JP2019174652A - Fixing device and image forming apparatus - Google Patents

Abstract

To appropriately control the temperature of a fixing member and a pressure member.SOLUTION: A fixing device comprises: a fixing member that heats an unfixed toner on a recording medium; a pressure member that is in pressure contact with the fixing member to form a pressure area and applies pressure to the recording medium passing through the pressure area; a heat source that heats the fixing member; a first temperature detection member that detects a first temperature that is the temperature of a first end of the fixing member; a second temperature detection member that detects a second temperature that is the temperature of a second end of the fixing member; and a cooling member that cools at least one end of the fixing member in a width direction orthogonal to a recording medium conveyance direction. A power supplied to the heat source is controlled according to the first temperature detected by the first temperature detection member, and the cooling member is controlled so that the at least one end is cooled according to the second temperature detected by the second temperature detection member.SELECTED DRAWING: Figure 11

Description

  The present invention relates to a fixing device including a fixing member for heating unfixed toner on a recording medium, and an image forming apparatus including the above fixing device.

  An electrophotographic image forming apparatus such as a copying machine or a printer includes a fixing device that fixes toner on a recording medium such as paper. The fixing device includes a fixing member that heats unfixed toner on the recording medium, and a pressure member that sandwiches and pressurizes the recording medium together with the fixing member.

  As an example of the fixing method, there is a hot roller method in which the toner is melted and fixed by a heated and rotating roller. In recent years, in order to reduce power consumption, it has been proposed to reduce the diameter and thickness of a roller to reduce the amount of heat of a member. In addition to the heat roller method, a fixing method using a belt or a film has been proposed.

  In the fixing device including the fixing member and the pressure member as described above, when performing the heat fixing operation on the recording paper continuously, the tolerance of the setting position of the heat source such as a heater, the paper passing position (passage area of the recording medium) ), The temperature balance between the fixing member and the pressure member (especially both ends) is likely to be disrupted when the amount of heat supplied from the heat source to the both ends of the fixing member or pressure member is changed. Exists.

  For example, when the temperature of the end portion of the fixing member and the pressure member rises (that is, when the temperature rise of the non-sheet passing portion increases), the end portion (non-sheet passing portion) may deteriorate, and the end portion volatilizes. In some cases, harmful substances such as volatile organic compounds (VOC) and ultrafine particles (UFP) are released (that is, chemical emission occurs). On the other hand, when the temperature of the passage region of the recording medium in the fixing member and the pressure member is lowered, a phenomenon that the toner is not sufficiently fixed to the recording medium (fixing failure) may occur.

  In response to the above problems, a technique for cooling the end portions of the fixing member and the pressure member has been proposed. For example, Patent Document 1 discloses a fixing unit that is disposed in the vicinity of a heating roller and includes a heat absorbing plate that absorbs heat from the heating roller and a Peltier element that moves heat absorbed by the heat absorbing plate to a heat radiating plate. Is disclosed. Japanese Patent Application Laid-Open No. 2005-228561 discloses an image forming apparatus including a fixing unit having a heating unit and a pressure member, and first and second blowing units that are sent to cool both ends that are non-sheet passing areas. An apparatus is disclosed.

JP 2007-279266 A JP2013-97055A

  As described above, the temperature of each part of the fixing member and the pressure member varies due to the tolerance of the setting position of the heat source, the tolerance of the sheet passing position, and the like. Due to the above temperature fluctuation, for example, there may be a case where the sheet passing portion temperature of the fixing member does not reach the temperature at which the toner can be fixed to the recording medium.

  In view of the above circumstances, an object of the present invention is to appropriately control the temperatures of the fixing member and the pressure member.

  The fixing device according to the present invention includes a fixing member that heats unfixed toner on a recording medium, a pressurizing region that is pressed against the fixing member, and a pressurizing unit that pressurizes the recording medium that passes through the pressing region. A pressure member, a heat source for heating the fixing member, a first temperature detecting member for detecting a first temperature which is a temperature of the first end of the fixing member, and a temperature of the second end of the fixing member. A second temperature detection member that detects a second temperature; and a cooling member that cools at least one end of the fixing member in a width direction orthogonal to the conveyance direction of the recording medium, the first temperature detection member The electric power supplied to the heat source is controlled according to the first temperature detected by the second temperature detection unit, and the at least one end is cooled according to the second temperature detected by the second temperature detection member. The cooling member is controlled by And features.

  Preferably, the cooling member of the above-described fixing device continues to cool the second end until the second temperature becomes equal to or lower than the first threshold when the second temperature exceeds the first threshold. A cooling unit, and a first cooling unit that continues to cool the first end until the second temperature becomes equal to or higher than the second threshold when the second temperature is lower than a second threshold lower than the first threshold; .

  Preferably, in the cooling member of the fixing device described above, the first cooling unit is a first fan that sends cooling air to the first end, and the second cooling unit is connected to the second end. On the other hand, the second fan sends cooling air.

  Preferably, in the cooling member of the fixing device described above, the first cooling part is a first Peltier element that cools in contact with the first end part, and the second cooling part is provided at the second end part. It is the 2nd Peltier element which contacts and cools.

  Preferably, in the above-described fixing device, the fixing member is hollow, and the cooling member faces the first end or the second end of the fixing member and is hollow in the fixing member. And a fan that generates an air flow that blows through the portion. If the second temperature is higher than the first threshold, the fan starts from the second end until the second temperature is equal to or lower than the first threshold. Continue to generate the air flow toward the end, and if the second temperature falls below a second threshold that is lower than the first threshold, from the first end until the second temperature is greater than or equal to the second threshold Continue to generate the air flow toward the second end.

