JPH0128523Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a fixing device used in electrophotographic devices such as copying machines, facsimile machines, printers, and the like. In particular, it is equipped with a heated fixing roller and a pressure roller that contacts the fixing roller with appropriate pressure, and a developer carrier such as paper or the like carrying developer is passed between these rollers. The present invention relates to a fixing device that fixes developer onto a developer carrier when the developer passes through the fixing device.

Prior Art In the fixing device described above, fixing of the developer is performed by applying heat to the developer, but of course it is sufficient if this heat is applied only to the developer. However, since heat generally has the property of being transmitted to various places by radiation and convection, conventionally, the heat generated in the fixing device is transmitted to various other devices installed close to the fixing device, and This resulted in an increase in the temperature of the equipment. Devices in which the temperature rises in this manner cause various problems. For example, if we take a photoreceptor as an example, the internal crystal structure of the photoreceptor changes due to an increase in temperature, which results in deterioration of the image quality of the copied image and, in turn, shortens the usable life of the photoreceptor itself. This causes an inconvenience.

As described above, in the conventional apparatus of the above type, the heat generated within the fixing device causes a temperature rise in other devices in the electrophotographic apparatus such as a copying machine, which significantly impairs the reliability of the electrophotographic apparatus. It had the disadvantage of being damaged.

In order to overcome this drawback, there is a fixing device that includes a heat shield plate provided at the paper entrance of the fixing device, and this heat shield plate prevents heat from being released to the outside of the fixing device. Publication No. 48-96135. However, in this type of device, it is necessary to move the heat shielding plate between a position where it does not interfere with the advance of the paper and a position where it shields the heat, and a drive device for this purpose must be specially provided. As a result, the structure of the fixing device including the control device becomes complicated, and at the same time, there is a fear that the manufacturing cost will increase.

Problems to be Solved by the Invention It is an object of the present invention to provide a fixing device that can move a heat shield plate at an appropriate timing and has a simple structure of a drive means therefor.

Means for Solving the Problems The means for solving the above problems includes a heated fixing roller and a pressure roller that contacts the fixing roller with an appropriate pressure. In a fixing device in which the developer is melted and fixed on the developer carrier while the developer carrier passes between these rollers, the above-mentioned rollers are in contact with each other during the fixing process and separate from each other during the non-fixing process. , at least one of the two rollers can move, and further includes a moving member that moves together with the moving roller, and a moving member that is attached to the moving member and that connects the developer carrier to both rollers. The fixing device includes a heat shielding member disposed at an entrance.

In the above configuration, the developer carrier is copy paper, a plastic sheet for copying, or the like.

Function: When the fixing roller 35 or the pressure roller 36 moves, the moving member 45 moves in accordance with the movement. When the movable member moves, the heat shielding member 44 provided at the tip of the movable member also moves at the same time to reliably shield the entrance of the developer carrier of the fixing device 33.

Embodiment FIG. 1 is a side view of essential parts of an electrophotographic copying machine showing an embodiment of the present invention. In the figure, a photoreceptor 1 formed as a drum and placed inside a copying machine is rotating in the direction of arrow A. This photoreceptor 1 is uniformly charged in the axial direction by a charging charger 2, and is exposed to a light image of a document (not shown) by an exposure device 3, thereby forming an electrostatic latent image on its surface. be done. This electrostatic latent image is turned into a visible image by being supplied with developer from the developing device 4.

Reference numeral 5 denotes a transfer paper (developer carrier) fed from a transfer paper supply section (not shown), and after this transfer paper comes into contact with the visible image formed on the photoreceptor, it is transferred to a transfer charger 6. receives an electric charge due to the discharge of The developer that forms a visible image on the photoreceptor 1 is transferred to the transfer paper 5 by the discharge of the transfer charger 6, and
As a result, an image corresponding to the visible image, a so-called transfer image, is formed on the transfer paper 5. In this way, the developer is carried on the transfer paper 5.

At a downstream position of the transfer charger 6 in the direction of rotation of the photoreceptor 1, that is, in the A direction, a separation belt 9, which is stretched between rollers 7 and 8 and rotates in the direction of arrow B, is arranged close to the photoreceptor 1. has been
The transfer paper that has come to carry the developer as described above is separated from the photoreceptor 1, and then the separation belt 9
conveyed above. Reference numeral 5a indicates the transfer paper being conveyed, and reference numeral 10 indicates the developer carried on the transfer paper 5a.

Incidentally, reference numeral 11 indicates a cleaning device for cleaning the developer remaining on the photoreceptor 1 after transfer.
Reference numeral 12 indicates a charger for eliminating static electricity from the photoreceptor 1 in advance of using the photoreceptor 1 for copying work again.

