JP2016070962A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that suppresses disposal of a toner in color that is not used in formation of an image to improve efficiency of use of toner.SOLUTION: An image forming apparatus includes: a plurality of image forming units each having a photoreceptor drum 111, a developing roller 113 that causes a developer to be adhered to an electrostatic latent image formed on the photoreceptor drum 111, contact members 114 and 115 that contact the developing roller 113; and a control part 120 that controls a voltage to be applied to the developing roller 113 and contact members 114 and 115 of each of the plurality of image forming units. The control part 120 reduces the absolute value of the voltage to be applied to the developing roller 113 and contact members 114 and 115 of an image forming unit of a color not used in image formation out of the plurality of image forming units to be smaller than the absolute value of the voltage when the color is used in image formation.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus.

  In a general image forming apparatus, the surface of a photosensitive drum, which is an image carrier uniformly charged by a charging device, is exposed by an exposure device to form an electrostatic latent image. In use, after a toner image is formed on the photosensitive drum, the toner image is transferred to a printing medium and fixed. In a single-pass tandem type image forming apparatus, four image forming units (K: black, M: magenta, Y: yellow, C: cyan) sequentially arranged on a transfer belt operate simultaneously, and there is a print medium. Full color printing is realized by passing the paper and superimposing and transferring the toner colors.

  Depending on the print data, all four colors may not be used, and printing may be executed by single color printing or only by superimposing two or three colors. At this time, the four image forming units operate together. If the toner that is not used for printing is continuously discharged without being discharged from the image forming unit, the overcharged toner will eventually move toward the photosensitive drum due to the effect of continuous frictional charging, so-called development. Dirt may occur.

  In order to prevent such contamination of the printing medium, the toner image of the fixed pattern is forcibly output from the image forming unit in which the amount of toner used is less than a predetermined amount, and the printing medium is not used. In this case, an image forming apparatus that discharges excessively charged toner to the outside of the image forming unit has been proposed (see, for example, Patent Document 1).

JP 2009-251202 A

  However, when a regular pattern is used to discard toner as in a conventional image forming apparatus, not only excessively charged toner that causes contamination but also many normal toners are discarded together. Usage efficiency is poor. For this reason, it is desirable to reduce the number of toner discards as much as possible.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus that suppresses the discarding of toners of colors that are not used for image formation as much as possible and has high toner utilization efficiency.

An image forming apparatus according to an aspect of the present invention includes an image carrier, a developing unit that attaches a developer to an electrostatic latent image formed on the image carrier, and a contact member that contacts the developing unit. An image forming apparatus comprising: a plurality of image forming units; and a control unit that controls a voltage applied to each of the developing unit and the contact member of each of the plurality of image forming units, wherein the control unit includes: Among the plurality of image forming units, the absolute value of the voltage applied to the developing unit and the contact member of the image forming unit of a color that is not used for image formation is the absolute value of the voltage when the color is used for image formation. It is characterized by being smaller than the value.

  An image forming apparatus according to another aspect of the present invention includes an image carrier, a developing unit that attaches a developer to an electrostatic latent image formed on the image carrier, and a contact member that contacts the development unit. An image forming apparatus comprising: a plurality of image forming units; and a control unit that controls a voltage applied to each of the developing unit and the contact member of each of the plurality of image forming units. Among the plurality of image forming units, the absolute value of the voltage applied to the contact member of the image forming unit of a color that is not used for image formation is set to be larger than the absolute value of the voltage when the color is used for image formation. It is characterized by being made small.

  According to one embodiment of the present invention, it is possible to provide an image forming apparatus that suppresses discarding of toner of a color that is not used for image formation as much as possible and has high toner utilization efficiency.

1 is a cross-sectional view schematically showing a configuration of an image forming apparatus according to Embodiment 1. FIG. FIG. 3 is a schematic diagram for explaining an image forming cartridge and its peripheral part in the first embodiment. 3 is a block diagram schematically showing main parts of a control system in the image forming apparatus according to Embodiment 1. FIG. (A) And (B) is a graph which shows the relationship between the applied voltage or printing time to a developing roller, a supply roller, and a toner control member, and the toner potential on a developing roller. 3 is a flowchart illustrating processing in the image forming apparatus according to the first embodiment.

