JP2008122469A - Image forming apparatus and facsimile device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent image formation from being hindered when a small amount of toner is left while appropriately controlling toner concentration in an image forming apparatus equipped with a two-component developing type developing device. <P>SOLUTION: The image forming apparatus is equipped with: a toner concentration sensor which detects the toner concentration of two-component developer; a toner cartridge in which toner to be supplied to the developing device is reservoired; an empty sensor which detects that the residual amount of toner in the reservoir means is small; and a control part which controls to hinder the image formation when a detected value by the toner concentration sensor is out of a prescribed range (S110). After the empty sensor detects that the residual amount of toner becomes small, the control part permits the image formation only by prescribed amount whatever value the detected value by the toner concentration sensor shows (S108 and S109). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and a facsimile apparatus. More specifically, the present invention relates to control when toner is low in an image forming apparatus that includes a two-component development type developer and controls image density using a toner density sensor.

Japanese Patent Application Laid-Open No. 2004-228688 describes a toner empty detection unit that detects that toner in a developing device has been reduced to some extent in an image forming apparatus that performs development with a two-component developer, and counts the number of images formed after toner empty detection. An image forming apparatus is disclosed that includes one counting unit and a prohibiting unit that prohibits an image forming operation when the first predetermined number is counted by the first counting unit.
Japanese Patent No. 2748542

  However, the configuration of Patent Document 1 only considers toner empty, and does not mention control of the toner concentration in the developer. Therefore, there is room for improvement in the configuration of Patent Document 1 from the viewpoint of more appropriately dealing with various situations related to the toner.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

  According to the first aspect of the present invention, the following configuration of an image forming apparatus including a two-component developing type developing device is provided. That is, the toner concentration sensor for detecting the toner concentration of the two-component developer of the developing device, the storing means for storing the toner to be supplied to the developing device, and the remaining amount of toner in the storing means are reduced. And an image formation control means for controlling to prevent image formation when the detection value of the toner density sensor is out of a predetermined range. After the empty sensor detects that the remaining amount of toner is low, the image formation control unit permits image formation by a predetermined amount regardless of the detection value of the toner density sensor.

  With this configuration, it is possible to prevent the image quality from deteriorating by controlling to stop image formation when the detection value of the toner density sensor is not within a predetermined range during normal operation. On the other hand, after toner empty is detected, even if the detection value of the toner density sensor is outside the predetermined range, control is performed to form an image. Image formation becomes possible. Therefore, flexible and convenient operation is realized, and the use efficiency of the image forming apparatus is improved.

  According to the second aspect of the present invention, the following configuration of an image forming apparatus including a two-component developing type developing device is provided. That is, the toner concentration sensor for detecting the toner concentration of the two-component developer of the developing device, the storage means for storing the toner to be supplied to the developing container, and the remaining amount of toner in the storage means is reduced. And an image formation control means for controlling to allow image formation only when the detection value of the toner density sensor is within a predetermined first range. After the empty sensor detects that the remaining amount of toner is low, the image formation control means has a subsequent image formation within a predetermined amount, and the detected value of the toner density sensor is in the first range. When it is within a predetermined second range that is wider, image formation is permitted.

  With this configuration, it is possible to prevent the image quality from deteriorating by controlling to stop image formation when the detection value of the toner density sensor is not in the first range during normal times. On the other hand, after the toner empty is detected, control is performed to permit image formation if the detection value of the toner density sensor is not in the first range but is in the second range wider than that. The density range that can be formed is automatically expanded. Accordingly, even when the storage means cannot be quickly replaced with a new one, a predetermined number of images can be formed, flexible and convenient operation is realized, and the use efficiency of the image forming apparatus is improved.

  According to a third aspect of the present invention, the following configuration of an image forming apparatus including a two-component developing type developing device is provided. That is, a toner concentration sensor that detects the toner concentration of the two-component developer of the developing device by a magnetic permeability detection method, a sensor control unit that controls an input control voltage applied to the toner concentration sensor, and a supply to the developer container The image forming apparatus permits the image formation only when the storage means for storing the toner for use, the empty sensor for detecting that the toner remaining in the storage means is low, and the detection value of the toner density sensor are within a predetermined range. Image forming control means for controlling as described above. After the empty sensor detects that the remaining amount of toner is low, the image formation control means is within a predetermined amount of subsequent image formation, and the detection value of the toner density sensor is within the predetermined range. Allow image formation only at certain times. The sensor control means changes the input control voltage after the empty sensor detects that the toner remaining amount is low.

