Fixing apparatus and image forming apparatus

Abstract

To prevent an increase in the temperature of a pressure rotating body and bring the pressure rotating body and a fixing belt into contact with each other or separating them from each other at the optimum speed according to a use state when suspending a continuous job.SOLUTION: When suspending a continuous job, a fixing device 8 increases the speed of contact and separation between a pressure roller 330 and a fixing belt 310 caused by a pressure driving unit 391 in a "productivity priority mode" compared to the speed of contact and separation in a "silence priority mode."SELECTED DRAWING: Figure 14

Description

Technical Field

[0001] The present invention relates to a fixing device for fixing a toner image formed on a recording material onto the recording material and an image forming apparatus including the same.

Background Art

[0002] An image forming apparatus based on an electrophotographic method fixes a toner image on a recording material such as a sheet on which the toner image has been transferred by heating and pressurizing the recording material with a fixing device. A general fixing device includes a heating member and a pressurizing member that presses against the heating member, and passes the recording material on which the toner image has been transferred through a fixing nip portion where the heating member and the pressurizing member are in pressure contact, thereby fixing the toner image on the recording material.

[0003] Also, conventionally, as a fixing device, there is known one that uses a belt fixing method using a fixing belt and a pressurizing roller. In an image forming apparatus using such a belt fixing method, the temperature of the fixing belt is an important factor affecting image quality because it greatly changes the melting state of the toner on the recording material. The surface temperature of the fixing belt that directly contacts the toner on the recording material is set to a higher temperature to melt the toner compared to the pressurizing roller that is an opposing member to the fixing belt. Also, when continuously forming images on a large number of recording materials, the temperatures of the fixing belt and the pressurizing roller must be kept constant in order to obtain optimal and uniform quality of the images on each recording material.

[0004] During continuous image formation, image formation may be temporarily stopped due to paper cassette switching, adjustment of the image forming unit, or post-processing operations on the recording material after it has passed through the fuser. If the fuser belt and the pressurizing member rotate in contact with each other without the recording material passing through during such a temporary stop in image formation, the heat from the fuser belt, which is set to a high temperature, will be transferred to the surface of the pressurizing member, causing the pressurizing member to overheat. If image formation is then resumed with the pressurizing member overheated, depending on the type of recording material, the toner on the recording material that is first formed after resumption may become over-melted, resulting in a decrease in image quality, such as excessive glossiness.

[0005] Patent Document 1 discloses an image forming apparatus that prevents the temperature rise of the pressure roller, which leads to such a decrease in image quality. The image forming apparatus of Patent Document 1 is equipped with a pressure-de-pressure mechanism that temporarily separates the fixing belt and the pressure roller, which are pressed against each other, when image forming is temporarily suspended, and presses the fixing belt and the pressure roller back into contact when image forming is resumed. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-124753 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, in Patent Document 1, time is required to move the pressure roller from the contact position to a separated position and then return it to the contact position. Therefore, in Patent Document 1, if the time for temporarily suspending image formation is shorter than the time required to move the pressure roller from the contact position to a separated position and then return it to the contact position, the pressure roller cannot be moved to the separated position. In such a case, Patent Document 1 has the problem that the fixing belt and the pressure roller come into contact without the recording material passing through, and the temperature rise of the pressure roller cannot be sufficiently suppressed.

[0008] Furthermore, Patent Document 1 has the problem that when the pressure roller is moved to a separated position in order to suppress the temperature rise of the pressure roller, a waiting time (downtime) occurs until the contact between the fixing belt and the pressure roller is completed before image formation can be resumed.

[0009] Furthermore, it is conceivable that users may want to adjust the speed at which the fixing belt and pressure roller come into contact and separate, taking into account the priority according to the usage situation. However, Patent Document 1 does not mention the speed at which the fixing belt and pressure roller come into contact and separate.

[0010] The object of the present invention is to provide a fixing device and an image forming apparatus that can suppress the temperature rise of the pressurized rotating body when interrupting a continuous job, and can bring the pressurized rotating body and the fixing belt into contact and separate at an optimal speed according to the usage conditions. [Means for solving the problem]

[0011] The fixing apparatus according to the present invention includes fixing means for fixing a toner image onto a recording material by heating and pressurizing the recording material on which a toner image has been formed using a pressurizing rotating body and a fixing belt, and contact / separation means for bringing the pressurizing rotating body and the fixing belt into contact and separate. A temperature detection means for detecting ambient temperature, The system includes a control means for executing a continuous job of forming images on multiple recording materials in succession, wherein the control means sets the time for interrupting the continuous job in a first mode to be a first time, and the speed at which the pressurizing rotating body and the fixing belt are brought into contact by the contact / separation means to be a first speed, and the time for interrupting the continuous job in a second mode to be a second time which is longer than the first time, and the speed at which the pressurizing rotating body and the fixing belt are brought into contact by the contact / separation means to be a second speed which is slower than the first speed. Furthermore, when the ambient temperature detected by the temperature detection means is below a predetermined temperature, the contact and separation speed in the first mode is slowed down compared to when the ambient temperature detected by the temperature detection means is above the predetermined temperature. It is characterized by the following: [Effects of the Invention]

[0012] According to the present invention, when interrupting a continuous job, it is possible to suppress the temperature rise of the pressurized rotating body, and to bring the pressurized rotating body and the fixing belt into contact and separate at an optimal speed depending on the usage conditions. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram of an image forming apparatus according to an embodiment of the present invention. [Figure 2] This is a perspective view of a fixing device according to an embodiment of the present invention. [Figure 3] This is a cross-sectional view AA in Figure 2. [Figure 4] Figure 2 is a cross-sectional view of BB. [Figure 5] This is a schematic cross-sectional view of a part of a fixing device according to an embodiment of the present invention. [Figure 6] This is a cross-sectional view showing the drive transmission section of a fixing device according to an embodiment of the present invention. [Figure 7] This is a cross-sectional view of CC in the separated state shown in Figure 2. [Figure 8] Figure 2 shows a cross-sectional view of CC under pressure conditions other than gloss priority mode. [Figure 9] Figure 2 is a cross-sectional view of CC under pressure in gloss-priority mode. [Figure 10] This is a block diagram showing the configuration of a fixing device according to an embodiment of the present invention. [Figure 11] This figure shows the relationship between the rotation angle of the cam and the cam radius of the fixing device according to an embodiment of the present invention, and is a schematic diagram of the cam. [Figure 12] This figure shows the relationship between the rotation angle of the cam of the fixing device according to an embodiment of the present invention and the on-axis torque of the motor M2. [Figure 13] This figure shows the relationship between the sound pressure level and the motor drive speed of a fixing device according to an embodiment of the present invention. [Figure 14] This is a flowchart of the image forming process performed by the fixing device according to an embodiment of the present invention. [Figure 15]This is a diagram showing the relationship between the rotation angle of a cam and the radius of the cam in the image quality priority mode of a fixing device according to an embodiment of the present invention. [Figure 16] This is a diagram showing a modification of the relationship between the rotation angle of a cam and the radius of the cam in the image quality priority mode of a fixing device according to an embodiment of the present invention. [Figure 17] This is a diagram showing the relationship between the rotation angle of a cam and the on-axis torque of a motor in the productivity priority mode of a fixing device according to an embodiment of the present invention. [Figure 18] This is a diagram showing a modification of the relationship between the rotation angle of a cam and the on-axis torque of a motor in the productivity priority mode of a fixing device according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments will be described in detail with reference to the drawings.

