JP2016022753A - Electric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric actuator which prevents the intrusion of a brake fluid which is scooped out by the slide movement of a piston into a ball screw mechanism, and is secured in a desired life, in a structure in which a screw shaft of the ball screw mechanism abuts on the piston of a hydraulic cylinder, and is directly displaced integrally with the piston.SOLUTION: In an electric actuator, a penetration hole 11 and a bag hole 12 for accommodating a screw shaft 10 are formed at a housing 2a, a hydraulic cylinder 21 is inserted into the penetration hole 11, a sealing device 26 is arranged between the hydraulic cylinder 21 and a ball screw mechanism 8, the sealing device 26 is composed of a telescopic cover in which the sealing device 26 can be elongated and contracted, a cross section U-shaped fixed part 26a and a flat abutment part 26b which abuts on a drive shaft 7 in a center part are arranged at an outside diameter part, a telescopic part 26c which is thinned in thickness thinner than the other region is arranged between the abutment part 26b and the fixed part 26a, the fixed part 26a is fit into an annular groove 27 which is formed in the penetration hole 11, and the ball screw mechanism 8 is sealed into the hydraulic cylinder 21.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an electric actuator having a ball screw mechanism used in a brake system or transmission of an automobile or the like, and more specifically, the ball screw shaft of the ball screw mechanism in the brake system is in direct contact with a piston of a hydraulic cylinder. The present invention relates to an electric actuator that converts a rotational input from an electric motor into a linear motion of a drive shaft via a ball screw mechanism in a structure that is displaced dynamically.

  In electric actuators used in various drive units, a gear mechanism such as a trapezoidal screw or a rack and pinion is generally used as a mechanism for converting the rotational motion of the electric motor into a linear motion in the axial direction. Since these conversion mechanisms involve a sliding contact portion, the power loss is large, and it is necessary to increase the size of the electric motor and increase the power consumption. For this reason, a ball screw mechanism has been adopted as a more efficient actuator with very low friction.

  As a conventional electric actuator, for example, a nut constituting a ball screw can be driven to rotate by an electric motor supported by a housing, and the nut is coupled to a screw shaft constituting the ball screw by rotating the nut. The output member can be displaced in the axial direction. A vehicle brake system as shown in FIG. 6 is known as one using such an electric actuator. The vehicle brake system 50 includes an input device 52 that inputs an operation when the brake pedal 51 is operated by an operator, a motor cylinder device (electric brake actuator) 53 that controls brake fluid pressure, and a stable vehicle behavior. The vehicle stability assist device 54 that supports the above is provided as a separate body.

  The motor cylinder device 53 includes an actuator mechanism 56 including an electric motor 55 and a cylinder mechanism 57 urged by the actuator mechanism 56. The actuator mechanism 56 meshes with a rotation angle sensor 58 that detects the rotation angle of the electric motor 55 and a plurality of gears including a gear coupled to the output shaft of the electric motor 55 to transmit the rotational driving force of the electric motor 55. A gear mechanism 59 and a ball screw mechanism 62 including a ball screw shaft 60 and a ball 61 that move forward and backward along the axial direction when a rotational driving force is transmitted through the gear mechanism 59 are provided.

  The ball screw mechanism 62 is connected to the gear mechanism 59, is rotatably supported via a rolling bearing 64 mounted on the housing 63, and is not movable in the axial direction, and has a helical thread groove formed on the inner periphery. The nut 65 includes a nut 65 and a screw shaft 60 that is inserted into the nut 65 via a large number of balls 61 and is coaxially integrated with the drive shaft 66.

  The cylinder mechanism 57 has a cylinder main body 67 as an outer shell thereof. In the cylinder main body 67, a first slave piston 68 and a second slave piston 69 that are spaced apart from each other along the axial direction of the cylinder main body 67 slide. It is arranged freely. The first slave piston 68 is disposed close to the ball screw mechanism 62 side, abuts against one end of the drive shaft 66, and is displaced integrally with the ball screw shaft 60 in the axial direction of the arrow X1 or X2. Further, the second slave piston 69 is arranged farther from the ball screw mechanism 62 side than the first slave piston 68.

