Detecting size of print medium using sensors available along paper path

An image forming apparatus includes a load detection sensor located on a feeder to detect whether a print medium is loaded on the feeder, an overload detection sensor to detect an overload state of a discharger, and a controller to detect a width of the print medium according to a combination of a feeder load state of a feeder load detection signal of the load detection sensor and an overload state of a discharger overload detection signal of the overload detection sensor and control an image former to perform printing by applying different print modes according to the detected width of the print medium.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is filed under 35 U.S.C. § 371 as a National Stage of PCT International Application No. PCT/US2019/023658, filed on Mar. 22, 2019, in the U.S. Patent and Trademark Office, which claims the priority benefit of Korean Patent Application No. 10-2018-0034769, filed on Mar. 26, 2018, in the Korean Intellectual Property Office. The disclosures of PCT International Application No. PCT/US2019/023658 and Korean Patent Application No. 10-2018-0034769 are incorporated by reference herein in their entireties.

BACKGROUND

An electrophotographic image forming apparatus forms a visible toner image on a photoconductor by supplying toner to an electrostatic latent image formed on the photoconductor, transfers the toner image to a print medium, fixes the transferred toner image on the print medium, and prints an image on the print medium.

A fusing unit may include a heating member and a pressing member that are engaged with each other to form a fixing nip. The print medium is subjected to heat and pressure as the print medium passes the fixing nip. Accordingly, the toner image is fixed onto the print medium.

DETAILED DESCRIPTION

A width of a heating member corresponds to a width of a print medium having a maximum available size. The entire width of the heating member is heated during a printing process.

When a print medium having a small width passes the fixing nip, since heat of a portion of the heating member where the print medium does not pass is not transmitted to the print medium, a temperature of the portion where the print medium does not pass may be higher than that of a portion passed by the print medium. When the print medium having the small width is continuously printed, a temperature of the portion where the print medium does not pass may be much higher than that of the portion passed by the print medium.

FIG.1is a view illustrating a configuration of an electrophotographic image forming apparatus according to an example. Referring toFIG.1, a feeder100on which a print medium P is loaded, and a discharger300on which the print medium P that has been completely printed is loaded are illustrated. A print path400connects the feeder100and the discharger300. An image former200is located in the print path400.

The print medium P loaded on the feeder100is taken out one by one, and is conveyed along the print path400. Although the feeder100is a feed cassette in the present example, the feeder100is not limited thereto. For example, the feeder100may be a multi-purpose feed tray.

FIG.2is a plan view of the feeder100. Referring toFIG.2, the print medium P may be loaded in a center alignment method on the feeder100. The feeder100may include one pair of guide members101and102. The one pair of guide members101and102guide both end portions of the print medium P in a width direction of the print medium P so that the print medium P is loaded in the center alignment method on the feeder100. In order to adjust an interval between the one pair of guide members101and102to correspond to a width of the print medium P, the one pair of guide members101and102may be moved toward/away from each other. The one pair of guide members101and102may be synchronized and may be moved toward/away from each other. In order to load a print medium P1having a large width, the one pair of guide members101and102may be located as indicated by a solid line ofFIG.2, and in order to load a print medium P2having a small width, the one pair of guide members101and102may be located as indicated by a dashed line ofFIG.2.

The image former200forms an image by using an electrophotographic method on the print medium P that is conveyed along the print path400. The image former200may include a developing unit210, an exposure unit220, a transfer roller230, and a fusing unit240. The developing unit210supplies toner contained in the developing unit210to an electrostatic latent image formed on a photosensitive drum21and develops the electrostatic latent image into a visible toner image.

The photosensitive drum21that is a photoconductor on a surface of which the electrostatic latent image is formed may include a conductive metal pipe and a photosensitive layer formed on an outer circumferential surface of the conductive metal pipe. A charging roller22charges a surface of the photosensitive drum21to a uniform potential.

