JP2010188532A - Image forming apparatus, method of estimating encoder life and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid the trouble that printing-out is interrupted by an encoder signal error generated because of an encoder life at an unexpected timing, leading to a downtime from generation of the error to replacement of the encoder. <P>SOLUTION: The light amount of a light source is reduced to a detection limit where an output pulse of the optical encoder is missed at a check time point, and a critical light amount is obtained (S105). An integrated use amount of ink at the time is calculated (S106) and stored in pairs in a storage medium. A curve showing a relationship between the critical light amount and the ink integrated use amount is approximated from a history of these amounts stored in pairs at each check time point (S109). An expectancy of how much can be used until the currently obtained critical light amount reaches a light amount of a preliminarily set life is expressed by the integrated amount of ink on the basis of the obtained estimation life function. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer that moves an image forming unit with respect to a recording paper surface to form an image in a scanning format, and more particularly, generates a position signal to control the movement of the image forming unit. The present invention relates to an image forming apparatus having a function of predicting the lifetime of an optical encoder, an encoder lifetime prediction method, and a program.

In an inkjet printer, a recording head as an image forming unit is mounted on a carriage, and the carriage is linearly moved in the main scanning direction with respect to the recording paper surface while performing an ink ejection operation by driving the recording head with image data. An apparatus that employs a format for performing an image forming operation is widely used.
In such an image forming apparatus that scans the image forming unit, carriage movement control is a large factor that affects image quality. Therefore, it is required to accurately detect the position of the carriage that is displaced during movement.
As a means for detecting the position of the moving carriage, an encoder that detects (reads) a scale scale installed in the moving direction and generates a position signal is used.

  An encoder that generates a carriage position signal during movement installs a scale over the movable range of the carriage, and acquires the carriage position information by reading the scale with a sensor mounted on the carriage side. In this type of image forming apparatus, an encoder that illuminates an optical scale with a light source, detects a light / dark change of the light due to the scale with an optical sensor during movement, and outputs it as a position pulse signal is often used (see FIG. 1 described later). , 2). The relationship with the image forming operation is that the position information of the carriage can be obtained by counting the position signal pulse output from the encoder when the carriage is moved from the reference position determined on the device. Based on the image data transfer and the ink ejection timing, the image formation is performed.

By the way, when an optical encoder is used in an ink jet printer, ink mist, paper dust, or the like adheres to the scale, so that a sensor that reads the scale may make a false detection, and accurate position information of the carriage may not be grasped. .
To solve the problem of erroneous detection of the optical encoder due to ink mist, paper dust, etc., a proposal has been made to maintain normal printing operation by a method of collecting ink by charging the ink mist (see Patent Document 1 below). ).
In addition, sensitivity deterioration due to a decrease in the amount of light input to the sensor that reads the scale due to contamination due to ink mist or the like is detected from the position signal pulse of the sensor, and control is performed to increase the amount of light source according to the detected amount, thereby preventing erroneous detection. A method has been proposed (see Patent Document 2 below).

However, in the method using the dust collecting electrode of Patent Document 1, the individual conditions of the scattered ink mist vary, for example, the ink physical properties for each color, the mass of the ink mist, the kinetic energy of the ink mist, and the like. It is difficult to collect all ink mist. For this reason, it is inevitable that the ink mist that could not be collected dust adheres to the linear scale, which hinders normal printing operation. If this appears as a problem that requires a service man call such as a position detection error or print image misalignment, downtime occurs due to machine repair such as replacing the encoder.
Further, in the case of the method of performing the control for increasing the light source light amount in accordance with the detected amount of sensitivity degradation in Patent Document 2, the light source light amount cannot be increased beyond a predetermined value due to element characteristics such as the maximum rating, and the upper margin. Therefore, it is unavoidable that the encoder has a lifetime and that a serviceman call occurs at an unexpected timing. For this reason, even in this method, downtime occurs due to machine repair such as replacement of the encoder.
The object of the present invention is that an encoder signal error due to the life of the encoder occurs at an unexpected timing, so that the time from the occurrence of the error to the replacement of the encoder in a state where the print output is interrupted or waited is downtime. This is to avoid the inconvenience caused by the prior art.

In the present invention, the position of the image forming unit that moves on the recording surface in the scanning direction is detected by an encoder that receives light from a scale illuminated by a light source that can control the amount of light and outputs a position signal. An image forming apparatus that controls the movement of the image forming unit based on the above and forms an image using ink on a recording surface, and detects whether or not the position signal output of the encoder is abnormal An abnormality detection control means for detecting the position signal output of the encoder by the output abnormality detection means while reducing the light source light quantity of the encoder, and acquiring the light source light quantity when an abnormality is detected in the position signal output; Ink integrated usage amount calculating means for calculating the cumulative ink usage amount, the amount of light acquired by the abnormality detection control means when the encoder signal output is abnormal, and the previous time Storage means for storing the ink integrated usage amount calculated by the ink integrated usage amount calculating means as a pair, ink integration based on the history of the light source light amount and the ink integrated usage amount stored for the storage means A relationship predicting unit that predicts a relationship between the usage amount and the light source light amount; and a currently detected light source light amount of a predetermined usage limit based on the relationship between the accumulated ink usage amount and the light source light amount predicted by the relationship prediction unit. It has a remaining life calculating means for calculating the remaining life of the encoder until the light source light quantity is reached.
In the present invention, the position of the image forming unit that moves on the recording surface in the scanning direction is detected by an encoder that receives light from a scale illuminated by a light source that can control the amount of light and outputs a position signal. An encoder life prediction method for controlling the movement of the image forming unit based on the above and predicting the remaining life of the encoder in an image forming apparatus that forms an image using ink on a recording surface. Output abnormality detection step for detecting whether or not the encoder position signal output is abnormal while reducing the output, and abnormality detection for acquiring the light source light quantity when an abnormality is detected in the encoder signal output in the output abnormality detection step Light amount acquisition step, ink integrated use amount calculation step for calculating the total ink use amount, light amount acquired in the abnormality detection light amount acquisition step, and A storage step for storing the ink cumulative usage calculated in the cumulative usage calculation step as a pair, and an ink cumulative usage and a light source based on a history of the light quantity and the ink cumulative usage stored as a pair in the storage step. Based on the relationship prediction step for predicting the relationship between the light amounts, and the relationship between the accumulated ink usage amount and the light source light amount predicted by the relationship prediction step, the currently detected light source light amount reaches the light source light amount at a predetermined use limit. And a remaining life calculating step for calculating the remaining life until.

