JP6594136B2 - Electric brake actuator - Google Patents

Description

  The present invention relates to an electric brake actuator used to drive a brake pad of an electric brake device.

  Conventionally, as a brake device for a vehicle, a hydraulic brake device using a hydraulic pressure as a drive source has been often adopted. However, the hydraulic brake device uses a brake oil, and thus has a high environmental load. Also, an ABS, a stability control system is used. It is difficult to further enhance the functions such as brake assist. Therefore, an electric brake device has attracted attention as a means for realizing further enhancement of the function of the brake device and reduction of environmental load.

  The electric brake device includes a brake disk that rotates integrally with a wheel, a pair of brake pads that are opposed to each other in the axial direction with the brake disk interposed therebetween, and an electric brake actuator that moves the brake pad. When the electric brake actuator moves the brake pad and presses it against the brake disc, a braking force is generated.

  In general, an actuator for an electric brake used in such an electric brake device is transmitted from the electric motor through the electric motor, a reduction gear that reduces and transmits the rotation output from the electric motor, and the reduction gear. A linear motion mechanism that converts the rotation to linear motion (see, for example, Patent Document 1). The speed reducer includes a plurality of gears that mesh with each other and a speed reducer housing that houses the plurality of gears. The reduction gear housing is configured to support a plurality of gears of the reduction gear.

JP2015-137667A

  The inventor of the present application examined whether the above-described electric brake actuator could be reduced in weight. The electric brake device is usually provided on the unsprung portion of the vehicle (that is, on the side of the wheel that supports the vehicle body via the suspension, not on the side of the vehicle body that is supported via the suspension). If this can be achieved, the unsprung weight of the vehicle can be suppressed, and as a result, the riding comfort of the vehicle can be improved.

  The inventor has come up with the idea of forming a reduction gear housing that houses the gears of the reduction gear with a resin that is lighter than metal in order to reduce the weight of the electric brake actuator. That is, the gear of the speed reducer is usually formed of a metal to ensure rigidity, but the speed reducer housing does not need to be as rigid as the gear, so it is possible to employ resin as the material of the speed reducer housing. I focused on the point.

  However, when the speed reducer housing is made of resin, generally, since the resin has a significantly larger linear expansion coefficient than that of metal, when the speed reducer becomes hot due to frictional heat of the brake pad, the gear of the speed reducer And a large difference in thermal expansion occurs between the reduction gear housing made of resin and supporting the central shaft of these gears. At this time, since the backlash between the gears changes due to the difference in thermal expansion, there is a possibility that the transmission efficiency of the speed reducer is remarkably lowered or abnormal noise is generated from the speed reducer.

  The problem to be solved by the present invention is to provide an actuator for an electric brake that is light in weight and is less likely to cause performance degradation due to temperature changes.

In order to solve the above problems, the present invention provides an electric brake actuator having the following configuration.
An electric motor;
A decelerator that decelerates and transmits the rotation output from the electric motor;
In an electric brake actuator having a linear motion mechanism that converts rotation transmitted from the electric motor via the speed reducer into linear motion,
The speed reducer has a plurality of metal gears that mesh with each other, and a speed reducer housing that houses the gears,
The reduction gear housing has a resin portion provided to cover the plurality of gears, and a metal support that is fixed to the resin portion and supports the plurality of gears in common. Electric brake actuator.

  If it does in this way, since the reduction gear housing has the structure which has a resin part, the actuator for electric brakes can be reduced rather than making the whole reduction gear housing metal. Also, since the gears of the speed reducer and the support that supports these gears in common are all made of metal, when the speed reducer becomes hot due to frictional heat of the brake pad, etc. The difference in thermal expansion is unlikely to occur between this gear and a support that supports these gears in common, and the backlash between the gears is unlikely to change. For this reason, the performance of the electric brake actuator is hardly deteriorated due to a temperature change.

  It is preferable that at least a part of the metal support is embedded in the resin portion. For example, insert molding can be adopted as a method of embedding at least a part of the metal support in the resin portion. That is, at least a part of the metal support is embedded in the resin portion of the speed reducer housing by resin molding the speed reducer housing in a state where the metal support is disposed in the mold of the speed reducer housing. State.

