JP5206739B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that uses a two-component developer and enables replacement of a toner cartridge without stopping the operation of the main body of the image forming apparatus.

  Conventionally, there is an electrophotographic image forming apparatus. In this image forming apparatus, generally, a photosensitive drum is uniformly charged and initialized, an electrostatic latent image is formed on the photosensitive drum by optical writing, and the electrostatic latent image is converted into a toner image. Is directly or indirectly transferred onto a transfer material such as paper and fixed by a fixing device.

  In a developing device of this type of image forming apparatus, toner is consumed as the electrostatic latent image is developed into a toner image, so that the developing device is sequentially replenished with toner in order to maintain good development performance. . For this toner replenishment, a removable and replaceable toner cartridge is often used.

  As the toner supply from the toner cartridge is repeated, the toner in the toner cartridge is eventually used up and the toner cartridge becomes empty. An empty toner cartridge must be replaced with a new one.

  By the way, when the operation panel notifies that the toner cartridge has been replaced, the user temporarily stops the operation of the image forming apparatus, replaces the old and new toner cartridges, turns on the operation switch of the image forming apparatus, and forms an image. It was common practice to resume processing.

  In addition, when the user does not store the replacement toner cartridge, the old and new toner cartridges cannot be replaced immediately. As a result, the image forming apparatus cannot be used, and the operability for the user is impaired.

  When the operation of the image forming apparatus is temporarily stopped, or when the image forming apparatus cannot be used without storing a new toner cartridge, there is no change in that the user operability is impaired.

  Therefore, in order to allow the toner cartridge to be replaced without stopping the operation of the image forming apparatus main body, the toner is supplied to the reserve tank from the toner cartridge that is detachable from the image forming apparatus main body, and the toner development is performed from the reserve tank. An apparatus for transporting toner to a container has been proposed. (For example, refer to Patent Document 1.)

  In addition, it has a reserve tank and can be applied to a tandem type color image forming apparatus in consideration of the miniaturization of the entire apparatus. The image forming operation position for transporting the developer to the developing device and the work for taking out the developing device There has been proposed a developer transport device that can be easily moved between maintenance work positions that can be performed (see, for example, Patent Document 2).

JP 2003-029518 A JP 2006-113137 A

  However, in the prior art of Patent Document 1, the toner cartridge and the reserve tank are arranged at positions away from the developing device. The reserve tank and the developing device are arranged at a distance from each other not only in a color image forming apparatus having a rotary developing device as in Patent Document 1, but also in other tandem type color image forming apparatuses. There is a problem to be solved that the toner conveying device becomes large.

  The prior art in Patent Document 2 aims to reduce the size of the developer conveying device, and there is no description that the toner cartridge can be replaced without stopping the operation of the main body of the image forming apparatus. Therefore, even if the developer conveying device can be reduced in size, there are still problems to be solved.

In order to solve the above problems, an image forming apparatus of the present invention develops a toner image on a photoreceptor with a two-component developer, and detects the toner concentration of the two-component developer provided in the developer. A toner concentration sensor; a toner replenishment reserve tank connected to the developing unit via a toner conveyance path; a toner cartridge detachably attached to the toner replenishment reserve tank; and detecting whether the toner cartridge is new. A new cartridge detecting device, a toner remaining amount sensor for detecting the remaining amount of toner in the toner cartridge, and a control unit, and having a normal print mode and a reserve tank print mode, In the normal print mode, when the remaining toner sensor detects that the toner cartridge is out of toner, the reserve tank print mode is entered. When the presence of toner is detected, the printing in the normal printing mode is continued. During the printing in the normal printing mode, the toner density indicated by the output value of the toner density sensor is equal to or higher than a preset toner supply threshold. Printing in the normal printing mode is continued, and when the toner density is lower than the toner replenishment threshold value, toner replenishment from the reserve tank to the developer and toner replenishment from the toner cartridge to the reserve tank are performed. Printing in the normal printing mode is continued, and in the reserve tank printing mode, the user is notified that the toner cartridge can be replaced, and the amount of toner consumed from the time of the notification is accumulated, and the toner concentration sensor When the toner density indicated by the output value is greater than or equal to the preset no-toner threshold Printing in the reserve tank print mode is continued until the new cartridge detection device detects that the toner cartridge has been replaced with a new toner cartridge, and the new cartridge detection device has replaced the toner cartridge with a new toner cartridge. When this is detected, the toner amount corresponding to the accumulated toner amount obtained by the dot counter is replenished from the toner cartridge to the reserve tank, and the notification that the toner cartridge can be replaced is canceled, and the normal It is configured to shift to printing in the printing mode .

The accumulation of the consumed toner amount is configured to be an accumulation obtained by a dot counter with respect to print data from the notification time .

  The control unit is configured to notify the user of the remaining amount of toner in the reserve tank based on, for example, an accumulated toner amount obtained by the dot counter in the reserve tank printing mode. Further, for example, when the toner density indicated by the output value of the toner density sensor is lower than the no-toner threshold, the operation of the image forming apparatus main body is forcibly stopped.

