JP6021411B2 - Developing device, cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device provided in an image forming apparatus using an electrophotographic system, a cartridge including the developing device, and an image forming apparatus including the developing device.

  2. Description of the Related Art Conventionally, as a developing device that visualizes an electrostatic latent image using a one-component toner, a configuration including a developing roller that conveys toner while carrying it and a supply roller that supplies toner to the developing roller is known. In this developing device, the toner is supplied to the developing roller while being frictionally charged by mechanical rubbing between the developing roller and the supply roller. The toner supplied to the surface of the developing roller is regulated so as to have a certain layer thickness by the regulating blade, and is then transported to an area close to the photosensitive drum, where an electrostatic latent image on the surface of the photosensitive drum is obtained. Visualize as a toner image.

  Toner remaining without being used for development in the development region on the surface of the developing roller is scraped off by mechanical rubbing at the contact portion with the supply roller. The toner is newly supplied from the supply roller to the surface of the developing roller. On the other hand, the scraped toner is mixed with toner inside and around the supply roller.

  In a conventionally proposed developing device, the surfaces of the developing roller and the supply roller are set so as to have a relative peripheral speed ratio in order to achieve both the toner supply amount and the undeveloped toner scraping performance. The As an invention relating to such a technique, the invention described in Patent Document 1 is disclosed.

  In the developing device described in Patent Document 1, for example, the surfaces of the developing roller and the supply roller move in the same direction at the contact portion between the developing roller and the supply roller, and the amount of biting Xmm of the supply roller into the development roller is 0 mm <Xmm <1. It is set to 8 mm. In the developing device described in Patent Document 1, the ratio between the peripheral speed VDR of the developing roller and the peripheral speed VSP of the supply roller is | VSP / VDR | ≦ 0.5 or 1.5 ≦ | VSP / VDR | ≦ 4 is set. According to such a configuration, since the peripheral speed ratio of the surface is set in the above range, the deterioration of the toner is reduced by suppressing the remaining undeveloped toner on the surface of the developing roller.

JP 2006-208619 A

  However, in the developing device described in Patent Document 1 in which the surfaces of the developing roller and the supply roller are arranged so as to move in the same direction at the contact portion, the following occurs. In other words, development (hereinafter referred to as “development ghost”) in which the HT density of the background color (meaning “halftone density” and “halftone density”, hereinafter the same) differs from the HT density immediately after solid printing occurs. There was a case. The development ghost is likely to occur when the relative peripheral speed ratio between the development roller and the supply roller is small. In order to reduce such a development ghost to a satisfactory level, in the developing device described in Patent Document 1, it is necessary to set the relative peripheral speed ratio between the developing roller and the supply roller as large as possible.

  However, in such a correspondence, although the development ghost is satisfactory, in an image forming apparatus with high productivity and high image forming speed, the supply roller rotates very fast, and the supply roller Problems such as melting of the bearing due to heat generation occurred. Further, when the mechanical rubbing force between the supply roller and the developing roller increases, the deterioration of the toner is promoted. When the toner deterioration, that is, the liberation and burying of the external additive on the surface of the toner is promoted, the degree of aggregation is increased and the charging performance of the toner is lowered, and the toner film in which the toner is fused to the surface of the developing roller. Problems such as ming occur, which hinders the longevity of the developing device.

  In view of the above circumstances, the present invention provides a developing device that reduces the level of development ghost that occurs when the relative peripheral speed ratio between a supply member and a developer carrier is set small in order to reduce toner deterioration. For the purpose.

In order to achieve the above object, a developing device according to the present invention includes a developer container that contains a developer, a developer carrier that rotates while carrying the developer inside the developer container, and the developer carrier. A supply member that rotates while supplying the developer to the body, and the supply member is set so that the surface rotates in the same direction at a contact portion with the developer carrier, and is conveyed from the developer container. A developing chamber that develops with the developing agent, and an intrusion member that extends from an inner wall of the developing chamber and enters the contact portion of the supply member and the developer carrier, and the supply member in the intrusion member The work function of the material on the side of the developer is set smaller than the work function of the material of the developer carrier .

  According to the present invention, the level of development ghost generated when the relative peripheral speed ratio between the supply member and the developer carrying member is set to be small in order to reduce toner deterioration.

1 is a cross-sectional view illustrating a configuration of an image forming apparatus including a developing device according to Embodiment 1 of the present invention. It is sectional drawing etc. which show the structure of a developing device. It is an image for developing ghost evaluation. (A) is a graph which shows the experimental result of Comparative Example 1-1, (b) is a graph which shows the experimental result of Example 1. It is sectional drawing which shows the arrangement | positioning relationship of a developing roller, a supply roller, and an intrusion sheet. It is sectional drawing which shows the structure of the developing device which concerns on the modification of Examples 1-3.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, since the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions, there is no specific description. As long as the scope of the invention is not limited to these, it is not intended.

  FIG. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus 100 including a developing device 4 according to Embodiment 1 of the present invention. The image forming apparatus 100 is an image forming apparatus using an electrophotographic image forming process. As shown in FIG. 1, the image forming apparatus 100 has an image forming apparatus main body (hereinafter, simply referred to as “apparatus main body”) 100A. Inside the apparatus main body 100A, an image forming unit 51 for forming an image is provided. Provided. The image forming unit 51 includes a photosensitive drum 1 that is an “image carrier”, a transfer roller 5 a that is a “transfer device”, and the like. At least the photosensitive drum 1 may be included in the process cartridge and may be detachably incorporated in the apparatus main body 100A as a process cartridge.