  According to the present invention, by predicting the remaining life of the encoder, it is possible to replace the encoder by selecting an appropriate time before the end of the life of the encoder. It is possible to avoid the inconvenience caused by the prior art that the downtime is from the occurrence of the encoder signal error to the replacement of the encoder.

1 is a diagram illustrating a schematic configuration of an image forming engine (image forming unit) of an ink jet printer according to an embodiment of the present invention. It is a block diagram which shows the structure of the prediction process system of the remaining life of an encoder. It is a control flow (basic form) figure concerning the processing process of an encoder life check. It is a flowchart which shows the subroutine of the pulse missing detection step of FIG. It is a flowchart which shows the other subroutine of the pulse missing detection step of FIG. FIG. 4 is a flowchart showing a subroutine of a step for calculating an accumulated ink usage amount in FIG. 3. It is a figure explaining the method of calculating | requiring the method of calculating | requiring a predicted life function and a remaining life. It is a figure explaining other ways of obtaining a predicted life function. It is a control flow (2nd Embodiment) figure of the processing process which concerns on an encoder lifetime check. It is a control flow (3rd Embodiment) figure of the processing process which concerns on an encoder lifetime check. It is a control flow (4th Embodiment) figure of the processing process which concerns on an encoder lifetime check.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
The following embodiment of the image forming apparatus according to the present invention shows an application example to an image forming apparatus using an inkjet head for image formation (hereinafter also referred to as “inkjet printer”).
The ink jet printer drives an ink jet head with image data, and linearly moves the carriage in the main scanning direction with respect to the recording paper surface while ejecting ink droplets to perform an image forming operation.
When the image forming operation is performed, the position of the image to be formed on the recording paper surface is set as an output condition. Therefore, the position of the carriage moving in the main scanning direction from the reference position determined on the apparatus is detected, and the detected value is set. The image data transfer and ink ejection timing are determined based on the above.

A linear encoder (hereinafter also simply referred to as “encoder”) is used to detect the position of the moving carriage. The encoder installs a scale over the movable range of the carriage, and reads this scale with a sensor mounted on the carriage side. The encoder of the present embodiment is optically operated, and an optical scale (usually having a transmissive or reflective grating at regular intervals as a scale graduation) with a light source, and the brightness of the light by the scale when moving. The change is detected by an optical sensor and output as a position pulse signal.
The use of an optical encoder in an ink jet printer as described above has been used in the past, but as described in the section [Background Art] above, erroneous detection due to the influence of adhesion of ink mist or the like. Over time, it gradually approaches a state where normal detection is not possible, and eventually exceeds the limit determined based on the encoder rating, and it is time to replace the encoder.
The ink jet printer according to the present embodiment predicts the remaining life until the encoder becomes unusable, that is, reaches the end of its life, in order to avoid an unexpected time when the encoder needs to be replaced. This is characterized by a function to inform the user of this (hereinafter also referred to as “encoder life check function”).

Hereinafter, the encoder life check function of the image forming apparatus according to the present embodiment will be described in detail, but before that, an outline of the inkjet printer as an object of implementation will be described.
"Inkjet printer overview"
FIG. 1 is a diagram showing a schematic configuration of an image forming engine of an ink jet printer.
FIG. 1 mainly shows the related configuration of the encoder that detects the movement of the carriage moving in the main scanning direction and the movement of the carriage. Therefore, the details of the ink jet head and the recording paper feed mechanism that are not directly related to the encoder, or the configuration of the paper discharge mechanism and the like can be omitted because they can use the existing configuration and need not be described.

In FIG. 1, a carriage 23 is held by a carriage guide 21 horizontally mounted between a front plate 101F and a rear plate 101R and a guide stay (not shown) provided on a rear stay 101B so as to be movable in the main scanning direction. When a driving force is applied by the motor 27 via the timing belt 29 spanned between the driving pulley 28A and the driven pulley 28B, the motor 27 moves in the main scanning direction.
On the carriage 23, recording heads 24k1 and 24k2 each composed of two droplet ejection heads that eject black (Bk) ink, and cyan (C) ink, magenta (M) ink, and yellow (Y) ink are ejected. A total of five droplet discharge heads, each of which is a recording head 24c, 24m, 24y (hereinafter referred to as "recording head 24" when not distinguishing colors and collectively), each comprising one droplet discharging head) are mounted. .
A shuttle type is used in which the carriage 23 is moved in the main scanning direction and droplets are ejected from the recording head 24 while the recording medium 5 is fed in the paper conveying direction (sub-scanning direction) by the conveying belt 31.
As the recording head 24, a piezoelectric plate is used as pressure generating means (actuator means) for pressurizing ink in the ink flow path (pressure generating chamber), and the vibration plate forming the wall surface of the ink flow path is deformed to change the ink flow path. A so-called piezo type that ejects ink droplets by changing the internal volume, or a so-called thermal that ejects ink droplets with pressure by heating the ink in the ink flow path using a heating resistor to generate bubbles The volume of the ink flow path is changed by deforming the vibration plate by the electrostatic force generated between the vibration plate and the electrode. For example, an electrostatic type that discharges ink droplets can be used.

  Further, a linear encoder scale (hereinafter also simply referred to as “scale”) stretched between the front plate 101F and the rear plate 101R along the main scanning direction of the carriage 23 (indicated by the up and down arrows in the figure). 128 and an encoder sensor (hereinafter simply referred to as “sensor”) 129 provided on the rear surface (rear stay 101B side) of the carriage 23 (see encoder 60 in FIG. 2 described later). The main scanning motor 27 is driven and controlled based on a position signal output in accordance with the movement of the carriage 23 from the linear encoder, and the main scanning control of the carriage 23 is performed at a required speed and moving amount.

Further, a maintenance / recovery mechanism 121 for maintaining and recovering the nozzle state of the recording head 24 is disposed in a non-printing area on one side of the carriage 23 in the scanning direction. This maintenance / recovery mechanism 121 is a cap member for capping the nozzle surfaces of the five recording heads 24, one suction cap 122 a that also serves as a moisture retention, four moisture retention caps 122 b to 122 e, and a recording A wiper blade 124, which is a wiping member for wiping the nozzle surface of the head 24, and a first idle discharge receiver 125 for performing idle ejection are arranged.
Further, a second idle discharge receiver 126 for performing idle ejection is disposed in the non-printing area on the other side of the carriage 23 in the scanning direction. Openings 127 a to 127 e are formed in the second idle discharge receptacle 126.

