JP2011017917A - Image forming apparatus and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus and a program thereof capable of detecting a warning sign for the failure of a fixing device.SOLUTION: The image forming apparatus measures the amount of current flowing to a direct current motor that rotatably drives a cylindrical body of the fixing device, and detects a magnitude of vibration of members disposed at the periphery of the fixing device; and the image forming apparatus evaluates the possibility of the fixing device failure, based on the difference between the magnitude of the amount of current and vibration measured or detected, when it is determined that there is no medium between the cylindrical bodies which are rotated by the direct current motor, and the magnitude of the amount of current and vibration measured or detected, when it is determined that there is a medium between the cylindrical bodies.

Description

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

  Japanese Patent Application Laid-Open No. 2004-133867 discloses a technique for detecting a current flowing in a motor that rotationally drives a pair of rollers by a current sensor and determining that the fixing device is to be replaced when the current is larger than a predetermined threshold.

JP 2001-005353 A

  There is a desire to detect a sign of a fixing unit failure.

  The invention according to claim 1 is an image forming apparatus, comprising a pair of cylindrical bodies, and fixing the image formed on the medium while sandwiching and feeding the medium between the pair of cylindrical bodies. A DC motor that rotationally drives the cylindrical body of the fixing device, a power supply unit that supplies power to the DC motor, current measuring means that measures the amount of current flowing from the power supply unit to the DC motor, Vibration detecting means for detecting the magnitude of vibration of a member disposed in the periphery, determination means for determining whether or not there is a medium between the cylindrical bodies, and the DC motor rotating the cylindrical body And when the determination means determines that there is no medium between the cylindrical bodies, the current amount and the magnitude of vibration measured or detected, and the determination means determine that there is a medium between the cylinders. When measured or detected Wherein the magnitude of the current amount and vibrations, based on the difference in, in which was to include an evaluation means for evaluating the possibility of failure of the fuser.

  The invention according to claim 2 is the image forming apparatus according to claim 1, further comprising means for acquiring information on the thickness of the medium, wherein the evaluation means rotates the cylindrical body by the DC motor. And when the determination means determines that there is no medium between the cylinders, the current amount and the magnitude of vibration measured or detected, and when there is a medium between the cylinders by the determination means The possibility of failure of the fixing device is evaluated on the basis of the difference between the amount of current and the magnitude of vibration measured or detected at the time of determination, and the acquired information on the thickness of the medium. is there.

  The invention described in claim 3 is a program, comprising a pair of cylindrical bodies, a fixing device that fixes an image formed on the medium while sandwiching and feeding the medium between the pair of cylindrical bodies, A DC motor that rotationally drives the cylindrical body of the fixing device, a power supply unit that supplies power to the DC motor, current measuring means that measures the amount of current flowing from the power supply unit to the DC motor, and a periphery of the fixing device A computer for controlling the image forming apparatus, comprising: a vibration detecting means for detecting the magnitude of vibration of the arranged member; and a judging means for judging whether or not there is a medium between the cylindrical bodies. Is rotating the cylindrical body, and the current amount and the magnitude of vibration measured or detected when it is determined by the determining means that there is no medium between the cylindrical bodies, and the cylindrical body by the determining means Between The size of the measured or detected the amount of current and the vibration when it is determined that there is a body, on the basis of the difference of one in which it was decided to function as a means for evaluating the possibility of failure of the fuser.

  According to the first and third aspects of the present invention, it is possible to evaluate the possibility of failure of the fixing device from both the increase of the driving force of the roller included in the fixing device and the generation of vibration due to the driving force increase and the shaft shake of the roller.

  According to the invention described in claim 2, it is possible to evaluate the possibility of failure of the fixing device in consideration of the thickness of the paper.

