JP6079419B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine having these functions in combination, and in particular, adopts a heat roller system that fixes an unfixed toner image by heating and pressing. The present invention relates to an image forming apparatus.

  2. Description of the Related Art Conventionally, as an image forming apparatus adopting an electrophotographic method, an apparatus having a so-called heat roller type fixing unit has been widely used. This heat roller type fixing unit is a recording in which an unfixed toner image is transferred to a fixing nip portion between a heating roller (heater) heated by a heat source and a pressure roller (pressure device) in contact therewith. The unfixed toner image is fixed on the recording material by conveying the material and heating and pressing.

  In recent years, there has been a demand for energy saving in each field, and image forming apparatuses are no exception, and various technologies for power saving have been developed. Among these, in the image forming apparatus employing the heat roller method, attention has been paid to reduction of power consumption in the heating operation of the fixing unit. As an image forming apparatus that realizes power saving of the fixing unit, for example, when forming an image with a low printing rate on a recording material, the power consumption in the heat source is suppressed by setting the fixing temperature low. Has been proposed (see Patent Document 1). In order to control the fixing temperature in the fixing unit with higher accuracy, there has been proposed a method in which the fixing temperature is set based on the content of gradation processing of an image to be printed (see Patent Document 2).

Japanese Patent Laying-Open No. 2005-043821 JP 2012-118496 A

  The image forming apparatuses disclosed in Patent Document 1 and Patent Document 2 can reduce the power consumption in the heating operation of the fixing unit by setting the fixing temperature according to the content of the image to be printed (printing rate and image pattern). It is. However, when the fixing temperature is controlled in order to reduce power consumption in this way, the fixability of the image on the recording material may not be ensured depending on the usage state of the image forming apparatus.

  For example, as shown in FIG. 16, when images having different printing rates were continuously printed on the same number of recording materials, the image quality was compared. As a result, images with a low printing rate in FIG. In this case, it is confirmed that the dot reproducibility is deteriorated due to toner rubbing and scattering. FIG. 16A is an enlarged dot diagram when 3000 images with a printing rate of 10% are printed, and FIG. 16B is an enlarged dot image when 3000 images with a printing rate of 1% are printed. FIG. For this reason, as in the image forming apparatuses of Patent Document 1 and Patent Document 2, simply setting the fixing temperature from the image to be printed cannot set the fixing temperature at which sufficient fixability can be secured, and vice versa. In addition, there is a problem that the fixability is deteriorated.

  In view of such a problem, an object of the present invention is to provide an image forming apparatus capable of maintaining good fixability regardless of the use state.

In order to achieve the above object, an image forming apparatus of the present invention includes an image carrier on which an electrostatic latent image is formed, and development that visualizes the electrostatic latent image formed on the image carrier with a developer. A transfer unit that transfers an image visualized with the developer onto the image carrier onto a recording material, and a fixing unit that fixes the image transferred by the transfer unit onto the recording material. In the image forming apparatus, a fixability index calculation unit that calculates a fixability index represented by a charge amount of the developer in the developing unit, and the fixability index and threshold value obtained by the fixability index calculation unit And a parameter setting unit that sets an operation parameter of the fixing unit based on the comparison result, the parameter setting unit, when the charge amount representing the fixability index exceeds the threshold value, In order to increase the fixing strength, the operating parameters of the fixing unit Set over, the fixing unit, said that operate according to the set operating parameters in the parameter setting unit, wherein the fixing strength of the image on the recording material is adjusted.

According to another aspect of the image forming apparatus of the present invention, an image carrier on which an electrostatic latent image is formed, and a developing unit that visualizes the electrostatic latent image formed on the image carrier with a developer. An image provided with a transfer unit that transfers an image visualized with the developer onto the image carrier onto a recording material, and a fixing unit that fixes the image transferred by the transfer unit onto the recording material. In the forming apparatus, a fixability index calculation unit that calculates a fixability index represented by an integrated print rate that is an average of the print rates for each print page , and the fixability index and threshold value obtained by the fixability index calculation unit And a parameter setting unit that sets an operation parameter of the fixing unit based on the comparison result, and the parameter setting unit is configured such that when the integrated printing rate representing the fixing property index falls below the threshold value. In order to increase the fixing strength, the operating parameters of the fixing unit Set, the fixing unit, said that operate according to the set operating parameters in the parameter setting unit, wherein the fixing strength of the image on the recording material is adjusted.

  In any of the above-described image forming apparatuses, the parameter setting unit may set the operation parameter based on the fixability index when the number of prints on the recording material exceeds a predetermined number.

  The recording medium further includes a resistance value acquisition unit that acquires a resistance value of the recording material, and the parameter setting unit determines the threshold value based on the resistance value of the recording material obtained by the resistance value acquisition unit. The operation parameter may be set based on a result of comparing the determined threshold value and the fixability index.

  In any one of the above-described image forming apparatuses, the fixing unit includes a heater that heats the recording material and a pressurizer that pressurizes the recording material, and the operation parameter set by the parameter setting unit is set. The fixing temperature in the heater or the pressing force in the pressurizer may be used. Further, the operation parameter set by the parameter setting unit may be a conveyance speed of the recording material passing through the fixing unit.

  According to the present invention, since the fixing section operating parameters are set and the fixing strength is adjusted based on the fixing index indicating the deterioration of the fixing performance to the recording material in the developer, the fixing performance is deteriorated. The optimum fixing strength can be obtained. Therefore, since the operation parameters of the fixing unit can be set according to the usage status of the image forming apparatus, unlike the conventional case where control is performed only for the currently printed image, the optimal fixing is always performed. Strength is obtained. In addition, since the operation parameter in the fixing unit can be set to a value that can realize low power consumption, it is possible to improve the fixing strength and at the same time save energy of the apparatus.

1 is a schematic configuration diagram showing an internal configuration of an image forming apparatus of the present invention. FIG. 2 is a schematic diagram illustrating a configuration of a developing unit in the image forming apparatus of FIG. 1. FIG. 2 is a schematic diagram illustrating a configuration of a fixing unit in the image forming apparatus of FIG. 1. FIG. 4 is a schematic cross-sectional view showing an internal configuration of a fixing unit in FIG. 3. FIG. 2 is a block diagram illustrating a configuration of a control unit of the image forming apparatus according to the first embodiment. These are flowcharts which show the control flow which concerns on printing operation by the control part of FIG. These are graphs showing the relationship between the toner charge amount and the image fixing rate. These are block diagrams which show the structure of the control part of the image forming apparatus in 2nd Embodiment. These are flowcharts which show the control flow which concerns on printing operation by the control part of FIG. These are graphs showing the relationship between the integrated printing rate and the toner charge amount. These are the flowcharts which show the control flow which concerns on printing operation by the control part of the image forming apparatus in 3rd Embodiment. These are graphs showing the relationship between the number of printed sheets and the toner charge amount. These are block diagrams which show the structure of the control part of the image forming apparatus in 4th Embodiment. FIG. 14 is a flowchart showing a control flow relating to a printing operation by the control unit of FIG. 13. FIG. 5 is a schematic cross-sectional view showing another configuration of the fixing unit in the image forming apparatus of FIG. 1. (A) is a dot enlarged view when 3000 images of a printing rate of 10% are printed, and (b) is an image of a printing rate of 1%. FIG. 6 is an enlarged view of dots when 3000 sheets are printed. .

