JP6035856B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus.

  In a fixing device that fixes a toner image on a sheet, temperature control of a heating member that heats the toner image is performed.

  Patent Document 1 discloses that the temperature is set to a high temperature increase target temperature when the temperature at the time of temperature rise of the heating member is low.

JP-A-7-114281

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device and an image forming apparatus that realize both shortening of the time until start of the first operation after startup and power saving.

Claim 1
A heating member having a heat source and heated by the heat source;
A pressure member for fixing the toner image on the paper in cooperation with the heating member by pressing the paper conveyed while holding the toner image between the surface of the heating member;
A temperature measuring device for measuring the temperature of the surface of the heating member;
A control circuit for controlling the heat source based on the temperature measured by the temperature measuring device,
The control circuit increases the temperature of the heating member surface from a first state that satisfies a predetermined determination condition for determining whether or not the temperature distribution on the heating member surface is in a relatively flat state. a first temperature rise target temperature is a temperature rise target temperature of the heating member surface in mode, the temperature of the heating member surface in a second mode to raise the temperature of the heating member surface from the second state which does not satisfy the determination condition it is set to increase the second temperature rise target temperature lower target temperature than a target temperature, a fixing device, characterized in that controls the heat source to raise the temperature of the heating member surface.

According to a second aspect of the present invention, in the fixing device according to the first aspect, the control circuit controls the heat source in the first mode to heat the surface of the heating member to the first temperature increase target temperature in the first mode. Then, after a predetermined first time has passed without performing the fixing operation, the surface of the heating member is further heated toward the second temperature increase target temperature in the second mode. It is characterized by being.
According to a third aspect of the present invention, in the fixing device according to the second aspect, the control circuit is predetermined without performing the fixing operation after heating the surface of the heating member to the second temperature increase target temperature in the second mode. The heating control is stopped after the given second time has elapsed.
According to a fourth aspect of the present invention, in the fixing device according to the third aspect, the control circuit controls the heat source in the first mode to heat the surface of the heating member to the first temperature increase target temperature in the first mode. Then, when a print signal is received before the first time elapses, the fixing operation is performed after further heating to the first fixing temperature that is higher than the first temperature increase target temperature. When the print signal is received before the second time has elapsed after the heating member surface is heated to the second temperature increase target temperature in the second mode, the second temperature increase target A fixing operation is performed after further heating to a second fixing temperature that is higher than the temperature.

According to a fifth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects, the temperature measuring device measures a temperature at each of a plurality of positions in the width direction intersecting the paper conveyance direction on the surface of the heating member. And the control circuit determines whether to perform the control in the first mode or the control in the second mode based on the temperatures measured by the plurality of temperature sensors. It is characterized by.

According to a sixth aspect of the present invention, the conveyance unit that conveys the paper, the image forming unit that forms a toner image and transfers the toner image onto the conveyed paper, and the downstream of the image forming unit in the paper conveyance direction. A fixing unit that fixes the toner image on the paper by heating and pressurizing the paper further conveyed after receiving the transfer of the toner image,
A heating member having a heat source and heated by the heat source;
A pressure member for fixing the toner image to the paper in cooperation with the heating member by pressing the paper conveyed while holding the toner image between the surface of the heating member; and
A temperature measuring device for measuring the temperature of the surface of the heating member;
A control circuit for controlling the heat source based on the temperature measured by the temperature measuring device,
The control circuit increases the temperature of the heating member surface from a first state that satisfies a predetermined determination condition for determining whether or not the temperature distribution on the heating member surface is in a relatively flat state. a first temperature rise target temperature is a temperature rise target temperature of the heating member surface in mode, the temperature of the heating member surface in a second mode to raise the temperature of the heating member surface from the second state which does not satisfy the determination condition is set to lower than the second temperature rise target temperature is raised the target temperature the target temperature, an image forming apparatus, characterized in that for controlling the heat source to raise the temperature of the heating member surface.

According to the fixing device of the first aspect and the image forming apparatus of the sixth aspect , compared with the case where the first temperature increase target temperature and the second temperature increase target temperature are the same, the time until the start of operation and power saving are reduced. Both will be realized.

  According to the fixing device of the second aspect, a reliable fixing operation is performed even if the time until the operation starts is prolonged.

According to the fixing device of the fifth aspect , erroneous determination of the mode can be prevented.

