Patent ID: 12214990

The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views.

DETAILED DESCRIPTION

In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.

Referring now to the drawings, embodiments of the present disclosure are described below. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Embodiments of the present disclosure are described below with reference to the attached drawings.FIG.1is a schematic diagram illustrating an internal configuration of an image forming apparatus100according to an embodiment of the present disclosure. As illustrated inFIG.1, the image forming apparatus100typically includes a first feeder110and a second feeder120, which may be collectively referred to as feeders110and120in the following description, a conveyor130, an image forming device140, and an output tray150. In the feeders110and120, multiple sheets M on which no images are formed yet are stacked and stored. The sheet M on which an image has been formed is stored in the output tray150.

The sheet M is an example of a sheet that is fed from the first feeder110or the second feeder120, conveyed by the conveyor130, and on which an image is formed by the image forming device140. However, the sheet M is not limited to a sheet of paper, and may be, for example, an overhead projector (OHP) sheet, or cloth. A conveyance path R1that is a space in which the sheet M is conveyed is formed inside the image forming apparatus100. The conveyance path R1is a path extending from the feeders110and120to the output tray150via a position facing the image forming device140.

Each of the feeders110and120stacks and stores multiple sheets M and supplies and feeds the stacked sheets M one by one to the conveyor130. More specifically, each of the feeders110and120floats and feeds an uppermost sheet M of the stacked sheets M. A detailed configuration of the feeders110and120will be described below with reference toFIGS.2and3.

The conveyor130conveys a sheet M fed from the feeders110and120in the conveyance path R1. Specifically, the conveyor130conveys the sheet M stored in the feeders110and120to the position facing the image forming device140in the conveyance path R1. The conveyor130ejects the sheet M on a surface of which an image has been formed by the image forming device140to the output tray150in the conveyance path R1.

The conveyor130includes multiple conveyance roller pairs131and132. Each of the conveyance roller pairs131and132includes, for example, a driving roller to which a driving force of a motor is transmitted to rotate, and a driven roller that contacts the driving roller to be driven to rotate. The driving rollers and the driven rollers rotate while nipping the sheet M to convey the sheet M in the conveyance path R1.

The conveyance roller pair131is disposed upstream from the image forming device140in the conveyance direction. The conveyance roller pair132is disposed downstream from the image forming device140in the conveyance direction. However, positions at which the conveyance roller pair131and the conveyance roller pair132are disposed are not limited to the two positions illustrated inFIG.1.

The image forming device140is disposed between the conveyance roller pair131and the conveyance roller pair132to face the conveyance path R1. The image forming device140forms an image on the surface of a sheet M conveyed by the conveyor130. The image forming device140according to the present embodiment forms an image on a sheet M conveyed in the conveyance path R1by an electrophotogaphic method. However, the image forming method of the image forming device140may be an inkjet recording method in which ink is discharged onto the sheet M to form an image.

More specifically, in the image forming device140, photoconductor drums141Y,141M,141C, and141K, which are referred to collectively as a photoconductor drum141in the following description, for the respective colors are arranged along a transfer belt142that is an endless moving conveyor. In other words, the multiple photoconductor drums141Y,141M,141C, and141K are arranged in order from upstream from the transfer belt142in the conveyance direction along the transfer belt142, on which an intermediate transfer image to be transferred to the sheet M fed from the feeder110or the feeder120is formed.

Toner contained in a toner bottle is supplied to the photoconductor drum141. Images of Y, M, C. and K colors developed with corresponding toner on surfaces of the photoconductor drums141Y,141M,141C, and141K, respectively, are superposed and transferred to the transfer belt142to form a full-color image. The fill-color image formed on the transfer belt142is transferred to the sheet M by the transfer roller143at a position closest to the conveyance path R1.

Further, the image forming device140includes a fixing roller pair144disposed downstream from the transfer roller143in the conveyance direction. The fixing roller pair144includes a driving roller that is driven by a motor, and a driven roller that contacts the driving roller to be driven by the driving roller. Then, the driving roller and the driven roller rotate while nipping the sheet M. In this process, the sheet M is heated and pressed to fix the image transferred by the transfer roller143onto the sheet M.

