JPH06282200A - Heating device and image forming device - Google Patents

Abstract

PURPOSE:To improve the safety and reliability of a device by providing, independently of a heating member, a heater for preheating a safety device, thereby securely preventing overheat runaway without a time lag when the heating member overheats. CONSTITUTION:When a print signal is not given, a changeover switch 38 is kept in a first changeover condition, and consequently a power supply circuit for the main heater 11 opens without the main heater 11 being heated; however, a power supply circuit for an auxiliary heater 27 opens and the auxiliary heater 27 is kept heated, and by the heat a temperature fuse 26 serving as the safety device is kept preheated at a temperature of 40-60 deg.C. Because the changeover switch 38 is kept in a second changeover condition by the detection of the print signal, the power supply circuit for the auxiliary heater 27 opens, and the power supply circuit for the main heater 11 opens. Thus, the power is supplied to the energizing/heating resistor of the main heater 11 to be heated, so that the temperature of the main heater 11 is risen.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Image forming apparatuses such as copying machines and printers
Image forming process means (electrophotographic process, electrostatic recording process, magnetic recording process, etc.) of appropriate principle and method for recording material (transfer material, electro-fax sheet, electrostatic recording paper, etc.) fed from the paper feeding section ) Form and carry an unfixed image (toner image) of desired image information by an indirect (transfer) method or a direct method, and heat the recording material (image heat fixing apparatus).
In general, the unfixed image is heated and heated to be subjected to a heat fixing process to be output as an image formed product (copy / print).

As a heating device for thermally fixing an unfixed image formed and carried on a recording material, a so-called heat roller (heat roller) type is widely used. Since it has various advantages, so-called film heating type heating devices have been put to practical use.

The heat roller type heating device is mainly composed of a rotating roller pair of a heating roller (fixing roller) as a heating member and a pressing roller as a pressing member pressed against the heating roller. A recording material, on which an unfixed image is formed and carried, is introduced as a material to be heated into the pressure contact nip part (fixing nip part) and is nipped and conveyed, and the unfixed image is transferred to the recording material surface by heat and pressure of the roller pair. It is heat-fixed.

A heat roller as a heating member is generally a hollow metal roller as a heat transfer member, which is usually made of aluminum, a halogen heater inserted into the hollow metal roller as a heat source, and an outer periphery of the hollow metal roller. P coated with good releasability for molten developer (toner)
It is composed of a release material layer such as TFE.

A pressure roller as a pressure member generally comprises a metal core rod as a reinforcing and rigid member and a heat-resistant elastic material layer such as heat-resistant rubber formed concentrically around the outer periphery of the metal core rod. The heat-resistant elastic material layer is elastically deformed to form a pressure contact nip portion with a proper width between the heat roller and the recording material introduced into the pressure contact nip portion and is pressed in surface contact with the heat roller.

The hollow metal roller of the heat roller as a heating member is heated by a halogen heater as a heat source incorporated therein, the surface temperature of the roller is detected by a temperature detecting device such as a thermistor, and the detected information is temperature controlled. The surface temperature of the heat roller is controlled to a predetermined fixing temperature by being fed back to the system and controlling the energization of the halogen heater. The heat of the halogen heater as the heat source is transferred to the unfixed image of the recording material introduced between the heat roller and the pressure roller via the hollow metal roller as the heat transfer member.

A film heating type heating device or an image heat fixing device is disclosed in JP-A-63-313182, JP-A-1-263679, JP-A-2-157878, and JP-A-4-44075-44083. It is known that the material to be heated is brought into close contact with the heating body (heating heater) as the heating member via the heat resistant film as the heat transfer member, and the heat resistant film to which the material to be heated is brought into sliding contact with the heating member. The heat of the heating member is transferred to the material to be heated through the heat resistant film.

In such a film heating type heating device, a heating member of a low heat capacity having a rapid temperature rise or a thin heat-resistant film such as polyimide (PI) can be used as a heating member, so that a heating roller type or other type can be used. Compared with a heating device, it has advantages such as power saving and shortening of wait time (quick start property), and lowering of temperature rise inside the main body device such as an image forming apparatus.

The heating element as a heating member is basically composed of a heat-resistant and insulating ceramic substrate and a thin-film energization heating resistor formed on the substrate by vapor deposition, sputtering, etc. A so-called planar ceramics heater that supplies heat to generate heat is used. The temperature rise of this heater is detected by a temperature detection device, and the detected information is fed back to the temperature control system to control the energization of the energization heating resistor, so that the temperature of the heater rises to a predetermined temperature. Key management.

Not only the heat roller system and the film heating system as in the above example, but also this type of heating device generally causes a runaway (overheating) trouble of the heating member due to malfunction of the temperature control system of the heating member. As a safety measure to prevent, a safety device is provided which detects a high temperature (overheat) of a heating member which is higher than a predetermined allowable value and physically cuts off energization to the heating member.

Generally, a thermo-protector such as a thermal fuse or a thermostat is used as the safety device. The thermo-protector is placed in contact with or close to the heating member to receive heat from the heating member, and the safety device is energized by the heating member. When the heating member reaches a temperature higher than a predetermined allowable temperature, the safety device operates (fuse blows, switch opens, etc.) to open the energization system of the heating member. It is to secure the safety by physically interrupting the power supply to the members.

[0013]

[Problems to be Solved by the Invention]

(A) Problem 1 As described above, safety devices such as thermal fuses and thermostats receive the heat of the heating member and follow the temperature rise as the temperature of the heating member rises. The safety (prevention of overheating of the heating device) is secured by opening and shutting off the power to the heating member.
There is a problem that the follow-up temperature rise of the safety device may be delayed with respect to the temperature rise of the heating member due to the heat capacity of the safety device and the rate of temperature rise of the heating member.

For example, in the case of a film heating type heating device using a ceramic heater having a small heat capacity as the heating member as in the above-mentioned example, the ratio of the heat capacity of the safety device such as the temperature fuse and the thermostat to the heating member is high. Since it is large, the safety device does not follow the sudden temperature rise such as when the heating member runs out of room temperature, and the safety device does not heat up sufficiently, and the safety device operates after the heating device smokes and ignites. There are times when you do not do.

Further, since the heating member removes heat from the safety device, the temperature rise in the heating member portion where the safety device is located becomes slow, and the heat distribution along the length of the heating member becomes uneven, resulting in the image heat fixing device. In that case, that portion may not reach a predetermined fixing temperature and may cause defective fixing.

