JPH06236128A - Picture forming device, thermal fixing device, and ceramic heater for thermal fixing - Google Patents

Abstract

PURPOSE:To enable reducing a rush current at the time of start of driving a heater, to enable extending the life time of a device of a thermal fixing means by using efficiently each heater, to shorten a warming-up time, while to reduce power consumption at the time of the constant temperature control state, in a picture forming device having a thermal fixing means provided with plural heaters. CONSTITUTION:In a picture forming device which outputs a formed picture by forming a picture on a recording medium by visible image material such as toner and the like and fixing thermally, a thermal fixing means 8 has plural heaters H1, H2,..., also the device is provided with a heater control means 101 which drives selectively the plural heaters H1, H2,... in accordance with an operational state of the device.

Description

Detailed Description of the Invention

[0001]

The present invention relates to electrophotography, electrostatic recording,
An image corresponding to the desired image information is indirectly formed on the recording medium (transfer paper, electro-fax paper, electrostatic recording paper, etc.) on the recording medium (transfer paper, electrofax paper, electrostatic recording paper, etc.) by means of an image forming process unit of an appropriate principle such as magnetic recording. A printer, a copying machine, a recording machine, a facsimile machine, etc., which forms and carries a (transfer) method or a direct method and outputs the image formed matter (print, copy) by thermally fixing the image on a recording medium as a permanently fixed image. The present invention relates to an image forming apparatus.

Further, the present invention relates to a thermal fixing device for fixing an image of a developing material such as toner formed and carried on a recording medium.

Further, the present invention relates to a thermal fixing ceramic heater, which has a ceramic substrate and a heating resistor arranged on the substrate as a basic component and supplies electric power to the heating resistor to generate heat.

[0004]

2. Description of the Related Art FIG. 21 shows a schematic structure of an example of an image forming apparatus as described above. The image forming apparatus of this example is a laser beam printer (printing apparatus / image recording apparatus) using a transfer type electrophotographic process.

Reference numeral 1 denotes a drum type electrophotographic photosensitive member as an image bearing member, which is rotationally driven in a clockwise direction indicated by an arrow at a predetermined peripheral speed (process speed).

The photosensitive member 1 has a primary charger 2 during its rotation process.
Is subjected to primary charging processing to a predetermined polarity / potential, and then the laser beam scanner 3 receives a laser beam scanning exposure L of the target image information, and an electrostatic latent image corresponding to the target image information is formed on the peripheral surface of the photoconductor 1. Is formed. Then, the latent image is visualized as a toner image by the developing device 4. In the transfer device 5, the toner image is transferred onto the surface of a transfer sheet P as a recording medium that is fed at a predetermined timing from a sheet feeding mechanism side, which will be described later, to a transfer portion between the photoconductor 1 and the transfer device 5. To go.

The transfer paper P, which has received the toner image transferred through the transfer section, is separated from the surface of the photoreceptor 1 and is introduced into the heat fixing device 8 through the conveying section 7 to undergo the heat fixing process of the toner image. , And is printed out from the pair of paper discharge rollers 9a and 9b to the paper discharge tray (stacker) 10. After the transfer of the toner image onto the transfer paper P, the photoconductor 1 is cleaned by the cleaning device 11 after removal of residual contaminants such as transfer residual toner.
It is repeatedly used for image formation.

The laser beam scanner 3 includes a semiconductor laser 31 as a light source and a polygon mirror (rotating polygon mirror) 32.
An f-θ lens 33, a reflection mirror 34, a beam detector 35, etc. The semiconductor laser 31 outputs a laser beam modulated in accordance with a time-series electric digital image signal of the target image information input to the printer side from a host computer, an image reading device, a word processor, etc. as an external device (not shown). To do. The beam detector 35 is arranged at the scanning start position of the beam, and detects the beam, and is the image writing timing B in the main scanning direction.
The D signal is output to the control circuit.

A reference numeral 12 designates a paper feed cassette which is attachable to and detachable from the printer main body, in which transfer paper P as a recording medium is stacked and stored. The sheet P in the sheet feeding cassette 12 is separated and fed from the cassette 12 by one sheet by the truncated circular sheet feeding roller 13 which is intermittently driven by one rotation based on the sheet feeding start signal, and the conveying roller pair 14 and the sheet path 15 are fed. It is conveyed to the registration shutter 16 through the.

When the leading edge of the conveyed paper reaches the position of the registration shutter 16, the conveyance of the paper is temporarily stopped by the registration shutter 16. In this case, the pair of transport rollers 14 generate a transport torque while continuing to rotate while slipping on the sheet P in the transport stopped state.

Next, when the registration solenoid 17 is energized at a predetermined control timing, the registration shutter 16 is pulled up and the stop of conveyance of the sheet by the registration shutter 16 is released, and the conveyance roller pair 14 continues to rotate. The paper is re-conveyed by the torque, and the paper is fed to the transfer portion between the photoconductor 1 and the transfer device 5 at a predetermined timing via the conveyance roller pair 18. That is, the registration shutter 16 is driven at a fixed timing with the image formation on the photoconductor.

Reference numeral 19 denotes a manual paper feed tray. When a paper P is inserted from the paper feed tray 19 into the printer, the paper P is drawn into the printer by the manual paper feed roller 20 and conveyed to the resist shutter 16. When the leading edge of the sheet reaches the position of the registration shutter 16, the registration shutter 16 temporarily stops the conveyance of the sheet. The manual paper feed roller 20 slips on the paper P and continues to rotate. The subsequent transportation sequence is the same as the case of the paper fed from the paper feeding cassette 12 side.

S1 is a reflection type photo sensor for detecting the presence / absence of paper in the paper feed cassette 12, S2 is a photo sensor (registration sensor) for detecting whether or not there is paper at the position of the resist shutter 16, and S3 and S4 are The sensors (inlet sensor and sheet ejection sensor) arranged on the sheet inlet side and the sheet outlet side of the fixing device 8 for detecting the presence or absence of the sheet.

FIG. 22 is a schematic diagram of the structure of the heat fixing device 8. The heat fixing device 8 of this example is of a heat roller type.

Reference numeral 81 is a fixing roller (heat roller), and reference numeral 82 is a pressure roller pressed against the fixing roller 81 with a predetermined pressing force. The fixing roller 81 generally comprises an aluminum hollow pipe roller having a toner offset prevention layer formed on the outer peripheral surface thereof, and a halogen heater (lamp) H as a heat source inserted and arranged in the roller, and is rotationally driven at a predetermined peripheral speed. It The pressure roller 82 is a heat-resistant rubber roller and rotates following the fixing roller 81. Reference numeral 83 is a thermistor as a temperature detecting means that is brought into contact with the surface of the fixing roller 81.

The fixing roller 81 is heated by the heat generated by the halogen heater H, and the surface temperature of the roller is the thermistor 83.
Is detected, and the detected information is fed back to the temperature control system to control the energization of the heater H, whereby the surface temperature of the fixing roller 81 is controlled to a predetermined fixing temperature.

As described above, the transfer sheet P, which has been transferred to the thermal fixing device 8 after receiving the transfer of the toner image at the transfer section, is pressed by the lower sheet guide 84 between the fixing roller 81 and the pressure roller 82 at the pressure contact nip portion (fixing nip). Part) to enter the nip part and the toner image is fixed on the paper surface by the heat and pressure of the roller pair 81, 82. Then, the sheet exiting the nip portion is sent out from the fixing device 8 by a pair of discharge rollers 9a and 9b. Reference numeral 85 is a fixing separation claw, and the paper P is the fixing roller 8.
It prevents it from wrapping around 1.

FIG. 24 shows the gear train of the drive system of the thermal fixing device 8. G2 is a fixing roller gear fixed to one end side of the fixing roller 81, G4 is a discharge roller gear fixed to one end side of the lower roller 9a of the discharge roller pair 9a and 9b, G4
Reference numeral 1 denotes a drive gear, which meshes with the fixing roller gear G2. The drive gear G1 and the discharge roller gear G4 are meshed with each other via a relay gear G3. The drive gear G1 receives a driving force from a main motor (not shown) via a transmission system (not shown) and is rotationally driven in a direction shown by an arrow.

