JP2013125071A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that reduces the time for device warm-up as short as possible.SOLUTION: A fixing unit 6 comprises, inside a heat resistant housing 45: a heat roller 46; a pressure roller 47; a heat generation roller 48 incorporating a heat source 49; a heat conductive belt 51 extended between the heat roller 46 and the heat generation roller 48; a drive belt 54 extended between the core shaft 52 of the heat roller 46 and the core shaft 53 of the pressure roller 47; and an eccentric rotation cam 68 that slides in contact with the peripheral surface of the shaft receiver 62 of the pressure roller 47. Every time rotation cam 68 rotates 180 degrees, the pressure roller 47 comes into contact with or separates from the heat roller 46. While the pressure roller 47 and the heat roller 46 are pressed against each other, the drive belt member 54 automatically slacks and loses driving force. When the pressure roller 47 and the heat roller 46 are not in contact with each other during the warm-up of the machine, the drive belt member 54 is automatically stretched and the drive from the pressure roller 47 to the heat roller 46 are transmitted.

Description

  The present invention relates to a fixing device, and more particularly to a fixing device that shortens warm-up operation time as much as possible.

  Conventionally, there are electrophotographic image forming apparatuses used for copying machines, printers, facsimiles, and the like. In this image forming apparatus, generally, a photosensitive drum is uniformly charged and initialized, an electrostatic latent image is formed on the photosensitive drum by optical writing, and the electrostatic latent image is converted into a toner image, that is, developed. Then, after the toner image is directly or indirectly transferred onto a transfer material such as paper, the transferred toner image is fixed on a paper surface by a fixing device.

  As the fixing device, the toner image is transferred by applying heat and pressure to the paper while the paper is sandwiched and conveyed by a heating roller in contact with the toner image side of the paper and a pressure roller in pressure contact with the opposite side of the paper. Many types are fixed to the surface. As a heat source, the heating roller usually has a built-in halogen lamp.

  By the way, when the user uses the image forming apparatus as described above, it is general that the user wants to execute printing as soon as possible after the power is turned on. However, the fixing device that is responsible for the final stage of forming the printed image on the paper needs to heat the toner of the toner image transferred onto the paper surface at a predetermined temperature, and therefore requires a warm-up operation time. is there.

  In this case, since the user generally dislikes the waiting time, the warm-up operation must be considered to be as short as possible. Also, shortening the warm-up operation time of the apparatus is an important issue in terms of energy saving.

  Therefore, in recent years, since the rise of the fixing temperature is slow in the roller pair method of the heating roller and the pressure roller, the type using a belt type fixing device is increasing. A belt-type fixing device is a type of fixing device that conducts heat from a heating roller to a heating roller via a fixing belt.

  In this type of fixing device, the thickness of the fixing belt is made thin, the outer peripheral thickness of the heating roller is reduced, the heat capacity is lowered, and the temperature raising function is increased, which is compared with the conventional method using only a pair of rollers. It is said that it can exhibit a fast-rise fixing function.

  In this belt-type fixing device, in order to further shorten the warm-up time (the time from when the fixing belt is rotated to the time when the fixing belt is reached, that is, the warm-up operation time), the heating roller has a cylindrical or cylindrical shape. There has been proposed a core metal (a peripheral configuration of a conventional heating roller), which is configured by a sponge layer on its outer peripheral surface and a resin tube covering the sponge layer. (For example, refer to Patent Document 1.)

  Such a belt-type fixing device is now widely used. For example, a heat generating roller as a heat source has a halogen heater or the like built in a thin cylinder made of, for example, aluminum having a high thermal conductivity, and the heating roller is a thin metal tube such as nickel electroformed having a thickness of several tens of microns. The outermost layer of a heat-shrinkable tube layer such as a PFA (polytetrafluoroethylene) resin, and a silicone rubber coating layer on the surface of the core metal.

  Such a belt fixing method is said to be a method in which the warm-up time can be shortened by a rapid temperature increase of the fixing belt and a continuous temperature recovery operation after fixing.

