JP2018146815A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately estimate remaining life time of a pressure roller regardless of the kind of a sheet to be used.SOLUTION: An image forming apparatus includes a fixing unit having a fixing roller and a pressure roller which applies pressure to the fixing roller, and fixing a toner image on a sheet by allowing the sheet to pass through a nip part formed by the fixing roller and the pressure roller. The image forming apparatus performs: measuring an outer diameter of the pressure roller (step S2); calculating the amount of change Δ1 in outer diameter of the pressure roller from the start of use (step S4); calculating a remaining value Δ2 left until an endurance limit (step S5); calculating a change ratio A from the days X elapsed from the start of using the pressure roller and the amount of change Δ1 (step S7); and calculating the days B left, from the change ratio A and the remaining value Δ2 (step S8).SELECTED DRAWING: Figure 5

Description

  The present invention relates to a fixing device and an image forming apparatus.

  In an electrophotographic image forming apparatus, a fixing device that fixes a toner image on a sheet by heating and pressurizing the sheet on which the toner image is transferred from an image carrier (photosensitive drum, intermediate transfer belt, etc.) is used. It has been. For example, the toner image is fixed on the paper by passing the paper through a nip formed by pressing the pressure roller against the heated fixing roller.

In general, the pressure roller is formed in an inverted crown shape in which the outer diameter of both end portions in the axial direction is larger than the outer diameter of the central portion. When the outer diameter of the pressure roller is reduced due to the use of the pressure roller, the reverse crown amount is reduced and paper wrinkles are likely to occur. For this reason, it is necessary to take measures such as grasping the usage state of the pressure roller and replacing it as necessary.
At present, the number of sheets that have been passed is counted, and the remaining life of the pressure roller is predicted based on the remaining number up to a predetermined number determined as a limit value.

  In addition, in a belt fixing type fixing device, a device that detects the position of a tension roller that applies tension to the belt member and determines that the life has reached when the tension roller bites into the belt member rather than a predetermined position is proposed. (See Patent Document 1). In this fixing device, the rate of change of the position of the tension roller with respect to the number of sheets passed is calculated, and the remaining life of the fixing device is calculated from this calculated value.

Japanese Patent No. 5504588

However, when the remaining life of the pressure roller is predicted based on the number of sheets passed, the predetermined number used as the limit value is based on the value when plain paper is passed. FIG. 9 shows changes in the outer diameter of the pressure roller with respect to the number of sheets that pass when plain paper, thick paper, and thin paper are used. When the pressure roller reaches the endurance limit, defects such as paper wrinkles are likely to occur. Since the damage to the pressure roller is different when plain paper, thick paper, and thin paper are passed, there is a problem that the remaining life is not predicted when heavy paper and thin paper are used frequently. For example, if heavy paper is used frequently, damage to the pressure roller is great, and the life may be reached earlier than a predetermined number. Conversely, if a lot of thin paper is used, damage to the pressure roller is relatively small and may be used longer than a predetermined number.
Thus, it has been difficult to accurately predict the remaining life of the pressure roller when using a mixture of thick paper and thin paper.

  The technique described in Patent Document 1 relates to a belt fixing type fixing device, and can be applied only when the distance between the fixing member and the pressure member is fixed.

  The present invention has been made in view of the above-described problems in the prior art, and an object thereof is to accurately predict the remaining life of the pressure roller regardless of the type of paper used.

  In order to solve the above problems, the invention described in claim 1 includes a fixing roller and a pressure roller pressed against the fixing roller, and is formed by the fixing roller and the pressure roller. A fixing device for fixing a toner image on a sheet by passing the sheet through a nip portion, measuring means for measuring a value related to a decrease amount of the outer diameter of the pressure roller, and a predetermined value related to the decrease amount Calculation means for calculating the amount of change from time, and prediction means for predicting the remaining life of the pressure roller based on the calculated amount of change.

  According to a second aspect of the present invention, in the fixing device according to the first aspect, the prediction unit calculates a change rate based on the change amount and the number of days elapsed from the predetermined time. The remaining life of the pressure roller is predicted based on the change rate and the endurance limit value relating to the reduction amount.

  According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the value relating to the reduction amount is an outer diameter of the pressure roller.

  According to a fourth aspect of the present invention, in the fixing device according to the first or second aspect, the value relating to the reduction amount is an inter-axis distance between the fixing roller and the pressure roller.

  According to a fifth aspect of the present invention, in the fixing device according to the first or second aspect, the value relating to the amount of reduction is a distance from a predetermined position of the pressure roller.

  According to a sixth aspect of the present invention, in the fixing device according to any one of the first to fifth aspects, the predetermined time is a start of use of the pressure roller.

