JP2006138942A - Fixing drive controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing drive controller capable of precisely controlling a peripheral speed of a heating/pressing roller according to simple arithmetic processing by storing a relation between the change of roller diameter due to thermal expansion of a heating roller and the number of printing accumulation sheets as a control data corresponding to elapsed time after using the controller to a control table beforehand. <P>SOLUTION: Rotation drive of the heating roller is controlled such that the peripheral speed of the heating roller has a predetermined speed difference with respect to the form conveyance speed from a transfer process up to a fixing process at all times. Specifically, the fixing drive controller is provided with the control table in which the change data of roller diameter of the heating roller based on the number of used years of an image forming apparatus and the number of printing accumulation sheets corresponding to the number of used years is stored. A control means controls the initial peripheral speed of the heating roller at an arbitrary peripheral speed in the range of the form conveyance speed of 100.5% to 103.0% on the basis of the change data of roller diameter of the heating roller stored in the control table and controls the peripheral speed of the heating roller thereafter in the range of ±0.5% with respect to the initial peripheral speed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a facsimile apparatus, and a printer, and more particularly, to a fixing drive control apparatus for a fixing apparatus including heating and pressure rollers.

  A fixing device used in an image forming apparatus usually employs a heat fixing roller system, and includes a heating roller, a pressure roller, a cleaning member, an oil application member, a temperature detection member, a paper separation claw, and the like.

  The heating roller has a heat generation source inside the roller, and the temperature of the roller surface is controlled by the amount of heat of the heat generation source so that it becomes a temperature necessary for fixing the unfixed developer on the paper to the paper. ing. In addition, the pressure roller is pressed against the heating roller at a predetermined pressure, and the sheet having unfixed developer passes through the pressure contact portion (nip portion), so that the developer is melted by the amount of heat and pressure from the heating roller. Let it settle.

  Such a heating / pressurizing roller usually has an elastic member such as silicone rubber to ensure the heat of heat generated from the heat source and the nip region at the pressure contact portion (nip portion). It is arranged on the surface of either or both of the pressure rollers.

  Also, in order to prevent unfixed developer on the conveyed paper from adhering to the heating roller when it melts at the nip, a method of applying silicon oil or the like to the surface of the heating / pressure roller is used. It has been.

  In the fixing device having such a configuration, when a heat history is received, a roller made of silicon rubber or the like swells with oil and expands over time as compared with the initial state. FIG. 7 shows the degree of expansion, and shows the change in the roller diameter of the heating roller with respect to the cumulative number of prints. Here, the total number of printed sheets is the total number of printed sheets corresponding to the number of years of use. In the figure, the graph indicated by a broken line is a graph showing the change when printing 40000 sheets in one year, and the graph indicated by a solid line is 4 is a graph showing a change when 40000 sheets are printed in 2 years.

  As can be seen from the figure, the change in the roller diameter of the heating roller decreases as the frequency of use increases, and the change in the roller diameter when printing the same 40,000 sheets in one year is 40,000,000. In contrast to the expansion of about 0.6 mm from φ50 mm to φ50.6 mm, the change in roller diameter when printing 40,000 sheets in two years is only about 0.3 mm from φ50 mm to φ50.3 mm. The reason why such a difference appears due to the difference in the number of years after the start of use even with the same number of printed sheets is as follows.

  In other words, even when the image forming apparatus is not used, for example, when the facsimile function is installed, the heating roller is always in a waiting state for reception, and the heating roller is always kept by a heat source. It is in a preheated state. In this case, if printing is frequently performed, the heat accumulated in the heating roller and the pressure roller due to the printing operation is frequently taken away to the paper side, so that the influence of heat can be reduced accordingly. . That is, the higher the frequency of use of the apparatus, the less likely the heating roller is affected by the expansion of the roller diameter due to heat. The experimental results shown in FIG. 7 are exactly what proves this.

  In the fixing process, when the roller diameter expands as described above, the peripheral speed of the fixing roller (heating / pressure roller) becomes faster than the paper transport speed (process speed), and the transported paper is pulled by the fixing roller. Phenomenon occurs. Accordingly, at the rear end portion of the sheet, the sheet is pulled when the transfer process is being performed, and a transfer shift (image shift) occurs.

  As a means for solving such a problem, for example, a fixing device described in Patent Document 1 has been proposed.