  By the way, in the belt-type fixing system, it is an essential requirement to form a holding portion for the sheet via the fixing belt by the heating roller and the pressure roller. Therefore, even if the temperature increase rate of the fixing belt itself during warm-up is high, there still remains a problem that the time for the fixing belt to reach a predetermined temperature is delayed due to heat being deprived by the clamping roller side.

JP 2011-002590 A

  Therefore, using the automatic pressure release mechanism that is normally provided in the fixing device, during the warm-up time, the pressure roller is moved away from the heat conduction belt portion of the heating roller, and only the heating roller is driven so that the heating roller has a predetermined temperature. It is considered that the warm-up time can be shortened by pressing the pressure roller toward the heating roller after reaching the temperature.

  However, this method of thinking has several problems. First, in order to separate the pressure roller from the heating roller side and drive the heat conducting belt to circulate, it is necessary to use the heating roller as a driving roller. However, if the heating roller is a driving roller, the heat conduction belt cannot be stably driven when the sheet passes through the holding portion with the pressure roller.

  Further, since the heating roller is composed of a low-hardness sponge having a normal thickness, if the heating roller is used as a driving roller, the heat conducting belt cannot be stably rotated. Further, the sheet feeding speed unevenness of the fixing device greatly affects the color superimposition accuracy of the image forming unit, so an unstable feeding mechanism in the fixing device is not allowed.

  The present invention solves the above-described conventional problems, and while keeping the pressure roller in a non-contact state from the heating roller, the pressure roller is used as a driving roller to reliably supply the rotational force to the heat conducting belt. An object of the present invention is to provide a fixing device that shortens the warm-up operation time as much as possible.

  In order to solve the above-described problems, a fixing device of the present invention includes a heating roller having a heat source that is controlled to generate heat, a pressure roller that presses the heating roller, and presses the pressure roller against the heating roller. A support member that is variably supported between a state and a non-pressed state, a drive mechanism that rotationally drives the pressure roller, and a rotational driving force of the pressure roller when the pressure roller changes to the non-pressed state And a drive belt that transmits the heat to the heating roller.

  In this fixing device, the support member is configured to bring the pressure roller into a non-pressing state with respect to the heating roller when the image forming apparatus main body is not operating or is warming up before starting the main operation. It is configured to change.

  In the present invention, during the warm-up operation, the pressure roller and the heat fixing roller are not pressed, and the heat transferred from the heat fixing roller to the pressure roller is limited to radiant heat to avoid direct conduction, so that the heat fixing roller is quickly Since it is heated, it is possible to provide a fixing device that shortens the warm-up operation time as much as possible.

1 is a cross-sectional view illustrating an internal configuration of a full-color image forming apparatus (printer, apparatus main body) according to Embodiment 1 of the present invention. 1 is an external perspective view of a printer according to Embodiment 1. FIG. (a), (b) is sectional drawing which takes out and shows only the fixing unit of the printer which concerns on Example 1, (c) is A arrow directional view of (b). (a)-(d) is a figure which changes the viewpoint of rotation of the eccentric rotation cam of the printer which concerns on Example 1, operation | movement of the pressure roller with respect to a heating roller, and operation | movement of a drive belt member. (a), (b) is a figure which shows the press release mechanism which abbreviate | omitted illustration until now of the pressure roller.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, “printing” and “printing” are used as synonyms.

  FIG. 1 is a cross-sectional view illustrating an internal configuration of a full-color image forming apparatus (hereinafter simply referred to as a printer or an apparatus main body) according to Embodiment 1 of the present invention.

  A printer 1 shown in FIG. 1 is an electrophotographic secondary transfer type tandem color image forming apparatus, and includes an image forming unit 2, a transfer belt unit 3, a toner supply unit 4, a paper feeding unit 5, a belt type thermal image forming apparatus. The image forming apparatus includes a fixing unit 6 (hereinafter, simply referred to as a fixing unit 6) and a duplex printing transport unit 7.

  The image forming unit 2 is in contact with the lower running unit surface 8a of the transfer belt 8 of the transfer belt unit 3 and multi-stages four developing devices 9 (9k, 9c, 9m, 9y) from right to left in FIG. It consists of a side-by-side configuration. The image forming unit 2 is held by a frame of the printer 1 main body so as to be movable up and down from a printing execution position shown in FIG. 1 to a maintenance position below it.

