Sheet Feeding Apparatus

This application is a continuation of International Patent Application No. PCT/JP2023/043963 filed on Dec. 8, 2023, which claims priority to and the benefit of Japanese Patent Application No. 2022-209533 filed on Dec. 27, 2022, the entire disclosures of which are incorporated herein by reference.

The present invention relates to a sheet feeding apparatus.

Japanese Patent No. 5075089, for example, is disclosed as a method for detecting the feeding state of sheets and avoiding feeding failure in a sheet feeding apparatus that sequentially separates and feeds a plurality of sheets and an image reading apparatus that reads images of sheets that are fed.

In the sheet feeding apparatus of Japanese Patent No. 5075089, a method is disclosed for detecting the rotation state of a separation roller (brake roller) when a sheet is fed, and holding a pickup roller in a non-contact state with respect to the next sheet to be fed (following sheet) when it is determined that the separation roller is not rotating. When a plurality of sheets enter between the feed roller and the separation roller opposing the feed roller in contact therewith while sheets are being fed by the feed roller (separator roller), the separation roller stops rotating and the sheets other than the sheet to be fed are regulated to be conveyed in the conveyance direction. On the other hand, if sheets other than the sheet being fed do not enter between the feed roller and the separation roller, the separation roller is turned around by the sheet being fed and rotates. Whether to bring the pickup roller in contact with the sheet or hold the pickup roller in a non-contact state is determined according to the rotation state of the separation roller. As a result of the above control, the pickup roller does not apply more pressure than necessary to the sheet, and issues such as multi-feeding and jamming of sheets is suppressed.

Here, the friction coefficient of the surface of the separation roller decreases due to factors such as adhesion of paper dust to the surface of the separation roller and deterioration of the separation roller, and the separation roller may not be turned around by the feed roller or the sheet that is fed. When the separation roller is not turned around due to the above factors, it will be determined, according to the method of Japanese Patent No. 5075089, that the following sheet has entered between the feed roller and the separation roller, even though the following sheet has not entered between the feed roller and the separation roller. At this time, the sheets cannot be fed because the pickup roller is in the non-contact state with respect to the following sheet, and feeding needs to be restarted by changing the pickup roller from the non-contact state to the contact state. Therefore, the time to complete the feeding operation is extended.

According to the present invention, there is provided a sheet feeding apparatus comprising: a sheet loading tray configured to be loaded with a sheet; an intake unit configured to take in the sheet loaded in the sheet loading tray to an apparatus body; a feeding unit configured to feed the sheet taken in by the intake unit; a separation unit configured to contact the feeding unit and separate a sheet to be fed from a plurality of sheets; and a sheet detection unit configured to emit light and detect presence or absence of a sheet between the feeding unit and the separation unit.

In an embodiment of the present invention, the presence or absence of a sheet within a range of the contact portion (nip portion) between the feed roller and the separation roller is detected using a sensor. Therefore, it is possible to readily detect whether the following sheet has entered between the feed roller and the separation roller immediately before feeding of the following sheet is started. At this time, use of the sensor avoids the problem of restarting the feeding of sheets due to being unable take in the following sheet because of the pickup roller being in the non-contact state with respect to the following sheet. As a result, the time to complete the feeding of sheets is not extended.

Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings. Note that the same reference numerals denote the same or like components throughout the accompanying drawings.

Hereinafter, embodiments will be described in detail with reference to the attached drawings. Note, the following embodiments are not intended to limit the scope of the claimed invention. Multiple features are described in the embodiments, but limitation is not made to an invention that requires all such features, and multiple such features may be combined as appropriate. Furthermore, in the attached drawings, the same reference numerals are given to the same or similar configurations, and redundant description thereof is omitted.

is a partial cross-sectional view schematically showing the configuration of an image reading apparatus which is an example of a sheet feeding apparatus according to a first embodiment, andis a schematic diagram schematically showing the configuration of a main part of the image reading apparatus in.

In, an image reading apparatusincludes a sheet intake unit. A plurality of sheets are loaded in a sheet loading tray, and the sheet loading trayis configured to be freely raised and lowered. A loading tray drive motorraises and lowers the sheet loading tray. A sheet detection sensordetects that a sheet loaded in the sheet loading trayis in a sheet intake position. When a sheet loaded in the sheet loading trayis not in the sheet intake position, the loading tray drive motoris driven, and the sheet loading trayis moved so that the uppermost sheet surface is in the intake position. A sheet loading detection sensordetects that sheets are loaded on a sheet loading surface la of the sheet loading tray.

