JP2012189770A - Fixing device and image forming device - Google Patents

Abstract

An appropriate temperature is detected both when a fixing member is rotating and when it is not rotating.
A fixing sleeve 21 of a rotating endless belt, a pressure roller 31 in contact with the outer peripheral surface of the fixing sleeve 21, and an inner peripheral side of the fixing sleeve 21, and the pressure roller via the fixing sleeve 21. An abutting member 26 that abuts 31 and forms a nip, a heating element 30 that is disposed on the inner peripheral side of the fixing sleeve 21, and that heats the fixing sleeve 21; A first temperature sensor 32 that detects the temperature of the fixing sleeve 21 at a position corresponding to a predetermined region where the planar heating element 22 heats the heating body 30 on the outer peripheral side of the fixing sleeve 21, and the fixing sleeve 21. At a position corresponding to the predetermined area where the heating element 30 heats the fixing sleeve 21, which is an area other than the predetermined area where the planar heating element 22 heats the heating element 30. Comprising a second temperature sensor 33 for detecting the temperature of the sleeve 21.
[Selection] Figure 11

Description

  The present invention relates to a fixing device that fixes a formed image on a recording medium at a nip between an endless belt-shaped fixing member and a pressure rotating member, and an image forming apparatus including the fixing device.

  Conventionally, various image forming apparatuses using an electrophotographic system have been devised as image forming apparatuses such as copying machines and printers, and are well known in the art. In the image forming process, an electrostatic latent image is formed on the surface of the photosensitive drum as an image carrier, and the electrostatic latent image on the photosensitive drum is developed with a toner as a developer to be visualized and developed. This is established by a process in which the transferred image is transferred onto a recording paper (also referred to as a paper or a recording medium) by a transfer device to carry the image, and a toner image on the recording paper is fixed by a fixing device using pressure or heat.

  In this fixing device, a fixing member and a pressure member constituted by opposing rollers or belts or a combination thereof are arranged so as to contact each other to form a nip portion, and a recording sheet is sandwiched in the nip portion, Heat and pressure are applied to fix the toner image on the recording paper.

  As an example of the fixing device, a technique using a fixing belt stretched around a plurality of roller members as a fixing member is known (for example, Patent Document 1). An apparatus using such a fixing belt is provided in a fixing belt (endless belt) as a fixing member, a plurality of roller members that stretch and support the fixing belt, and one of the plurality of roller members. And a heater, a pressure roller (pressure member), and the like. The heater heats the fixing belt via the roller member. Then, the toner image on the recording medium conveyed toward the nip formed between the fixing belt and the pressure roller is fixed on the recording medium by receiving heat and pressure at the nip. Belt fixing method).

  Further, in the fixing device used in the image forming apparatus described above, there is a fixing device having a fixing member that is in sliding contact with the inner surface of a fixing member that is a rotating body. For example, in Patent Document 2, a fixing nip portion is formed by sandwiching a heat-resistant film (fixing film) between a ceramic heater as a heating element and a pressure roller as a pressure member. A recording material on which an unfixed toner image to be image-fixed is formed and supported is introduced between the film and the pressure roller, and is nipped and conveyed together with the film. A film heating type fixing device is disclosed in which an unfixed toner image is fixed to a surface of a recording material by a pressure applied to a recording material through a fixing nip portion. This film heating type fixing device can be configured as an on-demand type device using a ceramic heater and a member having a low heat capacity as a film, and energizes the ceramic heater as a heat source only when the image forming apparatus performs image formation. Thus, it is only necessary to generate heat at a predetermined fixing temperature, the waiting time from the power-on of the image forming apparatus to the image forming executable state is short (quick start property), and the power consumption during standby is greatly reduced ( There are advantages such as (power saving).

  In Patent Documents 3 and 4, a rotatable heat-fixing roll whose surface is elastically deformed, an endless belt (pressure belt) that can run while being in contact with the heat-fixing roll, and a non-rotation inside the endless belt The endless belt is placed in pressure contact with the heat fixing roll, a belt nip is provided between the endless belt and the heat fixing roll to allow recording paper to pass, and the surface of the heat fixing roll is elastic. A pressure belt type image fixing device having a pressure pad to be deformed has been proposed. According to this fixing method, the lower pressure member is used as a belt, and the contact area between the paper and the roll is widened to greatly improve the heat conduction efficiency, and it is possible to reduce the energy consumption and at the same time realize the miniaturization. It has become.

  However, although the fixing device described in Patent Document 1 described above is suitable for speeding up the device as compared with a device using a fixing roller, the warm-up time (time required to reach a printable temperature) and the first print There is a limit to shortening the time (the time from when a print request is received to when the print operation is performed and the paper discharge is completed).

  On the other hand, the fixing device described in Patent Document 2 can reduce the warm-up time and the first print time by reducing the heat capacity, and also reduce the size of the device. However, the fixing device described in Patent Document 2 has a problem of durability and a problem of belt temperature stability. In other words, the wear resistance due to sliding between the ceramic heater, which is a heat source, and the inner surface of the belt is inadequate, and the surface that repeats continuous friction is roughened when operated for a long time, increasing the frictional resistance and making the belt run unstable. Or, a phenomenon such as an increase in the driving torque of the fixing device occurs, and as a result, the transfer paper forming the image slips and the image shifts, or the stress on the driving gear increases, causing damage to the gear. (Problem 1). In the film heating type fixing device, since the belt is locally heated at the nip portion, when the rotating belt returns to the nip entrance, the belt temperature becomes the coldest state (especially at high speed rotation). , There was a problem that fixing failure was likely to occur (Problem 2).

  On the other hand, in Patent Document 3, a glass fiber sheet (PTFE-impregnated glass cloth) impregnated with PTFE as a low friction sheet (sheet-like sliding material) on the surface layer of the pressure pad is used, and the slidability of the belt inner surface and the fixing member is improved. Means for improving the problem are disclosed. However, such a pressure belt type fixing device (Patent Documents 3 and 4) has a problem that it takes a long time to warm up because the heat capacity of the fixing roller is large and the temperature rise is slow. (Problem 3).

  With respect to the above problems 1 to 3, in Patent Documents 5 and 6, a substantially pipe-shaped counter member (metal thermal conductor) disposed on the inner peripheral side of the endless fixing belt, and the counter member By providing a resistance heating element such as a ceramic heater that is disposed on the inner peripheral side and heats the opposing member, the entire fixing belt can be warmed, the warm-up time and the first print time can be shortened, and There has been proposed a fixing device that can solve the shortage of heat during high-speed rotation. However, there may be a part where the flexible fixing belt is largely separated from the metal heat conductor during rotation, and heat transfer is not performed at the part. There was a problem that burns occurred and the rotational torque of the fixing belt increased.

  In Patent Document 7, an endless fixing belt, a pressure roller that presses against the fixing belt to form a nip portion on which a recording medium is conveyed, and an inner peripheral surface of the fixing belt are fixed. A resistance heating element that heats the fixing belt, and the resistance heating element is disposed in a minute gap so as not to be in pressure contact with the inner peripheral surface of the fixing belt, and heats the entire fixing belt with radiant heat. A device has been proposed. As a result, even when the warm-up time and the first print time are shortened and the apparatus is speeded up, it is possible to prevent problems such as defective fixing and wear and damage of the fixing member and the resistance heating element. It is supposed to be.

  However, in the fixing device described in Patent Document 7, since the fixing belt and the resistance heating element are disposed close to each other in order to suppress a decrease in heating efficiency, the flexible fixing belt rotates. In some cases, it may partially come into contact with the resistance heating element, and the fixing belt may be heated non-uniformly due to heat transfer at the contact portion, resulting in temperature unevenness.

  In the fixing device described in Patent Document 7, stress due to rotation and vibration of the pressure roller repeatedly acts on the resistance heating element, and the resistance heating element is repeatedly bent. Since the heating element is made of a metal material, the fixing belt may not be heated properly due to disconnection due to fatigue failure due to repeated bending.

