Sheet feeding apparatus and image forming apparatus

Abstract

The sheet feeding apparatus includes a sheet supporting portion, a sheet feeding portion configured to feed the sheet, a lifting unit including an urging portion and a shaft portion, wherein the damping unit includes a first gear supported rotatably on the shaft portion, a base portion, a second gear, and a damping portion, the damping unit being configured to be switched, in a state where the shaft portion is rotating, between a first state in which the damping unit damps the rotation of the shaft portion and a second state in which the damping unit does not damp the rotation of the shaft portion, and a distance between a center of rotation of the first gear and a center of rotation of the second gear is fixed regardless of whether the damping unit is in the first state or in the second state.

1 . A sheet feeding apparatus comprising:
 a sheet supporting portion configured to support a sheet;   a sheet feeding portion configured to feed the sheet supported on the sheet supporting portion;   a lifting unit comprising an urging portion configured to urge either one of the sheet supporting portion and the sheet feeding portion to the other of the sheet supporting portion and the sheet feeding portion, and a shaft portion configured to rotate in conjunction with lifting and lowering of the one of the sheet supporting portion and the sheet feeding portion, the lifting unit being configured to lift and lower the one of the sheet supporting portion and the sheet feeding portion to the other of the sheet supporting portion and the sheet feeding portion; and   a damping unit connected to the shaft portion and configured to damp rotation of the shaft portion,   wherein the damping unit comprises a first gear supported rotatably on the shaft portion, a base portion, a second gear meshed with the first gear and configured to relatively rotate with respect to the base portion, and a damping portion provided on the base portion and configured to damp the rotation of the shaft portion by relative rotation of the second gear with respect to the base portion, the damping unit being configured to be switched, in a state where the shaft portion is rotating, between a first state in which the damping unit damps the rotation of the shaft portion and a second state in which the damping unit does not damp the rotation of the shaft portion, and   a distance between a center of rotation of the first gear and a center of rotation of the second gear is fixed regardless of whether the damping unit is in the first state or in the second state.   
     
     
         2 . The sheet feeding apparatus according to  claim 1 , further comprising a frame unit configured to support the base portion rotatably, and
 wherein the damping unit comprises a regulating portion provided on the frame unit and configured to allow rotation of the base portion within a predetermined range and to regulate the rotation of the base portion by abutting against the base portion, the damping unit being configured to be in the second state if the base portion is separated from the regulating portion and in the first state if the rotation of the base portion is regulated by the base portion being abutted against the regulating portion.   
     
     
         3 . The sheet feeding apparatus according to  claim 2 , wherein the base portion is supported on the frame unit rotatably around the center of rotation of the second gear. 
     
     
         4 . The sheet feeding apparatus according to  claim 2 , wherein a position of the regulating portion is adjustable with respect to the frame unit. 
     
     
         5 . The sheet feeding apparatus according to  claim 2 , wherein the sheet supporting portion is configured to be lifted and lowered by the lifting unit between a lifted position where the sheet feeding portion is capable of feeding the sheet supported on the sheet supporting portion and a lowered position where the sheet feeding portion is separated from the sheet supported on the sheet supporting portion, and the damping unit is switched from the second state to the first state in a case where the sheet supporting portion moves on the way to the lifted position from the lowered position. 
     
     
         6 . The sheet feeding apparatus according to  claim 5 , wherein the lifting unit comprises a gear fixed to the shaft portion, and a pressing portion comprising a rack portion configured to mesh with the gear, the pressing portion being urged by urging force of the urging portion to press the sheet supporting portion toward the lifted position. 
     
     
         7 . The sheet feeding apparatus according to  claim 6 , wherein the lifting unit comprises a driving source, and a control gear configured to be rotated by driving force of the driving source,
 during one rotation of the control gear, the sheet supporting portion is configured to move from the lowered position to the lifted position by being pressed by the pressing portion lifted by urging force of the urging portion, and thereafter, move from the lifted position to the lowered position by the gear lowering the pressing portion against urging force of the urging portion, and   the shaft portion rotates in a first direction in a state where the sheet supporting portion moves from the lowered position to the lifted position and rotates in a second direction opposite to the first direction in a state where the sheet supporting portion moves from the lifted position to the lowered position.   
     
     
         8 . The sheet feeding apparatus according to  claim 7 , wherein the base portion is configured to rotate in a third direction by the rotation of the shaft portion in the first direction and also configured to rotate in a fourth direction opposite to the third direction by the rotation of the shaft portion in the second direction, and
 the regulating portion comprises a first regulating part configured to regulate the rotation of the base portion in the third direction and a second regulating part configured to regulate the rotation of the base portion in the fourth direction.   
     
     
         9 . The sheet feeding apparatus according to  claim 8 , wherein positions of the first regulating part and the second regulating part are respectively adjustable with respect to the frame unit. 
     
     
         10 . The sheet feeding apparatus according to  claim 1 , wherein the shaft portion is connected with play to the first gear such that the shaft portion is relatively pivotable within a predetermined angle with respect to the first gear, and
 the damping unit is configured to be in the second state in a case where the shaft portion pivots within a range of play with respect to the first gear, and in the first state in a case where the shaft portion rotates integrally with the first gear.   
     
     
         11 . The sheet feeding apparatus according to  claim 10 , further comprising a frame unit configured to support the base portion in a non-movable manner. 
     
     
         12 . The sheet feeding apparatus according to  claim 10 , wherein the shaft portion comprises an engagement portion, and
 the second gear comprises a hole portion in which the engagement portion is pivotable for the predetermined angle without abutting against the second gear.   
     
     
         13 . The sheet feeding apparatus according to  claim 10 , wherein the sheet supporting portion is configured to be lifted and lowered by the lifting unit between a lifted position where the sheet feeding portion is capable of feeding the sheet supported on the sheet supporting portion and a lowered position where the sheet feeding portion is separated from the sheet supported on the sheet supporting portion, and
 the damping unit is switched from the second state to the first state in a case where the sheet supporting portion moves on the way to the lifted position from the lowered position.   
     
     
         14 . The sheet feeding apparatus according to  claim 13 , wherein the lifting unit comprises a gear fixed to the shaft portion, and a pressing portion comprising a rack portion configured to mesh with the gear, the pressing portion being urged by urging force of the urging portion to press the sheet supporting portion toward the lifted position. 
     
     
         15 . The sheet feeding apparatus according to  claim 14 , wherein the lifting unit comprises a driving source, and a control gear configured to be controlled to rotate once by driving force of the driving source,
 during one rotation of the control gear, the sheet supporting portion is configured to move from the lowered position to the lifted position by being pressed by the pressing portion lifted by urging force of the urging portion, and thereafter, move from the lifted position to the lowered position by the gear lowering the pressing portion against urging force of the urging portion, and   the shaft portion rotates in a first direction in a state where the sheet supporting portion moves from the lowered position to the lifted position and rotates in a second direction opposite to the first direction in a state where the sheet supporting portion moves from the lifted position to the lowered position.   
     
     
         16 . An image forming apparatus comprising:
 the sheet feeding apparatus according to  claim 1 ; and   an image forming unit configured to form an image on a sheet fed from the sheet feeding apparatus.