JP2009198949A - Image heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image heating device capable of achieving energy saving because it does not require large motive power to keep a cam stopping. <P>SOLUTION: The image heating device having the cam 16 displacing pressure force by a nip part (interposing part) N between a heating roller 4 and a pressure roller 12 and a driving means 20 driving and rotating the cam 16 includes a reverse input interruption clutch 21 which transmits driving force input from the driving means 20 to the cam 16 and locks reaction force from the cam 16 to interrupt transmission of the reaction force to the driving means 20. Thus, the large motive power is not required to keep the cam stopping, the energy saving is achieved and the occurrence of abnormal sound caused by less backlash of a gear train is prevented. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is used in an electrophotographic copying machine, a printer, a FAX, or a multifunction machine having a plurality of these functions, and fixes an unfixed toner image on a sheet or heats a toner image fixed on a sheet. It is related with the image heating apparatus which improves the glossiness of an image by doing.

  Conventionally, an electrophotographic image forming apparatus heats and presses a toner image formed on a sheet at a fixing nip formed between a fixing roller 100 and a pressure roller 200, as shown in FIG. An image heating device for fixing by the above is mounted.

  In the image heating apparatus having such a basic structure, the shape of the fixing nip greatly fluctuates due to the temperature rise at both longitudinal end portions of the fixing roller 100 as compared with the central portion during the continuous fixing process. It is preventing.

  As a technique for this, the pressure applied to the pressure roller 200 is reduced when the number of times of copying reaches a predetermined value during the continuous fixing process. Therefore, a mechanism for displacing the lower pressure lever 400 using the circular cam 300 is employed.

  Specifically, the cam 300 is rotated by a drive motor (not shown) and the upper pressure lever 500 is pushed up via the lower pressure lever 400 and the compression spring 600, thereby applying pressure at the fixing nip as shown in FIG. Is trying to grow.

  On the other hand, when the number of times of copying reaches a predetermined value, the circular cam 300 is rotated 180 ° by the drive motor as shown in FIG. As a result, the upper pressure lever 500 is lowered and the compression spring 600 is extended, so that the compression force is reduced and the pressure applied at the fixing nip is reduced.

JP 09-179435 A

  However, in the conventional image heating apparatus, when the circular cam 300 is at a position of 180 ° (see FIG. 6), a large reaction force by the compression spring 600 is transmitted as it is to the drive motor via the inclined surface of the circular cam 300. End up.

  Therefore, in order to keep the circular cam 300 stopped at the 180 ° position while overcoming such reaction force, means for generating a large power for that purpose, such as continuing to excite the drive motor, is required. . As a result, the power consumption increases, which hinders energy saving.

  In order to respond without providing a means for generating such large power, for example, the shape of the upper surface of the circular cam 300 in the state of FIG. It is conceivable to use a vertical plane (see FIG. 8).

  FIG. 8 is a development view of the circular cam 300. FIG. The horizontal axis represents the reference (0 °) when the circular cam 300 is in the state shown in FIG. 7, and the vertical axis represents the distance (radius) from the center of rotation of the circular cam 300 to the outer surface.

  However, when a vertical surface is formed on the circular cam 300, the angular difference between the vertical surface and the inclined surface of the circular cam 300 increases. For this reason, when the circular cam 300 rotates and the contact portion of the circular cam 300 with the lower pressure lever 400 reaches the inclined surface from the vertical surface (α ° phase), an impact is applied to the drive motor and the durability of the drive motor is reached. Deteriorates.

  Also, in the case of a configuration in which the power of the drive motor is transmitted to the circular cam 300 via the gear train, the gear cam train is applied at the moment when the contact portion of the circular cam 300 with the lower pressure lever 400 approaches the slope surface from the vertical surface. An abnormal noise occurs due to looseness. Further, an impact is applied to the gear train and the durability of the gear train is deteriorated.

  The technical problem of the present invention has been made in view of the circumstances as described above, and an object thereof is to provide an image heating apparatus that does not require a large amount of power to keep the cam stopped and can save energy. That is.

  In order to achieve the above object, a typical configuration according to the present invention includes a first image heating unit that heats a toner image on a sheet at a nip portion between the first image heating unit, and the first image heating unit. An image heating apparatus comprising: a cam that acts on and displaces the second image heating unit so as to contact and separate the second image heating unit; and a driving unit that rotationally drives the cam. In addition to transmitting the input driving force to the cam, a reverse input blocking clutch that locks the reaction force from the cam and blocks transmission to the driving means is provided.

