JP6241249B2 - Latent image forming apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a latent image forming apparatus and an image forming apparatus.

Techniques described in Patent Documents 1 and 2 below are known regarding an optical static eliminator that eliminates static electricity by irradiating light on the surface of a charged image carrier.
Japanese Patent Application Laid-Open No. 2007-121536 as Patent Document 1 describes a position downstream of the charger (19) and upstream of the developing unit (14) with respect to the rotation direction of the photosensitive drum (11). An LD unit (20) having two LDs (201, 202) for irradiating a beam onto the surface of the photosensitive drum (11) is disposed, and one LD (201, 202) is arranged on the photosensitive drum (11). ) Is irradiated with a beam at a preset position on the surface of the photosensitive drum, a latent image is written on the surface of the photosensitive drum (11), and the photosensitive drum (11) charged by the other LD (201, 202) is charged. The surface is neutralized.
In the technique of Patent Document 1, a beam having a smaller energy is irradiated at the time of static elimination compared to the energy of the beam irradiated at the time of writing a latent image, and the magnitude of the beam energy at the time of writing is the same as that at the time of static elimination. , The energy of the irradiated beam is reduced. In addition, it is possible to extend the life of the LD unit (20) associated with beam irradiation as compared with the case where writing and static elimination are performed with one LD. Patent Document 1 describes a technique in which the beam energy is adjusted by changing the lighting ratio of the LD unit (20) during static elimination.

Japanese Patent Application Laid-Open No. 2010-271364 as Patent Document 2 is arranged at a position downstream of the charging roller (2) and upstream of the developing roller (3) with respect to the rotation direction of the photosensitive drum (1). An electro-optical device (8) for forming the latent image, a neutralizing LED (4) disposed at a position downstream of the transfer roller (6) and upstream of the charging roller (2), and a photosensitive drum ( 1) a sheet material conveyance belt (7) to which an image formed on the surface is transferred, and an image density detection sensor (5) for detecting the image density of the image transferred to the sheet material conveyance belt (7). The configuration of the obtained image forming apparatus is described.
In the technique of Patent Document 2, the image density of the solid black reference patch image (A) and the image density of the comparison patch image (B) formed by removing the charge from the area where the reference patch image (A) was formed. Are detected from the sheet material conveying belt (7). Then, the light quantity of the neutralization LED (4) is adjusted according to the difference in image density between the two detected patch images (A, B). Therefore, compared with the structure in which the light quantity of the static elimination LED (4) is always set to 100%, the light quantity of the static elimination LED (4) can be reduced and the life of the static elimination LED (4) can be extended. is there. Patent Document 2 describes a configuration in which a plurality of static elimination LEDs (4) are arranged side by side along the rotation axis direction of the photosensitive drum (1). The static elimination LEDs (4) are divided into at least two groups at a predetermined position on the surface, and one of the static elimination LEDs (4) and the other static elimination LED (4) are alternately irradiated with a beam. Thus, a technique for adjusting the total light emission amount of each static elimination LED (4) is described.
Patent Document 2 describes a technique for adjusting the amount of light emitted from the static elimination LED (4) by modulating the pulse width of the static elimination LED (4).

JP 2007-121536 A (“0031”, “0040”, “0058” to “0060”, “0064”, “0065”, “0068”, FIGS. 3 and 7) JP 2010-271364 A (“0019” to “0023”, “0025” to “0037”, “0041”, FIGS. 1 to 3)

  This invention makes it a technical subject to suppress the nonuniformity of static elimination, suppressing the increase in expense.

In order to solve the technical problem, the latent image forming apparatus of the invention according to claim 1 comprises:
A light emitting element that is disposed at a position downstream of the charger and upstream of the developing unit with respect to the rotation direction of the image carrier, and that irradiates light to the surface of the image carrier;
When forming a latent image on the surface of the image carrier, based on the image to be formed, to control the light emitting element, in the case of neutralizing the surface of the image carrier, part of the previous SL-emitting element Light emission control means for controlling the lighting ratio of the light emitting element so as to turn off the light,
Equipped with a,
The light emission control unit controls the light emitting element so that the lighting ratio is lower when both of the temperature and the humidity in the vicinity of the image holding body are higher than when the temperature is low. .

In order to solve the technical problem, an image forming apparatus according to claim 2 is provided.
An image carrier,
A charger for charging the surface of the image carrier;
The latent image forming apparatus according to claim 1 , wherein the latent image is formed on a surface of the image carrier.
A developing unit for developing the latent image formed on the surface of the image carrier into a visible image;
A transfer device disposed at a position downstream of the developing unit with respect to the rotation direction of the image carrier, and transferring the visible image on the surface of the image carrier to a transfer material;
It is provided with.

According to a third aspect of the present invention, in the image forming apparatus according to the second aspect ,
Applying a transfer voltage for transferring the visible image on the surface of the image carrier to the transfer material during image formation, and removing the surface of the image carrier when removing the surface of the image carrier A power supply control means for transferring,
It is provided with.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect ,
When both the temperature and humidity in the vicinity of the image carrier are high compared to the electricity for charge removal supplied to the transfer device when both the temperature and humidity in the vicinity of the image carrier are low, The transfer power supply control means for supplying the transfer device with electricity for charge removal,
It is provided with.

According to the first and second aspects of the invention, compared with the case where the configuration of the present invention is not provided, it is possible to suppress the occurrence of unevenness in static elimination while suppressing an increase in cost.
According to the first and second aspects of the present invention, it is possible to suppress excessive light emission of the light emitting element as compared with the configuration in which the lighting ratio does not correspond to temperature and humidity.
According to the third aspect of the present invention, the surface of the image carrier can be reliably neutralized as compared with a configuration in which the surface of the image carrier is not neutralized by the transfer device.
According to the fourth aspect of the present invention, it is possible to suppress an excessive supply of the electricity for discharging, compared to the configuration in which the electricity for discharging corresponding to the temperature and humidity is not supplied.

FIG. 1 is an overall explanatory view of an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a block diagram illustrating the functions of the control unit of the image forming apparatus according to the first embodiment. FIG. 3 is an explanatory diagram of a discrimination number correspondence table according to the first embodiment of the present invention. FIG. 4 is an explanatory diagram of a power supply correspondence table according to the first embodiment of the present invention. FIG. 5 is an explanatory diagram of a correspondence table of the static elimination image according to the first embodiment of the present invention. FIG. 6 is an explanatory diagram of a static elimination writing image corresponding to the writing ratio of the first embodiment of the present invention. FIG. 6A is a static elimination writing image corresponding to a writing ratio of “100%”, and FIG. FIG. 6C is an explanatory diagram of a write image for charge removal corresponding to a write ratio of “50%”. FIG. 7 is an explanatory diagram of a flowchart of the determination process of the start timing of the charge removal process according to the first embodiment. FIG. 8 is an explanatory diagram of a flowchart of the charge removal process according to the first embodiment.

Next, examples as specific examples of embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following examples.
In order to facilitate understanding of the following description, in the drawings, the front-rear direction is the X-axis direction, the left-right direction is the Y-axis direction, the up-down direction is the Z-axis direction, and arrows X, -X, Y, -Y, The direction indicated by Z and -Z or the indicated side is defined as the front side, the rear side, the right side, the left side, the upper side, the lower side, or the front side, the rear side, the right side, the left side, the upper side, and the lower side, respectively.
In the figure, “•” in “○” means an arrow heading from the back of the page to the front, and “×” in “○” is the front of the page. It means an arrow pointing from the back to the back.
In the following description using the drawings, illustrations other than members necessary for the description are omitted as appropriate for easy understanding.

FIG. 1 is an overall explanatory view of an image forming apparatus according to Embodiment 1 of the present invention.
In FIG. 1, the printer U of Embodiment 1 of the image forming apparatus of the present invention is provided with a discharge tray TH <b> 1 as an example of a discharge unit for discharging a sheet S as an example of a medium at the upper end. Below the discharge tray TH1, a control board SC on which various control circuits, storage media and the like are arranged is arranged. The control board SC includes a control unit C for performing various controls of the printer U, an image processing unit GS whose operation is controlled by the control unit C, a laser drive circuit DL as an example of a latent image forming device drive circuit, and a power source A power supply circuit E as an example of the apparatus is provided. The power supply circuit E supplies voltages to charging rolls CRy to CRk as an example of a charger described later, developing rolls G1y to G1k as an example of a developer holding member, and primary transfer rolls T1y to T1k as an example of a transfer unit. Apply.