  As shown in FIG. 1, the image forming apparatus 100 includes a drum-shaped photosensitive drum 1. Around the photosensitive drum 1, a charging roller 2, an exposure device 3, a developing device 4, an intermediate transfer belt 5, and a cleaning device 6 are arranged in this order. The charging roller 2 is a roller that uniformly charges the surface of the photosensitive drum 1. The exposure device 3 is a device that irradiates the photosensitive drum 1 with a laser beam or the like modulated based on image information. The developing device 4 is a device that develops the electrostatic latent image formed on the photosensitive drum 1 to form a toner image. The intermediate transfer belt 5 as an intermediate transfer body is a belt for transferring a toner image formed on the photosensitive drum 1. The cleaning device 6 is a device that removes toner remaining on the photosensitive drum 1 after transfer.

  In addition, the image forming apparatus 100 includes a registration roller pair 7, a secondary transfer roller 8, and a fixing device (not shown). The registration roller pair 7 is a roller pair that feeds and conveys a transfer sheet P as a “transfer medium” in synchronization with the rotation of the photosensitive drum 1 from a feed tray or the like (not shown). The secondary transfer roller 8 is a roller that transfers the toner image to the transfer sheet P at the end of the intermediate transfer belt 5. A fixing device (not shown) is a device that fixes the toner image on the transfer sheet P.

   In the image forming apparatus 100 configured as described above, the surface of the photosensitive drum 1 rotating in the direction of arrow a is uniformly charged to a predetermined positive or negative charging potential by the charging roller 2 and then modulated based on image information. The irradiated laser beam is scanned in the axial direction of the photosensitive member. Thereby, an electrostatic latent image is formed on the photosensitive drum 1. The electrostatic latent image formed on the photosensitive drum 1 is developed by attaching toner charged by the developing device 4 in the developing region to become a toner image.

  Thereafter, the toner image on the photosensitive drum 1 is temporarily transferred onto the intermediate transfer belt 5 by supplying the intermediate transfer belt 5 with a charge having a polarity opposite to that of the toner image. On the other hand, the transfer sheet P is fed / conveyed by a not-shown feeding / conveying device, and is sent / conveyed to the secondary transfer portion where the intermediate transfer belt 5 and the secondary transfer roller 8 face each other by a registration roller pair 7 at a predetermined timing. Is done. The toner image on the intermediate transfer belt 5 is transferred to the transfer sheet P by applying a charge having a polarity opposite to that of the toner image to the secondary transfer roller 8.

  Next, the transfer sheet P is separated from the intermediate transfer belt 5 and sent to a fixing device (not shown). After the toner image is fixed by the fixing device, the transfer sheet P is discharged out of the apparatus main body 100A. The surface of the photosensitive drum 1 after the toner image is transferred to the intermediate transfer belt 5 is cleaned by the cleaning blade 61 of the cleaning device 6, and the toner remaining on the photosensitive drum 1 is removed. The photosensitive drum 1 rotates in the direction of arrow a, and the developing roller 42 rotates in the direction of arrow b.

  FIG. 2A is a cross-sectional view showing the configuration of the developing device 4. As shown in FIG. 2A, the developing device 4 includes a developing chamber 41 and a toner storage chamber 40. The developing chamber 41 is a chamber for developing the electrostatic image on the surface of the photosensitive drum 1 with the toner T conveyed from the toner storage chamber 40. The developing chamber 41 is a developing roller 42 that is a “developer carrying member” that rotates while carrying the toner T inside the toner storage chamber 40, and a “supply member” that rotates while supplying the toner T to the developing roller 42. It has the supply roller 43 which is (developer supply member). Further, the supply roller 43 is set so that the surface rotates in the same direction (rotates in the width direction) at a contact nip N that is a “contact portion” with the developing roller 42. The developing roller 42 is disposed so as to face the photosensitive drum 1 with a part of the peripheral surface exposed from the opening. In addition, a regulating blade 44 as a developer regulating member is attached to the lower edge portion of the opening of the photosensitive drum 1 in the developing chamber 41, and the blowout prevention sheet 46 is attached to the upper edge portion thereof.

  The toner storage chamber 40 that is a “developer container” is a chamber that stores toner T that is a “developer”. The developing device 4 includes an agitator 45 as a developer conveying member in the toner storage chamber 40. Further, the developing device 4 includes an intrusion sheet 47 that is an “intrusion member” (contact nip intrusion member) that extends from the inner wall of the developing chamber 41 and enters the contact nip N of the supply roller 43 and the development roller 42. . The intrusion sheet 47 will be further described later.

  Hereinafter, an outline of the operation of the developing device 4 will be described. In the developing device 4, the toner T accommodated in the toner storage chamber 40 is pumped up by the agitator 45 to the developing chamber 41 where the developing roller 42 is disposed. The pumped toner T is stored at the upper side in the gravity direction of the contact portion between the developing roller 42 and the supply roller 43, and as the supply roller 43 rotates in the direction of arrow c and the developing roller 42 rotates in the direction of arrow b. The contact portion between the supply roller 43 and the developing roller 42 is mechanically rubbed. The toner is frictionally charged by this rubbing and is carried and supplied onto the developing roller 42.

