JP2019148778A - Fixing device - Google Patents

Abstract

To provide a simple and compact configuration of a fixing device having a pressurizing unit and a heating unit on an outer peripheral surface of a fixing roller.SOLUTION: A first tension spring S1 for energizing a pressurizing unit 81 toward a fixing roller 80 through a swingable first arm A1 and a second tension spring S2 for energizing a heating unit 82 toward the fixing roller 80 through a swingable second arm A2 are connected to a rotation body 83, so that energizing forces of the first tension spring S1 and the second tension spring S2 are changed by the rotation of the rotation body 83.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fixing device that fixes a developer on a sheet-like recording medium.

  Conventionally, as a fixing device used in an image forming apparatus, one that heats a fixing roller that forms a fixing nip region together with a pressure unit from the outside is known.

  For example, in Patent Document 1, a pressure unit and a heating unit (heater) are arranged so as to sandwich the fixing roller in a direction orthogonal to the rotation axis of the fixing roller. The pressure unit and the heating unit are urged toward each other by a tension spring and are pressed against the fixing roller. The pressure unit and the heating unit are configured so as to be able to release the pressing force to the fixing roller at the same time using cams (since the cams are interlocked by gears meshing with each other).

JP 2006-224158 A

  The mechanism of Patent Document 1 is difficult to apply except when the heating unit is disposed at a position opposite to the pressure unit with the fixing roller interposed therebetween. Moreover, it is necessary to provide each unit with a cam (pressure release mechanism), and the apparatus tends to be enlarged.

  In a fixing device in which a pressure unit and a heating unit are arranged on the outer peripheral surface of the fixing roller, while maintaining the function of applying and releasing the pressing force to both units, the degree of freedom in design is increased, the number of parts is increased, and the device It is desirable to suppress the increase in size.

  A fixing device including a fixing roller, a pressure unit, a heating unit, a rotating body, a frame, a first arm, a second arm, a first tension spring, and a second tension spring is disclosed. The pressure unit forms a fixing nip region with the fixing roller. The heating unit forms a contact heating area with the fixing roller. The frame supports the fixing roller and the rotating body. The first arm can swing with respect to the frame, and the pressing force in the fixing nip region can be changed by changing the position of the pressure unit with respect to the fixing roller. The second arm is swingable with respect to the frame, and the pressing force in the contact heating region can be changed by changing the position of the heating unit with respect to the fixing roller. The first tension spring connects the first arm and the rotating body, and biases the pressure unit toward the fixing roller via the first arm. The second tension spring connects the second arm and the rotating body, and biases the heating unit toward the fixing roller via the second arm. And the urging | biasing force of a 1st tension spring and the urging | biasing force of a 2nd tension spring change with rotation of a rotary body.

  According to this configuration, the pressing unit and the heating unit are each given a pressing force by the tension of the corresponding first tension spring and the second tension spring. Can be set. Therefore, the freedom degree of arrangement | positioning of a pressurization unit and a heating unit is high. In addition, since the rotation of the rotating body is used to change the urging force of the two springs, it is not necessary to provide a separate part for releasing the pressure such as a cam for each unit, and the parts can be simplified by the mechanism. The number of points can be reduced, the manufacturing cost can be reduced, and the apparatus can be made compact.

  If the example of specific arrangement | positioning is given, the said rotary body will have the 1st connection part to which the said 1st tension spring is connected, and the 2nd connection part to which the said 2nd tension spring is connected, The shortest distance from the rotating shaft of the rotating body to the first connecting portion is a first distance, and the shortest distance from the rotating shaft of the rotating body to the second connecting portion is a second distance shorter than the first distance. is there.

  According to this, the width of the change in the biasing force of the first tension spring accompanying the rotation of the rotating body can be made larger than the width of the change in the biasing force of the second tension spring. Therefore, for example, during the fixing operation, the pressing force in the fixing nip region of the pressure unit with respect to the fixing roller can be made stronger than the pressing force in the contact heating region of the heating unit with respect to the fixing roller. Further, when releasing the fixing nip, the pressing force in the fixing nip region of the pressure unit with respect to the fixing roller can be made weaker than the pressing force in the contact heating region of the heating unit with respect to the fixing roller.

  In the above configuration, the rotating body may include a crankshaft, and the first tension spring and the second tension spring may be connected to a crankpin of the crankshaft.

  According to this, it is possible to switch between applying and releasing the fixing nip pressure with a very simple configuration that does not take up space.

  More specifically, it can be configured as follows. The rotating body can be rotationally displaced between a first position and a second position, and the urging force of the first tension spring and the urging force of the second tension spring are both determined by the rotating body. When the rotary body is in the first position, the first tension spring pulls the first arm when the rotary body is in the first position. A direction in which the second tension spring pulls the second arm is parallel to a direction in which the pressure unit is pressed, and a direction in which the second arm presses the heating unit.

  According to this, for example, by setting the rotating body to be in the first position during the fixing operation, the tension of the tension spring can be utilized to the maximum efficiency.

  The frame includes a first stopper, and the first stopper contacts the rotating body when the rotating body is in the first position, and the biasing force of the first tension spring and the The rotation of the rotating body may be prevented against at least one of the urging forces of the second tension spring.

  According to this, it is possible to realize stable positioning of the rotating body when in the first position using the biasing force of the tension spring with a simple configuration in which the first stopper that contacts the rotating body is provided on the frame. .

  In the above configuration, when the rotating body is in the first position, the rotating body contacts the rotating body and resists at least one of the biasing force of the first tension spring and the biasing force of the second tension spring. In addition, an actuator capable of rotating the rotating body may be provided.

  According to this, for example, an operation of releasing the fixing nip pressure by rotationally displacing the rotating body that was in the first position to the second position by using the actuator can be easily executed. .

  The frame has a second stopper, and the second stopper contacts the rotating body when the rotating body is in the second position, and the biasing force of the first tension spring and the second The rotating body may be prevented from rotating against at least one of the biasing force of the tension spring.

  According to this, it is possible to realize stable positioning of the rotating body when it is in the second position using the biasing force of the tension spring with a simple configuration in which the second stopper that contacts the rotating body is provided on the frame. .

  The heating unit may be arranged at a position shifted from the position opposite to the pressure unit with the fixing roller interposed therebetween.