  This fixing device utilizes the fact that when the heating roller is thermally expanded, the heating roller not only expands in the radial direction but also extends in the axial direction. That is, the heating roller is supported at a fixed position with respect to the right side plate, and is supported so as to be expandable and contractable in the axial direction with respect to the left side plate. A drive V pulley and a V belt are provided at the expandable left end portion. A V-pulley that is drivingly connected via the shaft is fixed. The drive V pulley is divided into two at a plane perpendicular to the axis of the drive shaft and substantially at the lowest point of the V-shaped groove, and the left half moves in the direction of the axis via a ring provided on the drive shaft. It is configured to be installed.

  According to the fixing device having such a configuration, when the diameter of the heating roller is increased due to thermal expansion, the length in the axial direction is increased, and the left end portion of the heating roller supported by the left side plate extends to the left. For this reason, the left half of the V pulley divided into two parts also moves to the left and the V groove becomes wider. As a result, the V belt falls into the groove, and the rotational speed ratio between the driving V pulley and the V pulley changes. The rotational speed of the drive V pulley decreases, the rotational speed transmitted to the heating roller decreases, and the peripheral speed of the heating roller decreases.

  On the other hand, the problem that the heating roller diameter expands is a problem that occurs when silicon oil is applied to the surface of a heating roller made of silicon rubber or the like. In a non-oil type fixing device that does not apply silicon oil to the surface, On the contrary, the phenomenon that the roller diameter of the heating roller contracts by receiving a history for a long time appears.

  FIG. 8 shows the degree of contraction, and shows the change in the roller diameter of the heating roller with respect to the cumulative number of printed sheets. Here, the cumulative number of printed sheets is the cumulative number of printed sheets corresponding to the number of years of use, as in the case of FIG. 7, and the graph indicated by the broken line in the figure shows the change when printing 40,000 sheets in one year. A graph and a graph indicated by a solid line are graphs showing changes when 40000 sheets are printed in 2 years.

As can be seen from the figure, the change in the roller diameter of the heating roller decreases as the frequency of use increases, and the change in the roller diameter when printing the same 40,000 sheets in one year is 40,000,000. In contrast to the contraction of about 0.6 mm from φ50 mm to φ49.4 mm, the change in roller diameter when printing 40,000 sheets in two years is only about 0.3 mm from φ50 mm to φ49.7 mm. Even if the number of printed sheets is the same, this difference is caused by the difference in the number of years since the start of use, for the same reason as in the case of the thermal expansion.
JP-A-6-75500

  As described above, the technique of Patent Document 1 has been proposed as a means for solving the problem when the heating roller expands in response to a thermal history. However, the solving means of Patent Document 1 is a mechanical means in which the structure of the drive V pulley and the V pulley is devised, and there is a problem that the mechanism structure becomes complicated. Further, since the peripheral speed of the heating roller is mechanically adjusted, there is a problem that the control accuracy has to be low from the viewpoint of the peripheral speed control of the heating roller.

  Furthermore, the technique of the above-mentioned Patent Document 1 is a solution when the heating roller expands, and as described above, there is also a problem that it cannot be handled at all when the heating roller contracts due to a thermal history.

  The present invention was devised to solve such problems, and its purpose is to control the relationship between the change in the roller diameter due to the thermal expansion of the heating roller and the accumulated number of prints corresponding to the elapsed time after using the apparatus. It is an object of the present invention to provide a fixing drive control device capable of accurately controlling the peripheral speed of the heating / pressurizing roller by simple arithmetic processing by storing the data in a control table in advance.

  In order to solve the above-described problems, a fixing drive control device according to the present invention includes a transfer step of transferring image information formed on an electrostatic latent image carrier onto a sheet using an unfixed developer, and a sheet after transfer. A fixing step of melting and fixing the unfixed developer onto the paper by passing through a pressure contact portion of a fixing device composed of a heating / pressure roller, and a transfer step and a fixing step from a paper feed tray. A fixing drive control device in an image forming apparatus including a transporting process for transporting the paper to a paper discharge tray, wherein a peripheral speed of the heating / pressure roller is a paper transporting speed from the transfer process to the fixing process. The heating / pressure roller is controlled to rotate and control so as to always have a predetermined speed difference.

  Further, in the present invention, the heating roller pressure control based on the circumferential speed control of the heating / pressure roller as described above is based on the number of years of use after the image forming apparatus is installed and the cumulative number of printed sheets of the apparatus corresponding to the number of years of use. This is performed using a control table storing the change data of the roller diameter. That is, the control means controls the rotational driving of the heating / pressure roller so as to achieve the predetermined speed difference based on the change data of the roller diameter of the heating roller stored in the control table.