FIG.2is a schematic diagram illustrating a configuration of the first feeder110according to an embodiment of the present disclosure.FIGS.3A,3B,3C, and3Dare diagrams illustrating an operation of the first feeder110, according to the present embodiment. The first feeder110feeds the sheets M one by one to the conveyance path R1through a feed path R0. As illustrated inFIG.2, the first feeder110typically includes a sheet stacker111as a sheet stacker, an air blower112, a suction feeder113, a nip feed roller pair114, a lifting mechanism115, a lift detection sensor116, a feed detection sensor117, and a remaining amount detection sensor118.

The sheet stacker111is a tray or a cassette on which multiple sheets M can be stacked in a stacked state. Sheets M can be replenished in the sheet stacker111by a user. Further, the sheet stacker111is supported by a frame of the first feeder110to be movable up and down within a predetermined lift range by the lifting mechanism115.

The air blower112is disposed above the sheet stacker111and below the suction feeder113. Specifically, the air blower112is disposed at a position at which the air blower112can face the sheets M stacked on the sheet stacker111in the horizontal direction. Then, as illustrated inFIG.3A, the air blower112blows air from a lateral side to the multiple sheets Ni stacked on the sheet stacker111to float an uppermost sheet M.

The air blower112includes, for example, a float blower112aand a blower port112b. The float blower112agenerates air to float the sheets M. The blower port112bblows air generated by the float blower112aobliquely upward toward the sheets M stacked on the sheet stacker111. Then, the sheet stacker111is lifted or lowered by the lifting mechanism115so that the uppermost sheet M is positioned on a path of the air blown from the blower port112b. Thus, the uppermost sheet M is floated.

The suction feeder113is disposed above the sheet stacker111, the air blower112, and the lift detection sensor116. Further, the suction feeder113is disposed upstream from the nip feed roller pair114and the feed detection sensor117in the feed direction. The suction feeder113attracts a sheet M floated by the air blower112and conveys the sheet M in the feed direction in the feed path R0. The feed path R0is connected to the conveyance path R1.

The suction feeder113includes, for example, a driving pulley113a, a driven pulley113b, an endless annular belt113c, a feeding motor113d, a suction port113e, and a suction fan113f. The driving pulley113aand the driven pulley113bare rotatably supported at positions spaced apart from each other in the feed direction. The endless annular belt113cis wound around the driving pulley113aand the driven pulley113b. Multiple through-holes are formed on the surface of the endless annular belt113c. The feeding motor113drotates the driving pulley113a. The suction port113eis disposed inside a loop of the endless annular belt113cand is opened downward. The suction fan113fsucks air below the suction feeder113through the suction port113eand the through-holes of the endless annular belt113c.

As illustrated inFIG.3B, the suction fan113fis driven to generate an upward air flow. Accordingly, the sheet M floated by the air blower112is attracted to a lower surface of the endless annular belt113c. Further, as illustrated inFIG.3C, the feeding motor113dis driven to rotate the driving pulley113a(in other words, the endless annular belt113c) counterclockwise. Accordingly, the sheet M attracted to the lower surface of the endless annular belt113cis conveyed in the feed path R0and supplied to the nip feed roller pair114.

The nip feed roller pair114is disposed downstream from the suction feeder113in the feed direction and upstream from the feed detection sensor117in the feed direction. The nip feed roller pair114feeds the sheet M supplied from the suction feeder113, in the feed direction in the feed path R0. The nip feed roller pair114includes, for example, a driving roller114a, a driven roller114b, and a feeding motor114c.

Each of the driving roller114aand the driven roller114bis rotatably supported. The driving roller114aand the driven roller114bare in contact with each other with the feed path R0interposed between the driving roller114aand the driven roller114b. The feeding motor114crotates the driving roller114a. The nip feed roller pair114nips and feeds the sheet M, Which has entered between the driving roller114aand the driven roller114b, with the driving roller114aand the driven roller114b. Thus, the sheet M is fed to the conveyance path R1.

