JP4338673B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile machine that forms an electrostatic latent image on an image carrier such as a photosensitive drum and develops the latent image to obtain an image. In particular, the present invention relates to an image forming apparatus using a two-component developer for development.

  Conventionally, an image forming apparatus capable of forming an image in color on a recording material such as paper by an electrophotographic method is known. In the image forming process on the recording material by the image forming apparatus, first, the surface of the photosensitive drum as the image carrier is uniformly charged by the charger, and then the image exposure is performed by the exposure device to form the surface of the photosensitive drum. An electrostatic latent image is formed. Subsequently, when a developer is applied to the surface of the photosensitive drum by a developing device, the electrostatic latent image is developed and visualized as a toner image, and the toner image is further transferred to a recording material. This process is performed for four colors of magenta, cyan, yellow, and black, and toner images of four colors are superimposed and transferred onto the recording material. Subsequently, the toner image on the recording material is heated by the fixing roller and fixed on the recording material, whereby a color image is formed on the recording material.

  In a developing device of such an image forming apparatus, a two-component developer of a magnetic developer composed of toner and a magnetic carrier is widely used. Various image density control methods have been proposed in consideration of various restrictions on the development method and the configuration of the image forming apparatus. In general, the toner is consumed from the two-component developer by developing the image, and the toner is supplied to the developing device so that the gradually decreasing toner concentration is detected by the sensor to maintain an appropriate predetermined concentration. Supply control is performed from the toner container. Thereby, the color image on the recording material is controlled to an appropriate image density.

  As a method for detecting the toner concentration, for example, a magnetic permeability detection method is widely known. As a magnetic permeability detection method, as a detection unit, a detection coil is disposed near the developer in the developing device, a reference coil is disposed at a position not affected by the developer, and these two coils (magnetic sensors) are provided. A differential transformer system is known that is AC driven and detects the toner density of the developer based on the differential output of both coils. In the differential transformer method, when the developer concentration changes, the magnetic permeability μ of the developer changes, and the inductance of the detection coil arranged near the developer changes, so the difference between the reference coil and the detection coil The dynamic output changes, the change in the differential output is detected, and the toner density of the developer is detected.

In addition, since the magnetic permeability detection method is non-optical, the toner density of the black developer can be detected, and a solid toner patch is formed on the photosensitive drum, and the density of this toner patch is measured by an optical sensor. Direct detection that detects the toner density by directly measuring the developer characteristics in the developing unit and the developer in the developing device, such as the patch detection method that measures and detects the toner density, and the developer in the developing device. It is possible to perform highly reliable density detection without being affected by the dirt on the window of the optical sensor unit.
JP-A-5-265327

  Certainly, with the image forming apparatus having the above-described configuration, it is possible to control the toner density of each color required for reproducing a high-quality image from a low density to a high density part. In addition, since a magnetic permeability detection type detection coil used for toner density detection can be arranged in the developing device, it is possible to reduce the size of the apparatus main body and to reduce the manufacturing cost. is there.

  However, in the conventional image forming apparatus, it is possible to reduce the size of the apparatus body to some extent by arranging the detection coil in the developing device. However, in the color machine, each of the four sensors for detecting the toner density is used. Since the same stabilization circuit unit that stabilizes the output input from the sensor and outputs it again is necessary, it is difficult to further reduce the size of the apparatus body and reduce the manufacturing cost.

  Also, one antenna conductor (corresponding to a sensor for detecting the amount of toner) of each developing device is connected in common and connected in common to one signal generator, and the other antenna conductor opposed by the selection switch is connected. There has been disclosed and proposed an image forming apparatus that selects one and connects to one toner amount detection circuit to detect the toner amount of a desired developing device (see, for example, Patent Document 1). However, the image forming apparatus disclosed in Patent Document 1 does not describe specific control, and the possibility of erroneous detection of the amount of toner due to a change in fluidity due to toner agitation in the developing device is sufficiently high. To leave. For example, since the toner in the developing device is agitated, the detection level of the toner amount repeats the presence / absence of toner, and finally changes to a level indicating that there is no toner, but the sensor is periodically switched by the selection switch. If it is performed, the state of the change cannot be detected, so that an erroneous detection of the remaining amount of toner occurs.