  By the way, in the fixing device, the temperature of the fixing member is detected by a temperature sensor, and the heating means for heating the fixing member is controlled based on the detection result. For example, one temperature sensor is installed in the rotation direction of the fixing member, and temperature control is performed based on the sensor output value. Further, for example, the heating means at the central portion in the axial direction of the fixing member is controlled with a thermopile, and the temperature control is performed with respect to the heating means at the axial end portion with a non-contact thermistor.

  However, when the fixing member is not rotated, the internal member (heating body) which is a member provided on the inner peripheral side of the fixing member may be locally deformed due to heating, and may be deformed. In such a case, there is a problem that proper temperature detection cannot be performed and temperature control cannot be performed accurately.

  Accordingly, the present invention has been made in view of the above-described problems in the prior art, and in a fixing device that locally heats an endless belt-shaped fixing member, a first temperature detecting means and a second temperature detecting means are provided. Provided are a fixing device capable of detecting an appropriate temperature and controlling the temperature both when the fixing member is rotated and when the fixing member is not rotated by appropriately arranging the fixing member, and an image forming apparatus including the fixing device. For the purpose.

  In order to achieve such an object, the fixing device according to claim 1 is disposed on a fixing member of a rotating endless belt, a pressure member in contact with an outer peripheral surface of the fixing member, and an inner peripheral side of the fixing member, A contact member that contacts the pressure member via the fixing member to form a nip portion; a heating element that is disposed on the inner peripheral side of the fixing member and that heats the fixing member by contacting the fixing member; A heating element that heats a predetermined region of the body, a first temperature detection unit that detects the temperature of the fixing member at a position corresponding to the predetermined region where the heating element heats the heating body on the outer peripheral side of the fixing member, and a fixing member And a second temperature detecting means for detecting the temperature of the fixing member at a position corresponding to the predetermined area where the heating body heats the fixing member, except for the predetermined area where the heating element heats the heating body. Are provided.

  According to a second aspect of the present invention, in the fixing device according to the first aspect, the heating element is a sheet-like planar heating element.

  According to a third aspect of the present invention, in the fixing device according to the second aspect, the heating element includes a heating element support member that supports the planar heating element from a side opposite to the fixing member, and a rotation state of the fixing member. And a rotation support member that supports

  According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects, the first temperature detecting means is not deformed by the heating body and is deformed by thermal expansion of the heating body. In both cases, the heater is provided with a predetermined gap.

  According to a fifth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects, the first temperature detecting means has the highest temperature in a predetermined region where the heating element heats the heating element. It is provided at a position corresponding to the region.

  According to a sixth aspect of the present invention, in the fixing device according to any one of the first to fifth aspects, the second temperature detecting unit is configured such that the installation position of the first temperature detecting unit is a reference position. The fixing member is installed at a position of 80 ° to 110 ° upstream of the rotation direction of the fixing member with respect to the rotation center of the fixing member.

  According to a seventh aspect of the present invention, in the fixing device according to any one of the first to sixth aspects, the first temperature detecting means is predetermined in the axial direction in accordance with the axial position of the fixing member. It is provided with an inclination.

  An image forming apparatus according to an eighth aspect includes the fixing device according to any one of the first to seventh aspects.

  According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the temperature is controlled based on an output value from the first temperature detecting means when the fixing member is rotated, and when the fixing member is not rotated. Temperature control is performed based on the output value from the second temperature detection means.

  According to a tenth aspect of the present invention, in the image forming apparatus according to the eighth aspect, based on the output values from the first temperature detecting means and the second temperature detecting means, any temperature detecting means is used. This is to determine whether to perform control.

  According to the present invention, an appropriate temperature can be detected and temperature control can be performed both when the fixing member rotates and when it does not rotate.

FIG. 3 is a cross-sectional view illustrating a configuration of a reference example which is a premise of the fixing device according to the present invention. FIG. 3 is a schematic diagram illustrating an axial direction and a circumferential direction of a fixing sleeve. FIG. 2 is a cross-sectional view illustrating a configuration of a heat generating sheet used in the fixing device of FIG. 1. It is a figure which shows the structural example (1) of the planar heating element used with the fixing device of FIG. FIG. 3 is a top view showing a configuration example (2) of a planar heating element used in the fixing device of FIG. 1. FIG. 6 is a top view showing a configuration example (3) of a planar heating element used in the fixing device of FIG. 1. FIG. 6 is a top view showing a configuration example (4) of a planar heating element used in the fixing device of FIG. 1. It is a perspective view which shows the structure of the rotation support member used with the fixing device of FIG. FIG. 2 is a schematic diagram illustrating a configuration of an internal mechanism unit on a fixing sleeve side in the fixing device of FIG. 1. It is explanatory drawing of the thermal expansion of a heating body, Comprising: (a) Axial direction side view, (b) Circumferential direction sectional drawing. 2 is a cross-sectional view illustrating a configuration example of a fixing device according to the present invention. FIG. It is explanatory drawing of the thermal expansion of the heating body in the fixing device of FIG. 11, Comprising: It is an axial side view. It is a schematic diagram explaining the relationship of the installation position of a 1st temperature sensor and a 2nd temperature sensor. It is a graph which shows the relationship between a measurement location, a heating element deformation amount, and temperature. 3 is an example of a graph showing a relationship between a fixing member temperature and a deformation amount. FIG. 5 is an axial side view when the first temperature sensor is installed so as to be inclined with respect to the fixing member axial direction. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to the present invention. FIG. 6 is a cross-sectional view illustrating another configuration example of the fixing device according to the present invention.

  Hereinafter, the configuration according to the present invention will be described in detail based on embodiments shown in the drawings.

(Basic configuration of fixing device)
First, a reference example (basic configuration) which is a premise of the fixing device according to the present invention will be described. FIG. 1 is a cross-sectional view showing a configuration of a reference example which is a premise of a fixing device according to the present invention. As shown in FIG. 1, the fixing device 50 includes a fixing member (fixing sleeve 21 (also referred to as a fixing rotating body)) composed of a rotating endless belt, and a pressing member (pressurizing) that contacts the outer peripheral surface of the fixing member. A roller 31 (also referred to as a pressure rotator) and an abutting member (abutting member) that is disposed on the inner peripheral side of the fixing member and forms a nip portion by abutting the pressure member via the fixing member. 26), a sheet heating element (sheet heating element 22) that is disposed in contact with the fixing member on the inner peripheral side of the fixing member and heats the fixing member, and a sheet heating element on the inner peripheral side of the fixing member. A heating element support member (heating element support member 23) which is disposed so as to sandwich the planar heating element between the fixing member and supports the planar heating element at a predetermined position, and an inner peripheral side of the fixing sleeve 21. A pipe-shaped rotation support member (supporting the rotating fixing sleeve 21 provided) A rolling support member 27), a heat insulating support member (heat insulating support member 29) provided on the H-shaped outer surface of the core holding member 28 so as to be disposed on the inner peripheral side of the rotation support member 27 and downstream of the nip portion, Is provided.

  Here, the fixing sleeve 21 is a pipe-shaped endless belt having a length corresponding to the width of the recording medium P through which the paper is passed in the axial direction and having flexibility. At least a release layer is formed on a base material made of a metal material of 50 μm, and the outer diameter is 30 mm. Hereinafter, as shown in FIG. 2A, the pipe longitudinal direction of the fixing sleeve 21 is referred to as an axial direction, and as shown in FIG. 2B, the pipe circumferential direction of the fixing sleeve 21 is referred to as a circumferential direction.

  As a material for forming the base material of the fixing sleeve 21, a metal material having good heat conductivity such as iron, cobalt, nickel, or an alloy thereof can be used.

  The release layer of the fixing sleeve 21 is obtained by coating a fluorine compound such as PFA in a tube shape, and the thickness thereof is 50 μm. The release layer is for enhancing the toner release property on the surface of the fixing sleeve 21 with which the toner image (toner) T on the recording medium P is in direct contact.

