Electromechanical brake booster and control method thereof

Abstract

To enable control to be performed without requiring addition of a component even when a position of a detection object body reaches outside a detection range of a position sensor in an electromechanical brake assistor in which a control rod in conjunction with a brake pedal and a screw member operated by a motor part are linearly movable independently of each other.SOLUTION: Only in a case of shifting from a non-electric conduction state to an electric conduction state, when a detection object body 220 attached to a control rod 40 is not detected by a position sensor 52, a motor part is forcibly driven to advance the position sensor 52 attached to a bracket 90 until the detection object body 220 is detected. When the detection object body 220 advances over a detection range of the position sensor 52, return processing of returning the position of the detection object body 220 into the detection range of the position sensor 52 is executed.SELECTED DRAWING: Figure 8

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, and a control method thereof. [Background technology]

[0002] Conventionally, brake boosters that amplify the force applied when the brake pedal is depressed have been known 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 unit 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 unit, even in vehicles that do not have an engine.

[0007] This electromechanical brake booster detects the displacement of a detectable object attached to a control rod that is linked to an input rod connected to the brake pedal using a position sensor attached to a bracket that operates integrally with the screw member, thereby detecting when the brake pedal is depressed and driving the motor unit.A rotary-to-linear conversion unit converts the rotational motion of the motor unit into linear motion of the screw member, and combines the force applied when the brake pedal is depressed with the output from the drive of the motor unit, and uses the amplified force to advance the piston of the master cylinder and generate hydraulic pressure.It is also common that the piston of the master cylinder can be advanced by the force applied when the brake pedal is depressed alone even when no electricity is applied to the motor unit (when the power is turned off).

[0008] Therefore, since the control rod linked to the brake pedal and the screw member driven by the motor unit basically operate independently of each other, when the brake pedal is depressed, such as at start-up when the motor unit is not energized, the control rod moves linearly in the axial direction, but the screw member does not move as it is not driven by the motor unit, and therefore the positional relationship between the detectable object attached to the control rod and the position sensor attached to the bracket becomes significantly different.

[0009] Here, the motor unit that operates the screw member controls the positional relationship between the detectable object attached to the control rod and the position sensor attached to the bracket to maintain a constant position, and when the position of the detectable object reaches outside the detection range of the position sensor, a situation will arise in which it is not possible to control the motor unit.

[0010] Therefore, it becomes necessary to regulate the deviation in position between the object to be detected attached to the control rod and the position sensor attached to the bracket. For example, a structure is known in which an input member and an output member are engaged by a detachable clutch mechanism, as described in JP 2010-184699 A (Patent Document 4). In addition, a structure is also known in which movement is regulated by a link member, as shown in the schematic diagram of Figure 10.

[0011] As shown in FIG. 10(a), this structure is an electromechanical brake booster having a detectable body 46 attached to a control rod 40 and a position sensor 54 attached to a bracket 90 that moves linearly integrally with a screw member 81 and detects the detectable body 46, and has a link member 95 that moves integrally with the bracket 90.

[0012] When the brake pedal is depressed and the control rod 40 moves linearly in the direction of the black arrow shown in Figure 10(a), the control rod 40 comes into contact with the abutment piece 96 of the link member 95 as shown in Figure 10(b), thereby restricting the positional relationship between the detectable object 46 and the position sensor 54 to be within a predetermined range, in other words, the positional relationship between the detectable object 46 and the position sensor 54 is restricted so that the gap between the control rod 40 and the abutment piece 96 is the upper limit of the movement range, thereby preventing the detectable object 46 from departing from the detection range.