1 is a schematic configuration diagram of an image forming apparatus as an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a fixing device and a discharge device in the image forming apparatus shown in FIG. 1. FIG. 3 is a temperature control system diagram of a heating roll constituting a fixing device in the image forming apparatus shown in FIGS. 1 and 2. It is a temperature control conceptual diagram as a comparative example. It is temperature control principle explanatory drawing in this embodiment. It is the figure which showed the flowchart showing the temperature control algorithm of the heating roll in this embodiment.

  Embodiments of the present invention will be described below.

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

  The image forming apparatus shown in FIG. 1 incorporates a sheet conveying apparatus as an embodiment of the present invention.

  A print signal is input to the image forming apparatus 20 from an external apparatus such as a personal computer (not shown) that is an image information source. The print signal includes an image signal that is a basis of an image formed on a sheet, a setting signal that represents various setting contents for forming an image based on the image signal, a start signal that instructs image formation, and the like. include.

  The image forming apparatus 20 forms an image based on the input print signal as follows.

  The image forming apparatus 20 includes a control unit 21 that controls the movement of each component in the image forming apparatus 20. A print signal including a setting signal and an image signal input from an external device (not shown) is input to the control unit 21 of the image forming apparatus 20. The image forming apparatus 20 forms an image based on the input print signal under the control of the control unit 21.

  Two sheet trays 31 are accommodated in the lower part of the image forming apparatus 20. In these sheet trays 31, sheets P having different dimensions are stored in a stacked state for each sheet tray 31. Each paper tray 31 is configured to be freely drawn out for replenishing paper P.

  Of these two paper trays 31, for example, the paper P is picked up by the pickup roll 32 from the paper tray in which the paper P having a size suitable for the size of the document or a size set in the setting signal is stored. Sent out. The fed paper P is separated one by one by the separating roll 33, the separated single paper P is conveyed upward, and the leading edge of the paper P reaches the standby roll 34. The standby roll 34 plays a role of adjusting the subsequent transport timing and sending out the paper P. The standby roll 34 adjusts the subsequent transport timing of the paper P that has reached the standby roll 34. And further conveyed.

  The image forming apparatus 20 includes a photoreceptor 22 that rotates in the direction indicated by the arrow A above the standby roll 34. Around the photosensitive member 22, a charger 23, an exposure unit 24, a developing unit 25, a transfer unit 26, and a cleaner 27 are provided.

  The photosensitive member 22 has a cylindrical shape, holds charges by charging, and discharges the charges by exposure to form an electrostatic latent image on the surface.

  The charger 23 charges the surface of the photoreceptor 22 to a certain charging potential.

  In addition, the image signal in the print signal input from the external device is input from the control unit 21 to the exposure device 24. The exposure device 24 outputs exposure light modulated in accordance with the image signal. The photoreceptor 22 is exposed to the exposure light, and an electrostatic latent image is formed on the surface of the photoreceptor 22.

  Further, the photosensitive member 22 is exposed to exposure light to form an electrostatic latent image on the surface, and then developed by the developing unit 25. The developing device 25 includes a toner storage portion 25a, a toner supply path 25b, and a developing roll 25c. In the developing unit 25, the toner stored in the toner storage unit 25a is sent to the vicinity of the developing roll 25c through the toner supply path 25b. Then, the development is performed by supplying the toner to the photosensitive member 22 by the developing roller 25 c, and a toner image is formed on the surface of the photosensitive member 22.

  Here, the standby roll 34 sends out the paper P so that the toner image on the photosensitive member 22 reaches the position in accordance with the timing when the toner image reaches the position facing the transfer unit 26. The toner image on the photosensitive member 22 is transferred to the fed paper P under the action of the transfer device 26.

  The toner remaining on the photoconductor 22 after the transfer of the toner image is removed from the photoconductor 22 by the cleaner 27.

  A combination of the photosensitive member 22, the charger 23, the exposure unit 24, the developing unit 25, the transfer unit 26, and the cleaner 27 corresponds to an example of the image forming unit referred to in the present invention.

  The sheet P to which the toner image has been transferred proceeds further in the direction of arrow B, and is heated and pressed by the fixing device 100 to form an image composed of the fixed toner image on the sheet P.

  The sheet P that has passed through the fixing device 100 proceeds in the direction of arrow C toward the discharge device 200, and is further sent in the direction of arrow D by the discharge device 200 to be discharged onto the discharge table 28.