  A pair of slave piston packings 70 and 71 are mounted on the outer peripheral surfaces of the first and second slave pistons 68 and 69 via annular stepped portions, respectively. A first back chamber 74 and a second back chamber 75 communicating with the reservoir ports 72 and 73 are formed between the pair of slave piston packings 70 and 71, respectively. A first return spring 76 is disposed between the first and second slave pistons 68 and 69, and a second return spring is provided between the second slave piston 69 and the side end of the cylinder body 67. A spring 77 is provided.

  The cylinder body 67 of the cylinder mechanism 57 is provided with two reservoir ports 72 and 73 and two output ports 78 and 79. In this case, the reservoir port 72 is provided so as to communicate with a reservoir chamber (not shown) in the second reservoir 80. Further, in the cylinder body 67, a first hydraulic pressure chamber 81 for controlling the brake hydraulic pressure output from the output port 78 to the wheel cylinder (not shown) and the other output port 79 are output to the wheel cylinder. A second hydraulic pressure chamber 82 for controlling the brake hydraulic pressure is provided.

  In such a system state, when the depression of the brake pedal 51 by the driver is detected, the electric motor 55 of the motor cylinder device 53 is driven to displace the drive shaft 66 of the actuator mechanism 56, and the first return spring 76 and the first 2 The first slave piston 68 and the second slave piston 69 are displaced in the direction of the arrow X1 against the spring force of the return spring 77. Due to the displacement of the first slave piston 68 and the second slave piston 69, the brake fluid pressure in the first fluid pressure chamber 81 and the second fluid pressure chamber 82 is pressurized so as to generate a desired brake fluid pressure. (For example, refer to Patent Document 1).

JP 2012-121557 A

  In such a motor cylinder device 53, the first and second slave pistons 68 and 69 are slidably disposed on the cylinder body 67, and one end portion of the drive shaft 66 of the ball screw mechanism 62 is disposed on the first slave piston 68. The brake fluid enclosed in the first hydraulic pressure chamber 81 and the second hydraulic pressure chamber 82 is caused to displace with the first and second slave pistons 68 and 69. May be slightly leaked from the slave piston packings 70 and 71 to the actuator side. Such slightly leaked brake fluid may enter the housing 63 of the actuator mechanism 56. Then, this brake fluid may be mixed (deteriorated (softened)) with grease, which is a lubricant of the ball screw mechanism 62, to induce lubrication failure and lead to a short life.

  The present invention has been made in view of such problems of the prior art. In a structure in which the screw shaft of the ball screw mechanism is in contact with the piston of the hydraulic cylinder and is directly displaced integrally with the piston, the piston slides. It is an object of the present invention to provide an electric actuator that prevents a scraped brake fluid from entering a ball screw mechanism and ensures a desired life.

  In order to achieve such an object, the invention according to claim 1 of the present invention is a housing, an electric motor attached to the housing, and the rotational motion of the electric motor converted into a linear motion in the axial direction of the drive shaft. The ball screw mechanism is supported by a support bearing mounted on the housing so as to be rotatable and non-movable in the axial direction, and a helical screw groove is formed on the inner periphery. A nut, inserted into the nut via a number of balls, integrated with the drive shaft coaxially, and formed on the outer periphery with a spiral thread groove corresponding to the thread groove of the nut. And a screw shaft supported so as to be non-rotatable and movable in the axial direction, and the screw shaft is in contact with the piston of the hydraulic cylinder and is directly displaced integrally with the piston. A through hole and a bag hole are formed in the housing for accommodating the screw shaft, the hydraulic cylinder is fitted into the through hole, and the ball is interposed between the hydraulic cylinder and the ball screw mechanism. A sealing device for sealing the screw mechanism is provided.

  As described above, the housing, the electric motor attached to the housing, and the ball screw mechanism that converts the rotational motion of the electric motor into the linear motion in the axial direction of the drive shaft are provided. The ball screw mechanism is mounted on the housing. A nut that is rotatably supported through the support bearing and is not movable in the axial direction, and has a helical thread groove formed on the inner periphery, and is inserted into the nut via a large number of balls. And a screw shaft that is supported on the outer periphery of the housing so as to be non-rotatable and movable in the axial direction. In addition, in the electric actuator in which the screw shaft abuts against the piston of the hydraulic cylinder and is directly displaced integrally with the piston, a through hole and a bag hole for housing the screw shaft are formed in the housing. The hydraulic cylinder is inserted into the through-hole, and a sealing device for sealing the ball screw mechanism is provided between the hydraulic cylinder and the ball screw mechanism, so that the brake fluid scraped from the hydraulic cylinder penetrates. It is possible to provide an electric actuator that prevents the fluid from flowing along the inner peripheral surface of the hole and entering the ball screw mechanism to ensure a desired life.

