JPH10268698A - Heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently heat a material to be heated at a high speed without shortening the life of a heating device, by providing a heating body with plural heat generating members and making the heat generating member on the upstream side in the carrying direction of the material to be heated generate heat of higher calorific value than the heat generating member on the downstream side. SOLUTION: This heating device 10 is provided with the heating body 2 fixed and supported, and a film 3 sliding in contact with the heating body 2, and a pressure roller 4 is brought into press-contact with the heating body 2 in a state where the film (a) is put between them so as to form a nip 11 at the carrying path of the material to be heated. The heat generating member 8a on the upstream side in the carrying direction of the material to be heated (recording material P carrying an unfixed powder toner image T) out of two heat generating members provided in the heating body 2 generates the heat at higher calorific value than the heat generating member 8b on the downstream side. Namely, the wavenumber of AC voltage applied to the members 8a and 8b is controlled by a triac so that the current applied amount of the member 8a may be larger. Thus, the material to be heated passing the nip 11 is efficiently heated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film heating type heating device and an image forming apparatus using the heating device as an image fixing device.

[0002]

2. Description of the Related Art Conventionally, as a heating apparatus of the above-mentioned film heating type, a heating element is brought into close contact with one surface of a heat-resistant film and a material to be heated is adhered to the other surface, and the material to be heated travels with the film. 2. Description of the Related Art A heating apparatus of a type in which heat energy of a heating body is applied to a material to be heated via a film is known.
The present applicant has proposed such a heating device in Japanese Patent Application Laid-Open No. 63-313182 and Japanese Patent Application Laid-Open No.
No. 157878, JP-A-4-44075-4408
No. 3 publication. This method is used as a fixing device of an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile, that is, a recording material as a material to be heated according to a target image by using a toner made of a heat-meltable resin. (Electro-fax sheet, electrostatic recording sheet, transfer material sheet, printing paper, etc.) Unfixed image formed on the surface is fixed by applying heat and pressure to use as a device to form permanent fixed image is there.

[0003] Further, for example, it can be used as a device for improving the glossiness, water resistance, durability and the like of a recording material on which an image is formed irrespective of whether it is fixed or not fixed, by modifying the material (particularly the surface) of the recording material.

[0004] For example, a film heating type heating device is used in a fixing device in comparison with various other types and configurations such as a heat roller type, a flash heating type, an oven heating type and a hot plate heating type. In addition, since a heating element or a thin film having a low heat capacity and a rapid rise in temperature can be used, it is possible to reduce power consumption and shorten wait time (improve quick start performance).

[0005]

However, when an attempt is made to increase the conveying speed (process speed) of the material to be heated by using such a heating device, the material to be heated is heated in a shorter time than when the process speed is slow. Must. However, if the temperature of the heating element is increased or the pressing force is increased, the life of the apparatus is shortened.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a heating apparatus capable of heating a material to be heated at high speed and efficiently without shortening the life of the apparatus. To provide. Another object of the present invention is to provide a long-life image forming apparatus that can perform image formation with low power consumption by using such a heating device.

[0007]

In order to achieve the above object, in a heating apparatus according to the present invention, there is provided a heating body fixed and supported, a film which slides in contact with the heating body, and a material to be heated. However, in a heating device for providing heat energy to a material to be heated, the heating device has at least two heat-generating members. In addition, among these heat generating members, the heat generating member on the upstream side in the transport direction of the material to be heated generates heat with a heating value larger than the heat generating member on the downstream side.

At this time, control means for controlling the amount of heat generated by the heat-generating member is provided, and only one of the heat-generating members is controlled to generate heat, and the heat-generating member is controlled on the upstream side in the transport direction with respect to the heat-generating member. Is characterized by the fact that the heat-generating member generates heat with the maximum heat value, and the heat-generating member on the downstream side does not generate heat.

It is preferable that the heat generating member generates heat when energized, and that the amount of heat generated be controlled by controlling the phase of the energized current.

It is preferable that the heat-generating member generates heat when energized, and that the amount of heat generated be controlled by controlling the wave number of the energized current.