  In view of the above problems, the present invention can perform highly reliable detection control of the remaining amount of toner even if the stabilization circuit unit corresponding to the sensor for detecting the toner density of each developing device is shared. An object is to provide a possible image forming apparatus.

  In order to achieve the above object, an image forming apparatus according to the present invention accommodates a two-component developer in which a toner of a predetermined color and a carrier are mixed, and a latent image formed on an image carrier based on image data. A plurality of developing units that develop an image using the two-component developer, a plurality of sensors that are assigned to the respective developing units and that perform output in accordance with the density of the toner in the developing unit, and the developing unit A plurality of toner containers each containing a corresponding color toner; a replenishment unit that replenishes toner of a color corresponding to the plurality of developing devices from the toner container; and the plurality of sensors. Selecting means for performing electrical connection, one stabilizing circuit section for stabilizing and outputting the output of the sensor input from the selecting means, and the plurality of sensors for the selecting means. The electrical First control means for switching the connection at every first time, and determining whether the outputs of the plurality of sensors input along with the connection are lower than a predetermined threshold, and the first control means When it is determined that the output of any one of the plurality of sensors is lower than the predetermined threshold, only the electrical connection with the sensor corresponding to the determination is performed in the second time longer than the first time. A second control unit that switches to the selection unit and determines whether the output of the sensor corresponding to the determination is continuously lower than the predetermined threshold a plurality of times during the second time; Further, when the second control means determines that the output of the sensor is lower than the predetermined threshold value, the third supply means supplies the toner corresponding to the developing device assigned to the sensor to the supply means. Control means And it is to consist configuration.

  With such a configuration, it is possible to prevent erroneous detection of the remaining amount of toner in the developing device due to stirring and transporting of the two-component developer. Further, since the stabilization circuit portion can be shared, the apparatus main body can be reduced in size and the manufacturing cost can be reduced.

  In addition, the third control unit of the image forming apparatus having the above-described configuration, when the second control unit determines that the output of the sensor is lower than the predetermined threshold value, The electrical connection with the sensor is switched for a third time longer than the second time, and it is determined whether the output of the sensor is continuously lower than the predetermined threshold during the third time. When the third control means determines that the output of the sensor is continuously lower than the predetermined threshold during the third time, the toner corresponding to the developing device to which the sensor is assigned An exchange request means for requesting the exchange of the container is provided.

  With such a configuration, it is possible to request the user to replace the toner container that has run out of toner stored in the toner container.

  Further, the third control unit of the image forming apparatus having the above-described configuration may be configured such that the output of the sensor whose output is determined to be lower than the predetermined threshold by the second control unit is higher than the predetermined threshold. Until this occurs, the toner corresponding to the developing device to which the sensor is assigned is supplied to the supply means.

  With this configuration, an appropriate amount of toner can be supplied from the toner container to the developing device.

  As described above, with the image forming apparatus according to the present invention, it is possible to prevent erroneous detection of the remaining amount of toner in the developing device, and to reduce the size of the apparatus body and reduce the manufacturing cost. Become.