  Here, the control means controls the initial peripheral speed of the heating / pressure roller at an arbitrary peripheral speed within a range of 100.5% to 103.0% of the paper transport speed. That is, the peripheral speed of the heating / pressure roller is controlled to be slightly higher than the paper conveyance speed conveyed from the transfer process to the fixing process. This prevents the paper from coming into contact with any part other than the nip portion by pulling the paper with the unfixed developer transferred slightly and pulling it into the pressure roller contact portion (nip portion). This is because heat is applied only at the part to fix it.

  In such speed control, in the present invention, the control unit controls the subsequent peripheral speed of the heating roller within a range of ± 0.5% with respect to the initial peripheral speed. The peripheral speed of the heating / pressure roller corresponding to the lower limit value of this range is a control speed that is substantially close to the paper transport speed, and the peripheral speed of the heating / pressure roller corresponding to the upper limit value of this range is the print quality. It is the upper limit control speed to ensure.

  According to the fixing drive control device of the present invention, the change in the peripheral speed due to the expansion or contraction of the roller diameter of the heating roller is controlled by the calculation process using the control table. The peripheral speed of the pressure roller can be controlled with high accuracy.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

-Description of the entire image forming apparatus-
First, the overall configuration of an image forming apparatus in which the fixing drive control device of the present invention is mounted will be described.

  FIG. 1 is an explanatory diagram showing the configuration of the image forming apparatus according to the present embodiment.

  The image forming apparatus 1 uses an image read by an image reading apparatus (an unillustrated built-in unit) or data received from an apparatus (for example, an image processing apparatus such as a personal computer) externally connected to the image forming apparatus 1 as an image. This is an image forming apparatus equipped with a transfer device for recording and outputting, and used for printing a monochrome image (ordinary black printing) for transferring developer (toner) onto a sheet that is sucked and conveyed by an endless belt.

  In the image forming apparatus 1, each process unit responsible for each function for image formation is arranged around the photosensitive drum 3, and an image forming unit is configured by these process units. That is, an image in which a charging unit 5, an optical scanning unit 11, a developing unit 2, a transfer unit (transfer device of claim 6), a cleaning unit 4, a static elimination lamp 12, and the like are sequentially arranged around the photosensitive drum 3. A forming part is provided.

  The charging unit 5 charges the surface of the photosensitive drum 3 uniformly. The optical scanning unit 11 scans an optical image on the uniformly charged photosensitive drum 3 to write an electrostatic latent image. The developing unit 2 visualizes the electrostatic latent image on the photosensitive drum 3 with the developer supplied from the developer supply container 7. The transfer unit 6 transfers the developer image visualized on the photosensitive drum 3 onto the sheet. The cleaning unit 4 removes the developer remaining on the photosensitive drum 3 and enables a new image to be recorded on the photosensitive drum 3. The static elimination lamp 12 removes electric charges on the surface of the photosensitive drum 3.

  Under the image forming apparatus 1, a supply tray 10 that is housed in the main body of the image forming apparatus 1 is disposed.

  The supply tray 10 is a recording material storage tray that stores sheets. The sheets stored in the supply tray 10 are separated one by one by a pickup roller 16 and the like, conveyed to the registration roller 14, and the timing of the transfer process of the image on the photosensitive drum 3 is measured by the registration roller 14 to transfer the sheet. Sequentially supplied between the unit 6 and the photosensitive drum 3. Then, the developer image on the photosensitive drum 3 is transferred onto the sheet. The supply of the sheet to the supply tray 10 is performed by pulling out the supply tray 10 to the front side (operation side) of the image forming apparatus 1.

  On the lower surface of the image forming apparatus 1, sheets sent from a device having a multi-stage sheet supply tray (not shown) prepared as a peripheral device and a large-capacity recording material supply device capable of storing a large amount of sheets are provided. A sheet receiving port 17 for receiving and sequentially supplying sheets toward the image forming unit is provided.

  A fixing device 8 is disposed in the upper part of the image forming apparatus 1. The fixing device 8 employs a heat fixing roller system, which sequentially receives sheets on which images have been transferred, and is transferred onto the sheet by heat and pressure by a fixing roller (heating roller) 81 and a pressure roller 82. The image of the developed developer is fixed. As a result, the developer image is fixed on the sheet.