  The toner T supplied to the developing roller 42 is thinned to an appropriate layer thickness by a regulating blade 44 that is in contact with the developing roller 42 via the toner. At the same time, the toner T supplied to the developing roller 42 is rubbed between the developing roller 42 and the surface of the regulating blade 44 by being sandwiched between the developing roller 42 and the regulating blade 44, and is frictionally charged to a desired polarity. The

  Then, as the developing roller 42 rotates in the direction of the arrow b, the developing roller 42 is conveyed to a developing area which is a portion facing the photosensitive drum 1. In the developing area, the toner layer on the developing roller 42 develops the electrostatic latent image on the photosensitive drum 1 by a developing electric field by a bias applying unit (not shown), and is visualized as a toner image. The toner layer that is not used for development in the development region and remains on the development roller 42 is mixed while being rubbed at the contact portion with the supply roller 43.

  At the same time, the developer is newly supplied onto the developing roller 42 by the rotation of the supply roller 43. On the other hand, the undeveloped toner rubbed and mixed by the supply roller 43 is returned to the inside of the lower toner storage chamber 40 by the rotation of the supply roller 43 and mixed while being stirred in the toner storage chamber 40 by the rotation of the agitator 45. Is done.

  Hereinafter, detailed conditions of each part of the developing device 4 in the present embodiment will be described. As the toner T, a non-magnetic one-component negatively chargeable toner is used. In this embodiment, toner having an aggregation degree of 5 to 40% in the initial state is used. By using a toner having such a cohesion degree, it is possible to ensure the fluidity of the toner through durability. Further, the degree of aggregation of the toner was measured as follows.

  As a measuring apparatus, a powder tester (manufactured by Hosokawa Micron Corporation) having a digital vibrometer (manufactured by DEGITAL VIBRATION METERMODEL 1332 SHOWA SOKKI CORPORATION) was used.

  As a measurement method, set 390 mesh, 200 mesh, and 100 mesh sieves on the shaking table in the order of narrow opening, that is, 390 mesh, 200 mesh, and 100 mesh sieves so that the 100 mesh sieve comes to the top. did. Add 5 g of accurately weighed sample (toner) to the set 100 mesh sieve, adjust the displacement value of the digital vibrometer to 0.60 mm (peak-to-peak), and apply vibration for 15 seconds. It was. Thereafter, the mass of the sample remaining on each sieve was measured, and the degree of aggregation was obtained based on the following formula (1). The measurement samples at that time were each left for 24 hours in an environment of 23 ° C. and 60% RH in advance, and the measurement was performed in an environment of 23 ° C. and 60% RH.

  [Equation 1] Cohesion (%) = (Remaining sample mass on 100 mesh sieve / 5 g) × 100 + (Remaining sample mass on 200 mesh sieve / 5 g) × 60 + (Remaining sample mass on 390 mesh sieve / 5 g) × 20 (1).

  The supply roller 43 has a diameter (φ) of 15 mm and a flexible foamed polyurethane formed on a conductive core metal having a diameter (φ) of 6 mm. As the surface hardness, Asker-F can use 50 to 80 °. Further, the amount of intrusion with respect to the developing roller 42 is 1.0 mm.

The developing roller 42 has a diameter (φ) of 15 mm, a silicone rubber base layer formed on a conductive metal core having a diameter (φ) of 6 mm, and a urethane rubber surface layer formed thereon. In addition, as a volume resistance of the developing roller 42, a resistance of 10 × 10 ⁻⁴ to 10 × 10 ⁻¹² Ω can be used. Further, the surface hardness of Asker-C having a range of 30 to 75 ° can be used. The rotation speed of the developing roller 42 is 200 rpm.

  The supply roller 43 rotates in the opposite direction to the developing roller 42, that is, the supply roller 43 and the developing roller 42 are driven to rotate so that the surfaces thereof move in the same direction at the contact portion. The ratio of the surface peripheral speed VSP of the supply roller 43 to the surface peripheral speed VDR of the developing roller 42, that is, VSP / VDR is set to 140% in order to suppress toner deterioration.

  Next, the structure of the intrusion sheet 47 that is a feature of the invention will be described. The intrusion sheet 47 is a PET sheet having a thickness of 50 μm, and as shown in FIG. 2 (a), a sheet attachment base is provided on the inner wall of the developing device 4, and a base end portion is attached and fixed thereto with a double-sided tape. The Then, the front end portion (free end side) of the intruding sheet 47 is disposed in the contact nip N between the developing roller 42 and the supply roller 43 from the upstream side in the rotation direction of the developing roller 42.

  The length of the intrusion sheet 47 that enters the contact nip N in the rotation direction of the supply roller 43 is set to be shorter than the length of the contact roller nip N in the rotation direction of the developing roller 42. Here, the dimension (K in FIG. 5) of the developing roller 42 in the rotation direction of the contact nip N between the supply roller 43 and the developing roller 42 is about 5.5 mm, and the intruding sheet 47 is in contact with the contact nip N. The dimension (J in FIG. 5) (the amount of penetration) that penetrates in the rotational direction of 42 is 1.5 mm. Therefore, there is about 4 mm that does not penetrate (see FIG. 5).

  In this embodiment, as shown in FIG. 2A, the intrusion sheet 47 is disposed so as to enter from the upper side into the contact nip N of the supply roller 43 and the developing roller 42. In this way, the intruding sheet 47 enters the inside of the abutting nip N without resisting gravity, so that even when a thin sheet is used, there is an effect that the sheet is difficult to roll.

