JP2010217933A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein correct surface temperature of a heat roller can not be obtained and correct temperature controlling of the surface temperature of the heat roller can not be performed since detected temperature changes by a surrounding environment when the surface temperature of the heat roller of a fixing device is detected by a non-contacting thermistor. <P>SOLUTION: The surface temperature of the heat roller 21 is calculated by calculating the detected temperature T1 detected by the non-contacting thermistor 54 which is arranged near the peripheral surface of the heat roller 21, and the detected temperature T3 of a contacting-type thermistor 501 which detects temperature of a pressure roller 22 in order to detect the surface temperature of the heat roller 21, by starting rotation when the detected temperature T1 reaches predetermined rotation starting temperature, and by correcting the detected temperature T1 based on the detected temperature T3 after predetermined time passes. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

    The present invention relates to a fixing device and an image forming apparatus, and more particularly to temperature control of a heating member heated by a heat source.

  Conventionally, in this type of temperature control, for example, a non-contact temperature sensor is disposed in the vicinity of the outer peripheral surface of a heat roller (heating roller) of a fixing device, and the heat roller is based on a detected temperature detected by the non-contact temperature sensor. Proposes a method to correct when the heating element that heats the heater is turned on and off to control the surface temperature of the heat roller, depending on whether printing is in progress or the detected temperature is rising or falling Has been. (For example, refer to Patent Document 1).

Japanese Patent Laid-Open No. 2001-242741 (first page, FIG. 1)

  However, the temperature difference between the surface temperature of the heating member that heats the recording medium and the temperature detected by the non-contact temperature detecting member changes depending on the environmental temperature such as the cover temperature of the fixing device, and the measurement error due to this is corrected. I couldn't.

  An object of the present invention is to provide a fixing device capable of always accurately controlling the surface temperature of a heating member for heating a recording medium by always obtaining an accurate surface temperature of the heating member, regardless of the use state of the fixing device. An object of the present invention is to provide an image forming apparatus using the same.

A fixing device as a reference example is a fixing device that fixes a toner image on a recording medium.
A heating source that is heated by the heating source and that heats the recording medium, a first temperature detection member that detects the temperature of the heating member at a position spaced apart from the heating member, and the first A second temperature detection member provided in the vicinity of the temperature detection member; and a control unit that controls energization of the heat source based on the detected temperatures of the first and second temperature detection members. Features.

Another fixing example is a fixing device for fixing a toner image on a recording medium.
A heat generation source, a heating member heated by the heat generation source to heat the recording medium, a pressure member biased by the heating member to pressurize the recording medium, and a heat shield to prevent heat dissipation of the heating member. A cover, a temperature detection member for detecting temperature, and a movement drive means for moving the temperature detection member between a first position in the vicinity of the peripheral surface of the heating member and a second position in contact with the cover. And detecting the temperature of the heating member detected by the temperature detecting member at the first position and detecting the cover detected by the temperature detecting member at the second position. And control means for controlling the heat generation of the heat source based on the temperature.

A fixing device according to the present invention is a fixing device for fixing toner on a recording medium.
A heat source, a heating member heated by the heat source to heat the recording medium, a pressure member biased by the heating member to press the recording medium, and a position spaced from the heating member, A first temperature detecting member that detects the temperature of the heating member, a third temperature detecting member that detects the temperature of the pressurizing member, and the detected temperature detected by the third temperature detecting member. And a control unit that corrects the detected temperature of the temperature detection member and controls the energization of the heat source based on the corrected detected temperature, and the control unit determines the rotation start temperature of the heating member. The rotation is started when the temperature detected by the first temperature detection member reaches the rotation start temperature. After a predetermined time has elapsed, the rotation is started based on the detection temperature detected by the third temperature detection member. Compensates the detected temperature of the first temperature detection member Characterized in that it.

A fixing device according to another invention is a fixing device for fixing toner on a recording medium.
A heat source, a heating member heated by the heat source to heat the recording medium, a pressure member biased by the heating member to press the recording medium, and a position spaced from the heating member, A first temperature detection member for detecting the temperature of the heating member; a third temperature detection member for detecting the temperature of the pressure member at a position contacting the pressure member; and the first and third temperatures. Control means for controlling the heat generation of the heat source based on each detection temperature of the detection member, and the control means is in a warm state where the ambient temperature of the first temperature detection member is saturated and stable. It is determined whether there is a cold state that does not reach the warm state, and the temperature control in the warm state is different from the temperature control in the cold state.

Furthermore, an image forming apparatus according to the present invention includes:
A recording medium conveying unit that conveys the recording medium; a toner image forming unit that forms a toner image on the recording medium; and the fixing device that fixes the toner image formed on the recording medium. To do.

  According to the present invention, even when the surface temperature of the heating member of the fixing device is detected by the non-contact type temperature detection member, the surface temperature of the heating member is always accurately calculated regardless of the use state of the fixing device. Therefore, it is possible to provide a fixing device capable of always accurately controlling the surface temperature of the heating member, and an image forming apparatus using the same.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram illustrating a main configuration of a first embodiment of an image forming apparatus including a fixing device according to the present invention. FIG. 3 is a perspective view of the upper cover 51 and the heating roller 21 of the fixing device 213 according to the first embodiment of the present invention as viewed obliquely from above. FIG. 3 is a perspective view seen from obliquely below to show the internal structure of the upper cover 51. 2 is a cross-sectional view taken along line AA in FIG. 2 and shows a configuration of a main part of the position adjusting mechanism 62 of the non-contact thermistor 54. FIG. FIG. 2 is a cross-sectional view taken along the line BB in FIG. 2 and shows a main part configuration of the fixing device 213. 3 is a block diagram illustrating a configuration of a control system of the image forming unit 100 of the image forming apparatus 200. FIG. 6 is a graph showing changes over time in the actual temperature T0 of the surface of the heating roller 21, the detected temperature T1 by the non-contact type thermistor 54, and the detected temperature T2 of the upper cover 51 by the cover temperature detecting thermistor 60. 4 is an explanatory diagram for explaining a state of a temperature distribution between the surface of the heating roller 21 and a cover temperature detection thermistor 60 attached to the upper cover 51. FIG. 6 is a flowchart illustrating a flow of temperature control of the fixing device 213 performed by the print control unit 101. It is the perspective view which looked at the upper cover 51 and the heating roller 21 of the fixing device 300 of Embodiment 2 based on this invention from diagonally upward. It is the elements on larger scale which expanded the vicinity of the action gear 303 in FIG. FIG. 11 is a side view of a main part of the fixing device 300 shown in FIG. 10 as seen through from the plus side of the Y axis. FIG. 11 is a side view of a main part of the fixing device 300 shown in FIG. 10 as seen through from the plus side of the Y axis. It is sectional drawing which shows the principal part structure of the fixing device of Embodiment 3 based on the fixing device of this invention. FIG. 10 is a block diagram illustrating a configuration of a control system of an image forming unit of an image forming apparatus employing a fixing device according to a third embodiment. In Embodiment 3, when the heating roller is warmed from the room temperature state and maintains the vicinity of the predetermined temperature in the warm state, the actual temperature of the surface of the heating roller, the temperature detected by the non-contact thermistor, and the non-contact thermistor It is the graph which showed each time change of ambient temperature. In Embodiment 3, after the heating roller rises to a predetermined temperature and its rotation is started, the relationship between the pressure roller detection temperature and the detection temperature difference after N seconds has passed is obtained by experiment and plotted. is there. 10 is a flowchart illustrating a flow of temperature control of a fixing device performed by a print control unit based on a surface calculation temperature T in Embodiment 3. 10 is a flowchart illustrating a flow of temperature control of a fixing device performed by a print control unit based on a surface calculation temperature T in Embodiment 3. In Embodiment 4, when the heating roller is warmed from the room temperature state and maintains the vicinity of the predetermined temperature in the warm state, the actual temperature of the surface of the heating roller, the temperature detected by the non-contact type thermistor, the periphery of the non-contact thermistor 6 is a graph showing changes over time in the temperature of the roller, the pressure roller detection temperature, and the roller temperature cumulative index. In the fourth embodiment, the surface calculation temperature obtained by the equation (3) or (5) selected based on the roller temperature cumulative index Q is obtained, and the flow of temperature control of the fixing device performed by the print control unit is obtained. It is a flowchart to show. In the fourth embodiment, the surface calculation temperature obtained by the equation (3) or (5) selected based on the roller temperature cumulative index Q is obtained, and the flow of temperature control of the fixing device performed by the print control unit is obtained. It is a flowchart to show. (A) shows the change of the pressure roller detection temperature when the fixing device motor is changed from the rotating state to the stopped state in the cold state in the fifth embodiment, and (b) is the rotating state of the fixing device motor in the warm state. It is a graph showing the change of the pressure roller detection temperature when it makes it a stop state from. In the fifth embodiment, the relationship between the pressure roller temperature decrease rate obtained by the equation (6) and the initial value of the roller temperature cumulative index at the time when the decrease range of the pressure roller detection temperature is detected is obtained by experiment, and the result It is the graph which showed. In Embodiment 5, the flow of how to calculate the surface calculated temperature according to Equation (3) or (5), which is selected by newly adding the pressure roller temperature decrease rate obtained by Equation (6) to the determination criterion, is shown. It is a flowchart.

