Energization cut-off device, image forming device, and electrical apparatus

Abstract

To provide an energization cut-off device that, even if direct current is applied, can cut off energization to safely stop the device.SOLUTION: An energization cut-off device comprises: a conversion circuit 42 that converts alternating current input from a primary side into direct current and outputs the direct current from a secondary side; an output control unit 44 that controls the output from the secondary side of the conversion circuit 42; an energization cut-off unit 43 that is provided in series with the output control unit 44; a signal detection unit 47 that detects the frequency of power to be input to the conversion circuit 42; and a heating element 46 that is provided in proximity to the energization cut-off unit 43 and controlled on the basis of a result of detection performed by the signal detection unit 47. When the energization cut-off unit 43 is heated by the heating element 46, it cuts off energization to the output control unit 44.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a current interruption device that interrupts current flow, and an image forming apparatus and an electrical device that include the current interruption device. [Background technology]

[0002] Conventionally, in a fixing device used in an electrophotographic image forming apparatus such as a copier or printer, a toner image is fixed by applying pressure and heat to a sheet of paper on which an unfixed toner image has been formed. The fixing device is provided with a heater for heating the sheet of paper, and measures are taken to anticipate abnormalities in the heater control (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-115183 Summary of the Invention [Problem to be solved by the invention]

[0004] A conventional fixing device includes a heater section having a first heating element and a second heating element, a switching section that switches the connection between the heating elements and a power source, a cut-off means that cuts off the power supply if the heater section becomes overheated, and an abnormality detection means that detects overheating of the heater section; if overheating of the heater section is detected, the switching section connects the power source to the second heating element.

[0005] Image forming devices and other electrical equipment are required to be able to be installed in a variety of environments, and are generally often connected to AC power sources. In some cases, direct current (DC) is preferable for the operation of such devices, and the input alternating current (AC) is converted to DC within the device. However, there is a concern that the device may be connected to a DC power source due to human error, so it is necessary to quickly shut off the power in such cases.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a current cutoff device, an image forming apparatus, and electrical equipment that can cut off current and safely stop the apparatus even when direct current is applied. [Means for solving the problem]

[0007] The current interrupter of the present disclosure is a current interrupter comprising: a conversion circuit that converts alternating current input from the primary side into direct current and outputs it from the secondary side; an output control unit that controls the output from the secondary side of the conversion circuit; a current interrupter arranged in series with the output control unit; a signal detection unit that detects the frequency of the power input to the conversion circuit; and a heating element that is arranged in proximity to the current interrupter and controlled based on the detection result of the signal detection unit, wherein the current interrupter cuts off the flow of current to the output control unit when heated by the heating element.

[0008] In the current interruption device according to the present disclosure, the heating element may be configured to operate using power supplied from the conversion circuit.

[0009] In the power interruption device of the present disclosure, the signal detection unit may be configured to determine whether the frequency of the power input to the conversion circuit is a preset value, and to activate the heating element when the frequency changes from the set value to a value different from the set value.

[0010] The image forming apparatus according to the present disclosure is characterized by including the power interruption device according to the present disclosure.

[0011] The electrical device according to the present disclosure is characterized by including the current interruption device according to the present disclosure. [Effects of the Invention]

[0012] According to the present disclosure, if DC is accidentally applied to the primary side and the output control unit is unable to control the current flow, the heating element heats the circuit, activating the current cutoff unit to cut off the current and safely shut down the device. In addition, the signal detection unit detects the frequency of the current in the conversion circuit, making it possible to determine whether DC is being applied at startup. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a schematic diagram illustrating a schematic configuration of an image forming apparatus. [Figure 3] 4 is a characteristic diagram showing a voltage input to a conversion circuit and a signal output based on the voltage. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] A fixing device and an image forming apparatus according to an embodiment of the present disclosure will be described below with reference to the drawings.

[0015] FIG. 1 is a schematic cross-sectional view showing the configuration of an image forming apparatus according to an embodiment of the present disclosure.

[0016] The image forming device 100 is a multifunction device having a copy function, a scanner function, a facsimile function, and a printer function, and transmits an image of a document read by the image reading device 130 to an external device, and forms an image of a document read by the image reading device 130 or an image received from an external device in color or monochrome on a recording medium such as paper.