Embodiment 1 FIG.
(Description of configuration)
FIG. 1 is a cross-sectional view schematically showing a configuration of an image forming apparatus 100 according to the first embodiment.
The image forming apparatus 100 includes a cassette 101, a pickup roller 102, a conveyor belt 103, and toner containers 104K, 104Y, 104M, and 104C (hereinafter referred to as a toner container 104 when there is no particular need to distinguish between them. ), Image forming cartridges 110K, 110Y, 110M, and 110C (hereinafter referred to as the image forming cartridge 110 when there is no need to distinguish each of them), and exposure heads 105K, 105Y, 105M, and 105C (exposure sections). Hereinafter, when there is no particular need to distinguish each, it will be referred to as exposure head 105) and transfer rollers 106K, 106Y, 106M, 106C (hereinafter, when there is no need to distinguish each from each other, it will be referred to as transfer roller 106). A fixing device 107, a carry-out roller 108, an operation unit 109, Provided. Note that an image forming unit is configured by a combination of the toner container 104 and the image forming cartridge 110.

The toner container 104 stores toner as a developer.
The cassette 101 stores paper PA as a medium.
The pickup roller 102 feeds the paper PA one by one from the cassette 101 onto the transport path PP.
The conveyance belt 103 conveys the paper PA given from the pickup roller 102.

The image forming cartridge 110 performs development using toner on the transported paper PA or the transport belt 103. In the image forming apparatus 100, for example, an image forming cartridge 110K for black, an image forming cartridge 110Y for yellow, an image forming cartridge 110M for magenta, and an image forming cartridge 110C for cyan are arranged from the upstream in the paper conveyance direction. Arranged in this order, an image is formed independently for each color.
The exposure head 105 exposes the photosensitive drum included in the image forming cartridge 110 to form an electrostatic latent image on the photosensitive drum. In the image forming apparatus 100, for example, a black exposure head 105K, a yellow exposure head 105Y, a magenta exposure head 105M, and a cyan exposure head 105C are arranged in this order from the upstream side in the paper conveyance direction. Has been.
The transfer roller 106 transfers the toner image (developer image) formed on the image forming cartridge 110 to the paper PA. In the image forming apparatus 100, for example, a black transfer roller 106K, a yellow transfer roller 106Y, a magenta transfer roller 106M, and a cyan transfer roller 106C are arranged in this order from the upstream in the paper conveyance direction. Has been.

The fixing device 107 fixes the toner image on the paper PA by heat.
The carry-out roller 108 sends out the paper PA on which the toner image has been fixed out of the image forming apparatus 100.
The operation unit 109 receives input of various settings of the image forming apparatus 100.

FIG. 2 is a schematic view for explaining the image forming cartridge 110 and its peripheral portion.
The image forming cartridge 110 includes a photosensitive drum 111 as an image carrier, a charging roller 112, a developing roller 113 as a developing unit, a supply roller 114 as a supplying unit, a toner regulating member 115 as a regulating unit, And a cleaning device 116. Note that the exposure head 105 and the transfer roller 106 are disposed at predetermined positions of the image forming cartridge 110.

The photosensitive drum 111 is composed of a conductive support and a photoconductive layer. For example, the photoconductor drum 111 is an organic photoconductor formed by laminating a charge generation layer and a charge transport layer as a photoconductive layer in this order on an aluminum metal pipe as a conductive support. is there.
The charging roller 112, the developing roller 113, and the transfer roller 106 are configured by a metal shaft and a semiconductive rubber layer. The supply roller 114 includes a metal shaft and a foamed urethane rubber material. Independent power sources 132 to 135 are connected to the metal shafts of the respective rollers.

The exposure head 105 is a light source device having a plurality of dot exposure means in the main scanning line direction during printing (image formation) using LED light or laser light.
The toner regulating member 115 regulates the thickness of the toner layer formed on the developing roller 113. For example, the toner regulating member 115 is formed of a thin plate having a thickness of 0.08 mm and a length in the longitudinal direction substantially matching the width of the elastic body of the developing roller 113. Further, the toner regulating member 115 is installed such that one end in the short side direction is fixed to a frame (not shown), slightly bent from the tip of the other end, and the folded curved surface comes into contact with the developing roller 113. A power source 136 is also connected to the toner regulating member 115.
The cleaning device 116 is in contact with the photosensitive drum 111 and removes toner, paper dust, and the like on the surface of the photosensitive drum 111.