Embodiment 1 FIG.
FIG. 1 is a schematic configuration diagram showing the main configuration of Embodiment 1 of an image forming apparatus provided with a fixing device according to the present invention.

  In FIG. 1, an image forming apparatus 200 includes four process units 201 to 204 that respectively form toner images of yellow, magenta, cyan, and black, which are upstream of a conveyance path 220 of a recording medium 205. It is arranged so as to be detachable in order. Since the internal configurations of these process units 201 to 204 are common, the internal configuration will be described by taking, for example, a cyan process unit 203 as an example. Hereinafter, a portion of the image forming apparatus 200 excluding the detachable process units 201 to 204 is referred to as a main body of the image forming apparatus 200.

  In the process unit 203, the photosensitive drum 11 is rotatably arranged in the direction of the arrow, and electric charges are supplied to the surface of the photosensitive drum 11 around the photosensitive drum 11 in order from the upstream side in the rotation direction. A charging roller 12 for charging and an exposure device 13 including an LED head for forming an electrostatic latent image by selectively irradiating light onto the surface of the charged photosensitive drum 11 are disposed. Furthermore, a developing device 14 that generates development by attaching cyan toner to the surface of the photosensitive drum 11 on which the electrostatic latent image is formed, and when the development of the toner on the photosensitive drum 11 is transferred to the recording medium 205 A cleaning blade 15 that removes transfer residual toner remaining on the surface of the photosensitive drum 11 and a neutralization device 16 that removes variations in the surface potential of the photosensitive drum 11 are disposed. Note that the drums or rollers used in these devices rotate as a result of power being transmitted from a drive source (not shown) via gears, as will be described later.

  In addition, the image forming apparatus 200 has a paper cassette 206 for storing a recording medium 205 such as paper in a lower portion of the image forming apparatus 200, and the recording medium 205 is separated and conveyed one above the other. A hopping roller 207 is provided. Further, by sandwiching the recording medium 205 together with the pinch rollers 208 and 209 on the downstream side of the hopping roller 207 in the conveying direction of the recording medium 205, the conveying roller 210 for conveying the recording medium and the recording medium 205 are skewed. A registration roller 211 that is corrected and conveyed to the process unit 201 is disposed. The hopping roller 207, the conveying roller 210, and the registration roller 211 are rotated by power transmitted from a driving source (not shown) via a gear or the like.

  A transfer roller 212 formed of conductive rubber or the like is disposed at a position facing each photoconductor drum 11 of the process units 201 to 204. These transfer rollers 212 have a potential difference between the surface potential of each photoconductive drum 11 and the surface potential of each of these transfer rollers 212 when transferring the toner image of the toner attached on the photoconductive drum 11 to the recording medium 205. A voltage for applying the voltage is applied. The process units 201 to 204 and the transfer roller 212 correspond to a toner image forming unit that forms a toner image on a recording medium.

  The fixing device 213 includes a heating roller 21 and a pressure roller 22 as will be described later, and fixes the toner transferred onto the recording medium 205 by applying pressure and heating. The downstream discharge rollers 214 and 215 sandwich the recording medium 205 discharged from the fixing device 213 together with the pinch rollers 216 and 217 of the discharge unit and convey the recording medium 205 to the recording medium stacker unit 218. The fixing device 213, the discharge roller 214, and the like are rotated by transmission of power from a drive source (not shown) via a gear. The belt conveyance device 219 forms a conveyance path for the print medium 205 to move the process units 201 to 204, and conveys the recording medium 205 discharged from the registration roller 211 to the carry-in position of the fixing device 213. Along with the belt conveying device 219, the rollers 207 to 211 and 214 to 217 forming the conveying path 220 correspond to conveying means for conveying the recording medium.

  Note that the XYZ coordinates in the figure are the X-axis in the transport direction when the recording medium 205 passes through each process unit, the Y-axis in the rotational axis direction of the photosensitive drum 11, and are orthogonal to these two axes. The Z axis is taken in the direction. Further, when XYZ coordinates are shown in other drawings to be described later, the axial directions of these coordinates indicate a common direction. A portion indicated by a dotted line represents a medium reversing mechanism for performing double-sided printing, but detailed description in this embodiment is omitted.

  FIG. 2 is a perspective view of the upper cover 51 and the heating roller 21 of the fixing device 213 according to the first embodiment based on the fixing device of the present invention as seen obliquely from above. FIG. 3 shows the internal structure of the upper cover 51. It is the perspective view seen from diagonally downward for showing. 4 is a cross-sectional view taken along the line AA in FIG. 2 and shows a configuration of a main part of the position adjusting mechanism 62 of the non-contact type thermistor 54. FIG. 5 shows a line BB in FIG. FIG. 2 is a cross-sectional view showing the main configuration of the entire fixing device 213.

  As shown in FIG. 5, the fixing device 213 includes an external cylindrical heating roller 21 that is rotationally driven in a direction indicated by an arrow by a fixing device motor 122 (FIG. 6) (not shown), and rotates with the heating roller 21. Similarly, it has a cylindrical pressure roller 22. The rotary shaft 22 a of the pressure roller 22 is rotatably held by a moving bearing 23 that is held by a moving guide portion 52 a formed on the lower cover 52 so as to be movable in the vertical direction. The moving bearing 23 is urged upward by the pressure spring 24, that is, toward the heating roller 21. Therefore, the pressure roller 22 is configured to rotate along with the rotation of the heating roller 21 in a state where the peripheral surface is in contact with the peripheral surface of the heating roller 21 with a predetermined pressure.

  Inside the heating roller 21, for example, an outer cylindrical halogen lamp 53 as a heat source for heating a roller having an elastic layer formed of a rubber material extends in the direction of the rotation axis of the heating roller 21. The surface temperature of the heating roller 21 is adjusted by turning on / off the halogen lamp 53 at a timing described later. The non-contact thermistor 54 corresponding to the first temperature detection member is held at the tip of the sensor frame 55 to detect the surface temperature of the heating roller 21 and is positioned at a predetermined position near the peripheral surface of the heating roller 21. Be placed. The sensor frame 55 is held by the position adjusting mechanism 62 outside the upper cover 51, and holds the non-contact type thermistor 54 at the tip portion extending into the upper cover 51 through the opening 51a.

  The position adjustment mechanism 62 includes a plate spring 57, a pair of support members 58 (FIG. 4) that support both ends thereof, a frame holding portion 57a that sandwiches the sensor frame 55 at the center of the plate spring 57, and a sensor frame. 55 and the frame holding portion 57a, and an adjustment screw 56 that is screwed into the screw hole of the upper cover 51. The adjustment screw 56 is turned to adjust the height of the sensor frame 55, thereby adjusting the distance between the non-contact thermistor 54 held at the tip of the sensor frame 55 and the peripheral surface of the heating roller 21. At this time, the height of the sensor frame 55 is maintained by being pressed against the adjustment screw 56 by the restoring force of the plate spring 57.

  A closed space 59 (see FIG. 3) surrounded by the partition wall 51b and the heating roller 21 is formed inside the upper cover 51 from which the sensor frame 55 extends. A cover temperature detection thermistor 60 corresponding to a second temperature detection member for detecting the temperature of the upper cover 51 is disposed on the ceiling of the closed space 59. By forming the closed space 59, the temperature detection of the non-contact thermistor 54 is prevented from being disturbed due to the flow of air around the non-contact thermistor 54. The non-contact type thermistor 54 and the cover temperature detection thermistor 60 are disposed on substantially the same perpendicular line perpendicular to the tangent line of the predetermined peripheral surface of the heating roller 21.

  FIG. 6 is a block diagram illustrating a configuration of a control system of the image forming unit 100 of the image forming apparatus 200. In the figure, a print control unit 101 includes a microprocessor, a ROM, a RAM, an input / output port, a timer, and the like. The print control unit 101 receives print data and control commands from a host device (not shown), and controls the entire image forming unit 100 in sequence. And print operation. The I / F control unit 102 transmits information about the image forming unit to the host device, and analyzes and processes commands and data input from the host device. The reception memory 103 stores data received from the host device for each color of yellow (Y), magenta (M), cyan (C), and black (K) based on the control of the I / F control unit 102. The image data editing memory 104 stores image data edited by the print control unit 101 based on the print data.

