JP2014085654A - Heat-fixing device, and image forming apparatus including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-fixing device capable of achieving cost reduction, space saving, reduction in variation of applied pressure due to variation of components, reduction in deviation of the applied pressure in an axial direction, and stabilization of fixability.SOLUTION: A heat-fixing device includes: a fixing member 3 that heats to fix a toner image on a recording medium, and conveys the recording medium; a pressure roller 7 that presses the fixing member 3 to form a fixing nip part; and levers 11 and cam mechanisms 12 that are arranged on both ends of the pressure roller 7 to adjust the pressure roller 7 into a pressurized or non-pressurized state. The cam mechanisms 12 are connected to a single cam shaft 13 respectively via individual torque limiters 14, and no spring is used for lifting up the levers 11. The heat-fixing device has at least one worm gear 16 as means for not transmitting a rotation force generated by a counter load from the pressure roller 7 to a pressure drive mechanism 15 that applies a driving force to the cam shaft 13.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and more particularly, to a pressurizing / depressurizing mechanism in a fixing device provided in the image forming apparatus.

  Electrophotography in which charging, writing, development, transfer, cleaning, static elimination, etc. are repeated to form toner images on the image carrier in sequence, and the toner images are sequentially transferred to record images on recording media such as sheets and OHP films. Type image forming apparatus. Some of such image forming apparatuses include a thermal fixing device that fixes a toner image on the recording medium while conveying the recording medium after image transfer between a heated fixing member and a pressure member. . Such a thermal fixing device includes a mechanism that performs a pressure and pressure release operation using a torque limiter. In recent years, there has been an increasing market demand for energy saving, high speed, and high image quality for image forming apparatuses such as copying machines. In order to achieve these required performances, it is important to improve the thermal efficiency of the thermal fixing device provided in the image forming apparatus and to finely control the various rollers.

  In this type of image forming apparatus, various image forming processes such as electrophotographic recording, electrostatic recording, and magnetic recording are used, and an unfixed toner image is transferred to a recording sheet, printing paper, photosensitive paper, electrostatic recording by an image transfer method or a direct method. It is formed on a recording material such as recording paper. As a heat fixing device for fixing an unfixed toner image, a contact heating method fixing device such as a heat roller method, a film heating method, and an electromagnetic induction heating method is widely used.

  A heat roller type fixing device has a heat source such as a halogen lamp inside, and includes a rotating roller pair of a fixing roller that is adjusted to a predetermined temperature and a pressure roller that is in pressure contact with the heat roller as a basic configuration. . A recording material is introduced into a contact portion of these rotating roller pairs, that is, a so-called fixing nip portion, and conveyed, and an unfixed toner image is melted and fixed by heat and pressure from a fixing roller and a pressure roller.

  A film heating type fixing device has been proposed in, for example, Patent Document 1 and Patent Document 2. In this type of fixing device, a recording material is brought into close contact with a heating member fixedly supported by a supporting member via a thin fixing film having heat resistance, and the fixing member is slid with respect to the heating member. Heat is supplied to the recording material through the film material. As the heating body, for example, a ceramic heater provided with a resistance layer on a ceramic substrate such as alumina or aluminum nitride having characteristics such as heat resistance, insulation, and good thermal conductivity is used. As the fixing film, a thin film having a low heat capacity can be used. Therefore, the heat transfer efficiency is higher than that of the heat roller type fixing device, the warm-up time can be shortened, and quick start and energy saving can be realized.

  As an electromagnetic induction heating type fixing device, the one disclosed in Patent Document 3 induces an eddy current in a metal layer (heat generation layer) of a fixing sleeve by magnetic flux and generates heat by its Joule heat. Has also been proposed. This apparatus can directly generate heat in the fixing film by using the generation of induced current, and achieves a more efficient fixing process than a heat roller type fixing apparatus using a halogen lamp as a heat source.

  As an electromagnetic induction heating type fixing device, a fixing sleeve having a release layer, an elastic layer, a metal layer (heat generation layer), an elastic layer contained in the fixing sleeve, and a support (core metal) is used. There is a well-known configuration in which a pressure nip is formed by mutual pressure contact between a fixing roller and a pressure roller via a fixing sleeve.

  There is also known a fixing device in which a fixing sleeve is arranged on the outer periphery of a fixing member that is fixedly supported, and the recording material is conveyed while sliding on the outer periphery of the fixing member as the pressure roller rotates. The fixing sleeve in the apparatus having this configuration is heated by induction heating or other heating method from inside or outside the fixing member. In such a configuration, the fixing member is provided with a ring having a diameter larger than that of the fixing sleeve at the end of the fixing roller, thereby preventing movement (shift) in the thrust direction.

  On the other hand, in response to the demand for higher image quality, a configuration having a pressure mechanism and a pressure release mechanism that is completely separated from the fixing member as necessary in order to finely control the temperature of the pressure roller is also known. ing. As a configuration having such a mechanism, one having a mechanism in which a pressure lever operated by a cam mechanism is mounted on a bearing of a pressure roller and the pressure roller is pushed into a fixing member is known. The lever operated by the cam mechanism is generally configured such that a load is applied by a spring with a cam follower as a fulcrum, or a separate lever that applies a load by a spring using the lever operated by the cam mechanism as a base.

  As described above, in recent image forming apparatuses, in order to achieve energy saving, high speed, and high image quality, it is indispensable to press and release the pressure roller of the heat fixing apparatus. However, the pressurizing operation may lead to a complicated structure, high cost, and high space, and in the case of a thermal fixing device that stretches a belt, the pressure deviation may cause the belt to move.

  The present invention is low in cost in view of the fact that a complicated structure, cost, and space are required for the pressurizing operation and the depressurizing operation in recent heat fixing devices, and there is also a risk of belt deviation due to pressure deviation. It is an object of the present invention to provide a thermal fixing device including a pressure / depressurization mechanism that achieves a uniform pressure distribution with a space saving and simple structure, and an image forming apparatus including the thermal fixing device.

  The thermal fixing apparatus of the present invention heats a toner image on a recording medium to fix the toner image on the recording medium and conveys the recording medium, and presses the fixing member to form a fixing nip portion. A pressure member to be formed, and a pressure lever and a cam mechanism disposed at both ends of the pressure member in order to adjust the pressure member to a pressurized / depressurized state. The cam mechanisms arranged at both ends are connected to the same camshaft through independent torque limiters.

  According to the present invention, it is possible to achieve cost reduction, space saving, reduction of pressure variation due to component variation, reduction of axial deviation of pressure force, and stabilization of fixing ability.

1 is a diagram illustrating a schematic configuration of an image forming apparatus that can be a mounting target of a fixing device according to the present invention. Sectional drawing which shows the structure used for the fixing device as shown in FIG. 1 as a typical example of the pressurizing / depressurizing mechanism using the cam mechanism as a comparative example FIG. 2 is a cross-sectional view corresponding to FIG. 2 showing Embodiment 1 according to the present invention in which a pressurizing / depressurizing mechanism using a cam mechanism is used in a fixing device as shown in FIG. The top view which looked at the structure of FIG. 3 from the upper direction of FIG. FIG. 4 is a plan view corresponding to FIG. 4 showing Embodiment 2 of the present invention. FIG. 4 is a plan view corresponding to FIG. 4 showing Embodiment 3 of the present invention. Sectional view (A) viewed from the same direction in FIG. 3 showing the fourth embodiment of the present invention, and a side view (B) viewed from the right direction of (A)

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus that can be equipped with a thermal fixing apparatus according to the present invention. This apparatus is merely an example, but the basic specification for image formation is a so-called digital color multifunction peripheral.

  The illustrated image forming apparatus includes an intermediate transfer belt 56 at substantially the center of the inside thereof. The intermediate transfer belt 56 is an endless belt and is supported by being wound around four rollers 52, 53, 54 and 55, and is driven to rotate in the direction of arrow A in the figure. Below the intermediate transfer belt 56, four image forming units corresponding to yellow (Y), magenta (M), cyan (C), and black (K) toners are arranged along the belt surface of the intermediate transfer belt 56. It is set up.