  According to a seventh aspect of the present invention, in the fixing device according to any one of the first to fifth aspects, the predetermined time is a timing at which a predetermined number of sheets are passed from the start of use of the pressure roller. It is.

  According to an eighth aspect of the present invention, in the fixing device according to any one of the first to seventh aspects, the measurement unit sets a value related to the reduction amount when the temperature of the pressure roller is stable. When the temperature of the pressure roller is not stable, the value related to the reduction amount is not measured.

  According to a ninth aspect of the present invention, in the fixing device according to the eighth aspect, the temperature of the pressure roller is stable when the power is turned on.

  A tenth aspect of the present invention is the fixing device according to the eighth aspect, further comprising a heating unit that heats the fixing roller, and when the temperature of the pressure roller is stable, the warming up by the heating unit is performed. Is when it ends.

  According to an eleventh aspect of the present invention, in the fixing device according to any one of the eighth to tenth aspects, when the temperature of the pressure roller is not stable, it includes a time when paper feeding starts.

  According to a twelfth aspect of the present invention, in the fixing device according to any one of the eighth to eleventh aspects, when the temperature of the pressure roller is not stable, the type or basis weight of the paper to be used. Including when it was changed.

  A thirteenth aspect of the present invention is an image forming apparatus including the fixing device according to any one of the first to twelfth aspects.

  According to the present invention, the remaining life of the pressure roller can be accurately predicted regardless of the type of paper used.

1 is a schematic cross-sectional view showing an overall configuration of an image forming apparatus according to a first embodiment of the present invention. 2 is a block diagram illustrating a functional configuration of the image forming apparatus. FIG. It is a figure for demonstrating the measuring method of the outer diameter of a pressure roller. It is a figure which shows the example of a fixing temperature control table. It is a flowchart which shows a 1st pressurization roller remaining life prediction process. It is a flowchart which shows the 2nd pressurization roller remaining life prediction process in 2nd Embodiment. FIG. 10 is a diagram for explaining an inter-axis distance between a fixing roller and a pressure roller to be measured in Modification 1. It is a figure for demonstrating the distance from the predetermined position of the pressure roller used as a measuring object in the modification 2. FIG. It is a figure which shows the outer-diameter change of a pressure roller with respect to the number of paper passing when a plain paper, a thick paper, and a thin paper are used.

  Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings. The present invention is not limited to the illustrated example.

[First Embodiment]
FIG. 1 is a schematic cross-sectional view showing the overall configuration of the image forming apparatus 100 according to the first embodiment of the present invention.
The image forming apparatus 100 is a tandem type image forming apparatus that forms a color image by electrophotography based on image data obtained by reading an image from a document or image data received from an external device.

  As shown in FIG. 1, the image forming apparatus 100 includes an operation unit 10, a display unit 20, a scanner 30, an image forming unit 40, a fixing unit 50, a transport unit 60, and the like.

  The operation unit 10 includes a touch panel formed so as to cover the display screen of the display unit 20 and various operation buttons such as numeric buttons and a start button, and an operation signal based on a user operation is transmitted to the control unit 70 (see FIG. 2). ). The operation unit 10 receives an operation instruction from a user.

  The display unit 20 is configured by an LCD (Liquid Crystal Display) or the like, and displays various screens in accordance with instructions of display signals input from the control unit 70.

  The scanner 30 optically scans a document conveyed on the contact glass from an ADF (Auto Document Feeder) or a document placed on the contact glass, and light scanned from the light source to the document. The reflected light is imaged on a light receiving surface of a CCD (Charge Coupled Device) sensor, a document image is read, the read image is A / D converted, and the obtained image data is output to the control unit 70.

  The image forming unit 40 includes photosensitive drums 41Y, 41M, 41C, and 41K corresponding to colors of yellow (Y), magenta (M), cyan (C), and black (K), and charging units 42Y, 42M, 42C, and 42K. , Exposure units 43Y, 43M, 43C, and 43K, developing units 44Y, 44M, 44C, and 44K, primary transfer rollers 45Y, 45M, 45C, and 45K, an intermediate transfer belt 46, and a secondary transfer roller 47.

The charging units 42Y, 42M, 42C, and 42K uniformly charge the photosensitive drums 41Y, 41M, 41C, and 41K.
The exposure units 43Y, 43M, 43C, and 43K include a laser light source, a polygon mirror, a lens, and the like, and scan and expose the surface of the photosensitive drums 41Y, 41M, 41C, and 41K with a laser beam based on the image data of each color. An electrostatic latent image is formed.
The developing units 44Y, 44M, 44C, and 44K perform development by attaching toner of each color to the electrostatic latent images on the photosensitive drums 41Y, 41M, 41C, and 41K.