1 is a block diagram illustrating a configuration example of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a configuration example of a fixing unit of the image forming apparatus according to the embodiment of the present invention. 2 is a schematic diagram illustrating a configuration example of a fixing unit failure possibility evaluation unit and an example of its connection in the image forming apparatus according to the embodiment of the present invention. FIG. FIG. 6 is a flowchart illustrating an operation example of the image forming apparatus according to the embodiment of the present invention. FIG. 10 is an explanatory diagram illustrating an example of a change in the amount of current and the magnitude of vibration detected in the image forming apparatus according to the embodiment of the present invention. It is explanatory drawing showing the example of the evaluation information calculated in the image forming apparatus which concerns on embodiment of this invention. FIG. 5 is an explanatory diagram illustrating an example of reference information held in the image forming apparatus according to the embodiment of the present invention. It is explanatory drawing showing another example of the evaluation information calculated in the image forming apparatus which concerns on embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings. As illustrated in FIG. 1, the image forming apparatus 1 according to the present embodiment has a medium supply unit 10, a developing unit 20, a fixing unit 30, a controller unit 40, a fixing unit failure possibility evaluation unit 50, And a power supply unit 60.

  The medium supply unit 10 is, for example, a paper tray or the like, holds paper as a medium for receiving image formation, and sends the held paper one by one to the developing unit 20 according to an instruction input from the controller unit 40. . In the image forming apparatus 1 of the present embodiment, a roller or the like as a medium transport mechanism is arranged along a path along which the medium is transported.

  The developing unit 20 includes a drum, which is an image carrier that carries an image, a latent image forming unit that forms a latent image on the drum, and a developer that attaches toner according to the latent image. The developing unit 20 forms a latent image on the drum in accordance with an instruction input from the controller unit 40, and attaches toner or the like to the latent image. Further, the developing unit 20 presses the drum against the conveyed medium to transfer and form an image on the medium.

  As illustrated in FIG. 2, the fixing unit 30 includes a medium detection unit 31, a DC motor 32, and a heating roller 33 and a pressure roller 34 that are a pair of cylindrical bodies. When the medium arrives on the upstream side (medium supply unit 10 side) of the fixing unit 30 on the medium conveyance path, the medium detecting unit 31 can detect a signal (medium detection signal) indicating that the medium has been detected. To the sex evaluation unit 50 and the like. As an example, the medium detection unit 31 may be an optical sensor including a light emitting element and a light receiving element that are arranged to face each other with a medium transport locus interposed therebetween. The light emitted from the light emitting element arrives at the light receiving element until the medium arrives at the medium detecting unit 31, but when the light emitted from the light emitting element arrives at the light receiving element, the light emitted from the light emitting element arrives at the light receiving element. Disappear. The medium detection unit 31 outputs a medium detection signal when the light receiving element stops detecting light coming from the light emitting element.

  The DC motor 32 is driven by a DC power supply supplied from the power supply unit 60. The rotating shaft of the DC motor 32 is connected to the rotating shaft of the heating roller 33 via a gear, and rotates the heating roller 33. The heating roller 33 is provided with a heater, and is rotated by the DC motor 32 as described above. The pressure roller 34 is arranged with respect to the heating roller 33 with a medium conveyance path interposed therebetween, and conveys the medium while being sandwiched between the heating roller 33 and itself. The image formed on the medium is heated between the heating roller 33 and the pressure roller 34 and is fixed on the medium by being pressed.

  The controller unit 40 receives information (formation instruction information) representing an image to be formed on the medium. This formation instruction information may be received via communication means such as a network (not shown). The controller unit 40 controls the medium supply unit 10, the developing unit 20, and the fixing unit 30 to form an image represented by the formation instruction information on the medium. Since such a controller unit 40 is widely known, a detailed description thereof will be omitted.

  As illustrated in FIG. 3, the fixing unit failure possibility evaluation unit 50 includes a current measurement unit 51, a vibration detection unit 52, and a control unit 53. The current measuring unit 51 detects a current amount of a power source supplied from the power source unit 60 to the DC motor 32 of the fixing unit 30 and outputs information representing the current amount. The current measuring unit 51 can be realized using, for example, an ammeter and an A / D (Analog / Digital) converter.