  Of the four developing devices 9, three developing devices 9c, 9m, and 9y on the upstream side (the left side in the figure) are cyan (C), magenta (M), and yellow (Y), which are subtractive three primary colors, respectively. A mono-color image is formed with the color toner, and the developing device 9k forms a monochrome image mainly with black (K) toner used for characters and dark portions of the image.

  Each of the developing devices 9 has the same configuration except for the color of the toner that develops the image. Therefore, the configuration of the developing device 9y for yellow (Y) toner will be described below as an example.

  The developing device 9 includes a photosensitive drum 10 at the top. The photosensitive drum 10 has a peripheral surface made of, for example, an organic photoconductive material. A cleaner 11, a charging roller 12, an optical writing head 13, and a developing roller 15 of the developing device 14 are disposed around the periphery of the photosensitive drum 10.

  The developing device 14 includes a housing 16 that covers the outside, a partition wall 17 provided inside, a developing roller 15, a first stirring and conveying screw 18, and a second stirring and conveying screw 19. Although not specifically shown, the first and second agitating and conveying screws 18 and 19 include a screw shaft and a fin that is integrally formed with the screw shaft and rotates.

  The developing unit 14 includes a reserve tank 27 (27k, 27c, 27m, 27y) of the toner supply unit 4, and black (K) and cyan (C) as indicated by K, C, M, and Y in FIG. , Magenta (M) or yellow (Y) toner is supplied.

  The transfer belt unit 3 has an endless transfer belt 8 that extends in the shape of a flat loop in the left-right direction in the figure at approximately the center of the main unit, and the transfer belt 8 is stretched over the transfer belt 8. A driving roller 21 and a driven roller 22 are provided to circulate and move counterclockwise as indicated by an arrow a in the figure.

  The transfer belt 8 includes a primary transfer roller 20 that is integrated with the unit. The primary transfer roller 20 is pressed against the photosensitive drum 10 via the transfer belt 8 and directly transfers (primary transfer) the toner image to the belt surface that circulates below. The transfer belt 8 conveys the toner image to the secondary transfer unit 23 to the paper for further transfer (secondary transfer) to the paper.

  A belt cleaner 24 is disposed on the transfer belt 8. The belt cleaner 24 includes a cleaning blade 25 that comes into contact with the surface of the transfer belt 8 that is stretched over the drive roller 21. A waste toner collecting container 26 is detachably disposed below the belt cleaner 24.

  The belt cleaner 24 scrapes and removes the waste toner remaining on the surface of the transfer belt 8 by the cleaning blade 25, and sends the waste toner to the waste toner collection container 26 below by a conveying screw.

  The toner supply unit 4 includes four reserve tanks 27 (27k, 27c, 27m, and 27y) that are disposed above the upper running unit of the transfer belt 8 and are detachably disposed on the reserve tanks 27, respectively. Toner cartridge 28 (28k, 28c, 28m, 28y) for toner replenishment.

  The four toner cartridges 28k, 28c, 28m, and 28y accommodate black (K), cyan (C), magenta (M), and yellow (Y) toners, respectively, and four reserve tanks 27 (27k, 27c). , 27m, 27y) are replenished with toner from the toner cartridge 28 mounted thereon.

  These four reserve tanks 27 are hidden behind the opposite side of the transfer belt unit 3 in FIG. 1, but are connected to the corresponding developing devices 14 of the developing device 9 by toner supply paths.

  Although not particularly shown, the toner supply unit 4 is held on the frame of the printer 1 main body so as to be able to be raised and lowered from the printing execution position shown in FIG. 1 to a maintenance position above it.

  Two electrical parts 30 are disposed on the left side of the toner supply unit 4 from the left side of the belt cleaner 24 to above the drive roller 21. The electrical unit 30 includes a circuit board on which a control device including a plurality of electronic components is mounted.