  In the following description, the present invention is applied to a four-color drum full-color tandem copying machine as an example. FIG. 1 is a block diagram showing the configuration of the main part of a copying machine according to the present invention, and FIG. 2 is a longitudinal sectional view schematically showing the structure of the main part of the copying machine according to the present invention. As shown in both figures, the copier 1 of this embodiment includes a central processing unit 10 (hereinafter referred to as a CPU [Central Processing Unit] 10) that controls the operation of the entire apparatus, and a document transport that automatically transports a document. Unit 11, a document take-in unit 12 that takes in a document transported from document transport unit 11 and generates image data, and an operation display unit 13 that includes operation means (such as a numeric keypad or touch panel) and display means (such as a liquid crystal display). Then, an image forming unit 15 that forms (that is, transfers) a toner image that becomes a color or monochrome image on a sheet based on the image data, and a toner image formed on the sheet by the image forming unit 15 is fixed on the sheet. A fixing unit 16, a paper feeding unit 14 that feeds paper to the image forming unit 15, a paper discharge unit 17 that is a paper discharge destination, and a ROM [Read Only M] in which various control programs are stored. emory], a RAM [Random Access Memory] used as a work area, and a memory unit 18 including a hard disk in which various data are stored. The memory unit 18 stores programs and data necessary for carrying out the present invention. Further, the copying machine 1 of the present embodiment can copy a document image on a recording material such as paper or an OHP sheet.

In addition to controlling the overall operation of the apparatus, the CPU 10 causes the selection switch, which will be described in detail later, to switch the electrical connection with the plurality of magnetic sensors at each first time T1, and the plurality of magnetic fields input along therewith. A first control unit for determining whether an output corresponding to the toner density of the sensor is lower than a predetermined threshold; and the output of any of the plurality of magnetic sensors by the first control unit is lower than the predetermined threshold If it is determined that, only the electrical connection with the magnetic sensor corresponding to the determination is switched to the selection switch at the second time T2 longer than the first time T1, and the output of the corresponding magnetic sensor Is determined to be lower than the predetermined threshold value a plurality of times during the second time T2, and the output of the corresponding magnetic sensor is further output by the second determining means by the predetermined threshold value. A third control means for causing the supply means (toner motor in this embodiment) to supply toner corresponding to the developing device to which the corresponding magnetic sensor is assigned; As a role.

  As shown in FIG. 2, the sheet feeding unit 14 includes a plurality of (three in this embodiment) sheet storage units 141 a to 141 c serving as a sheet supply source to the image forming unit 15, and each sheet storage unit 141 a to 141 c. A sheet conveyance unit 142 serving as a common sheet conveyance path from the image forming unit 15 to the image forming unit 15.

  The image forming unit 15 includes a yellow image forming unit 15a that forms a yellow toner image on a paper, a magenta image forming unit 15b that forms a magenta toner image on the paper, and a cyan toner image on the paper. The image forming apparatus includes a cyan image forming unit 15c that forms an image and a black image forming unit 15d that forms a black toner image on a sheet.

  Further, as shown in FIG. 2, the yellow image forming unit 15a, the magenta image forming unit 15b, the cyan image forming unit 1c, and the black image forming unit 15d are arranged in each color of yellow, magenta, cyan, and black based on the image data. Image bearing member photosensitive drums 19a to 19d on which toner images are formed on the respective drum surfaces, chargers 23a to 23d for uniformly charging the surfaces of the respective photosensitive drums 19a to 19d to predetermined potentials, and image data Based on the exposure units 22a to 22d for forming electrostatic latent images on the surfaces of the photosensitive drums 19a to 19d by irradiating laser light, and yellow and magenta from the electrostatic latent images on the surfaces of the photosensitive drums 19a to 19d, respectively. , Cyan and black toner images are formed on the surfaces of the photosensitive drums 19a to 19d. And toner containers 21a to 21d for supplying toners of colors corresponding to the developing devices 20a to 20d and formed on the surfaces of the photosensitive drums 19a to 19d, respectively, containing toners of yellow, magenta, cyan and black. The transfer rollers 25a to 25d for electrostatically transferring the toner images to the conveyed paper and the recovery of the toner remaining on the surfaces of the photosensitive drums 19a to 19d and the charge removal on the surfaces of the photosensitive drums 19a to 19d. Cleaning units 24a to 24d to be performed. A solid line arrow in FIG. 2 indicates a sheet conveyance path.

