JP5578930B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine that forms a toner image on transfer paper by an electrophotographic method.

  In a conventional electrophotographic image forming apparatus, when a transfer bias is turned on when a toner image on a photoconductor is transferred to an intermediate transfer belt, it is affected by high voltage application on the photoconductor side and high voltage application on the primary transfer roller side. Load fluctuations such as the intermediate transfer belt sticking to the primary transfer roller may occur. Due to the influence of such load fluctuation, the speed fluctuation of the intermediate transfer belt occurs.

  In order to improve this, conventionally, the control is performed such that the applied voltage is increased stepwise when the transfer bias is on, and the applied voltage is decreased stepwise when the transfer bias is off. In other words, torque fluctuations of the intermediate transfer belt drive motor due to abrupt transfer bias application are suppressed, belt rotation speed fluctuations are suppressed, and color misregistration in the rotation direction of the intermediate transfer belt is reduced (see, for example, Patent Document 1). ).

JP 2001-296720 A

  However, the intermediate transfer belt may extend due to deterioration due to long-term use or may expand due to expansion in a high temperature / high humidity environment. When the intermediate transfer belt is extended, the slack is likely to stick to the primary transfer roller.

  In such a case, even if the technique described in Patent Document 1 is applied, torque fluctuations of the intermediate transfer belt drive motor occur due to the influence of the transfer bias application, and fluctuations in the rotation speed of the intermediate transfer belt can be suppressed. Have difficulty. For this reason, there is a limit in correcting the color shift in the rotation direction of the intermediate transfer belt.

  Therefore, the present invention prevents color misregistration in the rotational direction of the intermediate transfer belt even if the intermediate transfer belt is extended due to deterioration due to long-term use or expanded due to expansion in a high temperature / high humidity environment. An object of the present invention is to provide an image forming apparatus that can be suppressed.

  In order to achieve the above object, an image forming apparatus according to the present invention includes an irradiating unit that irradiates light on a surface-charged photoconductor to form an electrostatic latent image, and a surface of the photoconductor. The formed electrostatic latent image is developed with toner, and a plurality of image forming units each having a developing unit that forms a toner image, and the toner images formed by each of the plurality of image forming units are sequentially superimposed. An intermediate transfer belt to be transferred and a toner image formed by each of the plurality of image forming units is provided to the intermediate transfer belt by being applied to the plurality of image forming units and applied with a transfer bias. Among the plurality of image forming units after a transfer bias is applied to the transfer unit that performs the last transfer among the plurality of transfer units to be transferred and the plurality of transfer units corresponding to the plurality of image forming units, At first The image forming unit in which the toner image is formed first after the transfer bias is applied to the transfer unit that performs the last transfer so that the light is irradiated by the irradiation unit of the image forming unit in which the toner image is formed Setting means for setting a delay time until light is irradiated by the irradiation means; and after the transfer bias is applied to the transfer means, the irradiation according to the delay time set by the setting means elapses And control means for starting irradiation of light by the means.

  According to the image forming apparatus of the present invention, even if the intermediate transfer belt extends due to deterioration due to long-term use or expands in a high temperature / high humidity environment, the intermediate transfer belt rotates in the rotational direction. Occurrence of color misregistration can be suppressed.

1 is a cross-sectional view of an image forming apparatus. 2 is a control block diagram of the image forming apparatus. FIG. FIG. 6 is a diagram for explaining a change in torque for driving an intermediate transfer belt when a transfer bias is applied, and image writing timing. FIG. 4 is a diagram illustrating a relationship between a degree of deterioration of an intermediate transfer belt, environmental temperature / humidity, and torque fluctuation of an intermediate transfer belt drive motor. 6 is a flowchart for delaying image writing timing in the first embodiment. 12 is a flowchart when delaying image writing timing in the second embodiment. FIG. 6 is a diagram illustrating a relationship between a deterioration degree of an intermediate transfer belt and an output of a deterioration detection sensor.

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

<First Embodiment>
FIG. 1 is a cross-sectional view of the image forming apparatus.

  In FIG. 1, along the intermediate transfer belt 30 wound around a plurality of rollers, an image forming unit for each color of a yellow image (Y), a magenta image (M), a cyan image (C), and a black image (K). Is provided.

