JP2006145961A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve productivity by carrying out image forming actions according to a size of a recording medium on the basis of fixing unit temperature detected by a plurality of temperature sensors while adjusting the temperature of the fixing unit. <P>SOLUTION: The image forming apparatus is provided with: the fixing unit 65 having a plurality of exothermic bodies built in, a plurality of temperature sensors detecting the heating temperature by the fixing unit; a control part 80 selecting the size of the fixing unit in the width direction according to the detected heating temperature while adjusting the temperature of the fixing unit; and a paper supply part 70 having a plurality of paper supply trays 71, 72 and 73 storing the recording medium and extracting the recording medium and transporting it. The control part 80 makes the recording medium extracted from the paper supply tray standby at a specified position 74 when the size of the recording medium extracted from the paper supply tray is greater in the width direction than the selected size in the width direction according to the heating temperature. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, and in particular, includes a fixing device including a plurality of heating elements, and the plurality of heat generation depending on the size of a recording medium on which an image is formed. The present invention relates to an image forming apparatus capable of controlling power supply to a body. ○

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a recording medium onto which a toner image has been transferred is sandwiched between a pair of rolls composed of a heating roll and a pressure roll, and the toner image on the recording medium is held. A method of fixing a toner image on a recording medium by heating and pressurizing is widely used.

  However, since the heating roll has a large heat capacity, it takes a long time to warm up to a predetermined fixing temperature. For this reason, using a thermal head with a low heat capacity that raises the temperature instantaneously and a thin film to shorten the warm-up time, heat is not removed from the heating element during fixing in non-sheet passing areas. There is a problem that the temperature rises with respect to the area.

  Therefore, there is a heating element that can freely generate heat for each predetermined area in the longitudinal direction of the fixing unit pressure contact portion, and each heating area is detected by a separate temperature detection element, and the heating element is controlled independently for each heating area. Yes (Patent Document 1).

  However, a fixing device using a thermal head raises the temperature instantaneously, but has a small heat capacity, and is not suitable for forming an image on a large amount of recording media at a time.

  In addition, in a fixing device having a heater film that is independent in the circumferential direction in order to shorten the warm-up time and make it unnecessary to maintain the temperature during standby, a sliding electrode that applies a voltage to the heater electrode serving as a heater film feeding portion is provided. Since there is an unevenness, there is a configuration in which the power supply state becomes unstable due to contact and separation on the power supply unit so that power can be supplied smoothly by a plurality of contact members that are shifted from each other (Patent Document 2).

However, even if this technology is used, the heat capacity is as small as a fixing device using a thermal head, so the heating roll has a low heat storage effect, and in order to maintain the fixing temperature, it is necessary to rely on the power of the heater itself. Therefore, there is a limit to the number of sheets that can be printed at once.
Japanese Patent Laid-Open No. 06-274068 (paragraph numbers 0019 to 0027, FIGS. 3 to 6) Japanese Unexamined Patent Publication No. 09-34295 (paragraph numbers 0006 to 0020, FIGS. 1 to 9)

  In view of the above circumstances, the present invention shortens the warm-up time by using a thin heating roll, while adjusting the heat generation amount of each of the plurality of heating elements built in the fixing device, and to the plurality of heating elements. While controlling the power supply to adjust the temperature of the fixing device, the image forming operation according to the size of the recording medium is performed based on the fixing device temperature detected by a plurality of temperature sensors, thereby improving the productivity. An object is to provide an apparatus.

An image forming apparatus of the present invention that achieves the above object forms a toner image, and transfers and fixes the formed toner image on a recording medium, thereby forming a fixed toner image on the recording medium. In
A fixing device including a plurality of heating elements, and fixing the toner image on the recording medium by heating and pressurizing the toner image transferred to the recording medium;
A plurality of temperature sensors arranged to correspond to the plurality of heating elements and detecting a heating temperature by the fixing device;
The temperature of the fixing device is adjusted by supplying power to each of the plurality of heating elements, and the recording medium fixed by the fixing device according to the heating temperature detected by each of the plurality of temperature sensors, A control unit for selecting the size in the width direction intersecting the process direction of the fixing device;
A plurality of paper feed trays for storing the recording medium, and a paper feeding unit that pulls out and transports the recording medium from any one of the plurality of paper feed trays,
When the size in the width direction of the recording medium pulled out from the paper feed tray is larger than the size in the width direction selected according to the heating temperature, the control unit pulls out the paper from the paper feed tray. The recording medium is waited at a predetermined position.