  Next, the effect on the development ghost will be described. In describing the effect on the development ghost, a description will be given below using Comparative Example 1-1 and Comparative Example 1-2. In Comparative Example 1-1, the intrusion sheet 47 was not used. In Comparative Example 1-2, the contact member 50 is configured to contact the supply roller 43 at a place other than the contact nip N (see FIG. 2B). In Comparative Example 1-2, a PET sheet is attached to the contact surface where the contact member 50 contacts the supply roller 43.

  Table 1 is a table showing experimental results of determining the development ghost level using the developing devices 4 of Examples, Comparative Example 1-1, and Comparative Example 1-2.

  The development ghost was determined under the following conditions. In this image forming apparatus 100, the background potential of the photosensitive drum 1 is −500 V, the bright portion potential that is the potential after exposure is −100 V, and the developing bias applied to the core of the developing roller 42 is −300 V. The core of the supply roller 43 is set to the same potential as the developing bias. Accordingly, since the potential of the developing roller 42 is −300V, the potential of the supply roller 43 is also −300V. In a printing environment at a temperature of 23 ° C. and a humidity of 50%, an image for developing ghost evaluation shown in FIG. 3 is printed, and determination is made for all different HT concentrations, and no developing ghost is generated (O) or slightly occurring ( (Triangle | delta), It has generate | occur | produced clearly (x).

  In Example 1, the development ghost was improved. The development ghost generated in the case of the example and the comparative example is higher in the HT density after solid printing (hereinafter referred to as “after black”) than in the background portion (hereinafter referred to as “after white”). (Hereinafter referred to as “positive ghost”).

(First reason)
Hereinafter, the reason why the effect of the present invention is obtained will be described in detail. First, the factors that determine the toner charge amount (tribo) on the surface of the developing roller 42 that has passed through the regulating blade 44 after white and after black will be described together with experimental results. As described above, the configuration of Comparative Example 1-1 is configured such that the intrusion sheet 47 is not used in the developing device 4.

  Fig.4 (a) is a graph which shows the experimental result of the comparative example 1-1. Here, the horizontal axis is VSP / VDR, and the vertical axis is the toner charge amount (tribo) μC / g on the surface of the developing roller 42. VSP (Velocity Of Supply Roller) means the speed of the supply roller 43, and VDR (Velocity Of Developing Roller) means the speed of the developing roller 42. In the graph, the D roller is the developing roller 42. Note that arbitrarily changing VSP / VDR means arbitrarily changing the rotation speed of the supply roller 43 with respect to the developing roller 42. When the VSP / VDR on the horizontal axis is increased, the rotation speed of the supply roller 43 with respect to the developing roller 42 is increased as described above. Along with this, the tribo after white shown on the vertical axis rises gently. On the other hand, the post-black tribo shown on the vertical axis rises abruptly in the middle compared to the above-mentioned tribo after white. Details will be described below.

  After black, the tribo rapidly rises as VSP / VDR increases. This is because the relative speed difference between the supply roller 43 and the developing roller 42 becomes large, and the frictional charging of toner between the supply roller 43 and the developing roller 42 becomes active. After black, the toner on the surface of the developing roller 42 is consumed each time, so that the toner tribo after passing through the regulating blade 44 has an active frictional charging between the supply roller 43 and the developing roller 42. Great contribution. From the above, after black, VSP / VDR becomes higher than 140% compared to after white, and then the tribo rapidly rises as VSP / VDR increases.

  On the other hand, after white, the tribo gradually rises as VSP / VDR increases. The tribo after white is determined by the frictional charging ability of the regulating blade 44. After white, the undeveloped toner after passing through the regulating blade 44 cannot be charged completely by the supply roller 43. For this reason, the chances of relatively rubbing the same toner increases, and the toner charge amount according to the frictional charging ability between the toner T and the regulation blade 44 at the regulation blade 44 converges. Therefore, when VSP / VDR is increased, the ghost is improved. From the above, after white, the tribo rises more slowly as VSP / VDR increases than after black.

  The above is the tendency and the determinant of the charge amount of the toner on the surface of the developing roller 42 after passing through the regulating blade 44 with respect to after white and after black.

(Second reason)
Second, the relationship between the toner charge amount on the surface of the developing roller 42 and the ghost after passing through the regulating blade 44 after white and after black will be described under a comparison between Example 1 and Comparative Example 1-1. This will be described with reference to FIG. 4A described above and FIG. 4B described later. FIG. 4B is a graph showing the experimental results of Example 1. Here, the horizontal axis is VSP / VDR, and the vertical axis is the toner charge amount (tribo) μC / g on the surface of the developing roller 42. Note that arbitrarily changing VSP / VDR means arbitrarily changing the rotation speed of the supply roller 43 relative to the developing roller 42.

  In Comparative Example 1-1 (see Table 1 and FIG. 4A), VSP / VDR was set to 140% in order to prevent toner deterioration. As shown in FIG. 4A, the toner charge amount is lower in “tribo after black” than “tribo after black”. Thus, when the tribo after black is lower than the tribo after white, the development amount relative to the so-called development contrast is relatively greater in the rear of black and positive ghost is generated. In Comparative Example 1 shown in FIG. 4A, it is preferable that VSP / VDR is 190% because it is difficult for positive ghosts to occur. However, since the peripheral speed difference between the supply roller 43 and the developing roller 42 is too large, toner deterioration is caused. Can be said to be promoted.