  The pressure roller 31 is formed by sequentially forming a heat-resistant elastic layer such as silicon rubber (solid rubber) and a release layer on a metal core made of a metal material such as aluminum or copper, and has an outer diameter of 30 mm. It has become. The elastic layer is formed to have a thickness of 2 mm to 3 mm. The release layer is coated with a PFA tube and is formed to have a thickness of 50 μm. Further, a heating element such as a halogen heater may be incorporated in the cored bar as necessary. The pressure roller 31 is pressed against the contact member 26 via the fixing sleeve 21 by a pressing means (not shown), and the pressure contact portion forms a nip portion where the fixing sleeve 21 side is recessed. Then, the recording medium P is conveyed to the nip portion.

  Further, the pressure roller 31 is rotationally driven by a driving mechanism (not shown) while being in pressure contact with the fixing sleeve 21 (rotates in the clockwise direction in FIG. 1), and the fixing sleeve 21 is rotated along with the rotation of the pressure roller 31. It will rotate (rotating counterclockwise in FIG. 1).

  The contact member 26 has a length in the axial direction of the fixing sleeve 21, and at least a portion in pressure contact with the pressure roller 31 through the fixing sleeve 21 is made of an elastic body having heat resistance such as fluorine rubber. In addition, the core holding member 28 is fixed in a state of being held at a predetermined position on the inner peripheral side of the fixing sleeve 21. Further, the portion of the contact portion 26 that contacts the inner peripheral surface of the fixing sleeve 21 is preferably made of a material having excellent sliding properties and wear resistance, such as a Teflon (registered trademark) sheet.

  The core holding member 28 is a rigid member having a length corresponding to the axial length of the fixing sleeve 21 and having an H-shaped cross section. It is arranged at a substantially central portion on the circumferential side.

  The core holding member 28 holds various members arranged on the inner peripheral side of the fixing sleeve 21 at a predetermined position. For example, one of the H-shaped core holding members 28 (opposing the pressure roller 31). The abutting member 26 is housed and held in a recessed portion on the side), and is supported from the side opposite to the nip portion so that the abutting member 26 is not greatly deformed even when pressed by the pressure roller 31. The core holding member 28 holds the contact member 26 so as to slightly protrude from the core holding member 28 toward the pressure roller 31, so that the core holding member 28 does not contact the fixing sleeve 21 at the nip portion. Is arranged.

  In addition, a concave portion of the other of the H shapes of the core holding member 28 (the side opposite to the pressure roller 31 side) has a length corresponding to the axial length of the fixing sleeve 21 and has a T-shaped cross section. A terminal block stay 24 having a shape and a power supply line 25 that extends on the terminal block stay 24 and supplies electric power from the outside are housed and held. Further, the heating element support member 23 is held on the H-shaped outer surface of the core holding member 28. In FIG. 1, the heating element support member 23 is held in a region corresponding to a lower half circumference of the fixing sleeve 21 (a half circumference on the entry side of the nip portion). At this time, the heating element support member 23 and the core holding member 28 may be bonded in consideration of assembly. Alternatively, in order to prevent heat transfer from the heating element support member 23 side to the core holding member 28 side, both may be non-bonded.

  The core holding member 28 holds the end portion of the pipe-shaped rotation support member 27 formed by cutting the pipe peripheral surface in the axial direction before and after the nip portion in the circumferential direction. Holding. Note that both ends of the rotation support member 27 in the axial direction are held by side plates constituting a frame of the fixing device 50.

  The heating element support member 23 supports the planar heating element 22 in order to place the planar heating element 22 in contact with the inner peripheral surface of the fixing sleeve 21. Therefore, the heating element support member 23 has an outer peripheral surface having a predetermined arc length along the inner peripheral surface of the fixing sleeve 21 having a circular cross-sectional shape.

  Further, the heating element support member 23 has heat resistance sufficient to withstand the heat generation of the sheet heating element 22, and the sheet heating element 22 is not deformed when the rotating fixing sleeve 21 contacts the sheet heating element 22. It is preferable to have strength sufficient to support the heat and heat insulation so that the heat of the sheet heating element 22 is transmitted to the fixing sleeve 21 side without being transmitted to the core holding member 28 side. A molded body is preferred. When the sheet heating element 22 is in contact with the inner peripheral surface of the fixing sleeve 21, the force that the fixing sleeve 21 that rotates rotates pulls the sheet heating element 22 toward the nip portion acts on the sheet heating element 22. Therefore, the heating element support member 23 needs to have sufficient strength to support the planar heating element 22 without being deformed. In this case as well, a polyimide resin foam molded body is suitable. In addition, a solid resin member may be supplementarily provided inside the polyimide resin foam to improve the rigidity.

  As shown in FIG. 3, the sheet heating element 22 includes a resistance heating layer 22b in which conductive particles are dispersed in a heat-resistant resin on an insulating base layer 22a, and power to the resistance heating layer 22b. An electrode layer 22c to be supplied, and has a heat generating sheet 22s having a predetermined width and length corresponding to the axial direction and the circumferential direction of the fixing sleeve 21 and exhibiting flexibility. On the base layer 22a, an insulating layer 22d is provided that insulates between the resistance heating layer 22b and an electrode layer 22c of another power feeding system adjacent to the base layer 22a or between an edge portion of the heating sheet 22s and the outside. The planar heating element 22 includes an electrode terminal 22e (not shown, described later) that is connected to the electrode layer 22c at the end of the heating sheet 22s and supplies power supplied from the power supply line 25 to the electrode layer 22c. .

  Further, the thickness of the heat generating sheet 22s is about 0.1 to 1 mm, and is flexible enough to be wound around at least the outer peripheral surface of the heat generating element support member 23.

  Here, the base layer 22a is an elastic film made of a resin having a certain degree of heat resistance, such as PET or polyimide resin, and among them, a film member made of polyimide resin is preferable. Thereby, heat resistance, insulation, and a certain amount of flexibility (flexibility) are provided.

  The resistance heating layer 22b is a conductive thin film in which conductive particles such as carbon particles and metal particles are uniformly dispersed in a heat-resistant resin such as polyimide resin. It is configured to generate heat. Such a resistance heating layer 22b may be formed by applying a coating material in which conductive particles such as carbon particles and metal particles are dispersed in a precursor of a heat resistant resin such as polyimide resin on the base layer 22a.

  The resistance heating layer 22b is formed by first forming a thin conductive layer made of carbon particles or metal particles on the base layer 22a, and then laminating an insulating thin film made of a heat resistant resin such as polyimide resin on the conductive layer. It may be integrated.

  The carbon particles used for the resistance heating layer 22b may be ordinary carbon black powder, but may be carbon nanoparticles composed of at least one of carbon nanofibers, carbon nanotubes, and carbon microcoils.

  Further, the metal particles are particles made of Ag, Al, Ni, etc., and the shape thereof may be granular or may be a filament shape.

  The insulating layer 22d may be formed by applying an insulating material made of the same heat resistant resin as the base layer 22a such as polyimide resin.

  The electrode layer 22c may be formed by applying a conductive paste such as conductive ink or Ag, or may be formed by bonding a metal foil or a metal net.

  Since the heat generating sheet 22s constituting the sheet heating element 22 is a thin sheet, its heat capacity is small and rapid heating is possible. The amount of heat generated can be arbitrarily set by the volume resistivity of the resistance heat generating layer 22b. . That is, the heat generation amount can be adjusted by the constituent material, shape, size, dispersion amount, etc. of the conductive particles constituting the resistance heat generation layer 22b. For example, the heat generation amount per unit area is 35 W / cm 2 and the total power Realization of the planar heating element 22 capable of obtaining an output of about 1200 W is possible. In this case, the heat generating sheet 22s has a size of about 20 cm in width (axial direction) and 2 cm in length (circumferential direction), for example.