  According to a second aspect of the present invention, the sealing device comprises a disc-shaped shielding plate, is fixed to the tip end portion of the drive shaft, and has a radial clearance between the inner peripheral surface of the through hole. The labyrinth seal may be constituted.

  According to a third aspect of the present invention, the sealing device comprises a cover that can be expanded and contracted, and is attached to the inner peripheral surface of the through hole, and is a flat contact portion that contacts the drive shaft at the center. May be provided.

  Further, as in the invention described in claim 4, the sealing device includes a fixing portion having a U-shaped cross section at an outer diameter portion, and between the fixing portion and the abutting portion, than other portions. It may be formed to be thin and include an expansion / contraction portion having an arc-shaped cross section, and the fixing portion may be fitted into an annular groove formed in the through hole and fixed by a retaining ring.

  Further, if the sealing device is made of EPDM as in the invention described in claim 5, it is excellent in chemical resistance, can be prevented from deteriorating even when immersed in brake fluid, and has durability. Can be secured.

  An electric actuator according to the present invention includes a housing, an electric motor attached to the housing, and a ball screw mechanism that converts the rotational motion of the electric motor into a linear motion in the axial direction of the drive shaft. Is supported via a support bearing mounted on the housing so as to be rotatable and non-movable in the axial direction. The nut has a spiral thread groove formed on the inner periphery, and the nut is provided with a plurality of balls. It is inserted and integrated coaxially with the drive shaft, and a helical thread groove corresponding to the thread groove of the nut is formed on the outer periphery, and is supported so as to be non-rotatable and axially movable with respect to the housing. In the electric actuator in which the screw shaft is in contact with the piston of the hydraulic cylinder and is directly displaced integrally with the piston. A through hole and a bag hole for accommodating the screw shaft are formed, and the hydraulic cylinder is fitted into the through hole, and the ball screw mechanism is hermetically sealed between the hydraulic cylinder and the ball screw mechanism. Since the device is provided, an electric actuator that prevents the brake fluid scraped from the hydraulic cylinder from flowing along the inner peripheral surface of the through hole and entering the ball screw mechanism to ensure a desired life is provided. Can be provided.

It is a longitudinal section showing one embodiment of an electric actuator concerning the present invention. It is a longitudinal cross-sectional view which shows the actuator main body of FIG. It is a principal part enlarged view which shows a connection part with the hydraulic cylinder of FIG. It is a principal part enlarged view which shows the modification of FIG. (A) is explanatory drawing which shows the state at the time of shrinkage | contraction of the cover of FIG. 4, (b) is explanatory drawing which shows the state at the time of expansion | extension same as the above. It is a longitudinal cross-sectional view which shows the example of the motor cylinder apparatus which employ | adopted the conventional electric actuator.

  An aluminum alloy housing, an electric motor attached to the housing, a speed reduction mechanism for transmitting the rotational force of the electric motor, and a rotational movement of the electric motor via the speed reduction mechanism in a straight line in the axial direction of the drive shaft A ball screw mechanism for converting into motion, and this ball screw mechanism is supported by a support bearing mounted on the housing so as to be rotatable and non-movable in the axial direction. The formed nut and the nut are inserted through a large number of balls, are integrated coaxially with the drive shaft, and a helical thread groove corresponding to the thread groove of the nut is formed on the outer periphery. The screw shaft is supported so as not to rotate with respect to the housing and is movable in the axial direction. The screw shaft contacts the piston of the hydraulic cylinder and is directly displaced with the piston. In the electric actuator, a through hole and a bag hole for housing the screw shaft are formed in the housing, and the hydraulic cylinder is fitted into the through hole, and the hydraulic cylinder and the ball screw mechanism are inserted between the hydraulic cylinder and the ball screw mechanism. A sealing device for sealing the ball screw mechanism is provided, and this sealing device is made of an extendable cover. The outer diameter portion has a U-shaped fixing portion and the central portion is a flat contact that abuts the drive shaft. A contact portion and an expansion / contraction portion formed thinner than other portions between the contact portion and the fixing portion, and the fixing portion is fitted into an annular groove formed in the through hole. ing.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 is a longitudinal sectional view showing an embodiment of an electric actuator according to the present invention, FIG. 2 is a longitudinal sectional view showing an actuator body of FIG. 1, and FIG. 3 shows a connecting portion with the hydraulic cylinder of FIG. FIG. 4 is an enlarged view of an essential part, FIG. 4 is an enlarged view of an essential part showing a modification of FIG. 3, FIG. 5 (a) is an explanatory view showing a state when the cover of FIG. 4 is contracted, and FIG. It is explanatory drawing which shows the state of time.