  The image forming apparatus of the present invention is advantageous in that the toner cartridge can be replaced using a two-component developer without stopping the operation of the main body of the image forming apparatus. Further, there is an effect that toner can be replenished correctly with a simple device that does not require a toner amount detection mechanism in the reserve tank.

1 is a cross-sectional view illustrating an internal configuration of a full-color image forming apparatus (printer) according to Embodiment 1 of the invention. 1 is a circuit block diagram including a printer control device according to Embodiment 1. FIG. (a) is a diagram illustrating a developing device of the printer according to the first embodiment, a reserve tank and a toner cartridge of a toner supply unit in an easy-to-understand manner, and schematically showing them together with a transfer belt, and (b) is a diagram showing them from the side. FIG. (a), (b) is a figure which shows one example of the structure of the presence-and-absence detection apparatus which detects the presence or absence of the toner of the toner cartridge of the printer which concerns on Example 1. FIG. (a), (b) is a figure which shows the relationship between the output of the toner density sensor of the printer which concerns on Example 1, and control with respect to a image development part. 6 is a diagram illustrating a toner amount calculation method of a dot counter of the printer according to the first embodiment. FIG. 5 is a flowchart illustrating an operation of toner replenishment processing during printing in a normal printing mode by the printer control device according to the first exemplary embodiment. 7 is a flowchart illustrating an operation of toner replenishment processing during printing in the reserve tank printing mode by the printer control apparatus according to the first embodiment. FIG. 6 is a cross-sectional view illustrating an operation state of a toner replenishing unit corresponding to a toner replenishing process during printing by the printer according to the first exemplary embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, a two-component developer composed of toner and carrier is used.

  FIG. 1 is a cross-sectional view illustrating an internal configuration of a full-color image forming apparatus (hereinafter simply referred to as a printer) according to the first embodiment.

  A printer 1 shown in FIG. 1 is an electrophotographic secondary transfer tandem color image forming apparatus, and includes an image forming unit 2, a transfer belt unit 3, a toner supply unit 4, a paper feeding unit 5, and a belt type fixing device. It comprises a unit 6 and a transport unit 7 for duplex printing.

  The image forming unit 2 is in contact with the lower running unit surface 8a of the transfer belt 8 of the transfer belt unit 3 and multi-stages four developing devices 9 (9m, 9c, 9y, 9k) from right to left in FIG. It consists of a side-by-side configuration. The image forming unit 2 is held by a frame of the printer 1 main body so as to be movable up and down from a printing execution position shown in FIG. 1 to a maintenance position below it.

  Of the four developing devices 9, three developing devices 9m, 9c, and 9y on the downstream side (right side in the figure) are magenta (M), cyan (C), and yellow (Y), which are subtractive three primary colors, respectively. A mono-color image is formed with the color toner, and the developing device 9k forms a monochrome image mainly with black (K) toner used for characters and dark portions of the image.

  Each of the developing devices 9 has the same configuration except for the color of the toner that develops the image. Therefore, the configuration of the developing device 9k for black (K) toner will be described below as an example.

  The developing device 9 includes a photosensitive drum 10 at the top. The photosensitive drum 10 has a peripheral surface made of, for example, an organic photoconductive material. A cleaner 11, a charging roller 12, an optical writing head 13, and a developing roller 15 of the developing device 14 are disposed around the periphery of the photosensitive drum 10.

  The developing device 14 includes a housing 16 that covers the outside, a partition wall 17 provided inside, a developing roller 15, a first stirring and conveying screw 18, and a second stirring and conveying screw 19. Although not specifically shown, the first and second agitating and conveying screws 18 and 19 include a screw shaft and a fin that is integrally formed with the screw shaft and rotates.

  The developing unit 14 includes a reserve tank, which will be described later in detail, and a magenta (M), cyan (C), yellow (Y), and magenta (M) as shown by M, C, Y, and K in FIG. Either black (K) toner is supplied.

  The transfer belt unit 3 has an endless transfer belt 8 that extends in the shape of a flat loop in the left-right direction in the figure at approximately the center of the main unit, and the transfer belt 8 is stretched over the transfer belt 8. A driving roller 21 and a driven roller 22 are provided to circulate and move counterclockwise as indicated by an arrow a in the figure.

  The above-described transfer belt 8 is directly transferred to the surface of the belt that circulates below by a primary transfer roller 20 that is integrated with the unit and pressed against the photosensitive drum 10 via the transfer belt 8 (primary transfer). Then, the toner image is conveyed to the secondary transfer unit 23 to the paper for further transfer (secondary transfer) to the paper.

  The transfer belt unit 3 is provided with a belt cleaner 24 having a cleaning blade 25 that comes into contact with the surface of the drive roller 21. A waste toner collecting container 26 is detachably disposed below the belt cleaner 24.

  In the belt cleaner 24, the cleaning blade 25 abuts on the surface of the transfer belt 8 to scrape and remove the waste toner, and the waste toner is sent to a lower waste toner collection container 26 by a conveying screw.

  The toner supply unit 4 includes four reserve tanks 27 (27m, 27c, 27y, and 27k) that are disposed above the upper running unit of the transfer belt 8, and are detachably disposed on the reserve tanks 27, respectively. Toner cartridge 28 (28m, 28c, 28y, 28k) for toner replenishment.

