Sheet feed conveyance device and image forming apparatus

A sheet feed conveyance device includes a warning section, a pickup roller that feeds a sheet, a separation section, a speed sensor that detects a conveyance speed of the sheet, and a controller. The separation section includes a feed roller that feeds downstream the sheet fed by the pickup roller and a retard roller that returns a sheet involved in multiple sheet feeding toward the pickup roller. The controller recognizes the conveyance speed based on output of the speed sensor, integrate conveyance speeds detected in a measurement time period from rotation start of the pickup roller to elapse of a specific time period, and determines necessity for maintenance of the pickup roller according to a measurement distance as a result of integration.

INCORPORATION BY REFERENCE

The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2016-210828, filed on Oct. 27, 2016. The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND

The present disclosure relates to a sheet feed conveyance device that feeds a sheet using a roller. The present disclosure further relates to an image forming apparatus including the sheet feed conveyance device.

There are known image forming apparatuses such as a multifunction peripheral, a copier, and a printer. A sheet of paper is set in an image forming apparatus. The sheet of paper is fed and conveyed. A sheet feed roller may be included in the image forming apparatus for sheet feeding. The sheet feed roller comes in contact with the sheet. The sheet feed roller rotates during sheet feeding. Friction force of the feed roller with the sheet is utilized for feeding the sheet. Friction causes abrasion of the sheet feed roller. It is necessary to replace the sheet feed roller before the sheet feed roller is abraded to such a degree that the sheet feed roller is disabled from feeding a sheet. In view of the foregoing, the lifetime of the sheet feed roller may be detected (estimated).

A sheet feed conveyance device is known that feeds a recording medium from a recording medium accommodation site, performs separation on the fed recording medium using a recording median separation section, and then temporarily stops the separated recording medium. After temporarily stopping the recording medium, the sheet feed conveyance device conveys the recording medium with desired timing toward a registration roller disposed before a site where an image transfer is performed. The sheet feed conveyance device estimates the lifetime of the sheet feed roller based on a e period from restarting after temporarily stopping the recording medium to passing of the recording medium over a sensor disposed downstream. In a conveyance method using the above sheet feed device in which the recording medium is fed, subjected to separation, temporarily stopped after a specific time period, and then re-conveyed with predetermined timing, the lifetime of the sheet feed roller is detected.

SUMMARY

A sheet feed conveyance device according to the present disclosure includes a warning section, a pickup roller, a separation section, a speed sensor, and a controller. The warning section issues a warning. The pickup roller feeds a sheet placed on a placement plate. The separation section is disposed downstream of the pickup roller in a conveyance direction of the sheet. The separation section includes a feed roller and a retard roller. The feed roller feeds downstream the sheet fed by the pickup roller. The retard roller is in contact with the feed roller to form a nip and returns a sheet involved in multiple sheet feeding toward the pickup roller. The speed sensor is disposed upstream of the pickup roller in the conveyance direction. The speed sensor detects a conveyance speed of the sheet fed from the placement plate. The controller causes the pickup roller to rotate during sheet feeding. The controller recognizes the conveyance speed based on output of the speed sensor. The controller integrates conveyance speeds detected in a measurement time period that is a time period from rotation start of the pickup roller to elapse of a specific time period. The controller determines necessity for maintenance of the pickup roller according to a measurement distance that is a conveyance distance as a result of integration. Upon determining that maintenance of the pickup roller is necessary, the controller causes the warning section to issue a warning about maintenance of the pickup roller.

DETAILED DESCRIPTION

The following describes an embodiment of the present disclosure reference toFIGS. 1-9. In the following description, an image forming apparatus including a sheet feed conveyance device1will be discussed as an example. A printer100is adopted as an example of the image forming apparatus. Note that elements in the following embodiment such as configuration and positioning are merely examples provided to facilitate explanation and do not in any way limit the scope of the present disclosure.

(Brief of Image Forming Apparatus)

The printer100according to the embodiment will be described first with reference toFIG. 1.FIG. 1is a block diagram illustrating an example of the printer100according to the embodiment.

The printer100includes a controller2and a storage3. The controller2supervises overall operation of the printer100and controls respective elements of the printer100. The controller2also controls operation of the sheet feed conveyance device1. The controller2includes an image processing section22and a processor such as a CPU21. The CPU21performs arithmetic operation and processing for control on the printer100. The image processing section22performs image processing necessary for printing on image data. The storage3includes a storage device such as read only memory (ROM), random access memory (RAM), or a hard disk drive (HDD). The storage3stores therein control programs and data.

The controller2is communicably connected to an operation panel4. The operation panel4includes a display panel41(corresponding to a warning section), a touch panel42, and a hard key43. The controller2controls display of the display panel41. The controller2causes the display panel41to display a setting screen, a state of the printer100, and messages. The controller2further causes the display panel41to display an operation image. The operation image includes for example a soft key or a soft button. The controller2recognizes operation to an operation image based on output of the touch panel42. The controller2also recognizes operation to the hard key43. The controller2controls the display panel41to switch to a screen corresponding to the operation on the operation image or the hard key43. The controller2controls the printer100to operate according to setting set through the operation panel4.

The printer100includes a printing section5. The printing section5performs printing on a sheet. The printing section5includes a sheet feed section6, a conveyance section5a, an image forming section5b, and a fixing section5c. The controller2controls respective operations of the sheet feed section6, the conveyance section5a, the image forming section5b, and the fixing section5c. The controller2controls processing pertaining to printing such as sheet conveyance, and formation, transfer, and fixing of a toner image. The printing section5will be described later in detail.

