JP5193587B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using toner.

  In a color copier as an image forming apparatus, first, the surface of each of the four photosensitive drums is uniformly charged by a charging unit. Subsequently, an electrostatic latent image is formed on the surface of each of the four photosensitive drums by performing exposure scanning with the laser scanner unit. Subsequently, each electrostatic latent image formed on the surface of each of the four photosensitive drums is developed by a developing device. Then, the process of primary transfer of each color toner image developed on the surface of each of the four photosensitive drums onto the intermediate transfer belt is sequentially repeated to form a full color toner image obtained by superimposing the color toner images on the intermediate transfer belt. Form. The color copying machine forms a predetermined full-color image on the surface of the paper by secondarily transferring the full-color toner image on which the respective color toner images are superimposed onto the predetermined paper.

  Here, an abnormality may occur in the toner image primarily transferred onto the intermediate transfer belt. For example, there may be abnormalities such as missing characters including voids, dash marks (attachment of toner external additives to the drum), transfer scattering, white spots, and the like.

On the other hand, when the image pattern is a halftone, there has been proposed an image forming apparatus that suppresses the falling off by changing the transfer pressure (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 10-11607

  However, the image forming apparatus in Patent Document 1 suppresses the occurrence of abnormalities such as falling off by changing the transfer pressure according to the image pattern, but the adhesion of the toner becomes high in a high temperature and high humidity environment. This does not suppress the occurrence of missing characters or dash marks (attachment of toner external additives to the drum). Furthermore, it does not suppress the occurrence of transfer scattering and white spots due to an increase in the optimum transfer voltage due to an increase in the toner charge amount and an increase in paper resistance in a low humidity environment. That is, the image forming apparatus disclosed in Patent Document 1 does not suppress the occurrence of an abnormality in the transferred image corresponding to the environment such as temperature and humidity.

  In addition, the image forming apparatus disclosed in Patent Document 1 does not suppress the occurrence of an abnormality in the transferred image in response to toner deterioration or the like depending on the driving situation.

  The present invention relates to an image forming apparatus that suppresses occurrence of abnormality in a transferred image when a toner image is transferred.

  The present invention is formed on the image carrier by an image carrier having an electrostatic latent image formed on a surface thereof, a toner container that contains predetermined toner, and the toner that is contained in the toner container. A developer that develops a toner image on an electrostatic latent image, a counter member that is disposed to face the image carrier, and a transfer nip portion that is disposed between the developer and the counter member. The transfer pressure in the transfer nip can be increased by bringing the medium and the counter member closer to the image carrier, and the transfer pressure is reduced by separating the counter member from the image carrier. The toner is maintained at a high resistivity in a low electric field force band in which the volume resistivity of the toner is weaker than a predetermined electric field force. Condition and place A second state maintained at a low resistivity in a high electric field force band, which is an electric field force band stronger than the electric field force, and an intermediate electric field force between the low electric field force band including the predetermined electric field force and the high electric field force band The present invention relates to an image forming apparatus having a transition state that changes with a steep gradient from the high resistivity to the low resistivity as the electric field force increases in a band.

  Measuring means for measuring an environmental condition or a driving condition in the image forming apparatus, wherein the transfer pressure adjusting means is configured to detect the counter member based on the environmental condition or the driving condition measured by the measuring means. It is preferable to adjust the transfer pressure by moving.

  In addition, the measuring unit includes an environmental temperature measuring unit that measures an ambient environmental temperature in the image forming apparatus, and an environmental humidity measuring unit that measures an ambient environmental humidity in the image forming apparatus, and the transfer pressure The adjusting means is configured to place the image bearing member on the image carrier when the environmental temperature measured by the environmental temperature measuring means is higher than a predetermined temperature and the environmental humidity measured by the environmental humidity measuring means is higher than a predetermined humidity. The transfer pressure is weakened by separating from the body, and when the environmental temperature is lower than the predetermined temperature and the environmental humidity is lower than the predetermined humidity, the opposing member is brought closer to the image carrier. It is preferable to increase the transfer pressure applied to the transfer medium.

  In addition, the measuring unit includes a consumption measuring unit that measures the consumption amount of the toner, and a driving amount measuring unit that measures the driving amount of the developing device, and the transfer pressure adjusting unit includes the consumption measuring unit. The transfer member is moved by moving the counter member based on a toner deterioration state predicted from the toner consumption measured by the driving unit and the driving amount of the developing device measured by the driving amount measuring unit. It is preferable to adjust.

  A deterioration state prediction unit that predicts a deterioration state of the toner from a toner consumption amount measured by the consumption amount measurement unit and a driving amount of the developing device measured by the driving amount measurement unit; The transfer pressure adjusting unit increases the transfer pressure by bringing the opposing member closer to the image carrier when the deterioration state of the toner predicted by the deterioration state prediction unit is not deteriorated more than a predetermined deterioration state. It is preferable.

  A deterioration state prediction unit that predicts a deterioration state of the toner from a toner consumption amount measured by the consumption amount measurement unit and a driving amount of the developing device measured by the driving amount measurement unit; The transfer pressure adjusting unit reduces the transfer pressure by separating the counter member from the image carrier when the deterioration state of the toner predicted by the deterioration state prediction unit is lower than a predetermined deterioration state. It is preferable.

