JP2009008839A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having simple and inexpensive constitution and accurately obtaining ambient temperature of an image reading part and highly accurately correcting output of the image reading part based on the ambient temperature. <P>SOLUTION: The image forming apparatus includes an image forming part 3, an intermediate transfer part 2, a fixing part 4, a temperature sensor 81 detecting temperature outside the apparatus, a density sensor 8 reading a toner image, a timer part 95 measuring time elapsed from the end of the previous image forming, a calculation part calculating the present ambient temperature T of the density sensor 8 based on detection temperature by the temperature sensor 81 or the ambient temperature T of the density sensor 8 obtained when starting the previous image forming, the rise of the ambient temperature T of the density sensor 8 calculated based on a previous image forming condition and the time elapsed from the end of the previous image forming, and a control part 9 correcting the output of the density sensor 8 so as to correct characteristic change of the density sensor 8 due to the ambient temperature T based on a result obtained by calculating the ambient temperature T of the density sensor 8. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer, a copier, or a multifunction peripheral that forms an image by developing an electrostatic latent image with toner.

  Conventionally, a toner image is formed on an image forming apparatus such as a printer, a copier, or a multi-function printer capable of forming a color image, and the toner image is primarily transferred to an intermediate transfer member such as an intermediate transfer belt. Some toner images are formed by secondarily transferring a toner image on the body onto a sheet such as paper. For example, a full-color image forming apparatus forms a toner image of each color (for example, four colors such as black, yellow, cyan, and magenta), performs primary transfer while superimposing the toner images of each color on an intermediate transfer member, and performs intermediate transfer. Once a full color toner image is formed on the transfer body, the toner image is secondarily transferred to a sheet.

  In an image forming apparatus using such an intermediate transfer member, an image reading unit that reads a toner image primarily transferred to the intermediate transfer member may be provided. The image reading unit checks the amount of positional deviation of each color toner image in the primary transfer and the density of each color toner image from the read result. In this way, the density of the formed image is made appropriate, and the occurrence of positional deviation of the superimposed toner images of each color is prevented, thereby improving and maintaining the image quality.

  Specifically, for example, the image reading unit is configured using a light source or an optical sensor that irradiates light toward a detection target, and the optical sensor receives the light irradiated on the intermediate transfer member. Then, the output (for example, current) of the optical sensor changes due to the change in the light receiving state of the optical sensor, and the density of the toner image is detected by this change, and the position of the toner image on the intermediate transfer member is detected. However, in general, the output characteristics of an optical sensor can change depending on the temperature. In addition, the amount of light emitted from the light source (for example, LED) and the amplification factor of the amplification unit for amplifying the output of the optical sensor may vary depending on the temperature. That is, even if the same object is detected, the output changes depending on the temperature.

A change in the light amount of the light source, a change in the characteristics of the amplification unit, and the like due to this temperature lower the image reading accuracy. In order to prevent the adverse effect of the characteristic change due to the temperature of the image reading unit, for example, an invention described in Patent Document 1 has been proposed. Specifically, in Patent Document 1, an image reading unit (detecting unit) is arranged at a position where a toner image is read on an intermediate transfer belt that is substantially farthest from a fixing device that generates a lot of heat. An image forming apparatus in which a cooling fan for cooling is provided and temperature sensors are arranged in the vicinity of the image reading unit and in the vicinity of the fixing device is disclosed. With this configuration, an attempt is made to prevent the reading accuracy of the image reading means from deteriorating due to thermal factors (see Patent Document 1: Claim 7, Abstract, Paragraph 0118, FIG. 1, etc.).
JP 2001-027833 A

  However, in the invention described in Patent Document 1, it is necessary to additionally provide a cooling fan in order to cool the image reading unit. There is also a problem that a cooling fan installation space and a ventilation path to the image reading means must be secured. In the invention described in Patent Document 1, the detection result of the image reading means is corrected by the temperature sensor. However, a plurality of temperature sensors are provided (see Patent Document 1: Claim 41, Claim 50, etc.). However, there is also a problem that the manufacturing cost of the image forming apparatus increases.

  In order to improve the accuracy of the image reading unit, as another configuration, an optical sensor only for detecting the current light amount of the light source in the image reading unit is separately provided in the vicinity of the image reading unit. A temperature sensor for detecting the temperature of the optical sensor of the image reading unit may be separately provided near the image reading unit, and the detection result of the image reading unit may be corrected based on the output of the temperature sensor. It may be done. However, in either case, a separate optical sensor and temperature sensor must be provided, and there remains a problem that the manufacturing cost of the image forming apparatus increases.

  The present invention has been made in view of the above-described problems of the prior art. The ambient temperature of the image reading unit can be obtained with high accuracy with a simple and inexpensive configuration without providing a large number of sensors. It is an object of the present invention to provide an image forming apparatus capable of correcting the output of an image reading unit based on temperature and adjusting the density and positional deviation of a toner image on an intermediate transfer member with high accuracy.

  In order to solve the above-mentioned problems, an invention according to claim 1 is directed to an image forming unit for forming a toner image of one color or more, and a toner image formed by the image forming unit is primarily transferred, and the toner image is formed on a sheet. A secondary transfer intermediate transfer unit, a fixing unit that pressurizes and heats the secondary-transferred toner image and fixes the toner image on the sheet, an environmental temperature detection unit for detecting an external temperature in the installation environment of the apparatus, An image reading unit that reads the toner image primarily transferred to the intermediate transfer unit, a time measuring unit that measures the time elapsed since the previous image formation was completed, and a temperature detected by the environmental temperature detection unit or The ambient temperature of the image reading unit obtained by the calculation at the start of the previous image formation, the increase in the ambient temperature of the image reading unit calculated based on the image forming conditions in the previous image formation, and the elapsed from the end of the previous image formation did Based on the calculation result of the ambient temperature of the image reading unit based on the calculation result of the ambient temperature of the image reading unit based on the calculation result of the ambient temperature of the image reading unit by the calculation unit In order to perform correction, a control unit for correcting the output of the image reading unit is provided.

  According to this configuration, the increase in the ambient temperature of the image reading unit is calculated according to the image forming conditions based on the environmental temperature or the ambient temperature of the image reading unit at the start of the previous image formation, and the previous image formation is completed. The current ambient temperature of the image reading unit can be calculated by calculating the decrease in the ambient temperature based on the time elapsed since. That is, the ambient temperature of the image reading unit can be detected with a simple and inexpensive configuration without providing a temperature sensor for detecting the ambient temperature of the image reading unit. And since the output of an image reading part is correct | amended based on this detected temperature, the reading precision of an image reading part can be improved.

