JP6682861B2 - Fixing device and image forming apparatus using the same - Google Patents

Description

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

  In image forming apparatuses such as copying machines, printers, and facsimiles, 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 composed of opposing rollers or belts or a combination thereof, and the recording paper, which is a recording medium, is nipped in the nip portion, and a toner image is formed on the recording paper by heat and pressure. Establish.

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

  Usually, the lubricant has a high viscosity at a low temperature, and the viscosity decreases as the temperature increases, so that the contact frictional resistance of the sliding portion between the fixing belt and the fixing member becomes large in a low temperature state. When the contact frictional resistance is large, the load (torque) on the sliding portion between the fixing belt and the fixing member increases, which may damage or damage the rotary drive unit such as the motor.

  Therefore, the fixing device disclosed in Japanese Patent Application Laid-Open No. 2004-242242 is designed to rotate the fixing belt after heating the fixing belt until the viscosity of the lubricant becomes sufficiently low. 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 Japanese Patent Laid-Open No. 2004-242242, the temperature of the fixing belt rises rapidly when heated, so if the rotation is started after detecting a predetermined temperature with the temperature sensor, the temperature of the fixing belt will not be heat-resistant. There is a possibility that the fixing belt may be damaged when the temperature rises above the temperature.

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

In order to solve the above problems, a fixing device according to the present invention is rotatably provided, and a fixing member that fixes an unfixed image on a recording medium, and a rotatably provided fixing member that pressurizes the fixing member from the outer peripheral side. Between a pressure member, a fixing member located on the inner peripheral side of the fixing member and forming a fixing nip portion between the fixing member and the pressure member, and between the fixing member and the fixing member. An intervening lubricant, heating means for heating the fixing member, heating control means for controlling the heating means, driving means for rotationally driving the pressing member, and temperature detecting means for detecting the temperature of the fixing member. And in a state where the temperature detected by the temperature detecting means is below a certain temperature, when the heating start signal for starting heating of the fixing member is output from the heating control means to the heating means, the heating is started. The signal is A signal obtained by delaying a predetermined time the heating start signal from the timing output to the serial heating means, a delay circuit for outputting to said driving means as the rotation start signal for starting the rotation of the pressing member, the temperature sensing When a heating start signal for starting heating of the fixing member is output from the heating control unit to the heating unit in a state where the temperature detected by the unit is equal to or higher than a certain temperature, the heating start signal is the heating unit. And a switching circuit that outputs the heating start signal to the driving unit as a rotation start signal for starting the rotation of the pressure member at the same time when the fixing member is applied to the pressure member. is a configuration you driven rotation.

  The present invention provides a fixing device capable of preventing damage or damage to a driving source such as a motor while preventing an excessive temperature rise of the fixing member due to heating, and an image forming apparatus using the fixing device.

1 is a schematic configuration diagram of an image forming apparatus including a fixing device according to a first exemplary embodiment of the present invention. FIG. 3 is a cross-sectional view of the fixing device according to the first embodiment of the present invention. FIG. 3 is a block diagram showing 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 included in the fixing device according to the first embodiment of the present invention. FIG. 6 is a diagram illustrating an example of the timing of heating the fixing belt and rotating the pressure roller according to the first embodiment of the present invention. FIG. 9 is a block diagram for explaining control by a heating control unit included in the fixing device according to the second embodiment of the present invention. It is a figure explaining the example of a timing of heating of a fixing belt and rotation of a pressure roller in a 2nd embodiment of the present invention. It is a figure explaining the example which changes the rotation speed according to the detection temperature of the temperature sensor in the 3rd Embodiment of this invention. It is a graph which shows the example of a change 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.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

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

  First, the configuration will be described.

  The image forming apparatus 200 shown in FIG. 1 adopts an electrophotographic method 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 an 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 sheet 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 sheet feeding device 114 includes two sheet feeding cassettes 115 for storing the recording medium P in this embodiment. Then, on the upper right of each paper feed cassette 115, a paper feed roller 117 is provided, which feeds out the recording medium P in each paper feed cassette 115 one by one and puts it into the recording medium conveyance path 116.

