JP4630605B2 - Image forming apparatus - Google Patents

Description

  In the present invention, for example, an electrostatic latent image formed on an image carrier using an electrophotographic system or an electrostatic recording system is visualized by using a developing device to form a visible image. The present invention relates to an image forming apparatus that obtains a permanent image by being transferred and fixed thereon.

  Here, the electrophotographic image forming apparatus includes, for example, a copying machine, a printer (for example, an LED printer, a laser beam printer, etc.), a facsimile apparatus, and a word processor.

  The process cartridge is a cartridge in which a charging means, a developer carrier or a cleaning means and an electrophotographic photosensitive member (image carrier) are integrally formed, and the cartridge can be attached to and detached from the image forming apparatus main body. It is. Alternatively, at least one of the charging unit, the developer carrying member, and the cleaning unit and the electrophotographic photosensitive member are integrally formed into a cartridge that can be attached to and detached from the image forming apparatus main body. Alternatively, it means that at least the developer carrying member and the electrophotographic photosensitive member are integrated into a cartridge so as to be detachable from the image forming apparatus main body.

  2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, when toner as a developer is used and toner in the image forming apparatus is consumed, a toner supply container as a developer supply container that is detachable from the image forming apparatus is replaced with a new one. 2. Description of the Related Art An image forming apparatus that supplies toner to an apparatus by replacing the toner supply container is known.

  FIG. 11 is a cross-sectional view illustrating an example of a schematic configuration of a conventional image forming apparatus. As shown in FIG. 11, an electrophotographic photosensitive member (hereinafter referred to as a “photosensitive drum”) as an image carrier, for example, a photosensitive drum, that is, a photosensitive drum, is provided at almost the center of a conventional image forming apparatus. 100 is supported rotatably in the direction of the arrow.

  When the image forming operation is started, the charging unit 200 uniformly charges the surface of the photosensitive drum 100. Thereafter, for example, a laser irradiation unit 300 as an exposure unit exposes the surface of the photosensitive drum charged by a laser corresponding to the image information, and forms an electrostatic latent image on the surface. The developing device 400 is visualized by a developer that supplies the formed electrostatic latent image, and forms a so-called toner image.

  This toner image is electrostatically transferred onto the recording material P by a transfer electric field formed between the photosensitive drum 100 and the transfer roller 600 by, for example, a transfer roller 600 as transfer means. Thereafter, the unfixed toner image on the recording material P is fixed on the recording material P by heat and pressure in the fixing device 800.

  In addition, transfer residual toner or the like remaining on the surface of the photosensitive drum 100 after the transfer of the toner image is removed by, for example, a cleaning device 700 including a blade-shaped cleaning member, and the photosensitive drum 100 can continue to form an image. Become.

  Next, the developing device 400 used in the conventional image forming apparatus will be further described.

  The developing device 400 uses a one-component developer as a developer, and particularly uses a non-magnetic one-component developer. Hereinafter, unless otherwise specified, the non-magnetic one-component developer is simply referred to as “toner”.

  In the developing device 400, the developer container 416 contains toner, and has a developing roller 411 as a developer carrying member and a supply roller 413 as a developer supply means. The toner on the developing roller 411 is transferred to an electrostatic latent image on the photosensitive drum 100 as it rotates, and a toner image is formed on the photosensitive drum 100.

  The developing container 416 is rotatably provided with a stirring paddle 414 that is a means for stirring and transporting the developer. Further, a toner amount detecting means 415 made of a piezoelectric element or the like is provided in the vicinity of the stirring paddle. Above the developing container 416, a toner supply mechanism 500 including a removable toner container is provided.

  When the toner amount detection means 415 detects that the toner in the developing container 16 has decreased due to the use of the image forming apparatus, the image forming apparatus issues a toner replenishment request, and a constant amount of toner is replenished from the toner replenishment mechanism 500. When an appropriate amount of toner is supplied, the toner amount detection unit 415 does not detect a decrease in the toner amount, so that the toner supply request of the image forming apparatus is eliminated, and the normal printing operation is continued.

  In this patent document 1, the amount of the developer in the developer reservoir is determined in advance by the developer amount detection sensor in order to detect or estimate the amount of the developer in the developing device and replenish it sequentially. An image forming apparatus is described in which the developer supply means is driven to supply the developer to the developer reservoir when the amount is detected to be less than the predetermined amount.

  Japanese Patent Application Laid-Open No. 2005-228561 detects a remaining amount of developer in the developing chamber by a toner remaining amount detecting unit, and supplies a fixed amount of developer from the developer storage unit to the developing chamber according to the detection output. Is described.