The primary transfer rollers 45Y, 45M, 45C, and 45K sequentially transfer the respective color toner images formed on the photosensitive drums 41Y, 41M, 41C, and 41K onto the intermediate transfer belt 46 (primary transfer). That is, on the intermediate transfer belt 46, a color toner image is formed by superimposing four color toner images.
The secondary transfer roller 47 collectively transfers the color toner image on the intermediate transfer belt 46 onto one side of the paper supplied from the paper feed tray (secondary transfer).

  The fixing unit 50 includes a fixing roller 51, a pressure roller 52, and the like. By passing the sheet through a nip formed by the fixing roller 51 and the pressure roller 52, the toner image is formed on the sheet by heating and pressing. To fix.

  The fixing roller 51 is configured such that a surface of a cylindrical metal core is covered with a rubber layer, and a surface layer made of a PFA tube is further formed on the surface. The fixing roller 51 includes a halogen heater 53 inside the cored bar, and generates heat when energized under the control of the control unit 70. The halogen heater 53 is a heating unit that heats the fixing roller 51. The position of the shaft of the fixing roller 51 is fixed.

  The pressure roller 52 is configured by coating a rubber layer on the surface of a cylindrical cored bar and further forming a surface layer made of a PFA tube on the surface. The pressure roller 52 is pressed against the fixing roller 51 with a predetermined load by a spring. The pressure roller 52 may be heated by an external heating roller that is in contact with the pressure roller 52.

  The transport unit 60 includes a transport roller for transporting the paper, and the image formation is performed from the time when the paper stored in the paper feed tray is supplied to the image forming unit 40 until the paper after fixing is discharged out of the apparatus. A sheet is conveyed in the apparatus 100. The paper feed tray stores paper of a paper type and size predetermined for each paper feed tray.

FIG. 2 is a block diagram illustrating a functional configuration of the image forming apparatus 100.
As shown in FIG. 2, the image forming apparatus 100 includes an operation unit 10, a display unit 20, a scanner 30, an image forming unit 40, a fixing unit 50, a transport unit 60, a control unit 70, a communication unit 71, a storage unit 72, and a time count. The unit 73 is provided. Note that description of the functional units already described is omitted.

The fixing unit 50 includes a heater driving unit 54 and an outer diameter measuring unit 55.
The heater driving unit 54 energizes the halogen heater 53 to heat the fixing roller 51.

  The outer diameter measuring unit 55 is a measuring unit that measures a value related to a reduction amount of the outer diameter of the pressure roller 52. The value related to the amount of decrease in the outer diameter of the pressure roller 52 is a value that changes according to the decrease in the outer diameter of the pressure roller 52. Here, the outer diameter measuring unit 55 measures the outer diameter of the pressure roller 52.

As shown in FIG. 3, displacement sensors 55 </ b> A and 55 </ b> B provided on both sides of the shaft 52 </ b> A of the pressure roller 52 are used as the outer diameter measuring unit 55. The displacement sensors 55A and 55B detect the distance to the pressure roller 52. From the distance L1 to the pressure roller 52 obtained by the displacement sensor 55A, the distance L2 to the pressure roller 52 obtained by the displacement sensor 55B, and the distance L3 between the displacement sensor 55A and the displacement sensor 55B, the following formula ( 1), the outer diameter L4 of the pressure roller 52 can be calculated. The value of L3 is stored in the storage unit 72 in advance. There are no particular restrictions on the displacement sensor used.
L4 = L3- (L1 + L2) (1)

  In order to accurately measure the outer diameter of the pressure roller 52, it is preferable that the outer diameter measuring portions 55 are provided at both ends in the axial direction of the pressure roller 52, but either one may be provided.

  The control unit 70 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The CPU reads various processing programs stored in the ROM, expands them in the RAM, and centrally controls the operations of the respective units of the image forming apparatus 100 according to the expanded programs.

  The communication unit 71 transmits and receives data to and from an external device connected to a communication network such as a LAN (Local Area Network).

The storage unit 72 is configured by a nonvolatile storage device such as a hard disk or a flash memory, and stores various data. For example, the storage unit 72 stores a fixing temperature control table T1.
FIG. 4 shows an example of the fixing temperature control table T1. The fixing temperature control table T1 stores fixing temperatures corresponding to combinations of paper types (plain paper, high-quality paper, etc.) and basis weight. The fixing temperature is a temperature necessary for melting the toner when the sheet passes through the nip portion in the fixing unit 50.

  The timer unit 73 has a timer circuit (RTC: Real Time Clock). The timer circuit measures the current date and time and outputs it to the controller 70.