Further, in the image forming apparatus according to the present invention, a heating device having the above characteristics is provided as a fixing device.
Image forming means for forming an unfixed toner image on a sheet, conveying means for conveying the sheet carrying the unfixed toner image formed by the image forming means to the fixing device,
Is provided.

[0012]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The material, shape, relative arrangement, and the like are not intended to limit the scope of the present invention only to them unless otherwise specified.

(Embodiment 1) A heating apparatus according to a first embodiment of the present invention will be described with reference to FIGS. FIG.
FIG. 3 is a sectional view of a heating device.

In FIG. 1, a heating device 10 includes a fixedly supported heating element 2 (hereinafter, referred to as a heater) and a film 3 that slides in contact with the heating element. The pressure roller 4 is pressed against and sandwiched therebetween, and forms a nip 11 as a conveyance path for the material to be heated.

The heating element 2 has two heating members 8a and 8b, and is a part of the stay 1. The film 3 is an endless heat-resistant film, and is fitted on the stay 1. The inner peripheral length of the endless heat-resistant film 3 and the outer peripheral length of the stay 1 including the two heating elements 8a and 8b are determined by the film 3
Is made larger, for example, by about 3 mm, so that the film 3 is loosely fitted to the stay 1 with a margin of the circumferential length.

The film 3 has a thickness of 100 μm in order to reduce the heat capacity and improve the quick start property.
m, preferably 50 μm or less and 20 μm or more. The material may be a single layer of PTFE, PFA, FEP, or polyimide, polyamideimide, PEEK, PF
A, FEP or the like coated composite layer film can be used. In the present embodiment, a polyimide film in which the outer peripheral surface is coated with PTFE is used.

The heater 2 is formed on the surface of a substrate made of alumina or the like by screen printing or the like as an exothermic member 8a, 8b with an electric resistance material such as Ag / Pd (silver palladium) to a thickness of about 10 μm and a width of 1 to 5 mm. , And a protective layer 9 is coated thereon with glass, fluororesin, or the like.

The pressure roller 4 is made of a cored bar 5 and a heat-resistant rubber 6 having good releasability, such as silicone rubber, and is driven from the end of the cored bar 5 by driving means (not shown). Thus, the film 3 is also driven to rotate.

In the temperature control according to the present embodiment, the output of the thermistor 19 serving as a temperature detecting means provided on the heater 2 is A / D converted and taken into a CPU 20 serving as a temperature controlling means. (Not shown), the AC voltage applied to the heating members 8a and 8b is controlled by phase control.
This is performed by setting a desired value by wave number control or the like.

That is, when the detected temperature of the thermistor 19 is lower than a predetermined set temperature, the power supply is controlled so that the temperature of the heater 2 rises, and when the temperature is high, the temperature is lowered so that the temperature of the heater 2 is fixed at the time of fixing. Adjust the temperature to keep it constant.

Therefore, a recording material in which an unfixed powder toner image T is carried as a material to be heated, for example, in the nip 11 between the heater 2 and the pressure roller 4 formed through the film 3 as shown in FIG. When the material P is conveyed, the unfixed powder toner image T on the recording material P is melted by applying heat energy and pressure in the nip 11 and fixed on the recording material P.

As described above, the heating device according to the present embodiment can be used as a fixing device of an image forming apparatus such as a copying machine or a laser beam printer. The power supply to the heat generating members 8a and 8b can be started after waiting for the command, and the power supply to the heat generating members 8a and 8b can be stopped during standby for waiting for the print command.

Next, a method of generating heat by the heat generating member, which is a characteristic part of the present invention, will be described.

In the heating device 10 according to the present embodiment, of the two heating members provided on the heating element 2, the heating member 8a on the upstream side in the transport direction of the material to be heated is the heating member 8 on the downstream side.
Heat is generated with a heat value of b or more.

That is, by controlling the wave number of the AC voltage applied to the heating members 8a and 8b by a triac (not shown), the heating member 8a is controlled so that the amount of electricity supplied is larger.

On the other hand, considering that the lifespans of the two heat generating members are substantially the same, it seems that a method of uniformly controlling the heat generation of the heat generating members 8a and 8b may be used. However, in this method, the heat from the heat generating member 8a is effectively used for heating the recording material passing through the nip, but the heat from the heat generating member 8b wastes much. Can be heated more efficiently.