[0015] (Embodiment 1) <Configuration of the Image Forming Apparatus> The configuration of the image forming apparatus 1 according to Embodiment 1 of the present invention will be described in detail with reference to FIG. 1.

[0016] The image forming apparatus 1 exemplifies an electrophotographic full-color printer having a plurality of photosensitive drums 200a to 200d here. Also, the image forming apparatus 1 is of a tandem type in which the image forming units Pa, Pb, Pc, and Pd are arranged along the rotation direction of the intermediate transfer belt 204 described later. Note that the image forming apparatus 1 is not limited to an electrophotographic full-color printer, and may be various types of image forming apparatuses or a monochromatic image forming apparatus or the like.

[0017] Specifically, the image forming apparatus 1 includes an image reading unit 2, an apparatus main body 3, and an operation unit 4.

[0018] The image reading unit 2 is connected to the main body 3 of the device and converts the line-by-line electrical signal data sequence into an image signal by scanning the document in the direction of the arrow shown in Figure 1. The image reading unit 2 comprises a document glass 21, a light source 22, an optical system component 23, a CCD sensor 24, and a reader control unit 25.

[0019] The document is placed on the document glass 21.

[0020] The light source 22, under the control of the reader control unit 25, irradiates light onto the document placed on the document glass 21.

[0021] The optical system component 23 is a lens, etc.

[0022] The CCD sensor 24 obtains an image signal by forming an image of the reflected light, which is irradiated from the light source 22 and reflected from the document, via the optical system component 23. The CCD sensor 24 outputs the obtained image signal to the reader control unit 25.

[0023] The reader control unit 25 controls the operation of the light source 22 under the control of the control unit 30. The reader control unit 25 outputs the image signal input from the CCD sensor 24 to the control unit 30.

[0024] The main unit 3 forms a toner image (image) on a recording material (not shown) based on an image signal from the image reading unit 2 or a host device (not shown), such as a personal computer, which is connected to the main unit 3 in a communicative manner. Here, the recording material is a sheet material such as paper or plastic film.

[0025] The main body of the apparatus 3 comprises an image forming section Pa, Pb, Pc, Pd, an output tray 7, a fixing device 8, a cassette 9, an inversion transport section 10, a polygon scanner 31, an intermediate transfer belt 204, a secondary transfer roller 205, a secondary transfer roller 206, and a registration section 208.

[0026] The image forming units Pa, Pb, Pc, and Pd are provided to correspond to four colors: yellow, magenta, cyan, and black. The image forming units Pa, Pb, Pc, and Pd perform image formation through image processing in the control unit 30. The image forming unit Pa forms a yellow (Y) image. The image forming unit Pb forms a magenta (M) image. The image forming unit Pc forms a cyan (C) image. The image forming unit Pd forms a black (Bk) image.

[0027] Each of the image forming units Pa, Pb, Pc, and Pd has substantially the same configuration. Each image forming unit Pa, Pb, Pc, and Pd comprises a photosensitive drum 200a to 200d, charging rollers 201a to 201d, developing units 202a to 202d, primary transfer rollers 203a to 203d, and cleaners 207a to 207d.

[0028] The photosensitive drums 200a to 200d are charged to a predetermined potential by the charging rollers 201a to 201d. An electrostatic latent image is formed on the photosensitive drums 200a to 200d by the irradiation of a laser beam from the polygon scanner 31. A toner image is formed on the photosensitive drums 200a to 200d by toner supplied from the developer units 202a to 202d based on the image signal.

[0029] The charging rollers 201a to 201d are primary chargers that charge the surfaces of the photosensitive drums 200a to 200d to a predetermined potential, preparing them for electrostatic latent image formation.

[0030] The developing units 202a to 202d develop the electrostatic latent image on the photosensitive drums 200a to 200d to form a toner image on the photosensitive drums 200a to 200d.

[0031] The primary transfer rollers 203a to 203d discharge electricity from the back of the intermediate transfer belt 204 to apply a primary transfer bias with the opposite polarity to the toner, thereby transferring the toner image on the photosensitive drums 200a to 200d onto the intermediate transfer belt 204.

[0032] Cleaners 207a to 207d clean the surface of the photosensitive drums 200a to 200d after the toner image has been transferred by the primary transfer rollers 203a to 203d.

[0033] The recording material transported from the fixing device 8 is discharged into the discharge tray 7.

[0034] The fixing device 8 employs a belt heating method using an endless belt as the fixing means. The fixing device 8 heats and pressurizes the recording material conveyed from the secondary transfer rollers 205 and 206 to fix the toner image supported on the recording material to the recording material. The fixing device 8 then conveys the recording material with the fixed toner image to the discharge tray 7 or the inversion conveying unit 10. Details of the configuration of the fixing device 8 will be described later.

[0035] Cassette 9 contains the recording material.

[0036] The reversal transport unit 10 reverses the front and back sides of the recording material transported from the fixing device 8 and transports it to the registration unit 208 in order to transfer and fix the toner image to the second side (back side) of the recording material.

[0037] The polygon scanner 31 is an exposure device that scans by irradiating a photosensitive drum 200a to 200d with a laser beam corresponding to the image signal, under the control of the control unit 30.

[0038] On the intermediate transfer belt 204, the toner images of each color formed in the image forming sections Pa, Pb, Pc, and Pd are transferred from the image forming sections Pa, Pb, Pc, and Pd in ​​the order of Y, M, C, and Bk, so that a four-color image is formed on the surface.

[0039] The secondary transfer rollers 205 and 206 constitute a secondary transfer roller pair. The secondary transfer rollers 205 and 206 are subjected to a secondary transfer electric field with opposite polarity to the toner image on the intermediate transfer belt 204, thereby secondary transferring the toner image on the intermediate transfer belt 204 to the recording material. The secondary transfer rollers 205 and 206 then transport the recording material, on which the toner image has been secondary transferred, to the fixing device 8.

[0040] The registration unit 208 is composed of, for example, a pair of registration rollers and holds the recording material fed and transported from the cassette 9 or the recording material transported from the reversal transport unit 10 in standby. The registration unit 208 adjusts the timing of transporting the recording material in order to align the position of the toner image on the intermediate transfer belt 204 with the position of the recording material, and transports the standby recording material to the secondary transfer roller 205 and the secondary transfer roller 206.

[0041] The operating unit 4, which serves as a means of selection, is, for example, a touch panel or buttons that can be operated by touch, and outputs an electrical signal corresponding to the operation to the control unit 30.

[0042] <Configuration of the fixing device> The configuration of the fixing device 8 according to Embodiment 1 of the present invention will be described in detail with reference to Figures 2 to 10.

[0043] In Figure 2, the lower left is the front and the upper right is the rear. Also, the cross-sections F1 and F2 in Figure 2 are cross-sections perpendicular to the rotation axis of the pressure roller 330 of the fixing device 8. Figure 3 is a view of the fixing device 8 from the front at cross-section F1. In Figure 3, the recording material is transported from right to left as indicated by arrow α. Figure 4 is a view of the fixing device 8 from the rear at cross-section F1.

[0044] Furthermore, Figures 7 to 9 show the fixing device 8 of Figure 2 as viewed from the direction of arrow C when it is cut at the cross-section F2. Figures 7 to 9 show the pressurized state due to the transition of cams 329 and 336. Figure 8 shows the separated state where the pressure roller 330 is separated from the fixing belt 310. Since Figure 8 is a view from the direction of arrow C at the cross-section F2 of Figure 2, the pressure arm 334 and cam 336 are visible.

