JPS6252582A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent a fixing roller from deforming permanently in any state by providing two kinds of deformation preventing means. CONSTITUTION:A heater turns on until a thermistor 18 detects a specified temperature and a timer 19 starts counting right after the heater is turned on. When the fixing roller reaches the specified temperature, a pressure roller 2 is heated to make its temperature uniform, so preliminary rotating operation is started to prevent the fixing roller 1 from deforming. When copying operation is carried out and finished, a counter 20 begins to count at this moment, and a motor is driven through a controller 21 unless the fixing roller rotates even a specified time later to rotate the fixing roller, performing operation in stand-by mode. If the driving system for the motor becomes abnormal and the fixing roller does not rotate, the counter 20 keeps on counting without being reset and outputs another signal to the controller when counting up to a specified value to display the abnormality on a console panel 24 while generating an alarm tone 25.

Description

Detailed Description of the Invention (1) Purpose of the Invention (Field of Industrial Application) This invention relates to an image forming apparatus using an electrostatic transfer process;
Particularly related to the fixing device 0 (Prior art and issues to be solved) Utilizing an electrostatic transfer process, a toner image is formed on the surface of a sheet-like transfer material, mainly paper, by electrostatic adsorption, Next, the transfer material is passed through the pressure contact portion of a fixing device including a fixing roller heated to a predetermined temperature and a pressure roller that is in pressure contact with the fixing roller, and the toner image is fixed and fixed on the transfer material using heat and pressure. Such fixing devices have been widely used in practice. Figure 1 shows a fixing device as an embodiment of the present invention, which will be described later. To briefly describe a known fixing member, it has a heat source inside. It has a fixing roller l equipped with a heater 5 and a pressure roller 2 that comes into pressure contact with the fixing roller l.The surface of the fixing roller 1 is maintained at a predetermined temperature by the heater 5, and at an image forming area (not shown), A transfer material carrying a toner image is supplied from the right side of the drawing in the direction of arrow A to a nip portion where both rollers come into pressure contact, and is heated and pressurized to fuse and fix the toner to the transfer material.

In such a fixing device, the fixing roller is.

It has good thermal conductivity and takes a short time to reach the specified temperature.

Since it is easy to obtain temperature uniformity over the entire surface, an aluminum core metal 1af has been used, and a Teflon (trade name) layer formed on the surface to prevent offset has been widely used. Furthermore, although not shown, it is preferable to provide means for applying silicone oil as a mold release agent to the surface of the roller 1.

The pressure roller 2 has a silicone rubber layer 2a of an appropriate thickness arranged on the outer circumferential surface of the core metal, and presses this against the fixing roller l to form an appropriate nip portion in the middle for one-pass transfer. Heat and pressure are applied to sufficiently fix the toner image on the material.

As mentioned above, aluminum rollers are often used as fixing rollers due to their advantages, but on the other hand, aluminum has low strength.

If the roller is kept stationary for a long period of time in a heated state, permanent deformation may occur, leading to frequent jamming and skewing of the transfer material. In order to avoid such inconveniences, if the wall thickness is increased, the heat capacity will be increased and the warm-up time will be longer. Also, methods have been proposed that release the press-contact state when the heater is not in operation, or turn off the heater if the heater remains inactive for a certain period of time, but in the case of the former, the configuration is complicated because it requires an additional mechanism. The latter is undesirable because it leads to a sicosto amplifier.
For example, it cannot handle devices that are left on standby all day, such as facsimiles.

For this reason, recently, as seen in Japanese Patent Application Laid-Open No. 58-158671, a system has been proposed in which a roller is rotated by a certain angle at certain time intervals during standby.

On the other hand, in recent years, this type of image forming apparatus has become more compact due to the miniaturization of the apparatus, for example, developing devices, cleaners, etc.
Increasingly, cartridges are being developed in which a plurality of parts required for image formation, such as a photoreceptor, are integrated into a cartridge, which can be used continuously by replacing the parts. so that the user can start working immediately after replacing the cartridge.