  The operation unit 105 includes an LED for displaying the state of the image forming unit and a switch for giving an instruction from the operator to the image forming unit, and various sensors 106 include a plurality of sensors for detecting a print medium conveying device, A sensor for detecting temperature and humidity in the apparatus, a sensor for measuring density, and the like are included, and the output of each sensor is input to the print control unit 101.

  The charging voltage control unit 110 applies a voltage to the charging roller 12 disposed around the photosensitive drum 11 (FIG. 1) according to an instruction from the printing control unit 101 to charge the surface of each photosensitive drum 11. Take control. As shown in FIG. 1, this charging is individually applied to four photosensitive drums 11 arranged for each color of yellow (Y), magenta (M), cyan (C), and black (K). Therefore, the charging voltage control unit 110 and the charging roller 12 are provided for each color.

  In accordance with the image data stored in the image data editing memory 104, the head control unit 111 irradiates light onto the surface of the charged photosensitive drum 11 by the LED head 13a of the exposure device 13 (FIG. 1), thereby electrostatic latent. Control is performed to form an image. As shown in FIG. 1, this electrostatic latent image is formed by four photoconductors arranged for each of yellow (Y), magenta (M), cyan (C) and black (K). Since it is performed individually on the drum 11, the head controller 111 and the LED head 13a are provided for each color.

  The developing voltage control unit 112 forms a toner image in which toner is attached to the electrostatic latent image generated on the surface of the photosensitive drum 11 in accordance with an instruction from the printing control unit 101. Control for applying a voltage to 14a (FIG. 1) is performed. As shown in FIG. 1, this toner image is formed by four photosensitive drums 11 arranged for each color of yellow (Y), magenta (M), cyan (C) and black (K). Therefore, the developing voltage control unit 112 and the developing roller 14a are provided for each color.

  The transfer voltage control unit 113 controls the voltage applied to the transfer roller 212 (FIG. 1) in order to transfer the toner image generated on the surface of the photosensitive drum 11 to the recording medium 205 (FIG. 1) according to an instruction from the print control unit 101. The control for applying is performed. As shown in FIG. 1, this transfer is individually performed by four photosensitive drums 11 arranged for each color of yellow (Y), magenta (M), cyan (C), and black (K). Therefore, the transfer voltage control unit 113 and the transfer roller 212 are provided for each color.

  The motor control unit 114 includes various motors 120 such as a photosensitive drum 11, a charging roller 12, a unit motor for driving the rollers of the developing device 14, and a belt motor for driving the belt conveying device 219 shown in FIG. 1. Control to drive.

  As shown in FIG. 1, the transport motor control unit 115 includes a hopping roller 207 for feeding the recording medium 205 from the paper cassette 206, and rollers 210 and 211 for transporting the fed recording medium 205 to the belt transport device 219. And a transport motor 121 for driving the rollers 214 and 215 for discharging the printed recording medium.

  A fixing control unit 116 for controlling the fixing device 213 shown in FIG. 5 for fixing the toner image transferred to the recording medium 205 is a halogen lamp 53 disposed inside the heating roller 21 in accordance with an instruction from the printing control unit 101. Control to apply (energize) a voltage to is performed. The fixing controller 116 also detects the detected temperatures T1 and T2 from the non-contact type thermistor 54 for measuring the surface temperature of the heating roller 21 and the cover temperature detection thermistor 60 for detecting the temperature of the upper cover 51, respectively. As will be described later, the halogen lamp 53 is turned on / off based on both detected temperatures. Further, the fixing control unit 116 controls the fixing device motor 122 for rotationally driving when the heating roller 21 rises to a predetermined temperature. Further, a timer 116a for measuring intervals of temperature detection and temperature control, which will be described later, and a register 116b for storing the fixing target temperature are provided.

  Next, the operation of the main part of the image forming unit 100 of the image forming apparatus 200 configured as described above will be described.

  The print control unit 101 receives a control command transmitted from the host device via the I / F control unit 102. When a printing instruction is received by the host device, first, an instruction is given to the fixing control unit 116, and the heating roller 21 (calculated by a method described later based on the detected temperatures of the non-contact type thermistor 54 and the cover temperature detecting thermistor 60 ( It is determined whether or not the calculated surface temperature T in FIG. 5 is within a predetermined usable temperature range. If the calculated surface temperature T is not within the above temperature range, the halogen lamp 53 is turned on and the heating roller 21 is heated until it reaches the usable temperature range. When the surface temperature of the heating roller 21 rises to a predetermined temperature, the fixing control unit 116 instructs the fixing device motor 122 to drive the fixing device motor 122 to rotate the heating roller 21. This rotation operation may be performed simultaneously with the temperature control.

  Next, a unit motor for driving the respective photosensitive drums 11, the charging roller 12, and the roller of the developing device 14 shown in FIG. 1 and a belt motor for driving the belt conveying device 219 via the motor control unit 114. Is controlled. At the same time, an instruction is given to the charging voltage control unit 110, the development voltage control unit 112, and the transfer voltage control unit 113, and the charging roller 12 for each color of yellow (Y), magenta (M), cyan (C), and black (K). A predetermined voltage is applied to each of the developing roller 14a and the transfer roller 212.

  Then, the print control unit 101 instructs the transport motor control unit 115 to start transporting the recording medium 205 set in the paper cassette 206 shown in FIG. 1 and starts transporting the recording medium 205.

  The print control unit 101 monitors the timing at which the recording medium 205 has reached a predetermined printable position with a detector (not shown), and prints an image from the image data editing memory 104 at the detection timing at which the recording medium 205 has reached this predetermined position. Data is read and sent to the head controller 111. The head control unit 111 sends a latch signal to the LED head 13a of the exposure apparatus 13 when it receives the image data for one line, and holds the image data in the LED head. Then, the head controller 111 sends a print drive signal STB to the LED head. As a result, the LED head performs exposure line by line in accordance with the stored image data.

  The LED head 13a irradiates the surface of the photosensitive drum 11 charged to a negative potential, and forms an electrostatic latent image with dots whose potential has increased by this irradiation. Then, the toner charged to a negative potential is attracted to each dot by an electrical attraction force to form a toner image. Thereafter, the toner image is sent to a transfer portion formed between the photosensitive drum 11 and the transfer roller 212. On the other hand, the print control unit 101 instructs the transfer voltage control unit 113 to apply a positive transfer high voltage to the transfer roller 212. As a result, the transfer roller 212 transfers the toner image to the recording medium 205 that passes through the transfer portion.

  The above exposure, toner image formation, and transfer are sequentially performed each time the recording medium 205 passes through the yellow (Y), magenta (M), cyan (C), and black (K) process units 201-204. The toner images of each color are sequentially transferred onto the recording surface and superimposed.

  The recording medium 205 onto which the toner image has been transferred is sent to the fixing device 213 and is heated and pressed in the process of passing between the heating roller 21 and the pressure roller 22 that are rotated in contact with each other. The toner image is fixed on the recording medium 205. The recording medium 205 on which the toner image is fixed is sandwiched between discharge rollers 214 and 215 and pinch rollers 216 and 217 shown in FIG. 1 and discharged to a recording medium stacker unit 218 outside the image forming apparatus 200. Through the above process, a color image is formed on the recording medium 205. Further, the printing control unit 101 monitors the timing when printing is finished and the recording medium 205 passes through a paper discharge port sensor (not shown), and at this time, each of the charging roller 12, the developing roller 14a, and the transfer roller 212 is transferred. The voltage application is terminated and the operation of each motor is stopped simultaneously. Thereafter, the above-described operation is repeated.

  Next, a method for calculating the surface calculation temperature T of the heating roller 21 (FIG. 5) performed according to the present embodiment will be described.

  As shown in FIG. 5, the heating roller 21 is heated by a halogen lamp 53. The non-contact type thermistor 54 disposed at a predetermined interval from the surface of the heating roller 21 changes its temperature in response to the radiant heat radiated from the surface of the heating roller 21, and the detected temperature T1 is changed to the fixing controller 116 ( To FIG. 6). The cover temperature detection thermistor 60 attached to the upper cover 51 also sends the detected temperature T2 of the upper cover, which is heated by the radiant heat and changes in temperature, to the fixing control unit 116.

  FIG. 7 shows the actual temperature T0 of the surface of the heating roller 21 and the detected temperature T1 by the non-contact thermistor 54 when the heating roller 21 is heated from the room temperature state by the halogen lamp 53 and controlled at a constant temperature around 162 ° C. And a graph showing each time change of the detected temperature T2 of the upper cover 51 by the cover temperature detection thermistor 60.