[0045] Specifically, the fixing device 8 includes a control unit 30, a heating unit 300, a pressure arm support plate 326, a pressure arm support plate 327, a pressure arm 328, a cam 329, a pressure roller 330, a pressure spring 331, and a pressure arm 334. The fixing device 8 also includes a cam 336, a pressure spring 337, a halogen heater 341, a stay 360, a cam follower 372, a pressure screw 373, a fixing frame 380, and a gear train 385. Furthermore, the fixing device 8 includes a pressure drive unit 391, a thermistor 500, a motor driver 503, a motor M1, and a motor M2.

[0046] The control unit 30, acting as a control means, controls the entire image forming apparatus 1. Based on electrical signals input from the operation unit 4, the control unit 30 performs various settings and executes a continuous job of forming images on multiple recording materials in succession. Based on electrical signals corresponding to the selected mode type input from the operation unit 4 and electrical signals corresponding to the ambient temperature input from the thermistor 500, the control unit 30 executes the image forming process described later and controls the drive of the motor driver 503. The specific types of modes will be described later.

[0047] The control unit 30 includes a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory), none of which are shown in the diagram. The ROM stores a program corresponding to the control procedure. The RAM stores working data or input data. The CPU reads the program stored in the ROM and, based on the read program, controls each part while referring to the working data or input data stored in the RAM.

[0048] The control unit 30 receives image signals from an external host device (not shown), such as a print server. The control unit 30 controls the driving of the polygon scanner 31 by performing PWM (pulse width modulation control) on the image signals input from the reader control unit 25 or the external host device, thereby performing image processing according to each image forming unit Pa, Pb, Pc, and Pd.

[0049] The control unit 30 controls the halogen heater 341 so that the fixing belt 310 reaches a predetermined target temperature according to the type of recording material, based on the ambient temperature indicated by the electrical signal input from the thermistor 500.

[0050] The heating unit 300 heats the recording material conveyed by the secondary transfer rollers 205 and 206. The heating unit 300 includes a fixing belt 310, a fixing pad 390, a heating roller 340, a halogen heater 341, a steering roller 350, and a stay 360.

[0051] The fixing belt 310 has a thin-walled cylindrical shape and is an endless and rotatable belt. The fixing belt 310 is made of a material that has thermal conductivity and heat resistance. The fixing belt 310 is stretched by a fixing pad 390, a heating roller 340, and a steering roller 350. The fixing belt 310 is heated by the heating roller 340, which is heated by a halogen heater 341.

[0052] The fixing belt 310 has a three-layer structure consisting of a base layer (not shown), an elastic layer provided on the outer periphery of the base layer, and a release layer provided on the outer periphery of the elastic layer. The base layer is 60 μm thick and made of polyimide resin (PI). The elastic layer is 300 μm thick and made of silicone rubber. The release layer is 30 μm thick and made of fluororesin PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin).

[0053] The fixing pad 390 is supported by the stay 360 inside the fixing belt 310 and is positioned opposite the pressure roller 330 with the fixing belt 310 in between. The fixing pad 390 is made of LCP (liquid crystal polymer). The fixing pad 390 forms a nip portion N when pressed by the pressure roller 330 with the fixing belt 310 in between. The nip portion N has a predetermined width in the direction of transport of the recording material (left-right direction in Figure 3) and grips and transports the recording material.

[0054] The fixing pad 390 is a roughly plate-shaped member whose longitudinal direction is the width direction of the fixing belt 310. Here, the width direction of the fixing belt 310 is the direction intersecting the rotation direction of the fixing belt 310 and the same direction as the rotation axis direction of the heating roller 340, and is the direction perpendicular to the plane of the paper in Figure 3.

[0055] A lubricating sheet (not shown) is provided between the fixing pad 390 and the fixing belt 310. A lubricant such as oil is pre-applied to the contact surface of the lubricating sheet with the fixing belt 310 to improve sliding properties. Silicone oil is preferably used as the lubricant from the viewpoint of heat resistance, and various viscosities can be used depending on the operating conditions.

[0056] The heating roller 340 is positioned inside the fixing belt 310 and, together with the fixing pad 390 and the steering roller 350, tensions the fixing belt 310. The heating roller 340 is formed in a cylindrical shape from a metal such as aluminum or stainless steel. For example, the heating roller 340 is formed from a stainless steel pipe with a thickness of 1 mm.

[0057] The heating roller 340 is rotatably supported on the fixing frame 380. A gear 385a is fixed to one end (the rear end) of the heating roller 340 in a direction parallel to the axis of rotation shown by the dashed line in Figure 5, and is connected to the motor M1 via an idler gear 385b and a motor gear 385c. The heating roller 340 is rotationally driven by the motor M1. Multiple halogen heaters 341 are arranged inside the heating roller 340 to heat the fixing belt 310.

[0058] The halogen heater 341, under the control of the control unit 30, heats the heating roller 340 to a predetermined target temperature according to the type of recording material.

[0059] The steering roller 350 is positioned inside the fixing belt 310 and, together with the fixing pad 390 and the heating roller 340, tensions the fixing belt 310 and rotates in accordance with the fixing belt 310. The steering roller 350 controls the position (closer position) of the fixing belt 310 relative to the rotation axis of the heating roller 340 by tilting with respect to the rotation axis of the heating roller 340.

[0060] The steering roller 350 generates a tension difference between one end and the other end of the fixing belt 310 in the width direction, causing the fixing belt 310 to move in the width direction. The steering roller 350 is biased by a spring supported by a frame (not shown) of the heating unit 300, and is a tension roller that applies a predetermined tension to the fixing belt 310. By applying a predetermined tension to the fixing belt 310, the steering roller 350 causes the fixing belt 310 to come into contact with the fixing pad 390.

[0061] The stay 360 is positioned inside the fixing belt 310, provided along the width direction of the fixing belt 310, and has rigid reinforcing members with the width direction of the fixing belt 310 as its longitudinal direction. The stay 360 is positioned on the opposite side of the fixing pad 390 from the pressure roller 330, and contacts the fixing pad 390 to support and reinforce it. The stay 360 is made of a metal such as stainless steel, and its cross-section (transverse plane) cut by a plane perpendicular to the width direction of the fixing belt 310 is substantially rectangular. Both ends of the stay 360 in the longitudinal direction are supported by the fixing frame 380 of the fixing device 8.

[0062] The stay 360 is inserted into the heating unit positioning section 381 and the heating unit positioning section 382 and fixed to a fixing means (not shown), thereby positioning the heating unit 300 relative to the fixing frame 380. At this time, the stay 360 is fixed to the fixing means with its movement restricted by the pressurization direction restricting surface 381a and pressurization direction restricting surface 382a and the transport direction restricting surface 318b and transport direction restricting surface 382b (see Figures 3 and 4).

[0063] As shown in Figure 3, the pressure arm support plate 326 is fixed to the rear plate 321. The pressure arm support plate 326 rotatably supports the pressure arm 328.

[0064] As shown in Figure 4, the pressure arm support plate 327 is fixed to the front plate 320. The pressure arm support plate 327 rotatably supports the pressure arm 334.

