JP2017122899A - Fixing device and image forming apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that can prevent breakage of or damage to a driving source, such as a motor, while preventing an excessive increase in temperature of a fixing member due to heating, and an image forming apparatus using the same.SOLUTION: A fixing device comprises: a nip forming member that is located on the inner peripheral side of a fixing belt and forms a fixing nip part between the fixing belt and a pressure roller; a lubricant that is interposed between the fixing belt and nip forming member; heating means 23 and 45 that heats the fixing belt; a heating control part 48 that controls the heating means 45; driving means 40 and 46 that rotate to drive the pressure roller; and a delay circuit 51 that, when a heating start signal for starting heating of the fixing belt is output from the heating control part 48 to the heating means 45, outputs a signal obtained by delaying the heating start signal for a certain time to the driving means 46 as a rotation start signal for starting rotation of the pressure roller.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a thermal fixing device in an electrophotographic image forming apparatus, and an image forming apparatus such as a copying machine, a printer, and a facsimile equipped with the fixing device.

  In an image forming apparatus such as a copying machine, a printer, or a facsimile, a toner image is formed on an image carrier based on image information, and the toner image is transferred onto a recording medium such as paper or an OHP sheet. Thereafter, the unfixed toner image carried on the recording medium is fixed on the recording medium by the fixing device.

  The fixing device is provided with a fixing rotator constituted by opposing rollers or belts, or a combination thereof. A recording sheet as a recording medium is sandwiched at a nip portion, and a toner image is placed on the recording sheet by heat and pressure. To settle.

  Patent Document 1 discloses a fixing device configured to directly heat a thin-walled cylindrical heat-resistant film (fixing belt) as a fixing rotating body from the inside by a halogen heater. In this fixing device, a lubricant is applied to the inner surface of the fixing belt that contacts the fixing member so as to reduce the contact frictional resistance between the fixing belt and the fixing member.

  Normally, the lubricant has a high viscosity at a low temperature, and the viscosity decreases as the temperature increases. Therefore, the contact friction resistance of the sliding portion between the fixing belt and the fixing member increases at a low temperature. When the contact frictional resistance is large, the load (torque) at the sliding portion between the fixing belt and the fixed member increases, and the rotary drive unit such as a motor may be damaged or broken.

  Therefore, the fixing device disclosed in Patent Document 1 is configured to heat the fixing belt until the viscosity of the lubricant becomes sufficiently low and then rotate the fixing belt. At that time, the temperature of the fixing belt is monitored by a temperature sensor, and when the temperature detected by the temperature sensor reaches a predetermined temperature, the rotation of the fixing belt is started.

  However, in the fixing device as disclosed in Patent Document 1, since the temperature of the fixing belt during heating is fast, if the rotation is started after detecting a predetermined temperature by the temperature sensor, the temperature of the fixing belt is heat resistant. There is a concern that the fixing belt may be damaged by rising to a temperature or higher.

  The present invention has been made to solve such a conventional problem, and is capable of preventing damage and breakage of a driving source such as a motor while preventing an excessive temperature rise of a fixing member due to heating. It is an object to provide an apparatus and an image forming apparatus using the apparatus.

  In order to solve the above-described problems, a fixing device according to the present invention is rotatably provided and fixes a non-fixed image on a recording medium, and is rotatably provided and presses the fixing member from the outer peripheral side. A pressure member, a fixing member that is located on an inner peripheral side of the fixing member, and that forms a fixing nip portion between the fixing member and the pressure member; and between the fixing member and the fixing member An interposed lubricant, a heating means for heating the fixing member, a heating control means for controlling the heating means, a driving means for rotationally driving the pressure member, and heating of the fixing member from the heating control means. When a heating start signal for starting is output to the heating means, a signal obtained by delaying the heating start signal for a predetermined time is sent to the driving means as a rotation start signal for starting the rotation of the pressurizing member. Output delay And road, a configuration including.

  The present invention provides a fixing device and an image forming apparatus using the same, which can prevent a heating source such as a motor from being damaged or broken while preventing an excessive temperature rise of a fixing member due to heating.