[0017] An original transport device 110 that is supported so as to be able to open and close freely is provided above the image reading device 130. The original transport device 110 transports one or more originals one by one. The image reading device 130 scans a scanning optical system 130b to read an original placed on an original placement table 130a, or reads an original transported by the original transport device 110 to generate image data.

[0018] The image forming apparatus 100 includes a fixing device 1, a developing device 2, a photosensitive drum 3, a drum cleaning device 4, a charger 5, an intermediate transfer belt device 7, a secondary transfer device 11, an optical scanning device 12, and a paper feed section 18.

[0019] Image forming apparatus 100 handles image data corresponding to color images using black (K), cyan (C), magenta (M), and yellow (Y), or monochrome images using a single color (e.g., black). Image forming apparatus 100 is provided with four developing devices 2, four photosensitive drums 3, four drum cleaning devices 4, and four chargers 5 for forming four types of toner images, and four image stations Pa, Pb, Pc, and Pd are configured corresponding to black, cyan, magenta, and yellow, respectively.

[0020] The optical scanning device 12 exposes the surface of the photosensitive drum 3 to light to form an electrostatic latent image. The developing device 2 develops the electrostatic latent image on the surface of the photosensitive drum 3 to form a toner image on the surface of the photosensitive drum 3. The drum cleaning device 4 removes and collects residual toner on the surface of the photosensitive drum 3. The charger 5 uniformly charges the surface of the photosensitive drum 3 to a predetermined potential. Through the series of operations described above, a toner image of each color is formed on the surface of each photosensitive drum 3.

[0021] The intermediate transfer belt device 7 includes an intermediate transfer roller 6, an endless intermediate transfer belt 71, an intermediate transfer drive roller 72, an intermediate transfer driven roller 73, and a cleaning device 9. Four intermediate transfer rollers 6 are provided inside the intermediate transfer belt 71 so as to form four types of toner images corresponding to each color. The intermediate transfer rollers 6 transfer the toner images of each color formed on the surface of the photosensitive drum 3 onto the intermediate transfer belt 71, which moves around in a circular motion.

[0022] The intermediate transfer belt 71 is stretched over an intermediate transfer drive roller 72 and an intermediate transfer driven roller 73. In the image forming apparatus 100, the toner images of each color formed on the surface of each photosensitive drum 3 are sequentially transferred and superimposed to form a color toner image on the surface of the intermediate transfer belt 71. The cleaning device 9 removes and collects waste toner remaining on the surface of the intermediate transfer belt 71 without being transferred to paper.

[0023] The secondary transfer device 11 sandwiches and transports a sheet of paper transported through the paper transport path 21 in the transfer nip portion TN between the secondary transfer roller 11a and the intermediate transfer belt 71. When the sheet of paper passes through the transfer nip portion TN, the toner image on the surface of the intermediate transfer belt 71 is transferred onto the sheet of paper, and the sheet of paper is transported to the fixing device 1.

[0024] The fixing device 1 includes a fixing belt 31 that rotates around an axis and a pressure roller 32. The fixing device 1 sandwiches a sheet of paper onto which a toner image has been transferred in a nip portion N between the fixing belt 31 and the pressure roller 32, and applies heat and pressure to fix the toner image to the sheet. The fixing device 1 includes a heating section 33 (see FIG. 2, which will be described later) that heats the fixing belt 31.

[0025] The paper feed unit 18 includes a paper feed cassette that holds recording media (paper) used for image formation, and is provided below the optical scanning device 12. The paper is pulled out of the paper feed unit 18 by a pickup roller 16 and transported to a paper transport path 21. The paper transported to the paper transport path 21 passes through the secondary transfer device 11 and the fixing device 1, and is then discharged to a paper output tray 19 by a discharge roller 17.

[0026] Conveyance rollers 13, registration rollers 14, and discharge rollers 17 are arranged on paper conveyance path 21. Conveyance rollers 13 facilitate the conveyance of paper. Registration rollers 14 convey paper at a speed equal to the process speed at which an image is formed on the paper. Registration rollers 14 are provided between paper feed unit 18 and secondary transfer device 11, and adjust the timing of paper conveyance so that the toner image is transferred to the paper by secondary transfer device 11. For example, registration rollers 14 wait (temporarily stop) while clamping paper conveyed from paper feed unit 18, and then start conveying the paper at a constant speed in synchronization with secondary transfer device 11.

