JP2010139596A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multifunction peripheral including a fixing unit detachably attached to a body which can prevent the erroneous detection of the temperature of a thermistor. <P>SOLUTION: The image forming apparatus includes: a connection detecting means 501 which detects that a first drawer connector 312a and a second drawer connector 312b are connected to each other when the fixing unit 100a is connected to the multifunction peripheral 100; a connection switching means 502 which switches connection to a DC power supply 306 from the thermistor 311 to a second resistance element 402; and a voltage value determining means 503 which determines whether or not the voltage value of a DC power supply voltage divided by connection to the second resistance element 402 is included in a predetermined range. When the voltage value of the DC power supply voltage is included in the predetermined range as the determination result, the voltage value determining means 503 makes the connection switching means 502 switch the connection to the DC power supply 306 from the second resistance element 402 to the thermistor 311. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that can prevent erroneous detection of the temperature of a thermistor in an image forming apparatus that includes a fixing unit that is detachably attached to a main body.

  In general, a fixing heater (also simply referred to as a heater) used in an image forming apparatus such as a copying machine, a multi-function machine, or a laser printer is normally turned on when the heater is turned on, and the heater temperature is curved. The temperature is controlled to be kept at a preheating temperature during standby and at an operating temperature during operation, so-called driving.

  A conventional heater control device that controls the temperature of these heaters is provided with a thermistor whose electric resistance is lowered by temperature as a temperature sensor that senses the temperature of the heater in the vicinity of the heater. The thermistor is connected to the control unit of the apparatus main body (copier, etc.) of the heater control device via a connector, one end of the thermistor is connected to the control voltage, the other end of the thermistor is connected in series to the monitor resistor, Connected to ground (earth). The heater control device divides the control voltage by the thermistor and motor resistance, extracts the detected divided voltage corresponding to the heater temperature, inputs it to the control unit, and converts the detected divided voltage analog signal into a digital signal. Multi-value data is converted through a converter (A / D converter, also simply referred to as ADC), and this ADC output is output to a main control unit (also simply referred to as CPU). Based on the reading result of the ADC output, the CPU performs on / off control of the heater power so that a preset temperature is set.

  In such a configuration, when the power is turned on, the CPU turns on the heater and monitors the ADC. The heater continues to be turned on until the ADC output reaches a value corresponding to the above-described preheating temperature. When the ADC output reaches a value corresponding to the preheating temperature, the heater is turned off. Thereafter, the preheating temperature is maintained by repeatedly turning on and off using the heater temperature overshoot and undershoot as the threshold value of the corresponding value of the preheating temperature. Similarly, the CPU also maintains the operating temperature described above.

  However, in such a conventional fixing heater control device, if the connector for connecting the thermistor is disconnected when the power is turned on, the ADC output does not increase even when the fixing heater is turned on. The heater continued to turn on, and the temperature continued to rise forever, and finally there was a problem of generating smoke, ignition, etc. due to heat generation.

  In order to solve the above problem, Japanese Patent Application Laid-Open No. 5-109462 (Patent Document 1) discloses a thermistor that applies a control voltage to one end and monitors the temperature of the heater, and is connected to the other end of the thermistor and grounded. There is disclosed a heater control device comprising: a monitor resistor to be connected; and a control means for dividing a control voltage by the thermistor and the monitor resistor and controlling on / off of the heater based on the divided voltage. In the heater control device, when the thermistor is connected, connection means having a detection terminal for detecting the control voltage applied to the thermistor is provided, and the presence or absence of the control voltage output to the detection terminal is detected. Thus, a technique for detecting the missing of the thermistor is disclosed.

With this technology, it is possible to prevent the occurrence of failures due to thermistor disconnection, such as forgotten connection of the thermistor or defective connection, caused by human error during the manufacture of each product or during regular maintenance at the user site or when replacing parts. It is said.
JP-A-9-101718

  However, although the technique described in Patent Literature 1 can detect the missing of the thermistor, there is a problem that the elements provided around the thermistor are not the subject of the technique.

  On the other hand, a recent image forming apparatus employs a design in which constituent members are collected in a predetermined unit and can be removed as a unit so that the constituent members can be separated and divided from each other. When this design is adopted, various advantages can be obtained in terms of maintenance of the image forming apparatus.

  For example, when a paper conveyance failure (paper jam, also referred to as JAM) occurs in the image forming apparatus, the conveyance failure can be easily solved by removing the unit where the conveyance failure has occurred. Further, when a predetermined function of the image forming apparatus does not operate, the image forming apparatus can be easily restored by replacing the unit corresponding to the function. Furthermore, when a predetermined portion of the image forming apparatus is damaged or dirty, the predetermined portion can be easily repaired by replacing and cleaning the unit corresponding to the portion.

  In particular, when the paper conveyance failure described above occurs in the vicinity of the fixing device of the image forming apparatus, there is a possibility of causing smoke, ignition, etc. due to excessive heating of the fixing heater. For this reason, a design in which the image forming apparatus and the fixing device can be preferably removed is adopted in the vicinity of the fixing device. A detachable unit in the vicinity of the fixing device is referred to as a fixing unit.

  In the fixing unit, the problem of poor connection between the image forming apparatus and the fixing unit is more important than the problem of the thermistor missing described in Patent Document 1 described above. Specifically, when the connection between the image forming apparatus and the fixing unit is not properly performed, the image forming apparatus includes a temperature control unit that controls heating of the fixing heater, and the fixing unit. Communication with a thermistor that detects the temperature of the fixing heater is not properly performed. In such a state, for example, a divergence occurs between the temperature recognized by the temperature control unit from the thermistor and the temperature of the fixing heater actually detected by the thermistor, and the temperature control unit appropriately detects the fixing heater. The problem of not being able to recognize the temperature occurs. In this case, for example, the temperature of the thermistor is erroneously detected due to a poor connection between the image forming apparatus and the fixing heater, even though the fixing heater has already reached a fixing temperature, and the temperature control unit turns the fixing heater on. Continued heating causes secondary problems such as failure of the fixing heater, thermal damage of the thermistor, smoke generation due to heat generation, and ignition.

  Accordingly, the present invention has been made to solve the above problem, and in the image forming apparatus having a fixing unit that is detachably attached to the main body, it is possible to prevent erroneous detection of the thermistor temperature. An object is to provide a possible image forming apparatus.