The photosensitive drum 111, the charging roller 112, the developing roller 113, the supply roller 114, and the transfer roller 106 rotate in the direction of the arrow shown in FIG. Here, the developing roller 113 and the supply roller 114 rotate in the same direction, and these surfaces are in counter contact with each other.
The photosensitive drum 111, the charging roller 112, and the transfer roller 106 operate at substantially the same peripheral speed. The developing roller 113 rotates at a faster speed than the photosensitive drum 111. The relationship between the rotation direction of each roller and the peripheral speed has been described above as an example, but the present invention is not limited to such an example.

FIG. 3 is a block diagram schematically showing main parts of a control system in the image forming apparatus 100 according to the first embodiment.
The image forming apparatus 100 includes a control unit 120, a high voltage power supply unit 130, and a rotation drive unit 140.

The control unit 120 controls processing in the image forming apparatus 100. For example, the control unit 120 controls each unit of the image forming apparatus 100 such as the image forming cartridge 110 to form an image on the paper PA.
In particular, the control unit 120 controls the voltage applied to the developing roller 113, the supply roller 114, and the toner regulating member 115. Specifically, the control unit 120 applies the absolute value of the voltage applied to the developing roller 113, the supply roller 114, and the toner regulating member 115 of a color that is not used for printing when the color is used for printing. Smaller than the absolute value of. In this case, the control unit 120 determines the difference between the absolute value of the voltage applied to the supply roller 114 and the toner regulating member 115 of the color not used for printing and the absolute value of the voltage applied to the development roller 113 of the color not used for printing. Is less than or equal to the difference when the color is used for printing.

The control unit 120 includes a storage unit 121, an interface control unit (hereinafter referred to as an IF control unit) 122, an operation control unit 123, an arithmetic processing unit 124, a voltage control unit 125, a drive control unit 126, and an exposure control. Part 127.
The storage unit 121 stores data necessary for processing in the image forming apparatus 100. For example, the storage unit 121 is a ROM or RAM that stores a sequence control program such as a printing operation or a preliminary operation that is performed at times other than printing, various data for controlling the image forming apparatus 100, and various comparison prescribed values. The IF control unit 122, which is a semiconductor memory, controls the IF unit 150 to receive data from a higher-level device such as an information processing device. For example, the IF control unit 122 receives, from the IF unit 150, print instruction data (image formation instruction data) including image data indicating an image to be formed on a medium, transmitted from the host device, and receives the print instruction data from the arithmetic processing unit. 124.
The operation control unit 123 receives an operation input from the user via the operation unit 109 and supplies a signal indicating the input operation to the arithmetic processing unit 124.

The arithmetic processing unit 124 controls processing in the image forming apparatus 100. For example, the arithmetic processing unit 124 is a microprocessor or the like that performs arithmetic processing for operating the image forming apparatus 100 using data stored in the storage unit 121. In particular, the arithmetic processing unit 124 determines whether there is toner of a color that is not used for image formation based on the print instruction data from the IF control unit 122. For example, when the exposure head 105 does not perform exposure during printing, the arithmetic processing unit 124 determines that the image forming cartridge 110 including such an exposure head 105 is of a color that is not used for printing. In addition, when exposure is not performed at the time of printing, a toner image is not formed on such a photosensitive drum 111. Accordingly, the arithmetic processing unit 124 determines that the image forming cartridge 110 including the photosensitive drum 111 on which a toner image is not formed at the time of printing is of a color that is not used for printing.
The voltage control unit 125 receives the calculation processing result from the calculation processing unit 124 and sets and outputs a voltage output value to be applied to the charging roller 112, the developing roller 113, the supply roller 114, the transfer roller 106, and the toner regulating member 115. The drive control unit 126 that performs voltage ON / OFF control receives the calculation processing result from the calculation processing unit 124 and controls ON / OFF of the driving power of the rotation driving unit 140.
The exposure control unit 127 receives the calculation processing result from the calculation processing unit 124, and controls ON / OFF of exposure of the exposure head 105 including a plurality of LEDs arranged in dot units in the print main scanning line direction.

