JP6026381B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus accompanied by a heat fixing process when an image is formed on recording paper or the like.

In general, image forming apparatuses such as copying machines, facsimiles, and multi-function printers using dry electrophotography form an image with toner (toner, fine color developer) using static electricity on the surface of the photoreceptor, and record this image. After transferring to paper or the like, the toner is fixed by heating and pressurizing the recording paper or the like.
Heating and pressing methods include a method of heating with a heater from the inside of the heating roller, a method of heating the fixing belt with the heating roller, and sandwiching the fixing belt with the pressure roller, and further, the fixing belt is energy efficient. There is a method of generating heat by IH (Induction Heating, electromagnetic induction heating type) and sandwiching with a pressure roller.

  When the fixing belt is used for the fixing process as described above, if the fixing belt is damaged, the IH coil that originally generates heat may be abnormally overheated, but measures are taken to prevent various accidents due to this overheating. It is necessary to give.

JP 2011-128383 A

For example, in Japanese Patent Application Laid-Open No. 2011-128383, the state of magnetic flux is monitored by an antenna that detects a magnetic flux leaking from a belt, and for example, when the magnetic flux density exceeds a predetermined threshold value, it is determined that there is an abnormality and the fixing process is stopped. The configuration is shown.
However, in the above-described example, since it is necessary to provide an antenna for detecting the magnetic flux in the fixing unit, the space is restricted, the configuration is complicated, and the cost is restricted.

Now, in a fixing unit using a fixing belt, when the fixing belt is torn or damaged, the roller on which the fixing belt is stretched does not rotate. Therefore, in general, a control structure is provided that stops heating when the rotation stop of the stretching roller is detected.
However, for example, when the central portion of the fixing belt is damaged, the stretching roller may continue to rotate. In such a case, since the heating does not stop, the temperature of the roller continues to rise.

In such a fixing unit that performs heating and pressure fixing, a temperature detection element such as a thermistor and a position detection element are arranged, and the temperature of each part and the position of the recording paper are predicted so that the recording paper is wound around a roller or the like. JAM (paper jam) such as sticking is detected.
However, there are cases where JAM recording paper cannot be found even during maintenance in the fixing unit, or when the JAM recording paper is removed, the recording paper is torn and a part of it remains in the fixing unit. In other words, if the fixing belt is damaged, unless heating to the fixing belt is properly stopped, overheating of the JAM-recorded recording paper or the like may occur, which may lead to an unexpected accident.

  The present invention has been made in view of the above points, and an object of the present invention is to appropriately detect an abnormality of the fixing belt without adding a complicated configuration and to stop heating the fixing belt when the abnormality occurs. Or providing an image forming apparatus capable of notifying the occurrence of an abnormality.

The image forming apparatus according to the present invention includes the image forming unit that forms a toner image on the recording medium, the endless fixing belt that is heated by the heating unit, and the pressure roller. A fixing unit that fixes unfixed toner formed on the recording medium by a forming unit; a power input unit that inputs high-frequency power of a predetermined frequency to the heating unit; and a voltage detection unit that detects a voltage value of the high-frequency power. Control means for controlling the power input means, input / output means for informing various information by the control means, and initial information including a first voltage value of the high-frequency power when the fixing belt is normal. storage means for previously storing a temperature detection means for detecting a temperature of the fixing belt, provided from an AC power source for generating said high frequency electric power applied to the power-on means And an input voltage detection unit for detecting the voltage of the AC power as the input voltage, to the initial information, the voltage value of the high frequency power abnormality in the fixing belt is obtained in advance on the assumption that generated The threshold value of the fluctuation range includes at least a first boundary value at a stage for notifying the occurrence of abnormality by the input / output means and a second boundary value at a stage for stopping heating by the heating means, and the storage means The initial information includes a plurality of sets of combinations of the input voltage, the predetermined frequency of the high-frequency power, the temperature of the fixing belt, the second voltage value, the first boundary value, and the second boundary value. is stored, the fixing belt results in eddy currents by electromagnetic induction generated by the high frequency electric power applied to the heating means includes a conductive layer capable of heat generation by the eddy currents, before If the control unit, which determines the state of the fixing belt on the basis of the second voltage value sequentially measured and the initial information by said voltage detecting means determines that abnormal to the fixing belt has occurred Notifies the occurrence of abnormality by the input / output means, or controls the power input means to cut off the high frequency power supplied to the heating means, and the second voltage value exceeds the first boundary value. When the second voltage value exceeds the second boundary value, the input / output means informs the occurrence of abnormality, and controls the power input means to supply the high frequency power to be input to the heating means. Cut off, select one set from the plurality of sets based on the input voltage, the predetermined frequency of the high-frequency power, the temperature of the fixing belt, and the driving voltage, the first boundary value, and the second Determine the boundary value of To do .
In addition, when a defect occurs, the control unit may record a defect history in association with the selected set.

