JP2023007113A - Fixing device and image forming apparatus - Google Patents

Abstract

To provide a fixing device that can make heat uniform for various paper widths.SOLUTION: A fixing device comprises a rotatable fixing member, and a rotatable pressure member that is arranged opposite to the fixing member, and has heat sources 43A, 43B that heat the fixing member, a nip forming member that forms a fixing nip between the pressure member and the nip forming member with the fixing member therebetween, and a support member that supports the nip forming member. The nip forming member has a contact part 46 where the nip forming member and support member are in thermal contact with each other in an area other than an area for forming a nip and can change the contact position.SELECTED DRAWING: Figure 4

Description

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

Conventionally, a rotatable fixing member and a rotatable pressure member arranged opposite to the fixing member are provided, and a fixing nip is formed between a heat source for heating the fixing member and the pressure member via the fixing member. A fixing device is known that has a nip forming member and a support member that supports the nip forming member.
For example, in the fixing device disclosed in Patent Document 1, the temperature of the fixing member heated by the heat transfer assisting member as the nip forming member, the end heating member that heats the end region in the longitudinal direction, and the temperature of the fixing member heated by the end heating member and an edge temperature sensing member that senses the In this fixing device, the heat capacity in the longitudinal direction of the heat transfer assisting member is the second region in which the first region including the longitudinal position detected by the end temperature detecting member is closer to the longitudinal end than the first region. large compared to the area of . As a result, the heat generated by the heat source is dissipated to the longitudinal ends of the heat transfer assisting member, and the end temperature of the fixing belt that contacts and transfers heat to the heat transfer assisting member also decreases, thereby improving the fixability of the end of the recording medium. It is said that it is possible to avoid deterioration of

However, there is a demand for an improvement in dealing with the fact that the locations in the width direction where the edge temperature drops or rises differ depending on the width of the paper to be passed.

In order to solve the above-described problems, the present invention includes a rotatable fixing member, a rotatable pressure member arranged opposite to the fixing member, a heat source for heating the fixing member, and the fixing member. In a fixing device having a nip forming member that forms a fixing nip between itself and the pressing member via a fixing nip, and a supporting member that supports the nip forming member, the nip forming member has a region other than the nip, It is characterized in that the nip forming member and the support member can be thermally contacted and the contact position can be changed.

According to the present invention, uniform heat can be achieved for various sheet widths.

1 is a schematic configuration diagram of an image forming apparatus according to the present embodiment; FIG. FIG. 2 is an explanatory diagram of a fixing device according to the embodiment; FIG. 2 is a block diagram showing a control system that controls the fixing device of the embodiment; FIG. 4 is an explanatory diagram of movement control of a heat transfer member by a controller;

An embodiment in which the present invention is applied to a laser printer (hereinafter referred to as "printer"), which is an electrophotographic image forming apparatus, will be described below. FIG. 1 is a schematic configuration diagram of an image forming apparatus 1 of this embodiment. The image forming apparatus 1 includes an image forming section 100 that forms an image on a sheet of paper P that is a recording material. The image forming unit 100 includes image forming units 10Y, 10M, 10C, and 10K for yellow (Y), magenta (M), cyan (C), and black (K) on an intermediate transfer belt 20 as an intermediate transfer member. This is a tandem image forming apparatus arranged along the direction of rotation. The image forming units 10Y, 10M, 10C and 10K are provided with photosensitive members 11Y, 11M, 11C and 11K as latent image carriers, respectively.

In addition, each of the image forming units 10Y, 10M, 10C, and 10K includes a charging device as charging means for uniformly charging the surface of the photosensitive member 11Y, 11M, 11C, and 11K around the photosensitive member 11Y, 11M, 11C, and 11K, and a charging device. an optical writing device 9 as an electrostatic latent image forming means for writing an electrostatic latent image on the surface of the photoreceptor uniformly charged by light exposure according to image information; Developing device as developing means for creating a toner image by a development process of attaching toner of each color (Y, M, C, K), and primary transfer for transferring the toner image on the photoreceptor onto the intermediate transfer belt 20 A primary transfer device as means, and a cleaning device as cleaning means for removing transfer residual toner on the photoreceptor for cleaning.

The respective color toner images formed on the photoreceptors 11Y, 11M, 11C, and 11K are primarily transferred onto the intermediate transfer belt 20 by the primary transfer device so as to overlap each other, forming color toner images on the intermediate transfer belt 20. be done. The color toner image on the intermediate transfer belt 20 is conveyed to an area facing the secondary transfer device 30 (secondary transfer area) as the intermediate transfer belt 20 rotates.