Therefore, a first object of the present invention is to provide a heating device equipped with a safety device that functions to prevent overheating and runaway of the device when it receives heat from the heating member and rises above a predetermined temperature. The safety device heats up following a sudden heat rise such as a runaway from room temperature without delay, so that when the heating member overheats, the overheat runaway prevention operation can be reliably performed without a time lag. It is to improve the safety and reliability of the device. Another object is to prevent uneven heat distribution along the length of the heating member due to the presence of the safety device.

(B) Problem 2 As described above, in the film heating type heating device, the material to be heated is brought into close contact with the heating member via the heat resistant film, and the heat resistant film having the material to be heated is slid on the heating member. Since the heat of the heating member is moved and applied to the material to be heated via the heat resistant film, the sliding heating member and the contact surface of the heat resistant film against the heating member (inner surface of the film) are abraded by heat and sliding friction. May be promoted to cause scratches and significantly increase frictional resistance.

When the frictional resistance is increased in this way, the film transport is impaired, the film and the film transport roller slip, and the film transport is stopped, or the stick slip occurs between the film and the heating member. Squeaking occurs. When the heating device is an image heat fixing device, the film slip phenomenon described above becomes a serious defect that disturbs the fixed image.

A second object of the present invention is to increase the sliding friction resistance of the film heating type heating device by keeping the sliding friction resistance between the heating member and the inner surface of the film low for a long period of time. It is to prevent the occurrence of such a film transport obstacle and improve the reliability of the apparatus.

(C) Problem 3 An image forming process means for forming and carrying an unfixed image of desired image information on a recording material, and an unfixed image of the recording material from the image forming process means is heat-fixed. In an image forming apparatus having a heating device, a recording material (B5, A) of a size smaller than a recording material of the maximum size (for example, A4) that can be used to pass through the apparatus.
(5, postcards, envelopes, etc.) when 50 or 100 sheets are continuously passed to form an image, the non-sheet passing portion of the heating member of the heating device as the image heat fixing device is heated by the recording material. Since it is not taken away, heat is accumulated and the temperature of the heating member becomes higher than that of the sheet passing portion, and a so-called "non-sheet passing portion temperature rising" phenomenon occurs in which the temperature difference between the heating member and the sheet passing portion becomes large.

Such a temperature rise in the non-sheet passing portion of the heating member corresponds to an image portion corresponding to a portion in which the temperature rise in the non-sheet passing portion of the heating member occurs when a next large size recording material is passed. Then, the image fixability of the image portion differs from that of the other image portion, or high temperature offset of the developer occurs.

Further, the image heat fixing device uses, for example, an endless thin film as a heat-resistant film, and the film heating type heating device is configured to rotate the film by pressing it against a heating member with a rotary elastic pressure roller. In the case of, the degree of thermal expansion at both ends of the elastic pressure roller that presses the heat resistant film against the heating member is different due to the temperature rise in the non-paper passing portion of the heating member, and the roller outer diameter on the non-paper passing portion side is large. Become.

Therefore, the rotating speed of the thin film heat-resistant film, which is rotated by being driven by the rotary elastic pressure roller, becomes different at both ends, and the thin film is twisted, and when the thin film is further continuously fed. , That twist accumulates,
In the worst case, the thin film moves along the length of the heating member toward the slow-speed paper passing portion side, and the film edge on that side is pressed strongly against the film deviation regulating member and is damaged or wrinkled at the film edge. -Buckling or the like may occur, or the entire film may be completely twisted and may not function as an image heat fixing device.

Therefore, a third object of the present invention is to thermally fix an unfixed image on a recording material in the above-mentioned image forming apparatus even when a small-sized recording material is continuously fed to form an image. An object of the present invention is to prevent the temperature rise in the non-sheet passing portion of the heating device to be processed as much as possible, and solve the above-mentioned problems due to the temperature rise in the non-sheet passing portion.

[0025]

The present invention is a heating device and an image forming apparatus characterized by the following configurations.

(1) In a heating device equipped with a safety device that functions to prevent overheating and runaway of the device when the temperature of the heating member rises above a predetermined temperature, the heating member preheats the safety device. A heating device comprising a heater different from the above.

(2) The heating device according to (1), which is an image heat fixing device incorporated in the image forming apparatus and heat-fixing an unfixed image on a recording material.

(3) The material to be heated is adhered to the heating member via the heat resistant film, and the heat resistant film to which the material to be heated is adhered is slidably moved to the heating member so that the heat of the heating member is covered via the heat resistant film. In a heating device for applying to a heating material, a film guide member that supports the heating member and guides a sliding surface of the heat-resistant film so as to come into contact with the heating member is impregnated with a lubricant.

(4) The heating device according to (3) is characterized in that the lubricant impregnated in the film guide member seeps out to the surface of the film guide member when the heating member warms. .

(5) The heating apparatus according to (3), wherein a lubricant is applied to the sliding surface of the heat resistant film with the heating member.

(6) The heating device according to any one of (3) to (5), further comprising a member for bringing the material to be heated into pressure contact with the heating member via a heat resistant film.

(7) The heating device according to any one of (3) to (6), wherein the heat resistant film is an endless rotating film.

(8) The heating device according to any one of (3) to (7), which is an image thermal fixing device incorporated in an image forming apparatus and thermally fixing an unfixed image on a recording material. .

(9) An image forming process means for forming and carrying an unfixed image of desired image information on a recording material, and a heating device for thermally fixing the unfixed image of the recording material from the image forming process means. In the image forming apparatus having the image forming apparatus, the heater of the heating device is ON / OFF controlled by using an output signal of a recording material detection device provided upstream of the heating device in the recording material conveying direction. .

(10) The ON / OFF control is a control for turning off the heater in a period when the recording material does not exist in the image heat fixing section of the heating device. Image forming apparatus.

(11) The recording material detecting device is provided on a recording material conveying path from the image forming process means to the heating device, and recording in the main body of the image forming apparatus is performed immediately before starting the main body of the image forming apparatus. The image forming apparatus according to (9), which is a device that detects the presence or absence of a material, and has a control that prohibits activation of the apparatus main body when detecting the presence of a recording material.

(12) The recording material detecting device is provided on the recording material conveying path on the upstream side of the image forming process means in the recording material conveying direction, and the image forming process means is formed by a signal from the recording material detecting device. (9) The image forming apparatus described in (9), wherein writing of information to the image carrier is started.