The printer100further includes a communication section7(corresponding to warning section). The communication section7is a communication interface with a computer200. The computer200refers to a personal computer or a server. The communication section7receives print data from the computer200. The print data includes data indicating printing content (image data or data described in page description language) and data indicating setting content. The controller2causes the printing section5to perform printing based on the print data.

An example of the printing section5according to the embodiment will be described next with reference toFIG. 2.FIG. 2is a diagram illustrating an example of the printing section5according to the embodiment.

The printing section5includes the sheet feed section6, the conveyance section5a, the image forming section5b, and the fixing section5c. In printing, the controller2causes the sheet feed section6to feed a sheet S toward the conveyance section5a. The controller2also causes the sheet feed section6to convey the sheet S. The sheet S is for example plain paper, copy paper, recycled paper, glossy paper, or overhead projection (OHP) paper. The sheet feed section6will be described later in detail. The conveyance section5aincludes a registration roller pair51and an ejection roller pair52. The controller2causes the conveyance section5ato convey the sheet S fed from the sheet feed section6inside the printer100. The sheet S having been subjected to printing (fixing) is ejected out of the printer100by the ejection roller pair52.

The image forming section5bincludes a photosensitive drum53, a transfer roller54, a charger55, an exposure device56, and a developing device57. The controller2causes the image forming section5bto form a toner image (image) that is to be transferred to the sheet S conveyed by the conveyance section5a. The controller2further causes the image forming section5bto transfer the toner image to the sheet S. The fixing section5cincludes a heating roller58and a pressure roller59. The controller2causes the fixing section5cto fix the transferred toner image to the sheet S.

The conveyance section5aincludes a conveyance path extending vertically on the right side of the sheet feed section6. As illustrated inFIG. 2, a sheet sensor5sis disposed in the middle of the conveyance path. The sheet sensor5sis disposed between the sheet feed section6and the registration roller pair51. The sheet sensor5sis disposed downstream of the sheet feed section6in a sheet conveyance direction. The sheet sensor5sis disposed in the upstream vicinity of the registration roller pair51.

The sheet sensor5sdetects arrival of a leading edge of the sheet S (also referred to below as “leading edge arrival” or “arrival of a sheet S”) and passing of a tailing edge of the sheet S (also referred to below as “passing of a sheet S”). The sheet sensor5sis for example an optical sensor. The sheet sensor5schanges the level of its output signal according to whether the sheet S conveyed through the conveyance path is present or absent at a location corresponding to that of the sheet sensor5s. The output signal of the sheet sensor5sis input to the controller2. Based on the output signal, the controller2recognizes arrival and passing of the sheet S at and over the sheet sensor5sor the registration roller pair51in the vicinity of the sheet sensor5s.

The controller2controls a motor M1(seeFIG. 1) disposed in a main body of the printer100and an electromagnetic clutch (not illustrated) disposed at the registration roller pair51. The controller2controls rotation of the registration roller pair51. The controller2causes the registration roller pair51not to rotate at arrival of the sheet S. The leading edge of the sheet S abuts on a nip of the registration roller pair51. This warps the sheet S. The leading edge of the sheet S warped to have resilience is leveled off along the nip of the registration roller pair51. As a result, skew of the sheet S is corrected. After the sheet S is warped, the controller2causes the registration roller pair51to rotate. The controller2causes the registration roller pair51to feed the sheet S so that the toner image is transferred to the sheet S without displacement.

The controller2causes the motor M1(seeFIG. 1) to rotate during printing. The motor M1rotates rotors included in the printing section5for conveyance of the sheet S. For example, the motor M1rotates the registration roller pair51, rotors (photosensitive drum53and transfer roller54) of the image forming section5b, the rotors (heating roller58and pressure roller59) of the fixing section5c, and the ejection roller pair52.

An example of the sheet feed conveyance device1according to the embodiment will be described next with reference toFIGS. 2 and 3.FIG. 3is a block diagram illustrating an example of the sheet feed conveyance device1.

The sheet feed conveyance device1includes the warning section, the sheet feed section6, the controller2, the operation panel4, and the sheet sensor5s. The sheet feed section6includes a pickup roller8, a separation section9, and a speed sensor81. The sheet feed conveyance device1is included in the printer100(image forming apparatus). The warning section warns (alarms) a user. A combination of the display panel41and the communication section7corresponds to the warning section in the sheet feed conveyance device1.

Once execution of a print job starts, the sheet feed section6feeds sheets S one at a time. The sheet feed section6includes a cassette61. The cassette61accommodates the sheets S. The cassette61is capable of being pulled out from a casing of the printer100. After sheets S are supplemented or replaced, the cassette61is closed by the user (accommodated in the casing). The cassette61also includes a placement plate62. The sheets S (sheet sheaf) are placed on the upper surface of the placement plate62. Note that a regulation plate (not illustrated) is disposed in the cassette61for regulating the position of the sheets S.

The placement plate62has an upstream end that is supported in a pivotal manner. The upstream end of the placement plate62serves as a pivot. The placement plate62has a downstream end that is a free end that pivots in an up-and-down direction. As illustrated inFIG. 3, the sheet feed section6includes a raising and lowering mechanism63that raises and lowers the placement plate62. The raising and lowering mechanism63includes a raising and lowering motor64. The raising and lowering mechanism63is capable of raising and lowering the placement plate62by driving force of the raising and lowering motor64. When the user pulls out (opens) the cassette61, the raising and lowering mechanism63lowers the downstream end of the placement plate62until the placement plate62is laid down. In printing (sheet feeding), the controller2causes the placement plate62to be raised to an upper limit level.