[0013] However, the means for regulating the deviation in position between the detected body 46 and the position sensor 54 in the conventional electromechanical brake booster limits the degree of freedom in structure and requires the addition of link members. In particular, there are problems in that the range of braking by the control rod when the motor unit is not driven is limited and unnecessary load is added. [Prior art documents] [Patent documents]

[0014] [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 2010-184699 A Summary of the Invention [Problem to be solved by the invention]

[0015] The present invention has an objective to provide an electromechanical brake booster in which a control rod linked to a brake pedal and a screw member operated by a motor section are capable of linear motion independently of each other, and to enable control without the need for additional parts even when the position of the detected object reaches outside the detection range of the position sensor. [Means for solving the problem]

[0016] 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 the brake pedal; A detection object; a control rod to which the detection object is attached and which moves linearly in the axial direction in conjunction with the input rod in response to operation of the brake pedal; a position sensor that detects the displacement of the control rod by detecting the position of the detection object; 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 position sensor; a rotary-to-linear motion conversion unit that is disposed on the outer periphery of the control rod and that includes a cylindrical screw member having a screw thread formed on its outer periphery and a rotating member having a screw groove formed on its inner periphery that screws into the screw thread, the rotary-to-linear motion conversion unit being linked with the motor unit and converting the rotational motion of the rotating member into a linear motion of the screw member; a bracket to which the position sensor is attached, the bracket restricting the axial rotation of the screw member and moving in conjunction with the screw member in the axial direction; 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 screw member, the master cylinder generating hydraulic pressure by a piston moving back and forth in response to linear motion of the control rod or the screw member, an electromechanical brake booster in which the control rod and the screw member are capable of linear motion independently of each other, and when the control rod moves in a forward direction of the piston by more than a certain amount, the position of the detection object exceeds a detection range of the position sensor, Only when the motor unit and the position sensor transition from a non-energized state to an energized state, when the object to be detected attached to the control rod is not detected by the position sensor, the motor unit is forcibly driven by a drive command from the control unit, thereby moving the position sensor attached to the bracket in the forward direction of the piston until the object to be detected is detected, When the object to be detected has moved in the forward direction of the piston beyond the detection range of the position sensor, a return process is executed to return the position of the object to within the detection range of the position sensor.

[0017] According to the present invention, even though the control rod and screw member have a structure in which they move linearly independent of each other, no additional parts are required. For example, when the brake pedal is depressed in a non-energized state, such as when a vehicle is started (power OFF), and the detectable object attached to the control rod is outside the detection range of the position sensor, when the power is turned ON to transition to an energized state, a return process is executed, so that the position of the detectable object can be returned to within the detection range of the position sensor very effectively and reliably, and normal control can be transitioned to.

[0018] In addition, the return process can be executed only when the brake pedal is depressed while the motor unit and the position sensor are not energized, causing the control rod to move in the forward direction of the piston and the position of the detected object to exceed the detection range of the position sensor and thus not be detected.

[0019] Furthermore, it is particularly desirable that the input rod, the control rod, the motor section, the rotary-linear motion conversion section, the bracket, and the master cylinder are all arranged coaxially, as this allows for a compact overall configuration.

[0020] The method for controlling an electromechanical brake booster according to the present invention comprises the steps of: An input rod connected to the brake pedal; A detection object; a control rod to which the detection object is attached and which moves linearly in the axial direction in conjunction with the input rod in response to operation of the brake pedal; a position sensor that detects the displacement of the control rod by detecting the position of the detection object; 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 position sensor; a rotary-to-linear motion conversion unit that is disposed on the outer periphery of the control rod and that includes a cylindrical screw member having a screw thread formed on its outer periphery and a rotating member having a screw groove formed on its inner periphery that screws into the screw thread, the rotary-to-linear motion conversion unit being linked with the motor unit and converting the rotational motion of the rotating member into a linear motion of the screw member; a bracket to which the position sensor is attached, the bracket restricting the axial rotation of the screw member and moving in conjunction with the screw member in the axial direction; 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 screw member, the master cylinder generating hydraulic pressure by a piston moving back and forth in response to linear motion of the control rod or the screw member, a control method for an electromechanical brake booster, the control rod and the screw member being capable of linear motion independently of each other, and the position of the detection object being beyond the detection range of the position sensor when the control rod is moved by more than a certain amount in the forward direction of the piston, the method comprising: Only when the motor unit and the position sensor transition from a non-energized state to an energized state, when the brake pedal is depressed to move the control rod forward and the object to be detected attached to the control rod is not detected by the position sensor, the motor unit is forcibly driven by a drive command from the control unit to move the position sensor attached to the bracket in the forward direction of the piston until the object to be detected is detected, When the object to be detected has moved in the forward direction of the piston beyond the detection range of the position sensor, a return process is executed to return the position of the object to within the detection range of the position sensor.