The exposure unit220emits light modulated to correspond to image formation to the photosensitive drum21and forms the electrostatic latent image on the photosensitive drum21. A laser scanning unit (LSU) using a laser diode as a light source or a light-emitting diode (LED) exposure unit using an LED as a light source may be used as the exposure unit220.

A developing roller23supplies a developer, e.g., the toner, contained in the developing unit210to the photosensitive drum21and develops the electrostatic latent image into the visible toner image. A development bias voltage may be applied to the developing roller23. When a one-component development method is used, the toner may be contained in the developing unit210. When a two-component development method is used, the toner, or the toner and a carrier may be contained in the developing unit210. Although not shown, the developing unit210may further include a supply roller configured to supply the developer contained in the developing unit210to the developing roller23, a regulation member configured to regulate the amount of the developer attached to a surface of the developing roller23and supplied to a development area where the photosensitive drum21and the developing roller23face each other, and an agitator configured to agitate the developer contained in the developing unit210.

The transfer roller230is a transfer unit configured to transfer the toner image from the photosensitive drum21to the print medium P. A transfer bias voltage for transferring the toner image to the print medium P is applied to the transfer roller230. A coroner transfer unit or a transfer unit using a pin scorotron method may be used, instead of the transfer roller230.

The print medium P is picked up one by one from the feeder100by a pickup roller11, and is conveyed to an area where the photosensitive drum21and the transfer roller230face each other by conveying rollers12and13.

The fusing unit240fixes the toner image transferred to the print medium P onto the print medium P by applying heat and pressure to the toner image. The print medium P passing through the fusing unit240is discharged to and loaded on the discharger300by a discharging roller19.

A cleaning blade24is a cleaning unit for removing the toner and a foreign material remaining on the surface of the photosensitive drum21after a transfer process. Another type of cleaning device such as a rotating brush may be used, instead of the cleaning blade24.

In the above configuration, the exposure unit220forms the electrostatic latent image by scanning light modulated to correspond to the image information to the photosensitive drum21. The developing roller23forms the visible toner image on the surface of the photosensitive drum21by supplying the toner to the electrostatic latent image. The print medium P loaded on the feeder100is conveyed to the area where the photosensitive drum21and the transfer roller230face each other by the pickup roller11and the conveying rollers12and13, and the toner image is transferred to the print medium P from the photosensitive drum21due to the transfer bias voltage applied to the transfer roller230. When the print medium P passes through the fusing unit240, the toner image is fixed onto the print medium P due to heat and pressure. The print medium P that has been completely fixed is discharged by the discharging roller19and is loaded on the discharger300.

The fusing unit240may include a heating member241and a pressing member242that are engaged with each other and form a fixing nip through which the print medium P passes. The heating member241may be heated by a heat source243. The heating member241may be, for example, a metal roller or an endless belt. The heat source243may be, for example, a halogen lamp or a ceramic heater. A width of the heating member241may correspond to a width of the print medium P. While the print medium P passes through the fixing nip, heat of the heating member241is transmitted to the print medium P and the toner image. While printing is performed, the entire width of the heating member241is heated. When the print medium P2having a small width passes through the fixing nip, a surface of the heating member241is divided into a contact portion contacting the print medium P2and a non-contact portion not contacting the print medium P2in a width direction. Since heat of the non-contact portion of the heating member241is not transmitted, a temperature of the non-contact portion may be higher than a temperature of the contact portion. When a plurality of pieces of paper are continuously printed as the print medium P2having a small width, a temperature of the non-contact area may be much higher than that of the contact portion. A temperature increase of the heating member241may adversely affect a lifetime of the fusing unit240. Also, heat may be transmitted to other members in the image forming apparatus, and may adversely affect a lifetime of the image forming apparatus.