The high voltage power supply unit 130 is a power supply unit that applies a voltage to each unit of the image forming apparatus 100.
The high-voltage power supply unit 130 includes a voltage output unit 131 that can apply independent voltages to the charging roller 112, the developing roller 113, the supply roller 114, the transfer roller 106, and the toner regulating member 115. For example, the voltage output unit 131 includes a charging roller power source 132 that applies a voltage to the charging roller 112, a developing roller power source 133 that applies a voltage to the developing roller 113, a supply roller power source 134 that applies a voltage to the supply roller 114, A transfer roller power source 135 for applying a voltage to the transfer roller 106 and a toner regulating member power source 136 for applying a voltage to the toner regulating member 115 are provided.
The rotation drive unit 140 applies power to the rotation system member and the conveyance system member. The rotation drive unit 140 includes, for example, an electronic component such as a DC motor or a pulse motor and its peripheral gear. In particular, the rotation driving unit 140 supplies power to the charging roller 112, the developing roller 113, the supply roller 114, the transfer roller 106, the photosensitive drum 111, the conveyance belt 103, and the like.

(Description of operation)
First, the overall operation of the image forming apparatus 100 will be described.
The surface of the photosensitive drum 111 is uniformly charged to an arbitrary polarity and potential by a charging roller 112 as a charging device. In the present embodiment, the voltage applied to the charging roller 112 is around −1000V.
In accordance with the print instruction from the host device, based on the image data, the arithmetic processing unit 124 instructs the exposure control unit 127 to turn on or off the exposure corresponding to each dot in each color. The control unit 127 controls exposure ON / OFF for the exposure head 105. As a result, an electrostatic latent image corresponding to the image pattern is formed on the surface of the photosensitive drum 111.

The supply roller 114 is in contact with the developing roller 113 and rotates to supply the toner in the toner container 104 to the developing roller 113. The toner on the developing roller 113 is charged by friction between the toner regulating member 115 and the supply roller 114 as contact members that are in contact with the developing roller 113. The toner thickness on the developing roller 113 is determined by the pressing force of the toner regulating member 115 against the developing roller 113.
The developing roller 113 is in contact with the photosensitive drum 111. The toner on the developing roller 113 is attached to the electrostatic latent image on the photosensitive drum 111 when a voltage is applied to the developing roller 113. Thereafter, the toner on the photosensitive drum 111 is transferred onto the paper PA by the electric field generated by the voltage applied to the transfer roller 106. In the present embodiment, the voltage applied to the transfer roller 106 is + 1000V to + 3000V. The toner on the paper PA is fixed by the fixing device 107. Transfer residual toner remaining on the photosensitive drum 111 after the transfer is removed by the cleaning device 116.

Next, the toner discarding operation will be described.
When the state where the toner used for printing is excessively small continues, the toner adhering to the surface of the developing roller 113 is not discharged to the outside. The toner on the developing roller 113 that circulates in the same place continues to be rubbed against the contact points of the supply roller 114, the toner regulating member 115 and the photosensitive drum 111. For this reason, the potential of the toner on the developing roller 113 may rise abnormally due to frictional charging. It is desirable to remove the toner that has been overcharged in advance before the printing operation on the paper PA is performed in order to adhere to the photosensitive drum 111 more than necessary and stain the paper PA. When printing on the paper PA, the toner is attached to the electrostatic latent image on the photosensitive drum 111 as described above, and is transferred onto the paper PA by the electric field with the transfer roller 106. On the other hand, when a toner discarding operation is performed, no voltage is applied to the transfer roller 106 after the toner adheres to the electrostatic latent image on the photosensitive drum 111 and is visualized. As a result, no electric field is generated, and the toner remains on the photosensitive drum 111 and is completely scraped off and removed by the cleaning device 116.