1 is a schematic configuration diagram of an image forming apparatus including a fixing device according to a first embodiment of the present invention. 1 is a cross-sectional view of a fixing device according to a first embodiment of the present invention. FIG. 3 is a block diagram illustrating a functional configuration of a heating control unit included in the fixing device according to the first embodiment of the present invention. FIG. 3 is a block diagram for explaining control by a heating control unit provided in the fixing device according to the first embodiment of the present invention. FIG. 6 is a diagram illustrating an example of timing of heating of a fixing belt and rotation of a pressure roller in the first embodiment of the present invention. FIG. 10 is a block diagram for explaining control by a heating control unit provided in a fixing device according to a second embodiment of the present invention. FIG. 10 is a diagram illustrating an example of timing of heating of a fixing belt and rotation of a pressure roller in the second embodiment of the present invention. It is a figure explaining the example which changes a rotational speed according to the detection temperature of a temperature sensor in the 3rd Embodiment of this invention. It is a graph which shows the example of transition of the torque of a motor in a 4th embodiment of the present invention. It is a graph which shows the other example of transition of the torque of a motor in the 4th Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram illustrating a schematic configuration of an embodiment of an image forming apparatus including a fixing device according to an embodiment of the present invention, and illustrates an example in which the image forming apparatus is applied to an electrophotographic multifunction peripheral. ing.

  First, the configuration will be described.

  An image forming apparatus 200 shown in FIG. 1 employs an electrophotographic system, and includes an image forming apparatus main body 200K, an image reading apparatus 200C, and a duplex unit 300. In the image forming apparatus 200, an image reading apparatus 200C is provided on the image forming apparatus main body 200K, and a duplex unit 300 is attached to the right side surface.

  The image forming apparatus main body 200K includes a paper feeding device 114, an exposure device 113, an image forming device 112, an intermediate transfer device 110, a secondary transfer device 121, and a fixing device 20, in the order of the image forming process.

  The sheet feeding device 114 is disposed below the inside of the image forming apparatus main body 200K. The paper feeding device 114 includes two paper feeding cassettes 115 that store the recording medium P in this embodiment. A paper feed roller 117 is provided at the upper right of each paper feed cassette 115 to feed out the recording media P in each paper feed cassette 115 one by one into the recording medium transport path 116.

  The exposure device 113 is disposed above the paper feed cassette 115. The exposure device 113 irradiates the image forming device 112 with laser light based on image data of a document P (recording medium) or fixed document received by an image sensor, or image data received through a personal computer or a telephone line. It has become.

  The image forming device 112 includes image forming devices 112c, 112m, 112y, and 112k for each color of cyan (c), magenta (m), yellow (y), and black (k), and is provided above the exposure device 113. It has been. The image forming devices 112c, 112m, 112y, and 112k are arranged in a quadruple tandem manner along the stretch direction of the intermediate transfer belt 111. Each of the image forming devices 112c, 112m, 112y, and 112k is configured by installing a charging device, a developing device, a transfer device, a cleaning device, and the like around a drum-shaped image carrier that rotates clockwise in the drawing.

  The intermediate transfer device 110 is provided so that an endless intermediate transfer belt 111 wound around a plurality of rollers is stretched almost horizontally and runs counterclockwise. Here, “endless” refers to a state where both ends of the belt are joined and there is no joint. The intermediate transfer device 110 includes primary transfer devices 125c, 125m, 125y, and 125k that face each other with the image transfer members 31 of the image forming devices 112c, 112m, 112y, and 112k interposed between the intermediate transfer belt 111. The primary transfer devices 125c, 125m, 125y, and 125k transfer the toner image formed on the image carrier 31 to the intermediate transfer belt 111.

  The secondary transfer device 121 is disposed on the path of the recording medium conveyance path 116 and transfers a toner image, which is a primary transfer image formed on the intermediate transfer belt 111, to the recording medium P. Here, the recording medium conveyance path 116 is formed on the right side in the image forming apparatus main body 200K from the lower side to the upper side, and is formed on the image forming apparatus main body 200K with the image reading apparatus 200C. 118 is provided so as to communicate with 118. In the recording medium conveyance path 116, a conveyance roller 119, a secondary transfer device 121, a fixing device 20, a paper discharge device 123 including a pair of paper discharge rollers, and the like are sequentially provided so as to face the intermediate transfer belt 111.