  As shown in FIG. 1, the electric actuator 1 meshes with a cylindrical housing 2, an electric motor M attached to the housing 2, and an input gear 3 attached to a motor shaft 3a of the electric motor M. A reduction mechanism 6 comprising an intermediate gear 4 and an output gear 5 meshing with the intermediate gear 4, and a ball screw mechanism 8 for converting the rotational movement of the electric motor into an axial linear movement of the drive shaft 7 via the reduction mechanism 6. And.

  The housing 2 is formed by die casting from an aluminum alloy such as A6063TE or ADC12, and includes a first housing 2a and a second housing 2b abutted on the end face. An electric motor M is attached to the first housing 2a, and the first housing 2a and the second housing 2b have through holes 11 for receiving a screw shaft 10 constituting a ball screw mechanism 8 described later. A bag hole 12 is formed.

  The motor shaft 3a of the electric motor M has an input gear 3 made of a spur gear attached to its end portion so as not to be relatively rotatable by press-fitting, and is freely rotatable by a rolling bearing 13 made of a deep groove ball bearing mounted on the second housing 2b. It is supported by. The output gear 5 that meshes with the intermediate gear 4 is integrally fixed to a nut 18 constituting the ball screw mechanism 8 via a key 14.

  The drive shaft 7 is configured integrally with the screw shaft 10, and a locking pin 15 is implanted at one end (right end in the figure). Further, a bottomed sleeve 17 described later is fitted into the bag hole 12 of the second housing 2b, and concave grooves 17a, 17a extending in the axial direction are formed on the inner periphery of the sleeve 17 by grinding. The concave grooves 17a and 17a are arranged to oppose each other in the circumferential direction, and the locking pin 15 of the screw shaft 10 is engaged, and the screw shaft 10 is supported so as not to rotate but to be movable in the axial direction. .

  The sleeve 17 for supporting the screw shaft 10 is formed in a cup shape by cold forging from medium carbon steel such as S55C or case-hardened steel such as SCM415 or SCM420, and 55-62HRC is formed on the surface thereof by induction hardening or carburizing quenching. The area is hardened. The sleeve 17 is not limited to this, and may be formed of, for example, a so-called MIM (Metal Injection Molding) by adjusting a metal powder into a plastic shape and molding it with an injection molding machine.

  As shown in an enlarged view in FIG. 2, the ball screw mechanism 8 includes a screw shaft 10 and a nut 18 that is externally inserted to the screw shaft 10 via a ball 16. The screw shaft 10 has a spiral thread groove 10a formed on the outer periphery. On the other hand, the nut 18 is formed with a helical thread groove 18a corresponding to the thread groove 10a of the screw shaft 10 on the inner periphery, and a large number of balls 16 are rotatably accommodated between the thread grooves 10a and 18a. ing. The nut 18 is supported by the first and second housings 2a and 2b via the two support bearings 20 and 20 so as to be rotatable and non-movable in the axial direction. Reference numeral 19 denotes a piece member that constitutes a circulation member by connecting the screw grooves 18a of the nut 18, and the piece member 19 allows an infinite circulation of a large number of balls 16.

  The cross-sectional shape of each of the thread grooves 10a and 18a described above may be a circular arc shape or a gothic arc shape, but here, a gothic arc in which the contact angle with the ball 16 is large and the axial clearance can be set small. It is formed into a shape. Thereby, the rigidity with respect to an axial load becomes high and generation | occurrence | production of a vibration can be suppressed.

