JPS5846368A - Roller fixing device - Google Patents

Abstract

PURPOSE:To make stable fixing possible by preventing the sharp temp. drop of a heating roller and to shorten a preheating time by conducting electricity forcibly to the heating element in the heating roller by a prescribed time after the heating roller and a fixing roller start revolving in a press contacting state. CONSTITUTION:After a heating roller 1 and a press contacting roller 4 start revolving in a press contact state, electricity is conducted forcibly by a prescribed time to the heating element 2 in the roller 1. Thus the sharp temp. drop of the roller 1 is prevented, whereby stable fixing is made possible and the preheating time is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a roller that heat-fuses a toner image on a recording paper in a copying machine or the like that forms an electrostatic latent image on the surface of a photoreceptor, develops it, and transfers it onto a recording paper. The present invention relates to a fixing device, and more particularly relates to a roller fixing device in which a heating roller and a pressure roller come into pressure contact with each other when a copy button is turned on, and then start rotating.

Figure 1 is a specific configuration diagram of this type of roller fixing device. ing. A heating element 2 such as a heating lamp is disposed inside the heating roller l, and a temperature detection element 3 for detecting the temperature of the heating roller l is disposed facing the outer peripheral surface of the heating roller l. ing. Reference numeral is a pressure roller made of silicone rubber.While the heating roller 1 contacts the surface of the recording paper P with the toner image C@, this pressure roller 1 contacts the surface opposite to the toner image C@, and the roller shaft ! rotated by Note that the rollers 4C and 4C are rotated while maintaining a constant pressure contact state by a pressure mechanism (not shown).

In such a roller fixing device, the recording paper P is moved in the direction of the arrow while being sandwiched between the heating roller l and the pressure roller 4I and receiving heat from the heating roller l, and the toner image C is formed by heating during the movement. The heat roller fixing method is widely used because it has various advantages such as high thermal efficiency and high-speed fixing, but it requires a preheating time of about 3 minutes. First, the wait time is longer than other fixing methods (for example, pressure fixing, flash fixing, etc.).

In order to improve this point, methods are being considered to increase the amount of power supplied to the heating element or to reduce the heat capacity of the heating element. However, it is not possible to increase the amount of power supplied to the heating element from the power distribution of the entire copying machine, and the amount of power supplied to the heating element λ
It is also inefficient to constantly supply a large amount of electric power to the heating roller l only for the startup time. For this reason, the latter method is currently being used exclusively.

FIG. 2 is a diagram showing the relationship between the energization time t of the heating element 1 and the temperature T of the heating roller 1 in a roller fixing device using this method. FIG. 2B is a diagram showing the temperature characteristics of the heating roller. In the figure, Ts is the set temperature i of the heating roller l, TTJLIi is the lower limit fixing temperature,
This type of roller fixing device employs a start-off control in which the heating element is energized when the temperature of the heating roller 9 drops to T#, and the energization is stopped when the temperature of the heating roller 1 reaches Ts. are doing.

Now, in such a conventional roller fixing device, when the power switch is turned on (1=1.), electricity to the heating element is started. As a result, the temperature of the heating roller 21 rises rapidly due to its small heat capacity @Then, the temperature detection element 3 detects that the temperature of the heating roller exceeds Ts t- (
1=1. ), the power supply to the heating element is stopped, and the warm-up is completed. Note that the temperature of the heating roller I continues to rise for a while after the energization is stopped, and then gradually begins to drop. Here, when the copy button is turned on, at time 1=11 before the recording paper P reaches the fixing device, the heating roller I and the pressure roller start rotating in a state in which they are in pressure contact. However, as a result of reducing the heat capacity of the heating roller 1, the temperature of the heating roller 1 rapidly decreases due to the transfer of heat from the heating roller 1 to the pressure roller 1 during pressure contact.
Cut not only Ts but also To.