  Preferably, in the above-described fixing device, the fixing member is hollow, and the cooling member generates an air flow that faces the first end portion of the fixing member and blows through the hollow portion of the fixing member. And a second fan that generates an air flow that faces the second end of the fixing member and blows through the hollow portion. The second fan has a second temperature that exceeds a first threshold value. In this case, the air flow from the second end portion to the first end portion is continuously generated until the second temperature becomes equal to or lower than the first threshold value, and the first fan has the second temperature set to the first temperature. The air flow from the first end toward the second end is continuously generated until the second temperature becomes equal to or higher than the second threshold when the second temperature is lower than a threshold.

  Preferably, the cooling member of the fixing device described above performs a cooling process based on the second temperature when the first temperature is within a predetermined temperature range.

  Preferably, in the fixing device described above, the first threshold value is set to a temperature at which chemical substance release from the fixing member and deterioration of the fixing member can be suppressed, and the second threshold value is the additional value. The temperature is set so that the unfixed toner passing through the pressure region can be fixed to the recording medium.

  Preferably, in the above-described fixing device, the heat source includes a first heater that heats a central portion of the fixing member and a second heater that heats both ends of the fixing member, and the first heater Is supplied with a first power, and the second heater is supplied with a second power determined by a relative value with respect to the first power. When the second temperature exceeds a third threshold, the relative value is set. When the second temperature is lower than a fourth threshold value lower than the third threshold value, the relative value is increased.

  The image forming apparatus according to the present invention includes any of the fixing devices described above.

  According to the present invention, it is possible to appropriately control the temperatures of the fixing member and the pressure member.

1 is a configuration diagram of an image forming apparatus according to a first embodiment of the present invention. 1 is a configuration diagram of a fixing device according to a first embodiment of the present invention. FIG. 1 is a configuration diagram of a fixing device according to a first embodiment of the present invention. FIG. It is a block diagram of the control apparatus which concerns on 1st Embodiment of this invention. It is explanatory drawing of the half wave control which concerns on 1st Embodiment of this invention. It is explanatory drawing of the half wave control which concerns on 1st Embodiment of this invention. It is explanatory drawing of the half wave control which concerns on 1st Embodiment of this invention. It is explanatory drawing of the phase control which concerns on 1st Embodiment of this invention. It is explanatory drawing of the phase control which concerns on 1st Embodiment of this invention. It is explanatory drawing of the phase control which concerns on 1st Embodiment of this invention. It is a flowchart of the cooling control which concerns on 1st Embodiment of this invention. It is a block diagram of the fixing device which concerns on 2nd Embodiment of this invention. It is a block diagram of the fixing device which concerns on 2nd Embodiment of this invention. It is a block diagram of the fixing device which concerns on 3rd Embodiment of this invention. It is a block diagram of the fixing device which concerns on 3rd Embodiment of this invention.

  Hereinafter, a plurality of embodiments of the present invention will be described with reference to the accompanying drawings. The front side of the drawing in FIG. 1 and the like is the front surface, and “L” shown in each figure indicates “left”, “R” indicates “right”, “U” indicates “up”, and “Lo”. Indicates “down”, “Fr” indicates front, and “Rr” indicates rear.

1. First embodiment 1-1. Overall Configuration of Image Forming Apparatus The overall configuration of the image forming apparatus 1 will be described with reference to FIG. The image forming apparatus 1 of the present embodiment is a monochromatic printer that fixes toner on a sheet S that is a recording medium. FIG. 1 is a cross-sectional view schematically showing the internal structure of the image forming apparatus 1.

  The image forming apparatus 1 includes an apparatus main body 2 that forms a substantially rectangular parallelepiped appearance. A paper feed cassette 3 that stores paper sheets S is detachably provided at the lower portion of the apparatus main body 2. A paper discharge tray is provided on the upper surface of the apparatus main body 2. The sheet S as an example of the recording medium is not limited to paper but may be a resin sheet or the like.

  An exposure unit 5 constituted by a laser scanning unit (LSU) is provided below the discharge tray on the upper part of the apparatus main body 2. An image forming unit 6 is provided below the exposure unit 5. The image forming unit 6 is rotatably provided with a photosensitive drum 7 that is an image carrier. Around the photosensitive drum 7, a charger 8, a developing device 9 connected to a toner container, a transfer roller, and a cleaning device are provided along the rotation direction of the photosensitive drum 7. One end (for example, the rear end) of the rotating shaft of the photosensitive drum 7 is connected to a driving source such as a motor, and the photosensitive drum 7 is rotated by a rotational driving force transmitted from the driving source.

  A conveyance path 10 for the sheet S is provided inside the apparatus main body 2. The paper feeding device 4 is provided at the upstream end of the conveyance path 10 extending from the paper feeding cassette 3 to the paper discharge tray. The fixing device 11 is provided on the downstream side of the conveyance path 10, and the image forming unit 6 is provided between the paper feeding device 4 and the fixing device 11 in the conveyance path 10. Hereinafter, the direction in which the sheet S is conveyed on the conveyance path 10 is referred to as a “conveyance direction”.

  The apparatus main body 2 further includes a control device 12 that controls each part of the image forming apparatus 1. Further, the apparatus main body 2 includes a display unit that displays the state of the image forming apparatus 1 on an upper surface or a side surface. The display unit is configured by, for example, a touch panel or a display.

1-2. Image Forming Process An image forming operation by the image forming apparatus 1 having the above configuration will be described. In the image forming apparatus 1, when image data is input from an external computer or the like and an instruction to start printing is given, the control device 12 starts an image forming operation. The charger 8 of the image forming unit 6 charges the surface of the photosensitive drum 7. The exposure device 5 forms an electrostatic latent image on the surface of the photosensitive drum 7 by irradiating a laser beam corresponding to the image data. The developing device 9 of the image forming unit 6 develops the electrostatic latent image into a toner image using toner. The photosensitive drum 7 carries the developed toner image.

