CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of Korean Patent Application No. 10-2019-0031090, filed on Mar. 19, 2019, which is hereby incorporated by reference for all purposes as if set forth herein.

BACKGROUND

Field

Exemplary embodiments of the present invention relate to an electric booster for an automotive braking system, and more particularly, to an electric booster which can return a part to a preset position when a braking force is released, and prevent damage between parts and noise generation.

Discussion of the Background

An electric booster for an automotive braking system drives a motor to pressurize a master cylinder, and the master cylinder generates braking pressure. Such an electric booster includes a motor, a bolt screw rotated by the motor, a nut screw linearly moved by the bolt screw, and a piston configured to generate braking pressure while being moved by the nut screw. The nut screw is linearly moved along a groove formed in a booster body, while being restricted from rotating.

In the related art, when the motor generates braking force generation torque, the torque is transferred to the bolt screw from a motor shaft. The bolt screw is rotated by the transferred torque, and the nut screw is moved forward in the longitudinal direction of the bolt screw while restricted from rotating. The translational motion of the nut screw generates a braking force.

When braking force release torque is generated after the braking force is generated, the bolt screw generates counter torque, and the nut screw is reversed to release the braking force. At this time, the nut screw needs to be reversed and returned to the original position. However, when the bolt screw is excessively rotated due to abrasion of the booster body, the nut screw may deviate from the original position. Furthermore, a collision between the booster body and the nut screw returned to the original position may generate noise. Therefore, there is a need for a device capable of solving the problem.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and, therefore, it may contain information that does not constitute prior art.

SUMMARY

Exemplary embodiments of the present invention are directed to an electric booster which can return a part to a preset position when a braking force is released, and prevent damage between parts and noise generation.

In an exemplary embodiment, an electric booster includes: a motor driven as power is applied; a booster body coupled to the motor; a bolt screw rotatably installed in the booster body, connected to the motor, and rotated by power from the motor; a buffer mounted in the booster body and made of a material different from the booster body; and a nut screw restricted from rotating by the buffer, and screwed to the bolt screw so as to be linearly moved in the longitudinal direction of the bolt screw.

The buffer may include: a buffer body mounted on the body; and a rotation restriction part protruding from the buffer body, and configured to restrict the rotation of the nut screw.

The buffer may include a stopper part formed on the rotation restriction part, and configured to restrict the nut screw from moving beyond a preset range on the bolt screw.

The booster body may be made of a metallic material, and the buffer may be made of a plastic material.

The nut screw may include: a nut body screwed to the bolt screw; and a guide protrusion protruding from the outer surface of the nut body, and inserted into the rotation restriction part.

The buffer may be disposed at a plurality of positions of the booster body, and the number of the guide protrusions may be equal to the number of the buffers.

The bolt screw may include: a bolt connection part connected to the motor and rotated by power from the motor; a bolt-embedded part extended from the bolt connection part, and rotatably mounted on the booster body so as to be restricted from moving; and a bolt screw thread part extended from the bolt-embedded part and screwed to the nut screw.

The booster body may have a buffer mounting part convexly formed in the longitudinal direction of the nut screw, and the buffer body may be forced into the buffer mounting part.

In accordance with exemplary embodiments of the present invention, the buffer may prevent a collision between the nut screw and the booster body, such that the abrasion and damage of the nut screw and the booster body can be reduced to extend the lifetime of the electric booster.

Furthermore, the buffer can reduce noise generation by preventing a collision between the nut screw and the booster body, thereby providing a comfortable ride to a passenger in a vehicle.

Furthermore, the buffer may restrict the movement of the nut screw such that the nut screw can be prevented from excessively moving and returned to the preset position.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