[0065] The pressure arm 328 rotatably supports the pressure roller 330. The pressure arm 328 rotates around the rotation axis 333 by being pressed by the cam 329. As shown in Figures 7 to 9, the pressure arm 328 comprises an upper arm portion 328U and a lower arm portion 328L. The upper arm portion 328U and the lower arm portion 328L are each supported by the pressure arm support plate 326 so as to be able to rotate relative to each other around the rotation axis 333.

[0066] The cam 329 is connected to and fixed to one end of the camshaft 338, which serves as the axis of rotation, in the longitudinal direction (the direction perpendicular to the plane of the paper in Figures 7 to 9).

[0067] The pressure roller 330, acting as a pressurizing rotating body, is rotatably supported at both ends in the direction of its rotation axis (the direction perpendicular to the plane of the paper in Figures 7 to 9) by pressure arms 328 and 334. The pressure roller 330 contacts the fixing belt 310 and together with the fixing belt 310 forms a nip portion N.

[0068] The pressure roller 330 is formed by laminating a shaft, an elastic layer provided on the outer circumference of the shaft, and a release layer provided on the outer circumference of the elastic layer. The shaft of the pressure roller 330 is made of stainless steel. The elastic layer of the pressure roller 330 is 5 mm thick and is made of conductive silicone rubber. The release layer of the pressure roller 330 is 50 μm thick and is made of the fluororesin PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin).

[0069] The pressure spring 331, acting as a biasing means, biases the pressure roller 330 against the fixing pad 390 via the pressure arms 328 and 334. The pressure spring 331 is positioned in an elastically compressed state between the right end of the upper arm portion 328U in Figure 9 and the right end of the lower arm portion 328L in Figure 9. The pressure spring 331 biases the upper arm portion 328U and the lower arm portion 334L in a direction that widens the gap between the right end of the upper arm portion 328U and the right end of the lower arm portion 334L.

[0070] The pressure arm 334 rotatably supports the pressure roller 330. The pressure arm 334 rotates around the rotation axis 335 by being pressed by the cam 336. As shown in Figures 7 to 9, the pressure arm 334 comprises an upper arm portion 334U and a lower arm portion 334L. The upper arm portion 334U and the lower arm portion 334L are each supported by the pressure arm support plate 327 so as to be able to rotate relative to each other around the rotation axis 335. The pressure arm 334 has the same configuration as the pressure arm 328.

[0071] Cam 336 is connected to and fixed to the other longitudinal end of camshaft 338, which serves as the axis of rotation. Cam 336 has the same configuration as cam 329 and rotates in the same phase as cam 329.

[0072] The pressure spring 337, acting as a biasing means, biases the pressure roller 330 against the fixing pad 390. The pressure spring 337 is positioned in an elastically compressed state between the right end of the upper arm portion 334U in Figure 9 and the right end of the lower arm portion 334L in Figure 9. The pressure spring 337 biases the upper arm portion 334U and the lower arm portion 334L in a direction that widens the gap between the right end of the upper arm portion 334U and the right end of the lower arm portion 334L.

[0073] The cam follower 372 is rotatably supported on the lower arm portion 328L and the lower arm portion 334L, respectively, so as to contact the cam 329 and the cam 336.

[0074] The pressure screw 373 restricts the relative movement between the upper arm portion 328U and the lower arm portion 328L so that they do not spread apart beyond a predetermined distance. The pressure screw 373 also restricts the relative movement between the upper arm portion 334U and the lower arm portion 334L so that they do not spread apart beyond a predetermined distance.

[0075] The pressure screw 373 allows relative movement between the upper arm portion 328U and the lower arm portion 328L in a direction that narrows the gap between them. The pressure screw 373 also allows relative movement between the upper arm portion 334U and the lower arm portion 334L in a direction that narrows the gap between them.

[0076] As shown in Figure 2, the fixing frame 380 is composed of a front plate 320, a rear plate 321, a right stay 322, a left stay 323, and a bottom plate 324.

[0077] As shown in Figure 4, the front plate 320 is equipped with a heating unit positioning section 382.

[0078] The heating unit positioning section 382 includes a pressure direction restricting surface 382a facing the pressure roller 330, and a transport direction restricting surface 382b which is abutting surface in the insertion direction of the heating unit 300.

[0079] As shown in Figure 3, the rear plate 321 is equipped with a heating unit positioning section 381.

[0080] The heating unit positioning section 381 includes a pressure direction restricting surface 381a facing the pressure roller 330, and a transport direction restricting surface 381b which is abutting surface in the insertion direction of the heating unit 300.

[0081] The gear train 385 consists of gear 385a, idler gear 385b, and motor gear 385c. The gear train 385 transmits the driving force of motor M1 to heating roller 340.

[0082] Gear 385a is fixed to one end of the heating roller 340 in the direction of its rotational axis. Gear 385a transmits the driving force of the idler gear 385b to the heating roller 340.

[0083] The idler gear 385b is rotatably supported on a heating roller drive support plate 325 fixed to the rear plate 321. The idler gear 385b meshes with the motor gear 385c and the gear 385a. The idler gear 385b transmits the driving force of the motor gear 385c to the gear 385a.

[0084] The motor gear 385c transmits the driving force of the motor M1 to the idler gear 385b.

[0085] The pressurized drive unit 391, acting as a means of contacting and separating, transmits the driving force of the motor M2 to the cams 329 and 336, causing them to rotate. Details of the configuration of the pressurized drive unit 391 will be described later.

[0086] The thermistor 500, acting as a temperature detection means, detects the ambient temperature and outputs an electrical signal corresponding to the detected ambient temperature to the control unit 30.

[0087] The motor driver 503 controls the drive of the motor M2 under the control of the control unit 30.

[0088] Motor M1 rotates the heating roller 340 via the gear train 385 when driven.

[0089] Motor M2 is driven by the motor driver 503 to rotate cams 329 and 336. By rotating at a rotational speed controlled by the motor driver 503, motor M2 adjusts the contact and separation speed of the pressure roller 330 with respect to the fixing belt 310.

[0090] <Configuration of the pressurized drive unit> The configuration of the pressurizing drive unit 391 of the fixing device 8 according to Embodiment 1 of the present invention will be described in detail with reference to Figure 6.

[0091] The pressurized drive unit 391 includes a worm wheel 392, a worm gear 393, a pair of bearings 399, a pressurized drive gear 395, and a gear 394.

[0092] The worm wheel 392 is fixed to one end of the camshaft 338, which is the rotation axis of the cams 329 and 336, in the axial direction (the direction perpendicular to the plane of the paper in Figure 6).

[0093] The worm gear 393 is mounted on a rotating shaft that rotates under the drive of the motor M2, and meshes with the worm wheel 392.

[0094] The pair of bearings 399 support both ends of the worm gear 393 in the direction of its rotational axis (up and down in Figure 6).

[0095] The pressurized drive gear 395 is mounted on the drive shaft of the motor M2 and rotates when the motor M2 is driven.

[0096] Gear 394 is located at one end of the worm gear 393 in the direction of its rotational axis and meshes with the pressurized drive gear 395.

[0097] <Types of Modes> The types of modes selected by the operation unit 4 of the image forming apparatus 1 according to Embodiment 1 of the present invention will be described in detail.

[0098] The user can select "Image Quality Priority Mode," "Productivity Priority Mode," "Silent Mode," or "Glossiness Priority Mode" using the control unit 4.

[0099] The fourth mode, "Image Quality Priority Mode," is a mode for performing optimal fixing processing on various recording materials. The first mode, "Productivity Priority Mode," is a mode to meet the user's need to shorten the image formation pause time (downtime). The second mode, "Silent Operation Priority Mode," is a mode to reduce the operating noise of the pressurized drive unit 391 in order to meet the user's need to operate the image forming apparatus 1 quietly in an office environment, etc.