  With this configuration, it is possible to prevent the image quality from deteriorating by controlling to stop image formation when the detection value of the toner density sensor is not within a predetermined range during normal operation. On the other hand, after the toner empty is detected, the detection value can be controlled to fall within the predetermined range by changing the input control voltage of the toner density sensor. Accordingly, even when the storage means cannot be quickly replaced with a new one, a predetermined number of images can be formed, flexible and convenient operation is realized, and the use efficiency of the image forming apparatus is improved.

  According to another aspect of the present invention, a facsimile machine as the image forming apparatus is provided.

  Next, the image forming apparatus of this embodiment will be described with reference to the drawings. 1 is an external perspective view of a copy facsimile multifunction peripheral according to an embodiment of the present invention, FIG. 2 is a front sectional view showing the inside of the main body of the multifunction peripheral, and FIG. 3 is a front sectional view showing the state of an image forming unit in detail. It is an enlarged view. FIG. 4 is a graph showing the relationship between the toner density and the output voltage of the toner density sensor, and FIG. 5 is a block diagram relating to toner density control and empty control. FIG. 6 is a graph showing the relationship between absolute humidity, cumulative drive time, and input control voltage stored in the storage unit. FIG. 7 is a flowchart of toner density control, and FIG. 8 is a flowchart of another example of toner density control.

  As shown in the external perspective view of FIG. 1, a copy facsimile multifunction peripheral 91 as an image forming apparatus instructs an image reading unit 92 that functions as a flatbed scanner and an auto document feed scanner, and the number of copies, a facsimile transmission destination, and the like. An operation panel 93, a main body 94 incorporating an image forming unit for forming an image on a sheet as a recording medium, and a sheet feeding cassette 95 for sequentially supplying the sheet.

  The copy facsimile multifunction peripheral 91 includes a front cover 97 on the front side of the main body 94 (the side on which the operation panel 93 is provided) and a jam access cover 98 on one side surface. The front cover 97 and the jam access cover 98 are provided so as to be freely opened and closed. For example, when performing maintenance work, the inside of the main body 94 can be accessed by opening the covers 97 and 98.

  FIG. 2 shows the inside of the main body 94. As shown in FIG. 2, a paper feed cassette 95 that supplies paper 100 is provided at the bottom of the main body 94. The paper feed cassette 95 is configured to be able to be pulled out to the front side of the apparatus (the front side of the paper in FIG. 2). An image forming unit 11 is disposed above the paper feed cassette 95, and a fixing unit 81 and a paper discharge tray 96 are further provided above the image forming unit 11.

  Inside the main body 94, a transport path 85 for transporting the paper 100 from the paper feed cassette 95 to the paper discharge tray 96 is formed. The transport path 85 extends upward from one end side of the paper feed cassette 95 to reach the image forming unit 11, extends further upward, passes through the fixing unit 81, and then curves in the horizontal direction to discharge the paper discharge tray 96. It is configured to reach the top. Although not shown in FIG. 2, the image reading unit 92 and the operation panel 93 are disposed above the paper discharge tray 96.

  The paper feed cassette 95 is formed so as to be open upward, and a plate-like flapper 86 is rotatably provided at the bottom thereof. A plurality of sheets of paper 100 are stacked on the flapper 86. A temperature sensor 28 capable of detecting the temperature inside the main body 94 and a humidity sensor 29 capable of detecting humidity (relative humidity) are disposed at appropriate positions of the paper feed cassette 95.

  A paper feed roller 21 is disposed above the flapper 86. Then, the paper feed roller 21 is driven while pushing up the flapper 86 upward by a biasing spring (not shown), whereby the uppermost paper 100 is separated and picked up and sent out toward the transport path 85. .

  A separation roller 22 is disposed immediately downstream of the paper feed roller 21 in the transport path 85. The separation roller 22 is driven while the paper 100 is nipped between the rollers arranged opposite to the roller, and separates the paper 100 one by one. A registration roller 23 is disposed on the downstream side of the separation roller 22. The registration roller 23 is driven while the paper 100 is nipped between the registration roller 23 and a roller disposed opposite to the registration roller 23, thereby conveying the paper 100 to the downstream image forming unit 11 while correcting the skew of the paper 100.

