JP3494420B2 - Thermal fixing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a printer or a facsimile which heats unfixed toner transferred onto recording paper. The present invention relates to a heat fixing device for fixing by pressing while applying heat. 2. Description of the Related Art In an electrophotographic image forming apparatus as described above, a toner image formed on an image carrier is transferred onto recording paper, and then a pair of heat rollers (a heating roller and a pressure roller) are formed. Then, a step of performing heat fixing by a heat fixing device is performed. Further, this heat fixing device is provided with a cleaner means for cleaning and removing the developer adhered to the surface of the heat fixing roller which comes into contact with the toner image on the recording paper after fixing. As such a cleaner means, for example, as described in JP-A-50-57237,
There is disclosed a technique in which a movable web cloth is brought into pressure contact with a heat fixing roller. The web cloth is used not only for removing the developer as described above, but also for applying a small amount of a release agent such as silicone oil to the surface of the heat fixing roller. Further, it is sometimes used for applying an anti-offset liquid in order to prevent toner residue from adhering to the heat fixing roller at the time of fixing. [0003] In this type of heat fixing device, temperature control for controlling heating of the heat fixing roller is required, and therefore, a temperature detecting member as temperature detecting means is provided. Is required. However, in this case, there has been a problem that the developer from which the web cloth as the cleaning means has been removed is attached to the temperature detecting member, and this causes a temperature detection failure and a flaw of the heat fixing roller. Accordingly, for example, a structure is provided in which a temperature detecting means is provided inside a pressure contact member which presses the web to the heat fixing roller so that the temperature detecting member contacts the heat fixing roller via the web cloth. It is conceivable that In this case, as shown in FIG. 5, a structure using a pressure roller 6 as the pressure contact member is also conceivable. further,
An auxiliary roller is provided in addition to the pressure roller, and a pair of these rollers is arranged on both sides of the heat fixing roller, and the web cloth is pressed against the heat fixing roller between these rollers, thereby making contact between the web cloth and the heat fixing roller. A structure that increases the area is also conceivable. However, the structure in which the temperature detecting means is provided inside the pressure contact member as described above has a problem that the structure is complicated. Further, when a pressure roller is used as the pressure contact member as shown in FIG. 5, the contact area between the web cloth 2 and the heat fixing roller 1a is reduced as shown in FIG. Cannot be transformed. Further, in the structure using the auxiliary roller as described above, a pressing means for the auxiliary roller is required, and the configuration becomes more complicated. For this reason, a configuration in which the web cloth is brought into pressure contact with the heat fixing roller without using a pressure contact member is also conceivable. This example is shown in FIG. Here, FIG.
6 shows the initial state, and FIG. 6B shows the aging state. In FIG. 6A, the web cloth 2 is in contact with the heat fixing roller 1a, and after the recording paper conveyed from the image forming unit (not shown) is fixed, the web cloth 2 is attached to the heat fixing roller 1a. It moves while being taken up by the web roller 4b from the web roller 4a while cleaning the agent. Further, the temperature detecting member 3 is in contact with the heat fixing roller 1a via the web cloth 2. However, in the case of this configuration, the temperature detecting member 3 rises with the progress of the winding. In the state shown in FIG. 6B after the completion of the winding, the temperature detecting member 3 floats up from the heat fixing roller 1a, so that there is an inconvenience that a temperature detection failure occurs. In addition, as the winding position progresses, the contact position between the heat fixing roller 1a and the web cloth 2 fluctuates. As a result, it becomes difficult to appropriately determine the position of the temperature detecting member 3. An object of the present invention is to prevent the heat roller from being stained by the temperature detecting member, to have a simple structure, and to perform stable temperature detection by the temperature detecting member.