  Upstream of the transport roller 119, a paper feed path through which the recording medium P re-feeded from the duplex unit 300 or manually fed from the manual feed device 136 across the duplex unit 300 joins the recording medium transport path 116. 137 is provided. Further, a refeed conveyance path 124 to the duplex unit 300 is provided downstream from the fixing device 20 and is branched from the recording medium conveyance path 116.

  The image reading device 200C is a scanner device, and has, for example, a function of reading an image of a document P that is in the process of being transported by an automatic document transport device and a function of reading an image of a fixed document.

  At the time of image formation, the image forming apparatus 200 reads an original image with the image reading apparatus 200C and writes it with the exposure apparatus 113, and each color toner image is placed on each image carrier of each of the image forming apparatuses 112c, 112m, 112y, and 112k. Form. Further, the image forming apparatus 200 sequentially transfers the toner images by the primary transfer devices 125c, 125m, 125y, and 125k to form a color image on the intermediate transfer belt 111.

  Further, the image forming apparatus 200 selectively rotates one of the paper feed rollers 117 to feed out the recording medium P from the corresponding paper feed cassette 115 and transport it to the recording medium transport path 116, or the manual paper feeder 136. The manual feed recording medium is conveyed to the paper feed path 137. Then, the image forming apparatus 200 conveys the recording medium P to the secondary transfer position at the timing conveyed by the conveying roller 119 through the recording medium conveying path 116, and the color formed on the intermediate transfer belt 111 as described above. The image is transferred to the recording medium P by the secondary transfer device 121. The recording medium P after the image transfer is fixed by the fixing device 20, discharged by the paper discharge device 123, and stacked on the in-body paper discharge unit 118.

  The duplex unit 300 is provided on the right side of the image forming apparatus main body 200K. When an image is also formed on the back side of the recording medium P, the recording medium P having an image formed on the front side is put into the refeed conveyance path 124 and reversed by the duplex unit 300 and then fed again through the feed path 137. . The re-feeded recording medium P is subjected to a secondary transfer of a color image separately formed on the intermediate transfer belt 111 and then fixed again by the fixing device 20, and the in-body paper discharge unit 118 by the paper discharge device 123. To be discharged.

  Hereinafter, the configuration of the fixing device 20 will be described with reference to FIG.

  As shown in FIG. 2, the fixing device 20 includes a fixing belt 21 as a fixing member that contacts an unfixed image and fixes the unfixed image on the recording medium P, and a fixing belt that contacts the outer peripheral surface of the fixing belt 21. And a pressure roller 22 as an opposing member that presses the pressure 21 from the outer peripheral side. Both the fixing belt 21 and the pressure roller 22 are rotatably provided. The fixing device 20 includes a heat source 23 such as a halogen heater as a heating unit that heats the fixing belt 21 with electric power from a commercial power source. Further, the fixing device 20 is in contact with the pressure roller 22 from the inner peripheral side of the fixing belt 21, and a nip forming member 24 that forms a fixing nip portion N between the fixing belt 21 and the pressure roller 22. And a stay 25 as a support member that supports the forming member 24. Further, the fixing device 20 functions as a reflection member 26 that reflects heat from the heat source 23 to the fixing belt 21, a shielding member 27 that shields heat from the heat source 23, and a temperature detection unit that detects the temperature of the fixing belt 21. A temperature sensor 28 and the like are provided.

  The fixing belt 21 is composed of a thin and flexible endless belt member (including a film). Specifically, the fixing belt 21 is constituted by an inner peripheral base material and an outer peripheral release layer. The base material on the inner peripheral side is formed using a metal material such as nickel or SUS (stainless steel) or a resin material such as polyimide (PI). The release layer on the outer peripheral side is formed using, for example, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) or polytetrafluoroethylene (PTFE). Further, an elastic layer formed of a rubber material such as silicone rubber, foamable silicone rubber, or fluorine rubber may be interposed between the base material and the release layer.

  When there is no elastic layer, the heat capacity is reduced and the fixability is improved, but when the unfixed toner is crushed and fixed, minute irregularities on the belt surface are transferred to the image, and uneven glossiness occurs in the solid portion of the image. It can happen. In order to prevent this, it is desirable to provide an elastic layer having a thickness of 100 μm or more. By providing an elastic layer having a thickness of 100 μm or more, minute unevenness can be absorbed by elastic deformation of the elastic layer, so that occurrence of uneven gloss can be avoided.

