JP2005292511A - Development device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of stably maintaining a developer surface in a developing container at an appropriate position, and an image forming apparatus provided with the developing device.
A developer container 51 that contains a developer, a developer carrier 52 that supplies the developer in the developer container 51 to the development target 3, and a developer that transports the developer in the developer container 51. A developer container 51 including a conveying member 53 and a developer discharge port 56 for discharging the developer in the developer container 51 to the outside of the developer container 51; a developer for supplying the developer to the developer container 51; The developing device 5 having the replenishing means 55 is configured such that a detecting means 57A for detecting the developer surface F of the developer in the developing container 51 is provided in the developing container 51.
[Selection] Figure 2

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a printer, and a facsimile using an electrophotographic method or an electrostatic recording method, and an image forming apparatus provided with the developing device. The present invention relates to a developing device using a developer including toner and a carrier, and an image forming apparatus including the same.

  2. Description of the Related Art Conventionally, for example, in an electrophotographic image forming apparatus, a developing device that performs development with a so-called two-component developer, which is a mixture including a toner and a carrier, is widely used. In particular, many developing devices use a two-component developer in the color image forming apparatus from the viewpoint of the color of an image.

  In a developing device using a two-component developer, toner is consumed by a developing operation, and new toner is replenished by the consumed amount. On the other hand, the carrier remains in the developing container (developer tank) without being consumed. Therefore, the carrier stirred together with the toner is deteriorated by stirring. The deterioration of the carrier is caused by friction when stirring the developer or when passing through the gap between the developer carrier (developing roller, etc.) provided in the developing container and the developer layer thickness regulating member (regulating blade, etc.). This is caused by toner adhering to the carrier surface layer due to compression. When the carrier is deteriorated, the charging performance of the developer is deteriorated, and the developing performance is deteriorated to cause an image defect. Therefore, the carriers are regularly exchanged.

  In the carrier replacement, the developer is extracted from the developer extraction port provided in the developing container, and a new developer is filled in the developing device. During this replacement operation, powder toner may scatter and stain the image forming apparatus and its surroundings.

  In view of this, there has been proposed a developing device that suppresses the deterioration of the developer and does not require special developer replacement work (see, for example, Patent Document 1). The method adopted by such a developing device is generally referred to as a trickle method, and is excessively provided by providing an overflow outlet at a predetermined height on the side wall of the housing of the developing device and replenishing the developing device with a developer including toner and a carrier. By sequentially discharging the developer in the developing device thus formed from the overflow outlet, the characteristics of the developer are made constant (for example, see Patent Document 2).

  That is, in this method, the amount of the developer in the developing container is increased by replenishment, and the developer is discharged by overflowing the discharge port by an amount higher than the discharge port.

  However, since the conventional apparatus has no means for detecting when the developer stays in the discharge port, the amount of the developer in the developer container increases due to the replenishment of the developer, and the developer in the developer container The agent surface (upper surface) rises, and problems such as fluctuations in image density and toner scattering may occur. In addition, an increase in the developer amount may increase the rotational load on the developer carrying member and the agitating / conveying member disposed in the developing container, which may damage the developing device or the gear or motor for driving the developing device. There is.

Immediately after the developing device is placed in the image forming apparatus, the developer in the developing container is biased, and the distribution of the developer carried by the developer carrier becomes non-uniform, resulting in uneven density of the image. was there.
Japanese Patent Publication No. 2-21591 JP 2003-215903 A

  An object of the present invention is to provide a developing device that can stably maintain a developer surface in a developer container at an appropriate position, and an image forming apparatus including the developing device.

  The above object is achieved by the developing device and the image forming apparatus according to the present invention. In summary, the first aspect of the present invention is a developer container for storing a developer, the developer carrier for supplying the developer in the developer container to the development target, and the developer in the developer container. A developer container comprising: a developer conveying member to be conveyed; and a developer discharge port for discharging the developer in the developer container to overflow the developer container; and a developer for supplying the developer to the developer container And a replenishing device. The developing device is provided with a detecting means for detecting the developer surface of the developer in the developing container. According to an embodiment of the present invention, the output of the detection means changes when the developer level in the developer container rises by a predetermined amount from the normal state. According to another embodiment of the present invention, the detection means are arranged in a plurality of places, more specifically, in a height direction, and the output of the plurality of detection means is a developer in the developer container. It changes in stages as the surface of the liquid rises from the normal state. According to an embodiment of the present invention, a plurality of the detection means are provided in the developer transport direction by the developer transport member. In one embodiment, the driving speed of the developer conveying member can be changed according to the outputs of the plurality of detecting means.

  According to the second aspect of the present invention, a developer carrier for supplying a developer to the development target, a first developer transport member for transporting the developer along the axial direction of the developer carrier, and the first A first chamber in which one developer conveying member is accommodated, a second developer conveying member that conveys the developer in a direction opposite to the first developer conveying member, and the second developer conveying member. A developing device having a developing container that is housed and includes a second chamber that is disposed substantially parallel to the first chamber below the first chamber and communicates with the first chamber at both ends; There is provided a developing device comprising a plurality of detection means for detecting the developer surface of the developer in the first chamber along a developer transport direction by the first developer transport member.

  According to a third aspect of the present invention, a developer carrier for supplying a developer to a development target, a first developer transport member for transporting the developer along the axial direction of the developer carrier, and the first A first chamber in which one developer conveying member is accommodated, a second developer conveying member that conveys the developer in a direction opposite to the first developer conveying member, and the second developer conveying member. A developing device having a developing container that is housed and includes a second chamber that is disposed substantially parallel to the first chamber below the first chamber and communicates with the first chamber at both ends; There is provided a developing device having a detecting means for detecting the gradient of the developer surface of the developer in the first chamber.

  According to one embodiment of the second and third aspects of the present invention, the developer transport speeds of the first developer transport member and the second developer transport member are changed according to the output of the detection means. According to another embodiment of the second and third aspects of the present invention, the developer carrying speed of the developer carrying member changes according to the output of the detecting means.

  According to a fourth aspect of the present invention, there is provided a developer container for containing a developer, the developer carrier for supplying the developer in the developer container to the development target, and the developer in the developer container being conveyed. A developer transporting member, and a developer discharge port for discharging the developer in the developer container by overflowing the developer container, and supplying the developer to the developer container. And a developing device having a detecting means for detecting discharge of the developer from the developer discharge port. According to an embodiment of the present invention, the apparatus further includes a developer recovery container for storing the developer discharged from the discharge port, and the detection unit is the developer recovery container for the developer discharged from the discharge port. The developer is detected on the inward movement path.

  Furthermore, according to a fifth aspect of the present invention, there is provided an image forming apparatus comprising: an image carrier as a developing object on which an electrostatic image is formed; and the developing devices according to the respective aspects of the present invention. Provided.

  According to the present invention, it is possible to stably maintain the developer surface of the developer in the developer container at an appropriate position.

  Hereinafter, the developing device and the image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Example 1
First, an overall configuration and operation of an example of an image forming apparatus to which the present invention can be applied will be described with reference to FIG. The image forming apparatus 100 according to the present exemplary embodiment includes an image reading unit (reader unit) R that optically reads image information of a document connected to an image forming apparatus main body (hereinafter referred to as “apparatus main body”) 1 and converts the image information into an electrical signal. The copying machine includes an image forming unit (printer unit) P that forms an image on a recording material, for example, a recording sheet, an OHP sheet, a cloth, or the like by using an electrophotographic method in accordance with an image information signal from the printer. The image forming apparatus 100 can also form an image in accordance with an image information signal from an external device such as a personal computer that is communicably connected to the apparatus main body 1.

  The image forming apparatus 100 has an image reading unit R at the top in the drawing. The image reading unit R includes an original platen glass 11 on which an original to be read is placed. Below the platen glass 11, a lamp 12, a reflection mirror 12, a lens 13, a photoelectric conversion element 15 and the like for irradiating light to the document are provided. Thereby, the image information of the original can be optically read and converted into an electric signal and sent to the image forming unit P.

  An image forming unit P is provided below the image reading unit R in the drawing. The image forming portion P has a cylindrical electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 3 as an image carrier so as to be rotatable in the direction of the arrow in the figure. Around the photosensitive drum 3, a charger 4 as a charging means for uniformly charging the surface of the photosensitive drum 3, a laser scanner 2 as an exposure means, and an electrostatic latent image formed on the photosensitive drum 3 as a developer toner. The developing device 5 that visualizes the toner image by the toner, the transfer charger 6 as a transfer means for transferring the toner image on the photosensitive drum 3 to the recording material (sheet material) S, and the residual toner remaining on the surface layer of the photosensitive drum 3 are collected A cleaner 7 is disposed.

  The recording material supply unit 8 also feeds the recording material S at a predetermined timing, a cassette 81 for storing the recording material S, a recording material supply roller 82 for feeding the recording material S, a conveying roller 83 for conveying the recording material S, and the recording material S. It has a timing roller 84 and the like. Further, the fixing device 9 includes a heating roller 91 and a pressure roller 92, and fixes the toner image on the recording material S to the recording material S by heat and pressure.

  Since the image forming process itself is well known in the art, a detailed description thereof will be omitted, but is as follows. First, the surface of the rotating photosensitive drum 3 is uniformly charged by the charger 4. The laser scanner 2 scans and exposes the surface of the charged photosensitive drum 3 in accordance with an image information signal read by the image reading unit R, and an electrostatic image is formed on the photosensitive drum 3. Next, the electrostatic image on the photosensitive drum 3 is converted into a toner image by the developing device 5 supplying the toner of the developer according to the electrostatic image. On the other hand, the recording material S is conveyed from the recording material supply unit 8 to the opposing portion (transfer unit) between the photosensitive drum 3 and the transfer charger 6 so as to synchronize with the formation of the toner image on the photosensitive drum 3. come. Thus, the toner image on the photosensitive drum 3 is electrostatically transferred onto the recording material S by the action of the transfer charger 6. The recording material S to which the toner image has been transferred is separated from the photosensitive drum 3 and conveyed to the fixing device 9. The unfixed toner image on the recording material S is fixed to the recording material S by the heat and pressure of the fixing device 9, and then the recording material S is discharged out of the apparatus. Further, the toner image remaining on the photosensitive drum 3 after the transfer process is removed by the cleaner 7, and the photosensitive drum 3 is repeatedly used for image formation.

  Next, the developing device 5 will be described in more detail with reference to FIGS. FIG. 2 shows a schematic enlarged cross section of the developing device 5 provided in the image forming apparatus 100 of this embodiment. FIG. 3 is a schematic cross-sectional view seen from the direction of arrow A in FIG. In the following description, the vertical and vertical directions for each element of the image forming apparatus 100 refer to those in an appropriate installation state of the apparatus.

  In the present embodiment, the developing device 5 includes a developing container (developer tank) 51, a developer replenishing device 55, and a developer collecting container 58.

  In the developing container 51, a developing roller 52 as a developer carrying member, and a first and second screws 531 and 532 are rotatably arranged as a developer conveying member 53 that stirs and conveys the developer. A developer is accommodated in the developing container 51. The developer in the developer container 51 is a mixture mainly including toner and carrier. In this embodiment, the toner mass ratio (hereinafter referred to as T / D ratio) in the developer is 8%. In this embodiment, the developer includes nonmagnetic toner particles and magnetic carrier particles. In addition, the developer may contain a desired composition such as an external additive of toner, as conventionally performed.

  The developing roller 52 extends substantially parallel to the axial direction of the photosensitive drum 3. The first and second screws 531 and 532 extend substantially parallel to the axial direction of the developing roller 52, that is, substantially parallel to the axial direction of the photosensitive drum 3. The first and second screws 531 and 532 have spiral conveying portions 531b and 532b on the outer circumferences of the rotation shafts 531a and 532a, respectively. The first screw 531 conveys the developer along the rotational axis direction from the near side to the far side with respect to the paper surface of FIG. 2, and the second screw 532 faces from the far side to the near side with respect to the paper surface. The developer is conveyed along the rotation axis direction.