The pickup roller8and the separation section9are provided as sheet feeding and conveyance members. The pickup roller8is disposed above the downstream end of the placement plate62. The pickup roller8feeds an uppermost one of the sheets S placed on the placement plate62toward the separation section9and then the image forming section5b(registration roller pair51). The separation section9is disposed downstream of the pickup roller8in the sheet conveyance direction. The separation section9includes a feed roller91and a retard roller92. An upper roller of the separation section9inFIG. 2is the feed roller91. The feed roller91feeds downstream the sheet S fed by the pickup roller8. That is, the feed roller91feeds the sheet S forward. A lower roller of the separation section9inFIG. 2is the retard roller92. The retard roller92is in contact with the feed roller91to form a nip. The retard roller92feeds the sheet S backward (direction toward cassette61). That is, the retard roller92returns a sheet S involved in multiple sheet feeding toward the pickup roller8. The feed roller91has higher conveyance power than the retard roller92. As such, when a single sheet S is fed by the pickup roller8in the above configuration, the sheet S is conveyed downstream.

A support member93is disposed at a rotational shaft of the feed roller91. The rotational shaft of the pickup roller8is supported by the support member93. The support member93moves in an up-and-down direction. In the above configuration, the pickup roller8is also allowed to move in the up-and-down direction. When the placement plate62is raised, the pickup roller8is raised by the placement plate62in a state in which the sheets S are or are not placed thereon. As the downstream end of the placement plate62is raised, the pickup roller8comes in contact with the uppermost one of the sheets S. As illustrated inFIG. 3, the sheet feed section6includes an upper limit sensor94. The upper limit sensor94detects reach of the pickup roller8to a predetermined upper limit position (seeFIGS. 2 and 3). After the controller2causes the pickup roller8and the placement plate62to reach to the respective upper limit positions, sheet feeding is performed.

The upper limit sensor94changes an output level (high level or low level) of a signal between when the pickup roller8is and is not positioned at the upper limit position. The upper limit sensor94is for example a transmission type optical sensor. The controller2recognizes that the pickup roller8has reached the upper limit position according to the output level of the upper limit sensor94. When the controller2recognizes that the pickup roller8has reached the upper limit position, the controller2stops the raising and lowering motor64. In successive printing, the pickup roller8gradually descends in accompaniment to consumption of the sheets S. Each time the pickup roller8descends, the controller2causes the raising and lowering motor64to temporarily rotate. The pickup roller8is thus re-raised to the upper limit position.

When the sheet feed section6feeds the sheet S toward the conveyance section5a, the controller2causes the sheet feed motor65and rollers of the separation section9to rotate. The rollers of the separation section9refer to the feed roller91and the retard roller92. As illustrated inFIG. 3, the sheet feed section6includes a sheet feed motor65and a sheet feed clutch66. Rotation of the sheet feed motor65rotates the pickup roller8and the rollers of the separation section9. The sheet S is fed by friction force of the circumferential surface of the pickup roller8. The sheet S is fed downstream by the pickup roller8and the separation section9. The sheet feed clutch66is disposed in correspondence with the pickup roller8. The sheet feed clutch66is an electromagnetic clutch. The controller2controls engagement and disengagement of the sheet feed clutch66. When a specific time period elapses from rotation start of the pickup roller8, the controller2disengages the sheet feed clutch66so that sheets S are not successively fed. Through the above disengagement, rotation of the pickup roller8is stopped. Thereafter, rotors disposed downstream of the separation section9convey the sheet S.

The sheet feed section6includes a sheet set sensor67, an opening and closing sensor68, and a size sensor69. The sheet set sensor67detects presence or absence of a sheet S in the cassette61. The opening and closing sensor68detects opening and closing of the cassette61. The size sensor69detects the size of the sheet S placed on the placement plate62. Outputs of the respective sensors are input to the controller2.

The sheet feed section6further includes the speed sensor81. The speed sensor81is disposed upstream of the pickup roller8in the sheet conveyance direction. The speed sensor81detects a conveyance speed of the sheet S fed from the placement plate62(also referred to below as a “sheet conveyance speed”). Output of the speed sensor81is input to the controller2. The controller2recognizes the conveyance speed of the sheet S fed from the placement plate62based on the output of the speed sensor81.

The speed sensor81detects the speed of a measurement target (sheet S) based on the Doppler effect. A sensor capable of irradiating the measurement target with light (a laser beam) can be adopted as the speed sensor81. The speed sensor81includes a light emitting element and a photo detector. The light emitting element irradiates the measurement target with light having a specific frequency. The photo detector receives light reflected by the measurement target. Difference in frequency between the irradiation light and the reflected light differs according to the speed of the measurement target. The speed sensor81detects the conveyance speed of the sheet S based on the difference in frequency between the irradiation light and the reflected light. Note that another type of sensor may be adopted as the speed sensor81. For example, a sensor that emits sound waves rather than the laser beam may be adopted as the speed sensor81.