[0038]

[Action]

(A) In a heating device equipped with a safety device that functions to prevent overheating and runaway of the device when the heat of the heating member is raised to a predetermined temperature or higher, the safety device has a preheating treatment configuration. Even if the temperature of the heating member suddenly rises from room temperature due to a malfunction of the heating member temperature control system, the safety device follows the temperature rise and the preheating temperature is used as a base to raise the temperature without a time lag. The safety device is activated before the temperature reaches the ignition temperature of the material to be heated, and the safety of the device is reliably ensured.

Further, by preheating the safety device having a larger heat capacity than that of the heating member, it is possible to prevent the temperature rise of the heating member portion to which the safety device is attached from becoming slower than that of other portions, so that the length of the heating member is long. Does not cause uneven heat distribution along the Therefore, in the image heat fixing device, uniformity of image fixing is ensured.

(B) The material to be heated is adhered to the heating member via the heat resistant film, and the heat resistant film to which the material to be heated is adhered is slidably moved to the heating member so that the heat of the heating member is covered via the heat resistant film. In a heating device for supplying a heating material, the device is driven by impregnating a film guide member that supports the heating member and guides the sliding surface of the heat-resistant film with the heating member so that the sliding surface is in contact with the film guide member. The impregnating lubricant is applied to the film guide member on the inner surface of the film while the heat resistant film moves while contacting the surface of the film guide member.

Therefore, the lubricant applied to the inner surface of the film keeps the sliding frictional resistance between the heating member and the inner surface of the film low for a long period of time. Occurrence can be prevented, and the reliability of the device can be improved.

(C) An image forming process means for forming and carrying an unfixed image of desired image information on a recording material, and a heating device for thermally fixing the unfixed image of the recording material from the image forming process means. In the image forming apparatus having the above, the heating heater of the heating device is ON / OFF controlled by using an output signal of the recording material detection device provided on the upstream side of the heating device in the recording material conveyance direction, that is, the recording material is placed in the heating device. By controlling the heating member to be turned off when there is no paper, it is possible to prevent unnecessary heating of the heating member and the pressure member, and to continuously form small-sized recording material to form an image. Even when it is executed, the temperature rise in the non-sheet passing area of the heating device is prevented as much as possible,
It is possible to eliminate the adverse effect caused by the temperature rise in the non-sheet passing portion.

[0043]

【Example】

A. Examples 1 and 2 below are examples of a heating device (image heat fixing device) having the structure described in (1) and (2) [corresponding to claims 1 and 2]. The first object is achieved.

<Embodiment 1> (FIGS. 1 to 5) The heating device of this embodiment is disclosed in Japanese Patent Laid-Open No. 4-44075 to 4408.
It is a film heating type device known from Japanese Patent No. 3, etc.,
The image heat fixing device is mounted on a printer (not shown).

FIG. 1 is an exploded perspective view of the main part, FIG. 2 is a vertical sectional front view of the apparatus, FIG. 3 is a cross-sectional view of the main part, and FIG. 4A is a partially cutaway surface view of the heating member. 7B is a rear view, and FIG. 8C is an enlarged cross-sectional model view of the heating member. It should be noted that, in the drawings, the dimensional ratios such as the vertical length, the horizontal length, and the thickness of the respective constituent members and portions are not accurate.

Reference numeral 1 (FIG. 2) is a device frame, 2.2 is a left and right side plate of the frame, and 3.3 is a vertically long member-incorporating guide slot formed symmetrically on the left and right side plate surfaces. Yes,
The upper ends of the slots 3, 3 are opened to the upper sides of the side plates 2, 2, respectively.

Reference numeral 4 denotes a pressure roller as a member facing the heating member. The pressure roller 4 comprises a mandrel bar 5 and a heat-resistant rubber material layer 6, and bearings 7, 7 are fitted on the left and right ends of the mandrel bar 5, respectively. By fitting the bearings 7 and 7 into the guide groove holes 3 and 3 of the left and right side plates 2 and 2 of the frame body 1 from the upper end open portion and dropping them to the lower ends of the guide groove holes 3 and 3,
The pressure roller 4 is provided between the left and right side plates 2 and 2 of the frame 1
It is freely rotatably incorporated through 7. Reference numeral 8 denotes a drive gear fixed to one end side of the mandrel rod 5 of the pressure roller 4.

Reference numeral 9 denotes a film guide member having a substantially semicircular arc trough shape (FIG. 3) in cross section, and 10 and 10 are projecting portions integrally formed on both left and right ends of the guide member 9. A ceramics heater 11 as a heating member is provided on the lower surface of the guide member 9 along the length.

Reference numeral 12 denotes a cylindrical or tube-shaped endless thin film heat resistant film (fixing film) loosely fitted on the guide member 9 with the heater 11.

The guide member 9 with the heater 11 is fitted with the heat-resistant film 12 on the outer surface thereof, and the protruding portions 10 and 10 at the left and right ends are formed in the guide groove 3 of the left and right side plates 2 and 2 of the frame body 1, respectively. It is assembled by fitting it into 3 from the open upper end and dropping it between the left and right side plates 2 and 2 of the frame 1. By incorporating this guide member 9, the heater 1 on the upper surface of the pressure roller 4 and the lower surface of the guide member 9 which have been previously assembled.
1 and 2 face each other with the heat-resistant film 12 interposed therebetween.

Reference numeral 13 denotes an upper cover plate of the device frame 1, which is fixed to the left and right side plates 2.2 of the device frame 1 with screws 14 and 14 and assembled. 15 and 15 are pressure springs,
Overhanging portions 13a.1 at the left and right ends of the top cover plate 13
3a and the protruding portions 1 at the left and right ends of the guide member 9
It has been shrunk between 0 and 10. The left and right pressure springs 15 and 15 exert a pressing force on the guide member 9 so that the guide member 9 and the pressure roller 4 are heat-resistant.
2, the heat-resistant rubber material layer 6 of the pressure roller 4 is deformed, and the pressure roller 4 comes into surface contact with the heater 11 with the heat-resistant film 12 interposed therebetween, and a pressure contact nip portion (fixing nip) having a predetermined width. Part) N is formed.

The heat-resistant film 12 is made of, for example, a cylindrical polyimide (PI) film and has a toner release property P on the outer peripheral surface.
It is coated with a TFE layer and has heat resistance and toughness with a thickness of about 40 μm.