  If it does in this way, since the fixation strength of the metal support body with respect to a resin part becomes high, it will become possible to reinforce the resin part of a reduction gear housing with a metal support body effectively.

  It is preferable to adopt a structure having a plurality of cylindrical portions that respectively support the plurality of gears and a connecting portion that connects one ends of the plurality of cylindrical portions as the metal support.

  If it does in this way, position shift of each gear with respect to metal supports can be prevented certainly, and it becomes possible to prevent change of backlash between the gears of a reduction gear accompanying temperature change effectively.

  When the electric motor has a permanent magnet for generating a rotational force, since the resin has a lower thermal conductivity than the metal, the speed reducer housing having the resin portion has a heat insulating effect. . For this reason, when the reduction gear housing having the resin portion is employed, it is possible to prevent the permanent magnet inside the electric motor from being demagnetized by the frictional heat of the brake pad. In this case, it is more preferable that the reduction gear housing is provided with a motor seat surface to which the electric motor is fixed, and the motor seat surface is made of resin.

  In this way, since the resin has a lower thermal conductivity than the metal, it is possible to effectively prevent heat from being transmitted from the reducer housing to the electric motor, and the permanent magnet inside the electric motor can be It is possible to more effectively prevent demagnetization due to frictional heat.

  As the metal constituting the support, it is preferable to employ a metal having a linear expansion coefficient equivalent to that of the metal constituting the gear.

  In this way, when the speed reducer becomes hot due to frictional heat of the brake pads, a difference in thermal expansion occurs between the gear of the speed reducer and the support that supports these gears in common. Can be effectively prevented.

  The electric brake actuator according to the present invention is light in weight because the reduction gear housing has a resin portion. Also, since the gears of the speed reducer and the support that supports these gears in common are all made of metal, when the speed reducer becomes hot due to frictional heat of the brake pad, etc. The difference in thermal expansion is unlikely to occur between this gear and a support that supports these gears in common, and the backlash between the gears is unlikely to change. Therefore, performance degradation due to temperature change is unlikely to occur.

Sectional drawing which shows the electric brake device which uses the actuator for electric brakes of embodiment of this invention Sectional view along the line II-II in FIG. Sectional view along line III-III in FIG. Sectional view of the housing body shown in FIG. Sectional view of the housing lid shown in FIG.

  FIG. 1 shows an electric brake device using an electric brake actuator 1 according to an embodiment of the present invention. This electric brake device is opposed in the axial direction with a brake disc 2 rotating integrally with a wheel (not shown), a caliper body 3 having a shape straddling the outer periphery of the brake disc 2, and the brake disc 2 therebetween. A pair of brake pads 4 and 5 and an electric brake actuator 1 for moving the brake pad 5 are provided.

  The caliper body 3 brakes the claw portion 6 and the linear motion mechanism housing portion 7 disposed so as to face each other in the axial direction with the pair of brake pads 4 and 5 interposed therebetween, and the claw portion 6 and the linear motion mechanism housing portion 7. The outer shell portion 8 is connected on the outer diameter side of the disk 2. The caliper body 3 is supported with respect to the mount 9 so as to be movable in the axial direction by a pair of slide pins 10 (see FIG. 2). The mount 9 is fixed to a knuckle (not shown) that supports the wheel. Each brake pad 4, 5 is supported by a pad pin (not shown) attached to the caliper body 3 so as to be movable in the axial direction with respect to the caliper body 3.

  The electric brake actuator 1 converts an electric motor 11, a speed reducer 12 that decelerates and transmits rotation output from the electric motor 11, and converts rotation transmitted from the electric motor 11 via the speed reducer 12 into linear motion. And a linear motion mechanism 13.

  As shown in FIG. 3, the electric motor 11 is a motor (so-called permanent magnet synchronous motor) having a permanent magnet 14 for generating a rotational force therein. The electric motor 11 includes a rotor 15, a stator 16, and a motor housing 17. The rotor 15 includes a motor shaft 19 rotatably supported by a pair of bearings 18 attached to the motor housing 17, and a rotor core 20 fixed to the outer periphery of the motor shaft 19. The rotor core 20 has a plurality of permanent magnets 14 arranged so that N poles and S poles appear alternately in the circumferential direction. The stator 16 includes a stator core 21 fixed to the inner periphery of the motor housing 17 and an electromagnetic coil 22 wound around the stator core 21. When the electromagnetic coil 22 is energized, a rotational force is generated in the rotor core 20 by an electromagnetic force acting between the stator core 21 and the rotor core 20, and the motor shaft 19 rotates integrally with the rotor core 20.

