JPH0493972A - Fixing device - Google Patents

Abstract

PURPOSE:To obtain excellent fixing performance even in a state where the surface temperature of a pressure roller is low after the starting of a fixing device by taking the pressuring force of the pressure roller as 1st set pressuring force until a specified time and then switching it to 2nd set pressuring force. CONSTITUTION:As soon as a power source 12 is turned on, the heating source 1a of the fixing roller 1 is heated and the pressure roller 2 is brought into contact with the roller 1 by the 1st set pressuring force. When a timer is actuated and a set time elapses after warm-up is finished and copying is started, the pressuring force of the roller 2 is set at the 2nd set pressuring force gives pressure at the time of regular running. Since the pressuring force of the roller 2 to the roller 1 is set as the 1st set pressuring force which gives higher pressure than that at the time of regular running from the start up time when heating is started until the specified time and it is set to the 2nd set pressuring force in the regular running state where the temperature of the roller 2 rises to some extent, the excellent fixing performance is obtained by the increase of the pressuring force even when heat as sufficient as heat given at the time of regular running is not given to toner at the start up time, and the running is executed by the optimum pressuring force at the time of regular running.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention involves bringing a pressure roller into contact with a fixing roller equipped with a heat source under a predetermined pressure, and transferring a transfer sheet carrying an unfixed toner image to the contact portion. ! The present invention relates to a fixing device used in an image forming apparatus such as a copying machine that fixes a toner image in one pass.

Conventional technology In the fixing device of an image forming apparatus such as a copying machine, conventionally,
As shown in FIG. 4, when the heat source of the fixing roller is turned on and a copy is made after warm-up is completed, the heat of the fixing roller is consumed to raise the temperature of the pressure roller, and the heat source of the fixing roller is There was a problem in that the heat required to melt and fix the toner image was not applied to the transfer paper due to the drop in surface temperature, resulting in extremely poor fixability for a certain number of copies after the fixing device started up.

To solve this problem, during the warm amplifier period after the power is turned on until the temperature of the fixing roller reaches the set value, a pressure roller is brought into pressure contact with the fixing roller and rotated for a certain period of time to fix the temperature of the pressure roller. A fixing IT system has been proposed in which the temperature is raised to a temperature suitable for
(See Publication No. 1462).

However, such a device has problems in that the worm amplifier time becomes very long and noise is generated as both rollers rotate.

Problems to be Solved by Akira The present invention solves the above-mentioned problems in the prior art, provides good fixing performance even when the surface temperature of the pressure roller is lower than the temperature suitable for fixing, and eliminates unnecessary noise. An object of the present invention is to provide a fixing device that does not generate.

Means for Solving the Problems In order to solve the above problems, the present invention provides a transfer paper that carries an unfixed toner image on the contact portion by bringing a pressure roller into contact with a fixing roller equipped with a heat source under a predetermined pressure. In a fixing device that fixes a toner image by passing a toner image, the predetermined pressure is set as the first setting pressure from the time when heating by the heat source is started until a predetermined time, and after the elapse of the predetermined time, the predetermined pressure is set as the first set pressure. The pressure is set to a second set pressurizing force which is lower than the first set pressurizing force and is a pressurizing force during steady operation.

According to the present invention, the pressing force of the pressure roller against the fixing roller is set to the first set pressing force, which is a higher pressure than during steady operation, from the start-up time when heating starts until a predetermined time, and the pressure roller is applied to the fixing roller to a certain extent. When the temperature rises to steady operation, the second setting pressure is applied, so even if the toner does not receive as much heat as it would during steady operation, the increase in pressure will result in good fixing. In addition, during steady operation, it is possible to operate at the optimum pressing force without unnecessarily increasing the pressing force.

On the other hand, since there is no need to increase the temperature of the pressure roller by rotating the fixing roller and pressure roller together during warm-up at startup, the warm-up time is shortened and unnecessary noise is generated. I have nothing to do.

Example FIG. 1 is an explanatory diagram of a fixing device according to an embodiment.

The fixing device includes a fixing roller 1 that includes a heat source 1a inside, and a pressure roller 2 that is arranged to rotate in contact with the fixing roller 1.

The fixing device is provided in an image forming apparatus (not shown) such as a copying machine, and the transfer paper P on which the toner image T has been formed by a normal image forming process is introduced into the contact area between the fixing roller 1 and the pressure roller 2. The fixing roller I
The toner image T is melted and fixed on the transfer paper P by being pressed against the transfer paper P and heat is supplied thereto.