  The toner preferably has a lower volume resistivity as the pressure applied to the toner increases, and the volume resistivity increases as the pressure applied to the toner decreases.

  The toner preferably includes toner particles and conductive fine particles externally added to the surface of the toner particles.

  According to the present invention, it is possible to provide an image forming apparatus that suppresses occurrence of abnormality in a transferred image when a toner image is transferred.

  With reference to FIG. 1, the overall structure of a color copier 1 as an image forming apparatus in this embodiment will be described. FIG. 1 is a diagram for explaining the arrangement of each component in the color copier 1.

The color copying machine 1 includes a document feeding unit 70 that is arranged on the upper side of the color copying machine 1 and sends a predetermined document, an image reading unit 71 that reads an image formed on the document sent by the document feeding unit 70, and Is provided. The color copier 1 includes photosensitive drums 2a, 2b, 2c, and 2d as image carriers, charging units 10a, 10b, 10c, and 10d, laser scanner units 4a, 4b, 4c, and 4d, and a developing unit. 16a, 16b, 16c, and 16d, toner cartridges 5a, 5b, 5c, and 5d as toner storage units, toner supply devices 6a, 6b, 6c, and 6d, an intermediate transfer belt 7, and primary transfer as an opposing member. Rollers 37 a, 37 b, 37 c, 37 d, an intermediate transfer unit 200 including the secondary transfer roller 8, and a fixing device 9 are provided. Further, the color copier 1 includes a paper feed cassette 52 that is disposed so as to be able to be pulled out below the copier and that stores the paper T in a stacked state. The color copying machine 1 further includes a transport path 54 through which the paper T sent from the paper feed cassette 52 is transported.

  The photosensitive drums 2a, 2b, 2c, and 2d are cylindrical members. Each of the photosensitive drums 2a, 2b, 2c, and 2d is disposed so as to be rotatable around a rotation axis perpendicular to FIG. An electrostatic latent image is formed on the surface of each of the photosensitive drums 2a, 2b, 2c, and 2d.

  The charging units 10a, 10b, 10c, and 10d are disposed above the photosensitive drums 2a, 2b, 2c, and 2d, respectively. The charging units 10a, 10b, 10c, and 10d uniformly and positively (positively) charge the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d.

  The laser scanner units 4a, 4b, 4c, and 4d are disposed above the photosensitive drums 2a, 2b, 2c, and 2d and spaced apart from the photosensitive drums 2a, 2b, 2c, and 2d, respectively. Each of the laser scanner units 4a, 4b, 4c, and 4d includes a laser light source (not shown), a polygon mirror, a polygon mirror driving motor, and the like.

  Each of the laser scanner units 4a, 4b, 4c, and 4d scans and exposes the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d based on the image information related to the image read by the image reading unit 71. Scanning exposure is performed by each of the laser scanner units 4a, 4b, 4c, and 4d, so that charges charged on the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d are removed. Thereby, electrostatic latent images are formed on the respective surfaces of the photosensitive drums 2a, 2b, 2c, and 2d.

  Each of the developing devices 16a, 16b, 16c, and 16d is disposed on the side (left side in FIG. 1) of the photosensitive drums 2a, 2b, 2c, and 2d. Each of the developing devices 16a, 16b, 16c, and 16d develops toner images of the respective colors on the electrostatic latent images formed on the photosensitive drums 2a, 2b, 2c, and 2d. Each of the developing devices 16a, 16b, 16c, and 16d corresponds to four toner colors of yellow, cyan, magenta, and black. Each of the developing devices 16a, 16b, 16c, and 16d includes developing rollers 116a, 116b, 116c, and 116d that can be disposed to face the photosensitive drums 2a, 2b, 2c, and 2d, and a stirring roller for stirring the toner. The

  Each of the toner cartridges 5a, 5b, 5c, and 5d stores toner of each color supplied to each of the developing devices 16a, 16b, 16c, and 16d. Each of the toner cartridges 5a, 5b, 5c, and 5d accommodates yellow toner, cyan toner, magenta toner, and black toner.

  Each of the toner supply devices 6a, 6b, 6c, and 6d supplies the toners of the respective colors stored in the toner cartridges 5a, 5b, 5c, and 5d to the developing devices 16a, 16b, 16c, and 16d, respectively. Here, the toner used in this embodiment will be described in detail later.

  The toner images of the respective colors developed on the photosensitive drums 2a, 2b, 2c, and 2d are sequentially transferred to the intermediate transfer belt 7 as a transfer medium. The intermediate transfer belt 7 is arranged so as to be stretched between the driving roller 35 and the tension roller 36. Since the tension roller 36 is biased to the side away from the drive roller 35 by the spring 38, a predetermined tension is applied to the intermediate transfer belt 7.

Primary transfer rollers 37a, 37b, 37c, and 37d are arranged to face each other on the opposite side of the intermediate transfer belt 7 from the photosensitive drums 2a, 2b, 2c, and 2d.
Predetermined portions of the intermediate transfer belt 7 are sandwiched between the primary transfer rollers 37a, 37b, 37c, and 37d and the photosensitive drums 2a, 2b, 2c, and 2d, respectively. The predetermined portion thus sandwiched is pressed against the surface of each of the photosensitive drums 2a, 2b, 2c, and 2d. In this way, primary transfer nips N1a, N1b, N1c, and N1d as transfer nip portions are formed, and the respective color toner images developed on the photosensitive drums 2a, 2b, 2c, and 2d are sequentially transferred to the intermediate transfer belt 7. Is done. As a result, a full-color toner image is formed on the intermediate transfer belt 7.

