Electromechanical brake booster

Abstract

To provide an electromechanical brake boosting device which does not cause wiring complication, disconnection due to interference with an external component, an increase in a malfunction risk, or the like.SOLUTION: An electromechanical brake boosting device 1 includes a casing 10, an input rod 20, a control rod 40, a rod sensor part 50 for detecting a variation of the control rod 40, a motor part 60 that is actuated according to the variation of the control rod 40, and a control board 70 for driving the motor part 60 by using information acquired from the rod sensor part 50. The control board 70 and the rod sensor part 50 are connected by a harness 71 in the casing 10.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an electromechanical brake booster for amplifying the force applied when the brake pedal is depressed in an automobile. [Background technology]

[0002] Brake boosters that amplify the force applied when the brake pedal is depressed have been known for some time to assist in braking operations in automobiles. For example, a vacuum brake booster that utilizes the negative pressure of the engine, such as the invention described in JP 54-90459 A (Patent Document 1), has been commonly used.

[0003] In recent years, the movement towards carbon neutrality has been gaining momentum in countries around the world, and in order to achieve the goal of moving away from fossil fuels, the transition to vehicles that do not have engines as their power source, such as electric vehicles and fuel cell vehicles, has become an important issue for the future of the automotive industry.

[0004] In that case, one of the differences between conventional engine-equipped vehicles and non-engine vehicles such as electric vehicles is that, since they do not have an engine, the engine negative pressure (intake pipe negative pressure) used in conventional systems is not generated, which creates the problem that various parts that use negative pressure cannot be used.

[0005] Therefore, there is a need for a brake booster that can provide a high braking force that can be used in automatic braking as an alternative to a vacuum brake booster. For example, electromechanical brake boosters equipped with a motor as a power source are known, such as the inventions described in JP 2018-199448 A (Patent Document 2) and JP 2018 / 097278 A (Patent Document 3).

[0006] These conventional electromechanical brake boosters make it possible to amplify the force applied to the brake pedal by using an electrically powered motor, even in vehicles that do not have an engine.

[0007] Here, in conventional electromechanical brake boosters, the motor, which is the power source, is an independent component, and the various sensors are generally connected to a control board (motor driver) via external wiring. Also, as in the invention described in JP 2018-199441 A (Patent Document 4), for example, information obtained from the various sensors is first input to an electric control unit (ECU) mounted on a vehicle, etc., and then a signal is sent from the electric control unit (ECU) to the control board (motor driver) to perform feedback control (see Figure 8).

[0008] However, when wiring is performed externally as in the above-mentioned conventional example, there is a possibility that the wiring may become complicated and that the risk of disconnection or malfunction due to interference with external components may increase. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 54-90459 [Patent Document 2] JP 2018-199448 A [Patent Document 3] Re-tabled publication 2018 / 097278 [Patent Document 4] JP 2018-199441 A Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide an electromechanical brake booster that does not have the complicated wiring or increased risk of breakage or malfunction due to interference with external components, as occurs in the conventional examples. [Means for solving the problem]

[0011] The electromechanical brake booster of the present invention, which has been made to solve the above problems, is as follows: A casing; An input rod connected to the brake pedal; a control rod which moves linearly in an axial direction in response to operation of the brake pedal in cooperation with the input rod; a rod sensor unit for detecting a displacement of the control rod; a motor section that operates in response to the displacement of the control rod; a control board that drives the motor unit by utilizing information obtained from the rod sensor unit, The control board and the rod sensor unit are connected by a harness inside the casing.

[0012] According to the present invention, by wiring the control board and the sensor inside the casing, it is possible to provide an electromechanical brake booster that does not cause complicated wiring or increased risk of breakage or malfunction due to interference with external components.

[0013] a motor sensor unit that detects a rotational position, a rotational speed, or a number of rotations of the motor unit and outputs the information to the control board, the control board, the rod sensor unit, and the motor sensor unit are housed in the casing, It is particularly preferable that the control board drives the motor section using information obtained from the rod sensor section and the motor sensor section, since this allows for more advanced control.

[0014] Further, the motor sensor unit has a header and a socket is provided upright on the control board, When the control board and the motor sensor unit are connected by inserting the header into the socket, it is easy to position and assemble the parts, and it has the advantage of being possible to configure a compact structure.

