JP2017009647A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a force to hold and restore a separation member to a reference position that is in contact with a heating roller without increasing a pressure of the separation member against the heating roller.SOLUTION: A first elastic member 66, when a separation member 64 is present on a side of a second direction D2 with respect to a reference position P0, adds an elastic force in a first direction D1 to the separation member 64. A second elastic member 67, when the separation member 64 is displaced in the second direction D2 from the reference position P0, adds an elastic force in the first direction D1 to the separation member 64. The first elastic member 66 is in a natural state when present at a first position P1 on the side of the first direction D1. The second elastic member 67 is in a natural state when the separation member 64 is present at the reference position P0 or at a position closer to the reference position P0 on the side in the first direction D1.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fixing device and an image forming apparatus including the same.

  In general, an electrophotographic image forming apparatus includes a fixing device. The fixing device includes a heating roller and a pressure roller. The sheet material on which an image is formed by the developer passes through the nip portion between the heating roller and the pressure rotor, and the heating roller heats the sheet material. The heating roller may be referred to as a fixing roller.

  Furthermore, it is known that the fixing device includes a separation member having a separation claw formed at the tip and a spring (see, for example, Patent Document 1). The separation member is supported so as to be displaceable in a direction toward the heating roller and in the opposite direction. The spring applies an elastic force to the separating member in a direction in which the tip end is pressed against the heating roller.

  When the sheet material adheres to the heating roller, the sheet material is peeled from the heating roller at a position where the tip of the separation member is in contact with the outer peripheral surface of the heating roller.

JP 2002-14565 A

  By the way, when the pressure which the said separation member contacts with the said heating roller is too strong, the outer peripheral surface of the said heating roller will be easy to wear. This shortens the life of the heating roller. In particular, when the outer peripheral surface of the heating roller is coated with a high-purity fluororesin, the coating is easily peeled off due to wear. A high purity fluororesin coating is excellent in peelability of the sheet material, but is often inferior in wear resistance.

  In order to suppress wear of the heating roller, it can be considered that the elastic force applied from the spring to the separating member is adjusted to be as small as possible. In this case, when the separating member receives pressure from the sheet material, the force for holding and returning the separating member to a position in contact with the heating roller becomes weak. If it does so, the said sheet | seat material will penetrate | invade between the said separating member and the said heating roller, and it is easy to clog.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device and an image forming apparatus capable of increasing the force for holding and returning the separation member to a position in contact with the heating roller without increasing the pressure with which the separation member for peeling the sheet material contacts the heating roller. It is to provide.

  A fixing device according to one aspect of the present invention includes a heating roller, a separation member, a first elastic member, and a second elastic member. The heating roller is a roller for heating an image of the developer formed on the sheet material. The separation member is supported to be displaceable in a first direction toward the heating roller and a second direction opposite thereto. The separation member peels the sheet material from the heating roller at a reference position where a tip portion is in contact with the outer peripheral surface of the heating roller. The first elastic member applies an elastic force in the first direction to the separation member when the separation member is present at the reference position and the second direction side. The second elastic member applies an elastic force in the first direction to the separation member when the separation member is displaced from the reference position in the second direction. The first elastic member is in a natural state when the separating member is present at a first position on the first direction side with respect to the reference position. The second elastic member is in a natural state when the separating member is present at the reference position or the second position. The second position is a position closer to the reference position between the reference position and the first position.

  An image forming apparatus according to another aspect of the present invention includes an image forming unit and the fixing device according to one aspect of the present invention. The image forming unit forms an image of a developer on a sheet material.

  According to the present invention, there is provided a fixing device and an image forming apparatus capable of increasing the force for holding and returning the separation member to a position in contact with the heating roller without increasing the pressure with which the separation member for peeling the sheet material comes into contact with the heating roller. It becomes possible to provide.