In this regard, the controller500may control the image former200to print an image in one mode selected from different print modes, for example, a first mode and a second mode, according to a width of the print medium P. The controller500may stop the printing and may output a print error signal according to a feeding state of the print medium P. The first mode that is a normal print mode is applied to the print medium P1having a maximum size that may be loaded on the feeder100. The second mode that is a low-speed print mode is applied to the print medium P2having a width less than that of the print medium P1. For example, the print medium P1may be an A4 or LTR sheet, and the print medium P2may be an A5 or B5 sheet. When the print medium P2having a small width is used, a cooling time of the non-contact portion may be secured by reducing a print speed, thereby reducing the risk of overheating of the non-contact portion.

For example, the controller500may control the image former200to print an image at a first process speed in the first mode, and may control the image former200to print an image at a second process speed, which is less than the first process speed, in the second mode. The process speed that is a speed at which the image former200forms an image refers to a linear speed of the photosensitive drum21or a feed speed of the print medium P.

For example, during continuous printing, the controller500may set an interval between a previous printing operation and a next printing operation as a first interval in the first mode, and a second interval, which is greater than the first interval, in the second mode. In this case, the first process speed and the second process speed may be the same, or the second process speed may be less than the first process speed.

In order to distinguish the first mode from the second mode, a width of the print medium P needs to be detected. The controller500detects the width of the print medium P by combining detection signals of two sensors (a first sensor and a second sensor) for detecting the print medium P in an image forming process, and controls the image former200to perform printing in one mode selected from among the first mode and the second mode whose print speed is less than that of the first mode according to the detected width of the print medium P. The controller500may detect a feeding state of the print medium P by combining detection signals of two sensors (the first sensor and the second sensor) for detecting the print medium P in an image forming process and may stop printing and may output a print error signal according to the detected feeding state of the print medium P.

FIG.3is a view of a sensor according to an example. Referring toFIG.3, the sensor may include an actuator551that contacts the print medium P and is rotated, and a sensing unit552that is turned on/off by the actuator551. The sensing unit552may be a photointerrupter including, for example, a light emitter and a light receiver. For example, when the print medium P is not detected, the actuator551is located on a position indicated by a solid line ofFIG.3, light emitted from the light emitter is received by the light receiver, and the sensing unit552is turned off. When the print medium P pushes the actuator551and the actuator551is pivoted to a position indicated by a dashed line ofFIG.3, the actuator551is located between the light emitter and the light receiver, light emitted from the light emitter is blocked by the actuator551and is not detected by the light receiver, and the sensing unit552is turned on. The sensing unit552may be connected to the controller500by an electrical unit (not shown). A state of a detection signal of the sensor is an “on state” when the print medium P is detected by the sensor and is an “off state” when the print medium P is not detected.

FIG.4is a plan view illustrating positions of a first sensor and a second sensor. Referring toFIG.4, the first print medium P1to which the first mode is applied and the second print medium P2to which the second mode is applied are illustrated. The second print medium P2has a width less than a width of the first print medium P1. The second print medium P2is a print medium having a maximum width to which the second mode is applied.

The first print medium P1that is center-aligned includes a first end portion P1-1and a second end portion P1-2in a width direction. A second print medium P2C that is center-aligned includes a first end portion P2C-1and a second end portion P2C-2in the width direction. A first sensor561is located to detect the print medium P in a region S1between the first end portion P1-1of the first print medium P1that is center-aligned and the first end portion P2C-1of the second print medium P2C that is center-aligned. For example, the actuator551of the first sensor561may be located in the region S1. When the one pair of guide members101and102are appropriately adjusted as shown inFIG.2, the second print medium P2may be loaded as the second print medium P2C on the feeder100in a center alignment method as shown inFIG.4. In this case, the first print medium P1and the second print medium P2may be distinguishably detected by the first sensor561. For example, when a detection signal in an on state is input from the first sensor561, the controller500may recognize that the first print medium P1is detected. When a detection signal in an on state is not input from the first sensor561, that is, when a detection signal in an off state is input from the first sensor561, the controller500may recognize that the second print medium P2is detected. As such, when a feeding state of the print medium P is a normal feeding state, the controller500may detect a width of the print medium P and a feeding state of the print medium P according to a detection signal input from the first sensor561.