  Printing is started as described above when the heating roller 21 is warmed by the halogen lamp 53 from a cooled state and is heated to approximately 162 ° C. At this time, the detected temperature T1 indicated by the non-contact type thermistor 54 is lower than the actual surface temperature T0, and the difference Td between the actual surface temperature T0 and the detected temperature T1 is the initial value when the cover temperature (detected temperature T2) is low. The state is the largest, and as the cover temperature (detected temperature T2) increases with time, the difference is reduced.

  On the other hand, FIG. 8 is an explanatory diagram for explaining the state of temperature distribution between the surface of the heating roller 21 and the cover temperature detection thermistor 60 attached to the upper cover 51.

  As shown in the figure, a non-contact type thermistor 54 disposed between the surface of the heating roller 21 and a cover temperature detection thermistor 60 attached to the upper cover 51 reaches the surface of the heating roller 21. When the distance is L1 and the distance to the upper cover 51 is L2, it is expected that the position of the non-contact type thermistor 54 increases in proportion to approaching the surface of the heating roller 21. However, the maximum of the change range is the actual surface temperature T0 of the heating roller 21, and the minimum value is the detected temperature T2 of the upper cover.

  Therefore, in order to obtain the actual surface temperature T0 by calculation, the surface calculated temperature T is obtained by the following equation (1).

T = T1 + (T1-T2) * (L1 / L2) * C (1)
However, C: Coefficient T1: Detection temperature of the non-contact type thermistor 54 T2: Detection temperature of the upper cover by the cover temperature detection thermistor 60 The surface calculated temperature T shown in the graph of FIG. 7 is based on the above equation (1). ,
(L1 / L2) * C = 1/6 is obtained by calculating the coefficient C. It is understood from this experiment that the calculated surface temperature T substantially matches the actual surface temperature T0. However, L1 and L2 are about 1 mm and 8 mm, respectively, and the surface temperature of the heating roller 21 is about 150 ° C. to about 180 ° C.

  As described above, the actual surface temperature of the heating roller 21 can be accurately calculated based on the detected temperature T1 of the non-contact thermistor 54 and the detected temperature T2 of the cover temperature detecting thermistor 60.

  FIG. 9 is a flowchart showing a flow of temperature control of the fixing device 213 performed by the print control unit 101 based on the calculated surface temperature T. Hereinafter, a temperature control method of the fixing device 213 will be described with reference to this flowchart.

  The print control unit 101 (FIG. 6) starts the fixing temperature control by receiving a print control command (print start command) from the host device, and first, an execution interval time measured by a timer to determine the temperature control execution interval. Tm is set in the timer 116a in the fixing control unit 116, the fixing temperature is determined according to the type of printing medium and printing conditions (color printing, monochrome printing), and the determined temperature is used as the fixing target temperature in the fixing control unit 116. (Step 1).

  Next, the timer 116a is started (step 2). When the measurement time reaches a preset execution interval time Tm (here, 100 ms), the timer is stopped (steps 3 and 4), and the non-contact thermistor 54 is detected. The temperature T1 and the detection temperature T2 of the cover temperature detection thermistor 60 are taken in (step 5). Then, the above-described equation (1) is calculated, and a surface calculated temperature T corresponding to the surface temperature T0 of the heating roller 21 is calculated from these detected temperatures T1 and T2 (step 6).

  Note that L1, L2 and coefficient C indicating the positions of the non-contact type thermistor 54 and the cover temperature detection thermistor 60 in the same equation are set in advance in the memory of the print control unit 101 based on the experimental results. Here, L1 = 1 mm, L2 = 8 mm, and C = 4/3.

  Next, the calculated surface calculated temperature T is compared with a preset fixing target temperature (step 7), and if it is below the fixing target temperature, the halogen lamp 53 is turned on (step 8), and the fixing target temperature is exceeded. If so, the halogen lamp 53 is turned off (step 9). Next, it is determined whether or not the printing operation is finished (step 10). If the printing operation is continued, the process returns to step 2 and the same operation is repeated. When the printing operation is finished, the halogen lamp 53 is turned off. (Step 11) The fixing temperature control operation is terminated. Although the start of printing has not been described here, the printing is started after the calculated temperature T reaches the target temperature, and then the control of ST2 to ST9 is performed and the printing is performed so as to maintain the target temperature. It has been broken.

  The fixing device according to the present embodiment includes a fixing unit 213, a fixing control unit 116, and a part related to the control of the fixing unit 213 of the printing control unit 101, and the temperature of the fixing unit 213 of the fixing control unit 116 and the printing control unit 101. The part related to the control corresponds to a control means for controlling the heat generation of the halogen lamp based on the detected temperatures T1 and T2.

  As described above, the fixing device of the present embodiment accurately calculates the actual surface temperature of the heating roller 21 from the detected temperatures of the two thermistors, the non-contact type thermistor 54 and the cover temperature detecting thermistor 60. Therefore, temperature control for maintaining the surface temperature of the heating roller 21 at the fixing target temperature can be accurately performed.

Embodiment 2. FIG.
10 is a perspective view of the upper cover 51 and the heating roller 21 of the fixing device 300 according to the second embodiment of the present invention as seen obliquely from above. FIG. 11 is an enlarged view of the vicinity of the working gear 303 in FIG. It is an enlarged view. 12 and 13 are side views of the main part as seen through the fixing device 300 shown in FIG. 10 from the plus side of the Y axis.

  The fixing device employing this fixing device 300 is mainly different from the above-described fixing device employing the fixing device 213 of the first embodiment shown in FIG. 2 in that the thermistor 312 is arranged around the heating roller 21 shown in FIG. This is a point that is configured to be movable between a predetermined position P1 in the vicinity of the surface and an upper cover temperature detection position P2 that contacts the upper cover 51 shown in FIG.

  Accordingly, in the fixing device employing the fixing device 300, the same reference numerals are given to the parts common to the fixing device employing the fixing device 213 (FIG. 2) of the first embodiment described above, or the drawing is omitted. The explanation is omitted, and different points are explained mainly.

  As shown in FIGS. 12 and 13, the upper cover 51 has a sensor frame 315 that holds the thermistor 312 at its tip, a predetermined position P1 in the vicinity of the peripheral surface of the heating roller 21 shown in FIG. Between the upper cover temperature detection position P2 which contacts the upper cover 51, it hold | maintains so that a slide to a Z-axis direction is possible. The sensor frame 315 is formed integrally with a rack gear 311 that is outside the upper cover 51 and extends in the Z-axis direction. A compressed spring 310 is placed between the sensor frame 315 and the upper cover 51 to urge the sensor frame 315 in the negative direction of the Z-axis, that is, the direction in which the thermistor 312 is brought closer to the heating roller 21. .

  On the outer side of the upper cover 51, a slide drive mechanism 301 that slides the sensor frame 315 is formed. The slide drive mechanism 301 includes a drive shaft 304 that is rotatably held by the upper cover 51, and a transmission gear 302 that is disposed at one end of the drive shaft 304 to transmit the rotation of a rotary drive motor (not shown). And a working gear 303 which is disposed at the other end of the drive shaft 304 and meshes with a rack gear 311 formed integrally with the sensor frame 315.

  The operation of each part in the above configuration will be described.

  When the drive shaft 304 is rotated in the direction of arrow E by a rotation drive motor (not shown), the rack gear 311 that meshes with the action gear 303 and the thermistor 312 are positioned in the vicinity of the peripheral surface of the heating roller 21 together with the sensor frame 315. , And moves upward against the urging force of the spring 310, and eventually the thermistor 312 reaches the upper cover temperature detection position P2 where it contacts the upper cover 51, and stops moving as shown in FIG. Here, when the driving force by the rotation driving motor is released, the sensor frame 315 is again returned to the predetermined position P1 shown in FIG. Note that the slide movement mechanism 301, the sensor frame 315, the rack gear 311 and the spring 310 correspond to the movement driving means.

  Therefore, when the temperature control of the fixing device 300 is performed, the print control unit 101 (FIG. 6) performs the process according to the flow shown in FIG. 9 described above, but the process of step 5 is performed as follows. That is, in this step 5, the thermistor 312 detects the detected temperature T1 at a predetermined position P1 located in the vicinity of the peripheral surface of the heating roller 21, and then the drive shaft 304 is moved in the direction of arrow E by a rotary drive motor (not shown). It rotates and moves the thermistor 312 to the upper cover temperature detection position P2 that contacts the upper cover 51, and detects the detected temperature T2 of the upper cover 51. When the detected temperature T2 is detected, the driving force by the rotary drive motor is released, and the thermistor 312 is returned to the predetermined position P1 again.

  As described above, since temperature control is executed according to the flowchart shown in FIG. 9 except for step 5, the description of the overlapping parts is omitted here.