  Here, a roller driving device (not shown in FIG. 1) is attached to each of the primary transfer rollers 37a, 37b, 37c, and 37d. Each of the roller driving devices moves the primary transfer rollers 37a, 37b, 37c, and 37d so as to approach the photosensitive drums 2a, 2b, 2c, and 2d, and separates them from the photosensitive drums 2a, 2b, 2c, and 2d. Can be moved.

  Each roller driving device adjusts the transfer pressure in each of the primary transfer nips N1a, N1b, N1c, and N1d by moving the primary transfer rollers 37a, 37b, 37c, and 37d. Each roller driving device moves the primary transfer rollers 37a, 37b, 37c, and 37d, thereby transferring the transfer area, toner filling rate, and primary transfer in the primary transfer nips N1a, N1b, N1c, and N1d. The thickness (distance between the toner and the primary transfer roller) in each of the nips N1a, N1b, N1c, and N1d, the gap distance in the vicinity of each of the primary transfer nips N1a, N1b, N1c, and N1d, and the like are adjusted.

  The roller driving device is driven by a control signal from a CPU (not shown). The CPU controls the roller driving device based on an environmental situation or a driving situation measured by various sensors (not shown). As the environmental situation, ambient temperature and humidity in the color copier 1 can be raised. Further, as the driving status, toner consumption and driving amounts of the developing devices 16a, 16b, 16c, and 16d can be raised. The CPU predicts the toner deterioration state based on the toner consumption amount and the driving amounts of the developing devices 16a, 16b, 16c, and 16d. The CPU controls the roller driving device based on the predicted toner deterioration state.

The primary transfer rollers 37a, 37b, 37c, and 37d are respectively transferred to the intermediate transfer belt 7 with the respective color toner images developed on the photosensitive drums 2a, 2b, 2c, and 2d by a voltage application unit (not shown). The primary transfer bias is applied. The voltage application unit adjusts the voltage applied to each of the primary transfer rollers 37a, 37b, 37c, and 37d. Specifically, the voltage application unit adjusts the applied voltage according to the optimum transfer voltage in each of the primary transfer nips N1a, N1b, N1c, and N1d.
Here, the transfer operation and the like in the primary transfer nips N1a, N1b, N1c, and N1d will be described in detail later together with the description of the toner.

  The secondary transfer roller 8 secondarily transfers the toner image primarily transferred to the intermediate transfer belt 7 onto the paper T. A secondary transfer bias for transferring the toner image on the intermediate transfer belt 7 to the paper T is applied to the secondary transfer roller 8 by a voltage application unit (not shown).

  The secondary transfer roller 8 is brought into contact with and separated from the intermediate transfer belt 7. Specifically, the secondary transfer roller 8 is configured to be movable between a contact position where the secondary transfer roller 8 is in contact with the intermediate transfer belt 7 and a spaced position where the secondary transfer roller 8 is separated from the intermediate transfer belt 7. Specifically, the secondary transfer roller 8 is moved to the contact position when the toner image primarily transferred onto the surface of the intermediate transfer belt 7 is secondarily transferred to the paper T, and is separated from the other position. Moved to. Here, the contact / separation operation of the secondary transfer roller 8 is performed by rotating the entire intermediate transfer unit 200.

  The secondary transfer roller 8 is included in the intermediate transfer unit 200. The intermediate transfer unit 200 accommodates the secondary transfer roller 8 and rotatably supports the secondary transfer roller 8, a rotation drive gear 210 disposed on the side surface of the housing 201, and the secondary transfer roller 8, a roller side gear 220 disposed on the side surface of the housing 201 and an idle gear 230 disposed in contact with the rotation drive gear 210 and the roller side gear 220. The intermediate transfer unit 200 includes a position at which the secondary transfer roller 8 can contact the intermediate transfer belt 7 around a rotation shaft (not illustrated) and a position at which the intermediate transfer belt 7 does not contact the intermediate transfer belt 7 by a contact / separation unit (not illustrated). Is rotated.

A counter roller 108 is disposed on the side of the intermediate transfer belt 7 that faces the secondary transfer roller 8. A predetermined portion of the intermediate transfer belt 7 is sandwiched between the secondary transfer roller 8 and the opposing roller 108. Then, the paper T is pressed against the surface of the intermediate transfer belt 7 (the side on which the image is primarily transferred). In this way, the secondary transfer nip N2 is formed, and the toner image primarily transferred to the intermediate transfer belt 7 is secondarily transferred to the paper T.

  The fixing device 9 melts and fixes each color toner constituting the toner image secondarily transferred onto the paper T. The fixing device 9 includes a heating roller 9a heated by a heater, and a pressure roller 9b pressed against the heating roller 9a. The heating roller 9a and the pressure roller 9b convey the paper T onto which the toner image is secondarily transferred so as to sandwich the paper T. By being conveyed so as to be sandwiched between the heating roller 9a and the pressure roller 9b, the toner transferred onto the paper T is melted and fixed.