A feeding state of the print medium P may be an abnormal feeding state. For example, when the one pair of guide members101and102are located at positions indicated by a solid line ofFIG.2, the second print medium P2may be loaded on the feeder100. The second print medium P2may be side-aligned as a second print medium P2R with the first end portion P1-1of the first print medium P1as shown inFIG.4, or may be side-aligned as a second print medium P2L with the second end portion P1-2of the first print medium P1as shown inFIG.4. When the second print medium P2is side-aligned as the second print medium P2L with the second end portion P1-2of the first print medium P1, since the first sensor561is turned off, the controller500may distinguishably detect the first print medium P1and the second print medium P2based on the detection signal of the first sensor561. However, when the second print medium P2is side-aligned as the second print medium P2R with the first end portion P1-1of the first print medium P1, since a detection signal in an on state is input from the first sensor561, the controller500may not distinguishably detect the first print medium P1and the second print medium P2based on the detection signal of the first sensor561.

In the present example, a second sensor562is additionally used. The second sensor562is located to detect the print medium P in a region S2between a second end portion P2R-2of the second print medium P2(i.e., the second print medium P2R ofFIG.4) that is side-aligned with the first end portion P1-1of the first print medium P1that is center-aligned and the second end portion P2C-2of the second print medium P2(i.e., the second print medium P2C ofFIG.4) that is center-aligned. For example, the actuator551of the second sensor562may be located in the region S2. Since the second sensor562is located to detect the print medium P in the region S2, a plurality of sensors that detect the print medium P in an image forming process may perform their own functions and may be each used as the second sensor562.

The controller500may distinguishably detect the first print medium P1and the second print medium P2both when the first print medium P1and the second print medium P2are loaded on the feeder100in a normal feeding state in a center alignment method and when the second print medium P2is wrongly loaded in a side alignment method by combining detection signals of the first sensor561and the second sensor562. The controller500may control the image former200by applying one mode selected from among the first mode and the second mode according to a detection result of a width of the print medium P. The controller500may stop printing and may output a print error signal according to a detection result of a feeding state of the print medium P. Table 1 shows a type of the print medium P, a combination of detection signals of the first sensor561and the second sensor562, and a print mode.

When detection signals in on states are input from both the first sensor561and the second sensor562, the controller500may control the image former200to perform printing in the first mode. When a detection signal in an off signal is input from the first sensor561(in other words, when a detection signal in an on state is not input), the controller500may control the image former200to perform printing in the second mode. When a detection signal in an on state is input from the first sensor561and a detection signal in an off state is input from the second sensor562(in other words, when a detection signal in an on state is not input from the second sensor562), the controller500may recognize a feeding error state and may output a print error signal. Accordingly, a user may be guided to check a load state of the print medium P and a feeding state of the print medium P, and unnecessary printing and overheating of the fusing unit240may be prevented.

FIG.5is a block diagram of the controller500according to an example. Referring toFIG.5, the controller500may include a central processing unit (CPU)501and a memory502. First and second control factors respectively corresponding to the first mode and the second mode may be stored in the memory502. The controller500may select one mode from among the first and second modes by combining detection signals of the first and second sensors561and562, and may control the image former200by reading a corresponding control factor from among the first and second control factors from the memory502. For example, when a processor speed is controlled according to a print mode, the control factor may be a driving speed of a driving motor201that drives rotating members of the image former200. For example, when an interval between printing operations is controlled according to a print mode, the control factor may be, for example, an operation interval of a clutch202that controls driving of the pickup roller11.