On the other hand, below the image forming section 100, a paper feeding cassette 60 is arranged as a feeding section for feeding the paper P to be held. Sheets P are fed one by one from a sheet feed cassette 60 by a pickup roller 61 . Then, the paper P is transported to the secondary transfer area by the registration roller pair 62 along the transport path.

The color toner image on the intermediate transfer belt 20 is secondarily transferred by the secondary transfer device 30 onto the paper P conveyed by the pair of registration rollers 62 at a predetermined timing in the secondary transfer area. The paper P on which the color toner image is formed is then conveyed to a fixing device 40 as fixing means, and the color toner image is fixed on the paper P by the action of heat and pressure. After fixing, the paper P is transported along the transport path and discharged to the paper discharge tray 50 by the paper discharge rollers 63 .

FIG. 2 is an explanatory diagram of the fixing device 40 in this embodiment. FIG. 2(a) is a sectional view showing the schematic configuration thereof. A fixing device 40 includes a pressure rotating body (pressure roller 41 in the case of FIG. 2), a fixing sleeve 42, and a heat source 43 (halogen heater in the example of the drawing), and performs fixing by heat and pressure. Inside the fixing sleeve 42 of FIG. 2 is a nip forming member 45 held by a fixing stay 44, which slides directly on the inner surface of the fixing sleeve 42 (or indirectly via a sliding sheet). ing.

The nip forming member 45 may be an assembly composed of a plurality of resin and metal parts, or may be composed of a single resin or metal. In the illustrated example, it is composed of a heat soaking member 45a arranged on the nip surface and a supporting member 45b for supporting it. The heat soaking member 45a has, for example, a pad shape extending in the width direction of the fixing sleeve 42 . This heat equalizing member 45a is arranged to equalize the temperature in the axial direction. In a conventional fixing device using a sliding nip, in order to reduce the sliding resistance of the nip, a sliding sheet made of fibers such as PTFE impregnated with a lubricant such as silicone oil is used. There is a method of fixing to a flexible nip forming member. In order to increase the heat equalization effect more than the sliding sheet, a metal plate made of aluminum or copper (or a combination of these materials) with a sliding film formed on the surface (heat equalizing pad) may be used. . Since the slidable film adheres to the surface, high thermal conductivity can be maintained.

The pressure roller 41 has a metal roller with a silicone rubber layer, and has a release layer (PFA or PTFE layer) on the surface to obtain release properties. The pressure roller rotates when a driving force is transmitted through gears from a driving source such as a motor provided in the image forming apparatus. The fixing sleeve 42 rotates together with an external roller. Also, the pressure roller 41 is pressed against the fixing sleeve side by a spring or the like, and has a predetermined nip width due to the rubber layer being crushed and deformed. The pressure roller 41 may be a solid roller, but a hollow roller may have a smaller heat capacity. Further, the pressure roller 41 may have a heat source such as a halogen heater.

The fixing sleeve 42 is an endless belt (or film) using a metal belt such as nickel or SUS or a resin material such as polyimide. The surface layer of the fixing sleeve 42 has a release layer such as a PFA or PTFE layer, which has release properties so that toner does not adhere. Between the base material of the fixing sleeve 42 and the PFA or PTFE layer, there may be an elastic layer formed of a layer of silicone rubber or the like.

The fixing stay 44 is a hollow pipe-shaped metal body made of metal such as aluminum, iron, or stainless steel. Although the illustrated metal body has a square shape, it may have another cross-sectional shape. If the fixing stay 44 is heated by the radiant heat of the heat source 43 such as a halogen heater, the surface of the fixing stay 44 is heat-insulated or mirror-finished to prevent the heating, thereby reducing wasteful energy consumption. can be suppressed.

With the above configuration, it is possible to realize a fixing device that is inexpensive and warms up quickly.

In the fixing device of the present embodiment, since the nip forming member 45 includes the heat soaking member 45a, the effect of reducing the temperature rise at the edge portion during continuous sheet feeding can be expected. On the other hand, there is a problem that the heat of the surface of the fixing member flows into the interior due to the high thermal conductivity at the time of start-up, resulting in a longer recovery time.

In order to solve this problem, in this embodiment, the support member 45b that supports the heat equalizing member 45a and fixes it to the fixing stay 44 is made of a material (thermal insulator) that does not conduct heat, and the heat equalizing member 45a and the fixing stay 44 are thermally connected and disconnected. A contact portion 46 that thermally contacts the fixing stay 44 is provided on the heat equalizing member 45a.

