JP2001100558A - Heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating device and an image forming device capable of preventing the temperature rise of a paper non-passing part by preparing a plurality of heating elements having different lengths and selectively using the heating element having a length in accordance with the width size of transfer material; and to realize the effective utilization of the base plate by making the electrode of at least one part of the plurality of heating elements provided to be independently driven on an insulating substrate common and to make a connector connected to the end of the substrate common by making the number of electrodes provided at both ends of the substrate identical in the heating device and the image forming device. SOLUTION: In this heating device equipped with an insulating substrate and a heating body constituted of a plurality of heating elements formed in the direction orthogonal to the carrying direction of recording material on either surface of the insulating substrate, at least one of the plurality of heating elements is set so that the length of its heat generating part is made different from those of other heating elements.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a heating apparatus and an image forming apparatus.

[0002] For example, the present invention relates to a heat source of a heat fixing device for fixing a toner image formed by an electrophotographic process onto transfer paper. In particular, as a heating means, a plurality of independently drivable heating elements are provided on the same surface. The present invention relates to a thermal fixing device using a ceramic surface heater system.

[0003]

2. Description of the Related Art A conventional image forming apparatus using an electrophotographic process will be described.

A heat fixing device of an image forming apparatus fixes an unfixed image (toner image) formed on transfer paper by transfer means such as an electrophotographic process on transfer paper, and uses a halogen heater as a heat source. A heat fixing device of a heat roller type and a heat fixing device of a film heating type using a ceramic surface heater as a heat source are used.

In general, a ceramic surface heater has one or a single folded heating element formed on a first surface of an insulating substrate (such as AlN or Al ₂ O ₃ ), and one power supply. Power is supplied by the means. The power supply means detects the temperature of the heater by a temperature detection element arranged on or near the ceramic surface heater, and is controlled by the power control means.

The heating element on the insulating substrate is formed so as to uniformly generate heat in a region substantially equal to the maximum sheet passing width that the image forming apparatus can pass.

In such an image forming apparatus having a fixing means using a surface heater as a heat source, the heating element has a length corresponding to the maximum sheet passing width or a certain paper type (for example, A4 or B4).
4 standard recording paper, hereinafter referred to as normal size paper)
When the recording paper (small-size paper) having a paper passing width shorter than the length of the heating element is passed, the heat-generating area and the non-paper-passing area have a paper passing area. (Hereinafter, referred to as a non-paper passing portion temperature increase).

In this non-sheet passing area, if the temperature is too high, surrounding members such as a member supporting the surface heater may be damaged. Conventionally, in order to reduce this effect, the throughput of the transfer material has been reduced by detecting the temperature of the end portion or according to the width size of the transfer material.

[0009]

Therefore, in the present invention, a plurality of heating elements having different lengths are provided, and a heating element having a length corresponding to the width of the transfer material is selectively used to raise the temperature of the non-sheet passing portion. It is an object of the present invention to provide a heating apparatus and an image forming apparatus which can reduce the heating.

Further, in the heating device and the image forming apparatus, at least a part of electrodes of a plurality of heating elements provided so as to be independently driven on an insulating substrate is used in common, thereby effectively utilizing the substrate. Further, it is another object of the present invention to make the number of electrodes provided at both ends of the substrate the same and to use a common connector connected to the ends.

[0011]

According to the present invention, there is provided a heating apparatus and an image forming apparatus having the following constitutions.

[1] A heating apparatus including an insulating substrate and a heating element composed of a plurality of heating elements formed on one surface of the insulating substrate in a direction orthogonal to a recording material conveying direction. A heating device, wherein at least one of the plurality of heating elements has a different length of a heating portion as compared with the other heating elements.

[2] The heating device according to [1], further comprising a power supply unit capable of supplying power to the plurality of heating elements independently.

[3] The heating device according to [1] or [2], wherein the length of the heat generating portion is set in accordance with the width of the recording material that can be passed.

[4] The method according to [1], [2] or [3], wherein, among the plurality of heating elements, two or more heating elements having the length of the longest heating part are provided. Heating equipment.

[5]: Among the plurality of heating elements, the heating element having a longer heating portion is disposed on the upstream side with respect to the recording material conveying direction [1] to [1]. The heating device according to any one of [4].

[6]: A heating element having a plurality of heating elements having the same length of the heating section, and having a heating section shorter than the length of the heating section of the heating section, has a length equal to the length of the heating section. The heating device according to any one of [1] to [4], wherein a plurality of heating elements having the same length are arranged at intermediate positions in the recording material conveyance direction.

[7] The heating device according to any one of [1] to [6], wherein the width of the heating element is wider as the length of the heating section is longer.

[8]: The ratio of the heating element width for each heating element length obtained by summing the widths of the heating elements having the same length of the heating element is the ratio of the length of the heating element or the length of the heating element. Any one of [1] to [7], wherein the ratio is equal to the ratio of squares
The heating device according to Item.