  The vibration detection unit 52 includes a vibration sensor (for example, a piezoelectric element) that detects vibration, and outputs a voltage signal representing the magnitude of vibration detected by the vibration sensor. This vibration sensor is attached to a member disposed around the fixing device 30 where the vibration of the shaft (here, the shaft of the heating roller) driven by the DC motor 32 in the fixing unit 30 propagates. The specific mounting position of the vibration sensor of the vibration detection unit 52 differs depending on the internal configuration of the image forming apparatus 1, but around the fixing device 30 where the vibration generated by the shaft shake of the fixing unit 30 propagates. It will be attached to the arranged members. An example of such a member is a support member that supports the fixing unit 30.

  The control unit 53 is constituted by a microcomputer, for example. The control unit 53 includes a program control device such as a CPU (Central Processing Unit), a storage element, and an interface unit. Here, the program control device is assumed to be a CPU in this embodiment. The CPU operates according to a program stored in the storage element, and performs a process for evaluating the possibility of failure of the fixing unit 30. Detailed contents of this processing will be described later.

  The storage element of the control unit 53 is a nonvolatile memory and stores a program executed by the CPU. The program may be provided by being stored in a computer-readable recording medium such as a DVD-ROM (Digital Versatile Disc Read Only Memory) and copied to the storage element. Furthermore, this storage element also operates as a work memory for the CPU. The interface unit accepts a signal input from the medium detection unit 31 and outputs it to the CPU. The power supply unit 60 supplies power to each unit of the apparatus including the DC motor 32 of the fixing unit 30.

  Here, the operation of the control unit 53 of the fixing unit failure possibility evaluation unit 50 will be described. The control unit 53 stores information on the amount of current measured by the current measurement unit 51 and information on the magnitude of vibration detected by the vibration detection unit 52 in a storage element.

  The control unit 53 is a unit measured by the current measuring unit 51 during a period when the DC motor 32 of the fixing unit 30 rotates the heating roller 33 and there is no medium between the heating roller 33 and the pressure roller 34. The square value of the amount of current per hour (ie, the effective current value) and the square value of the magnitude of vibration detected by the vibration detecting unit 52 per unit time (ie, the effective vibration value) are used as information about the “medium-free period”. Remember.

  Further, the control unit 53 is measured by the current measuring unit 51 during a period when the DC motor 32 of the fixing unit 30 rotates the heating roller 33 and there is a medium between the heating roller 33 and the pressure roller 34. The square value of the current amount per unit time (that is, the current effective value) and the square value of the magnitude of vibration detected by the vibration detecting unit 52 per unit time (that is, the vibration effective value) Store as information.

  Further, here, the medium between the heating roller 33 and the pressure roller 34 is from the time T1 that is predetermined before the time when the medium detecting unit 31 detects the medium to the time when the medium detecting unit 31 detects the medium. The period between the heating roller 33 and the pressure roller 34 is the period from when the medium detection unit 31 detects the medium until after a predetermined time T2 has elapsed.

  That is, the control unit 53 accumulates information on the amount of current measured by the current measurement unit 51 and information on the magnitude of vibration detected by the vibration detection unit 52 in the storage element for a time Tmax (Tmax = T1 + T2). (Such storage can be performed using a well-known ring buffer). The control unit 53 starts a timer (not shown) from the time when the medium detection unit 31 detects the medium, and performs the process illustrated in FIG. 4 when the time T2 has elapsed from the time of the start. (During this process, information storage may be temporarily suspended).

  The controller 53 determines the time T1 determined in advance from the time when the medium is detected by the medium detector 31 among the stored information on the current amount and the information on the magnitude of vibration. The information from the previous time until the time when the medium detection unit 31 detects the medium, that is, the medium-free period, is extracted (S1). Then, the control unit 53 calculates the effective current value by dividing the square sum of the information on the amount of current stored in the medium-less period by the time T1, and information on the magnitude of vibration stored in the medium-free period. Is divided by time T1 to calculate a vibration effective value (S2).