Next, the relationship between the toner potential on the developing roller 113 and printing stain will be described.
FIG. 4A is a graph showing the relationship between the voltage applied to the developing roller 113 during printing and the toner potential on the developing roller 113. FIG. 4B is a graph showing the relationship between the printing time and the toner potential on the developing roller 113.
Here, the toner having a negative charging characteristic will be described. Here, it is assumed that the potential of the color toner that is not used for printing is measured. For example, it is assumed that the potential of yellow, magenta, or cyan toner during monochrome printing is measured. Furthermore, the voltage applied to the supply roller 114 and the voltage applied to the toner regulating member 115 are assumed to be the same.

As shown in FIG. 4A, since the voltage applied to the developing roller 113 (hereinafter referred to as DB) is larger in absolute value, the charge injection to the toner is more likely to occur. The toner potential increases. Here, if the absolute value of the voltage applied to the developing roller 113 is too small, so-called fogging occurs.
Further, as the difference between the applied voltage (hereinafter referred to as SB) to the supply roller 114 and the toner regulating member 115 and the applied voltage (DB) to the developing roller 113 increases, the toner moves from the supply roller 114 to the developing roller 113 by the Coulomb force. And the triboelectric charge easily proceeds, and the toner potential on the developing roller 113 increases. In this embodiment, the difference is obtained by subtracting the absolute value of the applied voltage (DB) to the developing roller 113 from the absolute value of the applied voltage (hereinafter referred to as SB) to the supply roller 114 and the toner regulating member 115 (| SB). |-| DB |). The absolute value of the applied voltage to the developing roller 113 may be larger than the absolute value of the applied voltage of the supply roller 114, but here, the absolute value of the applied voltage of the supply roller 114 is It shall be more than the absolute value of applied voltage. Furthermore, if this difference is too small, there may be a problem that the toner is not transferred from the supply roller 114 to the developing roller 113, so this difference is desirably 60V or more.

  As shown in FIG. 4B, even when the applied voltage to the developing roller 113 is the same, the toner potential gradually increases as the developing roller 113 and the supply roller 114 continue to rotate and the toner on the developing roller 113 continues to be rubbed. It tends to increase. There is a correlation between the toner potential on the developing roller 113 and the contamination. For example, in the toner according to the first exemplary embodiment, when the toner potential on the developing roller 113 is −90 V or less (the absolute value of the toner potential is 90 V or more), printing smearing starts to occur. As described above, the toner potential on the developing roller 113 is desirably larger than −90 V from the viewpoint of contamination, but if it becomes too high, so-called fogging occurs. Therefore, the toner potential is desirably −20 V or less. Further, in order to obtain a good printing result, it is desirable that the toner potential on the developing roller 113 is in the range of −60V to −40V.

  As described above, if a large absolute voltage (DB, SB) is continuously applied to the toner even though the toner is not used for printing, the toner potential on the developing roller 113 is increased, and contamination is easily induced. Therefore, more toner must be discarded. On the other hand, a toner applied only with a small absolute value of applied voltage (DB, SB) can maintain a charged state at a low potential close to that of a fresh toner, and therefore has little deterioration and does not require much disposal of the toner.

  The voltages to be applied to the developing roller 113, the supply roller 114, and the toner regulating member 115 are determined by comprehensively determining the density and afterimage on the print medium and other print qualities. In addition, since the four-color image forming cartridges 110 are simultaneously operated, even when the corresponding color toner is not used for printing, a voltage when the corresponding color toner is used for printing is generally applied as it is. It is. However, if the corresponding color is not used for printing, as shown in FIG. 4, it is possible to extend the life of the toner with less toner deterioration as described above by applying a smaller absolute voltage. In addition, the number of times of disposal as deteriorated toner (dirty toner) can be reduced.

  Therefore, in this embodiment, when there is toner of a color that is not used for printing in the printing operation, the toner is applied to the developing roller 113, the supply roller 114, and the toner regulating member 115 in the image forming cartridge 110 of the corresponding color. The absolute value of the voltage is made smaller than the absolute value of the applied voltage when the toner is used for printing. Here, if the difference between the voltage applied to the developing roller 113 and the voltage applied to the supply roller 114 and the toner regulating member 115 is increased, the toner potential is increased. Make sure that it is less than the difference in use. In order to reduce these differences, only the absolute value of the voltage applied to the supply roller 114 and the toner regulating member 115 may be lowered, or the absolute voltage applied to the supply roller 114 and the toner regulating member 115 may be reduced. The value reduction width may be larger than the absolute value reduction width of the voltage applied to the developing roller 113.