[0021] In addition, if a failure determination process is executed if the detected object is not detected by the position sensor within a certain period of time after the motor unit starts to drive in the recovery process, it can be quickly determined that the detected object has failed, such as broken or fallen off. Effect of the Invention

[0022] According to the present invention, even in a structure in which the control rod and screw member move linearly independently of each other, the position of the detectable object can be returned to within the detection range and normal control can be resumed without the need for additional parts, which not only saves space and makes the device more compact, but is also economically advantageous and allows for greater design freedom. [Brief description of the drawings]

[0023] [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] 2A and 2B are schematic diagrams showing the main parts of the embodiment shown in FIG. 1, in which (a) shows the state before operation, (b) shows the state when the object to be detected has moved and is outside the detection range, and (c) shows the state after operation. [Figure 9] 2 is a flow chart showing steps of a restoration process in the embodiment shown in FIG. 1. [Figure 10] 1A and 1B are schematic diagrams showing the main parts of a conventional example, in which (a) shows the state before operation and (b) shows the state after operation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] The control rod 40 is rod-shaped overall and can move axially. One end (the input rod 20 side) has a ball stud 210 fixed thereto by a flange portion 213, with a cylindrical detectable object 220, which is a magnet for position detection, attached thereto so that it cannot fall off. The other end has a step portion 42 for engaging with a plate 41 and a small-diameter tip portion 44 for attaching a coil spring 43 to the outside.

[0030] 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 crimped and connected by inserting the spherical head 212 of a ball stud 210 attached to 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 210, thereby forming a ball joint mechanism.

[0031] At this time, the biasing force of the coil spring 31 transmitted through the retainer 32 acts in a direction separating the ball stud 210 and the input rod 20 from each other, thereby exerting the same effect as a conventional spring for maintaining rod position, and preventing the input rod 20 from collapsing 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.

[0032] The sensor section 50 is composed of a sensor board 51 and a position sensor 52, and the amount of displacement of the detection target 220 detected by the position sensor 52 is output as a signal via the sensor board 51.

[0033] 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.

[0034] 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 motor rotation position sensor 72 via cables 73, 74, and drives the motor unit 60 using signals from each sensor.

[0035] In particular, in this embodiment, the information obtained from each sensor is not fed back to the motor via an electronic control unit (ECU), but is sent directly to the control board 71, which can then directly control the motor section 60. This has the advantage of separating the functions and eliminating the need for complex control.

[0036] In this embodiment, two sets of motor rotational position sensor 72 and corresponding detection gears 66, 67 are provided, and by using motor rotational position sensors with different performance, it is possible to achieve both high precision and high speed motor control, but it is also possible to provide only one set of rotational position sensor and corresponding detection gears.

[0037] In addition, the rotational position sensor is for detecting the rotational position of the motor unit 60 (the rotational shaft 63), but it 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 rotational shaft 63).

[0038] 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 screw member 81 having a thread formed on its outer circumferential surface, a nut-shaped rotating member 82 having a thread groove formed on its inner circumferential surface and screw-fitted with the screw member 81, and a cylindrical connecting member 83 that connects 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.

[0039] 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 screw 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 screw member 81 and allowing it to move in the axial direction in conjunction with the screw member 81.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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 45 of the control rod 40 comes into contact with the elastic body 133.

[0044] 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.

[0045] 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).