  The nut 18 is made of case-hardened steel such as SCM415 or SCM420, and its surface is subjected to hardening treatment in a range of 55 to 62 HRC by vacuum carburizing and quenching. Thereby, the buffing etc. for the scale removal after the heat treatment can be omitted, and the cost can be reduced. On the other hand, the screw shaft 10 is made of medium carbon steel such as S55C or case-hardened steel such as SCM415 or SCM420, and its surface is hardened in the range of 55 to 62 HRC by induction hardening or carburizing hardening.

  The output gear 5 constituting the speed reduction mechanism 6 is fixed to the outer peripheral surface 18b of the nut 18 via a key 14, and two support bearings 20 and 20 are provided on both sides of the output gear 5 via flanges 18c. It is press-fitted through a shimeshiro. Thereby, even if a thrust load is applied from the drive shaft 7, it is possible to prevent the axial displacement between the support bearings 20 and 20 and the output gear 5. Each of the two support bearings 20 and 20 is composed of a sealed deep groove ball bearing having shield plates 20a and 20a attached to both ends, and leakage of the lubricating grease sealed inside the bearing to the outside, It prevents wear powder from entering the bearing from the outside.

  Further, in the present embodiment, the support bearing 20 that rotatably supports the nut 18 is composed of deep groove ball bearings having the same specifications, and thus is loaded from the drive shaft 7 through the thrust load and the output gear 5 described above. Both radial loads can be applied, and confirmation work for preventing misassembly during assembly can be simplified, and assembling workability can be improved. Here, the deep groove ball bearings having the same specifications refer to bearings having the same inner diameter, outer diameter, width dimension, rolling element size, number, bearing internal clearance, and the like.

  Returning to FIG. 1, a hydraulic cylinder 21 constituting a brake system is connected to one end portion (right end portion in the drawing) of the first housing 2 a by a fixing bolt (not shown), and a piston 22 is placed in the hydraulic cylinder 21. It is slidably inserted in the axial direction. The drive shaft 7 integrated with the screw shaft 10 constituting the ball screw mechanism 8 abuts on the piston 22, and the piston 22 is integrally displaced in the axial direction corresponding to the movement of the screw shaft 10. ing. In the present embodiment, the screw shaft 10 and the drive shaft 7 are illustrated as an integral structure. However, the screw shaft 10 and the drive shaft 7 may be separate, and the drive shaft 7 and the screw shaft 10 may be joined or fixed to be integrally displaced in the axial direction. Anything is fine.

  The hydraulic cylinder 21 includes a cylindrical insertion portion 21 a that is inserted into the through hole 11 of the first housing 2 a and a flange-shaped fixing portion 21 b that is positioned and fixed in contact with the end surface of the through hole 11. . In addition, a packing (seal) 23 is attached to the outer peripheral surface of the piston 22 via an annular stepped portion to prevent the brake fluid filled in the hydraulic cylinder 21 from leaking into the through hole 11.

  A polyglycol system is used for the brake fluid filled in the hydraulic cylinder 21, and against this brake fluid, the ball screw mechanism 8 has HNBR (hydrogenated acrylonitrile butadiene rubber), EPDM (ethylene propylene rubber). Since a grease made of a polyglycol base oil (Kyodo Yushi Co., Ltd., Martemp (registered trademark) AC-M) is used, there is no major problem in compatibility between them. When mixed, there is a concern about the deterioration (softening) of the grease due to the difference in viscosity.

  Here, in the present embodiment, as shown in an enlarged view in FIG. 3, when reciprocating in the hydraulic cylinder 21, it is scraped from the packing 23 of the hydraulic cylinder 21 and the piston 22, and is a through hole in the first housing 2a. A sealing device 24 is provided between the hydraulic cylinder 21 and the ball screw mechanism 8 so that the brake fluid that has flowed out to the inner periphery of the ball 11 does not enter the ball screw mechanism 8 through the through hole 11. Specifically, the sealing device 24 is made of a disc-shaped shield plate made of polyacetal, and is press-fitted into a small-diameter portion 7a formed at a tip portion (left side in the drawing) of the drive shaft 7 on the hydraulic cylinder 21 side. The stepped portion 7b formed by the small diameter portion step 7a and the retaining ring 25 are fixed in a sandwiched state. And there is a slight radial clearance between the outer diameter of the sealing device 24 and the inner peripheral surface of the through hole 11 to constitute a labyrinth seal. As a result, the brake fluid scraped from the packing 23 of the hydraulic cylinder 21 and the piston 22 is prevented from entering the ball screw mechanism 8 through the through hole 11, and is used in the ball screw mechanism 8 by the intrusion of the brake fluid. Therefore, it is possible to provide the electric actuator 1 which is prevented from being deteriorated by being mixed with the grease, and which has ensured a desired life.