The sub-scanning transport unit changes the transport direction of the recording medium 5 fed from below by approximately 90 degrees and transports the recording medium 5 so as to face the image forming unit, and a driven roller as a tension roller and a driven roller as a tension roller. An endless conveyance belt 31 is provided between the rollers 33.
The transport belt 31 of the sub-scan transport section is configured to circulate in the paper transport direction (sub-scan direction) by rotating the transport roller 32 from the sub-scan motor 131 via the timing belt 132 and the timing roller 133. is doing.

Next, an encoder life check function for checking the life of a linear encoder that outputs a position signal in accordance with the movement of the carriage 23 in the above-described ink jet printer will be described.
In this check function, the sensitivity of the sensor that reads the linear scale gradually decreases due to the adhesion of ink mist, etc., and erroneous detection occurs and the encoder output becomes abnormal, but the current output status is abnormal. This function checks how much room is available for the output status. Here, the abnormal output state is defined as the state where the encoder has reached the end of its life, the current state is grasped by the remaining life (representing the remaining until the end of the life), and the replacement time of the encoder can be known in advance by the remaining life It can be so. Note that the remaining life can be acquired as a history up to the present time, the amount of ink ejected from the recording head, that is, the cumulative amount of ink used, and the light source in the encoder controlled to maintain a normal output state (light emission in FIG. 2 described later). 129c) Prediction is made based on the relationship between the amounts of light (the remaining life prediction method will be described in detail later with reference to FIGS. 7 and 8).

"Residual life prediction processing system"
In this embodiment, a prediction processing system is configured as means for realizing the encoder life check function. This processing system is capable of detecting the current output state of the encoder, means for obtaining the amount of ink ejected from the recording head up to the present time, that is, the ink accumulated usage amount, and checking the output state until now. As a constituent element, there are a prediction calculation means for predicting the relationship between the accumulated ink use amount and the light source light amount based on the history and a means for calculating the remaining life of the current encoder according to the prediction result.
FIG. 2 is a block diagram showing a configuration of an encoder remaining life prediction processing system.
The encoder 60 for detecting the position of the moving carriage includes a scale 128 having a transmission or reflection type grating (memory) at equal intervals, a light emitting unit 129e as a light source for illuminating the scale, and a grating on the light receiving side from the scale when moving. The sensor 129 includes a light receiving unit 129r that photoelectrically converts a change in brightness of light received through the light. The sensor 129 of the present embodiment can control the amount of light emitted from the light emitting unit 129e in order to adjust the detection sensitivity. Further, the position pulse whose phase is shifted by 90 degrees in order to improve the detection accuracy and determine the moving direction or the like. Signals (shown as A phase and B phase in FIG. 2) are output. The position pulse signal having a phase difference of 90 degrees is also used for detecting a missing pulse as described below.

The detection of missing pulses is one of the methods for detecting an abnormal state in which erroneous detection occurs because the detection of the linear scale decreases as time passes and false detection occurs. This method is adopted in the form. In the detection of the missing pulse employed here, a state in which the scale cannot be read normally at either the phase A or the B phase out of phase (pulse missing) is recognized as an abnormal state.
The pulse missing detection means 70 includes an A phase counter 71a that counts the A phase of the position pulse signal output from the sensor 129 of the encoder 60 at the rising edge or the falling edge, and a B phase counter 71b that similarly counts the B phase of the encoder. A counter comparison unit 73 that compares the counter values of the A phase and the B phase, and a pulse loss determination unit 75 that determines whether or not there is a missing pulse depending on whether the comparison results by the counter comparison unit 73 are equal.

In calculating the remaining life of the encoder, first, the state of the sensitivity of the sensor that reads the linear scale that decreases with time is first determined. Here, the light amount of the light source is reduced to the limit at which the above-described pulse omission occurs, the light amount at the limit is acquired, and at the same time, the current accumulated ink use amount is also acquired. Next, the relationship between the limit light quantity acquired as a history so far and the accumulated amount of ink used at that time until the end of the lifetime (hereinafter referred to as “predicted lifetime function”) is predicted. Thereafter, the remaining life until the light source light amount detected in the current state reaches the light source light amount at a predetermined use limit based on the predicted life function is calculated.
As means for calculating the remaining life, the light quantity changing means 61 for changing the light quantity of the light emitting portion 129e of the sensor 129, the ink integrated usage amount calculating means 81, the relationship between the limit light quantity and the ink cumulative usage quantity at that time. A storage unit 83 for storing a history and a remaining life prediction calculating unit 85 for obtaining a predicted life function and calculating a remaining life are provided. For example, when the LED is the light emitting unit 129e, the light amount changing unit 61 is configured to output a PWM waveform with an arbitrary DUTY, an integration circuit that smoothes the PWM waveform generated by the PWM generation module, and a smoothing by an integration circuit The current waveform is converted into a current flowing to the light emitting section. In the PWM generation module, the light amount of the light emitting unit can be changed by changing DUTY so that the current value desired to flow to the light emitting unit is obtained.
In addition, a notification unit 101 that notifies the user or service person of the calculated remaining life of the encoder is provided. Details of the operation of the remaining life prediction processing system will be described in the encoder life check control flow described later.

Next, an embodiment relating to a process process of encoder life check performed by operating the remaining life prediction processing system will be described.
This processing process is executed according to a program that is started when the main control unit of the ink jet printer satisfies a predetermined condition as a condition for starting the encoder life check.
Although not shown, the main control unit of the ink jet printer includes, as a hardware configuration, a CPU (Central Processing Unit) for operating software (program), a ROM (Read Only Memory) for storing the program, and a work memory for operating the program RAM (Random Access Memory) used as a component.
The ROM that constitutes the main control unit has an encoder life check function and the like shown in the control flow charts of FIGS. By recording a program for execution, the CPU of the main control unit constitutes means for realizing this function (in accordance with this embodiment, the remaining life prediction processing system in FIG. Constitute). The medium for recording the program is not limited to the ROM, and various storage media including disk types such as HDD (hard disk), CD-ROM, and MO (Magnet Optical Disk) can be used.