  The paper feed unit 5 includes two paper feed cassettes 29 (29a, 29b) arranged in two upper and lower stages. A paper take-out roller 31, a feed roller 32, a separating roller 33, and a standby conveyance roller pair 34 are disposed in the vicinity of the paper feed opening (right side of the drawing) of the two paper feed cassettes 29, respectively.

  A secondary transfer roller 35 that is in pressure contact with the driven roller 22 via the transfer belt 8 is disposed in the paper transport direction (vertically upward in the drawing) of the standby transport roller pair 34, and the secondary transfer onto the paper described above. Part 23 is formed.

  A fixing unit 6 is disposed downstream (upward in the drawing) of the secondary transfer portion. In the vicinity of the exit inside the upper part of the fixing unit 6, a pair of carry-out rollers 36 for carrying out the fixed sheet from the fixing unit 6 is disposed. Further, on the further downstream side of the fixing unit 6, a paper discharge roller pair 38 for discharging the paper carried out by the carry-out roller pair 36 to a paper discharge tray 37 formed on the upper surface of the apparatus is disposed.

  The conveyance unit 7 for double-sided printing also serves as an opening / closing member whose outer surface (right outer surface in the drawing) opens or shields the inside of the printer 1 from the side surface to the outside.

  This duplex printing transport unit 7 has a start return path 39a that branches rightward in the figure from just before the paper discharge roller pair 38, an intermediate return path 39b that bends downward, and a left lateral direction opposite to the above. Thus, a return path 39 including a terminal return path 39c for finally inverting the return sheet is provided.

  In the middle of the return path 39, five pairs of return rollers 41 (41a, 41b, 41c, 41d, 41e) are arranged. The exit of the end return path 39 c joins the conveyance path to the pair of standby conveyance rollers 34 corresponding to the sheet feeding cassette 29 b below the sheet feeding unit 5.

  FIG. 2 is an external perspective view of the printer 1 described above. In FIG. 2, the same components as in FIG. 1 are given the same reference numerals as in FIG.

  As shown in FIG. 2, the printer 1 is provided with a front door 42 on the front side and an opening / closing member 44 with a handle 43 on the right side. The double-sided printing conveyance unit 7 shown in FIG.

  As shown in FIG. 1, the printer 1 does not directly transfer a toner image onto a sheet. Instead, the printer 1 conveys a sheet conveyed vertically to a secondary transfer unit by a pair of standby conveying rollers 34 via a transfer belt 8. The toner image is transferred.

  Accordingly, since troubles such as paper jam do not occur in the arrangement section of the kits, the operation of attaching / detaching consumables such as kits concentrated on the left side of FIG. 1 is performed by opening the front door 42 shown in FIG. It is comprised so that a kind may be exchanged in a longitudinal direction (front door direction).

  Similarly, the printer 1 transfers the toner image to a sheet conveyed in the vertical direction to the secondary transfer unit via the transfer belt 8, and further conveys the sheet in the vertical direction to fix the transferred toner image on the sheet. It is a method to do.

  Therefore, it is possible to cope with the maintenance process for recovering from a problem such as a paper jam occurring in the paper transport path by simply opening the right opening / closing member 44 shown in FIG.

  However, even in the case of a paper jam occurring in the paper transport path, if it occurs in the fixing unit 6 and the whole paper has entered the fixing unit 6, the front door is not the right opening / closing member 44. 42 is opened and the fixing unit 6 is pulled out to the front of the apparatus to deal with it.

  FIGS. 3A and 3B are sectional views showing only the fixing unit 6 of the printer 1 having the above-described configuration, and FIG. 3C is a view taken in the direction of arrow A in FIG. 3A shows the state of the fixing unit 6 when the apparatus main body 1 is executing printing, and FIG. 3B shows the state of the fixing unit 6 when the apparatus main body 1 is not printing or is warming up. Is shown.

  3 (a), (b), and (c), the same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG. In FIG. 3C, the upper surface, the lower surface, and the left side surface of the heat insulating casing 45 of the fixing unit 6 shown in FIG.

  As shown in FIG. 3A, the fixing unit 6 includes a heat roller 46, a pressure roller 47, a heat roller 48, and the like inside a heat insulating casing 45. The heat roller 48 has a built-in heat source 49 made of, for example, a halogen lamp. A heat conducting belt 51 is stretched between the heating roller 46 and the heat generating roller 48.