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] In this embodiment, the space around the outer periphery of the input rod 20 is utilized, and the sensor base 51 and position sensor 52 of the sensor unit 50 are arranged on the upper surface of the bracket 90 in correspondence with the object to be detected 220, making it possible to detect the position of the object to be detected 220 in a space-saving manner.

[0053] The shaft 211 of the ball stud 210 is inserted into a through hole 221 formed in alignment with the axis of the cylindrical detectable object 220, which is a magnet, and one end 222 of the detectable object 220 is held by a flange portion 213 formed to protrude between the shaft portion 211 and the head 212, while the other end 223 of the detectable object 220 is held by the end of the control rod 40, thereby mounting the detectable object 220 on the control rod 40 so that it cannot fall off.

[0054] As shown in FIG. 6, an ON-OFF sensor 230 is attached to the brake pedal BP, which transmits an ON signal when the brake pedal is depressed and an OFF signal when the brake pedal is not depressed. The ON-OFF sensor 230 is connected to the control unit 70.

[0055] This ON-OFF sensor 230 can of course be used to determine whether the brake pedal BP is depressed, but it can also be used to correct the position of the detected object 220 to its initial position when an OFF signal is transmitted from the ON-OFF sensor 230 after the start of a vehicle, etc.

[0056] 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.

[0057] The operation of the electromechanical brake booster 1 according to this embodiment will now be described.

[0058] 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.

[0059] At this time, the control rod 40 and the screw member 81 are not synchronized and can move axially separately, so that only the control rod 40 moves without changing the position of the screw member 81.

[0060] Then, the control rod 40 advances the first piston 130 and the second piston 140 against the biasing forces of the coil springs 43 , 134 , and 144 .

[0061] 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.

[0062] In addition, a motor rotation position sensor 72 is separately provided which detects the motor rotation speed by detecting the rotation speed of detection gears 66, 67 attached to the rotating shaft 63, and when the control unit 70 controls the supply of power and operation signals to the motor unit 60, the signal sent from the motor rotation position sensor 72 to the control unit 70 via a cable 74 can be utilized.

[0063] 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 screw member 81 is restricted by the bracket 90, the rotational movement of the rotating member 82 with which it is screwed is converted into linear movement, and the screw member 81 moves in a direction that advances the first piston 130 and the second piston 140 on the axis.

[0064] At this time, the bracket 90 also moves in synchronization with the screw 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.

[0065] Then, the screw 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 42 .

[0066] 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 screw member 81 is applied to the first piston 130 and the second piston 140 of the master cylinder 120 via the screw 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.

[0067] 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.

[0068] 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, but since the axial rotation of the screw member 81 is restricted by the bracket 90, the rotational movement of the rotating member 82 with which it is screwed is converted into linear movement, and the screw member 81 moves in a direction that causes the first piston 130 and second piston 140 on the axis to retreat.

[0069] 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 spring forces of the coil springs 134, 144 and the return spring 110 cause the screw member 81 and the first piston 130 and second piston 140 of the master cylinder 120 to retreat and return to their original positions before operation.

[0070] The main points of the present invention will be described below with reference to Fig. 8, which is a schematic diagram of the embodiment shown in Fig. 1, and Fig. 10, which is a schematic diagram of a conventional example, and with reference to Fig. 9, which is a chart showing steps of a return process for returning the position of the detected object to within the detection range in this embodiment. Note that the same reference numerals as those shown in Figs. 1 to 7 are used to indicate the respective elements.

[0071] In this embodiment, as shown in FIG. 8(a), the control rod 40 and the screw member 81 are completely independent, and there is no link member 94 as in the conventional example shown in FIG. 10. Therefore, when the motor unit 60 is not driven, the screw member 81 can move linearly in the axial direction without following the control rod 40, and when the control rod 40 moves in the forward direction of the first piston 130 and the second piston 140 of the master cylinder 120 by more than a certain amount, the position of the detectable body 220 exceeds the detection range of the position sensor 52.