  The exposure device 113 is arranged 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 a fixed document received by the image sensor, or image data received through a personal computer or a telephone line. Has become.

  The image forming device 112 includes image forming devices 112 c, 112 m, 112 y, and 112 k for cyan (c), magenta (m), yellow (y), and black (k), respectively, and is provided above the exposure device 113. Has been. The image forming devices 112c, 112m, 112y, and 112k are arranged in a four-tandem tandem manner along the stretching 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 substantially horizontally and runs counterclockwise. Here, "endless" means a state in which both ends of the belt are joined and no joint exists. The intermediate transfer device 110 has primary transfer devices 125c, 125m, 125y and 125k that face each other with the image carrier 31 of the image forming devices 112c, 112m, 112y and 112k sandwiching the intermediate transfer belt 111. The primary transfer devices 125c, 125m, 125y, 125k transfer the toner image formed on the image carrier 31 onto the intermediate transfer belt 111.

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

  Upstream of the transport roller 119, a paper feed path for joining the recording medium P, which is re-fed from the duplex unit 300 or manually fed from the manual paper feeder 136 across the duplex unit 300, to the recording medium transport path 116. 137 is provided. Further, downstream of the fixing device 20, a sheet re-feeding conveyance path 124 to the duplex unit 300 is provided so as to branch 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 being conveyed by an automatic document feeder and a function of reading an image of a fixed document.

  At the time of image formation, the image forming apparatus 200 reads the original image with the image reading apparatus 200C and writes the original image with the exposure apparatus 113, and forms the toner image of each color on the 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 image 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 convey it to the recording medium conveyance path 116, or the manual paper feed device 136. The manually fed 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 a timing by conveying the recording medium P through the recording medium conveying path 116 with the conveying roller 119, and the color formed on the intermediate transfer belt 111 as described above. The image is transferred onto the recording medium P by the secondary transfer device 121. The recording medium P after the image transfer is subjected to image fixing by the fixing device 20, is discharged by the paper discharging device 123, and is stacked on the in-body discharging unit 118.

  The duplex unit 300 is provided on the right side surface of the image forming apparatus main body 200K. When an image is also formed on the back surface of the recording medium P, the recording medium P having the image formed on the front surface is put in the re-feeding conveyance path 124, inverted by the duplex unit 300, and then re-fed through the paper feeding path 137. . Then, the re-fed recording medium P is secondarily transferred with a color image separately formed on the intermediate transfer belt 111, and then is fixed again by the fixing device 20 and is ejected by the ejecting device 123 to the in-body ejecting unit 118. Is discharged to.

  The configuration of the fixing device 20 will be described below with reference to FIG.

  As shown in FIG. 2, the fixing device 20 includes a fixing belt 21 as a fixing member that contacts the unfixed image and fixes the unfixed image on the recording medium P, and a fixing belt 21 that contacts the outer peripheral surface of the fixing belt 21. And a pressure roller 22 as a facing member for pressing 21 from the outer peripheral side. Both the fixing belt 21 and the pressure roller 22 are rotatably provided. Further, 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 contacts the pressure roller 22 from the inner peripheral side of the fixing belt 21, and forms a fixing nip portion N between the fixing belt 21 and the pressure roller 22, and a nip forming member 24. A stay 25 as a supporting member that supports the forming member 24. Further, the fixing device 20 serves as a reflecting member 26 that reflects the heat from the heat source 23 to the fixing belt 21, a shielding member 27 that shields the heat from the heat source 23, and a temperature detecting 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 includes a base material on the inner peripheral side and a release layer on the outer peripheral side. The base material on the inner peripheral side is formed using, for example, 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-perfluoroalkylvinylether copolymer (PFA) or polytetrafluoroethylene (PTFE). In addition, an elastic layer formed of a rubber material such as silicone rubber, foamable silicone rubber, or fluororubber may be interposed between the base material and the release layer.