  As shown in FIG. 3C, the heating roller 46 is pivotally supported at both ends of the core shaft 52 by bearings 61 a and 61 b held by the standing portions 45 a and 45 b of the housing 45. The pressure roller 47 is also supported at both ends of the core shaft 53 by bearings 62 a and 62 b held by the standing portions 45 a and 45 b of the housing 45.

  The heating roller 48 is not visible behind the heating roller 46 in FIG. 3C, but is held by the standing portions 45a and 45b of the housing 45 in the same manner as the heating roller 46 and the pressure roller 47. The both ends of the core shaft are pivotally supported by the bearing.

  The pressure roller 47 is sandwiched between two flanges 63a and 63b fixed to the outside of the bearing 62b at one end of the core shaft 53 (the right end in FIG. 3C). The driven gear 64 is provided at the position. The drive gear 65 of the apparatus main body 1 is engaged with the driven gear 64.

  The pressure roller 47 is rotationally driven via a driven gear 64 by a drive system gear 65 of the apparatus main body 1. Further, the bearings 62a and 62b of the pressure roller 47 are not clearly seen in the figure, but are arranged in a predetermined direction (right and left directions in FIGS. 3 (a) and 3 (b)) by the standing portions 45a and 45b of the housing 45. 3 (c) is held with play that is movable in the vertical direction. The outer peripheral portions of the bearings 62a and 62b also serve as cam receivers.

  That is, the eccentric rotating cams 68a and 68b are in sliding contact with the outer peripheral portions of the bearings 62a and 62b. The eccentric rotating cams 68 a and 68 b are fixed to both ends of the cam shaft 69. Both ends of the cam shaft 69 are held by the standing portions 45 a and 45 b of the housing 45.

  A driven gear 71 is fixed to one end portion of the cam shaft 69 (the right end portion in FIG. 3C) outside the standing portion 45 b of the housing 45. The driven gear 71 meshes with a drive system gear (not shown) of the apparatus main body 1.

  The eccentric rotary cams 68a and 68b are driven to rotate by 180 degrees via the driven gear 71 and the cam shaft 69 by the drive system gear of the apparatus main body 1, and the sliding contact surface farthest from the rotation center of the cam shaft 69 and the cam The sliding contact surface closest to the rotation center of the shaft 69 is alternately stopped at the outer peripheral portions of the bearings 62 a and 62 b, and the pressure roller 47 is brought into contact with the heating roller 46.

  When the apparatus main body 1 performs printing, that is, when the fixing unit 6 is in the state shown in FIG. 3A, the sheet that has passed through the secondary transfer unit 23 shown in FIG. 6 is carried in from the bottom to the top as shown by the arrow b.

  Thereafter, the sheet is guided by guide plates 56 (56 a, 56 b) standing obliquely upward from both sides of the carry-in entrance 55, and the pressure roller 47 is formed in pressure contact with the heating roller 46 via the heat conduction belt 51. The leading edge of the sheet is held by the fixing unit.

  The heat conduction belt 51 radiates and preheats the heat received from the heat generation roller 48 heated by the heat source 49 to the sheet surface between the carry-in entrance 55 and the fixing unit, and directly heats the heating unit 46 together with the heating roller 46. The toner image is transmitted to the paper and assisted by the pressing of the pressure roller 47 to fix the toner image on the paper surface.

  The paper on which the toner image has been fixed on the paper surface and passed through the fixing portion is restrained from being wrapped around the heat conduction belt 51 or the pressure roller 47 by the separation claw 57 (57a, 57b) and sandwiched by the carry-out roller pair 36. It is conveyed, discharged from the carry-out port 59 along the conveyance path 58 indicated by a broken line, and discharged to the paper discharge tray 37 shown in FIG.

  Incidentally, between the heating roller 46 and the pressure roller 47, a driving belt member 54 having a predetermined stretchability is hung between the end of each core shaft 52 and the end of the core shaft 53. Has been passed.