[0100] The third mode, "Gloss Priority Mode," is a mode that changes the pressure (nip pressure) applied to the nip section N to meet user needs such as wanting to increase the glossiness of coated paper or wanting to print on special film paper. The "Gloss Priority Mode" is a mode that provides optimal fixing treatment for various recording materials such as plain paper, cardboard, or special papers such as film paper, due to the increasing diversity of media that image forming apparatus 1 can handle in recent years.

[0101] Thus, the "Image Quality Priority Mode" strikes a balance between productivity and quietness. The "Productivity Priority Mode" and "Glossiness Priority Mode" prioritize productivity or glossiness, respectively, at the expense of quietness. The "Quietness Priority Mode" prioritizes quietness at the expense of productivity. In this way, each mode is designed to meet the needs of the user according to their usage situation.

[0102] <Cam operation> The operation of the cams 329 and 336 of the fixing device 8 according to Embodiment 1 of the present invention will be described in detail with reference to Figure 11.

[0103] In Figure 11, Figure 11(a) is a cam diagram of cam 329 and cam 336, and Figure 11(b) is a schematic diagram of cam 329 and cam 336 corresponding to the cam diagram in Figure 11(a).

[0104] Cams 329 and 336 rotate clockwise from point D to point E in Figure 11(b). The cam diagram, which shows the relationship between the rotation angle (phase) of cams 329 and 336 and the radius of the cams, is shown in Figure 11(a). Note that in Figure 11(a), the cam radius is shown with point D as the reference point (0 mm).

[0105] As shown in Figure 11(a), cams 329 and 336 are provided with a cam flat surface 371a, a cam gradient surface 371b, and a cam transition surface 371c.

[0106] Here, the cam flat surface 371a is formed in the separated phase range where the pressure rollers 330 of cams 329 and cams 336 and the fixing belt 310 are separated, and is a surface that includes point A. Furthermore, the cam flat surface 371a is a flat surface that is approximately perpendicular to the direction of the reaction force acting from the cam follower 372 when cams 329 and cams 336 are in contact with the cam follower 372.

[0107] The cam gradient surface 371b is formed within the contact phase range of the pressure roller 330 that forms the nip portion N of the cams 329 and cams 336. The cam gradient surface 371b is also the surface for bringing the pressure roller 330 into contact with the fixing belt 310, and is the surface for changing the pressure applied by the pressure roller 330.

[0108] The cam transition surface 371c is a connecting surface that links the cam flat surface 371a and the cam gradient surface 371b. The cam transition surface 371c is also a connecting surface for moving the pressure roller 330 from a position where it is separated from the fixing belt 310 to a position where it is in contact with the fixing belt 310.

[0109] The cam gradient surface 371b and the cam transition surface 371c are formed such that when the cams 329 and 336 rotate in the direction of the arrows in Figure 11(b), the cam radius, which is the distance from the rotation center O, increases as the rotation angle increases.

[0110] Point B on the cam gradient surface 371b is the point where pressure is applied from the pressure roller 330 to the fixing pad 390 during fixing in "image priority mode," "productivity priority mode," or "quiet priority mode." Point C on the cam gradient surface 371b is the point where pressure is applied from the pressure roller 330 to the fixing pad 390 during fixing in "gloss priority mode." Thus, the cams 329 and 336 can change the pressure acting on the nip portion N in two stages at points B and C. Note that the pressure acting on the nip portion N is not limited to being changeable in two stages, but may be changeable in three or more stages.

[0111] <Operation of the fixing device> The operation of the fixing device 8 according to Embodiment 1 of the present invention will be described in detail with reference to Figures 2 to 12.

[0112] When the motor M2 is driven, the cams 329 and 336 rotate as the driving force of the motor M2 is transmitted to them via the pressurized drive unit 391 (see Figure 6), thereby causing the pressure roller 330 to move toward and away from the fixing belt 310.

[0113] Specifically, as shown in Figure 6, the pressurized drive gear 395 rotates due to the drive of the motor M2, and consequently, the gear 394 that meshes with the pressurized drive gear 395 rotates, as does the worm gear 393. Then, the worm wheel 392 that meshes with the worm gear 393 rotates, and the cam 329 and cam 336 rotate via the cam shaft 338 to which the worm wheel 392 is fixed.

[0114] The rotation of cams 329 and 336 changes the positions of pressure arms 328 and 334, causing the fixing belt 310 and the pressure roller 330 to come into contact or separate. The rotation of cams 329 and 336 also changes the pressure applied by the pressure roller 330 to the fixing pad 390, thereby changing the nip pressure at the nip portion N between the fixing belt 310 and the pressure roller 330.

[0115] Next, we will explain the operation of the fixing device 8 in more detail.

[0116] First, we will explain the details of the operation of the fixing device 8 when no fixing process is performed on the recording material.

[0117] When fixing to the recording material is not performed, cams 329 and 336 are rotated by the motor M2, moving the pressure arms 328 and 334 apart. As a result, the fixing belt 310 and the pressure roller 330 move apart and release the nip, as shown in Figure 7, and wait.

[0118] In this configuration, the cam follower 372 and the cams 329 and 336 are in contact at point A shown in Figure 11. Furthermore, the distance between the upper arm portion 328U and the lower arm portion 328L, and the distance between the upper arm portion 334U and the lower arm portion 334L are restricted by the pressure screw 373.

[0119] Next, we will explain the details of the operation of the fuser 8 when performing the fixing process in "image quality priority mode," "productivity priority mode," or "quiet operation priority mode."

[0120] When performing fixing in "Image Quality Priority Mode," "Productivity Priority Mode," or "Silent Mode," the cams 329 and 336 are driven by the motor M2 and rotate in the direction of the arrow in Figure 11(b) until they come into contact with the cam follower 372 at point B shown in Figure 11.

[0121] As a result, the lower arm portion 328L of the pressure arm 328 and the lower arm portion 334L of the pressure arm 334 are pushed up by the cams 329 and 336 via the cam follower 372. Consequently, the upper arm portions 328U and 334U are pushed up by the elastic force of the pressure springs 331 and 337. The pressure roller 330, supported by the upper arm portions 328U and 334U, then comes into contact with the fixing belt 310. This forms a nip portion N between the fixing belt 310 and the pressure roller 330.

[0122] In the nip section N, the recording material carrying the toner image is held and transported while the toner image is heated, and a fixing process is performed to fix the toner image to the recording material.

[0123] In this process, the upper arm portions 328U and 334U are restricted from moving by the pressure roller 330 coming into contact with the fixing belt 310. Meanwhile, the lower arm portions 328L and 334L move relative to each other upward. As a result, the pressure springs 331 and 337 are compressed by W1 as shown in Figure 9. Furthermore, the upper arm portions 328U and 334U are biased by the pressure springs 331 and 337, allowing them to apply pressure to the nip portion N. This pressure is, for example, 1000N.

[0124] Here, Figure 12 shows the driving torque required to rotate the pressure roller 330 at point B. In Figure 12, the solid line represents the driving torque when the ambient temperature is 23°C, and the dashed line represents the driving torque when the ambient temperature is 10°C. As shown in Figure 12, the driving torque at point B is 130 g·cm at an ambient temperature of 23°C, and increases to 160 g·cm when the ambient temperature is 10°C or lower. The reason for this increase in driving torque is that the rubber of the pressure roller 330 hardens as the ambient temperature decreases, increasing the driving resistance at the nip portion N.