  According to a second aspect of the present invention, in the first aspect of the present invention, the timekeeping unit also counts the time that has elapsed since the start of the current image formation and continues to a predetermined number of sheets or more. When the image formation is performed, based on the ambient temperature of the image reading unit at the start of image formation, the image formation conditions of the current image formation, and the time from the start of the image formation, During the image formation, the ambient temperature of the image reading unit is obtained, and the control unit, based on the current ambient temperature of the image reading unit obtained by the arithmetic unit when the predetermined number of image formations are performed, The output of the image reading unit was corrected.

  If image formation is performed continuously, the ambient temperature of the image forming unit and the intermediate transfer unit also rises, which may affect the image quality, and the operation of the image forming unit and the intermediate transfer unit may be calibrated. . When the calibration is performed, the reading accuracy of the image reading unit may be deteriorated due to the temperature rise. However, according to this configuration, when a predetermined number of images are formed, the ambient temperature of the image reading unit can be calculated, and the output of the image reading unit can be corrected even during image formation. . Therefore, calibration performed in the middle of image formation can be appropriately performed.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, a sheet on which a toner image is fixed on one side after passing through the fixing unit is conveyed again to the intermediate transfer unit to perform duplex printing. The calculation unit calculates an increase in ambient temperature of the image reading unit, with the presence or absence of double-sided printing as part of the image forming conditions.

  When double-sided printing is performed, a single-side printed sheet heated through the fixing unit is conveyed through the apparatus, so that the internal temperature of the apparatus and the ambient temperature of the image reading unit also increase. However, according to this configuration, since the ambient temperature of the image reading unit is calculated in consideration of the temperature rise due to double-sided printing, the accurate ambient temperature of the image reading unit can be calculated. Therefore, since the output of the image reading unit is corrected based on the detected temperature, the reading accuracy of the image reading unit can be improved.

  According to a fourth aspect of the present invention, in the first aspect of the present invention, the number of sheets on which an image is formed is a part of the image forming condition, and the calculation unit is configured to read the image. The increase in the ambient temperature of the part was calculated.

  When image formation is performed continuously, the ambient temperature of the image reading unit may rise due to the heat of the fixing unit depending on the number of sheets (especially in the case of duplex printing). However, according to this configuration, the ambient temperature of the image reading unit is calculated while taking into account the temperature rise due to the number of images formed, so that the accurate ambient temperature of the image reading unit can be calculated. Therefore, since the output of the image reading unit is corrected based on the detected temperature, the reading accuracy of the image reading unit can be improved.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the arithmetic unit is configured to determine the time elapsed since the last image formation and the temperature attenuation of the image reading unit. Based on the curve, the current ambient temperature of the image reading unit is calculated.

  According to this configuration, the current ambient temperature of the image reading unit can be calculated based on the temperature decay curve indicating the relationship between time and the decrease in ambient temperature of the image reading unit. In other words, since the temperature decay curve is used, the current ambient temperature of the image reading unit can be easily calculated. Therefore, since the output of the image reading unit is corrected based on the detected temperature, the reading accuracy of the image reading unit can be improved.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the image reading unit emits light toward the intermediate transfer unit and the toner image transferred to the intermediate transfer unit. A light emitting unit that emits light, a light receiving unit that outputs current according to the amount of reflected light, and a current amplifying unit that amplifies the current output by the light receiving unit. It was.

  According to this configuration, the image reading unit can be configured with these members at low cost. Furthermore, if these members are unitized, the image reading unit can be further reduced in size and cost. An example of a preferable configuration of the image reading unit is shown.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the control unit is configured to change a light amount of the light emitting unit according to a temperature and a current amplification of the current amplifying unit according to a temperature. Based on the change in rate, the voltage or current supplied to the light emitting unit is controlled to adjust the amount of light emitted from the light emitting unit, thereby correcting the output of the image reading unit.

  According to this configuration, even when the characteristics of each member of the image reading unit change due to a temperature rise or the like, when the same target is detected, the output of the image reading unit is the same. Therefore, since the output of the image reading unit is corrected based on the detected temperature, the reading accuracy of the image reading unit can be improved.

  According to an eighth aspect of the invention, in the invention according to any one of the first to seventh aspects of the invention, the control unit is configured to control the image forming unit and / or the output unit based on the corrected output of the image reading unit. The intermediate transfer portion is controlled to adjust the density of the formed toner image and to adjust the positional deviation in the primary transfer of the toner image.

  According to this configuration, the density of the toner image can be corrected based on the output of the image reading unit, and the toner density of the formed image can be maintained in an optimum state. Further, based on the output of the image reading unit, it is possible to correct misalignment during the primary transfer of the toner image. Therefore, it is possible to provide an image forming apparatus with high quality of the formed image.

  As described above, according to the present invention, the ambient temperature of the image reading unit can be detected with a simple and inexpensive configuration, and the output of the image reading unit can be corrected based on the detected ambient temperature. . That is, the reading accuracy of the image reading unit can be improved without adding a special configuration. By increasing the reading accuracy of the image reading unit, as a result, it is possible to effectively adjust various operations such as toner image formation in the image forming unit and primary transfer in the intermediate transfer unit.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. However, each element such as configuration and arrangement described in this embodiment does not limit the scope of the invention and is merely an illustrative example.

  First, the present invention can be applied to various image forming apparatuses. As an example, a case where the present invention is applied to a color-compatible printer 1 among image forming apparatuses will be described with reference to FIG. FIG. 1 is a schematic front sectional view showing a schematic structure of a printer 1 according to an embodiment of the present invention.

  The printer 1 in the present embodiment receives image data of an image to be formed from an external computer 100 (see FIG. 7) connected by a network, a cable, etc., and forms an image on a sheet. As shown in FIG. 1, the printer 1 includes an intermediate transfer unit 2, an image forming unit 3, a fixing unit 4, a sheet supply unit 5, a sheet conveyance path 6, a duplex printing conveyance path 7, a density, as shown in FIG. 1. A sensor 8 or the like is provided (the sheet conveyance path is indicated by a broken line).

  The intermediate transfer unit 2 and the image forming unit 3 are in contact with each other and are provided in a central portion inside the main body. In order to form toner images of a plurality of colors, the image forming unit 3 includes four image forming units 31 (31K, 31Y, 31C, 31M) (details will be described later).

  The fixing unit 4 fixes the toner image secondarily transferred to the sheet by the intermediate transfer unit 2. The fixing unit 4 includes a heating roller 41 provided with a heating element therein, and a pressure roller 42 in pressure contact with the heating roller 41. A sheet on which the toner image has been secondarily transferred is heated by the sheet conveyance path 6 through the heating roller 41. And enters the nip of the pressure roller 42, and is pressed and heated to fix the toner image.

  The sheet supply unit 5 is provided at the lowermost part and includes a cassette 51, a pickup roller 52, and the like. The cassette 51 has a box shape with an open top, and stores a bundle of various sheets such as printer paper, label paper, OHP sheet, and cardboard. The pickup roller 52 abuts on the uppermost sheet and feeds the sheets one by one to the sheet conveyance path 6 when forming an image.