  In the present embodiment, in order to reduce the heat capacity of the fixing belt 21, the fixing belt 21 is thin and has a small diameter. Specifically, the thicknesses of the base material, the elastic layer, and the release layer constituting the fixing belt 21 are set in a range of 20 to 50 μm, 100 to 300 μm, and 10 to 50 μm, and the overall thickness is set. It is set to 1 mm or less. The diameter of the fixing belt 21 is set to 20 to 40 mm. Furthermore, in order to reduce the heat capacity, the total thickness of the fixing belt 21 is desirably 0.2 mm or less, and more preferably 0.16 mm or less. The diameter of the fixing belt 21 is desirably 30 mm or less.

  Further, a lubricant 30 such as silicone oil or fluorine grease is applied to the inner surface of the fixing belt 21. Accordingly, the lubricant 30 is interposed between the fixing belt 21 and the nip forming member 24, and the contact friction resistance between the fixing belt 21 and the nip forming member 24 is reduced by the lubricant 30.

  The pressure roller 22 includes a metal core 22a, an elastic layer 22b provided on the surface of the metal core 22a, and a release layer 22c made of PFA, PTFE, or the like provided on the surface of the elastic layer 22b. ing. The elastic layer 22b is made of foamable silicone rubber, silicone rubber, fluorine rubber, or the like. The pressure roller 22 is pressed toward the fixing belt 21 by a pressing means such as a spring and is in contact with the nip forming member 24 via the fixing belt 21. At the location where the pressure roller 22 and the fixing belt 21 are in pressure contact, the elastic layer 22b of the pressure roller 22 is crushed to form a fixing nip portion N having a predetermined width. Note that the fixing member and the opposing member are not limited to being in pressure contact with each other, but may be configured to simply contact without pressing.

  The pressure roller 22 is configured to be rotationally driven by a motor 40 as a driving unit provided in the image forming apparatus main body 200K. When the pressure roller 22 is rotationally driven in the direction of the arrow B1, the driving force is transmitted to the fixing belt 21 at the fixing nip N, and the fixing belt 21 is driven to rotate in the direction of the arrow B2. As a result, the recording medium P to which the toner T is adhered by the transfer of the toner images of the respective colors is inserted from the direction of the arrow A1 toward the fixing nip N of the fixing device 20 and passes through the fixing nip N, whereby the toner T After fixing, the image is sent in the direction indicated by an arrow A2.

  In the present embodiment, the pressure roller 22 is a solid roller, but may be a hollow roller. In that case, a heat source such as a halogen heater may be disposed inside the pressure roller 22. The elastic layer 22b may be a solid rubber, but if there is no heat source inside the pressure roller 22, a sponge rubber may be used. Sponge rubber is more desirable because it improves heat insulation and makes it difficult for the fixing belt 21 to lose heat.

  The heat source 23 is disposed on the inner peripheral side of the fixing belt 21 and on the upstream side of the fixing nip portion N in the conveyance direction of the recording medium P. Specifically, in FIG. 2, assuming that a virtual line passing through the center Q in the conveyance direction of the recording medium P in the fixing nip portion N and the rotation center O of the pressure roller 22 is La, the heat source 23 is more than the virtual line La. The recording medium P is disposed on the upstream side in the conveyance direction (the lower side in FIG. 2). The heat source 23 is configured such that a power supply unit provided in the image forming apparatus main body 200K is output-controlled by a heating control unit 48 described later to generate heat, and the output control is performed by the temperature sensor 28 of the fixing belt 21. This is performed based on the detection result of the surface temperature. By such output control of the heat source 23, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature.

  Instead of the temperature sensor 28 for detecting the temperature of the fixing belt 21, a temperature sensor for detecting the temperature of the pressure roller 22 is provided, and the temperature of the fixing belt 21 is predicted based on the temperature detected by the temperature sensor. May be.

  In the present embodiment, two heat sources 23 are provided, but the number of heat sources 23 may be one or three or more according to the size of the recording medium P used in the image forming apparatus 200. In addition to the halogen heater, an IH heater, a resistance heating element, a carbon heater, or the like can be used as the heat source 23 for heating the fixing belt 21.