FIG. 1 is a configuration diagram of an image forming apparatus including a fixing device according to the first embodiment. FIG. 2 is a first configuration diagram of the fixing device according to the first embodiment. FIG. 3 is a second configuration diagram of the fixing device according to the first embodiment. FIG. 4 is a configuration diagram of the sheet separating mechanism in the first state in the fixing device according to the first embodiment. FIG. 5 is a configuration diagram of the sheet separating mechanism in the second state in the fixing device according to the first embodiment. FIG. 6 is a graph showing the relationship between the position of the separating member and the torque in the sheet separating mechanism of the fixing device according to the first embodiment. FIG. 7 is a configuration diagram of a fixing device according to the second embodiment. FIG. 8 is a graph showing the relationship between the position of the separating member and the torque in the sheet separating mechanism of the fixing device according to the third embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the following embodiment is an example which actualized this invention, Comprising: It does not have the character which limits the technical scope of this invention.

[First Embodiment]
First, the configuration of the image forming apparatus 10 including the fixing device 6 according to the first embodiment will be described with reference to FIG.

  The image forming apparatus 10 is an electrophotographic image forming apparatus. The image forming apparatus 10 shown in FIG. 1 is a printer. It is also conceivable that the image forming apparatus 10 is a copier, a facsimile machine, or a multifunction machine. The multifunction machine has both the printer function and the copier function.

  As shown in FIG. 1, the image forming apparatus 10 includes a sheet supply unit 2, a sheet conveying unit 3, an image forming unit 4, an optical scanning unit 5, and a fixing device 6 in a housing 100.

  The sheet supply unit 2 includes a sheet receiving unit 21 and a sheet sending unit 22. A plurality of sheet materials 9 are stacked and placed on the sheet receiving portion 21. The sheet material 9 is a sheet-like image forming medium such as paper, coated paper, postcard, envelope, and OHP sheet. The sheet sending unit 22 sends the sheet material 9 from the sheet receiving unit 21 toward the sheet conveyance path 30.

  The sheet conveyance unit 3 includes a registration roller 31, a conveyance roller 32, a discharge roller 33, and the like. The registration roller 31 and the conveyance roller 32 convey the sheet material 9 supplied from the sheet supply unit 2 toward the image forming unit 4. Further, the discharge roller 33 discharges the sheet material 9 after image formation from the discharge port of the sheet conveyance path 30 onto the discharge tray 101.

  The image forming unit 4 forms an image with the developer 90 on the surface of the sheet material 9 moving on the sheet conveyance path 30. The image forming unit 4 includes a drum-shaped photoreceptor 41, a charging unit 42, a developing unit 43, a transfer unit 45, a cleaning unit 47, and the like. The developer 90 is a powder. The photoconductor 41 is an example of an image carrier.

  The charging unit 42 uniformly charges the surface of the rotating photoconductor 41. Further, an electrostatic latent image is written on the surface of the photoreceptor 41 charged by the optical scanning unit 5 scanning the laser beam. The developing unit 43 supplies the developer 90 to the photoreceptor 41 to develop the electrostatic latent image.

  The transfer unit 45 transfers the image of the developer 90 formed on the surface of the photoconductor 41 to the sheet material 9 moving on the sheet conveyance path 30. The cleaning unit 47 removes the developer 90 remaining on the surface of the photoreceptor 41.

  The fixing device 6 includes a heating roller 61, a pressure roller 62, and a sheet separation mechanism 63. The heating roller 61 is a metal cylindrical rotating body that encloses a heater 610 such as a halogen heater. On the outer peripheral surface of the heating roller 61, a resin coating containing a fluororesin is formed. The heating roller 61 may be referred to as a fixing roller.

  The pressure roller 62 is a rotating body having an elastic layer formed on the outer periphery. The elastic layer is a rubber layer such as a thermosetting elastomer.

  The heating roller 61 and the pressure roller 62 sandwich the sheet material 9 on which an image is formed at the nip portion between them, and send it out to the subsequent stage. At that time, the heating roller 61 heats the sheet material 9 on which the image is formed, and fixes the image on the sheet material 9.