  Further, the control unit 53 determines the time T2 from the stored current amount information and vibration magnitude information for the last time T2 (that is, from the time when the medium detection unit 31 detects the medium). The information up to the elapse of time, that is, the medium existence period is extracted (S3). Then, the control unit 53 calculates the effective current value by dividing the square sum of the information on the amount of current stored in the medium-present period by the time T2, and information on the magnitude of vibration stored in the medium-present period. Is divided by time T2 to calculate a vibration effective value (S4).

  The control unit 53 calculates a difference between the effective current value Ie_p in the medium-less period calculated in process S2 and the effective current value Ie in the medium-existed period calculated in process S4, ΔIe = Ie−Ie_p, and calculates the differential current effective The value ΔIe is obtained. Also, the difference between the effective vibration value Ve_p for the medium-less period calculated in step S2 and the effective vibration value Ve for the medium-existing period calculated in step S4 is calculated as ΔVe = Ve−Ve_p. Obtain (S5).

  Then, the control unit 53 determines how far the differential current effective value ΔIe and the differential vibration effective value ΔVe are separated from the reference differential current effective value ΔIe_ref and the reference differential vibration effective value ΔVe_ref that are determined in advance as a reference. The evaluation information to be expressed is calculated (S6). This evaluation information may be calculated as Mahalanobis distance.

  The control unit 53 checks whether or not the Mahalanobis distance exceeds a predetermined threshold (S7). If the distance exceeds the predetermined threshold (S7), the controller 53 determines that there is a sign of a failure and notifies that ( S8). This notification may be performed by a method such as displaying it on a display unit (not shown) or by transmitting information indicating that to a predetermined destination via a communication means such as a network. Good.

  If the Mahalanobis distance calculated in step S6 does not exceed the predetermined threshold (if No), the control unit 53 ends the process.

  The Mahalanobis distance between the reference differential effective current value ΔIe_ref and the reference differential vibration effective value ΔVe_ref used in step S6 is calculated as follows. That is, in the present embodiment, a plurality of differential current effective values ΔIe and differential vibration effective values ΔVe are obtained using the fixing unit 30 that is known to be normal in advance (these are the reference differential current effective values). Value ΔIe_ref and reference differential vibration effective value ΔVe_ref). The average of the plurality of differential current effective values ΔIe is μIe, the average of the plurality of differential vibration effective values ΔVe is μVe, and the dispersion matrix (covariance matrix) is obtained as Σ. In the following description, μ is a vector value whose components are (μIe, μVe).

として、マハラノビス距離Ｄを算出する。 In step S6, a vector value X = (ΔIe, ΔVe) having the differential current effective value ΔIe calculated in step S5 and the differential vibration effective value ΔVe as components is generated.

As a result, the Mahalanobis distance D is calculated.

[Operation]
When the image forming apparatus 1 according to the present embodiment receives an image formation instruction, the controller unit 40 generates a bitmap image according to the instruction. When the controller unit 40 energizes the heater of the heating roller 33 of the fixing unit 30 and the temperature of the heater of the heating roller 33 reaches a predetermined temperature, the medium supply unit 10 supplies the medium, and the developing unit 20 Is controlled to form a latent image on the image bearing member, and a toner corresponding to the latent image is attached. When the medium passes through the developing unit 20, the toner is transferred to the medium.

  During this time, the heating roller 33 of the fixing unit 30 is rotationally driven by the DC motor 32, and the pressure roller 34 in contact with the heating roller 33 is also rotated according to the rotation of the heating roller 33. The image forming apparatus 1 detects the amount of current supplied to the DC motor 32 during this period and the magnitude of vibration propagating from the rotating shaft of the heating roller 33, and sets a predetermined time Tmax (Tmax = T1 + T2). Accumulate and memorize only minutes.