  Here, the sealing device 24 made of a disc-shaped shielding plate is illustrated as being fixed to the small-diameter portion 7a of the drive shaft 7 by the retaining ring 25. However, the present invention is not limited to this, and the tip of the drive shaft 7 is not limited thereto. It may be press-fitted and may be joined to the tip of the drive shaft 7 with an adhesive. Moreover, although the disk-shaped shielding board which has the labyrinth seal which consists of a slight radial clearance between the internal peripheral surfaces of the through-hole 11 was illustrated as the sealing device 24, although not illustrated, the outer diameter of a shielding board is shown. A contact seal type in which an elastic member such as rubber is integrally formed on the portion and the elastic member is slidably contacted with the inner peripheral surface of the through hole 11 may be used.

  FIG. 4 shows a modification of the sealing device 24 described above. It should be noted that the same parts and parts as those in the above-described embodiment (FIG. 3) or parts and parts having similar functions are denoted by the same reference numerals and detailed description thereof is omitted.

  The sealing device 26 is composed of an extendable cover, and is attached to the through hole 11 into which the hydraulic cylinder 21 is inserted. Specifically, the sealing device 26 is made of synthetic rubber such as EPDM (ethylene propylene rubber) having excellent chemical resistance, and has a U-shaped fixing portion 26a at the outer diameter portion and a drive shaft at the central portion. 7 is provided with a flat contact portion 26b that contacts the tip of 7 and an arc-shaped expansion / contraction portion 26c that is formed thinner than the contact portion 26b and whose cross section slightly protrudes toward the drive shaft 7 side. A fixing portion 26 a is fitted into an annular groove 27 formed in the through hole 11 and fixed by a retaining ring 28. Thereby, the ball screw mechanism 8 side is sealed with respect to the hydraulic cylinder 21, and not only the brake fluid scraped from the packing 23 of the hydraulic cylinder 21 and the piston 22, but also foreign matters such as dust generated in the hydraulic cylinder 21 are through-holes. 11 prevents the ball screw mechanism 8 from entering the ball screw mechanism 8, prevents the grease used in the ball screw mechanism 8 from deteriorating due to the mixing of brake fluid, and prevents foreign matter from entering the ball screw mechanism 8. Thus, it is possible to provide the electric actuator 1 that ensures a desired life.

  In addition to the exemplified materials for the sealing device 26, for example, general NBR (acrylonitrile-butadiene rubber), chloroprene rubber, HNBR (hydrogenated acrylonitrile-butadiene rubber) excellent in heat resistance, Can be exemplified by ACM (polyacrylic rubber), FKM (fluororubber), silicon rubber and the like which are excellent in heat resistance and chemical resistance.

  Next, the expansion / contraction state of the sealing device 26 accompanying the axial movement of the drive shaft 7 will be described with reference to FIG. (A) shows that when the drive shaft 7 is positioned at the retracted end, that is, on the ball screw mechanism 8 side (right side in the figure), the tip of the drive shaft 7 comes into contact with the flat portion 26b of the sealing device 26. The piston 22 is displaced in the axial direction through the sealing device 26 (leftward in the figure). And as shown in (b), the expansion / contraction part 26c of the sealing device 26 is deformed with the movement of the drive shaft 7, and does not become resistance to the movement of the drive shaft 7 (here, a stroke of about 10 mm). The hydraulic cylinder 21 side and the ball screw mechanism 8 side can be shut off.

  Here, the sealing device 26 made of an extendable cover is illustrated as being fixed to the through-hole 11 with a retaining ring 28. However, the present invention is not limited to this, for example, although not shown, the front end surface of the drive shaft 7 Alternatively, a so-called wiper seal type may be used in which the contact portion 26b of the sealing device 26 is joined and the outer diameter portion is slidably contacted with the inner peripheral surface of the through hole 11 instead of the fixed portion 26a.