  On the other hand, the sheet S is sent from the paper feed cassette 3 to the transport path 10 by the paper feed device 4. The sheet S on the conveyance path 10 is conveyed to the image forming unit 6 at a predetermined timing, and the toner image on the surface of the photosensitive drum 7 is transferred to the sheet S. The sheet S on which the toner image is formed is conveyed to the fixing device 11, and the toner image is fixed on the sheet S by the fixing device 11. The sheet S on which the toner image is fixed is discharged to a paper discharge tray.

1-3. Fixing Device The fixing device 11 will be described with reference to FIGS. 2 and 3. The fixing device 11 includes a fixing roller 21 (fixing member), a pressure roller 22 (pressure member), a heater 23 (heat source), a first temperature sensor 24 (first temperature detection member), and a second temperature sensor. 25 (second temperature detection member) and a cooling mechanism 26 (cooling member).

  The fixing roller 21 is a hollow and substantially cylindrical member that is long in the front-rear direction (rotational axis direction). The fixing roller 21 includes a core material 21a configured in a hollow cylindrical shape, an elastic layer 21b laminated on the outer peripheral surface of the core material 21a, and a release layer 21c that covers the elastic layer 21b. The core material 21a is configured using a metal such as aluminum. The elastic layer 21b is configured using, for example, elastic silicone rubber or the like. The release layer 21c is configured using a fluororesin such as PFA, for example.

  The pressure roller 22 is a substantially cylindrical member that is long in the front-rear direction (rotational axis direction). The pressure roller 22 includes a cored bar 22a configured in a columnar shape, an elastic layer 22b stacked on the outer peripheral surface of the cored bar 22a, and a release layer 22c that covers the elastic layer 22b. The cored bar 22a is configured using a metal such as SUS or aluminum. The elastic layer 22b is configured using, for example, elastic silicone rubber or the like. The release layer 22c is configured using a fluororesin such as PFA, for example. The pressure roller 22 is urged by a spring (not shown) and is pressed against the fixing roller 21. The pressure roller 22 is rotationally driven by a drive source such as a motor (not shown). The fixing roller 21 is driven and rotated by the rotation of the pressure roller 22.

  The heater 23 is a heat source configured by, for example, a halogen heater or a ceramic heater, and is provided in the internal space (hollow portion) of the fixing roller 21 (core material 21a). The heater 23 generates heat by power supplied from a power source (not shown), and heats the fixing roller 21 from the inside. When the heat generation portion of the heater 23 is longer in the width direction than the maximum passage region P including all the regions through which the sheet S passes, and is formed on the inner side in the width direction than the first temperature sensor 24 and the second temperature sensor 25. Is preferred. Heat generation of the heater 23 is controlled by the control device 12.

  The fixing roller 21 is a fixing member that heats unfixed toner on the sheet S while rotating around its rotation axis. The pressure roller 22 is a pressure member that presses against the fixing roller 21 to form a fixing nip N (pressure region) and pressurizes the sheet S passing through the fixing nip N while rotating around its rotation axis. . The toner is fixed to the sheet S by heating by the fixing roller 21 and pressing by the pressure roller 22.

  The first temperature sensor 24 and the second temperature sensor 25 are configured by, for example, a contact type thermistor, and are provided so as to contact the surfaces of both end portions of the fixing roller 21. As shown in FIG. 3, the first temperature sensor 24 and the second temperature sensor 25 are provided outside in the width direction from the maximum passage region P through which the sheet S passes (that is, in a non-passing region through which the sheet S does not pass). ing.

  In other words, the first temperature sensor 24 is a temperature detection member that detects the first temperature T <b> 1 that is the temperature of the front end (first end) of the fixing roller 21, and the second temperature sensor 25 is the temperature of the fixing roller 21. It is a temperature detection member that detects the second temperature T2 that is the temperature of the rear end (second end). A temperature signal indicating the detected temperature is output from each of the temperature sensors 24 and 25 and input to the control device 12. The control by the control device 12 based on the temperature signals from the temperature sensors 24 and 25 will be described in detail later.

  The cooling mechanism 26 includes a first fan 26 a that sends cooling air to the first end of the fixing roller 21 and a second fan 26 b that sends cooling air to the second end of the fixing roller 21. Yes. The first end is cooled by the first fan 26a, and the second end is cooled by the second fan 26b. The first fan 26a and the second fan 26b are operated (that is, rotated) by electric power supplied from a power source (not shown), and generate an air flow A. The rotation of the first fan 26 a and the second fan 26 b is controlled by the control device 12.

  The cooling mechanism 26 can have any configuration that can cool the end of the fixing roller 21. For example, the cooling mechanism 26 includes a first Peltier element that cools in contact with the first end of the fixing roller 21, and a second Peltier element that cools in contact with the second end of the fixing roller 21. It is also possible to employ a configuration that includes:

1-4. Control Device The control device 12 will be described with reference to FIG. The control device 12 is a device configured by a microcomputer, and includes an arithmetic processing unit 31 and a storage unit 32. The arithmetic processing unit 31 includes a microprocessor as a CPU (Central Processing Unit), and the storage unit 32 includes a ROM (Read Only Memory) and a RAM (Random Access Memory).

  The ROM is a readable storage medium and stores a program used for boot processing and control of the image forming apparatus 1. The RAM is a readable / writable storage medium, functions as a main storage device, and stores written information. The storage unit 32 may further include an auxiliary storage device such as a flash memory.

  The arithmetic processing unit 31 executes predetermined processing with reference to information stored in the RAM according to a program stored in the ROM. The arithmetic processing unit 31 logically configures various functional blocks realized by processing according to a program. In addition, the arithmetic processing unit 31 writes various information obtained by processing or the like in the storage unit 32.