[0015] Furthermore, when the control board and the rod sensor unit, and the control board and the motor sensor unit are each connected by a harness, it is possible to perform wiring between the control board and each sensor inside the casing while allowing freedom in placement, thereby improving convenience during design and manufacturing.

[0016] Furthermore, an electronic control unit mounted on a vehicle is connected to the control board, When the motor section is driven using information input in one direction from the electronic control unit and information obtained from the rod sensor section and the motor sensor section, the motor can be controlled directly by the control board without feedback control of the motor by passing the information obtained from each sensor through the electronic control unit once as in the conventional example, which has the advantage of separating the functions and eliminating the need for complex control.

[0017] The electromechanical brake booster according to the present invention is A casing; An input rod connected to the brake pedal; a control rod which moves linearly in an axial direction in response to operation of the brake pedal in cooperation with the input rod; a rod sensor unit for detecting a displacement of the control rod; a motor section that operates in response to the displacement of the control rod; a motor sensor unit that detects a rotational position of the motor unit; a control board that drives the motor unit using information obtained from the rod sensor unit and the motor sensor unit; a rotary-to-linear motion conversion unit arranged on an outer periphery of the control rod, the rotary-to-linear motion conversion unit including a shaft member and a rotating member, and interlocking with the motor unit to convert the rotary motion of the rotating member into linear motion of the shaft member; a bracket that restricts the axial rotation of the shaft member and moves in an axial direction in conjunction with the shaft member; A return spring for biasing the bracket to return to its original position after it has been moved; It is desirable to further include a master cylinder connected to the tip end side of the control rod and the shaft member, and operated by linear motion of the control rod or the shaft member.

[0018] In addition, it is particularly desirable that the input rod, the control rod, the motor section, the rotary-linear conversion section, the bracket, and the master cylinder are all arranged coaxially, as this allows for a compact overall configuration. Effect of the Invention

[0019] According to the present invention, by wiring the control board and the sensor inside the casing, it is possible to provide an electromechanical brake booster that does not cause complicated wiring or increased risk of breakage or malfunction due to interference with external components. [Brief description of the drawings]

[0020] [Figure 1] 1 is a perspective view showing a preferred embodiment of an electromechanical brake booster according to the present invention; [Diagram 2] FIG. 2 is a top view of the embodiment shown in FIG. [Diagram 3] FIG. 2 is a plan view of the embodiment shown in FIG. 1 with the cover removed. [Figure 4] Cross-sectional view taken along line AA in FIG. [Diagram 5] Cross-sectional view of line BB shown in Figure 2. [Figure 6] FIG. 3 is an enlarged cross-sectional view of the line CC shown in FIG. 2. [Figure 7] FIG. 2 is a block diagram showing a system configuration in the embodiment shown in FIG. [Figure 8] FIG. 1 is a block diagram showing a system configuration of a conventional electromechanical brake booster. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0022] 1 to 7 show a preferred embodiment of the electromechanical brake booster of the present invention, and this electromechanical brake booster 1 has a casing 10, an input rod 20, a biasing member 30, a control rod 40, a rod sensor unit 50, a motor unit 60, a control board 70, a motor sensor unit 170, a rotary-linear motion conversion unit 80, a bracket 90, a support 100, a return spring 110, and a master cylinder 120.

[0023] The casing 10 is composed of a cylindrical cover 11 and a doughnut-shaped bottom plate 12. Reference numeral 13 denotes a window formed in the cover 11 for mounting an external connector, reference numeral 14 denotes a fixing screw for fixing the cover 11 and the bottom plate 12, and reference numeral 15 denotes a fixing member for fixing the casing 10 to the body of an automobile.

[0024] The input rod 20 is rod-shaped overall, movable in the axial direction and swingable within a certain angular range, and has a connection hole 21 extending in the axial direction of the input rod 20 and a spring retaining hole 22 extending in the axial direction and having a smaller diameter than the connection hole 21 formed continuously on its end face at one end (the control rod 40 side), and a brake pedal connector 23 is attached to the other end, which is rotatable in the circumferential direction and is used to connect to the brake pedal BP.

[0025] The biasing member 30 is made up of a coil spring 31 that exerts a repulsive force, and a retainer 32. The retainer 32 has a conical shape as a whole, and has a mortar-shaped receiving surface 33 on the inside.

