JP2007156201A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To satisfactorily perform an image formation by appropriately suppressing the variation of image quality caused by the variation of respective environments even when external and internal environments (temperature and humidity conditions) of a housing of an image forming apparatus are varied by various patterns. <P>SOLUTION: The image forming apparatus is provided with: the housing 1 having an inner space in which image formation processing apparatuses 10, 20 are installed; an external environment detection means 4 for detecting at least the temperature of the outside of the housing 1; an internal environment detection means 5 for detecting an environment condition concerned with at least the temperature of the inner space of the housing 1; and a control means 6 (60) for correcting at least one of a plurality of control conditions concerned with the image formation processing operation on the basis of both of the detection result of the external environment detection means 4 and the detection result of the internal environment detection means 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, a facsimile machine, or a multi-function machine that finally forms an image made of toner (dry developer) on a recording medium, and in particular, an environment (temperature, The present invention relates to an image forming apparatus that can perform good image formation while suppressing fluctuations in image quality due to fluctuations in the environment such as humidity) and the environment inside the housing.

  In general, an image forming apparatus that forms an image made of toner on a recording medium such as recording paper by applying an electrophotographic method or an electrostatic recording method is generally a charging process, an exposure process, a developing process, a transfer process, etc. In this image forming process, electrostatic elements and actions such as electric charge and electrostatic attraction are utilized. For this reason, when the temperature conditions inside the device main body (housing), the temperature outside the device main body, and the conditions such as humidity change, for example, the electrostatic elements and the characteristics or effects of the action are likely to fluctuate. As a result, the operation of the image forming process may also fluctuate, and the image quality of the finally obtained image may be degraded without stability.

  For this reason, conventionally, an image forming apparatus is known in which measures are taken to perform good image formation even when the temperature and humidity inside and outside the apparatus main body fluctuate as described below.

  For example, a temperature detecting unit is provided in the vicinity of an image forming body such as a photosensitive member, and the gap between the image forming body and the developer conveying body is set to be wide based on the detection result (temperature information) of the detecting unit. In addition, there is an image forming apparatus configured such that the frequency of the AC bias component in the developing bias shifts to a low frequency (Patent Document 1). According to this image forming apparatus, it is said that a good image can be formed without change in developability due to a temperature change in the machine or a temperature change due to environmental conditions outside the machine.

  Also provided is a control means for changing the voltage applied to the transfer roller for transferring the toner image on the intermediate transfer member to the recording medium, a counter for counting the number of printed sheets, and a temperature / humidity sensor for measuring the temperature and humidity outside the apparatus. There is an image forming apparatus in which a control unit changes a voltage applied to a transfer roller in accordance with a count value of the counter and an output of a temperature / humidity sensor (Patent Document 2). According to this image forming apparatus, it is possible to determine an appropriate applied voltage to the transfer roller in accordance with the deterioration of the transfer roller or environmental change, and to perform optimal transfer that matches the state and environment of the transfer roller. It is supposed to be possible.

  Furthermore, an environment detection unit (actually only a sensor for measuring the temperature and humidity inside the apparatus) for detecting the internal and external environments of the image forming apparatus is provided, and a series of image formation is performed according to the environmental conditions detected by the detection unit. There is an image forming apparatus configured to change the operation speed of all or part of the processing (Patent Document 3). According to this image forming apparatus, a paper wrapping accident in the fixing device is surely avoided, and the original productivity of the apparatus is prevented from being lost as much as possible.

JP-A-11-167243 JP 2000-98771 A Japanese Patent Laid-Open No. 2004-98771

  However, these conventional image forming apparatuses also have the following problems.

  That is, each image forming apparatus appropriately adjusts the conditions such as the developing bias, the voltage applied to the transfer roll, and the operation speed according to any of the environmental conditions regarding the temperature and humidity inside the apparatus or the environmental conditions outside the apparatus. It has become. For this reason, even if one of the environmental conditions inside the apparatus or the environmental conditions outside the apparatus, which is the criterion for making the adjustment, is the same, the other condition changes over time, If both of these environmental conditions change over time, simply adjusting the conditions based on one of the environmental conditions may result in inappropriate condition settings. In such a case, the image quality will also fluctuate.

  For example, in an image forming apparatus that adjusts the above conditions according to the environmental conditions inside the apparatus, the installation location of the image forming apparatus (that is, outside the apparatus) even though the environmental conditions inside the apparatus are in the same state. When the temperature or humidity of the recording medium changes, the moisture absorption state of the recording medium may change. In such a case, if image formation is continued under the condition setting that considers only the environmental conditions inside the apparatus without considering the environmental conditions outside the apparatus, the toner image on the recording medium whose moisture absorption state has changed The transfer efficiency may fluctuate and image quality fluctuations may occur due to transfer defects.

  On the other hand, in an image forming apparatus that adjusts the above conditions in accordance with environmental conditions outside the apparatus, for example, continuous image forming operations or repeated intermittently even though the environment outside the apparatus is the same. When an image forming operation of a specific pattern such as an image forming operation is performed, the temperature conditions inside the device are changed over time depending on the presence or absence of heat released from a fixing device that heats and fixes the toner image on the recording medium. May fluctuate. In such a case, if the image forming operation is continued with the condition setting that considers only the environmental condition outside the apparatus without considering the change in the environmental condition inside the apparatus, the operation set based only on the environmental condition outside the apparatus Conditions relating to the image process may deviate from appropriate values, resulting in, for example, development failure or transfer failure. As a result, image quality fluctuations due to such factors may occur.