  Each image forming unit includes a photosensitive drum 18 as a photosensitive member, a charger 16 that uniformly charges the photosensitive drum 18, a scanner unit 11 that forms a latent image on the photosensitive drum 18 by a laser beam 13, and the latent image as a toner. A developing device 14 for developing the image. Each image forming unit includes a primary transfer roller 39 that transfers the toner image on the photosensitive drum 18 to the intermediate transfer belt 30, a secondary transfer roller 31 that transfers the toner image on the intermediate transfer belt 30 to transfer paper, and the like. Have. The symbols a to d are assigned to yellow (Y), magenta (M), cyan (C), and black (K), respectively.

  Reference numeral P denotes a transfer sheet as a transfer material, and the transfer sheet P is fed from the cassette 22. The fed transfer paper P waits at the registration roller 21 in order to take timing with the image forming unit. In the vicinity of the registration roller 21, a registration sensor 24 that detects the leading edge of the fed transfer paper P is provided. The registration sensor 24 detects the leading edge of the transfer paper P.

  Based on the timing at which the leading edge of the transfer paper P reaches the registration roller 21 by the registration sensor 24, the timing at which the laser beam 13 is irradiated is taken. Then, the electrostatic latent image formed on the photosensitive drum 18 by being irradiated with the laser beam 13 is developed with toner of each color by the developing device 14. The toner images (Y, M, C, K) of the respective colors on the photosensitive drum 18 are transferred in a state where they are sequentially superimposed on the intermediate transfer belt 30 by the primary transfer roller 39 so that there is no color shift.

  A deterioration detection sensor 19 that detects the degree of deterioration of the surface of the intermediate transfer belt is a diffuse reflection type sensor, which emits an LED to the surface of the intermediate transfer belt 30, receives the reflected light, and converts it into a voltage.

  The temperature of a heater (not shown) of the fixing device 23 is controlled to be a predetermined value. The transfer paper P waiting on the registration roller 21 passes through the secondary transfer roller 31 at the timing when the leading edge of the toner image on the intermediate transfer belt 30 and the leading edge of the transfer paper P meet. When the transfer paper P passes through the secondary transfer roller 31, the toner image is transferred to the transfer paper P. Then, the transfer paper P passes through the fixing device 23 having an appropriate temperature, is melted and fixed, and then is discharged out of the image forming apparatus.

  FIG. 2 is a control block diagram of the image forming apparatus.

  When an image formation start instruction is input to the controller unit 307 from the operation unit 306 having a touch panel display, the controller unit 307 instructs the printer control unit 301 to start an image forming job. The printer control unit 301 recognizes the environmental state by a temperature / humidity sensor 305 as an environment detection unit. Then, the printer control unit 301 outputs a drive start signal to the intermediate transfer belt drive motor control unit 303.

  In response to the drive start signal output from the printer controller 301, the intermediate transfer belt drive motor controller 303 starts the rotation of the intermediate transfer belt drive motor 304. The printer control unit 301 is connected to a temperature / humidity sensor 305 that detects environmental temperature and humidity.

  The printer control unit 301 outputs a primary transfer bias application start signal to the transfer bias driving unit 308. The printer control unit 301 delays the transfer bias application timing to the primary transfer rollers 39a to 39d in accordance with a mode manually set by a user operation input from the operation unit 306.

  FIG. 3 is a diagram for explaining the fluctuation of the torque for driving the intermediate transfer belt and the image writing timing when the transfer bias is applied.

  First, FIG. 3A will be described. A sudden torque fluctuation of the intermediate transfer belt 30 is generated by applying a transfer bias. This is because if a transfer bias is applied while the intermediate transfer belt drive motor 304 is in operation, an attractive force acts between the primary transfer roller 39 and the intermediate transfer belt 30 and the frictional resistance therebetween increases.

  The rotational speed of the intermediate transfer belt drive motor 304 is disturbed by the sudden torque fluctuation of the intermediate transfer belt 30. Following this, the surface speed of the intermediate transfer belt 30 varies. If the toner image is transferred to the intermediate transfer belt 30 while the fluctuation of the surface speed of the intermediate transfer belt 30 does not converge, a shift occurs between the images of the respective colors transferred onto the intermediate transfer belt 30.

  Next, FIG. 3B will be described. After the sudden speed fluctuation of the intermediate transfer belt 30 has converged, image writing is performed, and the Y image writing timing is set after the K transfer bias is turned on so that the image is transferred when the surface speed of the intermediate transfer belt 30 is stable. Delay time t. That is, normally, the Y image writing is performed simultaneously with the K transfer bias being turned on, but the Y image writing timing is delayed by t time than usual.

