JPH0493971A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent faulty fixing from occurring and to keep the surface temperature of a fixing roller from becoming extremely high by changing the heat capacity of the fixing roller in a longitudinal direction. CONSTITUTION:A recording paper 1 is carried to the fixing roller 6 and toner is fixed on the recording paper 1. The roller 6 is previously heated by a heating lamp 10 so as to be kept at a fixed temperature. The roller 6 is rotated together with a press-bonding roller 11 in a direction shown by an arrow and carries the recording paper 1 while heating and pressuring the paper 1 with the roller 11. A temperature detector 12 is energized in contact with the surface of the roller 6 and constitutes a temperature control means with a temperature control unit 13. This means drives and controls the lamp 10 so as to keep the surface temperature of the roller 6 at a fixing set temperature which is previously set. By changing the thickness of the roller 6, the heat capacity is changed in the longitudinal direction. Even in the case that the heat in the center part of the roller 4 is absorbed by the recording paper 1, the temperature in the center part is prevented from lowering suddenly in comparison with the end part thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat fixing device in a printing device such as a printer or a copying machine.

[Conventional technology]

This type of fixing device fixes a visible image such as toner formed on recording paper by applying pressure and heat.
2. Description of the Related Art A fixing device is generally known in which a fixing roller having a built-in heating means and a pressure roller co-rotate in a press-contact state, and recording paper is passed between the two rollers. In such a fixing device, the surface temperature of the fixing roller is maintained constant by a temperature control means composed of a temperature detector and a temperature controller.

Further, the heat capacity of the fixing roller was approximately constant in the longitudinal direction.

However, in recent years, printing devices with built-in fixing devices of this type have become multi-functional, and the recording paper used, also called copying machine paper, has a weighing capacity of 50 to 7 at/r.
P? The paper quality used is wide (and even heavy paper is usually used with a weight of qof/rr? or less.Also, most of the paper sizes were US letter A4 size.

In contrast to such copying machine paper, the recording paper that has come to be used due to the multifunctionality of printing devices is paper with a quality of 902/- or more in terms of weighing, and even original paper for envelopes, postcards, etc. It is a recording paper.

However, conventional fixing devices use a fixing roller that has the same heat capacity in the center where recording paper, envelopes, postcards, etc. pass through, where heat is easily absorbed, and at the edges, where heat is more likely to be absorbed. Ta.

[Problem to be solved by the invention]

In the conventional fixing device as described above, the cross section of the fixing roller has a constant thickness and a constant heat capacity in the longitudinal direction, as shown in Fig. 4, which causes the following problems. Ta.

An example will be described in which the center of the recording paper is made substantially coincident with the center of the fixing roller as a reference for the feeding posture of the recording paper. The temperature sensor is installed almost at the center of the fixing roller, and the center of the fixing roller is controlled at a constant temperature. As shown by curve A in Figure 5, the temperature distribution is lower at the edges than at the center.On the other hand, if the quality of the recording paper is thick (the width of the recording paper is narrow), the temperature distribution will be lower during printing. The amount of heat taken away is large, as shown by curve B in FIG. 5 (the temperature distribution of the fixing roller is much higher at the ends than at the center).

Actually, the set temperature T of the fixing roller. When the difference between the temperature T1 on the end side of the fixing roller in the standby state and the temperature T1 on the end side of the fixing roller in the standby state is 5°C to 15°C, the recording paper thickness is thick (the temperature T on the end side of the fixing roller during printing when the recording paper width is narrow is the fixing set temperature. 40℃ relative to T0
The temperature will rise by ~80°C.

Such a high temperature state at the end of the fixing roller causes an increase in the internal temperature of the printing apparatus and is very disadvantageous for the heat resistance and wear resistance of the constituent members, causing the apparatus to become complicated and expensive.

Furthermore, if a configuration is adopted in which the rise in the temperature T2 of the end side of the recording paper is suppressed, the temperature T1 of the end side of the fixing roller becomes too low in the standby state, and when printing starts after the standby state, the end side of the recording paper is not fixed. This had the problem of becoming defective.