Hereinafter, an embodiment of a processing process related to the encoder life check will be described based on the illustrated control flows I to IV.
"Control flow I"
FIG. 3 is a diagram showing a control flow of encoder life check of this embodiment.
The control flow I shows a basic form of processing from the start of the control flow at the timing when the execution condition of the encoder life check is satisfied until the remaining life is calculated and the calculation result is notified to the user or the like.
According to the control flow of FIG. 3, first, the light quantity of the light emitting unit 129e of the sensor 129 of the encoder 60 is initialized (step S101).
Next, it is confirmed whether or not the execution condition of the encoder life check is satisfied (step S102). If the occurrence of the execution timing can be confirmed (step S102-YES), the procedure proceeds to the execution procedure of the encoder life check. The encoder life check is performed when the printer (printer) status is turned on and energy saving is restored (returning from power saving mode, which is a state where the power consumption is reduced), or when the total number of sheets passed, Based on information such as the accumulated ink usage amount, it is possible to determine when these amounts have reached a predetermined amount. Here, if the occurrence of the execution timing cannot be confirmed (step S102-NO), this confirmation is repeated at a predetermined cycle.
If it is time to perform the encoder life check, the light amount changing means 61 performs control to lower the light amount of the light emitting unit 129e in the sensor of the encoder 60 by a predetermined amount (step S103). At this time, since the light amount of the light emitting unit 129e is in an initial state or an appropriate state in use, the light amount is decreased by a predetermined amount therefrom.

Next, the missing pulse detection means 70 is operated in a state where the amount of light is reduced, and the missing pulse is detected (step S104).
“Pulse missing detection I”
The pulse missing detection operation performed by the pulse missing detection means 70 at this time will be described based on a subroutine shown in FIG.
According to the flow of FIG. 4, the scale 128 or the sensor 129 of the encoder 60 is moved (step S104-1). In the printer of this embodiment shown in FIG. 1, the scale 128 does not move, so the sensor 129 is moved.
During this movement, the output signal pulses of the encoder 60 are simultaneously started by the respective counters 71 separately for the A phase and the B phase, and the number of pulses is counted. At a predetermined timing, the A phase counter value and the B phase counter value are obtained. Obtain (step S104-2). At this time, the acquisition timing is arbitrarily determined.

Next, a difference between the acquired A-phase and B-phase counter values is calculated by the counter value comparison unit 73 (step S104-3), and whether or not the calculated difference is equal to or greater than a predetermined value that is predetermined as a detection reference for missing pulses. Is determined by the missing pulse determination unit 75 (step S104-4). Since the A-phase and B-phase output signal pulses from the encoder 60 are output 90 degrees out of phase, the predetermined value of the pulse missing detection reference is at least 2 or more.
If the absolute value of the difference between the A-phase and B-phase counter values is greater than or equal to a predetermined value in step S104-4 (step S104-4-YES), it is determined that there is a missing pulse. If the absolute value of the phase counter value difference is not greater than or equal to the predetermined value (step S104-4-NO), it is determined that there is no missing pulse, and this subroutine is exited and the process returns to the main routine of FIG.

“Pulse missing detection II”
Here, another pulse missing detection operation that can be applied in place of the detection operation shown in FIG. 4 will be described with reference to FIG.
According to the flow of FIG. 4, first, the position address (AD1) of the encoder 60 is acquired (step S104-11). The position address of the encoder 60 can be obtained from the count value of the rotation synchronization signal (pulse) of the main scanning motor 27 used for moving the carriage 23. In this embodiment, the count value of the main scanning motor 27 is the encoder value. It is assumed that the data represents 60 proper position addresses.
Next, the scale 128 or the sensor 129 of the encoder 60 is moved until the counter 71 counts a predetermined number (n) of output signal pulses of the encoder 60 (this number is arbitrarily determined) (step S104-12). In the printer of this embodiment shown in FIG. 1, the scale 128 does not move, so the sensor 129 is moved.
Thereafter, the position address (AD2) of the encoder 60 after movement is acquired. The acquisition of the position address is obtained from the count value of the rotation synchronization pulse of the main scanning motor 27 as in step S104-11. In this case, the number of output signal pulses of the encoder 60 is counted by the respective counters 71 separately for the A phase and the B phase. Therefore, if there is a missing pulse on one side, the movement distance until the predetermined number of output signal pulses are counted, That is, the position address AD2 changes.

Next, a difference between the position address difference (AD1-AD2) of the encoder 60 before and after the movement and a predetermined count number (n) of the output signal pulse of the encoder 60 is calculated, and the calculated difference is determined in advance as a detection reference for missing pulses. It is determined whether or not the predetermined value is exceeded (step S104-14).
If the absolute value of the difference between the position address difference (AD1-AD2) and the predetermined count number (n) of the encoder 60 is greater than or equal to the predetermined value (step S104-14-YES) in step S104-14. On the other hand, if the absolute value of the difference is not greater than or equal to the predetermined value (step S104-14-NO), it is determined that there is no missing pulse.
Since the output signal of the encoder 60 has an A phase and a B phase, when the detection method of FIG. 5 is applied and the determination in step S104-14 is performed, only one of the A phase and the B phase is determined. Alternatively, both A-phase and B-phase can be judged, and detection can be made with variations such as when either missing pulse is detected in either one or when both missing pulses are detected. However, any method may be adopted.
After determining whether or not there is a missing pulse, this subroutine is exited and the process returns to the main routine of FIG.
As described above, the pulse missing detection operation described with reference to FIGS. 4 and 5 can detect the pulse missing of the encoder even when the carriage is in the acceleration or deceleration operation region. It has advantages not found in detection methods that require constant speed.

Returning to the main routine of FIG. 3, in step S104, the missing pulse is detected. If it is detected that there is no missing pulse (step S104-NO), the process returns to step S103, and the light emitting unit 129e in the sensor of the encoder 60 again. The light quantity changing means 61 performs control for lowering the quantity of light by a predetermined amount. In the loop from step S104 to step S103, a missing pulse occurs, that is, the missing light is detected by decreasing the light amount of the light emitting portion 129e by a predetermined amount until YES in step S104.
If a missing pulse is detected in step S104 (step S104-YES), then a light quantity (limit light quantity) when this missing pulse is detected is acquired (step S105).
Simultaneously with the acquisition of the limit light amount, the integrated ink use amount (Ia) is calculated as an amount representing the ink adhesion state that affects the detection sensitivity of the sensor 129 at this time (step S106).