The fixing roller 81 is rotationally driven by the rotation of the driving gear G1 via the gear G2, and the pressure roller 82 is rotated by being driven by the fixing roller 81. Also gear G3 ・ G
The lower roller 9a of the paper discharge roller pair 9a and 9b is rotationally driven via 4, and the upper roller 9b is rotated by being driven by the lower roller 9a.

Some fixing rollers 81 are provided with a plurality of heaters H (Japanese Utility Model Publication No. 63-92367, Japanese Utility Model Publication No. 4-3454, etc.). FIG. 23 shows the fixing roller 81.
A heat fixing device 8 in which two heaters (halogen heaters) H1 and H2 are arranged is shown.

In addition to the heat roller type heat fixing device 8 as described above, a film heating type heat fixing device has recently been put into practical use.

This heat fixing device is disclosed in JP-A-63-313182.
Japanese Patent Laid-Open No. 1-263679 / Japanese Patent Laid-Open No. 2-1
No. 57878 / JP-A-4-44075-44083
It is known in Japanese Patent Publication No. JP-A-2003-242, and a heat-resistant film is sandwiched between a heating means and a facing means to run, and a heat-resistant film and a facing means in a nip portion formed by the heating means and the facing means sandwiching the heat-resistant film. The recording medium on which the unfixed toner image is formed and carried is introduced between the recording medium and the heat-resistant film, and the heat of the heating means is passed through the nip portion together with the heat-resistant film to the recording medium through the heat-resistant film. The toner image is applied and the unfixed toner image is heated and fixed on the recording medium.

Since such a film heating type thermal fixing device can use a heating means having a low heat capacity and a thin heat-resistant film which can quickly raise the temperature, it saves power and shortens the wait time (quick start property). It is possible to reduce the temperature rise inside the main body of the image forming apparatus such as the image forming apparatus, and is effective.

As the heating means, there is a so-called planar ceramic heater having a heat-resistant and insulating ceramic substrate and an electric heating resistor formed on the substrate as a basic structure, and supplying electric power to the resistor to generate heat. It is used.

FIG. 25 is a cross-sectional model view of the essential part of the film heating type thermal fixing device 8A, and FIG. 26 is a partially cutaway plan view of the heater. 40 is a heater (heating body), a. Slender substrate 41 with electrical insulation, heat resistance and low heat capacity
And b. A heating resistor 42 formed in the shape of a straight strip along the length of the substrate at the center of the substrate 41 on one surface side (front surface side) in the substrate width direction; and c. Electrode patterns (electrode terminals) 43, 43 formed on the substrate surface by electrically connecting both ends of the heating resistor 42.
And d. Electrically insulating overcoat layer 44 as a heater surface protective layer covering the side of the substrate 41 on which the heating resistor is formed.
And e. The temperature detection element 45 and the like are provided on the other surface side (back surface side) of the substrate 41.

The substrate 41 has a width of 10 mm and a thickness of 1, for example.
It is a ceramic plate such as Al ₂ O ₃ , AlN, or SiC having a length of mm and a length of 240 mm.

The heating resistor 42 has a thickness of 10 μm, for example.
It is a pattern layer of Ag / Pd (silver-palladium alloy), RuO ₂ , Ta ₂ N, etc. coated by screen printing or the like with a width of 1 mm.

The overcoat layer 44 side of the heater 40 is a film contact sliding surface, and this surface side is exposed to the outside so that the heater 40 is fixedly supported by a heater supporting member 47 via a heat insulating heater holder 46.

Reference numeral 48 is a heat-resistant film in the form of an endless belt or a long web, such as polyimide having a thickness of, for example, about 40 μm, and 49 is a pressure roller as a pressure member for pressing the film 48 against the heater 40. is there.

The film 48 is driven by a driving member (not shown).
Alternatively, it rotates or travels while sliding on the surface of the heater 40 in a state of being in close contact with the surface of the heater 40 in a direction indicated by an arrow at a predetermined speed by the rotational force of the pressure roller 49.

The heater 40 and the heater holder 46 having the heater 40 attached thereto are fitted with power supply connectors 50, 50 at both ends thereof, and are connected to the electrode patterns 43, 43 at both ends of the heating resistor 42 of the heater 40, respectively. A contact (spring electrode, generally phosphor bronze) is pressure-contacted, a voltage is applied from the power supply between the electrode patterns 43, 43 at both ends through the power supply connector 50, and the heating resistor 42 generates heat to raise the temperature. To do.

The temperature of the heater 40 is detected by the temperature detecting element 45 on the back surface of the substrate, and the detected information is fed back to the energization control circuit to control the energization of the heat generating resistor 42 from the power source, so that the heater 40 has a predetermined temperature. Temperature control is controlled to the temperature of.

The temperature detecting element 45 of the heater 40 has a fixing surface having the best thermal response, that is, a substrate rear surface side partial position (corresponding to a position directly below the heat generating resistor 42) corresponding to a forming position of the heat generating resistor 42 on the heater substrate front surface side. It is arranged at a partial position on the back surface side of the substrate).

By energizing the heating resistor 42 of the heater 40, the heater 40 is heated to a predetermined temperature and the film 48 is heated.
The recording medium P is introduced into the fixing nip portion N, which is the pressure contact portion (pressure portion) between the film 48 and the pressure roller 49, with the unfixed toner image surface facing the film 48 surface side. Then, the recording medium P comes into close contact with the surface of the film 48 and moves through the fixing nip portion N together with the film 48, and heat energy is applied to the recording medium P from the heater 40 via the film 48 in the process of the movement and passage. The unfixed toner image t on P is heated and fused and fixed.

[0035]

[Problems to be Solved by the Invention]

(A) Problem 1 A plurality of heaters H1 and H2 as in the above example (FIG. 23).
With regard to the image forming apparatus having the heat fixing means (heat fixing device) 8 provided with, the conventional apparatus drives the plurality of heaters H1, H2, ... Without considering the state of the apparatus.

A. That is, in the conventional device, the plurality of heaters H1
・ H2 ・ ・ ・ ・ Each heater H1 ・ H2 ・ ・ ・ ・
Since the drive start timings of the heaters H1, H2, ... Are simultaneously overlapped with each other, the rush current may become very large.

B. Further, since a plurality of heaters are used regardless of the state of the apparatus, when all the heaters H1, H2, ... Are used, the life of each heater alone becomes the life of the heat fixing unit. Further, even in the constant temperature control state after the temperature of the heat fixing unit rises, the state of constantly consuming power continues.
Further, the electric power required for driving the heater for temperature control becomes large.

C. And the heaters H1 and H2 are in order, in small numbers.
When using ..., the amount of heat supplied per unit time is small, so the rise time during warming up is delayed.

Therefore, a first object of the present invention is to solve the above problems a, b, and c of the image forming apparatus having the heat fixing means having a plurality of heaters, that is, when starting driving the heater. The inrush current can be reduced, the heaters can be used efficiently to extend the device life of the heat fixing unit, the warm-up time can be shortened, and the power consumption during constant temperature control can be reduced. To make it lower.

(B) Problem 2 In the heat fixing device 8 of the heat roller type as the above-mentioned example (FIGS. 22 and 23) as the heat fixing means, the surface temperature of the fixing roller 81 is as high as 150 to 200 ° C. and the energy consumption is high. Is also big. For example, in a laser beam printer with eight sheets per minute, the energy consumption during printing is about 800 W and the energy consumption outside printing is about 80 W.

Therefore, a second object of the present invention is to save the consumed energy by suppressing the amount of heat that is wastefully escaped from the heat fixing means to the outside, for example, by suppressing the energy outside the printing to half or less. It is to improve thermal efficiency.

(C) Problem 3 In the conventional image forming apparatus, the processing relating to fixing is the same when plain paper is passed as a recording medium and when thick paper such as an envelope or a postcard is passed. Met.

Therefore, when thick paper such as an envelope is passed through, fixing failure may occur.

Therefore, a third object of the present invention is to prevent defective fixing even when thick paper such as an envelope is passed as a recording medium.

(D) Problem 4 The above-mentioned film heating type heat fixing means 8A (FIG. 25)
Sheet ceramic heater 4 used as heating means for
At 0, an NTC thermistor is generally used as the means 45 for detecting the temperature of the heater.