  The nip forming member 24 includes a base pad 24a and a low friction sliding sheet 24b provided on a surface of the base pad 24a facing the fixing belt 21. The base pad 24 a is disposed in a longitudinal shape over the axial direction of the fixing belt 21 or the axial direction of the pressure roller 22. The shape of the fixing nip portion N is determined when the base pad 24 a receives the pressure applied by the pressure roller 22.

  In the present embodiment, the fixing nip portion N has a flat shape, but may have a concave shape or other shapes.

  The sliding sheet 24b is provided to reduce sliding friction when the fixing belt 21 rotates. In addition, by including the lubricant 30 in the sliding sheet 24b, the sliding sheet 24b can supply and apply the lubricant 30 to the inner surface of the fixing belt 21 when the fixing belt 21 rotates. In addition, when the base pad 24a itself is formed of a low-friction member, a configuration without the sliding sheet 24b may be employed.

  The base pad 24a is made of a heat resistant material having a heat resistant temperature of 200 ° C. or higher. With such a configuration, the deformation of the nip forming member 24 due to heat is prevented in the toner fixing temperature range, and a stable state of the fixing nip portion N is secured to stabilize the output image quality. In addition, the base pad 24a is required to have appropriate rigidity to ensure strength.

  As a material of the base pad 24a that satisfies the above conditions, it is possible to use a resin such as polyethersulfone (PES) or polyphenylene sulfide (PPS). Alternatively, a resin such as liquid crystal polymer (LCP), polyether nitrile (PEN), polyamide imide (PAI), polyether ether ketone (PEEK), or the like can be used. In addition, the base pad 24a can be formed of metal or ceramic.

  The base pad 24 a is fixedly supported by the stay 25. Thus, the nip forming member 24 is prevented from being bent by the pressure of the pressure roller 22, and a uniform nip width is obtained in the axial direction of the pressure roller 22. The stay 25 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron in order to satisfy the function of preventing the nip forming member 24 from bending.

  The reflection member 26 is fixedly supported by the stay 25 so as to face the heat source 23. By reflecting the radiant heat from the heat source 23 to the fixing belt 21 by the reflecting member 26, heat is prevented from being transmitted to the stay 25 and the like, thereby efficiently heating the fixing belt 21 and saving energy. Yes. As the material of the reflecting member 26, aluminum, stainless steel or the like is used. In particular, in the case of using a material obtained by vapor-depositing silver having a low emissivity (high reflectivity) on an aluminum base material, the heating efficiency of the fixing belt 21 can be improved.

  The shielding member 27 is configured by forming a metal plate having a thickness of 0.1 mm to 1.0 mm into an arc-shaped cross-sectional shape along the inner peripheral surface of the fixing belt 21. The shielding member 27 is movable in the circumferential direction between the fixing belt 21 and the heat source 23.

  As shown in FIG. 2, in the present embodiment, in a circumferential region of the fixing belt 21, a heated region α that faces the heat source 23 and is directly heated by the heat source 23, and a non-heated region that is not directly heated by the heat source 23. β is formed. Other members (such as the reflection member 26, the stay 25, and the nip forming member 24) fixed to the side plate or the like are interposed between the non-heating region β and the heat source 23.

  When it is necessary to perform heat shielding, as shown in FIG. 2, the shielding member 27 is disposed at a shielding position set at one place or a plurality of places on the heated region α side. For example, the shielding member 27 is moved to the shielding position so as to shield the area where the paper is not passed according to the width of the paper that is passed by conveyance.

  On the other hand, when there is no need for heat shielding, the shielding member 27 can be moved to the non-heating region β side, and the entire shielding member 27 can be retracted to the back side of the reflecting member 26 and the stay 25.

  In this way, by rotating the shielding member 27, the area of the heated region α of the fixing belt 21 is changed, and the amount of radiant heat applied to the fixing belt 21 from the heat source 23 is adjusted. Since the shielding member 27 requires heat resistance, it is preferable to use a metal material such as aluminum, iron, stainless steel, or ceramic as the material.

  Next, the control configuration of the heating control unit 48 provided in the fixing device 20 of the present embodiment will be described with reference to FIG.