[0026] The control rod 40 is rod-shaped overall and can move axially. One end (the input rod 20 side) has a ball stud 41 fixed thereto with a position detection magnet 42 attached thereto so as not to fall off by a flange 43. The other end has a step 45 for engaging with a plate 44 and a small-diameter tip 47 for attaching a coil spring 46 thereto.

[0027] The rod sensor section 50 is composed of a rod sensor board 51 and a rod position sensor 52, and the amount of displacement of the magnet 42 detected by the rod position sensor 52 is output as a signal via the rod sensor board 51.

[0028] The motor section 60 is made up of a stator 61, a rotor 62, a rotating shaft 63 that rotates in synchronization with the rotor 62, and two bearings 64 and 65 that support the rotating shaft 63 rotatably in the circumferential direction. Reference numerals 66 and 67 denote detection gears for detecting the rotational position, and reference numeral 68 denotes a motor cover that is attached so as to stand from the bottom plate 12 and covers the motor section 60.

[0029] The control board 70 is a control board having a motor driver function for driving the motor unit 60 by controlling power and signals supplied from the outside via a harness (not shown). The control board 70 is connected to the rod position sensor 52 of the rod sensor unit 50 and the motor rotation position sensor 171 of the motor sensor unit 170 via harnesses 71, 72, and drives the motor unit 60 using signals from each sensor.

[0030] The motor sensor unit 170 has motor rotational position sensors 171, 172, which are disposed opposite the detection gears 66, 67 so as to form pairs with the detection gears 66, 67, respectively.

[0031] The rotary-linear motion conversion unit 80 is a mechanism for converting the rotary motion of the motor unit 60 into linear motion, and is configured by a feed screw mechanism including a cylindrical shaft member 81 having a thread formed on its outer periphery, a nut-shaped rotating member 82 having a thread groove formed on its inner periphery and screw-fitted with the shaft member 81, and a cylindrical connecting member 83 connecting the rotating member 82 to the rotating shaft 63. In this embodiment, the rotating member 82 and the connecting member 83 are formed separately and then integrally joined, but they may also be integrally molded.

[0032] The bracket 90 is a generally equilateral triangle in plan view, with through holes 91, 92 formed at the center and near each apex. The shaft member 81 is inserted and fixed into the through hole 91 at the center, and is attached to three posts 100 via flange bushes 93 attached to the through holes 92 near each apex, making the bracket 90 immovable in the axial direction but movable in the axial direction, restricting the axial rotation of the shaft member 81 and allowing it to move in the axial direction in unison.

[0033] Three pillars 100 are installed between the cover 11 and the bottom plate 12, and are positioned by inserting a small diameter portion 101 formed near one end into a mounting hole 16 formed in the bottom plate 12 and by bringing a large diameter portion 102 formed adjacent to the small diameter portion 101 into contact with the bottom plate 12. The pillars are fixed by attaching a nut 104 to a tip portion 103 of the pillar protruding from a mounting hole 17 formed in the cover 11.

[0034] The return springs 110 are used to urge the bracket 90 back to its original position after it has been moved, and are attached to three reinforcing pillars 100 suspended between the cover 11 and the bottom plate 12, with one end in contact with the bottom plate 12 and the other end in contact with the flange bush 93.

[0035] The master cylinder 110 comprises a cylindrical cylinder bore 121 with a bottom, a first output port 122 and a second output port 123 formed on the side, a first piston 130 arranged in the cylinder bore 121, and a second piston 140 arranged in the cylinder bore 121 closer to the bottom than the first piston 130. The master cylinder 110 is arranged so that the opening of the cylinder bore 121 faces the opening at the bottom of the casing 10 and closes it, and is fixed by a bolt 125 and a nut 126 inserted while communicating the mounting hole 124 of the cylinder bore 121 and the mounting hole 18 of the bottom plate 12.

[0036] Both ends of the first piston 130 are formed in a cup shape, and are formed with an H-shaped cross section partitioned by a partition wall 131. An elastic body 133 which is a reaction disk is fitted into a recess 132 formed on the base end side (the control rod 40 side) of the partition wall 131, and the tip end 47 of the control rod 40 comes into contact with the elastic body 133.

[0037] Both ends of the second piston 140 are formed in a cup shape, and have an H-shaped cross section partitioned by a partition wall 141. A recess 142 is formed on the base end side (the first piston 130 side) of the partition wall 141, and a retainer rod 148 described later comes into contact with the recess 142.

