Patent Application
20180113404
The present invention relates to a fixing apparatus that fixes a developer image on a recording material to the recording material, and an image forming apparatus that forms an image on a recording medium by using a developer.
In an electrophotographic image forming apparatus such as a copying machine or a laser beam printer, first, a photosensitive drum is charged by a charging roller and the charged photosensitive drum is exposed by an exposure device, whereby an electrostatic latent image is formed on the photosensitive drum. The electrostatic latent image formed on the photosensitive drum is developed as a toner image by a developing roller. Then, the toner image formed on the photosensitive drum is transferred to a recording material such as paper by a transfer roller. The toner image transferred to the recording material is fixed to the recording material by heating and pressurizing with a fixing apparatus. In this way, an image is formed on the recording material.
Here, the fixing apparatus sometimes includes a heater for heating the recording material and a thermistor for measuring the temperature of the heater. A heat generation pattern (metal resistor) is formed on the heater, an electric current flows in the heat generation pattern, and the heat generation pattern generates heat to heat the heater. Further, since the resistance value of the thermistor varies depending on the temperature, the temperature of the heater is measured by measuring the resistance value of the thermistor.
In addition, conventionally, since the power consumed by the heat generation pattern is large, the heat generation pattern is heated by power supplied from a primary-side circuit. Meanwhile, the thermistor is electrically connected to a secondary-side circuit. Since the heat generation pattern is connected to the primary-side circuit and the thermistor is connected to the secondary-side circuit, it is necessary to provide a sufficient insulation distance between the heat generation pattern and the thermistor. This is because a short circuit occurs when the heat generation pattern connected to the primary-side circuit and the thermistor connected to the secondary-side circuit are electrically connected. When it is thus necessary to provide a sufficient insulation distance between the heat generation pattern and the thermistor, the size of the fixing apparatus is increased which results in the increased size of the image forming apparatus.
Accordingly, in the technique disclosed in Japanese Patent Application Publication No. H11-344882, both the heater and the thermistor are connected to the primary-side circuit, thereby making it possible to eliminate the occurrence of a short circuit and to arrange the heater and the thermistor close to each other. As a result, the fixing apparatus is reduced in size, and the entire image forming apparatus can be reduced in size. Specifically, in the technique disclosed in Japanese Patent Application Publication No. H11-344882, the fixing apparatus includes the heater, the thermistor, a converting unit for converting the temperature of the thermistor into a predetermined signal, and a photocoupler for converting the signal converted by the converting unit into an electric pulse signal. The fixing apparatus is also provided with a switching unit for switching supply/cutoff of electric power from the primary-side circuit to the heater according to the electric pulse signal converted by the photocoupler.
The heater, the thermistor and the converting unit are driven by the primary-side circuit, and the switching unit is driven by the secondary-side circuit. Then, a predetermined signal (the signal relating to the temperature of the thermistor) converted by the converting unit is converted by the photocoupler into an electric pulse signal, and electric power is supplied/cutoff to the heater according to the electric pulse signal. In the technique disclosed in Japanese Patent Application Publication No. H11-344882, the photocoupler can send a signal from the converting unit to the switching unit in a state where the converting unit (by the primary-side circuit) and the switching unit are insulated. Therefore, it is possible to send a signal from the converting unit to the switching unit without causing a short circuit. In addition, both the thermistor and the heater receive the supply of electric power from the primary-side circuit, and even when the thermistor and the heater are arranged close to each other, the primary-side circuit and the secondary-side circuit cannot be electrically connected (there is no danger of short circuit).
However, Japanese Patent Application Publication No. H11-344882 does not disclose the feature of cutting off the power supply from a commercial power supply to the converting unit when the temperature of the heater exceeds a threshold value or when the image forming apparatus is switched to a power saving mode. Therefore, according to the technique disclosed in Japanese Patent Application Publication No. H11-344882, when the temperature of the heater exceeds a threshold value or the like, the power supply from the commercial power supply to the converting unit is not cut off and power is consumed in the converting unit.
A virtual technique can be considered in which the feature of cutting off the power supply from the commercial power supply to the heater and the converting unit when the temperature of the heater exceeds the threshold value or the like is used in the technique disclosed in JP-A No. H11-344882. In order to use the virtual technique, it is apparently necessary to send separate signals from a CPU to the conversion unit and a member that cuts off the power supply to the heater. Therefore, it is necessary to newly add a CPU control port (input/output port of CPU), a transistor, and the like. In this case, the manufacturing cost of the fixing apparatus increases.
It is therefore an object of the present invention to reduce the manufacturing cost of the fixing apparatus and to reduce power consumption in the fixing apparatus.
In order to achieve the object described above, a fixing apparatus of the present invention is a fixing apparatus comprising:
In order to achieve the object described above, an image forming apparatus of the present invention is an image forming apparatus comprising:
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
Hereinafter, a description will be given, with reference to the drawings, of embodiments of the present invention. However, the sizes, materials, shapes, their relative arrangements, or the like of constituents described in the embodiments may be appropriately changed according to the configurations, various conditions, or the like of apparatuses to which the invention is applied. Therefore, the sizes, materials, shapes, their relative arrangements, or the like of the constituents described in the embodiments do not intend to limit the scope of the invention to the following embodiments.
Meanwhile, image recording paper P (corresponding to the recording medium) fed from a paper feeding unit 111 by a paper feeding roller 112 is conveyed along a conveying path H, and nipped and conveyed together with the multicolor toner image formed on the intermediate transfer member 125 between the intermediate transfer member 125 and the transfer roller 113. Since a positive bias is applied to the transfer roller 113 from a transfer bias generator 114, the negatively charged multicolor toner image is transferred to the image recording paper P. Thereafter, the multicolor toner image on the image recording paper P is fixed to the image recording paper P by the thermal fixing apparatus 130. The image recording paper P on which the multicolor toner image has been fixed is finally discharged to a discharge tray 115.
Outline of Thermal Fixing Apparatus 130
Next, the thermal fixing apparatus 130 will be described with reference to
Generally, the heating element pattern 205 is connected to a commercial power supply through a switching element such as a TRIAC or a mechanical switching element such as a relay. By controlling ON/OFF of the switching element, electric power is supplied from the commercial power supply to the heating element pattern 205. The ON/OFF control of the switching element is performed based on the resistance value of the thermistor 207 (corresponding to the sensor) disposed in the vicinity of the heater 204 (for example, pressed against the back surface of the heater 204 with a predetermined pressure). Here, the resistance value of the thermistor 207 varies depending on the temperature of the thermistor 207. Therefore, in the present example, the temperature of the thermistor 207 is measured from the resistance value of the thermistor 207.
Further, a heater holder 203 serves for fixing and supporting the heater 204, and is formed of a material having heat resistance and heat insulating properties. A metal stay 211 is a member for imparting rigidity to the thermal fixing apparatus 130. A fixing film 201 is a cylindrical heat-resistant film material, and is disposed so as to cover the heater 204, the heater holder 203, and the like. A monolayer film, a composite film composed of a PI+PFA coating or SUS (stainless steel) with a rubber coating, or the like is used as the fixing film 201, and the inner circumferential surface of the fixing film 201 has high electric conductivity.
A pressure roller 208 is an elastic roller formed by providing a heat-resistant elastic layer 210 such as silicone rubber in a roller shape on the outer periphery of a metal pipe 209. Then, the pressure roller 208 is pressed against the heater 204, with the fixing film 201 being interposed therebetween, and is driven to rotate at a predetermined peripheral speed in the direction of an arrow B by a fixing drive motor (not shown in the figure). The pressure roller 208 rotates the fixing film 201 by the rotational driving of the pressure roller 208 and the frictional force between the outer peripheral surface of the pressure roller 208 and the outer peripheral surface of the fixing film 201. At this time, the fixing film 201 rotates in the direction of an arrow C while sliding on the insulating layer 206. Here, the heater holder 203 also plays a role of guiding the inner peripheral surface of the fixing film 201, so that the fixing film 201 can be easily rotated.
The image recording paper P onto which the multicolor toner image has been transferred is conveyed to a nip portion between the fixing film 201 and the pressure roller 208 in a state after the rotation of the fixing film 201 has been stabilized by the rotation of the pressure roller 208 and the temperature of the heater 204 has risen to a predetermined temperature. Here, as shown in
Circuit Constituting Thermal Fixing Apparatus 130
Meanwhile, the commercial power supply 11 supplies electric power to a heater 204 via a TRIAC 300. Further, the TRIAC 300 is connected through a photo-TRIAC coupler 302 to a transistor 304 connected through a resistor 303 to a CPU 5 as a control unit connected to the secondary-side circuit. In accordance with the two types of signals Hi and Lo, the CPU 5 causes an electric current to flow through a limiting resistor 305 to the diode side of the photo-TRIAC coupler 302. As a result, the CPU 5 controls the operation of the photo-TRIAC coupler 302 and switches supply/cutoff of electric power from the commercial power supply 11 to the heater 204. In this example, the CPU 5 controls the operation of the photo-TRIAC coupler 302 in accordance with the temperature of the heater 204 acquired by a thermistor circuit block 330 as the temperature acquiring unit, so that power supply from the commercial power supply 11 to the heater 204 is allowed or cut off.