  Hereinafter, an embodiment embodying the present invention will be described with reference to the drawings in a case where the embodiment is applied to a tandem color digital printer which is an example of an image forming apparatus. In the following description, when using terms indicating a specific direction or position (for example, “left / right”, “up / down”, etc.) as necessary, the direction perpendicular to the paper surface in FIG. ing. These terms are used for convenience of explanation, and do not limit the technical scope of the present invention.

<Overall configuration of image forming apparatus>
First, an outline of the image forming apparatus 1 will be described with reference to FIG. As shown in FIG. 1, the image forming apparatus 1 includes an image process unit 3, a sheet feeding unit 4, a fixing unit 5, and the like in an outer casing 2. A control unit 28 that controls the entire image forming apparatus 1 is disposed between the image processing unit 3 and the paper feeding unit 4 in the outer casing 2. Although not shown in detail, the image forming apparatus 1 is connected to a network such as a LAN, for example, and receives a print command from an external terminal (not shown) so as to execute printing based on the command. It is configured.

  The paper feed unit 4 located in the lower part of the outer casing 2 includes a paper feed cassette 21 that accommodates the recording material P1, a pickup roller 22 that feeds the recording material P1 in the paper feed cassette 21 from the uppermost layer, and a fed recording material. A pair of separation rollers 23 for separating P1 one by one and a pair of timing rollers 24 for conveying the recording material P1 separated into one sheet to the image processing unit 3 at a predetermined timing are provided. . The recording material P <b> 1 in each paper feed cassette 21 is sent out one by one from the top layer to the transport path 30 by the rotation of the pickup roller 22 and the separation roller pair 23. The conveyance path 30 passes from the paper feed cassette 21 of the paper feed unit 4 to the outer casing 2 via the nip portion of the timing roller pair 24, the secondary transfer nip portion of the image processing unit 3, and the fixing nip portion of the fixing unit 5. It reaches the discharge roller pair 26 at the top.

  The recording material P <b> 1 in the paper feeding cassette 21 is set so that the center of the paper passing width becomes the center reference when transporting toward the transport path 30. The paper feed cassette 21 is provided with a pair of side portion regulating plates (not shown) for shifting the recording material P1 before paper feed to the center reference. The pair of side part restricting plates are configured to move in close proximity to each other in the sheet passing width direction. By sandwiching the recording material P1 in the paper feed cassette 21 from both sides in the sheet passing width direction with a pair of side portion regulating plates, the recording material P1 in the paper feed cassette 21 is set to the center reference regardless of the standard. Accordingly, the transfer process in the image process unit 3 and the fixing process in the fixing unit 5 are also executed on the basis of the center.

  The image processing unit 3 located above the sheet feeding unit 4 plays a role of transferring a toner image formed on a photosensitive drum 13 which is an example of an image carrier to a recording material P1, and is an intermediate transfer member. And a total of four image forming sections 7 corresponding to the respective colors of yellow (Y), magenta (M), cyan (C) and black (K).

  The intermediate transfer belt 6 is an endless belt made of a conductive material, and is also an example of an image carrier. The intermediate transfer belt 6 is wound around a driving roller 8 located on the right side of the central portion in the outer casing 2 and a driven roller 9 located on the left side of the central portion. A secondary transfer roller 10 is disposed outside the portion of the intermediate transfer belt 6 that is wound around the drive roller 8. The intermediate transfer belt 6 rotates in the counterclockwise direction in FIG. 1 by rotating the driving roller 8 counterclockwise in FIG. 1 by power transmission from a main motor (not shown). The intermediate transfer belt 6 and the secondary transfer roller 10 constitute a transfer unit that transfers the toner image to the recording material P1.

  A secondary transfer roller 10 is disposed on the outer peripheral side of the portion of the intermediate transfer belt 6 that is wound around the drive roller 8. The secondary transfer roller 10 is in contact with the intermediate transfer belt 6, and a portion between the intermediate transfer belt 6 and the secondary transfer roller 10 (contact portion) is a secondary transfer nip portion as a secondary transfer region. . The secondary transfer roller 10 rotates in the clockwise direction in FIG. 1 with the rotation of the intermediate transfer belt 6 or with the movement of the recording material P1 held and conveyed by the secondary transfer nip portion. A transfer belt cleaner 12 for removing untransferred toner on the intermediate transfer belt 6 is disposed on the outer peripheral side of the portion of the intermediate transfer belt 6 wound around the driven roller 9. The transfer belt cleaner 12 is in contact with the intermediate transfer belt 6.

  The four image forming units 7 are arranged along the intermediate transfer belt 6 in the order of yellow (Y), magenta (M), cyan (C), and black (K) from the left in FIG. They are arranged side by side. In FIG. 1, for convenience of explanation, symbols Y, M, C, and K are attached to each image forming unit 7 according to the reproduction color. Each image forming unit 7 includes a photosensitive drum 13 as an example of an image carrier that rotates clockwise in FIG. Around the photosensitive drum 13, a charging unit 14, an exposure unit 19, a developing unit 15, a primary transfer roller 16, and a photoconductor cleaner 17 are arranged in order along the clockwise rotation direction in FIG. 1.

  The photosensitive drum 13 is negatively charged and is configured to rotate clockwise in FIG. 1 by power transmission from a main motor (not shown). A charging bias voltage output at a predetermined timing from a charging power source (not shown) is applied to the charging unit 14. The developing unit 15 makes the electrostatic latent image formed on the photosensitive drum 13 visible by reversal development using toner (developer) having a negative polarity.

  As shown in detail in FIG. 2, the developing unit 15 includes a developing roller 41 as a developer carrying member having a plurality of permanent magnets in a cylindrical developing sleeve 42, and a plurality of stirring members 43 having screw blades. I have. The developing roller 41 and the stirring member 43 are also configured to rotate by power transmission from a main motor that rotates the driving roller 8 and the photosensitive drum 13. The developing unit 15 contains a two-component developer containing toner and carrier, and a developing bias voltage output from the developing power source 150 is applied to the developing sleeve 42.

  The primary transfer roller 16 is located on the inner peripheral side of the intermediate transfer belt 6 and faces the photosensitive drum 13 of the corresponding image forming unit 7 with the intermediate transfer belt 6 interposed therebetween. The primary transfer roller 16 also rotates counterclockwise in FIG. 1 as the intermediate transfer belt 6 rotates. Between the intermediate transfer belt 6 and the primary transfer roller 16 (contact portion) is a primary transfer nip portion as a primary transfer region. The photoreceptor cleaner 17 is for removing untransferred toner remaining on the photoreceptor drum 13, and is in contact with the photoreceptor drum 13. An exposure unit 19 is disposed below the four image forming units 7. The exposure unit 19 forms an electrostatic latent image on each photosensitive drum 13 by laser light based on image information from an external terminal or the like.

  The density of the toner image on the intermediate transfer belt 6 is detected on the most downstream side in the circumferential direction of the intermediate transfer belt 6, that is, between the image forming portion 7K closest to the secondary transfer roller 10 and the secondary transfer nip portion. An IDC (Image Density Control) sensor 20 is disposed. The IDC sensor 20 basically uses a reference pattern (a test toner image) for each color formed on the intermediate transfer belt 6 during image stabilization processing such as color misregistration, gradation, and image density reproduction correction. Good). A hopper (not shown) that accommodates toner supplied to each developing unit 15 is disposed above the intermediate transfer belt 6.