[0020]

[9]: At the first end of the heating element formed with an even number of the heating elements in a direction orthogonal to the recording material conveyance direction, connected to the first heating element from the upstream side in the recording material conveyance direction. Connected to an even numbered heating element from the upstream side in the recording material conveyance direction, a common electrode connected to a heating element adjacent to the downstream side of the heating element, and a heating element positioned at the most downstream side. And a second end located opposite to the first end of the heating element, the odd-numbered heating elements from the upstream side in the recording material transport direction and the heating elements Any one of [1] to [8], characterized by having a common electrode connected to a heating element adjacent on the downstream side.
The heating device according to Item.

[10]: The first heat generation from the upstream side in the recording material conveyance direction at the first end of the heating body in which the plurality of heating elements are formed in an odd number in the direction orthogonal to the recording material conveyance direction. An electrode connected to the heating element, and a common electrode connected to an even-numbered heating element from the upstream side in the recording material conveyance direction and a heating element adjacent to the downstream side of the heating element. At a second end opposite to the first end of the heating element, the heating element is connected to an odd-numbered heating element from the upstream side in the recording material conveyance direction and a heating element adjacent to the downstream side of the heating element. The heating device according to any one of [1] to [8], further comprising a common electrode and an electrode connected to a heating element located on the most downstream side.

[11]: Any one of [1] to [10]
A heating device, wherein the insulating substrate constituting the heating device according to the above item is Al ₂ O ₃ or AlN.

[12]: A film that slides on the heating element, and a pressure roller that forms a nip with the film, wherein the material to be heated is heated by heat from heating means via the film. The heating device according to any one of [1] to [11], wherein an insulating substrate surface on which the heating element is formed is located on a side opposite to a nip surface.

[13]: In an image forming apparatus having an image forming means for forming an image on a recording material and an image heating means for heating the image on the recording material, the above-mentioned [1] is used as the image heating means. [12] An image forming apparatus, comprising the heating device according to any one of [11] and [12].

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A description will be given below with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram of an image forming apparatus using an electrophotographic process, and shows, for example, the case of a laser printer.

The laser printer main body 101 (hereinafter referred to as main body 1)
01) is a cassette 10 for storing recording paper (recording material) S
2, a cassette presence / absence sensor 103 for detecting the presence or absence of the recording paper S in the cassette 102, and the recording paper S in the cassette 102
Cassette size sensor 104 (comprising a plurality of microswitches) for detecting the size of
A paper feed roller 105 that feeds out the recording paper S is provided. The recording paper S is located downstream of the paper feed roller 105.
Are provided synchronously.

An image forming section 108 for forming a toner image on the recording paper S based on the laser beam from the laser scanner section 107 is provided downstream of the pair of registration rollers 106.

Further, a fixing device R for thermally fixing the toner image formed on the recording paper S is provided downstream of the image forming unit 108, and a conveyance state of a paper discharge unit is provided downstream of the fixing device R. A paper ejection sensor 110 for detecting, a paper ejection roller 111 for ejecting the recording paper S, and a loading tray 112 for loading the recording paper S on which recording is completed are provided. The conveyance reference of the recording paper S is set to be a length in a direction perpendicular to a conveyance direction of the recording paper S in the image forming apparatus, that is, a center with respect to the width of the recording paper S.

The laser scanner 107 includes a laser unit 113 for emitting a laser beam modulated based on an image signal (image signal VDO) sent from an external device 131 described later, and a laser beam from the laser unit 113. Are constituted by a polygon motor 114 for scanning a photosensitive drum 117 to be described later, an imaging lens 115, a return mirror 116, and the like.

Reference numeral 108 denotes an image forming unit, which is a photosensitive drum 117, a primary charging roller 119, a developing unit 120, and a transfer charging roller 12 necessary for a known electrophotographic process.
1, a cleaner 122 and the like. The fixing device R includes a fixing film 61, a pressure roller 63, a ceramic surface heater 24 provided inside the fixing film, and a thermistor 21 for detecting the surface temperature of the ceramic surface heater.

The main motor 123 applies a driving force to the sheet feeding roller 105 via a sheet feeding roller clutch 124 and a driving force to the pair of registration rollers 106 via a registration roller 125, and further includes a photosensitive drum 117. Each unit of the image forming unit 108, the fixing device R, the paper discharge roller 111
It also gives the driving force.

Reference numeral 126 denotes an engine controller, which controls the electrophotographic process by the laser scanner 107, the image forming unit 108, and the fixing device R, and controls the conveyance of the recording paper in the main body 101.

Reference numeral 127 denotes a video controller, which is a general-purpose interface (such as Centronics or RS232C) with an external device 131 such as a personal computer.
The image information transmitted from the general-purpose interface is expanded into bit data, and the bit data is transmitted to the engine controller 126 as a VDO signal.

FIG. 2 shows a drive and control circuit of the ceramic surface heater according to the present invention. Reference numeral 1 denotes an AC power supply for connecting the image forming apparatus.
Heating element 32 or heating element 3 constituting ceramic surface emitting heater 24 by supplying to heating element 32 or heating element 33 of ceramic surface emitting heater 24 via C filter 2.
3 is exothermic.

