Automatic back-washing liquid returning filter

The utility model provides an automatic back-washing liquid returning filter, belonging to the field of emulsion automatic back-washing filter device in coal mines. A cylinder body (10) is divided into an upper part and a lower part; the space in the cylinder body (10) is divided into a liquid passing chamber (1) and a filter chamber (2); a liquid inlet (14) and a liquid outlet (22) are symmetrically arranged at two sides of the upper part of the liquid passing chamber (1); the liquid passing chamber (1) is internally provided with two groups of back-washing devices correspondingly; the filter chamber (2) is internally provided with a filter core (9) by a shaft (42) and a bearing (43); the lower end of the filter chamber (2) is connected with a large nut (6) and a stopping part (5) by threads; the stopping part (5) is connected with a blowdown valve (4); a back-washing pipe (27) is arranged at one side in the filter chamber (2); a back-washing device is connected with the upper part of the back-washing pipe (