  If the elastic layer is not provided, the heat capacity will be small and the fixability will be improved, but when the unfixed toner is squeezed and fixed, the fine irregularities on the belt surface are transferred to the image, and uneven gloss on the solid part of the image occurs. Can occur. To prevent this, it is desirable to provide an elastic layer having a thickness of 100 μm or more. By providing the elastic layer having a thickness of 100 μm or more, minute irregularities can be absorbed by elastic deformation of the elastic layer, so that it becomes possible to avoid uneven gloss.

  In this 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 thickness of each of the base material, the elastic layer, and the release layer constituting the fixing belt 21 is set in the range of 20 to 50 μm, 100 to 300 μm, and 10 to 50 μm, and the total 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. Further, in order to reduce the heat capacity, it is desirable that the entire thickness of the fixing belt 21 is 0.2 mm or less, and more preferably 0.16 mm or less. The diameter of the fixing belt 21 is preferably 30 mm or less.

  A lubricant 30 such as silicone oil or fluorine grease is applied to the inner surface of the fixing belt 21. As a result, 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 cored bar 22a, an elastic layer 22b provided on the surface of the cored bar 22a, and a release layer 22c made of PFA or PTFE on the surface of the elastic layer 22b. ing. The elastic layer 22b is made of foamable silicone rubber, silicone rubber, fluororubber, or the like. The pressure roller 22 is pressed against the fixing belt 21 side by a pressing means such as a spring, and is in contact with the nip forming member 24 via the fixing belt 21. At a position where the pressure roller 22 and the fixing belt 21 are in pressure contact with each other, the elastic layer 22b of the pressure roller 22 is crushed to form a fixing nip portion N having a predetermined width. The fixing member and the facing member are not limited to being in pressure contact with each other, but may be configured to simply contact with each other without applying pressure.

  Further, 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 arrow B1 in the drawing, the driving force is transmitted to the fixing belt 21 at the fixing nip portion N, and the fixing belt 21 is driven to rotate in the direction of arrow B2 in the drawing. As a result, the recording medium P to which the toner T has been attached by the transfer of the toner images of the respective colors is inserted from the direction of the arrow A1 toward the fixing nip portion N of the fixing device 20 and passes through the fixing nip portion N to remove the toner T. After fixing is performed, the sheet is sent in the direction of arrow A2 in the figure.

  Although the pressure roller 22 is a solid roller in the present embodiment, it may be a hollow roller. In that case, a heat source such as a halogen heater may be provided inside the pressure roller 22. The elastic layer 22b may be solid rubber, but sponge rubber may be used when there is no heat source inside the pressure roller 22. When sponge rubber is used, the heat insulating property is improved, and the heat of the fixing belt 21 is less likely to be taken away.

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

  A temperature sensor that detects the temperature of the pressure roller 22 is provided instead of the temperature sensor 28 that detects the temperature of the fixing belt 21, 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 depending on the size of the recording medium P used in the image forming apparatus 200 and the like. Further, as the heat source 23 for heating the fixing belt 21, it is possible to use an IH heater, a resistance heating element, a carbon heater, or the like in addition to the halogen heater.

  The nip forming member 24 includes a base pad 24a and a low-friction sliding sheet 24b provided on the surface of the base pad 24a facing the fixing belt 21. The base pad 24a is arranged in a longitudinal shape across the fixing belt 21 or the pressure roller 22. The shape of the fixing nip portion N is determined by the base pad 24a being pressed by the pressure roller 22.

  Although the fixing nip portion N has a flat shape in the present embodiment, it may have a concave shape or another shape.

  The sliding sheet 24b is provided to reduce sliding friction when the fixing belt 21 rotates. Further, by including the lubricant 30 in the sliding sheet 24b, it becomes possible for the sliding sheet 24b to 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, the sliding sheet 24b may be omitted.

  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 in the toner fixing temperature range is prevented, a stable state of the fixing nip portion N is secured, and the output image quality is stabilized. Further, the base pad 24a is required to have appropriate rigidity in order to secure strength.