  Below the four image forming units, an exposure device 60 that exposes the surface of each charged photoconductor 50 (50Y, 50M, 50C, 50K) based on the image data of each color to form a latent image is provided. . A primary transfer roller 51 that primarily transfers a toner image formed on the photoconductor 50 onto the intermediate transfer belt 56 is disposed at a position facing each photoconductor 50 with the intermediate transfer belt 56 interposed therebetween. The primary transfer roller 51 is connected to a power source (not shown) to apply a predetermined voltage.

  A secondary transfer roller 61 is pressed against the outside of the portion of the intermediate transfer belt 56 supported by the roller 52. The secondary transfer roller 61 is connected to a power source (not shown) and applies a predetermined voltage. A contact portion between the secondary transfer roller 61 and the intermediate transfer belt 56 is a secondary transfer portion, and the toner image on the intermediate transfer belt 56 is transferred to transfer paper. An intermediate transfer belt cleaning device 57 for cleaning the surface of the intermediate transfer belt 56 after the secondary transfer is provided outside the portion of the intermediate transfer belt 56 supported by the roller 55.

  Above the secondary transfer portion, a fixing device 70 is provided for fixing the toner image on the transfer paper to the transfer paper semi-permanently. The fixing device 70 includes a heating roller 72 having a halogen heater therein and an endless fixing belt 71 wound around the fixing roller 73, and a pressure roller 74 disposed so as to face and press the fixing roller 73 via the fixing belt 71. It is composed of. Under the image forming apparatus, there is provided a paper feeding device 80 for placing the transfer paper and feeding the transfer paper toward the secondary transfer unit.

<Comparative example>
FIG. 2 is a cross-sectional view showing, as a comparative example, a configuration used in a fixing device as shown in FIG. 1 as a representative example of a pressurizing / depressurizing mechanism using a cam mechanism. The cam 12 rotates by the rotational force applied to the camshaft 13 and pushes up the pressure lever 11. By rotating the cam 12 by a predetermined angle, the pressure lever 11 stops at the target position. The pressure lever 8 is pushed up by the pressure spring 9 with the pressure lever 11 as a base. This pushing force pushes up both ends of the pressure roller 7, thereby forming a nip with the fixing roller 3. The depressurization operation is the reverse of the above.

<Embodiment 1>
FIG. 3 is a cross-sectional view corresponding to FIG. 2 showing Embodiment 1 according to the present invention in which a pressurizing / depressurizing mechanism using a cam mechanism is used in the fixing device as shown in FIG.
The fixing device heats the toner image 4 on the recording medium 5 to fix the toner image 4 to the recording medium 5, and presses the fixing roller 3 and the fixing roller 3 that are fixing members for conveying the recording medium 5 to fix them. A pressure roller 7 is provided as a pressure member for forming the nip portion. In order to adjust the pressure roller 7 to a pressure / decompression state, the pressure roller 11 includes pressure levers 11 disposed at both ends of the pressure roller 7 and cams 12 constituting a cam mechanism. Cams 12 arranged at both ends of the pressure roller 7 are connected to the same camshaft 13 via independent torque limiters 14, and no spring is used to lift up the pressure lever 11.

  The operation of the apparatus of this embodiment is almost the same as that of the comparative example shown in FIG. 2, but the rotational force of the camshaft 13 is transmitted to the cam 12 via the torque limiter 14. During the pressure operation, the pressure lever 11 receives a downward force in the figure due to the repulsive force that the fixing roller 3 exerts on the pressure roller 7. Therefore, load torque is generated in the camshaft 13 in the direction opposite to the driving direction. As the nip width increases, the torque increases and eventually exceeds the set value of the torque limiter, and the rotation operation of the camshaft 13 is not transmitted to the cam 12.

