Patent Application
20150292619
This application claims priority under 35 U.S.C. §119 to Korean Application No. 10-2014-0042474 filed on Apr. 9, 2014, whose entire disclosure is hereby incorporated by reference.
1. Field
The present disclosure relates to an electronic parking brake actuator, and more particularly, to an electronic parking brake actuator including a planetary gear set.
2. Background
An electronic parking brake (EPB) is an apparatus electronically control the driving of a parking brake. The EPB is installed on a general disc brake and performs a parking brake function. To operate the EPB, an additional actuator is necessary. The actuator of the EPB includes a motor installed inside a housing and a gear assembly for transferring power and reducing speed is disposed on an output shaft of the motor.
The gear assembly may include a planetary gear set for changing speed. The planetary gear set may include a linear gear coupled with a shaft, a plurality of planetary gears engaged with a circumference of the linear gear, and a ring gear engaged with the planetary gear. The ring gear is fixed inside the housing. In general, a coupling rib is formed to protrude from an outer circumferential surface of the ring gear, a slot is formed inside the housing, and the coupling rib is inserted into the slot, thereby mounting the ring gear on the housing.
Considering a state of the ring gear which continuously receives torque and a tolerance with respect to the slot of the housing which is injection-molded, a gap may occur between the coupling rib and the slot in a configuration in which the coupling rib slides on the slot. When a gap occurs between the ring gear and the housing, the performance and durability of a product may have serious defects.
The embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein:
In detail, the torque of the motor 110 may be transferred to a spindle of the parking brake through the power transfer assembly or gearing 120 and the planetary gear set 130. When the spindle rotates due to the power of the motor 110, a piston is pressurized and a pad and a disc rub against each other, thereby generating the braking force.
The motor 110 includes a shaft rotatably formed, a rotor coupled with the shaft, and a stator fixed inside the housing, in which the stator may be installed along a circumference of the rotor with a gap. A coil which forms a rotational magnetic field is wound on the stator and causes an electric interaction with the rotor, thereby inducing the rotation of the rotor. When the rotor rotates, the shaft rotates and transfers power necessary for a braking force to the spindle of the parking brake.
The power transfer assembly 120 is connected to an output shaft of the motor 110 and transfers the power of the motor 110 to the planetary gear set 130. In one embodiment, the power transfer assembly 120 may include an idle gear 121 and a drive gear 122. The idle gear 121 is engaged with a pinion gear 111 connected to the shaft of the motor 110. The drive gear 122 rotates while being engaged with the idle gear 121. A linear gear 131 may be coupled below with the drive gear 122 as a double gear.
The planetary gear set 130 shifts the power received from the power transfer assembly 120 to the spindle of the parking brake. In one embodiment, the planetary gear set 130 may include the linear gear 131, planetary gears 132, the ring gear 133, and a carrier 134.
The linear gear 131 is formed to be a double gear having the same shaft with the drive gear 122 and receives the torque of the motor 110. The three planetary gears 132 are disposed along a circumference of the linear gear 131 to be engaged therewith simultaneously with being engaged with the ring gear 133. The planetary gears 132 are supported by the carrier 134. The ring gear 133 is fixed to the housing 140.
As shown in
According to one embodiment of the present disclosure, different from general ring gears manufactured through sintering, the ring gear 133 of the planetary gear set 130 is manufactured through injection molding, thereby forming a plurality of insertion protrusions 133a on the bottom of the ring gear 133.
In one embodiment, three insertion protrusions 133a may be formed to be arranged to be separate from one another at regular intervals along a circumferential direction on the bottom of the ring gear 133. Each of the insertion protrusions 133a may be formed to have a cylindrical shape. Corresponding to the insertion protrusions 133a, three insertion grooves 142b may be formed on the bottom surface 142a of the ring gear accommodating portion 142. The insertion groove 142b may be formed to be cylindrically concaved corresponding to the insertion protrusions 133a.
The present disclosure is not limited thereto and/or the shape and number of the insertion protrusions 133a and the insertion grooves 142b may be variously modified. To form the insertion groove 142b, the housing 140 may be injection-molded while a mold is being injected with a material including a synthetic resin.
As shown in
As described above, compared with general configurations in which a coupling rib formed on an outer circumferential surface of a ring gear slides and is coupled to a housing, a configuration according to one embodiment of the present disclosure in which the insertion protrusion 133a is forcibly inserted into the insertion groove 142b, thereby fixing the ring gear 133 to the housing 140 may reduce the occurrence of a gap and has advantages in a tolerance design of a housing. A coupling configuration between the insertion protrusion 133a and the insertion groove 142b is more easily assembled than general configurations of being inserted to slide.
The above-described parking brake actuator according to an exemplary embodiment of the present disclosure is formed through injection molding in which an insertion protrusion is formed on a bottom of a ring gear, an insertion groove is formed in a bottom surface of a ring gear accommodating portion of a housing, and the insertion protrusion is forcibly inserted into the insertion groove, thereby preventing a gap between the ring gear and the housing.
The configuration described above increases the degree of freedom in a tolerance design with respect to the ring gear accommodating portion of the housing, thereby increasing the quality of products.
According to one embodiment of the present disclosure, the ring gear is formed through injection molding, thereby reducing manufacturing costs.
The present disclosure is directed to provide a parking brake actuator capable of preventing a gap between a ring gear and a housing of a planetary gear set.
The present disclosure is also directed to provide a parking brake actuator capable of reducing manufacturing costs.
One aspect of the present disclosure provides a parking brake actuator including a motor, a power transfer unit connected to an output shaft of the motor, a planetary gear set including a linear gear connected to the power transfer unit, a planetary gear engaged with the linear gear, and a ring gear engaged with the planetary gear and including an insertion protrusion formed on a bottom, and a housing including a motor accommodating portion in which the motor is accommodated and a ring gear accommodating portion in which the ring gear is accommodated, in which the ring gear accommodating portion includes an insertion groove formed on a bottom surface into which the insertion protrusion is forcibly inserted.
The ring gear may include the insertion protrusion having a cylindrical shape, and the ring gear accommodating portion may include the insertion groove having a cylindrical shape.
A plurality of the insertion protrusions and a plurality of the insertion grooves may be disposed along a circumferential direction to be separate from one another, respectively.
Three of the insertion protrusions and three of the insertion grooves may be disposed along the circumferential direction at regular intervals.
The ring gear may be formed through injection molding.
The housing may include a body including the motor accommodating portion and the ring gear accommodating portion, a gear cover which covers the motor accommodating portion and the ring gear accommodating portion, and a body cover which covers the gear cover.
A rotating shaft of the motor and a rotating shaft of the linear gear may be disposed in parallel while being separate from each other.
The power transfer unit may be disposed in an accommodating space formed by the gear cover and the body cover.
The power transfer unit may include an idle gear engaged with a pinion gear coupled with the output shaft of the motor and a drive gear engaged with the idle gear simultaneously with being connected to the linear gear.
The drive gear and the linear gear may be coupled with each other as a double gear on the same shaft.
Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments.
Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2014-0042474 | Apr 2014 | KR | national |
