JP2024061382A - Image forming device - Google Patents

Abstract

[Problem] To provide an image forming device capable of suppressing deterioration in image quality caused by toner deterioration without reducing the efficiency of toner use. [Solution] The image forming device has a developing device, a supplying means for supplying developer to the developer storage container, a developing device remaining life detecting means for detecting the remaining life of the developing device, and a developer total supply amount detecting means for detecting the total amount of developer supplied to the developer storage container, and determines a bias value to be applied to a developer supply member according to the result of the developing device remaining life and the total toner supply amount. [Selected Figure] Figure 1

Description

The present invention relates to image forming devices such as copying machines, printers, and facsimile machines that use electrophotographic or electrostatic recording methods.

Image forming devices using electrophotography, such as copying machines and laser beam printers, form an electrostatic latent image by irradiating a uniformly charged photoreceptor surface with light corresponding to image data. A developing device then supplies developer (hereafter simply referred to as toner) to this electrostatic latent image, making it visible as a toner image on the photoreceptor surface. This toner image is transferred from the photoreceptor surface to a transfer material such as recording paper by a transfer device, and fixed on the transfer material by a fixing device to form a recorded image. After the transfer material is separated, the photoreceptor surface is cleaned by a cleaning device to scrape off any remaining toner, and is then used repeatedly for image formation.

In general, a developing device has a developing roller as a developer carrier rotatably supported in a developing container, and a supply roller as a toner supply means is disposed in contact with the developing roller. In addition, a leaf spring-shaped developing blade is provided in the developing container as a developer layer thickness regulating member to apply pressure to the developing roller, and is in contact with the developing roller at a predetermined contact pressure.

A stirring paddle is rotatably installed in the toner storage chamber, which stirs the toner and transports it to the vicinity of the contact point between the developing roller and the supply roller. The transported toner is supplied to the contacting developing roller by the supply roller. The toner layer thickness of the toner supplied to the developing roller is regulated by the developing blade. At this time, the toner is given an electric charge by frictional charging caused by the rubbing between the developing roller and the developing blade. The electrostatic latent image formed on the photosensitive member is visualized by the toner with this charged toner.

The toner in the developing device deteriorates due to friction between the components that make up the developing device, causing deterioration in image quality. Patent Document 1 proposes suppressing image quality deterioration by forcibly consuming degraded toner. This is a configuration in which the amount of toner that is forcibly consumed increases in accordance with an increase in usage history data related to the amount of toner consumed, and degraded toner is forcibly discharged even if the proportion of degraded toner increases.

JP 2010-276705 A

However, the configuration of Patent Document 1 has the following problems. The configuration increases the amount of toner that is forcibly consumed in order to suppress toner deterioration, and the forcibly consumed toner is collected in the cleaning unit and is not used for printing on recording media. In other words, there is a possibility that the efficiency of toner usage will decrease.

In view of the above problems, the object of the present invention is to provide an image forming device that can suppress deterioration in image quality without reducing the efficiency of toner usage.

To achieve the above object, the image forming apparatus according to the present application has a developer in which particles that have a positive polarity in the triboelectric series with respect to the toner particles are added to the toner particles, a developer container that contains the developer, a developer carrier for carrying and transporting the developer, a developer supply member for supplying the developer to the developer carrier, a developer regulating member that contacts the developer carrier and regulates the developer layer thickness, a developer carrier bias application means that applies a bias to the developer carrier, and a developer supply member bias application means that applies a bias to the developer supply member, a supply means that supplies the developer to the developer container, a developing device remaining life detection means that detects the remaining life of the developing device, and a developer total supply amount detection means that detects the total amount of developer supplied to the developer container, and is characterized in that the amount of supply bias applied by the developer supply member bias application means is determined based on the detection results of the developing device remaining life detection means and the detection results of the developer total supply amount detection means.

As described above, according to the present invention, by determining the optimal bias to be applied to the supply roller based on the remaining life of the developing device and the total amount of toner replenished, it is possible to suppress deterioration in image quality without reducing the efficiency of toner usage.

1A is a flowchart showing a process for determining a bias applied to a supply roller in the first embodiment, and FIG. 1B is a diagram for explaining a relationship between a remaining life of a development unit and the bias applied to the supply roller. 13A is a flowchart showing a process for determining a bias applied to a supply roller in a second embodiment, and FIG. 13B is a diagram for explaining a relationship between a remaining life of a development unit and the bias applied to the supply roller. FIG. 1 is a diagram illustrating a configuration of an electrophotographic image forming apparatus to which a process cartridge according to the present exemplary embodiment is attached. FIG. 2 is a diagram illustrating a process cartridge according to the embodiment. FIG. 2 is a perspective view illustrating a process cartridge according to the embodiment. FIG. 2 is a perspective view illustrating a development unit according to the embodiment. 5A to 5C are diagrams illustrating a toner transport operation according to the embodiment. 2 is a main cross-sectional view of the toner cartridge (Y, M, C) according to the embodiment; FIG. 2 is a principal cross-sectional view of a toner cartridge (K) according to the embodiment. FIG. 2 is an overall perspective view of the toner cartridge (Y, M, C) according to the embodiment, seen from the rear.

The following describes in detail a preferred embodiment of the present invention by way of example, with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are not intended to limit the scope of the present invention to those alone. Furthermore, the materials, shapes, etc. of components once described in the following explanations will remain the same in subsequent explanations as they were in the initial explanation, unless otherwise specified.

<Overall Configuration of Image Forming Apparatus>
First, the overall configuration of an electrophotographic image forming apparatus (hereinafter referred to as an image forming apparatus) 100 will be described with reference to Fig. 3. As shown in Fig. 3, four detachable process cartridges 70 (70Y, 70M, 70C, 70K) are mounted by mounting members (not shown). The upstream side of the process cartridges 70 in the mounting direction of the image forming apparatus 100 is defined as the front side, and the downstream side of the mounting direction is defined as the rear side.