  As shown in FIG. 2, the speed reducer 12 includes an input gear 23 fixed to the motor shaft 19, an output gear 25 fixed to the rotary shaft 60 of the linear motion mechanism 13 (see FIG. 1), an input gear 23, An intermediate gear 24 that transmits rotation between the output gears 25 and a reduction gear housing 26 that accommodates these gears 23, 24, 25 are provided. The input gear 23 and the large gear 24a of the intermediate gear 24 mesh with each other, and the small gear 24b of the intermediate gear 24 and the output gear 25 mesh with each other. The speed reducer 12 sequentially transmits the rotation input to the input gear 23 from the motor shaft 19 of the electric motor 11 through the input gear 23, the intermediate gears 24 (24a, 24b), and the output gear 25 having different numbers of teeth. The reduced speed rotation is output from the output gear 25 to the rotary shaft 60 of the linear motion mechanism 13. The input gear 23, the intermediate gear 24, and the output gear 25 are each made of metal.

  As shown in FIG. 3, the speed reducer housing 26 is configured by combining a housing main body 27 and a housing lid 28. The housing body 27 is fixed to the caliper body 3 with bolts 29. The housing lid 28 is fixed to the housing body 27 by welding (for example, ultrasonic welding or laser welding).

The housing body 27 includes a resin part 30 and a metal support 31 fixed to the resin part 30. The resin portion 30 of the housing body 27 is formed so as to cover the input gear 23, the intermediate gear 24, and the output gear 25 from the linear motion mechanism 13 side. The metal support 31 includes a plurality of cylindrical portions 32 and 33 that respectively support the intermediate gear 24 and the output gear 25, and a connecting portion 34 that connects one ends of the plurality of cylindrical portions 32 and 33. As shown in FIG. 4, the support 31 is a metal member in which a plurality of cylindrical portions 32 and 33 are connected together so as to support the intermediate gear 24 and the output gear 25 in common. The metal constituting the support 31 is equivalent to the metal constituting the input gear 23, the intermediate gear 24, and the output gear 25 (specifically, the difference in linear expansion coefficient is less than 5 × 10 ⁻⁶ / ° C., preferably linear expansion) A metal having a coefficient of linear expansion of less than 3 × 10 ⁻⁶ / ° C. is used. Moreover, polybutylene terephthalate resin (PBT), polyphenylene sulfide resin (PPS), etc. are employable as the resin material which comprises the resin part 30. FIG. Moreover, if this resin material employs a composite of fiber reinforcing materials such as glass fibers and carbon fibers, it can ensure extremely high strength.

  As shown in FIG. 3, a shaft body 35 is fitted on the inner periphery of the cylindrical portion 32 of the metal support 31, and the intermediate gear 24 is connected via a rolling bearing 36 fitted to the outer periphery of the shaft body 35. It is rotatably supported. Further, a rolling bearing 37 is fitted on the inner periphery of the cylindrical portion 33, and the output gear 25 is rotatably supported via the rolling bearing 37.

  The metal support 31 is fixed to the resin portion 30 of the housing body 27 by insert molding. That is, at least a part of the metal support 31 is formed on the resin portion 30 of the housing main body 27 by resin molding the housing main body 27 in a state where the metal support 31 is disposed in the molding die of the housing main body 27. Is embedded, so that the metal support 31 is fixed to the resin portion 30 of the housing body 27. In this embodiment, insert molding is employed as a means for fixing the metal support 31 to the resin portion 30, but it is also possible to fix it by a fixing means such as screwing.