[0072] First, from a power-off state such as at the start of a vehicle or the like in which no current is applied to the motor member 60 and the position sensor 52 shown in FIG. 9 (step S1), when the brake pedal BP is depressed (step S2), the control rod 40 moves linearly toward the tip in the direction of the black arrow in FIG. 8(a) (step S3), and the first piston 130 and the second piston 140 of the master cylinder 120 are advanced by only the depression force, generating hydraulic pressure in the brake fluid and actuating the brakes (not shown).

[0073] At this time, only the control rod 40 moves linearly toward the tip in the direction of the black arrow in Figure 8(a), so that the detectable object 220 attached to the control rod 40 is positioned outside the detection range of the position sensor 52 as shown in Figure 8(b).

[0074] Thereafter, the power supply to the vehicle or the like is turned ON, and electricity is applied to the motor member 60 and the position sensor 52 (step S4). If the position sensor 52 is unable to detect the object to be detected 220 (step S5), the control unit 70 issues a forced drive command to the motor unit 60, which drives the motor unit 60, thereby causing the screw unit 81 and bracket 90 to move linearly in the direction of the black arrow in Figure 8(b), which is the direction in which the first piston 130 and second piston 140 of the master cylinder 120 move forward, via the rotating member 82.

[0075] By linearly moving bracket 90 in the direction of the black arrow in Figure 8 (b), the position sensor 52 attached to bracket 90 also moves in the same direction, making it possible to attempt to return the position of the object to be detected 220 to within the detection range of the position sensor 52.

[0076] At this time, as shown in FIG. 8(c), if the position of the object to be detected 220 returns to within the detection range of the position sensor 52 and the detection of the object to be detected 220 is successful (step S8a), the process can be shifted to normal control (step S9a), and the return process is completed.

[0077] However, if the object to be detected 220 cannot be detected within a certain time from the start of driving of the motor unit 60 (step S8b), a failure determination process is executed (step S9b). Note that the fact that a failure has been determined may be notified to the driver or the like in a recognizable manner by an output means (not shown) such as a lamp or a buzzer.

[0078] There are two possible conditions for the detectable object 220 to reach outside the detection range of the position sensor 52: either the control rod 40 to which the detectable object 220 is attached is ahead when the brake pedal BP is depressed, and the brakes are being operated by the pedal force alone, or the detectable object 220 has experienced a malfunction such as breakage or falling off. If there is no problem with the detectable object 220, the position of the detectable object 220 is returned to normal and control is resumed; if there is a problem with the detectable object 220, a malfunction determination can be made.

[0079] As described above, according to the present invention, even if the control rod and the screw member are structured to move linearly independently of each other, the position of the detection object can be returned to within the detection range and normal control can be resumed without requiring any additional parts, which saves space and allows the device to be made smaller, which is economically advantageous, and also improves the design freedom. Furthermore, even if the detection object breaks or falls off, it can be quickly identified. [Explanation of symbols]

[0080] 1 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 holding hole, 23 brake connector, 30 biasing member, 31 coil spring, 32 retainer, 33 receiving surface, 40 control rod, 41 plate, 42 step portion, 43 coil spring, 44 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 portion, 71 control board, 72 motor rotation position sensor, 73 cable, 74 cable, 80 Rotation-to-linear motion conversion portion, 81 screw member, 82 rotating member, 83 connecting member, 90 bracket, 91 through hole, 92 through hole, 93 flange bush, 100 support, 101 small diameter portion, 102 large diameter portion, 103 tip portion, 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 partition wall, 132 recess, 133 elastic body, 134 coil spring, 135 expanding member, 136 retainer guide, 137 stopper portion, 138 retainer rod, 139 flange portion, 140 second piston, 141 partition wall, 142 Recess, 143, 144 coil spring, 145 elastic 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, 210 ball stud, 211 shaft portion, 212 head portion, 213 flange portion, 220 detection object, 221 through hole, 222 one end, 223 other end, 230 ON-OFF sensor, BP brake pedal