FIG. 5 is a flowchart showing processing in the image forming apparatus 100 according to the first embodiment.
First, when print instruction data is received from the host device, the arithmetic processing unit 124 determines whether or not the received print instruction data is data for printing an image of the same pattern over a plurality of sheets (S10). If it is determined that the data is not such (No in S10), the process proceeds to step S11. If it is determined that it is such data (Yes in S10), the process proceeds to step S13.

In step S11, the arithmetic processing unit 124 regards the received print instruction data as data for instructing single printing, and instructs the voltage control unit 125 to output the DB and SB during normal printing from the voltage output unit 131. Thus, the image forming cartridge 110 is caused to perform printing as usual.
Further, the arithmetic processing unit 124 calculates an accumulated waste toner amount X to be discarded for each toner color (S12). For example, the arithmetic processing unit 124 adds the product of the waste toner amount Xi generated per certain print pattern and the waste coefficient A to the accumulated waste toner amount X stored in the storage unit 121. Here, it is assumed that the discard coefficient A is “1”. Then, the process proceeds to step S24.

In step S13, the arithmetic processing unit 124 uses a dot counter for each color of KMYC as a preparation for determining which of the four colors (KMYC) toner is included in the print pattern (image formation pattern). Reset and start counting the dot counter. For example, the arithmetic processing unit 124 stores a dot counter for each color in the storage unit 121. When the electrostatic latent image is formed on the photosensitive drum 111, the arithmetic processing unit 124 instructs the exposure control unit 127 according to the image data, and causes the exposure head 105 to perform exposure in units of dots. Increment the counter.
At the start of printing, the arithmetic processing unit 124 instructs the voltage control unit 125 to output the DB and SB during normal printing from the voltage output unit 131 in the four-color image forming cartridge 110 (S14). Then, the arithmetic processing unit 124 causes each unit of the image forming apparatus 100 to print the first sheet (S15).

  When the printing of the first sheet is completed, the arithmetic processing unit 124 determines whether there is a toner of a color that is not used for printing (S16). For example, the arithmetic processing unit 124 checks the dot counter of each color, and determines that the color is used for printing if the dot counter is advanced. If the dot counter is not advanced, the color is not used for printing. Judge. If it is determined that all color toners have been used for printing (No in S16), the process proceeds to step S17. If it is determined that there is toner of a color that is not used for printing (Yes in S16), the process proceeds to step S18.

  In step S <b> 17, the arithmetic processing unit 124 sets the discard coefficient A for all colors to “1” in order to discard toner of the discarded toner amount Xi generated in normal printing for all colors. In this case, the arithmetic processing unit 124 maintains DB and SB at the time of normal printing as applied voltages. Then, the process proceeds to step S20.

In step S <b> 18, the arithmetic processing unit 124 reduces the absolute values of the DB and SB of the image forming cartridge 110 corresponding to the color in order to prevent the deterioration of the toner of the color determined not to be used for printing.
In addition, by reducing the absolute values of DB and SB, the amount of discarded toner of the color can be reduced. Therefore, the arithmetic processing unit 124 sets the discard coefficient A of the color to be less than the normal value “1”. A small value is set (S19). Here, by setting the discard coefficient A for that color to “0.3”, the amount of toner to be discarded is 30% of that when the toner of that color is used for printing. Then, the process proceeds to step S20. The discard coefficient A of the color used for printing is set to “1”.

In step S20, the arithmetic processing unit 124 calculates a cumulative waste toner amount X to be discarded for each toner color.
Then, the arithmetic processing unit 124 controls each unit of the image forming apparatus 100 to perform printing for the second and subsequent sheets (S21), and uses the discard coefficient A set for each color to calculate the accumulated waste toner amount X. Calculate (S22).
The arithmetic processing unit 124 determines whether printing of all pages instructed to be printed has been completed. If pages that have not been printed remain (No in S23), the process returns to step S21. If all pages have been printed (Yes in S23), the process proceeds to step S24.