  Here, the image forming apparatus 20 is an apparatus capable of forming images on both sides of the paper P. When images are formed on both sides of the sheet P, the sheet P on which the image is formed only on the first side of the sheet P as described above is discharged by the ejector 200 in the directions of arrows C and D in the rear end of the sheet. Is transported to the reverse position where it enters the ejector 200. Thereafter, the discharger 200 reverses the paper transport direction in the direction of arrow E opposite to the arrow D direction at the reverse position, and the paper P is drawn in the arrow E direction. The drawn paper P now proceeds in the direction of arrow F, and is further transported in the directions of arrows G and H by the transport roll 35 and reaches the standby roll 34 again. When the paper roll P reaches the standby roll 34 again, the paper P is turned upside down. Then, the standby roll 34 sends out the paper P in a posture in which the second surface opposite to the first surface on which the image has already been formed is directed to the photosensitive member 22 side. Thereafter, an image is formed on the second surface in the same manner as the image formation on the first surface. The paper P on which images are formed on both sides in this manner is then discharged onto the paper discharge tray 28.

  Further, the image forming apparatus 20 is configured such that the rear panel 29 covering the fixing device 100 and the discharge device 200 is rotated and opened in the direction of arrow I around the fulcrum 29a. When the paper P is jammed between the fixing device 100 and the discharge device 200, the rear panel 29 is opened by the user. Then, the user opens the rear panel 29, inserts his hand, and removes the jammed paper P.

  FIG. 2 is a cross-sectional view showing a fixing device and a discharge device in the image forming apparatus shown in FIG.

  The fixing device 100 includes a heating roll 101 and a pressure roll 102. The heating roll 101 has a hollow cylindrical shape having a heat source 101 a therein, and the circumferential surface of the cylindrical pressure roll 102 is pressed against the circumferential surface of the heating roll 101. The paper that has advanced in the direction of arrow B and has reached the fixing device 100 is guided by the paper guide 103 to the contact portion between the heating roll 101 and the pressure roll 102. The sheet is sandwiched between the heating roll 101 and the pressure roll 102 at the contact portion.

  The heating roll 101 and the pressure roll 102 rotate in the direction of arrow J while being in contact with each other. For this reason, the paper guided to the contact portion is sandwiched between the heating roll 101 and the pressure roll 102 at the contact portion and proceeds toward the discharger 200. At that time, an image composed of a fixed toner image is formed on the sheet by being heated by the heating roll 101 and pressurized by the pressure roll 102.

  The fixing device 100 further includes a frame 100 a that rotatably supports the heating roll 101 and the pressure roll 102, and a cover 104 that covers a contact portion between the heating roll 101 and the pressure roll 102. The cover 104 is rotatably attached to the frame 100a at a fulcrum 104a. The cover 104 is closed so as to block the upper part of the first transport path 20a in a state where the cover 104 is in contact with the protruding portion 100a_1 protruding above the pressure roll 102 of the frame 100a. The tip is pushed up. Further, the fixing device 100 includes a fixing device side guide rib 100a_2 that guides the sheet to the discharge device 200 on the first transport path 20a. A plurality of the fixing device side guide ribs 100a_2 are arranged in the paper width direction (direction perpendicular to the paper surface of FIG. 2). When the cover 104 is closed, the tip opposite to the fulcrum 104a side enters between the fixing device side guide ribs 100a_2.

  The discharger 200 also includes a lower frame 201 that serves as a lower guide in the second transport path 20b that passes through the discharger 200, an upper frame 202 that serves as an upper guide, and a discharge that feeds paper. And a paper roll 203. Further, the ejector 200 includes a detector 300 that detects that the sheet has been conveyed.

  The detector 300 includes a rotatable shaft 311 extending in a direction perpendicular to the paper surface of FIG. 2 and a detection claw 312 fixed to the shaft 311. When the leading edge of the paper reaches the detector 300, the detection claw 312 rotates together with the shaft 311 in the direction lifted by the leading edge of the paper, and the rotation of the shaft 311 is detected photoelectrically. Thereby, it is detected whether or not the sheet has reached the position of the detector 300.