  Since the torque for rotating the heating roller 46 in a state where the heating roller 46 and the pressure roller 47 are separated from each other is very slight, the driving belt member 54 used for the rotation is, for example, heat resistant and of an appropriate size. The purpose can be sufficiently achieved by using a silicone ring-shaped member.

  The other ends of the core shaft 52 and the core shaft 53 of the heating roller 46 and the pressure roller 47 (the left end portion in FIG. 3C) are fixedly provided outside the bearings 62a and 62b, respectively. Individual flanges 66a, 66b and 67a, 67b are provided.

  The drive belt member 54 is stretched between the heating roller 46 and the pressure roller 47 while being sandwiched between the two flanges 66a and 66b and 67a and 67b.

  As described above, when the apparatus main body 1 is executing printing and the pressure roller 47 is in the pressing state against the heating roller 46 as shown in FIG. Since the 52 and the core shaft 53 move in directions relatively close to each other, the drive belt member 54 is configured to automatically loosen and lose the driving force.

  On the other hand, when the apparatus main body 1 is not printing or is warming up and the pressure roller 47 is not pressed against the heating roller 46 as shown in FIG. Since the roller core shaft 52 and the core shaft 53 move relatively away from each other, the driving belt member 54 is automatically stretched to exert a driving force from the pressure roller 47 to the heating roller 46. Configured to

  4A to 4D are views showing the rotation of the eccentric rotating cam 68 (68a, 68b), the operation of the pressure roller 47 with respect to the heating roller 46, and the operation of the driving belt member 54 from different viewpoints. It is. FIG. 4A is a view showing the main part of FIG.

  FIG. 4B is a diagram showing only one end (the left end in FIG. 3C) of the CC cross-sectional arrow view of FIG. 4A. FIG. 4C is a view showing the main part of FIG. FIG.4 (d) is a figure which shows only one edge part (same edge part as FIG.4 (b)) of DD sectional view taken on the line of FIG.4 (c).

  4 (a) to 4 (d), the same components as those shown in FIGS. 3 (a), (b) and (c) are shown in FIGS. 3 (a), (b) and (c). ) And the same number are given.

  4A and 4B show the case where the apparatus main body 1 is in a printing execution state. The eccentric rotary cam 68 (68a, 68b) has a sliding contact surface farthest from the rotation center of the cam shaft 69 as a bearing 62 ( 62a and 62b), and the pressure roller 47 is pressed toward the heating roller 46 as indicated by an arrow e.

  4 (c) and 4 (d) show the case where the apparatus main body 1 is in a print-stopped or warm-up state, and the slidable contact surface where the eccentric rotating cam 68 (68a, 68b) is closest to the rotation center of the cam shaft 69. Is brought into contact with the outer periphery of the bearing 62 (62a, 62b), and the pressure roller 47 is separated from the heating roller 46 by a distance g in the direction indicated by the arrow f.

  4 (b) and 4 (d) also show a play 45c formed between the upright portion 45a (45b) that holds the bearing 62a (62b) and the bearing 62a (62b). Due to the play 45 c, the pressure roller 47 is configured to be able to move away from the heating roller 46.

  When the state shown in FIGS. 4C and 4D is reached, the drive belt member 54 is automatically stretched to transmit the rotation of the pressure roller 47 to the heating roller 46. As a result, only the radiant heat is transmitted to the pressure roller 47 and there is no direct conduction of a large amount of heat due to contact with the heat conduction belt 51, so the heat conduction belt 51 and the heating roller are heated by the heat generated by the heat source 49 and the heat generation roller 48. 46 is quickly heated.

  5 (a) and 5 (b) are diagrams showing a pressing release mechanism of the pressure roller 47 that has been omitted so far. FIG. 5 (a) is a view showing a state where a press release mechanism is added to FIG. 4 (c), and FIG. 5 (b) is a view showing a state where a press release mechanism is added to FIG. 4 (d). 5 (a) and 5 (b), the same components as those in FIGS. 4 (a) to (d) are given the same numbers as those in FIGS. 4 (a) to (d) only for the portions necessary for explanation. It is given.