  The four toner cartridges 28m, 28c, 28y, and 28k accommodate magenta (M), cyan (C), yellow (Y), and black (K) toners, respectively, and four reserve tanks 27 (27m, 27c). , 27y, 27k) are replenished with toner from the toner cartridge 28 mounted thereon.

  These four reserve tanks 27 are hidden behind the opposite side of the transfer belt unit 3 in FIG. 1, but are connected to the corresponding developing devices 14 of the developing device 9 by toner supply paths.

  Although not particularly shown, the toner supply unit 4 is held on the frame of the printer 1 main body so as to be able to be raised and lowered from the printing execution position shown in FIG. 1 to a maintenance position above it.

  Two electrical parts 30 are disposed on the left side of the toner supply unit 4 from the left side of the belt cleaner 24 to above the drive roller 21. The electrical unit 30 includes a circuit board on which a control device composed of a plurality of electronic components, which will be described in detail later, is mounted.

  The paper feed unit 5 includes two paper feed cassettes 29 (29a, 29b) arranged in two upper and lower stages. A paper take-out roller 31, a feed roller 32, a separating roller 33, and a standby conveyance roller pair 34 are disposed in the vicinity of the paper feed opening (right side of the drawing) of the two paper feed cassettes 29, respectively.

  A secondary transfer roller 35 that is in pressure contact with the driven roller 22 via the transfer belt 8 is disposed in the paper transport direction (vertically upward in the drawing) of the standby transport roller pair 34, and the secondary transfer onto the paper described above. Part 23 is formed.

  A belt-type heat fixing unit 6 is disposed downstream (upward in the drawing) of the secondary transfer portion. On the further downstream side of the belt-type heat fixing unit 6, a pair of carry-out rollers 36 for carrying out the fixed paper from the belt-type heat fixing unit 6, and a paper discharge tray 37 formed on the upper surface of the apparatus. A paper discharge roller pair 38 for paper discharge is provided.

  The conveyance unit 7 for double-sided printing also serves as an opening / closing member whose outer surface (right outer surface in the drawing) opens or shields the inside of the printer 1 from the side surface to the outside.

  This duplex printing transport unit 7 has a start return path 39a that branches rightward in the figure from just before the paper discharge roller pair 38, an intermediate return path 39b that bends downward, and a left lateral direction opposite to the above. Thus, a return path 39 including a terminal return path 39c for finally inverting the return sheet is provided.

  In the middle of the return path 39, five pairs of return rollers 41 (41a, 41b, 41c, 41d, 41e) are arranged. The exit of the end return path 41 e joins the conveyance path to the standby conveyance roller pair 34 corresponding to the sheet feeding cassette 29 a below the sheet feeding unit 5.

  FIG. 2 is a circuit block diagram including the control device of the printer 1 described above. As shown in FIG. 2, the circuit block has a central processing unit (CPU) 42 as a center, and an interface controller (I / F_CONT) 43 and a printer controller (PR_CONT) 44 are connected to the CPU 42 via data buses. ing. A printer printing unit 45 is connected to the PR_CONT 44.

  Further, the CPU 42 has a ROM (read only memory) 46, an EEPROM (electrically erasable programmable ROM) 47, an operation panel 48 of the main body operation unit, a sensor unit 49 to which an output from a sensor arranged in each unit is input, and a dot counter. 54 is connected.

  The ROM 46 stores a system program, and the CPU 42 performs processing by controlling each unit in accordance with the system program.

  That is, in each unit, first, the I / F_CONT 43 converts print data supplied from a host device such as a personal computer into bitmap data and develops it in the frame memory 51. In the frame memory 51, a storage area is set for each of black (K), magenta (M), cyan (C), and yellow (Y), and data of each color is developed in a corresponding area.

  The data developed in the frame memory 51 is output to the PR_CONT 44, and is output from the PR_CONT 44 to the printer printing unit 45.

  The printer printing unit 45 is an engine unit, and under the control of the PR_CONT 44, a rotation driving system (not shown) including the photosensitive drum 10, the primary transfer roller 20 and the like shown in FIG. An image forming unit having a driven unit such as a head 13 and a driving unit (not shown) that drives the transfer belt unit 3 to move up and down and the transfer belt 8 to rotate are provided.

  Further, the printer printing unit 45 includes a belt driving unit 52 that drives the belt of the belt-type fixing unit 6, and a toner supply unit motor driving unit 53 that drives a cartridge motor, a reserve tank motor, and the like, which will be described later.

  Further, the printer printing unit 45 is a drive output to a process load such as a conveyance mechanism composed of rotationally driven parts such as the paper take-out roller 22 to the paper discharge roller pair 31, and a belt-type fixing unit 6 that is driven and heated. To control.

  The black (K), magenta (M), cyan (C), and yellow (Y) data output from the PR_CONT 44 are respectively sent from the printer printing unit 45 to the corresponding optical writing heads 13 shown in FIG. To be supplied.

  The dot counter 54 calculates the amount of toner used for printing based on the exposure area of the photosensitive drum 10 by the optical writing head 13 based on the data of each color supplied to the optical writing head 13.

