Abstract: An image forming apparatus includes an image forming unit forming an image on a recording sheet; a transport unit transporting the recording sheet; a support surface supporting the recording sheet; a rotating member having an outer peripheral surface pressed against the support surface and rotationally following the recording sheet when the recording sheet passes through between the support surface and the outer peripheral surface; an ascertaining unit ascertaining a length of the recording sheet on the basis of an amount of rotation of the rotating member; and a restricting unit restricting a movement of the rotating member that moves toward the support surface after the recording sheet passes through between the support surface and the outer peripheral surface, the restricting unit preventing the outer peripheral surface, which comes into contact with the recording sheet, and the support surface from coming into contact with each other.

Abstract: A position detection apparatus includes: a moving member in contact with a detection object that moves following movement of the detection object; and a support member that rotatably supports the moving member; a detection unit that detects a positional change of the moving member, the moving member being acted on by a first force as a force to press the moving member against the detection object, a second force as a force to press the moving member substantially in a direction of a rotation shaft of the moving member, and a third force as a force to press the moving member in a direction substantially orthogonal to the direction of the rotation shaft of the moving member.

Abstract: A rotation amount detecting device for a rotation body includes: a first rotation body having a first surface; a second rotation body having a second surface formed of a material different from that of the first surface and contacting the first surface, and rotating with rotation of the first rotation body; a first support member rotatably supporting the first rotation body at a first position and supporting thereof to be swingable around a first axis at a position different from the first position; a second support member rotatably supporting the second rotation body at a second position and supporting thereof to be swingable around a second axis provided at a position different from the second position, the second axis being the first axis or an axis in the first support member other than the first axis; and a detector that detects a rotation amount of the second rotation body.

Abstract: An information processor includes a storage unit storing a first coefficient in correspondence with a characteristic of a sheet of paper, a first acquisition unit acquiring a first signal based on the water content of a first sheet of paper not having an image formed thereon, a second acquisition unit acquiring a second signal based on the water content of the first sheet of paper having an image formed thereon and being heated for fixing, a determination unit determining the characteristic of the first sheet of paper, a first calculation unit calculating a variation in water content of the first sheet of paper using the difference between the first signal and the second signal and the first coefficient stored in correspondence with the determined characteristic, and a second calculation unit calculating an expansion and contraction ratio of the first sheet of paper using the variation in water content.

Abstract: A sheet measuring apparatus includes a first rotating member including a first peripheral surface portion that contacts a transported sheet; a second rotating member including a second peripheral surface portion that contacts the first peripheral surface portion; a first rotation amount detecting unit that detects a first rotation amount of the first rotating member; a second rotation amount detecting unit that detects a second rotation amount of the second rotating member; a sheet calculation unit that obtains a first rotating member correction value for correcting an error that is superposed on the second rotation amount due to a radius distribution of the first rotating member and that performs calculation related to the transported sheet; a radius distribution calculating unit that calculates a new radius distribution of the first rotating member; and an updating unit that updates the first rotating member correction value to a new first rotating member correction value.

Abstract: An abnormality detecting device for a rotation body includes: a rotation body rotating while coming in contact with a sheet transported at a predetermined speed; an output unit outputting pulses of a number in proportion to a rotation amount of the rotation body; an acquisition unit acquiring periodic information associating a position of the rotation body during a single rotation and a period of each of the pulses corresponding to the position with each other, the periodic information being acquired based on the plural pulses outputted from the output unit along with the rotation of the rotation body at the predetermined speed; a memory storing the periodic information as reference periodic information; and an abnormality detector detecting an abnormality occurred in at least one of the rotation body and the output unit based on the reference periodic information and new periodic information acquired after the reference periodic information is acquired.

Abstract: A sheet measuring apparatus includes a first rotating member that includes a first peripheral surface portion that contacts a transported sheet; a second rotating member that includes a second peripheral surface portion made of a material different from that of the first peripheral surface portion, the second peripheral surface contacting the first peripheral surface portion and not contacting the sheet; a first rotation amount detecting unit that detects a first rotation amount that is a rotation amount of the first rotating member; a second rotation amount detecting unit that detects a second rotation amount that is a rotation amount of the second rotating member, the second rotation amount being used for a calculation related to the transported sheet; and a fault detecting unit that detects a fault that has occurred in the first rotating member on the basis of the first rotation amount and the second rotation amount.