“Calculation of accumulated ink usage Ia”
The operation of calculating the ink integrated usage amount performed by the ink integrated usage amount calculating means 81 will be described based on a subroutine shown in FIG.
According to the flow of FIG. 6, first, it is confirmed whether or not image data used for image formation has been input. If input of image data can be confirmed (step S106-1-YES), ink droplets are input from the input data. The size and the number of ink droplets are counted (step S106-2). The ink droplet count is performed for each ink color in a color printer.
Further, the ink amount for each ink droplet size (for example, large droplet: 20 pl, medium droplet: 10 pl, small droplet: 2 pl) is acquired from a previously stored storage medium (step S106-3).
Next, the ink usage amount of the input image data is calculated (step S106-4). This process is calculated based on the droplet size for each ink color and the count value of the number of ink droplets obtained in step S106-2 and the ink amount for each droplet size obtained in step S106-3.
For example, the following formulas (1) and (2) are calculated:
Ink usage (Vc, Vbk, Vm, Vy) for each ink color (C, Bk, M, Y) = large droplet (20 pl) × a droplet + medium droplet (10 pl) × b droplet + small droplet (2 pl) × c drop ・ ・ ・ Formula (1)
Total ink consumption of input image = Vc + Vbk + Vm + Vy (2)
In accordance with the above, the ink usage amount of the image input this time is calculated.
Here, since the accumulated ink usage amount (Ia) is obtained, the calculated accumulated ink usage amount of the input image is added to the accumulated amount so far (step S106-5).

Thereafter, a printing operation is performed using the image data input this time (step S106-6).
Further, when this printing operation is performed, the number of idle ejections performed during the operation is acquired for each ink color (step S106-7). In the idle ejection, ink is ejected in addition to the printing of the input image. Therefore, it is necessary to count this number and reflect it in the accumulated ink usage.
Further, an empty ejection amount for each ink color (for example, C: 1000 pl, Bk: 1000 pl, M: 1000 pl, Y: 1000 pl) is acquired from a previously stored storage medium (step S106-8).
Next, the ink consumption amount due to idle ejection is calculated (step S106-9). This process is calculated based on the count value of the number of empty ejections for each ink color obtained in step S106-7, the empty ejection amount for each ink color obtained in step S106-8, and the correction coefficient.

The correction coefficient is a coefficient for adjusting the mist amount at the time of idle ejection to the mist amount estimated from the ink use amount at the time of normal printing. In normal printing, since most ink is placed on paper that is not far from the head, it is difficult for mist to occur. However, a large amount of empty ejection is performed at once to a waste liquid tank that is located far from the head. Since the ink is discharged, mist is likely to occur. For this reason, even when the number of ink drops during normal printing and the number of ink drops during idle ejection are the same, more mist is generated during idle ejection. This is a necessary correction. This correction coefficient is obtained from experiments and stored in advance in a storage medium.
For example, the amount of ink used by the idle ejection of the current printing operation after correction is calculated by the following equation (3):
Empty discharge ink usage = {C (1000 pl) × Number of empty discharges + Bk (1000 pl) × Number of empty discharges + M (1000 pl) × Number of empty discharges + Y (1000 pl) × Number of empty discharges} × Coefficient (3) )
According to the calculation.
Here, since the accumulated ink usage amount (Ia) is obtained, the calculated ink usage amount due to the idle ejection is added to the accumulated amount so far (step S106-10).
After calculating the accumulated ink use amount (Ia), the process exits this subroutine and returns to the main routine of FIG.

“Calculation of remaining life”
After calculating the current accumulated ink use amount (Ia) in step S106, the light amount (limit light amount) detected in step S105 when the missing pulse is detected is paired with the ink accumulated use amount calculated in step S106. The data is stored in the storage medium by the storage unit 83 (step S107). Since this storage process is performed every time this control flow is executed, a history of the amount of light stored in pairs and the accumulated ink use amount is accumulated in the storage medium.
Next, the process proceeds to a processing procedure for calculating the remaining life from the current detection state of the encoder, that is, the state represented by the limit light amount and the ink usage amount obtained in step S105.
The remaining life calculated here is obtained as a predicted life function from the history of the limit light amount and the accumulated ink use amount stored for the storage medium by the storage unit 83, and the current state is obtained based on the obtained predicted life function. The amount of ink that can be used until the limit light amount detected in step 1 reaches a predetermined life (use limit) light amount is expressed as an integrated amount of ink. That is, the difference (Ie−Ia) between the ink cumulative usage amount (Ie) corresponding to the usage limit light amount and the current ink cumulative usage amount (Ia) is calculated as the remaining life.

A process procedure of life prediction and remaining life calculation performed by the remaining life prediction calculating means 85 will be described based on the control flow of FIG.
According to the flow of FIG. 3, first, all the history of the accumulated ink use amount paired with the limit light amount stored in the storage medium (the light source amount when the missing pulse is detected in step S104) is acquired (step S104). S108).
Next, an approximate curve (predicted life function) representing the relationship between the limit light amount and the integrated ink use amount is calculated from the entire history information of the integrated ink use amount paired with the limit light amount acquired in the previous stage (step S109).

A method of calculating the approximate curve (predicted life function) will be described with reference to FIG.
In the graph shown in FIG. 7, the limit light amount (the light source light amount when the missing pulse is detected in step S104) is taken on the Y axis, and the integrated ink use amount (ml) is taken on the X axis. Each time the control flow shown in FIG. 3 is executed from the initial state where the accumulated ink use amount is 0, pulse missing is detected (step S104), and the relationship between the limit light amount obtained as a detection result and the accumulated ink use amount is shown in FIG. As shown in the black circle inside.
The graph of FIG. 7 shows an example represented by a function approximated by a curve described in FIG. 7 from the entire history of detection results of missing pulses from the initial state (all black circle samples). By calculating this approximate curve, the relationship between Y (limit light amount) and X (cumulative ink use amount) is expressed as a function, so that the use limit that will be reached can be predicted if the use is continued. . Here, the use limit value (light quantity) corresponding to the lifetime is experimentally determined in advance, and the ink use amount at the intersection of the approximate curve and the light use limit value is obtained, whereby the use limit is determined by the ink accumulation quantity Ie. Can be represented.