  Next, the configurations of the developing devices 20a to 20d and the toner containers 21a to 21d provided in the image forming units 15a to 15d will be described below. FIG. 3 is a longitudinal sectional view schematically showing an example of the configuration of the developing unit 20a and the toner container 21a in FIG. The configuration of the developing unit 20a and the toner container 21a of the yellow image forming unit 15a will be described as an example, but the other developing units 20b to 20d and toner containers 21b to 21d shown in FIG. The configuration is the same as in FIG.

  As shown in FIG. 3, the toner container 21a is disposed on the upper part of the developing device 20a, and is supplied via a driving force of a toner motor described later in order to supply yellow toner 33 to a second conveying path 28 described later. And has a supply port 32 that is opened and closed. The two-component developer 35 includes a magnetic carrier and a nonmagnetic toner 33.

  The developing device 20a is disposed to face the photosensitive drum 19a, and the inside thereof is separated into a first transport path 27 and a second transport path 28 by a partition wall 26.

  A developing sleep 29 for conveying a two-component developer 35 (including a magnetic carrier and non-magnetic toner) to the photosensitive drum 19a, with a predetermined number of magnets (not shown) fixedly disposed in the first conveying path 27. The first screw 30 that stirs and conveys the two-component developer 35 in the first conveyance path 27 and a differential transformer type magnetic sensor 34a (that is, a transparent member) that is used to detect the toner concentration of the two-component developer 35. Magnetic permeability sensor).

The toner 33 replenished from the replenishing port 32 of the toner container 21a is fed to the second transport path 28.
A second screw 31 for conveying the two-component developer 33 to the first conveyance path 27 while agitating the two-component developer 33 already in the developing device 20a to make the toner density uniform is disposed.

  In addition, the partition 26 communicates with the first conveyance path 27 and the second conveyance path 28 in the vicinity of the back and front ends of the first conveyance path 27 and the second conveyance path 28 in FIG. There is no passage. The two-component developer in the first conveyance path 27 that has been consumed by development and the toner concentration of the two-component developer 35 has decreased is conveyed from the front-side path (not shown) to the second conveyance path 28, and the second conveyance path The two-component developer whose toner density has been recovered in 28 is transported to the first transport path 27 from a rear path (not shown). During the copying operation, the developing sleep 29, the first screw 30, the second screw 31, and the like are rotationally controlled by a CPU 10 through a driving force (not shown) such as a motor. Moreover, the solid line arrow of FIG. 3 shows a rotation direction.

  In the magnetic sensor 34 a, a detection coil (not shown) is arranged in the first conveyance path 27, and a reference coil (not shown) is arranged outside the first conveyance path 27. These two coils are AC driven by a converter (not shown) that converts a DC voltage input to the magnetic sensor 34a into an AC voltage. Then, the differential output of both coils (not shown) is output from the magnetic sensor 34 a as a DC voltage corresponding to the toner concentration of the two-component developer 35. That is, when the toner concentration of the two-component developer 35 changes, the magnetic permeability μ of the two-component developer 35 changes and the inductance of the detection coil (not shown) changes, so that the reference coil (not shown) and the detection coil The differential output between (not shown) changes, and the DC voltage output from the magnetic sensor 34a changes.

  Next, a circuit configuration relating to detection of the remaining amount of toner in each developing device and replenishment of toner to each developing device in the copying machine 1 of the present embodiment will be described below. FIG. 4 is a circuit configuration diagram relating to detection of the remaining amount of toner in each developing device and supply of toner to each developing device. As shown in FIG. 4, the image forming unit 15 of the copier 1 of the present embodiment is provided in each of the developing devices 20 a to 20 d described above, and magnetic sensors 34 a to 34 d whose input sides are shared by one, A power supply 36 that supplies a DC voltage to each of the magnetic sensors 34a to 34d and an electrical connection between the magnetic sensors 34a to 34d are switched at predetermined time intervals based on an instruction command from the CPU 10, and a stabilization circuit described later A selection switch 38 that is electrically connected to the unit 37, and a stabilization circuit unit 37 that stably outputs an output voltage that is input by selecting one of the magnetic sensors 34 a to 34 d by the selection switch 38. And toner motors 39a to 39d as drive sources for opening and closing the supply ports 32 of the corresponding toner containers 21a to 21d based on drive commands from the CPU 10, respectively. Made. The toner motors 39a to 39d correspond to opening and closing of the supply ports 32 of the toner containers 21a to 21d, respectively. Further, the driving forces of the toner motors 39a to 39d are transmitted to the replenishing ports 32 of the corresponding toner containers 21a to 21d via gears (not shown).