  In addition, here, the expansion / contraction part 26c of the sealing device 26 is formed thinner than other parts so that the deformation of the sealing device 26 does not become a resistance to the movement of the drive shaft 7, but in addition to this, The expansion / contraction part 26c can also be made into the bellows structure in which several pleats were formed.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and is merely an example, and various modifications can be made without departing from the scope of the present invention. Of course, the scope of the present invention is indicated by the description of the scope of claims, and further, the equivalent meanings described in the scope of claims and all modifications within the scope of the scope of the present invention are included. Including.

  An electric actuator according to the present invention has a structure in which a ball screw shaft of a ball screw mechanism in a brake system abuts against a piston of a hydraulic cylinder and directly displaces integrally with the piston. It can apply to the electric actuator provided with the ball screw mechanism which converts into linear motion of a drive shaft via.

DESCRIPTION OF SYMBOLS 1 Electric actuator 2 Housing 2a 1st housing 2b 2nd housing 3 Input gear 3a Motor shaft 4 Intermediate gear 5 Output gear 6 Reduction mechanism 7 Drive shaft 7a Small diameter part 7b Step part 8 Ball screw mechanism 10 Screw shaft 10a, 18a Screw Groove 11 Through-hole 12 Bag hole 14 Key 15 Locking pin 16 Ball 17 Sleeve 17a Groove 18 Nut 18b Nut outer peripheral surface 18c Hook 19 Frame member 20 Support bearing 20a Shield plate 21 Hydraulic cylinder 21a Insertion portion 21b Fixing portion 22 Piston 23 Packing 24, 26 Sealing device 25, 28 Retaining ring 26a Fixing portion 26b Abutting portion 26c Telescopic portion 50 Brake system 51 for vehicle Brake pedal 52 Input device 53 Motor cylinder device (electric brake actuator)
54 Vehicle Stability Assist Device 55 Electric Motor 56 Actuator Mechanism 57 Cylinder Mechanism 58 Rotation Angle Sensor 59 Gear Mechanism 60 Ball Screw Shaft 61 Ball 62 Ball Screw Mechanism 63 Housing 64 Rolling Bearing 65 Nut 66 Drive Shaft 67 Cylinder Body 68 First Slave Piston 69 Second slave piston 70, 71 Slave piston packing 72, 73 Reservoir port 74 First back chamber 75 Second back chamber 76 First return spring 77 Second return spring 78, 79 Output port 80 Second reservoir 81 First hydraulic pressure Chamber 82 Second hydraulic chamber M Electric motor

Claims (5)

A housing;
An electric motor attached to the housing;
A ball screw mechanism that converts the rotational motion of the electric motor into linear motion in the axial direction of the drive shaft,
The ball screw mechanism is rotatably supported via a support bearing mounted on the housing and is not axially movable, and a nut having a helical thread groove formed on the inner periphery,
The nut is inserted through a large number of balls and is integrated coaxially with the drive shaft. A spiral screw groove corresponding to the screw groove of the nut is formed on the outer periphery, and the nut cannot rotate with respect to the housing. And a screw shaft supported so as to be axially movable,
In the electric actuator in which this screw shaft abuts against the piston of the hydraulic cylinder and is directly displaced integrally with the piston,
A through hole and a bag hole for accommodating the screw shaft are formed in the housing, and the hydraulic cylinder is fitted into the through hole, and the ball screw mechanism is interposed between the hydraulic cylinder and the ball screw mechanism. An electric actuator comprising a sealing device for sealing.   The said sealing device consists of a disk-shaped shielding board, is fixed to the front-end | tip part of the said drive shaft, has a radial direction clearance between the internal peripheral surfaces of the said through-hole, and comprises the labyrinth seal. The electric actuator according to 1.   2. The electric actuator according to claim 1, wherein the sealing device is formed of a retractable cover, is mounted on an inner peripheral surface of the through hole, and has a flat contact portion that contacts the drive shaft at a central portion.   The sealing device is formed in a U-shaped fixing portion at the outer diameter portion, and is formed between the fixing portion and the abutting portion so as to be thinner than other portions, and an expansion / contraction portion having an arc-shaped section. The electric actuator according to claim 3, wherein the fixing portion is fitted in an annular groove formed in the through hole and fixed by a retaining ring.   The electric actuator according to claim 3 or 4, wherein the sealing device is formed of EPDM.

Images