The image processing unit GS converts print information input from a personal computer PC or the like as an example of an external image information transmission device into four colors of yellow, magenta, cyan, and black, that is, Y, M, C, and K. Is converted into image information for forming a latent image corresponding to the image of, and output to the laser drive circuit DL at a preset timing.
When the document image is a single color image, so-called monochrome, only black image information is input to the laser drive circuit DL.
The laser drive circuit DL has drive circuits for the respective colors Y, M, C, and K (not shown), and forms a latent image arranged for each color at a preset time in accordance with input image information. Output to LED heads LHy, LHm, LHc, and LHk as an example of the apparatus.

In the lower center of the printer U, visible image forming apparatuses UY, UM, UC, UK that form toner images as examples of visible images of Y: yellow, M: magenta, C: cyan, and K: black. Is arranged. The black, that is, K-color visible image forming device UK includes a photosensitive drum Pk as an example of a rotating image carrier. Around the photosensitive drum Pk, a charging roll CRk as an example of a charger that charges the surface of the photosensitive member Pk, an LED head LHk as an example of a latent image forming device that forms an electrostatic latent image on the surface of the photosensitive member, A developing device Gk that develops the electrostatic latent image on the surface of the photosensitive member into a visible image, a drum cleaner CLk as an example of an image carrier cleaning device that removes the developer remaining on the surface of the photosensitive drum Pk, and the like are arranged. Yes.
The visible image forming apparatuses UY, UM, and UC of other colors are also configured in the same manner as the black visible image forming apparatus UK.

  The photosensitive drums Py to Pk are uniformly charged on the surface by the charging rolls CRy to CRk, and then latent images are written by the LED heads LHy to LHk in the latent image forming areas Q1y, Q1m, Q1c, Q1k. The written electrostatic latent image is developed into a toner image in the development areas Q2y, Q2m, Q2c, and Q2k facing the developing devices Gy to Gk. The developed toner image is conveyed to primary transfer regions Q3y, Q3m, Q3c, and Q3k that are in contact with an intermediate transfer belt B as an example of an intermediate transfer member. The intermediate transfer belt B according to the first exemplary embodiment is formed of an endless belt-like member, a so-called belt-shaped member, and is a belt driving roll Rd as an example of a driving member, an example of a driven member, and a secondary transfer counter member. As an example, it is rotatably supported by an intermediate transfer support system including a backup roll T2a and the primary transfer rolls T1y, T1m, T1c, and T1k arranged to face the respective photosensitive drums Py to Pk. . The intermediate transfer member is not limited to a belt shape, and a conventionally known form such as a drum shape can be employed.

  A primary transfer roll T1y, T1m, T1c, T1k as an example of a primary transfer unit disposed on the back side of the intermediate transfer belt B in the primary transfer regions Q3y, Q3m, Q3c, Q3k is provided by a control unit C. A primary transfer voltage having a polarity opposite to the charging polarity of the toner is applied from a power supply circuit E to be controlled at a preset time. Therefore, the toner images on the photosensitive drums Py to Pk are primarily transferred to the intermediate transfer belt B by the primary transfer rolls T1y, T1m, T1c, and T1k.

  Residue and deposits such as transfer residual toner and discharge products on the surface of the photosensitive drums Py, Pm, Pc, and Pk after the primary transfer are cleaned by the drum cleaners CLy, CLm, CLc, and CLk. The cleaned surfaces of the photosensitive drums Py, Pm, Pc, and Pk are recharged by charging rolls CRy, CRm, CRc, and CRk. A charger cleaner as an example of a charger cleaning member disposed in contact with the charging rolls CRy to CRk is a residue that cannot be removed by the drum cleaners CLy to CLk and adhered to the charging rolls CRy to CRk. Cleaning is performed by CCy, CCm, CCc, and CCk.

  On the upper rear side of the intermediate transfer belt B, a belt cleaner CLb as an example of an intermediate transfer body cleaner is disposed. The belt cleaner CLb is for a belt as an example of a cleaning container CLb1 and a cleaning member that is supported by the cleaning container CLb1 and that contacts the intermediate transfer belt B to remove residues remaining on the surface of the intermediate transfer belt B and cleans them. The cleaning blade CLb2, the film CLb3 as an example of a leakage preventing member for preventing the residue removed by the belt cleaning blade CLb2 from scattering and leaking, and the cleaning blade CLb2 disposed in the cleaning container CLb1 and removed. And a residue conveying member CLb4 for conveying and discharging the residue. The cleaning container CLb1 according to the first embodiment is disposed at a position corresponding to the upper side of the black photoconductor cleaner CLk.

A secondary transfer roll T2b as an example of a secondary transfer member is disposed facing the surface of the intermediate transfer belt B in contact with the backup roll T2a. The backup roll T2a and the secondary transfer roll T2b constitute a secondary transfer device T2 of Example 1. Further, a secondary transfer area Q4 as an example of an image recording area is formed by the areas where the secondary transfer roll T2b and the intermediate transfer belt B face each other.
The single-color or multi-color toner images transferred in sequence on the intermediate transfer belt B by the primary transfer rolls T1y, T1m, T1c, and T1k in the primary transfer regions Q3y, Q3m, Q3c, and Q3k Transported to region Q4.
The visible image forming apparatuses UY to UK, the intermediate transfer belt B, and the like constitute image recording apparatuses UY to UK + B that form an image recorded on the sheet S.

The primary transfer rolls T1y to T1k, the intermediate transfer belt B, the secondary transfer device T2, and the like constitute a transfer device T1 + T2 + B of Example 1.
As shown in FIG. 1, the intermediate transfer belt B of Example 1 is disposed in a state where the primary transfer regions Q3y to Q3k are inclined downward toward the rear side with respect to the horizontal plane, Correspondingly, the visible image forming devices UY to UK are also arranged at positions shifted downward in the gravitational direction as they go downstream in the belt rotation direction.

  Below the visible image forming apparatuses UY to UK, a paper feed tray TR1 as an example of a medium storage unit is provided. The paper feed tray TR1 includes a bottom wall TR1a as an example of a lower wall, a rear end wall TR1b extending upward from the rear end of the bottom wall TR1a, and an upper wall TR1c disposed to face the upper side of the bottom wall TR1a. And have. A replenishing port TR1d for replenishing a new sheet S is formed at the front end of the paper feed tray TR1. The front end portion of the upper wall TR1c is formed so as to incline upward toward the outside of the replenishing port TR1d, that is, the front side. Therefore, the replenishment port TR1d is formed such that the distance between the upper wall TR1c and the bottom wall TR1a increases as it goes to the front side, and widens as the replenishment port TR1d goes to the front side.

On the bottom wall TR1a, an elevating plate PL1 as an example of a medium stacking unit that supports the sheet S so as to be rotatable about the rotation center PL1a and stacks the sheet S and raises and lowers the sheet S is disposed. A lifting spring PL2 as an example of a biasing member that biases the rear end of the lifting plate PL1 upward is disposed at the rear end of the lifting plate PL1. When the image is not formed, the elevating plate PL1 is in a lowered position where the elevating plate PL1 is held in a state parallel to the bottom wall TR1a by the eccentric cam-like push-down members PL3 arranged at both left and right ends. Moving. While the image is being formed, the push-down member PL3 is rotated and supported by the lift spring PL2 so as to be movable between the lift position shown in FIG. 1 where the lift plate PL1 is lifted.
Therefore, when the replenishing port cover U2 as an example of the replenishing port opening / closing member is opened, the replenishing port TR1d is opened, and a new bundle of sheets S is inserted until the replenishing port TR1b hits the rear end wall TR1b. It is accommodated in a state of being loaded on the plate PL1.