[0125] In "Image Quality Priority Mode," if image formation is temporarily paused, motor M2 is driven at 2500 pps. In this case, if the pressure roller 330 is moved away from the contact position to prevent overheating of the pressure roller 330, the waiting time (downtime) until the re-pressure contact between the fixing belt 310 and the pressure roller 330 is completed before image formation can be resumed will be approximately 6 seconds.

[0126] Furthermore, if image formation is temporarily paused to switch the fixing temperature from 105gsm plain paper to 64gsm thin paper, the pause time is 4 seconds. Therefore, if image formation is temporarily paused in "image quality priority mode," the user will have to wait for approximately 2 seconds for the pressure roller 330 to contact and separate from the fixing belt 310.

[0127] In contrast, in "productivity priority mode," if image formation is temporarily suspended, motor M2 is driven at 4000 pps. In this case, if the pressure roller 330 is moved from the contact position to the separation position to prevent the pressure roller 330 from overheating, the waiting time (downtime) until the re-pressure contact between the fixing belt 310 and the pressure roller 330 is completed before image formation can be resumed will be approximately 4 seconds. Therefore, in this case, since the suspension time and the waiting time (downtime) are the same at approximately 4 seconds, the user will not be made to wait for the pressure roller 330 to contact and separate from the fixing belt 310.

[0128] By setting the system to "productivity priority mode," it becomes possible to address user needs such as wanting to shorten the image formation pause time (downtime).

[0129] However, as shown in Figure 12, the guaranteed torque when motor M2 is driven at 4000 pps is 180 g·cm, which is lower than the guaranteed torque when motor M2 is driven at 2500 pps. Therefore, when motor M2 is driven at 4000 pps, there is a risk that a sufficient safety factor cannot be ensured in low-temperature environments, and motor M2 may fail to drive (risk of motor M2 losing synchronization). Accordingly, the "productivity priority mode" is selectable when the ambient temperature is 18°C ​​or higher.

[0130] Next, we will explain the details of the operation of the fixing device 8 when fixing is performed in "gloss priority mode".

[0131] When fixing is performed in "gloss priority mode," the cams 329 and 336 are driven by the motor M2 and rotate in the direction of the arrow in Figure 11(b) until they come into contact with the cam follower 372 at point C shown in Figure 11.

[0132] As a result, the lower arm sections 328L and 334L are further pushed up, and the pressure springs 331 and 337 are further compressed. As the cams 329 and 336 rotate until they contact the cam follower 372 at point C, the amount of compression of the pressure springs 331 and 337 becomes W2 (W2 > W1), which is greater than the amount of compression W1 of plain paper, as shown in Figure 8. In addition, the upper arm sections 328U and 334U are biased by the pressure springs 331 and 337, allowing a pressing force of, for example, 1500N to be applied to the nip section N.

[0133] Here, Figure 12 shows the driving torque required to rotate the pressure roller 330 at point C. As shown in Figure 12, the driving torque at point C is 170 g·cm when the ambient temperature is 23°C, and increases to 240 g·cm in low-temperature environments below 10°C.

[0134] In "Gloss Priority Mode," if image formation is temporarily paused, motor M2 is driven at 3000 pps. In this case, if the pressure roller 330 is moved away from the contact position to prevent overheating of the pressure roller 330, the waiting time (downtime) until the re-pressure contact between the fixing belt 310 and the pressure roller 330 is completed before image formation can be resumed will be approximately 5 seconds.

[0135] Furthermore, if image formation is temporarily paused to switch the fixing temperature from thick paper with a basis weight of 200 gsm to thin paper with a basis weight of 64 gsm, the pause time is 5 seconds. Therefore, in "gloss priority mode," when image formation is temporarily paused, the pause time and the waiting time (downtime) are the same at approximately 5 seconds, so the user is not made to wait for the pressure roller 330 to contact and separate from the fixing belt 310.

[0136] However, when motor M2 is driven at 3000 pps, the guaranteed torque drops to 250 g·cm, as shown in Figure 12. Therefore, when motor M2 is driven at 3000 pps, there is a risk that a sufficient safety margin cannot be ensured in low-temperature environments, and motor M2 may fail to operate. Accordingly, the "gloss priority mode" is selectable only when the ambient temperature is 18°C ​​or higher.

[0137] By setting the printer to "Gloss Priority Mode," it becomes possible to meet user needs such as increasing the glossiness of coated paper or printing on special film paper.

[0138] Next, in "Silent Priority Mode," if image formation is temporarily paused, motor M2 is driven at 1000 pps. Here, as shown in Figure 13, to reduce the drive noise, it is effective to reduce the rotational speed and drive speed of motor M2 to reduce vibration energy.

[0139] In this case, if the pressure roller 330 is moved from the contact position to a separated position to prevent the pressure roller 330 from overheating, the waiting time (downtime) until the re-pressure contact between the fixing belt 310 and the pressure roller 330 is completed before restarting image formation will be approximately 8 seconds. However, in "silent mode," noise from the image forming apparatus 1 can be suppressed by reducing the rotation speed and drive speed of the motor M2. This makes it possible to meet the needs of users who want to operate the image forming apparatus 1 quietly in an office environment.

[0140] <Image Formation Processing> The image forming process performed by the image forming apparatus 101 according to an embodiment of the present invention will be described in detail with reference to Figure 14.

[0141] The image forming process shown in Figure 14 begins when the main power supply (not shown) of the image forming apparatus 1 is turned on.

[0142] First, the control unit 30 determines whether or not the image quality priority mode has been selected (S1).

[0143] When the image quality priority mode is selected (step S1: Yes), the control unit 30 acquires recording material information regarding the type and basis weight of the recording material from the operation unit 4, and starts image formation when the start key is selected on the operation unit 4 (S2).

[0144] Next, the control unit 30 interrupts the continuous job by temporarily suspending image formation, for example, by adjusting the image forming unit (S3).

[0145] Next, the control unit 30 drives the motor M2 at 2500 pps using the motor driver 503 (S4).

[0146] Next, the control unit 30 drives the motor M2 at 2500 pps and performs a separation operation to separate the pressure roller 330 from the fixing belt 310 (S5).

[0147] Next, the control unit 30 drives the motor M2 at 2500 pps and performs a contact operation to bring the pressure roller 330 into contact with the fixing belt 310 (S6). Here, when "image quality priority mode" is selected, the waiting time (downtime) from when the fixing belt 310 and the pressure roller 330 begin to separate until re-contacting is completed is approximately 6 seconds.

[0148] Next, the control unit 30 starts image formation (S7), and then terminates the image formation process after a predetermined number of sheets have been fed through.

[0149] On the other hand, if the "image quality priority mode" is not selected in the processing of step S1 (step S1: No), the control unit 30 determines whether or not the "glossiness priority mode" is selected (S8).

[0150] When "glossy priority mode" is selected (step S8: Yes), the control unit 30 acquires recording material information regarding the type and basis weight of the recording material from the operation unit 4, and starts image formation when the start key is selected on the operation unit 4 (S9).

[0151] Next, the control unit 30 interrupts the continuous job by temporarily suspending image formation, for example, by adjusting the image forming unit (S10).

[0152] Next, the control unit 30 determines whether the ambient temperature is 18°C ​​or higher (above a predetermined temperature) (S11).

