JP5453338B2 - Image forming apparatus and developing bias voltage control method - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus and a developing bias voltage control method in such an image forming apparatus.

  An image forming apparatus such as a copier, a printer, or a facsimile using an electrophotographic method emits light based on an image carrier (for example, a photosensitive drum or a transfer belt) and image data and statically puts it on the image carrier. An exposure apparatus for forming an electrostatic latent image and a developing apparatus for developing the electrostatic latent image by supplying a developer (toner) to the electrostatic latent image formed on the image carrier are provided.

  In such a developing device, when the developing bias voltage applied to the developing roller is increased, it becomes easier to supply the toner necessary for forming the toner image to the image carrier, while the peak of the developing bias voltage is reached. The potential difference between the value and the surface potential of the image carrier increases, and leakage (air discharge) tends to occur between the image carrier and the developing roller. When the leak occurs, a so-called development leak occurs, in which random black spots (noise) are generated on the image carrier, and a toner image with good image quality is not formed. In addition, peripheral devices are likely to fail.

  Conversely, if the developing bias voltage is lowered to avoid leakage, it becomes difficult to supply the amount of toner necessary for forming the toner image to the image carrier, and density unevenness occurs in the toner image. As a result, a good quality toner image is not formed.

  Therefore, it is necessary to set a developing bias voltage so that the developing roller does not leak. Conventionally, as described in Patent Documents 1 to 5, as a method for preventing leakage between the image carrier and the developing roller, the number of abnormal outputs from the power source (that is, the number of leaks) is counted. There are a method of stopping the printing operation when it continues for a predetermined number of times or a method of setting a developing bias voltage after detecting a voltage when a leak occurs by changing a voltage applied to the developing roller.

JP 2006-126878 A JP 07-287482 A JP-A-6-348116 JP 7-287482 A JP-A-6-148997

  However, the above method only stops the printing operation when the number of abnormal outputs continues for a predetermined number of times. When restarting printing, the user manually adjusts the development bias voltage. Was necessary. Further, the method of setting the optimum developing bias voltage by changing the voltage applied to the developing roller takes time and labor for setting.

  Therefore, the present invention has been made in view of such circumstances, and an object thereof is to provide an image forming apparatus and a development bias voltage control method that simplify the adjustment of the development bias voltage applied to the development roller. And

  An image forming apparatus according to an aspect of the present invention includes a developing roller that carries a toner, which is a developer, on a surface thereof and conveys the developing roller, and a voltage applying unit that applies a developing bias voltage to the developing roller; An image carrier that carries a toner image in which an electrostatic latent image based on image data is formed and the electrostatic latent image is visualized by toner supplied from the developing roller, the developing roller, and the image carrier Detecting means for detecting a voltage leak occurring between the calculating means, a calculating means for calculating a leak occurrence time from the occurrence of the voltage leak to the end using the detection result of the detecting means, and the calculating means A control unit that determines a reduction width of the development bias voltage in proportion to the calculated leak occurrence time, and controls the voltage application unit to reduce the value of the development bias voltage by the reduction width. It has a, and.

  According to a third aspect of the present invention, there is provided a developing bias voltage control method comprising: a developing roller for carrying and transporting toner as a developer on a surface; and a voltage applying unit for applying a developing bias voltage to the developing roller. Image forming apparatus comprising: an apparatus; and an image carrier that forms an electrostatic latent image based on image data and carries a toner image visualized by toner supplied from the developing roller. A developing bias voltage control method for an apparatus, comprising: a detecting step for detecting a voltage leak occurring between the developing roller and the image carrier; and the voltage leak is generated using a detection result in the detecting step. A calculation step for calculating a leak occurrence time from the start to the end, and a decrease in the developing bias voltage in proportion to the leak occurrence time calculated in the calculation step And a control step for performing control to reduce the value of the developing bias voltage applied to the developing roller by the voltage application unit by the amount of decrease determined in the determining step. It is.

  Conventionally, when a leak occurs, the printing operation is stopped and the development bias voltage is adjusted manually, or the optimum development bias voltage is set by detecting the voltage value at which the leak occurs while changing the development bias voltage. It took a lot of time and effort. However, according to the above invention, when a leak occurs, the control means determines a reduction width of the development bias voltage in proportion to the leak occurrence time, and the value of the development bias voltage is lowered by this reduction width. Therefore, it is possible to easily adjust the optimum developing bias voltage so as not to occur.

  Here, the control means "determines the reduction width of the development bias voltage in proportion to the leak occurrence time calculated by the calculation means," specifically, in proportion to the length of the leak occurrence time, That is, the control means determines the reduction width so that the reduction width of the development bias voltage becomes large.