  As shown in FIG. 5 (a) (see also FIG. 5 (b)), the pressure release mechanism includes a support shaft 72 disposed in a fixing unit frame (not shown), and a lower end portion that is rotatable on the support shaft 72. And a tension spring member 75 having one end locked to the upper end of the pressure release lever 73 and the other end locked to a fixing portion 74 of a fixing unit frame (not shown). ing.

  Since the upper end of the press release lever 73 is biased in a direction away from the heating roller 46 by the pulling spring member 75, the pressing release lever 73 is always rotated in a direction away from the heating roller 46 with the support shaft 72 at the lower end as a fulcrum. It is energized.

  Since the pressing release lever 73 is set so that its substantially central portion comes into contact with the end of the core shaft 53 of the pressure roller 47, the pressing release lever 73 is urged to rotate away from the heating roller 46 as described above. Thus, the pressure roller 47 is always urged away from the heating roller 46 via the core shaft 53.

  As a result, when the eccentric rotating cam 68a (68b) makes the slidable contact surface farthest from the rotation center of the cam shaft 69 abut on the outer peripheral portion of the bearing 62a (62b), the pressure roller 47 causes the pressing release lever 73 to move. As shown in FIG. 3 (a) or FIGS. 4 (a) and 4 (b), it is pressed against the heating roller 46 against the urging force from.

  On the other hand, when the eccentric rotating cam 68a (68b) abuts the sliding contact surface closest to the rotation center of the cam shaft 69 on the outer peripheral portion of the bearing 62a (62b), the eccentric rotating cam 68a (68b) and the bearing 62a ( As shown in FIGS. 5 (a) and 5 (b), the pressure roller 47 follows the urging force from the pressure release lever 73 in accordance with the movement of the contact portion with 62b) away from the heating roller 46. (As shown in FIGS. 3B and 3C or FIGS. 4C and 4D), the heating roller 46 is separated.

  As described above, according to the present embodiment, the driving force can be transmitted from the pressure roller to the heating roller side in the non-contact state during the warm-up operation time. The temperature rise efficiency can be improved as much as possible, and the warm-up operation time can be significantly shortened.

  Further, during the warm-up operation time, the temperature can be raised and heated without taking heat directly from the heating roller side to the pressure roller, so that an improvement in terms of energy saving is also achieved.

  In the above-described embodiment, the driving belt stretched between the heating roller and the pressure roller is a silicone ring-shaped member. However, the present invention is not limited to this, and the pressure roller is a heating roller. The belt material is not limited as long as the structure is set so that the belt is slackened when pressed against the heating roller and stretched when the pressure roller is separated from the heating roller.

  In addition, the drive belt is looped between the heating roller and the pressure roller in the form of a ring, but may be looped. If it does so, even if the rotation direction in the opposing part of both rollers becomes a rotation in the same linear direction even when it leaves | separates, the resistance at the time of a press is lose | eliminated.

  In this example, the belt type fixing device has been described as an example. However, the method of driving the roller side separated during the warm-up operation time by the driving belt in this example is a roller pair method including a heat roller and a pressure roller. Needless to say, it can also be applied to a fixing device.

Although several embodiments of the present invention have been described, the present invention is included in the invention described in the claims and the equivalents thereof. Hereinafter, the invention described in the scope of claims of the present application will be appended.
[Appendix 1]

A heating roller with a heat source that controls heat generation;
A pressure roller that presses against the heating roller;
A support member that variably supports the pressure roller with respect to the heating roller between a pressed state and a non-pressed state;
A drive mechanism for rotationally driving the pressure roller;
A fixing device comprising: a driving belt that transmits a rotational driving force of the pressure roller to the heating roller when the pressure roller changes to the non-pressing state.
[Appendix 2]

The support member changes the pressure roller to a non-pressing state with respect to the heating roller when the image forming apparatus main body is in an operation stop state or in a warm-up operation before the start of a main operation.
The fixing device according to appendix 1, wherein
[Appendix 3]

The driving belt automatically loosens when the pressure roller is in a pressing state against the heating roller and loses driving force, and automatically when the pressure roller is in a non-pressing state against the heating roller. Configured to exert a driving force by being stretched
The fixing device according to appendix 1 or 2, characterized in that:
[Appendix 4]