[0153] If the ambient temperature is below 18°C ​​(below a predetermined temperature) (step S11: No), the control unit 30 proceeds to the process in step S4. Here, when the "gloss priority mode" is selected, the waiting time (downtime) from when the fixing belt 310 and the pressure roller 330 begin to separate until the re-welding is completed is approximately 5 seconds.

[0154] On the other hand, if the ambient temperature is 18°C ​​or higher (above a predetermined temperature) (step S11: Yes), the control unit 30 drives the motor M2 at 3000 pps with the motor driver 503 (S12), and then proceeds to step S5. In step S5, the control unit 30 performs a separation operation to move the pressure roller 330 away from the fixing belt 310 while driving the motor M2 at 3000 pps (S5). In step S6, the control unit 30 performs a contact operation to bring the pressure roller 330 into contact with the fixing belt 310 while driving the motor M2 at 3000 pps (S6).

[0155] Furthermore, in the process of step S8, if the "glossy finish priority mode" is not selected (step S8: No), the control unit 30 determines whether the "productivity priority mode" is selected or not (S13).

[0156] When "productivity priority mode" is selected (step S13: Yes), the control unit 30 acquires recording material information regarding the type and basis weight of the recording material from the operation unit 4, and starts image formation when the start key is selected on the operation unit 4 (S14).

[0157] Next, the control unit 30 interrupts the continuous job by temporarily suspending image formation, for example, by adjusting the image forming unit (S15).

[0158] Next, the control unit 30 determines whether the ambient temperature is 18°C ​​or higher (S16).

[0159] If the ambient temperature is below 18°C ​​(step S16: No), the control unit 30 proceeds to the process in step S4. Here, when the "productivity priority mode" is selected, the waiting time (downtime) from when the fixing belt 310 and the pressure roller 330 begin to separate until the re-welding is completed is approximately 4 seconds.

[0160] On the other hand, if the ambient temperature is 18°C ​​or higher (step S16: Yes), the control unit 30 drives the motor M2 at 4000 pps using the motor driver 503 (S17), and then proceeds to step S5. In step S5, the control unit 30 performs a separation operation to move the pressure roller 330 away from the fixing belt 310 while driving the motor M2 at 4000 pps (S5). In step S6, the control unit 30 performs a contact operation to bring the pressure roller 330 into contact with the fixing belt 310 while driving the motor M2 at 4000 pps (S6).

[0161] Furthermore, in the process of step S13, if the "productivity priority mode" is not selected (step S13: No), the control unit 30 determines whether the "silent mode" is selected or not (S18).

[0162] When "Silent priority mode" is selected (step S18: Yes), the control unit 30 acquires recording material information regarding the type and basis weight of the recording material from the operation unit 4, and starts image formation when the start key is selected on the operation unit 4 (S19).

[0163] Next, the control unit 30 interrupts the continuous job by temporarily suspending image formation, for example, by adjusting the image forming unit (S20).

[0164] Next, the control unit 30 drives the motor M2 at 1000 pps using the motor driver 503 (S 21 ), and then proceed to step S5.

[0165] In step S5, the control unit 30 drives the motor M2 at 1000 pps and performs a separation operation to move the pressure roller 330 away from the fixing belt 310 (S5). In step S6, the control unit 30 drives the motor M2 at 1000 pps and performs a contact operation to bring the pressure roller 330 into contact with the fixing belt 310 (S6).

[0166] Thus, the control unit 30 makes the contact and separation speed of the pressure roller 330 with respect to the fixing belt 310 slower in the "silent mode" than in the "productivity mode".

[0167] In this case, when "Silent Mode" is selected, the waiting time (downtime) from when the fixing belt 310 and the pressure roller 330 begin to separate until re-welding is completed is approximately 6 seconds.

[0168] On the other hand, if the "Silent Priority Mode" is not selected (step S18: No), the control unit 30 returns to the process of step S1.

[0169] In this embodiment, when interrupting a continuous job, the contact and separation speed between the pressure roller 330 and the fixing belt 310 by the pressure drive unit 391 in "productivity priority mode" is made faster than the contact and separation speed in "quiet priority mode". This makes it possible to suppress the temperature rise of the pressure roller 330 when interrupting a continuous job, and to make the pressure roller 330 and the fixing belt 310 contact and separate at an optimal speed depending on the usage conditions.

[0170] (Embodiment 2) The configuration of the image forming apparatus according to Embodiment 2 of the present invention is the same as that shown in Figure 1, so its description is omitted. Similarly, the configuration of the fixing apparatus according to this embodiment is the same as that shown in Figures 2 to 10, so its description is omitted.

[0171] <Operation of the fixing device> The operation of the fixing device according to Embodiment 2 of the present invention will be described in detail with reference to Figures 15 to 18.

[0172] In the above embodiment 1, as shown in Figure 15, the motor M2 is driven at a uniform 2500 pps from point A to point B shown in Figure 11 in "image quality priority mode". In contrast, in this embodiment, as shown in Figure 16, the motor M2 is driven at 4000 pps from point A to the starting position of contact between the fixing belt 310 and the pressure roller 330 because it is not subjected to a load due to pressure, and then driven at 2500 pps from the starting position of contact to point B. This makes it possible to more effectively reduce the waiting time (downtime) from when the fixing belt 310 and the pressure roller 330 begin to separate until re-contacting is completed.

[0173] Furthermore, in the above embodiment 1, as shown in Figure 17, the motor M2 drives the forward and return paths between point A and point B at a uniform speed of 4000 pps in "productivity priority mode". Here, the forward path is the path that brings the pressure roller 330 into contact with the fixing belt 310 from a distanced position, and the return path is the path that moves the pressure roller 330 away from the fixing belt 310 from a contact position to a distanced position.

[0174] In contrast, in this embodiment, the forward stroke involves compressing the pressure springs 331 and 337, while the return stroke involves releasing the force stored in the pressure springs 331 and 337. Therefore, the on-axis torque of the motor M2 is smaller in the return stroke compared to the forward stroke. Consequently, as shown in Figure 18, the motor M2 can be driven at a contact speed of 4000 pps in the forward stroke and at a separation speed of 5000 pps in the return stroke. Here, the driving torque at point B is 130 g·cm in the forward stroke and 60 g·cm in the return stroke. Since the guaranteed torque when driven at 5000 pps is 150 g·cm, a sufficient safety factor can be ensured even when only the return stroke is driven at 5000 pps.

[0175] In this case, when "productivity priority mode" is selected, the waiting time (downtime) from when the fixing belt 310 and the pressure roller 330 begin to separate until re-pressure is completed is approximately 3.5 seconds. In this way, by making the return drive speed faster than the forward drive speed according to the on-axis torque of the motor M2, it is possible to effectively reduce the waiting time due to temporary pauses.

[0176] In this way, downtime due to pauses can be effectively reduced depending on the intended use. Furthermore, in cases where quiet operation is important, such as in an office, the operating noise level can be reduced, contributing to an improvement in the office environment.

[0177] Note that the operation of the fixing device according to this embodiment, other than those described above, is the same as the operation of the fixing device 8 according to Embodiment 1, so its explanation will be omitted.

[0178] The present invention is not limited to the embodiments described above, and it goes without saying that various modifications are possible without departing from the spirit of the invention.