  Next, connection of the circuit shown in FIG. 4 will be described below. As shown in FIG. 4, a common wire drawn from the input terminals 40 a to 40 d of the magnetic sensors 34 a to 34 d is connected to a grounded power supply 36. A DC voltage Vcc is supplied from the power source 36 to the input terminals 40a to 40d of the magnetic sensors 34a to 34d. The output voltages V1 to V4 output from the output terminals 41a to 41d of the magnetic sensors 34a to 34d are input to the input terminals 38a to 38d of the selection switch 38, respectively. Any one of the input terminals 38a to 38d of the selection switch 38 can be connected by the switch SW1 connected to the output terminal 38e of the selection switch 38. An output terminal 38 e of the selection switch 38 is connected to the stabilization circuit unit 37, and the stabilization circuit unit 37 is further connected to the CPU 10. The CPU 10 is connected to the selection switch 38 and the toner motors 39a to 39d.

  In addition, each output voltage V1-V4 output from each magnetic sensor 34a-34d is input into CPU10 as follows. Based on a predetermined instruction command from the CPU 10, the electrical connection between the magnetic sensors 34 a to 34 d and the stabilization circuit unit 37 is switched every predetermined time by the selection switch 38. The output voltage of the magnetic sensor selected by the selection switch 38 is input to the stabilization circuit unit 37. Then, the output voltage of the magnetic sensor stabilized by the stabilization circuit unit 37 is input to the CPU 10.

  Further, the CPU 10 reads a predetermined threshold value corresponding to an appropriate value of the toner density of the two-component developer stored in the memory unit 18, and further outputs the input output voltages V 1 to V 4 of the magnetic sensors 34 a to 34 d. Then, it is determined whether the voltage is lower or higher than a predetermined threshold value. As will be described later, this determination is used to perform toner replenishment control in order to keep the toner concentration of the two-component developer in the developing device at an appropriate value. At this time, a table or a relational expression indicating the relationship between the output voltages V1 to V4 of the magnetic sensors 34a to 34d stored in the memory unit 18 and the toner concentration of the two-component developer is used so that an appropriate amount of toner can be supplied. In addition, the toner container replenishment port is opened and closed by the driving force of the toner motor. The output voltage of each of the magnetic sensors 34a to 34d is a low voltage when the voltage is lower than a predetermined threshold, and is a high voltage when the output voltage is high.

  Next, the document copying operation in the copying machine 1 configured as described above will be described. In the document copying operation of the copying machine 1 of this embodiment, when a document is first transported from the document transport unit 11 to the document capture unit 12, the document capture unit 12 captures the document, and blue, green, and Image data color-separated into three red components is generated. The generated image data is converted into image data expressed by four colors of yellow, magenta, cyan, and black by the CPU 10, temporarily stored in the memory unit 18, and then read out again to the image forming unit 15. Sent out. Then, electrostatic latent images are formed by the exposure units 22a to 22d on the surfaces of the photosensitive drums 19a to 19d uniformly charged to a predetermined potential by the chargers 23a to 23d based on the image data. Subsequently, toner images of one color are formed on the surfaces of the photosensitive drums 19a to 19d from the electrostatic latent images by the developing devices 20a to 20d, respectively. The toner images formed on the surfaces of the photosensitive drums 19a to 19d are sequentially transferred onto the paper conveyed from the paper supply unit 14 by the transfer rollers 25a to 25d.

  Thereafter, the sheet carrying the unfixed toner image is sent to the fixing unit 16 and is heated and pressurized by the fixing unit 16 to fix the toner image on the sheet. It is discharged to the part 17.