The thermal connecting/disconnecting means is brought into a connected state, and heat is released from the contact portion 46 to the fixing stay 44 side. Since the heat capacity of the fixing stay 44 is sufficiently larger than that of the heat soaking member 45a, the effect of reducing the temperature rise at the end portion can be expected. On the other hand, at the time of start-up, the heat is prevented from flowing out from the heat soaking member 45a by setting it to a non-connected state (thermally cut off state) by the thermal connection/disconnection means, so that high-speed recovery from warm-up can be achieved. It becomes possible.

In this embodiment, the thermal connecting/disconnecting means is configured as follows. That is, as shown in FIG. 2(a), a clearance is provided between the contact portion 46 of the heat equalizing member 45a and the fixing stay 44, and when the edge temperature rises due to continuous paper feeding, the thermal conductivity is reduced. The clearance is filled with a heat transfer member 47 having good resistance to bring the two parts into thermal contact. Moreover, the heat transfer member 47 is formed in a V shape as shown in FIG. FIG. 2(c) is a diagram of the heat transfer member 47 alone. The shape may be a stepped shape that can be changed step by step, in addition to the V shape that can be adjusted steplessly.

The connecting position of the fixing stay 44 and the heat soaking member 45a can be arbitrarily changed by moving the position with the movable device as indicated by the arrow B in FIG. 2(b). Although the degree and position of temperature rise at the edge differ depending on the paper feeding conditions, the contact position can be changed steplessly, so various types and sizes of paper can be handled. A solenoid or the like can be used as the movable device. When the thermal cutoff state is to be taken, no part of the heat transfer member 47 is located in the clearance.

FIG. 3 is a block diagram showing an example of a main part of a control system that controls the fixing device of this embodiment. The controller 200 includes a CPU, RAM, ROM, nonvolatile memory, and the like. The controller 200 is connected to a transfer unit 31 including the optical writing device 9, image forming units 10Y, 10C, 10M, and 10K, a rotation driving unit for the intermediate transfer belt 20, and the like. The controller 200 is also connected to a sheet conveying unit 201, an external communication interface 202, an operation display unit 203, and the like.

The paper transport unit 201 drives transport roller pairs such as the pickup roller 61 and the registration roller pair 62 that transport the paper. An external communication interface 202 communicates with a personal computer or the like in which an external printer driver is installed. The operation display unit 203 has an operation unit such as a keypad operated by the user and a display unit such as a liquid crystal panel.

The controller 200 controls the heat source 43 of the fixing device 40 so that the first halogen heater 43A positioned at the center in the width direction, the second halogen heater 43B positioned at both ends, the center temperature detection sensor 28A, and the end temperature detection sensors 28B are controlled. It is connected. The controller 200 is also connected to a pressure roller driving motor 29 that rotationally drives the pressure roller 41 of the fixing device 40 and a movable device 204 that moves the heat transfer member 47 .

The controller 200 receives print job (image forming job) instructions and image data from a personal computer or the like in which an external printer driver is installed via the external communication interface 202 . The controller 200 executes a preinstalled control program to control an image forming operation for forming and outputting a color image on paper.

The non-volatile memory of the controller 200 stores information such as size information of the paper P set in the paper feed cassette 60 . Information about the size of the paper P set in the paper feed cassette 60 and the direction of transport is input by the user's operation of the operation display unit 203, and the input size information of the paper is stored in the non-volatile memory. Also, information such as the size of the paper P set in the paper feed cassette 60 is received from a personal computer in which an external printer driver is installed, and the information such as the size of the paper is stored in the non-volatile memory. Further, a paper size detection means for detecting the size of the paper set in the paper feed cassette 60 may be provided, and the results detected by this paper size detection means may be stored in the non-volatile memory.

4A and 4B are explanatory diagrams of movement control of the heat transfer member 47 by the controller 200. FIG. FIG. 4A shows the heat transfer member 47 when the paper P1 has a width longer than the emission length of the first halogen heater 43A, which is the central heater, and shorter than the interval between the second halogen heaters 43B, which are the end heaters. indicates the position of Although it is necessary to turn on the edge heater, the edge temperature rises because the paper P1 does not absorb the heat in the remaining portion (the portion not facing the paper P1 in the width direction). The heat transfer member 47 is moved so as to correspond to this position. Specifically, a contact point S1 is defined as a point facing the remaining portion of the end heater in the width direction. The drawing also shows the contact portion 46 of the heat equalizing member 45a.

In FIG. 4(b), even if the paper P2 is shorter than the light emitting length of the central heater, the paper does not take heat in the remaining portion of the central heater (the portion not facing the paper P1 in the width direction), so the edge portion A temperature rise occurs. The heat transfer member 47 is moved so as to correspond to this position. Specifically, the contact point S2 is a point facing the remaining part of the central heater in the width direction. The edge heater of the sheet P of this width is turned off or controlled at a relatively low temperature.