Each process cartridge 70 includes an electrophotographic photosensitive drum (hereinafter referred to as photosensitive drum) 1 (1a, 1b, 1c, 1d), a charging roller 2 (2a, 2b, 2c, 2d) around the photosensitive drum 1, a developing roller 25 (25a, 25b, 25c, 25d), a cleaning member 6 (6a, 6b, 6c, 6d), and other process means that are integrally arranged. The charging roller 2 uniformly charges the surface of the photosensitive drum 1, and the developing roller 25 develops the latent image formed on the photosensitive drum 1 with toner to make it visible. The cleaning member 6 removes any toner remaining on the photosensitive drum 1 after the toner image formed on the photosensitive drum 1 is transferred to a recording medium.

In addition, below the process cartridge 70, a scanner unit 3 is provided to selectively expose the photosensitive drum 1 based on image information and form a latent image on the photosensitive drum 1.

A cassette 17 containing a recording medium S is attached to the bottom of the device main body 100. A recording medium conveying means is provided so that the recording medium S passes through the secondary transfer roller 69 and the fixing unit 74 and is conveyed to the upper part of the device main body 100. An intermediate transfer unit 5 is provided above the process cartridge 70 (70Y, 70M, 70C, 70K) as an intermediate transfer means for transferring the toner image formed on each photosensitive drum 1 (1a, 1b, 1c, 1d). The intermediate transfer unit 5 has a primary transfer roller 58 (58a, 58b, 58c, 58d) facing the photosensitive drum 1 of each color, and an opposing roller 59 facing the secondary transfer roller 69, and a transfer belt 50 is stretched over the primary transfer roller 58. The transfer belt 50 circulates so as to face and contact all the photosensitive drums 1, and a voltage is applied to the primary transfer roller 58 (58a, 58b, 58c, 58d) to perform a primary transfer from the photosensitive drum 1 to the transfer belt 50. Then, by applying a voltage to the opposing roller 59 and the secondary transfer roller 69 arranged inside the transfer belt 50, the toner on the transfer belt 50 is transferred to the recording medium S.

When forming an image, each photosensitive drum 1 is rotated, and the photosensitive drum 1, which is uniformly charged by the charging roller 2, is selectively exposed to light from the scanner unit 3. This forms an electrostatic latent image on the photosensitive drum 1. The latent image is developed by the developing roller 25. This forms a toner image of each color on each photosensitive drum 1. In synchronization with this image formation, the pair of registration rollers 55 transports the recording medium S to the secondary transfer position where the opposing roller 59 and the secondary transfer roller 69 are in contact with each other with the transfer belt 50 interposed therebetween. Then, by applying a transfer bias voltage to the secondary transfer roller 69, the toner image of each color on the transfer belt 50 is secondarily transferred to the recording medium S. This forms a color image on the recording medium S. The recording medium S on which the color image has been formed is heated and pressurized by the fixing unit 74 to fix the toner image. After that, the recording medium S is discharged to the discharge unit 75 by the discharge roller 72. The fixing unit 74 is disposed at the top of the device main body 100.

The first to fourth toner cartridges 9 are arranged horizontally below the process cartridge 70 in an order corresponding to the color of toner contained in each process cartridge 70. That is, the first toner cartridge 9Y contains yellow (Y) toner, the second toner cartridge 9M contains magenta (M), the third toner cartridge 9C contains cyan (C), and the fourth toner cartridge 9K contains black (K) toner. Each toner cartridge 9 supplies toner to the process cartridge 70 that contains toner of the same color.

The toner cartridge 9 is replenished when a remaining amount detection unit (not shown) provided in the main body of the image forming device 100 detects that the toner remaining amount in the process cartridge 70 is insufficient. The toner cartridge 9 is detachable from the image forming device 100 via mounting means such as a mounting guide (not shown) and a positioning member (not shown) provided in the image forming device 100.

Below the toner cartridges 9, first to fourth toner transport devices 18 are arranged corresponding to each toner cartridge 9. Each toner transport device 18 transports the toner received from each toner cartridge 9 upward and supplies the toner to each development unit 4.

<Process cartridge>
Next, a process cartridge 70 embodying the present invention will be described with reference to Fig. 4. Fig. 4 shows a main cross section of the process cartridge 70 containing toner. The cartridge 70Y containing yellow toner, the cartridge 70M containing magenta toner, the cartridge 70C containing cyan toner, and the cartridge 70K containing black toner all have the same configuration.

The process cartridge 70 (70Y, 70M, 70C, 70K) has a cleaning unit 26 (26a, 26b, 26c, 26d) and a developing unit 4 (4a, 4b, 4c, 4d). The cleaning unit 26 has a photosensitive drum 1 (1a, 1b, 1c, 1d), a charging roller 2 (2a, 2b, 2c, 2d), and a cleaning member 6 (6a, 6b, 6c, 6d). The developing unit 4 has a developing roller 25.

As described above, the charging roller 2 and the cleaning member 6 are arranged on the circumference of the photosensitive drum 1. The cleaning member 6 is composed of an elastic member 7 formed of a rubber blade and a cleaning support member 8. The tip 7a of the rubber blade 7 is arranged in contact with the photosensitive drum 1 in the counter direction to the rotation direction. The residual toner removed from the surface of the photosensitive drum 1 by the cleaning member 6 falls into the removed toner chamber 27a. A scoop sheet (not shown) that prevents the removed toner from the removed toner chamber 27a from leaking is also in contact with the photosensitive drum 1. The photosensitive drum 1 is rotated in response to the image forming operation by transmitting the driving force of the main body drive motor (not shown), which is the driving source, to the cleaning unit 26. The charging roller 2 is rotatably attached to the cleaning unit 26 via the charging roller bearing 28, and is pressed toward the photosensitive drum 1 by a charging roller pressure member (not shown), and rotates following the photosensitive drum 1.