  According to the present invention, when a part of the IH fixing belt or the like is damaged in the fixing unit, even if recording paper or the like remains in the fixing unit, an accident caused by overheating of the recording paper or the like is suppressed. There is an effect.

FIG. 2 is a block diagram relating to an image forming unit and a fixing unit according to the image forming apparatus of the present invention, their control, and a schematic diagram showing a relationship between them. It is a block diagram which shows the electrical structure in this Embodiment. It is a figure which shows an example of the information memorize | stored in the memory | storage part in this Embodiment. It is a flowchart which shows the flow of a process of the control part in this Embodiment. It is a block diagram concerning the modification of this embodiment. It is a figure which shows another example about the storage format of the information memorize | stored in the memory | storage part of this Embodiment.

  Next, embodiments of the present invention will be specifically described with reference to the drawings. The image forming apparatus of the present invention is a copying machine or the like using an electrophotographic (dry electrophotographic) system. In this embodiment, as shown in FIG. 1, an image formed on the surface of a recording sheet P as an example of a recording medium by a toner in an image forming unit 11 as an example of an image forming unit is used as a fixing unit as an example of a fixing unit. 10 is fixed.

  The image forming unit 11 creates a toner image on the photosensitive drum based on the image data, and transfers the image to the recording paper P, a transport roller for transporting the recording paper P, etc. (all of the present invention). 1 is not a characteristic part, and detailed description thereof is omitted). A toner image is formed on the recording surface of the recording paper P taken from the lower part of the image forming unit 11 in FIG. It is conveyed to the fixing unit 10.

The fixing unit 10 has a structure in which the cylindrical pressure roller 12 is pressed toward the fixing roller 14 at the nip portion N.
At least the outer edge side of the fixing roller 14 is made of an elastic material, and the fixing belt 16 and the recording paper P are sandwiched between the pressure roller 12 and pressed from the pressure roller 12 side. As a result, the fixing belt 16 and the recording paper P are in close contact with each other in the nip portion N.

  The fixing belt 16 is made of a material in which an eddy current is generated by electromagnetic induction, and an electric resistance component is generated by the eddy current, and is stretched endlessly through the roller 18 and the heat generating roller 20 in addition to the fixing roller 14, It rotates in the direction of the dashed line arrow. The roller 18 is a tensioner that adjusts the tension of the fixing belt 16.

  The recording paper P is sandwiched between the pressure roller 12 and the fixing roller 14 in a state where the recording surface on which toner is not fixed and the outer surface of the fixing belt 16 face each other, and is heated and pressed. For this reason, the toner as the color former is melted and fixed on the recording paper P (the recording surface thereof). At the same time, the recording paper P adheres to the fixing belt 16 by the melted toner. A separation plate 30 is provided in the vicinity of the nip portion N in order to peel off the stuck recording paper P and the fixing belt 16.