  On the other hand, in Example 1 (see Table 1 and FIG. 4B), “tribo after black” rises more rapidly than the case of FIG. 4A as VSP / VDR rises. As a result. The “tribo after white” has a slight influence on the intrusion sheet 47 and the change is small. When VSP / VDR = 140%, “tribo after white” and “tribo after black” are substantially equal. From the above, as shown in Table 1, Example 1 resulted in a better positive ghost than Comparative Example 1-1. In Example 1 shown in FIG. 4B, a positive ghost hardly occurs when VSP / VDR is 140%, and the peripheral speed difference between the supply roller 43 and the developing roller 42 is moderate at 140%, and the toner deteriorates. Can be said to be more preferable than Comparative Example 1-1.

(Third reason)
Third, the reason why the above-described effect is obtained in the first embodiment will be described. FIG. 5 is a cross-sectional view showing the positional relationship among the developing roller 42, the supply roller 43, and the intrusion sheet 47. The relationship between the developing roller 42 and the intrusion sheet 47 and the relationship between the supply roller 43 and the intrusion sheet 47 will be described with reference to FIG. First, the intrusion sheet 47 enters between the supply roller 43 and the developing roller 42.

  As described above, the “tribo after black” on the surface of the developing roller 42 is dominated by the frictional charging ability between the supply roller 43 and the developing roller 42. The intrusion sheet 47 has a work function smaller than that of the developing roller 42 and has a strong negative charging ability for toner. In particular, the work function of the material on the supply roller 43 side of the intrusion sheet 47 is set smaller than the work function of the material of the developing roller 42. In other words, at least the “surface of the intrusion sheet 47 on the side of the supply roller 43” contacting the supply roller 43 and the “surface of the developing roller 42” contacting the supply roller 43 as viewed from the supply roller 43. In comparison, it can be said that the former is a material that easily charges the toner. The work function and negative charging capability are detailed below.

  The work function is the minimum energy required to extract one electron from the surface to infinity at the material surface. The fact that the work function of the intrusion sheet 47 is smaller than the work function of the developing roller 42 means that the intrusion sheet 47 is an object that can extract electrons with less energy than the developing roller 42.

  Here, the negative charging ability is the ability to charge negative toner to negative polarity. The fact that the negative charging ability of the intrusion sheet 47 is stronger than the negative charging ability of the developing roller 42 means that the intruding sheet 47 can easily charge negative toner more negatively than the developing roller 42.

  When the supply roller 43 and the developing roller 42 rotate while the intrusion sheet 47 is sandwiched, the toner immediately before being supplied from the supply roller 43 to the development roller 42 is rubbed between the supply roller 43 and the intrusion sheet 47. The Accordingly, the charge amount of the supplied toner is increased, and “tribo after black” is relatively increased as compared with the case of directly moving from the supply roller 43 to the developing roller 42.

  The behavior of “tribo after white” on the surface of one developing roller 42 will be described. As described above, the frictional charging ability between the developing roller 42 and the intrusion sheet 47 is higher than that without the intrusion sheet 47. However, since the frictional charging ability of the regulating blade 44 is higher than that of the intruding sheet 47 in terms of the size of the contact pressure and the material, the toner according to the frictional charging ability between the regulating blade 44 and the toner T is increased. It tends to converge to the charge amount.

  Further, as shown in FIG. 5, the intrusion sheet 47 enters only a part of the contact nip N between the supply roller 43 and the developing roller 42. That is, the dimension of the rotation direction of the developing roller 42 in which the entry sheet 47 enters between the supply roller 43 and the development roller 42 is J, and the rotation direction of the development roller 42 in the contact nip N between the supply roller 43 and the development roller 42. If the dimension of K is K, J <K is set. According to such a configuration, the supply roller 43 is less likely to deteriorate the peelability of the undeveloped toner on the surface of the developing roller 42. As described above, in the configuration of Example 1, the charge amount of the toner on the surface of the developing roller 42 after white and black is approached, and the positive ghost is improved.

  Hereinafter, the operational effects and characteristics of the configuration of the first embodiment will be summarized. First, the intrusion sheet 47 can increase the tribo by frictionally charging the black toner among the toners supplied from the supply roller 43 to the developing roller 42. Second, the intrusion sheet 47 is sandwiched in the contact nip N between the supply roller 43 and the developing roller 42, so that the contact pressure more than a certain amount necessary for frictional charging of the toner T is not increased. This can be ensured by the intrusion pressure between the supply roller 43 and the developing roller 42. Third, in combination with the configuration in which the supply roller 43 and the developing roller 42 rotate in the same direction, the intrusion sheet 47 is less likely to roll because the intrusion sheet 47 follows their rotation, and the configuration can be easily realized. .

  From the above description, the effect of Example 1 was not obtained in the configuration of Comparative Example 1-2 in Table 1. The friction after the black toner was immediately before the supply roller 43 was supplied to the developing roller 42. It turns out that it was because it was not charged. In the configuration as in Comparative Example 1-2, the contact member 50 is disposed so as to come into contact with the supply roller 43, but a place other than the contact nip N between the supply roller 43 and the developing roller 42. It is arrange | positioned so that it may contact. As described above, it is considered that the toner T is deteriorated because a strong mechanical rubbing force is applied to the toner T at a place other than the contact nip N.

  In the first embodiment, a PET sheet is used as the intrusion sheet 47 on the assumption that the work function is smaller than that of the developing roller 42 and the toner has a strong negative charging capability. However, the structure is not limited to this. . That is, the intrusion sheet 47 may have the same work function as the developing roller 42 and the same negative charging performance with respect to the toner. In that sense, it is sufficient that the intrusion sheet 47 has a work function equivalent to or less than that of the developing roller 42 and has a negative charge performance with respect to the toner equivalent or better. With this configuration, the same effect as in the first embodiment can be obtained.