The process cartridge 70 further includes a storage medium memory M (not shown), which is a non-volatile storage means. The memory M also stores information about the usage and lifespan of the developer. This makes it possible to accurately and quickly calculate the usage status of the developing device and the amount of remaining toner, even when the power to the image forming apparatus body is turned on/off or when the process cartridge 70 is replaced.

<Developing unit>
As shown in FIGS. 4 and 5, the developing unit 4 is composed of a developing roller 25 which rotates in contact with the photosensitive drum 1, and a developing frame 31 which supports the developing roller 25.

As shown in FIG. 6, the developing roller 25 is rotatably supported by the developing frame 31 via the developing front bearing 12 and the developing rear bearing 13, which are attached to both sides of the developing frame 31. Also arranged around the developing roller 25 are a supply roller 34 that contacts the developing roller 25 and rotates in the direction of arrow C, and a developing blade 35 for regulating the toner layer on the developing roller 25.

The developing blade 35 is composed of a support metal plate made of stainless steel and a thin plate (blade portion) machined into a leaf spring shape. The thin plate is integrated with the support metal plate (support portion) by YAG laser welding. The thin plate is made of SUS (stainless steel) machined into a leaf spring shape, with a thickness of 80 μm and a length of 230 mm in the longitudinal direction, and the contact portion located at the free end of the thin plate contacts the developing roller 25 with the required contact pressure.

As shown in FIG. 7, the toner storage chamber 31a of the developing frame 31 is provided with a toner transport member 36 for stirring the stored toner 200 and transporting the toner to the supply roller 34. The toner transport member 36 is composed of a stirring shaft 36a that can be rotated by an external driving force, and a sheet member 36b that is attached to the stirring shaft 36a and rotates together with the stirring shaft 36a. The toner is input to the developing unit 4 by engaging the main body developing coupling (not shown) of the device main body 100A with the drive side engagement portion of the Oldham coupling 21 (see FIG. 6) provided at the end of the shaft portion (not shown) of the supply roller 34, and is transmitted through the drive train of the developing unit 4 to rotate the toner transport member 36, thereby stirring and transporting the toner in the toner storage chamber 31a.

The toner storage chamber 31a contains toner 200. In this embodiment, a non-magnetic, single-component, approximately spherical toner with a particle size distribution centered on a weight-average particle size of approximately 7 μm is used. In addition, hydrotalcite particles, which have a triboelectric series with a chargeability of the opposite polarity to that of the toner particles, are added to the surface of the toner particles. When the toner particles and the hydrotalcite particles are rubbed together, the toner particles are charged negatively due to the triboelectric effect, whereas the hydrotalcite particles are charged positively, which is the opposite polarity to the toner particles. The hydrotalcite particles act as microcarriers, making it possible to uniformly charge the toner particles to a negative polarity.

The developing roller 25, the supply roller 34, and the developing blade 35 are each applied with an independent voltage from a high-voltage power source. During image formation, the predetermined DC voltage (developing voltage: Vdc) applied to the developing roller 25 is set to -300V. In addition, by applying a DC voltage to the supply roller 34 as well, the potential difference (ΔVr) between the supply roller 34 and the developing roller 25 is adjusted, and the amount of toner supplied to the developing roller 25 is adjusted. In this embodiment, the predetermined DC voltage (supply voltage: Vr) applied to the supply roller 34 in a new state is set to -500V. By setting such a magnitude relationship between the developing voltage and the supply voltage, ΔVr = Vdc - Vr can be set to +200V, and the potential setting is set so that the negatively charged toner 200 can easily move from the supply roller 34 to the developing roller 25. In this embodiment, the potential difference ΔVr is appropriately adjusted based on the remaining life of the developing unit 4 and the total amount of toner supplied to the developing unit 4 from the toner cartridge 9.

The toner supplied to the developing roller 25 by the supply roller 34 is triboelectrically charged by friction between the developing roller 25 and the developing blade 35, and the layer thickness is regulated at the same time as the charge is given. The regulated toner on the developing roller 25 is transported to the opposing portion with the photosensitive drum 1 by the rotation of the developing roller 25. The developing roller 25 and the photosensitive drum 1 each rotate so that their surfaces move in the same direction (from bottom to top in this embodiment) at the opposing portion (contact portion). At the developing portion where the toner is negatively charged by triboelectric charging, due to the potential difference between the photosensitive drum 1 and the developing roller 25, it transfers only to the bright potential portion to visualize the electrostatic latent image.

In this embodiment, the rotation distance of the developing roller 25 is accumulated, and the life of the developing unit 4 is judged based on the data of the total rotation distance. The total rotation distance of the developing roller 25 is found by accumulating the total number of rotations and the travel distance per rotation. The total number of rotations of the developing roller 25 is detected, for example, by a counter (not shown) that detects the number of rotations of the developing roller 25. The counter is a drive amount detection means that measures and detects the drive amount of the developing roller 25. The detection results by the counter are stored in a storage medium memory M attached to the process cartridge 70.