  The sheet conveyance path 6 is a path for conveying a sheet from the sheet supply unit 5 to the discharge tray 61. In the sheet conveyance path 6, a guide and a conveyance roller pair 62 and a switchback roller pair 63 that can be driven to rotate in the forward and reverse directions are provided at the sheet discharge port 64 in order to enable duplex printing. The switchback roller pair 63 rotates in the direction in which the sheet is discharged from the printer 1 (in the direction of arrow A in FIG. 1) during single-sided printing, and functions as a conveyance roller pair.

  The double-sided printing conveyance path 7 is a conveyance path for conveying a single-side printed sheet for double-sided printing. The double-sided printing conveyance path 7 conveys a sheet having a toner image fixed on one side through the fixing unit 4 toward the intermediate transfer unit 2 again. For this reason, one end of the duplex printing conveyance path 7 is connected (branched) to the sheet conveyance path 6 between the fixing unit 4 and the sheet discharge unit 64, and the other end is the driving roller 21, secondary of the intermediate transfer unit 2. Connected (joined) upstream of the transfer roller 25 in the sheet conveying direction. The duplex printing conveyance path 7 includes a switching guide 72 provided at a branch point 71 between the sheet conveyance path 6 and the duplex printing conveyance path 7 and configured to be rotatable, a duplex printing roller pair 73, and the like.

  Sheet conveyance during duplex printing in the printer 1 of the present embodiment is performed as follows. The sheet that has passed through the fixing unit 4 and has an image formed on one side is temporarily conveyed toward the discharge tray 61 (the switchback roller pair 63 rotates in the direction of arrow A in FIG. 1). However, before the sheet is completely discharged, the rotation direction of the switchback roller pair 63 is reversed (the direction of arrow B in FIG. 1). That is, the sheet is fed into the printer 1.

  At this time, the switching guide 72 closes the sheet conveyance path 6 so that the sheet switched back toward the fixing unit 4 does not enter. That is, the switched back sheet is guided to the duplex printing conveyance path 7. Then, the duplex printing roller pair 73 provided on the conveyance path conveys the sheet that has been printed on one side, and rejoins the sheet conveyance path 6 before the intermediate transfer unit 2.

  In the present embodiment, the density sensor is provided below the intermediate transfer belt 24 and between the secondary transfer roller 25 and the image forming unit 31K. The density sensor 8 reads the toner image primarily transferred to the intermediate transfer belt 24, and the density sensor 8 detects the density and displacement of the toner image primarily transferred by this reading (details will be described later). ).

  In the printer 1 according to the present embodiment, for example, a temperature sensor 81 (corresponding to an environmental temperature detection unit) for detecting an external temperature in the installation environment of the printer 1 is provided below the driven roller 22. The detection result of the temperature sensor 81 indicates that, for example, when the fixing unit 4 is warmed up, the heating roller 41 is heated evenly regardless of the environmental temperature. It is used to control the printer 1 so that image formation is performed appropriately while taking the temperature into consideration.

  Next, the intermediate transfer unit 2 and the image forming unit 3 will be described in detail with reference to FIG. FIG. 2 is an enlarged front schematic cross-sectional view of the intermediate transfer unit 2 and the image forming unit 3 of the printer 1 according to the embodiment of the present invention.

  The image forming unit 3 includes four image forming units 31K, 31Y, 31C, and 31M. Here, the image forming unit 31K forms a black toner image, the image forming unit 31Y forms a yellow toner image, the image forming unit 31C forms a cyan toner image, and the image forming unit 31M forms a magenta toner image. The image forming units 31K, 31Y, 31C, and 31M have substantially the same configuration although the colors of the toners to be used are different, and hereinafter, the characters K, Y, C, and M are indicated unless otherwise described. Omitted.

  Each image forming unit 31 includes a photosensitive drum 32, a charging device 33, an exposure device 34, a developing device 35, a cleaning device 36, and the like. The photosensitive drum 32 is rotated counterclockwise by a driving mechanism (not shown) including a motor, a gear, and the like. When forming a toner image, first, the charging device 33 provided below the photosensitive drum 32 charges the peripheral surface of the photosensitive drum 32 to a predetermined potential. Next, the exposure device 34 further below the charging device 33 irradiates the peripheral surface of each charged photosensitive drum 32 with laser light (illustrated by a broken line) corresponding to each color based on the input image data. The surface of the body drum 32 is scanned and exposed to form an electrostatic latent image. The developing device 35 supplies toner to the electrostatic latent image, and the electrostatic latent image is developed with the toner. Each image forming unit 31 has a different toner color supplied from the developing device 35. In this embodiment, four colors of black, yellow, cyan, and magenta are used. The cleaning device 36 performs cleaning by removing the toner remaining on the peripheral surface of the photosensitive drum 32 after the primary transfer.

  Next, the intermediate transfer unit 2 will be described. The intermediate transfer unit 2 includes a driving roller 21, a driven roller 22, a primary transfer roller 23, an intermediate transfer belt 24, a secondary transfer roller 25, and the like.

  The drive roller 21 is connected to a drive mechanism (not shown) including a motor, a gear, and the like, and is driven to rotate at a predetermined speed. The intermediate transfer belt 24 is stretched around the drive roller 21, the driven roller 22, and the primary transfer roller 23, and the intermediate transfer belt 24 circulates when the drive roller 21 rotates (in FIG. 2, the intermediate transfer belt 24 rotates clockwise). ). Further, a total of four primary transfer rollers 23 are provided and abut on the respective photosensitive drums 32 via the intermediate transfer belt 24. Further, in order to primarily transfer the toner image on the photosensitive drum 32 to the intermediate transfer belt 24, a predetermined voltage is applied to the primary transfer roller 23 at a predetermined timing. The specific primary transfer sequence is the start position of the primary transfer on the intermediate transfer belt 24, the transfer of the magenta toner image on the photosensitive drum 32 of the image forming unit 31M is started, and then the same as the magenta. A cyan toner image by the image forming unit 31C is overlaid at the start position of the primary transfer, and thereafter a yellow toner image by the image forming unit 31Y and a black toner image by the image forming unit 31K are overlaid in the same manner. In this way, a full-color toner image is formed on the surface of the intermediate transfer belt 24 so as to overlap.

  The secondary transfer roller 25 contacts the driving roller 21 via the intermediate transfer belt 24, and a predetermined voltage is applied to the nip at a timing when the toner image and the conveyed sheet overlap, and the toner image on the intermediate transfer belt 24 is applied. Is secondarily transferred to the sheet. The sheet on which the toner image is transferred is sent to the fixing unit 4. The intermediate transfer belt 24 after the secondary transfer is cleaned by removing residual toner and the like by a belt cleaning device 36 that contacts the driven roller 22 via the intermediate transfer belt 24.