In step S24, the arithmetic processing unit 124 determines whether or not the accumulated waste toner amount X is greater than or equal to a predetermined threshold Y for each color (S24).
If there is a color for which the cumulative waste toner amount X is equal to or greater than the threshold Y (Yes in S24), the arithmetic processing unit 124 controls the image forming cartridge 110 of that color and supplies the toner of that color. A predetermined amount Xo is discarded (S25). As the toner discard pattern by the toner discard operation, a rectangular pattern in which the exposure head 105 emits light for a predetermined time over the entire printable area in the print main scanning direction is generally used.
Next, the arithmetic processing unit 124 subtracts the discarded toner amount Xo from the accumulated discarded toner amount X of the color for which the toner has been discarded (S26). The accumulated waste toner amount X is held in the storage unit 121, and the waste toner amount is added during the next printing operation.

As described above, the absolute value of the voltage applied to the developing roller 113, the supply roller 114, and the toner regulating member 115 of the image forming cartridge 110 that is not used during printing (image formation) is the voltage used when printing. By making it smaller than the absolute value, it is possible to prevent the deterioration of the toner of the color that is not used during printing. For this reason, the number of times of discarding the toner of that color can be reduced, and the amount of discard of the toner of that color can be reduced.
That is, according to the image forming apparatus 100 according to the first embodiment, it is possible to prevent the toner charging characteristics from being deteriorated and to increase the life of the toner as much as possible with respect to the unused toner color for printing. It becomes possible. Therefore, the use efficiency of the toner can be improved, and the ecological image forming apparatus 100 can be provided.

  In order not to extend the printing processing time, the timing of the toner discarding operation is the timing of the printing operation from the feeding of the printing paper from the cassette 101 to the discharging of the printing paper, excluding the period during which the printing pattern is transferred to the paper PA. It is desirable to do it inside. In the flow shown in FIG. 5, the toner is discarded after the printing is completed. For this reason, it is desirable to discard the toner after the toner image is transferred to the paper PA and before the paper PA is discharged. Further, when the toner is discarded before the printing is started, it is desirable that the paper PA is conveyed until it is conveyed to the position where the image forming cartridge 110 is disposed. In such a case, when receiving another printing instruction, the arithmetic processing unit 124 discards the toner by comparing the accumulated waste toner amount X calculated during the previous printing with the threshold value Y. Or not.

  In the first embodiment, in order to simplify the description, the absolute values of DB and SB are changed when a plurality of the same print patterns are printed. However, the present invention is not limited to such an example. For example, the present invention can also be applied to a case where a plurality of originals such as materials covering several pages are printed. In such a case, for example, the arithmetic processing unit 124 determines whether the toner color to be used is present or not for each page, and when printing a page having an unused color, the DB and SB of that color are printed. By reducing the absolute value of the value compared with the case of printing, the amount of discarded toner can be similarly reduced.

In the first embodiment, the arithmetic processing unit 124 determines whether or not there is an unused color by counting the dots that cause the exposure head 105 to emit light. However, the present invention is limited to such an example. It is not a thing. For example, the arithmetic processing unit 124 can determine whether there is a color that is not used for printing by analyzing image data included in the print instruction data. In such a case, the DB and SB can be controlled even from the first printing. For example, the arithmetic processing unit 124 may determine the color used for printing by analyzing whether the print instruction data indicates color printing or monochrome printing.
Furthermore, the color that is not used for printing or the color that is used for printing can also be manually set via the operation unit 109 or the printer driver of the host device.

  In the first embodiment described above, the arithmetic processing unit 124 changes the absolute values of the voltages applied to the supply roller 114 and the toner regulating member 115 as contact members, but the present invention is limited to such an example. However, even if the absolute value of the voltage applied to any one of these is changed, the same effect as described above can be obtained.

  In the first embodiment described above, the absolute values of DB and SB are reduced, but only the absolute value of SB may be reduced. In such a case, since the difference between the voltage applied to the developing roller 113 and the voltage applied to the supply roller 114 and the toner regulating member 115 is reduced, the toner potential on the developing roller 113 can be reduced. it can.