(Warning in Relation to Pickup Roller8)

The following describes an example of a flow of warning in relation to the pickup roller8according to the embodiment next with reference toFIGS. 4-6.FIG. 4is a diagram illustrating an example of output signals of respective sensors in a situation in which no slip of the sheet S occurs on the pickup roller8and the rollers of the separation section9.FIG. 5is a diagram illustrating an example of output signals of the respective sensors in a situation in which a slip of the sheet S occurs on the pickup roller8.FIG. 6is a flowchart illustrating an example of a flow of warning in relation to the pickup roller8according to the embodiment.

InFIGS. 4 and 5, a time period T1refers to an ideal time period from rotation start of the pickup roller8to time when the sheet sensor5sdetects leading edge arrival of the sheet S. In other words, T1is a (theoretical) time period from rotation start of the pickup roller8to detection of leading edge arrival of the sheet S that is prescribed on the specification. A distance from a position of the leading edge of the sheet S ideally placed on the placement plate62to the sheet sensor5srefers to a theoretical distance A [mm]. A conveyance speed of the sheet S prescribed on the specification (theoretical value of sheet conveyance speed) refers to a theoretical speed V [mm/s]. The time period T1can be calculated using an expression A/V [s].

A time period T2inFIGS. 4 and 5is referred to as an ideal time period from rotation start of the pickup roller8to leading edge arrival of the sheet S at the nip of the rollers of the separation section9. In other words, the time period T2is a (theoretical) time period from rotation start of the pickup roller8to arrival of the sheet S at the nip that is prescribed on the specification. A distance from the position of the leading edge of the sheet S ideally placed on the placement plate62to the nip between the feed roller91and the retard roller92is referred to as a theoretical distance B [mm]. The theoretical distance B is smaller than the theoretical distance A (B<A). Further, the theoretical distance B is smaller than the length of the sheet S in a sub-scanning direction. The time period T2can be calculated using an expression B/V [s].

FIG. 4indicates a situation in which no slip occurs on the pickup roller8and the rollers of the separation section9. When a sheet S is fed in an ideal manner, the leading edge of the sheet S quickly enters into the nip between the rollers of the separation section9. The entrance of the sheet S coincides with an end of the time period T2. After the end of the time period T2, the sheet S is conveyed at a constant speed by the separation section9.FIG. 5indicates a situation in which a severe slip occurs on the pickup roller8. In the above situation, the conveyance speed of the sheet S increases not so fast. As a result, detection of arrival of the sheet S by the sheet sensor5sis delayed.

FIG. 6illustrates an example of a flow of warning in relation to the pickup roller8when a single sheet S is fed. In successive printing on a plurality of sheets S, the processing depicted in the flowchart ofFIG. 6is executed on each sheet. Sheet feeding starts at START inFIG. 6in execution of a print job (sheet feeding). First, the controller2causes the pickup roller8and the rollers (feed roller91and retard roller92) of the separation section9to rotate (Step #11).

The controller2performs conveyance speed integration during a predetermined measurement time period (Step #12). The measurement time period refers to a time period from rotation start of the pickup roller8(switching on sheet feed motor65or engagement of sheet feed clutch66) to elapse of a specific time period3a. The specific time period3acan be set at any appropriate value. In order to check the state of the pickup roller8, it is preferable to check the output of the speed sensor81during the time when the rollers of the separation section9do not pertain to conveyance of the sheet S. The measurement time period is set to a time period during which only the pickup roller8conveys the sheet S. In other words, the pickup roller8conveys the sheet S while the rollers of the separation section9do not convey the sheet S during the measurement time period. Note that a clock circuit23that times the specific time period3ais included in the controller2(seeFIG. 3.). The specific time period3acan be calculated using an expression (theoretical distance B)/(theoretical speed V) [s]. That is, the specific time period3acorresponds to the time period T2. The specific time period3ais stored in the storage3.

Speed integration can result in distance calculation. The controller2performs conveyance speed integration to calculate a measurement distance that is a conveyance distance by which the sheet S is conveyed in the measurement time period (Step #13). Specifically, the speed sensor81periodically outputs a conveyance speed as a result of detection. The controller2accordingly recognizes the conveyance speed periodically. The controller2recognizes the conveyance speed for example each time 10 ms elapses. In a configuration for example in which the measurement time period is 100 ms, the controller2performs conveyance speed integration approximately ten times. The controller2integrates the respective conveyance speeds recognized in the measurement time period. The integration is a calculation for obtaining an area. As such, the controller2adds up values each obtained by multiplying a conveyance speed by a specific period. Alternatively, the integration may be performed through another calculation.

Next, the controller2determines whether or not the measurement distance calculated by integration is smaller than a first reference value (Step #14). That is, the controller2determines whether or not the conveyance distance by which the sheet S is conveyed in the measurement time period is smaller than a value as a reference. The first reference value will be described later in detail.

When the measurement distance is smaller than the first reference value (Yes at Step #14), the controller adds a first addition value3dto a first count value3c(Step #15). The first count value3cis stored in a memory of the controller2or the storage3. The first addition value3dis for example 1. When the measurement distance is at least the first reference value (No at Step #14), the flow ends (END). In other words, the controller2does not add the first addition value3dto the first count value3c.

After Step #15, the controller2determines whether or not the first count value3cexceeds a predetermined first threshold value3e(Step #16). The first threshold value3ecan be set at any appropriate value. When the first count value3cexceeds the first threshold value3e(Yes at Step #16), the controller2causes the warning section to issue a warning to replace the pickup roller8(Step #17and then the flow ends). A combination of the operation panel4(display panel41) and the communication section7corresponds to the warning section. For example, the controller2causes the display panel41to display a message instructing to replace the pickup roller8. The controller2also causes the communication section7to transmit the message instructing to replace the pickup roller8to the predetermined computer200.