  Eventually, when the medium reaches the fixing unit 30 and is detected by the medium detection unit 31, and after the time T2 has elapsed, the image forming apparatus 1 stores the current amount information and the vibration magnitude information. Of these, only the first time T1 (that is, the time from when the medium detection unit 31 detects the medium to the time when the medium detection unit 31 detects the medium from the time T1 previously determined, that is, the medium-free period) Extract information. Then, the image forming apparatus 1 calculates the effective current value by dividing the square sum of the information on the current amount stored during the medium-less period by the time T1, and also calculates the magnitude of the vibration stored during the medium-free period. The effective value of vibration is calculated by dividing the square sum of information by time T1.

  Further, the image forming apparatus 1 determines the time T2 from the stored current amount information and the vibration magnitude information for the last time T2 (that is, from the time when the medium detecting unit 31 detects the medium). Information up to the point of time elapses, that is, a period with a medium). Then, the current effective value is calculated by dividing the square sum of the information on the amount of current stored in the period with the medium by the time T2, and the square sum of the information on the magnitude of vibration stored in the period with the medium is calculated. Divide by time T2 to calculate the effective vibration value.

  Shaking between the heating roller 33 and the pressure roller 34 of the fixing unit 30 is caused by wear due to use, and increases as the wear occurs. At this time, the amount of current required for driving increases. However, while a medium such as paper is sandwiched between these rollers, the rotation shafts of the heating roller 33 and the pressure roller 34 are pressed in one direction, so that the range of shaft shake is reduced. Apparently, the amount of shaft runout decreases. That is, the change in the amount of current and the amount of vibration before and after the medium passes through the fixing unit 30 is as illustrated in FIG. FIG. 5 shows that both the amount of vibration and the amount of current required for driving are relatively large before the medium passes (before the medium detector 31 detects the medium) and decrease while the medium is passing. .

  The image forming apparatus 1 calculates the difference between the effective current value Ie_p during the medium-free period and the effective current value Ie during the medium-present period, ΔIe = Ie−Ie_p, and obtains the differential current effective value ΔIe. Further, the difference between the effective vibration value Ve_p during the medium-free period and the effective vibration value Ve during the medium-present period is calculated, ΔVe = Ve−Ve_p, to obtain the differential vibration effective value ΔVe. In the image forming apparatus 1, how far the differential current effective value ΔIe and the differential vibration effective value ΔVe are apart from the reference differential current effective value ΔIe_ref and the reference differential vibration effective value ΔVe_ref that are determined in advance as a reference. Is calculated by calculating the Mahalanobis distance.

  An example of calculating the Mahalanobis distance is shown in FIG. In FIG. 6, the Mahalanobis distance (D1, D2) calculated when the fixing unit 30 is relatively new and the Mahalanobis distance (D1, D2) calculated in a state in which wear has progressed but no failure has been determined. D3) and Mahalanobis distance (D4) calculated in a state in which wear further proceeds and it is determined that there is a failure are illustrated.

  The image forming apparatus 1 checks whether or not the Mahalanobis distance exceeds a predetermined threshold value. If it exceeds the threshold value, the image forming apparatus 1 determines that there is a sign of failure and notifies the fact. This threshold value can be determined experimentally.

[Modification 1]
In the process illustrated in FIG. 4, the control unit 53 checks whether or not the Mahalanobis distance calculated in the process S <b> 6 exceeds a predetermined threshold value. It was supposed to be informed. That is, it has been determined that there is a sign of failure even if the Mahalanobis distance calculated in step S6 exceeds the predetermined threshold value only once. However, in the present embodiment, instead of this, when the number of times that the Mahalanobis distance calculated in step S6 exceeds a predetermined threshold becomes N predetermined (N is 2 or more), a sign of failure It may be determined that there is, and a notification to that effect may be made.