  According to this, compared with the case where the heating unit is disposed at the position opposite to the pressure unit with the fixing roller interposed therebetween, the space occupied by the heating unit on the opposite side of the pressure unit to the fixing roller is opened. be able to. Therefore, it is possible to arrange other parts in the vacant space and to make the device thinner accordingly, and the degree of freedom in design is improved.

  The swing center of the first arm is disposed upstream of the rotation axis of the fixing roller in the direction in which the second arm presses the heating unit, and the swing center of the second arm is The first arm may be disposed upstream of the rotation shaft of the fixing roller in the direction in which the pressure unit is pressed.

  According to this, the pressing unit and the heating unit, which are displaced from the opposite positions across the fixing roller, are appropriately pressed against the fixing roller by the swinging operation of the first arm and the second arm, respectively. Can be made.

  The fixing device further includes a sensor for detecting a surface temperature of the fixing roller, and the sensor is downstream of the fixing nip region and more than the contact heating region in the rotation direction of the fixing roller. It may be arranged upstream. Further, the sensor may be arranged so as to intersect a plane formed by a rotation axis of the fixing roller and a rotation axis of the rotating body.

  According to this, a sensor can be arrange | positioned in the appropriate position in the empty space by arrange | positioning a heating unit shifted from the space on the opposite side of a pressurization unit on both sides of a fixing roller. In particular, since the sensor can be moved away from the heating unit, the temperature of the fixing roller can be accurately detected without being affected by the temperature of the heating unit.

  The first tension spring and the second tension spring may be the same length spring having the same spring coefficient.

  According to this, since the same kind of tension spring can be used for the first tension spring and the second tension spring, it is convenient for procurement of parts and contributes to the efficiency of the manufacturing process.

  Here, the position of the swing center of the first arm may be configured to be equal to the position of the swing center of the second arm. For example, the frame includes a pin that is disposed on a swing axis that forms a swing center of the first arm and a swing center of the second arm and extends along the swing axis, and the first arm The second arm may be connected to the pin.

  According to this, it is possible to realize a function of applying a pressing force and releasing a pressing force with a compact arrangement configuration by two arms that swing coaxially. Further, since the two arms can be swingably supported by one pin, it contributes to a reduction in the number of parts.

  The pressure unit includes a pressure roller having a first shaft and a first holder that rotatably supports the first shaft, and the first arm engages with the first holder. It is good.

  The heating unit may include a heating roller containing a heating element and a second holder that rotatably supports the heating roller, and the second arm may be engaged with the second holder. .

  According to this, the urging force of the corresponding spring can be converted into the pressing force of each roller by engaging the holder serving as a bearing for the pressure roller and / or the heating roller with the arm.

  By configuring the pressure unit and the heating unit to be urged toward the fixing roller by the first tension spring and the second tension spring respectively connected to the rotating body, the pressing force is changed (applied and released) by the rotation of the rotating body. ) Can be switched. In addition, the pressing force of the pressure unit and the heating unit can be easily adjusted (optimized) by changing the specification of each spring and / or the connection position with the rotating body, while suppressing an increase in the number of parts. Compact size is possible.

It is sectional drawing which shows a laser printer. It is a side view showing a fixing device. It is a perspective view which shows a guide mechanism. It is a perspective view which shows a rotary body and its drive mechanism. 4A and 4B are side views showing a pressing force releasing operation of the fixing device, respectively showing (a) the releasing operation and (b) a state after completion of releasing. It is a side view which shows the 1st modification of a fixing device, (a) The press state at the time of fixing operation, (b) The state after completion | finish of cancellation | release is shown, respectively. It is a side view which shows the 2nd modification of a fixing device, respectively, (a) The press state at the time of fixing operation | movement, (b) The state after completion of cancellation | release is shown. It is a side view which shows the 3rd modification of a fixing device, and each shows (a) the press state at the time of fixing operation, and (b) the state after completion of cancellation | release.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, the directions are “front” on the left side of the page in FIG. 1, “rear” on the right side of the page, “left” on the back side of the page, and front side of the page. The side is “right”. In addition, the vertical direction toward the paper surface is “up and down”.

  As shown in FIG. 1, the laser printer 1 mainly includes a housing 2, a paper feed unit 3, an exposure device 4, a process cartridge 5, and a fixing device 8.

  The housing 2 includes a front cover 21 provided on the front side, a paper discharge tray 22 formed on the upper surface, and a rear cover 25 provided on the rear side. The front cover 21 and the rear cover 25 respectively cover the openings formed in the front wall and the rear wall of the housing 2 so as to be openable. The user can open the front cover 21 and the rear cover 25 at the time of replacement of consumables or paper jam processing.

  The paper feed unit 3 is provided at a lower portion in the housing 2 and mainly includes a paper feed tray 31 for storing paper S (sheet-like recording medium), a paper pressing plate 32, and a paper feed mechanism 33. Yes. The paper S stored in the paper feed tray 31 is moved upward by the paper pressing plate 32 and supplied to the process cartridge 5 by the paper feed mechanism 33.

  The exposure device 4 is disposed in the upper part of the housing 2 and includes a light source device (not shown), a polygon mirror, a lens, a reflecting mirror, and the like that are not shown. In the exposure device 4, the surface of the photosensitive drum 61 is exposed by high-speed scanning of the light beam emitted from the light source device on the surface of the photosensitive drum 61 based on the image data.

  The process cartridge 5 is disposed below the exposure device 4 in the housing 2 and is detachable from the housing 2 through an opening formed when the front cover 21 provided on the housing 2 is opened. The process cartridge 5 includes a drum unit 6 and a developing unit 7. The drum unit 6 mainly includes a photosensitive drum 61, a charger 62, and a transfer roller 63. The developing unit 7 is detachable from the drum unit 6 and mainly includes a developing roller 71, a supply roller 72, a layer thickness regulating blade 73, and a storage portion 74 that stores toner. .