When the first count value3cdoes not exceed the first threshold value3e(No at Step #16), the controller2determines whether or not the first count value3cexceeds a predetermined second threshold value3f(Step #18). It is confirmed at Step #18whether to warn that the lifetime of the pickup roller8is expiring although replacement of the pickup roller8is not yet necessary. In view of the foregoing, the second threshold value3fis smaller than the first threshold value3e. For example, the second threshold value3fis 10 or 20 when the first threshold value3eis 40.

When the first count value3cexceeds the second threshold value3f(Yes at Step #18), the controller2causes the warning section to issue a warning indicating that cleaning of the pickup roller8is necessary and the lifetime thereof is expiring (Step #19). The above warning is also referred to below as a “warning about cleaning and lifetime of the pickup roller8”. For example, the controller2causes the display panel41to display a message instructing to clean the pickup roller8and a warning that the lifetime thereof is expiring. The controller2also causes the communication section7to transmits the message instructing to clean the pickup roller8and the warning that the lifetime thereof is expiring to the predetermined computer200. When the first count value3cdoes not exceed the second threshold value3f(No at Step #18) or after processing at Step #19, the flow ends.

The controller2sets a value obtained by multiplying a reference distance3bby a first coefficient3gas the first reference value. The first coefficient3gis greater than 0 and no greater than 1. The reference distance3bcan be set at any appropriate value. For example, the reference distance3bcan be set according to an experiment. The reference distance3bis based on a distance measured when the pickup roller8is abraded to a specific degree or less. For example, the reference distance3bcan be set in a manner that the controller2causes a brand-new pickup roller8to convey a plurality of sheets S. The controller2then integrates conveyance speeds measured in the measurement time period for each of the conveyed sheets S to calculate respective measurement distances and the average value of the respective measurement distances, which is calculated as the reference distance3b, That is, the reference distance3bcan be set based on actual measurement values. The reference distance3bcan be set based on values obtained by actually performing integration. A slip may occur to some extent even if a roller is brand-new. The measurement distance may accordingly be less than the theoretical distance A even if the remaining lifetime of the pickup roller8is sufficiently long. In view of the foregoing, the reference distance3bmay be set shorter than the theoretical distance A.

The first reference value refers to a value obtained by multiplying the reference distance3bby the first coefficient3g. Sensitivity to detect abrasion of the pickup roller8increases as the first coefficient3gis increased. That is, a possibility that the first addition value3dis added to the first count value3cincreases as the first coefficient3gis increased. The sensitivity to detect abrasion of the pickup roller8can be decreased by reducing the first coefficient3g. That is, the possibility that the first addition value3dis added to the first count value3cdecreases as the first coefficient3gis reduced. The first coefficient3gcan be set at any appropriate value.

(Warning in Relation to Rollers of Separation Section9)

The following describes an example of a flow of warning in relation to the rollers of the separation section9according to the embodiment next with reference toFIGS. 7 and 8.FIG. 7is a diagram indicating an example of output signals of the respective sensors when a slip occurs on the rollers of the separation section9.FIG. 8is a flowchart illustrating an example of a flow of warning in relation to the rollers of the separation section9according to the embodiment.

The time periods T1and T2inFIG. 7are the same as those inFIGS. 4 and 5.FIG. 7indicates a situation in which a slip occurs on the rollers of the separation section9. It is known that a maximum conveyance speed decreases in the above situation. As a result, detection of arrival of the sheet S by the sheet sensor5sis delayed. That is, conveyance of the sheet S is delayed.

FIG. 8illustrates an example of a flow of warning in relation to the rollers of the separation section9when a single sheet S is fed. When multiple sheets S are successively printed, the processing depicted in the flowchart ofFIG. 8is executed on each of the sheets S. Sheet feeding starts at START inFIG. 8to execute a print job (sheet feeding). First, the controller2causes the pickup roller8and the rollers (feed roller91and retard roller92) of the separation section9to rotate (Step #21).

The controller2recognizes the sheet conveyance speed in a time period from elapse of the measurement time period until the sheet sensor5sdetects leading edge arrival of a sheet S (Step #22) as a maximum value of the sheet conveyance speed (maximum conveyance speed) in conveyance of the sheet S. After the sheet S enters into the nip of the separation section9, the rollers of the separation section9convey the sheet S. In view of the above, the maximum conveyance speed after elapse of the measurement time period is recognized as the maximum conveyance speed in relation to the rollers of the separation section9. In the above configuration, an abrasion degree of the rollers of the separation section9can be understood.

The controller2then determines whether or not the maximum conveyance speed is smaller than a second reference value (Step #23). That is, the controller2performs calculation for the maximum conveyance speed and then determines whether or not the maximum conveyance speed decreases due to abrasion of the rollers of the separation section9. The second reference value will be described later in detail. When the maximum conveyance speed is smaller than the second reference value (Yes at Step #23), the controller2adds a second addition value3J to a second count value3i(Step #24). The second count value3iis stored in memory of the controller2or the storage3. The second addition value3J is 1, for example. When the maximum conveyance speed is at least the second reference value (No at Step #23), the flow ends (END). In other words, the controller2does not add the second addition value3J to the second count value3i.