[0027] When an image is to be formed on the back side of the paper in addition to the front side, the conveying direction of the paper is changed by discharge rollers 17, and the paper is conveyed to reversing conveying path 22. In reversing conveying path 22, the paper is guided up to registration rollers 14 in a reversed state by reversing conveying rollers 15. Image forming apparatus 100 forms an image on the back side of the paper guided to registration rollers 14 in the same manner as on the front side, and discharges the paper to discharge tray 19.

[0028] FIG. 2 is a schematic diagram showing the schematic configuration of the image forming apparatus.

[0029] The image forming apparatus 100 is equipped with a current interrupter having a conversion circuit 42 that converts AC input from the primary side into DC and outputs it from the secondary side, an output control unit 44 that controls the output from the secondary side of the conversion circuit 42, and a current interrupter 43 that is arranged in series with the output control unit 44.

[0030] The current interrupter is configured integrally with a power supply circuit that supplies power to each component, and a conversion circuit 42 is provided between a power supply 41 and a load. For ease of explanation, the side of the conversion circuit 42 connected to the power supply 41 may be referred to as the primary side, and the side connected to the load may be referred to as the secondary side.

[0031] The power supply 41 is provided outside the image forming apparatus 100 and is connected to the image forming apparatus 100 via a terminal such as an outlet. An AC power supply is assumed as the power supply 41 connected to the image forming apparatus 100, and what happens if a DC power supply is mistakenly connected will be described later with reference to FIG. 3. In FIG. 2, the heating unit 33 provided in the fixing device 1 is shown as the load in the image forming apparatus 100, but this is not limiting, and the output from the conversion circuit 42 may be supplied to other parts provided in various parts of the image forming apparatus 100 that are operated by DC.

[0032] The conversion circuit 42 has the function of rectifying current and the function of transforming voltage, and is a circuit that combines electronic components such as diodes and coils.

[0033] As described above, the current interrupter 43 and the output control unit 44 are connected in series between the power supply 41 and the heating unit 33. The current interrupter 43 is a thermal fuse that is always on. A heating element 46 is provided near the current interrupter 43. When heated by the heating element 46, the current interrupter 43 turns off, cutting off power to the output control unit 44. The output control unit 44 is configured to be switchable between on and off, and when turned on, supplies power to the heating unit 33. The output control unit 44 may be configured to control the intermittent supply of power to the heating unit 33, or may be controlled to maintain a constant temperature when the heating unit 33 heats up.

[0034] A branched path is provided between the current interrupter 43 and the output control unit 44, and a heating element 46 is connected to the branched path via a relay 45. The relay 45 is a switch that switches between ON and OFF in response to an instruction from a signal detection unit 47, which will be described later. The heating element 46 is provided near the current interrupter 43, and when the heating element 46 operates, the current interrupter 43 is heated and the current to the output control unit 44 is cut off. In other words, the heating element 46 operates using power supplied from the conversion circuit 42.

[0035] A signal detection unit 47 that detects the frequency of the power input to the conversion circuit 42 is connected to the conversion circuit 42. The conversion circuit 42 outputs a signal based on the frequency of the input power to the signal detection unit 47, and based on this signal, determines whether the power input to the primary side of the conversion circuit 42 is AC or DC, and outputs a signal instructing each unit. The signals from the conversion circuit 42 to the signal detection unit 47 and the signals from the signal detection unit 47 to the relay 45 may be transmitted to each unit by providing appropriate corresponding circuits.

[0036] FIG. 3 is a characteristic diagram showing a voltage input to a conversion circuit and a signal output based on the voltage.

[0037] 3, the horizontal axis represents the passage of time, and the vertical axis represents the level of voltage. The voltage (input waveform AC) input to the conversion circuit 42 has a waveform that periodically switches between positive and negative, like a sine wave, until time Td, at which point the waveform changes, and after time Td, the voltage maintains a constant, high value. In other words, in the example shown in FIG. 3, AC is input to the conversion circuit 42 until time Td, and DC is input after time Td.