  As described above, according to the fixing device of the second embodiment, the same effects as those of the first embodiment can be obtained, and each surface of the heating roller 21 and each of the upper cover 51 can be obtained with one thermistor. Since temperature detection can be performed, an inexpensive fixing device can be provided.

  In the first and second embodiments, the example of detecting the temperature of the upper cover 51 has been shown as a reliable method for detecting the ambient temperature of the non-contact type thermistor 54. However, the present invention is not limited to this. It suffices if the ambient temperature of the non-contact type thermistor 54 can be detected inside the fixing device.

Embodiment 3 FIG.
FIG. 14 is a cross-sectional view showing a main configuration of a fixing device 500 according to the third embodiment based on the fixing device of the present invention. This cross section corresponds to the cross section taken along the line BB in the perspective view of FIG. 2 of the fixing device 213 of the first embodiment described above.

  The main difference between the fixing device 500 and the fixing device 213 of the first embodiment shown in FIG. 5 is that the cover temperature detection thermistor 60 (FIG. 5) is removed and the surface of the pressure roller 22 is contacted instead. The contact thermistor 501 for detecting the surface temperature is provided. Accordingly, parts common to the fixing device 213 of the first embodiment described above are denoted by the same reference numerals, or the drawings are omitted and the description thereof is omitted here, and different points are mainly described. To do.

  As shown in FIG. 14, the contact thermistor 501 is fixed to the lower cover 52 by a fixing screw 503 so as to be in contact with the circumferential surface of the pressure roller 22 while maintaining a predetermined pressure slightly. It is attached to the tip.

  FIG. 15 is a block diagram illustrating a configuration of a control system of the image forming unit 505 of the image forming apparatus employing the fixing device 500 according to the present embodiment. The image forming apparatus employing the fixing device 500 is different from the image forming apparatus 200 shown in FIG. 1 in that the fixing device 500 is used instead of the fixing device 213, and accordingly, as shown in FIG. The image forming unit 100 is an image forming unit 505 described later. Therefore, in the present embodiment, when describing the image forming apparatus, the image forming apparatus 100 in FIG. 1 is referred to.

  The image forming unit 505 (FIG. 15) differs from the image forming unit 100 of the first embodiment shown in FIG. 6 in that the configuration of the fixing device 500, that is, the cover temperature detection thermistor 60 (FIG. 6) is used. Thus, a contact thermistor 501 that detects the surface temperature of the pressure roller 22 by contacting the surface is employed, and a signal processing method performed by the print control unit 504 in accordance therewith. Accordingly, parts common to the image forming unit 100 of the first embodiment described above are denoted by the same reference numerals, description thereof is omitted, and different points are mainly described.

  A fixing control unit 116 for controlling the fixing device 500 shown in FIG. 14 for fixing the toner image transferred to the recording medium 205 (FIG. 1) is disposed inside the heating roller 21 according to an instruction from the printing control unit 504. Control for applying a voltage (energization) to the halogen lamp 53 is performed. The fixing controller 116 includes a non-contact thermistor 54 for measuring the surface temperature of the heating roller 21 and a contact thermistor 501 that contacts the surface of the pressure roller 22 and detects the surface temperature of the pressure roller. The detection temperatures T1 and T3 are received, and the halogen lamp 53 is on / off controlled based on both detection temperatures, as will be described later.

  Next, a method for calculating the surface calculation temperature T of the heating roller 21 (FIG. 14) performed according to the present embodiment will be described.

  FIG. 16 shows an actual temperature T0 on the surface of the heating roller 21 when the heating roller 21 is heated from the room temperature state (cold state) by the halogen lamp 53 and is maintained in the vicinity of a predetermined temperature in the warm state described later. 6 is a graph showing changes over time of a detected temperature T1 by the non-contact thermistor 54 and a temperature T2 around the non-contact thermistor 54 (internal atmosphere temperature, fixing device cover temperature, etc.).

  As shown in the graph, the temperature T1 detected by the non-contact type thermistor 54 is detected by a contact type thermistor (not shown) that is experimentally arranged to detect the actual surface temperature of the heating roller 21. When compared with T0, the non-contact type thermistor 54 detects a temperature lower than the actual surface temperature T0 by the distance from the surface of the heating roller 21. At this time, the difference between the detected temperatures becomes larger as the gap from the surface of the heating roller 21 to the non-contact type thermistor 54 becomes larger. Conversely, when the gap is set to 0, there is theoretically no difference. .

  However, even if a predetermined gap is maintained, the detected temperature difference T4 (= T0−T1) is not constant, and is experimentally arranged to detect the ambient temperature of the non-contact thermistor 54. After increasing once as the ambient temperature T2 detected by the thermistor (for example, the cover temperature detection thermistor 60 in the first embodiment (FIG. 5)) increases, it gradually decreases, and the ambient temperature T2 eventually reaches saturation. Then, it has been confirmed by experiments that the temperature becomes almost constant (although there is a slight difference when the overheating roller 21 is stopped / rotating / sheet feeding, there is no problem in fixing performance).

  This is because in the process of transition from the cold state to the warm state where the ambient temperature T2 is saturated, the air around the non-contact thermistor 54 is gradually warmed and the amount of radiant heat from the peripheral cover is reduced. The temperature difference between the actual surface temperature of the pressure roller 21 and the detected temperature of the non-contact type thermistor 54 fluctuates due to the gradual increase, but they are constant when reaching the warm region. Therefore, the temperature difference is considered to be stable.

  In the first and second embodiments, the method of obtaining the ambient temperature T2 as the detected temperature of the upper cover 51 and calculating the actual surface temperature T0 of the heating roller 21 by a predetermined calculation is shown. On the other hand, in the present embodiment, the pressure roller detection temperature T3 of the contact type thermistor 501 that contacts the surface of the pressure roller 22 and detects the surface temperature of the pressure roller 22 is obtained, and the actual surface temperature of the heating roller 21 is obtained. T0 is calculated, and the calculation method will be described below.

FIG. 17 shows that after printing starts and the heating roller 21 rises to a predetermined temperature and starts rotating, N seconds, which is the time required for the surface temperature of the pressure roller 22 to be further leveled, are passed. The relationship between the pressure roller detected temperature T3 (N) and the detected temperature difference T4 (= T0−T1) is obtained by experiment and plotted. From this experimental result, the relationship between the pressure roller detected temperature T3 (N) and the calculated detected temperature difference T4 ′ is expressed by the following linear expression (2)
T4 ′ [° C.] = A * T3 (N) [° C.] + B (2)
a, b: can be expressed as a constant. Note that the detected temperature difference obtained by calculation is distinguished from the actual detected temperature difference T4 as T4 ′.

  The reason for this is that immediately after printing is started and the fixing device motor 122 (FIG. 15) starts to rotate, the heating roller 21 gradually accumulates and rises because it does not have a heating element. It shows that the process of increasing the surface temperature of the pressure roller 22 is very correlated with the temperature increase inside the fixing device. Furthermore, the pressure roller detection temperature T3 (N) after N seconds has elapsed since the rotation of the pressure roller 21 is started can be used as an alternative to the means for reading the ambient temperature T2 at this time. Yes.

The relationship between the detected temperature T1 of the non-contact thermistor 54 and the actual surface temperature T0 of the heating roller is
T0 [° C.] = T1 [° C.] + T4 [° C.]
It is. Therefore, in order to obtain the actual surface temperature T0 by calculation, the surface calculated temperature T is obtained by the following equation (3).
T [° C.] = T 1 [° C.] + T 4 ′ [° C.]
= T1 [° C.] + A * T3 (N) [° C.] + B (3)
By using this relational expression (3), the detected temperature T1 of the non-contact type thermistor 54 and the pressure roller detected temperature T3 of the contact type thermistor 501 particularly in the fixing device 500 in the transition process from the cold state to the warm state. Based on (N), the actual surface temperature of the heating roller 21 can be accurately calculated.

  18 and 19 are flowcharts showing a flow of temperature control of the fixing device 500 performed by the print control unit 504 (FIG. 15) based on the surface calculated temperature T. Hereinafter, the temperature control method of the fixing device 500 will be described with reference to this flowchart.

  The print control unit 504 (FIG. 15) starts the fixing temperature control by receiving a print control command (print start command) from the host device, and first, the execution interval time measured by the timer to determine the temperature control execution interval. Tm (for example, Tm = 400 ms) is set in the timer 116a in the fixing controller 116, and the fixing temperature is determined according to the type of printing medium (thick paper, thin paper, OHP, etc.) and printing conditions (color printing, monochrome printing). The determined temperature is set as a fixing target temperature in the register 116b in the fixing control unit 116 (step S101).