  The control device 12 is electrically connected to each part of the image forming apparatus 1 such as the paper feed cassette 3, the paper feed device 4, the exposure device 5, the image forming unit 6, and the fixing device 11. In particular, the control device 12 controls the electric power supplied to the heater 23 according to the first temperature T1 detected by the first temperature sensor 24 and fixes according to the second temperature T2 detected by the second temperature sensor 25. The cooling mechanism 26 (the first fan 26a and the second fan 26b) is controlled so that at least one end of the roller 21 is cooled.

  Control of the power supplied to the heater 23 will be described. The control device 12 controls the heater 23 so that the first temperature T1 detected by the first temperature sensor 24 is maintained within a certain range. For example, the control device 12 may execute on / off temperature control with hysteresis around a target temperature (for example, 180 ° C.). In the above case, it is preferable that the difference between the temperature at which the current is turned on and the temperature at which the power source is turned off is set to any one of 2 ° C. to 5 ° C., for example. In addition, the control device 12 may execute feedback control (for example, PID control) of the amount of power input to the heater 23 based on the transition of the first temperature T1.

  A method of changing the amount of power input to the heater 23 will be described. 5 to 7 are explanatory diagrams of half-wave control. In the half-wave control of this embodiment, n (for example, 10) half-waves are treated as one cycle, and the number of half-waves supplied to the heater 23 (heat generating portion) among the half-waves included in one cycle is determined. By changing, the amount of power is changed.

  FIG. 5 shows an example in which all (100%) half waves out of 10 half waves included in one cycle are supplied to the heater 23. Similarly, FIG. 6 shows an example in which 50% half-wave is supplied to the heater 23, and FIG. 7 shows an example in which 20% half-wave is supplied to the heater 23. In the above drawings, the waveform supplied to the heater 23 is indicated by a solid line, and the waveform not supplied to the heater 23 is indicated by a broken line. The number of half-waves included in one cycle is arbitrary, and is not limited to 10 half-waves (n = 10), and may be 20 half-waves (n = 20), for example.

  Further, in order to control the amount of electric power supplied to the heater 23, phase control may be employed instead of half-wave control. 8 to 10 are explanatory diagrams of phase control. In the phase control of this embodiment, the full wave (two half waves) is treated as one cycle, and the amount of electric power is changed by changing the ratio of the full wave supplied to the heater 23 (heat generation part).

  FIG. 8 shows an example in which 100% of all waves are supplied to the heater 23. Similarly, FIG. 9 shows an example in which 50% of the full wave is supplied to the heater 23, and FIG. 10 shows an example in which 25% of the full wave is supplied to the heater 23. In the above drawings, the portion supplied to the heater 23 is indicated by hatching. Note that the number of half-waves constituting one cycle is arbitrary, and is not limited to the full wave, and one half-wave may be treated as one cycle.

1-5. Cooling control based on the detected temperature Generally, the temperatures of the both end portions (non-passing portions) of the fixing roller 21 (the detected temperatures of the first temperature sensor 24 and the second temperature sensor 25) are determined during the printing operation. It is preferable that the difference between the temperatures is maintained below a predetermined value (more preferably, substantially the same).

  However, in reality, there are tolerances in the setting position of the heater 23, tolerances in the passage region of the sheet S, and the like, so temperatures at both ends of the fixing roller 21 (detected temperatures of the first temperature sensor 24 and the second temperature sensor 25). ) Is likely to increase.

  Therefore, in the present embodiment, in the control of the power supplied to the heater 23 based on the first temperature T1 detected by the first temperature sensor 24, the cooling mechanism 26 is based on the second temperature T2 detected by the second temperature sensor 25. Employs a configuration in which the fixing roller 21 is cooled. That is, in this embodiment, the power control based on the output of the first temperature sensor 24 and the cooling control based on the output of the second temperature sensor 25 are executed together.

  The details of the control will be described below with reference to the flowchart of FIG. Hereinafter, the front side (first temperature sensor 24 side) end of the fixing roller 21 is referred to as a first end, and the rear side (second temperature sensor 25 side) end is referred to as a second end.

  The following cooling control based on the second temperature T2 may be executed at an arbitrary timing. For example, when the first temperature T1 is within a predetermined temperature range (for example, 180 ° C. or more and 190 ° C. or less). It is preferable to be executed in the following manner.

  When the cooling control shown in FIG. 11 is started, the control device 12 determines whether or not the second temperature T2 detected by the second temperature sensor 25 exceeds the first threshold Th1 (step S101). The first threshold Th1 is 190 ° C., for example.

  When the second temperature T2 exceeds the first threshold Th1 (S101: YES), the control device 12 controls the cooling mechanism 26 (second fan 26b) so as to start cooling the second end portion of the fixing roller 21. (Step S102). As a result of the above cooling control, the heat on the second end side begins to be deprived, and the temperature at the second end (second temperature T2 detected by the second temperature sensor 25) decreases.

  After step S102, the control device 12 controls the cooling mechanism 26 (second fan 26b) so as to continue cooling the second end until the second temperature T2 becomes equal to or lower than the first threshold Th1. In other words, the control device 12 enters the loop of step S103 for determining whether or not the second temperature T2 is equal to or lower than the first threshold Th1, and repeats this loop until the determination is YES.

  When the loop ends (S103: YES), the control device 12 controls the cooling mechanism 26 so as to stop the cooling by the second fan 26b (step S104).

  Next, the control device 12 determines whether or not the second temperature T2 detected by the second temperature sensor 25 is lower than the second threshold Th2 (step S105). The second threshold Th2 is a value indicating a temperature lower than the first threshold Th1, and is 180 ° C., for example.

  When the second temperature T2 is lower than the second threshold Th2 (S105: YES), the control device 12 controls the cooling mechanism 26 (first fan 26a) to start cooling the first end of the fixing roller 21. (Step S106). As a result of the above cooling control, the heat on the first end side begins to be deprived, and the temperature at the first end (the first temperature T1 detected by the first temperature sensor 24) decreases. As a result, the control device 12 performs control so that the electric power supplied to the heater 23 increases, so that the temperatures of the second end portions of the fixing roller 21 and the pressure roller 22 (the first temperature sensor 25 detects the first temperature). 2 Temperature T2) rises.