  As described above, the controller includes a plurality of temperature sensors, and the control unit selects a fixable size according to the heating temperature at each position of the fixing device detected by each temperature sensor. In the case of the recording medium, an image can be fixed at a predetermined position until the fixing temperature is reached. Speed up and improve productivity.

  According to the image forming apparatus of the present invention, the temperature of the fixing device is adjusted by controlling the power supply to the heating element of the fixing device, while the size of the recording medium is determined based on the fixing device temperatures detected by the plurality of temperature sensors. The image forming operation can be performed according to the above, and the productivity of image formation can be improved.

  Hereinafter, embodiments of the image forming apparatus of the present invention will be described.

  FIG. 1 is a schematic configuration diagram of a copying machine showing an embodiment of an image forming apparatus of the present invention.

  The copying machine shown in FIG. 1 represents a document by automatically feeding a document to a predetermined position and automatically irradiating the document with light, reading the reflected light with a CCD image sensor and converting it into an electrical signal. A document reading unit 40 that obtains an image signal, an image processing unit 50 that digitally converts the image signal read by the document reading unit 40 and performs color separation, γ conversion, and the like, and image data processed by the image processing unit 50 A toner image forming unit 60 for forming a toner image based on the paper feed trays 71, 72, and 73 for storing recording media of various sizes, and forming a toner image by pulling out a recording medium of a predetermined size from the paper feed tray A sheet feeding unit 70 that conveys the sheet to the printing unit and a control unit 80 are provided.

  The toner image forming unit 60 performs pulse modulation on the photosensitive drum 61 on which the toner image is formed and the image data on which image processing has been performed by the image processing unit 50, and laser light based on the pulse width modulated image data An exposure unit 62 that irradiates the charged photosensitive drum 61 to form an electrostatic latent image, a developing unit 63 that forms a toner image by applying toner to the electrostatic latent image, and a toner on the recording medium at a predetermined timing. A transfer unit 64 that transfers the image, a fixing device 65 that heats and pressurizes the toner image transferred onto the recording medium by the transfer unit 64 and fixes the toner image on the recording medium, and a recording medium on which the toner image is fixed And a discharge tray 66 for discharging the water.

  The paper feed unit 70 includes paper feed trays 71, 72, and 73 that store recording media of various sizes, a registration roll 74 that waits for a recording medium drawn from the paper feed trays 71, 72, and 73, and a paper feed tray 71. , 72, 73, a storage tray 75 that transports and temporarily stores the recording medium drawn out from the recording medium, and a paper sensor 76 that detects the recording medium stored in the storage tray 75.

  When making a copy of an original with this copier, the original is automatically sent to the original reading section 40 when the original is placed on the automatic original feeder 30 and a start key on an operation panel (not shown) is pressed. An image signal representing the document is obtained by reading the image recorded on the document. The image signal is sent to the image processing unit 50, subjected to predetermined image processing and converted into image data, and then converted into image data in the exposure unit 62 to become laser light pulse-modulated with the image data. The laser beam is applied to the charged photosensitive drum 61 to form an electrostatic latent image, and toner is applied to the electrostatic latent image from the developing device 63 to form a toner image on the photosensitive drum 61. Is done.

  On the other hand, the recording medium is pulled out from the paper feed trays 71, 72, 73 and conveyed to the transfer unit 64 via the registration roll 74. Then, after the toner image is transferred to the recording medium by the transfer unit 64 and the toner image is fixed by the fixing device 65, the recording medium on which the fixed toner image is formed is discharged to the discharge tray 66.

  On the other hand, when copying is performed immediately after the power of the copying machine of the present embodiment is turned on or in a standby state, when the temperature of the center portion in the width direction of the fixing device 65 reaches the fixing possible temperature, recording is performed. The medium is sent to the resist roll 74. At this time, when the original is placed in the A4 size vertically and the recording medium is conveyed in the A4 size vertically, the recording medium is immediately sent to the transfer unit 64. However, when the recording medium is transported horizontally in the A4 plate, or when the original is placed horizontally in the A4 plate (or A3 plate vertically) and the recording medium is transported in the A4 plate horizontally (or A3 plate vertically). The recording medium stands by on the registration roll 74 and power is supplied to the heaters at both ends of the fixing device 65. When the temperature at both ends of the fixing device 65 reaches the fixing possible temperature, the waiting recording medium is sent from the registration roll 74 to the transfer unit 64, and the toner image is transferred to the recording medium. However, when the standby time exceeds a predetermined time, the standby recording medium is once sent to the storage tray 75.

  Here, if the standby recording medium is once sent to the storage tray 75 and then a copy request is made while the temperature at both ends of the fixing device 65 does not reach the fixable temperature, the recording conveyed in the A4 plate longitudinal direction. An image can be formed by a medium.