[0038] In the cylinder bore 121 of the master cylinder 120, a primary chamber 127 is formed between a first piston 130 and a second piston 140, and a secondary chamber 128 is formed between the bottom of the cylinder bore 121 and the second piston 140. The inside of the cylinder bore 121 including the primary chamber 127 and the secondary chamber 128 is filled with brake fluid, which is a working fluid, and the brake fluid is supplied from a reservoir (not shown).

[0039] At this time, sealing members 151, 152 installed between the outer periphery of the first piston 130 and the inner periphery of the cylinder bore 121, and sealing members 161, 12 installed between the outer periphery of the second piston 140 and the inner periphery of the cylinder bore 121, prevent the brake fluid from leaking outside the designated compartment.

[0040] The primary chamber 127 and secondary chamber 128 of the master cylinder 120 are respectively connected to a first output port 122 and a second output port 123 formed on the side of the cylinder bore 121, and the hydraulic pressure of the brake fluid output from each output port via a separate system is supplied to the brakes (not shown) of each wheel to generate braking force.

[0041] A coil spring 134 is interposed between the first piston 130 and the second piston 140, and biases the first piston 130 and the second piston 140 in a direction separating them from each other. Inside the coil spring 134, an expandable member 135 consisting of a retainer guide 136 and a retainer rod 138 for maintaining a predetermined distance between the first piston 130 and the second piston 140 is arranged.

[0042] The retainer guide 136 is cylindrical and has a stopper portion 137 that protrudes inward at its tip. The retainer rod 138 is rod-shaped and has a flange portion 139 that protrudes radially outward at its base end. By inserting the retainer rod 138 into the retainer guide 136, the two can move relative to each other in the axial direction, and when the stopper portion 137 of the retainer guide 136 and the flange portion 139 of the retainer rod 138 interfere with each other, the expandable member 135 is expanded to a predetermined extent.

[0043] A coil spring 144 is interposed between the second piston 140 and the bottom of the cylinder bore 121, and biases the second piston 140 and the bottom of the cylinder bore 121 in a direction separating them from each other. An expandable member 145 consisting of a retainer guide 146 and a retainer rod 148 is disposed inside the coil spring 144 to maintain a predetermined distance between the second piston 140 and the bottom of the cylinder bore 121.

[0044] The retainer guide 146 is cylindrical and has a stopper portion 147 that protrudes inward at its tip. The retainer rod 148 is hollow rod-shaped and has a flange portion 149 that protrudes radially outward at its base end. By inserting the retainer rod 148 into the retainer guide 146, the two become capable of moving relative to each other in the axial direction, and when the stopper portion 147 of the retainer guide 146 and the flange portion 149 of the retainer rod 148 interfere with each other, the expandable member 145 is expanded to a predetermined extent.

[0045] In this embodiment, the input rod 20, the control rod 40, the motor section 60, the rotary-to-linear motion conversion section 80, the bracket 90 and the master cylinder 120, which are directly related to the operation of the brake booster, are all arranged coaxially (see Figures 4 and 5), making it possible to achieve a space-saving configuration overall.

[0046] The operation of the electromechanical brake booster 1 according to this embodiment will now be described.

[0047] With the electromechanical brake booster 1 installed in an automobile, when the driver depresses the brake pedal BP, the input rod 20 connected to the brake pedal BP moves axially, and the control rod 40 moves linearly in synchronization with the input rod 20.

[0048] At this time, the control rod 40 and the shaft member 81 are not synchronized and can move axially separately, so that only the control rod 40 moves without changing the position of the shaft member 81.

[0049] Then, the control rod 40 advances the first piston 130 and the second piston 140 against the biasing forces of the coil springs 46 , 134 , 144 .

[0050] In addition, when the control rod 40 moves, the control board 70 uses a signal sent from the rod position sensor 52 that detects the displacement to control the supply of power and an operating signal to the motor unit 60, causing the motor unit 60 to operate and rotate.

[0051] In addition, the motor is provided with motor rotational position sensors 171, 172 which detect the rotational position of the motor by detecting the rotational position of detection gears 66, 67 attached to the rotating shaft 63. When the control board 70 controls the supply of power and operating signals to the motor section 60, the signals sent from the motor rotational position sensors 171, 172 to the control board 70 can be utilized.

