JP2009080362A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent excessive heating and to rapidly warm a photoreceptor drum in an image forming apparatus, by providing heating elements of a plurality of systems that have different output in the photoreceptor drum and controlling energizing of the respective heating elements. <P>SOLUTION: The image forming apparatus includes the photoreceptor drum 61, a drum heater 9 provided in the photoreceptor drum 61 and is constituted of a plurality of heating elements H that are energized to generate heat and having different output from each other; a temperature sensor 92 for detecting temperature of the photoreceptor drum 61; and an energizing control part for controlling the energization of the plurality of heating elements H. The energizing control part energizes all of the heating elements H or the plurality of heating elements H in warming-up operation, and reduces the number of the energized heating elements H with temperature rise of an image carrier, and then maintains the predetermined temperature, by controlling energizing of the heating element H having the smallest output after reaching the predetermined temperature. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a multifunction machine, a printer, and a facsimile machine having a heating element for heating an image carrier such as a photosensitive drum.

  An image forming apparatus that forms an image using toner generally includes a photosensitive drum as an image carrier, generates an electrostatic latent image after charging the image carrier with a charging device based on image data, The electrostatic latent image is developed with toner to obtain a toner image. Then, the toner image is transferred to a sheet such as paper, and heated and pressurized by the fixing unit to fix the toner image, and a series of image forming operations is completed.

  In an image forming apparatus provided with such an image carrier (photosensitive drum), a heater is usually provided on the photosensitive drum in order to warm the photosensitive drum and prevent moisture from adhering to the circumferential surface of the photosensitive drum. If moisture adheres to the photosensitive drum, it may hinder the formation of an electrostatic latent image and appropriate development, or cause a so-called image flow, and may cause a deterioration in image formation quality (further, In some cases, the photosensitive drum is oxidized by ozone generated from the charging device and easily absorbs moisture). In short, a heater is provided on the photosensitive drum in order to prevent image quality deterioration.

  Here, a temperature sensor is generally provided, and ON / OFF of the heater is controlled based on detection of the temperature sensor. In other words, when the temperature of the photosensitive drum rises excessively, an image formed due to a change in sensitivity or the like is affected, and problems such as toner becoming easily fused to the photosensitive drum may occur. Therefore, the photosensitive drum is controlled so as to maintain a constant temperature.

  However, when the temperature sensor detects that the temperature has reached a certain temperature, even if the heater of the photosensitive drum is turned off, the photosensitive drum is further warmed by the heat of the heater at that time, resulting in overshoot. May occur, and the photosensitive drum may be heated above a certain temperature. If it does so, the above-mentioned malfunction may occur. In particular, when there is a difference between the temperature detected by the temperature sensor and the actual temperature of the photosensitive drum (for example, a non-contact sensor), this is likely to be a problem.

In order to prevent overshoot in the heating of the photosensitive drum, the invention described in Patent Document 1 has been proposed. Patent Document 1 discloses an image carrier, a heating unit for heating the image carrier, an energizing unit for energizing the heating unit, a temperature detecting unit for detecting the temperature of the image carrier, and energizing the heating unit. There is disclosed an image forming apparatus characterized in that the power supply control means has a mode in which power supply to the heating means is periodically stopped. (See Patent Document 1: Claim 1, FIG. 3, etc.).
JP 2005-99332 A

  According to the invention described in Patent Document 1, it seems to be easy to prevent overshooting of the photosensitive drum temperature. However, since the heater of the photosensitive drum is repeatedly turned ON / OFF, the photosensitive drum reaches a certain temperature. It takes time. That is, there is a problem that the time required for warming up to enable image formation becomes long when the power is turned on or when returning from the sleep mode. Therefore, there is a problem that the waiting time of the user increases.

  The present invention has been made in view of the above-described problems of the prior art. In order to warm the photosensitive drum, a plurality of systems of heating elements having different outputs are provided, and energization to the heating element is controlled to control the photosensitive body. It is an object of the present invention to provide an image forming apparatus capable of preventing excessive heating of a drum and warming a photosensitive drum quickly.

  According to a first aspect of the present invention, an image carrier having a photosensitive layer provided on the peripheral surface, and an image carrier that is provided in the image carrier to warm the image carrier to a predetermined temperature. A heating unit composed of a plurality of heating elements, a temperature detection body for detecting the temperature of the image carrier, and an energization control unit for controlling energization to the plurality of heating elements. In the warm-up operation, the controller first energizes all of the heating elements or a plurality of the heating elements, reduces the heating elements energized as the temperature of the image carrier increases, and after reaching a predetermined temperature The energization of one heating element is turned on / off to maintain a predetermined temperature.