  That is, in the embodiment shown in FIG. 3, the pressure / decompression system is a mechanism that pushes the pressure lever 11 toward the fixing roller 3 by a cam mechanism as in the prior art. The final load by the spring 9 is not performed. The pressure lever 11 that receives the operation from the cam 12 is a mechanism for directly pushing the pressure roller 7. The torque limiter 14 disposed between the camshaft 13 and the cam 12 causes the cam 12 to stop rotating when the repulsive load from the pressure roller 7 is set. The torque limiter 14 is disposed independently of the cams 12 disposed at both ends of the pressure roller 7, respectively.

  4 is a plan view of the configuration of FIG. 3 viewed from above in FIG. In the figure, reference numeral 15 denotes a pressurizing drive mechanism that applies a driving force to the camshaft 13. The pressure driving mechanism 15 has a mechanism that does not transmit a rotational force due to a counter load from the pressure roller 7.

  As described above, the pressure lever 11 and the cam 12 are disposed at both ends of the pressure roller 7, and the torque limiter 14 is also disposed at each of the cams 12 at both ends. Therefore, the rotation stop position of the cam 12 becomes an independent stop position by the torque set in the torque limiter 14. The drive system provided in the pressure drive mechanism 15 includes at least one worm gear 16. Therefore, even if the camshaft 13 receives a rotational force in the pressure-removing direction due to the load torque received from the pressure lever 11, the rotational force is more on the input side of the driving force than the worm gear 16 (upstream side in terms of the input direction of the driving force). ), For example, is not transmitted to the actuator 17. For this reason, even if the rotational force is not applied to the pressure drive mechanism 15 in the pressurized state, the pressure is not unintentionally released due to the load torque.

  In this embodiment, compared with the conventional pressurizing / depressurizing mechanism as shown in FIG. 1, the cost can be reduced and the space can be saved by reducing the number of parts. In addition, since the independent torque limiters 14 are arranged at both ends of the pressure roller 7, the axial pressure applied due to variations in parts such as spring force, fixing roller 3, axial hardness deviation of the pressure roller 7, and the like. Variations can also be reduced. The reduction in the axial deviation of the pressing force can stabilize the fixing property and also ensure high robustness against the belt in a thermal fixing device of a type in which the belt is stretched. Moreover, in order to stop in the pressurization state at the time of pressurization, it is usually necessary to continue to add torque to the pressurization drive mechanism. However, by providing a mechanism that does not transmit the torque from the output side to the input side, it is possible to suppress the power consumption required to maintain the pressurized state, and at the same time, it is possible to extend the life of the drive mechanism. Further, by using the worm gear 16, the function of the mechanism that does not transmit the torque from the output side to the input side can be easily achieved, and the cost can be further reduced. Further, since the worm gear 16 can have a high reduction ratio, it is possible to save the space of the pressure drive mechanism.

<Embodiment 2>
FIG. 5 is a plan view corresponding to FIG. 4 showing Embodiment 2 of the present invention.
In the second embodiment, the camshaft 13 transmits only the force from the pressure drive mechanism 15 (input side), and prevents the rotational force from the output side generated by the counter load of the pressure roller 7 from being transmitted. And a lock-type torque diode 18. The torque diode (registered trademark) is a unit having a reverse input preventing function in which the rotation from the input side can be transmitted to the output side, but the rotation from the output side is locked without being transmitted to the input side.

  The torque diode (registered trademark) 18 is of a lock type and is a mechanism that transmits torque from the input side to the output side but locks torque from the output side and does not transmit it to the input side. The torque diode (registered trademark) 18 is disposed in the pressure drive mechanism 15 or on the camshaft 13. That is, in this embodiment, instead of the worm gear 16 in the previous embodiment, the rotational force of the pressure drive mechanism 15 is transmitted to the camshaft 13 via a lock type torque diode (registered trademark) 18. As a result, the rotational force is not transmitted to the pressurizing drive mechanism 15 even if a rotational force is received in the pressure-removing direction by the load torque received from the pressure lever 11 as in the previous embodiment. By using the lock type torque diode (registered trademark) 18, the function of not transmitting the torque from the output side to the input side can be easily achieved, and the space can be saved. Further, since the torque transmission loss is lower than that of the worm gear, further energy saving can be achieved.