  The present invention has been made in view of such problems, and mainly, the environment (temperature, humidity) outside the housing of the image forming apparatus and the environment inside the housing vary in various patterns. Even if this is the case, an image forming apparatus capable of appropriately suppressing image quality fluctuations that may occur due to fluctuations in each environment and performing good image formation is provided.

  The image forming apparatus of the present invention forms an electrostatic latent image on an image carrier and then develops the electrostatic latent image into a toner image. The toner image is directly applied to a recording medium or via an intermediate transfer member. An image forming process device that performs a series of image forming process operations to be transferred; a housing having an internal space in which the image forming process device is installed; and an external environment detecting unit that detects at least the temperature outside the housing; An internal environment detecting means for detecting an environmental condition related to at least the temperature of the internal space of the housing; at least one of a plurality of control conditions related to the image forming process operation; And control means for correcting based on both detection results of the internal environment detection means.

  Here, the image carrier is only required to be capable of forming an electrostatic latent image and forming a toner image by development, and is, for example, a photoreceptor. Further, the image forming process device is a related device necessary for performing the series of image forming process operations. For example, the charging device that uniformly charges the image carrier, and the charged image carrier is converted into an image. An image exposure device that forms an electrostatic latent image by exposure based on information, a developing device that develops the electrostatic latent image with a developer (toner) to form a toner image, and a toner image on a recording medium or an intermediate transfer member It includes a transfer (primary) transfer device, an intermediate transfer member that temporarily carries and conveys a toner image on the image carrier, a secondary transfer device that transfers the toner image on the intermediate transfer member to a recording medium, and the like.

  The housing is a box-like structure having an internal space for installing various components including the image forming process device. Specifically, it is composed of a support frame, an exterior cover, components other than the exterior cover disposed on the surface side, and the like.

  The external environment detection means may be any temperature sensor or any other temperature / humidity sensor that can measure both temperature and humidity, as long as it can detect at least the temperature outside the housing as needed. Configured. The external detection means is normally installed at a predetermined position on the outer peripheral surface portion of the casing, but the installation site is not particularly limited as long as the temperature, temperature, and humidity outside the casing can be properly detected.

  The internal environment detection means may be any means as long as it can detect at least the temperature of the internal space of the housing, and if necessary, the environmental situation related to temperature and humidity. For example, the temperature and humidity are directly measured. It can be configured with a temperature sensor or a temperature / humidity sensor.

  The control means may be any means that corrects predetermined ones of the image forming process control conditions based on both the detection result of the external environment detection means and the detection result of the internal environment detection means. The plurality of control conditions related to the image forming process operation are control conditions required for stabilizing the image quality in each operation related to the image forming process, and particularly the environment outside the housing and the environment inside the housing. This is a control condition that may be affected by an operation result (effect) related to image quality due to various fluctuations.

  Such an image forming apparatus includes a primary transfer device in which the image forming process device transfers the toner image on the image carrier to the recording medium or the intermediate transfer member by electrostatic action by applying a primary transfer bias. In addition, the control unit can at least correct the value of the primary transfer bias applied in the primary transfer device.

  In this case, it is possible to correct at least the primary transfer that is easily influenced by the external environment of the casing and the internal environment of the casing, and therefore it is possible to accurately suppress fluctuations in image quality and is effective.

  Each of the image forming apparatuses includes a secondary transfer device in which the image forming process device transfers the intermediate transfer member and a toner image transferred to the intermediate transfer member to the recording medium of a secondary transfer member. In addition, the internal environment detection unit may be a measurement device that measures a voltage or current when detecting a system resistance of a secondary transfer unit configured by the intermediate transfer body and the secondary transfer device. it can.

  In this case, it becomes possible to configure a voltage measuring device at the time of detecting the system resistance with the power supply device of the secondary transfer device, and it is necessary to install a separate component as an internal environment detecting means. This is advantageous in terms of cost and installation space.

  Further, in each of the image forming apparatuses, the control unit corrects the control condition related to the image forming process operation selected based on the detection result of the external environment detection unit according to the detection result of the internal environment detection unit. It can be configured to be set to.

  In this case, the control conditions to be controlled are first selected based on the environmental conditions outside the housing that rarely change rapidly, and then the provisional condition selection values are determined according to the job pattern of the image forming operation. Thus, fine adjustment can be made according to the environmental conditions inside the casing that are likely to fluctuate, thereby making it possible to more appropriately correct the control conditions to be corrected.

  According to the image forming apparatus of the present invention, at least one of the plurality of control conditions related to the image forming process operation is appropriate based on both the detection result of the environment outside the casing and the detection result of the environment inside the casing. It will be adjusted to the condition contents. As a result, even if the environment (at least the temperature) outside the housing of the image forming apparatus and the environment inside the housing may fluctuate in various patterns, it may occur due to fluctuations in each environment. A change in image quality is appropriately suppressed, and a good image can be formed.

  FIG. 1 shows an outline of a full-color printer to which the present invention is applied.