  Next, the halogen lamp 53 which is the heater of the heating roller 21 is energized to turn it on (step S102). Thereafter, the detection temperature T1 of the non-contact thermistor 54 is detected, and the detection of the detection temperature T1 is repeated until the detection temperature T1 reaches the rotation start temperature (steps S102 and 103). The rotation start temperature is a temperature set in advance in consideration of a detection error of the detection temperature T1 in order to rotate the heating roller 21 after melting the toner adhering to the heating roller 21. When the detected temperature T1 reaches this rotation start temperature, the fixing device motor 122 is driven to rotate, the heating roller 21 and the pressure roller 22 are rotated in the directions of the arrows, respectively, and the surface temperature of the pressure roller 22 is further increased. Elapsed time (N seconds) for leveling is confirmed (step S105).

  Next, the timer 116a is started (step S106). When the measurement time reaches a preset execution interval time Tm (here, 400 ms), the timer is stopped (steps S107 and 108), and the non-contact type thermistor 54 is detected. The temperature T1 and the detected temperature T3 (N) of the contact type thermistor 501 are taken in (step S109). Then, the above-described equation (3) is calculated, and a surface calculated temperature T corresponding to the surface temperature T0 of the heating roller 21 is calculated from these detected temperatures T1 and T3 (N) (step 110). In the formula, a and b are constants obtained in advance by experiments.

  Next, the calculated surface calculated temperature T is compared with a preset fixing target temperature (step S111), and if it is below the fixing target temperature, the halogen lamp 53 is turned on (step S112), and the fixing target temperature is exceeded. If so, the halogen lamp 53 is turned off (step S113). Next, it is determined whether or not the printing operation is completed (step 114). When the printing operation is continued, the process returns to step S106 and the same operation is repeated. When the printing operation is completed, the halogen lamp 53 is turned off. At the same time, the rotation of the fixing device motor 122 is stopped (step 115), and the fixing temperature control operation is terminated. In step S114, the end of the printing operation is determined by, for example, detecting the trailing end of the recording medium 205 by a sensor (not shown) to detect the discharging operation of the recording medium 205 and confirming that there is no next print data. To judge.

  The fixing device according to the present embodiment includes a fixing unit 500, a fixing control unit 116, and a printing control unit 504 that are related to the control of the fixing unit 500, and the temperature of the fixing device 500 of the fixing control unit 116 and the printing control unit 504. The part related to the control corresponds to a control means for controlling the heat generation of the halogen lamp based on the detected temperatures T1, T3.

  As described above, according to the fixing device of the third embodiment, printing is started with respect to the heating roller temperature detected by the non-contact thermistor 54, and further pressurization is performed after each heating / pressurizing roller rotation is started. By obtaining the pressure roller detection temperature T3 (N) after the elapse of time (N seconds) for equalizing the roller surface temperature, the surface calculated temperature of the heating roller 21 corrected for the detection temperature of the non-contact thermistor 54 T can be obtained. In this case, it is not necessary to provide new temperature detection means for detecting the temperature T2 around the non-contact thermistor 54 such as the fixing device internal temperature and the fixing device cover temperature.

Embodiment 4 FIG.
The difference between the fixing device of the present embodiment and the fixing device of the third embodiment is a signal processing method in the print control unit 504. Therefore, in describing the signal processing method of the fixing device according to the present embodiment, refer to the cross-sectional view of the main part of the fixing device 500 in FIG. 14 and the block diagram showing the configuration of the control system of the image forming unit 505 in FIG. The description of common parts is omitted here, and different points are mainly described. The print control unit according to the present embodiment is different from the print control unit 504 according to the third embodiment in the signal processing method.

  A method for generating the calculated surface temperature T of the heating roller 21 (FIG. 6) performed according to the present embodiment will be described.

  FIG. 20 shows the heating when the heating roller 21 is heated from the room temperature state (cold state) by the halogen lamp 53 and the vicinity of a predetermined temperature in the warm state where the ambient temperature T2 is saturated is maintained. The actual temperature T0 of the surface of the roller 21, the detection temperature T1 by the non-contact thermistor 54, the temperature T2 around the non-contact thermistor 54 (internal atmosphere temperature, fixing device cover temperature, etc.), and the pressure roller detection temperature (contact type) It is the graph which showed each time change of T3 by the thermistor 501.

  As shown in the graph, the detection temperature T1 detected by the non-contact type thermistor 54 is detected by a contact type thermistor (not shown) that is experimentally arranged to detect the actual surface temperature of the heating roller 21. When compared with the temperature T0, the non-contact type thermistor 54 detects a temperature lower than the actual surface temperature T0 by the distance from the surface of the heating roller 21. At this time, the difference between the detected temperatures becomes larger as the gap from the surface of the heating roller 21 to the non-contact type thermistor 54 becomes larger. Conversely, when the gap is set to 0, there is theoretically no difference. . The detected temperature difference T4 shown in the graph is obtained by T4 = T0−T1 as described above.

Here, the roller temperature cumulative index Q indicating the cumulative amount of the detected temperature T1 and the pressure roller detected temperature T3 detected by the non-contact thermistor 54 after the halogen lamp 53 is turned on is obtained by the following equation (4). .
Q = {c * T1 (start) + τ * T3 (start)}
+ ∫ {κ (T1 + T3)} dt (4)
T1 (start): Temperature detected by the non-contact type thermistor 54 immediately after the halogen lamp 53 is turned on [° C.]
T3 (start): temperature detected by the pressure roller immediately after the halogen lamp 53 is turned on (detected by the contact type thermistor 501) [° C.]
c, τ, κ: constant As a characteristic of the roller temperature cumulative index Q obtained by this equation, as shown in FIG. 20, when the value is a predetermined value Q _S (for example, c = τ = 0.5, κ = 5000). The experimental result shows that the time S when Q _S = 100) and the time when the ambient temperature T2 of the non-contact type thermistor 54 is saturated substantially coincide.

The results of this experiment are shown in the following items.
(1) Process in which the halogen lamp 53 generates heat (input),
(2) A process in which the heat is transmitted to the heating roller 21 and the pressure roller 22 and the heat increases the fixing device internal temperature and the fixing device cover temperature through heat transfer or heat radiation,
(3) A process in which the paper takes heat from the heating roller 21 and the pressure roller 22 during paper feeding, and heat from the fixing device 500 is taken away by a cooling fan (not shown) (output).
This is considered to be because each process described above represents an increase in the internal temperature (ambient temperature T2) of the fixing device cover and the fixing frame in a form close to the accumulation of the heating roller temperature and the pressure roller temperature.

In the experimental example shown in FIG. 20, the value of Q is calculated by turning on the halogen lamp 53 in the room temperature state (cold state) of the fixing device 500. Therefore, for example, when the temperature T1 (start) detected by the non-contact type thermistor 54 is 25 ° C. and the pressure roller detection temperature T3 (start) is 25 ° C. when the first halogen lamp 53 is turned on, The initial value of the roller temperature cumulative index Q is (25 + 25) / 2 = 25 <Q _S = 100. Thus, if the obtained roller temperature cumulative index Q is smaller than the predetermined value Q _S, shown in the third embodiment described above equation (3)
T [° C.] = T 1 [° C.] + A * T 3 (N) [° C.] + B
The cold temperature correction for calculating the surface calculated temperature T is executed by

On the other hand, when the power of the halogen lamp 53 is turned on while the fixing device 500 is completely warm, for example, the detection temperature T1 (start) in the non-contact type thermistor 54 is 180 ° C., and the pressure roller detection temperature T3 ( If (start) is 100 ° C., the initial value of the roller temperature cumulative index Q at this time is (180 + 100) / 2 = 140> 100. Thus, if the obtained roller temperature accumulation factor Q is equal to or higher than the predetermined value Q _S, it executes the warm temperature correction to be described later.

Even when this warm temperature correction is executed, the relationship between the detected temperature T1 of the non-contact thermistor 54 and the actual heating roller surface temperature T0 is:
T0 [° C.] = T1 [° C.] + T4 [° C.]
However, as shown in FIG. 20, in the warm region where the ambient temperature T2 of the non-contact thermistor 54 is saturated after the time S, the detected temperature difference T4 becomes a substantially constant correction constant d. . Therefore, at the time of this warm temperature correction, in order to obtain the actual surface temperature T0 by calculation, the surface calculated temperature T is obtained by the following equation (5).
T [° C.] = T 1 [° C.] + D [° C.] (5)
d: Constant determined experimentally

  As described above, in the present embodiment, the roller temperature cumulative index Q is obtained, and thereby whether the ambient temperature T2 is saturated and stable, or whether it is in a cold state that does not reach the warm state. Judgment is made, and the surface calculation temperature T is obtained by calculation suitable for each state.

