the electric booster 1 of the present embodiment, the input rod 50 and the input rack 51 are disposed so as to overlap with the output rod 108 and the output rack 105 in a part thereof in the axial direction, and therefore, the electric booster 1 can be shortened in particular in the entire length of the total pump 2 in the axial direction.

Further, in the electric booster 1 of the present embodiment, the input rod 50 and the input rack 51 are arranged substantially in parallel with the output rod 108 and the output rack 105, and therefore, in the electric booster 1, the electric booster can be downsized particularly along the radial direction of the master pump 2. This improves the degree of freedom of layout when mounted on a vehicle.

In the electric booster 1 of the present embodiment, the receiving surface 93 of the receiving portion 91 of the output pinion 83 (output rotating portion 84) receives rotation in the same direction from the input surface 66 of the input side pressing portion 65 of the input flange 62 and the auxiliary surface 81 of the auxiliary side pressing portion 79 of the auxiliary flange 75, and therefore, the combination of the rotational forces can be performed in the same rotational direction.

Further, in the electric booster 1 of the present embodiment, since the reaction plate 98 made of an elastic body is provided between the receiving surface 93 of the receiving portion 91 of the output pinion 83 (output rotating portion 84) and the input surface 66 of the input side pressing portion 65 of the input flange 62 and the auxiliary surface 81 of the auxiliary side pressing portion 79 of the auxiliary flange 75, when the reaction plate 98 is pressed by the input surface 66, the reaction force of the reaction plate 98 can be applied to the brake pedal 40, and thus the pedal feel is improved.

In addition, in the electric booster 1 of the present embodiment, since the area of the auxiliary surface 81 of the auxiliary side pressing portion 79 of the auxiliary flange 75 pressed against the receiving surface 93 of the receiving portion 91 is larger than the area of the input surface 66 of the input side pressing portion 65 of the input flange 62 pressed against the receiving surface 93 of the receiving portion 91, the ratio of the hydraulic pressure output to the operation input (assist ratio) of the brake pedal 40 can be doubled, and a desired braking force can be generated.

In addition, in the electric booster 1 of the present embodiment, the rotation shaft of the input pinion 55 is disposed on the same axis as the rotation shaft 69, and the rotation from the electric motor 67 (output shaft 68) is transmitted to the rotation shaft 69, so that the electric booster 1 can be downsized.

In the electric booster 1 of the present embodiment, when the output pinion 83 is rotated only by the rotation of the electric motor 67, the input pinion 55 is configured to rotate following the output pinion 83. In this embodiment, when the master cylinder 2 generates hydraulic pressure only by the rotation of the electric motor 67, the brake pedal 40 is rotated about the fulcrum even if the depression force is not applied to the brake pedal 40. In the electric booster 1 according to another embodiment, when the output pinion 83 is rotated only by the rotation from the electric motor 67, the input pinion 55 is configured to be kept in a stopped state without following the output pinion 83. In this other embodiment, when the master cylinder 2 generates the hydraulic pressure only by the rotation of the electric motor 67, the brake pedal 40 is not pivoted about the fulcrum and stays at the initial position.

In the electric booster 1 of the present embodiment, the rotation from the electric motor 67 (output shaft 68) is transmitted to the rotating shaft 69, the rotating shaft 69 is disposed so as to be orthogonal to the input rod 50 (input rack 51) and the output rod 108 (output rack 105), and the electric motor 67 is disposed along the axial direction of the master cylinder 2 in parallel with the reservoir tank 3 attached to the master cylinder 2. Thus, in the electric booster 1, the size can be reduced particularly in the radial direction of the master pump 2, and the degree of freedom of layout when mounted on a vehicle is improved.

As the electric booster 1 according to the above-described embodiment, for example, the following embodiments are also conceivable.

In a first aspect, the electric booster 1 includes: an input member 55 for rotating the input member 55 in response to the operation of the input shaft members 50, 51; an electric motor 67 that drives the electric motor 67 in response to rotation of the input member 55; an output member 83 that rotates the input member 55 and the rotation of the electric motor 67 transmitted from one receiving portion 91 disposed opposite to the rotation direction of the electric motor 67 or the rotation direction of the input member 55; and output shaft members 105 and 108, and the rotation of the output member 83 is transmitted to the output shaft members 105 and 108 to move the pistons 7 and 8 of the master cylinder 2.