  The IDC sensor 20 is composed of, for example, a reflective optical sensor having a light emitting unit and a light receiving unit. At this time, the IDC sensor 20 irradiates the test toner image on the intermediate transfer belt 6 with the light from the light emitting unit, receives the reflected light at the light receiving unit and converts it into an electrical signal, and converts the electrical signal to the control unit. 28. Then, the control unit 28 confirms the measurement result of the test toner image of each color of YMCK based on the electrical signal received from the IDC sensor 20, and detects the toner adhesion amount of each color.

  In each image forming unit 7, when a laser beam corresponding to an image signal is projected from the exposure unit 19 onto the photosensitive drum 13 charged by the charging unit 14, an electrostatic latent image is formed. The electrostatic latent image is reversely developed with toner supplied from the developing unit 15 and becomes a toner image of each color. The toner images on the respective photosensitive drums 13 are primarily transferred from the photosensitive drum 13 to the outer peripheral surface of the intermediate transfer belt 6 in the order of yellow, magenta, cyan, and black at the corresponding primary transfer nip portions, and are superimposed. . Untransferred toner remaining on the photosensitive drum 13 is scraped off by the photosensitive cleaner 17 and removed from the photosensitive drum 13. Then, when the recording material P1 passes through the secondary transfer nip portion, the superimposed four color toner images are collectively transferred onto the recording material P1. Untransferred toner remaining on the intermediate transfer belt 6 is scraped off by the transfer belt cleaner 12 and removed from the intermediate transfer belt 6.

  The fixing unit 5 located above the secondary transfer roller 10 in the image processing unit 3 includes a heater 31 incorporating a heat source such as a halogen lamp heater, and a pressurizer 32 facing the heater 31. A contact portion between the heater 31 and the pressurizer 32 is a fixing nip portion which is a fixing region. The recording material P1 on which the unfixed toner image is placed after passing through the secondary transfer nip portion is heated and pressurized when passing through the fixing nip portion between the heater 31 and the pressurizer 32, and the recording material P1 is placed on the recording material P1. The unfixed toner image is fixed to the toner image. Thereafter, the recording material P <b> 1 is discharged onto the paper discharge tray 27 by the rotation of the discharge roller pair 26.

<Configuration example of fixing unit>
A configuration example of the fixing unit 5 in the above-described image forming apparatus will be described below with reference to FIGS. 3 and 4. FIG. 3 is a schematic diagram showing the configuration of the fixing unit in this configuration example, and FIG. 4 is a schematic cross-sectional view thereof.

  As shown in FIGS. 3 and 4, the fixing unit 5 has a heater 31 configured by a fixing belt 53 wound around a heating roller 51 and a fixing roller 52, and a cylindrical cored bar 301 as an axis. And a pressurizer 32 composed of a pressure roller. The pressurizer 32 rotates in the clockwise direction of FIG. 4 by the core metal 301 covered with the elastic layer 302 being pivotally supported by the roller support frame 54 and connected to the motor 56 so that power can be transmitted. Driven. At this time, the roller support frame 54 is urged and supported by a spring 57 to which one end thereof is connected, so that the pressurizer 32 is pressed against the fixing belt 53. Accordingly, a fixing nip portion is formed at a contact portion between the fixing belt 53 and the pressure device 32 in a state where the fixing belt 53 is sandwiched between the pressure device 32 and the fixing roller 52.

  On the other hand, the heating roller 51 in the heater 31 has a configuration in which a heater lamp 512 is provided inside a cylindrical cored bar 511. A thermopile 513 for detecting the temperature of the fixing belt 53 is disposed on the outer periphery of the heating roller 51 so as to face the surface of the fixing belt 53. At this time, the drive control unit 58 drives and controls the heater lamp 512 in accordance with the temperature detected by the thermopile 513, thereby setting the surface temperature of the fixing belt 53 heated through the heating roller 51 to a predetermined value. The fixing roller 52 has a configuration in which an outer peripheral surface of a cylindrical cored bar 521 is covered with an elastic layer 522 having elasticity and heat resistance. The core bars 511 and 521 of the heating roller 51 and the fixing roller 52 are pivotally supported by the roller support frame 55.

  Further, the fixing unit 5 functions as a mechanism for controlling the pressing force by the pressurizer 32, a spring receiver 571 that receives the other end of the spring 57, an eccentric cam 572 that displaces the spring receiver 571, and a motor that rotates the eccentric cam 572. 573. The drive control unit 58 controls the rotation of the motor 573 and rotates the eccentric cam 572, thereby moving the spring receiver 571 along the pressing direction of the spring 57 according to the rotational position of the eccentric cam 572. By moving the position of the spring receiver 571, the fixing device 5 controls the pressing force applied to the fixing roller 52 by the pressurizer 32 based on the spring 57.

  In the fixing unit 5 configured as described above, the fixing belt 53 and the fixing roller 52 are driven to rotate by the rotation of the pressurizer 32 as the motor 56 rotates. The fixing belt 53 is heated by the heating roller 51 while the driven rotation is performed, and the temperature is raised to a predetermined temperature. At this time, the drive control unit 58 controls the rotation speed of the motor 56, whereby the conveyance speed of the recording material P1 passing through the fixing nip portion between the heater 31 and the pressurizer 32 is controlled. Accordingly, after the fixing belt 53 is heated to a predetermined temperature, the recording paper P1 on which an unfixed toner image is formed enters the fixing nip portion. The toner image is fixed on the recording paper P1 while the recording paper P1 passes through the fixing nip formed by the fixing roller 52, the pressure device 32a, and the fixing belt 53.

  As described above, the heater lamp 512 serving as a heating source is provided in the heating roller 51, but a heating source may be provided inside the cored bar 301 of the pressurizer 32. Further, instead of the heater lamp 512, heating by an induction heating method may be performed, or these heating sources may be provided outside the fixing belt 53. Further, although a non-contact type thermopile 513 is provided as a temperature sensor for detecting the temperature of the fixing belt 53, a contact type sensor such as a thermistor may be provided.

<First Embodiment>
An image forming apparatus according to a first embodiment of the present invention will be described below with reference to the drawings. FIG. 5 is a block diagram illustrating a configuration of a control unit of the image forming apparatus according to the present exemplary embodiment, and FIG. 6 is a flowchart illustrating a control flow related to a printing operation by the control unit of FIG.

  As shown in FIG. 5, the control unit 28 in the image forming apparatus 1 of the present embodiment includes a CPU (Central Processing Unit) 81 that executes various arithmetic processes and controls, and a ROM (Read Only Memory) that stores a control program and the like. 82, a RAM (Random Access Memory) 83 that temporarily stores calculation data, an image processing unit 84 that generates image data serving as a basis of a toner image formed by the image processing unit 3, and an image processing unit 84 The image memory 85 that temporarily stores the received image data, the input / output interface 86 that transmits and receives signals to and from the image processing unit 3, the sheet feeding unit 4, and the fixing unit 5, and the external network 600. A communication interface 87 to be connected, a parameter setting unit 88 for setting operation parameters in the fixing unit 5 to adjust the fixing strength of the fixing unit 5, and a developing unit It includes a charge amount calculating unit 89 for calculating the toner charge amount at 5, and a bus 90 for transmitting and receiving signals in order to establish communication between the respective blocks within the control section 28, the.

  As described above, a developing bias is applied to the developing roller 41 in the YMCK color developing unit 15 (see FIG. 2) by the developing power source 150. As a result, the toner in the developing unit 15 is supplied from the developing sleeve 42 to the photosensitive drum 13. The developing power supply 150 includes a developing current detector 151 that measures a developing current flowing between the developing roller 41 and the photosensitive drum 13. The development current detection unit 151 measures the development current generated when the toner moves from the surface of the development roller 41 to the photosensitive drum 13 during development, and notifies the control unit 28 of the measured development current.

