Image reading apparatus

1. An image reading apparatus, comprising:

a feed tray configured to support sheets for being fed, the feed tray comprising a movable plate configured to move in a vertical direction between a standby position and a feedable position being higher than the standby position according to an amount of the sheets supported by the feed tray;

a conveyance guide configured to guide the sheets conveyed from the feed tray;

a feed roller movable in the vertical direction, the feed roller being configured to feed the sheets supported by the feed tray to be conveyed along the conveyance guide, a positional relation between the feed roller and an uppermost sheet in the sheets supported by the feed tray being maintained within a predetermined range by the movable plate located at the feedable position;

a separator configured to nip and separate the sheets fed by the feed roller from one another and convey the sheets separately along the conveyance guide;

a reading sensor configured to read images of the sheets conveyed along the conveyance guide; and

a controller configured to control at least rotating-and-stopping movements of the feed roller and the separator and ascending-and-descending movements of the movable plate,

wherein, while the feed roller feeds the sheets, the controller is configured to conduct a vibrating action, in which the movable plate located at the feedable position is moved to ascend and descend for a plurality of times, and

wherein the controller conducts the vibrating action at a first amplitude before the separator nips the sheets fed by the feed roller and at a second amplitude after the separator nips the sheets fed by the feed roller, and wherein the second amplitude is greater than the first amplitude.

2. The image reading apparatus according to claim 1 , wherein the controller is configured to conduct the vibrating action to move the movable plate within a range, in which the movable plate does not descend to be lower than the feedable position, before the separator nips the sheets fed by the feed roller.

3. The image reading apparatus according to claim 1 , wherein the controller is configured to end the vibrating action before the separator nips the sheets fed by the feed roller.

4. The image reading apparatus according to claim 1 , further comprising a pressing member configured to press the feed roller against the sheets supported by the feed tray,

wherein the controller is configured to

obtain thickness information concerning a thickness of the sheets supported by the feed tray,

move the movable plate to the feedable position, and

move the movable plate to one of ascend and descend for a distance corresponding to the thickness information.

5. The image reading apparatus according to claim 4 , further comprising a detector configured to detect the thickness of the sheets supported by the feed tray,

wherein the controller is configured to obtain a detected result from the detector as the thickness information.

6. An image reading apparatus, comprising:

a feed tray configured to support sheets for being fed, the feed tray comprising a movable plate configured to move in a vertical direction between a standby position and a feedable position being higher than the standby position according to an amount of the sheets supported by the feed tray;

a conveyance guide configured to guide the sheets conveyed from the feed tray;

a feed roller movable in the vertical direction, the feed roller being configured to feed the sheets supported by the feed tray to be conveyed along the conveyance guide, a positional relation between the feed roller and an uppermost sheet in the sheets supported by the feed tray being maintained within a predetermined range by the movable plate located at the feedable position;

a separator configured to nip and separate the sheets fed by the feed roller from one another and convey the sheets separately along the conveyance guide;

a reading sensor configured to read images of the sheets conveyed along the conveyance guide;

a pressing member configured to press the feed roller against the sheets supported by the feed tray; and

a controller configured to

obtain thickness information concerning a thickness of the sheets supported by the feed tray,

move the movable plate to the feedable position,

move the movable plate to one of ascend and descend for a distance corresponding to the thickness information, and

control at least rotating-and-stopping movements of the feed roller and the separator and ascending-and-descending movements of the movable plate,

wherein, while the feed roller feeds the sheets, the controller is configured to conduct a vibrating action, in which the movable plate located at the feedable position is moved to ascend and descend for a plurality of times.

7. The image reading apparatus according to claim 6 , wherein the controller is configured to conduct the vibrating action to move the movable plate within a range, in which the movable plate does not descend to be lower than the feedable position, before the separator nips the sheets fed by the feed roller.

8. The image reading apparatus according to claim 6 , wherein the controller is configured to end the vibrating action before the separator nips the sheets fed by the feed roller.

9. The image reading apparatus according to claim 6 , further comprising a detector configured to detect the thickness of the sheets supported by the feed tray,

wherein the controller is configured to obtain a detected result from the detector as the thickness information.