<Basic configuration and operation of the entire printer>
In this full-color printer, an image forming unit 10, an intermediate transfer unit 20, a paper feeding unit 30, a fixing device 40, and the like are installed inside the housing 1. The housing 1 is formed so that the overall appearance is substantially box-shaped by appropriately combining a plurality of support frames, exterior covers, and the like.

  The image forming unit 10 is provided with a photosensitive drum 11 as an image carrier that rotates in the direction of an arrow. Around the photosensitive drum 11, a charging roll 12 as a charging unit and a ROS (Raster Output as an image exposing unit). Scanner) 13, a rotation switching (rotary) type equipped with four color developing devices 14Y, 14M, 14C and 14K of yellow (Y), magenta (M), cyan (C) and black (K) as developing means. A developing device 14 and a primary transfer roll 15 as a (primary) transfer unit are disposed. Reference numeral 16 in the figure denotes a drum cleaner for the photosensitive drum 11, a cleaning blade 16 a installed in contact with the photosensitive drum 11, and a detachable waste toner box 16 b for storing unnecessary toner scraped off by the blade 16 a. And is mainly composed.

  Among these, the photosensitive drum 11 has a photosensitive layer made of an organic photosensitive material formed on the peripheral surface of a cylindrical drum support, and is installed to rotate at a predetermined speed by a driving device (not shown). The charging roll 12 is formed by forming an elastic layer or the like on a roll base material such as a metal, and is supported so as to rotate while being in contact with the peripheral surface of the photosensitive drum 11. A charging voltage is applied from a charging power source (not shown). The ROS 13 is mainly composed of a semiconductor laser emission source and a scanning optical system device such as a polygon mirror, a reflection mirror, and a lens. At the time of the image exposure process, a laser beam LB corresponding to an image signal processed and generated by an image processing apparatus (not shown) is emitted from a semiconductor laser based on image information input to the printer, and is exposed to light by a scanning optical system apparatus. Scanning exposure is performed toward the drum 11.

  The rotation switching type developing device 14 includes four color developing devices 14Y, 14M, 14C, and 14K arranged at an angle of 90 ° in the circumferential direction of the rotation support frame 18. Further, in the developing device 14, the developing unit 14Y, 14M corresponding to the color to be developed is obtained by rotating the rotation support frame 18 by a predetermined amount around the rotation shaft 18c at a predetermined timing during the developing process. , 14C, and 14K are moved to developing positions facing the photosensitive drum 11, respectively.

  Each of the developing devices 14Y, 14M, 14C, and 14K includes a hollow main body case 14a that is partially slit along the axial direction of the photosensitive drum 11, and includes a main body case 14a. A developing roll 14b that rotates with a portion exposed from the opening, and two developer agitating / conveying members that are positioned obliquely below the developing roll 14b and rotated in parallel with the developing roll Spiral augers 14d and 14e are installed. The main body case 14a contains a predetermined amount of a two-component developer containing non-magnetic toner and magnetic carrier as a developer. The main body case 14a is supplied with an appropriate amount of toner of each color from the toner cartridges 19Y, 19M, 19C, and 19K. When the spiral augers 14d and 14e are rotationally driven, the toner is agitated with the carrier and frictionally charged to a predetermined polarity (in this example, a negative polarity). A predetermined developing bias for forming a developing electric field with the photosensitive drum 11 is applied to the developing roll 14b from a developing bias power source (not shown). As the developing bias, a direct current on which an alternating current component is superimposed is applied.

  The primary transfer roll 15 is formed by forming an elastic layer or the like on a roll base material such as metal. The primary transfer roll 15 is supported so as to rotate while being in contact with the peripheral surface portion serving as the primary transfer position of the photosensitive drum 11, and a primary transfer power source (not shown) is provided on the roll base material at the time of the primary transfer process. The primary transfer voltage is applied. As the primary transfer voltage, a voltage having a polarity opposite to the charging polarity of the toner is applied.

  In this image forming unit 10, basically, after the surface of the photosensitive drum 11 is charged to a predetermined potential by the charging roll 12, a laser beam LB corresponding to the image signal is scanned and exposed from the ROS 13 to the charged surface. Then, the electrostatic latent image is formed, and then the electrostatic latent image is developed by a developer supplied from a predetermined developer 14 (Y, M, C, K) in a rotation-switching type developing device and is predetermined. Is formed. In this development, the developer is conveyed to the developing area by the developing roll 14b of each developing device, and the photosensitive drum is developed by a developing (vibrating) electric field formed between the developing roll 14b and the photosensitive drum 11 in the developing area. 11 is performed by moving toward the latent image and electrostatically adhering to the latent image.

  In particular, in the image forming unit 10, the above-described charging, exposure, and development processes are repeated a predetermined number of times according to the color of the image to be formed. For example, when a full-color image is formed, the charging, exposure, and development processes are repeated four times for each color of yellow, magenta, cyan, and black, whereby four colors are formed on the surface of the photosensitive drum 11. Corresponding toner images are sequentially formed.

  Next, the intermediate transfer unit 20 is installed in the vicinity of the transfer position of the photosensitive drum 11 in the image forming unit 10, and includes an intermediate transfer belt 21 as an intermediate transfer member and a secondary transfer roll 25 as a secondary transfer unit. Its main part is composed. Reference numeral 26 in the drawing is a belt cleaner that cleans the surface of the intermediate transfer belt 21.