  In Patent Document 3, the level detection means detects the level of the one-component developer inside the one-component developing device, and supplies the one-component developer from the developer container according to the detected level. An image forming apparatus is described in which the level of one-component developer inside the component developing apparatus is controlled to be constant.

  However, the image forming apparatus described above may have the following problems.

  FIG. 10 is a graph showing the transition of the toner amount in the developing container. In general, it is desirable to keep the toner amount in the developing container at a constant level without increasing or decreasing as much as possible. When the toner amount is extremely increased or decreased, an image when the toner amount is large and when the toner amount is small may appear as a density difference. Further, the increase / decrease in the toner amount indicates that the toner replenishment amount is large or the replenishment frequency tends to be small. If a large amount of toner is replenished at one time, the charge amount of the toner in the developing container and the new toner newly replenished from the replenishing device will not be uniform, resulting in uneven density and fogging.

  As the use of the developing device progresses and the toner in the developing container deteriorates, the difference in charge amount between the two toners becomes even greater. As a result, in the worst case, a toner with a low charge amount electrostatically aggregates around a toner with a high charge amount to form a large toner lump, which falls from the developing container into the recording material or the image forming apparatus main body. (Spotting) can also occur.

Conversely, in order to avoid such a situation, if the amount of toner to be replenished at one time is set to a small value, the toner consumption will increase if the toner consumption increases significantly as in the case of high-printing images. In some cases, the supply cannot catch up. In this case, the amount of toner in the developing container decreases despite the continuous replenishment, and there is a possibility that a part of the image is not developed and the image is whitened.

  Therefore, ideally, it is desirable that the amount of toner to be replenished at one time is small and the number of replenishments is increased accordingly. For this purpose, it is desirable to always read the toner amount in the developing container accurately and replenish an appropriate amount, and to keep the toner amount in the developing container constant at all times. However, the toner amount in the developing container can be accurately measured with a single sensor. It is very difficult to read.

This is because when a single sensor is used for replenishment, as described above, it is only possible to replenish a fixed amount with respect to the threshold value, so that an appropriate toner amount cannot be replenished in real time according to toner consumption. It is. As a result, the amount of toner in the developing container increases and decreases periodically, and in the worst case, either the toner replenishment amount tends to be excessive or insufficient, and the above-described problem may occur.
Japanese Patent Laid-Open No. 9-80894 Japanese Patent Laid-Open No. 10-20640 JP 2002-40776 A

  The present invention has been made in view of the above-described prior art, and an object thereof is to realize a highly accurate developer replenishment to the developing device.

In order to achieve the above object, in the image forming apparatus according to the present invention, an image carrier on which an electrostatic latent image is formed, a developing device that develops the electrostatic latent image, and consumption when developing. A developer consumption amount calculating means for calculating the developer consumption amount according to the image printing ratio of the electrostatic latent image, a developer supply device for supplying the developer to the developer device, and the developer consumption amount according to the developer consumption amount. Control means for controlling the amount of developer replenished from the developer replenishing device, wherein the developing device carries and conveys the developer, a developing container for housing the developer, A developer carrying member that develops the electrostatic latent image on the image carrying member; and a developer amount detecting unit that detects a developer amount in the developing container; and the developer amount detecting unit includes: Detecting at least two levels of developer in the developer container, and When a level with a small amount of developer is detected among the two levels, control is performed so that a developer replenishing amount larger than the developer consumption amount is replenished from the developer replenishing device, and the developer among the two levels is controlled. When a level with a large amount is detected, control is performed so that a developer replenishment amount smaller than the developer consumption amount is replenished from the developer replenishing device .

  According to the present invention, it is possible to provide an image forming apparatus capable of supplying a developer with high accuracy to the developing device.

  In addition, an image forming apparatus capable of forming a high-quality image over a long period of time can be provided.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings and embodiments. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. . Further, the materials, shapes, etc. of the members once described in the following description are the same as those in the first description unless otherwise described.

  FIG. 1 is a cross-sectional view illustrating a schematic configuration of the image forming apparatus according to the present embodiment. FIG. 2 is a cross-sectional view illustrating a schematic configuration of the developing device according to the present embodiment.