After Step #24, the controller2determines whether or not the second count value3iexceeds a predetermined third threshold value3k(Step #25). The third threshold value3kcan be set at any appropriate value. When the second count value3iexceeds the third threshold value3k(Yes at Step #25), the controller2causes the warning section to issue a warning to replace the rollers of the separation section9(Step #26and then the flow ends). For example, the controller2causes the display panel41to display a message instructing to replace the rollers of the separation section9. The controller2also causes the communication section7to transmit the message instructing to replace the rollers of the separation section9to the predetermined computer200.

When the second count value3idoes not exceed the third threshold value3k(No at Step #25), the controller2determines whether or not the second count value3iexceeds a predetermined fourth threshold value3L (Step #27). It is determined at Step #27whether to issue a warning that the lifetime of the rollers of the separation section9is expiring. In view of the foregoing, the fourth threshold value3L is smaller than the third threshold value3k. For example, the fourth threshold value3L is 10 or 20 when the third threshold value3kis 40.

When the second count value3iexceeds the fourth threshold value3L (Yes at Step #27), the controller2causes the warning section to issue a warning that cleaning of the rollers of the separation section9is necessary and that the lifetime thereof is expiring (Step #28). The above warning may be also referred to below as a “warning about cleaning and lifetime of the rollers of the separation section9”. For example, the controller2causes the display panel41to display a message instructing to clean the rollers of the separation section9and a warning about the lifetime thereof. The controller2also causes the communication section7to transmit the message instructing to clean the rollers of the separation section9and the warning about the lifetime thereof to the predetermined computer200. When the second count value3idoes not exceed the fourth threshold value3L (No at Step #27) or after the processing at Step #28, the flow ends.

The controller2sets as the second reference value a value obtained by multiplying a reference speed3hby a second coefficient3m. The second coefficient3mis greater than 0 and no greater than 1. The reference speed3hcan be set at any appropriate value. For example, the reference speed3his a sheet conveyance speed prescribed on the specification. That is, the reference speed3his for example the theoretical speed V. A slip may occur on the rollers of the separation section9to some extent even in a situation in which the separation section9is brand-new. The maximum conveyance speed may be lower than the theoretical speed V even in a situation in which a remaining lifetime of the rollers of the separation section9is sufficiently long. In view of the foregoing, the reference speed3hmay be set lower than the theoretical speed V For example, consider that the separation section9is brand-new and multiple sheets S are conveyed. The controller2determines a maximum conveyance speed of each sheet conveyed. The controller2then calculates the average speed of each maximum conveyance speed as the reference speed3h.

The second reference value is a value obtained by multiplying the reference speed3hby the second coefficient3m. Sensitivity to detect abrasion of the rollers of the separation section9is increased as the second coefficient3mis increased. That is, a possibility that the second addition value3J is added to the second count value3iincreases as the second coefficient3mis increased. The sensitivity to detect abrasion of the rollers of the separation section9can be decreased by reducing the second coefficient3m. That is, the possibility that the second addition value3J is added to the second count value3idecreases as the second coefficient3mis decreased. The second coefficient3mcan be set at any appropriate value.

(Setting of First and Second Coefficients3gand3m)

The following describes an example of setting of the first and second coefficients3gand3maccording to the embodiment next with reference toFIG. 9.FIG. 9illustrates an example of a coefficient setting screen44according to the embodiment.

The operation panel4receives operations to set the first and second coefficients3gand3m. The user is allowed to set the first and second coefficients3gand3mthrough the coefficient setting screen44.FIG. 9illustrates an example of the coefficient setting screen44. When a prescribed operation is done on the operation panel4, the controller2causes the display panel41to display the coefficient setting screen44.

The first coefficient3gcan be set through a first coefficient level setting button set K1. The first coefficient level setting button set K1includes ten buttons for setting a level of the first coefficient3g. The buttons are each labeled with a numeral indicating a level of the first coefficient3g. The user can set a level of the first coefficient3gby touching a site where one of the buttons is displayed.FIG. 9illustrates a situation in which a level “5” is selected for the first coefficient3g. The larger the selected level is, the larger the first coefficient3gcalculated by the controller2is. The smaller the selected level is, the smaller the first coefficient3gcalculated by the controller2is. The controller2calculates the first coefficient3gfor example using the following expression (Formula 1). The controller2determines as the first reference value a value obtained by multiplying the reference distance3bby the first coefficient3gcorresponding to the level thereof set through the operation panel4.
(first coefficient 3g)=0.5+(0.05×(numeral of selected level))  (Formula 1)

The second coefficient3mcan be set using a second coefficient level setting button set K2. The second coefficient level setting button set K2also includes ten buttons for setting a level of the second coefficient3m. The buttons are each labeled with a numeral indicating a level. The user can set a level of the second coefficient3mby touching a site where one of the buttons is displayed.FIG. 9illustrates a situation in which a level “7” is selected for the second coefficient3m. The larger the selected level is, the larger the second coefficient3mcalculated by the controller2is. The smaller the selected level is, the smaller the second coefficient3mcalculated by the controller2is. The controller2calculates the second coefficient3mfor example using the following expression (Formula 2). The controller2determines as the second reference value a value obtained by multiplying the reference speed3hby the second coefficient3mcorresponding to the level thereof set through the operation panel4.
(second coefficient 3m)=0.5+(0.05×(numeral of selected level))  (Formula 2)

Note that the storage3(seeFIG. 1) stores in a volatile manner therein the specific time period3a, the reference distance3b, the first count value3c, the first addition value3d, the first threshold value3e, the second threshold value3f, the first coefficient3g, the reference speed3h, the second count value3i, the second addition value3J, the third threshold value3k, the fourth threshold value3L, and the second coefficient3m, which are necessary for calculation and control. To achieve the above configuration, the storage3may be included in the sheet feed conveyance device1.