A gear 8 fixed to one shaft end of the pressure roller 4 meshes with a gear (not shown) of a drive system of the main body of the image forming apparatus, and has a predetermined peripheral speed in a counterclockwise direction in FIG. By being rotationally driven, the cylindrical film 12 is brought into close contact with the surface of the heater 11 by the surface frictional force of the pressure roller 4 and is rotationally driven clockwise around the film guide member 9.

The film 12 is being rotated by the rotation of the pressure roller 4, and the heater 11 is conveyed from an image forming process means (not shown) while the heater 11 is heated to a predetermined temperature as will be described later. A recording material (transfer material) P having an unfixed toner image t as a material to be heated carried on its upper surface.
Is introduced between the rotary film 12 and the rotary pressure roller 4 in the fixing nip portion N by a recording material guide guide (not shown).

The recording material P introduced into the fixing nip portion N comes into close contact with the surface of the rotating film 12 and passes through the fixing nip portion N together with the film 12, whereby the recording material P passes through the fixing nip portion N. In the process of passing, the thermal energy of the heater 11 is given to the recording material P via the film 12, and the toner image t is heated and fixed.

Ceramic heater 11 as a heating member
In this embodiment, as shown in FIG. Elongated substrate 21 with electrical insulation, heat resistance, and low heat capacity
And b. A thin film current-carrying heat-generating resistor 22 formed in a linear strip shape along the length of the substrate at a substantially central portion in the substrate width direction on the front surface side of the substrate 21; c. The power supply electrode terminals 23 (a) and 23 (a) and 23 (a) formed on the surface of the substrate by electrically connecting both ends of the heating resistor 22.
(B), and d. A glass coating layer 24 as a heater surface protection layer which covers the surface of the substrate on which the heating resistor 22 is formed for the purpose of insulating the surface of the heater 11 and preventing wear, and e. The temperature detection device 25, the safety device 26, etc. are provided on the back surface side of the substrate 21.

The substrate 21 of the heater 11 has, for example, a width of 10
Al ₂ O ₃ of mm · thickness 1 mm · length 240 mm, Al
It is a ceramic plate such as N or SiC.

The heating resistor 22 has a thickness of 10 μm, for example.
・ Ag / Pd (silver-palladium alloy), RuO coated by screen printing, vapor deposition, sputtering etc. with a width of 1 mm
₂ , a pattern layer of a thin film of Ta ₂ N or the like.

The temperature detecting device 25 is, for example, an NTC thermistor directly mounted on the back surface of the substrate 21.

The safety device 26 is a thermal fuse in the case of the present embodiment. The thermal fuse 26 is directly abutted against the back surface of the substrate 21 to make contact therewith, and the space between the thermal fuse 26 and the back surface of the heater substrate is It is filled with a sealing material 29 (FIG. 3) having good thermal conductivity, ensuring heat transfer from the heater 11 to the thermal fuse 26.

The heater 11 is mounted on the lower surface of the film guide member 9 with the front side facing downward. 9a
9b (FIG. 2) is a through hole formed on the lower surface of the guide member 9 for allowing the temperature detecting device 25 and the thermal fuse 26 provided on the back side of the heater to escape.

27 is a thermal fuse 26 as a safety device
This is an auxiliary heater for preheating, and in the case of the present embodiment, a PTC type thermistor which has the property that its resistance increases with temperature and heats to a constant temperature is used.

The ceramic heater 11, which is the main heating member of the apparatus with respect to the auxiliary heater 27, is hereinafter referred to as the main heater.

The auxiliary heater 27 is held by a holding member 30 as shown in FIGS. 2 and 3, and the film guide member 9 is held.
A spring 32 is contracted between a spring receiving plate 31 disposed inside the auxiliary heater holding member 30 and the auxiliary heater holding member 30 to apply a downward force to the auxiliary heater holding member 30.
7 is abutted against the upper part of the thermal fuse 26 to be in contact therewith.

The auxiliary heater 27 is connected to both electrodes of the auxiliary heater by the leaf springs 33, 33 attached to the holding member 30.

Reference numerals 28 (a) and 28 (b) denote a pair of left and right power supply connectors for the energization heating resistor 22 of the main heater 11, which are fitted to the left and right end portions of the main heater 11 respectively. 11 left and right power supply electrode terminals 2
Each connector 28 (a) ・ for 3 (a) ・ 23 (b)
The connector contact 28 (b) is pressure-contacted and electrically connected.

As shown in FIG. 1, the left connector 28
In (a), the bundle wire 34 is passed through the inside of the film guide member 9 and connected to one end of the temperature fuse 26 which is a safety device, and the other end of the temperature fuse 26 is connected to the power source S via a lead wire 35. It is connected to one pole.

The connector 28 (b) on the right side has its bundle 36
Is connected to the temperature control device 37. The temperature control device 37 is connected to the other pole of the power source S via a changeover switch 38 and a lead wire 39. The temperature detection device 25 is connected to the temperature control device 37 via a lead wire 40.

The changeover switch 38, the temperature fuse 26, and the auxiliary heater 27 are connected in series from the same power source S via lead wires 39, 41, and 35, and the main heater 11 and the temperature fuse 26 are connected in series. And form a parallel circuit.

The changeover switch 38 is the first fixed contact 3
8a and a second fixed contact 38b, the movable contact 38c is held in the first switching state in which the movable contact 38c is switched to the side of the first fixed contact 38a when the print signal is not received in cooperation with the control circuit. Moving contact 3 when print signal is detected
8c is held in the second switching state in which it is switched to the second fixed contact 38b side.

When the print signal is not received, the changeover switch 38 is held in the first changeover state so that the power supply circuit on the main heater 11 side is opened and the main heater 11 does not generate heat. The power supply circuit on the side of the auxiliary heater 27 is opened to keep the auxiliary heater 27 in a heated state, and this heat generation keeps the temperature fuse 26 as a safety device preheated to a temperature of, for example, 40 to 60 degrees.

By holding the changeover switch 38 in the second changeover state by detecting the print signal, the power supply circuit on the auxiliary heater 27 side is opened and the power supply circuit on the main heater 11 side is opened. As a result, power is supplied to the energization heating resistor 22 of the main heater 11 to generate heat and the temperature of the main heater 11 rises.