<Toner cartridge>
Next, the overall configuration of the toner cartridge 9 to be mounted in the image forming apparatus 100 according to the present embodiment will be described with reference to FIG. 6A. FIG. 6A is a cross-sectional view of the toner cartridges (9Y, 9M, 9C) according to the present embodiment at the center in the longitudinal direction (front-rear direction). FIG. 8B is a cross-sectional view of the toner cartridges (9Y, 9M, 9C) according to the present embodiment at the feed opening 52 on the rear side in the longitudinal direction (front-rear direction). FIG. 9A is a cross-sectional view of the toner cartridge (9K) according to the present embodiment at the center in the longitudinal direction (front-rear direction). FIG. 9B is a cross-sectional view of the toner cartridge (13K) according to the present embodiment at the feed opening 52 on the rear side in the longitudinal direction (front-rear direction). FIG. 10A is a perspective view of the toner cartridges (9Y, 9M, 9C) according to the present embodiment as viewed from the rear. FIG. 10B is a perspective view of the toner cartridges (9Y, 9M, 9C) according to the present embodiment as viewed from the rear with the side cover 62 removed.

The toner cartridge 9 includes a supply frame 50 that supports various components within the toner cartridge 9, and a supply toner storage chamber 51 that stores toner 200 inside. In addition, in the normal position (position during use), a supply frame opening 52 is provided on the bottom. A supply toner stirring member 53, a supply toner transport screw 54, and a partition member 55 are provided inside the supply toner storage chamber 51. In this embodiment, the fourth toner cartridge (9K) that stores black (K) toner is larger in the width direction (left-right direction) than the first to third toner cartridges (9Y, 9M, 9C) that store color (yellow (Y), magenta (M), cyan (C)) toners.

The supply stirring member 53 is disposed parallel to the longitudinal direction of the toner cartridge 9 and is rotatably supported by the supply frame 50. The supply stirring member 53 also has a rotating shaft 53a and a supply stirring sheet 53b, which is a flexible sheet and serves as a transport member. One end of the supply stirring sheet 53b is attached to the rotating shaft 53a and the other end of the supply stirring sheet 53b is a free end. When the rotating shaft 53a rotates, the supply stirring sheet 53b rotates in the direction of arrow G, causing the toner to be stirred by the supply stirring sheet 53b and sending the toner to the supply transport screw 54.

The supply toner transport screw 54 is disposed parallel to the rotation axis of the supply toner stirring member and is rotatably supported by the supply frame 50. As the supply toner transport screw 54 rotates, it transports the toner in the supply toner storage chamber from front to rear (from upstream to downstream in the toner cartridge installation/removal direction). In other words, it transports the toner toward the toner supply opening 52.

The partition member 55 and the supply frame 50 form a tunnel section 56. The tunnel section 56 is formed to correspond to the outer diameter of the supply toner transport screw 54, and serves to scrape and transport a fixed amount of toner transported by the supply toner transport screw 54. Similarly, the partition member 55 and the supply frame 50 form a toner discharge chamber 57.

The toner discharge chamber 57 is provided with a supply frame opening 52. A pump 65 with an expandable bellows portion 65a is also provided in communication with the interior. The pump 65 expands and contracts due to a drive train described below, allowing its internal volume to vary. As the pump 65 expands and contracts, the internal pressure of the supply toner storage chamber 51 and the toner discharge chamber 57 fluctuates, and toner can be suctioned and exhausted through the supply frame opening 52, allowing the toner to be discharged stably.

A drive train is arranged on the rear side of the toner cartridge 9. A drive input gear 59 receives a rotational drive from the image forming device 100 and transmits the rotation to the cam gear 60. A cam groove 60a is provided in the cam gear 60, and a link protrusion 61a of the link mechanism 61 engages with the cam groove 60a. The link mechanism 61 is supported by the side cover 62 so as to be movable in the front-rear direction. When the cam gear 60 rotates, the cam protrusion 61a passes alternately through the peaks and valleys of the cam groove 60a, so that the link mechanism 61 reciprocates in the front-rear direction. The link mechanism 61 is connected to a coupling portion 65b of the pump 65, and the coupling portion 65b of the pump 65 reciprocates in conjunction with the link mechanism 61. The internal volume of the pump 65 fluctuates as the bellows portion 65a of the pump 65 expands and contracts, resulting in fluctuations in the internal pressure of the supply toner storage chamber 51 and the toner discharge chamber 57. Next, a screw gear 64 is provided at the end of the aforementioned supply toner transport screw 54, and the screw gear 64 receives rotational drive from the cam gear 60 to rotate the supply toner transport screw 54.

In the toner discharge chamber 57, in the normal position (position during use), a supply frame body opening 52 and a supply port shutter 41 with a supply port 63 on the underside are supported by the supply frame body 50 so as to be movable in the front-rear direction. The supply frame body opening 52 is closed by the supply port shutter 41 when the toner cartridge 13 is not attached to the image forming device 100. The supply port shutter 41 is configured to move to a predetermined position in conjunction with the attachment and detachment of the toner cartridge 9, and is biased by the image forming device 100. When the supply port shutter 41 is attached to the image forming device 100, the supply frame body opening 52 and the supply port 63 communicate with each other, allowing toner to be discharged from the toner cartridge 9.

<Toner Supply Operation>
Next, the toner supply operation in this embodiment will be described.

As shown in FIG. 6, the developing unit 4 has a receiving port 40 at one end downstream in the attachment/detachment direction, and a receiving/transporting path 41 is provided in communication with the toner receiving port 40.

As shown in FIG. 7, a receiving and conveying screw 44 is disposed inside the receiving and conveying path 41. The receiving and conveying path 41 extends parallel to the rotation axis direction of the developing roller 25 and the supply roller 34. Furthermore, a storage chamber communication port 43 for supplying toner to the toner storage chamber 31a is provided near the longitudinal center of the developing unit 4, and connects the receiving and conveying path 41 to the toner storage chamber 31a. The toner discharged from the toner cartridge 9 is supplied to the toner receiving port 40 by a toner conveying device 18 attached to the main body.

In this embodiment, when the CPU of the image forming apparatus 100 receives a replenishment request, the toner replenishment operation is performed successively when the process cartridge 70 is driven during image formation and before and after image formation. The pump is driven to replenish approximately 0.5 g per second, and the amount of toner replenished is controlled by changing the time. In this embodiment, the total amount of toner replenished calculated from the time when the toner was replenished is written and stored in the memory M storage medium attached to the process cartridge 70.