  If the intrusion sheet 47 has a negative charging performance equivalent to that of the developing roller 42, the effect can be exhibited for the following reason. The intrusion sheet 47 is stopped when viewed from the supply roller 43. Thereby, the relative speed difference between the supply roller 43 and the intrusion sheet 47 becomes larger than the relative speed difference between the supply roller 43 and the developing roller 42. This is because the frictional charging capability between the supply roller 43 and the intrusion sheet 47 is higher.

  The material, VSP / VDR, the diameter of the supply roller 43 and the developing roller 42, and the amount of penetration of the supply roller 43 with respect to the developing roller 42 can be set as appropriate so that the charge amount on the developing roller 42 after white and black is aligned. It is.

  Among the configurations of the developing device according to the second embodiment, the same configurations and effects as those of the developing device 4 according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted as appropriate. Since the second embodiment can be applied to the same image forming apparatus as that of the first embodiment, the description of the image forming apparatus is omitted. The characteristic points of the developing device of Example 2 are as follows.

  That is, a potential difference is set between the supply roller 43 and the developing roller 42 so that the toner T is urged from the supply roller 43 toward the developing roller 42. That is, a supply bias is applied to the core metal of the supply roller 43 so that the toner is urged from the supply roller 43 to the developing roller 42. Specifically, in the developing device 4, −500 V is applied to the core of the supply roller 43, −300 V is applied to the core of the developing roller 42, and −200 V is applied as the supply bias. Note that VSP / VDR is set to 140% as in the first embodiment in order to suppress toner deterioration.

  In the first embodiment, since the potentials of the core of the supply roller 43 and the core of the developing roller 42 are set to be the same, the toner is not urged from the supply roller 43 to the developing roller 42 by the electric field. In contrast, the second embodiment is characterized in that the toner is urged from the supply roller 43 to the developing roller 42 by an electric field. Further, in the configuration of the second embodiment, the supply bias reduces the amount of toner supply capability from the supply roller 43 to the development roller 42 when the intrusion sheet 47 is sandwiched between the supply roller 43 and the development roller 42. It can also be said to be a configuration. In particular, the experiment was performed on the HT image in Example 1, but the experiment was performed on the solid image in Example 2.

  Hereinafter, the effect of Example 2 is demonstrated, comparing with Comparative Example 2-1 and Comparative Example 2-2. Comparative Example 2-1 has a configuration in which the supply bias is not applied and the potential of the core of the supply roller 43 and the potential of the core of the developing roller 42 are the same (corresponding to the configuration of the first embodiment). The comparative example 2-2 is configured such that the intruding sheet 47 is not sandwiched between the supply roller 43 and the developing roller 42. The experimental results are shown below.

  Table 2 is a table showing the results of verifying the solid followability in Example 2, Comparative Example 2-1, and Comparative Example 2-2 when the amount of toner in the developing device 4 is small. The solid followability was determined under the following conditions. In the image forming apparatus 100, the background potential of the surface of the photosensitive drum 1 is set to −500V, the bright portion potential that is the potential after exposure is set to −100V, and the developing bias applied to the core of the developing roller 42 is set to −300V. .

  The printing environment is a temperature of 23 ° C. and a humidity of 50%, and when a solid image is printed on one side of a vertically fed letter paper (11 × 8.5 inch), there is a sufficient density (◯), the density Was slightly insufficient (Δ) and the concentration was insufficient (×). The results of determining the development ghost level at the same time are shown in Table 2.

  According to the configuration of the second embodiment, the supply bias is applied to the side where the toner T is urged from the supply roller 43 to the developing roller 42, so that even if the amount of the toner T is small, the solid follow-up is performed. Property is improved.

  As is clear from Comparative Example 2-1 and Comparative Example 2-2, when the supply capability of the supply roller 43 decreases when the amount of toner is small, etc., depending on the configuration conditions of the intrusion sheet 47 and the supply roller 43. In some cases, the effect of sandwiching the intrusion sheet 47 may appear as poor solid followability. However, even in such a case, it is possible to achieve both solid followability and development ghost by applying a supply bias.

  Among the configurations of the developing device according to the third embodiment, the same configurations and effects as those of the developing device 4 according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted as appropriate. Since the third embodiment can be applied to the same image forming apparatus as that of the first embodiment, the description of the image forming apparatus is omitted. The characteristic points of the developing device of Example 3 are as follows.

  In other words, the work function of the material on the developing roller 42 side of the intrusion sheet 47 is characteristically set to be larger than the work function of the material of the supply roller 43. More specifically, the material of the intrusion sheet 47 on the developing roller 42 side is set to have a work function larger than that of the material of the supply roller 43 and weakly charge negative with respect to toner. In other words, at least the “surface of the intruding sheet 47 on the side of the developing roller 42” that contacts the developing roller 42 and the “surface of the supply roller 43” that contacts the developing roller 42, as viewed from the developing roller 42. In comparison, it can be said that the former is a material that is less likely to charge the toner.

  Specifically, a PPS (polyphenylene sulfide resin) sheet having a thickness of 50 μm was attached to the surface of the intrusion sheet 47 of Example 1 on the developing roller 42 side. Thus, the intrusion sheet 47 is a single sheet, and is set to a different material on the supply roller 43 side and the development roller 42 side.