In order to accurately control the temperature of the heater 40, it is preferable to mount the NTC thermistor 45 directly on the planar ceramic heater 40, and a high melting point solder or a conductor such as silver or gold is used for mounting and electrical conduction. An epoxy-based conductive adhesive containing it is used.

However, the planar ceramic heater 40
Has a high temperature of about 200 degrees when fixing a toner image and reaches room temperature when it is not operating. Therefore, excessive heat cycles are repeated, and the electrically conductive part using high melting point solder or conductive adhesive deteriorates, resulting in non-conduction. There was a problem that became.

Therefore, a fourth object of the present invention is to provide a ceramic heater for heat fixing of this type with high durability, high accuracy and high efficiency without the problems of deterioration and non-conduction of the electrically conductive portion as described above. It is to realize a reliable and low-cost heater.

[0049]

SUMMARY OF THE INVENTION The present invention is an image forming apparatus, a heat fixing device, and a heat fixing ceramic heater having the following features.

(1) In an image forming apparatus for forming an image on a recording medium with a developer such as toner and thermally fixing the image to output an image-formed product, the thermal fixing means has a plurality of heaters. An image forming apparatus comprising: a heater control unit that selectively drives the plurality of heaters according to an operating state of the apparatus.

(2) In the image forming apparatus described in (1),
An image forming apparatus comprising: heater control means for shifting the drive start timing of each heater when a plurality of heaters of the heat fixing means are used at the same time.

(3) In the image forming apparatus described in (1),
An image forming apparatus having a heater control means for switching between a mode in which a plurality of heaters are all used and a mode in which a small number of heaters are sequentially used according to an operating state of the apparatus.

(4) In the image forming apparatus described in (3),
A heater that uses all the heaters in the process of raising the temperature of the heat fixing unit from a low temperature to a predetermined temperature, and sequentially uses the heaters in a small number in a state of maintaining the constant temperature after reaching the predetermined temperature. An image forming apparatus having a control unit.

(5) In the image forming apparatus described in (4),
There is an input means for externally designating whether or not the temperature of the heat fixing means is quickly raised from a low temperature to a predetermined temperature, and all the heaters are turned on when a quick start-up is designated by the input means. An image forming apparatus comprising a heater control means for sequentially using a small number of heaters in a case where the heater is used and a quick start-up is not designated.

(6) In the image forming apparatus described in (5),
At least after the jam recovery process, after returning from the sleep state, and at the time of transition from standby to image formation, etc., have a heater control unit that uses all the heaters of the heat fixing unit regardless of designation from the outside. An image forming apparatus characterized by.

(7) In a thermal fixing device for fixing an image of a developing material such as toner formed and carried on a recording medium, at least part of the periphery of the thermal fixing means is covered with a heat insulating material. vessel.

(8) In the heat fixing device described in (7), the heat insulating material has a three-layer structure, one layer and three layers are made of metal, and at least two layers have thermal conductivity higher than that of the first layer and three layers. A heat fixing device characterized by low material.

(9) In the heat fixing device as described in (8), the heat insulating material has one and three layers made of stainless steel and two layers are vacuum.

(10) In the thermal fixing device according to any one of (7) to (9), an opening / closing window through which a recording medium passes is provided in a part of the heat insulating material, and A thermal fixing device characterized in that the window portion is opened and controlled at the time of feeding and discharging.

(11) In a thermal fixing device for fixing an image of a visible material such as toner formed and carried on a recording medium, at least a part of the inside of the teeth between the gear driving the thermal fixing means and the shaft is thermally conducted. A thermal fixing device characterized by being composed of a member having a low rate.

(12) In the heat fixing device described in (11),
A heat fixing device characterized in that a part of the inside of the tooth is hollow.

(13) In the heat fixing device described in (11) or (12), at least one of the gear trains for driving the heat fixing means.
A thermal fixing device characterized in that one gear is made detachable with respect to the other gear, and the position movement is controlled so that the gear does not mesh with the other gear except during fixing.

(14) In an image forming apparatus for forming an image on a recording medium with a developer such as toner and thermally fixing the image to output an image-formed product, the size of the recording medium fed in the apparatus in the conveying direction. A detection means for detecting
An image forming apparatus, wherein when the size detected by the detecting means is smaller than a predetermined size, the operation of the apparatus is executed by control corresponding to thick paper.

(15) In the image forming apparatus described in (14), the thick paper corresponding control is to control the fixing temperature of the heat fixing means to be higher than normal control.

(16) The image forming apparatus described in (14) is characterized in that the control corresponding to the thick paper is to control the paper feeding interval of the recording medium to be larger than the normal control.

(17) In a ceramic heater for heat fixing, in which a ceramic substrate and a heating resistor arranged on the substrate are used as basic constituents to generate heat by supplying electric power to the heating resistor, the heating resistor is provided on the substrate. Of the temperature detecting element, the electrode pattern for supplying electric power to the heating resistor is provided on the substrate, and the means for directly configuring the temperature detecting element is provided on the substrate. A ceramic heater for heat fixing, characterized in that the electric power of the heating resistor is controlled based on the output to control the temperature of the heater.

(18) In the thermal fixing ceramic heater described in (17), the temperature detecting element is formed on the substrate by a thick film printing / baking process.

(19) The ceramic heater for heat fixing according to (17) or (18), characterized in that the substrate is an alumina substrate.

[0069]

[Action]

(A) The items (1) to (6) are image forming apparatus configurations that solve the above-mentioned problem 1. That is, when a plurality of heaters are used at the same time for an image forming apparatus having a heat fixing unit having a plurality of heaters, a heater control unit that shifts the drive start timing is provided to reduce the rush current at the start of heater drive. It is designed so that it can be lowered.

Further, by providing a heater control means for switching between a mode in which a plurality of heaters are all used and a mode in which a small number of heaters are sequentially used according to the state of the apparatus, each heater can be used efficiently. Since the device life of the heat fixing unit can be extended and the amount of heat supplied can be changed as necessary, the warming-up time can be shortened and the power consumption in the constant temperature control state can be reduced. is there.

(B) The above (7) to (13) are image forming apparatus configurations which solve the above-mentioned problem 2. That is, with such a device configuration, the amount of heat that is wastefully escaped from the thermal fixing unit to the outside is suppressed, the energy consumption of the thermal fixing unit outside printing is saved, and thermal efficiency is achieved.

(C) The above (14) to (16) are image forming apparatus configurations which solve the above-mentioned problem 3. That is, the size of the fed recording medium in the conveying direction is detected, and if the detected size of the fed recording medium is smaller than the preset size, the fed recording medium is a thick paper such as an envelope. By recognizing and controlling by a sequence corresponding to thick paper such as increasing the temperature of the heat fixing means and increasing the paper feeding interval, the occurrence of fixing failure could be eliminated.

(D) The above (17) to (19) is the structure of the ceramic heater for heat fixing which solves the above-mentioned problem 4. That is, by using a thick film printing technique similar to the heating resistor / electrode pattern, a heater temperature detecting element such as a platinum resistor is formed to directly form the temperature detecting element on a ceramic substrate serving as a heater base, By electrically connecting the temperature detecting element to the electrode pattern using a printing technique, a highly durable ceramic heater for heat fixing capable of highly reliable temperature detection can be realized.

Further, since all are produced by using the thick film printing process, it is possible to realize a ceramic heater for heat fixing which is inexpensive in terms of cost.

[0075]

【Example】

A. Examples 1 to 4 below are examples of an image forming apparatus having the configuration described in (1) to (6) [corresponding to claims 1 to 6], and solve the above-mentioned problem 1. Is.

<Embodiment 1> (FIGS. 1 to 3) FIG. 1 is a schematic configuration diagram of an image forming apparatus of the present embodiment. The image forming apparatus of this example is a laser beam printer using a transfer type electrophotographic process. The same components, members, and parts as those of the printer shown in FIG. 21 are designated by the same reference numerals, and the description thereof will be omitted.

In the printer of this embodiment, the heat fixing means 8 has a plurality of heaters. Specifically, as shown in FIG. 23, the heat fixing means 8 is of a heat roller type having two halogen heaters H1 and H2. It is a heat fixing device.

Reference numeral 100 denotes a main control section for controlling the entire printer, and an external device 300 such as a host computer is connected via an external device interface 200.