The lifting mechanism115lifts or lowers the sheet stacker111. The lifting mechanism115includes, for example, a lifting motor115aand a driving force transmitter that transmits the driving force of the lifting motor115ato the sheet stacker111. The driving force transmitter may include, for example, a pulley that is rotatably supported, and a belt that is wound around the pulley, with one end of the belt being connected to the sheet stacker111and the Other end of the belt being connected to an output shaft of the lifting motor115a. The lifting mechanism115causes the lifting motor115ato rotate in a first direction to lift the sheet stacker111, as illustrated inFIG.3D. The lifting mechanism115rotates the lifting motor115ain a second direction opposite to the first direction to lower the sheet stacker111.

The lift detection sensor116is fixed at a detection position above the sheet stacker111and below the suction feeder113. More specifically, the lift detection sensor116is located above the sheet stacker111that is located at an upper end of the lift range. Further, the lift detection sensor116is disposed at a position at which the lift detection sensor116can face the sheets M stacked on the sheet stacker111in the horizontal direction. The lift detection sensor116detects whether the sheets M stacked on the sheet stacker111are present at the detection position. The lift detection sensor116determines that the sheets M are present at the detection position, for example, when the density of the sheets M present in a region including the detection position is equal to or higher than a predetermined value.

The lift detection sensor116is, for example, a reflection-type optical sensor including a light emitter and a light receiver. The light emitter emits light in a horizontal direction from the detection position. The light receiver receives the light emitted from the light emitter and reflected by the sheets M stacked on the sheet stacker111. When the light receiver receives the light, the lift detection sensor116outputs a presence signal indicating that the sheets M are present at the detection position to a controller160to be described later. On the other hand, when the light receiver does not receive the light, the lift detection sensor116stops outputting the presence signal to the controller160.

The feed detection sensor117is disposed downstream from the suction feeder113and the nip feed roller pair114in the feed direction. Further, the feed detection sensor117is disposed to face the feed path R0. The feed detection sensor117detects whether a sheet M has passed through the feed path R0, in other words, whether the sheet M has been properly fed.

The feed detection sensor117is, for example, a reflection type optical sensor including a light emitter and a light receiver. The light emitter emits light toward the feed path R0. The light receiver receives light emitted from the light emitter and reflected by the sheet M that passes through the feed path R0. When the light receiver receives the light, the feed detection sensor117outputs, to the controller160, a feed signal indicating that the sheet M has been fed. On the other hand, when the light receiver does not receive the light, the feed detection sensor117stops outputting the feed signal to the controller160.

The remaining amount detection sensor118detects a remaining amount of sheets M stacked on the sheet stacker111. The remaining amount of sheets M is indicated by, for example, a ratio when a maximum amount of the sheets M, i.e., a maximum number of the sheets M, that can be stacked on the sheet stacker111is set to 100%. The remaining amount detection sensor118is, for example, a rotary encoder attached to an output shaft of the lifting motor115a. The remaining amount detection sensor118outputs a pulse signal corresponding to a rotation amount of the lifting motor115ain the first direction to the controller160(seeFIG.4) to be described later. However, a specific configuration of the remaining amount detection sensor118is not limited to the above-described example as long as the remaining amount detection sensor118can detect the remaining amount of sheets M stacked on the sheet stacker111.

The configuration of the second feeder120according to the present embodiment is similar to the configuration of the first feeder110. Components common to the first feeder110and the second feeder120are denoted by reference numerals having a common suffix “x”, such as “11x” for the first feeder110and “12x” for the second feeder120. However, the specific configuration of the second feeder120is not limited to the above-described example. As another example, the second feeder120may feed sheets M by feeding rollers that contact and rotate an uppermost sheet M stacked on the sheet stacker111. As still another example, the second feeder120may feed a sheet M manually fed by a user.

FIG.4is a functional block diagram illustrating a hardware configuration of the image forming apparatus100, according to the present embodiment. The image forming apparatus100includes a central processing unit (CPU)101as a controller, a random access memory (RAM)102as a memory, a read only memory (ROM)103as a memory, a hard disk drive (HDD)104as a memory, and an interface (I/F)105. The CPU101, the RAM102, the ROM103, the HDD104, and the I/F105are connected to each other via a common bus109as a communication member. The CPU101, the RAM102, the ROM103, and the HDD104collectively serve as the controller160.