Here, another calculation method applicable instead of the approximate curve calculation method shown above with reference to FIG. 7 will be described with reference to FIG.
The graph shown in FIG. 8 performs pulse omission detection every time the control flow shown in FIG. 3 is executed, and the relationship between the obtained limit light quantity and the accumulated ink use amount is indicated by black circles in FIG. Then, it is not different from the above calculation method (see FIG. 7).
However, in the method shown in FIG. 8, the range of the history used for prediction is limited not to the entire history shown in FIG. In other words, as shown in FIG. 8, it is limited to a part of the range from the latest sample indicated by the current value to the time when X (cumulative ink use amount) is in a state where the predetermined value is small, Prediction is performed using (indicated by white circles). As shown in the example of FIG. 8, when the light amount approaches the use limit, the change in the limit light amount with respect to the ink cumulative use amount tends to gradually decrease. When the range is limited, prediction is made based on the entire history of FIG. 7. Life expectancy is longer than if
According to this approximate curve calculation method, even when the encoder scale or sensor is soiled by ink mist or the like, and the detection sensitivity of the encoder approaches the limit over time, more accurate life prediction can be performed.

Returning to the flow of FIG. 3, after calculating the approximate curve (predicted life function) in step S109, the predicted life is calculated as the integrated ink usage (Ie) based on the calculated predicted life function (step S110). That is, as described with reference to FIGS. 7 and 8, the estimated life value is represented by the ink integrated amount Ie by obtaining the ink integrated usage amount at the intersection of the predicted approximate curve and the light amount usage limit value.
Next, the prediction result is notified to the user or the like (step S111). Here, instead of simply notifying the estimated ink usage amount Ie predicted at the time of use limit, as the remaining life, the amount of ink that can be used until the use limit is reached is indicated by the cumulative amount of ink used. As the usable ink usage amount, the difference (Ie−Ia) between the ink cumulative usage amount (Ie) corresponding to the usage limit light amount and the current ink cumulative usage amount (Ia) is obtained. The obtained amount is displayed through a display screen of an operation panel (not shown) as the notification means 101. It should be noted that the recording paper may be notified by a method of indicating how many sheets of output of the standard chart correspond to the usable ink usage amount.
Thereafter, in order to wait in the initial state, the process returns to step S101 for initializing the light amount of the light emitting unit 129e of the sensor 129 controlled by the encoder life check operation.

  As described above, the encoder scale and sensor are soiled by ink mist, etc., and the detection sensitivity of the encoder decreases with time, predicts the lifetime reaching the use limit, and has the function of notifying the user of the remaining lifetime, Encoder replacement can be performed by selecting an appropriate time before the end of the encoder's life, so between the occurrence of an encoder signal error (missing pulse) and the replacement of the encoder with print output interrupted or waiting. Can avoid the inconvenience caused by the prior art that causes downtime.

"Control Flow II"
In the control flow I of the encoder life check, the basic form of the life check process is shown, but in this embodiment, the processing procedure of the control flow I is improved.
In the present embodiment, the life prediction and remaining life calculation processes are performed in the same manner as in the control flow I. However, when there is no point in performing these processes, an improvement is made to provide a procedure that allows the processes to be omitted. .
Here, as a condition for omitting the processing, at the beginning of using the encoder, dirt due to ink mist and the like hardly affects the error of the encoder output signal, and bears the processing load of life prediction and remaining life calculation. Until then, there is no point in informing the user or the like of the remaining life of the encoder.

Therefore, in the present embodiment, the limit light quantity indicating the current detection state of the encoder, that is, the light source light quantity of the encoder sensor is gradually lowered to lower the detection sensitivity, and the light quantity when the missing pulse is detected (the flow in FIG. 3). Steps S103 to S105 in FIG. 5) are acquired, and it is confirmed whether or not the acquired limit light amount is larger than a predetermined value. As a result, if the limit light amount is less than the predetermined value, life prediction and remaining life Allow calculation to be omitted. Note that the predetermined value needs to be determined by a numerical value corresponding to the amount of light by experimentally confirming in advance a period during which the encoder life check is not required.
However, even if life prediction and remaining life calculation are omitted, the current encoder detection state, that is, the detection state represented by the limit light amount and the total ink use amount, must be kept as a history. Even if the remaining life calculation is omitted, the processing procedure until the history is left is performed in the same manner as in the control flow I.

FIG. 9 is a diagram showing a control flow II of the encoder life check of this embodiment.
In the control flow shown in FIG. 9, step S208 is a newly added step.
Note that steps S201 to S207 and steps S209 to S212 other than step S208 correspond to steps S101 to S111 of the control flow I (FIG. 3), and the processing of each step is the same. Therefore, for these control flows, reference is made to the description of the control flow I (FIG. 3), description thereof is omitted, and only operations related to step S208 will be described below.
Through steps S201 to S207, the limit light quantity when the missing pulse is detected is acquired as data representing the current detection state of the encoder (step S205), and the current accumulated ink use amount is acquired in parallel (step S206). Then, the acquired limit light amount and the accumulated ink use amount are paired and stored in the storage medium (step S207).

Thereafter, it is determined whether or not the limit light amount acquired in step S205 is larger than a predetermined value that is predetermined in order to omit processing such as remaining life calculation (step S208).
Here, when the limit light amount is larger than the predetermined value (step S208-YES), the process of calculating the remaining life is performed based on the determination that the ink mist has been attached and the time for checking the encoder life has come. The process proceeds to step S209.
On the other hand, if the limit light amount is less than the predetermined value (step S208-NO), the process of calculating the remaining life is omitted based on the judgment that the ink mist is hardly attached and it is not time to check the encoder life. Then, in order to wait in the initial state, the process returns to step S201 for initializing the light amount of the light emitting unit 129e of the sensor 129 controlled for the operation of detecting the missing pulse.
As described above, by adding step S208, since the amount of ink used is small at the beginning of using the encoder, it is not necessary to calculate the remaining life until the processing burden is imposed, and pulse missing detection is performed. If the number of data at the time is small, the prediction accuracy by the prediction life function is not high and an error occurs. Therefore, processing such as remaining life calculation at this time can be omitted, and the performance can be optimized according to the state of the encoder .