  In the process cartridge 5, the surface of the photosensitive drum 61 is uniformly charged by the charger 62, and then exposed by a light beam from the exposure device 4, so that a static image based on image data is formed on the photosensitive drum 61. An electrostatic latent image is formed. The toner in the container 74 is supplied to the developing roller 71 via the supply roller 72 and enters between the developing roller 71 and the layer thickness regulating blade 73 to form a thin layer on the developing roller 71 with a constant thickness. Supported. The toner carried on the developing roller 71 is supplied from the developing roller 71 to the electrostatic latent image formed on the photosensitive drum 61. As a result, the electrostatic latent image is visualized and a toner image is formed on the photosensitive drum 61. Thereafter, the sheet S is conveyed between the photosensitive drum 61 and the transfer roller 63 so that the toner image on the photosensitive drum 61 is transferred onto the sheet S.

  The fixing device 8 is disposed behind the process cartridge 5 in the housing 2. The sheet S on which the toner image is transferred passes through the fixing device 8 to fix the toner image. In the following, the operation of fixing the toner image on the paper S by the fixing device 8 may be referred to as a fixing operation. Then, the paper S on which the toner image is fixed is discharged onto the paper discharge tray 22 by the transport rollers 23 and 24.

  As shown in FIG. 2, the fixing device 8 includes a fixing roller 80, a pressure unit 81, a heating unit 82, a rotating body 83, a frame 84, a first arm A1, a second arm A2, and a first arm. 1 tension spring S1, 2nd tension spring S2, solenoid 86 as an example of an actuator, and temperature sensor 87 are provided. The first arm A1, the second arm A2, the first tension spring S1, the second tension spring S2, the solenoid 86, and the elements associated therewith are arranged on the left and right sides of the fixing device 8 (that is, in the direction of the rotation axis of the fixing roller 80). ) Provided at both ends.

  FIG. 2 shows the arrangement of the fixing device 8 during the fixing operation.

  The fixing roller 80 is a roller body comprising a roller shaft 80S made of a solid core, an elastic layer such as silicone rubber formed on the outer periphery of the roller shaft 80S, and a release layer formed on the outer periphery of the elastic layer. 80M. Both ends of the roller shaft 80S are rotatably supported by the frame 84. Reference numeral 80A denotes a rotation axis of the fixing roller 80. The fixing roller 80 rotates in the clockwise direction in the drawing when a driving force is transmitted from a driving source (not shown).

  The pressure unit 81 includes a pressure roller 81R and a first holder 81H. The pressure roller 81R includes a pressure roller shaft 81S as a first shaft and a pressure roller body 81M, and the pressure roller shaft 81S is rotatably supported by the first holder 81H (its first bearing hole 81B). Has been. The first holder 81H is slidably engaged with the frame 84.

  The pressure roller body 81M is a cylindrical member. For example, an elastic layer made of silicone rubber or the like is formed on the outer peripheral surface of a metal core, and a release layer is formed on the outer periphery of the elastic layer. It is configured. The pressure roller body 81M forms a fixing nip region NP with the fixing roller 80 (roller body 80M). The fixing nip area NP is an area where the pressure roller 81R and the fixing roller 80 sandwich the paper S during the fixing operation.

  The heating unit 82 includes a heating roller 82R containing a heating element 82C and a second holder 82H. The heating roller 82R is a cylindrical member. For example, an elastic layer made of silicone rubber or the like is formed on the outer peripheral surface of a hollow metal core made of metal such as aluminum, and a release layer is formed on the outer periphery of the elastic layer. Thus, the heating roller main body 82M is configured. At both ends in the rotation axis direction of the heating roller 82R, there are exposed portions of the core bar on which the elastic layer and the release layer are not provided, thereby forming the heating roller end portion 82E. The heating roller end portion 82E is rotatably supported by the second holder 82H (its second bearing hole 82B). The second holder 82H is slidably engaged with the frame 84.

  A halogen lamp or the like is used as the heating element 82C disposed inside the heating roller body 82M. The heating element 82C is disposed on the rotation axis of the heating roller 82R. The heating roller main body 82M forms a contact heating region HR with the fixing roller 80 (roller main body 80M), and transmits the heat of the heating element 82C to the fixing roller 80. The contact heating area HR is an area where the heating roller 82R and the fixing roller 80 are in close contact with each other and transmit heat during the fixing operation.

  In the present embodiment, the heating unit 82 is arranged at a position shifted from the position opposite to the pressure unit 81 with the fixing roller 80 interposed therebetween. Specifically, the pressure unit 81 is in a substantially horizontal position (rear side) with respect to the fixing roller 80, whereas the heating unit 82 is not in a horizontal position (front side) with respect to the fixing roller 80 but in a substantially vertical position. Arranged in the relationship (lower side). In other words, in the fixing roller 80, the pressure unit 81, and the heating unit 82, the line segment connecting the rotation center of the pressure roller 81R and the rotation center of the fixing roller 80 is the rotation center of the heating roller 82R and the fixing roller 80. Are arranged so as to be substantially orthogonal to a line segment connecting the rotation centers of the two.

  The frame 84 supports a fixing roller 80, a first arm A1, a second arm A2, and a rotating body 83, which will be described later, so as to be rotatable or swingable about their respective axes 80A, AA, 83A. Further, a solenoid 86 and a temperature sensor 87, which will be described later, are fixed to the frame 84, and the first stopper 84SA and the second stopper 84SB that restrict the rotation of the rotating body 83, and the pressure unit 81 and the heating unit 82 are moved. A guide slot 84G (see FIG. 3) for guiding is provided.

  Both the first arm A <b> 1 and the second arm A <b> 2 are provided so as to be swingable with respect to the frame 84. In the present embodiment, the first arm A1 and the second arm A2 are configured to be swingable about a common swing axis AA. Specifically, each of the first arm A1 and the second arm A2 is connected to a pin AC provided on the frame 84 and can swing independently. That is, the pin AC is arranged on the swing axis AA so as to extend along the common swing axis AA (swing center).

  The first arm A <b> 1 is disposed at a position where the pressure unit 81 (first holder 81 </ b> H) can be pressed toward the roller shaft 80 </ b> S of the fixing roller 80. In other words, the first arm A1 is arranged on the opposite side of the fixing roller 80 with the pressure unit 81 interposed therebetween, and the pressure roller shaft 81S rotates perpendicularly to the longitudinal direction of the first arm A1. It arrange | positions so that the plane containing 80 A of axis lines may be crossed.

