JP2014008894A - Electric power booster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power booster which achieves sealing between a housing and a stud bolt fixed on the housing for connecting a master cylinder without an O ring.SOLUTION: In an electric power booster controlling revolutions of an electric motor according to the operation of a brake pedal and generating a brake liquid pressure with a master cylinder by propelling a piston through a ball screw mechanism, a stud bolt 91 for connecting the master cylinder is pressed into a bolt hole 95 of a front housing 4A, which stores the ball screw mechanism. An annular seal protrusion 97A and groove parts 97B, 97C are formed at a flange part 92 of the stud bolt 91. The seal protrusion 97A is bitten into a seal face 96 of the front housing 4A, and the deformed seal face 96 is inserted into the groove parts 97B, 97C. Thereby, the front housing 4A and the stud bolt 91 are sealed without an O-ring.

Description

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

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

JP 2012-35814 A

  In the electric booster described in Patent Document 1, a housing that houses an actuator including an electric motor, a rotation-linear motion conversion mechanism, and the like, and a master cylinder are fixed to the housing, and a nut is screwed onto a stud bolt. Are combined. In the case of adopting such a structure, conventionally, when the stud bolt is press-fitted into the housing and fixed, a sealing member such as an O-ring is interposed between the stud bolt and the housing, thereby improving the airtightness inside the housing. Trying to get.

  However, when airtightness is obtained using a seal member such as an O-ring, the seal member may be damaged by biting when the stud bolt is pressed into the housing. It is very difficult to confirm whether the seal member is damaged after the press-fitting, and there is a possibility that the assembly of the seal member may be forgotten.

  The present invention provides an electric booster that seals between a housing and a stud bolt fixed to the housing for coupling a master cylinder without using a seal member such as an O-ring. With the goal.

In order to solve the above problems, the present invention is coupled to a housing attached to a vehicle body, a rotation / linear motion conversion mechanism that is accommodated in the housing and converts rotation of an electric motor into linear motion, and the housing. In the electric booster equipped with a master cylinder that generates a brake fluid pressure by propelling the piston by the rotation / linear motion conversion mechanism,
A stud bolt for coupling the master cylinder is fixed to the housing, and an abutting portion whose one end abuts against the housing while being fixed to the housing is formed on the stud bolt. The portion is formed with an annular seal protrusion protruding so as to bite into the housing, and an annular groove adjacent to at least one of the inner peripheral side and the outer peripheral side of the seal protrusion.

  According to the electric booster according to the present invention, it is possible to seal between the housing and the stud bolt fixed to the housing for coupling the master cylinder without using a seal member such as an O-ring. .

1 is a longitudinal sectional view of an electric booster according to an embodiment of the present invention. It is a longitudinal cross-sectional view of the front housing in which the stud bolt of the electric booster shown in FIG. 1 was press-fitted. It is a front view of the front housing shown in FIG. FIG. 3 is a side view showing a partially broken stud bolt shown in FIG. 2. It is a perspective view of the stud bolt shown in FIG. It is a longitudinal cross-sectional view which expands and shows the press fit part of the stud bolt of the front housing shown in FIG.

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

  2 and 3, the front housing 4A is made of an aluminum alloy and is formed into a substantially bottomed cylindrical shape, and an opening 85 is provided at the bottom. A flat master cylinder mounting seat surface 90 is formed around the opening 85 outside the bottom of the front housing 4A. A stud bolt 91 protrudes from the master cylinder mounting seat surface 90. The master cylinder 2 includes a cylinder body 2A having a substantially bottomed cylindrical shape, and a mounting seat 2B extending in the diametrical direction is integrally formed on the side of the cylinder body 2A on the opening side. The master cylinder 2 is inserted into the mounting seat 2B in a state where the opening side of the master cylinder body 2A is inserted into the opening 85 at the bottom of the front housing 4A and the mounting seat 2B is in contact with the master cylinder mounting seat surface 90. The stud 6 is connected to the front housing 4A by screwing the nut 6 onto the stud bolt 91.

  4 to 6, the stud bolt 91 is formed with a flange 92 having an enlarged diameter to be a contact portion with the front housing 4 </ b> A at the base end, and a screw portion 93 and a flange 92 on the distal end side. A knurling portion 94 for press-fitting having a diameter larger than that of the screw portion 92 and smaller than that of the flange portion 91 is formed therebetween. The stud bolt 91 is inserted from the inside of the front housing 4A into a bolt hole 95 penetrating the master cylinder mounting seat surface 90 at the bottom of the front housing 4A, and the knurled portion 94 is press-fitted into the bolt hole 95 to The flange 92 is fixed in a state where the flange 92 is in contact with a flat seal surface 96 formed around the bolt hole 95 at the bottom.