Further, in the thermal fixing apparatus 130, the thermistor 207 and a protective element 301 for cutting off the energization to the heater 204 when the heater 204 abnormally generates heat are arranged in the vicinity of the heater 204. In addition, the thermal fixing apparatus 130 is provided with a relay 306 (corresponding to a first switching unit) for cutting off the energization to the heater 204 by a control signal from the CPU 5 on the basis of information on the temperature of the thermistor 207. The relay 306 is connected to the CPU 5 through a resistor 309 and a transistor 308 (corresponding to a third switching unit). The CPU 5 controls the supply/cutoff of electric power to the relay 306 by allowing an electric current to flow through the limiting resistor 307 to the coil inside the relay 306 in accordance with the two types of signals Hi and Lo. Here, in the present example, the photocoupler 39 (corresponding to a second switching unit), which will be described in detail hereinbelow, is connected in series with the relay 306. In this example, the relay 306, the photocoupler 39, and the transistor 308 are operated by supply of electric power from the secondary-side circuit.
Thermistor Circuit Block 330
Next, the thermistor circuit block 330 and circuits disposed on the periphery thereof will be described. In this example, the heater 204, the thermistor 207, and the protective element 301 are all disposed in the primary-side circuit of the transformer 24. As a result, the components connected to the secondary-side circuit are not disposed in the thermal fixing apparatus 130. Therefore, even though the heater 204, the thermistor 207, and the protective element 301 are arranged at positions close to each other, the primary-side circuit and the secondary-side circuit are prevented from being connected to each other (a short circuit does not occur) in the thermal fixing apparatus 130. Furthermore, there is no need to provide a safe distance between the heater 204, the thermistor 207, and the protective element 301, and since the heater 204, the thermistor 207, and the protective element 301 can be disposed close to each other, the thermal fixing apparatus 130 can be reduced in size.
A voltage is supplied to the thermistor circuit block 330 from an auxiliary winding Nb of the transformer 24. In the auxiliary winding Nb, similarly to the secondary-side power supply Vcc2, a primary-side power supply Vcc1 is generated by a rectification diode 25 and a capacitor 26 in accordance with the switching of the FET 23. The CPU 5 controls the supply/cutoff of electric power from the primary-side power supply Vcc1 to the thermistor circuit block 330 by controlling the operation of the photocoupler 39 through the resistor 309 and the transistor 308. In the thermistor circuit block 330, the detection signal of the thermistor 207 is converted into a PWM signal, which will be described hereinbelow, and fed back to the CPU 5 through the photocoupler 347 as a transmission portion.
PWM Conversion of Detection Signal of Thermistor 207
The thermistor circuit block 330 is mainly configured of a triangular wave generating portion 331 and a comparator 332 for comparing the triangular wave and the voltage of the thermistor 207. In the triangular wave generating portion 331, an operational amplifier 333, a resistor 334, and a resistor 335 form a Schmitt circuit, thereby generating a rectangular wave V1. In addition, an operational amplifier 338, a resistor 336, and a capacitor 337 form an integrator, thereby generating a triangular wave V2.
Here,
Here, in the present example, the signal is transmitted from the comparator 332 connected to the primary-side circuit to the CPU 5 connected to the secondary-side circuit by using the photocoupler 347. More specifically, the voltage V5 outputted from the comparator 332 is converted into a pulse signal having a pulse width by the photocoupler 347, and is thus transmitted to the CPU 5 as a voltage V6. The photocoupler 347 can transmit the output signal (output voltage V5) of the comparator 332 to the CPU 5 in a state in which the CPU 5 connected to the secondary-side circuit and the comparator 332 connected to the primary-side circuit are insulated from each other. Further, in this example, as a result of using the transistor 346, Hi and Lo logic of the voltage V5 and the voltage V6 are the same. The portion where the voltage is Vcc3 is a secondary-side circuit, and the voltage Vcc3 is generated from the secondary-side power supply Vcc2 by a DC/DC converter (not shown in the figure) or the like. In this manner, the temperature of the thermistor 207 is outputted as the voltage V5 by the comparator 332, and the outputted voltage V5 is fed back as the voltage V6 to the CPU 5.