  The sheet material 9 fed from the heating roller 61 to the subsequent stage may adhere to the outer peripheral surface of the heating roller 61. The sheet separation mechanism 63 is a mechanism for peeling the sheet material 9 from the heating roller 61.

  The sheet separation mechanism 63 includes a separation member 64 supported so as to be displaceable. The separation member 64 has its tip portion pressed against the outer peripheral surface of the heating roller 61 by a spring. For example, it is conceivable that the separating member 64 is a synthetic resin member obtained by injection molding.

  By the way, if the pressure at which the separation member 64 is in contact with the heating roller 61 is too strong, the outer peripheral surface of the heating roller 61 is easily worn. Thereby, the lifetime of the heating roller 61 will be shortened.

  In particular, when the outer peripheral surface of the heating roller 61 is coated with a high-purity fluororesin, the coating is easily peeled off due to wear. A coating of a high-purity fluororesin is excellent in peelability of the sheet material 9, but is often inferior in wear resistance.

  Further, it is conceivable that the elastic force applied to the separating member 64 is adjusted to be as small as possible in order to suppress wear of the heating roller 61. In this case, when the separating member 64 receives pressure from the sheet material 9, the force for holding and returning the separating member 64 to a position in contact with the heating roller 61 is weakened. If it does so, the sheet | seat material 9 will penetrate | invade between the separating member 64 and the heating roller 61, and will be easy to clog.

  The sheet separation mechanism 63 in the present embodiment can increase the force for holding and returning the separation member 64 to the position in contact with the heating roller 61 without increasing the pressure at which the separation member 64 contacts the heating roller 61. The details will be described below.

[Sheet separation mechanism 63]
As shown in FIG. 2, the sheet separation mechanism 63 of the fixing device 6 includes a separation member 64, a support shaft portion 65, a first spring 66, and a second spring 67. The fixing device 6 includes a plurality of sheet separation mechanisms 63. The plurality of sheet separation mechanisms 63 are provided at intervals along the direction of the rotation axis of the heating roller 61. 2 to 5 show the separation mechanism 63 viewed from the longitudinal direction of the support shaft portion 65.

  The separation member 64 is supported so as to be displaceable in a first direction D1 toward the heating roller 61 and a second direction D2 opposite thereto. The second direction D <b> 2 is a direction in which the separation member 64 is separated from the heating roller 61. In this case, the first direction D1 is a direction in which the distal end portion 642 of the separation member 64 rotates toward the heating roller 61. In addition, the second direction D <b> 2 is a direction in which the tip end portion 642 of the separation member 64 is separated from the heating roller 61.

  In the present embodiment, the separation member 64 is rotatably supported by the support shaft portion 65. The support shaft portion 65 penetrates the supported portion 641 of the separation member 64. The separation member 64 peels the sheet material 9 from the heating roller 61 at a position where the tip end portion 642 is in contact with the outer peripheral surface of the heating roller 61.

  The leading end 642 of the separation member 64 is a claw that peels off the sheet material 9 from the heating roller 61. A resin coating containing a fluororesin is formed in a region including at least the tip 642 on the surface of the separating member 64.

  In the following description, the position of the separation member 64 when the front end 642 of the separation member 64 contacts the outer peripheral surface of the heating roller 61 is referred to as a reference position P0. FIG. 2 is a configuration diagram of the fixing device 6 when the separation member 64 exists at the reference position P0.

  For convenience, the arrow indicating the position of the separation member 64 in each figure indicates the position of the tip portion 642 of the separation member 64. 2 and 3, illustration of the heater 610 and the pressure roller 62 is omitted.

  The first spring 66 applies an elastic force in the first direction D1 to the separation member 64 when the separation member 64 exists at the reference position P0 and the second direction D2 side thereof. FIG. 3 is a configuration diagram of the fixing device 6 when the separating member 64 is present on the second direction D2 side with respect to the reference position P0. The first spring 66 is an example of a first elastic member.