The CPU101is an arithmetic unit and controls the entire operation of the image forming apparatus100. The RAM102is a volatile storage medium capable of reading and writing data at high speed and is used as a work area when the CPU101processes the data. The ROM103is a read-only non-volatile storage medium in which programs such as firmware are stored. The HDD104is a large-capacity non-volatile storage medium capable of reading and writing data and stores, for example, an operating system (OS), various control programs, application programs.

The image forming apparatus100processes programs such as a control program stored in the ROM103, a data-processing program, which is an application program, loaded from a storage medium such as the HDD104into the RAM102, for example, by a calculation function of the CPU101. A software controller that includes various functional modules of the image forming apparatus100is implemented by the above-described processing. A combination of the software controller as described above and the hardware resources installed in the image forming apparatus100serves as a functional block that implements the functions of the image forming apparatus100.

The I/F105is an interface that connects the feeders110and120, the conveyor130, the image forming device140, and an operation panel170to the common bus109. In other words, the controller160controls the operations of the feeders110and120, the conveyor130, the image forming device140, and the operation panel170through the I/F105.

The operation panel170serves as a user interface that includes a display that displays, for example, current setting values and a selection screen and an operation device that includes, for example, a touch panel and a push button, that receives an input operation from a user.

As illustrated inFIG.4, a sheet feeding apparatus200includes the feeders110and120, the controller160, the I/F105, and the common bus109. In other words, the above-described embodiment of the present disclosure can be applied not only to the image forming apparatus100but also to the sheet feeding apparatus200that is independent from the image forming apparatus100.

FIG.5is a functional block diagram illustrating, components of the controller160, according to the present embodiment. The controller160typically includes a first feed processing unit161, a second feed processing unit162, a parameter setting unit163, a lift processing unit164, a remaining amount determination unit165, and a feed trial processing unit166. Each of the functional blocks that represents the first feed processing unit161, the second feed processing unit162, the parameter setting unit163, the lift processing unit164, the remaining amount determination unit165, and the feed trial processing unit166included in the controller160is implemented, for example, by the CPU101that executes a program stored in a memory. Each of the functional blocks that represents the first feed processing unit161, the second feed processing unit162, the parameter setting unit163, the lift processing unit164, the remaining amount determination unit165, and the feed trial processing unit166illustrated inFIG.5operates in conjunction with each other to feed a sheet M from one of the first feeder110or the second feeder120to the conveyance path R1.

The first feed processing unit161drives the float blower112a, the suction fan113f, and the feeding motors113dand114cto cause the first feeder110to perform the feeding operation illustrated inFIGS.3A,3B, and3C. The second feed processing unit162drives a float blower122a, a suction fan123f, and feeding Motors123dand124cto cause the second feeder120to perform the feeding operation.

The parameter setting unit163executes parameter setting processing illustrated inFIGS.6and7to set parameters such as a lift amount and a threshold, used in the feed processing illustrated inFIGS.8,10, and11. The lift amount indicates a lift amount per one time of the sheet stacker111. The threshold is a value to be compared with a remaining amount of sheets M on the sheet stacker111detected by the remaining amount detection sensor118. In other words, the threshold is the remaining amount of sheets M when the sheet stacker111is lifted excessively and the air blown from the air blower112is blocked by the sheet stacker111and does not reach the sheets M. The processing of the parameter setting unit163is described later with reference toFIGS.6and7.

The lift processing unit164causes the lifting mechanism115to lift the sheet stacker111based on the presence signal output from the lift detection sensor116and the lift amount set by the parameter setting unit163. In addition, the lift processing unit164causes the lifting mechanism115to lower the sheet stacker111at a timing when the sheets M are replenished to the sheet stacker111.

The remaining amount determination unit165determines the remaining amount of sheets M stacked on the sheet stacker111based on a pulse signal output from the remaining amount detection sensor118and the threshold set by the parameter setting unit163. The remaining amount determination unit165integrates the number of pulse signals output from the remaining amount detection sensor118. Then, the remaining amount determination unit165calculates the remaining amount of sheets M based on the integrated number of pulse signals. In other words, as the integrated number of the pulse signals increases, the remaining amount of sheets M decreases. Further, the remaining amount determination unit165resets the integrated number of pulse signals at a timing when the sheet stacker111is lowered by the lift processing unit164.