  The first chamber (development chamber) 511 that accommodates the first screw 531 of the developing container 51 and the second chamber (agitation chamber) 512 that accommodates the second screw 532 are partitioned by a partition wall 513. The first chamber 511 and the second chamber 512 communicate with each other at both longitudinal ends of the developing container 51 along the longitudinal direction of the roller 52. As a result, the developer can circulate and move between the first chamber 511 and the second chamber 512.

  The developing roller 52 has a built-in magnet roll as a magnetic field generating means over substantially the entire longitudinal direction. As a result, the carrier that is frictionally charged and has the toner attached to the surface is magnetically restrained on the surface of the developing roller 52. As the developing roller 52 rotates, the developer on the developing roller 52 passes between the developing roller 52 and a regulating blade 59 as a developer regulating member provided opposite to the developing roller 52. The amount is regulated and supplied to a portion (developing portion) facing the photosensitive drum 3. Thereafter, the developer after the toner is supplied to the photosensitive drum 3 in accordance with the electrostatic image in the developing unit is further conveyed along with the rotation of the developing roller 52 and collected in the developing container 51.

  A developer replenishing device 55 as a developer replenishing means is provided above the developing container 51 in FIG. The replenishment agent accommodated in the replenishment agent accommodating portion 551 of the developer replenishing device 55 is replenished to the developing container 51 from the replenishment port 514 when the supply screw 552 as a developer supply member is rotationally driven. In the present embodiment, the supply port 514 is provided above the second chamber 512. In this embodiment, the T / D ratio of the replenisher as a replenishing developer is 90%. Here, the replenisher is a mixture of the carrier and the toner. However, for example, two replenisher storage portions are provided so that the carrier and the toner are accommodated in each of the replenishers. Or you may replenish after mixing mutually.

  A developer discharge port (hereinafter referred to as “discharge port”) 56 is provided on the wall surface of the developer container 51, more specifically, on the rear wall 515 along the axial direction of the second screw 532 of the second chamber 512. . When the replenishment agent is supplied from the developer replenishing device 55 and the amount of the developer in the developing container 51 increases, the developer beyond the discharge port lower portion 56a which is the lower edge of the discharge port 56 from the discharge port 56. Overflows. The developer overflowing from the discharge port 56 is accommodated in a developer recovery container 58.

  Replenishment of the replenishing agent is performed by directly detecting the T / D ratio of the developer in the developing container 51 by a developer concentration sensor (optical sensor, inductance sensor, etc.) provided in the developing container 51, or by the number of dots of the image formation image Or indirectly by detecting the density of the image on the photosensitive drum 3 by detecting a density detection image on the photosensitive drum 3, etc. This is performed by controlling the drive of the supply screw 552 of the developer supply device 55. Then, the developer in the developing container 51 that has become excessive due to the replenishment of the developer overflows from the discharge port 56, and the carrier is mainly collected in the developer collecting container 58. In this embodiment, the developer overflowing from the discharge port includes at least a carrier. Thus, in a normal state, the developer surface (upper surface exposed in the developing container 51) F in the developing container 51 is maintained at a substantially constant height as shown by hatching in FIG. The automatic developer replenishment control itself is well known, and any available method can be adopted in the present invention, so that further detailed explanation is omitted.

  The wall of the developing container 51, more specifically, the rear wall 515 along the axial direction of the second screw 532 of the second chamber 512, further detects whether the developer is properly discharged from the discharge port 56. As a means for this, a piezoelectric sensor 57A serving as a detecting means for detecting the agent surface F in the developing container 51 is provided. The piezoelectric sensor 57A is the position of the piezoelectric sensor 57A (more specifically, the detection position of the piezoelectric sensor 57A: hereinafter, the position of the piezoelectric sensor 57A refers to the detection position unless otherwise specified. The sensor 57A changes its signal when the developer level F of the developer rises until the detection position is shown. Thereby, it can be detected that the agent surface F in the developing container 51 has reached the height of the piezoelectric sensor 57A.

  In other words, as described above, in the conventional apparatus, the amount of the developer in the developer container increases when the developer stays in the discharge port, causing problems such as fluctuations in image density and toner scattering, or the developer. As the amount increases, the rotational load on the developer conveying member or the like increases, which may damage the developing device or a gear or a motor for driving the developing device. Therefore, the present invention can prevent the developer in the developing container from becoming excessive, and the developer in the developing device becomes excessive, resulting in deterioration in image quality, scattering of the developer, and developing device. Another object of the present invention is to provide a developing device and an image forming apparatus capable of suppressing damage to the image forming apparatus.

  More specifically, the piezoelectric sensor 57A is disposed above the agent surface F in the normal state by a predetermined amount. In the present embodiment, the piezoelectric sensor 57A is disposed 5 mm above the discharge port lower portion 56a. That is, in this embodiment, normally, the agent surface F in the developing container 51 is maintained at substantially the same position as the height of the discharge port lower portion 56a, which is approximately 5 mm below the piezoelectric sensor 57A. Then, the discharge port 56 is clogged with the developer, or the developer accumulates on the discharge port lower portion 56a so that the height of the discharge port lower portion 56a is substantially increased, and the developer is discharged properly. If it is not performed, the agent surface F rises and can be detected when it is raised 5 mm.

  In this embodiment, the piezoelectric sensor 57 </ b> A is disposed upstream of the discharge port 56 in the developer conveyance direction in the second chamber 512. Such an arrangement relationship is advantageous in that it does not affect the size of the developing device because the piezoelectric sensor 57A need not be arranged further outside the discharge port 56.

  In this embodiment, the replenishing port 514 is provided upstream of the discharge port 56 in the developer transport direction in the second chamber 512, and the developer is replenished by the developer replenishing device 55 at this position. When the piezoelectric sensor 57A is disposed upstream of the discharge port 56 in the developer conveyance direction, the agent surface F near the piezoelectric sensor 57A is slightly higher than the discharge port lower portion 56a. Further, since the developer is conveyed by the rotation of the second screw 532 in the second chamber 512, the agent surface F is undulated at a screw pitch cycle as shown in the figure. In consideration of these, in this embodiment, it is preferable that the piezoelectric sensor 57A is disposed about 3 mm to 8 mm above the discharge port lower portion 56a.