  When the sheet heating element 22 made of a metal filament such as stainless steel is used, the surface of the sheet heating element is uneven due to the presence of the filament. When sliding with the inner peripheral surface, the surface is easily worn, but the heat generating sheet 22s used in the present invention is flat with no irregularities on the surface as described above. Excellent durability against sliding. Furthermore, it is preferable to coat the surface of the resistance heating layer 22b of the heating sheet 22s with a fluororesin because durability against contact with the inner peripheral surface of the fixing sleeve 21 is further improved.

  In addition, as an arrangement | positioning area | region in the fixing sleeve 21 internal peripheral surface of 22 s of heat_generation | fever sheets, you may arrange | position in arbitrary positions from the position on the inner peripheral surface of the fixing sleeve 21 on the opposite side to the nip part.

  Next, the detailed structure of the heat generating sheet 22s in the sheet heating element 22 used in the present invention will be described. The heat generating sheet 22s may be formed by forming the resistance heat generating layer 22b on the entire main surface of the base layer 22a or on a certain region, but each of the plurality of regions arbitrarily divided on the main surface of the base layer 22a has resistance. It is preferable that the heat generating layer 22b is formed so as to be able to generate heat independently. An example of the configuration is shown in FIGS.

  FIG. 4A is a top view showing a configuration example (1) of the planar heating element 22. Here, a state in which the planar heating element 22 is unfolded on a flat surface and viewed from above is shown before being attached to the heating element support member 23. Further, the horizontal direction in the figure is the width direction corresponding to the axial direction of the fixing sleeve 21, and the vertical direction is the length direction corresponding to the circumferential direction of the fixing sleeve 21.

  In FIG. 4A, the heat generating sheet 22s is roughly divided into three in the width direction (axial direction) and further divided into two in the length direction (circumferential direction) on its main surface. ing. Here, when viewing the six divided regions as a matrix matrix in which the length direction (circumferential direction) is composed of row components and the width direction (axial direction) is composed of column components (FIG. 4B), (1,2) A resistance heating layer 22b1 having a predetermined width and length is formed in a divided region of the component (a region corresponding to the central portion in the axial direction of the fixing sleeve 21), and a divided region of the (2, 1) component and the (2, 3) component. A resistance heating layer 22b2 having a predetermined width and length is formed in each of the regions corresponding to both axial ends of the fixing sleeve 21.

  In addition, an electrode layer 22c connected to the resistance heating layer 22b1 is formed in the divided region of the (1,1) component and the (1,3) component, and each of the electrode layers 22c has a heating sheet 22s. An electrode terminal 22e1 extending from one side (lower side in the figure) is provided to form a first heat generating circuit.

  In addition, an electrode layer 22c that connects the two resistance heating layers 22b2 is formed in the (2, 2) component divided region, and the length direction of the heating sheet 22s ( The electrode layer 22c extending in the circumferential direction and extending toward the one side (the lower side in the figure) is connected, and each electrode layer 22c has an electrode terminal 22e2 extending from the one side of the heat generating sheet 22s. A second heat generation circuit is formed.

  In addition, an insulating layer 22d is provided between the first heat generating circuit and the second heat generating circuit to prevent short circuit therebetween.

  In the planar heating element 22 having the configuration shown in FIG. 4A, when the electrode terminal 22e1 is energized, it generates heat as Joule heat due to the internal resistance of the resistance heating layer 22b1, and the electrode layer 22c does not generate heat due to low resistance. Only the divided region of the (1, 2) component of the heat generating sheet 22s generates heat, and the central portion in the axial direction of the fixing sleeve 21 can be heated.

  Further, when energized from the electrode terminal 22e2, heat is generated as Joule heat due to the internal resistance of the resistance heating layer 22b2, and the electrode layer 22c does not generate heat due to low resistance. Therefore, the (2, 1) component and (2 3) Only the divided region of the component generates heat, and both axial end portions of the fixing sleeve 21 can be heated.

  Therefore, when a small-size (narrow width) recording medium P is passed through the fixing device 50, only the electrode terminal 22e1 is energized to heat only the central portion in the axial direction of the fixing sleeve 21 and to widen the width. When the recording medium P is passed, the electrode terminals 22e1 and 22e2 are energized to heat the entire width in the axial direction of the fixing sleeve 21, thereby suppressing the energy consumption and appropriately depending on the width of the recording medium P. Fixing is possible. Further, since the amount of heat generated by the sheet heating element 22 can be controlled in accordance with the size of the recording medium P, the temperature of the non-sheet passing portion does not rise excessively even if small size paper is continuously fed. It is possible to prevent the device from being stopped for protection and the productivity from being lowered. Further, by providing the positional relationship of the different heat generating portions with the integrated planar heat generating element 22, a heat generating element having a smaller temperature deviation in the axial direction than that formed by a separate heat generating element can be obtained.

  In addition, in the heat generating sheet 22s, the heat generation amount tends to decrease due to the outflow of heat to the insulating layer 22d and the electrode layer 22c having a relatively high thermal conductivity at the ends of the respective resistance heat generating layers 22b1 and 22b2. It is in. Therefore, as shown in FIG. 4A, in the width direction (axial direction) of the heat generating sheet 22s, the boundary between the resistance heating layer 22b1 at the center and the resistance heating layer 22b2 at the end is the same surface. When the currents 22e1 and 22e2 were energized, the temperature distribution in the axial direction of the fixing sleeve 21 caused a temperature drop at the boundary between the resistance heating layer 22b1 and the resistance heating layer 22b2, and an abnormal image such as a fixing failure was generated. Accordingly, it is preferable to adopt the configuration shown in FIG. 5 or 6 to improve this problem.

  FIG. 5 is a top view showing a configuration example (2) of the planar heating element 22. The basic configuration of the planar heating element 22 shown in FIG. 5 is the same as that shown in FIG. 4A, but a part of the resistance heating layer 22b1 and the resistance heating layer 22b2 is in the width direction of the heating sheet 22s. The difference is that they overlap in the (axial direction) to form an overlap region. Thereby, it is possible to prevent a temperature drop at the boundary between the resistance heating layer 22b1 and the resistance heating layer 22b2 when the electrode terminals 22e1 and 22e2 are energized.

  FIG. 6 is a top view showing a configuration example (3) of the planar heating element 22. The basic structure of the planar heating element 22 shown in FIG. 6 is the same as that shown in FIG. 5, but in the overlapping region of the resistance heating layer 22b1 and the resistance heating layer 22b2, the resistance heating layers 22b1 and 22b2 and the electrodes respectively. The difference is that the boundary line with the layer 22c is inclined in different directions with respect to the length direction (circumferential direction) to adjust the overlapping amount of the resistance heating layers 22b1 and 22b2.

  This is because the area ratio of the overlapping regions of the resistance heating layers 22b1 and 22b2 is constant in the width direction (axial direction) in the configuration of FIG. 5, and the variation in the amount of heat generation increases as the overlapping width varies. However, in the configuration of FIG. 6, the area ratio in the overlapping region of the resistance heating layers 22b1 and 22b2 changes at a constant rate in the width direction (axial direction) to reduce the influence of adjustment of heat generation distribution and component variations. Thus, the temperature uniformity in the entire axial direction is improved, and the problem caused by the configuration of FIG. 5 is improved.

  In the heat generating sheet 22s having the configuration shown in FIGS. 4 to 6 described above, first, only the regions corresponding to the resistance heating layers 22b1 and 22b2 on the main surface of the base layer 22a are exposed, and the resistance heating layers 22b1 and 22b2 are formed by coating. Next, an insulating layer 22d made of only a heat-resistant resin is formed by application in a state where only the region corresponding to the insulating layer 22d is exposed, then only the region corresponding to the electrode layer 22c is exposed, and a conductive paste is applied to expose the electrode layer 22c. This is possible by forming Therefore, the resistance heating layers 22b1 and 22b2 having an arbitrary shape can be formed by adjusting the exposed shape of the region corresponding to the resistance heating layers 22b1 and 22b2.