  The controller 70 causes the outer diameter measuring unit 55 to measure the outer diameter of the pressure roller 52 when the temperature of the pressure roller 52 is stable, and the outer diameter when the temperature of the pressure roller 52 is not stable. The measurement unit 55 is not allowed to measure the outer diameter of the pressure roller 52.

  This is because the pressure roller 52 has a relatively thick rubber layer (for example, the outer diameter of the pressure roller 52 is 70 mm, the thickness of the rubber layer is 6.5 mm, etc.), and the rubber layer is Because the volume changes, the outer diameter of the pressure roller 52 is likely to fluctuate according to the temperature change.

  In the first embodiment, the time when the power (not shown) of the image forming apparatus 100 is turned on is used as the time when the temperature of the pressure roller 52 is stable. When the image forming apparatus 100 is left for a long time with the power off, the image forming apparatus 100 is substantially at room temperature. Therefore, when the power is turned on, the temperature of the pressure roller 52 is stable at about room temperature.

In addition, the time when the temperature of the pressure roller 52 is not stable includes the time when the paper is started and when the paper type or basis weight of the paper used is changed.
At the start of sheet passing, the temperature of the pressure roller 52 varies as the sheet passes through the nip formed by the fixing roller 51 and the pressure roller 52.
When the paper type or basis weight of the paper is changed, the fixing temperature is changed according to the paper type and the basis weight (see FIG. 4), so the temperature of the pressure roller 52 varies. Specifically, when the paper type or basis weight of the paper is changed by an operation from the operation unit 10 or a paper setting included in a print instruction received via the communication unit 71, the control unit 70 fixes the sheet. With reference to the temperature control table T 1, the heater driving unit 54 is controlled so that the fixing temperature corresponds to the paper type and the basis weight, and the heating of the fixing roller 51 by the halogen heater 53 is adjusted. Along with this, the temperature of the pressure roller 52 varies.

The control unit 70 calculates the amount of change from the predetermined time of the outer diameter of the pressure roller 52 measured by the outer diameter measuring unit 55 (a value related to the amount of decrease in the outer diameter of the pressure roller 52). That is, the control unit 70 functions as a calculation unit.
The predetermined time is set as the start of use of the pressure roller 52.

The controller 70 predicts the remaining life of the pressure roller 52 based on the calculated amount of change. That is, the control unit 70 functions as a prediction unit.
Specifically, the control unit 70 calculates the change rate based on the amount of change from the predetermined time and the number of days elapsed from the predetermined time, and calculates the change rate and the outer diameter (additional pressure) of the pressure roller 52. The remaining life of the pressure roller 52 is predicted based on the durability limit value of the value related to the decrease in the outer diameter of the pressure roller 52. The durability limit value is a value at the durability limit (usable limit) of the pressure roller 52.

  The control unit 70 and the fixing unit 50 constitute a fixing device according to the present invention.

Next, the operation in the first embodiment will be described.
FIG. 5 is a flowchart showing the first pressure roller remaining life prediction process executed by the image forming apparatus 100. This process is realized by software processing in cooperation with the CPU of the control unit 70 and the program stored in the ROM.

  First, in the image forming apparatus 100, when the power is turned on from the OFF state (step S1), the control unit 70 causes the outer diameter measuring unit 55 to measure the outer diameter of the pressure roller 52 (step S2). The control unit 70 acquires a measurement value from the outer diameter measurement unit 55.

  Next, the control unit 70 controls the heater driving unit 54 to energize the halogen heater 53 and starts warming up the fixing unit 50 (step S3).

Next, the control unit 70 calculates the amount of change Δ1 from the start of use of the pressure roller 52 based on the measurement value (outer diameter of the pressure roller 52) acquired from the outer diameter measurement unit 55 and the initial value. (Step S4). The initial value is the outer diameter of the pressure roller 52 at the start of use, and is stored in the storage unit 72 in advance.
Amount of change Δ1 = initial value−measured value (2)

Next, the control unit 70 calculates the remaining value Δ2 up to the endurance limit based on the measurement value and the endurance limit value acquired from the outer diameter measurement unit 55 (step S5). The durability limit value is the outer diameter of the pressure roller 52 at the durability limit, and is stored in the storage unit 72 in advance.
Remaining value Δ2 = Measured value−Endurance limit value (3)

Next, the control unit 70 determines whether or not the remaining value Δ2 is 0 or less (step S6).
When the remaining value Δ2 is larger than 0 (step S6; NO), that is, when the pressure roller 52 has not reached the endurance limit (life), the control unit 70 starts from the start of use of the pressure roller 52. A change rate A is calculated from the elapsed days X and the change amount Δ1 (step S7). When the pressure roller 52 starts to be used, it is stored in the storage unit 72. The control unit 70 calculates the number of elapsed days X based on the use start time and the current date and time acquired from the time measuring unit 73.
Change ratio A = Δ1 / X (4)