  As shown in FIG. 3, the heating control unit 48 is configured such that each element is connected to the CPU 41 via a bus, and the CPU 41 controls each element.

  An I / O circuit 42, a ROM (Read Only Memory) 43, and a RAM (Random Access Memory) 44 are connected to the CPU 41. The I / O circuit 42 is an interface for controlling input / output among the temperature sensor 28, the heater power supply circuit 45, the motor control circuit 46, the torque measurement unit 47, the delay circuit 51, and the switching circuit 52.

  The heating control unit 48 performs control to increase the output of the heat source 23 when the temperature detected by the temperature sensor 28 is lower than the target temperature, and conversely decreases the output of the heat source 23 when the detected temperature exceeds the target temperature. Take control. In this way, the heating control is performed so that the temperature detected by the temperature sensor 28 is maintained near the target temperature.

  For example, the control executed by the heating control unit 48 includes ON / OFF control in which the lighting rate of the heat source 23 is composed of two values of 0% and 100%, or the lighting rate is changed by a difference value between the target temperature and the current temperature. Two methods of PID control are conceivable, but either method may be used.

  As will be described below, the fixing device 20 of the present embodiment includes the heating control unit 48, so that heating of the fixing belt 21 is started in advance before the rotation of the pressure roller 22 and the viscosity of the lubricant 30 is increased. Rotation start is executed after lowering.

  As shown in FIG. 4, the heating control unit 48 heats the fixing belt 21 when the power of the fixing device 20 is turned on by a user operation or when there is a print request from the image forming apparatus 200. The heater ON signal for starting is output. This heater ON signal is input to the heater power supply circuit 45 and the delay circuit 51.

  The heater power supply circuit 45 is a circuit that supplies power to the heat source 23 under the control of the heating control unit 48. The heater power supply circuit 45 starts driving the heat source 23 by receiving a heater ON signal as a heating start signal output from the heating controller 48.

  The delay circuit 51 includes a transistor, a capacitor, and a resistor. The delay circuit 51 starts a rotation of the pressure roller 22 with a signal obtained by delaying the heater ON signal output from the heating control unit 48 by a predetermined time Δt. The rotation start signal is output to the motor control circuit 46. It is desirable that the delay time Δt can be set to an arbitrary value by the user.

  The motor control circuit 46 receives the rotation start signal output from the delay circuit 51, thereby starting current supply to the motor 40 and driving the motor 40.

  That is, as shown in FIG. 5, from the timing when the heater ON signal is output from the heating control unit 48, the driving of the motor 40 is started after the delay time Δt has elapsed, and the pressure roller 22 and the fixing belt 21 are rotated. As a result, the fixing belt 21 can be heated without overheating of the fixing belt 21.

  As described above, the fixing device according to the present embodiment is applied after the heating of the fixing belt 21 is started in order to reduce the viscosity of the lubricant at the sliding portion between the fixing belt 21 and the nip forming member 24. The pressure roller 22 is rotated. Thereby, the contact frictional resistance at the sliding portion between the fixing belt 21 and the nip forming member 24 is reduced, and the torque generated at the sliding portion is also reduced. At this time, the fixing device of the present embodiment does not control the rotation start of the pressure roller 22 according to the temperature detected by the temperature sensor 28, but the hardware of the pressure roller 22 by the delay circuit 51. Delay the start of rotation. As a result, it is possible to prevent damage and breakage of the drive source such as the motor 40 due to high torque while preventing an excessive temperature rise of the fixing belt 21 due to detection delay.

(Second Embodiment)
Hereinafter, a second embodiment of a fixing device according to the present invention will be described with reference to the drawings. The same components as those of the fixing device according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 6, the heating control unit 48 may be configured to output a heater ON signal for starting heating of the fixing belt 21 to the heater power supply circuit 45, the delay circuit 51, and the switching circuit 52.

  In the configuration of FIG. 6, the delay circuit 51 outputs a rotation start signal obtained by delaying the heater ON signal by a predetermined time Δt to the switching circuit 52.