  As shown in FIG. 2 and FIG. 3, which is an enlarged view of a main part thereof, the image forming unit 11 includes a charger 13, an LED head 14, a developing device 15, a transfer roller 16, around the photosensitive drum 12. The cleaner 17 is arranged.

  The photosensitive drum 12 is configured such that a photoconductive film made of an organic photoreceptor is formed on the surface and is rotated by an electric motor (not shown). The charger 13 is configured as a non-contact corona charging type so-called scorotron charger, and the surface of the photosensitive drum 12 is uniformly charged, for example, negatively by the charger 13.

  The LED head 14 as an exposure device is disposed downstream of the charger 13 (refers to the downstream side in the rotation direction of the photosensitive drum 12. Hereinafter, the same applies to the description of the developing device 15, the transfer roller 16, and the cleaner 17). In this configuration, a large number of light emitting diodes (LEDs) are arranged in the paper width direction. The LED head 14 selectively emits light corresponding to the image data of the facsimile document received via the telephone line or the image data read by the image reading unit 92. As a result, the surface of the photosensitive drum 12 is selectively exposed, and the electrostatic energy is formed by losing the charge energy of the exposed portion.

  The developing device 15 is disposed on the downstream side of the LED head 14. The developing device 15 is configured in a two-component developing system using toner (pigment powder) and carrier (magnetic powder) as developers. Specifically, the developing device 15 includes a developer container 35 made of a synthetic resin, two stirring screws 31 and 32 and a stirring paddle 37 disposed inside the developer container 35, and the photosensitive drum 12. A developing roller 33 as a developer carrying member that is disposed in close proximity while forming a slight gap, and a regulating blade 34 that is disposed in proximity to the surface of the developing roller 33; It has.

  The stirring screws 31 and 32 are driven to rotate, thereby circulating the two-component developer in the developer container 35. Further, the agitation paddle 37 is also rotationally driven so that the toner and the carrier are frictionally charged and adsorbed to each other by electrostatic force.

  The developing roller 33 is formed in a cylindrical shape from a non-magnetic material, and is rotatably fitted to the outside of a cylindrical magnetic body 36. The internal magnetic body 36 attracts the carrier to the surface of the developing roller 33 by the magnetism, and rotates the developing roller 33 in this state, so that the toner and the carrier are held on the surface of the developing roller 33 and the photosensitive drum. 12 side. Note that the thickness of the developer on the surface of the developing roller 33 is regulated to be uniform by the regulating blade 34.

  Thereafter, in the vicinity of the photosensitive drum 12 and the developing roller 33, only the portion of the two-component developer on the surface of the developing roller 33 where the toner corresponds to the exposed portion by the LED head 14 moves to the surface of the photosensitive drum 12. Move selectively. As a result, a toner image corresponding to the electrostatic latent image is formed on the surface of the photosensitive drum 12. The remaining toner that has not moved to the carrier and the photosensitive drum 12 side of the developer is collected in the developer container 35.

  A toner concentration sensor 38 is disposed at an appropriate position in the developer container 35. As the toner concentration sensor 38, a magnetic permeability detection method using an inductance component of a coil is employed in the present embodiment. The space in the developer container 35 is connected to the toner cartridge (storage unit) 8 through a toner supply pipe 39 as a toner supply path.

  The transfer roller 16 is disposed on the downstream side of the developing device 15 and is disposed on the opposite side of the photosensitive drum 12 with the conveyance path 85 interposed therebetween. A predetermined voltage from a power source is applied to the transfer roller 16. Accordingly, the toner image formed on the surface of the photosensitive drum 12 moves so as to approach the transfer roller 16 side by the rotation of the photosensitive drum 12, and is transferred to the paper 100 by the electric field attraction force.

  The cleaner 17 is disposed on the downstream side of the transfer roller 16 and is configured to scrape residual toner that has not been transferred to the paper 100 at the transfer roller 16 portion from the surface of the photosensitive drum 12. The collected residual toner is sent to the toner cartridge 8 via a return path (not shown) by a conveying member such as a paddle 25 and a screw 26 and stored in a waste toner storage chamber 43 described later.

  Of the configuration of the image forming unit 11, at least the photosensitive drum 12, the charger 13, the developing device 15 (including the developing roller 33), and the cleaner 17 are integrated as a process cartridge (process unit) 5. Composed. The process cartridge 5 is detachably attached to the image forming unit 11. For example, when the life of the developer or the photosensitive drum 12 is reached, the process cartridge 5 can be removed from the copy facsimile multifunction peripheral 91 and replaced with a new one. It has become. The sheet 100 on which the toner image is transferred in the image forming unit 11 is sent to the fixing unit 81 on the downstream side of the conveyance path 85 by the rotation of the photosensitive drum 12.

  As shown in FIGS. 2 and 3, the fixing unit 81 includes a heat roller 82 that incorporates a heating source (such as a halogen lamp) and is driven to rotate, and a press roller 83 that is disposed to face the heat roller 82. It is equipped with. The press roller 83 is pressed against the heat roller 82 by a biasing spring (not shown). With this configuration, when the paper 100 passes between the heat roller 82 and the press roller 83, the toner of the toner image is melted and fixed to the paper 100 by the heat of the high-temperature heat roller 82 and the pressure by the press roller 83. The fixing unit 81 is provided with a separation claw 84 for preventing the paper 100 from being wrapped around the heat roller 82 while being stuck.

  As shown in FIG. 2, a conveyance roller 87 is provided on the downstream side of the fixing unit 81, and a paper discharge roller 88 is provided on the further downstream side. With this configuration, the sheet 100 sent from the fixing unit 81 is nipped between the transport roller 87 and the driven roller disposed opposite thereto, and is sent downstream. Further, the sheet 100 is nipped between the sheet discharge roller 88 and a driven roller disposed opposite thereto, and is discharged onto the sheet discharge tray 96.

  Next, a configuration for supplying toner to the developing device 15 will be described. As shown in FIG. 3, the main body 94 includes a toner cartridge 8 that is detachable. The toner cartridge 8 includes a synthetic resin toner container 40, and a toner storage chamber 41, a toner buffer unit 42, and a waste toner storage chamber 43 are formed in the toner container 40.

  A predetermined amount of toner is sealed in the toner storage chamber 41, and a paddle 45 is installed therein. The paddle 45 is rotated to agitate the toner. Further, a screw 46 is disposed in a chamber adjacent to the toner storage chamber 41 so that the toner in the toner storage chamber 41 is transferred to the toner buffer unit 42.

  Further, the toner supply pipe 39 is connected to the toner buffer section 42, and a supply screw (toner replenishing means) 47 is disposed inside the toner supply pipe 39. With this configuration, when the toner density sensor 38 detects that the toner density of the developer in the developing device 15 has decreased, the supply screw 47 is driven to supply new toner in the toner buffer section 42 to the developer container. It is comprised so that it may supply to the inside of 35.

  A toner detection sensor (empty sensor) 48 is installed inside the toner buffer unit 42. As the toner detection sensor 48, for example, it is conceivable to use a piezoelectric vibration type sensor that detects powder by vibrating the vibration surface. The toner detection sensor 48 is disposed at a predetermined height in the toner buffer unit 42, and is configured such that when the toner in the toner buffer unit 42 falls below a predetermined amount, the toner detection sensor 48 transmits a predetermined signal. ing.

Next, the output voltage characteristics of the toner density sensor 38 will be described with reference to FIG. In the graph shown in FIG. 4, the horizontal axis indicates the toner density, and the vertical axis indicates the output voltage of the toner density sensor 38. As shown in this graph, the toner density sensor 38 has a characteristic that the relationship between the toner density and the output voltage is changed in accordance with a control voltage (hereinafter, input control voltage) input to the sensor (FIG. 4 shows the case where the input control voltages are 6V, 7V, and 8V, respectively). Therefore, for example, when the toner density is controlled so that the output voltage of the toner density sensor 38 becomes the predetermined reference voltage V _std , the corresponding developing device 15 depends on whether the input control voltage is 6V, 7V, or 8V. The toner density is different between D ₁ , D ₂ , and D ₃ .

In view of this characteristic, in general, the toner density is used so that an area in which the output voltage changes favorably following the change in the toner density (for example, an area in which the output voltage is around the reference voltage V _std ) is used. The input control voltage applied to the sensor 38 is set to a predetermined value and used. For example, when it is desired to keep the actual toner density in the developing device 15 in the vicinity of D ₂ , the input voltage of 7 V is applied to the toner density sensor 38 and development is performed so that the output voltage is in the vicinity of the reference voltage V _std. It is only necessary to control the supply of toner to the agent.

  However, the toner density sensor 38 has a characteristic that the detection value changes depending on an environmental factor (specifically, absolute humidity) in which the image forming unit 11 is installed. For example, even when the toner concentration of the developer is the same, when the absolute humidity is low, the charge retention amount of the carrier of the developer increases, so the repulsive force between the carriers also increases and the magnetic permeability per unit volume decreases. The toner concentration sensor 38 regards this decrease in magnetic permeability as a decrease in carrier (increase in toner) and detects the toner concentration higher than the actual one, so this needs to be corrected. On the other hand, when the absolute humidity is high, the charge retention amount of the carriers decreases, so the repulsive force between the carriers also decreases and the magnetic permeability per unit volume increases. The toner concentration sensor 38 regards this increase in magnetic permeability as an increase in carrier (a decrease in toner) and detects the toner concentration lower than the actual one, so it is necessary to correct this.

  Further, the carrier of the two-component developer generally deteriorates gradually as the cumulative driving time (cumulative usage amount) from the start of use of the developing device 15 increases, and the charging ability of the toner generally decreases. . As causes of this deterioration, it has been pointed out that the charge imparting ability is reduced due to adhesion of the toner component to the carrier surface, and the resistance is reduced due to wear of the coating film of the carrier. When the toner is insufficiently charged due to the deterioration of the carrier, the developability of the toner is increased, so that the image density is increased. Therefore, in order to stabilize the formed image, it is necessary to control the toner concentration of the developer in consideration of the above-described viewpoint of carrier deterioration.

  Next, an electrical configuration for controlling the toner density will be described with reference to FIG. As shown in the block diagram of FIG. 5, the outputs of the temperature sensor 28 and the humidity sensor 29 are input to an absolute humidity calculator 61, where the absolute humidity (environmental value) is calculated by a known equation. The temperature sensor 28, the humidity sensor 29, the absolute humidity calculation unit 61, and the like constitute an absolute humidity acquisition unit 66 for acquiring absolute humidity. The absolute humidity calculated by the absolute humidity calculating unit 61 is input to the control unit (image formation control unit, sensor control unit) 62.

  In addition, a timer circuit 65 is connected to the control unit 62 so that the cumulative driving time of the developing device 15 from the time when the developing device 15 is first used can be acquired. The timer circuit 65 and an appropriate storage unit (not shown) for storing the cumulative drive time constitute a drive time acquisition unit 67 for acquiring the cumulative drive time. Information on the drive time acquired by the drive time acquisition unit 67 is input to the control unit 62.

  The controller 62 is connected to the toner density sensor 38 and is configured to control an input control voltage applied to the toner density sensor 38. Further, the output of the toner density sensor 38 is input to the control unit 62. In addition, a storage unit 63 that stores information for various controls is connected to the control unit 62.

  Further, a toner replenishing motor 64 for driving the supply screw 47 and the like is connected to the control unit 62, and its driving / stopping can be controlled by the control unit 62. Further, the toner detection sensor 48 of the toner cartridge 8 is connected to the control unit 62. If the toner detection sensor 48 does not detect toner even if the paddle 45 and the screw 46 shown in FIG. 62 is configured to determine that the toner in the toner cartridge 8 is low.

  In the present embodiment, the absolute humidity calculation unit 61, the control unit 62, the storage unit 63, and the like are configured as a microcomputer and include a CPU, a ROM, a RAM, and the like (not shown). That is, the hardware described above is combined with the control software stored in the ROM or the like, and the above-mentioned absolute humidity calculation unit 61, control unit 62, storage unit 63, absolute humidity acquisition unit 66, drive is added to the multi-function device 91. A time acquisition unit 67 and the like are configured.

The storage unit 63 stores in advance the relationship between the cumulative drive time of the developing device 15 and the input control voltage for a plurality of absolute humidity. In the graph of FIG. 6, the absolute humidity is ^{2.0g / m 3, 6.0g / m} 3, are illustrated the three cases of 16.0 g / m ^3, which is example one in order to simplify the description The above relationship is actually stored for many absolute humidity cases. Various changes can be made to the absolute humidity for storing the relationship in the storage unit 63.

Here, as described above, the toner concentration sensor 38 tends to detect the toner concentration lower than the actual when the absolute humidity is high, and detects the toner concentration higher than the actual when the absolute humidity is low. In view of this point, in the relationship stored in the storage unit 63 in the multifunction peripheral 91 of the present embodiment, as shown in FIG. 6, when the absolute humidity is high (16.0 g / m ³ ), the input control voltage is low. Similarly, when the absolute humidity is low (2.0 g / m ³ ), the input control voltage is set to be high. Thereby, the deviation of the detection value of the toner density sensor 38 due to the change in absolute humidity is absorbed by the change of the input control voltage, and the toner density of the developer can be accurately controlled.