The temperature of the main heater 11 is detected by the temperature detecting device 25, and the detected information is fed back to the temperature control circuit 37, so that the energization of the energization heating resistor 22 of the main heater 11 from the power source S is controlled. The temperature of the main heater 11 is controlled to a predetermined fixing temperature, and the heat fixing process of the unfixed image t of the recording material P is executed as described above.

CP in the temperature detecting device 25 and printer body
When U fails, the main heater 11 loses the control mechanism. For example, when the switch is turned on, the main heater 11 receives the voltage applied from the power source S as it is, and the temperature rises rapidly. Exceeds the ignition point of the flammable material that composes the equipment.

The safety device 26 detects the temperature information of the main heater 11, and when the temperature exceeds a predetermined allowable constant temperature, the safety device 26 melts and opens the power supply circuit of the main heater 11 to open the main heater 11.
The main heater 11 is prevented from being overheated and the safety is ensured.

However, as described above, as in this embodiment, the ceramic heater 1 having a low heat capacity is used as the heating member.
In the case of the apparatus using the No. 1 as shown in FIG. 5B, the temperature of the main heater 11 has already reached the temperature at which the temperature fuse 26 melts and the recording material and the combustible member are ignited. It is easy to have a situation where you have exceeded the point.

In the case of the apparatus of this embodiment, as described above, when the print signal is not received, the power supply circuit on the side of the auxiliary heater 27 is closed, and the temperature fuse 26 as a safety device is closed.
Since the auxiliary heater 27 keeps the preheated state at 40 to 60 degrees, the print signal comes and the switch 38
Switching the power supply circuit on the main heater 11 side to raise the temperature of the main heater 11, and at this time the temperature detection device 25 or the like is malfunctioning and the temperature control of the main heater 11 cannot be performed and the main heater 11
Even if the temperature rises rapidly from room temperature, the temperature fuse 26 also rises in temperature following the temperature rise, and as shown in FIG. The thermal fuse 26 is melted before reaching the ignition temperature of the member, and the power supply to the main heater 11 is cut off, so that safety is surely secured.

Further, since the temperature fuse 26 as a safety device having a larger heat capacity than the main heater 11 is preheated by the auxiliary heater 27, the temperature rise of the main heater portion to which the temperature fuse 26 is attached becomes slower than that of other portions. The heat distribution along the length of the main heater 11, which is a heating member, is not uneven. Therefore, in the image heat fixing device, uniformity of image fixing is ensured.

When the power source is connected (when the print signal is not received), the self-temperature control function is destroyed due to the deterioration of the auxiliary heater 27 which is always heated by the voltage application and the temperature is limited. Although the temperature rise of the auxiliary heater 27 is slow even in this case, the temperature fuse 26 blows before the temperature of the main heater 11 reaches the ignition temperature of the recording material or the combustible member. Then, the power supply circuit on the side of the main heater 11 is opened to ensure safety.

<Embodiment 2> In the apparatus of Embodiment 1, when a member having a large heat capacity other than the safety device 26 is placed in contact with or close to the main heater 11 having a low heat capacity, the main heater portion having the member is provided. In this case, the temperature rise becomes slow, the heat distribution along the length of the main heater 11 becomes non-uniform, and the control may be adversely affected.

In the present embodiment, in the apparatus of the first embodiment, the temperature detecting device 25 is also preheated by the auxiliary heater as in the case of the safety device 26. By preheating the temperature detection device 25 as well, it is possible to prevent uneven heat distribution of the main heater 11 due to the heat capacity of the device 25, and also to prevent the temperature of the main heater 11 from rising rapidly. The temperature detection function of the detection device 25 can be ensured.

In addition to the safety device 26 and the temperature detecting device 25, the same effect can be obtained by preheating the main heater 11 and other members having a large heat capacity and adversely affecting the control.

By preheating the safety device as in the first and second embodiments, the heating device can secure safety without sacrificing the quick start property. Further, since the safety device is preheated, there is an effect that the temperature distribution in the longitudinal direction of the heating member is stabilized during normal use.

The heating device is not limited to the film heating type of the embodiment, and the same effect can be obtained by a heating device of another type such as a heat roller type.

B. The following Examples 3 and 4 are the same as those in (3) above.
To (8) [corresponding to claims 3 to 8], which is an embodiment of a heating device characterized by the above-mentioned.
Has achieved the purpose of.

<Third Embodiment> In this embodiment, in the film heating type heating apparatus of the first embodiment, the film guide member 9 is made of porous heat-resistant resin, metal or ceramic, and silicon oil or the like is used. The lubricant with good slipperiness was used.

When the apparatus is driven and the temperature of the main heater 11 is raised by energizing the energization heating resistor 22, the film guide member 9 is also warmed by heat conduction from the main heater 11 and the impregnated / filled lubricant expands inside. By slightly exuding to the surface of the guide member 9, and the inner surface of the rotating film 12 comes into contact therewith, the lubricant is appropriately applied to the inner surface of the film.

As described above, the film 12 is rotationally driven while the inner surface of the film 12 is in close contact with the surface of the main heater 11 by the frictional force μ1 generated by the pressure contact between the outer periphery of the film 12 and the rotationally driven pressure roller 4. To be done.

In this case, the above frictional force μ1 and the frictional force μ2 generated by the inner surface of the film and the surface of the main heater 11 are measured.
If the relationship between the film 12 and the main heater 11 is not μ1> μ2, the smooth transfer movement of the film 12 is impeded, the film 12 and the roller 4 slip, and the transfer movement of the film 12 is stopped, or between the film 12 and the main heater 11. Film squeaking will occur due to stick-slip that occurs in.

In this embodiment, the lubricant impregnated / filled in the film guide member 9 as described above is applied to the inner surface of the film 12 so that the inner surface of the film and the main heater 11 are covered.
The frictional force μ2 with the surface of the film 12 is kept small for a long period of time, wear is also reduced, and the smooth rotational driving state of the film 12 is always maintained.

In the film heating type heating apparatus of the present embodiment, the heating operation of the main heater 11 and the conveyance of the film 12 are carried out almost at the same time, that is, the warm-up time is extremely short, and therefore, the temperature is kept near a predetermined temperature in advance. Since it is not necessary to keep the heater warm, the lubricant impregnated and filled in the surface of the film guide member 9 does not exude abnormally during standby of the apparatus.

When the film 12 is not driven, the film 12 has a substantially circular cross section due to its self-restoring force as shown by the two-dot chain line in FIG. 3, and its inner peripheral surface is separated from the outer surface of the film guide member 9. ing.

When the film 12 is driven, as shown by the solid line in FIG. 3, the film 12 is attracted to the outer surface of the film guide member upstream of the fixing nip portion N in the film rotation direction, and the outer surface of the guide member is pulled. The film 12 is rotationally driven while the inner surface of the film is in contact with the inner surface of the film, and the lubricant is applied to the inner peripheral surface of the film by this contact.

That is, in the apparatus of this embodiment, the lubricant is applied to the inner surface of the film only when the film 12 is rotationally driven, so that an appropriate amount of the lubricant can be applied to the inner surface of the film.

<Embodiment 4> (FIG. 6) FIG. 6 shows a solid resin or metal end guide 42 (a) near the left and right ends of the film guide member 9 in the longitudinal direction.
FIG. 42 is an exploded perspective view showing the configuration of a film heating type heating device provided with 42 (b). 1 to 4 of the first embodiment
The same components and parts as those of the film heating type heating device of FIG.

The film guide member 9 is obtained by impregnating and filling a lubricant as in the case of the third embodiment.

In order to convey the film 12 without deviation, the diameter balance of the pressure roller 4 is balanced, the pressure balance between the heater 11 and the pressure roller 4 is balanced, and the axis of the pressure roller 4 and the film 12 is aligned. Many factors such as the deviation, the left-right balance of the diameter of the film 12 and the left-right temperature difference of the heater 11 are involved.

Since it is impossible to completely suppress these factors, there has already been proposed a method of regulating the deviation force by guiding the film end even if the film 12 generates the deviation force. The end guides 42 (a) and 42 (b) are supporting portions 10 provided at both ends of the film guide member 9.
-Supported by 10, pressure springs 15 and 15 are provided on the outside thereof.

The film 12 is longer than the film guide member 9, and the ceramic heater 11 is further provided with the film 12.
Longer. On the other hand, the pressure roller 4 is equal to or slightly longer than the film 12, but shorter than the ceramic heater 11.
Under these conditions, the end guides 42 (a) ・ 42
In (b), a solid resin or metal is used to provide an oil barrier function. The left and right ends of the film 12 are supported by solid end guides 42 (a) and 42 (b), so that the lubricant can be prevented from leaking from the ends of the film 12 to the outer surface of the film. .

As shown in FIG. 7, the film heating type heating apparatus of Examples 1 to 4 uses the endless heat-resistant film 12, the heater 11 as a heating member, the driving roller 43, and the turn roller 44. It is also possible to have a structure in which the film 12 is suspended around and the film 12 is driven to rotate by the drive roller 43, and the pressure roller 4 is a driven roller. As shown in FIG. An end film wound in a roll is wound, and the film 12 is interlocked with the winding shaft 46 via the space between the heater 11 and the pressure roller 4, and the recording material is fed from the feeding shaft 45 to the winding shaft 46 side. For example, it may be configured to run at the same speed as the P transport speed.

C. The following Examples 5 and 6 are the same as those in (9) above.
To (12) [corresponding to claims 9 to 12], an embodiment of an image forming apparatus characterized by the following:
The third object is achieved.

<Fifth Embodiment> (FIGS. 9 and 10) FIG. 9 is a schematic configuration diagram of an image forming apparatus according to the present embodiment. The image forming apparatus of this example is a laser beam printer using a transfer type electrophotographic process.

Reference numeral 50 is a main body casing of the printer, and 51 is an opening / closing cover of the main body casing, which is operated to open and close around the hinge portion 52, and by opening this cover, the inside of the printer is opened to open the process cartridge 53. It is possible to perform attachment / detachment operations, jam handling, and maintenance / inspection inside the printer.

The process cartridge 53 contains, in addition to the rotary drum type electrophotographic photosensitive member 54 as an image bearing member, process devices such as a primary charger, a developing device and a cleaning device, which are omitted in the figure.

Reference numeral 55 denotes a paper feed cassette in which transfer paper P as a recording material is stacked and accommodated, and is detachably operated from the front side of the printer with respect to the cassette mounting portion at the bottom of the printer main body.

Based on the paper feed signal, the transfer paper P in the paper feed cassette 55 is set to 1 by the intermittent circular intermittent rotation paper feed roller 56.
The sheet is delivered to the front of the cassette, and the reverse transport roller 57.
The auxiliary roller 58 and the guide plate 59 reversely convey (180-turn) the registration sensor 60 and the photoconductor 5.
4 and the transfer device 61 are in a pressure contact nip portion (transfer portion) A → conveyance guide 62 → image heat fixing device 63 which is a heating device → paper discharge roller 65 → ascending sheet path 69 composed of guide plates 66, 67 and 68. -> Paper discharge roller 70-> It is conveyed and discharged through the path of the paper discharge tray section 71 on the upper surface of the printer casing.

When the transfer paper P passes through the transfer portion A, it receives the transfer of the toner image corresponding to the target image information formed on the photoconductor 54.

The image heat fixing device 63 is the film heating type heating device described in the first, second, third, or fourth embodiment.

Reference numeral 72 denotes an integrated electrical board in which electrical components such as a power source, a CPU, a drive circuit for the main body, and a high-voltage section are mounted (mounted) on a single substrate.
5 and a conveyance guide 62 having a shielding function, which is made of sheet metal, and is provided in the space, and the electrical components such as the fixing device 63, the transfer device 61, and the laser scanner unit 73 are mounted on the main body when the electrical equipment substrate 72 is mounted. And a floating connector (not shown) automatically connect.

The electrical board structure as described above has the features that the heat efficiency of the image heat fixing device 63 is high, the warm-up operation is almost unnecessary, and the heat of the heater is efficiently transferred to the transfer paper P, so that the power supply capacity can be reduced. By using the film heating type heating device as in the above-described example, it is possible to reduce the size of the electrical components and the number of mounted components, and to realize a compact integrated electrical substrate 72. The printer is designed to be compact and low cost.

The laser scanner unit 73 outputs a laser beam modulated in accordance with a time series electric digital pixel signal of target image information input from an external device such as a host computer, an image reading device, and a word processor (not shown). Information is written by scanning and exposing the surface of the rotating photoconductor 54 via the mirror 74.

Reference numeral 60 denotes a registration sensor as a recording material detection device, which is arranged upstream of the transfer portion A in the transfer material conveyance direction. The registration sensor 60 is used for the paper feed cassette 6
The leading edge of the transfer paper P fed from the 5 side is detected, the timing of writing information on the surface of the photoconductor 54 by the laser scanner unit 73 is set, and the residual detection of the transfer paper P in the printer when the printer is started is performed.

Reference numeral 75 denotes a pre-fixing sensor as a recording material detection device, which includes a photo interrupter 76 and a sensor lever 77.
The lever holding member 78 is provided on the upstream side of the fixing device 63 in the transfer sheet conveyance direction and on the downstream side of the transfer section A in the transfer material conveyance direction. When the transfer material P comes into contact with the sensor lever 77, the pre-fixing sensor 75 detects the presence of the transfer paper by blocking the optical path of the photo interrupter 76 due to the lever 77 tilting.

Reference numeral 64 denotes a paper discharge sensor as a recording material detection device, which detects the leading edge of the transfer paper that has passed through the fixing device 63 and the escape of the trailing end of the transfer paper from the fixing device 63, and at the time of starting the printer. Detects transfer paper remaining in the printer.

When the transfer transfer paper P is wrapped around the rotating film 12 of the fixing device 63, the leading end of the transfer transfer paper P does not reach the discharge sensor 64, and the transfer paper front end is not detected, the CPU The time from the paper feed timing is counted, and it is judged from the time of the leading edge of the transfer paper that should reach the paper discharge sensor 64, it is detected as the occurrence of a winding jam of the transfer paper, and the operation of the printer is stopped.

At this time, the fixing nip portion N and the discharge sensor 64
Is a, the diameter of the fixing film 12 is d, and the circumferential length from the leading end of the wound transfer paper P to the fixing nip portion N is c.
Then, the wrapping is surely detected, and the fixing film 12
In order to prevent the transfer paper P from winding more than one round and to facilitate the jam processing, the main body is stopped so that the relationship between a, c, and d is πd>c> a. is there.

In order to reliably detect the presence or absence of jammed paper in such a state, the pre-fixing sensor lever 77 is held at a position where the generally used minimum size of plain paper (A5 size) can be detected. Is provided on the conveyance guide 62. Specifically, assuming that the length in the vertical direction of the A5 size paper is l and the distance from the fixing nip portion N to the pre-fixing sensor lever 77 is b, the pre-fixing sensor lever 77 is placed at a position such that lc> b. It is provided.

Then, when the CPU detects the jammed jam or the like from the timing of the paper discharge sensor 64 and stops the printer main body, the power of the main body is reset at least as long as the signal from the pre-fixing sensor 75 indicates the presence of paper. In addition, the jam paper is prevented from being further wound around the fixing film 12 by controlling the forced paper discharge. That is, the pre-fixing sensor 75 detects the presence or absence of residual paper when the printer body is stopped.

By the way, as described above, when the transfer paper of a smaller size (for example, B5) than the transfer paper of the maximum size (for example, A4) which can be used for passing through the apparatus is continuously passed, and continuous printing is executed, The heater 11 portion corresponding to the non-sheet passing portion D (FIG. 13) of the image heat fixing device, which is a heating device, accumulates heat because the transfer sheet P does not absorb heat, and is compared with the heater 11 portion corresponding to the sheet passing portion C. As a result, the temperature rises and the temperature rises in the non-sheet passing area.

The temperature rise in the non-sheet passing portion of the heater 11 is the image portion corresponding to the portion in which the temperature rise in the non-sheet passing portion of the heater 11 occurs when the next large-sized transfer material P is fed. When,
The fixing property may be different from that of the other image portion, or high temperature offset of the toner may occur.

The pressure roller 4 has a higher temperature in the portion corresponding to the non-sheet passing portion D than in the portion corresponding to the sheet passing portion C (Temp
_L <Temp _R ), the pressure roller diameter of the portion corresponding to the non-sheet passing portion D becomes larger than the portion corresponding to the sheet passing portion C due to thermal expansion (φD _L <φD _R ), and the driven film 12 is rotated.
There are problems such as twisting of the film and damage to the edges due to the deviation of the film.

Therefore, as shown in FIG. 10, the above-mentioned pre-fixing sensor 75 detects the trailing edge of the previous transfer sheet and the leading edge of the next transfer sheet, sends the information to the CPU, and sends it to the image heat fixing device 63. During a period when there is no transfer sheet (between sheets, a period between a previous sheet and a next sheet), the heater 11 as a heating member is turned off.
By performing the control so as to perform F, the pressure roller 4 is prevented from being unnecessarily heated, and thus the pressure roller 4 is prevented.
The temperature rise in the non-sheet passing portion is alleviated, and the above-mentioned problems are solved.

Since the trailing edge of the previous transfer sheet and the leading edge of the next transfer sheet are detected at the upstream side which is the closest to the image heat fixing device, it is possible to accurately detect the period when no paper is present in the fixing nip portion N. It is possible to perform heater OFF control between sheets with extremely high accuracy.

If the printer does not have the pre-fixing sensor 75, the registration sensor 60 located at a position distant from the fixing device 63 detects the leading edge of the conveyed transfer paper P, and the paper discharge sensor located downstream of the fixing nip portion N. Since it is necessary to detect the trailing edge of the paper at 64, it is not possible to cope with the change in the paper interval depending on the paper size, and it is also impossible to cope with the change in the paper transport speed due to the conditions such as the paper type and the environment. OFF control is difficult.

Like the printer of this embodiment, after the transfer paper wrapping jam occurs in the film heating type image heat fixing device 63 and the CPU stops the printer body, the printer is started unless the residual paper is removed. In a printer of a transfer paper one-sided reference transport system having a pre-fixing sensor 75 for detecting the presence or absence of residual paper for prohibition, the pre-fixing sensor 75 near the upstream side of the fixing device 63 is used to detect the trailing edge of the paper and the paper when passing. By detecting the leading edge, the heater 11 which is a heating member of the fixing device 63 is turned on during a period when the transfer nip portion N is not present in the fixing nip portion N, such as before or after the transfer nip portion is ejected.
By accurately performing control such as FF, it is possible to prevent the temperature rise in the non-sheet passing portion of the pressure roller 4 when continuously passing small size paper such as B5 and A5, and to prevent the film 12 from twisting or being damaged. Failure of the fixing device can be prevented by a simple method.

<Embodiment 6> (FIGS. 11 and 12) In the printer of FIG. 11, the transfer paper P is fed into the printer from the paper feed section 80 at the lower front of the printer, and the transfer paper is immediately fed into the printer. It is configured to be compact and have a short paper path by carrying out U-turns upward to perform printing.