FIG. 2 is a block circuit diagram of the control system. The main control unit (main control device) 100 of the printer is composed of a microprocessor that controls the entire device, a ROM that stores a control program, a RAM that stores data and the like, and a gate element, and the like. Fixing device control means 101 for controlling the temperature of the container 8; fixing device temperature storage means 102 for storing the fixing device temperature; state information storage means 103 for storing control state information by a state management means 105 described later; A print control unit 104 that causes the printer to perform a printing operation (image forming operation) in response to an instruction from the device 300, a state management unit 105 that manages the control state of the laser beam printer such as warm-up, standby, print, jam, and failure. -Self-diagnosis means 106 for detecting jams, abnormalities, etc.-Set the control temperature in the fixing device control means 101. The control temperature storage means 107, which is to be set, comprises an external device communication means 108 for controlling communication with the external device 300, and the like.

Further, the fixing device control means 101: The heater selection / switching means 10 for switching the usage method of the heaters H1 and H2 of the thermal fixing device 8 according to the state of the apparatus.
9. Heater drive control means 110 for controlling the drive of the heater based on the information of the comparison means 111, which will be described later. The heater drive is the result of comparing the temperature information of the fixing device temperature storage means 102 and the value of the control temperature storage means 107. It comprises a comparison means 111 for outputting to the control means 110.

The external device 300 is connected to the external device communication means 108 via the external device interface 200 to exchange information with the external device 300.

Further, the heater selection / switching means 109 is connected to the first side of the heat fixing device 8 side via the drivers 112 and 113.
And the second heaters H1 and H2 are connected to each other, and the information from the thermistor 83 as a temperature detecting element of the fixing roller 81 is written in the fixing device temperature storage means 102 via the input circuit 114.

The two heaters H1 and H2 of the fixing roller 81 of the thermal fixing device 8 are driven by the control of the printer main controller 100 via the drivers 112 and 113, respectively.

Further, the temperature of the fixing roller 81 is the thermistor 8
3 detected by the main controller 1 via the input circuit 114
Temperature information is input to the 00 side.

With the above configuration, the fixing device control means 101 performs the following fixing device temperature control.

First, the comparison means 111 always compares the value of the fixing device temperature storage means 102 in which the information from the thermistor 83 is written in real time with the value of the control temperature storage means 107, and the comparison result is the heater drive control means. Output to 110.

The heater drive control means 110 is the comparison means 11
According to the output of No. 1, a heater drive instruction is issued if the temperature of the thermal fixing device 8 (fixing roller 81) is lower than the control temperature, and a heater stop instruction is issued if the temperature of the thermal fixing device is equal to or higher than the control temperature. It is output to the means 109.

The heater selection / switching means 109 has two heaters H1.H according to the information in the state information storage means 103.
The usage of No. 2 is adjusted, and the corresponding heater is turned on and off according to an instruction from the heater drive control means 110. The control of the heater selection / switching means 109 will be described later in detail.

The state management means 105 sets the standby temperature in the control temperature storage means 107 when the power of the laser beam printer is turned on, and at the same time, the state information storage means 1
The information of the warming up state is set to 03.

Here, the standby temperature is a state in which when the laser beam printer receives a print start instruction from the external device 300, the thermal fixing device 8 can be immediately raised to the print temperature to start printing (standby state). It is the control temperature at.

As a result, the fixing device control means 101 controls the temperature of the thermal fixing device 8 to the standby temperature. After that, the state management unit 105 monitors the information in the fixing unit temperature storage unit 102, sets the standby state information in the state information storage unit 103 when the standby temperature is first reached, and sets other printing conditions (not shown). If all the information (paper presence or absence) is printable, a printable signal is sent to the external device 300 via the external device communication unit 108.

Upon receiving the print enable signal, the external device 300 sends a print instruction signal to the laser beam printer as necessary. Upon receiving the print instruction signal, the state management unit 105 sets the print temperature in the control temperature storage unit 107 and sets the print state information in the state information storage unit 103. The print control unit 104 also controls the print operation according to a predetermined process.

The state management means 105 is the print control means 104.
Has completed the printing operation and has not received a print instruction signal from the external device 300, the standby temperature is set again in the control temperature storage means 107 and the status information storage means 1 is set.
The information of the standby state is set to 03.

Further, the self-diagnosis means 106 informs the state management means 105 when a jam, failure or the like is detected. When the status management unit 105 receives the information indicating that the abnormality has occurred from the self-diagnosis unit 106, it immediately stops the drive control system such as the print control unit 104 regardless of the control state. Further, the stop temperature is set in the control temperature storage means 107, and the jam status or the failure status information is set in the status information storage means 103.

Here, the stop temperature is a minimum value that can be read by the thermistor 83, that is, a value smaller than the minimum value set in the fixing device temperature storage means 102, and the stop temperature is stored in the control temperature storage means 107. By setting, the comparison result of the comparison means 111 is always higher than the fixing device temperature, so that the heater is stopped.

In the case of a failure, it does not recover until the power is turned off, but in the case of a jam, the self-diagnosis means 106 resets the jam information when a predetermined jam recovery operation is performed.

As a result, the state management means 105 sets the control temperature storage means 107 to the standby state again, and sets the warming-up state information to the state information storage means 103. The subsequent operation is the same as the operation after the power is turned on.

The heater selection / switching means 109 is the status information storage means 10 that changes according to the status inside the machine as described above.
The information of 3 is checked, and the usage method of the two heaters H1 and H2 is switched.

FIG. 3 is a flow chart showing the control of the heater selection / switching means 109 in the apparatus of this embodiment.

First, in step S1, heater drive control means 1
It is checked whether or not the heater driving instruction is issued from 10. If the heater driving instruction is issued, step S2
The heater drive control of S6 is performed.

First, in step S2, it is judged from the information in the state information storage means 103 whether or not the warming-up state is set.
Go to 3 and select heaters H1 and H2 h1_fla
Check g.

If h1_flag is set, the heater H1 is driven in step S4, and if it is reset, the heater H2 is driven in step 5.

On the other hand, if the warming-up state is set in step S2, the process proceeds to step S6 and the heaters H1 and H
2 drive together. After performing the above processing, step S1
Return to.

If the heater driving instruction is not issued in step S1, the heater stop control of steps S7 to S11 is performed.

First, in step S7, all the heaters are stopped. Next, in step S8, the h1_flag is checked,
If h1_flag is set, the process proceeds to step S9 and h1_f
lag is reset, and if h1_flag is reset, the process proceeds to step S10 and h1_flag is set. After that, the process proceeds to step S11, and waits until a heater drive instruction is issued from the heater drive control unit 110, and when the heater drive instruction is issued, the process proceeds to step S2.

In step S6, the heater H1 and the heater H
When driving both of the two heaters, the driving start timings of the two heaters H1 and H2 are slightly shifted. The shift interval is 1
Set the time for the inrush current to drop sufficiently when two heaters are driven.

By the control as described above, in the warming-up state such as after the power is turned on, after the jam processing, after the sleep state is released, etc., the heat fixing device 8 is quickly activated by using the two heaters H1 and H2. During the control at a constant temperature after the rising of the heaters, the heaters H1 and H2 are alternately used for each driving of the heaters.
It is possible to prolong the life of No. 2 and to reduce the power required for driving the heater. Further, the inrush current can be reduced by shifting the drive start timing when the two heaters H1 and H2 are used simultaneously.

<Embodiment 2> (FIG. 4) In Embodiment 1, all the heaters H1 and H2 are used only when warming up the heat fixing device 8. However, after issuing a print instruction from the standby state, the heat fixing device 8 is turned on. By using all the heaters H1 and H2 when raising the printing temperature, the heat fixing device 8 can be started up earlier and the first printing time can be shortened.

The basic control configuration is the same as that of FIG. 2 of the first embodiment, but the heater selection / switching means 109 uses the two heaters H1 and H2 not only during warming up but also during the transition from the standby state to the printing state. To use.

FIG. 4 shows a flow chart of the control of the heater selection / switching means 109 in this embodiment.

First, as in the case of the first embodiment, it is checked in S21 whether or not a heater drive instruction is issued from the heater drive control means 110, and if a heater drive instruction is issued, the heater drive in steps S22 to S28 is performed. Take control.