  The control unit 28 configured as described above operates according to the flowchart of FIG. 6 to set the operation parameters of each unit in the fixing unit 5 in order to improve the fixing state of the toner image on the recording material P1. . At this time, as described later, the control unit 28 is referred to as a toner charge amount per unit mass (hereinafter, simply referred to as “toner charge amount”) based on signals given from the IDC sensor 20 and the development current detection unit 151, respectively. ) And the operation parameters are set according to the toner charge amount. Hereinafter, the control operation of the control unit 28 during the printing operation will be described in detail with reference to the flowchart of FIG.

  When the control unit 28 receives a print signal including image data from the image reading apparatus 2 or the external network 600 by either the input / output interface 86 or the communication interface 87, the control unit 28 starts a print processing operation according to the program stored in the ROM 82. (STEP 1). When the control unit 28 starts the print processing operation, the CPU 81 reads the toner charge amount stored in the RAM 83 and gives it to the parameter setting unit 88 (STEP 2). The parameter setting unit 88 determines whether or not the toner charge amount read from the RAM 83 exceeds the threshold C1, and sets operation parameters in the fixing unit 5 based on the determination result (STEPs 3 to 5).

Details of the operations of STEP 3 to STEP 5 will be described below with reference to the graph of FIG. The graph of FIG. 7 shows the relationship between the toner charge amount and the image fixing rate when the heating temperature of the heater 31 of the fixing unit 5 (hereinafter simply referred to as “fixing temperature”) is set to temperatures T1, T1 + ΔT. Is shown. The image fixing rate was obtained by a fixing property evaluation test using a cloth rubbing tester using a cloth applied with a pressure of 20 g / cm ² , and a symmetrical printed image was rubbed 15 times with the cloth. Thus, the optical reflection densities of the images before and after rubbing with the cloth rubbing tester are compared and calculated.

  As is clear from FIG. 7, at the fixing temperature T1 (see the solid line graph in FIG. 7), which is a limit point with power saving, the image fixing rate is higher than 80% when the toner charge amount is lower than the threshold value C1. On the other hand, when the toner charge amount is higher than the threshold value C1, the image fixing rate is less than 80%. At the fixing temperature T1 + ΔT (see the wavy line graph in FIG. 7) in which the fixing temperature T1 is increased by ΔT, even if the toner charge amount exceeds the threshold C1, the image fixing rate can be set to 80% and a high image fixing rate can be maintained.

  Based on the result of the graph of FIG. 7, in STEP 3, the parameter setting unit 88 compares the toner charge amount read from the RAM 83 with the threshold value C1. At this time, the toner charge amount read from the RAM 83 may be the average value or the maximum value of the toner charge amount of the toner in the developing unit 15 for each color of YMCK. When the parameter setting unit 88 confirms that the toner charge amount is equal to or less than the threshold C1 (NO in STEP 3), the parameter setting unit 88 sets the fixing temperature by the heater 31 of the fixing unit 5 to T1 (STEP 4). On the other hand, when it is confirmed that the toner charge amount exceeds the threshold C1 (YES in STEP 3), the parameter setting unit 88 sets the fixing temperature by the heater 31 of the fixing unit 5 to T1 + ΔT (STEP 5).

  As described above, when the parameter setting unit 88 sets the fixing temperature (STEP 4 or STEP 5), the control unit 28 controls each unit constituting the image forming apparatus 1 by sending a control signal from the input / output interface 86. Thus, a printing operation on the recording material P1 is performed (STEP 6). As a result, the operation parameter (fixing temperature) in the fixing unit 5 is set so that the fixing property of the toner image to the recording material P1 is good, so that the fixing property of the toner image to the recording material P1 is optimal. Will be adjusted. At this time, the image data stored in the image memory 85 is read out and applied to the image processing unit 3 from the input / output interface 86, so that the image processing unit 3 applies the recording material P1 based on the image data. The toner image is transferred.

  The fixing unit 5 recognizes each operation parameter set by the parameter setting unit 88 when the drive control unit 58 receives a control signal from the input / output interface 86. Accordingly, the drive control unit 58 confirms the temperature detected by the thermopile 513, and drives and controls the heater lamp 512 so that the heater 31 operates at the set fixing temperature. Furthermore, the drive control unit 58 also confirms the conveyance speed of the recording material P1 and the pressing force by the pressurizer 32 as operation parameters included in the control signal. Then, the drive control unit 58 drives and controls the motors 56 and 573 according to the confirmed operation parameter, thereby fixing the transferred toner image on the recording material P1.

  After instructing the printing operation in STEP 6, the control unit 28 counts the number of printed sheets stored in the RAM 83, stores the counted number of printed sheets in the RAM 83, and simultaneously supplies it to the charge amount calculating unit 89 (STEP 7 ). Upon receiving the number of printed sheets counted in STEP 7, the charge amount calculation unit 89 checks the amount of change from the number of printed sheets at the previous toner charge amount measurement, and determines whether the specified number of sheets has been exceeded since the previous measurement. (STEP8).

  At this time, when a specified number of print operations have been performed since the previous measurement by the print operation in accordance with the print operation instruction in STEP 6 (YES in STEP 8), the charge amount calculation unit 89 determines the toner charge amount of the toner in the developing unit 15. After the calculation (STEP 9), the calculated toner charge amount is stored in the RAM 83 (STEP 10). Then, the process proceeds to STEP 2 where the parameter setting unit 88 reads the newly obtained toner charge amount from the RAM 83 and sets the operation parameter in the fixing unit 5 to adjust the fixing property of the toner image to the recording material P1. (STEP 3 to 5). That is, the toner charge amount calculated by the charge amount calculation unit 89 corresponds to a “fixability index” for predicting the deterioration state of the toner fixability, and the charge amount calculation unit 89 calculates the fixability index. This corresponds to a “fixability index calculation unit”.

  Details of the operation of STEP 9 will be described below. When the control unit 28 receives a signal sent from the image processing unit 3 by the input / output interface 86, the charge amount calculation unit 89 calculates the toner charge amount based on the signal from the image process unit 3. At this time, the signal from the image processing unit 3 includes measurement signals from the development current detection unit 151 and the IDC sensor 20, and these measurement signals are given to the charge amount calculation unit 89.

  Then, the charge amount calculation unit 89 calculates the total charge amount per unit time of the toner moved from the development roller 41 to the photosensitive drum 13 based on the development current measured by the development current detection unit 151 (total charge amount of the developed toner). ) On the other hand, from the toner adhesion amount based on the optical density measured by the IDC sensor 20, the total mass of the toner moved from the developing roller 41 to the photosensitive drum 13 is recognized. Therefore, the charge amount calculation unit 89 divides the total charge amount of the toner confirmed from the development current by the total toner amount confirmed from the toner adhesion amount, thereby obtaining the toner that is the charge amount of the toner per unit mass. The charge amount is calculated.

  In the above example, the toner charge amount is measured based on the developing current and the toner adhesion amount from the optical density. However, the present invention is not limited to this, and the toner charge amount is measured by another method. It does not matter. Specifically, for example, the toner layer potential is obtained by measuring the potential on the photosensitive drum 13 before and after developing the toner with a non-contact surface potential meter, and based on the toner layer potential and the toner adhesion amount. Thus, the toner charge amount may be obtained.

  Further, when the number of printed sheets counted by the printing operation in STEP 6 has not exceeded the specified number of sheets since the previous measurement (NO in STEP 8), the control unit 28 checks whether or not there is a next printed page (STEP 11). ). At this time, when image data to be the next print page is stored in the image memory 85 (Yes in STEP 11), the process proceeds to STEP 6 and a control signal is sent to each unit to perform the print operation of the next page. On the other hand, when all the image data stored in the image memory 85 is read and there is no next print page (NO in STEP 11), the printing operation is terminated (STEP 12).

  An example of dimensions and materials of the fixing unit 5 in which the operation parameters are set as described above will be shown below. The heating roller 51 has an outer diameter of 25 mm and a length in the nip longitudinal direction of about 330 mm. The cored bar 511 constituting the heating roller 51 is formed of a hollow cored bar made of aluminum having a thickness of 0.6 mm, and the outer peripheral surface thereof is covered with a PTFE (polytetrafluoroethylene) coat having a thickness of 15 μm. The heater lamp 512 in the heating roller 541 is a halogen lamp heater with a power consumption of 999 W and a light emission length of 290 mm.

  The fixing roller 52 has an outer diameter of 30 mm, and a hollow cored bar made of iron having a diameter of 22 mm as the cored bar 521. The elastic layer 522 that covers the cored bar 521 is composed of rubber having a thickness of 4 mm and a sponge having a thickness of 2 mm that covers the rubber. Further, the fixing belt 53 has an outer diameter of 60 mm, and is composed of a polyimide having a thickness of 70 μm, a rubber having a thickness of 200 μm that covers the polyimide, and a PFA (polytetrafluoroethylene) having a thickness of 30 μm that covers the rubber. Is done. Further, the thermopile 513 is arranged in a non-contact state with respect to the fixing belt 53 at a position 40 mm away from the central sheet passing reference.

  On the other hand, the pressurizer 32 constituted by a pressure roller has an outer diameter of 35 mm and a cored bar 301 made of aluminum having a thickness of 2 mm. The elastic layer 302 covering the cored bar 301 is composed of rubber having a thickness of 2 mm and PFA having a thickness of 30 μm covering the rubber. Further, the conveyance speed of the recording material P1 by the rotation of the motor 56 is set to 165 mm / s.

  When driving and controlling the fixing unit 5 according to the configuration example, for example, the threshold C1 as a comparison reference is set to 50 μc / g in STEP3, and the fixing temperatures T1 and T1 + ΔT set in STEP4 and STEP5 are 150 ° C. and 160 ° C., respectively. Set to. By setting the threshold value and the fixing temperature in this way, the power consumption in the fixing unit 5 is reduced, and the image fixing rate can be maintained at 80% or more regardless of the toner charge amount in the developing unit 15.

  The fixing unit 5 performs a warm-up operation in which the surface temperatures of the fixing belt 53 and the pressurizer 32 are set as the print permission temperatures, for example, when the image forming apparatus 1 is powered on. In the above-described configuration example, the print permission temperature in the fixing unit 5 is set to 135 ° C., for example, and when the thermopile 513 is detected to reach 135 ° C., the ready state indicating the print permission temperature is set. At this time, in a state where the control unit 28 has not received the print signal, the image forming apparatus 1 is in a print standby state. On the other hand, when the control unit 28 receives the print signal, the image forming apparatus 1 performs the process according to the flowchart of FIG. Perform printing operation. In the fixing unit 5 in the print standby state, the heater lamp 512 is driven and controlled so that the temperature measured by the thermopile 513 is 145 ° C.

  In this embodiment, in STEPs 3 to 5, the parameter setting unit 88 sets the fixing temperature as the operation parameter of the fixing unit 5 based on the toner charge amount. However, the recording material is not limited to the fixing temperature. You may set the conveyance speed of P1, and the pressing force by the pressurizer 32. FIG. That is, when the parameter setting unit 88 sets the conveyance speed of the recording material P1 based on the toner charge amount, in STEP5, the conveyance speed is set to be delayed by ΔV with respect to the conveyance speed V1 set in STEP4. Set. On the other hand, when the parameter setting unit 88 sets the pressing force by the pressurizer 32 based on the toner charge amount, in STEP5, the pressing force is set so that the pressing force F1 set in STEP4 is increased by ΔF. Set.

<Second Embodiment>
An image forming apparatus according to a second embodiment of the present invention will be described below with reference to the drawings. FIG. 8 is a block diagram illustrating a configuration of a control unit of the image forming apparatus according to the present exemplary embodiment, and FIG. 9 is a flowchart illustrating a control flow related to a printing operation by the control unit of FIG. In the configuration of FIG. 8, the same parts as those of the configuration of FIG. 5 are denoted by the same reference numerals, and detailed description thereof is omitted. Also in the flowchart of FIG. 9, the same operation flow as that of the flowchart of FIG. 6 is denoted by the same reference numeral, and detailed description thereof is omitted.

  As shown in FIG. 8, the control unit 28a in the image forming apparatus 1 according to the present embodiment is different from the control unit 28 (see FIG. 5) according to the first embodiment. A printing rate calculation unit 89a that calculates the printing rate is provided. Like the charge amount calculation unit 89 (see FIG. 5) in the first embodiment, the print rate calculation unit 89a provided in the control unit 28a corresponds to a “fixability index calculation unit” and has an integrated print rate. This corresponds to the “fixability index”. Other configurations of the control unit 28a are the same as those of the control unit 28 in the first embodiment.

When the control unit 28a is configured in this way, the printing rate calculation unit 89a first confirms the content of the image to be printed next based on the image data stored in the image memory 85, and records one sheet of recording material. A region where toner is printed on P1 is calculated. Accordingly, the printing rate calculation unit 89a can calculate the printing rate of one recording material P1 by calculating the ratio of the printing area to the entire recording material P1. On the other hand, the integrated print rate serving as the fixing index is a value obtained by averaging the print rate in the image data to be printed next and the print rate when printing was performed in the past. That is, the printing rate calculation unit 89a performs the next printing based on the following equation (1) from the printing rate Xa based on the image data to be printed next, the integrated printing rate Xn already stored in the RAM 83, and the number N of prints. The integrated printing rate X (n + 1) is calculated. The integrated print rate may be calculated by averaging the print rates for each predetermined number of sheets (number of pages).
X (n + 1) = (Xn × N + Xa) / (N + 1) (1)

  Next, the control operation of the control unit 28a during the printing operation will be described in detail with reference to the flowchart of FIG. When the control unit 28a receives a print signal from the outside and starts a print processing operation (STEP 1), the control unit 28a reads the integrated print rate stored in the RAM 83 and gives it to the parameter setting unit 88 (STEP 102). The parameter setting unit 88 determines whether or not the cumulative printing rate read from the RAM 83 is less than the threshold value X1, and sets operation parameters in the fixing unit 5 based on the determination result (STEP 103, STEP 4 to 5). ).

  The threshold value X1 in STEP 103 will be described below with reference to the graph of FIG. The graph of FIG. 10 shows the relationship between the integrated printing rate and the toner charge amount when the number of printed sheets is N1, 2 × N1. As is apparent from FIG. 10, when the integrated printing rate is equal to or greater than the threshold value X1, the toner charge amount can be set to C0 or more and less than C1 regardless of the number of printed sheets. Therefore, considering the result of the graph of FIG. 7 together, the cumulative charge rate equal to or higher than the threshold value X1 is a toner charge amount that can maintain the image fixing rate higher than 80% even when the fixing temperature T1 is set.

  On the other hand, when the integrated printing rate is less than the threshold value X1, the toner charge amount can be about C1 in the number of printed sheets N1, but when the number of printed sheets is 2 × N1, the toner charge amount is considerably larger than C1. Large value. Therefore, considering the result of the graph of FIG. 7 as well, when the integrated printing rate is less than the threshold value X1, the image fixing rate is lowered when the fixing temperature T1 is set, so that the image fixing rate is 80% or more. In order to maintain the temperature, it is desirable to heat the fixing temperature to T1 + ΔT.

  Therefore, based on the results of the graphs of FIGS. 7 and 10, in STEP 103, the parameter setting unit 88 compares the integrated printing rate read from the RAM 83 with the threshold value X <b> 1. When the parameter setting unit 88 confirms that the integrated printing rate is equal to or higher than the threshold value X1 (NO in STEP 103), the parameter setting unit 88 sets the fixing temperature by the heater 31 of the fixing unit 5 to T1 (STEP 4). On the other hand, when it is confirmed that the integrated printing rate is less than the threshold value X1 (YES in STEP 103), the parameter setting unit 88 sets the fixing temperature by the heater 31 of the fixing unit 5 to T1 + ΔT (STEP 5).

  Thereafter, the control unit 28a gives a control signal to each part of the image forming apparatus 1 to control the printing operation, and then counts the number of printed sheets stored in the RAM 83 (STEP 6 and STEP 7). Further, the control unit 28a calculates the printing rate from the image data read when the printing rate calculation unit 89a supports printing in STEP 6 (STEP 108). The printing rate calculation unit 89a performs printing according to STEP 6 based on the above equation (1) from the integrated printing rate read at STEP 102, the number of printed sheets counted at STEP 7, and the printing rate calculated at STEP 108. The integrated printing rate after the operation is calculated (STEP 109), and the calculated integrated printing rate is stored in the RAM 83 (STEP 110).

  When the integrated print rate is stored in the RAM 83 in STEP 110, the control unit 28a checks whether or not there is a next print page (STEP 11). At this time, if there is a next print page (YES in STEP 11), the process proceeds to STEP 102 and the operations after STEP 102 are repeated. On the other hand, if there is no next print page (NO in STEP 11), the printing operation is terminated (STEP 12).

  In this embodiment, when the dimensions and materials of the respective parts constituting the fixing unit 5 are the same as those illustrated in the first embodiment, for example, the threshold value X1 as a comparison reference in STEP 103 is set to 5%. By setting the fixing temperatures T1, T1 + ΔT set in STEP4 and STEP5 to 150 ° C. and 160 ° C., respectively, the image fixing rate can be maintained at 80% or more regardless of the magnitude of the integrated printing rate. Also in the present embodiment, the parameter setting unit 88 sets the fixing temperature as an operation parameter of the fixing unit 5 based on the integrated printing rate (STEP 103, STEP 4 to 5), but the first embodiment. Similarly to the fixing temperature, the conveying speed of the recording material P1 and the pressing force by the pressurizer 32 may be set.

<Third Embodiment>
An image forming apparatus according to a third embodiment of the present invention will be described below with reference to the drawings. FIG. 11 is a flowchart showing a control flow relating to a printing operation by the control unit in the image forming apparatus of the present embodiment. The image forming apparatus of the present embodiment has the same configuration as that of the image forming apparatus of the second embodiment, and includes a control unit 28a shown in FIG. In the flowchart of FIG. 11, the same operation flow as that of the flowchart of FIG. 9 is denoted by the same reference numeral, and detailed description thereof is omitted.

  A control operation of the control unit 28a in the image forming apparatus 1 of the present embodiment will be described in detail with reference to the flowchart of FIG. When receiving a print signal from the outside and starting a print processing operation (STEP 1), the control unit 28a reads the number of prints stored in the RAM 83 and gives it to the parameter setting unit 88, unlike the case of the second embodiment. (STEP 112). The parameter setting unit 88 first determines whether or not the number of printed sheets read from the RAM 83 is less than the threshold value N1 (STEP 113).

  If the number of printed sheets is less than the threshold value N1 (Yes in SETP 113), the process proceeds to STEP 4 and the fixing temperature is set to T1. On the other hand, when the number of printed sheets exceeds the threshold value N1 (No in SETP 113), the process proceeds to STEP 102, and the fixing temperature is set based on the integrated printing rate as in the second embodiment. When the control unit 28a operates in this way, the operation after the transition from STEP 113 to STEP 4 and STEP 102 is the same as the operation in the second embodiment (see FIG. 9) until the presence of the next print page is determined in STEP 11. It becomes the same. If it is determined in STEP 11 that there is a next print page, the process proceeds to STEP 112 and the operations after STEP 112 are repeated.

  The threshold value N1 in STEP 113 will be described below with reference to the graph of FIG. The graph of FIG. 12 shows the relationship between the number of printed sheets and the toner charge amount when the integrated printing rate is X1, X2 (X2 <X1). As is apparent from FIG. 10, when the cumulative number is less than the threshold value N1, the toner charge amount can be C0 or more and less than C1 regardless of the magnitude of the cumulative printing rate. Therefore, considering the result of the graph of FIG. 7 as well, when the number of prints is less than the threshold value N1, even when the fixing temperature T1, the toner charge amount can maintain the image fixing rate higher than 80%.

  On the other hand, when the number of printed sheets exceeds the threshold value N1, if the integrated printing rate is X1, the toner charge amount can be about C1, but if the integrated printing rate is X2 lower than X1, the toner charging is performed. The amount is larger than C1. Accordingly, considering the result of the graph of FIG. 7 together, if the number of printed sheets exceeds the threshold value N1, depending on the size of the integrated printing rate, the image fixing rate is lowered when the fixing temperature T1 is set. As in the first embodiment, it is necessary to set the fixing temperature based on the integrated printing rate. As a result, in this embodiment, when the number of printed sheets is less than N1, the process proceeds to STEP 4 without performing the determination based on the integrated printing rate, and when the number of printed sheets exceeds N1, the determination based on the integrated printing rate is performed. It was supposed to be.

  In the present embodiment, when the dimensions and materials of the respective parts constituting the fixing unit 5 are the same as those illustrated in the first embodiment, for example, the threshold values X1 and N1 that are the comparison references in STEP103 and STEP113 are set. By setting the fixing temperatures T1, T1 + ΔT set in 5% and 500 sheets to 150 ° C. and 160 ° C. respectively, the image fixing rate is set to 80 regardless of the integrated printing rate. % Or more can be maintained. Further, the operation parameters of the fixing unit 5 set in STEP 4 and STEP 5 are not limited to the fixing temperature, but set the conveyance speed of the recording material P1 and the pressing force by the pressurizer 32, as in the second embodiment. It does not matter.

<Fourth Embodiment>
An image forming apparatus according to a fourth embodiment of the present invention will be described below with reference to the drawings. FIG. 13 is a block diagram illustrating a configuration of a control unit of the image forming apparatus according to the present exemplary embodiment, and FIG. 14 is a flowchart illustrating a control flow related to a printing operation by the control unit of FIG. In the configuration of FIG. 13, the same parts as those of the configuration of FIG. 5 are denoted by the same reference numerals, and detailed description thereof is omitted. Also in the flowchart of FIG. 14, the same operation flow as that of the flowchart of FIG. 6 is denoted by the same reference numeral, and detailed description thereof is omitted.

  As shown in FIG. 13, the control unit 28b in the image forming apparatus 1 of the present embodiment has a resistance value for acquiring the resistance value of the recording material P1 in the configuration of the control unit 28 (see FIG. 5) of the first embodiment. The acquisition unit 91 is added. In the control unit 28b configured as described above, the resistance value of the recording material P1 accommodated in the paper feeding unit 4 is stored in the RAM 83, and the resistance value obtaining unit 91 confirming the paper feeding unit 4 performing the paper feeding operation. Assume that the resistance value stored in the RAM 83 is acquired. At this time, for example, although not shown in FIG. 1, when the image forming apparatus 1 includes a plurality of paper feed units 4, the RAM 83 stores, for each recording material P <b> 1 accommodated in each paper feed unit 4. The resistance value is stored.

  The control operation of the control unit 28b will be described in detail with reference to the flowchart of FIG. When the control unit 28b receives a print signal from the outside and starts a print processing operation (STEP 1), first, after reading the toner charge amount stored in the RAM 83 (STEP 2), the resistance value acquiring unit 91 performs recording. A resistance value corresponding to the paper feeding unit 4 to which the material P1 is fed is acquired (STEP 122). Then, the parameter setting unit 88 first determines whether or not the resistance value of the recording material P1 obtained by the resistance value acquisition unit 91 has been read (STEP 123).

  At this time, when the resistance value of the recording material P1 to be printed is not stored in the RAM 83 (No in STEP 123), the process proceeds to STEP 3, where the parameter setting unit 88 determines the toner charge amount read from the RAM 83. It is determined whether or not the threshold value C1 has been exceeded. On the other hand, when the resistance value acquisition unit 91 receives the resistance value of the recording material P1 stored in the RAM 83 (Yes in STEP123), it is determined whether or not the resistance value of the recording material P1 is R1 or more (STEP124). ). When it is confirmed that the resistance value of the recording material P1 is lower than R1 (No in STEP124), it is determined whether or not the resistance value of the recording material P1 is R2 (R2 <R1) or more (STEP125).

  In STEPs 124 and 125, when the determination is made based on the resistance value of the recording material P1 to be printed, if the resistance value is R1 or more (Yes in STEP124), the process proceeds to STEP3. When the resistance value of the recording material P1 is lower than R2 (NO in STEP125), the process proceeds to STEP4, and the parameter setting unit 88 sets the fixing temperature of the fixing unit 5 to T1. Further, when the resistance value of the recording material P1 is equal to or higher than R2 and lower than R1 (Yes in STEP125), the parameter setting unit 88 determines whether the toner charge amount exceeds the threshold value C2 (C2> C1). (STEP 126).

  In STEP 126, as in STEP 3, when the toner charge amount is equal to or less than the threshold value C2 (No), the fixing temperature is set to T1 (STEP 4), and when the toner charge amount exceeds the threshold value C2 (Yes), the fixing temperature is set. Is set to T1 + ΔT (STEP 5). As described above, after moving from STEP3, STEP125, or STEP126 to STEP4 or STEP5 and the parameter setting unit 88 sets the fixing temperature of the fixing unit 5, the operation in the first embodiment (see FIG. 6) is performed. Perform the same operation.

  In the present embodiment, when the dimensions and materials of the fixing unit 5 are the same as those illustrated in the first embodiment, for example, the thresholds C1 and C2 that are comparison references in STEP3 and STEP126 are set to 50 μc / g, respectively. While setting to 60 μc / g, the resistance values R1 and R2 of the recording material P1 determined in STEP124 and STEP125 are set to 1E + 14Ω · cm and 1E + 13Ω · cm. In addition, by setting the fixing temperatures T1, T1 + ΔT set in STEP4 and STEP5 to 150 ° C. and 160 ° C., respectively, the image fixing rate can be maintained at 80% or more regardless of the magnitude of the integrated printing rate.

  In the present embodiment, the resistance value acquisition unit 91 reads out and acquires the resistance value of the recording material P1 stored in advance by the RAM 83 corresponding to the paper supply unit 4, but is applied to the secondary transfer roller 10. The resistance value of the recording material P1 may be calculated based on the bias voltage and the bias current flowing through the secondary transfer roller 10. Furthermore, a humidity sensor may be provided inside the image forming apparatus 1 and the resistance value of the recording material P1 that varies depending on the humidity may be estimated based on the humidity measured by the humidity sensor.

  Further, the operation parameters of the fixing unit 5 set in STEP 4 and STEP 5 are not limited to the fixing temperature, and the conveying speed of the recording material P1 and the pressing force by the pressurizer 32 are set as in the first embodiment. It does not matter. In this embodiment, the control operation according to the operation flow in the first embodiment is combined with the determination operation based on the resistance value of the recording material P1, but the operation flow in the second or third embodiment is used. It is also possible to combine the determination operation based on the resistance value of the recording material P1 with the control operation. In this case, when the resistance value of the recording material P1 is equal to or higher than R2 and lower than R1, the threshold value to be compared with the integrated printing rate is set to a low value, and when the resistance value of the recording material P1 is lower than R2, the integrated printing rate. The operation parameters of the fixing unit 5 are set without performing the determination according to.

  In each of the embodiments described above, the fixing unit 5 has been described by taking the example shown in FIGS. 3 and 4 as an example. However, the configuration of the fixing unit 5 is not limited to the above-described configuration. As shown in FIG. 15, another configuration may be used. Hereinafter, the configuration of FIG. 15 which is another configuration example of the fixing unit 5 will be briefly described.

  The fixing unit 5 shown in FIG. 15 includes a heater 31 composed of a heating roller having a cylindrical cored bar 311 as an axis, and a pressurizer 32 that presses an endless pressure belt 321 against the heater 31. Prepare. The heater 31 is rotationally driven in the counterclockwise direction of FIG. 15 by being connected to a motor so that power can be transmitted. The pressurizer 32 includes a pressurizing belt 321 that is supported at a position where the fixing nip portion is formed in pressure contact with the heater 31. The pressurizing belt 321 of the pressurizer 32 rotates following the rotation of the heater 31.

  The heater 31 has a configuration in which an outer peripheral surface of a cored bar 311 is covered with an elastic layer 312 and a release layer 313 in order, and a heater lamp 314 is disposed inside the cored bar 311. And the metal core 311 consists of metal materials, such as aluminum or iron, and the thickness has preferable about 0.1 mm-5 mm. The elastic layer 312 is made of an elastic material having heat resistance such as silicone rubber or fluorine rubber, and has heat resistance with respect to the fixing temperature and elasticity for securing the length of the fixing nip portion. The thickness of the elastic layer 312 is preferably in the range of 0.05 mm to 2 mm. Furthermore, the release layer 313 is made of a fluororesin material having excellent release properties and is configured by tubing or coating. The thickness of the release layer 313 is preferably in the range of 5 μm to 100 μm.

  The pressurizer 32 includes a pressing member 322 that is provided inside the pressurizing belt 321 and presses the pressurizing belt 321 against the heater 31. In order to arrange the pressing member 322 so as to press the pressure belt 321 from the inside, a holding frame 323 for fixing the pressing member 322 is installed in the pressure belt 321. Although not shown, a sliding sheet is disposed between the pressure belt 321 and the pressing member 322 so as to cover the pressing member 322. This sliding sheet is obtained by coating a heat-resistant glass cloth with a fluororesin, and has heat resistance, wear resistance, and slidability.

  The pressure belt 321 includes a base layer 325 in which heat resistance, strength, and surface smoothness are taken into consideration, and has a configuration in which the outside of the base layer 325 is covered with a releasable release layer 324. When the pressure belt 321 is cylindrical, its outer diameter is preferably in the range of 20 to 100 mm, for example. The release layer 324 is provided with a gas barrier property as well as a release property such as a fluorine tube or a fluorine coating, and the thickness is preferably 5 to 100 μm. Further, the release layer 324 may have a conductive configuration. On the other hand, the base layer 325 is formed of, for example, a heat-resistant resin such as polyimide, polyamide, or polyimideamide, or a metal material such as aluminum, stainless steel, or nickel. A lubricant such as grease or silicone oil is applied to the inner peripheral surface of the base layer 325 of the pressure belt 321 and the outer peripheral surface of the sliding sheet (not shown).

  As shown in FIG. 15, the pressing member 322 includes an elastic pressing member 326 that elastically deforms and presses the pressure belt 321, and a rigid pressing member 327 made of a material having higher hardness than the elastic pressing member 326. The elastic pressing member 326 is held by the rigid body pressing member 327. The elastic pressing member 326 is held by the rigid pressing member 327 by being inserted into a recess provided on the heater 31 side surface (left side surface) of the rigid body pressing member 327, and the surface of the heater 31 side is unaffected. It contacts the base layer 325 of the pressure belt 321 through the illustrated sliding sheet. Further, the rigid body pressing member 327 is fitted into the holding frame 323 by being fitted into a recess provided on the heater 31 side surface (left side surface) of the holding frame 323 held and fixed by the belt holding member 35. It is gripped and fixed in the pressure belt 321. As a result, the rigid body pressing member 327 presses the pressure belt 321 toward the heater 31 on the surface above the elastic pressing member 326 on the left side surface.

  The left side surfaces of the elastic pressing member 326 and the rigid pressing member 327 sequentially press the pressure belt 321 from the downstream side to the upstream side in the recording material P1 conveyance direction, thereby fixing the toner image on the recording material P1. Later, the recording material P1 is peeled off from the heater 31. That is, the recording material P1 is heated and pressed in a fixing nip portion formed by pressing due to elastic deformation of the elastic pressing member 326, whereby the toner on the paper surface is melted and fixed. Thereafter, the high-hardness rigid pressing member 327 presses the heater 31 via the pressure belt 321 to deform the elastic layer 312 of the heater 31, and the recording material P1 that has passed through the fixing nip portion is heated. Peel from 31.

  The image forming apparatus according to the present invention has been described by taking the intermediate transfer type image forming apparatus as an example. However, as long as the fixing unit is provided in each of the above-described embodiments, the direct transfer type, the rotary arrangement type, etc. An image forming apparatus using the above method may be used. In addition, as an image forming apparatus according to the present invention, any MFP (Multifunction Peripheral) having a copy function, a scanner function, a printer function, and a fax function can be used as long as it includes each of the sheet feeding unit and the sheet feeding mechanism in each of the above-described embodiments. Or a printer, a copier, a facsimile, or the like. In addition, the structure of each part is not limited to embodiment of illustration, A various change is possible in the range which does not deviate from the meaning of this invention.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Outer casing 3 Image process part 4 Paper feed part 5 Fixing part 6 Intermediate transfer belt 7 Image forming part 8 Drive roller 9 Driven roller 10 Secondary transfer roller 12 Two transfer belt cleaner 13 Photosensitive drum 14 Charging part DESCRIPTION OF SYMBOLS 15 Developing part 16 Primary transfer roller 17 Photoconductor cleaner 19 Exposure part 20 IDC sensor 21 Paper feed cassette 22 Pickup roller 23 Separating roller pair 24 Timing roller pair 26 Discharge roller pair 27 Discharge tray 28 Control part 30 Conveyance path 31 Heater 32 Pressurizer 33 Support frame 41 Developing roller 42 Developing sleeve 43 Stirring member 51 Heating roller 52 Fixing roller 53 Fixing belt 54, 55 Roller supporting frame 56 Motor 57 Spring 58 Drive controller 81 CPU
82 ROM
83 RAM
84 Image processing unit 85 Image memory 86 Input / output interface 87 Communication interface 88 Parameter setting unit 89 Charge amount calculation unit 89a Print rate calculation unit 90 Bus 91 Resistance value acquisition unit 150 Power supply for development 151 Development current detection unit 5
301 Core Bar 302 Elastic Layer 351 Frame Holding Unit 511 Core Bar 512 Heater Lamp 513 Thermopile 521 Core Bar 522 Elastic Layer 571 Spring Bearing 572 Eccentric Cam 573 Motor

Claims (7)

An image carrier on which an electrostatic latent image is formed, a developing unit that visualizes the electrostatic latent image formed on the image carrier with a developer, and a developer on the image carrier with the developer In an image forming apparatus comprising: a transfer unit that transfers the image that has been transferred to a recording material; and a fixing unit that fixes the image transferred by the transfer unit to the recording material.
A fixability index calculating section for calculating a fixability index represented by the charge amount of the developer in the developing section ;
A parameter setting unit that compares the fixability index obtained by the fixability index calculation unit with a threshold value, and sets operation parameters of the fixing unit based on the comparison result;
With
The parameter setting unit sets an operation parameter of the fixing unit to increase fixing strength when a charge amount representing the fixability index exceeds the threshold value,
The image forming apparatus, wherein the fixing unit operates according to an operation parameter set by the parameter setting unit, thereby adjusting an image fixing strength to the recording material. An image carrier on which an electrostatic latent image is formed, a developing unit that visualizes the electrostatic latent image formed on the image carrier with a developer, and a developer on the image carrier with the developer In an image forming apparatus comprising: a transfer unit that transfers the image that has been transferred to a recording material; and a fixing unit that fixes the image transferred by the transfer unit to the recording material.
A fixability index calculation unit that calculates a fixability index represented by an integrated print rate that averages the print rate for each print page;
A parameter setting unit that compares the fixability index obtained by the fixability index calculation unit with a threshold value, and sets operation parameters of the fixing unit based on the comparison result;
With
The parameter setting unit sets operation parameters of the fixing unit to increase fixing strength when an integrated printing rate representing the fixability index falls below the threshold .
The fixing portion, wherein by operating according to the set operating parameters in the parameter setting unit, images forming device you characterized in that the fixing strength of the image is adjusted to the recording material. The parameter setting unit, when the number of printed sheets to the recording material exceeds the predetermined number, the image forming apparatus according to claim 1 or 2, characterized in that for setting the operating parameters based on the fixation index . A resistance value acquisition unit for acquiring the resistance value of the recording material;
The parameter setting unit determines the threshold value based on the resistance value of the recording material obtained by the resistance value acquisition unit, and compares the determined threshold value with the fixability index to determine the operation. the image forming apparatus according to any one of claims 1 to 3, characterized in that to set the parameters. The fixing unit includes a heater that heats the recording material, and a pressurizer that pressurizes the recording material,
Wherein the operating parameters set by the parameter setting unit, an image forming apparatus according to any one of claims 1 to 4, characterized in that a fixing temperature in the heater. The fixing unit includes a heater that heats the recording material, and a pressurizer that pressurizes the recording material,
Wherein the operating parameters set by the parameter setting unit, an image forming apparatus according to any one of claims 1 to 4, wherein a pressing force in the pressurizer. The operating parameters set by the parameter setting unit, an image forming apparatus according to any one of claims 1 to 4, wherein a transport speed of the recording material passing through the fixing unit.