[0052] When the motor unit 60 rotates, the rotating member 82 rotates in synchronization with the rotating shaft 63 via the connecting member 83, but since the axial rotation of the shaft member 81 is restricted by the bracket 90, the rotational movement of the rotating member 82, which is screwed into the shaft member 81, is converted into linear movement, and the first piston 130 and second piston 140 move forward on the axis.

[0053] At this time, the bracket 90 also moves in synchronization with the shaft member 81 in a direction that advances the first piston 130 and the second piston 140 on the axis while compressing the return spring 110, but since the bracket 90 slides while being guided by the support 100 via the flange bush 93, smooth operation is possible.

[0054] Then, the shaft member 81 advances the first piston 130 and the second piston 140 against the biasing forces of the coil springs 134 , 144 via the plate 44 .

[0055] In this way, the force exerted when the driver depresses the brake pedal BP is applied directly to the first piston 130 and the second piston 140 of the master cylinder 120 via the input rod 20 and the control rod 40, and in addition, the pressing force obtained by converting the rotational motion of the motor section 60 into the linear motion of the shaft member 81 is applied to the first piston 130 and the second piston 140 of the master cylinder via the shaft member 81, thereby making it possible to amplify the force exerted when the driver depresses the brake pedal BP by using a motor driven by electricity.

[0056] Then, as the driver releases the brake pedal BP and the brake pedal BP returns to its original position, the input rod 20 and the control rod 40 connected to the brake pedal BP also return to their original positions, and as the control rod 40 moves, the control board 70 controls the supply of power and an actuation signal to the motor unit 60 in response to a signal from the position sensor 52 which detects the displacement, and the motor unit 60 is actuated to rotate in the reverse direction.

[0057] When the motor unit 60 rotates in reverse, the rotating member 82 rotates in reverse in synchronization with the rotating shaft 63 via the connecting member 83. However, since the axial rotation of the shaft member 81 is restricted by the bracket 90, the rotational motion of the rotating member 82 which is screwed into the shaft member 81 is converted into linear motion, and the first piston 130 and the second piston 140 on the axis move backward.

[0058] Furthermore, even if the motor unit 60 is unable to reverse normally due to a defect in the motor unit 60 or the control board 70, the biasing forces of the coil springs 134, 144 and the return spring 110 will cause the shaft member 81 and the first piston 130 and second piston 140 of the master cylinder to retract and return to their original positions before operation.

[0059] The main points of the present invention will be explained below by comparing FIG. 6 which is an enlarged view of the CC cross section showing the main parts, FIG. 7 which is a block diagram showing the system configuration, and FIG. 8 which is a block diagram showing the system configuration of a conventional electromechanical brake booster.

[0060] As shown in FIG. 6, in this embodiment, the control board 70 and the rod sensor board 51 of the rod sensor unit 50, and the control board 70 and the motor rotation position sensor 171 of the motor sensor unit 170 are connected by harnesses 71, 72, respectively.

[0061] In this way, the control board 70, the rod sensor unit 50 and the motor sensor unit 170, which are arranged inside the casing 10 consisting of a cover 11 and a bottom plate 12, are connected by harnesses 71, 72 that are wired through the casing 10, making it possible to achieve a compact configuration while avoiding complicated wiring and increased risk of breakage or malfunction due to interference with external components.

[0062] Furthermore, the motor rotation position sensor 172 of the motor sensor unit 170 has a header for connection, and a socket 73 is erected from the control board 70, and the control board 70 and the motor sensor unit 170 are connected by inserting the header into the socket 73.

[0063] In this way, by connecting the components by means of a header and a socket, rather than using a harness, it is possible to facilitate positioning and assembly of the components, and it has the advantage of being possible to achieve a more compact configuration.

[0064] As shown in FIG. 7, via an external connection connector (not shown) attached to the window 13, the control board 70 is connected to various sensors (vehicle speed sensor, engine RPM sensor, etc.), various units (ABS, ESC, etc.), brake ON-OFF sensor 5, brake angle sensor 6, electronic control unit (ECU) 7 and battery 8 mounted on a vehicle or the like in which the electromechanical brake booster 1 is used, and power and signals from the outside can be supplied to the control board 70.

[0065] At this time, information from the electronic control unit (ECU) 7 is input in only one direction, and instead of performing feedback control of the motor by passing the information obtained from each sensor through the electronic control unit (ECU) once as in the conventional example shown in FIG. 8, the motor section 60 can be controlled directly by the control board 70, which has the advantage of separating the functions and eliminating the need for complex control.