<Toner Transport Configuration>
Next, the toner transport configuration of the developing unit 4 will be described in detail with reference to Figures 6 and 7. With regard to the configuration of the developing unit 4, terms indicating directions such as up, down, vertical, and horizontal indicate the directions when viewed in the normal use state unless otherwise specified. In other words, the normal use state of the developing unit 4 is a state in which it is properly attached to the image forming apparatus main body that is properly arranged and is available for image formation operation.

The receiving and conveying screw 44 provided in the developing unit 4 extends parallel to the rotation axis direction of the developing roller 25 and the supply roller 34, and conveys the toner received from the toner receiving port 40 to the toner storage chamber 31a via the storage chamber communication port 43.

The toner storage chamber 31a is provided with a deformation portion 31a1 that abuts against the sheet member 36b below the opening 31c. The sheet member 36b abuts against the deformation portion 31a1 as it rotates. This causes the sheet member 36b to receive force from the deformation portion 31a1. As a result, the sheet member 36b deforms against the elastic force of the sheet member 36b. In addition, the sheet member 36b rotates in contact with the deformation portion 31a1, and thus conveys the toner while carrying it on the surface downstream of the rotation. In this embodiment, the deformation portion 31a1 refers to the portion of the inner wall of the toner storage chamber up to the point where the sheet member 36b leaves as shown in FIG. In addition, the toner storage chamber 31a is provided with a restoration portion 31a2 downstream of the deformation portion 31a1 and upstream of the opening 31c in the rotation of the sheet member 36b. Here, the restoration portion 31a2 is a portion for releasing the contact between the sheet member 36b and the inner wall of the toner storage chamber 31a. In this embodiment, the restoration portion 31a2 is located above a horizontal plane that includes the rotation axis of the stirring member.

Therefore, after the tip of the free end side of the sheet member 36b passes through the deformation portion 31a1 as the sheet member 36b rotates, the contact with the inner wall of the sheet member 36b is released at the restoration portion 31a2. Then, the sheet member 36b is released from the state in which it was deformed by the deformation portion 31a1 and is restored to its natural state (original shape) by its own elastic restoring force. Due to this change in shape of the sheet member 36b in the restoration direction, the toner carried and transported on the sheet member 36b flies against gravity toward the opening 31c. This opening 31c is located downstream of the restoration portion 31a2 in the rotation direction of the sheet member 36b. A part of the toner that flies toward the opening 31c is transported into the developing chamber 31b. On the other hand, the toner that does not reach the developing chamber 31b falls into the inside of the toner storage chamber 31a and remains at the bottom of the toner storage chamber 31a, and returns to its original state. By repeating this cycle, the toner is stirred and transported.

<Setting of DC voltage applied to supply roller in embodiment 1>
The toner particles 200 having a particle size distribution with a weight average particle size of about 7 μm in the center are negatively charged by friction due to the rubbing action between the developing roller 25 and the developing blade 35, and are developed.

However, toner on the smaller particle size side of the particle size distribution (hereinafter referred to as fine particle toner) tends to obtain a high charge due to frictional charging, and may be strongly electrically attracted to the developing roller 25, and may be collected directly into the developing chamber 31b without being used for development. This is particularly noticeable when a low-print image in which the toner particles 200 are not used much for development is repeatedly printed.

The fine toner particles that are once triboelectrically charged but not used in the developing section are collected and remain in the developing chamber 31b, are then supplied to the developing roller 25 again, and are collected again without being used in development. When this process is repeated, the fine toner particles gain an electric charge each time due to triboelectric charging. As a result, the fine toner particles are charged up to a negative polarity, and when the developing blade 35 regulates the layer thickness, they may strongly adhere to the metallic developing blade 35 near the contact point with the developing roller 25 due to image force.

In this embodiment, particles (hydrotalcite particles in this embodiment) whose triboelectric series has the opposite polarity to the polarity of the toner particles are added to uniformly charge the toner particles 200 to the negative polarity. In this configuration in which other particles are added to the surface of the toner particles 200, some of the other particles (hydrotalcite particles in this embodiment) added to the toner particle surface may peel off from the toner particle surface during rubbing between the developing roller 25 and the developing blade 35. This change from the initial toner state is called toner deterioration.

The hydrotalcite particles that have been rubbed against the negatively charged toner particles 200 are collected in the developing chamber 31b in a positively charged state. When the positively charged hydrotalcite particles are again supplied to the developing roller 25 and the layer thickness is regulated by the developing blade 35, they may adhere to the metallic developing blade 35 near the contact point with the developing roller 25 due to image force.

If there is toner-derived deposits near the contact area of the developing blade 35, it will hinder the developing blade 35 from regulating the layer thickness of the toner particles 200, causing the toner coat on the developing roller 25 to become non-uniform. This results in image quality degradation, such as non-uniform images.

In this embodiment, in order to suppress adhesion of toner components to the developing blade 35 described above, a determination is made as to whether or not the DC voltage (hereinafter simply referred to as supply voltage Vr) applied to the supply roller 34 should be changed based on the remaining life detection result of the developing unit 4 and the total amount of toner replenished from the toner cartridge 9 to the developing unit 4, and if it is determined that a change is necessary, the DC voltage value of the supply voltage Vr is determined. In this embodiment, thresholds 1 and 2 are set as thresholds for the remaining life of the developing unit 4. In addition, a total toner replenishment amount threshold T is set at the thresholds 1 and 2.

In this embodiment, the threshold value T is set to an integrated value obtained from the total rotation distance of the developing roller 25 at the time of threshold value 2 and the consumption amount at an average printing rate of 2%. The set value of the supply voltage Vr, and the values of threshold value 1, threshold value 2, and T are recorded in the storage medium memory M of the process cartridge 70.