In a second aspect, the electric booster 1 includes: an input member 55, the input member 55 rotating in response to the operation of the input shaft members 50, 51; an electric motor 67 for driving the electric motor 67 in response to rotation of the input member 55; an auxiliary member 75 to which the rotation of the electric motor 67 is transmitted; an output member 83, the output member 83 being rotated in a direction of rotation of the auxiliary member 75 or a direction of rotation of the input member 55 by receiving the rotation of the input member 55 and the rotation of the auxiliary member 75 at a surface 93; output shaft members 105, 108, the rotation of the output member 83 being transmitted to the output shaft members 105, 108 to move the pistons 7, 8 of the master cylinder 2; when the output member 83 rotates only by the rotation of the input member 55, the auxiliary member 75 is separated from the input member 55 and the output member 83 in the rotational direction.

In a third aspect, the electric booster 1 includes: an input member 55, the input member 55 rotating in accordance with the linear motion of the input shaft members 50, 51; an electric motor 67 for driving the electric motor 67 in accordance with the linear motion of the input shaft members 50, 51; an auxiliary member 75 connected to the rotation shaft 69 of the electric motor 67, the auxiliary member 75 being rotated in the same direction as the electric motor 67 and the input member 55 by driving of the electric motor 67; an output member 83 to which the rotation of the input member 55 and the rotation of the auxiliary member 75 are transmitted, the output member 83 rotating in the same direction as the input member 55 and the auxiliary member 75; output shaft members 105, 108, the output shaft members 105, 108 linearly move in accordance with the rotation of the output member 83, and move the pistons 7, 8 of the master cylinder 2.

In a fourth aspect, any one of the first to third aspects is arranged such that the input shaft members 50, 51 and the output shaft members 105, 108 partially overlap in the axial direction.

In a fifth aspect, in any one of the first to fourth aspects, the input shaft members 50, 51 and the output shaft members 105, 108 are arranged substantially in parallel.

In the sixth aspect, in the first aspect, the receiving portion 91 receives rotation in the same direction from an input surface 66 and an auxiliary surface 81, the input surface 66 is provided on the input member 55, and the rotation from the electric motor 67 is transmitted to the auxiliary surface 81.

In the seventh aspect, in the sixth aspect, an elastic body 98 is provided between the receiving portion 91 and the input surface 66 and the auxiliary surface 81.

In the eighth aspect, in the sixth or seventh aspect, a pressure receiving area of the auxiliary surface 81 with respect to the receiving portion 91 is larger than a pressure receiving area of the input surface 66 with respect to the receiving portion 91.

In a ninth aspect, any one of the first to eighth aspects, a rotation shaft of the input member 55 is disposed on the same axis as a rotation shaft 69 of the electric motor 67.

In the tenth aspect, in the second aspect, when the output member 83 is rotated only by the rotation from the electric motor 67, the input member 55 rotates following the output member 83.

In the eleventh aspect, in the second aspect, when the output member 83 is rotated only by the rotation from the electric motor 67, the input member 55 does not follow the output member 83.

In a twelfth aspect, in any one of the first to eleventh aspects, the rotary shaft 69 of the electric motor 67 is disposed so as to be orthogonal to the input shaft members 50, 51 and the output shaft members 105, 108, and the electric motor 67 is disposed along the axial direction of the master pump 2 in parallel with the reservoir tank 3 attached to the master pump 2.

Description of the reference numerals

1 electric booster, 2 master pump, 3 reservoir, 7 primary piston, 8 secondary piston, 50 input rod (input shaft member), 51 input rack (input shaft member), 55 input pinion (input member), 66 input face, 67 electric motor, 69 rotation shaft, 75 auxiliary flange (auxiliary member), 81 auxiliary face, 83 output pinion (output member), 91 receiving portion, 93 receiving face, 98 reaction plate (elastic body), 105 output rack (output shaft member), 108 output rod (output shaft member).