As described above, the sheet feed conveyance device1according to the embodiment includes the warning section (display panel41and communication section7), the pickup roller8, the separation section9, the speed sensor81, and the controller2. The warning section issues a warning. The pickup roller8feeds a sheet S placed on the placement plate62. The separation section9is disposed downstream of the pickup roller8in the sheet conveyance direction. The separation section9includes the feed roller91and the retard roller92. The feed roller91feeds downstream the sheet S fed by the pickup roller8. The retard roller92is in contact with the feed roller91to form a nip and returns a sheet S involved in multiple sheet feeding toward the pickup roller8. The speed sensor81is disposed upstream of the pickup roller8in the sheet conveyance direction. The speed sensor81detects the conveyance speed of the sheet S fed from the placement plate62. The controller2causes the pickup roller8to rotate during sheet feeding. The controller2recognizes the conveyance speed based on output of the speed sensor81. The controller2integrates the conveyance speeds detected in the measurement time period from rotation start of the pickup roller8to elapse of the specific time period3a. The controller2determines necessity for maintenance of the pickup roller8according to a measurement distance that is a conveyance distance as a result of integration. Upon determining that maintenance of the pickup roller8is necessary, the controller2causes the warning section to issue a warning about maintenance of the pickup roller8.

In the above configuration, the speed at which the pickup roller8feeds the sheet S can be recognized. The conveyance speed of the sheet S fed by the pickup roller8can accordingly be monitored. In the above configuration, the conveyance distance by which the sheet S is conveyed in the measurement time period (the specific time period3a, from sheet feed start) can be obtained. A sheet conveyance state can accordingly be recognized with precision based on the sheet conveyance speed. When abrasion of the pickup roller8advances, a slip tends to readily occur. The more severe a slip is, the less the conveyance speed of the sheet S increases. The conveyance distance becomes short as abrasion of the pickup roller8advances. Necessity for maintenance of the pickup roller8can be warned about with appropriate timing based on an actual sheet conveyance state. As a result, deficiency of the pickup roller8can be precisely determined and warned about.

When the measurement distance is smaller than the first reference value set based on the predetermined reference distance3b, the controller2adds the first addition value3dto the first count value3c. By contrast, when the measurement distance is at least the first reference value, the controller2does not add the first addition value3dto the first count value3c. When the first count value3cexceeds the predetermined first threshold value3e, the controller2causes the warning section to issue a warning to replace the pickup roller8. In the above configuration, the number of times that the conveyance distance in the measurement time period is less than a value as a reference can be counted. As abrasion of the pickup roller8advances, a slip may tend to readily occur. When a slip occurs, the conveyance speed of the sheet S fed to the pickup roller8decreases. The first count value3cindicates the number of times that the conveyance speed in the measurement time period is smaller than a value as a reference. The controller2can precisely detect based on the first count value3cthat a state in which the conveyance speed of the sheet S fed by the pickup roller8is low persists. When abrasion of the pickup roller8advances to such a degree that replacement of the pickup roller8is necessary, the warning section issues a warning to replace the pickup roller8. The warning section can issue a warning that abrasion of the pickup roller8is considerably advancing and that early replacement is necessary. The warning section can issue a warning to replace the pickup roller8with appropriate timing.

Moreover, when the first count value3cexceeds the predetermined second threshold value3f, the controller2causes the warning section to issue a warning about the cleaning and lifetime of the pickup roller8. The second threshold value3fis smaller than the first threshold value3e. In other words, the controller sets a value smaller than (for example, a half or less of) the first threshold value3eas the second threshold value3fThe controller2can detect abrasion or contamination of the pickup roller8based on the first count value3c. The controller2can precisely detect performance impairment of the pickup roller8caused by abrasion or contamination. When abrasion of the pickup roller8advances, the warning section can issue a warning to consider replacement of the pickup roller8.

Further, the controller2sets as the first reference value a value obtained by multiplying the reference distance3bby the first coefficient3g. The reference distance3bis a value set based on a conveyance distance obtained by integration of the conveyance speeds detected in a time period from rotation start of the pickup roller8to elapse of the specific time period3ain a situation in which the pickup roller is abraded to a specific degree or less. The first coefficient3gis greater than 0 and no greater than 1. In the above configuration, comparison can be made between the first reference value and a conveyance distance of the sheet S in a period when the sheet S is fed by only the pickup roller8(measurement time period). The controller2can adjust timing of issuance of a warning in relation to the pickup roller8. A possibility of addition to the first count value3cincreases as the first coefficient3gis increased. As a result, abrasion of the pickup roller8can be understood sensitively. By contrast, the possibility of addition to the first count value3cis decreased by reducing the first coefficient3g. As a result, sensitivity to abrasion of the pickup roller8can be reduced.

The sheet feed conveyance device1further includes the operation panel4that receives an operation to set the first coefficient3g. The controller2sets as the first reference value a value obtained by multiplying the reference distance3bby the first coefficient3gset through the operation panel4. The user can set the first coefficient3gthrough the operation panel4. In a situation in which productivity (printing speed) is considered important, the user may set the first coefficient3gto be large. In a situation in which it is desired to avoid replacement of the pickup roller8as far as possible in view of the cost, the user may set the first coefficient3gto be small. The first coefficient3gaccording to user's intention can be set.