  A belt cleaning device 40 for cleaning the intermediate transfer belt 7 is disposed between the secondary transfer roller 8 and the tension roller 36. The belt cleaning device 40 includes a cleaning brush 41 that is in sliding contact with the surface of the intermediate transfer belt 7, a cleaning roller 42 that is disposed so as to be in contact with the cleaning brush 41, and a tip that is in contact with the surface of the cleaning roller 42. The blade 43 is disposed, and the recovery spiral 44 is disposed below the blade 43.

  On the lower side of the color copying machine 1, a paper feed cassette 52 that accommodates the paper T is disposed so as to be pulled out in the horizontal direction. In the paper feed cassette 52, paper T is stored in a stacked state. In the paper feed cassette 52, a placement plate 60 on which the paper T is placed is disposed. The paper T placed on the placement plate is sent out to the transport path 54 by the cassette paper feed unit 51 disposed at the paper feed side end of the paper feed cassette 52 (right end in FIG. 1). The cassette paper feeding unit 51 includes a double feed prevention mechanism including a forward feed roller 61 for taking out the paper T on the placement plate 60 and a roller pair 63 for feeding the paper T one by one to the transport path 54.

  A conveyance path 54 for conveying the paper T is formed between the cassette paper feeding unit 51 and the discharge unit 50. The conveyance path 54 includes a first conveyance path 55 from the cassette paper feeding unit 51 to the secondary transfer roller 8, a second conveyance path 56 from the secondary transfer roller 8 to the fixing device 9, and a discharge unit 50 from the fixing device 9. And the third conveyance path 57. Further, a branching claw 58 is provided at the outlet of the fixing device 9, and the paper T is placed in the first conveyance path 55 between the branching claw 58 and a curved path 55 a described later in the first conveyance path 55. A return conveyance path 59 for returning is formed.

  The first conveyance path 55 conveys the paper T fed from the paper feed cassette 52 upward, while turning the conveyance direction to the left in FIG. 1 and the curved path 55a to the secondary transfer roller 8. Straight path 55b. In the first conveyance path 55, a guide plate and a roller pair that convey the paper T while guiding it are arranged. Further, a sensor for detecting the paper T and a registration roller pair 80 for adjusting the skew (oblique paper feeding) of the paper T and the timing of the toner image are arranged in the first transport path 55. The sensor is disposed immediately before (on the upstream side) the registration roller pair 80 in the transport direction of the paper T. The registration roller pair 80 conveys the paper T by performing the above-described correction and timing adjustment based on the detection signal information from the sensor.

  The second transport path 56 is a linear transport path that is inclined downward toward the fixing device 9 side. A transport belt 156 that transports the paper T in a state where the paper T is placed is disposed in the second transport path 56. A sensor for detecting the paper T is disposed at a predetermined position in the second transport path 56.

  The third transport path 57 is formed so as to extend obliquely upward to the left in FIG. 1 from the exit of the fixing device 9. The third conveyance path 57 is configured to have a vertical conveyance path 57 a that is located on the downstream side of the branch claw 58 in the conveyance direction and formed upward. The paper T transported by the third transport path 57 passes through the upper surface side of the branch claw 58, is transported substantially vertically upward, and is ejected from the discharge unit 50 to the outside of the color copier body. The third transport path 57 includes a guide plate and a roller pair that transport the paper T while guiding the paper T, like the other transport paths.

  The return conveyance path 59 branches from the branch claw 58 to the lower side opposite to the third conveyance path 57 and passes below the fixing device 9, the second conveyance path 56, the secondary transfer roller 8, and the registration roller pair 80. Furthermore, it forms so that it may go upwards. The return conveyance path 59 is formed so as to merge with the curved path 55 a in the first conveyance path 55. The return conveyance path 59 is a conveyance path for returning the paper T that has passed through the fixing device 9 to the upstream side of the registration roller pair 80 disposed on the upstream side of the secondary transfer roller 8. The return conveyance path 59 is a conveyance path that is used when performing so-called double-sided printing (printing) in which toner images (including characters and the like) are printed (printed) on both sides of the paper T. For example, the paper T is returned to the first transport path 55 via the return transport path 59 in a state where the front and back surfaces are reversed by the reverse roller 600. Like the other transport paths, the return transport path 59 has a guide plate and a pair of rollers that transport the paper T while guiding it, and a sheet detection sensor is disposed at a predetermined position.

  A manual paper feed unit 64 is provided on the right side surface of the color copier 1 in FIG. The manual paper feed unit 64 includes a manual feed tray 65 that forms a side wall in the closed state, and a paper feed roller 66. The manual feed tray 65 is attached to the vicinity of the curved path 55a of the first transport path 55 so that the lower end of the manual feed tray 65 can rotate (open and close). The manual paper feed unit 64 feeds the paper T placed on the open manual feed tray 65 to the curved path 55 a of the first transport path 55.

Next, the components for forming the primary transfer nip N1a and the toner in this embodiment will be described with reference to FIGS. FIG. 2 is an enlarged view of the vicinity of the primary transfer nip N1a in FIG. FIG. 3 is an enlarged view of a region X in FIG. FIG. 4 is a diagram when the primary transfer roller 37a moves in the arrow Y1 direction in FIG. FIG. 5 is a graph illustrating the electric field dependence of the volume resistivity of the toner.
Here, since the primary transfer roller 37a and the other primary transfer rollers 37b, 37c, and 37d have the same structure, only the primary transfer roller 37a will be described below.