  Further, the sheet heating element 22 used in the fixing device 50 is formed by laminating a plurality of heating sheets 22s, and the plurality of heating sheets 22s is formed in a resistance heating layer in an arbitrary region on the main surface of each base layer 22a. It is preferable that 22b is formed so that it can generate heat independently. FIG. 7 shows a specific configuration thereof.

  FIG. 7 is an exploded perspective view showing a configuration example (4) of the planar heating element 22. In FIG. 7, a planar heating element 22 is formed by laminating a first heating sheet 22s, an insulating sheet made of an insulating layer 22d, and a second heating sheet 22s in this order from the top.

  Here, the main surface of the first heat generating sheet 22s is divided into three in the width direction (axial direction), the resistance heat generating layer 22b1 is formed in the central divided region, and the resistance is formed in each of the divided regions on both sides thereof. An electrode layer 22c connected to the heat generating layer 22b1 is formed. The main surface of the second heat generating sheet 22s is divided into five in the width direction (axial direction), and the resistance heat generating layer 22b2 is formed in the second and fourth divided regions in the width direction (axial direction). An electrode layer 22c connected to the resistance heating layer 22b2 is formed in each of the remaining divided regions.

  The first heat generating sheet 22s and the second heat generating sheet 22s are stacked with an insulating sheet made of an insulating layer 22d interposed therebetween, and an independent first heat generating circuit is formed on the first heat generating sheet 22s. An independent second heat generating circuit is formed on the second heat generating sheet 22s.

  As a result, when the first heat generating circuit is energized, heat is generated as Joule heat by the internal resistance of the resistance heat generating layer 22b1, and only the central region in the width direction (axial direction) of the first heat generating sheet 22s generates heat. The central portion of the sleeve 21 in the axial direction can be heated. When the second heat generating circuit is energized, heat is generated as Joule heat by the internal resistance of the resistance heat generating layer 22b2, and only the both end regions in the width direction (axial direction) of the second heat generating sheet 22s generate heat. Both axial ends of the sleeve 21 can be heated.

  Like the planar heating element 22 shown in FIG. 4 to FIG. 6, the area of the entire planar heating element 22 is increased in order to secure a necessary amount of heat when it is divided up to the length direction (circumferential direction), In some cases, the fixing sleeve 21 having a small diameter cannot be used. Accordingly, as shown in FIG. 7, the heat generation sheets 22 s having different heat generation portions are stacked in the thickness direction of the sheet heating element 22, thereby different heat generation distributions as in the sheet heating element 22 illustrated in FIGS. 4 to 6. It is possible to achieve a high output while saving space (reducing the size) while realizing the planar heating element 22 that can be obtained.

  By the way, in the fixing device 50, during rotation, the fixing roller 21 is pulled by the pressure roller 31 at the nip portion, so that the fixing sleeve 21 on the upstream side of the nip portion becomes a tensioned side, and the inner peripheral surface of the fixing sleeve 21 is It slides on the sheet heating element 22 while being in pressure contact with the heating element support member 23. On the other hand, the tension is not applied to the fixing sleeve 21 on the downstream side of the nip portion, and the fixing sleeve 21 is in a relaxed state. If an attempt is made to increase the speed of the apparatus in this state, the fixing sleeve 21 on the downstream side of the nip portion. As a result, the degree of slackening of the fixing sleeve 21 becomes serious, and the rotational running stability of the fixing sleeve 21 is hindered.

  Therefore, the fixing device 50 is preferably provided with a rotation support member 27 that supports the rotation state of the fixing sleeve 21 on the inner peripheral side of the fixing sleeve 21 and at least on the downstream side of the nip portion.

  The rotation support member 27 has a pipe shape made of, for example, a thin metal such as iron or stainless steel having a thickness of 0.1 to 1 mm, and the outer diameter thereof is about 0.5 to 1 mm in diameter than the inner diameter of the fixing sleeve 21. It is small. Further, on the circumference of the pipe of the rotation support member 27, the inner peripheral surface of the fixing sleeve 21 is in contact with the outer peripheral surface of the rotation support member 27 at least from the position opposite to the nip portion and in the vicinity of the entrance of the nip portion. Further, the nip portion side is cut and opened in the axial direction on the outer peripheral surface of the rotation support member 27, and the end portion thereof is folded into the core holding member 28 side so as not to contact the nip portion.

  Further, as shown in FIG. 8, the rotation support member 27 is provided with an opening 27a by removing an outer peripheral surface of a certain region on the upstream side of the nip portion. As a result, as shown in FIG. 9, when the internal mechanism portion of the fixing sleeve 21 is configured, the entire surface of the sheet heating element 22 is exposed from the opening 27 a and the surface of the sheet heating element 22 is the rotation support member 27. The outer peripheral surface of the rotation support member 27 is slightly protruded from the outer peripheral surface of the rotation support member 27, and the planar heating element 22 contacts the inner peripheral surface of the fixing sleeve 21. become.

  Accordingly, the sheet heating element 22 (heating sheet 22s) is supported by the heating element support member 23 and is disposed in contact with the inner peripheral surface of the fixing sleeve 21, so that the fixing sleeve 21 can be efficiently heated. It is.

  As described above, the rotation support member 27 not only ensures the rotational running stability of the fixing sleeve 21 but also the fixing sleeve 21 can be supported by the rigid metal rotation support member 27, so that handling in assembly is easy. It is.

  The heat insulating support member 29 has a heat resistance sufficient to withstand the heat of the fixing sleeve 21 via the rotation support member 27 and a heat outflow (loss) from the rotation support member 27 in contact with the fixing sleeve 21 on the exit side of the nip portion. It has a heat insulating property to prevent, and a strength sufficient to support the rotating support member 27 so that the rotating fixing sleeve 21 does not deform when it contacts the rotating support member 27, and a heating element support member 23 is preferably the same foamed molded body of polyimide resin as 23.

  With the above configuration, the fixing device 50 can shorten the warm-up time and the first print time while saving energy. Further, since the heat generating sheet 22s in the sheet heating element 22 is a resin-based sheet, the stress caused by the rotation and vibration of the pressure roller 31 repeatedly acts on the heat generating sheet 22s, and the heat generating sheet 22s is repeatedly bent. Even if it breaks, it will not be damaged by fatigue and can be operated for a long time. In addition to this, by providing the rotation support member 27 (the heat insulation support member 29 as necessary), the rotational running stability of the fixing sleeve 21 can be improved, and the speed can be increased. Further, the heat support in the axial direction of the fixing sleeve 21 in the rotation support member 27 can assist the temperature uniformity in the axial direction of the fixing sleeve 21, so that it is possible to cope with a higher speed apparatus. Become.

  In the fixing device 50, the temperature at a predetermined position in the fixing sleeve 21 is detected by a temperature sensor, and heating control is performed by adjusting the power supply to the planar heating element 22 based on the detection result.

(Configuration of fixing device)
Hereinafter, in the fixing device, an internal member provided on the inner peripheral side of the fixing sleeve 21, and a heating element support member 23 that heats (heats) the fixing sleeve 21 by being heated by the planar heating element 22, and The rotation support member 27 is referred to as a heating body 30. In the case where the rotation support member 27 does not have the opening 27a (the configuration in which the heating element support member 23 does not contact the fixing sleeve 21) (see FIG. 18), the rotation support member 27 (heating member 27A) is used. It shall be called the heating body 30.

  As described above, the heating element 30 has sufficient heat resistance to withstand the heat generation of the sheet heating element 22 and the sheet heating element without being deformed when the rotating fixing sleeve 21 contacts the sheet heating element 22. However, when the inventors have made various studies, the fixing device 50 has a surface as shown in FIGS. 10 (a) and 10 (b). In the heating area (refer to FIG. 11, also referred to as a local heating area) by the heating element 22, thermal expansion of the heating element 30 may occur, while in the non-heated area, the thermal expansion of the heating element 30 may occur. It was found that does not occur. In FIG. 10, the dotted line portion indicates a state where thermal expansion has not occurred (also referred to as non-deformation), and the solid line portion represents a state where thermal expansion has occurred (also referred to as deformation), which is indicated by diagonal lines. The region is a deformed region.