The sheet feed conveyance device1further includes the sheet sensor5sthat is disposed downstream of the separation section9in the sheet conveyance direction and that detects arrival and passing of the sheet S. The controller2causes the rollers of the separation section9to rotate in sheet feeding. The controller2recognizes the conveyance speed based on output of the speed sensor81. The controller2recognizes as a maximum conveyance speed the conveyance speed detected in a time period from elapse of the measurement time period to detection of leading edge arrival of the sheet S by the sheet sensor5s. The controller2performs calculation for the maximum conveyance speed to determine necessity for maintenance of the rollers of the separation section9based on a calculated value. Upon determining that the maintenance for the rollers of the separation section9is necessary, the controller2causes the warning section to issue a warning about maintenance of the rollers of the separation section9. As abrasion of the rollers of the separation section9advances, the maximum conveyance speed decreases. In the above configuration, the speed of the sheet S fed by the rollers of the separation section9can be recognized. The conveyance speed of the sheet S fed by the rollers of the separation section9can accordingly be monitored. In other words, the warning section can issue a warning about necessity for maintenance of the rollers of the separation section9with appropriate timing based on the maximum speed detected in the time period from elapse of the measurement time period to detection of sheet arrival by the sheet sensor5s.

The controller2adds the second addition value3J to the second count value3iwhen the maximum conveyance speed is smaller than the second reference value set based on the predetermined reference speed3h. By contrast, when the maximum conveyance speed is at least the second reference value, the controller2does not add the second addition value3J to the second count value3i. When the second count value3iexceeds the predetermined third threshold value3k, the controller2causes the warning section to issue a warning to replace the rollers of the separation section9. In the above configuration, the number of times that the maximum conveyance speed of the sheet S fed by the separation section9until the sheet sensor5sdetects arrival of the sheet S is less than a value as a reference value can be counted. As abrasion of the rollers of the separation section9advances, a slip tends to readily occur. The maximum conveyance speed of the sheet S fed by the rollers of the separation section9accordingly decreases. The second count value3iindicates the number of times that the conveyance speed of the sheet S conveyed by the rollers of the separation section9is less than a value as a reference value. Accordingly, the controller2can precisely determine based on the second count value3ithat a state in which the maximum conveyance speed of the sheet S fed by the rollers of the separation section9is low persists. When the controller2determines by referencing the third threshold value3kas a reference that abrasion of the rollers of the separation section9has advanced to such a degree that replacement of the rollers of the separation section9is necessary, the warning section issues a warning to replace the rollers of the separation section9. In the above configuration, the warning section can issue a warning about immediate replacement of the rollers of the separation section9when abrasion of the rollers thereof considerably advances. As a result, replacement of the rollers of the separation section9can be warned about with appropriate timing.

Furthermore, when the second count value3iexceeds the predetermined fourth threshold value3L, the controller2causes the warning section to issue the warning about cleaning and lifetime of the rollers of the separation section9. The fourth threshold value3L is smaller than the third threshold value3k. In other words, the controller2sets the fourth threshold value3L to be smaller than (for example, a half or less of) the third threshold value3k. The controller2can precisely detect based on the second count value3ithat performance of the rollers of the separation section9is impaired due to abrasion or contamination. In the above configuration, the controller2can cause the warning section to issue a warning to consider replacement with appropriate timing in a situation in which abrasion of the rollers of the separation section9is advancing.

The controller2sets as the second reference value a value obtained by multiplying the reference speed3hby the second coefficient3m. The reference speed3his a sheet conveyance speed prescribed on the specification. The second coefficient3mis greater than 0 and no greater than 1. In the above configuration, the controller2can adjust timing of warning in relation to the rollers of the separation section9. As the second coefficient3mis increased, a possibility of addition to the second count value3iincreases. As a result, abrasion of the rollers of the separation section9can be understood sensitively. By contrast, the possibility of addition to the second count value3iis decreased by reducing the second coefficient3m. As a result, sensitivity to abrasion of the rollers of the separation section9can be reduced.

The sheet feed conveyance device1further includes the operation panel4that receives an operation to set the second coefficient3m. The controller2sets as the second reference value a value obtained by multiplying the reference distance3bby the second coefficient3mset through the operation panel4. The user can set the second coefficient3m. In a situation in which productivity (printing speed) is considered important, the user may set the second coefficient3mto be large. In a situation in which it is desired to avoid replacement of the rollers of the separation section9as far as possible in view of the cost, the user may set the second coefficient3mto be small. The second coefficient3mcan be set according to an intention of the user.

An image forming apparatus (multifunction peripheral) includes the above sheet feed conveyance device1and an image forming section5b. The image forming section5bforms an image on a sheet S conveyed by the sheet feed conveyance device1. The controller2can precisely recognize a state of the sheet S being conveyed by the respective rollers pertaining to sheet feeding based on the conveyance speed of the sheet S that is a detection result. As a result, an image forming apparatus can be provided that can precisely determine deficiency of a roller and issue a warning.

The embodiment of the present disclosure has been described so far. However, the scope of the present disclosure is of course not limited to the above embodiment and various alterations may be adopted in implementation so long as such alterations do not deviate from the essence of the present disclosure.