As shown in FIG. 2, the primary transfer roller 37a disposed opposite to the photosensitive drum 2a with the intermediate transfer belt 7 interposed therebetween is moved in the directions indicated by the arrows Y1 and Y2. A roller driving device 39a as a transfer pressure adjusting means is attached.

  The roller driving device 39a supports a shaft 139a that rotatably supports the rotary shaft member 137a of the primary transfer roller 37a, and moves the shaft support 139a toward the photosensitive drum 2a (in the direction of the arrow Y1) and also the photosensitive drum 2a. And an actuator portion 239a that moves in a direction away from the direction (arrow Y2 direction). The actuator unit 239a moves the shaft support 139a in the direction of the arrow Y1 or the direction of the arrow Y2, so that the primary transfer roller 37a rotatably supported by the shaft support 139a is on the photosensitive drum 2a side (the direction of the arrow Y1) or It is moved away from the photosensitive drum 2a (in the direction of arrow Y2). The actuator part 239a moves the shaft support part 139a by a control signal from the CPU. That is, the roller driving device 39a moves the primary transfer roller 37a in the direction of the arrow Y1 or the direction of the arrow Y2 in accordance with a control signal from the CPU.

  The roller driving device 39a can be moved from the state shown in FIG. 3 to the state shown in FIG. 4 by moving the primary transfer roller 37a closer to the photosensitive drum 2a. Conversely, the roller driving device 39a can move the primary transfer roller 37a away from the photosensitive drum 2a from the state shown in FIG. 4 to the state shown in FIG.

  The roller driving device 39a can adjust the transfer pressure in the primary transfer nip N1a by moving the primary transfer roller 37a. Further, the roller drive device 39a moves the primary transfer roller 37a, thereby transferring the transfer areas S1 and S2 of the primary transfer nip N1a and the thicknesses D1 and D2 of the primary transfer nip N1a (the surface of the primary transfer roller 37a). To the toner images T1 and T2), the filling rate of the toner images T1 and T2, and the like can be adjusted.

  The roller driving device 39a is driven based on a control signal output by a CPU (not shown). Specifically, the CPU controls the roller driving device 39a based on an environmental situation or a driving situation measured by various sensors (not shown) as measuring means.

  The color copying machine 1 includes an environmental temperature sensor that measures an ambient environmental temperature in the color copying machine 1 as a measuring unit that measures an environmental condition, and an environmental humidity sensor that measures the ambient environmental humidity. The CPU controls the roller driving device 39a based on the environmental temperature measured by the environmental temperature sensor and the environmental humidity measured by the environmental humidity sensor. The operation of the color copier 1 in this case will be described in detail later.

  Further, the color copier 1 includes a consumption measuring sensor that measures the consumption of toner as a measuring unit that measures the driving situation, and a driving amount measuring sensor that measures the driving amount of the developing device 16a. The drive amount measurement sensor measures the drive amount (for example, the rotation speed or the drive time) of the developing roller 116a.

  Based on the toner consumption measured by the consumption measurement sensor and the driving amount of the developing roller 116a measured by the driving amount measurement sensor, the CPU as the deterioration state predicting means predicts the toner deterioration state. Then, the CPU controls the roller driving device 39a based on the predicted toner deterioration state. Specifically, since the toner amount that has deteriorated tends to decrease in charge amount, the CPU performs the transfer state corresponding to the decrease in the charge amount in the toner based on the predicted deterioration state of the toner. The roller driving device 39a is controlled. The operation of the color copier 1 in this case will be described in detail later.

Next, the toner in this embodiment will be described. The toner includes toner particles and conductive fine particles externally added to the surface of the toner particles.
The toner particles can be obtained by mixing the binder resin and various compounding agents, then melt-kneading using a kneader such as an extruder, cooling, pulverizing and classifying. The volume-based center particle diameter of the toner particles is 4 μm to 12 μm, preferably 6 μm to 10 μm.

  Examples of the binder resin include styrene resin, acrylic resin, styrene-acrylic copolymer, polyethylene resin, polypropylene resin, vinyl chloride resin, polyester resin, polyamide resin, polyurethane resin, and polyvinyl alcohol. Examples thereof include thermoplastic resins such as vinyl resins, vinyl ether resins, N-vinyl resins, and styrene-butadiene resins.

Examples of various compounding materials mixed with the binder resin include waxes, colorants, and offset preventing agents.
Examples of waxes include plant waxes such as carnauba wax, sugar wax, and wood wax; animal waxes such as beeswax, insect wax, whale wax, and wool wax; Fischer-Tropsch (hereinafter “FT”) having an ester in the side chain. And synthetic hydrocarbon waxes such as waxes, polyethylene waxes, and polypropylene waxes. The addition amount of the wax is preferably in the range of 0.1 to 20 parts by mass with respect to 100 parts by mass of the binder resin. If the addition amount of the wax is less than 0.1 parts by mass, it is difficult to obtain a sufficient effect of the wax, and if the addition amount is more than 20 parts by mass, the blocking resistance may be lowered.