  The sheet on which the image is fixed is conveyed further upward by the conveying roller 25, passes through the switching gate 9, and is discharged to the stacking tray 15 by the reverse roller 26.

  In the upper and lower space portions of the optical scanning unit 11, a control unit 90 for accommodating a circuit board for controlling the image forming process, an interface board for receiving image data from an external device, and the like, various interface boards, and each of the images A power supply device 91 and the like that supply power to each unit that performs the formation are disposed.

  FIG. 2 is an explanatory diagram showing the internal structure of the fixing device 8 in more detail.

  That is, a cleaning roller 84, a temperature detection thermistor 85, and an oil application roller 86 that applies oil to the surface of the heating roller 81 are disposed around the heating roller 81 including a fixing heater 83 that is a heat source. A paper separation claw 87 for separating the paper from the rollers is provided above the heating roller 81 and the pressure roller 82.

  FIG. 3 is a functional block diagram showing the configuration of the main part of the control unit 90.

  The control unit 90 has an image information receiving unit 912, a document reading unit 913, an image processing unit 914, an operation unit (input / display unit) 915, a driving unit 916, and a paper feeding unit 917 around a CPU 911 which is a central processing unit. , A printing unit 918, a paper discharge unit 919, a post-processing unit 920, a fixing control unit 921, a timer unit 922 for measuring an elapsed time after installation of the image forming apparatus, and the like. The counter unit 923 and the like are included. The fixing control unit 921 also controls a fixing driving unit 9211 that controls the peripheral speeds of the heating roller 81 and the pressure roller 82, and a fixing temperature control unit 9212 that controls the temperature of the heating roller 81 (that is, controls the energization of the fixing heater). Etc. The drive unit 916 takes charge of control other than the peripheral speed control of the heating roller 81 and the pressure roller 82 by the fixing drive unit 9211. Specifically, control of the image forming unit centering on the photosensitive drum 3, control of the optical scanning unit 11, and control of paper conveyance from the paper feed tray 10 to the stacking tray 15 are performed. That is, in the present embodiment, the driving source of the fixing device 8 and the driving source other than the fixing device 8 are configured by separate driving.

-Description of drive control by the fixing drive unit 9211 which is the fixing drive control device of the present invention-
In the present embodiment, the fixing driving unit 9211 rotates the heating roller 81 so that the peripheral speed V1 of the heating roller 81 always has a predetermined speed difference with respect to the sheet conveyance speed V2 from the transfer unit 6 to the fixing device 8. Drive control is performed. Specifically, the fixing driving unit 9211 sets the peripheral speed V1 of the heating roller 81 within a range of 100.5% to 103.0% of the sheet conveyance speed V2 (V2 × 1.005 <V1 <V2 × 1. 03). That is, the peripheral speed V1 of the heating roller 81 is controlled to be slightly higher than the sheet conveyance speed V2 conveyed from the transfer unit 6 to the fixing device 8 (V1> V2).

  In such speed control, in this embodiment, the predetermined speed difference (difference of 0.5% to 3.0% with respect to V2) is set to ± the set speed difference set with respect to the paper transport speed V2. Within the range of 0.5%. The circumferential speed V1 (Lo) of the heating roller 81 corresponding to the lower limit value of this range is a control speed that is substantially equal to the sheet conveying speed V2, and the circumferential speed V1 (Hi) of the heating roller corresponding to the upper limit value of this range. Is the upper limit control speed that guarantees the print quality. That is, when the peripheral speed V1 (Hi) is exceeded, the leading edge of the sheet is strongly pulled by the fixing device 8, and the trailing edge of the sheet remaining in the transfer unit 6 is pulled, which may cause a transfer shift (image shift). Because it becomes higher.

  In the present embodiment, such a peripheral speed control of the heating roller 81 is performed by changing the roller diameter of the heating roller 81 based on the years of use after the image forming apparatus is installed and the accumulated number of prints of the apparatus corresponding to the years of use. This is done using a control table that stores data. This control table is stored in advance in an internal memory (not shown) of the CPU 911, for example. The roller diameter change data stored in the control table is data obtained through experiments.

 Hereinafter, Example 1 of fixing drive control by the fixing drive control device of the present embodiment will be described.