A pickup roll Rp, which is an example of a medium transport member and an example of a delivery member, is disposed behind the upper wall TR1c. The pickup roll Rp is disposed at a position where the uppermost sheet S of the bundle of stacked sheets S is pressed by the spring force of the elevating spring PL2 in a state where the elevating plate PL1 is moved to the raised position. A separating roll Rs is arranged above the rear end wall TR1b as an example of a separating member.
The sheets S stacked on the paper feed tray TR1 are fed out by the pickup roll Rp, separated one by one in the contact area between the separating roll Rs and the pickup roll Rp, and conveyed to the medium conveyance path SH. . The sheet S in the medium conveyance path SH is an example of a medium conveyance member, and is conveyed to a registration roll Rr as an example of a timing adjustment member that adjusts the conveyance timing of the sheet S, that is, a so-called timing. The sheet S conveyed to the registration roll Rr is sent to the secondary transfer area Q4 from the carry-out port Rr1 of the registration roll Rr in accordance with the timing when the toner image on the intermediate transfer belt B reaches the secondary transfer area Q4.

The intermediate transfer belt B after the toner image is transferred in the secondary transfer region Q4 is cleaned by removing residual toner and discharge products remaining on the surface by the belt cleaner CLb.
The sheet S on which the toner image has been transferred is conveyed to a fixing region Q5 of the fixing device F. The fixing device F includes a heating roll Fh as an example of a heat fixing member and a pressure roll Fp as an example of a pressure fixing member, and the heating roll Fh and the pressure roll Fp are set in advance. The fixing region Q5 is configured by the region that is in contact with the pressure. The unfixed toner image on the surface of the sheet S is fixed by heat and pressure when passing through the fixing region Q5.
The recording medium S on which the image is fixed is transported through the medium transport path SH and is discharged from a discharge roll Rh as an example of a medium discharge member to the discharge tray TH1.

(Description of image forming operation)
In the printer U of the first embodiment, the image processing unit GS uses print information input from a personal computer PC or the like as latent images corresponding to four color images of Y: yellow, M: magenta, C: cyan, and K: black. The image information is converted into image information for image formation and output to the laser drive circuit DL at a preset timing. When the original image is a single color image, so-called monochrome, the image processing unit GS inputs image information of only black to the laser drive circuit DL.
The laser drive circuit DL has drive circuits for the respective colors Y, M, C, and K (not shown), and at times when signals corresponding to input image information are set in advance, the LED heads LHy, LHm, LHc, Output to LHk.

  In FIG. 1, charging rolls CRy to CRk charge the surfaces of the photosensitive drums Py to Pk. The LED heads LHy to LHk write an electrostatic latent image by outputting an LED beam as an example of image writing light to the charged surfaces of the photosensitive drums Py to Pk. The developing devices Gy to Gk develop the electrostatic latent images on the surfaces of the photosensitive drums Py to Pk into toner images as an example of visible images of the respective colors Y, M, C, and K.

The primary transfer rolls T1y to T1k transfer the toner images on the surfaces of the photosensitive drums Py to Pk onto the intermediate transfer belt B. In Example 1, when a multicolor image, that is, a so-called color image is formed, the primary transfer rolls T1y to T1k sequentially apply the toner images of the respective photosensitive drums Py to Pk to the intermediate transfer belt B. Transfer in layers. In the case of only black image information, only the black photosensitive drum Pk and the developing device Gk are used, and only the black toner image is formed. Accordingly, only the black toner image is transferred to the intermediate transfer belt B.
After the toner image is primarily transferred to the intermediate transfer belt B, the drum cleaners CLy to CLk clean the toner remaining on the surfaces of the photosensitive drums Py to Pk. The toner image transferred to the intermediate transfer belt B is conveyed to the secondary transfer area Q4.

The pickup roll Rp takes out the sheet S from the paper feed tray TR1 at a preset paper feed time. When the pickup roll Rp takes out a plurality of sheets S, the separation roll Rs separates the sheets S one by one. The sheet S that has passed the separating roll Rs is conveyed to the registration roll Rr.
The registration roll Rr sends out the sheet S in accordance with the time when the toner image is conveyed to the secondary transfer region Q4. When the sheet S passes through the secondary transfer region Q4, the secondary transfer unit T2 transfers the toner image on the intermediate transfer belt B to the sheet S.

In the case of a color image, the toner images primarily transferred onto the surface of the intermediate transfer belt B are secondarily transferred to the sheet S at once. After the intermediate transfer belt B passes through the secondary transfer region Q4, the belt cleaner CLb cleans the toner remaining on the intermediate transfer belt B.
The second-transferred sheet S is conveyed to the fixing device F. When the sheet S passes through the fixing region Q5, the fixing device F heat-fixes the toner image on the surface of the sheet S. The discharge roll Rh discharges the sheet S on which the toner image is heated and fixed to the discharge tray TH1.

(Description of latent image forming apparatus)
In FIG. 1, the LED heads LHy to LHk are arranged at positions downstream of the charging rolls CRy to CRk and upstream of the developing devices Gy to Gk with respect to the rotation direction of the photosensitive drums Py to Pk. The LED heads LHy to LHk of Example 1 have a plurality of LEDs as an example of light emitting elements, and each LED is arranged in a line along the width direction of the sheet S. The LED emits the LED beam in accordance with an LED drive signal output from the laser drive circuit DL.

(Description of the control part of Example 1)
FIG. 2 is a block diagram illustrating the functions of the control unit of the image forming apparatus according to the first embodiment.
In FIG. 2, the control unit C of the printer U has an input / output interface I / O for inputting / outputting signals to / from the outside. In addition, the control unit C includes a ROM (read only memory) in which a program for performing necessary processing, information, and the like are stored. In addition, the control unit C includes a random access memory (RAM) for temporarily storing necessary data. The control unit C includes a central processing unit (CPU) that performs processing according to a program stored in a ROM or the like. Therefore, the control part C of Example 1 is comprised by the small information processing apparatus, what is called a microcomputer. Therefore, the control part C can implement | achieve various functions by running the program memorize | stored in ROM etc.

(Signal output element connected to control unit C)
The control unit C receives output signals from signal output elements such as the temperature sensor SN1 and the humidity sensor SN2.
SN1: Temperature sensor The temperature sensor SN1 as an example of the environmental temperature detection means detects the environmental temperature Te of the printer U as an example of the temperature, and inputs the detection signal to the control unit C.
SN2: Humidity Sensor The humidity sensor SN2 as an example of the environmental humidity detection means detects the environmental humidity Hu of the printer U as an example of humidity, and inputs the detection signal to the control unit C.

(Controlled element connected to control unit C)
The control unit C outputs control signals for the next controlled elements D1, DL, E and the like.
D1: Main motor drive circuit The main motor drive circuit D1 as an example of the main drive source drive circuit rotates the photosensitive drums Py to Pk, the intermediate transfer belt B, and the like via the main motor M1 as an example of the main drive source. To drive.
DL: Laser drive circuit The laser drive circuit DL controls the LED heads LHy to LHk to form a latent image.

E: Power supply circuit The power supply circuit E includes a power supply circuit Ea for charging, a power supply circuit Eb for development, a power supply circuit Ec for primary transfer, a power supply circuit Ed for secondary transfer, a power supply circuit Ee for fixing, and the like. Have.
Ea: Power Supply Circuit for Charging The power supply circuit Ea for charging applies a charging voltage for charging the surfaces of the photosensitive drums Py to Pk to the charging rolls CRy to CRk, respectively.
Eb: Power supply circuit for development The power supply circuit Eb for development applies a development voltage to the development rolls G1y to G1k of the development devices Gy to Gk.
Ec: Power supply circuit for primary transfer The power supply circuit Ec for primary transfer applies a transfer voltage to the primary transfer rolls T1y to T1k.
Ed: Power supply circuit for secondary transfer The power supply circuit for secondary transfer Ed applies a transfer voltage to the secondary transfer roll T2b.
Ee: Fixing power supply circuit The fixing power supply circuit Ee supplies heater heating power to the heating roll Fh of the fixing device F.