  More specifically, during heating in a state where the fixing sleeve 21 is not driven (rotated) (non-rotating state), a difference occurs in the thermal expansion amount of the heating body 30 due to the temperature difference, and the fixing sleeve 21 is heated in the heating region. However, the amount of deformation is maximized at the central portion in the axial direction of the fixing sleeve 21, and the amount of deformation decreases in an arc shape toward the end. In contrast, when the driving (rotation) of the fixing sleeve 21 is started, the local temperature deviation is eliminated, and the deformation deviation due to the thermal deformation is eliminated. Note that the time when the fixing sleeve 21 is not rotated is when the fixing device is started up or when waiting for the next print job.

  Further, in order to more appropriately control the temperature at the time of paper passing in the fixing device, it is effective to detect the temperature in the heating region as the installation position of the temperature detecting means (temperature sensor) for detecting the temperature of the fixing sleeve 21. It is considered. However, when a temperature sensor is installed at a position facing the planar heating element 22 in the heating region of the fixing device 50, there arises a problem that detection accuracy decreases due to deformation due to thermal expansion. For example, when a contact-type temperature sensor is used, it is conceivable that the contact terminal bends due to the deformation, and it is removed from a desired detection location, or accurate temperature detection cannot be performed.

  Moreover, since temperature detection by the temperature sensor needs to be performed in the image region and the result needs to be reflected in the control, it is preferable to use a non-contact temperature sensor. In this case, the difference between the detected temperatures during deformation and non-deformation is large. In other words, when the non-contact sensor is adjusted in accordance with the deformation, the temperature control during the non-deformation is greatly shifted. Conversely, when the non-contact sensor is adjusted in accordance with the non-deformation, the temperature control during the deformation is greatly shifted. It will be. Here, “adjustment” refers to correcting the output value output from the temperature sensor and performing correction to more appropriately read the temperature of the desired object (fixing sleeve 21).

  As described above, in order to read the temperature more appropriately by the temperature sensor in both cases of deformation and non-deformation of the fixing sleeve 21 due to the deformation of the heating body 30, an appropriate temperature sensor corresponding to the deformation is used. It is necessary to install the temperature sensor in a proper position at a proper position and install the temperature sensor corresponding to the non-deformation.

  Therefore, as shown in FIGS. 11 and 12, the fixing device 20 according to this embodiment includes a fixing member (fixing sleeve 21) of a rotating endless belt and a pressure member (pressing member) that contacts the outer peripheral surface of the fixing member. A pressure roller 31), an abutting member (abutting member 26) which is disposed on the inner peripheral side of the fixing member and abuts against the pressure member via the fixing member to form a nip portion, and an inner periphery of the fixing member And a heating element (a heating element 30 (the heating element support member 23 and the rotation support member 27)) that contacts the fixing member and heats the fixing member, and a heating element (surface) that heats a predetermined area of the heating element And a first temperature detecting means (first temperature sensor 32) for detecting the temperature of the fixing member at a position corresponding to a predetermined region where the heating element heats the heating body on the outer peripheral side of the fixing member. The heating element adds the heating element on the outer peripheral side of the fixing member. Second temperature detecting means (second temperature sensor 33) for detecting the temperature of the fixing member at a position corresponding to a predetermined area (area excluding the nip portion) where the heating body heats the fixing member, which is an area other than the predetermined area. ).

  Here, the first temperature sensor 32 and the second temperature sensor 33 are both arranged in a non-contact manner with respect to the fixing sleeve 21, and are sensors that detect the heating state of the fixing sleeve 21. Further, in the fixing device 20, the fixing sleeve 21, the sheet heating element 22, the heating element support member 23, the terminal block stay 24, the power supply line 25, the contact member 26, the rotation support member 27, the core holding member 28, and the heat insulation support member. 29 and the pressure roller 31 are the same as those constituting the fixing device 50 shown in FIG. 1 and are different from the fixing device 50 in that the first temperature sensor 32 and the second temperature sensor 33 are provided.

  The fixing device 20 performs temperature control based on the output value of the second temperature sensor 33 because the heating body 30 is deformed and the first temperature sensor 32 is affected by gap fluctuation when the fixing sleeve 21 is not rotated. It is preferable. On the other hand, when the fixing sleeve 21 rotates, the heating body 30 is not deformed (when not deformed), and the gap fluctuation is small. Therefore, it is preferable to perform temperature control based on the output value of the first temperature sensor 32. Hereinafter, a study example regarding the installation positions of the first temperature sensor 32 and the second temperature sensor 33 will be described.

  In the example shown in FIGS. 11 and 12, the second temperature sensor 33 is provided on the upstream side of the heating region and on the opposite side of the contact member horizontal direction with respect to the driving direction of the fixing sleeve 21. The effectiveness of this installation position will be described.

  The fixing device 20 includes a rotating support member 27 formed of stainless steel (SUS) with a base material thickness of 30 μm and a diameter of 30 mm, and a surface layer of a nickel belt with a thickness of 30 μm covered with silicon rubber with a thickness of 200 μm. The sheet-shaped sheet heating element 22 is brought into contact with the inner lower surface of the heating element support member 23.

  First, the pressure roller 31 is brought into contact with the contact member 26, and the heating element 22 is energized in a state in which the fixing sleeve 21 is not driven, the heating body 30 is heated, and the fixing sleeve 21 is heated to 150 ° C. at once. At this time, the deformation amount of the heating body 30 and the surface temperature of the fixing sleeve 21 when the temperature reached 150 ° C. were measured.

  As shown in FIG. 13, the measurement location is set to a reference position (0 °) where the temperature becomes highest in the heating region by the heating element 22, and 10 ° from the reference position to the downstream side in the driving direction of the fixing sleeve 21. The amount of deformation at a total of 19 locations up to the opposing position (180 °) of the reference position was measured while shifting. Note that the measurement position in the axial direction is the central portion of the axial heating region. An example of the measurement result is shown in the graph of FIG.

  At the reference position, the amount of deformation is large. For example, when the temperature reaches 75 ° C., the heating element 30 is deformed to the outer periphery side by about 1.3 mm. became.

  Further, when the temperature at the reference position reached 100 ° C., the temperature of the fixing sleeve 21 decreased at a stretch from the vicinity of the measurement position 110 °. That is, it can be seen that the heat generated from the heating element 22 is not sufficiently transmitted to the position of the fixing sleeve 21.

  In the above example, if the measurement position is between 80 ° and 110 °, it can be said that the temperature of the fixing sleeve 21 can be detected without being affected by gap fluctuation due to deformation of the heating element. Therefore, when the first temperature sensor 32 is installed at the reference position where the temperature is highest in the heating region, the installation position of the second temperature sensor 33 is on the upstream side in the driving direction of the fixing sleeve 21 and at the rotation center of the fixing sleeve 21. On the other hand, it can be said that it is preferable to install it at a position from 80 ° to 110 °.

  Further, in the fixing device 20, the fixing sleeve 21 was driven while being heated, and after the rise, the deformation amount of the heating body 30 was measured when continuously driven at a target temperature of 150 ° C. for 1 minute. Here, since the gap between the first temperature sensor 32 provided at the position facing the heating element 22 and the heating element 30 is narrowed when the heating element 30 is deformed, the initial position of the gap in anticipation of the deformation amount when the deformation occurs. Must be set. As a result of one minute after the start of driving, regardless of the measurement position, the amount of deformation of the heating body is a deformation amount of 0.1 mm or less with respect to the initial heating body shape. It has become clear that the gaps of the do not fluctuate greatly.