  The detector 300 plays a role of confirming that the apparatus is operating normally by monitoring the arrival of the sheet at the timing at which the sheet should arrive. The sheet detection result by the detector 300 is notified to the control unit 21 (see FIG. 1). If the paper does not arrive at the timing when the paper should arrive, it means that an abnormal condition such as paper jam has occurred in the middle. Be notified.

  The image forming apparatus 20 has a single-sided printing mode for forming an image only on one side of a sheet and a double-sided printing mode for forming an image on both sides of a sheet. The distinction between the single-sided printing mode and the double-sided printing mode is transmitted from the external device to the control unit 21 (see FIG. 1) as one of setting signals.

  In the double-sided printing mode, the paper discharge roll 203 reverses the rotation direction while conveying the paper on which an image is formed on one side (first side) of the paper in the direction of arrow D, and causes the paper to move to the direction of arrow E. Transport in the direction. The detector 300 also plays a role in determining the rotation inversion timing at this time. That is, the elapsed time after the detector 300 detects the leading edge of the sheet is measured, and the sheet is reversed when the trailing edge of the sheet reaches the branch point 20d and the cover 104 is closed again.

  Further, the discharger 200 includes a presser piece 204 that is pressed from above so that the sheet discharged on the sheet discharge table 28 floats and does not hinder the discharge of the next sheet discharged.

  The presser piece 204 is rotatable about its upper end, and is rotated by the paper ejected by the paper ejection roll 203 to open the paper path, and the rear end of the paper is ejected. When the roll 203 is removed, the posture returns to the illustrated state and the rear end of the sheet is pushed downward. As a result, a discharge path for the next sheet is secured.

  In the following, the description will focus on paper conveyance.

  The sheet that has been fixed on the first surface by the fixing device 100 and has passed through the fixing device 100 pushes the tip of the cover 104 in the direction of the arrow C on the first conveying path 20a and detects it. The claw 302 is pushed up to advance in the direction of arrow D on the second transport path 20b. When the leading edge of the paper is sandwiched between the paper discharge rollers 203, the paper is then further conveyed in the direction of arrow D by the paper discharge rollers 203. In the single-sided printing mode, the paper is discharged as it is onto the paper discharge tray 28.

  In the double-sided printing mode, the paper on which the image is formed only on the first side is conveyed in the direction of arrow D by the paper discharge roll 203 as in the single-sided printing mode, and the trailing edge of the paper is the branch point 20d. , The rotation of the paper discharge roll 203 is reversed, and the paper advances this time in the direction of arrow E. The cover 104 is prevented from entering the first transport path 20a that has passed immediately before, and is guided to the upper surface of the cover 104. And is conveyed in the direction of arrow F on the third conveyance path 20c. The third transport path 20c is a path that reaches the standby roll 34 (see FIG. 1) and joins the first transport path 20a. When the sheet is conveyed along the third conveyance path 20c, the front and back are reversed, and the second surface on which the image is not formed is oriented toward the photosensitive member 22 (see FIG. 1). This sheet is sent out by the standby roll 34 as in the case of image formation on the first surface. Thereafter, an image is formed on the second surface in the same manner as in the case of image formation on the first surface. In this way, the paper on which images are formed on both sides is discharged onto the paper discharge tray 28.

  FIG. 3 is a temperature control system diagram of a heating roll constituting the fixing device in the image forming apparatus shown in FIGS.

  The heating roll 101 has a hollow cylindrical shape, and includes a heat source 101 inside the hollow. The heat source 101 a has a shape extending in the longitudinal direction of the heating roll 101, generates heat with electric power supplied from the heat source power supply 401, and heats the heating roll 101 from the inside of the heating roll 101.

  First and second temperature sensors 402 a and 402 b are disposed outside the heating roll 101 and in the vicinity of the heating roll 101.

  Of these temperature sensors, the first temperature sensor 402 a is a temperature sensor that measures the surface temperature of the center portion in the longitudinal direction of the heating roll 101 in a non-contact manner. The other second temperature sensor 402 b is a contact-type temperature sensor that measures the surface temperature of the end portion in the longitudinal direction of the heating roll 101. In the second temperature sensor 402b, the maximum width sheet within the range that can be used in the image forming apparatus 20 shown in FIGS. 1 and 2 passes through the fixing device 100 (see FIGS. 1 and 2). When the paper is in contact with the heating roll 101, the paper is disposed just outside.