The supply of power to the heating element 32 is controlled by a triac 4 to be energized or cut off. Resistance 5, 6
Is a bias resistor for the triac 4, and the phototriac coupler 7 is a device for separating primary and secondary. The triac 4 is turned on by energizing the light emitting diode of the phototriac coupler 7. The resistor 8 is a resistor for limiting the current of the phototriac coupler 7 and is turned on / off by the transistor 9. The transistor 9 operates according to the ON1 signal from the engine controller 11 via the resistor 10. The supply of electric power to the other heating element 33 is controlled by the triac 13 to be energized or cut off. Resistance 1
Reference numerals 4 and 15 denote bias resistors for the triac 13, and the phototriac coupler 16 is a device for ensuring a creepage distance between the primary and the secondary. The triac 13 is turned on by energizing the light emitting diode of the phototriac coupler 16. The resistor 17 is a resistor for limiting the current of the phototriac coupler 16 and is turned on / off by the transistor 18. The transistor 18 is connected to the engine controller 1 via a resistor 19.
1 operates according to the ON2 signal.

Further, an AC power supply 1 is connected via an AC filter 2.
Is input to the zero-cross detection circuit 12. The zero-crossing detection circuit notifies the engine controller 11 that the commercial power supply voltage is lower than a certain threshold value as a pulse signal. Hereinafter, the engine controller 1
1 is called a ZEROX signal.

The engine controller 11 detects the edge of the pulse of the ZEROX signal and turns ON / OFF the triac 4 or 13 by phase control or wave number control.

Reference numeral 21 denotes a temperature detecting element for detecting the temperature of the ceramic surface heater 24 on which the heating elements 32 and 20 are formed, for example, a thermistor temperature sensing element. Bodies 32 and 20
It is arranged via an insulator having a withstand voltage so that an insulation distance can be secured. This temperature detecting element 21
The temperature detected by the engine controller 1 is detected as a partial pressure between the resistor 22 and the temperature detecting element 21.
1 is input as an TH signal as an A / D signal. The temperature of the ceramic surface heater 24 is monitored by the engine controller 11 as a TH signal.
The power to be supplied to the heating element 32 or 20 constituting the ceramic surface heater 24 is calculated by comparing with the set temperature of the ceramic surface heater 24 set inside the It is converted into a phase angle (phase control) or a wave number (wave number control).
An N1 signal or an ON2 signal is sent to the transistor 18.

If the means for supplying and controlling electric power to the heating element 32 or 20 fails and the heating element 32 or 20 goes out of control, the overheating prevention means 23 is used as one means for preventing overheating. Are disposed on the ceramic surface heater 24. The excessive temperature rise prevention means 23 is, for example, a temperature fuse or a thermoswitch. As a result of the failure of the power supply control means, the heating element 32 or 20 goes out of control, and
Exceeds a predetermined temperature, the excessive temperature rise prevention means 23
The state becomes EN, and the power supply to the heating elements 32 and 20 is cut off.

Next, FIG. 3 schematically shows the positional relationship among the ceramic surface heater 24, the temperature detecting element 21, and the excessive temperature rise prevention means 23. FIG. 3A is a cross-sectional view of a ceramic surface heater, FIG. 3B shows a surface on which heating elements 32 and 33 are formed, and FIG. A surface opposite to the illustrated surface is shown.

The ceramic surface heater 24 is made of SiC, A
a ceramic insulating substrate 31 such as 1N or Al ₂ O ₃ ,
Heating elements 32 and 33 are formed on the surface of the insulating substrate 31 by paste printing or the like, and a protective layer 34 made of glass or the like protects the two heating elements. Protective layer 34
A temperature detecting element 21 for detecting the temperature of the ceramic surface heater 24 is provided thereon.

The heating element 32 includes a portion 32a that generates heat when power is supplied, and a conductive portion 3 connected to the heating portion 32a.
2b and an electrode part 32 to which power is supplied via a connector
c, 32d.

The heating element 33 includes a portion 33a that generates heat when power is supplied, and a conductive portion 3 connected to the heating portion 33a.
3b and an electrode portion 32 to which power is supplied via a connector
c, 33d.

The electrode portion 32c includes a heating element 32 and a heating element 33.
, And serves as a common electrode for the heating element 32 and the heating element 33.

The common electrode 32 c is connected to the terminal on the HOT side of the AC power supply 1 via the overheating prevention means 23. The electrode section 32d is connected to the triac 4 that controls the heating element 32, and the electrode section 33d is connected to the triac 13 that controls the heating element 33, and is connected to the Neutral terminal of the AC power supply 1.