  In this example, the control unit 53 secures an area for storing the counter value in the storage element, and initially resets it to “0”. Further, the value of the counter may be reset to “0” when the power is turned on or when the fixing unit 30 is replaced.

  Then, the control unit 53 checks whether or not the Mahalanobis distance calculated in the process S7 exceeds a predetermined threshold value, and if so, increments the value of this counter by “1”. Then, when the value of the counter exceeds the predetermined number of times threshold, it is determined that there is a sign of failure, the process proceeds to step S8, and the fact is notified.

[Modification 2]
In the description so far, the failure possibility evaluation based on the calculated differential current effective value ΔIe and the differential vibration effective value ΔVe is performed based on the reference differential current effective value ΔIe_ref and the reference differential vibration effective. The difference current effective value ΔIe_ref and the reference difference vibration effective value ΔVe_ref differ depending on the type of medium used. That is, in general, since the unevenness of the medium surface, the thickness of the medium, and the like are different for different types of media, the reference differential current effective value ΔIe_ref and the reference differential vibration effective value ΔVe_ref may be different.

  Therefore, in the present embodiment, for each medium type, a plurality of reference differential current effective values ΔIe_ref and a reference differential vibration effective value ΔVe_ref are calculated, and from these, an average value vector μ for each medium type, The variance matrix Σ is obtained and stored for each type of medium as illustrated in FIG.

  In the example of FIG. 7, when information is formed using the fixing unit 30 that is known to be normal using the medium specified by the information for the information specifying the type of the medium, In this example, the measured and calculated reference differential current effective value ΔIe_ref, the average value vector μ based on the reference differential vibration effective value ΔVe_ref, and the dispersion matrix Σ are stored in association with each other.

  In this case, the control unit 53 of the image forming apparatus 1 acquires information specifying the type of the medium supplied from the medium supply unit 10 in accordance with an image forming instruction, and stores the average value associated with the acquired information. The vector μ and the variance matrix Σ are read out. Then, when the Mahalanobis distance is calculated in the process S6 illustrated in FIG. 4, an operation using the read average value vector μ and the dispersion matrix Σ is performed.

  Here, the information for specifying the type of medium may be the name of the type of paper as the medium (“plain paper”, “coated paper”, etc.), or information itself indicating the thickness of the paper as the medium. May be. Note that the information indicating the thickness of the paper may be expressed in terms of weight per square meter of paper (for example, 127 g / square meter).

  In view of the fact that vibration due to shaft shake, which is a sign of failure, is more likely to occur as the thickness of the medium is thinner, when image formation is performed on a medium exceeding a predetermined thickness threshold, It is good also as not performing the process shown in the form. In this case, the process shown in FIG. 4 is performed only when an image is formed on a medium that does not exceed a predetermined thickness threshold. In this case, for each medium that does not exceed the predetermined thickness threshold, the reference differential current effective value ΔIe_ref serving as a reference, the average vector μ based on the reference differential vibration effective value ΔVe_ref, and the dispersion matrix Σ are stored. The information for specifying the type of the medium supplied from the medium supply unit 10 according to the image formation instruction is acquired, and the average value vector μ stored in association with the acquired information and the variance matrix Σ are obtained. Read it out. Then, when the Mahalanobis distance is calculated in the process S6 illustrated in FIG. 4, an operation using the read average value vector μ and the variance matrix Σ may be performed.

[Modification 3]
Further, in the description so far, evaluation information indicating how far the differential current effective value ΔIe and the differential vibration effective value ΔVe are separated from the reference value is calculated using the Mahalanobis distance, and thereby the possibility of failure. However, the present embodiment is not limited to this.

とすればよい。 As an example, the Euclidean distance d indicating how far the differential current effective value ΔIe and the differential vibration effective value ΔVe are from the reference value may be calculated as evaluation information. In this case, the Euclidean distance d is

And it is sufficient.