Operation Control of Relay 306 and Photocoupler 39
In the present example, as described above, the photocoupler 39 and the relay 306 are connected in series, and the operation of the transistor 308 is controlled with one signal from the CPU 5. Specifically, in this example, the transistor 308 is connected to the CPU 5 through the resistor 309. Further, the photocoupler 39, the relay 306, and the limiting resistor 307 are connected in series to the transistor 308. Thus, ON/OFF of the relay 306 and the photocoupler 39 are simultaneously controlled. In other words, in the present example, the CPU 5 can cut off the power supply from the commercial power supply 11 to the heater 204 and the power supply from the commercial power supply 11 to the thermistor circuit block 330 by controlling the operations of the photocoupler 39 and the relay 306 with one signal.
Since the photocoupler 39 and the relay 306 are connected to the CPU 5 in this manner, power is supplied from the primary-side power supply Vcc1 to the thermistor circuit block 330 only when the relay 306 is turned on. As a result, power saving is achieved in the thermal fixing apparatus 130. Further, when no power is supplied to the thermistor circuit block 330 and the temperature of the thermistor 207 is not detected, the relay 306 is switched off and the energization to the heater 204 is also cut off, so that the safety of the thermal fixing apparatus 130 is enhanced. In this example, the operation of the transistor 308 is controlled with one signal from the CPU 5, so that ON/OFF of the relay 306 and the photocoupler 39 are simultaneously controlled, thereby making it possible to reduce the number of ports of the CPU 5.
As described above, in this example, the CPU 5 cuts off the power supply from the primary-side circuit to the heater 204 and the power supply from the primary-side circuit to the thermistor circuit block 330 by controlling the operations of the photocoupler 39 and the relay 306 with one signal. Thus, it is possible to cut off the power supply from the commercial power supply 11 to the thermistor circuit block 330 and the heater 204 without adding components such as a CPU control port or a transistor.
The abnormally high temperature detection block 410 monitors the voltage V7 generated by rectifying the voltage V6 outputted from the thermistor circuit block 330 by a resistor 411 and a capacitor 412. Further, when the voltage V7 falls below a voltage V8 which is set as abnormally high temperature, a comparator 401 is switched off. Thus, power supply to the relay 306 is cut off by switching off the transistor 308.
Therefore, even when an abnormality occurs in the firmware of the CPU 5 and the temperature of the heater 204 becomes abnormally high, the power supply to the relay 306 can be cut off and the power supply to the heater 204 can be cut off regardless of the CPU 5. In other words, in the present example, even when there is an abnormality in the firmware of the CPU 5, the abnormally high temperature detection block 410 can cut off the power supply to the heater 204 before the power supply to the heater 204 is cut off by the protective element 301.
Here, in the present example, unlike the Example 1, the relay 306 and the abnormally high temperature detection block 410, and the photocoupler 39 are connected in parallel to the CPU 5 so that the power supply of the thermistor circuit block 330 is not cut off at the same time as the transistor 308 is switched off. Therefore, in this example, a transistor 405 is added to ON/OFF switch the power supply to the photocoupler 39. In other words, in this example, unlike the Example 1, two transistors are used for one signal of the CPU 5.
As described above, in the present example, it is possible to cut off the power supply from the commercial power supply 11 to the thermistor circuit block 330 and the heater 204 without adding a CPU control port.
Further, in the present example, as described above, even when there is an abnormality in the firmware of the CPU 5, the abnormally high temperature detection block 410 can cut off the power supply to the heater 204 before the power supply to the heater 204 is cut off by the protective element 301.
In the examples, the switching unit for allowing or cutting off the power supply to the thermistor circuit block 330 and the heater 204 is not necessarily required to be turned on by the power supply to the switching unit. For example, the switching unit for allowing or cutting off the power supply to the thermistor circuit block 330 and the heater 204 may be switched off by the power supply to the switching unit.
Further, in the examples, the switching unit for allowing or cutting off the power supply to the thermistor circuit block 330 and the heater 204 is not necessarily a relay or a photocoupler. The configuration of the switching unit is not particularly limited as long as the power supply to the thermistor circuit block 330 and the heater 204 is allowed or cut off by a signal from the CPU 5.
The present invention can reduce the manufacturing cost of the fixing apparatus and reduce power consumption in the fixing apparatus.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2016-208503, filed on Oct. 25, 2016 which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-208503 | Oct 2016 | JP | national |