Normally, the moment when the temperature of the heating roller l drops below 1 day (t
” ts), energization of the heating element is started, but in reality, the temperature detection element 3 itself that detects the temperature of the heating roller l has a heat capacity, and until the energization is restarted, A certain time delay t occurs, leading to the situation described above.When energization is resumed at time t = t4,
Heating roller:) The temperature of the roller rises again, but the temperature of the heating roller
Because the temperature of the heating roller l has decreased and the pressure roller has also been subjected to heat load, the temperature of the heating roller l has not recovered to around 1 day by the time the recording paper P reaches the fixing device. Therefore, insufficient fixing will occur. Such inconveniences occur when the temperature detection element 3 is placed away from the heating roller l at the cost of sacrificing the response characteristics in order to prevent the heating roller l from being scratched, or when the temperature of the heating roller l is As shown in A in the figure, the rotation starts when the temperature detecting element 3 is in a high temperature state due to an overshoot exceeding the set temperature T8, which becomes noticeable when the rotation is started.

The present invention was made in view of the above points, and after the heating roller and the pressure roller start rotating in a state in which they are in pressure contact, the heating element is forcibly energized for a certain period of time, and the heating roller is suddenly turned on. The present invention has realized a roller fixing device that enables stable fixing by preventing a temperature drop and has a short preheating time.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 3 is a diagram showing the relationship between the energization time of the heating element and the temperature of the heating roller in an embodiment of the roller fixing device according to the present invention. Here, the heating roller I and the pressure roller start rotating in a state in which they are in pressure contact at time t! This constant time Δt
(Only 1, regardless of the output of temperature detection element 3,
The heating element is forcibly energized - Of the energization pulses shown in the same figure (ri), the shaded portion S is the forced energization time.

As a result, the temperature k of the heating roller does not fall much below the set temperature [T@] even by the pressure contact between the heating roller l and the pressure roller 1, and when the recording paper P reaches the fixing device, the temperature of the heating roller l is maintained near T8. Therefore, sufficient fixing is possible. The above-mentioned forced energization time Δt· is the pressure welding start time 1. , the temperature detection element 3 detects a decrease in temperature of the heating roller l and issues an energization signal to the heating element λ.The time and degree at t are required.If the forced energization time resistance is short, heat generation occurs. If the heating roller l is not sufficiently heated and the heating roller l cannot fully recover to 're', and on the contrary, if it is too long, the temperature of the heating roller l will rise too much. Therefore, the forced energization time Δt It is necessary to set it taking into account the specifications of λ, the heat capacity of the heating roller l, etc. Normally, this energization time Δt@ is 0. It will take about j seconds to j seconds.

By the way, such energization control can be performed in conjunction with reducing the heat capacity of the heating roller l, so in the device of the present invention,
It is also possible to shorten preheating time.

The above explanation applies when the pressure roller is cold.

In other words, this is intended for the case where the seventh copy operation starts after the power is turned on, but if the device is used in an environment where the ambient temperature is low, it may be possible to perform forced energization for each re-copy. . Furthermore, the present invention is equally applicable not only to copying machines but also to recording apparatuses that perform image processing by heat fixing.

As described in detail above, according to the present invention, which is configured to forcibly energize the heating element for a predetermined period of time after the heating roller and the fixing roller start rotating in a state in which they are in pressure contact, the temperature of the heating roller is rapidly decreased. It is possible to prevent this, sufficient fixing is possible, and at the same time, the preheating time can be shortened.

[Brief explanation of the drawing]

W, Figure 1 is an explanatory diagram showing the specific configuration of the roller fixing device,
FIG. 2 is an explanatory diagram showing the relationship between the energization time of the heating element and the temperature of the heating roller in a conventional roller fixing device, and FIG. 3 is an explanatory diagram showing the relationship between the energization time of the heating element and the temperature of the heating roller in an embodiment of the apparatus of the present invention. FIG. l... Heating roller C... Heating element 3... Temperature detection element Part 3... Pressure roller j... Roller shaft
P... Recording paper C... Toner image T...
・Settings @ degree T mouth... Lower limit of fixing temperature Patent applicant: Roku Konishi Photo Industry Co., Ltd. Patent attorney, Fujiharu Atsushi Ijima Figure 1 Figure 2

Claims (1)

[Claims] A roller fixing device in which a heating roller and a pressure roller come into pressure contact with each other when a copy button is turned on and start rotating in the next state, characterized in that a heating element in the heating roller is forcibly energized for a predetermined period of time from the start of rotation. .