  According to the present invention, the pressure at the nip portion is maintained without requiring a means for generating a large amount of power to keep the cam stopped, and energy saving can be achieved and the pressure at the nip portion can be changed. The generation of abnormal noise can be prevented.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 is a cross-sectional view showing a configuration of an image heating apparatus according to an embodiment of the present invention, and FIG. 2 is a perspective view of a driving unit of the image heating apparatus.

Embodiment 1

  In the image heating apparatus shown in FIG. 1, reference numeral 1 denotes an upper fixing unit. The upper fixing unit 1 is a hollow cylindrical first image heating unit supported at both ends by a bearing 3 so as to be rotationally driven. A heating roller 4 is attached.

  A heating heater 5 is provided inside the heating roller 4, and the heating heater 5 heats the heating roller 4 from the inside in order to keep the heating roller 4 at an appropriate temperature. Further, a cleaning web 6 for cleaning the outer circumferential surface is provided on the outer circumferential surface of the heating roller 4, and the web roller 7 of the cleaning web 6 presses the outer circumferential surface of the heating roller 4.

  In the figure, 8 is a cover that covers the upper fixing unit 1, and 9 is a frame of the upper fixing unit 1. Reference numeral 2 denotes a fixing lower unit. The lower fixing unit 2 includes an inlet guide 10 that guides the carry-in of the sheet, a pressure roller 12 that is a second image heating unit that is rotatably supported by bearings 11 at both ends and is in contact with and away from the heating roller 4. Is attached. Further, a pressure arm 13 for pressing the pressure roller 12 to the heating roller 4 is attached.

  One end of a pressure spring 14 is fixed to the pressure arm 13, and the pressure spring 14 is disposed in a direction substantially the same as the direction in which the pressure roller 12 is urged toward the heating roller 4. The other end of the pressure spring 14 is fixed to the pressure lever 15.

  The pressure lever 15 is rotatably attached to the lower fixing unit 2 so that the pressure spring 14 can be compressed in a direction substantially the same as the direction in which the pressure roller 12 is pressed against the heating roller 4. A cam 16 is disposed below the pressure lever 15, the cam 16 contacts the pressure lever 15, and when the cam 16 rotates, the pressure lever 15 swings around the support shaft 17, and the pressure spring 14 is compressed to generate a biasing force against the pressure arm 13. As a result, the pressure roller 12 is pressed against the heating roller 4, and the clamping roller N is formed by the pressure roller 12 and the heating roller 4.

  In FIG. 2, reference numerals 18a to 18i denote gears constituting the drive transmission means 18 for driving the cam 16. The gear 18 a is meshed with the cam shaft 19 of the cam 16, and the driving force is transmitted to the cam 16. Further, the gear 18i is engaged with a driving means 20 such as a motor, and the driving means 20 generates a driving force, whereby the cam 16 is rotated via the driving transmission means 18 and the position of the pressure lever 15 is displaced.

  A reverse input cutoff clutch 21 is provided between the gear 18c and the gear 18d of the drive transmission means 18. The reverse input cutoff clutch 21 locks the reaction force from the cam 16 so that the reaction force is not transmitted to the drive means 20, and the drive force of the drive means 20 is transmitted to rotate the cam 16.

  As a result, even when the cam 16 is stopped on the inclined surface of the cam 16 or when the cam 16 is given rotational force by other rotational biasing force, the driving force is transmitted to the driving means 20 through the drive transmitting means 18. Can be prevented and the cam phase can be maintained. Therefore, it is not necessary to supply a driving force for maintaining the cam phase, and power saving can be achieved.

  FIG. 4 shows a development view of the cam 16 shown in FIG. In FIG. 4, the cam surface of the cam 16 includes a cam gradient surface 22 at a preset phase position, a cam gradient surface 23 that is a roller pressure contact phase range excluding the cam gradient surface 22, and a cam that is a roller separation phase range. It consists of a sloped surface 24.