  As shown in FIG. 4, the piezoelectric sensor 57 </ b> A may be disposed downstream of the discharge port 56 in the developer conveyance direction in the second chamber 512. In such an arrangement, since the detection of the surface F is performed downstream of the discharge port 56, the height of the surface F may fluctuate due to the supply of the developer or the like if the developer is discharged without any delay. This is advantageous in that it is not. In the case of such an arrangement, normally, the agent surface F in the vicinity of the piezoelectric sensor 57A is at a position lower than the discharge port lower portion 56a, and therefore the piezoelectric sensor 57A is about 2 mm to 7 mm above the discharge port lower portion 56a. It is preferable to arrange in.

  Of course, how much the piezoelectric sensor 57A is disposed above the discharge port lower portion 56a can be appropriately selected according to the configuration of the developing device to which the present invention is applied.

  Further, when only one piezoelectric sensor 57A is arranged as shown in FIGS. 3 and 4, it is possible to detect whether or not the agent surface F is at a position higher than usual. On the other hand, as shown in FIG. 5, a plurality of piezoelectric sensors 57 </ b> A may be provided in the height direction in the developing container 51 to detect the developer surface F of the developer stepwise. In this case, the plurality of piezoelectric sensors 57A may be disposed upstream or downstream of the discharge port 56 as described above. In this way, if the height of the developer surface F of the developer can be detected in stages, it is possible to grasp the state in which the toner starts to accumulate on the discharge port lower portion 56a. That is, whether the developer level F of the developer in the developing container 51 is at a normal level, at a stage where it is rising, at a level that has risen enough to warn, or at a level that has risen enough to stop the apparatus immediately It can be detected step by step.

  Further, as described above, since the developer is conveyed by the rotation of the second screw 532 in the second chamber 512, the developer surface F of the developer is undulated with a screw pitch period. For this reason, depending on the amount of developer, the output of the piezoelectric sensor 57A may fluctuate with the rotation period of the second screw 532. Therefore, the output of the piezoelectric sensor 57A is obtained by averaging the results detected multiple times or continuously over at least one period of the rotation of the second screw 532, and detecting the developer surface F of the developer. It is preferable to determine whether or not the piezoelectric sensor 57A is located.

  For example, in this embodiment, the rotation speed (rotational speed) of the second screw 532 is 360 rpm, that is, 6 rotations per second. Therefore, if the piezoelectric sensor output for one second is averaged over time, the second screw 532 has 6 rotations. The average position of the agent surface F when rotated can be grasped. More specifically, the output of the piezoelectric sensor 57A is averaged as follows to determine whether or not the agent surface F is at the position of the piezoelectric sensor 57A. The piezoelectric sensor 57A outputs two values of Hi and Low depending on whether or not the developer is present on the detection surface. When sampling is performed 20 times every 50 ms (1 second in total), if the Hi level is 10 times or less, it is determined that the drug surface F has not reached the detection level, and if it is 11 times or more, the detection level has been reached. Judge. In this way, the position of the agent surface F can be detected without erroneous detection due to fluctuations in the screw pitch cycle of the agent surface F or sudden powder surface (agent surface) F abnormality.

  Thereby, the influence by the rotation period of the 2nd screw 532 can be eliminated.

  When it is detected that the surface F in the developing container 51 is higher than the normal state as described above, (i) the supply screw 552 of the developer supply device 55 is stopped, (ii) the image The operation of the forming unit P is stopped. (Iii) Display on the display unit 130 (FIG. 6) included in the apparatus main body 1 or the display unit of an external device connected to the apparatus main body 1 so as to be communicable, or appropriate The developer is not properly discharged from the discharge port 56 due to clogging of the discharge port 56 (or accumulation of developer on the lower portion 56a of the discharge port) by appropriate notification means such as an alarm sound. The operator informs the operator that the developer surface F of the developer is higher than the predetermined value, or (iv) the developer device 5 has the first and second components when the developer is clogged. Screws 531 and 532 only Rotate performed developer circulation, so that deposit toner outlet 56 falls, performs one or a combination of processing it.

  As described above, when the position of the agent surface F in the developing container 51 is detected step by step by providing a plurality of piezoelectric sensors 57A, any one or combination of the above-described processes is stepwise. Can be done.

  FIG. 6 is a block diagram of a control circuit according to the present embodiment. In this embodiment, the image forming apparatus 100 includes a control unit 110 that controls the operation of the image forming apparatus 100 in the apparatus main body 1. The control unit 110 may use a program and data stored in storage means 112 (EEPROM, FeRAM, or the like as rewritable nonvolatile memory may be used, or ROM: hereinafter referred to as “memory”) 112. The calculation control means (hereinafter referred to as “CPU”) 111 that causes the image forming apparatus 100 to perform a sequence operation in accordance with The CPU 111 of the control unit 110 is connected to the output of the piezoelectric sensor 57A provided in the developing container 51. The CPU 111 determines that the developer surface F in the developing container 51 has a piezoelectric sensor 57A from the change in the output of the piezoelectric sensor 57A. Can be detected. Further, the CPU 11 controls a driving device (driving motor) that transmits a driving force to the developer conveying member 53 (first screws 531, 532) provided in the developing container 51 to drive the developer conveying member 53. Controls the rotational movement of Further, as described above, the CPU 111 transmits a driving force to the developer supply member (supply screw) 552 of the developer supply device 55 in accordance with the detected T / D ratio in the developer container 51 (drive). The motor 140 is controlled to control the rotation operation of the supply screw 552.

  An image processing unit 120 is connected to the control unit 110, and the image processing unit 120 receives an image signal from an external device connected to the image reading unit R or the apparatus main body 1 so as to be communicable, and A signal related to image formation is transmitted to the control unit 30. The control unit 30 controls the operation of each unit of the image forming unit P according to the image forming signal.