  Resins such as polyether sulfone (PES) and polyphenylene sulfide (PPS) can be used as the material of the base pad 24a satisfying the above conditions. Alternatively, a resin such as liquid crystal polymer (LCP), polyether nitrile (PEN), polyamide imide (PAI), or polyether ether ketone (PEEK) can be used. In addition, the base pad 24a can be formed of metal or ceramic.

  The base pad 24a is fixedly supported by the stay 25. As a result, it is possible to prevent the nip forming member 24 from being bent by the pressure of the pressure roller 22, and to obtain a uniform nip width 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 reflecting 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, the heat is suppressed from being transferred to the stay 25 and the like, the fixing belt 21 is efficiently heated, and energy saving is achieved. There is. Aluminum, stainless steel, or the like is used as the material of the reflecting member 26. In particular, when an aluminum base material on which silver having a low emissivity (high reflectance) is deposited is used, it is possible to improve the heating efficiency of the fixing belt 21.

  The shielding member 27 is formed by forming a metal plate having a thickness of 0.1 mm to 1.0 mm in an arcuate cross-sectional shape along the inner peripheral surface of the fixing belt 21. Further, 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 the 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 and are formed. The non-heating region β is provided between the heat source 23 and another member fixed to the side plate or the like (the reflecting member 26, the stay 25, the nip forming member 24, etc.).

  When it is necessary to shield the heat, as shown in FIG. 2, the shielding member 27 is arranged at one or a plurality of shielding positions 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 sheet is not conveyed according to the width of the sheet conveyed by the conveyance.

  On the other hand, when it is not necessary to shield the heat, 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.

  As described above, 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 needs heat resistance, it is preferable to use a metal material such as aluminum, iron, and stainless steel, or a ceramic material.

  Next, the control configuration of the heating controller 48 included 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 between the temperature sensor 28, the heater power supply circuit 45, the motor control circuit 46, the torque measuring unit 47, the delay circuit 51, and the switching circuit 52.

  The heating control unit 48 controls 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 is higher than 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 is 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 the difference value between the target temperature and the current temperature. Two methods of PID control are possible, but either method may be used.

  As described below, the fixing device 20 according to the present exemplary embodiment includes the heating control unit 48, so that the fixing belt 21 is heated before the rotation of the pressure roller 22 is started, and the viscosity of the lubricant 30 is increased. After lowering, rotation start is executed.

  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 the image forming apparatus 200 requests printing. The heater ON signal for starting the operation 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, and delays the heater ON signal output from the heating control unit 48 for a predetermined time Δt to start the rotation of the pressure roller 22. It is output to the motor control circuit 46 as a rotation start signal. It is desirable that the delay time Δt can be set to an arbitrary value by the user.

  Upon receiving the rotation start signal output from the delay circuit 51, the motor control circuit 46 starts supplying current to the motor 40 and drives the motor 40.

  That is, as shown in FIG. 5, the drive of the motor 40 is started after the delay time Δt elapses from the timing when the heater ON signal is output from the heating control unit 48, and the pressure roller 22 and the fixing belt 21 rotate. As a result, the fixing belt 21 can be heated without excessive temperature rise of the fixing belt 21.

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

(Second embodiment)
Hereinafter, a second 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 device according to the first embodiment are designated by the same reference numerals, and detailed description thereof will be 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 is configured to output a rotation start signal obtained by delaying the heater ON signal for a fixed time Δt to the switching circuit 52.

  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, 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. It is supposed to do. That is, as shown in FIG. 7, the driving of the motor 40 is started at the same timing as the heater ON signal is output from the heating control unit 48, and the pressure roller 22 and the fixing belt 21 are rotated.

  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 start of heating of the fixing belt 21 by the heat source 23 is lower than a certain temperature. (Fig. 5).

  In this way, the timing of 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)
A third embodiment of the fixing device according to the present invention will be described below with reference to the drawings. The same components as those of the fixing device according to the first and second embodiments are designated by the same reference numerals, and detailed description thereof will be 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. 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). After that, 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 to be high, the pressure roller 22 is rotated at a low rotation speed a to prevent the motor 40 from being damaged. be able to.