  Note that the copying machine 1 of this embodiment is configured to detect the remaining amount of toner in each developing device and to supply toner to each developing device, which is realized based on a simplified circuit configuration for detecting the toner concentration of the two-component developer. It has a feature in supply control.

  Therefore, in the following, with reference to the drawings, detection of the remaining amount of toner in each developer realized based on the simplified toner concentration detection circuit configuration of the two-component developer in the copying machine 1 of the present embodiment. Also, toner replenishment control for each developing device will be described. FIG. 5 is a flowchart for explaining detection of the remaining amount of toner in each developing device and control for supplying toner to each developing device.

  In the copying machine 1 according to the present embodiment, as shown in FIGS. 4 and 5, in step S5-1, a document is set on the document transport unit, and a start key (not shown) on the operation display unit 13 is pressed. In step S5-2, based on the first instruction command from the CPU 10, the switch SW1 is switched every first time T1 (for example, 500 ms) based on the first instruction command from the CPU 10, and the outputs of the magnetic sensors 34a to 34d. Is input to the stabilization circuit unit 37. Then, the output voltages V1 to V4 of the magnetic sensors 34a to 34d stabilized by the stabilization circuit unit 37 are sequentially input to the CPU 10 at each first time T1.

  Subsequently, in step S5-3, if it is determined by the CPU 10 that any one of the magnetic sensors 34a to 34d has output a low voltage during the first time T1 (YES in step S5-3), the process proceeds to step S5-3. In S5-4, the CPU 10 changes the connection switching time with the magnetic sensor in which the Low voltage is detected to the second time T2 longer than the first time T1 (for example, twice the first time T1). A second instruction command for instructing to change to is input to the selection switch 38. Based on the second instruction command from the CPU 10, the selection switch 38 changes the connection switching time with the corresponding magnetic sensor to the second time T2. That is, the detection time of the corresponding magnetic sensor is set to the second time T2. Hereinafter, a magnetic sensor determined by the CPU 10 to detect a low voltage is referred to as a corresponding magnetic sensor.

  In step S5-3, if it is not determined by the CPU 10 that any of the input magnetic sensors 34a to 34d has output a low voltage during the first time T1 (S5-3 NO), In step S5-5, when all the copies of the document are completed (S5-5 YES), this operation is completed. If it is determined in step S5-5 that all the originals have not been copied (S5-5 NO), the process returns to step S5-2.

  Subsequently, in step S5-6, the CPU 10 outputs the Low voltage continuously for a plurality of times during the second time T2 (for example, three times during the second time T2). If it is determined (S5-6 YES), since the toner density in the two-component developer is not an appropriate value in step S5-7, the CPU 10 sets the second switching time for connection to the corresponding magnetic sensor. A third instruction command instructing to change to a third time T3 (for example, 30 sec) longer than the time T2 is input to the selection switch 38. Then, based on the third instruction command from the CPU 10, the selection switch 38 changes the connection switching time with the corresponding magnetic sensor to the third time T3. That is, the detection time of the corresponding magnetic sensor is set to the third time T3.

  In step S5-6, the CPU 10 outputs the low voltage continuously for a plurality of times during the second time T2 (for example, three consecutive low voltages during the second time T2). When the determination is not made (NO in S5-6), the toner concentration in the two-component developer is an appropriate value, and the process proceeds to step S5-2.

  Subsequently, in step S5-8, the supply port 32 of a toner container (hereinafter referred to as the corresponding toner container) for supplying toner to the developing device (hereinafter referred to as the corresponding developing device) to which the corresponding magnetic sensor is assigned is opened and closed. A toner motor (hereinafter referred to as a corresponding toner motor) serving as a driving source is started to be driven by an instruction command of the CPU 10 and the replenishment port 32 of the corresponding toner container is opened. As a result, toner supply from the toner container to the developer is started.