  Next, based on FIG. 3, the detail of the density | concentration sensor 8 which concerns on embodiment of this invention is demonstrated. FIG. 3 is an explanatory diagram for explaining the concentration sensor 8 according to the embodiment of the present invention.

  As described above, the density sensor 8 reads the toner image transferred onto the intermediate transfer belt 24. Therefore, the density sensor 8 is supported so as to face the intermediate transfer belt 24 while being provided with a certain gap (for example, 20 mm).

  The density sensor 8 includes an intermediate transfer belt 24 and a light emitting unit 82 (for example, an LED) that emits light toward the toner image transferred to the intermediate transfer belt 24, and an amount of light reflected by the intermediate transfer belt 24 and the toner image. The light receiving unit 83 (for example, a photodiode) serving as a photoelectric conversion element that outputs a current in response to the current and the current amplifying unit 84 (for example, a transistor) for amplifying the current output from the light receiving unit 83 are configured.

  In the density sensor 8, the output current changes depending on the light receiving state of the light receiving unit 83. Due to the change in the output current, the density sensor 8 can detect the passage of the toner image. For example, if the toner is black, it absorbs light from the light emitting portion 82 as compared with other color toners, and the higher the density of black toner, the more light is absorbed (on the other hand, the surface of the intermediate transfer belt 24). Is a glossy surface). As described above, the amount of light received by the light receiving portion 83 and the reflectance differ depending on the color and density of the toner, and the toner density on the intermediate transfer belt 24 can be detected from the color of the toner and the magnitude of the output current. .

  More specifically, as shown in FIG. 3, the toner is powder, and when the toner passes the detection area of the density sensor 8, the amount of light received by the light receiving unit 83 changes. Therefore, the output current of the light receiving unit 83 changes, and the passage of the toner image can be detected. Further, the toner density can also be detected by the amount of the output current that has decreased.

  Next, based on FIG. 4, detection of the toner image positional deviation amount and density by the density sensor 8 according to the embodiment of the present invention will be described. FIG. 4 is an explanatory diagram illustrating an example of detection of a positional deviation amount and density by the density sensor 8 according to the embodiment of the present invention. FIG. 4A is an explanatory diagram illustrating an example of positional deviation amount detection in the sub-scanning direction. . (B) is an explanatory view showing an example of positional deviation detection in the sub-scanning direction. FIG. 4 is a view of the intermediate transfer belt 24 and the density sensor 8 as viewed from below.

  As shown in FIG. 4A, when detecting the positional deviation amount of the toner image in the sub-scanning direction of the intermediate transfer belt 24, the image forming unit 3 is in a direction perpendicular to the sub-scanning direction (parallel to the main scanning direction). Then, a pattern image P1 composed of four color lines is formed, and this pattern image P1 is transferred to the intermediate transfer belt 24. Here, the black line K1, the yellow line Y1, the cyan line C1, and the magenta line M1 are sequentially arranged from the right side of FIG.

  The density sensor 8 detects the passage of each line. The rotation speed of the intermediate transfer belt 24 and the time required for the passage of each line (for example, the time measuring unit 95 of the control unit 9 to be described later) The interval between each line can be calculated from (measured from the change in output). From the difference between the actually obtained line intervals and the line intervals (ideal intervals) that the image forming unit 3 attempts to form, the amount of positional deviation of the toner image in the sub-scanning direction can be obtained. . Further, the ideal density of the toner image to be formed by the image forming unit 3 is compared with the actually detected density, and the difference between the ideal density and the actual image density can be obtained. That is, the density of the toner image can be detected from the output of the density sensor 8 when reading the pattern image P1.

  On the other hand, the amount of misalignment of the toner image in the main scanning direction is, for example, as shown in FIG. 4B with respect to a pattern image P2 formed with a diagonal line of 45 ° with respect to the sub-scanning direction (main scanning direction). It can be obtained by reading. Here, it is assumed that the pattern image P2 is formed from a black line K2, a yellow line Y2, a cyan line C2, and a magenta line M2 in order from the right in FIG.

  When the intermediate transfer belt 24 circulates and the density sensor 8 reads the pattern image P1, the interval between the lines can be obtained from the rotational speed of the intermediate transfer belt 24 and the time until the next line is detected. it can. Here, since each line is formed at an angle of 45 °, the interval in the sub-scanning direction and the interval in the main scanning direction are the same for each line, and the obtained interval is the interval between the lines in the main scanning direction. But there is. From the difference between the obtained interval and the interval (ideal interval) of each line that the image forming unit 3 is to form, the amount of positional deviation of the toner image in the main scanning direction can be obtained.

  From the obtained positional deviation amount and toner density, it is possible to adjust (calibrate, calibrate) the position of the toner image transferred to the intermediate transfer belt 24 and the density of the toner image. For example, when adjusting the positional deviation, the timing and scanning time of the exposure device 34 are adjusted, and when adjusting the toner density, the charging potential of the photosensitive drum 32 by the charging device 33 is adjusted. The voltage applied to the primary transfer roller 23 is adjusted. This calibration is performed at an arbitrary time such as when the printer 1 is turned on, when a predetermined number of images are continuously formed, or when a predetermined time has elapsed, to maintain the image quality.

  As described above, the density and positional deviation amount of the toner image are adjusted based on the output value of the density sensor 8, but there is a problem that the output characteristics of the density sensor 8 change depending on the ambient temperature T of the density sensor 8. . This point will be described with reference to FIGS. FIG. 5 is a diagram illustrating an example of a change in characteristics depending on the temperature of a member constituting the density sensor 8, and FIG. 5A is a graph illustrating an example of a temperature characteristic of the light amount of the LED serving as the light emitting unit 82. b) is a graph showing an example of the temperature characteristic of the amplification factor of the current amplifying unit 84; FIG. 6 is an explanatory diagram for explaining correction of a characteristic change due to temperature of the density sensor 8 according to the embodiment of the present invention.

  In the concentration sensor 8 of the present embodiment, an LED can be used for the light emitting unit 82. However, as shown in FIG. 5A, when the current flowing through the LED is made constant, the amount of light generally decreases as the temperature rises. To do. In other words, in order to make the light quantity of the LED constant, it is necessary to increase or decrease the current flowing through the LED depending on the temperature.

  On the other hand, the concentration sensor 8 of the present embodiment can use a transistor for the current amplifying unit 84. However, as shown in FIG. 5B, a semiconductor is generally affected by a temperature change. For example, when the temperature rises, Increases the current amplification factor.

  Considering these characteristic changes of the density sensor 8, a method for correcting the output of the density sensor 8 will be described with reference to FIG. In FIG. 6, the output value of the density sensor 8 in an environment where the ambient temperature T of the density sensor 8 is 20 ° C. is assumed to be 100.