  The temperature control of the heating roll 101 is performed based on the measured value of the first temperature sensor 402a that measures the temperature at the center in the longitudinal direction, which is a representative point of the area where the passing paper contacts. The second temperature sensor 402b placed at the end is used for mode determination described later.

  Here, it has been described that the first temperature sensor 402a is a non-contact type temperature sensor 402a and the second temperature sensor 402b is a contact type temperature sensor 402b. This is for the following reason. That is, since the sheet touches the heating roll 101 at the center of the heating roll 101 where the first temperature sensor 402a is arranged, a non-contact temperature sensor is employed so that image quality defects caused by the temperature sensor do not occur. . On the other hand, the end of the heating roll 101 on which the second temperature sensor 402a is disposed does not contact the paper, and therefore a relatively inexpensive contact type temperature sensor is employed. However, regarding the temperature control of the heating roll 101 described below, it is irrelevant whether the first and second temperature sensors 402a and 402b are non-contact type or contact type.

  Measurement results of the surface temperature of the heating roll 101 by the first and second temperature sensors 402 a and 402 b are input to the control unit 403. The control unit 403 is a control unit that controls the temperature of the heating roll 101 under the command of the control unit 21 that controls the entire image forming apparatus 20 shown in FIG. Or you may be united with the control part 21 which bears the whole control.

  The control unit 403 shown in FIG. 3 determines whether the first mode and the second mode are different from each other based on the temperature measurement results of the first and second temperature sensors 402a and 402b. In accordance with the determined mode, the heat source power supply 401 is controlled to control the temperature of the heating roll 101 based on the subsequent temperature measurement result by the first temperature sensor 402a disposed at the center.

  FIG. 4 is a conceptual diagram of temperature control as a comparative example. Here, a temperature control method as a comparative example will be described with reference to FIG.

  The horizontal axis in FIG. 4 is the elapsed time, and the vertical axis is the surface temperature of the heating roll 101.

  Here, it is assumed that the main power supply of the image forming apparatus 20 is turned on at time t = 0, and the temperature increase of the heating roll 101 is started. It is assumed that the heating roll 101 has cooled to room temperature at the time t = 0.

  Further, in FIG. 4, a curve a represents a temperature measurement result by the first temperature sensor 402a disposed at the center, and a curve b is not divided into modes here, but need not be measured. The temperature measurement result in the 2nd temperature sensor 402b arrange | positioned at the edge | end when it is assumed that it measured temporarily is represented.

When the main power source is turned on at time t = 0, the control unit 403 controls the heat source power source 401 to send electric power to the heat source 101a and heat the heating roll 101 toward the target temperature T. At this time, the surface temperature at the end of the heating roll 101 also increases according to the curve b. Control is performed so that the surface temperature at the center of the heating roll 101 reaches the target temperature T, and thereafter the temperature T is maintained. At this time, the temperature of the end of the heating roll 101 once rises with the center, but heat easily escapes from both ends of the heating roll 101. Therefore, after the center is maintained at the temperature T, it is lowered to some extent and stabilized. The threshold temperature _Tth shown in FIG. 4 represents the minimum temperature at which good fixing is performed. When the sheet comes into contact with the heating roll 101, the surface temperature of the heating roll 101 varies. For this reason, the surface temperature control of the heating roll 101 is performed based on the central temperature, which is a representative point, in order to quickly and accurately recover the temperature fluctuated by contact with the paper. However, it is necessary to sufficiently fix the end portion in the width direction of the sheet, and therefore, the end portion of the heating roll 101, that is, the curve b must be equal to or higher than the threshold temperature _Tth . Therefore, at the center, the threshold temperature _Tth is not set as the target temperature, but a target temperature T higher than that is set.

In the case of the comparative example shown in FIG. 4, the time from when the main power is turned on to when the preparation of the fixing device is completed is t = t ₁ .

  FIG. 5 is an explanatory diagram of the temperature control principle in the present embodiment.