  FIG. 3A shows the developing device 9 of the image forming unit 2, the photosensitive drum 10, the reserve tank 27 of the toner supply unit 4, and the toner cartridge 28 in the printer 1 according to the first embodiment. FIG. 3 is a diagram schematically showing the belt 8 and FIG. 3B is a cross-sectional view of the belt 8 as viewed from the side.

  3 (a) and 3 (b), the same components or functions as those shown in FIG. 1 are given the same numbers as in FIG. In FIG. 3B, the transfer belt unit 3 is indicated by a broken line block in place of the transfer belt 8 of FIG.

  The toner cartridge 28 shown in FIGS. 3A and 3B is placed in the reserve tank 27 in the front direction with respect to the main body of the image forming apparatus 1 shown in FIG. 1, that is, as indicated by the double arrow b in FIG. On the other hand, it is detachable.

  As shown in FIG. 3B, the toner cartridge 28 is provided with a detected part 55 indicating whether the toner cartridge 28 is new or old. The detected part 55 detects whether the toner cartridge 28 is new on the printer 1 main body side. A detecting unit 56 is disposed. The new cartridge detection device 57 for detecting such a new toner cartridge can be configured by a very general and inexpensive method.

  The toner cartridge 28 includes a toner supply mechanism 61 including a rotation shaft 58 and a spiral stirring fin 59 inside. A cartridge motor 62 is engaged with the rotation shaft 58 of the toner supply mechanism 61 from the outside.

  Further, the toner cartridge 28 is connected to the reserve tank 27 at the end opposite to the side engaged with the cartridge motor 62 and is connected to the reserve tank 27 to replenish the reserve tank 27 with the toner 63. The toner replenishing port 64 is formed.

  The toner replenishing mechanism 61 extends along the longitudinal direction of the toner cartridge 28 from the right end portion to the left end portion of the toner cartridge 28, and forms a fin-shaped change point 65 directly above the toner replenishing port 64. The toner 63 is sent out to the toner replenishing port 64.

  A toner remaining amount sensor 66 is disposed in the toner cartridge 28 at a position close to the fin-shaped change point 65 on the toner replenishing port 64. The output signal line of the toner remaining amount sensor 66 is automatically connected to the sensor unit 49 of the control circuit when the toner cartridge 28 is attached to the reserve tank 27.

  Inside one reserve tank 27, a toner replenishing mechanism 69 comprising a rotating shaft 67 and a helical stirring fin 68, which is also the same as the toner cartridge 28, is disposed. A reserve tank motor 71 is engaged with the rotating shaft 67 of the toner supply mechanism 69 from the outside.

  The toner replenishing mechanism 69 extends from the left end of the reserve tank 27 to the right end along the longitudinal direction of the reserve tank 27, and the toner 63 is replenished from the toner cartridge 28 via the toner replenishment port 64 at the left end. To the right end.

  A fin-shaped change point 72 of the toner replenishing mechanism 69 is formed at the right end. Immediately below the fin-shaped change point 72, an upper end portion of a toner conveyance path 73 that connects the reserve tank 27 and the developing device 14 is opened. The toner conveyance path 73 is arranged so as to wrap around the transfer belt unit 3.

  In the toner replenishing operation by the toner replenishing mechanism 69, the toner 63 stirred and conveyed by the stirring fin 68 up to the fin-shaped change point 72 falls from the upper side to the lower side of the toner conveying path 73 due to its own weight. As a result, the toner 63 is supplied from the reserve tank 27 to the developing device 14.

  The developing device 14 includes a fin screw 75 having the same configuration as the toner transport mechanism 61 of the toner cartridge 28 and the toner transport mechanism 69 of the reserve tank 27. In FIG. 3B, the first stirring and conveying screw 18 and the second stirring and conveying screw 19 shown in FIG. 1 are simply shown as one fin screw 75.

  A developing device motor (not shown) is connected to the rotating shaft of the fin screw 75. The developing device 14 generates a two-component developer 76 having an appropriate toner concentration while stirring and conveying the carrier and the toner 63 by a fin screw 75 driven by a developing device motor, and develops the toner 63 of the two-component developer 76. Supply to roller 15. In the developing device 14, a toner density sensor 81 is disposed at an appropriate location.

  In FIG. 3B, the toner remaining amount sensor 66 is of a type built in the toner cartridge 28. However, the toner remaining amount sensor 66 is a transmissive optical sensor, and the light emitting portion and the light receiving portion are printers. You may make it provide in 1 main body side.

  FIGS. 4A and 4B are diagrams showing an example in which the light emitting part and the light receiving part of the toner remaining amount sensor formed of a transmission type optical sensor are provided on the printer 1 main body side. FIG. 4A shows the end of the toner cartridge 28 on the toner replenishing port 64 side shown in FIG.

  Inside the left end of the toner cartridge 28 shown in FIG. 4A, a light emitting light guide 82 and a light receiving light guide 83 made of a glass member as shown in FIG. 4B are fixedly arranged. The left end faces 82 a and 83 a of the light emitting light guide path 82 and the light receiving light guide path 83 are exposed on the left end face of the toner cartridge 28.