The image forming apparatus may include a plurality of sensors that detect the print medium P conveyed along the print path400. In the present example, an additional sensor for detecting a width of the print medium P is not used. The controller500detects a width of the print medium P by combining detection signals of two sensors from among the plurality of sensors, and controls the image former200to perform printing in one mode selected from among the first mode and the second mode whose print speed is less than that of the first mode according to the detected width of the print medium P. Also, the controller500may detect a feeding state of the print medium P by combining detection signals of two sensors from among the plurality of sensors, and may stop printing and may output a print error signal according to the detected feeding state of the print medium P. In this configuration, since an additional sensor for detecting a width and a feeding state of the print medium P and an electrical wiring for transmitting a signal of the addition sensor to the controller500may be omitted, component costs may be reduced. Also, the image forming apparatus may be made compact.

For example, the plurality of sensors may include a load detection sensor (e.g., a paper empty sensor)510configured to detect whether the print medium P is loaded on the feeder100, an alignment sensor (e.g., a registration sensor)520configured to provide a reference position of the print medium P supplied to the image former200, a paper jam sensor530located at an outlet of the fusing unit240and configured to detect a jam on the fusing unit240, and an overload detection sensor540provided on the discharger300and configured to detect an overload of the discharger300.

Each of the load detection sensor510, the alignment sensor520, paper jam sensor530, and the overload detection sensor540may have, for example, a structure as shown inFIG.3. The load detection sensor510is located at a position indicated by a solid line ofFIG.3when the print medium P is not loaded on the feeder10, and a detection signal is maintained in an off state. The alignment sensor520may be located at an inlet of the conveying roller13. When the print medium P is detected by the alignment sensor520, the controller500recognizes that a front end of the print medium P passes through the alignment sensor520. Accordingly, a reference position of the print medium P may be provided. The controller500may control an exposure start time of the exposure unit220so that a front end of a toner image formed on the photosensitive drum21reaches a transfer nip at a time when the front end of the print medium P reaches the transfer nip where the photosensitive drum21and the transfer roller230face each other. The paper jam sensor530is turned on as indicated by a dashed line ofFIG.3when the print medium P passes. If the paper jam sensor530is not turned off even after a predetermined period of time elapses after the paper jam sensor530is turned on, the controller500may recognize that a jam occurs on the fusing unit240. The overload detection sensor540is turned on as indicated by a dashed line ofFIG.3by the print medium P discharged to the discharger300, and then is turned off as indicated by a solid line ofFIG.3after discharging is completed. When the overload detection sensor540is not turned off and is maintained in an on state, the controller500may recognize that the amount of the print medium P loaded on the discharger300exceeds a load capacity.

The first sensor561may be the overload detection sensor540. The overload detection sensor540is located to detect the print medium P discharged in the region S1ofFIG.4in a width direction.

The second sensor562may be selected from among sensors that are provided in the feeder100and in the print path400between the feeder100and the discharger300and detect the print medium P. Although the load detection sensor510, the alignment sensor520, and the paper jam sensor530are illustrated inFIG.1, an additional sensor may be further located between the pickup roller11and the conveying roller13. In the present example, any one of the load detection sensor510, the alignment sensor520, and the paper jam sensor530is used as the second sensor562. Any one of the load detection sensor510, the alignment sensor520, and the paper jam sensor530is located to detect the print medium P in the region S2ofFIG.4in the width direction. Since the second sensor562is located to detect the print medium P in the region S2, the plurality of sensors, for example, the load detection sensor510, the alignment sensor520, and the paper jam sensor530, may be used as the second sensor562. Since the load detection sensor510, the alignment sensor520, and the paper jam sensor530are located in the region S2, the sensors may perform their own functions and may also perform a function of the second sensor562that detects a width and a feeding state of the print medium P.

The controller500may control the image former200to perform printing in one mode from among the first mode and the second mode by combining detection signals of any one of the load detection sensor510, the alignment sensor520, and the paper jam sensor530functioning as the second sensor562and the overload detection sensor540functioning as the first sensor561as shown in Table 1. Also, the controller500may stop the printing and may output a print error signal according to a combination result of the detection signals. Accordingly, without employing an additional sensor that detects a width of the print medium P, the controller500may distinguishably recognize the first print medium P1and the second print medium P2(e.g., the second print medium P2C, P2L, or P2R ofFIG.4), and may control the image former200to print an image in the first mode for the first print medium P1and in the second mode for the second print medium P2. Also, when the second print medium P2is fed as the second print medium P2R, a print error signal may be output.