  In the present embodiment, in particular, the CPU 111 according to the program and data stored in the memory 112, as described above, due to clogging of the discharge port 56 (or deposition of developer on the discharge port lower portion 56a), the discharge port 56. When it is determined that the developer is not properly discharged from the printer, (i) the driving device 140 that drives the supply screw 552 of the developer supply device 55 is stopped. (Ii) the image forming unit P (Iii) The developer is not properly discharged from the discharge port 56 due to clogging of the discharge port 56 (or deposition of developer on the discharge port lower portion 56a), and the development in the developing container 51 is stopped. The fact that the surface F of the agent has reached a predetermined value is displayed on the display unit 130 or the like, or (iv) the developer conveying member 53 (the driving device 1 that drives the first and second screws 531, 532) And controls the driving of 0, the first developing unit 5, thereby driving only the second screw 531 and 532, to execute any or a combination of processing it.

  Further, as described above, when averaging the output of the piezoelectric sensor 57A, the CPU 111 averages the output of the piezoelectric sensor 57A according to the program and data stored in the memory 112, and the agent surface F in the developing container 51 is obtained. Determine the position.

  Further, as described above, in the case where a plurality of piezoelectric sensors 37A are provided, the CPU 111 detects the position of the piezoelectric sensor 37A detected as having the agent surface F among the plurality of piezoelectric sensors 57A according to the program and data stored in the memory 112. From the number, combination, etc., the height of the developer surface F in the developer container 51 is detected stepwise. Then, according to the detected level of the developer surface F in the developing container 51, any one or combination of the above-described processes can be executed in stages.

  In the present embodiment, the example in which the piezoelectric sensor 57A is used as the detecting means for detecting the position of the agent surface F has been described, but the present invention is not limited to this. For example, an ultrasonic level sensor may be provided above the developing container 51 to detect the reflection of ultrasonic waves and grasp the position of the agent surface F. Alternatively, the agent surface F may be detected using an optical sensor including a light emitting unit (such as a light emitting diode) and a light receiving unit (such as a phototransistor).

  As described above, according to the present embodiment, the developing device 5 that sequentially replaces the developer is configured to detect an abnormal increase in the developer in the developer container 51, so that the agent surface F in the developer container 51 is stabilized. Can be achieved. Further, damage to the developing device 5 and toner scattering can be prevented, and a stable image can always be formed.

Example 2
Next, another embodiment of the present invention will be described. Since the basic configuration and operation of the image forming apparatus of the present embodiment are the same as those of the first embodiment, elements having substantially the same or corresponding functions and configurations as those of the first embodiment have the same reference numerals. A detailed description is omitted.

  FIG. 7 shows a schematic cross section of the developing device 5 provided in the image forming apparatus 100 of the present embodiment. In this embodiment, a plurality of developer conveying members are arranged in the vertical direction.

  In other words, the developer container 51 of the developing device 5 supplies the developer to the developing roller 52 as the developing roller 52 as the developer carrying member and the developer conveying member 54 that stirs and conveys the developer. A developer recovery screw (second screw) 542 that recovers and conveys the developer from the developing roller 52 is positioned rotatably below the screw (first screw) 541 and the developer supply screw 541. Has been.

  The developing roller 52 extends substantially parallel to the axial direction of the photosensitive drum 3. The first and second screws 541 and 542 have spiral conveying portions 541b and 542b on the outer circumferences of the rotation shafts 541a and 542a, respectively. The first and second screws 541 and 542 extend substantially parallel to the axial direction of the developing roller 52, that is, substantially parallel to the axial direction of the photosensitive drum 3. The developer conveying directions of the first and second screws 541 and 542 are opposite directions, and the first screw 541 conveys the developer along the rotation axis direction from the back side to the near side with respect to the paper surface of FIG. The second screw 542 conveys the developer along the rotation axis from the near side to the far side with respect to the paper surface.

  FIG. 8 is a schematic cross-sectional view seen from the direction of arrow B in FIG. A first chamber (developing chamber) 511 that accommodates the first screw 541 and a second chamber (stirring chamber) 512 that accommodates the second screw 542 and is positioned substantially vertically below the first chamber are divided into partition walls (first The first chamber 511 and the second chamber 512 communicate with each other at both ends in the longitudinal direction of the developing container 51 along the longitudinal direction of the developing roller 52.

  The developer circulates in the developing container 51 by the first and second screws 541 and 542 as shown by arrows in FIG. At the same time, there is also a developer that is supplied from the first chamber 511 to the developing roller 52 and passes through a path to be collected in the second chamber 512 after being supplied to the developing process. Therefore, as shown by hatching in FIG. 8, the developer in the developing container 51 is supplied to the developing roller 52 in the first chamber 511 as the developer is conveyed (as it moves to the left in the figure). As a result, the amount decreases, and conversely increases in the second chamber 512 as the developer collected from the developing roller 52 joins as the developer is conveyed (as it moves to the right in the figure). In this way, the developer surface F of the developer in the first chamber 511 and the second chamber 512 developing container 51 increases in the first chamber 511 and the second chamber 512 as it goes to the right as shown in the figure. Have

  A developer replenishing device 55 is provided above the developing container 51 in FIG. 7, and the replenishing agent accommodated in the replenishing agent accommodating portion 551 is rotated in the present embodiment by rotating the supply screw 552. The replenishment port 514 provided above the first chamber 511 is replenished into the first chamber 511. The developer in the developing container 51 and the composition of the replenisher replenished to the developing container 51 from the developer replenishing device 55 are the same as those in the first embodiment. In this embodiment, the position of the supply port 514 in the longitudinal direction of the developing container 51 is the same as that in the first embodiment.

  A discharge port 56 is provided on the wall surface of the developing container 51, more specifically, on the rear wall 515 along the axial direction of the first screw 541 of the first chamber 511. When the replenishing agent is supplied from the developer replenishing device 55 and the amount of the developer in the developing container 51 increases, the developer beyond the discharge port lower portion 56 a overflows from the discharge port 56. The developer overflowing from the discharge port 56 is accommodated in a developer recovery container 58.

  On the wall surface of the developing container 51, more specifically, on the rear wall 515 along the axial direction of the first screw 541 in the first chamber 511, a piezoelectric sensor 57A similar to that in the first embodiment is disposed. In this embodiment, five piezoelectric sensors 57A are arranged on the rear wall 515 of the first chamber 511 in the developer transport direction. As in the first embodiment, the piezoelectric sensor 57A changes the signal when the developer surface F of the developer rises up to the piezoelectric sensor 57A. Thereby, it can be detected that the agent surface F has reached the height of the piezoelectric sensor 57A.