  Further, when a recording medium is stored in the storage tray 75 at the time of the next copy, the stored recording medium is preferentially supplied before being fed from the paper feed trays 71, 72, 73. Paper is fed.

  As described above, when the temperature of the central portion in the width direction of the fixing device 65 reaches the fixable temperature, the recording medium is sent to the registration roll 74, so that the size of the recording medium is large and is waiting on the registration roll 74. If the temperature of the fixing device 65 rises, the toner image is transferred as it is, and at least the time from when the recording medium is pulled out to the registration roll 74 is shortened. On the other hand, when the standby time becomes long, the recording medium is once sent to the storage tray 75 and image formation is possible with the recording medium conveyed in the A4 size longitudinal direction, so at least the time until image formation is shortened. The

  Here, the image forming apparatus according to the present embodiment has been described based on a direct transfer type copying machine. However, the copying machine is not limited to the direct transfer type. Even if it is a tandem type having Further, the image forming apparatus need not be limited to a copying machine, and may be a printer or a facsimile.

  FIG. 2 is a diagram illustrating temperature control of the fixing device by the control unit of the present embodiment.

  The heating roll 1 of the fixing device shown in FIG. 2 has a first heater 3 that heats the central portion in the width direction intersecting the process direction of the fixing device and a width direction intersecting the process direction of the fixing device. Two second heaters 4 that heat both ends and have a relatively small calorific value are incorporated. The heating roll surface 2 is provided with a first thermistor 6 that detects the surface temperature of the central portion and a second thermistor 5 that detects the surface temperature of the end portion. One terminal 21 of each of the first heater 3 and the second heater 4 in which the two are connected in series is connected to one end 20a of the AC power supply 20 via a contact 7a of the relay (RA1). The other terminal 22 of the first heater 3 is connected to a triac 12 having a switching function for connecting and disconnecting a circuit when a pulse signal is input to the gate, and is connected to the other end 20b of the AC power source via the triac 12. Yes. Further, the other terminal 22 of the second heater 4 connected in series with each other is connected to the triac 10, and is connected to the other end 20 b of the AC power source via the triac 10.

  The control unit includes a CPU 8, and the first thermistor 6 and the second thermistor 5 are connected to the CPU 8, and the temperature can be detected from the respective resistance characteristics. The CPU 8 is connected to the gate of the triac 10 through the diode 9 and is connected to the gate of the triac 12 through the diode 11. Further, the base of an emitter grounded transistor 15 is connected to the CPU 8 via a diode 14, and a relay (RA 1) 7 is connected to the collector of the transistor 15.

  When the power is turned on, the CPU 8 sends a pulse signal to the grounded emitter transistor 15, operates the relay (RA1) 7, and turns on the AC power supply 20 to the heater of the heating roll via the contact 7a of the relay (RA1) 7. . At the same time, a pulse signal is sent to the respective gates of the triac 10 and the triac 12 to make the triac 10 and the triac 12 “contact”, thereby supplying electric power to the first heater 3 and the second heater 4 respectively. .

  When the temperature of the central portion of the fixing device detected by the first thermistor 6 reaches the upper limit temperature at which copying can be performed, a pulse signal is sent to the gate of the triac 12 to turn off the first heater 3 and When the temperature at the center reaches the lower limit temperature at which copying is possible, a pulse signal is sent to the gate of the triac 12 to make the first heater 3 “contact”. Thereafter, the connection and disconnection of the first heater 3 are repeated in the same manner.

  When the temperature at the end of the fixing device detected by the second thermistor 5 reaches the upper limit temperature at which copying can be performed, a pulse signal is sent to the gate of the triac 10 to turn off the second heater 4 and fix. When the temperature at the end of the vessel reaches the lower limit temperature at which copying is possible, a pulse signal is sent to the gate of the triac 10 to turn the second heater 4 “contact”. Thereafter, the connection and disconnection of the second heater 4 are repeated in the same manner.

  Since the CPU controls the temperature of the central portion and the end portion of the fixing device independently in this way, for example, when transporting A4 size paper in the vertical direction, it is predetermined by repeatedly connecting and disconnecting the first heater 3. Enables the fixing operation. On the other hand, for example, when transporting A4 size paper in the horizontal direction, a predetermined fixing operation is enabled by repeatedly connecting and disconnecting the first heater 3 and the second heater 4.

  The CPU 8 of this embodiment is connected to a switch 24 for detecting the opening / closing of the main body cover of the copying machine. When it is detected that the main body cover is opened, the CPU 8 cancels the operation of the relay 7. Since the relay contact 7a is opened, all the heaters of the heating roll 1 are configured to be extinguished.