  The delay time t is set by the user inputting from the operation unit 306. Specifically, the user checks the environmental temperature and the degree of deterioration of the intermediate transfer belt 30 from the display of the operation unit 306, and switches between a plurality of modes in which different delay times t are set. In other words, the user sets the mode in which the delay time t becomes longer as the environment becomes higher in the temperature and humidity, or as the deterioration of the intermediate transfer belt 30 progresses.

  FIG. 4 is a diagram showing the relationship between the degree of deterioration of the intermediate transfer belt, the environmental temperature / humidity, and the torque fluctuation of the intermediate transfer belt drive motor.

  As shown in FIG. 4A, if the intermediate transfer belt 30 is a new one, the torque fluctuation is small, but as the intermediate transfer belt 30 deteriorates, the intermediate transfer belt drive motor 304 at the time of applying the transfer bias. The torque fluctuation becomes larger. Further, as shown in FIG. 4B, as the environmental temperature / humidity increases, the torque fluctuation of the intermediate transfer belt drive motor 304 when the transfer bias is applied increases.

  As the torque fluctuation of the intermediate transfer belt drive motor 304 increases, the time is increased until the surface speed of the intermediate transfer belt 30 is stabilized. For this reason, the mode is switched to a mode in which the delay time t becomes longer as the degree of deterioration of the intermediate transfer belt 30 becomes larger, and the mode is switched to a mode in which the delay time t becomes longer as the environmental temperature / humidity becomes higher.

  FIG. 5 shows a flowchart when the image writing timing is delayed in the first embodiment.

  First, the printer control unit 301 acquires the image writing delay time t input from the operation unit 306 by the user (S501). Next, the printer control unit 301 starts a copy operation in response to the start key on the operation unit 306 being pressed by the user (S502). Then, the printer control unit 301 instructs the intermediate transfer belt drive motor control unit 303 to turn on the intermediate transfer belt drive motor 304 (S503).

  When the driving of the intermediate transfer belt 30 is started, the printer control unit 301 applies a primary transfer bias to the transfer bias driving unit 308 in the order of yellow (Y), magenta (M), cyan (C), and black (K). A start signal is output (S504, S505, S506, S507). Then, it waits until the set image writing delay time t elapses (S508).

  Thereafter, the printer control unit 301 controls the scanner unit 11 so as to start image writing of each color on the photosensitive drum 18 in the order of yellow (Y), magenta (M), cyan (C), and black (K). (S509, S510, S511, S512).

  The image transferred to the photosensitive drum 18 is transferred to the intermediate transfer belt 30 by applying a primary transfer bias by the primary transfer roller 39. The image transferred to the intermediate transfer belt 30 moves in the direction of the secondary transfer roller 31 as the intermediate transfer belt 30 rotates. Then, the image is transferred from the intermediate transfer belt 30 to the transfer paper P by the secondary transfer bias applied to the secondary transfer roller 31 (S513).

  According to the first embodiment described above, even if the intermediate transfer belt 30 deteriorates due to long-term use or the intermediate transfer belt 30 expands and contracts due to changes in environmental temperature and humidity, the intermediate transfer belt. The occurrence of color misregistration in the rotation direction can be suppressed.

<Second Embodiment>
Next, a second embodiment will be described. In the description of the second embodiment, the description of the same parts as those in the first embodiment is omitted.

  FIG. 6 is a flowchart for delaying the image writing timing in the second embodiment.

  First, the printer control unit 301 detects the degree of deterioration of the intermediate transfer belt 30 using the deterioration detection sensor 19 (S601).

  As a method for detecting the degree of deterioration of the intermediate transfer belt, after driving the intermediate transfer belt, the LED is turned on to irradiate the intermediate transfer belt 30 with light, and irregularly reflected light from the surface (underground) of the intermediate transfer belt 30 is received. Light is received by the element. Then, the printer control unit 301 recognizes the detection voltage εV from the light receiving element as the degree of deterioration of the intermediate transfer belt 30.

  This is because, as shown in FIG. 7, when the deterioration of the intermediate transfer belt 30 progresses, the surface becomes rough and irregular reflection light increases, and the intensity of light received by the light receiving element of the deterioration detection sensor 19 increases.

  Next, the printer control unit 301 compares the detection voltage εV with a predetermined voltage RV as a threshold based on the detection result of the deterioration detection sensor 19 (S602). If the detection voltage εV is lower than the predetermined voltage RV, the intermediate transfer belt 30 has not reached a certain degree of deterioration, and the process proceeds to step S603.