An object of the present invention is to provide a heat fixing device. According to another aspect of the present invention, there is provided a heat fixing device, comprising: a heat fixing roller for thermally fixing an unfixed toner image on a recording sheet ; A pressure roller for nipping the recording paper therebetween, a web cloth for pressing and contacting the heat fixing roller, and a web roller pair for sending the web cloth to the heat fixing roller side and winding the web cloth from the heat fixing roller side And a temperature detecting unit which is in pressure contact with the heat fixing roller via the web cloth, wherein a straight line connecting the roller centers of the web roller pair is thermally fixed more than a tangent line of the heat fixing roller. Placed at the center of the roller and the web cloth
At the start of winding, of the web roller pair,
On the side of the web roller where the web cloth is wound up,
The point at which the web cloth separates from the heat fixing roller;
At the end of the winding of the web cloth, the web roller pair
In the web roller side of sending out the web cloth,
Between the point where the web cloth separates from the heat fixing roller.
The temperature detection in the constant contact area, which is the web cloth area of
Characterized in that the members are arranged in contact with each other.
You . An embodiment of the present invention will be described below. FIG. 1 shows a heat fixing device according to the present embodiment. This heat fixing device includes a heat roller pair composed of a heat fixing roller 1a and a pressure roller 1b, and a web roller 4 disposed on both sides of the heat fixing roller 1a.
a, 4b, a web cloth 2 provided between the web rollers 4a, 4b, and a temperature detecting member 3 which is in pressure contact with the heat fixing roller 1a via the web cloth 2. A heater 5 for heating the heat fixing roller 1a is provided inside the heat fixing roller 1a. And, for example,
The temperature of the heat fixing roller 1a is detected by the temperature detecting member 3, and the detected temperature signal is input to a control device (not shown) to control the temperature of the heat fixing roller 1a to be constant. Here, the web rollers 4a and 4b are driven by a drive unit (not shown) in a direction (direction indicated by an arrow) that rotates together with the heat fixing roller 1a. Thus, the web cloth 2 is wound from the web roller 4a to the web roller 4b. In addition, web roller 4
A straight line I connecting the center of the rollers a and b is located closer to the center of the heat fixing roller 1a than a tangent line II of the heat fixing roller 1a. As a result, the web cloth 2 comes into contact with the heat fixing roller 1a in a pressurized state. In the embodiment shown in FIG. 1, a toner image (toner visible image) is formed by an image carrier (photosensitive drum) not shown.
Is transferred from the heat fixing roll 1a and the pressure roller 1b, which are rotated in contact with each other, in the direction of arrow III and pass therethrough. At this time, the toner image on the recording paper P is melted and fixed on the recording paper P by the heat from the heat fixing roller 1a. Further, even if the developer adhered after the fixing process remains on the surface of the heat fixing roller 1a on the side in contact with the toner image on the recording paper P, the remaining developer contacts the heat fixing roller 1a. Is removed by the web cloth 2. This developer is contained in the toner image. FIG. 2A shows a state in which the web cloth 4 is started to be wound from the side of the fixing roller 1b by the web roller 4b (that is, the fixing roller 1b by the web roller 4a).
(A state in which delivery to the side is started). In this state, on the web roller 4b side, the web cloth 2 is separated from the surface of the heat fixing roller 1a at a point A. FIG. 2B shows a state in which the web roller 4 b finishes winding (the web roller 4 b).