  Considering various factors, the output current of the concentration sensor 8 of this embodiment gradually decreases when the ambient temperature T exceeds 20 ° C., as shown in the upper graph in FIG. On the other hand, even if the ambient temperature T decreases from 20 ° C., the output current slightly decreases (see FIG. 3). Therefore, when 20 ° C. is used as a reference, for example, when the ambient temperature T of the density sensor 8 becomes 60 ° C., the density detection of the toner image is particularly affected unless the output of the density sensor 8 is corrected. Detection accuracy decreases. In addition, since the density sensor 8 may not be able to detect the passage of the toner image, a problem may also occur in the detection of misalignment.

  Therefore, in the present embodiment, as shown in the lower graph of FIG. 6, the current flowing through the LED is changed according to the ambient temperature T of the concentration sensor 8 based on the correction curve corresponding to the temperature change of the output current of the concentration sensor 8. Increase or decrease. In other words, on the basis of the current flowing through the LED at 20 ° C., the voltage or current supplied to the LED is controlled based on the change in the light amount of the LED and the current amplification factor of the current amplifying unit 84 depending on the temperature. Adjustment is performed to correct the output of the density sensor 8.

  As a result, when the density sensor 8 reads the same target, the outputs of the density sensor 8 match regardless of the ambient temperature T of the density sensor 8. The characteristics shown in FIGS. 5 and 6 are not common to all density sensors 8, but differ depending on the light source used and the current amplifying unit 84. Therefore, actually, the voltage, current, and the like supplied to the light emitting unit 82 may be adjusted according to the characteristics of the members constituting the density sensor 8.

  Next, an example of correction control for the density of the printer 1 and the positional deviation of the toner image according to the embodiment of the present invention will be described with reference to FIG. FIG. 7 is a block diagram of the printer 1 according to the embodiment of the present invention.

  First, the printer 1 according to the present embodiment is provided with a control unit 9 for controlling each part of the printer 1. The control unit 9 is provided on a board appropriately provided in the printer 1, and is connected to each unit constituting the printer 1 by signal lines in order to transmit a control signal.

  Specifically, the control unit 9 includes a CPU 91, a RAM 92, a ROM 93, an HDD 94, a time measuring unit 95, a current control unit 96, and the like. The CPU 91 (corresponding to the arithmetic unit) is a central processing arithmetic device, and performs arithmetic processing necessary for control of the printer 1 and image formation. Further, calculation for obtaining the ambient temperature T of the density sensor 8, calculation for correcting the output of the density sensor 8 based on the obtained output of the ambient temperature T, and correction control of the actual output of the density sensor 8 are also performed.

  As the storage device, a RAM 92, a ROM 93, and an HDD 94 are used. For example, the RAM 92 temporarily develops a control program and data or is transmitted from the external computer 100 so that the CPU 91 controls the printer 1. It is used for storing image data. Further, the ROM 93 and HDD 94 are based on a program for controlling the printer 1, control data, data and program for calculating the current ambient temperature T of the density sensor 8, and the calculated current ambient temperature T. Then, data, a program and the like for correcting the output of the density sensor 8 are stored.

  The time measuring unit 95 is a so-called timer, and measures various times necessary for controlling the printer 1. For example, the time from the end of the previous image formation to the present time is measured (details of this point will be described later). The current control unit 96 is responsible for actual control of the current flowing through the LED (light emitting unit 82) of the image reading unit based on the current ambient temperature T of the density sensor 8.

  Next, the calculation of the ambient temperature T of the concentration sensor 8 according to the embodiment of the present invention will be described based on FIGS. FIG. 8 is a graph for explaining the calculation of the ambient temperature T of the density sensor 8 when duplex printing is performed in the previous image formation. FIG. 9 is a graph for explaining the calculation of the ambient temperature T of the density sensor 8 when single-sided printing was performed in the previous image formation. FIG. 10 is a graph for explaining the calculation of the ambient temperature T of the density sensor 8 during double-sided printing image formation. FIG. 11 is a graph for explaining the calculation of the ambient temperature T of the density sensor 8 during image formation for single-sided printing.

  First, as described above, the output of the concentration sensor 8 of the present embodiment is corrected by temperature. However, in order to perform appropriate correction, it is necessary to accurately know the ambient temperature T of the density sensor 8.

  Here, if any member such as a temperature sensor only for detecting the ambient temperature T of the density sensor 8, a photo sensor for detecting the light quantity of the LED, a cooling fan for cooling the density sensor, or the like is provided, Cost increases. Also, a space for installing these components and an interface for controlling the operation are required, and these points also have problems in terms of cost and space. However, since the present invention obtains the ambient temperature T of the density sensor 8 by calculation without providing these members separately, the manufacturing cost can be reduced and the printer 1 can be downsized.

  The calculation of the ambient temperature T of the density sensor 8 by this calculation is the ambient temperature detected by the temperature sensor 81 or the density sensor obtained by the previous calculation at the start of image formation if no image formation is currently being performed. 8, the temperature rise of the density sensor 8 calculated based on the image forming conditions in the previous image formation, and the elapsed time t1 from the end of the previous image formation. This calculation can be performed by, for example, the CPU 91 of the control unit 9.

  On the other hand, if image formation is continuously performed on a predetermined number of sheets or more, the ambient temperature T of the image reading unit at the start of image formation, the image formation conditions for image formation currently being performed, and image formation Based on the time from the start, the CPU 91 obtains the ambient temperature T of the image reading unit during image formation, and the control unit 9 obtains the current image reading unit obtained when a predetermined number of images are formed. Based on the ambient temperature T, the output of the density sensor 8 is corrected. That is, the output of the density sensor 8 is corrected in accordance with adjustment (calibration, calibration) of the image forming unit 3 and the intermediate transfer unit that are performed when image formation is continuously performed.

  Here, the predetermined number of sheets can be set to a certain number of sheets, for example, 10 sheets or 20 sheets. However, the heat discharge capability of the image forming apparatus and the size of the sheet on which the image is formed (for example, A4, A3, etc.) It can be set appropriately depending on the situation. It should be noted that the ambient temperature of the concentration sensor 8 may be obtained periodically at regular intervals instead of every predetermined number.

Furthermore, the present embodiment is characterized in that attention is paid to whether or not the image formation performed at the previous time or the current image formation is duplex printing. Therefore, the calculation of the ambient temperature T is roughly divided into four patterns. Specifically, it is as follows, and each pattern will be described below.
(Pattern 1) When the current image formation is not being performed and the previous image formation is duplex printing (FIG. 8).
(Pattern 2) The current image is not being formed and the previous image formation is not duplex printing (FIG. 9).
(Pattern 3) When an image is currently being formed and the image formation is duplex printing (FIG. 10).
(Pattern 4) When an image is currently being formed and the image formation is not duplex printing (FIG. 11).
Note that when image formation is performed for the first time after the printer 1 is turned on, there is no previous image formation itself. Therefore, when obtaining the current ambient temperature T, the temperature detection result of the temperature sensor 81 is used. The ambient temperature T of the current density sensor 8 may be set.