  Examples of the colorant include carbon black such as acetylene black, lan black, and aniline black as a black pigment; yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navels Yellow, Naphthol Yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake; orange pigment, reddish yellow lead, molybdenum orange, permanent orange GTR, Pyrazolone orange, Vulcan orange, Indanthrene brilliant orange RK, Benzidine orange G, Indanthrene brilliant orange GK; As red pigment, Bengala, Cadmium , Red lead, mercury cadmium sulfide, permanent red 4R, risor red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B; purple pigment As a blue pigment, bitumen, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, fast sky blue, induslen Blue BC: As a green pigment, chrome green, chromium oxide, pigment green B, malachite green lake, fanal yellow green G; white face As, zinc white, titanium oxide, antimony white, zinc sulfide; as white pigments include barite powder, barium carbonate, clay, silica, white carbon, talc and alumina white. The addition amount of the colorant is 1 to 20 parts by mass, preferably 2 to 8 parts by mass with respect to 100 parts by mass of the binder resin.

  The offset preventive agent is blended in order to impart an offset preventing effect to the toner. Examples of the offset preventive agent include aliphatic hydrocarbons, aliphatic metal salts, higher fatty acids, fatty acid esters or partially saponified products thereof, silicone oil, and various waxes. The addition amount of the offset inhibitor is 0.1 to 10 parts by mass, preferably 0.5 to 8 parts by mass with respect to 100 parts by mass of the binder resin.

  Conductive fine particles are externally added to the surface of the toner particles composed of the above-described materials. The conductive fine particles are made of titania, for example. The outer diameter of the conductive fine particles is 1 nm to 1 μm, preferably 50 nm to 400 nm. The conductive fine particles are externally added by 0.1 to 5% by mass, preferably 0.5 to 3% by mass with respect to the toner particles.

  Further, as shown in FIG. 5, the toner has a first state A in which the volume resistivity of the toner is maintained at a high resistivity in a low electric field force band L, which is an electric field force band weaker than a predetermined electric field force, and a predetermined electric field. A second state B maintained at a low resistivity in a high electric field force band H which is an electric field force band stronger than the force, and an intermediate electric field force between the low electric field force band L including the predetermined electric field force and the high electric field force band H A transition state C that changes from a high resistivity to a low resistivity with a steep gradient as the electric field force increases in the band M.

  As described above, the toner has three states of the first state A, the second state B, and the transition state C. Here, as shown in FIG. 5, since the transition state C is a state in the narrow intermediate electric field force band M, the toner is often in the first state A or the second state B. In other words, the toner changes from the first state to the second state or changes from the second state to the first state by changing the electric field force, and is in either the first state or the second state. It can be said that.

  Further, the toner has a feature that the volume resistivity decreases as the pressure applied to the toner increases, and the volume resistivity increases as the pressure applied to the toner decreases. Specifically, as shown in FIG. 5, with reference to a bent line I to which a predetermined pressure is applied, a bent line indicating a volume resistivity when a pressure smaller than the predetermined pressure is applied to the toner. I becomes a bending line II, and when a pressure larger than a predetermined pressure is applied, the bending line I becomes a bending line III.

  The toner maintains a high volume resistivity in the low electric field force band L. That is, the toner in the low electric field force band L maintains high chargeability. In addition, the toner maintains a low volume resistivity in the high electric field force band H. That is, the toner in the high electric field force band H has a low chargeability.

  As described above, the toner has a characteristic that the chargeability is greatly changed by changing the electric field force of the region including the toner. That is, the optimum transfer voltage in the toner can be greatly changed by changing the electric field force. Further, the transfer force (adhesion force) of the toner can be changed by changing the electric field force.

  Here, in addition to the voltage application means (not shown), the electric field force is the transfer areas S1 and S2 of the primary transfer nip N1a and the thicknesses D1 and D2 of the primary transfer nip N1a (from the surface of the primary transfer roller 37a to the toner image). (Distance to T1, T2), transfer pressure, filling rate of toner images T1, T2, etc. can be adjusted.

  That is, in the color copier 1 using toner in the present embodiment, the roller driving device 39a (see FIG. 2) can adjust not only the transfer pressure but also the electric field force. That is, in the color copier 1 using toner in the present embodiment, the roller drive device 39a can adjust the physical transfer state of the toner by adjusting the transfer pressure and adjust the electrical transfer state. it can.

Next, the operation of the color copier 1 will be described. First, the operation according to the environmental state will be described.
First, the environmental temperature measurement sensor measures the ambient environmental temperature in the color copier 1. The environmental humidity measuring sensor measures the ambient environmental humidity in the color copying machine 1.
Next, the CPU determines whether the measured environmental temperature is a low temperature lower than a predetermined temperature or a high temperature higher than the predetermined temperature. Further, the CPU determines whether the measured environmental humidity is a high humidity lower than a predetermined humidity or a high humidity higher than the predetermined humidity.

  Subsequently, when the CPU determines that the environmental temperature is high and the environmental humidity is high, the CPU drives the roller driving device so that the primary transfer roller 37a is separated from the photosensitive drum 2a. 39a is driven. Since the transfer pressure in the primary transfer nip N1a is adjusted to be weak, it is possible to suppress the toner having an increased adhesive force from being attached to the photosensitive drum 2a in a high-temperature and high-humidity environment during transfer. Further, since the electric field force is increased by moving the primary transfer roller 37a away from the photosensitive drum 2a, the volume resistivity of the toner is increased (see FIG. 5). That is, since the toner is maintained in a state where the charge amount is large, high transferability is maintained. Thereby, generation | occurrence | production of a hollow and a dash mark can be suppressed.