"Control Flow III"
In the control flow I of the encoder life check, the basic form of the life check process is shown, but in this embodiment, a part of the process procedure of the control flow I is changed.
In this embodiment, similarly to the control flow I, the process of life prediction and remaining life calculation is performed to notify the user of the remaining life, but the notification method is changed.
In the control flow I, the calculated remaining life is notified to the user. In this case, the user knows the remaining life, so that the user can not know the clear near end although it is a guideline for determining the near end time when the encoder needs to be replaced.

Therefore, in this embodiment, the notification to the user is performed at the time when the near end is reached, so that the notification is surely made without missing the replacement time of the encoder.
In the present embodiment, whether or not the near end has been reached is confirmed by checking whether or not the calculated remaining life is greater than a predetermined value. As a result, if the remaining life is less than the predetermined value, the near end can be notified. To. The predetermined value is experimentally confirmed in advance to determine how much ink is used until the end condition for stopping the image forming operation is reached, and compared with the calculated remaining life. It is necessary to set a numerical value that can be determined.
This numerical value may be calculated as the amount of ink used by determining how many standard charts can be passed from the number of ink droplets used in a standard chart (for example, J1 chart). In addition, by dividing the cumulative number of sheets passed from the cumulative amount of ink used, the average of the amount of ink used per user is calculated, and the number of sheets that can be used by the user is determined from the average value. It may be calculated as a quantity. In this case, the near-end notification content may indicate that the end is near-end, and the number of sheets passed after that will stop, indicating that the encoder needs to be replaced.

FIG. 10 is a diagram showing a control flow III of the encoder life check according to this embodiment.
In the control flow shown in FIG. 10, steps S311 and S315 are newly added steps.
Steps S301 to S310 other than steps S311 and S315 correspond to steps S101 to S110 of the control flow I (FIG. 3), and the processing of each step is the same, and step S312 is replaced with step S111. . Therefore, steps S301 to S310 in the control flow of FIG. 10 are referred to the description of the control flow I (FIG. 3), the description is omitted, and only operations related to steps S311, S312 and S315 are described below. explain.

After calculating the ink integrated usage amount Ie predicted at the use limit in step S310, the prediction result is notified to the user or the like. Here, the ink integrated usage amount Ie predicted at the use limit is not simply notified. As the remaining life, the amount of ink that can be used until the use limit is reached is indicated by the cumulative amount of ink used. This usable ink usage amount is represented by a difference (Ie−Ia) between the ink usage amount (Ie) corresponding to the light amount of the usage limit and the current ink usage amount (Ia). Further, it is determined whether or not the usable ink usage amount (Ie−Ia) is smaller than a predetermined value that is determined in order to determine whether or not the near end has been reached (step S311).
Here, when the accumulated ink use amount (Ie−Ia) that can be used is smaller than a predetermined value (step S311—YES), the near-end notification is issued based on the determination that the ink mist has progressed and the near-end has been reached. The process proceeds to step S312 to be performed.
The near-end notification notifies the user of the near-end and, as the remaining life, for example, how many sheets are to be stopped after that, and a message prompting the replacement of the encoder through the operation panel (not shown). S312).
After notifying the near end, in order to wait in the initial state, the process returns to step S301 for initializing the light amount of the light emitting unit 129e of the sensor 129 controlled for the operation of detecting missing pulses.

On the other hand, if the accumulated ink use amount (Ie-Ia) that can be used is equal to or greater than a predetermined value (step S311-NO), the near end has not been reached, so if the near end notification flag is set, this flag is canceled. (Step S315). The near-end notification flag is set when performing near-end notification based on the determination in step S311 based on the determination that the near-end has been reached. If the near-end notification flag is set, the near-end notification is performed in step S312. . However, after setting the near-end notification flag, the judgment of the encoder life check performed at the next execution timing may be reversed due to, for example, an error in detection of missing pulses, etc. When a determination is made, it is necessary to release the flag that has been set up so far.
After canceling the near-end notification flag, in order to wait in the initial state, the process returns to step S301 for initializing the light amount of the light emitting unit 129e of the sensor 129 that is controlled for the operation of detecting missing pulses.
By adding steps S311 and S312 as described above, the encoder can be reliably replaced at an appropriate encoder replacement time by notifying the user or the like that the encoder replacement time is near.

"Control Flow IV"
In the control flow I of the encoder life check, the basic form of the life check process is shown, but in this embodiment, a part of the processing procedure of the control flow I is changed. The near end notifying step common to the control flow III, and further, as a measure accompanying the near end notifying, are steps of performing a process of increasing the light source light amount of the encoder sensor from the current state in order to extend the use limit.
That is, in the control flow IV of the present embodiment, similarly to the control flow I, processing for life prediction and remaining life calculation is performed to notify the user of the remaining life. However, the remaining life notification method is the same as in the control flow III above, whether or not the near end has been reached, whether or not the calculated remaining life is greater than a predetermined value, and as a result, the remaining life is predetermined. If it is less than the value, the near end can be notified. Further, as a procedure peculiar to the control flow IV, a process for increasing the light amount of the light source of the encoder sensor from the current state is performed at the end of the control flow in association with the near-end notification.
This termination processing increases the light amount of the light source of the encoder sensor from the current state. The amount of light to be increased may be set to a target corresponding to the use limit value (light amount value when reaching the lifetime shown in FIGS. 7 and 8). This process does not respond to near-end notification, and is intended to use up the encoder to the end of its life even when the encoder is not replaced.

FIG. 11 is a diagram showing a control flow IV of the encoder life check according to this embodiment.
The control flow IV shown in FIG. 11 basically performs the same processing as the control flow III shown in FIG. 10, but steps S412 and S413 performed at the end of the control flow IV are procedures specific to the flow.
Note that steps S401 to S411 other than steps S412 and S413 correspond to steps S301 to S311 of the control flow III (FIG. 10), and the processing of each step is the same. Therefore, steps S401 to S411 in the control flow of FIG. 11 are referred to the description of the control flow III (FIG. 10), description thereof is omitted, and only operations related to steps S412 and S413 will be described below. .

After calculating the ink integrated usage amount Ie predicted at the use limit in step S410, the prediction result is notified to the user or the like. Here, the ink cumulative usage amount Ie predicted at the use limit is not simply notified. As the remaining life, the amount of ink that can be used until the use limit is reached is indicated by the cumulative amount of ink used. This usable ink usage amount is represented by a difference (Ie−Ia) between the predicted ink usage amount (Ie) corresponding to the usage limit light amount and the current ink usage amount (Ia). Furthermore, it is determined whether or not the usable ink usage amount (Ie−Ia) is smaller than a predetermined value that is determined in order to determine whether or not the near end has been reached (step S411).
Here, when the accumulated ink use amount (Ie−Ia) that can be used is smaller than a predetermined value (step S411—YES), the near-end notification is issued based on the determination that the ink mist has progressed and the near-end has been reached. The process proceeds to step S412 to be performed.