Abstract: An information processor includes a storage unit storing a first coefficient in correspondence with a characteristic of a sheet of paper, a first acquisition unit acquiring a first signal based on the water content of a first sheet of paper not having an image formed thereon, a second acquisition unit acquiring a second signal based on the water content of the first sheet of paper having an image formed thereon and being heated for fixing, a determination unit determining the characteristic of the first sheet of paper, a first calculation unit calculating a variation in water content of the first sheet of paper using the difference between the first signal and the second signal and the first coefficient stored in correspondence with the determined characteristic, and a second calculation unit calculating an expansion and contraction ratio of the first sheet of paper using the variation in water content.

Abstract: A sheet measuring apparatus includes a first rotating member including a first peripheral surface portion that contacts a transported sheet; a second rotating member including a second peripheral surface portion that contacts the first peripheral surface portion; a first rotation amount detecting unit that detects a first rotation amount of the first rotating member; a second rotation amount detecting unit that detects a second rotation amount of the second rotating member; a sheet calculation unit that obtains a first rotating member correction value for correcting an error that is superposed on the second rotation amount due to a radius distribution of the first rotating member and that performs calculation related to the transported sheet; a radius distribution calculating unit that calculates a new radius distribution of the first rotating member; and an updating unit that updates the first rotating member correction value to a new first rotating member correction value.

Abstract: A sheet measuring apparatus includes a first rotating member that includes a first peripheral surface portion that contacts a transported sheet; a second rotating member that includes a second peripheral surface portion made of a material different from that of the first peripheral surface portion, the second peripheral surface contacting the first peripheral surface portion and not contacting the sheet; a first rotation amount detecting unit that detects a first rotation amount that is a rotation amount of the first rotating member; a second rotation amount detecting unit that detects a second rotation amount that is a rotation amount of the second rotating member, the second rotation amount being used for a calculation related to the transported sheet; and a fault detecting unit that detects a fault that has occurred in the first rotating member on the basis of the first rotation amount and the second rotation amount.

Abstract: An image forming apparatus includes an image forming unit forming an image on a recording sheet; a transport unit transporting the recording sheet; a support surface supporting the recording sheet; a rotating member having an outer peripheral surface pressed against the support surface and rotationally following the recording sheet when the recording sheet passes through between the support surface and the outer peripheral surface; an ascertaining unit ascertaining a length of the recording sheet on the basis of an amount of rotation of the rotating member; and a restricting unit restricting a movement of the rotating member that moves toward the support surface after the recording sheet passes through between the support surface and the outer peripheral surface, the restricting unit preventing the outer peripheral surface, which comes into contact with the recording sheet, and the support surface from coming into contact with each other.

Abstract: A sheet length measurement apparatus including: a rotating member that comes in contact with a recording sheet conveyed on a conveying path, and rotates along with the conveyance of the recording sheet; a rotation amount detector that detects a rotational amount of the rotating member; a fixing support member that fixedly supports an rotating shaft of the rotating member at a fixed position; an opposed member that is disposed opposite to the rotating member so as to hold the recording sheet between the rotating member and the opposed member, the opposed member being disposed so that the rotating member rotates along with the conveyance of the recording sheet; and a support member that supports the opposed member in a movable state in a direction to separate from or come in contact with a surface of the recording sheet.

Abstract: A sheet feed device includes an air flow generating part that generates an air flow for floating a sheet; a feed member that feeds a sheet by rotating, while applying a load to the top one of sheets stacked; and a transport condition sensing unit that is positioned not to obstruct an air flow generated by the air flow generating part and senses a transport condition of a sheet fed by the feed member.

Abstract: A recording medium supply apparatus includes: a conveyance member that conveys a recording medium; a retard member, in contact with the conveyance member, that forms a contact portion between the conveyance member and the retard member and retards the recording medium by holding the recording medium in the contact portion; and a buckling prevention unit, configured to contact with the recording medium on the upstream side of the contact portion between the conveyance member and the retard member in a conveyance direction of the recording medium, that prevents buckling of the recording medium in the conveyance direction.

Abstract: An abnormality detecting device for a rotation body includes: a rotation body rotating while coming in contact with a sheet transported at a predetermined speed; an output unit outputting pulses of a number in proportion to a rotation amount of the rotation body; an acquisition unit acquiring periodic information associating a position of the rotation body during a single rotation and a period of each of the pulses corresponding to the position with each other, the periodic information being acquired based on the plural pulses outputted from the output unit along with the rotation of the rotation body at the predetermined speed; a memory storing the periodic information as reference periodic information; and an abnormality detector detecting an abnormality occurred in at least one of the rotation body and the output unit based on the reference periodic information and new periodic information acquired after the reference periodic information is acquired.

Abstract: A rotation amount detecting device for a rotation body includes: a first rotation body having a first surface; a second rotation body having a second surface formed of a material different from that of the first surface and contacting the first surface, and rotating with rotation of the first rotation body; a first support member rotatably supporting the first rotation body at a first position and supporting thereof to be swingable around a first axis at a position different from the first position; a second support member rotatably supporting the second rotation body at a second position and supporting thereof to be swingable around a second axis provided at a position different from the second position, the second axis being the first axis or an axis in the first support member other than the first axis; and a detector that detects a rotation amount of the second rotation body.

Abstract: A length measurement apparatus including: a measurement portion that measures a sheet length based on a rotational amount of a length measurement roll for a first detection period in which first and third sensors detect the sheet, and a sheet length based on a rotational amount of the length measurement roll for a second detection period in which the second sensor and any one of the first and third sensors detect the sheet, the any one of the first and third sensors being disposed at a position opposite to the second sensor via the length measurement roll; and a whole length calculation portion that selects the sheet length nearer to integral multiples of the circumference length of the length measurement roll from the sheet lengths measured for the first and second detection periods, and calculates the whole length of the sheet by using the selected sheet length.

Abstract: A sheet supply apparatus has a sheet storing part that stores sheets, a sheet transport part that feeds the sheets from the sheet storing part and transports the sheets, a sheet separating part that separates the sheets fed from the sheet storing part, a sheet thickness measuring part that measures a thickness of the sheets separated by the sheet separating part, a sheet separating strength varying part that causes the sheet separating part to apply one or more of a plurality of sheet separating strengths to separate the sheets, and a control part that controls the sheet separating strength varying part to cause the sheet separating part to apply, from among the plurality of sheet separating strengths, one or more sheet separating strengths, other than a weakest sheet separating strength, during a time period which begins upon a start of feed of the sheets.

Abstract: A sheet length measurement apparatus including: a rotating member that comes in contact with a recording sheet conveyed on a conveying path, and rotates along with the conveyance of the recording sheet; a rotation amount detector that detects a rotational amount of the rotating member; a fixing support member that fixedly supports an rotating shaft of the rotating member at a fixed position; an opposed member that is disposed opposite to the rotating member so as to hold the recording sheet between the rotating member and the opposed member, the opposed member being disposed so that the rotating member rotates along with the conveyance of the recording sheet; and a support member that supports the opposed member in a movable state in a direction to separate from or come in contact with a surface of the recording sheet.

Abstract: A sheet length measuring apparatus that includes: a rotating body that rotates in contact with a sheet delivered through a delivery path; detecting units that are located upstream and downstream of the rotating body respectively, and detect a position of the sheet delivered through the delivery path; a delivery unit that is located in at least one of positions between the detecting unit located upstream and the rotating body, and between the detecting unit located downstream and the rotating body, and delivers the sheet on the delivery path; and a rotation amount detecting unit that detects a rotation amount of the rotating body with using a period when the sheet is detected by the detecting units respectively located upstream and downstream of the rotating body as a measurement period.