(Function of control unit C)
The control unit C has the following function realizing means by a program for controlling the operation of each controlled element according to the output signal of the signal input element.
C1: Job Control Unit Job control unit C1 as an example of an image forming operation control unit is configured to charge rollers CRy to CRk, primary transfer rolls T1y to T1k, according to print information transmitted from the personal computer PC or the like. The operation of the fixing device F or the like is controlled to execute a job as an example of an image forming operation.
C2: Print Information Receiving Unit The print information receiving unit C2 receives and stores the print information. The print information receiving means C2 according to the first embodiment receives and stores print information previously input by the user via the personal computer PC. The print information of the first embodiment includes, in addition to image information as image information printed on each sheet S, print number information as information on the number of sheets S to be printed, and information on the images to be printed. Print setting information as setting information.

C3: Print Number Information Acquisition Unit The print number information acquisition unit C3 acquires the print number information. In the print number information acquisition unit C3 according to the first exemplary embodiment, as an example of the print number information, the total number of pages to be printed is acquired from the print information stored in the print information reception unit C2.
C4: Print Setting Information Acquisition Unit The print setting information acquisition unit C4 receives, as an example of the print setting information, image setting information indicating whether a “high density image” is to be printed on the sheet S, and receives the print information. Obtained from the print information stored in the means C2.
In the print setting information acquisition unit C4 according to the first embodiment, among the image settings of the image to be printed on the preset sheet S, the “high density image” is set as the “photo image” image setting, and other than the “photo image” Image setting information in which the image setting such as “standard image” is “image other than high-density image” is acquired from the print information stored in the print information receiving means C2.

FIG. 3 is an explanatory diagram of a discrimination number correspondence table according to the first embodiment of the present invention.
C5: Discriminated Number Table Storage Unit The discriminating number table storage unit C5 as an example of the discriminating number correspondence table storage unit stores a discriminating number table TA1 as an example of a discrimination number correspondence table. In the discriminating number table storage means C5 of the first embodiment, the discriminating number Na as an example of the discriminating time for discriminating whether or not the image setting information and the neutralizing process for neutralizing the surfaces of the photosensitive drums Py to Pk are started. Is stored. A discrimination number table TA1 indicating the correspondence relationship is stored. In the discrimination number table TA1 of the first embodiment, as shown in FIG. 3, “α ₁ ” as the discrimination number Na corresponding to the image setting of “high density image” and “image other than high density image” are displayed. “Α ₂ sheets” is stored as the discrimination number Na corresponding to the setting. In the discrimination number table TA1 of the first embodiment, α ₁ and α ₂ are set so as to satisfy the relationship of α ₁ <α ₂ .

C6: Discrimination number setting means The discrimination number setting means C6 is based on the image setting information acquired by the print setting information acquisition means C4 and the determination number table TA1 stored in the determination number table storage means C5. The discrimination number Na is set. In the discriminating number setting means C6 of the first embodiment, image setting is performed based on the image setting information acquired by the print setting information acquiring means C4 and the discriminating number table TA1 stored in the discriminating number table storage means C5. Is “high density image”, “α ₁ sheet” is set as the discrimination number Na. When the image setting is “an image other than a high-density image”, “α ₂ sheets” is set as the discrimination number Na.

C7: Image Density Detection Unit The image density detection unit C7 includes an image information expansion unit C7A and an image density calculation unit C7B, and detects the image density of the image recorded on the surface of the sheet S.
C7A: Image Information Expansion Unit The image information expansion unit C7A converts and expands the image information as print information for printing. In the image information expansion unit C7A according to the first exemplary embodiment, the image information for one page that is written on the sheet S by the LED heads LHy to LHk based on the image information acquired by the print information reception unit C2. Is converted and expanded as writing information for printing.

C7B: Image Density Calculation Unit The image density calculation unit C7B calculates the image density ρ _a of the image recorded on the sheet S based on the printing information developed on the image information expansion unit C7A. .
The computing means C7B image density in Example 1, the total number L _b of the pixels corresponding to the size of the sheet S, based on the write information for printing that was expanded, the number of pixels to be written on the sheet S L _a and the total number L _{b of} pixels corresponding to the size of the sheet S are counted, and the image density ρ _a is calculated as ρ _a = L _a / L _b .

C8: threshold storage unit C8 threshold storage means image density of the image density, as an example of a threshold to determine when to begin neutralization process, and stores the threshold value [rho _b of the image density. In the first embodiment, as an example, an image density threshold ρ _b = 20% is stored.
C9: Discriminating means for the start timing of the first static elimination process The discriminating means C9 for the start timing of the first static elimination process is an image density ρ _a calculated by the image density calculating means C7B and a threshold value storage of the image density. based on the threshold value [rho _b of the stored image density means C8, as an example of the neutralization start timing, determines whether it is the start timing of the first charge elimination of the neutralization process is started. In the first charge elimination start timing discriminating means C9 of Example 1, determined the image density [rho _a is when the is image density threshold [rho _b above, as it becomes the start timing of the first charge elimination To do.

C10: Cumulative Printed Number Counting Unit The cumulative printed number counting unit C10 obtains a cumulative printed number N obtained by accumulating the number of printed sheets S.
C11: Average Image Density Calculation Unit The average image density calculation unit C11 sets the image density ρ _a calculated by the image density calculation unit C7B and the cumulative print number N accumulated in the cumulative print number counting unit C10. based calculates an average image density [rho _N of the image recorded on the sheet S of accumulated print number N.
In operation means C11 mean image density in Example 1, the average image density [rho _N is, when the average image density up to the previous and the average image density [rho _N-1, image density [rho _a, and the cumulative number of printed sheets N Is calculated as ρ _N = {(N−1) × ρ _N−1 + ρ _a } / N.

C12: Discriminated sheet number discriminating unit The discriminating sheet number discriminating unit C12 is configured such that the cumulative printed sheet number N obtained by the cumulative printed sheet number counting unit C10 is equal to or larger than the discriminating sheet number Na set in the discriminating sheet number setting unit C6. It is determined whether or not it has been reached.
C13: threshold storage unit C13 of the threshold storage unit average image density of the average image density, stores a threshold value [rho _c mean image density as an example of a threshold value for determining whether or not it is time to start the neutralization process. In the first embodiment, as an example, an average image density threshold ρ _c = 10% is stored.

C14: Discriminating means for the start timing of the second static elimination process The discriminating means C14 for the start timing of the second static elimination process is the image density ρ _N calculated by the average image density calculating means C11 and the average image density. based on the threshold value [rho _c of the image density stored in the threshold storage unit C13, as an example of the neutralization start timing, it determines whether it is the start timing of the second charge elimination of the neutralization process is started. In the second charge elimination start timing determination means C14 of Example 1, the accumulated number of printed sheets N reaches the number of more than the determination number Na, and the average image density [rho _N is, the threshold value of the average image density if it becomes more than [rho _c, determined as it becomes the start timing of the second charge elimination.
C15: updating means C15 updating means average image density of the average image density, an average image density [rho _N calculated by the calculation means C11 of the average image density, and overwrites the average image density [rho _N-1 up to the previous The average image density ρ _N−1 up to the previous time is updated.

C16: Discriminating means for the start timing of the third static elimination process The discriminating means C16 for the start timing of the third static elimination process is an example of the start timing of the third static elimination process at which the static elimination process is started as an example of the static elimination start timing. It is determined whether or not. The determination unit C16 for determining the start timing of the third charge removal process according to the first exemplary embodiment includes a job to be executed after the job currently being executed based on the received information received and stored in the print information receiving unit C2. In this case, it is determined that it is time to start the third charge removal process.
FL1: Static elimination process start flag An initial value of the static elimination process start flag FL1 is "0", and the first static elimination process start time, the second static elimination process start time, and the third static elimination process It is “1” when it is determined that one of the charge removal processes has started, and “0” when the charge removal process ends.

FIG. 4 is an explanatory diagram of a power supply correspondence table according to the first embodiment of the present invention.
C17: Transfer Voltage Setting Table Storage Unit for Charge Removal The transfer voltage setting table storage unit C17 as an example of the power correspondence table storage unit sets the transfer voltage for charge removal as an example of the power correspondence table. Store table TA2. In the transfer voltage setting table storage unit C17 of the first embodiment, the environmental conditions including the environmental temperature Te and the environmental humidity Hu, and the transfer voltage for discharging applied to the primary transfer rolls T1y to T1k during the discharging process. setting table TA2 transfer voltage for neutralizing showing a correspondence relationship between V _T is stored.
In the transfer voltage setting table TA2 for charge removal of the first embodiment, as shown in FIG. 4, charge removal of “β ₁ (V)” is performed for “high temperature and high humidity” and “room temperature and high humidity” environments. Transfer voltage V _T is stored, and “β ₂ ((high temperature and humidity)”, “high temperature and humidity”, “normal temperature and humidity”, “low temperature and humidity”, and “high temperature and low humidity” environments are stored. transfer voltage V _T for neutralization of V) "is stored," cold humidity ", and, with respect to the environment of the" low temperature and low humidity, "transfer voltage V _T for neutralization of" beta _{3 (V)} "is stored ing. Note that in the transfer voltage setting table TA2 for charge removal in the _first embodiment, β ₁ to β ₃ are set in advance by experiments or the like. In the first embodiment, β ₁ , β ₂ , and β ₃ are set so as to satisfy the relationship β ₁ <β ₂ <β ₃ .

C18: Transfer Voltage Setting Unit for Charge Removal The transfer voltage setting unit C18 for charge removal as an example of the power setting unit includes the environmental temperature Te and the environmental humidity Hu detected by the sensors SN1 and SN2, and the charge removal. based on the setting table TA2 setting the transfer voltage of the for neutralizing stored in the table storage unit C17 of the transfer voltage use, sets the transfer voltage V _T for neutralization. In the transfer voltage setting means C18 for static elimination of the first embodiment, based on the detected environmental temperature Te and environmental humidity Hu and the transfer voltage setting table TA2 for static elimination, “high temperature and high humidity” and “ In the case of an environment of “normal temperature and high humidity”, a transfer voltage V _T for neutralization of “β ₁ (V)” is set. In the case of “low temperature and high humidity”, “high temperature and normal humidity”, “normal temperature and normal humidity”, “low temperature and normal humidity”, and “high temperature and low humidity”, the transfer voltage for static elimination of “β ₂ (V)”. V _T is set, if the environment of the "cold humidity" and "low temperature and low humidity," transfer voltage V _T for neutralization of "beta _{3 (V)"} is set.

C21: Transfer Voltage Control Unit for Charge Removal The transfer voltage control unit C21 for charge removal, which is an example of a transfer power supply control unit, performs the primary transfer rolls T1y to T1k when the discharge process starts. controlling the transfer voltage V _T for neutralization to be applied to. In the neutralization transfer voltage control means C21 of the first embodiment, when the static elimination start flag FL1 is "1", the static elimination transfer set by the neutralization transfer voltage setting means C18. the voltage V _T, is applied to the primary transfer rolls T1y to T1k, the application is started the transfer voltage V _T for neutralization, if the static elimination time t _a has passed, the transfer voltage V _T for neutralization End application.

FIG. 5 is an explanatory diagram of a correspondence table of the static elimination image according to the first embodiment of the present invention.
FIG. 6 is an explanatory diagram of a static elimination writing image corresponding to the writing ratio of the first embodiment of the present invention. FIG. 6A is a static elimination writing image corresponding to a writing ratio of “100%”, and FIG. FIG. 6C is an explanatory diagram of a write image for charge removal corresponding to a write ratio of “50%”.
C22: Write Ratio Setting Table Storage Unit The write ratio setting table storage unit C22 as an example of the write ratio correspondence table storage unit stores a write ratio setting table TA3 as an example of the write ratio correspondence table. In the writing ratio setting table storage unit C22 according to the first embodiment, the writing ratio as the ratio of the pixels to be written to all the pixels of the environmental conditions including the environmental temperature Te and the environmental humidity Hu and the writing pattern as an example of the image for static elimination. A write ratio setting table TA3 indicating the correspondence relationship is stored. The writing pattern of the first embodiment is composed of 4 × 4 16 pixels as shown in FIG.

C23: Write ratio setting means The write ratio setting means C23 includes the environmental temperature Te and the environmental humidity Hu detected by the sensors SN1 and SN2, and the write ratio stored in the write ratio setting table storage means C22. The write ratio corresponding to the environment is set based on the setting table TA3. In the writing ratio setting means C23 of the first embodiment, based on the detected environmental temperature Te and environmental humidity Hu and the writing ratio setting table TA3, the environment of “high temperature and high humidity” and “room temperature and high humidity” is set. In this case, a writing ratio of “50%” is set. In the case of “low temperature and high humidity”, “high temperature and normal humidity”, “normal temperature and normal humidity”, “low temperature and normal humidity”, and “high temperature and low humidity”, a writing ratio of “75%” is set. In the case of the environment of “low humidity” and “low temperature and low humidity”, a writing ratio of “100%” is set.

C24: storage means C24 memory means writing start time of writing start time, stores the start time _{t b} of the writing of the time charge elimination by the LED head LHy~LHk is started. In the writing start time storage means C24 according to the first embodiment, the time from when the charge removal processing start flag FL1 becomes “1” until the LED heads LHy to LHk start writing of the electrostatic latent image is set. It is stored as the write start time t _b. In Example 1, the surface portion of the passes through the primary transfer region Q3y~Q3k photosensitive drum Py~Pk is, the time taken to reach the position of the LED head LHy~LHk is, the start time of writing _{t b} Is set as

C25: storage means C25 storage means discharge time of the discharge time is and the primary transfer rolls T1y to T1k, stores discharge time _{t a} as time to charge elimination by the LED head LHy~LHk ends from the start To do. In Example 1, the photosensitive drum Py~Pk is time to rotate at least one revolution or more is set as the discharge time t _a.

C26: Timekeeping Means at the Time of Charge Removal Processing Time keeping means C26 at the time of charge removal processing measures the times stored in the storage means C24 for writing start time and the storage means C25 for charge removal time at the time of charge removal processing. Time measuring means C26 during neutralization process in Example 1, when the charge elimination start flag FL1 processing becomes "1", and starts counting the start time of writing t _b, the start time t _b of writing when the elapsed, the application of the transfer voltage V _T for neutralization starts counting down time t _a -t _b of application as time to stop. Further, when the application stop time t _a -t _b has elapsed, the timing of the write start time t _b is started.

C27: Control Unit for LED Head for Neutralization An example of the light emission control unit, and the control unit C27 for the neutralization LED head as an example of the control unit of the latent image forming apparatus for neutralization includes LED heads LHy to LHk. Control the behavior. The neutralization control unit of the LED head for C27 in Example 1, from the time when the charge elimination start flag FL1 processing becomes "1", when the start time t _b of the write has elapsed, the electrostatic latent image Start writing neutralization process. When the charge removal process is started, the LED heads LHy to LHk are electrostatic latent images on the surfaces of the photosensitive drums Py to Pk with a writing pattern corresponding to the writing ratio set in the writing ratio setting means C23. Write.
Note that the control unit C27 of the LED head for charge removal of Example 1 writes the writing pattern of “100%” shown in FIG. 6A when the writing ratio is “100%”. In the case of the writing ratio of “75%”, the writing pattern of “75%” shown in FIG. 6B is written, and in the case of the writing ratio of “50%”, the writing of “50%” shown in FIG. 6C. Write the pattern. The control means C27 of the LED head for neutralization of Example 1, when the static elimination time t _a has elapsed since the writing of an electrostatic latent image is started, ends the writing of an electrostatic latent image.

C28: initialization execution unit initialization execution unit C28 initializes the cumulative number of printed sheets N and the average image density [rho _N. In initialization execution unit 28 of Example 1, at the start of a job, or reset if the charge elimination during job runs, initializes the cumulative number of printed sheets N and the average image density [rho _N, i.e., to "0" To do.

(Description of flowchart of determination process of start timing of static elimination process)
FIG. 7 is an explanatory diagram of a flowchart of the determination process of the start timing of the charge removal process of the first embodiment.
7 is performed according to a program stored in the control unit C of the printer U. This process is executed in parallel with other various processes of the printer U.
The flowchart shown in FIG. 7 is started when the printer U is turned on.
In ST1 of FIG. 7, it is determined whether or not the job has been started. If yes (Y), the process proceeds to ST2. If no (N), ST1 is repeated.