[0038] As described above, when AC is supplied from the power supply 41, the voltage has a waveform that periodically switches between positive and negative. At the timing when the voltage switches between positive and negative, the voltage becomes zero, and the signal that detects this moment is called a zero-cross signal.

[0039] The conversion circuit 42 transmits an output signal FW corresponding to the zero-crossing signal to the signal detection unit 47. A predetermined reference value KV is set for the output signal FW, and if it exceeds the reference value KV, it is determined to be "High," and if it does not exceed the reference value KV, it is determined to be "Low." Until time Td, the output signal FW has a "High" value at the timing when the input waveform AC switches between positive and negative, and a "Low" value at other times. After time Td, the input waveform AC does not switch between positive and negative and remains at a high value, so the output signal FW remains "High."

[0040] The signal detection unit 47 refers to the timing (time) at which the output signal FW switches between "High" and "Low," and detects the frequency of the input waveform AC based on this. A preset value is set for the detected frequency, and by comparing it with the set value, it can be determined whether AC is being applied normally. The set value may be, for example, 50 Hz or 60 Hz, which is the frequency of a commercial power supply.

[0041] In the example shown in FIG. 3 , a zero-cross signal is periodically output from startup until time Td, indicating that AC is being applied. The current interrupter 43 is not activated, and power is supplied to the output control unit 44 (heating unit 33). At time Td, the input AC waveform changes, resulting in a corresponding change in frequency. The signal detector 47 activates the heating element 46. As a result, the current interrupter 43 cuts off power to the output control unit 44. In this way, if DC is mistakenly applied to the primary side and the output control unit 44 is no longer able to control the power supply, the heating element 46 heats the device, activating the current interrupter 43, thereby cutting off power and safely shutting down the device. Furthermore, the signal detector 47 detects the frequency of the current in the conversion circuit 42, making it possible to determine whether DC is being applied at startup. Furthermore, by supplying power from the conversion circuit 42, the heating element 46 can operate stably, regardless of the operating environment.

[0042] When the device is started up, it is possible to detect that AC is being applied to the conversion circuit 42 before energizing the heating unit 33, or to prevent DC from being applied to the heating unit 33 if DC is being applied at the time of start-up. In this case, it is preferable not to operate the current cut-off unit 43. By determining whether AC is being applied at the time of start-up in this way, it is not necessary to operate the current cut-off unit 43 unintentionally, and the cost of replacing parts can be reduced.

[0043] In this embodiment, whether or not DC is being applied is determined based on a change in frequency, so that even if the current is switched to DC during operation, the current cut-off unit 43 can be operated appropriately.

[0044] In this embodiment, the image forming apparatus 100 has been described as an example, but the invention is not limited to this, and the power interrupter may be incorporated into electrical equipment such as industrial equipment or factory equipment that uses an AC motor.

[0045] It should be noted that the embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present disclosure should not be interpreted solely by the above-described embodiments, but should be defined based on the claims. Furthermore, all modifications within the scope and meaning equivalent to the claims are included. [Explanation of symbols]

[0046] 1 Fixing device 41 Power supply 42 Conversion circuit 43 Power interrupter 44 Output control section 45 Relay 46 Heating element 47 Signal detection unit 100 Image forming device

Claims

1. A conversion circuit that converts AC input from the primary side into DC and outputs it from the secondary side; an output control unit that controls an output from the secondary side of the conversion circuit; a current interruption unit provided in series with the output control unit; a signal detection unit that detects the frequency of the power input to the conversion circuit; a heating element provided adjacent to the current interrupting unit and controlled based on the detection result of the signal detecting unit, The power interruption unit interrupts power supply to the output control unit when heated by the heating element. A power interrupter characterized by the above.

2. The current interruption device according to claim 1, The heating element is operated by the power supplied from the conversion circuit. A power interrupter characterized by the above.

3. The current interruption device according to claim 1, The signal detection unit determines whether the frequency of the power input to the conversion circuit is a preset value, and when the frequency changes from the preset value to a value different from the preset value, activates the heating element. A power interrupter characterized by the above.

4. An image forming apparatus comprising the power interrupter according to claim 1.

5. An electrical device comprising the current interruption device according to claim 1.

Images