The preconditions are the same as those in the comparative example described with reference to FIG. That is, it is assumed that the main power supply is turned on at time t = 0 and heating of the heating roll 101 that has been at room temperature is started. Temperature _{T th} in the vertical axis are the same as the threshold temperature _{T th} in FIG. 4, temperature _{T 2} is identical to the target temperature T of FIG. Here, another temperature T ₁ is set between these temperatures T _th and T ₂ = T. The temperature of the heating roller 101 increases from the time t = 0, where the first temperature T ₁ is set as the target temperature. The center of the surface temperature of the heating roll 101 is determined that rose to a fixable temperature at time t ₂ has been reached the temperature T _1. This time t ₂ is a time (t ₂ <t ₁ ) shorter than the time t ₁ shown in FIG. 4 when t = 0 is set as the starting point, and can be fixed in a shorter time than the case of FIG. . As described above, first increases with central temperatures for the ends of the heating roller 101, the temperature of the end portion at the time when the center of the temperature reaches temperatures T ₁ even once exceeds the temperature T _th. Thus it is possible to fix in this time t _2. However, 'if maintaining the central temperature, as shown in forever temperature T _1, the temperature of the end, the curve b' curve a as shown in, may be reduced than the temperature _th.

Therefore, while the temperature of the end portion is maintained above the temperature _th, i.e., in FIG. 5 at time t _3, reset the target temperature to the temperature T _2, the temperature of the center of the heating roller 101 is temperature It raises again the temperature to reach T _2. In this way, the time t ₂ later, so that the end portion is also maintained above the temperature temperature _th.

According to the temperature control principle shown in FIG. 5, compared with the comparative example shown in FIG. 4, the time from when the main power is turned on until the fixing operation is enabled is shortened (t ₂ <t ₁ ). Further, according to the temperature control principle shown in FIG. 5, the temperature T ₁ is maintained at a temperature T ₁ lower than the temperature T ₂ = T from the time t ₂ to the time t _3. It has become.

FIG. 5 is an explanatory diagram of the temperature control principle in the present embodiment, and the temperature control in the present embodiment is a little more complicated. Details will be described with reference to FIG. 6, which has a first mode in which the temperature increase target temperature is the temperature T _1, and a second mode in which the temperature increase target temperature is the temperature T ₂ from the beginning, and For each mode, a fixing temperature and a standby temperature lower than the fixing temperature are set, so that power savings can be achieved as much as possible.

  Further, the image forming apparatus 20 according to the present embodiment has a sleep state in which power is saved by leaving the heating roll 101 at a low temperature even when the main power is on. The temperature control algorithm of the roll 101 also considers the sleep state.

  FIG. 6 is a flowchart showing a temperature control algorithm of the heating roll 101 in the present embodiment.

  When the main power supply of the image forming apparatus 20 shown in FIGS. 1 and 2 is turned on (step S01), it is first determined whether or not the image forming apparatus 20 is currently in a sleep state (step S02). If the printer is in the sleep state, the process proceeds to step S03, and a print signal reception waiting state is entered. When the print signal is received, the sleep state is canceled (step S04), and it is determined whether the mode is the first mode or the second mode (step S05).

Here, the following three conditions are adopted as determination conditions.
(1) Center temperature ≤ 40 ° C
(2) Edge temperature ≦ 40 ° C
(3) −10 ° C. ≦ center temperature−end temperature ≦ + 10 ° C.
Here, “center temperature” refers to the temperature measured by the first temperature sensor 402 a that measures the surface temperature of the heating roll 101 shown in FIG. 3, and “end temperature” refers to the end of the heating roll 101. The temperature measured by the second temperature sensor 402b that measures the surface temperature of the part.

  Here, whether or not all three conditions (1) to (3) are satisfied is a determination condition. Here, a case where all of (1) to (3) are satisfied is referred to as a first mode, and a case where any one of the conditions does not satisfy one or more conditions is referred to as a second mode.

  That is, the first mode is determined to be substantially uniform, with both the center and end of the heating roll 101 falling to a temperature of 40 ° C. or less, which is close to normal temperature, and there is almost no temperature difference between the center and the end. Temperature (within ± 10 ° C.). Typically, the heating roll 101 is sufficiently cooled to near normal temperature.

  Here, the case where all the three conditions (1) to (3) are satisfied is the first mode. However, if both the center temperature and the end temperature are lowered, the entire heating roll 101 is used. Therefore, the first mode may be determined by satisfying the above two conditions (1) and (2). Or, as is clear from the description with reference to FIG. 5, whether or not the fixing temperature can be lowered is that the temperature distribution of the heating roll 101 is substantially flat rather than whether or not the heating roll 101 is cooled to near normal temperature. Whether or not there is a necessary condition. Therefore, the above (1) and (2) may be determined as the first mode by satisfying the condition (3) without being included in the determination conditions.

