A fan includes a bracket, a stator, a rotor, and a slanting portion. The bracket includes a tray, and a frame circling the tray. The stator is mounted to and circled by the frame. The rotor includes a shaft rotatably mounted to the stator, and a shell coupled to the shaft. The shell covers the stator, and the shell and the tray of the bracket cooperatively enclose the stator. An assembly clearance is formed between a bottom end of the shell and a top surface of the tray. The slanting portion circles the tray and extends down from the bottom end of the shell, slanting away and spaced from the tray.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is related to a co-pending U.S. patent application, titled “FAN”, with U.S. Ser. No. 12/779928, assigned to the same assignee as the present application, the disclosure of which is incorporated herein by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to a fan.

2. Description of Related Art

When a fan operates, dust seems to inevitably penetrate the rotor of the fan through an assembly clearance that is formed during assembly of the fan and is between the rotor and a bracket for mounting the rotor and a stator. The dust can damage and shorten the service life of the fan.

In order to reduce damage caused by dust, anti-dust devices, such as dust rings, have been used for fans. An anti-dust device is often mounted between the bracket and the rotor to prevent dust from going through the assembly clearance. However, using anti-dust devices will increase the cost of fans.

DETAILED DESCRIPTION

Referring toFIG. 1, in a first embodiment, a fan10includes a bracket20, a stator40, and a rotor60. The stator40and the rotor60are mounted to the bracket20.

The bracket20is a plastic part integrally formed. The bracket20includes a tray23, and a frame21circling the tray23.

The stator40is mounted to the tray23of the bracket20and circled by the frame21of the bracket20. The stator40includes a circuit board41mounted on a top surface of the tray23, a plurality of coils43, and a ring45. The circuit board41includes a control circuit for controlling rotation speed of the fan10.

The rotor60includes a shaft61, a shell63, a plurality of blades65, and a plurality of magnets67. The shaft61is rotatably mounted to the ring45of the stator40. The shell63is integrally formed together with the shaft61. The shell63covers the stator40. The shell63and the tray23of the bracket20cooperatively enclose the stator40. An assembly clearance80is formed between a bottom end of the shell63and a top surface of the tray23. The assembly clearance80is used to ensure that the shell63will not contact the tray23when the rotor60rotates. A slanting portion630that circles the tray23slantingly extends down from the bottom end of the shell63and passes the top surface of the tray23. The slanting portion630opposes an outmost surface of the tray, and is spaced from the tray23. The blades65extend from the shell63, and are located between the shell63and the frame21of the bracket20. The magnets67are attached to an inner surface of the shell63, and are disposed around the coils43of the stator40.

After research and testing, it is found that when a common fan operates, a part of the airflow caused by the fan will be rebounded by a tray of the fan to flow into a rotor of the fan, which is the main way that dust enters. When the fan10of the present disclosure operates, the slanting portion630will guide airflow away from the tray23preventing dust from entering the rotor60.

Furthermore, an inclination of the slanting portion630should not be too large, to avoid blocking a part of the airflow. In some embodiments, the inclination of the slanting portion630may be 10˜30 degrees.

Referring toFIG. 2, a fan10ain a second embodiment differs from the fan10inFIG. 1in that a side surface of a tray23a, facing a slanting portion630aof a shell60a, is a slanting surface230a. The slanting surface230ahas a same inclination as the slanting portion630a. The design of the slanting surface230acan narrow a space90abetween the slanting portion630aand the side surface of the tray23a, to further lower a probability that dust enters a rotor60a.