  In the present embodiment, as shown in FIG. 6, an annular seal portion 97 is formed concentrically on the end surface that contacts the seal surface 96 of the flange portion 92 of the stud bolt 91. The seal portion 97 is formed by a central seal protrusion 97A and groove portions 97B and 97C formed adjacent to the inner and outer peripheral sides of the seal protrusion 97A. The seal protrusion 97A is formed in a mountain shape having a top portion having a cross-sectional shape of about 90 °. The grooves 97B and 97C are formed in an arc shape or a curved shape whose cross-sectional shape is smoothly connected to the slope of the chevron of the seal protrusion 97A. The stud bolt 91 is formed of a material such as carbon steel that is harder than the front housing 4A. When the stud bolt 91 is press-fitted into the bolt hole 95 of the front housing 4 </ b> A, the flange portion 92 is pressed against the seal surface 96 and the seal protrusion 97 </ b> A of the seal portion 97 is bitten into the seal surface 97. At this time, the seal surface 96 plastically flows and enters the grooves 97B and 97C. As a result, the space between the front housing 4A and the stud bolt 91 is sealed.

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

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

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

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

  The intermediate portion of the primary piston 10 extending into the front housing 4A is inserted into a cylindrical spring receiving member 70 that fits into the opening 85 at the bottom of the front housing 4A, whereby the spring receiving member 70 extends along the axial direction. Are slidably guided. The spring receiving member 70 is fixed to the front housing 4A and the master cylinder 2 by fitting an outer flange portion 71 formed at one end thereof to the opening 85 at the bottom of the front housing 4A, and is attached to the cylinder bore 12 of the master cylinder 2. It is connected. The spring receiving member 70 seals between the primary piston 10 by a seal member 72 attached to the inner periphery of the rear end. The opening 12A of the cylinder bore 12 provided with the seal groove 22b and the seal member 22B of the master cylinder 2 is protruded radially inward, and the spring receiving member 70 is provided so that the axial length of the support portion of the primary piston 10 is increased. By increasing the length, the inclination of the primary piston 10 with respect to the cylinder bore 12 is suppressed.

  An input rod 34 is inserted into the cylindrical portion 8 of the rear cover 4B and the rear portion of the primary piston 10. The front end portion of the input rod 34 inserted into the rear portion of the primary piston 10 is connected to the rear end portion of the input piston 32. The connecting portion between the input rod 34 and the primary piston 10 forms a ball joint so that the inclination of the input rod 34 with respect to the primary piston 10 can be allowed to some extent. The rear end side of the input rod 34 extends from the cylindrical portion 8 to the outside, and a brake pedal (not shown) is connected to the rear end portion of the input rod 34 that extends to the outside. A stopper contact portion 34 </ b> A formed in a bowl shape is provided at an intermediate portion inserted into the cylindrical portion 8 of the input rod 34.

  A stopper 39 extending radially inward toward the input rod 34 inserted into the cylindrical portion 8 is formed at the rear end portion of the cylindrical portion 8 of the rear cover 4C. The stopper 39 is inserted into a guide groove 47B formed along the axial direction at a cylindrical rear end portion of a screw shaft 47 of a ball screw mechanism 41 described later. Then, when the stopper abutting portion 34A of the input rod 34 abuts against the stopper 39, the retracted position of the input rod 34 is defined.

  An annular spring receiver 35 is attached to the rear end portion of the primary piston 10. The primary piston 10 is urged in the backward direction by a return spring 36 that is a compression coil spring interposed between the rear end portion of the spring receiving member 70 and the spring receiver 35. The input piston 32 is elastically moved to the neutral position shown in FIG. 1 by springs 37 and 38 which are compression coil springs interposed between the intermediate piston 30 of the primary piston 10 and the spring receiver 35, respectively. Is retained.

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

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

  In the above example, the rotational motion of the rotor 45 of the electric motor 40 is directly transmitted to the nut member 46 of the ball screw mechanism 41. However, a planetary gear mechanism, between the electric motor 40 and the ball screw mechanism 41, The rotation of the electric motor 40 may be reduced and transmitted to the ball screw mechanism 41 via a known reduction mechanism such as a differential reduction mechanism.

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

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

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

Next, the operation of the electric booster 1 will be described.
When the input piston 32 is moved forward via the input rod 34 by operating the brake pedal, the displacement of the input piston 32 is detected by the stroke sensor, and the operation of the electric motor 40 is controlled by the controller based on the displacement of the input piston 32. The primary piston 10 is pressed by the step portion 50 of the screw shaft 47 of the ball screw mechanism 41 via the shim 81 and the spring receiver 35, and the primary piston 10 is advanced to follow the displacement of the input piston 32. Thereby, a hydraulic pressure is generated in the primary chamber 16, and this hydraulic pressure is transmitted to the secondary chamber 17 via the secondary piston 11. In this way, the brake hydraulic pressure generated in the master cylinder 2 is supplied to the brake caliper of each wheel via the hydraulic pressure port to generate a braking force. When the operation of the brake pedal is released, the input piston 32, the primary piston 10 and the secondary piston 11 are retracted, the brake fluid pressure in the master cylinder 2 is reduced, and the braking force is released.

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

  Here, as shown in Patent Document 1, when a seal member such as an O-ring is used to obtain airtightness between the stud bolt and the housing, the seal member may be damaged due to biting when the stud bolt is press-fitted into the housing. There is. In addition, it is very difficult to confirm whether the seal member is damaged after the press-fitting, and there is a possibility that the assembly of the seal member may be forgotten. Also, in order to improve the assembling property of the seal member, assembling liquid is generally applied. However, if the assembling liquid adheres to the threaded portion of the stud bolt, the tightening torque of the nut will fluctuate and loosen. Cause. Furthermore, it takes time for assembly of the seal member. Moreover, there exists a possibility that airtightness may fall by aged deterioration of a sealing member. In response to these problems, in the electric booster 1 of the present embodiment, the plastic flow of the metal is caused by the seal portion 97 formed integrally with the flange portion 92 of the stud bolt 91 between the front housing 4A and the stud bolt 91. I use it to seal it. By doing in this way, airtightness is acquired, without using separately sealing members, such as the conventional O-ring. As a result, it is possible to eliminate problems such as poor assembly of a seal member such as an O-ring, forgetting assembly, and deterioration of airtightness due to aging of the seal member. Also, assembly of the seal member and application of assembly liquid Assembling man-hours can be reduced.

  In the above-described embodiment, the seal portion 97 has a structure in which the groove portions 97 and 98 are formed on both the inside and the outside of the seal protrusion 97A in order to enhance the sealability. However, the necessary sealability is obtained. In that case, either the inner or outer groove 97 or 98 may be omitted. In the above embodiment, the electric motor 40 is housed in the housing 4 and directly drives the nut member 46 of the ball screw mechanism 41. However, the electric motor is disposed outside the housing 4, and the belt, The nut member 46 may be driven via a transmission mechanism such as a gear or a chain.

  In the present embodiment, an example in which the seal structure of the housing and the stud bolt is applied to the electric booster is shown. However, a booster using an aluminum alloy housing other than the electric booster, for example, a negative It can be applied to a pressure booster or a hydraulic booster. In this case, the seal structure is specified as follows.

In a booster having a housing made of an aluminum alloy that is built in a booster mechanism and is attached to a vehicle body, and a stat bolt that is fixed to the housing and to which a master cylinder is attached,
The stud bolt is formed with an abutting portion whose one end abuts against the housing in a state of being fixed to the housing, and an annular seal projection projecting so as to bite into the housing. A booster comprising an annular groove adjacent to at least one of an inner peripheral side and an outer peripheral side of the seal projection.

  DESCRIPTION OF SYMBOLS 1 ... Electric booster, 2 ... Master cylinder, 4A ... Front housing (housing), 10 ... Primary piston (piston), 40 ... Electric motor, 41 ... Ball screw mechanism (rotation linear motion conversion mechanism), 91 ... Stud bolt, 92 ... Flange (contact part), 97A ... Seal projection, 97B ... Groove, 97C ... Groove

Claims (2)

A housing attached to the vehicle body, a rotation / linear motion conversion mechanism that is accommodated in the housing and converts the rotation of the electric motor into a linear motion, and a brake that is coupled to the housing and propels a piston by the rotation / linear motion conversion mechanism In an electric booster equipped with a master cylinder that generates hydraulic pressure,
A stud bolt for coupling the master cylinder is fixed to the housing, and an abutting portion whose one end abuts against the housing while being fixed to the housing is formed on the stud bolt. The motor is characterized in that an annular seal protrusion protruding so as to bite into the housing and an annular groove adjacent to at least one of the inner peripheral side and the outer peripheral side of the seal protrusion are formed in the portion. Boost device.   The electric booster according to claim 1, wherein the housing is formed of an aluminum alloy, and the stud bolt is formed of a material harder than the housing.

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