A pickup rolleris provided opposing the sheet loading tray, and functions as an intake unit configured to send sheets loaded in the sheet loading trayto a feed rollerand taking the sheets into the apparatus body. A pickup motorrotates the pickup roller. In, the upper sheet surface is in the sheet intake position, and sheets will start being taken in when the pickup rolleris rotated.

The feed rolleris provided downstream of the pickup rollerin the conveyance direction, is driven to rotate in the direction in which sheets are fed downstream in the conveyance direction by a feed motor, and functions as a feeding unit. The feed rolleris coupled to the feed motorvia a one-way clutch not shown, and the drive of the feed motoris transmitted in only one direction. The drive force is transmitted to the feed rollerby the feed motorat the time of feeding, but when the sheets are conveyed at a speed exceeding the speed of the feed rollerby conveyance rollers,, and the like, the rotation of the feed motoris not transmitted by the one-way clutch and the feed rolleris turned around by the conveyance of the sheets and rotationally driven.

A separation rolleris provided opposing the feed rolleracross the conveyance path and is biased toward the feed roller. The separation rolleris subjected to a rotational force in a direction in which the sheets are pushed back upstream in the conveyance direction by a torque limiter not shown (counterclockwise direction in the diagram). When there is only one sheet between the feed rollerand the separation roller, the rotational force applied in the clockwise direction in the diagram by the friction force between the sheet that is fed and the separation rolleris greater than the upper limit of the rotational force applied in the counterclockwise direction in the diagram by the torque limiter, and thus the separation rollerfollows the feed rollerand rotates (is turned) clockwise in the diagram. On the other hand, when there are a plurality of sheets between the feed rollerand the separation roller, the separation rollerfunctions as a separation unit, and is subjected to a rotational force by the torque limiter in a direction in which the sheets are pushed back upstream in the conveyance direction, and only the sheet to be fed that is in contact with the feed rolleris conveyed.

As described above, the feed rolleracts to feed the sheets downstream, and the separation rolleracts to prevent the sheets from being fed downstream. When a plurality of sheets stacked one on the other are sent to the contact portion (nip portion) between the feed rollerand the separation roller, the stacked sheets are separated, with only the uppermost sheet, which is the sheet to be fed, being fed downstream, and the other sheets are not fed downstream.

Note that a plurality of sheets may be prevented from being conveyed downstream by replacing the separation rollerwith a separation pad and bringing the separation pad in contact with the sheets.

A multi-feed detection sensoris provided downstream of the feed rollerin the conveyance direction. The multi-feed detection sensordetects whether the sheets are being separated one by one by the separation roller. In the present embodiment, a detection device that uses ultrasonic transmitting/receiving units is used as the multi-feed detection sensor, and multi-feeding is detected by the attenuation amount of ultrasonic waves between the transmitting/receiving units on both sides of the conveyance path.

A conveyance motorrotates conveyance rollers,,, andto convey sheets to an image reading position where images of the sheets are read by image reading sensorsand. When the conveyance rollers,,, andare rotated, conveyance rollers,,, andrespectively disposed opposite thereto are rotationally driven, enabling the sheets to be conveyed. Also, the conveyance motordrives the rollers so as to be able to change the conveyance speed of the sheets according to the optimal speed for reading the sheets, and settings such as the resolution of the sheets. Note that a registration clutchdrives the conveyance rolleror stops the drive thereof, by transmitting the rotational drive force of the conveyance motorto the conveyance rolleror interrupting transmission thereof.

A conveyance roller pair constituted by the conveyance rollersand, a conveyance roller pair constituted by the conveyance rollersand, and a roller pair constituted by the conveyance rollersandconvey the sheets to a discharge roller pair constituted by discharge rollersandand a discharge stacking unitthat are further downstream. An upper guide plateand a lower guide plateguide the sheets that are conveyed by the pairs of rollers. Also, the lower guide plateforms a wall surface between the sheets loaded in the sheet loading trayand the separation roller, and covers the upstream and downstream sides of the separation rollersuch that part of the separation rolleris exposed in the conveyance path.