  In order to solve the above-described problems and achieve the object, an image forming apparatus according to the present invention includes a fixing unit that is detachably attached to a main body, and the fixing unit is connected to the main body. Connect the DC power supply connected to the analog-digital converter of the above to the thermistor in the fixing unit through the connector, and the DC power supply voltage is divided by the analog-digital converter and the thermistor, and the divided DC power supply voltage It is assumed that the image forming apparatus includes temperature detecting means for detecting the temperature of the thermistor based on the voltage value.

  In order that the thermistor of the fixing unit can detect the temperature of the fixing heater, the temperature detection unit of the thermistor is configured to contact or abut against a portion where the fixing heater supplies heat.

  In the image forming apparatus, when the fixing unit is connected to the main body, a connection detecting unit that detects that the first connector fixed in the main body and the second connector fixed in the fixing unit are connected. When the connection detection means detects a connection, the connection switching means for switching the connection with the DC power source from the thermistor to a resistance element having a predetermined resistance value, and when the connection switching means switches the connection, the connection with the resistance element By comparing the voltage value of the DC power supply voltage divided by the reference voltage value converted from the predetermined resistance value with the voltage value of the DC power supply voltage included in the predetermined range Voltage value determining means for determining whether or not to be detected.

  Unlike the thermistor, the resistance element employs a circuit element whose resistance value does not vary with respect to temperature variation (environmental variation).

  The reference voltage value is a reference voltage value converted from a condition in which no resistance value is generated between the connectors when the first connector and the second connector are connected, that is, the resistance value is zero. It is. When the resistance value of the resistance element is specified, the reference voltage value can be converted based on the circuit of the fixing unit, the circuit of the image forming apparatus, and the voltage value of the DC power supply voltage.

  The predetermined range determined from the reference voltage value corresponds to, for example, a range configured with the reference voltage value as a median value. The positive and negative width of the range when the reference voltage value is the median value is determined from, for example, an error in the voltage value generated in the circuit.

  Further, in the image forming apparatus, when the voltage value of the DC power supply voltage is included in a predetermined range as a result of the determination, the voltage value determination means connects the connection switching means to the DC power supply as a resistance element. Configured to switch from a to a thermistor.

  Further, the image forming apparatus includes a thermistor correction unit that corrects the temperature of the thermistor detected by the temperature detection unit based on the voltage value of the DC power supply voltage and a reference voltage value. When the voltage value of the power supply voltage is included in a predetermined range, the voltage value determination unit causes the thermistor correction unit to perform correction, and then causes the connection switching unit to connect the DC power supply from the resistance element to the thermistor. It can be configured to be switched.

  The correction method by the thermistor correction means may be any correction method, for example, a table calculated from the performance of the thermistor on the basis of the reference voltage value, and a table storing the voltage value and the temperature in association with each other. There is a method of rewriting based on the difference between the voltage value of the DC power supply voltage and the reference voltage value.

  Further, in the image forming apparatus, if the voltage value of the DC power supply voltage is out of a predetermined range as a result of the determination, the image forming apparatus stops the fixing heater and displays a stop screen on the display unit provided in the main body. It is possible to configure to include a fixing heater stopping means.

  Examples of the method of stopping the activation of the fixing heater include a method of shutting off a control signal related to heating control of the fixing heater and a method of stopping the supply of AC voltage to the fixing heater.

  According to the image forming apparatus of the present invention, when the fixing unit is connected to the main body, the connection detecting means for detecting that the first connector and the second connector are connected, and the connection between the DC power supply and the thermistor The connection switching means for switching from the resistance element to the resistance element, the voltage value of the DC power supply voltage divided by the connection with the resistance element is compared with a predetermined range determined from the reference voltage value, and the voltage of the DC power supply voltage is compared. Voltage value determining means for determining whether or not the value falls within a predetermined range. Furthermore, in the image forming apparatus, when the voltage value of the DC power supply voltage is included in a predetermined range as a result of the determination, the voltage value determination means connects the connection switching means to the DC power supply in a resistive element. It is configured to switch from a thermistor to a thermistor.

  Accordingly, before detecting the temperature of the fixing heater based on the thermistor in the fixing unit, the voltage value of the DC power supply voltage divided by the connection with the resistance element is determined, and the fixing unit and the main body are connected via the connector. It is possible to confirm whether it is connected properly. For this reason, although the fixing unit and the main body are poorly connected, the possibility of starting temperature detection of the fixing heater is eliminated, and erroneous detection of the thermistor temperature can be reliably prevented. Furthermore, secondary problems derived from erroneous detection of the thermistor temperature, for example, failure of the fixing heater, thermal damage of the thermistor, smoke due to heat generation, ignition, etc. can be prevented.

  Furthermore, when the voltage value of the DC power supply voltage is included in a predetermined range as a result of the determination, the voltage value determination means causes the thermistor correction means to perform correction, and then causes the connection switching means to Can be configured to be switched from a resistance element to a thermistor.

  As a result, for example, minor damage such as scratches or defects between the first connector of the main unit and the second connector of the fixing unit, poor connection due to impurities attached between the connectors, poor connection due to long-term use, etc. If a poor connection occurs between the fixing unit and the main body and the voltage value of the DC power supply voltage is within a predetermined range, the temperature of the fixing heater is corrected after correcting the temperature of the thermistor detected by the temperature detecting means. Will be detected. For this reason, even if a slight connection failure occurs, the image forming apparatus can be flexibly adapted in accordance with the connection failure and the temperature detection accuracy by the thermistor can be improved. As a result, it is possible to appropriately detect the temperature of the fixing heater and to reliably prevent erroneous detection of the temperature.

  Further, as a result of the determination, when the voltage value of the DC power supply voltage is out of a predetermined range, fixing heater stop means for stopping activation of the fixing heater and displaying a stop screen on the display unit provided in the main body is provided. It can be configured to comprise.

  Thereby, for example, scratches, defects, etc. generated between the first connector of the main body and the second connector of the fixing unit are remarkable, and at first glance, the first connector of the main body and the second connector of the fixing unit are Although connected, the connection between the main unit and the fixing unit cannot be connected to each other due to a connection failure or damage that prevents the main unit and the fixing unit from communicating with each other. When a severe connection failure such as the above occurs between the fixing unit and the main body, it is possible to stop the start of the fixing heater and notify the user to that effect. Therefore, despite the severe connection failure between the fixing unit and the main body, the possibility of starting the temperature detection of the fixing heater based on the thermistor in the fixing unit is surely eliminated, and fixing due to erroneous detection of temperature It is possible to reliably prevent the heater from being continuously heated. Furthermore, since the image forming apparatus informs the user of the fixing heater being stopped, poor connection, etc., it is possible for the user to discover the cause of the poor connection early, to promptly repair the image forming apparatus, and to enhance maintenance management. It becomes.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not. In addition, the alphabet “S” added in front of the numbers in the flowcharts means steps.

<Image forming apparatus>
The image forming apparatus according to the present invention will be described below.

  FIG. 1 is a schematic diagram of an image forming apparatus. However, details of each part not directly related to the present invention are omitted.

  The image forming apparatus according to the present invention corresponds to, for example, a printer, a scanner alone, or a multi-function machine equipped with a printer, a copy, a scanner, a fax, and the like, and includes a copy service, a scanner service, a facsimile service, a printer service, and the like. It functions as an image forming apparatus. Hereinafter, for example, an operation of the MFP 100 (Multi Function Peripheral) when using the copy service will be briefly described.

  When the user executes a copy function using the multifunction device 100, the document is placed on a document table provided on the upper surface of the multifunction device 100. Subsequently, the user inputs settings related to the copy function from the operation unit 101 (including the touch panel), and presses a start key provided in the operation unit 101, so that the multifunction peripheral 100 starts a printing process.

  When the multifunction peripheral 100 starts the printing process, the light emitted from the light source 103 is reflected by the image reading unit 102 on the document placed on the document table. The reflected light is guided to the image sensor 107 by the mirrors 104, 105, and 106. The guided light is photoelectrically converted by the image sensor 107, and image data corresponding to the document is generated. Note that the image reading unit 102 is also driven when executing the scan function of the multifunction peripheral 100.

  The image data may be transmitted to the multifunction device 100 via a cable 108 connected to the side wall of the multifunction device 100. In this case, the MFP 100 executes a facsimile transmission / reception function and a print function.

  An image forming unit 109 is a drive unit that transfers the image data as a toner image. The image forming unit 109 is provided with a photosensitive drum 110. The photosensitive drum 110 rotates in a predetermined direction at a constant speed, and around the charger drum 111, the exposure unit 112, the developing unit 113, the transfer unit 114, the cleaning unit 115, and the like in that order from the upstream side in the rotation direction. Is arranged.

  The charger 111 uniformly charges the surface of the photosensitive drum 110. The exposure unit 112 irradiates the charged surface of the photosensitive drum 110 with a laser based on the image data to form an electrostatic latent image. The developer 113 forms a toner image by attaching toner to the conveyed electrostatic latent image. The formed toner image is transferred to a recording medium (for example, a sheet) by the transfer device 114. The cleaning unit 115 removes excess toner left on the surface of the photosensitive drum 110. A series of these processes is executed by rotating the photosensitive drum 110.

  The sheet is conveyed from a plurality of paper feed cassettes 116 provided in the multifunction machine 100. When the sheet is conveyed, the sheet is pulled out from any one of the sheet feeding cassettes 116 by a pickup roller 117 to the conveying path. Each of the paper feed cassettes 116 stores sheets of different paper types, and the sheets are fed based on the settings relating to the image formation.

  The sheet pulled out to the conveyance path is fed between the photosensitive drum 110 and the transfer device 114 by the conveyance roller 118 and the registration roller 119. When the sheet is fed, the toner image is transferred to the sheet by the transfer unit 114 and conveyed to the fixing device 121. In addition, the sheet conveyed to the conveyance roller 118 may be conveyed from the manual feed tray 120 provided on the side surface of the multifunction peripheral 100.

  When the sheet on which the toner image has been transferred passes between a heating roller 122 and a pressure roller 123 provided in the fixing device 121, heat and pressure are applied to the toner image, and the visible image is fixed to the sheet. Is done. The amount of heat of the heating roller 122 is optimally set according to the paper type via a fixing heater (not shown), and the fixing is performed appropriately. A thermistor (not shown) capable of detecting the temperature of the fixing heater is provided in the vicinity of the fixing heater, and the image forming unit 109 detects a change in electrical resistance of the thermistor corresponding to the temperature change. Thus, the heating of the fixing heater is controlled (described later). The visible image is fixed on the sheet and the image formation is completed, and the sheet is stacked and accommodated as a printed material on a paper discharge tray 124 provided on the side wall of the multifunction peripheral 100.

  Through the above procedure, the multi-function device 100 provides a copy function to the user. When the multifunction peripheral 100 provides other functions, the image reading unit 102 and the image forming unit 109 are driven and provided. Hereinafter, means for receiving a predetermined processing condition (setting related to the copy function) from the user or displaying a predetermined screen on the touch panel is referred to as condition receiving means (described later).

  Further, the fixing device 121 of the multifunction peripheral 100 is configured such that constituent members constituting the fixing device 121 can be removed. For example, the fixing heater and the thermistor correspond to components constituting the fixing device 121 and are provided in a fixing unit that can be detached from the image forming unit 109 (described later).

  FIG. 2 is a diagram illustrating an example of the appearance of the operation unit 101 provided in the multifunction peripheral 100. The user uses the operation unit 101 to input setting conditions for providing the functions as described above. When the setting condition is input, the touch panel 201, the touch pen 202, and the operation key 203 provided in the operation unit 101 are used.

  The touch panel 201 has both a function for inputting the setting conditions described above and a function for displaying the input setting conditions and the like. That is, by pressing a selection item or the like in the screen displayed on the touch panel 201, a setting condition associated with the selection item or the like is input. Moreover, since the input item etc. are displayed on the touch panel 201 by changing the background color from white to gray, they are visually recognized by the user as needed. Further, when an error or an emergency situation occurs in the multi-function device 100, the touch panel 201 displays a screen for informing the user of the error or the like. The user can respond to an error or emergency according to the displayed screen. The stop screen displayed on the touch panel 201 will be described later.

  A touch pen 202 is provided in the vicinity of the touch panel 201, and when a user brings the tip of the touch pen 202 into contact with the touch panel 201, a sensor provided below the touch panel 201 detects the touch destination. Therefore, by touching the touch pen 202, a key on the keyboard screen can be pressed or predetermined handwritten information can be input.

  Further, a predetermined number of operation keys 203 are provided in the vicinity of the touch panel 201, and for example, a ten key 204, a start key 205, a clear key 206, a stop key 207, a reset key 208, and a power key 209 are provided. The numeric keypad 204 is used to input specific numbers when setting the number of copies and the magnification.

  Next, the configuration of the control system hardware of the multifunction peripheral 100 to which the fixing unit is connected will be described with reference to FIG. FIG. 3 is a schematic configuration diagram of control system hardware in the multifunction peripheral 100. However, details of each part not directly related to the present invention are omitted.

  The control circuit of the MFP 100 includes a CPU (Central Processing Unit) 301, a ROM (Read Only Memory) 302, a RAM (Random Access Memory) 303, a HDD (Hard Disk Drive) 304, a driver 305 corresponding to each driving unit, and a direct current. An A / D unit (A / D converter) 307 that converts an analog signal of a DC power supply voltage output from the power source 306 into a digital signal, and an I / O unit 309 connected to a fixing heater 308 provided in the fixing unit 100a. Are connected by an internal bus 310. The DC power source 306 is configured based on, for example, a rectifier that rectifies an AC voltage from an external power source into a DC voltage having a predetermined voltage value.

  The control circuit of the multifunction peripheral 100 is connected to the thermistor 311 and the fixing heater 308 provided in the fixing unit 100a via a pair of drawer connectors 312. The pair of drawer connectors 312 is used for transmission / reception of a predetermined control signal performed between the multifunction device 100 and the fixing unit 100a, and the first drawer connector 312a fixed in the multifunction device 100 and the fixing unit. And a second drawer connector 312b fixed in 100a. When a plurality of contacts provided on the first drawer connector 312a and a plurality of contacts provided on the second drawer connector 312b are connected, the connected contacts constitute a signal line, and the signal line Thus, the control circuit of the multifunction peripheral 100 and the circuit elements such as the thermistor 311 of the fixing unit 100a can transmit and receive predetermined control signals. Since a plurality of signal lines are configured, for example, different control signals are transmitted / received to / from each signal line.

  When the first drawer connector 312a and the second drawer connector 312b are connected, the DC power supply 306 in the multifunction peripheral 100 is connected to the thermistor 311 via the pair of drawer connectors 312 and the DC power supply voltage is A. / D unit 307 and thermistor 311 are input. In this configuration, the DC power supply 306 is connected in series to the A / D unit 307 before the DC power supply 306 is connected to the thermistor 311, but after the DC power supply 306 is connected to the thermistor 311, the DC power supply 306 is connected. Are connected to the A / D unit 307 and the thermistor 311 in parallel. Therefore, in parallel connection, the DC power supply voltage is divided into two according to the resistance value of the A / D unit 307 and the resistance value of the thermistor 311. One of the divided DC power supply voltages is input to the A / D unit 307, and the other divided DC power supply voltage is input to the thermistor 311. Since the DC power supply voltage holds a predetermined voltage value, for example, when the resistance value of the thermistor 311 varies, the ratio of the divided voltage to the DC power supply voltage, in other words, the DC power supply voltage input to the A / D unit 307 And the ratio of the DC power supply voltage input to the thermistor 311 fluctuates. The CPU 301 can detect and monitor the change via the A / D unit 307 to detect the temperature of the thermistor 311, that is, the temperature of the fixing heater 308 in contact with or in contact with the thermistor 311 at any time. Become.

  One end of the thermistor 311 in the fixing unit 100a is connected to a DC power source 306 via a pair of drawer connectors 312 and the other end of the thermistor 311 is connected to a ground 313 (earth) in the fixing unit 100a. .

  In addition, a control signal for controlling heating of the fixing heater 308 in the fixing unit 100a (for example, an on / off signal transmitted to a switching element such as a triac) is sent from the control circuit of the multifunction peripheral 100 to the pair of drawer connectors 312. Are sent and received via The CPU 301 fixes a predetermined control signal via the I / O unit 309 and the pair of drawer connectors 312 based on the digital signal (voltage value of the divided DC power supply voltage) converted by the A / D unit 307. It transmits to the heater 308 and controls the heating of the fixing heater 308. On the other hand, a power supply voltage (AC voltage) for heating the fixing heater is input to the fixing heater 308 from an AC power supply (not shown) provided in the multifunction peripheral 100 via a high voltage connector (not shown). Composed.

  Further, the CPU 301 uses, for example, the RAM 303 as a work area, executes a program stored in the ROM 302, the HDD 304, and the like, and based on the execution result, the driver 305, the A / D unit 307, I / O unit 309 exchanges data and instructions, and controls the operation of each driving unit shown in FIGS. As for each means (shown in FIG. 5) other than the above-described driving unit, the CPU 301 executes the program and exchanges data and instructions to realize each means. The ROM 302 and the HDD 304 store programs and data for realizing each means described below.

  The fixing unit 100a may include a CPU, a RAM, a ROM, and the like as a fixing unit control circuit.

<Embodiment of the present invention>
Next, main circuit configurations of the multifunction peripheral and the fixing unit according to the embodiment of the present invention will be described with reference to FIG. FIG. 4 is a diagram illustrating main circuits of the multifunction peripheral and the fixing unit according to the embodiment of the present invention. In addition, the detail of each part which is not directly related to embodiment of this invention is abbreviate | omitted.

  In the MFP 100, a DC power supply 306 that outputs a DC voltage (control voltage, DC power supply voltage) having a predetermined voltage value (for example, 3.3V), and a first power supply connected in series to the DC power supply 306 are provided. Resistance element 401, A / D unit 307 to which a DC power supply voltage is input from DC power supply 306 via first resistance element 401, and A / D unit 307 converted from a DC power supply voltage that is an analog signal. And a CPU 201 to which a voltage value which is a digital signal is input.

  In addition, the multifunction peripheral 100 includes a first drawer connector 312a that can be connected to the second drawer connector 312b of the fixing unit 100a. A wire provided between the first resistance element 401 and the A / D unit 307 is connected to a part of the contact of the first drawer connector 312a. Therefore, the DC power supply voltage input from the DC power supply 306 to the A / D unit 307 via the first resistance element 401 is input to the first drawer connector 312a so that the DC power supply voltage can be divided. Composed.

  As described above, when the first drawer connector 312a and the second drawer connector 312b are connected, the divided DC power supply voltage is input into the fixing unit 100a. On the other hand, when the first drawer connector 312a and the second drawer connector 312b are detached, the DC power supply voltage having a predetermined voltage value is not divided into the first resistance element 401 without dividing the DC power supply voltage. To the A / D unit 307. Therefore, the CPU 301 can detect attachment / detachment between the first drawer connector 312a and the second drawer connector 312b by detecting and monitoring the voltage value converted from the A / D unit 307.

  Specifically, when the DC power supply voltage is not divided, the CPU 301 detects a voltage value (voltage value A) corresponding to a predetermined voltage value of the DC power supply 306. Since the voltage value A is a voltage value via the first resistance element 401, the voltage value A is much lower than a predetermined voltage value. When the DC power supply voltage is divided, the CPU 301 detects a voltage value (voltage value B) lower than the voltage value A. The voltage value B takes a value significantly lower than a predetermined voltage value because the divided DC power supply voltage is input to the fixing unit 100a. When the DC power supply voltage (voltage value converted into the A / D unit 307) is input, the CPU 301 detects the voltage value A and the voltage value B, and the first drawer connector 312a and the second drawer connector. It is configured to detect attachment / detachment with 312b.

  On the other hand, the fixing unit 100a includes an analog switch 403 that switches connection between the thermistor 311 and the second resistance element 402 based on a predetermined control signal via a pair of drawer connectors 312. It comprises a thermistor 311 capable of detecting the temperature of a fixing heater (not shown) and a second resistance element 402 having a predetermined resistance value. When the analog switch 403 switches the connection to the DC power supply 306 to the thermistor 311 or the second resistance element 402, the input of the divided DC power supply voltage is switched to the thermistor 311 or the second resistance element 402.

  Here, when the input of the divided DC power supply voltage is switched to the thermistor 311 by the analog switch 403, the temperature of the thermistor 311 can be detected as described with reference to FIG.

  On the other hand, when the input of the divided DC power supply voltage is switched to the second resistance element 402 by the analog switch 403, the second resistance element 402 differs from the thermistor 311 in that resistance due to environmental change (temperature change or the like). Since the value does not fluctuate, a divided DC power supply voltage that does not fluctuate due to an environmental change (temperature change or the like) is input to the A / D unit 307. In other words, the divided DC power supply voltage, which fluctuates due to a connection failure (fitting failure) between the contact of the first drawer connector 312a and the contact of the second drawer connector 312b, is input to the A / D unit 307. Will be. The connection failure includes, for example, a connection failure due to a scratch or a defect generated between the first drawer connector 312a of the multifunction peripheral 100 and the second drawer connector 312b of the fixing unit 100a, and adhesion between the pair of drawer connectors 312. Minor connection failures such as connection failure due to impurities and connection failure due to long-term use are applicable.

  Note that the connection failure is, for example, a connection failure in which the contact of the first drawer connector 312a and the contact of the second drawer connector 312b are not connected at all, or the first drawer connector 312a and the fixing unit 100a of the multifunction peripheral 100. Scratches, defects, etc. generated between the second drawer connector 312b and the first drawer connector 312a of the multifunction machine 100 and the second drawer connector 312b of the fixing unit 100a are connected at first glance. The first drawer connector 312a of the multifunction device 100 and the second drawer connector 312b of the fixing unit 100a are almost connected for reasons such as poor connection and breakage where the multifunction device 100 and the fixing unit 100a cannot communicate with each other. Severe connection failures such as connection failures that cannot be made are not applicable.

  Here, when the pair of drawer connectors 312 is properly connected, that is, when there is no connection failure, the resistance value between the first drawer connector 312a and the second drawer connector 312b is almost zero. Become. Therefore, the voltage value of the DC power supply voltage input to the A / D unit 307 is the DC power supply voltage input to the second resistance element 402 from the voltage value of the DC power supply voltage before being divided, This corresponds to the value obtained by subtracting the voltage value of the DC power supply voltage after voltage division. The value can be converted from a predetermined voltage value of the DC power supply voltage, the resistance value of the first resistance element 401, and the resistance value of the second resistance element 402, and the pair of drawer connectors 312 is appropriately It is a voltage value that serves as a reference when determining whether or not it is connected. This value is set as a reference voltage value.

  Therefore, the CPU 301 compares the voltage value of the DC power supply voltage input via the A / D unit 307 with the reference voltage value, and determines whether or not the voltage value of the DC power supply voltage satisfies the reference voltage value. By determining, it becomes possible to determine whether or not the pair of drawer connectors is properly connected. The determination of whether or not the voltage value of the DC power supply voltage satisfies the reference voltage value is determined by taking into account the occurrence of an error, for example, whether or not the voltage value of the DC power supply voltage is included in a predetermined range. Is executed. In FIG. 4, the CPU 301 is configured to determine whether or not the voltage value of the DC power supply voltage is included in a predetermined range. The predetermined range is a range in which the reference voltage value is a median value.

  For example, when the predetermined voltage value of the DC power supply voltage is 3.3V, the resistance value of the first resistance element 401 is 10Ω, and the resistance value of the second resistance element 402 is 10Ω, the reference voltage value is 1.65V. Is converted. For example, the predetermined range with the reference voltage value as the median value is determined as a range from 1.5 V to 1.8 V (described later).

  In addition, one end of the second resistance element 402 in the fixing unit 100a is connected to the analog switch 403 similarly to the thermistor 311, and the other end of the second resistance element 402 is connected to the ground 313 (earth) in the fixing unit 100a. ).

  The analog switch 403 in the fixing unit 100a is configured to receive a predetermined control signal (switching signal) from the CPU 301 of the multifunction peripheral 100 via the pair of drawer connectors 312. The CPU 301 of the multifunction peripheral 100 is connected to the DC power source. Controls switching of the connection with 306.

Each means to be described later (shown in FIG. 5) is constituted by the main circuit described in FIG. 4 in addition to the circuit described in FIG. 3. Next, referring to FIGS. A procedure for preventing erroneous detection of the temperature of the thermistor provided in the fixing unit in the multifunction peripheral according to the embodiment of the present invention including the fixing unit provided detachably will be described. FIG. 5 is a functional block diagram of the multifunction peripheral and the fixing unit according to the embodiment of the present invention. FIG. 6 is a flowchart for illustrating the execution procedure of the embodiment of the present invention.

  For example, it is assumed that a paper conveyance failure occurs in the vicinity of the fixing device 122 of the multifunction peripheral 100. While viewing a predetermined error screen displayed on the touch panel 201 of the operation unit 101, the user removes the fixing unit 100a from the multifunction peripheral 100 and removes the paper that has caused the conveyance failure.

  When the fixing unit 100a is once removed from the multifunction device 100, the first drawer connector 312a fixed to the multifunction device 100 and the second drawer connector 312b fixed to the fixing unit 100a are detached. The DC power supply voltage of the DC power supply 306 of 100 is input to the connection detecting means 501 of the multifunction peripheral 100 without being divided. The connection detection unit 501 detects that the fixing unit 100a has been removed from the multifunction peripheral 100 by detecting a voltage value (voltage value A) corresponding to a predetermined voltage value of the DC power supply 306 (FIG. 6: S101). ).

  Further, the user who has removed the paper connects the fixing unit 100a to the multifunction device 100, and returns the multifunction device 100 to its original state. When the fixing unit 100a is connected to the multifunction device 100 again, the first drawer connector 312a and the second drawer connector 312b are connected, so that the DC power supply voltage input to the connection detecting unit 501 is divided. The The connection detection unit 501 detects the voltage value of the divided DC power supply voltage (voltage value (voltage value B) lower than the voltage value A), whereby the first drawer connector 312a and the second drawer connector 312b. Are connected, that is, it is detected that the fixing unit 100a is connected to the multifunction device 100 again (FIG. 6: S102).

  When the connection detecting unit 501 detects that the fixing unit 100a is connected to the multifunction peripheral 100, the connection switching unit 502 (analog switch) provided in the fixing unit 100a is connected to the DC power source 306 from the thermistor 311. The second resistance element 402 is switched (FIG. 6: S103). Specifically, the connection detection unit 501 transmits a predetermined control signal A (for example, an ON signal) to the connection switching unit 502 via the pair of drawer connectors 312. The connection switching unit 502 that has received the control signal A switches the connection with the DC power source 306 from the thermistor 311 to the second resistance element 402.

  When the connection with the DC power source 306 is switched from the thermistor 311 to the second resistance element 402, the connection detection unit 501 transmits a signal indicating that the connection has been switched to the voltage value determination unit 503 of the multifunction peripheral 100. The voltage value determination unit 503 that has received the signal receives the DC power supply voltage divided by the connection with the second resistance element 402, and the voltage value of the DC power supply voltage and the second resistance element 402 have By comparing with a predetermined range determined from a reference voltage value converted from a predetermined resistance value, it is determined whether or not the voltage value of the DC power supply voltage is included in the predetermined range (FIG. 6: S104). .

  The predetermined range is stored in a predetermined memory provided in the voltage value determination unit 503, for example. The predetermined range is that when the first drawer connector 312a and the second drawer connector 312b are properly connected, that is, the resistance value between the first drawer connector 312a and the second drawer connector 312b is zero. A range determined from an upper limit value obtained by adding a predetermined value preset by the user and a lower limit value obtained by subtracting the predetermined value, with the reference voltage value converted in the case of (or near zero) as the median value It is. The predetermined value takes into account the error that occurs.

  For example, as shown in FIG. 4, if the reference voltage value is 1.65V and the error of the voltage value measured by the circuit elements provided in the multifunction device 100 and the fixing unit 100a is 0.15V. The predetermined range is determined as a range from 1.5 V (lower limit value) to 1.8 V (upper limit value). The predetermined range is appropriately changed according to, for example, the accuracy limit of the thermistor 311 and the introduced circuit element.

  As a result of the determination by the voltage value determination means 503, when the voltage value of the DC power supply voltage is included in a predetermined range, the voltage value determination means 503 has a relationship between the first drawer connector 312a and the second drawer connector 312b. Recognizing that the state is properly connected, the thermistor correction means 504 executes correction (FIG. 6: S104 YES → S105).

  Specifically, the voltage value determination unit 503 transmits the voltage value of the DC power supply voltage and the reference voltage value to the thermistor correction unit 504. The thermistor correction means 504 divides the received DC power supply voltage value by the reference voltage value to calculate the ratio of the DC power supply voltage value to the reference voltage value.

  For example, when the voltage value of the received DC power supply voltage is 1.61 V and the reference voltage value is 1.65 V, the ratio (%) is 1.61 / 1.65 × 100 = 97.6%. Become. If the ratio is not 100%, the first drawer connector 312a and the second drawer connector 312b are properly connected, but the first drawer connector 312a and the second drawer connector 312b are connected. It shows that the resistance value between is not zero (or near zero). That is, the ratio corresponds to the deviation of the voltage value of the DC power supply voltage with respect to the reference voltage value.

  When the thermistor correction unit 504 calculates the ratio, the thermistor correction unit 504 refers to the temperature conversion table storage unit 505 that stores the voltage value and temperature for the thermistor 311 in association with each other as a table, and corrects the table. Since the table is created based on, for example, a reference voltage value, the correction method divides the ratio calculated by the thermistor correction unit 504 by the ratio of temperature change to the voltage value stored in the table. Is executed. The ratio of the change in temperature with respect to the voltage value is a ratio obtained by dividing the amount of increase in temperature by the amount of increase in voltage value. In a graph in which the temperature is plotted against the voltage value, it corresponds to the slope of the graph. In the above description, a table that stores the voltage value and the temperature in association with each other has been described. For example, the table that stores the resistance value of the thermistor in association with the temperature, the resistance value of the thermistor, You may employ | adopt the table (formula) which converts the voltage value of the divided DC power supply voltage.

  The correction method described above is applied to a configuration in which the voltage value of the DC power supply voltage increases as the temperature of the thermistor 311 increases. Therefore, for example, the correction method is appropriately changed according to the type of thermistor 311 provided (NTC (Negative Temperature Coefficient) thermistor whose electrical resistance decreases with increasing temperature, PTC (Positive Temperature Coefficient) thermistor, etc.). Is done.

  When the correction of the thermistor correction unit 504 is completed, the voltage value determination unit 503 confirms the correction, and then causes the connection switching unit 502 to switch the connection with the DC power source 306 from the second resistance element 402 to the thermistor 311. (FIG. 6: S106). Specifically, the voltage value determination unit 504 transmits a predetermined control signal B (for example, an off signal) to the connection switching unit 502 via the pair of drawer connectors 312. The connection switching unit 502 that has received the control signal B switches the connection with the DC power source 306 from the second resistance element 402 to the thermistor 311.

  When the connection with the DC power supply 306 is switched to the thermistor 311, the voltage value determination unit 503 transmits a signal indicating that the temperature of the thermistor 311 can be detected to the temperature detection unit 506 (temperature control unit). When the temperature detection unit 506 receives the signal, the temperature detection unit 506 transmits a predetermined control signal to the fixing heater 308 (or a switching element provided in the fixing heater 308) via the pair of drawer connectors 312 and transmits the predetermined control signal to the fixing heater 308. The AC voltage is applied and heating of the fixing heater 308 is started (FIG. 6: S107).

  The temperature detection unit 506 detects and monitors the temperature of the thermistor 311, that is, the temperature of the fixing heater 308 based on the voltage value of the DC power supply voltage divided by connection with the thermistor 311. When detecting and monitoring the temperature of the fixing heater 308, the temperature detection unit 506 refers to the temperature conversion table storage unit 505 that stores the corrected table, and determines the temperature corresponding to the voltage value of the divided DC power supply voltage. The calculated temperature is set as the temperature of the fixing heater 308, and the temperature of the fixing heater 308 is monitored. In this manner, the temperature detection unit 506 heats the fixing heater 308 to a temperature at which fixing can be performed, and the multifunction peripheral 100 shifts to a state where image formation is possible.

  On the other hand, when the voltage value determining means 503 determines that the voltage value of the DC power supply voltage is outside the predetermined range, the voltage value determining means 503 includes the first drawer connector 312a and the second drawer connector 312b. Is not properly connected, and the fixing heater stopping means 507 stops the fixing heater 308 from starting (FIG. 6: S104 NO → S108).

  For example, the fixing heater stop unit 507 controls the temperature detection unit 506 so as not to transmit a predetermined control signal to the fixing heater 308, thereby blocking input of a predetermined AC voltage applied to the fixing heater 308. Thereby, the heating of the fixing heater 308 is stopped.

  Further, the fixing heater stopping unit 507 displays a stop screen indicating that the fixing heater 308 has been stopped on the touch panel 201 (display unit) of the operation unit 101 via the condition receiving unit 508 (FIG. 6: S109).

  In the stop screen, as shown in FIG. 2, an error message 2001 “The fixing unit cannot be properly connected” indicating that the fixing unit cannot be properly connected to the multifunction peripheral is heated. Message 2002 “Stop heating the fixing heater” and message 2003 “Prompt the user to contact the administrator or service person.” The contact information 2004 of the administrator or service person is displayed. When the condition receiving unit 508 displays the stop screen, even if the user inputs a predetermined setting condition via the operation unit 101, the stop screen is displayed without receiving any input. .

  With this configuration, the user is urged to contact an administrator or a service person, and the user is allowed to use the multifunction device 100 in a state where the first drawer connector 312a and the second drawer connector 312b are not properly connected. Therefore, it is possible to prevent ignition and smoke generated by erroneous detection of the temperature of the thermistor 311.

  As described above, when the fixing unit is connected to the multifunction peripheral, the connection between the first drawer connector and the second drawer connector and the DC power source is connected from the thermistor to the connection detection means for detecting the connection between the first drawer connector and the second drawer connector. The connection switching means for switching to the resistance element of the second power source, the voltage value of the DC power supply voltage divided by the connection with the second resistance element is compared with a predetermined range determined from the reference voltage value, and the DC power supply Voltage value determination means for determining whether or not the voltage value of the voltage falls within a predetermined range. Furthermore, when the voltage value of the DC power supply voltage is included in a predetermined range as a result of the determination, the voltage value determination means connects the connection switching means to the DC power supply from the second resistance element to the thermistor. It is configured to be switched.

  Thus, before detecting the temperature of the fixing heater based on the thermistor in the fixing unit, the voltage value of the DC power supply voltage divided by the connection with the second resistance element is determined, and the fixing unit, the multifunction device, It is possible to confirm whether or not is properly connected via the connector. Therefore, in spite of the poor connection between the fixing unit and the multifunction peripheral, the possibility of starting temperature detection of the fixing heater is eliminated, and erroneous detection of the thermistor temperature can be reliably prevented. Furthermore, secondary problems derived from erroneous detection of the thermistor temperature, for example, failure of the fixing heater, thermal damage of the thermistor, smoke due to heat generation, ignition, etc. can be prevented.

  Furthermore, when the voltage value of the DC power supply voltage is included in a predetermined range as a result of the determination, the voltage value determination means causes the thermistor correction means to perform correction, and then causes the connection switching means to Can be configured to be switched from the second resistance element to the thermistor.

  As a result, for example, scratches or defects caused between the first drawer connector of the multifunction device and the second drawer connector of the fixing unit, poor connection due to defects, poor connection due to impurities attached between the drawer connectors, long-term connection Even if a minor connection failure such as a failure occurs between the fixing unit and the multifunction device, the temperature of the thermistor detected by the temperature detection means is corrected if the voltage value of the DC power supply voltage is within a predetermined range. Later, the temperature of the fixing heater is detected. For this reason, even if a minor connection failure occurs, the multifunction device can be flexibly adapted in accordance with the connection failure, and the temperature detection accuracy by the thermistor can be increased. As a result, it is possible to appropriately detect the temperature of the fixing heater and to reliably prevent erroneous detection of the temperature.

  Further, as a result of the determination, when the voltage value of the DC power supply voltage is out of a predetermined range, fixing heater stopping means for stopping activation of the fixing heater and displaying a stop screen on the display unit provided in the multifunction peripheral It can comprise.

  As a result, for example, scratches, defects, etc. generated between the first drawer connector of the multifunction peripheral and the second drawer connector of the fixing unit are remarkable. Although the second drawer connector is connected, the first drawer connector of the multifunction device and the second drawer connector of the fixing unit are not connected because the multifunction device and the fixing unit cannot communicate with each other. When a severe connection failure such as a connection failure that cannot be connected to the printer occurs between the fixing unit and the multifunction device, it is possible to stop the start of the fixing heater and inform the user to that effect. Become. For this reason, the possibility of starting the temperature detection of the fixing heater based on the thermistor in the fixing unit is surely excluded despite the severe connection failure between the fixing unit and the multifunction peripheral. It is possible to reliably prevent occurrence of continuous heating of the fixing heater. Furthermore, since the multifunction device informs the user of the fixing heater being stopped, poor connection, etc., it is possible for the user to quickly find the cause of the poor connection, promptly repair the multifunction device, and enhance maintenance management. .

  In the embodiment of the present invention, the MFP is configured to include a DC power supply, but the DC power supply may be configured to be included in the fixing unit.

  In the embodiment of the present invention, the fixing unit is provided with a fixing heater. However, the fixing heater may be provided in a unit separate from the fixing unit or in a multifunction machine.

  In addition, all or a part of each means constituting the embodiment of the present invention includes predetermined circuit elements (for example, diodes, operational amplifiers, resistors, transistors, switching elements, etc.) and hardware resources (for example, control elements, arithmetic elements). Or the like may be realized as a circuit.

  For example, a fixing unit that is detachably attached to the main body, and when the fixing unit is connected to the main body, a DC power source connected to an analog-digital converter in the main body is connected to the inside of the fixing unit via a connector. Forming a temperature detection circuit that detects the temperature of the thermistor based on the voltage value of the DC power supply voltage divided by the analog-to-digital converter and the thermistor. In the apparatus, when the fixing unit is connected to the main body, a connection detection circuit that detects that the first connector fixed in the main body and the second connector fixed in the fixing unit are connected, and When the connection detection circuit detects a connection, the connection switching circuit switches the connection with the DC power source from the thermistor to a resistance element having a predetermined resistance value, and the connection switching circuit. When the connection is switched, the DC power supply voltage value divided by the connection with the resistance element is compared with a predetermined range determined from the reference voltage value converted from the predetermined resistance value, and the DC power supply A voltage value determination circuit that determines whether or not the voltage value of the voltage is included in a predetermined range, and if the voltage value of the DC power supply voltage is included in the predetermined range as a result of the determination, the voltage value determination circuit The circuit may comprise the connection switching circuit including switching the connection with the DC power source from the resistance element to the thermistor. This configuration also has the effects of the present invention.

  In the embodiment of the present invention, the MFP is configured to include each unit. However, a program that realizes each unit may be stored in a storage medium, and the storage medium may be provided. In the above-described configuration, the above-described program is read by the multi-function peripheral, and the multi-function peripheral implements the above-described units. In that case, the program itself read from the recording medium exhibits the effects of the present invention. Furthermore, it is also possible to provide a storage method for storing the steps executed by each means in a hard disk.

  As described above, the image forming apparatus according to the present invention is useful not only for multifunction peripherals but also for copying machines, printers, and the like. In an image forming apparatus including a fixing unit that is detachably attached to a main body, the thermistor This is effective as an image forming apparatus capable of preventing erroneous detection of the temperature.

1 is a conceptual diagram illustrating an overall configuration inside a multifunction peripheral. FIG. 3 is a diagram illustrating an example of an appearance of an operation unit provided in the multifunction machine. FIG. 3 is a schematic configuration diagram of control system hardware in a multifunction machine. FIG. 2 is a diagram illustrating main circuits of a multifunction peripheral and a fixing unit according to an embodiment of the present invention. 2 is a functional block diagram of a multifunction peripheral and a fixing unit according to an embodiment of the present invention. FIG. It is a flowchart for showing the execution procedure of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 MFP 100a Fixing unit 306 DC power supply 307 A / D part 308 Fixing heater 311 Thermistor 312 Drawer connector 401 1st resistance element 402 2nd resistance element 403 Analog switch 501 Connection detection means 502 Connection switching means 503 Voltage value determination means 504 Thermistor correction means 505 Temperature conversion table storage means 506 Temperature detection means 507 Fixing heater stop means 508 Condition reception means

Claims (3)

The fixing unit provided detachably with respect to the main body, and when the fixing unit is connected to the main body, the DC power source connected to the analog-digital converter in the main body is connected to the thermistor in the fixing unit via the connector. In an image forming apparatus comprising a temperature detection means for detecting a temperature of the thermistor based on a voltage value of the divided DC power supply voltage by dividing the DC power supply voltage with an analog-digital converter and a thermistor ,
When the fixing unit is connected to the main body, connection detecting means for detecting that the first connector fixed in the main body and the second connector fixed in the fixing unit are connected;
When the connection detection means detects connection, connection switching means for switching the connection with the DC power source from the thermistor to a resistance element having a predetermined resistance value;
When the connection switching means switches the connection, the voltage value of the DC power supply voltage divided by the connection with the resistance element is compared with a predetermined range determined from a reference voltage value converted from the predetermined resistance value. Voltage value determination means for determining whether or not the voltage value of the DC power supply voltage is included in a predetermined range,
As a result of the determination, when the voltage value of the DC power supply voltage is included in a predetermined range, the voltage value determination means causes the connection switching means to switch the connection with the DC power supply from a resistance element to a thermistor. An image forming apparatus. Further, the thermistor correction means for correcting the temperature of the thermistor detected by the temperature detection means based on the voltage value of the DC power supply voltage and the reference voltage value,
As a result of the determination, if the voltage value of the DC power supply voltage is included in a predetermined range, the voltage value determination means causes the thermistor correction means to perform correction, and then causes the connection switching means to connect to the DC power supply. The image forming apparatus according to claim 1, wherein the connection is switched from a resistance element to a thermistor.   Further, as a result of the determination, when the voltage value of the DC power supply voltage is out of a predetermined range, fixing heater stop means for stopping activation of the fixing heater and displaying a stop screen on the display unit provided in the main body is provided. The image forming apparatus according to claim 1, further comprising:

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