  After step S106, the control device 12 controls the cooling mechanism 26 (first fan 26a) so as to continue cooling the first end until the second temperature T2 becomes equal to or higher than the second threshold Th2. In other words, the control device 12 enters the loop of step S107 for determining whether or not the second temperature T2 is equal to or higher than the second threshold Th2, and repeats this loop until the determination becomes YES.

  When the loop ends (S107: YES), the control device 12 controls the cooling mechanism 26 so as to stop the cooling by the first fan 26a (step S108).

  As understood from the above, the cooling mechanism 26 of the present embodiment is based on the control by the control device 12 until the second temperature T2 becomes equal to or lower than the first threshold Th1 when the second temperature T2 exceeds the first threshold Th1. If the second fan 26b continues to cool the second end and the second temperature T2 falls below a second threshold Th2 that is lower than the first threshold Th1, the first fan until the second temperature T2 becomes equal to or higher than the second threshold Th2. 26a is configured to continue cooling the large end.

  The first threshold value Th1 is preferably set to a temperature (for example, 190 ° C.) that can suppress the release of the chemical substance from the fixing roller 21 and the deterioration of the fixing roller 21. The second threshold Th2 is set to a temperature at which unfixed toner that passes through the fixing nip N can be fixed to the sheet S (for example, 180 ° C. that is a temperature at which the fixing nip N becomes 150 ° C. or higher). It is preferable.

1-6. Technical Effects of this Embodiment As described above, according to the configuration according to this embodiment, in the fixing device 11 including the fixing roller 21 and the pressure roller 22, the first position located at the first end of the fixing roller 21. The power supplied to the heater 23 is controlled according to the first temperature T1 detected by the first temperature sensor 24, and the second temperature T2 detected by the second temperature sensor 25 located at the second end of the fixing roller 21. In response to this, the cooling mechanism 26 is controlled so that at least one end is cooled. According to the above configuration, both the electric power supplied to the heater 23 and the cooling process by the cooling mechanism 26 are controlled according to the temperature at both ends of the fixing roller 21, so that the fixing roller 21 and the fixing roller 21 are pressed against each other. The temperature of the pressure roller 22 is appropriately controlled.

  Further, when the second temperature T2 exceeds the first threshold value Th1, the cooling mechanism 26 continues to cool the second end until the second temperature T2 becomes equal to or lower than the first threshold value Th1, and the second temperature T2 becomes the first threshold value. According to the configuration in which the first end is continuously cooled until the second temperature T2 becomes equal to or higher than the second threshold Th2 when the second temperature T2 is lower than the second threshold Th2 that is lower than Th1, the second temperature T2 is equal to or higher than the second threshold Th2. By controlling the cooling mechanism 26 to be equal to or less than the threshold value Th1, the temperatures of the fixing roller 21 and the pressure roller 22 can be maintained within an appropriate temperature range. In addition to being suppressed, fixing of unfixed toner onto the sheet S is also ensured.

  Further, according to the configuration in which the cooling mechanism 26 includes the first fan 26a that sends the cooling air to the first end portion and the second fan 26b that sends the cooling air to the second end portion, the cooling mechanism 26 is efficient. It is possible to cool both ends.

  Further, according to the configuration in which the cooling mechanism 26 includes the first Peltier element that cools in contact with the first end portion and the second Peltier element that cools in contact with the second end portion, an air flow is generated. Since the end can be cooled without making it possible to prevent dust and dust from scattering in the apparatus.

  Further, according to the configuration in which the cooling mechanism 26 performs the cooling process based on the second temperature T2 when the first temperature T1 is within the predetermined temperature range, the power control based on the first temperature T1 is effective to some extent. Since the cooling control based on the second temperature T2 is executed in the state where the cooling is performed, the frequency of the cooling control is suppressed and energy saving is realized.

  The first threshold value Th1 is set to a temperature at which the release of chemical substances (VOC, UFP, etc.) from the fixing roller 21 and the deterioration of the fixing roller 21 can be suppressed, and the second threshold value Th2 sets the fixing nip N. According to the configuration in which the temperature is set such that the unfixed toner passing therethrough can be fixed to the sheet S, the suppression of the emission due to the excessive temperature rise and the reliable toner fixing can be realized at the same time.

  Further, according to the configuration of the present embodiment, the image forming apparatus 1 including the fixing device 11 described above is realized.

2. Second Embodiment A second embodiment of the present invention will be described with reference to FIGS. In the following description, the same components as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof may be omitted.

2-1. Fixing Device The fixing device 11 will be described with reference to FIG. The fixing device 11 includes a fixing roller 21 (fixing member), a pressure roller 22 (pressure member), a heater 23 (heat source), a first temperature sensor 24 (first temperature detection member), and a second temperature sensor. 25 (second temperature detection member) and a cooling mechanism 26 (cooling member).

  The cooling mechanism 26 of the second embodiment is configured by a fan 26 c facing the second end of the fixing roller 21. The fan 26 c generates an air flow A that blows through the hollow portion of the fixing roller 21. The fan 26c is positive so that both the air flow A1 from the first end portion to the second end portion and the air flow A2 from the second end portion to the first end portion can be selectively generated. It is configured to be rotatable in both reverse directions. The air flow A1 is generated when the fan 26c rotates so as to suck air in the hollow portion of the fixing roller 21, and the air flow A2 rotates so that the fan 26c sends air into the hollow portion of the fixing roller 21. Occurs.