  When the CPU determines that the environmental temperature is low and the environmental humidity is low, the CPU sets the roller driving device 39a so that the primary transfer roller 37a approaches the photosensitive drum 2a. Drive. Here, when the environmental humidity is low, the charge amount in the toner increases. Then, the optimum transfer voltage for the toner having a large charge amount is increased. As a result, the gap electric field force in the vicinity of the primary transfer nip N1a is increased, and transfer scattering and white spots are likely to occur.

  On the other hand, by moving the primary transfer roller 37a closer to the photosensitive drum 2a by the roller driving device 39a, the transfer area in the primary transfer nip N1a is reduced as shown in S2 in FIG. 3 to S2 in FIG. Can be wide. Thereby, the transfer voltage (electric field force) in the primary transfer nip N1a can be lowered.

  Further, the transfer pressure can be increased by moving the primary transfer roller 37a closer to the photosensitive drum 2a. That is, the toner filling rate in the primary transfer nip N1a can be increased, and the thicknesses D1 and D2 of the primary transfer nip N1a are reduced (the distance from the surface of the primary transfer roller 37a to the toner image is shortened). can do. Thereby, similarly, the transfer voltage (electric field force) in the primary transfer nip N1a can be lowered.

Further, by increasing the transfer pressure, the bend line indicating the volume resistivity of the toner becomes the bend line III as shown in FIG. 5, so that the volume resistivity of the toner is lowered and the charge amount of the toner is reduced. Is done.
As described above, since the gap electric field force can be reduced, it is possible to suppress the occurrence of the above-described transfer scattering and white spots.

Next, operations according to environmental conditions will be described.
First, the consumption measuring sensor measures the toner consumption. The driving amount measuring sensor measures the driving amount of the developing roller 116a in the developing device 16a.
Next, the CPU predicts a toner deterioration state based on the measured toner consumption and the measured driving amount of the developing roller 116a.

  Subsequently, when the predicted deterioration state of the toner is not deteriorated more than the predetermined deterioration state, the CPU drives the roller driving device 39a to move the primary transfer roller 37a closer to the photosensitive drum 2a. . The roller driving device 39a moves the primary transfer roller 37a so as to approach the photosensitive drum 2a, and adjusts the transfer pressure in the primary transfer nip N1a to be strong.

  Since the toner that has not deteriorated has a large charge amount, the optimum transfer voltage becomes high. For this reason, since the gap electric field force in the vicinity of the primary transfer nip N1a becomes strong, transfer scattering and white spots are likely to occur.

  In contrast, by moving the primary transfer roller 37a closer to the photosensitive drum 2a, the transfer area in the primary transfer nip N1a can be increased as shown in S2 in FIG. 3 to S2 in FIG. . Thereby, the transfer voltage (electric field force) can be lowered.

  Further, the transfer pressure can be increased by moving the primary transfer roller 37a closer to the photosensitive drum 2a. That is, the toner filling rate can be increased, and the thickness of the primary transfer nip N1a can be reduced (the distance from the surface of the primary transfer roller 37a to the toner image can be reduced). Thereby, similarly, the transfer voltage (electric field force) in the primary transfer nip N1a can be lowered.

Further, by increasing the transfer pressure, as shown in FIG. 5, the bending line I indicating the volume resistivity of the toner becomes the bending line III. Therefore, the bending line indicating the volume resistivity of the toner becomes the bending line III. As a result, the volume resistivity of the toner is lowered, and the charge amount of the toner is reduced.
As described above, since the gap electric field force can be reduced, it is possible to suppress the occurrence of the above-described transfer scattering and white spots.

  When the predicted toner deterioration state is deteriorated from a predetermined deterioration state, the CPU drives the roller driving device 39a so that the primary transfer roller 37a is separated from the photosensitive drum 2a. By moving the primary transfer roller 37a away from the photosensitive drum 2a, the transfer pressure in the primary transfer nip N1a is adjusted to be weak.

  Since the transfer pressure in the primary transfer nip N1a is adjusted to be weak, it is possible to suppress the toner having a strong adhesive force due to the progress of deterioration from adhering to the photosensitive drum 2a during the transfer. Further, since the electric field force is increased by moving the primary transfer roller 37a away from the photosensitive drum 2a, the volume resistivity of the toner is increased. That is, since the toner is maintained in a state where the charge amount is large, high transferability is maintained. Thereby, generation | occurrence | production of a hollow and a dash mark can be suppressed.

  According to this embodiment, the toner as described above is used, and the primary transfer roller 37a is moved by the roller driving device 39a to transfer pressure at the primary transfer nip N1a and transfer areas S1 and S2 of the primary transfer nip N1a. By adjusting the thicknesses D1 and D2 of the primary transfer nip N1a (the distance from the surface of the primary transfer roller 37a to the toner images T1 and T2), the filling rate of the toner images T1 and T2, etc., the characters in the transferred image It is possible to suppress the occurrence of abnormalities such as voids, dash marks, transfer scattering and white spots.

  According to the present embodiment, the primary transfer roller 37a can be moved by the roller driving device 39a in accordance with environmental conditions and driving conditions, and the transfer pressure and the like at the primary transfer nip N1a can be adjusted. As a result, the color copier 1 adjusts the transfer pressure and the like in the primary transfer nip N1a in response to the environmental conditions and driving conditions, so that characters in the transfer image are omitted, dash marks, transfer scattering and white. Occurrence of an abnormality such as a point can be more suitably suppressed.