  The switching circuit 52 outputs the heater ON signal to the motor control circuit 46 as a rotation start signal without passing through the delay circuit 51 when the temperature detected by the temperature sensor 28 before the heating of the fixing belt 21 by the heat source 23 is equal to or higher than a certain temperature. It is supposed to be. That is, as shown in FIG. 7, the driving of the motor 40 is started simultaneously with the timing when the heater ON signal is output from the heating controller 48, and the pressure roller 22 and the fixing belt 21 rotate.

  On the other hand, the switching circuit 52 outputs the rotation start signal output from the delay circuit 51 to the motor control circuit 46 when the temperature detected by the temperature sensor 28 before the heating of the fixing belt 21 by the heat source 23 is lower than a certain temperature. (Figure 5).

  In this way, the timing for starting the rotation of the pressure roller 22 can be adjusted according to the temperature detected by the temperature sensor 28. As described above, if the temperature detected by the temperature sensor 28 is equal to or higher than a certain temperature, it can be determined that the viscosity of the lubricant 30 is low, so that the pressure roller 22 can be rotated without delay.

(Third embodiment)
Hereinafter, a third embodiment of a fixing device according to the present invention will be described with reference to the drawings. The same components as those of the fixing device according to the first and second embodiments are denoted by the same reference numerals, and detailed description thereof is omitted.

  The motor control circuit 46 shown in FIGS. 4 and 6 receives the rotation start signal from the delay circuit 51 or the switching circuit 52 according to the temperature detected by the temperature sensor 28 before the heating of the fixing belt 21 by the heat source 23 is started. The rotation speed of the pressure roller 22 may be controlled.

  For example, as shown in FIG. 8, when the temperature detected by the temperature sensor 28 before the start of heating is A or higher, the motor control circuit 46 starts the rotation of the pressure roller 22 at the rotation speed b. On the other hand, when the temperature detected by the temperature sensor 28 before the start of heating is less than A, the motor control circuit 46 starts the rotation of the pressure roller 22 at the rotation speed a (<b). Thereafter, when the temperature detected by the temperature sensor 28 becomes A or higher, the motor control circuit 46 may rotate the pressure roller 22 at the rotation speed b.

  With such a configuration, when it is considered that the temperature of the fixing belt 21 is relatively high and the viscosity of the lubricant 30 is low, the pressure roller 22 can be immediately rotated at the normal rotation speed b. Further, when the temperature of the fixing belt 21 is relatively low and the viscosity of the lubricant 30 is considered high, the motor 40 is prevented from being damaged by rotating the pressure roller 22 at a low rotational speed a. be able to.

(Fourth embodiment)
Hereinafter, a fourth embodiment of the fixing device according to the present invention will be described with reference to the drawings. The same components as those of the fixing devices according to the first to third embodiments are denoted by the same reference numerals, and detailed description thereof is omitted. The present embodiment relates to stop control when a drive system such as the motor 40 has an abnormality.

  The torque measuring unit 47 shown in FIG. 3 measures the transition of the torque of the motor 40 that rotates the pressure roller 22 from the time when the heat source 23 starts heating the fixing belt 21. The torque measuring unit 47 detects torque based on the current value output from the motor control circuit 46 to the motor 40.

  When the torque measured by the torque measurement unit 47 is equal to or greater than a predetermined determination threshold, the heating control unit 48 sends a heater OFF signal for stopping the heating of the fixing belt 21 by the heat source 23 to the heater power supply circuit 45. It is designed to output. Further, the heating control unit 48 outputs a heater OFF signal to the heater power supply circuit 45 even when the transition of the torque measured by the torque measuring unit 47 tends to increase.

  For example, in the configuration of FIG. 6, the heater OFF signal is also input to the switching circuit 52. The switching circuit 52 outputs the heater OFF signal as a rotation stop signal to the motor control circuit 46 without passing through the delay circuit 51 to stop the rotation of the motor 40.

  FIG. 9 is a graph showing an example of the transition of torque of the motor 40 measured by the torque measuring unit 47 with the heating start of the fixing belt 21 as a base point. As described in the first embodiment, when the fixing belt 21 is heated by the heat source 23 before the pressure roller 22 is rotated, the torque is decreased from the start of rotation as indicated by a solid line in a normal state.

