JPH02131269A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent a transfer material from smoking by detecting a driven rotary member which contacts the back surface of the transfer material being slowed down or stopped by a rotation detecting means and stopping feeding electricity to a heat generation body momentarily according to its detection signal. CONSTITUTION:At least one of pressure members which contacts the back surface of the transfer material is the driven rotary member and this device is equipped with the rotation detecting means 7 which detects the rotation of the driven rotary member and an electric feeding stopping means 8 which stops feeding electricity to the heat generation body 21 according to the signal of the rotation detecting means 7. Thus, the rotation detecting means 7 detects the driven rotary member which contacts the back surface of the transfer material being slowed down or stopped and the electric feeding to the heat generating body 21 is stopped momentarily according to the detection signal, so the transfer material is prevented from smoking.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an image forming apparatus that forms an image on a transfer material using heat-melting toner and heat-fixes the image. [Technology] Conventionally, the fixing device used in this type of device uses a heating roller maintained at a predetermined temperature and a pressure roller that has an elastic layer and presses against the heating roller to remove unfixed toner. A roller fixing method is often used in which the transfer material on which an image is formed is supported and conveyed while being heated.However, in the roller fixing method, firstly, it is necessary to maintain the heating roller at an optimal temperature; Second, since it is necessary to heat the transfer material as well, the heat capacity of the heating roller increases. Third, as a result, the energy necessary for fixing increases, and unnecessary heat is generated, causing damage to the inside of the machine.
There are some drawbacks, such as a temperature of 7 degrees. Recently, in order to solve the above-mentioned deficiencies in the roller fixing method, the transfer material is brought into close contact with a heating element via a fixing film that moves at the same speed as the conveyance speed of the transfer material, and pulse heating is applied to the transfer material. A film fixing method has been proposed that heats and melts unfixed toner images to fix them. [Problems to be Solved by the Invention] However, in the above-mentioned film fixing method, the temperature of the heating element instantly rises to 300°C or higher, so if the conveyance speed of the transfer material decreases or stops within the fixing device, the temperature of the heating element instantly increases. There is a problem in that the transfer material may emit smoke if the electricity to the heating element is not stopped. The present invention attempts to solve these problems. In other words, the present invention provides an image forming method that instantly stops energization of the heating element when the conveyance speed of the transfer material decreases or stops in the fixing device, thereby preventing the transfer material from emitting smoke. The purpose is to provide equipment. [Means for Solving the Problems] In order to achieve the above object, the present invention uses a pressurized conveying means that rotates and drives an unfixed toner image on a transfer material while pressing it against a heating body. The image forming apparatus has a fixing device that brings the transfer material into close contact with the heating body through a fixing film that moves at the same speed as the conveying speed of the transfer material, and fixes the transfer material by pulse heating. At least one of the pressure members is a driven rotating member, and further includes rotation detection means for detecting rotation of the driven rotation member, and energization stopping for stopping energization to the heating body according to the rotation detection means. and the means to do so. [Operation] According to the present invention, the rotation detecting means detects that the driven rotating member in contact with the back side of the transfer material has slowed down or has stopped, and instantaneously stops energizing the heating element in accordance with the detection signal. ．． [Embodiment] Fig. 1 is a block diagram showing a first embodiment of the wooden invention, and Fig. 2 shows an outline of its fixing device. In FIG. 2, 20 is a fixing device, and 21 is a heating element. The heating element 21 includes a heat-resistant and electrically insulating base material such as alumina, or a composite material containing the same, and a linear or band-shaped heat generating layer 28 made of, for example, Ta2H on the lower surface of the base material. Furthermore, lfTa205 is formed on its surface as a sliding protective layer. heating element 2
The lower surface of l is smooth, and the front and rear ends are rounded to enable sliding on the fixing film 23. The fixing film 23 is made of PET as a base material, heat-resistant treated, and has a thickness of about 6 m, for example, and is wound around a feed shaft 24 so as to be feedable in the direction of arrow a. The fixing film 23 comes into contact with the surface of the heating element 2l, and is wound onto a winding shaft 27 via a separation conveyance roller 26 having a large curvature. The heating layer 28 of the heating element 21 has a small heat capacity, and each time it is energized in a pulsed manner, the temperature rises instantaneously to around 300°C. By detecting the leading and trailing ends of a transfer material P such as a transfer paper using a transfer paper detection lever 25 and a transfer sensor 29, the heat generating layer 28 is energized at the appropriate timing when necessary. At this time, energization to the heating element 21 may be controlled by detecting the position of the transfer material using a paper feed sensor or the like of the image forming apparatus. On the other hand, the pressure roller 22 has an elastic layer made of silicone rubber or the like on a core made of metal or the like, and is driven by the frictional force between the transfer material P and the fixing film 23, and is guided by the conveyance guide 10. The transfer material P having the unfixed toner image T is brought into close contact with the heat generating layer 28 of the heat generating element 21 via the fixing film 23 that moves at the same speed as the transfer material P. Further, a tachometer (not shown) such as a rotary encoder is provided on the shaft of the pressure roller 22 to detect the rotational speed of the pressure roller 22.