Claims

1. An input rod connected to the brake pedal; A detection object; a control rod to which the detection object is attached and which moves linearly in the axial direction in conjunction with the input rod in response to operation of the brake pedal; a position sensor that detects the displacement of the control rod by detecting the position of the detection object; 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 position sensor; a rotary-to-linear motion conversion unit that is disposed on the outer periphery of the control rod and that includes a cylindrical screw member having a screw thread formed on its outer periphery and a rotating member having a screw groove formed on its inner periphery that screws into the screw thread, the rotary-to-linear motion conversion unit being linked with the motor unit and converting the rotational motion of the rotating member into a linear motion of the screw member; a bracket to which the position sensor is attached, the bracket restricting the axial rotation of the screw member and moving in conjunction with the screw member in the axial direction; 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 screw member, the master cylinder generating hydraulic pressure by a piston moving back and forth in response to linear motion of the control rod or the screw member, an electromechanical brake booster in which the control rod and the screw member are capable of linear motion independently of each other, and when the control rod moves in a forward direction of the piston by more than a certain amount, the position of the detection object exceeds a detection range of the position sensor, Only when the motor unit and the position sensor transition from a non-energized state to an energized state, when the object to be detected attached to the control rod is not detected by the position sensor, the motor unit is forcibly driven by a drive command from the control unit, thereby moving the position sensor attached to the bracket in the forward direction of the piston until the object to be detected is detected, An electromechanical brake booster characterized in that, when the detected object has moved in the forward direction of the piston beyond the detection range of the position sensor, a return process is executed to return the position of the detected object to within the detection range of the position sensor.

2. 2. The electromechanical brake booster according to claim 1, wherein the return process is executed only when the brake pedal is depressed with the motor unit and the position sensor not energized, the control rod moves in the forward direction of the piston, and the position of the detected body exceeds the detection range of the position sensor and is not detected.

3. 3. The electromechanical brake booster according to claim 1, wherein the input rod, the control rod, the motor section, the rotary-linear motion conversion section, the bracket, and the master cylinder are all arranged coaxially.

4. An input rod connected to the brake pedal; A detection object; a control rod to which the detection object is attached and which moves linearly in the axial direction in conjunction with the input rod in response to operation of the brake pedal; a position sensor that detects the displacement of the control rod by detecting the position of the detection object; 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 position sensor; a rotary-to-linear motion conversion unit that is disposed on the outer periphery of the control rod and that includes a cylindrical screw member having a screw thread formed on its outer periphery and a rotating member having a screw groove formed on its inner periphery that screws into the screw thread, the rotary-to-linear motion conversion unit being linked with the motor unit and converting the rotational motion of the rotating member into a linear motion of the screw member; a bracket to which the position sensor is attached, the bracket restricting the axial rotation of the screw member and moving in conjunction with the screw member in the axial direction; 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 screw member, the master cylinder generating hydraulic pressure by a piston moving back and forth in response to linear motion of the control rod or the screw member, a control method for an electromechanical brake booster, the control rod and the screw member being capable of linear motion independently of each other, and the position of the detection object being beyond the detection range of the position sensor when the control rod is moved by more than a certain amount in the forward direction of the piston, the method comprising: Only when the motor unit and the position sensor transition from a non-energized state to an energized state, when the brake pedal is depressed to move the control rod forward and the object to be detected attached to the control rod is not detected by the position sensor, the motor unit is forcibly driven by a drive command from the control unit to move the position sensor attached to the bracket in the forward direction of the piston until the object to be detected is detected, A control method for an electromechanical brake booster, characterized in that, when the detected object has moved in the forward direction of the piston beyond the detection range of the position sensor, a return process is executed to return the position of the detected object to within the detection range of the position sensor.

5. The control method for an electromechanical brake booster according to claim 4, characterized in that if, in the recovery process, the position sensor does not detect the object to be detected within a certain period of time from the start of driving of the motor unit, a failure determination process is executed.

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