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

  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 heating of the fixing belt 21 by the heat source 23 is started. The torque measuring unit 47 detects the torque based on the current value output from the motor control circuit 46 to the motor 40.

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

  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 the torque of the motor 40 measured by the torque measuring unit 47 with the heating start of the fixing belt 21 as the base point. As described in the first embodiment, by heating the fixing belt 21 by the heat source 23 before the pressure roller 22 rotates, the torque normally decreases from the start of rotation as shown by the solid line.

  Further, as shown in FIG. 10, when the fixing belt 21 is heated by the heat source 23 at the same time as the rotation of the pressure roller 22 is started, a constant torque is normally applied until the viscosity of the lubricant 30 decreases as indicated by the 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 started is a certain temperature or higher.

  On the other hand, in both cases of FIGS. 9 and 10, if the torque value immediately after the rotation of the pressure roller 22 is equal to or greater than the determination threshold value, the heating control unit 48 determines that the motor 40 as a drive source has an abnormality. . As a result, the heating controller 48 outputs a heater OFF signal to stop 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 of the pressure roller 22 immediately after the start of rotation 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 controller 48 uses the motor as a drive source. It is determined that 40 is abnormal. As a result, the heating controller 48 outputs a heater OFF signal to stop 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 according to the present embodiment measures the torque of the motor 40 from the start of heating the fixing belt 21, and if the torque value immediately after the rotation of the pressure roller 22 is greater than or equal to the determination threshold, 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 is started. If the torque value does not decrease, the heating of the fixing belt 21 and the pressure roller 22 are performed. The rotation can be stopped.

  Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. Further, 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 (driving means)
47 Torque measuring unit (measuring means)
48 Heating control section (heating control means)
51 delay circuit 52 switching circuit 200 image forming apparatus N fixing nip portion

JP, 2011-064726, A

Claims (7)

A fixing member that is rotatably provided and that fixes an unfixed image on a recording medium;
A pressing member that is rotatably provided and pressurizes the fixing member from the outer peripheral side;
A fixing member located on the inner peripheral side of the fixing member and forming 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,
Temperature detecting means for detecting the temperature of the fixing member,
In a state where the temperature detected by the temperature detection unit is lower than a certain temperature, when the heating start signal for starting heating of the fixing member is output from the heating control unit to the heating unit, the heating start signal is A delay circuit that outputs a signal obtained by delaying the heating start signal for a predetermined time from the timing output to the heating means to the drive means as a rotation start signal for starting the rotation of the pressing member,
In a state where the temperature detected by the temperature detection unit is equal to or higher than a certain temperature, when the heating start signal for starting heating of the fixing member is output from the heating control unit to the heating unit, the heating start signal is At the same time as the timing output to the heating means, a switching circuit that outputs the heating start signal to the drive means as a rotation start signal for starting the rotation of the pressing member ,
A fixing device wherein the fixing member is characterized that you driven rotation to said pressure member. Further comprising temperature detection means for detecting the temperature of the fixing member,
The fixing unit according to claim 1, wherein the driving unit controls the rotation speed of the pressing member according to the temperature detected by the temperature detecting unit before the heating unit starts heating the fixing member. apparatus. Further comprising a measuring means for measuring the transition of the torque of the driving means from the start of heating of the fixing member by the heating means,
The heating control means, when the torque measured by the measuring means is equal to or more than a threshold value, or the transition of the torque measured by the measuring means tends to increase, the fixing member by the heating means. The fixing device according to claim 1, wherein heating of the fixing device is stopped . The fixing device according to claims 1 to 3, characterized in that said heating means is a IH heater. It said heating means is a fixing device according to 3 claims 1, characterized in that a halogen heater. The fixing device according to claims 1 to 3, characterized in that it comprises a plurality of said heating means. An image forming apparatus comprising the fixing device according to claim 1.

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