The reason will be described with reference to FIGS.
When only the heat-generating member 8a located on the side of the recording material entering direction is heated, the temperature distribution on the heater surface is represented by the upper graph in FIG. Similarly, the temperature of the surface of the film 3 that comes into contact with the recording material is represented by the lower graph in FIG. This 2
The movement of the peaks in the two graphs is due to the movement of the film 3 during the time required for heat transfer from the inner peripheral surface to the outer peripheral surface of the film 3. Similarly, FIG. 3 shows a temperature distribution when only the heat generating member 8b generates heat. When only the heat generating member 8a generates heat, the temperature of the outer peripheral surface of the film 3 reaches a temperature peak almost at the center of the two heat generating members.
When only the heat-generating member 8b generates heat, the temperature peak is at the end of the heater, and a part of the foot protrudes from the heater substrate. That is, the heat of that part is wasted.

For example, since the fixing of an unfixed toner image is performed by applying both heat and pressure, the contribution of the recording material to the fixing property decreases as the temperature peak moves away from the nip center.

FIG. 4 shows the power supply waveform of this embodiment in the case of controlling the amount of heat generation as described above. When only the heat generating member 8a generates heat (FIG. 4 (a)), the wave number control is performed. When both of the heat generating members 8a and 8b generate heat (FIG. 4B), the heat generating member 8a is fully energized, and the insufficient portion is energized to the heat generating member 8b by wave number control, so that the recording material enters. By increasing the amount of heat generated by the heat generating member 8a located on the side in the direction, the recording material passing through the nip can be efficiently heated.

(Embodiment 2) FIG. 5 shows an electric power waveform to a heating member of a heating device according to a second embodiment of the present invention. In the above-described first embodiment, the control of the amount of heat generated by the heat-generating member is performed by controlling the wave number of energization. In the present embodiment, the control is performed by controlling the phase. Other configurations and operations are the same as those of the first embodiment, and a description thereof will be omitted.

FIG. 5A shows the case where only the heating member 8a is energized, and FIG. 5B shows the case where both the heating members 8a and 8b are energized. In FIG. 5A, only the heating member 8a is phase-controlled, and the heating member 8b is not energized. On the other hand, FIG.
In (b), the heat generating member 8a is fully energized, and the insufficient part is energized to the heat generating member 8b by phase control.

As a power control method, phase control is used when power is supplied only to the heating member 8a located on the recording material entry side. By controlling the phase, the response to disturbance such as load fluctuation is improved.

The wave number control used in the above-described embodiment is a system in which a plurality of half-waves of a power supply are used as one unit and the power is controlled by the number of half-waves to be supplied. Six levels of power control from 0 half-wave energization (no energization) to 5 half-wave energization (full energization) are possible, and if 2 half-waves out of 5 half-waves are energized, 2/5 = 40% It becomes the energization ratio. If the half-wave number of one unit is increased, the energization ratio can be controlled more finely. However, since the energization ratio for one unit cannot be changed to another energization ratio, the response is high.
Is reduced. For example, if the power supply frequency is 50 Hz and one unit has 20 half-waves, control can be performed only 50 × 2/20 = 5 times per second. On the other hand, in the phase control used in the present embodiment, one control is completed within one half-wave of the power supply.
In the case of z, control can be performed 50 × 2 = 100 times per second, and the response to disturbance can be improved in addition to the advantages described in the first embodiment.

In this embodiment, the case where the heating member 8b is driven only by the phase control has been described. However, it is needless to say that a combination with the wave number control described in the first embodiment may be used.

(Embodiment 3) This embodiment shows that the present invention can be applied to a case where three or more heating members are provided.

Here, a case in which the number of heat generating members is four will be described. The four heat generating members are denoted by 8a, 8b, 8C, and 8d in order from the entering direction of the material to be heated. When power is sufficient with only the heating member 8a, power is supplied only to the heating member 8a by phase control or wave number control. If the power is insufficient with only the heating member 8a, the heating member 8a is fully energized and the heating member 8b is energized by phase control or wave number control. If the power is not enough even at the heat generating members 8a and 8b, the power is similarly sequentially turned off.
Power is supplied in the order of c and 8d. At this time, power control is performed using only phase control or wave number control for only the most downstream heating member among the heating members that are energized. That is, the heating member upstream of the heating member that controls the power is fully energized and generates heat at the maximum heat generation amount, while the heating member downstream is not energized and does not generate heat.