The feed trial processing unit166causes the first feeder110to try the feeding operation based on an input operation of a user received through the operation panel170, the remaining amount of sheets M determined by the remaining amount determination unit165, and a feed signal output from the feed detection sensor117. First, the feed trial processing unit166receives an input operation indicating whether to try the feeding operation of the first feeder110from a user through the operation panel170. Then, after the feed trial processing unit166causes the first feeder110to try the feeding operation, the feed trial processing unit166determines whether the feeding operation has been normally completed based on whether a feed signal is output from the feed detection sensor117. Further, the feed trial processing unit166causes the second feeder120to execute the feeding operation instead of the first feeder110in case where the feed sural is not output from the feed detection sensor117even when the first feeder110tries the feeding operation N times (N is an integer of two or more).

FIG.6is a flowchart of parameter setting processing based on a thickness T of the sheet M, according to an embodiment of the present disclosure. The parameter setting unit163acquires a thickness T (mm) of sheets M stacked on the sheet stacker111. The parameter setting unit163, for example, may acquire the thickness T by, for example, a sensor disposed in the sheet stacker111or the user's input through the operation panel170. Next, the parameter setting unit163compares the acquired thickness T of the sheets M with predetermined thicknesses thresholds Tth1, Tth2, Tth3, and Tth4 (S601, S602, S603, and S604). Note that Tth1 is smaller than Tth2, Tth2 is smaller than Tth3, and Tth3 is smaller than Tth4 (Tth1<Tth2<Tth3<Tth4). Then, the parameter setting unit163sets the lift amount of the sheet stacker111and the threshold according to the thicknesses T of the sheets M stacked on the sheet stacker111(S605, S606, S607, S608, and S609).

More specifically, when the thickness T of the sheets M is smaller than the first reference threshold Tth1 (YES in S601), the parameter setting unit163sets the lift amount of the sheet stacker111to A mm and sets the threshold to α % (S605). When the thickness T of the sheets M is equal to or greater than the first threshold Tth1 and smaller than the second threshold Tth2 (YES in S602), the parameter setting unit163sets the lift amount of the sheet stacker111to B mm and sets the threshold to β % (S606). When the thickness T of the sheets M is equal to or greater than the second threshold Tth2 and smaller than the third threshold Tth3 (YES in S603), the parameter setting unit163sets the lift amount of the sheet stacker111to C mm and sets the threshold to γ % (S607). When the thickness T of the sheets M is equal to or greater than the third threshold thickness Tth3 and smaller than the fourth threshold thickness Tth4 (YES in S604), the parameter setting unit163sets the lift amount of the sheet stacker111to D mm and sets the thresholds to δ % (S608). Further, when the thickness T of the sheets M are equal to or greater than the fourth reference thickness Tth4 (NO in S604), the parameter setting unit163sets the lift amount of the sheet stacker111to E mm and sets the threshold to ε % (S609). Then, the parameter setting unit163notifies the lift processing unit164of the set lift amount of the sheet stacker111and notifies the remaining amount determination unit165of the set threshold.

FIG.7is a flowchart illustrating parameter setting processing based on a size, such as B4, A4, and letter size, of the sheet M, according to an embodiment of the present disclosure. The parameter setting unit163acquires a size S of the sheets M stacked on the sheet stacker111. For example, the parameter setting unit163may acquire the size S by, for example, a sensor disposed in the sheet stacker111or the user's input through the operation panel170. Next, the parameter setting unit163compares the acquired size S of the sheet M with predetermined threshold sizes Sth1, Sth2, Sth3, and Sth4 (S701, S702, S703, S704). Note that Sth1 is smaller than Sth2, Sth2 is smaller than Sth3, and Sth3 is smaller than Sth4 (Sth1<Sth2<Sth3<Sth4). Then, the parameter setting unit163sets the lift amount of the sheet stacker111and the threshold in accordance with the size S of the sheets M stacked on the sheet stacker111(S705, S706S707, S708, S709).