In ST2, in the job to be executed, the discrimination number Na corresponding to the image setting is set based on the discrimination number table TA1. Then, the process proceeds to ST3.
In ST3, the following processes (1) and (2) are executed, and the process proceeds to ST4.
(1) The accumulated number of printed sheets N is reset.
(2) The average image density ρ _N-1 is reset.
In ST4, the acquired image information for one page is converted and developed as writing information for printing. Then, the process proceeds to ST5.
In ST5, it calculates the image density [rho _a from the write information developed. Then, the process proceeds to ST6.
In ST6, who computed image density [rho _a is determined whether or not greater than the threshold value [rho _b of the image density. If yes (Y), the process proceeds to ST10. If no (N), the process proceeds to ST7.

In ST7, the following processes (1) and (2) are executed, and the process proceeds to ST8.
(1) The average image density ρ _N is calculated based on the calculated image density ρ _a , the cumulative number of printed sheets N, and the average image density ρ _N−1 up to the previous time.
(2) Add 1 to the cumulative number of printed sheets N, that is, N = N + 1.
In ST8, it is determined whether or not the cumulative print number N is larger than the determination number Na. If yes (Y), the process proceeds to ST9. If no (N), the process proceeds to ST13.
In ST9, who computed average image density [rho _N it is determined whether or not larger than the threshold value [rho _c mean image density. If yes (Y), the process proceeds to ST10. If no (N), the process proceeds to ST12.

In ST10, the static elimination start flag FL1 is set to “1”. Then, the process proceeds to ST11.
In ST11, it is determined whether or not the static elimination process start flag FL1 has become “0”. If yes (Y), the process proceeds to ST12. If no (N), ST11 is repeated.
In ST12, it is determined whether or not the job is finished. If yes (Y), the process proceeds to ST15. If no (N), the process returns to ST3.
In ST13, it overwrites the calculated average image density [rho _N as the average image density [rho _N-1 up to the previous. Then, the process proceeds to ST14.

In ST14, it is determined whether or not the job is finished. If yes (Y), the process proceeds to ST15. If no (N), the process returns to ST4.
In ST15, it is determined whether there is a job to be executed after the job currently being executed. If yes (Y), the process proceeds to ST16. If no (N), the process returns to ST1.
In ST16, the static elimination process start flag FL1 is set to "1". Then, the process proceeds to ST17.
In ST17, it is determined whether or not the static elimination process start flag FL1 has become “0”. If yes (Y), the process returns to ST1, and if no (N), ST17 is repeated.

(Description of the flowchart of the charge removal process of the first embodiment)
FIG. 8 is an explanatory diagram of a flowchart of the charge removal process according to the first embodiment.
The processing of each step ST in the flowchart of FIG. 8 is performed according to a program stored in the control unit C of the printer U. This process is executed in parallel with other various processes of the printer U.
The flowchart shown in FIG. 8 is started when the printer U is turned on.
In ST21 of FIG. 8, it is determined whether or not the start flag FL1 of the charge removal process has become “1”. If yes (Y), the process proceeds to ST22, and if no (N), ST21 is repeated.

In ST22, the following processes (1) and (2) are executed, and the process proceeds to ST23.
(1) The transfer voltage V _T for neutralization which corresponds to the detected environmental condition is set based on the setting table TA2 transfer voltage for charge elimination.
(2) A write pattern corresponding to the detected environmental condition is set based on the write ratio setting table TA3.
In ST23, the following processes (1) and (2) are executed, and the process proceeds to ST24.
(1) applies a transfer voltage _{V T} for neutralizing the primary transfer rolls T1y to T1k.
(2) to initiate the start counting the time _{t b} of writing.
In ST24, it is determined whether the start time t _b of the write has elapsed. If yes (Y), the process proceeds to ST25, and if no (N), ST24 is repeated.

In ST25, the following processes (1) and (2) are executed, and the process proceeds to ST26.
(1) Writing of the electrostatic latent image by the LED heads LHy to LHk is started.
(2) The timing of application stop time t _a -t _b is started.
In ST26, it is determined whether or not the application stop time t _a -t _b has elapsed. If yes (Y), the process proceeds to ST27, and if no (N), ST26 is repeated.
In ST27, the following processes (1) and (2) are executed, and the process proceeds to ST28.
(1) terminates the application of the transfer voltage V _T for neutralization.
(2) to initiate the start counting the time _{t b} of writing.
In ST28, it is determined whether the start time t _b of the write has elapsed. If yes (Y), the process proceeds to ST29, and if no (N), ST28 is repeated.
In ST29, the writing of the electrostatic latent image by the LED heads LHy to LHk is finished. Then, the process proceeds to ST30.
In ST30, the static elimination process start flag FL1 is reset to “0”. Then, the process returns to ST21.

(Effects of static elimination treatment)
In the printer U according to the first embodiment having the above-described configuration, when a job is executed, image information, print setting information, and the like are acquired from print information of the job to be executed. Then, the discrimination number Na is set based on the acquired print setting information. Further, based on the acquired image information, image density [rho _a of an image recorded on the sheet S is detected for each page. Then, the image density [rho _a one page of the case of more than the threshold [rho _b of the image density, charge elimination is started.
Further, when the cumulative number of printed sheets N becomes equal to or higher than the determination number Na, the average image density [rho _N of determined number Na sheet increases charge elimination in the case of more than the threshold [rho _c mean image density is started. Further, when there is a job to be executed next at the end of the job, the charge removal process is started.

In the charge removal process of the first embodiment, the writing pattern shown in FIG. 4 corresponding to the writing ratio is set based on the environmental temperature Te and the environmental humidity Hu. Then, based on each set writing pattern, the LED heads LHy to LHk output LED beams. Therefore, electrostatic latent images are written on the surfaces of the photosensitive drums Pk to Py, and the surfaces of the photosensitive drums Py to Pk are neutralized. In Example 1, the from the start of the neutralization treatment, after the lapse of the start time t _b of writing, writing of an electrostatic latent image of the LED head LHy~LHk is started. Then, since the writing start of the electrostatic latent image, after a lapse of the discharge time t _a, the writing of an electrostatic latent image is completed. Therefore, the surface portions of the photosensitive drums Py to Pk are neutralized by the LED heads LHy to LHk.

Here, in the configuration of Patent Document 1, in addition to the latent image writing LD (201, 202), a static elimination LD (201, 202) is separately provided. Therefore, there is a problem that the number of parts increases and the cost becomes high.
On the other hand, in the configuration of Patent Document 2, when neutralization is performed by the LED (4) that forms the latent image, based on the difference in image density between the solid black reference patch image (A) and the comparison patch image (B). Thus, the amount of light emitted from the LED (4) is reduced. However, when adjusting the amount of light in Patent Document 2, it is difficult to control the amount of light by changing the output of the LED (4), and a light amount different from the target amount of light is irradiated, or the output of the LED (4) is There is a risk that the light quantity to be irradiated may become uneven due to instability. When unevenness occurs in the amount of light emitted from the light emitting element, unevenness is generated in the electrostatic latent image written on the photosensitive drum (1), and there is a problem in that unevenness in discharging is generated on the sheet. there were.

  In contrast, in the printer U according to the first embodiment, when the LED heads LHy to LHk that perform image formation perform static elimination, an electrostatic latent image is formed with a writing pattern corresponding to a preset writing ratio. Here, each writing pattern is configured by combining pixels to be written and pixels not to be written. Therefore, in the LED heads LHy to LHk of Example 1, the LEDs are turned on or off according to the writing pattern. Therefore, the output of each LED and the light amount itself are not adjusted.