  If it is determined in step S06 in FIG. 6 that the mode is the first mode, the process proceeds to step S06, and the heating roll 101 is set to the standby temperature of the first mode (here, as an example (hereinafter, this comment is omitted) 115 ° C. ) Until the temperature rises. As described above, the temperature control at the time of temperature rise is based on the central temperature measured by the first temperature sensor 402a. The same applies to the following. Further, when the standby temperature (115 ° C.) of the first mode is reached (step S07), the target temperature is immediately increased and the temperature is increased to the fixing temperature (155 ° C.) of the first mode (step S08). . When the heating roll 101 reaches the fixing temperature (155 ° C.) of the first mode (step S09), printing, that is, image formation is performed (step S10). After printing, the process proceeds to step S32. Step S32 is a step of maintaining the standby temperature (155 ° C.) in the second mode.

  If it is determined in step S05 that the mode is not the first mode but the second mode, the process proceeds to step S11, and the temperature is raised to the standby temperature (155 ° C.) of the second mode. When the standby temperature (155 ° C.) of the second mode is reached (step S12), the target temperature is immediately set again to the fixing temperature (175 ° C.) of the second mode and the temperature increase is continued (step S12). Step S13). When the fixing temperature (175 ° C.) in the second mode is reached (step S14), printing is performed (step S10).

  The above is the flow of processing when it is determined in step S02 that the device is in the sleep state, but the following processing is performed when it is not in the sleep state at the time of main power-on (step S01).

If it is determined in step S02 that it is not in the sleep state, the process proceeds to step S21. Also in step S21, it is determined whether the first mode or the second mode is based on the above three conditions (1) to (3). If it is determined in step S21 that the mode is the first mode, the process proceeds to step S22, where the temperature is raised with the standby temperature (115 ° C.) of the first mode as the target temperature. When the standby temperature of the first mode is reached, the standby temperature is maintained (step S23). Thereafter, it is monitored whether or not a print signal has been received (step S24) and whether or not one minute or more has elapsed since the determination of the first mode in step S21 (step S25). The 1 minute is the time corresponding to the time t ₃ from time t ₀ in FIG. If the print signal is received within one minute (step S24), the temperature is raised with the fixing temperature (155 ° C.) of the first mode as the target temperature (step S26), and when the target temperature (155 ° C.) is reached (step S27). ) Is printed (step S10). After printing is performed, the process proceeds to step S32.

  If no print signal is received (step S24) and one minute or more has elapsed (step S25), the process proceeds to step S31 and the control is shifted to the second mode.

  If it is determined in step S21 that the mode is the second mode, the process proceeds to step S31, where the temperature is raised with the standby temperature (155 ° C.) of the second mode as the target temperature. When the standby temperature (155 ° C.) of the second mode is reached, the standby temperature is maintained (step S32). Thereafter, it is determined whether or not a print signal has been received (step S33) and whether or not 10 minutes have elapsed since the main power supply was turned on (step S01) (step S34). When a print signal is received within 10 minutes after the main power is turned on (step S33), the temperature is raised with the fixing temperature (175 ° C.) of the second mode as the target temperature (step S35), and the fixing temperature (second mode) ( When the temperature reaches 175 ° C. (step S36), printing is performed (step S10), the process proceeds to step S32, and the standby temperature (155 ° C.) of the second mode is maintained.

  In the state where the standby temperature of the second mode is maintained in step S32, the print signal is not received (step S33), and after 10 minutes have passed since the main power supply is turned on (step S01) (step S34), the sleep state is entered. (Step S37). This sleep state is a state in which a series of operations including the heating control of the heating roll 101 are stopped except that the main power supply remains on but the input of the print signal is accepted. When the sleep state is entered, the process proceeds to step S03, and a print signal reception waiting state is entered.

  In the present embodiment, as described above, the first mode and the second mode are divided, and the standby temperature and the fixing temperature in the first mode are lower than the standby temperature and the fixing temperature in the second mode, respectively. Since the temperature is set, the fixing device can be started up in a short time and power saving can be realized.