The ceramic surface heater 24 is supported by a film guide 62 as shown in FIG. 61 is a cylindrical fixing film made of a heat-resistant material,
The ceramic surface heater 24 is externally fitted to a film guide 62 supported on the lower surface side. Then, the ceramic surface heater 24 on the lower surface of the film guide 62 and the elastic pressing roller 63 as a pressing member are sandwiched by the fixing film 61 with a predetermined pressing force against the elasticity of the elastic pressing roller 63. A fixing nip portion N having a predetermined width as a heating portion is formed by pressing. Here, as shown in FIG. 4A, even if the heating elements 32 and 33 are on the side opposite to the nip portion, the heating element is located on the nip side as shown in FIG. 4B. It doesn't matter. Hereinafter, the heating element 3 will be described.
The case where the film guides 2 and 33 are supported by the film guide 62 so as to be located on the opposite side to the nip portion N will be described.

In FIG. 3, the heat generating portion 32a of the heat generating body 32
Is the length L1, which corresponds to the maximum recording paper width that can be passed, and the length L2 of the heating portion 33a of the heating element 33 corresponds to the small-size recording paper width. When a recording sheet having a recording sheet width larger than the length L2 of the heat generating portion 33a is passed, O
The triac 4 is controlled by the N1 signal, and the heating element 32 is controlled.
To control the energization of The triac 13 that controls the energization of the heating element 33 is kept off. When a recording sheet having a width equal to or smaller than the length L2 of the heat generating portion 33a is passed, the triac 13 is controlled by the ON2 signal sent from the engine controller 11 so that the power to the heat generating element 33 is supplied. Control. The triac 4, which controls the energization of the heating element 32, remains OFF. By such control, it is possible to suppress a temperature rise in a non-sheet passing area that occurs when a small size sheet is passed.

In this embodiment, the excessive temperature rise prevention means 23 and the temperature detecting element 21 are used as a reference for transporting the recording paper,
2a and the center a1 in the longitudinal direction of the heat generating portion 33a,
It is located at a position symmetrical to the left and right and inside the minimum width of the recording paper that can be passed.

With the above configuration, fixing can be performed according to the width of the recording paper that has been passed, and the temperature rise of the non-paper passing portion can be prevented. In addition, a part of the electrodes can be used in common, so that the substrate can be effectively used, and the size and cost of the device can be reduced.

Further, since the temperature detecting element 21 and the excessive temperature rise preventing means 23 can be arranged at a distance from each other, the primary and secondary
A sufficient distance can be taken to ensure insulation between the next. Further, since the temperature detecting element 21 and the excessive temperature rise prevention means 23 are arranged at the same temperature position, it is possible to improve the precision of the excessive temperature rise prevention control when the temperature of the fixing device R is excessively high. . Further, since the temperature detecting element and the excessive temperature rise prevention means are arranged inside the minimum sheet passing width, even if any recording paper is passed, the small size paper passing is not affected by the temperature rise in the non-sheet passing area. By detecting the temperature in the paper passing area, the accuracy of temperature control of the fixing device can be improved.

<Second Embodiment> FIGS. 5 and 6 show a second embodiment.

In this embodiment, a description of the same points as in the first embodiment will be omitted.

FIG. 5 shows a drive and control circuit of the ceramic heater in this embodiment. Reference numeral 1 denotes an AC power supply for connecting the present image forming apparatus.
Heating element 3 of ceramic heater 24 via filter 2;
By supplying the heat to the heating element 20 or the heating element 40, the heating element 3, the heating element 20, or the heating element 40 constituting the ceramic heater 24 is heated.

Electric power is supplied to the heating element 40 by the triac 41, similarly to the heating elements 3 and 20. The resistors 42 and 43 are bias resistors for the triac 41, and the phototriac coupler 44 is a device for securing insulation between the primary and the secondary. The triac 41 is turned on by energizing the light emitting diode of the phototriac coupler 44. Resistance 45
Is a resistor for limiting the current of the phototriac coupler 44, and the current is turned on / off by the transistor 46. The transistor 46 operates according to the ON3 signal from the engine controller 11 via the resistor 47. The engine controller 11 detects the edge of the pulse of the ZEROX signal and turns ON / OFF the triac 4, 13 or 41 by phase control or wave number control.

Reference numeral 21 denotes a temperature detecting element for detecting the temperature of the ceramic heater 24 on which the heating elements 3, 20 and 40 are formed, for example, a thermistor temperature sensing element. , 20 and 40
It is arranged via an insulator having a withstand voltage so that insulation can be ensured. The temperature of the ceramic heater 24 is monitored by the engine controller 11 as a TH signal, and is compared with a set temperature of the ceramic heater 24 set inside the engine controller 11 to thereby generate the heating elements 3, 20 constituting the ceramic heater 24. Alternatively, the power to be supplied to the power 40 is calculated and converted into a phase angle (phase control) or a wave number (wave number control) corresponding to the supplied power, and the engine controller 11 sends the ON1 signal to the transistor 9 or the transistor 18 and an ON3 signal to the transistor 46.

Power is supplied to the heating elements 3, 20, or 40,
If the control means breaks down and the heating element 3, 20, or 40 goes out of control, an overheating prevention means 23 is provided on the ceramic heater 24 as a means for preventing overheating. The excessive temperature rise prevention means 23 is, for example, a temperature fuse or a thermoswitch. When the heating element 3 or 20 or 40 reaches a thermal runaway due to a failure of the power supply control means and the overheating prevention means 23 becomes a predetermined temperature or more, the overheating prevention means 2
3 becomes OPEN, and the power supply to the heating elements 3, 20, and 40 is cut off.

Next, an outline of the ceramic heater 24 is shown in FIG. FIG. 6A is a cross-sectional view of the ceramic surface heater, FIG. 6B shows a surface on which the heating elements 3, 20, and 40 are formed, and FIG. )
Shows a surface opposite to the surface shown by.

The ceramic surface heater 24 is made of SiC, A
a ceramic insulating substrate 31 such as 1N or Al ₂ O ₃ ,
The heating elements 3, 20, and 40 are formed on the surface of the insulating substrate 31 by paste printing or the like, and a protective layer made of glass or the like protects the three heating elements.

The heating element 40 includes a portion 40a that generates heat when electric power is supplied, and a conductive portion 4 connected to the heating portion 40a.
0b and an electrode portion 32 to which power is supplied via a connector
c, 40d.

The pole part 32c is connected to all of the heating elements 32, 33, and 40, and the heating parts 32a, 33a, and 40
a common electrode.

The HOT of the AC power supply 1 is connected to the common electrode 32c.
It is connected from the side terminal via the excessive temperature rise prevention means 23. The electrode section 40d is connected to a triac 41 that controls the heating element 40, and is connected to the Neutral terminal of the AC power supply 1 together with the triacs 4 and 13.

In FIG. 6, the heat generating portion 32a of the heat generating body 32
The length of the heat generating portion 40a of the heat generating member 40 is L1, which corresponds to the maximum width of the recording paper that can be passed. It corresponds to the paper width. When a recording sheet whose recording sheet width is larger than the length L2 of the heat generating portion 33a is passed, the triacs 4 and 41 are controlled by the ON1 signal and the ON3 signal sent from the engine controller 11, and the heat generating elements 32 and 41 are controlled.
The energization to 40 is controlled. The triac 13 that controls the energization of the heating element 33 is kept off. When a recording sheet whose recording sheet width is equal to or smaller than the length L2 of the heat generating portion 33a is passed, the triac 13 is controlled by the ON2 signal sent from the engine controller 11, and
The power supply to the heating element 33 is controlled. The triacs 4 and 41 for controlling the energization of the heating elements 32 and 40 remain OFF. By such control, it is possible to suppress a temperature rise in a non-sheet passing area that occurs when a small size sheet is passed.

Excessive temperature rise prevention means 23 and temperature detecting element 21
Is a position symmetrical with respect to the recording paper conveyance reference, that is, the center in the longitudinal direction of the heat generating portions 32a, 33a, and 40a, and is disposed at a position inside the minimum recording paper width capable of passing the paper. ing.

When a recording sheet having a recording sheet width larger than 12 is passed, the heat generation ratio between the heating elements 32 and 40 is controlled to cause the heating elements 32 and 40 to generate heat. By setting the amount of heat generated when the number of heating elements of the length L1 is one and the total amount of heat generated by the two pieces are equal to each other, each heating element has a length L1 that is equal to that of a single heating element. The calorific value of the heating elements can be reduced, and the calorific value can be distributed to the respective heating elements.

With the above configuration, there are two heating elements corresponding to a recording sheet having a large recording sheet width.
A sufficient amount of heat can be secured. Therefore, it is possible to obtain a sufficient fixing property for thick paper and rough paper. In addition, since the heat value of each of the two heating elements corresponding to the width of the recording paper can be made smaller than that of a single heating element, by controlling the ratio of the two heating elements,
Harmonics / flicker can be reduced.

Further, by providing a heating element having a longer heating portion at a position upstream of the recording sheet in the transport direction of the recording sheet, sufficient fixability can be obtained when a recording sheet having a large width is passed. it can.

<Third Embodiment> FIG. 7 shows a third embodiment.

The points overlapping with the first and second embodiments will be omitted.

The drive and control circuit is the same as in FIG. 5 described in the second embodiment. The schematic diagram of the ceramic heater 24 shown in FIG. 7 is different from the schematic diagram of FIG. 6 in that the heating element 33 corresponding to the small size paper is located between the heating element 32 and the heating element 40 corresponding to the normal size paper. It is located in.

With the above configuration, the heating element 40 can be used as an auxiliary heating element.
When the small-size paper is passed, the heating element 33 generates heat to perform heating control. When the normal-size paper is passed, the heating element 32 is heated to generate a toner image on the recording paper. Can be fixed.

Further, in the case where normal size paper is passed and the amount of generated heat is not sufficient just by energizing the heating element 32 due to thick paper passing or environmental conditions, power is supplied to the heating element 40. It can be supplied to increase the amount of heat generated.