This embodiment is for the case where the total amount of toner replenishment does not exceed the set threshold value T. In other words, the state of the development unit 4 is such that the average print rate at the time threshold value 1 and threshold value 2 are reached is lower than 2%, and the operation when threshold value T is exceeded will be described in embodiment 2.

Figure 1(a) shows the flow for determining the supply voltage Vr, and Figure 1(b) shows the relationship between the remaining life of the development unit 4 and the supply voltage Vr.

When the image forming apparatus 100 is turned on or when a print signal is received, information stored in the memory M mounted in the process cartridge 70 is read (S101, S
If the remaining life of the developing unit 4 stored in the memory M has not reached the threshold value 1 (S103: N), it is determined that the supply voltage Vr does not need to be changed (S104), image formation is started (S109), and the supply voltage Vr determination flow ends (S110).

When the remaining life of the developing unit 4 stored in memory M reaches threshold 1 (S103: Y), it is determined whether the remaining life of the developing unit 4 has reached threshold 2 (S105). When the remaining life of the developing unit 4 has reached threshold 1 but has not yet reached threshold 2 (S105: N), it is determined to lower the supply voltage Vr (S106), and the supply voltage Vr is determined (S107). As shown in FIG. 1(b), when the process cartridge 70 is in a new condition and the remaining life of the developing unit is 100% up to threshold 1, the supply voltage Vr is set to -500 V, and when it is between threshold 1 and threshold 2, the supply voltage Vr is set to -400 V. The reason is as follows.

By applying a DC voltage of -300V as the development voltage Vdc to the development roller 25 and a supply voltage Vr of -500V to the supply roller 34, ΔVr = Vdc - Vr can be set to +200V, making it easier to supply negatively charged toner from the supply roller 34 to the development roller 25. This increases the opportunities for supplying negatively charged fine toner, which occurs when low print images are repeatedly printed, from the supply roller 34 to the development roller 25, and increases the opportunities for consumption in the development section. This reduces the fine toner ratio in the development chamber 31b from a new product until the threshold value 1 of the remaining life of the development unit, and suppresses adhesion to the development blade 35.

In addition, by applying a supply voltage Vr of -400V between threshold 1 and threshold 2 of the remaining life of the developing unit, ΔVr = Vdc - Vr becomes +100V, and the strength of the positive electric field between the developing roller 25 and the supply roller 34 can be weakened. This increases the opportunities for positively charged hydrotalcite particles that have peeled off from the surfaces of the toner particles to be supplied from the supply roller 34 to the developing roller 25, making it easier for them to be consumed in the developing section. This reduces the proportion of positively charged hydrotalcite in the developing chamber 31b, and suppresses adhesion to the developing blade 35.

Next, if the remaining life of the developing unit 4 reaches threshold 1 and also threshold 2 (S105: Y), a decision is made to increase the supply voltage Vr (S108), the supply voltage Vr is determined (S107), and image formation is started (S109). As shown in FIG. 1(b), the supply voltage Vr is set to -500 V after threshold 2. The reason is as follows.

By applying a supply voltage Vr of -400V between threshold 1 and threshold 2 of the remaining life of the developing unit, ΔVr = Vdc - Vr is set to +100V, and although the positively charged hydrotalcite particles can be consumed, the consumption of fine particle toner is suppressed. In order to suppress the resulting increase in the fine particle toner ratio in the developing chamber 31b, a supply voltage Vr of -500V is again applied and ΔVr = Vdc - Vr is set to +200V, increasing the opportunities for negatively charged fine particle toner to be supplied from the supply roller 34 to the developing roller 25, making it easier to consume in the developing section.

<Evaluation test>
A durability test was performed using the image forming apparatus 100 and the developing unit 4 of this embodiment. The evaluation conditions were continuous printing of 10,000 sheets of A4 size images with a print rate of 1.5%, and the lifespan of the developing unit 4 was determined to be 10,000 sheets. The evaluation environment was 25° C./50% RH. The threshold value 1 of the developing unit 4 described above was set to the total rotation distance of the developing roller 25 corresponding to 3,500 sheets, the threshold value 2 was set to the total rotation distance of the developing roller 25 corresponding to 7,000 sheets, and the threshold value T, which is the total amount of toner replenishment, was set to 35 g.

Comparative example 1-1 was a configuration in which the supply voltage Vr was set to -500V from a new product state throughout the life of the developing unit 4, comparative example 1-2 was a configuration in which the supply voltage Vr was set to -400V from a new product state throughout the life of the developing unit 4, and comparative example 1-3 was a configuration in which the supply voltage Vr was -500V from a new product state to threshold value 1 of the developing unit 4, and the supply voltage Vr was -400V from threshold value 1 to the end of the life of the developing unit 4. The results of image quality degradation at the time when the developing unit 4 reached the end of its life are shown below.

As a result, while the configuration of Example 1 was able to reach the end of the life of the developing unit 4 without any degradation in image quality, Comparative Examples 1-1, 1-2, and 1-3 all showed vertical streaks caused by fine toner particles and hydrotalcite particles adhering to the developing blade 35.

In Comparative Example 1-1, the supply voltage Vr was constant at -500V, so it was possible to efficiently supply negative polarity fine particle toner to the developing roller 25, but the ratio of positive polarity hydrotalcite particles in the developing chamber 31b increased. As a result, the hydrotalcite particles adhered to the developing blade 35, and the fine particle toner was electrically attracted to the adhered hydrotalcite particles, promoting adhesion. As a result, vertical streak images were generated.