Next, the control unit 70 calculates the remaining number of days B from the change rate A and the remaining value Δ2 (step S8). The remaining days B is a predicted value of the remaining life indicating how many days the pressure roller 52 will reach the endurance limit.
Remaining days B = Δ2 / A (5)

Next, the control part 70 displays the remaining days B on the display part 20 (step S9).
For example, it is assumed that the initial value of the outer diameter of the pressure roller 52 is 70 mm and the durability limit value is 69.5 mm. When the measured value of the outer diameter of the pressure roller 52 on a certain day is 69.8 mm, the change Δ1 is 0.2 mm and the remaining value Δ2 is 0.3 mm. When the period from the start of use to this day is 100 days, the rate of change A is 0.002 (mm / day) because it is 0.2 mm smaller in 100 days. Assuming that the outer diameter of the pressure roller 52 changes at this rate, the remaining number of days B is 150 days.

  Thereafter, when the warm-up of the fixing unit 50 by the halogen heater 53 is completed (step S10), the control unit 70 shifts the image forming apparatus 100 to a normal operation (step S11). For example, a temperature sensor is provided in the vicinity of the fixing roller 51, and the control unit 70 determines that the warm-up is completed when the output value of the temperature sensor reaches a set temperature (180 ° C. or the like).

  In step S6, when the remaining value Δ2 is 0 or less (step S6; YES), that is, when the pressure roller 52 has reached the endurance limit, the control unit 70 indicates that “the endurance limit has been reached. Please contact the service "message is displayed on the display unit 20 (step S12), and the machine is stopped.

  The user contacts the service call center of the image forming apparatus 100 and requests replacement of the pressure roller 52. Alternatively, a service call center or the like may be automatically notified via the communication unit 71 that the pressure roller 52 has reached the durability limit.

  As described above, according to the first embodiment, the outer diameter of the pressure roller 52 is actually measured as the value related to the amount of decrease in the outer diameter of the pressure roller 52, and the remaining days B are calculated. The remaining life of the pressure roller 52 can be accurately predicted regardless of the type of paper used (paper type / basis weight).

  Specifically, the change rate A is calculated based on the change amount Δ1 from the start of use in the outer diameter of the pressure roller 52 and the elapsed days X from the start of use, and the calculated change rate A and durability are calculated. Since the remaining number of days B of the pressure roller 52 is calculated based on the limit value, the remaining life of the pressure roller 52 can be predicted from the tendency of the decrease in the outer diameter of the pressure roller 52 so far. .

  Thereby, when the endurance limit (life) is near, downtime can be reduced by exchanging the pressure roller 52 in advance. On the other hand, if there is a certain margin to the endurance limit and the pressure roller 52 can be used without any problem, unnecessary replacement can be reduced.

  In addition, when the temperature of the pressure roller 52 is stable, the outer diameter of the pressure roller 52 is measured when the power of the image forming apparatus 100 is turned on. Can be excluded. Further, when the power is turned on, it is determined whether or not the pressure roller 52 has reached the endurance limit. Therefore, when the pressure roller 52 needs to be replaced, the end of the warm-up of the fixing unit 50 is waited. Therefore, it is possible to avoid unnecessary preparation for image formation.

[Second Embodiment]
Next, a second embodiment to which the present invention is applied will be described.
Since the image forming apparatus according to the second embodiment has the same configuration as that of the image forming apparatus 100 according to the first embodiment, FIG. 1 and FIG. 2 are used, and the configuration is illustrated and described. Omitted. Hereinafter, a configuration and processing characteristic of the second embodiment will be described.

  In the second embodiment, when the temperature of the pressure roller 52, which is the timing for measuring the value related to the decrease in the outer diameter of the pressure roller 52, is stable, the warming up of the fixing unit 50 by the halogen heater 53 is performed. The point of using the end time is different from the first embodiment. When the warm-up of the fixing unit 50 is finished, the temperatures of the fixing roller 51 and the pressure roller 52 are stable at a predetermined set temperature.

Next, the operation in the second embodiment will be described.
FIG. 6 is a flowchart illustrating a second pressure roller remaining life prediction process executed by the image forming apparatus according to the second embodiment. This process is realized by software processing in cooperation with the CPU of the control unit 70 and the program stored in the ROM.

  First, in the image forming apparatus, when the power is turned on from the OFF state (step S21), the control unit 70 controls the heater driving unit 54 to energize the halogen heater 53 of the fixing roller 51, thereby fixing the fixing unit. 50 warm-up is started (step S22).