  When the Euclidean distance d exceeds a predetermined threshold (or the number of times the predetermined threshold is exceeded (the number of times measured using the above-described counter)), the image forming apparatus 1 sets the predetermined number threshold. When it exceeds, it is determined that there is a sign of failure, and that fact is notified.

を算出して、これらを利用して故障の可能性を評価してもよい。ここでＩは、媒体あり期間で計測された電流量の平均値（または最大値など予め定めた統計量）、Ｉ_pは、媒体なし期間で計測された電流量の平均値（または最大値など予め定めた統計量）、Ｖは、媒体あり期間で計測された振動の大きさの平均値（または最大値など予め定めた統計量）、Ｖ_pは、媒体なし期間で計測された振動の大きさの平均値（または最大値など予め定めた統計量）である。 Furthermore, instead of the differential current effective value and the differential vibration effective value, as the current value fluctuation difference ΔI and the vibration magnitude fluctuation difference ΔV,

And the possibility of failure may be evaluated using these. Here, I is an average value (or a predetermined statistic such as a maximum value) of the current amount measured in the medium-present period, and I_p is an average value (or maximum value or the like of the current amount measured in the medium-free period). Statistic determined), V is an average value (or a predetermined statistic such as a maximum value) of the magnitude of vibration measured in the period with medium, and V_p is a magnitude of vibration measured in the period without medium It is an average value (or a predetermined statistic such as a maximum value).

  In this case as well, using the fixing unit 30 that is known to be normal in advance, a plurality of values ΔI_ref serving as a reference for the fluctuation difference of the current value and values ΔV_ref serving as a reference for the fluctuation difference of the magnitude of vibration are used. Get it. The plurality of ΔI_ref and the plurality of ΔV_ref are calculated with reference to the centroid (or average) of the current value variation difference and the centroid (or average) of the vibration magnitude variation difference, respectively.

  Next, in the process S2 shown in FIG. 4, the control unit 53 of the present embodiment replaces the current effective value and the vibration effective value with the current value statistic I_p and the vibration magnitude statistic instead of the medium effective value. The quantity V_p is calculated. Further, in the process S4 of FIG. 4, a current value statistic I and a vibration magnitude statistic V are calculated.

と表すことができる。制御部５３は、処理Ｓ７にて、この距離Ｒが予め定めた閾値を超えているか否かを調べ、超えていれば（Yesならば）、故障の予兆があると判断して、その旨を報知する。または、この距離Ｒが予め定めた閾値を超えた回数（上述のカウンタを用いて計測した回数）が予め定めた回数閾値を超えたときに、故障の予兆があると判断して、その旨を報知する。 Further, in the process S5 of FIG. 4, the control unit 53 uses the values calculated in the processes S2 and S4 to calculate the current value variation difference ΔI and the vibration magnitude variation difference ΔV. In step S6, instead of calculating the Mahalanobis distance, the point represented by the value calculated as the reference value on the plane spanned by the current value fluctuation difference and the vibration magnitude fluctuation difference is calculated in step S5. The distance R to the point represented by the calculated value is calculated as evaluation information. The distance R is expressed by ΔI_R and ΔV_R, where the centroids (or averages) of the plurality of ΔI_ref and the plurality of ΔV_ref, which are the reference values, are expressed as

It can be expressed as. In step S7, the control unit 53 checks whether or not the distance R exceeds a predetermined threshold value. If the distance R exceeds the predetermined threshold value (if Yes), the control unit 53 determines that there is a sign of failure, and indicates that. Inform. Alternatively, when the number of times that the distance R exceeds a predetermined threshold (the number of times measured using the counter described above) exceeds a predetermined number of times threshold, it is determined that there is a sign of failure, and this is indicated. Inform.