The near-end notification notifies the user of the near-end, and as a remaining life, for example, notifies the user through an operation panel (not shown) of how many sheets are to be stopped after that, and a message prompting the user to replace the encoder (step not shown). S412).
After notifying the near end, the light quantity of the light source of the encoder sensor is increased from the current state (step S413). By performing this processing, the detection sensitivity of the sensor is increased, and pulse omission is less likely to occur than in the current situation. Therefore, the use limit can be extended as compared to operating with the current light source light amount. If the amount of light is increased to an amount corresponding to the use limit value (the amount of light when reaching the life shown in FIGS. 7 and 8), the encoder can be used up to the end of its life.

On the other hand, when the accumulated ink use amount (Ie-Ia) that can be used is equal to or larger than the predetermined value (step S311-NO), since the near end has not been reached, the operation for detecting missing pulses is performed in order to wait in the initial state. The process returns to step S401 for initializing the light amount of the light emitting unit 129e of the sensor 129 controlled to.
As described above, by adding steps S412 and S413, the light amount of the light source of the encoder sensor is increased from the current state in association with the near-end notification, so that the encoder can be replaced at an appropriate encoder replacement time notified by the user or serviceman. If the replacement is not performed, the life of the encoder can be extended by the increased amount.

  60..Encoder, 61..Light quantity changing means, 70..Pulse missing detection means, 81..Integrated ink use amount calculating means, 83..Storage means, 85 .... Remaining life prediction calculating means, 128..Encoder scale 129 .. Encoder sensor.

JP 2005-349799 A JP 2004-138386 A

Claims (11)

The position of the image forming unit moving on the recording surface in the scanning direction is detected by an encoder that receives light from a scale illuminated by a light source capable of controlling the amount of light and outputs a position signal, and based on the detected position signal An image forming apparatus that controls movement of the image forming unit and forms an image using ink on a recording surface,
Output abnormality detection means for detecting whether or not the position signal output of the encoder is abnormal;
An abnormality detection control means for detecting the position signal output of the encoder by the output abnormality detection means while reducing the light amount of the light source of the encoder, and acquiring the light source light quantity when an abnormality is detected in the position signal output;
An ink cumulative usage calculation means for calculating the cumulative usage of ink;
A storage unit that stores a light amount acquired by the abnormality detection control unit at the time of an abnormal signal output in the encoder and an ink integrated usage amount calculated by the ink integrated usage amount calculation unit at that time;
Relationship prediction means for predicting the relationship between the accumulated amount of ink used and the amount of light source based on the history of the amount of light source and the accumulated amount of ink stored stored in the storage means;
Based on the relationship between the accumulated ink usage amount and the light source light amount predicted by the relationship predicting means, the remaining lifetime for calculating the remaining life of the encoder until the currently detected light source light amount reaches the light source light amount at a predetermined use limit. An image forming apparatus comprising a calculating unit. The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein the relationship prediction unit performs prediction again each time the abnormality detection control unit acquires the light amount of the light source. The image forming apparatus according to claim 1,
The relationship predicting unit performs prediction when the light source light amount acquired by the abnormality detection control unit is equal to or greater than a predetermined light amount in a history storage state in which a prediction error can be suppressed within a predetermined range. An image forming apparatus. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus according to claim 1, wherein the relationship predicting unit uses only a portion close to the present in the history stored in the storage unit for prediction. The image forming apparatus according to claim 1,
Near end check means for checking whether the remaining life calculated by the remaining life calculation means has reached a value corresponding to a predetermined near end;
An image forming apparatus comprising: a means for informing the near end on condition that the near end is checked by the near end check means. The image forming apparatus according to claim 1,
Near end check means for checking whether the remaining life calculated by the remaining life calculation means has reached a value corresponding to a predetermined near end;
An image forming apparatus, comprising: a control unit that increases a light amount of the light source of the encoder more than a current condition on the condition that the near end is checked by the near end check unit. The image forming apparatus according to any one of claims 1 to 6,
The image forming unit has a recording head for discharging ink droplets,
The image forming apparatus according to claim 1, wherein the integrated ink use amount calculation unit multiplies a predetermined correction coefficient when calculating the ink use amount during idle ejection. The image forming apparatus according to any one of claims 1 to 7,
The remaining life calculating means obtains a predicted integrated usage amount of ink corresponding to the light source light amount at the usage limit based on the relationship between the predicted accumulated ink usage amount and the light source light amount, and calculates the estimated cumulative usage amount of the obtained ink and the current obtained amount. An image forming apparatus that calculates a difference from the obtained accumulated ink use amount as an amount representing a remaining life. The position of the image forming unit moving on the recording surface in the scanning direction is detected by an encoder that receives light from a scale illuminated by a light source capable of controlling the amount of light and outputs a position signal, and based on the detected position signal An encoder life prediction method for controlling the movement of the image forming unit and predicting the remaining life of the encoder in an image forming apparatus that forms an image using ink on a recording surface,
An output abnormality detection step of detecting whether or not the encoder position signal output is abnormal while reducing the light source light amount of the encoder;
An abnormality detection light amount acquisition step of acquiring a light source light amount when an abnormality is detected in the encoder signal output in the output abnormality detection step;
An ink cumulative usage calculation step for calculating the cumulative usage of ink;
A storage step of storing a pair of the light amount acquired in the abnormality detection light amount acquisition step and the ink integrated usage amount calculated in the ink integrated usage amount calculation step at that time;
A relationship prediction step of predicting the relationship between the accumulated amount of ink used and the amount of light source of the light source based on the history of the amount of accumulated light and the accumulated amount of ink used stored in the storage step;
Based on the relationship between the accumulated ink usage amount and the light source light amount predicted by the relationship prediction step, the remaining life calculation step for calculating the remaining life until the currently detected light source light amount reaches the light source light amount at a predetermined use limit. An encoder life prediction method characterized by comprising:   The program for making a computer perform each process of the encoder lifetime prediction method described in Claim 9.   A computer-readable recording medium on which the program according to claim 10 is recorded.

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