  FIG. 4 is an explanatory diagram showing the contents of the roller diameter change data stored in the control table as a graph. However, the control table shown in FIG. 4 is an example when the diameter of the heating roller 81 expands with time. The graph shown in FIG. 4 is the same as the graph shown in FIG. 7 described in the section of the background art, and in order to simplify the description, a graph (printed with a broken line) when 40,000 sheets are printed in one year. Only two types of change data are shown: 42 and a graph (graph indicated by a solid line) 41 when 40 million sheets (that is, 20000 sheets per year) are printed for two years. However, actually, the change data classified in more detail is stored in the control table.

  Specifically, for example, on the basis of one year, a graph in which 2500 sheets are printed in one year, a graph in which 5000 sheets are printed in one year, a graph in which 7500 sheets are printed in one year, 1 A graph in which the number of printed sheets is changed by 2500 sheets per year is prepared, such as a graph for printing 10,000 sheets per year. For example, when 8500 sheets are printed per year, the change in the roller diameter by calculation from the graph when printing 7500 sheets per year and the graph when printing 10,000 sheets per year ( What is necessary is just to obtain | require expansion part. Or you may use the data of the graph of the nearer simply as it is.

  Here, the inventors set the paper transport speed V2 to about 149.25 mm / sec, and the initial peripheral speed V1 of the heating roller 81 is about 150 mm / sec (≈100.5% of the paper transport speed V2). 149.25 × 1.005), a printing experiment to meet two types of conditions when printing 400,000 prints per year and 40,000 prints per year (that is, 20000 prints per year) Went. Here, for convenience of explanation, the initial peripheral speed V1 of the heating roller 81 is a speed at which the heating roller 81 having a diameter of 50 mm rotates once per second. That is, 50 × π≈150 mm / sec. However, in the first embodiment, calculation is performed with π = 3. The results of this experiment are shown in Table 1.

表１に示すように、加熱ローラ８１のローラ径が４９．７５φｍｍ以下（つまり、加熱ローラ８１の周速度が約１４９．２５（＝４９．７５×π）ｍｍ／ｓｅｃ以下では、用紙の撓みが発生し、ローラ径が５０．２５φｍｍ以上（つまり、加熱ローラの周速度が約１５０．７５ｍｍ／ｓｅｃ）では、用紙搬送速度Ｖ２と加熱ローラ８１の周速度Ｖ１とに差が有り過ぎて用紙が必要以上に引っ張られ、転写部で画像ずれが発生した。

As shown in Table 1, when the roller diameter of the heating roller 81 is 49.75 φmm or less (that is, when the peripheral speed of the heating roller 81 is about 149.25 (= 49.75 × π) mm / sec or less), the sheet is bent. When the roller diameter is 50.25φ mm or more (that is, the peripheral speed of the heating roller is about 150.75 mm / sec), the paper conveyance speed V2 and the peripheral speed V1 of the heating roller 81 are too different, and the paper is necessary. As a result, the image was displaced at the transfer portion.

  Therefore, based on the results of Table 1, in the control table shown in FIG. 4, the upper limit value of the control range is set to 50.25 φmm (150.75 mm / sec as the peripheral speed) by changing the roller diameter. Note that the roller diameter 50.125 mm (peripheral speed 150.375 mm / sec), which is the lower limit value of the control range A shown in FIG. 4, is a value that takes into consideration the safety factor, and is the best control speed for the image forming apparatus. . However, based on the results of Table 1 above, the control range A shown in FIG. 4 may be in the range of 49.75 φmm to 50.25 φmm.

  Next, fixing drive control using the control table shown in FIG. 4 will be described with reference to the flowchart shown in FIG.

  The image forming apparatus equipped with the fixing drive control device of the present embodiment always measures the elapsed time from the start of use as a product by the timer unit 922, and each time printing is performed by a print request, the counter unit By 923, the number of printed sheets is accumulated.

  In the standby state in the process of performing such a printing operation, if there is a print request to the CPU 911 (step S1), the CPU 911 checks the elapsed use start time (device history) and the accumulated number of prints ( Step S2). Then, referring to the control table shown in FIG. 4, it is necessary to check the current control speed (circumferential speed) of the heating roller 81 by the fixing driving unit 9211 (step S3), and to change the peripheral speed of the heating roller 81. It is determined whether or not there is (step S4).