In Comparative Example 1-2, the supply voltage Vr was constant at -400V, so it was possible to efficiently supply positive polarity hydrotalcite particles to the developing roller 25, but the ratio of negative polarity fine particle toner in the developing chamber 31b increased. As a result, the fine particle toner adhered to the developing blade 35, and the hydrotalcite particles were electrically attracted to the adhered fine particle toner, promoting adhesion. As a result, vertical streak images were generated.

Comparative Example 1-3 has a configuration in which the supply voltage Vr is constant at -500V up to threshold 1, and is set to -400V from threshold 2 onwards. As a result, this configuration was able to consume fine particle toner and hydrotalcite particles more effectively than Comparative Examples 1 and 2, but because the supply voltage Vr was applied for a long period of time at -400V, the ratio of fine particle toner increased as the developing unit 4 was nearing the end of its life. As a result, the fine particle toner adhered to the developing blade 35, and the hydrotalcite particles were electrically attracted to the adhered fine particle toner, promoting adhesion. As a result, although the degree was better than Comparative Examples 1-1 and 1-2, vertical streak images were generated.

As explained above, the toner fine particle ratio and hydrotalcite ratio in the developing chamber 31b can be reduced by manipulating the supply voltage Vr. This makes it possible to suppress adhesion to each developing blade 35, and it is possible to suppress image quality degradation caused by toner degradation with only normal image formation operations, without forcibly consuming toner, which would reduce the efficiency of toner use.

In this embodiment, similar to the first embodiment, the DC voltage applied to the supply roller 34 is changed based on the remaining life of the developing unit 4 and the total amount of toner supplied from the toner cartridge 9 to the developing unit 4, depending on the usage conditions. In this embodiment, the operation when the average printing rate is greater than 2% is described.

<Setting of DC voltage applied to toner supply roller>
For the remaining life of the developing unit 4, a threshold value 1 was set at the first half of the life and a threshold value 2 was set at the middle of the life, and the total replenishment amount was set at threshold values T1 and T2 corresponding to the total replenishment amount at an average printing rate of less than 2% and less than 10%.

Figure 2(a) shows the flow for determining the supply voltage Vr, and Figure 2(b) shows the relationship between the remaining life of the development unit 4 and the supply voltage Vr.

When the image forming apparatus 100 is turned on or when a print signal is received, information stored in the memory M mounted in the process cartridge 70 is read (S201, S
If the remaining life of the developing unit 4 stored in the memory M has not reached the threshold value 1 (S203: N), it is determined that the supply voltage Vr does not need to be changed (S204), image formation is started (S209), and the supply voltage Vr determination flow ends (S210).

When the remaining life of the developing unit 4 stored in the memory M reaches threshold 1 (S203: Y), it is determined whether the remaining life of the developing unit 4 reaches threshold 2 (S205). When the remaining life of the developing unit 4 reaches threshold 1 but does not reach threshold 2 (S205: N), it is determined whether the total toner supply amount value reaches T1 or T2 (S206). Next, the supply voltage Vr to be applied to the supply roller 34 is determined according to the total toner supply amount result (S207). As shown in FIG. 2B, when the process cartridge 70 is in a new state and the remaining life of the developing unit is 100% to threshold 1, the supply voltage Vr is set to -500V, and when the remaining life of the developing unit is T1 or more and less than T2, the supply voltage Vr is set to -400V from threshold 1 to threshold 2, and when the remaining life of the developing unit is T2 or more, the supply voltage Vr is set to -350V.

Next, if the remaining life of the developing unit 4 reaches threshold 1 and also threshold 2 (S205: Y), it is determined whether the total replenishment amount has reached T1 or T2 (S208). The supply voltage Vr to be applied to the supply roller 34 is determined according to the remaining life threshold and the total replenishment amount result (S207), and image formation is started (S209). As shown in FIG. 2(b), from threshold 2 onwards, the supply voltage Vr is set to -350 V between T1 and T2, and -300 V for T2 or more.

The reason for determining the supply voltage Vr applied to the supply roller 34 in this embodiment is as follows. When new, a DC voltage of -300V is applied as the development voltage Vdc to the development roller 25, and a supply voltage Vr of -500V is applied to the supply roller 34, making ΔVr = Vdc - Vr +200V, and negatively charged toner can be actively supplied from the supply roller 34 to the development roller 25. This also addresses the problem of the density not tracking from the leading edge to the trailing edge of an all-black image, which is an issue when high-print images are repeatedly printed (hereinafter referred to as all-black tracking failure).

Hydrotalcite particles, which have an opposite charge polarity to the toner particles, are added to the surface of the toner particles. While the toner particles are negatively charged due to frictional charging, the hydrotalcite particles are positively charged, which is the opposite polarity to the toner particles. The hydrotalcite particles act as microcarriers, allowing the toner particles to be uniformly charged to the negative polarity.

In this embodiment, the hydrotalcite particles actively perform triboelectric charging, so that some of the hydrotalcite particles exist alone. When a high-printing image is repeatedly printed, toner is supplied into the developing chamber 31b according to the amount of toner consumed. During printing, the toner particles and the added hydrotalcite particles are consumed, but the hydrotalcite particles that exist alone remain in the developing chamber 31b. As the printing rate increases, the amount of replenished toner increases and more new toner is supplied, so the ratio of hydrotalcite particles in the developing chamber 31b increases relatively with durability compared to when it was new. As mentioned above, when the ratio of positively charged hydrotalcite particles increases, when the developing blade 35 regulates the layer thickness, they may adhere to the metal developing blade 35 near the contact portion with the developing roller 25 due to image force. If such adhesions exist, it will hinder the layer thickness regulation by the developing blade 35, making the toner coat on the developing roller 25 uneven and causing image quality deterioration.

On the other hand, as the ratio of hydrotalcite particles increases, the toner becomes more likely to be negatively charged. Even when high-print images are repeatedly printed, the chargeability does not decrease significantly and full-black tracking failure does not occur, making it possible to change the supply voltage Vr from the initial -500V to -400V to -300V depending on the printing rate.

In this embodiment, the supply voltage Vr is adjusted so that the ratio of hydrotalcite particles remains below a predetermined value throughout durability. The ratio of hydrotalcite particles increases as the remaining life of the development unit 4 decreases and as the total toner supply amount value increases. Therefore, as described above, the potential difference (ΔVr) between the development roller 25 and the supply roller 34 is reduced to increase the opportunities to supply positively charged hydrotalcite particles from the supply roller 34 to the development roller 25. By making it easier to consume in the development section, the ratio of positively charged hydrotalcite particles in the development chamber 31b can be reduced, and adhesion to the development blade 35 can be suppressed.

<Evaluation Test 2>
An experiment conducted to demonstrate the effect of this embodiment will now be described. In this experiment, continuous durability tests were conducted on 10,000 sheets at 4% and 20% horizontal lines in an environment of 25° C. temperature and 50% humidity, and image quality degradation was evaluated. The threshold value 1 of the developing unit 4 described above was set to the number of rotations of the developing roller 25 equivalent to 3,500 sheets, and the threshold value 2 was set to the number of rotations of the developing roller 25 equivalent to 7,000 sheets.

The supply voltage Vr applied to the supply roller 34 in this embodiment was set as described in FIG. 2(b) based on the remaining life of the developing unit 4 and the detection result of the total amount of toner supplied from the toner cartridge 9 to the developing unit 4. As Comparative Example 2-1 for comparing the effect of this embodiment, the supply voltage Vr was set to -500V over the entire life with a horizontal line of 4%, and as Comparative Example 2-2, the supply voltage Vr was set to -300V over the entire life with a horizontal line of 20%.

<Verification result 2>
The verification results are shown below.

The configuration of Example 2 did not experience image degradation until the development unit 4 reached the end of its life, but Comparative Example 2-1 experienced vertical streaks caused by hydrotalcite particles adhering to the development blade 35. On the other hand, Comparative Example 2-2 did not experience vertical streaks, but did experience poor all-black tracking.

In Comparative Example 2-1, the supply voltage Vr was constant at -500V, so the configuration was such that negative polarity fine particle toner could be efficiently supplied to the developing roller 25, but the ratio of positive polarity hydrotalcite particles in the developing chamber 31b increased. As a result, the hydrotalcite particles adhered to the developing blade 35, resulting in the generation of vertical streak images.

In Comparative Example 2-2, the supply voltage Vr was low at -300 V, so toner could not be actively supplied from the supply roller 34 to the developing roller 25, and an initial full black tracking failure occurred.

As explained above, the ratio of hydrotalcite in the developing chamber 31b can be set to a predetermined value or less by manipulating the supply voltage Vr. This makes it possible to suppress adhesion to the developing blade 35, and suppresses image quality degradation caused by toner degradation through normal image formation operations alone, without forcibly consuming toner, which would reduce the efficiency of toner use.

4 (4a to 4d) Developing unit 9 Toner cartridge 25 (25a to 25d) Developing roller 31a Toner storage chamber 31b Developing chamber 31c Opening 34 Supply roller 35 Developing blade 40 Toner receiving port 70 (70Y, 70M, 70C, 70K) Process cartridge 100 Image forming device 200 (200Y, 200M, 200C, 200K) Toner

Claims (5)

a developer in which particles that have a positive polarity in the triboelectric series with respect to the toner particles are added to the toner particles;
a developer container for containing the developer;
a developer carrier for carrying and transporting the developer;
a developer supplying member for supplying the developer to the developer carrying member;
a developer regulating member that is in contact with the developer carrying member and regulates a thickness of a developer layer;
a developer carrier bias applying means for applying a bias to the developer carrier;
a developer supply member bias applying means for applying a bias to the developer supply member;
a developing device including
A supplying means for supplying the developer to the developer container;
a developing device remaining life detection means for detecting a remaining life of the developing device;
a developer total supply amount detection means for detecting a total amount of developer supplied to the developer storage container,
an amount of supply bias applied by said developer supply member bias application means based on a detection result from said developing device remaining life detection means and a detection result from said developer total replenishment amount detection means; The image forming apparatus according to claim 1, characterized in that the timing for determining the amount of the supply bias applied by the developer supply member bias application means occurs at least twice throughout the period from when the developing device remaining life detection means starts detecting the life until it detects the end of the life, and has at least one total supply amount threshold for determining the amount of the supply bias applied from the total supply amount detection result by the total supply amount detection means, and the amount of the supply bias applied is determined based on the developing device remaining life detection result and the total supply amount detection result obtained at the timing for determining the amount of the supply bias applied. The absolute value of the supply bias application amount in the section up to the first change determination time of the supply bias application amount is |RS1|,
The absolute value of the supply bias application amount in the section from the first change determination time to the second change determination time is |RS2|,
The absolute value of the supply bias application amount in the section after the second change determination time is |RS3|,
An image forming apparatus as described in claim 1 or 2, characterized in that when the total replenishment amount detection result of the developer at the time of determining whether to change the amount of applied supply bias is less than the threshold value of the total replenishment amount detection result, the relationship between |RS1|, |RS2|, and |RS3| is |RS1|>|RS2| and |RS2|<|RS3|. The image forming apparatus according to any one of claims 1 to 3, characterized in that the relationship between |RS1|, |RS2|, and |RS3| when the total replenishment amount detection result of the developer at the time of determining whether to change the amount of applied supply bias is greater than the total replenishment amount threshold is |RS1|>|RS2| and |RS2|>|RS3|. The image forming apparatus according to any one of claims 1 to 4, characterized in that the developer regulating member is a metal leaf spring member.