  According to the above examination example, the following temperature control becomes possible using the first temperature sensor 32 and the second temperature sensor 33. First, the first temperature sensor 32 performs temperature detection and performs temperature control when there is little deformation during rotation. On the other hand, the second temperature sensor 33 detects the temperature when not rotating and controls the temperature. The first temperature sensor 32 needs to be installed away from the fixing member in anticipation of deformation during non-rotational heating. On the other hand, since it is not necessary to consider the influence of deformation, the second temperature sensor 33 can be installed in a range where temperature detection can be read more accurately and in a region where response delay is small.

  Here, with respect to the installation gap between the first temperature sensor 32 and the fixing sleeve 21, the extent to which the deformation at the time of non-rotation can be expected can be obtained as follows.

  First, when the relationship between the surface temperature of the fixing sleeve 21 at the measurement position 0 ° and the amount of deformation of the heating body was determined, the relationship between the two was directly proportional as shown in FIG. Therefore, in the image forming apparatus to which the fixing device 20 is applied, the heating element deformation amount can be estimated in advance based on the relationship shown in FIG. 15 depending on how many times (temperature) the reference position is used. it can. In consideration of the obtained heating element deformation amount, it is possible to determine how far the first temperature sensor 32 is placed from the fixing sleeve 21 so as to have a desired gap in that case as well. For example, in the above-described example, when the maximum temperature when not driven is 100 ° C., the deformation amount is 1.8 mm.

  Further, for example, when the maximum temperature reached when not driven is 75 ° C., it is necessary to install the gap about 1.3 mm apart. Accordingly, it is desirable to optimize the installation gap and select the sensor in consideration of the responsiveness and detection error of the temperature sensor with the gap being more than that.

  Each value in the above example is a value that should be appropriately defined depending on the configuration of the target fixing device, heating element conditions, and the like, and thus the above value is an example when the present invention is implemented.

  The first temperature sensor 32 is preferably provided with a predetermined inclination in the axial direction according to the position of the fixing sleeve 21 in the axial direction. FIG. 16 shows an example in which the opposed surface of the first temperature sensor 32 is inclined and installed in accordance with the deformation state of the heating body 30 and the fixing sleeve 21. In addition, the inclination of the 1st temperature sensor 32 should just be determined suitably according to the heating body shape at the time of a deformation | transformation.

  As described above, when the heating body 30 is deformed, the deformation amount is maximized at the central portion in the axial direction of the heating body 30, and the deformation amount is small at the end portion in the axial direction, so depending on the installation position of the first temperature sensor 32, It is also conceivable that the sensor detection surface and the fixing sleeve 21 are inclined, and the detection accuracy is shifted. Therefore, as described above, the temperature can be detected without degrading the detection accuracy by installing the first temperature sensor 32 with the sensor surface inclined from the beginning with respect to the predicted inclination at the time of deformation.

  Further, in normal temperature control at the time of rotation, it is not necessary to incline and install in this way. However, if the gap is made too far in consideration of the amount of deformation, the temperature detection accuracy during sheet passing will be lowered. Therefore, by doing as described above, it is possible to install as close to the fixing sleeve 21 as possible, and it is possible to detect the temperature without degrading the detection accuracy.

(Configuration of image forming apparatus)
Next, the image forming apparatus according to the present invention will be described. FIG. 17 is an overall configuration diagram showing the configuration of the image forming apparatus according to the present invention. As shown in FIG. 17, the image forming apparatus 1 is a tandem type color printer. Four bottles 102Y, 102M, 102C, and 102K corresponding to each color (yellow, magenta, cyan, and black) are detachably (replaceable) installed in the bottle housing portion 101 above the image forming apparatus main body 1. ing.

  An intermediate transfer unit 85 is disposed below the bottle housing portion 101. Image forming portions 4Y, 4M, 4C, and 4K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 78 of the intermediate transfer unit 85.

  Photosensitive drums 5Y, 5M, 5C, and 5K are disposed in the image forming units 4Y, 4M, 4C, and 4K, respectively. Further, around each of the photosensitive drums 5Y, 5M, 5C, and 5K, a charging unit 75, a developing unit 76, a cleaning unit 77, a charge removal unit (not shown), and the like are disposed. Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on each of the photoconductive drums 5Y, 5M, 5C, and 5K, and each photoconductive drum 5Y, 5M, 5C, An image of each color is formed on 5K.

  The photosensitive drums 5Y, 5M, 5C, and 5K are rotationally driven in a clockwise direction in FIG. 17 by a drive motor (not shown). The surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are uniformly charged at the position of the charging unit 75 (charging process). Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser light L emitted from the exposure unit 3, and electrostatic latent images corresponding to the respective colors are formed by exposure scanning at this position. (Exposure process).

  Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach a position facing the developing device 76, and the electrostatic latent image is developed at this position to form toner images of each color (developing process). ). Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the positions facing the intermediate transfer belt 78 and the first transfer bias rollers 79Y, 79M, 79C, and 79K, and at these positions, the photosensitive drums 5Y, 5M. , 5C, 5K are transferred onto the intermediate transfer belt 78 (this is a primary transfer process). At this time, a small amount of untransferred toner remains on the photosensitive drums 5Y, 5M, 5C, and 5K.

  Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach a position facing the cleaning unit 77, and untransferred toner remaining on the photosensitive drums 5Y, 5M, 5C, and 5K is removed at this position. It is mechanically recovered by a cleaning blade 77 (cleaning process). Finally, the surfaces of the photoconductor drums 5Y, 5M, 5C, and 5K reach a position facing a neutralization unit (not shown), and the residual potential on the photoconductor drums 5Y, 5M, 5C, and 5K is removed at this position. The Thus, a series of image forming processes performed on the photosensitive drums 5Y, 5M, 5C, and 5K is completed.

  Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 78 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 78. Here, the intermediate transfer unit 85 includes an intermediate transfer belt 78, four primary transfer bias rollers 79Y, 79M, 79C, and 79K, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, and an intermediate transfer cleaning unit 80. , Etc. The intermediate transfer belt 78 is stretched and supported by three rollers 82 to 84 and is endlessly moved in the direction of the arrow in FIG.

  The four primary transfer bias rollers 79Y, 79M, 79C, and 79K respectively sandwich the intermediate transfer belt 78 with the photosensitive drums 5Y, 5M, 5C, and 5K to form primary transfer nips. Then, a transfer bias reverse to the polarity of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K. The intermediate transfer belt 78 travels in the direction of the arrow and sequentially passes through the primary transfer nips of the primary transfer bias rollers 79Y, 79M, 79C, and 79K. In this way, the toner images of the respective colors on the photosensitive drums 5Y, 5M, 5C, and 5K are primarily transferred while being superimposed on the intermediate transfer belt 78.

  Thereafter, the intermediate transfer belt 78 onto which the toner images of the respective colors are transferred in an overlapping manner reaches a position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 sandwiches the intermediate transfer belt 78 between the secondary transfer roller 89 and forms a secondary transfer nip. The four color toner images formed on the intermediate transfer belt 78 are transferred onto the recording medium P conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 78. Thereafter, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning unit 80. At this position, the untransferred toner on the intermediate transfer belt 78 is collected. Thus, a series of transfer processes performed on the intermediate transfer belt 78 is completed.

  Here, the recording medium P transported to the position of the secondary transfer nip is transported from the paper feeding unit 12 disposed below the apparatus main body 1 via the paper feeding roller 97 and the registration roller pair 98. It is a thing. Specifically, a plurality of recording media P such as transfer paper are stored in the paper supply unit 12 in an overlapping manner. When the paper feed roller 97 is driven to rotate counterclockwise in FIG. 17, the uppermost recording medium P is fed between the rollers of the registration roller pair 98.

  The recording medium P conveyed to the registration roller pair 98 is temporarily stopped at the position of the roller nip of the registration roller pair 98 that has stopped rotating. Then, the registration roller pair 98 is rotationally driven in synchronization with the color image on the intermediate transfer belt 78, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

  Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing device 20. At this position, the color image transferred to the surface is fixed on the recording medium P by heat and pressure generated by the fixing sleeve 21 and the pressure roller 31. Thereafter, the recording medium P is discharged out of the apparatus through a pair of paper discharge rollers 99. The transferred P discharged from the apparatus by the discharge roller pair 99 is sequentially stacked on the stack unit 100 as an output image. Thus, a series of image forming processes in the image forming apparatus is completed.