  A second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the voltage application unit generates a development bias voltage by superimposing an alternating voltage and a direct current voltage, and the development bias voltage is generated. When the leak occurrence time is shorter than a predetermined time, the control unit lowers the voltage value of either the AC voltage or the DC voltage, and applies the predetermined voltage to the developing roller. If it is longer than the predetermined time, control is performed to lower the developing bias voltage by lowering the voltage values of both the AC voltage and the DC voltage.

  The invention according to claim 4 is the developing bias voltage control method according to claim 3, wherein the voltage applying unit generates a developing bias voltage by superimposing an alternating voltage and a direct voltage, A developing bias voltage is applied to the developing roller. In the control step, when the leak occurrence time is shorter than a predetermined time, the voltage value of either the AC voltage or the DC voltage is decreased. When the predetermined time is exceeded, control is performed to lower the developing bias voltage by lowering the voltage values of both the AC voltage and the DC voltage.

  According to these inventions, when the leak occurrence time is shorter than a predetermined time, the control means changes only one of the AC voltage and the DC voltage to lower the development bias voltage, so that the adjustment of the development bias voltage is performed. Can be carried out easily and in a short time.

  According to the present invention, when a leak occurs, the control unit lowers the development bias voltage in proportion to the leak occurrence time, so that the optimum development bias voltage can be easily adjusted to prevent the leak from occurring.

FIG. 3 is a cross-sectional view illustrating an example of a mechanical configuration of the image forming apparatus. FIG. 2 is a cross-sectional view illustrating a schematic configuration of a developing device. The figure which shows an example of the voltage waveform of a developing bias voltage. The figure which shows the relationship between an atmospheric | air pressure and the developing bias voltage when leak arises. 6 is a flowchart showing a flow of a method for adjusting a developing bias voltage.

  Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. In this embodiment, a printer is described as an example of the image forming apparatus 1. However, an electrophotographic copying machine, a facsimile, or a multifunction machine having a plurality of these functions may be used.

  FIG. 1 is a cross-sectional view illustrating an example of a mechanical configuration of an image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 includes an exposure device 11, a developing device 12, a charger 13, a photosensitive drum 14, a transfer roller 15, and a fixing device 16.

  The photosensitive drum 14 is a cylindrical member, and rotates in the clockwise direction in FIG. 1 in response to a driving force from a motor (not shown). The charger 13 charges the surface of the photosensitive drum 14 substantially uniformly. The exposure apparatus 11 includes a light source such as a laser diode, and irradiates light corresponding to image data onto the surface of the photosensitive drum 14 that is substantially uniformly charged by the charger 13 to form an electrostatic latent image. Form. The image data is data received by the image forming apparatus 1 that is transmitted by a personal computer or the like connected to the image forming apparatus 1.

  The developing device 12 includes a toner container that stores toner, and supplies toner to the surface of the photosensitive drum 14 on which the electrostatic latent image is formed to form a toner image. A toner image formed on the photosensitive drum 14 is transferred onto a sheet or a transfer belt (not shown) conveyed on the conveyance path P by a transfer roller 15 described later.

  A transfer roller 15 is disposed at a position facing the photosensitive drum 14. The transfer roller 15 is made of a conductive rubber material or the like, and transfers the toner image formed on the photosensitive drum 14 onto a sheet or transfer belt that is transported along the transport path P.

  The fixing device 16 includes a fixing roller 160 having a built-in heater and the like, and a pressure roller 161 provided at a position facing the fixing roller 160. The fixing device 16 is transferred to the paper by heating and conveying the paper on which the toner image is formed. Fix the toner image.

  Next, an image forming operation of the image forming apparatus 1 will be briefly described. First, the surface of the photosensitive drum 14 is charged almost uniformly by the charger 13. Then, the charged surface of the photosensitive drum 14 is exposed by the exposure device 11, and an electrostatic latent image is formed on the surface of the photosensitive drum 14. Then, the toner is supplied to the surface of the photosensitive drum 14 by the developing device 12 to visualize the electrostatic latent image into a toner image, and the toner image on the surface of the photosensitive drum 14 is transferred to the paper by the transfer roller 15. Transcribed. The toner image transferred to the paper is fixed by the fixing device 16.

  FIG. 2 is a cross-sectional view showing an outline of the configuration of the developing device 12, and shows an enlarged peripheral portion of the developing device 12 shown in FIG. The developing device 12 includes a developing roller 72, a magnetic roller 73, a paddle mixer 74, a stirring mixer 75, a panning blade 76, a partition plate 77, and a voltage application unit 80.