Actually, an image is successfully printed on the first print medium P1and the second print medium P2loaded as the second print medium P2C, and an image is not successfully printed on the second print medium P2loaded as the second print medium P2L or the second print medium P2R. That is, only a part of an image to be printed is printed on the second print medium P2loaded as the second print medium P2L or the second print medium P2R. When a distance between a user and the image forming apparatus is large, for example, when the image forming apparatus is a network printer, the user may not know a load state of the print medium P on the feeder100. However, since the second mode may be applied to the second print medium P2L or the second print medium P2R that is inappropriately loaded on the feeder100as well as the second print medium P2that is appropriately loaded on the feeder100as the second print medium P2C, in particular, overheating of the fusing unit240may be effectively prevented when a plurality of pieces are continuously printed as the second print medium P2. Also, since a print error signal is output when the second print medium P2is fed as the second print medium P2R, unnecessary printing and overheating of the fusing unit240may be prevented.

When a state of a detection signal of the load detection sensor510is an off state in an image forming process, it means that the print medium P is not loaded on the feeder100, the print medium P loaded on the feeder100has been completely used, or the second print medium P2is loaded as the second print medium P2R. Since normal printing may not be performed in any of the above cases, the controller500may stop printing and may output a print error signal. Accordingly, the user may be guided to check a load state of the print medium P. Also, since an image is not appropriately printed on the second print medium P2loaded as the second print medium P2R, unnecessary printing may be prevented. A print error signal may be output through an output device503(seeFIG.5). The output device503may be, for example, a buzzer, a display, a lamp, or the user's host device.

When a detection signal of the alignment sensor520is not changed from an off state to an on state in an image forming process, it means that conveyance failure occurs in the print path400from the feeder100to the alignment sensor520or the second print medium P2is loaded as the second print medium P2R. Assuming that the alignment sensor520is used as the second sensor562, when a detection signal of the alignment sensor520is not changed from an off state to an on state, the controller500may drive the image forming apparatus for a time long enough for the print medium P to reach the discharger300and may check whether a detection signal in an on state is input from the overload detection sensor540during the driving time. When a detection signal in an on state is input from the overload detection sensor540, it means that the second print medium P2is loaded on the feeder100as the second print medium P2R. Since an image is not appropriately printed on the second print medium P2loaded as the second print medium P2R, the controller500may stop printing and may output a print error signal. When a detection signal in an on state is not input from the overload detection sensor540, it means that conveyance failure occurs. Accordingly, the controller500may stop printing and may output a print error signal. The print error signal may be output through the output device503(seeFIG.5). The output device503may be, for example, a buzzer, a display, a lamp, or the user's host device.

When a detection signal of the paper jam sensor530is not changed from an off state to an on state in an image forming process, it means that conveyance failure occurs in the print path400from the feeder100to the fusing unit240, or the second print medium P2is loaded as the second print medium P2R. Assuming that the paper jam sensor530is used as the second sensor562, when a detection signal of the paper jam sensor530is not changed from an off state to an on state, the controller500may drive the image forming apparatus for a time long enough for the print medium P to reach the discharger300, and may check whether a detection signal in an on state is input from the overload detection sensor540during the driving time. When a detection signal in an on state is input from the overload detection sensor540, it means that the second print medium P2is loaded as the second print medium P2R. Since an image is not appropriately printed on the second print medium P2loaded as the second print medium P2R, the controller500may stop printing and may output a print error signal. When a detection signal in an on state is not input from the overload detection sensor540, it means that conveyance failure occurs. Accordingly, the controller500may stop printing and may output a print error signal. The print error signal may be output through the output device503(seeFIG.5). The output device503may be, for example, a buzzer, a display, a lamp, or the user's host device.