  Here, for example, if the elapsed time is 3 months and the cumulative number of printed sheets at this time is 5000 sheets, the actual operation of the apparatus follows the graph 42 indicated by the broken line in the figure from the control table shown in FIG. Can be judged. The roller diameter of the heating roller 81 when the cumulative number of printed sheets of the graph 42 is 5000 can be determined from the control table to be approximately 50.15 mm, and the peripheral speed of the heating roller 81 at this time falls within the control range A. Therefore, since the operation proceeds to step S5, the current control speed, that is, 150.45 (= 50.15 × π (= 3)) mm / sec, is applied to the heating roller 81. Is performed, and the printing process requested to be printed is performed (steps S7 and S8).

  On the other hand, for example, when the elapsed time is 6 months and the cumulative number of printed sheets is 10,000 at this time, the actual operation of the apparatus is indicated by the broken line in the figure from the control table shown in FIG. Can be judged. Then, the roller diameter of the heating roller 81 when the cumulative number of printed sheets of the graph 42 is 10,000 can be determined from the control table to be approximately 50.3 φmm, and the peripheral speed 150.9 (= 50.3) of the heating roller 81 at this time. Since x.pi. (= 3) mm / sec is outside the range of the control range A, it is determined Yes in step S4, the operation proceeds to step S6, and the current control speed is changed.

  Here, as a first example of changing the control speed, as indicated by reference numeral 42a in FIG. 4, the current control speed of 150.9 mm / sec is 150.75 (= It is conceivable to change to 50.25 × π (= 3) mm / sec. Further, as a second example, as indicated by reference numeral 42b in FIG. 4, with respect to the current control speed of 150.9 mm / sec, the best control value considering the safety factor is 150.375 (= 50.125). It can be considered to change to xπ (= 3) mm / sec. In any case, it may be changed to an arbitrary peripheral speed within the control range A.

  Then, the peripheral speed control of the heating roller 81 is performed at the changed control speed, and the printing process requested to be printed is performed (steps S7 and S8).

  In the process of executing such fixing drive control, when the heating roller 81 is replaced with a new one, for example, when the service life has passed, the timer unit 922 is reset to set the elapsed time. The number of prints accumulated by the counter unit 923 is also reset to zero.

  Next, an embodiment in which a non-oil type fixing device is used, that is, an embodiment 2 in which the roller diameter of the heating roller 81 contracts with time will be described.

  FIG. 6 is an explanatory diagram showing the contents of the roller diameter change data stored in the control table as a graph. The graph shown in FIG. 6 is the same as the graph shown in FIG. 4, for the sake of simplicity of explanation, a graph (graph indicated by a broken line) 62 when 40,000 sheets are printed in one year and 400,000 million in two years. Only two types of change data of a graph (graph indicated by a broken line) 61 when printing sheets (that is, 20000 sheets per year) are shown. However, actually, the change data classified in more detail is stored in the control table.

  Here, based on the results of Table 1 above, in the control table shown in FIG. 6, the lower limit value of the control range is set to 49.75 φmm (149.25 mm / sec as the peripheral speed) by changing the roller diameter. A roller diameter of 49.875 φmm (a peripheral speed of 149.625 mm / sec), which is the lower limit value of the control range B shown in FIG. 6, is a value considering the safety factor.

  Next, fixing drive control using the control table shown in FIG. 6 will be described with reference to the flowchart shown in FIG.

  The image forming apparatus equipped with the fixing drive control device of the present embodiment always measures the elapsed time from the start of use as a product by the timer unit 922, and each time printing is performed by a print request, the counter unit By 923, the number of printed sheets is accumulated.

  In the standby state in the process of performing such a printing operation, if there is a print request to the CPU 911 (step S1), the CPU 911 checks the elapsed use start time (device history) and the accumulated number of prints ( Step S2). Then, referring to the control table shown in FIG. 6, it is necessary to check the current control speed (circumferential speed) of the heating roller 81 by the fixing driving unit 9211 (step S3) and to change the peripheral speed of the heat roller 81. It is determined whether or not there is (step S4).

  Here, for example, when the elapsed time is 1.5 months and the cumulative number of printed sheets at this time is 2500, the actual operation of the apparatus is indicated by a broken line 62 in the figure from the control table shown in FIG. It can be judged that The roller diameter of the heating roller 81 when the cumulative number of printed sheets of the graph 62 is 2500 can be determined from the control table to be approximately 49.94 mm, and the peripheral speed of the heating roller 81 at this time falls within the control range B. (No in step S4), the operation proceeds to step S5, and the heating roller 81 is operated at the current control speed, that is, 149.82 (= 49.94 × π (= 3)) mm / sec. Is performed, and the printing process requested to be printed is performed (steps S7 and S8).