The drive belt is stretched between two flange-shaped protrusions formed around a core bar exposed at an outer end portion of the pressure roller and the heating roller than the outer peripheral surface material of each. The fixing device according to any one of appendices 1 to 3.
[Appendix 5]

A heat-generating roller spanned by a heat transfer belt between the heat roller and the pressure roller, the pressure roller being variable between a pressed state and a non-pressed state with respect to the heat roller;
The fixing device according to any one of appendices 1 to 4, characterized in that:

  The present invention can be used for a fixing device that shortens the warm-up operation time as much as possible.

1 Full-color image forming device (printer, device body)
2 Image forming unit 3 Transfer belt unit 4 Toner supply unit 5 Paper feeding unit 6 Belt type fixing unit (fixing unit)
7 Transport unit for double-sided printing 8 Transfer belt 8a Surface of lower running portion 9 (9m, 9c, 9y, 9k) Developing device 9r, 9r-1, 9r-2 Preliminary developing device for special toner 10 Photosensitive drum 11 Cleaner 12 Charging roller DESCRIPTION OF SYMBOLS 13 Optical writing head 14 Developing device 15 Developing roller 16 Housing | casing 17 Partition 15 Developing roller 18 1st stirring conveyance screw 19 2nd stirring conveyance screw 20 Primary transfer roller 21 Drive roller 22 Driven roller 23 Secondary transfer part 24 Belt Cleaner 25 Cleaning blade 26 Waste toner collection container 27 (27m, 27c, 27y, 27k) Reserve tank 28 (28m, 28c, 28y, 28k) Toner cartridge 29 (29a, 29b) Paper feed cassette 30 Electrical component 31 Paper take-out roller 32 Feed roller 33 Roller 4 Standby conveyance roller pair 35 Secondary transfer roller 36 Unloading roller pair 37 Paper discharge tray 38 Paper discharge roller pair 39 Return path 39a Start return path 39b Intermediate return path 39c End return path 41 (41a, 41b, 41c, 41d, 41e) Return roller pair 42 Front door 43 Handle 44 Opening / closing member 45 Insulating housing 45a, 45b Standing portion 45c Play 46 Heating roller 47 Pressure roller 48 Heating roller 49 Heat source 51 Heat conduction belt 52, 53 Core shaft 54 Drive belt member 55 Carry-in port 56 (56a, 56b) Guide plate 57 (57a, 57b) Separation claw 58 Carriage route 59 Carry-out port 61 (61a, 61b) Bearing 62 (62a, 62b) Bearing 64 Driven gear 65 Drive system gear 66 (66a) 66b), 67 (67a, 67b) Flange 68 (68a, 68b) Heart rotating cam 69 the cam shaft 71 the driven gear 72 supporting shaft 73 pressing release lever 74 fixed part 75 pulls the spring member

Claims (5)

A heating roller with a heat source that controls heat generation;
A pressure roller that presses against the heating roller;
A support member that variably supports the pressure roller with respect to the heating roller between a pressed state and a non-pressed state;
A drive mechanism for rotationally driving the pressure roller;
A driving belt that transmits a rotational driving force of the pressure roller to the heating roller when the pressure roller changes to the non-pressing state;
A fixing device comprising: The support member changes the pressure roller to a non-pressing state with respect to the heating roller when the image forming apparatus main body is in an operation stop state or in a warm-up operation before the start of a main operation.
The fixing device according to claim 1. The driving belt automatically loosens when the pressure roller is in a pressing state against the heating roller and loses driving force, and automatically when the pressure roller is in a non-pressing state against the heating roller. Configured to exert a driving force by being stretched
The fixing device according to claim 1, wherein   The drive belt is stretched between two flange-shaped protrusions formed around a core bar exposed at an outer end portion of the pressure roller and the heating roller than the outer peripheral surface material of each. The fixing device according to claim 1. A heat-generating roller spanned by a heat transfer belt between the heat roller and the pressure roller, the pressure roller being variable between a pressed state and a non-pressed state with respect to the heat roller;
The fixing device according to claim 1, wherein