is a diagram showing a completion state) delivery according to a. In this state, on the side of the web roller 4a, the web cloth 2 is separated from the surface of the heat fixing roller 1a at a point B. And the range from these points A to B is
Fixing roller 1 by web roller 4b of web cloth 2
This is the range of constant contact between the heat fixing roller 1a and the web cloth 2 from the start to the end of the winding from the b side (from the start to the end of the feeding to the fixing roller 1b by the web roller 4a). For this reason, by arranging the temperature detecting member 3 in a constant contact area between the heat fixing roller 1a and the web cloth 2, the temperature detecting member 3 floats up from the heat fixing roller 1a, and the temperature detecting member 3 has a temperature detection defect. Does not occur. In addition, in the present embodiment, the temperature detecting member 3
Is pressed into contact with the heat fixing roller 1a via the web cloth 2, so that the temperature detecting member 3 is not stained on the heat fixing roller 1a. Therefore, stable temperature detection by the temperature detecting member 3 can be performed. Further, since a pressure contact member unlike the conventional configuration is not used, the configuration can be simplified. FIG. 3 shows a heat fixing device according to another embodiment of the present invention. The heat fixing device of FIG. 3 has the same configuration as the embodiment of FIG. 1 except that auxiliary rollers (auxiliary roller pairs) 6a and 6b are provided. Therefore, the same components as those in the embodiment of FIG. 1 are denoted by the same reference numerals, and the description of the same components will be omitted. That is, in the present embodiment, the web cloth 2 comes in contact with the heat fixing roller 1a from the web roller 4a through the auxiliary roller 6a, and is wound on the web roller 4b through the auxiliary roller 6b. These auxiliary rollers 6a and 6b are arranged in non-contact on both sides of the heat fixing roller 1a. Here, the straight line I connecting the center of the pair of auxiliary rollers 6a and 6b is located closer to the center of the heat fixing roller than the tangent line II of the heat fixing roller 1a. This allows
The web cloth 2 is pressed against the heat fixing roller 1a. For this reason, the conventional auxiliary roller 6
The pressurizing means a and 6b become unnecessary. The auxiliary roller 6a is rotatably held between the bearings 7a and 7b as illustrated in FIG.
The auxiliary roller 6b has the same configuration. As a result, the auxiliary rollers 6a and 6b have a rotatable structure, and rotate with the web cloth 2 during operation of the heat fixing device. For this reason, the friction between the auxiliary rollers 6a and 6b and the web cloth 2 is reduced, so that the driving torque is increased and the web cloth 2 due to the friction is increased.
Can be prevented from being scattered. The web cloth 2 includes auxiliary rollers 6a,
6b, the contact area does not change because it is in contact with the heat fixing roller 1a. Therefore, the installation range of the position of the temperature detecting member 3 can be increased. In addition, since the positions of the web rollers 4a and 4b can be made farther from the paper sheet position, it is possible to easily increase the winding amount of the web cloth 2. According to the first aspect of the present invention, the straight line connecting the center of the pair of web rollers is disposed closer to the center of the heat fixing roller than the tangent line of the heat fixing roller, and the temperature detecting member is provided. Is disposed in a range where the heat fixing roller and the web cloth are always in contact, so that the temperature detecting member is not stained by the heat fixing roller, and the temperature detecting member does not float from the heat fixing roller. As a result, stable temperature detection can be performed. Further, since no pressure contact member is used, the configuration can be simplified. [0025]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing a heat fixing device according to an embodiment of the present invention. FIGS. 2A and 2B are explanatory diagrams of the operation of the heat fixing device of FIG. 1; FIG. 3 is an explanatory diagram showing a heat fixing device according to another embodiment of the present invention. 4 is an exploded perspective view of an auxiliary roller used in the heat fixing device of FIG. FIG. 5 is an explanatory diagram showing an example of a conventional heat fixing device. FIGS. 6A and 6B are explanatory views showing another example of a conventional heat fixing device. [Description of Signs] 1a, 1b Heat fixing roller 2 Web cloth 3 Temperature detecting member 5 Heaters 4a, 4b Web rollers 6a, 6b Auxiliary rollers

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 13/20 G03G 15/20

Claims (1)

(57) Claims: 1. A heat fixing roller for thermally fixing an unfixed toner image on a recording sheet, a pressure roller for sandwiching the recording sheet between the heat fixing roller, and A web cloth which is in pressure contact with the heat fixing roller, a web roller pair which sends out the web cloth to the heat fixing roller side and winds up from the heat fixing roller side, and presses and contacts the heat fixing roller via the web cloth; A straight line connecting the center of the web roller pair to the center of the heat fixing roller with respect to a tangent to the heat fixing roller, and winding the web cloth. At the start
Wrapping the web cloth of the web roller pair
The web cloth is heated on the side of the web roller to be wiped.
The point away from the fixing roller and the winding of the web cloth
At the end of the web roller pair,
On the web roller side that sends out the cloth, the web cloth is
Web cloth area between the point away from the heat fixing roller
The thermal fixing device , wherein the temperature detecting member is disposed in contact with the constant contact area .