More specifically, when the size S of the sheets M is smaller than the first threshold size Sth1 (YES in S701), the parameter setting unit163sets the lift amount of the sheet stacker111to A mm and sets the threshold to α % (S705). When the size S of the sheets M is equal to or larger than the first threshold size Sth1 and smaller than the second threshold size Sth2 (YES in S702), the parameter setting unit163sets the lift amount of the sheet stacker111to B mm and sets the threshold to β % (S706). When the size S of the sheets M is equal to or larger than the second threshold size Sth1 and smaller than the third threshold size Sth3 (YES in S703), the parameter setting unit163sets the lift amount of the sheet stacker111to C mm and sets the threshold to γ % (S707). When the size S of the sheets M is equal to or larger than the third threshold size Sth3 and smaller than the fourth threshold size Sth4 (YES in S704), the parameter setting unit163sets the lift amount of the sheet stacker111to D mm and sets the threshold to δ % (S708). Further, when the size S of the sheets M is equal to or larger than the fourth reference size Sth4 (NO in S704), the parameter setting unit163sets the lift amount of the sheet stacker111to E mm and sets the threshold to ε % (S709). Then, the parameter setting unit163notifies the lift processing unit164of the set lift amount of the sheet stacker111and notifies the remaining amount determination unit165of the set threshold.

InFIGS.6and7, the lift amount of the sheet stacker111is set so that, for example, A is smaller than B, B is smaller than C, C is smaller than D, and D is smaller than. E (A<B <C<D<E). In other words, the larger the thickness T of the sheets M or the larger the size S of the sheets M, the parameter setting unit163increases the lift amount of the sheet stacker111per one time. InFIGS.6and7, the threshold is set so that, for example, α is smaller than β, β is smaller than γ, γ is smaller than δ, and δ is smaller than ε(α<β<γ<δ<ε). In5other words, the larger the thickness T of the sheets M or the larger the size S of the sheets M, the parameter setting unit163increases the threshold to be compared with the remaining sheet amount of the sheets M. In the parameter setting processing ofFIGS.6and7, only one of the lift amount of the sheet stacker111and the threshold may be set or changed, and the other may be a predetermined fixed value.

FIG.8is a flowchart of the feed processing according to an embodiment of the present disclosure.FIG.9is a schematic diagram illustrating the feeders110and120during the feed processing, according to the present embodiment. The controller160executes the feed processing at a timing when an image formation instruction is input to the image forming apparatus100. The feed processing is executed by the first feed processing unit161, the second feed processing unit162, the lift processing unit164, the remaining amount determination unit165, and the feed trial processing unit166. On the other hand, the parameter setting processing by the parameter setting unit163is assumed to have been executed before the start of the feed processing.

First, the lift processing unit164determines whether a presence signal is output from the lift detection sensor116, in other words, whether the sheet is detected by the lift detection sensor116(S801). When the presence signal is not output from the lift detection sensor116(NO in S801), the lift processing unit164rotates the lifting motor115ain the first direction to lift the sheet stacker111by the lift amount set by the parameter setting unit163(S802), and executes the processing of step S801again. In other words, the lift processing unit164lifts the sheet stacker111until the sheets M stacked on the sheet stacker111reach the detection position.

In response to the output of the presence signal from the lift detection sensor116(YES in S801), the lift processing unit164causes the remaining amount determination unit165to execute the processing in steps S803and S804. Based on the integrated value of pulse signals output from the remaining amount detection sensor118, the remaining amount determination unit165determines whether the sheets M are stacked on the sheet stacker111(S803) and Whether the remaining amount of sheets M on the sheet stacker111is smaller than the threshold set by the parameter setting unit163(S804).

When it is determined that the remaining amount of sheets M on the sheet stacker111is equal to or greater than the threshold (NO in S803and NO in S804), the remaining amount determination unit165causes the first feed processing unit161to execute the processing of step S805. In step S805, the first feed processing unit161drives the float blower112a, the suction fan113f, and the feeding motors113dand114cto cause the first feeder110to execute the feeding operation. Accordingly, as illustrated inFIGS.3A,3B, and3C, one sheet M is fed from the first feeder110to the conveyance path R1. Then, the first feed processing unit161causes the lift processing unit164to execute the processing of step S801.