2-2. Cooling Control Based on Detected Temperature Since the control flow of the second embodiment is the same as that of the flowchart of FIG. 11, details of the control will be described with reference to the flowchart of FIG. The following cooling control based on the second temperature T2 may be executed at an arbitrary timing. For example, the cooling control is executed when the first temperature T1 is within a predetermined temperature range (for example, 180 ° C. or higher and 190 ° C. or lower). Is preferred.

  When the cooling control shown in FIG. 11 is started, the control device 12 determines whether or not the second temperature T2 detected by the second temperature sensor 25 exceeds the first threshold Th1 (step S101). The first threshold Th1 is 190 ° C., for example.

  When the second temperature T2 exceeds the first threshold Th1 (S101: YES), the control device 12 controls the fan 26c so as to start cooling the second end portion of the fixing roller 21 (step S102). The fan 26c generates an air flow A2 from the second end portion toward the first end portion. When the cold air from the outside of the fixing roller 21 hits the second end portion, the heat on the second end side begins to be taken away, and the temperature of the second end portion (second temperature T2 detected by the second temperature sensor 25). Will go down.

  After step S102, the control device 12 controls the fan 26c so as to continue cooling the second end until the second temperature T2 becomes equal to or lower than the first threshold Th1. In other words, the control device 12 enters the loop of step S103 for determining whether or not the second temperature T2 is equal to or lower than the first threshold Th1, and repeats this loop until the determination is YES.

  When the loop ends (S103: YES), the control device 12 controls the cooling mechanism 26 so as to stop the cooling by the fan 26c (step S104).

  Next, the control device 12 determines whether or not the second temperature T2 detected by the second temperature sensor 25 is lower than the second threshold Th2 (step S105). The second threshold Th2 is a value indicating a temperature lower than the first threshold Th1, and is 180 ° C., for example.

  When the second temperature T2 is lower than the second threshold Th2 (S105: YES), the control device 12 controls the fan 26c so as to start cooling the first end portion of the fixing roller 21 (step S106). The fan 26c generates an air flow A1 from the first end toward the second end. When the cold air from the outside of the fixing roller 21 hits the first end, the heat at the first end begins to be taken away, and the temperature at the first end (the first temperature T1 detected by the first temperature sensor 24). Will go down. As a result, the control device 12 performs control so that the electric power supplied to the heater 23 increases, so that the temperatures of the second end portions of the fixing roller 21 and the pressure roller 22 (the first temperature sensor 25 detects the first temperature). 2 Temperature T2) rises.

  After step S106, the control device 12 controls the fan 26c so as to continue cooling the first end until the second temperature T2 becomes equal to or higher than the second threshold Th2. In other words, the control device 12 enters the loop of step S107 for determining whether or not the second temperature T2 is equal to or higher than the second threshold Th2, and repeats this loop until the determination becomes YES.

  When the loop ends (S107: YES), the control device 12 controls the cooling mechanism 26 so as to stop the cooling by the fan 26c (step S108).

  As can be understood from the above, the cooling mechanism 26 of the present embodiment is based on the control by the control device 12, and when the second temperature T2 exceeds the first threshold Th1, the second temperature T2 becomes the first threshold Th1 or less. If the second temperature T2 is lower than the second threshold Th2 lower than the first threshold Th1, the second temperature T2 becomes equal to or higher than the second threshold Th2. The air flow A1 from the first end toward the second end continues to be generated until the first end. The first threshold Th1 and the second threshold Th2 are preferably set as exemplified in the first embodiment.

  As shown in FIG. 13, the cooling mechanism 26 may include two fans (a first fan 26d and a second fan 26e), and generate the air flows A1 and A2 as described above. That is, the cooling mechanism 26 faces the first end of the fixing roller 21 and generates the air flow A1 that blows through the hollow portion of the fixing roller 21 and the second end of the fixing roller 21 for fixing. And a second fan 26e that generates an air flow A2 that blows through the hollow portion of the roller 21.

  In the configuration of FIG. 13, when the second temperature T2 exceeds the first threshold value Th1, the second fan 26e moves from the second end portion to the first end portion until the second temperature T2 becomes equal to or lower than the first threshold value Th1. The first fan 26d continues to generate the air flow A2 (steps S102 and S103). When the second temperature T2 is lower than the second threshold Th2 that is lower than the first threshold Th1, the second temperature T2 is equal to or higher than the second threshold Th2. The air flow A1 from the first end portion to the second end portion is continuously generated until (S106, 107).

2-3. Technical Effects of the Present Embodiment According to the configuration of the second embodiment described above, the same technical effects as the first embodiment are exhibited.

  Further, when the second temperature T2 exceeds the first threshold Th1, the cooling mechanism 26 generates an air flow A2 from the second end toward the first end until the second temperature T2 becomes equal to or lower than the first threshold Th1. When the second temperature T2 is lower than the second threshold Th2 lower than the first threshold Th1, the air flow A1 from the first end toward the second end is continued until the second temperature T2 becomes equal to or higher than the second threshold Th2. According to the configuration that continues to generate (FIGS. 12 and 13), the cooling mechanism 26 is controlled such that the second temperature T2 is equal to or higher than the second threshold Th2 and equal to or lower than the first threshold Th1, whereby the fixing roller 21 and the pressure are applied. Since the temperature of the roller 22 can be maintained within an appropriate temperature range, excessive temperature rise at both ends is suppressed, and fixing of unfixed toner to the sheet S is ensured.

  In the above configuration, according to the configuration in which the cooling mechanism 26 includes one fan 26c capable of generating both the air flow A1 and the air flow A2 (FIG. 12), both ends can be cooled by a simple configuration of one fan. It becomes possible. On the other hand, according to the configuration (FIG. 13) in which the cooling mechanism 26 generates the first fan 26d that generates the airflow A1 and the second fan 26e that generates the airflow A2, the cooling mechanism 26 is effective for each end. The cooling process can be executed.