According to the above embodiment, a rotatable fixing member and a rotatable pressure member arranged opposite to the fixing member are provided, and the heat source for heating the fixing member and the pressure applying member via the fixing member are provided. In a fixing device having a nip forming member that forms a fixing nip with a member and a supporting member that supports the nip forming member, the nip forming member is provided with the nip forming member in a region other than the nip forming region. It can be thermally contacted (or thermally coupled) with the support member, and the contact position can be arbitrarily changed. Therefore, compared with the conventional fixing device, the following effects can be obtained.

That is, fixing devices used in electrophotographic image forming apparatuses widely use a fixing film method in which heating rises quickly. There is a technique in which a fixing nip portion is formed by bringing a pressure roller into contact with a nip forming member via a thin fixing film, and the inner surface of the fixing film and the surface of the nip forming member are slid through a lubricant. Further, there is a conventional technique in which the nip forming member is formed by a heat transfer assisting member that contacts the inner surface of the fixing film and a nip supporting member that supports the heat transfer assisting member.

By using a metal having a high thermal conductivity such as copper or aluminum for the nip forming member, the temperature deviation in the longitudinal direction of the fixing film can be reduced. That is, it is possible to suppress the temperature rise in the non-sheet-passing portion that occurs when small-size sheets are passed, and to improve the continuous productivity of small-size sheets. However, since the nip forming member with high thermal conductivity tends to take heat from the fixing film, there is a problem that the warm-up time becomes long.

In order to solve this problem, it has been proposed that a part of the nip forming member is made to be in thermal contact with the support member, and that this part is switched between contact and separation by a member such as a cam depending on the situation. . In this case, contact/separation switching is performed only at preset positions. On the other hand, the position where the temperature rises in the non-sheet-passing portion varies depending on the paper size. Therefore, there are patterns that cannot be dealt with by the above-described method.

According to this embodiment, the heat equalizing member is provided with a portion in thermal contact with the fixing stay, and the connection/disconnection of this contact portion with the fixing stay is switched by the connecting/disconnecting means, thereby preventing the outflow of heat during startup. As a result, the recovery time can be prevented from deteriorating, and the heat accumulated at the end of the fixing sleeve during continuous sheet feeding can be released to the fixing stay through the heat equalizing plate. Therefore, it is possible to both shorten the recovery time and reduce the temperature rise at the end portion. Moreover, since the position of contact with the nip forming member in the axial direction moves as the heat transfer member moves, the contact position can be changed according to the paper size, etc., and can be adapted to various paper passing patterns such as the paper size. to make contact with the part that you want to heat the most. The contact position can also be changed according to the detection result of the temperature detection means.

As described above, the image forming apparatus can cope with temperature rises at the edges that occur in various patterns without sacrificing the recovery time, so it is possible to reduce the CPM down as much as possible and improve usability for the user. can provide

1: Image forming device 9: Optical writing device 10C: Image forming unit 10K: Image forming unit 10M: Image forming unit 10Y: Image forming unit 11C: Photoreceptor 11K: Photoreceptor 11M: Photoreceptor 11Y: Photoreceptor 20: Intermediate Transfer belt 28A: Center temperature detection sensor 28B: End temperature detection sensor 29: Pressure roller driving motor 30: Secondary transfer device 31: Transfer unit 40: Fixing device 41: Pressure roller 42: Fixing sleeve 43: Heat source 43A : First halogen heater 43B : Second halogen heater 44 : Fixing stay 45 : Nip forming member 45a : Soaking member 45b : Supporting member 46 : Contact portion 47 : Heat transfer member 50 : Paper discharge tray 60 : Paper feed cassette 61 : Pickup roller 62 : Registration roller pair 63 : Discharge roller 100 : Image forming unit 200 : Controller 201 : Paper conveying unit 202 : External communication interface 203 : Operation display unit 204 : Movable device P : Paper S1 : Contact point S2 : Contact point

JP 2018-169467 A

Claims (4)

A rotatable fixing member and a rotatable pressure member arranged opposite to the fixing member are provided, and a fixing nip is formed between a heat source for heating the fixing member and the pressure member via the fixing member. In a fixing device having a nip forming member and a support member supporting the nip forming member,
A fixing device, wherein the nip forming member can thermally contact with the support member in a region other than the nip forming region, and the contact position can be changed. The fixing device according to claim 1,
The fixing device, wherein the contact position is changed according to the paper size. 3. The fixing device according to claim 1, wherein
A fixing device, wherein a contact position is changed according to a detection result of a temperature detection means. In an image forming apparatus equipped with a fixing device,
An image forming apparatus using the fixing device according to claim 1 .

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