  According to the image forming apparatus of the present invention described above, the fixing device 20 is provided, and a temperature sensor (that is, an output value of one of the temperature sensors) used for temperature control is selected according to the driving state of the fixing sleeve 21. By performing temperature control based on the output value, an appropriate temperature can be detected and temperature control can be performed both when the fixing sleeve 21 is not rotating and when it is rotating. Therefore, warm-up time and first print time are short, and appropriate image formation can be performed. Note that the image forming apparatus may determine which sensor is used for temperature control based on output values from the first temperature sensor 32 and the second temperature sensor 33.

  Specifically, in a heating situation in which the heating body 30 is deformed (during non-rotation), it is preferable to perform temperature control using the second temperature sensor 33, and heating in which the deformation of the heating body 30 has not occurred. In the case of a situation (during rotation), it is desirable to perform temperature control using the first temperature sensor 32.

  In addition, for example, when the fixing sleeve 21 is not driven as in standby, but the heating body 30 heats the fixing sleeve 21 minutely, the temperature control is performed using the first temperature sensor 32. Is also preferable. By continuing the minute heating during standby, the fixing sleeve 21 has a uniform temperature distribution (not a local temperature distribution), no difference in thermal expansion occurs, and deformation of the heating body is reduced. Therefore, the gap between the fixing sleeve 21 and the first temperature sensor 32 is kept constant, so that the detection accuracy of the first temperature sensor 32 can be improved.

  The above-described embodiment is a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

  For example, in FIG. 11, the example using the sheet-like planar heating element 22 as the heating element has been described. By using the planar heating element 22, it is possible to clearly separate the heating area and the non-heating area in the heating body 30 as compared with the case where a halogen heater or the like is used, and therefore the influence of deformation on the second temperature sensor 33. Although the detection accuracy of the second temperature sensor 33 can be further improved, the heating element is not limited to the planar heating element, and a halogen heater, an electromagnetic induction heating mechanism, etc. It is good also as a structure which uses and uses local heating about the heating area | region at the time of non-rotating heating. FIG. 18 shows the configuration of the fixing device when the heating element is a halogen heater.

  As shown in FIG. 18, the fixing device 20 is disposed on a fixing sleeve 21 of a rotating endless belt, a pressure roller 31 in contact with an outer peripheral surface of the fixing sleeve 21, and an inner peripheral side of the fixing sleeve 21. An abutting member 26 that abuts against the pressure roller 31 through the fixing sleeve 21 to form a nip portion, and is disposed on the inner peripheral side of the fixing sleeve 21, and abuts on the fixing sleeve 21 to heat the fixing sleeve 21. It comprises a pipe-shaped heating member 27A and a halogen heater 22h for heating a predetermined region of the heating member 27A, and further includes the first temperature sensor 32 and the second temperature sensor described above. Further, the contact member 26 is supported from the back by a reinforcing member 28A, and the reinforcing member 28A defines a heating region of the heating member 27A by the halogen heater 22h.

  In the fixing device 20, the rotation support member 27 and the heating element support member 23 are not fixed to the frame (side plate) of the fixing device 20 at both ends in the axial direction. It is also applicable to the state. That is, in any state, when the apparatus is started up by performing heat generation control of the sheet heating element 22 while the fixing sleeve 21 is not rotated, the rotation support member 27 or This is because local heat expansion of the heat generating member support member 23 occurs, and the planar heat generating member 22 and the fixing sleeve 21 are deformed so as to protrude to the outermost side in the axial central portion and become convex. However, when the rotation support member 27 and the heating element support member 23 are fixed to the frame of the fixing device 20 at both ends in the axial direction, the planar heating element 22 and the fixing sleeve 21 are convex at the center in the axial direction. Since the deformation is more remarkable, the present invention is more effective.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Exposure part 4Y, 4M, 4C, 4K Image forming part 5Y, 5M, 5C, 5K Photosensitive drum 12 Paper feed part 20, 50 Fixing apparatus 21 Fixing sleeve 22 Planar heating element (heating element)
22a Base layer 22b, 22b1, 22b2 Resistance heating layer 22c Electrode layer 22d Insulating layer 22e, 22e1, 22e2 Electrode terminal 22s Heating sheet 22h Halogen heater 23 Heating element support member 24 Terminal block stay 25 Feed line 26 Contact member 27 Rotation support member 27a Opening 27A Heating member 28 Core holding member 28A Reinforcing member 29 Heat insulating support member 30 Heating body 31 Pressure roller 32 First temperature sensor (first temperature detecting means)
33 Second temperature sensor (second temperature detecting means)
75 Charging unit 76 Developing unit 77 Cleaning unit 78 Intermediate transfer belts 79Y, 79M, 79C, 79K First transfer bias roller 80 Intermediate transfer cleaning unit 82 Secondary transfer backup roller 83 Cleaning backup roller 84 Tension roller 89 Secondary transfer roller 85 Intermediate Transfer unit 97 Paper feed roller 98 Registration roller pair 99 Paper discharge roller pair 100 Stack portion 101 Bottle storage portions 102Y, 102M, 102C, 102K Toner bottle L Laser light P Recording medium T Toner 1

Japanese Patent Laid-Open No. 11-2982 JP-A-4-44075 JP-A-8-262903 Japanese Patent Laid-Open No. 10-213984 JP 2007-334205 A JP 2008-154822 A JP 2008-216928 A

Claims (10)

A fixing member for a rotating endless belt;
A pressure member in contact with the outer peripheral surface of the fixing member;
An abutting member disposed on an inner peripheral side of the fixing member and abutting the pressure member via the fixing member to form a nip portion;
A heating element that is disposed on the inner peripheral side of the fixing member and that heats the fixing member in contact with the fixing member;
A heating element for heating a predetermined region of the heating element;
First temperature detecting means for detecting the temperature of the fixing member at a position corresponding to a predetermined area where the heating element heats the heating body on the outer peripheral side of the fixing member;
The temperature of the fixing member at a position corresponding to a predetermined region where the heating element heats the fixing member, on the outer peripheral side of the fixing member, and in a region other than the predetermined region where the heating element heats the heating member. And a second temperature detecting means for detecting the fixing device.   The fixing device according to claim 1, wherein the heating element is a sheet-like planar heating element.   The heating element includes a heating element support member that supports the planar heating element from a side opposite to the fixing member, and a rotation support member that supports a rotation state of the fixing member. 3. The fixing device according to 2.   The first temperature detecting means is provided with a predetermined gap with respect to the heating body both when the heating body is not deformed and when the heating body is deformed by thermal expansion. The fixing device according to claim 1.   The said 1st temperature detection means is provided in the position corresponded to the area | region where temperature becomes the highest among the predetermined | prescribed area | regions where the said heat generating body heats the said heating body. The fixing device described.   When the installation position of the first temperature detection means is a reference position, the second temperature detection means is 80 ° upstream from the reference position with respect to the rotation center of the fixing member in the rotation direction of the fixing member. The fixing device according to claim 1, wherein the fixing device is installed at a position of ˜110 °.   7. The fixing according to claim 1, wherein the first temperature detection unit is provided with a predetermined inclination in the axial direction in accordance with an axial position of the fixing member. apparatus.   An image forming apparatus comprising the fixing device according to claim 1.   Temperature control is performed based on an output value from the first temperature detection means when the fixing member rotates, and temperature control is performed based on an output value from the second temperature detection means when the fixing member is not rotating. The image forming apparatus according to claim 8.   9. The image formation according to claim 8, wherein the temperature detection unit to be used for temperature control is determined based on output values from the first temperature detection unit and the second temperature detection unit. apparatus.

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