  According to this configuration, at the start of warming-up, all or a plurality of heating elements are energized to warm the image carrier, and heat is applied as it approaches a predetermined temperature, which is the ideal temperature of the image carrier. Therefore, the photosensitive drum can be rapidly warmed to a predetermined temperature, the time required for warming up can be reduced, and excessive heating of the image carrier due to overshoot can be prevented. Further, after reaching the predetermined temperature, only one heating element is energized, so that the temperature can be maintained without overheating the image carrier.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, when the energization control unit reduces the heating element to be energized, the energization is turned off from the heating element having a large output, and a predetermined temperature is set. After reaching, the energization of the heating element with the smallest output is controlled to maintain a predetermined temperature.

  According to this configuration, since the image carrier is gently warmed by the heat generating element having a small output among the plurality of heat generating elements near the predetermined temperature, even if overshoot occurs, the amount can be reduced and the image to be formed can be reduced. There are no problems such as adverse effects on image quality. In addition, after reaching the predetermined temperature, only the heating element with the minimum output is energized, so that the predetermined temperature can be maintained substantially.

  According to a third aspect of the present invention, in the image forming apparatus, an image carrier having a photosensitive layer provided on a peripheral surface thereof, and the image carrier in order to warm the image carrier to a predetermined temperature. A heating unit composed of a plurality of heating elements that generate heat and have different outputs; a temperature detection body for detecting the temperature of the image carrier; and an energization control unit that controls energization of the plurality of heating elements. In the warming-up operation, the energization control unit first energizes all of the heating elements or a plurality of the heating elements and reaches an energization cutoff temperature set at a temperature lower than a predetermined temperature. In addition, the power supply to all the heating elements is cut off and the temperature of the image carrier reaches a predetermined temperature due to residual heat. After reaching the predetermined temperature, the current supply to one heating element is turned ON / OFF. Maintaining a predetermined temperature and It was.

  According to this configuration, since the energization of all the heating elements is turned off at the energization cut-off temperature and the temperature of the image carrier reaches the predetermined temperature due to the residual heat, it is possible to prevent the image carrier from being excessively warmed. In addition, since the heating is performed by a plurality of heating elements up to the energization cutoff temperature, the photosensitive drum can be quickly warmed.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the energization control unit determines a combination of the heating elements to be energized based on a detection result of the temperature detection body in a warm-up operation. It was decided.

  According to this configuration, since the heating element to be energized during warm-up is performed based on the detected temperature, it is not always energized to all the heating elements, but only to the heating element necessary for warming the image carrier. Energization can be performed and power saving can be achieved.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, a plurality of the image carriers are provided, and the heating unit and the temperature detector are respectively provided on the image carrier. The energization control unit controls the energization to the heat generating body so as to reach a predetermined temperature for each image carrier.

  According to this configuration, for example, when installed in the vicinity of a fixing device that generates a large amount of heat, or installed in the vicinity of a vent for introducing or exhausting outside air, Even if there is a difference in temperature rise depending on the installation position of the image carrier, it is possible to quickly warm each image carrier to a predetermined temperature and maintain the predetermined temperature while accommodating the difference.

  As described above, according to the present invention, the photosensitive drum can be quickly warmed up, and the user does not have to wait for a long time until the image forming apparatus can be used. A forming apparatus can be provided. In addition, since there is no excessive overshoot, it is possible to provide an image forming apparatus that maintains the quality of the formed image in a high state.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. However, each element such as configuration and arrangement described in each embodiment does not limit the scope of the invention and is merely an illustrative example.

  First, an outline of the copying machine 1 (corresponding to an image forming apparatus) according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic front sectional view of a copying machine 1 according to an embodiment of the present invention. FIG. 2 is a partially enlarged schematic cross-sectional view of the image forming unit 60 of the copying machine 1 according to the first embodiment of the present invention.

  The copying machine 1 in the present embodiment forms an image on a sheet based on image data obtained by reading a document or image data transmitted from a computer (not shown). As shown in FIG. 1, the copying machine 1 is provided with an automatic document feeder 2 at the top, and a copying machine 1 at the bottom of the copying machine 1 includes a document reading unit 3, a sheet supply unit 4, a sheet conveyance path. 5, an image forming unit 6, an intermediate transfer unit 7, a fixing unit 8 and the like. The image forming unit 6 will be described separately with reference to FIG.

  The original reading unit 3 reads an original and forms image data of the read original. An exposure lamp, a reflector, a mirror, a lens, a CCD sensor, etc. (all not shown) are provided in the document reading unit 3 to optically scan the document and generate image data. Further, a contact glass 31 is provided on the upper surface of the document reading unit 3, and is conveyed so as to be in contact with the feed reading contact glass 31 b by a document placed on the placement reading contact glass 31 a or the automatic document feeder 2. The document is scanned and read to generate image data.

  The automatic document feeder 2 automatically and continuously conveys the document placed on the document tray 21 so as to come into contact with the feed reading contact glass 31b. The automatic document feeder 2 includes a document tray 21, a plurality of document conveyance roller pairs 22, a document conveyance path 23, and a document discharge tray 24. The documents on the document tray 21 are sent out one by one to the document transport path 23. Further, the automatic document feeder 2 can be lifted upward by a fulcrum provided on the back side of the paper surface. For example, a document such as a book can be placed on the placement reading contact glass 31a.