Further, as the multi-function device 91 is continuously used and the cumulative driving time of the developing device 15 is increased, the carrier of the developer is deteriorated as described above, the developability of the toner is increased, and the image density is increased. From this point of view, the relationship stored in the storage unit 63 is such that the input control voltage of the toner density sensor 38 decreases as the cumulative driving time of the developing device 15 increases from zero for any of the curves shown in FIG. , The relationship is defined. When the input control voltage is lowered, the toner density corresponding to the reference voltage V _std is lowered. Therefore, the above relationship is controlled so that the toner density of the developer is lowered as the cumulative driving time is increased (development is increased). Means that. As a result, the density of the formed image can be kept constant, and deterioration in image quality such as fogging can be prevented.

  Next, the toner density control described with reference to FIG. 5 will be described in more detail with reference to the flowchart of FIG. When this control is started, first, it waits until an image formation command based on reception of a facsimile, copy operation, or the like is received (S101). When the image formation command is received, the absolute humidity and the cumulative driving time are acquired (S102). Specifically, the temperature sensor 28 detects the temperature, the humidity sensor 29 detects the humidity, the absolute humidity calculation unit 61 calculates the absolute humidity from both detection values, and the cumulative driving time of the developing device 15 is calculated based on the driving time. Obtained from the time obtaining unit 67.

Next, the obtained absolute humidity and accumulated drive time are applied to the relationship stored in the storage unit 63 (FIG. 6) to obtain an input control voltage (S103). The input control voltage obtained by the above processing is input to the toner concentration sensor 38 while driving the agitating screws 31 and 32 of the developing device 15 to flow the developer, and the output voltage V _out at this time is input. Obtain (S104). Then, the obtained output voltage _Vout is compared with the reference voltage _Vstd (S105).

When the output voltage _Vout is higher than the reference voltage _Vstd , the replenishment count value, which is the number of attempts to replenish toner, is counted up, and it is checked whether the replenishment count value is within a predetermined number of times (S106). If it is within the predetermined number of times, the toner replenishing motor 64 is driven by a predetermined amount, and the supply screw 47 is rotated to replenish the toner to the developing device 15 (S107). That is, if the output voltage V _out is larger than the reference voltage V _std , it means that the toner density is smaller than the target, so that the toner is replenished to increase the toner density.

Then return to S104, until the output voltage V _out of the toner density sensor 38 becomes equal to or lower than the reference voltage V _std, it repeats the processing of S104 to S107. However, when the replenishment count value exceeds a predetermined number, the detection value of the toner detection sensor 48 is checked to check whether the remaining amount of toner is low (whether toner is empty) (S108). If there is a sufficient amount of toner, it is considered that the toner density cannot be controlled even if the replenishment is repeated a predetermined number of times due to a failure of the supply screw 47, the toner replenishment motor 64, etc. Cancel.

  On the other hand, when toner empty is detected, it is checked whether the count value for counting the number of image forming pages after empty is equal to or smaller than a predetermined value (S109). If this count value is equal to or smaller than the predetermined value, it is considered that the number of images to be formed is small and a certain amount of toner still remains in the toner buffer section 42 and the developer container 35 of the toner cartridge 8. The process jumps to the image forming step to perform an image forming process described later. If the count value exceeds the predetermined number, it is considered that the toner is consumed and almost empty, so the process proceeds to S110 and image formation is stopped.

If the output voltage _Vout of the toner density sensor 38 is equal to or lower than the reference voltage _Vstd as determined in S105, image formation by the image forming unit 11 is started (S111), and the process waits until the image formation is completed (S112). At this time, the driving time acquisition unit 67 measures the time by the timer circuit 65 as needed, and updates the driving accumulated time of the developing device 15. If it is determined that the toner is empty in S108, the image formation count value after the toner empty is incremented and updated every time the image for one page is formed. After completion of image formation, after stopping control of each part (S113), the process returns to S101 and waits for an image formation command again.

