Automatic oil injection device for bearing and oil smoke exhaust box type fan

The utility model relates to the technical field of fan lubrication, and discloses an automatic oil injection device for a bearing and an oil smoke exhaust box type fan. The automatic oil injection device for the bearing comprises an oil storage shell and an oil injection assembly, an oil injection cavity and an oil return cavity which are communicated are formed in the oil storage shell, an oil injection outlet capable of being communicated with an oil inlet of the bearing box is formed in the oil injection cavity, and an oil return inlet capable of being communicated with an oil outlet of the bearing box is formed in the oil return cavity; the oil injection assembly comprises a first piston, a second piston and an elastic driving part, the first piston is arranged in the oil injection cavity in a sliding mode, the second piston is arranged in the oil return cavity in a sliding mode, and the elastic driving part can drive the first piston to move downwards so as to inject lubricating grease in the oil inject