Since the pressure roller 22 rotates as a result of the transfer material P and the fixing film 23, when the transfer material P stops, the pressure roller 23 also stops. In FIG. 2, 30 is a fixing film sensor, 32
is a guide, and 33 is a pack attachment roller.

Next, Fig. 1 will be explained. In Fig. 1, 2
1 is a heating element, 2 is a temperature detection element, and 3 is a power source for supplying power to the heating element 21. 4 is a temperature control circuit which operates the second switch 6 to control the temperature of the heating element 2l. 1st
Switch 5 is in the ON state under normal conditions. When the rotation stop control circuit 8 receives the signal from the driven rotating member detection stage 7 and determines that the transfer material is stopped within the fixing device, the rotation stop judgment circuit 8 sends an OFF signal to the first switch 5. , and stops the power supply to the heating element 21. Figure 3 shows the rotation stop detection means. In FIG. 3, 34 is a rotary encoder, 35 is an f-v converter, 36 is a voltage comparator, and 37 is a transistor. That is, the pulse output of the rotary encoder 34 is
-V converter 35 and convert it into a voltage value. Then, the output voltage of the f-v converter 35 and Vr are determined by the voltage comparator 36.
ef are compared, and the first switch 5 is operated according to the comparison value. A transistor 37 is provided for driving the switch 5. When the transfer material is not stopped, rotary encoder 3
4 outputs pulses with a constant period. At this time, when the output value of the f-v converter 35 is greater than V ref, the transistor 37 turns on the ONL and the first switch, such as a non-contact switching circuit such as a relay circuit or FET. Then, when the transfer material stops or its speed slows down and the output frequency of the rotary encoder 34 decreases, f-v
When the output voltage of the converter 35 also decreases and becomes smaller than Vref, the transistor 37 is turned off, disconnecting the first switch and stopping the current supply. Figure 4 shows the relationship between points A, B, and C in Figure 3. In this way, by stopping the power supply to the heating element 21 when the transfer material P stops, it is possible to prevent one location of the transfer material P from receiving high temperature heat, thereby preventing fires. It also protects the fixing film 23 when it is attached to the transfer material P and moving. FIG. 5 is a block diagram showing a second embodiment of the present invention. In this second embodiment, the driven rotating member stop detection means 7 (
The output signal of the rotation stop judgment circuit) is input to the temperature control circuit 4, which judges the output of the detection means 7 and stops the output signal to the switch 6. Furthermore, as another embodiment of the present invention, the backup roller 33 in FIG. 2 may be a pressure driven roller, a rotation detecting member may be provided on the axis of the roller 33, and the same operation as described above may be carried out. ．． [Effects of the Invention] As described above, according to the present invention, the rotation detecting means detects that the driven rotating member in contact with the back surface of the transfer material has slowed down or has stopped, and the heating member is activated according to the detection signal. Since the energization can be stopped instantaneously, smoke generation of the transfer material can be prevented, and a safer image forming apparatus can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the first embodiment of the present invention. FIG. 2 is a cross-sectional elevational view of the fixing device. FIG. 3 is an explanatory diagram of a circuit for stopping power supply to the heating element. 3 is an explanatory diagram of signals at each point, and FIG. 5 is a block diagram of the second embodiment of the present invention. 4... Temperature control circuit 5.6... Switch 7...
- Followed rotating member detection means 8...Rotation stop judgment circuit 20...Fixing device 21...
-Heating element 22...Pressure roller 23...Fixing film 28...Heating layer 34...Rotary encoder 35...F-V conversion unit 36...Voltage comparator 37
...Transistor C Fig. 3 Fig. 4 Fig. 2

Claims (1)

[Scope of Claims] 1. An unfixed toner image on a transfer material is transferred through a fixing film that moves at the same speed as the transfer speed of the transfer material using a pressurized conveying means that rotates and presses the unfixed toner image against a heating body. The image forming apparatus includes a fixing device that brings the transfer material into close contact with the heating body and performs pulse heating to fix the transfer material, wherein at least one of the pressure members in contact with the back surface of the transfer material is driven to rotate. An image forming apparatus comprising a rotation detecting means for detecting rotation of the driven rotating member, and an energization stopping means for stopping energization to the heating body in accordance with the rotation detecting means. .