  The developing roller 72 carries the toner on its surface and conveys it, thereby developing the electrostatic latent image formed on the surface of the photosensitive drum 14 as a toner image. The magnetic roller 73 attracts the two-component developer by a magnet disposed therein to generate a magnetic brush, and supplies toner to the developing roller 72.

  The paddle mixer 74 and the agitation mixer 75 have spiral blades, and agitate the toner while conveying the two-component developer in opposite directions to charge the toner. Further, the paddle mixer 74 supplies a two-component developer containing charged toner and a carrier to the magnetic roller 73. The ear cutting blade 76 regulates the thickness of the magnetic brush formed on the magnetic roller 73. The partition plate 77 is provided between the paddle mixer 74 and the stirring mixer 75 so that the two-component developer can freely pass outside the both end sides of the partition plate 77.

  The voltage application unit 80 is a power source that applies a development bias voltage to the development roller 72 and the magnetic roller 73. The development bias voltage is output according to control by the control unit 100 described later. FIG. 3 shows a voltage waveform applied to the developing roller 72 by the voltage application unit 80. The waveform in FIG. 3 is shifted by superimposing a DC voltage of 200 [V] on an AC voltage having a frequency of 3 [kHz], a positive duty of 30%, and a peak voltage of 1.6 [kV].

  4 shows the relationship between the atmospheric pressure and the developing bias voltage when a leak occurs between the photosensitive drum 14 and the developing roller 72. The peripheral surfaces of the photosensitive drum 14 and the developing roller 72 are similar to each other. Is the distance when t = 0.3 [mm]. According to FIG. 4, for example, the discharge voltage (voltage at which leakage starts) is about 1.82 [kV] in the flat area of 760 [mmHg], whereas it is about 1.7 [in the area of 700 [mmHg]. kV]. In other words, leaks are likely to occur when the peak voltage exceeds 1.82 [kV] on flat ground, but leaks occur when the peak voltage exceeds 1.7 [kV] in high altitude areas (low atmospheric pressure). It becomes easy. Therefore, if the same image forming apparatus is used in an area where the altitude is high (atmospheric pressure is low) after setting the development bias voltage in an area where the altitude is low, such as a flat ground, leakage tends to occur, and the development bias voltage is reset. There was a need.

  Even if no leakage occurs in the initial operation of the image forming apparatus, the load fluctuation increases as the operation time becomes longer, and the leakage may occur due to a slight change in atmospheric pressure, etc., causing the toner image to be disturbed. In order to prevent such a leak from occurring, it is necessary to adjust the developing bias voltage. Conventionally, however, the printing operation is stopped and the developing bias voltage is adjusted manually, or a voltage that causes a leak while changing the developing bias voltage. It took time and effort to detect the value and set the optimum development bias voltage.

  Therefore, the image forming apparatus 1 according to the present embodiment simplifies the setting of the optimum developing bias voltage that does not cause a leak. Hereinafter, a method for setting the developing bias voltage will be described in detail.

  The control unit 100 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and controls the overall operation of the image forming apparatus 1, and includes a leak detection unit. 101, a leak occurrence time measurement unit 102, and a development bias voltage control unit 103. The leak detection unit 101 detects the occurrence of leak by detecting an overcurrent flowing between the photosensitive drum 14 and the developing roller 72. The leak occurrence time measurement unit 102 uses the detection result of the leak detection unit 101 to calculate the time from when a leak is detected until the detection is completed, that is, the time during which the leak is occurring (leak occurrence time). measure.

  The development bias voltage control unit 103 determines a reduction width of the development bias voltage based on the leak occurrence time, and adjusts the development bias voltage. When a leak occurs, it is necessary to change the developing bias voltage to be low. However, if the leak occurrence time is long, it is necessary to set the developing bias voltage lower than when the leak is short. In other words, if the adjustment is made using the development bias voltage reduction range that was used when the leak occurrence time was long, even though the leak occurrence time was short, it would be far from the optimum value of the development bias voltage, causing deterioration in image quality. It becomes. Therefore, the development bias voltage control unit 103 determines the reduction width of the development bias voltage in proportion to the leak occurrence time measured by the leak occurrence time measurement unit 102.

  This will be specifically described with reference to FIG. FIG. 5 is a flowchart showing a flow of a method for adjusting the developing bias voltage when a leak occurs. When the leak detection unit 101 detects a leak occurrence (step S11), the leak occurrence time measurement unit 102 starts time measurement (step S12). When the leak detection unit 101 no longer detects a leak (step S13; YES), the leak occurrence time measurement unit 102 ends the time measurement (step S14), and the development bias voltage control unit 103 determines the development bias from the leak occurrence time. The amount of voltage decrease is determined (step S15).