3. Third Embodiment As described above, the fixing device 11 of the first embodiment and the second embodiment includes one heater 23. The fixing device 11 according to the second embodiment includes two heaters (a first heater 23a and a second heater 23b).

3-1. Fixing Device The fixing device 11 will be described with reference to FIGS. 14 and 15. The fixing device 11 includes a fixing roller 21 (fixing member), a pressure roller 22 (pressure member), a first heater 23a and a second heater 23b (heat source), and a first temperature sensor 24 (first temperature detection member). ), A second temperature sensor 25 (second temperature detecting member), a third temperature sensor 28, and a moving mechanism 26 (moving member).

  The first heater 23a and the second heater 23b are heat sources configured by, for example, a halogen heater, a ceramic heater, or the like, and are provided side by side in the inner space of the fixing roller 21 (core material 21a) while being separated in the vertical direction. The first heater 23a and the second heater 23b generate heat by power supplied from a power source (not shown), and heat the fixing roller 21 from the inside.

  The heat generation part of the first heater 23 a is configured to have heat distribution to the central part of the fixing roller 21, and the heat generation part of the second heater 23 b is configured to have heat distribution to both ends of the fixing roller 21. Yes. That is, the first heater 23 a heats the central portion of the fixing roller 21, and the second heater 23 b heats both end portions of the fixing roller 21. Heat generation of the first heater 23 a and the second heater 23 b is controlled by the control device 12.

  The third temperature sensor 28 is configured by, for example, a non-contact type thermistor, and is provided so as to face the central portion of the fixing roller 21. As shown in FIG. 15, the third temperature sensor 28 is provided to face the maximum passage region P through which the sheet S passes.

  The third temperature sensor 28 is a temperature detection member that detects a third temperature T <b> 3 that is the temperature at the center of the fixing roller 21. Similar to the first temperature sensor 24 and the second temperature sensor 25, a temperature signal indicating the temperature detected by the third temperature sensor 28 is input to the control device 12.

3-2. Control of Supply Power Control of supply power to the first heater 23a and the second heater 23b will be described. The control device 12 controls the first heater 23a so that the third temperature T3 detected by the third temperature sensor 28 is maintained within a certain range. For example, the control device 12 can execute on / off temperature control or feedback control similar to the above-described embodiment. Based on the above control, the electric power (first electric power) supplied to the first heater 23a is determined.

  The electric power (second electric power) supplied to the second heater 23b is determined by a relative value with respect to the electric power (first electric power) supplied to the first heater 23a. It is preferable that the relative value described above is determined according to the size of the sheet S passing through the sheet passing area P. For example, the sheet S having a size that covers the entire area of the sheet passing area P is 100%, and the sheet S having a size that covers a half area of the sheet passing area P is 50%, and only the center of the sheet passing area P is covered. In the case of the size sheet S, it is determined as 0%. That is, it is preferable that the relative value is set to increase as the size of the sheet S increases.

  When it is preferable that the amount of power corresponding to 50% of the amount of power supplied to the first heater 23a is supplied to the second heater 23b (that is, when the above-described relative value is 50%), the control device No. 12 sets the power amount to the second heater 23b to 35% when the power amount to the first heater 23a is 70%.

  Even if the control is executed as described above, there are variations in the heat distribution of the first heater 23a and the second heater 23b, the tolerance of the set position, the tolerance of the passing region of the sheet S, and the like. The first temperature T1 detected by 24 is likely to vary.

  Therefore, in the present embodiment, when the first temperature T1 detected by the first temperature sensor 24 exceeds the third threshold Th3, the control device 12 reduces the relative power (relative value) to be supplied to the second heater 23b. (For example, change from 50% to 20%). On the other hand, when the first temperature T1 detected by the first temperature sensor 24 falls below the fourth threshold Th4, the control device 12 increases the relative power (relative value) to be supplied to the second heater 23b (for example, 50 % To 80%). By controlling as described above, the first temperature T1 detected by the first temperature sensor 24 is maintained between the third threshold Th3 and the fourth threshold Th4.

  The third threshold Th3 is preferably set to a temperature (for example, 190 ° C.) that can suppress the release of the chemical substance from the fixing roller 21 and the deterioration of the fixing roller 21. The fourth threshold Th4 is lower than the third threshold Th3, and is a temperature at which unfixed toner that passes through the fixing nip N can be fixed to the sheet S (for example, a temperature at which the fixing nip N becomes 150 ° C. or more). It is preferable that the temperature is set to 180 ° C.

3-3. Cooling Control Based on Detected Temperature In a state where the above control is executed, the control device 12 performs cooling based on the detected temperature described in the first embodiment (1-5) or the second embodiment (2-2). Execute control. Since the specific operation is the same as described above, the description is omitted.

  As described above, in the cooling control based on the detected temperature, control using the first threshold Th1 and the second threshold Th2 is executed, but the first threshold Th1 and the third threshold Th3, and the second threshold Th2 and the fourth threshold Th4. May be set to the same value.

3-4. Technical Effects of the Present Embodiment According to the configuration of the third embodiment described above, the same technical effects as those of the first and second embodiments are achieved.

  The fixing device 11 includes a first heater 23a that heats the central portion of the fixing roller 21 and a second heater 23b that heats both ends of the fixing roller 21. The first heater 23a includes a first electric power. Is supplied, and the second heater 23b is supplied with the second power determined by the relative value with respect to the first power. When the second temperature T2 exceeds the third threshold Th3, the relative value is decreased and the second temperature is decreased. According to the configuration in which the relative value is increased when T2 is lower than the fourth threshold Th4 lower than the third threshold Th3, the power to be supplied to the two heaters is appropriately controlled.

4). Modifications The above-described embodiment can be variously modified. The modification of embodiment is shown below. Two or more aspects arbitrarily selected from the embodiments and modifications can be appropriately combined as long as they do not contradict each other.