  The relationship between the gradient (tilt angle) θ2 of the cam gradient surface 22 and the gradient θ1 of the cam gradient surface 23 is set so that (Fsin θ2 cos θ2) / L> M and θ1> θ2. Here, F is the force in the cam center direction received from the pressurizing lever 15 on the cam surface 22, L is the distance from the cam center on the cam surface 22, and M is attached so that the camshaft 19 does not rattle the drive train 18. This is the torque required to support

  As a result, it is possible to make the fluctuation of the clamping pressure due to the slight deviation of the clamping position phase set in advance smaller than the cam gradient surface 23 that is the clamping position change phase area, and adjust it by adjusting the clamping pressure at that phase position. Improve accuracy.

  Further, within the roller pressure contact phase range with respect to the cam 16, a rotational biasing force is continuously applied by the reaction force from the cam gradient surface in the direction in which the pressure lever 15 is depressurized. In order to change the clamping pressure of the clamping portion of the cam 16 from the cam gradient surface 22, the generation of noise and impact of rattling due to sudden torque generation when the phase is changed to the cam gradient surface (clamping position change phase region) 23 Is suppressed.

  The embodiment of the present invention has been described in detail above, but the present invention is not limited to the above-described embodiment, and the scope does not depart from the spirit of the invention described in the claims of the present invention. Thus, various changes can be made.

Embodiment 2

  For example, FIG. 5 is a development view of a cam according to another embodiment. In the figure, the cam surface of the cam has a clamping position phase region 28 which is a phase corresponding to a plurality of preset clamping pressures. The relationship between θ1 and θ2 is (Fsin θ1 cos θ1) / L> M and θ2> θ1 when the gradient angle of the sandwiching position phase region 28 is θ1 and the gradient angle of the sandwiching position change phase region 29 is θ2. Is set.

  Here, F is the force in the cam center direction received from the pressure lever on the cam surface 28, L is the distance from the cam center on the cam surface 28, and M is the cam shaft 19 so that play of the drive train 18 does not occur. This is the torque required to support

  As a result, the fluctuation of the clamping pressure due to the slight deviation of the clamping position phase set in advance is made smaller than that of the clamping position change phase area 29. Further, the rotation urging force is continuously applied to the cam 16 by the reaction force from the cam gradient surface in the direction in which the pressure lever 15 is depressurized.

  This suppresses the generation of noise and shock due to sudden torque generation when the phase is changed from the clamping position phase area 28 to the clamping position change phase area 29 for changing the clamping pressure of the clamping portion of the cam 16. can do.

It is sectional drawing which shows the structure of the image heating apparatus which concerns on one embodiment of this invention. It is a perspective view of the drive means of the image heating apparatus shown in FIG. It is a schematic diagram of the cam shown in FIG. FIG. 4 is a development view of the cam shown in FIG. 3. It is an expanded view of the cam which concerns on other embodiment of this invention. It is operation | movement explanatory drawing of the conventional image heating apparatus. It is operation | movement explanatory drawing of the conventional image heating apparatus. FIG. 7 is a development view of the cam shown in FIG. 6.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper fixing unit 2 Lower fixing unit 3 Bearing 4 Heating roller 5 Heating heater 6 Cleaning web 7 Web roller 8 Cover 9 Case
10 Entrance guide
11 Bearing
12 Pressure roller
13 Pressure arm
14 Pressure spring
15 Pressure lever
16 cams
17 Spindle
18 Drive transmission means
19 Camshaft
20 Drive means
21 Reverse input cutoff clutch
22 Energizing force adjustment phase region
23 Nipping position variable phase region
24 Roller separation area
28 Nipping position phase region
29 Nipping position change phase area N Nipping part

Claims (3)

First and second image heating units that heat a toner image on a sheet at a nip portion between the second image heating unit and the second image heating unit to make contact with and away from the first image heating unit. In an image heating apparatus having a cam that acts on and displaces the heating unit, and a driving means that rotationally drives the cam.
An image heating comprising: a reverse input blocking clutch that transmits a driving force input from the driving unit to the cam and locks a reaction force from the cam to block transmission to the driving unit. apparatus. With respect to the shape in which the cam is unfolded, a cam gradient surface that separates the second image heating unit from the first image heating unit, and the second image heating unit is brought into contact with the first image heating unit. 2. The inclination angle of a cam gradient surface that causes the second image heating unit to abut on the first image heating unit with respect to an inclination angle between the cam gradient surface and the cam gradient surface is reduced. Image heating device. The image heating apparatus according to claim 1, further comprising a gear train that transmits a driving force of the driving unit to the cam.

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