  The sheet supply unit 4 supplies a sheet toward the intermediate transfer unit 7. The sheet supply unit 4 includes a cassette 41 that stores sheets such as sheets of various sizes, a pickup roller 42 that feeds the sheets from the cassette 41 one by one to the sheet conveyance path 5, and the like. For example, when an input for image formation is made to the copying machine 1, the pickup roller 42 is rotationally driven, and the sheets are supplied to the sheet conveyance path 5 one by one.

  The sheet conveyance path 5 conveys the sheet supplied from the sheet supply unit 4 toward the intermediate transfer unit 7 and the fixing unit 8, and discharges the fixed sheet to the discharge tray 52. For this reason, the sheet conveyance path 5 is provided with a plurality of conveyance roller pairs 51, a guide plate for guiding the sheet conveyance direction, and the like.

  The intermediate transfer unit 7 is provided below the image forming unit 6 and receives a primary transfer of a toner image from the photosensitive drum 61 and performs a secondary transfer onto a sheet. The intermediate transfer belt 71 is stretched between a driving roller 72, a driven roller 73, and four primary transfer rollers 74 so that the upper outer peripheral surface of the intermediate transfer belt 71 and each photosensitive drum 61 are in contact with each other. The Here, driving means (not shown) including a motor, a gear, and the like is connected to the driving roller 72, and the intermediate transfer belt 71 rotates in the clockwise direction (arrow direction) in FIG. 1 by driving the driving roller 72.

  Further, the primary transfer roller 74 is rotatably arranged one by one at a position where it comes into contact with each photosensitive drum 61 via the intermediate transfer belt 71. By applying a voltage having a polarity opposite to the charging polarity of the toner to the primary transfer roller 74 with a predetermined magnitude in synchronization with each other, each color toner image is superimposed on the intermediate transfer belt 71 from the photosensitive drum 61. Primary transfer is performed, and a full-color toner image is formed on the intermediate transfer belt 71.

  The toner image transferred to the intermediate transfer belt 71 contacts the driving roller 72 via the intermediate transfer belt 71 and is secondarily transferred to the sheet by a secondary transfer roller 75 that is rotatably supported. Specifically, the secondary transfer roller 75 is applied with a predetermined voltage when the sheet and the toner image enter the secondary transfer portion (nip between the secondary transfer roller 75 and the intermediate transfer belt 71). The belt cleaning device 76 removes residual toner or the like that has not been transferred to the sheet from the intermediate transfer belt 71.

  The fixing unit 8 fixes the toner image transferred to the sheet. The fixing unit 8 in this embodiment is mainly composed of a heating roller 81 and a pressure roller 82 in pressure contact with the heating roller 81. The heating roller 81 includes a fixing heat source 83. When the toner image passes through the nip between the heating roller 81 and the pressure roller 82, the toner is melted and heated, and the toner image is fixed on the sheet.

  Next, the image forming unit 6 will be described with reference to FIG.

  The image forming unit 6 forms a toner image based on image data of an image to be formed. The image forming unit 6 includes four image forming units 60K (black), 60Y (yellow), 60C (cyan), and 60M (magenta) according to the color of the toner image to be formed. Accordingly, the copying machine 1 of the present embodiment can perform full-color image formation. Although each image forming unit 60 uses different toner, the basic configuration is the same, and therefore the symbols K, Y, C, and M are omitted in the following description unless otherwise specified (FIG. 2). The same).

  As shown in FIG. 2, each image forming unit 60 is disposed around a photosensitive drum 61 (corresponding to an image carrier) that is rotatably supported in the direction of the arrow shown in FIG. A charging device 62, an exposure device 63, a developing device 64, and a cleaning unit 65.

  The photosensitive drum 61 is rotationally driven in a predetermined direction. The charging device 62 is provided below the photosensitive drum 61 and uniformly charges the surface of the photosensitive drum 61 to a predetermined potential. The exposure device 63 is provided below the charging device 62 and emits light to each photosensitive drum 61 based on image data formed by the document reading unit 3 or image data transmitted from an external computer (not shown). Output and scan / exposure to form an electrostatic latent image. The developing device 64 is provided on the right side of the photosensitive drum 61 and supplies toner to the electrostatic latent image for development (visualization). The developed toner image is primarily transferred to the intermediate transfer belt 71, and the cleaning unit 65 cleans the surface of the photosensitive drum 61 after the primary transfer.

  Next, the drum heater 9 provided in each photosensitive drum 61 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 3A is an enlarged sectional view of each photosensitive drum 61 according to the first embodiment of the present invention, and FIG. 3B shows an example of the drum heater 9 according to the first embodiment of the present invention. FIG.