Therefore, in the configuration of the first embodiment, the LED heads LHy to LHk that are common to image formation perform static elimination and control of lighting or extinguishing, and the output is compared with the case of adjusting the light amount during lighting. Can be stabilized. Therefore, compared with the structure of patent document 1, 2, it can suppress the generation | occurrence | production of static elimination nonuniformity, suppressing cost increase.
Further, the configuration of the first embodiment forms an electrostatic latent image for charge removal with an image density corresponding to the writing ratio, and the cumulative light emission amount of each LED is reduced. Therefore, it is possible to extend the life of the LED heads LHy to LHk as compared with the case where static elimination is performed by turning on all the LEDs.

In particular, in the configuration of the first embodiment, the write ratio of the write pattern is set according to the environmental temperature Te and the environmental humidity Hu. For example, in Example 1, compared with other environments, “100%” for “low temperature and low humidity” and “room temperature and low humidity” environments in which the charges charged on the surfaces of the photosensitive drums Py to Pk are difficult to spontaneously discharge. The write pattern of the write ratio is set. In addition, a lighting pattern with a writing ratio of “75%” is set for environments of “low temperature and high humidity”, “high temperature and normal humidity”, “normal temperature and normal humidity”, “low temperature and normal humidity”, and “high temperature and low humidity”. . Then, a lighting pattern having a writing ratio of “50%” is set for an environment of “high temperature and high humidity” or “room temperature and high humidity”.
Therefore, in Example 1, the writing pattern is set according to the environment, and excessive light emission of the LED heads LHy to LHk is suppressed. Therefore, it is possible to reduce the accumulated light emission amount of each LED as compared with the configuration in which the writing ratio of the writing pattern is not adjusted according to the environmental temperature Te and the environmental humidity Hu.

Moreover, although the description of Patent Documents 1 and 2 does not include a description of the time when static elimination is performed, if it is performed for each sheet, productivity is deteriorated too much. Therefore, when continuous printing is performed, it is conceivable that static elimination is performed for each preset number of sheets. Therefore, in the conventional configuration, the next image may be printed continuously after a high-density image such as a “photo image”.
Here, the “photo image” is not only a high-density image including only the “photo image” but also a low-density image in which an image such as a character string other than the “photo image” is printed. May contain images. When a “photographic image” is printed on a sheet, a high-density image toner image and a low-density image toner image may be formed on the surface of the photosensitive drum. In addition, when an image of each color of Y, M, C, and K is formed in a full-color image, for example, a Y-color image may be formed only in a portion that is offset from the whole. That is, a high density portion and a low density portion may occur in an image for one page.

When a high-density image such as a “photographic image” is formed, there is a difference in the residual charge between the high-density part and the low-density part on the surface of the photosensitive drum, There is a risk of unevenness. If the next image is continuously printed in this state, the unevenness of the charge adversely affects the next image, and the image may be defective.
On the other hand, in the configuration of the first embodiment, when the average image density ρ _{a for} one page of the image is equal to or higher than the image density threshold ρ _b , the photosensitive drums Py to Pk are printed before the next image is printed. The surface charge is removed.
Therefore, continuously higher than the threshold value [rho _b of image density "high density image", as compared with the conventional configuration if there is the next image is printed, it is reduced that the defect occurs in the image .

Further, in the configuration of the first embodiment, when the cumulative number of printed sheets N is equal to or greater than the determined number of sheets Na, static elimination is performed even when the average image density ρ _N for the determined number of sheets Na is equal to or greater than the threshold ρ _{c for the} average image density. Done.
Here, in the printer U, when continuous printing is performed, the unevenness of the charge remaining on the surfaces of the photosensitive drums Py to Pk may be accumulated. For example, when a plurality of copies of an image including a photograph in a part of one page are printed, unevenness in charge is likely to be accumulated. When the next image is printed with the charge unevenness accumulated on the surfaces of the photoconductive drums Py to Pk, the charge unevenness may adversely affect the next image and the image may be defective. It was.

That is, the average image density ρ _{a for} one page of each page is lower than the image density threshold ρ _b , and even if it is difficult to affect the next page, the average image density ρ _N for the number of discriminating sheets is _N. If higher than the average image density [rho _c is the accumulated charge unevenness, which may adversely affect.
In contrast, in the configuration of the first embodiment, when the average image density ρ _{N for} the cumulative number of printed sheets N is equal to or greater than the average image density threshold ρ _c , the photosensitive drum Py is printed before the next image is printed. The surface of ~ Pk is neutralized. Therefore, the occurrence of defects in the image is reduced as compared with the conventional configuration in which unevenness of charge may be accumulated.

In the configuration of the first embodiment, the determination number Na for determining whether or not to neutralize the surfaces of the photosensitive drums Py to Pk is set according to the image setting. That is, in the first embodiment, when the image setting is a “high-density image” in which charge unevenness is likely to occur compared to “an image other than a high-density image”, “α ₁ ” is smaller in number than “α ₂ ”. The discriminating number Na is set to “sheets”.
Therefore, in the first embodiment, in the case of a “high-density image” in which unevenness in charge is likely to occur, it is frequently determined whether or not static elimination is performed. Therefore, in the first embodiment, the occurrence of image defects is reduced as compared with the case where the discrimination number Na is not set according to the image setting.

In the charge removal process of the first embodiment, the surfaces of the photosensitive drums Py to Pk are supplementarily discharged by the primary transfer rolls T1y to T1k before being discharged by the LED heads LHy to LHk. Therefore, as compared with the case where the charge removal is performed only by the LED heads LHy to LHk, the configuration of the first embodiment in which the charge removal is performed auxiliary by the primary transfer rolls T1y to T1k is easy to surely remove the charge.
In Example 1, the application is started the transfer voltage V _T for neutralization, after the passage of the static elimination time t _a, the application of the transfer voltage V _T for neutralization is completed. Accordingly, the primary transfer rolls T1y to T1k neutralize the surface of the photosensitive drums Py to Pk for at least one turn.

Here, the primary transfer rolls T1y to T1k have variations in resistance values in the axial direction. Therefore, when static elimination is performed by the primary transfer rolls T1y to T1k, a portion that can be sufficiently neutralized and a portion that is insufficient are generated due to variations in resistance value. Therefore, there is a risk that unevenness of static elimination may occur on the surface of the photosensitive drums Py to Pk after passing through the primary transfer regions Q3y to Q3k.
In addition, as the surface of the photoconductive drums Py to Pk wears with time and the film thickness of the surface of the photoconductive drums Py to Pk becomes thin, the charge removal amount on the primary transfer rolls T1y to T1k tends to decrease. In particular, as the film thickness decreases, the environmental influence of the environmental temperature Te and the environmental humidity Hu increases. Therefore, if the charge removal is performed with the LED heads LHy to LHk after performing the charge removal with the primary transfer rolls T1y to T1k, there is a possibility that the charge removal becomes insufficient over time. Therefore, if the charge removal is performed by the primary transfer rolls T1y to T1k after the charge removal is performed by the LED heads LHy to LHk, the photosensitive drums Py to Pk may not be sufficiently discharged.

  On the other hand, in the charge removal process of the first embodiment, the surface portions of the photosensitive drums Py to Pk that have been previously discharged with the primary transfer rolls T1y to T1k are discharged to the LED heads LHy to LHk. In the LED heads LHy to LHk, the neutralization unevenness in the axial direction as in the primary transfer rolls T1y to T1k is small, and it is possible to remove the charges uniformly compared to the case where the primary transfer rolls T1y to T1k are used. Therefore, compared to the configuration in which the primary transfer rolls T1y to T1k are discharged after the LED heads LHy to LHk are discharged, the configuration of Example 1 can reduce the unevenness of the discharging of the photosensitive drums Py to Pk. It is.

Moreover, in the neutralization process in Example 1, based on the environment of the environmental temperature Te and ambient humidity Hu, transfer voltage V _T for neutralization to be applied to the primary transfer roll T1y~T1k is set. For example, in Example 1, corresponding to the natural discharge ease of charges on the surface of the photosensitive drum Py to Pk, are set transfer voltage V _T for charge removal, the more likely environment natural discharge, a discharge The transfer voltage V _T for use is set low.
Thus, in Example 1, depending on the needs of the neutralization, the transfer voltage V _T for neutralization is set. Therefore, the transfer voltage V _T for static elimination can be reduced in an environment where natural discharge is less likely to occur than in environments where natural discharge is difficult. Therefore, as compared with the configuration in which the transfer voltage V _T for neutralization is not set depending on the needs of the neutralization, the application of the transfer voltage V _T of excess for neutralization is suppressed. Therefore, it is possible to reduce the power consumption consumed for the charge removal process.