[0066] In this embodiment, the motor rotational position sensors 171, 172 are for detecting the rotational position of the motor unit 60 (the rotating shaft 63), but may also be, for example, a rotational speed sensor or a rotational number sensor for detecting the rotational speed or number of rotations of the motor unit 60 (the rotating shaft 63).

[0067] As described above, according to the present invention, by wiring the control board and each sensor inside the casing, it is possible to provide an electromechanical brake booster that does not complicate the wiring or increase the risk of breakage or malfunction due to interference with external components. [Explanation of symbols]

[0068] 1 electromechanical brake booster, 5 brake ON-OFF sensor, 6 brake angle sensor, 7 electronic control unit (ECU), 8 battery, 10 casing, 11 cover, 12 bottom plate, 13 window, 14 fixing screw, 15 fixing member, 16 mounting hole, 17 mounting hole, 18 mounting hole, 20 input rod, 21 connection hole, 22 spring holding hole, 23 brake connection tool, 30 biasing member, 31 coil spring, 32 retainer, 33 receiving surface, 40 control rod, 41 ball stud, 42 magnet, 43 flange, 44 plate, 45 step portion, 46 coil spring, 47 tip portion, 50 rod sensor portion, 51 rod sensor board, 52 rod position sensor, 60 motor portion, 61 stator, 62 rotor, 63 rotating shaft, 64 bearing, 65 bearing, 66 Detection gear, 67 detection gear, 68 motor cover, 70 control board, 71, 72 harness, 80 rotary-linear conversion part, 81 shaft member, 82 rotating member, 83 connecting member, 90 bracket, 91 through hole, 92 through hole, 93 flange bush, 100 support, 101 small diameter part, 102 large diameter part, 103 tip part, 104 nut, 110 return spring, 120 master cylinder, 121 cylinder bore, 122 first output port, 123 second output port, 124 mounting hole, 125 bolt, 126 nut, 127 primary chamber, 128 secondary chamber, 130 first piston, 131 bulkhead, 132 recess, 133 elastic body, 134 coil spring, 135 elastic member, 136 retainer guide, 137 Stopper portion, 138 retainer rod, 139 flange portion, 140 second piston, 141 partition wall, 142 recessed portion, 143, 144 coil spring, 145 expandable member, 146 retainer guide, 147 stopper portion, 148 retainer rod, 149 flange portion, 151 seal member, 152 seal member, 161 seal member, 162 seal member, 170 motor sensor portion, 171, 172 motor rotation position sensor, BP brake pedal

Claims

1. An electromechanical brake booster, A casing; An input rod connected to the brake pedal; a control rod which moves linearly in an axial direction in response to operation of the brake pedal in cooperation with the input rod; a rod sensor unit for detecting a displacement of the control rod; a motor section that operates in response to the displacement of the control rod; a control board that drives the motor unit by utilizing information obtained from the rod sensor unit; a motor sensor unit that detects a rotational position, a rotational speed, or a number of rotations of the motor unit and outputs information to the control board; the control board, the rod sensor unit, and the motor sensor unit are housed in the casing, the motor sensor unit has a header, a socket is provided upright on the control board, and the control board and the motor sensor unit are connected by inserting the header into the socket, The control board and the rod sensor unit are connected by a harness inside the casing. An electromechanical brake booster.

2. An electronic control unit mounted on a vehicle is connected to the control board, driving the motor unit using information input in one direction from the electronic control unit and information obtained from the rod sensor unit and the motor sensor unit; 2. An electromechanical brake booster as claimed in claim 1.

3. The electromechanical brake booster is a rotary-to-linear motion conversion unit arranged on an outer periphery of the control rod, the rotary-to-linear motion conversion unit including a shaft member and a rotating member, and interlocking with the motor unit to convert the rotary motion of the rotating member into linear motion of the shaft member; a bracket that restricts the axial rotation of the shaft member and moves in an axial direction in conjunction with the shaft member; A return spring for biasing the bracket to return to its original position after it has been moved; a master cylinder connected to a tip end side of the control rod and the shaft member and operated by linear motion of the control rod or the shaft member.

3. An electromechanical brake booster as claimed in claim 1 or 2.

4. the input rod, the control rod, the motor unit, the rotary-linear motion conversion unit, the bracket, and the master cylinder are all coaxially arranged.

4. An electromechanical brake booster as claimed in claim 3.

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