An upstream sensorand a downstream sensorare respectively provided upstream and downstream of the conveyance rollerin the conveyance direction. The upstream sensorand the downstream sensordetect the arrival of the leading edge and the trailing edge of a sheet. At the timing at which the leading edge or trailing edge of a sheet arrives, rotation of the pickup roller, the feed rollerand the like is started or stopped. A detailed description will be given later when describing the sheet feeding flow.

Note that the image reading apparatusincludes a control unitthat controls the operations of the entire apparatus. The control unitincludes one or more processors (CPUs), and one or more storage devices such as memories in which programs to be executed by one or more processors are stored, for example.

The pickup rolleris provided with a lifting mechanism and can be moved by a moving unit between an intake position where the pickup rollercan take in sheets by coming in contact with the sheets and a retracted position away from the sheets.are cross-sectional views of the area around the pickup roller, withshowing the state when the pickup rollerhas been moved to the retracted position, andshowing the state when the pickup rollerhas been moved to the intake position.

In, the drive force of the pickup motoris transmitted to a pickup motor drive gear. The drive force from the pickup motor drive gearis transmitted to the pickup rollervia a timing beltand a gear. The pickup motor drive gear, the gear, and the pickup rollerare attached to a pickup roller frame. The pickup rolleris freely detachable from the pickup roller frameso as to be replaceable. The pickup roller frameswings freely with the center of the pickup motor drive gearas the rotation axis. A pickup lifting motoris a pulse motor that generates a force for swinging the pickup roller frame.

When the pickup rolleris in the retracted position shown in, the pickup roller frameis in an upper limit position, and a frame detection sensordetects that the pickup roller frameis in this position. The pickup rolleris moved to the intake position shown inby driving the pickup lifting motorfor only a predetermined number of pulses, starting from the position where the frame detection sensordetects the pickup roller frame.

A control unit executes control to move the pickup rollerto the sheet intake position when taking in a sheet from the sheet loading tray, and to move the pickup rollerto the retracted position away from the sheet intake position when the pickup rollerhas finished taking in a sheet to the feed rollerand when sheets are being conveyed by downstream rollers, using the lifting mechanism of the pickup rollerdescribed above.

is a partial cross-sectional view schematically showing the disposition of components in the vicinity of the feed rollerand the separation roller, and is a cross-section taken at the position of an optical axis R described later.is a partial cross-sectional view schematically showing the disposition of components when the vicinity of the feed rollerand the separation rolleris viewed from upstream in the conveyance direction (from the left side in).

In, a light emitting sensorthat emits light including infrared light and a light receiving sensorthat received light, which are optical sensors that function as a sheet detection unit configured to detect the presence or absence of sheets, and a light guidethat changes the direction of light emitted from a light emitting sensorand guides the light to the light receiving sensorare shown, in addition to the feed roller, the separation roller, the upper guide plate, and the lower guide plateout of the members shown inbeing shown in an extracted manner. Furthermore, a separation roller holding memberthat holds a rotation shaft portion of the separation rolleris shown. The sheets are fed from the left side to the right side of the diagram in, and from the near side to the far side of the surface of the diagram in.

In the feed roller, a first feed roller partand a second feed roller partformed of rubber material or the like are installed on a feed wheel partIn the separation roller, a first separation roller partand a second separation roller partformed of a rubber material or the like are installed on a separation wheel partThe first and second feed roller partsandand the first and second separation roller partsandeach partially protrude into the conveyance path. Also, the first and second feed roller partsandand the first and second separation roller partsandare provided substantially symmetrically with respect to the center of a fed sheet in the width direction (left-right direction in). The interval between the first feed roller partand the second feed roller partand the interval between the first separation roller partand the second separation roller partare set to be narrower than the minimum feedable sheet width. A nip range(illustrated with double-headed arrow) inis the range over which the feed rollerand the separation rollercome in contact with each other. Note that, when the nip rangeis viewed from the sheet feeding direction, a first nip rangeand a second nip rangedescribed later are observed (see).

The light emitting sensorwhich is a light emitting unit and the light receiving sensorwhich is a light receiving unit are respectively mounted on a light emitting substrateand a light receiving substrate. The light emitting substrateand the light guideare provided on the separation rollerside (lower side in) across the conveyance path, and the light receiving substrateis provided on the feed rollerside (upper side in) across the conveyance path.