  Next, as shown in FIG. 3A, each of the photosensitive drums 61 is provided with a photosensitive layer (not shown) such as amorphous silicon on the surface of the drum main body made of a metal such as aluminum. . Each of the photosensitive drums 61 is heated to a predetermined temperature to prevent condensation and the like, and to prevent moisture from adhering to the photosensitive layer, heat is generated by energization, and a plurality of heating elements H having different outputs from each other. A drum heater 9 (corresponding to a heating unit) is provided. As shown in FIG. 3B, the drum heater 9 is formed in a sheet shape, for example, and is provided along the inner peripheral surface of the photosensitive drum 61.

  The drum heater 9 formed in a sheet shape has elasticity, and when the drum heater 9 is provided in each photosensitive drum 61, the drum heater 9 is rolled into a cylindrical shape and is placed inside each photosensitive drum 61. When the drum heater 9 is released after being inserted, the drum heater 9 is fixed and installed. In other words, the drum heater 9 sticks to the inner peripheral surface of each photosensitive drum 61 by the force of the drum heater 9 itself to spread. Note that the length of each side of the drum heater 9 is aligned so as to cover the inner peripheral surface of each photosensitive drum 61 without overlapping when it spreads inside the photosensitive drum 61.

  In the present embodiment, the drum heater 9 has three types of outputs, such as 25 W (first heating element H 1), 12 W (second heating element H 2), and 5 W (third heating element H 3). Different heating elements H are combined (mixed), and the total output of the drum heater 9 per photosensitive drum 61 is about 40 W. Accordingly, since the copying machine 1 of the present embodiment includes four photosensitive drums 61, the output of the drum heater 9 is about 160 to 170 W in total in the entire copying machine 1.

  More specifically, as shown in FIG. 3B, each heating element H is composed of different heating wires such as nichrome wires. Also, the heating wire EL1 (= first heating element H1, shown by a broken line) that outputs 25 W, the heating wire EL2 that outputs 12 W (= the second heating element H2, shown by a solid line), and the electricity that outputs 5 W. A heat ray EL3 (= third heating element H3, illustrated by a two-dot chain line) is arranged in parallel and meandering. As a result, the photosensitive drum 61 can be easily warmed evenly. Note that the wiring shown in FIG. 3B is merely an example, and the intervals between the heating wires may be made closer, different wirings may be used, and the photosensitive drum 61 may be warmed. .

  And the electricity supply control part 91 (refer FIG. 4) mentioned later controls the electric power supply with respect to each heat generating body H (1st heat generating body H1, 2nd heat generating body H2, 3rd heat generating body H3). In other words, depending on the situation, the energization control unit 91 energizes only one heating element H or energizes two or more heating elements H to generate the first heating element H1 and the second heating element H2. The power supply to the third heating element H3 can be controlled to change the output of the drum heater 9 stepwise.

  The output of each heating element H is not limited to three types of heating element H, but may be two types or four or more types. The power consumption can be set as appropriate while taking into consideration the power consumption of the fixing unit 8 and other power consumption.

  Further, as a configuration for detecting the temperature of each photoconductor drum 61, one temperature sensor 92 (corresponding to a temperature detector) is provided in each photoconductor drum 61. The installation position of the temperature sensor 92 may be outside the photosensitive drum 61. The temperature sensor 92 may employ a thermistor, for example, but is not limited to this, as long as the temperature can be detected.

  Next, control in the copying machine 1 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 4 is a block diagram for explaining the control of the copying machine 1 according to the first embodiment of the present invention.

  As shown in FIG. 4, the copying machine 1 according to the present embodiment includes a control unit 10 provided on a control board appropriately disposed in the copying machine 1. The control unit 10 controls the operation of the entire copying machine 1 and includes, for example, a CPU 11 and a storage unit 12.

  The CPU 11 is a central processing unit, and controls and performs each part of the copier 1 based on a control program stored in a ROM or HDD of the storage unit 12 and expanded in the RAM. The storage unit 12 stores control programs and various data, and includes a storage device such as a ROM, a RAM, and an HDD. The ROM stores a control program and control data for the copying machine 1, and is used when the CPU 11 reads the control program. The RAM is used for temporarily expanding a control program or the like, or for temporarily storing image data. The HDD is a large-capacity storage device, and is used for storing control programs, control data, image data scanned by the document reading unit 3, and setting information of the copier 1 by the user. The

  The control unit 10 is connected to the image forming unit 6, the energization control unit 91, and the like constituting the copying machine 1, and controls each unit so that image formation is appropriately performed based on a control program and data developed in the storage unit 12. To control the operation.