The transfer paper 5a conveyed on the separation belt 9 and the developer 10 carried on the transfer paper 5a are not yet fixed at this point, so the transfer paper 5a and the developer 10 are Before being ejected to the outside of the copying machine, it must undergo a fixing process. Reference numeral 33 indicates a fixing device for performing the fixing work, and in particular, this fixing device 33
is related to this invention.

After passing through the intermediate member 34, the transfer paper 5a conveyed by the separation belt 9 is sent to a so-called nip portion, which is a contact portion between a fixing roller 35 and a pressure roller 36, which are in contact with each other under appropriate pressure. The fixing roller 35 rotates in the direction of the arrow E while being heated by the heater 37 contained therein, while the pressure roller 36 rotates in the direction of the arrow F in accordance with the rotation of the fixing roller 35.
It rotates in the direction.

The transfer paper 5a sent to the contact area between both rollers 35 and 36 is conveyed between both rollers by the rotation of the fixing roller 35, and at the same time is pressed by both rollers 35 and 36, and is transferred from the heated fixing roller 35. receive heat. At this time, the developer 10 carried on the transfer paper 5a also receives heat, thereby fixing the developer 10 on the transfer paper 5a. The transfer paper on which the fixing has been completed is discharged by paper discharge rollers 20 and 21 to a paper discharge tray 22 provided outside the copying machine.

During the above fixing operation, the heat generated from the heater 37 is transmitted to other devices, especially the photoreceptor 1 (the first
(Figure). code 5
0 is a frame plate of the fixing device located at the paper entrance.

The heat shielding member 44 is attached to the tip of the arm 45, as shown in FIG. Arm 45
The other end is attached to the main body of the copying machine via a fulcrum 46. The arm 45 is rotatable around a fulcrum 46, but its base 45a is pressed against the shaft 36a of the pressure roller 36 by the action of a tension spring 47.

Here, the pressure roller 36 is generally movable up and down, and comes into contact with the fixing roller 35 as shown in the figure during fixing, but when not fixing, it can be moved downward to separate both rollers. Normal. This is because if the fixing roller 35 and the pressure roller 36 are constantly in pressure contact with each other, both rollers will be plastically deformed.

FIG. 3 shows the non-fixing state, in which the pressure roller 36 has been moved downward, so that the fixing roller 35 and the pressure roller 36 are separated from each other. In this case, the arm 45 rotates downward together with the movement of the shaft 36a of the pressure roller 36 under the action of the tension spring 47, but at this time, the heat shielding member 44 attached to the tip of the arm 45 also moves downward. do. Since the heat shielding member 44 moving in this way enters the hole 34a provided in the intermediate member 34, the paper conveyance path from the separation belt 9 to the fixing roller 35 via the intermediate member 34 is controlled by the heat shielding member 44. It is completely shut off, and therefore the heat emitted from the heater 37 is also completely shut off.

Since the movement of the heat shielding member 44 is performed by utilizing the movement of the pressure roller 36, when moving the heat shielding member 44, the driving means and the transfer paper for that purpose are attached to the heat shielding member 44. There is no need to add a detection means or the like to detect the approach. Therefore, an efficient heat shielding effect can be obtained with a small number of parts.

Although the above explanation takes as an example the case where the pressure roller 36, that is, the lower roller moves, the present invention is not limited to this, and when the upper roller moves, the movement of the upper roller is used to move the heat shielding movable roller. Just move the board.

Effects The heat shielding member 44 moves in conjunction with the movement of the fixing roller 35 or the pressure roller 36. Therefore, there is no need for a special drive means, control circuit, etc. for moving the heat shielding member, and the structure of the fixing device is simplified and the cost of the fixing device is reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional side view of a main part of an electrophotographic copying machine using a fixing device according to an embodiment of the present invention, and FIGS. 2 and 3 are views showing the fixing device in detail. 35... Fixing roller, 36... Pressure roller, 1
0...Developer, 5a...Transfer paper (developer carrier),
45... Arm (moving member), 44... Heat shielding member.

Claims (1)

[Claims for Utility Model Registration] The device is equipped with a heated fixing roller and a pressure roller that contacts the fixing roller with an appropriate pressure, and a developer carrier carrying a developer passes between these rollers. In a fixing device in which the developer is melted and fixed on a developer carrier during the fixing process, at least one of the above-mentioned rollers is in contact with each other during the fixing process and separated from each other during the non-fixing process. a moving member that moves together with the moving roller; and a heat shielding member attached to the moving member and disposed at the entrance of the developer carrier to both rollers. A fixing device comprising: