Filter having back-flushing cleaning device

A filter with a backwashing unit, comprising a filter cartridge, the filter cartridge being internally provided with a filter element, the filter cartridge being provided with a water inlet and a drain outlet in an inlet region of the filter element and being provided with a water outlet in an outlet region, wherein the filter further comprises a two-position three-way valve, a second valve and a third valve, the two-position three-way valve being provided with a port P1, a port A1 and a port B1, the second valve being provided with a port P2 and a port A2, and the third valve being provided with a port P3 and a port A3;

• the port P1 being connected with the water inlet, the port A2 being connected with the water outlet, the port A3 being connected with the drain outlet, the port A1 and the port P3 being connected with the inlet region of the filter element, and the port B1 and the port P2 being connected with the outlet region of the filter element;
• and
• a filtering channel being formed by the water inlet, the port P1, the port A1, the inlet region of the filter element, the filter element, the outlet region of the filter element, the port P2, the port A2 and the water outlet 4 when the port P1 communicates with the port A1, the port P2 communicates with the port A2 and the port P3 does not communicate with the port A3, and a backwashing channel being formed by the water inlet, the port P1, the port B1, the outlet region of the filter element, the filter element, the inlet region of the filter element, the port P3, the port A3 and the drain outlet 5 when the port P1 communicates with the port B1, the port P2 does not communicate with the port A2 and the port P3 communicates with the port A3;
• wherein the filter cartridge is provided with a cylindrical outlet passage, the port P2, the port A2, the port P3 and the port A3 are cross-shaped on the circumferential wall of the outlet passage, the port P2 and the port A2 are oppositely arranged, the port P3 and the port A3 are oppositely arranged, the outlet passage is internally provided with a rotatable valve element, and the valve element is provided with a communicating hole and baffles at two sides of the communicating hole;
• and
• the valve element is provided with a first station where the communicating hole communicates with the port P2 and the port A2, and the port P3 and the port A3 are shielded by the baffles, and a second station where the communicating hole communicates with the port P3 and the port A3, and the port P2 and the port A2 are shielded by the baffles.