  In the present embodiment, as described above, since the developer surface F of the developer in the first chamber 511 has a gradient, the position of each piezoelectric sensor 57A in the height direction is arranged substantially along the gradient. .

  More specifically, in this embodiment, each of the five piezoelectric sensors 57A is disposed above the agent surface F in the normal state by a predetermined amount. In the present embodiment, normally, the height is approximately 5 mm below each piezoelectric sensor 57A. As in Example 1, the developer surface F rises when the developer is not properly discharged, and detection is possible when the agent surface F rises 5 mm at the position of each piezoelectric sensor 57A. .

  Further, as described above, by arranging a plurality of piezoelectric sensors 57A substantially along the gradient of the developer surface F, the rise of the developer surface F can be detected as described above, and the agent surface F is also detected. It is possible to grasp the situation of the slope. As described above, in this embodiment, the plurality of piezoelectric sensors 57 </ b> A that detect the agent surface F constitute a plurality of detection units that are means for detecting the gradient of the agent surface F in the developing container 51.

  That is, as described above, the developer in the developing container is biased and the distribution of the developer carried by the developer carrying member becomes non-uniform immediately after the developing device is placed in the image forming apparatus. The density unevenness of the image may occur. Therefore, the present invention can prevent the bias of the developer in the developing container, and when the developer surface of the developer in the developing container is inclined more than a predetermined amount, It is another object of the present invention to provide a developing device capable of suppressing deterioration in image quality such as unevenness and an image forming apparatus including the developing device.

  Specifically, when any one of the five piezoelectric sensors 57A detects an increase in the surface of the liquid, development from the discharge port 56 due to clogging of the discharge port 56 (or deposition of developer on the lower portion 56a of the discharge port). It can be determined that the developer is not properly discharged or that the developer is biased.

  For example, when the left two of the five piezoelectric sensors 57A in the drawing are Low and the right three detect Hi, the gradient of the developer surface F of the developer is abnormal. It can be determined that the allowable value has been exceeded.

  When the gradient of the agent surface F in the first chamber 511 is larger than a predetermined amount, the rotational speed of the first screw 541 and the second screw 542 is increased, and the developer circulation path does not pass through the developing roller 52 described above. The developer conveying speed of the path is relatively increased. Thereby, the gradient in the first chamber 511 can be reduced.

  Here, if the amount of developer conveyed by the first screw 541 and the second screw 542 is relatively sufficiently larger than the amount of developer conveyed by the developing roller 52, the developer surface F of the developer in the first chamber 511. However, increasing the stirring and conveying speed of the developer leads to faster deterioration of the developer. Therefore, it is desirable that the developer conveying speed of the first and second screws 541 and 542 be a minimum necessary speed. In this embodiment, since there is a means for detecting the gradient of the agent surface F in the developer container 51, that is, a plurality of piezoelectric sensors 57A, the developer agitating and conveying speed changes due to environmental fluctuations, etc. Even if the gradient of the agent surface F changes, it can be detected and reduced. Thereby, normally, the rotational speeds of the first and second screws 541 and 542 can be set as low as necessary. For example, as the environmental variation, the gradient of the developer surface F of the developer may be steep in a high humidity environment.

  In the developing device 5 of the present embodiment, when the rotation speed of the first and second screws 541 and 542 is 360 rpm, the gradient of the coating surface F exceeds the allowable value. When the rotational speed is increased to 420 rpm, the coating surface is increased. The slope was within acceptable limits.

  More specifically, when it is determined that the developer in the first chamber 511 is biased from the output of the piezoelectric sensor 57A or the gradient of the agent surface F exceeds the allowable value, the processing shown in FIG. 9 is performed. That is, normally, when the first and second screws 531 and 532 are driven at 360 rpm (step 1) and driven for 5 seconds (step 2), the output of the piezoelectric sensor 57A is detected (step 3), and the piezoelectric sensor 57A is detected. Is detected, the rotational speeds of the first and second screws 541 and 542 are increased by 30 rpm (step 4). Thereafter, the first and second screws 541 and 542 are driven for 5 seconds (step 2). When the determination in step 3 is performed again and the Hi signal of the piezoelectric sensor 57A is detected, the first and second screws 541 and 542 are detected. Increase the number of revolutions by 30 rpm. On the other hand, when the Low signal is detected from all the piezoelectric sensors 57A in the determination of Step 3, the rotation of the first and second screws 541 and 542 is not increased, and the apparatus is driven after completion of the image formation. Stop. This process can be executed even during image formation.

  Further, when it is determined from the output of the piezoelectric sensor 57A that the developer in the first chamber 511 is biased or the gradient of the agent surface F exceeds the allowable value, processing as shown in FIG. 10 may be performed. That is, normally, when the first and second screws 541 and 542 are driven at 360 rpm (step 1) and driven for 5 seconds (step 2), the output of the piezoelectric sensor 57A is detected (step 3), and the piezoelectric sensor 57A is detected. Is detected, the rotational speeds of the first and second screws 541 and 542 are increased by 30 rpm (step 4). Then, after the rotational speed of the first and second screws 541 and 542 is increased by 30 rpm in step 4, if it is determined that the rotational speed is equal to or higher than a predetermined value (here, 500 rpm), the image forming apparatus main body 1 An error display to the effect that the developer in the developing container 51 is biased or the gradient of the agent surface F has exceeded an allowable value is displayed on the display unit 130 (FIG. 6) provided in the operation unit provided (step 6). ). Thereafter, the drive of the apparatus is stopped after completion of image formation (step 7). If the rotational speed of the first and second screws 541 and 542 is less than 500 rpm in the determination in step 5, the first and second screws 541 and 542 are driven for 5 seconds (step 2), and the determination in step 3 is performed again. When the Hi signal of the piezoelectric sensor 57A is detected, the rotational speeds of the first and second screws 541 and 542 are increased by 30 rpm. On the other hand, when the Low signal is detected from all the piezoelectric sensors 57A in the determination of Step 3, the rotation of the first and second screws 541 and 542 is not increased, and the apparatus is driven after completion of the image formation. Stop.