When the door of the device is opened to replace the cartridge, the moving parts in the device stop and the high-pressure parts are turned off, but the heater of the heat fixing roller does not turn off and is maintained at a predetermined temperature. Something like this has been proposed.

For such products, if the user leaves the opening/closing door open for a long time, does not close the door securely, or if an abnormality occurs in the motor or its drive system, , by adopting the means seen in the above-mentioned patent publication, the roller does not actually rotate even if there is a rotation signal for the fixing a-ra at regular intervals, and there is a possibility that the roller may be deformed. I can't avoid it.

The present invention has been made in order to cope with such a situation, and an object of the present invention is to provide an entire fixing device in which the fixing roller having a heating means will not be permanently deformed under any circumstances. That is.

(2) Structure of the invention (technical means for solving the problem and its operation) In order to achieve the above object, the present invention includes a pair of fixing rollers and a heating means provided on at least one of the pair of rollers. a driving means for rotating the pair of fixing rollers; and a first deformation prevention means for rotating the pair of rollers to prevent deformation of the rollers when a stopped and pressurized state continues for a predetermined period after the pair of fixing rollers has stopped rotating. and a second deformation prevention means different from the first deformation prevention means, which operates when the roller deformation prevention is not performed by the first deformation prevention means.

With this configuration, it is possible to obtain a fixing device that does not cause deformation of the fixing roller of the fixing device that uses a heat fixing method under any conditions of the image forming apparatus.

(Description of Embodiments) FIG. 1 is a schematic side view showing an embodiment of a fixing device according to the present invention. Since the fixing roller 1 having a heating means, the pressure roller 2, etc. have already been described, their explanation will be omitted.

In this embodiment, a clock plate 3 is installed coaxially with the fixing roller, and a detection means 4 such as a photo interrupter is arranged on this clock plate to detect the entire rotation of the fixing roller. It is assumed that the temperature is detected by a thermistor 18.

FIG. 2 shows the control means of the fixing device of the present invention. After power is turned on to the image forming apparatus, the heater is turned on to heat the fixing roller. The heater remains on until the thermistor detects the entire predetermined temperature, and the timer 19 starts counting by 1 when the heater is turned on. When the fixing roller reaches a predetermined temperature, pre-rotation is started in order to heat the pressure roller 2 and make the temperature uniform, and continues until the predetermined temperature is reached.

Along with this pre-rotation, the rotation of the clock plate 3. It is detected by the detection means 4, and the counter 20 is reset by the signal. As a result, after the previous rotation is completed, the counter starts again, and when a predetermined count is reached, a signal is applied to the controller 21, and a signal is output from the controller 21 to the driver 22 for a predetermined period of time, so that the motor operates at a predetermined time. The fixing roller l also rotates by a predetermined angle. As the fixing roller 1 rotates, a pulse is generated by the clock plate, and the counter 20 is reset.

When the image forming apparatus is in a standby state, the above operations are repeated, and the fixing roller 1 is rotated by a predetermined angle at predetermined time intervals to completely prevent the deformation.

A copy operation is performed and when it is finished.

From this time, the counter of Kara 7/20 is started, and if the fixing roller does not rotate after a predetermined time has elapsed, the motor is activated via the controller 21 in response to a signal from the counter 20, the fixing roller rotates, and the above-mentioned standby occurs. operation is performed.

When an abnormality occurs in the motor drive system and the fixing roller does not rotate, the counter 20 continues counting without being reset, and at a predetermined count, another signal is output to the controller, and an abnormality display is displayed on the operation panel 24. , a warning sound 25 is generated, and the warning sound stops after a predetermined time,
The trouble details are displayed on the panel.

The Maino motor 23 is equipped with an abnormality detection circuit 26, which applies a signal to the controller 21 in the event of a motor abnormality, which activates the counter and timer in the controller', and after a predetermined period of time has elapsed, the SSR is turned on and off. An off signal is sent and the heater is turned off.