As described above, the copy facsimile multifunction peripheral 91 according to the present embodiment includes the two-component developing type developing device 15, a toner concentration sensor 38 that detects the toner concentration of the two-component developer of the developing device 15, and A toner cartridge 8 for storing toner to be supplied to the developing device 15, a toner detection sensor 48 for detecting that the remaining amount of toner in the toner cartridge 8 is low, and an output voltage V _{out of the} toner concentration sensor 38. And a control unit 62 that controls to stop image formation when the image is out of a predetermined range (S110). Then, after the toner detection sensor 48 detects that the remaining amount of toner is low (toner empty), the control unit 62 performs image formation on a predetermined page regardless of the detection value of the toner density sensor 38. Only the number is permitted (S108, S109).

As a result, when the output voltage V _out of the toner density sensor 38 is not within the predetermined range, it is possible to prevent the image quality from being deteriorated by controlling the image formation to be stopped. On the other hand, after the toner empty is detected (S108, S109), the toner cartridge 8 is quickly replaced with a new one by performing image formation even if the output voltage _Vout of the toner concentration sensor 38 is outside the predetermined range. Even when this is not possible, a predetermined number of images can be formed. As a result, flexible and convenient operation is realized, and the usage efficiency of the multifunction device 91 is improved.

Next, another control example of the toner density will be described with reference to FIG. In the control of FIG. 8, the processing from S101 to S103 is the same as that of FIG. In the control example of FIG. 8, after the input control voltage is determined in S103, the detection value of the toner detection sensor 48 is checked to check whether the remaining amount of toner is low (whether toner is empty) (S104). . When toner empty is detected, it is checked whether or not the count value for counting the number of image forming pages after empty is equal to or less than a predetermined value (S105). When the count value is equal to or smaller than the predetermined value, it is conceivable that the number of formed images is small and a certain amount of toner still remains in the toner buffer portion 42 and the developer container 35 of the toner cartridge 8. However, in order to continue image formation even if the density detected by the toner density sensor 38 becomes thinner than usual, the reference voltage V _std that is a comparison reference of the output voltage of the toner density sensor 38 is changed so as to increase ( S106). On the other hand, if the count value exceeds the predetermined number in S105, it is considered that the toner is consumed and almost empty, so the process proceeds to S107 and image formation is stopped.

When it is determined in S104 that the remaining amount of toner is sufficient, and when toner empty is detected and the subsequent image formation is within the predetermined number of sheets, the agitating screws 31, 32, etc. are driven to remove the developer. While flowing, the input control voltage obtained by the above processing is input to the toner concentration sensor 38, and the output voltage _Vout at this time is acquired (S108). Then, the obtained output voltage V _out is compared with the reference voltage V _std (S109).

When the output voltage _Vout is higher than the reference voltage _Vstd , the replenishment count value, which is the number of attempts to replenish toner, is counted up, and it is checked whether the replenishment count value is within a predetermined number (S110). If it is within the predetermined number of times, the toner replenishing motor 64 is driven by a predetermined amount, and the supply screw 47 is rotated to replenish the toner to the developing device 15 (S111). Then return to S108, until the output voltage V _out of the toner density sensor 38 becomes equal to or lower than the reference voltage V _std, it repeats the processing of S108～S111. However, if the replenishment count value exceeds a predetermined number of times, it is considered that the toner density cannot be controlled even if the replenishment is repeated a predetermined number of times due to a failure of the supply screw 47, the toner replenishment motor 64, or the like. Proceed to, and image formation is stopped.

If the output voltage V _out of the toner density sensor 38 is equal to or lower than the reference voltage V _{std in} the determination of S109, image formation by the image forming unit 11 or the like is performed. Note that the processing of S113 to S115 is exactly the same as the processing of S111 to S113 in FIG.

In the control example of FIG. 8, after the toner detection sensor 48 detects that the remaining amount of toner has decreased, the controller 62 determines that the subsequent image formation is within a predetermined number of sheets and the toner density When the output voltage _Vout of the sensor 38 is within the reference voltage _Vstd (S106) which is larger than the reference voltage _Vstd before the change, the image formation is permitted (S109).

As a result, the toner density tends to decrease when the remaining amount of toner becomes low, but by automatically increasing the reference voltage _Vstd , the density range in which image formation is possible is expanded to avoid the situation where image formation cannot be performed. can do.

Note that instead of changing the reference voltage V _std in the process of S106 in FIG. 8, the input control voltage determined in S103 may be changed (to the lower side) so as to detect the toner density higher than the actual density. According to this configuration, when the remaining amount of toner decreases, the input control voltage is automatically lowered to increase the toner density detected by the toner density sensor 38, thereby avoiding a situation where image formation cannot be performed.

  Although the preferred embodiment of the present invention and the modification thereof have been described above, the above-described configuration can be changed as follows, for example.

  The method of measuring the image formation amount after toner empty is not limited to the number of pages (number of sheets), and for example, the driving time of the developing device 15 or the rotation count value of the developing roller can be used.

  The relationship between the cumulative drive time of the developing device 15 and the input control voltage of the toner density sensor 38 can be stored in, for example, a lookup table format instead of being stored in the storage unit 63 in the form of a function.

  For example, the accumulated rotation count value of the developing roller 33 can be used as the accumulated use value of the developing unit 15 representing the deterioration of the carrier, instead of acquiring the accumulated driving time from the start of use of the developing unit 15.

  In the above embodiment, the absolute humidity is calculated from the detection values of the temperature sensor 28 and the humidity sensor 29, and the input control voltage to the toner concentration sensor 38 is determined based on the absolute humidity. However, for example, only the detection value of the temperature sensor 28 is determined. The input control voltage can also be determined based on In this case, the storage unit 63 stores the relationship between the cumulative drive time and the input control voltage for a plurality of temperatures. Also, the input control voltage can be determined based only on the detection value of the humidity sensor.

  The configuration of the present invention can be applied to, for example, a printer, a copier, a facsimile machine, and the like instead of the copy facsimile multifunction machine 91.

1 is an external perspective view of a copy facsimile multifunction peripheral according to an embodiment of the present invention. Front sectional drawing which shows the mode inside a main body. The front cross-sectional enlarged view which shows the mode of an image formation part in detail. The graph which shows the relationship between a toner density and the output voltage of a toner density sensor. FIG. 3 is a block diagram regarding toner density control and empty control. The graph which shows the relationship of absolute humidity, the accumulation drive time, and input control voltage which are memorize | stored in a memory | storage part. FIG. 6 is a flowchart of toner density control. FIG. 10 is a flowchart of another example of toner density control.

Explanation of symbols

8 Toner cartridge (storage means)
15 Developing Device 38 Toner Concentration Sensor 48 Toner Detection Sensor (Empty Sensor)
62 Control section (image formation control means, sensor control means)
63 Storage section (storage means)
91 Copy Facsimile MFP (image forming device)

Claims (4)

In an image forming apparatus including a two-component developing type developing device,
A toner concentration sensor for detecting the toner concentration of the two-component developer of the developing device;
Storage means for storing toner to be supplied to the developer;
An empty sensor for detecting that the remaining amount of toner in the storage means has decreased;
Image formation control means for controlling to prevent image formation when a detection value of the toner density sensor is out of a predetermined range;
With
The image formation control unit permits image formation by a predetermined amount regardless of the detection value of the toner density sensor after the empty sensor detects that the toner remaining amount is low. Image forming apparatus. In an image forming apparatus including a two-component developing type developing device,
A toner concentration sensor for detecting the toner concentration of the two-component developer of the developing device;
Storage means for storing toner to be supplied to the developer container;
An empty sensor for detecting that the remaining amount of toner in the storage means has decreased;
Image formation control means for controlling to allow image formation only when the detection value of the toner density sensor is within a predetermined first range;
With
After the empty sensor detects that the remaining amount of toner is low, the image formation control means has a subsequent image formation within a predetermined amount, and the detected value of the toner density sensor is in the first range. An image forming apparatus that permits image formation when it falls within a predetermined second range that is wider. In an image forming apparatus including a two-component developing type developing device,
A toner concentration sensor for detecting a toner concentration of a two-component developer of the developing device by a magnetic permeability detection method;
Sensor control means for controlling an input control voltage applied to the toner density sensor;
Storage means for storing toner to be supplied to the developer container;
An empty sensor for detecting that the remaining amount of toner in the storage means has decreased;
Image formation control means for controlling image formation only when the detection value of the toner density sensor is within a predetermined range;
With
After the empty sensor detects that the remaining amount of toner is low, the image formation control means is within a predetermined amount of subsequent image formation, and the detection value of the toner density sensor is within the predetermined range. Allow image formation only at certain times,
The image forming apparatus according to claim 1, wherein the sensor control unit changes the input control voltage after the empty sensor detects that the remaining amount of toner is low.   A facsimile apparatus as an image forming apparatus according to any one of claims 1 to 3.

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