  The development bias voltage control unit 103 stores in advance a table, a calculation formula, and the like that indicate an optimal reduction range of the development bias voltage with respect to the leak occurrence time, and determines a reduction range of the development bias voltage according to the table and the calculation formula. . As a specific example of the decrease width of the developing bias voltage, when the leak occurrence time is 1 [ms], the decrease width is 50 [Vpp], when the leak occurrence time is 50 [ms], the decrease width is 100 [Vpp], and the leak occurs. When the time is 100 [ms], the decrease width is 200 [Vpp]. These numerical values are determined by the designer through experiments and the like when designing the apparatus.

  Next, when the leak occurrence time is shorter than the predetermined time T (step S16; YES), the development bias voltage control unit 103 changes either the peak voltage or the direct current voltage and determines the reduction amount determined in step S15. Control is performed to lower the developing bias voltage by the amount (step S17). On the other hand, when the leak occurrence time is equal to or longer than the predetermined time T (step S16; NO), the development bias voltage control unit 103 changes both the peak voltage and the DC voltage and develops the development bias voltage by the above-described decrease width. Control to lower is performed (step S18).

  This time T is a threshold value that determines whether leakage can be avoided by reducing either the peak voltage or the DC voltage, or if both the peak voltage and the DC voltage are not reduced. Is. When the leak occurrence time is shorter than the time T, the development bias voltage control unit 103 only needs to change either the peak voltage or the DC voltage to lower the development bias voltage. Can be done in time. This time T is also determined by the designer conducting experiments or the like when designing the apparatus.

  As described above, the development bias voltage control unit 103 determines the reduction amount of the development bias voltage in proportion to the leak occurrence time measured by the leak occurrence time measurement unit 102 and adjusts the voltage value to thereby adjust the leak value. It is possible to easily adjust the developing bias voltage so as not to occur. Further, when the leak occurrence time is shorter than the predetermined time T, the development bias voltage control unit 103 changes only one of the peak voltage and the DC voltage to lower the development bias voltage, thereby reducing the development bias voltage. Adjustment can be performed easily and in a short time.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 12 Developing apparatus 14 Photosensitive drum (image carrier)
72 Developing roller 80 Voltage application unit 100 Control unit 101 Leak detection unit (detection means)
102 Leak generation time measurement unit (calculation means)
103 Development bias voltage controller (control means)

Claims (4)

A developing device having a developing roller that carries and transports toner as a developer on the surface; and a voltage applying unit that applies a developing bias voltage to the developing roller;
An image carrier that carries a toner image in which an electrostatic latent image based on image data is formed and the electrostatic latent image is visualized by toner supplied from the developing roller;
Detecting means for detecting a voltage leak generated between the developing roller and the image carrier;
A calculation means for calculating a leak occurrence time from the occurrence of the voltage leak to the end using the detection result of the detection means;
Control means for determining a reduction width of the development bias voltage in proportion to the leak occurrence time calculated by the calculation means, and for controlling the voltage application unit to reduce the value of the development bias voltage by the reduction width; ,
An image forming apparatus. The voltage application unit generates a development bias voltage by superimposing an AC voltage and a DC voltage, and applies the development bias voltage to the development roller.
The control means reduces the voltage value of either the AC voltage or the DC voltage when the leak occurrence time is shorter than a predetermined time, and when the leak occurrence time is equal to or longer than the predetermined time, The image forming apparatus according to claim 1, wherein control is performed to lower the developing bias voltage by lowering both the AC voltage and the DC voltage. An electrostatic latent image is formed based on image data, a developing device having a developing roller for carrying and transporting toner as a developer on the surface, and a voltage applying unit for applying a developing bias voltage to the developing roller, A developing bias voltage control method for an image forming apparatus, comprising: an image carrier that carries a toner image in which an electrostatic latent image is visualized by toner supplied from the developing roller;
A detection step of detecting a voltage leak occurring between the developing roller and the image carrier;
A calculation step for calculating a leak occurrence time from the occurrence of the voltage leak to the end using the detection result in the detection step;
A determining step for determining a reduction width of the developing bias voltage in proportion to the leak occurrence time calculated in the calculating step;
A control step of performing control to reduce the value of the developing bias voltage applied to the developing roller by the voltage application unit by the lowering width determined in the determining step;
Development bias voltage control method including The voltage application unit generates a development bias voltage by superimposing an AC voltage and a DC voltage, and applies the development bias voltage to the development roller.
In the control step, when the leak occurrence time is shorter than a predetermined time, the voltage value of either the AC voltage or the DC voltage is decreased, and when the leak generation time is equal to or longer than the predetermined time, 4. The developing bias voltage control method according to claim 3, wherein control is performed to lower the developing bias voltage by lowering both the AC voltage and the DC voltage.

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