  The intermediate transfer belt 21 in this example is supported by being wound around a plurality of rolls 22 (a, b, c, d,...) And wound around an outer peripheral surface serving as a transfer position of the photosensitive drum 11. It is installed so as to rotate in synchronism with the photosensitive drum 11 in the (lapped state). The primary transfer roll 15 is disposed in contact with the inner peripheral surface portion of the intermediate transfer belt 21 that is in contact with the photosensitive drum 11. The roll 22a is a backup roll constituting a part of the secondary transfer portion, the roll 22d is a wrap-in roll, and the roll 22e is a wrap-out roll.

  The secondary transfer roll 25 is disposed so as to be in contact with the outer peripheral surface that is the secondary transfer position of the intermediate transfer belt 21. The secondary transfer position is an intermediate transfer belt portion supported by the backup roll 22a. The secondary transfer roll 25 is obtained by forming an elastic layer or the like on a roll base material such as metal. Further, it is supported so as to be able to come into contact with and separate from the intermediate transfer belt 21 and abuts on the intermediate transfer belt 21 only when the secondary transfer process is executed. Further, a secondary transfer voltage is applied to the roll base material of the secondary transfer roll 25 from a secondary transfer power source (not shown) at the time of the secondary transfer process. As the secondary transfer voltage, a voltage having a polarity opposite to the charging polarity of the toner is applied.

  The paper feed unit 30 is a sheet cassette 31 that is attached in a state where it can be pulled out to the lower side of the internal space of the housing 1, and a plurality of sheets 2 that are stacked and stored in the paper cassette 31 one by one. A feeding device 32 for sending out, a pair of registration rolls 33 for feeding the paper 2 sent out from the sending device 32 to a secondary transfer position at a predetermined timing after being temporarily stopped, a paper transport guide, and the like. Yes.

  The fixing device 40 is arranged on the upper side above the secondary transfer position in the internal space of the housing 1. The fixing device 40 includes a box-shaped housing (cover) 41 in which an inlet and an outlet of the paper 2 are opened, a heating roll 42 installed so as to be driven to rotate inside the housing 41, and a heating roll 43. It is mainly composed of a pressure roll (or belt) 43 that is pressed and rotated so as to form a fixing nip, and a paper discharge roll pair 44 for discharging the paper 2 after fixing.

  In such an intermediate transfer unit 20, the toner image formed on the photosensitive drum 11 of the image forming unit 10 is primarily transferred to the intermediate transfer belt 21 when passing through the primary transfer position. The primary transfer at this time is transferred to the intermediate transfer belt 21 side by receiving an electrostatic action (electrostatic force) due to the primary transfer voltage applied to the primary transfer roll 15 by the toner on the photosensitive drum 11 mainly. It is done by being held. When selecting a color print for forming a color image, a plurality of color toner images sequentially formed on the photosensitive drum 11 are multiple-transferred in a state of being sequentially superimposed on the intermediate transfer belt 21. After completion of the primary transfer process, the photosensitive drum 11 is cleaned by removing residual toner or the like adhering to the surface by the drum cleaner 16.

  Subsequently, when the toner image primarily transferred to the intermediate transfer belt 21 passes through the secondary transfer position, the toner image is transferred from the paper feeding unit 30 to the space between the intermediate transfer belt 21 and the secondary transfer roll 25 at a predetermined timing. Secondary transfer is performed on the sheet 2 to be fed. In the secondary transfer at this time, the toner image receives an electrostatic action (electrostatic force) due to the secondary transfer voltage applied to the secondary transfer roll 25 and moves to the sheet P side to be electrostatically held. Is done. After the secondary transfer process is completed, the secondary transfer roll 25 moves in a direction away from the secondary transfer belt 21 and the intermediate transfer belt 21 is cleaned by the belt cleaner 26.

  The sheet 2 on which the toner image is secondarily transferred in the intermediate transfer unit 20 passes through the secondary transfer position and is conveyed toward the fixing device 40. In the fixing device 40, the sheet 2 after the secondary transfer is heated and pressed by being introduced into and passing through the fixing nip between the rotating heating roll 42 and the pressing roll 43. As a result, the toner image on the paper 2 is melt-pressed and thermally fixed to the paper 2. In the normal print mode, the fixed sheet 2 is discharged as it is onto the discharge tray portion 1 a formed on the upper outer surface of the printer housing 1 by the discharge roll pair 44. A one-dot chain line with an arrow in FIG. 1 indicates a basic conveyance path of the sheet 2 from the sheet feeding unit 30 to the discharge tray 1a.

<Configuration and operation of control system related to imaging process>
In this printer, the following configuration is applied to the control system of the image forming process.

  That is, in the printer, an external temperature / humidity sensor 4 for measuring the temperature and humidity outside the housing 1 (corresponding to the place where the printer is installed) is installed, and the temperature and humidity in the internal space of the housing 1 are also installed. An internal environment sensor 5 for measuring the environmental state is installed. Further, by using both the detection result of the external temperature / humidity sensor 4 and the detection result of the internal environment sensor 5, at least the value of the primary transfer current in the image forming unit 10 and the intermediate transfer unit 20 can be corrected as appropriate. A control device 6 as a control means is provided.