  In the present embodiment, similarly to the first embodiment, the outputs of the respective piezoelectric sensors 57A can be averaged to determine whether or not the agent surface F exists at the position of each piezoelectric sensor 57A.

  The control mode of the present embodiment is basically the same as that of the first embodiment shown in FIG. 6, but in this embodiment, the CPU 111 is particularly configured as described above according to the program and data stored in the memory 112. Further, from the outputs of the plurality of piezoelectric sensors 57A provided in the developing container 51, the developer is properly discharged from the discharge port 56 due to clogging of the discharge port 56 (or deposition of developer on the discharge port lower portion 56a). It can be determined that the developer level F of the developer in the developing container 51 has risen. When it is determined that the developer is not properly discharged from the discharge port 56 due to clogging of the discharge port 56 (or developer accumulation on the discharge port lower portion 56a), the same processing as in the first embodiment is performed. Can be executed.

  In the present embodiment, the CPU 111 changes the developer stirring and conveying speed from the outputs of the plurality of piezoelectric sensors 57A provided in the developing container 51 as described above according to the program and data stored in the memory 112. Thus, it can be determined that the developer in the developer container 51 is biased or the gradient of the developer surface F exceeds the allowable value. When it is determined that the developer in the developing container 51 is biased or the gradient of the developer surface F exceeds the allowable value, the first and second screws 541 and 541 in the developing container 51 are driven. By controlling the driving of the driving device 150 to be transmitted, the developer surface F of the developer is made appropriate by the processing as described above.

  In this embodiment, the rotational speeds of the first and second screws 541 and 542 are increased in order to make the gradient of the developer surface F of the developer appropriate. However, the present invention is not limited to this. For example, even if only the first screw 541 and the second screw 542 are rotationally driven by lowering or stopping the rotation speed of the developing roller 52, the developer conveyance amount of the first and second screws 541 and 542 is relatively increased. It will be done. However, in this case, since the ability of the developing roller 52 to supply the toner to the photosensitive drum 3 is reduced, it is desirable to carry out at a predetermined timing other than the time of image formation. Examples of the predetermined timing other than the time of image formation include a pre-rotation which is a preparatory operation before image formation (or a post-rotation which is a preparatory operation after image formation).

  In this embodiment, the rotational speeds of the first and second screws 541 and 542 are increased in order to make the gradient of the developer surface F appropriate. However, the present invention is not limited to this. When the gradient of the liquid surface F exceeds the allowable value, the user may be notified by an alarm or the like.

  As described above, according to the present embodiment, the same effects as those of the first embodiment can be obtained, and further, the deviation of the developer in the developer container 51 can be detected and the developer transport speed of the developer transport member 54 can be appropriately changed. Thus, image defects can be prevented while minimizing the deterioration of the developer.

Example 3
Next, another embodiment of the present invention will be described. Since the basic configuration and operation of the image forming apparatus of the present embodiment are the same as those of the first embodiment, elements having substantially the same or corresponding functions and configurations as those of the first embodiment have the same reference numerals. A detailed description is omitted.

  FIG. 11 shows a schematic cross section of the developing device 5 provided in the image forming apparatus 100 of the present embodiment. As shown in the figure, the developing device 5 of this embodiment is basically the same as that of the first embodiment shown in FIG. In this embodiment, as a means for detecting whether or not the developer is properly discharged from the discharge port 56, the discharge is performed from the discharge port 56 instead of the piezoelectric sensor 57A provided in the developing container 51 in the first embodiment. The optical sensor 57B is disposed in the developer moving path (falling path).

  The optical sensor 57B includes a light emitting diode 571 that is a light emitting portion and a phototransistor 572 that is a light receiving portion. Then, when the developer overflowing from the discharge port 56 passes between the light emitting diode 571 and the phototransistor 572 and interrupts the optical path, the output of the phototransistor 572 changes. From the output of the phototransistor 572, it can be detected whether the developer is discharged from the discharge port 56.

  In this embodiment, the discharge port 56 is clogged with the developer or the discharge port lower portion 56a if the output of the phototransistor 572 does not change even though the supply agent is supplied from the developer supply device 55. It is determined that the developer is deposited on the surface.

  More specifically, when the supply screw 552 of the developer supply device 55 of this embodiment is rotationally driven, the surface F near the discharge 56 rises after about 2 seconds. Although the amount higher than the discharge port lower portion 56a overflows due to the rise of the surface F, the toner is discharged relative to the amount replenished by the supply screw 552 because it is supplied to the photosensitive drum 3 as described above. The amount is slightly smaller and it takes time to discharge. The supply screw 552 replenishes 0.8 g of developer in 1 second, but discharge from the discharge port is 0.1 to 0.3 g in 1 second. It is not necessarily discharged from the outlet 56 immediately after being replenished. Accordingly, the detection by the optical sensor 57B determines that the developer is not discharged from the discharge port 56 only when the developer discharge is not detected for 15 seconds after the supply screw 552 is driven to rotate. As described above, based on the output of the optical sensor 57B, it is determined that the developer is not properly discharged from the discharge port 56 due to clogging of the discharge port 56 (or deposition of developer on the discharge port lower portion 56a).

  FIG. 12 is a block diagram of a control circuit according to the present embodiment. As shown in the figure, the control mode in this embodiment is basically the same as that in the first embodiment shown in FIG. 6. In this embodiment, however, the CPU 111 is an optical unit provided in the developer recovery container 58. From the output of the sensor 57B, it is determined that the developer is not properly discharged from the discharge port 56 due to clogging of the discharge port 56 (or deposition of developer on the discharge port lower portion 56a). When it is determined that the developer is not properly discharged from the discharge port 56, the same processing as that in the first embodiment is executed.