  In addition, as shown in FIG. 4, an energization control unit 91 is provided inside the apparatus as a configuration for controlling each heating element H (the CPU 11 does not energize the heating element H without providing the energization control unit 91). You may control.) The energization control unit 91 energizes the three types of heating elements H (first heating element H1, second heating element H2, and third heating element H3) constituting the drum heater 9 in each photosensitive drum 61. For example, it can be configured by a switchable element such as various LSIs, FETs, and digital ICs. Further, the installation position of the energization control unit 91 may be provided inside the photosensitive drum 61, in the vicinity of the outside of the photosensitive drum 61, or may be provided on the same substrate as the control unit 10.

  Specifically, the output of the temperature sensor 92 provided in each photosensitive drum 61 (in this embodiment, four temperature sensors 92 are provided, but only one is shown in FIG. Alternatively, the energization control unit 91 controls the energization of each heating element H based on the output of the temperature sensor 92 input to the control unit 10.

  In this embodiment, since the four photosensitive drums 61 are provided, each of the photosensitive drums 61 is provided with one drum heater 9 and one temperature sensor 92, and the energization control unit 91 has a total of twelve heating elements. The energization to H may be controlled. As a result, when the photosensitive drum 61 is close to the ventilation opening of the copying machine 1 or easily heated by the heat from the fixing unit 8, the situation depends on the situation for each installation position of the photosensitive drum 61 in the copying machine 1. Therefore, the temperature of the photosensitive drum 61 can be kept constant. In the present embodiment, a plurality of drum heaters 9 and the like are provided, but are simplified in FIG. Further, the energization control unit 91 may be provided in each photosensitive drum 61 (four in total), and energization control may be performed for each photosensitive drum 61.

  A power supply device 13 is provided inside the copying machine 1. The power supply device 13 is connected to a commercial power supply and serves as a motor for driving circuits and elements such as the CPU 11, energizing the heating element H, and rotating the photosensitive drum 61 and rollers in the copying machine 1. Therefore, AC can be rectified to DC. And the energization control part 91 controls energization to each heat generating body H so that the power consumption which can be supplied from this power supply device 13 is not exceeded.

  Next, a specific example of energization control to each heating element H by the energization control unit 91 during warm-up will be described with reference to FIG. FIG. 5 is a graph showing an example of energization control of the drum heater 9 and an increase in temperature according to the first embodiment of the present invention.

  First, the energization control of the drum heater 9 according to this embodiment relates to the warming up of the copying machine 1. The warming-up of the present invention refers to a warming-up operation of the copying machine 1 for making an image formable state when the photosensitive drum 61 or the like is cold. In other words, this corresponds to a case where the difference between the target temperature to be warmed and the current temperature of the photosensitive drum 61 is, for example, 10 ° C. or more. For example, when the main power supply of the copier 1 is turned on at the next sunrise company after the power is turned off after the end of work yesterday, or in the sleep mode (drum heater which reduces the power consumption in the copier 1 to save power) For example, a case where the photosensitive drum 61 is cooled after a long time has passed since the energization of the power supply 9 is also OFF) is applicable.

  As described above, when the photosensitive drum 61 is completely cooled, moisture due to condensation or the like may adhere to the surface of the photosensitive drum 61 and high-quality image formation may not be performed. That is, if water adheres to the photosensitive drum 61, the water hinders the formation and development of an electrostatic latent image, and causes image deterioration such as image flow. In short, the drum heater 9 is provided on the photosensitive drum 61 in order to prevent the image quality from being deteriorated.

  Therefore, the energization control to the drum heater 9 at the time of warming up according to the present embodiment will be described with reference to FIG. In the following description of the embodiment, the temperature of the photosensitive drum 61 at the start of warming up when the main power supply of the copying machine 1 is turned on is 20 ° C., and the photosensitive drum 61 is made up of all three heating elements H. The case where it warms to predetermined temperature using is demonstrated.

  Here, the predetermined temperature is a target temperature when the photosensitive drum 61 is warmed, and is an optimum temperature of the photosensitive drum 61 in image formation, and is described as 40 ° C. in the description of the present embodiment. To do. Then, the energization control unit 91 performs energization control to each heating element H so that the photoconductor drum 61 is quickly warmed and the predetermined temperature is maintained by the photoconductor drum 61. The predetermined temperature is appropriately determined depending on the material of the photosensitive drum 61, toner, specifications of the copying machine 1, and the like, and is not limited to 40 ° C.

  First, the control unit 10 and the energization control unit 91 confirm the temperature detected by the temperature sensor 92, and after confirming that the current temperature of the photosensitive drum 61 is 20 ° C., the energization control unit 91 performs the first heating element H1. The second heating element H2 and the third heating element H3 are all energized. As a result, the output of the drum heater 9 is the highest, and the photosensitive drum 61 can be warmed up the fastest. In addition, the period which energizes all the heat generating bodies H is shown in FIG. 5 as t1.