  The detected temperature correction when the power of the halogen lamp 53 is turned on is performed as described above. However, if the printing operation is not performed for a predetermined period in a series of printing processes in the image forming apparatus, the apparatus is in a standby state. Migrate to In this case, the detected temperature T1 and the pressure roller detected temperature T3 in the non-contact type thermistor 54 are measured as T1 (start) and T3 (start), respectively, at the start of the next printing operation (ie, at the start of temperature control). Then, it is determined whether the cold temperature correction is started or the warm temperature correction is started.

  21 and 22, as described above, the surface calculated temperature T obtained by the equation (3) or (5) selected based on the roller temperature cumulative index Q obtained by the equation (4) is obtained and printed. 16 is a flowchart showing a flow of temperature control of the fixing device 500 performed by a control unit 504 (FIG. 15). Hereinafter, the temperature control method of the fixing device 500 will be described with reference to this flowchart.

  The print control unit 504 (FIG. 15) starts the fixing temperature control by receiving a print control command (print start command) from the host device. First, the detected temperature T1 (start) and pressurization by the non-contact type thermistor 54 are started. The roller detection temperature T3 (start) is detected and stored (step S201). Next, an execution interval time Tm (for example, Tm = 400 ms) measured by the timer to determine the temperature control execution interval is set in the timer 116a in the fixing control unit 116, and the type of print medium (thick paper, thin paper, OHP). Etc.), the fixing temperature is determined according to the printing conditions (color printing, monochrome printing), and the determined temperature is set as the fixing target temperature in the register 116b in the fixing control unit 116 (step S202).

  Next, the halogen lamp 53 which is the heater of the heating roller 21 is energized to turn it on (step S203). Thereafter, the detection temperature T1 of the non-contact thermistor 54 is detected, and the detection of the detection temperature T1 is repeated until the detection temperature T1 reaches a predetermined temperature (rotation start temperature) (steps S204 and 205). The predetermined temperature (rotation start temperature) is a temperature set in advance for rotating the heating roller 21 after melting the toner adhering to the heating roller 21. When the detected temperature T1 reaches this predetermined temperature, the fixing device motor 122 is driven to rotate, the heating roller 21 and the pressure roller 22 are rotated in the directions of the arrows, respectively, and the surface temperature of the pressure roller 22 is further increased. Elapsed time (N seconds) for leveling is confirmed (step S206).

Next, the timer 116a is started (step S207), and when the measurement time reaches a preset execution interval time Tm (here, 400 ms), the timer is stopped (steps S208 and S209), and the non-contact type thermistor 54 is detected. The temperature T1 and the detected temperature T3 of the contact type thermistor 501 are taken in (step S210). And the above-mentioned formula (4)
Q = {c * T1 (start) + τ * T3 (start)}
+ ∫ {κ (T1 + T3)} dt
To calculate the roller temperature cumulative index Q (step S211).

Here, it is determined whether or not the roller temperature cumulative index Q is larger than 100 (step S212).
T [° C.] = T 1 [° C.] + A * T 3 (N) [° C.] + B
Based on the above, the surface calculated temperature T of the heating roller 21 is calculated (step S213). When the roller temperature cumulative index Q is 100 or more, the above-described formula (5)
T [° C.] = T 1 [° C.] + D [° C.]
Based on the above, the calculated surface temperature T of the heating roller 21 is calculated (step S214).

  Next, the calculated surface calculated temperature T is compared with a preset fixing target temperature (step S215), and if it is below the fixing target temperature, the halogen lamp 53 is turned on (step S216), and the fixing target temperature is exceeded. If so, the halogen lamp 53 is turned off (step S217). Next, it is determined whether or not the printing operation is finished (step 218). If the printing operation is continued, the process returns to step S207 to repeat the same operation. When the printing operation is finished, the halogen lamp 53 is turned off. At the same time, the rotation of the fixing device motor 122 is stopped (step 219), and the fixing temperature control operation is ended. In step S218, the end of the printing operation is determined by, for example, detecting the trailing end of the recording medium 205 with a sensor (not shown) to detect the discharging operation of the recording medium 205 and confirming that there is no next print data. To judge.

  As described above, according to the fixing device of the fourth embodiment, the roller temperature cumulative index Q is obtained, so that the ambient temperature T2 is saturated and stabilized, or the cooling that does not reach the warm state is reached. It is possible to correct the detected temperature with higher accuracy by determining whether the temperature is in the intermediate state and obtaining the surface calculated temperature T by calculation suitable for each state.

Embodiment 5 FIG.
The difference between the fixing device of the present embodiment and the fixing device of the third embodiment is a signal processing method in the print control unit 504. Therefore, in describing the signal processing method of the fixing device according to the present embodiment, refer to the cross-sectional view of the main part of the fixing device 500 in FIG. 14 and the block diagram showing the configuration of the control system of the image forming unit 505 in FIG. The description of common parts is omitted here, and different points are mainly described. The print control unit according to the present embodiment is different from the print control unit 504 according to the third embodiment in the signal processing method.

In the fixing device of the fourth embodiment described above, the roller temperature cumulative index Q is calculated, and control is performed to switch the temperature correction method between the cold time and the warm time. However, when the power supply of the halogen lamp is momentarily cut off in the cold state and immediately turned on again, the temperature of each roller is, for example, a detected temperature T1 (start) = 170 ° C. by the non-contact type thermistor 54 of the heating roller 21. When the pressure roller detection temperature T3 (start) = 50 ° C., the initial value of the roller temperature cumulative index Q at this point is (170 + 50) / 2 = 110 (c = τ = 0.5) in the equation (4). ), Which is equal to or greater than a predetermined value 100 (when Q _S : c = τ = 0.5, κ = 5000).

  Therefore, in such a case, the place where the cold temperature correction should be performed originally executes the warm temperature correction. Such misjudgment is experimentally weighted to constant c and τ, and even if it is set to an optimal value, it is difficult to completely prevent it in all cases, and another judgment criterion is considered. There must be. The present embodiment adds a new criterion for preventing these erroneous determinations, and an example thereof will be described below.

  FIG. 23 is a graph showing the results of an experiment performed using the fixing device 500. FIG. 23A shows a state where the fixing device motor 122 (see FIG. 15) is changed from a rotating state to a stopped state in a cold state. FIG. 4B shows a change in the pressure roller detection temperature T3 when the fixing device motor 122 is changed from the rotation state to the stop state during the warm time. The rotation time at this time is about 20 seconds, and it is assumed that the heating roller 21 has reached the above-described rotation start temperature when the fixing device motor 122 rotates.

  As is apparent from the respective graphs in the drawing, the pressure roller 22 (see FIG. 14) takes its heat away from the heating roller 21 having a heat source during its rotation, and its detected temperature T3 rises. When the motor 122 is stopped and the rotation is stopped, the pressure roller surface temperature of the portion detected by the contact thermistor 501 installed at a predetermined distance from the joint with the heating roller 21, that is, the pressure roller detection temperature T3 is descend.

Here, in the cold state and the warm state, the decrease range ΔT3 of the pressure roller detection temperature T3 after the lapse of Δt seconds from the stop of the fixing motor is expressed as ΔT3A (in the cold state) and ΔT3B. (When warm)
ΔT3A> ΔT3B
Thus, it can be seen that the temperature drop of the pressure roller 22 after the fixing motor is stopped in the cold state is larger. This seems to be because the pressure roller 22 is warmed from the core in the warm state, so that the temperature drop is delayed. Here, the temperature drop rate ΔT of the pressure roller 22 is expressed by the following equation (6).
ΔT = ΔT3 / (T1-T3) × 100 [%] (6)
Ask for.

FIG. 24 is a graph showing the relationship between the pressure roller temperature decrease rate ΔT calculated by the equation (6) and the initial value of the roller temperature cumulative index Q when ΔT3 is detected, and showing the result. As shown in the figure, in the region where the pressure roller temperature decrease rate ΔT is 30% or more, the pressure roller temperature decrease rate ΔT and the initial value of Q are proportional to each other.
Q (initial value) = − 2.7 × ΔT + 166.7 (7)
Can be expressed approximately. In the region where the pressure roller temperature decrease rate ΔT is 30% or more, Q is smaller than a predetermined value Q _S (for example, Q _S = 100 when c = τ = 0.5, κ = 5000), and the cold region described above. It corresponds to. On the other hand, in the region where the pressure roller temperature decrease rate ΔT is 30% or less (corresponding to the warm region), the initial value of the roller temperature cumulative index Q shows a random value of 100 or more.