Claims (15)

1. An electric power assist device is characterized by comprising:

an input member that rotates in response to an operation of the input shaft member;

an electric motor that is driven in accordance with rotation of the input member;

an output member that rotates when the rotation of the input member and the rotation from the electric motor are transmitted to one receiving portion disposed opposite to a rotation direction of the electric motor and a rotation direction of the input member;

an output shaft member to which rotation of the output shaft member is transmitted to move a piston of a master cylinder;

the rotation of the input member is transmitted to the receiving surface of the receiving section.

2. An electric power assist device is characterized by comprising:

an input member that rotates in response to an operation of the input shaft member;

an electric motor that is driven in accordance with rotation of the input member;

an auxiliary member to which rotation of the electric motor is transmitted;

an output member that rotates in a rotation direction of the auxiliary member or a rotation direction of the input member by receiving the rotation of the input member and the rotation of the auxiliary member in a plane;

an output shaft member to which rotation of the output shaft member is transmitted to move a piston of a master cylinder;

when the output member is rotated only by the rotation of the input member, the auxiliary member is separated from the input member and the output member in the rotational direction.

3. An electric power assist device is characterized by comprising:

an input member that rotates in accordance with a linear motion of the input shaft member;

an electric motor that is driven in accordance with a linear motion of the input shaft member;

an auxiliary member that is coupled to a rotating shaft of the electric motor and rotates in the same direction as the electric motor and the input member by driving the electric motor;

an output member to which the rotation of the input member and the rotation of the auxiliary member are transmitted together, the output member rotating in the same direction as the input member and the auxiliary member;

and an output shaft member that moves linearly in accordance with rotation of the output member and moves a piston of the master cylinder.

4. An electric power assist device according to any one of claims 1 to 3,

the input shaft member and the output shaft member are partially arranged to overlap in a direction of a rotation axis of the electric motor when viewed in a cross section along the rotation axis of the electric motor.

5. An electric power assist device according to any one of claims 1 to 3,

the input shaft member and the output shaft member are arranged substantially in parallel.

6. The electric assist apparatus of claim 1,

the receiving portion receives rotation in the same direction from an input surface provided to the input member and an auxiliary surface to which rotation from the electric motor is transmitted.

7. The electric assist of claim 6, wherein,

an elastic body is provided between the receiving portion and the input surface and the auxiliary surface.

8. The electric booster of claim 6 or 7,

the pressure receiving area of the auxiliary surface with respect to the receiving portion is larger than the pressure receiving area of the input surface with respect to the receiving portion.

9. An electric power assist device according to any one of claims 1 to 3,

the rotation shaft of the input member is disposed on the same axis as the rotation shaft of the electric motor.

10. Electric power assist device according to claim 2,

when the output member is rotated only by rotation from the electric motor, the input member rotates following the output member.

11. The electric power assist device of claim 2,

the input member does not follow the output member when the output member is rotated only by rotation from the electric motor.

12. An electric power assist device according to any one of claims 1 to 3,

a rotation shaft of the electric motor is disposed so as to be orthogonal to the input shaft member and the output shaft member,

the electric motor is arranged in parallel with a liquid storage tank arranged on the master cylinder along the axial direction of the master cylinder.

13. An electric power assist device is characterized by comprising:

an input member that rotates in response to an operation of the input shaft member;

an electric motor that is driven in accordance with rotation of the input member;

an output member that rotates when the rotation of the input member and the rotation from the electric motor are transmitted to one receiving portion disposed opposite to the rotation direction of the electric motor or the rotation direction of the input member;

an output shaft member to which rotation of the output member is transmitted to move a piston of a master cylinder,

the receiving unit receives rotation in the same direction from an input surface provided to the input member and an auxiliary surface to which rotation from the electric motor is transmitted.

14. The electric assist device of claim 13,

an elastic body is provided between the receiving portion and the input surface and the auxiliary surface.

15. The electric booster of claim 13 or 14,

the pressure receiving area of the auxiliary surface with respect to the receiving portion is larger than the pressure receiving area of the input surface with respect to the receiving portion.

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