  Subsequently, in step S5-9, whether the toner density in the developing unit theoretically obtained from the dot count of the image data is lower than a predetermined density by the CPU 10 for each developing unit other than the corresponding developing unit. Judgment is made. For other developing units in which the toner density in the developing unit determined from the dot count of the image data is determined to be lower than the predetermined density (YES in S5-9), the CPU 10 develops the toner in step S5-10. The replenishment port 32 of the toner container corresponding to the developing device in which the toner density in the container is determined to be lower than the predetermined density is opened by the driving force of the toner motor. Then, a theoretical amount of toner obtained from the dot count so that the toner density in the developing unit exceeds a predetermined density is supplied to the developing unit from the supply port 32 of the toner container. When the toner supply is completed, the supply port 32 of the toner container is closed by the driving force of the toner motor. Then, the dot count of the image data corresponding to the color of the replenished toner is reset.

  As described below, the toner density of the two-component developer for each developing device is theoretically obtained from the dot count of the image data for each copying operation and updated and stored in the memory unit 18 as described below. After the CPU 10 determines that the toner is supplied from the toner container to the developing unit and the magnetic sensor outputs a high voltage as described later, or after the theoretical amount of toner in step S5-10 is supplied, From the image data, the counting of the dot count of the same color as the toner of the color accommodated in the developing unit is started. Then, a predetermined theoretical formula indicating the relationship between the dot count stored in the memory unit 18 and the toner concentration of the two-component developer is used, and the toner concentration of the two-component developer in the developing device is calculated from the counted dot count. It is obtained and updated and stored in the memory unit 18 for each copying operation.

  In step S5-9, the CPU 10 determines that the toner density in the developing device obtained from the dot count of the image data is not lower than the predetermined density (S5-9 NO). ) Since the toner amount is appropriate, the process proceeds to step S5-11 without replenishment of the theoretical amount of toner.

  Subsequently, in step S5-11, supply of toner from the corresponding toner container to the corresponding developing device is started in step S5-8, and the CPU 10 recovers the output during the third time T3 by the CPU 10. If it is determined that the High voltage has been output (YES in S5-11), the toner amount in the developing device (that is, the toner concentration of the two-component developer) has reached an appropriate value, and the process proceeds to Step S5-2. . As a result, an appropriate amount of toner can be supplied from the corresponding toner container to the corresponding developing device via the driving force of the toner motor (replenishment means).

  On the other hand, if the CPU 10 does not determine in step S5-11 that the corresponding magnetic sensor has recovered its output and output a high voltage during the third time T3 (NO in step S5-11), in step S5-12, Since the toner in the corresponding toner container is exhausted, the operation display unit 13 displays that the CPU 10 requests replacement of the corresponding toner container, and this operation is completed. Note that the CPU 10 serving as the first to third control units also serves as a replacement request unit that requests replacement of the corresponding toner container.

  As described above, in the copying machine 1 according to the present embodiment, an output corresponding to the toner density of each developing device from each magnetic sensor is input via the selection switch, and the stability for stabilizing the output. Even if the number of circuit units 37 is reduced to one, the CPU 10 first determines that the magnetic sensor whose output from the magnetic sensor is a low voltage lower than the predetermined threshold is the first time by the selection switch. Since the toner is replenished to the corresponding developing device based on the determination of the output, the developing device is agitated or transported by the two-component developer because it is electrically connected intensively for the second time T2 longer than T1. It is possible to prevent erroneous detection of the remaining toner amount. Further, when toner is supplied to the corresponding developing device and the output of the corresponding magnetic sensor does not become a High voltage higher than a predetermined threshold value during the third time T3, replacement of the toner container is requested. be able to. In addition, when the toner is supplied to the corresponding developing device, the other developer is supplied with the toner supply determined from the image data. It is possible to prevent toner shortage in other developing units. On the other hand, since the toner replenishment control to the developing device is performed as described above, and the erroneous detection of the remaining amount of toner does not occur, the stabilization circuit unit 37 can be used in common. Can be reduced.

  The configuration of the present invention can be variously modified in addition to the above embodiment without departing from the spirit of the invention.

