Electromechanical brake booster

Abstract

To provide an electromechanical brake booster, which is configured to eliminate a spring that is attached to an outer peripheral part of an input rod in order to maintain the input rod upright by repulsive force so as to avoid a restriction in design and the device from being enlarged in size.SOLUTION: An electromechanical brake booster comprises an input rod 20 connected to a brake pedal BP of an automobile, and an urging member 30 arranged concentrically with the input rod 20 and urges the input rod 20 in an axial direction by repulsive force to keep the rod in a constant posture, where the urging member 30 is arranged inside the input rod 20.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 when stepping on the brake pedal by using an electrically powered motor, even in vehicles that do not have an engine.

[0007] Here, when connecting the brake pedal to the brake booster, since the brake pedal is usually a hanging type that moves in a circular motion, an input rod and a control rod are used and fixed by fitting or crimping so that the input rod can rotate freely relative to the control rod and can swing freely within a specified angular range.

[0008] In addition, in order to prevent the input rod from falling over under its own weight or the occurrence of a gap between the input rod and the control rod, which would result in the generation of abnormal noises or erratic behavior, a structure is generally used in which a spring is provided on the outer periphery of the input rod and the repulsive force of the spring keeps the input rod upright relative to the brake pedal, as described, for example, in Patent Document 2, Patent Document 3, and JP 2016-22744 A (Patent Document 4).

[0009] Explaining in detail with reference to the drawings, the structure of a conventional electromechanical brake booster 2, as shown in FIG. 8, comprises an input rod 20 having a connecting hole 21 on one end and a brake pedal connector 23 on the other end which is rotatable in the circumferential direction and for connecting to a brake pedal BP, a control rod 40 which moves linearly in the axial direction as the input rod 20 moves back and forth, and a conical spring 35 which is attached to the outer periphery of the input rod 20 and fixed by a fixing bracket 36 in a state where it is contracted by a certain amount, and the input rod 20 and the control rod 40 are crimped together with the ball stud 41 of the control rod 40 inserted into the connecting hole 21 of the input rod 20, so that the repulsive force of the conical spring 35 keeps the input rod 20 in an upright position.

[0010] However, when a spring is provided on the outer periphery of input rod 20 as in the conventional inventions described in the above-mentioned patent documents and the conventional example shown in FIG. 8, it is not possible to arrange parts within the range where they interfere with the spring around input rod 20, which causes problems such as design restrictions and an increase in the size of the device itself. [Prior art documents] [Patent documents]

[0011] [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 2016-22744 A Summary of the Invention [Problem to be solved by the invention]

[0012] An object of the present invention is to avoid design limitations and the increase in size of the device itself by eliminating the spring that is attached to the outer periphery of the input rod to maintain the input rod in an upright position using repulsive force, as in the conventional inventions and examples. [Means for solving the problem]

[0013] The electromechanical brake booster of the present invention, which has been made to solve the above problems, is as follows: an input rod connected to a brake pedal of an automobile; and a biasing member arranged coaxially with the input rod for biasing the input rod in an axial direction by a repulsive force to maintain the input rod in a constant position, The biasing member is disposed inside the input rod.

[0014] According to the present invention, it is possible to eliminate the need for a spring attached to the outer periphery of the input rod, making it possible to effectively utilize the surrounding space, and avoiding design restrictions and an increase in the size of the device itself.

[0015] In addition, in the electromechanical brake booster, The biasing member includes a coil spring and a retainer, a control rod which moves linearly in the axial direction in response to operation of the brake pedal in conjunction with the input rod and has a ball stud at one end; the input rod has, at one end thereof, a connection hole extending in the axial direction of the input rod and a spring retaining hole extending in the axial direction and having a smaller diameter than the connection hole, which are formed continuously; the retainer is placed in the connection hole with its cone-shaped receiving surface facing outward, and the coil spring is placed between the spring retaining hole and the retainer, When the input rod and the control rod are crimped together with the ball stud of the control rod inserted into the connecting hole of the input rod and the receiving surface of the retainer in contact, the ball joint mechanism formed by the combination of the connecting hole with the crimped end, the retainer and the ball stud enables reliable operation with a simple structure.

[0016] Furthermore, if a magnet for position detection is attached to the ball stud of the control rod, it is possible to detect the positions of the input rod and control rod by utilizing the space on the outer periphery of the input rod.

[0017] The electromechanical brake booster according to the present invention comprises: 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 sensor unit that detects a displacement of the control rod; a motor section that operates in response to the displacement of the control rod; a control unit that drives the motor unit by using information obtained from the 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 eliminating the need for a spring attached to the outer periphery of the input rod, design restrictions and the increase in size of the device itself can be avoided, and the space on the outer periphery of the input rod can also be utilized. [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. 2 is a cross-sectional view of a main portion of the embodiment shown in FIG. [Figure 7] 2 is an exploded perspective view showing an input rod, a biasing member, and a control rod in the embodiment shown in FIG. 1. [Figure 8] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the same reference numerals are used to designate the same components as those of the conventional electromechanical brake booster 2.

[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 sensor unit 50, a motor unit 60, a control unit 70, 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 sensor section 50 is composed of a sensor board 51 and a position sensor 52, and the amount of displacement of the magnet 42 detected by the position sensor 52 is output as a signal via the 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, 65 that support the rotating shaft 63 rotatably in the circumferential direction. Reference numerals 66, 67 denote detection gears for detecting the number of rotations, 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 unit 70 is a control board 71 having the function of a motor driver for controlling the power supplied from outside via a power cable (not shown) to drive the motor unit 60. The control board 71 is connected to the position sensor 52 and the rotation speed sensor 72 via cables 73, 74, and drives the motor unit 60 using signals from each sensor.