<Embodiment 3>
FIG. 6 is a plan view corresponding to FIG. 4 showing Embodiment 3 of the present invention. However, the heating roller 1 and the fixing belt 2 are not shown. In the present embodiment, a photosensor 19 that is a detection mechanism for detecting the rotation angle of the camshaft 13 is provided in the vicinity of the camshaft 13. A pattern mark 20 with a constant interval is provided on a part of the camshaft 13, and a photosensor 19 is disposed at a position facing the pattern mark 20. Then, by reading the pattern mark 20 with the photo sensor 19, it is possible to detect how much the camshaft 13 has been rotated, and thereby to control the rotation angle of the camshaft 13. That is, by detecting the rotation angle of the camshaft 13, the camshaft 13 is not rotated more than necessary.

<Embodiment 4>
7 is a cross-sectional view (A) of the fourth embodiment of the present invention as viewed from the same direction in FIG. 3, and a side view (B) as viewed from the right direction of FIG. However, the heating roller 1 and the fixing belt 2 are not shown in the same manner as in FIG.

  In the fourth embodiment, the absolute position detection filler 21 disposed on the cam 12 is read by the photo sensor 22 so that the absolute angle of the cam 12 with respect to the heat fixing device casing can be detected regardless of the rotation angle of the cam shaft 13. Yes. That is, since the absolute angle with respect to the housing of the heat fixing device can be detected, multi-stage pressurization control can be performed as long as the pressure is within a range of weaker pressure than the maximum pressurization regulated by the torque limiter 14. Become.

  The present invention is not limited to the embodiments described above, and many variations are possible by those having ordinary knowledge in the art within the technical idea of the present invention.

1: Heating roller 2: Fixing belt 3: Fixing roller 4: Toner image 5: Recording medium 7: Pressure roller 8: Pressure lever 9: Pressure spring 11: Pressure lever 12: Cam 13: Camshaft 14: Torque Limiter 15: Pressure drive mechanism 16: Worm gear 17: Actuator 18: Torque diode 19: Photo sensor 20: Pattern mark 21: Absolute position detection filler 22: Photo sensor 50: Photoreceptor 51: Primary transfer roller 52: Roller 55: Roller 56: Intermediate transfer belt 57: Intermediate transfer belt cleaning device 60: Exposure device 61: Secondary transfer roller 70: Fixing device 71: Fixing belt 72: Heating roller 73: Fixing roller 74: Pressure roller 80: Paper feeding device A: Arrow

JP-A-63-313182 Japanese Patent Laid-Open No. 1-263679 Japanese Utility Model Publication No. 51-109739 Japanese Patent Publication No. 01-000701 JP 2009-258434 A

Claims (6)

Heating a toner image on a recording medium to fix the toner image on the recording medium and conveying the recording medium; a pressure member pressing the fixing member to form a fixing nip; and A pressure lever and a cam mechanism disposed at both ends of the pressure member in order to adjust the pressure member to a pressurized / depressurized state,
The heat fixing device, wherein the cam mechanisms arranged at both ends of the pressure member are connected to the same camshaft via independent torque limiters.   2. The heat according to claim 1, further comprising a mechanism that does not transmit a rotational force due to an anti-load from the pressure member to the pressure drive for a pressure drive mechanism that applies a drive force to the camshaft. Fixing device.   The thermal fixing apparatus according to claim 1, wherein the pressure driving mechanism includes at least one worm gear.   The camshaft includes means having a reverse input preventing function for transmitting a force from the input side of the pressurizing drive mechanism and not transmitting a force from the output side generated by a counterload of the pressurizing member. The thermal fixing device according to claim 1, wherein the thermal fixing device is a thermal fixing device.   The thermal fixing apparatus according to claim 1, further comprising a detection unit configured to detect a rotation angle of the camshaft. An image forming apparatus comprising the thermal fixing device according to claim 1.