  3 to 5 are flowcharts illustrating the recording medium selection operation by the control unit.

  As shown in FIG. 3, the control unit monitors the temperature of the central portion of the heating roll using the first thermistor. It is determined whether or not the temperature detected by the first thermistor has reached the fixable temperature (S-1), and when the central portion of the heating roll reaches the fixable temperature, for example, the A4 plate is conveyed in the vertical direction. Therefore, it is determined that the fixing operation to the recording medium to be performed is possible, and a size of A4 size or less is selected (S-2). And control which connects / disconnects a 1st heater is performed so that the temperature of the center part of a heating roll may be settled in the range of upper limit temperature and lower limit temperature (S-3).

  On the other hand, when the central portion of the heating roll has not reached the fixing possible temperature, electric power is supplied to the first heater (S-4). Then, it is determined that any recording medium cannot perform the fixing operation, and neither the size smaller than the A4 size vertical width nor the size larger than the A4 size vertical width is selected (S-5, S-6).

  As shown in FIG. 4, the control unit monitors the temperature of the end portion of the heating roll using the second thermistor. It is determined whether or not the temperature detected by the second thermistor has reached the fixable temperature (S-11). When the end of the heating roll reaches the fixable temperature, for example, the A4 plate is conveyed in the horizontal direction. It is determined that the fixing operation to the recording medium to be performed is possible, and a size larger than the A4 size vertical width is selected (S-12). And control which connects / disconnects a 1st heater and a 2nd heater is performed so that the temperature of the center part and end part of a heating roll may be settled in the range of upper limit temperature and lower limit temperature (S-13).

  On the other hand, when the end portion of the heating roll has not reached the fixable temperature, power is supplied to the second heater (S-14). Then, it is determined that at least the fixing operation for the recording medium transported in the horizontal direction of the A4 size is impossible, and the size exceeding the vertical width of the A4 size is not selected (S-15).

  As shown in FIG. 5, the control unit determines whether or not at least a size equal to or smaller than the A4 size vertical width has been selected by the selection in FIGS. 3 and 4 (S-21), and the size equal to or smaller than the A4 size vertical width. Is selected, for example, the start key lamp of the copying machine is turned on to enable the copying operation (S-22). When the size of the A4 size or less is not selected, the copying machine, for example, the start key lamp is kept off to disable the copying operation (S-23).

  FIG. 6 is a flowchart showing the entire copy operation by the copying machine of this embodiment.

  As shown in FIG. 6, when the start key is pressed to start the copying operation in the copying machine, the selection state of the recording medium size by the control unit is determined (S-31), and the copying operation is impossible. Disables the operation of the start key.

  On the other hand, when the copy operation is possible, the width of the recording medium is checked (S-32), and when the width is not more than the A4 size vertical width, the recording medium is stored in the storage tray by the paper sensor. (S-33), and when it is determined that the recording medium is stored, the recording medium is fed from the storage tray (S-34) and sent to the transfer unit to transfer the toner image. Then, the toner image is fixed by the fixing device, and a fixed toner image is formed on the recording medium (S-36). On the other hand, when the recording medium is not stored in the storage tray, paper is fed from the paper feed tray (S-35), and a fixed toner image is formed on the recording medium in the same manner (S-36).

  If it is determined by the check of the width of the recording medium (S-32) that the width exceeds the A4 size, the size exceeding the A4 size is selected by the control unit. (S-37), and when a size exceeding the A4 plate length is selected, it is determined by the paper sensor whether the recording medium is stored in the storage tray (S-33). The following steps (S-34) to (S-36) are executed.

  On the other hand, when the size exceeding the A4 size vertical width is not selected in the selection of the control unit, the recording medium conveyed from the paper feed tray to the registration roll is made to wait and the waiting time is counted (S-38).

  Then, during standby, it is determined whether or not a size exceeding the A4 plate length is selected in the selection of the control unit (S-39). The recording medium that has been transported to the standby state is released from the standby state, sent to the transfer unit, and a toner image is transferred and fixed to form a fixed toner image on the recording medium (S-40). ).

  On the other hand, when a size exceeding the A4 size vertical width is not selected, it is determined whether or not a predetermined time has elapsed in the standby time count (S-41). The recording medium being moved is temporarily transferred to a storage tray, and a paper feed tray storing a recording medium having a size equal to or smaller than the A4 size vertical width is searched (S-42). If there is no paper feed tray in which a recording medium of A4 size or less is stored, the process ends (S-43), and even if there is a paper feeding tray, no recording medium is stored in the paper feeding tray. When the recording medium is accommodated, a fixed toner image is formed on the recording medium by feeding from the paper feed tray (S-45).

  As described above, the fixing device of the present embodiment is configured such that the central portion reaches the fixing possible temperature quickly. Accordingly, when the temperature sensor detects that the temperature in the central portion has reached the fixable temperature, the control unit enables the copy operation, and the A4 size portrait copy immediately performs the copy operation, while the A4 size landscape Copying of the size (horizontal placement of A4 plate, vertical placement of A3 plate) waits until the temperature at the end of the fixing device reaches the fixable temperature. However, if the standby time becomes longer, the recording medium is temporarily copied to the storage tray and changed to the A4 size vertical copy to perform the copy, so at least the time until the copy is made is shortened.

1 is a schematic configuration diagram of a copying machine showing an embodiment of an image forming apparatus of the present invention. It is a figure which shows temperature control of the fixing device by the control part of this embodiment. It is a flowchart which shows the selection operation | movement of the recording medium by a control part. It is a flowchart which shows the selection operation | movement of the recording medium by a control part. It is a flowchart which shows the selection operation | movement of the recording medium by a control part. 3 is a flowchart showing an entire copy operation by the copying machine of the present embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating roll 2 Heating roll surface 3 1st heater 4 2nd heater 5 2nd thermistor 6 1st thermistor 7 Relay 7a Relay contact 8 CPU
9, 11, 14 Diode 10, 12 Triac 20 AC power supply 20a One end 20b Other end 21 One terminal 22, 23 The other terminal 30 Automatic document feeder 40 Original reading unit 50 Image processing unit 60 Toner image forming unit 61 Photosensitive drum 62 Exposure unit 63 Developing device 64 Transfer unit 65 Fixing device 66 Discharge tray 70 Paper feed unit 71, 72, 73 Paper feed tray 74 Registration roll 75 Storage tray 75 Paper sensor 80 Control unit

Claims (7)

In an image forming apparatus that forms a toner image and forms a fixed toner image on the recording medium by transferring and fixing the formed toner image on the recording medium.
A fixing device including a plurality of heating elements, and fixing the toner image on the recording medium by heating and pressurizing the toner image transferred to the recording medium;
A plurality of temperature sensors arranged to correspond to the plurality of heating elements and detecting a heating temperature by the fixing device;
The temperature of the fixing device is adjusted by supplying electric power to each of the plurality of heating elements, and the recording medium fixed by the fixing device according to the heating temperature detected by each of the plurality of temperature sensors, A control unit for selecting the size in the width direction intersecting the process direction of the fixing device;
A plurality of paper feed trays for storing the recording medium, and a paper feeding unit that pulls out and transports the recording medium from any one of the plurality of paper feed trays,
When the size in the width direction of the recording medium pulled out from the paper feed tray is larger than the size in the width direction selected according to the heating temperature, the control unit pulls out the paper from the paper feed tray. An image forming apparatus, wherein the recording medium is placed on standby at a predetermined position. 2. The heating element disposed at a central portion in the width direction that intersects the process direction of the fixing device among the plurality of heating elements has a larger amount of heat generation than any of the other heating elements. Image forming apparatus. The control unit releases the standby of the recording medium when selecting the size in the width direction larger than the size in the width direction of the recording medium that has been waiting at a predetermined position in the previous period. The image forming apparatus according to 1. When the size in the width direction of the recording medium pulled out from the paper feed tray is larger than the size in the width direction selected according to the heating temperature, the control unit is pulled out from the paper feed unit. 2. An image forming apparatus according to claim 1, wherein electric power is supplied to a predetermined heating element for fixing the recording medium. The paper supply unit includes a storage tray that temporarily stores the recording medium drawn from the paper supply tray,
2. The storage unit according to claim 1, wherein when the standby time of the recording medium waiting at the predetermined position exceeds a predetermined time, the paper supply unit temporarily stores the standby recording medium in the storage tray. Image forming apparatus. A paper sensor for detecting the recording medium stored in the storage tray;
When the recording medium is detected by the sheet sensor, the sheet feeding unit pulls out and conveys the recording medium stored in the storage tray before pulling out the recording medium from the sheet feeding tray. The image forming apparatus according to claim 5. A first temperature sensor of the plurality of temperature sensors is disposed at a center of the fixing device in the width direction, and a second temperature sensor is disposed at an end of the width direction,
When the heating temperature detected by the first temperature sensor exceeds a predetermined temperature, the control unit sorts the A4 plate vertical size, and the heating temperature detected by the second temperature sensor. 2. The image forming apparatus according to claim 1, wherein when the temperature exceeds a predetermined temperature, the A4 size is selected.

Images