  On the other hand, for example, if the elapsed time is 6 months and the cumulative number of printed sheets at this time is 10,000 sheets, the actual operation of the apparatus follows the graph 62 indicated by the broken line in the figure from the control table shown in FIG. Can be judged. The roller diameter of the heating roller 81 when the cumulative number of printed sheets of the graph 62 is 10,000 can be determined from the control table to be approximately 49.7 mm, and the peripheral speed of the heating roller 81 at this time is 149.1 (= 49.7). Since × π (= 3) mm / sec is outside the range of the control range B, it is determined Yes in step S4, the operation proceeds to step S6, and the current control speed is changed.

  Here, as a first example of changing the control speed, as indicated by 62a in FIG. 6, 149.625 (= 49) which is the lower limit for guaranteeing the print quality with respect to the current control speed 149.1 mm / sec. It is conceivable to change to .875 × π (= 3)) mm / sec. Further, as a second example, as indicated by 62b in FIG. 6, the initial peripheral speed is 150.0 (= 50.0 × π (= 3) with respect to the current control speed 149.1 mm / sec. ) It can be considered to change to mm / sec. In any case, it may be changed to an arbitrary peripheral speed within the control range B.

  Then, the peripheral speed control of the heating roller 81 is performed at the changed control speed, and the printing process requested to be printed is performed (steps S7 and S8).

  In the process of executing such fixing drive control, when the heating roller 81 is replaced with a new one, for example, when the service life has passed, the timer unit 922 is reset to set the elapsed time. The number of prints accumulated by the counter unit 923 is also reset to zero.

1 is an explanatory diagram illustrating a configuration of an image forming apparatus equipped with a fixing drive control device of the present invention. FIG. FIG. 2 is an explanatory diagram showing the internal structure of the fixing device in more detail. It is a functional block diagram which shows the structure of the principal part of a control part. It is explanatory drawing which showed the content of the roller diameter change data stored in the control table which concerns on Example 1 as a graph. 5 is a flowchart illustrating a processing procedure of fixing drive control according to the first exemplary embodiment using the control table illustrated in FIG. It is explanatory drawing which showed the content of the roller diameter change data stored in the control table which concerns on Example 2 as the graph. It is a graph which shows the relationship between the expansion | swelling change of the roller diameter of a heating roller, and the print cumulative number corresponding to time passage. It is a graph which shows the relationship between the shrinkage | contraction change of the roller diameter of a heating roller, and the print cumulative number corresponding to time passage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Developing unit 3 Photosensitive drum (electrostatic latent image carrier)
DESCRIPTION OF SYMBOLS 4 Cleaning unit 5 Charging unit 6 Transfer unit 8 Fixing apparatus 11 Optical scanning unit 12 Static elimination lamp 81 Heating roller 82 Pressure roller 90 Control part 911 CPU
921 Fixing control unit 9211 Fixing driving unit 9212 Fixing temperature control unit 922 Timer unit 923 Counter unit

Claims (4)

A transfer process for transferring image information formed on the electrostatic latent image carrier onto a sheet using an unfixed developer, and a pressure contact portion of a fixing device including a heated / pressure roller for the transferred sheet. A fixing process for melting and fixing the unfixed developer on the paper by passing the paper; and a transporting process for transporting the paper from a paper feed tray to the paper discharge tray through the transfer process and the fixing process. A fixing drive control device in an image forming apparatus,
Control means for rotationally controlling the heating / pressure roller so that the peripheral speed of the heating / pressure roller always has a predetermined speed difference with respect to the sheet conveyance speed from the transfer process to the fixing process. A fixing drive control device. A control table storing change data of the roller diameter of the heating roller based on the number of years of use after installation of the image forming apparatus and the cumulative number of prints of the apparatus corresponding to the number of years of use;
The control means controls the rotational driving of the heating / pressure roller so that the predetermined speed difference is obtained based on change data of a roller diameter of the heating roller stored in the control table. Item 4. The fixing drive control device according to Item 1.   The control means controls an initial peripheral speed of the heating / pressure roller at an arbitrary peripheral speed within a range of 100.5% to 103.0% of the paper transport speed. Alternatively, the fixing drive control device according to claim 2.   The fixing drive control device according to claim 3, wherein the control unit controls a peripheral speed of the heating roller thereafter within a range of ± 0.5% with respect to the initial peripheral speed.

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