Also, as shown in, the light emitting sensorand the light guideare provided upstream in the conveyance direction from the rotation center of the separation roller. The light receiving sensoris provided downstream in the conveyance direction from the rotation center of the feed roller. Note that the light emitting sensor, the light guide, and the light receiving sensormay be disposed at different positions from the positions shown in. For example, the light emitting sensorand the light guidemay be provided downstream in the conveyance direction from the rotation center of the feed roller, and the light receiving sensormay be provided upstream in the conveyance direction from the rotation center of the separation roller.

The light guideis provided upward of the light emitting sensorand the light emitting substrate. As shown in, the light guidehas a shaft portion extending vertically and a shaft portion inclined at an angle θ from the upstream side in the conveyance direction to the downstream side in the conveyance direction. The length of the light guideis the combined length of the shaft portion extending vertically and the shaft portion inclined at the angle θ. At this time, the length of the light guideis preferably a length at which the separation rollerand the light guidedo not interfere with each other when the user attaches and detaches the separation roller, but is not limited thereto. The position and angle θ of the light guideare set such that the light emitted from the light emitting sensoris incident at an angle so as to be not be blocked by the feed wheel partthe separation wheel partand the nip range. Here, in, the light emitted from the light emitting sensorpasses along an optical path that does not overlap with the nip rangein a direction from the near side to the far side of the surface of the diagram (i.e., same range as first nip rangeand second nip range(i.e., same range as nip range) in the conveyance direction of the sheet described later and in a direction perpendicular to the sheet surface, and a detection range consisting of a range in an intermediate position between first nip rangeand second nip rangein the sheet width direction). Note that the light reflected inside the light guideis omitted, and the direction in which the light is guided is representatively indicated in a simplified manner by a dotted line (optical axis R).

Note that, when the light emitting sensoris disposed such that the axis thereof is vertical, and the shaft portion of the light guidethat extends vertically is disposed between the lower guide plateand the separation roller holding member, as in the present embodiment, the light emitting sensor, the light emitting substrate, and the light guidecan be disposed in a minimal space, and the entire apparatus can be made more compact.

The light receiving sensorand the light receiving substrateare provided such that the central axis of the light receiving sensorsubstantially coincides with the optical axis R inclined at the angleby the light guide.

As shown in, the light emitting sensor, the light guide, and the light receiving sensorare provided such that the optical axis R passes between the first separation roller partand the second separation roller partand between the first feed roller partand the second feed roller part

Accordingly, when the range (nip range) over which the first feed roller partand the first separation roller partcome in contact with each other is given as the first nip rangeand the range (nip range) over which the second feed roller partand the second separation roller partcome in contact with each other is given as the second nip rangethe light emitted from the light emitting sensorpasses, as the detection range, through the same range as the first nip rangeand the second nip range(i.e., same range as the nip range) in the conveyance direction of the sheet and in a direction perpendicular to the sheet surface, and through a range in an intermediate position between the first nip rangeand the second nip rangein the sheet width direction.

The interval between the first feed roller partand the second feed roller partand the interval between the first separation roller partand the second separation roller partare set narrower than the minimum feedable sheet width, and thus, when there is a sheet in the detection range, it may be determined that the sheet is being nipped by the feed rollerand the separation roller. When there is a sheet in the detection range, the light emitted from the light emitting sensoris attenuated when passing through the sheet, and the amount of light detected by the light receiving sensoris greatly reduced compared to when there is no sheet. Accordingly, by comparing the magnitude of the light amount detected by the light receiving sensorwith a predetermined threshold value, it can be determined whether or not a sheet is in the detection range (is being nipped).

If the following sheet is in the detection range when feeding of the following sheet is started, the following sheet does not need to be taken in by the pickup roller, and thus the feed motoris immediately driven to rotate the feed rollerand the following sheet is fed. If the following sheet is not in the detection range when feeding the following sheet is started, the following sheet needs to be taken in by the pickup roller, and thus the pickup rolleris moved to the intake position and brought in contact with the following sheet, after which the pickup motoris driven to rotate the pickup rollerand the following sheet is taken in.

Controls of the present embodiment will be described on the basis of the flowchart in. The flowchart starts from a state where sheets are loaded in the sheet loading trayand the sheet loading detection sensorhas detected the sheets. Also, the sheet loading trayactually rises such that the uppermost sheet is in the intake position whenever the number of loaded sheets decreases, but, in this flowchart, the rising operation of the sheet loading trayis omitted. Also, this flowchart starts from a state in which the separation motoris in a holding state.

First, the conveyance motoris driven to rotate the conveyance rollers,,, and(S). Next, the feed motoris driven to rotate the feed roller(S).