(Example of change)
As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to the said Example, A various change is made in the range of the summary of this invention described in the claim. Is possible. Modification examples (H01) to (H013) of the present invention are exemplified below.
(H01) In the above embodiment, the printer U is illustrated as an example of the image forming apparatus, but the present invention is not limited to this. For example, the present invention can be applied to a copying machine, a FAX, or a multifunction machine having a plurality of these functions. Further, although a multi-color, so-called color image forming apparatus has been illustrated, the present invention is not limited to this, and the present invention can also be applied to a single-color, so-called monochrome image forming apparatus.

(H02) In the above embodiment, and the write pattern, a setting condition of the transfer voltage V _T for neutralization, illustrate environmental temperature, the parameter setting table TA2, TA3 consisting environment such as humidity environment when the charge elimination is carried out However, the present invention is not limited to this, and it is possible to eliminate one of these parameters or add another parameter. In addition, in the setting tables TA2 and TA3, the environmental temperature is divided into three stages of “high temperature”, “normal temperature”, and “low temperature”, and the environmental humidity is divided into three stages of “high humidity”, “normal humidity”, and “low humidity”. However, the present invention is not limited to this. For example, the number of divisions of environmental temperature and environmental humidity can be arbitrarily changed according to the design and specifications, such as dividing one or both parameters into two stages or dividing into four or more stages.

(H03) In the above embodiment, the writing ratio divided into three stages of “100%”, “75%”, and “50%” is exemplified, but the present invention is not limited to this. For example, the numerical value of the write ratio can be arbitrarily changed according to the design and specifications such as “90%”, “80%”, and “70%”. Also, the write ratio is not limited to three stages, and the write ratio stage can be arbitrarily changed, for example, the write ratio is two stages or four or more stages.
(H04) In the above embodiment, as shown in FIG. 6, the writing pattern composed of 4 × 4 16 pixels is exemplified, but the present invention is not limited to this, and the writing pattern composed of 5 × 5 25 pixels. Etc., and can be arbitrarily changed according to the design and specifications. Further, although the write pattern array corresponding to the write ratio of “75%” and the write ratio of “50%” is illustrated in FIG. 6B and FIG. 6C, the present invention is not limited to this, and the write pattern corresponding to the write ratio is used. The arrangement of the patterns can be arbitrarily changed according to the design and specifications.

(H05) In the above embodiment, the primary transfer rolls T1y to T1k that transfer the toner images on the surfaces of the photosensitive drums Py to Pk to the intermediate transfer belt B are exemplified as the transfer device. However, the transfer device is not limited to this configuration. The present invention can also be applied to a transfer device that directly transfers the toner image on the surface of the photosensitive drum to the sheet S.
(H06) In the above-described embodiment, it is desirable that the LED heads LHy to LHk and the primary transfer rolls T1y to T1k be used to neutralize the surface of the photosensitive drums Py to Pk, but the primary transfer rolls T1y to T1k. It is also possible to omit the configuration of eliminating the charge.
(H07) In the above-described embodiment, the configuration is shown in which the timing of the application stop time t _a -t _b is started when the write start time t _b elapses. However, the present invention is not limited to this. A configuration is also possible in which the timing of the application stop time t _a -t _b is started at the same time as the timing of the time tb is started.

(H08) In the above-described embodiment, as the start condition for the charge removal process, when the image density ρ _{a for} one page is equal to or higher than the image density threshold ρ _b, or the average image density ρ _N for the number of discriminating sheets is the average image density for more thresholds [rho _c, a case has been exemplified where the job is completed, but is not limited thereto. For example, it is possible to eliminate one or more of the exemplified conditions or add other conditions.

(H09) In the above-described embodiment, when performing static elimination, a transfer voltage V _T for neutralization is applied to the primary transfer rolls T1y to T1k, and the surface of the photosensitive drums Py to Pk is supplementarily neutralized. However, the present invention is not limited to this. For example, in addition to a power supply for applying a charging voltage to the charging rolls CRy to CRk, a power supply capable of applying a discharging voltage is provided, and a charging voltage is applied to the charging rolls CRy to CRk, A configuration in which the surface of the photosensitive drums Py to Pk is supplementarily neutralized using CRy to CRk is also possible.

(H010) In the above embodiment, when determining whether to start the static elimination process, the image density ρ _a and the average image density ρ _N are calculated based on the acquired image information before actually forming a visible image. However, the present invention is not limited to this. For example, a density detection member is provided in the vicinity of any one of the photosensitive drums Py to Pk, the intermediate transfer belt B, and the sheet S to detect the density of the formed visible image, and the photosensitive drums Py to Pk are detected. A configuration in which the start of the charge removal process is determined based on the image density formed on the surface is also possible.
(H011) In the above-described embodiment, it is desirable that the start condition of the neutralization process is that the average image density ρ _N for the determined number Na of sheets is equal to or greater than the threshold ρ _c of the average image density when the determined number Na is reached. However, the present invention is not limited to this. For example, when the average image density [rho _N of determined number Na sheet increases without discrimination of not less than the threshold value [rho _c mean image density, the cumulative number of printed sheets N becomes equal to or higher than the determination number Na, performing charge elimination Configuration is also possible.

(H012) In the above-described embodiment, the configuration in which the electrostatic latent image is written on the entire page with the writing pattern corresponding to the environmental temperature Te and the environmental humidity Hu is illustrated, but the configuration is not limited thereto. For example, the area for one page of the sheet S is divided by preset sections, the image density is calculated for each section, and a writing pattern is set for each section according to each calculated image density. A configuration is also possible in which static elimination is performed with the written pattern.
(H013) In the above embodiment, the values α ₁ , α ₂ , β _{1 to} β ₃ corresponding to the parameters of the respective conditions are exemplified in the setting tables TA1 and TA2 in FIGS. 3 and 4. It is not limited and can be changed arbitrarily according to the design, specifications, and the like.

B, S ... transfer material,
C27 ... light emission control means C21 ... power supply control means for transfer,
CRy ~ CRk ... Charger,
Gy to Gk ... developer,
LED ... light emitting element,
LHy to LHk ... latent image forming device,
Hu ... humidity,
Py to Pk: Image carrier,
T1y to T1k ... transfer device,
Te ... temperature,
U: Image forming apparatus,
V _T : Electric power for static elimination.

Claims (4)

A light emitting element that is disposed at a position downstream of the charger and upstream of the developing unit with respect to the rotation direction of the image carrier, and that irradiates light to the surface of the image carrier;
When forming a latent image on the surface of the image carrier, based on the image to be formed, to control the light emitting element, in the case of neutralizing the surface of the image carrier, part of the previous SL-emitting element Light emission control means for controlling the lighting ratio of the light emitting element so as to turn off the light,
Equipped with a,
The light emission control means controls the light emitting element so that the lighting ratio is lower when both of the temperature and the humidity in the vicinity of the image carrier are lower than when both are low. Latent image forming apparatus. An image carrier,
A charger for charging the surface of the image carrier;
The latent image forming apparatus according to claim 1 , wherein the latent image is formed on a surface of the image carrier.
A developing unit for developing the latent image formed on the surface of the image carrier into a visible image;
A transfer device disposed at a position downstream of the developing unit with respect to the rotation direction of the image carrier, and transferring the visible image on the surface of the image carrier to a transfer material;
An image forming apparatus comprising: Applying a transfer voltage for transferring the visible image on the surface of the image carrier to the transfer material during image formation, and removing the surface of the image carrier when removing the surface of the image carrier A power supply control means for transferring,
The image forming apparatus according to claim 2 , further comprising: When both the temperature and humidity in the vicinity of the image carrier are high compared to the electricity for charge removal supplied to the transfer device when both the temperature and humidity in the vicinity of the image carrier are low, The transfer power supply control means for supplying the transfer device with electricity for charge removal,
The image forming apparatus according to claim 3 , further comprising:

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