  In the present embodiment, the separation member 64 is rotatably supported. Therefore, the first spring 66 applies torque in the first direction D <b> 1 to the separation member 64. The torque that the first spring 66 applies to the separating member 64 is referred to as a first torque T1.

  The first spring 66 in the present embodiment is a tension coil spring. The first end of the first spring 66 is connected to a part of the casing 68 that supports the components of the fixing device 6. The second end of the first spring 66 is connected to the first force point 643 of the separation member 64.

  In a state where the separation member 64 is present at the reference position P0, the first spring 66 is in a state of being extended more than the natural state. As a result, the first spring 66 moves relative to the separation member 64 in a state where the separation member 64 exists in the rotation range from the position on the first direction D1 side to the position on the second direction D2 side with respect to the reference position P0. Then, an elastic force in the first direction D1 is applied.

  The first spring 66 applies a larger first torque T1 in the first direction D1 to the separation member 64 as the displacement amount of the separation member 64 in the second direction D2 increases.

  The second spring 67 applies an elastic force in the first direction D1 to the separation member 64 when the separation member 64 is displaced from the reference position P0 in the second direction D2. The second spring 67 is an example of a second elastic member.

  In the present embodiment, the second spring 67 applies a torque in the first direction D1 to the separation member 64 that is displaced from the reference position P0 in the second direction D2. The torque that the second spring 67 applies to the separating member 64 is referred to as a second torque T2.

  The second spring 67 in the present embodiment is a torsion coil spring. On the side of the separation member 64, the support shaft portion 65 passes through the coil portion of the second spring 67. The first end of the second spring 67 is hooked on a part of the casing 68. The second end of the second spring 67 is hooked on the second force point portion 644 of the separation member 64.

  FIG. 4 shows the sheet separating mechanism 63 when the first spring 66 is in a natural state. FIG. 5 shows the sheet separating mechanism 63 when the second spring 67 is in a natural state. 4 and 5, the heating roller 61 is indicated by a virtual line (two-dot chain line). The natural state of the spring is a state in which no elastic force is applied from the spring to other members.

  As shown in FIG. 4, the first spring 66 is in a natural state when the separating member 64 is present at the first position P1 on the first direction D1 side with respect to the reference position P0. Moreover, as FIG. 5 shows, the 2nd spring 67 will be in a natural state, when the separation member 64 exists in the 2nd position P2. The second position P2 is a position near the reference position P0 between the reference position P0 and the first position P1.

  Here, the first torque T1 applied to the separation member 64 at the reference position P0 by the first spring 66 is N10. The second torque T2 applied to the separation member 64 at the reference position P0 by the second spring 67 is N20. In this embodiment, N10> N20.

  In other words, in the present embodiment, the second spring 67 has the second torque T2 in the first direction D1 weaker than the first torque T1 (= N10) applied from the first spring 66 to the separation member 64 at the reference position P0. (= N20) is added.

  FIG. 6 is a graph showing the relationship between the position P of the separating member 64 and the torque T applied to the separating member 64. Here, the combined torque of the first torque T1 and the second torque T2 is referred to as total torque T3. Further, the position P of the separating member 64 has the second direction D2 as the positive direction (right direction on the horizontal axis in FIG. 6). Further, the torque T has the first direction D1 as the positive direction (upward direction of the vertical axis in FIG. 6).

  In the present embodiment, when the separation member 64 is located in the range on the first direction D1 side from the second position P2, only the first torque T1 acts on the separation member 64 (T1 = T3). Further, when the separation member 64 is positioned on the second direction D2 side with respect to the second position P2, both the first torque T1 and the second torque T2 act on the separation member 64 (T1 + T2 = T3).

  Further, the difference between the reference position P0 and the second position P2 is very small. Therefore, the total torque T3 when the separation member 64 is present at the reference position P0 is substantially equal to the first torque T1 (= N10) at the reference position P0.

  For example, it is conceivable that the difference between the reference position P0 and the second position P2 of the separating member 64 is approximately the same as the maximum positioning error of the separating member 64 caused by various dimensional tolerances. In this case, the second torque T2 (= N20) applied from the second spring 67 to the separation member 64 at the reference position P0 is very small.