  The image forming apparatus main body X according to this embodiment includes an image carrier (hereinafter referred to as “photosensitive drum”) 1 which is a drum-shaped electrophotographic photosensitive member on which an electrostatic latent image is formed, and an electrostatic latent image. A developing device 4 for developing, a developer consumption calculating means for calculating the developer consumption consumed in developing according to the image printing ratio of the electrostatic latent image, and a development for supplying the developer to the developing device 4 And a control unit (not shown) for controlling the replenishment of the developer from the toner hopper 5 in accordance with the developer consumption amount. Here, for example, a CPU or a dedicated electric circuit can be used as the control means.

  The image forming apparatus main body X supports the photosensitive drum 1 so as to be rotatable in the direction of the arrow at substantially the center thereof. When the image forming operation starts, the charging unit 2 uniformly charges the surface of the photosensitive drum 1. Thereafter, an exposure device 3 comprising laser irradiation means exposes the surface of the photosensitive drum 1 with a laser beam corresponding to image information, and forms an electrostatic latent image on the photosensitive drum 1.

  In this embodiment, the charged charge of the photosensitive drum 1 is negative. Then, the electrostatic latent image corresponding to the image information is formed in the portion where the negatively charged charge is attenuated by the exposure with the laser beam from the exposure device 3.

  Thereafter, the electrostatic latent image is visualized by toner as a kind of developer supplied by the developing device 4 as the photosensitive drum 1 rotates, and a toner image is formed on the photosensitive drum 1.

  In this embodiment, the developing method is a reversal developing method. Therefore, toner having the same polarity (negative polarity) as the charged charge adheres to the portion (image portion) on the photosensitive drum 1 where the negative charged charge is attenuated. The toner is supplied from the toner hopper 5 to the developing device 4.

  On the other hand, the recording material P accommodated in a cassette (not shown) is transferred to the transfer area where the photosensitive drum 1 and the transfer roller 6 serving as a transfer unit abut with each other by the paper feed roller 9. It is conveyed synchronously.

  When the toner image on the photosensitive drum 1 and the recording material P reach the transfer area, the toner image is transferred onto the recording material P by the transfer electric field formed in the transfer area by the transfer roller 6. Thereafter, the unfixed toner image carried on the recording material P is heated by a fixing unit (heat roller) 8a included in the fixing device 8 and is pressed by the pressing unit 8b, so that a permanent image is formed on the recording material P. As established.

  Further, after the toner image transfer is completed, the transfer residual toner remaining on the surface of the photosensitive drum 1 is removed by a cleaning device 7 including a blade-like cleaning unit, and the photosensitive drum 1 is prepared for a subsequent image forming operation.

  Next, the developing device will be described with reference to FIG.

  The developing device 4 supplies a toner to the developing container 16 that stores toner, a developing roller 11 that carries and carries the toner, and develops the electrostatic latent image on the photosensitive drum 1, and the developing roller 11. A supply roller 13 as a developer supply means, a blade 12 as a developer restriction means for regulating the toner supplied by the supply roller 13 to form a toner layer on the photosensitive drum 1, and replenishment from the toner hopper 5 Agitating paddle 14 as a developer agitating means that is movable to mix the toner and the toner in the developing container 16, and a toner surface detecting means 15 as a developer amount detecting means that detects the amount of toner in the developing container 16. And having. Here, the developing device 4 is configured to be detachable from the image forming apparatus main body X. According to this configuration, the developing device can be easily replaced.

  The developer used in this embodiment is a negatively chargeable non-magnetic one-component developer (hereinafter referred to as “toner”). Further, the process speed of the image forming apparatus main body X according to this embodiment, that is, the peripheral speed of the photosensitive drum 1 is 150 mm / Sec, and the peripheral speed of the developing roller 11 is 225 mm / Sec.

The developing roller 11 has a volume resistivity of 1 Ωm (10 ² Ωcm) to 10 ⁸ Ωm (10 ¹⁰ Ωcm) in which a conductive agent such as carbon is dispersed. This is a semiconductive elastic roller having an outer diameter of 20 mm constituted by the combination. The developing roller 11 includes an elastic body and is in contact with the photosensitive drum 1 with a predetermined contact pressure.

  The supply roller 13 as a developer supply / collection means is an elastic roller including an elastic body, and is arranged so that an insulating sponge roller having an outer diameter of 16 mm contacts the development roller 11.

  The developing container 16 is partially open on the side facing the photosensitive drum 1. A developing roller 11 as a developer carrying member is supported by the developing container 16 so as to be partially exposed from the opening so as to be rotatable in the arrow direction.