(Pattern 1) When image formation is not currently being performed and the previous image formation is duplex printing.
First, in the pattern 1, as shown in FIG. 8, the reference for calculating the ambient temperature T is the ambient temperature T <b> 1 of the density sensor 8 calculated at the start of the previous image formation detected by the temperature sensor 81. For example, the ambient temperature T1 is calculated every time image formation is performed and stored in the RAM 92 or the like. Based on the ambient temperature T1, the ambient temperature T2 of the density sensor 8 at the end of double-sided printing is obtained.

  Here, the reason for paying attention to the difference between the double-sided printing and the single-sided printing in the present invention is that the double-sided printing is heated by the fixing unit 4 (the fixing unit 4 itself is heated to about 200 ° C.) during the single-sided printing. This is because the sheet is conveyed while being circulated toward the intermediate transfer unit 2, so that the temperature in the printer 1, and hence the ambient temperature T of the density sensor 8, increases compared to the case of single-sided printing.

  Specifically, when calculating the ambient temperature T2, the CPU 91 calculates the temperature rise curve CL1 shown in the graph on the right side of FIG. 8 (the horizontal axis is the number of images formed (number of printed sheets), and the vertical axis is the density sensor 8 surroundings. Calculation based on temperature. Note that the data of the temperature rise curve CL1 is stored in the ROM 93 or the like, and the CPU 91 reads this data into the RAM 92 as appropriate. Then, from the point of the ambient temperature T1 on the curve, the ambient temperature T2 is calculated corresponding to the number of printed sheets at the previous image formation.

  Next, the CPU 91, for example, the elapsed time t1 from the end of the previous image formation to the present time counted by the time measuring unit 95, and the temperature decay shown in the graph on the left side of FIG. The current ambient temperature T3 of the density sensor 8 is calculated based on the curve CL2 (the horizontal axis is the elapsed time t from the end of the previous image formation, and the vertical axis is the ambient temperature T of the density sensor 8).

  This temperature decay curve CL2 can be used in, for example, about three types (hereinafter the same) because the ambient temperature T of the concentration sensor 8 decreases depending on the environmental temperature. Specifically, a temperature decay curve CL2A when the environmental temperature is less than 10 ° C. (shown with a two-dot chain line), and a temperature decay curve CL2B when the ambient temperature is 10 ° C. or more and less than 25 ° C. (shown with a solid line) Thus, a temperature decay curve CL2 corresponding to the environmental temperature can be prepared, such as a temperature decay curve CL2C when the temperature is 25 ° C. or higher. Further, the CPU 91 may appropriately deform the temperature decay curve C by calculation, for example, by transforming the temperature decay curve CL2 according to the lowest temperature in accordance with the environmental temperature. The number of temperature decay curves CL2 is not limited to three, and three or more temperature decay curves CL2 may be used.

  As described above, in pattern 1, considering the temperature rise due to double-sided printing, the ambient temperature T1 calculated in the previous image formation is used as a reference, and the number of images that have been imaged is determined based on the temperature rise curve CL1. The ambient temperature T2 at the end of the image formation is calculated, and the current ambient temperature T3 is calculated from the elapsed time t1 from the end of the previous image formation based on the temperature decay curve CL2.

(Pattern 2) The current image is not being formed and the previous image formation is not duplex printing.
In pattern 2, the previous image formation is a single-sided printing, and the ambient temperature T of the density sensor 8 does not increase as in the case of double-sided printing. Since it has a thermal mechanism (not shown), it can be regarded that there is no increase in the ambient temperature T. Therefore, as shown in FIG. 9, in the pattern 2, based on only the temperature decay curve CL2 and based on the ambient temperature T4 at the start of the previous image formation and the elapsed time t1 from the end of the previous image formation, The ambient temperature T5 of the concentration sensor 8 is obtained. Note that the calculation method of the ambient temperature T5 itself is the same as that of the pattern 1 such that the CPU 91 reads out the data of the temperature decay curve CL2 from the ROM 93 and the like, and the temperature decay curve CL2 is prepared in plural according to the environmental temperature. .

  In the pattern 2 as well, due to factors such as the distance between the density sensor 8 and the fixing unit 4, the ambient temperature T of the density sensor 8 increases when a large amount of images are formed continuously even in single-sided printing. If the temperature rise curve CL1 for single-sided printing is stored in a memory or the like in the same manner as the pattern 1 and the current ambient temperature T is calculated as in the case of the pattern 1, the ambient temperature can be further increased. The detection accuracy of the temperature T can be increased.

(Pattern 3) When an image is currently being formed and the image formation is duplex printing.
When a large amount of double-sided printing is continuously performed, a temperature increase inside the apparatus during image formation may not be ignored. For example, an increase in temperature may affect the image forming unit 3 and the intermediate transfer unit 2, and a toner image density change or a primary transfer may be displaced. In order to maintain and improve the image quality, it is desirable to adjust the operations of the image forming unit 3 and the intermediate transfer unit 2 during image formation. For example, this adjustment is performed once by interrupting the image forming operation, and by the density sensor 8, as described in the description of FIG.

  Therefore, in the present embodiment during image formation, as shown in FIG. 10, calculation is performed for the ambient temperature T of the density sensor 8 based on the temperature rise curve CL1, and the output of the density sensor 8 is corrected. Specifically, based on the ambient temperature T6 at the start of image formation (the ambient temperature T6 itself is obtained from the pattern 1 or 2), the current ambient temperature T7 is determined based on the number of images formed (number of printed sheets). Ask. The control unit 9 corrects the output of the density sensor 8 based on the calculated ambient temperature T7, and controls the adjustment of the operation of the image forming unit 3 and the intermediate transfer unit 2 based on the corrected density sensor 8 output. Part 9 performs.

(Pattern 4) When an image is currently being formed and the image formation is not duplex printing.
In the case of single-sided printing, as compared with the case of double-sided printing, there is almost no increase in temperature even when image formation is continuously performed. Rather, the ambient temperature T of the density sensor 8 may decrease. Then, contrary to the case of double-sided printing, image density and positional deviation may occur due to a temperature drop inside the apparatus. Therefore, it may be desirable to perform calibration in the operation of the image forming unit 3 and the operation of the intermediate transfer unit 2 during image formation.