[0030] In this embodiment, two sets of the rotation speed sensor 72 and the corresponding detection gears 66, 67 are provided. For example, by using rotation speed sensors with different performance, it is possible to achieve both high precision and high speed motor control. However, it is also possible to provide only one set of the rotation speed sensor and the corresponding detection gear.

[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 120 comprises a cylinder bore 121 which is cylindrical with a bottom and has a first output port 122 and a second output port 123 formed on the side, a first piston 130 arranged within the cylinder bore 121, and a second piston 140 arranged within the cylinder bore 121 closer to the bottom than the first piston 130. The master cylinder 120 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 which are inserted while communicating a mounting hole 124 of the cylinder bore 121 and a 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 unit 70 uses a signal sent from the 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, a separate rotation speed sensor 72 is provided which detects the motor rotation speed by detecting the rotation speed of detection gears 66, 67 attached to the rotating shaft 63. When the control unit 70 controls the supply of power and an operating signal to the motor unit 60, the signal sent from the rotation speed sensor 72 to the control unit 70 via a cable 74 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 control rod 40 connected to the brake pedal BP also return to their original positions. As the control rod 40 moves, the control unit 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 malfunction of the motor unit 60 or the control unit 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 described below while comparing FIG. 6, which is a cross-sectional view of a main portion, FIG. 7, which is an exploded perspective view of some components, and FIG. 8, which is a cross-sectional view of a conventional example.

[0060] As shown in Figures 6 and 7, in a preferred embodiment of the present invention, the retainer 32 is positioned in the connecting hole 21 of the input rod 20 with the receiving surface 33 facing outward, and the coil spring 31 is positioned between the spring holding hole 22 and the retainer 32. The input rod 20 and the control rod 40 are connected by inserting the ball stud 41 of the control rod 40 into the connection hole 21 of the input rod 20 and deforming the outer edge of the connection hole 21 to reduce its diameter with the receiving surface 33 of the retainer 32 in contact with the ball stud 41.

[0061] The force of the coil spring 31 transmitted through the retainer 32 acts in a direction separating the ball stud 41 and the input rod 20 from each other, thereby achieving the same effect as the conical spring 35 of the conventional example, and preventing the input rod 20 from falling over under its own weight and preventing a gap from occurring between the input rod 20 and the control rod 40, which could result in abnormal noise or erratic behavior.

[0062] Therefore, while the biasing member 30 exerts the effect of maintaining the input rod 20 in a predetermined position, unlike the conventional electromechanical brake booster 2 shown in FIG. 8, there is no need to provide a spring on the outer periphery of the input rod 20, which makes it possible to avoid design restrictions and the increase in size of the device itself, and also makes it possible to utilize the space on the outer periphery of the input rod where parts could not be placed in the past due to interference with the spring.

[0063] In fact, in this embodiment, the space around the outer periphery of the input rod 20 is utilized, and a ball stud 41 is fixed to one end of the control rod 40 (the input rod 20 side) with a position detection magnet 42 attached to it by a flange 43 so that it cannot fall off, and a sensor unit 50 is arranged on the upper surface of the bracket 90 in correspondence with the magnet 42, making it possible to detect the positions of the input rod 20 and the control rod 40 in a space-saving manner.

[0064] In addition, since the coil spring 31 of this embodiment is smaller than the conical spring 35 of the conventional example, the spring force may be relatively weak, but the spring force is sufficient to maintain the input rod 20 in a predetermined position.

[0065] As described above, according to the present invention, by eliminating the need for a spring attached to the outer periphery of the input rod, it is possible to avoid design restrictions and the increase in size of the device itself, and it is also possible to utilize the space on the outer periphery of the input rod. [Explanation of symbols]

[0066] 1,2 electromechanical brake booster, 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 retaining hole, 23 brake connection device, 30 biasing member, 31 coil spring, 32 retainer, 33 receiving surface, 35 conical spring, 36 fixing bracket, 40 control rod, 41 ball stud, 42 magnet, 43 flange, 44 plate, 45 step portion, 46 coil spring, 47 tip portion, 50 sensor portion, 51 sensor board, 52 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 section, 71 control board, 72 RPM sensor, 73 cable, 74 cable, 80 rotary-linear converter, 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 section, 102 large diameter section, 103 tip section, 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, BP brake pedal

Claims

1. An electromechanical brake booster comprising: an input rod connected to a brake pedal; and a biasing member arranged coaxially with the input rod for biasing the input rod in the axial direction by a repulsive force to maintain the input rod in a constant position, 2. An electromechanical brake booster, comprising: a biasing member disposed inside the input rod;

2. The biasing member includes a coil spring and a retainer, a control rod which moves linearly in the axial direction in response to operation of the brake pedal in conjunction with the input rod and has a ball stud at one end; the input rod has, at one end thereof, a connection hole extending in the axial direction of the input rod and a spring retaining hole extending in the axial direction and having a smaller diameter than the connection hole, which are formed continuously; the retainer is placed in the connection hole with its cone-shaped receiving surface facing outward, and the coil spring is placed between the spring retaining hole and the retainer, the input rod and the control rod are connected by crimping in a state in which a ball stud of the control rod is inserted into a connection hole of the input rod and a receiving surface of the retainer are in contact with each other.

2. An electromechanical brake booster according to claim 1.

3. A magnet for detecting position is attached to the ball stud of the control rod.

3. An electromechanical brake booster according to claim 2.

4. The electromechanical brake booster is 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 sensor unit that detects a displacement of the control rod; a motor section that operates in response to the displacement of the control rod; a control unit that drives the motor unit by using information obtained from the 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; 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.

4. An electromechanical brake booster according to claim 1, 2 or 3.

5. 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.

5. An electromechanical brake booster according to claim 4.

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