  Also, as shown in FIG. 10, when the fixing belt 21 is heated by the heat source 23 simultaneously with the start of the rotation of the pressure roller 22, a constant torque is normally maintained until the viscosity of the lubricant 30 decreases as indicated by a solid line. Is measured, and then the torque decreases. In the example of FIG. 10, the temperature detected by the temperature sensor 28 before the heating of the fixing belt 21 by the heat source 23 is equal to or higher than a certain temperature.

  On the other hand, in either case of FIGS. 9 and 10, if the torque value immediately after the start of rotation of the pressure roller 22 is equal to or greater than the determination threshold, the heating control unit 48 determines that the motor 40 as the drive source is abnormal. . Accordingly, the heating control unit 48 outputs a heater OFF signal, and stops the heating of the fixing belt 21 by the heat source 23 and the rotation of the pressure roller 22 by the motor 40.

  Even if the torque value immediately after the start of rotation of the pressure roller 22 is less than the determination threshold value, if the transition of the torque value immediately after the start of rotation tends to increase, the heating control unit 48 uses a motor as a drive source. 40 is judged to be abnormal. Accordingly, the heating control unit 48 outputs a heater OFF signal, and stops the heating of the fixing belt 21 by the heat source 23 and the rotation of the pressure roller 22 by the motor 40.

  As described above, the fixing device of the present embodiment measures the torque of the motor 40 based on the start of heating of the fixing belt 21, and if the torque value immediately after the start of rotation of the pressure roller 22 is greater than or equal to the determination threshold value, The heating of the fixing belt 21 and the rotation of the pressure roller 22 can be stopped.

  Further, the fixing device of the present embodiment measures the transition of the torque value immediately after the rotation of the pressure roller 22 starts, and if the torque value does not decrease, the fixing belt 21 is heated and the pressure roller 22 is heated. The rotation can be stopped.

  Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment. The present invention can be variously modified or changed in light of the appended claims.

20 Fixing device 21 Fixing belt (fixing member)
22 Pressure roller (Pressure member)
23 Heat source (heating means)
24 Nip forming member (fixing member)
24a Base pad 24b Sliding sheet 28 Temperature sensor (temperature detection means)
30 Lubricant 40 Motor (drive means)
45 Heater power supply circuit (heating means)
46 Motor control circuit (drive means)
47 Torque measurement unit (measuring means)
48 Heating control unit (heating control means)
51 delay circuit 52 switching circuit 200 image forming apparatus N fixing nip portion

JP 2011-066426 A

Claims (8)

A fixing member provided rotatably and fixing an unfixed image on a recording medium;
A pressurizing member that is rotatably provided and pressurizes the fixing member from an outer peripheral side;
A fixing member that is located on the inner peripheral side of the fixing member and that forms a fixing nip portion between the fixing member and the pressure member;
A lubricant interposed between the fixing member and the fixing member;
Heating means for heating the fixing member;
Heating control means for controlling the heating means;
Drive means for rotationally driving the pressure member;
When a heating start signal for starting heating of the fixing member is output from the heating control unit to the heating unit, a signal obtained by delaying the heating start signal by a predetermined time is started to rotate the pressure member. And a delay circuit that outputs the rotation start signal to the driving unit as a rotation start signal. Temperature detecting means for detecting the temperature of the fixing member;
When the temperature detected by the temperature detecting means before starting the heating of the fixing member by the heating means is equal to or higher than a certain temperature, the heating start signal is output as the rotation start signal to the driving means without passing through the delay circuit. The fixing device according to claim 1, further comprising a switching circuit. A temperature detecting means for detecting the temperature of the fixing member;
3. The drive unit according to claim 1, wherein the driving unit controls a rotation speed of the pressure member according to a temperature detected by the temperature detection unit before the heating unit starts heating the fixing member. Fixing device. A measuring unit that measures a transition of torque of the driving unit from the start of heating of the fixing member by the heating unit;
When the torque measured by the measuring unit is greater than or equal to a threshold value, or when the transition of the torque measured by the measuring unit tends to increase, the heating control unit is configured to fix the fixing member by the heating unit. The fixing device according to claim 1, wherein the heating of the fixing device is stopped.   5. The fixing device according to claim 1, wherein the heating unit is an IH heater.   The fixing device according to claim 1, wherein the heating unit is a halogen heater.   The fixing device according to claim 1, comprising a plurality of the heating units.   An image forming apparatus comprising the fixing device according to claim 1.

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