  The second arm A2 is disposed at a position where the heating unit 82 (second holder 82H) can be pressed toward the roller shaft 80S of the fixing roller 80. In other words, the second arm A2 is disposed on the opposite side of the fixing roller 80 across the heating unit 82, and the heating roller end portion 82E is perpendicular to the longitudinal direction of the second arm A2 and the rotation axis of the fixing roller 80. It arrange | positions so that it may cross | intersect the plane containing 80A.

  The rotating body 83 is downstream of the rotation axis 80A of the fixing roller 80 in the direction in which the first arm A1 presses the pressure unit 81, and the fixing roller 80 in the direction in which the second arm A2 presses the heating unit 82. It is arranged downstream of the rotation axis 80A. The rotating body 83 is supported by the frame 84 so as to be rotatable about the rotation axis 83A.

  The swing axis AA (swing center) of the first arm A1 and the second arm A2 is upstream of the rotation axis 80A of the fixing roller 80 in the direction in which the first arm A1 presses the pressure unit 81, and The second arm A2 is disposed upstream of the rotation axis 80A of the fixing roller 80 in the direction in which the heating unit 82 is pressed.

  That is, the fixing roller 80 is located between the swing axis AA of the first arm A1 and the second arm A2 and the rotation axis 83A of the rotating body 83. The pressure unit 81 and the heating unit 82 are located between the swing axis AA of the first arm A 1 and the second arm A 2 and the rotation axis 80 A of the fixing roller 80.

  The distal end side of the first arm A1 is connected to the rotating body 83 by the first tension spring S1. The distal end side of the second arm A2 is connected to the rotating body 83 by the second tension spring S2. The pressurizing unit 81 is disposed between the first tension spring S1 and the swing axis AA in the longitudinal direction of the first arm A1. Further, the pressurizing unit 82 is disposed between the second tension spring S2 and the swing axis AA in the longitudinal direction of the second arm A2.

  In the present embodiment, the first tension spring S1 and the second tension spring S2 are the same length springs having the same spring coefficient. By using springs of the same standard, it is convenient for procuring, stocking, and exchanging parts, contributing to streamlined manufacturing processes and reduced manufacturing costs.

  The first tension spring S1 biases the pressure unit 81 toward the fixing roller 80 via the first arm A1. The second tension spring urges the heating unit 82 toward the fixing roller 80 via the second arm A2.

  Therefore, the first arm A1 swings about the pin AC and changes the position of the pressure unit 81 with respect to the fixing roller 80, so that the first arm A1 with respect to the fixing roller 80 of the pressure unit 81 due to the tension of the first tension spring S1. The pressing force (the pressing force in the fixing nip region NP) can be changed. Further, the second arm A2 also swings around the pin AC to change the position of the heating unit 82 with respect to the fixing roller 80, whereby the pressing force of the heating unit 82 against the fixing roller 80 due to the tension of the second tension spring S2. (Pressing force in the contact heating region HR) can be changed.

  The temperature sensor 87 is a sensor that detects the surface temperature of the fixing roller 80. The temperature sensor 87 is disposed downstream of the fixing nip region NP and upstream of the contact heating region HR in the rotation direction of the fixing roller 80 (clockwise in the drawing). Specifically, in the direction in which the first arm A1 presses the heating unit 82, the fixing roller 80 is downstream of the rotation axis 80A of the fixing roller 80 and in the direction in which the second arm A2 presses the heating unit 82. Is located downstream of the rotational axis 80A. More specifically, the temperature sensor 87 is disposed so as to intersect a plane PL configured to include the rotation axis 80A of the fixing roller 80 and the rotation axis 83A of the rotating body 83.

  In this manner, the temperature sensor 87 is disposed on the opposite side of the fixing nip region NP and the contact heating region HR of the fixing roller 80, particularly at a position that is offset from just above the heating unit 82 and sufficiently away from the heating unit 82. Therefore, it is difficult to be influenced by heat from the heat source, and good detection accuracy can be realized.

  Here, a guide mechanism for guiding the sliding of the second holder 82H will be described with reference to FIG. Since the configuration for guiding the first holder 81H is the same as the guide mechanism of the second holder 82H except that the sliding direction is different, the illustration and description are omitted. The configuration shown in FIG. 3 is provided on both left and right sides of the fixing device 8 (that is, in the direction of the rotation axis of the fixing roller 80). Here, the vicinity of the second holder 82H on the left side of the heating unit 82 is shown in an enlarged manner. Yes.

  As shown in FIG. 3, at the lower end (end on the second arm A2 side) of the frame 84, the second tension spring S2 is connected to the second arm A2 in the pressing direction of the second arm A2 (in the arrangement during the fixing operation shown in FIG. A guide slot 84G is provided that extends substantially parallel to the direction A2 is pulled).

  On the other hand, the second holder 82H has a second bearing hole 82B (see FIG. 2), an engagement surface 82F, and a pair of sliding grooves 82G. The second bearing hole 82B rotatably supports the heating roller end 82E. The engaging surface 82F is the lower surface of the second holder 82H (the surface facing the second arm A2 side), forms a gently convex surface, and is in sliding contact with the second arm A2. The pair of sliding grooves 82G extend in the same direction as the direction in which the guide slot 84G extends, and have a width slightly larger than the thickness of the edge portion of the guide slot 84G of the frame 84.

  By inserting the sliding groove 82G into the guide slot 84G and sliding the second holder 82H upward, the heating roller body 82M of the heating roller 82R of the heating roller 82R in which the heating roller end portion 82E is supported by the second bearing hole 82B. The surface comes into contact with the surface of the roller body 80M of the fixing roller 80. The second holder 82H is supported between the second arm A2 and the fixing roller 80 by connecting one end of the tension spring S2 to a predetermined position on the distal end side of the second arm A2 having the base end connected to the pin AC. Is done.

  FIG. 4 is a perspective view showing the configuration of the end portion of the rotating body 83 including the crankshaft 83S. The crankshaft 83S of the rotator 83 extends along the fixing roller 80, and the first crankpin P1 and the second crankpin P2 are provided at both ends of the fixing device 8 (that is, in the direction of the rotation axis of the fixing roller 80). It has been. Here, a configuration including a first crankpin P1 and a second crankpin P2 provided at the right end of the crankshaft 83S is shown.