In other words, the controller160causes the first feeder110to repeatedly execute the feeding operation (S805) during a period of time in which the remaining amount of sheets M on the sheet stacker111is equal to or greater than the threshold (No in S804) while lifting the sheet stacker111(S802). Accordingly, as illustrated in an upper part ofFIG.9, the amount of sheets M stacked on the sheet stacker111gradually decreases, and the sheet stacker111gradually elevates.

When the remaining amount determination unit165determines that the remaining amount of sheets M on the sheet stacker111is greater than 0% and smaller than the threshold (NO in S803and YES in S804), the remaining amount determination unit165causes the feed trial processing unit166to execute the processing of step S806. The feed trial processing unit166substitutes one for the number of feed trials stored in the RAM102or the HDD104(S806), and causes the first feed processing unit161to execute the processing of step S807.

In step S807, the first feed processing unit161drives the float blower112a, the suction fan113f, and the feeding motors113dand114cto cause the first feeder110to execute the feeding operation. In other words, when the controller160determines that the remaining amount of sheets M on the sheet stacker111is smaller than the threshold (NO in S804), the controller160causes the first feeder110to try the feeding operation (S807). Then, the first feed processing unit161causes the feed trial processing unit166to execute the processing of step S808.

The feed trial processing unit166determines whether the feed signal is output from the feed detection sensor117(S808). In other words, the feed trial processing unit166determines whether the sheet M is fed to the conveyance path R1by the feeding operation tried by the first feeder110in step S807(S808). When the feed trial processing unit166determines that the feed signal is output from the feed detection sensor117(YES in S808), the feed trial processing unit166causes the lift processing unit164to execute the processing of step S801.

On the other hand, when the feed trial processing unit166determines that the feed signal is not output from the feed detection sensor117(NO in S808), the feed trial processing unit166determines whether the number of feed trials has reached N times (S809). When the feed trial processing unit166determines that the number of feed trials is smaller than N times (NO in S809), the feed trial processing unit166adds one to the number of feed trials (S810) and causes the first feed processing unit161to execute the processing of step S807. In other words, the controller160causes the first feeder110to try the feeding operation N times at the maximum until the feed signal is output from the feed detection sensor117(S806, S807, S808, S809, S810).

When the feed trial processing unit166determines that the number of feed trials has reached N times (YES in S809), the feed trial processing unit166causes the second feed processing unit162to execute the processing of step S811, In step S811, the second feed processing unit162drives the float blower122a, the suction fan123f, and the feeding motors123dand124cto cause the second feeder120to execute the feeding operation. In other words, when the feed signal is not output from the feed detection sensor117even if the first feeder110tries the feeding operation N times (NO in S808and YES in S809), the controller160causes the second feeder120to feed a sheet M instead of the first feeder110as illustrated inFIG.9(S811).

In addition, when the remaining amount determination unit165determines that sheets M are not stacked on the sheet stacker111(YES in S803), the remaining amount determination unit165causes the second feed processing unit162to execute the processing of step S811without executing steps S804, S805, S806, S807, S808, S809, and S810. Further, the remaining amount determination unit165may notify the user that the sheets M are not stacked on the sheet stacker111through the operation panel170.

According to the above-described embodiment, for example, the following functional effects are achieved.

According to the above-described embodiments, when the remaining amount of sheets M on the sheet stacker111is smaller than the threshold (YES in S804), the controller160causes the second feeder120to execute the feeding operation instead of the first feeder110(S811). Accordingly, in a case in which the sheet stacker111approaches the endless annular belt113cand air blown from the air blower112is unlikely to reach an uppermost sheet M, the feeding operation is switched so that the second feeder120, instead of the first feeder110, executes the feeding operation. Accordingly, the operation rate of the image forming apparatus100and the sheet feeding apparatus200can be enhanced. On the other hand, when the remaining amount of sheets M on the sheet stacker111is equal to or greater than the threshold (NO in S804), the controller160causes the first feeder110to execute the feeding operation (S805). Accordingly, replenishing the sheet M at an unnecessary timing by a user can be prevented.