  The present invention can be widely applied to color image forming apparatuses using two-component developers such as printers and facsimiles in addition to copying machines, and is a technique useful for toner replenishment control and downsizing of the apparatus main body. is there.

FIG. 2 is a block diagram showing a main configuration of a copier according to the present invention. These are the longitudinal cross-sectional views which show typically the principal part structure of the copying machine which concerns on this invention. FIG. 3 is a longitudinal sectional view schematically showing an example of the configuration of the developing unit 20a and the toner container 21a in FIG. FIG. 3 is a circuit configuration diagram relating to detection of the remaining amount of toner in each developing device and supply of toner to each developing device. FIG. 5 is a flowchart for explaining detection of a remaining amount of toner in each developing device and control of toner supply to each developing device.

Explanation of symbols

1 Copier 10 Central processing unit (CPU)
DESCRIPTION OF SYMBOLS 11 Document conveyance part 12 Document take-in part 13 Operation display part 14 Paper feed part 15 Image formation part 15a Yellow image formation part 15b Magenta image formation part 15c Cyan image formation part 15d Black image formation part 16 Fixing part 17 Paper discharge part 18 Memory Sections 19a to 19d Photosensitive drums 20a to 20d Developers 21a to 21d Toner containers 22a to 22d Exposure units 23a to 23d Chargers 24a to 24d Cleaning sections 25a to 25d Transfer rollers 26 Partitions 27 First transport path 28 Second transport path 29 Development Sleep 30 First screw 31 Second screw 32 Supply port 33 Toner 34a to 34d Magnetic sensor 35 Two-component developer 36 Power source 37 Stabilization circuit section 38 Selection switch 38a to 38d, 40a to 40d Input terminal 38e, 41a to 41d Output terminal 39a ~ 9d toner motor SW1 switch

Claims (3)

A plurality of developers each containing a two-component developer in which a toner of a predetermined color and a carrier are mixed, and developing a latent image formed on the image carrier based on image data using the two-component developer; A plurality of sensors that are assigned to each of the developing units and perform output in accordance with the density of the toner in the developing unit, a plurality of toner containers that respectively store toners of colors corresponding to the developing units, Image forming comprising: a replenishing unit that replenishes toner of a color corresponding to a plurality of developing units from the toner container; and a selecting unit that selects one of the plurality of sensors and performs electrical connection In the device
One stabilization circuit unit that stabilizes and outputs the output of the sensor input from the selection unit, and causes the selection unit to switch the electrical connection with the plurality of sensors every first time, A first control means for determining whether or not the outputs of the plurality of sensors inputted together are lower than a predetermined threshold; and the output of any of the plurality of sensors by the first control means If it is determined that it is lower than the threshold value, only the electrical connection with the sensor corresponding to the determination is switched to the selection means in a second time longer than the first time, and the determination corresponds to the determination A second control means for determining whether the output of the sensor is continuously lower than the predetermined threshold value a plurality of times during the second time; and further, the output of the sensor by the second control means. Is greater than the predetermined threshold The Most When it is determined, the image forming apparatus characterized by comprising a toner corresponding to the developing device the sensor is assigned, a third control means for replenishing the replenishing means. When the second control means determines that the output of the sensor is lower than the predetermined threshold, the third control means causes the selection means to make an electrical connection with the sensor. Switching at a third time longer than two times and determining whether the output of the sensor continues for the third time below the predetermined threshold;
When it is determined by the third control means that the output of the sensor is continuously lower than the predetermined threshold during the third time, a toner container corresponding to the developing device to which the sensor is assigned 2. The image forming apparatus according to claim 1, further comprising exchange request means for requesting exchange of the image.   The third control means causes the sensor to be supplied to the replenishing means until the output of the sensor, which has been determined by the second control means to have an output lower than the predetermined threshold, is higher than the predetermined threshold. The image forming apparatus according to claim 1, wherein the toner corresponding to the assigned developing device is replenished.

Images