FIG. 6 shows a case where the number of the heating members 8 is four.
A and 8b represent the state of full power supply, the heating member 8c represents the phase control, and the power supply to the heating member 8d is not supplied with power.

Even when the number of heat generating members is three or more, by heating the entire heating body while controlling the amount of heat generated in this manner, more effective heating properties can be obtained as in the above-described embodiment.

(Other Embodiments) FIG. 7 is a schematic configuration diagram showing an example of an image forming apparatus (laser beam printer) in which the heating device of the film heating type shown in the above embodiment is incorporated as a fixing device. is there.

Reference numeral 21 denotes an organic photosensitive drum serving as an image carrier, 22 denotes a charging roller serving as a charging member, 23
Is a laser exposure device, 24 is a developing device including a developing sleeve, a developing blade, and a one-component magnetic toner, 25 is a cleaning blade, 26 is a transfer roller, and 27 is a heater unit including a heating device according to the present invention. By the operation of the main unit described above, the paper feed roller 29
An image is formed on the transfer material 30 fed by the above-described method using a well-known electrophotographic process, and is output.

When the heating device according to the above-described embodiment is applied to such an image forming apparatus, a toner image on a transfer material can be effectively fixed in a process of image formation, and the process speed is improved. be able to.

[0042]

As described above, according to the present invention, the heating element has at least two heat-generating members, and among these heat-generating members, the heat-generating member on the upstream side in the conveying direction of the material to be heated is the downstream one. Since heat is generated with a heat generation amount equal to or larger than the heat generation member on the side, the material to be heated can be efficiently heated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration sectional view of a heating device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a temperature distribution on an inner surface of a film and an outer surface of the film when only a heating member 8a of the heating device according to the first embodiment of the present invention is energized.

FIG. 3 is a diagram showing a temperature distribution on the inner surface of the film and the outer surface of the film when power is supplied only to the heat generating member 8b of the heating device according to the first embodiment of the present invention.

FIG. 4 is a diagram showing an example of a power supply power waveform of the heating device according to the first embodiment of the present invention.

FIG. 5 is a diagram showing an example of a power supply power waveform of a heating device according to a second embodiment of the present invention.

FIG. 6 is a view showing an example of a power supply waveform of a heating device according to a third embodiment of the present invention.

FIG. 7 is a schematic sectional view of an image forming apparatus using the heating device of the present invention as a fixing device.

[Explanation of symbols]

 Reference Signs List 1 stay 2 heating element 3 film 4 pressure roller 5 pressure roller core 6 heat-resistant rubber 8 (8a, 8b) heating member 19 thermistor 20 CPU T toner P recording material

Claims (5)

[Claims] 1. A fixedly supported heating element, a film that slides in contact with the heating element, and a conveyance path through which the material to be heated is conveyed together with the film while being in close contact with the heating element via the film. In the heating device for applying thermal energy to the material to be heated, the heating element has at least two heat generating members, and among those heat generating members, the heat generating member on the upstream side in the transport direction of the material to be heated is downstream. A heating device that generates heat with a heating value equal to or greater than the heating member on the side. 2. A control means for controlling the amount of heat generated by the heat generating member, wherein only one of the heat generating members controls the heat generated by the heat generating member, and the heat generated upstream of the controlled heat generating member in the transport direction. The heating device according to claim 1, wherein the member generates heat at a maximum heat value, and the downstream heat generating member does not generate heat. 3. The heating device according to claim 1, wherein the heat generating member generates heat when energized, and the amount of heat generated is controlled by phase control of a current to be energized. 4. The heating apparatus according to claim 1, wherein the heat generating member generates heat when energized, and the amount of generated heat is controlled by controlling the wave number of the energized current. 5. An image forming means comprising the heating device according to claim 1 as a fixing device, for forming an unfixed toner image on a sheet, and carrying the unfixed toner image. An image forming apparatus comprising: a conveying unit configured to convey a sheet to the fixing device.