First, in step S22, it is determined from the information in the state information storage means 103 whether or not it is in the warming up state. If it is not in the warming up state, the process proceeds to step S23 to check whether or not it is in the printing state.

If the print state is set in step S23, the flow advances to step S26 to check p_flag indicating that the print state has just been changed (that is, the thermal fixing device 8 is being raised from the standby temperature to the print temperature).

If p_flag is reset in step S26, that is, the temperature is being adjusted at the print temperature, or if it is not in the print state (and is not in the warm-up state) in step S23, the process proceeds to step S24, and h1_flag indicating that the heater H1 is selected Check. Where h1_fla
If g is set, heater H1 is set in step S25.
Is reset, the heater H2 is returned in step S27.
To drive.

If the warm-up state is set in step S22, or if p_flag is set in step S26, that is, if the thermal fixing device 8 is being set to the print temperature, the process proceeds to step S28.
2 drive together. After performing the above processing, step S2
Return to 1.

On the other hand, if the heater driving instruction is not issued in step S21, the heater stop control of steps S29 to S36 is performed.

First, in step S29, all the heaters H1.
Stop H2. Next, as in the first embodiment, step S3
The h1_flag is set in 0 to S32, and the process proceeds to step S33.

In step S33, it is checked whether or not it is in the print state, and if it is in the print state, the step S33
34, the p_flag is reset, and if it is not in the print state, the process proceeds to step S35 and the p_flag is set.

Thereafter, the process proceeds to step S36, and waits until the heater drive instruction is issued from the heater drive control means 110, and if the heater drive instruction is issued, the process proceeds to step S22.

By such control, p_flag is set when the heater driving instruction is issued from the state other than printing, and p_flag is reset when the heater driving instruction is issued in the printing state. Further, since the heater driving instruction is continuously issued while the thermal fixing device 8 is raised to the printing temperature, p_fl is set at the time of step S26.
ag indicates that the printing temperature is being set up.

Therefore, by controlling as described above,
After the power is turned on, the jam is cleared, the sleep state is released, and the warm-up state is reached, the thermal fixing device 8 can be quickly started up even when the standby state is changed to the printing state. Time delay can be reduced.

<Embodiment 3> (FIGS. 5 and 6) In Embodiments 1 and 2, all the heaters H1 and H2 were used unconditionally when the thermal fixing device 8 was started up. How to use the heaters H1 and H2 Can be selected from the outside.

FIG. 5 shows a block diagram of the control configuration of this embodiment. Although it is almost the same as in FIG. 2, the heater selection / switching means 109 is provided with information about how to use the heater from the external device communication means 108, as indicated by the thick line. Here, the external device 300 gives an instruction of a method of starting the thermal fixing device 8 to the laser beam printer via the external device interface 200. If you want to start printing as soon as possible after turning on the power, instruct the thermal fuser 8 to start up quickly (hereinafter referred to as "quick warm-up mode"), and if there is enough room, you need to supply enough power. When it is desired to reduce the size, the quick warm-up mode is not designated.

The heater selection / switching means 109 receives this information via the external device communication means 108, and switches the usage method of the heaters H1 and H2 according to the designation.

FIG. 6 shows a flow chart of the control of the heater selection / switching means 109 in this embodiment.

The steps S43 to S52 are
This is the same as each step of steps S2 to S11 of FIG. 3 in the first embodiment, but when the heater drive instruction is issued from the heater drive control means 110 in step S41, the quick warm-up mode is designated in step S42. If the quick warm-up mode is not designated, the process proceeds to step S44 to use one of the two heaters H1 and H2 regardless of whether the warm-up state is set.

By controlling in this way, the method of using the heater at the time of starting the thermal fixing device is switched according to the instruction from the external device 300, and the two heaters H1.
H2 can be used.

<Fourth Embodiment> (FIG. 7) In the third embodiment, the usage of the heaters H1 and H2 can be selected from the outside.
Only when warming up later, if it is determined that quick startup is always required, such as after clearing a jam, returning from sleep mode, or when shifting from the standby state to the print state, etc. It is also possible to use all the heaters H1 and H2 regardless of the designation.

The basic control configuration is the same as that of FIG. 5 of the third embodiment, but the heater selection / switching means 109 is powered on.
Only after the first warm-up, the usage method of the heaters H1 and H2 is switched according to the designation from the external device 300. In other cases, the two heaters H1 and H2 are simultaneously used when the heat fixing device 8 is started up to a certain temperature. Then
When the temperature is kept constant, the two heaters H1 and H2 are controlled to be used alternately one by one.

FIG. 7 shows a flow chart of the control of the heater selection / switching means 109 in this embodiment.

After the power is turned on, first the power is turned on in step S61.
Pwon_fla that indicates warming up immediately after N
Set g.

Next, in step S62, it is checked whether or not a heater drive instruction has been issued from the heater drive control means 110, and if a heater drive instruction has been issued, the heater drive control in steps S63 to S71 is performed.

First, in step S63, the pwon_flag is checked. If pwon_flag is set, that is, if it is the first warm-up after turning on the power, the process proceeds to step S64, and it is determined whether or not the quick warm-up mode is designated by the external device 300. To check.

If pwon_flag is reset in step S63, step S64 is skipped and step S65 follows. Steps S64 to S71 are the same as steps S42 to S47 of FIG. 6 in the third embodiment.

On the other hand, when the heater drive instruction is not issued in step S62, the heater stop control of steps S72 to S80 is performed.

Of these steps, steps S72 to S79 are steps S29 to S36 of FIG. 4 in the second embodiment.
However, if the heater drive instruction is issued in step S79, the process proceeds to step S8 before proceeding to step S63.
0 will reset pwon_flag. This allows the power source O
Pwon_flag except in warming up state immediately after N
Is reset.

By performing the above control,
In the case of warming up immediately after the power is turned on, the usage method of the heaters H1 and H2 is selected according to the instruction from the external device 300, and when the heater startup is required thereafter, the two heaters H1 and H2 are used. To recover quickly, and when controlling the temperature at a constant temperature, use one heater in sequence to improve the effectiveness of the heaters H1 and H2.
Can be used.

As described in Examples 1 to 4 above,
For image formation with heat fixing means having a plurality of heaters,
By providing a heater control unit that selectively drives a plurality of heaters according to the operating state of the apparatus, it is possible to reduce the inrush current when a plurality of heaters are used at the same time, and, if necessary, a thermal fixing device. 8 can be quickly started up, and the life of the heat fixing device 8 can be extended.

In each of the above embodiments, the number of heaters is two, but the same effect can be obtained by the same control even when the number of heaters is more than two.

B. The following fifth to eighth examples are examples of the image forming apparatus having the configuration described in (7) to (13) [corresponding to claims 7 to 13], which solves the problem 2. is there.

<Embodiment 5> (FIGS. 8 and 9) In this embodiment, with respect to the heat fixing device 8 shown in FIG. 22, as shown in FIG. 8, a fixing roller 81 and a pressure roller 82 as heat fixing means.
A part of the periphery of is covered with a heat insulating material 86. In the present embodiment, the heat insulating material 86 is a heat insulating box having a three-layer structure wall composed of first to third layers 86a, 86b, 86c as shown in a partially enlarged sectional view of FIG. Third layer 86c
Is made of stainless steel in consideration of rust prevention, and the second layer 86
b is a vacuum layer. The second layer 86b need not be a vacuum layer as long as it is a material layer having a lower thermal conductivity than the first layer / third layer 86a / 86c.

By disposing the heat insulating material 86 as described above, it is possible to suppress wasteful heat radiation escaping from the heat fixing means 81 and 82 and improve the heat efficiency. It is possible to reduce the energy consumption outside the printing of the image forming apparatus to about half.

<Sixth Embodiment> (FIGS. 10 and 11) In this embodiment, the heat fixing device 8 of the fifth embodiment can be opened / closed to the recording medium inlet side and the recording medium inlet side of the heat fixing means 81/82. Shutter members 87 and 88 are provided.
These shutter members 87 and 88 are also heat insulating materials.
87a and 88a are opening / closing hinge portions of the shutter members 87 and 88, respectively.

These shutter members 87 and 88 are outside the printing of the image forming apparatus, respectively, as shown in FIG. 10, by the spring pressure of a spring member (not shown) on the inlet side and the outlet side of the recording medium of the heat fixing means 81 and 82. Is kept closed.

As a result, the heat fixing means 81 and 82 are substantially surrounded by the heat insulating box 86 and the shutter members 87 and 88 made of heat insulating material, and the energy loss can be further reduced as compared with the sixth embodiment.

During the printing of the image forming apparatus, the shutter members 87 and 88 are closed as shown in FIG. 11 by receiving the torque of the motor for driving the fixing roller 81 via the transmission means (not shown). By maintaining the state, the recording medium inlet side and the outlet side of the heat fixing means 81/82 are opened, so that the recording medium is introduced into the heat fixing means 81/82 without any trouble, and the heat fixing process of the image is performed. .

<Embodiment 7> (FIG. 12) In this embodiment, the thermal fixing device drive gear train G1 shown in FIG. 24 is used.
12, the slits (hollow portions) S are formed in the flesh portions of the teeth of the gears G1 to G4 as shown in FIG.

In the case of the conventional thermal fixing device 8 shown in FIGS. 22 and 23, the heat of the fixing roller 81 is transmitted through the gear G2 and the other mechanism portion (for example, the gears G1 → G3 → G4).
Escape to a).

However, as shown in FIG. 12, the slits S are formed in a part of the flesh of the gears G1 to G4, so that the thermal conductivity becomes half or less as compared with the conventional case, and the gears are reduced. It is possible to suppress the heat radiation by less than half, and it is possible to realize a thermal fixing device with good energy efficiency.

In addition to providing the slit S in the gear, at least a part of the meat portion of the gear can be made of a member having a low thermal conductivity.

<Embodiment 8> (FIG. 13) In this embodiment, the thermal fixing device drive gear train G1 shown in FIG. 24 is used.
Regarding G4, the first position where the drive gear G1 is engaged with the gear G2 and the gear G3 as shown by the chain double-dashed line in FIG. 13 and the first position where the drive gear G1 is not engaged with the gear G2 and the gear G3 as shown by the solid line are shown. This is a moving gear which is selectively switched in position 2 by a switching means (not shown) along a guide slot R into which the shaft O of the gear G1 is fitted.

During printing by the image forming apparatus, the driving gear G1 is moved to the first position indicated by the chain double-dashed line, and the thermal fixing device 8 is driven.

Outside the printing of the image forming apparatus, the drive gear G1 is changed to the second position shown by the solid line, and the gear G2 is disengaged from the gear G2 so that the heat conduction between the gears is greatly reduced. It is possible to realize a heat fixing device that can suppress heat dissipation and that has good heat efficiency.

As in the fifth to eighth embodiments, the heat fixing means is surrounded by a heat insulating material, a part of the gear is made of a member having poor heat conduction, and the gear is moved out of printing. As a result, it is possible to realize an energy-saving type device with good thermal efficiency that consumes less than half the energy consumed by the thermal fixing device outside printing.

C. The following Examples 9 and 10 are the same as the above (14).
(16) An example of an image forming apparatus having the configuration described in [corresponding to claims 14 to 16], which solves the problem 3.

<Embodiment 9> (FIGS. 14 to 16) FIG. 14 is a schematic configuration diagram of an image forming apparatus of the present embodiment.
The apparatus of this embodiment is a laser beam printer using a transfer type electrophotographic process, and the same components, members and parts as those in FIG. 1 or FIG. To do.

In the printer of this embodiment, the transfer timing of the transfer sheet P as a recording medium to the transfer section is set by the registration roller 16A. Registration roller 16
At A, the front end of the fed paper is abutted to correct the skew, and the timing of writing the image on the photoconductor 1 and conveying the paper is set. The primary charging unit 21 of the photoconductor uses a charging roller. Further, the transfer means 5 uses a transfer roller. FIG. 15 is a circuit block diagram of a control system of the printer.

Reference numeral 400 denotes a printer controller which develops image code data from an external device such as a host computer into bit data necessary for printing by the printer, reads internal information of the printer by communication or the like, and displays it.

Reference numeral 401 denotes an engine control unit which controls the operation of each unit of the printer engine in accordance with instructions from the printer controller 400 and notifies the printer controller 400 of printer internal information.

Reference numeral 402 denotes a paper conveyance control unit that controls the driving and stopping of motors, rollers and the like for paper conveyance in accordance with instructions from the engine control unit 401.

Reference numeral 403 is a high-voltage control unit which controls the high-voltage output of charging, development, and transfer in accordance with instructions from the engine control unit 401.

Reference numeral 404 is an optical system control unit which drives / stops the scanner motor and blinks the laser based on an instruction from the engine control unit 401.

Reference numeral 405 is a sensor input unit for transmitting information of the registration sensor and the paper discharge sensor to the engine control unit 401.

Reference numeral 406 indicates the temperature of the fixing device by the engine control unit 4.
A fixing device temperature control unit that adjusts the temperature to a designated value of 01.

FIG. 16 shows the control sequence of the engine control unit 401 when the manual feed is designated in such a control system. This flowchart shows a control sequence from the reception of the print request signal from the printer controller 400 to the manual sheet feeding and the comparison between the designated sheet size and the sheet actually conveyed.

First, when the power is turned on, the printer engine is initialized (step S1). This initialization is performed by the central processing unit (CP) in the engine control unit 401.
U) initialization and heating of the temperature of the heat fixing device 8 to a predetermined standby state are included.

When the initialization of the printer engine is completed,
The engine control unit 401 waits for a print request from the printer controller 400. Loop processing of step S2).

Print request (/ PRNT = "LOW")
When receiving, the paper conveying system including the photoconductor 1 is driven, and each high voltage for charging, developing and transferring is started. Also, start the scanner motor up to the specified rotation speed. Further, control is started so that the temperature of the heat fixing device 8 becomes a predetermined print temperature (T1).

When these processes are completed, the paper feed operation from the manual paper feed port of the designated paper feed port is started (step S).
3). At this point, the registration roller 16A is stopped and waits until the leading edge of the paper hits.

After that, when the registration sensor S2 enters the state with paper and the time corresponding to the tip of the paper reliably hitting the registration roller 16A elapses, the manual feed operation is stopped and the vertical synchronization request signal is sent to the printer controller 400. (/ VSREQ) is output (steps S4 to S
5).

When the vertical synchronizing signal (/ VSYNC) is received from the printer roller 400, the driving of the registration roller 16A is started (steps S6 and S7).

After driving the registration rollers 16A, the engine controller 401 activates the paper size detection timer (step S8).

When the sheet is conveyed and the registration sensor S2 detects that there is no sheet (step S9), the timer is stopped, the timer value t ₁ is read, and the engine control unit 401 is read in advance.
Is compared with the value t ₀ programmed in (step S10-
S12), if t ₀ ≧ t ₁ , the temperature of the heat fixing device 8 is controlled to be T ₂ (step S13), and t ₀ ≧ t
If it is not ₁ , the temperature of the heat fixing device 8 is controlled to be T ₁ , the image forming process is performed (step S14), and the fixing process is performed (step S15).

T ₀ is the time for recognizing a predetermined paper size. When the predetermined paper size is l and the transport speed is v, it is given by t ₀ = l / v.

As described above, when manually feeding paper, the length of the paper is detected, and if the length of the paper is less than a predetermined length, control is performed to raise the temperature of the heat fixing device so that a thick paper such as an envelope can be obtained. Even when the sheet is manually fed, it is possible to obtain an image-formed product having a suitable fixing property.

<Embodiment 10> (FIG. 17) FIG. 17 is a control flowchart in this embodiment.
Steps S1 to S11, S14 and S15 are the same as those in the ninth embodiment.
Since it is the same as the control flowchart of FIG. 16 of FIG.

In step S21, it is determined whether or not the sheet is being conveyed. If the sheet is currently being conveyed, the timer value t ₁ read in step S11 is compared with the preprogrammed value t ₀ (step S22). If t ₀ ≧ t ₁ is not set, the next paper feed timing is set to t ₂ , which is the timing for opening the normal paper interval (step S23), and if t ₀ ≧ t _1, it is the timing for opening the paper interval more than usual. Is t
Set the next paper feed timing to ₃ (step S2
4) Manually feed the paper.

That is, when the paper is shorter than the predetermined length, the timing of feeding the next paper is delayed to prevent the temperature of the heat fixing device 8 from being lowered when the thick paper such as the envelope is manually fed. An image-formed product having fixability can be obtained.

As described in the ninth and tenth embodiments, when the size of the manual feed sheet in the conveying direction is equal to or smaller than the predetermined length, the sequence for thick paper is performed such that the fixing temperature is raised or the gap between sheets is increased. Even when a thick paper such as an envelope is manually fed, it is possible to obtain an image-formed product having a suitable fixing property.

The same control can be performed when a thick paper such as an envelope is fed from a cassette whose paper size can be identified.

D. The following Examples 11 to 13 are based on the above (1
It is an embodiment of the ceramic heater for heat fixing having the structure described in 7) to (19) [corresponding to claims 17 to 19], and solves the problem 4.

<Embodiment 11> (FIGS. 18 and 19) FIG. 18 shows a schematic structure of a ceramic heater 40 for heat fixing of the present embodiment. (A) is a partially cutaway surface view of the heater. , (B) is a rear view, and (c) is a longitudinal sectional view.

41 is an alumina substrate as a heater base,
Reference numeral 42 denotes a heating resistor formed on the front surface side of the substrate 41 in a linear strip shape along the length of the substrate, and 43a and 43e denote first and second electrode patterns (first and second electrode patterns respectively formed on the front and back surfaces on one end side of the substrate 41). Electrode terminals, electrode pads). The first electrode pattern 43a and one end of the heating resistor 42 are electrically connected. 43b is connected to the other end of the heating resistor 42 so as to be electrically connected to the heating resistor 42, and the heating resistor 4 is provided on the front surface side of the substrate.
2 is an electric path pattern formed substantially in parallel with 2 and having an appropriate turn back length, and 43d is an electric path pattern formed by extending the second electrode pattern 43e on the back surface side of the substrate 41 in series. The end portion of the pattern 43b on the side opposite to the heating resistor 42 side and the end portion of the electric path pattern 43d on the rear surface side of the substrate opposite to the second electrode pattern 43e side are electrically connected by a through hole pattern. There is. Reference numeral 44 denotes a protective glass layer covering the heater surface side in order to protect the heating resistor 42 and ensure the smoothness of the heater surface.

45a and 45b are a pair of electrode patterns arranged side by side on the back surface of the other end of the substrate 2, and 45c and 45d are formed by extending the electrode patterns 45a and 45b to one end of the substrate 41 by an appropriate length. The pair of substantially parallel electric path patterns 45 is a temperature detecting element formed between the tip ends of the pair of electric path patterns 45c and 45d so as to be electrically connected to the electric path patterns 45c and 45d.

Reference numeral 50a denotes a power supply connector fitted to one end side of the heater 40, and has first and second electrode patterns 43a existing on the front and back surfaces on one end side of the heater substrate 41, respectively.
The pair of connector contacts on the side of the power supply connector 50a are pressed against 43e to be electrically connected.
The voltage of the power supply is applied between the first and second electrode patterns 43a and 43e through the connector 50a, so that a current is supplied to the first electrode pattern 43a → the heating resistor 42 → the electric circuit pattern 43b → the through hole pattern 43c. -> Electric circuit pattern 43d-> Flowing in the path of the second electrode pattern 43e (or the reverse path), the heating resistor 42 generates heat, and the heater 40 rises in temperature. In order to secure a creeping distance when a commercial power source is supplied to the heating resistor 41, it is necessary to separately provide a power supply circuit for the heating resistor 42 on the front surface side and the back surface side of the substrate 41 as in the present embodiment. This is an effective means configuration.

Reference numeral 50b denotes a sensor connector fitted to the other end side of the heater 40, and a pair of electrode patterns 45a and 45b respectively present on the other end side back surface side of the heater substrate 41.
Then, a pair of connector contacts on the connector side are pressed to be electrically connected. The temperature of the heater 40 is detected by the temperature detecting element 45 on the back surface of the substrate, and the detected information is fed back to the temperature adjustment control circuit via the connector 50b to control the energization of the heating resistor 42 to control the heater 40.
Is controlled to a predetermined temperature.

Electrode patterns 43a, 43e, 45a, 4
5b, electric circuit patterns 43b, 43d, 45c, 45d,
Silver palladium is generally used for the through-hole pattern 43c. The temperature detection element 45 uses, for example, a platinum resistance. Platinum resistors can be manufactured by a thick film printing process.

In the heater 40, the front surface side and the back surface side of the substrate 41 are usually processed in separate steps. The electrode pattern 43a and the electric circuit pattern 43b are printed on the front surface side of the substrate 41,
After drying and firing, the heating resistor 42 is printed, dried and fired. Further, the electrode pattern 43e.4 is formed on the back surface side of the substrate 41.
5a / 45b and electric circuit patterns 43d / 45c / 45d are printed, dried and fired, and then the temperature detection element 45 is formed.

Usually, the heating resistor 42 is trimmed so that the resistance value falls within a predetermined range. Similarly, the temperature detecting element 45 is also trimmed so that the resistance value falls within a predetermined range. Finally, glass coating 4 to protect the heater and ensure the smoothness of the surface.
Do 4.

After the heating resistor, the electrode pattern, the electric path pattern, and the temperature detecting element are printed and dried, it is possible to carry out baking at once.

FIG. 19 shows an outline of the control circuit of the heater 40. Reference numeral 51 is a 100V or 200V commercial power source, 52 is a triac for turning on / off the power supply of the heating resistor 42, 53 is a zero cross circuit for obtaining the zero cross timing of the power source, and 54 is a C for switching noise elimination.
It is an R filter. 55 is a photo triac coupler,
Reference numeral 56 is a photocoupler, which performs on / off control of the triac 52 after performing primary / secondary separation, respectively. Reference numeral 57 is a drive transistor for on / off control of the heating resistor 42, and 58 is a main control unit for controlling the temperature of the ceramic heater 40.

Based on the information of the temperature detecting element 45, the main controller 5
The electric power of the heating resistor 42 is controlled via 8 to control the temperature.

<Embodiment 12> (FIG. 20 (a)) In this embodiment, as shown in FIG. 20 (a) in order to protect the temperature detecting element 45 on the back side of the heater 40 of the heater 40 of the 11th embodiment. The protective glass layer 44A is provided by covering the part of the element 45. Since the temperature detecting element 45 is protected in this manner, the reliability is further increased against environmental changes.

<Embodiment 13> (FIG. 20 (b)) In this embodiment, the heater 40 of the embodiment 11 has a heater back surface similar to the heater front surface side as shown in FIG. 20 (b).
As described above, the protective glass layer 44A is provided on substantially the entire surface. It is effective as a countermeasure against migration of the silver / palladium pattern, which is the electrode pattern / electric circuit pattern on the backside of the heater, and the silver pattern, and the reliability of the ceramic heater is greatly increased.

As described in Embodiments 11 to 13 above, the temperature detecting element 45 is directly formed on the heater substrate serving as the heater base by using the thick film printing technique similar to that for the heating resistor / electrode pattern. With this structure, it is possible to realize a ceramic heater for heat fixing that enables highly reliable temperature detection. Further, by using the same thick film printing process, an inexpensive ceramic heater for heat fixing can be manufactured.

[0196]

As described above, According to the image forming apparatus having the structure according to any one of claims 1 to 6, the rush current at the start of driving the heater in the image forming apparatus having the heat fixing unit having a plurality of heaters. It is possible to obtain the effects that the temperature can be lowered, the heaters can be efficiently used to extend the device life of the heat fixing unit, the warm-up time can be shortened, and the power consumption in the constant temperature control state can be reduced. The purpose of 1 can be achieved well.

.. According to the thermal fixing device having the structure according to any one of claims 7 to 13, there is provided a thermal fixing device for fixing an image material image such as toner formed and carried on a recording medium.
Energy consumption can be saved by reducing the amount of heat that escapes from the heat fixing unit to the outside as much as possible. For example, it is possible to reduce the energy outside the printing of the image forming apparatus to less than half and improve thermal efficiency. Therefore, the second purpose can be achieved well.

.. According to the image forming apparatus of the fourteenth to sixteenth aspects, even when a thick paper such as an envelope is passed as a recording medium, the fixing failure does not occur, and the third object can be achieved well.

.. According to the ceramic heater for heat fixing characterized by the constitutions of claims 17 to 19, the problem of deterioration / non-conduction of the electrically conductive portion is solved, and high durability /
This kind of heater having high precision and high reliability and low cost can be realized, and the fourth purpose can be achieved well.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment.

FIG. 2 Block diagram of control system

FIG. 3 is a flowchart showing control of heater selection / switching means.

FIG. 4 is a flowchart showing control of a heater selection / switching unit of the image forming apparatus according to the second embodiment.

FIG. 5 is a circuit block diagram of a control system of the image forming apparatus according to the third embodiment.

FIG. 6 is a flowchart showing control of heater selection / switching means.

FIG. 7 is a flowchart showing the control of the heater selection / switching means of the image forming apparatus of the fourth embodiment.

FIG. 8 is a cross-sectional view of the heat fixing device according to the fifth embodiment.

FIG. 9 is a partially enlarged sectional view showing a layer structure of a heat insulating material.

FIG. 10 is a cross-sectional view of the thermal fixing device according to the sixth exemplary embodiment when the shutter member is closed.

FIG. 11 is a cross-sectional view of the thermal fixing device when the shutter member is open.

FIG. 12 is a diagram of a driving gear train of a heat fixing device according to a seventh exemplary embodiment.

FIG. 13 is a diagram of a driving gear train of the heat fixing device according to the eighth embodiment.

FIG. 14 is a schematic configuration diagram of an image forming apparatus according to a ninth embodiment.

FIG. 15 is a circuit block diagram of a control system

FIG. 16 is a control sequence diagram.

FIG. 17 is a control flowchart of the image forming apparatus according to the tenth embodiment.

FIG. 18 shows a schematic structure of a ceramic heater for heat fixing of Example 11, (a) is a partially cutaway front view of the heater, (b) is a rear view, and (c) is a longitudinal sectional view.

FIG. 19 is a schematic diagram of a heater control circuit.

FIG. 20 (a) is a rear view of the heater of Example 12,
(B) is a rear view of the heater of Example 13.

FIG. 21 is a schematic configuration diagram of an example of an image forming apparatus.

FIG. 22 is a schematic configuration diagram of a heat fixing device.

FIG. 23 is a schematic configuration diagram of a thermal fixing device having a plurality of (two) heaters.

FIG. 24 is a diagram of a driving gear train of the heat fixing device.

FIG. 25 is a schematic cross-sectional view of the essential parts of a film heating type thermal fixing device.

FIG. 26 is a partially cutaway plan view of the heater.

[Explanation of symbols]

 1 Rotating Drum Type Electrophotographic Photoreceptor as Image Carrier 2 Primary Charger 3 Laser Beam Scanner 4 Developer 5 Transfer Device 8 Thermal Fixer (Heat Lara Type) 81 Fixing Roller (Heat Roller) 82 Pressure Roller 83 Temperature Detection element (thermistor) 86 Insulation material (insulation box) 87/88 Open / close shutter member H / H1 / H2 heater 12 Paper feed cassette P Transfer paper as recording medium 13 Paper feed roller 16 Registration shutter 16A Registration roller 19 Manual paper feed Table 20 Manual feed roller G1 to G4 Thermal fixing device drive gear train 8A Thermal fixing device (film heating type) 40 Ceramic heater 41 Heater substrate 42 Heating resistor 44 Surface protective layer 45 Temperature detecting element 46 Heater holder 47 Heater supporting member 48 Heat resistance Film (fixing film) 49 Pressure roller 0 power supply connector

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Nakahara 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takashi Seiya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Akihiro Shibata 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (19)

[Claims] 1. An image forming apparatus for forming an image on a recording medium with a developing material such as toner and thermally fixing the image to output an image-formed product, wherein the heat fixing means has a plurality of heaters. An image forming apparatus comprising: a heater control unit that selectively drives the plurality of heaters according to the operating state of. 2. The image forming apparatus according to claim 1, further comprising a heater control unit that shifts the drive start timing of each heater when a plurality of heaters of the heat fixing unit are used at the same time. apparatus. 3. The image forming apparatus according to claim 1, wherein the heater control means switches between a mode in which a plurality of heaters are all used and a mode in which a small number of heaters are sequentially used in accordance with an operating state of the apparatus. An image forming apparatus comprising: 4. The image forming apparatus according to claim 3, wherein all the heaters are used in the process of raising the temperature of the heat fixing means from a low temperature to a predetermined temperature, and after the temperature reaches the predetermined temperature, the temperature is kept constant. An image forming apparatus characterized by having a heater control means for sequentially using the heaters in a state of being maintained at the temperature. 5. The image forming apparatus according to claim 4, further comprising an input unit for externally designating whether or not to quickly start up in the process of starting from a low temperature of the heat fixing unit to a predetermined temperature. An image forming apparatus having heater control means for using all the heaters when a quick start-up is designated by the input means and for sequentially using a small number of heaters when a quick start-up is not designated . 6. The image forming apparatus according to claim 5, wherein at least after jam recovery processing, after returning from a sleep state, and when transitioning from standby to image formation, regardless of designation from outside. An image forming apparatus comprising a heater control unit that uses all the heaters of the heat fixing unit. 7. A thermal fixing device for fixing an image material image such as toner formed and carried on a recording medium, wherein at least a part of the periphery of the thermal fixing means is covered with a heat insulating material. . 8. The heat fixing device according to claim 7, wherein the heat insulating material has a three-layer structure, and the first and third layers are metal.
A thermal fixing device, wherein at least two layers are made of a material having a lower thermal conductivity than one layer and three layers. 9. The heat fixing device according to claim 8, wherein the heat insulating material comprises one and three layers of stainless steel and two layers of vacuum. 10. The thermal fixing device according to claim 7, wherein an opening / closing window through which the recording medium passes is provided in a part of the heat insulating material, and the recording medium is supplied to and discharged from the thermal fixing means. A thermal fixing device characterized in that the window portion is opened and controlled at the time of paper. 11. A thermal fixing device for fixing a visible material image such as toner formed and carried on a recording medium, wherein at least a part of teeth inside a gear for driving the thermal fixing means and a shaft has a thermal conductivity. A heat fixing device characterized by being configured with a low material. 12. The heat fixing device according to claim 11, wherein a part of the inside of the tooth is hollow. 13. The thermal fixing device according to claim 11 or 12, wherein at least one gear in a gear train for driving the thermal fixing means is a gear that is detachable from another gear,
A thermal fixing device characterized in that the position of the gear is controlled so as not to mesh with other gears except during fixing. 14. An image forming apparatus for forming an image on a recording medium with a developing material such as toner and thermally fixing the image to output an image-formed product, wherein the size of the recording medium fed in the apparatus in the conveyance direction is set. An image forming apparatus, comprising: a detecting unit for detecting, wherein when the size detected by the detecting unit is smaller than a predetermined size, the device operation is executed by control corresponding to thick paper. 15. The image forming apparatus according to claim 14, wherein the cardboard-corresponding control is to control the fixing temperature of the heat fixing unit to be higher than normal control. 16. The image forming apparatus according to claim 14, wherein the control for handling thick paper means controlling a paper feeding interval of a recording medium to be larger than a normal control. 17. A ceramic heater for fixing heat, which comprises a ceramic substrate and a heating resistor arranged on the substrate as a basic component and supplies electric power to the heating resistor to generate heat, wherein the heating resistor is provided on the substrate. An output of the temperature detecting element, which has a structure for printing and generating, has an electrode pattern for supplying electric power to the heating resistor on the substrate, and has means for directly configuring the temperature detecting element on the substrate Based on the above, a ceramic heater for thermal fixing, characterized in that the electric power of the heating resistor is controlled to control the temperature control of the heater. 18. The ceramic heater for thermal fixing according to claim 17, wherein the temperature detecting element is a thick film printed on the substrate.
A ceramic heater for heat fixing, characterized by being formed using a firing process. 19. The thermal fixing ceramic heater according to claim 17 or 18, wherein the substrate is an alumina substrate.