Next, in order to take in a sheet with the pickup roller, the pickup lifting motoris driven to lower the pickup rollerto the intake position shown in, after which the pickup motoris driven to rotate the pickup roller(step S). When the pickup rolleris rotated after the pickup rollercomes in contact with the sheet and the posture of the sheet and the load on the sheet are stabilized, the sheet can be stably taken in.

When the sheet taken in by the pickup rollerreaches the nip range of the feed rollerand the separation roller, the sheet is fed by the feed roller. The peripheral speed of the feed rolleris set faster than the peripheral speed of the pickup roller, and the sheet is pulled out by the feed roller.

Next, the upstream sensorprovided upstream in the conveyance direction from the conveyance rollersanddetects the presence or absence of a sheet, and it is determined whether the leading edge of a sheet is detected (step S). When the upstream sensordetects the leading edge of a sheet, the drive of the pickup motoris stopped to stop the rotation of the pickup roller, and, thereafter, the pickup lifting motoris driven to raise the pickup rollerto the retracted position shown in, and the pickup rollermoves out of contact with the sheet (step S).

When the sheet reaches the conveyance rollersand, the sheet is conveyed by the conveyance rollersand. The peripheral speed of the conveyance rollersandis set faster than the peripheral speed of the feed rollers, and the sheet is pulled out by the conveyance rollersand.

Next, the downstream sensorprovided downstream in the conveyance direction from the conveyance rollersanddetects the presence or absence of a sheet, and it is determined whether the leading edge of a sheet is detected (step S). When the downstream sensordetects the leading edge of a sheet, the drive of the feed motoris stopped to stop the rotation of the feed roller(step S).

Next, the upstream sensordetects the presence or absence of a sheet, and it is determined whether the trailing edge of a sheet is detected (step S). When the upstream sensordetects the trailing edge of a sheet, it is known that the trailing edge of the sheet has already passed through the nip range of the feed rollerand the separation roller, and taking in of the next sheet (following sheet) loaded in the sheet loading trayis started.

In taking in the following sheet, the configuration consisting of the light emitting sensor, the light receiving sensor, and the light guidedetects whether the following sheet is in the nip range (step S). Since the pickup rollerdoes not need to take in the following sheet when the following sheet is detected in the nip range, the feed motoris driven to rotate the feed rollerwhile keeping the pickup rollerin the retracted position (step S). The following sheet fed by the feed rollerpasses through the detection position of the upstream sensor, reaches the conveyance rollers,and is conveyed by the conveyance rollers,, and then reaches the detection position of the downstream sensor. When the downstream sensordetects the leading edge of the following sheet (step S), the subsequent feeding operation is the same as the operation performed when the preceding sheet was fed.

When the following sheet is not detected in the nip range in step S, the presence or absence of sheets in the sheet loading trayis detected (step S). When there are no sheets on the sheet loading tray, the drive of the conveyance motoris stopped to stop the rotation of the conveyance rollers,,, and(step S), and the feeding operation is stopped. Since the pickup rollerneeds to take in the following sheet when there are sheets in the sheet loading tray, the feed rolleris rotated (step S), after which the pickup lifting motoris driven to lower the pickup rollerto the intake position and bring the pickup rollerin contact with the sheet, after which the pickup rolleris rotated (step S). The subsequent feeding operation is similar to the operation when the preceding sheet is fed.

According to the above control flow, the pickup rolleris brought in contact with the following sheet only when the intake operation by the pickup rolleris necessary, by determining whether or not the sheet is in the nip range of the feed rollerand the separation rollerat the stage at which taking in of the following sheet is started. Detection of whether or not the following sheet is in the nip range can be performed immediately before the feed rolleris rotated to feed the sheet, and thus there is no chance for the following sheet that was in the nip range to move out of the nip range in the opposite direction to the conveyance direction from when the following sheet is detected until when the feed rolleris rotated. Therefore, following sheet can be reliably fed.

Next, a sheet feeding apparatus according to a second embodiment will be described. Parts common to the first embodiment will be omitted, and description will mainly focus on the differences from the first embodiment with reference to.

In the first embodiment, the lower guide platecovers the separation rolleras shown in. In the present embodiment, in order to enable the separation rollerto be easily detached from the feed port side, a separation coveris provided in a part of the lower guide plate, as shown in. The separation coveris provided to be attachable and detachable with respect to the lower guide plate.