  Hereinafter, the operational effects of Example 3 will be described in comparison with Comparative Example 3-1 and Comparative Example 3-2. Comparative Example 3-1 has a configuration using only a PET sheet as the intrusion sheet 47. In Comparative Example 3-2, the intruding sheet 47 is not sandwiched between the supply roller 43 and the developing roller 42. The experimental results are shown below.

  The experiment was conducted in a low-temperature and low-humidity environment with a temperature of 15 ° C. and a humidity of 10%. Solid white printing was performed under the same image forming conditions as in Table 1, with no fogging (◯), with slight fogging (Δ), The level of fogging was judged as poor fogging (×). Note that fog does not occur at the temperature of 23 ° C. and the humidity of 50%, which are the experimental environments shown in Table 1. At the same time, the results of determining the development ghost level are shown in Table 3.

  According to the configuration of Example 3, the result that the fog is improved as compared with the case where only the PET sheet is used as the intrusion sheet 47 in an environment where the chargeability of the toner in the low temperature and low humidity environment is high is obtained. This is because the fog due to the toner tribo after whitening becomes too high, and by placing a PPS sheet on the surface on the developing roller 42 side, the triboelectric charging ability for the toner between the developing roller 42 and the intruding sheet 47 is an appropriate value. It is because it can fall to.

  FIG. 6 is a cross-sectional view illustrating a configuration of a developing device 504 according to a modification of the first to third embodiments. In the first to third embodiments, a sheet sticking base is provided on the inner wall of the developing device 4, and the intruding sheet 47 enters the contact nip from there. The present invention is not limited to this, and as shown in FIG. 6, the “intrusion sheet” may also be configured to serve as a blowout prevention sheet 46 that prevents the toner T from blowing out from the opening of the developing chamber 41. Even when such a blow-out prevention sheet 46 is extended to enter the contact nip N, the same effects as in the first to third embodiments can be obtained.

  Among the configurations of the developing device according to the fourth embodiment, the same configurations and effects as those of the developing device 4 according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted as appropriate. Since the fourth embodiment can be applied to the same image forming apparatus as that of the first embodiment, the description of the image forming apparatus is omitted. The characteristic points of the developing device of Example 4 are as follows.

  That is, the surface roughness Rz of the surface on the developing roller 42 side of the intrusion sheet 47 is characteristically set to be equal to or less than (same as and / or smaller than) the surface roughness Rz of the developing roller 42. . Further, in the axial direction of the developing roller 42, the surface on the developing roller 42 side of the intruding sheet 47 has a surface roughness Rz of a non-image area portion where an image is not formed, and a surface roughness of an image area portion where an image is formed. It is characteristic that it is set below Rz (same and / or smaller).

  This will be described below with reference to FIG. The intrusion sheet 47 is a PET sheet having a thickness of 50 μm. The intrusion sheet 47 is formed so that the contact surface side with the developing roller 42 is polished and the surface is rough. As described above with reference to FIG. 2A, the intrusion sheet 47 is attached to the wall surface of the developing chamber 41 upstream of the contact nip N of the developing roller 42 in the rotational direction of the developing roller 42 by a double-sided tape. It is fixed by sticking the end. The leading edge of the intrusion sheet 47 is disposed so as to enter the contact nip N from the upstream side in the rotation direction of the developing roller 42 with respect to the contact nip N between the supply roller 43 and the developing roller 42. Here, the contact nip between the supply roller 43 and the developing roller 42 is 5.5 mm, and the amount of penetration of the penetration sheet 47 into the contact nip N is 1.5 mm.

  The ten-point average roughness (hereinafter referred to as Rz) of the surface of the developing roller 42 is 12.0 μm, and the Rz on the contact surface side of the intruding sheet 47 with the developing roller 42 is 8.0 μm. Here, the surface roughness is a 10-point average roughness Rz indicating a value based on JISB0601-1994. Here, it measured using the non-contact type surface roughness of an ultra-deep color 3D shape microscope (Keyence Corporation make: VK-9500). The measurement conditions are a measurement magnification of 1000 (objective 50 × 20), a measurement length of 0.25 mm (measurement direction is the longitudinal direction of the photosensitive drum 1), a cutoff wavelength of 0.08 mm, and a measurement pitch of 0.05 μm.

  According to such a configuration, an effect that toner leakage is suppressed can be obtained. That is, since the intruding sheet 47 has entered the contact nip N between the supply roller 43 and the developing roller 42, the intruding sheet 47 is pulled by the supply roller 43 and the developing roller 42. Therefore, the phenomenon of toner leakage from the area surrounded by the developing chamber 41, the developing roller 42, and the intruding sheet 47 to the outside of the developing device is suppressed.

  As described above, as a configuration for suppressing the phenomenon that the toner T leaks from the developing roller 42, Rz of the contact surface of the intruding sheet 47 with the developing roller 42 is set to be equal to or less than Rz of the surface of the developing roller 42. The reason for this will be described.

  Table 4 shows the toner leakage when the polishing conditions are changed and the ten-point average roughness Rz, which is compatible with the surface transport force of the toner T, is changed on the contact surface of the intruding sheet 47 with the developing roller 42. The experimental results are shown.