  When the separation member 64 at the reference position P0 receives pressure from the sheet material 9, both the first torque T1 and the second torque T2 act as forces for holding and returning the separation member 64 to the reference position P0.

  Therefore, according to the present embodiment, the force with which the separation member 64 is held and returned to the reference position P0 can be increased without increasing the pressure with which the separation member 64 contacts the heating roller 61.

  By the way, in order to increase the force for holding and returning the separating member 64 to the reference position P0, it is conceivable to employ the first spring 66 having a large spring constant without using the second spring 67. In this case, it is difficult to set the pressure at which the separation member 64 contacts the heating roller 61 within a predetermined appropriate range due to dimensional errors of the separation member 64, the first spring 66, and their peripheral members. This is because a slight dimensional error leads to a large variation in elastic force applied to the heating roller 61.

  On the other hand, in the present embodiment, the first spring 66 having a relatively small spring constant can be employed. Therefore, the variation in the contact pressure from the separating member 64 to the heating roller 61 due to the dimensional error can be reduced.

  In the example shown in FIG. 6, when the separation member 64 is displaced from the reference position P0 in the second direction D2, the increase rate of the first torque T1 in the first direction D1 is increased by the second torque T2 in the first direction D1. Is equivalent to the rate. It is also conceivable that the increase rate of the first torque T1 in the first direction D1 is larger than the increase rate of the second torque T2 in the first direction D1.

  If the relationship of the torque increase rate as described above is adopted, the ratio of the second torque T2 to the total torque T3 when the separating member 64 is displaced from the reference position P0 in the second direction D2 is increased. Thereby, the force which hold | maintains and resets the separation member 64 to the reference position P0 can be heightened, suppressing the pressure which the separation member 64 contacts the heating roller 61 lower.

[Second Embodiment]
Next, a sheet separation mechanism 63A provided in the fixing device 6A according to the third embodiment will be described with reference to FIG. In FIG. 7, the same components as those shown in FIGS. 1 to 5 are given the same reference numerals. Hereinafter, a difference in the sheet separating mechanism 63A from the sheet separating mechanism 63 will be described.

  The sheet separating mechanism 63A has a configuration in which the first spring 66 in the sheet separating mechanism 63 is replaced with the first spring 66A. Also in this embodiment, the separation member 64 is supported by the support shaft portion 65 so as to be rotatable.

  The first spring 66A in the present embodiment is a torsion coil spring. FIG. 7 shows the separation mechanism 63 </ b> A viewed from a direction orthogonal to the support shaft portion 65.

  The first spring 66 </ b> A and the second spring 67 are two torsion coil springs through which the support shaft portion 65 penetrates on both sides of the separation member 64. By adopting such a configuration, the first spring 66A and the second spring 67 can be arranged in a compact manner.

  Note that the first spring 66A and the second spring 67 of the sheet separation mechanism 63A also exert an elastic force on the separation member 64 in the same manner as the first spring 66 and the second spring 67 of the sheet separation mechanism 63.

[Third Embodiment]
Next, a sheet separation mechanism provided in the fixing device according to the third embodiment will be described with reference to FIG. In the sheet separation mechanism in the present embodiment, the position of the separation member 64 when the second spring 67 is in a natural state is different from that of the sheet separation mechanism 63 and the sheet separation mechanism 63A. Other than that, the sheet separation mechanism in the present embodiment has the same configuration as the sheet separation mechanism 63 or the sheet separation mechanism 63A.

  The graph of FIG. 8 represents the relationship between the position P of the separating member 64 and the torque T in the sheet separating mechanism in the present embodiment. The horizontal axis and vertical axis of the graph of FIG. 8 are the same as the horizontal axis and vertical axis of the graph of FIG. Hereinafter, differences of this embodiment from other embodiments will be described.

  In the present embodiment, the reference position P0 and the second position P2 match. This point is different from the other embodiments.