  A motor seat surface 38 to which the electric motor 11 is fixed is formed on the housing body 27. The electric motor 11 is fixed to the housing body 27 with bolts 39 (see FIG. 2). The motor seat surface 38 is formed with a through-hole 41 into which an annular step 40 formed in the motor housing 17 is fitted so as to surround the motor shaft 19 of the electric motor 11. The input gear 23 is positioned at a predetermined position that meshes with the intermediate gear 24 by fitting the stepped portion 40 of the motor housing 17 and the through hole 41 of the housing body 27. The housing main body 27 is formed such that the motor seat surface 38 that contacts the electric motor 11 is made of resin, so that the motor housing 17 and the metal support 31 are not in direct contact with each other.

  As shown in FIG. 4, the housing body 27 has a through hole 41 that fits into the stepped portion 40 of the electric motor 11 and a through hole 42 through which the rotation shaft 60 of the linear motion mechanism 13 is inserted. The metal support 31 is formed to have an annular portion 43 along the periphery of the through hole 41. As a result, rigidity for supporting the electric motor 11 is given to the housing body 27. Further, the metal support 31 has a portion 44 formed as a part of the connecting portion 34 so as to connect the cylindrical portion 32 and the cylindrical portion 33 in a straight line. Thereby, reinforcement of the resin part 30 by the metal support body 31 is performed effectively.

  As shown in FIG. 3, the housing lid 28 has a resin portion 50 and a metal support 51 fixed to the resin portion 50, similarly to the housing body 27. The resin portion 50 of the housing lid 28 is formed so as to cover the input gear 23, the intermediate gear 24 and the output gear 25 from the side opposite to the linear motion mechanism 13. The metal support 51 includes a plurality of cylindrical portions 52 and 53 that respectively support the intermediate gear 24 and the output gear 25, and a connecting portion 54 that connects one ends of the plurality of cylindrical portions 52 and 53. As shown in FIG. 5, the support 51 is a metal member in which a plurality of cylindrical portions 52 and 53 are connected so as to support the intermediate gear 24 and the output gear 25 in common. As the metal constituting the support 51, a metal having a linear expansion coefficient equivalent to that of the metal constituting the input gear 23, the intermediate gear 24, and the output gear 25 is employed. Therefore, the metal which comprises the support body 31 of the housing main body 27 and the support body 51 of the housing cover body 28 is a metal having the same linear expansion coefficient.

  A shaft body 35 is fitted on the inner periphery of the cylindrical portion 52 of the metal support body 51, and the intermediate gear 24 is rotatably supported via a rolling bearing 36 fitted to the outer periphery of the shaft body 35. . A rolling bearing 55 is fitted on the inner periphery of the cylindrical portion 53, and the output gear 25 is rotatably supported via the rolling bearing 55. The intermediate gear 24 is rolled and supported at both ends by a rolling bearing 36 on the housing body 27 side and a rolling bearing 36 on the housing lid 28 side. The output gear 25 is supported at both ends by a rolling bearing 37 on the inner periphery of the cylindrical portion 33 of the housing body 27 and a rolling bearing 55 on the inner periphery of the cylindrical portion 53 of the housing lid 28.

  The metal support 51 is fixed to the resin portion 50 of the housing lid 28 by insert molding. That is, the housing lid 28 is resin-molded in a state where the metal support 51 is disposed in the molding die of the housing lid 28, whereby the metal support 51 is formed on the resin portion 50 of the housing lid 28. At least a part of the support 51 is embedded, whereby the metal support 51 is fixed to the resin portion 50 of the housing lid 28.

  As shown in FIG. 5, the metal support 51 includes a part 56 formed as a part of the connecting part 54 so as to connect the cylinder part 52 and the cylinder part 53 in a straight line. Thereby, the reinforcement of the resin part 50 by the metal support body 51 is performed effectively.

  As shown in FIG. 3, the linear motion mechanism 13 is disposed coaxially with the rotary shaft 60 so as to surround the rotary shaft 60 to which the rotation of the electric motor 11 is transmitted via the speed reducer 12. A cylindrical outer ring member 61, a plurality of planetary rollers 62 provided in the circumferential direction between the outer periphery of the rotating shaft 60 and the inner periphery of the outer ring member 61, and each planetary roller 62 can rotate. And a carrier 63 for holding the revolving motion.

  Each planetary roller 62 is in rolling contact with the outer periphery of the rotating shaft 60. The contact portion of the rotating shaft 60 with respect to the planetary roller 62 is a cylindrical surface. When the rotating shaft 60 rotates, each planetary roller 62 revolves inside the outer ring member 61 around the rotating shaft 60 while rotating around the roller shaft.

  The outer ring member 61 is supported on the inner surface of the linear motion mechanism accommodating portion 7 of the caliper body 3 so as to be slidable in the axial direction. A spiral ridge 64 is provided on the inner periphery of the outer ring member 61. The spiral ridge 64 is a ridge that extends obliquely with a predetermined lead angle with respect to the circumferential direction. On the outer periphery of each planetary roller 62, a plurality of circumferential grooves 65 that engage with the spiral ridges 64 are formed at intervals in the axial direction.

  The carrier 63 incorporates a thrust bearing 66 that supports each planetary roller 62 in a rotatable manner. Also, a bearing support member 67 formed in an annular shape is fixed between the carrier 63 and the speed reducer 12 so that the rotary shaft 60 passes therethrough. A thrust bearing 68 for supporting the carrier 63 so as to be revolved is incorporated therebetween. A rolling bearing 69 that rotatably supports the rotating shaft 60 is incorporated in the inner periphery of the bearing support member 67. The bearing support member 67 is fixed so as not to move in the axial direction by a retaining ring 70 mounted inside the linear motion mechanism accommodating portion 7 of the caliper body 3.

  At the end of the outer ring member 61 on the brake disk 2 side, an engagement concave portion 72 that engages with an engagement convex portion 71 formed on the back surface of the brake pad 5 is formed. The outer ring member 61 is prevented from rotating by the engagement of 72.

  An example of the operation of the electric brake device will be described.

  When the electric motor 11 (see FIG. 3) rotates, the rotation of the electric motor 11 is input to the rotary shaft 60 via the speed reducer 12, and the planetary roller 62 revolves while rotating. At this time, the outer ring member 61 and the planetary roller 62 are moved relative to each other in the axial direction by the engagement of the spiral ridge 64 and the circumferential groove 65. However, the planetary roller 62 is restricted from moving in the axial direction together with the carrier 63. The roller 62 does not move in the axial direction, and the outer ring member 61 moves in the axial direction. In this way, the linear motion mechanism 13 converts the rotation transmitted from the electric motor 11 into a linear motion of the outer ring member 61, presses the brake pad 5 with the outer ring member 61 and moves the brake pad 5 in the axial direction, Press against the brake disc 2. At this time, the brake disc 2 is braked by the friction between the brake pad 5 and the brake disc 2.

  The electric brake actuator 1 has a structure in which the housing main body 27 has the resin portion 30 and the housing lid 28 also has the resin portion 50, so that the weight of the reduction gear housing 26 is lighter than that made of metal. It is.

  In addition, the electric brake actuator 1 has a metal support 31 fixed to the resin portion 30 of the housing body 27 and a metal support 51 fixed to the resin portion 50 of the housing lid 28. The rigidity of the housing body 27 and the housing lid 28 can be easily secured. Therefore, the wall thickness of the housing main body 27 and the housing lid 28 can be made thinner than those in which the entire reduction gear housing 26 is made of resin, and the size is small.

  In the electric brake actuator 1, the plurality of gears 24 and 25 of the speed reducer 12 and the support body 31 that supports these gears in common are both made of metal. The difference in thermal expansion is less likely to occur. Similarly, since the plurality of gears 24 and 25 of the speed reducer 12 and the support body 51 that supports these gears in common are both made of metal, there is a difference in thermal expansion between the gears 24 and 25 and the support body 51. Hard to occur. Therefore, when the speed reducer 12 becomes high temperature due to frictional heat of the brake pads 4 and 5, the backlash between the intermediate gear 24 and the output gear 25 hardly changes, and the performance of the electric brake actuator 1 deteriorates due to temperature change. (For example, a reduction in transmission efficiency of the speed reducer 12 and generation of abnormal noise due to a change in backlash between gears due to a temperature change) hardly occur.

  The electric brake actuator 1 is formed such that the metal support 31 of the speed reducer housing 26 has an annular portion 43 along the periphery of the positioning through hole 41 of the electric motor 11. Therefore, the backlash between the input gear 23 and the intermediate gear 24 hardly changes when the speed reducer 12 becomes high temperature due to frictional heat of the brake pads 4 and 5. Therefore, performance degradation of the electric brake actuator 1 due to temperature change is unlikely to occur.

  In addition, the electric brake actuator 1 is in a state in which at least a part of the metal support 31 is embedded in the resin portion 30 of the housing body 27 by insert molding, so that the metal support for the resin portion 30 is supported. The fixing strength of the body 31 is high, and the resin part 30 of the housing body 27 can be effectively reinforced by the metal support 31. Similarly, since at least a part of the metal support 51 is embedded in the resin part 50 of the housing lid 28 by insert molding, the fixing strength of the metal support 51 to the resin part 50 is high. The resin portion 50 of the housing lid 28 can be effectively reinforced with a metal support 51.

  Moreover, since resin has lower thermal conductivity than metal, the reduction gear housing 26 having the resin portions 30 and 50 has a heat insulating effect. Therefore, the permanent magnet 14 inside the electric motor 11 can be prevented from being demagnetized by the frictional heat of the brake pads 4 and 5. Furthermore, since the reduction gear housing 26 is formed so that the motor seat surface 38 is made of resin, it is possible to effectively prevent heat from being transmitted from the reduction gear housing 26 to the electric motor 11. It is possible to more effectively prevent the permanent magnet 14 inside 11 from being demagnetized by the frictional heat of the brake pads 4 and 5.

  Further, the electric brake actuator 1 employs a metal having a linear expansion coefficient equivalent to that of the metal constituting the intermediate gear 24 and the output gear 25 as the metal constituting the supports 31 and 51, so that the brake pad When the speed reducer 12 becomes high temperature due to frictional heat of 4, 5 and the like, it is effectively prevented that a difference in thermal expansion occurs between the intermediate gear 24 and the output gear 25 and the supports 31 and 51. It is possible.

  In the above embodiment, an example in which the planetary roller mechanism using the planetary roller 62 is adopted as the linear motion mechanism 13 that converts the rotation transmitted from the electric motor 11 into linear motion has been described. A moving mechanism 13 (feed screw mechanism, ball ramp mechanism, etc.) may be used.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Electric brake actuators 4, 5 Brake pad 11 Electric motor 12 Reduction gear 13 Linear motion mechanism 14 Permanent magnet 23 Input gear 24 Intermediate gear 25 Output gear 26 Reduction gear housing 27 Housing main body 28 Housing lid body 30 Resin part 31 Support body 32 , 33 Tube portion 34 Connection portion 38 Motor seat surface 50 Resin portion 51 Support body 52, 53 Tube portion 54 Connection portion

Claims (5)

An electric motor (11);
A speed reducer (12) that decelerates and transmits the rotation output from the electric motor (11);
In the electric brake actuator having the linear motion mechanism (13) for converting the rotation transmitted from the electric motor (11) through the speed reducer (12) into a linear motion,
The speed reducer (12) includes a plurality of metal gears (24, 25) that mesh with each other, and a speed reducer housing (26) that houses the gears (24, 25).
The reduction gear housing (26) is fixed to the resin portion (30) provided to cover the plurality of gears (24, 25) and the resin portion (30), and the plurality of gears (24, 25). And an electric brake actuator characterized by having a metal support (31) that supports the same in common.   The electric brake actuator according to claim 1, wherein at least a part of the metal support (31) is embedded in the resin portion (30).   The metal support (31) connects a plurality of cylindrical portions (32, 33), which respectively support the plurality of gears (24, 25), and ends of the plurality of cylindrical portions (32, 33). The actuator for electric brakes of Claim 1 or 2 which has a connection part (34) to do. The electric motor (11) has a permanent magnet (14) for generating a rotational force inside,
The said reduction gear housing (26) has a motor seat surface (38) to which the said electric motor (11) is fixed, and is formed so that the motor seat surface (38) may become resin. The actuator for electric brakes in any one of 3.   The electric brake actuator according to any one of claims 1 to 4, wherein the metal constituting the support (31) is a metal having a linear expansion coefficient equivalent to that of the metal constituting the gear (24, 25).

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