1 is a schematic cross-sectional view of an embodiment of an image forming apparatus according to the present invention. 1 is a schematic cross-sectional view of an embodiment of a developing device according to the present invention. FIG. 3 is a schematic cross-sectional view of the developing container as viewed from the direction of arrow A in FIG. 2. It is a schematic sectional drawing of the developing container seen from the same direction as FIG. 3 for demonstrating the other arrangement | positioning aspect of a piezoelectric sensor. It is a schematic sectional drawing of the developing container seen from the same direction as FIG. 3 for demonstrating the other arrangement | positioning aspect of a piezoelectric sensor. It is a general | schematic control block diagram which concerns on one Example of this invention. It is a schematic sectional drawing of the other Example of the image development apparatus concerning this invention. FIG. 8 is a schematic cross-sectional view of the developing container as viewed from the direction of arrow B in FIG. 7. It is a flowchart of control concerning other examples of the present invention. It is a flowchart of control concerning other examples of the present invention. It is a schematic sectional drawing of the other Example of the image development apparatus concerning this invention. It is a general | schematic control block diagram which concerns on the other Example of this invention.

Explanation of symbols

5 Developing Device 52 Developing Roller (Developer Carrier)
53 First and second screws (developer conveying member)
54 First and second screws (developer conveying member)
55 Developer Supply Device (Developer Supply Unit)
56 Discharge port 56a Discharge port lower part 57A Piezoelectric sensor (detection means)
57B Optical sensor (detection means)
100 Image forming apparatus

Claims (26)

A developer container for containing a developer, a developer carrying member for supplying the developer in the developer container to a developing target, a developer transport member for transporting the developer in the developer container, and the developer container A developer container comprising a developer discharge port for discharging the developer in the developer container by overflowing the developer inside,
Developer supply means for supplying developer to the developer container;
In a developing device having
A developing device, wherein the developing container is provided with a detecting means for detecting the surface of the developer in the developing container.   The developing device according to claim 1, wherein the detection unit is disposed upstream of the developer discharge port in a developer transport direction by the developer transport member.   The developing device according to claim 1, wherein the detection unit is located downstream of the developer discharge port in the developer conveyance direction by the developer conveyance member.   The developing device according to any one of claims 1 to 3, wherein the output of the detecting means changes when the developer level in the developer container rises by a predetermined amount from a normal state.   The developing device according to claim 1, wherein the detection unit is arranged at a plurality of locations.   The developing device according to claim 5, wherein the plurality of detection units are arranged side by side in the height direction.   7. The developing device according to claim 6, wherein the outputs of the plurality of detecting means change stepwise as the developer level in the developer container rises from a normal state.   The developing device according to claim 1, wherein a plurality of the detection units are provided in a developer conveying direction by the developer conveying member.   9. The developing device according to claim 8, wherein a driving speed of the developer conveying member is changed in accordance with outputs of the plurality of detecting units.   The developer conveying member conveys the developer by rotating around a rotation axis along the developer conveying direction by the developer conveying member, and outputs the detection means to the developer conveying member. 10. The developer level in the developer container is detected by detecting and averaging a plurality of times or continuously over at least one rotation period or more. 10. Development device.   The developing device according to claim 1, wherein the developer in the developing container includes toner and a carrier. The developing device according to claim 1, wherein the developer supplied by the developer supply means includes toner and a carrier. Housed in a developer carrier for supplying the developer to the member to be developed, a first developer transport member for transporting the developer along the axial direction of the developer carrier, and the first developer transport member A first chamber, a second developer conveying member that conveys the developer in a direction opposite to the first developer conveying member, and the second developer conveying member. A developing device having a developing container provided with a second chamber disposed substantially parallel to the first chamber at a substantially lower position and communicating with the first chamber at both ends;
A developing device comprising a plurality of detection means for detecting the developer surface of the developer in the first chamber along a developer transport direction by the first developer transport member. Housed in a developer carrier for supplying the developer to the member to be developed, a first developer transport member for transporting the developer along the axial direction of the developer carrier, and the first developer transport member A first chamber, a second developer conveying member that conveys the developer in a direction opposite to the first developer conveying member, and the second developer conveying member. A developing device having a developing container provided with a second chamber disposed substantially parallel to the first chamber at a substantially lower position and communicating with the first chamber at both ends;
A developing device comprising a detecting means for detecting a gradient of the developer surface of the developer in the first chamber.   The detection unit includes a plurality of detection units for detecting the developer level of the developer in the first chamber along a developer conveyance direction by the first developer conveyance member. Development device.   The developer transport speed of the first developer transport member and the second developer transport member is changed according to the output of the detection means. The developing device described.   The developing device according to claim 13, wherein a developer conveyance speed of the developer carrying member is changed according to an output of the detection unit.   The first developer conveying member conveys the developer by rotating around a rotation axis along the developer conveying direction by the first developer conveying member, and outputs the detection means. The developer level of the developer in the first chamber is detected by detecting and averaging a plurality of times or continuously over at least one rotation period or more of the first developer conveying member. The developing device according to any one of 17 items.   The developing device according to claim 13, wherein the developer in the developing container includes toner and a carrier.   In addition, a developer replenishing means for replenishing the developer to the developer container is provided, and the developer container is discharged outside the developer container by overflowing the developer in the first chamber to the first chamber. The developing device according to claim 13, further comprising a developer discharge port.   21. The developing device according to claim 20, wherein the developer replenished by the developer replenishing means includes toner and a carrier. A developer container for containing a developer, a developer carrying member for supplying the developer in the developer container to a developing target, a developer transport member for transporting the developer in the developer container, and the developer container A developer container comprising a developer discharge port for discharging the developer in the developer container by overflowing the developer inside,
Developer replenishing means for replenishing the developer into the developer container;
In a developing device having
A developing device comprising a detecting means for detecting the discharge of the developer from the developer discharge port.   Furthermore, a developer recovery container for containing the developer discharged from the discharge port is provided, and the detection unit develops the developer discharged from the discharge port through a movement path into the developer recovery container. 23. The developing device according to claim 22, wherein the developer is detected.   24. The developing device according to claim 23, wherein the developer in the developing container includes toner and a carrier.   25. The developing device according to claim 23 or 24, wherein the developer replenished by the developer replenishing means includes toner and a carrier.   An image forming apparatus comprising: an image carrier as a developing object on which an electrostatic image is formed; and the developing device according to claim 1.

Images