The pressure roller 2 is brought into or out of pressure contact with the fixing roller 1 by moving the other end of the pressure arm 4 whose one end side is supported by a support pin 3 in the vertical direction in the figure by an air cylinder 5. be done.

The air cylinder 5 is operated by being supplied with compressed air from an air conditioner 7 via a solenoid valve 6.

Inside the frame of the figure is the solenoid valve control surface that controls the signal supplied to the solenoid valve 6! 10 is shown.

In this embodiment, the output signal of the solenoid valve switching signal output circuit 13 is controlled by detecting the input of a copy start signal from a copying machine (not shown) to the timer 11 and the turning on of the power supply 120. The valve drive circuit 14 is manually operated to control the pneumatic pressure set value to the solenoid valve 6, thereby controlling the pressing force of the pressure roller 2 and pressurization/pressurization release.

FIG. 2 shows an example of control of the pressurizing force by the solenoid valve control circuit [0].

At the same time as the power supply 12 is turned on, the heat source 1a of the fixing roller]
is heated, and the pressure roller 2 is brought into contact with the fixing roller 1 with a first set pressure force.

After the warm amplifier is finished and copying is started, the timer is activated and a set time has elapsed, and the pressure of the pressure roller 2 is set to the second set pressure, which is the pressure during steady operation. That is, in this embodiment, the predetermined time is determined by the copy start signal and the set time of the timer 11.

The setting time of this timer ] can be approximately determined by the temperature characteristics at the start of the fixing roller shown in FIG. That is, the heat capacity of the fixing roller 1 and the pressure roller 2,
It is determined based on the relationship such as the amount of heat carried away by the transfer paper (varies depending on the type, size, conveyance speed, etc. of the transfer paper).

As shown in Fig. 3, the internal temperature of the fixing device is detected,
The setting time of the timer 11 may be determined based on this internal temperature. In this case, the temperature of the pressure roller 2 may be detected instead of detecting the temperature inside the machine.

On the other hand, in normal copying machines, etc., 5 to 1
The fixing properties of copies of about 0 sheets often deteriorate, and if the characteristics of such a copying machine can be understood, it is possible to set the timer 11 accordingly. Further, in such a case, instead of using the timer 11, the predetermined time can be set based on the number of first copies.

Regarding the pressing force of the pressure roller 2, the first set pressing force is:
This means a pressure that can provide good fixing performance even when the surface temperature of the pressure roller 2 is low and the temperature has not risen to a temperature suitable for fixing with the normal set pressure.

Further, the second setting pressure force refers to the pressure force that can ensure the necessary fixing performance when the surface temperature of the pressure roller 2 reaches a temperature suitable for fixing, that is, in a steady state. means the applied force.

The value of the first set pressing force is determined based on various conditions related to fixing performance such as the capacity of the heat source 1a (for example, electric power W), the material, wall thickness, and heat insulation properties of the roller, the copying speed, and the type and size of transfer paper. In this embodiment, by adjusting the air pressure of the solenoid valve 6, the pressurizing force can be easily set to an appropriate pressure.

Effects As described above, according to the present invention, the pressing force of the pressure roller is set to the first set pressing force until a predetermined time, and then switched to the second set pressing force. Good fixing properties can be obtained even when the surface temperature is low. Furthermore, since there is no need to rotate the pressure roller during the warm-up of the fixing device, there is no need for a long warm-up time or generation of noise.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the fixing device of the embodiment, FIG. 2 is a diagram of the set pressure of the pressure roller, FIG. 3 is a diagram of the set time of the timer, and FIG. 4 is a diagram of the roller surface temperature. Figure 3: Fixing roller a: Heat source: Pressure roller: Air cylinder: Solenoid valve 0...'@ Magnetic valve control circuit

Claims (1)

[Scope of Claims] In a fixing device that fixes a toner image by bringing a pressure roller into contact with a fixing roller equipped with a heat source under a predetermined pressure, and passing a transfer paper carrying an unfixed toner image through the contact portion. , The predetermined pressure is set as a first set pressure from the time when heating by the heat source is started until a predetermined time, and after the predetermined time has elapsed, the predetermined pressure is lowered than the first set pressure and is operated in a steady state. A fixing device characterized in that the fixing device uses a second set pressure force that is a pressure force at a time.