  In the first embodiment described above, the arithmetic processing unit 124 determines the absolute value of the voltage applied to the developing roller 113 from the absolute value of the voltage applied to the supply roller 114 and the toner regulating member 115 as contact members. These differences are calculated by subtracting the values, but the present invention is not limited to such an example. For example, the arithmetic processing unit 124 may calculate these differences based on the absolute value of a value obtained by subtracting the voltage applied to the developing roller 113 from the voltage applied to the supply roller 114 and the toner regulating member 115 as the contact member. Good.

  In the first embodiment described above, an example in which the image forming apparatus 100 is a printer has been described. However, the present invention is not limited to such an example. For example, the image forming apparatus 100 may be an MFP, a facsimile apparatus, or a copying apparatus. The present invention is not limited to the above-described embodiments, and various modifications can be made based on the spirit of the present invention. The description of the embodiments does not exclude such modifications from the scope of the present invention.

  DESCRIPTION OF SYMBOLS 100 Image forming apparatus, 101 Cassette, 102 Pickup roller, 103 Conveyor belt, 104 Toner container, 105 Exposure head, 106 Transfer roller, 107 Fixing apparatus, 108 Unloading roller, 109 Operation part, 110 Image forming cartridge, 111 Photosensitive drum 112 charging roller, 113 developing roller, 114 supply roller, 115 toner regulating member, 116 cleaning device, 120 control unit, 121 storage unit, 122 IF control unit, 123 operation control unit, 124 arithmetic processing unit, 125 voltage control unit, 126 drive control unit, 127 exposure control unit, 130 high voltage power supply unit, 140 rotation drive unit, 150 IF unit.

Claims (8)

An image carrier, a developing unit that attaches a developer to the electrostatic latent image formed on the image carrier, and a plurality of image forming units having a contact member that contacts the developing unit;
A control unit that controls a voltage applied to each of the developing unit and the contact member of each of the plurality of image forming units;
The controller is
Among the plurality of image forming units, an absolute value of a voltage applied to the developing unit and the contact member of an image forming unit of a color that is not used for image formation is a voltage when the color is used for image formation. An image forming apparatus characterized by being made smaller than an absolute value. The control unit includes an absolute value of a voltage applied to the contact member of an image forming unit of a color not used for image formation and an absolute value of a voltage applied to the developing unit of an image formation unit of a color not used for image formation. The image forming apparatus according to claim 1, wherein the difference is less than or equal to a difference when the color is used for image formation. The control unit determines, based on image data indicating an image to be formed, an image forming unit that does not form a developer image on the image carrier during image formation as an image forming unit of a color that is not used for image formation. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. Each of the plurality of image forming units further includes an exposure unit that exposes the image carrier to form an electrostatic latent image,
The control unit determines, based on image data indicating an image to be formed, an image forming unit that is not exposed by the exposure unit during image formation, as an image forming unit of a color that is not used for image formation. The image forming apparatus according to claim 1. The control unit analyzes whether the image formation instruction data for instructing image formation is an instruction to form an image in color or an instruction to form an image in monochrome. The image forming apparatus according to claim 1, wherein it is determined whether or not the image forming unit is an image forming unit of a color used for image formation. A power supply for supplying power to each of the plurality of image forming units;
The said control part changes the absolute value of the voltage applied to the said image development part and the said contact member by controlling the said power supply part, The Claim 1 characterized by the above-mentioned. Image forming apparatus. The contact member is at least one of a supply unit that supplies the developer to the development unit and a regulation unit that regulates the thickness of a layer formed by the developer supplied to the development unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. An image carrier, a developing unit that attaches a developer to the electrostatic latent image formed on the image carrier, and a plurality of image forming units having a contact member that contacts the developing unit;
A control unit that controls a voltage applied to each of the developing unit and the contact member of each of the plurality of image forming units;
The controller is
Among the plurality of image forming units, the absolute value of the voltage applied to the contact member of the image forming unit of a color that is not used for image formation is set to be larger than the absolute value of the voltage when the color is used for image formation. An image forming apparatus characterized by being made smaller.

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