As described above, since the heating element 40 generates heat supplementarily, the heating element 40 can be arranged on the downstream side in the conveying direction of the recording paper. However, even if normal size paper is passed, 2
The same control as in the case of the present heating element can be performed, and satisfactory fixing can be performed even when fixing is difficult due to thick paper passing or environmental conditions.

<Fourth Embodiment> This embodiment is different from FIG.
In the schematic diagrams of the ceramic heater 24 shown in FIGS. 6 and 7, the ratio of the total width (W1 + W3) of the heating elements 32 and 40 having the heating length L1 and the width w2 of the heating element L2 is (W1 + W3) / w2. = L1 / L2... Or (W1 + W3) / w2 = (L1 / L2) ² .

When the same material is used as the paste material of the heating elements 32 and 40, the heat generation length L
It is possible to make the total heat value of the one heat generating element equal to the total heat value of the heat generating element having the heat generation length L2.

With the configuration described above, the total heat generation per unit length of the heating element having the heating length L1 can be made equal to the total heat generation per unit length of the heating element having the heating length L2.

As described above, in the heating elements having different heating lengths, the heating value or the heating value per unit length can be equalized.

With these configurations, each heating element 3
The power supply control in the engine controller 11 that performs the power control of 2, 40 can be shared.

<Fifth Embodiment> FIG. 8 shows a drive and control circuit of a ceramic surface heater which is a feature of this embodiment.

The description of the same points as those of the above-described embodiment will be omitted.

The power supply to the heating element 80 is turned on and off by the triac 4. Electric power is supplied to the heating element 82 or the heating element 81 by the triac 13.
Perform cutoff. The output from the HOT terminal of the AC power supply 1 is A
The signal is input to the switching relay 73 via the C filter 2 and the excessive temperature rise prevention means 23. The switching relay 73 supplies power to the heating element 80 or the heating element 81 according to ON / OFF of a current supplied to the coil side, or switches the heating element 8
2 to supply power.

In the present embodiment, the energizing OF on the coil side
It is assumed that the power is switched to the side for supplying power to the heating element 80 or the heating element 81 at F, and the side is switched to the side for supplying power to the heating element 82 when turned on. Of course, the reverse setting may be used. ON / OFF of the current supplied to the coil side of the relay 73 is as follows.
In accordance with ON / OFF of the transistor 75, the transistor 75 is turned ON / OFF by the engine controller 11 via the resistor 76. The resistor 77 is the transistor 7
5 is an element for stabilizing the operation of
Is an element for preventing breakdown of the transistor 75 due to a back electromotive voltage induced on the coil side of the relay 73.

Next, an outline of the ceramic heater 24 is shown in FIG. The ceramic surface heater 24 is made of Si
Ceramic insulating substrate 3 such as C, AlN, Al ₂ O _3, etc.
1, heating elements 80, 81, 82 formed by paste printing or the like on the surface of the insulating substrate 31, and the three heating elements 80,
It is composed of a protective layer 34 of glass or the like that protects 81 and 82.

The heating element 80 includes a portion 80a that generates heat when power is supplied, a conductive portion 80b, and a conductive portion 80b.
And electrode portions 80c and 80d to which power is supplied via a connector (not shown). The heating element 81 includes a portion 81a that generates heat when electric power is supplied,
The conductive portion 81b and an electrode portion 80 connected to the conductive portion 81b and supplied with power via a connector (not shown).
c, 81d. The heating element 82 includes a portion 82a that generates heat when power is supplied, and a conductive portion 82b thereof.
And electrode portions 82c and 81d connected to the conductive portion 82b and supplied with power via a connector.

The number of the heating elements 80, 81, 82 is an odd number (3
At the first end of the formed heating element 24 in a direction orthogonal to the recording material transport direction, an electrode 80d connected to the first heating element 80 from the upstream side in the recording material transport direction, The heating element includes a common electrode 81d connected to an even-numbered (second) heating element 81 from the upstream side in the material conveying direction and a heating element 82 adjacent to the downstream side of the heating element 81. At a second end opposite to the first end of the heating element 24, an odd-numbered (first) heating element 80 from the upstream side in the recording material conveyance direction and a heat generation adjacent to the downstream side of the heating element 80. It has a common electrode 80c connected to the body 81 and an electrode 82c connected to the heating element 82 located on the most downstream side.

The terminal r1 of the relay 73 is connected to the common electrode 80c.
Is connected, and the terminal r2 of the relay 73 is connected to the electrode portion 82c. The electrode section 80d is connected to the triac 4 that controls the heating element 80, and the common electrode section 81d is connected to the heating element 8
1 and 82 are connected to the triac 13 and connected to the Neutral terminal of the AC power supply 1.