According to the above-described embodiment, when the remaining amount of sheets M on the sheet stacker111is smaller than the threshold (YES in S804), the controller160causes the first feeder110to try the feeding operation N times at the maximum (S806, S807, S808, S809, S810). Accordingly, the feeding operation can be switched so that the second feeder120, instead of the first feeder110, executes the feeding operation after the sheets M stacked on the sheet stacker111are consumed as much as possible. Accordingly, replenishing the sheet M at an unnecessary timing by a user can be further prevented. Note that the maximum number of feed trials N may be a predetermined fixed value or may be set by the user through the operation panel170.

In addition, according to the above-described embodiment, the rotary encoder attached to the lifting motor115ais Used as the remaining amount detection sensor118. For this reason, the number of components of the image forming apparatus100can be reduced as compared with a case in which the remaining amount detection sensor118is disposed separately from the rotary encoder.

Further, according to the above-described embodiment, the lift amount of the sheet stacker111and the threshold are variable in accordance with the thickness T or the size S of the sheets M. Accordingly, an appropriate lift amount of the sheet stacker111and an appropriate threshold in accordance with the type of the sheet M can be used. However, the lift amount of the sheet stacker111and the threshold may be predetermined fixed values or may be set by the user through the operation panel170.

First Modification

Feed processing according to a first modification of the feed processing ofFIG.8is described with reference toFIG.10.FIG.10is a flowchart illustrating a procedure of the feed processing according to the first modification. A detailed description of points that are similar to the above-described embodiment is omitted, and points that are different from the above-described embodiment are mainly described. The feed processing illustrated inFIG.10is different from the feed processing illustrated inFIG.8in that steps S806, S809, and S810are omitted in the feed processing ofFIG.10.

When it is determined that the remaining amount of sheets M on the sheet stacker111is smaller than the threshold (YES in S804), the controller160according to the first modification causes the first feeder110to try the feeding operation only once (S807). Then, when it is determined that the feed signal is not output from the feed detection sensor117(NO in S808), the controller160causes the second feeder120to feed the sheet instead of the first feeder110(S811).

Second Modification

Feed processing according to a second modification is described with reference toFIG.11.FIG.11is a flowchart illustrating a procedure of feed processing according to the second modification. A detailed description of points that are similar to the above-described embodiment is omitted, and points that are different from the above-described embodiment are mainly described. The feed processing illustrated inFIG.11is different from the feed processing illustrated inFIG.8in that steps S806, S807, S808, S809, and S810are omitted in the feed processing ofFIG.11.

In the second modification, when the remaining amount of sheets M on the sheet stacker111is determined to be smaller than the threshold (YES in S804the controller160causes the second feeder120to feed the Sheets without causing the first feeder110to try the feeding operation (S811). In other words, in the second Modification, the feed trial processing unit166is omitted.

According to the second modification, in a case in which the sheet stacker111is lifted excessively and the feeding operation by the first feeder110is highly likely to fail (YES in S804), the controller160causes the second feeder120to feed the sheets M without causing the first feeder110to try the feeding operation (S811). Accordingly, a time loss in the feed processing can be reduced.

Note that the controller160may switch between the feed processing illustrated inFIG.8or10, which causes the first feeder110to try the feeding operation, and the feed processing illustrated inFIG.11, which causes the second feeder120to feed sheets M without causing the first feeder110to try the feeding operation, according to an input operation received through the operation panel170. Such a configuration as described above allows the feed trials of the feeding operation performed by the first feeder110to switch between valid and invalid in accordance with the use environment of the user.

Each of the functions according to the embodiments described above can be implemented by one processing circuit or multiple processing circuits. In the above-described embodiments of the present disclosure, the processing circuit includes a processor programmed to execute each function by software such as a processor implemented by an electronic circuit, and a device such as an application specific integrated circuit (ASIC), a digital signal processor (DSP), a field programmable gate array (FPGA), or a conventional circuit module designed to execute each function described above.

Note that the present disclosure is not limited to specific embodiments described above, and numerous additional modifications and variations are possible in light of the teachings within the technical scope of the appended claims. It is therefore to be understood that the disclosure of the present specification may be practiced otherwise by those skilled in the art than as specifically described herein. Such embodiments and modifications thereof are included in the scope and gist of the embodiments of the present disclosure and are included in the embodiments described in claims and the equivalent scope thereof.

The above-described embodiments are illustrative and do not limit the present disclosure. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present disclosure.