  Accordingly, in the region where the pressure roller temperature decrease rate ΔT is 30% or more, first, the initial value of the roller temperature cumulative index Q is obtained using the above equation (7), and this initial value is obtained from the equation (4) described above. Instead of the first term {c * T1 (start) + τ * T3 (start)}, the roller temperature cumulative index Q is calculated. Therefore, when the pressure roller temperature decrease rate ΔT is 30% or more, the initial value of the roller temperature cumulative index Q becomes a value smaller than 100. Therefore, the cooling for selecting the formula (3) described in the fourth embodiment is performed. Start with temperature compensation. On the other hand, when the pressure roller temperature decrease rate ΔT is 30% or less, it is determined that the initial value of the roller temperature cumulative index Q is 100 or more, and the temperature for selecting the formula (5) described in the fourth embodiment is used. Start with temperature compensation.

  As described above, by setting the initial value of the roller temperature cumulative index Q based on the pressure roller temperature decrease rate ΔT, the roller temperature cumulative index Q having desired characteristics can be obtained even when the power supply is momentarily cut off. Therefore, it is possible to perform highly accurate detection temperature correction with few malfunctions.

  FIG. 25 shows the calculation of the surface calculated temperature T according to the formula (3) or (5), which is selected by adding the pressure roller temperature decrease rate ΔT calculated by the formula (6) as a new criterion as described above. It is a flowchart which shows the flow of this. Hereinafter, a method for calculating the surface calculation temperature T of the fixing device 500 will be described with reference to this flowchart.

  The print control unit 504 (FIG. 15) starts to generate the surface calculated temperature T by the temperature correction control by receiving a print control command (print start command) from the host device. First, after the fixing device motor 122 is rotated for a certain time (for example, about 20 seconds), this rotation is stopped (step S301). When rotating the fixing device motor 122, it is assumed that the halogen lamp 53 is turned on as described above, and the surface temperature of the heating roller 21 has reached the above rotation start temperature. At this time, the reduction width ΔT3 of the pressure roller detection temperature T3 after the lapse of Δt seconds after the fixing device motor 122 is stopped is obtained, and the temperature reduction rate ΔT of the pressure roller 22 is obtained by the above equation (6) (step S302). ).

  Here, it is determined whether or not the obtained temperature decrease rate ΔT is ΔT ≧ 30 (step S303). If it is less than 30, warm temperature correction is immediately started (step S310), and printing is started here. (Step S311), the surface calculated temperature T of the heating roller 21 obtained by correcting the detected temperature T1 of the non-contact thermistor 54 by the above-described equation (5) is obtained.

  On the other hand, if it is determined in step S303 that the obtained temperature decrease rate ΔT is ΔT ≧ 30, the initial value of the roller temperature cumulative index Q at this time is obtained by the above-described equation (7) (step S304). The roller temperature cumulative index Q is calculated by replacing the initial value of Q obtained here with the first term {c * T1 (start) + τ * T3 (start)} in the equation (4) (step S305). ).

  Next, it is determined whether or not the roller temperature cumulative index Q calculated in step S305 is Q <100 (step S306). If it is larger than 100, step S310 is reached to start warm temperature correction, and the above-described steps S311 and 312 are performed. Then, the surface calculated temperature T according to the equation (5) is obtained. On the other hand, if Q is 100 or less, printing is started here (step S307), and the pressure roller detection temperature T3 (N) after N seconds from the start of rotation of the heating roller 21 is detected. (Step S308), the calculated surface temperature T of the heating roller 21 obtained by correcting the detected temperature T1 of the non-contact thermistor 54 by the above-described equation (3) is obtained (Step S309). Next, it is determined whether or not the printing operation is completed (step S313). If the printing operation is continued, the process returns to step S306 and the operation is repeated in the same manner.

  Note that the flowchart shown in FIG. 25 shows a process for obtaining the surface calculated temperature T. Therefore, the flow relating to the on / off control of the halogen lamp 53 performed by obtaining the surface calculated temperature T and the timer operation are excluded. ing.

  As described above, according to the fixing device of the fifth embodiment, the temperature reduction rate ΔT of the pressure roller at the time of stopping after rotating the fixing device motor for a predetermined time immediately after the power is turned on is obtained. By setting the initial value of the roller temperature cumulative index Q based on the rate ΔT, it is possible to generate the roller temperature cumulative index Q having desired characteristics even when the power supply is momentarily cut off. Accurate correction of detected temperature is possible.

  DESCRIPTION OF SYMBOLS 11 Photosensitive drum, 12 Charging roller, 13 Exposure apparatus, 13a LED head, 14 Developing apparatus, 14a Developing roller, 15 Cleaning blade, 16 Static elimination apparatus, 21 Heating roller, 22 Pressure roller, 22a Rotating shaft, 23 Moving bearing, 24 pressure spring, 51 upper cover, 51a opening, 51b partition, 52 lower cover, 52a moving guide part, 53 halogen lamp, 54 non-contact thermistor, 55 sensor frame, 56 adjustment screw, 57 leaf spring, 57a frame holding part , 58 support member, 59 closed space, 60 cover temperature detection thermistor, 62 position adjustment mechanism, 100 image forming unit, 101 print control unit, 102 I / F control unit, 103 reception memory, 104 image data editing memory, 1 5 operation unit, 106 various sensors, 110 charging voltage control unit, 111 head control unit, 112 developing voltage control unit, 113 transfer voltage control unit, 114 motor control unit, 115 transport motor control unit, 116 fixing control unit, 116a timer, 116b register, 122 fixing device motor, 200 image forming apparatus, 201-204 process unit, 205 recording medium, 206 paper cassette, 207 hopping roller, 208 pinch roller, 209 pinch roller, 210 transport roller, 211 registration roller, 212 transfer roller , 213 fixing device, 214 discharge roller, 215 discharge roller, 216 pinch roller, 217 pinch roller, 218 recording medium stacker unit, 219 belt transport device, 220 transport Path, 300 fuser, 301 slide drive mechanism, 302 transmission gear, 303 working gear, 304 drive shaft, 310 spring, 311 rack gear, 312 thermistor, 315 sensor frame, 500 fuser, 501 contact type thermistor, 502 sensor holding arm, 503 fixing screw, 504 printing control unit, 505 image forming unit.

Claims (7)

In a fixing device for fixing toner on a recording medium,
A heat source,
A heating member heated by the heat source to heat the recording medium;
A pressing member that is biased toward the heating member to pressurize the recording medium;
A first temperature detection member for detecting the temperature of the heating member at a position spaced from the heating member;
A third temperature detection member for detecting the temperature of the pressure member;
Control means for correcting the detected temperature of the first temperature detecting member based on the detected temperature detected by the third temperature detecting member, and controlling energization to the heat source based on the corrected detected temperature. And
The control means sets a rotation start temperature of the heating member, starts rotation when the temperature detected by the first temperature detection member reaches the rotation start temperature, and after the elapse of a predetermined time, A fixing device that corrects the detected temperature of the first temperature detecting member based on the detected temperature detected by the temperature detecting member. In a fixing device for fixing toner on a recording medium,
A heat source,
A heating member heated by the heat source to heat the recording medium;
A pressing member that is biased toward the heating member to pressurize the recording medium;
A first temperature detection member for detecting the temperature of the heating member at a position spaced from the heating member;
A third temperature detection member for detecting the temperature of the pressure member at a position in contact with the pressure member;
Control means for controlling the heat generation of the heat source based on the detected temperatures of the first and third temperature detecting members,
The control means determines whether the ambient temperature of the first temperature detection member is in a warm state where the ambient temperature is saturated and stable or in a cold state where the warm state is not reached. The fixing device is characterized in that the temperature control in the cold state and the temperature control in the cold state are different controls. When the detected temperature of the first temperature detecting member is T1, and the detected temperature of the third temperature detecting member is T3, the following equation is obtained: T = T1 + a * T3 + b (a and b are constants)
The fixing device according to claim 1, wherein the control is performed based on a calculated surface temperature T of the heating member obtained by the step. An accumulated value Q of the detected temperature T1 of the first temperature detecting member and the detected temperature T3 of the third temperature detecting member is obtained, and when the accumulated value Q is equal to or greater than a predetermined threshold, the following expression T = T1 + d (d Is a constant)
The fixing device according to claim 3, wherein the control is performed based on a calculated surface temperature T of the heating member obtained by the step.   The heating member and the pressure member are both rollers, and the accumulated value Q is corrected according to a temperature decrease rate of the detected temperature T3 when each roller is rotated for a predetermined time and stopped. Item 5. The fixing device according to Item 4. The temperature decrease rate ΔT of the detected temperature T3 is expressed by the following equation: ΔT = ΔT3 / (T1-T3) × 100
When the temperature decrease rate ΔT is not less than a predetermined value, the initial value of the cumulative value Q is Q (initial value) = − e × ΔT + f (e and f are constants)
The fixing device according to claim 5, wherein: A recording medium conveying means for conveying the recording medium;
Toner image forming means for forming a toner image on the recording medium;
An image forming apparatus comprising: the fixing device according to claim 1 for fixing a toner image formed on the recording medium.

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