  That is, according to the present embodiment, it is possible to provide the color copier 1 that suppresses the occurrence of abnormality in the transferred image when the toner image is transferred.

  As mentioned above, although preferred embodiment was described, this invention can be implemented with a various form, without being limited to embodiment mentioned above. For example, in the present embodiment, the color copying machine 1 is described as the image forming apparatus, but the present invention is not limited to this, and may be a monochrome copying machine, a printer, a facsimile machine, or a multifunction machine of these.

  In this embodiment, the intermediate transfer belt 7 is described as a transfer medium. However, the present invention is not limited to this, and a sheet T may be used. That is, the image forming apparatus may be of a type that employs a method of directly transferring from the photosensitive drum 2a to the paper T.

2 is a diagram for explaining the arrangement of each component in the color copier 1. FIG. FIG. 2 is an enlarged view of the vicinity of a primary transfer nip N1a in FIG. FIG. 3 is an enlarged view of a region X in FIG. 2. FIG. 4 is a diagram when the primary transfer roller 37a is moved in the arrow Y1 direction in FIG. 6 is a graph for explaining electric field dependence of volume resistivity in toner.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Color copier (image forming apparatus), 2a, 2b, 2c, 2d ... Photosensitive drum (image carrier), 5a, 5b, 5c, 5d ... Toner cartridge (toner container), 7 ... Intermediate transfer belt (transfer medium), 8 ... secondary transfer roller, 16a, 16b, 16c, 16d ... developer, 37a, 37b, 37c, 37d ... primary transfer roller ( opposing member), 39a ... roller Driving device (transfer pressure adjusting means) A ... first state B ... second state C ... transition state N1a, N1b, N1c, N1d ... primary transfer nip (transfer nip)

Claims (6)

An image carrier having an electrostatic latent image formed on the surface;
A toner container for storing predetermined toner;
A developing unit for developing a toner image on an electrostatic latent image formed on the image carrier by the toner contained in the toner containing unit;
A facing member disposed to face the image carrier;
A transfer medium disposed between the developing unit and the facing member to form a transfer nip portion;
It is possible to increase the transfer pressure in the transfer nip portion by bringing the opposing member closer to the image carrier, and to reduce the transfer pressure by separating the opposing member from the image carrier. A transfer pressure adjusting means that is possible;
Measuring means for measuring environmental conditions and driving conditions in the image forming apparatus,
The toner is
In a first state in which the volume resistivity of the toner is maintained at a high resistivity in a low electric field force band which is an electric field force band weaker than a predetermined electric field force, and in a high electric field force band which is an electric field force band stronger than the predetermined electric field force As the electric field force becomes stronger in the second state maintained at a low resistivity and the intermediate electric field force band between the low electric field force band and the high electric field force band including the predetermined electric field force, A transition state with a steep slope at a low resistivity,
The transfer pressure adjusting means includes
Based on the environmental situation and the driving situation measured by the measuring means, the counter member is moved to adjust the transfer pressure,
The measuring means includes
Consumption amount measuring means for measuring the toner consumption amount, and driving amount measuring means for measuring the driving amount of the developing device,
The transfer pressure adjusting means includes
The opposing member is moved based on a toner deterioration state predicted by the consumption amount of the toner measured by the consumption amount measurement unit and the driving amount of the developing device measured by the driving amount measurement unit. An image forming apparatus for adjusting the transfer pressure.
Image forming apparatus. The measuring means includes
Environmental temperature measuring means for measuring ambient environmental temperature in the image forming apparatus;
Environmental humidity measuring means for measuring the ambient environmental humidity in the image forming apparatus,
The transfer pressure adjusting means includes
When the environmental temperature measured by the environmental temperature measuring unit is higher than a predetermined temperature and the environmental humidity measured by the environmental humidity measuring unit is higher than the predetermined humidity, the facing member is separated from the image carrier. To reduce the transfer pressure,
The transfer pressure applied to the transfer medium is increased by bringing the facing member closer to the image carrier when the environmental temperature is lower than the predetermined temperature and the environmental humidity is lower than the predetermined humidity. The image forming apparatus according to 1. Deterioration state predicting means for predicting the deterioration state of the toner from the toner consumption measured by the consumption measuring means and the driving amount of the developing device measured by the driving amount measuring means,
The transfer pressure adjusting means includes
2. The image according to claim 1, wherein when the deterioration state of the toner predicted by the deterioration state prediction unit is not deteriorated more than a predetermined deterioration state, the transfer pressure is increased by bringing the facing member closer to the image carrier. Forming equipment. Deterioration state predicting means for predicting the deterioration state of the toner from the toner consumption measured by the consumption measuring means and the driving amount of the developing device measured by the driving amount measuring means,
The transfer pressure adjusting means includes
4. The transfer pressure according to claim 1 or 3, wherein when the deterioration state of the toner predicted by the deterioration state prediction means is deteriorated from a predetermined deterioration state, the facing member is separated from the image carrier to weaken the transfer pressure. The image forming apparatus described. The toner is
The greater the pressure applied to the toner, the lower the volume resistivity,
The image forming apparatus according to claim 1, wherein the volume resistivity increases as the pressure applied to the toner decreases.   The image forming apparatus according to claim 1, wherein the toner includes toner particles and conductive fine particles externally added to a surface of the toner particles.

Images