  An agitation paddle 14 as a developer agitating / conveying means is provided at the inner side opposite to the opening of the developing container 16 to be rotatable in the direction of the arrow. The agitation paddle 14 agitates the toner in the developing container 16 and conveys the toner to a region in the vicinity of a contact portion between the developing roller 11 and a supply roller 13 described later. As the supplied toner 13 rotates in the direction of the arrow, the conveyed toner is charged with toner due to frictional charging due to rubbing against the developing roller 11 in contact therewith. The charged toner is carried on the developing roller 11 by receiving a reflection force from the developing roller 11 by the charged charge.

  The developing container 16 is provided with a blade 12 as a developer layer pressure regulating member so as to pressurize the developing roller 11. The blade 12 is a leaf spring made of SUS having an L-shape, and comes into contact with the developing roller 11 at an L-shaped edge as understood in FIG.

  The toner supplied onto the developing roller 11 is subjected to layer thickness regulation and charge application by the blade 12, and a thin layer of toner is formed on the developing roller 11 and supplied to the developing region.

  On the other hand, the toner that does not contribute to the development and remains carried on the developing roller 11 is peeled off from the developing roller 11 by rubbing by the supplying roller 13, and a part of the toner is newly supplied onto the supplying roller 13. The supplied toner is supplied again onto the developing roller 11 by the supply roller 13, and the rest is returned to the developing container 16.

  In this embodiment, the supply roller 13 has two functions as the developer supply and recovery means. However, the present invention is not limited to this, and the developer supply means and the developer recovery means are provided. It may be provided separately.

  The developing device 4 is configured to be detachable from the image forming apparatus main body X, and can be replaced with a predetermined life (in this embodiment, set to 30,000 sheets in terms of A4 size). Yes.

The image forming apparatus main body X detects the toner amount in the developing container 16 by obtaining the toner surface height information from the toner surface detecting means 15, and is within the movable range of the stirring paddle 14 by the control procedure described later. The replenishment from the toner hopper 5 is controlled so that the toner surface is maintained within a certain range from the toner surface control level γ ′ to δ ′ in FIG.

  In the toner hopper 5, a stirring member 54 for loosening the toner in the toner hopper 5 and a supply roller 53 for supplying toner from the toner hopper 5 to the developing device 4 are arranged. Then, a constant amount of toner per predetermined driving time can be supplied to the developing device 4 by a replenishment command from the developing device 4.

  Next, a description will be given of a video count device as a developer consumption amount calculating means for calculating the amount of toner consumed when developing in accordance with the image printing ratio of the electrostatic latent image. In this embodiment, the amount of toner consumed by the video count device and the method of optically detecting the toner surface height in the developing container are used together to determine the amount of toner to be replenished and control the operation of the toner hopper. is doing. Accordingly, since an appropriate amount of toner consumed according to the image printing ratio is supplied, the toner amount in the developing container can be maintained at a constant level without increasing or decreasing each time the toner is supplied. That is, according to the image forming apparatus of the present embodiment, it is possible to supply toner with high accuracy and to perform image formation with high image quality.

  First, the video count method will be described with reference to FIGS. FIG. 5 is a block diagram of the video count integrating device in the image forming apparatus according to the first embodiment. FIG. 6 is a schematic diagram for explaining the principle of the video count method.

  In the image forming apparatus main body X according to the present embodiment, the level of the output signal of the exposure device 3 is counted for each pixel so as to sequentially replenish the toner in the developing container consumed by the development of the electrostatic latent image. In this embodiment, this counting is performed as follows.

  The exposure device 3 is a laser scanner device, and includes a semiconductor laser (not shown), a rotating polygon mirror (also called a polygon mirror), a lens, and the like. Laser light emitted from the semiconductor laser is swept by a rotating polygon mirror, and is spot-imaged on the photosensitive drum 1 by a lens such as an f / θ lens and a fixed mirror that directs the laser light toward the photosensitive drum 1. The imaged laser light scans the photosensitive drum 1 in a direction (main scanning direction) substantially parallel to the rotation axis of the photosensitive drum 1 to form an electrostatic latent image.

  An image that becomes an electrostatic latent image enters a pulse width modulation circuit 31 from a personal computer or an image input scanner via an image processing circuit 30 and has a width (time length) corresponding to the level for each input pixel image signal. The laser drive pulse is supplied to the exposure device 3.

  Specifically, as shown in FIG. 6A, a wider laser drive pulse W is used for a high density pixel image signal, and a narrower laser is used for a low density pixel image signal. For the drive pulse S, a medium-width laser drive pulse I is formed for a medium-density pixel image signal.

  The laser drive pulse output from the pulse width modulation circuit 31 is supplied to the exposure device 3, and the exposure device 3 causes the semiconductor laser to emit light for a time corresponding to the pulse width. Therefore, the semiconductor laser is driven for a longer time for a high density pixel and is driven for a shorter time for a low density pixel.

  Therefore, the photosensitive drum 1 is exposed in a long range in the main scanning direction for high density pixels, and is exposed in a short range in the main scanning direction for low density pixels. That is, the dot size of the electrostatic latent image is different according to the pixel density. Therefore, the toner consumption amount for the high density pixel is larger than the toner consumption amount for the low density pixel. FIG. 6D schematically shows the shapes L, M, and H of the electrostatic latent images of low, medium, and high density pixels.

  In addition to the above processing, the output signal of the pulse width modulation circuit 31 is supplied to one input of the AND gate 33. A clock pulse (pulse shown in FIG. 6B) from the clock pulse oscillator 32 is supplied to the other input of the AND gate 33. Accordingly, as shown in FIG. 6A, the AND gate 33 makes a number of clock pulses corresponding to the pulse width of each of the laser driving pulses S, I and W, that is, a number of clock pulses corresponding to the density of each pixel. Is output. The number of clock pulses is accumulated by the counter 34 for each image, and the video count number corresponding to the image printing ratio of the electrostatic latent image is finally calculated by adding the respective pixels to the output image.

  The video count number substantially corresponds to the amount of toner consumed by the developing device 4 to form a toner image of the output image. Therefore, this video count number is supplied to the CPU 35. The CPU 35 calculates the amount of toner consumed by the developing device 4 based on the video count number, and drives the toner hopper 5 for a necessary time to replenish the developing container 16 with toner. Here, the developer consumption calculation means is constituted by the counter 34 and the CPU 35.

  Generally, when the video count number is large, the driving time of the toner hopper 5 is longer. When the video count number is small, the driving time of the toner hopper 5 is shorter.

  Although the amount of toner in the developing container 16 can be kept constant by supplying toner based on the video count, the amount of toner consumed for the same image actually varies slightly due to fluctuations in image density. When the image is dark, the toner consumption is larger than the calculation, and when the image is light, the toner consumption is smaller than the calculation. If toner supply based on the video count is continued in such a state, the toner amount in the developing container gradually increases or decreases. Therefore, in this embodiment, a means for directly detecting the toner amount in the developing container is also used.

  Next, a toner surface detection unit that detects the amount of toner in the developing container 16 will be described.

  The developing container 16 is provided with a stirring paddle 14 so as to be rotatable in the direction of the arrow, and has a stirring region for stirring the toner in the developing container 16 and the toner replenished from the toner hopper 5. Further, a toner surface detection unit 15 as an optical detection unit for detecting the height of the toner surface in the stirring region is disposed on the outside of the developing container 16 with the stirring region interposed therebetween.

  The toner surface detecting means 15 has a light emitting part 15a made of a light emitting element, a window part 15b through which light is transmitted, and a light receiving part 15c made of a light receiving element. Then, when the surface of the toner changes as the stirring paddle 14 rotates, the ratio of the light transmission time to the time during which the stirring paddle 14 rotates once is measured to obtain the height information of the toner surface in the stirring region. ing.

  The toner surface detecting means 15 according to this embodiment can detect at least two levels of developer in the developing container 16. When a CPU (not shown) serving as a control unit detects a level where the toner amount is low among the two levels, the toner hopper 5 supplies a toner replenishment amount larger than the toner consumption amount calculated by the developer consumption amount calculation unit. If the toner level is detected from the two levels, the toner hopper 5 is controlled to supply a toner supply amount smaller than the toner consumption amount. According to this configuration, it is possible to reliably avoid a situation in which the toner consumption calculated from the image printing ratio does not match the actual due to density fluctuation.

More specifically, the image forming apparatus main body X receives the information on the height of the toner surface from the toner surface detection means 15 and determines that the toner surface has decreased to the first level γ ′ (see FIG. 2) or less. If detected, it is determined that the toner amount has decreased below a predetermined amount, and a toner level Low signal is issued. When the toner surface height information from the toner surface detecting means 15 is received and it is detected that the toner surface has increased to the second level δ ′ (see FIG. 2) or more, the toner amount is larger than a predetermined amount. It is determined that the toner level has increased, and a toner level Hi signal is issued. Here, when it is determined that the toner surface is between the first level γ ′ and the second level δ ′, no signal is generated.

  Next, the replenishment operation of the image forming apparatus in this embodiment will be described. FIG. 3 is a flowchart of the toner supply operation of the image forming apparatus according to the first embodiment.

  When it is detected that the power source of the image forming apparatus main body X is turned on (step S1), a predetermined start-up preparation is performed and a standby state (step S2) is entered. When the input of the print signal (step S3) is detected in the standby state (YES), the printing operation starts (step S4), and the photosensitive drum, the charging device, the exposure device, etc. are sequentially activated.

  The developing device 4 stands by until it is time to develop, and the developing roller 11 rotates only when developing is performed (step S5). Simultaneously with the rotation of the developing roller 11, the stirring paddle 14 rotates to start stirring the developer.

  The exposure device 3 operates to form a latent image on the photosensitive drum 1 (step S6), and acquisition of video count data is started at the same time (step S7). Further, the toner surface (toner amount) detecting means 15 is activated (step S8), and the toner surface height (toner amount) in the developing container 16 is measured (step S9). When the latent image formation is completed, the exposure apparatus 3 is stopped (step S10), and at the same time, the video count integration is completed and the integrated value is acquired (step S11).

  The CPU determines the presence / absence of a toner level Low signal and a toner level Hi signal from the toner surface height information obtained in step S9 (step S12). If there is no signal, the toner replenishment amount calculated based on the video count value is not corrected (step S13). On the other hand, when the toner level Hi signal is detected, it means that the amount of toner consumption is less than expected, and the correction coefficient is manipulated so that the amount of toner replenishment calculated based on the video count value is reduced (step). S14). Further, when the toner level low signal is detected, it means that the amount of toner consumption is larger than expected, and the correction coefficient is manipulated so that the toner replenishment amount calculated based on the video count value increases (step). S15).

  Based on the correction, a toner replenishment amount is determined (step S16), the toner hopper 5 is driven for a time corresponding to the toner replenishment amount, and toner is replenished (step S17), and the developing roller 11 is stopped (step S16). S18).

  Here, the CPU determines whether or not the job has ended (step S19), and if there are prints that have not been completed yet and are to be continuously performed (No), the image forming apparatus body X enters the next cycle again. Therefore, the process returns to step S5. On the other hand, if there is no remaining number of jobs, it is determined that the job has ended (Yes), and the post-rotation toner supply mode is entered to return to the standby state.

  The various conditions in this embodiment assume that the toner remaining amount in the developing container 16 is 60 g, and the toner surface height detection means 15 is adjusted so that a toner level low signal is output when it is 50 g or less and a toner level Hi signal is output when it is 70 g or more. did. Further, the replenishment amount is reduced by 10% by negative correction by the toner level Hi signal, and the replenishment amount is increased by 10% by positive correction by the toner level Low signal.

In this embodiment, assuming that the toner loading amount on the photosensitive drum 1 is A, the paper area is S, the image printing ratio is R, and the correction coefficient by the optical detection means is X.
(I) No correction, A = 0.6 mg / cm ² , S = 21.0 × 29.7 cm ² (for A4 size), no correction,
When the printing ratio is 100%, 0.6 × 21.0 × 29.7 × 1.00 = 374 mg,
When the printing ratio is 5%, 0.6 × 21.0 × 29.7 × 0.05 = 19 mg,
It becomes.

(Ii) Under the condition of minus correction (10%) by the toner level Hi signal,
When the printing ratio is 100%, 0.6 × 21.0 × 29.7 × 1.00 × 0.90 = 337 mg,
When the printing ratio is 5%, 0.6 × 21.0 × 29.7 × 0.05 × 0.90 = 17 mg,
It becomes.

(Iii) Under the condition of plus correction (10%) by the toner level Low signal,
When the printing ratio is 100%, 0.6 × 21.0 × 29.7 × 1.00 × 1.10 = 412 mg,
When the printing ratio is 5%, 0.6 × 21.0 × 29.7 × 0.05 × 1.10 = 21 mg,
It becomes.

  That is, according to the present embodiment, the CPU as the control unit performs the toner consumption calculated by the developer consumption calculation unit and the toner amount (agent surface) in the developer container 16 detected by the toner surface height detection unit 15. By correcting the toner replenishment amount to be replenished from the toner hopper 5 based on the height level), it is more accurate than the case where the developer consumption calculating means and the developer amount detecting means are used alone. In addition, the amount of toner in the developing container can be controlled, and the image quality can be improved.

  For example, when the image forming apparatus main body X forms an image with a printing ratio of 100%, if the control unit determines that the amount of toner in the developing container 16 is more than 70 g, the toner consumption amount 374 mg with a printing ratio of 100%. Accordingly, the toner hopper 5 is controlled so that the developer supply amount 337 mg calculated by negatively correcting the toner consumption amount (−10%) is supplied to the developing device 4. Further, when it is determined that the toner amount in the developing container 16 is less than 50 g, the developer replenishment amount 412 mg calculated by positively correcting the toner consumption amount (+ 10%) according to the toner consumption amount 374 mg with the printing ratio of 100%. The toner hopper 5 is controlled to replenish the toner to the developing device 4.

  According to this configuration, even if the toner consumption amount calculated from the image printing ratio does not match the actual amount due to image density fluctuation, etc., the toner amount in the developing container 16 is corrected by the means for detecting. It is possible to prevent the toner amount in the developing container from deviating from a desired range because the toner replenishment amount does not match.

  FIG. 4 is a graph showing a toner amount transition in the developing container when the above control is performed in the image forming apparatus according to the first embodiment.

  In the image forming apparatus according to the present embodiment, since toner is replenished by the video count method, consumed toner can be replenished in real time. Therefore, the amount of toner in the developing container is always kept constant at a high level without abrupt fluctuation. Therefore, since a large amount of toner is not replenished at a time as in the conventional method, it is replenished little by little and sufficiently stirred in the developing container, so the charge amount between the toner in the developing container and the replenished toner It is possible to reduce the occurrence of density unevenness, fogging and blurring caused by the difference between the two.

  Further, since the toner replenishment amount to be replenished by the video count is corrected by the means for detecting the toner amount in the developing container, the replenishment toner amount calculated by the video count method due to fluctuations in the image density or the like is Even in a case where the toner consumption amount deviates, more accurate toner replenishment control can be performed. As a result, the developer amount in the developing container always converges within a desired range, and the height of the toner surface in the developing container is always kept constant.

  Using the configuration of the present embodiment, a durability test of 30,000 sheets, which is the durability life of the developing device, was performed. However, density unevenness, fogging and blurring due to poor mixing of the replenishing toner did not occur, and a good image was maintained. I was able to.

  Next, Example 2 which is another aspect of the present invention will be described.

  FIG. 7 is a cross-sectional view of a main part of a color laser printer using an electrophotographic process according to the second embodiment. FIG. 8 is a schematic sectional view of the process cartridge, and FIG. 9 is a schematic sectional view of the replenishing cartridge.

  The second embodiment is different from the first embodiment in that (1) the developing device is integrated with the photosensitive drum, the charging roller, and the cleaner unit, and can be replaced with the image forming apparatus main body X when a predetermined endurance life is reached. (2) The image forming apparatus has four color process cartridges of yellow (Y), cyan (C), magenta (M), and black (K) arranged in a row. It is an inline full-color image forming apparatus that forms an image.

  The image forming apparatus main body Y shown in FIG. 7 is a full-color laser beam printer, and an intermediate transfer body 620 that is a second image carrier that multiplex-transfers each color toner image formed on the photosensitive drum to form a full-color toner image. Is arranged.

  The developing device 24 (Y, M, C, K) having the same form as that of the first embodiment is assembled integrally with the photosensitive drum 21, the charging roller 22, and the cleaner unit 27, and is attached to and detached from the image forming apparatus main body Y. The process cartridge PC is configured as possible. According to this configuration, it is possible to easily replace consumable parts, and the maintainability is greatly improved.

  The process cartridge PC is configured to be replaceable with respect to the image forming apparatus main body Y with a predetermined endurance life. The image forming apparatus main body Y includes four process cartridges PC (Y, M, C, K) that respectively contain toners of four colors, yellow, magenta, cyan, and black, which can be attached to and detached from the image forming apparatus main body (see FIG. 8). It has.

  Since the configuration, operation, and the like of the photosensitive drum, the developing roller, the charging roller, and the like in each process cartridge PC (Y, M, C, K) are the same as those in the first embodiment, description thereof is omitted.

  The toner image formed on the surface of the photosensitive drum 21 is multiple-transferred as a color toner image onto the intermediate transfer body 620 in accordance with the arrangement order of the process cartridges PC (Y, M, C, K) of yellow, magenta, cyan, and black. The color toner image on the intermediate transfer member 620 is conveyed by a paper feed roller 920 and transferred to a recording material, and then heated and pressure-fixed by a fixing device (not shown) to be discharged as a full color image.

As shown in FIG. 9, toner hoppers 520 (Y, M, C, K) similar to those in the first exemplary embodiment are detachably attached to the image forming apparatus main body X. According to this configuration, the toner hopper 520 can be replaced with the image forming apparatus main body Y, and the toner can be easily supplied without being stained or scattered.

  In the toner hopper 520, a stirring member 524 for loosening the toner in the toner hopper 520 and a supply roller 523 for supplying toner from the toner hopper 520 to the developing device 24 are arranged. The replenishing roller 523 replenishes toner to the developing device 24 in accordance with a replenishment command from the control unit.

  In the image forming apparatus main body Y according to the present embodiment, since a multicolor image overlaps a sheet of paper, a level much higher than that of an apparatus that performs monochrome image formation is required for fogging and density unevenness. The Therefore, the toner replenishing method described in the present invention can be more suitably used for such a full-color image forming apparatus.

  In addition, these components can be easily replaced. Accordingly, the maintainability of the image forming apparatus is greatly improved. Also, by exchanging the process cartridge, important components of electrophotography are replaced with new ones, so that high quality images can always be maintained.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to Embodiment 1. FIG. 1 is a cross-sectional view of main parts of a developing device and a toner hopper according to Embodiment 1. FIG. 3 is a flowchart of a toner supply operation of the image forming apparatus according to the first embodiment. 6 is a graph showing a toner amount transition in a developing container according to Example 1. 1 is a block diagram of a video count integrating device in an image forming apparatus according to Embodiment 1. FIG. It is a schematic diagram for demonstrating the principle of a video count system. 6 is a schematic cross-sectional view of an image forming apparatus according to Embodiment 2. FIG. 6 is a schematic cross-sectional view of a process cartridge according to Embodiment 2. FIG. 6 is a schematic cross-sectional view of a toner hopper according to Embodiment 2. FIG. 7 is a graph showing a change in toner amount in a conventional developing container. It is sectional drawing which shows schematic structure of the conventional image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging means 3 Exposure apparatus (laser irradiation means)
DESCRIPTION OF SYMBOLS 4 Developing device 5 Toner hopper 8 Fixing device 11 Developing roller 12 Blade 13 Supply roller 14 Agitation paddle 15 Toner surface detection means 16 Developing container 30 Image processing circuit 31 Pulse width modulation circuit 32 Clock pulse oscillator 33 Gate 34 Counter 53 Supply roller 54 Agitation Member 520 Toner hopper 523 Replenishment roller 524 Stirring member P Recording material PC Process cartridge X Image forming apparatus main body Y Image forming apparatus main body

Claims (7)

An image carrier on which an electrostatic latent image is formed;
A developing device for developing the electrostatic latent image;
A developer consumption amount calculating means for calculating a developer consumption amount consumed when developing in accordance with an image printing ratio of the electrostatic latent image;
A developer supply device for supplying developer to the developing device;
Control means for controlling a developer replenishment amount to be replenished from the developer replenishing device according to the developer consumption amount;
In an image forming apparatus comprising:
The developing device includes:
A developer container containing the developer;
A developer carrying body for carrying and transporting the developer and developing an electrostatic latent image on the image carrying body;
Developer amount detecting means for detecting the amount of developer in the developer container;
Have
The developer amount detecting means detects at least two levels of developer amount in the developer container;
The control means controls to replenish a developer replenishment amount larger than the developer consumption amount from the developer replenishment device when a level with a small amount of developer is detected among the two levels.
2. An image forming apparatus according to claim 1, wherein a developer replenishing amount less than the developer consumption amount is controlled to be replenished from the developer replenishing device when a level with a large amount of developer is detected among the two levels . The developer detecting unit, an image forming apparatus according to claim 1, characterized in that the optical detection means for detecting the developer surface height of the developer in the developing container. The developing device further includes:
Developer supplying means for supplying the developer to the developer carrying member;
Developer regulating means for regulating the developer supplied by the developer supplying means to form a developer layer on the developer carrier;
Developer agitation means movable to mix the developer replenished from the developer replenishing device and the developer in the developer container;
The image forming apparatus according to claim 1, further comprising: The developer, the image forming apparatus according to any one of claims 1 to 3, characterized in that a single-component developer. The developing device may be any of the image forming apparatus according to claim 1 to 4, characterized in that it is detachably attached to the image forming apparatus main body. And the image bearing member, said developing device, but assembled integrally, any of the image forming apparatus according to claim 1 to 4, characterized in that provided in a process cartridge detachably mountable to the image forming apparatus main body . The developer replenishing apparatus, one of the image forming apparatus according to claim 1 to 4, characterized in that it is detachably mountable to an image forming apparatus.

Images