  As shown in FIG. 4, the rotating body 83 includes a crankshaft 83S, an operation block 83B, and a gear 83C. In the present embodiment, the gear 83S is provided only at the right end shown in FIG. The crankshaft 83 </ b> S is disposed such that its rotation axis 83 </ b> A is substantially parallel to the rotation axis 80 </ b> A (see FIG. 2) of the fixing roller 80. Further, as can be seen from FIG. 4, the first arm A1 and the second arm A2 are connected to a position shifted in the direction of the swing axis AA in the pin AC.

  The crankshaft 83S has a first crankpin P1 and a second crankpin P2 at positions corresponding to the first arm A1 and the second arm in the direction of the rotation axis 83A substantially parallel to the swing axis AA, respectively. A first tension spring S1 is rotatably connected to the first crank pin P1, and a second tension spring S2 is rotatably connected to the second crank pin P2.

  The operation block 83B is provided outside the first crank pin P1 in the direction of the rotation axis 83A, and is fixed so as to be rotatable integrally with the crankshaft 83S. A gear 83C for inputting a driving force from a driving source (not shown) is fixed to the outside of the operation block 83B in the direction of the rotation axis 83A.

  The end portion of the crankshaft 83S shown in FIG. 4 is supported by shaft support members B1, B2, B3, and B4 so as to be rotatable with respect to the frame 84 around the rotation axis 83A. Unlike the two outer shaft support members B1 and B2, the support openings of the two shaft support members B3 and B4 that support the crankshaft 83S on the inner side of the outer first crankpin P1 are different from those of the first arm A1. A notch C is provided on the side opposite to the pressing direction (the direction in which the first tension spring S1 is pulled).

  When mounting the crankshaft 83S to the frame 84, first, a portion of the crankshaft 83S between the first crankpin P1 and the second crankpin P2 is fitted into the shaft support member B3, and the crankshaft 83S A portion on the inner side in the rotation axis 83A direction than the second crankpin P2 is fitted into the shaft support member B4. Next, the shaft support member B2, the operation block 83B, and the shaft support member B1 are inserted in this order into both ends of the crankshaft 83S (outside the first crankpin P1 in the direction of the rotation axis 83A). Then, the shaft support members B1 and B2 are fixed to the frame with screws or the like (not shown). In this way, the crankshaft 83S can be attached to the frame 84.

  The shaft support members B3 and B4 that support the crankshaft 83S at positions adjacent to the first crankpin P1 and the second crankpin P2 have notches C, and the first tension spring S1 and the second tension spring S2 crank. Since the opening is formed in a direction different from the direction in which the shaft 83S is urged, the crankshaft 83S can be stably supported during the operation of the fixing device 8.

  As shown in FIG. 2, the first crankpin P1 and the second crankpin P2 of the crankshaft 83S are provided at positions where the shortest distance from the rotation axis 83A is different. Specifically, the distance (first distance D1) from the rotation axis 83A of the point (first connection portion) where the first tension spring S1 is locked to the first crankpin P1 on the first crankpin P1. When the distance (second distance D2) from the rotation axis 83A of the point (second connecting portion) where the second tension spring S2 is locked to the second crankpin P2 on the second crankpin P2 is compared, D1 > D2 holds.

  As shown in FIG. 2, a first stopper 84SA and a second stopper 84SB are provided in the frame 84 in the vicinity of the rotating body 83. The first stopper 84SA is an element that positions the rotating body 83 during the fixing operation at the first position shown in FIG. At this time, the first stopper 84SA is in contact with the operation block 83B and prevents the rotation of the rotating body 83 against the urging force of the first tension spring S1 and the urging force of the second tension spring S2.

  In the first position of the rotating body 83 shown in FIG. 2, the pressing force against the fixing roller 80 in the fixing nip region NP applied by the first tension spring S1 to the pressure unit 81 via the first arm A1 is suitable for the fixing operation. The fixing nip region NP is set to be formed. Similarly, in the first position, the pressing force against the fixing roller 80 in the contact heating region HR applied by the second tension spring S2 to the heating unit 82 via the second arm A2 is an effective heating control during the fixing operation. Therefore, it is set to form a contact heating region HR suitable for the purpose.

  When the rotating body 83 is in the first position, the direction in which the first tension spring S1 pulls the first arm A1 is substantially parallel to the direction in which the first arm A1 presses the pressure unit 81. Similarly, the direction in which the second tension spring S2 pulls the second arm A2 is substantially parallel to the direction in which the second arm A2 presses the heating unit 82. Therefore, the tension of the first tension spring S1 and the second tension spring S2 can be utilized to the maximum efficiency.

  FIG. 5 shows an operation when the pressing force of the pressure unit 81 and the heating unit 82 against the fixing roller 80 is released. When releasing the pressing force from the pressing state during the fixing operation shown in FIG. 2, the solenoid 86 is operated and the operating block 83B of the rotating body 83 is pressed as shown in FIG. The rotating body 83 is rotated clockwise in the figure against the urging force of the tension spring S1 and the urging force of the second tension spring S2. When the position of FIG. 5 (a) is exceeded, the solenoid 86 returns to the initial state shown in FIG. 2, but the rotating body 83 is further rotated clockwise by the biasing force of the first tension spring S1 and the second tension spring S2. Rotates and reaches the release state shown in FIG.

  In the released state shown in FIG. 5B, the first tension spring S1 and the second tension spring S2 still apply the clockwise torque shown in the figure to the rotating body 83 with a small tension. The second stopper 84SB comes into contact with the operation block 83B and prevents further rotation of the rotating body 83 against the urging force of the first tension spring S1 and the urging force of the second tension spring S2. Thus, the second stopper 84SB positions the released rotating body 83 at the second position shown in FIG.

  When the urging force of the first tension spring S1 and the urging force of the second tension spring S2 are both in the first position shown in FIG. 2 than in the second position of the rotating body 83 shown in FIG. 5B. Is bigger. Accordingly, in the second position, the pressing force of the pressing unit 81 in the fixing nip region NP and the pressing force of the heating unit 82 in the contact heating region HR are sufficiently smaller than the pressing force in the first position, respectively. The pressing force of the unit 81 and the heating unit 82 is released.

  When returning from the released state shown in FIG. 5 (b) to the pressed state shown in FIG. 2, the rotator 83 is driven by the driving force input from the gear 83C (see FIG. 4) and the urging force of the tension spring S1. The actuator block 83B is rotated counterclockwise against the urging force of the tension spring S2 to bring the operating block 83B into contact with the first stopper 84SA. Note that a clutch is provided between the gear 83C and a drive source (such as a motor), and the clutch is disengaged after the return operation to the pressed state.

  As described above, according to the present embodiment, the following effects can be obtained in addition to the above-described effects.

  Since the urging force of the first tension spring S1 and the urging force of the second tension spring S2 are changed by the rotation of the rotating body 83, a pressure such as a cam is applied to each of the pressure unit 81 and the heating unit 82. It is not necessary to provide a part for release, and the number of parts can be reduced by simplifying the mechanism, the manufacturing cost can be reduced, and the fixing device 8 can be compactly designed.

  The first distance D1 from the rotation axis 83A of the rotating body 83 to the portion (first connecting portion) to which the first tension spring S1 of the first crank pin P1 is connected is the second tension spring S2 of the second crank pin P2. (D1> D2), which is shorter than the second distance D2 to the portion (second connecting portion) to which the is connected, the width of the change in the first tension spring S1 with the rotation of the rotating body 83 is set to the second tension spring. It can be made larger than the width of change of S2.

  Therefore, for example, during the fixing operation, the pressing force in the fixing nip region NP of the pressure unit 81 against the fixing roller 80 can be made stronger than the pressing force in the contact heating region HR of the heating unit 82 against the fixing roller 80. Appropriate nip pressure can be applied. Further, when the fixing nip is released, the pressing force in the fixing nip region NP of the pressure unit 81 against the fixing roller 80 can be made weaker than the pressing force in the contact heating region HR of the heating unit 82 against the fixing roller 80. The workability at the time of releasing the pressure for the paper jam processing can be improved.

  By adopting the crankshaft 83S, it is possible to switch between applying and releasing the fixing nip pressure with a very simple configuration. Even if the crankshaft 83S is rotated by 180 ° or more, the shaft portion located at the center of rotation does not interfere with the first tension spring S1 or the second tension spring S2. Accordingly, the urging force of the first tension spring S1 and the second tension spring S2 is used to enable the first stopper 84SA and the second stopper 84SB to position the rotating body 83 at the first position and the second position. A separate member for locking the rotating body 83 at the first position or the second position is unnecessary, and stable positioning can be realized with a simple configuration.

  In the above-described embodiment, the first stopper 84SA and the second stopper 84SB prevent the rotation of the rotating body 83 against the urging force of the first tension spring S1 and the urging force of the second tension spring S2, respectively. Although configured, the urging forces of both of the two tension springs S1 and S2 do not have to act at the first position and the second position. That is, the first stopper 84SA and the second stopper 84SB each prevent rotation of the rotating body 83 against at least one of the urging force of the first tension spring S1 and the urging force of the second tension spring S2. That's fine.

  Since the solenoid 86 is used to rotationally displace the rotating body 83 from the first position to the second position, the operation is simpler than the configuration in which a lever or the like arranged in the housing of the apparatus is manually operated, Since there is no need to secure an operating lever or a space for access in the housing of the apparatus, the apparatus can be made compact.

  Since the heating unit 82 is disposed at a position shifted from the position opposite to the pressure unit 81 with the fixing roller 80 interposed therebetween, the heating unit 82 is disposed at a position opposite to the pressure unit 81 with the fixing roller 80 interposed therebetween. In this case, the space occupied by the heating unit 82 on the opposite side of the pressure unit 81 from the fixing roller 80 can be opened. Therefore, other parts such as the temperature sensor 87 can be arranged in the vacant space, and the apparatus can be made thinner accordingly, and the degree of freedom in design is improved.

  Since the first arm A1 and the second arm A2 are configured to be swingable by arranging and connecting one pin AC at a common swing center, the functions of applying and releasing the pressing force are compact. Is feasible. In addition, compared with the case where the position of the swing center is different, the two arms can be supported so as to be swingable with one pin, which contributes to a reduction in the number of parts.

  In addition, this invention is not limited to the said embodiment, It can utilize with various forms so that it may illustrate below. In the following description, the same reference numerals are given to substantially the same structures as those of the above embodiment, and the description thereof is omitted.

  In the embodiment, the configuration including the crankshaft 83S is illustrated as the rotating body 83. However, the rotating body 83 may be configured not to include the crankshaft as in the first modification shown in FIG. Here, the rotator 83 includes a worm wheel 83W and a spring connecting member 83V. The spring connecting member 83V is provided on the worm wheel 83W so as to be rotatable integrally with the worm wheel 83W. In the first modified example, unlike the above embodiment, the rotating body 83 rotates counterclockwise in the process of transition from the pressed state shown in FIG. 6A to the released state shown in FIG. 6B.

  According to the first modification, the rotating body 83 does not use the two crankpins of the crankshaft as the first connection portion and the second connection portion, but rotates in the clockwise direction as shown in the embodiment. Therefore, the first tension spring S1 and the second tension spring S2 can be implemented without interfering with the rotation axis of the rotating body 83.

  In the first modification, instead of positioning the rotating body at the first position and the second position by the first stopper 84SA and the second stopper 84SB provided on the frame 84 as in the above embodiment, the worm wheel 83W is used. By rotating the worm 88 meshing with the forward and reverse directions by the stepping motor M, the rotational displacement between the first position and the second position and the positioning at these positions are realized. Therefore, it is not necessary to provide the first stopper and the second stopper.

  In the first modified example, the drive mechanism by the stepping motor M is adopted, so that the solenoid 86 that realizes the rotational displacement of the rotating body 83 from the first position to the second position in the embodiment is unnecessary. . Furthermore, the rotational displacement of the rotating body 83 from the second position to the first position by the input of the driving force from the gear 83C is also realized using the stepping motor M.

  As described above, by adopting the worm gear device including the worm wheel 83W and the worm 88, the rotating body 83 can be moved to an arbitrary position (for example, the third position, the fourth position) other than the first position and the second position. Etc.).