In FIG. 9, a heating section 80a of a heating element 80 is shown.
The length of the heat generating portion 81a of the heat generating member 81 is L1, which corresponds to the maximum recording sheet width that can be passed. It corresponds to the paper width. When a recording sheet having a recording sheet width larger than the length L2 of the heat generating portion 82a is passed, the RLD signal sent from the engine controller 11 is turned off, and the relay 73 is set to supply power to the heat generating element 80 or 81. Switch to O sent from the engine controller 11
The triac 4 is controlled by the N1 signal to control the power to the heating element 80, and the triac 13 is controlled by the ON2 signal to control the energization to the heating element 81.

Further, the recording paper width is equal to the length L2 of the heat generating portion 82a.
If a recording paper equal to or smaller than the above is passed, the RLD signal sent from the engine controller 11 is turned on,
The relay 73 is switched to a side that supplies power to the heating element 82. The triac 13 is controlled by the ON2 signal sent from the engine controller 11 to control the power to the heating element 82. The ON1 signal for controlling the triac 4 remains OFF. By such control, it is possible to suppress a temperature rise in a non-sheet passing area that occurs when a small size sheet is passed.

With the above configuration, the number of switching means (triacs and the like) for driving the heating element can be reduced. Further, switching between normal size paper and small size paper can be performed by a switching relay. When normal-size paper is passed, switching to normal-size paper is performed by a switching relay, power supply to the heating elements can be controlled by two switching means, and small-size paper can be passed. In this case, switching to small-sized paper is performed by the switching relay, and power supply can be controlled by one of the two switching units.

Further, since the number of electrodes on the insulating substrate can be evenly arranged on the left and right in the longitudinal direction of the insulating substrate, the connectors connected to the electrode portions can be shared, and the insulating substrate can be used effectively. Thus, costs can be reduced.

<Sixth Embodiment> FIG. 10 shows a schematic configuration of a ceramic surface heater showing the features of this embodiment.

[0092] Points that are the same as those of the above-described embodiment will be omitted.

The ceramic surface heater 24 is provided on the insulating substrate 3.
1, four heating elements 80, 81, 82, 83 formed on the surface of the insulating substrate 31 by paste printing or the like, and a protective layer 34 made of glass or the like for protecting the heating elements 80, 81, 82, 83. .

The heating elements 80, 81, and 82 are substantially the same as those in the fifth embodiment. The heating element 83 includes a portion 83a that generates heat when power is supplied, a conductive portion 83b, and a conductive portion 83b. The electrodes 82c and 83d are connected to the power supply 83b and supplied with power via a connector (not shown).

In this embodiment, at the first end of the heating element 24 in which the plurality of heating elements are formed in an even number (four), in the direction orthogonal to the recording material conveying direction, the heating element 24 is upstream in the recording material conveying direction. The electrode 80d connected to the first heating element 80 from the side
And even-numbered (second) from the upstream side in the recording material conveyance direction
A heating element 81, a common electrode 81d connected to the heating element 82 adjacent to the downstream side of the heating element 81, and an electrode 83d connected to the heating element 83 located at the most downstream side. At a second end opposite to the first end, odd-numbered (first and third) heating elements 80 and 82 from the upstream side in the recording material conveyance direction and downstream of the heating elements 80 and 82. It has common electrodes 80c, 82c connected to the heating elements 81, 83 adjacent to the side.

Then, the heating elements 80, 81, 82, 83 can be independently driven in accordance with the width of the passed recording paper,
The heating and fixing are performed by simultaneously driving the heating element 80 and the heating element 81 or simultaneously driving the heating element 82 and the heating element 83 according to the thick paper passing or environmental conditions.

As described above, according to the present embodiment, the electrode 8
0c and 81d82c can be made common, and the insulating substrate 31 can be effectively used. Further, good heat fixing can be performed under various conditions such as the width and thickness of the recording paper and the surrounding environment.

[0098]

As described above, according to the present invention, a plurality of heating elements having different lengths are provided, and the heating elements having a length corresponding to the width of the transfer material are selectively used to raise the non-sheet passing portion. A heating device and an image forming apparatus capable of reducing the temperature can be provided.

Further, in the heating device and the image forming apparatus, at least a part of electrodes of a plurality of heating elements which can be independently driven on an insulating substrate is used in common so that the substrate can be effectively used. Further, the number of electrodes provided at both ends of the substrate can be made the same, and the connectors connected to the ends can be shared.

[Brief description of the drawings]

FIG. 1 illustrates an image forming apparatus according to the present invention.

FIG. 2 is a diagram showing a control and drive circuit of a fixing device according to the present invention.

FIG. 3 is a schematic positional relationship diagram of a ceramic heater, a temperature detecting element, and an overheating prevention means according to the present invention.

FIG. 4 is a diagram illustrating an image forming apparatus according to the present invention.

FIG. 5 is a diagram showing a second embodiment of the present invention.

FIG. 6 is a diagram showing a second embodiment of the present invention.

FIG. 7 shows a third embodiment of the present invention.

FIG. 8 is a view showing a fifth embodiment of the present invention.

FIG. 9 is a view showing a fifth embodiment of the present invention.

FIG. 10 is a view showing a sixth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Filter 3 Heating element 4,13,41 Triac 5,6 resistance 7,16,44 Phototriac coupler 8 Resistance 9 Transistor 10 Resistance 11 Engine controller 12 Zero cross detection circuit 14,17 Resistance 18 Transistor 19 Resistance 20 Heating element DESCRIPTION OF SYMBOLS 21 Thermistor (temperature detection element) 22 Resistance 23 Excessive temperature rise prevention means 24 Ceramic surface heater (heating body) 31 Insulating substrate 32, 33, 40, 80, 81, 82, 83 Heating body 32a, 33a, 40a, 80a, 81a, 82a, 8
3a Heating part 32b, 33b, 40b, 80b, 81b, 82b, 8
3b conductive parts 32c, 32d, 33d, 40d, 80c, 80d, 8
1d, 82c, 83d electrode part 34 protective layer 42, 43, 45 resistor 46 transistor 47 resistor 61 film 62 film guide 63 elastic pressure roller 73 relay 74 diode 75 transistor 76, 77 resistor 101 laser printer main body 102 cassette 103 cassette presence / absence sensor 104 cassette size sensor 105 paper feed roller 106 registration roller pair 107 laser scanner unit 108 image forming unit 110 paper discharge sensor 111 paper discharge roller 112 stacking tray 113 laser unit 114 polygon motor 115 imaging lens 116 mirror 117 photosensitive drum 119 primary charging roller 120 developing device 121 transfer charging roller 122 cleaner 123 main motor 124 paper feed roller clutch 125 registration roller 126 engine controller 13 External device r1 terminal r2 terminal N nip R fuser S recording material (recording paper)

Claims (13)

[Claims] 1. A heating apparatus comprising: an insulating substrate; and a heating element including a plurality of heating elements formed on one surface of the insulating substrate in a direction orthogonal to a recording material conveying direction. A heating device, wherein at least one of the plurality of heating elements has a different length of a heating portion as compared with other heating elements. 2. A power supply means capable of independently supplying power to said plurality of heating elements.
A heating device according to claim 1. 3. The heating device according to claim 1, wherein a length of the heat generating portion is set in accordance with a width of a recording material that can be passed. 4. The heating device according to claim 1, wherein at least two of the plurality of heating elements have the longest heating section. 5. The recording medium according to claim 1, wherein, among the plurality of heating elements, a heating element having a longer heating section is disposed on an upstream side with respect to a recording material conveyance direction. The heating device according to claim 1. 6. A heating element having a plurality of heating elements having the same length of a heating section, and having a heating section shorter than the length of the heating section of the heating element, the heating section having a length equal to the length of the heating section. The heating device according to claim 1, wherein the plurality of equal heating elements are arranged at intermediate positions in a recording material conveyance direction. 7. The heating device according to claim 1, wherein the longer the length of the heating portion, the wider the width of the heating element. 8. The ratio of the width of the heating element for each heating element length obtained by summing the widths of the heating elements having the same length of the heating element is the ratio of the length of the heating element or the square of the length of the heating element. The heating device according to any one of claims 1 to 7, wherein the ratio is equal to: 9. A heating element in which an even number of the plurality of heating elements are formed, a first end of the heating element in a direction orthogonal to a recording material conveyance direction, the first heating element being located upstream from the recording material conveyance direction. Connected electrodes, an even-numbered heating element from the upstream side in the recording material transport direction, a common electrode connected to the heating element adjacent to the downstream side of the heating element, and a heating element located at the most downstream side. An electrode connected thereto, and at a second end located opposite to the first end of the heating element, an odd-numbered heating element from the upstream side in the recording material conveyance direction and the heating element The heating device according to any one of claims 1 to 8, further comprising a common electrode connected to a heating element adjacent on the downstream side of the heating element. 10. A heating element having an odd number of the plurality of heating elements formed at a first end in a direction orthogonal to a recording material conveyance direction, wherein a first heating element from an upstream side in the recording material conveyance direction is provided. And a common electrode connected to an even-numbered heating element from the upstream side in the recording material conveyance direction and a heating element adjacent to the downstream side of the heating element. At a second end opposite to the first end of the heating element, a common heating element connected to an odd-numbered heating element from the upstream side in the recording material conveyance direction and a heating element adjacent to the downstream side of the heating element The heating device according to any one of claims 1 to 8, further comprising: an electrode connected to a heating element located on the most downstream side. 11. The heating device according to claim 1, wherein the insulating substrate comprises Al ₂ O ₃ or Al.
N. 12. A film that slides on the heating element, and a pressure roller that forms a nip with the film, wherein a material to be heated is heated by heat from a heating unit via the film. The insulating substrate surface on which the heating element is formed is located on a side opposite to the nip surface.
The heating device according to any one of the above. 13. An image forming apparatus comprising: an image forming unit for forming an image on a recording material; and an image heating unit for heating the image on the recording material, wherein the image heating unit comprises An image forming apparatus comprising the heating device according to any one of the preceding claims.