[0179] Specifically, in Embodiments 1 and 2 described above, the following modes are selectable: "Image Quality Priority Mode," "Productivity Priority Mode," "Silent Mode," or "Glossiness Priority Mode." However, the system is not limited to these modes, and other modes can also be selected. In this case, the motor M2 is driven at a speed corresponding to each mode.

[0180] Furthermore, in Embodiments 1 and 2 described above, the driving speed of the motor M2 was set differently depending on whether the ambient temperature was 18°C ​​or higher. However, the motor M2 may be set differently depending on whether the ambient temperature is 18°C ​​or higher. [Explanation of symbols]

[0181] 1 Image forming unit 2 Image reading unit 3. Main unit of the device 4 Control section 8. Fixing device 30 Control Unit 300 heating units 310 Fixing belt 328 Pressure Arm 330 Pressure Roller 331 Compression spring 340 heating rollers 341 Halogen heater 360 Stay 372 Cam Followers 380 Fixing Frame 385 gear train 390 Fixing Pad 391 Pressurized drive unit 500 Thermistor 503 Motor Driver

Claims

1. Fixing means for fixing the toner image onto a recording material by heating and pressurizing the recording material on which the toner image has been formed using a pressurizing rotating body and a fixing belt, A means for bringing the pressurized rotating body and the fixing belt into contact with and away from each other, A temperature detection means for detecting ambient temperature, A control means for executing a continuous job that performs image formation on multiple recording materials in succession, It has, The control means is In the first mode, the time for interrupting the continuous job is the first time, and the speed at which the pressurizing rotating body and the fixing belt are brought into contact by the contact / separation means is the first speed; in the second mode, the time for interrupting the continuous job is the second time, which is longer than the first time, and the speed at which the pressurizing rotating body and the fixing belt are brought into contact by the contact / separation means is the second speed, which is slower than the first speed. When the ambient temperature detected by the temperature detection means is below a predetermined temperature, the contact and separation speed in the first mode is slowed down compared to when the ambient temperature detected by the temperature detection means is above the predetermined temperature. A fixing device characterized by the following features.

2. The second mode is, This is a mode that quiets the operating noise of the aforementioned contact / disconnection means. The fixing device according to feature 1.

3. The system has a selection means that allows the user to select either the first mode or the second mode. The control means is The contact / separation means brings the pressurizing rotating body and the fixing belt into contact and separate positions according to the contact / separation speed in the first mode or the second mode selected by the selection means. The fixing device according to claim 1 or 2.

4. The control means is When interrupting the continuous job, the approach / disengagement speed in the third mode is made slower than the approach / disengagement speed in the first mode and faster than the approach / disengagement speed in the second mode. A fixing device according to any one of claims 1 to 3.

5. The third mode is, This mode enhances the glossiness of the image on the recording material or forms an image on a special recording material. The fixing device according to feature 4.

6. The control means is The nip pressure of the nip portion formed by the pressurizing rotating body and the fixing belt in the third mode is made greater than the nip pressure in the first mode and the second mode. The fixing device according to feature 5.

7. The control means is When interrupting the continuous job, the approach / disengagement speed in the fourth mode is made slower than the approach / disengagement speed in the first mode and the third mode, and faster than the approach / disengagement speed in the second mode. The fixing device according to any one of claims 4 to 6.

8. The fourth mode described above is, This mode prioritizes image quality. The fixing device according to feature 7.

9. The fixing belt has a biasing means that biases the pressurizing rotating body in a direction that separates it from the fixing belt, The control means is The separation speed when separating the pressurizing rotating body and the fixing belt is made faster than the contact speed when bringing the pressurizing rotating body and the fixing belt into contact. A fixing device according to any one of claims 1 to 8.

10. A fixing device according to any one of claims 1 to 9, Image forming means for forming an image on a recording material, An image forming apparatus characterized by having the following features.

11. An image forming unit that forms a toner image on the recording material, A fixing belt that heats the recording material, A pressurizing rotating body is configured to pressurize the outer surface of the fixing belt, form a nip portion between itself and the fixing belt, and apply heat and pressure to the recording material at the nip portion. The pressurized rotating body and the fixing belt are connected and disconnected by a means for connecting and disconnecting them, A drive source that drives the aforementioned contact / separation means, Control means for controlling the drive source, A temperature detection means for detecting ambient temperature, Equipped with, In an image forming apparatus capable of interrupting the image forming operation and performing a separation operation to separate the fixing belt and the pressurizing rotating body using the contact / separation means during a continuous job in which images are formed on multiple recording materials in succession, The control means is If the ambient temperature detected by the temperature detection means is above a predetermined temperature, a first mode is executed in which the drive speed of the drive source is controlled to a first speed such that the movement time for moving the contact / separation means from the contact position where the fixing belt and the pressurizing rotating body are located during the fixing operation to the separation start position where the pressurizing rotating body begins to separate from the fixing belt is a first time. The system is configured to execute a second mode in which, when the ambient temperature detected by the temperature detection means is below a predetermined temperature, the drive speed of the drive source is controlled to a second speed that is slower than the first speed, so that the travel time becomes a second time that is longer than the first time. An image forming apparatus characterized by the following features.

12. The first mode is, The pressing force from the aforementioned pressurizing rotating body is the first pressure at which the fixing operation is performed. The second mode is, In this mode, the fixing operation is performed with a second pressure that is higher than the first pressure applied by the pressurizing rotating body. The image forming apparatus according to feature 11.

13. The control means is When the second mode is executed, the movement speed when moving from the separation start position to the separation end position where the separation operation between the anchoring belt and the pressurizing rotating body ends is set to a third speed that is faster than the second speed. The image forming apparatus according to feature 11.

14. An image forming unit that forms a toner image on the recording material, A fixing belt that heats the recording material, A pressurizing rotating body is configured to pressurize the outer surface of the fixing belt, form a nip portion between itself and the fixing belt, and apply heat and pressure to the recording material at the nip portion. The pressurized rotating body and the fixing belt are connected and disconnected by a means for connecting and disconnecting them, A temperature detection means for detecting ambient temperature, A drive source that drives the aforementioned contact / separation means, Control means for controlling the drive source, Equipped with, In an image forming apparatus capable of interrupting the image forming operation and performing a separation operation to separate the fixing belt and the pressurizing rotating body using the contact / separation means during a continuous job in which images are formed on multiple recording materials in succession, The control means is When the ambient temperature detected by the temperature detection means is above a predetermined temperature, a first mode is executed in which the drive speed of the drive source is controlled to a first speed so that the movement time for moving the contact / separation means from the contact start position where the fixing belt and the pressurizing rotating body start to contact the contact position where the fixing belt and the pressurizing rotating body are located during the fixing operation is a first time. When the ambient temperature detected by the temperature detection means is below the predetermined temperature, a second mode is executed in which the drive speed of the drive source is controlled to a second speed slower than the first speed so that the movement time is a second time, which is longer than the first time. An image forming apparatus characterized by the following features.

15. The first mode is, The pressing force from the aforementioned pressurizing rotating body is the first pressure at which the fixing operation is performed. The second mode is, In this mode, the fixing operation is performed with a second pressure that is higher than the first pressure applied by the pressurizing rotating body. The image forming apparatus according to feature 14.

16. The control means is If the ambient temperature detected by the temperature detection means is below a predetermined temperature, and the second mode is executed, the drive speed of the drive source is set to a third speed that is faster than the second speed when moving the contact / separation means from the separated position where the fixing belt and the pressurizing rotating body are separated to the contact start position. The image forming apparatus according to feature 14.

Images