  Here, this description is given for the case where all of the first heating element H1, the second heating element H2, and the third heating element H3 are energized during warm-up, but the temperature of the photosensitive drum 61 is, for example, 30 ° C. or higher. In this case, for example, the first heating element H1 may not be energized (see Table 1 to be described later), and only a part of the heating elements H may be energized. That is, the energization control unit 91 may determine the combination of the heating elements H to be energized based on the detection result of the temperature sensor 92 in the warm-up operation. In other words, it is not always necessary to energize all the heating elements H at the start of warm-up, and the combination of the heating elements H to be energized may be changed depending on the detected temperature.

  Thereafter, for example, when the temperature sensor 92 detects that the temperature of the photosensitive drum 61 has risen to about 35 to 36 ° C., the energization control unit 91 moves to the first heating element H1 having the largest output and the amount of heat generation. Turn off the power. This is to prevent the photosensitive drum 61 from being warmed greatly exceeding 40 ° C. (overshoot). That is, when the temperature sensor 92 detects that the temperature reaches 40 ° C., even if the first heating element H1 is turned off, the first heating element H1 has heat, so the remaining heat ( Since the photosensitive drum 61 continues to be warmed by the residual heat) and overshoot occurs, when the temperature reaches 35 to 36 ° C., the power supply to the first heating element H1 is turned off.

  Next, when the temperature sensor 92 detects that the temperature of the photosensitive drum 61 has risen to about 36 to 38 ° C., the energization control unit 91 has the second output and the second heating element H2 with the heat generation amount. Turn off the power to the. Again, in order to prevent overshoot of the photosensitive drum 61, the energization to the second heating element H2 is turned off before reaching the predetermined temperature. In addition, the time from turning off the energization to the first heating element H1 to turning off the energization to the second heating element H2 is shown as t2 in FIG.

  And until it reaches the predetermined temperature, the energization control unit 91 energizes only the third heating element H3 having the smallest heat generation amount. This time is shown as t3 in FIG. In this way, as the temperature approaches the predetermined temperature, among the plurality of heating elements H, the number of heating elements H to be energized can be reduced, and the amount of overshoot can be extremely reduced.

  After reaching the predetermined temperature, the power supply to the third heating element H3 is turned off at one end. Since only the third heating element H3 is energized when the predetermined temperature is reached, as a result, as shown in FIG. 5, the temperature of the photosensitive drum 61 reaches the predetermined temperature without causing a large overshoot. Become. If the energization of all the heating elements H is turned off, the temperature of the photosensitive drum 61 decreases. Therefore, the energization control unit 91 refers to the temperature detected by the temperature sensor 92 and falls below 40 ° C. At this stage, energization to any one of the first heating element H1, the second heating element H2, and the third heating element H3 is resumed.

  Thereafter, the energization control unit 91 repeats energization ON / OFF to maintain the temperature of the photosensitive drum 61 at a predetermined temperature (this period is indicated as t4 in FIG. 5). This temperature maintenance of the photoconductive drum 61 is continued while the temperature of the photoconductive drum 61 needs to be maintained, such as when the main power of the copying machine 1 is turned off or the sleep mode is entered. In this temperature maintenance, in order to reduce the fluctuation range (pulsation) of the temperature, in this embodiment, the power supply to the third heating element H3 is controlled to maintain the temperature of the photosensitive drum 61 at a predetermined temperature. Can be.

  In short, in the warm-up operation, the energization control unit 91 first energizes all or a plurality of the heating elements H, and turns off the energization from the heating element H having a large output as the temperature of the photosensitive drum 61 rises. Thus, after the heating element H to be energized is decreased and reaches a predetermined temperature, the energization of the heating element H having the smallest output is controlled to maintain the predetermined temperature.

  Here, the rate of temperature rise in each section of the graph shown in FIG. 5, that is, the slope of the graph in each section, becomes gentle as t1 → t2 → t3 and the heating element H is turned off. This inclination is not determined only by the output of each heating element H. In other words, even if the first heat generating element H1 and the second heat generating element H2 are turned off before reaching the predetermined temperature, the photosensitive drum 61 continues to be warmed by the remaining heat, so that the temperature rise of the photosensitive drum 61 becomes extremely slow. Do not mean. That is, even if the output of the third heating element H3 is 5W (period t3) and the output becomes 1/8 with respect to the output 40W (period t1) of all the heating elements H, the inclination does not become 1/8. The warm-up time of the photosensitive drum 61 is quickly warmed to a predetermined temperature within a sufficiently practical time.

Based on Table 1, energization control in the case where the warm-up is once completed and the photosensitive drum 61 has not been cooled will be described. For example, when the main power supply is turned off once for inspection of the copying machine 1 or error elimination such that the temperature difference between the predetermined temperature and the current photosensitive drum 61 is less than 10 ° C., or to some extent for power saving. Corresponds to the return from the standby state in which the photosensitive drum 61 and the fixing unit 8 are warmed.

As shown in Table 1, the explanation will be divided into cases.
(1) When the temperature detected by the temperature sensor 92 is 35 ° C. or higher In this case, the difference from the predetermined temperature (40 ° C.) is not so large. Until the photosensitive drum 61 is warmed. Thereby, the power consumption more than necessary can be suppressed.
(2) For example, when the temperature detected by the temperature sensor 92 is not less than 30 ° C. and less than 35 ° C. In this case, for example, the photosensitive drum 61 starts to be warmed by the second heating element H2 and the third heating element H3.
(3) When the temperature detected by the temperature sensor 92 is less than 30 ° C. In this case, since the difference from the predetermined temperature (40 ° C.) is large, for example, all the heating elements H reach the predetermined temperature. Start warming drum 61.

  In the case of (2) and (3), the heating element H to be energized may be reduced as the temperature of the photosensitive drum 61 rises, as described above. Further, this Table 1 is only an example. For example, when the temperature detected by the temperature sensor 92 is 35 to 36 ° C., the second heating element H2 and the third heating element H3 are set to 38 ° C. as in the control described above. In the above, energization may be performed only on the third heating element H3, and the temperature and the heating element H to be used can be appropriately set.

  Thus, according to the configuration of the present embodiment, at the start of warm-up, all or a plurality of heating elements H are energized to warm the image carrier (photosensitive drum 61), and the image carrier Since the heating element H to be energized is reduced as the temperature approaches the ideal temperature, which is an ideal temperature, the photosensitive drum 61 can be rapidly warmed to the predetermined temperature, and the time required for warming up can be reduced. It is possible to prevent the image carrier from being excessively warmed. In addition, since only one heating element H is energized after reaching the predetermined temperature, the temperature can be maintained without overheating the image carrier.

  Also, in the vicinity of a predetermined temperature, the image carrier is gently warmed by the heat generating element H having a small output among the plurality of heat generating elements H. Therefore, even if an overshoot occurs, the amount thereof can be reduced and the image quality of the image to be formed is reduced. There will be no inconveniences such as negative effects. In addition, after reaching the predetermined temperature, only the heating element H with the minimum output is energized, so that the predetermined temperature can be maintained substantially. Further, since the heating element H that is energized during warm-up can be performed based on the detected temperature, it is not always necessary to energize all the heating elements H, but is necessary to warm the image carrier. Only the heating element H can be energized, and power saving can be achieved.

  Further, since the energization control unit 91 controls the energization of the drum heater 9 for each photosensitive drum 61, for example, when the energization control unit 91 is installed in the vicinity of a fixing device that generates a large amount of heat, or for introducing or exhausting outside air. Even when there is a difference in temperature rise depending on the installation position of each image carrier in the image forming apparatus, such as when installed near the ventilation opening, each image carrier is brought to a predetermined temperature while accommodating the difference. While warming up quickly, a predetermined temperature can be maintained.

  Next, energization control of the drum heater 9 according to the second embodiment of the present invention will be described based on FIG. FIG. 6 is a graph showing an example of energization control of the drum heater 9 and an increase in temperature according to the second embodiment of the present invention.

  Here, in the present embodiment, there is a difference in energization control to each heating element H when the photosensitive drum 61 is warmed to a predetermined temperature during warm-up. In addition, since the big difference of 1st Embodiment and 2nd Embodiment is the point of this electricity supply control, below, only a different part from 1st Embodiment is demonstrated and it is the same about the part which overlaps. The description is omitted because it is applicable.

  Specifically, in the first embodiment, the number of heating elements H to be energized is reduced as the temperature approaches a predetermined temperature. However, in the second embodiment, all heat generation is performed at a certain temperature below the predetermined temperature. The difference is that the energization of the body H is turned off, and the temperature of the photosensitive drum 61 reaches a predetermined temperature by the heat remaining in each heating element H.

  Assuming that the predetermined temperature is 40 ° C., in this embodiment, the energization control unit 91 sets a certain temperature lower than the predetermined temperature (for example, 38 to 39 ° C. All the heating elements H are energized until the temperature is called “temperature” (this period is shown as t5 in FIG. 6). When this energization cut-off temperature is reached, energization of all the heating elements H is turned off.

  In other words, when the temperature sensor 92 detects that the energization cutoff temperature has been reached, the energization of all the heating elements H is turned off, and the photosensitive drum 61 is warmed to a predetermined temperature by the residual heat of the heating elements H (see FIG. 6 shows this period as t6). If such energization control is performed, although the overshoot is slightly higher than the predetermined temperature, the photoconductor drum 61 is not excessively warmed, and the photoconductor drum 61 can be quickly warmed. The amount of chute can be kept small.

  Here, the conduction cutoff temperature in the present embodiment is set lower than the predetermined temperature due to its property, but if set too low, it does not reach the predetermined temperature due to residual heat. Accordingly, although there is a balance with the output of the drum heater 9, the energization cutoff temperature can be set lower than the predetermined temperature within a range of the predetermined temperature, for example, within 3 ° C, more preferably within 2 ° C. Then, after reaching the predetermined temperature, energizing only one system (only one of the heating elements H) while monitoring the temperature detected by the temperature sensor 92 among each heating element H, the temperature is adjusted. What is necessary is just to maintain (it shows this period as t7 in FIG. 6).

  In short, the energization control unit 91 first energizes all of the heating elements H or a plurality of heating elements H in the warm-up operation, and when all the energization cut-off temperatures set at a temperature lower than the predetermined temperature are reached, After the energization of the heating element H is interrupted and the temperature of the photosensitive drum 61 reaches a predetermined temperature, and the predetermined temperature is reached, for example, the energization of the heating element H having the smallest output is controlled to maintain the predetermined temperature. To do.

  In this way, according to the configuration of the present embodiment, all the heating elements H are turned off at the energization cut-off temperature, and the temperature of the image carrier reaches a predetermined temperature due to residual heat. It can eliminate being warmed. Therefore, even with this configuration, the photosensitive drum 61 can be rapidly warmed to a predetermined temperature to reduce the time required for warming up, and the image carrier can be prevented from being excessively warmed due to overshoot. .

  Hereinafter, other embodiments will be described. In the above embodiment, the tandem type copying machine 1 having four photosensitive drums 61 has been described, but the present invention is also applicable to a monochrome image forming apparatus or a rotary type image forming apparatus having only one photosensitive drum 61. be able to. In this case, the output of the heating element H in the drum heater 9 may be the same as that in the above embodiment, for example, about four times the output (the first heating element H1 is 100 W, the second heating element H2 is 50 W, the third heating element) If H3 is 20 W), the total output is equivalent and the power consumption of the drum heater 9 does not increase. That is, the output of the drum heater 9 may be appropriately determined in consideration of the size and number of the photosensitive drums 61, power consumption, and the like.

  Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention.

  The present invention is applicable to an image forming apparatus having a heater for heating an image carrier such as a photosensitive drum.

1 is a schematic front sectional view of a copying machine according to a first embodiment. 1 is an enlarged schematic cross-sectional view of an image forming unit of a copying machine according to a first embodiment. (A) is an expanded sectional view of the photoconductive drum which concerns on 1st Embodiment of this invention, (b) is a figure which shows an example of a drum heater. 1 is a block diagram illustrating an example of a configuration of a copier according to a first embodiment. The graph which shows an example of electricity supply control of the drum heater which concerns on 1st Embodiment, and a temperature rise It is a graph which shows an example of energization control of the drum heater which concerns on 2nd Embodiment, and a temperature rise.

Explanation of symbols

1 Copying machine (image forming device)
61 Photosensitive drum (image carrier)
9 Drum heater (heating unit)
91 Energization control unit 92 Temperature sensor (temperature detector)
H1 First heating element (part of heating section)
H2 Second heating element (part of heating section)
H3 3rd heating element (part of heating section)

Claims (5)

An image carrier having a photosensitive layer on the peripheral surface;
A heating unit that is provided in the image carrier to warm the image carrier to a predetermined temperature, and that includes a plurality of heat generators that generate heat when energized and have different outputs;
A temperature detector for detecting the temperature of the image carrier;
An energization control unit for controlling energization to the plurality of heating elements,
In the warm-up operation, the energization control unit first energizes all or a plurality of the heating elements, decreases the heating elements energized with the temperature rise of the image carrier, and reaches a predetermined temperature. Thereafter, the image forming apparatus is characterized in that energization of one heating element is turned on / off to maintain a predetermined temperature.   The energization control unit turns off the energization of the heating element having a large output when the heating element to be energized is reduced, and after reaching a predetermined temperature, controls the energization of the heating element having the smallest output to The image forming apparatus according to claim 1, wherein the temperature is maintained. An image carrier having a photosensitive layer on the peripheral surface;
A heating unit that is provided in the image carrier to warm the image carrier to a predetermined temperature, and that includes a plurality of heat generators that generate heat when energized and have different outputs;
A temperature detector for detecting the temperature of the image carrier;
An energization control unit for controlling energization to the plurality of heating elements,
In the warming-up operation, the energization control unit first energizes all of the heating elements or a plurality of the heating elements, and when the energization cutoff temperature set at a temperature lower than a predetermined temperature is reached, After the energization of the heating element is interrupted and the temperature of the image carrier reaches a predetermined temperature due to residual heat, and after reaching the predetermined temperature, the energization of one heating element is turned on / off to maintain the predetermined temperature. An image forming apparatus.   4. The image forming apparatus according to claim 1, wherein the energization control unit determines a combination of the heating elements to be energized based on a detection result of the temperature detection body in a warm-up operation. 5. . A plurality of the image carriers are provided,
The heating unit and the temperature detector are provided on the image carrier, respectively.
5. The image forming apparatus according to claim 1, wherein the energization control unit controls energization to the heat generating body so that a predetermined temperature is reached for each of the image carriers.

Images