  The right ends of the main body of the light emitting light guide 82 and the light receiving light guide 83 inside the toner cartridge 28 are bent in a direction approaching each other, and the tips are notched obliquely with respect to the shaft to form planes 82b and 83b facing each other. The toner presence / absence detecting portion is formed by the facing portion 84.

  The transmission type optical sensor 85 shown in FIG. 4B installed outside the toner cartridge 28 receives the light emitting part 86 and the light receiving part 87 from the light emitting light guide path 82 of the toner cartridge 28 attached to the attachment part. The toner remaining amount sensor 66 is configured to be in close contact with the outer end faces 82 a and 83 a of the light guide path 83 and together with the light emitting guide path 82 and the light receiving guide path 83.

  That is, the light emitted from the light emitting portion 86 toward the outer end surface 82a as shown by the arrow c is guided by the light emitting light guide path 82, reaches the plane 82b facing the other, and blocks the light at the facing portion 84 ( That is, when there is no toner 63), it enters the other flat surface 83b as shown by the arrow d, is guided by the light receiving light guide path 83, and returns to the light receiving portion 87 from the outer end face 83a as shown by the arrow e.

  As a result, when the toner 63 is present in the toner cartridge 28, the light is blocked by the facing portion 84, so that the output of the transmissive optical sensor 85 (output of the light receiving portion) is almost “0”. When the toner 63 is used up, there is no light blocking at the facing portion 84, so that the output of the transmissive optical sensor 85 becomes the maximum output.

  The CPU 42 of the control device monitors the output of the transmissive optical sensor 85 input via the sensor unit 49 and determines the presence / absence of the toner 63 in the toner cartridge 28.

  5A and 5B are diagrams illustrating the relationship between the output of the toner density sensor 81 of the printer 1 according to the first embodiment and the control for the developing device 9. 5A and 5B, the horizontal axis indicates time (second (s)), and the vertical axis indicates the output (voltage (v)) of the toner density sensor 81. Solid line graphs 88 (88a, 88b) show examples of output values of the toner density sensor 81.

  In this example, the output of the toner density sensor 81 is inverted, and the values on the vertical axis shown in FIGS. 5 (a) and 5 (b) are lower toward the top and higher toward the bottom. A value indicated by a broken line in FIG. 5A indicates “toner supply threshold v1”. Also, the broken line above the toner replenishment threshold v1 in FIG. 5B indicates the “no toner threshold v2”.

  In FIG. 5A, printing is started at time t1, and the output of the toner density sensor 81 reaches the toner replenishment threshold value at time t2 (the toner density is reduced to almost the limit of the appropriate value). The toner 63 in the tank 27 begins to be replenished to the developing device 14, and the toner density becomes an appropriate value at time t3, indicating that the output of the toner density sensor 81 has recovered below the toner replenishment threshold.

  In FIG. 5B, printing starts at time t1, the output of the toner density sensor 81 reaches the toner replenishment threshold at time t2, and the toner replenishment mechanism 69 of the reserve tank 27 is used to replenish the developer 63 with toner 63. Even when is driven, since the reserve tank 27 is empty, the toner 63 is not replenished, and the output of the toner density sensor 81 exceeds the no-toner threshold value v2 at time t3.

  Here, in order to explain the output of the toner density sensor 81, the two-component developer 76 in the developing device 14 is returned to the original state and divided into the carrier and the toner 63. The carrier is mixed and stirred with the toner 63 in the developing device 14 to give the toner 63 a predetermined charge. The charged toner 63 temporarily adheres to the surface of the carrier and covers the surface of the carrier.

  The carrier of the two-component developer 76 rotated and conveyed by the developing roller 15 carries the charged toner 63 to a position where the photosensitive drum 10 and the developing roller 15 are opposed to each other and forms an electrostatic latent image on the photosensitive drum 10. The toner 63 is transferred to develop the toner image on the electrostatic latent image. The carrier that has released the toner 63 on the surface remains on the developing roller 15 and returns to the developing device 14 again.

  The carrier that has returned to the developing device 14 is mixed and stirred again with new toner 63, charges are applied to the toner 63, and the toner 63 is conveyed onto the photosensitive drum 10 and is used repeatedly. When the amount of toner 63 in the developing device 14 decreases (toner density decreases), new toner 63 is supplied from the outside.

  Since the developer used in the developing device 14 of this example is a two-component developer 76 composed of a carrier and toner 63, a magnetic permeability sensor is used as the toner concentration sensor 81 shown in FIG. This magnetic permeability sensor is for detecting that the amount of toner 63 in the developing device 14 has decreased in the two-component development, and is a toner density sensor such as a type that uses an inductance component of a coil, a frequency type, or a magnetic bridge type. As a general thing.

  In the two-component development, the carrier is a magnetic material while the toner is a non-magnetic material. When a two-component developer, which is a mixture of carrier and toner, is viewed through the magnetic permeability sensor, the developer mixed at a constant weight ratio can always obtain a constant sensor output value.

  Therefore, if there is a lot of toner relative to the carrier, that is, if the toner concentration is high, the magnetic permeability of the two-component developer is lowered and the output value of the magnetic permeability sensor, that is, the toner concentration sensor 81 is lowered. On the other hand, if the toner is less than the carrier, that is, if the toner concentration is low, the permeability of the two-component developer increases and the output value of the toner concentration sensor 81 increases.

  In the printer 1 of this example, for example, the toner concentration of the two-component developer suitable for development during normal image formation is about 10%, so the toner concentration of the developing device 14 is set to 10% during image formation, that is, during printing. Controlled to maintain.

  Therefore, the output value of the toner density sensor 81 corresponding to a desired developer density (for example, 10% toner density) is set in advance as a “toner replenishment threshold v1” in a predetermined area of the control device such as the EEPROM 47, for example.

  Thereby, the decreased toner density in the developing device 14 can be detected by comparing the output value of the toner density sensor 81 with the toner replenishment threshold. Further, when the replenishment of the toner 63 to the developing device 14 is interrupted for some reason, the toner density is lowered below the toner replenishment threshold by continuing the printing.

  Since the upper and lower widths of the toner density suitable for development have a certain tolerance, printing can be continued for a certain period of time even if the toner density falls below the toner replenishment threshold.

  However, if the toner density is less than the lower tolerance suitable for development, the quality of the formed image cannot be guaranteed, and the printer 1 main body must be forcibly stopped. In this example, the lower tolerance of the toner density is set in advance in another predetermined area of the EEPROM 47 as the “no toner threshold v2”.

  FIG. 6 is a diagram for explaining a toner amount calculation method of the dot counter 54 shown in FIG. In FIG. 6, the horizontal axis represents the exposure area (m ^ 2) of the photosensitive drum 10 by the optical writing head 13, and the vertical axis represents the toner consumption (g). In other words, FIG. 6 shows the relationship between the toner consumption amount and the exposure amount by the optical writing head 13.

  In the present invention, the toner remaining amount detecting device is not disposed inside the reserve tank 27. Instead, the toner consumption is determined by the dot counter 54 shown in FIG. 2 based on the characteristic diagram shown in FIG.

  To calculate the toner consumption from the relationship of “toner consumption (g) = A × exposure area (m ^ 2)”, where A is the development efficiency for a certain amount of light output from the optical writing head 13. Can do.

  FIG. 7 is a flowchart showing the operation of toner replenishment processing during printing in the normal printing mode by the CPU 42 of the control device shown in FIG.

  FIG. 8 is a flowchart showing the operation of toner replenishment processing during printing in the reserve tank printing mode by the CPU 42 of the control device shown in FIG.

  FIG. 9 is a cross-sectional view showing the operation state of the toner supply unit 4 corresponding to the toner replenishment process during printing shown in the flowchart from the state A to the state E.

  This process is based on the premise that the printer 1 starts printing when the user is in use (not operating). In the case of a new printer 1, it is assumed that the initial filling of the toner in the reserve tank 27 is completed and the printer is in use and is in a suspended state.

  By the way, in the new printer 1 at the time of shipment from the factory, unused toner 63 is put in the developing device 14, but the reserve tank 27 is not filled with the toner 63.

  However, in this example, for example, the toner capacity that can be accommodated in the reserve tank 27 is 100 g, and the toner replenishment capability of the toner replenishment mechanism 61 of the toner cartridge 28 is determined to be 0.5 g / sec. When the toner supply for 200 seconds is executed, the reserve tank 27 can be filled.

  A state A in FIG. 9 shows a state in which the empty reserve tank 27 is filled by executing toner replenishment from the new toner cartridge 28 to the reserve tank 27 for 200 seconds. The amount of toner 63 in the new toner cartridge 28 is reduced by almost half as much as the reserve tank 27 is full.

  The state B in FIG. 9 shows a state when the toner 63 of the toner cartridge 28 is just emptied. In this state, the toner remaining amount sensor 66 detects “no toner” in the toner cartridge 28.

  A state C in FIG. 9 shows a state where the toner cartridge 28 is empty (that is, no toner is present) and has not yet been replaced with a new toner cartridge 28. Since the printing is continued, the toner 63 that is full in the reserve tank 27 is reduced by almost half.

  In the state D of FIG. 9, the refillable toner amount in the reserve tank 27 is indicated by a hatched area 89. This replenishable toner amount is obtained by the dot counter 54 calculating the amount of toner consumed during printing from state B to state C.

  The state E in FIG. 9 is a state in which the new and old toner cartridges 28 are replaced at the time of the state D, and the toner 63 is replenished from the new toner cartridge 28 to the reserve tank 27 by the amount calculated by the dot counter 54. Is shown.

  The toner 63 is replenished to the developing device 14 from the reserve tank 27 through the toner transport path 73 by the toner replenishing mechanism 69 in the old and new step h and the old and new space g of the left and right toner 63 inside the reserve tank 27. It will be averaged over time.

  In FIG. 7, when printing is started, first, it is determined whether or not a print end instruction from the user or a print data end command is input from the host device (step S1). Since the printing process is the same sequence process that is repeated for each sheet of paper, it is thus determined whether or not the process is completed at the beginning of the process.

  Since this determination is No immediately after the start of printing, the CPU 42 next reads the output values of the toner remaining amount sensors 66 of the four toner cartridges 28m, 28c, 28y, and 28k of the toner supply unit 4 (step). S2).

  Then, the CPU 42 determines whether or not the read output value indicates that there is a remaining amount of toner (step S3). If there is a remaining amount of toner in this determination (Yes in S3), then the CPU 42 reads the output value of the toner density sensor 81 (step S4), and whether the read output value is equal to or less than the toner replenishment threshold v1. A determination is made (step S5).

  If the output value of the toner density sensor 81 is equal to or less than the toner replenishment threshold value v1 (Yes in S5), the toner density of the developing device 14 is in the density range appropriate for development (FIG. 5A). CPU 42 returns to step S1 and continues printing in the normal print mode in steps S2 to S5.

  When the output value of the toner density sensor 81 exceeds the toner replenishment threshold value v1 in the determination in step S5 (No determination in S5), the toner density of the developing device 14 is lower than the density appropriate for development. Therefore (see the period after time t2 in FIG. 5A), the CPU 42 replenishes the developing device 14 with the toner 63 from the reserve tank 27 corresponding to the developing device 14 (step S6).

  Then, the toner amount supplied to the developing device 14 is supplied from the toner cartridge 28 to the reserve tank 27 (step S7), the process returns to step S1, and printing in the normal print mode is continued in steps S2 to S5.

  If it is determined in step S3 that there is no remaining toner in the toner cartridge 28 (No in S3) (see state B in FIG. 9), the toner color printing process corresponding to the toner cartridge 28 is reserved. In order to perform the printing process in the tank printing mode, the CPU 42 shifts to the reserve tank printing mode (step S8).

  In the reserve tank printing mode shown in FIG. 8, the CPU 42 first replaces the target toner cartridge 28 of the developing device 9 (the toner color corresponding to the toner cartridge 28 having no remaining toner, the same applies hereinafter) while printing continues. The fact that it is possible is displayed on the operation panel 48 to notify the user (step S11).

  Subsequently, the CPU 42 starts measuring the toner consumption amount of the target developing device 9 by the dot counter 54 (step S12). Then, while executing printing, the remaining amount of toner in the reserve tank 27 is calculated (step S13).

  Since the reserve tank 27 is full of toner 63 when the toner cartridge 28 runs out of toner, and the toner storage amount is determined to be 100 g, the consumed toner measured by the dot counter 54 from 100 g is determined. If the amount is subtracted, the remaining amount of toner in the reserve tank 27 can be calculated. The state C in FIG. 9 shows the state at this time.

  Next, the CPU 42 notifies the operation panel 48 of the calculated remaining toner amount in the reserve tank 27 as the remaining toner amount of the target developing device 9 (or in terms of the printable number) (step S14). If the display notification has already been performed, the display is updated and represented again.

  Subsequently, the CPU 42 reads the output value of the toner density sensor 81, and determines whether or not the read output value exceeds the no-toner threshold value v2 (step S15).

  Then, when the output value of the toner density sensor 81 does not exceed the no-toner threshold value v2 (No in S15) (see the period before time t3 in FIG. 5B), the new cartridge detection is subsequently performed. With reference to the output of the device 57, it is determined whether or not a new toner cartridge 28 has been replaced (step S16).

  When the toner cartridge 28 has not been replaced (No at S16), the CPU 42 returns to step S13 and repeats the processes at steps S13 to S16.

  If it is determined in step S15 that the output value of the toner density sensor 81 exceeds the no-toner threshold value v2 (Yes in S15) (see the state after time t3 in FIG. 5B), the CPU 42. Determines that there is no toner 63 in the target developing device 14, stops the operation of the main body of the printer 1, and displays "no toner" on the operation panel 48 (step S20).

  If it is determined in step S16 that the toner cartridge 28 has been replaced (Yes in S16), the CPU 42 calculates the free capacity of the reserve tank 27 of the target developing device 9 (step S17). .

  In this process, the remaining capacity of the reserve tank 27 calculated in step S13 can be subtracted from the total toner storage capacity 100g of the reserve tank 27 to calculate the free capacity of the reserve tank 27. A hatching area 89 in the state D in FIG. 9 indicates the free capacity (replenishable capacity) of the reserve tank 27.

  Then, the CPU 42 replenishes the reserve tank 27 with the toner 63 for the empty capacity of the reserve tank 27 just calculated by driving the toner replenishment mechanism 61 of the newly replaced toner cartridge 28 (step S18). The state E in FIG. 9 shows the state at this time.

  Subsequently, the CPU 42 cancels the display of “toner cartridge 28 is replaceable” displayed on the operation panel 48 in step S11 (step S19), and performs the printing process in the normal printing mode shown in FIG. Return.

  As described above, steps S1 to S8 and S11 to S19 are repeated while the empty toner cartridge 28 is replaced before the output value of the toner density sensor 81 exceeds the no-toner threshold v2. Eventually, when printing is finished (Yes in S1), the CPU 42 stops the operation of the printer 1 and finishes the printing process (step S9).

  As described above, according to the present exemplary embodiment, in the image forming apparatus using the two-component developer, it is possible to replace the toner cartridge without stopping the operation of the apparatus main body.

  Further, there is an effect that toner can be replenished correctly with a simple device that does not require a toner amount detection mechanism in the reserve tank.

  The present invention can be used for an image forming apparatus that uses a two-component developer and that allows replacement of a toner cartridge without stopping the operation of the main body of the image forming apparatus.

1 Full-color image forming device (printer)
DESCRIPTION OF SYMBOLS 2 Image formation part 3 Transfer belt unit 4 Toner supply part 5 Paper feed part 6 Belt type fixing unit 7 Conveyance unit for double-sided printing 8 Transfer belt 8a Lower running part surface 9 (9m, 9c, 9y, 9k) Drum 11 Cleaner 12 Charging roller 13 Optical writing head 14 Developer 15 Developing roller 16 Housing 17 Bulkhead 15 Developing roller 18 First agitating and conveying screw 19 Second agitating and conveying screw 20 Primary transfer roller 21 Drive roller 22 Driven roller 23 Secondary transfer section 24 Belt cleaner 25 Cleaning blade 26 Waste toner collection container 27 (27m, 27c, 27y, 27k) Reserve tank 28 (28m, 28c, 28y, 28k) Toner cartridge 29 (29a, 29b) Paper feed cassette 30 Electrical equipment Part 31 Paper removal 32 Feeding roller 33 Separating roller 34 Standby conveying roller pair 35 Secondary transfer roller 36 Unloading roller pair 37 Paper discharge tray 38 Paper discharge roller pair 39 Return path 39a Start return path 39b Intermediate return path 39c End return path 41 (41a, 41b) 41c, 41d, 41e) Return roller pair 42 CPU (central processing unit)
43 Interface Controller (I / F_CONT)
44 Printer controller (PR_CONT)
45 Printer printing section 46 ROM (read only memory)
47 EEPROM (electrically erasable programmable ROM)
48 Operation Panel 49 Sensor Unit 51 Frame Memory 52 Belt Drive Unit 53 Toner Supply Unit Motor Drive Unit 55 Detected Unit 56 Detection Unit 57 New Cartridge Detection Device 61 Toner Supply Mechanism 62 Cartridge Motor 63 Toner 64 Toner Supply Port 65 Change in Fin Shape Point 66 Remaining toner sensor 67 Rotating shaft 68 Stirring fin 69 Toner replenishment mechanism 71 Reserve tank motor 72 Change point of fin shape 73 Toner conveyance path 75 Fin screw 76 Developer 81 Toner density sensor 82 Light emitting light guide path 82a Left end face 82b Plane 83 Light receiving light guide 83a Left end face 83b Plane 84 Opposing part 85 Transmission type optical sensor 86 Light emitting part 87 Light receiving part 88 (88a, 88b) Example of output value of toner density sensor 89 Replenishable capacity

Claims (4)

A developing device for developing a toner image on a photoreceptor with a two-component developer;
A toner concentration sensor provided in the developing device for detecting the toner concentration of the two-component developer;
A reserve tank for replenishing toner connected to the developing unit via a toner conveyance path;
A toner cartridge detachably attached to the toner supply reserve tank;
A new cartridge detection device for detecting whether or not the toner cartridge is new;
A toner remaining amount sensor for detecting the remaining amount of toner in the toner cartridge;
A control unit;
With
Normal printing mode,
Reserve tank printing mode,
Have
The control unit, in the normal printing mode,
When the toner remaining amount sensor detects that the toner cartridge is out of toner, it shifts to the reserve tank print mode, and when it detects the presence of toner, it continues printing in the normal print mode,
During printing in the normal printing mode, printing in the normal printing mode is continued when the toner density indicated by the output value of the toner density sensor is equal to or higher than a preset toner supply threshold, and the toner density is set to the toner supply threshold. When lower, the toner supply from the reserve tank to the developing device and the toner supply from the toner cartridge to the reserve tank are continued to continue printing in the normal print mode ,
In the reserve tank printing mode,
Notifying the user that the toner cartridge can be replaced, and accumulating the amount of toner consumed from the time of the notification,
When the toner concentration indicated by the output value of the toner concentration sensor is equal to or greater than a preset toner-free threshold,
Continue printing in the reserve tank print mode until the new cartridge detection device detects that the toner cartridge has been replaced with a new toner cartridge,
When the new cartridge detection device detects that the toner cartridge has been replaced with a new toner cartridge, the toner amount corresponding to the accumulated amount of consumed toner is replenished from the toner cartridge to the reserve tank, and the toner cartridge Cancel the exchangeable notification and shift to printing in the normal printing mode.
An image forming apparatus. 2. The image forming apparatus according to claim 1 , wherein the accumulated toner amount is accumulated by a dot counter for print data from the notification time . The control unit, in the reserve tank printing mode,
Informing the user of the remaining amount of toner in the reserve tank based on the accumulated toner amount obtained by the dot counter;
The image forming apparatus according to claim 2. The control unit, in the reserve tank printing mode,
3. The image forming apparatus according to claim 2, wherein when the toner density indicated by the output value of the toner density sensor is lower than the no-toner threshold, the operation of the image forming apparatus main body is forcibly stopped.