Actuator for an electric parking brake system

1. An actuator for an electric parking brake system, comprising:

an outer housing;

a planetary gear train and an electric motor received in the outer housing; and

at least one gear connected between the planetary gear train and the electric motor, the electric motor being arranged to drive the planetary gear train through the at least one gear;

wherein the planetary gear train comprises a multi-stage planetary gear mechanism, an output driven by the planetary gear mechanism, a gear housing for receiving the planetary gear mechanism, and a gear cover connected to one end of the gear housing, wherein the planetary gear mechanism has a first stage through to a Nth stage that are sequentially meshed from one end to the other end of the planetary gear train, N is an integer greater than 1, each stage of planetary gear mechanism comprises a sun gear, a ring gear, a plurality of planet gears meshed with the sun gear and ring gear, and a planet carrier supporting the planet gears, and the output is fixed to the planet carrier of the Nth stage; and

wherein the planetary gear train further comprises a centering pin extending through the planetary gear mechanism, such that stages of the planetary gear mechanism rotate about the centering pin; and

wherein the centering pin is fixed to the sun gear of the first stage of the planetary gear mechanism or one of the output and the planet carrier of the Nth stage.

2. The actuator of claim 1 , wherein the outer housing of the actuator further comprises a mounting bracket and a top cover, the electric motor is mounted on one side of the mounting bracket, the top cover is connected to another side of the mounting bracket, with the at least one gear being received between the top cover and the mounting bracket; a through hole is defined through the mounting bracket, the at least one gear is aligned with and connected to the gear housing through the through hole, such that the gear housing is received in the through hole.

3. The actuator of claim 2 , wherein a shock absorber is attached around an outer periphery of the mounting bracket.

4. The actuator of claim 2 , wherein the top cover is connected to the mounting bracket by a plurality of snap fit connectors.

5. The actuator of claim 2 , wherein the top cover is connected to the gear housing by a plurality of snap fit connectors.

6. The actuator of claim 1 , wherein the gear housing comprises N portions, two adjacent ones of which are connected to form a stepped structure, an inner surface of each portion of the gear housing is provided with teeth thereon forming ring gears for meshing with the planet gears of a corresponding stage of the planetary gear mechanism.

7. The actuator of claim 6 , wherein the gear in the at least one gear that is connected with the planetary gear train is configured to have a hollow structure, the gear is disposed around an outer periphery of an upper portion of the gear housing.

8. The actuator of claim 1 , wherein the at least one gear comprises a first gear to which the sun gear of the first stage of the planetary gear mechanism is fixed, one end of the centering pin is fixed to the sun gear of the first stage of the planetary gear mechanism, and the planet carrier of the Nth stage of the planetary gear mechanism rotates about the other end of the centering pin.

9. The actuator of claim 1 , wherein one end of the centering pin is fixed to one of the output and the planet carrier of the Nth stage, and the sun gear of the first stage rotates about the other end of the centering pin.

10. The actuator of claim 1 , wherein the planet carrier of each stage of the planet gear mechanism comprises a plurality of planet pins for rotatably supporting the planet gears, the planet pins are made from metal and are fixed to the corresponding planet carrier in an interference fit manner.

11. The actuator of claim 1 , wherein the gear cover is connected to the gear housing by a plurality of snap fit connectors.

12. An actuator for an electric parking brake system, comprising:

an outer housing;

a planetary gear train and an electric motor received in the outer housing; and

at least one gear connected between the planetary gear train and the electric motor, the electric motor being arranged to drive the planetary gear train through the at least one gear;

wherein the planetary gear train comprises a multi-stage planetary gear mechanism, and a centering pin extending through the planetary gear mechanism, such that stages of the planetary gear mechanism rotate about the centering pin;

wherein the outer housing of the actuator further comprises a mounting bracket and a top cover, the top cover is connected the mounting bracket, the at least one gear is received between the top cover and the mounting bracket; and

wherein the centering pin is fixed to the top cover.

13. The actuator of claim 12 , wherein the planetary gear train further comprises an output driven by the planetary gear mechanism, a gear housing for receiving the planetary gear mechanism, and a gear cover connected to one end of the gear housing, wherein the planetary gear mechanism has a first stage through to a Nth stage that are sequentially meshed from one end to the other end of the planetary gear train, N is an integer greater than 1, each stage of planetary gear mechanism comprises a sun gear, a ring gear, a plurality of planet gears meshed with the sun gear and ring gear, and a planet carrier supporting the planet gears, and the output is fixed to the planet carrier of the Nth stage.

14. The actuator of claim 13 , wherein a through hole is defined through the mounting bracket, the at least one gear is aligned with and connected to the gear housing through the through hole, such that the gear housing is received in the through hole.

15. An actuator for an electric parking brake system, comprising:

an outer housing;

a planetary gear train and an electric motor received in the outer housing; and

at least one gear connected between the planetary gear train and the electric motor, the electric motor being arranged to drive the planetary gear train through the at least one gear;

wherein the planetary gear train comprises a multi-stage planetary gear mechanism and an output driven by the planetary gear mechanism, wherein the planetary gear mechanism has a first stage through to a Nth stage that are sequentially meshed from one end to the other end of the planetary gear train, N is an integer greater than 1, each stage of planetary gear mechanism comprises a sun gear, a ring gear, a plurality of planet gears meshed with the sun gear and ring gear, and a planet carrier supporting the planet gears, and the output is fixed to the planet carrier of the Nth stage;

wherein the planetary gear train further comprises a centering pin extending through the planetary gear mechanism, such that stages of the planetary gear mechanism rotate about the centering pin; and

Wherein the centering pin is fixed to the sun gear of the first stage of the planetary gear mechanism or one of the output and the planet carrier of the Nth stage.