  Here, the printer control unit 301 detects the environmental temperature / humidity based on the output from the temperature / humidity sensor 305 (S603). The operation mode of the image forming apparatus is classified into four types according to the detection result (α ° C., β%) of the temperature / humidity sensor 305. The detected temperature α ° C. is divided into a case where the temperature is lower than the predetermined temperature A ° C. and a case where the temperature is equal to or higher than the predetermined temperature A ° C. (S604). The detected humidity β% is divided into a case where it is lower than the predetermined humidity P% and a case where it is equal to or higher than the predetermined humidity P% (S605, S606).

  In step S602, if the detection voltage εV is equal to or higher than the predetermined voltage RV, the intermediate transfer belt 30 has reached a certain degree of deterioration, and the process proceeds to step S611.

  Here, the printer control unit 301 detects the environmental temperature and humidity based on the output from the temperature / humidity sensor 305 (S611). Similarly in this case, the operation mode of the image forming apparatus is divided into four types according to the detection result (α ° C., β%) of the temperature / humidity sensor 305. The detected temperature α ° C. is divided into a case where the temperature is lower than the predetermined temperature A ° C. and a case where the temperature is equal to or higher than the predetermined temperature A ° C. (S612). The detected humidity β% is divided into a case where it is lower than the predetermined humidity P% and a case where it is equal to or higher than the predetermined humidity P% (S613, S614).

There are 8 modes in total. The 8 modes are described below.
Mode 1: Low belt degradation / low temperature and low humidity (S607)
Mode 2: Low belt degradation / low temperature and high humidity (S608)
Mode 3: Low belt degradation / high temperature and low humidity (S609)
Mode 4: Low belt degradation / high temperature and high humidity (S610)
Mode 5: High degree of belt degradation / low temperature and low humidity (S615)
Mode 6: High degree of belt degradation / low temperature and high humidity (S616)
Mode 7: High degree of belt degradation / high temperature and low humidity (S617)
Mode 8: High degree of belt degradation / low temperature and high humidity (S618)

  In steps S607 to S618, the printer control unit 301 sets transfer bias application timing. That is, the printer control unit 301 sets the image writing delay time t according to each mode.

  According to the second embodiment described above, the same effect as that of the first embodiment is obtained, and the effect that the user does not need to set the delay time t is achieved.

DESCRIPTION OF SYMBOLS 11 Scanner unit 14 Developing device 18 Photosensitive drum 19 Deterioration detection sensor 30 Intermediate transfer belt 39 Primary transfer roller 301 Printer control unit 305 Temperature / humidity sensor 306 Operation unit

Claims (6)

Respectively, against the sensitive light member charged surface, and irradiating means for forming an electrostatic latent image by irradiating light, an electrostatic latent image formed on the front surface of the front Symbol feeling light body is developed with toner A plurality of image forming units having a developing unit for forming a toner image ;
An intermediate transfer belt on which toner images formed in each of the plurality of image forming units are sequentially superimposed and transferred;
Said provided corresponding to the plurality of image forming unit by being applied a transfer bias, a plurality of transfer means for transferring the toner image formed by each of the plurality of image forming unit on the intermediate transfer belt,
Of the plurality of transfer units corresponding to the plurality of image forming units, a toner image is formed first among the plurality of image forming units after a transfer bias is applied to a transfer unit that performs transfer last. as light is irradiated by the irradiation unit of the image forming portion, the light by the irradiation unit of the image forming section to which the toner image on the first of the last transfer bias is applied to the transfer means transfer is performed is formed A setting means for setting a delay time until irradiation,
A control means for starting light irradiation by the irradiation means in response to a delay time set by the setting means after the transfer bias is applied to the transfer means;
An image forming apparatus comprising: It further has an operation means for accepting manual operation input,
The image forming apparatus according to claim 1, wherein the setting unit sets the delay time based on an operation input from the operation unit. An environmental detection means for detecting environmental temperature and environmental humidity;
The image forming apparatus according to claim 1, wherein the setting unit sets the delay time based on an environmental temperature and an environmental humidity detected by the environment detection unit. A deterioration detecting means for detecting the degree of deterioration of the intermediate transfer belt;
The image forming apparatus according to claim 1, wherein the setting unit sets the delay time based on a degree of deterioration of the intermediate transfer belt detected by the deterioration detection unit. The image forming apparatus according to claim 3, wherein the setting unit sets the delay time to be longer as the environmental temperature is higher and as the environmental humidity is higher. The deterioration detection means includes an irradiation means for irradiating light to the intermediate transfer belt, and a light receiving means for receiving reflected light from the intermediate transfer belt,
The image forming apparatus according to claim 4, wherein the setting unit sets the delay time based on a magnitude of a detection voltage from the light receiving unit.

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