  Thereafter, after the warm-up of the fixing unit 50 by the halogen heater 53 is finished (step S23), the control unit 70 causes the outer diameter measuring unit 55 to measure the outer diameter of the pressure roller 52 (step S24).

About the process of step S25-step S30 and step S32, since it is the same as that of the process of step S4-step S9 and step S12 of a 1st pressurization roller remaining life prediction process (refer FIG. 5), description is abbreviate | omitted.
However, as the initial value used in step S25, the outer diameter of the pressure roller 52 at the start of use, measured after the warm-up of the fixing unit 50 is used.
Further, as the durability limit value used in step S26, a value corresponding to the end of the warm-up of the fixing unit 50 is used.

  After step S30, the control unit 70 shifts the image forming apparatus to a normal operation (step S31).

  As described above, according to the second embodiment, the outer diameter of the pressure roller 52 is actually measured as the value related to the amount of decrease in the outer diameter of the pressure roller 52, and the remaining days B are calculated. Regardless of the type of paper used, the remaining life of the pressure roller 52 can be accurately predicted.

  In addition, when the temperature of the pressure roller 52 is stable, the outer diameter of the pressure roller 52 is measured at the end of the warm-up of the fixing unit 50, so the influence of expansion / contraction due to temperature change is excluded. Can do.

[Modification 1]
In 1st Embodiment and 2nd Embodiment, although the outer diameter measurement part 55 demonstrated the case where the outer diameter of the pressure roller 52 was measured, in the modification 1, the outer diameter of the pressure roller 52 is demonstrated. A case where the interaxial distance between the fixing roller 51 and the pressure roller 52 is used as a value related to the decrease amount of the toner will be described.

  In comparison with the image forming apparatus 100 according to the first embodiment, the image forming apparatus according to the first modification replaces the outer diameter measuring unit 55 with an inter-axis distance measuring unit 56 (FIGS. 7A and 7B). See). Other parts are the same as those of the image forming apparatus 100 in the first embodiment.

  FIG. 7A is a schematic diagram showing a schematic cross section of the fixing roller 51 and the pressure roller 52. Since the position of the shaft 51A of the fixing roller 51 is fixed and the pressure roller 52 is pressed against the fixing roller 51, the shaft 52A of the pressure roller 52 decreases as the outer diameter of the pressure roller 52 decreases. Is approaching the fixing roller 51 side. That is, as the outer diameter of the pressure roller 52 becomes smaller, the inter-axis distance L11 between the shaft 51A of the fixing roller 51 and the shaft 52A of the pressure roller 52 becomes smaller.

The inter-axis distance measuring unit 56 is provided at the position of the shaft 51A of the fixing roller 51 and measures the distance of the pressure roller 52 to the shaft 52A. The inter-axis distance measuring unit 56 is composed of a displacement sensor.
In order to measure the interaxial distance between the fixing roller 51 and the pressure roller 52 with high accuracy, it is preferable that the interaxial distance measurement unit 56 is provided at both ends in the axial direction of the pressure roller 52. Either one is fine.

  FIG. 7B shows a schematic cross section of the fixing roller 51 and the pressure roller 52 after being used to some extent from the state shown in FIG. The inter-axis distance L12 between the fixing roller 51 and the pressure roller 52 in FIG. 7B is smaller than the inter-axis distance L11 between the fixing roller 51 and the pressure roller 52 in FIG.

When using the interaxial distance between the fixing roller 51 and the pressure roller 52 as a value related to the amount of decrease in the outer diameter of the pressure roller 52, the measured value by the interaxial distance measurement unit 56 becomes larger as the pressure roller 52 is used. It gets smaller.
In Modification 1, instead of step S2 of the first pressure roller remaining life prediction process (see FIG. 5), the interaxial distance between the fixing roller 51 and the pressure roller 52 is measured, and the initial value used in step S4 The distance between the axes of the fixing roller 51 and the pressure roller 52 at the start of use is used, and the distance between the axes of the fixing roller 51 and the pressure roller 52 at the durability limit is used as the durability limit value used in step S5. Thus, the remaining number of days B can be calculated as in the first embodiment.

  According to the first modification, the distance between the fixing roller 51 and the pressure roller 52 is actually measured as the value related to the reduction amount of the outer diameter of the pressure roller 52, and the remaining days B are calculated. Regardless of the type of paper, the remaining life of the pressure roller 52 can be accurately predicted.

  In the first modification, as in the second pressure roller remaining life prediction process (see FIG. 6), the interaxial distance between the fixing roller 51 and the pressure roller 52 is determined at the end of the warm-up of the fixing unit 50. It is also possible to measure and calculate the remaining days B.