  FIG. 8 shows a point represented by a reference value calculated for each sheet thickness, and a current calculated at the time of failure (not at the time when there is a possibility of failure but at the time when it was actually determined as a failure). FIG. 4 illustrates a value difference ΔI_failure and a point represented by a vibration magnitude difference ΔV_failure. At this time, the threshold for determining that there is a possibility of failure is α × | ΔI_failure−ΔI_R |, vibration in the direction along the axis of the current value variation difference, centering on the point represented by the reference value. Expressed as an ellipse having a diameter of β × | ΔV_failure−ΔV_R | (where α and β are parameters greater than 0 and less than 1) in the direction along the axis of the fluctuation difference in size of Also good. When doing so, in step S6, when the fluctuation difference ΔI of the actually measured current value and the fluctuation difference ΔV of the magnitude of vibration are out of this ellipse (or the current value of the actually measured current value). When there is a sign of failure at the number of times that the fluctuation difference ΔI and the fluctuation difference ΔV of the magnitude of vibration are out of this ellipse (when the number of times measured using the counter described above exceeds a predetermined number threshold). to decide.

  Here, α and β of the above parameters are relatively small for the purpose of detecting a sign of failure, and for example, both of them may be values below 0.5.

  According to the present embodiment, a plurality of phenomena that are signs of failure are used, and the occurrence of the plurality of phenomena is examined when the medium passes through the fixing device and when the medium does not. Compared to the case where no is used, the accuracy of detection of a sign of failure can be improved.

  DESCRIPTION OF SYMBOLS 1 Image forming apparatus, 10 Medium supply part, 20 Developing part, 30 Fixing part, 31 Medium detection part, 32 DC motor, 33 Heating roller, 34 Pressure roller, 40 Controller part, 50 Fixing part failure possibility evaluation part, 51 Current measurement unit, 52 vibration detection unit, 53 control unit, 60 power supply unit.

Claims (3)

A fixing device comprising a pair of cylindrical bodies, fixing the image formed on the medium while sandwiching and feeding the medium between the pair of cylindrical bodies;
A DC motor for rotationally driving the cylindrical body of the fixing device;
A power supply for supplying power to the DC motor;
Current measuring means for measuring the amount of current flowing from the power source to the DC motor;
Vibration detecting means for detecting the magnitude of vibration of members disposed around the fixing device;
Determining means for determining whether there is a medium between the cylindrical bodies;
The current amount and the magnitude of vibration measured or detected when the DC motor is rotating the cylindrical body and the judging means judges that there is no medium between the cylindrical bodies, and the judging means Evaluation means for evaluating the possibility of failure of the fixing device based on the difference between the amount of current and the magnitude of vibration measured or detected when it is determined that there is a medium between the cylindrical bodies;
An image forming apparatus including: Means for obtaining information on the thickness of the medium;
The evaluation means includes
The current amount and the magnitude of vibration measured or detected when the DC motor rotates the cylindrical body and the determination means determines that there is no medium between the cylindrical bodies, and the determination means. Based on the difference between the amount of current and the magnitude of vibration measured or detected when it is determined that there is a medium between the cylinders, and the information on the thickness of the acquired medium, the failure of the fixing device The image forming apparatus according to claim 1, wherein the possibility is evaluated. A fixing device that includes a pair of cylindrical bodies and fixes the image formed on the medium while sandwiching and feeding the medium between the pair of cylindrical bodies;
A DC motor that rotationally drives the cylindrical body of the fixing device;
A power supply for supplying power to the DC motor;
Current measuring means for measuring the amount of current flowing from the power source to the DC motor;
Vibration detecting means for detecting the magnitude of vibration of a member disposed around the fixing device;
A computer for controlling the image forming apparatus, comprising: a determination unit that determines whether there is a medium between the cylindrical bodies;
The current amount and the magnitude of vibration measured or detected when the DC motor rotates the cylindrical body and the determination means determines that there is no medium between the cylindrical bodies, and the determination means. A program that functions as means for evaluating the possibility of failure of the fixing device based on a difference between the amount of current and the magnitude of vibration measured or detected when it is determined that there is a medium between the cylindrical bodies.

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