  In the first modification, the spring connection member 83V is exemplified as a V-shaped form in a side view. However, as long as the rotation shaft, the first connection portion, and the second connection portion can be appropriately arranged, any spring connection member 83V can be used. It can be a shape.

  In the above-described embodiment and the first modification, an example in which the solenoid 86 and the worm gear device (worm wheel 83W and worm 88) are employed as the actuator is shown, but another known drive mechanism is selected as the actuator. Is possible. Alternatively, the rotating body 83 may be provided with a lever or the like and manually rotated and displaced.

  In the above embodiment, the rotating body 83 has exemplified the form in which the first tension spring S1 and the second tension spring S2 are connected to the first crankpin P1 and the second crankpin P2 of the crankshaft 83S, respectively. As shown, the crankshaft 83Y may include only one crankpin P. In the second modification shown in FIG. 7, the first tension spring S1 and the second tension spring S2 are connected to one crank pin P of the crankshaft 83Y. Further, in the process of transition from the pressed state shown in FIG. 7A to the released state shown in FIG. 7B, the rotating body 83 rotates counterclockwise in the drawing. In this second modified example, a solenoid or the like as an actuator is not provided, and, for example, a lever (not shown) that rotates the crankshaft 83Y is provided to move the crankshaft 83Y from the first position to the second position, or from the second position. The first position can be configured to be rotationally displaced about the rotation axis 83A.

  In the embodiment, the first modification, and the second modification, the position of the swing center of the first arm A1 is illustrated as being equal to the position of the swing center of the second arm A2. The position of the swing center of A1 and the position of the swing center of the second arm A2 may be different.

  In the embodiment, the first modification, and the second modification, the heating unit 82 is illustrated as being disposed at a position shifted from the position opposite to the pressure unit 81 with the fixing roller 80 interposed therebetween. The pressurizing unit 81 and the heating unit 82 may be arranged at positions opposite to each other with the fixing roller 80 interposed therebetween.

  For example, in the third modification shown in FIG. 8, the swing centers AA1 and AA2 of the first arm A1 and the second arm A2 are disposed at different positions, and the pressure unit 81 and the heating unit 82 are fixed. It is arranged at the opposite position across the roller. The pressure unit 81 and the heating unit 82 are rollers, and the pressure roller shaft 81S and the heating roller end portion 82E are rotatably supported by the first arm A1 and the second arm A2, respectively.

  The rotating body 83Z is positioned closer to the tips of the first arm A1 and the second arm A2 than the pressure roller shaft 81S and the heat roller end portion 82E of the pressure unit 81 and the heating unit 82 sandwiching the fixing roller 80. It is connected to the first arm A1 and the second arm A2 via the first tension spring S1 and the second tension spring S2. The rotating body 83Z is a Z-shaped plate-like member in a side view, and includes a first connection portion to which the first tension spring S1 is connected and a second connection portion to which the second tension spring S2 is connected. It is at a position opposite (axisymmetric) with respect to the rotation axis 83A.

  As an example, the tension spring S1 employs a spring having the same length and a large spring coefficient as the tension spring S2. Therefore, during the fixing operation of FIG. 8A, the tension spring S1 biases the pressure unit 81 via the first arm A1, and the tension spring S2 forces the heating unit 82 via the second arm A2. Greater than energizing force. In the process of transition from the pressed state shown in FIG. 8A to the released state shown in FIG. 8B, the rotating body 83Z rotates about 90 ° counterclockwise in the drawing.

  As described above, also in the third modification, the arrangement of the first connection portion and the second connection portion in the rotating body 83Z, the lengths of the first tension spring S1 and the second tension spring S2, the spring coefficient, and the like are appropriately set. Thus, the pressing force of the pressure unit 81 and the heating unit 82 can be easily adjusted.

  In FIG. 8, the rotating body 83Z is illustrated as being rotated about 90 °. However, the first position shown in FIG. 8A of the rotating body 83Z is the second position shown in FIG. 8B. Can be set to any angle up to 180 °. Further, the shape of the rotating body 83Z is not limited to the illustrated plate shape, and may be a V-shape in a side view as in the first modification shown in FIG. 6, and the embodiment shown in FIGS. Alternatively, a crankshaft such as that of the second modification shown in FIG. 7 may be employed.

  Further, the positions of the rotating body 83Z, the first tension spring S1, and the second tension spring S2 are not limited to the illustrated arrangement. The first tension spring S1 is disposed closer to the swing center AA1 of the first arm A1 than the pressure unit 81, and the pressure roller shaft 81S of the pressure unit 81 and the swing center AA1 of the first arm A1 are located. The second tension spring S2 is arranged closer to the swing center AA2 side of the second arm A2 than the heating unit 82, and the heating roller end 82E of the heating unit 82 and the second arm A2 are connected to each other. You may comprise so that it may connect between rocking | swiveling center AA2.

  In the embodiment, the first modification, the second modification, and the third modification, the pressure unit 81 rotates the first shaft and the pressure roller 81R having the first shaft (pressure roller shaft 81S). Although the form which has the 1st holder 81H supported as possible was illustrated, it is not limited to this. For example, the pressure unit includes a cylindrical pressure belt, a nip forming member that is disposed inside the pressure belt, sandwiches the pressure belt between the outer peripheral surface of the fixing roller, and forms a fixing nip region; A stay that supports the nip forming member, and the first arm may be configured to engage with the stay. As the nip forming member, an elastic pad made of silicone rubber or the like, or a plate-like hard member made of metal or resin can be used. Moreover, you may have a heater (heating element) inside the pressurization unit.

  In the embodiment, the first modification, the second modification, and the third modification, the heating unit 82 includes a heating roller 82R that includes a heating element 82C and a second roller that rotatably supports the heating roller 82R. Although the form which has the holder 82H was illustrated, it is not limited to this. For example, the heating unit includes a cylindrical heating belt, a plate-shaped heating element that is disposed inside the heating belt and sandwiches the heating belt between the outer peripheral surface of the fixing roller, and a second stay that supports the heating element. And the second arm may be configured to engage with the second stay. Note that a plate-like heating element may be brought into direct contact with the outer peripheral surface of the fixing roller without using a cylindrical heating belt. That is, the heating unit may include a plate-like heating element and a second stay that supports the heating element, and the second arm may be configured to engage with the second stay.