[Modification 2]
In 1st Embodiment and 2nd Embodiment, although the outer diameter measurement part 55 demonstrated the case where the outer diameter of the pressure roller 52 was measured, in the modification 2, the outer diameter of the pressure roller 52 is demonstrated. The case where the distance from the predetermined position of the pressure roller 52 is used as a value related to the decrease amount of the pressure roller 52 will be described.

  In the image forming apparatus in the second modification, a distance measuring unit 57 (see FIGS. 8A and 8B) is used instead of the outer diameter measuring unit 55 in comparison with the image forming apparatus 100 in the first embodiment. Is provided. Other parts are the same as those of the image forming apparatus 100 in the first embodiment.

  FIG. 8A is a schematic diagram showing a schematic cross section of the fixing roller 51 and the pressure roller 52. Here, the reference position 58 is set at a fixed position below the pressure roller 52 (on the side opposite to the fixing roller 51). Since the position of the shaft 51A of the fixing roller 51 is fixed and the pressure roller 52 is pressed against the fixing roller 51, the shaft 52A of the pressure roller 52 decreases as the outer diameter of the pressure roller 52 decreases. This position moves away from the reference position 58. That is, as the outer diameter of the pressure roller 52 decreases, the distance L21 from the reference position 58 to the shaft 52A of the pressure roller 52 increases.

The distance measuring unit 57 is provided at the reference position 58 and measures the distance to the shaft 52A of the pressure roller 52. The distance measuring unit 57 is composed of a displacement sensor.
In order to accurately measure the distance from the reference position 58 to the shaft 52A of the pressure roller 52, the distance measuring unit 57 is preferably provided at both ends in the axial direction of the pressure roller 52. Either one is acceptable.

  FIG. 8B shows a schematic cross section of the fixing roller 51 and the pressure roller 52 after being used to some extent from the state shown in FIG. The distance L22 from the reference position 58 to the shaft 52A of the pressure roller 52 in FIG. 8B is larger than the distance L21 from the reference position 58 to the shaft 52A of the pressure roller 52 in FIG.

When the reference position 58 is positioned below the pressure roller 52 and the distance from the reference position 58 to the shaft 52A of the pressure roller 52 is used as a value related to the amount of decrease in the outer diameter of the pressure roller 52, the pressure roller 52 is used. As a result, the measured value by the distance measuring unit 57 increases.
In Modification 2, instead of step S2 of the first pressure roller remaining life prediction process (see FIG. 5), the distance from the reference position 58 to the shaft 52A of the pressure roller 52 is measured.

Further, the change amount Δ1 in step S4 is obtained by the following equation (6).
Change amount Δ1 = measured value−initial value (6)
In the above formula (6), the initial value is the distance from the reference position 58 to the shaft 52A of the pressure roller 52 at the start of use, and is stored in the storage unit 72 in advance.

The remaining value Δ2 in step S5 is obtained by the following equation (7).
Remaining value Δ2 = endurance limit value−measured value (7)
In the above formula (7), the endurance limit value is the distance from the reference position 58 at the endurance limit to the shaft 52A of the pressure roller 52, and is stored in the storage unit 72 in advance.
The change ratio A and the remaining days B can be obtained by the above formulas (4) and (5).

  According to the second modification, the distance from the reference position 58 to the shaft 52A of the pressure roller 52 is measured as the value related to the decrease amount of the outer diameter of the pressure roller 52, and the remaining days B are calculated. The remaining life of the pressure roller 52 can be accurately predicted regardless of the type of paper to be printed.

  In the second modification as well, the distance from the reference position 58 to the shaft 52A of the pressure roller 52 at the end of the warm-up of the fixing unit 50, as in the second pressure roller remaining life prediction process (see FIG. 6). And the remaining number of days B may be calculated.

  When the reference position 58 is located above the pressure roller 52 (on the same side as the fixing roller 51), as the pressure roller 52 is used, the measured value (from the reference position 58 to the shaft 52A of the pressure roller 52). Therefore, the change amount Δ1 and the remaining value Δ2 can be obtained from the above equations (2) and (3).

[Modification 3]
In the first embodiment and the second embodiment, when the pressure roller 52 starts to be used as a reference time when calculating the amount of change in the value related to the amount of decrease in the outer diameter of the pressure roller 52. In the third modification, the case where the timing at which a predetermined number of sheets are passed from the start of use of the pressure roller 52 will be described as the predetermined timing.

The image forming apparatus according to the third modification includes a counter that counts the number of sheets passing through the fixing unit 50 from the start of use of the pressure roller 52.
The controller 70 sets the counter to 0 when the pressure roller 52 is replaced, that is, when the pressure roller 52 starts to be used.