  Here, as shown in FIG. 3, the temperature is divided into the first mode and the second mode by measuring the temperatures of both the center and the end of the heating roll 101. However, the present invention is not limited to this, and the first temperature sensor 402a that measures the temperature at the center may be left for temperature control, and the cost may be reduced without including the second temperature sensor 402b that measures the temperature of the end portion. . In this case, the first mode may be determined when a sufficient time has passed for the heating roll 101 to cool down after the main power is turned off or the sleep state is entered.

  Here, the example in which the present invention is applied to the monochrome image forming apparatus 20 shown in FIGS. 1 and 2 is shown, but the present invention can be applied to an image forming apparatus of a type that forms a color image as it is. is there.

20 Image forming apparatus 21 Control unit 22 Photoconductor 28 Discharge stand 100 Fixing device 101 Heating roll 101a Heat source 102 Pressure roll 200 Discharger 203 Discharge roll 300 Detector 401 Heat source power supply 402a, 402b Temperature sensor 403 Control unit

Claims (6)

A heating member having a heat source and heated by the heat source;
A pressure member for fixing the toner image on the paper in cooperation with the heating member by pressing the paper conveyed while holding the toner image between the heating member surface; and
A temperature measuring device for measuring the temperature of the heating member surface;
A control circuit for controlling the heat source based on the temperature measured by the temperature measuring device,
The control circuit raises the temperature of the surface of the heating member from a first state that satisfies a predetermined determination condition for determining whether or not the temperature distribution on the surface of the heating member is in a relatively flat state. The first temperature increase target temperature, which is the temperature increase target temperature of the heating member surface in the first mode, is increased in the second mode in which the temperature of the heating member surface is increased from the second state that does not satisfy the determination condition. a temperature rise target temperature of the heating member surface is set to a second temperature rise target temperature lower target temperature than a, characterized in that for controlling the heat source to increase the temperature of the heating member surface Fixing device.   The control circuit controls the heat source in the first mode to heat the surface of the heating member to the first temperature increase target temperature in the first mode, and then does not perform a fixing operation. Further, after a predetermined first time has elapsed, the surface of the heating member is further heated toward the second temperature increase target temperature in the second mode. Item 4. The fixing device according to Item 1.   The control circuit stops heating control after a predetermined second time has elapsed without performing a fixing operation after heating to the second temperature increase target temperature. The fixing device according to claim 2. The control circuit controls the heat source in the first mode to heat the surface of the heating member to the first temperature increase target temperature in the first mode, and then performs the first time. If a print signal is received before the passage of time, the heating member surface is further heated to a first fixing temperature that is higher than the first temperature rise target temperature, and then a fixing operation is performed. Is heated to the second temperature increase target temperature in the second mode, and the print signal is received before the first time has elapsed, the second temperature increase target temperature 4. The fixing apparatus according to claim 3, wherein the fixing operation is performed after further heating to a second fixing temperature which is a higher temperature. The temperature measuring device has a plurality of temperature sensors for measuring the temperature of each of a plurality of positions in the width direction intersecting the paper conveyance direction on the surface of the heating member,
The control circuit determines whether to perform the control in the first mode or the control in the second mode based on temperatures measured by the plurality of temperature sensors. Item 5. The fixing device according to any one of Items 1 to 4. A transport unit for transporting paper;
An image forming unit that forms a toner image and transfers the toner image onto the conveyed paper;
A fixing unit that is disposed downstream of the image forming unit in the sheet conveyance direction and that heats and pressurizes the sheet that has been further conveyed after receiving the transfer of the toner image, and fixes the toner image on the sheet;
The fixing unit is
A heating member having a heat source and heated by the heat source;
A pressure member for fixing the toner image on the paper in cooperation with the heating member by pressing the paper conveyed while holding the toner image between the heating member surface; and
A temperature measuring device for measuring the temperature of the heating member surface;
A control circuit for controlling the heat source based on the temperature measured by the temperature measuring device,
The control circuit raises the temperature of the surface of the heating member from a first state that satisfies a predetermined determination condition for determining whether or not the temperature distribution on the surface of the heating member is in a relatively flat state. The first temperature increase target temperature, which is the temperature increase target temperature of the heating member surface in the first mode, is increased in the second mode in which the temperature of the heating member surface is increased from the second state that does not satisfy the determination condition. a temperature rise target temperature of the heating member surface is set to a second temperature rise target temperature lower target temperature than a, characterized in that for controlling the heat source to increase the temperature of the heating member surface Image forming apparatus.

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