  The determination of toner leakage was performed under the following conditions. In the image forming apparatus 100, the background potential of the photosensitive drum 1 was −500 V, the bright portion potential that is the potential after exposure was −100 V, and the developing bias applied to the core of the developing roller 42 was −300 V. The core of the supply roller 43 is set to the same potential as the developing bias. In a printing environment at a temperature of 23 ° C. and a humidity of 50%, 100 white images were continuously flowed to confirm whether toner leaked from the developing device. Toner leakage does not occur (◯), occurs slightly (Δ), or clearly (×).

  From this experiment, when the Rz of the contact surface of the intruding sheet 47 with the developing roller 42 is equal to or greater than Rz of the surface of the developing roller 42, the toner T coated on the developing roller 42 can be returned to the developing chamber 41. The toner T on the developing roller 42 leaked out of the developing device. On the other hand, when the Rz of the contact surface of the intruding sheet 47 with the developing roller 42 is set to be equal to or less than the Rz of the surface of the developing roller 42, leakage due to the toner T on the developing roller 42 does not occur.

  The reason is described below. By forming the contact surface of the intrusion sheet 47 with the developing roller 42 roughly, the charging ability of the white toner on the surface of the developing roller 42 is lowered. When the charge amount of the toner T on the surface of the developing roller 42 decreases, the mirroring force between the toner T on the surface of the developing roller 42 and the developing roller 42 decreases, and the transportability of the developing roller 42 decreases.

  In particular, when the Rz of the surface of the developing roller 42 is set to be equal to or less than the Rz of the intruding sheet 47, the unevenness on the surface of the intruding sheet 47 can easily peel off the toner T on the surface of the developing roller 42. For this reason, the toner on the surface of the developing roller 42 has dropped and toner leakage has occurred. Therefore, by setting Rz of the intrusion sheet 47 to be equal to or less than Rz on the surface of the developing roller 42, toner leakage from the developing roller 42 is suppressed. From the above, the toner leakage from the developing chamber 41 and the developing roller 42 is suppressed by setting the Rz of the contact surface where the intrusion sheet 47 contacts the developing roller 42 to be equal to or less than the Rz of the surface of the developing roller 42.

  According to the configurations of the first to fourth embodiments, the level of developing ghost generated when the relative peripheral speed ratio between the supply roller 43 and the developing roller 42 is set to be small in order to reduce the deterioration of the toner T is reduced. As a result, it is possible to provide the developing device 4 that can cope with long life with high image quality. In addition, according to the configuration of the second embodiment, the solid followability is improved, and according to the configuration of the third embodiment, it is possible to achieve both fogging and development ghost.

  In the first to fourth embodiments, the configuration as the developing device 4 has been described. However, a configuration as a part of a cartridge that is detachable from the apparatus main body 100A may be used.

4 Developing device 40 Toner storage chamber (developer container)
41 Developing chamber 42 Developing roller (developer carrier)
43 Supply roller (supply member)
47 Intrusion sheet (intrusion member)
N Contact nip (contact part)
T Toner (Developer)

Claims (10)

A developer container for storing the developer;
A developer carrying member that rotates while carrying the developer inside the developer container; and a supply member that rotates while supplying the developer to the developer carrying member, and the supply member carries the developer carrying member. A developing chamber which is set so that the surface rotates in the same direction at the contact portion with the body, and develops with the developer conveyed from the developer container;
An intrusion member that extends from the inner wall of the developing chamber and enters the contact portion of the supply member and the developer carrier;
With
The developing device according to claim 1, wherein a work function of a material on a surface of the supply member in the intrusion member is set smaller than a work function of a material of the developer carrying member . A developer container for storing the developer;
A developer carrying member that rotates while carrying the developer inside the developer container; and a supply member that rotates while supplying the developer to the developer carrying member, and the supply member carries the developer carrying member. A developing chamber which is set so that the surface rotates in the same direction at the contact portion with the body, and develops with the developer conveyed from the developer container;
An intrusion member that extends from the inner wall of the developing chamber and enters the contact portion of the supply member and the developer carrier;
With
2. A developing device according to claim 1, wherein a work function of a material on a surface of the developer carrying member in the intrusion member is set larger than a work function of a material of the supply member . 2. The length of the intrusion member that enters the contact portion in the rotation direction of the developer carrier is shorter than the length of the contact member in the rotation direction of the supply member.
Alternatively, the developing device according to claim 2 . The said intrusion member is arrange | positioned so that it may penetrate | invade from the upper direction with respect to the said contact part of the said supply member and the said developer carrier, The Claim 1 thru | or 3 characterized by the above-mentioned. The developing device described. Wherein the surface roughness of the side surface of the developer carrying member in the penetration member is any one of claims 1 to 4, characterized in that it is set below the surface roughness of the developer carrying member The developing device according to 1. In the axial direction of the developer carrier,
The developer carrier side surface of the intrusion member is
Surface roughness of the non-image area portion where no image is formed, according to any one of claims 1 to 5, characterized in that the image is set below the surface roughness of the image region portions formed Development device. The penetration member includes a developing device according to any one of claims 1 to 6 developer is characterized in that also serves as a blowout prevention sheet to prevent the blown from an opening of the developing chamber. The potential difference is set between the supply member and the developer carrier so that the developer is biased from the supply member toward the developer carrier. The developing device according to claim 7 . A developing device according to any one of claims 1 to 8 ,
An image carrier on which an electrostatic latent image is formed;
Have
A process cartridge that is detachable from the main body of the image forming apparatus. An image forming unit for forming an image;
A developing device according to any one of claims 1 to 8 ,
An image forming apparatus comprising: