JP3158129B2 - Heating equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device for heating a recording medium, and more particularly to a heating device having a heating roller made of a self-heating type conductive ceramic material.

FIG. 4 is a configuration diagram showing an example of an electrophotographic apparatus using a conventional heating device 82. As shown in FIG. The electrophotographic apparatus includes a cylindrical photosensitive drum 7 having a photoconductive layer formed on a surface thereof.
1, a charger 72 for charging the surface of the photosensitive drum 71, an optical system 73 for irradiating the photosensitive drum 71 with a desired image pattern, and a toner 76 on the electrostatic latent image formed on the photosensitive drum 71. A developing device 75 for adhering, a transfer device 79 for transferring the toner 76 on the photosensitive drum 71 to the recording paper 70, a cleaning device 80 for collecting the toner remaining on the surface of the photosensitive drum 71, and a recording paper 70 Heating device 82 for fixing toner 76 transferred thereon
It is composed of

[0003] The operation will be described. The surface of the photosensitive drum 71 is uniformly charged by the charger 72 while the photosensitive drum 71 rotates in the direction of arrow A. Next, the surface of the photosensitive drum 71 is irradiated with modulated light from a laser, an LED (light emitting diode), or reflected light from a document, and an electric charge in an area irradiated with the light is discharged to form an electrostatic latent image. . next,
The toner 76 stored in the developing device 75 is
a, and forms a toner image corresponding to the electrostatic latent image on the photosensitive drum 71. Next, the recording paper 70 is transported in the direction of arrow B by the transport rollers 77 and 78 in accordance with the rotation of the photosensitive drum 71, and the photosensitive drum 7 is transferred by the transfer device 79.
1 is transferred to the recording paper 70 as it is. Next, the recording paper 70 to which the toner has adhered is sent to a heating device 82 and is sandwiched between a heating roller 83 and a pressure roller 84 that are driven to rotate, so that the toner is heated and melted, and the recording paper 70 is heated. Settled on top and discharged.
Thus, the image pattern formed by the optical system 73 is recorded on the recording paper 70 as a toner image. The toner remaining on the photosensitive drum 71 without being transferred onto the recording paper 70 is cleaned and collected by a blade 81 provided in a cleaning device 80.

A heating roller 83 used in a conventional heating device 82 is provided with a heating element such as a nichrome wire for generating Joule heat or a halogen lamp for generating radiant heat on a shaft of a cylindrical roller made of metal or glass. Incorporated ones are common. However, since there is a certain space between the heating element and the roller, the heat transfer efficiency is low, and the time required from the start of energization of the heating element to the time at which the roller surface reaches a predetermined temperature at which the toner can be fixed is increased. A preheating time of about 1 minute to 10 minutes is required.

In view of this, a ceramic heating roller in which a roller and a heating element are integrated using a conductive ceramic material has recently been proposed. By supplying power to the heating roller, the heating roller itself generates Joule heat. As a result, the heat transfer efficiency is improved, the heat loss is small, and the preheating time can be shortened.

[0006]

SUMMARY OF THE INVENTION In a conventional heating device,
Since the circuit breaker that detects the abnormal temperature and plays a role of a safety device is installed near the surface of the heating roller, the size of the heating device increases.

Further, when the circuit breaker is installed near the surface of the heating roller, the heat generated from the heat roller is dispersed around the heating roller because it is in contact with the outside air near the heating roller, and the circuit breaker is measured by the circuit breaker. And the temperature of the heat actually generated by the heating roller. Therefore, in consideration of the above difference, it is conceivable that the set temperature at which the circuit breaker operates is previously set low. For example, when the fixing operation of the toner 76 is generally performed, the surface temperature of the heating roller is performed at 150 to 170 ° C. However, when the temperature of the heating roller increases, the temperature of the circuit breaker and the temperature of the heating roller are reduced to 200 ° C. The temperature at which the circuit breaker operates is set to 120 ° C. so that the circuit is broken, and a difference is provided in advance. However, even with this setting, it is 15
Since printing is performed for a long time at 0 to 170 ° C., the temperature of the circuit breaker gradually increases to reach the set temperature of 120 ° C., and the circuit is operated in spite of the state in which the heating roller is operating normally. Is interrupted.

In view of this, it is conceivable to provide a circuit breaker inside the heating roller, which is considered to be capable of detecting the average temperature of the heating roller. In addition, since a heating element such as a nichrome wire or a halogen lamp is incorporated, a circuit breaker cannot be provided inside.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem by eliminating the difference between the temperature measured by the circuit breaker and the heat actually generated in the heating roller, thereby preventing erroneous operation of the circuit breaker. To provide a highly reliable heating device.

[0010]

According to the present invention, there is provided a heating apparatus including a hollow heating roller made of a self-heating type conductive ceramic material, wherein the heating roller includes an abnormal temperature detecting element inside the heating roller. Is a heating device provided on a shaft portion of a heating roller and supported by a spacer having heat resistance and electrical insulation.

Further, according to the present invention, the abnormal temperature detecting element comprises:
A circuit breaker for breaking a circuit when a predetermined temperature is reached, wherein power is supplied to the heating roller via the circuit breaker.

[0012]

According to the present invention, by providing an abnormal temperature detecting element inside a hollow heating roller made of a self-heating type conductive ceramic material, space saving of the heating device can be realized. In addition, the average temperature of the heating roller can be accurately detected by supporting the abnormal temperature detecting element with a spacer having heat resistance and electrical insulation and providing the element at the shaft core of the heating roller. As a result, the difference between the temperature of the heat generated from the heating roller and the temperature detected by the abnormal temperature detecting element is reduced, and malfunction of the abnormal temperature detecting element can be prevented.

The abnormal temperature detecting element is connected in series to the heating roller, operates as a circuit interrupting element for interrupting a circuit when a predetermined temperature is reached, and supplies power to the heating roller via the circuit interrupting element. Therefore, when an abnormality occurs due to a rise in temperature, the circuit for supplying power to the heating roller is shut off, so that safety can be further improved.

[0014]

FIG. 1 is a sectional view showing the structure of a heating apparatus according to an embodiment of the present invention. This heating device has a hollow cylindrical heating roller 1 made of a self-heating type conductive ceramic material, a driving gear 12 for transmitting a driving force for rotationally driving the heating roller 1, and a surface covered with silicone rubber. It comprises a cylindrical pressure roller 24, compression springs 26 a and 26 b for urging the pressure roller 24 against the heating roller 1 to obtain a nip of a predetermined width, and a housing 3 for accommodating these. ing.

The heating roller 1 is obtained by adding a rare earth element oxide such as lanthanum or yttrium as a dopant to a semiconductor ceramic mainly composed of, for example, barium titanate and having an electric resistance characteristic exhibiting a positive temperature coefficient. It is formed by sintering a conductive ceramic material having self-temperature control ability. As an example, trade name “Inflex Burke” (manufactured by Asahi Glass Co., Ltd.) has an outer diameter of 18 mm, a wall thickness of 3 mm, a length of 250 mm, Specific resistance 1.
A roller molded into a hollow cylindrical roller of 41 Ω · cm can be used. The surface of the formed cylindrical roller is flattened by polishing, and the inner wall of a predetermined length extending inward from both end surfaces and each end surface, that is, a portion where a conductive film described later is formed is subjected to sandblasting. It has been roughened.

A part of the outer peripheral surface of the heating roller 1 to which the pressure roller 24 is pressed is coated with a release layer 2 having a thickness of 20 μm, for example, obtained by adding a small amount of carbon particles to fluororesin. In order to prevent the surface of the release layer 2 from being charged, the volume resistivity of the release layer 2 is 10 ⁶ Ω · cm or more, and the surface resistance is adjusted to a range of 10 ⁶ to 10 ⁹ Ω. Preferably, the conductive material has a high conductivity.

The heating roller 1 includes a bearing 4 provided on a housing 3.
a, 4b so as to be rotatable. The bearings 4a and 4b are preferably formed of, for example, PPS (polyphenylene sulfide) or the like having heat resistance and wear resistance, and can maintain low frictional resistance with respect to the heating roller 1 at a high temperature.

The conductive film 9, 9 is melted by spraying a metal such as aluminum to form fine particles on the inner surfaces of the heating roller 1 at both end surfaces and a predetermined length extending from each end surface. Preferably, 19 is formed, whereby the rough surface of the ceramic material is smoothed and the contact resistance can be reduced. The base on which the conductive films 9 and 19 are formed is roughened by sandblasting, so that the adhesive strength of the conductive films 9 and 19 is improved. In addition, since the conductive coatings 9 and 19 are formed of a ductile metal and are extremely thin, it is possible to eliminate the occurrence of peeling due to a difference in thermal expansion with the ceramic material.

FIGS. 2 and 3 are exploded perspective views showing the structure of both ends of the heating roller 1 shown in FIG. In FIG. 2, an electrode member 8 for supplying power to the heating roller 1 is formed with three comb-shaped protrusions 8a which are curved in an arc shape on each side, and a lead wire 14a is crimped to the end of the protrusions 8a. A caulking portion 8b for making a connection is formed. The material of the electrode member 8 is made of an elastic material such as phosphor bronze or stainless steel. When the electrode member 8 is mounted on the inner wall of the heating roller 1, an elastic force acts so that the projection 8a tends to spread outward. As a result, the electrical connection between the tip of the projection 8a and the inner wall of the heating roller 1, particularly the conductive coating 9 formed on the inner wall, is stably secured.

A cylindrical drive gear holder 10 is fixed to the outer periphery of the heating roller 1 by a heat-resistant adhesive 10a so as to cover the end of the heating roller 1. At the center of the end face of the drive gear holder 10, the shaft 11 of the drive gear 12
A substantially D-shaped hole 10b is formed so as to conform to the cross-sectional shape of the shaft 11 by caulking the hole 10b.
And the drive gear holder 10 are integrally fixed. In addition,
The connection structure between the shaft 11 and the drive gear holder 10 may be attached with a spring pin or the like. The end face of the drive gear holder 10 is provided with a communication hole 28 for communicating the inner space of the heating roller 1 with the outside air, whereby the pressure of the inner space increases due to the temperature rise of the heating roller 1. Can be maintained at atmospheric pressure.

Next, in FIG. 3, an electrode member 18 for supplying power to the heating roller 1 has a cylindrical outer peripheral surface.
The electrode member 18a has a shape in which a plurality of elastic pieces 18a whose tips are bent outward are formed at equal intervals on the circumference.
Is attached to the heating roller 1, an elastic force is applied to the elastic piece 18 a so as to spread outward.
, And the inner wall of the heating roller 1, in particular, the electrically conductive coating 19 formed on the inner wall is stably secured. The material of the electrode member 18 is made of an elastic material such as phosphor bronze or stainless steel, similarly to the electrode member 8. When the electrode member 18 is elastically fixed to the heating roller 1, a heat-resistant adhesive may be used in combination.

A cylindrical projection 17a is formed to fit into the elastic piece 18a of the electrode member 18, for example, P
The lead wire 14b is led into a disk-shaped insulating spacer 17 made of PS or the like, and as shown in FIG.
b. Note that the insulating spacer 17 and the electrode member 18 are fixed with a heat-resistant adhesive. A conductive plate 15 having substantially the same diameter is fixed to an end surface of the insulating spacer 17 with a heat-resistant adhesive.
7b and the terminal block 15a of the conductive plate 15 are electrically connected, so that the lead wire 14b and the conductive plate 15 are electrically connected.

At the center of the conductive plate 15, a conductive protrusion 16 having a spherical tip is formed, and the protrusion 16 and the elastic piece 20a of the fixed electrode 20 are slidably in contact with each other. . Therefore, a stable electrical connection can be obtained even if the heating roller 1 and the conductive plate 15 rotate integrally. The fixed electrode 20 is made of an elastic material such as phosphor bronze or stainless steel, similarly to the electrode members 8 and 18. In addition, since the projection 16 abuts on the elastic piece 20a with a constant force, a helical gear is used as the drive gear 12 so that the entire heating roller 1 can be moved in the right thrust direction in FIG. Can be generated.

In FIG. 1, a power supply bearing 21 for supplying power to the outer peripheral surface of the electrode member 18 includes a conductive inner ring fixed to the electrode member 18, a conductive outer ring fixed to the fixed electrode 22, an inner ring and an outer ring. Rolling bearing consisting of a conductive ball interposed between the heating roller 1 and the electrode member 1 is used.
A stable electrical connection can be obtained even when the rotary members 8 are integrally rotated. In addition, instead of such a conductive rolling bearing, as a material of the outer ring and the inner ring, a conductive material having good slidability, a high conductive metal such as copper or silver and graphite were mixed and sintered. A brush, for example, a sliding bearing made of trade name “Sliding Contact / GTS-04B” (manufactured by Opax) may be used. The fixed electrode 22 electrically connected to the power supply bearing 21 and the fixed electrode 20 electrically connected to the conductive plate 15 are held in an electrically insulating electrode housing 23 made of, for example, PPS. 23 is attached to the housing 3.

The lead wire 14a connected to the electrode member 8 and the lead wire 14b connected to the terminal block 17b of the insulating spacer 17 are disposed along the axis of the heating roller 1,
Two places in the middle are supported by a ring-shaped spacer 7 made of, for example, PPS having heat resistance and high electrical insulation, and a thermal fuse 5 is connected in series between them. The thermal fuse functions as an abnormal temperature detecting element for detecting an abnormal temperature of heat generated from the heating roller 1, and the thermal fuse 5 is blown when the heating roller 1 becomes abnormally high temperature, and stops supplying power to the heating roller 1. It is provided as a circuit interrupting element, and is provided on a shaft core portion showing an average temperature distribution of the heating roller. Therefore, the average temperature of the heat generated by the heating roller 1 can be accurately detected, and the circuit can be automatically cut off when the temperature of the heating roller 1 is abnormally high, thereby further improving safety. The circuit can be accurately cut off only at such an abnormally high temperature, so that stable power supply can be performed at the normal operating temperature of the heating roller 1. The surface of the thermal fuse 5 is covered with a coating layer 6 having heat resistance and high electrical insulation, for example, a polyimide resin.

In this manner, the power supply bearing 2
1, the electrode member 18, the conductive film 19, and the heating roller 1, pass through the conductive film 9, the electrode member 8, the lead wire 14a, the thermal fuse 5, the lead wire 14b, the terminal block 17b, the terminal block 15a, and the conductive plate 15. An electric circuit up to the projection 16 and the fixed electrode 20 is formed. These fixed electrodes 20 and 22
By supplying an alternating current of, for example, AC 100 V from the temperature control device 40, the heating roller 1 made of a self-heating type conductive cella material uniformly generates heat throughout.
In order to detect and control the temperature of the heating roller 1, a temperature detecting element 41 such as a thermistor is fixed by a mounting member 42 so as to contact the outer surface of the heating roller 1, and the output of the temperature detecting element 41 is The temperature is input to a temperature control device 40 connected to a CPU (Central Processing Unit) 43 and is controlled so that the temperature of the heating roller 1 is stabilized.

The pressure roller 24 has an outer diameter of about 20 mm covered with silicone rubber having a thickness of about 5 mm around a shaft core 24a.
The roller is a roller having a length of 220 mm and a length of 220 mm. Both ends of the shaft core 24a are supported by bearings 25a and 25b having heat resistance and slidability and made of, for example, PPS, and a compression spring 26a is provided for the bearings 25a and 25b. , 26b press against the heating roller 1 side with a force of, for example, about 2 kgf.

Next, the operation of the heating device shown in FIG. 1 will be described. When the power of the electrophotographic apparatus equipped with the heating device is turned on, the temperature control device 40 is controlled based on a command from the CPU 43 so that the heating roller 1 has a predetermined preheating temperature.
Controls the amount of power supply to the heating roller 1. Then the CPU
When a print command is sent from the printer 43, the temperature controller 40 increases the amount of power supplied to the heating roller 1 so that the temperature of the heating roller 1 becomes a fixing temperature in the range of 150 ° C. to 200 ° C. from the preheating temperature, and performs recording. The driving gear 12 is rotationally driven by a driving system (not shown) in accordance with the operation of the paper conveying device, so that the heating roller 1 is rotated and the pressure roller 24 is driven to rotate. Then, when the recording paper on which the unfixed toner is placed is carried into the heating device and transported while being nipped by the heating roller 1 and the pressure roller 24, the unfixed toner is heated and melted and fixed on the recording paper.

By supplying power of, for example, AC 100 V, 400 W to the heating roller 1 in this manner, the surface temperature of the heating roller 1 becomes 155 ° C., the peripheral speed of the heating roller 1 is 39 mm / sec, and the pressure is increased. When the nip width of the roller 24 was set to 18 mm, it was possible to obtain a toner-fixed image having excellent fixability and less image disturbance.

When the heating roller 1 rises from room temperature to the fixing temperature, the metal electrode members 8 and 18 thermally expand, whereas the ceramic heating roller 1 does not expand much. Tip and electrode member 18
Of the elastic piece 18a is relatively displaced. However, since the electrode members 8 and 18 are elastically fixed, the electrical connection between the heating roller 1 and the electrode members 8 and 18 is stably maintained. Further, the electrode members 8, 18 are electrically conductive coatings 9, 19.
The contact resistance is extremely small by contacting the heating roller 1 through the heating roller 1, so that a stable energization is performed even by the rotation of the heating roller 1, the temperature fluctuation of the heating roller 1 is reduced, and a good fixed image is obtained. Obtainable.

In the above embodiment, an example has been described in which the conductive coatings formed on both ends of the heating roller 1 are formed by spraying aluminum, but other metals may be sprayed. Further, by plating or vapor-depositing a metal, for example, a single-layer film of Ni only or Ni + Cu + Ni
May be formed, or a conductive non-metal may be used.

In the above embodiment, an example was described in which a power supply electrode slidable on one end of the heating roller 1 was provided to supply power to the heating roller 1.
Power supply electrodes that can rotate and slide on both ends of the
A configuration in which power is supplied along the thrust direction of the heating roller 1 may be used.

In this embodiment, the temperature fuse 5 is used as a circuit breaker. However, a temperature switch may be used in which the conduction of the circuit is restored when the detected temperature falls below a set temperature.

As described above in detail, according to the present invention, since the abnormal temperature detecting element is provided inside the hollow heating roller made of a self-heating type conductive ceramic material, space saving of the heating device can be realized. . In addition, the average temperature of the heating roller can be accurately detected by supporting the abnormal temperature detecting element with a spacer having heat resistance and electrical insulation and providing the element at the shaft core of the heating roller. As a result, the difference between the temperature of the heat generated from the heating roller and the temperature detected by the abnormal temperature detecting element is reduced, and malfunction of the abnormal temperature detecting element can be prevented.

The abnormal temperature detecting element operates as a circuit interrupting element for interrupting the circuit when the temperature reaches a predetermined temperature. Therefore, when the temperature of the heating roller is abnormally high, the circuit is automatically interrupted to further enhance safety. Since the circuit can be cut off only when the temperature is abnormal, the power can be stably supplied at the normal operating temperature of the heating roller.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a heating device according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a structure of both ends of a heating roller 1 shown in FIG.

FIG. 3 is an exploded perspective view showing a structure of both ends of a heating roller 1 shown in FIG.

FIG. 4 is a configuration diagram showing an example of an electrophotographic apparatus using a conventional heating device 82.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating roller 2 Release layer 3 Case 4a, 4b Bearing 5 Thermal fuse 7 Ring spacer 8, 18 Electrode member 9, 19 Conductive film 10 Drive gear holder 11 Shaft 12 Drive gear 15 Conductive plate 16 Projection 17 Insulating spacer 20 , 22 Fixed electrode 21 Power supply bearing 23 Electrode housing 24 Pressure roller 25a, 25b Bearing 26a, 26b Compression spring 28 Communication hole 40 Temperature control device 41 Temperature detection element

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-260077 (JP, A) JP-A-62-18582 (JP, A) JP-A-3-144684 (JP, A) Actually open 64-64 13070 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 13/20 G03G 15/20

Claims (2)

(57) [Claims] 1. A heating device including a hollow heating roller made of a self-heating type conductive ceramic material, wherein an abnormal temperature detecting element is provided inside the heating roller, and the abnormal temperature detecting element includes a shaft core of the heating roller. Provided in
A heating device characterized by being supported by a spacer having heat resistance and electrical insulation. 2. The heating device according to claim 1, wherein the abnormal temperature detecting element is a circuit interrupting element that interrupts a circuit when a predetermined temperature is reached, and supplies power to the heating roller via the circuit interrupting element. 2. The heating device according to 1.