In general, in the image forming apparatus as shown in the present embodiment, an image is not formed at the end of the recording surface of the recording paper P in order to facilitate separation of the recording paper P and the fixing belt 16. A margin is provided.
Accordingly, the blank portion of the recording paper P does not stick to the fixing belt 16, so that it floats up from the fixing belt 16 and a gap is formed. One end portion of the separation plate 30 enters the gap between the recording paper P discharged from the nip portion N and the fixing belt 16, thereby peeling the adhered recording paper P and the fixing belt 16. The recording paper P peeled from the fixing belt 16 in this way is conveyed in the direction of the two-dot chain line arrow.

In the present embodiment, a thermistor 33 is provided in the vicinity of the fixing belt 16. The thermistor 33 may detect the temperature in contact with the fixing belt 16 or may detect the temperature from the immediate vicinity without contacting.
In the fixing unit 10 of the present embodiment, an IH coil unit 40 as an example of a heating unit is provided so as to substantially cover a portion where the fixing belt 16 is stretched around the heat roller 20. The IH coil unit 40 is supplied with high-frequency power of a predetermined frequency (in this embodiment, supplying high-frequency power to the IH coil unit 40 is referred to as input), and the adjacent fixing belt 16 is opposed to the adjacent portion. An eddy current is generated by electromagnetic induction, thereby causing the fixing belt 16 to generate heat.

  The image forming apparatus to which the present invention is applied has, for example, a control unit 50 as an example of a control unit and an operation unit 51 as an example of an input / output unit outside the fixing unit 10. In general, in order to input high frequency power of a predetermined frequency (for example, about 40 kHz) to the IH coil unit 40, an inverter 60 is provided as an example of power input means.

  The inverter 60 includes a switching element (described later) such as a CPU (Central Processing Unit) or an IGBT (Insulated Gate Bipolar Transistor) that outputs a high-frequency signal having a predetermined driving frequency described above. Electric power is supplied from an AC power supply 70 (commercial power supply of 100V to 240V). The power is supplied to the IH coil unit 40 with a predetermined drive frequency, a predetermined waveform, or a predetermined duty ratio by turning this power on / off by a switch element.

Next, the electrical configuration of the present embodiment will be described. FIG. 2 generally shows an electrical configuration around the fixing unit 10.
In FIG. 2, parts corresponding to those shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the inverter 60, an input circuit portion 72 is provided at a power input portion from the AC power supply 70. The input circuit unit 72 includes a fuse for overcurrent protection, a relay for turning on / off energization under the control of the control unit 50, a filter for blocking noise components, and the like. The electric power that has passed through the input circuit unit 72 is supplied to the pressure roller 12 via the switch element 74 and to the rectifier 62 a via the input voltage detection unit 61.

  The switch element 74 controls the power supplied to a heater (for example, a halogen heater) provided in the pressure roller 12 by the control unit 50. The pressure roller 12 and the fixing roller 14 are provided with thermistors, and these temperature information is input to the control unit 50.

  One input voltage detector 61 measures the voltage of the AC power supplied from the AC power supply 70 immediately before the rectifier 62a. The input voltage information measured here is input to the inverter CPU 63. A part of the power rectified by the rectifier 62 a is stepped down and stabilized by the DC power supply circuit 62 b and supplied as operating power for the inverter CPU 63.

  In addition to the input voltage information described above, a control signal is input from the control unit 50 to the inverter CPU 63. On the other hand, the inverter CPU 63 sends data such as an input voltage value based on the inputted input voltage to the control unit 50 and PWM (Pulse Width Modulation, pulse width modulation) which is a basis of high frequency power supplied to the IH coil unit 40. The signal is output to the driver 63d.

The PWM signal output from the inverter CPU 63 is input to the gates of the switch elements 64 and 64 (a base or the like depending on the form of the switch element) via the driver 63d. As a result, the switch elements 64, 64 generate high-frequency power from the power rectified by the rectifier 62a, and this high-frequency power is supplied to the IH coil unit 40 via the drive voltage detection unit 66 as an example of voltage detection means.
The drive voltage detector 66 includes, for example, a current transformer or a coupling capacitor and a voltage dividing resistor, measures the voltage across the resonance circuit 40 ′, and this measurement information is input to the controller 50.

The IH coil unit 40 of the present embodiment includes an IH coil 42 and a center core 44. The center core 44 is for appropriately transmitting the induction electromagnetic field to the fixing belt 16 and adjusting the inductance of the IH coil 42.
Further, a resonance capacitor 46 is connected in parallel with the IH coil unit 40 so that the resonance circuit 40 ′ is constituted by the IH coil 42. As an example, the resonance capacitor 46 is determined to have a capacitance such that the resonance frequency of the resonance circuit 40 ′ is equal to the driving frequency of the high frequency power supplied to the IH coil unit 40 together with the inductance of the IH coil 42.

The controller 50 receives the temperature measurement signal from the thermistor provided on the pressure roller 12 and the fixing roller 14 as described above, and controls the relay and the switch element 74 in the input circuit unit 72, so that the IH coil unit A control signal for controlling the high frequency power supplied to 40 is sent to the inverter CPU 63.
In addition, the control unit 50 includes a calculation unit 52 and a storage unit 54 as an example of a storage unit. The controller 50 receives temperature information from a thermistor 33 that measures the temperature of the fixing belt 16. Further, the control unit 50 exchanges data with the operation unit 51. Although not shown, the operation unit 51 includes a display device such as a keyboard and a liquid crystal display or a touch panel, a backlight attached thereto, a buzzer, a speaker, and the like.

The present invention detects the breakage of the fixing belt 16 based on the impedance change of the resonance circuit 40 ′. Various types of information that serve as the determination criteria are stored in the storage unit 54. FIG. 3 is a diagram (memory map) showing an example of area allocation of the storage unit 54 in the present embodiment.
The storage unit 54 generally includes an HDD (Hard Disk Drive), a flash memory (a type of electrically rewritable semiconductor storage device), a RAM (Random Access Memory), It is composed of a combination of ROM (Read Only Memory) and the like, and many of them are a volatile area that requires operating power to hold the memory, and a non-volatile area that holds the memory even when there is no power supply have.

The storage unit 54 of the present embodiment also has a volatile area and a nonvolatile area as an example, and sequentially stores measurement data, image data, and the like in the volatile area. The sequential measurement data is data input from the inverter CPU 63, the drive voltage detector 66, and the like as data for knowing the state of the fixing belt 16, such as the input voltage and the drive frequency.
The image data is data of an image formed on the recording paper P, and the pixel configuration and color configuration of an image input from outside the image forming apparatus are corrected or changed, or a plurality of identical pages are formed (replicated). Temporarily stored in case.

As an example, the non-volatile area stores a defect history necessary for maintenance of the image forming apparatus according to the present embodiment, as well as initial data and the like related to the characteristic part of the present invention.
This initial data is used as reference data for determining the state of the fixing belt 16 and detecting a defect, for example, a numerical value that may be indicated as an input voltage, a driving frequency, or a temperature of the fixing belt 16, and these numerical values. This is a threshold value that serves as a reference for determining the malfunction of the fixing belt 16 calculated. The initial data is stored at the time of assembly at the factory, at the time of adjustment for each user (for use environment and for regional use) at the time of shipment / delivery, or at the time of maintenance inspection or parts replacement.

Here, the threshold value stored in advance in the storage unit 54 will be described. As described above, in the present invention, the breakage of the fixing belt 16 is detected based on the impedance change of the resonance circuit 40 ′.
The IH coil 42 constituting the resonance circuit 40 ′ is coupled to the fixing belt 16 via the center core 44. For this reason, when the fixing belt 16 is extremely deformed, the area is changed due to breakage, or the fracture is broken, the impedance of the resonance circuit 40 ′ is changed. When the frequency (drive frequency) of the high frequency power supplied to the resonance circuit 40 ′ (IH coil unit 40) is constant, the drive voltage changes due to the change in impedance. Needless to say, the greater the change in impedance, the greater the change in drive voltage.

Therefore, as an example, at the time of assembly in a factory, the input voltage, the driving frequency, and the temperature of the fixing belt 16 are set to an initial state, and the value of the driving voltage at that time is measured.
The threshold 1 (increased as an example) is a value obtained by increasing or decreasing n1 percent, which is a change ratio assumed when the fixing belt 16 is slightly damaged, such as deformation or partial loss, with respect to the driving voltage in the initial state. The upper limit is the calculated value and the lower limit is the decreased value.
Further, a value obtained by increasing / decreasing n2 percent (n2> n1), which is a change ratio assumed when the fixing belt 16 is damaged before the possibility of causing overheating of the fixing belt 16 without transmitting heat during the fixing process, is obtained. Threshold value 2 (for example, an increased value is an upper limit and a decreased value is a lower limit).

Next, an example of a fixing belt abnormality detection method and an example of an operation when an abnormality is detected will be described with reference to FIG. The processing shown in FIG. 4 is performed in parallel (time division) with other image forming processing when high frequency power is supplied to the IH coil unit 40.
In the process of FIG. 4, first, various operations are received from the operation unit 51 as Step 1.

In Step 2, it is determined whether or not a predetermined time (as an example, 100 milliseconds) has elapsed since the previous process (determination of drive voltage). If not, the process returns to the beginning (Step 1) of FIG.
In Step 2, if a predetermined time has elapsed since the previous process, in Step 3, the drive voltage information is fetched from the drive voltage detector 66, and various information is fetched from the inverter CPU 63 and the thermistor 33.

  After fetching the drive voltage information, it is determined in Step 4 whether or not the drive voltage is within the threshold 1 range. That is, if the drive voltage captured in Step 3 is within the range of the threshold value 1, the impedance of the resonance circuit 40 'does not change greatly, and no abnormality has occurred in the fixing belt 16, so the processing of FIG. Return to the top (Step 1).

If the drive voltage deviates from the range of the threshold value 1 in Step 4, it means that the impedance of the resonance circuit 40 ′ may have changed, and some abnormality has occurred in the fixing belt 16. It can also be judged.
In this case, as Step 5, a message such as “Maintenance is required” is notified by the operation unit 51.

  After Step 5, it is determined in Step 6 whether or not the driving voltage is within the range of the threshold value 2. In other words, if the drive voltage is within the range of the threshold value 2, the impedance of the resonance circuit 40 ′ may have changed (for example, even when the characteristics have changed due to deterioration of the elements in the drive voltage detector 66, etc.). Since the driving voltage may change), the other processing accompanying the heating of the fixing belt 16 can be continued, so that the processing returns to the top (Step 1) of FIG.

If the driving voltage deviates from the range of the threshold value 2 in Step 6, it indicates that there is a possibility that the impedance of the resonance circuit 40 ′ has changed greatly, and the fixing belt 16 becomes overheated or other May affect the site.
In this case, as Step 7, the high frequency power supplied to the IH coil unit 40 is cut off, and the heating of the fixing belt 16 is stopped.

  In this way, according to the present invention, it is possible to appropriately detect an abnormality of the fixing belt without adding a complicated configuration, and to stop heating the fixing belt or to notify the occurrence of the abnormality when the abnormality occurs. It is possible to realize a control method for an image forming apparatus.

Note that the present invention is not limited to the above-described embodiments, and it is obvious that the embodiments can be appropriately changed within the scope of the technical idea of the present invention.
For example, the block diagram shown in FIG. 5 is a modification of the configuration shown in FIG. In the example shown in FIG. 5, a resonance circuit 40 ′ is formed by a resonance capacitor 46 connected in series with the IH coil 42. In this case, the drive voltage detector 66 is connected in parallel with the resonant capacitor 46 and measures the voltage across the resonant capacitor 46. Further, there may be a transformer 65 between the inverter 60 and the IH coil unit 40.
Even with such an electrical configuration, the method for detecting an abnormality occurring in the fixing belt 16 is the same as that described in the above-described embodiment.

  Further, the threshold value stored in advance in the storage unit 54 is not limited to the threshold value 1 and the threshold value 2. For example, by having more combinations (threshold value 1, threshold value 2, threshold value 3...), The state of the fixing belt 16 and other parts can be determined more precisely, or a plurality of notification contents can be determined depending on the state. It is possible to use different processing operations.

Further, for example, in the area allocation of the storage unit 54 in FIG. 3, only the threshold value 1, threshold value 2, threshold value 3... When the input voltage and drive frequency are one value are shown. If it changes, each threshold value also changes. Therefore, as shown in FIG. 6, a plurality of areas for storing combinations of initial data may be provided in the storage unit 54.
In this case, in Step 4 or Step 6 described with reference to FIG. 4, a combination of initial data 1, 2,..., N that most approximates the various information captured in Step 3 is selected, and among them, threshold 1, threshold 2, threshold 3,.・ Determine based on

  On the other hand, the threshold value to be stored is only threshold value 1 (the contents stored as threshold value 2 are stored in the threshold value 1 area in the above-described embodiment), thereby simplifying the process and the storage capacity (permitted) of the storage unit 54. (Capacity) can be reduced. In this case, Step 6 is not applicable (unnecessary) in the flowchart shown in FIG. 4, and even if Step 5 is omitted, the main object of the present invention can be achieved.

  Further, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiment, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention. In each figure, the same numerals are given to the same component.

DESCRIPTION OF SYMBOLS 10 Fixing unit 11 Image forming unit 12 Pressure roller 14 Fixing roller 16 Fixing belt 33 Thermistor 40 IH coil unit 40 'Resonance circuit 42 IH coil 46 Resonance capacitor 50 Control part 51 Operation part 52 Calculation part 54 Storage part 60 Inverter 61 Input Voltage detector 63 Inverter CPU
64 Switch element 66 Drive voltage detector P Recording paper

Claims (2)

Image forming means for forming a toner image on a recording medium;
Fixing means for fixing the unfixed toner formed on the recording medium by the image forming means by sandwiching and transporting the recording medium by an endless fixing belt heated by a heating means and a pressure roller;
Power input means for supplying high-frequency power of a predetermined frequency to the heating means;
Voltage detection means for detecting a voltage value of the high-frequency power;
Control means for controlling the power input means;
Input / output means for informing various information by the control means;
Storage means for storing in advance initial information including the first voltage value of the high-frequency power when the fixing belt is normal;
Temperature detecting means for detecting the temperature of the fixing belt;
An input voltage detection unit that detects, as an input voltage, a voltage of AC power supplied from an AC power source to generate the high-frequency power to be input to the power input unit;
With
The initial information includes, as a threshold value of the fluctuation range of the voltage value of the high-frequency power obtained in advance assuming that an abnormality has occurred in the fixing belt, at least a step of notifying the occurrence of the abnormality by the input / output means. A boundary value of 1 and a second boundary value of the step of stopping heating by the heating means,
The storage means includes a combination of the input voltage, the predetermined frequency of the high-frequency power, the temperature of the fixing belt, the second voltage value, the first boundary value, and the second boundary value as the initial information. Is stored in multiple sets,
The fixing belt has a conductor layer that generates eddy current by electromagnetic induction generated by high-frequency power input to the heating unit, and can generate heat by the eddy current,
The control means includes
Determines the state of the fixing belt on the basis of the second voltage value sequentially measured and the initial information by said voltage detecting means, said input and output when the abnormality in the fixing belt is determined to have occurred Announcing the occurrence of an abnormality by means, or controlling the power input means to cut off the high frequency power input to the heating means ,
When the second voltage value exceeds the first boundary value, the input / output means informs the occurrence of an abnormality, and when the second voltage value exceeds the second boundary value, the power Control the charging means to cut off the high frequency power to be input to the heating means,
One set is selected from the plurality of sets based on the input voltage, a predetermined frequency of the high-frequency power, a temperature of the fixing belt, and a driving voltage, and the first boundary value and the second boundary value are selected. Determining an image forming apparatus. The image forming apparatus according to claim 1 , wherein, when a defect occurs, the control unit records a defect history in association with the selected set .

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