In addition, a door open/close detector 28 is provided, and if the user leaves the door of the device open or does not completely close the door, a door open signal will be sent to the controller after a predetermined time, and the heater will be activated in the same way as above. In the above embodiments, the heater was eventually turned off, but it is also possible to easily lower the temperature of the fixing roller to an appropriate value at a corresponding point in time without turning it off. It is easy to understand what can be done. By doing so, it is possible to shorten the warm-up time when using the device again.

In addition, by using an appropriate pressure release mechanism, the pressure contact between the roller pair can be released only when the rotation of the fixing roller is prevented for a certain period of time or more. Release: Unlike the case where the roller □ is released, frequent release operations will not adversely affect the life of the roller □, and its deformation can be prevented.
1. Also, FIG. 3 shows a flowchart outlining the outline of the present invention. In the case of a heat fixing device, this is a flowchart from the time when the start-up state 9 is completed, and in the case of a pressure fixing device, this is a flowchart from the time when the main switch is turned on.

First, check whether the fixing roller pair is rotating or not.
In the case of 1 motor, the rotary body such as a photosensitive drum is detected by an encoder, and in the case of a fixing motor, it is detected by direct load detection (torque), and the determination is made in step 1. As a result, if a rotation is in progress, the system is reset in step 2 and the timer count is started in step 3 only after the rotation has ended. If there is a rotation signal for copying or fixing processing during this counting, the process proceeds to step 1, but if there is no one rotation signal, the count number is compared with a predetermined allowable limit value N in step 5.

As a result, when the count number reaches N, the rotation control means, which is the first deformation prevention means, is activated to move the roller circumferential surface of the pressure contact portion of the roller pair, and to cause the first means to rotate a large number of times. operation is permitted. Here, in step 6, it is determined whether the roller pair has actually rotated, that is, whether the first deformation prevention means has been activated. Normally, the process goes to step 1 and the above-mentioned flow continues, but in the event of an abnormality in which the first means is inoperative, the second deformation prevention means (control in a mode different from the first means: for example, the amount of pressurization, amount of heating, etc. etc.) 1-It is activated in step 7 and at the same time an abnormality display is performed in step 8.

As a result, an abnormality is determined while safety measures have been taken completely, so that deformation of the roller can be prevented until repairs are carried out, thereby extending the service life and maintaining the reliability of the entire device.

Thereafter, when the repair is confirmed in step 9, the process ends and the entire process is reset.

As understood in a flowchart like this.

The present invention can produce excellent effects.

(3) Effects of the invention Since the present invention has the above-described configuration 1 effect, 1
If trouble occurs in the drive system of the fixing device of the image forming apparatus, or if the door is opened or closed incompletely, permanent deformation of the fixing roller can be prevented and operability is improved.

[Brief explanation of drawings]

FIG. 1 is a side view showing an embodiment of the fixing device, FIG. 2 is a block diagram showing its control means, and FIG. 3 is a flow chart showing an outline of the present invention. l... Fixing roller, 2... Pressure roller, 3... Chronograph Figure 1 Figure 2

Claims (3)

[Claims] (1) A pair of fixing rollers, a heating means provided on at least one of the pair of rollers, a driving means for rotating the pair of fixing rollers, and a stopped pressurized state that continues for a predetermined period after the pair of fixing rollers stops rotating. a first deformation prevention means that rotates the pair of rollers to prevent deformation of the rollers when the roller pair is rotated, and is activated when the first deformation prevention means does not prevent the roller deformation; A fixing device comprising a second deformation prevention means different from the fixing means. (2) The fixing device according to claim 1, wherein the second deformation prevention means is means for stopping the heating action of the heating means. (3) The fixing device according to claim 1, wherein the second deformation prevention means is means for lowering a roller temperature control reference value of the heating means.