Reference numeral 81 denotes a registration sensor that detects the leading edge of the transfer paper and adjusts the timing of writing information to the photoconductor 54 by a laser. Reference numeral 82 is a paper discharge sensor.

In the case of such a printer, since the registration sensor 81, the transfer portion A, and the fixing device 63 are close to each other, the pre-fixing sensor (7) is provided between the fixing device 63 and the transfer portion A.
5) It is not necessary to place, and at the same time, the registration sensor 81 adjusts the timing of writing information to the photoconductor 54 by the laser, and at the same time, the leading edge of the paper enters the fixing device 63.
The CPU controls the timing of turning on / off the heater 11 by detecting the escape of the trailing edge of the paper as shown in FIG.

In the case of this embodiment, the pre-fixing sensor (75)
Since it is unnecessary, the cost will be reduced.

In the fifth and sixth embodiments, the image heat fixing device 63, which is a heating device, is not limited to the film heating type, and may be a heating device of another type such as a heat roller type. Can also alleviate the temperature rise phenomenon of the non-sheet passing portion of the apparatus, and solve the problems caused by it.

[0131]

As described above, according to the present invention, there is provided a heating device equipped with a safety device that functions to prevent overheating and runaway of the device when receiving heat from the heating member and raising the temperature above a predetermined temperature. The safety device follows up the temperature substantially without delay even when the heating member suddenly rises from room temperature, and when the heating member overheats, the overheat runaway prevention operation is performed reliably without a time lag. The safety and reliability of the device is improved. Also, uneven heat distribution along the length of the heating member due to the presence of the safety device is prevented.

Further, in the film heating type heating device, the sliding frictional resistance between the heating member and the film inner surface is kept low for a long period of time to prevent the occurrence of film transport trouble and the like due to the increased sliding frictional resistance. Therefore, the reliability of the device can be improved.

Then, in the image forming apparatus, even when the small-sized recording material is continuously fed to execute the image formation,
It is possible to prevent the temperature rise of the non-sheet passing portion of the heating device that heat-fixes the unfixed image of the recording material, and it is possible to eliminate the adverse effect caused by the temperature rise of the non-sheet passing portion.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of essential parts of a heating device (image heat fixing device) according to a first embodiment.

[Figure 2] Longitudinal section

FIG. 3 is an enlarged cross-sectional view of the main part

4A is a partially cutaway front view of the ceramic heater, FIG. 4B is a rear view, and FIG. 4C is an enlarged transverse sectional view.

5A and 5B are graphs showing a relationship between a circuit disconnection time by a safety device and a recording material ignition time, respectively.

FIG. 6 is an exploded perspective view of a main part of a heating device according to a fourth embodiment.

FIG. 7 is a schematic view of another configuration example of a film heating type heating device.

FIG. 8 is a schematic view of still another configuration example of the film heating type heating device.

FIG. 9 is a schematic configuration diagram of an image forming apparatus (laser beam printer) according to a fifth embodiment.

FIG. 10 is a relationship chart between ON / OFF timing of a pre-fixing sensor and ON / OFF timing of a fixing device heater.

FIG. 11 is a schematic configuration diagram of an image forming apparatus according to a sixth embodiment.

FIG. 12 is a timing chart of ON / OFF control of the fixing device heater.

FIG. 13 is an explanatory diagram of a temperature rise in a non-sheet passing portion.

[Explanation of symbols]

4 Pressure Roller 9 Film Guide Member 11 Heating Member (Ceramics Heater) 12 Heat Resistant Film 25 Temperature Detector 26 Safety Device (Temperature Fuse, Thermostat, etc.) 27 Auxiliary Heater (Heater to Preheat Safety Device) 60 Registration Sensor 64 Paper Ejection Sensor 75 Pre-fixing sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinori Sugiura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tatsuo Hamada 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (12)

[Claims] 1. A heating device equipped with a safety device that functions to prevent overheating and runaway of the device when the heat of the heating member is raised to a predetermined temperature or higher, wherein the heating device preheats the safety device. Is a heating device characterized by comprising another heater. 2. The heating device according to claim 1, wherein the heating device is incorporated in an image forming apparatus and heats and fixes an unfixed image on a recording material. 3. The material to be heated is adhered to a heating member via a heat resistant film, and the heat resistant film to which the material to be heated is adhered is slidably moved to the heating member to heat the heat of the heating member via the heat resistant film. A heating device for applying heat to a material, characterized in that a film guide member that supports the heating member and guides the heat-resistant film so that the sliding surface of the film contacts the heating member is impregnated with a lubricant. 4. The heating apparatus according to claim 3, wherein the lubricant impregnated in the film guide member seeps out to the surface of the film guide member when the heating member warms. 5. The heating device according to claim 3, wherein a lubricant is applied to a sliding surface of the heat-resistant film with respect to the heating member. 6. A member for bringing a material to be heated into pressure contact with a heating member via a heat resistant film.
The heating device according to any one of to 5 above. 7. The heating device according to claim 3, wherein the heat resistant film is an endless rotating film. 8. The heating device according to claim 3, wherein the heating device is an image heat fixing device that is incorporated in an image forming apparatus and heat-fixes an unfixed image on a recording material. 9. An image forming process unit for forming and carrying an unfixed image of desired image information on a recording material, and a heating device for thermally fixing the unfixed image of the recording material from the image forming process unit. In the image forming apparatus, the heating heater of the heating device is ON / OFF controlled by using an output signal of a recording material detection device provided upstream of the heating device in the recording material conveying direction. 10. The image according to claim 9, wherein the ON / OFF control is control for turning off the heating heater in a period when the recording material is not present in the image heat fixing portion of the heating device. Forming equipment. 11. The recording material detecting device is provided on a recording material conveying path from the image forming process section to the heating device, and the recording material in the image forming apparatus main body is immediately before starting of the image forming apparatus main body. The image forming apparatus according to claim 9, wherein the image forming apparatus is a device that detects the presence or absence of the recording material, and has a control that prohibits activation of the apparatus main body when the presence of the recording material is detected. 12. The recording material detecting device is provided on a recording material conveying path on the upstream side of the image forming process means in the recording material conveying direction, and a signal of the recording material detecting device causes the image forming process means to operate. The image forming apparatus according to claim 9, wherein writing of information to the image carrier is started.