  Therefore, in this embodiment during image formation, as shown in FIG. 11, the calculation of the ambient temperature T of the density sensor 8 and the correction of the output are performed based on the temperature decay curves CL2A to CL2. Specifically, based on the ambient temperature T8 at the start of image formation (the ambient temperature T8 itself is obtained from pattern 1 or 2), the current ambient temperature T9 is obtained based on the elapsed time t1 from the start of image formation. . The control unit 9 corrects the output of the concentration sensor 8 based on the calculated ambient temperature T9, and a plurality of temperature decay curves CL2 are prepared in accordance with the environmental temperature, and the corrected concentration sensor 8 output is obtained. Based on this, the control unit 9 adjusts the operations of the image forming unit 3 and the intermediate transfer unit 2 in the same manner as the pattern 1. In the pattern 4, the gradient of the temperature decay curve CL2 may be made gentle in consideration of the presence or absence of a temperature rise due to continuous image formation.

  Next, based on FIG. 12, the flow of calculation of the ambient temperature T of the density sensor 8 of the printer 1 according to the embodiment of the present invention will be described. FIG. 12 is a flowchart for explaining the flow of calculation of the ambient temperature T of the density sensor 8 of the printer 1 according to the embodiment of the present invention.

  First, when calculating the ambient temperature T of the current density sensor 8, the controller 9 checks whether or not image formation is in progress (step # 1). If the image is not currently being formed (Yes in step # 1), the control unit 9 checks whether or not the image formation is the first after the power is turned on (step # 2). If it is the first image formation (Yes in step # 2), the internal temperature of the printer 1 is considered to be the same as the environmental temperature, so the CPU 91 captures the environmental temperature detected by the temperature sensor 81 and stores it in the RAM 92 or the like. (Step # 3) The environmental temperature is set as the current ambient temperature T of the concentration sensor 8, and the current ambient temperature T is written in the RAM 92 or the like (steps # 4 and 5). When the output of the density sensor 8 is corrected, the control unit 9 corrects the output of the density sensor 8 based on the written ambient temperature T (step # 6), and the output correction of the series of density sensors 8 is performed. Control ends (END).

  On the other hand, if the first image formation is not performed after power-on (No in step # 2), the CPU 91 first reads the ambient temperature T of the density sensor 8 at the start of the previous image formation into the RAM 92 or the like (step # 7). . The control unit 9 further reads the image forming conditions (for example, whether double-sided printing, the number of printed sheets, etc.) of the previous image formation stored in the RAM 92, HDD 94, etc. into the RAM 92 (step # 8). Further, the CPU 91 reads the time elapsed from the end of the previous image formation from the timer unit 95 (step # 9).

  Next, the CPU 91 confirms from the read image forming conditions whether or not the previous image formation was double-sided printing (step # 10). In case of duplex printing (Yes in step # 10, corresponding to the above pattern 1), the CPU 91 reads the temperature rise curve CL1 and the temperature decay curve CL2 from the ROM 93 and HDD 94 (step # 11), and the current density sensor 8 Is calculated (step # 12). Then, after the calculation of the ambient temperature T of the density sensor 8 is completed, the process proceeds to steps # 5 and # 6.

  On the other hand, if the previous image formation was single-sided printing (No in step # 10, corresponding to the above pattern 2), the CPU 91 reads the temperature decay curve C from the ROM 93 or the like (step # 13), and the current density sensor 8 is calculated (step # 14).

  When the current ambient temperature T of the density sensor 8 is calculated, if an image is being formed (No in step # 1, corresponding to the pattern 3), the CPU 91 first starts the density sensor 8 at the start of image formation. Ambient temperature T and the image forming conditions for the current image formation are read (steps # 15 and # 16). Thereafter, the control unit 9 checks whether or not the current image formation is double-sided printing (step # 17). If the current image formation is double-sided printing, the CPU 91 increases the temperature from the ROM 93 or the like. The curve CL1 is read (step # 18), and the current ambient temperature T of the concentration sensor 8 is calculated based on the temperature rise curve CL1 (step # 19). After completing the calculation of the ambient temperature T of the concentration sensor 8, the process proceeds to steps # 5 and # 6.

  On the other hand, if the current image formation is single-sided printing (No in step # 17, corresponding to pattern 4), the CPU 91 reads the temperature decay curve C from the ROM 93 or the like (step # 20), and has the temperature decay curve C. Then, the current ambient temperature T of the concentration sensor 8 is calculated (step # 21). In this case as well, after the calculation of the ambient temperature T of the density sensor 8 is completed, the process proceeds to steps # 5 and # 6.

  As described above, according to the present invention, the ambient temperature T of the image reading unit is increased depending on the image forming condition with reference to the environmental temperature or the ambient temperature T of the image reading unit (density sensor 8) at the start of the previous image formation. , And the decrease in the ambient temperature T is calculated based on the time elapsed since the previous image formation was completed, whereby the current ambient temperature T of the image reading unit can be calculated. That is, since the ambient temperature T of the image reading unit is detected, the ambient temperature T of the image reading unit can be detected with a simple and inexpensive configuration without providing a separate temperature sensor. And since the output of an image reading part is correct | amended based on this detected temperature, the reading precision of an image reading part can be improved.

  Further, when image formation is continuously performed, the ambient temperature T of the image forming unit 3 and the intermediate transfer unit 2 also increases, which may affect the quality of the image, and the operation of the image forming unit 3 and the intermediate transfer unit 2 may be affected. May be calibrated. When the calibration is performed, the reading accuracy of the image reading unit may be deteriorated due to the temperature rise. However, when a predetermined number of images are formed, the ambient temperature T of the image reading unit is calculated, and the output of the image reading unit can be corrected even during image formation. Therefore, calibration performed in the middle of image formation can be appropriately performed.

  When double-sided printing is performed, the single-side printed sheet that has been heated and passed through the fixing unit 4 is conveyed through the apparatus, so that the internal temperature of the apparatus and the ambient temperature of the image reading unit also increase. However, according to this configuration, the ambient temperature T of the image reading unit is calculated in consideration of the temperature increase due to double-sided printing, and therefore the accurate ambient temperature T of the image reading unit can be calculated. Therefore, since the output of the image reading unit is corrected based on the detected temperature, the reading accuracy of the image reading unit can be improved.

  When image formation is performed continuously, the ambient temperature T of the image reading unit may increase due to the heat of the fixing unit 4 depending on the number of sheets (particularly in the case of duplex printing). However, since the calculation of the ambient temperature T of the image reading unit is performed in consideration of the temperature increase due to the number of images formed, the accurate calculation of the ambient temperature T of the image reading unit can be performed. Therefore, since the output of the image reading unit is corrected based on the detected temperature, the reading accuracy of the image reading unit can be improved.

  Further, the current ambient temperature T of the image reading unit can be calculated based on the temperature decay curve CL2 indicating the relationship between the time and the decrease in the ambient temperature T of the image reading unit. In other words, since the temperature decay curve CL2 is used, the current ambient temperature T of the image reading unit can be easily calculated. Therefore, since the output of the image reading unit is corrected based on the detected temperature, the reading accuracy of the image reading unit can be improved.

  In addition, the image reading unit can be configured with members such as the light emitting unit 82, the light receiving unit 83, and the current amplifying unit 84 at low cost. Furthermore, if these members are unitized, the image reading unit can be further reduced in size and cost.

  Further, the control unit 9 controls the output of the image reading unit to be the same when the same target is detected even if the characteristics of each member of the image reading unit change due to a temperature rise or the like. Therefore, since the output of the image reading unit is corrected based on the detected temperature, the reading accuracy of the image reading unit can be improved.

  Further, it is possible to correct the density of the toner image based on the output of the image reading unit and maintain the toner density of the formed image at an optimum state. Further, based on the output of the image reading unit, it is possible to correct misalignment during the primary transfer of the toner image. Therefore, it is possible to provide an image forming apparatus (printer 1) with high quality of the formed image.

  Hereinafter, another embodiment will be described. In the above-described embodiment, the tandem color printer 1 has been described. However, the printer 1 can also be applied to an image forming apparatus such as a rotary color printer, and further applied to an image forming apparatus such as a monochrome printer. Is possible.

  Moreover, although the embodiment of the present invention has been described, the scope of the present invention is not limited to this, and various modifications can be made without departing from the spirit of the invention.

  The present invention is applicable to an image forming apparatus such as a printer, a copying machine, or a multifunction machine that reads a toner image that has been primarily transferred to an intermediate transfer unit and detects the density or positional deviation amount of the toner image.

1 is a schematic front sectional view showing a schematic structure of a printer according to an embodiment of the present invention. FIG. 2 is an enlarged front schematic cross-sectional view of an intermediate transfer unit 2 and an image forming unit 3 of a printer according to an embodiment of the present invention. It is explanatory drawing for demonstrating the density | concentration sensor which concerns on embodiment of this invention. FIG. 8A is an explanatory diagram illustrating an example of detection of a positional deviation amount and density of a density sensor according to an embodiment of the present invention, and FIG. (B) is an explanatory view showing an example of positional deviation detection in the sub-scanning direction. It is a figure which shows an example of the change of the characteristic by the temperature of the member which comprises a concentration sensor, (a) is a graph which shows an example of the temperature characteristic of the light quantity of LED as a light emission part, (b) is current amplification. It is a graph which shows an example of the temperature characteristic of the amplification factor of a part. It is explanatory drawing for demonstrating correction | amendment of the characteristic change by the temperature of the density | concentration sensor which concerns on embodiment of this invention. 1 is a block diagram of a printer according to an embodiment of the present invention. It is a graph for demonstrating the calculation of the ambient temperature of a density sensor at the time of performing double-sided printing in the last image formation. It is a graph for demonstrating the calculation of the ambient temperature of a density sensor at the time of performing single-sided printing by the last image formation. It is a graph for demonstrating calculation of the ambient temperature of a density sensor during the image formation of double-sided printing. It is a graph for demonstrating calculation of the ambient temperature of a density sensor during image formation of single-sided printing. It is a flowchart for demonstrating the flow of calculation of the ambient temperature of the density sensor of the printer which concerns on embodiment of this invention.

Explanation of symbols

1 Printer (image forming device)
2 Intermediate transfer unit 3 Image forming unit 4 Fixing unit 7 Duplex printing conveyance path 81 Temperature sensor (environmental temperature detection unit)
8 Density sensor (image reading unit),
82 Light Emitting Unit (LED)
83 Light-receiving part (photodiode)
84 Current amplifier (transistor)
9 Control unit 91 CPU (calculation unit)
95 Timekeeping section C1 Temperature rise curve C2 Temperature decay curve

Claims (8)

An image forming unit that forms a toner image of one or more colors;
An intermediate transfer unit for primary transfer of the toner image formed by the image forming unit and secondary transfer of the toner image to a sheet;
A fixing unit that pressurizes and heats the secondary transferred toner image and fixes the toner image on the sheet;
An environmental temperature detector for detecting the outside temperature in the installation environment of the device;
An image reading unit for reading the toner image primarily transferred to the intermediate transfer unit;
A timing unit that counts the time that has elapsed since the last image formation;
The temperature detected by the environmental temperature detection unit or the ambient temperature of the image reading unit obtained by calculation at the start of the previous image formation and the ambient temperature of the image reading unit calculated based on the image forming conditions in the previous image formation. A calculation unit that calculates the current ambient temperature of the image reading unit based on the rise and the time elapsed since the end of the previous image formation;
In order to correct a change in characteristics due to the ambient temperature of the image reading unit based on the calculation result of the ambient temperature of the image reading unit by the calculation unit, a control unit that corrects the output of the image reading unit is provided. An image forming apparatus. The timekeeping unit also counts the time that has elapsed since the start of the current image formation,
When image formation is continuously performed on a predetermined number of sheets or more, the ambient temperature of the image reading unit at the start of image formation, the image formation conditions for the current image formation, and the time from the start of image formation The calculation unit obtains the ambient temperature of the image reading unit during image formation,
The control unit corrects the output of the image reading unit based on the current ambient temperature of the image reading unit obtained by the calculation unit when the predetermined number of images are formed. The image forming apparatus according to claim 1. A double-sided printing conveyance path for carrying out double-sided printing by conveying the sheet having the toner image fixed on one side through the fixing unit to the intermediate transfer unit again;
The image forming apparatus according to claim 1, wherein the calculation unit calculates an increase in ambient temperature of the image reading unit, with the presence / absence of double-sided printing as a part of image forming conditions.   4. The apparatus according to claim 1, wherein the number of sheets on which an image is formed is a part of an image forming condition, and the calculation unit calculates an increase in ambient temperature of the image reading unit. 5. Image forming apparatus.   The calculation unit calculates a current ambient temperature of the image reading unit based on a time elapsed from the end of the previous image formation and a temperature decay curve of the ambient temperature of the image reading unit. The image forming apparatus according to any one of claims 1 to 4. The image reading unit
A light emitting unit that emits light toward the toner image transferred to the intermediate transfer unit and the intermediate transfer unit; and a light receiving unit that outputs an electric current according to the amount of light reflected by the intermediate transfer unit and the toner image. The image forming apparatus according to claim 1, further comprising a current amplifying unit that amplifies the current output from the light receiving unit.   The control unit controls the voltage or current supplied to the light emitting unit based on a change in light amount of the light emitting unit due to temperature and a change in current amplification factor of the current amplifying unit due to temperature. The image forming apparatus according to claim 6, wherein the output of the image reading unit is corrected by adjusting the amount of incident light.   The control unit controls the image forming unit and / or the intermediate transfer unit based on the corrected output of the image reading unit to adjust the density of the toner image to be formed and The image forming apparatus according to claim 1, wherein a positional deviation in the transfer is adjusted.

Images