  Therefore, in the present embodiment, when the separation member 64 is located in the range on the first direction D1 side from the reference position P0, only the first torque T1 acts on the separation member 64 (T1 = T3). Further, when the separation member 64 is positioned on the second direction D2 side with respect to the reference position P0, both the first torque T1 and the second torque T2 act on the separation member 64 (T1 + T2 = T3).

  Further, the total torque T3 when the separation member 64 is present at the reference position P0 is equal to the first torque T1 (= N10) at the reference position P0.

  For example, when the dimensional tolerances of the separating member 64, the first springs 66 and 66A, the second spring 67, and their peripheral members are small, the configuration of the present embodiment may be employed. Also according to the present embodiment, it is possible to increase the force for holding and returning the separation member 64 to the reference position P0 without increasing the pressure with which the separation member 64 contacts the heating roller 61.

[Application example]
In the sheet separating mechanism 63 of the fixing device 6, the first spring 66 may be a torsion coil spring and the second spring 67 may be a tension coil spring. It is also conceivable that one or both of the first spring 66 and the second spring 67 is another type of elastic member such as a spring or rubber.

  In the sheet separation mechanism 63, it is also conceivable that the separation member 64 is supported by the slide mechanism so as to be displaceable in the first direction D1 and the second direction D2. In this case, it is conceivable that both the first spring 66 and the second spring 67 are tension coil springs.

  Note that the fixing device and the image forming apparatus according to the present invention can be freely combined with the above-described embodiments and application examples within the scope of the invention described in each claim, or the embodiments and application examples can be appropriately selected. It is also possible to configure by deforming or omitting a part.

2: Sheet feeding unit 3: Sheet conveying unit 4: Image forming unit 5: Optical scanning unit 6, 6A: Fixing device 9: Sheet material 10: Image forming device 21: Sheet receiving unit 22: Sheet sending unit 30: Sheet conveying path 31: Registration roller 32: Conveyance roller 33: Discharge roller 41: Photoconductor 42: Charging unit 43: Development unit 45: Transfer unit 47: Cleaning unit 61: Heating roller 62: Pressure roller 63, 63A: Sheet separation mechanism 64: Separating member 65: support shaft portions 66, 66A: first spring (first elastic member)
67: Second spring (second elastic member)
68: casing 90: developer 100: casing 101: discharge tray 610: heater 641: supported portion 642: tip 643: first force point 644: second force point D1: first direction D2: second direction P0 : Reference position P1: First position P2: Second position

Claims (5)

A heating roller for heating the sheet material on which the image is formed;
A separation member that is supported so as to be displaceable in a first direction toward the heating roller and a second direction opposite to the first direction, and that peels off the sheet material from the heating roller at a reference position where a tip portion is in contact with the outer peripheral surface of the heating roller; ,
A first elastic member that applies an elastic force in the first direction to the separation member when the separation member is present on the reference position and in the second direction side;
A second elastic member that applies an elastic force in the first direction to the separation member when the separation member is displaced from the reference position in the second direction;
The first elastic member is in a natural state when the separating member is present at a first position on the first direction side with respect to the reference position,
The second elastic member is in a natural state when the separating member is present at the reference position or the second position,
The fixing device, wherein the second position is a position closer to the reference position between the reference position and the first position.   The fixing device according to claim 1, wherein the second elastic member applies a force in the first direction that is weaker than a force applied from the first elastic member to the separation member at the reference position.   When the separation member is displaced from the reference position in the second direction, an increase rate of the force in the first direction applied from the second elastic member to the separation member is changed from the first elastic member to the separation member. The fixing device according to claim 1, wherein the fixing device is equal to or greater than an increasing rate of the applied force in the first direction. The separation member is rotatably supported by the support shaft portion,
4. The fixing device according to claim 1, wherein the first elastic member and the second elastic member are two torsion coil springs through which the support shaft portion penetrates on both sides of the separation member. 5. . An image forming unit for forming an image on a sheet material;
An image forming apparatus comprising: the fixing device according to claim 1.

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