  The external temperature / humidity sensor 4 is not affected by heat generated by heat-generating components such as the fixing device 40 and the high-voltage power supply device, and is a predetermined part of the housing 1 that is suitable for appropriately measuring the temperature and humidity outside the housing 1. Installed. In this example, the detection unit for detecting the temperature and humidity outside the housing is attached to the side wall surface portion on the upper side of the housing 1 so as to be exposed to the outside of the housing.

As the internal environment sensor 5, a secondary transfer portion resistance measuring device 50 capable of measuring a voltage when detecting the system resistance of the secondary transfer portion is applied. As shown in FIG. 2, the secondary transfer portion resistance measuring device 50 includes a system resistance (combined resistance) obtained by adding up the resistances of the secondary transfer roll 25, the intermediate transfer belt 21 and the backup roll 22a constituting the secondary transfer portion. ) Is measured. The secondary transfer portion resistance measuring device 50 in this example includes a measurement power source (constant current power source device) 51 that applies a constant current (I ₀ ) for measurement to the secondary transfer roll 25, and a second power source from the measurement power source 51. It comprises a voltmeter 52 that measures a voltage (Vmon) when a constant current (I ₀ ) is applied to the next transfer roll 25.

Here, the measurement power supply 51 is also used as a secondary transfer voltage application (constant current control system) power supply device, and the voltmeter 52 is a voltmeter provided in the power supply device. . The measurement power supply 51 and the voltmeter 52 may be configured to use dedicated ones. Incidentally, the system resistance value (Rsys) can be obtained as Rsys = Vmon / I ₀ .

  As shown in FIG. 3, the control device 6 includes an image forming process control unit 60 that controls the overall operations related to the image forming process (charging process, exposure process, developing process, transfer process, etc.). The image forming process control unit 60 includes at least a primary transfer control unit 61 that controls the operation of the primary transfer process as a control unit that uses both the detection result of the external temperature / humidity sensor 4 and the detection result of the internal environment sensor 5. It has a configuration.

  The image forming process control unit 60 in the control device 6 is connected to at least the external temperature / humidity sensor 4 and the internal environment sensor 5 (secondary transfer unit resistance measuring device 50). As a result, the image forming process control unit 60 has the measurement information of the temperature and humidity outside the housing 1 and the environmental condition regarding the temperature and humidity inside the housing 1 (voltage corresponding to the system resistance of the secondary transfer unit). Are input respectively.

  The primary transfer control unit 71 of the image forming process control unit 70 is connected to a power supply circuit 150 for applying a primary transfer current. As will be described later, an external temperature and humidity are applied to the primary transfer voltage to be applied. It adjusts and determines based on both the detection information of this and the detection information regarding internal temperature and humidity.

  As shown in FIG. 4, the primary transfer control unit 61 in this example uses the primary transfer current reference value selected based on the detection result of the external temperature / humidity sensor 4 for the primary transfer current as the detection result of the internal environment sensor 5. By making corrections according to the above, a formal (after correction) primary transfer current value is obtained. The “environment area number” in FIG. 4 is determined based on discrimination data as shown in FIG. 5, for example. 5, T1 to T15 are values that divide the assumed temperature measurement range, and H1 to H15 are values that divide the assumed humidity measurement range, and each value may be a numerical value having a certain range. .

  The control device 6 having such a primary transfer control unit 61 operates according to the procedure shown in FIG. The control operation (program) and the reference data are stored in advance in storage means that constitutes the control device 61. The execution timing of the control operation related to the correction of the primary transfer current can be arbitrarily set. In this example, for example, when the power is turned on, when a series of print jobs are started, during the continuous print job, It is set to be executed at the time of execution of process control control related to density adjustment or the like.

  Next, the control operation relating to the correction of the primary transfer current in the control system of this image forming process will be described.

When the execution time of the control operation comes, as shown in FIG. 6, the external temperature and humidity are measured by the external temperature / humidity sensor 4 (step: S101), and the secondary transfer as the external environment sensor 5 is performed. The voltage (Vmon) when measuring the system resistance of the secondary transfer portion by the partial resistance measuring device 50 is measured (S102). As a result, information about the environmental conditions outside the printer casing and the environmental conditions inside the casing is input to the image forming process control section 60 (primary transfer control section 61). The voltage (Vmon) is measured by applying a constant current (I ₀ ) from the power supply device (51) for the secondary transfer voltage to the secondary transfer roll 25 and installing the voltage (Vmon) at that time in the power supply device. This is done by measuring with a voltmeter (52). Either the external temperature / humidity measurement or the monitor voltage measurement of the secondary transfer portion may be performed first or simultaneously.

  Subsequently, the image forming process control unit 60 determines the environment area number of the external environment from the reference data (lookup table) as shown in FIG. 5 based on the temperature and humidity detection information outside the housing. (S103). At this time, the environmental area number is determined as “1” when the detected temperature is “T3” and the humidity is “H5” based on the data in FIG. 5, and the temperature is “T7”. When the humidity is “H8”, it is determined as “2”, and when the temperature is “T12” and the humidity is “H11”, it is determined as “3”. For example, the environmental area number “1” is classified to indicate a low temperature and low humidity environment, “2” is a normal temperature and normal humidity environment, and “3” is a high temperature and high humidity environment.

  Next, the primary transfer control unit 61 selects a primary transfer current reference value based on the environmental area number information (S104). That is, as shown in FIG. 4, the primary transfer current reference value is “I-A1” when the environmental area number is “1”, and “I-A2” when the environmental area number is “2”. When "3" is "I-A3". Here, for example, I-A1 indicates a primary transfer current reference value when the environment area number is 1 (the external environment is in a low temperature and low humidity condition).

Subsequently, the primary transfer control unit 61 determines the level of the monitor voltage (Vmon) when measuring the system resistance of the secondary transfer unit, and selects a correction value for the primary transfer current (S105). Level determination of the monitor voltage (Vmon) is partitioned on the basis the threshold _{(V L1 -A1, V L2 -A1} , such as V _L1 -A2) previously set for each environment area as shown in FIG. 4 This is done by determining which one of the predetermined levels is applicable. The example shown in FIG. 4 is divided into three levels. The correction value of the primary transfer current is automatically selected as a correction value set in advance according to each level of the monitor voltage as shown in FIG.

 For the threshold value in the voltage level determination, a value suitable for estimating the temperature and humidity states (for example, a low temperature and low humidity state, a high temperature and high humidity state) inside the printer housing 1 is selected based on experimental data. Is done.

  For example, continuous printing is performed in a low-temperature and low-humidity environment (environment area number: 1), and the voltage in the power supply device of the constant current control system of the secondary transfer unit at that time is detected (by the secondary transfer unit resistance measuring device 50). At the same time, when the actual temperature (internal temperature) in the vicinity of the secondary transfer portion is measured by the temperature sensor, the result shown in FIG. 7 is obtained. That is, as apparent from the results of FIG. 7, the internal temperature tends to gradually stop after increasing gradually as the number of printed sheets increases, whereas the monitor voltage (Vmon) of the secondary transfer portion. Shows a tendency to gradually stop decreasing after gradually decreasing. Further, when intermittent printing is performed in the same external environment, as illustrated in FIG. 8, the internal temperature rises due to the intermittently performed printing operation, but the intermittent printing operation is not performed for a while. When stopped without being performed (stopped: not printing), there is a tendency to decrease. On the other hand, the monitor voltage (Vmon) at the secondary transfer portion tends to decrease almost in conjunction with the fluctuation in the internal temperature and rises almost in conjunction with the fluctuation in the internal temperature.

  Therefore, by quantifying the change in the monitor voltage (Vmon) of the secondary transfer unit in light of the actual internal temperature fluctuation, the temperature inside the housing is indirectly determined from the value of the monitor voltage (Vmon). It can be seen that it can be detected automatically.

Finally, the corrected primary transfer current value is determined in the primary transfer control unit 61 (S106). That is, as shown in FIG. 4, the corrected primary transfer current value is set to the primary transfer current reference value selected according to the external environment (area number), and to the primary transfer current selected according to the monitor voltage (Vmon). It is a value obtained by adding the correction value. For example, when the external environment area number is “1” and the secondary transfer monitor voltage (Vmon) is at the level of “V _L2 -A1 <Vmon”, the correction value is “IH” according to the reference data shown in FIG. As a result, the corrected primary transfer current value becomes “I−A1 + (IH−A1−3)”.

  Then, the primary transfer control unit 61 finally transmits the corrected primary transfer current value (data) to the power supply circuit 150 of the primary transfer current. Thus, during the primary transfer process after this control operation (and until the next control operation), the primary transfer is performed under the condition that the corrected primary transfer current is applied to the primary transfer roll 15.

  Therefore, in this printer, at least the primary transfer current in the primary transfer process is the detection result of the temperature and humidity outside the housing 1 and the detection result of the monitor voltage when measuring the system resistance of the secondary transfer portion inside the housing 1. It is corrected as appropriate based on both. As a result, even if the environment (temperature, humidity) outside the printer casing and the environment inside the casing fluctuate in various patterns, the primary transfer current is appropriate depending on the environmental conditions of both. Since the values are appropriately corrected, fluctuations in print image quality (especially image unevenness due to primary transfer failure) that may occur due to various fluctuations in both environments are appropriately suppressed. Good print is made.

For example, in this example, the low temperature and low humidity environment (environment area number: 1) shown in FIG. 4 is set to 10 ° C. or less and 15% RH or less, and the primary transfer current reference value (I-A1) in that environment is “17 μA”, the lower limit threshold (V _L1 -A1) of the monitor voltage of the secondary transfer portion is “2500 V”, the upper limit threshold (V _L2 -A1) is “2800 V”, and the primary transfer current correction value is “IH−” “A1-1 = 3 μA”, “IH-A1-2 = 1 μA”, and “IH-A1-3 = 0 μA” are set. Under such a setting, for example, when the detection result of the temperature and humidity outside the housing is 10 ° C. and 15% RH and it is determined that the temperature and humidity are low, the secondary at the detection current of 20 μA. When the monitor voltage (Vmon) detection result of the transfer portion is “3000 V”, the primary transfer current is not corrected, and when the monitor voltage (Vmon) is “2700 V”, the primary transfer current is corrected to “18 μA”. When the monitor voltage (Vmon) was “2400 V”, the primary transfer current was set to be corrected to “20 μA”.

  With this setting, when the outside of the printer casing is in a low-temperature and low-humidity environment, the temperature conditions inside the casing are the contents of the printing operation (continuous printing operation, intermittent printing operation, etc.) (Refer to FIGS. 7 and 8). In this case, if the primary transfer current (reference value) at the time of low temperature and low humidity, which is the external environment, is used as it is, the primary transfer failure is particularly caused. May occur. However, since the primary transfer current is corrected to an appropriate current value according to the monitor voltage (Vmon) of the secondary transfer portion by the above setting, it is possible to perform good printing without causing the primary transfer failure or the like. become. Further, even when the external environment changes to a different situation (such as high temperature and high humidity) over time, such an effect is achieved by the primary transfer current depending on the monitor voltage (Vmon) of the secondary transfer portion in the different environment. Since the value is corrected separately, it is obtained in the same manner.

<Modification>
In the printer, the primary transfer control unit 61 is configured to correct the primary transfer current as the primary transfer control unit 61, but may be configured to correct the primary transfer voltage. In this case, for example, the current value when a constant measurement voltage is applied to the secondary transfer roll 25 from the power supply device (of the constant voltage control method) when measuring the system resistance in the secondary transfer portion resistance measurement device 50 is used. The primary transfer control unit 61 corrects the primary transfer voltage based on the measured current value in accordance with the environmental conditions inside and outside the housing in the same manner as the primary transfer current correction method. Configure.

  Further, the primary transfer control unit 61 of the printer performs correction such that the monitor voltage (Vmon) obtained when measuring the system resistance of the secondary transfer unit is divided into three levels and the correction value of the primary transfer current is determined. However, it is possible to perform a correction for determining the corrected primary transfer current in more detail using an approximate expression based on the result of the monitor voltage (Vmon). For the approximate expression, the relationship between the monitor voltage (Vmon) and an appropriate primary transfer current value is examined in advance through experiments, etc., and an approximate expression for calculating the corrected primary transfer value for the monitor voltage (Vmon) is formulated from the result. It is obtained with. When determining the corrected primary transfer current using such an approximate expression, the system resistance of the secondary transfer section is mainly used from the viewpoint of improving the accuracy of the approximate expression and simplifying correction control. It is preferable to apply at least one of the intermediate transfer belt 21 and the secondary transfer roll 25 that has a characteristic that the resistance value changes substantially linearly with temperature and humidity. For example, the intermediate transfer belt 21 or the secondary transfer roll 25 configured using a member having ion conductivity can be used.

  In the printer, the secondary transfer unit resistance measuring device 50 is applied as the internal environment sensor 5, but a temperature / humidity sensor capable of measuring temperature and humidity may be applied instead of the resistance measuring device 50. Is possible. In this case, the temperature / humidity sensor may be installed in an empty space that can be installed, for example, in the vicinity of the primary transfer portion inside the housing 1. In addition, as the external environment sensor 4, it is possible to use a temperature sensor that measures only the temperature. In this case, only the temperature is used as the environmental area condition (number) as a judgment material when correcting the primary transfer current. What is necessary is just to apply what was reset based on.

  Further, the image forming process control unit 60 of the printer corrects the value of the primary transfer bias such as the primary transfer current as a control condition of the image forming process to be corrected according to the environmental conditions inside and outside the housing 1. However, the image forming process conditions other than the primary transfer bias may be corrected. For example, other image forming process control conditions include an exposure amount in the exposure unit, a developing bias in the developing unit, a rotation speed of the developing roll, a replenishment amount of the developer, and the like. The image forming process control unit 60 may be configured to correct a plurality of image forming processes according to the environmental conditions inside and outside the casing as necessary. In this case, one image forming process control condition is set. Higher quality image formation can be realized than when correction is performed.

  When correcting the control condition related to the exposure amount, as illustrated in FIG. 3, the exposure control unit 63 of the image forming process control unit 60 corrects the exposure amount of the semiconductor laser of the ROS 13 according to the environmental conditions inside and outside the housing. The correction amount may be transmitted to the semiconductor laser drive circuit 130 of the ROS 13. In this case, the exposure control unit 63 corrects the exposure amount of the semiconductor laser of the ROS 13 in accordance with the environmental conditions inside and outside the housing, thereby adjusting the latent image potential on the photosensitive drum 11 and the development potential. By adjusting the difference (development potential difference), the density of the toner image on the photosensitive drum is adjusted. As a result, it is possible to stabilize the developing performance against fluctuations in the environmental conditions inside and outside the casing, and as a result, it is possible to ensure the stable transfer of the developed toner image, thereby stabilizing the image quality. It becomes possible.

  When correcting the control condition relating to the developing bias, as illustrated in FIG. 3, the developing bias value of the developing device 14 in the developing control unit 64 of the image forming process control unit 60 is set according to the environmental conditions inside and outside the housing. The correction may be configured so that the correction amount is transmitted to the developing bias drive circuit 141 of the developing device 14. In this case, the development control unit 64 corrects the development bias value of the development device 14 in accordance with the environmental conditions inside and outside the housing, and thereby the difference between the development potential and the latent image potential on the photosensitive drum 11 ( The density of the toner image on the photosensitive drum is adjusted by adjusting the development potential difference. As a result, it is possible to stabilize the development performance with respect to changes in the environmental conditions inside and outside the housing, and consequently to stabilize the image quality.

  When correcting the control condition relating to the rotation speed of the developing roll, as illustrated in FIG. 3, the rotation speed of the apparatus that rotates the developing roll 14 b of the developing device 14 in the development control section 64 of the image forming process control section 60. The value may be corrected according to the environmental conditions inside and outside the housing, and the correction amount may be transmitted to the rotation driving circuit 142 of the developing roll of the developing device 14. In this case, the rotation speed of the developing roll 14b is corrected by the development control unit 64 in accordance with the environmental conditions inside and outside the housing, thereby adjusting the charge amount of toner (by frictional charging) on the developing roll. As a result, the density of the toner image on the photosensitive drum is adjusted. As a result, it is possible to stabilize the development performance with respect to changes in the environmental conditions inside and outside the housing, and consequently to stabilize the image quality.

  When correcting the control conditions relating to the developer replenishment amount, as illustrated in FIG. 3, the developer replenishment (with respect to the toner cartridge 19) of the developing device in the development control unit 64 of the image forming process control unit 60 is performed. The drive amount (developer transport amount) of the apparatus is configured to be corrected according to the environmental conditions inside and outside the housing, and the correction amount may be transmitted to the developer supply drive circuit 143 of the developing device 14. . In this case, the driving amount of the developer replenishing device of the developing device 14 is corrected by the developing control unit 64 according to the environmental conditions inside and outside the housing, and accordingly, the charge amount of the toner in the developing device 14 is appropriately set. By adjusting, the density of the toner image on the photosensitive drum is adjusted. As a result, it is possible to stabilize the development performance with respect to changes in the environmental conditions inside and outside the housing, and consequently to stabilize the image quality.

  In addition to the above, in the above-described embodiment, toner of four colors (Y, M, C, K) is obtained by repeating the image forming process of charging, exposing, developing, and transferring four times using one photosensitive drum. An example of a so-called four-cycle printer (image forming apparatus) in which a full-color image is formed by sequentially forming an image has been illustrated. However, the present invention is an image forming apparatus that forms an image made of toner. If it is necessary to correct at least one of the image forming process conditions in accordance with the environmental conditions, the image forming method can be applied without any particular limitation. For example, the present invention can be applied to an image forming apparatus of another color image forming system (for example, a tandem system) or an image forming apparatus of a system that forms a single color image such as a monochrome image.

It is explanatory drawing which shows the principal part of the printer of this invention. It is explanatory drawing which shows the structure of the system resistance measuring apparatus of a secondary transfer part. It is a block diagram which shows the structure of the control system of an image formation process. 7 is a control reference comparison table when correcting a primary transfer current according to environmental conditions inside and outside a housing. It is a contrast table of the environmental area number with respect to the environmental condition outside a housing | casing. It is a flowchart which shows the control operation | movement which correct | amends a primary transfer current according to the environmental condition inside and outside a housing | casing. FIG. 10 is a graph showing an outline of a detection result of a monitor voltage of the secondary transfer unit and a temperature inside the casing when (continuous) printing is performed when the outside of the casing is in an environmental condition of low temperature and low humidity. FIG. 6 is a graph showing an outline of a detection result of a monitor voltage of the secondary transfer unit and a temperature inside the casing when (intermittent) printing is performed when the outside of the casing is in an environment of low temperature and low humidity.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Housing | casing 2 ... Paper (recording medium), 4 ... External environment detection means, 5 ... Internal environment detection means, 6 ... Control apparatus, 10 ... Image formation unit (a part of image formation process apparatus), 11 ... Photosensitivity Drum (image carrier), 15 ... primary transfer roll (part of primary transfer device), 20 ... intermediate transfer unit (part of image forming process equipment), 21 ... intermediate transfer belt (intermediate transfer body), 25 ... second Next transfer roll (part of the secondary transfer device), 50... System resistance measuring device, 60... Image forming process control unit (control means), 61.

Claims (4)

A series of image forming process operations in which an electrostatic latent image is formed on an image carrier and then developed into a toner image, and the toner image is transferred directly to a recording medium or via an intermediate transfer member. Imaging process equipment to perform,
A housing having an internal space in which the imaging process equipment is installed;
An external environment detection means for detecting at least the temperature outside the housing;
An internal environment detection means for detecting an environmental condition related to at least the temperature of the internal space of the housing;
Control means for correcting at least one of a plurality of control conditions related to the image forming process operation based on both the detection result of the external environment detection means and the detection result of the internal environment detection means. An image forming apparatus. The image forming process device has a primary transfer device that transfers a toner image on the image carrier to the recording medium or an intermediate transfer member by electrostatic action by applying a primary transfer bias,
The image forming apparatus according to claim 1, wherein the control unit corrects at least a value of a primary transfer bias applied in the primary transfer apparatus. The image forming process device has a secondary transfer device that transfers the intermediate transfer member and a toner image transferred to the intermediate transfer member to the recording medium of a secondary transfer member,
3. The measuring apparatus according to claim 1 or 2, wherein the internal environment detecting means is a measuring device for measuring a voltage or a current when detecting a system resistance of a secondary transfer portion constituted by the intermediate transfer member and the secondary transfer device. The image forming apparatus described.   The control means is set to correct a control condition related to the image forming process operation selected based on a detection result of the external environment detection means according to a detection result of the internal environment detection means. The image forming apparatus according to any one of 1 to 3.

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