  In the embodiment, the halogen lamp is exemplified as the heat source of the heating unit. However, the present invention is not limited to this, and the heater may be, for example, a carbon heater.

  In the above embodiment, the first tension spring and the spring having the same length as the second tension spring have the same length, but the first tension spring and the second tension spring are exemplified in the third modification. Further, they may have different spring coefficients, or may have different lengths. Further, the urging force may be adjusted by combining two or more springs as the first tension spring or the second tension spring.

  In the embodiment, the shortest distance (first distance D1) from the rotation axis 83A of the crankshaft 83S to the first crankpin P1 is the shortest distance (second second) from the rotation axis 83A of the crankshaft 83S to the second crankpin P2. Although an example in which the distance is larger than the distance D2) is illustrated, the first distance D1 and the second distance D2 may be equal, and the first distance D1 may be smaller than the second distance D2. Even in this case, the first tension spring and the second tension spring have different spring coefficients, and the connection position between the first tension spring and the first arm and the connection position between the second tension spring and the second arm are adjusted. By doing so, the pressing force in the fixing nip region and the pressing force in the contact heating region can be changed.

  In the above-described embodiment, the present invention is applied to the monochrome laser printer 1 having one process cartridge 5. However, the present invention is not limited to this, and a color printer or other image forming apparatus such as a copying machine or a multifunction machine is used. For example, the present invention may be applied.

  Moreover, you may implement combining each element demonstrated by above-described embodiment and modification arbitrarily.

8 Fixing Device 80 Fixing Roller 81 Pressing Unit 81H First Holder 81R Pressing Roller 82 Heating Unit 82H Second Holder 82R Heating Roller 83 Rotating Body 83A Rotating Axis 83B Operating Block 83S Crankshaft 84 Frame 84G Guide Slot 84SA First Stopper 84SB 2nd stopper 86 Solenoid 87 Temperature sensor A1 1st arm A2 2nd arm AC pin D1 1st distance D2 2nd distance HR Contact heating area NP Fixing nip area P1 1st crankpin P2 2nd crankpin S1 1st tension spring S2 Second tension spring

Claims (16)

A fixing roller;
A pressure unit that forms a fixing nip region with the fixing roller;
A heating unit that forms a contact heating area with the fixing roller;
A rotating body,
A frame that supports the fixing roller and the rotating body;
A first arm that is swingable with respect to the frame and capable of changing a pressing force in the fixing nip region by changing a position of the pressure unit with respect to the fixing roller;
A second arm that is swingable with respect to the frame and capable of changing a pressing force in the contact heating region by changing a position of the heating unit with respect to the fixing roller;
A first tension spring connecting the first arm and the rotating body, and urging the pressure unit toward the fixing roller via the first arm;
A second tension spring that connects the second arm and the rotating body and biases the heating unit toward the fixing roller via the second arm;
The fixing device according to claim 1, wherein the urging force of the first tension spring and the urging force of the second tension spring are changed by rotation of the rotating body. The rotating body includes a first connection portion to which the first tension spring is connected, and a second connection portion to which the second tension spring is connected,
The shortest distance from the rotating shaft of the rotating body to the first connecting portion is a first distance, and the shortest distance from the rotating shaft of the rotating body to the second connecting portion is a second distance shorter than the first distance. The fixing device according to claim 1, wherein:   The fixing device according to claim 1, wherein the rotating body includes a crankshaft, and the first tension spring and the second tension spring are connected to a crankpin of the crankshaft. . The rotating body can be rotationally displaced between a first position and a second position,
The urging force of the first tension spring and the urging force of the second tension spring are both greater when the rotating body is in the first position than when it is in the second position,
When the rotating body is in the first position, a direction in which the first tension spring pulls the first arm is parallel to a direction in which the first arm presses the pressure unit, and the second tension spring The fixing device according to claim 1, wherein a direction in which the second arm is pulled is parallel to a direction in which the second arm presses the heating unit. The frame has a first stopper;
The first stopper contacts the rotating body when the rotating body is in the first position, and resists at least one of the biasing force of the first tension spring and the biasing force of the second tension spring. The fixing device according to claim 4, wherein rotation of the rotating body is blocked.   When the rotating body is in the first position, the rotating body contacts the rotating body and rotates the rotating body against at least one of the biasing force of the first tension spring and the biasing force of the second tension spring. 6. The fixing device according to claim 4, further comprising an actuator that can be operated.   The frame has a second stopper, and the second stopper contacts the rotating body when the rotating body is in the second position, and the biasing force of the first tension spring and the second tension spring are in contact with the rotating body. The fixing device according to claim 4, wherein the rotation of the rotating body is prevented against at least one of the urging forces of the fixing device.   The fixing device according to claim 1, wherein the heating unit is disposed at a position shifted from a position opposite to the pressure unit with the fixing roller interposed therebetween. The swing center of the first arm is disposed upstream of the rotation axis of the fixing roller in the direction in which the second arm presses the heating unit.
The fixing center according to claim 8, wherein the swing center of the second arm is disposed upstream of a rotation shaft of the fixing roller in a direction in which the first arm presses the pressure unit. apparatus. A sensor for detecting a surface temperature of the fixing roller;
The fixing device according to claim 9, wherein the sensor is disposed downstream of the fixing nip region and upstream of the contact heating region in the rotation direction of the fixing roller.   The fixing device according to claim 10, wherein the sensor is arranged so as to intersect a plane formed by a rotation axis of the fixing roller and a rotation axis of the rotating body.   The fixing device according to claim 1, wherein the first tension spring and the second tension spring are springs having the same spring coefficient and the same length.   The fixing device according to claim 1, wherein a position of a swing center of the first arm is equal to a position of a swing center of the second arm. The frame includes a pin that is disposed on a swing axis that forms a swing center of the first arm and a swing center of the second arm and extends along the swing axis;
The fixing device according to claim 13, wherein the first arm and the second arm are connected to the pin. The pressure unit includes a pressure roller having a first shaft, and a first holder that rotatably supports the first shaft,
The fixing device according to claim 1, wherein the first arm is engaged with the first holder. The heating unit has a heating roller containing a heating element, and a second holder that rotatably supports the heating roller,
The fixing device according to claim 1, wherein the second arm is engaged with the second holder.

Images