  In the above description of the embodiment, the end on the front side of the fixing roller 21 is the first end and the end on the rear side is the second end, but the rear side is the first end and the front side is the front side. It may be the second end.

  In the above description of the embodiment, the fixing roller 21 is employed as the fixing member, but any fixing member may be employed. For example, a fixing film or a fixing belt may be employed as the fixing member.

  In the above description of the embodiment, the heater 23 (23a, 23b), which is a halogen heater or a ceramic heater, is employed as the heat source, but any heating member may be employed. For example, an IH heating unit that heats the fixing roller 21 from the outside may be employed as the heat source. The IH heat generating unit includes a plurality of IH coils supported by a substantially semi-cylindrical holder. The plurality of IH coils are covered with an arch core formed of a ferromagnetic material such as ferrite. Each IH coil is supplied with electric power from a power source (not shown), generates a high-frequency magnetic field, and heats the fixing roller 21.

  In the above description of the embodiment, the first temperature sensor 24 and the second temperature sensor 25 are configured by contact-type thermistors and are provided so as to contact the surfaces of both ends of the fixing roller 21. Any sensor capable of detecting the temperature at both ends of 21 can be employed. For example, the first temperature sensor 24 and the second temperature sensor 25 may be configured using a non-contact type thermistor. Further, the non-contact type first temperature sensor 24 and the second temperature sensor 25 may be close to both end portions of the passage region instead of the non-sheet passing portion.

  In the above description of the embodiment, the case where the present invention is applied to a single color (monochrome) printer is shown as an example. However, the present invention is not limited thereto, and the present invention is applied to, for example, a color printer, a copying machine, a facsimile machine, or a multifunction machine. May be applied.

  The description of the above embodiment shows one aspect of the fixing device and the image forming apparatus according to the present invention, and the technical scope of the present invention is not limited to the above embodiment.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Fixing apparatus 12 Control apparatus 21 Fixing roller (fixing member)
22 Pressure roller (pressure member)
23 Heater (heat source)
23a 1st heater 23b 2nd heater 24 1st temperature sensor (1st temperature detection member)
25 Second temperature sensor (second temperature detection member)
26 Cooling mechanism (cooling member)
26a, 26d First fan 26b, 26e Second fan 26c Fan 27 Housing N Fixing nip P Maximum passage area S Sheet (recording medium)
T1 first temperature T2 second temperature Th1 first threshold Th2 second threshold

Claims (10)

A fixing member for heating unfixed toner on the recording medium;
A pressure member that presses against the fixing member to form a pressure area, and pressurizes the recording medium passing through the pressure area;
A heat source for heating the fixing member;
A first temperature detection member that detects a first temperature that is a temperature of the first end of the fixing member;
A second temperature detecting member for detecting a second temperature which is a temperature of the second end of the fixing member;
A cooling member that cools at least one end of the fixing member in the width direction orthogonal to the conveyance direction of the recording medium,
The electric power supplied to the heat source is controlled according to the first temperature detected by the first temperature detection member, and the at least one end according to the second temperature detected by the second temperature detection member. The fixing device is characterized in that the cooling member is controlled so that the portion is cooled. The cooling member is
A second cooling unit that continues to cool the second end until the second temperature falls below the first threshold when the second temperature exceeds a first threshold; and the second temperature is greater than the first threshold. 2. A first cooling unit that continues to cool the first end until the second temperature becomes equal to or higher than the second threshold when the second temperature is lower than the lower second threshold. Fixing device.   The first cooling unit is a first fan that sends cooling air to the first end, and the second cooling unit is a second fan that sends cooling air to the second end. The fixing device according to claim 2.   The first cooling unit is a first Peltier element that contacts and cools the first end, and the second cooling unit is a second Peltier element that contacts and cools the second end. The fixing device according to claim 2. The fixing member is hollow,
The cooling member includes a fan that is opposed to the first end or the second end of the fixing member and generates an air flow that blows through a hollow portion of the fixing member.
The fan continues to generate the air flow from the second end to the first end until the second temperature is less than or equal to the first threshold when the second temperature is above a first threshold; When the second temperature falls below a second threshold value that is lower than the first threshold value, the air flow from the first end portion toward the second end portion is generated until the second temperature becomes equal to or higher than the second threshold value. The fixing device according to claim 1, wherein the fixing device is allowed to continue. The fixing member is hollow,
The cooling member is opposed to the first end portion of the fixing member and generates a flow of air that blows through the hollow portion of the fixing member, and the hollow portion is opposed to the second end portion of the fixing member. A second fan for generating an air flow that blows through the air,
The second fan generates the air flow from the second end toward the first end until the second temperature becomes equal to or lower than the first threshold when the second temperature exceeds the first threshold. The first fan continues from the first end to the second end until the second temperature becomes equal to or higher than the second threshold when the second temperature falls below a second threshold lower than the first threshold. The fixing device according to claim 1, wherein the air flow toward the portion is continuously generated.   The said cooling member performs the cooling process based on said 2nd temperature, when said 1st temperature exists in a predetermined temperature range, The any one of Claims 1-6 characterized by the above-mentioned. The fixing device according to 1.   The first threshold value is set to a temperature at which the release of the chemical substance from the fixing member and the deterioration of the fixing member can be suppressed, and the second threshold value is the unfixed toner passing through the pressure region. The fixing device according to any one of claims 2 to 7, wherein the fixing device is set to a temperature at which the recording medium can be fixed. The heat source includes a first heater that heats a central portion of the fixing member, and a second heater that heats both ends of the fixing member.
The first heater is supplied with a first power, the second heater is supplied with a second power determined by a relative value to the first power,
The relative value is decreased when the second temperature exceeds a third threshold, and the relative value is increased when the second temperature is lower than a fourth threshold lower than the third threshold. The fixing device according to claim 1.   An image forming apparatus comprising the fixing device according to claim 1.

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