The present invention is intended to solve these problems, and its purpose is to ensure that even if the recording paper takes heat from the center of the fixing roller, the temperature of the center of the fixing roller is equal to the temperature of the edges. The goal is to provide an extremely low fixation rate.

[Means to solve the problem]

In order to solve the above problems, the present invention is characterized in that the heat capacity of the fixing roller is changed in the longitudinal direction.

[Effect]

According to the above configuration of the present invention, for example, if the heat capacity of the center part is larger than that of the end parts, even if the heat of the center part is taken away by the recording paper, the temperature of the center part of the fixing roller will be lower than that of the end parts. It will not drop sharply.

〔Example〕

An embodiment of the present invention will be described based on the drawings. FIG. 1 is a main sectional view of a printing device incorporating a fixing device of the present invention;
FIG. 2(α)(b) is a detailed explanatory diagram of the fixing device,
The figure (α) is a sectional view in the longitudinal direction, and the figure (b) is a sectional view in the transverse direction. In FIG. 1, a recording paper 1 is supplied from a paper feed tray 2 to a paper feed row 24 by a pickup roller 6, and includes a paper feed roller 4, a photoreceptor drum 5, a fixing roller 6,
The sheets are sequentially conveyed to the paper discharge roller 7. In this process,
Information such as characters is written onto the photosensitive drum 5 by the writing head 8.
optically written as an electrostatic latent image. Thereafter, toner from the developing device 9 adheres to the writing area on the photosensitive drum 5, making the electrostatic latent image visible, and the toner is further transferred onto the recording paper 1 as a visible image. be. Next, the recording paper 1 is conveyed to a fixing roller 6, and the toner is fixed onto the recording paper 1.

As shown in FIG.
0 and is kept at a constant temperature, and rotates together with the pressure roller 11 in the direction of the arrow to convey the recording paper 1 while pressurizing and heating it. A temperature detector 12 is urged into contact with the surface of the fixing roller 6, and together with a temperature controller 13 constitutes a temperature control means. This temperature control means controls the driving of the heating pump 10 and maintains the surface temperature of the fixing roller 6 at a preset fixing temperature.

In this embodiment, the heat capacity is varied in the longitudinal direction by varying the thickness of the fixing roller. In this embodiment, as shown in figure (α), the thickness of the central portion 6α is made thicker than the other portions.

Before the recording paper passes through the fixing device, the temperature at the center is slightly higher (as shown by curve A in Figure 6).When the recording paper passes through the fuser, the heat capacity is constant in the longitudinal direction as in the conventional case. In the fixing roller, the temperature difference between the center part and the end part was about 30°C, whereas in the fixing roller of this example, the temperature difference in the curve 0 in Fig. 3 was about 30°C.
As shown in , the temperature can be lowered to 25°C or lower.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to prevent fusing failure even when fusing original recording paper other than copy machine paper, such as recording paper of various paper widths and paper thicknesses, including envelopes, postcards, etc. (And since the surface temperature of the fixing roller does not become extremely high, the internal temperature of the printing device with a built-in fixing device does not rise much (and the highly durable fixing device has an extremely simple configuration. It has the great effect of being able to provide it at a low price.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of a printing device incorporating a fixing device of the present invention. Figure 2 (α) (6) is the second detailed EiA diagram of the fixing device.
Figure (α) is a longitudinal sectional view, and Figure 2 (b) is a lateral sectional view. FIG. 5 is a diagram showing the temperature distribution of the fixing roller. FIGS. 4(a) and 4(b) are cross-sectional views in the longitudinal direction and the lateral direction of a conventional fixing roller. 1... Recording paper 2... Paper feed tray 6... Hiccup 7 Roller 4...
... Paper feed roller 5 ... Photoconductor drum ... Fixing roller ... Paper ejection roller ...・・Writing head ・・・Developing device ・・Heating lamp ・・・Crimping roller ・・・Temperature detector・・・・・・・Temperature controller or higher

Claims (1)

[Claims] A roller-type thermal fixing device for fusing and fixing a visible image on recording paper, the fixing device comprising a fixing roller having a heat capacity that changes in the longitudinal direction.