  Based on the value of the counter, the control unit 70 determines the timing at which a predetermined number of sheets have been passed from the start of use of the pressure roller 52. The predetermined number can be arbitrarily set and is stored in the storage unit 72 in advance. The control unit 70 causes the outer diameter measuring unit 55 to measure the outer diameter of the pressure roller 52 at a timing when a predetermined number of sheets are passed from the start of use of the pressure roller 52, and the acquired measured value is an initial value. Is stored in the storage unit 72.

  When calculating the change amount Δ1, this initial value is used, and as the elapsed days X, the elapsed days from the timing when a predetermined number of sheets are passed from the start of use of the pressure roller 52 are used. This is the same as the first pressure roller remaining life prediction process (see FIG. 5) or the second pressure roller remaining life prediction process (see FIG. 6).

  According to the third modification, the outer diameter of the pressure roller 52 is actually measured as the value related to the amount of decrease in the outer diameter of the pressure roller 52, and the remaining number of days B is calculated. Therefore, regardless of the type of paper used The remaining life of the pressure roller 52 can be accurately predicted.

  Specifically, with reference to the timing (predetermined timing) when a predetermined number of sheets are passed from the start of use of the pressure roller 52 as a reference (predetermined timing), the amount of change Δ1 from the predetermined timing in the outer diameter of the pressure roller 52 and the predetermined timing Since the change rate A is calculated based on the number of days elapsed from X and the remaining number of days B of the pressure roller 52 is calculated based on the calculated change rate A and the durability limit value. The remaining life of the pressure roller 52 can be predicted from the tendency of the decrease in the outer diameter of the pressure roller 52.

Note that the descriptions in the above-described embodiments and modifications are examples of the image forming apparatus according to the present invention, and the present invention is not limited thereto. The detailed configuration and detailed operation of each part constituting the apparatus can be changed as appropriate without departing from the spirit of the present invention.
For example, a characteristic configuration may be combined with each of the above embodiments and modifications.

  In the above description, an example in which a ROM is used as a computer-readable medium storing a program for executing each process is disclosed, but the present invention is not limited to this example. As other computer-readable media, a non-volatile memory such as a flash memory and a portable recording medium such as a CD-ROM can be applied. A carrier wave may be applied as a medium for providing program data via a communication line.

40 image forming unit 50 fixing unit 51 fixing roller 51A shaft 52 pressure roller 52A shaft 53 halogen heater 54 heater driving unit 55 outer diameter measuring unit 55A, 55B displacement sensor 56 inter-axis distance measuring unit 57 distance measuring unit 58 reference position 70 control Unit 72 storage unit 100 image forming apparatus

Claims (13)

A fixing roller and a pressure roller pressed against the fixing roller, and fixing the toner image on the paper by passing the paper through a nip formed by the fixing roller and the pressure roller. A fixing device,
Measuring means for measuring a value related to a reduction amount of the outer diameter of the pressure roller;
Calculation means for calculating a change amount from a predetermined time of the value relating to the reduction amount;
Prediction means for predicting the remaining life of the pressure roller based on the calculated change amount;
A fixing device.   The prediction means calculates a change rate based on the change amount and the number of days elapsed from the predetermined time, and based on the calculated change rate and an endurance limit value of the value related to the reduction amount, The fixing device according to claim 1, wherein the remaining life of the pressure roller is predicted.   The fixing device according to claim 1, wherein the value relating to the reduction amount is an outer diameter of the pressure roller.   The fixing device according to claim 1, wherein the value relating to the amount of decrease is an interaxial distance between the fixing roller and the pressure roller.   The fixing device according to claim 1, wherein the value relating to the amount of decrease is a distance from a predetermined position of the pressure roller.   The fixing device according to claim 1, wherein the predetermined time is a start of use of the pressure roller.   6. The fixing device according to claim 1, wherein the predetermined time is a timing at which a predetermined number of sheets are passed from the start of use of the pressure roller.   The measurement means measures a value related to the reduction amount when the temperature of the pressure roller is stable, and does not measure a value related to the reduction amount when the temperature of the pressure roller is not stable. The fixing device according to any one of 1 to 7.   The fixing device according to claim 8, wherein the temperature of the pressure roller is stable when the power is turned on. A heating means for heating the fixing roller;
The fixing device according to claim 8, wherein the temperature of the pressure roller is stable when the warm-up by the heating unit is finished.   11. The fixing device according to claim 8, wherein the time when the temperature of the pressure roller is not stable includes a time when paper feeding starts.   12. The fixing device according to claim 8, wherein the time when the temperature of the pressure roller is not stable includes a time when the paper type or basis weight of the paper to be used is changed.   An image forming apparatus comprising the fixing device according to claim 1.

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